Serta acta SEES Lest =a07 '" i R yer. ne) 4 \ Balt cory per » ion A, a Malt ei yao id ty Ar a q ey ta ai Y ‘ rn i 4, Wt, ; ; iy! a rs * F i : ie Li) \ f " i) 1 iy i b Vy int ] OMe iy ; : , 4 \ is : ar i er | hed at ‘ at Abd ‘I i k d w, x ~ \ > - 7 — 4s, _ >, or > ‘ A ‘ : > 7 Mee [ iN ‘i ‘ey ; ate | J — - : i ~ Geta eg dea ition. i ce ee ”, f ee ee ee i A = ive, a mG! Jea5 : : . ee ioe hs * a) J 7 7 A . ' 7 1 \ 1W j# ‘ ay 7, van tens | me " E J si) ‘is ts : Malis a I 8 ila a ibn ; mvt . n i “si vs Senta ek eet | pee pes a my Ay ‘Ai, Pee A 2 a oP Veé > . ; A . z F Saale cel? 1 = Random — B SOU Oe Ne ee -L. 92 =~ NATURAL PHILOSOPHY, CHEMISTRY, AND THE ARTS: ILLUSTRATED WITH ENGRAVINGS. BY WILLIAM NICHOLSON. Va@ teat LONDON: PRINTED FOR G. G. AND J. ROBINSON, PATERNOSTER-ROW,. M.DCC,XCVI1I. it. pede: bat aay ie es Te $ b ’ elt, 1 OM eet Ruy a 2 ano. ge arepenaet pete Pe aren 7 ike . ae Oe = Pe tae ¢ - Pe a CB. "Turre is fcarcely a more difficult tafk than to convey an adequate notion of a plan of fome extent, within the limits of a fhort difcourfe. Whatever may be the promifes, the hopes, or the intentions of an Author or Editor, the world, as in juttice it ought, will fuf- pend its judgment till the actual performance fhall afford the knowledge which is indif- penfable for that purpofe. Correfpondents will arrange for themfelyes fuch materials as they think fit to publifh, without committing to memory any of the outlines which the authors of Journals may have drawn up. For thefe reafons, little more need be faid con- cerning the plan, than is prefented in the title-page. Whatever the activity of men of feience or of art may bring forward, of invention or improvement, in any country or nation, within the poffibility of being procured, by means as refpeétable as the motives that call for them, fhall appear in this Journal; either in the form of fhort notices, or the full defcrip- tions of their refpective authors, or the more ample report deduced from actual vifitation and enquiry. The relative magnitude of each objet will eftablifh the rule from which either of thefe modes will be adopted. Arrangements have already been made, channels of communication opened, and other correfpondences are jn profpect, which mutt increafe, in value and extent, proportionate to the importance and curiofity of the fubjeéts to be dif- played in this work, and the impartiality and care with which they fhall be treated. In a former Addrefs to.the Public the Author has mentioned the advantages in regard to accuracy and fidelity which he apprehends muft refult from the conductor of a work of this nature becoming, in a certain degree, refponfible by name for its contents: he has alluded to the general tenor of his purfuits, as known to the Public, and in fome refpect qualifying him to engage in fuch a tafk; and he has deprecated the fuppofition of any vain pretence to fuperiority, by remarking, that no one could ferve the Public in this way if he were to wait with the abfurd hope of firft bringing his own knowledge to a ftate of per- fection. ‘This is all that need be faid relating to himfelf. The leading character on which the fele€tion of objects will be grounded is utility; and next to this, novelty and originality. The Author’s refearches and colleétions, and thofe of his friends, will afford a confiderable portion of new and curious matter, fufficient to ren- der the work interefting, even to that extreme few who are fo fortunate as to have accefs to all the expanded fources of philofophical intelligence. But in the department of perfedtly original matter, much of prudence is required to be exercifed, in order that the claim of no- velty may not operate to the exclufion of much more valuable and important fubjeéts. It is certain that, if every article in a journal of f{cience were to be profeffedly original *, it would be a work of comparatively much lefs value to Philofophers'and the Public. Such a plan would in a great meafure defeat the attempt to convey the beft difcoveries of our cotem- poraries in the moft authentic manner, namely, in their own words. And when we reflect * Lewis's Philofophical Commerce of Arts, and various other publications of inferior note, have failed of pubs lie fupport, chiefly from this circumftance in their plan. , on iv PREFACE. on the very limited circulation of academical Tranfactions, from their price, their number, their extent, diftance of publication, difference of language, labour of perufal, and the efforts of mental abridgment, it is alfo certain that, from one or other of thefe caufes, even the beft memoirs they contain muft continue unknown to a very large clafs of men of fcience. Under the impreffion of thefe truths, while no exertions will be {pared to obtain immediate original information, Concerning any object prefented to the world in this colleGtion, the aim at originality mutt neverthelefs be fubordinate to the lefs eafy but more eflential requifites of public utility and interefting refearch. Whenever, in the progrefs of invefligation, dif- coveries thus buried from the knowledge of the world, fhall prefent themfelves, the rational plan of a public journal will require them to be brought forward, though years may have elapfed fince their firft publication. It would be eafy to exhibit a numerous catalogue of errors retained in the works of authors.of the firft eminence, from the want of fuch general communication. ; . After this fhort account of the materials, it might be expected that fomething fhould be faid of the manner in which this Journal is to be conducted. On this occafion it would not be difficult to point out imperfections in the works of others, and promife to avoid them; .or to enumerate the various requifites which ought to characterife the journalift of ability and: integrity, and promife to-exert them. Such fpecific. engagements may have their value, and: are probably entered into with great fincerity. But it appears more natural and eafy to leave-every individual of principle, and. underftanding to imagine what ought to be done. As the.events, prefent themfelves, the proper mode of conduct will itfelf ftand forward and leave no-caufe for hefitation. Yet, while the Author himfelf avows the decided purpofe of exhibiting his fources of communication in the moft unreferved manner, it is no lefs proper that he fhould pay every. attention to the rights of others. He will never take upon him to decide for another, how far he hall or fhall not come forward as the author of any communications he may receive, and till lefs will he dare to infringe that firft and moft facred property which men hold in the produéts of their own underftanding. It is not, in his opinion, for any man or fet-of men to decide what are the cafes of moral obligation: in an inventor to communicate his difcoveries, or his private arrangements in bufinefs. Philofophers, manufaéturers, and others, may therefore reft affured, that he will publith no communications he may ac- quire either in converfation or otherwife, nor mention the name of any individual-in his writings; unlefs the objet be already before the Public, or unlefs he fhall receive per- miffion dire€ily, or moft clearly implied, to that effe&. But in every cafe of anonymous communication. he will be careful, according to the nature of the object, to mention the degree of credit he himfelf is difpofed to attach to the feveral facts. ; Such papers as have no name or fignature are written by himfelf. This will in general appear alfo from the manner, chiefly with refpe& to the ufe of the firft perfon fingular. The firft perfon plural will probably be ufed in fuch occafional fentences as refer to the Author and the Reader in the joint confideration of any fubjet;, but never in the manner adopted by anonymous writers, to denote the concealed individual. PDL DL DLL OL LAL LO OAS A JOUR- nr ee ee ADVERTISEMENT. Lonpon, Marcu ft, 1798. A YEAR has nearly elapfed fince this Journal firft appeared. A complete Volume is now before the Public ; on which occafion it feems neceflary to mention the nature of its contents. Enough has already been faid of the utility of {uch a Work and the duties of the Editor; among which fidelity and accuracy are undoubtedly the chief. Whatever defeéts of ability may appear in the fhare I have had in this colleétion, I can with con- fidence affert my claim to thofe moral requifites. I have defcended to none of the arts of Book-makers. No commendatory letters have flowed: from my pen: no imaginary congratulations are echoed : no pretended fuccefs forms the fubje€t of my acknowledge- ments. I have confided in the fincere performance of my engagement with the Public ; and have folicited the approbation of good men by fuch means only as my heart could thoroughly approve. I truft it will give pleafure to many of my Readers to hear that I have not been difappointed. The friendfhip and correfpondence of men whofe talents and virtues I revere, men whofe approval conftitutes the only eftimable part of fame; have amply overpaid my exertions: and in a commercial view, though I havé found the fale of my book unequal to what might have been expected in times of lefs general diftrefs, yet it has been progreflively increafing, and fufficient to encourage my perfeverance. The copious Table of Contents will render it unneceffary to recapitulate any of the ex- cellent works I have received or colleéted. I have adhered to the principles of feleftion which are expreffed in the Preface publifhed laft year, and have been more folicitous to offer productions of real merit and utility than fuch as were chiefly remarkable for their noyelty. It will be feen, however, that’ nearly half the papers in this volume are ori- ginal and interefting ; that above a third confifts of new and important works which have never yet appeared in our language 5 and that the remaining part confifts either of digefted reports and abridgments of excellent, but voluminous papers difperfed in academical col- leGtions, or fuch as from other circumf{tances deferved to be copied intire. Men of information will hence perceive that this work is not an indifcriminate compi- lation of things neareft at hand, nor a loofe temporary record of tranfaétions which a few years muft render worthy of the oblivion they will experience. It is reafonable to hope that it will every year become of more value, as the Repofitory of Difcoveries in Science and the Arts; and that it will tend to accelerate the progrefs of both. Vou. L—Marcu 1798.—Surrl: a ERRATA, Page 13-1. 4. t. ofber engagements. Page 186.1. 5. of the Mathematical queftion, r. Then D's 15.1, 27. ras in the figure ; thefe lines were parallel chance, to the threads of the cloth. , 207. 1.31. r. meteorslogical apparatus. p 17. |, 26. r. Inftrument. And in the plate certain let- 266.1. 41. dele and repelled, ters are omitted, which however may be cafily fup- 304. 1. re. x. of the water. : plied from the text. 313-1. 24. for communication r. paper. 64.1. 15. 7. 0.0166, 38r. to the note add 1, page 252. 66, 1, 39.1. one-third more, 382. 1. 37+ 1. Surfaces. 399. 1. 5. r+ as it would have otherwife. 73. 1. 15. 1. Market. gee 418, 1. 22. x. place of percuffion. elie gn rie carats ae] ESL tac to By opting ai 1.8, whi . —s ne 5 OF pi _ 107. 1. 8, of the note, r. which are of the fame nature stiee hs dup tor, © eee fad 124. Ll. 2. r, be divided the whole. HX bX radi tei 5 ; . fine radius; or pu radius 139+. = throughout the mathematical part, for unity, Col. A oa a r a) —r* a 144.1024. 1. Analyfes. — 1. 26, read Mr. William Cafticau, 274 bottom line, r. eightemts Volume. 68. 1. 10, r. Figure rr. ‘ TABLE TABLE or CONTENTS TO THIS FIRST VOLUME. Fs A Sake 08S ae Fe uTue Principles and Application of a New Method of conftru&ting Achro- ' matic Telefcopes. By Robert Blair, M. D. — _ page 1 Imperfeétions of achromatic lenfes—arife chiefly from the glafs. Propofed remedy by theufe of fluids. Prifmatic apparatus for meafuring the refractive and difperfive qualities of fluids, Hadley’s uadrant applied to meafure the abfolute refra€tive denfities. Enumeration of the optical proper- ‘ties of various fluids. Conftruétion of a lens including a fluid. Obfervations. New and fingular cafes of refrangibility—Explanation. Coloured {petra formed by different mediums are not divi- ded into proportional intervalsh—Confequence of this, and its remedies, The doétrine of optical- aberration from figure, and method of obviating it; from Huyghens—Application to telefcopes. ImperfeGtion of compound lenfes from the want of perfe€t compenfation in the coxtrary powers of difperfion through the whole {pe€&trum. Difcovery of an adequate remedy. Conftruétion of Jenfes, in which the aberrations from figure and difperfion of colour are both remoyed. Prefent fate of the invention. Il. A remarkable Effeé of the Inflection of Light paffing through Wire Cloth, * wotyet clearly explained _— _ _— _ p.13 Singular appearance of a-diftant lamp feen through an handkerchief. Variation of the experiment— Inferences—Remarks on thofe inferences, and new experiments. Deduétions, Experiments with wire cloth, Extremely brilliant folar fpeétram. Obfervations. II. Defcription of an Inftrument which renders the Electricity of the Atmo- {phere and other weak Charges very ceptible, without the Poffibility of an equivocal Refult — — _— —_ p. 16 Hittory of the invention. Defcription of a {pinning inftrument—Its power. IV. Obfervations on the Art of printing Books and Piece Goods by the Action of Cylinders — — — _— — p. 18 Three methods of writing—by the pen or brufh—by the type or block—-and by the engraved plate. az duetier viii CONTENTS. Letter-prefs deferibed. Block printing. Diftingtions between letter-prefs and block-prinfing.’ Copperplate printing. Cylinder printing. General view of the commercial impediments to the fuccefs of invenrions—Phyfical difficulties—particularly wich regard to cylinders—Remedies, How far paper-itainers and callico-printers are prevented from ufing machinery by the operations of the Excife Laws, V. An Account of the Diamonds of Brazil. By M.D’Andrada — p. 24 Defeription of the province of Brazil, which affords diamonds. Hiltory of the difcovery. Natural hiftory of the diamond. Method of exploring. VI. Abftra&t of the’ Specification of Mr. William Defmond’s new Method of Tanning, with Obfervations relative to that Subject _-_ — Pp. 26 Art of tanning. Method of obtaining the tanning principle, and the principle of aftringency, from oak bark feparately—Criterions for diftinguifhing them. Procefs with itrong hides—with lighter ikins.. Tanning propofed initead of tar for ropes, and falt for flehh meat. Keflections. Refults of a@tual enguiry. Prefent flate of the invention. VII. Defcription and Account of a new Prefs operating by the Action of Water on the Principle of the Hydroftatic Paradox. Invented by Jofeph Bramah, En ineer _ — a _— —_ 29 Defeription of the inftrument, and its mode of aétion. “Computation of its force. —Compared with a ferew ; in theory—and in practice. Experiments or trials. VIII. The Procefs for giving a beautiful White Colour to Raw Silk, without- Scouring. By M. Baumé — — _ P- 32 Hiftorical fa&ts. Quality of Chinefe filk, Baumé’s procefs—1. Killing the chryfalis—z. winding off the filk on a reel. Apparatus for bleaching with marine acid and fpirit of wine.x—The pro- ceis,—Precautions in drying.—Chinefe filk probably bleached in this way. 1X. On the Hydrometer of Baumé — _ _ P: 37 Hydrometer for falts;—and for fpirits. Dedu€tions of the fpecific gravities indicated by thefe ine ftruments, difpofed in tables. X. Obfervations on the Soap of Wool, and its Ufes in the Arts. By J. A. Chaptal, Inftitutor of the Polytechnic School _ — p40 Preliminary obfervations. Proceéfs for making foap of alkali and wool. Enumeration of the fa&ts. Choice and preparation of materials, Management of the operation. Singular effeé&t of this foap on cottons. : XI. Extract of a Memoir concerning three different Species of Carbonated Hy- drogenous Gas obtained from Ether and Alcohol by different Proceffes, for- warded to the National Inftitute of France by the Society of Dutch Chemitts ; being Part of a Report read to the Firft Clafs of the Inftitute by Citizen Four- croy at the Sitting of the 26th Frimaire, 16th December 1796 — p. 44 General account of the olefiant gas. Procels for obtaining it. Phenomena, 6 aie Mathe- CoN fF E NUTS. , ix Mathematical Cortefpondence | _ or Se Ps 45 Scientific News — —_ _ — p-. 46 Revival of the Journal des Savans andthe Annales de Chimie. Sitting of the French National Ia- ftitute. Accountsof foreign books. Wate Yorzg J, Extract of a Memoir concerning three different Species of Carbonated Hydro- genous Gas obtained from Ether and Alcohol by different Proceffes, forwarded to the National Inititute of France by the Society of Dutch Chemilts ; being Part of a Report read to the Firft Clafs of:the Inftitute by Citizen Fourcroy, at the Sitting of the 26th Frimaire, 16th December 1796 [concluded] p. 49 Purification of olefiant gas—Phyfical properties—negative—affords an oil when mixed with oxyge- nated muriatic acid gas—Properties of this oil. Compolition of the olefiant gas. It contains hy- drogene and carbone. Appropriate name. Olefiant gas from ether treated with fulphuric acid, or from alchol and ether pailed through an ignited tube of pipe clay. Gas afforded by pafling ether and alcohol through an ignited glafs tube—is not olefiant, &c. Various experiments. Two other elaftic fluids obtained from ether and alcohol. Recapitulation.. Queftions and enquiries relating to theory. i : I]. On the Methods of obviating the Effects of Heat and Cold in Time- pieces _ —. _— _ — p» 56 ‘ Inftruments for meafuring time. Hour-glafs—Sand-clock—Water-clock—Common clock and watch— : Trains of wheels—move uniformly when aéted upon by a weight, becaufe friétion prevents the ac- celerated motion. Of clocks regulated firft by a fly—then by a balance—and laft of all by a pen- dulum. ~Detached efcapements and compenfations for temperature. Effet of temperature on ‘ elocks. Deal pendulum. ~Graham’s quickfilver pendulum—improved by Troughton. Harrifon’s gridiron pendulum. Elicot’s lever pendulum—improved by Cumming, Fixed compenfations, Pro- je& for a gridiron balance. Curious contrivance of a compound bar which bends when its tem- erature is changed. ‘Theoretical and praétical confiderations. Experiments with a bar of this Kind. The expanfion balance deferibed. Application of the fame principle to pendulums, In- ftruction to a¢tual workmen, re 3 Ill. Obfervations and Experiments on the Light, Expence and Conftrudtion of Lamps and Candles, and the Probability of rendering Tallow a Subftitute for Wax ~ ied a _ — p. 67 Artificial light is an objet of the firft neceflity—means of producing it—meafure of its intenfity, Obferyvations on lamps—purification of oil—accefs of air—inconvenience of lamps. _Obfervations on the candle.—Fulibility, or freezing points of tallow, {permaceti, fatty matter of flefh, pela, bees-wax and bleached wax. A lamp for tallow, very defirable. Experiment.—Confiderations re[pecting the fnuffing of candles. Chinefe candle with wax on the outfide. Imitation. Expe- riments er rendering tallow lefs fufible. IV. A Memoir upon the Difcovery of America. By Mr. Otto > — Ps 73 Tntroduétory remarks, Hiftorical documents refpeCting Martin Behem—who failed in ye from : , ortugal, = Coan REaEM TD BB “Portugal, eight years before Columbus, and. difcovered Brazil and other parts.of South Ameriex Various callateral proofs. V. Analyfis of the Oriental Lapis Lazuli. By M.Klaproth —- p77 Former experiments enumerated. Analyfis. Blue colour not changed by ignition ;—but it becomes “blueith grey with enamel. Other experiments in the dry and humid methods. Component parts of the ftone, - VI. Ufeful Notices refpecting various Objeéts—Rofe Water—Eau de Luce— Soap of Wool—Sea Sicknels — — — p. 80 Rofe-water, how to be procured frefh at all times. Eau de luce, experiments for making. Repetition of Chaptal’s operation for making foap of wool, Ether faid to be a cure for fea ficknefs. VII. A‘Comparifon between Electrical Machines with a Cylinder, and thofe which produce their Effe&t by Means of a circular Plate of Glafs. With a Defcription of a Machine of great Simplicity and Power, invented by Dr. Martinus Van Marum _ _ — a p- 83 Qbfervations on the a@tion of machines with a cylinder. Undulation of eleGtricity. Defcription of a machine with a plate of glafs exhibiting both powers. Numerical eftimates of the force of dif- erent electrical machines. VIII. The Procefs for giving a beautiful White Colour to Raw Silk, without Scouring. By M. Baumé. (Concluded from page 32.) — p. 88 Methods of recovering the alcohol after ufing it in ‘bleaching—by adding alkali and diftilling—or by diftillation alone. Inftructions. Difficulties of the new method of.bleaching. Purification of vitriolic acid. Procefs to obtain the marine acid. f Mathematical Correfpondence — en _ — p 9 2 Scientific News _ oe ene “— |p. 93 Analyfis of the four firft eahiers of the Journal of the Polytechnic School. New Publications _— | _ << — P: 95 f CUNY ge soopaiiagn dt bas enoitne ik 1. A Letter from Mr. de Humboldt to M. Piéet, on the Magnetic Po- larity of a Mountain of Serpentine — — -- Pp: 97 Situation and appearance of the ‘mountain. Experiments. Obfervations on the ftone: which forwarded to Sir Jofeph Banks with the memoir. : fae II. An Account of fome Experiments upon Coloured Shadows. By ikdtebane General Sir Benjamin Thompfon, Count of Rumford, F.R.S. In a Letter to Sir Jofeph Banks, Bart. P, R.S, _ “= _— p- v0r Difference in colour between candle-light and day-light—Obfervations, Experiments with d giafies, candles and lamps. Senfations of colour afforded by mere outa harere lee el aoa 2 col Ne TS Ef wD s: _ IM. A Memoir upon the Difcovery of America. By Mr. Otto: (Concluded from page 77.) — _ —_ — Pp. 107 Death of Chevalier Behem—Critical remarks and obfervations to prove that he was the difcoverer of America. ; IV. Defcription of a Gravimeter, or Inftrument for meafuring the Specific Gravity of Solids and Fluids. By Citizen Guyton — — p.ito On {pecific gravities—and hydrometers. Obfervations of the hydrometer of Nicholfon. Defcrip- _tion of an improved inftrument—Additional remarks, Formula- for finding {pecific-gravities without diftilled water, or the thermometer or barometer. Ufeful application of the inftrument. Table of f{pecific gravities of alcohol. Specific gravities of alloys of tin and lead. . Account of Gilpin’s tables of ardent {pirit. V. Defcription of the Improved Air-Pumps of Prince and Cuthbertfon: With Obfervations — —_ _— _ — Pp: FI9 Familiar elucidation of the principles of the air-pump. Air-pumps with {top-cocks and with valves, Smeaton’s pump: Brooks’s experiments. Defcription of Prince’s air-pump, which has no lower valve or ftop-cock. Advantages. Remarks on condenfing engines. Defcription of Cuthbertfon’s air-pump, in which the yalves are all metallic—Its great power. Comparifon between thefe twopumps. Project for a pump which may unite the advantages of both. VI. Ufeful Notices refpeéting various Objects.—A Method. of preventing Heat in grinding. Concerning Gold, Silver, and other Metals» reduced into very thin Leaves by the Hammer. Globules for Microfcopes. ‘On the Plumb-Line and Spirit-Level _ — — —p. 131 Heat developed in grinding. A German grindftone which does not heat. Experiments to invefti- gate this fubje€&t. Succefs and advantages. 'Thicknefs of leaf gold, filver, brafs or Dutch gold, tin or Dutch filver, and tin-foil. Method of forming very clear fpherules of glafs. Breadth of the fineft wire in feconds of meafure. Spirit-level defcribed. Its adjuftment and degree of ac- curacy. How to procure good tubes for levels. Method of grinding the infide of the tube. Im- perfeétions of the fpirit. level. Mathematical Corréefpondence — _ _ Pp. 137 Scientific News —_ _- —- —_ a p- 14% Memoirs of the Polytechnic School. J ybhiaDei Xn GR 7OF 1, Obfervations on Horizontal Refraétions which affect the Appearance of Terreftrial Objects, and the Dip or Depreffion of the Horizon of the Sea, By Jofeph Huddart, Efg. F. R. S. — — _— Pp. 14.5 Elevation of points of land by refraétion. Theory. Inverted appearance of a veffel at fea. Ex- lanation. Remarkable difference in the intenfity of Portland Lights dependent on this theory. rhe dip of the vifible horizon is rendered uncertain by this refraction—Remedy. General annotation. Ill. Re- xii CO; Ny Ty Ep Ny To S: fe Il. Remarkable Effect of Terreftrial Refraction ona diftant Headland.—Ex- tra of a Letter from Andrew Ellicot to David Rittenhoufe, Efq. dated at Pittfburg, Nov. 5, 1787, concerning Obfervations made at Lake Erie p. 152 Phenomenon called Looming. Prefqu’ Ifle feen double, with frequent and fingular changes. Ill. Extract of a Memoir of Mr. Benediét Provoft, of Geneva, on the Emana- «tions of Odorant Bodies. By Citizen Fourcroy . «) ;—- ), = P+ 153 Faéts fuppofed to depend on odorant efluyia. Motions of camphor upon, water. Inferences tend. ing to eltablifh a theory. , Ap" fig) IV. A Method ‘of Meafuring the Force of an Eledtric Battery during the Time of its being charged. By Lieutenant Colonel Haldane .— p. 156 The charge meafured by the number of explofions of a jar connected with the external furface of a battery. Experiments. V. On the Mechanical Conftrution and Ufes of the Screw — p. 158 Short defeription and theory of the fcrew, Computation of its effeét. Lofs by friftion. Scientific ufe for meafuring lines or {paces. How far it may be relied on. Account of the method of making fcrews—by hand—by the tap and ferew-tool—and dies. Principal fources of ‘error in tapping :—1. Wave from change of hands—z. Drunk ftom preffure downwards—3. Undulation from the firft aétion of the dies—4. Bad fitting or unequal hardnefs of material—s. Setting up of the dies not being in the plane of the thread; and 6. Their cutting on one fide only taufes irregular depths and crookednefs—7. Uncertain effects, by an aétion of the. nature of wire- drawing. A {crew of forty threads in the inch will meafure to greater precifion than the hun- dred thoufandth part of an inch. Stock with four pair of dies. Its advantages. VI. The Method of obtaining the Fixed Alkalis in. Cryftals of the greateft Purity. By Lowitz, Profeflor, &c. at Peterfburg i — p- 164 Defcription of the procefs, with numerous obfervations. - Solution in alcohol does not afford pure alkali. I ’ gt 5 VII. Experiments on Eau de Luce. By a Correfpondent — —p. 166 Trial of various fubftances. VIII. An Account of Experiments defcribed, and-in part repeated, at the Sitting of the National Inftitute of France on the 15th Germinal, in the Year 4. By Citizens Fourcroy and Vauquelin—On Detonations produced by Concuffion o- — _ _ p- 168 Detonations afforded by the fuper-oxygenated muriate of pot-afh_mixed—with fulphur—with ful- phur and charcoal—crude antimony, zinc, metallic antimony, fulphuret of iron, cinnabar, fugar, gum, oil, alcohol, ether. | 1X. A Memoir on the Combination of Oils with Earths, Volatile Alkali, and Metallic Subftances, - By M. Berthollet _ _— = p.170 Combinations of fat oil with lime—with ammoniac—with magnefia—with clay—with barytes—with mercury, zinc, tin, iron, copper, lead, filver, gold, magnefia, volatile oils, and c > - eral fatts and Hemaviads ‘ Athy 2 » Gores ky ¢ ? opper. Ge X. Analyfis GerOro Ne TE, Ee Nest ,.S. lit X. Analyfis of a Memoir of Citizen Bonhomme on the Nature and Treatment _.of Rachitis or the Rickets ~ — — _ p- 174 Nature of Rachitis. Treatment with alkaline lotions—and phofphate of lime internally. Obferva- tions on urine and its depofitions—particularly of rachitic fubjects. XI, On the Nature of the Diamond. By Smithfon Tennant, Efg. F.R.S. Pp. 177 Hiftorical remarks on the combuttibility of the diamond. Combuftion with nitre in a veflel of gold, Eltimates of the quaptity of fixed air or carbonic acid afforded by the diamond—It affords nothing but the fluid called fixed air, XII. Ufeful Notices refpecting various Obje&ts—Improvement of Telefcopes —Imperfections of Optical Glafs—Purification of Mercury p. 180 Advantages of an iris, or changeable aperture to telefeopes —Mechanical contrivances for that pur- pofe. Method of examining glafs by the microfcope. Experiments. Mercury purified by agitation. XIII. A Memoir containing fome Refults arifing from the AGtion of Cold on the Volatile Oils, and an Examination of the Concretions found in {everal of thofe Oils. By Citizen Margueron, Member of the Societé des Phar- maciens at Paris _ _ _ _ p. 182 Effe& of cold on the pure oils of peppermint, orange-flower, lemon-peel, bergamot, lavender, thyme, turpentine, and cinnamon. Alfo on thofe oils mixed with water. Mathematical Correfpondence —~ _ — p. 186 Scientific News _ — a = p. 188 Letter from Sir Benjamin Thompfon, Count of Rumford, F.R. S. to the Right Hon. Sir Joleph Banks, Bart. K. B. P. R. S. announcing a Donation to the Royal Society for the Purpofe of inftituting a Prize Medal p. 188 Biennial premium of Count Rumford for the beft improvement or difcoveries refpecting heat or light. New Publications — — shhh xo fe p. 10 Table of fpecific gravities of water with common falt. Hi, GU 455T 4.5797. J. An Account of the New Syftem of Meafures eftablifhed in France. By Ch. Coquebert — — ~ — p.193 Origin of the fyftem. Two univerfal meafures, length of the pendulum, and magnitu ts, Preference given by the French Republic to the eae Matas as at ices A aaa uadrant of the meridian from the equator to the pole, taken as the fundamental unity. Deevhal ‘fubdivifion. Nomenclature. Lines. Surfaces. Solids. Weights—monetary. T'ables—z, OF the nomenclature of the new meafures, and their relation to the old French and Englith. 2, Pro- portions of the new and old French meafures. Annotation refpecting the limits of error. Vox. L—Marcu 1798.—Surrt. b II, Analyfis xiv € 0 N Fi Nh Ss II. Analyfis of a Memoir of Citizen Bonhomme on the Nature and Tveaiment of Rachitis or the Rickets. (Concluded from p. 177.) — — p- 200 Singular experiments, in which offification was promoted by calcareous phofphate. Application of this refult,to the cafe of rachitis. Account of cures. Inferences and refle@ions. 1II.. Abftraét of a Memoir read at the Sitting of the French National Inftitute on the 26th Pluviofe, containing an Account of fome Experiments concerm- ing the Seétion which Cylinders of Camphor undergo at the Surface of Water ; with Reflections on the Motions which accompany this Se¢tion. By J. B. Venturi, Profeffor of Natural Philofophy at Modena, Member of the Inftitute of Bologna, -&c. _ — — Pp. 205 Motions of camphor upon water. Scétion at the furface of water. Explanation of this fatt—and of the rotation. Apparent caprice or uncertainty of the effeéts accounted for. Several other motions refembling the preceding. Additional faéts and reflections. IV. Analyfis of four Specimens of Steel; with Reflections on the new Methods employed in this Analyfis. By Citizen Vauquelin = — _ Pp: 210 Account of the fteel—and report concerning its qualities when made ‘nto tools. Excellence of the hook-tool. Prefent fate of the analylfis of fteél—Its uncertainty and difficulties. New proceffes with fteel, to feparate phofphorus, carbone, and manganefe. Infufficiency of Bergman’s method of feparating manganefe. : V. Defcription of an Artificial Rock-Cryftal produced in the Humid Way. By Mr. Trommfdorff, Profeffor of Chemiftry at the Univerfity of Erfurt p-.217 Previous remarks. Hiftory of the fa&t. Rock-cryftal feparated from liquor of flints during five years repofe. . VI. Geological Obfervations on North-Wales. By Mr. Arthur Aikin— p- 220 No proper volcanic produétions in North-Wales, Gradation of the ridges of lime, flate, ftratified rocks, and granite in the greater chains of mountains. Figure of primitive, fecondary, and déri- vative mountains. Beds of rounded pebbles on the tops of the flate mountains. Theoretical remarks, Metals. Coal. Primitive ftate and fubfequent changes in the face of the earth in North-Wales. \ VII. An Account of the Fata Morgana or-the Optical Appearance of Figures in the Sea and the Air in the Faro of Meffina. With an Engraving — p. 225 Defcription of the phenomenon. Strange figures in the fea—and in the air—fometimes vividly eoloured with prifmatic fringes. Remarks and obfervations, VIII. A Memoir containing fome Refults arifing from the Action of Cold on the Volatile Oils, and an Examination of the Concretions found in feveral. of thofe Oils. By Citizen Margueron, Member of the Societé des Pharma~ ciens at Paris. (Concluded from p. 186.) © 9 — — =p. 227 Nature of the concretions in’ volatile oils. IX, On Gea N Tt EF Mts XV IX. On the Cold Winds which iffue out of the Earth. By Profefflor De Sauffure and others ; with Obfervations _— ~ p: 229 Accounts of the cold caves of Mont Teftaceo, Ifchia, St. Marino, Cefi, Chiavenna, Caprino, and Hergifweil ; together with thofe of Roquefort. Theory of the author ; from fuppofed refervoirs. Objections. Another explanation from the imperfeét conducting powers of bodies. Similar facts in common buildings. X. The Combuftion of Phofphorus in the Vacuum of the Air-Pump. By Dr. Martinus Van Marum* _ — — p. 230 ombutftion of phofphorus in oxygene. Unexpetted {pontaneous combuftion in vacuo. Mathematical Correfpondence = _ — ~—s—~p- 237 New Publications — ~ KEL with a Defcription of the Apparatus for thefe Experiments. By George Pearfon, M.D. F.R.S. (Cencluded from p. 305) — P+ 349 Obfervations and inferences concerning the effect of eleGtricity on water, in the experiments recited ; and the general doctrines of chemiftry which they tend to explain. IV. Obfervations on the Electrophore, tending to explain the Means by which the Torpedo, and other Fifth, communicate the electric Shock P: 355 Aion of the eleGtrophore. Experiments with eleétrophores of tale.—Computations.—Figure and dimenfions of the eleétric organs of the Torpedo. Induétion of their capacity or charge. ~ Facts, which fhew that a mechanical Torpedo might be made, capable of giving innumerable fhocks, and retaining its power for an unlimited time. ConjeCtures on the a¢tual means of operation in the ‘Torpedo. _Y. A Letter from Mr. Von Humboldt, to Mr. H. Van Mons, on the chemical Procefs of Vitality ; together with the Extract of a Letter from Citizen Fourcroy, to Citizen Van Mons, on the fame Subject _ P=359 Experiments on the effets of chemical agents upon the irritability of the limbs of animals.—Caution of Citizen Fourcroy againft multiplying hypothefes. VI. Concerning the Properties of the Sulphureous Acid, and its Combinations with Earthy and Alkaline Bafes. By Citizens Fourcroy and Vauquelin (Concluded from p. 318.) “ _ —_— — p- 364 Habitudes of the fulphates of foda, of ammoniac, of magnefia, of barytes, and of alumine, VII. An Account of the Great Copper-Works in the Ifle of Anglefey. By Mr. Arthur Aikin — _— _ — p- 367 Account of the mines. They are for the moft part open quarries. Nature of the ores; working procefles; number of men employed. Port and town of Amlwch, Afpeét of the fhore. Village of Cemmaes; eftimable manners of the inhabitants. VIM. A Method of difpofing Gunter’s Line of Numbers, by which the Divifions are enlarged, and other Advantages obtained _ Pp. 372 Theorems. Conftruétion of a Gunter’s line, in which the divifions are enlarged eight times.— Conftrugtion of a fpiral logarithmic line, feven inches in diameter, but of equal power to that of a Gunter’s rule 40 feet long. 1X. On the mechanical Projeéts for affording a perpetual Motion De 375 What is a perpetual motion? Projeéts of Bifhop Wilkins—of the Marquis of Worcefter— of Orfyreus—of Dr. Shiviers. Confiderations on the caufes of thefe deceptions. Inftrument of Defaguliers, and of the author, to fhew the fallacy of the notion from which proje¢tors of fuch {chemes reafon, Effential requifite to a perpetual motion, Enumeration of fuch natural agents as may keep a machine in motion, as long’ as it retains its form, or till it is worn out. XK. Ufeful Notices refpeGing various Objeéts—Silver alloyed with crude Platina—Tempering of Steel—Rifled Shot — — p- 380 Attempt to unite filver and platina. Sudden increafe of ignition at the inftant of congealing. On the herduets and tenacity of fteele Tempering by the colour ;—by blazing ;—and by oil. Rifled fhot. Experiments which fhew that they revolye, but do move with more precifion than round fhot. ‘Mathematical Correfpondence FO Rib 19 fan a P» 383 DECEMBER xXx cS OD. Nave Ww TS. DE CuEIM' Ben R 2767.09 Mey uta} I. Concerning the fpontaneous Adtion of concentrated Sulphuric Acid on Ve- getable and Animal Subftances; its Action upon Alcohol, and the Formation of Ether. By Citizens Fourcrey and Vauquelin — p- 385 Ancient and pneumatic theories erronéous. Aion of fulphuric acid’ on vegetables—fuppofed to ~ . deprive the acid of oxygene—but does not. | The acid attraéts oxygene and, hydrogene, and be- comes diluted; the vegetable depofits coal, and forms acetous acid, The Sifpofing affinity. Synthetical inferences. A@tion of fulphuric acid on fome vegetable aud animal fubftances is more complicated. New path opened for the analyfis of vegetables, Popular theory of ether erroncous. Experiment detailed, Induétions, The true theory, as pointed out by experiment. II. On the Multiplier of Electricity. By the Inventor, Mr. Cavallo: with - Obfervations _— — _ _— P- 394 Quotation refpeting the {pinning inftrument. It differs in principle from the multiplier, and is a condenfer, The multiplier does not demand a {tock of electricity, but operates by means of an ubfolutely {mall quantity. Hitlory of inftruments for fhewing weak electricity. | Compenfations in the jar, the conjugate conduétors, the can and chain, the electrical well, ribbands, and filk ftock- ings, vindicating detricity, and the eleGrophore. Firft procefs of doubling. Volta’s condenfer. Bennet’s doubler. Mechanical doublers of Darwin and Nicholfon, Theirambiguity. Cayallo’s very perfe& condenfer,—does not remove the ambiguity of the doubler—ncither does the {pinning inflrument, which is an improvement on the condenfer. Cavallo’s multiplier; operation and power. Uncertainty of the doubler exifts in the other inftruments, though the doubler alone can fhew it. : HI. A Memoir on certain Methods of Economy, and Improvement in the Manufacture of Hats. By Citizen Chauffier _ _— P: 399 Political confiderations. Art of the hatter, Operation of felting explained by.Monge. Why cock and ben feathers are inferior to thofe of geefe. Probable remedy. Sulphuric acid in the bath for felting hats. Advantages. Stiffening. j 1V. Doubts concerning the Exiftence of a new Earth in the Mineral from New South Wales, examined by Wedgwood in the Year 1790 Pp. 404 Examination of the Sydney earth, by Klaproth—by Wedgwood—Contraft of the experiments of both. They did not examine the fame fubftance. ; V. A philofophical Memoir, containing, 1. Experiments relative to the Pro- pagation of Sound in different fotid and fluid Mediums.—And, 2. An experimental Enquiry into the Caufe of the Refonance of Mufical Inftru- ments. By Mr. Perrole: with Annotations _ p- 411 Tranfmiffion of found through wood—metals—frings—and other folids;—through fluids. Refonant property of various bodies. Undulations of the air, and of fonorous bodies. Whether air be the medium of found. Why found is beft heard in the night. Obfervations relating to an acouftic tube, Sonorous bodies vibrate. On the external ear, and the tympanum. General requifites of an inftrument for magnifying found. VI. Concerning the Steam Engine, as originally invented by the Marquis of Worcefter, and the Improvements fince made in Steam Engines without the Pifton, or Lever. With a Defcription of an Engine of this Kind conftruéted by Mr. Peter Keir, of Kentifh-Town _ - P- 419 Marquis G2QOr Nn To EY Nir sg. xxi Marquis of Worcelter's defcription—Savery’s engine, Hiftory and adjuftment of the claims of the Marquis of Worcefter and Savery as to the invention of the fteam engine. Papin’s fteam engine. The engine with a pifton. Comparifon of Savery’s and Newcomen’s engines. Keir’s engine on Savery’s principle. Defcription, Peculiarities. ‘Steam engine with lifts. VII. On the Mechanifm by which the Mariner’s Compafs is fufpended p. 426 Introduétion. Sufpenfion of the magnetic needle on a cap—requifites for fteadinefs. Compafs-box fupported on a point—or by gimbals. Adjuftment of the gimbals for fteadinefs. Eafy trial of a goodcompafs, Lorimer’s fufpenfion of the dipping needle by gimbals. VIII. On the maintaining Power in Clocks and Watches — P- 429 Vibrations of pendulous bodies—Train of wheels. Mathematical and Philofophical Correfpondence _ _ Pp 430 optical queftion concerning the glory in water anfwered, Vifible emanation from reétified animal oil. Anfwers to mathematical quettions. Vor. Marcu 1798.—Suerr, c JANUARY XXik Cca2Or NV TH EYNW TC S: JANUAR Y 1598 I. Experiments made with a View to afcertaid “the ‘Cafe of Buildings, which have metallic Conductors belonging to them, being, ftruick by Light- ning. By Lieutenant-Colonel Haldane — Pp: 433 General remarks, Defcription of the apparatus. Experiments. Conclufion. II. New Conftrution of the Air Pump. ~ By James Sadler, Efq. Chemift to the Admiralty — — — — — P. 444 Two conftruCtions of air pumps, in which the vacuum is rendered more perfeé&t by the interpofitiom of a fluid. : Leet ditlatrat athe Ill. Obfervattons on Phofphorus. By Citizen Brugnatelli, Profeffo rof » Chemiltry, &c. at Pavia —_ — — - 'p. 444 Solution of phofphorus in oxygene gas becomes luminous by the addition either of the oxygenated muriatic acid gas or nitrous gas. Phofphorus diffolved in hydrogene gas—Appearances of phof- phorus in oxygenated muriatic acid gas—in carbonic acid gas—and atmofpheric air. Solution in oil of turpentine, and alcohol ; effects of water om the latter folution—and of other fluids. Phof- phorated ether. Recapitulation. IV. On the Advantage of inverting the Slider in many Operations on the common Sliding Rule. By the Rev. W. Pearfon, of Lincoln p- 450 Methods of working arithmetical queftions on Gunter’s rule with the inverted flider. V. Abftract of a Memoir entitled “* Enquiries concerning the Nature of Pruffian Blue.” By Mr. Prouft —_ —_ — — Pp 453 Tron is not oxidable at the intermediate terms between the extreme proportions of oxygene. It affords two fulphates only; the green cryftallizable, and the red not cryftallizable ; and there is no inter- mediate falt. Properties of thefe. The green fulphate affords a white pruffiate ; which rapidly abforbs oxygene and becomes blue. The red fulphate affords the moft lively blue pruffiate. The yellow oxide of iron is as completely faturated with oxygene as the red. Pruffian blue is difoxy- genated, and converted into the white pruffiate, by keeping in a clofe veffel with water and plates of iron ortin, Other facts concerning the definite oxidation of metals. Ufeful obfervations on ink and the black dye. - VI. An Account of fome Experiments to determine the Foree of fired Gun- powder. By Benjamin Count of Rumford, F.R.S. M.R.I.A. P- 459 Gunpowder fired in a clofe veffel, Attempts to meafure its elaftic force. Detail of the appa- ratus and experiments. An heavy weight was applied to the mouth of a metallic barrel, in order that the explofion might tend to raife it. When the force was infufficient to raife the weight, it did not continue to exert the fame aétion after the explofion as at the inftant of that event. Sin- gular hard black refidue, of a pungent alkaline tafte and hepatic fmell—concluded to have been in the elaftic ftate during the explofion. A barrel } inch bore, and 2} inches external diameter, burft by 28 grains of gunpowder. Experiments and deduétions from which it is inferred that a force of 54750 atmofpheres was exerted in producing this effe€t. Other experiments. Table of refults. VII. Ob- feOnNn TENS FS. xNhi VII. Obfervations and Experiments on Steel refembling shat of Damafcus ; with an ealy Teft for determining the uniform Quality of Steel before it is employed in Works of Delicacy or Expence § > — _ p. 468 Deleription of a fabre of Damafcus. Its reputed properties. Suppofed procefs for making Damaf- cus fteel. Experiments by which a fimilar fleel was made. Inferences which explain the proper- ties of this iteel, Examination of ail kinds of fteel by the application of a weak acid. Great utility of fuch an examination, ye VIII. On the Irritability of the Pollen of Plants. With an Account of a Com- pofition for clofing wide-mouthed Veffels (continued from page 313) p. 471 Irritation of pollen by ardent fpirit. Wide-mouthed veflels clofed by fpermaceti and caoutchouc. IX. Experimental Refearches to afcertain the Nature of the Procefs by which the Eye adapts itfelfto produce diftinct Vifion _ -- Pp. 472 Imbricated texture of the felerotica in the eyes of birds. Obfervations. Probability that fome birds are direGted in their flight by the re-aGtion of the air rather than by fight. Inftance of bats de- prived of their eyes, and fuppofed to have a fixth fenfe. Mr. Home’s leéture. 1. Examination of the variable convexity of the cornea, by obferving the image in its virtual focus. 2. Attempts to difeover whether the axis be elongated. 3, Probability that the eye is adjufted by changes in the "curvature of the cornea and in the axis of vifion, together with a motion of the cryftalline lens. 4. Peculiarities of the eyes of quadrupeds—are fuch as increafe their power of feeing near objects. -5--Peculiarities in birds ;—tend to increafe the fteadinefs of adjuftment, and adapt the eye to very near objects. 6. Peculiarities in the eyes of fith. ‘New Publications css! _ — = P: 479 C2 FEBRUARY xxiv Ceo N SSW T'S. FE B Rath iA RaiY 01798: I, An Attempt to accommodate the Difputes among the Chemifts-concerning Phlogifton. Ina Letter from Dr. Mitchill of New York, to Jofeph Prieftley, LL.D, F.R.S. &c. &c. Dated November 20, 1797 — p- 481 Ignited charcoal urged by the eolipile. Suppofed combultion of water. Objeétions to the term hydrogene—inflead of which the word phlogifton is propofed. Nomenclature. Prefumption that hydrogene exifts in fulphur, phofphorus, zinc and iron;—but not as a conftituent part.—Conclufion. Annotations. On the afion of fteam from the eolipile. The word phlogifton. Whether the appearance of flame neceflarily indicates the prefence of hydrogene. Remarks on the difference between the funétions of Dr, Mitchill’s phlogifton and that formerly maintained by Kirwan. II. Experiments on the Compofition and Proportion of Carbon in Bitumens and Mineral Coals. By Richard Kirwan, Efg. F.R.S. L. & E. M.R.LA. &c. p. 487 Ufes of mineral coal—On the combuftion of coal—and its decompofition by nitre. The carbon in mineral coals is proportioned to the nitre decompofed by equal quantities of each. Analytic courfe grounded upon this faét. Kilkenny coal. Table of Kirwan’s-Numbers ufed to diftinguifh the luftre, tranfparency, fraéture and hardnefs of minerals. Maltha. ~Afphalt. Cannel coal. Slaty Cannel coal. Whitehaven coal. Wigan coal. Swanfey coal, Leitrim coal. Newcaftle coal. The refults tabulated. III. Obfervations on the belt Methods of producing artificial Cold. By Mr. Richard Walker —_ _ _ —_ Pp. 497 Preparation of ice in powder. Congelation of mercury in a few minutes where the air is not hotter than 85°. Cheaper procefs. ‘Table of freezing mixtures, and the cold produced by them. Various repetitions of the experiments. Freezing by ether. Defcriptions of the apparatus ufed in the preceding experiments. IV. The Defcription of a new portable Eleftrical Machine. Invented by the Rey. W. Pearfon of Lincoln _ ~~ a p: 506 Defcription and ufe of the machine. Eftimate of its power, &c. V. A Memoir concerning a remarkable Phenomenon in Meteorology. Read to the Society of Naturalifts of Geneva. By M; de Sauflure, October 1797. Pp. 51% Times of greateft drynefs are the precurfors of rain. Explanation of the caufe. VI. On the various Denominations given to the Alkali of Tartar. By a Cor- refpondent — = “— oa 12 SLRS so = the terms kali, fixed vegetable alkali, potafh, {podium and tartarin. Preference given (to the laft. VII. An GT OV.NG TY EA NGS? S. XXV VII. An Account of fome Experiments to determine the Force of fired Gun- powder, By Benjamin Count of Rumford, F,.R.S. M.R.I.A. (concluded from p- 468) cas a re ar Ps 515 Why fire-arms do not burft by the extreme force of gunpowder. Much of the gunpowder is blown out of fire-arms unburned. This was probably on fire, but extinguifhed by rapid motion through the air, Dire& experiments by firing gunpowder againft a number of paper fcreens. Remedies for the flow combuftion of gun-powder. Windage. Probability that the force of gunpowder is owing to fteam. cd VIII. Obfervations on Strontian: By Citizen Pelletier. Read to the National Inftitute, April 30, 1796 — — — p. 158 Difcovery of ftrontian. ee account of the diftin@ive charaGter of carbonate of ftrontian. Comparifon of ftrontian and barytes. Procefs for feparating the carbonic acid from the carbonates of barytesand ftrontian. Habitudes of the carbonates of barytes and ftrontian. IX. Philofophical News, and Accounts of Books _ _ P> 523 Garnerin’s defcent_by a parachute from an elevation of 600 feet, Theory of the parachute. MARCH XN CT OUNZ TT EVNOTDS. Mi) AARI@n 1 1798. _ — Op. .g Pe Ovfervarions on Sirontian.> "By Citizen | Pelletier.’ “Read ‘to ‘the National "ypttitutes zorh April 1395 (concluded from p."522) 9) =!" 629 ike CaMiowates of hatytes and froatian treated with acids. The nitrates and the stravatee OF ftrontian and of lime afford a red flame wi i: ee .—Strontian contains no lime—It is not precipitated’ by pruil ates, like bayytes—Ci mit ititue parts of the native paroustee. Goreral conc liags. Ad ‘ditional ee éxperimntes 69 6 S951) f 9 v1 1. Abftrast, of two Ve US 0h). a Meshad Baretta SL. pure, aia oa ihe Properties of this Earth cempared with thofe of Strontian. By Citizens Fourcroy aad Vavqueliny Read to'the National Pet “goth April and 2iit September 1790 _— — © Innidamotiae? S89 eo. bn idaato P yoperties of the pure barytes, ahaha y igniting the sitestee It is faut efllorefcent, foluble ia water; chyttallizable, &c. Properti¢s‘oF Rrontian chiefly with” refpe& to its difference from barytes: LI. Extract of a Letter from Count Muffin Pufchkin, Vice-Prefident of the Department of Mines at Peterfburg. On the Salts, Precipitates and Amal- gam of Platina; on Cobalt ; on Antimonial Soap ; and on the Decompofition of Soap by the acid Extraéts of colouring Matters _ _— P: 537 Brick-coloured precipitate by fal ammoniac is foluble in water. Other precipitates. Amalgam. The fingular properties, Cobalt. Antimonial foap. Soap decompofed and charged with vegetable colour. : IV. Obfervations on the fundamental Property of the Lever. With a Proof of the Principle affumed by Archimedes in his Demonftration. By the Rev. S. Vince, A.M. F.R.S. -— — oa — p.54t Former demonftrations enumerated and examined. New demonftration. V. Obfervations on the Acid of Tin, and the Analyfis of its Ores. Read at the Sitting of the Clafs of Mathematical and Philofophical Sciences of the Na- tional Inftitute of France, the firft of Meffidor, inthe Year 5. By Citizen Guyton _ —_ — _ —_ Pp: 543 Acidification of tin. State of this metal in certain ores, Analyfis and obfervations. VI. On Fairy Rings a — _ — p- 546 Figure and caufe of fairy rings. Circles of burnt grafs produced by lightning. VII. Experimental Refearches to afcertain the Nature of the Procefs by which the Eye adapts itfelfto produce diftiné&t Vifion — — P- 547 Peculiaritics of the eyes of fifhes. How the eye is adjufled. Its difeafes. Indiftin&tnefs. Double vifion. Squinting. Difeafes of the cornea treated by ftimulating applications. Cafe of Tobit in the Apocrypha confirmed by modern practice, 5 VII. Ex- €.O N Tf © N as. XXVi VIII. Experiments and Obfervations on the Inflexion, Reflexion, and Colours of Light. By Henry Brougham, jun. Efq. _ — pe ogt Propofitions refpeéting the means by which light is made to alter its direction. Experimentsand ob- Mervations. The leatt refrangible rays are fueh as deviate moft by inflexion—and alfo by deflexion. _ Flexion, refraction and reflexion are performed by a force acting at a definite diftance. Coloured fpeGtrum by reflexsion—Order of the colours. They are not produced by any new modification, but by the ordinary decompofition of light, The colour-making rays thus feparated are homo- geneous and unchangeable. The leaft refrangible rays are the moft reflexible, or rebound neareft the perpendicular. Spectrum by reflexion is divided in the/fame proportions as the Newtonian fpectrum by refraGtion. Meafurement of the colours. On the phyfical caufe of reflexibility. TX. An Account of the Manner in which Heat is propagated in Fluids, and its general Confequences in the Economy of the Univerfe. By Benjamin Count of Rumford. (Concluded from p. 348) — —_ Pp. 563 Experiments of the fufion of ice by water fuffered to repofe upon it. Precautions. Refults with boiling hot water, exhibiting the quantities of ice melted in a given time. Experiments with cold water at 41 degrees, by which a greater quantity of ice was melted than by boiling water. Ge- neral confequences applied, at length, to the diftribution of heat over the furface of the globe, by virtue of the internal motions of water, and currents which take place in the feas, fimilar to the ., trade winds in the atmofphere. X. Ufeful Notices refpecting various Objeéts.— Welding of Caft-Steel—Flexure of Compound Metallic Bars by Change of Temperature — P- 575 Sir Thomas Frankland’s method of welding caft-{cel to iron, Experiments to determine the pro- * portion between the thicknefs af compound metallic bars and their flexure by heat. SU P- XXViil C0 Nees ol iF vs, 5 PP PRE Or SEIN I. Obfervations on Water-fpouts feen from Nice. By Mr. Michaud, Corre- fpondent with the Koyal Academy of Sciences at Turin — P- 577 State of the weather previous to the appearance of water-{pouts. Vaporous foot of a water-fpout, unaccompanied by the fpoutitfelf. Defcription of another water-{pout of extreme magnitude, the lower part of which threw out lap flreams of vapour and jets of fea water. ‘Termination of water-{pouts on their approach to the fhore. Inftance of the foot and ftem being formed at fe- veral miles diftance from each other; the former of which remained ftationary on the fea until the winds had brought the cloud from which the latter was to iffue, immediately over the mafs of vapour. Additional faéts. Obfervations ; and explanation of the drawings. II. Experiments and Obfervations on the Inflexion, Reflexion, and Colour of Light. By Henry Brougham, jun. Efq. (Concluded from p. 563) p. 585 Explanation of phenomena dependent on the flexibility of light. Interference of the penumbre of bodies. Colours of light through mediums partially tranfparent. Colours of aflame. Blue fha- dows. Coloured fringes. Colours furrounding the fun’s image—and the flame of a candle. Sir Ifaac Newton’s coloured rings by reflexion from a concave glafs mirror. . Admeafurement of the flexibilities of the feveral primary rays. Summary of optical feience. Explanation of various phe- nomena dependent on reflexibility. Bright ftreaks from a candle when the eyes are nearly fhut. Other ftreaks varioufly coloured formed by reflexion from furfaces of a fibrous ftru€ture. Colours from {cratches in a piece of metal ;—from the minute particles of unpolifhed bodies ;—from hairs, {piders’ webs, certain foffils, &c. Whether thefe principles be fufficient to explain the natural ‘colours of bodies. The rays of light are not varioufly reflexible in the manuer taught by Newton in his celebrated experiment of internal reflexion by a prifm. In that experiment the rays were varioufly refle&ed, for no other reafon than becaufe their incidences were different. Images formed by reflexion of one uniform colour. Experiment and obfervations to thew that the natu- ral colours of bodies may be produced in this way. Colours of thin plates by reflexion. Sum- mary of propolitions. 11]. On certain Points of Nomenclature. By a Correfpondent — Pp. 597 New Publications _ —_ ar re P- $99 A} OURS een nr ne ——— = - —— ae nas a A POOR: Nowe OF NALUBRAL, PHILOSOPHY, CHEMISTRY; AND TE By ARPS: ARTICLE I, The Principles and Application of a New Method of conffrufting Achromatic Telefcopes. By Ropert Brarr*, M. D. Avrnr a fhort hiftorical retrofpe&t to the difcoveries of the unequal refrangibility of light by Newton, and the fubfequent correction of its effects in optical inftruments by Dollond, together with the remedy which is afforded in compound lenfes for the aberration arifing from fphericity, our author remarks, that it was expeCted by men of fcience that an increafe of the aperture and power of the refra€ting telefcope would be the neceflary confe- quence of fuch important fteps towards the perfection of its theory. Thefe expeétations have not hitherto been fully anfwered: for it is certain, that no Achromatic Telefcopes have yet been made of equal aperture with the fingle object-glafles of Huyghens and others, nor in this refpeét comparable to reflectors, though the errors of workmanfhip: are much more noxious in thefe laft than in lenfes. The general anfwer made by artifts to enquiries of this nature is, that the fault lies in the imperfection of glafs, and particularly in the denfe glafs known by the name of flint-glafs. The imperfection of glafs, for optical purpofes, arifes partly from its opacity and colour, but chiefly from irregularities in the refractive denfities of its parts. The refearches of chemifts and manufacturers to remove this defect have been confiderable, but hitherto without much fuccefs. From the confideration that it is not impoflible to introduce a fluid medium to fupply the place of one of the lenfes in the compound objeét-glafs, Dr. Blair was led to the experi- mental enquiry, whether nature afforded fluids poflefled of the requifite qualities. © The original paper, from which I have made the above abridgement or {election of parts, is inferted in the Tranfactions of the Royal Society of Edinburgh, vol. ii. It occupies 76 pages. N. Vou, L—Aprix 1797. B In a Methods of determining the Refractive and To afcertain the mean refractive and difperfive qualities of fluids, the Doctor made ufe of two kinds of apparatus. The firft, intended to afford a grofs knowledge of their pro- perties, confifted of an apparatus of prifms. In the fecond method, where the fluids pro- mifed to be of praétical ufe in Optics, they were more critically examined by means of lenfes, in which the flee, from being magnified, is rendered more confpicuous. The prifmatic apparatus confifts of a fmall, equi-angular, three-fided prifm, of brafs. Through this prifm, and parallel to one of its fides, are bored two holes, at a fmall dif- tance-from each other, equal in fize to the pupil of the eye.” The fides of the prifm are ground flat, and there are two pieces of glafs with parallel fides, of the fame dimenfions as the fides of the prifm. ‘There are alfo prifms of the fame fize, and with the fame angles, of different kinds of glafs ; and fome crown-glafs prifms with fmaller angles, which, by being applied to the large prifm, or to cach other, vary the refraéting angle at pleafure. When it is propofed to try the properties of any fluid, one of the fmall plates of glafs is. applied over the holes on the fide of the brafs prifm. A few drops of the fluid are then dropped into the hole, and, when it is full, the other plate is laid over the holes upom the oppofite fide, and the whole is fecured by tying a piece of packthread round the ends. One of the glafs prifms is new to be applied to the brafs prifm contiguous with one of the . parallel plates, the refracting angles of the two prifms being placed in oppofite directions fo. | as to form a fmall parallelopiped. Nothing farther is neceffary than to apply the eye to the hole which contains the fluid,, in fuch a way as to obferve through it any bright well-defined obje&t. The bars of the window anfwer the purpofe very well in the day-time, and the moon or a candle in the night. The intention of the two holes is for the fake of greater expedition. The proper- ties of two fluids may thus be examined and compared at the fame time. As the prifma- tic portion of fluid and the glafs prifm have equal refraGting angles, and refract in oppo-= fition to each other, it will eafily be underftood, that, if the object feen through the two. prifms coincides with the fame object feen dire@tly, the mean refractive denfity of both mediums will be the fame. When this is. the cafe, if the object feen through thefe prifms appears free from prifmatic colour, the difperfive power of the’fluid medium is alfo the fame with the difperfive power of the glafs prifm. But otherwife they will be different. Thofe mediums, it is to be obferved, are faid to have the fame mean refractive denfity, which, under equal obliquities of incidence, equally refraét the mean refrangible rays; and two niediums are faid to have the fame difperfive power, which produce an equal inclina- tion of rays of the fame colour to the mean refrangible ray, when the whole refraction of the mean refrangible ray is equal in both. When an objet feen through the equal wedges of glafs and fluid appears coloured, one of the fmaller glafs wedges is to be applied, and fhifted, till the object appears colourlefs. It is eafy to diftinguifh, by the order in which the prifmatic colour lies, whether the fmall prifm is to be applied in fuch a way as to increafe the difperfion of the rays occafioned by the fluid fo as to enable it to counterbalance that of the glafs, or whether the refracting angle of the glafs prifm requires to be enlarged, to enable it to counteract the difperfion occafioned by the fluid. By proceeding in this way to fhift the angles of the prifms till, firft, the dire& and re- fracted images of an object coincide, without regarding the colour, and, next, till the re- fratted Difperfive Powers of Fluid Mediums. a fracted image appears colourlefs, without regarding the coincidence, the ratio of the mean re- fractive and difperfive powers of that kind of fluid, and that kind of glafs, with which the ex- periments are made, will be obtained from the angles of the prifms being given in both cafes. In order to afcertain the abfolute refractive denfity of glafs, or any other medium, that is to fay, the general ratio of the fines of the angles of incidence to the fines of the angles of refration of the mean refrangible ray which obtains in that medium, the Doétor took a dire& method, fimilar in principle to that employed by Sir Ifaac Newton, and defcribed by him in the feventh propofition of the firft book of his Optics, and likewife in his Optical Letures, p- §43 but which, as he juftly remarks, will be found much eafier, and perfectly accurate. Inftead of caufing the rays to pafs through the fights of a large and accurate quadrant at the diftance of ten or twelve feet, as direéted by Sir Ifaac Newton, the Doctor employed a Hadley’s quadrant, inethe following manner : Plate I. fig. 1—I repyefents the index-glafs, and H the horizon-glafs of a Hadley’s quadrant. SI reprefents a folar ray irtcident on the index-glafs, thence reflected to the horizon-glafs H, and from it to the eye atE. ‘he line /g reprefents another folar ray, incident on the prifm P, and through it refrafled to the eye at E. When the prifm is turned flowly round its axis till the fpectrum G appears at its greateft height, this is its proper pofition. The angle formed by the dire€t and refracted ray is then the leaft poffible, and the angles of incidence and emergence are equal. Let the prifm be fecured in this pofition. A flight infpetion of the figure will thew, that when the reflected and refracted images of the fun are made to coincide, the angle marked by the index of the quadrant is the fame which the incident ray fg forms with the refracted ray PE produced. For SZH is the angular dif- tance of the fun, and his doubly refleCted image marked by the index ; and the angle /g G, which the ray incident on the prifm forms with the refraCted ray produced, is equal to its {g and SI being parallel, and PZ and HZ being coincident. The manner in which the ratio of the fines of the angles of incidence and refra€tion may be computed, from the above angle and the refracting angle of the prifm being given, is fully explained in the celebrated works which have juft been quoted. The Doétor here remarks, that as it is the ratio of refraGtion of the mean refrangible ray which is wanted, the centre of the reflected image of the fun ought to be made to coin- cide with the centre of the coloured {pectrum, as reprefented in the figure ; and if, inftead of this, the coincidence be formed with the moft or leaft refrangible ray, or any of the in- termediate rays, it will be the ratio of refraflion of thefe rays, and not of the mean refran- gible ray, which will be found from the obfervation. Hence this method might be prac- tifed for determining the difperfive power, as well as the mean refractive denfity of any tranfparent fubftance, whether folid or fluid; but the Door has preferred a combination of prifms or lenfes, becaufe it is the relative ratios, more than the abfolute ratios, which are mott immediately wanted. By this prifmatic apparatus, the optical properties of a great variety of fluids were exa- mined. The folutions of metals and femi-metals proved in all cafes more difperfive than crown-glafs. Some of the falts, as, for example, fal-ammoniac, greatly increafed the dif- perfive power of water. The marine acid difperfes very confiderably, and this quality in- creafes with its ftrength, The moft difperfive fluids were accordingly found to be thofe in which this acid and the metals were combined. The-chemical preparation called cau/fficum B2 antimoniale, 4 Experiments on the Refra&rve and antimoniale, or butyrum antimonii, in its moft concentrated ftate, when it has juft attracted fuflicient humidity to render it fluid, poffefles the quality of difperfing the rays in fuch an altonifhing degree, that three wedges of crown-glafs are neceflary to remove the colour produced by one wedge of this fubftance, of an equal refracting angle oppofed to them. ‘The great quantity of the femi-metal retained in folution, and the highly concentrated ftate: of the marine acid, are confidered by the author as the caufe of this fcarcely credible effect. Corrofive fublimate mercury, added toa folution of /a/ ammoniacum in water, poflefles. the next place to the butter of antimony among the difperfive fluids which he. examined. It may be made of fuch a degree of ftrength as to: require a wedge of crown-glafs-of. double the refraéting angle, to remove the colour which a prifm of it produces. ‘Che mercury and marine acid contained in this folution are manifeftly the caufe of its difperfive power: for neither the water, nor the volatile alkali, which are its ether component parts, will be found capable, if tried feparately, of contributing towards this effect. The effential oils were found to hold the next rank to metallic folutions, among fluids which poffefs the difperfive quality. The moft difperfive were found ’to be thofe obtained from bituminous minerals, fuch as the native petrolea, pitcoal, and amber. When the re- fraction is without colour, the proportion of the refracting angle of a prifm of thefe, to the refraGling angle of a prifm of crown-glafs acting in oppofition, is about two to three. The difperfive power of the effential oil of faflafras, is not much inferior to thefe. The effential oil'of lemons, when genuine, requires the refra€ting angles of the prifms neceflary to produce a colourlefs refraction, to be as three to four. In oil of turpentine, this pro- portion is as feven to fix; and the effential oil of rofemary is ftill lefs difperfive. Some expreffed oils, which were examined, were-found not to differ fenfibly in difperfive power from crown-glafs; which was alfo the cafe with rectified {pirits, and with nitrous and vitriolic ether. 7 Having been thus fuccefsful beyond his hopes in difcovering fluids capable of removing the great imperfeétion of tclefcopes arifing from the different refrangibility of lights, the next object of the author was to fele& from this varicty thofe that feemed beft adapted to optical purpofes. ‘Fhere was no doubt that thofe mediums which moft difperfe the rays were ceteris pa= ribus to be preferred. It will alfo be found, when the method of correcting thofe errors which arife from the fpherical figures of lenfes comes to be confidered, that there is ap- parently an advantage in ufing a difperfive medium, whofe mean refractive denfity exceeds the mean refraétive denfity. of crown-glafs, As the antimonial cauftic poffefles both thefe advantages in a degree far beyond what was to be expected in any fluid, fome of it was included between.two double convex len{es of crown-glafs, whofe radii of convexity were as two to one. The leaft convex fides of, thefe were turned toward each other, and they were kept at a proper diftance by means of a glafs ring. The cavity was then filled with the ftrongeft butter of antimony. Here it is evident, that there is a concave lens of the difperfive fluid ating in oppofition to the two convex lenfes of crown-glafs, and that the proportion of the radii of thefe is the. fame which was found by the prifms to corre the colour, namely, three wedges of crown-glafs to-one of the butter of antimony. This compound objeét-glafs being put into a tube, an eye-glafs. was applied, and, accord, ing Difperfive Powers of Fluids. 5 ing to expeétation, the colour was found to be removed. But the Doétor was furprifed to fad. on direéting the inftrument to a planet, and ufing a deep eye-glafs, that this fluid, in its highly concentrated ftate, was fubject, like flint-glafs, to great irregularities in its denfity, difcoverable by ftreams of light, like comets’ tails, iffuing in different direétions from the difk of Venus, which was the planet obferved. By fhaking the objedt-glafs, thefe might be in a great meafure removed, but foon returned; and, after ftanding all night, broad veins, in different parts of the included fluid, were perceptible to the naked eye. It was neceflary, on this account, to reject very denfe fluids. ‘he antimonial preparation was found to be reducible to a fufficient degree of fluidity, by mixing it with fpirit of wine or vitriolic ether, into which a {mall quantity of the marine acid had been previoufly dropped. This prevents any precipitation of the femi-metal in the form of acalx. In this diluted form, either this preparation, or the folution of corrofive fublimate mercury alone in fpirit of wine or in water, with the addition of crude fal ammoniacum, may be employed for pro- ducing refraction without colour, and without being fubject to that irregularity of denfity te which flint-glafs and very denfe difperfive fiuids are fubject. But as folutions of faline fubftances in this diluted ftate do not differ materially in dif- perfive power from the effential oils, thefe two kinds of fluids may be ufed indifferently. In one cafe, however, our author remarks, that water, or vitriolic ether, impregnated with antimony or mercury, will have the advantage from being lefs denfe than effential oils, and that is, where it is required to produce a fingle refraction, in which there fhall be no differ- ence of refrangibility of heterogeneal light. _ As this expreflion might found ftrange in the ears of Opticians, the Doctor has employed a confiderable part of his paper to explain what is meant by it. He fhews, that there are cafes of fingle refraction in which the violet rays are. the leaft refrangible ; or in which all the rays are equally refrangible ; or in which the red rays are refracted from the perpendicular, and the violet rays towards the perpendicular, while the mean refrangible rays fuffer no refraction. Thefe pofitions muft, no doubt, at firft confideration, appear paradoxical; but their fin- gularity will vanifh on attending totwo circumflances: 1ft, That thefe refractions, though fingle, are not effected by the fimple agency of one medium on the confine of a vacuum, but by the difference of the contrary actions of two mediums at their common furface; and, 2dly, That Opticians, from the habit of contemplating the crown and flint glafles, have affociated the notion of a greater difperfive power with that of a greater power of mean refraction.—But our author, having afcertained various faéts in which the greater power of difperfion accompanies the lefs mean refra€tive power, has in confequence fhewn that an achromatic lens may be conitruéted, in which all the refractions are made in the fame dire€tion*. The cafes of fingle refraétion here mentioned are very perfpicuoufly and at fome length fhewn, with fuitable diagrams, as well from the general facts: before enumerated, as from aflumed powers of attraction of the mediums on the rays of light, after the fup- pofition of Sir Ifaac Newton. For the fake of brevity, however, 1 fhall give the fubftance of his explanation, without particularly attending to the order of arrangement. * In an objett-glafs formediof oi! of turpentine mcluded between two double convex lenfes, the radii of whofe convexities are as fix to one, and the decp fides inwards, there are four fefraétions, all towards the axis ; This compound lens has twenty inches focal b. and the aberration, from difference of refrangibility, is removed. length, and one inch and half aperture, ‘ Its performance'as a telefcope is not cenremptible. Uf 6 Uncommon Effedts of Refra&tion. If a pencil of compounded light be imagined to'pafs obliquely out of the plane furface of any denfe medium into a vacuum, it is well known that the refraction will be made from the perpendicular, the violet rays being moft refracted and the red leaft, fo that thefe rays will be inclined to each other. But fuppofe, again, that inftead- of the rays being {uffered to pals into the vacuum, another medium were applied, having a plane furface in contact with that of the former, and that its power of difperfion were fuch as precifely to counteract the difperfive power exerted on the rays by the former medium: in this cafe it is evident that the pencil of light’ would pafs forward cofourlefs. Neverthelefs, as the dif- perfive power may be equal in two mediums which differ in mean refractive power, it is no lefs clear, that'refra€tion will take place wherever thefe two powers are not precifely equal ; and that either towards the perpendicular, if the power, or, as it is called, refractive denfity of the fecond medium, be greater than that of the firfl, or from it if lefs. ; In the next place, fuppofe the two mediums not to agree in difperfive power, but that the fecond medium difperfes more than the other. The violet ray will not only be prevented from feparating on the one fide of the red, but, by the excefs of difperfive power, it will be drawn fo far as to make an angle with that ray on the other fide, and the difperfion will be made the contrary way. If the mean refra€tion of the fecond medium exceed that of the firft, the whole pencil will be bended towards the perpendicular, and towards the fame region as the difperfion carried the violet ray; fo that the effect will be fimilar (though lefs in power) to that of a common refraétion and difperfion by a fingle denfe medium in vacuo. This happens in the tranfition from crown-glafs into flint-glafs. But if the mean refractive power of the fecond medium be leaft, the pencil will be bended from the perpendicular, though the violet ray will notwithftanding continue neareft the fame perpendicular. ‘The red ray will therefore be the. moft deflected, and the violet leaft. This effeét takes place when light is refra€ted in the confine of crown-glafs and oil of turpentine, and alfo of many other fluids. If the refraCtive powers of the two mediums upon the mean ray be equal, the dire€tion of this ray will continue unaltered at its tranfition from the oneto the other. But if the difperfive power differs, the extreme rays will form an angle, of which the red rays, will be either at the one or the other limit, according to cireumftances. For example, if the difperfive power of the firft medium be greateft, the angle will merely be diminifhed by the ation of the fecond medium; fo that the violet ray will be the moft, and the red the leaft, refra€ted from the perpendicular; as would have happened (though more ftrongly) in the tranfition into a vacuum. But if, on the contrary, the difperfive power of the fecond me-' dium were greateft, the violet ray will be carried more towards the perpendicular than the red by the difference of the two powers. ‘This cafe of refraétion is found to take place in the confine of crown-glafs and butter of antimony, when the latter is fo far diluted as that both mediums equally refraét the mean ray under equal angles of incidence.” In the cafe of refraétion without colour, as before explained, the power of difperfion in the fecond medium was affumed to be fuch as precifely to counteract the effect of the firft; that is to fay, not only with regard to the extreme red and violet rays, but alfo with regard to the mean and all the intermediate rays. But Door Blair’s Experiments thew, that,"in mediums which difperfe the light but little, the green is the mean refrangible ray ; that in by far the greateft number of more difperfive mediums, including flint-glafs, metallic folutions, and eflential oils, the green light is not the mean refrangible order, but forms one 6 of Achromatic Lens by a fingle Refrattion. ° 4 of the lefs refrangible orders of light, being found in the prifmatic fpeétrum nearer to the deep red than to the violet; and that in another clafs of difperfive mediums, which includes the muriatic and nitrous acids, this fame green light becomes one of the more refrangible orders, being now found nearer to the extreme violet than to the deep red. Whenever, therefore, the light pafles out of one of thefe three claffes of mediums into another of a different clafs, the difperfive powers will not accurately counteract each other, even though they may be adopted to caufe the extreme red and violet rays to become parallel; but the rays which would occupy the interior parts of the fpeétrum will be difperfed, and that in a greater‘degree the more remote they are from the extremes. Thefe feveral cafes of refraction were likewife tried with compound object-glaffes, which thew the effect better than prifms. Thus, if a plano-convex lens have its plane fide turned toward a diftant objet, the rays will enter it, as to fenfe, perpendicularly, and will therefore faffer no refra€tion. If the convex furface of this lens be brought in contact with a fluid ‘of lefs mean refractive denfity than the glafs, but exceeding it in difperfive power in that degree which occafions an equal refraction of all the rays, all thefe rays will then be con- verged to the fame point, which are incident at the fame diftance from the axis of the lens. The focal diftance of this compound lens will be greater or lefs, in proportion to its radius of convexity, and to the difference of refraction between it and the fluid made ufe of. While the fluid is confined on one fide by the plano-convex lens, let the lens which is brought in contact with it on the oppofite fide have one of its fides ground convex, and the other concave; the radii of their {phericities being equal to the focal diftance at which the rays are made to converge by the refraQtion which takes place when light paffes from the plano-convex lens into the fluid. It is manifeft that the light will now both enter into this compound lens, and emerge from it, perpendicularly, and will therefore fuffer no refrac- tion, except in the confine of the convex fide of the plano-convex, and the difperfive fluid where all the rays are equally refrangible. A compound lens of this kind is reprefented i in the fecond figure, PI. I. which requires no farther explanation ; excepting only, that, inftead of being fpherical, it is reprefented with that curvature which converges homogeneal rays incident at all diftances from the axis to the fame point. If the required curvature could be given to lenfes with fufficient accuracy,‘ this figure feems to reprefent as perfe& a conftruc- tion of the objeét-glafs of a telefcope as can be defired, But there is reafon to think that a fpherical figure may be communicated, not only much eafier, but with greater accu- racy than a fpheroidal or hyperboloidal, which would then be required ; and even if this difficulty could be got over, there would ftill remain a fundamental fault in the theory. Before relating the obfervations by which this was detected, Dr. Blair explains the method - of removing the fpherical aberration by a combination of convex and concave lenfes For, next to the indiftin@tnefs arifing from the unequal refrangibility of light, this aberra- tion occafioned by the fpherical figures of lenfes is the great obftacle to the advancement of the powers of vifion. The aberration from the {pherical figure has been treated of, in all the variety of cafes which can occur in fingle glafs lenfes by the great Hugenius in his Dioptrics, a pofthumous work. He there demonftrates, that the quantity of this aberration is very different in different lenfes of the fame focal diftance, according to the convexities or concavities of their two fides, and the manner in which they are expofed to parallel rays. , In 8 5 Optical Aberration from Figures > In, convex lenfes, thofe rays which pals, at a diftance fram the axis are converged'to.a point nearer to the Jens than its geometrical focus. ‘The diftance between the point at which the external ray of a pencil incident on a lens interfeéts its axis, and the geometri- cal focus, is called the linear aberration of-that lens. Hugenius demonfirates, that when a plano-convex lens is expofed to parallel rays, with its plane fide towards them, this aberration will amount to four times and a half the thick- nefsof the glafs. By the thicknefs of a convex lens, is meant its greateft thicknef§ in the middle, after fubtraéting its thicknefs, if it has any, at the outer edge; and by the thick- nefs of a concave lens, is meant its thicknefs at the external edge, after deducting its thick- nefs in the middle. ‘ On turning the eonvex fide of the lens towards the light, the linear aberration will only execed the thicknefs of the lens by one fixth part. When both fides of a lens are convex, and the proportion of their convexities is as one to fix; if the molt convex fide be expofed to parallel rays, the aberration will exceed the thick, nefs of the lens one fourteenth, which is the fmalleft poflible aberration of any convex lens: ly itis required to increafe the aberration, this may be done by grinding one fide of the lens convex, and the other fide concaye, toa longer radius. Such a lens, with its con- cave fide turned towards parallel rays, will haye more aberration than APY plano-convex or double conyex lens of the fame focal diftance. Hugenius proceeds to fhew, that the fame aberration’; is produced by concave lenis as by fimilar convex ones, When a plano-convex lens is expofed to parallel rays with its plane fide outward, the external ray of the pencil being produced backward, after refraction, will interfe&t the ayis of the lens nearer to it than its focus by four times and a half the thick- nefs of the lens. But if its concave fide be expofed to the parallel rays, the aberration will only exceed the thicknefs of the lens one fourteenth part. A double concave, whofe radii are as one to fix, with the moft concave fide turned outward, difperfes the rays with the leaft aberration; and a concave menifcus, with its convex fide outward, produces more aberration than any plano-concave or double concave lens of an equal focal diftance. Thefe are fufficient data for correéting the aberration from the fpherical figure, in cafes where both a convex and concave lens are required in the conftruction of the compound objed-glals. Fig. 3- Pl. I. Let AB reprefent a convex lens receiving a pencil of rays from the object S, and converging rays incident near the axis at ST to the point F, and external rays as SB to the point D, fo that DF reprefents the greateft linear aberration in this cafe. Again, let GH (Fig. 4.) reprefent a concave lens receiving the parallel rays SH, RK, which it refraéts in the lines HX and-KV. This ray KV being produced backward, will interfect the axis of the lens nearly at the point N, which is called the virtual focus of the concave 5 and the external ray HX produced backward, will interfe& the axis in fome point P nearer to the lens than its focus PN, being the linear aberration. . It may here be obferved, that the convex is in that pofition which produces the leaft aberration, and the concave in the pofition which produces moft aberration. Hence, to render the aberrations DF (Fig. 3.) and PN (Fig. 4.) equal, the focal diltance of the con- vex muft be much fhorter than that of the concave; and if the diftances of the points F 4 and Optical Aberration from Figure.” 2 and N, from the convex and concave lenfes, be required to be the famé as reprefented in the figures, then muft the obje& be placed much nearer to the convex. Hence the image of the near object S is reprefented at the fame diftance from the convex lens in Fig. 3, as the virtual focus-of the concave in Fig. 4, where it is reprefented as receiving parallel rays which are fuppofed to come from an infinitely diftant object. Now when the diftance between K and N, which is the point from which parallel rays are made to diverge by the concave lens, is equal to the diftance between 'T and F, which is the point to which rays ifluing from S are made: to converge by the convex, and when the aberrations DF and PN are alfo equal; it will follow in this cafe, that if the two lenfes be placed contiguous, in the manner reprefented in the twelfth figure, parallel rays incident on thefe lenfes will be converged to the point $, without any aberration of the external ray. For it is an axiom in optics, that if a ray of light after refra€tion be returned directly back to the point of incidence, it will be refraéted in the line which was before defcribed by the incident ray. If, therefore, we conceive the whole of the light emitted from the point S (Fig. 3.) and converged by the convex lens towards the points D and F, to be returned directly back from thefe points, it will be accurately converged to the point S, whence it iflued. Now the parallel rays SH, RK (Fig. 4.) after their emergence from the concave lens in the lines HX, KV, are precifely in the fame relative fituation as the rays fuppofed to be re« turned direétly back from F and D are in at their incidence on the convex 3 and therefore, when thefe lenfes are placed contiguous in the manner reprefented in the twelfth figure, parallel rays incident on the concave lens, and immediately after their emergence from it, entering the convex lens, will be accurately converged to the point S without any aberration. ‘ This, which is the moft fimple cafe, will fuffice to explain the nature of that aberration which arifes from the fpherical figures of lenfes, and a method of obviating it, by com- bining a convex and concave. The demonftration is perfect as far as regards the external tay, which is here reprefented pafling from the external part of the concave into the external part of the convex, in immediate conta& with it ; and if the furfaces of the two lenfes, which refpeé each other, were cither in conta& or parallel, it would be true with regard to all the rays. But as this is not the cafe, there arifes a {mall fecondary aberration, the effe@t of which only be- comes fenfible in large apertures. Hence may be underftood the reafon why the indiftinGinefs arifing from the fpherical figures of lenfes, may, in'the common Achromatic Telefcope, be more nearly removed int thofe conftrudtions of objeét-glaffes in which three lenfes are employed, than in thofe compofed only of two; and alfo the advantages in this refpect which may be derived from introducing fluid mediums which differ from glafs in their mean refractive denfity, and in the quantity of aberration produced by their refractions. For it will be found upon com= putation, that when the fluid medium is rarer than glafs, the aberration from the fpherical figure is increafed, and becomes greater in proportion as its denfity diminifhes. Now, by making the denfity of the fluid medium approach nearer and nearer to the denfity of the glafs with which it is in contaét, we may increafe the ratity of our refracting medium, or, Vow. L—Arrin 1797. Cc which 10 Various Alerrations in compound Lenjes. which amounts precifely to the fame thing, diminifh the difference of denfity of the two mediums at pleafure. It will appear from what has been explained, that the aberration from the figure cannot be correéted by interpofing a difperfive Auid between two convex lenfes of a greater re« fractive denfity than the interpofed fluid. For all the refraétions, being made the fame way, tend to converge the external rays to points nearer the lens than its geometrical focus. Hence, when rare fluids are made ufe of to remove the aberration from the difference of refrangibility, fome farther contrivance becomes neceflary to correct the fpherical aberration. The moft obvious way, and which on trial was found fuccefsful, is to include the rare difperfive fluid between two glafles, ground concave on one fide and convex on the other, and thus form fuch a concave as fhall be required. An Achromatic Objeét-glafs may be formed by combining this with a convex. The objection to this conftruétion is, that one of the advantages arifing from the ufe of fluids is given up, namely, the prevention of that lofs of light, by refleQion, which is a confequence of the fluid being in immediate contaét with the glafs, whereas in the prefent cafe the fpace between the convex and concave is occupied by air. On this account, Dr. Blair attempted to introduce a third medium, by filling this vacancy with a fluid of the leaft difperfive kind, and of lefs mean refraétive denfity than the dif- perfive fluid. For this purpofe he employed fometimes reétified fpirit of wine, and fome- times vitriolic ether ; and by giving to the lenfes the proper degree of curvature, in which great variety may be introduced, he fucceeded in forming object-glafles in which both aberrations are removed, and hardly any more light loft than in a fimple objeét-glafs. Having gained this point, he now determined to try how far the aperture of the object- glafs might be increafed, without increafing its focal length, expeéting, at leaft, to equal refleGtors in this refpect. But the firft trials to execute object-glaffes on this principle, though they left no reafon to complain of want of fuccefs when compared with fuch in- ftruments as are now in ufe, exhibited new phenomena and new obftacies to the perfection of the theory of Telefcopes more unaccountable and perplexing than any he had before en- countered. “he hiftory of thefe interefting facts, and the regular progrefs of difcovery by which they were remedied, conftitute a large part of the paper, which well deferves to be confulted by thofe who wifh effectually to profecute this fubjeét. Brevity, however, demands a lefs hiftorical narration in this place. Thefe new difficulties arofe from the effects of contrary powers of difperfion, which though equal upon the extreme rays, were not found to be the fame upon the rays that oc- cupy intermediate fpaces in the coloured f{peCrum. From what has been already ftated on this fubjeét, the attentive reader may underftand, that fuch intermediate rays from a compound lens of the kind here defcribed, would not be aflembled at the common focus. The particular nature of this difperfion is much more accurately feen by applying a deep eye-glafs to the focal image, than by experiments with prifms. When the image of a lucid point is formed in the focus of a fimple lens, the violet or moft refrangible rays are con- verged to a focus nearcft tothe lens, and the deep red rays are converged to a focus at the greateft diftance from it- The confequence of this is, that if the image be examined by an eye-glafs nearer to the lens than is required for diftin¢t vifion, it will be furrounded with a red Aberration from Colour totally removed. ig red fringe, which is the prevailing colour of the leaft refrangible rays; and if the eye- glafs be placed at a diftance beyond that which is required for diftinét vifion, it will be furrounded with a blue fringe, which is the prevailing colour of the moft refrangible rays. The reafon of this will appear more clearly from infpeéting the fixth figure, where the red rays appear outermoft within the focus at A, and the violet rays appear outermoft be- yond the focus at B. ‘Thefe colours are alfo vifible when an image of any luminous object, as the fun, is formed by a lens on a white ground; and they will be fo much the more confpicuous, the greater the diameter of the lens in proportion to its focal diftance. The reverfe of this happens in compound lenfes, when the medium employed to correét the colour difperfes more than it ought to do. In this way the correction of the colour may be examined, and the qualities of refracting mediums inveftigated, to an extreme degree of accuracy. Yet the effect will be rendered fill more fenfible by covering half the object-glafs. For, when this is done, the colour pro- duced by the uncovered half of the objeét-glafs appears, without being mixed with that of the oppolite fide, even when the eye-glafs is adjufted to diftin€ vifion. Thus, in Fig. 6, the colours produced by both fides of the lens are mixed at the general focus F. But if the rays coming from one fide be intercepted, thofe which are refracted by the other fide will appear in their proper colours. By thefe means, and by employing a very luminous object furrounded by a dark ground, and a high magnifying power, the leaft uncorreéted colour may be rendered fenfible. The firft conje€ture which prefented itfelf on the obfervation of irregularities of this kind, in compound lenfes adjufted fo as to corre€l the aberration of the extreme rays, was, ‘that the colour might fomehow proceed from the compenfation at different diftances from the axis of lenfes not correfponding as the plane furfaces of prifins everywhere do. Trials on the images formed by the central parts, and afterwards by the parts near the circum- ference, proved, however, that this conjeCture did not reach the caufe. Subfequent expe- riments and examinations of the coloured fringes led the author to the true caufe, that is to fay, the want of proportionality in the difperfive powers of the different mediums, as has been already ftated. It remained, therefore, to difcover, by a new procefs of experimental enquiry, the adequate remedy for fuch an extreme fource of imperfection. This led to the valuable doétrine, that one clafs of difperfive mediums throw the green nearer to the violet, while another clafs throw the fame colour nearer to the red, than is feen in the fpefrum formed by crown-glafs and other mediums, which difperfe but in a fmall degree. ‘Chefe mediums were therefore applicd in oppofition to each other, to correct this fecondary aberration in lenfes more compounded than might have been required if fuch a difficulty had not prefented itfelf. And laflly, the greater degree of compofition in thefe perfeé lenfes was got rid of by the happy expedient of mixing the two different kinds of difperfive me- diums, which, as it fortunately turned out, did produce a compofition of an intermediate nature, with regard to this proportionality in the arrangement of the prifmatic colours. It has already been remarked, in the order of this abridgement, that, in metallic folutions and eflential oils, the green light is among the lefs refrangible rays; but that, in the marine and nitrous acids, the fame green light becomes one of the more vefrangible. It was not probable that the effential oils could be united with marine acid fo as to form a colourlefs C2 fluid 1a Conftrudion of Aplanatic Lenfes. fluid fit for optical ufes; but nothing could be better adapted for this purpofe than metallic folutions. The firf trial was made with butter of antimony. On increafing the proportion of ma-~ rine acid, the fringes of green and purple, which, being the intermediate rays, were irre- gularly refraéted by the metallic folution, grew narrower and narrower, till they entirely difappeared ; and if more was then added, they re-appeared in an inverted order. The fame thing was tried with a folution of crude fal ammoniac and corrofive fublimate. With a cer- tain proportion of thefe two fubftances, the rays of all colours emerge from. the compound object-glafs equally refraéted. If the proportion of the ammoniacal falt, and confequently of the marine acid it contains, be increafed, the green rays which were the mean refrangible, in the difperfive fluid as well.as ia crown-glafs, draw nearer to the violet, making a part of the more refrangible half of the fpectrum, and confequently emerge lefs refracted than the united red and violet rays, and are converged to a focus at a greater diftance from the object-glafs; fo that the green fringe now appears within the focus, and the purple fringe beyond it. But, on increafing the proportion of mercurial particles, thefe fame green rays. fhift their fituation to the lefs refrangible half of the {petrum, which appears from their now emerging moft refraéted, and being converged to a point nearer to the objet-glafs than the united red and violet, whofe refrangibility does not appear to be affected by thefe admixtures. which occafionfuch remarkable fluctuations in the refrangibility of the green rays and other intermediate orders. It may poflibly feem ftrange at firft view, that the green rays fhould emerge moft refracted from the compound object-glafs, when their refrangibility in the difperfive medium is diminifhed, and leaft refracted under the contrary circumftances. The caufe of this is, that the principal refraction of the compound object-glafs is performed by the indifperfive convex lens, which is oppofite to the refraction produced by the difperfive concave. Fig. 7. reprefents an object-glafs of this kind in Dr. Biair’s poffefion, in which the metallic particles are fo far diminifhed, and the particles of marine acid fo far increafed, as to render the refraétion of the feveral orders of rays proportional in both mediums, There are two refraétions in the confine of glafs and the fluid, but not the leaft colour whatever. Hence it is inferred that, notwithftanding the confiderable difference of denfity, and the refraétion which, on account of the anterior furface being plain, and the pofterior furface fpherical, having the focus of parallel rays for its centre, is performed only at the two furfaces of the fluid, there is no unequal refrangibility of light. The rays of dif. ferent colours are, as the Doétor obferves, bent from their reétilineal courfe with the fame equality and regularity as in refraction. As cuftom has already appropriated the word Achromatic to that kind of refra€tion in which there is only a partial corre€tion of colour, the author propofes to diftinguith this entire removal of aberration by the term Aplanatic. Thus far 1 have endeavoured, partly by abridgement, partly by extracts, and partly by taking greater liberties of narration and arrangement, to convey the fubftance of Dr. Blaix’s important difcoveries to the public. It is now fome years fince the attention of the world was firft dire€ted to his improvements. I have therefore been induced to make enquiry, among the artifts of this metropolis, into the ftate of the undertaking Experiment on the InfleGtion of Light. 13 undertaking confidered as a manufactory. Thefe enquiries led me to the Door him- felf; from whom I underftand, that all the practical difficulties are removed, and that the delay which has prevented the philofophical world from being yet fupplied with thefe inftruments has arifen merely from the interruption of engagements. And as I have reafon to expect fome communications from him on this fubject in future, it becomes unneceflary to enter into any of thofe remarks, in this place, which the immediate con- fideration of the fubjeét might fuggetft. 2 nn Tle A Remarkable Effect of the Inflection of Light paffing through Wire Cloth, not yet clearly explained. In the fecond volume of the Tranfa@tions of the American Philofophical Society, p. 201, an optical problem is propofed in a letter from Mr. Hopkinfon to Mr. David Ritten- houfe, who has given a-folution in his anfwer. Mr. Hopkinfon, upon looking through. the threads of a filk handkerchief, held clofe before his face, at a diftant Jamp, was furprifed to obferve what he thought to be the threads magnified; and ftill more, that thefe fup- pofed threads remained ftationary, notwithftanding any motion he gave the handkerchief to the right or left. Mr. Rittenhoufe, in his remarks on this phenomenon, obferves very juftly, that the appearance, which is that of certain ‘luminous points regularly arranged in right lines crofling each other, cannot confift of any image of the threads of the handkerchief, but muft be certain images of the lamp formed by the inflection of light pafling near the threads. He appears to have confidered the handkerchief as a very imperfect inftrument, and therefore too haftily threw it afide for an inftrument confifting of parallel hairs not crofled by others. With this he obferved that the line of light or portion of the fky feen through a window-fhutter very nearly clofed, appeared multiplied, fo as to confift of three parallel lines almoft equal in brightnefs, and on each fide four or five others, much fainter, and growing more faint, coloured and indiftin& the farther they were from the middle‘line.. When the hairs were thicker, but at the fame diftance apart, or number in the inch, fo as to diminifh the opening between them, the middle lines were lefS bright, but the others ftronger and more diftin€&t ; and he could count fix on each fide of the middle line feem- ing to be equally diftant from each other, eftimating the diftance from the centre of the one to the centre of the next. In this experiment, the hairs were the 1go0th of an inch in diameter, and were regulated by pafling them over the threads of a fcrew of 106 turns in the inch : fo that the opening or interval between hair and hair was ,?=th of an inch. The middle line was well defined and colourlefs; the next two were likewife pretty well defined, but fomething broader, having their inner edges tinged with blue and their outer with red. The others were more indiftiné&, and_confifted each of the prifmatic colours in the fame order; which, by {preading more and more, feemed to touch each other at the fifth or fixth: line; but thofe neareft the middle were feparated from each other by very dark lines much broader than the bright lines. From experiments made by applying this frame of parallel hairs before the object-glafs of a fmall telefcope furpithed with a micrometer, he found that. the pofition of the two: nearelt 14 Experiments on the Infle@tion of Light. neareft fide-lines indicated an angle of defleGion equal to 7’ 453 and, from eftimate founded on the appearance of the lines, he judged that the other: ftreaks were deflected in angles of double and triple the fame original angle. After this ingenious philofopher had proceeded fo far, and found a ready folution for the faéts he had obferved, by referring them to the Newtonian doctrine of inflection, he went on, with more hafte than precifion, to account for the appearance exhibited by the hand- kerchief. He remarks, that, if the handkerchief be held before the eye, fo that its threads may be difpofed horizontally and perpendicularly, and a luminous fpot be viewed, the perpendicular threads will, by infleGion, on the principle explained in his frame of hairs, caufe it to appear as a row or horizontal line of fpots, for example, five; and that the horizontal threads will, on the fame principle, convert every one of thefe into five perpen- dicular rows; by which means, a fquare figure, compofed of twenty-five luminous points, will be feen, of which he gives the figure. On thefe laft induétions it may be fuflicient to remark, that though his frame of parallel hairs might have converted a real row of luminous points into fuch a fquare, yet it is in- conceivable how the fame effeé& could have followed, with regard to rays of light which muift have already pafled through the handkerchief in order to receive the firft modifica- tion. But as Mr. Rittenhoufe, from his figure of 25 fpots, which are in no cafe produced by the handkerchief, fhews that hé did not ftri@ly attend to the phenomena, but wrote in this inftance from recolleétion and reafoning, I fhall difmifs thefe particulars of the original obfervers, and mention the facts I have myfelf remarked. When this problem was firft pointed out to me a few months ago by a very active pro- moter of the fciences, I took the earlieft opportunity of looking at a ftreet lamp through a piece of muflin containing one hundred threads in the inch. Inftead of one {pot of light, there appeared nine; four of which occupied the corners of a fquare, one the centre, and four others the middle points, in a right line between the corners. Upon examining them with an achromatic perfpective magnifying fourteen times, I faw that the {pots were true images of the flame of the lamp, the central one being perfedt, all the others coloured, with the red outermoft, and the corner lights leaft luminous and diflin@. It made no difference in the appearance, whether the cloth was applied clofe to the obje@-glafs, or at any diftance to which the arm could reach before it; or moved fideways in its own plane; but the apparent dimenfions of the fquare were lefs when the cloth was applied between the object-lens and its focal image, in proportion (by eftimate) as the diltance of the cloth from the focus was lefs. When coarfer muflins were ufed, the fquare was fmaller according to the coarfenefs, but in what proportion was not examined, becaufe it was fuppofed to follow no very fimple ratio. No effect of this kind took place with the ob- je&t-glafs of a microfcope. From thefe faéts I inferred as follows :—The middle flame is formed of all the pencils of light which pafs through the central parts of the holes in the cloth without any deflection, The four flames in the middle of the fides of the fquare, are formed by the pencils of light inflected towards the fhort threads bounding each fquare hole in the cloth, affifted by the defleétive power of the oppolite threads refpe€tively. The corner flames are formed by the combined aétion of the two threads contiguous to the angles of every hole ; the fum of which force, acting in the diagonal with a power varying from the diftance of the refpective 1 parts Solar Speétrum of uncommon Brilliancy. 15 parts of the lines about the angle, cannot produce an image fo clear and definite as the fides. The images are farther afunder the finer the cloth, becaufe the nearnefs of the threads increafes the infleétion, infomuch that when the interval is about =5,th of an inch there will be no central image *. As the images are produced by an equal number of claffes of pencils parallel to each other, any motion of the cloth either parallel or perpendicular to its own plane before the objet glafs will not affe&t them, becaufe they come to the object- lens under the fame circumftances of parallelifm. But when the deflections were made by the cloth between the objeét-lens and its focus, the pofitions or diftance of the images were affeGed more or lefs upon the principle of the prifmatic micrometer. And, lafltly, the microfcope does not fhew this effect, becaufe the rays from the object, not being parallel, are not uniformly defleted, and have no virtual foci. I was well fatisfied at firft with this theory, and ftill think the greateft part will, upon further examination, prove to be well founded. But upon repeating the experi- ment with a piece of new cloth made of brafs wire about fifty-five threads in the inch, the wire itfelf being by eftimate about the ,1,th of an inch thick, other lights became vifi- ble, the caufe of which does not appear fo obvious. Befides the fquare, confifting of nine lights, there were others much fainter, more coloured, and elongated, as in Fig. r1. In order to difcern thefe to the greateft advantage, the fmall focal image of the fun was viewed in a concave metallic reflector of two inches focus, by means of the achromatic perfpective before mentioned, at the diftance of nine feet, with a power of only eight +. All the images, except that in the centre, were coloured fpeétra, extremely brilliant and beautiful ; the original nine, however, ftill retaining their pre-eminence. They were fainter and more elongated, the more remote from the centre to which they all pointed; that is to fay, an ima- ginary line drawn through the middle of all the colours of any one of the {pectra, would have interfected the central colourlefs fun. Neverthelefs their arrangement with regard to each other was not radial, but in lines forming prolongations of the fides of the middle fquare, as in the figure of the cloth: thefe lines were parallel to the threads. ‘The interval be- tween each range of images, meafured from the centre, was greater the farther off, but not regularly increafing ; thofe near the middle fquare being almoft equal. Seven ranges were counted beyond the fquare on each fide, anda very long triple line of whitifh faint light extended ftill farther. There were alfo a great number of much fainter images irregularly feattered in the angular {paces between the crofs, all pointing to the centre, and pro- duced, as I conje€tured, by irregularities in the cloth. As the diftance of the cloth before the object-glafs did not affeét the pencils of light, it readily occurred, that by inclining its plane to the axis of vifion in fuch a manner as that one fet of the wires might ftill remain perpendicular to that axis, the other fet would apparently crowd together, and diminifh the openings through which the rays were to pafs. In thismanner the cloth might be made, in effect, of any required finenefs. When the crofs wire or weft of the cloth was inclined to the axis, that part of the crofs in Fig. 11 which correfponded with the direétion of the inclined wires, had the intervals of its fpeétra enlarged, at the fame time that they became broader and more coloured, but fainter, and in particular the central colourlefs image nearly vanifhed. I have no doubt * Newton's Optics, III. obf. 6. + This was for the fake of light, as the chamber was not darkened. The objeét-glafs of 9 inches focus and 1 inch aperture bears a magnifying power of fifty, without producing any colour. but 16 New EleGrical Infirument. but it would have difappeared totally, if the want of perfect Aatnefs in the cloth had not prevented its being inclined beyond a certain angle with regularity. The branches of the crofs at right angles-to the inclined wires alfo nearly vanifhed. But when the warp or longitudinal wires were inclined to the axis of vifion, the images were altered in their relative brightnefs and pofition, ina manner which it would be too prolix to relate. Thefe changes terminated in an hexagon with fix radii, as in Fig. 12. when the inclination was about 45 degrees. In this, a8 in all the changes, the {pe€tra were co» loured with the red fartheft from the centre, and they all pointed to the centre. This unexpeted appearance led to an examination of the cloth by a fimple magnifier in both pofitions of inclination, when it was found, that in the firft deferibed pofition the inters ftices of the wires appeared to be nearly long fquares, or parallelograms; but in this laft defcribed pofition the threads of the warp being in reality bended by the operation of weav- ing over the weft, in angles of about 35° out of the plane, did apparently meet, fo as to leave apertures of the form of equiangular triangles, and no doubt caufed the hexagonal combination in Fig. 12. After this imperfeét defcription of a phenomenon of fome curiofity, I muft decline en- tering into any difcuffion of the confequences to which it feems to lead. Sir Maac New- ton’s Experiments on Inflection, with the edges of two knives, are fimple, and at firft con- fideration do not appear difficult to be underftood. Yet, fimple as they are, there are cer- tainly many variations yet to be made, and admeafurements to be taken, before the popular explanations of the mutual agency of bodies and light upon each other can be admitted without hefitation. This precefs of examination affords fome peculiar facilities, on account of the great quantity of light which is fimilarly affeéted, and the pofhbility of applying a magnifying power and-micrometer. Subfequent meditation may perhaps fuggeft the caufe why the radii in thefe figures are triple, and parallel to each other, while all the fpectra indi+ vidually diverge from a centre : but | have rather chofen-to refer them as they are to the ex» amination of philofophers. And I am the more induced to hope that this examination will be made, when it is confidered, that the appearance prefents itfelf through any fine muflin or cambric to the naked eye, though ftill better with the opera-glafs or perfpectives, which are in the hands of every one, and that the wire-cloth of fine fieves or wine-ftrainers is a mas terial eafy to be procured. ee Il. Defeription of an Inflrument which renders the Eleétricity of the Atmofphere and other weak Charges very perceptible, without the Poffibility of an equivocal Refult. In the year 1787, when the electrical doubler engaged the attention of philofophers, for its aftonithing power of magnifying the minuteft quantity of fimple eleétricity, and the fubfe- quent difcovery of its fpontaneous electricity had greatly reduced its apparent utility, I had the pleafure of a converfation with the Reverend Abraham Bennet, of Wirkfworth, the inventor, who fhewed me his method of depriving this inftrument of much of its adhe- rent eleétricity, by working it for a time with all its partsin communication with the earth. But at the fame time he remarked, that if he were to make an inftrument in which this 7 electricity - New EleArical Inftrument. 17 eleétricity fhould be totally removed, he would have recourfe to a fimple multiplier, and not a doubler. I did not apprehend the contrivance from this flight defcription, which at my requeft, however, he readily extended, and convinced me of the full value of his in- vention. I then mentioned my intention to conftruét an inftrument on that principle, which foon afterwards I did. It was fhewn to Sir Jofeph Banks and his friends, at his houfe, nearly at the fame time, and in the fame year transferred to the celebrated Mr. van Marum of Harlem, who now poffefles it. From various other avocations, I was prevented from caufing any others.to be made. It isnot therefore wonderful that the fame thought fhould fince have occurred to fo great a mafter of the fubjeét as M. Cavallo, who in the third volume of his Eleétricity, publifhed in 1795, gives a defcription and engravings of an inftrument very different in form, but the fame in principle. The form I have given it, which is all the fhare I had in the contrivance, is more calculated for a fpeedy repetition of the”procefs than M. Cavallo’s: but his inftrument is much eafier to be made by one who is not profeflionally a workman. Mr. Bennet’s notion with regard to form was very differ- ent from either. Both inftruments have the property, that a fimple or {mall aggregate of eleétricity will not be multiplied unlefs its intenfity exceed that of the adherent electricity of the plates, fuppofed to be contrary; and both are capable of deftroying their own elec- tricity, and exhibiting unequivocally what they receive by communication, however weak it may naturally be, provided the fupply be kept up. They are both alfo limited as to the ‘extent of their multiplication; that is to fay, the effect will be denoted by a fixed number or multiplier, fo long as the neareft diftance of the plates continues unaltered. For ex- ample, if this number were 100, the inftrument would fhew no eleétricity which was lefs intenfe than the 73,th part of what the ele€trometer demanded to act upon it. This co- efficient is neverthelefs capable of being enlarged at pleafure, by adjufting the plates toa lefs diftance afunder. _ Fig. 8. reprefents a vertical fe€tion of the inftruments. A isa metallic vafe, having a long fteel axis which paffes through an hole in the ftand H at K, and refts on its pointed end in an adjuftable focket at C. The ufe of the vafe is, by its weight, to preferve, for a confi- derable time, the motion of fpinning which is given by the finger and thumb applied to the nob at the top of the inftrument. The fhaded parts D and E reprefent two circular plates of glafs nearly 15 inch in diameter. The upper plate is fixed to the vafe, and revolves with it ; the lower is fixed to the ftand. In the lower plate are inferted two metallic hooks, diame- trically oppofite each other, at Fand G, They are cemented into holes drilled in the edge of the glafs, which is near two-tenths of aninch thick. In the upper plate are inferted in the fame manner two fmall tails of the fine flatted wire ufed in making filver lace. Thefe tails are bended down fo as to ftrike the hooks in the revolution, but in all other pofitions. they remain freely inthe air without touching any part of the apparatus. At C isa {crew, which by raifing or lowering the vafe keeps the faces of the glafs plates from each other at whatever diftance may be required. The faces of the glafs plates which are oppofed to each other are coated with fegments of tin foil, as reprefented Fig. 9 and 10, the latter of which reprefents the upper plate. Each of the tails communicates with the tin foil coat- ing to which it is contiguous, as does alfo the hook F with that coating of the lower plate neareft to it. But the hook G is entirely infulated from the whole apparatus, and is in- tended to communicate only with the eleérified body or atmofpherical conductor L. Vou. I.—Aprin 1797- D The 18 EleAvical Inflrument.—Printing. The lower coating neare{t to G is made to communicate permanently with the ftand H, and confequently with the earth. In this Gtuation, fappofe the motion of {pinning to be given to the apparatus, and the ef- fe€ts will be thefe :—One of the tails will ttrike the hook G, by which means the upper coating annexed to that tail will aflume the eleric ftate of L by communication. But this ftate, on account of the proximity of the lower uninfulated plate to which it is, at that inftant, direétly oppofed, will be as much ftronger than that of L, as a charge exceeds fimple eleétrization. The tail G with its plate or coating proceeds onward, and after half a revo- lution arrives at the fituation to touch the hook F. The upper coating, the lower on the fide of F, the hook F itfelf, and the tail V, muft then conftitute one jointly infulated metallic mafs, in which no charge fubfifts, but which is fimply eleétrified by the whole charge received at G. And of this mafs the furfaces of the plates themfelves, conftituting the eleétric well of Franklin, will throw out all their electricity to the hook and tail. But the coating and its tail inftantly pafs round, leaving F eleétrified, and proceed to bring another charge from G and depofit it as before. The balls at F are therefore very fpeedily made to diverge. It is fearcely neceffary to remark, that the two upper coatings do nothing more than double the fpeed of the operation; one of the tails being employed in colleéting, while the other is depofiting: and that the gold leaf eleGtrometer may be ad~ vantageoufly fubftituted for the cork-balls. The inftrument I caufed to be made was five inches high. The receiving fide G was conneéted with a coated jar of four fquare feet coating, and the giving fide F was con- neéted with Bennet’s gold leaf ele€trometer. The ele€trometer was rendered as ftrongly pofitive as it was capable of being, and the jar was rendered negative, by giving it as much of that power as was produced by drawing a common ftick of fealing-wax once through the hand. In this ftate the jar was incapable of attraCting the fineft thread. ‘The vafe was then made to fpin; and the effet was, that the leaves of the electrometer firft gradually collapfed, and then in the fame manner gradually opened, and ftruck the fides of the glafs of the eleCtrometer with negative electricity. The experiment was re~ newed and repeated with every requifite variation. IV. Obfervations on the Art of Printing Books and Piece Goods by the Aétion of Cylinders. —— Experte credite, W E may conceive three ways of delineating figures, or writing. The firft and moft ancient confifts in making the traces fucceflively by a brufh, a pen, or other inftrument. This is defign, painting, or writing. In the latter methods, either the whole or the greater part of the figures are made by the action or preffure of an original pattern againft the material intended to be written or painted upon. It is the art of printing. The colouring matter is either depofited from the face of prominent parts of the original form, which is ufually called a block or type; or elfe it is prefled from cavities cut in the face of the original, which in this cafe is called an engraved plate. Molt books are printed Various Methods of Printing. 19 printed from original patterns, in relief; and moft of the imitations of paintings are per- formed by means of engravings. Thefe arts are moft frequently diftinguifhed by the names of letter-prefs and copper-plate printing. i Tt can fearcely be matter of new information to thofe who are but moderately acquainted with the ftate of the Arts, to be told that letter-prefs or book-printing is performed by an aflemblage of fingle metallic letters, called types, made of lead hardened by an addition of antimony in the metallic ftate ; that thefe letters are compofed in the form of book pages, and wedged together in iron frames called chafes; that the ink is a compofition of linfeed oil and lamp black, of fo fingular a nature, that it will adhere to a ball covered witha pelt or fheep’s {kin foaked in water, and kneaded to extreme foftnefs under the feet, but quits this fkin with great readinefs to apply to the face of the letter when dabbed with the ball; and {till more, that it almoft totally quits the letter to adhere to paper rendered femi- tranfparent by foaking in water ; or laftly, that the paper is applied and preffed againft the form of compofed letter by means of a flat piece of wood urged downwards by a fcrew. Thefe and numerous early difcovered principles of this moft ufeful art are generally known, and require no more than mere recapitulation in this place. The genius of the Chinefe language not permitting that people to analyfe its founds into an alphabet, as has been done by moft other nations, has induced them to retain thofe figns of things, and of their correfpondent words, which probably conftituted the firft picture or hieroglyphic writings of every rude fociety. Changed and complicated as thefe may,have become by the rapidity of tranfcription, the corruption of ignorance, or whatever other caufes may have operated through a long {ucceffion of ages, they {till for the moft part ufe words that properly denote things, and not founds. Such words cannot, therefore, be fub- divided ; and it has accordingly been found moft convenient, by thefe firft poffeffors of the art, to print from entire blocks, as was alfo done by the firft printers in Europe. But our artifts foon difcovered that a few of the fimpleft chara€iers, namely, the letters of the al- phabet, would be in many refpects more ufeful, as the elements for compofing blocks for printers, than a number of blocks originally cut for every page of every individual book. Book-printing, therefore, though in fact of the fame nature as block-printing, has been ' carried into effect by very different machinery from that made ufe of in the arts which ftill retain the latter method. In book-printing, the heavy metallic form lies on a kind of table, and the colour and the paper are fucceflively applied to its face: but in block-print- ing, the block is carried and applied to the colour, and afterwards to the work intended to be printed. Thus, for example, in the printing of paper-hangings, the colour is {pread with a brufh upon a woollen cloth ftretched over a furface of parchment or {kin evenly fupported by a half fluid mafs of water and mafhed paper. To this the block is carefully applied by a flight perpendicular ftroke or two; after which it is applied to the dry paper on a table, and preffed againft it either by one or more blows witha mallet, or by the regu- lar a€tion of a lever. The mechanical part of callico-printing is effected nearly in the fame manner; but with fmaller blocks, becaufe of the greater difficulty of making the fucceffive fittings on fo flexible a material. And in both thefe arts, as. well as in book-printing, in red and black, the variety of colours are produced by repeated applications of forms or blocks, of which the prominent parts are made to fit each other according to the nature of the defign. D2 In * 20 Printing Proceffts.—Inventions. In the art of printing from copper-plates, a colour fomewhat more fluid than for book- — printing is made ule of. It is preffed into the cavities of the plate by {mearing it over the furface; and by fubfequent careful wiping the redundant colour is cleared away. In this ftate, if foaked paper, for which purpofe the moft fpongy texture is the beft, be ftrongly preffed againft the plate, by pafling both together between two cylinders of metal, or hard wood, properly defended by woollen cloth, the greateft part of the colour adheres to the paper, and forms what is called a print. In all thefe proceffes, it is eafily feen, that in the fucceffive applications of colour, the ac- curate filling of the form or original with the material intended to receive the impreflion, and in various other parts of the manipulation, there is much room for the difplay of {kill, or for injury from the want of it. It may moreover be collected, that the motions attendant on the various fteps of manufacture are in many inftances difficult to be performed with rapidity and eafe, until by long continued habit the workman himfelf is converted as it were into amachine. A very flight degree of attention to this fubject mufl alfo fhew that, if the originals were of a cylindric form, with a contrivance for regularly applying the colour and performing the fubfequent operations, it would be eafy to print books and piece-goods with a degree of rapidity and uniformity, of which the ufual method of fuc- ceflive applications feems fcarcely capable without uncommon care and {kill. This obvious conclufion has no doubt led to numerous experiments; none of which, as far as I can gather, whatever may have been their particular utility, have given much promife to fuper- fede the ordinary methods. But as the increafed demand for the manufacture of printed goods has rendered fuch an improvement an interefting object to manufacturers, as well as to thofe indefatigable artifts who have directed their efforts towards improvements; and as the latter generally take up a new objet under a ftrong perfuafion that it has not before been purfued by others, it will certainly be of advantage to thefe deferving claffes of men), torelate a few of the difficulties of this new art. The difficulties attendant on any improvement in the arts may be confidered either as moral or phyfical. Under the moral, I would clafs every thing that relates to the prejudices. of men in favour of the old methods, and their fears of rifk, together with the ceconomi- cal and commercial inconveniencies attending the new procefles. The phyfical difficulties are fuch as attend the actual performance of any projet after the fame has been carefully arranged in the mind of the inventor. It happens unfortunately here alfo that the inventor is feldom aware of the moral impediments, but almoft always concludes, that if he can f{ucceed in accomplifhing the purpofe he has in view, his cares and labour will then be at anend; and that the manufacturer, in particular, inflead of pointing out new impediments difcernible only from long continued experience, will more readily embrace and approve of the new procefles, in confequence of his fuperior knowledge of their intrinfic value. Every good invention appears fimple in the profpect, but it fcarcely ever happens in the execution that the moft direct road is taken; and in every cafe there will infallibly be many things unknown or unforefeen, which praétice only can point out as neceffary to be done for the complete accomplifhment of the objectin view. Hence, and likewife becaufe few men poffefled of independent fortune are likely to engage or perfevere in a labour of this kind, it almoft invariably happens that the expences exceed the ability of the inventor him- felf. For thefe and other reafons, new undertakings are generally brought forward by the inventor, Moral and Phyfical Obftacles to Improvements. 21 inventor, a man flrongly prejudiced in favour of his leading purfuit, together with a moneyed friend, who hopes fpeedily to increafe his capital from the abilities of the other. It is not neceffary in this place to defcribe the ufual confequences of a partnerfhip, where the minds, the views, and the circumftances of both individuals are fo very different, and which may be modified ftill more effentially if either of the parties be deficient in the common principles required to bind men to each other. It is certainly of the higheft im- portance to both, that the circumftances of fuch conneétions fhould be very maturely weighed before they are entered into. The commercial difficulties or facilities attending any invention are alfo of great confequence. Every inventor ought to enquire, not only what has been done before, but likewife into the prefent ftate of the manufaCture he means to improve. In this way it is afcertained how fmall a part the mere prefs-work conftitutes in the price of a book. He will find that twelve yards of paper-hangings are printed for one penny, ina fingle colour, by hand, which afterwards by the accumulation of price, in paper, colour, duty, and ordinary profit, are fold for three fhillings; none of which the inventor can pretend to dimi- nifh: and if he could annihilate the whole labour, his advantage would therefore be lefs than three per cent. without reckoning the coft and operation of his machinery. In the callico-printing, with a more expenfive material, dyeing and field proceffes, duty and pro- fits of manufaéturer and vender, the price of laying the block will turn out to be an objeét ftill lefs confiderable. Again: it will be feen that {mall flat blocks coft but little money, ix comparifon with cylinders of fufficient diameter to retain their figure, and long enough to. apply to the whole breadth of the cloth. Under thefe and other fimilar points of view, the inventor, who may confider the fubject in a fuperficial manner, would be ready to abandon his undertaking. But this again ought not to be rafhly done. It is true, that where the great force of capital is employed on ob- jects not comprehended within his projeét, the faving, however large in its abfolute amount, or defirable to a manufaturer, will fcarcely come within the reach of the inventor by any bargain he can make fhort of an actual partnerfhip. But it may be poflible to feparate the ref{pective departments of a manufactory. A fpinner is not neceflarily a weaver, nor a printer a linen-draper or a dealer in paper-hangings. The feveral departments of manufac- ture and commerce are, generally fpeaking, in the hands of acute men, who feldom reafon ill with regard to the advancement of their peculiar interefts; and thefe departments are continually flu€tuating in their arrangement, as convenience, profit, or the accumulation of capital may lead. Experiments are for ever on foot, from day-work to piece-work, and from piece-work to the employ of mafter-workmen with others under them, all fupported, by the capital of the large manufacturer, who himfelf in many inftances is the mere in- ftrument maintained by the advances or acceptances of the warehoufeman, the factor, or the merchant. Aninventor who has not capital may feek for employ on the goods or the capital of others ; and if he has {kill to maintain his ground againft the numerous enter- prifes which the aétivity of oppofite interefts will raife again{ft him, he will find that the old order of things will readily alter, as foon as an evident intereft in favour of the new is. fhewn by aétual and continued proofs in the market. Moft of the phyfical difficulties'attendant on any new procefs are fuch as experience only can fhew. Thus, in the forging of iron by the preflure of rollers inftead of ham- mers, 22 Experimental Refults and Obfervations mers, a feheme upon which many thoufands of pounds have been expended in this coun- try, it was apprehended that the more impure parts, which are alfo the moft fluid, might be prefied out by the action of cylinders, with equal or perhaps more advantage than by that of hammers; at the fame time that the determinate figure of bars of any required fize might be given without {kill in the operator. Experience neverthelefs has fhewn, that the more fluid part is driven out much more effectually by the fudden action of a blow, than by the flower compreffion of a cylinder, which allows time for much of the fluid matter to extend itfelf within the mafs. Various fimilar effeéts prefent themfelves when.cylinders for printing are fubftituted inftead of planes. Inftead of the action of dabbing, the colour is ufuallyapplied by fimple and gradual contaét, to much lefs effect ; and the impreffion, though not effentially different from that of the block, is performed by a gradual action, which affords time for the cloth or paper to fold itfelf in a minute degree into the cavities of the fculpture. Hence it is found that the length of paper or cloth printed from a cylinder by a definite number of revolutions, will be greater or lefs than another piece manufaétured precifely in the fame way, but with a lefs or greater degree of preffure. Ina block this defect is much lefs, not only from the confiderable hold it takes upon the furface of the material, but alfo becaufe the error is rectified at every fucceflive application. One of the chief difficulties of cylinder printing confifts, there- fore, in the difficulty of laying one colour after another ; and this would continue to be fo cven if the materials were not fufceptible of change, the contrary to which is the fact. There are two projeéts for obviating this. The one confifts in confining the whole piece to a long table, or to the circumference of alarge cylinder, and caufing the printing cylin- der to move, not by the fucceflive appofition of its carved furface, but of a bearing face regulated by a toothed wheel. ‘The other method confifts in the ufe of a frame to confine two or more cylinders, each provided with its own toothed wheel, and revolving againft a large clothed cylinder provided with a fuitable wheel to drive the others. The piece is caufed to pafs between the large cylinder and the others, in order to receive the impreffion Wich regard to the firft of thefe methods, it does not appear eafy to confine paper, and ftid Jefs cloth, in fuch a manner that its parts may continue without fhift or wrinkle during the aétion of a cylinder, which not being allowed to roll without the check of a wheel, muft draw the furface either the one way or the other. The difficulty of confinement will be very much increafed, by the indifpenfable requifite that the paper fhould be afterwards hung up to dry, and the callico be carried to the dye-houfe and the bleach-field, between the fucceflive impreflions, by which means the dimenfions of both will be greatly altered. In the fecond method, it is obfervable that no colours’ can be printed but fuch as fall clear of each other. In this way, moreover, the gathering action of the cylinders may prove very mifchievous. For, if we fuppofe the paper or cloth to pafs between the great cylinder and the firft printing roller by an aétion of the latter which tends to make it flip forward on the face of the great cylinder, and that when it arrives at the fecond printing roller it there experiences an action of a contrary nature, the confequence will be, that the material will become flack between the two rollers, and the fittings will be falfe. Not to dwell on that experience which brings forward this obftacle among others, its great probability may be deduced from the allowable fuppofition that the circumference of the firft printing cylinder fhould be one thoufandth part of an inch too large, and that of the fecond the fame quantity 4 too concerning the Art of Printing by Cylinders. 23 too fmall. For in this cafe the material will be fhifted one-twentieth of an inch in fifty turns by the firft cylinder, and the fame quantity in the contrary dire€tion by the fecond ; a quantity upon the whole quite fufficient to deftroy the effe(l of the colours in the pro- grefs of one fingle picce. Such minute differences can hardly be avoided in the firft in- ftance ; in addition to which we may place the varying dimenfions of the printing cylinder, if not made of metal ; and of the great clothed cylinder, which in effet has a larger or {maller diameter in proportion to the preffure which operates to render its elaftic covering either thicker or thinner. The only method of diminifhing thefe evils feems to be, that all the printing. cylinders fhould by dimenfion or preflure, or both, be made to draw the fame way, the outer cylinder moft, and the others gradually lefs and lefs, fo that the material fhould have a tendency to apply itfelf more tightly during its paflage through the apparatus. The application of the colour to the furface of a cylinder block is attended with fome difficulty. An ingenious mechanic may contrive various means to produce the action of dabbing, if required. When a fluffed cylinder covered with cloth is made to revolve in the colour, and thence after pafling a fcraper to apply itfelf to the block cylinder, it is found to be no inconfiderable difficulty that its dimenfions change, and its covering becomes wrinkled by the action of the fcraper as well as that of the block. A better method, therefore, confifts in a revolving web of woollen cloth, like a jack-towel, ftretched over three horizontal cylinders parallel to each other, two of which fupport the elaftic furface of the web, which in its revolution accompanies the block cylinder, and the other ferves to guide the fame web to the colour, or a cylinder revolving in: it. This method would be very eafy and pleafant in its operation, if it were not’ for a property common to all {traps which revolve on the furface of two or more wheels. 'Thefe are obferved always to feek the higheft place; fo that if a cutler’s wheel’ were made with a groove to carry a ftrap, inftead of a round edge, the ftrap would infallibly mount the ledge, inftead of re~ maining in the groove*. On this principle, the web would very {peedily fhift itfelf to one end of the cylinders, if it were not confined fideways, or the lower roller were not made confiderably thickeft in the middle, and gradually tapering towards its extremities. This laft imple expedient is not without its difficulties 3 but asI have not actually tried it, I fhall defer entering into-any difcuffion on that head. The running of the paper or piece-goods towards one end of the leading cylinder is alfo one of the greateft difficulties attending this method of printing. It is not perfe@ly removed by tapering the leading cylinders. The nature of the trade of paper-ftaining in this country, which requires a large fum to be immediately vefted in the payment of the excife duty, and confequently prevents any confi- derable ftock from being manufa@ured until orders are a€tually received, and the varying fafhions in printed callicoes, which render the expence of cutting the block by far the hea- vieft part of the difburfement for printing, are probably the chief reafons why manufac- turers in this country have been lefs folicitous for the conftru€tion of machines calculated to afford profit only in the cafe of very numerous impreffions. The phyfical difficulties of this art haye likewife confpired, in no fmall degree, to prevent its having been applied in the large way to any but a few fimple defigns of the fort called running patterns in one colour. * This curious effeét arifes froma flexure produced in the edge of the ftrap, by the elevated part of the wheel, which throws the advancing part af the ftrap more and more towards that elevation, It cannot be explained in afew words, but may eafily be feen by wrapping a firaight flip of paper round an extinguifher or any other cone. An 24 Diamonds of Brazil. a7 Vy din Account of the Diamonds of Brazil. By M. D'ANDRADA. As the Society * is defirous of an account of the Diamonds of Brazil, I thal! endeavour to fatisfy them to the utmoft of my power; but previous to a defcription of their form, the place where they are found, and the manner of fearching for them, I think it will be ufeful to convey an idea of the country in which thefe diamonds are found. The province of Brazil which produces diamonds is fituated inland between 224 and 16 degrees of fouth latitude. Its circumference is near 670 leagues. On the eaft it is limited by the captainry or province of Rio Janeiro; on the fouth, by that of St. Paul; on the north, by the Sertcens, or interior part of the maritime province of the bay of All Saints, and part of that of the mines of Goyarel; on the weft, laftly, by another part of the laft-mentioned province, and by thofe deferts and forefts which are inhabited by the favages, and extend to the frontiers of Paraguay. On the fide neareft St. Paul there are vaft uncultivated plains; the interior is divided by chains of mountains and hills, with fuperb valleys and luxuriant fertile plains. It abounds with wood, and is watered by a great number of rivers and brooks,. that facilitate the working of the mines of gold, which is obtained by wafhing in fpangles from the river fands, or in veins open to the day. This province is divided into four comarcas or diftris, which, reckoning from north to fouth, are Santo Foao del Rei, Villa Rica, Sabara and Sero Do/rio, or cold moun- tain, called in the language of the favages Yritauray. The diamonds are found in this laft diftriét. The whole province is very rich in the ores of iron, antimony, zinc, tin, filver and gold. The Paulifts and inhabitants of the ancient captainry of St. Vincent were the firft who difcovered thefe mines, and peopled in great part the whole of this rich province, as well as thofe of Mato Groff, Cuiaha, Goyares, and Rio grande de San Pedro. In a word, almoft the whole of the interior of Brazil, with its immenfe riches, would have been ftill unknown but for them. The metropolis at prefent enjoys the fruit of their eccentric activity and hazardous difcoyeries. Conftantly with their arms in their hands to defend themfelves againft the favages, in the midft of impenetrable forefts and folitary waftes, expofed for twelve years to famine and the inclemency of the feafons, they overcame every obftacle ; nothing could check their unconquerable fpirit. There is not a fingle mountain, brook, or mine, which has not been traverfed, difcovered, and vifited by them. Antonio Soary, a Paulift, who gave his name to one of thefe mountains, was the firft who difcovered and vifited the Sera Dofrio. Gold only was fought for, but at laft diamonds were difcovered in the Riacho Fundo, whence they were firft obtained, and afterwards in the Rio de Peire ; a great number were likewife obtained from the Gigwitignogna, a very rich ftream; and laitly, at the end of 1780 and beginning of 1781, a gang of near three thoufand inter- lopers, called Grimpeircs, difeovered diamonds, and obtained an immenfe quantity from the Terra de Santo Antonio: but they were forced to abandon this fpot to the Royal Farm, who took poffeflion of it. Then it was that the fufpicion was confirmed, that the moun- tains are the true matrix ef diamonds; but as the work in the beds of rivers and on their banks is lefs tedious, can be conduéted on a larger feale, and affords larger diamonds, the * The Society @ Natural Hiftory of Paris. This account is inferted in the Annales de Chimie, XV. 82» from which this trauflation is made, | Farm Diamonds of Brazil. 25 Farm abandoned the mountains, and formed great eftablifhments in the river of Toucan- birnen, which flows through:the valleys of this chain, and is near ninety leagues in length. It was found by examination and digging, that the whole furface of the ground, imme- diately beneath the vegetable fratum, contained more or lefs of diamonds, diffeminated and attached to a matrix ferruginous and compaét in various degrees, but never in veins, or in the divifions of geodes. : Attempts were made at firft to prohibit the working; but the aStivity of individuals who infringed the order of Government, and fent home diamonds by the fhipping from Brazil, under the denomination of oriental diamonds, induced Government to eftablifh a ‘ farm. The firft farmer was Rifberto Caldera, a Paulift, with the condition that no more than 600 negroes fhould be employed in this work. This condition has always been evaded ; for the number of flaves employed are from fix to eight thoufand: and this num- ber was fcarcely diminifhed when the Portuguefe Government, to put an end to this fraud and the depreciation in price of diamonds proportional to the quantity brought to market, caufed the undertaking to be carried on for its own account. But at prefent, from other confiderations, it is farmed again to individuals. Notwithftanding the great profits which enter the royal treafury, it is certain that the inhabitants of the province are greatly injured by it; becaufe the DiftriGt of Diamonds being continually enlarged, has condemned to deftruc- tive repofe immenfe tracts very rich in gold. Let us now proceed to the diamonds. The figure of the diamonds of Brazil varies. Some are oftahedral, formed by the union of twotetrahedral pyramids. This is the adamas offaédrus turbinatus of Wallerius, or the o€tahedral diamond of Romé de I’'Ifle. Thefe are almoft always found in the cruft of the mountains; others are nearly round, whether by a peculiar. cryftallization or by rolling. They refemble thofe oriental ftones which the Portuguefe and the natives of India call reboludos, which fignifies rolled. And laftly, others are oblong, and appear to me to be the adamas hexaédrus tabellatus of Wallerius. The two. laft are ufually found in the beds of rivers and broken places of their banks. Diamonds are alfo found, as 1 have remarked, in the cruft or external covering of moun- tains.. Thefe maffes are formed of a bed of ferruginous fand, with rolled flints, forming an ochreous pudding-ftone from the decompofition of emery and muddy iron-ore; it is called cafcalho, and the beds or ftrata taboleiros. Thefe taboleiros have different names, according to their fituation or their nature. When the ftratum is horizontal, and in the plane of the bed of the river, it is properly a taboleiro; but if it rifes in banks, it is called gopiara ; \aftly, if the pudding-ftohe contains much emery, it is then denominated taban- “hua cauga in Brazilian, that is to fay, black-ftone, or iron-ftone. In fome places the ca/calho is uncovered; in others, it lies beneath a kind of vegetable muddy earth, Aumus damafcena Linn. or beneath a reddith fat fand, which fometimes con- tains rounded flints. This happens in the returns of the mountains, or upon the banks of great torrents. This farid is called piferra. The bank or flratum beneath the ca/calho is either fhifkus rather fandy, or the folid bog-ore of iron. It is likewife in the cafca/bo that gold in fpangles and in pyrites is found; the former of which is in my opinion afforded by the decompofition of the auriferous pyriics. For the gold in veins has another form, Vor. IL—Aprit 1797. E and 26 Diamonds. — New Precefs of Tanning. and its matrix is either fat quartz or fine-grained tender cos, micaceous gneis, or the quart- zofe ore of iron, tophus ferreus Linn. The exploring of diamonds is performed by changing the beds of ftreams, in order that the fand or gravel may be wafhed, and the diamonds feleéted;, or by breaking the. ea/calko with large hammers, and afterwards wafhing it in troughs. ‘This wafhing differs from that of gold, becaufe it requires a fmall quantity of very clear water, and very little of the ca/ca/ho at a time; proportions which are precifely contrary to’ thofe required in wafhing gold. Black flaves are employed in this bufinefs, entirely naked excepting a cloth: round their middle, in order that they may not embezzle any of the diamonds ;, but in {pite of every precaution, and the vigilance of numerous infpeétors, they neverthelefs find means of concealing them, which they fell at a very low price, to the interlopers, for tobacco and rum. This is all the information I can with certainty ftate refpe€ting diamonds. I have only to remark, that other provinces likewife afford them ; as Cuiaba, and the diftriéts of Guara~ puara, in the province of St. Paul; but thefe parts are not explored. VI. Abftvad of the Specification of Mr. Wroerram Des MoNp’s new Method of Tanning ; with Obfervations relative to that Subjeé. Farry laft year * a patent was taken out by Mr. William Defmond for the method or procefs of tanning prattifed, as it is faid, with great fuccefs in France by Seguin. The fubftance of Mr. Defmond’s fpecification is as follows : The art of tanning confifts in impregnating fkins with a principle obtained from. tan, with which they form a compound, infoluble in water, and poflefling other qualities well known in the fubftance called leather. He obtains the tanning principle by digefting oak-bark, or other proper material, in cold water, in an apparatus nearly fimilar to that ufed in the falt- petre works. That is to fay, the water which has remained upon the powdered bark for a certain time, in one veffel, is drawn off by a cock, and poured upon frefh tan. This is again to be drawn off, and poured upon other frefh tan; and in this way the procefs is to be continued to the fifth veflel. The liquor is then highly coloured, and marks, as Mr. Defmond fays, from fix to eight degrees on the hydrometer for falts }. He calls this the tanning lixivium. The criterion to diftinguifh its prefence is, that it precipitates glue from its aqueous folution, and is alfo ufeful to examine how far other vegetable fubftances, as well as.oak-bark, may be fuitable to the purpofe of tanning. ‘The ftrong tanning liquor isto be kept by itfelf. It is found by trials with the glue, that the tanning. principle of the firft digefter which receives the clear water, is, of courfe, firft exhaufted. But the fame tan will ftill give a certain portion of the aftringent principle, or gallic lixivium, to Jan. 15, 1795. + Probably that of Baume, defcribed in his Elemens de Pharmacie. For the correfponding fpecific gravity jw the ufual form, {ee p. 39, 0f this Journal, water, New Proce/s of Tanning. 27 water. The prefence of this principle is afcertained by its ftriking a black colour when added toa {mall quantity of the folution of vitriol of iron or green copperas. As foon as the water from the digefter ceafes to exhibit this fign, the tan is exhaufted, and mutft be replaced with new. ‘The gallic lixivium is referved for the purpofe of taking the hair off from hides. Strong hides, after wafhing, cleaning, and flefhing, in the ufual-way, are to be immerfed. for two or three days in a mixture of gallic lixivium and one thoufandth part by meafure of denfe vitriolic acid*. By this means the hair is detached from the hides, fo that it may be fcraped off with around knife. When {welling or raifing is required, the hides are to be immerfed for ten or twelve hours in another vat filled with water and one five-hundredth part of the fame vitriolic acid. The hides being then repeatedly wafhed and dreffed, are ~ ready for tanning ; for which purpofe they are to be immerfed for fome hours in a weak tanning lixivium of only one or two degrees; to obtain which, the latter portions of the infufions are fet apart; or elfe fome of that which has been partly exhaufted by ufe in tanning. The hides are then to be put into a ftronger lixivium, where in a few’ days they will be brought to the fame degree of faturation with the liquor in which they are immerfed. The ftrength of the liquor will by this means be confiderably diminifhed, and mutt therefore be renewed. When the hides are by this means completely faturated, that is to fay, perfectly tanned, they are to be removed, and flowly dried in the fhade. Calf-fkins, goat-fkins, and the like, are to be fteeped in lime-water after the ufual flefh- ing and wafhing. Thefe.are to remain in the lime-water, which contains more lime than it can diffolye, and requires to be ftirred feveral times a-day. After two or three days, the fkins are to be removed, and perfeétly cleared of their lime by wafhing and prefling in water. The tanning procefs is then to be accomplifhed in the fame manner as for the ftrong hides, but the lixivium mult be confiderably weaker. Mr. Defmond remarks, that Jime is ufed inflead of the gallic lixivium for fuch hides as are required to have aclofe grain; becaufe the acid mixed with that lixivium always {wells the fkins more or lefs; but that it cannot with the fame convenience be ufed with thick fkins, on account of the -confiderable Jabour required to clear them of the lime, any part of which, if left, would render them harfh and liable to crack. He recommends, likewife, as the beft method to bring the whole furface of the hides in contaé with the lixivium, that they fhould be fufpended yer- tically in the fluid by means of tranfverle rods or bars, at fuch a diftance as not to touch each other. By this practice much of the labour of turning and handling may be faved. Mr. Defmond concludes his fpecification by obferving that in fome cafes it will be ex- pedient to mix frefh tan with the lixivium; and that various modifications of ftrength and other circumftances will prefent themfelves to the operator, He affirms that, in addition to the great faving of time and labour in this method, the leather, being more completely tanned, will weigh heavier, wear better, and be lefs fufceptible of moiflure than leather tanned in the ufual way; that cords, ropes, and cables, made of hemp or {peartery, im- pregnated with the tanning principle will fupport much greater weights without br eaking, be lefs liable to be worn out by friction, and will run more {moothly on pulleys; infomuch that, in his opinion, it will render the ufe of tar in many cafes, particularly in the rigging of thips, unneceflary ; and, laftly, that it may be fubftituted for the prefervation of animal food unftead of falt. * Marking 66 degrees on the hydrometer for acide. Sp. gr, 1.848 of Baumeé. E2 The 28 Experiments and Objervations on Tanning. The intelligent manufaturer will readily perceive that this new method is grounded on two particular circum{tances, befides a more fcientific management of the general procefs than has been ufual. The firft confiftsin the method of determining the prefence and quantity of the tanning principle, by the hydrometer and the precipitation of glue: the fecond, in applying this principle in a concentrated flate, more early in point of time than has, perhaps, been hitherto done. Our tanners, after the common previous procefles and unhairing by acids, by lime, or by piling the hides that they may heat and begin to pu- trefy, apply the folution of tan, which they call ouze, in a great number of pits in the tan- yard. They begin with the weakeft folution, which has been ufed, and is of a lighter colour than the other. And they pafs the hides, according to their judgment and experience, into- ouzes which are ftronger and ftronger, until at laft, in certain cafes, the hides come to be buried for acertain time in a folid mafs of tan or oak-bark. The oak-bark itfelf, in the pits, is not only. the fource from which the water extracts the tanning principle ; but feems, likewife, in fome meafure, during the laft ftages of the procefs, to operate mechanically by keeping the furfaces of the hides from touching each other. On the occafion of this apparently important difcovery, I applied to one of the firft manu- faéturing houfes in the Borough of Southwark, to make enquiries concerning its value. One of the partners, who appeared to have paid confiderable attention to the procefles of his manufactory, informed me, that the {trong folution obtained from tan had_been well known: to them for fome years under the name of effence of tan; and that it had been’ propofed to’ ufe it as the means of bringing out the complete leather ina fhort time. I afked whether the objection to its ufe might confift in the outer part of the fkin becoming more per- feQlly tanned in a fhort time than the inner part; fo as-to defend this laft from the fub-- fequent change that might have taken place by a flower operation. He anfwered, that this- was partly the reafon why it was neceflary that the ouzes fhould be gradually applied from the loweft to the higheft ffrength. But the chief reafon he urged in favour of the flow pro- cefs was, that the hides were found to feed and improve in their quality by remaining in the pit. Lcould not gain-fatisfatory information what the nature of this feedingand improvement might be. The fact, as loofely ftated, appeared to be, that the fkin became much thicker, denfer,. and heavier in: the firft ouzes during a certain time; and that thefe advantages of thicknefs, denfity, and weight continued to exift in a certain degree to the very end of the entire procefs. For, as he remarked,. they know very well that, by bringing the fkins. more haftily into the flronger ouzes, they will be fooner converted into leather; and that: a skin which ordinarily requires fifteen months, might be tanned.in-nine. But then, added. he, the fkin which comes forward in nine months, from its thinnefs, and other inferior qualities, will afford ninepenny foles forfhoes; whereas, if it had undergone the longer pro-- cefs, the foles would have been worth a fhilling :—a.difference which largely repays the common intereft of capital for the excefs of time. On the other hand it may be remarked, that refults of this nature require to be grounded on experiments carefully undertaken, under circumftances differing only with regard to the object of inveftigation, and often repeated. It does not-appear from my enquiries that this- has actually been the cafe; and I have been informed that excellent leather has been pro- duced in the new method. But I have heard nothing of its appearance in the market, though upwards.of a year has elapfed fince this patent was-fealed. A very Defeription of a New Hydroftatic Prefs. 29 A very full and circumftantial account of this procefs, which Mr. Defmond affirms he received from a certain learned foreigner, was inferted in the Moniteur, and thence tranflated and publifhed in the Englith Courier fome time in the month of Auguft 1795. VIL. Déefeription and Account of a New Prefs operating by the Action of Water, on the Principle of the Fydroftatic Paradox. Invented by FosEpPH BramaH, Engineer. F, G. 1, Plate I, is a front fection of a common prefs for books and papers, and the like. Fig. 2 exhibits a perfpective view of the fame inftrument on that fide to which the pump is fixed. The letters diftinguifh the fame parts in both. ABCD is the frame. 1 is a ftrong metallic cylinder, in which the rammer or pifton EF moves. To the upper part of this pifton is applied an iron table, by the motion of which upwards the preffure is communi- cated to the articles H. QR reprefents a {mall ciftern, containing water. Within this ciftern is fixed a fmall forcing pump, of which K is the barrel, L the pifton, M a fide valve formed of metal, and opening inwards beneath the piflon. ‘The nature and effeét of this valve may be eafily underftood from the figure. It confifts of a metallic rod, at one end of which there is a nob turned conical next the ftem, fo as accurately to fit the conical face of the hole into which it 1s put. The tail is filed on one fide, fo that it does not entirely fill the cylindrical hole which it occupies; by which means a paflage is afforded for water when the head of the valve is raifed. In the ftate of ination, the valve is kept fhut by the operation of a fpiral fpring at the other end of the tail. N is another valve of the fame kind opening downwards. O reprefents the rod of the pifton, with a contrivance for keeping a ver- tical pofition during the working. The effe& of this contrivance will be underftood without difficulty by comparing the two drawings.. S is the lever or handle for working the engine. Ts action is as follows: When the handle S is raifed, it brmgs up the pifton L, which would leave a vacuum beneatii if the preffure of the atmofphere did not force the water in through the fide valve M. The lever is then to be prefled down, which caufes the fide valve to fhut, and forces the water through the bottom valve N, whence it paffes through the pipe P into the cavity F of the' great cylinder I, and raifes the pifton or prefling rammer. A repetition of the fame procefs forces more water in, and the preffure may in this manner be carried to-a great extent. When it is propofed to relieve the aétion, the lever S mutt be prefled down, which, by the mechanical conta& of the lower extremity of the pifton L againft the tail of the lower valve N, keeps that valve open. In this fituation, the lever TU is to be prefled towards R, and will open the vaive M. Both valves being in this manner opened at once, the paflage between the internal part of the great cylinder and the ciftern QR becomes free, and confequently the table G and the rammer EF defcend by | their own weight, and reftore the engine to its original fituation. There is no difficulty in computing the force of this inftrument. If the diameter of the barrel K be one quarter of an inch, and that of I one inch, that is to fay, four quarters of an inch; one pound lodged upon the pifton-rod W will be in equilibrio with fixteen pounds lodged upon the table G; the weights of the parts. of the engine attached to, and moving with, each pifton, being refpectively included. And if the length of the lever SY be fifteen inches, and the diftance XY between the centres of motion and of ation be 6 two 30 Experiments and Obfervations. on two inches, one pound at the end of 5 will gain an advantage of 74 times when compared with that at W. Inftead, therefore, of fixteen pounds upon the table G being equal in cite to counterpoife this lait ation, there will be required upwards of 120 pounds. But a man, in this action of pumping by a downward preflure, can without difficulty apply his whole weight, and with great cafe one third or one fourth of his weight, fuppofe 50 pounds. In this cafe the preflure will be equivalent to fifty times 120 pounds, or 6000 pounds, that is to fay, nearly three tons. To compare this engine with a ferew, in theory, we muft enquire what finenefs of thread and length of lever would afford a purchafe of 120 to one, Let us fuppofe the thread of a fcrew, fubftituied in the place of the barrel I, to be one tenth of an inch thick ; the diftance from the top of one thread to the top of the next will in this cafe be one fifth of aninch. ‘his is the fpace through which the weight muft rife in one revolution. The power muft therefore move through 120 times that fpace, namely twenty-five inches; but a lever or radius four inches long will defcribe a circle fomewhat larger than this, and confequently fuch an engine would in theory be equal in power to the hydraulic engine we have beea contemplating. But when the fubject is viewed practically, the difference between the two engines ap- pears to be very remarkable, All practical men know how very large a- part of the force operating by. means of engines is employed in overcoming frictions. Every one is aware of the extreme fri€tion between folids, and the very flight friction which takes place between the parts of fluids. his is feen in the common expedient of oiling the pivots of wheels, and in the very gradual decay of motion in fluid bodies ; while folids moving on cach other ftop at once, as foon as the force is diminifhed to a certain degree. ‘The fcrew is an organ peculiarly liable to frition, and this fri€tion is always much greater than the whole of the reaéting force ; for there are few inftances where a fcrew will return from ex- treme preflure, when the agency upon the lever is withdrawn. It is alfo to be confidered, that the whole force of the weight or refiftance aéts dire€tly upon the face of the fcrew, at which the motion is required to take place. It has not been appretiated in what degree this refiftance or frition increafes with the weight. In lighter a€tions the fimple ratio has been inferred ; but under more fevere preflures the two metallic faces extrude the greater part of the half-fluid matter between them, and appear by the magnitude of their refiftance to be attached to each other by a procefs of the nature of cohefive attraction. For thefe and other reafons, it appears nearly impracticable to form any comparifon between two engines fo different in principle, but fuch as fhall be deduced from immediate experiment of their effects. 1 am not in poffeffion of numerical data to indicate the actual power of {crew-engines or prefles; which are perhaps the lefs neceflary, becaufe thofe who are the moft interefted in the fuccefs of an improvement like the prefent, are for the moft part able to come at thefe without difficulty. J intend, befides, to make thefe the fubjeét of a future communication. The effeéts which I obferved were thefe. A machine of the new conftruction here defcribed, was employed to prefs fome papers. The force applied to the lever was fo flight, that the inftrument required no faftening to the table on which it ftood: but the effect on the upper bar, A B, which was 34 inches thick, was fuch as bended it out of a ftraight line upwards of a quarter of an inch, and I apprehend that it might have eafily been broken by continuing the preffure. With a ferew- 4 prefs, a New Hydroftatic Profs. 31 prefs, the ferew of which was iron, and nearly of the dimenfions before mentioned, except- ing that the lever was twelve inches long inftead of four inches, and the aétion on the lever upwards of two hundred weight, applied with a jerk, the effe@ was nearly the fame. Here I fhould eflimate the advantage to be very much in favour of the hydraulic engine. In another engine of this kind, the diameter of the great pifton was four inches, and of the fmaller three-eighths of an inch ; and the advantage given by the lever or handle was twelve to one. Above the pifton of the great cylinder was applied a long lever, at one end of which was an axis, and at the other end a large {cale to hold weights: it contained twenty hundred weight. The diftance between the axis of motion of this lever and the part where it acted on the pifton was fix inches; and the diftanee from the fame axis to the extremity where the fcale was hung, was 126inches. Every hundred weight in the fcale confequently prefled upon the pifton witha force equal to\twenty-one hundred weight ; whence the whole preflure was twenty-one tons. It was eafy to work the lever brifkly with one hand, and each ftroke raifed the feale near one-third of an inch. Forty-feven pounds hung at the end of the lever, carried it down with a moderate fwiftnefs of working; but a weight of only -forty- three pounds remained in equilibrio, and did not defcend. Now, as the true weight in theory was thirty-two pounds, as deduced from the action of the parts in the manner al- ready done with regard to the {mall machine, it follows that lefs than one-third of the a€tual power was employed to give velocity and overcome all friction. It may be remarked, that the principal fri@ions in thefe machines mutt be at the circum- ferences of the piftons, and that thefe do not imcreafe in the fimple, but in lefs than the fub-duplicate ratio of the power. For if the diameter of the great cylinder were double, every thing elfe remaining unchanged, the furface of its pifton, and confequently the power; would be quadrupled. But the frition would be only doubled, and that merely at the lea- thering of the greater pifton. As the preflure in the experiment latt mentioned amounted to 47040 pounds upon the great pifton of four inches diameter, or fixteen circular inches furface, it amounted to 2940 pounds upon each round inch. But the medium preflure of the atmofphere on a round inch is near twelve pounds, confequently the action was equal to 245 atmofpheres: and as each of thefe correfponds with a column of 34 feet of frefh water at a medium, the water in the cylinder was preffed in the fame manner as if the whole column had been 8330 feet, or 13 mile, long. Large prefles of this conftruction are made with two pumps of 14 inch bore, and a cy- linder of feven inches. ‘Thefe have been ufedin prefling hay and cotton for package ; and, as I am informed, are effective in producing a greater condenfation on the material with - amuch lefs application of moving power and confumption of time. But of this and other particulars, as I have not yet had am opportunity of examining the facts myfelf, I fhall for- bear to {peak at prefent *. * Mr. Bramah, who conftruéts thefe engines, has obtained a patent for the invention, VU. The n Procefs for Bleaching Raw. Silk. w- Vil. The Proce/s for giving a beautiful White Colour to Raw Silk, without Scouring. By M. BaumeE*. : Berrnoiet, in his Elemens de l’Art de la Teinture, publifhed in the year “1791, after defcribing the ufual methods of depriving filk of its refinous or gummy matter +, -pro- ceeds to remark, that, inthe manufa€ture of blonds and gauzes, the natural elaflicity and {tiffnefs of this article are required to be preferved ; whence it has become a defideratum to render the yellow filk of Europe white like that of China, without depriving it of its gum. He adds, that Mr. Baumé has folved this interefting problem, but had kept his procefs a fecret ; but from the faéts he had poflefled the means of obtaining, it appeared liable to accidents, and that the chief difficulty confifted in giving an uniform white colour when large quantities were operated upon. He alfo mentions a difficulty in drefling the whitened filk fo as to prevent its curling, and obferves that it ought certainly to be kept conftantly ftretched. during the drying. It is befides requifite that the fpirit of wine fliould be recovered after the procefs, which would elfe be rendered too expenfive. This author does not fay whether the white Chinefe filk is fubjeé& to the fame inconvenience of curling when dyed, which, it may be remarked, is a property of no confequence where the material is to be applied in the manufa€ture of white goods. The motives which led Mr. Baumé to communicate his procefs to the world, originally retained by him asa lucrative fecret, do not appear. Whether the miftakes of thofe who carried it into effet in the large way might have led him to vindi- cate the reality of his difcovery by publication; or whether the commercial advantages derived from fuperiority of quality and cheapnefs in his article over the Chinefe filk in the market of France, might in the end have proved of lefs value than the fcientific reputation to be derived from its difclofure ; are circumftances which will, no doubt, have their proper weight with fuch manufacturers as may be induced gradually to adopt this procefs. The filk of Nankin is perfe€tly white, filvery, brilliant, and poffeffes all the elafticity of raw filk. Our author affirms, that the value of this article imported into Europe amounts to upwards of twenty millions of livres t, of which France confumes about four or five millions in gauzes, blonds, ribbons, &c. This was formerly fuppofed to be produced of a white colour from the worm. The late Mr. Trudaine, intendant of commerce, procured the eggs of the filk-worm from China, and cultivated them. ‘The produce confifted of yellow cocons, and others of the moft perfect whitenefs.- ‘The latter afforded filk equal in this refpect to that of Nanking But Mr. Baumé affirms, that moft of the Nankin filk is bleached by art, and, as he thinks, by a procefs fimilar to his own. As it is impoffible to wind off a large quantity of filk in the fhort time previous to that of the infeéts eating their way through the mafs, it is ufual, in the firft place, to deprive them of life. ‘This is commonly done by expofing the cocons, properly wrapped up, for two hours to the heat of about 158 degrees of Fahrenheit in an oven; after which they are * The original Memoire from which the faéts here related are taken, is inferted in the Journal de Phyfique, xlii. 375—399. + Tom. i. p. 146; or p. 141 of Dr. Hamilton’s tranflation. ¢ About eight hundred and thirty thoufand pounds fterling. kept Procefs for Bleaching Raw Silk, 33 kept for a certain time ina mafs to preferve their heat, and effeCtually deftroy fuch of the infects as might have efcaped'the power of the oven. The effect of this procefs is, that the filk is hardened, and is more difficult to wind off than before. Hence the product of filk is lefs by one ninth part in quantity, and inferior in quality to what might have been ob- tained by winding off without this previous baking. Mr. Baumé, not only from thefe views, but likewife becaufe the filk which has not been baked proves fufceptible of a greater lnftre, was induced to deftroy the chryfalis by fpirit of wine. For this purpofe he difpofes them in a wooden box in a ftratum fix inches deep: upon each fquaré foot half a chopin, or fomewhat more, of fpirit of wirz is to be fprinkled with a {mall watering-pot made for that purpofe. ‘This quantity anfwers fufficiently near to our half-pint. The liquid is to be equally diftributed, but it is not neceflary that all the cocons fhould be wetted. They are then to be mixed by hand. In the next place another {tratum is to be formed over the firft, nearly of the fame depth, which is to be fprinkled and treated as before. By this method of proceeding, the box becomes filled, and muft then be covered; and left for twenty-four hours, during which time they become fpontaneoufly heated to about 100 degrees, and the yapour of the fpirit of wine exerts itfelf with wonderful activity... Five hundred French pounds * of the cocons require ten French pints, which is nearly the fame number of Englifh quarts. After this treatment they muft be fpread out to dry, which happens in a fhort time, and is abfolutely neceflary previous to winding off. When the operator propofes in this manner to extinguifh various parcels of cocons be- longing to different individuals, each parcel may be tied up loofely in a canvas bag, and wetted on the outfide previous to clofing the box. _ The fpirit of wine to be ufed in this operation, ought to be of the ftrength of 34 degrees of Baumé’s hydrometer at the temperature of 55 degrecs. It is of the greateft importance to ufe that fpirit only which has been kept in veffels of glafs, of tinned copper, or of pure tin. Leaden veffels are abfolutely to be rejected ; wooden veffels tinge the fpirit, which gives the filk a degree of colour of confiderable folidity, and very inimical to the bleaching procefs. With regard to the advantages of this method of extin@tion, in-preference to that of the oven, the author remarks, that the coft of labour and fuel added to the lofs of filk, and the probability of injury from too much or too little heat, conftitute a fum of difadvantage much greater than the coft of the fpirit of wine. It is befides a confiderable advantage, that the fpirit of wine renders more diftinguifhable fuch cocons as have perifhed previous to the application of the fpirit. ‘Thefe afford a much worfe filk, and muft be picked out. The filk is wound off upon a reel, while the cocons are kept immerfed in water almoft boiling. Upon this part of the procefs Mr. Baumé remarks, rft, That the dead cocons muft be feparated. Thefe are known by the brown or black fpots on their furface. 2. ‘That well-water, which on account of its clearnefs is almoft univerfally ufed in the filk manufactories, moftly contains nitre, and is extremely prejudicial to the bleaching pro- cefs. The preferice of nitrous acid gives a yellow colour, which refifts bleaching and even fcouring ; he therefore recommends river-water. 3. In fome countries a {mall quantity of * The Paris pound is to the Englith avoirdupois pound as 756 to 700. I haye not reduced thefe quantities, becaufe cht operation requires no great precifion, M. ; Vou. LL—Aprit 1797. r . ~—aluns 34 Procefs for Bleaching Raw Silk, alum is ufed. Neither this nor any other faline fubftance is of the leaft advantage to the colour, beauty, or quality of the filk. At the four places of contact of the filk upon the reel, all the threads flick together. It: is abfolutely neceflary that this fhould be remedied. The method confifts in foaking the filk in afuflicient quantity of warm water, at about go degrees, for about two hours; after which the threads are to be feparated by opening the hanks upon a pin, and lightly rubbing the parts which cohere. When the filk is dry, it is to be loofely folded in its original form, and is ready for bleaching. The filk while wet is foft, and part of its gummy matter is in fuch a ftate, that its threads would readily adhere, if wrung while warm for the purpofe of clearing it of the water. After fuch improper treatment there would be no other remedy than to foak it: again in warm water. The apparatus for bleaching the filk confifts of a ftone-ware veffel, nearly of a conical form,. capable of holding about twelve gallons, having a large opening at the one end, and a fmaller, of about an inch diameter at the other end. Common pottery cannot be ufed in this opera- tion, becaufe it is {oon rendered unferviceable by the action of the marine acid, and the- ftone-ware itfelf is not very durable. This veflel muft be carefully examined, to afcertain: that it does not leak in the flighteft degree ; after which the infide is to be rubbed with a pumice-ftone, to clear it of afperities which might break the threads. A cover of the fame material is to be fitted on by grinding; and the fmaller aperture, which in the ufe is the loweft, is to be clofed with a good cork, in the middle of which is thruft a fmall glafs tube about a quarter of an inch in diameter; this is likewife {topped with a cork, except-- ing at the time when it is required to draw off the liquid contents of the jar. A fmall per- forated falfe bottom is placed within the veffel, to prevent this tube from being obftrudted. This jar, or as many of them as the purpofes of the manufactory may require, is fup~ ported by a wooden frame or table, at fuch a height that a cafk may. be conveniently placed beneath to’receive what may flow from the glafs tube in the feveral periods of the-operation. Six pounds of yellow raw filk are to be difpofed in the earthen pot; upon this is to be poured a mixture, previoufly made, of forty-eight. pounds * of fpirit of wine at 30 degrees, with twelve ounces of very pure marine acid, abfolutely exempt from all prefence of nitrous acid, and of the ftrength of 14 or 15 degrees of Baumé’s hydrometer. The pot isthen to be covered, and the whole left in digeftion till the following day, or until the liquor, which at firft afflumes a fine green colour, fhall begin to aflume that of a dufky brown (feuile morte), The acidulated fpirit is then to be drawn off. To prevent evaporation, M. Baumé thrufts a cork in the bung-hole of the receiving cafk, in which is a-fliding glafs tube. The ufe of this tube is completely to furround the fmall tube proceeding from the earthen veffel. When the whole of the fluid is thus almoft entirely drawn off, clean fpirit of wine is poured upon the filk, and drawn off repeatedly until it paffes colourlefs. The filk is then fuffered to drain without ftirring it. In this ftate it.is ready for a fecond infufion. Forty-eight pounds of fpirit of wine acidulated with twelve ounces of marine acid is now to be poured on the filk, and the whole fuffered to remain for twenty-four hours or longer, until the filk becomes perfeétly white. The time required for this fecond infufion * The pound is nearly a pint, and is divided into fixteen ounces, With regard to the ftrengths, fee Article IX. p. 37. -- . 18 Procefs for Bleaching Raw Silk. 35 is commonly longer than for thie firft: it fometimes amounts to two, three, or even fix days, according to circumftances, particularly the temperature and the nature of the filk. Silk which has been in the oven is in general more difficult to bleach. When the filk has thus obtained its utmoft degree of whitenefs, the acidulated {pirit is to be drawn off into a feparate veflel. This fluid is but flightly coloured, and may be ufed again in the fir{t infufion of other yellow filk, with the addition of fix ounces more of ma- rine acid. The receiving veflel is to be removed, and another clean veffel fubftituted in its place. The filk is then fprinkled with clean fpirit, and occafionally prefled down with the hand. As foon as the fpirit of wine comes off abfolutely colourlefs, a third infufion is to be made by pouring upon the filk forty-eight pounds of the pure fpirit without acid, which is to remain till the following day: it is then to be drawn off, and referved for wafhing other filk after the firft infufion. : After the filk has been left to drain, and affords no more fpirit, it ftill retains its own weight of that fluid. This is recovered by the very fimple procefs of {prinkling the filk with a {mall quantity of very clear river-water at a time. While the water applies itfelf and fubfides along the filk, it drives the fpirit of wine before it, fo that the firft portions which flow from the tube are fcarcely diminifhed in ftrength. The addition of water is to be continued until nothing but mere water comes off below. In this fituation the filk is found to be well bleached, but ftill retains a portion of marine acid fufficient to render it harfh to the touch, and after a time brittle. It mult be wafhed off with water. The beft method is to put the filk loofely into a coarfe woollen bag, which is to be fecured loofely in another cloth like a fmall bed or pillow, then placed in a bafket and left in a running ftream for five or fix hours; but where the convenience of a ftream is wanting, the earthen pot containing the filk is to be covered with a cloth, and water pumped through it for five or fix hours, or until that which iffues from the lower aperture gives no red colour to the tincture of tournfol. At this period the lower opening is to be clofed and the veffel filled with water, which muft be changed once or twice in twenty-four hours. eer The time required for wafhing was occafionally abridged by pafling fpirit of wine, or river- water impregnated with a {mall portion of alkali, through the filk. The neutral falt thus produced is in faét lefs adherent to the filk than the acid itfelf, but neverthelefs requires to be wafhed off with a very large quantity of water. In thefe as in every other procefs relating to the filk, great care muft be taken to afcer- tain that the water made ufe of contains no nitrous acid, which would infallibly occas fion imperfection of*colour, or fpots in the article. After this treatment the filk is-rexdy for drying and luftering; previous to the de(cription of which, the author makes feveral re- marks to the following purport : Though the mineral acids are the moft powerful and deftruétive of all faline fubftances, yet they may be applied to filk when diluted with fpirit of wine in very confiderable dofes. In trials made to afcertain the maximum, two ounces of marine acid were added to one poundof fpirit of wine, without altering the filk. Two drams of marine acid caufe a very perceptible alteration in one pound of filk. I fuppofe he means pure acid, or perhaps di- luted with water; for the paflage as it ftands is obfcure. Numerous experiments have 1 es fhewn 36 Procefi for Bleaching Raw Silt. fhewn that the marine acid is preferable to any other. The proportions admit of much latitude, though he prefers the dofe hereinbefore deferibed. Spirit of wine which has been mixed with nitrous acid, cannot be ufed in bleaching, even though afterwards rectified upon an alkali, becaufe it ftill retains a portion of nitrous as. ; Pure fpirit of wine without acid extracts a fine yellow colour from filk, which does not feparate for years, even though expofed to the fun’s light. Yellow filk expofed to the fun lofes its colour in a fhort time. The acidulated fpirit which has been ufed in the infufion of filk, is changed by expofure to the fun, but not in fuch a manner as.to be rendered fit for ufe a fecond time. In order to obtain a beautiful white oolour, it is eflential that the filk fhould be immerfed in a large quantity of the fluid, efpecially at the firft infufion, Without this management it would become neceflary to make three infufions in the acidulated fpirit. When the firft infufion is well managed, the filk will have loft all its yellow colour, and become confi- derably white, at the {ame time that the liquor will have begun to change colour a little. As long as it continues of a fine green, it is certain that it has not exhaufted its whole ation upon the filk. The duration of this -firft infufion may be longer or fhorter, without inconvenience, ac« cording to the temperature. When the temperature is at 20 degrees of Reaumur, which anfwers to 77 of Fahrenheit, the firft infufion is often made in ten or twelve hours. In fmall experiments the heat of the atmofphere may be fupplied by the water-bath; in which cafe, all the infufions are eafily made in the courfe of a day. When the firft infafion is finifhed and the liquor drawn off, the filk appears greenifh : the fubfequent wafhings in fpirit of wine clear it of the liquor it retained. This {prinkling fhould be made with the watering-pot, otherwife the quantity poured will be greater, and the management more watteful. 4 The cocons may be bleached in this way, but the inconveniences are too great to render this procefs defirable. Pieces of gauze and entire garments of filk have been fuccefsfully bleached in this way. The fineft natural white filks are rendered infinitely whiter by this procefs. Spirit of wine alone has the property of depriving yellow filk of its colour, which it brings to the ftate of the naturally white filk. In this ftate the filk is difpofed to acquire a greater de- gree of brightnefs by a fingle infufion in the acidulated’fpirit. This procefs has its ad- vantages over the other, to which it is alfo inferior in certain refpects ; 5 concerning neither of which the author has entered into any detail. The colouring matter was found to be a refin perfectly animalized, affording a diftilla- tion the fame produéts as other animal matters, and the concrete volatile alkali. Silk whitened by fcouring may be dried freely in the air without affeCting its Inftre. This is not the cafe with the filk bleached in the gum: if it be left at liberty to dry in the air, it refembles white flax without any luftre. The beauty of this filk confifts in its fhining brilliancy; to fecure which, it muft be dried in a ftate of tenfion. Mr. Baume has contrived a fimple machine for this purpofe. It confifts of a {trong {quare frame of wood ftanding upright upon feet: the upper horizontal bar is fix feet long, and has fix iron pins driven / through Procefs for Bleaching Raw Silk. 37 - through it at equal diftances, fo as to project on each fide for the purpofe of receiving twelve bobbins. ‘The lower horizontal bar is moveable up and down in a mortice by means of a {crew at each end: it is furnifhed with fix holes, adapted to receive as many pins to correfpond with thofe above. The fkains of filk are to be drefled and arranged upon wooden pins, as they are taken out of the fack from wafhing. As foon as there are twelve together, they are to be wrung with a ftaff; after which the fkains are to be hung one by one upon as:many bobbins put upon the upper pins of the fquare frame. Another bobbin with tails ‘is to be inferted in the lower loop of the fkain, and faftened to the cor- refponding pin of the lower bar, by means of a ftrap and hook, which need not be de- feribed to fuch as are lightly acquainted with mechanical objects. When the machine is thus fupplied with fkains on both fides, the lower bar of the frame is to be prefled down by the ferews until the:filk is moderately ftretched. When it is dry, the ferews are to be equally flackened, the fkains taken off, and folded with a flight twift, that they may.not be- come entangled. ; After this defeription of the whole of his procefs, the author proceeds to make: certain general remarks onthe white China filk. He obferves, that in-his procefs the filks acquire the perfect -whitenefs without much handling, and confequently that there is little caufe for them to become entangled. Accordingly the lofs in unwinding is found to be no greater than when they are unwound in the yellow ftate: that is to fay, from a dram to a dram and a half in the pound. This faving is of the greateft importance in the price of the filk. The filk of Nankin, which he fuppofes to be bleached by fome procefs of the fame na- ture, is probably handled much more. The Jofs is nearly twelve per cent. when it comes to be opened, and not unfrequently even tweiity-five per cent. ;“a lofs which cannot in any refpect arife from the package. The quality of the Nankin filk differs much in the pack- age ; the external part being always of the beft quality, and that whith is packed within is of fuch an inferior quality as fometimes not to exceed half the value. On examining this filk, it not only exhibited unequivocal marks of alkali, but its imperfections were alfo of the fame kind as thofe which had occurred to Mr. Bsumé during the progreflive im- - provement of-his own manipulations. The betft China filk was neither improved nor in- jured by the procefs of Baumé ; whence he concludes that they are not naturally white, but . have undergone a procefs fimilar to his. The refult of the whole is, that the yellow filks of Europe may be bleached to equal or - greater perfection than thefe of Nankin; and that thele may be even greatly exceeded by winding the naturally white filk apart from the other, and bleaching it by itfelf. ' The methods of recovering the fpirit fo as to be ufed again, and of obtaining the marine acid in the requifite ftate of purity, will be defcribed in our next. ‘ IX.’ On the Hydrometer of BAUME. As many French chemifts refer to the pefe-liqueur of Baume, which has never been ufed in this country, it will be of advantage to defcribe the method by which it is con- ftru€ted, and thew the fpecific gravities indicated by the graduations upon the tem. In- . Mitar: flead. . 38 Conftruétion and Graduation of BAUME's Hydrometer. ftead of adopting the fimpler method of immediate numerical reference to the denfity of water expreffed by unity, as is done in all modern tables of fpecific gravity, he had recourfe to a procefs fimilar to that of graduating the ftems of thermometers from two fixed points. The firft of thefe points was obtained by immerfing his inftrument, which is the common areometer, confifting of a ball, tem, and counterpoife, im pure water. At that point of the ftem which was interfeéted by the furface of the fluid, he marked zero, or the commence- ment of his graduations. In the next place he provided a number of folutions of pure dry common falt in water: thefe folutions contained refpeCtively one, two, three, four, &c. pounds of the falt; and in each folution the quantity of water was fuch, as to make up the weight equal to one hundred pounds in the whole; fo that in the folution containing one pound of falt, there were ninety-nine pounds of water; in the folution containing two pounds of falt, there were-ninety-eight pounds of water, and fo of the reft. The inftrument was then plunged in the firft folution, in which of courfe it floated with a larger portion of the {tem above the fluid, than when pure water wasufed. The fluid, by the interfe€tion of its furface upon the ftem, indicated the place for marking his firft degree ; the fame ope- ration repeated, with the fluid containing two pounds of falt, indicated the mark for the fe- cond degree ; the-folution of three pounds afforded the third degree; and in this manner his enumeration was carried as far.as fifteen degrees. The firfl fifteen degrees afterwards, applied with the compaffes repeatedly along. the ftem,.ferved to extend the graduation as far as eighty degrees, if required. This inftrument, which is applicable to the admeafurement of denfities exceeding that of pure water, is commonly diftinguifhed by the name of the Hydrometer for falts. The Hydrometer for fpirits is conftruéted upon the fame principle; but in this ‘the counterpoife is fo.adjufted, that moft part of the ftem rifes above the fluid when immerfed jn_pure water, and the graduations to exprefs inferior denfities are continued upwards. A folution of ten.parts by weight of falt in ninety parts of pure water, affords the firft point, _ or zero, upon the ftem ; and the mark indicated by pure water is called the tenth degree $ whence, by equal divifions, the remaining degrees are continued upwards upon the {tem as far as the fiftieth degree. Thefe experiments, in both cafes, are made at the tenth degree of Reaumur, which anfwers very nearly to fifty-five of Fahrenheit. M. Baumé affirms, that all his inftruments, conftructed in thefe methods, agreed together with the utmoft precifion. From a few experiments, which however require to be care- fully repeated, I am difpofed to apprehend that the folutions of common falt do not give a fufficiently accurate original point, and that they may differ not only from the comparative alrynefs of the falt in different experiments, but likewife the ftate of its cryftals, whether haftily or flowly feparated in their original fabrication, the purity being fuppofed the fame. Such differences muft confiderably affe@t the remote terms formed by repetition of the experi- mental interval in either inftrument. I fuppofe all M. Baumé’s inftruments were conftru&ted from folutions made once for all, and referved for this purpofe; and that the French chemifts who ufed them were fupplied under his dire@tion. For thefe reafons I am more inclined to deduce the fpecific gravities from the experiments of himfelf and another accurate pof- felfor of thefe inftruments, than to recur to the original method of conftrudtion. 6 M. Baumé, Specific Gravities indicated by BaumeE’s Hydrometer. 39 M. Baumé, in his Elemens de Pharmacie *, from which the whole of this account is deduced, has given a table (p. 410.) of the degrees of his Hydrometer, indicated by different mixtures of ardent fpirit and pure water ; where, he fays, the fpirit made ufe of gave thirty- feven degrees at the freezing point of water; and in a column of the table he ftates the bulk of this fpirit, compared with that of an equal weight of water, as 35$ to 30. The laft proportion anfwers to a fpecific gravity of 0.842, very nearly. A mixture of two parts, vy weight, of this {pirit, with thirty of pure water gave twelve degrees of the Hydrometer at the freezing point. This mixture, therefore, contained 63 parts of Blagden’s ftandard to 100 water, and, by Gilpin’s moft excellent tables }, its fpecific gravity muft have been 0.9915: By the fame tables, thefe fpecific gravities of 0.842 and 0.9915 would, at 10° Reau- mur, or 55° Fahrenheit, have fallen to 0.832 and 0.9905. Here then are two fpecific gra- vities of fpirit correfponding with the degrees 12 and 37, whence the following table is con- ftructed. Baume’s Hydrometer for Spirits. Temperature 55° Fahrenheit, or 10° Reaumur, Degrees Sp. Grayity Degrees Sp. Gravity. 10 = I.000 | 26 = -892 Ir = “990 | 27 = -886 12- = -985 | 28 = - .880 13° = ‘977 | 29 = 874 14. = -970 | 30 = +867 15 = -963 | 31 = -871 16 = 955 | 32 = -856 17 = 949 | 33 = -852 18 = -942 | 34 = 847 19 = 935 | 3 = 842 20 = 928 | 3 = 837 21 = +922 | 37 = +832 22 = ‘ 915 | 38 = 827 23 = +909 | 39 = 822 24 = +903 | 40 = 817, 25 = 897 With regard’to the Hydrometer for falts, the learned author of the firft part of the En- cyclopédie , M. de Morveau, who by no means confiders this an accurate inftrument §, affirms, that the fixty-fixth degree correfponds nearly with a fpecific gravity of 1.848 ; and as this number lies near the extreme of the fcale, I fhall ufe it to deduce the reft, Bavume’s Hydrometer for Salts. Temperature 55° Fahrenheit, or 10° Reaumur. Deg. Sp. Gr | Deg. Sp. Gr. 4 Deg. Sp. Gr. | Deg. Sp. Gr. | Deg, Sp. Gr. O - 3.000] 15 = 3.114] 30 = 1.261 | 45 = 1.455] 60 = 1.717 3 - 1.020] 18 - 4.140 | 33 - 1.295] 48 - 1-500] 63 - 1.779 6 - 1.040] 21 - 1.170 | 36 - 1.333] 51 - 1.547 | 66 -- 1.848 9 - 1.064 | 24 = 1.200 | 39 - 1.373 | 54 - 1-594 | 69 =~ 1.920 12 - 1.089 | 27 = 1.230 | 42 - 14-414 | 57 - 1.659 | 72 =~ 2.000 * Fifth edition, Paris 1784. + In Philofoph, Tranf. 1794. } Tomel. p. 360, aParis 1796. § Ibid, p- 361, X. Obfervations 42. On the Ujes of Scap'in the Woollen Manufacory. x. "Dihereetions on the Soap of Weel, and its Ufis inthe Arts*, By Ff. A. CHaPrat, Inflitutor of the: Polytechnic School, : I HAVE fhewn. the method of forming, at any time or place, and at a {mall charge} a faponaceous liquid adapted to fupply’ the place of foap for domeftic purpofes+. On the prefent occafion [ fhall offer a fupplement to my former work, by exhibiting, as’ a fubftitute for the foft foap ufed in fulling almoft every kind of woollen ftulf, a foap of little expence, which may be eafily made in every manufa€tory. In every manufactory of broad-cloth, and other fabrics of wool, it is ufual to full the ftuff immediately after it has pafled the loom. This operation is performed not only for the purpofe of clearing them of the oil, but to give them the requifite denfity. For this purpofe about thirty pounds of foap are ufed for every eighty pounds of the ftuff. This foap in the fouth (of France) coft twenty livres the hundred weight before the Revolution. It confumed a large part of our oils, as well as thofe of Italy, and all the wood-athes of the domettic fires in the refpeCtive countries in which it was made. Hence it is’ obvious how greatly beneficial it muft prove to the manufacturer, as will as to commerce in general, to be able to fubftitute without difficulty, inftead of the foft foap, another compound of materials, eafy to be procured, and of moderate coft. . In addi- tion to the faving in the fabrication of the ftuff, very great advantage would be derived ° _ from the wood-afhes of our fires being left for domeftic ufe, or for the falt-works, or ma- nufaétories of green glafs; at the fame time that the oil formerly confumed would remain to be totally applied to fuch works as cannot be conduéted without it. In all ages this problem has offered itfelf for folution to the Manufaéturer and. the Go-« vernment. Fullers’-earth, pure alkalis, and other agents, have been fucceflively employed. The firft of thefe is of inferior quality, either for bleaching or fulling; the fecond diflolves the ftuff. The manufaéturers of Lodéve ftill recolleét with terror a charlatan fent to them by Government a few years ago, who pretended to fubftitute the mineral alkali in the place of foap. To thefe inconveniencies we muft add that of not rendering the cloth fupple, but leaving it in poffeffion of that harfhnefs which foap alone removes. It is requifite; there- fore, that whatever fubftance may be offered as a fubflitute for this article fhould poflefs the qualities of cleaning, fulling, and foftening, the ftuff. ‘1 he compofition I am about to defcribe -poffeffes all thefe advantages. Experiments have been made at my requett, at Lodéve, by Citizen Michel Fabriguette, who is intimately acquainted with natural philo- fophy, and a fkilful manufacturer of drapery. The whole operation confifts in making an alkaline lixiviam of wood-afhes or pot-ath, and diffolving therein, at the boiling heat, old rags $, or clippings of wool, to ‘the point of © * Nearly a literal tranflation from the Annales de Chimie, XXT. 27. + See the Report of Citizens Pelletier, D'Arcet, and*Le_Lievre, on the fabrication of Soap. / } Old woollen tags are avery cheap article in this country, But, as. every other, kind af hair muft cer- tainly anfwer, and horns and hoofs probably will, there muft’be an immenfe and probably cheaper fource in the refule of the tanners, hog-butchers, horners, and comb-cutters, All thefe, at prefent, are uféd only asinia- nure, WN, Fi faturation. Preparation of Soap from Alkali and Wool. 41 faturation. The produ& is a foft foap, very foluble in water, of a green greyith colour, well blended (bien lie); and poffefing an animal fmell, which the cloths lofe by wathing and expofure to the air. ; The various experiments I have made on this fubje@t have prefented the following refults; 1. As foon as the wool is plunged in the boiling liquid, the filaments adhere together, and a flight agitation is fufficient to effect the complete folution. 2. The lye becomes coloured, and gradually thickens, in proportion as more wool is added. 3. The foap is more or lefs coloured accordingly as the wool is lefs or more clean and white. 4. The pile or hairs which are mixed with the wool are more difficult of folution. 5. The quantity of wool the alkaliis capable of diffolviag, depends upon the ftrength of the lixivium, its caufticity, and the degree of heat. Two pounds three ounces and fix drams of caultic alkali, at twelve degrees * of concentration, and at the boiling heat, diffolved ten ounces four drams of wool. The foap, when cooled, weighed one pound four ounces. An equal quantity of alkali, at the fame degree of caufticity, heat and concentration, in which I diffolved four ounces of wool, did not acquire confiftence fufficient to anfwer feveral of the purpofes required. An equal quantity of alkali, marking four degrees, diffolved only two ounces feven drams of wool. The foap, when cooled, weighed fourteen ounces. It was of a good confiftence. 6. In proportion as the wool is diffolved in the lixivium, the folvent power of the alkali decreafes, and at laft it takes up no more. It is at this period, namely, when the wool being agitated in the fluid is no longer diffolved, that the operation muft be terminated. I. The Choice and Preparation of Materials. The materials required to form this foap are two, alkaline matters and wool. The alkaline fubftances may be obtained from the afhes of common culinary fires}, and the lye made by the well-known procefles, Lime is to be flaked with a fmall quantity of water; the pafte is to be mixed with fifted wood-afhes, in the proportion of one-tenth part of quicklime compared with the weight of the afhes. The mixture is to be put into a fmall ftone trough (for wooden veffels colour the lye, and become fpeedily ufelefs); water isto be poured on tothe depth of feveralinches. After a certain time, the folution may be drawn off at an aperture formed in the bottom of the veffel for that purpofe. It muft not be drawn off but at the moment previous to its ufe, and may have the ftrength from four to fifteen degrees. But, indeed, it is of little confequence what the ftrength may be, becaufe the only difference refulting from the ufe of a weak or a ftrong lye is, that the quantities of wool which are diffolved, will differ accordingly. The potafh of commerce may be employed in the fame manner, by mixing one-third of its weight of quicklime. As to the choice of the wool, every one knows, that in the manufaélories of woollen cloths of * Qu. By what meafure ?—It is greatly to be withed that all meafures derived from the denfity of fluids were reduced to the common expreffion of the tables wherein water is taken as unity or I.ooo. N. + Wood being much more ufually burned in France than in England, their common afhes are what in London are obtained only from the bakers, The wninftruéted workman fhould be aware that coal-afhes are unfit for this purpofe; Vor. I.—Aprit 1797. G every 42 "Preparation of Soap from Wool, every kind, there are a number of operations performed, from the firft wafhinig of the ma+ terial to the laft package of the finifhed article, which occafion more or lefs of lofs. The water in which the wool is agitated to cleanfe it, the floor on which it is fpread out, the warehoufe where it is depofited, all afford wafte wool; as do the operations of beating, carding, fpinning, weaving, fulling, napping and folding. In all thefe feveral manipulations we every where fee a refidue of wool, which, it is true, is collected with fome care; but many of thefe operations are of fuch a nature, that the remains of wool they afford are foiled and mixed with foreign matters, or elfe cut and rendered too fhort to enter into fome fabrics; fo that they are moftly thrown on the dunghill. This manufa&ture of foap affords the means of converting them all to ufe. Nothing more is required, but to colfet them all in thofe bafkets in which the wool is wafhed, and to wafh them with care, for the purpofe of fepa- rating impurities and foreign fubftances ; after which, they are to be referved for this ufe. The cuttings of all the woollen ftuffs, afforded by the fhops of manufacturers, dealers, tay- lors, and the like, may be advantageoutfly colle€ted for this purpofe; and the fame advantage may be derived from the remains of garments after they are worn out. - ‘ Il. Method of Making the Soap. When the lye and the wool are both ready, it remains only to caufe the lye to boil ina veflel of the common form. When it has arrived at this point, the wool is to be added by fmall quantities at a time, and agitated to caufe a more fpeedy folution. Care muft be taken not to add more wool, until the firft portions are diflolved, ‘The operation muft be ftopped the moment the liquor refufes to diffolve more. £ From the operations in the large way, made by Michel Fabriguette, with foaps of his own fabrication, after the method I communicated to him, it is certain that this foap cleans, felts, and fupples the cloths perfectly well. But its ufe requires a few important obfervations to be made. 1. When the foap is not made with the requifite care, or when dirty or coloured wool has been employed, the fabric receives from the foap a grey tinge, which it is very difficult to eradicate. This tinge is of no confequence when the ftuff is intended to be dyed; but it would injure the beauty of that white colour which in certain goods is intended to be pre- ferved. ‘The remedy confifts in employing the moft felect materials to form the foap in- tended for fuch delicate applications. z 2. Stuffs fulled with this foap contract an animal odour, which, though not very ftrong, is neverthelefs difagreeable ; but water and the air completely remove it. After having fucceeded in the employ of this foap in fulling cloths ‘made of wool, I at- tempted to fub{titute foda for potafh, and to form, according to the procefs here defcribed, a folid foap, proper for the operations of dyeing cottons. My experiments have fucceeded be- yond my hopes. Forty-fix pounds of foda at eight degrees diflolved at the temperature of ebullition five pounds of wool *, and afforded, by cooling, fixteen pounds fourteen ounces of foap fufficiently fulid not to be fpread (couler). The » Tris affirmed, that when common fea faltis thrown into the combination of oil and vegetable alkali in the pro- cefs of foap-making, the effeCconfilts not merely inthe feparation of the foap fromthe water, now rendered falt, but that the alkalis change place; fo that the foap obtains the mineral alkali, and the fluid, inftead of contain. ing Preparation of Soap from Wool. 43 The firft wool which is thrown into the foda diffolves readily ; but it is afterwards feen that the fluid gradually becomes thicker, and that the diffolution becomes more difficult and flow. The firft folutions render the liquor green; after which it becomes black, and the foap, when cooled, preferves a blackifh green colour. This foap has been employed in every manner, and under every form, in my manufaétory for dyeing cottons; and [ am at prefent convinced that it may be fubftituted, inftead of the faponaceous liquid we make from the lixivium of foda and oil, to prepare /appréter) the cot- tons. J have conftantly cbferved, that by diffolving a fuslicient quantity of this foap in cold water to render the fluid milky, and by working (foulant) the cotton with the apparatus which is well known, it is fufficient to pafs the cotton three times through, drying it each time, in order that it may be as well difpofed to receive the dye as that which has been pafled feyen times through the ordinary folution of foap. ‘This will not appear furprifing when it is confidered that animal matters are very proper to difpofe thread and cotton to receive the dye, and that fome of the operations of our dye-works confift fimply in impregnating them with thefe fubftances. It is to be obferved, that cotton which has. paffed through a folution of this foap acquires a grey tinge nearly fimilar to what it gains by aluming, while the common foap liquors give it the moft beautiful white colour. But this grey colour is not at all prejudicial to the dye- ing proceffes, as we have remarked in fpeaking of woollens. I muft remark, in confirmation of this laft ufe, which I attribute to the foap of wool, that after having impregnated cotton with it by the ordinary procefs, I caufed it to pafs through all the operations to which wool is fubje&ted to produce the fcarlet dye. The cotton ac- quired a deep and very agreeable fleth colour ; whereas the cotton which had not received this preparation came out of the bath with its natural colour. This firft eflay promifes ad- -vantageous refults, which I mean to purfue. It may be of fome utility to obferve, that the foap of wool may be beneficially fub{tituted inftead of common foap. In domeftic operations I have profitably applied it to wath linen, and particularly woollen garments and other articles. Ihave no doubt but the facility and economy which it prefents in its fabrication * will ferve to extend its ufe ftill further; but in the mean time I have thought it proper to flew the various objects to which I have applied it. Obfervation. ; As the foap of wool gives a grey tinge to piece-goods, which it is difficult to eradicate, it follows, that it cannot be ufed for bleaching linen, unlefs it be made of white wool feleéte _and carefully wafhed, : ing common falt, will be found to contain the combination of marine atid and vegetable alkali, Ido not know if this has been fhown to be really the cafe, nor whether this indireét procefs be of much value, IF it be fully as here fated (which I doubt), our foaps muft owe their inferiority to thofe of Spain to the animal oil they contain, and not to their alkali, N. * The effect of the Excife Laws in Britain confines the manufaékure of foap to premifes regiftered in forms and regularly vifited. What 'the general effeéls of this arrangement may prove on our great national manufaéture of woollens, more efpecially if the prefent invention fhould amply come up tothe expectations here excited, isa queftion that well deferves to be inveftigated. N. G2 : XI. Extra& 44 Olefiant Gas. XI. Extra& of a Memoir concerning three different Species of Carbonated Hydrogenous Gas, obtained’ jrom Ether and Alcohol by different Proceffis, forwarded to the National Infiitute of France by the Society of Dutch Chemi/ts ; being Part of a Report read to the Firf? Cla/s of the Inftitute, by Citizen FOURCROY, at the Sitting of the 26th Frimaire, 16th December 1796*. ms Citizens Bondt, Deiman, Van Trooftwyk and Lauwerenberg, chemifts, of Amfterdam, who for feveral years paft have made experiments together, and have already rendered great fervices to thefciences, fent on the firft Frutidor of the fourth year to the Inftitute, a Memoir addreffed to that body by C. Van Mons of Bruffels, its affociate. As the fubject it treats of relates intimately to the progrefs‘ and ftate of modern chemiftry, it becomes neceffary to give an account as ample as the novelty and importance of the fubje€t demand. Several months before the arrival of this Memoir, the Inftirute had received an account. of the difcovery it announces. The contents of the letters of C. Van Mons, on: this difco-. very made in Holland, forwarded to the Inftitute in Ventofe the fourth year (March 1796), were as follows: The olefiant gas, which is fo called from its charatteriftic property of forming oil in a: circum{tance which fhall be defcribed, is formed of a mixture of feventy-five parts of con- centrated fulphuric acid with twenty-five parts of alcohol, even without the aflfiftance of foreign heat. It is likewife formed by pafling alcohol or ether in vapour over filex or alu- mine in a tube of glafs, or fimply in a tube of pipe earth ignited without addition. It is. not formed by the paffage of the alcoholic or ethereal vapour in a tube of glafs ignited with-. out filex or alumine, nor in the fame tube containing lime or magnefia.. The inflammable: gas, which is obtained in this laft cafe, is no longer fufceptible of becoming olefiant, by a fecond tranfition through filex or alumine. ‘The olefiant gas is not abforbed nor altered by remaining over water; with a fmall quantity of oxigenated muriatic acid gas it forms an: ethereal oil. Mixed with this gas in equal proportions, and fet on fire, it lets fall a great quantity of carbone; when 0.25, or 0.20, or 0.15 of oxigenated muriatic acid gas is added to 0.75, or 0.80, or 0.85, of olefiant gas, and the mixture fet on fire, the carbone appears immediately in the form of very fine lamp-black. The greater the proportion of the olefiant gas, the more perceptible is the appearance of carbone during the inflammation. Too large a portion of oxigenated muriatic acid converts it into carbonic acid. This experi- ment proves that the hydrogene attracts oxigene more ftrongly than the carbone does. C. Van Mons thinks, in his letters on this fubje€, that the olefiant gas is a true carbonated, hydrogenous gas. : Five months after this firft account, on the firft of Fructidor, in the fourth year of the Re- public of France (18th Auguft 1796), C. Van Mons forwarded to the Inftitute the Memoir- ef Citizens ‘Bondt, Deiman, Van Trooftwyk and Lauwerenberg, in which thefe chemifts. have with great care defcribed the properties of this gas, which they had difcovered, and which was already known by the name of the olefiant gas. This, Memoir, which is very well drawn up, confifts of twenty-four paragraphs ; the fub{tance of which we fhall here relate. In the Srft paragraph the authors obferve, that the gas which is difengaged during the mu-. tual aétion of concentrated fulphuric acid and alcohol, which was known to occafion frequent ruptures of the veflels, to burn with an oily flame, which had canfed it to be preferred in * Annales de Chimie, XXI. 48. lamps Mathematical Correfpondence. 45 lamps fupported by inflammable air, appeared to them deferving of a particular examination in confequence of the curious properties it prefented, particularly when compared with the gaffes afforded by alcohol and ether treated by other methods. Secondly, From having remarked that the gas is difengaged towards the end of the procefs for making ether, they took the proportions of the mixture which exifts at this period of the etherification; that is to fay, four parts of concentrated fulphuric acid and one of alcohol, and treated this mixture in a common glafs body appropriated to the pro- duétion of aeriform fluids, f The third paragraph defcribes the feries of phenomena which take place during the pro- duction of this gas. The mixture heats and becomes brown; gas is extricated without the application of external heat; but when fuch heat is applied, the effervefcence greatly increafes, the colour of the mixture becomes black, the gas paffes abundantly; it is even neceflary, to prevent the whole of the liquor from quitting the veffel, that the heat fhould be withdrawn. The refidue, after the extraction of the gas, confiits of fulphureous acid mixed with coal, which renders it black. Citizen Fourcroy remarks, that the defcription makes no mention of ether being produced. [Lo be concluded in the next Number.] MATHEMATICAL CORRESPONDENCE. As the prefent Journal is defigned to embrace every branch of ufeful knowledge, both in fcience and the arts, a certain portion of it will be devoted to the infertion of fuch mathe- matical differtations and queftions, as by their novelty or importance appear to deferve the attention of the public. Every communication, therefore, of this kind, directed to the Edi- tor, poft paid, will be thankfully received, and publihed as early, in fome of the fucceeding numbers, as the plan of the work will admit; but it is particularly requefted that the con- tributors of queftions will dire&t them, as much as poflible, to practical or theoretical im- provement ; as none that are forcec, or framed upon obfcure enigmatical principles, which when difcovered are of no value, will be inferted. The following QUESTIONS are propofed for Solution. Question F. By 7. B. IT’ is required to divide the half of a given right line into a given number of parts, fo that each part, and the fum of that part and the remainder of the whole line may be in geome- trical progreflion; this being a queftion of practical utility in the: divifion of the monochord or mufical {tring. Question II. By Capt. W. Munez. IT is required to determine the centrifugal force of a body moving in the circumference of a circle, by the pure principles of fluxions, inftead of deriving it from the doétrine of indi- viGbles, as is done by Newton in the Principia. SCIEN- 46 Sitting of the Naticnal Inflituté of France. SCIENTIFIC NEWS. Tue Public will hear with much pleafure, that the Journal des Scavans and the Annales de Chimie are both revived. The former work, as ufual, is anonymous, though the papers are marked by initials or characters. The latter prefents the refpe€table names of its au- thors, Guyton, Monge, Berthollet, Fourcroy, Adet, Seguin, Vauquelin, Pelletier, C. A, Prieur, Chaptal, and Van Mons. Of the Journal des Scavans, four numbers have reached England, commencing 16 Nivofe, an. 5 (Jan. 5, 1797), continued on the 3oth of the fame trimeftre, and afterwards publifhed on the fame days of each trimeftre refpectively. The laft, 30 Pluviofe, therefore anfwers to Feb. 18. Regular extras will in future be given in our Journal. The firft number contains an introdu€tion anda general fketch of the ftate of letters, fciences, and arts in Europe, at the commencement of the fifth year.of the French Republic (23 Sept. 1796). The latter is drawn up with the hand of a matter. Scientific matters contained in the fecond number are: 1. The public fitting of the Na- tional Inftitute of the rsth Nivofe. Citizen Prony announced three aftronomical memoirs of Citizen Flaugergue, affociate ; and the continuation of the great work of Citizens Delambre and Mechain on the’ Midian from Bayonne to Dunkirk, which will be finifhed in the year 6, Citizen Lacepede announced the following memoirs:—On the fulphureous acid, by C. Fourcroy and Vauquelin—Various works of C. Lamarque on the general principles of Chemiftry, from which a chromometric feale is obtained—Defence of the new chemical theery againft a German, by C. Van Mons, affociate—On the fubftance of gold, by C. Chaptal, affociate—On vegetable juices, by the fame—On the gluten of wheat, by C. Texier—-On the teeth of animals, particularly the horfe, by C. Tenon—On the nature and caufes of vertigo in horfes, by C. Huzard—Refearches on the epidemical diforders of cattle, by the fame—An elementary table of the hiftory of animals, by C. Cuvier—On the ufe of mercury in the fmall-pox, by C. Defeffarts. : The travels continued with fuccefs by yarious members of the Inftitute, afforded Citizen Lacepede an opportunity for a well-timed digrefhon in form of an invocation to Peace, which was greatly applauded. . ; The Citizen Talleyrand, one of the fecretaries of the fecond clafs, gave an account of its Jabours. They confift of two memoirs on Ideology, by C. Tracy, aflociate—T wo memoirs of C. Laromiguiere, aflociate ; one on the operations of the human underftanding; the other on the fignification of the word Idea—On the converfion of the territorial impoft into a duty on fucceffions, by C. Duvillard, affociate—On public credit, by C. Dyanniere, aflociate—Inquiries refpeCting the Arabian Gulf, by C. Goffelin—Concerning the manners of the Greeks in the time of Homer, by C. Levefque—Three hiftorical memoirs; one re- {peéting the Egyptians, another on the Swifs, and the third concerning Peru, by C. Anquetil —Notice refpeéting Sylvain Bailly, by C. Delifle de Sales. Citizen Seguin, affociate, read a memoir on the tanning of fkins. His procefs, of which fome account has already been given*, is faid to produce the fame effe&t in one month, as by the ancient procefs required fifteen or eighteen. “ : * Page 26 of this Journal. Citizen Accounts of Foreign Publications. 43. Citizen Desfontaines read a memoir on the cultivation of {pices in Guiana. Three hun- dred exotic trees were carried thither by C. Martin ; and it appeared that the clove, among others, afforded a very confiderable product. Citizen Dupont de Namours read a memoir on the fauimbitiey and morality of the dog, the fox, and the wolf. The title excited the public attention; and the effeéts of the dif- courfe, which was original, philofophical, and lively, was fuch that it gained much applaufe. ACCOUNTS OF FOREIGN PUBLICATIONS. Befchreibung einer Reife, 5c. or Travels in Germany and Switzerland in the Year 1781, with Obfervations on the Sciences, Induftry, Religion and Manners. By Frederick Nicolai. Vol. XI. and XII. Berlin and Stettin, 1796, in octavo. Nicolai publifhed the firft volumes of his Travels in 1783, at that time offered for fub- fcription, and he has fince brought them out two volumes at atime. The oth and roth appeared in 1795. ‘This work is greatly efteemed in Germany. The title of Travels, though the author really paffed through the countries he defcribes, is, properly {peaking, no more than a vehicle for numerous obfervations on manners, population, induftry, and fcience. Particular differtations on various objects are inferted. Thus the xith volume con= tains differtations on the Celts, the Suabians, the Celtic language, &c.; and the xiith, ob- fervations of much importance on certain geographical denominations, which Pliny, Pto- lomy, and others, give to places fituated at the Black Foreft and in Helvetia. It muft not be concluded that this account contains little novelty becaufe the Travels publifhed by the author were made in 1781. To the recital of his a€tual travels Nicolai has added a work. of the clofet, perhaps much too extended, which confifts in a numerous ¢ollection of notes and tables relative to ftatiftics. Some are dated in the year 1796. The works of Nicolai are more particularly efteemed in Germany, in refpect to the ob- jects of political ceconomy they contain. Ueber die Kultur-verhélinife, &'c. or An Effay on the comparative Culture of Land in the various States of Europe ; in which an Attempt is made to determine, by the Magnitude and Population of the feveral States, the Degree of Cultivation of the European Dominions, With fixteen large Tables, exhibiting the Surface and Population of the European States. By Aug. Fred. Guil. Crome. Leipfick, 1792; 1 vol. oftavo; 398 pages of text, and 112 of additions. Statiftiche Ueberficht, &'c. A Statiflical View of the Provinces of the Ruffian Empire, with regard to the comparative Cultivation of the Land. By H. Storch, Riga,1795; Hart- knock; 1 vol. fmall folio,131 pages. Geographifch-Statiftiche Tabellen ; Tables of the Statiftical. Geography of Switzerland. By H.K. Zurich, 1795 ; Ziegler and Sons; 1 vol. {mall folio; feven tables. Annalen der Staatskriifte von Europa. Annals of the Powers of the feveral States of Eu- rope confidered, with regard to the prefent State of Natural Philofophy, Commerce, Science, and Political Relation. The whole drawn up in the Form of Tables. By Ad. Frid. Randel. Berlin, 1792; Frid. Vieweg; 1 vol. {mall folio. Der Pelynomifche Lebrfatz, {S'c. Principles of the Doétrine of Polynomials, the moft interefting Problem.of Analytical Science, with fome other Theorems relating thereto, explaincd and developed, ‘by Tetens, Kluegel, Kramp, Pfaff, amd Hindenburg. The 2 {mallers 48 Accounts of Foreign Publications, latter has added an abridged Summary of the Method of Combinations, and their Ufe in analytical Proceffes. Leipfick, Fleifcher the younger, 1796, 8yvo. Ueber die Methode des Hrn. La Grange, &c. A Differtation on the Method of Mr. La Grange, for refolving all Equations by means of Series. By F. W. A. Murhard.—Gottin- gen, Rofenburg, 1796, 4to. —16 pages. Die neueften Entdeckungen, &c. The new Difcoveries in EleAricity confidered with regard to Natural Philofophy and Medicine, collected by Charles Gottlicb Kuenh. Part I. Leipfick, 1796, 8vo. Dr. Lorenz Decrell has tranflated into German the firft volume which has appeared of Kirwan’s improved edition of Mineralogy, with Obfervations. , It is printed for Nicolai at Berlin. } Handbuch der neueften Erdbefcbreibung ; or, A Manual of the moft modern Geography. By Gafparis, Profeffor at Jena. Vol. I. 8vo. Weimar, December 1796. Ada Eleét. Mogunt. Scientiarum utilium, que Erfurti eft, ad Annum 1794 & 1795) cum Figurisin 4to maj. Erfort, G. A. Reyfer. Traité d’Harmonie &¥ de Modulation. Par H. F. M. Langlé. A Treatife of Harmony and Modulation. By H. F. M. Langlé, fome time Firft Matter of the Confervatory of Piety at Naples, and Profeffor at the Confervatory at Paris.—This treatife is divided into two parts. The firfl exhibits all the practicable concofds in harmony, and the fecond all the poflible modulations. “ The authors have treated this fecond part,” fay the Journalifts, “ in fuch a manner as to facilitate to beginners on the piano-forte and the harp the difficult ac- complifhment of preludes.” Boyer, Paris. Two Tranflations of Spalanzani’s Travels in the Two Sicilies have appeared ; the one at Berne, by Senebier ; and the other at Paris by Tofcan and Duval, with Notes by Faujas. Neither of thefe can yet be complete, as Spalanzani’s Travels are to form fix volumes in 8vo. The Encyclopédie Methodique par ordre de Matiéres, which was interrupted in its pro- grefs by the French Revolution, is again continued. The fixtieth and fixty-firft livraifons are publifhed for Agafle, Rue des Poitevins, No. 18. The fixtieth livraifon contains three half-volumes : 1. The feventeenth Part of the Plates of Natural Hiftory, forming the feventh Century ‘of Botany; by Citizen Lamarck, of the National Inftitute, Profeffor and Adminiftrator of the Mufeum of Natural Hiftory. 2. The fecond Part of the third and laft Volume of Ancient Geography; by Citizen Mentelle, of the National Inftitute. 3. The Dictionary of Fithery ; by Citizen Lacombe, Author of feveral Diétionaries of the Encyclopédie, particularly that of Arts and Trades. The price of this is thirty- one livres in fheets, or thirty-three ftitched. A table is given of the parts already pub- lithed, by which it is feen that the work is already far advanced, and that there is no probability of its not being completed. The price of the fixty-firft livraifon is the fame as the foregoing. It contains the eighteenth part of the plates of Natural Hiftory, confifting of one hundred plates of Infects. Vol. 1V. Part 1, Diétionary of Botany, by Lamarck. Vol. VII. Part 2, of the Hiftory of Infe&s. [Accounts of Englifh Publications in the next Number-] 4 bi Philos» Journal Vols Pla jing P71. te ee aes ” *t led re) Supt LOUCHTL cont (se compound objet = Senses. s ‘ ag Big.a! a B V Hi\ | \ F175 - \ Wig 6. a! \ \ A ¥ {=a B \ \ » | yy | wy Da et - 4m Caconimen ' Solar Spectrum . P43 t 5 » + a Vigvswe . c.—The firft Chriflian voyages to the newly difcovered iflands became frequent under the reign of Henry, fon of John, King of Lufitania. After his death Alphonfus V. pro- fecuted the defign; and John, who fucceeded him, followed the plan of Alphonfus, by the af- fiftance of Martin Bohem, a very {kilful navigator; fo that in a fhort time the name of Lufi- tania became famous over the whole world.” Cellarius, one of the moft learned men of his age, fays exprefsly, “ Behaimeus non modo, &5'c.—Bochm did not think it enough to furvey the ifland of Fayal, which he firft difcovered, or the other adjacent iflands which the Lufi- tanians call Azores, and we, after the example of Bochm’s companions, call Flemifh iflands, but advanced ftill farther and farther fouth, until he arrived at the remotelft ftrait, through which, Ferdinand Magellan, following his track, afterwards failed, and called it after his own name.” All thefe quotations, which cannot be thought tedious, fince they ferve to prove a fact almoft unknown, feem to demonftrate, that the firft difcovery of America is due to the Portuguefe, and not to the Spaniards; and that the chief merit belongs to a German aftronomer. ‘The expedition of Ferdinand Magellan, which did not take place before the year 1519, arofe from the following fortunate circumftance: This perfon, being in the apartment of the King of Portugal, faw there a chart of the coaft of America, drawn by Behem, and at once conceived the bold projet of following the fteps of this great navigator. Jerome Benzon, who publifhed a defcription of America in 1550,' {peaks of this chart; a copy of which, fent by Behem himfelf, is preferved in the archives of Nurenberg. The celebrated aftronomer Riccioli, though an Italian, yet does not feem willing to give his countryman the honour of this important difcovery. In his Geographia Reformata, book iii. p. go, he fays, “Chriftopher Columbus never thought of an ex- pedition to the Weft Indies until his arrival in the ifland of Madeira, where, amufing himfelf in forming and delineating geographical charts, he obtained information from. Martin Beehm, or, as the Spaniards fay, from Alphonfus Sanchez de Huelva, a pilot, | who had chanced to fall in with the ifland afterwards called Dominica.” And in another place: ‘* Let Bochm and Columbus have each their praife; they were both ex- cellent navigators ; but Columbus would never have thought of his expedition to America, had not Boehm gone there before him. His name is not fo much celebrated as that of Columbus, Americus, or Magellan, although he is fuperior to them all.” But the moft pofitive proof of the great fervices rendered to the crown of Portugal by Behem, is the recompenfe beftowed on him by King John, who in 1485 knighted him in the moft folemn manner, in the prefence of all his court. I have before me a‘German paper, extra&ted from the archives of Nurenberg, to the following purport: ‘ In the year 1485, on the 18th of February, in Portugal, in the city of Allafavas, and in the church of St. Salvador, after the mafs, Martin Behem of Nurenberg was made a knight, by the hands of the moft puiffant Lord John the Second, King of Portugal, Algarve, Africa, and Guinea; and his chief Squire was the King himfelf, who put the {word in his belt; and the Duke of Begia was his fecond Squire, who put on his right fpur; and his third Squire was Count Chriftopher de Mela, the King’s coufin, who put on ‘his left fpur; and ‘his fourth Squire was Count Martini Marbarinis, who put on his iron helmet ; and the King himfelf gave him the blow on the thoulder; which was done in the prefence of -all the princes, : Analyfs of the Oriental Lapis Lazuli. oe princes, lords, and knights of the kingdom; and he efpoufed the daughter of a great lord, in-confideration of the important fervices he had performed ; and he was made gover- nor of the ifland of Fayal.” Thefe marks of diftinction, conferred on a ftranger, could not be meant as a recompenfe for the difcovery of the Azores, which was made twenty years before, but asa reward for the difcovery of Congo, from whence the Chevalier Behem had brought gold and different kinds of precious wares. This difeovery made much greater impreffion than that of a weftern world, made at the fame time, but which neither increafed the wealth of the royal treafury, nor fatisfied the avarice of the merchants. In 1492 the Chevalier Behem, crowned with honours and riches, undertook a journey to Nurenberg, to vifit his native country and his family. He there made a terreftrial globe, which is looked on as a mafter-piece for that time, and which is ftill preferved in the library of that city. The outline of his difcoveries may there be feen, under the name of weftern lands ; and from their fituation it cannot be doubted that they are the prefent Coafts of Brazil, and the environs of the Straits of Magellan. This globe was made in the fame year that Columbus fet out on his expedition; therefore it is impoffible that Behem could have profited by the works of this navigator, who befides went a much more northerly courfe. ; [Zo be concluded in the next Number.] ooooeEEeeeEeEeEEeeEEEEeEEeeeeeEEeeeeooooooEoooooooEeeEeeEeEeEeEeEeEeEeEeEeEh EE EeE—E|E|]]EEE—E—=E=E=ES_SNS =’ We Analyfis of the Oriental Lapis Lazuli*, By M. Kzaprorn. HE analyfis of lapis lazuli made by Margraff has fhewn that the blue colour of this ftone is not owing to copper, as has commonly been thought, but that it arifes from iron. But as we have not hitherto poffeffed any accurate analyfis of this ftone, I have thought it might be ufeful to examine it anew. In faét, Margraff informs us, that lime, gypfum, and filex, together with iron, are its component parts ; but he does not determine their propor- tions; and his analyfis is incomplete, as he does not mention the alumine which this ftone alfo contains. ; According to Rinmann, the lapis lazuli contains lime, quartz, iron, and the acid of fluor. ° I have not found the latter; and it is probable that Rinmann’s opinion was grounded upon . the phofphorefcence of this {tone when it is heated. Cronftedt and fome others have affirmed that the lapis contains a quantity of filver, after the rate of two ounces per quintal. But my effays have afforded no certain indication of the prefence of this metal. I feleéted for experiment a fpecies of the lapis of a beautiful deep blue colour, and care- fully feparated the white and pyritous {pecks. A. One hundred parts of lapis lazuli in thin flakes were kept in a ftate of ignition for half an hour in a porcelain crucible. They loft two parts of their weight; the colour-was. not at all changed, This permanence at a great heat induced me to think. that the ftone might be of advantage in enamelling; to which opinion I was the more inclined, from. * From the Annales de Chimie, XXI, 150, The French tranflation is made from the German, by Citizen Taffaert, but whence taken is not faid, Bergmann 78 Analyfis of the Oriental Lapis Lazuli. Bergmann having prefumed that the Chinefe and Japanefe make ufe of it for the blue colour of their porcelain*. ‘Lo afcertain the truth, I mixed fome of the very fine powder of lapis lazuli with a proper flux, and difpofed it upon porcelain, which I afterwards placed in the enameller’s furnace. My expectations were not realifed, for the colour changed to a blueifh grey. ‘B. By expofure to a more violent fire the lapis was deprived of twelve centenaries of -its weight, and was vitrified. I apprehend that the two parts loft by the firft ignition con- fifted merely of water, and that the additional ten in the fecond effay confifted for the moft part of carbonic acid. This opinion is fupported by the effervefcence of the ftone, which takes place when an acid is poured upon it, and indicates, though very fecbly, that part of the calcareous earth is united to carbonic acid. C, Upon two hundred grains of the lapis in impalpable powder I poured muriatic acid diluted with an equal meafure of water (€tendu de moitié eau), and digefted the whole together by a progreflive heat. The colour became gradually changed to a grey afh-colour 5 and when the ebullition commenced the powder was more ftrongly attacked, and at length became converted into a thick jelly. This was diluted with water; after which nitric acid was added, and the whole boiled until the refidue had become white. The filtered folution was of a pale yellow colour. D. The produét which remained upon the filter had the appearance of fand, and weighed “one hundred and thirty-eight grains, When this was mixed with three parts of cauftic pot-ath, and ignited, it afforded a greenifhy mafs. The folution of the mafs in water was perfectly colourlefs. By an excefs of mutiatic acid I feparated the filex, which after ignition weighed 57 grains. E. The folutions C and D, decompofed by the Laaleotit of pot-afh, afforded a yellow white precipitate, which, when dried, amounted to 221 grains, and was re-diffolved in the muriatic acid. F. Ammoniac feparated from the folution Ea gelatinous precipitate. This was thrown ftill wet into a cauftic lixivium, in which I digefted it, It was not totally diffolved, but left a yellowifh refidue weighing 113 grains. G. The fluid which remained after the precipitation by ammoniac was treated with car- ‘onate of pot-afh, and afforded 59 grains of the carbonate of lime. H. Upon the 113 grains which were infoluble in the cauftic pot-afh, I poured fulphuric acid diluted with water. This mixture, after having been heated, aflumed the form of a jelly. It was diluted with a large quantity of water, and afforded a precipitate of filex which after ignition weighed 29 grains. I, After the feparation of the filex I poured ammoniac into the folution. The precipitate, till humid, being mixed with a cauftic lixivium, depofited brown flocks in the liquor, which when dry weighed 13 grains. I diffolved thefe in the muriatic acid; and this folution treated with ammoniac let fall the oxide of iron, which after ignition weighed fix grains. Phe carbonate of ammoniac likewife precipitated five grains of calcareous earth. K. The folutions F and I by the cauftic alkalis were treated with the muriatic acid. The * Opufcules Phyfiques et Chymiques de Bergmann, Vol. IV. page 32, From the good quality of the cobalt at prefent ufed for this purpofe in England and elfewhere, there is no reafon to think that any other material is ufed for full deep blues in thc Eaft, N. precipitate Analyfis of the Oriental Lapis Lazuli. 79 precipitate which was formed and re-diffolved by excefs of acid, and afterwards formed again by carbonate of pot-ath, was diflolved again by fulphuric acid. A new precipitate of filex was thus obtained, which after ignition weighed fix grains, The filex was feparated, and pot-afh being then added, cryftals of alum were obtained. Thefe were diflolved in water, and the alumine, after precipitation, drying, and ignition, weighed 29 grains. L. I had afcertained by a previous experiment, that all the calcareous earth contained in the lapis was not faturated by the cerbonic acid, but that part was combined with the fulphuric acid. I had boiled in a large quantity of water a portion of the pulveriféd ftone ; the water, after filtration, did not appear very tranfparent. I poured in the muriate of barytes, and a precipitate was immediately formed confifting of fulphate of barytes. In order to afcertain the proportion of fulphate of lime, I fuperfaturated with muriatic acid the ljquor which remained from the precipitate C and the water of edulcoration; after which T poured in muriate of barytes, and obtained a iat ic of fulphate of barytes, which when perfeétly dried weighed 19% grains. I fufpected that the alkalis made ufe of in the experiments D and E might contain a fmall portion of fulphate of pot-afh, and by that means have contributed to the precipitate of the fulphate of barytes. To afcertain this faG, I diffolved an equal quantity of alkali; and having fuperfaturated it with muriatic acid, and treated it with the muriate of barytes, the fulphate of barytes which fell down was carefully collefted and dried, and weighed 1+ grain; a quantity to be deducted from the foregoing, and leaves 18 grains of fulphate of barytes to determine the proportion of the fulphate of each; and by computation I find that 200 grains of the lapis contain 8.18 of fulphuric acid, of the fpecific gravity 1.850, or in combination with calcareous earth 13 grains of fulphate of lime. This calculation is founded upon my experiments, which fhew that with the difference of a very {mall frac- tional quantity, 100 parts of fulphuric acid of the fpecific gravity 1.850 form 220 of ful- phate of barytes. The fame quantity of acid for its faturation with calcareous earth de- mands cither 100 parts of carbonate of lime, or 55 of pure lime, and forms 160 of fulphate of lime. The 200 grains of lapis lazuli contain therefore as component parts : Grains, me D 57 Siliceous earth — 4 *9 _ _ = 92 Calcareous earth — {ce 59} 64 but ignited — 35 Alumine — — K a nos 29 Oxide of iron — iI — _ — 6 Sulphuric acid — L — —_ aS 8 Carbonic acid — B — _ — 20 Water — — A — ae 4 194 Lofs 6 . 200 But Bo Ujeful Notices refpefting various Objels. But becaufe the calcareous earth is combined partly with the fulphuric acid and puns with the carbonic acid, it follows that the combination of the lapis is Grains. Silex _ a — 46 Alumine - _ — 14-50 Calcareous carbonate _ — 28 Calcareous fulphate — _— 6.50 #99 Oxide of iron — _ _ 3 Water _ _ _ 2 The fum is here complete, becaufe I have confidered the calcareous earth as perfeétly faturated with the carbonic acid ; which does not however appear in faét to be the cafe. VI. Ufeful Notices refeeding various Objects.—Rofe-Water—Eau de Luce—Soap of Wol— Sea Sicknefs. 1. Rofe-Water. Tue fimple diftilled water from rofe-leaves, which is fold by the name of rofe-water, has the difadvantage of lofing its fragrance, by a fpontaneous change which feems to be of the nature of the putrid fermentation. This happens in much lefs time than muft elapfe between the annual feafons when freth rofe-leaves are to be had. The article is never- thelefs to be purchafed at any time of the year; from which circumftance it has been fup- pofed that the manufaCturing perfumers were in poffeflion of fome method of preventing the procefs by which it is changed. A philofophical friend affures me that this is not the cafe, but that they diftil only fo much rofe-water at a time as they know will keep during the period of the regular demand for that quantity; at the end of which they diftil the fame quantity from other rofe-leaves. Their management for infuring a regular dupply confifts in packing the frefh rofe-leaves with common falt in a mafs, to a portion of which, when required, they add water, and diftil from the mixture. 2. Eau de Luce. THE fame intelligent friend informs me, that the ufual recipes in the London Pharma- copceia and other books, for making the fragrant alkaline liquor called eau de luce, the lead- ing perfeCtion of which is, that it fhall poffefs and retain a milky opacity, do not fucceed, but that a feparation takes place, and the fluid becomes more of lefs clear by keeping. The ufe of matic in this compofition’ has hitherto been kept a fecret. Upon his aflurance that this is the chief ingredient, I made the following trials. One dram of the reCtified oil of amber was diffolved in four ounces of the flrongeft ardent fpirit of the fhops; its {pecific gravity being .840 at Go degrees of Fahrenheit. This is the oily fpirit which is to be added to volatile alkali to form eau de luce, according to Macquer, in his Diétionary, who {peaks highly of a recipe to this effe€t, but with the addition of ten or twelve grains of white foap to the fpirit, previous to the oil. The purpofes of my experiment did not require the foap. A portion of the clear {pirit was poured upon a larger quantity of fine 3 powdered . a ' Upeful Notices refpeting various Objefs. 81 powdered maftic, than it was judged could be taken up. This was occafionally agitated without heat, by which means the gum refin was for the moft part gradually diffolved. One part of the oily folution was poured into a phial, and to this was added one part of the folution of maftic. No opacity or other change appeared. Four parts of ftrong cauftic volatile alkali were then poured in, and immediately fhaken. The fluid was of adenfe opake white colour, affording a flight ruddy tinge when the light was feen through a thin portion of it. : In a fecond mixture four parts of the alkali were added to one of the folution of mattic ; it appeared of a lefs denfe and more yellowifh white than the former mixture. More of the gum refinous folution was then poured in, but it ftill appeared lefs opake than that mixture. It was ruddy by tranfmitted light. The laft experiment was repeated with the oily folution inftead of that of maftic. The white was much lefs denfe than either of the foregoing compounds, and the requifite opacity was not given by augmenting the dole of the oily folution, No ruddinefs nor other rée- markable appearance was feen by tran{mitted light. Thefe mixtures were left at repofe for two days; no feparation appeared in either of ‘the compounds containing maftic; the compound confilting of the oily folution and alkali became paler by the feparation of a cream at the top. It appears, therefore, that the firft of thefe three mixtures, fubject to variation of the quan- tity of its ingredients, and the odorant additions which may be made, is a good eau de luce. Chemical writers fpeak of a milky fluid, under the name of Jac virginale, made by pouring tinéture of benzoin into fome perfumed water. As this fragrant balfam promifed to be in fome refpects fuperior to maftic, I was induced to try it. A fpirituous folution was made of the brown benzoin, which happened to be at hand. To one part of the oily folution firft mentioned was added one part of the clear filtered folution of benzoin. Thefe mixed uniformly. Tour parts of the cauftic volatile alkali were then added. The mixture became opake, fawn-coloured and curdled, with much lefs pungency of fmell than was afforded by the other alkaline compounds. ‘The next day the opake part had confiderably fubfided, and left a brownifh tranfparent though turbid fluid above. It appears probable, therefore, that the acid of the benzoin had not only united with part of the volatile alkalt, but that the oily and refinous parts had likewife been difpofed to coagulate in this ar- rangement. It is undoubtedly of no value in the prefent point of view. 3. Soap of Wool. I HAVE made a few experiments on the faponaceous combination of wool and alkali *. A cauftic lixivium was made by mixing a folution of the cryftals of foda with a due portion of lime and water. To the clear ley, in a ftate of ebullition, wool was added, a little at 2 time. It was fpecdily diffolved by ftirring; but on account of the lixivium being too ftrong, the compound appeared thick, and was poured out before, as it afterwards appeared, the faturation of the alkali was effected. The compound, after being left in an earthen vefie! for feveral days, was found to be fearcely more confiftent than treacle. Its fmell was offenfive, though not {trong ; it readily diflolved in water, but fearcely lathered at all; and * Philof. Journal, I. 40. Vor. I.—May 1797- M by 82 Ujeful Notices refpeéting various Objects. by its aQion when f{meared on the hands it appeared to poffefs a confiderable portion of dif- engaged alkali. The whole was then diffolved in water, and left for feveral days on account of «ther avocations. In the mean time a weaker lixivium was boiled with the addition of wool in fmall portions, till the laft quantity added remained for a confiderable time un- diffolved, and was taken out. The fluid poured into cups had the confiftence of treacle. It fathered fearcely at all with water, in which, however, it readily diffolved ; and upon being ufed with a piece of flannel, it feemed admirably adapted for fcouring that cloth, Four fucceffive rinfings in different clear waters feemed to have wafhed off the foap; but the fmell ftill remained very ftrong ir in the flannel. It went off in fix or feven hours com- pletely. I was defirous of afcertaining the ftate of the wool when it fhould be again feparated by means of an acid. For this purpofe I added diluted vitriolic acid to the aqueous folution of the firft imperfe& foap, which contained about half a pound of wool. A feparation inftantly followed ; and, to my furprife, upon ftirring the liquor, it lathered very well. The next day the confiftent part had fettled to the bottom. ‘The clear liquor, which was con- fiderably acid, and had a fulphureous fmell, lathered with agitation. The conliftent part had the appearance as if moftly compofed of broken fibres. ‘The whole was poured into a coarfe cloth, and, after ftraining away the acid, water was fuffered to run from a cock into the bag of the cloth, and fell clear into a {mall bafon which it overflowed below. It was remarkable that this clear taftelefs water bore a {trong bead or head by agitation. The edulcorated matter, when dry, weighed lefs than half anounce, Hence it fhould feem in this loofe experiment that the acid had not only faturated the difengaged alkali, but had either combined with the wool of the foap, or formed a triple compound with the foap itfelf, which was moftly carried off in the edulcoration. The refidue was probably wool, which had not been completely deprived of its organization in the firft boiling. But I mean to examine the perfect foap with greater attention to quantities. 4. Sea Sicknefs. IN an account of the iflands of Goree and Senegal, by Citizen Prélong, printed in the xviiith volume of the Annales de Chimie, the author mentions that he fuffered prodigioufly and for a long time by the fea ficknefs, but was greatly, and afterwards habitually, relieved by taking ten drops of vitriolic ether in a fpoonful of water. I have alfo been aflured by the commander of a packet conftantly paffing between Harwich and Helvoetfluys, that he always found this diftrefling illnefs greatly relieved in his paffengers by a {mall quantity of red wine heated-with fpices. The fea ficknefs feems to be a {pafmodic affeGtion of the ftomach, produced by the alternate preflure and recefs of the contents of that vifcus againft its lower internal furface, accordingly as the rife and fall of the fhip oppofes or recedes from the action of gravity. Hence it is relieved by change from the ereé to the prone polture, or by removing from the extremity of the veffel to the vicinity of axis of the pitching motion, near the mainmaft ; and hence alfo, when the organs have become habituated toa regular vibration of one kind in a fhip for feveyal months, the ficknefs may neverthelefs be again generated by a different vibration in a boat. As it is a habit which requires fome time to be generated, and comes on gradually, it is not difficult to oppofe it by mental effort or diverfion; but, to {uch as have not acquired this facility, it may be acceptable to know 2 that Comparifon between Cylinder and Plate Machines for Elericity. 83 that the above fpirituous ftimuli have been found of fervice in counteracting it. The ftimulus of food, taken even againft the inclination, has alfo been frequently found to be beneficial. a gp VIL. A Comparifin between ElePrical Machines with a Cylinder, and thofe which produce their Efe F ly means of a Circular Plate of Glafs. W “ith a Decription of a Machine of great Simplicity and Power, invented by Dr. Martinus Van Marum. I- is a remarkable cireumftance that the plate-machine for electricity, firft invented and publifhed in this country by Dr. Ingenhoufz, hag never been much ufed here, though it has been well received on the Continent, and almoft univerfally preferred to the machine with acylinder. This may in fome meafure be owing to the improvements in our manufafture of blown glafs, by which we have been fupplied with cylinders of confiderable dimenfions at a moderate price, inftead of the globes which were originally ufed for this purpofe. Some years ago (1787) I improved the cylinder-machine by a contrivance for changing the ele&tri- city of the conductor from plus to minus almoft inftantly, Which is defcribed in the Philofo- phical Tranfations for 1789. From a comparifon of the quantities of electricity accumu~ lated by the friction of a {quare foot of glafs, I was induced to adopt the opinion, that cylin- ders were preferable to plates in every refpect, excepting the great quantity of furface afforded by the latter in machines conftru€ted without regard to expence. The labours of the celebrated Dr. Van Marum, together with fome. obfervations of my own, have fince that time tended to alter my opinion: for which reafon I thall, in’ the firft place, enume- rate a few general facts, and then proceed to defcribe his excellent improvement of my con- trivance. ; I. Eletricalemachines were formerly made to revolve with confiderable velocity by 2 mul- tiplying wheel. ‘This has fince been rejected in confequence of the ftrong excitation and increafed friétion produced by a more advantageous application of the amalgam of zinc and mercury. The machines with a fingle winch demand the fame labour as before to work them. They exhibit much more fire in the form of flafhes and fparks. But, as far as my experience fhews, the {park from the old machine was denfer and more pungent, the excitation more tteady, and the time employed in charging fomewhat fhorter. Il. A cylinder with a fingle winch requires larger terminations of its metallic parts to prevent the fire from flafhing out, than are required either in the old machine, or one of thofe conftructed with a flat plate. III. It frequently happens that the fimple machine will be in a ftate to throw out ramifi- cations to the table, to the face of the operator, and into the air ; though the actual {park is not very denfe, nor the power great, Rehan examined by the time required to charge a bat- tery or jar. IV. From thefe circumflances it appeared probable that the electric matter in a charged condudlor may be thrown into a ftate of undulation by an irregular fupply from the cylinder, and that in this flate it will fly off more reatlily than when fupplied by a morouniform ftream. Thus, when the cylinder is of an irregular figure, the aQion of the cufhion will be flronger M2 ‘om 84 Experiments on the Undulation of Eleéiricity. on the one fide than the other, and this irregularity may be increafed alfo from other caufes, ‘The irregular fupply will therefore be made at more diftant intervals by the fimple ma- chine, at more frequent reiterations in the machine with the multiplying wheel, and per- haps uniformly from a plate. V. The eff of this undulation may be fhewn from various facts. 1. A {mall wire of many yards in length, communicating from a ball to the ground, will be rendered luminous through its whole length, by {parks of pofitive eleétricity given to the ball ; but it will not be at all luminous when the fame quantityiof eleAtricity is given in a more continued flream by placing the ball in conta& with the prime conduétor. 2. Ifa metallic rod be infulated with a ballat one end, of adiameter fuflicient to prevent the fpontaneous flafhing of elec- tricity when it forms part of the prime conduétor, and at the other end of the ftem be fixed another ball of a proper fize to draw the fpark; when this laft ball is placed in con- tact with the prime conduétor, the other ball will not throw out flathes ; but if it be with- drawn fo as to receive fparks, the external ball, though certainly no more ele€trified than before, will throw out a flafh every time the {park is emitted. 3. A brafs ball of four inches diameter was conneéted by a metallic {tem to the end of the prime condudior of an eleGtrical machine in the pofitive {tate, fufficiently vigorous to throw a flafh into the air now andthen. The metallic ftem, which was about fix inches long, was then changed for ano= ther of the fame dimenfions of deal wood. In this ftate the ball threw out continual flafhes into the air. The experiment was frequently repeated, and the laft refult may naturally be fuppofed to depend on the imperfetion or difcontinuity of the conduéting matter in the wooden ftem. 4. A pointed wire was inferted in the pofitive conductor of Nairne’s elec- trical machiné, with the point upwards. It was then covered with a clean Florence flafk. ‘Lhe point of the wire occupied the centre of the bottle. Whenever the pofitive {park was drawn from the conduétor, the point of the wire exhibited the luminous negative fign. But when the experiment was repeated on the negative condu€tor and the fpark drawn, the point emitted the pofitive flath fo as to fill the whole capacity of the bottle with ramified light. In thefe experiments it may be prefumed, that the efcape at the point was occafioned by un- dulation. 5. The lateral fpark in difcharging a jar may be urged as an inflance of the fame kind. : Thefe obfervations feem to give the advantage in favour of plate-machines as far as re- lates to the efcape. I fhall therefore proceed to defcribe that of Dr. Van Marum*, and afterwards ftate from his report, compared with my own experiments, what may be the proportions of eleétricity collected from each fquare foot, which paffes the cufhion in ma- chines of both kinds. Plate HI exhibits a perfpective view of the machine, and Plate IV a fe€tion, exclufive of the cufhions. In the view it may be obferved that the cufhions are each feparately infu- Jated upon pillars of glafs, and are applied nearly in the dire¢tion of the horizontal diameter of the plate, inftead of the vertical diameter as heretofore. ‘Uhe ball diametrically oppofite to the handle is the prime condu@tor, and the femicircular piece with two cylindrical ends ferves, in the pofition of the drawing, to receive the electricity from the plate. By the happy contrivance of altering the pofition of this femicircular branch from vertical to nearly hori- * Abridged from, the Seconde Continuation des Expériences faites par le Moyen de la Machine EleGrique Teyle- rienne. , zontal, Defer iption of a Simple and Powerful Elerical Machine. 85 zontal, the cylindrical ends may be placed in conta& with the cufhions, and the prime con- ductor inftantly exhibits negative electricity. Butas it is neceflary that the cufhions fhould communicate with the ground when the pofitive power is wanted, and that they fhould be infulated when the negative power is required, there is another femicircular branch applied to the oppofite fide of the plate nearly at right angles. to the firft. That is to fay, when pofitive electricity is wanted, this fecond branch denoted by I. I in the feGtion Fig. 1, Pl.IV, is placed nearly horizontal, and forms a communication from the cufhions to the ground through a metallic rod from K behind the mahogany pillar which fupports the axis; but when on the contrary the negative power is wanted, and the branch from the prime con- ductor is placed in contaét with the cufhions, this other branch from the axis is put into the vertical fituation, and carries off the eleétricity emitted from the plate of glafs. The axis of the plate Bh, Fig. 1, Plate IV, is fupported by a fingle column A, which for- that purpofe is provided with a bearing-piece K, on which two brafs collar-pieces DD, re- pretented more at large and in face in Vig. 3, are fixed, and carry the axis itfelf. ‘Lhe whole of Fig. 1, is reduced to one-eighth of its real dimenfions, unlefs contracted by the fhrinking of the paper after printing; to obviate which, it may be remarked that the dia- meter of the plate is 31 Englifh inches. The axis has a counterpoife O, of lead, to prevent too great friGtion in the collar D neareft the handle. The arc of the conductor EE, which- carries the two fmall receiving conduétors FF, is fixed to the axis G, which turns in the ballH. On the other fide of the plate is feen the other arc U, of brafs wire, half an inch ia diameter, fixed to the extremity of the bearing-piece K, fo that it may be turned in the fame manner asthe arc EE. The two receiving conductors KF are fix inches long,.and two and a half inches in diameter. The double line P reprefents a copper tube terminating in a ball Q. It moves like a radius upon the ftem R of the ball S, which being ferewed into the- condu@tor H, ferves to confine the arm Pin any pofition which may be required. The dia=. meter of the ball S is only two inches, which, together with certain other lefs rounded parts . of this apparatus, may ferve to fhew that the confiderable electricity from this machine is lefs difpofed to efcape than if it had proceeded from a cylinder. The diifipation of elec- tricity along the glafs fupports is prevented by akind of cap T, of mahogany, which affords an eleétrical well or cavity underneath, and likewife effectually covers the metallic caps in- to which the glafs is cemented. _ The lower extremity of the cap is guarded in the fame manner by a hollow piece or ting V, of mahogany, which covers the metallic focket into which the glafs is cemented. The'three glafs pillars are fet in fliding-pieces, as marked on. the platform of Plate III, which are g inches long. ‘The rubbers of this machine differ in no effential particular from thofe defcribed by the inventor in the Journal de Phyfique for February 17913 and the apparatus for applying them is defcribed in the fame work for April 1789. Vig. 2. reprefents a fe€tion of this ju- dicious piece of mechanifm feen from above, and one-fourth of the real ize. A metallic - fliding-piece bb, is flided into a correfpondent face, on the ball Z, which is one of thofe fixed. on the top of the glafs pillars near the circumference of the glafs plate in. Plate Il. To. this is affixed the piece dd, which terminates in two hinges gg, that allow the {pringsice to. move in the plane of the horizon. The pieces gg reprefent the wood-work of the cuthions attached to the extremitics of the fprings by the hingeshh. The fprings are-regulated by - the bolt and fcrew.ii, ‘The two. cufhions are thus made to apply to the plate equally through their ; 85 Defcription of an Eleétrical Machine. their whole length; the actions on the oppofite fides of the plate are accurately the fame 5 and the play of the hinges gg, prevents the plate from being endangered by any ftrain in the dire€tion of its axis. It is certain that, before this adequate provifion was made to fecure thofe effential requifites, it was impracticable to apply the cufhions to a plate with the fame fafety and effe&t as to cylinders, which poflefs much ftrength from their figure. An inge- nious workman will probably find little difficulty in conftru€ting thefe rubbers from this defcription and drawing; but the moft precife information refpeCting every circumftance and dimenfions is to be found in the letters above quoted. The inner extremities of the cufhions are defended by the plates ef gum-lac YY, which cover the three fides or edges, and prevent their attraCting the ele€tric matter from the ends of the receiving conductor. That part of the axis which moves between the collars is made of fteel. The middle of the non-conducting part of the axis is a cylinder of walnut-tree wood aaaa, baked until its infulating power is equal to that of glafs, and then foaked in amber varnifh, while the wood {till remains hot. The two extremities of this cylinder,which are of a lefs diameter, are forced, by ftrong blows, with a mallet, into the ftout brafs caps b and c, in which they are retained by three iron ferews dd. The cylinder aa, and the brafs caps are covered with a layer of gum-lac eeee, to preferve the infulating ftate of the wooden cylinder more perfe@ly, and to prevent the cap b from throwing flafhes to the rubbers. The bottom of the cap b is ferewed home on the tapped extremity of the fteel axis b. The bafe of the cap c, which is four inches in diameter, terminates in an axis one inch thick, and two in length; the extremity of which is formed into a fcrew. The glafs plate is put on this projeCting part, and fecured inits place by a nut of box-wood, forced home by a key, applied in the holesii. ‘Two rings of felt are applied on each fide of the glafs, to defend its furface from the contact of the wood and the metal ; and the central hole in the glafs, which is two inches. in diameter, contains a ring of box-wood, which prevents its immediate application to the axis. f As it is neceffary that the axis G fhould be parallel to the axis of the plate, in order that the conductors FF may move parallel to the plate itfelf, the pillar M is rendered adjuftable by three bearing ferews RR at the bottom, which re-aé& againft the ftrong central fcrew ‘T, and this is drawn downwards by its nut. The conduétors FF are alfo adjuftable by the fliding-pieces vy, and the binding-fcrews ww, which alfo afford an adjuftment to bring the axis of each {mall conductor parallel to the face of the glafs plate. A fimilar adjuftment may be obferved at the extremities of the arc II. Fig. 4. reprefents a fection of the moving part of the branch IT, one-half of its real fize. A brafs plate aa is ferewed to the face of the capital K by three iron {crews 8. To this is {crewed another ring 33, which affords a groove for the moveable ring yy, into which the arms II are fixed. ‘Vhis is accordingly applied in its place before the ring dd is fixed. The wooden part of the rubbers GG, Fig. 2, Plate IV, is covered with thin plates of iron, excepting the furface neareft to the glafs. ‘The intention of this is to maintain a more per- fect communication between the rubbed part of the cufhion and the earth or negative con- ductor, as the cafe may be. The plates of gum-lac YY, are applied to the rubbers, each by means of a thin plate of brafs, to which they are affixed by heat. There are two wires riveted in thefe plates, which are thruft into correfpondent holes in the wooden part of the cufhion. The | Computations of the Power of Eleétrical Machines. 87 The mahogany column A ends ina fquare ¢@, upon which the piece K is fitted and firmly applied, by means of the fcrew and nut exhibited in the feCtion. To afcertain the power of this machine, Dr. Van Marum relates an experiment made be- fore the Dire€tors of the Teylerian Eftablithment, and other philofophical gentlemen, in cir- cumftances not very favourable to the apparatus; but to which he gives the prefgence, on account of the refpeétability of the afliftants. A battery of ninety jars, each containing up- wards of a fquare foot of coated glafs, was charged to the higheft degree by 150 turns of the plate, fo that it difcharged itfelf. The great Teylerian machine with two plates of fixty- five inches diameter in its original ftate, before Dr. Van Marum’s improved rubbers were applied to it,never chargedthe fame battery, in the moft favourable circumftances, in lefs than 66 turns. It follows, therefore, that this {mall and fimple machine exhibited ;{%ths, or about 4ths of the power of that great machinein its firft ftate ; and probably, if the circumftances had been alike favourable in each, ic would have amounted to one half. The Door has grounded a calculation upon thefe faéts ; but as he ftates the rubbed furfaces of thefe two machines, probably by fome miftake in calculation, to be 1243 and 9636 fquare inches ref{pectively, I hall repeat the calculation in this place. The diameter of the plate is 31 inches, and the length of the cufhion 9 inches. Then 31 -7854—31 —18|2.7854=522 fquare inches rubbed by one cufhion on one fide. And 522X4=2088 {quare inches rubbed by the four cufhions. Again in the great machine, the two plates having a diameter of 65 inches, and eight cufhions of 15; inches long, 65\?.7854—65—31)2.7854=2410.4. And 2410.4X8=19283 fquare inches rubbed. But the intenfity of the ele@tric power of a machine will be in the compound ratio inverfely of the furfaces and number of turns when the charge is the fame; Or 1502088 : 66X 19283 >: 1 = the intenfity of the larger machine: 4 = the intenfity of the fmaller. To have increafed the power of fteady excitation four-fold, is certainly an aftonifhing ac- quifition. “This expreffion, however, of the intenfities appears to be lefs generally ufeful than that-of the ratio of the furface rubbed, to that which is charged. This laft exprefhon becomes very fimple when the latter quantity is reduced to 1, or unity. ‘Thus, in the two 19283 X66 machines here mentioned, the rubbed furfaces in inches for the battery are ge goX 144 88 3 ¢ and ar which are equal to the fimple numbers go.5 and 24.0, which refpedtively denote the number of inches rubbed to charge one inch of coated glafs. The great machine charged a fingle foot of glafs, by rubbing 66.6 feet ; and a battery of 224 feet at the rate of 94.8 feet rubbed per foot. If the gradual decay of excitation be fuppofed the fame in the fmall machine here defcribed, it muft have commenced with an intenfity of 17.6. In the Philofophical ‘Tranfactions, already quoted, I have ftated the com- mencing intenfity of a cylinder, excited by the amalgam of zinc, as tried by a jar of 22 feet to be 18.03 and 19.34. But, from my notes, I find that this jar was charged with lefs than 15.0 when the hand was conftantly prefled againft the filk-flap; and alfo, that this preflure increafed the intenfity as 49 to 39 in fome few trials, not enough varied and repeated. "The: labour of turning was very great; much more than, from various circumftances, I am in- clined to fuppofe Mr. Van Marum’s method requires. From this confideration, as well as from the numbers, and the probability that, on account of the lefs undulation, the charges. by a plate may be higher before they explode than thofe by a cylinder, and likewife from D the: $8 Procefs for Bleaching Raw Silk. the large furface expofed to fri€tion, I conclude, that the machine defcribed in this paper is at leaft equalin fleady intenfity, and much fuperior in power of charging, to any cylinder- machine which has ever been made. ” Vil. The Procefs for giving a beautiful White Colour to Raw Silk without Scouring. By M. Baume*. [Concluded from page 32.] To complete the defcription of M. Baumé’s procefs for bleaching filk, nothing more re- mains, than to fhew in what manner he recovers the ardent {pirit, and enfures the purity of the acids made ufe of. Thefe circum{tances are of effential importance to the art: for the procefs would be much too expentfive if the fpirit were loft, and it could not be made to fucceed at all if the acid were impure. The alcohol which has been ufed in bleaching filk, is at and loaded with colouring matter. In this ftate it cannot be again ufed. There are two methods of diftilling it; which have their refpeGtive advantages and inconveniences. By the firft, the acid is loft ; which is faturated with pot-afh, in order that the diftillation may be afterwards performed in a copper alembic. ‘The fecond is performed by diftilling with glafs retorts, or an alembic of filver. In either of thefe veflels, which are not ated upon by the marine acid, the diftil- lation may be performed, and the greater part of the acid recovered. ‘Ihe inventor moft generally practifed the faturation of the acid from reafons of convenience; but recom- mends the ufe of a filver alembic, as being moft economical upon the whole, in a manu- faQlory. A folution of pot-afh is to be poured into the acid fpirit and flirred about to promote the faturation. Carbonic acid is difengaged with ftrong effervefcence from the alkali, and the point of faturation is known by the ufual teft, that the fluid does not redden the tincture ofturnfol. The diftillation is then to be made in the copper alembic, and the alcohol re- ferved in proper veffels, as mentioned at the beginning of this Memoir. If too much alkali fhould have been added, the liquor remaining in the alembic may be ufed in another faturation. ‘Che alkali in this procefs being an expenfive article, Mr. Baumé endeavoured to fupply its place by chalk, quick-lime, and Jime which had been flaked by expofure to the air. But he found that the aCtion of the fpirit upon the calcareous earth, or perhaps the abfence of water, prevented the acid from uniting with that fubffance. The union does not take place to perfeé& faturation in lefs than five or fix wecks, even when the alcohol is diluted with upwards of fifty times its bulk of water. In the fecond procefs for diftilling without alkali, the acid fpirit is diftributed into a great number of glafs retorts, placed in the fand-bath, on the gallery of a furnace. The firft product is {carcely acid ; but what follows is more and more fo, and mutt be kept in veffels of glafs or ftone ware, which become embarraffing on account of their number. The fluid which remains in the retorts has the colour of beer flightly turbid, and contains the greateft part of the marine acid. It muft be poured into one or more retorts, and concentrated by * The Editors of the Journal de Phyfique, to which reference was made at the beginning of this Abftraét, omitted to mention how they obtained it. I find in the Annales de Chimic, XVII. 156, that it was read at the Public Mceting of the Academy at Paris, April 10, 1793. . heat Procefi for Bleaching Raw Silk. 89 heat gradually applied. The firft liquor which comes over is flightly red, turbid, and fcarcely acid. This is to be thrown away, and the receivers changed. ‘The fucceeding product is the colourlefs marine acid, of an aromatic fmell refembling the buds of poplar. ‘The refin of the filk remains in the retort decompofed by the acid. The marine acid thus obtained is weaker than it originally was; which is in fact of little confequence, as it is pure, and may be fafely ufed, either by increafing the dofe proportional to its diminifhed ftrength, or by cohcentrating it, if required, in the ufual way. If this diftillation be made in a filver alembic, inftead of retorts of glafs, and a capital and worm of pure tin be annexed, the alcohol will be obtained fo flightly acid as fcarcely to redden the tin@ure of turnfol; but it is fufficiently acid to receive injury if preferved in a copper veffel. If a cucurbit of filver be prepared, of the capacity of three or four quarts, with a glafs head, the refidues of the firft diftillation may be treated in this veflel in the fame manner as has been direéted for glafs retorts. M. Baumé affirms that he has practifed all thefe operations with glafs retorts and a {mall filver alembic, with the moft perfect fuccefs; but that he made ufe of pot-afh to faturate the marine acid, becaufe he had not a filver veffel of fufficient capacity. From the danger of diftilling large quantities of ardent fpirit in glafs veflels, he is of opinion that no motives of economy are fufficient,to juftify the rifk attend- ing this method. In the ufe of tin, it is neceffary to be careful that it contains no adulte- ration of lead, becaufe the vapours of marine acid have fufficient power to alter this laft metal very confiderably. : ph Upon the firft intimation of this new procefs in France, manufactories were immediately eftablifhed, to the number of twenty or more, without the concurrence of Mr. Baumé, by perfons who confequently were not aware of the apparently minute but very important circumftances neceflary to infure its fuccefs. In particular, the inventor ftates that the marine acid of commerce is unfit for this purpofe. Thisgacid was formerly prepared with the marine falt of the faltpetre manufacturers ; and even when it is made with good falt, the decompofition is effected with common vi- triolic acid which contains nitrous acid. Marine acid mixed with a fmall quantity of nitrous acid does not prevent the filk from being beautifully whitened : it even accelerates the procefs confiderably, and in the moft fatisfactory manner. But the alcohol, every time it is ufed and reétified, becomes charged with the acid and gas of nitre, which aflume the charaéters of the nitrous anodyne liquor. In this ftate, neither diftillations nor repeated retifications from alkali are fufficient to feparate the nitrous matter from the alcohol. Then it is that the fuccefs of the operator vanifhes, with a degree of rapidity equal to the advances which encouraged his hopes at the commencement. The fame difappointments befel M. Baumé at the beginning of his labours; to prevent which, he directs the prepa- ration of the vitriolic and marine acids to the following effect. : ; The vitriolic acid of commerce is obtained by burning fulphur in chambers of lead, with the addition of faltpetre, either crude or of the fecond cryftallization, and a {mall portion of flax. This acid is concentrated and reétified in France, at the place of its fabrication, to 66 degrees of Baumé’s hydrometer, or fpecific gravity in the ufual form 1.848. It contains fulphur, lead, vitriolated tartar, Glauber’s falt, alum, felenite, and particularly the nitrous and marine acid. Vor. L—May 1797. N To 90 Preparation of Acids for Bleaching Raw Silk. To purify it, one hundred pounds of this vitriolic acid is to be mixed in a large bafon of copper with the fame quantity of river water, and flirred with a wooden fpatula. The mixture inftantly becomes heated to the boiling-water point, and a great quantity of red vapour is difengaged, which has the fmell of aqua-regia, and arifes from the nitrous and marine acids. When this mixture is made, it is proper to immerfe the bafon to a fuitable depth in a large veflel of water, to haften the cooling. As foon as it is fufficiently cooled it is to be drawn off into bottles, and left to become clear during feveral days. Great part of the fulphur falls down. ‘The author obtained from four to fix drams. A gallery mult be provided, on which two rows of iron pots of eleven or twelve inches in diameter are to be properly placed for feparate fand-baths, as M. Baumé always praétifed in the fublimation of fal-ammoniac. By this means the retorts are ifolated, and if one breaks, the acid cannot diffufe itfelf and break the others in its vicinity. An empty retort is then to be placed in each pot, and covered with fand. In this way they are much more convenient to arrange, and are attended with no rifk. ; The acid is in the next place to be decanted and conveyed into the retorts by a fyphon funnel, and the rectification ‘proceeded upon until it becomes perfectly white. ‘lowards the end of the operation a {mall quantity of fulphur fublimes in the neck of the retort. Inftead of receivers a fmall glafs cup is placed beneath the aperture of each retort, in order to facilitate the diffipation of the nitrous and marine acids. When the acid in the retorts is fufficiently cooled, it is poured a fecond time into the copper bafon, and mixed with 100 pounds of river water, as at firft, and again concen- trated in the retorts till it becomes perfe&tly clear. Sulphur has been afforded in fome inftances by the fecond re€tification. The liquor which diftills is received in the cups as before, and the acid in the retorts is then fufficiently pure: that is to fay, it is purified from all volatile matter. The lead and neutral falts {till remain combined with the acid, but fortunately they can in no refpe&-injure the purity of the marine acid. This concentrated acid exhibits 68 degrees by the hydrometer, or fpecific gravity 1.896. It {till contains a portion of gas, but fo fmall in quantity as not to injure the puricy of the marine acid, to which it only gives the property of cryftallifing when the temperature of the air is near the freezing point. During the rectification of this acid, what firft comes over is mere water, and mutt be thrown away; but that which fucceeds is the aqueous acid. If this be fet apart, and con- eentrated, a confiderable quantity of vitriolic acid is obtained of the greateft purity. As it has been carried over in diftillation, it contains no foreign matter. The author attempted, but in vain, to diffipate the nitrous acid from the acid of vitriol by ebullition in an open veffel without concentration. The experiment was made with 50 pounds of common vitriolic acid and 60 of river water. ‘This was kept boiling in the copper bafon for four days, water being added from time to time to fupply the lofs by eva- poration. The copper bafon, by weighing before and after the operation, had loft by folution no more than ten drams of copper. The acid was blue, but became white as ufual during the reétification in the retorts. From this experiment, as the author obferves, it is feen not only that the nitrous acid cannot be difipated by fimple ebullition without concen- tration, but that the action of the vitriolic acid upon copper is extremely flight. The marine acid is to be difengaged from common falt by the application of this vitriolic acid Preparation of Acids for Bleaching Raw Silk. gt acid in the ufual manner. But as M: Baumé’s experience led him to various fimple mani- pulations and remarks of importance, and more efpecially as he confiders the defcription of this procefs as part of the new art of bleaching filk, he has annexed it to his memotr. The vitriolic acid obtained by the foregoing” procefs being too concentrated, muft be di- luted in the copper bafon as before with river water. It is convenient to add 18 ounces of water to-each pound of the acid, becaufe the marine acid is not wanted in a ftate of high concentration. ‘This mixture ought to give 35 or 36 degrees by Baumé’s hydrometer; which laft anfwers to a fpecific gravity of 1.333. When ic is cold it may be preferved in bottles for ufe. In the next place, four pounds of marine falt dried, becaufe in that ftate it pours beft, is to be put into a retort of the capacity of five or fix French pints, or Englifh quarts. This may be done by means of a paper funnel, or a long-necked funnel of glafs, which muft enter the body of the retort in order that the neck may remain clean. A number of thefe muft be difpofed on a gallery in two oppofite rows, with the necks properly enclofed and enveloped in fand as ufual. A bottle or gauge being provided of fuch a fize as by previous experiment is known to hold four pounds of the vitriolic acid before mentioned; this quantity of the acid muft be meafured into each of the retorts by means of a curved funnel, the tube of which may pafs into the body, to prevent the acid being fpilled in the neck. If neverthelefs a few drops fhould fall, no inconvenience will follow, as this pure acid is not detrimental to the bleaching procefs. The fupports for the receivers are then to be placed, and the receivers applied, each being pierced with a fmall hole. The junétures are to be made good with pafted paper, and the diftillation begun. A gradual heat is to be applied until the fluid boils gently. The marine acid which firft rifes is volatile and expanfible *, and requires the {mall holes of the receiver to be occafionally opened; but after one fourth part of the time of diftillation the acid comes over freely, and the vapours ceafe to be elaftic. _ This diftillation lafts two days; but it is praCticable to avoid fitting up the intermediate _ night. The fire mutt be fo managed that the contents of the retort may be very liquid in the evening: if it begins to thicken, there is reafon to apprehend that it may be too hard. the next day; in which cafe the heat will dilate the concrete matter before it liquefies, and break the containing veffel. Towards the clofe of the diftillation the matter fwells up confiderably. When this happens, it is proper to empty the receivers, and raife the retorts, that more fand may flow in beneath them. When the matter is dry, and nothing more comes over, the operation is finifhed. ' Each retort affords five pounds of marine acid, of the ftrength of 14 or 15 degrees; fpecific gravity 1.114. When the retorts are half cooled, one pound of hot river water is te be poured into each, and the diftillation being refumed affords 24 ounces of the fame marine acid from cach retort. It is remarkable, that in this procefs fome of the retorts afford the colourlefs and fome the yellow acid ; which is an object of no confequence with regard to the bleaching. The author thinks the yellow colour is owing to a portion of fulphur ftill remaining in the * Tt might be of advantage, even in the large way, to adapt a fimple pneumatic apparatus to condenfe the marine acid air in water, as is ufual in philofophical proceffes. N. i N2 vitriolic 92 Bleaching Raw Silk.—Mathematical Correfpondence. vitriolic acid. And if from curiofity the produéts of feveral of the retorts be received in eight different parts, it will be feen that in fome the acid which paffes firft is the moft concentrated, and gives 20 degrees by the hydrometer; that the produéts diminifh fuc- ceflively in the progrefs of concentration, till ‘the la{t exhibits fometimes no more than eight degrees; but that others afford the moft concentrated acid at the beginning and end, while that in the middle of the diftillation is the weakeft. All thefe produéts mixed together afford a mean refult of 14, 15 or 10 degrees *. The hard compact faline matter in the retort confifts of much Glauber’s falt, and a fmall quantity of undecompofed common falt. M. Baumé’s method of extraéting it is fimple and ingenious. He fills the retort with water, corks it, and inverts it in an open veflel alfo containing water, over which is fixed a board with holes for receiving the neck of the retort. It is proper that the faline mafs fhould be detached, which foon happens in the filled retort, and fuffered to flide down towards the neck before it is placed in the hole of the board. The cork is then taken’ out, and by that means the water in the retort communicates with that of the open veffel. As the falt diffolves, the brine flows down, and is replaced by purer water from below, which from its lefs denfity rifes to the uppermoft place in the retort. In this way the evacuation is made in two days without trouble, which could not fafely be effected in eight or ten days PY fucceflive filling and emptying the retorts. M, Baumé concludes his memoir by defcribing the method of giving a bright yellow to filk, whether raw or bleached. For this purpofe ten gros or drams of nitrous acid are to be mixed with one pound of alcohol, and into this a few ounces of filk are to be immerfed, and kept on the water bath at between 30 and 40 degrees of Reaumur, or roo® and 130° of Fahrenheit. The filk acquires a tarnifhed brown colour, and muft be cleared of its acid by wafhing in feveral waters, and afterwards fcoured with foap in the ufual manner. When thus cleaned and dry, it has the appearance of gold threads when feen in the fun’s light. Different fhades may be given by keeping it a fhorter time in the acidulated fpirit ; all which are equally permanent, and refift wafhing and every other teft. The author propofes them to be ufed in articles of furniture wrought in defigns which require light and fhade. eee ee Se MATHEMATICAL CORRESPONDENCE. In order to accommodate fuch mathematical correfpondents as may refide at a diftance from the metropolis, and are difpofed to contribute_to this part of the work, the folutions to the queftions propofed in any number of the Journal will be uniformly given the fecond month after their publication ; but it is requefted that they may be fent as early as poffible, that proper time may be allowed to prepare them for infertion. - QUESTIONS propofed for Solution, Question III. By Anazrricus. IT is required to determine the odds againft the dealer, at the game of whift, having all the thirteen trumps in his own hand. a * Forthe correfpondent fpecific gravities fee p. 39 of this Journal. 6 QUESTION Fournal of the Polytechnic School at Paris. 93 Question IV. By F. B. GIVEN the time in which mercury is raifed to the boiling point by the heat of a furnace, and the rate of cooling per minute, after it has been removed, to determine the heat of the furnace, or that to which the mercury has been expofed. SCIENTIFIC NEWS. Tuer particular memoirs contained in the four firft cahiers of the Journal of the Poly- technic School at Paris are thirteen in number *: two on ftereotomy; one on fortification; fix on chemiftry; three on general phyfics; and one on the application to the arts. The memoirs of ftereotomy treat: 1. On the determination of tints in defigns, by feveral pupils of the fchool; and 2. On the curve lines of the furface of the ellipfoid, by Monge. The folution of the interefting problem of the determination of tints is deduced from the leffons which Monge has given upon perfpeétive. This folution depends on the funda- mental principle, that all bodies refle&t the white rays; and that the quantity of rays of this colour, reflected from each point of a body, depends on its polifh, and the angles formed by the incident and refleéted rays which come to the eye; that the more white rays are reflected, the more luminous the body will appear; and on the ea the lefs of thefe rays are refleCed, the more obfcure it will be. All polifhed bodies prefent a white fpot or line; the line is vifible say cylinders, cones, &c.; the point, upon furfaces of double curvature. When bodies are perfe€tly polifhed, a white point or determinate furface is perceived ; but when they are obfcure, a fucceflive degradation of tints is feen, which depends on the form of the body. From the point, the line, or the moft enlightened furface, it is poffible to trace a fucceflion of curves of equal tint: thefe are the curves of which the authors of this memoir have in the firft place determined the equation, and afterwards fought to afcertain the law of the de- gradation of the tints. If it be affumed that any tint laid on white paper will poffefs an intenfity dependent on the quantity of colour fpread, and the proportion of white points left uncovered, the authors of the memoir have fought to determine whether the law of the application of tints upon each other ought to depend on their degradation: by this means they have fucceeded in giving the theory of wafhed tints, properly fo called. The folution of this problem, fo interefting to thofe who cultivate the art of defign, and are capable of purfuing the calculation it demands, proves the extended knowledge to which the pupils have arrived, and the progrefs they daily make, under their Inftitutor. The memoir on the curve lines of the furface of the ellipfoid, which Monge has given in the fecond cahier of the Journal Polytechnique, contains an application of the property of curve furfaces with regard to their curvature, to the configuration of {tones for arches. The joints of arch-work ought to be made agreeable to a number of conditions; the chief of which are: “1. They muft be everywhere perpendicular to the arch, * This Analyfis is tranQated from the Journal des Scavans, p. 127. in o4 Fournal of the Polytechnic School at. Paris. in order that the angles of two contiguous key-ftones being refpeCtively equal, they may alike refift difunion by the ation they exercife upon each other. 2. They muft be per- pendicular between the ftones, for the fame reafon. 3. They muft be generated by the motion of a right line ; for the furfaces generated in this manner are alone fufceptible of being accurately wrought ; and it is neceflary that the joints of the contiguous {tones fhould be perfectly well executed, becaufe very flight irregularities would produce a rupture of the arch.” All thefe conditions may be obtained by dividing the curved furfaces of a vault by lines drawn from the one to the other of the two curves; and formed by the movement of a point .of the furface which meets a feries of normals placed. in the fame direction. The diftance between thefe lines muft be a finite quantity, dependent on the nature of the materials. 7 “ The operations of artifts having been conftantly direéted to this general folution, they have obtained it only for the moft eafy cafes of cylindric and conical furfaces, and fuch as are generated by the revolution of a plane. But with regard to curved furfaces of which they know not the lines of curvature, they almoft generally excluded them from the conftrudiion of arches, even when circumi{tances urgently demanded them; and it is principally to this that we are to attribute the bad effe€&t generally produced in architeCture by leaning arches, or portions of arch-work (les morceaux de trait de coupe des pierres), becaufe, in order to render this praCticable, a furface or curvature is chofen for the arch which is not always fuch.as ithe nature of things demands.” The example chofen by Monge for the aaa of his principles, is apparently the moft happy he could have fele&ted in the prefent fituation of the French government, in which architeéts are bufied in the con{tru@tion of halls deftined for the fittings of the Le- giflative Council. Now the form moft favourable to the diftribution of the members of a deliberative affembly, and the fituation of the orator, is the elliptic curve commonly called an oval. From the projeétion of thefe curves, traced on the defigns at the end of, this ‘memoir, it may be feen what agreeable and elegant forms are thus produced; and how eminently the architect may avail himfelf of the principles here eftablifhed, even for the objects of decoration. Students in architecture will find this memoir highly deferving of their perufal. It will more and more convince them of the immenfe refources afforded by the ftudy of ftereotomy for the folidity of conftru€tion, and even for beauty of new forms, afforded by this theory to the fyftem of ornament. ; The art of fecuring thofe who defend a rampart from the ftroke -of balls and thot is known in French by the term defilement. Say, affiftant profeflor in the Polytechnic School, has given a memoir on this fubjeét in the fourth cahier of the Journal of that inf{titution. He fhews in the firft place, that the outline of the defilement is the fame as that of a fhadow afforded by a row of luminous points fituated in the fpace from which the de- fenders of a fortification may be fired on. He divides his ground into two parts: the exterior {pace in which the attacking party may be placed, and the interior {pace which is to be defended. He examines the art of fecuring a work (de filer) in two different cafes: 1. That in which the parapet is determined. 2. That in which the ground plan is given, but not ab- folutely Accounts of New Publications. 95 folutely the relief or profile. To thefe two cafes he adds certain rules for tracing for- tifications, deduced fingly from confiderations relative to their defilement. Thefe three queftions are preceded by fome preliminary notions; and by the method - in which Say has treated his fubjeét, we have acquired in this memoir a more com- plete treatife than any which has yet appeared on defilements. He has the merit of having fixed with clearnefs and precifion, a feries of principles which hitherto have been only tranfmitted in a fugitive and as it were traditional manner, in the School de Me- ziéres, appropriated to the inftrudtion of the é/éves du génie, and deftined again to receive them, according to the meffage long ago fent from the Government to the Legiflative Body, The fix memoirs of chemiftry are: 1. Defcription and ufe of an eudiometer of fulphate of pot-afh (liver of fulphur), by Guyton. 2 Obfervations on the eudiometric properties of phofphorus, by Berthollet. 3. Analyfis of the calcedony of Creufot,. by Guyton. 4. Experiments on the fufibility of earths, and their habitudes with faline fluxes, together. with the folvent aétion they exert on each other, by Guyton. 5. Experiments on the formation of the colouring pruflic principle, by Bonjour. 6. Uhe properties of the ful- phureous acid, and its combination with earths and alkaline bafes, by Fourcroy and: Vauquelin. “+ [Lo be continued. ] NEW PUBLICATIONS, Travels in Hungary, with a fhort Account of Vienna in the Year 1793: By Robert Townfon, LL. D. F.R.S. Edin. &c. &c. Illuftrated with a map and fixteen other cop- per-plates. 4to. 506 pagesincluding the Index. Printed for Robinfon. Price rl. 1s. To thofe who attend chiefly to diplomatical politics, or the balance of power, the king- dom of Hungary will probably afford an objeét of.fubordinate value; but on the larger, more extended and important confiderations of internal government, political economy, and the ftate of man with regard to {cience and manners in the progrefs of civilization, it will prove highly interefting. Mr. Townfon has publifhed the prefent work from the cor- rected notes of a five-months’ tour ; in which thefe and other objects of utility and enter- tainment have engaged his attention. As I hope fhortly to give a fuller account of this: work, the prefent notice is intended only to announce the publication of a valuable and en- tertaining book. The Hiftoire Naturelle of Valmont de Bomare, rangée par ordre de matieres par L. Blondelin of the Univerfity of Bale, ornamented with coloured plates engraved by* J. J. de Méchel, was announced for publication in the middle of February laft, in the Decade Philofophique, &c. It will be printed at Bale; and the Quadrupeds were: then ready for the prefs. It will amount to about 150 fheets, or 6 or 7 volumes in o¢tavo, with at leaft the fame number of plates. One number, containing feven fheets and eight plates, will appear every fecond decade, or one volume of three numbers-every two months. - The price four livres per number, with the figures plain; or fix, if coloured. The fub-- {eribers to the firft sco copies will have the advantage of a deduétion of one-fourth. The plates may be had at the price of two livres, plains” or fix, coloured. Subferibers pay in advance for one number or volume; and.the reft, on delivery, to Cit. 2 Fuchs, , 96 Accounts of New Publications. Fuchs, bookfeller, rue des Mathurins, hotel de Cluny, 4 Paris ; and at Bale, by Cit. L. Blon- delu (perhaps Blondelin as above), agrégé a ’Univerfité. Refutation de la Théorie Pneumatique, &'c. A Refutation of the Pneumatic Theory, © or the New Doétrine of the Modern Chemifts, prefented Article by Article, in a Series of Replies to the Principles colleéted and publithed by Cit. Fourcroy in his Philofophie Chi- mique: to which is prefixed, a Complementary Supplement to the Theory exhibited in a Work entitled Recherches fur les Cau/fes des Principaux Faits Phyfiques ; or, Refearches into the Caufes of the Principal Phyfical Faéts, to which this forms a neceffary Continuation. By J. B. Lamarck, of the National Inftitute of France. O€tavo, 481 pages. Publifhed at Paris, by the Author, at the Mufeum of Natural Hiftory ; and by Agaffe, rue des Poitevins. L’an 4. I have not yet procured the Recherches here mentioned ; ibe, when in poffeffion of both, it will become an object of careful enquiry, whether an abftract of the leading points of difference in this author’s theory and that which ¢ attempts to refute per be of value to the feientific world. i ash si Specimens of Britith | Minerals feledted from the Cabinet of | Philip Rathleigh, of Mena- billy, in the county of Cornwall, Efq. M,P. -E.R.S. and i A.S. with general defcriptions of each article: 4to—s6 pages—33 plates coloured. Nicol a ite. Price 2], 12s. 6d. This magnificent work difplays with great effect the ee confifting of tin, copper and lead ores, with calcareous fpars and quartz. The defcriptions are intended to complete the knowledge, in part and very ftrikingly, conveyed by: the plates. Little is faid in general concerning analyfis, or the component parts. _ Cit. Prony, of the French National Inftitute, has publithed the ead part of the Nouvelle Architeture Hydraulique. This part contains the defcription of fteam engines. It is fold by Firmin Didot, No. 116, rue de Thionville. Quarto, 240 pages, with 40 plates. Price 4o liv, M. Lalande, in the Journal des Scavans page 125, gives the following account of this work: «« Since the appearance of the firft part of the Architeture Hydraulique in 1790, the pub- lic has waited with impatience for the continuation. This part is a complete Treatife on Steam Engines. It contains new experiments on the expanfive power of heat; an account of pumps which have the pifton acted on by the fteam alternately on both fides (pompes.a double effet), and thofe which are fimple ; inftructions for difpofing the latter to a€& in the manner of the former; the theory of the right-lined motion of the pifton by a combination of circular movements; and a method of interpolation applicable to phenomena which depend on elaftic fluids. The analytic part of this work is no lefS-curious than the mecha- nical and experimental parts. Noone but a geometer could have treated thefe fubjects in a manner fo perfpicuous for the leasnghs nor could a lefs able engineer have rendered them fo fatisfatory to practical men.’ Citizen Garnier, Profeffor of Mathematics, has added feveral ufeful explanations of parts of the firft volume of Citizen Prony, which render this work {till more complete. Philos. Journal Vol PW frcrg 2.90 h- j Dy Sil SRT hace 7 ee 2¥ eo.) ee. eee ’ finn ; a cade) > a OE ag c 7 = x 4 ! i . i il | ae a | / ut eatin A f Of aR N AGT OF NATURAL PHILOSOPHY, CHEMISTRY, AND THE: ARTS. : : JUNE 1707. ARTICLE T. A Letter from M. de Humporpr to M. PIcreT, on the Magnetic Polarity of a Mountain of Serpentine *, Ar the beginning of the eighteenth century the attention of natural philofophers was entirely fixed on the phenomena of, magnetifm. ‘The progrefs which has fince been made in the theory of eletricity, and the preponderance which chemiftry has acquired over all the other branches of natural hiftory, have diminifhed the intereft with which enquiries into the nature of the magnetic fluid ought to have been purfued. It is true that your celebrated countrymen Mefirs. de Sauffure and Prevdt have given vigour to this: purfuit by: difcoveries worthy of their fagacity : the firft, by inventing an inftrument capable of meas furing the comparative intenfity of the magnetic forces in different regions of the globe 5, and the other, by reducing the laws of polarity to the fimple laws of attraétion. But thefe difcoveries have not afforded inducement fufficient to lead philofophers into a path fo ho- nourably explored. The moft valuable work on the origin of magnetic forces has been neglected, together with the calculations of the ingenious Coulomb,. and his experiments: with the balance of Torfion. Having trayerfed with the compafs in my hand great part of the mountains of Europe, I became convinced that declinations caufed by maffes of iron in beds or im veins are in- finitely lefs frequent than naturalifts afirm. The obfervations which Meffis. de Sauflure and ‘Trembley have made on the fummit of Cramont ts appear to me the more curious, as * T received this communication in manufcript from the Right Hon. Sir Jofeph Banks, Bart. P. R. $. &c. Ir is written in French, under the title of « Lettre quatriéme de M. de Humboldt a M. Piétet, fur la Polarité Magnetique d’une Montagne de Serpentine.” The fame liberal promoter of {cience has favoured me with a Specimen of this rock, with permiffion to make experiments upon it. A few obfervations on this fpecimen are added at the end of this memoir.+ N, + Voyage dans les Alpes, T. I, P- 375-—T. II, p. 343. VoL. IL—June 1797. 1@) it gs ‘Singular Magnetic Mountain. < it ftands alone, and prefents to our knowledge a very extended image of the dimenfions of magnetic fpheres. It is among the Alps of Sweden and Norway, thofe northern regions which nature has enriched with an enormous depofit of iron lefs oxided than in our country, that we were entitled ta expect fimilar phenomena. : I haften to communicate to you a difcovery I made in the moftth of November, and which appears to me of confiderable importance in the progrefs of geology. You are ac- quainted, Sir, with the laws and the harmony which I have obferved in the direGtion and inclination of the primitive ftrata, from the banks of the Mediterranean to thofe of the Baltic Sea. You have even condefcended, jointly with our friend Dolomieu, to exprefs an intereft with regard to this laborious undertaking; which, in more fkilful hands than mine, would, I am well affured, throw great light on the conftruétion of the globe. I traverfed the chain of mountains of the High Palatinate and the margraviate of Bayreuth; and I found, in the bottom of the Fichtelgebirge, between Munichberg and Goldcronach, an ifolated hill, which rifes to the elevation of fifty toifes above the furrounding plain. Its height above the level of the fea may be eftimated at two hundred and eighty, or three hundred, toifes. This hill extends in length from weft to eaft, and forms a pyramid extremely. obtufe. The rocks which crown the fummit or ridge are compofed of ferpentine of confiderable purity, which, by its colour and foliated fra€ture, approaches in various parts to the chlorithfchiefer of Werner (/chiffous chlorite). This ferpentine is divided into ftrata rather diftin&, of which the inclination to the north-weft prefents an angle between 60 and. 65 degrees. It repofes on a foliated granite, mixed with hornblende; a mixture which we diftinguifh by the name of fyenite. I approached this ferpentine with the compafs, in order to determine more accurately the angle it formed with the meridian. The magnetic needle was ina ftate of continual agitation. I advanced two fteps farther, and beheld that the north pole was entirely turned to the fouth. I called two friends, Meffrs. Godeking and Kil- linger, who aflifted me in my geological purfuits; and we were alike penetrated with that joy which the contemplation of interefting phenomena produces in the minds of thinking men. 1 fhall not detain your attention by a full recital of our obfervations; but fhall merely prefent the refults, to which I may hereafter make additions, if my occupations fhould not lead me from this part of Germany. The aétion of this mountain of ferpentine upon the magnet fhews itfelf in a very curious manner. The uncovered rocks which are feen on the northern flope, and thofe on the declivity towards the fouth, have poles direétly oppofite. The former exhibit only fouth poles, and the latter north poles. ‘The whole mafs of foliated ferpentine does not therefore poffefs a fingle magnetical axis, but prefents an infinity of different axes perfectly parallel to each other. This parallelifm alfo agrees with the magnetic axis of the globe, though the poles of the ferpentine are inverted ; fo that the northern pole of the hill is oppofed to the fouth pole of the earth. The eaft and weftern flopes prefent what in the theory of mag- netifm would be called points of indifference. The magnet does not at this part appear to be in any refpect affected, though the fubftance of the rock differs in no external cha- raéter from the other parts. It is the fame on the fouth fide of the fummit*. I have ob- ferved not only that the magnetic axes are not difpofed in the fame horizontal plane ; but I * I fufpeét an error of the copyift, as the words “ Il en eft de méme du cété meridional de la fommité” contradiét the general de{cription immediately preceding. N. : have er Magnetical Obfervations and Enquiries. 99 have likewife remarked, that two points, of which the ation is very ftrong, are joined by rocks which do not exert the leaft attraftion. The chemical analyfis of thefe compounds affords the fame refults; and it would be no lefs difficult to difcover any difference of ag- gregation between them, than between iron which has received the touch, and other iron which had never acquired the magnetic power. On this occafion a queftion prefents itfelf which cannot be refolved in lefs than half a century. The tables founded on the obfervations of Picard, La Hire, Maraldi, Caffini, and Le Monnier, fhew that the needle has declined fince 1660 towards the weft; and that this declination continues to increafe, though the ofcillations caufed by the heats of the fouth, and the temperature of the feafons, often produce a retrograde courfe. If the magnetic axis of our mountain were aftronomically determined by the culmination of the ftars, whether its direction would remain the fame until the year 1850, or whether its fouth-pole would turn towards the weft, in connetion with the variation of the magnetic needle ? ‘From our profound ignorance of the caufes of the declination, as well as of moft geological phenomena, it is not in our power to refolve fo complicated a problem, Other obfervations equally interefting may be made on the identity of magnetic forces. I have difcovered a mafs of rocks which affeét the needle at the diftance of twenty-two feet. With an apparatus fimilar to the magnetometer of M. de Sauflure, we might obferve whether the intenfity of the forces of magnetic a€tion remains the fame in winter and in fummer ; whether it be ftronger in the morning, at noon, at the folftices, during the aurora borealis, or in an atmofphere loaded with ele€tric fluid? I fuppofe that thefe fame rocks might aé on the needle fometimes at 16, and fometimes at 28 feet diftance. It has been obferved, that metals expofed to the air gradually imbibe the magnetic fluid. A flight oxidation of the iron feems to favour this effe€t. I have myfelf obferved, that in a magnetic bed of iron thofe parts only which were in contact with the air affeéted the needle. This phenomenon is confidered as the effe€&t of atmofpheric eleétricity. Lam aware that lightning converts a bar of iron into a magnet; that the difcharge of the Leyden vial fometimes increafes the intenfity of magnetic forces; but I do not fee why the atmofpheric electricity fhould aé fimply on the external furface of a bed of magnetic iron, which is a good conductor of the eleétric fluid. Does not the oxygene of the atmofphere rather act a part in this operation? Without wandering in the {phere of probabilities, I have chofen to adhere to enquiries refpe€ting facts. Ihave obferved the rocks which were covered with turf, from which I detached pieces that had not been in conta&t with the air.. T found that the magnetic force was conftantly the fame. The mountains of the Harz prefent a granite rock called the fchnarcher, which is elevated in the form of a tower, or broken pyramid. This granite likewife affeéts the needle ; but it acts only in the mafs, and in a fingle band or perpendicular vein, Detached pieces fhew no action upon the needle. It is to Mr. de Trebra, celebrated for his refearches concerning the internal parts of mountains, that we are indebted for this important difcovery. Some philofophers pretend that the {chnarcher contain in their bowels a mafs of magnetic iron; others prefume that a ftroke of lightning has caufed the magnetic vein in thefe mountains. ‘The nature of the rocks which I have the honour to prefent to your notice in this paper does not admit of fimilar explanations, The ferpentine not only aéts in a mafs, in its na- O2 tural 190 Experiments and Obfervations on the Magnetic Serpentine. tural fituation, but all the pieces, when broken, to infinity, ftill exhibit two very diftin& poles. Pieces of five inches diameter a& on the needle at the diftance of half a fcot. The examination of the magnetic axcs affords an object of curious enquiry. They are moftly found in a dire€tion parallel to that of the foliated grain; neverthelefs, I have found-fome which crofs it perpendicularly. Fragments extremely fmall, of the magnitude of 0.01 of a cubic line, few a very ftrong polarity in proportion to their maffes. You fee them turn very fuddenly when the poles of the weakeft magnet are fucceflively prefented to them. It is a very ftriking phenomenon, that a ftone pofleffed of fo high a degree of polarity fhould exhibit no attraGtion for iron which is not magnetifed. I have never obferved the fmalleft particle of filings of iron adhere to the ferpentine; but the ferpentine, reduced to powder, attaches itfelf very readily to the magnet. You will enquire with impatience, if it be well proved that my ferpentine is not mixed with magnetic iron; whether this mixture may not be fufliciently intimate to enter into the ccompolition of each particle of the rock? I can aflure you, that 1 have made the moit afli- duous enquiries in this refpeét. All my experiments were made in conjunétion with Mr. Godeking, whofe knowledge and abilities are a fufficient affurance againft error; but we were decidedly convinced, that if the magnetic force cannot adhere to the earthy fub- ftances which form the bafe of the ferpentine, it can be attributed only to the oxide of iron with which it is coloured. Thefe are our reafons: The rock has no mixture of me- tallic fubftances. It prefents only here and there a few fragments of tale or amianthus; but neither pyrites, nor fchoerl, nor o€tahedrons of magnetic iron. When reduced to very fine powder, itrefembles pounded chalk. The microfcope difcovers only earthy parts, of a clear whitifh green. The {pecific gravity of this ferpentine is very fmall. I find it only from I.gol to 2.04 alluming water to be 1.2. There are not confequently any minerals but pumice-ftone, mountain-leather, and fome varieties of the opal, which do not equal our ferpentine in denfity. The chemical experiments we have hitherto made, prove that it con- tains, like the jade or lapis ollaris, oxided iron; but not iron capable of attraction by the mag- net. The folutions in muriatic acid, mixed with the nitric acid, are yellow, and not green like thofe which the micaceous iron, and all the ores which contain pure or metallic iron, afford. Here then is a very ftriking phenomenon, namely, the polarity of fuper-oxigenated iron. We learn by the valuable experiments of my celebrated countrymen Klaproth and Wenzel, that pure nickel and cobalt are attracted by the magnet; we know that iron flightly oxided (the black oxide) is alfo affected; but how great the difference between this ftate of oxida. tion, and that of the iron which colours the ferpentine, various calcareous ftones, and perhaps even certain vegetable matters ! What difference between a fubftance which aéts alike on the two extremities of the needle, and a ftone of which the fmalleft portions exer- cife a fpontaneous polarity! Let us purfue the path of obfervation; Jet us collect indubi- table faéts. By this method the theories of natural philofophy will be eftablifhed on folid and durable foundations. : Obfervations on the Stone which was forwarded to Sir FOSEPH BANKS with the preceding Memoir. DrscriptTion.—IT is of a blueith opake black colour, every where interf{perfed with mi- nute particles of a yellowith rather filky white, and of no regular figure. No appearance of fymmetry or cryftallization prefents itfelf, except on one fide, where a rough. indication - of Se Experiments and Obfervations on the Magnetic Serpentine. lor of laming is feen. This is in the dire€tion of the magnetic poles. The tenacity is very confiderable, as it was not broken but by a violent blow on around flint. Hardnefs be- tween 6 and 7 of Kirwan; that is to fay, it yields to the knife and file, but greatly injures thofe inftruments. Powder white, or greenifh-white. Fracture coarfe, earthy. Frag- ments rather angular. No fmell, nor adhefion to the tongue; but when two. pieces are ftruck together its {mell is the fame as is given in like circumftances by rock cryftal. Under the hammer it gives fire, but rarely with the fteel. Specific gravity 2.91. Does not im- bibe water. When touched with nitrous acid, a very flight effervefcence took place, which was general and diftin&, but fcarcely vifible without the magnifier. When ftrongly urged with the blow-pipe, it acquired an irregular light-brown colour, and was much lefs tenacious, but fuffered no other change. Acid of borax and microcofmic falt diffolve it with little effervefcence, and very flowly. The glafs of the former is clear green, the latter clear white. Its whole weight was 8238 grains; and that of the piece broken off for experiment, without the contaét or ufe of iron, was 614 grains. It weighed 403 grains in water, and 7 61 si : confequently loft 211 grains. Hence ~4 = 2.91, or the {pecific gravity to water afflumed as1.coo. This differs from the refults found by Mr. Humboldt. The fra€ture was made acrofs the line of magnetical dire€tion. The furfaces which had been thus feparated, exhibited oppofite poles, in the fame manner as when any other na- tural magnet is broken. ‘The fmaller piece was then broken into many fragments, and in part pulverifed. All the pieces were pofleffed of polarity. A fmall five-bar horfe-fhoe magnet took up the fmaller fragments, and the powder, though weakly, as they were eafily fhaken off. Icould not fatisfa€torily afcertain that any part of the ftone did either eee the fineft iron filings, or influence their arrangements when laid upon paper. A very delicate magnetic needle, 13 inches long, moving on an agate focket, was fuffered to difpofe itfelf in the magnetic meridian. The larger piece was prefented due eaft from- the centre, and then moved upon its own centre, to find the pofitions of the*greateft at- traction and repulfion. At the diftance of 18 inches from the middle of the ftone, the needle was perceptibly affeCted ; but its greateft deviation did not exceed ten minutes of a degree. At 12 inches the deviation was one degree, and at fix inches it was about 14 degrees. By application of the ftone clofe to the compafs-box, the needle was led into any pofition at pleafure. It was found on comparifon with various pieces of natural magnet, that its directive force or effeé& on the needle is much weaker than that of any of the pieces. But whether a natural magnet as weak in directive power as this ftone would be equally inactive with regard to iron filings, does not appear from the faéts I have hitherto obferved. II. An Account of fome Experiments upon Coloured Shadows. By Lieutenant General Sir Ben- JAMIN THOMPSON, Count of Rumford, F.. R.S8. In a Letter to Sir FoszeH BANKS, Bart. P. R. 8. * DEAR SIR, INCE my latt letter, being employed in the profecution of my experiments upon light, I was ftruck with a very beautiful, and what to me appeared to be a new appearance. De- * From the Philofophical Tran{aétions, 1794) p. 107- fivous 102 Objervations on Coloured Shadows. firous of comparing the intenfity of the light of a clear fky by day with that of a common wax-candle, I darkened my room, and letting the day-light from the north, coming through a hole near the top of the window-fhutter, fall at an angle of about 70° upon a fheet of very fine white paper, I placed a burning wax-candle in fuch a pofition that its rays fell upon the fame paper, and, as near as I could guefs, in the line of refleCtion of the rays of day-light from without; when, interpofing a cylinder of wood, about half an inch in diameter, before the centre of the paper, and at the diftance of about two inches from its furface, I was much furprifed to findthat the two fhadows projected by the cylinder upon the paper, in- ftead of being merely fhades without colour, as I expected, the one of them, that which, correfponding with the beam of day-light, was illuminated by the candle, was yellow; while the other, correfponding to the light of the candle, and confequently illuminated by the light of the heavens, was of the moft beautiful blue that it is poflible to imagine. This appearance, which was not only unexpeéted, but was really in itfelf in the higheft degree ftriking and beautiful, I found upon repeated trials,and after varying the experiment in every way I could think of, to be fo perfectly permanent, that it is abfolutely impoffible to produce two fhadows at the fame time, from the fame body, the one anfwering to a beam of day-light and the other to the light of a candle or lamp, without thefe fhadows being coloured, the one yellow, and the other blue. The experiment may very eafily be made at any time by day, and almoft in any place, and even by a perfon not in the leaft degree verfed in experimental refearches. Nothing more is neceflary for that purpofe than to take a burning candle into a darkened room, in the day-time, and open one of the window-fhutters a little, about half or three-quarters of an inch for inftance ; when, the candle being placed upon a table or ftand, or given to an affiftant to hold, in fuch a fituation that the rays from the candle may meet thofe of day- light from without af an angle of about 40° at the furface of a theet of white paper, held in a proper pofition to receive them, any folid opake body, a cylinder, or even a finger, held before the paper, at the diftance of two or three inches, will project two fhadows upon the paper, the one blue and the other yellow. If the candle be brought nearer to the paper, the blue fhadow will become of a deeper hue, and the yellow fhadow will gradually grow fainter; but if it ‘be removed farther off the yellow fhadow will become of a deeper colour, and the blue fhadow will become fainter; and the candle remaining ftationary in the fame place, the fame varieties in the ftrength of the tints of the coloured fhadows may be produced merely by opening the window- fhutter a little more or lefs, and rendering the illumination of the paper, by the light from without, ftronger or weaker. By either of thefe means, the coloured fhadows may be made to pafs through all the gradations of fhade, from the deepeft to the lighteft, and vice verfa; and it is nota little amufing to fee fhadows thus glowing with all the brilliancy of the pureft and moft intenfe prifmatic colours, then pafling fuddenly through all the varieties of fhade, preferving in all the moft perfe&t purity of tint, growing ftronger and fainter, and vanifhing and returning, at command. With refpeét to the caufes of the colours of thefe fhadows, there is no doubt but they arife from the different qualities of the light by which they are illuminated; but how they are produced, does not appear to me fo evident. That the fhadow correfponding to the beam of day-light which is illuminated by the yellow light of a candle, fhould be of a yellowith hue, is not furprifing ; but why is the fhadow correfponding to the’light of the 2 candle, 4 Obfervations on Coloured Shadows. 103 eandle, and which is illuminated by no other light than the apparently white light of the heavens, blue? I at firft thought that it might arife from the bluenefs of the fky; but find- ing that the broad day-light refle€ted from the roof of a neighbouring houfe covered with the whiteft new-fallen fnow produced the fame blue colour, and, if poffible, of a ftill more beautiful tint, I was obliged to abandon that opinion. To afcertain with fome degree of precifion the real colour of the light emitted by a candle, I placed a lighted wax-candle, well trimmed, in the open air, at mid-day, at atime when the ground was deeply covered with new-fallen fnow, and the heavens were overfpread with white clouds; when the flame of the candle, far from being white, as it appears to be when viewed by night, was evidently of a very decided yellow colour, not even approaching to whitenefs. The flame of an Argand’s lamp, expofed at the fame time in the open airy appeared to be of the fame yellow hue. But the moft ftriking manner of fhewing the yellow hue of the light emitted by lamps and candles, is by expofing them in the direct rays of a bright meridian fun. In that fituation the flame of an Argand’s lamp, burning with its greateft brilliancy, appears in the form of a dead yellow femi-tranfparent {moke. How tranfcendently pure and inconceivably bright the rays of the fun are when compared to the light of any-of our artificial illuminators, may be eee from the refult of this ex- periment. It appearing to me very probable that the difference in the whitenefs of the two kinds of light which were the fubjeéts of the foregoing experiments, might fomehow or other be the occafion of the different colours of the fhadows, I attempted to produce the fame effects by employing two artificial lights of different colours; and in this I fucceeded completely. In a room previoufly darkened, the light from two burning wax-candles being made to fall upon the white paper, at a proper angle, in order to form two diftinét fhadows of the cylinder, thefe fhadows were found not to be in the-leaft coloured ; 5*but upon interpofing a pane of yellow glafs, approaching toa faint orange colour, before one of the candles, one of the fhadows immediately became yellow, and the other blue.’ When two Argand’s lamps were made ufe of, inftead of the candles, the refult was the-fame: the fhadows were conftantly and very deeply coloured, the one yellow, approaching to orange, and the other blue, approaching to green. I imagined that the greenith caft of this blue colour was owing either to the want of whitenefs of the one light, or to the orange hue of the other, which it acquired from the glafs. When equal panes of the fame yellow glafs were interpofed before both the lights, the white paper took an orange hue ; but the fhadows were to all appearance without the leat tinge of colour; but two panes of 'the yellow glafs being afterwards interpofed before one of the lights, while only one pane remained before the other, the colours of the fhigows immediately returned. The refult of thefe experiments having confirmed my Galpicions that the colours of the fhadows arofe from the different degrees of whitenefs of the two lights, I now endeavoured, by bringing day-light to be of the fame yellow’ tinge with candle-light by the interpofition of fheets of coloured glafs, to prevent the fhadows being coloured when day-light and candle-light were together the fubjects of the experiment; and in this I fucceeded. I was even able to reverfe the colours of the fhadows, by caufing the day-light to be of a deeper . ycllow 104 Obfervations on Coloured Shadows. yellow than the candle-light. In the courfe of thefe experiments I obferved that different fhades of yellow given to the day-light produced very different and often quite unexpected effets: thus one theet of the yellow glafs interpofed before the beam of day-light changed the yellow fhadow to a lively violet colour, and the blue fhadow to a light green ; two theets of the fame glafs nearly deftroyed the colours of both the fhadows; and three fheets changed the fhadow which was originally yellow to blue, and that which was blue to a purplith yellow colour. When the beam of day-light was made to pafs through a fheet of blue glafs, the colours of the fhadows, the yellow as well as the blue, were improved and rendered in the higheft degree clear and brilliant ; but when the blue glafs was placed before the candle, the colours of the thadows were very much impaired. In order to fee what would be the confequence of rendering the candle-light of a ftill deeper yellow, 1 interpofed before it a fheet of yellow or rather orange-coloured glafs 5 when a very unexpeéted and moft beautiful appearance took place. ‘The colour of the yellow thadow was changed to orange, the blue fhadow remained unchanged, and the whole furface of the paper appeared to be tinged of a moft beautiful violet colour, approach- jing to a light crimfon or pink; almoft exaétly the fame hue as I have often obferved the diftant fnowy mountains and valleys of the Alps to take about fun-fet. Is it not more than probable that this hue is in both cafes produced by nearly the fame combinations of coloured light ? In the one cafe it is the white fnow illuminated at the fame time by the pureft light of the heavens, and by the deep yellow rays from the weft; and in the other it is the white paper illuminated by broad day-light, and by the rays from a burning candle, rendered {tilk - more yellow by being tranfmitted through the yellow glafs. The beautiful violet colour ‘ which fpreads itfelf over the furface of the paper will appear to the greateft advantage if the pane of orange-coloured glafs be held in fuch a manner before the candle, that only a part of the paper, half of it, for inftance, be affected by it, the other half remaining white. To make thefe experiments with more convenience, the paper, which may be about eight or ten inches fquare, fhould be pafted or glued down upon a flat piece of board, fur= nifhed with a ball and focket upon the hinder fide of it,and mounted upon a ftand, and the cylinder fhould be faftened to a fmall arm of wood or of metal, projecting forward from the bottom of the board for that purpofe. A fmall ftand, capable of being made higher or lower as the occafion requires, fhould likewife be provided for fupporting the candle; and if the board with the paper faftened upon it be furrounded with a broad black frame, the experiments will be fo much the more ftriking and beautiful. For ftill greater convenience, 1 have added two other ftands for holding the coloured glafs through which the light is occafionally made to pafs in its way to the white furface upon which the fhadows are projected. It will be hardly neceflary to add, that, in order to the experiments appearing to the greateft advantage, all light which is not abfolutely neceffary to the experiment mutt be carefully fhut out. 4 Having fitted up a little apparatus, according to the above directions, merely for the pur= pole of profecuting thefe enquiries refpecting the coloured fhadows, I proceeded to make a great variety of experiments, fome with pointed views, and others quite at random, and merely in hopes of making fome accidental difcovery that might lead to a knowledge of the caufes of appearances which {till feemed to me to be enveloped iu much obfcurity and uncertainty- Having Obfervations on Coloured Shadows. 105 Having found that the fhadows correfponding to two like wax candles were coloured, the one blue and the other yellow, by interpofing a theet of yellow glafs before one of them; I now tried what the effect would be when blue glafs was made ufe of inftead of yellow, and I found it to be the fame; the fhadows were ftill coloured, the one blue and the other yellow, with the difference, however, that the colours of the fhadows were re- verfed, that which with the yellow glafs was before yellow being now blue, and that which was blue being yellow. I afterwards tried a glafs of a bright amethyft colour, and was furprifed to find that the fhadows ftill continued to be coloured blue and yellow. The yellow, it is true, had a dirty purple caft; but the blue, though a little inclining to green, was neverthelefs a clean, bright, decided colour. Having no other coloured glafs at hand to pufh thefe particular enquiries farther, I now removed the candles, and, opening two holes in the upper parts of the fhutters of two neighbouring windows, I let into the room, from above, two beams of light from dif- ferent parts of the heavens; and placing the inftrument in fuch a manner that two diflin@ fhadows were projected by the cylinder upon the paper, I was entertained by a fucceflion of very amufing appearances. The fhadows were tinged with an infinite variety of the moft unexpected, and often moft beautiful colours, which, continually varying, fometimes flowly ‘and fometimes with inconceivable rapidity, abfolutely fafcinated the eyes, and, commanding the moft eager attention, afforded an enjoyment as new as it was bewitching. It wasa windy day, with flying clouds; and it feemed as if every cloud that paffed brought with it another complete fucceffion of varying hues and moft harmonious tints. If any colour could be faid to predominate, it was purple ; but all the varieties of browns, and almoft all the other colours I ever remembered to have feen, appeared in their turns; and there were even colours which feemed to me to be perfeCtly new. Refleing upon the great variety of colours obferved in thefe laft experiments, many of which did not appear to have the leaft relation to the apparent colours of the light by which they were produced, I began to fufpect that the colours of the fhadows might in many cafes, notwithftanding their apparent brilliancy, be merely an optical deception, owing to " contraft, or to fome effect of the other neighbouring colours upon the eye. To determine this fa&t by a dire&t experiment, I proceeded in the following manner : Having, by making ufe of a flat ruler, inftead of the cylinder, contrived to render the fhadows much broader, I fhut out of the room every ray of day-light, and prepared to make the experiment with two Argand’s lamps, well trimmed, and which were both made to burn with the greateft poflible brilliancy ; and having affured myfelf that the light they emitted was precifely of the fame colour, by the fhadows being perfectly colourlefs which were projected upon the white paper, I direéted a tube about 12 inches long, and near an inch in diameter, lined with black paper, againft the centre of one of the broad fhadows ; and looking through this tube with one eye, while the other was clofed, I kept my attention fixed upon the fhadow, while an affiftant repeatedly interpofed a fheet of yellow glafs before the lamp, whofe light correfponded to the fhadow I obferved, and as often removed it. The refult of the experiment was very ftriking, and fully confirmed my fufpicions with refpect to the fallacy of many of the appearances in the foregoing experiments. So far from being able to obferve any change in the fhadow upon which my eye was fixed, 1 was not able Vox. I.—JuNeE 1797: P even 106 Objervations on Coloured Shadozws. even to tell when the yellow glafs was before the lamp, and when it was not; and though the afliftant often exclaimed at the ftriking brilliancy and beauty of the blue colour of the very fhadow I was obferving, I could not difcover in itthe leaft appearance of any colour at all. But as foon as I removed my eye from the tube, and contemplated the fhadow with all its neighbouring accompaniments, the other fhadows rendered really yellow by the effeét of the yellow glafs, and the white paper, which had likewife from the fame caufe acquired a yellowifh hue, the fhadow in queftion appeared to me, as it did to my afliftant, of a beautiful blue colour. I afterwards repeated the fame experiment with the apparently blue thadow produced in the experiment with day-light and candle-light, and with exaétly the fame refult. How far thefe experiments may enable us to account for the apparent blue colour of the fky, and the great variety of colours which frequently adorn the clouds, as alfo what other ufeful obfervations may be drawn from them, Ileave to philofophers, opticians, and painters to determine. In the mean time, I believe it isa new difcovery; at leaft it is undoubtedly a very extraordinary fa&, that the eyes are not ut always to be believed, even with refpe& to the prefence or abfence of colours. I cannot finith this letter without mentioning one circumftance which ftruck me very forcibly in all thefe experiments upon coloured fhadows, and that is, the moft perfect har- mony which always appeared to fubfift between the colours, whatever they were, of the two fhadows; and this harmony feemed to me to be full as perfect and pleafing when the fhadows were of different tints of brown, as when one of them was blue and the other yellow. Tn fhort, the harmony of thefe colours was in all cafes not only very ftriking, but the ap- pearances were altogether. quite enchanting; and I never found any body to whom I thewed thefe experiments, whofe eyes were not fafcinated with their bewitching beauties. It is however more than probable, that a great part of the pleafure which thefe experi- ments afforded to the {peétators, arofe from the continual changes of colour, tint, and fhade with which the eye was amufed, and the attention kept awake. We are ufed to feeing colours fixed and unalterable, hard as the folid bodies from which they come, and juft as motionlefs ; confequently dead, uninterefting, and tirefome to the eye; ein in thefe experi- ments, all is motion, life and beauty. It appears to me very probable, that a further profecution of thefe experiments upon coloured fhadows may not only lead to a knowledge of the real nature of the harmony of colours, or the peculiar circumftances upon which that harmony depends; but that it may alfo enable us to conftru& inftruments for producing that harmony for the entertainment of the eyes, in a manner fimilar to that in which the ears are entertained by mufical founds. I know that attempts have already been made for that purpofe; but when I confider the means em- ployed, I am not furprifed that they did not fucceed. Where the flowing tide, the varying fwell, the crefcendo is wanting, colours muft ever remain hard, cold, and inanimate maffes, Tam very forry that my more ferious occupations do not at prefent permit me to purfue’ thefe moft entertaining enquiries. Perhaps at fome future period I may find leifure to re- fume them *. Iam; &c.‘ Munich, March 1, 1793. © * Otto Guericke, Buffon, Mazcas, Beguclin, and many other philofophers, have paid attention to the coloured Shadows of bodies which form the fubjeét of this ee letter. An abridgement of their obfervations and Original Difcovery of America. 107 Ill. A Memoir upon the Difcovery of America. By M.-Orro. [Concluded from page 77.] “Aprer having performed feveral other interefting voyages, the Chevalier Behem died at Lifbon in July 1506, regretted by every one, but leaving behind him no other. work than the globe which we have juft been fpeaking of. It is made from the writings of Ptolemy, Pliny, Strabo, and efpecially from the account of Mark Paul, the Venetian, a celebrated traveller of the thirteenth century; and of John Mandeville, an Englifhman, who, about the middle of the fourteenth century, publifhed an account of a journey of thirty-three years in Africa and Afia. He has alfo added the important difcoveries made by himfelf on the coafts of Africa and America. From thefe circumftantial accounts, little known to modern writers, we muft conclude that Martin Behenira, of whom Garcilaffo makes mention, is the fame Chevalier Behem, upon being the place of whofe birth Nurenberg prides itfelf fo much. It is probable that, as foon as he was knighted in Portugal, he thought it neceflary to give a Portuguefe ter- mination to his name, to make it more fonorous and more conformable to the idiom of the country. Garcilaffo, deceived by this refemblance of found, has made him a Spaniard, in order to deprive Chriftopher Columbus of the honour of having procured to his country fo great.an advantage. And what ought to confirm us in this opinion is, that we neither find in Mariana, nor any other Spanifh hiftorian, the name of this Martin Behenira, who was certainly a man of too much importance not to have had a diftinguifhed place in hiftory. Befides, the Spanith pride would have been flattered in giving to a native thofe laurels with which it crowned Chriftopher Columbus. It is then very unlikely that this navigator was treated as an enthufiaft, when he offered to the Court of Portugal to make difcoveries in the weft. The fearch after unknown countries was at that time the reigning paflion of this Court; and even if the Chevalier Behem had not offered the interefting ideas which he had procured, the novelty of the project would undoubtedly have engaged King John to fupport the views of Columbus: but it appears that this prince declined it, becaufe all his thoughts were turned at that time to the coaft of Africa, and the new paffage to the Indies, from whence he procured great riches; whilft the fouthern coatt of Brazil, and the territories of the Patagonians, feen by Behem, offered to him only barren lands inhabited by unconquerable favages. The refufal of John IL, very far from weakening the teftimony of Behem’s difcoveries, is then and deduétions may be feen in Pricftley’s Optics, p. 436. Count Rumford is the firft, as far as T know, who has thewn that the effeét depends not immediately on the nature of the light, but principally upon the manner in which the organs of fight, or perhaps the organs of thought (if in truth there be any difference here betweenthem ), are atfeéted by the ficceflive actions they undergo. The colours called accidental, which are rene dered permanent for atime after the impreffion of bright objeéts upon the eye, and the effeéts of lefs forcible impreflions, for which the laft quoted work, p. 631, and the authors there referred to, may be confulted ;—the harmony and difcord of colours, probably arifing from the pleafure or difgutt afforded by the admixture of an accidental colour with anew fenfation, or real colour;—the phenomena of dazzling, which is of the fame nature ae this Jaft combination ;—~and the general arrangement and inferences to be found in the Zoonomia of Darwin, all bear evident relation to the faéts exhibited by Count Rumford, and open a wide field for curious refearch. .N, P2 rather 108 Original Difeovery of America. rather a proof of the knowledge which this politic prince had already procured of the exiftence of a new continent: and it was only in 1501, that is to fay, three years after the voyage of Vafco de Gama to the Indies, that Emanuel thought proper to take advantage of the difcoveries of Behem, by fending Albarez Cabral to Brazil; a meafure which was perhaps rather owing to the jealoufy which has always exifted between Portugal and Spain, than to a defire of making advantageous eftablifhments, for which the Indies were much more proper than this part of America. If any doubts yet remain refpeéting the important difcovery made by the Chevalier Behem, it is particularly the authority of Dr. Robertfon which attacks the teftimony of the different authors we have tranfcribed. This learned writer treats the hiftory of Behem as a fiction of fome German authors, who had an inclination to attribute to one of their countrymen a difcovery which has produced fo great a revolution in the commerce of Europe. But he acknowledges, neverthelefs, after Herrera, that Behem had fettled at the ifland of Fayal; that he was the intimate friend of Chriftopher Columbus; and that Ma- gellan had a globe made by Behem, by the help of which he undertook his voyage to the South Sea; a circumftance which proves much in favour of our hypothefis. He relates alfo, that in 1492 this aftronomer paid a vifit to his family at Nurenberg, and left there 2 map drawn by himfelf, of which Dr. Forfter procured him a copy, and which, in his opinion, partakes of the imperfection of the cofmographical knowledge of the rsth century: that he found init, indeed, under the name of the ifland of St. Brandon, land which appears to be the prtefent coaft of Guiana, and lies in the latitude of Cape Verd; but that there is reafon to believe that this fabulous ifland, which is found in many ancient maps, merits no more at= tention than the childith legend of St. Brandon himfelf. Although Dr. Robertfon does not appear difpofed to grant to Behem the honour of having difcovered the new continent, we find the means of refuting him in his own Hiftory. He allows that Behem was very intimate with Chriftopher Columbus; that he was the greateft geographer of his time, and fcholar of the celebrated John Miiller, or Regiomontanus; that he had difcovered, in 1483, the kingdom of Congo upon the coaft of Africa; that he made a globe which Magellan made ufe of; that he drew a map at Nurenberg, containing the particulars of his difcoveries; and that he placed in this chart land which is found to be in the latitude of Guiana. Dr. Ro- bertfon afferts, without any proof, that this land was but a fabulous ifland. We may fuppofe, upon the fame foundation, that the Chevalier Behem, engaged in an expedition to the king- dom of Congo, was driven by the winds to Fernambouc, and from thence by the currents very common in thofe latitudes towards the coaft of Guiana; and that he took for an ifland the firft land which he difcovered. The courfe which Chriftopher Columbus afterwards fered makes this fuppofition {till more probable; for if he knew only of the coaft of Brazil, which they believe to have been difcovered by Behem, he would have laid his courfe rather to the fouth-weft. ‘The expedition to Congo took place in 1483 : it is then poflible that at his return Behem propofed a voyage to the coafts of Brazil and Patagonia; and that he requefted the affiftance of his fovereign, which we have mentioned above. It is certain that we cannot have too much deference for the gpinion of fo eminent a writer as Robertfon; but this learned man not having it in his power to confult the original German documents which we have quoted, we may be allowed to form a different opinion without being too prefumptuous. 4 But Origimal Difcovery of American 209 But fhould it be afked, Why we take from Chriftopher Columbus the reputation which alt Europe has to this day allowed him?—why fearch into the archives of an imperial city for the caufes of an event which took place in the moft weftern extremity of Europe ? —why the enemies of Chriftopher Columbus, who were numerous, did not take ad- vantage of the pretended Chevalier Behem to leffen his confequence at the Spanifh Court? —why Portugal, jealous of the difcovery of the New World, has not protefted againft the affertions of the Spaniards —why Behem, who died only in 1506, had not left to pofterity any writing to confirm to himfelf fo important a difcovery? To anfwer all thefe queftions, I fhall fubmit to the aespareel reader the following * remarks : 1. Before Columbus, the great merit of a navigator confifted rather in conceiving the poflibility of the exiftence of a new continent, than in fearching for lands in a region where he was fure to find them. If it is then certain that Behem had conceived this bold idea before Columbus, the fame of the latter muft be confiderably diminifhed. 2. The hiftorical proofs which we have given above leaving us no doubt of the fact, we have only to explain the moral caufes of the filence of the 5A reg and Portuguefe authors, of the enemies of Columbus, and of Behem himfelf. 3. It is well known that, previous to the reign of Charles V. there was little communi- cation between the learned men of different nations. Writers were fcarce, excepting fome monks, who have related, well or ill, the events which came to their knowledge, in chro- nicles which are no longer read; or they had but little notion of what pafled in foreign countries. Gazettes and Journals were unknown, and the Learned were obliged to travel, to inform themfelves of the progrefs of their neighbours. Italy was the centre of the arts, and what are called fciences, at that time. The frequent journeys of the German emperors to Rome gave them an opportunity of knowing perfons of merit, and of placing them in the different univerfities of the empire. It is to this circumftance that we ought to attribute the- great progrefs which the Germans made, particularly in mathematics, from the four- teenth to the fixteenth century; during which time they had the beft geographers, the beft hiftorians, and the moft enlightened politicians. They were particularly attentive to what pafled in Europe; and the multiplied connections of different princes with foreign powers affifted them greatly in colleéting, in their archives, the original pieces of the molt important events of Europe. It is to this fpirit of criticifm and enquiry that we are in- debted for the reformation of Luther ; and we cannot deny that, particularly in the fifteenth century, there wes more hiftorical and political knowledge in Germany than in all the reft of Europe, Italy excepted. It is not then aftonifhing that we fhould find, in the archives of one of the moft ancient imperial cities, the particulars of an expedition planned upon the banks of the Tagus, by a German, a man of great repute in his own country, and whofe every action became very interefting. 4. It was different in Portugal, where the whole nation, except the king, was plunged in the moft profound ignorance. Every one was either merchant, failor or foldier; and if this nation has made the moft important difcoveries, we mutt afcribe them rather to avarice than to a defire of knowledge. ‘They were fatisfied with feraping together gold in every quarter of the known world, whilft the German and the Italian took up the pen to tranfmit to poflerity the remembrance of their riches and. cruelties. The Spaniards were not 119 Difeovery of America. Grawimeter. not much more informed before Charles Vs introduced at Madrid the learned men of Flanders and Germany. It is then very poflible that the Chevalier Behem made very in- terefting difcoveries in geography in 1485, without the public being acquainted with them. If he had brought back from his expedition gold or diamonds, the news-would have been fpread in a few weeks; but fimple geographical knowledge was not of a nature to intereft men of this turn of mind. 5. The long ftay which Chriftopher Columbus made at Madeira makes his interview with Behem more than probable. It is impoflible that he fhould have negleéted feeing a man fo interefting, and who could give him every kind of information for the execution of the plan he had formed. ‘The mariners who accompanied the Chevalier Behem might alfo have fpread reports at Madeira and the Azores concerning the difcovery which they had been witneffes of. What ought to confirm us in this is, that Mariana fays himfelf (book xxvit chap. iii.) that a certain veflel going to Africa was thrown by a gale of wind upon certain unknown lands; and that the failors, at their return to Madeira, had communicated to Chriftopher Columbus the circumftances of their voyage. All authors agree that this learned man had fome information refpecting the weftern fhores; but they fpeak in a very vague manner. The expedition of the Chevalier Behem explains this myftery. 6. This aftronomer could not be jealous of the difcoveries of Columbus, becaufe the laft had been farther north, and that in a time when they did not know the whole extent of the New World; and when geographical knowledge was extremely bounded, it might be believed that the country difcovered by Columbus had no conneétion with that difcovered by Behem. It appears however certain, that Behem difcovered this continent before Columbus; and _that this queftion, which is only curious in Europe, becomes interefting to the American patriot. The Grecians have carefully preferved the fabulous hiftory of their firft founders, and have raifed altars to'them: Why are not Behem, Chriftopher Columbus, and Vefpucius deferving of ftatues in the public fquares of American cities? Thefe precious monuments would tranfmit to pofterity the gratitude which thefe benefactors of mankind fhould infpire. Without knowing it, they have laid the foundation of the happinefs of many millions of ‘inhabitants; and Sefoftris, Phul, Cyrus, Thefeus, and Romulus, the founders of the greateft empires, will be forgotten before the fervices rendered by thefe illuflrious navigators can be effaced from the memory of man. IV. Défeription of a Gravimeter,or Infrument for meafuring the Specific Gravity of Solids and Fluids. By Citizen Gurron *. Ever fince the art of chemiftry, by an approach to the accurate feiences, has fhewn that the phenomena of combinations produced or deftroyed are not the refult of occult qualities, but of a rupture of equilibrium determined by forees which afford the hope of ad- meafurement by computation, philofophers have been aware of the neceflity of conduéting their experiments with precifion, that they might take account of all the circumftances * Read to the National Inftitute on the rth Germinal, in the 4th year of the Republic. Iris inferted in the ewenty-firt volume of the Annales de Chimie. This tranflatiow is nearly verbal. ; which ——— ae New Infirument for Meafuring Specific Gravities. III which might impede or favour this motion. The fpecific gravity of bodies muft neceffarily conftitute part of thofe obfervations: for it ferves not only to indicate the nature of bodies under examination, but likewife affords information refpeéting their purity, and the ftate of their aggregation, condenfation, or rarefa€tion, which are alfo the immediate caufes of divulGion or repofe. It is therefore of importance. that the inftruments for meafuring this property of bodies fhould be brought to the utmoft perfection they are capable of receiving, and that they fhould be rendered as convenient as pofible for habitual ufe. Of all the hydrometers hitherto known, that of Fahrenheit is acknowledged to be the riot accurate. The well known principle of this inftrument is, that it afcertains the weight of a conftant bulk of the feveral fluids under examination. Such hydrometers as are conftructed to meafure the denfity by the degree of immerfion; may ferve, in fome manufactories, to give an approximation fufficiently near for the purpofe required. But without confidering the inequality of the ftem, the tedious work. of graduating by obfervation,and the uneer- tainty of eftimate from one divifion to another, it may be remarked, that they are not capable of correétion for the different temperatures. Ina word, they are not fit for the hand of the philofopher. The form which Nicholfon gave fome years ago to the hydrometer of Fahrenheit *, ren- dered it proper to meafure the denfity of folids, At prefentit is very much ufed. It gives, with confiderable accuracy, the ratio of the f{pecific gravity to the fifth decimal, water being taken as unity. It is fufceptible of correction for the variations of temperature, and the impurity of the water which it is fometimes more convenient to ufe, as may be feen in the article Areometer, in the chemical part of the Encyclopedie Methodique. It does not ap- pear that any better inftrument need be wifhed for in this refpect. But this hydrometer has hitherto been conftructed in metal only; fo that it could not be applied either to falts or acids. It is known likewife that areometers conftructed on the principles of Fahrenheit, for fpirituous, faline, and acid liquors, require to be varied in magnitude, form, and quantity of ballaft. In the one kind, the lower weight muft be at a great diftance from the buoyant part, to maintain the vertical fituation; in the other, it is brought nearer, to operate on fmaller mafles of the fluid. Thofe inftruments which are intended for alcohol mutt be light, and thofe applied to determine the denfity of concen- trated acids muft be heavy. The mafs and dimenfions of every inftrument of this nature muft be adjufted in fuch a manner that the additional weight may operate not only as a load, but as ballaft. It cannot be applied in the upper bafon without deranging the ver- tical fituation. From all which circumflances it happens, that a colle€tion of thefe inftru- ments would be required, to anfwer every purpofe of experiment. As a remedy for part of thefe inconveniences, it was ingenioufly propofed that the areometer fhould terminate be~ neath in a hook, to which were fufpended at pleafure certain glafs balls filled with mercury, * From Lowthorpe’s Abridgement of the Philofophical_Tranfaétions, I. 604, or Boyle’s Works, in quarto, London, 1772, 1V. 204, it appears that the hydrometer was firft invented by Boyle, and deferibed under the name of anew Effay Inftrument. It hada graduated ftem, and, by means of a ftirrup or clip underneath, it was. epplied, as perfectly as a graduated inftrument could be, to afcertain the {pecific gravities of folids as well as, fluids. Fahrenheit firft applied a dith for weights at the top, to afcertain the fpecific gravities of fluids only ; as may be feen in Read and Gray’s Abridgement of the Philofophical Tranfaétions, Vol. VI. Part I. p. 294. My infirument, referred to by Citizen Guyton, is a combination of both, It is defcribed in the 2d volume of the Manchefter Memoirs, and is reprefented in Plate VI. Fig. 1. N. and 112 : New Lifrument for Meafuring Specific Gravities. and conflituting different ballafts; but this did not anfwer in every refpect. In all the inftruments of this kind which I have had occafion to examine, no attempt had been made, or at leaft the object had not been accomplifhed, to render the point of interfection of the item with the fluid, common to all the ballafts. Whence it followed, that, upon changing the ballaft, it was likewife neceflary to change the ilip of glafs which carries the mark within the upper ftem. I have thought it poffible, by following the principles of Fahrenheit and executing the inftrument of Nicholfon in glafs with a flight addition, to render it more generally ufeful and commodious, without dinbiithieg its accuracy in any refpeét. I was well aware of the prejudice which is naturally entertained againft polychreft, or univerfal inftruments, mott of which are rendered of no ufe from the attempt to extend their application too far; but at the fame time I was convinced that it would be a real advantage to every philofophical obferver, to require only one fingle meafure for determining the denfity of all bodies, whether folid or liquid. This is the object I propofe to accomplifh. It will be feen how far I have fucceeded. I muft obferve, on this occafion, that the name hydrometer (pe/e- Jiqueur ) as well as that of areometer, is fcarcely applicable to an inftrument poffefling thefe qualities: for thefe terms fuppofe that the liquid is always the thing weighed; whereas, with regard to folids, the liquid is the term of comparifon which is known, and to which the unknown weight is referred. I propofe therefore to make ufe of the name gravimeter, which will eafily be underftood, and applied with propriety in every cafe. This inftrument, being executed, as already remarked, in glafs, is of a cylindric form, being that which requires the fmalleft quantity of the fluid, and is on that account pre- ferable, except fo far as it is neceflary to deviate for the fecurity of a perpendicular pofition. Like the inftrument of Nicholfon, it carries two bafons ; the one fuperior, at the extremity of athin flem; towards the middle of which the fixed point of immerfion is marked. The other lower bafon terminates in a point; it contains the ballaft, and is attached to the cylinder by two branches. The moveable fufpenfion by means of a hook has the incon- venience of fhortening the lever which is to fecure the vertical pofition. The cylinder is 22 millimeters (0.71 inches) in diameter; and 21 centimeters (6.85 inches) in Jength. It carries in the upper bafon an additional conftant weight of five grammes. Thefe dimenfions might be increafed, fo as to render it capable of receiving a much more confiderable weight; but it will hereafter be fhewn, that this is unneceflary. I have added a piece which I call the diver (plongeur ), becaufe in fact it is placed in the lower bafon when ufed, and confequently is entirely immerfed in the fluid *. It is a bulb of glafs, loaded with a fuflicient quantity of mercury, in order that its total weight may be equal to the conftant additional weight, added to the weight of the volume of water dif placed by this piece. It will readily be underftood, that the weight being determined at the fame temperature at which the inftrument was originally adjufted, it will fink tothe fame mark on the ftem, whether it be loaded with a conftant additional weight in the upper bafon, or whether the effeét of this weight be produced by the additional piece in the lower dith. From this explanation there will be no difficulty in deducing how this inftrument may be adapted to every cafe of practice. * As we have no word in the Englith language which can. with propriety be ufed as the tranflation of the word f/longeur, 1 fhall take the liberty to call this weight the additional piece. N, fs , New Inftrument for Meafuring Specific Gravities. 113 It may be ufed, 1. for folids. It is the hydrometer of Nicholfon, from which it differs in no refpe€t. The only condition will be, as in his inftrument, that the abfolute weight of the body to be examined fhall be rather lefs than the conftant additional weight, which in this inftrument is five grammes (115 grains). 2. For liquids of lefs {pecific gravity than water, the inftrument, without the additional weight above, weighs about two decagrammes (459 grains) in the dimenfions before laid down. It would be eafy to limit its weight to the utmoft accuracy. We have therefore the range of one-fifth of buoyancy, and confequently the means of afcertaining all the in~ termediate denfities from water to the molt highly reétified fpirit of wine, which is known to bear in this refpect the ratio of eight to ten with regard to water. 3- When liquids of greater fpecific gravity than water are to be tried, the conftant weight being applied below, by means of the additional piece, which weighs about fix grammes (138 grains), the inftruments can receive in the upper bafon more than four times the ufual additional weight, without lofing the equilibrium of its vertical pofition. In this ftate it is capable of fhewing the fpecific gravity of the moft concentrated acids. 4. It poffefles another property common to the inftrument of Nicholfon, namely, that it may be ufed as a balance to determine the abfolute weight of fuch bodies as do not exceed its additional load. 5. Laftly, the purity of the water being known, it will indicate the degrees of rarefaCtion and condenfation in proportion to its own bulk. ' I have little to fay refpeting the conftrudtion of this inftrument. Every workman in glafs who fhall once fee it, will be able to make it without difficulty. The additional piece for the lower bafon will require fome attention to make it perfeétly agree with the con- flant upper weight, as to the immerfion of the inftrument. But this obje€t may, by careful adjuilment, be afcertained with the utmoft certainty and accuracy. The bulb of glafs is for this purpofe drawn out to a fine point; a fufficient quantity of mercury is then introduced to fink it, and the aperture clofed with a morfel of wax. ‘The bulb being then placed in the lower bafon of the inftrument, the upper bafon is to be loaded until the mark on the ftem becomes accurately coincident with the furface of the water. The fum of the weights added above is precifely equal to that of the quantity of mercury neceflary to be added to that in the glafs bulb; which done, nothing more is neceflary than to feal the point by fufion, taking care not to change its bulk. Though this inftrument is rather delicate in form, it has no other imperfe€tion than the natural brittlenefs of the material, which muft neceffarily be ufed for experiments with faline and acid liquors. For fix months paft I have made very frequent ufe of one of thefe inftruments in the Polytechnic School, without any other inconvenience than that onc of the branches of the lower bafon was accidentally broken. Nothing more remains but to render it portable. I apprehend that this ‘object is wit ficiently fecured by means of a cafe in which all the delicate parts are fecured from preilure, and the heavier parts fupported in fuch a manner as to refift the excefs of motion they are capable of acquiring by virtue of their mafs. This laft circumftance is frequently overlooked by fuch workmen as are employed in the package of inftruments; whence it ne- cefflarily follows, that fome ftrain or fraCture mufl be produced when matters of very unequal denfity are expofed to receive a common impulfe. Vor, L—June 1797. Or . The 114 New Inflrument for Meafuring Specific Gravities. The method of fecuring this inftrument in its cafe will be better underftood from the figure, than from the moft extended verbal defcription. ; ADDITION to the foregoing MEMorR. THE conftant ufe I have made of the gravimeter fince I prefented the defcription to the National Inftitute, has led me to make fome flight changes, by which its conftruétion is rendered more eafy, and the effects of brittlenefs in one of its principal parts are removed. It has alfo appeared to be of fome utility to annex to this memoir the formula, by means. of which, the gravimeter being once well adjufted, we are enabled, by a very Gimple calcu- lation, to find the fpecific gravity of any fubftance whatever in proportion to that of diftilled water at the temperature of 12.5 degrees of the decimal thermometer, and 757.7 millimeters of preffure, without the ufe either of diftilled water, or the thermometer or barometer. ‘The afto- nifhment which I have fometimes remarked when the problem has been thus announced, induces me to think that the folution here added will be acceptable, inftead of the reference to the article dreometer of the Diétionary of Chemiftry, in the Encyclopédie Methodique. I fhall likewife add an explanation of the figures which reprefent the inftrument and its cafe, together with examples of the application of the gravimeter to tables of {pecific ravity. ae Dé&eription of a Solid Additional Piece for the Lower Bafen. THE condition of hermetically fealing the additional piece without changing its volume neceflarily requires that the part near the aperture fhould be very thin. Hence it has fome- times happened that the point was broken without any external blow, but merely in con- fequence of the motion of the mercury contained within. A fimilar glafs bulb might in- deed be added; but this conftitutes but a fmall part of the remedy. For it is neceflary to adjuft the inftrument again to preferve the property of meafuring the fpecific gravity of the denfer fluids, and it has been found that this operation was not exempt from difficulties when the delired degree of precifion was to be fought. I have remedied this inconvenience by fubftituting in the place of the glafs bulb loaded with mercury a {mall mafs of folid glafs, as the ftopper of a bottle, which is firft brought to the proper form by grinding, and afterwards carefully diminifhed, until, when placed in the lower bafon of the inftrument, its immerfion in diftilled water at the required de- grees of temperature and preffure fhall be exattly the fame as when the inftrument is floated in the fame liquid with its conftant additional weight in the upper bafon only. By this means there is a certainty of acquiring the utmoft degree of precifion at firft trial; becaufe the whole procefs is reduced to the mere adjuftment of a weight. Concerning the Application of the Gravimeter, to find the Specific Gravity of any Subftance what- ever, without requiring Diftilled Water, or the Thermometer or Barometer, or any fubfequent Correftion*. THE gravimeter being fuppofed to be well regulated, let x reprefent the {pecific gravity fought; the additional weight neceflary to fink the inftrument to the mark in the unknown fluid ; * There is a corre&tion overlooked by the celebrated author of this paper, and by almoft every writer on this fubjeét. It arifes from the expanfion or contraétion of the inftrument itfelf, and of the folid under exa- mination. a General Theorem for afcertaining Specific Gravities. 115 fluid; ¢ the weight which placed with the folid in the upper bafon immerfes the inftrument to the mark; d the additional weight to produce the fame effect when the body is in the lower bafon; TH the fpecific gravity of diftilled water, at the temperature of 12.5 degrees of the decimal thermometer, and the preflure of 757.7 millimeters = 1; II’ the fpecific gravity of the water made ufe of. The following formula gives the folution*: x = ae The value of II’is firft to be found, which is greater than unity when the water made ufe of is heavier than diftilled water, and in the contrary cafe is a fraétion. Let P reprefent the weight of the gravimeter without any additional weight +; V the con- ftant volume of the immerfed part; a the additional con{tant weight in the upper bafon, or that which immerfes it to the mark in diftilled water II; and we fhall have P+a = VII; P whence V = + é Again 4 reprefents the weight more or lefs than a, which muft be fubftituted to produce the fame immerfion in another liquor different from diftilled water. + We hall therefore have H'’= Eh Bat be Vv P+a The value of II’ being found, every thing elfe is known ; nothing more being neceflary than to fubftitute this’value in the formula. I am perfuaded that philofophers will immediately perceive the advantages of this method. Diftilled water was wanting; but this praxis renders it unneceffary. Even if diftilled water were at hand, it would feldom happen that the times of the ftandard temperature and preflure would agree with thofe of the experiment ; and when an artificial temperature is produced, it is fubject to vary during the courfe of the experiment. All thefe difficulties are removed; and even when diftilled water is at hand, I prefer, more efpecially in fummer, water containing a fmall portion of neutral falt. Two motives juftify this preference: mination. I am not prepared to ftate the method of applying this correétion; and fhall only remark, in this place, that the mere change of dimenfions from temperature in a piece of fteel (independent of the greater change in the whole inftroment) will alter the fourth figure at every third degree of Fahrenheit. For pyrometrical data fee Philof. Journal, I. 58. N. * Bor the fake of thefe who are unacquainted with fymbols, I fhall here give the rule in words at length: From the weight in the upper difh, when the inftrument is properly immerfed in the unknown fluid, take the weight which is placed with the body in the fame feale at the like adjuftment. The remainder is the abfolute weight of the folid- Multiply this by the fpecitic gravity of the fluid, and referve the produét. From the ad- ditional weight when the body is placed in the lower bafon, take the additional weight when it was placed in the upper. The remainder will be the lofs of weight by immerfion. Divide the referved produét by the lofs by immerfion, andthe quotient will be the {pecific gravity of the folid with regard to diftilled water at the ftandard temperature and preffure. N. “+ In the upper difh. For as the lower additional piece aéts only by its refidual weight, and this muft vary with the fluid, it is clear that it muft be confidered as part of the inftrument, and enter into the value of P whenever it is ufed. In faét, the gravimeter with this piece is an inftrument perfeétly diftin& from that in which it is not ufed, and the adjuftment may then be made as well (and. perhaps more eafily) by a conftant foalh weight in the upper difh, as by the very delicate procefs of the author. N. t Orin words: To the weight of the gravimeter add the weight required in the upper bafon to fink it in the unknown fluid, Again, to the weight of the gravimeter add the weight required ia the fame manner to fink it in diftilled water, Divide the firft fum by the latter, and the quotient will be the fpecific pravity of the fiuid in queftion, N, Q2 rk 116 Inftrument for Meafuring Specific Gravities. 1. It is more convenient to add a few milligrams to the conftant additional weight, than to compofe a lefs by a feries of fub-multiples ; 2. By making ufe of a liquid, at the tempera- ture of the furrounding air, it is evidently lefs expofed to fudden variations. Thefe cir- cumitances are more favourable to accuracy in the refult. x Explanation of the Figures. Fig. 2, Plate VIL—The gravimeter. a. The lower bafon. b. The upper bafon. c. The point of immerfion marked on a thin piece of glafs in the infide of the ftem. Fig. 3. The piece called plongeur, which is placed in the lower bafon a when experiments are made on fluids of greater denfity than water. Fig. 4. The gravimeter in the cylindric veflel filled with water, in which it floats, im- merfed to the mark c, by means of the additional conftant weight d. It is convenient to choofe a veffel of fuch a depth that the inftrument may be at liberty to float at the level of the mark, or even beneath it, without its being poflible that the bottom of the upper bafon fhould ever defcend to the furface of the water. Fig. 5. The gravimeter in its cafe. ' A. The cylindrical part of the inftrument lodged “in a groove in the cafe, and fecured above by the two projections ee which leave the ftem at liberty. It is fecured at the middle by the brafs button f, and is prefled below by a piece of cork g, which refts on the fixed block h. : i. Sliding piece and fcrew to fupport the ballaft-piece, and prevent the branches from being endangered by any internal movement of the mercury. k. The additional ballaft-piece, or plongeur in its feparate cell. 1. The conftant additional weight placed in a cell cut in the folid wood, and cleared out at the fides, fo that it may be conveniently taken up when wanted. m. The inner furface of the cover hollowed out at n to receive without friction the projecting part of the upper bafon. A_paper is pafted on the inner furface of the cover, to fhew the weight of the gravimeter with or without the ad- ditional ballaft-piece, and the volume of water it difplaces in either cafe, which are often required to be accurately known. j On the ufeful Application of the Gravimeter to the Refults of Tables of Speci fc Gravity. IT is frequently neceffary, in philofophical as well as commercial tranfaCtions, to deter- mine the proportions of a mixture of two liquids, or an alloy of two metals; and it has been for fome time known, that in order to render this operation eafy and certain, recourfe muft be had to tables drawn up from obfervation with the afliftance of an inftrument ca- pable of giving the fpecific gravity to at leaft three decimals. The gravimeter will perfeétly anfwer this purpofe. To thew this more effectually, I fhall apply it to the mixture of alcohol and water, and the alloy of tin and lead. Thefe two compofitions are precifely what in a commercial point of view moft frequently require to be examined in this refpect. And I am convinced that an exhibition of the moft accurate refults of experiments of fuch extent and minutenefs, cannot fail to prove acceptable in this place. A TABLE Specific Gravities of Alcohol and Water. TI7 A TABLE of the Specific Gravities of the Mixtures of Alcohol and Water, with the Proportion of thefe Fluids at the Temperature of 60 Degrees of the Scale of Fahrenheit, 12;44 of Reaumur, 15,55 of the Decimal Thermometer. Note. I haye placed in this table the ratios publifhed by Citizen Chavffier, from the Memoirs of Citizen Gouvenain, at the article ALconox of the Encyclopédie Methodique, and thofe given in the tables of Mr. Gilpin, which are recommended by the philofophers of Germany. Journ. Phyf. de M. Gren, 1796, Tom. III. p. 128. 2 Specific Gravities. : % US aaa _ a “nit Centefimal parts of According to According to Gilpin . the mixture *. Chauffier.: (laft table. N.) Alcohol - 100 0.7980 0.825 E 95 0.8165 . 0.83887 go 0.83 40 0.85244 85 0.8485 0.86414 80 0.8620 0.87606 75 0.87525 0.88762 70 0.8880 0.89883 65 0.9005 0.90941 60 0.9120 0.91981 55 0.9230 0.92961 50 © 9334 0.93882 45 0-94265 0-94726 40 O19514 905495 35 0.95865 0.96158 30 0.96535 0.96736 25 O23) 0.97239 20 .0:907605 0.97723 15 0.9815 0.98213 10 0.9866 0.98737 5 POO RS5 - 0.99327 ° 0.99835 1.00000 We thall not be furprifed at the difference between thefe two tables, if we attend to the circumftance that the alcohol ufed by Chauflier was more highly reQtified, its fpecific gra- vity having been only 0.798 at the fame temperature at which the fpirit ufed by Gilpin gave .0825. But it is not eafy to conceive that this difference could produce fo confiderable a change in the penetration or diminution of volume'of the mixtures; that indicated by Gilpin at equal parts of fpirit and water being 0.025, whereas, according to Chauflier, it is 0.0454 t.. TABLE © By meafure, the water being added as the fpirit is diminifhed, fo as to keep the volume conftantly = 100, + For want of that part of the New Encyclopedie which contains the tables of Chauffier, I am not-qualified to give an account of the degree of accuracy they may poffefs. The tables of Gilpin are to be found in the fecond part of the Philofophical Tranfaétions for 1794. They are comprehended in one hundred quarto pages, and exprefs—for every fingle degree of Fahrenlicit, from 30° to 80° inclufive ;—and for all mixtures of ardent {pirit and water, formed by the addition of 1, 2, 3, 8c. parts by weight of water, as far as roo, to the conftant quantity 100 of Spirit, at 0.825 fpecific gravity when at Go ;—and for all mixtures formed in like manner by 4 ce adding 1318 Specife Gravities of Alloys of Tin and Lead. TABLE of the Correfpondencies of the Specific Gravities of Alloys of Tin and Lead, with the refpeétive Proportions of thefe Metals. In conftruGting this table, I have made ufe of the obfervations publifhed by M. Ber- genftierna in the Memoirs of the Academy of Stockholm for 1780, and reprinted in the Manuel Sy{tematique of M. Gren (§ 3195). But as he grounded all his ratios on the variations of abfolute weight under equal volumes, and made ufe of foreign weights, I have been obliged to change the expreffion for the more fimple and ufual proportion to diftilled water, taken as unity. At every fifth line [ have added the mathematical fpecific gravity, or that which is deter- ~ mined by calculation, in order to fhew the changes of bulk which refult from the combina- tion, and in this particular cafe diminifh the denfity inftead of increafing it. The fpecific gravity of pure lead to water is as 11.1603 to I. The fpecific gravity of pure tin is 7.2914 to 1. Mathematical | Real Specific Mathematical | Real Specific Compound Metal, pecificGravity.| Gravity, Compound Metal. Specific Gravity. Grawity. Tin. Lead. Tin. { Lead. 99 I} 7.3300 79-3252 89 | II 7-6468 98 2 79-3552 88 | 12 7.6787 97 3 7-397 87° | 13 7:7106 96 4 7-418 86 | 14 7-7425 95 5 7-4848 | 7-450 85 | 15 78717 | 7-7744 94 7.4828 84 | 16 7.8063) $3 47 7-5146 ~83 | 1 7.8382 92 8 75511 82 | 1 7.8701 gt 9 7-5835 81 | 19 7.9020 go Jo} 7.6782 76149 80 | 20 8.0652 7-9339 adding 1, 2, 3, &c. parts by weight of the fpirit, to the conftant quantity 100 of water. (1) The fpecific gravity to five places of figures; (2) the proportion of water by meafure to the fpirit taken as 100; (3) the aétual bulk of this laft mixture; (4) the diminution of bulk by mixture; (5) the quantity of {pirit per cent.; and (6) a decimal multiplier, which being applied to the bulk of the mixture gives the meafure of the pure fpirit in a mixture of that denfity. Hence it may be inferred how extenfively ufeful this table muft prove to all practical philofophers and manufaéturers. With regard to-its accuracy, I muft refer to the ample reports of Dr. (now Sir Charles) Blagden, in the Tranfadtions for 2790, and fhalk only obferve that the experiments were made with the balance of the Prefident of the Royal Society; of the admirable mechanifm and fenfibility of which, fome account, though imperfect, is given inthe Journal de Rozier, Vol. XX XIII. and that the.term or ftandard {pirit -825 was arbitrarily chofen from motives of convenience and accuracy. F The fpirit was obtained from malt. The greateft ftrength obtained by adding hot cauftic alkalé to {pirit and then carefully diftilling, gave-a fpecific gravity of 0.813 at 60 degrees. Perhaps the circumftances of M. Gou- venain’s experiments may fhew by what means he fucceeded in arriving at 0.7980 at the fame temperature. No ufeful purpofe would be anfwered by conjeAlure im this place. From the laft line in the table here given by Citizen, Guyton, the {pecific gravity of mere, water is {uch as to indicate a temperature of 75 degrees inftead of 60 in Chauflier’s column, In which cafe Gilpin’s ftandard fpirit would have a fpecific gravity of 0.8178. With regard to the confiderable difference in the penetration or diminution of bulk, it remains to be fhewn whether ir depends, upon any part of the praceffes by which the alcohol was ebtained and concentrated, or, as is more probable, upon, {ome mifake in the calculations or methods of exprefling the quantities. N, Compound Specific Gravities of Alloys of Tin and Lead. Mathematical Compound Metal. |specific Gravity. Tin. Lead. 79 21 78 22 77 23 76 | 24 75 25 8.2586 74 | 26 73 27 72 28 at 29 72 | 30 8.4520 69 31 68 32 67 odes 65 | 35 | 8.6455 64. 36 63 | 37 62 38 61 39 60 40 8.8397 59 41 58 | 42 57 43 56 | 44 ne Wes 9-0333 54 | 46 53 47 52 48 5! 49 5° | 50 92258 49 | 51 48 52 47 | 53 46 | 54 45 55 9+4203 44 | 56 43 57 42 58 41 59 49 | 60 9-6139 Real Specific Gravity. 49-9658 7:9977 8.0296 8.0615 8.0934 8.1253 8.1572 8.1891 8.2210 8.2529 8.2848 8.3167 8.3486 8.3828 8.4170 pies 8.4853 8.5195 — 8.5537 8.5879 8.6228 8.6562 8.6904 8.7246 8.7588 8.7929 8.8271 8 8613 8.8955 8.9319 8.9729 9-01 39 9-0550 g-0g60 9-1373 9.1552 9-2190 9.2600 9-3033 ° 9-34.06 Om NWSE ONT COO Mathematical Compound Metal. Specific Gravity 10.0010 10.1945 10.3881 10.5799 10.7734 10.9668 11.1216 Real Specific Gravity. -_ 9-4727 9-4355 9-4788 9-5221 9-5676 9-6132 9-6565 9-7025 9-7454 9-7887 9-8297 9.8730 9 9163 9-9573 9-9983 10.0416 10.0871 10.1350 10.1806 10.2261 10.2717 10.3173 10.3629 10.4084 10.4586 10.5062 10-5543 10.6024 10.6500 10.7004 10.7479 10.7958 10.84.14 10.8869 10.9354 10.9781 11.0236 11.0692 11.1148 11.1603. 119 Deferiptions of the Improved Air Pumps of PRrincE and CUTHBERTSON ; with Obfervations. | HE important ufes of the Air Pump are too many and too well known to require enu- meration. It is an engine, not only calculated to demonftrate many of the leading princi- ples in natural philofophy, but indifpenfable for the performance of fome of the moft accu. 3 rate £28 Comparifen beteveen the Effects of the Common Pump and the Air Pump. rate experiments in the Pneumatic Chemiftry. The air is exhaufted out ‘of a receiver by this inftrument, by an ation nearly fimilar to that of the common fucking pump, as it is called. In the common pump there is a bucket, which by leathering is made to flide, water-tight, up and down the pipe; but inftead of a bottom, it is provided with a valve or flap opening up- wards. By this contrivance the bucket may be moved downwards through a column of water without producing any progreflive motion in the fluid, becaufe the valve then optns and affords a free paflage ; and, on the contrary, when it is moved upwards, it muft alfo move the whole of the column above the flap or valve, which is then fhut. Another valve, alfo opening upwards, is fixed in the pipe below the ordinary range of the bucket, and ferves to prevent the return of any fluid which may lie between the two valves during the defcent of the bucket itfelf. In working this common and very ufeful engine, it is firft neceffary to pour a {mall quan- tity of water into the pipe above the bucket; after which, the handle being moved pro- duces the following effect: As the bucket defcends, the fpace between the two valves be- comes diminifhed, and the air contained in that {pace lifts the upper valve, and in part rifes with noife through the water; after which, as the bucket rifes, and again enlarges the fpace, the remaining air expands by its fpring, which is thus weakened. ‘The air in the pipe beneath the lower valve will therefore aé&t more ftrongly upwards by its entire {pring than the air above does downwards. It will open the valve, and rife up into the upper fpace ; at the fame time that the preflure of the external air, upon the water in the well, will drive part of the water after it into the lower part of the pipe. By continuing the work for a few ftrokes the included air is thus entirely drawn out and fucceeded by water, provided the height from the furface of the fluid in the well to the upper valve be not fo great as to include a column of upwards of thirty-three feet. For fuch a column would be fufficiently heavy to counter- poife the whole preflure of the atmofphere, dnd would accordingly prevent any farther afcent. : If this laft-mentioned cafe were to exift, or if the lower aperture of the pipe were clofed, it may without difficulty be underftood that in theory, that ‘is to fay, with a perfeét inftru- ment, the air beneath the lower valve would become more and more rarefied to a certain point as the procefs was continued. And the progrefs_and extent of this rarefaction would be computable from the known ratios of the greateft and leaft fpaces between the valves when in their extreme pofitions, together with the aflumed conditions that the air, however greatly rarefied, would diffufe itfelf equally through the containing fpace, and that the lower valve fhall afford no refiftance to the power aod to open it when the bucket is elevated. It will alfo follow, that the fame rarefaction might be produced in any veffel con- taining air, and communicating only with the pipe of the pump beneath the lower valve. Thus it is feen that the common fucking pump is, in.faQ, an air pump before it operates as a pump for water; and that nothing more is required to conflitute the philofophical air pump than convenience of fize, accuracy of ssilapacapania| and, that the refiftance at the valves be either diminithed or removed. It would be to little purpofe to enter into any difcuflion concerning the original conftruc- tion of the air pump, as invented by Otto Guericke, and afterwards improved and moft ufe- fully employed by our eminent countryman Robert Boyle. It is generally allowed at pre- fent, that fuch air pumps as operated by means of ftop-cocks inftead of the lower yalye, are x not Parious Methods of conftruéting Air Pumps. 125 not durable, but foon become leaky. If ever thefe pumps, of which engravings are to be feen in the works of Mufchenbroek and S’Gravefande, were ufed in England, which I think was not the cafe, they muft have been long fuperfeded by the cheaper and more fimple contrivance of valves formed by tying a ftrip of bladder over a {mall hole through which the air is allowed to pafs in one dire€tion only. Mr. Smeaton was of opinion, that the opera- tion of the air-pump is rendered defective from the {mall furface of preflure at which the air acts againft the bladder of the lower valve, as well as from the preflure of the external air, which is fuppofed to prevent the upper valve from opening in the laft {tages of the pro- cefs. To remedy thefe imperfections, he made a number of hexagonal holes inftead of the one {mall hole in the valve ; and by pafling the rod of the pifton through a collar of leathers at the top of the barrel, which was clofed, with the exception of a valve opening outwards, he prevented the external air from ating upon the valve of the pifton in its defcent *. Mr. Abraham Brooke of Norwich, by experiments with the common air-pump, has rendered it at leaft doubtful, whether, in pumps equally well made, thefe be improvements at all +. But, previous to the time this laft author wrote, there exifted two other air-pumps, con- taining improyements both in principle and workmanfhip fufficient to annihilate any contro- verfy re{pe€ting the merits of the common pump, and that of Smeaton. Thefe were made by the Rev. Mr. Prince, of Salem in North America, and Mr, John Cuthbertfon of Amfter- dam. The firft is defcribed in the only volume of Memoirs publifhed by the American Academy, and is fcarcely known in the philofophical world. The other is defcribed in a publication { by the inventor; of which the circulation muft, in the ordinary courfe of things, be confiderably limited. I have thought it my duty to prefent both to the world in this place. Mr. Prince’s paper contains a confiderable portion of matter relative to he air-pump of Smeaton, partly defcriptive of the improvements made by that, ingenious mechanic, and partly by way of comparifon with his own. For the fake of brevity, I have omitted thefe, and other matters of lefs confequence ; but in the effential parts of the account I have ii as nearly as poflible tothe words of the author. From the account of Mr. Smeaton’s fuccefs in facilitating the opening of the valves at the bottom of the barrel and in the pifton, Mr. Prince fuppofed, if thofe valves were en- tirely removed, and the remaining air in the barrel could be more perfeétly expelled, the rarefa€tion might be carried ftill further. Upon this plan he conftructed his pump. He removed the lower valve, and opened the bottom of the barrel into a ciftern on which it was placed, and which had a free communication with the receiver. For the valve on the plate at the top of the barrel (which is conftructed like Smeaton’s) makes it unneceflary, as he remarks, that there fhould be any at the bottom in order to rarefy the air in the receiver. The ciftern is deep enough to allow the pifton to defcend into it below, the bottom of the barrel. Suppofe then the pifton to be folid, that is, without a valve. in it; when it enters the barrel and rifes to the top plate, which is made air-tight with a collar of leathers, &c. * Philofophical Tranfadtions, XLVII. + Mifcellaneous Experiments and Remarks on Eleétricity, &c. by A. Brooke, Norwich, 1789. P. 123, and elfewhere. 2 } Defcription of an improved Air Pump. By John Curhbertfont’ Oftave, 41 pages. Londons no date, This artift is at prefent fertled in London, : p09 Ot Mdlw estale Vox. I.—June 1797. : R like 122 Con/trutticn-of an Air Punip without the Lower Valve. Wke"Smieaton’s, ft forces out all the air above it; and, as the air cannot returh into the bar- rel on account of the valve on the top plate, when the pifton defeends, there will be a va- cuum fornied between that and the plate, every thing being fuppofed perfeét. But in working the pump, the pilton is not allowed to defcend entirely into the ciftern fo far as to leave the bottom of the barrel open ; becaufe, as the ciftern, for another purpofe, is made jarger than the bore of the barrel, this might make the pifton-rod work unfteadily in the collar of leathers, and caufe it to leak; buc it defcends below a hole in the fide of the barrel near the bottom, which opens a free communication between the barrel, ciftern, and receiver. Through this hole the air ruthes from the ciftern into the exhaufted barrel, when the pifton has dropped below it; and by its next afcent this air is ‘forced out as the other was before. If now, the capacity of the receiver, ciftern, pipes, &c. below the bottom of the barrel, taken together, be equal to the capacity of the barrel, half the remaining air will be'expelled by every ftroke. Bur as the working 2 pump of this kind with a folid pifton would be labotious, on ac- count ‘of the ‘refiftance it would meet with in its defcent'from the air beneath (though this ‘would be leffened by every ftroke as the-air became more rarefied), the inventor, to re- iiédy ‘this inconvenience, pierced three holes in the pifton at equal diftances from each other; and a circular piece of bladder, ‘which is tied over the fop of the pifton, to make the joint more perfeét with the top plate, and to defend them from injury when the pifton is Brdéught up ‘againft it, forms a kind of valves over the holes, which open eafily enough to prevent any labour in workig the pump, as it allows the air to pafs through the pifton when it defcends. But the air does not‘neceflarily depend upon a paflage through the pifton in order to get into the barrel: for when the air becomes fo weak from its rarefaction that it banhot open this valve, it will flill get into the barrel when the communication is opened by the hole’at'the bottom. ‘This pifton, therefore, will defcend as eafily as any other ; and thefe valves do not'impede'the rarefaction, fince it is of no confequence, as to this, whether they open or ‘nét. ‘By this conftruétion the valves, which Mr. Smeaton only made to open with more eafe, are rendered unneceflary in rarefying the air, and that at the bottom of the barrel; which is the’ molt difficult to be made and kept in order, is entirely removed ; the valve’on the top plate being the only one neceflary in rarefying the air. ; Bat as in’a fingle-barrelled pump of this conftruction, where there is no valve at the bottom to prevent the air, which follows ‘the pifton in its afcent, from returning into the receiver in its defcent, a flu€tuation would be produced which might prove detrimental in fome experiments, this pump is made with two barrels, which rarefy the air at every ftroke of the winch. In this conftruétion, the capacity of the two barrels taken together below the piftons is always the fame; for while one is defcending the other afcends, and what js taken from tlhe one is added to the other. ; ‘Having this fet afide the valves which in fome meafure prevented the air from entering the barrel “above the’ pifton, he “next attempted to expel the air more perfeétly out of the barrel than Mr. Smeaton had done, by making a better vacuum between the pifton and the top plate, which would allow more of the air to expand itfelf into the barrel from the re- eeiver. ; : Upon Mr. Smeaton’s plan, our author alfo contrived to connect the valves on the top plates with the receiver occafionally, by means of a pipe and-cock, by the turning of which the ' machine i eee ‘ Confiruétion of an Air Pump without the. Lower Valve. 123 machine may be made to exhauft or condenfe at pleafure.. This is done in the following manner: There is a crofs piece laid over the valves extending from one barrel to the other, which has a dué through it conneéted with a {mall pipe {tanding between the barrels; through this pipe the air paffes into a duct at the bottom piece leading to the cock. In this Piece is likewife the duct leading from the ciftern to the cock; and with this cock alfo is connected the pipe leading to the receiver. The key is pierced with two holes, in fuch a manner, that one of them will conneé the pipe coming from the receiver with the dud ia the bottom piece leading to the ciftern, or with the other leading to. the valves, as may be required for exhaufting or condenfing. The other hole through the key will open, occa- fionally, to the atmofphere either of thefe du€ts round the cock: fo that, having the direc- tion of the air which paffes through the valves under the command of this cock, the pump may exhautft or condenfe at pleafure ; for when the key conneéts the pipe from the receiver and the dué& leading to the cifterns together, the pump will exhauft; and when it conneéts the Piperveith the duct leading to the valves, it will condenfe, as the other hole in the key at the fame time opens to the atmofphere the duct leading to the cifterns, by which paflage the air enters the barrel from the atmofphere, is forced out at the valves, and through the pipe and cock into the receiver. In this part of the machine which is contrived for condenfa- tion, the inventor has, by an additional part, endeavoured to get the air more perfectly our of the barrel. : We have feen, fays he, that Mr. Smeaton, by making the pifton of his pump fit more exaCtly to the bottom of the barrel, and by fhutting up the top to prevent the preflure of the atmofphere on the pifton valve, was able to get more of the’ air above it than could be effected in the common pump: but ftill the difficulty, though fo far removed, remains i1 the top of the barrel; for, as the pifton cannot be made to fit fo exaétly to the top plate, but that there will be fome lodgement for air, it is impoflible to expel it entirely. ' More pethaps might be expelled if the valve on the top could be made to open more eafily, by removing the weight of air from it; for the atmofphere prefling on this valve will prevent its opening freely, in the fame manner as, when prefling on the pifton valve, it obftrué’s the opening of that in the common pump. : The difficulty which Mr. Smeaton removed from the pifton valves, Mr. Prince endeayour- ed to remove from the valve on the top plate ; that this valve, having the preffure of the atmo- {phere taken off, might open with the fame eafe as the pifton valve does in his pump. To effect this, there is conne¢led with the duét on the bottom piece which conveys the air from the valves to the cock, a {mall pump of the fame conftruétion as the large one ; having the barrel opening into a ciltern, the pifton rod moving through a collar of leathers, and a valve near the top, through which the air is forced into the atmofphere. This pifton is folid : be- caufe the diameter being only half an inch, does not make it work hard. “This pump, which is of one barrel only, he calls the valve pump; its chief ufe being to rarefy the air above the Valves, or remove the weight of the atmofphere from off them. To ufe’ this pump, it is neceflary the key of the cock fhould be pierced differently from that of Mr. Smeaton’s; for, as the pipes round his are placed at equal diftances, when the one from the bottom of the barrel is connected with that from the receiver to exhauft it, the other from the valve on the cop plate is opened tp the atmofphere by the other paflage through the cock. But in order to rarefy the air aboye the valve in my pump, it is neceflary this laft paflage fhould be fhut R 2 up 124 Con/ftrudtion of an Air Pump without the Lower Valve. up when the valve pump is ufed. Inftead, therefore, of placing the three duds at equat diftances round the cock, I have divided the whole into five equal parts; leaving the dif- tance of one fifth part between the duéts leading from the ciftern and the valves to the cock, and two fifths between each of thefe and the one leading from the cock to the re- ceiver. By this adjuftment, when the communication is open between the receiver and the valves for condenfation, the other hole through the cock opens the cifterns to the atmo- {phere ; but when the communication is made between the cifterns and the receiver for ex- hauftion, a folid part of the key comes againft the duét leading to the valves, and fhuts it up, and the air which is forced out of the barrel pafles through the atmofphere into the valve pump ; for the valve of the fmall pump may be kept open while the great one is worked. Upon this conftruétion alfo we are able to make the pump with two barrels like the com- mon pump, which cannot be done conveniently where the lower valve is retained ; becaufe it would be difficult to make the pifton in one barrel come exattly to the bottom, at the fame time that the pifton in the other touched as exactly at the top; it would at leaft require a nicety in the workmanthip which would be troublefome to execute. In this pump the pittons do not move the whole length of the barrels: there is a horizon- tal fe€tion made in them a little more than half way from the bottom where the top plates are inferted. See Fig. 6.P1.VI. By this means the pump is.made more convenient and fimple, as the head of it is brought down upon the top of the barrels in the fame manner as in the common air pump. The barrels alfo ftand upon the fame plane with the receiver plate, and this plane is raifed high enough to admit the common gauge of thirty-two or three inches, to ftand under it without any inconvenience in working the pump, as the winch moves through a lefs portion of an arch at each ftroke, than it would if the piftons moved the whole length of the barrels. There is alfo placed, between the barrels in this pump, on the crofs piece over the valves, a gauge to meafure the degree of condenfation, having a free communication with the valves, cock, &c. This gauge is fo conftructed that it will alfo ferve to meafure the rarefaction above the valves when the air is worked off by the valve pump. It confifts of a pedeftal, which forms a ciftern for the mercury, a hollow brafs pillar, and glafs tube her- metically fealed at one end, which moves up and down in the pillar through a collar of Iea- thers. The die of the pedeftal is made of glafs, as well to hold the quickfilver as to expofe its furface to view, that it may be feen when the open end of the tube is put down into it or raifed out of it. The body of the pillar is partly cut away to expofe the tube to view in the fame manner. If the pump be ufed as a condenfer, the degree of condenfation is fhewn by a fcale marked on one edge of the pillar: if it be ufed as an exhaufter, the degree of the rare- faétion of the air above the valves is fhewn by a fcale marked on the other edge of the pillar. This gauge will alfo ferve to fhew when the valves: have done playing, either with the weight of the atmofphere on them or taken off. If we want to know when they ceafe open- ing with the weight of the atmofphere on them, draw the pifton of the valve pump into its barrel, to prevent any air efcaping through that valve : in this fituation work the great pump again; andif any air paffes through the valves into the pipe, the gauge will rife by condenfation. This condenfed air muft then be let out by opening the communication at the 6 cock Conftruttion of an Air Pump without the Lower Valve. 125 cock with the outward air. By repeating this till the gauge rifes no longer, we may know the valves will open no more while the weight of the atmofphere lies on them; and the rare- faction in the receiver can be carried no further. When'the weight of the atmofphere is to be removed, after conducting as in the former experiment, raife the open end of the tube above the furface of the mercury, and then work the valve pump, and the air will be rarefied over the valves and in the tube to the fame degree (we may fee when the valve of this pump has done playing, by unfcrewing the cap that covers it). The open end of the tube is then to be immerfed into the mercury, and the great pump worked. The air which paffes through the valves will then raifle the gauge by condenfation ; and thus by alternately raifing and deprefling the tube, and working the two pumps in their turns, we may carry the rarefaction of the air in the receiver as far as the power of the pump willgo. If one of Mr. Smeaton’s pear gauges be ufed in the receiver, as he direéts, the difference of the rarefaétion in the two experiments may be known. And as the air above the valves may be rarefied to different degrees, it may be known, by the two gauges, what proportion the rarefaction above the valves bears to the degree of excefs in the receiver. This condenfing gauge can be taken off, and a button fcrewed into the hole in its ftead, in any cafe wherein a greater degree of condenfation is required than the glafs will bear. When a glafs receiver is ufed, this gauge may be placed within it, where it will meafure any degree of condenfation the re- ceiver will bear without danger to the gauge ; or the capacity of any receiver may be mea- fured by this gauge before it is removed from its place, by fhewing how many ftrokes of the winch will throw one atmofphere into the receiver; then turning the cock to prevent any air efcaping, change the gauge for the button. When this is done, the degree of condenfa- tion may be further meafured by the number of ftrokes. As in cafes where great condenfation is required, there muft be a great deal of labour, and a great ftrain on the teeth of the wheel and pifton rods, on account of the great diame- ter of the piftons *; to remedy this, Mr. Prince has fitted a condenfer of a fmaller bore than the barrel of the great pump to the ciftern of the valve pump, to be fcrewed on occa- fionally, by which the condenfation may be finifhed, inftead of the great pump. Or, to fave the work and expence of this condenfer, the valve pump, if made a little larger, may be eafily fitted for the fame purpofe, by having a plate made to {crew into the bottom of the cylinder occafionally, with a valve on it opening into the ciftern: a hole muft alfo be made to be opened on the fame occafion near the topiof the cylinder, to let air in below the pifton when this is drawn up above it. The common gauge, which is generally placed under the receiver plate in this pump, is placed in the front, that it may be feen by the perfon who is working the pump, and that the place may be left free for other ufes. The plate is fo fixed to the pipe leading to the cock, that it may be taken off at pleafure, and ufed as a transferer; or any tube or apparatus may be fixed to it to perform fome ex- periments without removing it, which will fave trouble and make lefs apparatus neceflary. * In this pump the piftons are two inches diameter; fo that there will be about forty-eight pounds added to the refiftance in opening the valves for every atmofphere thrown into the receiver, P. It is certainly an injury to an exhaufting pump to ufe it for condenfing. This operation ought always to be performed with a long fyringe of fmall bore. Such an inftrument would coft much lefs than the condenfing part of an air pump, and will at the fame time have much more power, N, The 126 Confiruétion of an Air Pump without the Lower Valve. The head of this pump is not divided as the common one is, to:diflodge the teeth bf the wheel from the pifton rods when the pump is to be taken apart, but is made whole, except a {mall piece in the back, where the wheel is let in; which makes it much more conyenient to remove the head, or place it on the barrels. ‘The whecl is freed from the piftoyi rods when required, by pufhing it into the back part of the head; and when it is drawn into its place and conneéted with them again, a button is {crewed into the focket of the axis be- hind, to keep it in-its place. This makes the head lefs troublefome to remove ; -but its chief ufe is to diflodge the pifton rods from the wheel, that they may be put down into the cifterns when the pump is not in ufe, where they will ftand uncompreffed, and retain their elafticity better than if kept in the barrels. In thefe cifterns they may alfo ftland co- vered with oil, if neceflary, as they are large enough to admit of it. "The principal joints of the pump are funk in fockets, that the leathers which clofe them may be covered with oil to prevent leaking *. For convenience, the lower part of the pump is fitted with drawers to contain the appa- ratus. A door opens behind one range to a place referved the whole height, to get at the under part of the receiver plate, and fix apparatus to it for fome. experiments. In this place ftand the long tubes, and fuch tall glaffes belonging to the apparatus as will not go into the drawers. The barrels, &c. of the pump are covered with a cafe or head, which keeps them from duft and accidents when the pump is not in ufe. The apparatus is fecured between fliders, &c. in the drawers, fo that the whole machine may be eafily removed in one body, without danger. As there was no glafs manufa€tory in Mr. Prince’s vicinity, he fent to Europe for his apparatus; but unluckily the gauges, with fome other parts, had not been forwarded to him when he wrote his account. He had only a {mall tube of two-tenths inch bore, which he ufed as a common gauge; but this was not fufficient to determine the power of the pump. All that he could fay of the inftrument was, that he found it much more convenient to ufe than one of the common fort ; that it would exhauft a receiver much fooner, and keep in order much longer, for being made without valves, which muft depend on the {pring of the air to open them. When a common pump in his pofleffion had been fitted up with valves, leathers, &c. at the fame time with this, the valves of the common pump have be- come too dry and ftiff to ufe, while this pump has continued in good order. He attributes this, in part, to the moifture which the valves on the top plates receive from the piftons every time the pump is ufed; the piftons being always kept moiflened with oil in the cif- terns, where they fland when the pump is not in ufe; and in part to the power. which the piftons have over thefe valves, by condenfing the air againft them. Fig. 6, Plate VI, reprefents a perpendicular feCtion of one of the barrels, the two cifterns, condenfing gauge, &c. where AB reprefents the barrel ; CD is the ciftern on which it ftands ; aaaa the leathered joint, funk into a focket and buried in oil: EF is the pifton; the cylin- drical rod pafling through a collar of leathers, GG, in the box HI. K fhews the place of the valve on the top plate K, coygged by the crofs piece MM, into which the pipe OO 7) , + This, I find, is very effeétual 3 having never known one of the joints fecured in this way to leak, though the pump has ftood for a long time; whereas a portable pump which I have, made by Mr, Nairne, London, has leaked, and repeatedly been refitted with new oiled leathers in the fame time. P. is Confirudtion of an Air Pump without the Lower Valve. 127 is foldered, that conveys the air from the valves to the duct going under the valve pump, as may be feen in Figure 8; 0 is part of the faid du@; p is the joint funk into a focket in the crofs piece P?, which conneéts the cilterns, and has a duct through it leading to them, Into this duét open the ducts q and r,the firlt leading to the gauge in front of the pump, the other to the cock and receiver. The other barrel is left out of the figure to fhew fome of the parts more diftinétly, ex- cept Q, which is the top of the barrel retained and brought down out of its place to thew the top plate that fhuts up the barrel, feparated from the box which contains the collar of Jeathers. 3 fhews one of the holes in the plate over which the valve lies, and which is covered by R in the crofs piece. VV is the piiton fhewing the valve open on the top, which is to prevent labour when the pump condenfes. WX is the ciftern, in which is more diftin€tly feen the fhoulder for the leather which clofes the point between this and the barrel, and alfo the focket in which the oil lies over the leather. YZ is the condenfing . gauge, with the orifice of the tube raifed above the furface of the quickfilver. ee is the col- lar of leathers, through which the glafs tube moves. i is a {mall pipe coming up through the quickfilyer to make a communication between the valves and the gauge. Fig. 7. is a view of the upper furface of the top plate which clofes the barrel, being foldered into it, fhewing the place of the valve over the three {mall holes, one of which only can be feen at S in Fig. 3. Fig. 8. is a perpendicular fe€tion of the bottom piece, pipes, valve pump, cock, &c. at right angles with the other fection, Fig.6. AB is the pipe between the barrels, as repre- fented in Fig 6. The button o is here ferewed into the top inftead of the gauge. CD is the valve pump and its ciftern, e the place of the valve under the cap. EF the cock, fhewing the duct through it leading to the atmofphere. GH the pipe leading from it to the ftem of the receiver plate, in which is the cock I, to fhut up the dué& when the plate is ufed as a transferer. KK is the plate. L, a piece to fhut up the hole, into which tubes &c. are occafionally ferewed to perform experiments without removing the plate. The dotred line at O fhews the place of the {crew which preffes the plate againft the pipe: PQ. the pipe and common gauge ftanding in front of the pump. Fig. 9. is a horizontal fection of the cock, and pieces containing the duéts leading from it to the receiver, the cifterns, and the valves on the top of the barrels. AB the du@t con- neCting the cifterns together. CD the duét leading from the cifterns to the cock. GH the duct leading from the cock through the pipe AB (Fig. 8.) to the valves. DE the du@ through the cock, which occafionally conneéts the two laft mentioned duéts with the du@ EF, leading from the cock to the receiver. I, the. duct in the cock leading to the atmo- {phere, which, when ,conneéted with the duc at D, lets the air into the. cifterns and bar- rels for condenfation; the other duct through the cock at the fame time connecting H and E. This dué alfo, when connested with E, reftores the equilibrium in the receiver. KL is part of the duét leading from the cifterns. to the gauge. ‘Lhe dotted circles fhew the places of the pipe and yalve pump oncthe piece, and r. the place where the air enters the valve pump from the duct GHJ,.and is thrown into the atmof{phere when the pump ex- haufts. ; Fig. 10. fhews the under furface of the boxes which contain the collars of leathers with the crofs piece which conneéts them together, having a duct through it, as reprefented by the 3 dotted ~ 128 Conftruétion of an Air Pump with Metallic Valves. dotted line, through which the air paffes from the valves to the pipe.- This Fig. is defigned chiefly to thew the places in which the valves play, as at I. Fig. 11. is a fide view of the pump, fhewing the fituation of the valve pump and handle of the cock; where A isthe pump, and B the handle. Fig. 12, Plate VII. is a perfpective view of Cuthbertfon’s pump, with its two principal gauges {crewed into their places: thefe need not be ufed together, except in cafes where the utmoft exactnefs is required; for in common experiments either of the two may be taken away, anda {top fcrew put into its place. When the pear gauge is ufed, a {mall round plate, large enough for the receiver to itand upon, muft firft be fcrewed into a hole at A; but when this gauge is not ufed, this hole muft be clofed with a ftop fcrew. When all three gauges are made ufe of, and the receiver is exhaufted, the ftop {crew B, at the bottom of the pump, muft be unfcrewed, to admit the air into the receiver ; but when the gauges are not all ufed, the ftop ferew at A, or either of the other two which are in the place of the gauges, may be unfcrewed for this purpofe. In Figure 1, CD reprefents one of the barrels of the pump, F the collar of leathers, G a hollow cylindrical veffel to contain oil; R is alfo an oil veffel, which receives the oil that is driven with the air through the hole a a, when the pifton is drawn upwards; and when this is full, the oil is carried over with the air along the tube T into the oil veffel G. cc is a wire which is driven upwards, from the hole a a, by the paffage of the air; and as foon as this has efcaped, falls down again by its own weight, fhuts up the hole, and prevents any air from returning by that way into the barrel: at d d are fixed two pieces of brafs, to keep the wire c c in fuch adireétion as may preferve the hole air-tight. H is a cylindrical wire which carries the pifton I, and is made hollow to receive a long wire q q that opens and clofes the hole L, which forms the communication with the receiver ftanding on the plate. m is part of a pipe, one end of which is fcrewed into L, and the other into the centre of the receiver plate. M is a ftop fcrew, ferving only to clofe that hole. OP is a {mall fteel fcrew, one end of which is {crewed into the wire q q, that opens and fhuts the hole L; and upon the other end O is {crewed a nut, which, ftopping in the {fmalleft part of the hole, prevents the wire from being lifted or carried too high. This wire and fcrew are more clearly fhewn in Fi- gure 2 and in Figure 6; they flide through a collar of leathers rr, Figure 2 and Figure 5, in the middle piece of the pifton. Figures 4 and 5 are the two main parts which compofe the pifton; and when the pieces in Figures 3 and 6 are added to it, the whole is reprefented by Figure 2. Figure 5 is a piece of brafs, turned in a conical form, with a fhoulder or ledge at the bottom; a long female fcrew is cut in it, about two thirds of its length; and the re-_ maining part of the hole, in which there is no fcrew, is about the fame diameter as the fcrew part, except a thin plate at the end, which is of a width exactly equal to the thicknefs of q q. That part of the infide of the conical piece of brafs, in which no thread is cut, is filled with oiled leathers with holes in them, through which q q can flide air-tight; there is alfo a male {crew with a hole in it, which is fitted to q q, and ferves to prefs down the feathersrr. In Figure 4, a a aa is the outfide of the pifton, the infide of which is turned exaétly to fit the outfide of Figure 5. bb are round leathers, about 60 in number ; cc is a circular plate of brafs, of the fize of the leathers; and-d d is a fcrew, which ferves to prefs them down as tight as is neceflary. The male fcrew at the end of Figure 3, is made to fit the female fcrew in Figure 5: now if Figure 6 be pufhed into Figure 5, this into Figure 4, and Figure 3 fcrewed eo Conftrudtion of an Air Pump with Metallic Valves. 129 {crewed into the end of Figure 5, thefe will compofe the whole pifton, as reprefented by Figure 2. H in Figure 1 reprefents the fame part as H in Figure 2, and is that to which the rack is fixed. If this therefore be drawn upwards, it will make Figure 5 fhut clofe into Figure 4, and drive out the air above it; and when it is pufhed downwards, it will open as far as the fhoulders aa Figure 4 will permit, and fuffer the air to pafs through. A A Figure 7, is the receiver plate ; B B is a long fquare piece of glafs {crewed to the undermoft fide of the plate, through which a hole is drilled, correfponding with that in the centre of the receiver plate, and with the three female {¢rews b b c. Suppole the pifton to be at the bottom of the barrel, and a receiver to ftand upon the plate, the infide of the barrel, from the top of the pifton to a, is full of air, and the pifton fhut; when drawn upward, by the hollow cylindrical wire H, it will in its courfe drive the air be- fore it, through the hole a a, into the oil-veffel R, and out into the atmofphere by the tube T. The pifton will then be at the top of the barrel at a, and the wire gg will ftand nearly as it is reprefented in the figure, juft raifed from the hole L, and prevented rifing higher by means of the nut 0. While the pifton is moved upwards, the air will expand in the receiver, and be driven along the bent tube m into the infide of the barrel. Thus the barrel will be filled with air, which, as the pifton rifes, will be rarefied, in proportion as the capacity of the re- ceiver pipes and barrel is to the capacity of the barrel alone. When the pifton is moved: downwards again by H, it will force the conical part, Figure 5, out of the hollow part, Figure 4, as far as the fhoulders a a: Figure 2 will reft upon a a Figure 4, which will then be fo far open as to permit the air to pafs freely through it, while at the fame’time the end of qq is forced againft the top of the hole, and clofes it in order to prevent any air from returning into the receiver. Thus the pifton, while moved downwards, fuffers the'air to pafs out between the fides of Figure 4 and 5, and when itis at the bottom of the barrel will have ‘ the column of air above it; confequently, when drawn upward, it will (hut and drive out this’ air, and by opening the hole L give a free paffage to more air from the receiver. This procefs being continued, the air will be exhaufted out of the receiver as far as its expanfive power will permit; for inthis machine there are no valves, as in the‘common air pumps, to be forced open by the air in the receiver, which, when its elafticity is diminithed, it becomes unable to effe& ; but every thing is contrived to open by the motion of the pifton, and there’ is nothing to prevent the air from expanding to its utmoft degree. In exhaufting with this machine; no other direCtions need be obferved, but fuch as are common to all air pumps’; nor is any peculiar care required to prefetve it in’ order, except . that the oil veffel G be always kept about half full of oil. When‘it has ftood’a confiderable time without being ufed, it will be proper to draw'a table-{poonful or two through it, by pouring it into the hole in the middle of the receiver plate’ when the pifton is at the hottom of the barrel; then, by moving the winch backward and forward, to raife and deprefs the - pifton, the oil will be drawn through all the parts of ‘the machine; and what is more than | is neceffary in the infide will be forced out through the tube T into'the oil veflel G. Near the top of the cylindrical wire H isa fquare hole, which is intended to'let‘in fome of the oil | from the veffel G, that the oiled leathers through which the ‘wire'g q flides, may always -be fufficiently fupplied with it. When the pump is required to'condenfe, either at the fame time that it exhaufts, or fepa- rately, the piece which contains the bent/tube'T muft’be‘taken away, and Figure 8 put into Vou. I.—June 1797. S its 130 Conftrudtion of an Air Pump with Metallic Values, its place, and faftened by the ferews which had before confined that piece. Figure 8 is drawn in the 'plate as it is made fora double-barrelicd pump; but fora fingle barrel es one piece is ufed, reprefented by b a a, the double piece being cut off at the dotted line a In this picce is a female fcrew, to receive the end of along brafs tube; to which a saedded’ if fuflicient for the experiment, mutt be tied; or elfe a glafs, properly confined for this pur- pofe, muft be {crewed to it, Then the air, which is exhaufted out of a receiver ftanding on the plate, will be forced into the bladder, or glafs connected with the brafs tube, But if the pump be double-barrelled, the apparatus, as reprefented by Figure 8, muft be ufed, and the long brafs tube {crewed into the female ferew at C. - Figures 9 and 10 reprefent the two gauges; namely, the fyphon gauge, and the baro- meter or long gauge. When thefe are ufed, Figure g mutt be {crewed into the female {crew c b, or into that at the other end'c Figure 7, and Figure 10 into the female ferew ab Figure 7. If it be ufed asa fingle air pump, either to exhauft or condenfe, the fcrew K, w hich faftens the rack to the cylindrical wire H, muft be taken out; then turning the scitich till this wire is depreffed as low as poflible, the machine will be rendered fit to exhauft as a fingle air pump: and if it be required to condenfe, the diretions given in the laft paragraph but one, with ‘re~ gard to the bent tube T, and Fig. 8, muft be obferved. Mr. Cuthbertfon’s treatife contains a relation of various experiments made with this air pump, which fhew its great power of exhaufting, and are in other refpects entitled to the confideration of philofophers. With the double fyphon gauge, and alfo with the long gauge, compared with an attached barometer, in which the mercury had been repeatedly boiled, the difference between the heights of the mercurial columns proved to be no more than one fortieth of an inch, the barometer then ftanding at 30 inches. This gives an exhauftion of 1200 times. On fome occafions, when the air was in a very dry ftate, he obferved the dif- ference to be as low as one hundredth of an inch, which indicates more than double the rare- faétion. On a review of thefe papiomeeteads of the air pump, I perceive in each inftstiensae fo happy a combination of philofophical acutenefs and mechanical {kill, that it is with a de- gree of diffidence that I venture to {peculate on their refpective merits and blemifbes.. There is no provifion to open the upper fixed valve of Prince’s greater barrel; except the difference between the preflures of the elaftic fluid on each fide of the ftrip:of bladder ; and this may reafonably be inferred to limit the power of his {mall pump. In Cuthbertfon’s pump, the fame valve is expofed to the aétion of the atmofphere, together with that’ of a column of oil in the oil veflel. The mifchief in either inftrument is’ probably trifling ; but in both the valve might have been opened mechanically. If this were done, the fmall pump of Prince might perhaps be unneceflary-in moft ftates of the atmofphere. | With regard to the lower valves, Cuthbertfon, by an admirable difplay of talents asa workman, has infured their action. Prince, on the other hand, has, by the procefs of reafoning, fo far improved the inftrument that no valves are wanted. In this refpect' he»has' the advantage ‘of fim-' plicity and cheapnefs, with equal effect. The mechanical combination of Cuthbertfon’s’ pump reduces the operation to one fimple aét of the handle: but Prince’s engine requires - fome manipulation with regard to the play of the fmall pump; say this might have been remedied by a more fkilful difpofition of the fir mover: |) dri ! The > = a Proje for an Air Pump.—Ujeful Notices. 131 The moft perfect {cheme for an air pump, taking advantage of the labours of thefe ju- dicious operators, feems to be that in which two pittons of the conftruction of Prince fhould work in one barrel; one pifton being fixed at the lower end of the rod, and the other at the middle. The lower pifton muft come clear out of the barrel when down, and work air-tight through a diaphragm at an equal diftance from the effective ends of the barrel. In the diaphragm muft be a metallic valve of the form of Cuthbertfon’s lower valve, but with a fhort tail beneath, that it may be mechanically opened when the pifton comes up. Above the diaphragm, mutt work the other pifton fimilar to the firft; but as it cannot quit the barrel when down, a fmall portion of the barrel muft be enlarged juft above the diaphragm, fo that the leathers may be clear in that pofition. Laftly, the top of the barrel mutt be clofed and fitted with a valve and oil veffel, according to the excellent contrivance of Cuthbertfon. If we fuppofe the workmanfhip of fuch a pump to Jeave the {pace between the diaphragm and lower pifton, when up, equal to one-thoufandth part of the {pace pafled through by the ftroke of that pifton, the rarefaction preduced by this part of the engine will in theory bear the fame proportion to that of the external air. And the fame fuppofition applied to the upper pifton would increafe the effe&t one thoufand times more. Whence the rarefaction would be one million times. How far the practical effect might fall fhort of this from the imperfections of workmanfhip, or the nature of the air, which in high rarefaétions, may not diffufe itfelf equally through the containing fpaces, or from other yet unobferved circum- ftances, cannot be deduced from mere reafoning without experiment. ; VI. Ufeful Notices vefpefing various Objects. —A Method of preventing Heat in Grinding—Con- cerning Gold, Silver, and other Metals reduced into very thin Leaves by the Hammer— Globules for Micrefcopes—On the Plumb-Line, and Spirit-Level. 1. On the Art of Grinding. A CURIOUS fa& was mentioned to me, fome years ago, refpecting grinding, which promifes to be of fome ufe in the arts. Daily experience, as well as philofophical ex- periment, fhews us that heat is produced or developed by friction. The fact of {parks » flying from a dry grindflone when a piece of iron or fteel is applied to its furface during the rotation, has been feen by every one. The heat produced during this procefs is fuck that the. {teel very foon becomes ignited, and hard tools are very frequently foftened and {fpoiled, for want of care during the grinding. When a cylindrical {tone is partly immerfed in a trough of water, the rotation muft be moderate and the work flow, otherwife the water would foon be thrown off by the centrifugal force ; and when this fluid is applied by a cock from above, the quantity is too {mall to preferve the requifite low temperature. It is even found, that the point of a hard tool, ground under a confiderable mafs of water, will be foftened if it be not held fo as to meet the ftream; fparks being frequently afforded even under the water. My informant aflured me, that fine cutlery is ground in Germany on a cylinder of a peculiar kind of pottery inftead of ftone, upon the face of which pul- $2 verifed 132 The modern Do&rine of Heat applied to the Art of Grinding. verifed hone is occafionally applied by means.of tallow. The peculiar advantage of this kind of pottery was ftated to be, that it never heats, however rapid the motion. This objeé& feemed to deferve an experimental inveftigation. The three bodies fub- jeéted to experiment were pottery, pulverifed filex, and tallow. The effe&, namely that it could fupport violent and rapid fri€tion without increafe of temperature, appeared at firft fearcely credible. The mind was rather difpofed to rejeét the evidence, than inveftigate the caufe. No indication was given refpecting the nature of the pottery. It did not feem probable that any peculiarity in the filiceous fand fhould produce this defirable effect ; but an eafy procefs of reafoning might have pointed out the effect of the tallow, which is indeed curious. I cannot however aflume the merit of inveftigating the fubject 2 priori ; for my apparatus was ready for experiment, and the fact fpoke for itfelf before I had fy{tematifed the notions which occurred to me. The pottery grindftone was not eafily atcainable. I therefore procured a Newcaftle grindftone of a fine grit and ten inches in diameter ; and alfo a block of mahogany to be ufed with emery on its face. Both the ftone and the wooden block were mounted on an axis to be occafionally applied between the, centres of a ftrong lathe. In this fituation both ’ were turned truly cylindrical, and of the fame diameter. The face of the wood was grooved obliquely in oppofite directions, to afford a lodgement for the emery. The face of the ftone was left fmooth, and there was a trough of a proper fize applied beneath the ftone to hold water. The grindftone was then ufed with water, and the wooden cylinder was faced with emery and oil. The inftrument ground was a file, out of which it was propofed to grind all the teeth. The rotation was produced by the mechanifm of the lathe ; the velo- city being fuch as to turn the grinding apparatus about five revolutions in a fecond. The ftone operated but flowly, and the water from the trough was foon exhaufted, with incon- venience to the workman, who could fcarcely be defended from it but by flackening the velocity. The emery cylinder cut rather fafter. But notwithftanding the friction was made to operate fucceflively and by quick changes on the whole furface of the file, it foon became too much heated to be held with any convenience; and when a cloth was ufed to defend the hand, the work not only became awkward, but the heat increafed to fuch a degree that the oil began to be decompofed, and emitted an empyreumatic f{mell. ‘The ftone was then fuffered to dry, and the file tried upon its face. It almoft immediately became blue, and foon afterwards red-hot. Both the cylinders were then covered with tallow, by ap- plying the end of a candle to each while revolving, and emery was fprinkled upon the cylinder of wood. The fame tool was then applied to the grindftone in rapid motion. At the firft inftant the fri€tion was fcarcely perceptible ; but very f{peedily afterwards the zone of tallow preffed by the tool became fufed, and the ftone cut very faft. The tool was fearcely at all heated for along time ; and when it began to feel warm, its temperature was immediatly lowered by removing it to a new zone of the cylinder. The fame effect took place when the experiment was repeated with the wooden qylinder. It is not difficult to explain this by the modern dottrine of heat. When oil was ufed upon the wooden cylinder, the heat developed by the friction was employed in raifing the temperature of the tool and of the fluid oil. But when tallow was fubftituted inftead of the oil, the greateft part of the heat was employed in fufing this confiftent body. From the increafed capacity of the tallow, when melted, this heat was abforbed, and became latent, inftead Compofition, Purity, and Thicknefs of Gold and Silver Leaf, &'c. 133 inflead of being employed to raife the temperature : and whenever, by continuing the pro- cefs, the tallow already melted began to grow hot, together with the tool, it was eafy to reduce the temperature again by employing the heat on’ another zone of confiftent tallow. I ufed thefe two cylinders with much fatisfa€tion, in a confiderable quantity of work. In this ftage of experiment, I concluded that the cylinder of pottery mentioned to be ufed in Germany was either of no particular utility beyond that of a common grindftone, or that the report might be inaccurate in this refpe&t. But it happened that the {mall ftone here mentioned was laid afide for about three years. At the end of this term it was again brought into ufe, and it was found that the tallow had undergone fome change, either from the ftone itfelf, or the action of the external air, which enabled it to defend the grit much more effectually than at firft. It feemed to have become lefs fufible. Ithink it probable that this might not have happened with a pottery cylinder, or at leaft that it would have been more eafy to clean and reftore the furface to its firft ftate. 2. Concerning Gold, Silver, and other Metals reduced into very thin Leaves by the Hammer. IT is generally thought by chemifts, and others, that leaf gold confifts of the metal in a high ftate of purity. It is never pure, becaufe pure gold is too ductile to be worked between the gold-beaters’ fkin. The neweft fkins will work the fineft gold, and make the thinneft leaf, becaufe they are the fmootheft. Old kins, being rough or foul, require coarfer gold. The finer the gold, the more duétile ; infomuch that pure gold, when driven out by the hammer, is too foft to force itfelf over the irregularities, but would pafs round them, and by that means become divided into narrow flips. The fineft gold for this pur- pofe has three grains of alloy in the ounce, and the coarfeft twelve grains. In general the alloy is fix grains, or one-eightieth part. That which is called pale gold contains three pennyweights of filver in the ounce. ‘The alloy of leaf gold is filver, or copper, or both, and the colour is produced of various tints accordingly. Two ounces and two penny- weights of gold is delivered by the mafter to the workman, who, if extraordinarily fkilful, returns two thoufand leaves, or eighty books, of gold, together with one ounce and fix pennyweights of wafte cuttings. Hence one book weighs 4.8 grains; and as the leaves reafure 3-3 inches in the fide, the thicknefs of the leaf is one two hundred and cighty-two thoufandth part of an inch. Silver leaf is faid to be pure filver. It is extenfible in this way when compared with gold, sather more than in the proportion of the fpecific gravities. Some leaf filver which I tried was thicker than the go)d in the proportion of feven to four. So that the weight of metal covering equal furfaces approached to equality. . The yellow metal called Dutch gold is fine brafs. It is faid to be made from copper- plates, by cementation with calamine, without fubfequent fufion. Its thicknefs, com- pared with that of leaf gold, proved as 19 to 4, and under equal furfaces it is confiderably more than twice as heavy as the gold. The Dutch filver appears to be tin, not only from its habitudes with re-agents, but from the confideration that there is no other cheap white metal of fufficient duétility. It is fomewhat more than ten times as thick as ie leaf, and about two and a half times as heavy under equal furfaces. 3 * The 134 Globules for Microfcopes.—ImperfeEtions of the Plumb- Line. The thinneft tin-foil in fmall fheets for filvering looking-glaffes, is about one-thoufandth of an inch thick, or near three hundred times the thicknefs of gold leaf. It ufually con- tains lead. 3. Globules for Microfcopes. AT the beginning of the prefent century, the fimple microfcope was very much ufed. Among other advantages, it pofleffes the very defirable requifites of fimplicity and cheapnefs. In particular it is an inftrument not difficult to be conitructed by fuch ingenious philofo- phers as by narrow circumftances and remote fituations are obliged to have recourfe to their own {kill and ingenuity for experimental implements. The hiftory of natural philofophy abounds with inflances of eminent men who come under this defcription. To thefe at leaft it will be of importance to know a ready method of forming very bright {pherules of glafs for microfcopic ufes. The ufual method has been to draw outa fine thread of the foft white glafs called cryftal, and to convert the extremity of this into a f{pherule by melting it at the flame of a candle. But this glafs contains lead, which is difpofed to become opake by partiel reduétion, unlefs the management be very carefully attended to. I find that the hard glafs ufed for windows feldom fails to afford excellent f{pherules. This glafs is of a clear bright green colour when feen edgeways. ¢ (r val x) ¥ 29x — ** ¢ (r = n) r VoL. I.—June 1797. 44 or 138 Mathematical ee Fr S| c/2rx — x* But when the body, in revolving, comes to D, x then becomes = rj in which café, =— —, and confequently F = ——— — firs = —-*x Pent /Ba= ae 2h t= — or.F is as a or as the fquare of the velocity divided by the radius. NEW MATHEMATICAL QUESTIONS. : Question V. By VW. Simpson. A BOTTLE which held exa@lly 5 oz. 106 gr. of diftilled water, was capable of contain- _ ing 5% oz. and 170 gr. of a folution of common falt in diftilled water : Required the weight of the falt held in folution, its {pecific gravity being 2.8 ? Question. VI. By F. B. THE ‘mean annual temperature of any two latitudes, in the fame hemifpliere, being given, to determine the mean annual temperature of any other latitude in that hemifphere ? To Mr. NrcHoxson, Editor of “The Fournal of Natural Philofophy, Chemiftry, and the Arts.” STR, I DO not know whether you will confider the following as of fufficient importance to merit a place in your valuable publication ;—if fo, I fhall perhaps occafionally, in future, trouble you with other attempts of a fimilar nature. Being about four years ago engaged in fome mathematical fpeculations, in ‘the courle of which the refolution of pretty high equations became frequently neceflary, I was induced to fet about the inveftigation of an eafy arithmetical rule for the folution of an adfected qua- dratic, in order to fhorten the bufinefs of approximation. —It is, indeed, you know, on ac- count of the prolixity of the ordinary methods by completing the fquare or exterminating the fecond term, that Dr. Halley's method of obtaining the approximate value of the root, by taking fuch terms of the aflumed equation as involve the fquare of the converging quantity, is now feldom ufed; fuch only as contain its fitft power being ufually admitted into the cal- culation. The mode which | adopted for this purpofe will be beft underftood by a flate- ment of the principles from which it is deduced. Let x? + ax be = 6. Then will the affirmative value of x be = 3 (Wa* + 4b—a.) = 4 42.8% 1.3.43.03. 1.3.5.4°.0%. 1.315.7-45.05. I Pees, ts bee a pee — 2 oe - aie 2.4). 2:4-03, 2.4.6.45. 2.4.6.8.a7. " 2.4.6.8.10.a9. cia RO fain Aarenoetes LF b3. A, bs, r é 4 4 = ea 0 — 2 4 = &ec. But in order to obtain this latter feries, a a’. a. al, a’, we have only to divide 4 by a, adding to the original divifor a, every time of repeating the divifion, double the quotient already found, together with the term which fuch new. divifion fhall produce, as in the common operation for extracting the f{quare root, as follows: a+ Mathematical Correfpondence. 139 a, 53. ae 65, BS. é b 2.53 5.0 14.6 42 kc. b Bas ta hii Sanat aM el a sa ala thee ae BE . 5B. b+ — a’. b a, ) b. a —— FE mee B. 2.53, 4, Tatty we 2b 2b? =) - 253, b+. OF a Oh ak te Le ORS. a 2.53 4.54, 4.55, + a Sar we, ° » Se. 2b 2b -b3 Bt. 5.0%, 4bs ye ATR TREES aerate ) 72 emai oo a’, ce. : 554. 10.45 Than ate eae reoeGe 2.5 Ce ny CLE 10.5+. V4B5..y) 14.05. a ear? Oh Geierals ea oe ae See | 4.55 Lap se 1CCs a. The variations which a change of figns in the original equation will produce are too ob- vious to need defcription. Hence we get the following rules for the arithmetical folution of the three forms of qua- dratics, which may be reduced to two-cafes. CyA'S EO Ihtix* Sian: RULE.—Place the numerical values of a and b as divifor and dividend, asin common divifion, —Having found the firft figure of the quotient, add it in its proper place (which is the fame. as that of fuch figure of the dividend b as ftands over the units place of the firft produ& of the increafed divifor into Juch quotient figure, when placed for /ubtradlion ) to the original divifor a3; multiply the Jum by fuch added figure, and fubtrac the product from the dividend, as in common divifion. Then, if the next figure of the quotient to be found will fall under any of the figures of the fir/t increafed divifor, fo as not to increafe the number of its digits when added to it, bring down the next figure of the dividend, as in common divifion ; byt, if fuch next figure of the quotient will, when added in its proper place, increafe the number of figures in the divifor, bring down the two next figures, asin the extrathion of the fquare root.— Bind fuch next figure of the quotient, and add both the figures of the quotient tothe firft increaftd divifor for a new divifor (as in extraéting the Square root) ; multiply fuch laft increafed divifor by the laft found figure ; fubtra® the produé? ; bring down another figure or figures of the dividend, and proceed as before : always adding to the laff divifor the two laft figures of the quotient, including the quotient-figure obtained by each divifion, for a new divifor, as in extra€ling the fquare root; and fo on till the operation be finifbed. io) ; The 140 Mathematical Correfpondence. The quotient fo obtained is a value of x, what fign is the fame as that of the fecond term of the original equation :—for it’s other value add to juch quotient the original divifor a, and prefix to the Jum the contraryfign. EXAMPLE I. Given . . . x* + 5613x = 2579080. Quere x. i -» 5613 + 4. ift Divifor = 6013 . + ) 2579080 ( + th + 42 24052 5613. 20.D.° s+, = 6493 |. o«,) 798hie =— $040, = &. + 27 “12866 3d D = 6460 . ) 45220. 45220 20. EXAMPLE 2. Given x2 4+ 13.24687% = 123.45678932. Quare x. ee = he -24687. ift Divifor = 19,24687. ) 123.45678932 ( + 6.3120464569.. &c. = x + 63> 115-48122/7! 13-24687 ad D.. . = 2554687. 7975569 — 19.5589164569.. &c. = x = One 3115083 —— oe ke 5293962 3d D... = 2585687 1201880. S 12 167045. . ——— 11820. ; | 4th D. . . = 2586887. 1472. 20: 2, 179- SS

Sulphuric Acid.—Ccngelation of Mercury. —Elaftic Fluids. 145 The memoir of Fourctoy and Vauquelin on the fulphureous acid, confifts in an exami- nation or hiftory of its aélion on every oun fubftance. They, in the firft place, examined this aétion caloric upon oxygene gas, fulphuric x E potatir “REE, Spee Co AME) BPS with the alkalis< foda muriatic , pe BOMAGs ‘hydrogen a EH phofphorus afterwards on the combuftibles J phofphoratedhydrogengas with the earths? , ; barytes fulphurated hydrogen gas magnefia, carbon In every cafe wherein the fulphureous acid formed a falt by combination, thefe chemifts have defcribed the form of its cryftals, its fuGbility, the affinities and proportion of confti- tuent parts. This memoir prefents a complete table of the binary combinations of the fulphureous acid, and renders it very defirable that the authors fhould continue, for the advancement of feience, to publifh fimilar accounts of a great number of fubftances, on which our notions are yet very incomplete. : The three memoirs of general phyfics: 1. Of the congelation of mercury, by Haffen- fratz, Bonjour, and Welte. 2. The laws of dilatation in elaftic fluids, by Prony. 3. The influence of {now and rain on vegetation, by Haffenfratz. _ Ithas long been known, that mercury was rendered folid at Peterfburg by cold 24 degrees of Reaumur below zero, and that in this ftate it becomes malleable. The experiment was repeated at London by Cavendifh, by producing the fame degree of artificial cold; but this refult had never been obtained in France. The memoir of Haffenfratz on the congelation of mercury contains only a repetition of this experiment, in which the proportion of caloric, abforbed during the congelation of the metal, is determined, which had not before been done by any philofopher. This experi- ment has afforded a very curious refult. In water the caloric, abforbed during the tranifition from the folid to the fluid ftate, is fufficient to have raifed its temperature 60 degrees Reau- mur ; and in mercury the'-quantity to produce the fame efe& would have been fuficient to raife the temperature 64 Uegrees. e Tn order to efcertain the principle and the laws to which a great number of phenomena ‘are referab!, it is neceflary to make a feries of reiterated experiments on'the fame facts. This is attended with two kinds of difficulties, namely, the time they require, and‘the im- perfection of the inftrument. Neverthelels, when the'exiftence of a 1 law inthe progrefs of any phenomenon is afcer- tained, it is always poflible, from a fmall number of experiments, to difcover by analyfis an equation which may exprefs the law. ‘This is the object of the memoir which Prony has printed in the fecond Cahier of the Journal.of the Polytechnic School. It is divided into two parts. Inthe firft he inveftigates a method of interpolation applicable to the phenomena which depend on elaflic fluids; in the fecond he applies this method to afcertain the law of 144 Scientific News. of dilatability in thefe fluids. For this application he avails himfelf of the experiments made: by Prieur, and publifhed by Guyton, on the dilatability of oxygene gas, azote, hydrogenous, nitrous, carbonic acid, and ammoniacal gafes; and laftly, on the expanfive force of the va- pour of water and that of alcohol. This memoir contains tables deduced from the equations afforded by the methods made ufe of by the author, and the refults.obtained: by Prieur. They are likewife exprefled by engraved curves. It was formerly obferved, that fnow preferves the vegetative power, and that rain accele- rates the growth of plants more than artificial waterings. Haffenfratz has enquired, in his memoir; imto the caufe of thefe comparative effects. He fhews, from feveral experiments, that the preferving power of {now arifes from two circumftances—its imperfect conducting * power, and its oxygenation. This philofopher has proved, that fhow is water oxygenated and converted into the folid form. He has alfo fhewn, that rain is more oxygenated than any other water, and that a large portion of its good effects is to be attributed to this circum- ftance. _ Phe memoir on the arts is written by Chauffier. Its objetiis to defcripe the compofition of a liquor proper to be fubftituted inftead of wine lees in fulling, to obtain the greateft effe& with the moft facility and economy. The liquor indicated by Chauflier is a fmall quantity of fulphuric acid... This acid bath which experience has affured him may. be ufed with invariable fuccefs, likewife affords the advantage of obtaining a very white colour in hats, becaufe the felt does not become co- loured in the working. ee Extrad of a Letter from Profeffor LoRENZ DE CRELL. MR. KLAPROTH*is continuing his chemical analyfis, and will fhortly publifh a fecond yolume of them. He has found that the newly difcovered Titanium is by no means fo rare as might be fuppofed from its not having been known till lately. He has detected it in a fin- gular kind of mineral found at Afchaffenberg by Prince Gallitzin, and in fome other mine- rals, as well as in menakanite, in which it is mixed with iron. —Mr. Weftrumb’s method of obtaining ardent fpirits from different forts of grain, proves to be excellent, and fucceeds well on a large feale as a branch of trade.—Sulphate of barytes does not require more than an equal quantity of well aérated alkali for its decompofition both in the humid and dry way. Muriate of barytes is obtained perfeétly pure by boiling it in ten times its weight of highly reétified alkohol vini, which diffolves nothing but this muriate.—To feparate hepatic gas and carbonic acid gas when united, employ acidulated acetite of filver or mercury. Either of thefe metallic falts will abforb the hepatic gas, and leaye the carbonic acid gas un- touched. » This article was forwarded to the learned editor of the Englifh tranflation of Crell’s Journal ; from whom I received it in a letter, containing very encouraging expreffions of approval and good wishes for the fuccefs of the prefent undertaking. - se Ber ad Philos Journal VolLPLAVI facing 244, AIR PUMP by the REVS SOHN PRINCH HZ q ie Mca | "lumina . os ie 7 Re. Se em meee emer Cel ye en lily a is mint a spam, een te Pe ine eS)! Pe an ot el hale gE ey i The AIR PUMP of CUTHBERTSON Philos Journal VoAtrL!. 7. fiteing P24 To A Toa Roy ne OF NATURAL PHILOSOPHY, CHEMISTRY, AND LE: ARTS. FULT 1707. ARTICLE I. ‘Obfervations on Horizontal Refractions which affect the Appearance of Terreftrial Objects, and the Dip or Depreffion of the Horizon of the Sea. By FosePH HuDDART, Ejq. F. R.S.* Tuer variation and uncertainty of the dip in different ftates of the air, taken at the fame altitude above the level of the fea, was the reafon of my turning my thoughts to this fubje@t as it renders the latitude obferved incorreét, by giving an erroneous zenith diftance of a veleftial object. Ihave often obferved, that lowlands, and the extremity of headlands, or points forming an acute angle with the horizon of the fea, and viewed from a diftance beyond it, appear ele- vated above it, with an open {pace between the land and the fea. The moft remarkable in- ftance of this appearance of the land, I obferved at Macao, for feveral days previous to a typhon, in which the Locko loft her topmafts in Macao roads; the points of the iflands and lowlands appearing the higheft, and the fpaces between them and the fea the largeft, I ever faw. I believe it arifes and is proportional to the evaporation going on from the fea. And in refle€ting upon this phenomenon, I am convinced that thofe appearances mutt arife from refraction, and that, inftead of the denfity of the atmofphere increafing to the furface of the fea, it muft decreafe from fome fpace above it; and that evaporation is the principal caufe which prevents the uniformity of denfity and refra€tion being continued by the ge- neral law down to the furface of the earth. And I am inclined to believe, though I men- tion it here as a conjecture, that the difference of fpecific gravity in the particles of the at- mofphere may be a principal agent in evaporation; for the corpufcles of air, from their affinity with water, being combined at the furface of the fluid from expanfion, form air * Philofophical Tranfaétions for 1797. Vou: L—Jury 1797. U fpecifically 146° -- + The Effedts and Theory of Refra&tion near the Surface of the Sea, fpecifically lighter than the drier atmofphere; and therefore float or rife, from that principle, as {team from water; and in their rifing (the {urrounding corpufcles from the fame caufe imbibing a part of the moifture) become continually drier as they afcend, yet continue ~ afcending untilthey become equally denfe with the air*. However, thefe conjeCtures I fhall leave, and proceed to the following obfervations upon refraétions : In the year 1793, when at Allonby in Cumberland, I made fome remarks on the ap-~ pearance of the Abbey-head in Galloway, which in diftance from Allonby is about feven leagues; and from my window, at fifty feet above the level of the fea, at that time of tide, I obferved the appearance of the land about the Head.as reprefented in Pl. VILL. Fig. 1. There was a dry fand xy, called Robin Rigg, between me and the Head, at the diftance from my houfe of between three and four miles; over which I faw the horizon of the fea HO; the fand at this time was about three or four feet above the level of the fea. The hummock ¢ is a part of the headland ; but appeared infulated or detached from the reft, and confiderably elevated above the fea, with an open {pace between. I then came down about twenty-five feet, when I had the dry fand of Robin Rigg xy in the apparent horizon, and loft all that floating appearance feen from above; and the Abbey-head appeared everywhere diftin& from the furface of the fand. This being in the afternoon, the wet or moifture on the fané would in a great meafure be dried up. I have reafon therefore to conclude, that evaporation is the caufe of a lefs refraétion near the furface of the fea; and when fo much fo as to make an objet appear elevated wholly above the horizon (as at d in Fig. 1.) there will from every point of this objeét iffue two pencils of rays of light which enter the eye of the obferver, and that below the dotted line AB (parallel to the horizon of the fea HO) the ob- jects on the land will appear inverted. To explain this phenomenon, I thall propofe the following theory, and compare it with — the obfervations which I have made. Suppofe HO, Fig. 2. to reprefent the horizontal fur- face of the fea, and the parallel lines above it the lamina or ftrata of corpufcles, which, next the fluid, are moft expanded, or the rareft; and every lamina upwards increafing in denfity, till it arrive at a maximuni (and which I fhall in future call the maximum of denfity) at the line D C, above which it again decreafes in denfity ad infinitum. Though this in reality may be the cafe, 1 do not wifh to extend the meaning of the word denfity farther than to be taken for the refractive power of the atmofphere; that is, a ray of light entering obliquely a denfer lamina, to be refracted towards a perpendicular to its fuxface; and in entering a rarer lamina the contrary; which laminz being taken at in- finitely {mall diftances, the ray of light will form a curve agreeable to the laws of dioptrics. In order to eftablith this principle in horizontal refra€tions, ¥ traced over various parts of this fhore, at different times, when thofe appearances feemed favourable, with a good telefcope, and found objeéts fufficient to confirm it; though it be difficult at that diftance of the land to get terreftrial objeéts well defined fo near the horizon, as will afterwards appear. * Mr. Hamilton, in his very curious Effay on the Afcent of Vapours, does not allow of this principle even as an affiftant; though by a remark (page 15) he takes notice of thofe appearances in the horizon of the fea, and fays they arife from a ftrong or unufual degree of refraction; the contrary of which I hope to illuftrate in the courfe of this paper. Ohe Taverfion of Objects by Hortzontal Refraction. : 147 One day, obferving the land elevated, and feeing a {mall veffel at about eight miles dif- tance, 1 from my window dire&ted my telefcope to her, and thought her a fitter objet than any other Ihad feen for the purpofe of explaining the phenomena of thefe refra€tions. The telefcope was forty feet above the level of the fea: the boat’s maft about thirty-five feet ; the being about twenty to thirty tons burthens The barometer at 29.7 inches, and Fah- renheit’s thermometer at 54°. The appearance of the veffel, as magnified in the telefeope, was as reprefented in Fig. 3, and from the maft-head to the boom was well defined. I pretty diftinétly faw the head and fhoulders of the man at the helm; but the hull of the veffel was contracted, confufed, and ill defined. The inverted image began to be well defined at the boom (for 1 could not clearly perceive the man at the helm inverted), and from the boom to the horizon of the fea the fails were well defined; and I could fee a fmall opening above the horizon of the fea in the angle made by the gaff and maft; and had the maft been fhorter by ten feet (to the height of y), the whole would have been elevated above the horizon of the fea, and from y to dan open fpace. This drawing was taken from a fketch I took at the time, and repre- fents the proportion of the inverted to the ereét objeét, as near as I could take it by the eye; the former being about two thirds of the latter in height, and the fame breadth re- {peGtively ; though at one time, during my obfervation, whieh I continued for about an hour, I thought the inverted nearly as tall as the ereét objet. The day was fine and clear, with a very light, air of wind, and I found very little tremor or ofcillation in viewing her through the telefcope. ; Ihave laid down Fig. 4. for the explanation of the above phenomena, in which A reprefents the window I viewed B the veflel from; HO the curved furface of the fea; CD parallel to HO the height of the maximum,of denfity of the atmofphere; the lines marked with the {mall letters aa, bb, cc, dd, the pencils of rays under their various refractions from the veffel to the eye or object-glafs of the telefcope. The pencil of rays aa, from a point near the head of the mainfail, is wholly refracted in a curve convex upwards, being everywhere above the maximum of denfity ; and the pencil of rays d d, which iffues from the fame point in the fail, and paffes near the horizon of the fea at *, is convex upwards from the fail to W, where it paffes the line of maximum of denfity, which is’ the point of infle€tion; there it becomes convex downwards, pafling near the horizon at.x to y, where it is again inflected, and becomes convex upwards from thence to the eye. The pencil of rays 44, from the end of the boom, paffing nearly parallel to the horizon, and near the maximum of denfity, fuffers very little deviation from a right line in the firft part; but in afcending (from the curvature of the fea) will be con- ‘vex upwards to the eye. The pencil of rays ¢c, from the fame point in the boom, may hhave the fmall part to ¢ convex upwards: fromc to z it will be convex downwards, and from = to the eye convex upwards. From this invefligation it appears that two pencils of rays cannot pafs from the fame point and enter the eye from the law of refraction, except one pencil pafs through ,a medium which the other has not entered; and therefore the maximum of denfity was below the boom, and could not exceed ten fect of height above the furface of the fea at the time thefe obfervations were made.’ Refpecting the hull of the veflel being confufed and ill defined in the telefcope, as by Fig. 3, it arifes from the blending of the rays from the different parts of the objedt U2 refracted 148 Theory of Horizontal Refraflion.—Light-Houfes, refracted through the two mediums; fome parts of the hull appearing erect, and fome inverted. Suppofe the dotted line 77, Fig. 4. an indefinite pencil of rays paffing from be- tween the inverted and ere&i parts of the objeét, or the upper part of the hull of the veflel to the eye (for the lower part of the hull could not be obferved), the objects cannot appear inverted, except the angles at the eye aAc andaAd excced the angle aAi; for the intermediate fpace could only be contraéted by the fecondary pencil of rays. The lengths of the inverted, compared with the ereét image of the fail, is as the fines of the angles at the eye aAitoiAd; and the angle at the eye a Ad, made by the two pencils of rays from the fame point near the head of the fail, muft be double the angle a Ai, when the inverted image is as tall as the ere€&t. In this cafe the fines of the angles a Ad, aAcgaA d, Fig. 4, are proportional to the altitudes a4, ac, ad, in the magnified view of the veffel Fig. 3. © Under this confideration, no inverted image of the fail will be formed, until the angle at the eye, made by the two refradted pencils of rays aa and dd, exceed the angle made by aaand 64, the apparent height of the fail of the veffel; for, were thofe angles equal, the inverted fail would only be contracted into the parallel of altitude of the boom 4, and render the appearance confufed, as in the hull of the veflel. Refpeéting the exiftence of two pencils of rays entering the eye from every point of am objeé& not more elevated than a, or lefs than i, Fig. 3, in this ftate of the atmofphere, I cannot bring a f{tronger proof than that of the ftrength of a light when the rays pafs near the horizon of the fea, proved by the following obfervations : Going down Channel about five years ago in the ‘Trinity yacht, with feveral of the elder brethren, to infpe&t the light-houfes, &c. I was told by fome of the gentlemen who had®been on a former furvey, that the lower light of Portland was not fo {trong as the upper light at near diftances; but that at greater diftances it was much ftronger. I fufpected that this difference arofe from the lower light being at or near the horizon of the fea, and mentioned it at the time; but afterwards had a good opportunity of making the obfervation. We paffed the Bill of Portland in the evening, {teering towards the Start; a frefh breeze from the northward, and clear night. When we had run about five leagues from the lights, during which time the upper light was univerfally allowed to be the ftronger, (feveral gentlemen keeping watch to make obfervations thereon), the lower light drawing near the horizon fuddenly fhone with double luftre: Mr. Strachan, whofe fight is weak, had for fome time before loft fight of both lights; but could then clearly perceive the lower light. I then went aloft (as well as others), but before I got half maft up, the lower light was weaker than the upper one. On coming down upon deck, I found it again as ftrong as before. We proceeded on, and foon loft the lower light from the deck; and upon draw- ing the upper light near the horizon, it, like the former, fhone exceeding bright. I again went aloft, when it diminifhed in brightnefs; but from the maft-head I could then fee the lower light near the horizon as {trong as before. This is in confequence of the double quantity of light entering the eye by the two pencils of rays from every point. To illuftrate which, we compare the veffel Fig. 4. to a light-houfe built upon the fhore, and A the place of the obferver; and having brought down the light fo low as to view it in the direétion aa, another light would appear in the horizon at x, from the pencil dd; and had the veffel been ftill enough to have obferved it at this time with a good glafs, I doubt not but the two images might have been diftinétly feen. As the light dropped (by ; increafing Theory of Horizontal Refraction. 349 inereafing the diftance) the two images would appear continually to approach each other, till blended with double light in one, and difappear at the altitude i, above the apparent horizon of the fea. But, as explained before, if the ftrength of evaporation did not fe- parate by refraction the pencils aa and dd to a greater angle ‘than double the angle that the lamps and refle€tors appear under, the two images would be blended, and the ftrong ap- pearance of light would be of fhorter duration. The diftance run from the lights during the time each of the lights fhone bright, would have been ufeful; but this did not occur at the time, nor have I had the like opportunity fince. However, I recommend to the mariner to ftation people at different heights in looking out fora light, in order to get fight of it near the horizon, when it is always ftrongeft. Refpe@ing the appearance of the Abbey-head, before mentioned, Fig. 1, the dotted line * AB reprefents the limit, or the loweft points of the land that can be feen over the fea; for, as above ftated, all the objects appearing below this line are the land above it inverted ; and where the land is low, as at d and m, it muft appear elevated above the horizon of the fea. In Figure 5, let HO reprefent the curve of the ocean, and d the extreme top of the mount vifible at A by the help of refraction ; the dotted pencil of rays cc pafling from d to the eye, in fome part a little below the maximum of denfity, where inverfion begins;. therefore no and lower than this can be feen; for any pencil from a point in the land: lower than this muft, in the refraftion, have a contrary flexure in the curve, and therefore pafs above the obferver. Let AD bea tangent to the curve at A, then the obje& d will appear to be elevated by refraétion to D; alfo let Av be a tangent to the pencil Aw at A, then’ the angle DA x will appear to be an open fpace, or between D and the horizon of the fea. Suppofe a ftar fhould appear very near and over the mount ¢/, as at *, two pencils would iffue from every point of it, and form a ftar below as well as above the hummock d. There are always confufed or ill defined images of the objects at the height of the dotted line, Fig. 1, above the level of the fea, as before mentioned; and inftead of the points of d:end- ing fharp in that line, they appear blunted, and the Abbey- head is frequently infulated at - the neck m. Ihave viewed from an elevated fituation a point or headland at a diftance beyond the horizon of the fea, forming, as in Fig. 6, a ftraight line AB, making an acute angle BAO with the horizon of the fea. Seeing the extreme point blunted and elevated, I defcended ; and though in defcending the horizon cut the land higher, as at HO, HO, yet the point had always the fame appearance as aaa, Fig. 6, though the land is known to continue in the dire€tion of the ftraight line AB to beneath the horizon, or nearly fo, as viewed from the height above. If then, from a low fituation, we view this headland through a telefcope, the inclination of the furface AB to the horizon being known to be a ftraight line, it will appear as in Fig. 7; the dotted line (at the height of the point wherea perpendicular x y would touch the extreme of the land) being at the limit or loweft point of ereé&t vifion. And if a tangent to the curved appearance of the land ab is drawn parallel to the inclined furface of the land AB, Fig. 6, touching it at C, the point C will fhew the height of the maximum of denfity, where the pencil of the rays of light from thence to the eye approaches neareft the fea; for pencils of rays from this land, taken at {mall diftances from C, will form parallel curves nearly through the refraéting mediums, and C will be the point of greateft refrac- tion ; 150 Effed of Refraction on the Vifible Horizon. tion; for above C, as toB, the refraction fomewhat decreafing, will appear below the line a 5, or the parallel to the furface of the land, and the refractions decreafe below the point C; for, had they increafed uniformly down to the furface of the fea, it would render the apparent angle of the point of land = more acute than the angle C aQ, contrary to all obfervations. Thus I have endeavoured to explain the phenomena of the diftorted appearance of the land near the horizon of the fea when the evaporation is great, and when at the leaft I never found the land quite free from it when I ufed a telefcope, and from thence infer that we “cannot have any expedtation to find a trye correction for the effect of terreftrial refraction by taking any certain part of the contained arc; for the points z CB, Fig. 7, will have various, refractions, though they are at nearly the fame diftance from the obferver. And if the ob- fervations aré made wholly over dand, if the ground rifes to within a {mall diftance of the rays of light, in their paflage from the obje@ to the eye, as well as at the fituation of the object and obferver, the refractions will be fubjeét to be influenced by the evaporation of rains, dews, &¢.; whichis fufficiently proved by the obfervations of Colonel Williams, Captain Mudge, and Mr. Dalby, Phil. Tranf. 1795, p. 583. The appearances mentioned by Colonel Williams, Captain Mudge, and Mr. Dalby (Phil. *Tranf. 1795, p- 586, 587) cannot be demonftrated upon general principles, as they arife from evaporation producing partial refractions. In thofe general principles it is fuppofed that the fame lamina of denfity is everywhere at an equal diftance from the furface of the fea, at leaft as far as the eye can reach a terreftrial object; but in the partial refraCtions, the lamina of the expanded or rarefied medium may be of various figures, according to’ cir- cumftances, which will refra€t according to the incidence of the rays, and affect the ap- pearance of the land accordingly, which I have often feen to a furprifing degree. But my principal view is to fhew the uncertainty of the dip of the fea, and that the effect of eva~ poration tends to deprefs the apparent horizon at x when the eye is not above the maximum of denfity ; and from hence the difficulty of laying down any correct formula for thefe re- fra€tions whilft the law of evaporation is fo little underftood; which indeed feems a tafk not eafy to furmount. The effect indicated by the barometer and thermometer is infuf- ficient; and fhould the hydrometer be improved to fix a ftandard for moifture in the at- mofphere, and fhew the variations near the furface of the ocean, which certainly muft be taken into the account (evaporation going on quicker in a dry than a moift atmofphere), the theory might ftill be incomplete for correéting the tables of the dip. I fhall therefore conclude this paper, by fhewing a method I ufed in praétice, in order to obviate this error in low latitudes. When I was defirous to attain more accurately the latitude of any headland, &c. in fight, I frequently obferved the angular diftances of the fun’s neareft limb from the horizons upon the meridian both north and fouth, beginning afew minutes before noon, and taking alternately the obfervations each way, from the poop, or fome convenient part of the fhip, where the fun and the horizon both north and fouth were not intercepted; and having found the greateft and Jeaft diftances from the refpective horizons, which was at the fun’s paffing the meridian, and corre&ted both for refraction, by fubtraéting from the leaft, and adding to the greateft altitude, the quantity given by the table; and alfo having correted for the error of the inftrument, and the fun’s femi-diameter, the fum of thefe two angular diftances reduced as above—180° is equal to double the dip, as by the following Example. Correction far the Dip deduced from Obfervation. 151 Example. The fun’s declination 4° 32’ 30” and its femi-diameter 15’58” took the following ob- fervation : The meridian diftance of the fun’s neareft limb from South. North, the horizon of the fea 78° 36’ 30” = 101° 1/20” Refra€tion per table — — — oir = + o1r Diftances corr. for refraction — — =78 36 19 =I101 1 31 Error of the fextant — —— + 1 32 + -1 32 Sun’s femi-diameter _—— — + 15 58 +15 58 78 53 49 Ioli19 & Half difference-or the dip found —_> - —-— — «2625 78 53 49 Altitude reduced —_——- — —— =78 47 24 180 12 50 Zenith diftance _—— — =I1 12 36 180 . Diff. -12 50 _ The fun’s declination N. _ — = 4 32 30 Half=6 25 -- Dip. Latitude of the fhip N. ——. “—— =15 45 06 I regret that I cannot in this paper infert the dip which I have found in my obferva+ tions ; for I only retained the latitude of the fhip determined thereby as is ufual at fea. I generally reje€ted the error of the inftrument, the dip, and femi-diameter, as they affeét both obfervations with the fame figns; and reduced the obfervation by the following. method : South. North. Sun’s diftance as before — 78°36 30” 301° 1’20" Refration — — — ol! + our Dif. corr. for refraction — 78 36 19 HOLT. Zi prow “zl o ny! + 78 36 19 —— Sum 179 37 50 Sum of femi-diameter, dip, and refrac- tion = half difference —— + Il 5 180 san Ne 78 47 24 Diff 22 10 ———-__— Half 11 5 Yor 12 36 » go 9° The zenith diftance as before —— =111236 Zenith dift. =11 12 36 It may be obferved, that neither the dip, femi-diameter, or index error can affe& the zenith diftance of the fun’s centre ; and the refraction being fmall near the zenith, the refult muft be true, if the angles are accurately taken ; and it is only neceffary to obferve, that when the fum of the diftances is lefs than 180, the half difference muft be added to 5 the 152 Remarkable Effe@ of Refraétion on Diflant Land. the diftances, as by the laft redu@tion. There is a difficulty in making this obfervation when the fun paffes the meridian very near the zenith, as the change in the azimuth from eaft to weft is too quick to allow fufficient time: nor can it be obtained by the fextant when the fun paffes the meridian more than 30 degrees from the zenith; for I never could adjuft the back obfervation of the Hadley’s quadrant with fufficient accuracy to be depended upon *. Il. Remarkable Effe? of Terrefrial Refraétion on a Diflant Headland. Extra& of a Leiter from ANDREW Exxicor to Davin RirrENHOUSE, Efg. dated at Pitifburg, Nov. 5, 1787, concerning Objfervations made at Lake Erie +. On the 13th of laft month, while we lay on the banks of Lake Erie, we had an oppor- tunity of viewing that fingular phenomenon by, feamen termed looming. It was preceded by a fine aurora borealis on the evening of the 12th. The 13th was cloudy, but without rain. About 10 o'clock in the morning, as I was walking on the beach, I difcovered fomething that had the appearance of land in the dire€tion of Prefqu’ifle; about noon it became more confpicuous, and when viewed by a good achromatic telefcope, the branches of the trees could be plainly difcovered. From three o’clock in the afternoon till dark, the _ whole peninfula was confiderably elevated above the horizon, and viewed by all our com- pany with admiration. There was a fingular appearance attending this phenomenon, which I do not remember to have feen taken notice of by any writer. ‘The peninfula was fre- quently feen double, or rather two fimilar peninfulas, one above the other, with an ap- pearance of water between. The feparation and coincidence was very frequent, and not unlike that obferved in fhifting the index of an adjufted Godfrey’s quadrant. As fingular as this may appear, it isnot more fo than the double refraction produced by the Iceland eryftal. The next morning Prefqu’ifle was again invifible, and remained fo during our ftay at that pofition. Prefqu’ifle was about 25 miles diftant ; its fituation very low. The fame evening the wind began to blow brifkly from about two points weft of north, * The optical phenomena which relate to the conftitution of the atmofphere have not yet been much invefti- gated. ‘From the barometrical admeafurement of héights, as well as from experiments with the macrometer, or marine barometer of Halley (Roy, in Phil. Tranf. Vol. LXVII.), it is afcertained that air abounding with humidity is more expanfible by heat, and lefs denfe at like temperatures than air which is more dry. And from Sir Lfaac Newton's table, the refraétive power of air, in refpeét to its denfity, compared with that of water in the fame refpeét, is as 4160 to 7845 (Optics, Part III. Prop. 10.). Thefe and other facts thew that the rays of light muft be varioufly affeéted, according to the nature and circumftances of evaporation, condenfa- tion, and other procefles carried on in the-air, and particularly near the furface of water. That a lighter and lefs refractive ftratum of air may thus be generated near the furface of the fea to a confiderable elevation, and re- main for a time in equilibrio without afcending, is highly probable; and in this cafe, whenever the quiefcent ftate is from local or temporary circumftances deftroyed, it feems a natural confequence, that fudden and irre- gular currents of the lower air, and defcending blafts of the upper, may occafion all the ftrange effedts of the typhon and other phenomena, not well defcribed in that interefting tropical combination of fea and land to the caftward of Sumatra and Malacca. The Mediterranean Sea affords fimilar appearances, particularly the afto- niifhing {pe€tra in the Strait of Reggio, defcribed by Kircher, Minazi, and others, called Fata Morgana, of which d purpofe thortly to give an account, with an engraving. N, 4+ American Philof. Soc. III: 62. ‘ and Motions prodtrced by the Emanations of Odorant Bodies. 153 and continued to increafe till the evening of the 14th, when it was more violent than any ‘thing of the kind I had ever been witnefs to before, and continued till the evening of the 16th, without the leaft intermiffion. Our tents were all blown down, and we were under the neceflity of fortifying our camp by driving pofts near to each other firmly intosthe ground on the windward fide, and filling up the vacuities with bufhes in the form of an hedge. During the continuance of this wind we frequently obferved {mall black clouds ‘hanging over the lake : they had but little velocity, and were fometimes exhaufled, and dif- appeared without reaching the fhore. From the large bodies of timber blown down about the lakes, it appears that hurricanes are not uncommon. Coxe obferves in his Travels through Rufha, that the lakes in that country are fubject to terrible ftorms. lll. Extradl of a Memoir of M. Benenicr Prevost, of Geneva, on the Emanations of Odorant Bodies. By Citizen FourcRor *. Grew Duc la Chapelle, Dire€tor of the Society of the Sciences and Arts at Mont- auban, in the department of Lot, has forwarded to the Firft Clafs of the Inftitute, in the name of the Society, a Memoir of M. Benedié Prevoft, of Geneva, concerning various means of rendering the emanations of odorant bodies perceptible to the fight. ‘The Firft Clafs of the In- ftitute heard the reading with great intereft at its fitting of the 16th Pluviofe, in the year 5. The following are the faéts configned in this Memoir : 1. A concrete odorant fubftance, laid upon a wet glafs, or broad faucer, covered with 2 thin ftratum of water, immediately caufes the water to recede, fo as to form a {pace of feveral inches around it. + 2. Fragments of concrete odorant matter, or fmall morfels of paper or cork, impregnated with an odorant liquor, and wiped, being placed on the furface of water, are imme- diately moved by a very fwift rotation. Romieu had made this obfervation on camphor, and erroneoufly attributed the effet to eleCtricity. The motion was perceptible even in pieces of camphor of feven or eight gros. 3. An odorant liquor being poured on the water ftops the motion till it is diffipated by evaporation. Fixed oil arrefts the motion for a much longer time, and until the pellicle it forms on the water is taken off. 4. When the furface of the water is cleaned by a leaf of metal, of paper, or of glafs, plunged in and withdrawn fucceflively until the pellicle is removed, the gyratory motion is renewed. Ifa piece of red wax or of taper be dipped in water, and the drops fhaken off into a glafs of water containing odorant bodies in motion, the movement will be ftopped. The fame effect is not produced by metal. 5- An atmofphere of elaftic fluid is formed round odorant fubftances, and is the caufe of the effeéts here defcribed. 6. A morfel of camphor plunged to the depth of three or four lines in water, without floating, excites a rhovement of trepidation in the furrounding water, which repels fmall * Annales de Chimic, XXI. 2¢4—Tranflation. N. Vou. l.—Jury 1797. X bodies 154 Motions produced by the Emanaticns of Odoraat Bodies. bodies in its vicinity, and carries them again to the camphor by ftarts The author cone cludes that an elaftic fluid efcapes from, the odorant body in the manner of the fire of a fufee, or the difcharge of fire-arms. ® g- When there is. a certain proportion between the height of the water and that of the fmall fragment of camphor, the water is brifkly driven off, returns again.to the cam- phor, and again retires, as if by an explofion, the recoil of which often canfes the camphor to make part of a revolution on its axis. 8. Fragments of camphor of the fize of'a pea, floated upon water in a dith of metallic leaf four or fave lines in diameter, communicated motion to. thefe difhes, though lefs {wift than was exhibited by the camphoralone. If the glafs in which this experiment is made be nearly filled with water, and covered by a (plain) glafs which Sik ied a the contact of the air, the motion decays and ceafes. 9. Camphor alone moves more rapidly than when it is placed upon the metallic plate, The author infers that the immediate contact. of the water favours the difengagement of the fluid which produces the motion. 10. Camphor evaporates thirty or forty times more fpeedily when placed upon water, than when entirely furrounded with air. 1s. Camphor, during the act of diffipation im the’ air, preferves its form and its opake whitenefs; upon water it is rounded, and becomes tranfparent, as if it had undergone a kind of fufion. It may be inferred that it arifes from the acquired motion, which caufes it to prefent a greater furface to the air. 12. In faét, out of 12 equal {mall pieces of camphor, fix being fufpended under @ glafs with quick-lime, and very dry, and fix others being fufpended in a moiftened glafs, _ together with a wet fponge, the volatilization was alike in each; and the water in this cafe not touching the camphor did not appear to contribute to the effec. 13. It is neceflary for this purpofe that the water fhould direétly touch the camphor. Accordingly, fragments of camphor placed on blotting-paper continually wetted, are difli- pated with the fame f{peed, and become equally tran{parent, as when actually placed. on- water, though they exhibit no motion. 14. When fmall pieces of camphor are plunged in water, the camphor becomes rounded and tranfparent, does not ‘acquire any motion, and its dillipation is lefs perceptible than in the air.. The concurrence of air and water is therefore neceflary to difengage the fluid which is the caufe of the motion and total diflipation of odorant bodies. 15. The motion of odorant bodies upon water decays and ceafes fpontaneoufly at the end of a certain time; becaufe, the water having then contracted a ftrong fmell, the volatilization takes place i in all the points of its furface; and the {mall mafs being thus, fur- rounded by the odorant fluid, which is no longer air, diffolves, as im the ordinary odorant fluids, without forming the gafeous jet which is the caufe of the motion. The author compares the volatilization of the aromatic fubftance to.a combuftion excited by water. In this place the author dwells for .a fhort time on the phenomena he had defcribed. He obferves that thefe effects may be rendered palpable by touching the furface of the water on which the odorant fubftances move, with a pin dipped in oil, At the very inftant, quick as Jightning, thefe particles, as if ftruck, ceafe to move. A coloured pellicle, formed: - by the oil, is feen on the furface of the water. The water penetrates the pores of the oil, > ke Motions produced by the Emanations of Odorant Bodies. TEs like thofe of the camphor, and difengages a fluid which prevents the water from pene- trating the odorant fubftance. The motion ceafes, bécaufe this fubftance is then plunged in a fluid formed by the oil, which fluid is not air. 16. All bodies which are not odorant prefent, when hot, the fame phenomena as odorant bodies. In fact, the heat gives them a degree of fmell. To this phenomenon our author refers the bubbles and the motion, which are feen when an ignited piece of money is thrown into water. The elaftic fluid is according to him the caloric, which is difengaged in pro- portion. as the water penetrates the pores of the metal. It is neverthelefs much more fimple to attribute this phenomenon to the water converted into vapour round the ignited metal, and fometimes to hydrogene gas, when the metal is capable ‘of decompofing water, efpecially at this temperature. After the explanation of thefe experiments, Mr. Prevoft hopes with reafon that they will contribute to the theory of odours, which fo early refembles that of the gafes. He does not flatter himfelf with having exhaufted this fubje&t, but confiders his difcoveries as the means of rendering odour perceptible by water not only to the fight but even to the touch, as are likewife the vibrations of fonorous bodies. Men deprived of the fenfe of {mell, and even the blind, according to him, may in this manner diftinguith odorant bodies from thofe which have no fmell. ‘ Perhaps,” fays he, “ this kind of odorofcope may, by improve- ment, become an odorimeter. The exceptions, fuch for example as that of the cerumen of the ears, which produces much effeéton water without being perceptibly odorant, and that of the fingers when hot or moift, are merely apparent; for, if our fenfes do not in thofe cafes difcover odour, thofe of animals more powerfully energetic, fuch as the dog, perceive and diftinguith individuals by its peculiar charater. The odorofcope may afford the in- formation which is wanting refpecting thefe effluvia. Thus it isthat the fat of game, the {mell of which is nearly to us imperceptible, is very much fo to dogs, and exhibits fenfible marks by the odorofcope.” ; Mr. Prevoft, who profeffes much brevity in this memoir, affirms, that water placed on the odorant liquor, inftead of this laft being put upon the water, affords a phenomenon confiderably interefting, but which he has not defcribed. A {peedy communication of the reft of this interefting work is much'to be defired. : We fhall not in this place explain the-manner in which it appears neceflary to confider - the ptinciple of fmell, which no longer appears to us proper to be regarded as a peculiar matter, and one of the immediate materials of vegetables, always identical, and enjoying the fame properties. We hall have occafion in future to enter more fully into this fubjec, and perhaps to rectify the notions which have hitherto been formed concerning the fpi- ritus rector or aroma of plants. We fhall contént ourfelyes with obferving, that the '_ phenomena defcribed with clearnefs and precifion by Mr. Prevoft, as well as the theory he has given, are referable to the attraction of the odorant matter in the.mafs for air and water, and the folution which takes place in one or the other, or in both at the fame time. ; X 2 IV. 4 156, 4 new Method of meafuring the Ele&rie Charge. IV. A Method of meafuring the Ferce of an Electrical Battery during the Time of its being charged. By Lieutenant Colonel HALDANE *. Ler the battery be infulated ; and at a {mall diftance from it place an uninfulated elec- trical jar; alfo near to the jar place one of Mr. Cuthbertfon’s eletrometers. The ele€trometer being adjufted according to the degree of force which is intended to be employed as a meafure of force to be communicated to the battery, conneét the elettro- meter with the jar; make a metallic communication between the interior fide of the jar and the exterior fide of the battery, amd conneét the interior fide of the battery with the conduétor of an eleétrical machine. : Then, by the operation of the eleétrical machine, the battery receives a quantity of the: ele€trical fluid, and becomes charged. The fluid which departs from the exterior fide of the battery, is received by the ele&rical jar, which alfo becomes charged; but this jar; being connetted with the ele@rometer, explodes as foon as it acquires’a force fuflicient to put the ele&trometer into motion. Now, the quantity of the eleétrical fluid which is received by this jar, between each of the explofions, is a meafure of the quantity of the fluid in the battery; and the number of explofions or difcharges of this jar fhews the number of meafures which the battery cons tains, and confequently the force which it is capable of exerting when difcharged. Demonftration. _ "THE eleétrometer remaining under the fame adjuftment will require the fame force to put it in motion: this force refults from the quantity of eleétrical fluid received by the jar; nd fince it is admitted, that, when effects are the feme, the caufes of them mutt be equal, it is evident that the quantity of eleétrical fluid contained in the jar at the time of each explofion is the fame. : It is alfo obvious, that the fum of all thefe equal quantities of the eleGtrical fluid which was contained in the jar at the time of each explofion, is equal to the whole quantity con- tained in the battery; for, the battery being infulated, the jar received all the eleCtrical fluid which departed from the exterior fide of the battery; and that quantity is faid (in the theory of Dr. Franklin) to be equal to the quantity in the interior of the battery. Therefore it is manifeft that the number of explofions or difcharges of the ele@trical jar, is the number of equal meafures of the ele¢trical fluid which the battery contains. - But without putting too much confidence in any philofophical theories, the effects of this operation may be more fatisfactorily fhewn by the following experiments: Experiments. A PIECE of iron wire, about 0.045 inches in diameter, and about two inches in length, was placed in the circuit through which the difcharge of a fmall eleétrical battery, which contained about fix feet fuperficial of coated glafs, was to pafs. The eleétrical jar employed as the meafure of the charge of the battery contained about go fquare inches 5 and the adjuftment of the eleCtrometer was varied in each fet of * Communicated by the Author. experiments, —— A new Method of meafuring the Elefrie Charge. 157 experiments, by changing the weight applied to the balance, and alfo the diftance of the difcharging bails. Experiment 1.. THE cle&rometer being adjufted with its leaft weight; the difcharging balls placed: at the diftance of one inch; and the other parts.of the apparatus arranged as before de- feribed ; the electrical machine was put in motion, the battery and alfo the jar began to: receive a charge, as was fhewn by the repulfiom of a pith-ball on a graduated quadrant placed upon the electrometer: : 1. After the firft explofion of the eleétrical jar, that is, after the battery had received. one meafure of the eleétrical fluid, a difcharging rod was applied to complete the circuit in which the iron wire was placed; but, upon the difcharge of the battery, no change of appearance was vifible in the wire: 2. Tlie operation of the ele€trical machine being continued) the difcharging - rod, after two explofions of the jar, that is, after the battery had received two meafures, was applied as. before ; but, upon the difcharge of the battery, no change appeared on the wire. 3. The battery was then charged. with three meafures; and upon difcharging it as before, luminous particles of the wire were thrown off. 4. The battery, having received four meafures, the wire, upon the difcharge, exhibited se the fame appearance as before. . The battery, having zeceived five meafures, was difcharged ;- the wire was red-hot, a feparated. 6. The battery, having received fix meafures, was difcharged’; the wire was difperfed: in red-hot globules. . The battery, upon receiving between nine and ten meafures, made a fpontaneous: difcharge.. Experiment 2 IN the feeond fet of experiments, the apparatus was arranged as before, and the elec— trometer adjufted with the fame weight, but the difcharging balls were placed at the dif= tance of two inches. The refults were, upon difcharging the battery, after having received 1 Meafure, - No alteration in the wire. 2Meafures, - Luminous particles thrown. off 3 Meafures, - The fame, with fmoke. 4 Meafures, - Red-hot, and feparated. 5 Meafures, - Difperfed in red-hot globules. Between 7 and 8 Meafures, + A fpontaneous difcharge of the battery... Experiment 3. THE apparatus being arranged as before, the ele€trometer was adjufted with its greateft! weight, and the difcharging-balls placed at the diftance of one fa the refults were, upom difcharging the battery, after having received 1 Meafure, - No alteration in the wire. 2 Meafures, - Luminous particles thrown off.. 3 Meafures, - The fame. 4: Meafures,, 158 Meafure of the EleGric Charge. 4 Meafures, - Red-hot, and feparated. 5 and 6 Meafures, + Red-hot, and difperfed in globules. Between 8 and 9 Meafures, - A fpontaneous difcharge. Experiment 4. THE electrometer being adjufted with the greateft weight, the difcharging-balls wore placed at the diftance of two inches. The refults were : : 1 Meafure, - Luminous particles thrown off. 2 Meafures, _ - The fame, with fmoke. 3 Meafures, - Red-hot. 4 Meafures, = The wire was difperfed in red-hot globules. Between 6 and 7 Meafures, - In filver there will be pieces of one franc weighing five grammes, and of five francs weighing twenty-five grammes. Laftly, in gold, there will be pieces of ten grammes. This explanation is fufficient to exhibit the fyftem in its true light, and to thew its beauty, fimplicity, and numerous advantages. ‘Thofe who are defirous of more extenfive developments, ‘ 198 New Sy/tem of Weights and Meafures of France. developments, will find them in the works publithed by the temporary Commiflion of Weights and Meafures, and by the Agency inftituted to conduét this great and ufeful ope- ration to its end. We have thought it neceflary to annex to this memoir, 1. A table of the new fyftem. 2. Tables of the relation between the old (French) meafures and the new ; by which it is eafy to reduce the one to the other, The object of thefe tables is to reduce all the calculations relative to this transformation to fimple addition. They will likewife ferve to determine the price of the new meafures from that of the old. In order to render ' them lefs voluminous, the fimple unities are given from one to nine only. From the value of the unities it is-eafy to infer the value of decimal multiples or fractions, by fhifting the decimal point. To thefe tables we have added the logarithms of the ratios between the old and the new meafures. By this means every one who is engaged either in the art of mining, or the fciences re- lating to the fame, will find colle&ed in one view all that is wanting to facilitate the ftudy and the praétice of the new fyftem. j *,* The table numbered 2 in the original, occupies confiderable fpace, and, though of great utility to the in- habitant of France, is comparatively of {mall importance to any other nation. It is merely a table for facilitating reduétion’ of the old and new meafures of France into each other, and does not convey any additional informa- tion to that in the memoir. For thefe reafons I have not copied it. In the way of curfory ohfervation on the objeéts of this honourable and ufeful undertaking, it may be remarked, that arguments deduced from confiderations of the immediate numerical application of an original meafure, are of little confequence as to the choice of the means of obtaining it, The chief, and’ indeed the fole, motive of pre= ference muft confift in the greater degree of accuracy, or more perfect agreement of the refults wrought out by different obfervers. In experiments to determine the length of a pehdulum vibrating through any known por- tion of the time employed by the earth in its rotation, we have to enquire, 1. Whether that rotation be theo- retically uniform? and if not, what are the quantities and periods of irregularity, perceptible in fuch an experi- ment? 2. What are the beft methods and limits of error in meafuring the length of a pendulum between its centres of ofcillation and fufpenfion? 3. Whether the errors from temperature can be rendered infenfible in this meafure of time and length; and if not, what are their limits? And above all, 4. What are the effects of the efcapement part, or fimpleft maintaining power in a clock ; and what are the beft means of diminifhing or re- moving them altogether. In the method of deriving an original ftandard from the meafurement of lines and angles upon the earth, the objeéts of enquiry are certainly not lefs numerous than in the pendulum; but the fuperiority of one method beyond the other would require a complete treatife for its difeuffion. Among the lateft modern furveys, thofe of Genéral Roy, in the Philofophical Tranfaétions, made with inftruments of wonderful accuracy, will afford the greateft inftruétion to fuch as may with to enter this path of inveftigation. In the laft paper of the continuation of this furvey, by Liewtenant Colonel Williams, Captain Mudge, and Mr. Dalby, inferted in the Tranfaétions for 1795» 2 fundamental bafe was meafured on Hounflow Heath, equal to 27404.2 Englifh feet, and conneéted, by obfervation of the angles of feventeen triangles, With a bafe of verification meafured on Salifbury Plain. As the triangles prefented feveral ranges of conneétion, thefe were computed from the fundamental bafe, and gave the numbers 36¢74.8 and 36573.8 for the extreme refults, exprefling the bafe of verification in feet. The mean of thefe, namely, 36574.3, proved to be aboutone inch fhort of the actual admeafurement of the bafe of verifications» Itfeems probable that there may have been fome fortunate compenfation of errors in this wonderful co-incidence ; but the refult appears to prove, that the method of terreftrial admeafurement will give an original meafure to be depended on for more than four places of figures, and léfs than five. ~ When furfaces and folids are to be derived from linear meafures, if there be any error in the original line; che error in the furface or area will be twice as great, and that in the folid three times as great, as in the line very nearly, as may be eafily deduced from the common procefs of involution, That is to fay, in moft cae it will affeét the fame figure of the refult, N, TABLE 199 New Syftem of Weights and Meafures of France. ‘soumuies3 $ SurySiom Souy syyuat-autu yo I9AqI jo adard Be jo yey. St anjeaA st fsyouano} edly jyusiour ayy wos} Japp 100 sop IUUAT eUuL *“SeueIjue U9} OWUL Papratp st autIJITT BY puy, “Saray U2] OUUL Paptatp st ue1g au *ouv.uT paiqeo st Ajit Arejauour ay f “N 1 0°9 *payn aq Jou T TIM ‘9.1937 dy) UI Paulos are YS ajoua [pe pur ‘aavozry “sappaag se yony ‘spunoduros Aur “G°N *“(yjygugq sures8 gg6z7z"0 . aunjaut pos 10) urraS ysuerg-e yo syigt=£ ynoge o} Jenba b ‘Qmuresd & jo jaed Ypaspuny ommuvs31j137 B jo 193120 *(qyifug sayour £g£6-E| BUO to ‘AT 1GOU Jo) JPY e pue sayour (youerg) aa.q) ynogr 0} yenba ‘ayaure jo jred yiual the latter fimple liquids. They muft not be confounded togei her. Ihave pethaps dwelt too long upon a fubject which feems rather to be matter of curiofity than immediate utility. But it is always a pleafure to me to embrace an opportunity of exprefling my efteem and attachment to you. J.B. VENTURL Vox. l—Aveusr 1797. Ee IV, Analyfs: 210 Examination of Steel. IV. Analyfis of four Specimens of Steel; with Refleétions on the new Methads employed in this Analyfis. By Gitizen Vauguezin *. Preliminary Nove of the (French) Eprror. Tu E fteels which Citizen Vauquelin has analyfed were fent to the Council of Mines numbered 8642, 8644, 977 and 1024. ‘Thefe fteels were produced at the forge of Rem- melfdorff, fituated in the canton of Grofs-Remmelfdorff, in the department of the Mofelle, at the diftance of 5000 metres north from Bouzonyille, and the left fide of the Nied. The crude irons which are. there refined come from the furnaces of Dilling and Betting, 7 which, according to the report of Citizen Dietrich, obtain their iron ftone from the com- munes of Grefaubach and Steinbach, as well as from the foreft of Hommelfwald; and their calcareous flux (caftine) ftom the woods of the commune of Merfching. The eftablifh- ment confifts of two fineries, one large hammer, two fmaller, and a heating furnace. Citizen Soller, the proprietor, had eftablifhed before 1785 a manufactory of fteel by cementation, which, after having been abandoned for feveral years, has again been put into activity. The cementing furnace contains, according to the account furnifhed by this citizen him- felf to the Council of Mines, about fix thoufand weight of iron, and can be charged two or three times a month. ‘Citizen Dietrich, who vifited this eftablifiment in 1785 by order of Government, infpeéted the procefs, and the furnace of Citizen Soller, of which he gave the moft advantageous account. By this report it is feen that Citizen Soller ufes coak for cementation}. We think it may be of advantage to tranfcribe in this place the report which was made on thefe fame fteels in 1786, by the Commiflaries of the Academy of Sciences. It is thus by com- paring the refults of operations performed in manufatories under the infpeétion of learned men, with thefe afforded by the chemical analyfis, that we may hope to learn to what extent the nature and proportion of the conftituent parts may influence the qualities of fteel; and whether we may expect from chemical fcience new and direct methods of afcertaining what kinds are beft appropriated to the different ufes of this fubftance in the arts.- Extra from the Regiflers of the Academy of Sciences, March 15, 1786. ° : ON the 15th of February laft, Mr. Soller: prefented fome fteel of cementation from his works at Remmelfdorff, in Lorraine, near Saar-Louis. The Academy has charged Mr. Vander Monde and myfelf to give an account of the fame. We mutt diftinguifh three kinds of fteel, each of which poffefles properties relative to thé different ufes they are applied to. 1. Natural fteel (agier de fonte) is obtained immediately from the crude iron. This fteel is ufually unequal in its quality; fubject to have cracks and fcales; is lefs hard and brittle than the two other kinds; welds better, and is principally ufed for inftruments of * Journal des Mines, publié par le Confeil des Mines par la République, NC XXV. 1, + Houille, Doubtlefs as the fuel ; not as the cementing compound, N. husbandry, Examination of Steel. 21L hufbandry, common cutlery, and fprings. As this kind of fleel demands lefs expence in its fabrication, it is of courfe the cheapeft. ‘The greatelt quantity is imported (into France) from Germany. Bihiat 2. The fecond kind is fteel of cementation. It prefents a more equal grain in its frac- ture, and takes a better polifh than the former. It is alfo harder, more brittle, and requires more particular attention in the forging. This kind being more perfeét, is of great ufe in all the circumftances which require the qualities here mentioned. 3. Laflly, the third kind is caft-fteel, obtained by fufion of one of the other of the fore= going kinds. It is characterifed by its uniformity of texture, and is deprived of thofe fea- brous places which are obfervable even in the fteel of cementation. This third kind of fteel is therefore fufceptible of the moft beautiful polith, and is proper to form razors, lan- cets, ornamental work, wire-plates, laminating rollers, &c. The Englith have hitherto been almoft totally in pofleffion of the manufactory of caft-fteel, which is the moft valuable of any. Your bars of cemented fteel, manufactured by Mr. Soller, and chofen from among the fteels of different qualities in his warehoufe at Paris, were fubmitted to the following ex~ periments : : With the firft piece fome hook-tools* for turning iron were made. They forged very well, the fteel being very hard in the fire, and confequently eafy to be wrought. The hook- tools, on trial, proved very good. A graver for turning iron in the turn-bench was made out of the fame piece. It was tried upon fteel, and found to be as good as an Englifh graver. The fecond piece was ufed to make a plane iron for metal. It fucceeded perfeatly well, and kept its edge in planing iron as long as thofe which are made of Englith fteel. Out of the third piece, which was doubled into three; and welded upon a piece of iron, a carpenter’s chifel was made 26 lines in breadth. The fteel welded perfetly, without re- quiring any particular care. ‘The edge proved very good, and on comparifon with an Englih chifel of the fame dimenfions it was found to poflefs the fame qualities. A carpenter’s chifel, 14 lines broad, was made out of the fourth piece of fteel. It welded extremely well, and proved to be as good as the foregoing inftrument. The workmen éftimate that a greater number of Englith chifels would be found at the venders’ below than above this quality. ° Mr. Soller likewife fent to the commiffioners a fample of iron, which was part of the tie * The hook-tool is ufed by the turners of ftrong metallic work ; but from its fteadinefs, and other good qua- lities, it well deferves to be applied in many delicate operations with fteel and brafs, by a numerous fet of work- men in this capital who are entirely unacquaintéd with it. Its ufual form is that of a hook or claw, lefs than half an inch long, proceeding nearly atright angles from the fide of a ftraight tem, which laf terminates below ina point, The cutting edge is at the extremity of the claw, and is varioufly fizured, according to the nature of the work. By bearing the angular point on the Rett of the Jathe, the claw may be applied to the work with great power and fteadinefs, while the perpendicular handle bears againft the fhoulder of the workman. The fteel commonly ufed in London for this inftrument is called fheer-fteel, from its mark. The edge ftands very well againft foft fteel, when the tool is a little harder than a hard faw, or juft capable of yielding to a good Lancafhire file. If it be harder, there is a greater probability of its breaking. This kind of work is performed by a flow motion, with the conftant application of water to the picce to prevent heating. It is obvious from thefe facts that tenacity is the requifite moft wanted here. N. Ee 2 of 312 Objfervations on the Analyfis of Steel. of a faggot of fteel, and manufadtured out of a mixture of ‘half its weight of old iron with the fame. quantity of pig-iron. This iron, from which the fteel prefented to the Academy appears'to have been made, is of the firft quality. It cannot be broken without tearing, _ dt extends.under the hammer with the greateft facility, whether heated or cold. The famples of {teel from Mr. Soller exhibited in thefe trials the qualities of the ordi- nary fteel of cementation which we receiye from England under the name of acier punte *, Like that fteel, they may be twifted while hot without cracking, but they cannot be com- pared with the fine Englith fteels. Mr. Soller has likewife commynicated to us the details of his procefs, and the defign of his furnaces. We have every reafon to believe that he may fabricate fteel of an excellent quality. But to prevent the obje€tions which might be made on the fuppofition that thefe pieces had been feleéted, he has drawn-out the whole contents of a cafe of fteel made by a new cementation. This fteel will be fent to us, with every atteftation in form which can be defired. We fhall fubmit it in like manner to different trials, and render an account to the Academy. In the mean time, we are of opinion, that the enquiries and the under- taking of Mr. Soller are among thofe which the Academy will never fail to applaud. Done at Paris, at the Academy, March 15, 1786. f VANDER MONDE F (Signed) AND \ BERTHOLLET. I certify that the stoi extra& agrees with its original, and the judgment of the Academy. » Paris, March 18, 1786. (Signed) . CONDORCET. SECTION | INTRODUCTION +. THE analyfis of fteels is one of the leaft advanced and moft difficult parts of chemiftry, more efpecially when the accurate proportions of conflituent parts are required to be de- termined. The agents commonly made ufe of to difunite thefe principles do themfelves fuffer part of their elements to cfcape, which re-aét on thofe of the ftéel, and put them into a fitua- tion which renders it difficult to form any eftimate. Thus, for example; we find, that when fteel is diffolved in the fulphuric acid, diluted with water, the hydrogene gas which is developed, diflolves, and carries with it a portion of carbone, the quantity of which varies from a great number of circumftances. The infufficiency of the methods hitherto propofed for acquiring this knowledge is well fhewn from the refults they have afforded to thofe who invented them, and who were no Jefs fkilful in experiments than in the art of reafoning. It is well known that we are indebted to Bergman for the firft analytical procefles with iron and fteel; and that little addition has been made to them fince. But thefe procefles * Is this {pur-fteel > N. + This word, and feveral other fentences or fubordinate titles, appear in the margin of the original as fide- notes, I have inferted them in the text. N, 7 are Obfervations on the Analyfis of Steel, 203° are inaccurate, as we fhall thew in the courfe of the prefent memoir, and as it alfo appears from the different refults he obtained from the analyfis of various kinds of fteel, the ufual properties of which did not indicate fo great a difference. It is admitted, fince the ‘valuable experiments of Bergman, and particularly thofe of Berthollet and Monge, that fteel differs from pure iron only from the prefence of a cer- tain quantity of carbone, which is intimately combined; a proportion which perhaps may admit of fome degree of latitude; but which, neverthelefs, if above or below If, therefore, it be required to explain a greater degree of coolnefs than 4 or § degrees, fuch as that of Lugan and Hergifweil, and it be not fuppofed that evaporation in thefe cir- cumftances can produce more refrigeration than three degrees, it will be neceflary to fup- pofe the mean temperature of the refervoir to be lower than 10 degrees; a fuppofition, as the author obferves, by no means forced, at leaft for the vicinity of the Alps; where alone obfervyations have been made of caves poflefling fo low a temperature. M. De Sauffure anticipates the objeétion againft his theory, that if the air in thefe ca- verns be already faturated with humidity, it cannot produce evaporation, nor confequently © cold. But he remarks, that caverns are not all humid; that the caverns here fuppofed muft be of vaft extent, in order that the dilatation caufed by a few degrees fhall afford confider- able currents of air through the whole fummer; and confequently, that a great quantity of cold dry air muft enter in with the winter, which will be very deficcative when expanded ! by Remarks on the Fheay of Cold Surbterraneous Winds. 235 by heat, and will dry the fides of thefe caverns. Whence he thinks that the air may be confidered as fuficiently dry to produce an evaporation which may cool it three degrees. After having given fo interefling and accurate a detail of faéts on this curious fubject, from the work of a philofopher to whom the world is fo greatly indebted, I have thought it a point of juftice to relate his theory ina manner fcarcely lefs copious, and that the more particularly, asthe notions which occur to me on the fubjeét have led me to differ from him in opinion. In the firft place I muft remark, that we have no a€tual information of the exiftence of fuch vaft caverns, efpecially fo near the furface of the earth.- 2. By the author’s own. ex- periments it appears, that at very inconfiderable depths, compared with the thicknefs re- quired for the roofs of fuch caverns, the influence of the feafons is fearcely perceptible. He found the greateft difference at the depth of 29} feet, in compa& ground, during three years, was only from 8,95 degrees to 7,75 degrees, or 1,2 degrees in the whole. gu ie the roof were ever fo thin, it appears from Count Rumford’s experiments *, that heat, which in air, and very probably in all fluids whatfoever, is {carcely tranfmitted but by the afcent of the heated parts or defcent of the parts cooled, would not pafs downwards, be- caufe the rarefied parts could not defcend ; confequently the expanfion, even in this moft improbable fituation, could not take place. 4. From the expetiments of Duvernois, re- lated in the Encyclopédie Méthodique, article Arr, page 686, which are alfo to be found in the firft volume of the Annales de Chimie, it appears that common dir dilates rather more than 3th part of its bulk by the firft twenty degrees of Reaumur, and therefore fcarcely more than “th part by the difference of temperature fuppofed by M. De Sauffure. This cave mutt therefore contain near the furface of the earth, to be within the reach of the feafons, eighty times as much air as flows out of all the apertures during the whole fummer. For want of data, that is to fay, the apertures and velocities of emiflion, it is impoffible to infti- tute a calculation; but it feems utterly improbable that fuch a volume of air fhould have been referved in an appropriate veffel. At all events, it is not in the fmalleft degree likely, that Mont Teftaceo contains, or communicates with, fuch a refervoir. 5. Laftly, it feems a gratuitous fuppofition, that the refervoir fhould be always dry, and the paffage through which the air iffues always wet. : After this undifguifed examination of the confiderations of M. De Sauffure, I thall myfelf prefent a few notions refpecting the caufe of this phenomenon; with the perfeé with to fee them refuted, if exifting facts, future difcoveries, or undete€led errors fhould render it neceffary. The whole, then, appears to me to depend upon the fimple cireumftance of the cavity be- ~ tween a confiderable mafs of {tones or other fubftances not being capable of {peedily changing its temperature, by any other means than the contaét of the air, or other fluids, which may pafs through it. Let us fuppofe, for example, the cathedral of St. Paul’sin London, the dome of which is near 400 feet in height, to be filled with fragments of broken pottery. This large mafs might be fuppofed at firft to poffefs the temperature of the air at the time when it was accumulated. From the imperfeét conducting power of pottery and moft earthy fub- ftances, the effect of the fun’s rays, or of the actual heat of the furrounding air, would pene- * Experimental Effays, VII, Hh2 trate 236 Theory of Cold Subterraneous Winds. trate to a very little depth. From feveral known faéts, it does not feem probable that the variations from thefe caufes would extend to the depth of three feet. Suppofe now the external air to be cooled ten degrees ; ; the whole body 6f air contained in the interftices of the pottery, being lighter than that without, would afcend through the upper openings of the mafs, in confequence of the preflure from the denfer air into the lower apertures. This procefS would continue until the contents of the-edifice had acquired the common temperature; that is to fay (without attending to the capacities of pottery and of air for heat, and the relative bulks of the interftices to the folid parts, but fuppofing thefe to be equal), it would follow that a quantity of air near one thoufand times the bulk of the edifice muft pafs through the interitices before the common temperature would be reftored. As the winter advanced, the current would continue to flow in at the doors, or near the bafe of the heap, and out from the fuperior parts. This would continue fo long as the temperature of the external air continued to be colder than the internal parts of the heap ; and the velocity would be greater the greater the difference between thefe temperatures. But when the winter had reduced the whole mafs nearly to the freezing point, or perhaps below it, the return of fpring, rarefying the outward air, would fuffer the internal cold denfe air to flow out below. The warm air would neceflarily prefs in above, become cooled, and flow out again beneath in that ftate of diminifhed temperature. And in this cafe alfo the velocity of the cutrent would be greater the hotter the external air. , It is eafy to fuppofe a prodigious variety of cafes. If the mafs be very large, the extreme vaiiations will be more confiderable, and the effet more permanent and fteady. Ifthe - fragments be large, the current will be fwifter, but the refrigeration lefs. And if among thefe fragments there be a conftant caufe of humidity, it may be inferred that this will vender the defcending current colder by evaporation than it would otherwife have been. I was led to mention the cathedral of St. Paul’s, from having very frequently in hot weather - met a ftrong eool blaft iffuing out of the doors and vaults of that edifice, produced, as I fuppofe, by the refrigeration of the air againft the ponderous maffes of mafonry within its area. As the probable caufe did not occur to me till the prefent inveftigation offered itfelf, I have not examined all the circumftances of this laft fat. Currents of this nature are however very common. ‘The well-known experiment of holding a candle firft at ‘the top and then at the bottom of a door, is of this kind. If the air within the room, or the walls, be warmer than the external air, the flame will be blown outwards at the top, and inwards at the bottom of the door; but the contrary will happen if the walls of the room or its contents be colder. in this cafe, the lower current refembles the cooling blaft of the caves. There is no doubt, if two holes were bored in the door of a cellar in fummer, the one near the top and the other near the bottom, that the upper hole would draw in the air, and the other emit acold ftream, until the walls had acquired the heat of the external air. x. The Combuftion of Phofphorus in the Vacuum of the Air Pump. By DR. Martinus Van Marum *. i H AVING propofed in December 1794 to exhibit in one of the le€tures on the Tey- terian foundation the combuftion of phofphorus in oxygene, and its combination with that * Annales de Chimie, XXL. 18. 7 t fubftance \ ' ee eS a ' « Combuftion of Phofphorus in Vacno. bg ye fubftance in a glafs veffel, after the manner of M. Lavoifier ; but not being able to avail myfclf of the burning-glafs to fet fire to the phofphorus, I fuppofed I might fucceed by electric fparks. I attempted therefore to give fire to the phofphorus by eleétrical {parks or fmall difcharges. Neither of thefe being attended with fuccefs, I attached to a fmall piece of phofphorus a little cotton fearcely weighing three quarters of a grain, which I fprinkled with a little finely powdered refin. I afterwards placed this cotton, which rofe about one- fourth of an inch above the phofphorus, in fuch a pofition between the extremities of two conducting wires within the glafs receiver, that the eleCtric {park might pafs through it. In this manner, on the 4th of December 1794, I attempted for the firft time the inflam- mation and combuftion of phofphorus ; without any other defign, however, in this firft ex- periment than to afcertain, before the le€ture, that there fhould be no fault in the appara- ‘tus or method of making the experiment; and the time I could give on that day to this experiment being already expired, I did not rarefy the air in the receiver, more than till the mercury in the barometer gauge was about one inch lower than inthe ftandard barometer befide it. I then-paffed the oxygene gas from the gafometer into the receiver : I fet fire to ‘the phofphorus after the receiver was thus filled, and the experiment was made-without any difficulty. II. As I thought I could now repeat the experiment in my Ie€ture without any rifk of failure, I made the attempt afew days afterwards. I placed another {mall piece of phof- phorus in a fmall crucible of platina, which hung in the centre of a glafs receiver thirteen anches in diameter, haying firft furrounded the upper part of the {mall ftick of phofphorus with alittle cotton powdered with refin. I then proceeded to rarefy the air as much as _ poflible ; but an unexpected appearance prevented me. The candles had been removed, for the better obfervation of the light at the furface ef the phofphorus. We faw the light in- creafe very perceptibly in magnitude and ftrength, when the height of the mercury in the barometric gauge ftill differed one inch from that m the barometer. This light increafed in proportion as the air was more rarefied. I was far from fuppofing that the phofphorus would take fire, for which reafon I continued to work the pump; but, contrary to all expeétation, we faw the phofphorus take fire when the mercury was about half an inch lower than that in the barometer. [To be continued.} MATHEMATICAL CORRESPONDENCE. Question V. Anfwered by J. Bascnee Re Tae bulk or volume of a chemical compound being very feldom, and perhaps never, equal to the fum of thofe of its component parts before their union, it follows that the relative quantities of its ingredients cannot be inferred from its fpecific gravity by the mere rule of alligation; but recourfe muft be had to the refults of aétual experiment. Perhaps M. Baumé’s experiments on the fpecific gravities of different folutions of common falt in water, preparatory to the conftruction of his pefe-liqueur (an account of which will be found in this work, p. 38.), with the appreciation of the feale, deduced from the obfervation of M. De Morveau, will afford us the belt data for the folution of the prefent queftion. The {pecific 238 Mathematical Correpandence. {pecific gravity of the folution given being 1.1213, we fhall find, from the table in p. 39, that it contained about 0.1584 of falt, or 444 grains inthe whole; being near 29 grains lefs than what would refult from mere computation. - cr rt cae A *,* The above was the anfwer fent previous to the appearance of the Editor’s note, p. 192+ F. was fufficiently aware that the abovementioned table was not to be relied on to indicate the {pecific gravities of all poilible folutions of common falt in water ; which indeed he con- ceived to be fo obvious as to preclude the neceflity of more reftriftive terms. It is however certainly true, that, if Baumé’s conftru@ion of the inftrument, and De Morveau’'s obferva- tion, were both correct, the tabular fpecifie gravity anfwering to 15° would be accurately that of the folution of 0.15 of falt ufed by the former; and that the errors of the table, for all inferior degrees of faturation, would be thofe only arifing from the hypothefis of equal gtaduation on which it is calculated; which, as the Editor obferves, p. 192, are pro- hably not very confiderable. According, therefore, to this mode of reafoning, the table ought to be perfectly correét about that degree, and ferve well enough for giving nearly the fpecific gravities of all aqueous folutions of common falt, in which its propor- tion does not exceed 0.17. or 0.18. ‘The great difference between this table and that of Dr. Watfon (p. 192.), which gives upwards of o.18 of falt, inftead of 0.15, for the {pecific _ gravity of 1.114, feems only to be attributable to the reafons affigned p. 38. Perhaps M. Baumé had either expofed the falt to a confiderable heat before he diffolved it, or fuffered the folution to evaporate before he ufed it for the inftrument which fell into the hands of M. De Morveau ; or poffibly even its {cale had been transferred from another whofe {tem bore a fmaller proportion to its bulb. The latter table is probably the moft to be depended on in all cafes. NEW MATHEMATICAL QUESTION. Question IX. By TriGoNOMETRICUS. THE angles of elevation of a terreftrial object fituated above the horizon, taken at three given ftations in a horizontal plane, being given; it is required to determine from thence its perpendicular height. NEW PUBLICATIONS. Count Rumford’s Experimental Effays, Political, Economical, and Philofophical. Effay VII. Of the Manner in which Heat is propagated in Fluids. Of a remarkable Law which has been found to obtain in the Condenfation of Water with Cold, when it is near the Tem- perature at which it freezes; and of the wonderful Effeéts which are produced by the Operation of that Law in the Economy of Nature. Together with Conjectures refpecting the final Caufe of the Saltnefs of the Sea. Odtavo, 108 pages, with two plates. Piice as. ftitched. Cadell and Davies, 1797. Tu IS effay, which contains important difcoveries and applications of the doctrine of heat, will demand particular and more ample notice in the prefent work than can be here given. The author had before proved that the communication of heat through air is almoft totally effefled New Publications. 239 effeéted by the circulation of its parts. He has fince afcertained, that water, and thence probably all other fluids, conduét that quality or matter by a fimilar procefs; and from the general faéts obferved by him, he concludes that they are non-conductors of heat. ‘The experiments contained in this eflay are very {triking and ingenious, and the author has availed himfelf of them in forming a fet of deduétions of great ufe in the Ades hi of the economy of heat on the furface of the planet we gnhabit. Traité dela Fonte des Mines, Sc. ; or, A Treatife on the Fufion of Ores by Pitcoal, and the Conftruétion and Ufe of Furnaces proper for the Fufion and Refining of Metals and Minerals by means of Pitcoal. Together with the Method of rendering this Coal fit for the fame Ufes as Charcoal of Wood. By Mr. De Genflane, of the .Royal Academy of Sciences at Montpellier, &c. Sold at Paris at the Veterinary Library of M. R. Huzard, Rue de L’Eperon-Saint-Andre-des-Arcs, No. 11. 2 volumes in quarto; the firft con- taining 400 pages, with 34 plates, and the fecond 534 pages, with 42 plates. Price 20 francs for the two volumes in boards, and 12 francs for the fecond feparately. The firft volume of this work appeared in 1770, and the fecond, which was retarded at firft to verify certain faéts, and afterwards for other reafons, was printed in 1776. Other circumf{tances, unneceffary to be detailed, have prevented the proprietor from offering the work regularly to fale until lately.—— Journal des Mines. Anfangsgrunde der Chemie zum Grundriffe Academifcher Vorlefungen nach dem neuen Sy/fleme, &c.; or, Elements of Chemiftry, to ferve as the Plan of Academical Leffons according to the new Theory. By M. G. Fr. Hildebrandt, Profeffor of Medicine and Chemiftry at the Univerfity of Erlang. Printed at Erlang 1794, 3 volumes, large o¢tavo. The celebrated L. B. Guyton, in the Annales de Chimie, XXI. 333, {peaks very highly of this work, for its order and perfpicuity. The author begins by exhibiting the general principles of mixture, folution, afnity, precipitation, &c. together with the operations of chemiftry. In the next place he treats in feparate fe€tions on caloric, light, oxygene, azote, atmofpheric air, hydrogene water, the earths, alkalis, acids, and compound falts. Thefe fubjects occupy his firft volume.—The fecond volume treats of metals, their alloys, and combinations.—And in the third the chemiftry of organized fubftances is explained. Notizie, &c. An Account of the Siliceous Incruftations of the Thermal Baths of Italy; - and certain remarkable Produéts found under the Lava which buried Part of the Town of Torre del Greco in 1794. By M. Tompfon. Odctavo. Naples, 1795- The author has obferved filiceous ftalaétites in the mountain of Santa Fiora in Tufcany, jn the Euganean mountains, in the ifle of Ifchia, and in the crater of the Solfatara or Pozzuolo. In moft of thefe places there are likewife foda, humid and hot vapour, and fulphur, either in fubftance or in the ftate of fulphuric acid. The folution of the filex may therefore be attributed to the combined aétion of thefe three chemical agents, particu- larly the foda. A kind of liquor filicum is formed. ‘The author has difcovered that the arundo donax of the family of the bamboos contains fea-falt, and confequently foda; and it is known that the knots of the bamboo contain filiceous concretions. The celebrated Black afcertained the prefence of mineral alkali in the Geyfer fpring in Iceland; round which Gliceous incruftations are formed.—Edinburgh Tranfactions, Vol. 2 and 3. By digging into the houfes of the town of ‘Torre det Greco, which were buried under the lava in 1794, among other things were found: 4. Glafs changed into Reaumur’s. 5 porcelain, 240 Ls : New Publications. porcelain. © 2, Tron ‘mineralized, augmented in volume to’thrice its former bulk; eryftal- lized within in grains or plates, fome of them three lines in length, with the argentine brilliancy; other portions in red rofettes‘of {pecular iron ore, more or lefs participating of} the nature of fulphate of iron. 3. Silver coin’ fufed in the fame degree of heat which copper money refifted. 4. A candleftick of brafs (chandelier de laiton) entirely me- tamorphofed, the outfide cryftallized into blende, intermixed with o€tahedrons of copper, more or lefs red: the fra€ture of the ‘candleftick towards the centre prefents very fine cubes of red copper. 5. Lead converted in fome inftances to litharge, and in othets to minium, which is folid, compact, and of the moft beautiful red colour.—Pidtet, Biblio- theque Britannique. An Inaugural Differtation on the Chemical and Medical Hiftory of Septon, or Azote. By Winthorp Saltonftall. Odtavo. New York, 1796. T find this work announced in the 22d volume of the Annals of Chemiftry, No. 64, for laft April, with the following obfervations: It is known that azotic gas forms 73 parts out of 100 in the atmofphere. Cayendifh made the important difcovery, that 68 parts of oxygene, with 32 of azote, produced nitrous gas. Berthollet has proved that 6 parts of azote and 1 of hydrogene form ammoniac. Deimann and Van Trooftwyk have lately proved that 37 parts of oxygene, chemically united to 63 of azote, form that gafeous oxide called dephlogifticated nitrous air by Prieftley, which has the fingular property of fupporting combuftion, though it deftroys the Jife of animals which refpire it. So that we know of four degrees of oxidation or combuftion of azote: 1. The dephlogiflicated nitrous air of Prieftley, called by the modern chemitts. oxide of azote. 2. Nitrous gas. 3. Nitrous acid gas. .4. Nittic acid.» This author thinks that the putrefa€tion of animal fubftances has an epocha in which the azote, at the inftant of its diféngagement, coming jnto contact with oxygene, may comi- bine with it without requiring a very elevated temperature. The oxide of azote thus’ formed may become a very active poifon; and the cancer, with the whole family of ‘cor-. roding ulcers, has probably no other origin. The exhatations of azotic fubftances which putrefy in marfhes, in prifons, and in damp hot countries, form, according to the hypothefis of the author, a certain chemical combination of azote with oxygene, which becomes the caufe of contagion, and of various endemic and epidemic diforders. This deftru€tive oxide . may introduce itfelf into the animal fyftem by the lungs, and produce putrid fevers and afthmatic fymptoms ; it may penetrate with the aliments into the ftomach, and become the leaven of epidemic bilious diforders. Does not the yellow fever of America depend on’ the fame morbific gas, fince we know that it is azote which gives the more or lefs intenfe orange colour to wool, fk or fkin, when it is abundantly contained in thofe fub- ftances, and combined with a {mall portion of oxygene ?, Laftly, The oxide of azote; may aét on the abforbent veflels of the animal, and produce peftilential bubos and fores. Here, fay the editors, are conjectures not entirely without fome appearance of truth; but, which require many experiments and obfervations before they can be admitted in the extenfive. degree propofed by this author. or example, ‘it is fo far from being demonftratedy:as the author thinks, that the orange colour of wool, &c. is owing to azote, that it rather appears: to arife from an excefs of carbone. The fame may be remarked of the oxide of fepton’ of this author, or dephlogifticated nitrous acid. “This gas appears to be nitrous vapour mixed’ with oxygene gas, which laft does not unite with the furplus of nitrous gas in the acid. X facing page 270. Lae iweb iG han amemils HOM thy mn mls ATED Darr piri ———— = ——— 1 AITRT AT net ——$S—S oma SS : / Ds op C WHO O, Vip nl = Philos Journal VoIA PLX racing page 2/0. Z i in ai F 7 TOY, J 7 , , 5 = G f- / 10 O, Me (, iy / tt yr” Ee Myles Va be p yn Plone Gila»: aM oper di ( C4 \ Se a = ———— J O2 WRN Avie OF NATURAL PHILOSOPHY, CHEMISTRY, AND THE ARTS. SEPTEMBER 1797. 3 AR TCL E ok Experiments and Obfervations made with the View of afcertaining the Nature of the Gaz pro- duced by paffing EleGric Difcharges through Water ; with a Defeription of the Apparatus for thefe Experiments. By GEORGE PEARSON, M.D. F.R.S.* : In the Journal de Phyfique for the month of November 1789, were publifhed the very curious and interefting experiments of Mefirs. Pacts Van Trooftwyk and Deiman, with the affittance of Mr. Cuthbertfon, on the apparent decompofition of water by electric difcharges. The apparatus employed was a tube 12 inches in length, and its bore was 1-8th of an inch in diameter, Englith meafure; which was hermetically fealed at one end, and, while it was fealing, 12 inch of gold or platina wire was introduced within the tube, and fixed into the clofed end, by melting the glafs around the extremity of the wire. Another wire of Platina, or of gold, with platina wire at its extremity, immerfed in quickfilver, was intro- duced at the open end of the tube, which extended to within 5-8ths of an inch of the upper wire, which, as was jutt faid, was fixed into the fealed extremity +. , The tube was filled with diftilled water, which had been freed from air by means of Communicated by the Author. This paper was read before the Royal Society; and an abftraét of the fame publifhed in the Tranfaétions for 1797. N. + In another part of Mr. Van Troofwyk's memoir it is ftated that the diftance was 1} inch from the end of the upper wire to the top of the lower wire; and that the diftance between the infulated ball and prime con- duétor was at firtt 3-4ths of an inch, but that. afterwards it was increafed toone inch. Although the wire fattened into the top of the tube was faid to be 14 inch jo length, it is obferved, that when a column of 3-8ths of an inch of air was collected, it, was almoft at the extremity of the upper wire, From thefe and other inace ciiracies, it will be,made appear, that no one, from the account publithed, has been ableto repeat the experiment, ‘Vou. IL—Sepremprr 1797+ Ti Cuthbertfon’s 242 Decompofition of Water by Eleétricit. Pa Cuthbertfon’s laft improved air pump, of the greateft rarefying power. As the open end of the tube was immerfed-in a cup of quickfilver, a little common air was let up into the con- vex part of the curved end of the tube, with the view of preventing fra€ture from the eleétri- cal difcharges. The wire which paffed through the fealed extremity was fet in contaé with a brafs infu- lated ball; and this infulated ball was placed at a little diftance from the prime condu‘tor of the eleétrical machine. ‘The wire of the lower or open extremity, immerfed in quickfilver, communicated by a wire or chain with the exterior coated furface of a Leyden jar, which contained about a fquare foot of coating; and the ball of the jar was in contact with’ the prime conductor. The eleétrical machine confifted of two plates of 31 inches in diameter, and fimilar to that of Teyler. It poffeffed the power of caufing the jar to difcharge itfelf 25 times in 15 revolutions. When the brafs ball and that of the prime conductor were in contaét, no air or gaz was difengaged from the water by the ele&trical difcharges; but on gradually in- creafing their diftance from one another, the pofition was found in which gaz was-difen- gaged, and which afcended immediately to the top of the tube. By continuing the dif- charges, gaz continued to be difengaged, and afcend, till it reached nearly to the lower extremity of the upper wire ; and then a difcharge occafioned the whole of the gaz to difap- pear, a {mall portion excepted, and its place was confequently fupplied by water. The refiduary portion of gaz being let out after each experiment, and the difcharges being continued in the fame-water, this refiduary gaz was left in fmaller and fmaller quantity ; fo that after four experiments, probably made on the fame day, it did not amount to more than 1-80th of the bulk of gaz which had been produced. If it had been’ poflible to pafs ele&tric {parks through this very fmall quantity of gaz a fecond time, or oftener, it was fuppofed it would have been diminifhed ftill more. But when the tube had been left for a night only filled with water, the refiduary gaz was in greater quantity than after the laft experiment the preceding day *._ It was concluded that the gaz produced by the eleétrical difcharges was oxygen and» hydrogen gaz, from dtcompounded water: 1. Becaufe nother gaz hitherto known inftantly difappears on pafling through it an, eleGtric fpark. 2. The gaz obtained muft have been the oxygen and hydrogen of decompounded water, becaufe they were in exaétly thofe proportions in which by combination they reproduce water; the trifling refidue being confidered to be merely a portion of air which had been diffolved in the water. : 3. Liquids which are not compounded of hydrogen and oxygen, as.fulphuric and nitric acids, afforded gaz by the eleétric difcharges, but which did not difappear on pafling. through it an electric fpark; but which did difappear on adding to it nitrous gaz over. water. Mr. Schurer alfo afferts, on the authority of Mr. Van Trooftwyk, that even liquid * In at leaf fifty experiments I have never feen the refidue of gaz léfs than 1-goth of the gaz produced, al- though the water had been freed from air by the moft effeétual means. But Mr. Schurer ( Annales de Chimie, tom. Vv. p. 276.) teftifies that he faw Mr. Van Trooftwyk make the experiment; and that after it was re- peated many times, on the fame parcel of waver, (bere cvas no refidue at all. (have very good grounds for cai lieving,.that this is one of the number of inaccurasies in the account published of this fubject. muriatic Difficulties attending the Experiment. ; 243 muriatic acid, which contains a very large proportion of water, aftords hydrogen gaz only, the oxygen being abforbed by the muriatic acid, and becoming oxy-muriatic acid. From much experience I can fafely affirm, that it is fcarcely poffible for the ftudent, or even the proficient, to inftitute the above experiment with fuccefs from the explanation publifhed. Hence, during the fix years which have elapfed fince its publication, no con- firmation has been publifhed except the experiment repeated by Mr. Cuthbertfon, for my fatisfaction, as related in my work on the chemical nomenclature; but I have heard of many perfons, and fome of whom were experienced electricians and chemifts, who made the attempt. Since Mr. Cuthbertfon came to refide in London, I have learned from him the circum- ftances requifite to the fuccefs of the experiment; and I have received from him alfo very great afliftance in continuing a procefs with the objects I had in view, the tedioufnefs and. ‘even difficulties of which can only be conceived by thofe who have been engaged in the fame purfuit. Tam very fenfible that it would be unneceffary for me to explain the importance of a pro- cefs which may at laft afford demonftration of the compofition of water, by the fulleft and unequivocal evidence of its analyfis and-fynthefis; a demonftration which no other fingle procefs but the prefent promifes to afford. I propofe therefore in this paper : 1. To give fuch a defcription of the experiment of rendering water into gaz by eleétric difcharges, as fhall enable any perfon who is verfed in pneumati¢ chemiftry, and acquainted with the theory and pradtice of electricity, to repeat it with fuccefs. By this defcription, alfo, I apprehend I fhall make known more generally the very elegant, and frequently moft ° fatisfa@tory, mode of decompounding and compounding bodies, by means of the fire of the electric difcharge. . a. It is propofed to relate the additional evidence which I have already obtained from this procéfs, concerning the compofition of water. For although it feems moft probable that water is really decompounded in Mr. Van Trooftwyk’s experiment, it muft be confeffed that it does not make appear a fingle unequivocal and decifive property of hydrogen and oxygen in the gaz produced. The difappearance of this gaz by combuttion, or in fome other way, inftantly on pafling through it an eleétric fpark, it is true, is a property known only to belong to the mixture of oxygen and hydrogen gaz; but it is well afcertained, that things of totally different fpecies may agree in one or more properties. And there is at leaft a poffi- ‘bility, that eleétric difcharges may produce various other kinds of gazes in water, befide ‘hydrogen and oxygen from decompounded water; and which may have the property of inflantly difappearing on palling through them an ele@tric fpark. 3. I thall attempt to refolve the phenomena of the procefs into a general law of the action of fire, or of the joint aétion of caloric and light. SECTION + Of the Manner of condu€ling the Proceft. ~~ ELECTRIC difcharges may be employed in two different manners to decompound water. One of thefe is by what has been termed the interrupted explofions which was the me- li2 , thod, 244 Infruflions for Decompofing thod, altheugh ‘not fo explained, of Mr. Van Trooftwyk. And the other-method is by meats of the uninterrupted or complete explofion; for which there’ are two. different kinds of ap- paratus. Thefe were invented by Mr. Cuthbertfon in the courfe of my inveftigation of this fubjed. To fecceed by the method of the interrupted explofion, the following are the neceflary parts -of the apparatus to be ufed, and the circumftances to be attended to: 1. The eleftrical machine muft poffefs fufficient power. 1 do not think any cylindrical machine can be made to anfwer in this procefs if a large quantity of gaz be required; becaufe they cannot be made to at with due regularity, con{ftancy, and force. Inequality of the furface of the cylinder is unavoidable, which -caufes undulation. « Avcylindrical. machine never continues in full force above five or fix. minutes, without frefh amalgam. « Hence, from the repeated amalgamization, the difcharges will be fo variable that the tubes muft be frequently broken. * I ufed plate machines of a peculiar conftru€tion by Cuthbertfon. Thefe machines do not-require frefh amalgamization oftener than once in eight hours, and they poflefs fuperior powers of acting, in point of regularity, force, and duration. A plate of 24 inches in dias meter, with a jar containing 15> fquare inches of coating, afforded an adequate difcharge every fecond or third revolution, for feveral hours; and for a {till longer time every third or fourth revolution, with one application of amalgam, A 31 inch platé-machine-afforded a due difcharge at firft every revolution, and afterwards every feeond’ revolution for many hours, with one application of amalgam. ‘Phe moft ufeful and expeditious machine was that with two plates, each 24 inches in diameter, and fimilar to that’ of Teyler. It produced 25 difcharges every 15 revolutions for an hour or two; and for four or five hours longer a difcharge was produced by lefs than two revolutions; with one atalgamization. 2. The Leyden jar muft have a fufficient quantity of coaled furface ; without which the dift charge will not be fufliciently powerful to produce the gaz required. The proper quantity, as found by experience, was about 156 or 160 fquare inches, with an ufual proportional prime conductor. 3. The diftance between the infulated ball, and the prime condu€tor, muf? always be lefs than the diffance between the extremities of the wires. Not the leaft notice of this circumftance has been taken; yet without attention to it the experiment can never fucceed, or only for a very fhort time, Accordingly, as the diftance between the extremities of the wires within the tube anfwered beft when it was 5-8ths or 7-8ths of an inch, the diftance between the infulated ball and prime condu€tor was feldom more, but frequently lefs, than 5-8ths or 6-8ths of an inch, The eye muft be kept upon.the {parks within the tube, and by prac- tice a perfon may become a judge of their force by their viyidnefs; 3. which will dire him to bring the receiving ball nearer to the prime conductor, when there appears danger of the tube being broken; and on the contrary, to remove them to a greater diftance from one another when the fparks do not produce gaz duly from the water, When the difcharge is of the moft productive force, both énds of the wire within the tube will be illuminated by a fpark; but, when it is weaker, one end only of the wire will be illuminated; and when this is the cafe, there is no rifque of the tube being fractured, but gaz will rife from the end of one wire only inftead of two. 4. The extremities of the upper and under wire within the tube muff be at a certain diftance 5 from eee ——e — a eS Water by the EleGric Explofion. é 245 from one another. If they be too near one another, the points of them will not be illuminated; and provided the infulated ball be as near to the prime condudtor as the two wires are to one another, the tube will be broken, becaufe there will be a complete explofion., But if the wires be at too great a diltance from one another, the ele€tric fluid of the difcharge will be fo diffufed through the water that no gaz will be produced. If the Leyden jar con- tain, as above ftated, 150 og 160 {quare inches of coated furface; and the ball of the prime conductor and of the infulated ball be about three inches in diameter, the diftance between the wires which generally anfwered beft, was about 5-8ths or 7-8ths of an inch, as above faid. ‘The narrower the bore of the tube, the greater may be the diftance between the two wires; accordingly, the diftance may be one inch with a tube 1-14th of an inch wide. 5- The upper wire fixed into the clofed extremity of the tubes mu be of a proper length and thicknefs. If this wire be too long, either the difcharge will not be carried through to the end of the lower wire in fufficient quantity to produce gaz; or, if it be in fufficient quantity to produce gaz, the tube will be fraétured. The fmaller the diameter of the tube, the longer may be the upper wire, for a reafon to be-given under the next head. I generally found that the difcharge requifite to produce gaz fractured the tube, if the upper wire was more than 6-8ths or 7-8ths of an inch in length, within a tube of more than 1-8th of an inch in diameter. But'with very narrow tubes, fuch as thofe of 1-16th of an inch in dia- meter, I frequently fucceeded when the upper wire was | 3th of an inch in length. It is obvious, that the fhorter the upper wire the more readily will gaz be produced: the procefs, however, will be rendered ftill more tedious in thofe cafes in which a quantity of gaz is to be colleted in a refervoir for examination; on account of the time confumed in transferring fuch fmall parcels of gaz by each experiment. "The diameter of the upper wire cannot, perhaps, be too fmall; for the greater its fuper- ficies, the more ele€tric fluid will be parted with to the furrounding water. Hence platina wire of the fineft fort, as that of 1-240th of an inch in diameter, may be ufed with fuperior advantages. ‘This fort of wire alfo cannot be melted while it is foldering to the glafs, which can hardly be prevented with fine wire of other metals. However, I found that copper, brafs, or gilc wire, of about 1-8cth or 1-1coth of an inch in diameter, could be foldered to the glafs, and anfwered perfe@ly. I did not find that any of the metal wires were affected by the difcharge ; but iron or fteel ones are not proper, on account of their being fo foon oxidified by the water, and confequently extricating from it hydrogen gaz. I did not find any advantage from ufing feveral {mall wires twifted together, but feparated at the end within the tube; for gaz was extricated generally, at the point of one of them only, namely, the undermoft. I think care fhould be taken to fix the upper wire fo that it fhall be in the middle of the tube; as in that cafe the tube will be lefs liable to be broken. As to the under wire, the diameter of it feems to be of little importance; for, if it be a thick one, as much gaz will be extricated as if it were a fmall one; becaufe the eleétric difcharge will take the firft point of the furface of the wire where the gaz is produced. 6. The tubes muff be of a proper length and diameter. \f they be fhorter than feven inches, the difcharge will be liable to pafs over the outfide; and if they be longer than twelve inches, they will be of an inconvenient length. I found the moft convenient length: to be from nine to ten inches, exclufive of the curved part. ‘The curved part was found very ufeful in preventing air afcending, which was accidentally Tet into the tube, by which the produc 246 , Inftrudtions for Decomp sie ing product of gaz from the experiment would have been contdminated. Such curved ex- tremities were however lefs convenient thanftraight ones, on account of the greater difi- culty of transferring from the former than from the latter. See Fig. 1 and'2, Plate XI. ‘The diameter of the tubes fhould not be more than 1-8th or lefs than 1-1 2th of an inch, At leaft in my experiments thefe tubes anfwered beft. If they were wider, the difcharge requilite to produce gaz broke the tube. If the tubes be narrower than juft mentioned, the experimenter will find it difficult and tedious to transfer the gaz, through the curved part, into a refervoir, in thofe cafes in which a large quantity is wanted for examination. ‘Where however the object is merely to thew the produétion of gaz by means of the ele€rical difcharge paffed through water, between two wires; and the inftant difappearance of gaz fo produced by pafling through it an ele@ric fpark, the narrowelt tubes are moft eligible; as with them the experiment can be made in a fhorter time. But there was one incon- venience experienced from very narrow tubes, namely, the bubbles of gaz were very apt to hang near the end of the upper wire inftead of afcending; and they were apt to form large bubbles, with water between each; in which fituation the difcharge frequently fraGtured the tube, or made gaz to difappear by combutftion in the courfe of the experiment. To poffefs at once the advantages of the narrow and wide tubes; about three to fix inches of narrow tube were joined by fufion to a bottom part of wider tube (fee Fig. 3)5 into the curve of which tube the gaz produced was let up from time to time ; fo that this part frequently contained the products of ten or more experiments before the gaz was transferred into the refervoir. The vaft number of tubes which were broken in this experiment induced me to try various different kinds of them, I experienced no advantages from annealing tubes but their being feemingly rendered more brittle, and harder, by this treatment, was an -effe& which I leaft of all expected. Tubes with thin fides anfwered juft as well as with thick ‘ones. Bohemian green glafs tubes were found excellent for this experiment, as they were ‘much lefs apt to be cracked by the difcharges than any kind of Engiith glafs. To fave time and trouble in fo frequently letting out gaz produced in very narrow tubes, a {mall bulb was made at the fealed end (fee Fig. 4). In this cafe, however, as the upper wire mult be fhorter than other narrow tubes, it was more difficult to regulate the explofion. Although common atmofpherical air is an eleétric, and water is a conductor of ele€tricity, it appears that the difcharge paffes with more refiftance from wire to wire through wer in the above experiment, than through common air under otherwife the fame ‘circumftances. The reafon of which is this: air being an elaftic and very rare fluid, it more readily gives way to the ele@tric difcharge than water; and it can therefore pafs through a longer and thicker column of air between two wires, without breaking the glafs tubes, than it can ‘through watet. For although water is a conduétor, yet in a very {mail quantity it is a very indifferent ones fo that its denfity and defect of elafticity more than compenfate for its con- ducting power. Hence alfo, andon account of the conducting power of water, the reafon of the upper wire in this experiment being fhorter in proportion as the tube is wider; and on the fame account will be feenthe reafon of the advantages of a {mall upper wire over thicker ones. It will be neceffary to add, that the tubes with curved extremities can only be filled by fetting them in water under a receiver, and exhaufting the air from the receiver, tubes, and water; then, by letting in the air again, the water will be forced up into the tubes. Some- ‘times, however, I have filled the tubes by fetting them in Papin’s digeftor. a Thefe og) ee Water hy the Electric Explofion. 247 Thefe are the dire€tions for making the experiment; but the rationale of it cannot be underftood unlefs the nature of the interrupted explofion be explained; becaufe I believe books on electricity do not contain the neceflary information. It muft be confidered, in the above experiment, that if in place of water the tubes be filled with air, the whole of the charge of the Leyden jar will pafs, at each explofion, from the upper to the under wire, and no in- terruption in the difcharge will happen; but if they are filled with water, then an inter- rupted difcharge may be caufed; by which is meant that a part of the charge only paffes at each explofion through the water, from wire to wire, and with much diminifhed velocity. The refiduary electricity in the Leyden jar is nearly one half; as may be accurately de- monftrated from the difference in point of denfity, elafticity, and conducting power of the medium of water and air as already obferved. It muft be added, that although water in large quantity is a good conduétor, and air is not; yet water being here in very {mall quantity, it proves a bad conduétor, as is the cafe with the very beft conductors. A cubic foot of water is only juft capable of receiving, or letting pafs through it, a full difcharge from a jar of one foot of coated furface; and the quantity of water employed in this experi- ment not being >5~Socth part of a cubic foot, it is a very imperfe& conductor; fo that an interrupted difcharge only can pafs through the tube, without difperfing the whole of the water. But if the difcharge be not feemingly as ftrong as the tube can bear without break- ing, the gaz is not produced from it; and on this point hinges this extremely delicate procefs. The fituation of the different parts of the above defcribed apparatus is fhewn by Fig. 5. To fucceed by the method of the complete or uninterrupted explofion, the following apparatus muft be ufed, and rules obferved: 1..A tube (Fig. 6.) is employed, about four or five inches in length, and r-5th or 1-6th of an inch in diameter. One end is mounted with a brafs cap (Big. 7.), and the other end is fealed at the lamp, with a wire about 1-4oth of an inch in thicknefs fixed into it, as above: defcribed; which extends into the brafs cap, fo as to be almoft in contaé&t when the explofion- is made. If the wire touches the brafs cap there will be no explofion. The tube being filled with, and fet in, a cup of water, the difcharge may be made into it as in the above deferibed procefs; but here the infulated ball muft be placed at a greater diftance from the prime conductor, and a Leyden jar, with only 50 fquare inches of coating, will anfwer the purpofe. In this way of making the experiment, gaz is produced by each difcharge in the brafs tube, and in much greater quantity, and with much lefs frequent accidents, and lefs trouble, than in the former method with the interrupted difcharge. But the gaz obtained with this apparatus always contains a larger proportion of atmofpherical air, on account of the quantity of water, and more immediate and extenfive communication of it with the atmofphere. By repeated difcharges there is an impreffion made in the brafs tube, in the part where the difcharge pafles through it, and at laft a {mall hole is made in that part. On this account the fame mounted tube cannot ferve for producing a large quantity of gaz. The other fort of apparatus invented by Mr. Cuthbertfon is reprefented by Tig. 8. At firft it confifted of a glafs tube half an inch wide and about five inches in length, mounteds at one end with a brafs funnel, and inverted in a brafs difh; but afterwards the tube was blown funnel-wife at the end, as fhewn by Fig. 9. The other end muft have a wire about 248 Analyfis of Steel. about 1-4oth of an- inch thick, fealed into it at the lamp; which wire extends to nearly the bottom of the brafs difh in which the tube ftands. The exact diftance between the end of the wire and brafs difh muft be found by trials ; that which generally anfwered in my experiments was about 1-20th of an inch. Ifit be properly arranged, gaz will be produced at each difcharge. The Leyden jar ufed with this apparatus muft contain about 150 fquare inches of coating. The diftance between the infulated ball and the prime eohduetor, at which the experi- ment fucceeded, was commonly about half an inch. If experiments be propofed in which eletrical difcharges muft be paffed through water or other fluids, for even a much longer time than was confumed in performing thofe referred to or related in this paper, it may be an object to employ the wind, or per- haps the power of a horfe, to turn the eleétrical machines, the expence of labourers being confiderable. L t [To be continued. ] \ Il. Analyfis of four Specimens of Steel; with RefleGions on the new Methods employed in this Analyfis. By Citizen VauUQUELIN. [Continued from page 217.] Sea DLO Ne Ils STEEL No. 864—LARGE PIECE. E-yrERIMENT I. 1152 grains, or 61,14 grammes, of this fleel, broken into fmail particles, were diflolved in the fulphuric acid diluted with five parts of water. There re- mamed at the bottom of the folution 5,5 grains, or 0,292 grammes, of black powder of the earburet of iron. In another experiment, the fame quantity of this fteel afforded 6,4 of carburet of iron; a quantity, the medium of which is 5,95, and confequently the refidue forms a fraction of the diflolved mafs equal to 0,0051. Experiment II. 1009 grains, or 5,3 grammes, of the fame fleel, diffolved in the fulphuric acid, afforded 121 inches, or 2420 cubic millimetres of hydrogene gas. The black refidue weighed fearcely 0,75 grains. Experiment III. The 5,5 grains of carburet of the firft eesaene being fubjef&ted to heat under a muffle, took fire, and left three grains of a grey yellowifh mafs, which, when treated with boiling muriatic acid, afflumed a white colour, while the acid became yellow. It was reduced to 1,66 grains, which amounts to 0,0014 of the mafs of fteel. This fub- ftance pofleffed all the charaéters of filex. _ The muriatic acid ufed in this boiling contained a perceptible quantity of iron, which ap- peared to be the caufe of the yellow colour it poffefled previous to the operation. Experiment IV. The folution of 1152 grains of iron in the fulphuric acid having been treated as in Experiment III. Se@tion 2, afforded 58 grains of phofphate of iron, which ' makes Analy/is of Steel. 249 taakes about 0,05 of the weight of the fteel employed. The fluid likewife depofited by ebullition 96 grains of a deep red matter, which did not perceptibly contain, phofphate, of iron, From this refult it appears that the prefent fteel contains nearly three times the quantity of phofphorus exhibited by No. 864, the {mall piece. For 576 afforded only 19 of phof- phate of iron, whereas 1152, or only twice the quantity, afforded 58 grains. This fteel muft confequently be more brittle when cold, if, as there is no reafon-to doubt from»the numerous experiments of Bergman and other chemifts, that phofphorus is the effential caufe of the cold fhort quality of iron and fteel. Experiment V. 288 grains of fteel No. 864, the large piece, diffolved in fulphureous acid, as before mentioned, left 6,5 of carburet.of iron, which, fuppofing it to contain as much fulphur and iron.as that of No. 864, the {mall piece, would give 3,71 of carbone, or about the 0,o1oth part, or rather more than one-hundredth part of the fteel employed. Experiment VI. This fteel was fubjected to all the proofs calculated to fhew the prefence of manganefe, but without any exhibition of that fubftance. Ir may therefore be concluded that this fteel, as well as the other examined before, does not contain any perceptible quantity of manganefe, at leaft fo far as the prefent methods of chemiftry are capable of fhewing it *. - (SECTION i. [ STEEL No. 977. _ Experiment I. 144 grains, or 7,631 grammes, of this fteel, diffolved in the fulphuric acid, diluted with five parts of water, afforded 164,94 cubic inches of°hydrogene gas, and left 0,941 grains, or about ©,05 grammes, of carburet of iron, or nearly 0,007 of its mafs. Experiment II, 504 grains, or about 26,7 grammes, of the fame fteel, diffolved’ in the fulphuric acid, diluted with: five parts of ‘water, the folution ‘being diluted with'a large quantity of water, and its excefs of acid faturated with carbonate of pot-afh, depofited, a few in{tants afterwards, a large quantity-of a white matter, flightly inclining to grey, which acquired a flraw-colour by conta& of the air. This matter was phofphate of iron, and weighed 22 grains, or about 1,16 grammes. Experiment IE. The liquid whence the phofphate of iron had been’ precipitated by the carbonate of pot-afh was fubmitted to ebullition, and’ again depofited 22 grains, or) 1,16 grammes, of matter, in which,however, there was fcarcely any phofphate of iron. So that 504 grains of the fteel No. 977 contained 23 or 24 grains of aie of irons that is to fay, 0,047 of its mafs. Experiment IV. Thefe 24 grains of phofphate of iron, treated by long ebullition with cauftic foda, affumed a deep red colour, and after wafhing, and drying in the air, weighed only 15,33 grains. They loft therefore 8,67 grains of phofphoric aie which afforded 17,54 grains of cryftallized phofphate of foda, * The oxide of iron formed with this ftecl, ftrongly oxided by the aétion of fire, and afterwards treated with the nitric acid and fugar, afforded an oxide which threw down a very beautiful blue with the pruffiate of pot-afh, The fame oxide fufed with borax afforded a greenifh globule ; but when heated with the external flame at the extremity of a pair of forceps it acquired a flight purple colour, which difappeared as the globule became cold, Vou, I.—SerTEMBER 1797. Kk Experiment 250 Analyfis of Steel. Experiment V. This ftecl, diffolved in the fulphureous acid, afforded very nearly the fame quantity of carbure of iron as No. 864, the fmall piece. SECT LON: Ve STEEL NO. 1024, Experiment I. One hundred grains, or about 53,gtammes, of filings of this fteel af- forded 108 cubic inches of hydrogerie gas during their folution in the fulphuric acid. I have remarked that the hydrogene gas produced by this fteet had an extremely fetid: {mell, infinitely {tronger than that of the gafes afforded by the other fteels, which appears to arife from the greater quantity of phofphorus it contains *. Experiment IT. 288 grains of filings of the fame fteel being diffolved in the fulphuric acid, diluted with five parts of water, the carburet of iron feparated, the folution diluted with water, and the excefs of acid faturated with carbonate of pot-afh, afforded a very confider— able white depofition of phofphate of iron, which, when well wafhed and dried, remained; white, and weighed 26 grains, or about 0,09 of the mafs of fteel made ufe of. Thefe 26 grains of phofphate of iron, treated with cauftic foda, afforded 22 grains of phofphate of. foda, and the ferruginous refidue weighed 47 grains. Experiment III. 288 grains of fteel, diffolved in the fulphureous acid, left a carbona- ceous refidue, which, treated with pot-alfi i in the manner defcribed SeGtion II. and dried, weighed 3,5 grains. But on account.of the minute Jofles which it is impoflible to avoid in a numeroas feries of manipulations, the quantity of this fubftance may be eftimated at-four grains; and that the more reafonably,.as the other kinds. of fteel gave nearly the fame refults, The quantity of carburet. of iron.in ‘this fteel was therefore. fomewhat Jefs. than 0,014 of the mafs of the fteel. Experiment IV... This fteel, febiettats to ae prot requilite to difcover the aforeet tt of manganefe, prefented no trace 'thereof.,, —_—— SECTION Vr ‘ Table of the Quantities of Hydrogene Gas afforded by each Kind of Steck By uniting the different quantities of hhydrogene gas afforded by the docimaftic quintal: ofeach of the fteels diffolved in the fulphuric acid, we have the following refults for each. x00 grains, Cubic inches. Steel, No. 864, {mall piece. —_ —- 108 No, 864, large piece —— _— =. 12h No. 977 — 254 Table of the Quantities of Carburet of Iron, contaminated with Silex, afforded by each of the Steels, converted into Decimal Parts. Steel, No. 864, fmall piece —— — 0,015 No. 864, large piece —— _ 0,013 No. 977 —_— ee — 0,012 No. 1024 _—— — 0,015 As it was afcertained by feveral experiments made upon the carburets of iron extracted from the different kinds of fteel, that this fubftance contains at a medium 0,526 carbone; and 0,474 filiceous iron, it follows: I. That the 15 thoufandth parts of No. 864, {mall piece, are compofed of Carbone _ 0,00789 Siliceous iron —- —_— = 0,00711 2. That the o,013th parts of No. 864, large piece, are compofed of. Carbone _— -_—— — 0,00683 Siliceous iron —— —— or 000616 3. That the o,o1sth parts of No. 977 are formed of Carbone —_—- — _0,00789 Siliceous iron oe O;00911 ' 4. That the o,o12th parts of No. 1024, are compofed of Carbone — ee — 0,00631 Siliceous iron —— —_— — —0,00568 1 do not think it neceflary in this place to afcertain the proportion between the iron and, the filex which exifts in the carburet of iton, becaufe this earthy fubftance being to all ap- pearance accidentally in the fteel, muft vary according to a great number of different cir- cumftances. The-following, however, are the mean refults obtained from feveral epee on the carburet of iron: x. Carbone —— — 0553 2. Iron —_ _ _ 0326 ‘i 3- Silex ——— ——e _ 0,21 1,00 Table of the Quantities of Phofphate of Iron afforded by the four Kinds of Steel. By comparing the quantities of phofphate of iron obtained from the four kinds of fteel here fubmitted to examination, very remarkable differences appear ; as follows : No. 864, {mall piece —— _— 0,0210 No. 864, large piece ee — 0,0504 No. 977 —_— — = —-0,0474 No. 1024 ees a = 09,0900 Kk2 Table 252 Component Parts of Steel. Table of the Quantities of Phofphorus contained in each of the Samples of Steel. Analyfis having fhewn me that phofphate of iron is compofed of 0,58 of oxide of iron, and 0,42 of phofphoric acid, and this laft being formed, according to Lavoifier, of 0,39 phofphorus, and 0,61 oxygene, it follows that the fteel . No. 864, fmall piece, contained phofphorus — 0,00345 No. 864, large piece — 0,00827 No. 977 eure eeerl ot aaa _ 0,00791 No. 1024 —— —_—_ _ 0,01580 T cannot venture, however, to affirm that there really exifts fo great a difference between the quantities of phofphorus contained in each of thefe pieces of ftecl as is here given by experiment. For fo little is required to change the refults in this refpeét, particularly when {mall quantities are fubjected to trial, that two or three ‘thoufandth parts may foon be obtained either way. Neverthelefs, I cannot fuppofe, that, with the fame proceffes.and equal care, the difference between the maximum and minimum of thefe quantities will prove to be the confequence of uncertainty in the methods of analyfis._ A Synoptic Table of the Proportions of Principles ‘contained in the four Kinds of Steel ~ before examined. © 1. Carbone - - = 0,00789 . ‘2. Silex - - - 0,003 15 Steel, No. 864, fmall piece . Phofphorus .. - ce 0,003.45 4- Tron | - - - 00,9855. - 1,0Q000 1.Carbone = =e 0,00683° 2. Silex -. - - 0,002.73 eae No, 864, large piece Ge Phofphorus = = 000827 4: Iron - - - 0,98217 : 1400000, 1.Carbone == += = — 0;00789 2, Silex st v= =~ 0;00315 ——No. 977 oo SoZ a -~ = = 0400791 4. Iron - - ©,98105- 1,00000 1. Carbone art cir = 0,00631 Dy S'S ae Boa = 0,00252 —— No. 1024. “a 3. Phofphorus 222 © 0,01520. 4. Iron - SA hte 9397597 300000 SECTION Variable Refults in fepavating Carburet from Irons 253 SECTION. VIL Refleftions on the Caujes of the variable Quantities of Carburet of Iron afforded by Steel diffalved in the Sulphuric Acid. MANY circumftances may influence the carburet of iron by the fame fteel; and it is’ not eafy to obtain equal mafles of this fubftance, in two different experiments, from fteel of the fame nature. Bergman obtained from 0,002! to 0,008 of carburet of iron from different fteels. Is it probable that there was really fo great a difference in the proportions of a fubftance to which the fteels owe their qualities, without there having been likewife a very fenfible difference in their ufual properties ? Among the caufes of uncertainty which may occafion the refults to vary, we may prin- cipally remark the following: 1. The greater or lefs concentration of the acid employed to diffolve the iron. 2. Its mixture with water at or before the time of the experiment. 3. The more or lefs confiderable divifion of the metal. 4. The length of time during which the folution is effeSted. 5. The time during which the depofition of carburet remains in contact with the liquor after the folution is effected. 1. It is evident that the more concentrated’ the fulphuric acid, the more rapid the folu- tion, andthe greater the quantity of caloric developed in’a given time. Now experiment proves that the folution of carbone by hydrogene is in the dire& pro= portion of the caloric which penetrates it, or at leaft that it follows fome progreflive ratio of increafe with the temperature. It follows, therefore, that the more elevated the tem- perature during the folution of fteel’ in acids, the lefs of carbone will remain. It alfo follows that it is advantageous not to ufe an acid too concentrated: 2. As the too great concentration of the acid is inconvenient for the folution of fteel from which the carburet is to be extraéted, it is alfo equally inconvenient: to dilute it too much. It is in faét known, that when acids are too much diluted with water, they exert a lefs affinity on other bodies ; and this is the cafe with refpect to very diluted fulphuric acid, and fteel in a high fate of divifion. The folution then takes place very flowly ; part of the fteel decompofes the; water by its own attractive power, and paffes to the ftate of the black oxide, which cannot be diffolved by diluted vitriolic acid. Hence, inftead of carburet of iron, the refidue confifts of a mixture of this fubftance with the. black. oxide of the metal. 3. The duration of the experiment is likewife of confiderable inportanee. Tt: may arife from two caufes. The firft is the concentration of the acid. In this cafe; the fulphate of iron which is formed abforbs for its cryftallization the fmall quantity of water which yemains, with which it falls down, and entirely ftops the folution. The feeond is the too confiderable weaknefs of the acid, the particles of which being feparated: too far from thofe of the metal by the water which retains them, cannot in this cafe act but very flowly: I am well convinced that whenever the carburet of iron remains in contaét with the me- tallic folution, particularly when it contains difengaged acid, it is fubjet to remarkable changes. Its black colour becomes yellow, or yellowith grey, and it diminifhes in volume by the actual lof of part of its mafs. From thefe obfervations it follows, that in order to: obtain: ra 256 Bergman's Procefi for difeavering Phofphorus in Iron. obtain the greate(t poflible quantity of carburet of iron from any kind of fteel, the acid muft be neither too much nor too little concentrated. I have ebferved that the beft proportion between the acid and the water was one of the former to five of the latter, and that coarfe filings or turnings of fteel were preferable to fine filings or pieces of confiderable fize. Moft of the inconveniences here mentioned do not exift with regard to the muriatic acid, at leaft in fo evident a manner; becaufe it is never fo concentrated as the fulphuric acid, has a ftronger affinity for the oxide of iron, and forms with this metal a very foluble fait. But it cannot be employed to determine, in one and the fame operation, the proportions of earburet of iron and of phofphorus ; becaufe it decompofes the phofphate of iron, and renders it neceflary to ufea cauftic alkali to precipitate it by double affinity, which may be attended with fome inconvenience. "The method we have propofedto determine the quantity of carbone contained in ftcel, is therefore preferable to this in every refpect. SES FLOW “vir: Reflections on the Means propofed by Bergman to difcover the Prefence of Phofphorus in Irox and Steel. BERGMAN, in his Differtation on the AnalyGs of Iron and Steel, does not {peak of the prefence of phofphorus or fiderite, which he found only in cold fhort iron. It is neverthelefs very unlikely, that, among the very numerous famples of iron and fteel which he examined, there fhould have been none which contained phofphorus, fince the four fteels which conftitute the fubjeét of this memoir all prefented quantities very con- fiderable, though they appeared of fufliciently good quality for the ufes in the arts. I fuf- pet, therefore, that this chemift’s not having found it was owing to a want of attention to the probability of its exiftence, or elfe, that the means he made ufe of were not adapted to . dete& its prefence. ‘ The following is the method he propofes for this purpofe, in his Diflertation on the eaufe of the brittlenefs of cold fhort iron: He takes a bottle A, of the capacity of about 12 cubic inches, into which he puts 16 loths of crude iron, which affords the cold fhoyt iron. Upon the iron he pours fix cubic inches of diftilled water, and half an inch of concentrated fulphuric acid. As foon as the effervefcence is ended, he filters the liquor, and receives it in another bottle B, of the fame contents as the firft. He wafhes the refidue in the bottle A, until the filtration fills the ~ bottle B. This being done, it is obferved that the fluid in B, which at firft was clear, becomes turbid and white. The powder does not fettle until after feveral hours. He pours on the iron which remained in the bottle A a fecond quantity of water and acid equal to the firft; when the effervefcence is over, he pours the liquid into a third bottle C. He repeats this manceuvre a third and fourth time, &c. and colledts the liquors in the veffels marked D, E, &c. The phenomena were the fame in each of thefe operations 3; but the fifth folution in F remained clear for feveral weeks, at the end of which it formed a - flight cloud. ‘The fixth folution depofited nothing in the fame fpace of time, though much iron remained undiffolved. 9 T repeated Infufficiency of the Methods of feparating Phiphorus and Manganefe from Iron. 255 Irepeated this procefs on the fteels treated in this memoir, and did not difcover the leaft trace of phofphate of iron, though they would have afforded confiderable quantities by the method I have before propofed. This juitifies the affertion that Bergman did not find this fub{tance in the different irons he analyfed, becaufe his method was infufficient. I prove its infufficiency as follows :—Iron and phofphorus united together, and brought Into-contact with acidulated water, both tend to unite with oxygene by virtue of a pre= difpofing attraction between the acid which is added, and that which is formed, towards the oxide of iron, whence the refult is fulphate and phofphate of iron. This laft is infoluble in water; but it has an affinity for acids, by virtue of which it com bines, and: becomes foluble in water. This affinity of the phofphate of iron for acids is fufficient to impede and even fufpend the folution of new quantities of iron; fo that it is not without difficulty, and after a length of time, that the phofphate of iron can. be com- pletely feparated from the fulphuric acid by means of metallic iron. : It happens therefore in every cafe when iron or fteel which contains phofphorus is: diflolved in an acid, that the acid divides itfelf into two. parts, one of which unites with the oxide of pure iron, and the other with the phofphate of iron as it is formed; andi that when the acid is faturated by the oxide of iron and the phofphate of iron, the folution is almoft totally ftopped, though the liquor reddens blue vegetable: colours. ‘ [t may be hence inferred, that the fulphuric acid, united with the phofphate of iron, no longer exerts: an equal power on the oxide of iron ; and that the metal does not decompofe the water, nor unite to the oxygene of this fubftance but by its own peculiar force, which occafions.a re- tardation or even a complete fufpenfion of the folution. Now, if in fuch a folution the’ phofphate of iron fhould be {mall in quantity, no fign of this metallic falt will appear, even by the addition of a great quantity of water: and this is what happens inthe procefs of Berg-- man; whereas, by adding an alkaline carbonate to this folution until it ceafes to effervefce, the alkali unites with the fulphuric acid ; and the phofphate of iron, whatever may be i its. quantity, falls down in the form of a white powder. SECTION, Ix ReflePions on the Infufficiency of the Methods hitherto propofed to difcovey and feparate Mangane/e’ from Iron. BERGMAN is the firft who found manganefe in fron; and almoft every kind of iron which he examined afforded quantities more or lefs confiderable. The maximum of this: quantity in fteel, according to this chemift, amounts to 0,30, and the minimum to 0,005, a latitude extremely great, and which appears fcarcely probable, as we fhall proceed to thew. In order to deteét manganefe in iron or fteel, the profeflor of Upfal propofes two methods. The firft, having for its obje€t. to afcertain the prefence of this metal, and being fpeedy, cheap, and eafy to be performed, may be called explorative. It confifts inithrowing. into: five parts of fufed nitrate of pot-afh, one part of filings of iron or fleel, and to bring the: mafs into ftrong fufion after the detonation has taken place. If the crucible when cold? exhibits towards its fuperior edge a vitreous circle of a greenith blue colour, it is, according to him, a fure fign of the exiftence of manganefe in the iron, The other method may be calledi i» 256 Analy fis of Steel —Experiments on Galvani/in. called determinative, becaufe it is not ufed until it has previoufly been afcertained thatthe iron contains manganefe, and that nothing remains but to find its quantity, It is per formed by diffolving in the nitric acid a known weight of iron or of fteel, containing, man- ganefe, and, after having evaporated the folution, by flrongly calcining the ferruginous re- fidue, which is treated with more diluted nitric acid, into which a certain quantity of fugar has been put. By this means (fays Bergman) the manganefe will be diffolved, and the oxide of iron will remain untouched. Thefe proceffes, carefully repeated, did not afford me the fame refults. I muft even fay that they are falfe, and capable of leading to erroneous conclufions. In faét, with regard to the firft, itis known that nitrate of pot-afh, decompofed in a crucible of pure earth or fine filver, leaves the pot-afh in the form of a mafs of a greenifh or blueifh colour. It is in vain to object, that this colour is owing to the manganefe contained in the pot-afh of commerce; for this alkali, when purified by alcohol, prefents the fame phenomena. And even fuppofing it to be a certain fign of the prefence of manganefe, it would alfo prove a fource of error, becaufe the nitrate of pot-afh, and pot-afh alone, exhibit this colour by fufion, Pure iron itfelf might produce deception in this refpect; for, when it has been oxided by the nitrate of pot-afh, it combines by the affiftance of the alkali with the filiceous matter of the crucible, and forms a glafs which has often a greenifh colour. Common crucibles alfo are not without inconvenience ; for they may contain the oxide of manganefe, which is well known to be often mixed with earthy matters. The fecond method of Bergman is attended with ftill more danger of error than the firft, by fixing the opinion of the exiftence of manganefe, and producing a decifion with regard to its fuppofed quantity. Bergman, who was perfuaded that the nitric acid mixed with fugar does not diffolve (the oxide of) iron, muft frequently have attributed appearances to manganefe which really arofe from iron only; for we have proved, that the vegetable acid which is formed in this operation diffolves a confiderable quantity, Ill. Extra& of a Letter from Mr. Humpoipr to Mr. BLUMENBACH, containing new Experiments on the Irritation caufed by the Metals with Refpec? to their different Impreffions on the Organs of Animals *, Mae. HumsorpT is one of the philofophers who has made the moft numerous obferya- tions on the phenomenon difcovered by Galvani concerning the irritability produced by the contact of different metals with the parts of animals in which the principle of life is appa- rently extinguifhed. As long ago as the year 1795 he obferved that the animal irritability was augmented by the oxygenated muriatic acid. Not having difcontinued his attention to this objeét, the perufal of the phyfiological writings of Reil, and his correfpondence with Scarpa and Volta, afforded him indications for new enquiries, of which he has occafionally had the courage to make himfelf the fubject. * This Letter forms part of Gren’s (German) Journal of Natural Philofophy for the month of O€tober aft. The extraét was read to the Inftitute of France, by Citizen Guyton. _ il In Surprifing Eiffel of the Galvanic Irritation on Wounds. 257 ** In a converfation,” fays he, * with M. Scarpa, at Pavia, on the effeis which Galvanifm produced upon myfelf, nothing furprifed him more than the appearance of a lymphatic and ferous humour on my back. ‘ What can be the nature,’ faid he, £ of this ftimulant, which in a few inftants changes the nature of the vefftls to fuch a degree as to caufe them to prepare humours, which, the inftant they touch the epidermis, excite inflammation, and mark their courfe by a rednefs which lafts for whole hours ? ” M. Humboldt promifed to repeat the experiment; and the account he gives of the faéts conftitutes one of the moft interett- ing articles in his letter. : For this purpofe he caufed two bliftering platters to be applied on the deltoid mufcle of both fhoulders. When the left blifter was opened, a liquor flowed out which left no other pearance on the fkin than a flight varnifh, which difappeared by wafhing. The wound was afterwards left to dry up: this precaution was neceflary, in order that the acrid humour which the Galvanic irritation would produce might not be attributed to the idiofyncrifis of the veffels. This painful operation was fcarcely commenced on the wound, by the applica- tion of zinc and filver, before the ferous humour was difcharged in abundance: its colour became vifibly dark ima few feconds, and left on the parts of the fkin where it paffed traces of a brown inflamed red. This humour having defcended towards the pit of the ftomach, and ftopped there, caufed a rednefs of more than an inch in furface. The hu- mour, when traced along the epidermis, left ftains, which after having been wafhed ap- peared of a blucifh red. The inflamed places having been imprudently wathed with cold water, increafed fo much in colour and extent, thaf Mr. Humboldt, as well as his phyfician Dr. Schalleru, who affifled at thefe experiments, entertained fome apprehenfion for the confequences. Mr. Humboldt has not undertaken to determine the nature of the fluid which produces fuch aftonifhing effects; but he applies himfelf to circumfcribe the phenomena in the real circumftances which produce them. He judicioufly varies the preparations, and carefully notes all the refults; being perfuaded that the caufe of Galvanifm cannot be explored with fuccefs, but by obferving the proportions in which the chain of metals either irritates or has no effect: and to extend ftill more this vaft field of obfervation, he employs various means to raife or diminifh the irritable capacity of the animal organs. What is the fenfation which the Galvanic irritation produces ? Mr. Humboldt has difcuffed this queftion. No one (fays he) can fpeak more decidedly on this fubjeét than myfelf, * having made feveral experiments on my own perfon, the feat of which, in fome inftances, was the focket of a tooth which I had caufed to be extracted ; in others, certain wounds which I made in my hand; and in others, the excoriations produced by four bliftering plafters.” ‘The following is his anfwer : The Galvanic irritation is always painful, and the more fo in proportion as the irritated part is more injured, and the time of irritation more prolonged. The firft ftrokes are felt but flightly ; the five or fix following are much more fenfible, and even {carcely to be endured, until the irritated nerve becomes infenfible from continued ftimulus. The fenfation does not at all refemble that which is caufed by the eleétric commotion and the eleétric bath; it is a peculiar kind of pain, which is neither tharp, pungent, penetrating, nor by intermiffions, like that which is caufed by the eleélric fluid. We may diftinguih a violent ftroke, a regular preffure, accompanied by an unintermitting glow, which is incomparably more active when VoL. IL—S£rTemBer 1797. LI the 258 Experiments on the Irritation caufed by Metals the wound is covered with a plate of filver, and irritated by a rod of zinc, than when the plate of zine is placed on the wound, and the filver pincers are ufed to eftablith the com- munication. When the communication is made by the contact of the epidermis, it produces no effect; it appears to infulate like glafs, when interpofed between the wound and the metal: but if the fkin be removed, by making two wounds af eight inches diftance, and a plate of zinc be placed on one of them, and on the other a leg of a frog prepared, this lafl is feen to contract itfelf when it communicates with the zinc by the filver wire; which proves that the Galvanic fluid then paffes beneath the epidermis. This fluid produced in fome circumftances a very fenfible acid tafte. The two wounds of Mr. Humboldt having been covered, one with filver, the other with zinc, an iron wire of feveral fectin length,attached to the zinc,was conveyed between his upper lip and the fpongy fubftance of the teeth, and thence'to the tongue of another perfon. When the iron wire was made to touch the filver, a {trong contraétion of the feapular mufcle taok place, and at the fame inftant the perfon whofe tongue formed part of the chain of communication perceived the fenfation of acidity. ‘here are alfo cafes in which the fluid acts on the organs of tafte without producing any fenfible effet on the organs of motion: fuch is that where the epidermis ferves as the. - conduétor from zinc to the frog ; for there is not then any contra€tion, but merely an acid ” tafte on the tongue. The author, having learned from Mr. Volta that he employed the folution of pot-ath (éleum tartari per deliquium ) in order to augment the conducting power, availed himfelf fuccefsfully of this means to raife the capacity of the animal organs. He moiftened one of his wounds with this liquor, which produced little pain; but the Galvanic irritation was more violent, and accompanied with more heat; {parks appeared and difappeared before his eyes; tha tongue moiftened with the fame diftinétly perceived the acid fenfation, although the com- munication was eftablifhed only between zine and zinc. The thigh of the frog, moiftened with the alkaline folution and laid upon a plate of glafs, without touching’ either metal or carbonic matter, fell of itfelf into violent convulfions, the antagonift mufcles of the legs and toes being inceflantly agitated. Irritability has been re-eftablifhed by this application in the animal parts, where it had been extinguifhed by warm folutions of the oxide of arfenic. Laftly, the irritation (which does tot commonly take place when the nerve and the mufcle are armed with the fame metal, the different metals being between the coatings) becomes manifeft after this preparation ; which feems to indicate that the alkali not ‘ory irritates the nerve, but likewife adds to its irritability. The author applied this method to amphibious animals, which he roufed from their winter’s fleep, and m which he perceived a peculiar fymptom of irritability. Thefe obfervations led him to diftinguifh two ftates of the animal organ. The firft, of irritability naturally or artificially raifed or excited ; the fecond, irritability in a lefs degree. Thefe two fates, which he calls pofitive and negative, are merely, as he remarks, different degrees, and not phenomena abfolutely diftin& from each other. In individuals naturally fenfible, the effe€ts produced by alkaline folutions, by the oxy- genated muriatic acid, by the folution of oxide of arfenic, are very rarely of the fame in- tenfity- In the cafe of increafed irritability, mufcular motions are obferved without metal or 5 carbonic when applied to the Organs of Animals. 259 carbonic matter. They may be obtained with metals, though without communication be- tween the nerve and the mufcle; that is to fay, without the regular connetion or chain. They may be alfo obtained by forming the chain of fimilar metals. Let the crural nerve of an animal naturally tenacious of life be placed upon glafs. Leta fmall piece of frefh mufcular fleth be fixed on a ftick of fealing-wax, and then brought into contact with the crural mufcle.. The refult will bea violent convulfion at the inftant when the chain of communication is completed. The fame thing happens if, inftead of the {mall piece of mufcular flefh, a detached piece of the crural nerve be fixed on the ftick of fealing- wax. The-conneétion is therefore formed of two things, nerve and mufcular fibre. How in this fimple cafe can the fluid which pafles from the nerve into .the mufcle caufe it to be contraéted ? Mr. Humboldt thinks that it becomes ftimulant, merely becaufe it returns from the nerve into the nerve by a foreign animal matter ; that is to fay, not organically connected with the nerve. The difparity of the metals forming the chain has hitherto appeared as a neceffary con- dition to produce Galvanic irritation. ‘This hypothefis, however, is overturned by the ex~ periments of Mr. Humboldt. If it be true that, in the ftate of lefs irritability, there is very rarely contraction with fimilar metals (as Volta affirms, contrary to Aldini), this circumftance becomes indifferent in the cafe of increafed irritability. Mr. Humboldt put into a china cup fome mercury exactly purified; he placed the whole near a warm ftove, in order that the entire mafs might afflume an equal temperature: the furface was clear, without the appear- ance of oxidation, humidity, or duft. A thigh of a frog, prepared in fuch a manner that a crural nerve and a bundle of mufcular fibres of the fame length hung down feparately, was fufpended by two filken threads above the mercury. When the nerve alone touched the furface of the metal, no irritation was manifefted ; but as foon as the mufcular bundle and the nerve touched the mercury together, they fell into convulfions fo brifk that the fkin was extended as in an attack of tetanus. We ought not to be furprifed at the precaution here taken by Mr. Humboldt to heat the mercury. This is required in confequence of the opinion which he announces, that the parity of the metals does not depend on the homogeneity of their chemical conftituent parts, but of their heat, polifh, hardnefs, and form. ‘ Gold, placed between two armatures of zinc, produces irritation only when the gold is moiftened by fome volatile fluid, or by the moiftuye of refpiration. Laftly, Mr. Humboldt has attempted to include all the cafes in the following formula : 1. In the State of increafed Irritability, Frog—mufcular flefh. Frog—zinc—zinc. Frog—zinc—mufcular flefh—filver. Frog—zine—filver—zine. Frog—mufcular flefh—filver—zine. Frog—zinc—mufcular flefh—filver—mufcular flefh—zinc. Pofitive cafes. 2. In the State of diminifhed Irritability. Frog—zinc—filver. Pofitive cafes. » @rog—zinc—mufcular flefh—filver—zinc. Frog—zinc—mufcular fleth—filver—mufcular fleth—filver—zinc. ‘ Ll2 Negative 260 Galvanic Experiments.—Ufeful Notices Frog—zinc—zine. Negative cafes.) Frog—zine—mufeular flefh—filver. le Frog—zinc—ntufcular flefh—filver—zine. Mr. Humboldt finifhes this letter by fome obfervations which he has colleéted’in the courfe of his experiments on the /henic or a/thenic virtue of chemical agents; that is to fay,, their energy or their inefficacy to produce irritation. Alkalis appear to be to the fenfible fibres what acids are to mufcular groups. ‘The muriatic acid augments the iritability of the mufcle while it extinguifhes that of the nerves, which does not re-appear even after the acid. has been faturated with alkali. By continuing to bathe the nerve with an alkaline folution, an entire atony is at length pro- duced by excefs of irritation; but if a few drops of muriatic acid be let fall on the part, the irritability is re-eftablifhed, A thigh of a frog, irritated even to total relaxation by a warm folution of oxide of arfenic, has exhibited new conyulfions, after having been immerfed for two minutes in a folution of pot-afh. The fthenic virtue of the oxygenated muriatic acid is not lefs remarkable. Thighs of frogs naturally flaccid, and weakened flill more by the Galvanic procefs for feven hours, which afforded no fign of motion when filver ferved as a conduétor between zinc and the nerve, exhibited violent contraGtions when the nerve was moiftened with oxygenated mu- riatic acid. The author refers to this fubjeét the experiment which he publifhed in 1793, in his Flora Fribergenfis, by which it is afcertained that ordinary muriatic acid retards the germination of plants, but that oxygenated muriatic acid had caufed a plant to germinate in feven hours, which required thirty-eight in pure water in order to arrive at the fame de- velopment. This fact appears to him to indicate fome relation between the vegetable and animal organization. A judgment may be formed from this extract of the number of important faéts contained in this letter, and of the intereft they will excite when they fhall be colleted, arranged, and amplified, in the large work which the author is preparing. IV. Ufeful Notices refpeGting various Objedis *.— Methods of clofing wide-mouthed Veffels—Preferva- tion of Gunpowder—Granulation of Shot—Precipitation of Magnefia. 1. Methods of clofing wide-mouthed Veffels. Tur means of clofing the apertures of large jars and other fimilar veffels, fo as to render them air-tight, has long prefented, to perfons who are engaged in philofophical purfuits, an obje&t of fome intereft. Thofe in particular who are in the habit of preferving animal fubftances in fpirit for anatomical or phyfiological cabinets, find that, notwithftanding all the care which can be taken, the evaporation of the liquor in which they are immerfed is a fub- jeét which requires conftant attention. Perhaps nothing with which we are acquainted is * The whole of the prefent article was received from my anonymous correfpondent, J. F—:—:—:—r, whofe former communications have, no doubt, engaged the attention of the reader. more ——EOeeeEeEeEeEeeeeee ee Clofuare of Veffle. 261 more convenient and proper for ftopping {mall circular apertures, whofe interior furfaces are fmooth enough to admit of their ufe, than common phial-corks : for a certain time at leaft, where the contents of the veflel are not corrofive, they fit more clofely than moft of the glafs flopples which are ufed for this purpofe.. Where however the area of the aperture is confiderable, the porofity of cork and bladders, the neceflity of ufing veflels whofe mouths are elliptical, and the unavoidable irregularities in the form of the ground glafs covers, which are befides of confiderable expence, are circumftances which render the folution of this pro- blem lefs eafy than might be wifhed. The clofenefs of texture which charaéterifes me- tallic fub{tances feems to afford the beft means of removing thefe difficulties; and a quantity of an amalgam of tin is accordingly in fome mufeums fpread over the edges of the covers, by which means the mifchief is in a good meafure prevented : but perhaps no method of effect- ing this end is fo applicable to general purpofes, as that which confifts in the ufe of tin foil, which is alfo in frequent praétice. It may be applied in two ways: a piece of bladder, foaked in warm water, having been ftretched tightly over the mouth of the jar, and tied, a piece of the thickeft tinfoil, previoufly examined by interpofing it between the eye and the fun, in order to deteét the fmall fiflures which are frequently found in it, is to be laid fmoothly over it with the palm of the hand, without ftretching, and, that being alfo tied, a fecond piece of bladder again ftretched over it: or, where the veffel may require to be fometimes-opened, the foil may be laid fmoothly over the furface of a bung, and, a picce of bladder being ftretched over it, the whole applied in the ufual way. The following feems to be another effectual-method of clofing a jar :—Let ab (Plate XII. Fig. 1.) be a fection of its mouth ; ¢d, that of a circular rim of tin, A, an inch high, whofe internal diameter is half an inch larger than the exterior diameter of the mouth of the veffel ; ay; that of a common tin cover, B, whofe diameter is a quarter of an inch lefs than that of the tinrim, A. The rim being cemented round the neck. of the jar with fealing-wax, or the common eleétrical cement, and the interval between it and the neck filled to the depth of two-tenths or a quarter of an inch, with olive-oil *, it is clear, that if the jar be placed horizontally, and the cover B put on, it becomes hermetically fealed, except in the event of an elaftic fluid making its way through the oil. The only care neceflary will be, not to put fo much oil into the tin rim as to occafion it either to flow over or into the jar, on a change taking place in the preffure of the atmofphere. The mouth of the veffel fhould alfo be ftopped, to prevent any of the oil from being thrown into it on removing the cover. In the laboratory, a thoufand ufes of thefe modes of preferving different fubflances muft occur; and it feems not improbable that, if they were extended to the purpofes of ordinary life, and glafs veffels fubftituted for the porous earthen-ware at prefent in ufe, feveral ar- ticles of culinary preparation, fuch as pickles, preferved fruits, potted meats, and the like, would receive lefs injury from the effects of time than they are now found to-do. * Lavoifier ufed mercury for a fomewhat fimilar purpofe, but its depth was confiderably greater. Tt feems, from fome experiments of Prieftley’s, in which he found his gales contaminated with atmofpheric air, though - the tubes had been immerfed to the depth of an inch or more in this Auid, that, in a thin ftratum, oil would be more effeétual, F. If this confiruétion, as Tunderftand it, be fuch as to admit the oil into contact with the refinous cement, this lat will foon become foft by the procefs of folution, To prevent this effect, I fuppofe it would be convenient to faften the rim by a mixture of plafter of Paris and white of egg. N, 2. Prefervation 262 Prefervation of Gunpowder. <% 2. Prefervation of Gunpowder. GUNFOWDER, by reafon of the nitre which enters into its compofition, having been partially deprived of its water of cryftallization, and the known attraction of charcoal for humidity, is always fomewhat difpofed to deliquefce; and although it docs not a€tually liquefy, or become unfit for fome of the purpofes to which it is applicable, yet, for thofe of the fport{- man, to whom the quicknefs of its communication is of the higheft confequence, it is generally in a ftate very inferior to that in wich it would be found, if a greater degree of care was taken in its prefervation. It is only when it has received but avery flight injury from damp, that the mifchief is capable of a remedy: when once it has become at all concreted, drying it will no longer reftore its power: the nitre will be found, on examination with a mag-. nifier, to have cryftallized, and the ftrength and quicknefs of the powder are confiderably and permanently impaired ; probably even before this fymptom has appeared. It is evident that no veffelis fufficiently clofe to preyent this circumftance from taking place, but fuch as is perfeétly air-tight. ‘There cannot perhaps be a much ftronger proof of the infufficiency of the packages in general ufe for this purpofe, than the opinion of a confiderable dealer in this article, to whom the matter was lately mentioned. He faid he was convinced that powder would be found to “ give” in fome {tates of the weather, though the veffel which contained it was ever fo clofe : a notion which may perhaps have contributed to prevent the adoption of more effe€tual means. He added, that it is found to do fo in the tin canifters, as much as when packed in brown paper. ‘The remedy is however extremely eafy. Nothing more is neceflary, than to cut off the communication with the atmofphere : any veffel in which falt . of tartar can be preferved dry, will of courfe keep gunpowder in the fame ftate of per- fection as when firft enclofed. For a quantity not exceeding a few pounds, which is not intended to be frequently removed from place to place, common ten or twelve-ounce phials anfwer extremely well; and if half adozen of them be put into a cafe, there cannot perhaps be a more convenient magazine. They fhould be filled as full as pofible, and the powder well corked up at the mills, the corks being tied over with bladder and tinfoil. As, how- ever, there might be fome danger of explofion from the accidental fraéture of one of thefe, if this method were to be adopted for large quantities, it would in that cafe be neceflary to ufe fome other material than glafs; and if, inftead of the flider now inferted into the tin canifters, a turned brafs or pewter neck, like that of a common phial, and capable of being likewife topped with a fmall cork, were foldered into the top, they would alfo anfwer as well. A proje@tion would perhaps render them inconvenient for package; and it would therefore be proper that the neck fhould be funk into the top; and, in order to get out the contents, that it fhould be let into a femi-cylindrical hollow in the fide of the canifter. When corked up, the top of the cork might be cut off, and the whole aperture covered with a plafter of thick drying paint, or wax and turpentine, fpread on a piece of tinfoil. None of the flafks, the Deft of which are thofe of copper or tin, are fit for preferving the powder longer than whilft they are in ufe, during which the charger fhould be kept corked ; a precaution the effeéts of which will be found confiderable. There are fome, perhaps, who may not conceive thefe remarks to be very materially con- duciveto the general interefts of philofophy; but he to whom it has frequently happened to mifs an excellent crofs thot, from his powder hanging fire—quaque ipfe miferrima vidi— will fearcely confider this as the leaft important article in the September Journal. 3. Gra- Wir Ls Poe tics. wide « Granulation of Shot. 263 3: Granulation of Shot. THE manufadture of common fowling fhot confifts merely in caufing the fufed metal to fall in equal f{pherical drops into water. ‘The lead is melted with the addition of a fmall proportion of arfenic, which, being reduced to a metallic ftate, by means of greafe ftirred in during the fufion, renders it lefs fluid. An oblong fhallow veffel of iron, perhaps 10 inches wide, 14 long, and 2} deep, called a card, whofe bottom is pierced with holes pro- portionate to the intended fize of the fhot, is placed at the height of from one to three inches, over the furface of a tub of water, covered with a thin film of oil. The card is previoufly heated to the temperature of the metal by immerging it in the cauldron; and a flratum of foft drofs or feorie, which are found on the furface of the fufed alloy, is then placed on its perforated bottom, and, being flightly prefled down with the ladle, forms a kind of filter, which partly chokes up the apertures, and prevents the metal from flo.ving through them in continuous ftreams. ‘The fufed metal is then poured by ladlefulls into this veffel, and appears notwithftanding to run through it with confiderable velocity ; fo that it feems difficult to believe that it falls in feparate drops, till convinced by taking up a quantity of fhot from the bottom of the water. The fhot thus made is not without confiderable imperfeGtions. ‘The exterior coat of the lower part of the drop becoming fuddenly fixed by the conta of the water, its fuperior portion, which is ftill liquid, as it alfo cools and contracts, neceflarily pits, like the furface of metal in the channel-of a mould, fo that the greater part of the fhot are fomewhat hollow and of an irregular form; confequently too light for the purpofe to which they are deftined, and liable to unequal refiftance in their paflage through the air. Thefe defects are remedied in the patent fhot, the manufacture of which differs only from that of the preceding kind in the addition of a larger portion of arfenic, which varies according to the quality of the lead; in dropping it from fuch a height that it becomes folid before it enters the water, which is from 40 to 100 feet; and in fome fubfequent operations, which are as follows: It is firft dried and fifted. It is then boarded, which confifts in feattering it on feveral polithed flabs or trays of hard wood, with rims, in the form of a [, except that the fides converge towards the lower part, to which a flight inclination and alternate motion in their own planes are given by boys employed in the manufacture. ‘The fhot whofe form is imperfe@ are de- tedted by the fluggifhnefs of their motion, and remain behind, whilft the others roll off from the board. The laft operation is the polithing; which is performed by agitating it, with the addition of a very {mall quantity of black lead, not exceeding two fpoonfuls to a ton, in an iron veflel, turning on an horizontal axis, like a barrel-churn. It does not appear that any higher degree of perfe€tion than that which is thus attained remains to be defired. The argentine brilliancy of the thot when newly made, the beautiful accuracy of its form, and the curious inftance of inanimate taétics which it prefents when fcattered on a plate, render it even an agreeable object of contemplation. . 4. Precipitation of Magnefia. THE moft ftriking chara€ters of common magnefia, and thofe which are mott relied on by a purchafer who has not the means of analyfis at hand, as indicative of its purity, are its Jevity and impalpability: it is therefore a matter of fome importance to thofe who deal in this 264 Precipitation of Magnefia.—Air-Veffels of Fifh, this article, that it be made to poffefs thefe qualities in as high adegree asis.poMfble. It had long fince occurred to the writer of this, that the effects which are attributed, by all who treat op the fubje€t, to a very fmall quantity of other earths in the alkali which is ufed in the pre- cipitation, were fomewhat difproportionate to the afigned caufe, and that a part of them were probably rather owing to a deficiency of carbonic acid *. An accidental piece of in- formation’ which he received lately from a praétical man, that magnefia was always to be obtained “ beautifully light” by the addition of a fmall proportion of fal fodz to the vege- table alkali employed, and a very loofe experiment which he has fince made with a view to this objeét, appear to corroborate fuch an idea. ‘The magnefia contained in four ounces of Epfom-falt was precipitated with a filtered folution of common pearl-ath, wafhed, dried, and a portion of it then re-diffolved by vitriolic acid, and again precipitated with the fame alkali, with the addition of one-fourth of carbonate of foda. The powder was certainly more light and impalpable after the fecond precipitation. An addition of carbonic acitto the alkaline folution employed, will probably operate in two ways: it will not only render the magnefia lighter, butin fome degree actually purer, by precipitating the aluminous and filiceous earths before held in folution by the pot-afh in a more cauftic ftate. In this refpe&, and in this only, perhaps, if a fufficiently fmall quantity of water be ufed, the aqua kali of the prefent Pharmacopceia is inferior to the oil of tartar per deliquium of the old ones. There is poflibly a limit to the proportion of this ingredient, which can be admitted into the procefs with a due regard to economy 5 perfectly neutralifed carbonate of magnefia being by no means infoluble. Ifan alkalty i in an highly effervefcent ftate, be added to a weak folution of any magnefian falt, it is well known that no precipitation whatever will take place. What remained in the fupernatant liquor might, however, if thought of fufficient value, be after- wards precipitated with a cauftic alkali, and referved for calcination; or indeed would of itfelf fubfide during the fubfequent evaporation for obtaining the vitriolated tartar. The beft procefs in all refpeéts may be eafily afcertained by experiment, and the matter appears to deferve it. V. On the Elaflic Fluid contained in the Air-Veffels of Fifh. Dr. Francis Rigby Brodbelt, of Jamaica, in a letter to Dr. Duncan }, gives the fol- lowing account of fome obfervations and experiments which he has made on the gas con- tained in the air-bladder of the fword-fith : «| will relate to you a few experiments which I made during my paflage to this ifland. I had often wifhed to determine what is the nature of the gas which is contained in the air- * I find, on examination of the common magnefia with a deep magnifier, that its levity proceeds from an aétual radiated cryftallization, like that of fhow: its form may be adyantageoufly feen when juft feparating into Aocks in a glafs tube. Hence perhaps it would be improved by the addition of the alkali in very fmall por- tions, at intervals. Mere wafhing, by deftroying the ramifications of the cryftals, confiderably augments the fpecific gravity of magnefia: an effect which would perhaps be beft prevented by performing this operation carefully with diftilled water, previoufly boiled on a portion of it more than fufficient for its faturation. F. + Annals of Medicine, by Drs. Duncan, for 1796, p. 393- ees bladder pitimdeinnen Onygene in the Bladdevs of FifhomThunder-Stovim. 265 bladder of fiths and I was perhaps prevented from finding it out, by hearing Dr. Monro in his le€tures fay, it was natural to fuppofe it fixed air. However, although this authority prevented me from putting it to the tet of experiment for fome time, yet one day, on our voyage, having caught a yery large {word-fith, I collected the contents of ail the air-bladders; for in that fith the bladder appeared divided into innumerable cells, which had no commu- nication with each other. They afforded fo much air that I collected a quart bottle full. My furprife was great to find that the gas contained was oxygene. A flame was brightened, au ignited ftick was made to re-kindle, and it was fo {trong and pure, that the common ex- periment of a piece of fteel wire, heated and put into it, fucceeded well, and threw out a moft vivid light when melting. I have committed to writing my thoughts on this fubje& at greater length, and I wifh to infer that this pure air is to ferve the purpofes of life when the animal is far below the furface of the water.” The preceding difcovery of oxygene is, I believe, perfectly new. Dr. Prieflley, in his Experiments in Natural Philofophy abridged and methedized, vol. ii. page 462, mentions the commencement of a courfe of experiments on the ftate of the air which js contained in the bladders of fifhes. He remarks, that when thefe ate taken out of the fith, the air cannot ‘be got from them by preffure through any exifting aperture, but that he was always obliged to cut or burft them. The firft time that it occurred to him to examine the air contained in thefe bladders, he found it ina great number of them to be not at all affe@ed by nitrous "air. But at another time he found air from the fame kind of fifh, namely, roaches, to be flightly affefted by that re-agent. It appears, therefore, from thefe trials, that he feldom met with oxygene, and then in fmall quantity; but what the other portion of air might confift of was not afcertained by his experiments. Fourcroy afterwards made experiments on the air contained in the air-veffel of the carp, which, at certain feafons, he afirms, may be had very cheap and in abundance at Paris. It was perfeCtly pure azotic gas, for the moft part, though fometimes it contained a fmall quantity of carbonic acid gas. He thinks, from the nature of this fluid, that the air inthe bladders of fithes is produced in the ftomach. (Ann, de Chim. I. 47.) The obfervations of Dr. Brodbelt feem to render this general conclufion at leaft doubtful, ES VI. Account of certain remarkable Changes of Colour and DireStion of the Clouds during a Thunder- Storm. Awnonc other circumftances enumerated by Dr. Prieftley in the defcription of the clouds, in athunder-ftorm, in his Hiftory of EleGricity, mention is made of a certain luminous ap= pearance, evidently independent of folar reflection. I have always fuppofed this expreffion to denote the opake whitenefs of the upper or arched outline of certain thunder-clouds, con- trafted with others apparently in contaét with them, but of a dull leaden hue; and accord- ingly I was difpofed to conclude that the whole was an optical delufion, arifing from the pofition of the fpectator, who imagined, though falfely, that the latter clouds were as much expofed to the fun’s direét light as the former. But the ftorm which happened on Sunday morning, the 30th of July laft, exhibited faéts which feem to thew that the tranfition of electricity may caufe the clouds to emit a fteady permanent light, very different from the fudden flath called lightning. Vou. .—Serpremprr 1797s Mm I wae 266 Changes of Colour and Direétion in Thunder-Clouds, I_ was called at five o’clock in the morning, The fky was then covered with clouds, not very denfe except to the fouth, and flying with great rapidity to the W. by S, or W. S. W. It lightened very frequently in the N. W. and S. W. quarters, by doubled and trebled flafhes of a bright illumination (for the a€tual flath was not feen), with very loud thunder, ufually at theinterval of 11 or 12 feconds after the flath. The lower prominences, or ragged extremities. of the clouds, were conftantly tinged with red, and I was. informed that they had been very: much redder before I got up. : ? At about ten minutes after five, no'rain having fallen, but a few heavy drops, a fudden: darknefs came on, and the duft rofe in Newman-fireet, where I refide, beginning at the fouth end, about 250 yards diftant from my houfe, and proceeding to the north. It was very denfe, and rofe to the height of about fixty feet by eftimate, which is much higher than the houfes in the ftreet. At about a quarter paft five, the darknefs being then: greateft, the houfes on the oppofite fide of the ftreet appeared as if feen through a deep blue glafs, par- ticularly the white ftone work above the windows; and upon looking upwards, the clouds were feen of a deep leaden blue colour, and moving fwiftly in a direction precifely oppofite to that before obferved, namely, to the E. by N. or E. N. E. Soon afterwards, the light- ning and thunder continuing during the whole of thefe changes, there fella heavy fhower,, which beat againft the weftern face of the houfe, and the darknefs gradually went off At half paft five the clouds were much higher, and moved with a moderate angular motion to the north, while the fmoke of a chimney oppofite my window was gently driven to the fouth. We have yet much to learn concerning the theory of thunder-ftorms. It is well known by experiments with the ele€trical doubler *, that almoft all bodies poffefs a certain degree of eleétrization, which is variable from a confiderable number of circumftances. It is alfo. known from Franklin’s experiments of the can and chain, as well as from numerous other facts, that the intenfity of the eleétric ftate will be augmented by diminifhing the furfaces of bodies. In this way, as well as from other caufes, it is inferred that clouds become highly eleCtrified during the progrefs of their condenfation; fo that flathes of lightning pafs: be-. tween them and the earth, and between each other. From other obfervations and deduc- tions, it has been alfo rendered highly probable that the long range of clouds in a ftorm. of this nature does ferve as a conductor, through which flafhes of eleétric fire are conveyed: from one part of the earth to another partin a different ftate. The facts above defcribed feem uncommon, and, if collated with other more ufual events, may afford fome inftruc- tion concerning this clafs of phenomena. I do nothighly efteem the conjectures which pre- fent themfelves to me on this occafion ; but fhall communicate them, becaufe they tend to point out future objects of refearch. , The fingularity of this thunder-ftorm’ appears to have arifen from-the mafs of aque- ous vapour having been much too {mall to afford a favourable communication. between the two oppolite fates of eleétricity on the furface of the-earth. If the mafs of clouds be fuppofed to have. been at firft near the eaftern portion. of the earth, and to have become electrified and repelled, they would, on the common principle of. bodies in that flate, be re- pelledy and pafs {wiftly to the weftern part of the furface to depofit their electricity as foon, * New Experiments on Eleétricity. By the Rey. A, Bennet, F.R.S, oftayo. London, - , aS Tranfition of Lightning —Hungarian Bread. 267 ‘as they came within the ftriking diftance. In this fituation, it may be imagined that the fup- ply or communication might continue to be made by the eaftern part of the cloud aéting in the manner of a point, while the weftern part emitted flafhes; a fuppofition which is ren- ‘dered more probable by the confideration that moft thunder-clouds are ragged or pointed on ‘one fide, and round or fwelled on the other; and alfo that the difpofition of any conductor to receive electricity without explofion is much greater than to give filently, even when the ter- minations are alike. I conjecture, therefore, that the lightning came from the eaft, and paffed through the clouds to the weft; that the pofterior extremities of the clouds were illuminated as points ufually are; that the ele€tric motion of thefe low clouds at firft caufed an eafterly wind; that fome change in the general {tate of ele€tricity, or perhaps the mere ex- haufted ftate of the clouds, caufed them to pafs rapidly back to the original refervoir, as in the moft common experiments of electricity; that this return produced firft a ftrong eddy in the lower air, which threw-up the duft, and afterwards a contrary ftream of wind, by which the rain was beaten againft the weft front of the houfe. But why the clou:s fhould have been illuminated with a red colour during their weftern courfe, and afterwards with blue, does not feem deducible from any facts I know of. It may perhaps be -analogous to the colours of ‘the aurora-borealis. ‘The contrary lower current, when the clouds were moving to the north, feems to have been a natural confequence of their remotenefs. It is pro- bable that the returning current of the air, which muft have been driven before the mafs of clouds when they were moving very near the earth, took place entirely in the upper part of the air, where, in that cafe, there was more room. VIL. The Method of making excellent Bread without Yeaft ; as prattifed at Debretzin in Hungary*, By Ropert Townson, LL.D. F.R.S. Edin. Licurre, whiter, and better-flavoured bread than that made here:I never ate, nor did I ever fee elfewhere fuch large loaves. Were I not afraid of being accufed of taking ad- vantage of the privilege of travellers, I fhould fay they were near half a yard cubed. As this bread is made without yeaft, about which fuch a hue and cry is often raifed, and with a fubftitute which is a dry mafs, that may be eafily tranfported, and kept half a year or more, I think it may be of ufe to my country for me to detail the Debretzin art of making bread. The ferment is thus made: Two good handfuls of hops are boiled in four quarts of water: this is poured upon as much wheaten bran as can be well moiftened by it: to this are added four or five pounds of leaven; when this is only warm, the mafs is well worked together to mix the different parts. This mafs is then put in a warm place for twenty-four hours, and after that it is divided into fmall pieces, about the fize of a hen’s egg, or a {mall orange, which are dried by being placed upon a board, and expofed to a dry air, but not to the fun; when dry, they are laid by for ufe, and may be kept half a year. This is the ferment, and it may be ufed in the following manner: For a baking of fix large loaves, fix good handfuls + of thefe balls are taken and diffolved in feven or eight quarts of warm * Travels‘in Hungary, 4to, London, 1797, page 242. Pri he + I fuppofe broken into fragments ; the balls themfelves being too larga to be meafured by handsful. N. : M m 2 water, 268 | Hungarian Bread—-New Eudiometer. water. This is poured through a fieve into one.end of the bread-trough, and three quarts more of warm water are poured through the fieve after it, and what remains in the fieve is well prefied out. This liquor is mixed up with fo much flour as to form a mafs of the fize of a large loaf: this is {trewed over with flour, the fieve, with its contents, is put upon it, and then the whole is covered up warm, and left till it has rifen enough, and its furface has begun to crack; this forms the leaven. ‘Then fifteen quarts of warm water, in which fix handfuls of falt have been diffolved, are poured through the fieve upon it, and the neceflary quantity of flour is added, and mixed and kneaded with the leaven: this is covered up warm, and left for about an hour. It is then formed into loaves, which are kept in a warm ‘room half an hour; and after that they are put in the oven, where they remain two or three hours, according to the fize. The great advantage of this ferment is, that it may be made in great quantities at a time, and kept for ufe. Might it not on this account be ufey ful on board of fhips, and Jikewife for armies when in the field ? Vill. : d Defcription and Uje of an Eudiometer with Sulphuret of Pot-Afo. By Citizen Gurron *. Narv RAL philofophers and chemifts have long been defirous of poffefling an eudio- meter which might accurately thew the quantity of oxygene mixed in any kind of gas. Citi- zen Berthollet has clearly fhewn, in his late leffons to the Normal School }, that the eudio- meter of Scheele, which he with juftice confiders as the beft, has neverthelefs great defects 5. becaufe the abforption requires feveral hours, and becaufe there is a decompofition of water towards the end, which confequently difengages hydrogene gas, and renders the meafure of abforption doubtful. ini, This confideration induced me to feek a material which might immediately, and with con- yenience, afford a refult more to be depended on than thofe obtained by nitrous gas, hy- drogene gas, phofphorus, and the mixture of fulphur and iron; the only fubftances which have been, as far as I know, hitherto ufed or propofed for that purpofe. ‘The fulphuret of pot-ath appeared to me to deferve trial in this refpe&t. I well knew that ‘at the ordinary temperature it is only fufceptible of a combination ftill more flow and in- fenfible than the mixture of fulphur and iron moiftened ; but I prefumed that by raifing the ‘temperature, merely by the approach of a {mall taper, the a€tion of chemical affinity might be fo much favoured as to determine rapidly an abforption which in that cafe would not be -affefted by any foreign circumftance. ‘The effe&t has completely juftified my conje€ture ; fo that nothing more remains than to defcribe the apparatus required to form this eudiometric inflrument. TI thought that the reverfed retort, or infle&ted receiver (recipient cornu) as I have namedit in the article dir of the Encyclopédie Methodique, I. 706, would unite fimplicity, convenience, and every de- firable advantage. ‘The experiment was made in the laboratory of the third divifion of the Polytechnic School, according to the following defcription: * Journal de I’Ecole Polytechnique, IT. 166. + Séance des Ecoles Normales, &c. tom. v. p» 73+ AB, Platé Eudiometer with Sulpburet of Pot- Afb. 289 AB, Plate Kil, Fig. 2. reprefents a very {mall glafs retort, with a long neck, its-whole capacity being from 12 to 15 centilitres (between feven and mine folid inches Englith). It mutt be chofen of fuch a curvature, that, when the neck is fet upright, the bulb. may form at its lower part a cavity to retain the matters introduced. ; The extremity of the neck of this retort is ground with emery: toventer the glafs tube CD, which is.open at both ends, and about 20 or 25 centimetres in length (eight or nine inches Englifh). ‘Che retort then clofes the tube in the manner of a ground ftopper,.and intercepts- all external communication *. A cylindrical glafs veffel, F, is provided, of the form of a common jar, in which the glals- tube CD may be entirely. plunged beneath the level of the water. Laftly, the fulphuret of pot-afh is prepared and broken into pieces fufficiently {mall to be introduced into the retort. Thefe are to be enclofed, dry and even hot,, in a bottle for ufe. Thefe conftitute the whole apparatus and preparation of materials. When it is required to examine an aériform fluid, by feparating its refpirable part, two or three pieces of the fulphuret, of the fize of a pea, are put into the retort. It is then filled with water, taking care to incline it fo that all the air may pafs out from the bulb. The orifice of the retort is then to be clofed, and inverted into the pneumatic tub, in order that the gas propofed for examination may be transferred into it in the ufual manner. By an eafy manoeuvre of alternately inclining the retort in different direflions, all the ‘water is made to flow out of the bulb in which the fulphuret remains. When this is done, the retort is placed in the vertical fituation, and its extremity intro~« duced into the tube of glafs CD, which muft always be under water. A {mall lighted: taper is then to be placed under the bulb. To fupport the retort in its pofition, the jar is provided with a wooden cover,. in which: there is a notch to receive it. ‘The firft impreffion of the heat dilates the gafeous fluid fo much that it defcends almof ‘to the bottom of the tube, which is difpofed exprefsly for its reception ;. otherwife the partial efcape would prevent an accurate determination of its change of bulk. But as foon as the fulphuret begins to boil, the water quickly rifes, not only in the inferior: tube, but likewife in the neck of the retort, notwithftanding the application and even the increafe of the heat. If the fluid be abfolutely pure vital air, the abforption is total. In this cafe, to prevent the rupture of the veffel by too fudden refrigeration, the afcent of the water muft be rendered flower, either by removing the taper, or inclining the retort +5. which will not pre=- *-Citizen Chapflier had before conftruéted, for eudiometric experiments with phofphorus, an apparatus little different from this, compofed of a long tube of a fingle piece, one end of which is bended and blown into a bulb, and has at € a projecting tube,.which is clofed with a cork, after having caufed the water to rife within the tube to about one-third of its height. This inftrument may alfo be applied for experiments with the fulphuret of pot-ath. I mult obferve, however, that the practice is nor fo eafy as it. appears at firft fight : befides which, - if the projeéting tube renders it very convenient. for operating onthe air of the atmofphere, it is not the fame with regard to the other gafes, which cannot be introduced but by transferring them. G. + Lt does not appear that inclining the retort would diminifh whe rapidity of afcenfion. If the perpendicular Beight were increafed, by partly raifing the tube above the water, or if the aperture were partly clofcd, this effect would follow. N, vens 270 Eudigmeter.— Improved EleFrometer. vent thie ‘abforption from continuing while arly gas remains which is proper to fupport combuftion. If the fluid be common air, or vital air mixed with any other gas, the quantity of water which has entered the retort muft be accurately meafured after the cooling. It reprefents the volume of air abforbed. Care muft be taken to enclofe the remaining gas under the fame preflure, by plunging the retort to the level of the line at which the enclofed water relts, before the orifice is ftopped. This operation of meafuring, which is very eafy when meafuring veffels are at hand, may be habitually performed by a flip of paper pafted on the neck of the retort, upon which divifions are drawn from obfervation, and which muft be covered with varnifh, to defend it from the action of the water. Defeription of an improved Elerometer, in which the Senfibility of the Gold-Leaf is confiderably augmented, and the Intenfities are diftinguifbed by numerical Graduation, if is fearcely to be fuppofed that any philofopher who is converfant with eleCtricity can be unacquainted with the electrometer of Bennet, in which two pendent flips of gold-leaf are fubftituted in the place of the pith-balls of Canton, and ferve to indicate the nature and quality of yery minute intenfities of the eleétric ftate. There are two particulars in which this excellent inftrument appears capable of improvement : the firft, to render it portable, without danger to the gold-leaf, and the fecond, to exprefs its various degrees of eleCtriza- tion by a fcale of divifions. Ihave refieCted much on the probable means of fecuring the gold-leaf from fraQure by car- riage, but hitherto with little profpect of fuccefs. There was fome hope thata fingle flip of this gold might be preferved in a fheath or box, with its fides very nearly in contact ; but when I placed fuch a flip upon a gilded piece of wood of the fame fuperficial dimenfions, to which it was faftened at one end, its flexibility was fuch that the leaf very readily flided along the furface of the wood, and became full of folds, by inclining the faftened end a very few, degrees lower than the other extremity. There was ftill lefs immediate expectation that the flips could be actually and repeatedly confined between two leaves or cufhions, as in the book of the gold-beaters, without their being broken by occafional agitation. ‘To this, however, my attention will probably be dire€ted when I may again refume this object. In the mean time, [recommend it to other philofophers, as a very defirable improvement in the mine- ralogical apparatus, and fhould rejoice to be anticipated by their fuccefsful refearches. The weight of one flip of gold-leaf, in the eletrometer of Bennet, is about one-fix- hundredth part of a grain; but this, as well as the fenfibility of the inftrement, muft vary, not only from the figure and dimenfions of the piece, but the nature and thicknefs of the gold itfelf*. It feemed, therefore, unnecefflary to endeavour to render two of thefe inftru-\. ments comparable with each other, All that could be done was, to diftinguifh the different - intenfities as fhewn by the divergencies of the leaf; or, as I have taken it, the diftances at * Philofophical-Journal, I. 133. 6 which ee EleBrometer.—Scientific Procefs of Tanning. 27% which they ftrike a pair of uninfulated metallic bars. In Plate XII. Fig. 3, A reprefents the infulated metallic cap, from which, at C, depend the two narrow pointed flips of gold- leaf. BB is the glafs thade, which ferves to fupport the cap, and defend the leaves from the motion of the furrounding air. DD are two flat radii of brafs, which open and fhut by means of one common axis, like a pair of compafles. By a contrivance of {prings, they are _ difpofed to open when left at liberty ; but the micrometer fcrew E ferves to draw a nut, which has two fteel bars, with a claw at the end of each, that enters into a correfpondent flit, in two fmall cylindrical pieces, to which the radii. are fixed refpe@tively. This appa- ratus is feen in another pofition in Fig. 4. KL reprefents a piece of brafs, which ferves as the frame for the work, and fits the lower focket of the eleétrometer, FF, Fig. 3. In this the letters 1H indicate the cylindrical pieces which carry the radii, and are feen from beneath. On the fide of the riut G, one of the flecl drawing pieces is feen 5 the other being on the oppofite fide, and confequently not vifible. Towards L appear the two re-action {prings. The other parts require no verbal defcription. In the common conftruétion of the gold-leaf eleGtrometer, there are two pieces of tinfoil pafted on oppofite parts of the internal furface of BB; againft which the gold-leaf ftrikes when its electricity is at the maximum. If the radii DD:be left at the greateft opening, ourinftrument does not then differ from that in common ufe. - But if the divergence pro- duced by the contaét of an atmofpheric condudtor, or any other fource of eleétricity, be fo {mall as to render it doubtful whether the leaves be eleétrified or not, the radii may then be: brought very gradually together by means of the fcrew, until the increafed divergency from their attractive force be fufficient to afcertain the kind of electricity poffeffed by the leaves. In this and all other cafes, the divifion on the micrometer head, which ftands oppofite the fixed index, at the time the leaves ftrike the radii, will fhew the greater or lefs degree of intenfity.. : ; x. The improved Procefs of Tanning. By Citizen SEGUIN*. Iw confequence of our knowledge of the multiplied refearches and important difcoveries. of Citizen Seguin refpe€ting aftringent fubftances, and the happy application of thofe dif- coveries to fimplify and perfe&t the art of tanning, we invited him to-vifit the public la- boratory, for the purpofe of communicating his procefles and obfervations. Far different from thofe felfifh manufaéturers, who carefully conceal under the cloak of pretended myf- tery, operations in themfelves fimple, frequently tranfmitted by oral tradition, and which have coft them neither trouble: nor expence, the Citizen Seguin did not hefitate to comply ~ with our wifhes, and has devoted to this object two fittings, at which all the pupils, and the greateft part of the inftitutors and agents of the fchool, were prefent. He not only exhibited without referve all that experience and meditation had difcovered to him, but he likewife came attended by fkilful workmen, with proper inftruments to execute all the procefles. Laflly, he furnifhed gratuitoufly the fkins, and a confiderable quantity of tan,, * Reported by Citizen Chauffier ; being part of the Tranfaétions of the Polytechnic School.of France. From their Journal, LV. 678, in 27% Preparation of Leather: in order that each of the pupils might himfelf repeat the experiments, follow the de= tail af all the procefies, and render himfelf completely mafter of the method. We could have withed to render an exaét account of the two leQures delivered by Citizen Seguin at the fchool; but circumftances oblige us to confine our narration to the principal objects. Want is the parent of the arts. ‘Though man in the poffeffion of all his forces is formed to fupport the difference of feafons and climates; though the parts of his body which are fubjeCled to preflure, as in quadrupeds, are fo difpofed as to acquire by habit and exercife a degree of denfity and compaétnefs, which renders them little fenfible to the a€tion of foreign bodies : yet accidents, and circumftances which it is eafy to fuppofe, have determined him to feek the means of fecuring his feet from the impreflion of an unequal, flinty, or humid foil. The thepherd mutt have firft made ufe of foft and flexible bark, mats, and fimilar fabrica- tions of different kinds; the hunter mutt have taken a piece of the frefh fkin of fuch animals as ferved for his fupport, which he muft have fafhioned, modelled upon his foot, and retained with ftraps*. Thefe fimple means are fufficient in a climate which is ufually dry; but they would be of little advantage on wet ground, or in a climate fubjeé& to the alterations of wet and dry weather. : Skins {well up, and become foft, by moifture, which renders them permeable to water. Hence they are eafily deftroyed by the putrid procefs which enfues, and they become dry and brittle when the moifture is evaporated. Accident, no doubt, occafioned the difcovery of the means of preventing thefe inconveniences by the ufe of certain vegetable fubftances, particularly the bark of oak. It was feen that fkins prepared with thefe fubftances acquired new properties; that without lofing their flexibility they became lefs permeable to water; more firm, more compact, and in fome meafure incapable of putrefaction. Thefe obferva~ tions gave birth to the art of the tanner. This art, no doubt of high antiquity, becaufe founded on one of the earlieft wantl of man in fociety, comprehends a fucceffion of procefles which was executed by habit and imitation, without a knowledge of the effential objeéts. The preparation of fkins accordingly required feveral years, and frequently, in fpite of the care, expence, and flownefs of the operation, the tanning was incomplete; the fkin formed a foft and porous leather, which was foon deftroyed by moifture. Thefe defects effentially fprung from ignorance of the pa princi- ples of this operation, becaufe no difcovery had been’ made refpecting the action of tan upon the fkin, and the circumftances or conditions which might accelerate or retard the procefs. To arrive at this knowledge in an accurate manner, it is neceflary to confider, firft, the mature and properties of tan, and fecondly, the ftru€ture and compofition of the fkin, We fhall not enter into the detail of fuch precautions as are requifite in the choice of oak bark, the time and manner of feparating it from the tree, preferving it, or pulverifing it. It will be fufficient for our object to remark, that water poured into a veffel upon tan ac- quires, after fome hours infufion, at the common temperature of the atmofphere, a brown * According to the relations of travellers, thefe ufages are ftill to be found among certain nations, Sparman affirms, that the Hottentots make their fhoes with a piece of freth fkin, the edges of which they raife up, and tie with traps; the hairy fide is outwards, No other preparation is made than to beat and moiften the fkin, If it be ftrong and thick (fuch is the {kin of the buffalo, for example), it is left for fome hours in cow-dung, which renders it foft and flexible. 4 colours j ee ae me Thi Soluble Principles of Oak Bark. 273 colour, an aftringent tafte, and becomes charged with the mof foluble fubftances contained in the tan; that by drawing off the water, and adding a fimilar quantity to the tan repeat- edly, the whole of the foluble parts may be fucceflively extracted, the water ceafes to acquire colour, and there remains in the tub a mere fibrous matter, or parenchymatous texture, in- foluble in water, and no longer adapted to promote the operation of tanning. ‘This refidue is therefore always rejected in the manufactories as ufelefs. It is only ufed by gardeners for their hot-beds; but might probably be advantageoufly applied in the fabrication of coarfe paper. It is therefore in the water of infufion, or the lixiviations of tan, that we muft feek for the foluble fubftances which alone are efficacious in tanning. On examination of the water of the laft filtration, it is found to be not only clearer, lefs impregnated, and lefs acrid than the water of the firft lixiviation, but likewife that it pof; feffes all the properties of the gallic acid. It reddens the infufion of tournfol, aéts upon metallic folutions, and more particularly it precipitates a black fecula from fulphate of iron, &c. And it is alfo found that a piece of freth fkin, divefted of its fat and fanguine humours, and macerated in this liquor, inftead of becoming compa&, is foftened and {wells up. The liquor of the firft lixiviation exhibits a very different character. It is more coloured and aftringent ; it not only exhibits the properties of the gallic acid, by the alterations it caufes in the blue colours of vegetables, and the black precipitate it forms with the fulphate of iron; but it likewife poffeffes the remarkable quality of forming, with animal gelatin, or glue, a yellowifh abundant precipitate, infoluble in water, not putrefcible, which becomes hard and brittle by drying; and if a piece of {kin properly prepared be immerfed in this fluid, it becomes gradually more compact, and is converted into leather. There exift, therefore, in the fame fluid, two very different fubftances: the one, which precipitates a black matter from iron, is the gallic acid or principle; the other, which precipitates animal gelatin or glue, is called the tanning principle, on account of its efficacy in the preparation of leather. To leave no doubt on this important point, it was proved, by a number of experiments eafy to be repeated, x. That the liquor of the laft lixiviation, though coloured, and of an aftringent tafte, af- fords no precipitate with glue; a faét, which feems to fhew that the gallic acid contained in the bark is lefs foluble than the tanning principle. In faét, as has already been remarked, when water is fucceflively poured on the tan, an infufion is at laft obtained which no longer precipitates glue, though it precipitates fulphate of iron very well. 2. The liquor of the firft lixiviation, after having been faturated with glue or animal ge- fatin, and forming an abundant precipitate with that fubftance, is entirely deprived of the tanning principle. It no longer differs from the liquor of the laft filtrations, and contains merely a portion of the gallic acid. Hence the addition of fulphate of iron affords a new precipitate with this liquor. 3. As the tanning principle has a ftrong attraction to the animal gelatin, with which it always forms an infoluble precipitate, this property affords a very convenient re agent to af- certain its prefence immediately in any fluid, and to determine with precifion its quantity. Accordingly, the infufion of tan poured into milk, whey, ferum, broth, &c. forms, with Vox. L—Serrember 1797: Nn thele 274 Scluble Principles of Aftringent Vegetables. thefe liquors, a precipitate more or lefs abundant, according to the quantity of gelatin they contain. This peculiar property of the tanning principle affords an application which may become of great importance in the art of treating difeafes, to determine the nature of urine, and to afcertain fome of itschanges. In the healthy fubjeét, all whofe funétions are duly exercifed, the urine does not contain gelatin, nor afford a precipitate with the infufion of tan: on the contrary, in all the gaftric affe€tions, the urine is more or lefs charged with gelatin, and forms, with the infufion of tan, a precipitate more or lefs abundant. The fame obfervation is applicable to acute and chronical difeafes, in which the aflimilating or digeftive forces are troubled, deranged, or perverted. 4: The gallic acid, or, if other terms be preferred, the principle which precipitates the fulphate of iron, is often found alone, or at leaft without being accompanied by the tanning principle. Thus quinquina, crude or torrefied coffee, the roots of the ftrawberry-planty,, ferofularia, milfoil, arnica, the flowers of Roman camomile, and all the multitude of plants: vaguely comprifed under the title of aftringents, contain the gallic acid only. All thefe form with the fulphate of iron a precipitate more or lefs coloured and abundant; but none of them produce the flighteft change in the folution of animal glue. On,the contrary, the tanning’principle has never been found alone, but always united or combined with the gallic ptinciple. It was long fuppofed to exift exclufively in the oak, the nut-gall, and fumac, the only fubftances ufed at the tan-works; but it is found more or lefs abundantly in the fili- quaftrum, the rofe-tree, the larix, fuveral fpecies of pines, the acacias, the lotus, the fquill,. the roots of biftort, of rhubarb, of parella, and feveral other plants, of which we fhall here~ after give a lift. We have alfo found this principle in the produéts of diftillation of dif- ferent vegetable fubftances, where it was in fome meafure formed during the operation. From thefe different confiderations, founded on experiment, the following general prin-- ciples may be deduced: 1. Every fub{tance of which the infufion is capable of precipitating: animal jelly, poffefles the tanning property. 2. Every fubftance which poffefles the tanning: property, likewife precipitates the fulphate of iron black. 3. Every fubftance which preci- pitates the fulphate of iron, but not the folution of glue, does not poffefs the tanning pro- perty *. We fhall difmifs the confideration of the tanning principle, by fhewing fome of the re- markable changes to which its infufion is fubjeét. 1. A few days after its preparation a yellowifh precipitate is fpontaneoufly formed, which is more abundant in proportion as the liquor is more faturated, and the time of in- fufion longer. This precipitate, when feparated, is converted by drying into a very fine, light, afh-coloured powder, totally infoluble in water, oil, alcohol, and ether, even at the temperature of ebullition. When thrown on burning coals, it readily takes fire, and emits a thick fmoke. By deftruétive diftillation it affords a confiderable quantity of carbonic acid gas, an aqueous acid, and a brownifh oil, leaving in the retort a light fpongy coal. * The folution of glue is a convenient re-agent to afcertain the prefence of the tanning principle. It is there= fore advantageous to have it in readinefs in the laboratory.. To prevent the fpeedy putrefaétion to which ani= mal fubftances are liable, we have added one-twentieth part of alcohol, which. anfwers the purpofe very well, witMout altering the properties of the fluid... C. 6 As , é Spontaneous Changes of the Infufion of Tan. 275 As this precipitate by its infolubility approaches to the nature of wood, and as it falls down even when the lixivium of tan is preferved in well clofed veflels entirely filled, it might be fuppofed that it is merely a gradual and fucceflive depolition of the remains of the woody and parenchymatous parts of the bark difleminated and fufpended in the fluid; it might be imagined that the contact of air has nothing todo with this phenomenon. But we mult obferve, that this precipitate is found in the moft limpid folution; even after it has been fil- tered ; that it is moft abundant when the infufion has been prepared from bark ground long before, and preferved without care 3 and that it is more readily depofited when the liquor pre- fents a great furface to the contaét of the air. In this cafe the furface of the fluid becomes tarnifhed by an extremely fine pellicle, which covers it, and becomes thicker and firmer the longer the fluid remains thus expofed and at reft. If it be divided by agitating the liquor, it is again renewed, and in this manner produces the precipitate we {peak of. We may de- termine, in fome refpeét, at pleafure, the formation of this pellicle and precipitate, by ex~ pofing the liquor to the contac of oxygene gas, or by pouring into it the oxygenated mu- riatic acid. It is fufficient even to bring a bottle containing the oxygenated muriatic acid into the vicinity of the infufion of tan. A pellicle is inftantly formed, refembling a flight gauze, which floats and fpreads inftantly over the whole furface, affuming in a regular order the moft beautiful colours of the iris, and at laft becomes brownith. If the experi- ment be continued for a few minutes, the pellicle thickens, and the precipitate begins to fall. The formation of this precipitate, and the properties it acquires, depend, therefore, on the combination of oxygene, which operates either during the infufion and filtration of the lixivium, or after its having been drawn off clear with the contact of atmofpheric oxygene. Hence are fhewn the neceflity and advantage of ufing tan recently prepared *, and of pre- ferving the tan as well as the infufions defended from the conta& of the air. - Thefe phenomena are common to all the preparations of vegetables made by means of water, whether by infufion, deco€tion, or even diftillation. We have feen thefe precipi-~ tates gradually formed in the infufion or decoétion of nut-gall, fumac, gentian, quinquina, and even of the moft infipid as well as of the moft aromatic and acrid plants. The ex- prefled juice of frefh plants, fuch as hemlock, forrel, anil, &c. prefents the fame phenomena, and affords, more particularly when the action of air is promoted by agitation, a coloured pulverulent depofition which has long been diftinguifhed by the name of fecula. Laftly, all the diftilled waters which are kept for feveral years become turbid, by the formation of filaments and whitith flocks, more or lefs abundant, but always infoluble. It is toa com-* bination of oxygene, as Fourcroy in his excellent analyfis of quinquina has fhewn, that we ought to attribute the formation of thefe precipitates, the infolubility they acquire, and their approach to the nature of the ligneous fibre. Neverthelefs, the {pontaneous precipitation which is effeéted by the contact of atmofpheric oxygene in the hixivium of tan does not change its properties, at leaft in any fenfible manner; and as in a lixivium confiderably faturated the precipitate is moft abundant on the firft days, it might perhaps be of advantage to wait until this firft precipitate was formed before * The: obfervations are applicable to all vegetable fubftances which are reduced to powder. They not only tofe their peculiar aroma, but Jikewife change their nature by the contaét of light and atmofphericair. Their properties being thus confiderably altered, the dofe at which it is proper to employ them becomes uncertain, ‘The phyfician ovglit not therefore to preferibe in his formula any powders but fuéh as are recently prepared. Cj Nn2 immerfing = 276 Strufture and Compofition of the Skins of Animals. immerfing the fkins. For this fubftance, when depofited, attaches itfelf to the furface of the fkins, where it forms a coating more or lefs thick, which foils them, clofes their pores, and retards in a {mall degree the direét aétion of the tan. 2. The lixivium of tan, particularly when highly concentrated, and prepared in hot wea- ther, acquires after a few days a vinous {mell, which feems to announce a commencement of fermentation, and might lead to an apprehenfion that its progrefs might impair the tanning properties. In order to afcertain how far thefe notions might be well founded, different vegetable acids were mixed with the tanning lixivium, but none of them fenfibly altered its properties. And {till more we may add, that for near two years a bottle of the infufion of tan has been kept in the laboratory, and, in fpite of the alterations of temperature to which it has been expofed, and the change neceffarily produced by the contaét of air, its properties appear the fame, and it is ftill daily ufed with advantage as a re-agent to afcer- tain the prefence of gelatin. As a knowledge of the properties of tan affords obfervations of importance, which confti-= tute the bafis of Seguin’s method, we have not been apprehenfive of dwelling too long on the fubjeét; but we fhall confine our remarks on the ftruCture and chemical compofition of the {kin to a few general confiderations. This membrane, as is fhewn by anatomifts, is effentially formed of a great number of Jaminz or fibres, which are white, broad, fhort, and clofely adherent, but interwoven, and - difpofed in different dire€tions, fo as to leave between them an infinity of {mall {paces or pores. From this conftruétion it exhibits a denfe but foft fpongy texture, and is fufceptible of extenfion and contraction. In the midft of this fubftance are found a great number of nerves and veffels of different kinds, the very fine and multiplied ramifications of which ferve to fupport and maintain the lamellated ftru€ture of the fkin, and convey into the vacuities between the fibres thofe fluids which ferve for the fupport and nutrition of this membrane. ‘The external part is the epidermis. This thin tranfparent membrane is of a very different texture. It contains neither the apparatus of veflels, nor the difpofition of fibres or lamin; which by their interfeétion form a kind of fpongy net-work. It is in fome meafure a fimple uniform covering, which prefents no diftin& organization, but adheres ftrongly to the fkin, entering into its folds and numerous porofities. Laftly, the hairs.are implanted in the fkin by a fort of bulb or oval root, interfperfed with {mall veffels filled with a kind of mucus. The compofition of the fkin, the changes it undergoes by different preparations, by chemical agents, and the properties it acquires in thefe feveral ftates, prefent other confiderations. If the freth fkin of an adult animal be macerated for fome hours in water at the tem- perature of the atmofphere, and if, to accelerate the effeét, agitation and preffure be ufed, a feparation is made of the blood, the juices, and the different foluble fubftances contained in the veflels or vacuities; and by examining the nature of the matter thus extracted, it is found that a {mall portion only confifts of gelatin, which has little confiftence or tenacity. Subfequent macerations, at the fame temperature, afford no more gelatin, the fibrous texture remains infoluble, and undergoes no further lofs. It therefore appears, that in the naturak ftate the fkin contains but a fmall portion of gelatin perfectly formed, and foluble. It may even be apprehended, that the fmall quantity obtained by the firft maceration was. merely included in the pores of the fkin adherent to the furface of the fibres; and that the vital force had not yet time to aflimilate and convert it to the ftate of fibre. 7 But Fibrous Matter.—Operation of Tanning. a7 . But if the temperature be raifed to ebullition the fibrous texture is altered, becomes foft, and fucceffively diffolves. It affumes the character of gelatin, and may be entirely converted into a vifcid and tenacious glue. The fibre which forms the folid ftruéture of the fkin does not therefore effentially differ from gelatin, but in its texture, its concretion, and its infolu- bility in cold water; and as it is obferved that fubftances capable of abforbing oxygene de- prive the fibrous matter of its folidity, and haften and determine its converfion into gelatin, we are authorifed to conclude that thefe diftinét qualities of the fibre depend only upon a proportion of oxygene which the vital action and progrefs of life combine with the gelatin. Multiplied experiments appear to leave no doubt on this point. ‘* They have proved to me (fays Seguin) that the fibre is oxygenated glue, which in that ftate cannot combine with the tanning principle, but which acquires that property by pafling to the ftate of gelatin in con- fequence of the lofs of a portion of oxygene.” , Fhe effential point in the operation of tanning is therefore to afcertain, and to dire&t in a: precife and invariable manner, the circumftances and conditions which determine the trar- fition of fibre to the ftate of gelatin, and to feize the inftant in the procefs to effect a pro- per combination with the tanning principle. This object is too important not to recall fome: of the obfervations made by Seguin. Glue, as has before been remarked, poffeffes a great attralion for the tanning principle. It immediately forms with this fubftance an infoluble matter, which is not fubject to putre- fa€tion; but it muft be well remarked that the precipitate is dry and brittle. Hence it is evident that a fkin, the pores of which might contain gelatin ready formed, or of which the fibrous texture fhould have been altered and:converted by certain preparations to the gelatinous ftate, would tan very fpeedily, but would afford a kind of leather which would be harfh, brittle, and difpofed to crack or peel inthe wear. On the contrary, the operation will be long, incomplete, and will afford only a foft, fpongy, and putrefcible leather, if the fibre preferves its ftate of oxygenation, if it do not pafs by fucceflive degrees into the ftate of gelatin, or if the tanning principle do not penetrate its thicknefs in proportion to the converfion of the fibre into glue. Thefe inconveniences are avoided, and’ the propofed object is obtained with precifion, by the ufe of the lixivium of tan, This fluid has been fhewn to contain two very different principles, of which the union and aétion are alike neceffary for the fuccefs of the operation. On the one fide the gallic principle, which, as is known, readily feizes the oxygene of me- tallic folutions, and reduces them or brings them nearer to the metallic ftate, acts nearly in the fame manner upon the fibre; it unburns it, or deprives it of oxygene, and converts it into the ftate of gelatin. On the other hand, the tanning principle, which alfo exifts in the fo- lution, exercifes its action as foon as the fibre is fufficiently reduced to the ftate of gelatin. The tanning procefs is not, therefore, inftantly effected, like the precipitation of animal glue; but it operates gradually, and in fucceflion, by {trata from the furfaces of the fkin to the centre; and:as the aétion of the tanning principle immediately follows that of the gallic acid, the fibre is furprifed in its pofition, the felted texture of the ikin is totally preferved, and its compolition alone is changed. Accordingly, the leather prepared by this procefy has the advantage of being fupple, flexible, infoluble, imputrefcible, more durable, and Jefs difs- pofed than any other to imbibe humidity. The new method of Seguin. for the preparation of leather is founded upon this feries of obfervations 278 Arts of Tanning and of Dyeing compared. obfervations and experiments. We fhall not in this place enter into the detail of the changes and improvements he has made in the different branches of the tanning art; but we muft add, that the procefles have been repeated in all the laboratories of the Polytechnic School, by the greateft number of the pupils; that the operations on different Kinds of fkins were all concluded in eight, ten, twelve, or fourteen days at moft; that the leather thus manu- fa&tured was completely faturated with tan, and of a quality fuperior to the leather prepared by the old method which is to be-met with in the market; and Jaftly, that to thefe advantages the method of Seguin unites fimplicity, facility, and certainty,of fuccefs. A difcovery of this importance, in an art fo neceflary to our wants, entitles the author to the efteem and gratitude of the public; and thefe fentiments are more efpecially due to the citizen who facrifices his individual intereft to the general profperity, and is defrous of communicating the fruits of his refearches. ‘The advantage of public utility conftitutes his recompenfe, and enables him to difregard the clamours which envy, ignorance, and the prejudice of ’ old habits never fail to raife again{t every ufeful innovation. After the two fittings employed by Citizen Seguin to explain the nature and properties of tan, the order adopted in the courfe of vegetable chemiftry was refumed in the fchool. ‘The alkalis, the ligneous part, and the colouring matter were fucceffively examined ; the laft of which naturally led to an explanation of thé principles of the art of dyeing, the different proceffes for fixing colours, and afcertaining their qualities. In treating of thefe different objects, fome confiderations were prefented re{pe€ting the new properties which ftuffs ac- quire by tintorial proceffes. The procefs of dyeing ought not to afford fimply a colour to pleafe the eye, but fhould effect a kind of colouring tannage capable of adding to the properties of the web, and to render it lefs foluble or putrefcent. This objet is generally neglefted or little known, but it cannot be indifferent. It is not only of importance with regard to economy, but we do not hefitate to fay, equally fo for the prefervation of health. This may eafily be conceived if attention be paid to the circumftances, that cloths of the fame kind and fabric differ con-~ fiderably according to the dye; that fome are dry, brittle, of little durability, not adapted to preferve or retain caloric; others are foft, fpongy, capable of retaining damps and exhala- tions of every kind; and by the fucceflive aétion of light, air, and caloric, may either un- dergo a fort of oxidation that deftroys their texture, or elfe pafs to a kind of putrefadtion, which forms a continual atmofphere round the body, and more or lefs affects the health. It is in the midft of armies under tents, in camps, where a great number of men are ex- pofed to the fame kinds of fatigue and intemperance, and differ only in the colour of their clothing, that we may afcertain the truth of thefe obfervations. It is in the magazines of the military hofpitals, where the clothing of men is depofited, that a very marked difference in the fmell and porofity of the ftuffs is obferved, according to the colour with which they are charged. , After a fucceflive examination of the different produéts of vegetables, the attention of the fchool was direéted to the alterations they undergo after death, by the action of light, caloric, air and water. Thefe fubje€ts led to the theory of the vinous and acetous fer- mentations, and the production of alcohol and ether; and laftly, the courfe was terminated by an examination of the phenomena of putrefaction, whieh reftores to the atmofphere and to the earth thofe principles which the a¢tion of vitality had before extracted. During Combuftion of Phofphorus in Vacitos 279 During the concluding months of this courfe, the pupils continued to operate in the par-' ticular laboratories appointed for their ufe, either in repeating the principal experiments which had been exhibited in the le€tures, or in making others which had been pointed out or imagined by themfelves. ‘Their attention was principally direéted to the application of chemical knowledge to the progrefs of arts and manufa€tures. With this view they fuc- ceflively prepared different kinds of foap, varnifhes, and pigments, and they executed im fmall the different procefles of dyeing, tanning, &c. Some of the pupils attended particu- larly to the experimental refearch of fubftances proper to form the oxalic acid; others en- gaged in the experimental enquiry after thofe vegetables which contain the tanning principle, and might be ufed as a fubftitute for oak bark. From thefe refearches a table has been formed, which is already very ample, wherein thofe vegetables which afford a precipitate with the fulphate of iron alone, are diftinguifhed from thofe which afford a depofition with the folution of glue. This table is already very interefling; but it may eafily be imagined that it fill prefents vacuities to be filled up by time and experiments. This will form the object of the work of another year; and when it fhall be finifhed, we fhall haften to prefent the labours of the pupils of the {chool. XI. The Combuftion of Phofphorus in the Vacuum of the Air Pump. By Dr. Martinus. Van Marum. [Concluded from page 237. ] Berne defirous of afcertaining the caufe of this fingular inflammation in air fo rarefied, I put, on another day, a {mall ftick of phofphorus, wrapped in the fame manner in cottom powdered with refin, under a receiver containing about four hundred cubic inches, on the plate of the air pump, in order to obferve the phenomenon with accuracy a fecond time. The temperature of the place where I made the experiment was nearly the fame as on the former occafion, namely 56 degrees of Fahrenheit’s feale. To obferve the degree of rarefaction more eafily, I placed a fhort barometer gauge under the receiver. When the air was rarefied fo that the mercury was fupported in the gauge to the height of about an inch, the light began to be enlarged on the furface of the phofphorus, chiefly at the upper part of the fmall cylinder. This light increafed by degrees during the fubfequent ex- hauftion, and the inflammation took place when the mercury ftood at the elevation of 5 lines. The flame was much paler and weaker than is afforded by phofphorus when burned in an atmofphere of the ufual denfity. I obferved the flame to become weaker and weaker, and about two minutes afterwards the phofphorus ceafed to exhibit any light. IV. To afcertain whether the cotton powdered with refin, which was wrapped round the phofphorus, might be the caufe which gave place to the inflammation, I placed under the fame receiver two fmall {ticks of phofphorus of the fame fize, one of which only was wrapped in the powdered cotton. Thefe two fmall pieces began to fhine at the fame time, when the mereury ftood at the height of about an inch in the fhort barometer gauge, Neverthelefs, the piece which was furrounded by the cotton and powdered refin alone took fire when the rarefaétion was more advanced. I then 236 Combuftion of Phofphorus in the Vacuum of the dir Pump. I then thought there was fome reafon to fuppofe that the refin might be the caufe of the inflammation ; and to determine this point, I put under the fame receiver three fimilar fmall fticks of phofphorus, one of them fimply powdered with refin, another wrapped in cotton without refin, and the third wrapped in cotton powdered with refin, in the fame manner as in the former experiments. The light began to increafe at the fame time in all three, namely, as foon as the mercury had fallen to about one inch in the barometer. The phof- phorus wrapped in cotton_powdered with refin took fire firft; a fhort time afterwards that which was wrapped fimply in cotton took fire; and that alone which was fimply powdered with refin did not take fire at all. V. After thefe refults, the queftion was, to know in what manner the cotton could caufe inflammation in air fo rarefied, in which every other combuftible, though fet on fire, would ceafe to burn; and ftill farther, how phofphorus could fpontaneoufly take fire when the experiment was made in an atmofphere where the temperature does not exceed 56 or 58 degrees of Fahrenheit, though the phofphorus does not take fire in the open air unlefs heated to about 112 degrees of Fahrenheit. After fome reflections and experiments, I found that this fingular phenomenon could be very eafily explained according to ihe principles of the modern chemiftry. The increafe of the light which precedes the in- flammation when the air is rarefied to a certain degree, fuggefted to me this explanation. I fhall therefore, in the firft place, explain the evident caufe of the increafe of light in the phofphorus in the rarefied air. VI. Exhalations continually rife from the furface of phofphorus when expofed to the at- mofphere, as is proved by its {peedy diffipation in that circumftance: but as foon as the air is rarefied to a certain degree, the exhalations cannot rife; for thefe particles will not be elevated but during the time that the furrounding air is heavier than themfelves. When- ever, therefore, the air is rarefied to this degree, the exhalations muft remain, and furround the phofphorus from which they came. The union of oxygene with thefe phofphoric ex- halations muft be then made only in the vicinity of the phofphorus, whence the light from the difengaged caloric muft be feen there only. It is evident that this light will be much ftronger when the phofphoric exhalations do not rife, becaufe the difengagement of the fame quantity of caloric isthen made in a more confined {pace than when the phofphoric exhala- tions could rife and be difperfed in the receiver. VII. The caloric which is ‘difengaged from the oxygene, and is feen in ‘the rarefied air round the phofphorus in the form of a ftronger light than ordinary, muft, alfo, on ac- count of its greater denfity, give heat to the phofphorus. Hence may be clearly feen the reafon of the combuftion of phofphorus on rarefying the air when it is furrounded with cotton, as before defcribed. Woollen and cotton {tuffs have the property of preventing the difperfion of caloric*. The caloric which is difengaged round the phofphorus in the rare~ fied air is thus retained by the cotton, until its accumulation on the furface of the phof- phorus becomes at length fufficient to fet it on fire. When a piece of phofphorus is not enveloped in cotton or fome fimilar fubftance, it does not take fire in the rarefied air, becaufe the caloric which is difengaged near the phofphorus is fo fpeedily difperfed when it is not arrefted by the cotton, that the poe cannot acquire the degree of inflammation ne- ceffary to inflame it. * Becaufe they impede the circulation of the air, by which the heat would elfe be conduéted off. N. Vill, Combuftion of Phofphorus in the Vacuum of the Air Pump. 281 VIII. Though this explanation appeared to me to be very evidently founded upon the knowledge we already poffefs, 1 was neverthelefs defirous of fhewing the truth by a dire& experiment. I endeavoured to afcertain, by means of a thermometer, that the temperature near the furface of the phofphorus which is wrapped in cotton, is more elevated before the inflammation, when the light is perceptibly ftronger. For this purpofe, I ufed a thermo- meter, the bulb of which was about one quarter of an inch in diameter. I faftened the cotton with which the fmall ftick of phofphorus was furrounded, as in the preceding ex~ periments, to the ball of this thermometer, fo that it was entirely furrounded with it, at the fame time that its diftance from the furface of the phofphorus was about half a line. The refult of this experiment anfwered my expectations. I obferved that the mercury rofe, after the light had increafed, and that from 52 degrees, which was the original temperature, it had rifen to 67 of Fahrenheit before the phofphorus had taken fire. The fize of the ball of this thermometer appeared to me to be the caufe why the mercury did not rife higher before inflammation. I had alfo admitted fome diftance between the bulb and the phofphorus,in order that its conta& might not prevent the phofphorus from acquir- ing the requifite degree of heat which is neceflary for its inflammation. I therefore refolved to repeat the experiment with a thermometer of the fame kind as was ufed by Dr. Hunter in his obfervations on the heat of animals and plants, the ball of which was not more than one line in diameter. I faftened cotton to this in the fame manner, which was attached to a {mall ftick of phofphorus; but the ball of the thermometer was placed in contaét with one.of the ends of the flick of phofphorus, which was half a line in diameter, and four lines in length. I then faw that while the light round the phofphorus became ftronger and ftronger, the ther- mometer rofe from 46 to 76 degrees before the phofphorus took fire. ‘The fudden heat broke the ball of the thermometer ; which prevented my ufing fimilar thermometers in the repetition of this experiment. Though this thermometer did not mark the degree of heat which was neceffary to fet fire to phofphorus in the open air, it is feen, neverthelefs, from the experiment, that the tem- perature rifes very confiderably at the furface of the phofphorus before it takes fire. The ball of the thermometer which I ufed for this experiment had its glafs extraordinarily thick at bottom, which was probably one of the reafons why the thermometer did not indicate an higher temperature before the inflammation, as there is no reafon to fuppofe that phofphorus will take fire in rarefied air at a lefs temperature than in the atmofphere *. TX. Laftly, I examined whether the air could be rarefied to fuch a degree that phofphorus fhould be incapable of taking fire in it. I faw it take fire in air fo rarefied that the mercury in the gauge itood at the height of one fingle line only. The phenomenon here defcribed is hitherto, as far as I know, the only example of a true inflammation in air rarefied to the higheft poflible degree by the air pump. ‘This faét, however, does in no refpeét prove that a true inflammation can take place in vacuo. When the mercury in the gauge placed beneath the receiver ftands at the height of one @ As the folidity of the ball of the thermometer was about half a cubic line, and the phofphorus little more than three quarters, it fhould feem that, as the heat was fhared between the mercury and the phof{phoric vapour, the thermometer could not be expeéted to rife to the point of combuttion unlefs it had remained unbroken for a longer time. N Vor. I.—Serremner 1797. Oo line, 282 ; Combuftion of Phofphorus in Vacus. line, which indicates the utmoft degrce of rarefation of the air which I have ever obferved -to take place, the rarefied air {till pofleffes 1- 300th of the denfity of the air of the atmo- fphere, in cafe the mercury in the barometer be fuppofed at 30 inches elevation. It is certainly very fingular, that the fmall quantity of oxygene gas which remains in air fo rarefied fhould be fuficient for the inflammation of phofphorus; more efpecially as all other combuftible fubftances are extinguifhed in air rarefied to a much lower degree. I have already explained the principal reafon. ‘There is another circumftance which probably favours this inflammmanops of which I hall fpeak hereafter, when I fhall have made fome experiments. X The phenomenon exhibited by the phofphorus in rarefied air, as here defcribed, is certainly a real combultion, as is proved by the very remarkable diminution of weight of the phofphorus after the experiment has been made in a large receiver, or has been feveral times repeated. The phofphoric acid produced by the combination of Sigs with the fubftance burned is alfo found on the plate of the air pump. XI. The combuftion of phofphorus in air highly rarefied is accompanied with feveral very fingular phenomena, which I fhall here mention. . The phofphorus ufually emits, a fhort time after the commencement of the inflamma. tion, a Br in the form of fmall ignited balls, which are difperfed on all fides in the receiver, and exhibit a very curious and furprifing appearance. I have not hitherto been able to explain this phenomenon. Fie 2. The flame which furrounds the phofphorus when it burns in the rarefied air, extends farther and farther in a globular form. Its light at the fame time becomes paler and paler, and at length difappears. This enlargement of the flame, and diminution of the light, are probably to be attributed to the oxygene, to which the phofphoric exhalations may unite, being gradually exhaufted. The light at Jaft entirely difappears, when all the oxygene gas which exifted in the rarefied air, and could be reached by the phofphoric exhalations, is combined with them; for, as foon as there is no more oxygene to which the phofphoric exhalations may unite, there ceafes to be any further feparation of caloric, which caufes the flame and the illumination. g. When a fmall quantity of atmofpheric air or oxygene gas is fuffered to enter the upper part of the receiver by a cock after the combuftion or light of the phofphorus has difappeared, a pale light is then feen to difperfe itfelf through the whole capacity of the re- ceiver This light muft certainly be attributed to the combination of the oxygene, of the gas which has entered, with the phofphoric exhalations which exift in the receiver. ‘The exhalations which the phofphorus emits after it has been heated by the inflammation, are apparently more fubtle and light than thofe which preceded that phenomenon; and it is probably owing to this reafon that they can fupport themfelves in the gas which remained in the receiver, though very highly rarefied. 4. When the apparatus is left untouched for fome time after the combuftion of the phof- phorus in the rarefied air has ceafed, and the whole has become cooled, then the phofphoric exhalations defcend in this rarefied air. In proof of this, when the experiment is made in a receiver, on the plate of the air pump, and air is fuffered to enter by a cock beneath the plate, as ufual, it is then feen that the light occafioned by the entrance of the air takes place only near the plate upon which the phofphoric exhalations have fallen. XI. Combuftion of Pho/pherus.—— Correfpondence. 283 XI. When the atmofpheric air or oxygene gas enters the receiver by a cock from above, a little before or the inftant after the light of the combuftion has difappeared, and when care is taken to admit no more air or gas than fhall be fufficient to raife the gauge one or two lines, the phofphorus ufually takes fire a fecond time. In this manner the phenomenon may be made to appear repeatedly; and accordingly as a greater or lefs quantity of air is fuffered to enter, the circumftances are found to vary in a very remarkable manner. This communication would be too long if I were to attempt to defcribe the variety of appear- ances which I have obferved in thefe experiments. They are not entirely the fame, in cir- cumftances which appear perfeétly fimilar. I have obferved that pieces of phofphorus obtained by different operations have exhibited different phenomena. The fiery globules emitted by the burning phofphorus are in fome cafes larger and more numerous than in others. MATHEMATICAL anp PHILOSOPHICAL CORRESPONDENCE. Question V. : Anfwered by the PROPOSER. Ler * denote the weight of the falt, ands its fpecific gravity; a the weight of the bottle of diftilled water, and W that of the folution; the magnitude, or content, of the bottle, and the fpecific gravity of the water, being each confidered as 1. Then, fince the magnitudes of bodies of the fame kind are as their weights, w: W—x:: W—« w of bodies of different kinds are as their weights divided by their fpecific gravities, = = magnitude of the aqueous part of the folution: and, becaufe the magnitudes a: x 1's W—*. x sore magnitude of the falc. Whence +— =13 from which equation ws ws x is found = = (W —w) = weight of the falt. And fince s = 2.8, W = 2810 pre and w = 2506 gr. by the queftion, we fhall have x = - = 3 ~ (2810-2506) = = x 304 = 472% gr. the quantity of falt required. And if the cafe be reverfed, by fuppofing x to be known, the value of s will be readily found from the general formula; by which means we fhall be enabled to make a proper allowance for the difference in the fpecific gravity of the falt, arifing from chemical con- denfation, as was done in the propofing of the queftion, where it is taken as 2.8 inftead- of 2§, which it is fuppofed to be in its feparate ftate. ; QuEsTION VI. Anfwered by C. W. LET m be put for the mean temperature at the equator, » for the difference between. this temperature and that of the north pole, and / for the Jatitude of any place, radius being 1; then the mean temperature of that latitude will be m — 1 X fine ?/, For the heat 002 produced 284 Mathematical and Philofophical Correfpondence. produced by the direét a€tion of the fun, is as the fine of the fun’s altitude; fo that if the earth were equally heated at the equator and poles, the quantity to be added to the polar heat would be 7 X fine of the fun’s altitude, radius being 1. But it has been afcertained from obfervation, that the heat on the earth’s furface (ceteris paribus ), and confequently the heat emitted by the earth itfelf, is always proportional to the direét folar heat; whence the quantity to be added muft be » X the fquare of the fine of the fun’s altitude : or, fince the mean annual altitude of the fun, in any latitude, is equal to the complement of that latitude, the quantity to be added to the polar heat (m—) will be a x cof.+/; but cof./ = 1 —fine*/; confequenily, m—n-+ 1 X cofLadsm—n +n—2 X fine 7 =m—n-x fine +/. Hence, if the mean temperature of any two latitudes be known, the temperature under the equator, at the ‘pole, and in every intermediate latitude, may be, readily afcertained. : The mean temperature of lat. 40° is found to be 62.1, and of lat. 50° to be 52.95 but the fquare of the fine of 40° is +413, and the fquare of the fine of 50° is -586 3 whence mt —"4130 = 62'T_ m— *586n = 52°93 » From which equations » is found = §3 nearly, and m= 84. So that, the mean annuaf temperature at the equator being 84%, that of the pole muft be’ 8g-—~53 = 31°; and the mean anaual temperature of every intermediate latitude will be 84 — 53 the fquare of the fine of that latitudes NEW MATHEMATICAL QUESTION. Question X. By WH: Taomson. IT is required to find at what time of the longeft day it is the hotteft in London, fup- pofing the heat to be as the fine of the fun’s altitude, and the time of its continuance above the horizon. PHILOSOPHICAL QUESTION. THERE is an optical appearance fo frequent, that it is rather furprifing that writers on that fcience have never mentioned it. Whenever the fun fhines upon agitated water not abfolutely loaded with opake matter, and the fpedtator is fo placed that the fhadow of his head may be projected upon the furface of the fluid, he will fee an innumerable quantity of divergent rays within the water, of which that fhadow is the centre. ‘Phey are inceffantly fhifting their place laterally; and if more perfons than one are prefent, each fees a fy{tem of radiations or glory round his own head, but no fuch appearance round the fhadows of the other perfons, though thefe alfo are very vifible to him. As this phenomenon has a ftriking effe&t when obferved, and may be accounted for upon the common principles of optics and perfpedtive, it is offered to correfpondents as an object for explanation. To Philofophical Correfpondente.—New Publications. 285 To Mr. NicHOLson. SIR, London, 22d Auguf? 1797. UPON perufing the. account given in your laft number, of the phenomenon of the Fata Morgana, and upon confulting the plate annexed by way of explanation, I was very much puzzled to comprehend how the fpe€tator, ** placed on an eminence of the city, with his back to the rifing fun, and his face to the fea,” looking of courfe towards the weft, could at once enjoy the fight of this truly admirable phenomenon, a diftant view of the we/fern afpect of the city, and alfo of the mountains Jedind him. A-few words in a future number, in explanation of this ftrange combination, will much oblige, . Sir, Your conftant reader, — DAVUS. *,* THE difficulty lated by this correfpondent, together with feveral others, engaged my attention at the time the account {(p. 225) was drawn up: but as they feemed fearcely cas - pable of being cleared up by reafoning, while the theory remained fo very uncertain, 1 thought it befl to avoid: entering the ample field of conje€ture which offered itfelf. It feems altogether improbable, that the rays of light fhould be reflected immediately back ‘to the city, and eyery part of the drawing direétly contradiéts this fuppofition. I am therefore inclined to conclude that the defcription, though literally tranflated, is faulty, fo far as it contradicts the notion of the obferver being fo placed as to view the city over a portion of the bay. | imagine that the people, when they run haftily to the fea exclaiming Morganat do not run to the ramparts of the town, but to the fouthern point of the bay, at the diftance of half a mile or lefs from the town ; whence, with the fun * behind them, they may have an oblique view of Reggio flrongly illuminated, and a more direé& profpedt of the northern fhore of the bay. i ee NEW PUBLICATIONS: An Account of two Cafes of the Diabetes Mellitus, with Remarks as they arofe during the Progrefs of the Cure’; to which are added, A general View of the Nature of the Difeafe, and its appropriate Treatment; including Obfervations on fome Difeafes depending on Stomach AffeCtion, anda Detail of the Communications received on the Subje&t fince the Difperfion of the Notes onthe firft Cafe. By John Rollo, M. D. Surgeon General, Royal Artillery.——With the Refults of the Trials with various Acids and other Sub- ftances in the Treatment of the Lues Venerea, and fome Obfervations on the Nature of Sugar, &c. By William Cruickthank, Chemift to the Ordnance, &c. mm two Volumes O€tavo, 148. Dilly. In this treatife Dr. Rollo has confidered the diabetes mellitus as a difeafe of the organs of digeftion, and not of the kidneys; he conceives that the fugar which paffes off by urine * The fon’s rays can never make an angle of 45° on the fea/at Reggio, from the azimuth of the image in the drawing, 6 : is 286 “ Accounts of Books. is formed in the ftomach, and depends chiefly upon fome vitiated, but increafed a&tion of this organ. ,He was led to take this view of the difeafe from refle&ting on the ftate of the ftomach and habits of life which preceded, the voracious appetite which always accom- panies it, and the ftate of the blood, the ferum of which, although not fenfibly. fweet, had not'the ufual faltifh tafte. The Doctor fuppofes, that in this complaint the vegetable matter taken into the ftomach has not, from: fome defeét in this organ, undergone a fuflicient change to form proper chyle; that in confequence of this much faccharine matter is evolved, which, when carried into the circulation, proves a general ftimulus, producing head-aches, and quicknefs of pulfe, but that it acts more remarkably on the kidneys, occafioning a conftant and copious fecre- tion of {weet urine. From this hypothefis, he was naturally led to adopt a plan of cure, which has proved completely fuccefsful. The indications he lays down are: 1. To prevent the formation of faccharine matter in the ftomach;,and, 2.'To remove the morbidly in- creafed aétion of this organ, and reftore it to a healthfut condition. Thefe indications are to be an{wered by a complete diet of animal food, and by the ufe of fuch medicines as fhall diminifh the aétion of the ftomach, and at the fame time counteract the formation of faccharine matter. The remedies employed for this purpofe have been emetics, kali ful- phuratum, lime-water, hepatized ammonia, and vegetable narcotics. But the -principak dependence is to be placed on a total abftinence from all vegetable matter, which alone can fupply the faccharine principle. . By a regular perfeverance in this plan, the firft patient was completely cured in four weeks, although the difeafe had been of feven months continuance. The urine, which at the commencement of the treatment was {weet, and amounted to 24 pints daily, was at laft reduced to 13 pint, being atthe fame time free from any faccharine impregnation. " The fecond patient, from his age and other sien Santini although relieved from the diabetic affection, did not regain his wonted ftate of health; but even in this cafe, the effects produced by the treatment, when properly attended to, were moft decidedly in con- firmation of this plan of cure. ~The Doétor has received feveral communications in confequence of the difperfion of the printed notes on the firft cafe. The moft important are the refult of two’ cafes treated in this way by Dr. Cleghorn of Glafgow, and one by Drs. Currie and Gerard at Liverpool; all of which afford the ftrongeft corroboration of the efficacy of this mode of treatment. To this account of the diabetes are added fome experiments on adiueee? and the effects of different acids in the lues venerea. The cafes of lues venerea treated in this way, and detailed at fome length, are: 17 by Mr. Cruickfhank, 2 by Dr. Irwin, 5 by Dr. Jamefon, and 8-by Dr. Wittman—making in all 32. Of thefe 19 were cured by the nitrous acid, 4 by the oxygenated muriatic acid, 3 by lemon-juice, or the citric acid, and 6 by the oxy- genated muriate of pot-afh. The affections in all thefe were of the primary kind, being chancres and buboes, but diftin€tly marked. The effects produced by the different reme- dies were nearly the fame, and fuch as feemed to indicate a general increafed action of the fyftem. There was an increafe of appetite, more thirft than ufual, a white tongue, an augmentation in the quantity of urine, and the blood when drawn was generally fizy: nothing, however, like falivation was obferved. The Acctiinrs of Books. 287 The cures in general feemed to have been performed in lefs time than would have been neceflary undet the mercurial plan; and without any confinement or particular regimen. The effect is fuppofed to have been produced by the difengagement of oxygene from the different fub{tances employed, inducing a new difeafe in the fyftem. Of the different re- medies, the preference is given to the nitrous acid and the oxygenated muriate of pot-afh:— of the firft, from one to three drachms were given daily, diluted with about a quart of water, and of the oxygenated muriate of pot-afh from fix to fixteen grains four times a-day. No external applications were employed, but milk and water, or a very dilute folution of the cerufla acetata, merely to keep the parts clean. At the time this publication went to prefs, no relapfes had taken place, although fome of them had been cured upwards of three months. z Annals of Medicine for the Year 1796. Exhibiting a concife View of the lateft and moft important Difcoveries in Medicine and Medical Philofophy. By Andrew Duncan, Sen. M. D. and Andrew Duncan, Jun. M.D. Fellows of the Royal College of Phyficians, Edinburgh, Vol. I. o€tavo, 469 pages. Edinburgh, printed for Mudie and Son, and for » Robinfons, London, 1796. The Medical Commentaries of the elder Dr. Duncan, in twenty volumes, publifhed at Edinburgh, are well known to the public. The Annals of Medicine are offered as a con- tinuation of that work, from which the plan will not materially differ. The editors, from whofe preface I give this account, expect that, when peace fhall be again eftablifhed, their accounts of foreign medical literature will be fuperior to what the Englifh reader has been hitherto accuftomed to receive. Reflecting practitioners are invited to ufe this work occafionally as a channel of public communication of fuch practical obfervations and faéts as they may think worthy of being fo diffufed. Thefe may be tranfmitted either to Dr. Duncan of Edinburgh, or Dr. Pearfon of Leicefter Square, London. The volume confifts of four fe&tions. The firft contains analyfes of books, twenty in number; the fecond, medical obfervations or cafes; the third, medical news; and the fourth, a lift of new books. ’ Profeffional men will not require to be informed of the utility of publications of this nature ; and there is no queftion refpeéting the ability of the editors. If it were practica- ble, with confiftent brevity, to give any analyfis of the contents of fuch a work, it would on» thefe accounts be the lefs neceffary to make the attempt. I fhall therefore only remark, that the number of new and interefting articles in this volume is confiderable. ~= A Narrative of the fuccefsful Manner of cultivating the Clove-Tree, in the Ifland of Do- minica, one of the Windward Charibbee Iflands. By William Urban Buée, Efq. London, printed 1797. Quarto, 31 Pages, with an Engraving of the Clove-Tree, and fome Implements for planting it. No bookfeller’s name, nor price known, This pamphlet was printed by order of the Privy Council, in confequence of a Report from the Right Hon. Sir Jofeph Banks, Bart. to whom it was referred, as appears in a letter from that gentleman to the Earl of Liverpool, which forms part of the Appendix. From that communication it appears, that Mr. Buée is the firft perfon who has obferved that 3 the 283 Plantation of the Clove-Tree. the pimento tree profpers beft in thofe fterile foils where trees whofe wood is of a hard texture abound, and that fugar cannot be cultivated to advantage in fuch places; and alfo, on the other hand, that where trees whofe wood is foft are naturally found, pimente trees are rarely met wih, and fugar plantations will fucceed. Mr. Buee obferves, that in the Weft Indies, particularly in Dominica, moft lands facing the eaft are of a yellowith or reddith {tiff clay ; a foil which, with few exceptions, is hardly fit for any cultivation, but is productive of the hard wood trees. Partly by the obfervation of incidents which prefented themfelves, and partly from a rational procefs of inveftigation of the fubje¢t, the author has applied thefe facts to the clove-tree, which is of a hard clofe grain, though not fo tough as the pimento. In the Moluccas, where the clove-trees growy the ground is coyered with them, and will not admit the culture of any thing elfe. It was not, however, till after a number of experiments, during a feries of years, that he arrived at the poffeflion of feveral bearing clove-trees. The hiftorical account of his proceedings with regard to the beft method of planting the tree, and of rendering the cloves merchant: able, is intelligent and clear. For this, however, I muft refer the reader to the work itfelf. Mr. Buee has alfo fucceeded in propagating the cinnamon-tree, of which he poflefles a great number, and promifes to make it the fubje& of his future, remarks, Thefe obfervations, to ufe the words of Sir Jofeph Banks, open to the cultivators of hot climates a new fource of wealth, which will not probably be confined to the growth of cloves. Other {pices may alfo profper beft in the barren foils of the Weft Indies, as la- vender, thyme, and other aromatic plants are known to do in thofe of Europe. Befides the letter of Sir Jofeph Banks, the Appendix contains a lift of the ufeful plants cultivated in the Royal Gardens at the Ifle of France in 1790; and a letter from Mr. Rutton of Charing-Crofs, exprefling the uniform opinion of feveral eminent grocers, that certain famples of Mr. Buée’s cloves, forwarded to the Council by Sir Jofeph, will anfwer every culinary purpofe as well as thole of the Spice Iflands in the Eaft Indies. SSDWSISGIISDIIIOVPVOSGS eae mf ol plea le. tintig lage 2% ty i r < , , : ’ { (e 5 SON DY Be 2 ¢ | wilh Sol haret t - ri Lie Latics Figs pir A JOURNAL OF NATURAL PHILOSOPHY, CHEMISTRY, AND THE: ARTS: eles Attlee syed ld a te ai OCTOBER 1707. So ——— ART CLE 1. An Account of the Manner in which Heat is propagated in Fluids, and its general Confequences in the Economy of the Univerfe. By Benyamin Count of Rumrorp*. HE do€trine of heat is of fuch fingular importance, not only in the experiments of phi- lofophers, but in the whole economy of animated and of inanimate beings, that at firft fight it appears wonderful the greateft part of the difcoveries relative to this natural power fhould have been made by our cotemporaries. Not many years ago, our knowledge amounted to little more than that bodies, by the communication of heat, acquire a common temperature ; a faét which, fimply expreffed, denotes nothing more than that there is a ftate of equilibrium, at which two bodies may be in contaét, without the communication of heat from the one to the other; and again, that the communication of heat is more rapidly effected through fome bodies than through others. The difcoveries of Doors Black, Irvine, Crawford, and others, have taught us, that when bodies equal in weight or bulk, or alike in any other attribute (their intimate nature or compofition excepted), are brought into contaét, they do not, by acquiring the common temperature, occafion an equal change in the fenfible heat of each. In fome in{tances the heavier body muft part with a greater number of degrees of its temperature before an equilibrium of communication be- comes eftablithed between itfelf and a lighter body; and in other inflances the contrary will be the cafe. If, therefore, water be ufed as a ftandard, and applied in like tempera- tures and circumftances to different bodies, the common temperature will differ accordingly as the bodies themfelves require a greater or lefs portion of heat to occafion fimilar changes * Abftraé or abridgement from his writings, chiefly the VIIth Experimental Effay. Vor, I.—Ocrozer 1797. Pp in 290 General Doéfrine of Heat. in their fenfible heat. Thefe important refults conftitute the foundation of the theory of the different capacities of bodies for heat, or their fpecific heats when at the fame tem- perature. Another difcovery, of no lefs ageiniadie't feemed to render us acquainted with the prin- cipal caufes by which the mutations of temperature are originally effected. It was found by experiment, not only that different bodies require greater or lefs quantities of heat to be communicated in order to raife their temperature through equal numbers of degrees, but alfo that the capacity of any individual fubftance is leaft when in the folid ftate, greater in the fluid ftate, and greateft of all when converted into elaftic vapour or air. So that, asa natural confequence, a much greater portion of hear will bé required to convert ice into water, and raife its temperature ten degrees, than would have been neceflary to have equally elevated the temperature of cold ice without melting it. And fo likewife the vaporiza- tian of water, without raifing its temperature beyond the boiling-water point, requires a much larger quantity of heat than would have heated the fame a of water from the freezing to the boiling point. A great number of interefting dedutions, from thefe fds, have-been applied to explain the general mutations of heat in_ the univerfe around us. For, in the firft place, fince every change of chemical combination is attended with a greater or lefs change of the ca- pacities of the aggregate, it almoft invariably happens that the temperature of the new compound is either above or below the common temperature of the atmofphere ; and as the fufibilities of thefe compounds are alfo affe€ted according to laws of which at prefent we know nothing, there is very frequently a change of temperature on this account alfo. Such is the moft luminous and beautiful theory of heat which our cotemporaries have begun to develop, and which is at prefent explained at confiderable length in moft ele- mentary works. But as this fubje€t appears to depend upon fats fcarcely capable of being extended farther by hypothefis or analogical reafoning, it has happened that induétions experiments and applications, though of the greateft value, haye been but flowly made. The effeét of chemical operations on the temperature of bodies has been applied with great fuc- éefs to explain the at of combuftion; and the general confequences of the change of capacity in the folid, fluid, and vaporous ftates have been confidered with regard to their extenfive influence upon the face of the globe. But thofe refults which originate chiefly from the differences of conducting power in, bodies with regard to heat, have {carcely con- ftituted an objeét of dire& enquiry among philofophers, excepting by Count Rumford in the Philofophical Tranfaétions, and in his Experimental Effays, at prefent in the progrefs of publication. On the prefent occafion I fhall not enter into the confideration of the extenfive economical ufes to which this philofopher has applied the refults of his experiments and deductions, but fhall chiefly confine the prefent memoir to the confequences which he has fhewn to arife from the imperfect condu€ting power of fluids with regard to heat. ’ "The free paflage of heat, in all direétions, through all kinds of bodies, has never yet been called in queftion, though the rapidity of its tranfmiffion is well known to differ exceedingly in various kinds of bodies. Under the influence of this opinion Count Rumford began his experiments on heat. His former experiments fhewed that air is a non-conduétor of heat; and the late experiments contained in his feventh Effay afcertain that water is in the fame predicament. He thinks that all other fluids have the fame property.. He was led i to Curious Effetis-of the Mmnper fect Ti ranfinifion of Heat. 29% to\an experimental inveftigation of this curious fubjeé&t by certain accidental events which he relates. ‘Thefe thewed, that when-the circulation of water is impeded by mucilage or by fibrous matter, as in apple-pie arid thick rice-foup, the heat is not only a long time in efcap. ing, but may be very confiderable in one part of the mafs, while other parts are nearly cold. The baths of Baia afforded another inftance of the fame nature, which is very ftriking. When the Count was ftanding on the fea-fhore, near the baths, where the hot fteam was iffuing out of every crevice of the rocks, and even rifing up out of the ground, he had the curiofity to put his hand into the water. He was not furprifed to find that the waves of the fea, which inceffantly followed each other over the beach, fhould feel cold; but he was more ‘than furprifed when, on running the ends of his fingers into the fard beneath the water, he found the heat quite intolerable. The fand was perfectly wet, and yet the temperature was fo very different at the finall diftance of two or three inches !_He even found that the furface of the fand was to all‘appearance quite as cold as the water which flowed over it. He could not reconcile this to the fuppofed great conduing power of water; and then, for the firft time, in confequence of his doubts refpe€ting the exiftence or intenfity of this power, he determined to make experiments to afcertain the fa&. Thefe however were delayed, and probably might have remained undone, if another unexpected appearance had not revived his curiofity. ; In the courfe of a fet of experiments on heat, Count R. had occafion to ufe thermome- tets of uncommon fize, their globular bulbs being above four inches in diameter filled with various liquids. One of thefe, containing alcohol much heated, was placed ‘in a win- dow where the fun happened to be fhining; when, cafting his eyes on the tube, which was guite naked, and divided by means of a diamond, he faw the whole mafs of its contents in a moft rapid motion, in two oppofite dire€tions, up and down at the fame time. Thefe motions were rendered vifible by fome particles of fine dutt that happened to be in the ball before it was filled. The tube. was sosths of an inch in diameter 3 and upon examina- tion with a lens, the rifing current of fpirit was feen to occupy the axis or internal part of the tube, and the defcending ftream was contiguous to the fides. When the tube was in- clined, the rifing current occupied the uppermoft fide, and the defcending ftream the lower, The velocities were perceptibly increafed by wetting the tube with ice-cold water ; they became gradually lefs as the thermometer Was cooled, and ceafed when the fluid had ac- quired the common temperature of the room; and the motion was greatly prolonged when the cooling of the bulb was impeded by wrapping it in furs or any other warm covering, The fame experiments, with motion of the fame kind, and quite as rapid, were repeated with a fimilar thermometer filled with linfeed-oil. j From thefe faéts Count Rumford was led to conclude that the fluids he had tried, and probably all others, are in fact non-conductors* of heat; that they tranfmit this matter * Throughout this moft valuable effayy the author fpeaks of fluids, and particularly water, as perfe? non- condultors of beat; which feems to me to be an inaccurate expreffion of the fats. His experiments, hereafter to be related, may prove that the direé communication of heat through a line of particles of a Auid, on the fup- pofition of their continuing immoveable, is extremely flow; but not that it does not take place. If each indi- vidual particle were not capable of receiving and giving heat, the Procels by circulation could not happen; and if on the contrary they be capable, the propagation of heat from particle to particle is poflible, and mutt doubtlefs happen; though from the fats it appears that the heat conveyed by the internal motion is very much greater thanwhat paffesin thi¢ Way Fluids then are very imperfeét conductors of heat, bitnot perfect non-condudtors: N, Pr p 2 or 292 Methed of meafuring the condudting Powers of Fluids, oy quality, by aQual motions, from the heated to the cold bodies with which they may fuc+ ceflively come into contact; and that.every means of obftructing or retarding thofe motions would render the propagation of heat more flow and difficult, Hehad before found that this was actually the cafe with air, and on the prefent occafion he proceeded to give the {ub- jet athorough and careful inveftigation. The apparatus made ufe of for the firft courfe of experiments confifted of a large ther- mometer, which he calls the paflage thermometer, confifting of a cylindrical veffel with he- mifpherical ends, forming the bulb, anda glafs tube fitted into a neck by means of a good cork. Its dimenfions were as follow :—Diameter of the bulb 1.84 inches—Length 4.99— Capacity or contents 13.2099 cubic inches—External fuperficies 28.834 fuperficial inches —Thicknefs of the fheet copper 0.03 inch— Weight when empty 1846 grains, and it con- tains 3344 grains of water at 55° of temperature. The glafs tube is 24 inches long, and fsths of an inch in diameter, and the cylindrical neck of copper into which it is fitted by means of cork is one inch long, and ,&dths of an inch in diameter. This thermometer, being filled with linfeed-oil, and its feale graduated, was fixed in the axis of a hollow cylinder of thin fheet copper, 114 inches long, and 2.3435 inches in dia- meter internally. This cylinder, which is open at one end, is clofed at the other with an hemifpherical bottom with its convex fide outwards. The bulb of the thermometer was confined in the axis of this cafe, by three fmall wooden pins, inferted in fockets within the large brafs tube, and the upper end was properly fecured by caufing the glafs tube to pafs through a cork ftopper adapted to the fame metallic cylinder. The bottom of the bulb re{ted on a wooden pin fixed in a focket in the. middle of the hemifpherical bottom of the cafe. All the pins terminated in blunt wooden points, to reduce ‘the contaéts as much as poflible. The {pace between the thermometer when in its place, ana the internal furface of the furrounding cylinder, was defigned to contain the fubftance through which the heat was made to pafs into or out of the thermometer; the temperature of this aft mafs being fhewn by the graduations on the glafs tube. The quantity of water required to fill the fpace, and cover the bulb of the thermometer about one quarter of an inch, was found to weigh 2468 grains. When the bulb of the thermometer was furrounded i in its place by water or any other liquid or mixture intended to be tried, a cylinder of cork, rather lefs in diameter than the internal cavity, was flipped down upon the tube, not quite fo low as the water or mixture.’ Above this was placed a quantity of eider-down, fufficient to fill the remaining cavity, ex- cept what was occupied by the cork ftopper, laft of all to be inferted. ‘The thermometer was divided according to Fahrenheit’s {cale, and the whole {cale, ote the freezing point to the boiling-water point, was above the ftopper. The operations with this apparatus were performed by placing the prepared inftrument in melting ice till the thermometer fell to 32°. It was then immediately plunged into a large veffel of boiling water, and the conducting power of the fub‘ance under examination was eftimated by the time the heat employed in pafling through it into the thermometer; the time being carefully noted when the liquid in the thermometer arrived at the goth degree of its feale; and alfo when it came to every 2oth degree above it. In the reverfe operation, the inftrument was kept in boiling water till its temperature appeared iy Experiments refpecling the Tranfition of Heat through Fluids. 293 appeared ftationary, when it was taken out, and immediately plunged in melting ice, and the times of its defcent carefully noted. As foon as this apparatus was completed, the Count was defirous of afcertaining whether apples which continue hot fo long in pies mrade of that fruit, do really poffefs a power of retaining heat greater than that of pure water, of which for the moft part they confit; but in the firft place he afcertained the quantity of fibrous matter in apples, by ftewing two ounces troy of the pulp, and wafhing off the foluble matter with a large quantity of cold water. ‘The fibrous remainder, when thoroughly dried, weighed only 25 grains, which, by remaining for feveral days in a plate on the top of a heated German ftove, was further re- duced to 18;°cths, or lefs than 1-soth part of the whole mafs. The refults obtained by furrounding the bulb of the paflage thermometer with a quantity of ftewed apples, fo confiftent as not to exhibit figns of fluidity, and then expofing the ap- paratus to the heating and cooling procefles, are tabulated in the original Eflay. The con- ducting power of the ftewed apples proved to be little more than half that of pure water; that is to fay, the heat was nearly twice as long in palling through the former as the latter. As the attention of our author was fteadily fixed on the pofition that heat is communi- cated by fluids, only by its being tranfported by virtue of their inteftine motion produced by the change of fpecific gravity, he concluded that there may be two ways of ob/tructing this propagation of heat ; namely, by diminifhing their fluidity, which may be done by folution of any mucilaginous fub{tance; or, more fimply, by impeding the motion of their particles, which may be effected by mixing any folid fubftance with them which is an imperfect conduétor of heat, and of an enlarged furface by being divided into fmall mafles. In the experiments with ftewed apples, the paflage of the heat in the water, which con- ftituted by far the greateft part of the mafs, was doubtlefs ob{tructed in both thefe ways. The mucilaginous part of the apples diminifhed very much the fluidity Sy the water, at.the fame time that the fibrous parts ferved to embarrafs its motions. In order to difcover the comparative effe€ls of thefe two caufes, water was boiled with about 1-12th part of its weight of ftarch, and:examined by the apparatus. The fame weight of eider-down was alfo boiled with a like quantity of water. The intentioi of this laft boiling was to free the eider-down from water. From the tabulated experiments, it appears that thefe feveral additions impaired the condu€ting power of water nearly to a degree of equality with the ftewed apples. In the Philofophical Tranfaétions for 1792, where Count Rumford has afcertained that heat is actually propagated in air in the fame manner as it is here ftated to be propagated in water, he found that the thicknefs of a {tratum of air, which ferved as a barrier to heat, re~ maining the fame, the paflage of heat through it was fometimes rendered more difficult by increafing the quantity of the light fubftance, which was mixed with it to obltrué its in- ternal motion. ‘To fee if fimilar effe€ts would be produced with water, he repeated the experiménts with eider-down, reducing the quantity of it mixed with water to one-fourth of the quantity ufed in the former experiments. ‘he refiftance to the paflage of heat was confiderably diminifhed. The refults of thefe experiments are extremely interefting; they not only make us ac- quainted with anew and very curious fact, nz ramelys that feathers, and other like fub{tances, which 294 Advantages enjoyed by the Individuals of the Vegetable Syflem from which in air are known to form very warm coverings for confining heat, may ferve the fame purpofe in water, but that their effedls in preventing the paflage of heat are even greatet in water than in air. ‘This difcovery is very happily applied by the Count to elucidate fome of the molt sntereft- ing parts of the economy of nature, on which fubject I fhall give his inferences very nearly in his own words. ; As liquid water is the vehicle of heat and nourifiment, and’ confequently of life in every living thing; and as water, left to itfelf, freezes with a degree of cold much lefs than that which frequently prevails in cold climates, it is agreeable to the ideas we have of the Creator of the world, to expeét that effeQual meafures would be taken to preferve a fufficient quan- tity of that liquid in its fluid fate, to maintain life during the cold feafon : and this we find has achually been done; for both plants and animals are found to furvive the longeft and mot fevere winters: but the means which have been employed to produce this admirable cffeGt have not been inveftigated ; at leaft not’as far as they relate to vegetables. But as animal and vegetable bodies are effentially different in many refpedéts, it is very natural to fuppofe that the means would be different which are employed to pteferve thent againtt the fatal effeéts which would be produced in each by the congelation of their fluids. Among organized bodies which live on the furface of the earth, and which of courfe are expofed to the viciflitudes of the feafon, we find, that as the proportion of fluids to folids is greater, the greater is the heat which is required for the fupport of life and health; and the lefs are they able to endure any confiderable change of their temperature. The proportion of fluids to folids is much greater in animals than in vegetables; and in _ order to preferve in them the great quantity of heat which is neceffary to the prefervation of life, they are furnifhed with lungs, and are warmed by a procefs fimilar to that by which heat is generated in the combuftion of inflammable bodies. Among vegetables, thofe which are the moft facculent are annual. Not being furnifhed with lungs to keep the great mafs of liquids warm which fill their large and flender veffels, they live only while the genial influence of the fan warms them, and animates their feeble powers; and they droop and die as foon as they are deprived of its fupport. ‘There are many tender plants to be found in cold countries which die in the autumn, the roots of which remain alive during the winter, and fend off frefh fhoots in the enfuing fpring. In thefe we hall conftantly find the roots more compact and denfe than the {talk, or with fmaller veffels and a fmaller proportion of fluids. Among the trees of the foreft, we fhall conftantly find that thofe which contain a great proportion of thin watery liquids not only fhed their leaves every autumn, butare fometimes frozen and aétually killed in fevere frofts. Many thoufands of the largeft walnut-trees were killed by the froft in the Palatinate during the very cold winter in the year 17885 and it is well known that few, if any, of the deciduous plants of our temperate climate would be able to fupport the exceflive cold of the frigid zone. The trees which grow in thofe inhofpitable climates, and which brave i cold of the fevereft winters, contain very little watery liquids. The fap which circulates in their veffels is thick and vifcous, and can hardly be faid to be fluid. Is there not the ftrongeft reafon to think that this was fo contrived for the exprefs purpofe of preventing their being deprived of all their heat, and killed by the cold during the winter? , “ We ’ ~ the flow Tranfition of Heat through Fluids confined by Fibrous Matter. 205 We have feen by the foregoing experiments, how much the propagation of heat in a liquid is retarded by diminifhing its fluidity; and who knows but this may continue to be the cafe as long as any degree of fluidity remains ? As the bodies and branches of trees are not covered in winter by the fnow which protects their roots from the cold atmofphere, it is evident that extraordinary meafures were ne- ceflary to prevent their being frozen. The bark of all fuch trees as are defigned by nature to fupport great degrees of cold, forms a very warm covering ; but this precaution alone would certainly not have been fuflicient for their protetion. The fap, in all trees which are ca- pable of fupporting a long continuance of froft, grows thick and vifcous on the approach of winter. What more important purpofe could this change anfwer, than that here indicated? And it would be more than folly to pretend that it anfwers no ufeful purpofe at all. We have feen by the refults of the foregoing experiments, how much the fimple em- barraflment of liquids in their internal motions tends to retard the propagation of heat in them, and confequently its paflage out of them: and when we confider the extreme fmall- nefs of the veflels in which the fap moves in vegetables, and particularly in large trees ;— when we recollect that the fubftance of which thefe {mall tubes are formed is one of the beft non-condutors of heat known *;—and when we advert to the additional embarraflments to the paffage of the heat which arife from the increafed vifcofity of the fap in winter, and to the almoft impenetrable covering for confining heat which is formed by the bark, we fhall no longer be at a lofs to account for the prefervation of trees during the winter, notwith- ftanding the long continuation of the hard frofts to which they are annually expofed. On the fame principles we may, I think, account, ina fatisfatory manner, for the preferva- tion of feveral kinds of fruit; fuch as apples and pears, for inftance, which are known to fupport, without freezing, a degree of cold which would foon reduce an equal volume of pure water to a folid mafs of ice. ; At the fame time that the compaé fkin of the fruit effe€tually prevents the evaporation of its fluid parts, which, as is well known, could not take place without occafioning a very great lofs of heat, the internal motions of thofe fluids are fo much obftructed by the thin partitions of the innumerable fmall cells in which they are confined, that the communica- tion of their heat to the air ought, according to our hypothefis, to be extremely flow and dificult, Thefe fruits do, however, freeze at laft, when the cold is very intenfe; but it muft be remembered that they are compofed almoft entirely of liquids, and of fuch liquids as do not grow vifcous with cold; and moreover that they were evidently not defigned to fupport for a long time very fevere frofts. \ Parfnips and carrots, and feveral other kinds of roots, fupport cold without freezi+* fill * I lately by accident had occafion to obferve a very ftriking proof of the extreme difficulty with which heat paffes in wood, ‘ Being prefent at the foundry at Munich when cannons were caflings I obferved that the founder ufed a wooden inftrument for ftirring the melted metal. Jt was a piece of oak plank, green, or unfeafoned, about ten inches fquare, and two inches thick, with a long wooden handle, which was fitted into a hole in the middle of it. As this inftrument was frequently ufed, and fometimes remained a confiderable time in the fur- nace, in which the heat was moft ihtenfe, 1 was furprifed to find that it was not confumed ; but Iwas {till more furprifed, on examining the part of the plank which had been immerfed in the melted metal, to find that the heat had penetrated it to fo inconfiderable a depth, that at the diftance of one-twentieth of an inch below its furface the wood did yor feem to have been in the leatt affeéted by it. The colour of the wood remained un- changed, and it did not appear to have loft even its moiftuue. R. longer -. 296 L Fulminating Gold and Silver. longer than apples and pears; but thefe are lefs watery, and I believe the veflels in which their fluids are contained are fmaller: and both thefe circumftances ought, according to our aflumed principles, to render the paflage of their heat out of them more difficult, and’ confequently to retard their congelation. [To be continued.] II. Experiments and Obfervations on the fulminating Preparations of Gold and Silver ™. HE bett procefs for the preparation of fulminating gold being fhewn; the principles furnifhed by the acids during the folution of the gold, and thofe furnifhed by the ammoniac during the precipitation, and the order neceffary in the application of them, were con- fidered, and divers experiments were related, by which it appeared that this fubftance con- fits of oxygen, azote and hydrogen feverally pambines with caloric, and feverally attached to the gold as a common bafe. Twelve grains of this fulminating gold being placed in a conical heap on a thin plate ms brafs, were gradually heated. At a temperature between 300 and 400°, the whole exploded, with a very fharp and loud report, and the plate was pierced and torn. The round aperture was about an inch in diameter, and the lacerations extended much farther. It was obferved that the fame effe& might be produced by applying a {park to fulminating gold lefs heated, and that the accenfion of all fuch fulminating compounds, by a fpark ap- plied to any part, or by due augmentation of the temperature of the whole, is eafily expli- cable on the grounds mentioned inthe minutes of the laft meeting, provided aay attention be paid to the ftate of the active ingredients. In fulminating gold, for inftance, the attractive powers tending to produce the new com- binations, which take place in the inftant of combuttion, feem to be almoft equal to thofe by which the aggregation of this compound is maintained at low temperatures. For a {mall augmentation of temperature, or fri€tion, or percuflion, or any thing which difturbs the ar- rangement of the gafeous principles and caloric which adhere but weakly to the gold, is fuf- ficient for the explofion of the whole, provided the fulminating gold be pure and dry. In refpeét to the perforation of the brafs plate, it was obferved that all bodies which ex- plode inftantaneoufly would imprefs it in a fimilar manner. For the refiftance of the air to projectiles or to expanfions of this kind, being in the ratio of the fquares of the velocities of the moving or expanding bodies, the refiftance of the air to fuch inftantaneous explofions as thofe lately mentioned, is almoft equal to that of a folid, or of the metallic plate on which the fulminating body js heated. SMALL portions of Aybnineing filver, Aes weighing lefs than a grain, were fucceflively exploded, fome by the touch of a flender brafs wire, others by that of a feather. * From the Minutes of a Society for Philofophical Experiments and Communications: B. Higgins, M.D. ° Operator. I do not hear that the fociety is continued fince the departure of the able Operator for the Weft- Indics. WN. A defcrip- Experiinents on Fulminating Silver. - 27 A defeription was given of many other fpecimens which had been inadvertently exploded and loft; fome by overheating them to about go°, in the place where they were to be dried; and others by an accidental concuffion of a great iron plate, on which they were placed in feparate cups. The experimenter faid, that he had often exploded fulminating filver, in covered veffels of the {malleft capacity that could be ufed with fafety; and that this fubftance had frequently exploded unexpectedly in his hand, with a report louder than that of a mutket. A luminous and momentary gleam was always vifible, but he could not difcover any other adequate effe@ of the emitted caloric ; and therefore he concluded, that in fuch inftantaneous explofions the caloric was expelled with velocity fuflicient to conftitute light. Mr. Berthollet, the inventor of fulminating filver, having contented himfelf with a general and concife defcription of this fubje&, many practical chemifts have failed in their attempts to prepare it; and others, forming their opinions from the fpecimens which they had made, have been expofed to great danger ; as will appear from the following relation, which is the only part of the Minutes on this fubjeét that can be introduced in the prefent publication. An ounce of fine filver was diffolved in the courfe of eight hours in an ounce of pure nitrous acid, of the London Pharmacopceia, diluted previoufly with three ounces of diftilled water, in a glafs matrafs. The folution being poured off, the refiduary black powder and the matrafs were wafhed with fever or eight ounces of warm diftilled water, and this was added to the folution. “The black. powder being gold was rejected; fome ea being thus feparable from any filver of commerce. To the foregoing diluted folution, pure lime-water prepared with diftilled water was added gradually ; for the folution ought not to be poured into the lime-water. ‘When about thirty pints of lime-water had been expended, and the precipitate had fubfided, more lime- water was added, by fucceflive pints, as long as it caufed any precipitation: For it was deemed fitter that the precipitation fhould not be perfeéted, than that an excefs of lime- water fhould be ufed ; the earthy pellicle of the exceflive lime-water being apt to mix with the precipitate. The clear liquor being poured! away, the precipitate was poured off, and wafhed into-a filter. : When the faline liquor had drained from it, two ounces of diftilled wate? were poured on the magma; and when this water had paffed, freth- portions were’ fucceflively added and pafled, until the whole quantity of water thus af tii in wafhing away the nitrous cal- ccareous falt amounted to a quart. The filter being then unfolded, to let the magma of otide of filver fpread on the flattened paper, it was placed on a chalk-ftone to accelerate the exficeation, and was gradually’ dried in the open air; a cap of paper being placed loofely over it to.exclude the duft. When the weather ferved, the cap was removed, to\expofe the oxide’ to the rays! of the fun; although this was not «leemed neceflary, ‘and’ the exficeation was promoted by cutting the oxide into thin flices. When perfeétly dry it weighed 1 oz. 4:dwts. and about one-fifth of it was. confidered as oxygenc. When aqua ammonie pure of any Pharmacopeeia is ufed with this oxide; either in the fmall-quantity which blackens it completely, on in a) greater quantity}: the black matter’. which fubfides; and which has been reprefented by fyitematic writers’ ag. the fulminating Vou. L.—Ocroser 1797. Q.4 compound, 298 Dangerous fulminating Compounds of Silver. compound, has no fuch property, any farther than may be owing to the matter depofited from the alkaline folution during the exficcation. “© The alkaline liquor containing the fulminafing filver ought to be poured off from the infoluble powder, and expofed in a fhallow veffel to the air. In confequence of the ex- halation; black fhining cryftals form on the furface only, and foon join to form a pellicle. As this pellicle adheres a little to the fides of the veflel, or maintains its figure, the liquor may be poured off by. gentle inclination of the veflel. “ This liquor will yield another pellicle in the fanie way ; but the third or fourth pellicle will be paler than the former, and weaker in the explofion. The firft pellicles, when flowly dried, explode by the touch of a feather, or by their being heated to about 96°. 3 “ The quantity of water in the ordinary aqua ammoniz pure renders it lefs ative in the folution of the oxide, and is an impediment to the fpeedy formation and feparation of the fulminating filver; and an experimenter who has often ufed twenty grains of the oxide to produce fucceflive pellicles of fulminating’ filver, which may be feparately exploded with fafety, and who has perceived that the pellicles never explode whilft wet, if they be not heated, would in all probability refolve on the following improvement, and expofe himfelf to the unforefeen danger of it.” DISTILLED water was impregnated with as much pure ammoniac as it could eafily re- tain under the ordinary temperature of the air. A quantity of this ftrong ammoniacal liquor, equal in bulk to a quarter of an ounce of water, was placed in a {mall bottle, and 24 grains of the oxide of filver, ground to fine powder, were added. The bottle, being al- mott filled, was corked, to prevent the formation of that film which ufually appeared in confequence of the exhalation of the ammoniac in other experiments, ; During the folution of the oxide, bubbles of the gafeous kind arofe from it, and the folu- tion acquired a blue colour. As no film appeared, the bottle was agitated three or four times in the courfe of as many hours, in order to promote the folution of a fmall quantity of blackened oxide which re- mained at the bottom. ‘The experimenter confidering this as an ample, provifion for twenty different charges, to be exploded in different circumftances, in the prefence of the fociety, intended to pour off the folution into as many fmall veffels, and to weigh the refiduary black powder, after al- lowing two hours more for the folution. On the fixth hour he took his ufual precaution of wearing fpetacles ; and obferving that a {mall quantity of black powder {till remained undiffolved, and that no film was yet formed at the furface, he took the bottle by the neck to fhake it; knowing that it might explode by the heat of his hand, if he were to grafp it, and that the explofion in this circumftance might wound him dangeroufly. In the inftant of fhaking, it exploded with a report that flunned him. The bottle was blown into fragments fo {mall as to appear like glafs coarfely powdered. The hand which held it was impreffed as by the blow of a great hammer, and loft the fenfe of feeling for fome feconds ; and about fifty-two {mall grains of glafs were lodged, many of them deeply, in Pulminating Siluer.—Decompofition of Vater by EleBricity. 209 in the fkin of the palm and fingers. The liquor ftained his whole drefs, and every part of the fkin that it touched. Thus it appeared that fulminating filver may be made which will explode even when cold and wet, by the mere difturbance of the arrangement of its parts, in the aqueous fluid. In fubfequent experiments, privately and carefully condu@ed, it feemed that the pro- perty of exploding in the cold liquor, by mere commotion, depended on the urufual quan- tity or proximity of the explofive molecules in a giyen bulk of the liquor. And the flat bottoms, as well as the fides, of the thick veflels of glafs or potters-ware, whether they ftood on boards or on iron plates, were always beaten to {mall fragments. This afforded a curious inftance of the poffible équilibrium between. the powers tending to retain the caloric, and thofe which effet the expulfion of it; and experiments and con- fiderations of this kind feemed to promife a true folution of the phenomena of Rupert’s drops. SMALL charges, each confifting of a grain of oxygenated muriate of ‘pot-ath, finely powdered, and mixed with an equal quantity of flowers of fulphur, were exploded by mere trituration. And Mr. Godfrey’s relation of the danger of keeping fuch a mixture ‘in a bottle was duly noticed ; for, after he had kept it thus for fome time, he found that it had exploded fpontaneoufly. — i Ill. Experiments and Obfervations made with the View of afcertaining the Nature-of the Gaz pro- duced by paffing Eleétric Difcharges through Water ; with a Defcription of the Apparatus for thefe Experiments. By Gzorcz Pearson, M. D. F.R.S. {Continued from page 248.] SC DO Ni EXPERIMENTS. From my Journal of the numerous experiments made during the courfe of nearly twe years, I hall fele& thofe which will ferve to explain the nature of the procefs, and fhew the power of the plate electrical machines ; and I fhall particularly relate thofe experiments which afforded the moft ufeful refults concerning the nature of the gaz obtained. 1. With interrupted Difcharges. Experiment A. About 1600 of thefe difcharges by means of a 34 inch fingle plate electrical machine, in nearly three hours, produced, from New River water taken from the ciftern, and which had not been freed from air by the air pump or boiling, a column of gaz, two-thirds of an inch in length, and 1-gth of an inch wide. On pafling through this gaz, between the two wires of the tube in which it was produced, a fingle eleétrical {park, its bulk was inftantly diminithed to two-thirds. In other experiments the bulk of gaz was only diminifhed to about one half. And the refult was the fame with diftilled water. , Q.q2 B. The a 300 Experiments and Objervations made avith the View of afcertaining B. The experiment A being repeated feveral times with di(tilled, and New River water; freed from air by the air pump or long boiling, the quantity of gaz juft mentioned was ob- tained in about four hours. On pafling an eleétric {park through this gaz in the fituation above mentioned, its bulk was inftantly diminifhed in fome cafes 15-16ths, and in others 19-20ths. C. 1600 interrupted difcharges, by means of a 32 inch plate machine, produced from New River water, and diftilled water, freed from their air by the air pump, a column of gaz, about 3-4ths of an inch in length and. 1-oth of an inch in diameter, in the fpace of three hours. It was reduced in bulk 19-20tlis by paffing through it a fingle eleétrical fpark. D. soorevolutions of the 32 inch plate machine, in three quarters of an hour, produced €0o interrupted difcharges in river water freed from air by the air pump, by which a column of gaz, half an inch in length and 1-roth of an inch in diameter, was obtained. It was diminifhed as ufual by an eleétric fpark 19-2oths of its bulk. y E, . Nearly four days inceffant labour with the 32 inch machine produced only 56,5488 cubes of gaz, of 1-10th of aninch each, on account of the ufual accidents during the pros cefs. ‘The air had been exhaufted by fetting the water under the receiver of the air pump. F. It was found that 6000 interrupted difcharges produced about three inches in length | of gaz, meafured in a tube 3-20ths of an inch in width from water out of which its air had been drawn by the air pump. : G. Itappeared from many experiments, that the fame unboiled water, or water from which the air had not been exhaufted by the air pump, which had repeatedly yielded gaz by pafling through it electrical difcharges, always left a refidue of gaz which the elec- trical {park did not diminifh; and this refidue was in nearly the fame quantity after fix or feven experiments, each of which afforded a column of gaz half an inch in length and oth of an inch in diameter, as was left on pafling the ele@tric {park through the gaz afforded by the third or fourth experiment.“ ~ Hence it feems that water is decompounded by the ele@tric difcharge, before the whole of the common or atmofpherical air is detached from the water by merely the impulfe of each difcharge. Yet I think it probable that, after the difcharges have been paffed through the fame water for a certain time, the whole of the air contained in water will be expelled, and no gaz be produced, but that compounded by means of the electric fire from water ; in which cafe, fuppofing the gaz fo produced to be at leaft merely hydrogen and oxygen gaz, it will totally difappear on paffing through it an electrical fpark. But I have never been able to determine this point, becaufe the tubes were always broken after obtaining a few products, or long before it could reafonably be fuppofed the whole of the air of the water was ex- pelled from it. ‘ ; H. To the gaz obtained in the experiment E was added, over water, an equal bulk of almoft pure nitrous gaz. Fumes of nitrous acid appeared, and the gaz examined was re- duced almoft one-third of its bulk. A: fmall bubble’ more of nitrous gaz being let up, no further diminution took place. To this refidue was'added half its bulk of oxygen gaz, ob- tained from oxy-muriate of pot-afh. “Chis mixture of gazes having ftood feveral days over well burnt lime and boiled quickfilver, an ele&tric fpark was paffed through the mixture over quickfilver, by which its bulk was in{tantly diminifhed one-fourth. But no moifture could be perceived’ upon the fides of the tube or.on the quickGlver. The failure of the appearance tps of the Nature of the Gaz produced by paffing Eleftric Difcharges through Water. jor of moifture was imputed to’a bit of lime accidentally left-in the tube which was burft by the explofion, and difperfed through the tube; or elfe the quantity of water produced was fo - fmall, comparatively with the refiduary gaz, that the water was diffolved by it in the moment of its compofition. For, fuppofing water to have been compounded, it could not amount to the r-rooth part of a grain, and the refiduary gaz was at leafl 2000 times this bulk. That a quantity of water can be compounded under the fame circumftances as in this ex- periment, and be apparently diffolved in air, fo as to efeape obfervation, even with a lens, was proved by paffing an electric fpark through a mixture of hydrogen and oxygen gaz, well dried by ftanding over lime. 2. With complete or uninterrupted Difcharges. ~ THE gaz obtaine| by the firft defcribed kind of apparatus for the uninterrupted dif. charges, p. 145, and Fig. 6, and 7, always left a refidue of at leaft one-fourth of its bulk, on pafling through it the eleétric {park ; even when water was ufed which had been freed from air by boiling or the air pump. — Nor will this refult appear furprifing, when it is con= fidered how liable the water in this apparatus is to mix and abforb air during the experiment. However, this method would have been extremely valuable, if: the next other method had not been difcovered; for gaz may be obtained by it with fewer accidents, and much more rapidly, than with the interrupted difcharges. ‘he apparatus is alfo much more eafily fitted up, and is more fimple. But I think it unneceflary to particularly relate any experiments, as they afforded the fame refults as thofe already defcribed, and as thofe next to be related. The following experiments were made with the apparatus defcribed p. 146, and fhewn. by Fig. 8, 9, and ro: Experiment I. At oh. 40' P. M. began to produce difcharges with a double plate twenty- four inch machine, in water taken from the ciftern 5 and at 12 h. 6’ P. M. of the fame day there had been written down 10200 difcharges, each of which occafioned air to afcend from the.bottom of the wire and brafs cup. The quantity of air obtained was now apparently about one-fourth of a cubical inch, and it occupied nearly half of the tube, the water in: which was by this time very muddy. iy After ftanding till the day following at noon, when the procefs was again commenced, it did not appear that any of the gaz had been abforbed by the water over which it ftood. At 2h. 35’ P.M. began to produce difcharges, and at 8h. P.M. had pafled 6636; which, together with thofe of the preceding day, amounted to 16,836. The tube was now 5-8ths full of gaz, and there feemed to be almoft half a cubical inch; for it was ob- ferved that the gaz was this day yielded at double the rate it had been the day before. This was accounted for from the diminifhed preflure upon the eleétric fire, by the tube con- taining gaz inftead of water. At this time, namely at 8 h. P. M.I was furprifed on the paffing of a difcharge by a vivid illumination of the whole tube, and a violent commotion within it, with, at the fame time, the rufhing up of water, inftantly to occupy rather more than 5-Sths of the {pace which had been occupied by gaz. ‘ The refidue of gaz was not diminifhed further by an eleétric {park ; and to the teft of nitrous gaz it appeared to be rather worfe than atmofpherical air, as it confifted of rather Jefs than one part of oxygen, and three parts of nitrogen or azotic gaz, 3 It 302 Experiments and Obfervatious made with the View of afcertaining It feemed as if the ele@trical difcharge had kindled the oxygen and hydrogen gaz of the de> compounded gaz, by flying from the bottom of the wire to the brafs funnel, fo that the fire returned into the tube where it paffed through the gaz. Or the combuftion might be oc- cafioned by a chain of bubbles reaching from the brafs difh to the furface of the water in tthe tube, which was fet on fire in its afcent, and thus produced combuftion of the whole of the gaz of decompounded water. That this phenomenon was from the combuftion here fuppofed, was in fome degree proved, by finding that the mixture of hydrogen gaz and atmofpherical air, under the fame circum{tances, was kindled in the fame manner. : Experiment I. With a double plate ele&trical machine, 24 inches in diameter, and a fimilar apparatus to that in the laft experiment, 14,600 difcharges produced at leaft one- third of a Gubical inch of gaz, While I was meafuring with a pair of compaffes the quan- tity of gaz produced, the points of them being in conta with the part of the tube occu- pied by gaz, I was again furprifed, on the pafling of a difcharge, by an illumination of the whole tube, and the rufhing up with confiderable commotion of water, to occupy about two- thirds of the fpace filled by gaz. The refiduary air was found, as in the former experiment, to be rather worfe than at+ mofpherical air. It was concluded that the points of the compaffes had attraéted ele€trical fire from the wire to the fides of the glafs, and thereby kindled the hydrogen and oxygen gaz of decom- pounded water. But to determine this queftion, I introduced into the fame tube a mixture of one meafure of oxygen and two meafures of hydrogen gaz, to occupy nearly the fame {pace in the tube as the gaz had occupied; then pafling an eleCtrical difcharge through it, no combuftion was excited ; but on pafling a difcharge, while the compaffes were in contact with the tube, as juft mentioned, an illumination and violent commotion were produced, with the rufhing up of water, to leave only 1-8th of the gaz as a refidue. On repeating this experiment with two meafures of atmofpherical air, and one of hydrogen gaz, combuftion could not be excited; nor with one meafure of atmofpherical air, and two of hydrogen ; but on adding to this laft mixture one meafure of oxygen gaz, the eleétrical difcharge produced the phenomena of combutftion juft mentioned, with the rufhing up of water, to occupy about two-thirds of the {pace which was occupied by the gazes. Experiment ILI. Waving pafled 12,000 difcharges through water, with the apparatus of the preceding experiment, and thereby obtained only one-fifth of a cubical inch of gaz; and having obferved that the quantity of gaz was not greater than it was when only 8000 difcharges had been paffed, and yet bubbles had been feen to be produced.on each difcharge, as copioufly, or more fo, by the laft three or 4000 difcharges, as before; I began to fufpect that part of the gaz had been deftroyed during the procefs, or had-been abforbed. While I was confidering how to account for this difappearance of gaz, and was at the fame time looking at the tube through which the difcharges were palling, I obferyed one of them to be attended with a diminution, inftantly, of about one-fifth of the gaz produced, and with a flight explofion. I was now fure, from this phenomenon, and from the unequal aug~ mentation of the bulk of the gaz at given times during the procefs, that combuftion had been excited feveral times before, not only in the prefent experiment, but perhaps in the former ones, without obferving it, I conceived that a gradual combutftion alfo very pro« bably the Nature of the Gaz produced by paffing Eledtvic Difcharges through Water. 303 bably took place in this procefs by the kindling of bubbles of gaz in their afcent through the water. I now perceived that the difcharges ought to be produced more flowly, or the tubes to be wider, to allow the bubbles to pafs quite through the water, in order to avoid the afcenfion of gaz during the procefs. My calculation, alfo, that 35 to 40,000 difcharges were requifite to produce one cubical inch of gaz from water containing its ufual quantity of common air, was_rendered much more vague by this afcenfion, fo often liable to be eccafioned. To the gaz which remained in the tube in this experiment was added an equal bulk of nitrous gaz; the mixture diminifhed to 1,5; and on adding to the.refidue half its bulk of oxygen gaz, and pafling through it the eleCtrical fpark, no accenfion or diminution of bulk was produced. Hence all the hydrogen gaz and oxygen gaz, produced by the decompo- fition of the water, had been burnt during the procefs; the oxygen gaz thus detected being eonfidered to be only that expelled from the water. Experiment IV. By means of electrical difcharges with the apparatus ufed in the pre- ceding experiment, I obtained gaz from New-River water, letting it up into a refervoir,. as foon as about 1-20th of a cubic inch was produced, till I had colle&ted 1-8th of a-cubic inch. To this was added an equal bulk of nitrous gaz, on which the mixture diminifhed to 1,25 and on the addition of a little more nitrous gaz, no further diminution took place. To this refidue half its bulk of oxygen was added; and this mixture of gazes being well dried, by ftanding over lime and boiled quickfilver, an eleétric {park was paffed through it, by which a diminution of one-fixth of its bulk took place. A little dew was then feen upon the fides of the tube where the quickfilver had rifen; and with the aid of a lens the fame appearance was'perceived on the part of the tube containing the refidue of gaz. It may now be expected, that 1 fhould have made the experiment with this apparatus on diftilled water, freed from its air, not only by long boiling or the air pump, but by fending through it feveral hundred eleétrical difcharges. It would alfo have been, to fome perfons, more fatisfactory, if the experiment had been made upon.a larger fcale, fo as to have pro- duced the combuftion of a much larger quantity of gaz, and confequently have produced a greater quantity of water. As, however, I apprehend, the, experiments contained in this paper, when well confidered by competent judges, will be found to explain the nature of the gaz procured from water by eleCtric difcharges; and as another very important fubje& de- mands my attention, the honour of more fplendid and convincing experiments mutt be re- ferved for other enquirers. If the fame facrifices be made by them, as have been made in performing the prefent experiments, I think it is fcarcely poffible but that ftill further light concerning the compofition of water fhould be procured, as well as concerning oils, alcohol, acids, &c.; to the inveftigation of the compofition of which, the mode of analyfis and fyn~. thefis here indicated may be applied, : P SEC TION + tk On the Mode of Aétion of EleSric Difcharges. THE mere concuflion by the eletric difcharges, appears to extricate not only the air dif- folved in water, which can be feparated from it by boiling and the air pump, but alfo that which 304 Nature of the Gaz extricated from Water by Electricity. which remains in water, notwithftanding thefe means of extricating it have been em ployed. The quantity of this air varies in the fame, and in different waters, according to circum- ftances. New-River water from the ciftern yielded one-fifth of its bulk of air, when placed by Mr. Cuthbertfon under the receiver of his moft powerful air pump; but in the fame fituation, New-River water taken from a tub expofed to the atmofphere for fome time yielded its own bulk of air. Hence the gaz procured by the firft one, two, or even three hundred explofions in water containing its natural quantity of air, is diminifhed very little by an eleétric fpark. The gaz thus feparable from water, like atmofpherical air, confifts of oxygen and nitrogen, or azotic gaz; which may bein exaétly the fame proportions as in atmofpherical air; for the water may retain one kind of gaz more tenacioufly than the other; and on this account the air feparated may be better or worfe than atmofpherical air at different periods of the procefs for extricating it. With regard to the gaz which inftantly difappears on paffing through it an eae {park, its nature is fhewn by (a) this very property of thus ‘diminifhing ; and by the following” properties : (6) A certain quantity of nitrous gaz inflantly difappeared, apparently compofing ni- trous acid, on being ‘added to the gaz (a) p. 303, Exp. IV. Oxygen gaz being added to the refidue after faturation with nitrous gaz, and an cledtric fpark being applied to the mixture of gazes, well dried, a confiderable diminution imme- diately took place, and water was produced. (c) Combuftion from hydrogen and oxygen gaz took place when the tube was about three- fourths full of gaz, p, 301, Exp. I.; which was confirmed by paffing an ele¢tric difcharge, un- der the fame cireumftances, through a mixture of hydrogen and oxygen gaz, p. 302, Exp. II. (d) Combuftion from hydrogen and oxygen gaz took place when the points of the com- paffes were accidentally applied to the part of the tube containing gaz, p. 302; which was confirmed by pafling a difcharge, under the fame circumftances, through a mixture of hy- drogen and oxygen gaz, while the points of the compaffes were applied to the tube. (e) The obfervations made of the kindling of gaz, in {mall quantities, from time to time, during the procefs of obtaining it, particularly while it was afcending in chains of bubbles, or was adhering to the funnel of the tube, p. 302, Exp. TIL. confirm the evidence in favour of this gaz being hydrogen and oxygen gaz. The evidence contained under the above heads (a)—(e) confidered fingly and conjunc- tively, I apprehend, mutt be admitted by the moft rigorous reafoner, or fevereft logician, to be demonftrative that hydrogen and oxygen gaz were produced by pafling eledtric dif charges through water. With regard to the origin and mode of production of thefe two gazes, our prefent ob- fervations and experiments do not afford complete demonftrative evidence ; but although fome hypothefes muft be admitted, £ conceive that the body of evidence we poflefs can af- ford a fatisfactory interpretation of the phenomena. It is demonftrable that the eletric difcharge and fpark contain fire; and yery probably they are merely a ftate of fire. Fire may be confidered as confifting of caloric and light ; but itis atleaft as coufiftent with the phenomena, and it is more philofophical, becaufe it is more Experiments on the focal Adjufiment of the E yee 305 more fimple, to confider light not as a diftinet {pecies of matter, but asa {tate of caloric, whictt is manifefted by its producing the fenfation termed vifion. It is demonttrable alfo, that the ponderable parts of oxygen and hydrogen gaz corftitute water. There is {trong evidence that thefe gazes confift of a peculiar {pecies of matter which is ponderable; and of im- ponderable matter, which is that which is feparable from them in the ftate of fire, or flame. If fire could be applied in a fufficiently denfe ftate and quantity, it is warrantable, from a full induétion of fa&ts, to concluide, that it is able to difunite the conitituent fubftances of all the compound fubftances in nature. {To be concluded in the next Number] es, IV, Experimental Refearches to afcertain the Nature of the Procefs by which the Eye adapts itfelf te produce diftin® Vifion. "Tas ftrudture of the eye, and particularly its provifions for adjuftment to produce diftin& vifion, have engaged the attention of feveral philofophers during the laft five years, who have delivered papers on thefe fubjeéts to the Royal Society. I purpofe to give the fubftance of their difcoveries in the prefent communication. In the year 1793, Mr. Thomas Young’s Obfervations on Vifion appeared in the Tranf- actions. He gives a fhort fummary of the theories of adjuftment propofed by various earlier authors. Kepler fuppofed the ciliary proceffes to contract the diameter of the eye, and lengthen its axis by a mufcular power. Defcartes imagined the fame effe€ to be produced by a mufcularity of the cryftalline humour, but did not attribute much to the change of figure which he fuppofed to take place in that lens. De la Hire, and alfo Haller, adopted the opinion that the eye undergoes no change to produce diftin& vifion, but the contraCtion and dilatation of the pupil. Pemberton fuppofed the exiftence of mufcular fibres in the eryftalline humour, by which the curvatures of its furfaces are changeable. Dr. Porterfield conceived that the ciliary procefles draw forward the cryftalline, and render the cornea more convex. Dr. Jurin maintained the hypothefis, that the uvea, at its attachment to the cornea, is mufeular, and capable of increafing the convexity of that humotir, ’ by its con- traétion towards the axis of the eye. Mufchenbroek conjectures that the’relaxation of his ciliary zone; which appears'to be nothing but the capfule of the vitreous humour; ‘permite the coats of the eye to puth forward the cryftalline and cornea. Andy: laftly, an elongation of the axis of the eye has been fuppofed to be produced by the’ preffure of the external mufcles, efpecially the two oblique mufeles ; and, on the other hand, the mufcular ation has been fuppofed to produce a contrary effect, namely; a contraction of the’axisy'9 1 0/08 In the enumeration of thefe refpective hypothefes, Mr. Young makes remarks tending’ to their feveral reftation. I have not tranfcribed them, principally becaufe they chiefly tend to fhew that effects of this nature deferve, if poflible, to be fubmitted to a@ual ex? periment. ‘ : e From the confideration of the whole fubjeét, our author concluded that the rays of light emitted by objects at afmall diftance could only be brought to foci on thé retina by'a Voi. I.—Ocroxer 1797. Rr nearer 306 Whether the Cryftalline Eens be the Infirument nearer approach of the cryftalline toa fpherical form; and he could imagine no other power capable of producing this change than a mufcularity of part or the whole of its capfule. But on clofely examining, with the naked eye, the cry{talline from an ox turned out of its capfule, he difcovered a ftructure which he thinks fufficient to remove all the difficulties with which this branch of optics has long been obfcured. The cryftalline lens of the ox is an orbicular, convex, tran{parent body, compofed of a confiderable number of fimilar coats, of which the exterior clofely adhere to the interior. Each of thefe coats confilts of fix mufcles, intermixed with a gelatinous fubftance, and attached to fix membranous tendons. Three of the tendons are anterior, three pofterior ; their length is about two-thirds of the femi-diameter of the coat; their arrangement is that of three equal and equidiftant rays, meeting in the axis of the cryftaine; one of the anterior is direéted towards the outer angle of the eye, and one of the pofterior towards the inner angle; fo that the pofterior are placed oppofite to the middle of the interflices of the anterior; and planes paffing through each of the fix, and through the axis, would mark on either furface fix regular equie diftant rays. The mufcular fibres arife from both fides of each tendon; they diverge till they reach the greateft circumference of the coat; and having paffed it, they again converge till they are attached refpeétively to the fides of the neareft tendons of the oppofite furface. The anterior or pofterior portion of the fix viewed together exhibits the appearance of three penniform-radiated mufcles. The anterior tendons of all the coats are fituated in the fame planes, and the pofterior ones in the continuations of thefe planes beyond the axis: Such an arrangement of fibres cam be accounted for on no other fuppofition than that of mufcularity. This mafs is enclofed in a {trong membranous capfule, to which it is loofely conneéted by minute veflels and nerves; and the connection is more obfervable near its greateft circumference. Between the mafs and its capfule is found a confiderable quantity of an aqueous fluid, the liquid of the cryftalline. He conceives, therefore, that whea the willis exerted to view an object at a {mall diftance; the influence of the mind is conveyed through the lenticular ganglion formed from branches of the third and fifth pairs of nerves, by the filaments perforating the {clerotica to the or- biculus ciliaris, which may be confidered as an annular plexus of nerves and veflels; and thence, by the ciliary proceffes, to the mufcle of the cryftalline ; which, by the contraétion of its fibres, becomes more convex, and collects the diverging rays to a focus on the retina. The difpofition of fibres in each coat is admirably adapted. to produce this change ; for fince the leaft furface that can contain a given bulk, is thavof a {phere (Simpfon’s Fluxions, p. 486), the contraétion of any furface muft bring its contents nearer to a fpherical form. The liquid of the cryftalline feems to ferve as a fynovia in facilitating the motion, and to admit a fuf- ficient change of the mufcular part, with a fmaller motion of the capfule. To afcertain whether thefe fibres can produce an alteration in the form of the lens fuf- ficiently great to account for the known effects, this author ftates, that the diameter of the ¢xyftalline of the ox is 700 thoufandths of an inch, the axis of its anterior fegment 2265 5 of its pofterior 350. In the atmofphere it collects parallel rays, at the diftance of 235 thoufandths. From thefe data he finds, by means of Smith’s Optics, article 366, and a quadratic, that its ratio of refra€lion is as 10000 to 6574. Haukfbee makes it only as 30000 to 6832,7; but we cannot depend on his experiment, fince he fays, that the image of the candle which he viewed was enlarged and diftorted ; a circumftance that he does not explain, of Focal Adjufiment in the Eye ? 307 explain, but which was evidently occafioned by the greater denfity of the central parts. Suppofing, with Haukfbee and others, the refra€tion of the aqueous and vitreous humours equal to that of water, viz. as 10000 to 7465, the ratio of refra@tion of the cryftalline in the eye will be as 10090 to $806, and it would colleét.parallel rays at the diftance of 1226 thoufandths of an inch; but the diftance of the retina from the cryftalline is 550 thou- fandths; and that of the anterior furface of the cornea 250; hence (by Smith, art. 367.) the focal diftance of the cornea and aqueous humour alone muft be 2329. Now fuppofing the cryftalline to affume a fpherical form, its diameter will be 642 thoufandths, and its focal diftance in the eye 926. Then, difregarding the thicknefs of the cornea, he deduces (by Smith, art. 370.) that fuch an eye will colleét thofe rays on the retina which diverge from @ point at the diftance of 12 inches and 8-1oths, This is a greater change than is ne- ceflary for an ox’s eye: for, if it be fuppofed capable of diftin& vifion at a diftance fome- what lefs than 12 inches, yet it probably is far fhort of being able to colleét parallel rays. The human cryftalline, he fays, is fufceptible of a much greater change of form. ” The ciliary zone may admit of as much extenfion as this diminution of the diameter of the cryftalline will require ; and its elafticity will affift the cellular texture of the vitreous humour, and perhaps the gelatinous part of the cry(talline, in reftoring the indolent form. He queftions whether the retina takes any part in fupplying the lens with nerves; but from the analogy of the olfactory and auditory nerves, he thinks it more reafonable to fuppofe that the optic nerve ferves no other purpofe than that of Romening fenfation to the brain. Although a flrong light and clofe examination are required in Werdes to fee the fibres of the cryftalline in its entire ftate, yet their direCtion was demonftrated, and their attach- ment {hewn, without much difficulty. In a dead eye, the tendons are difcernible through the capfule, and fometimes the anterior ones even through the cornea and aqueous humour. When the dry cryftalline falls, it very frequently feparates, as far as the centre, into three portions, each having a tendon in its middle. If it be carefully ftripped of its capfule, and the {mart blaft of a fine blow-pipe be applied clofe to its furface, in different parts, it will be found to crack exaétly in the dire¢tion of the fibres above defcribed, and all thefe cracks will be dtopped as foon as they reach either of the tendons. The application of a little ink to the cryftalline is of great ufe in fhewing the courfe of the fibres. Mr. Young was not at firft aware that the mufcularity of the cryftalline had. ever been fufpeéted, either by Defcartes or any other perfon. But the laborious and ac- curate Lewenhoek, to whofe writings he refers, has defcribed the courfe of the fibres of the cryftalline in a variety of animals, and has even gone fo far as to call ita mufcle. He did not, however, attempt to account for the focal adjuftment of the eye from its muf- cularity. The remaining part of Mr. Young’s paper is employed in the folution of te optical queries, not immediately relating to the prefent object. In Plate XIL, Fig. 1. reprefents a vertical fe€tion of the ox’s eye, of the natural fize. A, the cornea covered by the tunica conjundtiva; BCB, the felerotica, covered at BB by the tunica albuginea and tunica conjunétiva; DD, the choroid, confifting of two laminas ; EE, the circle of adherence of the choroid and {elerotica; FG, FG, the orbiculus ciliaris; Rr2 HY, Tk, 308 Whether the focal Adjufiment of the Eye HI, HK, the trvea; its anterior furface the iris; its pofterior furface lined with pigmentuny nigrum; IK, the pupil; Hk, HL, the ciliary proceffes covered with pigmentum nigrum ; MM, the retina; N, the aqueous humour; O, the cryftalline lens; P, the vitreous humour; QR, QR, the zona ciliaris; RS, RS, the annulus mucofus. . Fig. 2. The ftru€lure of the cryftalline lens, as viewed in front, likewife of the naturak fize ;—Vig. 3. a fide view of the cryftalliné. In the following year, 1794, acommunication was made to the Royal Society, by Everard Home, Efq. F.R.S. of fome facts relative to a preparation for the Croonian Leature, by the late Mr. John Hunter. He ftates that this celebrated anatomift had for many years entertained the notion, that the cryftalline humour was enabled by its.own internal actions to adjuft itfelf fo as to adapt the eye to different diftances; and when the tenia hydatigena firft came under his obfervation as a living animal, he was furprifed to fee the quantity of contraction that took place in a membrane devoid of mufcular fibres ;, but made ufe of the fa& in his inveftigation of the flru€ure of the cryftalline humour of the eye. Some time after this, he diftovered the fibrous ftruéture of the cryftalline humour in the eye of the cuttle-fifh, in which it is peculiarly diftin 5. and thence he was led to confider the: exterior part of this humour as fimilar in all animals. It was his.intention to have afcer- tained by experiment, whether mufcular aGtion does in faé&t take place; and having found: that a certain degree of heat applied through the medium of water will excite mufcular a€tion,. after almoft every other ftimulus had failed, it was propofed to apply this to the’ cryftalline” humour, and afcertain its effects. The cryftalline humour taken from animals recently killed muft be confidered as being ftill alive. Such humours were to be immerfed in water of different temperatures, and placed in fuch a manner as to form the image of a lucid, well~ defined obje€t, by a proper apparatus for that purpofe, fo that any change of the place of that image, from the ftimulating effe&ts of the warm water upon the humour, would be- readily afcertained. Thefe were the experiments which Mr. Hunter had inftituted and! begun, but in which he had not made fufficient progrefs before his death to enable him to» draw any conclufions, This communication contains an unfinifhed letter from Mr. Hunter to Sir Jofeph Banks,. containing fome prefatory obfervations leading to the ftatement made by Mr. Home. It appears, in fact, as that gentleman remarks, that the difcovery of a fibrous*appearance in: the cryftalline appertains to Lewenhoek; but that the difcovery of an. eye in which the ftru€ture is uncommonly diftiné, is due to Mr. Hunter. To this paper is annexed a plate exhibiting two fections of the cryftalline humour of the: cuttle-fith. In the fecond part of the Tranfa€tions for the fame year, I find a paper of fome length on vifion, by Dr. Hoffack. This author fhews in the firft place, that the enlargement or con- traétion of the pupil of the eye is infufficient to produce the adjuftment by which the rays of light fhalt converge to a point in the retina; and in fact a flight obfervation of what hap-, pens is fufficient to thew that the variations of the pupil are governed by different circum- ftances. He controverts Mr. Young’s deduétions with regard to the mufcularity of the cryftalline, and even difputes the faéts. He quotes fome authorities to fhew that the eye is capable of accommodating itfelf to different diftances without the afliftance of the cryf= g* talline, be produced by the external Mufcles ? 309 talline, as after couching or extra@tion. For thefe and other reafons his attention was more particularly dire€ted to the external mufcles. Upon carefully removing the eyelids, the mufcles of the eye prefent themfelyes to view in number fix; four called reéti or ftraight, and two oblique, fo named from their direction. In Plate XIII. Fig. 4, AAAA reprefent the tendons of the reéti mufcles, where they are in- ferted into the fclerotic coat, at the anterior part of the eye. B, the fuperior oblique, or trochlearis, as fometimes called, from its pafling through the loop or pulley connected to the lower angle of the orbit or notch in the os frontis ; it pafles under the fuperior reétus mufcle, and backwards to the pofterior part of the eye, where it is inferted by a broad flat tendon into the {clerotic coat. Cy, the inferior oblique, arifing tendinous from the edge of the orbit or procefs of the fuperior maxillary bone, pafling flrong and flefhy over the in- ferior rectus, and backwards under the abductor to the poflerior part of the eye, where it is alfo inferted by a broad flat tendon into the fclerotic coat. DDD, the fat in which the eye is lodged. In Figure 5, the bones forming the external fide of the orbit, with a por- tion of the fat, are removed, by which we have a diftin& view of the abdu€tor. ABC, three of the reéti mufcles, arifing from the back part of the orbit, pafling ftrong, broad and flefhy over the ball of the eye, and inferted by flat broad tendons into the felerotic coat, at its in- terior part. D, the tendon of the fuperior oblique mufcle. E, the inferior oblique. In Fig.-6, A reprefents the abductor of the eye. B,the flethy belly of the fuperior oblique, arifing ftrong, tendinous and flefhy from the back part of the orbit. C, the optic nerve. D and E, the recti mufcles. The ufe afcribed to thefe different mufcles is that of direling the axis of the eye towards the different objects, or to exprefs the paffions of the mind. But Dr. Hoflack rationally in- fers, from the general application of the combined forces of mufcles through the whole of the animal fyftem, that this fet of mufcles, which he conceives to be well adapted to produce the focal adjuflment, may alfo be employed on that object. He affumes, as the neceffary confequence of contraétion in thefe mufcles, that the axis of the eye will be elongated, and the elaftic cornea rendered more convex 3, both which circumftances would tend to preferve diftinétnefs of vifion with regard to near objeéts. For as fuch objeéts afford a focal image more diftant from the refracting furface, through which the light may pafs, the elongation of the axis will be of advantage, by removing the retina further back ; and the increafed convexity and fhortened focus of the cornea will conduce to the fame end. How far the aétion of the re€ti mufcles might produce an elongated figure, is perhaps eapable of difpute; though this effect will probably be admitted without hefitation, as a con- fequence of the contraction of the oblique mufcles. But to put the matter out of doubt,. whether this organ be capable of having its focal adjuftment confiderably. varied by external preflure, our author applied the common fpeculum oculi to his own eye. With a very moderate preflure, while directing his attention to an objeét at the diftance of about twenty yards, he faw it diftinétly, as alfo the different intermediate objets; but endeavouring to look beyond it, every thing appeared confufed: he then increafed the preflure confiderably: in confequence of which he was enabled to fee objects diltin€lly, though placed much nearer than the natural focal diftance. For example : he held before his eye, at thie diflince of about “wo inches, a printed book, In the natural ftate of the eye, he could neither diftinguifh the ines or 310 : : Probable Ufes of the Cryfiailine Humour. nor letters; but, upon making preflure with the fpeculum, he was enabled to diilinguiflh both the lines and the letters of the book with eafe. Such being this author’s conception of the aétion and effect of the external mufcles, he has proceeded to apply the doétrines in explanation of the changes the eye is known to undergo at different periods of life or habits of occupation, from their itrength in early life, their debility in old age, and their habitual ation from ule. ‘Lhefe and other general facts are accounted for with confiderable addrefs. Mr. Home, the brother-in-law of Hunter, and vindicator of his pofthumous fame, was appointed to read the Croonian lecture on mufcular motion, for the feflion of the Royal Society beginning in the year 1794. His lecture is peculiarly valuable forthe experimental refults it exhibits. In profecuting the enquiry projefted by Mr. Hunter, he had the great advantage of the afliftance of his friend Mr. Raimfden, who, in converling upon the different ufes of the cryftalline humour, made the following obfervations : He faid that, as the cryftalline humour confitts of a fubftance of different denfities, the central parts being the moft compaét, and from thence diminifhing in denfity gradually in every direction, approaching the vitreous humour on one fide, and the aqueous humour on the other, its refra€tive power becomes nearly the fame with that of the two contiguous fubftances. That fome philofophers have ftated the ufe of the cryflalline humour to be, for accommodating the eye to fee objects at different diftances; but the firmnels of the cen- tral part, and the very fmall diffrence between its refractive power near the circumference, and that of the vitreous or the aqueous humour, feemed to render it unfit for that purpofe; its principal ufe rather appearing to be for correcting the aberration arifing from the fpheri- cal figure of the cornea, where the principal part of the refraction takes place, producing the fame effect that, in an achromatic object-glafs, we obtain in a lefs perfeét manner by proportioning the radii of curvature of the different lenfes. Jn the eye the correction feems perfect, which in the objeét-glafs can only be an approximation; the contrary aberrations of the lenfes not having the fame ratio; fo that, if this aberration be perfectly corrected, at any given diftance from the centre, in every other it muft be in fome degree imperfect. Purfuing the fame comparifon: In the achromatic object-glafs we may conceive how much an object mutt appear-fainter from the great quantity of light loft by reflection at the furfaces of the different lenfes, there being as many primary reflections as there are fur- faces; and it would be fortunate if this reflected light was totally loft. Part of it is again refle€ted towards the eye by the interior furfaces of the lenfes; which, by diluting the image formed in the focus of the objeét-glafs, makes that image appear far lefs bright than it would otherwife have done, producing that milky appearance fo often complained of in viewing lucid objeéts through this fort of telefcope. In the eye, the fame properties that obviate this defect ferve alfo to corredt the errors from the fpherical figure, by a regular diminution “of denfity, from the centre of the cryf- talline outward. Every appearance fhews the cryftalline to confift of laminz of different denfities; and if we examine the junction of different media, having a very fall difference of refraétion, we fhall find that we may have a fenfble refraction without refletion. Now, if the difference between the contiguous media in the eye, or the laminze in the cryftalline, be very fmall, we fhall have refraction without having reflection ; and this appears to be the ttate Adjufiment of the Eye deprived of the Cry ftalline. jit fate of the eye; for although we have two furfaces of the aqueous, two of the cryftalline, and two of the vitreous humour, yet we have only one reflected image ; and that being from the anterior furface of the cornea, there can be no furface to reflect it back, and dilute an image on the retina. This hypothefis may be put to the teft whenever accident fhall furnifh us with a fubjeét having the cryftalline extraéted from one eye, the other remaining perfect in its natural ftate; at the fame time we may afcertain whether or no the cryftalline is that part of the organ which ferves for viewing objets at different diftances diftin@ly. Seeing no re- flection at the furface of the eryftalline, might lead fome perfons to infer that its refra€tive power is very inconfiderable; but many cireumftances fhew the contrary: yet what it really is may be readily afcertained by having the focal length and diftance of a lens from the operated eye, that enables it to fee objects the moft diftin€tly ; alfo the focal length of a lens, and its diftance from the perfect eye, that enables it to fee objects at the fame dif- tance as the imperfel cye: thefe data will be {ufficient whereby to calculate the refractive power of the cryftalline with confiderable precifion. _ Again, having the fpherical aberration of the different humours of the eye, and having afcertained the refra€tive power of the cryftalline, we have data from whence to determine the proportional increafe of its denfity as it approaches the central part, on a fuppofition that this property correéts the aberration. : An opportunity prefented itfelf for bringing the obfervations of Mr. Riamfden refpecting the ufe of the cryftalline lens, tothe proof. A young man came into St. George’s Hofpital, with a cataract in the right eye. The cryftalline lens was readily extraéted, and the union of the wound in the cornea took place unattended by inflammation, fo that the eye fuf- fered the fmalleft degree of injury that can attend fo feverean operation. The man himfelf was in health, 21 years of age, intelligent, and his left eye perfe&t: the other had been am uncommonly fhort time “in a difeafed' ftate, and 27 days after the operation appeared to be free from every other defe&t but the lofs of the cryftalline lens: A number of experiments were made on the imperfect eye, allifted by 2 lens, and com= pared with the perfe& eye. The aim of thefe trials, which were judicioufly varied, was to- afcertain whether the cye which had been deprived of the cryftalline lens.was capable of ad- jufting itfelf to diftinct vifion at different diftances. Among other refults, the perfect eye, with a glafs of 6 inches focus, had diftin€& vifion at three inches; the near limit was 17 inch, the diftant limit lefs than 7 inches. The imperfet eye, with a glafé 24,ths inches focus, with an aperture ,3,ths of an inch, had diftin& vifion at 22 inches, the near limit 14 inch, and the diftant limit 7 inches. ‘The accuracy with which the eye was brought to the fame point, on repeating the experiments, proved it to be uncommonly corre&t; and as he did not himfelf fee the fcale ufed for admeafurement, there could be no fource of fallacy. From the refult of this experiment it appears that the range of adjuftment of the imperfeét eye, when the two eyes were made to fee at nearly the fame focal diftance, exceeded that of the perfect eye. Mr. Ramfden fuggefted a reafon why the point of diftin@ vifion of the imperfect eye might appear to the man himfelf nearer than it was in reality; namely, that from the imperfection of this organ, he might find it eafier to read the letters when’ they fubtended a greater angle than at his real point of diftin& vifion. The experiments, however, appear to fhew that the internal power of the eye, by which it is adjufted to fee at different gt2 Faviations of Carvaturein the Cornea. > different diflances, does not refide in the cryftalline lens ; at leaft, not altogether ; and that at any agency in this refpect can be proved to refide in the cryftalline, the other powers, what- ever they may be, are capable of exertion beyond their ufual limits, fo as to perform its office in this refpect. From thefe confiderations; and’in confequence of other refleGtions tending to Gen that an clongation of the optical axis isnot probably the means of adjuftment, thefe philofophers dircted their enquiries to afcertain how far the curvature of the cornea might be fubje& to change. They found by trial that this part of the organ poflefles a degree of elafticity which . is very confiderable, both for its perfeétion and its range; and by anatomical’ diflection it was found, that the four f{traight mufcles of the eye do in effect terminate in the cornea at their tendinous extremities; that the whole external lamina of the cornea could by gentle force be feparated, by means of thefe mufcles, from the eye; fo that the tendons feem loft in the cornea, and this laft hasthe appearance of a central tendon. It was alfo feen that the central part of the cornea is the thickeft and the moft elaftic. Thefe were confiderable advances towards eftablifhing the hypothefis of adjufiment by the external curve of the eye. It remained to be fhewn, by experiments on the living fub- ject, that this curve does really vary in the due dire€tion, when the mind perceives the dif- tint vifible fenfation of objects at different diftances. For this purpofe Mr. Ramfden pro- vided an apparatus, confifting of a thick board fteadily fixed, in which was a fquare hole large enough to admit a-perfon’s face ; the forehead and ‘chin refting againft the upper and lower bars, and the cheek againft either of the fides; fo that when the face was protruded, the head was fteadily fixed by. refling on three fides ; and in this pofition the left eye projedted _ beyond the outer furfaceof the board. A microfcope, properly mounted, fo as with eafe to be fet in every requifite pofition, was applied to view the cornea with a magnifying power of thirty times. In this fituation, the perfon whofe eye was the objec of experiment was defired to look at the corner of a chimney, at the diftance of 235 yards, through a {mall hole in a brafs plate, fixed for that purpofe,'and afterwards to look at the edge of the hole itfelf, which was only fix inches diftant. After fome management and caution, which the delicate nature of thefe experiments requires, the motion of the cornea, which was imme~ diately perceptible, became very diftinét and certain. The’ circular fe€tion of its furface remained in a line with the wire in the field of the microfcope, when the eye was adjufted to the diftant object, but projected confiderably beyond it when adapted to the near one. When the diftant obje& was only go feet from the obferver, and the near object fix inches, the difference in the prominence of the cornea was eftimated at 1-80oth of an inch. Thefe experiments were repeated and varied at different times and on different fubje€ts. ‘The obferver at the microfeope fonnd no difficulty in determining, from the appearance of the corneay whether the eye was fixed on the remote or the near, objeét. From thefe different experiments Mr, Home confiders the following faéts to have been afcertained: 1. That the eye has a power of adjufting itfelf to different diftances when deprived of the cryftalline lens; and therefore, the fibrous and laminated ftruture of that lens is not in- tended to alter its form, but to prevent refle€ions in the paflage of the rays through the furfaces of media of different denfities,‘and to corre& f{pherical aberration. 2. That the cornea is made up of lamin ; that it is elaftic, and when ftretched is capable ; - é of se? 4 Focal Adjuftinent of the Eye—Sulphureous Acid. 313 of being elongated 1-1 1th part of its diameter, contracting to its former length immediately upon being left to itfelf. 3. That the tendons of the four ftraight mufcles of the eye are ¢ontinued on to the edge of the cornea, and terminate, or are inferted, in its external lamin; their a@tion will there- fore extend to the edge of the cornea. 4. That in changing the focus of the eye from feeing with parallel rays to a near dif- tance, there is a vifible alteration produced in the figure, of the cornea, rendering it more convex; and when the eye is again adapted to parallel rays, the alteration by which the cornea is brought back to its former ftate is equally vifible. The remaining part of Mr. Home’sleCture contains fome obfervations upon the mufcularand elaftic powers, which by their oppofition produce fo curious an effect in the adjuftment of the eye. The feparate aétion of the mufcles produces a change in the dire€tion of the axis of the eye. A {mall force of contraction in the whole fyftem will fteady the eye, and a greater force will comprefs the lateral and pofterior parts of the eye, and render the cornea more convex. The experiments prove that the eye-ball cannot recede in its orbit by thefe ations. Other inftances in the animal ceconomy, by means of which the expenditure of mufcular action is faved by the operation of elaftic antagonifts, are alfo flated by this author. The exertion required to adjuft the eye to near diftances, and the eafe with which it was adapted to re- mote dbjeéts, prove that the firft was a pofitive a€tion, and the fecond a relief. The de- feét of elafticity inferred to arife from age is happily applied to explain the changes of vifion which take place in advanced life. Two other communications to the Royal Society by this philofopher, and one by Mr. Smith on the eyes of birds, remain to be confidered ; but, on account of the length of this communication, I fhall for the prefent defer them. SSS SS. Vv. Concerning the Properties of the Sulphureous Acid, and its Combinations with earthy and alkaline Bafes. By Citizens FourcRorY and VAUQUELIN *. : Srver AL philofophers have paid attention to the properties of the fulphureous acid, and fome of its combinations; but no one has given a complete account of this acid. Berthollet is almoft the only chemift who has opened this inveftigation. He is the firft who publifhed any accurate account of the fubje& +. We {hall not in this place defcribe either the apparatus or method of pteeising this acid, becaule both are well known to fuch as are moderately acquainted with chemiftry. I. Ph; fical Properties of the Sulphureous Acid. THIS acid conftitutes a permanent elaftic fluid at the ordinary preflure and temperature of our atmofphere. Its odour is ftrong and fuffocating. -It cannot maintain combuttion, nor the refpiration of animals. Beryman, in ‘his Treatife on Elective AttraCtion, affirms that the fulphureous acid, pre- * Journal de l’Ecole Polytechnique, cahjer TV. ps 445+ + Annalesde Chimie, IT, 54, Vous I.—Oc'roner 1797. Sf pared 3'4 Properties and Habitsudes of pared in the pneumatic apparatus over mercury, cannot be reduced to the liquid ftate by any known means, ‘Monge and Clouet affirm, on the contrary, that by the application of extreme cold, and a ftrong preffure exerted at the fame time on this gas, they rendered it liquid. , Its {pecific gravity, according to Bergman, is 0,00246, and 0,002§1, according to La- voifier; which correfponds with 1.508 grain the inch cube, and 4 oz. § gros the foot cube (French weights and meafures). H. Chemical Properties of the Sulphureous Acid. ABion of Caloric] Prieftley and Berthollet affirm, that the fulphurcous acid gas, expofed to an elevated temperature, depofits a portion of fulphur, and becomes converted into ful- phuric acid. Bergman relates the fame faét. This experiment, Tepeated in feveral dif. ferent ways, did not afford us the fame refult. Ill. Aétion of Oxygene Gas. ONE part of dry oxygene gas, and two parts of fulphureous acid gas, prepared in the mercurial apparatus, and mixed together, fuffered no remarkable change during the courte. of feveral months. If a {mall quantity of water be added to the mixture, a fucceflive ab- forption, after the diminution which is produced by the combination of a portion of the. fulphureous acid, is perceived ; which proves the exiftence of a true combination between thefe two bodies. In fat, when the mixture is wafhed, after the expiration of feveral months, the refidue of oxygene is found to be lefs than the original quantity. ‘The attraction of the water for the fulphuric acid is therefore favourable to the union of the oxygene with the fulphureous acid. We were not able, however, to convert the whole. of the fulphureous acid into fulphuric acidy though in all our experiments oxygene gas re- mained in the apparatus. : ‘The fulphureous acid is immediately converted into fulphuric acid, by paffing a mixture of this gas and of oxygene gas through an ignited tube. A very denfe white fume is formed, which becomes condenfed into the liquid form, in a bottle placed for that purpofe at the other extremity of the tube. ‘ It feveral times happened, when by accident we had ufed the exaé proportions, that the two gafes were entirely deftroyed, and not an atom of (elaftic) refidue was perceived. IV. The AGtion of Water. WHEN the fulphureous acid gas was pafled into water cooled by means of ice, the combination was made with fuch rapidity that not a fingle bubble rofe to the furface of the liquor until it was faturated. ‘The ice is {peedily melted ; which proves that much caloric is difengaged. The water acquires at this temperature the o,15th part of its weight. Its fpecific gravity, compared with that of pure water, is as 1020 to 1000, Water thus faturated with the fulphureous acid, and expofed to the temperature of 15 degrees above zero (Reaumur), immediately becomes filled with an infinity of {mall bubbles, which fucceflively increafe, and rife to the furface. If a bottle full of this acid -be plunged in hot water, it boils with aftonifhing rapidity;~and lofes by this operation part of its odour and acidity. Is cannot, however, be ecafily deprived of thefe qualities, even by 2 boiling, the Sulphureous Acid. 315 boiling. This acid freezes at a few degrees below zero, or the freezing point of water; and what may appear aftonifhing is, that not the fmallefl portion of gas is difengaged, as happens when the other gafes are diffolved in, water. Thefe experiments prove, 1. That the colder the water the more it abforbs of fulphureous acid. 2. That the combination of thefe bodies is accompanied with heat. 3. That fuch a combination cannot preferve at a more elevated temperature all the acid it was charged with at a lower degree of heat. 4. That this combination paffés to the folid ftate by cooling, without undergoing decompofition; a faét which fhews a great affinity of water for the fulphureous acid, and a weak attraction of this laft for caloric. V. Aition of Acids upon the Sulphureous Acid. Aion of the Sulphuric Acid.) We caufed fulphureous acid gas to pafs through the fulphu- ric acid cooled by a mixture of ice and falt. in proportion as the acid gas was extricated, it combined with the fulphuric acid without one fingle bubble arriving at the upper part. Soon afterwards the whole of the acid became congealed ; notwithftanding which the com- -bination continued to be made. From time to time, the tube through which she fulphureous acid pafled was obftrufted, -and required to be withdrawn out of the fluid. By this treatment the matter flowed, and a quantity of gas was difengaged in the form of bubbles. The folid combination had no very perceptible fmell while it retained the form of ice ; but when a portion was taken out, and Jaid upon a plate of glafs, it exhibited an effervefcence like that of marble when an acid is poured on it, and foon afterwards it became liquid and very odorant. When the temperature of the mixture of falt and ice had rifen to the freezing-water point, part of the folid mafs became liquid, and bubbles were formed which rofe up in the empty part of the vafe; but as this was exactly clofed, they cryftallized on the fides in the form of the leaves of fern. Aion of the Nitric Acid.} The fulphureous acid decompofes the nitric acid, particularly when this laft is ina concentrated f{tate. The fluid immediately becomes red, and foon after- wards hot, witha difengagement of nitrous gas frequently mixed with a {mall quantity of fulphureous acid. The fulphureous acid is changed by this operation into fulphuric acid, for it abundantly precipitates the muriate of barytes. Hence it is proyed, that the fulphureous acid has more affinity with oxygene than the nitrous oxide. ‘This truth is confirmed by the converfion of fulphur into fulphuric acid by means of the nitric acid, Ation of the Oxygenated Muriatic Acid.) Vf the oxygenated muriatic acid gas and the fulphureous acid gas be brought into contact, white fumes are afforded ; the two gafes become immediately liquid, and Jofe their odeur, if they have been employed in fuitable proportions, The fame effects take place when thefe two acids are mixed together in the liquid ftate, namely, the lofs of odour and colour. From the aétion of thefe two hadies on each other, fulphuric acid and common muriatic acid are produced. The theary of this operation is nearly the fame as that of the preceding experiment. VI. Aétion of combuftible Bodies on the Sulphureous Acid. The Adlion of Hydrogene.| Thefe two fubftances have no mutual action in the cold; but if they be paffed through a tube of glafs or porcelaine well heated, in the proportion of three parts by meafure of hydrogene gas and one part of fulphureous acid gas, the latter is S{2 decompofed. 316 Habitudes and Combinations of decompofed. Sulphurated hydrogene gas is formed; and at the extremity of the tube oppofite to that at which the gafes were.introduced, very abundant cryftals of fulphur are depofited. Hydrogene therefore, at an clevated temperature, has more affinity with oxygene than fulphur has. Confequently it is not probable, as fome perfons imagine, that fulphur may be burned by means of water to convert it into fulphuric acid. The Aion of Phofphorus.] Phofphorus does not alter the fulphureous arid. When thefe two fubftances are flrongly heated in a glafs tube, nothing paffes which indicates the decompofition of the fulphureous acid. The phofphorus becomes fixed in cooling in the form of tranfparent drops which do not contain an atom of fulphur, and the fulphureous acid gas is ftill found to poffefs all its properties. In this cafe, therefore, there is a ftronger adhefion between the fulphur and oxygene than between the phofphorus and the fame principle. And accordingly this combuttible fub- ftance, heated with fulphuric acid, does not deprive it of more oxygene than exceeded the conftitution of the fulphureous acid. Aion of Phofphorated Hydrogene'Gas.] As foon as ithe fulphureous acid gas and phofpho- rated hydrogene gas come into contact, a white fume appears, and they lofe their fluid ftate. Plates of a yellow matter are precipitated en the fides of the containing veflel, which take fire on a hot iron, firft, in the manner of phofphorus, and afterwards with the charadters of fulphur. It follows from this experiment, that the hydrogene is the only fubftance which burns, or combines with oxygene, in thefe circumftances, fince the gafes lofe their elafticity, and the phofphorus and fulphur are found combined together. Aétion of Sulphurated Hydrogene Gas.] The {ulphureous acid gas is decompofed by the fulphurated hydrogene gas. The hydrogene takes the oxygene from the fulphur, and this laft principle is feparated on both fides. It therefore forms a very abundant depofition. When thefe gafes are diffolved in water, they mutually undergo the fame decompofition, and the fulphur then precipitates to the bottom of the liquor *. If fuitable quantities of thefe folutions be taken, the odour of both difappears. Aétion of Carbone.| We pafled fulphureous acid gas through a tube of glafs containing ignited charcoal. At the extremity of the apparatus cryftallized fulphur was depofited, and carbonic acid was produced, together witha fmall quantity of fulphurated hydrogene gas, from a portion of the water which was decompofed. ‘This decompolition does not take place in the cold: VII. Combinations of the Sulphureous Acid with Alkalis. THE fulphureons acid readily unites.with alkalis and earths. The generic name of fulphites has been given to thefe combinations. They may be prepared in two ways; either by pre- fenting the aqueous folution of the fulphureous acid to the bafes, or by applying the acid in the ftate of gas to thefe bodies, either diffolved or mixed with water. The latter method is preferable, for feveral reafons too long to be detailed here. The fulphureous acid being very different from the fulphuric acid, it may eafily be con- ceived that its combinations ought to poflefs properties not at all refembling thofe of the fulphates. It will in fact be feen, that thefe falts poffefs peculiarities of tafte, folubility and form, which belong only to themfelves; and that they are fubje&t to laws of attraftion and decompofition altogether different from thofe of the fulphates, * Fourcroy, Analyfe de I’ Eau d’Enghien, The the Sulphureous Acid. —Sulphite of Pot-App. 317 The proportions of principles which conflitute the fulphites not having been yet deter- mined, we endeavoured to afcertain a method which might lead us as near as poflible to the truth ; but it could not be applied to all the kinds of fulphite, on account of the difa- greement of their properties ; fo that we were under the neceflity of employing feveral methods. ‘ The Sulphite of Pot-afa.| Sulphureous acid gas was paffed into a faturated folution of very pure carbonate of pot-afh, until the effervefcence entirely ceafed. During this combi- nation, a fmall quantity of caloric is difengaged, and the folution cryftallizes by cooling. This falt is ufually white and tranfparent ; fometimes it is flightly yellow and femi-tran{pa~ rent, if its folution has been very concentrated, and the cryftallization confufed. Its tafte is penetrating and fulphureous, its figure that of a long rhomboidal plate ; its cryftallization often prefents fmall needles diverging from a common centre, When expofed to a fudden heat it decrepitates, and lofes its water of cryftallization ; afterwards by ignition it emits fome vapours of fulphureous acid; and at length a portion of fulphur is feparated, and the refidue is fulphate of pot-afh with a flight excefs of alkali. By expofure to air it flightly efflorefces, becomes opake and hard, its penetrating fulphu- reous tafte difappears, and it acquires another, which is acrid and bitter. In this ftate it no longer effervefces with acids. If this experiment be made in a clofed apparatus with oxygene ‘gas, it is found that the volume of the gas is diminifhed, and that it is even totally abforbed when the quantity is pro- perly regulated. We fee therefore that the fulphite of pot-afli may be converted into ful- phate. by depriving it of a portion of its fulphur by fire, or by introducing a quantity of oxy- : gene ata low temperature, The fulphite of pot-afh is foluble ina quantity of water nearly equal to its own mafs; and this folubility is increafed by heat. This falt is decompofed by lime and by barytes, as may be fhewn by pouring lime water into a folution of the fulphite of pot-afh. A white precipitate is afforded, which is the ful- phite of lime, and the pot-afh remains difengaged in the water. The fulphureous acid does not therefore follow the fame laws of affinity as the fulphuric acid, fince this laft adheres more ftrongly to pot-afh than to lime. The alkalis do not change the nature of the fulphite of pot-ath. Among the acids, fome decompofe the fulphite of pot-afh by feparating the fulphureous acid; others change its nature without driving off its acid, but by affording a portion of oxygene, and converting it into fulphuric acid. The firft of thefe effets is produced by the fulphuric, muriatic, phofphoric and fluoric acids; the fecond is effected by the nitric and the oxygenated muriatic acids. The acids of borax and of carbo do not occafion any change in the cold. When the fulphuric acid is poured’ on the fulphite of pot-afh, a rapid effervefcence takes place with a crackling noife, at the fame time that much caloric is difengaged. The nitric acid, on the contrary, emits red vapours, mixed only with a fmall quantity of fulphureous acid, and the refidue is \compofed of a mixture ‘of the fulphate and nitrate of pot-afh. The oxygenated muriatic acid mixed with the fulphite of pot-afh immediately lofes its {mell, and the fluid. is deprived of its fulphureous talte, If 318 Sulphate of Pot-Afi.mAlum. ‘If the folution of the fulphite of pot-afh, and alfo that of the oxygenated muriatic acid, “be both concentrated, eryftals of the fulphate of pot-ath are formed immediately-on the muxture. «Charcoal converts the fulphite of pot-ath into the fulphuret of pot-ath, Salts with bafes of pot-ath do not decompofe ‘his falt. ‘Thofe with'bafes of foda, except the borate and the carbonate, are decompofed by the ful- phite of pot-ahh. All the other falts, of which the acids are ftronger than the fulphurcous acid, are equally decompoted by the fulphite of pot-afh. The fuper-oxygenated nitrate and muriate of pot-afh, when heated with the dry fulphite of pot-afh, take fire, and are-changed into fulphate. Several metallic oxides a& upon this falt. Some are entirely reduced to the metallic ftate; ‘fuch as the oxides of gold, filver and mercury: others are brought nearer that ftate ; fuch as thofe of lead, iron and manganefe, at the maximum of oxygenation. ‘There are others ewhich change the nature of the fulphite of pot-afh in an oppofite direétion to thofe which -take place in the foregoing cafes; that is to fay, which convert it into fulphate by depriving {tof a certain quantity of fulphur, with which they form fulphurated oxides, fuch as the exides of arfenic, and of iron flightly oxided ; but in order that this operation may fucceed, it is neceffary to boil thefe fubftances a long time in water, and afterwards to add to the folution an acid, which occafions a coloured precipitate, at the fame time that the fmeil of fulphurated hydrogene gas is emitted. All the metallic folutions except the carbonates are decompofed by the fulphite of pot- afh ; and as moft of the metallic fulphites are infoluble, different coloured precipitates are formed, according to the nature of the metal and its ftate of oxidation. [To be continued.) VI. A Memoir on the Nature of the Alum of Commerce, on the Exiffence of Pot-afh in this Salt, and on various fimple or triple Combinations of Alumine with the Sulphuric Acid, Read before the National Infiitute of France. By Citizen VAUQUELIN *. ! 1x my memoir on the leucite or white grenate, 1 have announced that many natural earths and ftones contain pot-ath in a ftate of combination ; and I founded my opinion at that time on the impoffibility of obtaining folid cryftallized alum in oétahedrons by the imme- diate combination of fulphuric acid and pure alumine, whatever precautions were taken to clear it of the excefs of acid, without the addition of alkali. ; The neceffity of this addition has long been known in the alum works, more particu- larly in the treatment. of the mother waters ; and it was thought that the ufe of pot-afh in this circumftance was merely to faturate the excefs of acid, which was fuppofed to prevent the cryftallization of the alum. Neverthelefs, the remark made by Bergman, that foda and * This-important Memoir is inferted inthe Annales de Chimic, XXII. 2¢8, whence I have tranflated it. lime, <= ia > Obfervations on Alum f 3tD fime, employed inftead of pot-afh or ammoniac in the treatment of the mother waters, de riot favour the cryftallization of the alum, ought to have produced a change in the general opinion refpecting the action of pot-afh or ammoniac*. This learned chemift had like- wife afcertained, that feveral alums decompofed by ammoniac afforded by evaporation the true fulphate of pot-afh, the bafis of which might be afforded, according to him, either from the argillaceous earth in which vegetables had been deconipofed, or from the wood-athes intentionally added, or, laftly, from a cafual mixture during the calcination of the oress And he concluded from thefe obfervations, that the fulphates of pot-afh and ‘of alumine unite together in the ftate of a triple falt +. Though Bergman appears to fufpeét that pot-afh is neceflary to the formation of alum; yet he does not venture to affirm it ; as may eafily be-feen in the courfe of his differtation : fo that this queftion remained ftill undecided. In fact, we fee by another paflage +, that Berg- man falls into the common opinion, by confining the effect of the alkalis to the fimple fatu- ration of the excefs of acid, exifting, according to him and all other authors, in the aluminous waters; and even by confidering the new falts formed by thefe alkaline fubflances as foreign bodies, lefs noxious in faét than the excefs of acid, but which cannot however be fold for alum §. if ms only effeét of alkalis in the management of aluminous lixivia were to faturate the excefs of acid they are fuppofed to contain, it is evident that any other fubftance capable of abforbing this acid would anfwer the fame purpofe. But experience has proved the cons trary, and it has been long known that this remarkable property belongs exclulively to pot- ath and ammoniac. In order to explain this obfcure circumftance by experiment, I diffolved very pure alumine in fulphuric acid of equal purity. I evaporated the folution feveralitimes fucceflively, even to drynefs, for the purpofe of expelling the fuperabundant acid. I rediffolved the dry and pulverulent refidue in water, and reduced the folution to different degrees of fpecific gravity, with a view to feize the point moft favourable to cryftallization : but whatever precautions £ took, I could not obtain any thing but a magma formed of faline plates without confiftence * Notatu dignum eft, quod’hoc cryftallifationis obf&aculum alcali volatill zqué tollatur, non vero alcali mine-- ralict calce, Bergman de Confcét. Aluminis, pag. 325, tom. i. Opufeula. + Hoc alcali quod ineft, vel ex ipfa argilla repetenduin que vegetabilium putrefactorum refiduis fuit inqur nata, vel ex cineribus ftudio additis, vel denique fub calcinatione et uftione fortuito immixtis, Interea hinc con» ftat, quod alumen et alcali vegetabile vitriolatum facilé connubium ineant, quo fal oritur triplex. Berg. ibid. } Allata momenta fufpicionem movent, quod alcali vegetabile alumine perficiendo fir neceflarium, ideoque emne alumen perfeétum inftar falis triplicis refpiciendum : fed hee conjectura vacillat; nam eadem perfectio alcali» volatili et fpontanea evaporatione obtinetur. Non tamen improbandam puto padirienen alcali vegetabilis et de- purati, nam heterogenea magis nocent quam juvant. Berg, ibidem, § Ur eo purids obtineatur alumen in alter cryftallizatione nonnullis in locis additamenta ufurpantur alcalina, ealx et urina, Scilfcer multorum annorum experientid compertum eft, lixivium aliquando tantam et adquirere confiftentiam (quod in officinis pinguefcere dicitur) ut et cryftalli egré fecernantur, et que prodeunt variis hete- rogenets irretite reperiantur, His incommodis alcalinis praefertim obicem ponere tentatum fuit, quim lixivium aciditate abundaret. Cineris clavettati ct calx, five ufta five cruda, acidum abforbenr, et fi jufa addentur dofi, peregrina noxia re-vera pracipitando minuunt, quod, cognita lixiviorum indole, $, IX. Juculentius patebit, Urina tamen nihil efficit, nifi quatenus alcali volatili pradita. Negari tamen non poteft quin novi fales peregrini immifceantur, nimirum alcali vegetabile vitriolatum, vel alii pro diverfo additamento, fine dubio, fublatis magis innocui, fed nihilominus pro alumine vendendi, Berg, ibid. p. 310+ or 320 ; The Efiais of Alkalis in Alum. or folidity. The folution here deferibed, which had conftantly refufed to afford cryflallized alum alone, afforded it immediately by the addition of a few drops of the folution of pot- ath ; and as I had employed thefe two fubfances in the requifite proportion, the reft of the folution afforded to the very end pure alum without any mixture of fulphate of pot-ath. Into another portion of the fame folution of pure alumine I dropped the fame quantity of carbonate of foda as I had added of that of pot-ath to the former. No ery Salligatinn was formed, even by the help of evaporation. Lime and barytes produced no better effect. Thefe experiments began to confirm the opinion I had, that the cryftallization of alum is not prevented by an excefs of acid, as !.as hitherto been thought, and that pot-ath was not of-ufe fimply to faturate this acid, but that it performed an office of more importance. For I reafoned, that if the common opinion were true, foda, lime, barytes, and all the fubftances which by a more powerful force would take this acid from alum, ought to give the fame re- fult. Another argument likewife prefented itfelf, which feemed decifive. If the alkalis, pot- afh and ammoniac do nothing more than unite to the fuperabundant acid of the alum, the fulphates of pot-ath and of ammoniac ought not to occafion any change in pure alum in its acidulated flate ; but if thefe alkalis enter as a conftituent part into the alum, and are necef- fary to its exiftence, they ought to produce the fame effects as pure pot-afh or ammoniac. I therefore added to a third portion of the folution of fulphate of alumine before men- tioned, fome drops of the folution of fulphate of pot-ath ; immediately upon which octahedral alum wasformed. The fulphate of ammoniac prefented the fame effect. This refult gave ftill greater confirmation to my firft notions, though it did not yet afford a demonttration perfe€tly without objeQion. For it might have happened that the two falts I made ufe of might determine the cryftallization of the alum, fimply by abforbing te fuper- fluous acid, of which they are very greedy *. To determine this pofible fact, I mixed in the uncryftallizable folution of alumine fome of the acid fulphate of pot-ath, and obtained a cryftallization no lefs abbngept than with the neutral fulphate of pot-afh. This laft experiment does not therefore leave any doubt with ble to the influence and mode of action of pot-afhand ammoniac in the fabrication of alum. This action is fill more ftrongly confirmed, by the, examination of the alums which have been formed by the procefles above related. For in this manner it is proved that they contain notable quantities of the fulphates of pot-afh and ammoniac. > Thefe experiments naturally led me to an examination of the different alums of commerce, Bergman had already announced, though in an indiftin@ manner, that net only the common alum, but likewife that of Rome, when decompofed by ammoniac, afforded traces of the fulphate of pot-ath 5 3 and Scheele had remarked on his fide, that alum which does not con- tain pot-afh is not fit for making pyrophorus. Bergman, quoting this fact from Scheele, fhews likewife that he confidered the fulphate of pot-afh in alum as a foreign fubftance }. * Ceterum alumen non tantum vulgare, fed etiam romanum alcali volatili precipitarzm liquorem exhibet, qvi haud raro alcali vegetabile vitriclatum continet- ibid. + Alumen hoc inquinamento fpoliatum pyrophoro generando ineptum eft: quod facile experiri licet, nam magma aluminofuin diftinétam refpuens cryftallizationem, nullym prebet pyrophorum, modo confueio tragta- rum, quamvis idem addito alcali vegetabilis pauxillo, eximium porrigat, &c. ; a In Analyfis of the Alum of Commerce. 32% In fact, ifthis chemift-had thought pot-afh effential to the conftitution of alum, he certainly would not have thought it adyifable to ufe a portion of the clay of Cologn to deftroy the excefs of acid in aluminous waters. For this addition is extremely vicious, and I am con- vinced that it was fuggefted by reafoning rather than by experiments *. Out of all the kinds of alum which | had fubmitted to analyfis, I did not find one which did not afford fulphate of pot-afh or of ammoniac, and frequently both at once. I ufed the following method of analyfis: In the firft place, to direét my operations, I take a {mall quantity of the alum I with to aflay, which I diffolve in the aqueous folution of pure pot-afh, and flightly heat the mixture. If it contain fulphate of ammoniac, a ftrong fimell _ of volatile alkali is immediately perceived. I then put intoa tubulated retort a given quan- tity of this fulphate of alumine ; I adapt a receiver containing a {mall quantity of water, and then pour on the alum a folution of pot-afh in a proper quantity to decompofe the ful- phate of ammoniac and alumine at once. I boil this mixture for a quarter of an hour, at the end of which all the ammoniac is volatilized, provided no more than three or four doci- maftic quintals be operated upon. I combine this ammoniac to faturation with the ful- phuric acid, and the quantity of falt which I obtain indicates that which was contained in the ammoniacal fulphate of alumine. When the pot-afh does not indicate the prefence of ammoniac, which is very feldom, I follow another method to. feparate the fulphate of pot-afh. Idecompofe the alum by means of ammoniac, and, after having wafhed the precipitated alumine, I evaporate the liquor to drynefs, and heat the remaining falt in a crucible, till it emits no more white vapours of the fulphate-of ammoniac. The remainder is the pure fulphate of pot-afh. By thefe analytical methods, I found that one pound of cryftallized alum contains about one ounce 64 grains of fulphate of pot-afh; but as the alum contains about 0,44 water of cryf- tallization, this raifes the quantity of the fulphate to one ounce 7 gros 17 grains, for a pound of alum, or otherwife for cryftallized alum, about 0,070, and for dry alum, 0,125. When the alum has been formed with volatile alkali, it is found to contain the fulphate of ammoniac, nearly in the fame proportion as the fulphate of pot-afh. Whence it follows, that a quintal of alum prepared with pot-afh contains, 1. Sulphate of alumine — — _ 49 2. Sulphate of pot-afh _ = i 7 3- Water _ —_— _ _ 44 ' 100 When the alums contain both the falts here mentioned at once, which frequently enough happens, I ufe lime inftead of pot-afh to difengage the ammoniac, and proceed with the refidue as before. It may therefore be afcertained, by thefe fimple effays, whether pot-afh or ammoniac or both together have been ufed in a manufactory for the preparation of alum. This proof * Hujus (lixivii magiftralis) cantharo duas addidi drachmas argille Colonienfis in fubtilem comminate pul- verem, et pauci aque humeétate ; calore ebullitionem provocavi, qua per decem minute continuata, et poftea, refrigeratione peraéta, refiduam feparavi argillam ; lotam ficcavi; tandemque ponderatione inveni 2s.5 grana foluta, quz aluminis augmentum 141 granoruin indicant. Derg. ibidem Vou. L—Ocroner 1797. at may 322 Alithh fibiirdted aouh its Barth, 4. niay-be of fome utility ; fot Berghian pretends, I don’t know on what foundation, that urine communicates td alliny propertits whiclt até Hurtfillin dyeing : it if Hot probable, however, that this chemi(t afferted the fact without proof. In all the works where putrid urine is employed for the treatment Of aliini waters; the Alani coftdins the fulphates of pot-afh aiid of animoniac; becaufe the coimbultibles whith ferve to roaft the ores depofit a certain quantity of alkali; which unites with the fulphutic acid; and contributes; according to its proportion, to the formatioii of a greater or lefs quantity * It is known; frord the experinients of Bergman and feveial other chemiits, that by boiling a folution of ordinary alin’ with puré aluminé in a very divided ftate, this laft combines with the alum, and renders it infoluble in water; that is to fay, it converts it into the itate of neutral fulphate of alumine, or faturatéd with its earth. Ihave repeated this ex- periment with the defign to’ afcertain whether the fulphdtes of pot-afh and aimmoniac are precipitated with the alum; and I immediately obferved, that the combination does not take place but by means of heat, though I ufed alumine recently pre [Inches. Juches. flons of 282}ions of 231 in Grains, ea | Inches. Inches. : 22.966 || 51 | 2008.5 3115.2.) 11.047 | 13.486 |, 1171.3. 45-932 || 52 1 9017.9 | 3176.3 | 11.964 | 13.750] 1194.2 68.898 || 53.] 2087.3 | 3237.4 | 11.4809 14.015 } 1217.2 91.864 || 54°} 21267. | 3298.5.) 11.697 | 14.279 | 1240.2 114,83 499 2166.1 | 3359.6 | 11.913 | 14.544.) 1263.1 137.79 ||. 56 | 2905.4 | 3420.6 | 121.80 | 14.808 | 1286.1 160.76 || 57 | 2944.8 }°3481.7 | 19.347 | 15.072'| 1309.1 183.73,1}:58 | 9284:2'1°3542.8 | 12-563 |15.387 «1832.0 206.69 i 59+} 2323.6 | 3603.9:|} 12.780 | 15.601 | 1355.0 229.66 60" 2363.0 | 3665.0 | 12.996 | 15.866 | 1378.0 252.63 | 61 | 2402.4 | 3726.1 | 13-213 | 16.130 | 1400.9 975.59 | 62 | 9441.7 + 3787.1 | 13-430 116.395 | 1423.9 298.56 |} 63 | 2481.1 }| 3848.2 | 13.646 |. 16.659 | 1446.9 321.52 || 64 | 2520.5 | 3909.3 | 13.863 | 16.923 | 1469.8 344.49 65: 2559.9 | 3970.4 | 14.079 | 17 188 | 1492.8 B67.46 |} 66 | 2599.3 | 4031.5 | 14.296 | 17 452 | 1515.8 390.42 |}67 | 2638.7 }:4099.6 | 14.513 | 17.717 | 1538.7 413.39 168 | 2678.0 | 4153.6 | 14.729 | 17.981 | 1561.7 436.35 || 69 | 2717.4 | 4214.7.) 14.946 | 18.246 | 1584.7 459.32 |! 70 | 2756.8 | 4975.8 | 15.162 | 18.510 | 1607.6 482.29 || 71 | 2796.2 | 4336.9 | 15.379 | 18.774 | 1630.6 505.25 |) 72 | 2835.6 | 4398.0 | 15.596 | 19,039 | 1653.6 528.22 || 73 | 2875.0 | 4459.1 | 15.812 | 19.303 | 1676.5 551.18 || 74 | 2914.3.) 4520:) | 16.029 | 19.568 | 1699.5 574.15 || 75 | 2958.7 | 4581.2 | 16.245 | 19.832 | 1722.4 597.12 || 76 | 2993.1 | 4642.3 | "16.462 | 20.097 | 1745.4 620.08 || 77 | 3032.5 | 4703.4 | 16.679 | 20.361 | 1768.4 643.05 || 78 | 3071.9 | 4764.5 | 16.895 | 20.625 | 1791.3 666.01 |} 79 | 3111-3 | 4825.6 | 17.112 | 20.890 | 1814.3 688.98 || 80 | 3150.6 | 4886.6 | 17.328 | 21.154 | 1837.3 711.95 || 81 | 3190.0 | 4947-7 | 17.545} 21.419 | 1860.2 734.91 || 82 | 3929.4 | 5008.8 | 17.762 | 21.683 | 1883.2 757.88 || 83 | 3268.8 | 5069.9 | 17.978 | 21-948 | 1906.2 780.84 || 84 | 3308.2 | 5131.0 | 18.195 | 22,212 |} 1929.1 803.81 || 85 | 3347.6 | 5192.1 | 18.412 | 22.476 | 1952.1 826.78 || 86 | 3386.9 | 5253.1 | 18.628 | 29.741 | 1975.1 849.74 || 87 |-3426.3 | 5314.2 | 18.845 | 23.005.| 1998.0 $72.71 || 88 | 3465.7 | 5375.3 | 19.061 | 23.270 | 2021.0. 895.67 || 89 | 3505.1 | 5436.4 | 19.278 | 93.534 | 2044.0 918.64 || 90 | 3544.5 | 5497.5 | 19-495 | 23.799 | 2066.9 941.61 || 91 | 3583.9 | 5558.6 | 19.711 | 24.063 | 2089.9 964.57 || 92 | 3623.2 | 5619.6 | 19.928 | 24.327 | 2112.9 987.54 || 93 | 3662.6 | 5680.7 | 20.144 | 94,592 | 2135.8 1010.5 |} 94 | 3702.0 | 5741.8} 20.361 | 24.856 | 2158.8 1033.5 |} 95 | 3741.4 | 5802.9 | 20.578 | 25.121 | 2181.8 1056.4 || 96 | 3780.8 | 5864.0 | 20.794 | 25.885 | 2204.7 1079.4 |} 97 | 3820.2 | 5925.1 | 21.011 | 25.650, | 2227.7 1102.4 || 98 | 3859.5 | 5986.1 | 21.227 | 25.914 | 2250.7 1125.3 || 99 | 3898.9 | 6047.2 | 21.444 |. 26.178 | 2273.6 1148.3 |}100 | 3938.3 | 6108.3 | 21.661 | 26.443 | 2296.6 1649.2 1710.3 1771.4 1832.5 1893.6 | 6.7148 1954.7 2015.7 | 9076.8 | | 2137.9 | 2260.1 2321.2 2382-2 2565.5 2626.6 2687.7 2748.7 2932.0 2993.1 1969.1 | 3054+] Me Gal- ons of 2§ Inches. 0.2166 0.4332 0.6498 0:8664 1.0880 | I. = Vine Gal ons of 2314 ach $ 0.2644 | 0.5289 | 0.7933'| 15162 1.7328 -| 2.1661 3.1657 3.6823 38989 4.1155 4.3321 5.4151 5.6318 | 6.8752 5-8484 | 7.1396 6.0650 | 7:4040 6-2816 | 7.6684 6-4982 | 7 9329 6.9314 7.1480 7.3646 7.5812 8.0144 8.2310 8.4476 8.6642 Solutions of Mathematical Queftions. 333 MATHEMATICAL anp PHILOSOPHICAL CORRESPONDENCE. Question VIL. An/wered by i F—:—:—:—R. Tx E order in which the firft 51 cards are diflributed being of no importance with re- fpeét to the chance for trumps, the folution of this queftion eo be fomewhat fimplified by conceiving the hands of the dealer’s two adverfaries to confift of the firft 26 cards dealt off. The chance that thefe may be all of them of the 39 which are not trumps will evidently BO so 27 1 gO» Cree oie TE) AG ZAHA Qi 2 ee OGY «oie ate 14 LS I 2 FT 50% 404/48). oC 2s 20 0) SLnsOe do ABlon Kens. 1040 = 580027 3052735; fo that the odds againft it are 30526;* to 13 and yet it is 5200300 times more pro- bable that the dealer and his partner fhould have the thirteen. trumps between them, than that the dealer himfelf fhould hold them all in his own hand. De Moivre, in his “ Doétrine of Chances,” (2d edit. cor. to prob. xix.) gives a theorem refpecting the chance of drawing any certain number of black and white counters, which. is applicable in fuch an infinite variety of cafes, that it is perhaps worth mentioning. It may be thus generalifed’:—!f a and 4 be the refpective numbers of things of two different kinds, heaped promifcuoufly together, the following formula will exprefs the value of the chance, that out of ¢ of them, taken at hazard from amongft the whole number 7 ( = a+4) there be found the exact number #, and no more, of that kind whofe whole number is a: cc—1.c—2..&c.(p terms) Xd.d—1.d—2...&c. (a—p terms) X Re balan Z 3 * ke. (p terms) A.n—1.N—2.n—3..&e. (a ae wherein dis =» —c. A proper fubftitution in this expreffion will alfo give us the fame refult as above. ; QUESTION VIW. Anfawered by ie [i Po aeey LET aandb be the hyperbolic logarithms of @ and J. ‘Then will ax.be =h.l. a” at a? a3 and 1 + a.” + — x? —— x3 4 2 23 2.34. bs b4 x . . xt....&c. =a 3 and, in like manner, Bt clans CCCs = ag the fum of which 2 + (a + b)x ta 3 3 4 tk Ne Bs at +b a4, 2 j lu2agis 2iZQege o—2, and a, f, ¥5 2 s, &c:=the above co-efficients of the feveral powers of ~ in the latter feries, we get x = — i d— 2 py hmen ah yiry Saha eee ort, 4.5. &ee As, . &c. = c, by the queftion. Hence, putting d= however, this feries does not, when d is great in refpect of a, begin.to converge till after.a confiderable number of terms, it feems better to ufe the common tentative procefs, repeat- edly affuming two values of x, and applying the following proportion :—Difference of re- fults : difference of affumed values :: leaft error : correétion for the’ neareft value.—This method, though an indire& one, has. certainly great practical advantages in a variety of eafes wherein the expreffions are fo entangled with furds or unknown exponents as not to be otherwife reducible without a great deal of trouble, 5 : Another 334 Mathematical and Philfophical Correondence. > Another method of obtaining the value of x is by means of a table of artificial fines, as follows :—Let r be the logarithmic radius, a, b, and cthe common logarithms of a, 4, and ¢, - and d =r — $c. Find an artificial fine, and its correfpondent cofine, f and s, in the tables, rae! each of which quantities will then be = x. The demon- {tration becomes obvious by confidering, that if one of three quantities be equal to the fum of the other two, their fquare-roots are the fides of a right-angled triangle. © nay be = e fo that Sa Naarly a fimilar anfwer was given to this queftion by ANaLyticus. NEW MATHEMATICAL QUESTIONS. Question XI. By W. Srupson. 1F H, 4, be the heights of any two fignals above the horizon of an obferver, A, the angle which they fubtend, and a, the fame angle reduced to the plane of the horizon, then will cof, A = cof, a x cof. H X cof.4 + fine H x fine 4. Required the demonttration. QUESTION XII. By W. C. of Greenwich. ON the 1ft of May 1797, the fun’s declination being 15° 9’, it was obferved that his altitude, azimuth, and the latitude of the place were all equal. Required the hour and place where the obfervation was made. *.* I SHOULD be glad to give «a defcription and drawing of Mr. Varley’s machine for prédteiiy perpetual motion, as requeéfted by Mr. Notlem of Wifbech, ifan attentive perufal of the {pecification enrolled in Chancery had fhewn me any thing tending to improve the theory or practice of mechanics. The defcription in the periodical work he mentions is not fufficiently clear to fhew the whole of what the writer meant to explain, and I found the original equally imperfe&t. Mr. Varley’s notion, obfcured by fome extraneous and unimportant circumftances, appears to be, that if an exhaufted cylinder be fixed to one part of the periphery of a wheel, and a pifton fitted therein, the preffure of the atmofphere on this laft, fuppofed alfo to be attached to the wheel by a {pring and chain :(parallel.to.a tangent), will tend to drive it into the yacuum, and, if prevented’ by the fhortnefs of the chain, will draw the wheel round. It is obvious to any perfon moderately acquainted with ftaties, that the preffurés on his wheel muft counterbalance each other, nr cannot produce “motion. Tt has always been eafy to fhew the fallacy of fchevies for veespllaiti motion inthe ‘par- ticular inftances ; but I have met with no‘clear enunciation of this project’ fo geweral as’to include every poffible fcheme, and evince its own abfurdity. The difficulty of iperSerming this feems to arife from a want of dire& and concife demonftrations of ‘the fundameatal principle of the lever, and of the equal'preflure of fluids in all direQtions. tip fag 6 THE Foreign Publications, 335 *,* THE correfpondent who defires an explanation whence'the fulphate: of pot-afh men- ddoned' in the laft paragraph of page 218,)was derived, is reminded, that this fal is the mot abundant impurity in the common vegetable alkali. Kirwan, in the Irifh Memoirs for 1789, ftates its amount in Dantzick pearl-ath at 505 grains in the pound troy, which is upwards of one feventh of the weight of the pure alkali. As Profeffor Siegling made his Niquor of flints by the ordinary proce/i, it is not to be fuppofed-that his alkali had undergone any very laborious purification. PUBLICATIONS oN GALVANISM. Te E celebrated Aldini, Profeffor of Natural Philofophy at Bologna, has forwarded to the firft clafs of the National Inftitute a collection of works publithed in Italy, fince the difco- very made by Galvani, of the irritation produced: in animal matters by the metals, and which treat on that fubje&t. 'Thefe works having beem hitherto little circulated, Citizen Guyton, from whofe annonce in the 22d volume of the Annals of Chemiftry, page 323, this extract is taken, naturally concluded that the lift would be acceptable to the world. The paper of Mr. Humboldt, of which I have given a tranflation* ; another memoir by the fame author, on the chemical procefs of vitality, together with certain truly philofophi- cal remarks upon the fame by Citizen Fourcroy, all which are inferted in the 22d volume of the fame Annals, have fhewn the great importance of a phenomenon which has engaged the attention of all Europe. The firft clafs of the Inftitute of France has confidered this as an object moft worthy of inveftigation, and has for that purpofe nominated a commiffion of feven members, who for five months paft have been engaged in experiments proper to determine the circumftances, and develop its nature. The following is the lift. The annexed remarks are made by Citizen Guyton. Aloyfii Galvani in Bononienfi Archigymnafio Profefloris, ete. de Viribus Ele@tricitatis in Motu mufculari, Commentarius. Cum Joan. Aldini Differtatione et Notis. Munibes 1792. Small folio, 80 pages, with three engraved plates. This work contains a letter of Baflani Carminefi, which exhibits the opinion of Volta : concerning the feat of animal electricity. Joannis Aldini de Animali Eleétricitate Diflertationes due. Bononiz, 1794. Small folio, 41 pages, with figures. Dell’ Ufo e dell’ Attivita dell’ Arco Conduétore nelle Contrazioni dei Mufcoli. In Bo- logna, 1794. Small quarto, 168 pages. Witha Supplement of 23 pages. Memoria intorno all’ Eleétricita Animale, del Sig. Dott. Gio. Aldini, Prof. di Fifica nell? Univerfita di Bologna, etc. 10 June, 1794, In quarto, 12 pages. * Philof. Journ. I. 256, : Prima 336 Rudiments of the Brunonian Theory. Prima Brunonis Theorie Rudimenta, Bononix, 1797. Octavo, 16 pages. This paper of Aloyfius Zanottus is written in the form of a letter addreffed to Charles Mundini. It contains a development of Dr. Brown's opinion, that irritability is one and indivifible relative to the fyftem of the nerves; that is to fay, that this force is diftributed through every point of the fyftem, in the fame manner_as velocity, impreffed on any body or fyftem of bodies, appertains equally to all the elements of this body or fyftem. Irritants are diftinguifhed into extrinfic and intrinfic. The extrinfic are heat, light, found, food, &c. The blood and other animal fluids, though appertaining to the fyftem of the animal, appear to act on its economy like extrinfic objects. The intrinfic irritants are the fun@tions of the fyftem, fuch as the mufcular contraction, the exercife of the fenfes, the action of thought, the movements of the brain, &c: The common effect of thefe forces-is motion. Each poffeffes a certain a€tivity called {timulus. There cannot be‘fuch an agent as a fedative; for, when the irritants produce weaknefs, this weaknefs muft be attributed to a defeé&t of the ftimulating power in degree, &c. &e. : BSQOCOOTHOSSTOSOOSOENVOS ‘halos Journal Vol \.PtXU vaca Page 336. ¢ 2 Fe) Ze ge ‘a a i “ 4 eye LMCI Loca ‘ - ‘ wat Yea ; fe “ ~ fe =, d ' a v Loe 7’ = z , a = . ~ er ‘ ae a lente, ap or —— ‘ Philos. Journal Vol 1 PAX Lacing P3306 Section pPersh 7 Nee ok . ity pean ; care) il * ae e “ih wind A POR Near OF NATURAL PHILOSOPHY, CHEMISTRY, AND. THE ARTS. Sees et ke Sa)” al NOVEMBER 1797. ARTECEE oR Experiments and Obfervations on the Nature of Sugar. By Witttam CRUICKSHANK, Chemift to the Ordnance, and Surgeon of Artillery. Sucar has been fuppofed to be a fubftance intermediate between mucilages and ve~ getable acids, containing more oxygene than mucilage, and lefs than the acids. ‘To afcertain this and fome other circumftances, the following experiments were inftituted : Two ounces of refined fugar were introduced into a retort, and expofed to a heat gra- dually increafed until its bottom became red-hot: there came over into the receiver fever drachms of a fharply acid liquor, which required 132 grains of a folution of pot-ath to: fa- turate it: this liquor was mixed with a little empyreumatic oil: the charry refiduuny which remained in the retort weighed feven drachms; the quantity of gas which efcaped’ during the operation muft therefore have amonnted to two drachms: fome of this was ex- amined, and found to confift of a mixture of carbonic acid gas and hydro-carbonate. Two ounces of gum-arabic were introduced into a retort at the fame time, and expofed to a heat in every refpeét fimilar: the quantity of acid liquor which came over into the-re+ ceiver amounted to feven drachms and 1 5 grains ; this contained a little more empyreu- matic oil, but was not fo fharp as that obtained from the fugar, and required only 117 grains of the fame folution of pot-ath to faturate it: the charry refiduum which remained in the retort weighed five drachms and 45 grains; the quantity of elaftic fluid or gas which ef- caped during this procefs muft therefore have amounted to three drachms: it confifted, like the former, of a mixture of hydro-carbonate and carbonic acid gas; but towards the end of the operation the proportion of hydro-carbonate was more remarkable. From thefe experiments it would appear that fugar yields by diftillation more pyromucous acid. than Vou. I.—Novemaer 1797. Xx gum,. Sf Experiments on Sugar.— Malting. gum, in the proportion of 132 to 117. The refiduary charcoal of the fugar alfo exceeded that of the gum by 1-7th; but this may in fome meafure be accounted for from the greater quantity of the hydro-carbonate yielded by the latter. As oxygene is now allowed to be the univerfal acidifying principle, and as the acid yielded in both inftances (viz. the pyro- mucous) was exadtly of the fame kind, it may be reafonably inferred, that the fugar which afforded the greateft quantity of acid contained likewife the greate{t proportion of oxygene ; for it is probable that both the carbonic acid and the hydro-carbonate were formed from the decompofition of the water by the carbone of thefe fubftances, as neither was produced in any quantity until near the end of the operation : the oxygene, therefore, contained in the former fhould not be confidered as ciitering effentially into the compolition of either the gum or fugar. It is well known that vegetable mucilages and fecula are fomehow converted into fugar by malting : we conceived, therefore, that it would throw confiderable light on this fubject, to obferve with more attention than had hitherto been done, the particular changes and decompofitions which take place during this procefs: it was with this view that the follow- ing experiments were made: December 1, 1796. A quantity of barley, after being foaked in water for 24 hours, was put into a wine-glafs, and introduced into a jar containing common air, and inverted over water: the temperature in this and the following experiments was preferved between 60 and 70 as nearly as poflible. At the end of five days it began to grow, and on the 28th the greateft part had thrown out fhoots at Jeaft halfan inch in length. On January 7, vegetation was ftill going on, and the air in the jar had fomewhat diminithed : the barley being now withdrawn was found to be very {weet, and nearly converted into the {tate of malt. The air in the jar was found to confift of azotic and carbonic acid gas in the proportion,’ of 20 to 6, the whole of the oxygene being either abforbed, or converted into carbonic acid. January 19, 1797- A quantity of barley, previoufly fteeped in water for 48 hours, was introduced, as in the laft experiment, into a jar containing oxygene gas, and inverted over water to which fulphuric acid had been added. At the end of three days it began’to grow, and this procefs went on tothe 29th. The water’had now rifen confiderably in the jar,» the gas having fuffered a diminution of about one-third. The barley being withdrawn {melled completely of malt, and tafted {weet...The gas in the. jar, on examination, was found to confift of 64 parts carbonic acid, 32 azote, atid 4 oxygene; from which it would appear that the air employed in this experiment;had contained originally about 20 per cent.) of azotic gas. To be more certain of the nature of the change which the pure air undergoes in:this pro- cefs, the experiment was repeated as follows: B January 23. A quantity of barley, foaked in water for two days, v was introduced into a jar containing 46 meafures of very pure oxygene gas, and inverted over mercury. At the end of three days the barley began to grow; and this procefs continued for ten days, al-. though very flowly: the column of gas remained exadUly of the fame height, fo that'it had undergone no. apparent diminution or increafe: the-barley being withdrawn, the airin the yar was examined, and found to confit of carbonic acid gas, mixed with only r-gcth of its bulk of oxygene gas. The barley was partly converted into malt, the quantity of. oxygene being in{ufficient to produce this change upon the whole. TAsoier Experiments on Sugar.—-Maltings 339 Another experiment with common air was made at the fame time, and exaéily under fimilar cireumftances. In this cafe the barley did not begin to grow until the end of the fourth day; and at the end of ten days had made much lefs progrefs than that in the oxy- gene gas. It was now withdrawn, and the air in the jar, which had increafed a little, ex- amined ; when it was found to confift of carbonic acid and azotic gas, in the proportion of one to two very nearly, mixed with a very {mall quantity of oxygene gas. A little of the barley tafted fweet. Being now fatisfied that during the evolution of the faccharine principle from vegetable: mucilage, a quantity of oxygene was either abforbed or converted into carbonic acid, we wifhed to know if this procefs could take place in any degree without the prefence of this gas. \ In order to determine this point the following experiments were made: January 20. A quantity of barley, foaked as in the former experiments, was introduced into a jar filled with, and inverted over, mercury. At the expiration of 12 daysa very con= fiderable quantity of gas was produced, at leaft five or fix times the bulk of the barley; but nothing like vegetation was perceivable. The gas, on examination, was found to confift, of carbonic acid, being entirely abforbed by lime-water. The barley had not the leat fweee tafte, nor did it appear to have undergoné any fenfible change. On January 20th, another portion of the fame foaked barley was introduced into ‘2: wine-glafs, and placed in a jar containing nitrous gas inverted over water. At the éx- piration of ten days the gas had undergone a flight diminution, but there was not the fmalleft appearance of vegetation. The barley being withdrawn and examined was found’ to have undergone no apparent change. The gas contained about one-ninth of its bulk of carbonic acid, the remainder being pure nitrous gas, as was’ manifeft from the diminution it underwent when mixed with pure air. The nitrous gas which difappeared in this in- ftance muft have been abforbed either by the barley or the water. The carbonic acid which: was found mixed with it is accounted for by the laft experiment. be Two other portions of foaked barley were introduced into jars, the one containing hy- drogenous and the other azotic gas, and inverted over mercury. At the expiration of 12 or 14 days there was not the leaft appearance of vegetation in either, but the gas in’ both had increafed in bulk about one-fifth. The barley being withdrawn and examined, that in the hydrogenous gas tafted mufty, but not in the leaft fweet; the portion’ in the azote appeared to have undergone no change. ‘The gas in both jars contained from one-third to one-fourth of its bulk of carbonic acid, the remainder being the original gafes:not fenfibly. changed. ; ‘ ‘ From thefe experiments, therefore, it is'manifett that oxygene is abfolutely necefury for: the converfion of vegetable mucilage into fugar ; as in no one inftance»was faécharine mate ter formed where this was not prefent, and the quantity of the former was always in prot portion to that of the latter; for we found in all the experiments, that’ when ‘the Oxyforie- was confumed this procefs immediately ceafed. [lok pe biol nl It may ftill remain doubtful, whether the oxygene is abforbed by the barley, or merely: converted into carbonic acid : we are inclined to think that it is chiefly abforbed, althoiyhi part may alfo be confumed in the formation of this acid; for we have féeti! that! earbonie! acid is formed without the prefence of oxygene gas, and that in very confiderablé quiiistiry sy? Xx2 which 340 Experiments on Sugar.—~Its Converfion into Gun, which we conceive muft proceed from the decompofition of the water, whofe oxygene unites with the carbonaceous principle of the barley, whilft its hydrogene is fixed, and may be ne- ceflary tothe production of the faccharine principle. We fuppofe, therefore, that vegetable mucilage is converted into fugar by being deprived of part of its carbone, whilft at the fame time it is combined with a greater proportion of oxygene, and probably alfo with hydrogene from the decompofition of the water. ‘Thus, then, both from anaiyfis and fynthelis, it would appear that fugar contains more oxygene than gum or mucilage. From this hypothefis it fhould follow, that if fugar be deprived of part of its oxygene, it muft lofe its fweetnefs, and form fomething like a gum. ‘To fee how far this might be accoinplifhed was the object of the following experiments: A quantity of fyrup was introduced into a jar, filled with, and inverted over, mercury : to this was admitted about an equal quantity of the phofphuret of lime: a confiderable pro- duétion of phofphoric gas almoft immediately took place, and the mercury defcended in the jar. At the expiration of eight days the fyrup was withdrawn and examined : it had no fenfibly fweet tafte, but rather a bitter aftringent one: when filtered, alcohol produced a copious white precipitate in flakes, very much refembling mucilage feparated from water by. the fame fubftance. ‘This experiment was fomewhat varied, as follows: A little refined fugar was diffolved in alcohol, and to this folution a little phofphuret of lime was added : no phofphoric gas was difengaged, nor was there any apparent ation produced~ More phofphuret being added; the mixture was allowed to remain in an open phial for feveral days. The alcohol haying now evaporated, fome diflilled water was added; but this produced no difengagement of gas, as the phofphuret had been decompofed, and converted principally into phofphate of lime. The mixture being filtered, and the clear liquor evaporated, there remained a fub- ftance extremely:tenacious, and which had much the appearance of gum-arabic: its tafte was bitter, with a very flight degree of {weetnefs : when fqueezed between the teeth it had exaétly the feel of gum, but more tenacious. It did not appear to be foluble in alcohol, or at Jeaftin any confiderable quantity: when thrown upon a red-hot iron it burned like gums and left a bulky and infipid charcoal. 344 _ [would appear that the faccharine principle had been deftroyed in thefe experiments; and conyetted into fomething refembling a gum. ‘Chat this was effected by the ab{traction of oxygene is rendered highly probable from the nature of the fubftance employed, and the change whiclvit was found to have undergone ; for there are few fubftances which have fo iirong.a tendency to. combine with oxygene as the phofphuret of lime. Some other trials of a fimilar nature were made by mixing folutions of fugar with the, different fulphurets, afd by agitating them with nitrous gas in clofe veflels. The fulphurets, more efpecially that of pot-ath, manifeftly deftroyed the faccharine tafte; but on account of! the folubility of the different produéts, the particular change produced could not be fo eafily’ aishagouratély afcertained. The action of the nitrous gas was more doubtful. In order to be fatisfied how far the effe&ts produced on the fugar in the former experi-, ments might beowing to the abftraction of oxygene, I added to folutions of this {ubftance iptowater bath lime and pure pot-ath, and boiled the mixtures for fome time: the lime ap- peared; manifeltly to combine with the fugar, to which it communicated a very bitter af- tringent taltey ut it was ftill {weet : a little alcohol, added to the filtered folutions, pro- tts duced Experiments on Sugar.—Propagatiin of Heat. 341 tuced:a ‘precipitate! in white flakes, fomewhat fimilar to that in the experiments with the fulphuret of lime, and which appeared to be a combination of fugar with lime. Some of the filtered folution being evaporated‘by a gentle heat; there remained a femi-tranfparent fubftance, much more tenacious than the thickeft fyrup, but not equal to that produced by the phofphuret of lime; and it had a rough bitter tafte, mixed with a certain degree of fweet- nefs. The pot-afh, likewife, appeared to combine with the fugar, the {weet tafte being more completely deftroyed than by'the lime: but on the addition of fulphuric acid, fulphat of pot-afh was formed; and this being precipitated by alcohol, the fweetnefs appeared to be completely reftored. It may likewife be proper to obferve, that when alcohol was added to a portion of the folution of fugar and pure pot-ath, after it had been boiled to the con- fiftence of a fyrup, no union took place ; but the alcohol, notwithftanding the mixture was completely and repeatedly agitated, {till f{wam pure on the top: a cireumftance which would feem to prove that a new compound is formed by thefe fubftances, which is not folu- ble in this fluid, although they are both completely fo in a feparate ftate. Having found that fugar might be converted into a fpeciesiof gum by depriving it of part of its oxygene, we conceived that gum might, by the addition of oxygene, be changed into a fubftance refembling fugar: but although feveral trials were made with a view of combinining oxygene in different proportions with gum-arabic, no remarkably {weet fafte was ever perceived; on the contrary, in every experiment, it feemed to run very readily into the acid ftate, particularly when it was expofed to the aétion of the oxygenated muriatic acid gas. Indeed, when we reflect on the change which vegetable mucilage muft undergo in the procefs of malting, the fimple addition of oxygene does not appear to be fufficient; for it is probable, from the decompofition of the water, that fome of its hydrogene is fixed, whilft its oxygene difengages and unites with a certain portion of charcoal, forming the carbonic acid. Although, therefore, fugar and mucilage confift of the fame principles, viz. carbone, hydrogene, and oxygene; yet unlefs thefe are combined in certain determinate proportions, the former, which when pure is no doubt alwaysa fubftance of exa€tly the fame nature, cannot be produced: the hydrogene and carbone mutt be accurately proportioned, as well as the beet a II. + Then 4n Account of the Manner in which Heat is propagated in Fluids, and its general Confequences in the Economy of the Univerfe.. By BenyzAMIN Count of RUMFORD. ' [Continued from page 296: ] From the internal motions of the particles of fluids during the Ricgacaticn of heat, and from this propagation being impeded by every thing which obftruéts thofe motions, refults amounting to a theory of confiderable perfection were obtained. But the fubjeét in the hand, of our author naturally produced other interefting confequences, It was by * This paper is, with the author’s confent, extraéted from Dr. Rollo’s account of two cafes of Diabetes Mellitus, of which an account is given in this Journal, p. 235. tire 342 Motions of Fluids during Tranf/miffion of Heat. the motions of very fine particles of duft, accidentally mixed’ with the fpirits of wine im hie large thermometer, and ftrongly illuminated by the fun, that he! firft difcovered the inter nal motions which take place.in that fluid during the | time ofits cooling. Reflecting on this fact, he immediately concluded that the internal motions of water might be rendered equally vifible if he could find any folid body of the fame fpecific gravity as water, and not liable to be diffolved by it; but fuch a fubftance was not to be found. © On refleftion, it occurred to him, that/it is very fortunate'that fuch fubflances do not abound; fox ouhnrwzite we fhould find great difficulty in'procuring water in a pure’ ftate. As the folid could not be found, he determined to adapt the fpecific gravity,of the fluid to that of a folid very little heavier than the water in its pure ftate. The folid he made choice of was tranfparent yellow amber, of the fpecific gravity 1,078, .and he increafed the denfity of the water by the addition of a certain quantity of pure alkaline falt. The amber was broken into pieces about the fize of muftard-feeds, and. put into a glafs yellel with water, to the bottom of which it funk. Upon the gradual addition of an alkaline folution fome of the pieces rofe to the top, and others fubfided,to the| bottom. ‘The former were removed, and the fluid was carefully adjufled with regard to denfity, until the latter, at 60° of Fahrenheit, remained permanently fufpended in the different parts of the fluid. A glafs veffel, confifting of a globe about two inches in diameter, with a cylindrical neck three quarters of an inch in diameter and twelve inches long, was filled with this prepared liquid. . The firft experiment made with this inflrument was to plunge it into a tall glafs jar, nearly filled with water almoft boiling hot. Two currents, in oppofite directions, began to move at the fame inftant with great celerity in the liquid im the cylindrical tube, the afcending current occupying the fides of the tube, while that which moved downwards occupied its axis. ; As the faline liquor grew warm, the velocity of thefe currents Saale diminithed ; and at length when the liquor had acquired the temperature of the furrounding water in the jar the motion ceafed entirely. On taking the glafs body out of the water, the internal mo- tions of the liquor recommenced: but the currents had changed their direCtions; that which occupied the axis of the tube being now the afcending current. When the cylin drical tube was inclined a’little, the afcending current occupied the upper fide, and the de~ fending current the lower. Both ceafed when the inftrument had noquired the ¢ common. oe io temperature of the room. In all cafes when the inftrument Neaeead heat, the current in the axis of the es or on its lower fide if inclined, moved downwards; but when it parted with heat this motion was in the oppofite dire€tion. A change of a few degrees was fufficient to fet the contents of the inftrument in motion. By the application of an heated body, the fluid neareft the place of contaét was made to afcend; but the contrary effet took place if the body were colder than the inftrument. And in either cafe the motion thus produced was attended with a contrary motion in fome other part of the inftrument. Among the applications made by this enlightened philofopher to an inftrument fo calcue lated to deteét the fecret operations of nature, one confifted in applying a lighted candle to the middle of the tube while,it was inclined in an angle of about 45 degrees from the per- pendicular. In this fituation the motion of the fluid in the upper part of the tube became exceflively rapid, while that in the lower end, where it was united to the globe, as well as that Experiments on the Fufion of Ices 343 that im the globe itfelf, remained/almoft perfectly at reft. He even found that he could make the fluid, inthe mpper part of the tube aQually boil, without that, in the lower part of it appearing to the hand; to he ferfibly warmed. | ‘This fact not only ferved to-fhew that heat is propagated in fluids chiefly, if not altogether, by virtue of thefe motions which arife from change of denfity, but alfo that this tranfportation cannot be efleGted in a downward direGtion, . | SW 29 It is an opinion generally received; among philofophers, that water cannot be heated in contact with ices, Qur author, faw that this pofition mutt, bein a great meafure true with regard to, water upon which ice floats; becaufe-the hot water; muft afcend and be cooled by caufing part of the ice:to melty while the cold water from this laft would defcend to the bottom, and tend’to preferve the uniformity of temperature. But he faw likewife that the cafe would be very different if the ice were at the bottom. The inferences which this courfe of argument would point.out are. fingular and ftriking, and they are not lefs fo for being announced to us under the incontrovertible fanction of experiment. Natural as the induc- tion is, from the valuable experiments of Count Rumford, it {till feems in fome meafure aftonifhing to affert, that water may be a@tually made to boil, and kept in that ftate without melting a piece of ice, plunged in it, with more rapidity than could be effeted by cold water at 4o-degrees. — The dire€t experiments with i ice and hot water are related at large in the Effay. A cir- cular cake of ice, three inches and an half thick, weighing To ounces, and nearly as large as the internal diameter of a cylindrical glafs jar, which was 4,7 inches (it3 height being 14 inches), was géntly put into the jat containing fix pounds tL ounce troy of boiling-hot water. Tt was entirely melted in two minutes and fifty-eight feconds. The fame experiment was ‘repeated; but inftead of the ice being fuffered to {wim at the furface, it was faftened down in the bottom of the jar, and the hot water poured upon it. The ice was retained in the jar by means of two flender and elaftic pieces of deal about 1-8th of an inch thick, and 1-4th_ of an inch wide, which, being a very little longer than the internal diameter of the jar, were of courfe flightly bended when they were introduced into it horizontally ; and on being ] put down to the ice at right angles to each other, they con- fined it from rifing to the furface when the water was added. A circular piece of ftrong writing-paper was laid upon the ice to protet it from the ation of the boiling-hot «water while poured, whichWas afterwards removed, as gently as poflible, ‘by means of a {tring faftened on one fide (and to prevent the glafs jar from being cracked by the fudden appli- cation of the boiling-Hot water, 2 fmall quantity of cold water was firft poured in, to cover the ice to the height of about a quartér of an inch: The hot water was poured againft the middle of the circular piece of paper. The jar with the icé and the hof water in it being placed on a table near’a window, the paper which covered the furface ofthe ice was gently drawn away, and the'Count prepared himfelf to obferve at his eafe the refult of this moft interefting experiment. | A very few. moments were fuficient to fhew that his expeCtation with regard toit would not be difappointed. In the former experiment a fimilar cake of ice had been entirely melted in lefs than three minutes ; but in this, after more than twice that time had elapfed, the ice did tot thew any apparent figns of beginning to melt. Its furface remained fmooth and tithing, Anamtie writer’ ere in contact wich it Appeared to be perkedtly at rett 5 . oe" Routh 344 Experiments on the Bufion of Ice. though the internal motions of the hot water above it, which was'giving off its heat to the fides of the jar and to the air, were very rapid, as was diftin@tly perceived by means of fome earthy particles or other impurities which this water happened to contain. : The ice was examined with avery good lens, but it was a long time before any figns of its melting could be perceived. The edges of the cake remained fharp 5 and the minute par- ticles of duft, which by degrees were precipitated by the hot water as it grew colder, remained motionlefs as foon as they touched the furface of the ice. : As the hot water had been brought from the kitchen in a tea-kettle, it was not quite boil- ing-hot when it was poured into the jar. After it had-been in the jar one minute, a ther- mometer was plunged into it, and its temperature found to be at 180. After 12 minutes had elapfed, its temperature at the depth of one inch under the fur- face was 170%. At the depth of feven inches, or one inch above the furface of the ice, it was at 169,%;3 while at only 3-4ths of an inch lower, or 1-4th above the furface of the ice, its temperature was 40°. When 20 minutes had elapfed, the heat in the water at different depths was found to be as follows: ‘ Degrees, Immediately above the furface of the ice — _ 40 At the diftance of half an inch above it —— 46 At 1 Inch — — atts 130 At 3 Inches —- — = 159 At 7 Inches _ - -_—_— _ 160 When 35 minutes had elapfed, the heat was as follows : At the furface of the ice — — - 40 Half an Inch above it — — _- 76 r Inch above it — —_— _ 110 2 Inches _ —_- — 144 3 Inches — — —_— _ 148 . 5 Inches - _ —_— _ _ T4845 05" 7 ok 7 Inches Sa — — 149 At the end of one hour the heat was as follows : At the furface of the ice se — -_ 40 1 Inch above it —— _ 80 2 Inches _—— Pare — 118, 3 Inches _—_—_ ————— _ 128 4 Inches — —— —_ —_ 130 7 Inches -__ — 131 After one hour and 15 minutes had clapfed, the heat was found to be as follows : TeCS. At the furface of the ice —_> so — - ee 1 Inch above it sae _ 82 2 Inches —- — _ 106 3 Inches bu 123 The heat of the water had hitherto been taken near the fide of the jar:—in the two fol- lowing trials it was meafured in the middle or axis of the jar. When Experiments on the Fifion of Ice. 345 When one ‘hour and 30 minutes (reckoning always from the time when the boiling water was poured into the jar) had elapfed, the heat of the water in the middle of the jar was found to be as follows: . Degrees. At the furface of the ice — — = 40 1 Inch above it — es abe 84 2 Inches — poles ae 11g 3 Inches ——- — —— — 116 7 Inches pened pie = 117 , When two hours had elapfed, the heat in the middle of the jar was found to be as follows; ree Degrees. At the furface of the ice ee — 4o ,,1 Inch above it ow — — 76 2 Inches — —— fee ee O4 3 Inches — — a — 106 4 Inches —- a yes 108 6 Inches —— = ses =e 1085 i 7 Inches —— —— eee ss, 1082 An end being now put to the experiment, the hot water was poured off from the ice ; and on weighing that which remained, it was found that five ounces fix grains troy (= 2406 | grains) of ice had been melted. Taking the mean temperature of the water at the end of the experiment at 106°, our author remarks that the mafs of hot water (which weighed 731 ounces) was cooled 78 de- grees, or from the temperature of 184° to that of 106° during the experiment. Now as it is known that one ounce of ice abforbs juft as much heat in being changed to water as one ounce of water lofes in being cooled 140 degrees, it is evident that one ounce of water which is cooled’78 degrees, gives off as much heat as would-be fufficient to melt xoths of an ounce of ice; confequently the 73% ounces of hot water,which in this experiment were cooled 78 degrees, a€tually gave off as much heat as would have been fufficient to have “spt 7 = 40,5, ounces of ice. But the quantity of ice aGtually melted was only about, five ounces; and hence it ap- pears that lefs than one-eighth part of the heat loft by the water was communicated to the ice, the reft being carried off by the air. As the fame quantity of hot water was ufed in this experiment and in that which im- mediately preceded it, and as this water was contained by the fame veffel, it appears that ice melts more than eighty times flower at the bottom of a mafs of boiling-hot water than when it is fuffered to {wim on its furface. For as in the one experiment 10% ounces of ice were melted in two minutes and 58 feconds, five ounces at leaft muft have been melted in one minute and 29 feconds; but in the other experiments two hours or 120 minutes were employed in melting five ounces. _ Vou. I—NovemeBer 1797. Yy The 346 Extremely flow Fufion of Ice at the The ice however was melted, though very flowly, at the bottom of the hot water; and that circumftance alone would have been fufficient to have overturned the hypothefis refpecting the propagation of heat in fluids folely by means of the inteftine motion. This confidera- tion demanded an attentive enquiry into the circumftances of the experiment. One of the moft f{triking among thefe was, that at the end of the firft half-hour, on examining the fur- face of the ice it was feen that it had been melted, excepting only where it had been covered, or as it were fhadowed, by the dat flips of deal which fecured the ice in its place. It was. fingular that the ice was defended, not only by the undermoft piece of wood, but by the other, which, lying-acrofs the under piece, did not touch the ice any where except at its ends. It was natural to imagine, from this event, that the ice had been melted by radiant heat or calorific rays from the water, and that a portion of thefe had been intercepted by the flips of deal. This fuppofition pointed out another courfe of experimental enquiry. Into a cylindrical glafs jar, 64 inches in diameter, and eight inches high, was put a circular cake of ice, as long as could be made to enter the jar, and about 35 inches thick ; and on the flat and even furface of the ice was placed a circular plate of the thinneft tin that could be procured, near 64 inches in diameter, or fufliciently large juft to cover the ice. This plate of tin (which, to preferve its form or keep it quite flat, was flrengthened by a flrong wire,. which went round it at its circumference) had a circular hole in its centre juft two inches in diameter; and it was firmly fixed down on the upper furface of the cake of ice, by- means of feveral thin wooden wedges which pafled between its circumference and the fides. of the jar. A fecond circular plate of tin, with a circular hale in its centre,,two inches in diameter, and in all other refpeéts exaétly like that already defcribed, was now placed over the firft, and parallel to it, at the diftance of juft one inch, and, like the firlt, was firmly fixed in its place by wooden wedges. Thefe perforated circular plates being fixed in their places, the jar was placed in a room where Fahrenheit’s thermometer {tood at 34°, and ice-cold water was poured into it, till the water juft covered the upper plate; and then the jar was filled to within half an inch of its brim with boiling water, and, being covered over with a board, was fuffered to remain quite two hours. At the end of this time, the water, which was {till warm, was poured off, and, the circujar plate being removed, the ice was examined. A circular excavation, juft as large as the hole in the tin plate which covered the ice (namely, two inches in diameter), and correfponding with-it, perfectly well defined, and about 2-1oths of an inch deep in the centre, had been made in the ice. This was what our author expected to find; but there was fomething more which he did not expeét, and which for fome time he was quite at alofs to account for. Every part of the furface of the ice which had been covered by the tin plate appeared to be perfedt, level, and fmooth, and fhewed no figns of its having been melted or diminifhed, excepting only in one place, where a channel about an inch wide, and a little more than 2-1oths of an inch deep, which fhewed evident marks of having been formed by a ftream of warm water, led from the excavation juft mentioned in the centre of the upper part of the cake of ice to its circumference. As the edge or vertical fide of the cake of ice was evidently worn away where this ftream paffed, there could be no doubt with refpect to its direction. I Ik Bottom of a Veffel of Boiling Water. 347 Tt cettainly ran out of the citcular excavation’ in the middle of the ice; and though it might at firft appear difficult to explain the, fa&t, and to thew how this hot water could ar- rive at that place; yet it was quite evident that the immediate caufe of the motion of this ftream of water could be no other than its {pecific gravity being greater than that of the reft of the water at the fame depth; and that this greater fpecific gravity was at the fame time accompanied. by a higher degree of heat, is evident from the deep channel which this ftream had melted in the ice, while other parts of the furface of the ice at the fame level were not melted by the water which refted on it. This experiment, though attended with remarkable circumftances, did not clearly thew that the fufion of the uncovered part of the ice had been effected by radiant heat. It oc- curred to the author, tat radiant heat, like light, might probably be reflected downwards in part from the internal furface of the water; and confequently, that it might be expected that a light black body, namely, a circular piece of deal board, covered over with black filk, would abforb a portion of the whole body of rays which were directed to the ice. This trial was made, but with no fenfible effect. As it is uncertain whether heat in the radiant ftate can be reflected in this manner, the experiment may perhaps be confidered as -likely to afford a lefs equivocal conclufion than might have been obtained from the application of a polifhed metallic furface to the fuperior termination of the cylinder of water. But the appearance of a channel worn in the plate of ice in the preceding experiment gave rife to meditations which clearly pointed out the manner in which the ice was melted, and rendered the attempts to detec the fup- pofed operation of latent heat unneceflary. The Count’s explanation, in his own words, is as follows : Though it is one of the moft general laws of nature with which we are acquainted, that all bodies, folids as well as fluids, are condenfed by cold, yet, in regard to water, there ap- pears to be a very remarkable exception to this law. Water, like all other known bodies, is indeed condenfed by cold at every degree of temperature which is confiderably higher than that of freezing; but its condenfation, on parting with heat, does not go on till it is changed to ice; but when in cooling its temperature has reached to 40 degrees of Fahrenheit’s fcale, or eight degrees above freezing, it ceafes to be farther condenfed ; and on being cooled {till farther it a€tually expands, and continues to expand as it goes on to lofe more of its heat, till at Jaft it freezes; and at the moment when it becomes folid, and even after it has become folid, it expands ftill more on growing colder. This fact, which is * noticed by M. de Luc, in his excellent Treatife on the Modifications of the Atmofphere, has fince been farther inveftigated and put beyond all doubt by Sir Charles Blagden. (See Philofophical Tranf- actions, vol. xxviii.) Now, as water in contaét with melting ice is always at the temperature of 32°, it is evi- dent that water at that temperature muft be fpecifically lighter than water which is cight degrees warmer, or at the temperature of 40°: confequently, if two parcels of water at thefe two temperatures be contained in the fame veffel, that which is the coldeft and lighteft mut neceflarily give place to that which is warmer and heavier, and currents of the warmer water will defcend in that which is colder, * The fimple faét was alfo obferved by the celebrated Robert Boyte. YTyEa ' . 348 Remarkable Conclufion refpefting the Melting of Ice. In the two laft experiments, as the circular tin plate which covered the furface of the ice ferved to confine the thin fheet of water which was between the plate and the ice—as this water could not rife upwards, being hindered by the plate—and as it had no tendency to defcend—it is probable that it remained in its place; and as it was ice-cold, it was not capable of melting the ice on which if repofed. But as the tin plate had a circular hole in its centre, the furface of the ice in that part was of courfe naked; and the ice-cold water in contaét with it being difplaced by the warmer and heavier water from above, an excavation in the form of a fhallow bafin was formed in the ice by this defcending warm current. ; : The warm water contained in this bafin overflowed its banks as foon as the bafin began to be formed ; and iffuing out on that fide’which happened to be the loweft, opened itfelf a paflage under the tin plate to the edge of the ice, over which it was precipitated, and fell down to the bottom of the jar. The water of this rivulet being warm, it foon formed for itfelf a deep channel in the ice ; and at the end of the experiment it was found to be-every- where deeper than the bottom of the bafin where it took its rife. This manner of accounting for the appearances in queftion feemed to the Count to be quite fatisfa&tory ; and the more he meditated on the fubjeét, the more he was confirmed in his fufpicions that all liquids muft neceflarily be perfect non-condudtors of heat. On thefe principles he was now enabled to account for the melting of the ice at the bottom of the hot water, as alfo for the flownefs with which that procefs went on; and encouraged by this fuccefs he proceeded with confidence to plan and to execute {till more decifive experiments ;- from the refults of which he confiders the important faéts in queftion to-have been put beyond all poflibility of doubt. . If water be in fact a perfect non-conduétor of heat, that is to fay, if there be no commu- nication whatever of heat between neighbouring particles or molecules of that fluid (which is what he fuppofes) ; then, as heat cannot be propagated in it, but only in confequence of the motions occafioned in the fluid by the changes in the fpecific gravity of thofe particles which are oceafioned by the changes of their temperature, it follows that heat cannot be propagated downwards in water, as long as that fluid continues to be condenfed with cold; and that it is only in that dire€tion (downwards) that it can be propagated after the water has arrived at that temperature where it begins to be expanded by cold; which has been found to be at about the goth degree’of Fahrenheit’s feale. _ Reafoning on thefe principles, he was led to this remarkable conclufion: namely, that water which is only eight degrees above the freezing point, or at the temperature of 40 degrees, muft be able to melt as much ice in any given time, when flanding on its furface, as an equal volume of water at any higher temperature, even though it were boiling-bot. The experiments by which this unexpected refult was confirmed and eftablifhed mutt be deferred to the concluding part of this abftract. : UII. Experi. Explanation of the Efe of the Eleétrie Difcharge on Water. 349 Ill. Experiments and Obfervations made with the View of afcertaining the Nature of the Gaz pro- duced by paffing Elefric Difcharges through Water; with a Defcription of ‘the Apparatus for thefe Experiments. By Georc& Pearson, M.D. F.R.S. [Concluded from page 248.] Was fire of the eleétric difcharge, in a very condenfed ftate, pafles with inconceivable velocity through the whole length of the upper wire, in the cafe of the interrupted explofion, P- 243—247, and of the fingle wire in the cafe of the complete explofion, p. 247, 248; fo that it neither exerts its energy on the wire, nor on the water, ull it arrives at the extremity of the wire. There it is momentarily interrupted and accumulated 3 and, in the moment before its diffufion through the water, it is fo denfe and in fuch quantity as to manifeft itfelf by a fpark at, or nearly in contact with, the extremity of the wire. In the moment of its dif- fufion, a {mall part of this condenfed fire interpofes betwixt the conftituent elements of the ultimate and invifible particles of water, that is, betwixt the hydrogen and oxygen, of which water is compounded, fo as’ to place them beyond the fphere of their chemical at- traction for one another; and each ultimate particle of hydrogen and of oxygen uniting with a determinate quantity of fire, new compound ultimate particles, confifling of hydro- gen and caloric, and of oxygen and caloric, that is, hydrogen gaz and oxygen gaz, are com: pounded. This mode of aétion of eleAric fire on water is confirmed by the effect of ele€tric fire and common fire, of a due degree of denfity, on oxide of quickfilver, which is by them refolved into oxygen gaz, and quickfilver in the vapour ftate. All calculation mutt needs be extremely vague; yet, perhaps, fome elucidation will be obtained by con- fidering that as it probably requires 70 or 80 thoufand difcharges to produce a cubic inch of gaz from the fuppofed decompounded water, the gaz produced by each difcharge cannot amount to one 200,000dth of a grain weight. The quantity of condenfed fire at the ex- tremity of the wire muft be immenfely great, comparatively with the quantity of it which enters into the compofition of the gazes from decompounded water; otherwife it is not ‘eafy to conceive how even the minuteft particle of water could be decompounded, the eleGtric fire being in contact with a large body of water, and palling through it with a ye- locity which is incalculable. ‘ The reafon of the metal wire not uniting to the oxygen of the decompounded water, as in the experiment of pafling water through red-hot iron tubes, might be afligned from the intenfity of the fire only 5 but it is alfo on account of the rapid motion of the difcharge, as well as, partly, from the great quantity of light. Ina very low temperature, light decom- pounds oxide of filver, and of feveral other metals; alfo oxy-muriatic acid, nitric acid, &e. Hence light both decompounds bodies, and prevents oxygen from coming within the {phere of chemical attraétion of the metal, It is fuppofed that but a very minute”proportion indeed, of the ele@ric difcharge, is confumed at the end of the wire in the compofition of gazes, during a momentary inter- ruption, as above faid; for it diffufes itfelf through the water, between the wires, yielding a volume of vivid light, till it arrives at the extremity of the under wire or point of the 6 convexity 350 Osfervations and Inferenees refpeting Combuftion. convexity of the metal cup, where it is again condenfed by the fuperior condudting power of the metal to that of water, and where, if it be in due quantity, and of fufficient denfity, it manifelts itfelf by a fpark, and infallibly again decompounds water : hence bubbles are {een to rife from the end of the lower wire, and from the metal cup, as well as from the point of the upper wire. ' - From thefe interpretations it will not be difficult to explain the reafon of a {park appear- ing in fome cafes at the points of both the upper and under wire; why in other cafes it appears at the point of the upper wire only; why in others it appears at the point of tle lower wire only; namely, according to the denfity of the fire of the difcharge there ac- cumulated. Concerning the agency of ele€trical fire in caufing the hydrogen and oxygen gaz of the fuppofed decompounded water to undergo combuftion and produce water, it is well known that the fimalleft vifible park, or particle of flame, or fire, can kindle as rapidly a very large quantity of hydrogen and oxygen gaz, as the greaieft quantity of flame, fparks, cr fire, can kindle the fmalleft quantity of thefe two gazes; while, on the other hand, the largeft mals of matter, heated moft intenfely, but fhort of ignition, cannot produce com- bution of oxygen and hydrogen gaz. Although, as hath been above explained, caloric and light, in a fufficiently denfe ftate, may decompound every compound fubftance in nature; it is alfo well afcertained, that caloric, in certain ftates, univerfally promotes chemical combinations. The mode of agency, in this latter cafe, I apprehend to be in a different way from that commonly accepted; for I think it is unneceffary to fuppofe that it operates by increafing the power of chemical at- traction, and I conccive its agency to be merely diminifhing or deftroying the powers which counteraét chemical union; efpecially diminifhing cohefive attraction, and exciting motion among the particles of the different fubftances: hence thefe fubftances are applied to one another, within their fpheres of chemical attra€tion; or the chemical attraction aéts be- tween a greater number of points of the different bodies, as when caloric renders folids and inclaftic fluids into the elaftic fluid ftate. i Accordingly, when an eleG&tric fpark, or the {malleft particle of flame, or of an ignited fub{tance, is applied to the gaz produced in the above procefs, or to the mixture of hydro- gen and oxygen gaz, the ultimate particles of thefe gazes neareft ‘to ‘the flame are driven from it in all direétions, as from a centre, by the interpofition of fire, or of caloric and light; fo that they are brought within the fphere of their chemical attra€tion for the ultimate particles of the gazes at‘a certain diftance from the centre of application of fire; which therefore unite, and the caloric and light, difengaged by that union, act ina fimilar manner in producing union among the next fet in order of proximity, of the ultimate particles of the gazes; the difengaged caloric and light of which a&t in producing union of the next fet of ultimate particles in order; and fo on fucceflively, but with inealculable velocity, the greateft bulk of ultimate particles of the two gazes unite with one another; the known predacts of which union are fire and water; or light, caloric, and water. According to this hypothefis, if caloric or fire, or merely caloric of fufficient imtenfity and’ quantity, be applied to a given bulk of hydrogen and oxygen gaz, no combuftion fhould be produced 5 asthe caloric will be interpofed in fuch quantity that all the ultimate particles muft be at the fame inftant driven from one another in all dire@tions, fo that they are beyond their fpheres Obfervations and Inferences refpeing Combuffion. 35 fpheres of chemical attraQion for one another; and in various inftances common experience verifies this hypothefis. If light be confidered as a different {pecies of fubftance from caloric, then the theory of its agency, lately publifhed by Dr. Parr, M. D. may be applied very happily to explain the explofion from the combuftion of oxygen with hydrogen gaz. From a very large induction of facts, Dr, Parr infers that, although light-and caloric fubfift together very commonly in the fame compound fubftance, they fimultaneoufly repel each other on the decompofition of the fubftances with which they were united; and from this repulfion, and alfo the re- pulfion of oxygen and light of one another, he chiefly accounts for the combutftion of oxy- gen gaz. j On my principles above ftated, we can explain why quickfilver of the temperature of 1000°, or more, of Fahrenheit’s fcale, cannot unite to the oxygen of oxygen gaz; but why at this temperature caloric feparatés oxygen in the gaz ftate from oxide of quickfilver: and why at the temperature of between 600 and 1000° quickfilver does unite to the oxy- gen of oxygen gaz; but at which temperature oxygen gaz is not feparable from the oxide of this metal: and again, why at below 600° oxygen of oxygen gaz can neither unite to quickfilver, nor be feparated from its oxide.. Thefe principles may be applied yarioufly to the interpretation of the phenomena of com- buition, and other cafes of chemical combination, according to the ftate of aggregation of the fubftances which have a chemical attraction for one another. For example ; the oxygen of oxygen gaz cannot unite to the conftituent fubftances of a wax. or tallow candle, in a low temperature ; becaufe the cohefive attra€tion of the wax or tallow, as well as the che- mical attraction between their conftituent fubftances—hydrogen and carbon—counteraét the chemical attraction between the oxygen of oxygen gaz, and the ultimate particles of hydro- gen and carbon of the candle. But at a pretty elevated temperature, when the wax and tallow are in the vapour ftate, the cohefive attraction no longer fubfifting among the ulti- mate particles of thefe fubftances, and the motion excited by the ignited portion of wax or tallow bringing the ultimate particles of thefe fubftances within the fphere of chemical at- traction of the particles of oxygen gaz, thefe latter unite fir(t to the carbon, by virtue of the ftronger attraction between the oxygen and carbon, than that between the oxygen and hy- drogen; but, in the inftant of this difengagement of the carbon from the hydrogen, a por- tion of this hydrogen unites alfo to oxygen, and thus not only carbonic acid gaz but water is produced: hence the blue flame, as appears on other cccafions, in which there is combuflion of hydro-carbonate gaz. The remainder of the hydrogen of the decompounded wax or tallow, afcending in the gaz ftate, it unites to the oxygen of oxygen gaz; and, as in other cafes of combuftion of oxygen gaz with hydrogen, a white or fraw-coloured flame is produced. ‘The wick anfwers the purpofe, by means of capillary at- tration, of applying the wax and tallow in fuch quantities as can be decompounded and combine with the oxygen of atmofpherical air ; hence the combuftion is gradual and equal. The wick itfelf contains hydrogen and carbon; hence, in combining with oxygen of oxygen gaz, it alfo produces a blue flame. Hydro-carbonate gaz being fpecifically heavier than hy- drogen gaz, is another reafon for the blue flame appearing diftiné&t from the white, and at the inferior part of the fruflum of a cone of flame from a burning candle. It is fcarcely neceflary to fay that hydrogen and carbon are conftituent fubftances of wax and tallow ; and 352 Phenomena of Combuftion.—Compofition of Water. and that when they combine with oxygen, as above explained, the produdts are water and hydro-carbonate gaz. If I did not ufe'the term demonfration in a more ftri& and»precife fenfe than is ufual, except in mathematics, I would venture to affirm that this theory is almoft demonftrated by the agency of fire and carbon on black oxide of manganefe. If colourlefs vitrifiable matter, and that oxide be melted together, by means of the wife part of the flame of a candle, purple-coloured glafs will be produced; for then the hydrogen of this part of the flame carries off little or none of the oxygen from the oxide: but if thefe fubftances be melted together by the J/ve part of the flame, colourlefs glafs will be produced ; for then the carbon of this part of the flame carries off oxygen from the black oxide, and produces white oxide. By combining oxygen anew with colourlefs glafs, containing manganefe, it will become purple; and this is effeQed by melting fuch colourlefs glafs with a little nitrate of pot-afh, or by melting it in opén veflels by the yellow flame of a candle. By feparat- ing oxygen from glafs rendered purple by manganefe, colourlefs glafs is produced; and this is effefted by melting fuch coloured glafs with a little carbon, or by the blue flame of acandle. Ihave not thought it neceflary to diftinguith between the indigo and violet rays; or to notice the extremely thin film of violet flame, which an attentive obferver may perceive furrounding the inferior part of the white, extending as high but fearcely higher than the wick; becaufe the explanation is perfetly obvious from the preceding diitinction of the two kinds of gazes afforded by the candle. If I have explained more fatisfactorily than former members of this fociety the above phenomena of combutftion, I owe this ad- vantage to fome experiments of combuftion of inflammable gazes which [ have siade for fome years palt, in my chemical le€tures ; by which the colours are fhewn to be very dif- , ferent, and correfpond to the above theory. JI apprehend the theory of an ingenious member of this fociety cannot explain adequately the phenomena, and does not appear fup- ported by any facts: for there is no evidence that the white flame is not equally the effec of immediate decompofition as well as the blue; or that the blue becomes white flame by ignition; and I prefume that the experiments which I have mentioned fhew that thefe dif- ferences depend upon different decompounding fubftances contained in the candle. With regard to the evidence afforded by the foregoing experiments concerning the com- pofition of water and of hydrogen and oxygen gaz. Thefe fubftances are now accounted for in two ways only; namely, 1. By faying that thefe two gazes confilt of water and im- ponderable matter; and that during combuftion the water is precipitated. 2. By faying that the two gazes confift of a peculiar bafis, one of which is named oxygen and the other is hydrogen, each of which is rendered into the gaz ftate by uniting to caloric, and perhaps alfo to light; and that during combuftion thefe bafes unite with one another, thus’ com- pounding water and difcharging caloric and light. If complete demonftration could be given, there would not be two opinions; for its proofs, if underftood, command univerfal affent: but the cafe being otherwife, that opinion muft be adopted on the fide of which the evidence preponderates according to the laws of reafoning in phyfical fcience. Now with “regard to the former of thefe opinions, I can perceive but two facts in fupport of it. The firft of thefe is fuppofed to afford a fort of fynthetical proof: it is the inftance of water being required to obtain, by fire, the whole of the carbonic acid from carbonate of baryt. Here the fact, if admitted, is true only of carbonic acid ; but even in this cafe it has nor been aa ae bose 2" 353 Obfervatians and Induéions refpefting the Compofiticn of Water. 3 been fewn, that the water enters into the compofition of carbonic acid; and until that is proved, it is warrantable to fuppofe that the water ferves to difengage the carbonic acid, by attracting and uniting with the baryt; efpecially as this acid gaz may be wholly feparated from other fubftances without the intermediation of water, and as it can be compounded by uniting the drieft carbon to the drieft oxygen gaz. Further, although carbonic acid gaz be very apt to contain water, it may be obtained in fo dry a ftate as not to indicate moifture to the moft delicate tefts. The next fa&t affords a fort of analytical proof; which is the exiftence of water in air or gaz in general, as fhewn by muriate of lime, acetite of pot-afh, fulphuric aeid, quicklime, pot-afh, &c. But the abforption of water by thefe fubftances only fhews that it may be fufpended or diflolved in gazes; but not that it enters into their compofition. Gaz may be obtained or rendered quite free from water, as juft faid; and as the compounds by the combination of the gazes with various different fubftances are quite different from the com- pounds by the combination of water with the fame various different fubftances, there does not appear to be in this cafe any admifible evidence of water being an effential conflituent fubftance in the compofition of gazes. The experiments of feparating oxygen and nitrogen gaz from water by boiling, and by expofing it in vacuo and applying caloric, only fhew how much more tenacioufly, and in how much greater quantity, thefe gazes are contained in water than is commonly fuppofed; for however long a given quantity of water yielded gaz, fo that there feemed no limit to the quantity, the water which afforded it was {till very confiderably greater than the weight or quantity of gaz. \ With refpeét. to the other opinion, that hydrogen and oxygen gaz are compounded of a peculiar bafis and caloric, and that water is compounded of thefe two bafes—r. It has been fhewn by an experiment, the accuracy of which is not queftionable, that when thefe two gazes produce water by combutftion, the amount of the weight of the water is exatly the weight of the gazes confumed, and that no ponderable maiter but’ water is produced when nothing but the bafes of thefe two gazes unite ; but that when other fubftances, fuch as nitrous acid and carbonic acid, were produced, as well as water, then nitrogen and carbon were prefent. 2. It has been fhewn, that when oxygen in a concrete ftate, as in metallic oxides, unites to the hydrogen of hydrogen gaz, the water thus compounded is equal in weight to that of the hydrogen gaz confumed, and the deficient weight of the oxide. 3. It appears that when hydrogen in a concrete ftate, as in alcohol, is united to the oxygen of oxygen gaz, the water compounded is equal in weight to the weight of the alcohol and oxygen gaz confumed, provided the addition be made of the carbonic acid alfo produced by the carbon of the alcohol. The carbon of alcohol can be fhewn by analyfis ; and its exiftence in carbonic acid can be fhewn both by analyfis and fynthefis, 4. When water is . applied to certain fubftances, nothing but hydrogen gaz is obtained, and new compounds, the conftituent parts of which are oxygen and the fubftance applied; for thefe new com- pounds have the fame properties as the compounds of the fame fubftances fo applied to water, and of the oxygen of oxygengaz. And in thefe cafes the additional weight derived from the water, together with the weight of the hydrogen gaz feparated from the water, is equal to the water deftroyed. 5. It has been rendered at leaft very probable, that when oxygen and hydrogen are rendered into the gaz ftate, they abforb or unite with a Vox. IL—Novemper 1797. ZZ : large. uw S4 Indudions refpetting the Compofition of Water. large quantity of caloric, or of both caloric and light, I might add, that befides the pofi- tive evidence juft ftated, there does not appear to be any evidence to contravene the con- clufion that wateris compounded of hydrogen and oxygen; and that thefe gazes are com- pounded of a peculiar balis, called hydrogen and oxygen, united to caloric: for it would be eafy to fhew, but it would be digrefling too far, that the remaining partizans of the phlogiflic feet have advanced erroneous evidence in fome cafes, and in others have neglefted the confideration of oppofing but well authenticated evidence. In the experiments. contained in this paper no fupport can be found for the former opinion concerning water, and hydrogen and oxygen gaz; but they confirm the latter opinion. For, 1, the combuflion of thefe gazes, rendered perfectly dry, afforded water, p- 303, Exp. IV. 2. The evidence from the procefs above defcribed is peculiar; for no one other procefs affords oxygen and hydrogen gaz from water. In all other proceffes for -decompounding water, either the decompounding concrete fubftance receives fomething from the water applied, and at the fame time hydrogen gaz is produced ; as in the inftance of pafling water through a red-hot iron tube: or the decompounding concrete fubftance receives fomething from the water; and this compound unites to that in water, which pro- duces hydrogen gaz with caloric; as in the inftance of applying water to red-hot carbon : or two decompounding fub{tances being applied, each of them receives a different thing from the water, namely, hydrogen and oxygen. Hence, by the procefs above defcribed, the objeétion is removed, that the hydrogen gaz might be feparated from the decompounding fubftance itfelf, by water taking its place. 3. The production of hydrogen and oxygen gaz, and the production of water by the combuftion of them, in the above procefs, afford an additional evidence of the decompofition and compofition of water, and of hydrogen and oxygen gaz; as the mode of their produétion by this procefs is perfedtly confiftent with the rationale of their production in all other cafes. Thus it appears that the grandeft difcovery ever made in chemical philofophy, by an illuftrious member of this Society, in 1781, Bes been confirmed by a number of fubfequent experiments. The body of evidence is indeed fo numerous, and of fuch a nature, that, in the minds of thofe who underftand its import, and who rely on the accuracy of the weights and meafures employed, it produces as much conviction concerning the compofition of water as can be obtained by the evidence of almoft any other cafe of compofition. I muft, however, beg leave to proteft againft thofe able philofophers, who have maintained, that the compofition of water, and feveral gazes, has received full and complete demonftration ; by fuch unwarrantable pretenfions their adverfaries have obtained over them fome advantages. For in the chain of caufes and effeéts there are fome links which cannot be explained by the direct evidence of fenfe ; and there, in fo far as we admit hypothefes, although con- fiftent with the phenomena, we may be faid to quit day-light, notwithftanding we at the next ftep emerge into light derived from the perceptions of fenfe. For inftance, if I com- bine a certain known weight of hydrogen and oxygen by combuftion of their gazes, and produce water equal in weight to that of thefe gazes; and if 1 again refolve this water, by means of the eleétric fire, or red-hot iron, into the original quantity of hydrogen gaz and oxygen, I cannot give the full and complete demonftration of the compofition of water and thefe gazes: for, as I proceed in the interpretation, Tat length come to demonftrate the mode of agency of the particles. of the hydrogen and oxygen gaz on one another when Compofition of Water.—EleBrophore. 355 when they produce water, caloric, and light. But here I muft call in the ald of the ima- gination: accordingly I imagine that the gazes confit of hydrogen and oxygen, which are ponderable—united to caloric, and perhaps light, which are imponderable; that thefe pon- derable particles unite with one another, and their caloric and light are fet at liberty. Now here I have not any evidence of fenfe; for | cannot perceive, by the fenfes, the exift- ence of the compofition of the gazes juft {tated, nor of their decompofition, and union of their ponderable parts. This being the cafe, other kinds of imponderable matter may unite, or efcape, befides caloric and light; confequently I cannot give the full and com- plete demonitration in thefe inftances. But the’ fame objeQions may be made to the pre- tenfions to demonttsate fully and completely the compofition of fulphate of foda, fulphate of pot-afh, or any double falt, perhaps, whatever. for caloric is feparated, and poflibly , other imponderable matter, when thefe fubflances are compounded ; and caloric, and perhaps other matter, may unite when the fulphuric acid and alkali are difunited. Hence chemiftry, in its prefent ftate, ought not to pretend to vie with mathematical phi- lofophy in its demonftrations. But it does not appear improbable, that the fame certainty as in mathematics may hereafter be attained in chemiftry. We are encouraged to enter- tain this hope, from finding that the art of obfervation, and the invention of artifices for rendering the properties of matter evident to the fenfes, have been proportionate to the advances of knowledge of fa&ts ; as was prediéted by Chancellor Bacon, IV. Obfervations.on the Eleétrophore, tending to explain the Means by which the Torpedo and other Fifh communicate the Eleétric Shock. Tuost who are converfant with eleétrical experiments know that the eletrophore confifts of a flat metallic plate with an infulating handle, and another feparate plate of non-conducting matter, either varnifhed glafs, or fome refinous fubftance, coated with metal beneath, and placed with its uncoated fide uppermoft. When this uncoated face is ele€trified by fri€tion or otherwife, and the plate of metal placed upon it, this laft is found to give a {mall {park to the finger, which is of the fame nature as the eleCtricity of the non-conducting furface ; but when the plate is lifted by its infulating handle, it will emit a {park to the finger which is much ftronger, and of the oppofite kind to that of the non- conducting plate. This phenomenon, which was at firft confidered as very difficult to be explained, was afterwards found to be produced throughout by the fame energies, what- ever they may be, which govern the eleétric charges. For, as I have elfewhere obferved ve the charge confifts of two eleétricities, ufually called plus and minus, which compenfate each other ; and alfo of a portion of eleétricity on the infulated fide, which in equal charges is greater, the greater the diftance between the two eledtrified furfaces, and in unequal mo- derate charges is nearly in proportion to the charge itfelf. When the non-conducting fur- face of the eleétraphore is rubbed, it acquires both thefe eleétricities, namely, the charge by virtue of the compenfating power of the uninfulated coating beneath, and alfo the por- tion of fimple elettricity requifite to maintain the charge. If the metallic plate be then. * Philofophical Tranfaétions, 1789, Z22 placed 356 Aition of the EleBrophore. placed upon it, and touched by the finger, a portion of the eleétricity may really pafs to the metal at the few places of aétual contaét ; and another part, if the intenfity be ftrong, may itrike through the thin plate of air interfperfed between the metal and the refinous face, What remains on the refinous furface will lofe by far the greateft part of its intenfity, in confequence of its becoming a charge to that fmall plate of air, while the metallic plate, poffefling the oppofite part of the charge, will have its intenfity equally low. During thefe charges, the {park which pafles from the metal muft therefore be of the fame charaéter as that of the refinous plate; in the fame manner as the outer coating of the jar emits pofitive {parks during its tranfition to the negative ftate. The commencing intenfity of this fpark cannot exceed that which belonged to the charge between the refinous furface and the lower coating : but as the intenfity requifite to maintain a charge on the thin plate of air is ex- tremely minute, by far the greater part of the electricity will be employed in conftituting that charge, and the fpark given off by the plate will be much fhorter and more gradual than af the fame quantity had pafled at once from the plate in a ftate of fimple ele€trization ; that is to fay, the fpark will be apparently very fmall. But when the plate is raifed up by its infulating handle, part of the charge on the refinous furface will begin to acquire its former itate with regard to the lower coating; and that which continues to be compenfated by the upper moveable plate, will require a greater portion of uncompenfated ele€tricity to main- tain it. The intenfity of the plate will rapidly increafe as it rifes. It will throw out {parks and ramifications to the lower plate, and to the furrounding bodies; and at a certain diftance the whole remaining portion of its former charge may be confidered as fimple electricity, which will {trike the finger at a greater diftance, and with more fuddennefs and brilliancy. ‘This fpark, though in fact confifting of lefs ele€tricity than the former, will neverthelefs be more perceptible both to the eye and the ear, and confequently will ‘be thought larger: the firft is the gradual explofion of a charge; the fecond confifts of the fudden efcape of a portion of fimple eleétricity. If we fuppofe the non-conducting matter of the ele€trophore to be exntiniel} thin, and the fpark when in contaét to be made to pafs from the upper to the lower metallic plate, the effect will be nearly the fame as the tranfition of the fhock from fuch a coated ele€tric with a charge of the quantity of eleétricity which paffes; and when the moveable plate is raifed, the effect will be fimilar to that of a {park from the ‘prime conduétor. Or rather, per- haps, by a comparifon familiar to ele€tricians, the firft may be confidered as the fhock from a large battery charged bf only one turn of the handle of the machine, and the latter as the fhock from a fmall jar capable of being charged high by the very fame quantity of ele&tric matter. It is certain that the fhock, as well as the {park from the battery, would in thefe circumftances be inconfiderable, though the effects of the jar might be very ftriking. When the eleétrophore is thus compared with the jar, its charge will be found to be won- derfully fmall, as it confifts of no more electricity than, when uncompenfated, would pafs off int the fimple {park which was obtained. I found that two fquare inches of Mufcovy talc, about one-hundredth part of an inch thick, which is an exceedingly good non-condustor, required, when coated with tinfoil, one turn of a {mall cylinder to difcharge through one-tenth of an inch; and one turn of the fame cylinder charged a fimple conduétor of about fix fquare feet furface, fo as to give a {park about nine inches long. Now if we afflume the quantities of eleétricity in 4 conductors Organs of Eleéric Fifh. 357 condvétors to be as the length of the fpark, which, though a doubtful pofition in great in- tenfities, may ferve the prefent occafion, and that a talc ele€trophore of two fquare inches furface on each fide have the intenfity to give a {park of one-tenth of an inch, its whole eleétricity will be exprefled by 4 X 0,1 = 0,4. But the whole electricity of the conductor which gave the nine inch fpark will be exprefled by 6 X 144 X 9 = 7776. And this num- ber doubled, or 15552, for a double ele€trophore, @lfo exprefles fuch a charge of the talc as gives a {park of explofion or difcharge of 0,1 inch. ‘The length of the explofive {park, on applying fuch a fimple eleCtrophore to its plate, will therefore be fhorter than 0,1 in the proportion of 0,4 to 15552, or 1 to 388803 the fpark would therefore be the ,oo0002 of an inch long. And as Mr. Cavendith has found that electric fhocks nearly equal are pro- duced when the quantities of eletricity are inverfely as the lengths of the fpatk of dif charge, and alfo that the quantities of ele€tricity in charges are as the furfaces, it will fol- low, that the fhock of two fquare inches of the talc with a fpark of 0,1 inch, will be equal to the fhock of 77760 {quare inches with a fpark of 0,000002 inches. This furface is equi- valent to an eleétrophore of 279 inches fquare, or meafuring 23 feet by the fide; or 19440 of the double electrophores of two inches furface. To elucidate this, I conftructed a fmall ele€trophore adapted to perform the experiments which Beccaria called vindicating electricity. It confifted of two metallic plates with in- fulating handles. Each was a fquare whofe fide meafured two inches, and the face of each was coated with the thin talc. When the two uncovered furfaces of the talc were applied together, and the whole charged as one plate, the difcharge gave a denfe fhock of con- fiderable feverity. ‘The fparks, on feparation, were about one-eighth of an inch long, and very weak, No perceptible fpark was exhibited on bringing them together. The opera- tion appeared capable of being repeated almoft inceffantly, as in the ele&trophore. lt may perhaps be fimpler to confider the electrophore as a compound jar or plate variable in its thicknefs.. When the plates of the inftrument juft defcribed are together, the two electricities on the contiguous furface compenfate each other, and the external coatings may be fuppofed nearly in the natural ftate. But when they are feparated, the portion of compenfated ele€tricity will be lefs, and the intenfities would rife if it were not for the ex- ternal coatings, which in a great meafure prevent it; each plate becoming charged like a fimple jar, and the equilibrium being pofible to be reftored by communication between the external coatings. ‘This fecond charge, intenfity, and explofion will be greater the furthet the plates are removed. It appears, therefore, that in a deduétion of the manner in which electric fifh may communicate the fhock, we may fafely avoid the more complicated con- fideration of the eleCtrophore, and compare the a€tion immediately to that of a fimple jar. Mr. Hunter, in the 63d volume of the Philofophical Tranfactions, page 434, defcribes the electric organ of the torpedo to confift of a number of columns varying in their length from an inch and an half to a quarter of an inch, and their diameters about 2-roths of an inch. The number of columns in each organ of the torpedohe prefented to the Royal Society was about 470; but in avery large torpedo the number of columns in one organ was 1182. ‘Thefe columns were compofed of films parallel to the bafe of each, and the diftance be- tween cach partition of the columns was 1-15oth of an inch. If we fuppofe thefe films to be charged with ele€tricity, and to be 1-300th of an inch thick; and a middling fize tors pedo to contain in both organs on the whole 1000 columns of an inch long, and. 0,03 ) {quare 358 Deduftions concerning Eleftric Fifb. 4 fquare inches area at the bafe; then 1000 X 150 x 0,03 = 4500 fquare inches. Now IT found that Mufcovy talc, of 0,0: inch thick, has twelve times the capacity of the glafs of a jar of 421 fquare inches, which, from former experience, I know to be as thin as fuch jars can be without danger of breaking by explofion; and the torpedinal membrane, being lefs than one-third the thicknefs of the talc, will have three times the capacity; that is to fay, its capacity will be thirty-fix times that of ftout glafs4 or both organs will be equivalent te 4soc X 36 = 1620c0 fquare inches, or 1125 fquare fect. My large jar, with Lane’s ele€trometer, meafuring a fpark about 1-20cth of an inch long, gave very fenfible and rather unpleafant fhocks acrofs the hand, and alfo the tremulous fen- fation caufed as I fuppofe by the imperfe& conducting power of the fkin with fo low an intenfity. When the fpark was 1-1ooth of an inch long, the fhock was ftrong enough to conyulfe the hand, and at lefs than 1-soth it was painfully ftrong. This laft was probably ftronger than the fhock of the torpedo. If we therefore avail ourfelves of Mr. Cavendith’s deduction, that, the quantity of eleétricity being increafed in proportion as the length of {park is diminifhed, the fhock will be rather greater than before, we may compute the length of the fpark in the torpedinal fhock of the magnitude laft mentioned. For the organs of the torpedo, compared as to their capacity with that of the jar, will be equivalent to 162000 Aaa 375 timesas great, and they will give fuch a fhock when charged as to afford a {park she of 34 of an inch = Tyee inch. No wonder, therefore, that the fhock will not pafs through an interrupted circuit, and that the fpark is not exhibited. Refpe@iing the manner of operation, there are no facts which fhew how this charge is a€tually produced, maintained, and communicated. Whether electricity be actually col- leéted, compofed, or decompofed in the organs of the fifh, or whether it fimply exifts in thofe organs, as perhaps it may in all bodies, in the ftate cf what is called compenfation, are quef- tions concerning which we in faét know nothing. It has appeared to me, from the obfer- vation of the high eleétric ftate which talc naturally poffeffes, and from the innumerable fhocks the eletrophore is capable of giving by mere change of arrangement, that a machine might be conftruéted alfo capable of giving numberlefs thocks at pleafure, and of retaining its. power for months, years, or to an extent of time of which the limits can be determined only by experiment. { will not here defcribe the mechanical combinations which have occurred to me in meditating on this fubje&t, but fhall fimply fhew that the dimenfions of the organs of the torpedo are fuch as by certain very poflible motions, and the allowable fuppofition of con- du@ing and non-conduéting powers, may produce the effets we obferve. How far it may be probable muft undoubtedly be left to future experimental refearch. In new talc, which had never been excited nor eleétrified, and exhibited no figns of ele€tricity when applied to Bennet’s electrometer, I found that the laminx were naturally in ftrong, oppolite, eleétric ftates, counterbalancing each other. When they were torn afunder in the dark, they gave flathes at leaft 1-roth of an inch long to each other. This is 1875 times the intenfity of the torpedinal eleétricity, as before deduced. If, therefore, one or more columns of tale, or other thin eleétric plates 1-z00th of an inch thick, and making up the furface of the electric organs of the torpedo, were fo conftructed as that the plates might touch each other by pairs only, naturally in oppofite ftates, and coated on the out- fide ; —— : Eleivic Fifb.—Procefs of Vitality. 359 fide; if, moreover, there were one common conductor communicating with the upper plate of every pair, and another in the fame manner with the lower;—then a feparation of all the pairs to the diftance of only ,4, inch would produce the torpedinal intenfity ; the equi- librium would be reftored by the two conduétors if made to communicate, and whatever living creature was in the circuit would receive a fhock: and on reftoring the original fituation of the apparatus, a fhock might alfo be given. The force of thefe fhocks would differ according to the quantity of the apparatus made ufe of at the time, or the diftance to which the plates were drawn afunder. If different columns were exploded in rapid fuc-~ ceffion, the quick repetition of fmall fhocks would produce the tremulous fenfation. If we were to conjecture that the torpedo aCtually operates like a machine of this kind, we fhould find our fuppofition to include the following fubordinate parts :—1. The mem- branes may be non-conduétors, and the fluid between them a conduétor. 2. They may act as ele&trophores. 3. The white reticular matter between the columns may confift of con- duétors feparately leading to the two oppofite furfaces. 6. Thefe feparate conduétors, in all their fubdivifions, may be well kept afunder by a covering of non-ele¢tric matter. If this be of the fame kind as the membranes, and ~=%5,5th of an inch thick, it would be fufficient for the purpofe, becaufe the intenfity of the ele€tric ftate is deduced from its power of breaking through a much more permeable eleétric, namely, air, at nearly twice that interval. 7. The effeéts may alfo be produced by the motion of conducting plates in a non-conducting fluid. ee ee rr Se ee ne Sor eee ner men es ee Vv. 4 Letter fron Mr. Von Humporor to M. H. Van Mons on the Chemical Proceft of Vitality ; together with the Extract of a Letter from Citizen Fourcror to Citizen Van Mons on the fame Subject *. ‘ I HAVE lately addreffed feveral letters to Meflrs. Dolomieu and Fourcroy at Paris, and perceive by thofe I have réceived from the former that mine have mifcarried. Permit me, ‘Sir, to addrefs myfelf to you. By your means I may perhaps fucceed in forwarding to Paris fome explanations refpeCting fa&ts which, as I underftand; employ part of the time of the National Inftitute. Be pleafed to accept my affurances of the great refpect which your zeal and your chemical difcoveries have infpired me with. The natural philofophers of Europe ought to form a fingle family. They are in purfuit of the fame interefting objets; and this is a fufficient motive to produce that ufeful degree of intimacy which is calculated to promote their refearches. , You are probably acquainted with my Efflays on the Vegetable Philofophy, fuch as my Aphorifini ex dodtvind phyfolgie chimice plantarum, annexed to my Flora fubterranea Fri- bergenfis, and feveral memoirs which I have prefented to the National Inftitute. The memoir on the action of oxygenated muriatic acid upon the vegetable and animal fibre, which is printed in the Magazin Encyclopédique of Millin, Noél, and Warens, feems to have * Annales de Chimie, XXII. 64. had 360 Chemical Proeefs of Vitality. had more fuceefs. Iam happy to hear that Meffrs. Vauquelin and my friend Dolomies have begun to repeat my experiments, As the memoir which was read to the National Inftitute related principally to the germination of vegetables, I have thought it my duty to announce to you certain facts more ftriking refpeéting the animal fibre. The ftrongeft ftimulus of the nervous fibre is that of the alkalis. It appears that thefe falts affe& the irritable and fenfible fyftem by means of their azote. Let the thigh of a frog be thrown into the oxygenated muriatic acid, or the nitric acid, and it will remain motionlefs. Let it be put into a folution of pot-afh, or of foda, and it will undergo contra@ions no lefs ftrong than when irritated by the metals. Thefe motions always commence at the lower extremities, The toes move firft, afterwards the mu/culus ga/frocnemius, and then the thigh. If the nerve be very fenfible (for nothing mere is required than fimply to immerfe the extremity of the crural nerve in the oleum tartari per deliquium), the contra@tions will end in an univerfal tenfion or rigidity. ‘The leg rifes up perpendicularly, the membrane of the feet extends itfelf, and the tetanus appears. In this fituation all the irritability of the fibre appears to be extinguifhed; and if an electric ftroke be pafled through the limb, the exhauftion becomes. real. It isa ftriking phenomenon to fee the laft remaining figns of tetanus difappear in aninftant. But there is another method by which the tenfion difappears, and by which I am able to reftore the irritability to the organs. It feems that the acidifiable bafes of the alkali, principally the azote, have confumed all the oxygene contained in the fibre. The chemical procefs of vitality ceafes. If I pour an acid, for example the nitric acid, upon the nerve, an effervefcence will take place; part of the alkali becomes latent, and the reft will have a proper proportion with refpect to its oxygene. From this moment the con traction with zinc and filver is again produced. Increafe the quantity of acid, and the” movements are again weakened. In this manner it is, that by forming an equilibrium be- tween the azote of the alkali and the oxygene of the acid applied to the animal fibre, the irritability of the organs may be taken away or reftored three or four times in fucceflion. You may eafily perceive, Sir, that thefe experiments require fteady attention. ‘The degree of infenfibility to which the nerve is reduced by repeating them may be very different. It is poflible to determine exactly the quality of the chemical agents, their weight and tempera- ture; notwith{tanding which, many experiments do not fucceed. The reafon is, that there are conditions which depend on the individuality of the organization, and concerning which we mutt ftill confefs our total ignorance. ‘The influences of the oxygenated muriatic acid upon the animal fibre are lefs marked than thofe of the alkalis; but they are neyerthelefs of much importance. I fteeped the feet of a frog (I mention this animal by preference, though I have made the fame experiments on other fpecies) in a folution of opium in al- cohol. The metals, or galvanifm, excited no motion. I threw one leg into pure water, and the other into the oxygenated muriatic acid; the firft remained motionlefs, the fecond gave very {trong contractions, and fhewed that its irritability was reftored. The common acids deprefs the irritability of the nervous fibre. A crural nerve, rendered infenfible by the ordinary muriatic acid, remains fo though it has been fteeped in the folution of pot-afh: but the mineral acids exhauit the forces of the mufcles, by condenfing the elements of the mufcular fibre. Thefe acids a€t in the fame manner as cold, which deprefles the nerves, and is beneficial to the mufcles. The mufcles and the nerves have {pecific ftimuli, agree- able to the diverfity of the elements. ‘The terrible action which the alkalis exercife on the nerves Ghemical Proce/s of Vitalily. 264 nerves appeats to explain the effect of the fecretion of the feminal liquor on the blood. It is this alkali which, diftributed throughout the fyftem, anfwers the purpofe of a ftimulus beneficial to the animal fibre. By this aQion I account for the ferocity of the ichthyophagi. My eldeft brother, who is very fkilful in the ftudy of anatomy, applied zinc and filver to the mouth and the brain of a dead fih; it afforded no motion. I poured oxygenated muriatic acid on the nerves, and at that inftant the contra€tions became very fltrong. Mr. Herz and feveral learned men of Berlin were prefent at thefe and many other experiments. The heart of the fame fifth, which had entirely ceafed to palpitate, began to perform this movement with regularity when I threw it into the oxygenated muriatic acid. The fame experiment fucceeded very often with the hearts of frogs: when a heart is immerfed in a folution of pot-afh, it lofes its irritability for ever; fo that azote is not the fpecific ftimulus of the heart. : Mr. Pfaff, while employed in my experiments refpecting germination in the oxygenated muriatic acid, has difcovered that frogs fuffocated in the oxygenated muriatic acid gas exhibit a very high degree of irritability after their death. I beg you will fix the attention of Mr. Vauquelin on the action of fulphate of pot-afh upon the nerves. I have been afto- nifhed at every thing I beheld. Two legs of frogs in a very lively flate were fteeped in the folution of the fulphate of pot-afh. I tried them three or four minutes afterwards with the metals. The contractions had increafed in force, and were even convulfive. It ap- peared that the three acidifiable bafes contained in the folution hydrogene, azote, and ful- phur, acted ftrongly on the oxygene conveyed by the arterial blood. This aétion revives the procefs of vitality. After fourteen or fixteen minutes the whole thigh became of a blackifh brown. All the oxygene of the blood was abforbed, aud the carburet of hydrogene appeared in a difengaged ftate. The zinc and the filver are not then capable of exciting the {malleft motion. Yet it would be a great miftake to conclude that all irritability is exhaufted in this cafe. I have feen the contra€tions re-appear feveral times on reftoring oxygene to the fibre by means of a folution of the oxide of arfenic. The flame is thus renewed which feemed ready to expire. The oxide of arfenic produces a tetanus and perfect infenfibility if the nerve remains long immerfed. It feems then that the too great quantity of oxygene abforbs as it were the acidifiable bafes which fupport the chemical procefs of vitality. I have thrown the whole thigh into the folution of pot-afh, and I obferved that galvanifm after-* wards had the power of exciting motion. : You fee, Sir, what‘an immenfe number of experiments remain to be made on thefe ob- jects of vital chemiftry. It is enough that a method has been pointed out of meafuring the degree of irritability of the organic parts by means of galvanifm. I fhall have the honour to fend you my work on the nervous and mufcular fibre, and on the chemical pro- cefs of vitality. I collect facts, and miftruft my own hypothetical ideas. You will perceive with me how miftaken the notion is that oxygene performs the principal part in this procefs. My experiments prove that the irritability or tone of the fibre depends only on the mutual equilibrium between all the elements of the fibre, azote, hydrogene, carbone, oxygene, fulphur, phofphorus, &¢e. The chemical combinations of phofphorus and of azote, for example, appear to be in no refpeét lefs important than thofe of oxygene with the acidi- fiable bafes. How much light may we not expect from the advances of yourfelf, Four- croy, and Vauquelin on thefe objeéts! Von Humsoipr. VoL. I.—NovemBer 1797. 3A ADDITION — 362. . Chemical Precefs of Vitality. ADDITION to the foregoing LETTER. HAVING preferved fome frogs for the winter, I have this morning repeated fome ex- periments, of which I venture to fend you an account. In the preceding letter I have re~ marked that, as we are only fuperficially acquainted with the principles of vital chemiftry;. we ought not to be furprifed if we do not always obtain the fame refults. A negative ex- periment proves nothing againft another of an affirmative nature. 4 Tam very fure that a nerve rendered infenfible by alcohol will not recover its irritability by fulphate of pot-ath- But it may very well happen that a thigh, of which the tetanus has been caufed by the oxide of arfenic, fhould remain in a ftate of tenfion notwithftanding the action of the folution of pot-afh. i . I have feen the following fa&ts within this quarter of an hour. I took the four extremi- ties of a very lively frog. The right arm and the right leg leaped on zinc and filver. TF fleeped them for four minutes in alcohol. The hydrogene ated ftrongly on the fibre. The toes of the foot trembled during the firft minute. Soon afterwards a total rigidity’ came on; the mufcle became white, the blood having apparently loft its oxygene. I re- ‘placed the arm and the leg on the zinc and filver, but there was not the flighteft contraction. I then quickly threw them into the oxygenated muriatic acid, which I had fhaken ftrongly before it was poured out; the limbs remained in it for three minutes. A flight tremulous motion fhewed, even in the cup, that the vital forces were reftored. I replaced the arm and the leg on the metals; the contractions were again produced, not only with zinc and, filver, but with zine and iron. Here I think is a very fimple and decifive experiment. I then changed the method in order to obferve the effect. I took the left thigh, and immerfed it for nine minutes in alcohol. It loft all irritability, and the oxygenated muriatic acid was no longer capable of reftoring the vital force. The left arm had remained untouched for fifteen or eighteen minutes. I prepared its nerve, but it fhewed only very weak and flow contractions with zine and filver. I threw it into alcohbl. After the firft minute its irritability was increafed, the galvanifm aéted more ftrongly ; but after three minutes all the irritability was exhaufted, and I applied in vain the remedy of oxygenated muriatic acid. I fteeped the arm in the folution of the oxide of arfenic, and it then afforded contraétions, though very weak. Here are four experiments, two of which fucceeded, and in the two’others the vital forces were not reftored. I think, neverthelefs, that in good logic we ought to admit the afirm- ative experiments. Examine the conditions, and you will fee they are very different. ‘The left leg remained too long, nearly nine minutes, in the alcohol. The right arm was al- ready very weak when the experiment began. Who can boaft of reviving the dead ?—If of two chemifts the one fhould-obtain oxygene gas by heating the red oxide of mercury, while the other did not obtain it, we fhould always believe that the apparatus of the latter was not hermetically clofed. Inever faw an organ rendered infenfible by alcohol which recovered its irritability by being left to itfelf. It neceflarily follows, therefore, that in the experiments I have ventured to relate, and of which my work contains a yery great number, the oxygene of the muriatic acid muft have been a principal agent. The art of medicine will be infinitely benefited if.we fhould fucceed in obferving the pheriomena which the Yeveral elements produce in contact with the irritable fibre. It is proper to begin 3 with Chemical Proce/s of Vitality. 363 ‘with fimple combinations, and afterwards proceed to combinations of two, three, and four principles. I have fent to the National Inflitute a memoir on the nature of light, and its chemical ‘combinations. Mr. Wedgwood pretends that the phofphorefcence of calcined bodies is not altered in hydrogene and azotic gas. I think he did not purify thefe gafes by means of phofphorus, as I did. I have feen luminous wood extinguithed in the azotic and hydro- gene gafes. A fmall quantity of oxygene, being admitted into the veflel, caufes the whole of the phofphorefcence * to revive. I have alfo converted morilles (Phallus Efculentus) into a fubflance which refembles tallow, by means of the fulphureous acid. Ihave made foap of it. ‘ Bayreuth, December 29, 1796- Von HumsBoipr. er Extra of a Letter from Citizen Fourcror to Citizen Van Mons on the Subject of that of Mr. HumpoLpr. I THINK Mr. Humboldt proceeds with rather too much expedition in his folutions. It is to be feared that he may find it neceffary to retraét. 1 am apprehenfive that he admits. too many hypothefes +: that he does not repeat each experiment fufficiently before he forms aconclufion. This in particular is much more important with regard to the philo- fophy of animal bodies than any other branch of fcience, becaufe it is furrounded by num- berlefs difficulties and multiplied fources of error and illufion. I fear that if certain chemifts continue to advance with fuch rapidity, the phyficians will foon have reafon to exclaim again{t this encroachment. If applications be too fuddenly made, and arbitrary fuppofitions accumulated, it may perhaps come to pafs that this fcience may a fecond time be reje&ted from the healing art, as it was formerly by Stahl and Boerhaave, in confequence of the exceflive abufe of hypothefes committed before their time in this refpe€t by Tachenius, Willis, and others. Too much earneftnefs may be equally pernicious to chemiftry as well as medicine, and impede the progrefs which the firft is capable of producing, and ought to produce, in the fecond. Meffis. Girtanner and Valli appear to me to make an ill ufe of their abilities and know- ledge in this refpect. They fuffer themfelves to be carried away by the ingenious notions they derive from modern chemittry. All this, however, does not prevent my being of pastes that the experiments of Mr. Humboldt are extremely interefting, and that he ought to continue them with affiduity ; but I fhould with that he would vary them more, repeat each in particular more frequently, and be moderate in his conclufions. I cannot, for example, repeat to you how many new ideas and chemical explanations, very probable in themfelyes, have occurred to me during * Spallanzani obferved the fame phenomena ; and, what is more remarkable, he obferved the phofphoric or fining animals ceafed to emit light in the azote, hydrogene and carbonic gafes, and that they emitted a light infinitely nyove vivid in oxy gene gas than in the atmofpheric aire Chimico Efame degli Efperimenti de Goete- ling. Modena, 1796. 4 For example, in the preceding memoir he {peaks of the azote of alkalis as if it were Hemanticatial fl that azote is one of the principles of thefe bodies, I firt announced or fufpeéted this eight years ago, but it 1s not yet proved, F, - a 3A2 feveral 2 364 Sulphureous Acid Combinations, feveral years paft, in confequence of my refearches into the animal analyfis. They would’ be fufhicient to change the afpeét of phyfiology and medicine; but I have been careful not to publifh them until well matured and proved by experience, left I fhould otherwife em- barrafs two fciences at once. I with to rifk nothing of this kind, but proceed gently, and’ hope to arrive at folid conclufions in the courfe of time. I am earneftly defirous of feeing the work of Mr. Hildebrandt, as well as that of M. Humboldt. Notwithftanding the fpeed they appear to fhew in their chemical explanations of vegetable and animal life, I know not why I am perfuaded that they are lefs advanced than we in the analyfis and true in- timate knowledge of the materials of thefe two kingdoms. I very much commend their zeal, and admire their bold advances; but they cannot blame our well-grounded caution and prudent flownefs. Ht is admirable to proceed with expedition, and make great advances in. the paths of nature ; but it is ftill better to obferve well, to fee clearly, and to communi- cate with accuracy what we obferve in our progrefs. Iam ftill on my journey, and confefs that F am very far from having arrived at the place I am defirous of reaching. The young men have attended with ardour my courfe of Animal Chemiftry at the School of Medicine. Nothing can equal their with to learn, The twenty lectures I give on this part of chemiftry, which is fo new, produce, as I fee, a great movement in this branch of the ftudy of nature. But I moderate their enthufiafm as much as I can. I fear left by too much precipitation this beautiful machine fhould be broken in my hands. It would be much to be regretted if expeCtations fo rich and fo happy were to be diflipated in fmoke; and this will not fail to happen if the edifice be built on hypothefes, or too much hafte be made in conitruétion before the materials are ready. I colleé& them by degrees, but they are ftill too fcanty to rifk the formation of a fyftem. Yet, to fpeak plainly, I think there are few chemifts who poffefs more faéts than myfelf on the animal analyfis: but they are not yet fufficiently connected in their relations to each other to form an entire work. If the at- tempt were made, it certainly would not be 4re perennius, &c. &c.. Wir. Concerning the Properties of the Sulphureous Acid, and its Combinations with Earthy and Alkaline Bafes. By Citizens Fourcror and VAUQUELIN. Concluded from page 318. Sulphite of Soda.) Tus falt is white, and perfectly tranfparent. Its figure a four~ fided prifm, two of the fides being very broad, and two narrow, terminating in dihedral pyramids. Its tafte is cool, and afterwards fulphureous. Its habitudes in the fire are abfolutely the fame as thofe of the fulphite of pot-afh, ex- cepting only that it commences its alterations by the aqueous fufion. By expofure to the air it efflorefces, and is afterwards converted into fulphat, but lefs fpeedily than the fulphite of pot-ath. It requires four parts of water for its folution; is more abundantly foluble in hot water, and readily cryftallizes by cooling. Barytes, Sulphite of Ammoniac—Sulphite of Lime, : 345 Barytes, lime, and pot-afh decompofe the fulphite of foda, Tt is not foluble in alcohol. ~ Salts with bafes of pot-ath, except the carbonate, do not decompofe this falt; the other genera decompofe it like the fulphate of pot-ath. The metallic oxides, and their folutions in acids, have the fame effects with the fulphite of foda as with that of pot-ath. It contains per quintal—r. Soda :8,8;—2. Sulphuric acid 31,2 ;—3. Water so. Sulphite of Ammoniac.} This falt has the form of a prifm of fix fides, terminated by fix- fided pyramids. It fometimes aflumes the figure of a {quare tablet, the borders of which are floped fo as to form a folid of fix irregular faces. Its tafte is cool and penetrating, like that of the ammoniacal falts; but it leaves a fulphureous impreffion in the mouth. By expofure to the air it attra&ts moilture, and foon afterwards paffes to the ftate of fulphat. It is very foluble, and requires at moft its own weight of water for its folution. Heat increafes its folubility, and it cryftallizes by cooling. On the fire it is volatilized without decompofition. Barytes, lime, pot-afh, and foda decompofe it in the cold; magnefia produces: the fame- effect by the afliftance of heat. ; The acids a& on the fulphite of ammoniac in the fame manner as‘on thofe of pot-afh and. foda ; but the refults are different. Charcoal does not convert it into fulphuret, becaufe it rifes too {peedily by heat. It does not decompofe falts with bafes of pot-ath or of foda, but it decompofes thofe of lime, magnefia, barytes, and alumine, with which it forms infoluble precipitates. Its habitudes with the metallic oxides and falts are nearly the fame as thofe of the ful-- phites of pot-afh and of foda, excepting that it forms with feveral of them triple falts, as we fhall more amply explain in another memoir on the metallic fulphites. Its component parts in the quintal are—1. Ammoniac 29,073—2. Sulphuric acid 60,063. —Water 10,87. Sulphite of Lime.) The form of the fulphite of lime is that of a fix-fided prifm, termi- nating in a very long pyramid. Its tafte at firft is {carcely perceptible; but when it has been: kept for fome time in the mouth, it communicates to the tongue a tafte which is manifeftly- fulphureous. : This-falt, when well neutralifed, is very {paringly foluble in water; but it becomes folu-- ble by an excefs of acid. In this way it may be obtained “in eryftals; that is to fay, by expofing its felution in the fulphureous acid to the air. The acid is diffipated, and leaves. the falt in a ftate of purity. Barytes alone, among the earths, is capable of decompofing it. This may be afcertained by mixing a folution of that earth with a folution of the neutral fulphite of lime, when a light precipitate is formed. Heat converts it into fulphate, by depriving it of a portion. of fulphur. The mineral acids decompofe it, like the other fulphites. The alkalis produce no change in this falt ; for the alkaline fulphites are decompofed by lime. Among the“neutral falts, the alkaline carbonates, as well as the alkaline phofphates andi fuates, alone decompofe it. 4 It does not acquire the ftate of fulphat by contact of the air, but very flowly. ; Metallic. 366 ‘Sulphite of Magnefia—of Barytes—of Alumine, Metallic folutions decompofe it, at leaft for the moft part. > The quintal contains—1. Lime 47;—2.- Sulphuric acid 4853. Water 5. Sulphite of Magnefia.| This falt is white and tranfparent. " Its form a deprefled tetra- hedron ; its tafte is mild and earthy at firft, and afterwards fulphureous. ; By expofure to heat, it foftens, fwells up, and becomes ductile, like gum ; it lofes about 0,45 of its weight by the deficcation. If the heat be kept up after it has loft its water of cryftallization, the fulphureous acid flies off, and the refidue in the retort is magnefia, nearly pure. In this way. we found that a quintal of this falt is compofed of 16 parts magnefia, 39 fulphureous acid, and 45 water. This falt is fparingly foluble in water, but very foluble in an excefs of acid ; and this fo- lution, expofed to the air, cryftallizes very readily, by lofing its excefs of acid. It becomes opake in the air, and changes by degrees into fulphate ; but for this purpofe ‘much time is required. The fixed alkalis, lime and barytes, aoe it completely ; ammoniac decompofes it in part only, and a triple falt is formed. The alkaline and earthy falts, except thofe of alumine, decompofe it likewile. The mineral acids.and metallic folutions produce the vee effets on this falt as on the other fulphites. Sulphite of Barytes.] This falt does not cryftallize, has no perceptible tafte, and is per- feétly infoluble in water. For this reafon the fulphureous acid carries down a precipitate from the aqueous folution of barytes. It is not rendered foluble by an excefs of acid, like the other earthy-fulphites: Heat changes it into fulphate ; but it does not pafs to this flate by expofure to the air, but avith extreme difficulty. No earth nor alkali decompofes it. The acids decompofe it; whence the fulphureous acid does not precipitate the barytic falts, as the fulphuric acid does. Among the neutral falts there are none but the alkaline carbonates which decompofe i it. “The other properties of this'falt are fuch as are corfimon to the fulphitesy It is compofed of—1. Barytes 59 ;—2. Sulphureous acid 39;—3. Water 2. Sulphite of Alumine.] It is infoluble in water, but becomes abundantly fo by excefs of acid. Its diffolution does not cryftallize by the contact of air, and becomes converted into a foftith dudtile mafs. : - Fire difengages the fulphuric acid without alteration. All the alkalis and earths decompofe it, as do alfo the mineral acids. Its component parts are—44 alumine, 32 fulphureous acid, and 24 water. From the faéts defcribed in this memoir it is evident that the fulphites poflefs very dif- ferent properties from thofe of the fulphates; and that they follow peculiar laws of folution, cryftallization, affinity, and decompofition. In fat they poffefs—1. A fulphureous tafte, fimilar to that of their acid. 2. They are - decompofable by fire, either by the efcape of their acid without alteration, or by lofing a portion of fulphur and becoming converted into fulphates. 3. ‘They are converted into ful- phates by the contaét of air, or of any other fubflance capable of affording oxygene; and their weight is increafed by this converfion. 4-They are decompofed by moft acids; which expel the Copper Wi wake in the Ife of Ariglefey, 367 the fulphureous acid with effervefcence, and the produétion ofa {trong penetrating odour. 5- They burn rapidly, and with flame, when heated with fuper-oxygenated muriate of pots , ath, or with faltpetre, and become fulphates. 6. The alkaline fulphites are more foluble than the fulphates, and the earthy fulphites are much lef fo. 7: Laftly, the fulphite of lime is not decompofed by the alkalis, like the fulphate. 5 a VII. An Account of the Great Copper Works in the Ile of Anglefey. By Mr. ArrHuR AIKIN *. Auguf 13, 1796. il HIS has been a moft interefting and entertaining day, being fpent in vifiting the vaft copper works connected with the Parys Mountain. We breakfafted at Amlwch, a con- fiderable town on the coaft, about two miles from the mine, and almoft entirely peopled by. the miners and their families, = : We had no difficulty in diftinguifhing this celebrated mountain, for it is perfe@ly barren ° from the fummit to the plain below ; not a fingle fhrub, and hardly.a blade of grafs, being able to live in this fulphureous atmoiphere. ‘© No grafly mantle hides the fable hills, No flowery chaplet crowns the trickling rills ; Nor tufted mofs nor leathery lichen creeps In roffet tapeftry o’er the crumbling fteeps.” Darwin. ‘ The nearer we approached the fcene of bufinefs, the more penetrating was the fume of the fulphur; but we had very foon too many objects of attention to regard this incons- venience. The mountain is about a mile in length, and is the property of Lord Uxbridge ° and the Rev. Mr. Hughes, and the fortunate difcovery of the copper took place a little more than thirty years ago; thus converting a piece of ground, originally of very little value, into one of the moft profitable eftates in the kingdom, - The fubftance of the mountain being ore, the work is carried on in a very different manner from the cuftom of other mines : here are, comparatively, few fhafts or levels, the greater part being quarried out, fo as to leave a vaft excavation open to the day. There are two of thefe quarries or mines, which are worked by two different companies : the firft goes by the name of the Mona Mine, andis the fole property of Lord Uxbridge; the other, called the Parys Mine, is fhared between the. Earl and Mr. Hughes. The view down this fteep and extenfive hollow is fingularly flriking. The fides are chiefly of a deep yellow or dufky flate colour, ftreaked, however, here and there, by fine veins of blue or green thooting acrofs the cayern, mingled with feams of greyifh yellow, The bottom of the pit is by no » means regular, but exhibits large and deep burrows in various parts, where a richer vein has been followed in preference to the reft. Every corner of this vaft excavation refounds with the noife of pickaxes and hammers: the edges are lined with workmen drawing up the ore * Tour through North Wales, from 368 Defeription of the Anglefey Copper-Weorks. from below; ‘and at fhort intervals is heard, from different quarters, the loud explofion of the gunpowder by which the rock is blafted, reverberated in pealing echoes from every fide. The exterior covering of the mountain is an aluminous' flate; the matrix black-grey chartz ; the ore copper, chiefly I. The yellow fulphurated : of which the richeft contains, according to miners’ computa- tion, that is, in the proportions of the ounce troy, Sulphur — 5 dwt. (25 per cent.) Copper _ — Ditto. Refufe a 10 dwt. (50 per cent.) "The wortt ore yields nearly the fame quantity of fulphur, but of metal no more than fix grains (12 per cent.); this inferior kind, however, is chiefly worked for the fulphur. The other {pecies and varieties of ore that the mine produces are, II. Black ore, containing copper, mixed with galena, calamine, and a little filver. TII. Malachite, or green and blue carbonate of copper. IV. Native copper, but in very fmall quantity. V. Sulphate of copper, cryftallized and in folution. VI. Sulphate of lead in confiderable reeih bie containing a pretty large proportion of filver. VII. Native fulphur. Procefs.—The ore is got from the mine by blafting ; after which it is broken into fmaller pieces by the hammer (this being chiefly done by women and children), and piled into a kiln, to which is attached by flues a long fulphur chamber. It is now covered clofe; a little fire is applied in different places, and the whole mafs becomes gradually kindled; the fulphur fublimes to the top of the kiln, whence the flues convey it to the chamber appointed for its reception. This fmouldering heat is kept up for fix months, during which the ful- phur chamber is cleared four times, at the expiration of which period the ore is fufficiently roafted. The pooreft of this, that is, fuch as contains from 1} to 2 per cent. of metal, is then conveyed to the fmelting-houfes at Amlwch-port; the reft is fent to the company’s furnaces at Swanfea and Stanley near Liverpool. The greater part of the kilns are very long, about fix feet high; and the fulphur chambers are of the fame length and height, conneéted by three flues, and on the fame level with the kilns; four new ones, how- ever, have been built at Amlwch-port, by which much fulphur is preferved that would have been diffipated in the old kilns. The new ones are made like lime-kilns, with a contri- vance to take out the roafted ore at the bottom, and thus keep up a perpetual fire. From the neck of the kiln branches off a fingle flue, which conveys the fulphur into a receiving chamber, built on the rock, fo as to be on a level with the neck of the kiln, that is, above the ore. ; ‘ The two fmelting-houfes, of which one belongs to each company, contain 31 reverberatory furnaces, the chimnies of which are 41 feet high; they are charged every five hours with 12 cwt. of ore, which yields } cwt. of rough copper, containing 50 per cent. of pure metal; the price of rough copper is about 21. ros. per cwt- ‘The coals are procured from Swanfea and Liverpool, a great part of which is Wigan flack. From experiment it appears, that though a ton of coals will reduce more ore than the fame quantity of flack, yet, owing to the Defcription of the Anglefey Copper-Works. 369 the difference of price, the latter is, upon the whole, preferable; the prices of the two at Liverpool being—coals 8s. 6d. per ton—flack 5s. per ditto. The fulphate of copper, however, is the richeft ore that the mine yields, containing about 50 per cent. of pure metal. ‘This is found in folution at the bottom of the mine, whence it is pumped up into cifterns, like tanners’ pits, about two feet deep: of thefe pits there are many ranges, each range communicating with a fhallow pool of confiderable extent. Into thefe cifterns are put caft-iron plates, and other damaged iron veffels procured from Coal- brook Dale; when the fulphuric acid enters into combination with the iron, letting fall the copper in the form of ared fediment very flightly oxided. The cifterns are cleared once in a quarter of a year, when the fulphate of iron in folution is let off into the thallow pool, and the copper is taken to a kiln, well dried, and is then ready for exportation. The ful- phate of iron remaining in the pool partly decompofes by fpontaneous evaporation, and lets fall a yellow ochre, which is dried and fent to Liverpool and London. , The fulphur produced in the roafting, after being melted and refined, is caft into rolls and large cones, and fent to London. The cones are ufed chiefly for the manufaQory of gunpowder and fulphuric acid. ; Green vitriol and alum are alfo made in {mall quantities by a feparate company ; but to thefe works ftrangers are not admitted. The number of men employed by the two companies is 1200 miners, and about go {melters; the miners are paid by the piece, and earn in general from a fhilling to twenty- pence per day. ri The depth of the mine in the loweft part is 50 fathoms, and the ore continues as plen- tiful as ever, and of a quality rather fuperior to that which lay nearer the furface. With regard to the annual quantity of ore raifed, little certain can be mentioned. The Parys Mine has furnifhed from 5000 to 10,000 tons per quarter, exclufive of what is pro- cured from the fulphate of copper in folution ; and as the two mines employ nearly equal numbers of workmen, they probably afford about the fame quantity of ore. Adjoining to the fmelting-houfes is a rolling-mill, upon the fame conftruétion as malt- mills, for grinding the materials for fire-bricks ; thefe confift of fragments of old fire-bricks, with clunch (a kind of magnefian clay found in coal-pits) procured from near Bangor-ferry, The port of Amlwch is chiefly artificial, being cut out of the rock with much labour and expence, and is capable of containing 30 veffels of two hundred tons burthen; it is greatly expofed, and dangerous of accefs during high northerly winds, which drive a heavy fea up the neck of the harbour. The two companies employ 15 brigs from 100 to 150 tons burthen, befides floops and other craft, all of which lie dry at low water. ‘The various articles, the produce of the mines, which are exported, are the following : I. Coarfe regulus of copper from the fmelting-houfes, Il. The richer copper ore roafted. Ill. The dried precipitate of copper from the vitriol pits. IV. Refined fulphur. V. Ochre. VI. Alum. VIE. Green vitriol. ’ Vor. 1—November 1797. 3B ; The 37° Account of the Country in the The towh of Amlwch, which about 30 years ago had no more than half a dozen houfes in the whole parifh, now fupports a population of four or five thoufand inhabitants; and was at prefent, being market-day, thronged with miners and country-people. After dinner we walked along the fea fhore, climbing the fteep flate rocks, whence the water below ap- peared of a beautiful green, and fo tranfparent as to fhew the fhelving rocks to a great depth beneath. Having heard that at Camlyn Bay, about eight miles weft of Amlwch, there were fome marble quarries, and that it furnifhed afbeftos, we refolved to fpend this day in vifiting it: the road lay in general about half a mile from the coaft; the fubftratum was waved green magnefian flate. When we arrived at Camlyn Bay, we looked in vain for marble or afbeftos, and proceeded homewards along the coaft. ‘The fhore of Camlyn Bay confifts entirely of green and purple waved magnefian flate rock, with large veins of quartz. Having arrived at a promontory that feparates Cemmaes Bay from the former, we found it to confift of a fine blue-veined limeftone, or common marble. Some way on, near the village of Cem- maces, this limeftone is cut through by a ftratam defcending to the water, about 40 yards wide, of black flate, containing iron pyrites; and in the caverns dug in this, probably in a fruitlefs fearch after metals, are efflorefcences of fulphate of iron and chalybeate fprings. To this fucceeds a beautiful water-grey fand, mixed with lime but of little coherence, on expofure to the air, taking an ochrey ftain.’ Adjoining to this are a few yards of calcareous free-ftone, and then a cliff of very hard white and water-grey marble ; 2 range of fand and loofe free-ftone fucceeds, and the bay terminates with a marble promontory. The foil of the land furrounding the bay is for the moft part, efpecially near the village, a deep fand. The limeftone terminates fhortly after, and the green-waved magnefian flate continues the boundary of the ifland. This ridge of lime ism general higher than the flate, deferibing an irregularly indented line of coaft, about four miles long : its breadth varies from a’ quar- ter to half a mile; anda narrow valley, forming its outline towards the land, feparates it entirely from the afbeftine flate, thus preventing any intermediate ftrata. ; The whole of this coaft is cut out into bays or receffes. of various forms and dimenfions, with lofty proje€ting promontories, which are for the moft part fine fheep-walks. A num- ber of iflands alfo are formed by ledges of rock, many of them a good way out at fea, and at high water juft appearing like black fpots in the midft of the waves: many of thefe creeks are fecure havens for {mall veffels, which are protected from weft and fouth-weft winds by the rocks. The village of Cemmaes ftands upon a little creck opening into a moft beauti- ful bay about a mile acrofs; its entrance into the main fea is guarded on each fide by a craggy promontory, the one of grey, the other of fnow-white marble, gliftening above the green fea, fmooth as the furface of a mirror, and whofe fparkling | tranfparency baflles de- {cription. In the interior recefs of the bay, the bank of black flate, mentioned above, was finely contrafted with a lofty irregular projecting arch of white marble, pierced by the con- ftant dafhing of the waves; while the founds of laughter and merriment, proceeding from two boats’ crews of young people, that had juft pufhed out of the creek on a party of plea- fure, added double life and intereft to this lovely fcene. The land adjoining the cliffs, that everlook the fea, produces a great deal of corn, chiefly oatsand barley. A golden tinge already Vicinity of the Anglefey Copper-Works. 371 already begins to appear, that will ufher in the harveft, as foon as the crop of hay with which the farmers are now bufied is fafely houfed. As we approached Amlwch, we were much pleafed with feeing the {cars of rock between the town and fea occupied by numerous groupes of men, women and children, all neat and in their beft clothes, it being Sunday, who were enjoying the mild temperature of a fummer evening rendered refrefhing by the neighbourhood of the fea. In one place we obferved a circle of men gathered round a point of rock, in which was feated the orator of the party reading a newfpaper aloud, and commenting upon it; on other litfle eminences were feen family parties, the elder ones converfing, and the younger children gamboling about them, or running races with each other: in a new-mown meadow clofe to the town, we pafled by a large company of lads and laffes feated on a green bank, chatting, laughing, and full of mirth and frolic. To one who had been a fpeétator of the grofs and riotous delight too frequent on holyday-evenings in the outfkirts of the metropolis, or any large town in Eng- land, the contraft could not fail of being very ftriking, and much to the advantage of the inhabitants of Amlwch:. out of the whole number we did not fee one drinking party ; the pleafures of fociety and mutual converfe needed not the aid of intoxication to heighten their-relifh. Mean time the fong went round, and dance and fport, Wifdom and friendly talk, fucceffive, ftole Their hours away: while in the rofy vale Love breath’d his infant fighs, from anguith free, And full replete with blifs; fave the fweet pain That inly thrilling but exalts ir more. Harmonious Nature too look’d fmiling on: Clear fhone the fkies, cool’d with eternal gales, And balmy fpirit all. THOMSON, Tam acquainted with no place the manners of whofe inhabitants are fo unexceptionable (as far at leaft as a flranger is enabled to judge of them) as Amlwch; and the fayourable ‘opinion which I was led to entertain of them, on vifiting the town laft year, is confirmed by what I have obferved at prefent. Not a fingle inftance have I known of drunkennefs ; 3 not one quarrel have I witneffed during two very crowded market days, and one of them aday of unufual indulgence, that I paffed at this place ; and I believe no gaol or ‘bridewell, or houfe of confinement, exifts in the town or neighbourhood. Moft of the miners are me- thodifts, and to the prevalence of this religious fect is chiefly to be attributed the good order that is fo confpicuous. Men who have been long confirmed in habits of vice and ir- regularity, need arguments the moft potent that. can be offered to counterbalance the affo- ciated power of habit and inclination: were it poflible forcibly to tear them from their conneétions, and to place them in an entirely different fituation, reafon might then be called in gradually to perfect the cure; but where this canngt be done, (and in moft cafes it is impratticable,) what argument can*be urged of fuch overbearing force as to combat with and overthrow the moft rooted propenfities, even upon their own territory, unaflifted by ex- ternal coercion, except a {trong and impreflive appeal to their hopes and fears ; and, by pre- 3B2 fenting 372 Theory of an improved Line of Logarithms. fenting both exaggerated and in full contraft, to overwhelm the mind by furprife and alarm ? After fupper we ftrolled up to the mountain, which now no longer refounded with the confufed noife of pickaxes and hammers; all was huthed in profound filence; and the moon-beams, which were reflected bright from the fides of the vaft excavations, could fcarcely penetrate the deep abyfs below. As we returned we were ftruck with the clear red vivid flames iffuing in a large body from the long range of {melting-houfes on the coaft, and cafting their rays to a great diftance. VIII. A Method of difpofing Gunrer’s Line of Numbers, by which the Divifins are enlarged, and other Advantages obtained. O; the many ingenious inftruments for computation which were in ufe during the laft century, among mathematicians, fearcely any are to be found at prefent except the fector and the logarithmic line of Gunter. The eafe and accuracy of computation by thofe ad- mirable numbers have rendered the others of little importance; but the feQor has main- tained its {tation from its utility in graphical operations, and the Gunter’s line is not only of great value in nautical and other proportions which do not exceed three places of figures, but alfo as a check to affure the truth of the leading figures in more extended calculations. About ten years ago I communicated to the Royal Society a method of extending the range of this laft inftrument, which I {till confider as lefs generally known. than its utility may perhaps claim. The principles depend on the following confiderations : 1. If two geometrical feries of numbers, having the fame common ratio, be placed in or= der with the terms oppofite each other, the ratio between any term in one feries and its oppofite in the other will be conftant *. 2. And the ratio of a term in one feries to any term in the other, will be the fame as ob- tains between any other two terms having the fame relative pofition and diftance f. 3- In all fuch pairs of geometrical feries as have the fame common ratio, the laft-men- tioned property obtains, though the firft antecedent and confequent be when in one. pair, and the fecond in any other pair }. 4, If the differences of the logarithms, of numbers be laid in order upon an axranetenk of equti-dittant parallel right lines, in fuch a manner as that a right line drawn acrefs, the ; a an an® an? an* b bn bn* bn3 bn* Then a: &::,.an: bn :: an? : bn*, &e. + In the foregoing feries a : bn* :: an® : bn* :: an: bn, &e. @ an an? an} an* 5 bn bn? bn3 bnt d dn dn» dn? dn Geom, feries {ie bdn bdn*® bdn? bdn* — a £2" 8 oe Then a; bu? 3: dns = ke. * Geom. feries + Geom, feries Theory of an improved Line of Logarithms. 373 whote fhall interfe& it at divifions which denote numbers in geometrical progreffion; then, from the condition of the arrangement, and the property of this logarithmic line, it follows, firft, that every right line fo drawn will, by its interfe€tions, indicate a geometrical feries of numbers *; fecondly, that fuch feries as are fo indicated by parallel right lines, will have the fame common ratio +; and thirdly, that the feries thus indécated by two parallel right lines, fuppofed to move laterally without changing either their mutual diftance, or parallelifm to themfelves, will have each the fame common ratio; and, in all pairs of feries indicated by fuch two lines, the ratio between an antecedent on one parallel and the oppofite term on the other, taken as a confequent, will be conftant +. 5. In the foregoing paragraphs the logarithmic line has been confidered as unlimited. On fuch a line, therefore, any antecedent and confequent being given, it would be poflible to find both on the arrangement, and to draw two parallel lines, one over each number: and if the lines be then fuppofed to move without changing either their diftance or abfolute direQion, fo that the line, which before marked an antecedent, may in the fecond ftation mark * Let AB, CD, EF (Plate XVI. Fig. r.) be portions of the logarithmic line arranged according to the condition ; let GH be a right line drawn acrofs, {o as to pafs through points of divifion ¢, c, a, denoting num- bers in geometrical progreffion; then will any other line IK, drawn acrofs.the arrangement, alfo pafs through points f, d, 6, denoting numbers in geometrical progreffion, DemonsTRATION. From one of the extreme points of interfection f, in the laft named line IK, draw the right line fg parallel to GH, and interfecting the arrangement in the points 7, 4; and the ratios of the num- bers ¢: fc: i, and a: 4, will be equal, becaufe the intervals on the logarithmic line, or differences of the loga- rithms of thefe numbers, are equal : Ori= Food pf aE c i a ieh But - a < by the condition. Therefore Ba = 53 or the nnmbers f,, 4, are in the fame continued ratio as the numbers ¢, ¢, a. i Again, the point f, the line /d, and the line 44, are in arithmetical progreffion, and denote the differences of the logarithms of the numbers f and f, / and d, 4 and 4, The quotients of the numbers themfelves are therefore im geometrical progreffion, that is, fav 3 i db i hs Or 43> 7 by fubftituting < F £ fon. its equal = rr Whence 5 = Sor f: d:b. QE.D + In the fame manner, as it was proved that the line fg parallel to GH paffes through points of divifion denoting numbers in the fame continued ratio as thofe indicated by the line GH, it may alfo be fhewn, that the line LM, parallel to any other line IK, will pafs through a feries of numeral points having the fame con- tinued ratio as the feries indicated by that line IK to which itis parallel. + Becaufe the lines preferve their parallelifm to their former fituation, they will indicate geometrical feries having the fame common ratio as before; and, becaufe their diftance meafured on the logarithmic line remains unchanged, the differences of the logarithms of oppofite numbers, and confequently their ratio, will be conftant. 374 Tinprovements of Gunter’s Scale. mark a new antecedent, the other (by 2. and 3.) will mark a number at the fame rela- tive pofition and diftance, which will be the confequent to this laft antecedent, after the fame ratio. 6. Suppofe a logarithmic line to contain no more thana fingle range of numbers from r to 10, it will not be neceffary, for the purpofes cf computation, to repeat it; for, if a flider or beam have two fixed points at the diftance of the interval between 1 and 10, and a moveable point be made to range between thefe (always to indicate the antecedent), in this cafe, if the confequent fixed point fall without the rule, the other fixed point will fhew the divifion it would have fallen on if the rule had been prolonged. This may be eafily applied to the arrangement defcribed, N° 4. 7. If the arrangement confift only of the logarithms from I to 10, and the parallel crofs lines interfeQl that geometrical feries whofe fucceffive ratios altogether, with that of the laft to the firft, make by compofition the ratio rs, the contrivance N°. 6. may be applied to fhew fuch confequents as fall, laterally, without the rule- 8. It will be convenient that the arrangement of the lines fhould be difpofed fo as to oc- cupy a reétangular parallelogram ; or, in other words, that the crofs line, cutting the feries laft mentioned, may be at right angles to the length of the rule. The conftruGtion of an inftrument on the principles here explained will admit of various difpofitions of the graduated lines and apparatus for meafuring intervals upon them. In’ the Tranfaétions I gave a figure of a rule confifting of ten parallel lines, equivalent to a double line of numbers, upwards of twenty feet in length, with a beam compafs for meafur- ing intervals. Fig. 2. Plate XVI. reprefents a Gunter’s. fcale, equivalent to that of a9, inches in length, publifhed by the late Mr. Robertfon. Itis, however, but one eighth part of the length, and contains only one-fourth of the quantity of divifion. In the flider GH is a moveable piece AB, acrofs which a fine line is drawn; and there are alfo lines CD, EF, drawn acrofs the lider, at a diftance from each other equal to the length of the rule. The fketch No. 4. reprefents one face or fide of the inftrument, and No. 2. reprefents the oppofite face. Each contains one-fourth part of the line of numbers. When it is ufed, the flider muft be fet fo that the line on the piece AB may be placed at the antecedent, andone of the end marks CD, or EF, may be oppofite the confequent. After this ad- juftment of the flider, the whole may be moved at pleafure, till the piece AB is fet at any other required antecedent ; and then the fame line CD or EF, as before, will indicate the confequent at the fame diftance or pofition as before. Butif the confequent mark of the flider fhould fall without the rule, the other line will indicate the required confequent upon the rule, though at the diftance of one line on the rule farther off in pofition than the other confequent mark would elfe have fhewn it. The operations are obvious and familiar upon the rule itfelf. Another inftrument was defcribed in the Tranfa€tions, which was equivalent to the fame rule, but of a circular’ figure, one inch and a-half diameter. The graduations were made upon three concentric circles, and a feétor was applied inftead of the flider. On account of the larger figure I have here given, it becomes unneceflary to defcribe this. — I approve Improved Gunter’s Scale.—Perpetual Motion, 375 I approve of this conftruétion as fuperior to every other which has yet occurred to me, not only in point of convenience, but likewife in the probability of being better executed, becaufe fmall ares may be graduated with very great accuracy, by divifions transferred from a larger original. The circular inftrument is a combination of the Gunter’s line and the fetor, with the improvements here pointedout. The property of the fe€tor may be ufeful in magnifying the differences of the logarithms in the upper part of the line of fines, the middle of the tan- gents, or the beginning of the verfed fines. It is even pofhble, as mathematicians will eafily conceive, to draw fpirals, on which graduations of parts, every where equal to each other, will fhew the ratios of thofe lines by means of moveable radii fimilar to thofe on fuch an inftrument. After the publication of the account in the Tranfactions of the Royal Society, the men- ~ tion of circular and fpiral inftruments brought to the recolleGtion of the late Mr. George Adams, of Fleet-ftreet, (who had feen the ftraight inftrument fome years before it was com- municated to the Society,) that he had a fpiral engraved on a brafs plate by his father. He made me a prefent of the plate, and fhewed me, by a manufcript, that it was conftruéted in the year 1748. The fpiral has ten turns, and its external diameter is twelve inches. It contains the numbers, fines and tangents, the latter being twice repeated, and may with eafe be ufed to compute to four places and an eftimate figure; which is to the full as much as could be done with a common Gunter’s fcale of fixty feet in length. : " Fig. 3. Plate XVI. reprefents the line of numbers drawn according to this fyftem. The fe&tor ACB is ufed to meafure the ratios. One thread muft be fet to the antecedent, and the other to the confequent. If the antecedent thread be then removed without altering the angle to any other antecedent, the other thread will mark a confequent at the diftance of the fame number of turns of the fpiral in the fame dire€tion. In cafe the number of turns fhould proceed without the fyftem, it will be neceffary to return and reckon onward from the oppofite extremity of the fpiral to complete the number. SSeS eee IX. On the Mechanical Projects for affording a Perpetual Motion. Ix confequence of the notice * taken of Mr. Varley’s attempt to produce a perpetual motion, I have been requefted by feveral correfpondents to ftate how far the mechanical fcheme for which Dr. Conrad Shiviers took out a patent in the year 1790, for the fame object, may be worthy of attention. Ihave, on that occafion, mentioned the difficulties which have prevented any clear general demonttration of the abfurdity of this purfuit from being produced, though it has not been difficult to thew the fallacy of the individual plans. It docs not indeed feem eafy to enunciate the fcheme itfelf. What in univerfal terms is * Philof Journ. I, 334. the 376 Schemes for Perpetual Motion. the thing propofed to be done ? Is it tocaufe a body, or fyitem of bodies, to aét in fuch a manner that the re-action fhall be greater than the aétion itfelf, and by that means generate forcé by the accumulation of the furplus? Or, can the motion communicated be greater than that loft by the agent? Since thefe pofitions are evidently contrary to the phyfical axioms called the Laws of Nature, and friGtions and refiftances would fpeedily deftroy all motions of fimple uniformity, it may be prefumed that s’Gravefande, who thought that all the demonftrations of the abfurdity of fchemes for perpetual motion contained paralogifm, would have ftated the propofition under different terms. But without entering into this ap- parently unprofitable difquifition, it may be ufeful, as well as entertaining, to make a few obfervations on the mechanical contrivances which dependon a miftaken dedu€tion from the general theorem refpeéting the balance, among which that of Dr. Shiviers muft be claffed. There is no doubt but numerous arrangements have been made, and ftill are laboured at by various individuals, to produce a machine which fhall poflefs the power of moving itfelf perpetually, notwithftanding the inevitable lofs of force by friction and refiftance of the air. Little, however, of thefe abortive exertionghas been entered upon record. The plans of Bifhop Wilkins, the Marquis of Worcefter, and M. Orfyreus, are all which at this time oc- cur to my recollection. There is no doubt but the celebrated Wilkins was a man of learning and ability. His Effay towards a real character and a philofophical language is fufficient to render his name immortal. Twenty years before the appearance of that work he publifhed his Mathema- tical Magic, namely in the year 1648, containing 295 pages fimall o€tavo, which, from the number of copies ftill in being, I fuppofe to have been a very popular treatife. It is in this work that I find, among other contrivances for the fame purpofe, a wheel carrying fixteen loaded arms, fimilar to that delineated in fig. 4, plate xv. in which, however, for the fake of fimplicity, I have drawn but fix. Each lever A B C DE F is moveable through an angle of 45°, by a joint near the circumference of the wheel, and the inner end or tail of each is confined by two ftuds or pins, fo that it muft either lie in the direction of a radius, or elfe in the required pofition of obliquity. If the wheel be now fuppofed to move in the direction EF, it is evident that the levers A B C D,by hanging in the oblique pofition againft the an- tecedent pins, will defcribe a lefs circle in their afcent, than when on the other fide they come to defcend in the pofitions EF. Hence it was expected that the defcending weights, having the advantage of a longer lever, would always predominate. Dr. Wilkins, by re- ferring the weights to an horizontal diameter, has fhewn that in his machine they will not. A popular notion of this refult may alfo be gathered from the figure, where there are three weights on the afcending, and only two on the defcending fide ; the obliquity of pofition giving an advantage in point of number, equal to what the other fide may poffefs in inten- fity. Or if this contrivance were to be ftrilly examined, on the fuppofition that the levers and weights were-indefinitely numerous, the queftion would be determined by thew- ing that the circular arcs AK, HI, are in equilibrio with the ares AG, GL. ‘The fimpleft method of examining any fcheme of this kind with weights, confifts in en- quiring whether the perpendicular afcents and defcents would be performed with equal maffes in equal times. If fo, there will be no preponderance, and confequently no motion. This is clearly the cafe with the contrivance before us. = ; The Schemes for Perpetual Motion. 377 The Marquis of Worcefter, who will ever be remembered as the inventor of the fteam engine, has defcribed a perpetual motion in the 56th number of his Century of Inventions, publithed in the year 1655, and fince reprinted in 1767 by the Foulis’s at Glafgow. His words were as follow: “ To provide and make, that all the weights of the defcending fide of a wheel fhall be perpetually further from the centre than thofe of the mounting fide, and yet equal in num=- ber, and heft to the one fide as the other. A moft incredible thing if not feen, but tried before the late King (of bleffled memory) in the Tower by my direétions, two extraordinary ambaffadors accompanying his Majefty, and the Duke of Richmond and Duke Hamilton, with moft of the Court attending him. The wheel was 14 feet over, and 40 weights of 50 pounds a piece. Sir William Balfour, then Lieutenant of the Tower, can juftify it with feveral others. They all faw, that no fooner thefe great weights pafled the diameter line of the lower fide, but they hung a foot further from the centre; nor no fooner paffed the dia- meter line of the upper fide, but they hung a foot nearer. Be pleafed to judge the con- fequence.” Defaguliers, in his courfe of Experimental Philofophy, vol. I. page 185, has quoted this paflage, and given a fketch of a pretended felf-moving wheel, fimilar to that of fig 5, plate xv. as ‘refembling the contrivance mentioned by the Marquis of Worcefter. * The defcription of this laft engineer agrees, however, fomewhat better with the contrivance fig. 4. It muft of courfe be a miftake in terms, when he fays the weight receded from the centre at the lower diameter, and approached towards it at the upper: the contrary being in fact neceflary to afford any hope of fuccefs; and accordingly in the quotation it is fo ftated. Iam therefore difpofed to think that fig. 5 reprefents the whee! of Orfyreus at Heffe Caffel, much talked of about the year 1720, and which probably was made to revolve, | curing the time of exhibition, by fome concealed’ apparatus. It confilts of a number of cells or partitions diftinguithed by the letters of the alphabet, which are made between the interior and exterior furfaces of two concentric cylinders. The partitions being placed obliquely with refpe& to the radius, and a cylindrical or {pherical weight placed on each, it is feen from the figure, that thefe weights will lie againft the inner furface of the large cylinder, whenever the outer end of the bottom partition of any cell is loweft; and on the contrary, when that extremity is higheft, the weight will reft on the furface of the interior cylinder. Let the wheel be made to revolve in the dire€tion ABC; the weights in CDEFGHI being clofe to the external circle, and the weights K LM AB clofe to the inner, for the reafons laft mentioned. As the cell B defcends, its weight will likewife run out, at the fame time that the weight in the cell I will run in, in confequence of its par- tition being elevated. By the continuation of this procefs, fince all the weights on the de- fcending fide pafs down at a greater diftance from the centre, while thofe on the afcending fide rife for a confiderable part of their afcent at a lefs diftance from the fame point, it is concluded that the wheel will continue to maintain its motion. On this, however, it is tobe remarked, that the perpendicular afcent and defcent are alike, both in meafure, and in time of performance; and that the familiar examination, even to thofe who know lite of fuch fubjects, is fufficient to fhow that the preponderance is not quite fo palpable as at firft it ap- pears. For the weights G and ¥, H and E, I and D, are evidently in equilibrio, becaufe at the fame horizontal diftance from the centre; and if the favourable fuppofition that the Vot. I.—Novemper 1797. gC . Weight 378 Schemes for Perpetual Moticn. weight B hath already run out be admitted, it will then remain a queftion whether thefe two exterior weights, B and C, can preponderate over the four inner weights K L M A. The more accurate examination of this particular contrivance will lead to the following theorem. In two concentric circles, if tangents be drawn at the extreme points of a dia~ meter of the {maller, and continued till they interfe&t the larger, the common centre of gravity of the arc of the greater circle included between the tangents, and of the half pe- riphery of the fmaller circle on the oppofite fide of the diameter, will be the common centre of the circles. If, therefore, the balls were indefinitely numerous and fmall, the fuppofed effeétive parts of the wheel, fig 5, would be in equilibrio, as well as the parts beneath the. | horizontal tangent of the inner circle. Fig. 6 reprefents the contrivance of Dr. Shiviers, which, in a periodical publication, in: other particulars refpectable, has been faid to continue in motion for weeks, and even months together. There is not the fmalleft probability that it fhould continue in motion for half a minute, or nearly as long as a fimple wheel would retain part of its firft impulfe. The external circle denotes a wheel carrying a number of buckets, ABIL, &c. Crepre= fents a toothed wheel, on the fame axis, which drives a pinion D; and this laft drives another pinion E upon the axis of a lanthorn, or wheel intended to work a chain pump with the fame number of buckets as in the large wheel AB. The lanthorn G is made of fuch 2 fize as to raife the buckets abil with a due velocity. K reprefents a gutter, through which a metallic ball, contained in the bucket m may run and lodge itfelf in the bucket A of the wheel. Each of the buckets of the wheel BILM, which are below the gutter, is fupplied with a metallic ball, and fo likewife are the afcending buckets abilm of the chain-pump. As the pump fupplies the wheel, it is itfelf again fupplied at M, where the balls fall into ‘its afcending buckets. Now it is prefumed that the balls in the wheel, I fup- pofe on account of their diflance from the centre of motion, will defeend with more than fuflicient force to raife thofe on the chain, and confequently that the motion will be perpetual. . The deception in this contrivance has much lefs feduétion than in the two foregoing, be- caufe itis more eafily referred to the fimple lever. This, like the others, exhibits no profpect of fuccefs, when tried by the fimple confideration of the equality of the afcent and defcent in the whole time of the rotation of a fingle ball. It may alfo be fhewn from the prin- ciples of wheel work, which are familiar to artifans, that whatever is gained by the excefs of the diameter of the great wheel beyond that of the wheel C, is again loft by the excefs of the lanthorn A beyond the pinion E. The fundamental propofition of the fimple lever or balance, that equal bodies at an ear diftance from the fulcrum will equiponderate, but that at unequal diflances the moft remote will defcend, has in thefe and numberlefs other inftances led mechanical workmen and fpeculators to purfue this fruitlefs enquiry with labour and expence often ill-afforded, and with a degree of anxiety and infatuation which can hardly be conceived by thofe who have never fuffered the pain of hope long deferred. Tor this reafon chiefly, it has appeared defirable and ufeful to treat the fubje& in a familiar way, without defcending to thofe ex- preflions of contempt, which ignorance, harmlefs to all but itfelf, is furely not entitled to. If fuch reafoners were well-convinced that the power of a machine is to be eftimated by the excefs of motion referred to the perpendicular, without any regard to the apparent centre Schemes for Perpetual Motion. 379 centre of the machine, and that in machines very little compounded it is poffible to pro- duce effects direétly contrary to the rule which is true of the fimple lever, they would probably renounce many flattering projeéts, grounded only on the fuppofition of its univer- fality. Defaguliers contrived an apparatus in which two equal weights may be placed at any diftance whatever from the centre of motion, and ftill continue in equilibrio. Fig. 3 reprefents this inftrument, AD denotes a balance with equal arms, and EF another of the fame dimenfions. Thefe move on the centres B and C, and are connected by the inflexi- ble rods AE and DF; the motion being left free by means of joints at the corners. Acrofs the rods AD, EF, are fixed two bars IK, LM. Now it is unneceflary to fhew that the weight G will defcribe exactly the fame line or circular arc, when the levers are moved into the pofition a d fe, or any other pofition, asit would have deferibed in cafe it had been fuf- pended at A, or K, or E; and thatit is of no confequence in this re{pect at what part of the line AE, or IK, it be fixed. The fame obfervations are true of the weight H on the other fide. And accordingly it is found, that thefe equal weights may be fufpended- any where on the lines IX and LM without altering their equilibrium. By this contrivance it is moft evidently proved, to thofe who are totally unacquainted with the theory, that weights do not preponderate in compound engines, on account of their diftance from the centre. Several other contrivances may be made to the fame effet. ‘The following combination of wheel-work prefented itfelf to me as one which would moft probably be miftaken for a perpetual motion. Fig. 2. Plate XV. The five circles reprefent the fame number of wheels, of equal diameter and number of teeth, acting together. The middle wheel A is fixed between two upright pillars, fo that it cannot revolve. The other four wheels are pinned in a frame HI, in which they can revolve, and through which the axis of A likewife pafles. From the extremity of the axis of D, and alfo of d, proceed the ho- rizontal levers HK and IL, which are equal, and point in the fame diretion parallel to the plane of the wheels. At the extremity of thefe arms hang the equal weights P and p. Let it now be imagined that the end I of the frame is depreffled; the wheel B will tura round by the re-aétion of the fixed wheel A in the fame dire€tion as HI, and it will make one revolution, in the fame time, relative to the frame, or two with regard to abfolute fpace by reafon of its being carried round. The aétion of B upon D will produce a rotation re- lative to the frame in the oppofite direGtion during the fame time. Inftead therefore of two revolutions, like the wheel B, this wheel D, with regard to abfolute fpace, will not re- volve atall, and in every pofition of the apparatus the arm IL will continue horizontal, and point the fame way. For fimilar reafons the arm HK will retain its pofition. Con- fequently, it is feen that the defcending weight will move at a great horizontal dillance from the centre N, while the afcending weight rifes very near that centre. But there will not on this account be a perpetual motion : for the actions of the levers HK and IL upon the frame HI, by means of the toothed wheels, will in the detail be found precifely alike, and in the general confideration of the motions of P and p, the oppofite motions in the circle EF G will be accurately the fame. It has always been confidered as effential to a perpetual motion, that it fhould be derived from fome energy which is not fuppofed to vary in its intenfity. Such are the inertia, the gravity or magnetifm of bodies. For an occafional or periodical variation of intenfity in any force is evidently produétive of motion, which requires only to be accumulated or 37°C 2 applied, 380 Perpetual Motions.— Alloy of Silver and Platina. applied, and the apparatus for applying it cannot be confidered as a machine for perpetual motion. Neither in firi€tnefs can any machine, whofe motion is derived from the motion or rotation of the earth, and the confequent change of feafons and rotation of events, be fo confidered, becaufe it does not generate, but only communicates. The perpetual flow of rivers, the viciflitudes‘of the tides, the conftant, periodical and variable winds, the expanfions and contra€tions of air, mercury, or other fluids, by daily or other changes of temperature, the differences of expanfion in metals by the fame change, the rife and fall of the mercury in the barometer, the hygrometric changes in the remains of organized beings, and every other mutation which continually happens around us, may be applied to give motion to mills, clocks, and other engines, which’ may be contrived to endure as Jong as the apparatus retains its figure. X. Ujeful Notices refpecting various Objeets.—Silver alloyed with Crude Platina.—Tempering of Steel—Rifled Shot. 1. Silver alloyed with Crude Platina. < Bercmay, in his Treatife on the Blow-Pipe, in one of the earlier editions, dire&ted that the {poon for blow-pipe experiments fhould be made of filver alloyed with one tenth of platina, of which the purification wasat that time little known. Dr. Lewis, in his Philo- fophical Commerce of Arts, mentions the fufion of filver with crude platina. The metals united but imperfectly, with a remarkable projection of particles of the metal, as if by a kind of ebullition over the infide of the crucible. Several years ago, being defirous of making fuch a fpoon, I felected ten grains of crude platina, in particles poffefling very little magnetifm, and fufed the fame with one hundred grains of pure filver in a blaft fur- nace, ufing a large proportion of nitre, with the intention of fcorifying any of the bafer metals. The effect which Lewis mentions took place; and the compound, when poured out, had a feabrous or unfound appearance. I thought the grains of platina might have been merely furrounded by the adherent filver ; but this did not feem to be the cafe, for it bore laminating between two fteel rollers very well. After this laft procefs, I fubjeted it. to fufion again with a ftronger heat, and again laminated it into a thin plate. This. eperation of fufing and rolling was repeatedly performed, but ftill the metal appeared rough in certain parts of the furface. As a laft effort, I therefore expofed it to the moft violent heat I could urge, and determined to leave it to cool in the crucible beneath the nitre which flowed above it. The crucible in the ignited ftate was taken, from fome motive I cannot now recolleé, to a window, and fet down upon atile. As I ftood atten- tively obferving the appearance of the metallic globule through the tranfparent and tran- quil bath of nitre, the ignition gradually went off, fo as to be fearcely vifible in that clear light. Buc on a fudden it recovered itfelf in an inftant, and the nitre boiled up fo as to filk the vacant fpace of the crucible. ‘The button of metal, when cooled, was f{cabrous; but I 4 neverthelef Hardening and Tempering of Steel. 38x neverthelefs formed it into a fpoon, by rolling, hammering, and afterwards polifhing it. It was then expofed to a low red heat, ina common fire, and became bliftered all over. The above fats poflefs the utility which attends unfuccefsful experiments, namely, that the narration may fave others from a repetition of the labour. But, philofophically fpeaking, there are no new experiments which would be unfucce(sful if we thoroughly underftood them. I think the decay and recovery of ignition in this is a curious inftance of what feems to be a _ general law of the congelation of fluids. It is probable that all fluids, as well as water, are capable of being cooled below their freezing point, and afterwards become hotter by the efcape of latent heat when they congeal. Thus water cooled below 32 degrees is fuddenly raifed to that temperature the inftant ice is formed, becaufe the ice gives out the difference of the heat which was latent in the fluid ftate. And fo it appears to have happened with the fluid metallic compound in thefe experiments. As its temperature was diminifhed, it became lefs luminous or ignited ; but, at the inftant of congelation, that portion of heat which had been employed in maintaining the fluid ftate, was extricated, and became employed in _taifing the temperature. The effect of this increafe was {een in the greater emiflion of light, and the boiling of the nitre. 2. Tempering of Steel. INSTRUMENTS of fteel are required to be hard, in order that they may penetrate and , divide the fubftances intended to be cut; and tenacious, that they may not break during the operation. The hardeft fleel is the moft brittle ; for which reafon, though hardnefs would in every cafe be a defirable quality, yet, for the fake of tenacity, it isin many inftances neceflary to diminifh it. We fee, therefore, that there muft be a precife mean between too foft and too brittle, which: will be beft fuited for the refpective purpofes to be ac- complifhed. A fpring muft be tenacious, and need not be very hard. A knife for cutting leather, and foft fubftances, muft be fomewhat harder than a fpring. Pen-knives and razors muft be ftill harder; and files and tools for working metal mutt be hardett of all, though even in thefe care muft be taken not to deftroy their tenacity by making them too hard. Steel is hardened by ignition, and {ubfequent plunging in water. The chief art of this procefs confifts in covering the fleel with fome mixture, which fhall prevent its being degraded in the fire to the {tate of iron. The file-makers ufe the grounds of beer mixed. with common falt. Others ufe the cementing mixture. No greater heat is to be ufed with any fteel, than by experience is found fufficient to produce hardnefs at leaft equal to that of a file. More heat would render the grain coarfe and open. Urine is thought to be better for quenching the fteel than water, probably becaufe it may be a better conductor of heat, and perhaps on account of its phofphoric ingredient, which is now with juftice fup- pofed * to be an eflential part of fteel. When fteel is not intended to poflefs the utmoft hardnefs, it is afterwards foftened by the application of a lower degree of heat. This. operation is called tempering. ‘The greateft difficulty confilts in applying the proper de= gree of heat uniformly over the whole mafs. ‘Ihe common method is to judge by the colour aflumed by the clean furface of the fleel when thus heated. ‘The heat may be ap— plied by the fire, or a pan of charcoal, or the flame of a candle or lamp, or by laying the * Philofophical Journal. preee- 382 Tempering of Steel by Oil.—Rifled Shot. piece upon fand to be gradually heated, or upon melted lead. The faw-makers, and fome makers of {prings, heat the article, rub it with greafe, and then heat it ftill farther till the fumes take fire; this is called blazing, and affords a temper nearly the fame as when the fteel by heat has acquired a deep blue colour. When the temper is given from the colour, the firft tinge which appears is a faint ftraw colour, which is fuitable to pen-knives and hard cutting-tools, The next colour, whiclris purple, is rather too foft for a knife, and too brittle for a fpring. After this follows the blue, of which there are feveral fhades. The deepeft is very foft, and is fucceeded by a whitifh yellow, which indicates too great a degree of foft- nefs for any cutting-tool. Mr. Hartley, in the year.1789, took out a patent for a method of tempering fleql. His fpecification, which is fo general as perhaps to include no method at all in the way of monopoly, indicates that the heat is to be meafured by a pyrometer or thermometer ap- plied near the article. The actual praétice of this method appears to confift in ufing oil and 2 mercurial thermometer. In this way many dozens of razors or tools may be tempered at once with the utmoft facility: The different degrees of heat for various kinds of fteel, and their feveral ufes, may fpeedily be determined by experiment. For want of a thermometer graduated to the higher degrees, I have not yet made any experiments. ‘The only fact I have at prefent to communicate is, that Mr-Stodart, who ufes this method, ftates that the requifite temper on fteel for a pen-knife is 450 degrees of Fahrenheit’s fcale *. 1 find, on trial, that a good pen-knife is as hard as any tool which can admit of depip brig! Hard gravers, for turners’ ufe, mutt not be foftened at all. 3. Rifled Shot. IN the latter end of the year 1789, I was, by various confiderations, induced to thirik, that the effe€&t which is produced by rifling mufquetry might be produced in artillery by giving a fuitable figure to the fhot. It is almoft needlefs to explain this effeét. When a bullet is driven along the bore of a piece, it muft be a€ted upon by the internal furface fo as to caufe a rotation, the axis of which motion will lie acrofg the line of dire€tion. In con- fequence of this, the re-ation of the air will be flronger on one fide of the bullet than on the other, and it will deviate from the intended courfe according to no certain rule. The method of rifling confifts in cutting one or more fpiral grooves in the hollow furface of the mufquet, into which the ball is either forcibly rammed down, or elfe conveyed to its place by an aperture at the breach, or near the chamber. The lead is thus made to fit the internal ferew, and ufually takes about half a turn during its courfe through the barrel. The axis of this rotation being parallel to the line of direction, it muft follow that the refiftance of the air will be equal on all fides of the bullet, and it will fly with more certainty to the object of aim. It feemed to me, that if a cylindrical thot, with hemifpherical ends, were thrown out of a common barrel, it might be poflible, by means of certain fpirals cut on the end furface, to caufe the blaft of the powder and the refiftance of the air to concur in producing the fame rotation. For this purpofe I took a wooden pattern, and cut the fpherical furface into twelve {pirat planes, by dividing the equator into the like number of equal parts, and drawing {pirals from * Philofophical Tranfaétions 179s, p. 326. the Rifted Shot.—Mathematical Correfpondence. 383 the points of divifion obliquely towards the poles. The wood between every pair of conti- guous fpirals was then taken away, by cutting from the one line parallel to the axis, and from the other perpendicular to a plane pafling through it. By this procefs, when the axis was fet upright, there appeared, as it were, twelve roads floping upwards from the equator towards the pole, bounded on the fide next the wood by upright walls; and the fhot, when fufpended on an axis or centre point, could be blown round very fwiftly by the breath directed towards the pole. Shot of this kind were made and tried at a foundery in North Wales. By an experi- ment with a brafs gun newly bored, it was afcertained that the fhot did really revolve in its courfe along the bore; but the trials with fhot of different weight and dimenfions did not promife more accuracy of effect than was obtained by common fpherical fhot-ufed at the fame time. Particular notice was taken of the manner in which the fhot ftruck the butt: the greateft number of times, it {truck with the anterior end; fometimes the ftroke was made with the broad fide, and, in a few inftances, the end which came laft out of the gun arrived firft at the mark. Hence it appears, that the very flight angular deviation at the mouth of the piece is more than fufficient to counteract any effeét which might elfe have been derived from the fubfequent ation of the air upon a projectile duly figured. Tt feems, neverthelefs, that this principle might be applied to advantage in bar fhot.. If the ends of this projectile were chamfered or floped with refpe& to the axis, it would pafs through the air with a revolution of its extremities, inftead of one end following the path of the other, as may fometimes be fuppofed to happen. With regard to the execrable pra&tice of war, I think it a decided queftion, that increafe of power is, on the whole, in favour.of rectitude and virtue; and that wars are likely to be fewer, lefs durable, and lefs pernicious, the more {cientifically they are conducted. ; MATHEMATICAL CORRESPONDENCE. Question IX. An/wered by F. F—:—:—:—R. In order to a folution of this problem, we have only to find the point in the plane of the horizon, which is perpendicularly under the elevated objeét ; the diflances of which point from the three ftations are as the cotangents of the angles of elevation taken at each re- fpectively. This will be effected by the following CONSTRUCTION. LET A, B, and C be the three ftations (Plate XV. Fig. 1.) and a, b, and c the cotan- gents of the refpective angles of elevation taken at each. Produce AB and CB towards E and F, and make BF = BA, and BE = BC. Take FG to FB asc to 4, and EG to EB as ato, and about the centres F and E with the refpective radii FG and EG defcribe arcs interfecting in G. Draw FG, BG, EG, and in GB produced take BD to AB as BE to BG. I fay the point D is the required point in the horizontal plane, For, 384 } Mathematical Correfpondence. For, draw AD and CD.—Then the triangle GBE being fimilar to ABD, and GBF to CBD, we have AB (= FB)? 5 AB ( =FG)::4:¢:: BD: CD and BC ( = BE) : $ BC (=EG)::5:a:: BD: AD. Therefore AD, BD and CD being as a,b, and c ref{pec- tively, the point D is rightly found. Q.E. D. Hence alfo, if with AD (: AB::EG: BG) and CD (: CB :: FG : BG) as radii, arcs be defcribed about A and C, they will interfe&t each other, and each of them will in- terfe& GB produced in the required point. CALCULATION. FROM the values of FB, BE, FE, FG, and EG, find BG trigonometrically, and from thence AD, BD, or CD. THIS queftion was anfwered in nearly the fame manner by ANALYTICUS, who obferves, that if the three ftations are at unequal diftances from the objeét, its apparent altitude will vary at each of them, according to the effeét of refraétion, and of courfe occafion a three- fold error in the refult; which may be avoided by taking the ftations fo that the angles of elevation fhall be all equal, in which cafe a fingle refraction only will be concerned, which indeed is fufficient to render this, or any other fimilar method of determining the heights of terreftrial objeéts, very inaccurate. If, befides the angles of elevation, thofe formed by the bafe and hypothenufes drawn from each extremity of it, to the top of the objeé, be taken, there is no occafion for more than two ftations ; which being chofen in fets, in the way laft mentioned, will enable us to afcertain the difference of refraction at different diftances. OOWIDOIOSIOCLIVIVWVOVWIO I VOSS Phileas. Jourval Vee LPI NV Hv ing furge B87) Compound Batlanee Fig 3. > Zy Bishop Wilkins N 2g. 3. Spiral Lrtbpument utvaternt to Gurntershule L FO Leet long. Thitel Journal Voll Plate AVL. tactieg 72.387. Seale eguivatent to Gunters Rule of 29 2 Liches long. dL 12 | EERO OES | PN | Ae ‘ al ‘, . . ‘ . : 2 ; 3 - ict 2a ; ee ae ‘ ’ ‘ 4 ah » yo J. ie ie. a i ‘ j 3? < ie, nny Caio exe c ‘ ait of, Pee. A [x eae as mete 2 goat a! ale re ea agi ea nee! - ae ae nae Reine: Kaa) pag mt ate J OUR N AE OF NATURAL PHILOSOPHY, CHEMISTRY, 4ND Be oe GSO ose : DECEMBER 1797. ARTICLE TI. Concerning the Spontaneous Adon of Concenivated Sulphuric Acid on Vegetable and Animal Sub- Stances ; its Action upon Alcohol, and the Formation of Ether. By Citizens Fourcror and VAUQUELIN: I. has been long known that the concentrated fulphuric acid deftroys the texture of or- ganic matters, by converting them into coal, in confequence of an a€tion which refembles that of an elevated temperature ; but this action has not yet been properly explained, fo as to determine in what it may confift, or the produéts it affords. The ancient theory of che- -miftry attributed this effeét, in a loofe manner, to the affinity of phlogifton for the fulphuric acid, and was content to compare it to combuftion. The authors of the pneumatic theory difcerned fome of the data of this phenomenon, and arrived fomewhat nearer the truth ; but they did not comprehend the whole. They have even committed fome miftakes, doubt- lefs becaufe they did not ftudy all the details of this remarkable ation, nor obferve with fufficient care every thing that paflés in the fubje&ts of the experiments. My affociate Vauquelin has long been employed, in conjunétion with myfelf, upon various methods of analyfing vegetables; and having fubmitted a great number to the energy of the principal te-agents among which the acids occupy the firft rank, along ftudy of the aétion and curious effects of the concentrated fulphuric acid has led us to difeover what had hitherto efcaped the obfervation of chemifts refpe€ting its manner of aétion upon organic fubftances. Though the refult of our enquiries in this refpect belongs direttly to the vegetable analyfis, which we fhall offer to the fcientific world as foon as our Jabour fhall have acquired all the maturity we are defirous it fhall poflefs, we have neverthelefs thought proper to detach this (mall part, becaufe it appears worthy to intereft the cultivator§ of chemiftry, and at the fame Vor. L—Decesver 1797. 3D time 386 Effeét of Sulphuric Acid on Vegetable Matter. time proper in fome refpeéts to explain and ameliorate their daily proceffes, particularly thofe which relate to feyveral pharmaceutical operations. When a dry vegetable fubftance, fuch as wood, ftraw, or gum, is plunged i in the concen- trated fulphuric acid, this matter becomes coloured and foft, appears to diffolve in the acid, and forms with ita magma or kind of brown or black imperfe€tly fluid matter, well known to every chemift as the product of their experiments. If, after the mutual aétion of thefe bodies is exhaufted, the mixture be diluted with a fufficient quantity of water, two pheno- mena equally interefting are obferved, The one is the precipitation of a black powder, pofleffing all the charaéters of carbone nearly pure; the other is the flight degree of heat which the mixture produces with the water. It is far beneath the temperature which an equal quantity of the fulphuric acid, originally employed, would have exhibited with a like quantity of water. The vegetable matter is certainly much altered, and has undergone a great decompofition in this experiment; fince the carbone which entered into its compofition is feparated, nearly pure, from the other principles with which it was combined. It is.well proved at prefent, that vegetable fubftances are compofed of carbone, hydrogene, and oxygene united in various proportions, and remaining in a con{tant equilibrium of compofition, fo long as new attractions do not come to deftroy it. In the prefent cafe theequilibrium is manifeftly broken, becaufe the carbone is feparated from the two other principles. It was at firft imagined, and in this manner it is that Citizen Berthollet has particularly determined the caufe of this phenomenon in feveral of his works; namely, that the hydrogene of the vegetable fubftance united with the oxygene of the fulphuric acid, and, by thus forming water and fulphureous acid, the carbonic principle was feparated and thrown down. We have ourfelves adopted and admitted the fame explanation, until repeated experiments fhewed us that this opinion is erroneous. In fat, in the cafe here mentioned, and obferved for a great number of times with the utmoft attention and care, we have not perceived that an atom of fulphureous acid was produced, but that the fulphuric acid remains entire without any alteration or change in the proportion of its conttituent parts. Since, therefore, this acid is not decompofed in the cold by vegetable matters, it is neceflary te conclude, that the changes produced in thofe bodies are the confequence of a re-action between their proper principles; _a re-aétion of which the fulphuric acid is only the occafional or fubfidiary caufe. But in order to determine by what energy this acid produces fuch an alteration in ve- getable matters, it is requifite to examine with accuracy what the alteration may confift in; and this examination, to which we have a great number of times directed our attention, has fhewn the error adopted with regard to the pretended decompofition of the acid, and the true caufe of the changes thus produced in organic bodies. When the carbonic pre- cipitate of the experiment above;defcribed is feparated, it is found that the fulphuric acid which floats above it, is fingularly weakened, and contains the acid of vinegar, which may be feparated by diftillation. Here therefore we fee the vegetable matter converted into acetous acid and carbone. If the quantity of this lafl, together with that of the vinegar, be compared with the quantity of vegetable matter employed, a confiderable lofs is perceived in the mafs of thefe produéts, compared with that of the fubftance which afforded them. Nothing can have been loft in the experiment, becaufe no elaftic fluid is difengaged; and as the fulphuric acid has lof much of its denfity, and becomes much lefs heated with watery Efe? of Sulphuric Acid on Vegetable Matter. 3387 water, fince itris, in a word, extremely diluted, it is evident that the water it has acquired could not have been. formed but at the expence of the principles of the vegetable, and that it contains the weight which is wanting to the carbone and acetous acid to reprefent the whole of the vegetable matter fubmitted to experiment. For it. is very certain that an action perfectly the fame, and a refult accurately identical, takes place in clofed veffels, as well as in fuch as are open; and that the water which faturates the fulphuric acid does not come from the atmofphere. Weare therefore forced to conclude, from this examination, that the ve- getable fubftance treated with the concentrated cold fulphuric acid, has fuffered a decom- pofition or analyfis by feparating a portion of its carbone nearly pure, and that another part of carbone has united with hydrogene and oxygene to form the acetous acid, at the fame time that a fecond portion of oxygene has united with a fufficient quantity of hydrogene to form. the water which dilutes the acid. All thefe changes in the vegetable fub{tance are therefore made at the expence of its own proper principles. Nothing has come to pafs but a change of equilibrium between them, a feparation and unequal combination of their component parts, which produce the three new produéts obtained. In what manner does the concentrated fulphuric acid determine this change of equili- brium ? How can it convert an homogeneous organic matter into acetous acid and coal? What is the force or forces whofe energy or concurrence deftroys the connection which united the principles of the vegetable fubftance, while it has no influence on the fulphuric acid? A fingle argument well applied, from the refult of experiments, will lead us to the {olution of this problem, Since a vegetable fubftance requires a new equilibrium of prin- ciples after the total aCtion of the concentrated and cold fulphuric acid, and remains in the triple ftate of carbone, acetous ‘acid, and water, at which period the fulphuric acid has become much lefs denfe and concentrated than before;—we muft conclude, that the affinity of this acid for water, as well as that of the oxygene for hydrogene and carbone, at the fe- veral proportions required to form vinegar, prevail over the attractions which held thefe three principles united in other proportions under the original form of homogeneous vegetable. matter. But, in this new fum of ele€tive attra€tions, the only caufe which determines the change that takes place is the affinity of the fulphuric acid for water, of which the prin- ciples do not unite nor the compofition take place, till the moment at which this affinity acts. When once this tendency of the acid for water is fatisfied, the equation between the feveral principles is effeed, an equilibrium is eftablifhed, and no further alteration follows. It feems, however, at firft fight, that the imagination refufes to admit, in the fulphuric acid, an affinity for a body which does not exift completely formed, or to conceive the formation of the water as refulting from the attraction which the acid exerts upon it, though it do not yet exift in the vegetable matter, but in its principles. But whatever repugnance a _refult of this kind feems at firft to produce, it does not appear lefs certain, fince it is evi- dent, as matter of fact in this experiment, that the acid originally concentrated becomes feeble and aqueous; that the water did not exift ready formed in the vegetable matters that it was not taken from the atmofpheric air; and that, when once the acid has become diluted, every fubfequent action ceafes. hefe four points are equally eftablifhed, and there can be no doubt of their certainty. Befides which, a great number of faéts are at prefent well known to chemifts, which compel them to admit fuch affinities as are pro. 2103 ductive 358 Explanation of the Efe of ductive of fubfequent events, and have been denoted for fome years by the name of difpofing. affinities. Thus it is that the attraétion of acids for the metallic oxides favours the decom- pofition of water by means of the metals, which do notin fatt become oxided to unite to acids, but at the expence of the oxygene which they take from the hydrogene. Thus likewife it is, that the affinity of the cauftic earths and alkalis for the fulphuric acid determines the combuttion of the fulphur of fulphurets by means of water, and the feizure of oxygene from the latter, which would not take place without the exiftence of this difpofing affinity. When the long confideration of chemical phenomena, the habit of beholding them, and of appres. ciating their refults, has deftroyed this firft repugnance in the mind of the chemift, he foon conceives that it is not more difficult to admit and explain this difpofing affinity, than it is in natural philofophy to adopt, and admit as proved, the attraction at great diftances which takes place between the planetary bodies. We may exprefs the refults of the chemical effeét as it has here been at length explained by a fimple formula, which in reality is nothing more than an argument difpofed in a clofe arrangement, like all the algebraic formulz ; and this method, by prefenting chemical phe-. nomena in a concife language, will poflefs the advantage, when more generally employed, of reprefenting, with clearnefs and precifion, every thing that happens in the moft complicated operations. Thus we may fay, Aqueous fulphuric acid + liquid acetous acid + precipitated carbone = concentrated fulphuric acid + entire vegetable matter. In this manner it was that Lavoifier exhibited the whole myftery of the vinous fermentation in this fimple form of an equation :—Juice of grapes = carbonic acid + alcohol; becaufe, in faét, the refult of this interefting obfervation, formerly fo obfcure, but at prefent fo perfpicuous, is the converfion of mutt, or liquid fac- charine matter, into alcohol and carbonic acid. If the effects be truly fuch as we have here explained, it muft be neceffary for their ex- iftence that the fulphuric acid fhould be concentrated, and the vegetable matters in the dry ftate: for, if they contained water ready formed, this, by its immediate application to the fulphuric acid, would faturate it, and prevent its re-a€tion upon the principles of thefe fub- ftances. The fame thing would happen if the acid employed was already weakened by the previous addition of water. This, in fact, takes place in both cafes, as the experience of every chemift muft fhew. It muft, however, be obferved in this place, that in order that the ation between vegetable matter and fulphuric acid combined with water fhould be nothing, the water ought to be enough to faturate the acid: for, if its tendency to combination with water be not entirely fatisfied, its decompofing aétion on vegetable fubftances muft be in proportion to its want of faturation. In faét,.the decompofition here mentioned, namely the formation of water and vegetable acid with the precipitation of carbone, cannot be ob- tained but by increafing the quantity of acid. This alfo is confirmed by experience, which fhews that the quantities of fulphuric acid neceffary to produce the required decompofi- tion, do not follow the fimple ratio of the quantities of water they contain, but are at leaft in proportion to the fquares of thofé quantities. So that if we fuppofe, for example, that the moft concentrated fulphuric acid contains a quantity of water equal to two, and that another acid contain a quantity equal to four, there will be required not only the double of this laft to produce the fame effect upon a vegetable fubftance, but it will be found neceflary to ufe at leaft fixteen times as much. And this agrees very well with reafoning, fince it is known 5 thas Sulphuric Acid on Vegetable Matters. 389 that the affinity of the fulphuric acid for water diminifhes in proportion to the fquare of the quantity of water it contains. Though we have reduced the general action of the concentrated fulphuric acid upon ve- getable matters to the formation of water, of acetous acid, and the feparation of carbone, we mutt here remark, that in fome cafes the action becomes more complicated; that fome- times, alfo, vegetable acids are formed; that the formation of a {mall quantity of alcohol, even in fubftances not faccharine, fuch as gum, unfized paper, &e. likewife occafionally accompanies the foregoing phenomena; and, laftly, that there is in many circumftances: a difengagement of carbonated hydrogene gas more or lefs abundant. But thefe multiplied products do not take place fo frequently as the compofition of water, of vinegar, and the precipitation of carbone, the conftancy of which is invariable during the a€tion of concen- trated fulphuric acid upon vegetable matters. They are in fome meafure phenomena ne- ceffary to the former. They depend upon the different proportion of the principles which compofe vegetable fubftances. ‘They take place more efpecially in thofe which contain a greater quantity of hydrogene. ‘The defcription of thefe, and the confiderations to which they may lead chemilts, belong to the general and complete hiftory of vegetable analyfis which we propofe to publifh- when our work fhall be finifhed. Liaftly, thefe produ@tions of alcohol, of various acids at the fame time, and of carbonated hydrogenous gas, indicate a more profound alteration in the vegetable matters treated by the fulphuric acid; a compli- cation of effects, which, though it originates in the change of equilibrium occafioned by the powerful attraction of this acid for water, cannot be well developed until after the explana tion of the new procefles of analyfis, the methods and refults of which we fhall hereafter prefent to the chemical world. Befides this multiplication of effe€ts and complicated combinations which are fome- times obferved in vegetable matters treated with the concentrated fulphuric acid, an- other alteration fometimes takes place in this laft. When the fubftances placed in contact with it contain too {mall a proportion of oxygene to form the water required for its faturation, their hydrogene then unites with a portion of the oxygene of the acid itfelf, and the fulphureous acid is formed. This effet is more particularly remarked in oily fub{tances, It takes place only till the quantity of water neceflary for the faturation of the acid is af- forded, and ceafes as foon as this faturation is effeéted. This action of the concentrated fulphuric acid is {till more complicated on animal than on vegetable matters, becaufe the animal matters themfelves are more compounded. ‘Though the affinity of the acid for water be the caufe, the formation of this liquid is not only ac- companied with that of a vegetable acid and the precipitation of carbone, but ammoniac is likewife formed. No efcape of any volatile principle is perceived. The azote, which forms part of thefe fubftances, unites with a portion of hydrogene, and conftitutes the volatile alkali, which combines with the fulphuric acid, or with the acid which is at the fame time com- pofed, while another part of the hydrogene forms with the oxygene of the fame fubftances that water which is requifite to faturate the fulphuric acid. But in thefe cafes, as in the experiments with vegetable fub{tances, the quantity of carbone, which exceeds that required to compofe the new acid, together with a portion of hydrogene and oxygene, will be fet at Ii- berty, and falls down in the form of magma, of flocks, or of black powder. In this manner it xs that in the cafe of burns, frequently fo dangerous, which are produced by the concentrated fulphurie 390 - Formation of Ether. fulphuric acid, there is formed, at the expence of the fin, water, vegetable acid, and am- _moniac, while carbone is precipitated, and a complete deftruétion of the’burned parts is the refult of thefe fimultaneous effeQs, as appears by the brown or black fear which afterwards falls off, and is feparated as a foreign body. Hence may be deduced how great the diforganiz- ing power of this concentrated acid muft be on the coats of the ftomach or the ocfophagus, and the utility of prefenting to it, at the moment it is {wallowed, a mucous liquid fub- ftance, on which its action may be direétly and {peedily exercifed. From the whole of what is here fated concerning the reciprocal a‘tion of concentrated fulphuric acid, and the ternary or quaternary. compounds which belong to the vegetable and animal kingdoms, we may perceive that its tendency to deftroy thefe complicated compo- fitions, and convert them into others more fimple, muft open a new path in the vegetable analyfis. We may perceive that, fince its effects are confined to thofe here defcribed, while the fubftances and the fulphuric acid are permitted to aét {pontaneoufly and without foreign afliftance, the energy of the acid will proceed much further in this decompofition when it is increafed by the addition of new quantities of this fluid, or the application of accumulated heat. But the new refults thus produced would carry us from the fubject here treated, and to which we at prefent mean to confine ourfelves. In this accurate defcription of the fpontaneous aftion of fulphuric acid upon vegetable and animal matters, our intention was to fhew more particularly that this knowledge may have a direct influence upon pharmaceutic operations. Our affociate Vauquelin has fhewn in another memoir, which forms the continuation and ufeful refult of the prefent, that the principles here explained are alone capable of developing the theory of the formation of ether, hitherto fo vague and uncertain; and at the fame time to perfeé the operations proper to afford thefe important produéts. This firft work, which we offer jointly to the ichool of pharmacy, will be a confirmation of the truth configned in’ the difcourfe on the jndiffoluble union of chemiftry and pharmacy, namely, that the former cannot make the flighteft advance, without the latter receiving immediately a proportional degree of perfection. Concerning the Aion of the Sulphuric Acid upon Alcohol, and the Formation of Ether. THE preparation of ether is a complicated pharmaceutic operation, the refults of which are no lefs known than the theory is obfcure. This is proved by the different explanations given by the chemifts who have treated of this operation before the eftablifhment of the pneumatic doétrine. The greater number of modern philofophers are in general of opinion, that the whole me- chanifm of the formation of ether confifts in the decompofition of the fulphuric acid, and the tranfition of part of its oxygene to the elements of the alcohol. According to this hypothefis, water, carbonic acid, and fulphureous acid are formed. ‘This opinion contains the fame error as was pointed out in the foregoing memoir. In order to explain the opera- tion with perfpicuity and effect, we fhall defcribe its circumttances from the beginning to the end. And while we thus treat ona fubje& familiar to every chemift, we hope to prove that this operation, fo common, and fo often repeated, does neverthelefs offer, in the feries of its phenomena, certain faéts which have not yet been properly defcribed, and of which the accurate knowledge alone can afford a folid theory of etherification. : . Experiment Experiments on Ether. 391 Experiment I. Equal parts of concentrated fulphuric acid and -reétified aleohol being mixed together, difengage a quantity of caloric capable of elevating the temperature of the mafs to 70 degrees {190 Fahrenheit). Bubbles of elaftic fluid are formed, the liquor be- comes turbid, affumes an opal colour, and at the end of feveral days becomes of a deep red colour. Experiment I. A combination of two parts of fulphuric acid and one part of alcohol elevates the temperature to 75 degrees (20: Fahrenheit), becomes immediately of a deep red colour, which changes to black a few days afterwards, and emits a {mell perceptibly ethereal. Experiment IL. When we carefully obferve what happens in the combination of equal parts of alcohol and concentrated fulphuric acid expofed to the action of caloric in a proper apparatus, the following phenomena are feen: 1. When the temperature is elevated to 78 degrees (208 Fahrenheit), the fluid boils, and emits a vapour which becomes condenfed by cold into a colourlefs, light and odorant liquor, which, from its properties, has received the name of ether. If the operation be properly conducted, no permanent gas is difengaged until about. half the alcohol has paffed over in the form of ether. Until this period there paffes abfolutely nothing but ether and a fmall portion of water, without mixture of fulphureous or of carbonic acid. 2. If the receiver be changed as foon as the fulphureous acid manifetts itfelf, it is ob- ferved that no more ether is formed, but, the fweet oil of wine, water, and acetous acid, without the difengagement hitherto of aifingle bubble of carbonic acid gas. When the fulphuric acid conftitutes about four-fifths|of the mafs which remains in the retort, an in- flammable gas is difengaged which has the fmell of ether, and burns with a white oily flame. This is what the Dutch chemifts have called carbonated hydrogene gas, or olefiant gas, becaufe, when mixed with the oxygenated muriatic acid, it forms oil *. At this period the temperature of the fluid’ contained in the retort is elevated to 88 or go degrees (230 or 234 of Fahrenheit). 3. When the {weet oil of wine ekes to oihovd if the receiver be again changed, it is found that nothing more pafles but fulphureous acid, water, carbonic acid gas; and that the refidue in the retort is a black mafs, confifling for the moft part of fulphuric acid thickened by carbone. The feries of pheneinienes here repel will juftify the following general induétions : 1. A {mall quantity of ether is formed f{pontaneoufly, and without the affiftance of heat, by the combination of two parts of concentrated fulphuric acid and one part of alcohol. 2. As foon as ether is formed, there is a prodnétion of water at the fame time; and while the firft of thefe compofitions takes place, the fulphuric acid Bpdenaors no change in its intimate nature. 3+ As foon as the fulphureous acid appears, no more ether is formed, or at leaft very little; but then there paffes the {weet oil of wine, together with water and acetous acid. 4. The fweet oil of wine having ceafed to come over, nothing further is obtained but the fulphureous and carbonic acids, and at laft fulphur, if the diftillation be carried to drynefs. The operation of ether is therefore naturally divided into three periods; the firft, in which a fmall quantity of ether and water are formed without the afliftance of heat; the * Philofophical Jourpal, I. 44. fecond, 392 Theory of the Formation of Ether, &s'c. fecond, in which the whole of the ether which can be obtained is difengaged without the accompaniment of fulphpreous acid ; and the third, in which the {weet oil of wine, the tcetous acid, the fulphureous acid, and the carbonic acid are afforded. The three ftages have no circumftance common to all, but the continual formation of water, which takes place during the whole of the operation. ‘The principles eftablifhed in the preceding me- moir, and the comparifon of the phenomena here defcribed, would in ftrictnefs be fuflicient to explain how the fulphuric acid aéts upon alcohol in the formation of ether; but as this operation includes feveral particular cireumftances which are not comprifed in the ex- pofition of the general principles fketched out in the firft memoir, we fhall in this place enter into fome details neceflary for the folution of the propofed prablem. The ether which is formed without the affiftance of caloric, and the carbone which is fe- parated without decompofition of the fulphuric acid, prove that this acid aéts on alcohol in a manner totally different from what has hitherto been fuppofed. It cannot, in fact, be affirm- ed, that the acid is altered by the carbone, becaufe daily experience fhews that no fenfible attraction takes place between thefe two bodies in the cold; neither can it be affected by the hydrogene, for in that cafe fulphureous acid would have been formed, and it is known that no trace is exhibited during this firft period. We muft therefore have recourfe to another fpecies of adtion, namely, the powerful attraction exercifed by the fulphuric acid upon water. Itis this which determines the union of the principles which exift in the alcohol, and with which the concentrated acid is in contaét: but this a€tion is very limited if the acid be fmall in quantity; for an equation of affinity is foon eftablithed, the effect of which is to maintain the mixture in a ftate of repofe. Since it is proved that ether is formed in the cold by the mixture of any quantities of alcohol and fulphuric acid, it is evident that a mafs of alcohol might be completely changed into ether and vegetable acid by ufing a fufficient abundance of fulphuric acid. It is equally evident that the fulphuric acid would not by this means undergo any other change than that of being diluted with a certain quantity of water. This obfervation proves, at the fame time, that alcohol contains oxygene, becaufe water cannot exift without this principle, which mutt be afforded by the alcohol only, fince the fulphuric acid fuffers no decompo- fition. It likewife fhews that the fulphuric acid here, inftead of favouring the decompo- fition of water as in many other cafes, does, on the contrary, determine its formation; fo that its aétion on the oxides of carbone and hydrogene, which conftitute vegetable matters in general, is abfolutely the reverfe of that which it exercifes upon the fimple combuttible bodies, fulphur and metals, for example, of which it effeéts the oxidation by the decom- pofition of water. ; We mutt not however imagine, from thefe faéts, that ether is alcohol minus oxygene and hydrogene. Its properties alone would contradict this, for a quantity of carbone propor- tionally greater than that of the hydrogene is at the fame time feparated. It may in fact be conceived, that the oxygene, which in this cafe combines, with the hydrogene to form water, not only faturated that hydrogene in the alcohol, but likewife the carbone. So that, inflead of confidering ether as alcohol minus hydrogene and oxygene, we muft, by keeping an account of the precipitated carbone and the {mall quantity of hydrogene con- tained in the water which.is formed, regard it as alcohol plus hydrogene and oxygene. We mutt obferve, that the comparative analyfis of alcohol and of ether, of which the details would Theory of the Formation of Ether, oc. 393 would be out of place in this memoir, correfpond perfectly with the refult afforded by the! theory. The foregoing are the effeéts produced by a combination of alcohol and fulphuric acid, {pontaneoufly produced without foreign heat. Let us in the next place obferve how this combination is effected when caloric is added. The phenomena are then very different, though fome of the refults are the fame. Tn the firft place we muft obferve, that a combination of fulphuric acid and alcohol in equal parts does not boil at lefs than 78 degrees of temperature, while that of alcohol alone boils at 64. Now fince ebullition does not take place till the higher temperature, it is clear that the alcohol is retained by the affinity of the fulphuric acid, which fixes it more confi- derably. Let us alfo confider that organic bodies, or their immediate products, expofed to alively brifk heat, without the poflibility of efcaping {peedily enough from its ation, fuffer a partial or total decompolition, according to the degree of temperature. Alcohol under- goes this laft alteration when paffed through an ignited tube of porcelain. By this fudden decompofition it is converted into water, carbonic acid, and carbone. ‘The reafon, there- fore, why alcohol is not decompofed when it is fubmitted alone to heat in the ordinary ap- - paratus for diftillation, is, that the temperature at which it rifes in vapours is not capable of effe€ting the feparation of its principles; but when it is fixed by the fulphuric acid or any other body, the elevated temperature it undergoes without the poflibility of difengage- ment from its combination is fufficient to effeé&t a commencement of decompofition, in which ether and water are formed, and carbone is depofited. Nothing more therefore happens to the alcohol in thefe circumftances than what takes place in the diftillation of every other vegetable matter in which water, oil, acid, and coal are afforded. ” Hence it may be conceived that the nature of the produéts of the decompofition of alcoho! muft vary according to the different degrees of heat, and this explains why at a certain period no more ether is formed but the fweet oi] of wine and acetous acid. In fact, when the greateft quantity of the alcohol has been changed into ether, the mixture becomes more denfe, and the heat which it acquires previous to ebullition is more confiderable. The af- finity of the acid for alcohol being increafed, the principles of this acid become feparated ; fo that, on the one hand, its oxygene feizes the hydrogene and forms much water, which is gradually volatilized,; while, on the other, the ether retaining a greater quantity of carbone, with which at that temperature it can rife, affords the fweet oil of wine. This laft ought, therefore, to be confidered as an ether containing an extraordinary portion of carbone, which gives it more denfity, lefs volatility, and a lemon-yellow colour. During the formation of the fweet oil of wine, the quantity of carbone which. is preci- pitated is no longer in the fame proportion as during the formation of ether. What we have here ftated concerning the manner in which ether is formed by the fimul- taneous aétion of the fulphuric acid and heat, appears fo conformable to truth, that nearly the fame effects may be produced bya caultic fixed alkali. In this cafe alfo a kind of ether and a fweet oil of wine are volatilized, and coal is precipitated. It is therefore only by fixing the alcohol that the fulphuric acid permits the caloric to Operate a fort of decom- ° pofition. It may alfo be urged as‘a proof of this affertion, that the fulphuric acid, which has ferved to make ether as fat as the period at which the fweet oil of wine begins to appear, is capable of faturating the fame quantity of alkali as before its mixture with the alcohol. Vor I.—Decemper 1797. 3z With ‘ 394 Theory of Ether.—Mulsiplier of Electricity. With regard to the formation of the oil of wine by the augmentation of temperature frony the concentration of the fulphuric acid, it is fo true, that if water and alcohol be added in the fame proportion as the volatile product comes over, oil of wine will never be formed, and all the alcohol will be converted into ether. : It is to the fame caufe, namely the heat ata higher degree of intenfity, that we mutt at- tribute the development of carbonated hydrogene gas, or the olefiant gas, which feems to be nothing elfe but the {weet oil of wine, with a {mall portion lefs of oxygene and more of caloric. ; CONCLUSION. From the faéts and obfervations contained in this memoir, it follows: 1. That the formation of ether is not owing, as has. been thought, to the immediate action of the principles of the fulphuric acid upon thofe of the alcohol, but to a true re- aétion of the elements of the alcohol upon each other, and particularly the oxygene and hydrogene, occafioned merely by the fulphuric acid. 2. That we might in ftri@tnefs change any quantity whatever of alcohol into ether; with- out the affiftance of heat, by fufficiently increafing the proportion of fulphuric acid. 3. That the operation is divided into two principal ffages, in one of which ether and: water are only formed; and inthe other, the fweet oil of wine, water, and the acetous acid, 4: That fo long as ether is formed, the fulphuric acid is not decompofed, and there is no product of fweet oil of wine ; but as foon as this laft appears, little, if any, ether is af- forded, and the fulphuric acid is at the fame time decompofed. 5. That the formation of fweet oil of wine may be prevented, by keeping the temperature of the mixture between 75 and 78 degrees; which may be eafily done, by fuffering a few drops of cold water to fall from time to time into the retort. 6. That alcohol differs from ether by containing more carbone and lefs of hydrogene and oxygene, and that the fweet oil of wine is to ether nearly what alcohol is to the oil*. IL. On the Multiplier of Eleftricity. By the Inventor, Mr. T. CAVALLO; with Obfervations. To Mr. NicHOLSON, Editor of “ The Fournal of Natural Philofophy, &S'ca” SIR, , Havine a few days ago feen for the firft time your Journal of Natural Philofophy, Chemiftry, &c. I found in the third ’article of No. 1. an erroneous account of my Multiplier of Eleétricity, a defcription of which is contained in the third volume of my Treatife on Ele@ricity ; and trufting that your candour will allow a corre&tion of this etror to, come before the Public, I have taken the liberty to fend you the following explanation, witha re- queft that you will be pleafed to infert this letter in your next number. In the firft paragraph of the above-mentioned article, you compare an ele¢trical inftrument of your contrivance (which you defcribe in the fequel) with my multiplier, in the following words :—“ I then (viz. in the year 1787) mentioned my intention to conftruct an inftrument on that principle, which foon afterwards I did. It was fhewn to Sir Jofeph Banks and his * Thefe Memoirs are tranflated from the Annales de Chimie, XXIII. 186. 48a friends, Erronesus Comparifon of the Elefrical Multiplier and Spinning Inflrument. 395 friends, at his houfe, nearly at the fame time, and in the fame year transferred to the cele- brated Mr. Van Marum of Haerlem, who now poffeffes it. From various other avocations I was prevented from caufing any others to be made. It is not therefore wonderful that the fame thought fhould fince have occurred to fo great a mafter of the fubjec& as Mr. Ca- vallo, who, in the third volume of his Electricity, publithed in 1795, gives a defcription and “engravings of an inftrument very different in form, but the fame in principle, &c.” Now the error I allude to confifts in the aflertion that the tavo inflruments are the fame in principle ;. and I flatter myfelf that the following explanation will be fufficient to thew that they are fo far from it as to be totally different in principle and in effect. Your inftrument does nothing more than colleét a confiderable quantity of diffufed elec- tricity into a {mall compafs, which is exactly the fame office as is performed by Mr. Volta’s condenfer, or by my colletor of eleQtricity, which is defcribed in the Philofophical Trant- adtions for the year 1788; whereas my multiplier renders an abfolutely {mall quantity of electricity manifeft, by accumulating a confiderable quantity of the contrary ele€tricity. ‘Or, to be more explicit, your inftrument cannot communicate to the eletrometer a greater quantity of electricity, or rather not nearly fo much of it, as is contained in the electrified body which is to be examined; whereas my multiplier accumulates a quantity of electricity many times greater than that of the body in queftion, and of courfe much more perceptible. Suppofe, for inftance, that a certain body, having its furface equal to that of the eleétro- meter which belongs to your inftrument, contain 100 parts of eleCtricitys and fuppofe, likewife, that the faid eleStrometer requires 200 fuch parts of eleétricity in order to thew any divergency. Now your inftrument- will be found incapable of manifefting the elec- tricity of the given body ; for, when the upper tinfoil fegments have conveyed the greateft portion, or we may even fay all the 100 parts of ele€tricity from the given body to the hook with the eleCtrometer, they cannot, in the fubfequent rotations of the inftrument, colle& any more. The electrometer, therefore, being at moft loaded with 100 parts of electricity, _cannot fhew any divergency ; fince, according to the fuppofition, at leaft 200 parts of eleQtricity are required in order to produce any divergency in it. But if the above-mentioned eleétrified body be applied to the plate A of my multiplier, and the inftrument be worked, the plate C, and of courfe an eleétrometer which is con- nected with it, will foon acquire 300 or 4oo parts, or, in fhort, a much greater quantity of electricity than is fufficient to caufe a divergency in the eletrometer ; becaufe, by working the inftrument, the original quantity of electricity in the plate Ais not diminithed, or removed from it; but the contrary electricity (which is repeatedly and unlimitedly in- duced upon the plate B by the plate A) is accumulated upon the plate C, &c. Sir, I remain your obedient humble Servant, Wells-Street, OF. 305 1797. T. CAVALLO. Senn ee AFTER returning my fincere thanks to Mr. Cavallo for the detection of the error he mentions, into which I certainly fhould not have fallen if I had confulted his Treatife at the time the paper he alludes to was written, I thall take the prefent opportunity of making fome remarks on the inftruments we at prefent poflefs for manifefting the prefence and kind of weak cleétricities. Thefe are: the condenfer, the fimple doubler, the doubler with me. 382 chanifm, 306 Proceffes for accumulating Eleftricity. chanifm, two inftruments by Mr. Cavallo, and the inftrument defcribed at p. 17 of this Journal. After the difcovery of the method of infulation by Stephen Gray, the firft form in which compenfated electricity was obferved appears to have been in the combination called the ele&tric jar; in the explanation of which fo many of the earlier electricians have fhewn their ingenuity. The next inftance confifled in the application of conductors to each other > - by which it was fhewn, that electricity is not equally diffufed over the furface of a conduct- ing body, while any part of the eleétrified mafs which differs in intenfity is feparated from the reft by the interpofition of air or other non-conductors. The cann and chain of Franklin, and the eleétrica! well of Beccaria, exhibited the principle of compenfation in another light; and the fubje&t was rendered {till more difficult when the {trong oppolite eleétricities of tibbands and filk ftockings, placedin contaét, expofed to friction in that fituation, and then feparated, were fhewn in the experiments of Cigna and Symmer. The vindicating ele€tricity of Beccaria appeared to be {till more remote fram the fimple general laws which had been applied to explain the effe& of the jar; and the eleCtrophore of Wilcke prefented difficulties f{earcely lefs confiderable. The firft procefs for accumulating eledtricity, which differs from that of mere frition, appears to have been invented by Profeffor Lichtemberg*, and alfo by Dr. Klincock +, of Prague.° It was performed by means of two refinous plates like thofe of the common ele€trophore, and one metallic plate with an infulating handle. When one of the refinous plates had been flightly rubbed, it was ufed to produce the oppofite eleAricity in the me- tallic plate. This plate was then conveyed to the other refinous plate, and made to de- polit its electricity by applying its edge, or otherwife, to the non-conducting furface. The laft-mentioned furface could then be ufed in the ordinary manner to give an ele€tricity to the metallic plate of the fame kind as that of the original refinous furface, to which it was again applied by the edge. The eledtricity of the firft refinous plate became thus | in- creafed, and, by the firft-mentioned procefs, the metallic plate was returned to the other refi- nous furface in a higher ftate of eleCtrization. By a repetition of thefe manceuyres, the two plates were fpeedily put into as high a ftate of electricity as they were capable of retaining, An accidental circumftance direéted the attention of Profeffor Volta to the advantages which might be derived from the increafed eleétrical capacity of the metallic plate of the ele&trophore, when placed not upon the refinous plate, but on an imperfectly conduéting fubftance}. If the laft-mentioned fubftance were a good conduétor, it would at fome part of its furface be fo far in contaét with the upper plate as to carry off any electricity com- municated to this laft; and if it were a non-conduétor, it might, and in moft cafes probably would, poffefs an eleétric ftate of its own which would influence that of the upper plate. But the imperfect conduétor will not readily produce the firft effet, and is incapable of the latter. It therefore ferves only to aflume the contrary ftate of the upper plate when- eyer eleétricity is communicated to this laft, and renders it fufceptible of abforbing a much greater quantity than it elfe could have done ; the nature and intenfity of which becomes per- * Journal de Rozier, January 1780, p. 20. + Philofophical Tranfaétions, LXVIII. p. 1029. } Journal de Phyfique for May and Auguft 1733, and alfo the Philofophical TranfaGtions, Vol. LXXII. 237 , , 5 ceptible Manipulation of the EleArical Doubler. 397 ceptible when the plate is lifted up. Mr. Cavallo improved this inftrument, by communi- cating the eleGtricity of the metallic plate, when raifed up, to another plate of the fame kind, but much fmaller, and in contact with an imperfectly conducting furface. And the Rev. Mr. Bennett adapted the fame to his eleftrometer *. This is the condenfer of Volta; and the imperfectly condudling plate may be a piece of dry marble, or a common wooden table, or any kind of plate covered with thin filk. : Mr. Bennett was, I believe, the firft who improved the condenfers of Volta, by making ufe of a manipulation fimilar to that of the Profeffors Lichtemberg and Klincock. His inflrument, called the doubler, confifts of three metallic plates, capable of being applied to each other with their flat furface, but prevented from contaQ in this fituation by a thin - eoating of varnith. They have infulating handles at the fide, and may be brought into a€tual contact edgewife. Let the three plates be called A, B and C; and the manipulation for in- creafing the intenfity of one of them, for example A, will be as follows : The plate A being infulated, place B upon it. In this fituation communicate ele@ricity to it, while B is touched with the finger. The confequence will be, that A will receive a much larger quantity of eleétritity than it would elfe haye abforbed if B had not been prefent. Remove the communication from A, and the finger from B, and raife the latter by its infulating handle. A and B will'then exhibit the oppofite eleétric flates more ftrongly © than while together. Place C upon B, and touch C with the finger. It will aflume the oppofite ftate to B, or, in other words, the fame ftate as A. Place B upon A, as before, touching B with the finger; and at the fame time apply C edgewife to A. In this fituation, C, being without compenfation, will give the greateft part of its ele€tricity to A. Remove C; take the finger from B, and feparate B from A- The oppofite eleétricities will be ftronger than before, on account of the increafe afforded by C. Place C upon B again, as in the third ftage of the original procefs, and repeat the fub- fequent manipulations. In each of them the intenfities of A and B will be nearly doubled. Though this procefs is fimple and evident, yet it requires to be learned, and takes a cer- tain time for the performance. It therefore appeared a defirable objeét to form an inftru- ment which fhould by fome very fimple movement complete this fmall feries of operations. In the month of December 1787 Mr. Partington lent me an inftrument contrived by Dr. © Darwin, and confifting of four metallic plates, two of which were moveable by wheel-work into pofitions which required them to be touched with the hand in order to produce the effe&t. It appeared to me that the whole operation, including the touching, might be done by a fimple combination without wheel-work by the direé rotation of a winch. This was foon afterwards effected, and communicated by me to the Royal Society in the year 1788. The inftrument is alfo defcribed in Mr. Bennett’s Nea Experiments on Elericity, publifhed in 1789, and in other books, Mr. Bennett and Mr. Cavallo obferved, foon after the difcovery of the doubler, that it never fails to exhibit an electric {tate by the mere operation, without any communication * Philofophical Tranfaétions, LXXVII. p. 32. of 398 Inftruments for exhibiting weak Elefricities. of electricity having been previoufly made: The former made feveral valuable obferva- tions and experiments to inveftigate the caufes and remove the uncertainty produced by this fpontaneous eleétricity ; and the latter prefented to the Royal Society * an account of a new inftrument called a colle€tor of ele€tricity, in which, as he aflerts, this imperfection does not take place. It confifts of a plate of tin, fupported by two upright ficks of glafs 5 on each fide of which plate are two frames of wood, covered with gilt paper, which do not touch the tin plate, but ftand parallel to it at a fmall diftance. Thefe frames are faftened to the platform of the inftrument by hinges; fo that if eleétricity be communicated to the plate, it will receive a large quantity without any confiderable intenfity, becaufe its capacity is much augmented by the vicinity of the plane of gilt paper on each fide. But if thefe planes be thrown back into the horizontal pofition, which is eafily done by means of their hinges, the eledtricity, which before was compenfated in the plate, will have its intenfity greatly increafed. An ele€trometer connected with this plate will therefore thew figns of ele€tricity by means of a communication made between a large ftock of eleAtricity, and the tin plate in its firft pofition, though the intenfity of that ftock may have been too fmall to have affeéted the ele€rometer without this contrivance. It does not appear, in the author’s defcription of this inflrument, that it removes the equivocal effeé&t of the doubler; for it is evident that it does not, in its fimple pro- cefs, enter the province of the doubler in which this effet takes place. The doubler requires fix or feven turns before it will exhibit fpontaneous eleétricity; at which period the firft charge is- magnified above twelve thoufand times: but his fimple inftrument will {carcely exceed one hundred ‘times, and therefore requires the electricity to be one hundred and twenty times as flrong as that which caufes the uncertainty of the doubler. Whence it may be inferred, that the doubler would have aéted unequivocally with all fuch eleétricities as this inftrument is capable of exhibiting. But the {pinning inftrument, as Mr. Cavallo in the foregoing letter juftly obferves, does nothing more than colleét a confiderable quantity of diifufed eleétricity into a {mall compafs, though it does not appear to be exaétly the fame office as is performed by M. Volta’s con- denfer, or his collector, as defcribed by their refpective inventors. For thofe mftruments, if very fmall, may exhibit very little intenfity in conjunétion with an ele&trometer of con- fiderable furface; whereas the {pinning inftrument, befides its facility in performing the operations, may be confidered as poffefling a furface indefinitely great. Thefe advantages, {uch as they are, conftitute all the difference I perceive between them. Mr. Cavallo’s multiplier, defcribed in the third volume of his Complete Treatife on Elec- tricity, which I had miftakenly compared with the {pinning inftrument, confifts of four me- tallic plates, A, B, C, and D. The plate A is fupported on a ftick of glafs fixed in the platform of the inftrument. The plate B is alfo fupported on a ftick of glafs which is fixed on a radius or arm, by means of which it can be brought very near and parallel to A, and again removed, fo as to touch the third plate C, by means of a wire projecting from B. The plate C is fupported, like A, by a ftick of glafs fixed in the platform. And, laftly, the plate D is fixed by a metallic tem upon a fliding-piece, by means of which it can be brought very near and-parallel to C, and occafionally removed. * Philofophical Tranfactions for 1788. The EleGtrical Inftruments.--Manufadture of Hats. 399 The operation is this:—Let B be brought as near to A as the conftruétion will admit. In this cafe it muft be remarked that the wire proceeding from B will touch another wire that communicates with the earth. Let electricity be then communicated to A. The plate A will receive about one hundred times as much eleCtricity when B is thus applied at about 1-40th of an inch diftance, than it would have otherwife acquired at a like intenfity, and B will poffefs the contrary ftate nearly equal. Let B then be removed fo as to come in contact with C, of which the capacity is no lefs increafed by the vicinity of D. ‘The eleétricity of B will be thared between itfelf and C in proportion to their Capacities ; that is to fay, about 99 parts in C, and 1 in B. At the next repetition B will bring 100 parts, which, together with the gg parts in C, will be fhared in the fame manner ; that is to fay, 197 inC, and 2in B. In this manner, without entering into the confideration of feries where the data cannot pretend to minute accuracy, it is clear that the procefs, indefinitely prolonged, - can never produce a greater charge in C than 100 times the quantity conveyed at each fingle motion by B; that is to fay, 100 X I00 times, or 10,000 times the intenfity of the original eppofite electricity given to A, provided D be drawn back to leave C in a difen- gaged ftate. ‘ It has always appeared to me that the doubtful refults of the doubler mutt arife from the natural or fpontaneous ftate of the plates A and B, at their firft conjunction. If this charge be too ftrong to be deftroyed by the energy of the communicated electricity, the doubler muft in the refult thew the fame eleéricity as it would have {hewn without fuch communi- cation, though fomewhat later. And if the fame circumftance were to obtain in the plates AA and B of Mr. Cavallo’s laft inftrument, or any other contrivance operating by a charge, I do not fee but that the refults muft be equally uncertain. If the ele€tricity of B, inftead of being accumulated in C of the multiplier, had been employed to produce the contrary ftate in D, and thence by communication to A, as in the doubler, it does not appear that any uncertainty could follow, provided only that the firft effe€t of the conjunction of A and B had been governed by the cos#:municated electricity. And if this reafoning be true, it will follow from that and the faéts, that the uncertainty of the doubler exifts alfo in the condenfer, the colle€tor, the {pinning inftrument, and the multiplier, though the firft-men- tioned inftrument alone is delicate enough to fhew it; and that in all electricities which are {trong enough to affect any of the latter, the doubler may be ufed without fear of an equivocal refult. ; SSS ees Ii. 4 Memoir on certain Methods of Economy and Improvement in the Mamuifadture of Hats, a By Citizen CHAUSSIER *. : ive Tue progrefs of the arts has been long retarded by prejudice, and the fervile difpofition which attaches itfelf without enquiry to the ancient practices of bufinefs ; and more particu- larly by the fpirit of individual intereft and fufpicion which have prevailed among artifts, and induced them to conceal their operations under a kind of myfterious veil. By this means * Journal Polytechnique, cahier I. p, 160, the 403. Manufacture of Hats. —Texture of Hair. the knowledge of the arts was in a great meafure confined to thofe who adtually practifed them. Error was propagated under the fhade of fecrecy, at the fame time that ufeful pro- cefles and improvements, which fortunate experiments had difcovered, were alfo confined to the limits of individual works, beyond which they were never extended. At prefent, how- ever, the arts cannot but participate in the falutary reform which has taken place on the foil of equality. Every effort ought to be directed to the fame objeét, and every petty intereft ought to be facrificed to the public welfare. Thofe myfterious refervations, thofe practices fo carefully concealed under the name of fecrets, ought to be difclofed. The means of amelioration and improvement ought not to remain concentrated in any particular work- fhop. As foon as experience fhall have confirmed their efficacy, they ought to become the public property *. ‘Chefe confiderations induce me to point out certain procefles relative to the art of the meee which for fome time paft have been employed with much fuccefs in a large manufaétory in the department of La Cote d’Or. The art of the hatter is well known to confift of a method of forming, with the wool or fur of different animals, a kind of {tuff of a denfe compact texture, capable of afluming and preferving any figure which may be given to it. To obtain this objeé a variety of procefles are employed, partly chemical and partly mechanical, which may be reduced to four prin- cipal operations; namely, felting, fulling, dyeing, and preparation. I fhall not here deferibe the operation of felting, nor the previous preparations which fe- veral kinds of hair demand in order that they may be ufed in manufaétures. This would lead us too far from our prefent obje&t, and would be merely a repetition of what is gene- rally well known; efpecially fince the publication of the interefting memoir + of — Monge, in the fixth volume of the Annales de Chimie. : : Oval * The learned author has been carried a little too far by attending to one fide of the queftion only. No private property can be better grounded than a man’s right to the refults of his own intellect ; and there is none that he can better defend. How far the public may acquire a right of the kind here mentioned, by propofing an » adequate equivalent for individual exertions and expence, is a queftion of great difficulty, whether it be spainad or politically confidered. N. + As this memoic is not generally known in England, it will be ufeful to infert an abftraét in this place, Annales de Chimie, VI. 300. 1. When a fingle hair is infpeéted by the microfcope, under w hatever magnifying power, it appears fmooth and polifhed : 2. Yet it is certain that the furface is not equally fmooth when rubbed in different longitudinal direétions, but is‘compofed either of feales like thofe of fith, or imbricated zones like the horns of animals. For, 3- when a hair is held by the root, and drawn between the finger and thumb, there is little friétion, and no noife ; but, onthe contrary, when it is held by the point, and drawn in the oppofite direction, the refiftance is more confiderable, the motion tremulous, and attended with a chirping noife. And again, 4. If an hair be held between the finger and thumb, and ribbed, by alternately moving them in the direétiom of its length, a progreffive motion will be produced, which is always with the root end foremoft. 5. The fame ftru€ture may be thewn by tying two hairs together, and then giving the knot a few blows between the palms of the hands; for the knot will either untie itfelf, or draw clofer, accordingly as the afperities of the furfaces are placed in the x tying. ~ 6. From this mechanifm, which is common to wool and every ether kind of hair, may be deduced the harth feel of woollens againft the fkin compared with linens, and their irritating effeét upon wounds, 7, [t is the difpofition to progreffive motion endwife which caufes hair to entangle and felt itfelf together, wheh preffed by the hatter between two linen cloths; to which laft they do riot unite, becaufe its fibres are fmooth. 8. Cut hair is better than fuch as is plucked, becaufe.the bulbous reots of the latter prevent the progreflive motion. g- The fibres of wool, being crooked, muft naturally move in curve lined direétions; bt thofe of the hare, the rabbit, Manufalture of Hats.—Texture of Hair. 4ot I thal! confine myfelf .to the obfervation, that a. workman, by, means of the bow, beats, fpreads, and diftributes equally in {mall flocks upon a plane furface the quantity of wool he has felected : that he then covers it with a linen cloth lightly moiftened, and by means of a gradual preflure in every direction he conneéts the different fibres, which, by inter- twining and crofling each other, form a piece of ftuf of a fof and {pongy texture. Upon this firft piece he applies another formed in the fame manner, and fometimes a third or fourth, according to the nature of the materials, and the intended thicknefs and confiftence of the work. Thefe different pieces are fucceflively brought together, and difpofed in a form tuitable to the article * he propofes to fabricate; and, in order to effeét the cohefion, he ufes a number of preflures and alternate motions in different dire€tions, during which he pre- ferves the fupplenefs and flexibility of the material by flight afperfions of warm water. _ This work, which is entirely mechanical, forms the felt, which is a kind of foft fpongy ftuff, of greater or lefs thicknefs, and in its firft flate of a loofe imperfe& texture. The fibres Sit is compofed of, are yet weakly conneéted, and would foon difunite again. In order to give the requifite denfity and confiftence, it is neceflary that it fhould undergo the operation of fulling. This operation, which is in a certain re{pect the completion of felting, has for its objects the intimate conne@tion of the fibres, and a more perfect and durable cohefion of the whole mafs. But for this purpofe the mere mechanical a@ of preffure is infufficient. In this way the refult would be a formlefs mafs, without confiftence, Experience has long fhewn, that for the fulling it is neceflary to make ufe of a bath of water heated nearly to ebullition, into which are put ten or fifteen pounds of lees of wine (Jie) for each hundred pounds of water. The heat is kept up during the whole time of working, and every three or four hours a new. quantity of lees is added. : Into this bath the. workmen plunge their felt, and begin their fecond procefs. The felt rabbit, and the beaver, being fraight, cannot be ufed alone in félting till after a previous operation, which confifts in rubbing them with a nitrous'folution: of mercury, by means of a bruth, before they are feparated from the Skin. The folution, aGling on one fide of the hairs only, renders them crooked. 10. The ftraight hairs are ufed for facing hats, in which operation the aGtion mutt be continued for a determinate time only, otherwife they would pafs through and; come out on the oppofite fide. 11, The- difpofition of wool-to felt itfelf is an impedi- ment to the carding and fpinning procefless in which the Operators therefore ufe.oil, which diminifhes the power of the hairs to aét on each other. .t2. But at the fulling-mill foap and marle are ufed, which carry off the oil, and feftore the wobl to its former ftate ;‘in confequence of whiéh the fulling procefs takes place, and the clotlis are rendered narrower, fhorter, clofer, ftronger, and thicker. 13. The ‘balls of hair ia the ftomachs of certain animals which lick’ oie another ate felted by the action of the Romach. 14. To which I may add, that a fimilar caufe is the chief. reafon why. beds of cock, und hen feathers are inferior to thofe of goofe feathers. The latter being much firaighter do not form the hard flat balls which abound in the former. If a machine were conftruéted either to cut off the quill part of cock and hen, feathers, or to bre. the fem in three or four places, it would probably render the article of much more values’ This Jat operation might be done by two Hated ‘cylinders, NW. 13 : " , * Felt may be ufefully employed in a variety of objeéts. Some time ago an artift imagined it might be'ap- plicable to the foles of fhoes, and made feveral pair. They were of good ufe in dry weather; but, notwith- fianding bis having placed a refinous fubftance between the inner and oyter fole, they eafily abforbed moifture, anid became heavy and unpleafant. Bur it may be practicable, by a farther attention to the fubjec&t and new expedients, to give more compactnefs and lefs px rmeability to the felt. The trial deferyes to he made; for which reafon Phave mehtioned itio this'place, C, Vor. L—Drcrmeix 1797, 3F voUriag 402 Meanufadtive of Hats. is dipped in, and immediately i again taken out ‘and fqueezed bended and rolled, by preffure in different diretions, fometimes with the hand defended by leather, and fometimes by means of a roller or other fimilar inftrument. The immerfion and working of the felt is repeated, and the operation continued until the ftuff is well condenfed, and has acquired the requifite folidity. Such are the proceffes ufed in manufaétories, and they conttitute the pore of what is explained in the Defer} iption des Arts, and in the new edition of the Encyclopédie Methodique. Since the operation of fulling is employed to form a denfe and compact ftufF with the fibres or hairs, and to determine the intimate cohefion of its component parts; and fince the mere mechanical operation is not fufficient for this purpofe, even with the affiftance of a water-bath at the boiling-heat, without the addition of the lees as a neceflary condition ;— this laft mult be confidered as a chemical folvent, which acts diretly on the fubftance of the hairs themfelves, and produces, either by foftening or fwelling them, an alteration neceflary to infure the cohefion of the different fibres of the ftuff. But the Ices being compofed of the mucilaginous and colouring parts which are feparated, together with a great quantity of tartar, or the acidulous tartrite of pot-afh, it became neceflary to afcertain, in a pofitive manner, what might be the principle of its a¢tion. The editor of the Encyclopédie has not hefitated to affirm, that it is the alkali or pot- -ath of the lees which determines the fulling. But i in order to ‘thew how erroneous this affertion is, nothing more is neceflary than to dip a piece of blue | ‘paper into the bath, by which the former becomes inftantly red; and if, after feveral hours work, the ftate of the bath be again examined, it is found that the bytes tartrite of pot-afh is partly exhautted, and the workmen foon perceive, from the difliculty of continuing their work, that a new quan- tity is required to be added. And again, if we confider the {paring folubility of the acidulous tartrite of pot-afh in cold water, it is eafily feen why in this procefs ‘the water mult be kept nearly boiling. Whence it is evident that it muft a& by the portion of acidule it contains. This firft obfervation induced me to think that the fulphuric acid might be advantageoufly fubftituted in the place of the lees; and as twelve pounds of lees are ufually added to one hundred of water, I eftimated by approximation that one gros of fulphuric acid would be equivalent to at leaft one pound of the lees, and confequently that twelve gros of fulphuric acid would be fufficient for one hundred pounds of water. ‘ Experiment foon confirmed. my conjectures; and after a firft trial, which the manufac- turer did not confent to make without trepidation, it was afcertained that the ufe of the fulphuric acid is greatly ta be préferred to that of wine-lees; that it is not only much more economical, but ftill more convenient in the ufe; and, what is ftill more important, the health of the workman is not injured by the excefs and duration of the heat, the thick va- ,pours, and the difgufting odour which exhales from the bath, particularly when the lees have been altered by mouldinefs and putrefaction, which is very common in thefe manu- fa€tories *. ® I cannot avoid mentioning a fmall inconvenience which was experienced the firft time the fulphuric acid was ufed. A bottle was filled with the quantity requifite for the bath intended to be made ufe of; and as the acid was poured out from fome height without any precaution, fome drops were difperfed, which, falling on the hands or clothes of the operator, occafioned {pots by corrofion, To avoid this, it is only required that the bottle fhould be plunged in the bath, and its contents poured out, fo as to occafion no fcattering of drops. C. In Manufacture of Hats. 403 In fa&, when the fulphuric acid is employed, it is ufelefs to keep the bath nearly boiling, as was formerly done. A degree of heat of twenty-five or thirty degrees (g0° or 100° of Fahrenheit) is {ufficient for good fulling. The faving of fuel is an objeét of importance in manufactories; and as yery little fire is neceflary when fulphuric acid is ufed, cauldrons of lead may be fybftituted inftead of copper boilers, the firft coft and annual repair of which are very confiderable. The felts prepared by the new procefs are alfo of a very fuperior quality to thofe which haye been worked in the bath with wine-lees. In fact, the mucilaginous and colouring matters of the lees, which are fufpended in the bath, penetrate the texture of the ftuff, and adhere with more or lefs farce; and when after having paffed the hats through the dye they are beaten, a fine black duft flies off in great abundance, which not only weakens the texture of the felt, but by diffufing itfelf through the manufactory greatly incommodes the workmen, and frequently occafions coughs and diforders of the throat. The manufacturer, accordingly, who made this firft trial, continues to employ it in pre- ference to the old procefs; and, according to his report, the advantages are incalculable : ** Hats felted in this manner,” fays he, in one of his letters, ‘* are not only clear of the powder which abounds in the others, but they take the dye better, s/s Sejarrent mieux, and are cleaner. The workman has not his bath fo hot, which is to him a convenience no lefs valuable than the faving of fuel to the mafter. Befides thefe advantages, the wine-lees formerly made ufe of by the hatters in large quan- tities will remain for other ufes, in the fabrication of faltpetre, foft foaps, and for other de- firable purpofes *. When I had afcertained that the fulling of hats was principally deseniied by the por- tion of acid which exifts in the lees, I aborted to fubftitute the oil of vitriol, or fulphuric acid, becaufe it is foundin the market at a reafonable rate. But though all the acids have common properties in which they refemble each other, they have alfo others by which each is peculiarly diftinguifhed. It would therefore be of importance to examine, among the numerous clafs of acids, whether fome one might not have a more direé& ation upon the ftuff than any of the others, fo as to fhorten the labour, without prejudice to the article or the economy of its preparation. Could not acid liquors be prepared in the manufatory itfelf, by fermenting barley, or bran, or fome fuch material ? This is an object of refearch, to which we may invite manufaéturers, and others who are attached to the cultivation of the arts. I fhall not here defcribe the proceffes of dyeing. In the manufactory of La Céte d’Or, the nut-gall is not ufed; and oak-bark has been {ubftituted with advantage: but thefe methods are known, and have been already publifhed. I proceed to the fourth and laft operation of hat-making. : Tt confifts in lining the inner furface of the crown, as well as of the brim of the hat, with a glutinous fubftance, which in drying gives firmnefs to the work, and preferves its form. The ufual compofition is made of gum arabic, common gum, and Flanders glue, which are * The fulphuric acid, more or lefs diluted with water, might be advantageoufly wfed in many of the arts, Thus the braziers ufvally employ Ices to clean and brighten their work ; and moft certainly they would obtain the fame effeét by fimply dipping the piece in water flightly acidulated with fulphuric acid, which would alfo fare them the trouble of rubbing the work fora long time, as they are obliged to do when they ufe lees, &c. C. 3fF2 diffolved 404 retest of Hats. Giffolved together i ina fufficient quantity ¢ of water, and brought tothe a rn thicknefs by boiling. This preparation, fimple and eafy as it appears, is not ‘indifferent di regard to the beauty and duration of the work. If it'be too tenacious, it renders the ta? dry and brittle, and after fome months’ ufe, a kind of greyifh incruftation is formed on the furface, which alters the texture.. It appeared to me, that this effect was caufed by the gum arabic which is added to the glue. I therefore fought among the plants of our oWn country for 4 fimple preparation, which might be fubftituted inftead of thefe hatural and friable gums. ‘The mu- cilaginous principle abounds in a great number of plants, and may be eafily extracted by ebullition; and a gum may even be formed by evaporation, which preferves its fupplenefs and flexibility. Whefe confiderations induced me to recommend, inftead of the ufual pre- paration, a folution of glue in a decoétion loaded with the mucilage of linfeed-oil. This preparation has long been ufed with popes in the’ viper and advantage in the excellence of the rae Since that time Citizen Margueron having’ dobniinmntented to me his obfervations on the mucilage which may be extra€ted from the leaves of the horfe-chefnut-tree (marronier @’Inde), and having afcertained how great a portion of mucous and adhefive matter thefe leaves afford, efpecially when the foliation isin its vigour; a ftrong decoftion of thefe leaves has been ufed with much fuccefs to make the preparation with glue. - There are a great many other native plants, which would be equally proper to afford factitious gums, and of which the ufe would be very advantageous in the arts. «We are at prefent bufied upon this objeé, and hope in the courfe of time to J ip the refults of our refearches. P, S. Since this memoir was written, a philofopher attached to the Leck a who has obferved much, has informed me that oil of vitriol or fulphuric acid is ufed in fome foreign manufactories in the fulling of hats, and that the procefs is confidered as a great fecret. I was ignorant of this. The publications I have examined make no mention of it, and the workmen I have confulted had no knowledge of its ufe. Befides which, truth is always new while it continues unknown, and ufeful obfervations require to be repeated in order to make them generally adopted. rv a Doubts concerning the Exiffence of a new Earth in the Mineral from New South Wales exam mined by WEDGWOOD in the Year 1790. A PORTION of the fame mineral from Sydney Cove in New South Wales as was fore merly analyfed by the late Mr. Wedgwood, and had been prefented to M. Haidinger, Coun- fellor of Mines, by Sir J. Banks, has been lately examined by the celebrated M. Klaproth*. As the refult feems to have inclined this able chemift to reje& the new earth of Wedgwood, the fubjeét appears fuficiently interefting to admit of being {tated to the public. * Beytrage zur Chemifchen Kenntnifs der Mineral. Koerper, b. ii. M. Klaproth Doubts concerning the Sydney Earth. 405 M. Klaproth had two famples; the firft confifling for the moft part of black brilliant feales, which might have been taken for plumbago or carburet of iron, but appeared to him to be ferruginous mica; the fecond, which contained much lefs of this fubftance, was con- fidered by him as ) purer, and fubjected to experiment. Thirty grains were reduced to fine powder. The greyifh colour it Haturally poffeffed be- came blueifh by levigation. Upon this powder the concentrated muriatic acid was boiled, and Yecanted off when cold. New acid was boiled upon the refidue, and this operation was three times repeated. The acid after filtration through double paper v was not rendered turbid by water gradually added in fufficient quantity. The mixture, when expofed to heat, preferved its tranfparency. By faturating the acid with carbonate of pot-afh, a-fmall quantity of precipitate was af- forded in light flocks, which, being collected on the filtre, edulcorated and dried, weighed 3.25 grains. This precipitate being added to diluted folpeerier acid, afforded eryftals of alum, and left a-fmall portion of filiceous earth. The refidue, which was not acted upon by the muriatic acid, was treated in the dry way with three parts of pot-afh, and afterwards with the muriatic acid. The gelatinous infoluble: portion, feparated by the filtre, edulcorated and dried, weighed 19.5 grains. It was filex. The muriatic folution, effayed by pruflic acid, afforded a blue precipitate, correfponding- with about 0.25 grains of iron. * From this folution, when decompofed by carbonate of pot-ath, a quantity of alumine was. feparatiéd; which, when edulcorated, and dried by heat, weighed 8.5 grains, and upon being combined with fulphuric acid was totally converted into alum. The whole of what this chemift obtained from the fand of Sydney Cove was alumine, filex, and iron, without the leaft indication of any other principle. Though he operated upon’. thirty grains only, and it was impoflible for him to repeat his analyfis, he obferves that the refult is fufficient to render the prefence of anew earth doubtful: He refers the folution of this doubt to time; and on the fuppofition of error in Mr. Wedgwood’s experiments, ‘he is difpofed to think he did not filtre his acid folution before he added water to it, and that the: ‘earth depofited by the diluted acid was probably nothing but filex chemically united to alumine.. Previous to a difcuflion of the probability how far Wedgwood could be miftaken in his. faéts and deductions, and on what the difference between his refults and thofe of M. Klap- roth might depend, I had purpofed to give an abridgment of the paper of the former chemift from the eighticth volume of the Philofophical Tranfactions. But after having made the fame, and begun my comparative remarks, I found that fo much of thefe la(t would depend upon the ftrict ftatement of experiments, that I determined to give fo much of the entire: paper as relates to the new earth. And this I do the more willingly, as it is not, as I am. aware, to be found in any work of general circulation. What follows, therefore, is in the- words of Mr. Wedgwood *. Analytical Experiments on a Mineral from Sidney Cove in Nea South Wales. THIS mineral is a mixture of fine white fand, a foft white earth, fome colourlefs mica- ceous particles, and a few black ones, refembling black mica or black lead, partly loofe; or detached from one another, and partly cohering together in little friable lumps. * Phil, Tranf, LXXX, 307, one> 406 Analy/is of a Mineral from New South Wales. None of thefe fubftances feem to be at all a€ted upon by the nitrous acid, concentrated or dilated; mor by oil of vitriol diluted with about equal its meafure of water. In the, cold, or ina boiling heat, the mineral remained unaltered in its appearance, and the acids had ex- tra€ted. nothing from it that could be precipitated by alkali. Oil of sud boiled upon the mineral to drynefs, as in the procefs of making alum from clay, produced no apparent change in it; but a lixivium made from this dry-mafs with ‘water, on being faturated with alkali, became fomewhat turbid, and depofited, exceeding flowly, awhite earth in a gelatinous ftate, too fmall in quantity fogany particular examina- tion, but which, from its afpe@t, from the manner in which it was obtained, and from the tafte of the lixivium before the addition of the alkali, was judged to be the aluminous earth. The marine acid during digeftion feemed to have as little a€tion as the other two; but -on pouring in fome water, with a yiew only to dilute and wafh out only the remaining part of the acid, a remarkable difference prefented itfelf; the liquor became inftantly white as milk, with a fine white curdly fubftance intermixed; the ftrong acid having extracted fome- thing which the fimple dilution with water precipitated. The white matter being wathed off, more fpirit of falt was added to the remainder, and the digeftion repeated with a long tube inferted into the mouth of the glafs, fo as nearly to prevent evaporation. The acid, when cold, and fettled fine, was poured off clear, and .on diluting it with water the fame milky appearance was produced as at firft. The digeftion was repeated feyeral times fucceflively with frefh quantities of the acid, till no milkinefs appeared on dilution, The quantity of mineral employed was 24 grains, and the refiduum, after the operations, wafhed and dried, weighed fomewhat more than 19 _ grains, fo that about one-fifth of it had been diffolved. In fome parcels of the mineral, taken up promifcuoufly, the proportion of foluble matter was much lefs, and in none greater. It is only the white part, and only a portion of this, that the acid appears to ac upon; the white fand, much of the white foft earth, and all the black particles remain unaltered. To try whether this tedious procefs of folution could be expedited by triture or calcina= tion, fome of the mineral was rubbed in a mortar; and in doing this, it appeared pretty remarkable, that though the black part bore but an inconfiderable proportion to the reft, yet the whitenefs of the other was foon covered and fuppredfed by it ; the whole becoming an uniformly black, fhining, foft, unétuous mafs, like black lead, rubbed in the fame man- ner with a few gritty particles, perceptible on prefling hard with the peftle. A penny- weight of this mixed, {pread thin on the bottom of a porcelain veffel, was calcined about an hour, with a fire between 30 and go degrees *; it became of an uniform, dull, white or grey colour, excepting a very few, and very fmall, fparkling, black particles, fufpected to be thofe which had eluded the aétion of the peftle ; it loft in weight fix grains, or one-fourth, The mineral thus ground and calcined was found to be juft as difficult of folution as in its crude ftate, with this additional difadvantage, that the undiffolved fine particles are in- difpofed to fettle from the liquor. * By degrees of fire or heat above ignition, I mean thofe of my thermometer; and fome idea may be formed of their value by recolleéting that they commence at vifible rednefs ; and that the extreme heat of a good air-furnace of the commen conftruétion is 160° or alittle more. Ws In Analyfis of a Mineral from New South Wales. 407 Th all the experiments of diffolution, as often asthe heat was at or near the: boiling point of the acid, frequent and pretty fingular burfts or explofions happened, though the matter lay very thin in a broad-bottomed glafs. They were fometimes fo confiderableas to throw of a porcelain cup with which the glafs was covered, and once to fhatter the glafs in pieces. In a heat a little below this, the extraGtion feemed to be equally complete, though more flow ; but a heat a little below that in which wax melts, or below 140° of Fahrenheit’s thermometer, appeared infufficient. To determine the degree of folution neceflary for the precipitation of the diffolved fub- ftance, and whether the precipitation by water be total, a meafure of the folution was poured into a large glafs, and the fame meafure of water added repeatedly. ‘The third addition of water occafioned a flight milkinefs, which increafed more and more to the fixth. The liquor being then filtered off, another meafure of water produced a little freth milkinefs, and: an eighth rather increafed it; a ninth and a tenth had no effe@. “The liquor being now again paffed through a filter, folution of falt of tartar did not in the leaft alter its tranfparency; fo that after the folution has been diluted with eight or nine times its meafure of water, there is nothing left in it that alkali’can precipitate. From the manner in which the folution is neceffarily prepared, it cannot but contain a great redundance of acid; for the fmall quantity of acid fufficient for holding the foluble part fufpended, would be foked up or entangled by the undiffolved part, fo as fearcely to . admit of any being poured off; and it cannot be diluted or wafhed out but: by the ftrong acid irfelf. The folution “with which the above experiment was made, was reckoned to have only about fix grains of the foluble matter to three ounces of fpirit of falt, having been Prepared by digefting that quantity of the fpirit, by half an ounce at atime, on thirty grains, of the crude mineral. A faturated folution was obtained by digefting, on a.fmall portion of the folutions thus. prepared, the precipitate thrown down by water from the larger portions till the acid would take up’no more. A folution thus faturated cannot bear the fmalleft quantity of water; a. {ingle drop, on the firft contact, producing a milky circle round it. - Examination of the above Subflance, extraGted From the Mineral by Marine Acid, and precipitated] by Water. THIS fubftance wafhed and dried is indiffoluble in water, as indeed might be expected; from the manner of its preparation. ; Nor is it a&ted upon by the nitrous or vitriolic. acids, concentrated or diluted, cold or: hot, nor by alkaline folutions, mild or cauflic, of the volatile or fixed kind. It is diffolved by ftrong marine acid, but not without the afliftance of nearly the fame.de-- gree of heat that is neceflary for its extraction from the mineral. From this folution it is; precipitated by water; and after repeated diflolutions and. precipitations it appears to have fuffered no decompofition or change. Spirit of nitre, added to the faturated folution, makes no precipitation; and if the quan-~ tity of nitrous acid exceeds, or at leaft does ‘not fall much fhort of, that of :marine acid in: the folution, the mixture fuffers no precipitation from water, ‘Nor ‘doesiany precipitation ; happen, , 408 \\ Bxathinationmofithe fufible Earth. shappen, though the nitrous fpirit be previoufly mixed with even a:large quantity of water, provided the quantity of folution added to it does not exceed thatof the nitrous fpirit in the anixture. The appropriate menflruum for this fubfance (thatis, for keeping it in a flate of dilute folution) appears, therefore, to be aqua regia ;/ and, the due proportion of the two acids, of any given ftrength, might be determined, if neceflary,;with greater accuracy and facility for this than for any other body. I know of ; becaufe,/if there be even a very minute furplus of marine acid in the folution, that furplus will inftantly betray itfelf, on dropping a Jittle into water; all that was diffolved by it, and no more, being precipitated by the water. It may be obferved,, however, that where an addition of nitrous acid is ufed, a faturated folution cannot be obtained (unlefs by fubfequent evaporation), the fame quantity of marine acid being neceilary with as without that addition : the change or modification which the nitrous acid produces in the marine, ferves, in the prefent inftance, not for effecting the folution, as in the cafe of gold and fome other metals, but merely for enabling it to bear water without depofiting its contents. Oil of vitriol dropped into the faturated marine folution, occafions no change till its quate tity comes to be about equal to that of the folution; a confiderable effervefcence and heat are then produced, the liquor becomes milky, and the marine acid is extricated in its ufual white fumes. The mixture, heated nearly to boiling, becomes tranfparent, and afterwards continues fo in the cold. » This vitriolic folution is precipitated by water, and the preci- pitate is rediffolved by marine acid. The faturated marine folution, is indifpofed to cryflallife., By veh evaporation ‘in gentle heat it becomes thick and butyraceous, and in this flate it foon liquefies again on ex- pofure tothe air, The butyraceous mafs, in colour whitifh or pale yellow, is not, corrofive, like the fimilar preparations made from fome metallic bodies, nor is it more pungent in tafte, but rather lef$ fo, than the combination of the fame acid with calcareous earth. In,a heat increafed nearly to ignition, the acid is difengaged, and rifes in white fumes, which, received in acold phial, condenfe into colourlefs drops, without any appearance of fublimate. From the remaining white mafs, fpirit of nitre extracts fo littlé as to exhibit only.a flight milkinefs on adding alkali; a proof that nearly all the marine acid had been expelled; for, while that acid remains, the whole is diffoluble by the nitrous. The fubltance in queftion is.not precipitated by Pruffianlixiyium. A drop or two of the lixivium do indeed occafion a little white or blueith white precipitation in the faturated ma- rine folution; but in the more dilute no turbidnefs appears till the quantity of lixivium is fuch as to produce that effect by its meré water; and when the precipitate has at length been formed, it rediflolves in marine acid as eafily as that made by water; whereas the precipi- tates refulting from the union of the Pruflian mattér are not aéted upon by acids till that matter has been extraéted from them by an alkali. For further fatisfa€tion, in this im- ‘portant point, the experiment was repeated with a folution in aqua regia. Here the Pruflian lixivium, in whatever quantity it was added, occafioned no precipitation at all (only the ufual blueifhnefs arifing from the iron always found itythe common acids); and pure alkali added afterwards precipitated the original white fubftance unchanged. The following experiments of precipitation by alkalis were made with the marine folu- tion before the effect of an addition of nitrous acid had been difcovered ; and they were made with fo much care and, attention, that it was not, thought neceflary to repeat them 4 afterwards, Examination of the fufble Earth. 409 afterwards. To obviate as much as poflible the equivocal refults that might arife from water contained in the precipitants, the different alkalis were applied in the drieft ftate I could reduce them to; viz. pure falt of tartar, kept for fome time. in a heat juft below rednefs 5 cryftals of marine alkali melted and dried in the fame manner; volatile alkali in cryftals, a little furplus acid being in this inftance previoufly added to ‘the folution to counteract the water of cryftallization in the alkali; /a/t of tartar cau/ticated by quicklime, and haftily evae porated to drynels; the marine alkali caufficated in like manner; and the vapour of caultic volatile alkali, arifing with a very gentle heat from a retort into a phial containing the fo- lution. All thefe alkalis occafioned copious precipitations. All the precipitates, after wafhing and drying, were found to rediffolve in marine acid5 and from all thefe folutions the original fubftance was precipitated unaltered on diluting them with water. In ftrong fire, from 142 to 156 degrees, this fubftance difcovers a much greater fufibility than any of the known fimple earths. Ina fmall veffel made of tobacco-pipe clay, it melted, and glazed the bottom; and on a bed of powdered flint, prefled fmooth in the manner of a cupel, it did the fame. Magnefia or chalk would indeed vitrify in the clay veffel; but on flint no one of the known earths fhews any tendency to vitrification in that heat*. Ina cavity fcooped in a lump of chalk, this fubftance, in the heat above mentioned, ran into a fmall round bead, fmooth, whitifh, and opake, not in the leaft adhering to the calcareous mafs. On a bed of powdered quick-lime, it formed a brownifh fcoria, which in great part ‘had funk into the lime, and feemed to have united with it, On Mr. Henry’s magnefia, uncalcined, it melted and funk in completely, leaving only a flight brownifh ftain on the furface where it had lain. Onbeds of the baro-felenite, and barytic quick-lime, it likewife melted and funk in, leaving a difcoloured fpot behind; but whether it really united with the fubftrata, or only penetrated into their interfticés, could not be determined with certainty, on account of the fmallnefs of the quantity of the mineral I had to work upon. On a bed of powdered charcoal, in a crucible clofely luted, this fubftance likewife melted: and therefore it may be prefumed not to have owed its fufion in the above experiments to the fame caufe to which fome of the common fimple earths, in certain circumftances, owe theirs, namely their union with the matter of the veffel or fupport ;. that is, with an earth or earths of a different kind from themfelves; but to poffefs a fufibility ftridtly its own, which takes place ina fire of 150 degrees, or perhaps lefs. As charcoal in fine powder aflumes a kind of fluidity in the fire, fimilar to that which powdered gypfum exhibits in a fmall heat, its furface had changed from concave to hori- zontal, and the bead had funk to the bottom; it was rough and black on the outfide, and whitith within. On repeating the experiments in a cavity {cooped in a piece of charcoal, * It may be proper juft to mention that I find this to be a very commodious and fure method of trying, in fmall, whether any given earthy body be fufible with ether earths. Ifthe body is difpofed to vitrify with any proportion of clay or flint, for inftance, it will equally vitrify when a little of it is applied, or even dufted only, on the bottom ofa fmall cup made of clay, or on a finooth clofe bed of finely powdered flint. The body, in this mode of application, feems to unite with only juft fo much of the matter of the fub{tratum as is requifite for their moft perfect fufion together, and has nothing cle in contaét with it, fo that no deception can arife ; whereas, if mixed with the fame matter, there might be no appearance of fufion, unlefs certain favourable pro- portions of the two fhould chance to be hit upon; and even shen, if the quantity be fmall, it would not be cer- tain but that the fufion might have originated from the matter of the crucible. W. Vou. L—Decemper 1797. 3G the 410 Doubts refpeGing the Sydney Earth. the refult was a blackith bead like the former, only fmooth on the -outfide, with fomething of metallic brightnefs, not unlike that of black-lead. Both beads were very light, and had a confiderable cavity within... All the internal part was whitith, without the !caft metallic afpeét; and the external glofly blacknefs appeared to be only the ftain which charcoal powder communicates in {trong fire to fome earthy bodies that have a tendency to vitrify. By boiling in concentrated marine acid, a part of the beads was diffolved, precipitable, as at firft, by water; but an accident prevented the procefs from being continued fufliciently to determine whether the whole could be diffolyed or not. By this fufibility in the fire, folubility in one only of the common mineral acids, and parting with the acid in a heat below ignition, precipitability by water, and non-precipitability by Pruf- fian lixivium, this fubftance is ftrongly difcriminated from all the known earths and metallic calces. And as it fuffers no decompofition from any of the alkalis in any of the ufual modes of application, I prefume it cannot be confidered as a combination of any of thofe earths or calces with any of the known acids ; for all the combinations of this kind would, in one or other of the above methods of trial, have’had the earth or metal difengaged from the acid. Whether this fubftance belongs to the earthy or metallic clafs, 1 cannot abfolutely deter- mine ; but am inclined to refer it to the earthy; becaufe, though brought into perfeé fufion in contaét with inflammable matter and in clofe veflels, it does not aflume the appearance: which metallic bodies do in that circumitance *. The black fubflance, which feems to have compofed about one-fifth part of the crude mineral, was found to refemble plumbago in its leading properties, but its refidue did: not appear to beiron. The remaining three-fifths of the mineral, which refifted the humid at- tacks in Mr. Wedgwood’s experiments, was probably filex; but he does not {peak of any dire€t examination of its properties by fufion with alkalis, the fparry acid, or otherwife. On the preceding experiments of M. Klaproth and the late Mr. Wedgwood, the quef- tion which in the firft place appears to demand folution, is, whether the fame mineral-was. examined by both chemifts? If this fhould not appear probable, it willbe unneceffary to enter upon the fubfequent enquiry, which fet of experiments is moft likely to be erroneous? On the hiftorical evidence, as far as regards the famenefs of the parcels of mineral, I think there is little to be faid. Both were obtained from Sir Jofeph Banks; the firft direétly, and the latter with the intervention of the refpectable, and as it may be concluded careful, M. Haidin- ger. Neverthelefs, if the obvious defcription and decided experiments fhould point out a difference, it will afford more than a prefumptive proof that they were not the fame. 1. M. Klaproth’s mineral was greyith, and became blueifh by levigation. Mr. Wedgwood’s was a fine white fand, a foft white earth, with fome colourlefs micaceous particles, and a few refembling plumbago. When levigated, it became black, fhining, foft, and unétuous. 2. Klaproth’s marine folution, after filtration, afforded no precipitate by the addition of water. Wedgwood’s folution in the fame acid, when cold, fettled fine ; and, decanted off clear, afforded a white precipitate with water to the whole amount of its contents. After fix meafures of water had caufed much of the precipitate to fall, the liquor was filtered, * Here ends the extract in Mr, Wedgwood's own words, and Sydney Earth.—Experiments on Sound. qr and more woter threw down a little more. 3: Klaproth’s marine folution afforded a pre- cipitate by the addition of an alkali which was foluble in vitriolic acid, and afforded alum. Wedgwood’s precipitate by means of water was infoluble in the nitrous or vitriolic acids: The indire& folution of this matter in vitriolic acid was precipitated by water. 4. M. Klap- roth’s experiments fhewed nothing but filex, alumine, and a minute portion of iron. He thinks it probable that Wedgwood’s precipitate by water was filex combined with alumine. But in Wedgwood’s experiments this matter was fufed without addition in an hole fcooped in charcoal, and alfo in an hole in a lump of chalk, to which it did not adhere. Kirwan * found equal parts of alumine and filex infufible at 160° of Wedgwood; and Achard found them infufible in a porcelain furnace, in all proportions; not to mention that very refractory veffels are made out of the fame two earths mixed together. 5. I do not fee how Wedg- wood’s method of fubfidence and decantation could have left any thing fufpended which Klaproth’s filtre could have detained. Hence it feems fair to conclude that the two minerals were not the fame, however this may have happened ; and that the exiftence of the new fuSble earth of Wedgwood flands on the fame evidence as before, namely, his experiments, which have not yet been repeated, that I know of. : 2 V. A Philofophical Memoir, containing—1. Experiments relative to the Propagation of Sound in dif- Serent Solid and Fluid Mediums.—And 2. An Experimental Enquiry into the Caufe of the Refonance of Mufical Infiruments. By M. PERROLE t- With Annotations. As the tranfmiffion of found through water t, through air of greater or lefs denfity ¢, and through different gafeous fubftances'|}, has added to the amount of our philofophical knowledge, I have thought an abundant harvett of new facts might be obtained by caufing found to pafs through a great number of bodies of different kinds, as well folid as fluid, and comparing their effects together. . Thefe are the views which: have direéted the experiments of which I fhall give an account in the firft part of this memoir; and in the fecond | thall avail myfelf of the refults in an endeavour to afcertain the caufe of the refonance of bodies. PSA RTS dy AS all the trials depend upon the following experiment, it is neceflary to give particular attention to its detail. - Experiment I. and chief. Clofe the ears with chewed or mafhed paper; fufpend a watch by an hook. Place the ear at the diftance of two lines from the watch, and you will not hear its * Mineralogy, i.<8. + Mem. del’ Acad. Royale de Turin, v. 195. t Nollet, Mem. de I’Acad. Royale de Paris, 1743. § Mufchenbroek, n, 1442.—Nollet, Lecons de Phyfique, iii. 3¢5. | Prieftley’s Experiments and Obfervations, “&c. and my Experiments in the Turin Memoirs for 1786, 1787. P, 3G2 vibrations, 412 Experiments on the Tranfmiffion of Sound. vibrations. Then take a folid body, fuch as a fmall cylinder of wood, of one foot or one foot and a half in length, and oné or two lines in diameter. Place it in contact at one, extremity with the watch, and apply the other end to one of the numerous parts of the head which propagate found by the touch*; for example, with the cartilaginous parts of the ear ; you will hear the found much better than if the ear had not been clofed, and the fonorous body had been placed in the air at the fmalleft diftance from the organ. - As the found was not perceptible at the diftance of two lines in the firft. difpofition, and was very ftrongly perceived.in the fecond ; it is evident that the fmall cylinder propagated found better than atmofpheric air. 1 When we refle& on this experiment, and the refult it affords, we may, without difli- culty, perceive, that, in order to afcertain the refpective force of the propagation of found through folid bedies, nothing. more is required to be done than to procure fubftances of different natures, to give them the fame form, and fubjeét them to an experiment of this kind. In this manner I made the following experiments : Experiment I, Y procured fmall cylinders-of the dry wood of fir, oak, box, cherry-tree, chefnut-tree, and logwood, each one. line in.diameter, and one foot in Jength. The ears, being then clofed, I placed them fucceflively in contaé& with the watch, and at the fame time with the cartilaginous part of the ear, as in the preceding experiment. The different cylinders tranfmitted the found very well; but its tone +feemed to vary whenever anew cylinder was ufed, and the intenfity appeared to be never exactly the: fame. We had no means of afcertaining the difference of the tone (timbre), but the in- tenfity appeared in the following ordér, beginning with thofé cylinders which appeared to propagate found with the greateft activity: fir, logwood, box, oak, cherry-tree, chefnut. : Experiment III. 1 determined. extend my refearches to the metals, and conftruded metallic cylinders fimilar to the former. When fubjeéted to the fame trial, they tranf- mitted the found in general rather worfe than the cylinders of wood. The nature of the found appeared likewife to differ in the cylinders. of wood and thofe of metal. ‘The tone was not exaétly the fame in the different metals, and the intenfity followed this order: iron, copper, filver, gold, tin, lead. Experiment IV. 1 hung my watch fucceflively to firings of filk, of wool, of. hemp, of flax, hair, and gut, which were nearly of the fame diameter and exactly of the fame length as the folid cylinders. One extremity of the ftring was applied by the hand in contaét with the cartilage of the ear, while the watch refted-on the oppofite extremity of the ftring, which touched no part of the body. The ftrings thus extended propagated the, found with Jefs * Almoft every part of the head propagates found when in immediate contact with a fonorous body. This may be eafilf proved by applying a watch to the fev eral’ parts after having clofed the ears. See my Differt. Anate &c. and my Recherches fur l’Organe de l’Ouie et la Propr. des Sons, tom. iii, des Mem. de la Soc. R. dé Medec. et le Journal de Phyfique, 1773, tom. it. P. + Son timbre, which does not, as Lapprehend, imply any difference of acutenefs or gravity in found, bur another relation for which I know no Englifh word but tone. Thus the tone (#/mbre) of the hautboy differs greatly from that of the flute when both are in unifon, and for likewife do the different, topes (tons) of the fame kind of inftrument. It does not appear from the text, whether the acutenefs or gravity of thefe tranfimitted founds did differ from each other. N. force Experiments on the Tranfmiffion of Sound. 413 force than folid bodies, and modified it in a remarkable manner. The tone in each of the ftrings appeared to be different, and the intenfity followed this arder :—gut, hair, filk, hemp, flax, wool, cotton, 5 From the foregoing experiments it follows:—1. That hard bodies and ftretched ftrings tran{mit found much better than atmofpheric air. 2. That each of thefe mediums tranfnits itn a manner which is peculiar to itfelf, fo that the kind and intenfity of the found are never exactly the fame, as far as can be judged on trials which do not always prefent very ftriking refults*. 3. That in general wood tran{mits found very well; that the metals tranfmit it with fomewhat lefs energy, and that ftretched firings occupy the third place in the fcale of power in this refpect. Experiment V. Being determined to extend my refearches, I caufed the found of the watch to"pafs through pieces of zinc, antimony, glafs, fal gem, gypfum, dried clay, and marble. As I could not give the fame form to thefe different {ubftances, I was unable to determine with precifion their refpeClive powers of tranfmiflion ; but I obferved that all thefe bodies tranfmitted founds better than air, and that it was modified in a particular manner by each of them. Marble was remarkable for the little force with which it tranfmitted the fonorous movements. ‘I'wo pieces of this fubftance, of different form and fize, propagated it ina weak -and-almoft infenfible manner. Thefe are the experiments I have made with folid bodies. To complete the feries, it re- mained to fubmit fluids to fimilar trials. I have already publifhed my experiments on aériform fubftances +. In this place I fhaH relate thofe Ihave made upon liquids. This part of my operations required a different procefs. ; Experiment VI, 1 clofed all the joints of my watch with foft wax, and then fufpended it by a filk thread. In this ftate I hung it by an iron branch fixed in the wall, fo that the watch remained fufpended in the middle of a glafs veffel five inches in diameter, and feven inches high, taking care that neither the watch’nor the thread touched the veflel in any part. Tremarked the kind of found afforded by the watch, and the diftance at which I ceafed to hear it. After having marked«this point, I then filled the veflel with water, into which I again fuffered the watch to defcend, with ‘the fame precaution of not fuffering- it or the thread to touch the veffel. ” - The tone (timbre) was changed in the water in a ftriking manner. The found was pro- pagated in: fo lively a manner that'the glafs, and a fmall table of wood, on which it ftood at a diftance from the wall, feemed to undergo direét percuflions from a folid body. But what appeared ftill more altonifhing was, that in the midft of all thefe agitations the fluid in which the watch was plunged was perfeéLly tranquil, and its furface not in the flighteft de- gree agitated. By {ubftituting different liquids in the place of the water, I had refults in general ana-. logous to thofe I had obtained with that fluid; but each medium gave a different modifi-. eation to the found, of which the intenfity was noted as follows : * Such chiefly are thofe which were obtained with the cylinders of wood, and ftretched firings. P,. . t+ Mem, de }’Acad. Roy, des Sc, de Turin, 1786, 1757. Intenfity 4t4 Experiments on the Tranfiniffion of Sound. Intenjity of Sound obferved in different Fluids. r. In the air ferving as the term of comparifon, it ceafes to be heard at the dif- pe tance of ——— Ls. 8 2. In the water, at that of ——— aa a — 20 3- Oil-olive — oa Se ah 4. Oil of turpentine — —- ss ssh ry _—_— — 242 5. Spirit of wine Tt is proper to obferve, that on repeating thefe trials I obferved fome variations in the in- tenfity, which appeared to depend on the organ of fenfe’or accidental noifes. From the experiments made upon liquids, it follows :—1. That thefe as well as folids do tranfmit founds much better than air, and that even the fat oils are not to be excepted *. 2. That each fluid upon trial is found to modify the found in a peculiar manner. 3 Philofophers maintain the opinion that found is propagated in the air by means of certain motions or undulations, which the tranfparence of that fluid prevents our feeing. My experiments with fluids which do not elude the fight, and in which no motion was perceived, notwith{tanding the very effectual tranfmiffion of found, may render this in fome refpet doubtful. 4. Laftly, the experiments on folids, fluids, and thofe I have publifhed on the gafes t, afford the probable conclufion that all mediums produce particular modifications in the tone (timbre ) and the intenfity of found ; or otherwife, that the fame found varies as often as it paffes through a different medium. I fhall now pafs to the experiments which conftitute the fecond part of this memoir. Se ee in EVERY one has obferved, that if a watch be placed upona table, the found is very eyi- dently increafed. The difference between the found of a tuning-fork, when it vibrates without being placed in contact with any folid body, and that which it affords when its handle is prefled againft a folid body with a large furface, is alfo well known. ‘The experi~ ments related in the former part of this memoir having led me to expect that the increafe of force and harmony in thefe circumftances was owing to the property poflefled by wood of propagating found better than the external air, and modifying its tone; I determined to afcertain the truth by experiment. The different powers 1 had obferved in wood and marble, with regard to the propagation | of found, appeared proper to throw fome light on this important queftion. In faét, if the modifications of the found of the tuning-fork and the watch, when placed ona table of wood, be owing to the energy with which this fubftance tranfmits the found, and the marble pro- pagating it very weakly, it would follow that a table of marble ought not to fortify the © Morhof, Steut. pag. 104. affirmed that fat oils could not tranfmit fonorous modulations. P, + Loco citato. Ak ' found, Experiments on the Tranfmiffion of Sound. 40g found, or at leaft to produce very little effe€&t on thefe fonorous bodies. On thefe confi- derations I made the following experiments : Experiment I. \ applied the tuning-fork upon a table of wood, and when it had ceafed to vibrate I applied my watch to the fame furface. The found in each was increafed in pro- portion to their refpective intenfities. I then removed the wooden top of the table, and fubftituted in its place another of marble, of the fame dimenfions. The tuning-fork and watch were applied as before. The found of the former was augmented, though much lefs than when it'was applied on the wooden covering. The found of the watch was fearce perceptibly increafed. I could perceive little difference between its found, whether it touched the marble or hung in the air at the fame diftance from the ear. ‘Though this experiment ftrongly confirms my conjeQure, I determined, neverthelefs, to fubjeét it to another proof : Experiment I. J placed my watch on the wooden table, and clofed my ears with chewed paper. When the ear was at a few lines diftance from the table, I could not hear the vibrations of the watch. I then placed my ear in contaét with one of the fmall wooden cylinders ufed in the experiments already defcribed. The oppofite end of the cylinder was placed in conta&t with the table. : The found of the watch immediately and forcibly ftruck the ear. I made this application’ to every part of the table, not excepting even the feet; and the found was in every cafe dif- tinétly heard. The experiment was then repeated with the marble covering inftead of the wood. The vibrations of the watch were heard in an imperfeét or indiftin€t manner, and only when the wooden cylinder was applied at a fhort diftance from the fonorous body. I did not ufe the tuning-fork in this experiment, becaufe, in fpite, of every precaution, it was not poflible to clofe the ears fo perfectly but that the found ftill remained per- ceptible. In order to eftablifh my conje€ture on the moft folid bafis, it remained to repeat the ex- periments upon tables of all the fubftances ufed in the experiments related in the firft part of this memoir, and to fhew that the refonances follow the proportion of the condudting powers of the bodies. But the difficulties which oppofed the execution of this plan in- duced me to confine my eriquiries to afcertain whether the refonance does not vary in dif= ferent bodies, as well as the power of tranfmitting found. Experiment Il]. J therefore placed the tuning-fork fucceflively upon plates of earthen- ware, of porcelain, on plates of glafs, and upon thin ifolated plates of copper and tinned iron. The found was fortified by thefe bodies, and the tone never appeared to be exaétly the fame in any two experiments. t Thefe trials naturally led me to examine the fame founds upon mufical inftruments. With this view I applied firft the tuning-fork and afterwards the watch, upon bafes, violins, mandolins, guitars, harpfichords, and horns. Both founds were proportionally increafed. They appeared to acquire more force and melody by means of the mufical,inftruments than on the other bodies. ‘The intenfity feemed direétly in proportion tothe volume of the inftrument. From thefe experiments it follows :—1. That all the fubftances which were tried, which pofleffed extended furfaces, fortify the weak founds produced by bodies which touch them, and modify the tone in a manner peculiar to each. 2. That 416 Experiments on the Tranfmiffion of Sound. 2, That thefe effeéts arife from the tranfmiflion of found by folid bodies being in general better than by the air, and the peculiar modification of the tone by each. 3- That the refonance of mufical inftruments is more particularly to be attributed to this caufe *. : 4. The experiments with mufical inflruments afford reafon to conclude that the volume - of bodies has an influence on their refounding properties. 5. M. de Maupertuis + has affirmed that the refonance of mufical inftruments is owing to the inftrument containing fibres of every poflible length; each found puts thofe in motion which are either in unifon or concord with -itfelf, while the others remain motionlefs {. But the fecond experiment, in which it is fhewn that there is no part. of any refounding body which does not tranfmit the found, will not admit of the adoption of. the ingenious thought of that celebrated author. : . 6. As. marble in fome degree extinguifhes found, and bears the fame rank among folid bodies as inflammable air among fluids, it is not advifable to ufe it in the conflru€ion of churches, concert-rooms, theatres, or other edifices in which the propagation. of found is defirable. Such are the principal refults of experiments which, on the whole, have engaged ‘my at- tention for a number of years ; notwith{tanding ‘which, 1 have. not been yet able*to extend them, particularly thofe belonging to the fecond part, as far as they are capable of being earried. 1 fhall not, however, have the mortification to think my endeavours ufelefs, if the fociety to whom my works are addreffed fhall think they may conftitute an addition to the fum of the difcoveries in fcience which they continually prefent to the world. ‘Annotations to the Paper of M. PERROLE on Sound. -THE philofophy of found is {till exceedingly imperfeét. Mathematicians have efta- blifhed theories upon the fimple data that fonorous bodies vibrate, and that thefe vibrations are communicated to the furrounding elaftic fluid, of which the denfity and fpring are mea- furable. M. Perrole’s experiments thew that.the objeét of refearch.comprehends much more than this. The following queries and remarks may perhaps prove of fome advantage to the curious enquirer: 1. There can be no doubt but that undulation in the air accompanies its. propagation of found, and that fonorous bodies are put into a vibrating ftate by percuffion. The proofs of this are too numerous to be detailed. Sound propagated through fluids feems to diminifh in proportion to the diftance, and fo probably it does in folid bodies. Its intenfity muft depend upon the elafticity and denfity jointly. The military practice of lying down on the ground to liften for footfteps is well known; and Dr. Franklin relates that he heard the blow of two ftones firuck together at the diftance of near a mile, fmart and ftrong as if clofe at the ear §. We have no information refpeting the velocities of founds propagated through folid bodies. * The numerous furfaces which thefe inftruments prefent muf likewife render them more fonorous. ~P. 4 Acad. Paris, 1724. “y The memoir of M, de Maupertuis relates to flringed infruments only, P. § Expe réments and Obfervations. . London, 1774) ps 445. si 2. As Obfervations on Sound and Acouftic Inftruments. Al? 2, As found paffes through the air with a velocity of 1142 feet in a fecond, and the iwifteft wind does not pafs with a velocity of go feet in the fame time; it might naturally be inferred that the velocity of found with or againft the wind ought to be fomewhat af. ' fected, but its intenfity very little. ‘The contrary, however, is the cafe; from which, and other circumftances, fome philofophers have been difpofed to conclude that the medium by which found is tranfmitted is not air, but another fluid of greater fubtilty. 3. Sounds feem more intenfe, and are heard to a greater diftance, by night than by day. In a ftill night, the voices of the workmen at the diftillery at Batterfea may be heard at Weftminfter Bridge, over an interval of about three miles; the watch-word at Portfmouth may be heard at Ride in the Ifle of Wight, the diftance of which is between four and five miles; and numerous inftances are related of the propagation of weak founds to much greater diftances, without mentioning thofe of which the intenfity is greater. It is a prac= tical queftion of fome importance to afcertain whether this difference may arife from the different ftate of the air, the greater acutenefs of the organ, or the abfence of the ordinary noifes produced in the day. By attentive liftening to the vibrations of a clock in the night, and remarking the difference between the time when no other noife was heard, and when a coach pafled along, it has appeared clear to me that this difference arifes from the greater or lefs ftillnefs only, and that no yoluntary effort or attention can render the near found much more audible, while another noife acts upon the organ. In this fituation the ear is nearly in the ftate of the eye, which cannot perceive the ftars in the day time, nor an ob- je& behind a candle. : 4. It would be impoflible to ufe optical inftruments in the day time, if the light of other objects belides thofe to which the attention is direCted were fuffered to mix itfelf with the rays admitted into the field of view. In the fame manner it feems that we have little to hope with regard to the improvement of acouftic inftruments for day ufe, if the firft re- quifite, namely, the exclufion of unneceflary found, cannot be obtained. 5. Numerous experiments have fhewn that found can be refleéted, and that the im- preflion on the ear is greater or lefs, according to the difpofition of the refle&ting bodies. Optical inftruments are difpofed in tubes of fuch a length, that the rays of light which arife froma fmall portion of the vifible hemifphere can alone reach the organ of perception. All the others ftrike the furface of the tube, and after one or more reflections are almoft “totally abforbed or loft. It remains to be afcertained from reafoning and experiment, how far the fame effet may be produced with regard to found. With a cylindrical wooden pipe, three inches in diameter and eight feet in length, at the diftance of two miles from London, I liftened tothe noifes which came from that capital. I think I did not deceive myfelf by any prepofléflion, when I diftin@ly heard the noife and agitation of wheels on the pavement much more ftrongly than any other kind of found. Nearer founds, not in the direction of the tube, were lefs perceived; and fuch as were loud af- fumed a mufical tone; moft probably from the reiterated reflections under the feveral angles of its reception. I confider this experiment as of little other value than as ferving to convey an hint, that a tube lined with cloth might defend an acouftic inftrument from founds out of the line of its diretion, while the inftrument itfelf might magnify and render diftinét the found required to be heard. 6. M. Perrole conjectures, at the end of the firft part of his memoir, that fonorous Vou. I.—Decemser 1797. 3H bodies Ais Objervations refpecting Acouftic Inftruments. bodies do not vibrate during the propagation of found, becaufe the water in his curioas: experiment of the watch was not feen to move. He has overlooked the very great num- ber and minutenefs of the vibrations required to produce found. They cannot be vifible but in cafes of extreme fimplicity and intenfity. The ftring of a mufical inftrument emits: found long after its vibrations have ceafed to be vifible. He likewife, at the end of his fecond part, objects to the theory of Maupertuis, which fuppofes that fonorous and refonant bodies fubdivide themfelves fo as to vibrate differently in different parts. But the body in queftion may be confidered under different points of view. 1. As the medium of found, it’ may conduct or tranfmit every found indifferently. 2. Hf its fimplicity of figure and tex- ture be fuch as to produce very few founds at a time, it will, upon the whole, emit a mufi- cal tone. For I confider a mufical tone as one or more fimple founds in concord with each. other ; and a noife, as a greater number not poffefling the fame relation. Thus, the noife produced by prefling down an indiferiminate number of contiguous keys in the organ, is fo far from being mufical, that it feems aftonifhing that the aggregate of pipes fo melodious. fhould produce a found fo harfh. 3. Or the body in queftion may aflift or impede the found of another fimple body, fuch as a ftring with which it isin contaé&t. When it affifts that found, it does not feem improbable that the effeét pointed out by Maupertuis may really take place. For the divifion of bodies, his fuppofition requites, is known to take place inv the fingle ftring which gives the trumpet notes, and has on that account been called the trumpet marine; and alfo in bells, which not only give a fet of diftinct contemporaneous. tones differing in acutenefs, but to a certain extent are found to alter the fyftem according to the plan of percuflion. And again, it will readily be imagined by thofé who take fo much pains in experiments for fixing the found poft of the violin, that the refonance which js fo much affected by this difpofition, is more’ probably of the whole inftrument than merely of its parts as conductors of found. 7. The figure of the external ear, which is made up of a feries of concavities with ftops or bridges interpofed, is an object which, as far as I know, has never yet been explained or enquired into. In the cat and other animals this ftru€ture appears to be very compli- cated. After the found or aérial undulation has beer modified and conveyed into the ear through this apparatus, it is received upon the ftretched membrane called the tympanum. This, as well asthe other membranous parts of the internal ear, feems evidently adapted to vibrate by the aétion of found ; and moft probably after the manner that a mufical {tring yibrates when another ftring is made to found in its vicinity, and emits a tone in concord not too remote from unifon. From this faét and the formation of the ear, a queftion may be propofed of fome confequence with regard to the conftruétion' of acouttic inftruments : Whether the found produced by a remote body or that which is emitted bya correfpondent vibrating body, at alefs diftance from the organ, be the moft perceptible? For example, if two ftrings, A and B, be tuned in unifon, and the ftring A be ten feet from the ear, while the ftring B is placed at the diftance, for example, of one inch from the fame organ 3—whether the fecondary found of B, when A is ftruck, may not be more perceptible than the original found of A? Itis unneceffary to enter into confiderations of the mechanical circumftances under which, from theory; this or the contrary effe&t may take place. It may be fufficient in this very remote view of the fubje‘t to remark, that in point of faé& the influence of founds may extend further than the organ can perceive them. I was once in aroom facing the Acouftics:— Marquis of Worcefter’s Steam-Eneine. 1 q' g 419 the ftreet, in London, when I perceived the window to be agitated with certain tremulous motions, attended with a confiderable found. ‘The reiterations were fhort and diftin, three or four at a time; and then ceafed till a fecond and a third repetition of the fame effect took place. This remarkable procefs continued to increafe in intenfity of found, and en- gaged my attention for about a quarter of an hour; after which the nearer approach of one of thofe inftruments called a tambourin, compofed of parchment ftretched on a hoop, and played upon by rubbing the extremity of the finger upon its furface, evinced that the agita- tion and found emitted by the window had been caufed by the vibrations of that inftrument. Hence it fhould appear, that the judicious conftruétion of an inftrument for receiving and magnifying founds would not only require a {cientific arrangement of an external part to exclude foreign founds, and refleQling furfaces to modify and augment the dire& undula- tions ; but that the laft effe& fhould be received on a tympanum capable of adjuftment in its tenfion, and thence conveyed by a proper veftibule to the organ of perception itfelf. Ifthe {cience of receiving and augmenting founds were once improved to the degree here fketched out, there would probably be no difficulty in magnifying founds intended to be conveyed from one place to another. eae VI. Concerning the Steam-Engine as originally invented by the Marquis of WorcEsrer, and the Improvements fince made in Steam-Engines without the Pifton or Lever. With a Defeription of an Engine of this Kind conftrued by Mr. PETER Krzr, of Kentifh Town. Tue Marquis of Worcefter is the undoubted inventor of the fteam-engine, which is deferibed in his Century of Inventions. From the title, he appears to have conftructed. one before the year 1655. His words, No. 68, areas follow : ‘ An admirable and moft forcible way to drive up water by fire, not by drawing or fuck- ing it upwards; for that muft be, as the philofopher calleth it, intra {pheram activitatis, which is but at fuch a diftance. But this way hath no bounder, if the veflels be ftrong enough ; for I have taken a piece of a whole cannon whereof the end was burft, and filled it three quarters full of water, ftopping and {crewing up the b:oken end, as alfo the touch- hole ; and making a conftant fire under it, within 24 hours it burft and made a great crack ; fo that, having a way to make my veffels fo that they are ftrengthened by the force within them, and the one to fill after the other, I have feen the water run like a conftant foun- tain {tream forty foot high. One veffel of water rarefied by fire driveth up forty of cold water. And a man that tends the work is but to turn two cocks, that; one veflel of water being confumed, another begins to force and re-fill with cold water, and fo fucceffively; the fire being tended and kept conftant ; which the felf-fame perfon may likewifely abundantly perform in the interim between the neceflity of turning the faid cocks.” Plate XVII. Fig. 1, reprefents the fteam-engine which was made by Captain Savery, and generally fuppofed to be the fame as the Marquis of Worcefter’s. A reprefents a boiler containing water, the fteam of which may be tranfmited into either of the yeflels BandC by means of the cocks DE. The veffels have a communication at bottom with the ver- 3H2 tical 420 Hiftorical Incidents and Remarks concerning tical pipe FG. Thefe communications are made between twoovalvess EDT and KoL open- ing upwards ; and the effect is as follows : Imagine the upper part of the» pipe to'be filled with water-for the purpofe of rendering the valves tight,’ -anid'Iet ‘the cock D'be turned. ‘he fteam from the boiler, being lighter than the air included in the vefleh B, expels that air, which, not being permitted to pafs through the valve ’H, iffues upwards through In this fituation, let the cock D be fhut, and cold water be thrown upon’ B, or, which-is much better, fpouted into it; and the fteam will become condenféd, and leave an-empty {pace into which the preflure of the atmofphere at F will force the water upwards through the valve H. While this is performing, the cock E is to be opened, and the air from the veffel C ex- pelled by the fteam in the fame manner. ‘This is the regular feries of operations, and is repeated a fecond time by fhutting the cock E, cooling the veffel C, and opening the cock D. By thefe means the water rifes from F into the veflel C, while the fteam from the boiler prefles the water out of B, through the valve I, to G. The whole procefs therefore, fimpli- fied’ by attending to one of the veffels only, is found to confift in expelling the air by fteam ; forming a vacuum by condenfation into which the water rifes, and then forcing that water upwards by new fteam, which, being condenfed as before, is replaced by new water; and fo forth. . “To what practical extent the experiments of the Marquis of Worcefter were carried, does not appear ; but it was near the end of the feventéenth century, when Captain Savery propofed this engine as an invention of his own, for raifing water and draining mines.. Prony, in his Architecture Hydraulique, i. 564, fays, he publithed his Adiner’s Friend about 1699. Defaguliers, in his Courfe of Experimental Philofophy, 3d edition, ii. 465, does not {cruple toaflirm, that Savery had this invention from the Marquis of Worcefter’s book ;. but has not, it muft be confeffed, given to his affertion all the proof it might require. He -fays, that Savery bought up all the copies of the Century of Inventions which he could procure,.and burned them ;.and that he ufed'to relate a {tory as the firft hint of his inven- tion : that having drank a flafk of Florence ata tavern, and thrown the ewpty flafk upon the fire, he called for a bafon of water to wafh his hands; and perceiving the little wine left in the flafk had filled it with fteam, he took it by the neck and plunged its mouth in the water, which was immediately driven up by the preffure of the air. On thisincident, Dr. D. remarks, that it could not have fo happened ; becaufe when he himfelf had repeated the experiment by boiling -half a glafs of wine ina flafk, and, putting on a thick glove to defend his hand, had plunged its mouth beneath the furface of water, the preflure of the atmofphere was fo. ftrong as to beat the flafk out of his-hand againft the cieling—a circum- ftance with which he does not doubt but that the pater would have embellifhed his tale: \if he had made the experiment. Jt appears to me, neverthelefs, that fomewhat more: than thefe incidents ought to be re- quired to eflablith the charge of deception againft Savery, who, in the courfe of probabilities,. might have invented the fteam-engine half a century after the Marquis of Worcefter, whofe defcription, clear as it now feems to us who know the engine, was not perhaps enough fo as to attract much attention, in company with one hundred other enigmatical.propofals. Captain: Savery, being a patentee, and having probably a confiderable intereft depending, might be as ftrongly urged to fupprefs the Marquis of Worcefter’s book on:that account, as for the rea- fon alerted. by Defaguliers., And with regard to the experiment of the-flafk, it is-hardly allowable the original Invention of the Steam-Enginé. 42 allowable for a philofopher to conclude that the experiments of another are falfe or impofli- ble; becaufe they do not agree with his own. I fuppofe Defaguliers made his experiments with more wine and‘more heat than Savery ; and if I were difpofed to reafon againft the relation of a pefitive fact, I fhould be inclined to doubt the projection of the flafk againft the ceiling by an exertion of atmofpherical preflure, which mutt have been as ftrong on the outer as on the inner furface of the veflel. And in this doubt I fhould be {till more fettled, from having myfelf very often repeated the experiment without any fuch refult. But the integrity of Defaguliers forbids any fuch infinuation. Under certain’ circumftances the flak might have been beaten out of his hand; but it does not follow that thofe circum~ ftances were prefent in Captain Savery’s experiment. Lhe Marquis of Worcefter was the firft inventor of the fteam-engine. Savery was either ‘the fecond inventor, or he had the ingenuity to difcern a valuable invention in the midft of loofe hints, and to give it-organization and effect. We do not know how the Marquis of Worcefter condenfed’ his fteam, or, indeed, whe- ‘ther he condenfed it at all; for it certainly does not require condenfation unlefs for what is- called fucking. It is faid, that the condenfation in’ the firft engines was effected by water on the outfide of the veflel ; but in Savery’s engines it was performed within the veflel. Seve- ral of his engines were made with only one {team-veffel, and Defaguliers found by experiment,. that this kind is confiderably better than fuch as have two; becaufe the aétion of the fteam is rendered more fudden, and the chemical condenfation during the procefs of forcing is Jefs. This excellent philofopher and practical engineer made feveral.other improvements in this engine and its parts, which may be feen in-his work laft quoted: but the fubfequent invention of the fteam-engine with a pifton and lever, and the improvements which have been made therein, feem to have greatly retarded the progrefs of the original fimple machine. Dr. Papin, well known for his invention of the digeflor, was bufied in experiments on fteam. Prony, in his Archité€ture Hydraulique, i. 566, mentions a work of his, printed at “Caffel in 1707, under the title of Nowvelle Maniere d’élever ? Eau par la Force de Feu, in which a fteam-engine is defcribed which differs from that of Savery, but may equally.accord with the defcription of the Marquis of Worcefter. From the engraving, fig. 268, in his fecond vo- " Jume, it appears to have confifted of a fpheroidal boiler, a cylindrical fteam-veflel into which was fitted a float or pifton, and an air-veflel which received the water from. each-ftroke previous to its being forced by re-aétion to a greater height. The water flowed through a pipe with a valve opening downwards, whence it paffed beneath the pifton which floated upon it. ~The’ defcéent of the pifton was effected by the fteam, aitd its afcent by}the action of the wa- ter from the original ftock; at which period the {team was fuffered to efcape into the air by means of a cock, and the communication between the boiler was fhut off In thefe engines it may readily be apprehended that the aétion of the direét fteam on any definite furface, fuch, for example, as a fquare inch, will be accurately equal to the.re- action of the water which is forced up; and confequently, that Savery’s engine will require fteam more elaftic than the air of the atmofphere, in every cafe except that wherein the water is raifed by fu€tion, and afterwards fuffered to flow out of the bottom,of the veflel into a chantiel or ciftern: But if this a€ion of fleam be, by. the intervention of fome me- chanifm, tranfmitted to the placé where it is intended it thal! operate, it: will be peffible to régulate the proportions in any defired thanner.' Itwas very early in. the prefent century I that 422 Comparifon of Steam-Engines. that Newcomen and Cawley began their trials of improvement of the fleam-engine with a cylindrical fteam-veflel and pifton depreffed by the weightof the atmofphere, by which means they obtained a fafe application of power for raifing water to heights far beyond any in which the old engine could be trufted, on account of the extreme ftrength required in the boiler and fteam apparatus. This event is probably the caufe why fo little has fince been done to remedy that leading imperfe€tion, or to adapt the original machine to work irfelf without an attendant. It is certain, however, that the weight of the apparatus, and fric- tions of the parts, in all {team engines with a pifton and lever, have prevented their being extenfively ufeful in fmall undertakings, fuch as the blowing of fmall furnace-bellows, the drawing of boats and carriages, with numberlefs other operations where forces not exceeding one, two, or three horfes are wanted. In thefe operations it is highly probable that the engine of Savery would be very ufeful, if it were made to work without an immediate attend- ant; for Defaguliers found the advantage greatly in favour of Savery’s engine, on a fmall fcale, compared with Newcomen’s lever-engine, He had an engine of the former conftruc- tion in his garden, which raifed ten tons of water an hour, about thirty-eight feet high ; and a friend of his ereéted a working model of the lever-engine on the fame fpot. ‘The boiler of this laft was exaétly of the fame fize as that of Defaguliers, and his cylinder was fix inches bore and about two feet in length. It raifed four tons per hour into the fame ciftern. It coft three hundred pounds ; but the engine on Savery’s conftruétion, having all copper pipes, coft but eighty pounds. It muft not be overlooked, however, that this account affords no ftatement of the quan- tity of fuel confumed under each boiler. _ It might perhaps have been the cafe, that Savery’s boiler could have fed a larger cylinder. But at all events there is no doubt of the fact, that the belt lever-engines cannot be advantageoufly ufed when {maller than a determinate fize ; and that, on account of the charge of attendance to open and fhut the.cocks, no trials have been made tofhew upon how fmall a fcale Savery’s engine might be rendered ufeful. Anengine upon Savery’s principle, with various judicious improvements, was erected four years ago by Mr. Kier, at his manufaCtory of coach axle-trees near Pancras, where it has almoft conftantly been worked without repair. It is perhaps on too large a feale to afford much information refpe€ting this queftion ; but is certainly of confiderable value, not only becaufe it works without an attendant, and regulates its own motions, but alfo becaufe, as might naturally be expeted, the wear and tear is altogether inconfiderable. He has per- mitted me to give an account of this engine. The tketch Fig. 2. Plate XVII. reprefents this engine, without extreme pretenfions to ac- curacy, but upon {cale of a quarter of an inch toa foot. KR reprefents an oval boiler feven’ feet long, five inches wide, and five deep. The proprietor confiders it as being of di- menfions fufficient to work a larger engine ; a circumftance which muft, in a certain degree, diminith the effets of the prefent. It feeds itfelf in the ufyal manner, with water conveyed through a pipe at the end of which is a valve. This valve does not open until the fall of the water within the boiler has fuffered a float to fubfide, which by its aGtual weight aflifts to draw it open, but by its tendency upwards, as the water in the boiler rifes, ferves effec- tually to clofe it. The boiler, therefore, remains conftantly at or near the fame degree of fullnefs. The fteam is conveyed by a pipe TAV to abox B, through which, by the open- ing and fhutting of a valve, it can be conyeyed to the working chamber E, The axis C 6 PE se ferves Improvement of Savery's Steam-Engine. 423 ferves as a key to open and fhut the valve. NOis a ciftern of water, from which the fup- ply is made through the vertical pipe in which the valve Q_is placed; and GG is another ciftern into which the water is delivered through the pipe F, which is provided with a valve H opening outwards. IM reprefents an overfhot wheel eighteen fect in diameter, moving on the axis KL, and communicating its motion to the lathes and other rotatory engines of the manufaétory. The water in both the cifterns becomes warmer than the hand after working a fhort time ; for which reafon' the inje@tion-water is forced up by a pump from a well fupplied by the fmall ftream on which thefe works are eftablifhed. A leaden pipe pafles from this forcing pump to the upper or conical part of the chamber E, for the pur- pofe of inje&ting cold water at the proper time. Neither of thefe could be reprefented with convenience in the prefent feGtion. The manner in which the fteam and cold water are altermately admitted into the chamber FE, remains to be explained. Upon the extremity K of the axis of the overfhot wheel there is fixed a folid wooden wheel about four feet in diameter, reprefented in fig. 3, as feen in front, and alfo in profile, where the {mall letters denote the fame things as are marked by the large letters of the alphabet in the front view. ABCD are four cleats, allor any number of which may be fixed on the wheel at atime. Each cleat has its correfpondent block EFGH on the oppofite furface of the wheel. The ufe of thefe is to work the engine. Suppofe the wheel 1M or. any part of the revolving apparatus be drawn round by hand, one of the cleats meets in its rotation with a lever which opens the fteam-valve by a bar of com- munication reaching to the handle of the axis C, fig. 2. The fteam confequently paffes into the chamber E, and the fteam-valve fhuts again as foonas the cleat has pafled. Speedily after this the correfpondent block on the. otiier fide of the wheel meets. another lever, which is fimilarly attached to the handle of the forcing pump, and therefore throws a jet of cold water into the chamber, and condenfes the fteam. The preflure of the atmofphere then forces the water from the ciftern NO through the valve Q towards the chamber E. When the engine has been long out of work, I fuppofe two or three ftrokes may be neceflary to raife the water to the top of the chamber. As foon as this is the cafe, the injection of the fteam fuffers the whole body of water above the valve H to overcome the preflure of the atmofphete and ruth out. The water which is raifed is fuffered to flow upon the overfhot wheel through a fluice, and by that means keeps the work in motion, and replenifhes the lower ciftern. Hence we fee that in effeét this engine is the fame as figure 1. excepting that it is not ap- plied for the immediate purpofe of raifing water, but gives motion to other apparatus. It is therefore unneceffary to infift more largely upon the mere operation; but the peculiarities of Mr. Kier’s engine are deferving of notice. In the firft place it may be obferved, that he ufes no refetvoir for his injeftion water, but drives the requifite quantity up at each ftroke. ‘The advantage of this is, that the pump fuftains the aétion of a very fhort column of water, though it apparently forces to the height of about 26 feet. For the column in the pipe and chamber PE by its re-aétion takes off the effet of an equal length of column which would elfe have a€ted again{t the forcer, and thus renders the injeCtion more eafy and quick. In the fecond place it may be obferved, that he has proceeded direCtly oppofite to the firft re- mark of the Marquis of Worcefter; who reje&ts drawing or fucking upwards. For this engine does not force at all. The water merely falls out of the chamber, and confequently never 424°> Improved Steam-Engine without a Pifton. never requires {team ftronger than the atmofphere. From the effeé& of this -engine-under circumftances of fuch advantage, it may fairly be concluded that the ation of fteam againft water in forcing can never be beneficial except’ at a place where fuel could be had ex- tremely cheap. Thirdly, it was found at the firft’conftruction of this engine, that the con- fumption of fleam by contact with the water was fo great that it could not be worked with , the fmalleft advantage. ‘This defect was remedied in the prefent engine, as well as in an- other at Norwich, by fixing a {mall air-valve -in the fteam-box, which was {truck for an in- ftant immediately before the admiffion of the fteam. It:may be prefumed that the air oc- -cupied a fpace above the water, and prevented their coming together. Mr. Kier, however, is difpofed to think that the effeét-does not take-place.in this manner, but by fome mixture and fudden dilatation of the two fluids; becaufe he imagines the mifchief from the wet cylinder would be the fame upon defcending fteam. Much, however, may be faid in defence -of the oppofite opinion. ‘The air-valve is not at prefent ufed, becaufe the engine does very well without it ; which is fuppofed to arife from its being Jefs air-tight than it was at firft. Fourthly, the motion of the overfhot wheel‘is regulated by an apparatus called a-governor, invented, 2s 1 think, by Mr. Watt, and reprefented i in figure 4. The bar HI revolves by «communication with the engine, and carries round the balls A and B, which move on a fixed jomt’C. ‘When the rotation is very ~quick, the balls fly out, and draw down the points DE, and confequently F, which is fo conftructed as to flide upon the bar or axis HI. A lever, FG, conneéted with the fluice of the upper-ciftern\GG, fig. 2.:is therefore made to fall or rife accordingly as the velocity is -greater or lefs.» By this difpofition, when the wheel moves very fpeedily, from lightnefs of work or any other caufe, the quantity of water thrown down from the upper ciftern is immediately diminifheds and,.contrarywife, the quantity of water is rendered greater when the flownefs of the movement fhews that it is wanted. When I faw the engine at work, it had but one cleat and block upon its wheel, and two men were at work at ftrong lathes, roughing out certain pieces.of iron about two inches in diameter. Whether-it were the unfteadinefs of this work, or-the -want of fuf- ficient celerity of communication, I know not: but the variations in this. governor were upon the whole more confiderable than L-have remarked in a lever-engine with a.fly and this apparatus alfo. Fifthly, as the injeCtion=water makes.a conftant addition to the fum of the water contained in the cifterns NO and GG, the furplus is allowed to overflow. If it were to overflow the lower ciftern, it would warm the water in the injection well; for which reafon a contrivance becomes neceflary to prevent that effect. Mr, Kier’s contrivance is this: —The water of ‘the upper ciftern, when at a certain elevation, overflows into a com- munication which conveys the water to the lower ; for which reafon its contents can never rife above a certain level. There is alfo a pipe from the bottom of the upper ciftern, which is recurved upwards to communicate with a gutter a little lower than the place of overflowing juft mentioned.’ It is clear, therefore, that the upper ciftern would always over- flow at this pipe fooner than at the place of communication with the lower ciflern, if.there were not a valve within'the upper ciftern, over the mouth of the recurved pipe. Now it is fo managed by means of a float in the lower ciftern, that this valve in the upper fhall be opened whenever the water below rifes to acertain level. And confequently, as foon as ever the lower ciftern has received this portion, it can receive no more, becaufe all the fubfe- quent addition of water will pafs away by the recurved pipe, This Improvements of the Simple Steam Engine. 425 This: engine:confumes fix bufhels of good coals in twelve hours’ work when in its beft ‘tate, or feven bufhels when at the worft. Under thefe circumftances it gives ten ftrokes :per minute, each throwing out feven cubic feet of water, at an aperture twenty feet above the water beneath. ‘This quantity, namely 70 cubic feet per minute, will weigh 4345 pounds, which being doubled, to reduce it to Defaguliers’s ftandard height of ten feet, will amount to 8690. And this divided by 580, the number of pounds in a hogfhead, will give a quotient of 15, reprefenting fo many men, according to the eftimate of that author, which he reckons equivalent to three horfes. This refult is not more than half what is performed by the improved engines with a pifton of fuch a fize as to be equal to 20 or 25 horfes. But how far thofe engines would prove effective upon the fmall fcale of three horfes, or the ftill {mailer fcale of one or even lefs, remains to be decided. The-engine here defcribed has been at work four years, and from the fimplicity of its conftruction ‘has yet exhibited no proofs of wear. Mr. Kier thinks it a profitable engine to himfelf, and that it would be ferviceable for raifing water where coals are cheap. A con- trivance he made in the year 1783 might, perhaps, with proper modifications, be ufed to obviate the negeflity of forcing where the heights are confiderable. It is liable, however, to fome flrong objeCtions, and certainly requires to be maturely weighed with regard to dimenfions and effects before it fhould be attempted to be put in practice. Fig. 5. reprefents the contrivance for forcing, as I find it in the original drawing ; and I thought it unneceflary to make any alteration to adapt it to what is called fucking, which might, if required, be eafily done by any perfon flightly acquainted with the fubject. A is a boiler, and B a fteam-veflel. This laft communicates with the veflels MLK, each of which, except the lower one, confifts of two veflels; an interior veffel, clofed on all fides -excepting where it communicates with B ; where pipes P, O, N, I, enter the upper part of each; and alfo where there is a valve at the bottom, opening upwards: the pipes INO likewife communicate with the three exterior veffels K, L, M. If fteam be let pafs from A to B, it is inferred that the air will be driven from B, and prefs upon the water in the lower veffel T, which will be driven into the exterior veffel of K, but not into the interior veffel, becaufe the preflure of the air through the tube H is more than fufficient to keep the valve of the apparatus K fhut. The next ftep in the operation confifts in clofing the cock C, and opening D, out of which the re-action of the water forcing itfelf into T to its natural level, and into the interior veffel of K on the fame account, will drive a portion of fteam. D is then to be clofed, and C opened ; in confequence of which, the contents of T will be forced up to K, as before; and the interior veffel K will evacuate its contents into the exterior of L. The fteam being fhut off at C, and the cock D being opened as before ; the veffel T, the interior veffel K, and the interior veffel L will fill as before, and a larger portion of fteam will iffue from D. A third repetition of the procefs will drive the contents of thefe three interior veffels a ftep higher; and a fourth repetition will caufe the contents of the upper interior veflel M to flow out at P ; after which every alternation of the work with the cocks C, D will throw out the fame quantity from P. I fhall only remark on this contrivance, that the veficl B muft neceflarily contain a quan- tity of air capable of occupying the whole interior {pace contained in the clofed veilels T KLM, with an allowance for the lofs of bulk in condenfation under the preflure of a Vox, 1.—DecemBER 1797. 31 column 426 On the Mechanifin by which the Mariner's Compafs.is. fufpended. column of water equal to one of the lifts, and that the quantity of fteam to be sdifcharged at each ftroke muft occupy a fpace equal to that of all the water moved at each ftroke, and mutt in all cafes be confiderably {tronger than the atmofphere. 4. 1 tag SoeeeeeEe—e—e—eEeoEoEoEooEoEOoooEoEoEooEoEoEoaoaoaoaoaoaoaoa™eaoaoESEeeEEe——eeeeeeEe———eEESS VIL. On the Mechanifm by which the Mariner's Compafs is fufpended. Ir a bar of iron be rendered magnetical, by sabbity it on a-natural magnet, or ae any of the well-known procefles for that purpofe ; it acquires the property of difpofing itfelf nearly in a north and fouth line, whenever it is fufpended fo much at liberty that the energy of this power is fuflicient to overcome the friction or other impediments to. its motion. ‘The mariner’s compafs is an apparatus in which a bar of this kind, called the needle, is fup- ported, for the highly ufefal purpofe of determining the pofition of the meridian at fea, and confequently of enabling fhips to fteer their courfe by day or. night, without, obfervation of the ftars, or any other external objects, as was neceflary before the difcovery of this in- ftrument. In a well-conflru€ted mariner’s compafs the needle is defended from, the im- pulfe of the air, and is little fubje&t to be difturbed by the external motions or agitation, of a fhip at fea. As this difturbance is, however, the chief impediment to the convenient. ufe of the compafs in a boat, where the motions are fudden and fhort, or ina fhip, -when the wayes are very turbulent; and as the artifts in this. branch have endeavoured to perfuade the world that certain pieces of mechanifm were much fuperior in their ufe to others dif- ferently difpofed ;—I thought it might be of fome utility to explain the fimple principles of a good fufpenfion. When the needle of the compafs difpofes itfelf in the magnetical meridian, dere: is acer- tain line within the piece of fteel, which joins its two poles, and may be confidered effec- tively as the needle itfelf. But as this line is not vifible, the admeafurements of pofition mutt be made with regard to fome marks on the extremity of the needle ; which marks will be truly placed when the needle is found to occupy the fame’ pofition with refpeét to a fixed point, upon being reverfed, fo that the lower fide fhall become the upper. If the magneti- cal power had been found on experience to occupy the fame parts of the needle with pro- portional intenfity, during its decay, to that it poffefled immediately after the touch, thefe marks, once made, would continue to fhew the true magnetical points as long as the needle _ poflefled any direCtive force. But it is well known that foft fteel lofes its magnetifm fooner than hard ; and confequently it may be inferred that, unlefs both fides of a needle were equally hard, i agnetic power would deviate in procefs of time towards the harder fide. ‘Thefe confiderations lead to an obvious method of diminifhing fuch growing error. It confifts in making the needle flat and thin, and fufpending it with its edge, and not its flat Gde, uppermoft, as is more commonly done, The needle is ufually fupported on a fteel point, which occupies the axis of a cylindrical box called the compafs-box. For this purpofe there is formed in the needle itfelf a cap or hollow conical centre of brafs, ftcel, or hard ftone, which is, applied over the point. ‘The tendency of the needle to be difturbed by agitation will greatly depend upon the pofition of J the ~ the Mariner s Compafs i is Jufponded. ' ae | ' Ps vertex of the conical cavity: It is neceflary that it fhould be above the centre of gras, vity.; but this diftance muft be fo, {mall as that the libration of the needle when.one end-is deprefied fhall be very flow, and yet {peedy enough to recover the horizontal pofition in-a reafonably fhort time, Jn faét, the whole of the fteadinefs of the compafs and its box ap- pears to depend on this principle of flow vibration. For, if a needle perform its vertical vibration in eight feconds, it will be very little difturbed by an alternate action that lafts but a fecond or two. The greater number of workmen ie imagined that the agitation of the compafs is com- ‘municated by frition at the points or edges of fufpenfion, and have accordingly exerted their ingenuity to diminih this fri€tion, by contrivances. fimilar to that of a conical cap balanced on a point, and itfelf affording another pointtofupportthe needle. But it is very, readily proved by experiment, as, well as argument, that. the greateft difturbance of the; needle is produced, by the, quantity of, horizontal progreffive motion, and not by the mere, inclination, or.angular motion... .A, compafs-necdle, {upported on ja fimple point will fuffex. very little agitation from any angular motion or moderate deviation from perpendicularity. in the pin; but it will inftantly begin to vibrate if moyed horizontally, Thus the common experiment of tilting the compafs-box-in all pofitions while its centre remains, immoyeable is fallacious, and there are. very few compafles indeed which will, bear to be flided, back- wards and forwards upon a table. : It appears therefore that the fteadinefs of a bce which ery flowly, is thi /confe- quence not only of the length of time it allows for alternate a@iions to operate, and deftroy each other ; but alfo of the difficulty with which it yields to {uch impreffions. If the centres of fufpenfion and of gravity in the needle were coincident, no angular motion would be produced by any action of the pin, excepting by the effects of friction; and the angular. motion produced in other cafes will be lefs, the fhorter the diftance between -thefe ¥8 centres, or the lever by which it is propagated. The fimple fufpenfion of the needle on a point has been applied to the compafs- ips, ris which it is little fuited, not only becaufe of the wear upon fo.fmall.a furface, but alfo becaufe it admits the box.to trayerfe horizontally; an effect which is inconvenient, and cannot be. remedied by any means not calculated in fome refpeét to increafe.the effects of agitation. The method moft generally received, and in fact the beft adapted to this inftruments are the gimbals. This well-known contrivance confifts of an hoop fupported upon two pins diasmrsalodlie oppofite each other, and ifluing from the external furface of the ring in fuch a dire@tion that both lie in the fame diametrical line. . When the hoop is fufpended on thefe pins, it is at liberty, to turn freely round thediameter of which they conftitute the prolongation. The notches or holes of fupport are difpofed horizontally... ‘The compafs-box itfelf is’ placed in a Gmilar, ring with two projeéting pivots; and thefe pivots are inferted in holes made in the former ring at. an equal diftance from each of its pivots. If, therefore, we fuppofe the whole,to be left at liberty, the compafs-box, may vibrate upon the diametral line of the outer ring, and alfo upon a line formed by its own pivots, at right angles, to that diametral lines The eonfequence of this arrangement is, that the centre of gravity, of the compafs- box will difpofe itfelf immediately beneath the interfe€tion of both lines on which it is at ats liberty 428 On the Meckanifin by which the Mariner's Compafs is fufpended. liberty to move :—that is tosfay, if the weight of the box or its parts be properly difpofed,.. the compafs will aflume a pofition in which its upper furface fhall be horizontal. The fame principles wiiich were applied to the fingle centre of the magnetic needle will’ alfo apply to-the axis of the gimbals. If the centre of gravity of the compafs-box be fo placed with refpeé to either axis as that its vibrations fhall be quick, every horizontal action will greatly difturb it, and it will not fpeedily fettle. The molt favourable pofition of the pivots or edges of fupport in the gimbals will be when they all lie in the fame plane, and’ the centre of gravity of the compafs-box is very little below that plane. The pra@tical application of thefe inferences appears to be, that, without pretending, as has been done, that any peculiar fecret or great difcovery is required to give ftability to this ufeful inftrument, nothing more is required than good workmanfhip, and a proper adjuft- ment of the weight with regard to the centres or axes of fufpenfion. The needle ought to be adjufted either by means of its cap, or by proper filing away, or elfe by additional pieces to the card, fo that it fhall vibrate very little, and that flowly, when placed upon a point and moved horizontally, whether in the direftion of the needle or at right angles to that direc- tion. The card is then ready for the compafs-box. The box itfelf muft be adjufted ‘with the card in its place, fo that it fhall exhibit the fame fteadinefs when moved in the line of dire€tion of the outer pivots. And laftly, the fame difpofition muft be made with regard to the motion in the dire€tion of the inner pivots. It is fcarcely neceffary to add, that the means of this adjuftment confift in fhifting the pivots themfelves, or; which is much better, in-alteting the difpofition of weight about the compafs-box. An external ring of metal, encircling the box, and raifed or lowered until the proper place for fixing it is found). would perhaps afford the moft convenient method. Upon the whole, the reader will perceive, that the leading aim of the prefent paper is to enforce the truth, that the compafs is very little difturbed, at fea or elfewhere, by tilting the: box on one fide, but very muchi by fudden horizontal changes of place; and, confequently, that’ a fcientific provifion againft the latter is the chief requifite in a well-made inftrument of this - kind. And‘again, thatnothing is more eafy than to afcertain whether-a compals poffefles ftability ; ince nothing more is requifite than'to flide it upon a table in the feveral direQtions above-mentioned, and remark how far it is difturbed. The good workmanfhip of the cap- and pin of the needle may be afcertained by infpe&ion with a magnifier, and alfo by drawing the card with a-fmall key or other piece of iron, a very little quantity, for example a quarter of a degree, out of its {tation or pofition, and remarking whether itreturns accu+ rately to its original ftatiom. Before I’ quit this fubje&,; I-muft take notice, that; as the fufpenfion on a point has been applied to the compafs-box, fo, onthe other hand, the gimbals have been applied to the nee- die. This was-done by the late Dr. John Lorimer, who difpofed'a dipping needle on its own axis between the cheeks of a frame-parallel to the diameter of a circle of brafs gra duated to fhew the angle of dip. This circle or'meridian had pivots at its zenithand ‘nadir, which moved in holes-diametrically perforated im another circle. The needle was by this means not only permitted to difpofe itfelf in a line forming the angle of dip with the hori- zon, but was enabled to carry the meridional circle into the line of the magnetic meridian. It does not appear from the Doétor’s paper and drawing in the 65th volume of. the Philofo- phical On the Maintaining Power in Clocks and Watches. 429 phical Tranfadtions, that he had added the fimple expedient of an horizontal gimbal-hoop to the-crofs circle which fupported the meridional pivots. Such a circle, divided, inftead of the fixed horizon in his figure, would have rendered it a complete inftrument for general pur- pofes:. It is probable however, that for ordinary naval ufe the fimpler compafles of . the: prefent con{truétion would be preferable. VIII. On the Maintaining Power in Clocks and Watches. Tx a former paper.on the compenfations for change of temperature-in pendulums,-a flight view was taken of the methods by which a train of wheels might be made to move either uniformly or by equal intervals of progreffion, fo as to afford'a meafure for the lapfe of - time. The pendulum and the balance are at prefent the regulators which for juft reafons - are preferred to every other:contrivance. If we fuppofe a body to be fufpended at the ex- tremity of a ftring, its gravity, as is well known, will caufe the ftring to point towards the centre of the earth’s gravitation at that part of the furface. If the body be then drawn afide out of this perpendicular pofition, it is equally clear that it will be removed: further from : the earth’s-centre, towards which, when again fet at liberty, it will falk through the are of a-circle, which is the only line the ftring will permit it to defcribe: At the inftant the per- pendicular pofition is thus-regained; the. body will not be.at-reft, but will poffefs a por-» tion of velocity in a-direCtion at right angles to that of gravity. It will not, therefore, be in the power-of gravitation to affect that velocity ;.and confequently the body will proceed : onwards on the oppofite fide of the perpendicular, in a fecond circular arc, which ele-'- mentary writers demonftrate to be in theory-perfectly fimilar, and equal to the are of de- fcent :—that is to fay, the action of-gravity. will more and more oppofe the afcending mo-' tion, as its direction becomes more remote from the horizontal line, and will at length not» _only deftroy the motion of afcent, but again generate a falling motion precifely the fame - as the firft. Such a pendulum would, therefore, if no other circumftances prefented them- - felves than have yet been ftated, vibrate for ever; and its vibrations would be performed in times precifely equal. But the truth is, that fuch a body muft in aétual experiment: give - motion to the air through which it pafles; and muft alfo. overcome: a certain degree of rigidity to which the ftring, or any other fubftitute'in- nature which might be propofed, is fubject. On thefe accounts, the quantity of motion im the pendulous body will be con= tinually diminifhed, and at length become infenfible. It may alfo be eafily apprehended, that a pendulum, though conftructed with fuclt delicacy as to move for many. hours before it comes to apparent reft, could not be of much practical utility without fome ready means to. - keep an account of its vibrations. For both reafons, therefore, a pendulum without any other addition can fcarcely be ufed.as a time-keeper. A train of wheels, urged by a-weight or {pring, is therefore attached to the pendulum for thefe two purpofes, namely, to maintain its motion by a {mall impulfe given at each vibration, or at moft at each fecond vibration, and to keep account of the number of times. The principle of the balance is, that its fimilar vibrations are performed. in equal times, .. like thofe of the pendulum. The methods of adapting the train of wheels to one of thefe regulating organs will not therefore eflentially. differ from thofe of connecting. it with the other. - svt. Optical Phenomenon explainediMh. 3% 0 others {In mot ‘of thefe tont?ivances; the ‘pendulum or balance is, diving fdimepart of its! motion, broughtimithe way ofsone'of the tecth of the laft wheel of ‘the train, at the’ time! when the whole 'fyftem of wheelsare at’ liberty to move. The tooth, therefore): ftrikes’ either the pendulum, ora part ‘of the moyement conneéted with it, and then flips off, or efeapes from that obftacle. The whole fét of parts‘in’a time-piece by which this ‘alter n ionis effeGted,-is-for that reafon.called the.efeapement. : — [To be continued. | —————————————— eee MATHEMATICAL anv PHILOSOP HIGAL CORRESPONDENCE. : : ANSWER, TO, THE Pui.osornigaL QuesTign, Dy B84eip0.¢d To vlimaodicn > Sefer . : é ol au rots ce ae | STR, i qi tad ory > - net ‘ ss Tf! y's i t twee zt at T Mr. Nicuorson. " x ; yw : yim ate "ROM the defcription of the divergent rays feen in agitated water furrounding the fhadow of the obferver’s head, which forms part of the queftion in your fixth number, T did? not fail to; look for the appearance on the firft: opportunity of’ funfhine which offered: °P obferved'the fact-as you deféribe it, and found ‘that the! radiations appear ‘without being” modified in any refpeét by the:diftance of the’ obferver from the ‘furface of the water. © “This! circumflance indicatéd a probability, that ‘the ‘caufe'which'l could not inveftigate by direge reafoning, might be developed. by a nearer infpeétion than could with convenience be made’ on the bank of a river. Withthis view I placed a veflel of water, which was three feet deep,” in an out-houfe, in fuch a'manner that the fun ‘fhone upon ‘its furface. > When I 'placed™ myfelf fo that the fhadow of my Head fell upon’ thé water} I perceived no radiations what! ever; but upon agitating the water with my hand, the water appeared full ‘of the lines called” fun-beam$s, parallel to each other no doubt, but which; on’ account “of the fmaller’ optical” diftance between their remoter than between'their Nearer extremities, Had the appearance” of convergence towards the fhadow. As it is perfetly intelligible from the well-known truth in perfpeétive, that all ‘lines’ /parallel’to the line of fight will vanifh in’ the’ point oF” fight 5 it remains only to be fhewm how thefe diftinét parallél beams ate produced! ©) ©) -When the furface of the water is‘at reft, and forms ‘one plane, the fun’s light forms one ' uniform mafs in which no ‘lines ate! diftinguifhable; ' but when: the agitation takes place, a’ number of convexities and concavitiés are’ produced. Thefe fcatter ‘the rays in all di- re€tions, except at that {mall portion where the contrary curvatures join. The fame phyfical -effe&t is produced as from fo -many ‘fmall planes’; that isto fay, ‘the ‘rays pafs ftraight through each furface, and afford:the patallel diftinct beams’ of light. “And though ” thefe {mall planes are continually forming and'difappearing, yet there ‘are always ‘certain number in exiftence, and the effu@of their tranfient individual variations is nothing more than to produce an undulation in the general fyftem of radiations. 9) 84” And now, Sir, after having refoved your queftion, as I think, fatisfactorily ; I fhall take the liberty to propofé anothet it'the fame department of feience. °°"! RP When the fun thinesy if'two' bédies, fet example hands or fingers, be bradually moved, fo that their thadows'may meet 5 it i oblerved that the fhadow ‘of the body farthelt'from the a Optical Phenomenon.— Odors rendered vifible, AGE the ea will {well out,,and join the) other! shadow when the diftance becomes diminifhed to a certain) quantity, while the fhadow of, the body neareft. the fun undergoes no alteration. What is the nature of) the infle€tion of light which occafions this appearance)?.,,. Lam, Sir, yours, &c. A. Y. *,,* The fact mentioned in the laft paragraph of this letter has. been ftated and explained. elfewhere, though I cannot now recolleét where I have feen it. It does not depend upon inflection, but upon the different widths of the penumbre. When the penumbrze firft inter- fere, a faint lenticular fhade is produced, which is nearer the fhadow of the moft remote body than that of the other; and as foon as the remoter body itfelf comes in contact with the bounding ray of the greater penumbra, it begins totally to intercept the fun’s light on the fide next its own fhadow. . The time employed in pafling from one extreme ray of the penumbra to the other will be lefs the nearer the bodies are to each other, becaufe the diftance of thofe rays is lefs the nearer the vertex. ‘The fhadow of the remoter body will confequently run over the penumbra with greater {peed than that of its former progrefs; and if any part be. convex, it will advance beyond the others.» ; To Mr. NicHoLson. SIR, HAVING obferved in the’ 4th Number of your Journal *, and likewife in the Annales: de Chimie, an extraé& of Mr. Prevoft’s’ Memoir on the means of rendering vifible the emanations of odorant bodies ; I take the liberty of communicating an obfervation which occurred to me a few years ago, while making experiments with different “fubitances ex- pofed to the oxigenated muriatic acid-gas. That which afforded- the ¢ curious phenomenon . to which I allude, was fome highly-reCtified animal ‘oil. ‘ This’ matter, immediately on being expofed to the gas (which was in ‘avery dry flate),"was feet to'emit’a copious fteam, the particles of which rifing to the height-of-about four inches above the fmall phial in which the oil was contained, were then obferved gradually to defcend, forming avery cu- rious and pleafing A pein! Seca {truck at the time with ‘the fingularity of this. phenometion, and endeavouring to acéount for the formation ‘of the vapdur by a fuppofed union of the hydrogen of the emanating matter with the fupéabundaint oxigen of the gas; yet I omitted’ at the time, and have fince neglected, to endeavout to verify my conjeCtures by further trials—The circumftance, however, revived in my recolle€tion on reading your Journal ; and conceiving it to be an expetiment that affords a nearer approach to the abfolute perceptibility of an odorant vapour, than thofe {tated in the Memoir of Mr. Prevoft, . r impart it ie your further invetigations if thought worthy your attention) and’am 1 Your obliged reader; Now, 245 4997s sie HOWARD. N. B. The oil was the only odorant fubftance tried : perhaps many others might afford a fimilar or varied appearance. *,,* The philofophical confideration of odorant bodies is fomewhat obfcured by the old method of generalifing, or referring the properties of bodies to fome diftin& principle or * Page 153. “See alfoon thisfubjectyypr 20g N. ‘ thing bad 432 ' Mathematical and Philofophical Correfpondence. thing fuppofed capable of being feparated from the body itfelf. Thus’ the odors of bodies have been fuppofed to-depend on a fubftance imagined in a loofe way to be common to them all and feparable from them. Hence the terms, principle of : fmell, f{piritus reGtor 5 and even in the modern nomenclature we-find arama. ‘There does not in effect feem to be any more reafon to infer the exiftence of a common principle of fmell than of tafte. The fmell of ammoniac is the action of that gas upon. the organ of fenfe ; and this odorant invifible matter is exhibited to the fight when combined with an acid gas. But in’ the {ame manner as ammoniac emanates from water and leaves ‘moft part of that fluid be- hind, fo will the volatile parts of bodies be moft eminently produdtive of this a€tion ; and very few, if any, natural bodies will be found which rife totally. The moft ftriking circum- ftance in the effect is, that an act of fuch power fhould be attended with a lofs by exhala- tion which is fcarcely to be appreciated by weight, or in any other method during a fhort interval of time. But we know fo little of nervous action, and of other phenomena of electricity, of galvanifm, or even of heat, which ftrongly affect the fenfes but elude Admeafurement by gravitation, that the difficulty of weighing the effluvia of odorant bodies - becomes lefs aftonifhing. “Question XI. An/wered by F. F—:—:—:—R. “LET H+ be the altitudes of the two fignals or other objects, A their dire& angular diftance, and a their difference of azimuth, as ftated in the queftion. It is proved by the writers on fpherics, that, in any fpherical triangle, Cof. any angle : radius :: radius X cof. oppofite fide —re€tangle cofines including fides : rectangle fines including fides; which analogy, applied to the triangle formed by the zenith-diftances and direét angular dif- tance of the elevated objects, gives, Cof. a: radius :: radius X cof. A — fine H x fine 4 : cof. H x cof. 4; fothat cof. A xX radius = cof.a x cof.H xX cof. 4 + fineH x fine 4; or, putting radius =.unity, Cof. a = cof. a x cof.H x cof.4+fineH x fines. Q.E.D. Question XII. Anfwered by Mr. WriL1aM CASTILAD, of Uffington, Salop. LET ZP © reprefent the zenith, pole, and fun refpectively ; x the cof. of 4 PZ @: then,.per data and a well-known theorem in fpherics, SZ © x SPZ-X cof. 4 © ZP + cof, Z © xX cof. PZ = cof. P © (rad. being 1); that is (putting d for fine of the fun’s dec. 15° 9 or .26135) * X* Xx + 1—a2x.=d: this equation ordered is x3 —2*=d—1 = —.73865, whence x = —.66588 = cof. 131° 45' .*. 48°15' will be the azim. when equal to the lat. and alt. on the given day. The 4 ZP © alfo = 2"3'54”. Per Naut. Alm. the fun’s declination for noon, on the given day (at Greenwich), is 15° 18’ 28’’, and its change for 24™* = 18/7” .*. As 18/7" : 24" :: 15° 18’ 28.— 15° 9’: 12" 32’ 27” the time from noon at Greenwich when the obfervation was made. ‘The latitude of ‘the place of obfervation, then, is 48°15’ N. and its longitude (12° 32" 277 —2" 3’ 54”) 10" 28/33” E. of Greenwich. > The fame was anfwered by 7. F—:—:—:—-2, GOVOCOCCCCVICO GV CC OOOO 4a ' fete \) i eee 3 ttl : -* i. * The eregenal Steam CMDR WIL Lnprever CVS. a zi < Shelos. foarnat Vell Plate MM Laci jos 4: A aie 9 ie i A eA 6 ns NATURAL PHILOSOPHY, CHEMISTRY, . AND F THE ARTS. sy ANUARY 1798. ARTICLE I. Experiments made with a View to alcertain the Caufe of Buildings, which have Metallic Con du€tors belonging to them, being firuck by Lightning. By Litutenant-Colonel HALDANE. Ir is not neceflary, in the prefent communication, to enquire what may be the nature of electricity ; whether it exift in the form of one fluid only, and all its phenomena depend upon the prefence of a greater or lefs quantity than naturally belongs to all bodies; whether its effets may depend upon the influence of oppofite polarities, and the operations of at- tractive and repellent powers in a fingle fluid; or, laftly, whether it exifts in the form of two different, though always co-exifting, fluids, produced by the union or the feparation of certain gafes, which belong to electric and non-ele€tric fubftances, according to their various ele€tive attractions, and which may be brought into aétion by the attrition of thofe fub- ftances, either in the form of heat or of electricity, according to their different combina- tions. Thefe, it muft be admitted, are points of curiofity and importance ; but at prefent it is only neceffary to admit, what was clearly afcertained by Dr. Franklin, and fince confirmed by the obfervations of many other ingenious and able philofophers, that there is a famenefs between the matter of lightning and the electrical fluid. And ele€trical experiments, al- though the refults of them cannot be compared with the effects produced in the yaft and ex« tenfive operations of nature ; yet, by exhibiting to our view fimilar appearances, they may furnifh us with notions of, at leaft, the proximate, though we may for ever remain ignorant of the more remote, caufes which produce thofe moft wonderful, and fometimes moft dreadful, effeéls. Electricity, attached to the fame kind of fubftances, fhews itfelf in two different forms, Von. L.—Janvary 1798, 4 3K which 434 The Elefric Charge Natural and Artificial. which have been diftinguifhed by the terms poftive and negative electricity. Thefe alge- braical terms are well fuited to defcribe either two different fluids, or two different ftates of the fame fluid; for it is well known by experiment, that eleétricity, under thefe different forms, has the property (like pofitive and negative quantities in algebraical. computations) of deftroying the effects of each other, when united insequal quantities. The enquiries hitherto made upon the fubje&t of this paper, have in general been con- fined to what relates to the operation of onefluid only ; but in thefe experiments the joint operations of the pofitive and negative ele€tricities are confidered, to which probably many appearances, that have hitherto occafioned much controverfy arene y refpecting the forms of conduétors, may be afcribed. It is a known faét in ele€tricity, that if the furfaces of two metallic bodies be placed op- pofite and near to each other, the one infulatéd, and the other conne&ted with the earth; if a thin plate of any electric fubftance be introduced between thefe furfaces, and extending beyond their extremities, if eleCtricity be then communicated to the electric by means of the infulated metallic fubftance, the orher metallic fubftance conneéted with the earth has the power of putting the fide of the ele&tric with which it is in contaét into the oppofite ftate of ele€tricity ; and the pofitive and. negative ele@ricities on the oppofite furfaces of the ele€tric, by their attraétive powers, retain each other in their refpective fituations. And, in folid ele€trics, even after the removal of the metallic fubftances, if the fame, or other conduéting fubftances, having a condu€ting communication between them, be applied again to the oppofite fides of. the charged eleCtric, all cleétricity will difappear, filently, or with an explofion. Thefe are the phenomena of the eleétric jar. It is alfo well known, that if a body of atmofpheric air, included between metallic fur- faces, be the eleétric employed in the experiment above defcribed,. fimilar effects will be produced. “Hence it may be inferred, that the effets of lightning.may arife from the.difcharge of large bodies of eleétrified air; the upper furface of which will be in one ftate of electricity, and the furface adjoining the earth and terreftrial bodies will be in the oppofite flate; and when thefe bodies of charged air pafs over lofty buildings capable of forming a conducting communication between their oppofite furfaces, the explofion of lightning takes place. The lower furface of a body of charged air may extend over the whole, over a part, or over no part, of a building, at the time it is ftruck. by lightning; the building forming only a part of the condu€ting communication. Buildings in general have many metallic fubftances belonging to them: it is to thefe fub- ftances, and to their imperfe@ conne€tion with the earth, that moft of the mifchief that arifes from the effects of lightning is generally afcribed. To prevent this milchief, metallic conduétors have been attached to buildings. The adyantage expected from thefe conduétors is founded upon a fuppofition, that the matter of lightning will always prefer, in its paffage to the earth, a contifued conduéting © fubftance to one that is broken or interrupted by non-conducting fubftances ; and therefore it is fuppofed that a conduétor, conftruéted of a perfectly continued metallic fubftance, and extending from above the upper furface of a building into the earth, below its foundation, will receive and convey the matter of lightning into the earth, and prevent the mifchief. that Apparatus for Ele&rical Experiments. 435 that might happen by its ftriking any metallic fubftance which is not continued to the earth. . But buildings furnithed with fuch condudtors have been ftruck by lightning : it is obvious,. therefore, that the lightning muft either have pajfed to the damaged part without approach- ‘ing the conduétor, or it’ mutt have ftruck from the conduétor to the damaged part: for, al- though all metailic fubftances belonging to a building may be placed at a diftance from the conductor, yet it cannot be fuppofed that any diftance within the limits of a building can exceed the friking diflance of lightning. vu The apparatus with which this experiment was performed, confifts of an ele€trical ma- chine having a glafs cylinder of about 18 inches diameter, conftruéted by Mr. Nairne, in the form of his patent electrical machines. : Two hollow cylinders *, made of thin wood covered within and without with tinfoil, are placed, in a vertical pofition, upon two infulated circular boards; the glafs pillars which fupport the infulated boards are about a foot in height, and are fixed into thick circular: boards, covered alfo with tinfoil, and refting upon the floor of the room. The interior diameter of each of thefe cylinders is 18 inches; the height from the infu- Jated board upon which it ftands, eight feet fix inches, including an hemifpherical top; and the diftance between them is about five feet. From the centre of each of the boards, that reft upon the floor, rifes a thick’glafs pillar, which paffes through a hole of a foot diameter in the centre of the infulated board into the hollow of the cylinder. This pillar of glafs extends about fix inches above the infulated board, and fupports, in a vertical pofition, another cylinder made. of wood, and covered with tinfoil. This interior cylinder is one foot in diameter, and its height is fix feet fix inches, includ-- ing an hemifpherical top, It is placed exaétly parallel to the exterior cylinder, the interval in every part being three inches. To this interior cylinder is fixed a metallic chain, by which it can he connected with the exterior cylinder, fo as to form only one infulated body covered with tinfoil; or can be connected with the earth, whilft the exterior cylinder remains infu- lated. The apparatus has alfo a moveable.infulated body, made of cork covered with tinfoil, to reprefent a cloud moving in the air. And alfo two metallic rods placed upon infulated ftands, that they may be connected with, or detached from, the earth at pleafure. Thefe rods are ufed to reprefent the conductors, or any metallic fubftances that belong to buildings; their forms are varied by fixing balls or points upon their upper extremities; and the ftand in which they are placed being hollow, they can be placed at any height by means of a fcrew. To thew the effeéts of the paflage of the eleétrical fluid, two infulated metallic balls are placed within the /rriking diftance of each other; and, in the interval between them, is put fome inflammable fubftance, fuch as dried powdered rofin mixed with cotton. * Te may be of advantage to the reader to.confult the literal references atthe end of this memoir before he proceeds. N. 3K2 EXPE: 436 Experiment with an Artificial Thunder-Cloud. EXPERIMENT. THAT this experiment might refemble, as much as an eleétrical apparatus is capable of exhibiting, the operations of nature, it was performed by charging and difcharging plates of air. Arrangement of the Apparatus. THE metallic chains affixed to the interior tinfoiled cylinders are connected with the tin foiled boards which reft upon the floor of the room. A metallic communication is then made between thefe boards, and another metallic communication between the exterior cy- linders, which remain infulated. The exterior cylinders, thus united, are conneéted with one of the conductors of the elec- trical machine (in this experiment it is with the pofitive); the other conductor (or rubber) being connected with the earth. The eleétrical machine being put in action, the exterior tinfoiled cylinders become electri- fied; and, the interior cylinders being connected with the earth, the body of air between them becomes charged ;- and, if a circuit be made between the exterior and interior cylin- ders, an explofion takes place, and a ftrong eleétrical thock may be felt. The exterior cylinders reprefent the upper furface, and the interior cylinders reprefent the lower furface of a body, of charged air in the atmofphere, The moveable body, reprefenting a cloud moving in the air, is conneéted with the exte- rior cylinders, by which means it becomes a part of the upper eleétrified furface of the body of charged air, and can be made to pafs over the building at pleafure. One of the metallic rods, placed in perfe&t communication with the earth (but feparate from the communication of the interior cylinders with the earth), reprefents a metallic con- duétor attached to a building. The infulated metallic balls, with the rofin placed in the interval between them, are fup- pofed to reprefent any metallic fubftances belonging to the building. A glafs tube filled with water, and about 18 inches in length, is placed between the con- duétor and one of thefe balls, to reprefent a conducting communication, which muft fre- quently occur during a thunder-{torm, between the conductor and other metallic fabftances belonging to the building. Since a conduétor may be raifed to any height at pleafure, it is, in this experiment, fup- pofed to be raifed rather beyond the diftance at which any pointed metalli¢ fubftances be- longing to the building might, by their influence on the operations of the electrical fluid, endanger the building, This experiment may be divided into three cafes. 1ft, The eletricity oppofite to that of the cloud may extend over. the conduétor, and all other metallic fubftances belonging to ‘the building. dly, It may extend over fome metallic fubftances, but not over the conduc- tor. gdly, It may not.extend over the conductor, or oyer-any part of the building. CASE Experiment with an. Artificial Thundev-Cloud. 437 CASE I. THE eletricity oppofite to that of the cloud, that is, the lower furface of the body of charged air, is fuppofed to extend over the conduétor, and over all metallic fubftances be- longing to the building. The conduétor is therefore conneéted with the communication between the interior cy- linders; and one of the infulated balls being conneéted by means of the glafs tube with the | conductor, let the other ball be conneéted with the interior cylinders. RESULT. WHEN the conductor was terminated by a point, and the cloud paffed near it, an explo~ fion took place upon the point, and the eleétrified air between the cylinders was inftantly, dif- charged, When the cloud paffed at a greater diftance, no explofion took place; but the electricity difappeared from the-tinfoiled cylinders, and the plate of air between them was filently difcharged, as was fhewn by the ele&trometer. When the conductor was terminated by a ball, and the cloud paffed near it; the ball was ftruck, and the plate of air between the cylinders difcharged as before : but when the cloud pafled beyond the /friking difiance to the ball, the tinfoiled cylinders continued eleGtrified, as was fhewn by the electrometer ; and the plate of air remained in a charged ftate. In this cafe no fparks paffed between the balls where the rofin was placed. PAUSE) oii: THE lower furface of the body of charged air is now fuppofed to extend ’over fome of the metallic fubftances belonging to the building, but not over the conduétor. The communication between the conduétor and the interior cylinders being removed, the remainder of the apparatus was arranged as in the firft cafe. f RESULT. WHEN the conductor was terminated by a point, and the cloud paffed near to it; a fpark took place on the point, and the rofin in the interval between the balls was inftantly fet on fire. When the cloud pafled at a greater diftance, the eleétricity of the charged air difap- peared filently, as in the firft cafe. When the conduétor terminated by a ball, and the cloud paffed near to it; it was ftruck, and the rofin between the balls inftantly fet on fire: but when no fpark paffed between the cloud and the ball, no {parks paffed where the rofin was placed, and no decreafe of elec- tricity appeared upon the tinfoiled cylinders. CASE ill. THE lower furface of the body of eleétrified air'is now fuppofed not to extend’ over any part of the building, and confequently not over the conduétor, or over any other metallic f{ubftance belonging to it. 3 There- 438 Experiments on the Chargé of a Plate of dir, Ge. Therefore the metallic rod, which reprefents the condu¢tor, remaining as in the laft cafe ; the metallic ball which was conneéted with the communication between the interioy cylin- ders has now a feparate communication with the earth only. RESULT. WHEN the conduétor was terminated by a point, and the cloud paffed near it; fome weak {parks paffed from it to the point on the conductor. If the cloud pafled at a greater diftance, no fparks appeared, but the electricity on the tinfoiled cylinders was diminifhed as in the former cafes. When the conductor was terminated by a ball, weak {parks paffed between the cloud and: the ball, and the electricity of the tinfoiled cVlinders decreafed; but-when the cloud pafled at a diftance above the point at which no {parks paifed, there was no variation to be obferved' in the eleétricity of the charged air. In this cafe no fparks paffed in the interval between the balls where the rofin was placed. To the three cafes already exhibited, a fourth may be added, to fhew that the lightning may have paffed to the damaged part of the building without having {truck the condudor. Although a conduétor may be extended to a confiderable diftance aboye the building, yet: fome part of the upper furface of the body of charged air may approach as’ near to fome of. the metallic fubftances belonging to the building as to the conductor ; and which may be ex+- hibited in this cafe in two parts. Ee CASE IV.—Part I. THE metallic rod, which reprefents the conductor, has a.perfeét communication with the earth only ; the glafs tube filled with water, which conneéted it with one of the infulated balls, t being remoyed. The other metallic rod, which is to reprefent any pointed metallic fubftance, is placed upon an infulated ftand, and is conneéted by a metallic communication with the infulated ball to which the tube of water had been attached; the other infulated ball remaining conneAed with the communication between the interior cylinders as before. The lower furface of the body of charged air is here fuppofed not to extend over the conductor, or over the other metallic body, buf to extend over fome fubftance within ftrik- ing diftance of it. That the cloud might pafs at nearly the fame diftance from the point on the metallic rod as from the conductor, the point on the metallic rod was fixed nearly at the fame height as the upper extremity of the conductor. RESULT. WHETHER the conduétor was terminated by a point or by a ball, and the cloud pafféd near to it as well as to the point upon the metallic rod, fometimes the conductor was ftruck, fometimes the point upon the metallic rod was Bruck; and which inftantly fet fire to the rofin between the balls. Sometimes, when a fpark paffed between the cloud and condu€tor, and no {park upon the point of the other metallic rod; {parks would appear between the infulated balls, and of fuf- ficient ftrength fometimes to light the rofin. Thefe Experiments on the Charge of a Plate of Air, &'c. 439 Thefe fparks were the weakeft when the conductor was terminated by a point, and «much ftronger-when it was terminated by a ball. This circumftance feemed to fhew, that the paflage of the ele€trical fluid is not confined to one circuit only. CASE IV.—Parr II. THE lower furface of the body of charged air is now fuppofed to extend over the con- -dutor; the other metallic fubftances remaining in the fame ftate as before. The conduétor is now connected with the communication between the interior cylinders. RESULT. “WHEN the cloud paffed near to the condu€tor, and alfo within ftriking diftance of the point upon the other metallic rod; no explofion or {park appeared in any of the intervals; but the body of air was filently difcharged, aswas fhewn by the ele€trometer : and the fame effect was produced, when, by lowering the point upon the conduétor, the cloud pafled nearer to the point on the metallic rod than to the conduétor. When the conduétor was terminated by a ball, the ball was ftruck when the cloud pafled near to it; and if the ball was fituated as the point was, fo that the cloud pafled nearer to the point upon the metallic rod than to the ballon the conduétor, the point on the metallic rod was ftruck, and the rofin inftantly lighted. CONCLUSION. FROM this experiment it appears to be manifeft, that the advantages arifing from me- tallic conductors, ere€ted for the purpofes of fecuring buildings from [the effects of light- ning, depend more upon the lower furface of the body of charged air extending over them, than upon their form or conftruétion. It is not eafy to decide, from the refult of the experiment, whether they fhould be ter- minated by points or by balls. Probably, with refpect to the large operations of nature, there may be no difference. The ball ufed in this experiment is three inches diameter; the largeft furface of charged air fearcely exceeded 70 fquare feet’: but if fome acres of charged air were brought into aétion, the ball of three inches would foon be reduced to a point. However, as the fubjeét has occafioned much controverfy, we may take the oppor- tunity of inveftigating it from the data afforded by this experiment. If we reafon upon what is exhibited in the firft and third Cafes, it is obvious that pointed conduétors are to be preferred to thofe terminated by balls. They have the property of act- ing at a much greater diftance than balls, and have the power of deftroying, filently, the effeéts of lightning, when balls can only accompliflr it by means of an explofion, which mutt always be attended with fome danger. But if we reafon upon the refult in the fecond Cafe, we fhall find that the power which points have of aéting at a greater diftance than balls, will make them more liable to produce the mifchief fhewn in that experiment. 1 Under . 440 On the Terminations of Condufiors for Lightning. Under thefe confiderations, the conduétor terminated by a ball might be thought pre- ferable to one terminated by a point: but when we recollect that moft of the metallic fub- ftances which belong to buildings are generally terminated in edges and points; that.they have the fame influence as the point upon the conduétor; that their operation may be at- tended with more danger, and that they may extend their influence beyond that of a con- dudor terminated by a ball; we may therefore conclude, that the height to which a pointed conduétor is generally raifed above thé other metallic fubftances b@longing to a building, when compared with the.vaft diftances at which lightning can aét, will not increafe, in any great degree, the danger to which a building may be expofed under the circumftances exhi-+ bited in the fecond cafe of this experiment: and therefore condu€ors that are terminated by points are more likely to produce the good effets expected from them than thofe which are terminated by balls. Thefe confiderations upon the effeéts that may be produced by the joint operations of po- fitive and negative electricity, have, thus fir, been confined to what may happen within a {pace occupied by a building; but they may be extended to much greater {paces upon the furface of the earth. A conductor may be ftruck by lightning, and (if the lower furface of the body of charged air extends over no part of the building) may convey the lightning in- to the earth, without the leaft mifchief being done to the building; but when the lightning arrives at the lower extremity of the conductor, there is no proof that by its union with the earth it becomes decompofed. That decompofition cannot happen until it becomes united with its oppofite eleCtricity, which may be attached to a body of earth or fubftances far re- moved from the conduétor. - The lightning will therefore continue its operations until it ar- rives at the place where the oppofite ele€tricity is prefent, and in its paflage will occafion much mifchief if it does not meet with good conducting fubftances. + The accidents which have been known to happen at a diftance from the place which was feen to be ftruck by lightning, haye been afcribed (by reafoning according to the theory of Dr. Franklin) to what is called a returning /lroke; but it might, with an equal degree of probability at leaft, be afcribed to the objec to which the accident happened being within the circuit which the lightning makes between the oppofite furfaces of a body of charged air. London, Nov. 295. 1797- HENRY HALDANE. In addition to what has been already. written two figures are annexed (Plate XVIII), The firft is a drawing to reprefent a building furnifhed with a conduétor, which is fuppofed’ to-be ftruck by lightning. The fecond is a plan of apart of the eleCtrical apparatus, arranged.as defcribed in. the fecond Cafe of thefe Experiments. References to Fig. I A A reprefents the upper furface of a body of charged air. B BB the lower furface of the fame body of charged air, which is attached to the earth and terreftrial bodies, and in an oppofite ftate of eleAricity to that of the upper furface A. A. This lower furface may extend:to the places. marked 1, 2,-3 ; that is, the limit-of charged air may be reprefented by the dotted lines ite 1; A 2, A 3; as:defcribed-in the three: Cafesiof the Experiment. C the conduétor. } CF The Elesvical Apparatuso—New Air-Pump. 441 CF, the paffage which the lightning‘may take, according to the fecond Cafe of this Experiment, and damage the fame building at F; if the limit of charged air be at A 2; or the building near to it, if the limit of charged air be at A 3. , References to Fig. I. A A, the exterior cylinders. B B, the interior cylinders. The interval between them is fhaded, and contains the air which is charged. A A, the metallic rod which connects the exterior cylinders, B B, the metallic rod which connects the interior cylinders. C, the conductor. D and E, the two infulated metallic balls. CD, the glafs tube of water which connects the condudtor-C with the ball D. ER, a metallic rod, which conneéts the ball E with the communication B B, between the interior cylinders. F, fome inflammable fubftance, as rofin-mixed with cotton, placed between the balls D E, G, a metallic rod, to reprefent any metallic fubftance belonging to the building, to be placed or removed at pleafure. (It was ufed in the fourth Cafe, but was removed from the apparatus in the fecond Cafe.) HH, circular pieces of cork covered with tinfoil, fixed to a metallic rod PH. _ This rod P-H is fixed at O, into a glafs pillar of about ten inches in height ; the lower end of the glafs-pillar is fixed into the centre of a wheel S, which turns upon a pivot that is fixed into the table T. The edges of the wheel S being grooved, two cords-are applied to oH two grooves. Thefe cords, pafling through pulleys in the table and alfo.in the ftand of it, are conveyed to the hand of the perfon who is turning the cylinder of the ‘elegtrical machine, by which means he can make the body H revolve at pleafure. _ From the rod at O rifes a metallic ftem, with a feareln upon the top of it. To this Fetvcl is fixed K L, which conneéts it with the exterior cylinder A. Over the top of this ftem below the fwivel pafles a cord, fixed at one end to the centre of H, and at the other to the balance weight P, which ferves to keep PH in an horizontal pofition. M N, a metallic rod which connects the exterior patasens A A with the pofitive cons duGor of the electrical machine. - The metallic rod M N is about eight feet above the floor of the room, and the moveable rod P H trayerfes at about fix feet above the floor. H. H, Il. New Confiruftion of the Air-Pump. By FaMES SavLeER, Efy. Chemif} to the Admiralty, I HE conftruétion of the air-pump, with the improvements of Mr. Cuthbertfon and the Rev. J. Prince, have been explained in a former communication *. In order that the effec of this inftrument may be as perfect as its theory will allow, it is neceflary that its valves ; fim Philofophical Journal, i, 119, Vor, L—Janvary 1798. “3 L thould 442 New Conftru&tions of the Air-Pump. fhould infallibly open at the requifite periods of the operation, and that the {pace between the pifton and the upper or the lower valve, when at its extreme pofitions, fhould be the leaft poffible, or rather that there fhould be no vacuity remaining. It has been fhown that in the air-pump of Prince the lower fpace is abfolutely out of the queftion, becaufe there is no lower valve ; and the upper fpaee may be, and probably is, much diminifhed by the effect of theoil. The air-pump of Cuthbertfon, in which the conftruéction of the valves is moft admirable, and their aétion abfolutely fecured, feems to poffefS a ftill greater portion of this Jaft advantage from the circulation of the oil, though not dire¢tly intended to anfwer this purpofe. Mr. Sadler has direéted his attention immediately to the good effets which a due application of that fluid is calculated to produce, and has conftructed an air-pump, pof- felling the defirable requifites of fimplicity, cheapnefs and power, of which Figure r, Plate XIX. is a fketch. , A Breprefents the barrel, Qa folid pifton or plunger fitted into the barrel, and leathered fomewhat loofely. O is the pifton-rod, capable of being raifed and deprefied in the ufual way by a handle and toothed wheel which aéts upon the flraight rack-work. The barrel commu- nicates, by means of the pipe C, with a chamber D, at the upper part of which is a valve K, opening upwards into acifternL. P is the plate for the receiver, through which a commu- nication-pipe N E paffes to the interior part of the veffel, D. At the lower extremity I of this pipe there-is a valve, connected with the lever F H, by a wire F E paffing through a collar of leathers. G is the axis of the lever FH, upon which, by means of a weight at H, an ation is produced which preffes the valve E upwards into its place. H [ is another wire or tail, by means of which the extremity H of the lever may be raifed, and confe- quently the valve E opened. From thefe particulars the effeét of the machine may be explained. Let the pifton be drawn out and the barrel filled with oil, which will of courfe rife to the fame level in D. Let the pifton then be put inand preffed downwards by turning the handle. The oil will be driven from the barrel into D, driving the air before it through the valve K fo com- pletely, that a portion of the oil itfelf will follow into the ciftern L. Let the pifton be again drawn upwards, and the oil will follow, becaufe D is higher than the valve, and will confequently leave an empty fpace in this veffel D. As foon as the pifton-rod has ar- rived at acertain height, it will a€t by means of a prominence upon the catch I, and open the valve E. A portion of the air in the receiver will therefore rufh into D. Upon the return of the pifton the valve E will in the firft place fhut, and the air in D will be ex- truded through K. This extrufion will be as complete as before, becaufe at every ftroke a portion of oil from the. ciftern L will pafs through the pipe L M to the upper part of the barrel, and efcape befide the pifton while rifng, on account of the loofe manner in which it js leathered. From this contrivance it is provided that the internal part of the machine fhall contain oil fufficient not only to difplace the air, but even to pafs through in a fmall ” quantity after it by means of the valve K ; and confequently, by working the apparatus the exhauftion may be carried to any defired degree. Fig. 2. reprefents the fame machine viewed in another direétion. ; In the prefent pump the valve K may be confidered as reprefenting the valve which clofes the upper part of the barrel in Cuthbertfon’s pump, and the valve E as the lower fixed valve, We fee therefore from this combination that the folid pifton is made to a&t both ways, in the New ConftiuEion of the Air-Pump. 443 the fame manner as if a fide valve had been made in Cuthbertfon’s barrel, opening out- wards beneath the pifton, and the pifton itfelf had been made folid. Forin fuch an arrange- ment the rifing ftroke would have drawn the air out of the receiver, and the defcending ftroke, would have driven it out fideways. But Mr. Sadler has removed the objections which might be made to fuch a difpofition, by making his pifton in effect fluid, and therefore capable of adapting itfelf to every cavity or irregularity in the veffel D. How far it might be found, in procefs of time, that the oil might become changed by the circulation, and lefs fit for the purpofe ; whether it might carry minute bubbles of air along with it, and whether mercury or any other fluid in veffels of fuitable materials might be pre- ferable, I know not. But thus much is certain, that the means of conftructing an inftrument of this kind, with a few flight variations to facilitate the execution, are within the power of many ingenious philofophical men who have neither the ability nor the skill to procure a good air-pump of the other conftructions. Fig. 3 reprefents a barrel in which the imperfeétion of a {pace-between the pifton and lower valve is obviated, and the aétion of this laft valve fecured. A is reprefents the barrel ; ©, the pifton rod ; C, the valve in the pifton; I, the leathers 3 LL, a hollow cylindrical piece of metal, which nearly fits the cavity M M, which furrounds the lower valve D and itstube. The piece L L doesnot touch the barrel, and there are two holes, K K, commu- " nicating with the central cavity in the pifton, from the fpace between L and the barrel. This pifton alfo is not leathered very tight, becaufe it is intended that the preflure of the atmofphere thall force a portion of oil into the lower cavity of the barrel during the afcent of the pifton. P is the tube which communicates with the receiver. N is a flopping {crew ferving to clofe a hole through which any fuperfluous oil may be drawn. GEisa ‘ lever applied to open the lower valve D, when the pifton has rifen to a certain height, and by a proper communication aéts upon the extremity G by the wire H. Let it be fuppofed that the pifton is down, and that oil is poured into the barrel above it. While the pifton is drawn up, a portion of the oil will infinuate itfelf paft the leathering into the partial vacuum below. As foon as the pifton has rifen nearly to its limit, the valve D will be opened, and part of the air in the receiver will pafs into the barrel through P. Upon the return of the pifton the valve D will in the firft place clofe ; and when the pifton fhall arrive at its lower ftation, the oil in M M, being difplaced by the piece LL, will rife through all the cavities: of the pifton, and drive out whatever portion of air may not have efcaped through C during the defcent. “And fince every rifing ftroke of the pifton will be attended with the tranfition of a portion of the oil from the upper to the under part of the barrel, the fpace M M will, at the end of every defcending ftroke, be found to contain not only. a fufficient quan- - sity to ill the place which would elfe have been occupied by air, but alfo another portion, “which will pafs through C at the termination of the ftroke, and complete the effect. 3L2 WI, Obfervations 444. Experiments with Phofphorus and Il. Obfervations on Phofphorus. By Citizen’ BRUGNATELLI, ‘Profiffir’ of Chemifiry, ‘| at Pavia*. Ix one of the’public meetings of theLaboratory of the Univerfity, when the fubject related to the peculiar properties of Kunckel’s phofphorus, and required thofe experiments to be re peated upon which Gcettling has built: his theory in oppofition to that of the French ches mifts.; I repeated the valuable experiments of Fourcroy and Vauquelin, which are defcribed in the prefent volume +, which fhew the error of the German chemilts ; and as I have ob- ferved fome peculiar circumftances not mentioned by the Parifian chemjits, I flatter myfelf that a detail of thefe experiments will not difpleafe my readers. EXPERIMENT I.—The rapid Solution of Phofphorus in pure Oxygene Gast ; and its Cambufion, which takes s place by the Mixture of other Gajfes. I Sepa ae a cylindfical piece of | phofphorus fupported-on a tube of, glafs i into a long- jar, the upper,part/of which contained fix cubic inches of oxygene gas obtained from nitre- The reft. of the jar was full of water. It:was formed of thin white glafs, three inches in diameter ; and the experiment was made in the moft perfect darknefs with the hydro-pneu- matic apparatus. The thermometer of Reaumur ftood at 12 degrees above 0, (59, of Fahren- heit). After the phofphorus hed remained in this pofition for one minute, it-was withdrawn, and a few bubbles of inflammable gas were introduced. This.gas was obtained by diffolving iron in the fulphuric acid: § diluted. with water, which was conftantly, ufed in thefe experi- ments. As foon,as.the bubbles of this gas had entered the phofphorated oxygene gas,"the whole mafs of elaftic fiuid beneath the.glafs appeared: phofphorefcent. Azotic gas, obtained from animal fibre by means of nitric acids, produced the fame effect. In fome inftances. the phofphorus introduced. into» the oxygene gas produced a flight pliofphoric vapour, which immediately, ceafed ; but the fame phenomenon was produced by introducing inflammable gas into this gasy, But;when by. accident the phofphorus intro-_ ducedsinto the oxygene gas began) to thine; the gas itfelf, which had thus been. placed in contact with the phofphorus, no longer fhone, evenafter the expiration of fome time by the addition of the afore-mentioned |gafes, in whateyer proportion they, were added, -unlefs the white vapour was condenfed and |the phefphors FREE hn %gAnnali di Chimica e Hiftoria Naturale, tome xiii. ann. 1797, page 275 Ido not poffefs this work, but. have followed the tranflation of Citizen Van Mons in the 24th volume of the Annales de Chemie, whole ac- curacy and knowledge, of the fubjeét, afford the moft perfeét affurance of his fidelity. . ¥ + Ibid. page 3. t The author calls this gas therm-oxygent. § The author calls this acid x/-fulphuric. He prefixes to the name of each acid the fyllables ox, fuch as oxi-nitric, oxi-phofphoric, &c. M. Van Mons has preferred the nomenclature prefented by the French chemifts ; and juftly remarks, that, if every chemift were to make one, it would foon become impoffible to diftinguith the fubfances concerning which shey might write. . . EXP. A i ra i + the various Kinds of Air. : 445° EXP. W.e—Pholphorated Oxygene Gas. becomes luminous by: the Contac? of the Oaygenated Muriatic Acid Gas: AFTER having left a cylinder of phofphorus for one minute in feveral cubit inches of pure oxygene gas, in which it did not thine at all, nor affe&t the tranfparency by white va- pours when brought into the light; a bubble of oxygenated muriatic acid gas, obtained by diftillation of the ordinary muriatic acid from the black oxide of manganefe, was introduced. The mixture of the two gafes produced a foft light through the whole mafs of elaftic fluid contained in the veflel. EXP. Il, Phofphorated Oxygene is alfo luminous with Nitrous Gas. NITROUS gas is very greedy of oxygene, in order to convertitfelf into nitrous acid. The nitric acid fuddenly. takes this gas from the oxygene gas, while heat is developed, and the combination is fhewn in red vapours. I was defirous of afcertaining what- would happen when nitrous gas was introduced into phofphorated oxygene gas, according to the ufual procefs. As I performed my experiment in the dark, I could not obferve the moment in which the nitrous gas arrived at the upper part of the jar in‘contaét with the phofphorated gas. A very perceptible azure light was feen, which was more confiderable than had been afforded by the ufe of any other kind of gas. A fecond introdu€tion of nitrous gas produced no further effect. “The veffel being afterwards infpe€ted by the light of a candle, the mixture of the two gafés appeared fo opake, and the glafs fo loaded with white vapours, that it ap- peared as if filled with milk. EXP. 1V.—Phofphorus is foluble in Hydrogene Gas. INFLAMMABLE gas diffolves phofphorus as {peedily as oxygene gas in the-firft: Experi- ment, and the whole volume of this gas|isimpregnated and becomes phofphorefcent by the contact of oxygene gas, or the oxygenated muriatic acid gas. But, in order to obferve' this phe- nomenon in perfection, it isneceflary to operate with pure inflammable gas, which has not’ long been in contaét with water, becaufe this would prevent its aQing upon the phofphorus with the fame energy; and as this gas abforbs a certain portion of pure air from the water, it would follow that the phofphorus would produce more or lefs of white vapour, and readily emit light. It)is therefore neceflary to operate over mercury. EXP. V. VI. and VII.—The Appearances of Phofpharus in the Oxygenated Muriatic Acid Gas. A PIECE of phofphorus was introduced into a cylinder of glafs filled with oxygenated muriatic acid gas over water. It did not burn perceptibly in the dark; but in the light, white vapours were feen through the whole of the glafs in fuch plenty as to render it opake, A-fhort time afterwards the phofphorus was fufed and ran like wax by heat, or camphor by-the nitric acid! - The phofphorus in this ftate floated on the water, inftead of falling to the bottom as before its fufion. ‘The temperature of the atmofphere at the time of making. this experiment, was about ten degrees above o. I put a large cylindrical piece of phofpho- ” rus into a cryftal decanter; placed ona table, and full of very pure oxygenated muriatic acid. gas. The-capacity of the bottle was eight cubic inches, and it was entirely full. The phof- phorus’ took fire with flame, and threw out ‘a great number of very brilliant fparks againft the fides of ‘the veffel, which it heated, and itfelf became entirely fufed. The vefle!l way filled. 446 Fixperiments wtih Phofphorus and filled with white vapours. Afterwards, in proportion as the veffel, which was not broken in this experiment, became cool, the phofphoras congealed, but continued to fhine, though without emitting {parks. When the veffel was opened under mercury ; the metal entered, and filled one third of its capacity. The gas which remained after the rapid com- buflion of the phofphorus was -tried “over mercury; firft, by mixing oxygene gas, and _ afterwards the hydrogene and azotic gafes ; but no light or other phenomenon appeared, to deferve attention. I covered the ball of a thermometer with two grains of phofphorus melted in hot water, and immediately conveyed this inftrument, which marked 10 degrees above 0, into a fayall bottle full of oxygenated muriatie acid gas. 1 foon obferved white vapours, by the afiftauce of a light; for the experiment was performed in the dark. The phofphorus be- came foft, lowed, and took fire ; and the mercury in the thermometer was feen to rife from 10 to $0 degrees. E XP. VIM.—The Phenomena of Phofphorus in the Carbonic Acid Gas. AS the carbonic acid gas, at a low temperature, pafles readily enough through water, without being abforbed, to be fubje€ted to experiment even in the hydro-pneumatic ap- paratus ; 1 difengaged this gas from the carbonate of lime by means of the diluted fulphuric acid. 1 colleéted the pureft gas, and included fix cubic inches in a large tube clofed above, and having its lower end plunged in a veflel of water. A cylinder of phofphorus which was introduced in the dark did not immediately fhine, but after about two minutes it began to emit a glimmering light, which increafed to a greater degree of brilliancy than would have been exhibited’in atmofpheric air. The temperature was about ten degrees above zero. Little fatisfied with thefe trials, I repeated the fame experiments over mercury, and obtained the following refults. The phofphorus did not fhine in the pure carbonic acid gas, and did not appear to me to be diffolved in the fame manner as in fome of the pre- ceding gafes; for the carbonic acid gas mixed with oxygene gas did not afford any light, though it had been long in contaét with a large cylinder of phofphorus. Confequently the light which appeared in the carbonic acid gas over water depended on a portion of pure air which was difengaged from the water itfelf, and mixed with the carbonic acid gas, while this laft combined with the water, and diminifhed the affinity of that fluid for the portion of oxygene it ufually holds in folution. EXP. 1X.—Some Phenomena of Phofphorus with Atmofpheric Air. I PUT feveral pieces of phofphorus into two phials of cryftal glafs, of the capacity of about four cubic inches, half filled with pure water, and the other half containing atmo- fpheric air. Thefe phials were agitated from time to time: after three days, the temperature of the air being at 18 degrees above zero, the water in the bottles emitted a very per- ceptible fmell of phofphorus, and was a little turbid. The phials being afterwards clofed and gently agitated in obfcurity, I obferved that the included air, which was at firit ob- feured, immediately fhone by a flame which ftruck the infide of the phial. By the affiftance of light it was feen that the tran{parency of the air was affe€ted by white vapours. When the vapours had ceafed, I agitated the phial again in the dark, and the fame phenomenon appeared, ’ the various Kinds of Air, 447 “appeared, and was frequently renewed, by brilliant points from the furface of the water; fome of which produced the illumination through the air. I faw the fame thing feveral times, as did likewife a number of {peCtators, who were much furprifed at the effect. I at firft fuppofed that the water of the phial in which the phofphorus was placed might hold fufpended certain {mall particles of the phofphorus, which were afterwards diffolved by the atmofpheric air of the veffel ; and that fome part of this phofphorus, afterwards taking fire in confequence of the agitation of the water, might produce through the whole of the air, the flame I have here fpoken of. But the ready combuttion of phofphorus in atmofpheric air at the temperature of 18 degrees contradicted this explanation ; not to Mention that it was-difficult to conceive that the air fhonld occafion the folution rather than the combuftion of this fubftance. I could not even fuppofe that the atmofpheric air of the veffel was decompofed by the phofphorus diffolved in the water, or by very {mall particles of this fubftance which might float upon the liquid; fo that the azotic gas remaining alone might act on the phofphorus, partly diflolving it, and by this means conflituting a phofphorated gas, which might thine by the agitation of the water, in con- fequence of the difengagement of a quantity of oxygene fufficient to occafion combuttion. For I had often obferved that, when the phial was uncorked with the greateft care, in order to avoid any agitation, there was no production of flame notwith{tanding the accefs of atmofpheric air; but the phofphorefcence appeared immediately upon agitating the phial, whether the phofphorus had or r had not a communication with the air of the atmo~ {phere. 5 On one occafion, when I had. fix phials prepared in. this manner, and obferved them for fome time in the dark, I faw that fome of them afforded a flame fpontaneoufly, and without agitation. ; I attributed this flame which appeared in the air of the phials, containing water charged. with particles of phofphorus, toa combultion and inflammation of the phofphoius, produced, at the inftant of the agitation of the furface of the water, by the immediate folution of this combutftible in the atmefpheric air. I tmagined that this phenomenon might be repro- duced as long as there was any oxygene gas in the phial. It might, in fact, take place for a number of times fucceffively, becaufe a very {mall quantity of oxygene is required for the purpofe. The agitation of the water appeared to me to be neceffary to detach the cover- ing of phofphoric acid with which the parcels of phofphorus might eafily be covered, and which might hinder their combuftion, more particularly when the phofphorus was very much divided; that, if this covering fhould be fpontaneoufly detached, either by elevation of temperature or any other circumftance, the phofphorefcence mu(t appear in the end of the bottles even without agitation ; and that the fpontaneous flafhes are produced in this manner. I took a piece of phofphorus, which I caufed to burn in the air of a phial of the fame- capacity as thofe employed in the foregoing experiment, at the bottom of which was a \jttle water. The phofphorus, fufpended by a filk thread in the upper part of the bottle; burned vifibly (the temperature being 15 degrees above zero), and, as ufual, emitted) white vapours, which dcfcended to the furface of the water. L left the phofphorus in the air of the bottle until.it no longer fhone, which effe&t happened: in phe courfe of the days The- 448 Experiments on the Solutions of Phofpharus The bottle, when’ obferved in the dark, exhibited no light sthe water’ agitated in ‘every direQtion produéed no light ; but it was feen to inflame immediately upon the eontad 6f the atmofphere by taking out the cork; \and when the light -difappeared, it was capable of being produced again by agitating the fame water, which immediately before did not ex- shibit any light by the ftrongeft agitation. f by In this experiment the flame likewife-arofe from the phofphoric particles on the furface of the water, with the vapours of -theiphofphorus which it condenfed by burnings The total want of light in the included:air before it was open arofe’ from the total want of ‘pure air, which is neceffary for the produétion of this phenomenon. EXP. xX. I DISSOLVED a {mall piece of phofphorus in pure oil of turpentine. The oil be- eame flightly turbid, afterwards clear, aflumed a yellowith colour, and emitted a flight fmell of phofphorus. A cryftal phial was half filled with this folution. I was defirous of ob- ferving whether agitation would afford a flame in the air, asin the former experiment ; but I did not perceive the leaft light, I obferved the fame thing with the prepared oil of “thyme, containing phofphorus. The temperature of the atmofphere was 15 degrees above zero. . EXP. XI.—Odfervation on Phofphorated'Alkohol. “PHOSPHORUS diffolves in alkohol when it is very pure. In proportion as the folution is effe€ted, the alkohol lofes its proper fmell, and affumes that of phofphorus, which is very difagreeable. The alkohol takes up very little of the phofphorus, and continues en- tirely limpid. I attempted, but conftantly in vain, to obferve the phenomenon of the flame in the air of the veflels, which I had partly filled with phofphorated alkohol. Its habitude was in every refpeét fimilar to that of phofphorated oil of turpentine at the ordinary tem- perature of the atmofphere. ; EXP. XII. Water caufes Phofphorated Alkohol to foine very ftrongly. IF in perfect darknefs a drop of phofphorated alkohol be poured into a cry{tal decanter at the bottom of which is a {mall quantity of pure water, a very fingular phenomenon is ob- fervable. At the moment when the phofphorated alkohol comes into contact with the - yyater, a brilliant light is difengaged, which paffes with a ferpentine motion, and rapid, crackling along the furface of the water. The air within the veffel then becomes entirely luminous, and remains for fome time in this ftate. Ifthe bottle be unclofed, and air blown juto it; the white vapours difappear, the air becomes tranfparent, and the phofphorefcence difappears: but if the mixture be again agitated, feveral luminous points are feen at its furface, the air of the bottle becomes again inflamed ; and this may be renewed until ‘the whole of the phofphorated alkohol has been confumed. ‘ If a pen be dipped in water, and in this ftate it be plunged in phofphorated alkohol ; at the moment of contact of the two fluids a fudden light fpreads through the air, and very perceptible flames are feen, in a dark place, to iflue from time to time out of the mouth of the phial. : EXP. XIII. Water is not the only Subftance which fets fire to Phofphorated Alkchol. I HAVE obferved that the phenomenon of the inflammation: of phofphorated alkohol not only takes place with cold and with boiling water, but alfo with concentrated fulphuric acid, l Experiments on the Solutions of Phofphorus. 449 acid, with the folution of pot-afh, with the liquid nitrate of lime, and with the folution of various alkaline falts. EXP. XIV. Sulphuric Ether diffolues Phofphorus. I LEFT, during fixteen days, in a well clofed cryfial decanter, two cylinders of good phofphorus, with fome ounces of fulphuric ether. This liquid did not appear to have loft its ufual fmell, as was the cafe with alkohol.- It was very tranfparent; and, upon being decanted into another bottle and agitated in ob- fcurity, there were no figns of phofphorefcence. I afterwards poured fome drops into water which I had put in another bottle; but here alfo I obferved no appearance of light, though the place of operation was perfeétly dark. The phofphorated ether was feen in the light floating upon the water, and very limpid. I added a {mall quantity of alkchol to this mixture, which immediately rendered it turbid like milk. This phenomenon may afford a {ure means of afcertaining the purity of ether. The mixture agitated in every dire€tion afforded no light ; but light appeared with much Vivacity and at feveral repetitions after the mixture had been a little heated. A great number of luminous points appeared on the furface of the water after it had been long agitated. I made this experiment in a bottle of a certain fize, clofing and unclofing it fometimes in order that the white vapours might iffue out, in proportion as they were formed. The following are the confequences which I have deduced from the foregoing. experi- ments + 1. Phofphorus is very readily diflolved in pure oxygene gas at a mean temperature (Exp. I.) without emitting light; and the phofphorated oxygene gas fhines when it is dif- fufed in any other azotic or mephitic gas. (Exp. II. and III.) This phenomenon appears to me to depend on the agitation which the integral parts of the oxygene gas and phof- phorus undergo when another gas is mixed with them, and from the diminution of afhnity between the integral parts even of the oxygene gas, effeéted by the addition of the new gas. By this diminution of affinity, if phofphorus is placed in the fphere of chemical at- traction with the oxygene, the oxygene gas becomes decompofed, and the phofphorus burns. 2. Phofphorus is likewife fpeedily diflolved in inflammable gas (Exp. JV.) and this phofphorated gas burns when it is brought into contaét with any oxygene gas. 3. The oxygenated muriatic acid gas fuddenly burns phofphorus. The oxygene gas which contains this acid is decompofed by the phofphorus, which rapidly combines with the oxygene (Exp. VY. VI. VII.) to form phofphoric acid; and the concrete caloric, or other component principles of the oxygenated muriatic acid gas, being fet at liberty, raifeg the temperature, and melts the phofphorus which is not yet oxygenated. 4: Phofphorus is not foluble in pure carbonic acid gas (Exp. VII.) ; neverthelefs, at the temperature of 12 degrees above o of the thermometer of Reaumur, it burns better in this gas mixed with a {mall portion of oxygene gas, than when in atmofpheric air at the fame temperature. 5. Water does not diflolve phofphorus, but it holds very fmall particles in a ftate of fufpenfion, more efpecially thofe which are impregnated with a principle of combuflion, Vor. L—Janvary 1798, 3M and 459 Sclutions of Phofphorus.—Gunter's Rule. and have been fufed by caloric (Exp. V. VI. and VIII). The air of the atmofphere dit folves phofphorus at the moment it burns it, and the folution is fenfibly phofphorefcent when the experiment is made in a cryftal glafs bottle. ‘This caufes a flamé more or lefs brilliant, in proportion to the greater or lefs quantity of phofphorus which is burned at the fame time. 6. Phofphorus which is burned in a decanter with water at the bottom, not only de- compofes the oxygene of the air in which it burns, but likewife that of the air which is found mixed with water (2xp. X-). 7. Oil of turpentine and oil of thyme, containing phofphorus, do not burn in contact with atmofpheric air at the ordinary temperature (Exp. XT. ). 8. Alkohol diffolves phofphorus, and lofes its agreeable fmell. Phofphorus fhines in the atmofpheric air of clofed veflels, by pouring phofphorated alkohol upon fomefubftance which fhall combine with the liquid and feparate the phofphorus; fuch are water, ful- phuric acid, &c. (Exp. XU. XIU. XIV.) Sulphuric ether likewife diffolves phofphorus, and this folution is not decompofed by water, upon which it floats; but when phofphorated ether is diluted with alkohol, or is changed into anodyne liquor, it then combines with water, and quits the phof- phorus, which, being divided into very fine white particles, gives the mixture the colour” of milk. = . IV. - On the Advantage of inverting the Slider in many Operations on the Common Sliding Rulg. By the Rev. W. PEARSON, of Lincoln. Io Mr. NicHoLtson, Author of the “ Fournal of Natural Philofophy,” &c. SIR, ‘ O N perufing the eighth number of your Journal, I was much_pleafed with the ingeni- ous inftruments mentioned in the VILIth article, upon which the graduations of Gunter’s Line of Numbers are fo difpofed as to be very confiderably enlarged, whilft yet the whole range of a fingle line is contained in a {mall compafs. If an inflrument of either the pa- rallel, circular, or fpiral conftruction, of a convenient fize, were manufactured for fale, with a proper degree of accuracy, I am fully perfuaded that confiderable advantageqwould be derived therefrom by purchafers; particularly by thofe perfons whofe profeflion is to make practical calculations. But as the public are in poffeflion of a fliding rule, in the operations of which long ufage has made every mechanic expert, it is to be apprehended that pre- judice would in this, as im other inftances, prove an obftacle to the general fale of fuch an inftrument, were the introduction of one into general ufe attempted. This obfervation is, I believe, verified by the flow fale of the patent, and alfo of the new improved fliding rule, in comparifon of that of the common one, amongft artificers, who conftitute the moft numerous Clafs of purchafers. I have been informed by a reputable tradefman, who retails fliding rules of the different con{tructions, that for every patent, or new improved fliding tule that is purchafed, more than twenty of Cogthall’s, or the common fliding rules, are fold. 7: Inverfion of the Slider on Gunter’s Rule. 45% fold. By the fame prejudice, probably, any ew method of working by the old rule, though more expeditious and equally accurate, would be rejected in practice if fuch method were’ offered to the public. But, be this as it may, I think the confideration that the probability is but fmall of any particular improvement being generally adopted in praétice, is not a fufficient reafon why that improvement fliould be withheld from the public eye, whilft it is confidered as fuch. There are always individuals whofe minds are unfettered by prejudice *, and to whom any hint tending to produce an improvement always proves acceptable. The logarithmic line of numbers, known by the name of Gunter’s line, is fo well un- der{tood by every’ one who is acquainted with the properties of logarithms, as to renderany obfervation on the conftru€tion of it unneceflary. The ufe of two fuch lines, ufually de- riominated A and B, working together by means of a direct flider, fuperfedes the appli- cation of compaffes, and is taught in moft practical books of arithmetic. - There is however another, and I think more commodious method of applying the flider, than the one generally practifed (except in working dire& proportions), which I have not feen’explained, nor practifed by any perfon; and which, therefore, I fhall beg the favour of you to communicate to the public through the medium of your interefting Journal, provided you deem it of fufficient importance. The method I have to communi- cate lays no claim to fuperior accuracy when compared to the common method, the powers of the inftrument being the fame in both; but, befides novelty, I truft it will be found to have facility to recommend it. The method is fimply this: Invert the -flider B on any common fliding rule, whereby the numerical figures will afcend on it, and on the fixed line A, in contrary directions : now, as the diftance from unity to any multiplier, on Gunter’s line, will invariably extend from any multiplicand to their produ@, it follows, that if any particular number on the in- verted flider B be placed oppofite to any other given number on A, the produé& of thofe numbers will ftand on the flider B, againft unity on A ; for, in any pofition of the inverted: flider, the diftance from unity to.the multiplier on A, inftead of being carried forward on B, as when the flider is in a dire& pofition, is brought back thereby to unity again; fo that unity (or fen on fingle lines where the flider is too fhort for the operation) is invariably = index for the product of any two coincident numbers throughout the lines. In divifion, by the fame procefs, if the dividend on B be put to the index, or unity on ‘A, the divifion and quotient will coincide on the two oppofite lines ; fo that when one is given, and fought for on either line, the other is feen on its oppofite line at the fame time. * This prejudice is the effeét of habit, and can feldom be eradicated from the minds of fuch individuals as confider the ready occurrence of a propofition as a teft of its truth. To eftablifh a new philofophical theory has, sn every inflance, required time fifficient to educate an entire generation of men. The rejeétion of the Ari- fiotelian philefophy, the adoption of experimental refearch, the fubftitution of the doétrine of gravitation in- ficad of that of vortices, and the rejection of phlogifton by our contemporaries, are fufficiently illuftrative of this affertion. New practices are ftill more difficult to be introduced. The new grammar, the new rudiments ef fcience, or the new inftrument, however fuperior to the old in fimplicity, facility, and truth, mutt be lef valuable to the ordinary teacher or artifan, whofe memory is familiarized with the precepts of the latter, and whofe only ambition is to carn his fubfiftence with the leaft poffible exertion. N. gM2\."s The 452 Inverfion of the Slider on Gunter’s Rule. The next operation which offers itfelf here is reciprocal proportion, which can be effefted by no other method than by inverting the flider, but which is rendered as eafy by. this ap- plication, as direét proportion is in the common way; for if any antecedent number on B inverted be fet to its confequent on A, any other antecedent on B, in the fame pofition, will ftand againft its confequent on A, fo as that the terms may be in a reciprocal ratio. In fquaring any number, it will appear from what has been already faid, that if the number to be fquared be placed on B, inverted againft the fame on A, the fquare will ftand on B,, againft unity on A. Therefore, to extract the {quare root of any number, Jet that number on B ftund againft unity on A; and then wherever the coincident numbers are both of the fame value, that point indicates the root. If two dividing lines of the fame value do not exaily coincide, the coincident point will be at the middle of the {pace contained between thofe two which are neareft a coincidence ; and as there is only one fuch point, there can be no miftake in readily afcertaining it. ‘The finding of a mean proportional between any two numbers is extremely eafy at one operation; for if one of the numbers on B inverted be fet to the other on A, the coincident point of two fimilar numbers fhews either of thofe. to be the mean, or {quare root of their product, according to the preceding procefs. Thus have we a fhort and eafy method of multiplying, dividing, working reciprocal proportion, fquaring and extracting the fquare root, at one pofition of the inverted flider, whereby the eye is direéted to only one point of view for the refult, after the flider is fixed: where- as, by the common method of extracting the fquare root by A and B direct, the flider re- quires to be moved backwards and forwards by adjuftment, the eye moving alternately to two points, till fimilar numbers ftand, one on B againft umity on A, and the other on A againft the fquare number on B; which fquare number, in the cafe of finding a mean pro- portional, muft be found by a previous operation. Hence, for more convenience in the extraction of roots, and meafuring of folids, an additional line called D, has been added to the rule, which renders it. more complex, and confequently feldom underftood by an artificer. Upon examining the patent rule with a graduated piece of brafs, to be attached to, or detached from the flide at pleafure; and alfo Mr. Horton’s new improved rule with two fliders; I perceive that the method of multiplying length, breadth, and depth into one another at one pofition, in which their excellence confifts, is nothing more than a com- bination of the two methods on the common rule; for the product of the two firft numbers, effected by means of an inverted and a direét line, forms the multiplier to be ufed with the third number, by a third direct line, at the fame pofition of the fliders. Hence, a gauger’s rule will anfwer the fame purpofe, if an additional flider be held in a proper fituation inverted. No reafon, however, has been given for the effect of this procefs in any book that I have yet feen, nor of the application of an inverted flider to any other {pecies of calculation *. * In reply to the obliging poftfcript of the author of this paper, I have only to remark, that the appro- pation of the intelligent cultivators of fcience is the moft eftimable reward ef my endeavours to diffufe knowledge ; and that inclination, as well as duty, will induce me to pay every attention to his future com= munications. N, ! , V. Abfrad Sulphates of Iron variatfly onideds 453 Vv. Abfira® of a Memoir entitled “ Enquiries concerning the Nature of Prufian Blue* By Mr. Proust *. I F iron were fufceptible, as chemifts imagine, of uniting with oxygene in all the inter- mediate proportions between 2%, and 34%, which appear to be the two extreme terms of its union with that principle, ought it not to afford, with any given acid, as many dif- ferent combinations as it is fuppofed capable of producing oxides? Why, for example, does not this metal, which affords, with the fulphuric acid, a falt conftant in its properties when oxided no farther than #27,, exhibit different combinations, equally conftant in their tefpective properties, when it contains 34, 3%, or 745, of oxygene? A great number of facts prove, on the contrary, that iron does not reft indifferently at all the different degrees of oxidation between the two terms abovementioned ; and, not- withftanding the different degrees of oxygenation through which iron is fuppofed to pafs when its fulphate is expofed to the air, we are acquainted with no more than two fulphates of this metal. The firft is the green, or cryfallizable fulphate, in which Lavoifier has proved that the: iron contains °%, of oxygene. This falt, when pure, is infoluble in fpirit of wine; its foe lution in water is of a very pale fea green colour. It is not altered by the gallic acid, af- fords no blue with alkaline pruffiates, &c. The fecond kind of fulphate, no lefs conftant in its properties, is that red deliquefcent incryftallizable combination which is foluble in alkohol, and is known by the name of mother water of vitriol ; but is not really fuch, unlefs when it produces no alteration in the oxygenated muriatic acid; that is to fay, when its oxide contains ,3, of oxygene. This fulphate is eafily obtained by treating it with nitric acid until its folution no longer difengages nitrous gas, by the addition of a new quantity of acid. This fulphate, befidess poffefles exclufively the property of forming a black precipitate with the gallic acid, and of affording Pruflian blue with the alkaline prufliates, as will hereafter appear. Between thefe two fulphates, which Mr. Prouft calls the green fulphate and the red fuk- phate, there is no intermediate point. If the green fulphates, by expofure to the contact of air, aflume a colour which appears to belong to neither of thefe fpecies, it may be de- cidedly fhown that they are fimply a mixture of the two, by feparation by means of al- kohol. Each falt will then exhibit all its diftinétive properties. The green fulphate will conftantly produce a green precipitate with the cauftic alkalis; which precipitate will foon become black if preferved under water without the contatt of the air, becaufe its particles continually approach each other, and render the colour more and more in- tenfe. The red fulphate, on the contrary, will afford, with the fame alkalis, a yellow red pres * This abftraA is tranflated from the Annales de Chimie XXILI. $s. ‘The editors do not fay whore the original is to be found, fr cipitate, asa? White PPuffate of Iron. cipitate, which is an oxide, incapable of attra&ting any thing si the air of the atmofphere, nor from the oxygenated muriatic acid. This oxide, according to the experiments of Mr. Proutt, contains we of oxygene, and is capable of forming the bafis of a feries of combinations, which bear the fame relation to thofe which afford the black oxide, as the red fulphate of iron bears to the green fulphate. So that in whatever degree of alteration an ordinary fulphate may be examined, it will be found: to confift merely of thefe-two falts, mixed in different proportions. Whence it follows, that a, fulphuric or; muriatic olution of this metallic fubftance is nothing but a mixture of the two falts, one of which has for its bafis the oxide of iron, containing 27; of oxygene, and the other the fame oxide, containing ,%% of oxygene. And as little attention has hitherto been paid to the diftinétive properties of thefe falts; effets have frequently been attributed to .the one, which belong exclufively to the other. We mutt therefore diftinguifh two fulphates, two muriates, two arfeniates, two pruf fiates, &c.: the latter faits more particularly conititute the object of Mr. Prouft’s Memoir. The White Pri fate. IN order to obtain this falt, a folution of the perfedly pure green fulphate muft be taken, and mixed with a well faturated folution of the prufliateof pot-afh. ‘This laft folution, if perfeét, affords cryftals of,a beautiful orange-yellow in tetrahedral Pytampidsy truncated near their bafe. “'The green fulphaté of iron is obtained and preferved ina ftate a purity, by ESepiuaatl it in a well clofed veffel quite full, in which a {mall piece of iron or tin issput. The fame purpofe is anfwered by reducing the red oxide, which may exift in the folution, to the ftate of black oxide, by a mixture of water charged with fulphurated hydrogene gas. This ful- phate, after purification, ought not to change by the addition of the gallic acid. In this ftate, its colour is an extremely weak fhade of fea-green. The green colour does not appear, unlefs the folution be in contact with the atmofpheric air.. After having poured the folution of the pruffiate upon the fulphate of iron, the bottle muft be immediately clofed. A plentiful white precipitate immediately falls down, which foon afterwards affumes a green tint, occafioned by the air contained in the bottle, and likewife by another caufe. Butif the veffel remain clofed this fhade does not bécome deeper, and light alone does not produce any change. It is advifable to pour an excefs of the pruffiate upon the fulphate, in order to com- plete the decompofition. After feveral hours reyofe, this pale prufliate is covered with a yellow liquor, which is a mixture of the pruffiate and the fulphate of pot-ath. This liquor retains in folution afmall quantity of white pruffiate, which acquires a blue colour by ab- forption of oxygene, when it is placed in contact with the atmofpheric air... By this union, it becomes infoluble, and falls upon that which is at the bottom. The laft-mentioned pre- cipitate receiving in its turn the impreflion of the atmofphere, foon becomes blue at its fur- face. Theintenfity of colour fucceflively increafes, and proceeds downwards, until at length the white pruffiate becomes conyerted into Pruffian blue. The action of the oxygene of the atmofphere, in thefe circumftances, is ftill more con- firmed by the phenomena which are feen when the white pruffiate'is expofed to the a€tion of 4 Blue Pruffiate of Ivoit. 455 of the airona filter. It becomes blue by abforbing oxygene; and the colour does not ac- quire its greateft intenfity until the oxide of iron has obtained +55 Of that principle. Of all the faline combinations of iron, there is none of which the bafis becomes faturated with oxygene fo rapidly as the pruffiate. The carbonate of iron is not to be compared with it. : The fulphuric and muriatic acids poured on the white pruffiate of iron occafion no ehange. The oxygenated muriatic acid, on the contrary, enlivens the pruffiate in an inftant, and lofes its odour. ‘The nitric acid likewife converts it to blue, but more flowly, becaufe it does not abandon its oxygene with the fame facility as the oxygenated muriatic.acid. The folution of fulphurated hydrogene, which does not alter the green fulphate, as has already been remarked, has likewife no a@tion on the white prufhate. It merely reduces to white the fmall quantity of pruffiate which had become blue by the accefs of air; or, in other words, it deprives it of that portion of oxygene which, it may already be feen, con= ftitutes the difference between the white and the blue prufliates. Tt may perhaps be an anticipation of the facts, to diftinguifh that prufiate by the name of white, which in ftri€tnefs is fuch only at the moment of its formation, and afterwards becomes covered with a greenith white ;. but it is very probable that it acquires this fhade merely from the air contained in the veffel, and in the liquids made ufe of. There exifts like- wife another caufe in the fmall portion of red oxide, from which the alkaline and even the calcareous -pruffiates derive their yellow colour. ‘This oxide becomes converted into blue pruffiate, and mixes with the white prufliate at the moment wherein the pruffic acid, being difengaged from the alkalis, is at liberty to unite with the different oxides it meets with. Thefé oxides are, as we have feen,a great quantity of the black oxide mixed with the red oxide of the alkaline pruffiate. It muft therefore neceflarily follow, that a {mall portion of the blue pruffiate will be mixed with a great quantity of the white prufliate ; whence this laft acquires its greenifh tinge. From the whole of thefe faéts, it is evident that the oxide, which conftitutes the bafe of the white pruffiate, poffefles the fame degree of oxidation as when it formed the bafis of the green fulphate. This oxide in effeG@ paffes from the fulphate to the white pruf- fiate, without the interference of any caufe which can either increafe or diminifh the pro- portion of oxygene. Hence it follows, that fince the alkalis feparate the’oxide of the green fulphate of a grafs-green colour, they ought alfo to' feparate it from the white pruffiate under the fame tinge. This in fact happens at the inftant when the cauftic alkali, or ammoniac, is poured om the white prufiate. But in order to judge better of the thades, it is advifable to ufe thefe folutions diluted with water. The green oxide is not completely deprived of pruffic acid till after the repeated application of alkalis. This may be fhewn by taking up the green oxide, by an acid which does not diffolve the white undecompofed prufliate. The Blue Pruffiate. AFTER what has been faid, it is eafy to foretel the habitudes of the nitrate, and all the folutions of which the oxide is at its maximum of oxidation, when alkaline pruffiates aré applied. No interval is perceived between the precipitation and the moft liyely blue. The cglour 456 Effects of Oxygene in Pruffan. Blue, Se. colour is perfect at the inftant of precipitation, and expofure to the atmofphere:adds no- thing to its intenfity. Pruffian blue is, in a word, that pruffiate, whofe bafis contains 345; of oxygene. It is the fame with refpeét to the white pruffiate as the red fulphate is to the green. Thefe two pruffiates do not differ with regard to their acid. ‘Their diftinétive charaCters arife from the different oxidation of their bafes. The blue pruflfate is not altered by acids. The oxygenated muriatic acid changes it, by rendering it green, at the fame time that itfelf undergoes alteration, as Berthollet has difco- vered. Butthe aétion of this deftruétive acid is exercifed on the pruflic acid, and not on the oxide, which can receive no greater dofe of oxygene than it has already acquired from the nitric acid, the air, &c. The acids which are ufed to brighten fuch Pruffian blues as are imperfea, are of no other ufe than to diffolve the great quantity of carbonate of iron, precipitated by the pot-afh which is not faturated with pruffic acid, and fuper-abounds in ill-prepared lixiviums. If white prufliate were to’ exift in fuch precipitates, it would be in no refpect changed by the acid, and would acquire a blue colour only by abforbing from the atmofpheric air the quan tity of oxygene neceflary for that purpofe. 3 In order to fhew that oxygene is the principle which in the blue pruffiate of iron affords the diftinétive colour, nothing more is neceflary than to remark the colour of the oxide when precipitated by alkalis. In the green fulphate the precipitate was black; after the precipitation from Pruffian blue it is red. No other principle but oxygene could have oc~ cafioned this difference in thefe oxides. Mr. Prouft having fpoken indifferently of the yellow and the red oxide of iron, as being completely faturated with oxygene, obferves, that he ufes thefe expreilions without diftinc- tion, becaufe a number of faéts have convinced him that there is no difference between them. Every red oxide, fays he, when diffolved in any acid whatever, is precipitated of a yellow colour by alkalis, whether pure or faturated with carbonic acid. This laft acid oc- eafions no difference in the precipitate, becaufe it has no tendency to unite with iron at that degree of oxidation. The red oxides when dried are brown, obfcure and often black, accord- ing to the degree of drynefs or denfity they may have acquired. But if they be pounded in a mortar, the charaéteriftic colour foon appears. It is affirmed, that thefe oxides have the power of decompofing ammoniac ; but our author kept them for feveral years in ammoniac, without obferving that they were in any refpect changed. Hehad no better fuccefs with the oxide of manganefe at the ordinary temperature of the air. . The folution of fulphurated hydrogene gas, when kept in a veflel with the blue pruffiate, isdecompofed. It feizes from the oxide that portion of oxygene which conflitutes the dif- ference between the blue and the white pruffiates; and the pruffiate thus rendered white exhibits the fame phenomena with alkalis, as if it had been obtained immediately from the green fulphate. The white prufate kept under hepatic water undergoes no alteration; in which refpect it refembles the green fulphate. Either of thefe readily yield to the hydro- gene diflolved inthis water all the oxygene they poflefs, exceeding 27 per cent. ‘The fame theory explains, why the red fulphate and the nitrate of iron decompofe ful- phurated hydrogene. The oxide of iron burns the hydrogene, the fulphur is depofited, and the fupernatant liquor, inftead of affording a red precipitate by alkalis, exhibits a green. r This Confiderations vefpeffing the Oxides of Iron and other Metals. 457 This obfervation points out a method of reftoring the copperas of the fhops to the ftate of green fulphate. . When brown, depolitions are formed, it contains copper. The folution of fulphurated hydrogene is not the only practicable means to reduce the blue prufliate to the ftate of white pruffiate. The requifite abftraction of oxygene is made by keeping Pruffian blue with water and plates of iron or tin in a well clofed veffel. By this treatment it acquires all the properties of the white pruffiate. The diftribution of oxygene between a metal and its oxide is not an uncommon fact in chemiftry. By keeping a red fulphate or muriate with iron, they are enabled to recover their firft tate. Mercury kept in a folution of corrofive fublimate becomes changed, as does likewife the metallic falt itfelf, into the mild muriate of calomel. Mercury undergoes the fame change in a folution of the red muriate of iron, but ig not altered in a folution of the green muriate of the fame metal. In the red fulphate, the mercury is converted into that kind of fulphate which does not become yellow by the affufion of water, that is to fay, in which the oxide is at its minimum. Many other faéts of the fame kind might be mentioned. It has been afferted in this paper, that the oxygenated muriatic acid does not a& upon the oxide of Pruffian blue. The following affords a proof of the truth of this affertion : All the known red oxides, whether natural or artificial, colcothar, the iron ore of Elba*, undergo no alteration in this acid; but the native brown oxides, which for the moft part are mixtures of the black and red oxides, are affected by fuch treatment. | It is found by means of. the oxygenated muriatic acid, that the oxides of the nitrate, the acetite and the muriate of lead are not at their maximum of oxidation. All thefe falts, when kept beneath this acid, are decompofed.. A brown or puce- -coloured oxide is foon de- pofited, and even cryftallized round the fides of the veflels: and the nitric acid no longer aéts upon the new oxide. In procefs of time, however, that acid aflumes a fine rofe colour, bubbles of air rife from the mixture at the bottom, and at length the nitrate is produced, as foon as the oxide, continually folicited to union by the nitric acid, has parted with the dofe of oxygene which oppofed that union. The muriatic acid does not diflolve fuper-oxygenated lad without producing at the fame time abundance of the oxygenated acid; but in order to procure this oxide in greater quan- tity, it is only neceffary to treat the minium of commerce with a weak nitric acid, which; ‘ feparates 13 or 14 per cent, of brown oxide, difcovered, as is well known, by Scheele. ‘The red lead of Siberia i is nothing elfe, as Mr. Macquart has fhewn, but a natural fuper-oxida- tion of this metal. It would be interefting to. know, whether by carrying the calcination beyond the point which affords minium, it might not be poflible. to render the oxide brown. Such a procefs might perhaps fupply the want of manganeles for Preparing the oxygenated, muriatic acid. a Mr. Prouft defers to a future communication an account of the pature of lead, oxided i ia a lefs degree than conftitutes the bafis of the nitrate of this metal, ie From, the foregoing faéts Mr. Prouft draws the following conclufions ; The oxide which alkalis feparate from Pruffian blue is red, though it originally was black in the green fulphate which afforded this blue. * The ore of Elba often contains fulphate of iron. It may be extraéted by greatment with nitric acid, and fubfequent precipitation with ammoniac or cauftic pot-afh. Vor. L.—Janvary 1798. 3N The 458 Prujjian Blue; Black Dye; Se) The white pruffiate is n falt which is afleQed by atmofpheric air in No other manner than the green fulphates, muriates and carbonates, or, in a word, moft of ‘the faline combinations which contain iron oxided to the minimam. There is no other difference with refpeé to their fuper-oxidation, but the greater or els time thefe metallic falts demand; for‘he ob- ferved that the muriates and phofphates of which the oxide is at the minimum are not per- ceptibly altered by expofure to the air. ‘The prufliate of iron is not the only combination of this metal which owes its blue colour to atmofpheric oxygene. ‘That which is called native Pruffian blue is merely the phofphate of iron oxided toa certain point. Mr. Prouft intends to thew artificial phof- phates which are grey, blue, and white, according to ‘the degree of oxidation. We are at prefent well acquainted, adds the author, with the caufe of thofe dull greenifh tinges which frequently appear in the newly-made prufiates. Tt often happens that they are not bright- ened well by acids, and do not acquire their peculiar lively colour but by expofure to the air. This faQ is well known to, manufacturers, who accordingly take care not to wafte their acid in attempting to render fuch blues perfeét. It has been obferved, that thespure green fulphate does not afford a black with the gallic acid. This is very true of it at the firft moment. But ‘the contact of air foon colours the mixture at its furface. A few drops of the oxygenated muriatic acid immediately produce the fame effects throughout the fluid. We fee therefore that iron does not form ink with the gallic acid, -but in proportion as it is oxided. ‘ This'black colour may likewife be de- ftroyed by including the black mixture in a bottle with a ceftain quantity of hepatic water. From thefe facts it alfo very evidently appears why itis the eftablithed practice to expofe ftuffs to the air after the black dye ; and why ink newly made and pale becomes black very fpeedily after it is fpread upon paper, &c. For in all thefe mixtures the ful- phate of commerce is ufed, which contains little of the red fulphate, and much of the green. When the gallic acid is poured into folutions of the fulphate and muriate, containing the red calx of iron, ink is inftantly produced. The bafis of ink and of every black dye is therefore merely the gallate of iron, of which the iron is oxided to the maximum. Laftly, we cannot but obferve in all thefe faéts that chemifts have hitherto erred with refpeét to the property of the ordinary fulphate of iron to become black with the acid of galls, to afford a blue with alkaline area &c. Thefe: Lsbenhy morons a exclufively to the combinations of which the oxide contains ,¢%; of oxygene, and-not 7%, only. I thall conclude, fays Mr. Prout, by de- ducing from iefe experiments the pitncipte T have eftablithed at the commencement of this. memoir; namely, that iron, like many other metals, is fubjefted to the law of nature, which prefides at every true combination ; that is to fay, that it unites with two conftant propor- tions of oxygene. In this refpe& it does not differ from tin, mercury, lead, and, in a word, almoft every known combuftible. He intends fhortly to explain’ the nature of that kind of oxide which refults from the union of oxygene with ey ina lefs preeise than is required to coiisake the carbonic acid. | : Combuftion of Gunpowder in a Clofed Vefil. 459 Vil. An Account of fore Feperiroonic to italia the Force of Fired Gunpowder. By BENJAMIN Count of Rumford, F. RS. M, RI. A.* Arie obferving that no human. invention, except perhaps the art of printing, appears to have produced fuch important changes in civil fociety as the invention of gunpowder ; that notwithftanding the extenfive ufes to which this wonderful agent is applied, it feems not hitherto to have been examined with the attent ion it merits, and that probably this want of inveftigation may have arifen from the danger attending the experiments; our author proceeds to relate his own experiments and obfervations, ’ Several eminent philofophers and mathematicians have, from time to time, directed their attention to this fubje&t. The modern improvements in chemiftry have greatly elucidated the caufe and circumftances attending the explofion of gunpowder. But the great defide- ratum, namely, the real meafure of the initial expanfive force of this agent, has not yet been determined. Robins, from his experiments, concluded that the elaftic force of the fluid generated in the combuftion of gunpowder, is one thoufand times greater than the mean preffure of the atmofphere ; but the celebrated Daniel Bernouilli determines its force to be not lefs than ten thoufand times the fame mean preflure. Count Rumford, being ftruck with the great difference i in thefe refults, has occafionally, for many years, endeavoured to afcertain the truth by experiment. Jn a paper printed in the year 1781, in the Tranfa€tions, he gave an account of an experiment, No. 92, by which it appeared that, calculating even upon Mr. Robins’s own principle, the force of gunpowder muft be at leaft 1308 times greater tham the mean preffure of the atmofphere ; and from that, and many other experiments, he be- came convinced that it was neceflary to abandon the methods of that philofopher, and make others with a very different apparatus. His firft attempts were to fire gunpowder in a confined fpace, thinking that when he kad accomplifhed this he fhould find means of meafuring its elaftic force without difficulty. A very ftrong fhort gun-barrel was prepared, and attempts made to fire gunpowder in the fame, by means of a {mall vent, provided in one inftance with a valve, and in another expe- riment lined with gold to prevent corrofion.. Thefe attempts were unfuccefsful; the force of the explofion proving fufficiently great to enlarge the hole, and fo rapid as not to allow time for elofure of the valve. It became neceffary, therefore, to endeavour to fire the gun- powder by means of heat conveyed through the mafs of the metal itfelf. This was fuccefs- fully performed in a barrel of the beft forged iron, 3,45 inches long, the diameter of its bore cths of an inch, and its ends clofed up by two ferews, each one inch in length, which were firmaly and immoveably fixed in their places by folder. ‘The vacuity between them in the barrel was confequently 1,45 inch in length, and conftituted the chamber of the piece, whofe capacity was nearly ths of a cubic inch. The thicknefs of the metal was equal to the bore of the piece. An hole 0,37 of an inch in diameter was bored through both fides of the barrel, through the centre of the chamber, and at right angles to its axis. Two tubes of iron, 0,37 of an inch in diameter, the diameter of whofe bore was ith of aninch, were &rmly fixed in thefe holes with folder, in fucha manner, that, while their internal openings © Abridged from the Philofophical Tranfaétions for 1797, p. 222. 3N2 were 460 Combuftion of Gunpowder in a Chfed. Veffel. were exaCtly oppofite to each other, and on oppofite fides of the chamber, the axes of their bores were in the fame right line. The fhorteft of thefe tubes, which projeCted 1,3 inch beyond the external furface of the barrel, was clofed at its projecting end; or rather it was not bored quite through its whole length, ?,ths of an inch of folid metal being left at its end, which was rounded off in the form of a blunt point. The longer, tube, which projected 2.7 inches beyond. the furface of the barrel on the other fide, and which ferved for intro- ducing the powder into the chamber, was open ; but. it could occafionally be clofed by & ftrong {crew furnifhed with a collar of oiled leather which was provided for that purpofe. The method of making ufe of this inftrument was as follows: The barrel being laid down, or held in a horizontal pofition with the long tube upwards, the charge, which was of the very beft fine-grained glazed powder, was poured through this tube into the chamber. In doing this, care muft be taken that the cavity of the fhort tube be completely filled with powder ; and this can beft be done by pouring in only a {mall quantity of powder at firlt, and then, by ftriking the barrel with a hammer, caufe the powder to defcend into the fhort tube. When, by introducing a priming-wire through the long tube, it is found that the fhort tube is full, it ought to be gently preffed together, or rammed down by means of the prim- ing-wire, in order to prevent its falling back into the chamber, upon moving the barrel out of the horizontal pofition. The fhort tube being properly filled, the reft of the charge may be introduced into the chamber, and the end of the long tube clofed up by its fcrew. More effectually to prevent the elaftic fluid generated in the combuftion of the charge from finding a paflage to efcape by this opening after the charge was introduced into the © chamber, the cavity of the long tube was filled up with cold tallow, and the fcrew that clofed up its end (which was 2 an inch long, and a little more than th of an inch in dia- meter) was preffed down yin, § its leather collar with the utmoft force. The manner of fetting fire to the charge was as follows: A block of wrought iron, about 1 inch fquare, with a hole in it capable of receiving nearly the whole of that part of the fhort tube which projects beyond the barrel, being heated red hot, the end of the fhort tube was introduced into this hole, where it was fuffered to remain till the heat, having penetrated the tube, fet fire to the powder it contained, and the inflammation was from thence communicated to the powder in the chamber. The refult of this experiment fully anfwered the expectation of the author. ‘The gene- rated elaftic fluid was fo completely confined that no part could make its efcape. The report of the explofion was fo very feeble as {carcely to be heard. It certainly could not have been heard at the diftance of 20 paces. It refembled the noife occafioned by breaking a very {mall glafs tube. The quantity of powder made ufe of in this experiment was not more than 1-8th of what the chamber was capable of containing. The next attempt was to meafure the force of the elaftic vapour thus confined. A hole was bored in the axis of one of the fcrews, or breech pins, which clofed up the end of the barrel juft defcribed, and a pifton of hardened fteel was fitted into this hole, which was +,ths of an inch in diameter. The end of the pifton, which projected beyond the end of the barrel, was then caufed to aét upon a heavy weight, fufpended as a pendulum to a long iron sod. It was hoped that a deduétion of the preflure of the elaftic vapour might be made from the length of the arc defcribed by this pendulum; but the experiment was not found to anfwer, though yarious alterations and improvements were made in the apparatus before the Combuftion of Gunpowder in a Clofed Veffel. 461 the method was abandoned. It was found almoft impoflible to prevent the efcape of the elaftic fluid by the fides of the pifton; and the refults of apparently fimilar experiments were exceedingly different, and fo uncertain, that the Count was often at a lofs to conjeéture the reafons of thefe extraordinary variations. In order to elucidate thefe in a difcurfive way, the Count proceeds to remark, that Mr. Robins’s two affumed pofitions, namely, that the operation of gun-powder is performed by the rarefaction of a permanently elaftic fluid, and that the whole of any charge is fet on fire before the ball is fenfibly moved from its place, are not to be admitted. On the con- trary, from his own experiments, the Count is difpofed to refer the prodigious expanfion of fired gun-powder to the aétion of water in the ftate of {team at a very elevated temperature; and he fhews by various obfervations, feveral of which mutt be familiar to every one who . is habituated to ufe this agent, that the accenfion of gun-powder is fo far from being per- formed in an extremely minute portion’of time, that it is in every inftance gradual and ‘progreflive. But having found it impoffible to meafure the elaflic force of fired gun- powder with any degree of precifion by the methods already mentioned, he totally changed hjs plan of operations, and, inftead of endeavouring to determine its force by caufing the generated tlaftic fluid to a€t upon a moveable body through a determinate f{pace, he con- ‘trived an apparatus in which this fluid was made to act by a determinate furface againft a weight, which being increafed at pleafure fhould at laft. be fuch as would be juft able to confine it, and in that cafe would juft counterbalance, and confequently meafure its elaftic force. A folid block of very hard ftone, four feet four inches fquare, was placed upon a bed of folid mafonry, which defcended fix feet below the furface of the earth. Upon this block of ftone, which ferved asa bafe to the whole machinery, was placed the barrel in which the explofions were made, It was made of hammered iron 2,78 incheslong, and 2,82 inches in diameter at its lower extremity, which was flat in order to reft upon its fupporter. Its bore was one quarter of an inch in diameter, 2,13 inches long, meafured from the upper fur- face of the barrel, and it ended in a very narrow opening below, notmore than 0,07 of an inch in diameter, and 1,715 inch long, which formed the vent or paflage by which the fire is communicated to the charge. This paflage, however, was not open below, but terminated in a projection from the centre of the bottom of the barrel about 0,45 of an inch in diameter, and 1,3 inch long, which formed the vent tube clofed below... When this barrel is, placed upon its ftand, which is of gun metal, the vent tube paffes, through a hole, into,a cavity in the ftand which has a lateral opening. Into this lateral opening a ball of red hot iron is introduced, having » proper cavity within for the reception of the vent tube, which it {peedily ignites, and fets fire to the powder through the folid fubftance of \the tube itfelf. The opening of the bore of the barrel, which is placed in the vertical pofition when.in ufe, is clofed by a folid hemifphere of hardened fteel, whofe diameter was 1,16.inch, its plain fide being downwards. tis confined laterally by three upright cylindrical pins, which allow it to rife only in the vertical direStion. Upon this hemifphere is placed, the weight made ufe of for confining the claftic fluid generated from the powder in its combuftion. This weight,which in fome of the experiments was a heavy twenty-four pounder placed, ver- tically upon its cafcabel, being fixed to certain timbers, was capable of fliding up and down 6 in 462 Combuftion of Gunpowder in'a Clfed Vefel. in’a vertical frame, and could be raifed and lowered in the intervals between ‘the experi- ments by a {trong lever. The end of the barrel was covered with gold; in order to prdvehe as much as poffible its being corroded by the elaftic vapour, which, when the weight is not heavy enough to con- fine it, efcapes between the end of the barrel and the flat furface of the hemifphere ; but even this precaution was not found to be fufficient to defend the apparatus from injury. "The fharp edge of the barrel, at the mouth of the bore, was''worn away almoft imme- diately; and the flat furface of the hemifphere, notwithftanding it was of hardened ftcel, and very highly polifhed, was fenfibly corroded. The corrofion of the mouth of the bore, by which the dimenfions of the furface, upon which the generated elaftic fluid ated, were rendered very uncertain, would alone have been fuflicient to have rendered all the ‘Count’s attempts to determine the force of fired gun-powder abortive, had he not found ‘means to remedy the evil. The method he purfued for this purpofe was as follows: Hay- ing provided fome pieces of very good, compact fole-leather, he caufed them to be beater upon an anvil with a heavy hammer, to render them {till more compact; and then, by means of a machine made for that purpole, cylindrical {toppers of the fame diameter pre- cifely as the bore of the barrel, and 0,13 of an inch in length, (that is to fay, the thick- nefs of the leather) were formed of it 5 and one of thefe floppers, which had previoufly been greafed with tallow, being put into the mouth of the piece afterthe powder had been in- troduced, and being forced into the bore till its upper end coincided with the end of the barrel, upon the explofion taking place, this ftopper (being preffed on the one fide by the generated elaftic fluid, and on the other by the hemifphere loaded with the whole weight employed to confine the powder) fo completely clofed the bore, that when the force of the powder was not fufficient to raife the weight to fuch a height that the ftopper was actually blown out of the piece, not a particle of the elaftic fluid could make its efcape. And in thofe ‘cafes in which the weight was a€tually raifed, and the generated elaftic fluid made its efcape, as it did not corrode the barrel in any other part but juft at the very extremity of the bore; the experiment by which the weight was afcertained, which was juft able to counter- balance the preflure of the generated elaftic fluid, was in no wife vitiated either bythe in- creafed diameter of the bore at its extremity, or by any corrofion of the hemifphere itfelf; for as Iohg’as the bore retained its form and its dimenfions in that part to which the: efforts ‘of the claftic fluid were confined, that is, in that part of the bore immediately in contact with ‘the lower part of the topper, the oo eg ti cone not be opines by ee renee of ‘the bore eithér above’or below. ten ‘+ The powder made ufe of in thefe experiments was of ‘the beft quality, being that kind -called'poudre de'chaffe by the French, and very fine grained, and it was all taken from the fame'parcel. © Care was taken to dry it very thoroughly, and the air of the room in whieh it was weighed out for ufe was very dry. The weights employed for weighing the powder ‘were German apothecary grains, 104,8 of which make 100 grains troy. The weights em- ployed to confine the elaltie vapour generated in'the combuftion of the powder, are reduced | from Bavarian pounds, in which they were originally expreffed, to pounds avoirdupois. ‘The meafures of length were all taken in Englith feet andinches. The experiments were all veneidi in the open air, in the court-yard of the arfenal at Munich, aud they were all made in fair Combuftion of Gunpowder in a Clofed Veffl 463 fair weather, and between the hours of nine and twelve in the forenoon, and two and five in the afternoon ; but the barrel was always charged, and the extremity of the bore clofed by its leather {topper in the room where the powder was weighed. In placing the barrel upon the block of ftone, great care was taken to put it exactly under the centre of gravity of the weight employed to confine the generated elaftic vapour. Upon applying the red- hot bail to the vent tube, and fixing ic in its place by its lever, which fupported i it, the explo- fion very foon followed, When the force of the generated elaftic vapour was fufficient to raife the weight, the ex- plofion was attended by a very fharp and furprifingly loud report ; but when the weight was not raifed, as alfo when it was only a little moved, but not fufficiently to permit the leather ftopper to be driven quite out of the bore, and the elaftic fluid to make its efcape, the report was fearcely audible at the diftance of a few paces, and did not at alt refemble the report which commonly attends the explofion of gunpowder. It was more like the noife which attends the breaking of a fmall glafs tube, than any thing elfe to which it could be compared. In many of the experiments in which the elaftic vapour was confined, this feeble report at> tending the explofion of the powder was immediately followed by another noife totally dif- ferent from it, which appeared to be occafioned by the falling back of the weight upon the end of the barrel after it had been a little raifed, but not fufficiently to permit the leather ftopper to be driven quite out of the bore: In fome of thefe experiments a very fmall part only of the generated elaftic fluid made its efcape; in thefe cafes the report was of a pe- culiar kind ; and though perfeétly audible at fome confiderable diftance, yet not at all refem- bling the report of a mufket. It was rather a very ftrong fudden hifling, than a clear, diftin€, and fharp report. Though it could be determined with the utmoft certainty by the report of the explofion, whether any part of the generated elaftic fluid had made its efcape ; 3 yet for {till greater pre- caution, a light collar of very clean cotton wool was placed round the edge of the ftecl hemifphere, where i it repofed upon the end of the barrel, which could not fail to indicate, by the black colour it ‘acquired, the efcape of the elaftic fluid, whenever it was ftrong enough to raife the weight by which it, was confined, fufliciently to force its way out of the barrel. Though the end of the Bari at ithe mouth of the bore was covered with a circular plate of gold, in order the better to defend the mouth of the bore againft the effects of the corro- five vapour; yet, this plate being damaged in the courfe of the experiments (a piece of it being blown away), the remainder of it was removed, and it was never after thought ne- ceffary to replace it by another. When this plate of gold was taken away, the length of the. barrel was of courfe diminithed as much as the thicknefs of this plate amounted to, which. was, about xeoth | part of ; an inch ; but i inorder that even this {mall diminution of the length of | the barrel might have no effet on the refulrs of the experiments, its bore was deepened gtoth, of an inch when this plate was removed, fo that the capacity of the bore remainedythe: fame as before. After making ufe of a great variety of expedients, the beft and molt convenient method of clofing the‘end/ of ‘the bore, and defending’ the flat furface of the fteel hemifphere from: the corroding vapours, was found to be this: Firft, to cover the’ end of the bore with a eircular plate of thin oiled leather; then to lay upon this a very thin circular plate of 4 hammered! 4b4 Combuftion of Gunpowder.in a Clofed Veffely—its Refidue. hammered brafs, and upon this brafs plate the flat furface of the hemifphere. . When the elaftic fluid made its efcape, a part of the leather was conftantly found to have been torn away, but never in more places than one; that is to fay, always on one fide only. What was very remarkable, in all thofe experiments in which the generated elaftic va- pour was completely confined, was the fmall degree of expanfive force which this vapour appeared to poffefs after it had been fuffered to remain a few minutes, or even only a few feconds, confined in the barrel; for upon raifing the weight by means of its lever, and fuf- fering this vapour to efcape, inftead of efcaping with a loud report, it rufhed out with a hiffing noife, hardly fo loud or fo fharp as the report of a common air-gun ; and its effeAs ‘again{t the leathern ftopper, by which it aflifted in railing the weight, were fo very feeble as not to be fenfible. Upon examining the barrel, however, this diminution of the force of the generated elaftic fluid was eafily explained; for what the Count thinks was undoubtedly in the moment of-the explofion in the form of an elaftic fluid, was now found transformed into a folid body as hard as aftone. It may eafily be imagined how much this unexpected appear- ance excited his curiofity ; but, intent on the profecution of the main defign of thefe experi- ments, the afcertaining the force of fired gun-powder, he was determined not to permit him- felf to be enticed away from it by any extraordinary or unexpected appearances or accidental difcoveries, however alluring they might be; and faithful to this refolution, he poftponed the examination of this curious phenomenon to a future period, and fince that time he has not found leifure toengage in it. He thinks it right, however, to mention fuch curfory obfer- vations ashe was able in the midft of his other purfuits to make upon this fubject. This matter was very hard, and fo fi irmly attached to the infide of the barrel, and parti- cularly to the infide of the upper part of the vent tube, that it was always neceflary, in order to remove it, to make ufe ofa drill, and frequently to apply a confiderable degree of force. It was of a black colour, or rather of a dirty grey, which changed to black upon being ex- pofed to the air, had a pungent acrid alkaline tafte, and {melt like liver of fulphur. Tt ate tracted moifture from the air with great avidity. Being moiftened with water, and fpirit of nitre being poured upon it, a ftrong effervefcence enfued, attended with a very offenfive and penetrating fmell. Nearly the whole quantity of matter of which the powder was compofed feemed to have been transformed into this fubftance * ; for the quantity of elaftic fluid which efcaped upon removing the weight was very inconfiderabe, But this fubftance was no longer gun-powder ; it was not even inflammable.’ ‘What change had it undergone ? demands our ‘author,—What could it have loft ? ? Itis very certain the barrel was confiderably heated in thefe experiments. ‘Was this occafioned, by the caloric, difengaged from the powder in its combuftion, making its efcape through the iron? And is this a proof of the exiftence of caloric confidered as a fluid fui generis; and. that it a€tually enters into the compofition of inflammable bodies, or of pure air, and is ne~ ceflary to theit combuftion ? He dares not take upon him to decide upon fach important queftions. He once thought that the heat acquired by a piece of ordnance in being fired arofe from the vibration or fri€tion of its parts, occafioned by the violent blow it received in’ * Iris much to be regretted that no experiment was made of the weight of this fubftance afforded by a given weight of gunpowder, NL. “the Refidue of Gunpowder burned in a chfe Veffil. 463 the explofion of the powder, but acknowledges fairly that it does not feem to be poffible to account in a fatisfaftory manner for the very confiderable degree of heat which the barrel acquired in thefe experiments, merely on that fuppofition. That this hard fub{tance found in the barrel, after an experiment in which the generated elaftic vapour had been completely confined, was aétually in a fluid or elaftic ftate in the moment of the explofion, is evident, as he thinks, from hence: that in all thofe cafes in which the weight was raifed, and the {topper blown out of the bore, nothing was found remaining in the barrel. It was very remarkable, that this hard fubftance was not found diftributed about in all parts of the barrel indifferently, but there was always found to be more of it near the middle of the length of the bore than at either of its extremities, and the upper part of the vent tube in particular was always found quite filled with it. It fhould feem therefore, fays he, that it attached itfelf to thofe parts of the barrel which were fooneft cooled; and hence the reafon, moft probably, why none of it was ever found in the lower part of the vent tube, where it was kept hot by the red-hot ball by which the powder was fet on fire. He found by a particular experiment, that the gunpowder made ufe of, when it was well fhaken together, occupied rather lefs fpace in any given meafure than the fame weight of wa- ter; confequently when gunpowder is fired in a confined {pace which it fills, the denfity of the generated elaftic fluid muft be at leaft equal to the denfity of water. The real fpecific gravity of the folid grains of gunpowder, determined by weighing them in air and water, is to the fpecific gravity of water as 1,868 to roco. But if a meafure whofe capacity is one cubic foot hold 1000 ounces of water, the fame meafure will hold juft 1077 ounces of fine- grained gunpowder, fuch as was ufed in thefe experiments, that is to fay, when it is well fhaken together. When it was moderately fhaken, together its weight was exaétly equal to that of an equal volume, or rather meafure, of water. Butit is evident that the weight of any given meafure of gunpowder muft depend much upon the forms and fizes of its grains; He adds one obfervation more relative to the particular appearances which attended the ex- periments, in which the elaftic vapour, generated in the combuftion of gunpowder, was con- fined, and that is with regard to a curious effe€t produced upon the inferior flat furface of the leathern ftopper where it was in contact with the generated elaftic vapour. Upon re- moving the ftopper, its lower flat furface appeared entirely covered with an extremely white powder, refembling very light white afhes, but which almoft inftantaneoufly changed to the moft perfect black colour upon being expofed to the air. The fudden change of colour in this fub{tance, upon its being expofed to the air, led:‘him to fufpeét that the folid matter found in the barrel was not originally black, but that it be- came black merely in confequence of its being expofed to the air. ‘The dirty grey colour it appeared to have, immediately on being drilled out of the cavity of the bore where it had fixed itfelf, feems to confirm this fufpicion. An experiment made with a very ftrong glafs barrel would not only decide this queftion, but would moft probably render the experiment peculiarly beautiful and interefting on other accounts. ‘The Count thinks a barrel of glafs might be made ftrong enough for the experiment, if it could withftand the fudden heat, and on the whole feems difpofed to think the trial worth making. All the parts of the operation being ready, it was in the autumn of the year 1792 that the firft experiment was made. VoL. I.—Janvary 1798. 30 The 466 Prodigious Force of Gunpowder. The barrel being charged with 10 grains of powder, its contents when quite full amount- ing to about 28 grains, and the end of the barrel being covered by a circular piece of oiled leather, and the flat fide of the hemifphere being laid down upon this leather, and a heavy cannon, a twenty-four pounder, weighing 8081 pounds avoirdupois, being placed upon its cafcabel in a vertical pofition upon this hemifphere, in order to confine by its weight the generated elaftic fluid, the heated iron ball was applied to the end of the vent-tube; and after waiting but a very few moments in anxious expectation of the event, Count Rumford had the fatisfaction of obferving that the experiment had fucceeded. The report of the explo- fion was extremely feeble, and fo little refembling the ufual report of the explofion of gun- powder, that the by-ftanders could not be perfuaded that it was any thing more than a cracking of the barrel, occafioned merely by its being heated by the red-hot ball: yet, as the Count had been taught by the refult of former experiments not to expect any other reporty. and as he found, by putting his hand upon the barrel, that it began to be fenfibly warm, he was foon convinced that the powder muft have taken fire ; and after waiting four or five minutes, upon caufing the weight which refted upon the hemifphere to be raifed, the con- fined elattic vapour rufhed out of the barrel. Upon removing the barrel and examining it, its bore was found to be choked up by the folid fubftance already defcribed, and from which it was with fome difficulty that it was freed, and rendered fit for another experiment. The extreme feeblenefs of the report of the explofion, and the fmall degree of force with which the generated elaftic fluid rufhed out of the barrel upon removing the weight which had’ confined it, had infpired the afliftants with no very favourable idea of the importance of thefe experiments. It was feen indeed from the beginning by their looks, that they thought the precautions to confine fo inconfiderable a quantity of gunpowder as the barrel could contain, perfectly ridiculous; but the refult of the following experiment taught them more refpeét for an agent, of whofe real force they had conceived fo very inadequate an idea. ‘ ; In this fecond experiment, inftead of ro grains of powder, the former charge, the barrel was now quite filled with powder, and the ftcel hemifphere, with its oiled leather under it,. was prefled down upon the end of the barrel by the fame weight as was employed for that purpofe in the firft experiment, namely, a cannon weighing 8081 pounds. The barrel: (which, though fimilar to it in all refpeéts, was not the fame that has already been defcribed) was made of the beft hammered iron, and was of uncommon ftrength. Its length was 2 inches ; and though its diameter was alfo 23 inches, the diameter of its bore was no more than + of an inch, or lefs than the diameter of a common goofe quill. The length of its bore was 2.15 inches. Its diameter being 23 inches, and the diameter of its bore only 4 of an inch, the thicknefs of the metal was 14 inch; orit was 5 times as thick as the diameter of its bore. The charge of powder was extremely fmall, amounting to but little more than 7th of a cu-. bic inch; not fo much a3 would be required to load a fmall pocket piftol, and not one-tenth part of the quantity frequently made ufe of for the charge of a common mutket. This in- confiderable quantity of gunpowder, when it was fet on fire by the application of the red-hot ball to the vent-tube, exploded with fuch inconceivable force as to burft the barrel afunder jn which it was confined, notwithftanding its enormous ftrength, and with fuch a loud re- port as to alarm. the whole neighbourhood. ‘The fpectators turned pale with affright and: aftonifhment, and it was fome time before they could recover themfelves, The barrel was mot Efiimate of the Force employed in burfting an Iron Barrel. 467, ‘not only completely burft afunder, but the two halves of it were thrown upon the ground in different direCtions ; one of them fell clofe by the Count’s feet, as he was ftanding near the machinery to obferve more accurately the refult of the experiment. From fome former experiments with fmall iron wire, Count Rumford deduces, that a cy- linder of that metal, whofe tranfverfe fe€ion is one inch, would be able to fuftain 63466 pounds without being broken. But for greater accuracy, he caufed feveral {mall pieces to be cut out of the folid half of the barrel which was broken. From four experiments with pieces whofe diameters were refpe€tively in thoufandth parts of an inch, fifty, fixty, fixty- fix and feventy-fix parts, which were broken by a direé pull, it was found that the medium weight required to break one inch of this iron was in pounds avoirdupois 63173. The varia- tions in the refult were fuch as to'render the fecond figure (exprefling thoufands) uncer- tain. Our author computes the refiftance of the barrel from the area of the furface of frac- ture, namely, 65 inches, by ufing this as a fimple multiplier, which gives 410624 pounds, And this force being confidered as applied to a furface of half an inch, which is the area of a longitudinal fe@tion of the bore of the barrel, and reduced into atmofpheres, by allowing 15 pounds avoirdupois for the medium preffure of the air upon a {quare inch, gives 54750 - atmofpheres for the meafure of the force exerted for overcoming fuch a refiftance. This force, enormous as it may appear, is fuppofed by the Count to be fhort of the real initial _ force of the elaftic fluid generated in the combuftion of gunpowder, becaufe he thinks it probable that the barrel was in faét burft before the generated elaftic fluid had exerted all its force. On this head of probabilities 1 would venture to make a remark, that the iron in the barrel may perhaps be confidered as not exaétly in the fituation of the pieces which our author broke in his engine by a dire pull. For in thefe laft it may reafonably be fuppofed, that the whole preflure of cohefion was equally acted on till the moment of fraéture ; whereas in the barrel the fra€ture may, from the {pring of the metal and other circum- ftances, be fuppofed to have proceeded from the inner to the outer furface by a progreffion or tearing afunder, which, however fwift, muft have rendered the divifion more eafy. But at all events, whatever may be the force of this remark, it can in no refpeét invalidate fuch conclufions as were drawn from the aétual lifting of great weights by raifing the hemifpheri- eal cover of the barrel. A fet of experiments were inftituted with an apparatus of the kind here defcribed, for the purpofe firft of determining the expanfive force of the elaftic vapour generated in the come buftion of gunpowder in its various ftates of condenfation, and the ratio of its elatlicity to its denfity ; and fecondly, of meafuring by one decifive experiment the utmoft force of this fluid in its moft denfe ftate ; that is to fay, when the powder completely fills the {pace in which it is fired, and in which the generated fluid is confined. A numerous feries of experiments are tabulated in the Count’s Memoir. The dimenfions of the barrel made ufe of in thofe experiments were as follow ;’ Diameter of the bore at its muzzle = 0,25 of an inch. Joint capacities of the bore and of its vent-tube exclufive of the fpace occupied by the leathern {topper = 0,08974 of acubic inch. Quantity of powder contained by the barrel and its vent-tube when both were quite full, exclufive of the fpace occupied by the leathern ftopper, 25,641 German apothecaries grains, = 24% grains troy. 20'2 The 468 Experiments on Gunpowder. Dama/cus Steel. The Table, in the original, contains a great number of experiments, in which the weight or piece of ordnance was cither not raifed, or was thrown up with aloud report. Thofe expe- riments, in which the weight jult moved without a rgport, are obvioufly fuch as indicate the elaitic force to have been equal to the preflure. 1 have accordingly felected thefe only in the following table as fuitable-to form the bafis of computations. The day, hour, and mi- nute when each experiment was made, are likewife to be found in the original, though it did not feem neceffary to infert them in this abridgment. ‘The expreflon of the weight on atmofpheres is grounded on the aflumption, that the mean preflure of the atmofphere is equal to fifteen pounds avoirdupois upon a fquare inch, TABLE 1.—Experiments on the Force of Fired Gunpowder. The Charge of Weight employed ips meagre Reet ute wo confine the elaf- State of the At-) The Charge of], | oo Srne the elaf- mofphere- Powder. - |. Guig. mo(phere. Powder. edule? Se eee ESS eae eS SSE 47319 8's mo te é - |eo 83 8] Te lbs.) ry atmo fe SE] tn tbs), atmon BS [ESI Sg 2 lsvoirdu- | otercs as = voirdu- |e beres Ren he) Se 5 . a . . Z 3 2 Eee pois. = SE [pois 4 lbs. | Parts. Ibs. .| Eng-Inch. 390 | 138755 |1884,3 429 |1634 |2219 460 {189551 )257357 507 12422 13288,3 546 |2951 4008 585 |3477 |472235 624 |5220 |7090 702 |8081 {10977 504,8} 685,6 5754| 77,86 134,2| 182,3 212,24) 288,2 281,57] 38254 413,27| 561,2 97,66} 811,7 57164]1164,8 1£42,3)1§5153 OC CIMbWHNHQ O In the laft experiment, with near eleven thoufand atmofpheres, the weight was raifed’ with a very fharp report, louder than that of a well-loaded mufket ; and in the experiment immediately following with the fame charge, but with the addition of fix hundred and nine= teen pounds to, the weight, the vent-tube of the barrel burft. ‘This experiment was the 5th of the Table, probably the 85th time of heating the tube: (To be concluded in the next Number. dg Se eee nnn VII. ; Objervations and Experiments on Steel, refembling that of Damafcus; with an eafy Tefi for de- termining the uniform Quality of Steel before it is employed in Works of Delicacy or Expence. In the infancy of fociety the hardeft bodies, fuch as ftones, and certain kinds of wood, were feleéted and ufed for cutting inftruments, and ftill are applied to that purpofe in fe- veral parts of the world. Thefe materials were fucceeded by copper, hardened by a mixture of tin, of which numerous weapons yet remain in the cabinets of the curious. And Jaftly, fteel, Examination of a true Damafeus Blade. 469 fteel, whether obtained dire@tly from the ore, or by cementation of malleable iron, has defervedly taken place of every other article, on account of the united qualities of tenacity and hardnefs *. When the {word was the chief weapon of war, it muft have been an objeét of grea intereft and demand to give to its blade a durable keen edge, and a degree of firm- nefs or ftrength, which, without rendering it unwieldy, fhould enfure the warrior againft expofure to the fatal accident of its breaking in the aét of combat. The fabres of Da- mafcus have been famous for ages, and ftill bear a great price in the Eaft; but we have no decided account of the manner in which this fteel is manufactured or made up. Some years ago I was favoured with the poffeffion of a true blade of this kind for a few days, which, if my recolletion be accurate, had coft the pofleflor twelve guineas at Con{tan- tinople. I know the fum was not lefs than this. As I was not permitted to make any experiments upon it, I could only ground my procefs upon reafoning from its external ap- pearance and obvious qualities. It had a dull grey or blueifh appearance, was fearcely harder than common ftect from the forge, was not eafily bended, and when bended had no fpring to recover its figure. Its back was fmooth, as were alfo two narrow floped furfaces which formed its edge under an angle of abont 40 degrees; but its flat fides were every where covered with minute waving lines in maffes in all direCtions, not crofling each other, and, for the moft part, running in the direétion of its length. The lines were in general as fine as harpfichord wire, not extremely well defined nor continued ; and their diftinGtion from each other was effeted by no perceptible indentation of the furface, but rather by the fucceflion of parts differing in the degree of polifh or brightnefs. No one, upon infpe€tion of this furface, would for a moment have imagined or allowed that it could have been done by engraving or etching, as the falfe blades are damafked. I was informed that if any part of this blade were made fmooth by grinding or whetting, the wavy appearance, called the water, could be again produced by means of lemon juice ; and that its excellencies were, that it could be depended upon not to break, and that it would cut deeper into a foft fubitance, fuch as a pack of wool, or into flefh, than any other kind of blade. From thefe circumftances, as well as from the price, I was induced to think that the blade was compofed of fteel and iron, and that the procefs of forging was fuch as greatly to enhance the coft, by the labour and management it might require. Por if we fuppofe the pieces to be united together at the welding heat, and then forged or drawn out, it is certain that no fmall degree of {kill and care would be required to render all the parts found, and at the fame time preferve the fteel and iron in poffefion of their characteriftie pro- perties. Too great a heat would probably render the whole mafs more uniform than is confiftent with the fubfequent production of the water or wavy appearance, In my attempt to imitate this fteel, | endeavoured to fubftitute a mechanical contrivance in the place of this fuppofed careful forging. I caufed a cylindrical hole of about one inch in diameter to be bored through a piece of caft iron, the lower part of which could be fo placed upon an anvil as to clofe one end of the hole.” A forged iron plug was made nearly to fit the cylindrical hole, but confiderably ‘longer. Equal weights of German fteel and Swedith iron, both in filings, were then well * Philofophical Journal, I, 381- mixed 47° Imitation of Damafcus Steel—Tef} of Uniformity in Steel. ‘mixed with oil, and wrapped ina papery which had before been Yolled upon the shi and confequently fitted the cylinder. ,"The ends of the paper were neatly folded ; and the whole mafs being then put into the caft-iron cylinder placed upon the anvil, a few blows were given by driving the plug into the hole with a heavy hammer. By this means the mafs of filings, when thruft out of the cylinder, was compact and manageable. Ie was then placed in a charcoal fire, and urged to a welding heat by the double bellows. Thence it was taken with the tongs; again haftily put into the cylinder, and hammered by means of the plug and the heavy hammer. When it was taken out, the whole was found to be confolidated; but upon forging it into a plate, a confiderable portion flew off inacrumbly form. The plate, however, was filed up, fmoothed, and examined. ’ Its colour prefented nothing remarkable. When weak nitrous acid was poured upon it, it became mottled in confequence of the numerous fmall black {pots which appeared upon the particles of fteel, while thofe ofiron remained clean. On the nitrous acid being wafhed off, the furface appeared wavy like the Damafcus fteel, but fcarcely at all fibrous ; doubtlefs be- caufe the folid had not been drawn out by forging. An attempt was made to harden it by ignition and cooling in water ; but it ftill remained foft enough to be cut with the graving tool, the point of which did not indicate any difference in that refpect between the parts of iron and of fteel, though it is very probable fuch a difference did really exitt. lL infer, therefore, that the Damafcus fteel is in fact a mechanical mixture of fteel and iron; that it is incapable of any confiderable degree of hardnefs, and confequently is in no danger of breaking from its brittlenefs; that its tenacity is enfured not only from the admixture of iron, but likewife from the facility with which its foundnefs may be afcer- tained throughout, by the fame procefs which exhibits the water or fibrous appearance : and, laftly, that the edge of a weapon formed of this material muft be rough, on account of the different refiftance which the two fubftances afford to the grindftone, in confequence of which it will operate as a faw, and more readily cut through yielding fubftances than fuch cutting tools as are formed of a more uniform fubftance. This experimental enquiry directed my attention to a method of afcertaining the uni- formity of texture in iron or fteel, which perhaps may have been noticed by others, but is certainly unknown in moft manufactories, though I have found it of great utility. If a weak acid, for example the nitrous, which I have ufually taken in a very diluted ftate, be applied to the face of iron or fteel previoufly cleaned with the file, or with emery paper, the parts which contain the greateft portion of carburet of iron (or plumbago) immedi- ately thew themfelves by their dark colour. It very frequently happens that articles of con- fiderable value, intended to be fabricated in iron or fteel, are not “known to be defeétive until much expence has been.laid out in manufacturing them. A piece of iron, which has a vein of fteel running through it, as is too often the cafe, will require at leaft three times the labour and care to turn it in the lathe, which would have been demanded by a piece ef greater uniformity. Steel which abounds with fpots, or veins, or fpecks called pins, may be fafhioned completely, and will not fhew its defects, until the final operation when the attempt is made to polifh it. Other articles, fuch as meafuring {crews, blades of fheers, fine circular cutters, &c. either bend in the hardening, from the difference of expanfion, or refift the tool when wrought in the tempered flate, or exhibit other incurable defeés when they come to be tried ; which the teft. by nitrous acid would haye indicated before any _ Irritability of the Pollen of Plants, 471 any expence had been incurred. In thefe, and in numberlefs other inftances, it would haye been incomparably more advantageous to have rejected the material upon the firft trial, rather thar have proceeded to the very expenfive procefs of manufaCturing the article, and then finding it of no value. By this fimple expedient I have feen bars of fteel as full of veins and irregularities as wood, and have been enabled to feleét the beft and moft uniform pieces for works of the greateft delicacy ; whereas, before I thought of this mode of trial, I have very often had the mortification to fail in the laft {tage of experimental procefles, upon which much coft ang labour had been beftowed. SN SSS _VIIi. On the Irritability of the Pollen of Plants. With an Account of a Compofition for clofing Wide-mouthed Vi effels. n To Mr. NrcHoLson, Editor of the Philofophical Fournal.. SIR, A FEW fummers ago a friend of mine chanced to make a curious difcovery relative to» the irritability of the pollen or fecundating duft of plants ; which, as I know not that it has. yet met the eye of the public, you are at liberty, if thought fufficiently interefting, to com. municate through the channel of your Journal. Whilft making obfervations with one of Adams’s compound microfcopes on the figure: of the particles of pollen colleéted’ from different plants, he applied a drop of water to a fmall group (which was placed on the glafs plate of the flage), in order to increafe the bulk; and, by that means, more accurately determine the figure of the particles. Happen-. ing, at the fame time, to have a {mall phial of {pirits of wine at hand, he next tried a drop of that liquid to freth pollen, when he was agreeably furprifed with feeing it produce a quick gyration, as well as a darting of the particles backward and forward in the drop: this motion continued for a few minutes, and then gradually fubfided ; the particles un- ravelling into a continuous filmy thread, and at other times appearing to burft and emit a multitude of particles *-infinitely fmaller, and which conglomerated together, leaving the capfular veflel empty, or only filled with the {pirit. : The {peedy evaporation of the fpirit appearing at times to prevent the completion of the phenomenon, he afterwards tried, and with better fuccefs, a little common brandy, The motions, in this cafe, were continued longer, and the appearances were more complete. It will appear that thefe do not proceed from the mere evaporation of the liquid, becaufe thofe particles which have been once faturated, though from fome caufe they may not have burft or unravelled, are incapable of excitation, at leaft in any fimilar degree, by the application of more fpirit. © Different kinds of pollen were made ufe of for this experiment ; but that of the “* Caius flagelliformis” was moftly employed, as affording the moft ftriking appearance, on account of the magnitude of its particles. * At leat it prefented this appearance at times to my eye; which, I doubt not, has been the occafion of its Dbtaining from fome botanifts the appellation of the fpermatic aura of pollen, I ; I T avoid! 472 Cement for wide-mouthed Veffels.—Eyes of Birds. I avoid entering into any theoretical obfervations on the aforefaid phenomenon, until more fully illuftrated by experiment, and content myfelf with merely announcing it to the curious inveftigators in the paths of philofophical botany. I take this opportunity of communicating another method, or at leaft another compo- fition for cementing wide-mouthed veffels, in addition to thofe mentioned in your Journal for September. It is a mixture of fpermaceti and caoutchouc: the former to be melted in a ladle, and the latter added in fmall bits, which will be gradually but effe€tually dif- folved, and the compound forms a cement perfectly air-tight when poured on fluid and fuffered to cool. It is alfo, I believe, very little, if at all, attacked by acids, and on that account might be of confiderable ufe in philofophical laboratories. The quantity of caout- cheuc may be varied according to the intended purpofe, or any hardening fubftance, as mattic,.added if required. If this latter communication fhould prove of any ufe to you perfonally, or to your chemical friends, it will amply gratify Your obliged reader, Dec. ff, 1797+ AMICUS, eEaEaEa—_——eenaarwKF———— === IX. Experimental Refearches to afcertain the Nature of the Procefs by which the Eye adapts itfelf to produce diftine Vifion. [Continued from page 313.] ES the former part of this article, refpecting the adjuftment of the eye, a confiderable number of original experiments and remarks were related from communications to the Royal Society. Thefe have for their obje€s the determination, whether the cryftalline hu- mour by its fuppofed mufcularity, the external mufcles by their greater or lefs preflure up- ‘on the orbit, or the cornea bya variation in its curvature, be each the fole or chief agent ip caufing the ‘pencils of light from vifible objeéts to arrive in all cafes at thofe foci which diftin€& vifion requires. I fhall now proceed to give the fubftance of the other Memoirs publithed by the Royal Society upon the fame fubject. In the volume for 1795, page 263,.I find a paper of Obfervations on the Eyes of Birds, by Mr. Pearce Smith. This gentleman relates, that, in the year 1792, he obferved, while diffefting the eyes of birds, an irregular appearance of the {clerotica in that part which fur- rounds the cornea,.and which in them is general y flat. On a more minute examination, it - appeared to be fcales lying over each other, and which appeared capable of motion on each other. .On inveftigating this ftruCture, the fcales were found tobe of bony hardnefs, at leaft much more fo than any other part of the fclerotica. On the infide of the fclerotic coat there was no appearance of thefe fcales. Tendinous fibres were detected f{preading over the fcales, terminating in the four rei mufcles of the eye, fo that upon the ,contrace tion of thofe mufcles the fcales would be moved. By reflecting on the probable ufes of this conformation, Mr. Smith deduced, that the in- ternal capacity of the eye willbe greateft when the recti mufcles are not in ation; and the feveral circles of {cales being fuffered.torepofe upon each other in fucceflion, are upon 5 the d Peculiarities.of Vifion in Birds. 473 the whole, nearer, the anterior extremity of the optic axis, than pat any, other, time; 'thaty when by voluntary effort thofe mufcles are made to act, the feveral circles of fcales will be drawn back, and diminifh the periphery of the eye at their refpective pofitions in this laft fituation ; and that confequently the internal capacity of the organ being rendered lefs, the moft elaftic part, namely, the cornea, will yield to the preflure of the included humour, and become more.convex.. This he concludes muft render {mall objects, near the animal, very difling, On the relaxation of the mufcles, the original flatnefs of the cornea will be reftored by the elafticity (as he affirms) of the fclerotica ; and he proceeds to make remarks on the ad- vantage the animal fyftem derives from elafticity being oppofed to mufcular force, giving nearly the fame inftances as were offered with regard to the elafticity of the cornea a few months before by Mr. Home *. He does not explain in direct terms the peculiar excellence this imbricated fyftem of fcales may be imagined to poilefs, but thinks it particularly necef- fary to birds, which, without it, would, as he fays, be continually expofed to dath themfelves again{t the trees of a thick foreft. He conceives alfo, that the extraordinary alteration in the focus of the eye of an eagle in almoft an inftant of time when it darts from the upper air and feizes an obje&t on the ground, and the purfuit and feizure of a gnat or {mall fly by a fwallow, muft require the aid of this apparatus, which in them is very diftin@. But with regard to thefe particulars, or final purpofes, fomewhat more of inveftigation feems to be wanting. For itis certain, that no bird will dare to fly rapidly through a thick wood, but either pafs leifurely from branch to branch, or foar above the tops of the trees when {peed is the object of their aim. And however confiderably the bony circles may be fhewn to add to the range of adjuftment for near objects, it does not appear that any greater fuddennefs of change, in the eagle and other birds of the fame fpecies, is wanted, than is within the power of animals not pofféfling that ftructure 5 becaufe the adjuftment from remote to near ob- jects is effected in the human, and probably every other eye, in a time incomparably fhorter than that of an éagle’s defcent upon his prey. Neither do {wallows purfue gnats or flies, put fcud through the. air with at leaft twelve times the velocity of thofe {mall creatures, which ‘they probably catch by opening their mouths without the leaft ufe of fight. ~ The mention of {wallows, and: the probability, of winged, animals flriking themfelves again{t trees in their flight, brings to my recollection fome particulars which do not feem altogether foreign to the prefent fubje&t.’ Ina certain ftate of the atmofphere, it is ufua) for {wallows to fly rapidly along near the face of a row of hhoufes, at the diftance of three or four inches from the wall. Now Ltake it for granted, that they cannot poflibly diftinguith the houfes during their courfe, on account of the rapid angular motion ; and I doubt very much whether they fee objeéts before them with any precifion—not to mention the probability that the eye itfelf would be immediately dried if the nictitating membrane were not almoft con- ftantly upon it. With thefe refleétions, on an occafion of this kind, it did not feem furprifing that many of thefe birds came fo near my face, while obferving them from a window, that they fcarcely feemed to have noticed me. But the moft remarkable circumftance was, that they did, in fa& turn afide fo as to avoid ftriking me 5 though in fome inflances fo near that I i isto ¥ Philoh Tranf. 1795, p» 29; or this Journal, p. 313. Vor, L—Janvary 1798. 7P Bieta ™ both 474 Suppafed Sixth Senfe in Bais. both heard and felt the agtion of the air to which they gave motion. On more attentive confideration, however, it appeared to me, that this motion of the air is the very inftrument which by its re-a€tion may warn them of the prefence and pofition of an obftacle the in- ftant they approach it; which they may habitually and fpeedily avoid. For, as_the intelli- gent blind are faid to know, by the motion of air and its echo, the fize of rooms, the width of fircets, and other local attributes, which are commonly afcertained by the fenfe they are depri- ved of; and as boats move more fluggifhly in fhallow or contraéted channels ; and air itfelf cannot be forced with rapidity through long tubes ;—in all which circumftances the re-action muft be very confiderable; fo, on the other hand, it can fearcely be doubted, that the object of fuch re-aétions, if capable of perception, would be fufliciently aware of their prefence or ab- fence. I fuppofe the re-aStion of the air dafhed againft my faceby the {wallow, and the noife I heard, were as perceptible and as impreflive to the bird as to myfelf; and from this reafoning Lam lefs difpofed to wonder at the refult of the cruel experiment performed in Italy a few years ago upon bats. As I have feen the notice only ina voluminous periodical publication to which I cannot now turn, I muft fimply relate, that bats have been thought to poffefs a fixth fenfe, becaufe, when the eyes of one of thofe animals were diffected out, it flew round a room with the fame fpeed and prectfion as before, avoiding the walls and obftacles as readily as if ftill poffeffed of fight. If my conje€tures have any foundation, thefe creatures did never ufe the eye to warn them of impediments to their flight, but had conftantly attended to the re-action of the fluid in which they moved ; which would be very different in the vicinity of an obftacle compared with that in open fpace. From the re- action of a direét obftacle, they would turn to the fide where the preffure was Jeaft, or the {pace moft open ; and if the obftacle were oblique, it may eafily be imagined that the re- quifite deviation from their courfe would be equally obvious. To return to Mr. Smith’s Memoir. He was led from the examination of the eyes of birds to thofe of quadrupeds, and found by tearing and diffecting that the reéti mufcles ter- minate in the cornea; in which, and im his inferences, he entirely agrees with Mr. Home in the paper before. mentioned *. The Croonian Leéture, read before the Royal Society in November 1795, was written by Everard Home, Ef. and contains a profecution of the enquiry refpecting vifion, of which an abridgement has already been given. The explanation of the adjuftment of the eye by an aflumed change in the radius of the cornea being different from the theories before formed on that fubject, it was thought right to put it to the teft of every experiment which might appear likely to refute or con- firmthe obfervations already made. The reader has feen that a perceptible variation in the figure of this part of the organ of fight, was afcertained by obferving its outline by means of a microfcope. Another method fuggefted itfelf; namely, that if the convexity of the cornea were increafed to a certain degree, it could be meafured by applying an achromatic microfcope, with a divided eye-glafs micrometer, to view the image in the virtual focus of its furface. The firft {tep in this experimental procefs was to afcertain, by experiments upon convex mirrors, what difference of curvature could be decidedly obferved by an apparatus of this kind. ‘Two convex mirrors, one of +4,ths of an inch focus, the other ;4,ths, had their * .” Philof, Tranf. or this Journal as laft quoted, s Bat Experiments on the Cornea. 478 flat furfaces made rough and blacked, to prevent an image being feen from both furfaces. One of thefe was ftuck upon a piece of wood, dire@tly oppofite a window, at 12 feet diftance from it. A board, four feet long, and fix inches broad, was placed perpendicularly againft the fath of the window, and its image reflected from the mirror upon the objet glafs of an achromatic microfcope, with a divided eye-glafs micrometer. The two images were feparated by means of the divided eye-glafs till their furface of contact, which appears like a black line, was rendered as fmall as poffible. When this effect was produced on the images from the mirror of ,4,ths of an inch focus, that mirror was removed and the other put in its place. The contac of the two images, which before appeared like a line, had now acquired confiderable breadth, correfponding exa@tly to the difference between the convexities of the mirrors. When the fame experiment was repeated upon the eye, there was a perceptible, though extremely fmall, change in the micrometer at firft when the eye was frefh. This was not however feen afterwards, and the eye very foon became fo much fatigued, that it was ne- ceffary to defift. It was found that every time the eye adapted itfelf to different diftances it became neceflary to alter the diftance of the objet-glafs of the microfcope from the cornea. This experiment was repeated on four different days with the fame refult ; namely, a change in the micrometer at firft, which in the fubfequent trials could not be detected. Two f{uppofitions offered themfelves as likely to account for this effect, namely, a motion of the. head forwards, or an action of the mufcles of the head itfelf; but, as the author remarks, this effe&t ought in the firft cafe to have been more frequent, the greater the fatigue of the eye ; and the latter circumftance would have produceda contrary refult. It appeared, therefore, that the effeé&t on the micrometer did really arife from a change in the cornea, though too fmall to be detected with certainty in this way. With two other mirrors, of which the focal diftances were -4,ths and ,+°* ths of an inch, the difference between the fize of the images was juft vifible in the micrometer ; but it did not appear probable that the fame difference would have been vifible had the mirror not been perfectly at reft. From the unfteadinefs of the eye, it might therefore be reafonably fup- pofed that a change of this magnitude might take place in the cornea without being dif- tinétly feen. _ ; To give an idea of the fhort time that a’part can remain nicely adjufted by mufcular ac- tion, the author points out an experiment which any one may make upon himfelf, Let him take a glafs fpirit level, and reft one end of it on a table, fupporting the other with his hand, and endeavour to keep the air bubble in the middle. If the hand is very fteady, the bub- ble may be kept nearly in its place, but not exactly fo; for it will undulate in correfpon- ence with the aétion of the mufcles, making up for want of fleadinefs, by fhort mo- tions, in contrary directions. From thefe experiments, the change in the curvature of the cornea could not be more than }sth part of an inch, as any greater quantity would probably have been diftinly feen in the micrometer. This, however, is flill more than was afcertained by the former expe- riments, which made it to exceed ,+,,th part of an inch, This change in the cornea, at firft view of the fubject, appeared fuflicient to account 3P2 » for 476 Enumerotions of the Means of Adjuflinent in the Eye. for the adjultment of the’ éye, and may probably be fufficient when the lens is removed, but not when the eye is entife. The author therefore proceeded to'examine what alteration thé figure of the’ human eye might be fufceptible of when air was thrown into its cavity, through the optic nerve, fo as to diftend its coats. From the experiments it was found that the axis of vifion was lengthened_.a fmall degree in the eye of a boy fix years old, forty- five minutes after death, while the tranfverfe diameter and axis from the optic nerve were fhortened. A fimilar though lefs effet was’ obferved in the eye of a’ man 25 years old, ore hour after death; but no alteration took place, by the like treatment, in the eye of 4 man 50 years old, 20 minutes after death. The objeét of thefe experiments does not clearly appear, as there is no fufpicion of an ation of this kind in the living fubjeCt; but they ap- pear to fhew that the cornea is the part moft variable from elafticity ; and when the preifure is made laterally, and from without, the elongation muft be ftill greater, the action of the ftraight mufcles being the molt advantageous that could be imagined for this purpofe. This lateral preflure, Mr. H. obferves, will not only elongate the eye, and increafe the con- vexity of the cornea, but will produce an effect upon the cryftalline lens and ciliary pro- cefles, pufhing them forward in proportion as the cornea is flretched. For, as thefe procefles form a complete feptum between the vitreous and aqueous humours, the cavity of the aqueous humour will be always of the fame fize, and the cornea and lens at the fame dif- tance from each other ; in the accurate produétion' of which effeéts, he fuppofes'it likely that the ciliary ptoceffes may operate by mufcular action 5 an opinion which other faéts'in the courfe of the leture tend to confirm. ' The refult of this enquiry, which was not carried on, as he remarks, in fupport of any particular thcory, but with the fole view of difcovering the truth, appears to be, that the ad- juftment of the eye is produced by three different changes i in that organ 5, an increafe of cur- vature in the cornea, an elongation of the axis of vifion, and. a motion of the cryftalline lens. Thefe changes, in a gteat meafure, depend upon the contraction of the four ftraight mufcles of theeye. Mr. Ramfden, from computations grounded on the principles of optics and ge- neral flate of the faéts, eftimates, that the increafe of curvature of the cornea may be capable of producing oné-third of the effect, and that the change of place of the lens, and elongation of the axis of vifion, fufficiently account for the other two-thirds of the quantity oF adjuft- ment neceflary to make up the whole. ~ After this explanation of the mode by which the axis of vifion can be elongated, and the convexity of the cornea increafed i in the human eye, for the purpofe of its adjuftment, Mr. Home was defirous of applying thefe obfervations to the eyes of other animals, Quadrupeds in general muft have their eyes fitted to fee very near objects, as many of them.collect their food with their mouths, in which a€tion the obj ects are brought very clofe to the eye. Birds are under the fame circumftances in a fill greater degree with re- {pect to their food; but from their mode of life, they alfo require the power of feeing objects at a great diftance from the eye. Fithes, from the nature of the medium in which they live, muft have fome other mode of adjufting the eye than that, of a change in the cornea, becaufe that fubftance is poffeffed of the fame refractive power as the furrounding fluid. Quadrupeds haye three modes.of procuring: their food; one by their fore-paws only, which they ufe like hands, as in the monkey, tribe ; the fécoud by their fore-paws and a mouth, Peculiarities of Structure in the Byes of Quadrupeds and Birds. 477 mouth, as-the lion and eat tribe; the third by the mouth, only,’ as all ruminating animals, Thefe three diflerent modes require the food being brought from different diftances from the eye, and it is curious that the mufcles of the eye are different in-all the three tribes. In the monkey tribe the mufcles of .the eye are exaily the fame-as in the human: In the lion tribe they are double in number, and the four intermediate mufcles are loft in the. {clerotic coat at a greater diftance from the cornea than the others. In the ruminating tribe there are four mufcles, as in the human eye’; but there is\alfoa mufcle furrounding the eye-ball attached to the bottom. of the orbit, round the hole through which the optic nerve pafles, and loft upon the fclerotic coat immediately before the broadeft diameter of the globe “of the eye. The upper portion of this mufcle is rather the longeft, the infertion being nearly in a circular line at right angles at the axis of vifion, but not to the axis of the eye from the entrance of the optic nerve. In quadrupeds in general, the ball of the eye is broader in proportion to its depth than in the human fubjec. In the bull the proportion is 14% inch to 15%. 'Thecornea is larger and more prominent, its real thicknefs not eafy to be afcertained, becaufe, like that of the human eye, it readily imbibes moifture after death. When dried, it is thinner than the fcle- Totic coat in the fame ftate. In ruminating animals, the cornea, though circular, has an oval appearance, arifing from an opake portion which is covered by amembrane. ‘The ci- liary proceffes, as in the human eye, are connected with the choroide coat; but they are larger, and are united at their origin with the iris. ; This ftru€ture of the eye im quadrupeds, as far as ity thiteoh from that of tig human eye, appears calculated to increafe the power of adjufting it tomear objeéts ; and from the mode of life which thefe animals purfue, fuch additional powers ee neceflary to enable them to procure their food with eafe. That birds, procuring their food by their beak, muft require an adjuftment to fee very near objects, and that a degree of precifion and facility, with regard to remote objeéts, is‘no lefs neceflary from their fituation during flight, are obvious circumftances. Mr. Home men- tions fome inftances, in which birds are fuppofed to have feen diftant obje€ts with peculiar _ diftinétnefs. It is related, that vultures and other birds very fpeedily repair to the place where a dead animal or other prey is expofed to them; and though there is nothing, pers haps, in thefe facts which fuppofe an acutenefs of fight greater than that of other animals, yet it cannot be doubted, upon the whole, that’ thefe animals fee with very great precifion at vaft diftances. The eyes of birds are larger in proportion than thofe of ethes animals, and broader in proportion to their depth, with a more prominent cornea than in the quadruped. . The cor= nea in the goofe is not united to the fclerotic coat by the terminating of one abruptly in the other; but the two edges are bevelled off and laid over each other’ for nearly.,!,th’of an inch. This cireumftance, as alfo the bony rim: or apparatus furrounding the balis of the cornea, which is peculiar to this clafs of animals, and defcribed by Mr. Smith, was well known to Haller. Mr. Home defcribes it more particularly, and ftates ‘its ufe in the focal adjuftment'to be nearly the fame as that defcribed by Mr. Smith. The ciliary procefles» are Jarger and longer‘in birds than in other animals whofe eyes are of the fame fize ; and the marfupium or membranous procefs peculiar to. the clafs of birds, is hewn by him to !be very fimilar to that of the ciliary proceffes ; but ftronger in all its parts, and, like them, con~ a 4 nected. 478 ~ Strudlure of the Eyes of Birds. nected with the eryftalline lens at the one extremity, and at the other with the bottom of the eye. By experiments on this membrane he afcertained, that it is capable of mufcular con- traion: for, when the marfupium and cryftalline lens of a goofe’s eye were expofed im- mediately after death, and the lens was pufhed forwards fo as to elongate that membrane from 3.,ths to }$ths of an inch, it repeatedly recovered its original dimenfion when the preflure was ebket off. But when the parts had been left until all remains of life were gone, and the tenfion was then made as before to 3°ths of an inch, it contracted only to geths ; whence it was concluded, that the Litedence between the contractions was the, effect of mufcular a&tion. It was obfervable, however, that in fo minute a quantity it was eafy to be deceived. Another experiment was therefore inftituted upon the well-known fa&t, that in the aét of dying, the mufcles are found to contract to their utmoft where there is no refiftance to prevent fuch action; and that this is alfo found to take place in the greateft degree when the animal is killed by any violence committed upon the brain or fpinal marrow. The cryftalline lens of a turkey’s eye was extracted, and immediately afterwards the turkey was killed by wounding the fpinal marrow. The.two eyes were taken out and put into fpirits. In the one the marfupium had-nothing to prevent its contracting to the utmoft ; while in the other the lens being in its natural fituation could not allow of any un- ufual contraction. Some days afterwards the two eyes were examined: in the perfect eye the marfupium meafured 4*,ths of an inch, and its different folds were femi-tran{pa- rent ; in the imperfect eye the iiiceipitind meafured .3,ths of an ‘ich, and the folds were much more opake. Here then was a difference of 7 rth of an inch in the length of the two marfupiums: which could arife from no other aig than the one having contracted fo much more than the other, which contraGtion muft be confidered to be mufcular. On a review of the peculiarities in the eyes of birds the author infers, that they tend to fa- cilitate the lengthening of the axis of vifion, and increafing the convexity of the cornea. The bony rim to which the mufcles are attached, confines their effect to the broadeft part of the eye 5 and as their a€tion throws the cornea forward, the anterior rim of the bony edge yields to adapt itfelf to that change. The ciliary procefles are Jong, and admit of the lens being moved forward during the adjuftment for very near objects, which is performed with more facility than in other animals, while their action ferves to bring it back to its place. The marfupium ferves alfo to draw it backwards, and, by fuflaining part of the pref- fure from behind, renders the cornea flatter, while the anterior edge of the bony rim is adapted to it in this ftate. It may be faid that no fuch great change is neceflary for vifion with parallel rays; but Mr. Home remarks, that where vifion is to be very diftin€, a cer- tain nicety of adjuftment becomes neceffary, and the aétion of the marfupium is probably ° intended for that purpofe. The fubjeé of vifion in birds is concluded by an obfervation, that one of the moft beau- tiful iluftrations of the combination of mufcular and elaftic fubftances is feen in the motion of the ni€titating membrane. ‘This membrane is claftic, and is connected by means of a tendon with two mufcles fituated upon the pofterior part of the eye-ball. The action of shefe mufcles brings the membrane over the cornea; and the inftant they ceafe to contrat, the elafticity of the membrane draws it back again. The eyes of fifhes have feveral peculiarities, and in many refpeds their ftructure differs fsom that which is obferved in the quadruped and bird. The Eyes of Fifois— New Publications. 479 The mufeles of the eye, that correfpond to the ftraight mufcles in the quadruped, are four in number: they are however differently placed; they do not furround the eye-ball, but two of them are on that fide of the orbit next to the nofe of the fifth, the other two on the oppofite fide; their attachment to the eye is clofe to the edge of the cornea; they do not pafs round the eye-ball towards the pofterior part, as in other animals, but are con- neéted with the bones of the head at fome diftance from the eye on each fide, fo that they cannot at all comprefs the eye laterally; they can only pull it backward by the combined effect of their actions. " The bottom of the orbit on which the eye-ball refts is folid and adapted to it, there being no fat interpofed between them as in other animals; and where the eye is removed toa great diftance from the fkull, and that cannot be the cafe, there is a {trong cartilage pro- jecting from the fkull to the bottom of the eye, and that end-of it next to the eye is con- cave, and fitted to the portion of the eye-ball dire@ly oppofite the cornea, juft above the entrance of the optic nerve. This is confidered as a fixed point upoa which the eye moves; but it will alfo, from the fituation of the mufeles, allow the eye to be forced back upon it, and the whole eye to be flattened. The fhape of the eye differs confiderably in different fifhes ; but in all of them the tranf- verfe diameter is the longeft. In the haddock the proportion is }iths to ths of an inch, and in fome fifhes it differs much more. The fize of the eye does not correfpond with that of the fifh; the falmon’s eye being fmaller than the haddock’s. The fclerotic coat is in fome fifhes membranous*, in fome partly bone +}, in others en- tirely fot; but in general the pofterior part is membranous, although the lateral parts are bone §. The cornea is in general flat, not always circular in its fhape, is very thin, made up of la- minz, and does not Jofe its tranfparency in fpirits, appearing like talc||. In others it is more convex, as in fifh of prey; this appears to adapt it to the {pherical cryftalline lens, which in them lies dire&tly behindit{. The tunica conjunctiva forms the anterior layer of the cornea **, and in fome fifhes is quite detached. (The Subftance of Mr. Home’s Concluding Leéture upon the Eye will be given in a future Number. ) NEW PUBLICATIONS. Philofophical Tranfaétions of the. Royal Society of London, for the Year 1797, Part II. Quarto, 541 pages, exclufive of the title, contents, lift of prefents, and index, with nine plates. Sold by Elmfly, London. Tuis part contains the following papers: 1. On the Aétion of Nitre upon Gold-and Platina, by Smithfon Tennant, Efq. F.R.S. 2. Experiments to determine the Force of Fired Gun-powder, by Benjamin Count of Rumford, F.R.S. M.R.I. A. (fee Philof. Journal, i. p» 459)» 3- A third Catalogue of the comparative Brightnefs of the Stars; with an in- % Haddock. + Sword-fith, } Devil-fifhh, § Mackarel, || Sword-filh. ] Pike, * Haddock. troductory i . £33 New Pablications. trodudtory Attount of the Index to ea a Obfervations of the fixed Stars con- tained in the Second Volume ‘of ‘the Hi {tis +> h ch are dded feveral-ufeful: - Refults derived from that Index, by William Herfchell, DL. DF. Ris. alte Aelicusise of the Means employed to obtain an overflowing Well, in'a Letter to the Right Hon. Sir Jofeph Banksy K. B: P. R. S. from Mri Benjamin ‘Vulliamy. 5+ Obfervations of the: changeable Brightnefs of the Satellites of Jupiter,’ and of thé Variation in their apparent: Magnitude with a Determinationlof the Time of their ro Otions on their Axis. ‘Loy which is added a Meafure of the Diameter of the Second Satellite, and an Eftimate of tlie, comparative Size of all the four, by William Herfchell, LL. D. F. R. S. 6. Farther Experiments ‘and QObfervations on the Aifeétions and Properties of Light, by Henry Brougham jun. Efq. °7..On Gouty and Urinary Concretions, by William Hyde Wollafton, M.D. F. R. S.. 8. Experiments on Carbonated Hydrogenous Gas, with a View to deter- mine whether Carbon be a Simple or a Compound Subftance, by Mr. William Henry. 9: Obfervations and Experiments on the Colour of Blood, by William Charles Wells, M.D. F.R.S. 10. An Account of the Trigonometrical Survey carried on in the Years 1795 and 1796, by Order of the Marquis Cornwallis, Mafter General of the Ordnance, by Colonel Edward Williams, Captain William Mudge, and Mr. Ifaac Dalby. ‘A Le@ture introdu@ory to a Courfe of Popular Inftruétion on the Conftitution and Ma- ~ Printed for Cottle in Briftol, and fold in London by Johnfon, 1797, _ nagement of the Human Body, by Thomas. Beddoes, M.D. octavo, 72 pages, price 1s. 6d. _ ~The author of this pamphlet was accidentally informed, by a practitioner in furgery, in the courfe of the year juft expired, that he was defirous of giving a courfe of anatomical leGures in Briflol. To furnifhindividuals with fo much knowledge of themfelves as fhould enable them to guard agaiaft habitual ficklinefs, and a variety of Frown avauehet been an object of Dr. Beddoes’s contemplation. He, therefore, propofed that the courfe fhould be modelled according to this idea. He remarked that a diftin&t exhibition of the larger lines of anatomy and phyfiology would be alfo the mode of inflru€tion beft adapted to young ftudents in me- dicine ; much obfervation of letures having convinced him that extreme minutenefs is only perplexing to beginners, This, joined to fome other confiderations, prevailed. Meff. Bowles and Smith undertook the courfe, the intention of which is, to exhibit the ftruéture of the body in a manner neither fuperficial nor tedious; to explain the funétions of the parts as far as they have hitherto been invefligated ; to illuftrate, by fpecimens, the prin- cipal deviations of thefe parts from their healthy conformation, and to interfperfe fuch re~ fletions as may be ufeful in phyfical education, and the whole conduét of life. Dr. Bed- does purpbfes to contribute his utmoft affiftance to the defign, in whatever way that affift- ance fhall, upon reflection, appear moft likely to be-effectual. This introductory lecture conttitutes part of his exertions in a plan fo truly calculated to promote , individual happi- nefs, and public welfare. He is defirous that its publication may produce fimilar under- takings elfewhere, and juftly fuppofes that a communication of the fae, that thefe! le€tures are attended by an audience more than twice as numerous as the friends of that defign ek« pected, will tend to promote this purpofe. After this concife {tatement of an undertaking to which every friend of mankind muft with fuccefs, I muft decline analyfing the leéture, and content myfelf with obferving, that the fubject, which itfelf is highly interefting tp all defcriptions of men, is treated in a very perfpicuous and impreflive manner, mr ETSI FE rt wt ee Philos. Journal VoL LPL XVI percrreg / 420 ir: ‘A , 7 ~ & , cy 4 i! ' D= fs “ © gee . Se ~~. a ad a 7 L ‘ og ashlee a= . > oy oy tee bho weenie na a i 4 « . - r + s -* es een ee eee ee ed lel. plehe AP + ~ oe yen io eee aris Beare OM a : ie. TE ea ALO, ‘ aw ” alte. Pont ae Me ee ie 2 is : . z fq | 8 Og oO Ha Sos ———_—_——-. — cea = Shey ay —— 10) 4 % hey aS 0GE A PRAY SIVA £7 0A WUANO C BOLMLT —pihete.. we 4 M ‘ ; —— ee er A { OCUCR NPAtL OF NATURAL PHILOSOPHY, CHEMISTRY, AND THE ARTS. ‘FEBRUARY 1798. ART 1 CLE, 1: An Attempt to accommodate the Difputes among the Chemifts concerning Phlogifton. In a Letter from Dr. Mrrcurit of New York to FoszPH PrrestLer, LL.D. F. R. 8. Ge. Be Dated November. 20, 1797 *. On reviewing the ftate of philofophical controverfy as carried on both in Europe and America between the Phlogiftians and their opponents ; it has of late appeared to me, that much of the difficulty which attends the fubjeét arifes, as in abundance of other cafes, from the want of a precife language and of a right underftanding of each other’s meaning. This was fo evident to me in the prefent cafe, that I informed my audience of it in one of my public le€tures in Columbia College, and added my belief, that due attention to terms, their application and ufe, would have great influence in bringing the difpute to a termination. i Having fubjected water heated to the temperature of fteam in an eolipile, and directed the fteam iffuing from it to the furface of red-hot charcoal ; the coal brightened, and a greater flame was obferved near the fpot againft which the fteam was made to play. Here was an occurrence oppofing the common obfervation of mankind, that water will always extinguifh fire by reafon of its own incombuftibility. Water kept at or below a certain temperature will extinguifh fire, and fo will oil; but if water be raifed to a heat fufficiently high, it will alfo burn or undergo decompofition like oil. As far as I could judge from the phenomena before me, water in proper circumftances underwent a true combuftion, and was inflammable for the fame reafon that oil was, becaufe it contained a fomething that would burn ; and this fomething feemed to be exaétly fimilar to that which made oil capable of exhibiting flame. It ftruck me inftantly, that the inflammability of * Communicated by the Author, N. Vor. ].—Fenrvary 1798. ZOE this 283 Propofl for fubpititing the Term this vapour proceeding from burning fat, from heated alcohol, from camphor, ether, coal, and a multitude of other fubftances, gave evidence of their poffeffing a principle enabling them to burn with flame after the fame manner that water did. If there was this fimilarity or indeed identity of the inflammable radical among them, there appeared to be no more propriety in calling that radical hydrogene thah in terming it olegene, alcohologene, etherigeney coalegene*, &c. To give the radical fubftance enabling oil, alcohol, ether and coal to burn with flame a name derived from water, becaafe it enabled water to burn with blaze too, appeared to me partial, illogical and wrong, inafmuch as it conftantly and unneceflarily brought water aid its’ properties to mind whenever any thing was thought of that contained hydrogene; and by this unhappy aflociation, befides the difficulty which attends the fubje& ’ in point of faét, vaftly greater difficulty was made to furround it by reafon of the ill chofen and badly afforted terms employed in talking about it. I had entertained no doubt, for two years, that Aydrogene was an improper word for a nomenclature of fcience, and deferved to'be ftruck out of the lift: but as I was engaged in reforming another article of that arrangement, I chofe not then to meddle with it; and [am glad I did not; fince the prolonged difputes between the parties afford more weighty caufes for an alteration of terms at this day than exiftedat'any former time. The circumftance common to all the proceffes I-have mentioned, is “ burning with flame or blaze,” which, wherever it occurs, feems to indicate the prefence of what has been called hydrogene. According to my prefent conception of the matter, this principle or fubftance common to fo many bodies, and enabling them to undergo inflammation, may in Rtri& propriety be called phlegiffon. Talways thought phigifion a well conceived word, and have objeéted to it, not on account of the impropriety of the term as fuch, but becaufe of the vague and unfatisfa€tory way in which it was ufed. If a definite fignification can be affixed to it, I think the adoption of it will be ftilla great acquifition to philofophical language, and have a tendency to fettle at Ieaft half the controvetfy which divides the chemitts. I propofe, then, to expunge Aydrogene and fubttitute phlogi/fon in its place. Phlogi/fon will thus be the radical term, and ftri@ly mean the thing in combuitible bodies Which forms blaze or ignited vapour. The union of this with mere caloric will, make pAlogi/fous or inflammable air, the air which burns with blaze. The combination of phlogifton with oxygene will conftitute water or the oxyd of phlogiffon, one of the produéts of inflammation, and, like fixed air and other compounds formed during the fame procefs, incombuftible in common tem- peratures and circumftances afterwards. And the caufe of this flownefs to burn, of water and the other compounds, which combuftion furnifhes, is owing to the large dofe of oxygene with which they are charged, giving them little or no appetite for more. If this bafe be united to a yet larger quantity of oxygene, it will form the acid of phlogiflon, or water foured by excefs of oxygenc, as perhaps (though I do not believe it) in what is termed the pyro-lignic and pyro-inucic acids, and perhaps in fome other cafes; but the readinefs with which phlogifton parts with its furplufage of oxygene, turns back to water, and preferyes itfelf in that oxydated form (as proved by the operation of fharp-pointed filaments under water in effecting the feparation) fhews that nature, in enabling the princi- * So in the original: doubtlefs by overfight. N. ple ~ Phlogifton inflead of Hydrogene. 483 ple of inflammability to combine with oxygene, difqualifies the latter in moft cafes from becoming an acid with the former; unlefs it fhould be found (and in this I have no faith) that the formation of the native acids of vegetables is a procefs of this kind. Should this latter conjecture turn out to be the faét, there would be inftances enough of phlogiftic and phlogiftous acids. The nomenelature will then ftand thus: in} 2s. 3. 4 Phlogifton 4 Phologiftous gas Oxyd of phlogifton ( Gafeous oxyd of phlogifton for for for for Hydrogene. { Hydrogenous or Water or oxyd of | Aqueous gas, or watery fteam. inflammable air. hydrogene. 5. 6. 7. Phlogiftous and phlogiftic acids. -Phlogiflates and phlo- Phlogiftures and phlogifturets ; Probably no fuch things; the | giftites. Probably no of fulphur, coal, phofphorus, hydrogene or phlogifton not | fuch combination. iron and zinc, being capable of combining _ inftead of with oxygene beyond the de- ; The common fulphur, &c. gree of oxyd. i of the laboratories and fhops, &c. &e. On the decompofition of fat and oil by fire, it is known that a large quantity of water is formed, and this probably by an union of the bafe of vital air with phlogifton or hydrogene. The like obtains in the inflammation of alcohol, camphor, ether and coal, part of the phlogifton or hydrogene of which apparently turns to water by jun@ion with oxygene. And the principle which in the firft inftance readily exhibits the blazing appearance is changed by and during that operation to a fomething much more difficult to inflame by any after-procefs. : If hydrogene or phogifton is the material which inflames in the fubftances already mentioned, there is prefumptive evidence, upon the face of the fubject, of its exiftence alfo in the common fulphur, phofphorus, zinc, and iron of the laboratories. q I do not mean to fay itis a neceffarily conftituent part of either of thofe bodies; for I believe they may exift without it, or at leaft they may be conceived to exift abftractedly from it. They therefore ftand very well in the nomenclature as fimple fubftances. But if thefe fubftances, fuch as we commonly get them after expofure to the common atmofphere in ordinary Femperatures, are taken for fimpie or pure elementary bodies, the perfons who conilider them fo fall into a great miftake. In their ufual forms they are all incorporated wath hydrogene or phlogif- ton, and from it derive their capacity to burn with flame. This will be the more clearly - idering them more particularly one by one. ; nes a aa rhe Phlogiftians fay fulphuris compofed of Phlogifton united to vitriolic acid ; confequently if any thing takes away that ingredient from the acid, this will turn to brimftone. ‘The antiphlogiftians affirm fulphur to be a fimple body, uncombined chemically with any thing; and that it becomes fulphuric acid by junction with oxygene. Now both parties have reafoned in a manner that does not by any means fatisfy me, They have viewed the combuftion of fulphur in the abftraét, rather than taken it up as it ia. The fact is, that the acid formed in the si ah e of fulphur is not the folid cryftallized sa 3Q2 c 484 Oifervations upon Eppes fuppofed — ter of the glacial oil of vitriol, but a folution of thefe cryftals in water. The exiftence of vitriolic acid in a fluid form implies neceflarily the co-exiftence of water. The formation of the water in the inflammation of fulphur appears to have been paffed over by both parties, though the interpretation of this part of the procefs feems to me to furnifh the means of reconcilement. ‘Thus, while the pure fulphur combines with one portion of oxygene to make the acid, the hydrogene or phlogiflon unites with another parcel of it to form the water in which the acid diffolves. Common brimftone then is not a fimple fub- ftance, but is a phlogijture of fulphur. And this is confirmed by the fa& that, where com- buftion is reftrained, the fuiphur may be refolved into hepatic gas; the phlogifton turning with caloric into inflammable air and diflolving fome of the fulphur. The formation of common hepatic gas feems to evince the fame thing; for while the potafh feizes the ful- phur, the hydrogene or phlogifton is fet loofe, turns with caloric to hepatic gas, and {natches, as it departs, a portion of the fulphur from the alkali. Thus it appears that the two fy{tems are reconcileable with each othet. When the Old Chemifts talk of phlogifton, they fhould define it to be that thing which burns with flame, and when united to oxygene forms water. When the new ones make experiments on fulphur, they fhould remember that the common material called by that name is not the abftraét, pure, uncombined elementary thing they intend in.their nomenclature. 2. In like manner the phenomena attending the inflammation of phofphorus feem ‘to have been as negligently interpreted. Phlogifton added to phofphoric acid was faid by fome to conftitute phofphorus; while oxygene added to phofphorus made phofphoric acid in the opinion of others. But thefe were a kind of chemical theorems, true only in the abftraét experiments. We find that phofphorus burns qith flame, and water is exhibited during the procefs. All that needs be faid about it is, that in common circumftances phof- phorus, though capable of exifting per fe, has a very flrong attraction for hydrogene or phlogifton; and in ordinary cafes attaches more or lefs of it to itfelf. During its inflam- mation part of the oxygene, as in the cafe of the fulphur, combines with the phlogifton into water ; and another part of it joins the oxygene to conftitute the acid. In eftimating the whole of- the procefs, the candid partifans of both fides will allow that the fubftance under confideration parts with its phlogifton and borrows oxygene, and thus water and the acid diffolyed in it are formed. Where is the harm of owning that common phofphorus contains a portion of hydrogene united with it? It does not invalidate the modern theory; but it fhews that the obje€tions of the ancient doctrine were not frivolous, as they have by fome been deemed to be; but on the contrary very fubftantial, and not capable of reconcilement upon any other plan, that I know, than the one herein fuggefted. 3. Zinc may be abftra&tedly confidered as a fimple body, and with propriety placed as fuch in the catalogue.- Commonly, however, it is prefented to us in clofe conneétion with hydrogene, for which its attraétion is fo ftrong that they commonly appear in the form of a phlogifiure of zinc. When that compofition is employed for experiments, it is very eafy to conceive how, when fuch zinc is expofed to a fufficient heat in an open fire, the phlogifton diflodged, and immediately becoming phlogiftous gas or inflammable air, fhall take upon itfelf the form of flame and conftitute water; while the oxygene combines with the metal into a white oxyde, the flowers of zinc. So if the fame compound be diffolved in fulphuric : acid, ~ to be produced by Hydrogene. 485 acid, the phlogifton difplaced will turn to inflammable air, while the acid and the zinc form white vitriol. In this way fome of the phlogiltous or inflammable gas may be ac- counted for, as extricated from the metallic preparation: and at the fame time I fee no objection to deriving the reft of the great quantity afforded by this procefs, from the de- compofition of part of the water or oxyd of phlogifton. To accommodate matters then, the advocates of the Lavoifierian theory fhould concede that zinc, in common circum- ftances, is affociated with hydrogene or phlogifton. And the difciples of Stahl fhould on their fide allow that’zinc cannot be confidered as a pure metal, while alloyed or biended with phlogifton or any other foreign ingredient. The material they have all worked upon is not the uncombined metal, but a phlogifture of zinc. 4. Some forts of iron treated by heat alone afford phlogiftous or inflammable air. The fame metal may be made to burn with flame, and, when treated with fulphuric acid, affords much phlogiftous air, What then is the thing commonly called iron ? Is it a pure and unmixed fubftance? Or is it a compound of elementary iron with hydrogene or phlo- gifton? The fa@s enumerated lead conclufively to the latter opinion. The’ Phlogiftians are right then, when they fay common iron is a compound : and they are right when they fay the inflammable air obtained from it is nearly pure phlogifton. And the Antiphlo- giftians are juftifiable in placing in their enumeration of fimple bodies, fuch a thing as elementary iron is or may be imagined to be; and in afcribing the production of hydro- genous or phlogiftic gas to a decompofition of part of the water. The compound called iron then gives out fomething, and takes in fomething, in all the common procefles. And the modern chemifts fhould corre&t the miftake they appear generally to have fallen into, of taking it for granted, that was a fimple fubftance which in faét is a chemical compofi- tion of iron with hydrogene. ‘And thus finery cinder, which evidently differs from hema- tites or any pure oxyd of iron, may be a triple compound of iron, hydrogene or phlo- gifton, and oxygene; which juft about correfponds with your idea that it confifts of iron and water. Tt will not follow from all this, that becaufe phlogiflon or hydrogene fo. generally exifts in combination with zinc and iron, it muft be an ingredient in all metals. For gold, arfenic, filver, platina, mercury, copper, tin, lead, bifmuth, cobalt, antimony, and manga- nefe are capable of exifting without it, and accordingly do not commonly burn with flame, nor afford inflammable air by folution in. acids; though if ever they exhibit in any of their ftates blaze by burning, or phlogiftous air with acids, this will only evince the exiftence of hydrogene in them in fuch cafes. Both parties may thus allow that fome metals contain phlogifton, and fome do not. Nor will charcoal, as has fometimes happened, be confounded with phlogifton according to this view of the matter; though hydrogene is often. blended with it. If coal at any time affords inflammable air, this is no evidence of the converfion of that fubftance into phlogiftous gas, but merely a proof that. the coal when fubmitted to ~ experiment was combined with the bafis of inflammable air, which it could part with and ftill remain coal, though in that cafe incapable of burning with flame; but, in/a fufficient expofure to heat and oxygenous air, taking on without blaze the form of carbonic acid gas. It may be conceded then on both fides, that, though phlogifton or hydrogene may exift with coal, neverthelefs coal can exift without phlogilton. I know not in what manner thefe confiderations may imprefs your mind. I have 3 flattered 486 Oa Hydrogene.as the Principle of Flame. = flattered myfelf they have a tendency to accommodate and reconcile the gentlemen of both fides to each other, and to the'truth. But in this if I have deceived myfelf, I have only to appeal to your known experience and candour. It does however feem to me capable of getting through with much of thé difcuffion not yet folved between Mr. Kirwan and the French philofophers; and between yourfelf and Mefirs. Adet and Maclean; and I fuf- peét the celebrated experiments of Mrs: Fulhame are in no wife repugnant to this mode of interpretation. Permit me to exprefs my fatisfaction, before I conclude, that you have not given up the points before the philofophical world, without due examination. I no more like unani- mous decifions in hafte upon a queftion of fcience than of legiflation. ‘The fure way to in- troduce errors both into laws and into philofophical performances, is to affent to new bills and projeéts upon the credit and authority of the propofer, ‘without compelling them to undergo the amendments of debate. And I cannot help confidering your refufal to agree to all that the New Nomenclature Men have afferted and recommended, as a fortunate event in philofophy; as I am fure, with refpeét to myfelf, the oppofition you have made has caufed me to confider the fubjects in difpute with greatly more attention than I otherwife fhould have done. With much refpeét I beg leave to affure you that I am, &c. SAM. L. MITCHILL. ——— ANNOTATIONS upon the preceding LETTER. Steam in an colipile.] It is well known that ignited charcoal in the gunabarrél decompofes water, and that the produéts are hydrogene and carbonic acid gas. In this cafe the carbone is burned, and the hydrogene unburned. Are we to fuppofe that the water was firft decom- pofed in Dr. Mitchill’s experiment, and then -recombined by a fecond combuftion of the hydrogene? or was the effeét any thing more than an increafed energy of combuftion by the greater afflux of atmofpheric air. mechanically impelled by the fteam? Dr. Lewis * found that the fteam from the eolipile always extiriguifhed his fires, unlefs the vapour was made to pafs through a portion of the atmofphere. Whence I infer that the quantities of heat carried off and rendered latent in’ giving clafticity to the hydrogene and carbonic acid are fo great as fpeedily to diminifh the temperature, and terminate the combuftion of the charcoal; unlefs, as in the experiment of the gun-barrel, there be a fufficient fupply of heat from without. : by this unhappy afficiation.] The argument of affociation of ideas feems to militate ftrongly againft the reception of the word phlogifton in a new fenfe. Burning with flame or blaze.) Though the author’s arguments in favour of hydrogene, as the exclufive caufe of flame, may be hypothetically applied to all the inftances in which this appearance is feen; yet the contrary pofition, namely, that bodies, whether mechanically di- vided, fuch as the powder of refin or'coal, or chemically, as zinc im’ the claftic flate during {ublimation, may be fet on fire and exhibit the appearance of an ignited tranfparent fluid, fuch as fame, feems at leaft equally probable. It cannot therefore be ftated as matter of faét, that where flame is there muft neceflarily be hydrogene. ‘ * Philofoph, Commerce of Arts, p. 21. In - On Fydrogeue.—Bitumens and Mineral Ccal. 487 Ia the decampofition of fat and oil by fire, &'e.] The difference between the leading aflump- tion in Profeffor Mitchill’s letter, and the theory formerly maintained by. Mr. Kirwan, and ftated by him in the Introduétion to his Work upon !’hlogifton, appears, to be, that the former does not fuppofe his phlogifton, or principle which affords flame, to be effential to the metallic ftate, but merely, as I conceive it, accidental in that ‘clafs of combuftible fub- ftances, He follows Mr. Kirwan, by firft dire@ing his attention to the univerfality of hy- drogene in organized bodies, and then endeavouring to fhew that it exifts in fulphur, phof- phorus, zinc, and iron, in their ordinary combuftible ftate. It has not yet been fhewn that aqueous fulphuric acid can be produced by the combination of fulphur and oxigene, without the prefence of water ready formed. The fame obfervation more ftrongly applies to phofphorus, which Lavoifier converted into the folid acid by the burning glafs in a veflel of oxigene gas over mercury. In the obfervations on zinc and on iron, we look in vain-for the experimentum crucis, which myft be exhibited before the fuppofed fa@ that metals contain hydrogene can be admitted. Ihave ventured to make thefe remarks on the Profeffor’s ingenious communication, with- out aiming at the eftablifhment of pofitions contrary to thofe he has offered. The queftions he treats muft be decided by plain facts, if fuch can.be found. ‘Till this be done, they re- main among the mafs of unknown propofitions, concerning which, we ought neither to affirm nor deny. : IL becom on the Compofition and Proportion of Carbon in Bitumens and Mineral Coal. By RiguarD Kirwan, Efy. F. R.S8.L. & E. MR. A. &c. An exa& knowledge. of the component parts of the different {pecies of mineral coal, and alfo of bitumens (fubftances which, moft of them contain) forms an object of fome im- portance, not only to the naturalift whofe yiews are merely fpeculative, but to the praétical ecconomift, who withes to extra€t from each {pecies all the advantages it is capable of yield-, ing, and to be enabled to compare the various kinds afforded by different countries, in order to obtain and employ that which fhall on the comparifon appear to him beft fuited to his intentions. In effeét, coals are not only applicable to the more ufual purpofes of combuftion—an ufe, fimple as it may appear, attended, according to their various fpecies, with a confiderable dif. ference of calefactive power both in intenfity and duration, but alfo to the produGtion of varnifhes, much more advantageoufly applicable in many inftances than thofe extracted from the Vegetable Kingdom, as Lord Dundonald has difcovered, and abundantly proved*, and alfo of that charred refiduum called coak, the only one that can be reforted to in many cafes, and, in moft, fuperior to vegetable charcoal. * Upon the moft minute enquiry why coal-varnifh is not more commonly employed in paying the bottoms of thips, I have been informed the principal reafon is, that it fuccceds too well ; the fhips not requiring fuch frequent repair, K. Coals 488 Proportions of Carbon in Mineral Coal, &'c. Coals and bitumens are, however, fubftances that refift the ufual modes of analyfis; they. elude the action of aqueous, acid, alkaline, or fpirituous menftruums ; and diftillation, the only mode hitherto ufed, confounds and varies their natural contents. | Reflecting on thefe obftacles to an exact difcrimination of bitumens and coals, and of the various kinds of thefe laft, it occurred to me, that partly by combuftion and partly by their efficacy in decompofing nitre, the fecret of their internal compofition might poflibly be unveiled. . Combuttion. I have obferved that all the fpecies of folid bitumen properly fo called, wie laid on a red hot iron, burn with a large bright flame, fmoke and = leaving none or fearce any coaly refiduum, and only a little afhes: That the fofter bitumens, as maltha, burn in the fame manner, leaving no coal, but only a little afhes, and requiring no increafe of heat for their entire confumption : That afphalt burns with flame and foot, but melts and fwells, and requires for its entire confumption an increafe of heat, leaving fcarce any coal, and but little afhes. It is moreover well known that liquid bitumens contain inflammable air and carbon : that they abforb atmofpheric air when long expofed to it and light: that, in confequence of this abforption, they are thickened, blackened, and condenfed, firft into mineral tar, then into mineral pitch or maltha, and Jaftly into afphalt: that almoft all fpecies of mineral coal yield more or lefs of both fpecies of bitumen in diftillation, leaving a fhining coaly refiduum ; but that the proportion is variable in. every fpecies according to the degree of heat applied; that the refiduum always obftinately retains a proportion of bitumen, and that confequently diftillation, in addition fo its other imperfeétions, is an infufficient medium whereby to difcern the proportion of carbon and bitumen, and confequently to difcriminate the various forts of mineral coal from each other. 2. Decompofition of nitre. It has long ago been remarked by the juftly celebrated Macquer *, that nitre detonates with no oily inflammable matter, until fuch matter is re- duced to a coal, and then only in proportion to the carbonaceous matter it contains. An obfervation the truth of which will fully appear in the fubfequent experiments. Hence it occurred to me that, fince in the aé of detonation nitre is always totally or par- tially decompofed, and fince, where carbonaceous compounds are employed, this decompo- fition arifes folely from the mere carbonaceous parts, and, every thing elfe being equal, is proportioned to the quantity of mere carbon they contain; and fince moft fpecies of coals are compounds of mere carbon and bitumen, as appears by the produéts of their diftil- lation ; it fhould follow, that, by the decompofition of nitre, the quantity of mere carbon in a given quantity of every fpecies of coal may be difcovered ; and this being known, that of bitumen may be inferred ; and, the other uneflential ingredients being deteCted by incine- ration, the whole contents of coaly fubftances might be afcertained. The compofition of bitumens alfo, as far as relates to their proportion of carbon and oil, may be evidenced in the fame manner; and here it is to be obferved, that the bitumens I here confider are thofe that are found in a dry or folid ftate, and that thefe contain a larger proportion of carbon than the liquid bitumens ; for, though thefe aft alfo contain carbon, it being an effential component part of all oils, yet this portion does not extricate or educe # Didion, Chym, fecond edition, 481. any Proportions of Carbon in Mineral Coal. 489 ‘any air from nitre, nor confequently contribute to its decompofition, as the fubfequent experiments fufliciently evince; but is confumed partly by the pure air fpontaneoufly emitted by nitre during its ignition, and partly by the ambient atmofpheric air. Nay, when mineral coal is employed in the decompofition of nitre, the fhare which the mere carbonaceous part of the bitumen contained in it contributes to the decompofition will be found fo fmall that it merits no confideration in the general account. The’ firft ftep towards carrying this analytic plan into execution muft therefore be, to determine the quantity of pure carbon neceflary to decompofe a given quantity of pure nitre. But here many practical difficulties occur, which fhall prefently be mentioned. The moft perfect method-of obviating them was that employed by the ever memorable Lavoifier : he mixed the pureft nitre with charcoal alfo purged of the inflammable as well as other airs and water which it ufually abforbs, in the proportion which, after feveral trials, he found requifite for ‘the entire decompofition of that alt, rammed. them into a copper tube, fired them, and continued the inflammation under water ; ‘by which means the charcoal was acted on folely by the air educed from the nitre to the entire exclufion of the external air, _and this air was educed folely by the ignited charcoal to the entire exclufion of external heat ; advantages that cannot be procured by the ufual mode of effecting this decompo- fition. Thus he found the proportion of charcoal neceflary for the entire decompofition of nitre, to be as I to 7,57, or, in other words, that 13,21 parts charcoal decompofe 100 of nitre *: and yet eyen in this experiment I find a {mall inaccuracy, as he did not take the water employed in mixing the nitre and charcoal into the account; and hence, and for fome other reafons, the detail of which would lead me too far, I think the proportion fhould be as 1 to 7,868 nearly, or that 12,709 charcoal decompofe 100 of nitre; but the difference is of little importance. This mode of experimenting, however, is inapplicable on the prefent occafion; the dif- ferent fpecies of mineral coal being not fo readily inflammable as to carry on the combuftion inthis manner. Hence I contented myfelf with the common manner only, ufing fuch pre- cautions as to render its refults tolerably uniform, and repeating each experiment f{everal times. ¢ I examined the purity of the nitre I employed by nitrated filver, and found by the quan- tity of falited filver produced, that 480 grains of the nitre contained 3,5 grains of common falt (135 grains of muriated filver; indicating 100 of common falt): hence the conftant quan- tity of nitre I ufed was 483,5 grains, except in the experiments on bitumens, ag I had not enough of them to expend in fo large a quantity of nitre. The nitre was heated barely to rednefs, before any coal was projected on it, in a wind fur- nace and a very large crucible; upon this uniform degree of heat much of the uniformity of different experiments on the fame fpecies of coal depends. In my firft experiments the coals were reduced to a very fine powder, and then projeéted on the ignited nitre; but I obferved that by this method much more of each {pecies of coal was requifite to alkalize the ftandard quantity of nitre, than when it was reduced to a coarfe powder about the fize of a pin’s head, or fomewhat larger; and the reafon is, that by the force of the explofion much of the finer powder is carried off, without having been in * +1 Mem. Scav. Etrang. 626. Vor, l.—Feervary 1798. 3K contact 490 Preportious. of Carbon in Mineral Coal. contact with the nitre. Hence in the experinients of Mr. Hielm-on the quantities of char coak of different woods requifite to alkalize 100 parts of nitre,: we find thefe quantities to bear for the moft part fome analogy to their {pecific gravitizs, being generally fmaller wher the fpecific gravity of the charcoal is lighter; thus *: Grains requifite to alkalize 100 grains of. nitre. Specific gravity. Firft experiment. Second dittos Oak-coal _—_ 0,332 _— 35 —— 30 Birch-coal —— 0.542 —— 22 — 22 Pine-coal — 0.280 —_— 29 — 20% Fir-coal ——— 0.441 — 33 ee 25: Coak — 0.744 — 1g Another cireumftance of great importance towards procuring juft and’ uniform refults ig,. that the proje€tions of coal fhould fucceed each other without delay as foon ‘as the flame eeafes; for, as ignited nitre gives out pure air {pontaneoufly, and fo much the more as it is more heated, the acid will be decompofed, and the nitre alkalized, by a quantity of coal fo: much the fmaller as the intervals of projection are longer. From inattention, perhaps, to this and the laft-mentioned particular, ne well as from various conditions of common char- coal, which feldom contains !efs than 44, and often. + of its weight of moifture and ab- forbed air, proceeded the various refults of different chemifts, with refpe to the proportion: of it neceflary to-alkalize nitre. ~ Tt is almoft fuperfluous to. add, that the charcoal fhould be projected in very {mall por- tions. J feldom projeéted more than one or two grains: at-a time : each el pag ane from 20 to 25 minutes nearly. There is always fome portion of nitre undecompofed, being protééted by the furrounding alkali. ‘This error is unavoidable, but very fmall. Even the pofition of the crucible in the furnace is not indifferent; for, if it be near the flue, more coal muft be employed, which I. attribute to the torrent of air, which, in that cafe, affe€ls and carries away more than when the crucible is nearer to the anterior part of the furnace. It may, perhaps, be fulpected that this and fome other inciderital errors may Be-avoided by previoufly mixing the nitre and coal, and projeéting the mixture in {mall portions into a red-hot crucible ; but not to mention that this method fuppofes the due proportion of thefe two fubftances to be known, which cannot be till after the experiment, and that alfo every atom of thefe fubftances is in perfe€t contact with the other fubftance, elfe they can- not act om each other—independently, I fay, of thefe unfounded fuppofitions, this. mode of experimenting is ftill more fallacious than the former, as during thefe projections a con- fiderable proportion of the nitre is feattered and difperfed, and may be feen.adhering to the fides of the crucible. This lofs being repeated at every projection, becomes at laft intolerable. I now proceed to relate the experiments themfelves, conduéted in the manner Ihave _ mentioned. ‘The different fpecies of coal and bitumen, whofe compofition I have thus examined, were Kilkenny coal, Maltha, Afphalt, Lancafhire cannel, Slaty, Scotch cannel, Whitehaven, Wigan, Swanfey, and Leitrim; fele€ting of each fort the pureft fpecimens, free from pyrites and vifible ftony matter. * Schwed. Abhandl. 1781, 188. ° 5 Kilkenny Proportions of Carbon ie Mineral Coal. 49h, ~\ ay ' i red nF macs ooredo A obit Kilkenny Coal. ATs colour is is black, and, when freth broken, frequently violet. “Luftre 4, “Metallic. Tranfparencyo *. _Fradture foliated, the courfe of the lamellz varioufly and confufedly direQed. pac atents rather fharp, and often difcovering between the diflin@ concretions whitifh illinitions. Hardnefs 7. Specific gravity 1,526. : Does not burn until wholly ignited, and then flowly confumes without caking or emitting flame or fmoke. 266 grains of it expofed toa heat of 27° Wedgwood in a crucible for five hours, did not lofe their luftre until almoft 2, of them had difappeared, and at laft left red- difh afhes amounting to 7,13 grains, nearly 2,7 per cent. Projecting this coal in fine powder on 480 grains of pure ignited nitre, I found the falt required 65 grains of the coal to alka- lize it, but only 50 grains when in coarfe powder ; and in a third experiment, when the cru- cible was farther from the flue of the furface, only 49 grains; fo that 1 look upon 50 grains as being in round numbers neareft to the truth, That is, in the proportion of one part of Kilkenny coal to 9,6 of nitre: or, 100 parts of nitre require for their decompofition 10,416 of Kilkenny coal. ; This proportion of coal is much fmaller than that of charcoal in Mr. Lavoifier’s experi- ment, which we have feen to be as 1 to 7,57, Or as 13,21 to 100, which I attribute to the advantageous mode in which his experiment was inftituted, as already explained; whereas in mine, and the ufual way, the decompofition of /nitre is:promoted by the external, heat applied, as well as by the coal, and confequently lefs of the coal is employed. From the experiments of Scheele one might be led to infer, that the proportions of char- eoal and nitre neceflary to the alkalization of this latter, approach ftill nearer to each other “ #The figures made ufe of by this author to denote degrees of luttre, tranfparency, hardnefs, and tharpnefs of firtgments, are explained 1 inthe following Table, which I have conftruéted from his feétion upon the diftinétive charaéters of minerals. Numbers or Tperets. Luftre. | Tranfparency. | Fi ragments. ° { None; | None, ' (|, Perfeétly blunt. | Exceedingly weak. ; or a few fhining | Only at the edges. | » Lefs blunt. ,..., particles. r Tranimits light, but nor fufhcient to mae AIRC Gloffy ; not more than of filk, | difcern,objeéts: Sharp. Shining; as of cryftals or of metals | Tranfmits light enough to thew ob- More fh not much polifhed, jeéts imperfeétly through the mafs. D2 Objects clearly dittinguifhed through | Meft fharp; as of the mafs.- glafs, “© 5 Brightest; as of diamonds or po- wes lithed metals. 7 On account of the higher range of numbers, degrees of hardnefs could noticonveniently be includedyin the shove Table. No. 3, denotes the hardnefs of chalk; 4, a fuperior hardnefs, but yet what yields. to the nail;, x, that which will not yield tothe nail, but eafily and without grittinefs to the knife; 6, that which yields’ more difficultly to the knife; 7, that which {careely yields to the knife ; $8, that which cannot be feraped by @ knife, but does not give fire with ftecl.; 9, that which gives a few feeble spare with fteels, as bufales oe that which gives plentiful lively fpark«sas flint. WN. f; 0 3R2 thax , 492° Proportions of Carbon in Mineral Coal. than in Lavoifier’s ftatement, and confequently much nearer than in mine: for, in his Effay on Plumbago, he tells us that five parts nitre are fufficient to confume one of charcoal, and confequently it fhould feem that one part charcoal fhould decompofe no more than fiye of nitre, The confequence however is not juft, for undoubtedly five parts nitre. ‘would con- fume one, of charcoal, but it does not thence follow that they would not confume till more. On the other hand, he found that ten parts nitre were neceflary for the confumption of one part of plumbago; whence it follows, that one part of phimbago decompofes ten of nitre, otherwife nine parts nitre would fuflice to confume it, and the tenth would have been unneceflary, as it acts only as it is decompofed. Now this oid ‘approaches iis nearly to my refults ; namely, one of charcoal to 9,6 of nitre. Hence, and fince Kilkenny coal in the preceding experiments fliewed no fign of its con- taining any thing bituminous, I take it for granted that it confifts almoft entirely of pure carbon; and fince §0 grains of it alkalize 480 grains of pure'ignited nitre, that in all the fubfequent experiments on other fpecies of coals or bitumens free from fulphur and iron, the decompofition of this ftandard quantity of nitre will indicate, inthe quantity = coal. neceflary for that decompofition, the prefence of 50 parts of mere carbon. — il Before I proceed to the recital of other experiments, I muft mention another Srouriftnde that occurs in making them, which is, that, after the inflammation ceafes, a hiffing noife is perceived for a long time, and is increafed'on adding frefh quantities of coal, even when the nitre is feemingly decompofed. This feemed to me tovarife from the decompofition of: the nitrous air, er mephitized nitrous acid, of which a portion is always retained by the, alkali ; and confequently I paid no attention to it, but always ceafed adding coal when the, inflammation totally ceafed. Maltkas. 2 ITS colour is dark-brown, or black. Luftre o. Tranfparency o. Fracture uneven, tough. Specific gravity 2,070.. ‘Tt feels fomewhat greafy, yields to compreffion, has a heavy fmell, acquires a polith when: feraped, does not adhere to the tongue, or flain the fingers; its flame high and bright, leaving no coal, but only a little athes. | ‘Having but a fmall quantity of this fubftance, I on this occafion ufed only 240 grains of. nitre : when it was heated to rednefs, I threw on it one grain of vegetable pitch; it im- mediately inflamed, but floated quietly on the furface of the nitre, and decrepitated like comnion falt from the moifture it contained : the flame was partly white from the a¢tion-of the air fpontancoutly emitted by the nitre, and-partly yellowith from the-aétion of the-am- ‘bient atmofpheric air, but fleady, and unattended with thofe turbulent gufhes that attend: the decompofition of nitre by carbonaceous fubftances. I then gradually projeéted on it 55 grains of maltha, which was all'I had: this burned’ jut as the pitch, but attended with a blacker fmoke; yet the nitre was fo far from being alkalized, that, to produce this effe&ty I was obliged to throw on. it 29 grains of cannel coal. Now 33,5 grains of cannel coal, if it alone had been ufed,, would fuffice to alkalize 40 grains of nitre; it will pre‘ently be feen, therefore, the 55 grains of maltha-and. the one grain of pitch contained no more carbon than 33,5 — 29 = 45 grains. Therefore 100 grains, of of. ‘maltha contain no more than 8 grains of carbon. And as thefe 8 grains of car- bon provoked no turbulent eruption of air from the nitre, it is plain they did not contribute : to Proportions of Carbon in Mineral Coal. 493 to its decompofition, but were taken up by the airit frenfncgiity emitted, and partly by the ambient atmofpheric:air,. gait pls oi c Afpbalt. ITS colour is greyifh black. Luftte 2.3. greafy. ° Tranfparency 6. Fraéture perfeétly conchoidal. Hardnefs from 7 to 8, very brittle. Specific gravity from 1,07 to 1,165 by iny trials. It feels fmooth, but not greafy; has no fmell, except while pounding ; 3 does not ftain the fingers; when heated’ it melts, fwells, ‘and at laft inflames 5 but it requires, for mintaietnatioe, a eam ye than maltha ‘does, ‘and leaves ‘no ood; and fcarce any afhes. ° Of this bitumen I found 8x grains’ seGuis ite to alkalize the ftandard’ quantity! of nitre : it vifiblyeduced air from the nitre; for there were eruptions from time to time. - I fuppofe when the more oily part was confumed, and the carbonaceous laid bare, much of the flame was alfo yellowith Hence 16r. grains of ean contain only 5° of mere carbon, that is, nearly 31 per ‘ent. ree Mr. Thory, burning it in a low heat, found it to leave about | of its weight of coal after melting, {welling and inflaming as ufual *: however, Fi afphalt was not perfe@tly pure, as he obtained fulphur from i it. 1 bodsorm 2°23 58% Cannel Coal. ITS colour is Sonat ‘Luftre 2. > Cominon when’ — broken, often ot I. Tranfpa- rency 0. ' bi cohnyG i Crofs fra€ture cofchoidal.” °Fragments with fharp. Hardnets fon 7 to 8. Specific gravity by my trials 1,232, by Dr’ Watfon’s 1,273; does not ftain the fingers, eafily kindles without melting, and burns with a large bright flame, but of fhort duration, leav- ing a large coaly refiduum ;, does not cake. 240 grains of it, heated until all the coaly part was confumed, left 7,5 grains of reddith brown athes, moftly sree that is, 3,12 per cent. 66,5 grains of it were fufficient to alkalize the ftandard gaanecy of nitre., It'burned: with a large bright flame, except the laft portion, which was yellowith, the pure'air of the nitre being then exhaufted. Hence 66,5 grains contained 50 of pure carbon, and 2,08 of athes; then deduéting 52,08 from 66,5, we find the quantity of bitumen equal 14,42. Then 100 parts of it contain 75,2 of carbon, 21,68 bitumen of the fort called maltha, and 3,1 of afhes, I take this bitumen to be maltha, from its quick inflammability, and the fhort duration and brightnefs.of its flame, both which properties indicate the moft inflammable of the bitumens, and whofe flame is leaft durable from its refufal to cake (caking being a pro- perty arifing from the fufion of afphalt),.and the dificult combuftibility of the carbonaceous fubftance that remains after the ceffation of its flame—qualities that counter-indicate af phalt. Slaty Cannel Coal. THAT which I employed was from Ayrfhire in Scotland,, the only one of this fort. im- ported to Dublin. lts colour is blacks. P ‘ Lis * 6 Crejl’s Chym, Jour. 62s Its 49% Proportions of Car bervin Mineral Coal. Tes luftre 2. Common.) Tranfparencyios 21) ¢ 5) atow dud atolhageiodb ase « Its fracture partly flaty, partly imperfectly « reasicbhidals pnt iqtoram: moidia Its hardnefs from 5 to 8. Specific gravity-%)426 by my trials. It burns like the compact cannel, but .ceafes fooner-to-flame 5, does, not , cake leaves 2 ftony refiduum, 240 grains of it, treated as.| before mentioned, leaye, $2. of xeddith grey athes, equal 20,83,per.cent,, From, the, {mell that, ies from it during i feriree I am led to think it contains fome portion of fulphur,.. risdw : sat ody cind To alkalize 480 igrains of \nitre; 105 grains of hia: goal were, employed. “Tt burned like the former with a large white continued flame, except the laft portions. Henee this quan tity contained 50 grains.of mere.carbon;, and. fince it alfo, contained 20,8 3.0f£ afhes, the remainder, namely 34,15,muft have been. bitumen. Then 100 parts of it contain 47,62 of carbon, 3295? of bitumen, and about 20 of, afhes. Some. seneien. however from thefe It is ante a coal of this fort that Lon Dundonald parity his tar, as Moalths cally diftils = but it is probably of a better kind, as this ftony kind exifts moftly in Ayrihire. By his Lordthip’s mode of diftillation, however, much feems to be loft during the internal combuftion. I fhould think the Prince of Naffau Saarbruck’s method in this refpeét more advantageous. Mr. Sage tells us, that, by-diftillation, he, obtained from, cannel coal ~of its weight of tar *;“but Mr. Faujas, who ufes Lord Dundonald’s method, obtains from. the coal of Decire, which feems to be of. this kind, only 4 per cent. of tar f. . Faujas alfo ob- ferved, that this tar is gradually converted. into afphalt by long expofure to the air, whicly confirms the difference I have eftablifhed between the two bitumens. ede Weitebaven Coal, °° ri ITS colour is black. 7 Re RRR ree saleeeb ty Sty Ay ete Its luftre 3. Greafy. Tranfparency o. Its fraéture plane foliated. Its fragments 2, often Rleoveliag quadrangular or “cubic diftiné concretions, fometimes interfected with brownith red flakes. = Its hardnefs 6, very brittle. Specific gravity 13257 by my trials. Stains the, ite particularly when moift. It burns at firft with a clear flame, and for a long time ;- but at laft cakes. 240 grains of it, after five hours ftrong heat, left only 4 grains of reddih afhes, or about 1,7 per cent. “The ftandard quantity of nitre was alkalized by 88 grains of this coal. Hence 100 grains of it contained nearly 57 of mere carbon, 41,3 of a mixture of maltha and afphalt, and 1,7 of afhes. That it contains both maltha and afphalt is evident from its flame and caking. The Proportion L.cannot exaétly afcertain, but moft probably the afphalt predominates. Wigan Coal. ITS colour is black. : ; Its luftre 3. Greafy.. Tranfparency o. ’ Its fraéture plane foliated. The lamellz, fome uniformly, fome promifvildedty directed. Inthe grofs often flaty ; forms feparate concretions, often with bright-yellowi(hillinitions. * Rez. Journ. p. 387. ; ‘+ Roz. Journ. p» 288. Its Proportions of Carbon in Mineral Coal. 495 frs hardnefs 6,. Specific gravity 1,268 by my trials. It burns with a bright flame and quicker than the foregoing, and is lefs apt to cake. 328 grains of it, expofed as the former to a ftrong heat, left 5,13 grains of athes, that is, 1,57 per cent. 81 grains of it decompofed 480 grains of nitre. Hence roo grains of it contain 61 373 Of carbon, 36,7 of a mixture of maltha and afphalt, and 1,57 of athes. , It feems to contain a larger proportion of maltha, with refped to its quantity of afphalt, than Whitehaven coal does. s Swan/ey Coal. ITS colour is black. c Its luftre 2. Tranfparency o.. Its fracture foliated; but fome lamellz’ being at right angles with the other, give it a. Gibrous or ftriated appearance. Fragments 2. eee Its hardnefs 5, very brittle. Specific gravity 1,357 by: my trials. Tt burns more flowly than the former, and’cakes. _ tay 240 grains of it, treated as the former kinds, left 8 grains of yellowifh red afhes ;. that is,, equal 3,33 per cent. , Of this coal 68 grains were requifite to decompofe 480 grains of nitre. Then roo grains of it-contain 73,53 of carbon, 23,14 of a.mixture.of maltha. and afphalt, and 3,33 of afhes. The afphalt feems to predominate. ©: islt io 2k Leitrim Coal. ITS colour is black.. Its luftre when frefh broken 3. Tranfparency o. Its fracture foliated. Its fragments 2. nity Its hardnefs 6, very brittle. Specific. gravity 15351, by.my trials... It flightly cakes: 240 grains| of it lefty after: thrée hours expofure! to. heat, 12,5 grains of réddith: gfey afhes, that is, equal 5,2 per cent.. f ton ; The decompofition of the ftandard’quantity,of nitre required 7o grains of this coal. Henct noo grains of it contain 71,43 of carbon, 23,37 of a mixtute of maltha and afphalt; and 5,2 of afhes. 2008 y} tof (ilpdNeweaffle. Coal. ist ti I HAD none’of this kind of coal’; but, according to Dr. Watfon’s experiment, it left on diftillation a coaly refiduum amounting to 58 per cent. and hence contained about 40 of a mixture of afphalt and maltha, in which the former: appears to predominate. Hence it much refembles the Whitchayen coal ; but it evidently contains fulphur alfo, which that of Whitehaven feldom does, ig s08 ne bbs ihe bert: bvG A fynoptical 496 Proportions of Carborin Mineral Coal. A fynoptical View of the Contents of Bitumens and different Sorts of Mineral Coat! 100) parts Carbon; {. Bitumen. | “Athes. | Specific gravitys.:' Maltha 8 — — 2,070 * 4 Afphalt gy 68 inh one > 57 Ai Kilkenny te 0} Doplagglgw yeessmL tp gy Cole! 4,526 © Compaét cannel 7592 21,68 maltha | 3,1 fobay2z200r oie Slaty cannel 47,62 | 32,52 maltha| 20 1,426 Whitehaven 57 41,3 mixt 1,7 1,257, Wigan 61,73 | 36,7 mixt 1557 1,268 Swanfey 73953 | 23.14 mixt 39330 |) 19357 Leitrim 71943 | 23537 mist... | 5:20 4] 357 Newcattle 4 58 4o. , mixt, _—_ 1,27! To thefe refults I fhall add a few more taken from ‘a Treatife on Pit Coal, lately publifhed by Signior Fabroni. The Italian coals were examined by himfelf; the French and German by other chemifts—All by diftillation. “** Teo parts ““Afhes.’ | Specific gravity. we: > Ags | ee Coals of Halles — ee : of Tudertino —, eae of Cortolla 12 1,403 of Macinaia 3 1,411 Stony of ditto 50 1,666 of Mocaio 33 1,403 fuccinous. » bats According to Mr. Jars, 100 parts of the beft Englith coal give when charred 63 of coaks +; but Hielm found the refiduum of the beft Englifh coals diftilled, to amount to 73 percent. and Dr. Watfon found the refiduum of Newcaftle coal to amount only to 58 per cent.. Thefe refults neceffarily differ according to the degree of heat applied, the du- ration of the combuftion, and the variable admiflion of air. It is plain the bitumen is never totally expelled, at leaft not until moft of the carbon is confumed ; but much more of it is expelled by combuftion than by diftillation. Watfon, p. 27 and 28 ft. * Probably 1,07. + 1 Jans, 329. 3 + This paper is taken from the Secend Volume of Elements of Mineralogy, lately publifhed. Ill. Obfervations Freezing Procefier. 497 Ill. Obfervations on the bef? Methods of producing Artificial Cold. By Mr. RicHarp WALKER *. H AVING already inveftigated the means of producing artificial cold, and at the con< clufion of my Jaft paper (on the Congelation of Quickfilver) difmiffed that part of the fub- ject, the beft method of making ufe of thofe means naturally becomes a defideratum; to that therefore I have lately given my attention, and flatter myfelf that the following obfer- vations may be confidered as an ufeful Appendix to my former papers. The freezing point of quickfilver being now as determined a point on the fcale of a thermometer, viz. 39% as the freezing point of water ; and as this metal, exhibited in its folid ftate, affords an in- terefting as well as curious phenomenon, | fhall apply what I have to fay principally to that object. Frequent occafions having occurred to me of obferving the fuperiority of faow in experi- ments of this kind to falts, even in their fitteft ftate, that is, freth cryftallifed, and reduced to very fine powder, I refolved upon adopting a kind of artificial fnow. The firft method which naturally prefented itfelf was by condenfing fteam into hoar froft. This anfwered the purpofe, as might be expected, exceedingly well; but the difficulty and expence of materials in collecting afufficient quantity determined me to relinquifh this mode for another, by which I can eafily and expeditioufly procure ice in the fitteft form for ex- periments of this kind; the method I mean is, by firft freezing water in a tube, and after- wards grinding it into very fine powder. Thus poffeffed of the power of making ice, and afterwards reducing it to akind of fnow, the congelation of quickfilver becomes a very eafy and certain procefs; for, by the ufe of a very fimple apparatus, (Plate XX. fig. 1.) quickfilver may be frozen perfeétly folid in a few minutes, wherever the temperature of the air does not exceed 85°: thus, one ounce of nitrous acid is to be poured into the tube 6 of the veffel, obferving not to wet the fide of the tube above with it; a circular piece of writing-paper, of a proper fize, is to be placed over the acid, refting upon the fhoulder of the tube, and the paper brufhed over with fome melted white wax. Thus prepared, the veffel is to be in- verted, and filled with a mixture of diluted nitrous acid, phofphorated foda, and nitrous ammoniac, in proper proportions for this temperature *, and tied over fecurely, firft with waxed paper, and upon that a wet bladder. The veffel being then turned upright, and placed in a fhallow seta viz. a faucer or plate, an ounce and a half of rain or diftilled water is to be poured into the tube, which is to be covered with a {topper or cork, and, as foon as frozen folid, ground to very fine pow- der, an affiftant holding it firmly and fteadily the while ; obferving occafionally to work the inftrument in different dire€tions up and down, that no lumps may be formed. When the whole of the ice is thus reduced to powder, and the lumps, if any, broken, the frigorific mixture is to be let out quickly, by cutting or untying the ftring, and removing the bladder, &c. which confines it; a communication made by forcing a rod of glafs or wood through the partition; and the whole mixed expeditioufly together. * Philofophical Tranfaétions, 1795. 4+ Ihave, by a very accurate preparation of this mixture, funk a thermometer from 8% deprees (tempera- gure of the veffel and materials) to + 2 degrees. Vor. 1.—Fesrvary 1798. 35 Te 498 Obfervations and Experiments on In this climate a mixture much lefs expemfive will be fufficient ; viz. that compofed of diluted pitrous acid, Glauber’s falt, fal-ammoniac and nitre ; a mixture of this kind finking ‘ 4 thermometer in the warmeft weather to near o°. At the temperature of 70 degrees, ora little higher, the quantity of diluted nitrous acid may be about one-fourth lefs than is men- tioned in the table for 50 degrees. Thefé methods ‘aré the moft expeditious, and attended with the leaft trouble; but as ice may be ufed With "equal certainty, and with much lefs expence, I fhall give a particular de- tail of an experiment made with the ufe of it, firft mentioning a preparatory experiment, to which I'was immediately led by the recollection that Sir Charles Blagden, in his paper «on the Point’ of Congelation,” (Phil. Tranf. vol. Ixxviii.) had found that common fal- ammoniac and common falt mixed with {now produced a cold of — 12 degrees, whereas the latter ufed alone with fnow produces only — 5 degrees. I ufeda mixed powder of equal parts of common fal-ammoniac and nitre with the common falt, by which the ther- mometer funk to — 18 ‘degrees ; and when I ufed nitrous ammoniac with common falt, to — 25 degrees. This cold I could not increafe by the addition of any other falts, nor could I equal it by any other combination of falts. Thofe I tried were, Glauber’s falt, falt of tartar, foda, and fal catharticus amarus. By feveral trials, I found the beft proportions to be, fnow, or pounded ice twelve parts, common falt five parts, and of nitrous ammoniac, or a powder of equal parts, fal-ammoniac and nitre mixed, five parts; or one-third of common falt, when I ufed that alone with fnow or pounded ice. My apparatus then (Dec. 28. laft) confifted of two veffels (fig. 3 and 4.); an inftrument (fig. 6.) to grind or rather ferape the ice to powder; a kind of fpatula (I ufe a marrow fpoon) to ftir the powder occafionally; a thermometer (fig. 8.) and a fmall thermo- meter glafs, with the bulb three-fourths full of quickfilver (fig. 7.) I filled the veffel fig. 3, holding when inverted two pints, fratum Juper /Iratum, with pounded ice, common falt, and a powder confifting of equal parts fal-ammoniac and nitre mixed together; by firft putting in fix ounces of pounded ice, thentwo ounces and a half of common falt, and, after ftirring thefe well together, two ounces and a half of the mixed falts, mixing the whole well together : this was repeated in the fame manner until the veffel was quite full. It was then tied over fecurely with a wet bladder, turned upright, and one ounce and a half ef rain water poured into the tube through a funnel, the tube covered with a cork, and the vefiel left undifturbed till the water was frozen perfectly folid. The inftrument for grinding it was then put in to acquire cold, whilft the veffel fig. 4, holding a pint, was filled in the fame manner, with the fame proportions of materials; a bladder tied over it, fet upright, and one ounce of fuming nitrous acid poured in to be cooled. The ice was then ground to powder; and when finifhed, the nitrous acid being found to have ac- quired a fufficient degree of cold, viz. — 13 degrees, the frigorific mixture of ice and falts was let out of the veflel which contained the nitrous acid, and the powdered ice ({till furrounded by its frigorific mixture) added to the acid as quick as pofible ; when the ther- mometer funk to near — 50 degrees, and the mixture foon froze the quickfilver in the glals bulb. In this experiment 18 minutes were required to freeze the water perfectly folid, and 15 to reduce the ice by moderate labour to very fine powder. The experiment was over in 55 minutes, and the temperature of the preparatory cooling mixture then found to be — 10 degrees. _ Thad the beft Methods of producing Artificial Cota. ; 499 » Thad.a fpirit thermometer by me} but a mercurial thermometer being much more fen- fible, and confequently defcending much quicker, I prefer it in experiments made. merely to freeze quickfilver—knowing from experience how the congelation is going on, from the irregular: defcent of the mercury when a few degrees below its freezing point, and from having ufually found that the quickfilver in the thermometer glafs begins to freeze as foon as the mercurial thermometer reaches — 40°. Whenever I have oceafion to uf ice in fummer for this purpofe, I ufually pound to- gether firft fome ice and falt ina ftone mortar, about two parts of the former to one of the latter; throw this away, and wipe the peftle and mortar perfeGtly dry: the mortar being thus cooled, the ice may afterwards be pounded fmall without melting. And as a mixture made of fnow or ice in powder and falts does not give out its greateft cold till it is become partially liquid by the action of the ice and falts on each other, it is neceflary that the whole be ftirred well together, till it is become of an uniformly moitt pulpy confiftence; efpecially fince, in becoming liquid, the mixture fhrinks fo much, that, if this be not attended to, the vefiel will not be near full, and confequently the upper part of the tube not furrounded, as it ought to be, by the frigorific mixture. The diffolution of the ice and falts may, if required, be haftened, by adding occafionally a little water; but then the cold produced will be lefs intenfe, and not fo durable. ‘That particular form of the veflel in which the ice is made and reduced to powder is chofen, becaufe it fubjects the powdered ice in the tube to the conftant aétion of the freezing mix- ture, without which it would be lefs fit, particularly in warm weather, for the intended ufe; and becaufe in it the ice is not liable to be impregnated with the falts of the mixture, by which it would be utterly fpoiled; and that for cooling the nitrous acid, and making the fecond mixture in, becaufe it is fteady, and is befides infulated, as it were, from the ex- ternal warm air, and furrounded in its ftead by an atmofphere much colder. ; Tt is fcarcely neceflary to add, that when fpow which has never thawed:can be procured, it may be cooled in this apparatus by a mixture of fnow (inftead of the pounded ice) and the falts, and the trouble of reducing the ice into powder faved. : ' Iprefer the red fuming nitrous acid, becaufe, as I have obferved in a former paper, it requires no dilution. Being under the neceflity at one time of ufing the pale nitrous acid; I found it required to be diluted with one-fifth its weight of water. The beft and only way of trying or reducing any acid to the proper ftrength, is by adding fndw, as Mr. Ca- vendifh direéts, or the powdered ice to it, until the thermometer ceafes to: rife ;) then cool the acid to the fame temperature of the {now again ; add more fnow, which will make the thermometer rife again, though lefs; cool it again, and repeat this until the addition of fnow or powdered ice will not make the thermometer rife: to be very accurate, it fhould be reduced in this manner to the proper ftrength, at the temperature, whatever it be, at which the nitrous acid and fhow, or powdered ice, ate to be mixed together when cooled. In the courfe of my experiments I have endeavoured to afcertain the comparative powers of ice to produce cold with nitrous acid in the different forms I have had occafion to ufe it, The refult is, that frefh fnow funk a thermometer to — 32 degrees, ground ice to — 34 degrees, and the moft:rare frozen vapour to below'+~ 35: degrees; the veflel and ma- serials cach time being ++ 30 degrees. ee | The goo Oijervations and Experiments on The veffels for thefe mixtures, particularly that in which the quickfilver is to be frozen, fhould be thin, and made of the beft conductors of heat; firft, becaufe thin veffels rob the mixture of lefs cold at mixing, that is, if two mixtures of the fame kind are made, one in a thin, the other in a thick veffel, the former will be coldeft; fecondly, becaufe the air is a fufficiently bad conduétor; and thirdly, for the very obvious reafon that the cold is tranfmitted through them quicker. % For thefe reafons, and from the difficulty I have found in procuring veffels of glafs, which are undoubtedly fitteft for experiments of this kind, I have ufed tin, which is readily had in any form, and, if coated with wax, is fufficiently fecured againft the action of the acids. I give the infide fuch a coating by pouring melted white wax into. the veffel, previoufly clean and dry, and turning it about by hand, fo as to leave no point of the metal uncovered for the acid to a&t on, pouring the furplus away. In the experiments above defcribed, I ufed a fingle veffel for cooling the nitrous acid; a cupping-glafs (reprefented by the dotted line at b fig. 4.) being cemented into the tin, and thereby forming that part in which the nitrous acid was firft cooled, and the mixture afterwards made in which the quickfilver was frozen; but from the trouble and impedi- ments arifing from letting outthe mixture, and clearing the bottom from the lumps of ice, &c. adhering to it, I was led to the addition of the other part (fig. 5.) by which all thefe difficulties are got rid of: and it is befides a much more comfortable and neat way of condudting it; the upper part, which contains the nitrous acid, being lifted off, and placed on the table immediately before the powdered ice is added. The whole of this apparatus may be of tin; that part only (when the cooling mix- tures are made without ufing any corrofive acid) in which the acid mixture is to be made being previoufly coated in the manner above mentioned ; or a thin glafs tumbler; of a proper fize, may be cemented in. Thave occafionally ufed a thin glafs tumbler for the mixture in which the quickfilver is to be frozen, immerfing it, with the acid, in a frigorific mixture, till the acid is fufficiently cooled; then adding the ground ice to it, previoufly removing the tumbler out of the frigorific mixture, as in the experiment above mentioned : this fimplifies the apparatus, but is lefs convenient on many accounts. The fcale of this apparatus may be diminifhed or increafed at the will of the opera- tor; for there is no doubt that a fmall quantity of quickfilver may be frozen at any time with one-fourth of this quantity, with an apparatus of this kind, by any one converfant in fuch experiments. Ihave frequently frozen quickfilver by mixing together at 0°, three drams of ground ice with two drams of nitrous acid. Whenever the intention is, as in thefe experiments, to cool the materials to nearly the fame temperature with the frigorific mixture in which they are immerfed, the proportion of the frigorific mixture to the intended mixture (or materials to be cooled) fhould not be lefs than twelve to one; a greater difproportion is ftill better. By attending to the directions particularly mentioned in the experiment made on December 28, a thermometer may be always difpenfed with; the. proportions of the ma- terials the beft Methods of producing Artificial Cold. sou terials to be cooled being exaétly adjufted, and, when they are to be mixed, precifely deter- mined by the time: employed in grinding the ice to powder. The proportions of fnow or pounded ice and falt or falts may be gueffed fufficiently near without weighing, unlefs in very nice experiments. Imagining that a recapitulation of the different mixtures defcribed in my former paper for producing artificial cold, brought into one view, might not be unufeful, I have fubjoined atable of the falts, their powers of producing cold with the different liquids, and the proportions of each, according to a careful repetition of each; the temperature being 50 degrees. Temperature of SALTS. Liquor. Cold produced. * Sal-ammoniac 5, nitre 5 —— — | Water 16| — -+ 10? Sal-ammoniac 5, nitre 5, Glauber’s falts 8 —_ | 1} — + 4 * Nitrous ammoniac 1 —— — |— I — + 4 Nitrous ammoniac 1, fal foda 1 ~ =_ }— 7 Glauber’s falt 3 — — |D.nitr.acid 2) — 3 Glauber’s falt 6, fal-ammoniac 4, nitre 2 — 4, — Io Glauber’s falt 6, nitrous ammoniac 5 — — |——_ 4] — 14 Phofphorated foda 9 - —- 4; — 12 Phofphorated foda 9, nitrous ammoniac 6 — 4, — 2u Glauber’s falt 8 — |Marineacid 5} — ° Glauber’s falt 5 = — — |D.vitr.acid 4] — + 3 N.B. Ihave chofen the temperature of 50 degrees, becaufe the materials may at any time, by immerfion in water drawn from a fpring, be cooled nearly to that temperature, and the experiment for freezing with any of thefe mixtures commence there. At a higher temperature than 50 the quantity of the falts muft be increafed, and the ef- fe& will be proportionably greater: at a lower temperature diminifhed, when. the effect will be proportionably lefs. It muft be obferved, that, to produce the greateft effect by any frigorific mixture, the falts fhould be frefh cryftallized +, not damp, and newly reduced to very fine powder; the veflel in which they are made, very thin, and juft large enough to contain the mixture; and the materials mixed intimately together as quickly as pofhible, the proper proportions. at any temperature (thofe in the table being adjufted for the temperature of 50° only) having been. * The falts from each of thefe may be recovered by evaporating the mixture to drynefs, and ufed’ again. repeatedly. N. B. The figures after each falt, and after the liquor, fignify the proportion of parts by Troy weight to»be ufed; the trouble of weighing the water may be faved by obferving, that a full ounce of it by wine meafure, correfponds exaétly with one ounce of it by Troy weight: likewife it muft be noticed, when more kinds of falts than one are ufed, to add them to the liquor one after the other in the order they ftand in the table, be~ ginning on the left hand, and ftirring the mixture well between each addition, D. nitr. acid is red fuming nitrous acid two parts, and rain or diftilled water one,part by weight, well agitated together and become cool, D. vitr. acid is firong vitriolic acid, and rain or diftilled water equal parts by weight, thoroughly mixed (very cautioufly ) and cooled, + Soda, phofphorated foda, and Glauber’s falt, are belt cryftallized afrefh, becaufe their effect, efpecially the two laft, in the acids, depends upog the quantity of water they contain in a folid ftate. previoufly 502 Objfervations and Experiments on previoully triedy by adding the powdered, falts gradually to the liquid till the thermometer ceafed to fink; obferving to produce the full effect of one falt before a fecond is added, and likewife of the fecond before a thitd is added, Neither foda, phofphorated foda, nor Glau- ber’s falt, fhould be mixed with nitrous ammoniac, or the powder compofed of fal am- moniac and nitre, unlefs at a’ low temperature, that is, below 0; but pounded and kept apart. In the experiments alluded to in the table, the precaution of freth-cryftallizing the falts was not obferved, becaule } chofe to'give the ordinary effects only. I therefore then ufed falts in their common ftate, taking care, however, to choofe fuch as had not in the leaft efflorefced. Since it is always ufeful, and generally abfolutély neceffary, to know how much room in a veflel the feveral materials take up feparately ; and when mixed, it will be right to ob- ferve, that {now or ice in powder, at near 0°, occupy in meafure nearly two thirds more than their weight; that is, one ounce weight of water will, when in the form of {now, or ice ground to powder, nearly fill a veffel w vhich holds three ounces wine meafure; powdered falts, nearly double their weight; ftrong nitrous acid, about three-fourths its weight; and a mixture made of falts and diluted nitrous acid; meafures rather lefs than two-thirds of the weight of the ingredients. Without a previous knowledge of this, it is impoflible to adjuft the fize of the veflels to the mixtures which are to be made; becaufe, in moft nice experi- ments of this kind, the height to which a veffel will be filled is. indifpenfably neceffary to be known beforehand. The long continuance of the late froft having afforded me opportunities of repeating thefe experiments in various ways, I fhall mention briefly the refult of fuch as appear te me to be material. R I have found, that ice may be ground fo fine as to be equal to frozen vapour; and the harder it is frozen, the finer it is ground, but with more labour. That quickfilver may be frozen by cooling the nitrous acid only, faving the trouble and inconvenience of cooling the fnow likewife ; either by adding fnow at 4+ 32 degrees, to nitrous acid at — 29 degrees; or {now at + 25 degrees, to nitrous’ acid at — 20 degrees ; or fnow at +20 degrees, to nitrous acid at — 12 degrees. Moft winters offer an oppor- tunity of doing it in this way; the nitrous acid may be cooled in a mixture of {now and nitrous acid. That it may likewife be frozen by mixing expeditioufly together eee and nitrous acid, when the temperature of each is + 7 degrees. Or by mixing ground ice and nitrous acid at + 10 degrees. Hence it follows, that the cold of this climate offers occafionally opportunities of freezing quickfilver, without previoufly cooling by art the materials to be mixed; for I-have once feen the thermometer at + 6 degrees—and others, I believe, have feen it lower. I expe€ted an opportunity would have offered this winter, but the loweft point I faw my thermometer at this feafon was only ++ 10 degrees. At this temperature I-mixed nitrous acid (cooled out-of-doors to the temperature of the air) and fnow on January 23d laf; but the cold produced was not quite fufficient to freeze the quickfilver, although very near it, as indicated by a thermometer. From what I have obferved fince thefe latter experi- ments were made, I think it may be reafonably expeéted that powdered ice and nitrous acid at + 14 degrees, or fnow at + 10 degrees, will fucceed, if mixed expeditioufly. Strong the beff Methods of producing Artificial Cold. 503° Strong fpirit of vitriol,. whofe {pecific gravity is 1,848, required to be diluted with half its weight of water, and produced with fnow at the temperature of +- 30 degrees, about eight degrees lefs than with nitrous acid, finking the thermometer to — 24 degrees; four parts of the diluted vitriolic acid required at that temperature fix parts of fnow, It perhaps will be remarked, that I have taken no notice before of the vitriolic acid. The reafonis, becaufe, the freezing point of quickfilver being 39, it may be frozen tolerably hard by a mixture of nitrous acid with fnow or ground ice, though the utmoft degree of cold this acid can produce with {now is — 46°, which degree of cold may be produced by mixing the {now or ground ice and nitrous acid at 0°. If it be required to make it perfe@tly folid and hard, a mixture of equal parts of the di- luted vitriolic acid and nitrous acid fhould be ufed with the powdered ice ; but then the materials fhould not be lefs than — 10° before mixing. If a ftill greater could be required than a mixture of this kind can give, which is about — 56 degrees, the diluted vitriolic acid alone fhould be ufed with fnow or powdered ice, and the temperature at which the materials are to be mixed not lefs than — 20 degrees. Select, according to the intention, either of the three following mixtures : Firft, fnow or pounded ice two parts, and common falt one part, which produces a cold of — 5 degrees. Second, {now or pounded ice twelve parts, common falt five parts, and a powder, con- Gifting of equal parts of common fal-ammoniac and nitre mixed, five parts, which produces a cold of — 18 degrees. Third, {now or pounded ice twelve parts, common falt five parts, and nitrous ammoniac in powder five parts, which produces a cold of — 25 degrees, The proportions which I have found to be the beft for mixing the fnow or powdered ice with the different acids at different temperatures are thefe : viz. at + 30 degrees, feven of of the former to four of the nitrous acid ; at + 5 degrees, (with a trifling allowance, if any,, for a few degrees above or below) three to two; at — 12 degrees, four to three, the mixed acids, and at — 20 degrees, with the diluted vitriolic acid, equal parts. If it be required to prepare the materials in a frigorific mixture without the ufe of ice, a mixture of the proper ftrength may be chofen from the table. ; It is immaterial, when the exa& Proportions of each are known, whether the powdered ice be added to the acid, or the acid poured upon that, provided the powdered ice be kept ftirred to prevent lumps forming, and the materials be mixed as quick as poflible. But when the proportion is not known, it is better to be provided with more powdered ice than: is expected to be wanted, and add it to theacid by degrees, until the greateft effect is pro- duced, as fhewn by a thermometer. The confiftence is a pretty fure guide to thofe accuftomed to mixtures of this kind, viz. when frefh additions of {now or ice do not readily diffolve in the acid, though well ftirred, and the mixture acquires a thickith flocculent appearance, Snow or powdered ice that have ever been fubjeted to a cold Jefs than freezing are fpoiled, or rendered much lefs fit for experiments of this kind. I prefer the method of adding the powdered ice or fnow to the acid ina feparate veflel, principally becaufe the fize of that veffel may be exactly adjufted to the quantity of mixture it is f contain. ' i 1 A mix- 504 ~ Obfervations and Experiments on A mixture made of diluted nitrous acid, phofphorated foda, and nitrous ammoniac, (by much the moft powerful of any compounded of falts with acids,) prepared with the greateft accuracy, is not quite equal to a mixture of fhow and nitrous acid, each mixed at +- 30 degrees, although very nearly fo. Though quickfilver may be frozen by falts diffolved in acids, it is necefMlary that the ma- terials be cooled previoufly to mixing, much lower than when fnow or ground ice are ufed. 7 If it be required to mix the powdered falts and acids at a low temperature, the beft me- thod is this :—Put firft the nitrous ammoniac into the tube of fuch an apparatus as fig. 1, thaking it down level, gently prefling the upper furface f{mooth; then the phofphorated foda or Glauber’s falt: cover this with a circular piece of writing paper, and pour a little melted white wax upon it, and when cold pour upon this the diluted nitrous acid: immerfe this in a frigorific mixture till it is fufficiently cold, as found by dipping the thermometer into the liquor occafionally ; force a communication through, and ftir the whole thoroughly to- gether, contriving that the upper ftratum of falt, that is, the phofphorated foda or Glauber’s falt, be mixed with the liquor firft, and then the nitrous ammoniac ; the powdered falts do not require ftirring whilft cooling, like {now, for, however hard they are frozen, they will readily diffolve in the acid: care muft be taken that the partition be perfeét between the falts and the liquor, and thatin this and every inftance where the materials are to be cooled they be immerfed below the furface of the frigorific mixture. The ftrength of the red fume ing nitrous acid ufed in thefe experiments I found to be 1,510, and that of the vitriolic acid 1,848. I have thought it better, for the fake of brevity, not to ufe in this, as in my former papers, the new chemical names, efpecially as the old ones are more generally known. Thefe experiments were chiefly made ina warm room, not far from the fire-fide. I have now finifhed my propofed plan refpecting the beft modes of conducting experi- ments on cold ; in which it will appear, that I have reduced the congelation of quickfilver, in any climate, at any feafon, to a certain and almoft as eafy a procefs as that I originally fet out with for the freezing of water, (Phil. Tranf. vol. Lxxvut.) viz. by previoufly cooling the materials in one mixture, to produce the effet in a fecond. It may very likely appear to fome, that I have been too minute in a few particulars; yet, as perhaps experiments of this kind, all circumftances confidered, are inferior to few in the delicacy required to make them fucceed completely, I truft I fhall be excufed by thofe who choofe to repeat them, particularly fuch as are not in the habit of making experiments of this kind—efpecially if it fecure them from an unfuccefsful attempt, and that perhaps without being able to account for it. Oxford, March 1, 1795. It is very well known, that vitriolic ether will produce fufficient cold by evaporation to freeze water. This circumftance is noticed by many ; and feveral different methods have been propofed, particularly one by Mr. Cavallo, with a very ingenious apparatus for the purpofe (Phil. Tranf. vol. :xx1.); neverthelefs, as I am upon the fame fubject, and the following experiments differ, as well in the effet produced, as in the particular mode of conduéting them, from any I have met with, I have ventured to mention them, June the beft Methods of producing Artificial Cold. 505 “June.29, 1792, temperature of the air 71 degrees, I funk a thermometer (the bulb being covered with fine lint tied over it and clipped clofe round) by dipping it in ether,, and. fan- ning it to 26 degrees; then by expofing the thermometer to the brifk thorough air of an open window, to 20 degrees; and again, by ufing fome of the fame ether, but which had been purified by agitating it with eight times its weight of water, applied exadtly as in the laft experiment, the thermometer funk to 12 degrees. Water tried in the fame manner at the fame temperature, funk the thermometer to 56 degrees. A whirling motion was given the thermometer during each experiment. , The lint was renewed for each experiment, and the bulb required to be dipped into the ~ ether thrice ; the firft time fufliciently to foak it; after which the thermometer was held at the window till it ceafed to fink ; then a fecond quick immerfion, and likewife athird, ex- pofing the thermometer im like manner after each immerfion. x In this manner, a little water in a {mall tube may,be frozen prefently, by good ether not purified, at any time, efpecially if a {mall wire be ufed to fcratch or {crape the fides of the tube below the furface of the water. : . During the warmeft weather of laf fummer, I frequently froze water in this way. Explanation of Plate XX. FIG. t. is a-veffel in one piece, open at the bottom; aa the body, holding, when inverted, two pints ; 4 the tube, holding five ounces ; the lower or {maller part (formed by acontraétion or leflening of the tube in diameter, merely for the purpofe of leaving a fmall fhoulder for a temporary partition), holding rather Jefs than one-fifth of the whole. Fig. 2. is a veffel confifting of two parts; a a the body, holding two pints ;' 5 the tube, _ holding five ounces; which, together with the lid c, forms.a cover to take off and on the - veffel. N. B. This veffel may, if preferred, be ufed inftead of fig. 1. the parts correfponding with it, except in not being open at bottom, and the continuation of the tube upwards juft fufi- cient to ferve for a handle. Fig. 3. is a veffel in one piece, open at the bottom, holding, when inverted, two pints ; 4 the tube, holding four ounces and a half. Fig. 4. a veflel open at bottom, holding, inverted, one pint. Fig. 5. a cover to fig. 4. @ a the body, fitting exa€tly over, and é the cup-part (holding three ounces) fitting exactly within the correfponding parts of fig. 4. 2 Fig. 6. the inftrument for grinding the ice into powder; it works upon a fhort’ centre- point, and has the edge bevilled contrary ways on each fide the point, fo asto follow. The finenefs of the powder is regulated by the degree of: preffure ufed. The handle is wood, the reft metal ; a is a fliding cover fitting on the tube in which the ice is ground, to exclude the external air, and to keep the inftrument fteady; 4 is the fhoulder or guard, to prevent the point of the inftrument from touching fo as to endanger injuring ‘the bottom of the tube. It fhould be made, fo as to fit without grating the infide of the tube in ufing. The tubes of each of the veflels fhould be fomewhat fhorter than the veflel, fo as not quite to reach the bottom of it. Fig. 7. a thermometer-glafs, with the bulb three-fourths full of quickfilver. Fig. 8. a thermometer with the lower part of the feale-board turned up with a hinge, Vor, L—Freruary 1798. gas for 506 Portable Ele&rical Machine. for the convenfence of taking the:temperature of {mall quantities, or of mixtures in which mineral acids form 2 part. ; : 12% N. B. Thefe vefivls are reprefented as in -glafs, that being undoubtedly fitteft for pur- pofes in which corrofive acids are to be ufed. : IV. The Defcription of a New Portable Elefrical Machine. Invented ly the Rev. W. PEARSON, } ; of Lincoln. An ele€trical machine fufficiently portable, and at the fame time poffeffing power, ade- quate to all the purpofes of medital eletricity, has long been a defideratum among thofe profeffional gentlemen who attend the infirm, and are perfuaded that eleétricity has a fanative influence in many diforders of the human body. ‘The ele&trophore and medica bottle, as alfo the prepared ribbon and apparatus attached thereto, do both poffefs the for- mer property, but are found to be greatly deficient in the latter. Mr. Colman *, in his inge- nious treatife on the means proper to be ufed for reftoring fufpended refpiration, propofes an eleétrical machine (fuch as is both portable, and likewife poffeffes power fufficient to give a thock of 35 inches of coated furface at about a quarter of an inch ftriking diftance} to conftitute one important article of his improved apparatus for the recovery of perfons apparently drowned or fuffocated ; but feems to lament that we have no machine anfwer- ing fuch a defcription. A confideration of fuch magnitude as the want of an inftrument which promifes to benefit fociety in fo critical a moment as is that of the apparent extindionr of the vital principle, has turned the mind of the writer of this article frequently upon the fubjeét, as having fome relation to his clerieal fun@tion : he has in theory projected various conftructions of a portable machine, which mature confideration convinced him would be objectionable in practice. For to anfwer all the purpofes requifite for conftituting an elec~ trical machine fuitable for Mr. Colman’s purpofe, it appears neceflary not only that it have the two defired properties of portability and power, but alfo that its power be guarded fo as npt to be annihilated by the moifture wher ufed in the open air ; that it be capable of keing ufed without a table or ftand in eafes of neceffity; that it be rendered fit for ufe- upon the fhorteft notice ; that when ufed it charge the coated furface without confiderable lofs of time; and laftly, that it be not liable to be eafily broken. ' The writer, however, flatters himfelf he has at length hit-upon a conftru€tion which comprehends ail thefe properties, and which he recommends to the notice of inftrument makers, from a conviction that it is practicable. Indeed he has conftru&ed more than one machine, which anfwer his moft fanguine expeCation, and which therefore he will the: raore-circumftantially defcribe. : ‘ t Fig. 1. Plate XXI. reprefents a view of the machine with the eye placed ‘directly over it at a {mall diftance ; ABC Dis a fmall mahogany box 9} by 7} inches within, and 6 inches * As it is two years fince I perufed this treatife, and I’have not feen it fince, I cannot be certain of the exact words of the title, nor whether the name be Colmen or Coleman, W.P. drep,, Portable EleGrical Machiue. 507 deep, made of half-inch board : upon the bottom of the box lies a plate of glafs, alfogd by »t inches, cemented to the wood at the four corners by common electrical cement; this plate is coated on both furfaces with tin-foil 7 inches by 5, as reprefented at Qin figure 2 (except that the flips of tinfoil at H and I are pafted or gummed upon the under fide only); and is ufed as a fubftitute for a jar of 35 inches of coated furface, it being of no confe- quence what the fhape of the glafs be, provided it have a proper quantity of coating. MEN is’ a cylinder of glafs of four inches diameter, the body of which is 73 inches Yong: at M and N are brafs or * boxen caps cemented as in other machines, upon the {mall cylindrical ends of which the cylinder revolves by means of a fimple winch C, which maybe taken off or put on at pleafure, either by fcrewing, or by being inferted upon a fquare fhoulder. The central points of revolution of N and M are at about 2} inches from the top of the box, the firft inferted into a circular hole in one end of the box, and the other /et down in an open place made down through the other, which has 2 detached piece of fimilar wood to fit it, and to keep the cylinder in its place. L is the cufhion, and E the filk placed in the ufual way; D is a {crew with a milled head, which,’ by the afliftance of a tapped nut, placed faft in the infide of the box at 4 inches from the bot- tom, prefles againft the elaftic part of the /upport of the cufhion which is hid from the eye : this fupport, which may be of elaftic-wood, coated above D with tinfoil, or of any elaftic metal, is ferewed faft to the back of the box near the bottom in the infide. The chain at D is hung on the fcrew at picafure, as the wood is found to be ina good or bad conducting ftate. ' Fis a piece of light wood turned very fmooth in a lathe, and neatly covered with tinfoil, its ends being rounded. This piece, which I fhall call the collector, is furnifhed with about a dozen fixed pins of brafs, projeling againft the fide of the cylinder, as reprefented in the figure, as near as may be without touching it. The collector is 6 inches long, and fomewhat more than an inch in diameter, and is fupported by two folid glafs pieces, C C, of an inch and three quarters in length, and nearly half an inch in diameter, cemented into the fide of the box at 42 inches from the bottom, and each at an inch from the end of the colle€tor: by this means the colle€tor becomes infulated, and has a chain to be hooked on an eye of wire fixed on any part thereof, fo as to fall occafionally upon the upper infulated coating of the plate of glafs in the bottom of the box : the chain, however, mutt not be fo long as to extend beyond the coating by any motion of the box. B is a glafs tube + of about one-eighth of an inch bore, and about 3 or 3} inches long, with a ring of brafs or horn, that has a male {crew, cemented upon the middle of it, to fcrew into another ring that has a female fcrew, and is cemented or otherwife faftened into the * When caps are made of. wood, they muft be turned fo as to admit the glafs neck of the cylinder into a {pace or cavity which it fhall nearly fit. By this difpofition, the glafs is cemented to the wood at both furfaces, and the cap itfelf will be ftronger. W. P. + Mr. Nicholfon may have teen aware, that glafs-tubes of a {mall bore, however thick, are liable to be broken by a fhock paffing through them, when unguarded; and alfo that a lining of any kind will ufually prevent fuch an effect, Mr. Fell-of Ulverfton, in Lancafhire, an excclient electrician, has tubes placed over the wires of a very large battery, lined with paper or tinfoil, which do not break with a difcharge that melts pretty thick brafs wire, The tubes are uled as a guard againft,any accidental touch when the battery is charged. W,P, ; i te Quis qT 2° a ; front 508 Portabh EleBrical Machine. front fide of the box at 41 inches from the bottom. Through this tube (when coated with varnifh or fubftance of any kind within, to prevent its breaking by a difcharge) paffes a brafs wire as thick as will cafily move in it, about 4} inches long, tapped about an inch at each end and a little fmoothed ; on each end of this wire is a tapped nut which fcrew back or forwards to or from the ends of the tube, fo as to hold the wire in any fituation that may be required with regard to the diftance of its ends from thofe of the tube. The wi has alfo two brafs balls, one of which has its diameter Jefs than that of the tube, that ay move through the circular hole into the box, to prevent its falling on the glafs plate, whi it might do if ferewed off and on within the box. O O are the direétors with handles of glafs, or baked wood varnifhed, each Gx inches: Yong, befides the balls and wires; the balls are faft upon the wires, and the wires {crew into fockets on the ends of the handles. There is yet one part of the apparatus which it was not neceflary to exhibit in the plate, wiz. the infulating ftool; this is made exactly of a fize to cover the box, namely 105 inches by 81, and has four feetof glafs, or baked wood varnifhed, almoft 6 inches longy Underneath that part of the ftool which covers the colle€tor flides a little drawer, fig. 3. by means of the end-pieces P P, which drawer contains the tube, with its ap- pendages, milled nut, chains, handles of the direGtors, and amalgam, and muft be taken. from the ftool when ufed. The three compartments of the drawer, by being made to fit the dircétors and tube, prevent their fhaking in carriage. When packed, the four feet of the ftool go exaétly into each corner, and the edge of the drawer juft within the fide of the box, by which means the ftool is kept im its place as a cover; and laftly the wires of the dire€tors pafs through the ftool, which is of inch plank, at the middle near, the two ends, and, by ferewing into the fixed nuts in the edges of the box’s ends at_K and. K, until the balls touch the wood of the ftool, fix the whole fo firm that a handle, fuch as is ufed in a cheft of drawers, fixed on the centre of the ftool, ferves for carrying the whole apparatus by, which has the appearance of a lady’s {mall travelling-box, and weighs. eight pounds. After having been thus prolix in the defcription of the {eparate parts of this fmall machine, I come next to fay a few words’about the ufe.of it. As it is neceflary before- ufing any machine to have it perfeatly dry, andsas the feparate parts require to be fuccef- fively placed before the fire, this: machine wil] be found to poflefs an advantage even in the- preparation, which greatly conduces to expedition ; for after the box is difengaged from the ftool, and has the tube ferewed into its place (both which may be done in one minute), the box may be held in the hand before the fire, where all its parts will be alike dried at the fame time ; or it may be placed on the end A or fide D at any convenient diftance fromy the fire on the floor, as occafion may require, whilft the amalgamated leather is preparing. The machine being fréed from moifture and duft, and amalgam applied to the cylinder, _ the thock is adminiftered in the following manner, viz. Let the fmall chain fall from the eolieGor upon the upper coating of the glafs plate, and place the inner ball at the required: {triking diftance, fuppofe a quarter of an inch, as the cafe may require, and fix it there by means of the adjufting nuts, and the quantity of the charge will be limited in the fame manner as by Lane’s ele€trometer ; then conneé& one chain with the conducting wire which paffes through the tube, and the other with a brafs ring connected with the flip of the under coating at H (as appears im figure 1, or at J, as is.moft convenient), and hook the . oppofite Portable Elefrical Machine. 509 oppofite ends uponsthe wires uf the directors, whereby a fhock may be fent through any’ particular part of the body, as well as if the medical jar were ufed with Lane’s eleétrome- ter. It is immaterial whether the machine, in this operation, be held on a table’or ftand, the operator's knee when fitting, the bed of a patient, or even the ground by the fide of a ' river in cafe of neceflity where the patient is apparently drowned : nay, it may be held, by a perfon ftanding, in one arm, whilft the other hand turns the winch. When the {park only is required, the {mall chain is removed from the colleor, and alfo thelong chain, conneéted with the hook at H, is taken away ; the inner ball is then fixed fo as to touch the collector, by means of the adjufting nuts ; in which cafe the colleQtor, the wire in the tube, hd the fecond long chain conneéted therewith, form together: one con- duétor. After the exterior end of this chain is attached to the wire of one of the directors, the {park may be dire€ted into any particular part of the body; when the eye is the part alfe€ted, a pointed wire muft be ufed inftead of the wire carrying the ball, which mutt be made to fcrew into the focket of the direétor. When a {park is taken owt of the body, the patient muft ftand on the ftool, and hold the chain, conneéted as before, in his hand ; and then the operator, or affiftant, may take fparks. from him, as in other machines. If the patient be nervous, or afraid of the {park, it would be fafer to hook the chain to: _ the collector for fear of breaking the tube, and hold it at a diftance from the edge of the box in a perpendicular dire€tion. The fparks taken from an infulated body are ftronger than thofe fent into any perfon by reafon of the {mallnefs of the conductor, which is per- haps the greateft defect of the machine: this defe€t may, however, be remedied by placing any rounded metallic fubftance, fuch as a large candleftick, upon the {tool near the ma-. chine, and conneéting the chain with it, fo as to make it a part of the’ conductor, and then _ the {parks will become more denfe. . There is yet another way of adminiftering the eleétric fluid, which cannot properly be called adminiftering either the fpark or the fhock; in which cafe the fenfation is not fo momentary as is that caufed by the fhock, but more pungent than that of the fimple {park ; it may be called the interrupted fhock, and jis thus effe€ted: Let the thort chain fall from the’ colle€tor upon the coating of the plate, and connect one of the long ones with the hook at H or I, and fuffer it to be extended on the table; then, the inner ball touching the col- tector, turn half a dozen rotations before the finger be prefented to the outer ball; and becaufe the circle is not completed between the two coated furfaces of the plate by per fee conductors, a continuous ftream of denfe fparks will iffue into the finger, caufing a more pungent fenfation than would be felt froma fimple fpark of a much more powerful ma- chine. I fhould fuppofe the ftimulant power of this mode of eleQrifying any particular limb to be very great, and I underftand it has been practifed by fome electricians, by. means of a charged jar where the circle is not’ completed by perfect conductors. If a {mall pocket-jar, in a cafe, be added to this machine, it will be capable of producing either a negative or pofitive charge in it; for if the jar held by the ball conneted with its inner coating be prefented fo as to receive a pofitive charge on its outer coating from the outer ball of the machine, the inner coating will of courfe be negatively charged; and if it be placed upon the ftool, or inverted goblet, till the hand has taken hold of the outfide,, the negative charge will be retained, . Thus sro Portable EleAtvical Machine. Thus this Tittle niachine is capable of affording much amufement, and even of trying ex » periments ‘with, befides its being adapted for medical purpofes; and, which is not the fmall-© c#recommendation, may be manufa€tured at a fmall expence, compared with the larger’ machines. But, {mall as it is, I have frequently fired ardent fpirits with it, and have feen ” its power fuch aS to caufe 35 inches of coating to difcharge at a quarter of an inch ftriking * diftance at every third revolution; and at fourteen or fifteen revolutions it will, when in * good order, difcharge at half an inch. A fecond ‘machine of this conflrution, which I Jately’made for a friend, contains 42 inches of coated furface, with a cylinder of the fame ' fize as the one already defcribed, and is better adapted for making experiments, the box» being larger, and the infulation more perfeét; but is not fo portable. eve Before the former machine was completed, apprehended that the proximity of the wood to the colletor would take off much of the fluid ; but it does not appear that this is the cafe at all in giving fhocks, nor even in taking fparks, unlefs the diftance of the body to be electrified from the ball ufed- be greater than the diftance from the colle€tor to’ the wood, or rather from the adjufting ferews to the wood, for here the tendency to ef- cape feems to be the greateft. Onthis account the parts of the box where the fluid has the greateft tendency to efcape, are varnifhed' with feveral coats af fealing-wax melted in fpirits © of wine. How far baked wood would be preferable to mahogany in its working ftate for the front and ends of the box, 1 have not attempted to afcertain. ? As this machine is calculated to keep out the humidity of the air, when the hole for the tube is corked, and all the glafs, or infulating parts, well varnifhed with proper electrical varnifh ; the exciting power of the cylinder, when packed in good order, will remain but little impaired for feveral hours, and fometimes days if kept in a dry room, without freth amalgam. And what may appear rather remarkable, as the ftool is near the cylinder when packed, if the chains and tube be firft properly fixed, and the drawer removed, a fhock may be adminiftered with the {tool fcrewed on, as well as when off, and to all appearance in as powerful a manner: hence the ftool may be ufed as a prefervative againft humidity in the open air, in cafes of neceflity. } ’fter what has been faid of the conftruétion and ufes of this little machine, it “may be . afked; ** Has its efficacy ever been brought to the teft ” I anfwer, Yes. A gentleman, whe is a near relative of the writer of this article, was feized with a paralytic affection, dur- ing breakfaft, on September 15, 1797, which totally deprived him of the ufe of any part of his left fide, but which was not attended with pain. The beft medical affiftance was re- curred to for nearly a fortnight, without producing any apparent alteration. The appe- tite and tendency to fleep remained nearly as ufual; but the diftortion of one fide of the mouth rendered the fpeech fo inarticulate as to be nearly unintelligible. On the 27th of the fame month I was permitted to adminifter partial fhocks through different parts of the affeéted fide, which I began at the ftriking diftance of one-eighth of an inch with the ma- ~ chine already defcribed, while the patient was extended ona fofa; the firft two or three fhocks fent through the hand, were fcarcely if at all felt; by and by a fenfation was per- ceived ; a few larger fhocks at one-fixth were then adminiftered, which convulfed the hand a little, and were fenfibly felt; a great many more, at the fame ftriking diftance, were then fent through moft of the joints of the difeafed fide; laftly, a few more, at the diftance of one-fourth - Partgtle Elefrical Mackine.-Meteorolegy. _ gue one-fourth of an inch, were direéted from the fhoulder to the hand, and from the knee to the foot. After being thus eleGlrified, the patient felt fome pain in the knee, where the Jargeft fhocks entered, and upon trial could raife the leg alittle from the ground; but the hand and arm were motionlefs. On the morning of the 28th, the patient, after a good fleep, could raife the leg as before; and, to my great fatisfaétion, fuch an alteration had taken place, that by a motion proceeding apparently from the fhoulder, the arm was carried back and forward, as if fufpended by a pin; but the hand appeared no more than a dead weight. Partial fhocks of one-fourth of an inch were adminiftered as on the preceding evening, after which a pain fimilar to what had been before felt in the knee was now felt in the fhoulder; the knee became fomewhat ftronger, and the arm more aétiye in its mo- _ tion, but the hand remained apparently dead.. In the evening of the 28th, the patient was in bed, and cletrified as before, after which the thumb and firlt finger could be moved in -afmall degree. This rapid advance on the firft application of electricity, could not, I think, be attributed to the effeéts of medical affiftance, which had been omitted to be ufed a few days before, except that a feton remained (which ftill remains) ; nor yet to what is called the “ vis medicatrix nature,” for this ufually operates flowly. Shocks have continued to be ufed fometimes from one extremity to the other, in general twice a day, ever fince, to the prefent time, January 13, 1798, whilft the ftriking diftance has been gradually enlarged to nearly 4-10ths of an inch, and the increafe of {trength and a‘tivity has been hitherto re- gular. The patient at this time can walk into the ftreet, or up and down ftairs, without the affiftance of a ftick, and can handle any thing of {mall weight im his weaker hand: in fhort, he is happily become capable of fuperintending the affairs of his family, and, I truft, has reafon to hope for {till greater ftrength by perfevering in the means hitherto ufed. Other inftances could be adduced in which this machine has been ufed with as good efle as a larger one in difeafes of the human body; but a particular detail would enlarge the bounds of this article, which perhaps will be deemed already fufficiently long. Lincoln, Fanuary 13, 1798. V. A Memoir concerning a remarkable Phenomenon in Meteorology. Read to the Society of Na- turalifis of Geneva. By M. DE Saussure, O&sber 1797 *. As foon as I had rendered my hygrometer fufficiently perfect to compare one inftru- mient with another, and at the fame time fo delicate as to immediately thew the changes in the atmofphere, 1 wasin hope that I might avail myfelf of it ta foretell the changes of the weather. 1 expected that the hygrometer would move towards dry'on the approaching fine weather, or towards moi/? when wet weather was at hand; and it is true that, in ge- neral, the north-eaft wind, which ufually with us accompanies fine weather, does caufe it to move towards dry; and, on the other hand, that it indicates humidity during the feafons of rain. Burt I have fince obferved a very remarkable exception; namely, that the times of greateft drynefs are generally the precurfors of rain. al * This paper was communicated to tie Editor of a Decade Philofophique, &c by Felix D {portcs, Refis dcps of the French Republic at Geneva. 1 have tranflated it from this lait work, No, 4. N, Rver 512 Rentartable Phenomenon in Meteorology. Ever fince I made this obfervation, my thoughts have been frequently directed to account for it; and it was not till lately at Plombieres that I found a fatisfactory caufe, which I fhall make the fubje@ of the prefent Memoir. : In order to give every poflible degree of certainty to my obfervations, I kept my inftru- ments defended not only from the direct rays of the fun, but from every refle€lion 3; andI obferved their ftation daily at the fame hours, but more particularly at four in the after- noon, when the greateft drynefs ufually prevails. During the two months that | remained at Plombicres, the greateft drynefs I obferved was on the 2d of Auguft. The hygrometer indicated 68,5°, the thermometer being at 225% Three or four days before, the hygrometer at the fame hour had ftood higher or nearer to humid, that is to fay, 86°, or 87°, though the thermometer was near a degree higher, namely 23,1°, which muft have proportionally raifed the hygrometer, It rained in the evening of the fame day on which it had been drieft, namely, on the 2d of Auguft, At the fame time that the hygrometer defcended, the barometer alfo fell near two lines. Now I have proved, in my Effays on Hygrometry, and by feveral experiments, that in an air which is rarefied the hygrometer defcends, and denotes a greater degree of drynefs. I therefore aesiaiee this extraordinary drynefs to the rarefaction of the air. © Cn my return from Plombieres, I purfued my obfervations with the fame care. On the 2gth of Auguf of this prefent year, at 20 minutes after 4 in the evening, I obferved the hy- grometer at 74°, while the thermometer ftood at 22,5°. -On the following day, at 50 mi- nutes after one, I found the thermometer exatly at'the fame degree as the evening before, namely, 22,5°, the hygrometer being at 59,5°, that is to fay, 145° higher than the evening before. I noted this moment, as affording a valuable obfervation, on account of the iden- tity of height in the thermometer. It was therefore evident that the drynefs of the air had been increafed, not by its heat, but by fome other agent, fuch as its rarity. In fact, the ba- rometer had defcended more than half a line. A wind from the fouth-weft prevailed at the fame time, and it rained early the next morning. But the moft ftriking inftance is to be found in my Effay on Hygrometry. I made this obfervation at Chamouni on the 23d of July 1781. The hygrometer ftood at 41,2°, the ther- mometer indicating at the fame time 20,2°. But this degree of heat was far front fufficient to produce fuch a degree of drynefs ; for, by calculating from the table at page 87 of my Effay on Hygrometry, we find that the difference of 4; degrees of heat between that day and the preceding could not deprefs the hygrometer more than g degrees, inftead of 20, which it really defcended. The excefs, namely 11 degrees, muft therefore be attributed to another caufe, which I conclude to ‘be the rarefaction of the air. The air may be rarefied cither by the fall of the barometer, or the direétion of the wind. In faét, the fouth and fouth-weft winds coming from lower countries than ours, and from the fea, muft neceflarily rife, and thence become rarefied, and confequently, as I have faid, caufe the hygrometer to advance towards dry. It is probable likewife that the fingular elevation of the valley of Chamouni above the level of the fea, was one of the principal caufes of the drynefs which predominated in that valley on the 26th of July 178r. We may therefore conceive the reafon of this phenomenon, which at firft fight appears fo ftrange ; namely, that extraordinary drynefs fhould precede rain, and that the hygrometer fhould become, in this manner, an affiftant to the barometer, and afford one of the moft cer- tain Mineralogical Phenomenon—Alkali. 513 tain indications of change of weather. It is to be obferved, that it rained at Chamouni the i next-morning. Nature has exhibited figns of drynefs which do not deceive the inhabitants of the coun- try, and ferve to predict ftorms long before hand ; fuch as the flaccidity or drooping of plants with large and thin leaves; fuch as the gourd and the beet in our gardens, the pe- tafite in the fields, and the cacalia in the mountains. It is obferved, that the leaves of thefe plats droop and incline towards the ground on the approach of ftormy weather; and that -on the contrary they fpring up, and aflume an appearance of vigour, when the dew or rain has reftored the elafticity and natural frefhnefs to their fibres. I muft add, that the heavy rain in the month of September laft was preceded by a wind of extraordinary drynefs: and as we are defirous of knowing the purpofe, or at leaft the ufe, of each of the laws of na- ture, I would remark, that thefe great droughts which precede ftorms feem intended to put vegetables into a proper ftate to obtain the greateft advantage from ‘the rains,on which their growth isto depend. A dry air relaxes and empties their veflels, and gives them the power of abforbing the rain-water which fucceeds. This water finds the air through which it falls loaded. with carbonic acid and other exhalations which give fertility to plants. It is in fact obferved, that the rain of ftorms which fucceed uncommonly dry weather gives to vegetables a peculiar growth and ftrength, much greater than are found to fueceed: other rains or long continued wet weather. Hence we perceive, that the more attention we pay to natural slcuanasad the more rea= fon we find to admire the order and uniformity which prevail in the laws to which they are fubject. VI. On: the various Denominations given to the Alkali of Tartar. By a Correfpondent. To Mr. NicHOLSON, Lditor of The Fournal of Natural Philofophy, Se.” SIR, . Aoncst the numerous innovations which have taken place within thefe few years, nothing perhaps has undergone fuch an infinite variety of modifications as the chemical no- menclature : fo far indeed has the rage for novelty been carried in this refpeét, that every perfon who, without ademonftrable neceffity for the change, propofes at prefent cither a new fyftem, or an alteration in any one already received, mutt juftly incur the cenfure of in- ereafing the confufion. which fuch an endlefs mutation of names has already produced. T fhall however beg leave to mention a circumftance which has frequently appeared to me to be a remarkable one. We have no tolerable appellation univerfally received in our own _ language for a fubftance which is indifputably in more ordinary ufe in the laboratory, and more frequently fpoken of in chemical writings, than any other—the pure alkali of tartar. Let us only fee what are the appellations which have been given to it. Kali, the name applied to this falt by the London College of Phyficians, is not only im- proper, as being already that of a genus of plants, but has in fact been long ufed as the dif- Vou, l—Fesrvary 1798. 3.U tinctive sik Denominations of the Atkali of Tartar. tinétive appellation of the other fixed alkali, in confequence of ts extra&tion from thofe ve- getables. “Fixed vegetable alkaline falt, the defignation of this fubftance in the Edinburgh Pharmaco- pccia, to fay nothing of its being rather a defcription than a name, is no lefs objeétionable’ on account of its impropriety. ‘This alkali does not feem to be any more a product of ve~ getation than foda. Potaff, the barbarous corruption of our word pot-q/ by the French chémitts, has with them at leaft-one advantage ; it does not fignify any thing elfe: but when re-tranflated by us into pot-a/b, it certainly becomes in the higheft degree objeGtionable, as tending to confound a fimple fubftance ina ftate of chemical purity, with a heterogencous compound of very dif- ferent qualities. . " Spodium, the appellation propofed by Dr. Hopfon, is alfo inappropriate. This falt is ccr= tainly not formed by the procefs of incineration any more than the other fixed alkali is: indeed barilla, from which the greater part of the foda ufed in this country is obtained, is as immediately in the ftate of a cinder as any fubftance in commerce. Tartarin, or, better perhaps, tartarine, is a word, which, if not every thing wé could with, has feveral great advantages. ft. It fignifies nothing elfe. 2dly. It is perfe€tly appro- priate. ‘Tartar isa fub{tance which has been Jong and univerfally known, and which con- tains this alkali only in combination with an acid which is deftruatible by fire 5 fo that the pureft fpecimen of its carbonate, which is commonly met with in the fhops, is obtained from it by mere combuftion; on which account it has been long called by feveral compound names analogous to the one here fpoken of, as /alt of tartar, alkali of tartar, &c. gdly. The name itfelf recalls to the mind one of the readieft and moft ordinary means of diftinguifhing the folution of this falt from that of foda by the teft of ‘the acid of tartar. And 4thly. It has already been ufed throughout the whole of a work of fome importance, which is in the hands of every chemift ;—a circumftance perhaps effential to the eftablifh- ment of any new chemical appellation. As the Latin, on account of its faving the necef- * fity of auxiliary particles, and for fome other reafons, feems better adapted to fome of the pur- pofes of a chemical nomenclature than the modern languages, the feminine fartarina may ferve well enough in this cafe. The word propofed in the French nomenclature will not by this means become abfolutely ufelefs:—the claffical chemift may {till label his common pot-ath * Potaffa Ruffica,” and its titles, if not of equal antiquity, will not perhaps be inferior in elegance to thofe of its next-door-neighbour, the “ Cineres Perlati” Cady But as it is rather my intention to point out the difficulty than to propofe the remedy, [ fhall add no more on the fubjeét. The with of every one muft be, that by the univerfal re- ception of fome unobjetionable appellation, we may be enabled to {peak of this fubftance ~ ‘without impropriety, or the appearance of affe@tation. Iam, Sir, your obedient fervant,’ PHILONOMUS. January 18, 1798. VII. dn Phenomena of the Combuftion of Gunpowder. 513 VII. An Account of fome Experiments to determine the Force of fired Gunpowder. B y BENJAMIN Count of Rumrorp, F.R.S. MRI. A. ’ [Concluded ore page 468. ] Apter tabulating the experiments, of which an abftra& was given in our laft number, the Count proceeds.to afcertain the law, according to which the elafticities-increafe in pro- portion to the quantities of powder ufed forthe charge. For the fake of brevity, as well as becaufe the fubje¢t appears to require {till further inveftigation than he has beftowed upon it, I fhall refer the reader to the paper itfelf, inftead of attempting to give an abridged ac- count of this part, and fhall proceed to relate the other experimental refults contained in his paper. After having {hewn the extreme force of fired gunpowder, he adverts to an objection which may be made againft his dedu€tions. How does it happen that fire-arms and ar- tillery of all kinds, which certainly are not calculated to-withftand fo enormous a force, are not always burft when they are ufed? Inftead of anfwering this queftion, by afking how it happened that the extremely {trong barrel ufed in his experiment could be burft by the force . of gunpowder, if this force be not in fact much greater than it has ever been fuppofed to be, he proceeds to fhew that the combuftion of gunpowder, inftead of being inftantaneous, as Mr. Robins’s theory fuppofes, is much lefs rapid than has hitherto been apprehended ; an obfervation, which, if eftablifhed, is certainly fufficient to anfwer the objection. He remarks, that it is a well known fact, that on the difcharge of fire-arms of all kinds, cannon and mortars. as well as mufkets, there is always a confiderable quantity of uncon- fumed grains of gunpowder blown out of them ; and what is very remarkable, as it leads dic rectly toa difcovery of the caufe of this effe&, thefe unconfumed grains are not merely blown out of the muzzles of fire-arms, but come out alfo by their vents or touch-holes, where the fire enters to inflame the charge, as many perfons who have had the misfortune to ftand with their faces near the touch-hole of a mufket, when it has been difcharged; have found to their coft. It appears extremely improbable to our author, if not abfolutely impoMble, that a grain “of gunpowder actually in the chamber of the piece, and completely furrounded by flame, fhould, by the action of that very flame, be blown out of it without being at the fame time fet on fire. And, if this be true, he confiders it as a moft decifive proof not only that the combuttion of gunpowder is lefs rapid than it has generally been thought to be, but that a grain of gunpowder aétually on fire, and burning with the utmoft violence over the whole of its furface, may be projected with fuch a velocity into a cold atmofphere, as to extinguith the fire, and fuffer the remains of the grain to fall to the ground unchanged, and as inflammable as before. This extraordinary fa& was afcertained beyond all poflibility of doubt by the Count’s ex- periments. Having procured from a powder-mill in the neighbourhood of the city of Mu- nich a quantity of gunpowder, all of the fame mafs, but formed into grains of very different fizes,fome as {mall as the grains of the fineft Battle powder, he placed a number of vertical aw 2 {creens 516 Combuftion of Gunpowder. fcreens of very thin paper, one behind another, at the diftance of 12 inches from each other 5 and loading a common mufket repeatedly with this powder, fometimes without and fome- times with a wad, he fired it againft the foremoft fcreen, and obferved the quantity and ef- fe€ts of the unconfumed grains of powder which impinged againft it. ; The fcreens were fo contrived, by means of double frames united by hinges, that the pa- per could be changed with very little trouble, and it was a€tually changed after every expe- riment. . The diftance from the muzzle of the gun to the firft {creen was not always the fame; in fome of the experiments it was only 8 feet, in others it was 10, and in fome 12 feet. The charge of powder was varied ina great number of different ways ; but the moft i in- terefting experiments were made with one fingle large grain of powder, propelled by fmaller and larger charges of very fine grained powder. Théfe large grains never failed to reach the fcreen ; and though they fometimes appeared to have been broken into feveral pieces by the_force of the explofion, yet they frequently reached the fereen entire ; and fometimes paffed through all the fereens (five in number) without being broken. When they were propelled by large charges, and confequently with eteat velocity, they were feldom on fire when they arrived at the firft fcreen, which was evident not only from their not fetting fire to the paper (which they fometimes did), but alfo from their being found fticking in a foft board, againft which they ftruck, after having paffed through all the | five fereens; or leaving vifible marks of their having been impinged againft it, and being broken to pieces and difperfed by the blow.” Thefe pieces were often found lying on the ground ; and from their forms and dimenfions, as well as from other appearances, it was of- ten quite evident that the little globe of powder had been on fire, and that its diameter had been diminifhed by the combuftion before the fire was put out, on the globe being projected into the cold atmofphere. The holes made in the fcreen by the little globe in its paflage through them, feemed alfo to indicate that its diameter had been dintinifhed. That thefe globes or large grains of powder were always fet on fire by the combuftion of the charge, can hardly be doubted. This certainly happened in many of the experiments 5 for they arrived at the fereens on fire, and fet fire to the paper: and in the experiments in which they were projected with {mall velocities, they were often feen to pafs through the nir on fire; and when this was the cafe, no veftige was to be found. : © They fometimes pafled on fire through feveral of the foremoft fereens without fetting flem on fire, and fet fire to one or more of the hindmoft, and then went on and im- pinged againft the board, which was acy at the diflance of 12 inches behind the laft fereen. The Count then proceeds to mention another experiment, in which the progreflive com- buftion of gunpowder was fhewn in a manner ftill more ftriking and not lefs conclufive. A fmall piece of red-hot iron being dropped down into the chamber of a common horfe- piltol, and the piflol being elevated to an angle of about 45 degrees, upon dropping down into its barrel, one of the fmall globes of powder (of the fize ofa pea), it took fire, and was projected into the atmofphere by the elaftic fluid generated in its own combuttion, leaving avety beautiful train of light behind it, and difappearing all at once like a falling ftar. This amufing experiment was repeated very often, and with globes of different fizes. When aif Innprovements in Fire-dvms, 2c. 517 When very {mall ones were ufed fingly, they were commonly confumed entirely before they came out of the barrel’of the piftol; but when feveral of them were ufed together, fome, if not all of them, were commonly projected into the atmofphere on fire. As the flownefs of the combuftion of gunpowder is undoubtedly the caufe which has prevented its enormous and almoft incredible force from being difcovered, our author de- duces, as an evident confequence, that the readieft way to increafe its effeCts, is to contrive matters fo as to accelerate its inflammation and combuttion. This may be done in various ways; but, in his opinion, the moft fimple and moft effeCtual manner of doing it would be to fet fire to the charge of powder, by fhooting (through a {mall opening) the flame of a fmaller charge into the midft of it. He contrived an inftrument on this principle for firing cannon three or four years ago, and it was found, on repeated trials, to be ufeful, convenient in practice, and not liable to accidents. It likewife fuperfedes the neceflity of ufing priming, of vent-tubes, port-fires, and matches; and on that account he imagined it might be of ufe in the Britifh navy. Whether it has been found to be fo or not he has not yet heard. Another infallible method of increafing very confiderably the effe&t of gunpowder in fire- arms of all forts and dimenfions, would be to caufe the bullet to fit the bore exa@tly, or without windage, in that part of the bore at leaft where the bullet refts on the charge; for, when the bullet does not completely clofe the opening of the chamber, not only much of the elaftic fluid, generated in the firfl moment of the combuftion of the charge, efcapes by the fide of the bullet; but, what is of ftill greater importance, aconfiderable part of the un- confumed powder is blown out of the chamber along with it in a flate of a€tual combuttion, and, getting before the bullet, continues to burn on as it paffes through the whole length of the bore ; by which the motion of the bullet is much impeded. The lofs of force which arifes from this caufe, is in fome cafes almoft incredible; and it ts by nomeans difficult to contrive matters fo as to render it very apparent, and alfo to pre- vent it. If a common horfe-piftol be fired with a loofe ball, and fo fmall a charge of powder that the ball fhall not be able to penetrate a deal board fo deep as to ftick in it when fired againft it from the diftance of fix feet; the fame ball, difcharged from the fame piftol with the fame charge of powder, may be made to pafs quite through one deal board, and bury itfelf in a fecond placed behind it, merely by preventing the lofs of force which arifes from Witae i is called windage, as he found more than once by a€tual experiment. ~ He has in his poffeffion a mufket, from which, with a common mufket-charge of powder, fires two bullets at once with the fame velocity that a fingle bullet is difchargéd from a mufket on the common conftruction with the fame quantity of powder. And, what ren- ders the experiment ftill more ftriking, the diameter of the bore of his mufketis exaétly the fame as that of acommon mutket, except only. in that part of it where it joins the chamber, in which part it is juft fo much contraéted, that the bullet, which ‘is next tothe powder,’ may flick faft init. He adds, that though the bullets are of the common fizé, and are confe~ quently confiderably lefs in diameter than the bore, means are ufed which effeaually prevent tlic lofs of force by windage; and to this laft circumftance, he concludes, it is doubtlefs owing, Ve in a great mealure, that the charge appears to exert fo great a force in propelling the bullets, 1 That: 518 Elafiic Force of Gunpowder.—Strontian. That the conical form of the lower part of the bore where it unites with the chamber has a confiderable fhare in producing this extraordinary effect, is, however, very certain, as he has found by experiments made with a view merely to afcertain that fad. The remaining pages of the Count’s paper are occupied by a computation, tending to fhew, that the fotce of the elaftic fluid, generated in the combuftion of gunpowder, may. be fatisfactorily accounted for upon the fuppofition that its force depends folely on the elafticity of watery vapour or fteam. For this purpofe he recurs to the experiments of Mr. Betancour, publifhed in Paris, under the aufpices of the Royal Academy of Sciences, in the year 1790, which thew that the elafticity of fteam is doubled by every addition of, temperature equal to 30° of Fahrenheit. From the Count’s reference, it appears that the experiments were carried as far as 280 degrees of that {cale, in which cafe the preflure was found to be equal to abaut four atmofpheres. He affirms, that there does, not appear to be any reafon why the fame Jaw fhould not hold in higher temperatures, and has there- fore extended his computations through thirteen more terms of the geometrical feries, the laft of which affords an elaftic force equal to more than fixty-five thoufand atmofpheres. As an excufe for not giving this computation in detail, I muft fimply remark, that fome- thing more than a negative reafon feems neceflary to juftify the extenfion of this law of in- creafe from fo limited a feale of experiments. For which reafon I fhall add no more of this fpeculative part, than merely that the water of cryftallization in the nitre, and the moifture which the charcoal may be conceived to retain, appear to be fully fuffitient to ae- count for the explofive force by means of {team only, if the dedutions from Mr. Betancour’s. experiments be admitted. VUI. Objervations on Strontian. — By Citizen Pexzerrer. Read to the National Inflitute } 30th April, 1796.* 3 Srrontran is at prefent confidered by many foreign chemifts asa peculiar earth. Its difcovery feems to me to be due to Dr. Hope, profeflor of chemiftry at Glafgow ; he hav- ing firft defcribed its characters and chemical properties ina differtation which he publithed 4th November, 1793, and which has fince been printed in the Tranfations of the Royal Society of Edinburgh. This memoir is neverthelefs pofterior to Dr. Crawford’s differtation on the internal ufe.of muriate of barytes, in which he announces that he thinks it probable “that the ftrontian mineral contains an earth different from barytes +. M. Klaproth. * Tranflated from the Annales de Chimie, xxi. p. 113, by J. E—r. + The falt obtained from the combination of ftrontian earth with muriatic acid is much more foluble in hor water than in cold, and confequently cafily cryftallizes by cooling: muriate of barytes, on the contrary, is nearly as foluble in cold water as in hot, and cryftallizes by evaporation, é An ounce of diftilled water at the temperature of 70 degrees, diffolves 9 drachms and so grains of muriate ef frontian : the fame quantity of water, at the fame temperature, only diffolves 3 drachms and 35 grains of miriateof barytes. ; The former produces at leaft x5 degrees of cold by irs olution ; the latter not more than 5 degrees at the moh. , Muriate Obfervations on Strontian. 519 M. Eilaproth has alfo examined ftrontian, but, as it appears, fubfequently to Dr. Hope ; or at leaft, as he does not fpeak in his work of Dr. Hope’s experiments, there is reafon to believe that they were not known to him. Strontian isalfo mentioned in M. Schmeiffer’s mineralogical work, as different from the other known earths. It is in the ftate of carbonate that it is found in Argylefhire in the weftern part of the north of Scotland, accompanying a vein of lead-ore. Klaproth, Blumenbach, and Sulzer of Ronnébourg, called it Jfirontianite; Hope called itfrontite. 1 conceive that the name of /rontian, taken from the place where it is found, may be properly afligned to it, as this word initfelf has no fignification, and cannot confe- quently render it liable to be confounded with other fubftances. "The carbonate of ftrontian has been for a long time confidered asa variety of native car= bonate of barytes ; 1 myfelf looked upon it as fuch in 1791, from fome affays to which I had fubjected a {mall {pecimen, which Mr. Greville of London had the goodnefs to pro- cure me. Having aflayed it comparatively with the carbonate of -barytes from Anglezark, ‘ which was then called witherite, I thought I did not at that time perceive any remarkable difference between the two fubftances. Both of them when fufed by the blow-pipe afforded white opaque vitreous globules, which, when expofed for fome time to the air, became re- duced to powder. Expofed to diftillation in a moderate heat, carbonate of ftrontian does not, any more than carbonate of batytes, emit any carbonic acid gas, though they are both diffolved by the nitric and muriatic acids with effervefcence and a difengagement of this gas. The falts which refulted-from thefe combinations were by no means deliquefcent, and I therefore took thofe of the ftrontian for nitrate and muriate of barytes, and ftill rather becaufe their folutions were decompofed by sa alkaline, calcareous, and other fulphates, 4s is the cafe'with the barytic falts. _ Itis fome months fince we have been acquainted in France with the labours of M. Klap- roth on the carbonate of ftrontian ; but thofe of Dr. Hope, although prior, were unknown to us, and it is only within a few days that'I have been apprized of them by M. Schmeiffer- In a letter which M. Hermbftcedt wrote me fix months ago, he announced that M. Klap- roth had eftablifhed the properties of ftrontian as a new earth, the difcovery of which had been made feveral years fince by M. Sulzer, and had been publifhed by M. Blumenbach in his treatife on natural hiftory. The diftin@tive characters which M. Klaproth had found in the carbonate of ftrontian were : Firft, That it was {pecifically lighter than native carbonate of barytes (witherite) ; * Secondly, N Muriate of barytes affords by evaporation flattened oftagonal cryftals, two of whofe oppofite fides are always much longer than the others : muriate of ftrontian, by rapidly cooling, cryftallizes in clongated filaments, aud, when flowly cooled, in hexagonal columns, of which three fides aré alternately wider, and the ethers narrower, and terminated in obtufe triangular pyramids. Thus, though the carbonate of ftrontian much refembles that of barytes, thefe two fubftances have very different qualities. It is probable that the ftfontian mineral has for its bafis a new fpecies of earth which has not hitherto been examined, and which it is of importance not to fubs fiture for barytes for medical ufes. Extrad from Dr. Crawford's Differtation. P. The above is a tranflation of Citizen Pelletier’s note. Not having Dr. Crawford's fraét on the terra ponderofa Jfalita, or muriate of barytes,at prefent by me, Ihave not been able to examine the accuracy of the quotation, but have no reafon to doubt it, except that I think he ufes a different nomenclature. T, 520 Obfervations, on Strontian. Secondly, That it produced with the nitric, muriatic, and other -acids, falts which were more foluble than thofe of barytes ; Thirdly, that the falt which it formed with the muriatic acid, Fetis didiolved i in 1 alcohol, gave it the property of burning with a red flame ; Fourthly and laftly, That it might be deprived of its carbonic acid by valcination; and that. it became by this means foluble in water, and the moft fo in boiling water ; fo that by cooling a portion was feparated in a cryftalline form. 9 : he fpecimen of carbonate of ftrontian, which I had in my colle@tion, © was not confide- rable enough toadmit of a great number of experiments; it was however fufficiently fo to enable me to repeat a part of thofe which are related by Meffis. Hope and Klaproth; and what moftly determined me to appropriate it to this purpofe was, that Cit. Coquebert had _ publithed in No.5 of the Journal des Mines, that from fome aflays which we had made of the carbonate of ftrontian, Ihad doubted whether it contained a peculiar, earth. The fol- lowing are the reafons on which my doubts were founded : if I. Iti is feveral years fince I had fucceeded in difengaging carbonic acids gas from carbo- nate of barytes by calcination ; and, having then diffolved the calcined barytes in hot water, had obtained a cryftallization : I could not therefore confider this charaéter as exclufively belonging to ftrontian. Ba 2. I knew alfo that calcareous muriate diffolyeds in alcohol. gave it the property of burn- ing with a red flame. This confideration induced me therefore to fufpe& a mixture of calcareous carbonate in that of ftrontian, and the {pecimen which I had was in fact com- bined with this fubftance. I thall now defcribe the experiments which I have. made to en- deavour to deteét this ingredient ; and, as they were made comparatively with a fimilar fet on the native carbonate of barytes (witherite), I have thought it proper to prefent them to- gether, that it may be feen in what refpedts the carbonate of ftrontian refembles, and in what it differs from it. 4. Comparifen of Strontian and Barytes. 1. CARBONATE of barytes is found with fulphate of barytes in a lead-mine at Anglezark, (near Chorley)in Lancafhire*. Carbonate of ftrontian is found at Strontian in te lacy alfo accompanying a lead-ore with fulphate of barytes. 2. The carbonate of barytes from Anglezark, taken internally, is poifonous, fo that in that country it is, known by the name of rat-ftone [pierre contre les rats]. A little dog to which I had given fifteen grains was feized with vomiting, and died eight hours afterwards ; and having given to another, of apparently equal ftrength fifteen grains of carbonate of barytes obtained from the decompofition of the fulphate, it was alfo feized with vomiting, and died fifteen hours afterwards : the latter was opened by Cit. Chauffier. Another dog to which J had given a like quantity of carbonate of barytes, prepared from fulphate of barytes from the ci-devant province of Auvergne, had vomitings, but did. not die, though he took. it two days fucceflively : he vomited each time. , I purpofe to repeat thefe experiments with carbonates of barytes procured from different barytic fulphates, and efpecially thofe which -are not accompanied by any metallic ores. “The carbonate of ftrontian, on the contrary, say be taken internally without danger.’ I gave 29 grains of it to a little dog, but he was * See the Manchefter Memoirs, i. 598. i biaye not Objervations on Strontian. §2t not feized with any vomiting, and twenty hours afterwards I did not at all perceive that he had felt the fmalleft inconvenience. It will be proper to repeat this experiment with ftronger-dofes. Blumenbach was alfo convinced that the carbonate of ftrontian, taken in- ternally, did not at all derange the animal ceconomy. Thefe obfervations, therefore, point out a difference between ftrontian and barytes. 3: The colour of the carbonate of barytes from Anglezark is a grey white: it is fome~ times found cryftallized, but more commonly in a ftriated mais. Its fpecific gravity is from 4.2919 to 4.3710. The colour of carbonate of ftrontian js alight green, though it is fome- times found colourlefs and tranfparent : it is ftriated, and fometimes of a regular cryftalline form. Its {pecific gravity is from 3.6583 to 3.6750*. This carbonate is-confequently lighter than that of barytes. 4. Native carbonate of barytes, expofed to a fire which is not too violent, fcarcely lofes any thing of its weight: in a ftronger one it attacks the crucible, and paffes into fufion. Carbonate of ftrontian alfo retains the carbonic acid pretty ftrongly ; but with caution, and a proper continuance ef heat, the carbonic acid may be feparated in the proportion of five or fix hundredths of the falt, without its attacking the crucible : fome care muft, however, be taken not to have the fire too ftrong, as the earth would, in that cafe, attack the cru- cible, and run into a chryfolite-coloured glafs. The carbonic acid therefore is lefs ftrongly retained in carbonate of ftrontian than in that of barytes. 5. Meffrs. Hope and Klaproth had obferved, that calcined ftrontian was foluble in water, and that, when boiling, it diffolved a fufficient quantity to afford cryftals by cooling ; fo that thefe two chemifts regarded this property in ftrontian as a diftin@tive character. M. Klap- roth efpecially never fucceeded in calcining the native carbonic of barytes fufliciently to try its folubility in that ftate. When he gave it but a fmall degree of heat, it was not deprived of its carbonic acid ; and when he applied a greater, it became vitrified. Dr. Hope an- nounced, ina fupplement to his memoir, that he had found means to calcine the native carbonate of barytes in a black-lead crucible, and that he found this earth, thus calcined, was, as well as ftrontian, foluble in boiling water, and fufceptible of cryftallization ; which properties he has accordingly ceafed to confider, fince that time, as charaéters peculiar to ftrontian. I have alfo fucceeded in feparating with facility the carbonic acid from both the native and artificial carbonates of barytes, as well as that of {trontian, without ufing black-lead crucibles ; and I fhall here defcribe the method which has conftantly proved fuccefsful with me, and the comparative experiments which I have made on this fubject. ~ Proceft for feparating the Carbonic Acid Srom the Carbonates of Barytes and Strontian. 1. TO 100 grains of native carbonate of barytes in powder, I added 10 grains of pow= dered charcoal; and, the whole being well mixed, I made it into a {tiff pafte with boiled ftarch, and rolled it into a ball. Having put into a crucible a little frefh-burnt charcoal *Tn the fpecific gravities in the original, that of diftilled water is fuppofed to be 10, the decimal point being put one place more forward than is here done. I have ventured, in conformity to the more vfual, and, as I think, more convenient, method of putting unity for this common meafure, to point them as above. T. ; Vou. I—Fepruary 1798. 3X in §22 Odjervations on Strontian. in powder, and laid the ball on it, I covered it with powdered charcoal, and Juted on-a cover with common loam. Things being thus difpofed, the crucible was kept in,a very {trong fire for a full hour, which time was fufficient to difengage the carbonic acid. The crucible being cold, 1 opened it, and found the little ball perfeétly compact ; but it now weighed only 70 grains. I then triturated it in a glafs-mortar with about nine ounces of boiling water, filtrated the liquor, and, in order to difpofe it the more to cryftallization, put it into a glafs retort, to feparate a portion of the water by diftillation. By cooling, there were formed in the retort cryftals feveral lines in length. 2. One hundred grains of carbonate of barytes prepared from the fulphate by the ordi- nary procefles were treated with 10 grains of powdered charcoal, as above defcribed, and the crucible equally expofed to heat for only an hour. Having then treated the refidue with boiling water, and concentrated the liquor in a retort, I obtained, on its cooling, cryftals fimilar to thofe before mentioned. 3. One hundred grains of carbonate of ftrontian being treated in the fame manner, the refidue, after calcination, weighed only 72 grains. Its folution in hot water appeared to me more faturated than that of barytes; and, without having recourfe to concentration, I obtained cryftals on its cooling, though I had ufed about the fame quantity of water as in the preceding experiments. Ido not, however, believe that ftrontian is much more foluble than barytes; for in feveral other experiments I have had folutions of barytes fo fully fatu- rated as to cryftallize by cooling confufedly and in a mafs. -Thus it is very evident that the aétion of fire feparates carbonic acid from barytes and ftrontian, and that thefe earths then become foluble in water, and in larger quantity if boiling, fo as to give cryftals by cooling, This character does not therefore belong exclufively to ftrontian, as M. Klaproth fup- poles. I have alfo ee that the aqueous folutions, both of barytes and ftrontian, ae pure or calcined, have an odour fomewhat fimilar to that of cauftic pot-afh or foda, or what is commonly called a lixivious odour. Habitudes of the Carbonates of Barytes and Strontian. With nitric acid. NATIVE carbonate of barytes was totally diffolved by diluted nitric acid, and the folution attended with a difengagement of carbonic acid gas, in the proportion of twenty-two parts in the hundred. The concentrated liquor afforded cryftals, the moft ordinary figure of which was o€tahedral. One hundred grains of carbonate of ftrontian were alfo diffolved in’ nitric acid; but the difengagement of carbonic acid gas was more confiderable than in the preceding ex- periment, the proportion being thirty hundredths. The falt which refults from this com- bination alfo cryftallizes in o€tahedrons. [To be continued.) PHILO- Experiment with a Parachuie. 523 PHILOSOPHICAL NEWS anp ACCOUNTS or BOOKS. On the firft of Brumaire (21 O&. 1797.) Citizen Garnerin made the experiment of the parachute at the Garden de Mouffeaux*. This experiment has not been before attempted at Paris. Blanchard had the notion foon after the difcovery of balloons ; and at feveral dif- ferent towns, particularly Lifle, he let fall from the veflel of his balloon dogs and other ani- mals. Some years ago he ventured to defcend in perfon in an experiment he made at Bale; but either from the bad conftruétion of his parachute, or by falling among trees, he had the misfortune to break one of his legs. Citizen Garnerin was more fortunate, and has given the moft fatisfa€tory proofs of his kill, firmnefs, and intrepidity, which the impatient public had feemed to doubt at the Garden Biron. WNotwithftanding the hafte with which this philofopher was obliged to make his preparations, and feveral accidents which happened to his apparatus, he afcended from the Garden de Mouffeaux at half paft five in the evening. Between the balloon and the veffel was placed the parachute, half opened, and forming a kind of tent over the aérial traveller. The wind, which through the courfe of the day had been violent, was now be- ~ come calm, as if to favour his enterprife, and carried him to the northward, over the plain of Mouffeaux. Full of that intereft, that infurmountable emotion which feizes us on beholding a man quit the earth and advance towards the clouds by an apparatus fo majeftic, the eyes of the {pectators were fixed on the balloon, which rofe with rapidity. When it was at a con- fiderable height, the parachute and veffel were feen at once to feparate from the balloon ; the latter of which burft (celui-ci éclate), emptied itfelf, and floated down with the wind. The parachute unfolded itfelf, while the veffel which ferved as ballaft drew it towards the earth. Its fall was at firft flow and vertical; but foon afterwards it exhibited a kind of balancing or vibration, and a rotation gradually increafing, which might be compared with that of a leaf falling from a tree. Cries expreflive of the general terror and aftonifhment were heard on all fides. The crowd ruthed towards the place of his defcent, where at length the aéronaut landed, and without injury. Emotions of joy and congratulation fucceeded thofe of alarm, and he was brought back in triumph to the Garden of Mouffeaux. Such was the experiment. The narrator then proceeds to give the following detail :—The parachute, which refembles a vaft umbrella, is of cloth, and its diameter, when unfolded, is 25 feet. Citizen Garnerin eftimates the height from which he fell at 300 toifes, but C, Say reckons it no more than one-third of that {pace}. He had 75 pounds of ballaft in his car at the moment of his fall, which he fays he fhould have thrown out, if he had not been apprehenfive of wounding the fpectators below. C. Say thinks he would have done very wrong; becaufe the danger to which he was expofed did not arife from the velocity of his fall, but the vibration of the car, which might have {truck him againft the earth, or againft walls, trees, or other prominences. Now, if he had thrown out his ballaft, the remarker thinks he would have rendered the vibration much more rapid, extenfive, and dangerous, and perhaps even have caufed his parachute to overfet, and the whole to fall in a mafs, The author explains the theory of the parachute by obferving that the refiftance of the air * This account was drawn up by J. B. Say, Editor of La Decade philofophique, literaire, et politique, No. 4. + In the way of rough illuftration, this may be flated at once and a half the height of St. Paul's Cathedral in London. N. 3X2 and 524 Scientific News.—Accounts of Books. and gravitation are two forces which aét at the fame time on the whole fyftem of the machine; that gravitation acts as if the whole mafs were united at its centre of gravity, while the re- fiftance aéts as if the whole of this mafs was united at another centre little diftant from the centre of gravity of the cloth which forms the parachute, and very different from the former. The parachute may be confidered as fufpended in the air by this centre of refiftance. If the centre of gravity be not vertically beneath the centre of refiftance when the para- chute is properly placed, it is evident (fays he) that it will incline to one fide, defcend ob- liquely, ofcillate, and the fmalleft irregularity in its figure will caufe it to turn round its vertical axis. It is alfo important that thefe two centres fhould be at a diftance from each other, fince the ofcillations will more readily take place the nearer they are. If they were coincident, there would be no caufe why the whole apparatus fhould not overfet. C. Say therefore propofes that the car or part of the ballaft fhould be fufpended at a confiderable diflance below the parachute. ACCOUNTS or BOOKS. Recherches expérimentales fur le Principe de la Communication latérale du Mouvement dans les Fluides, appliqué a YExplication de différens Phénoménes hydrauliques. Par le Citoyen J. B. Venturi, Profefleur de Phyfique expérimentale 4 Modéne, Membre de la Societé Italienne, &c. &c. A Paris, chez Houel & Ducros, Rue du Bacq, No. 940— Théophile Barrois, Rue Haute-feuille, No. 22. Ann. VI. 1797.——Or, Experimental Refearches concerning the Principle of the lateral Communication of Motion in Fluids, applied to the Explanation of various Hydraulic Phenomena. By Citizen J. B. Venturi, Profeffor of Experimental Philofophy at Modena, &c. &e. I HAVE been favoured with a copy of this curious and interefting work by the learned Profeffor, which I have read with much pleafure. The commiffion nominated for that pur- pofe by the National Inftitute of France haye given a very correct analyfis, which I fhall _ chiefly follow in my account. Citizen Venturi has introduced an horizontal current of water into a veffel filled with the fame fluid at reft. This ftream entering the veffel with a certain velocity, paffes through a portion of the fluid, and is then received in an inclined channel, the bottom of which gradually rifes, until it paffes over the border or rim of the veffelitfelf. The effect is found to be, not only that the ftream itfelf paffes out of the veffel through the channel, but carries along with it the fluid contained in the veffel; fo that after a fhort time no more of the fluid remains than was originally below the aperture at which the ftream enters. This fact is adopted as a principle or primitive phenomenon by the author, under the denomination of the Jateral communication of motion in fluids, and to this he refers many important hydraulic fats. He does not undertake to give an explanation of this principle, but fhews, P- 37> that the mutual attraétion of the particles of water | is far from being a fufficient caufe to account for it. The firft phenomenon which the author propofes to eae by this eftablithed principle is the emiffion of a fluid through different adjutages applied to the refervoir which contains it. It is known that the vein of fluid which iffues from an orifice or perforation through a thin plate, becomes contracted, fo as to exhibit a feétion equal to about 0,64 of the orifice itfelf, {uppofed to be circular; and that the place of the greateft contraction is ufuaily at the dif- tance Accounts of Books, 525 tance of one femi-diameter of the orifice itfelf. If a {mall adjutage be adapted to the ori fice, having its internal cavity of the fame conoidal form as the fluid itfelf affeéts in that interval, the expenditure is the fame as by the fimple orifice. But if at the extremity of this adjutage a cylindric tube be affixed, of a greater diameter than that of the contraéted vein, or a divergent conical tube, the expence of fluid increafes, and may exceed the double of that which paffes through the aperture in the thin plate, though the adjutage poflefs an horizontal or even afcending direction. By the interpofition of a {mall adjutage, adapted to the form of the contraéted vein,. Citizen Venturi afcertained, in the firft place, that there is an increafe of velocity in the tubes he employed, though the velocity of emiflion itfelf be lefs than:that of the ftream which iffues from an hole ina thin plate. He afterwards proves, by the faét, that the interior velocity and expenditure of fluid, which is increafed through tubes, even in the horizontal or afcending dire¢tion, is owing to the preflure of the atmofphere. If the fmalleft hole be made in the-fide of the tube near the place of contraétion of the vein, the increafed. expenditure does not take place; and when a vertical tube is inferted in fuch a hole, the lower end of which tube is immerfed in water or mercury, it i found that afpira- tion takes place, and the water or mercury rifes; and this afpiration in conical tubes is lefs in proportion, as the place of infertion of the upright tube is more remote from the fection where the greateft contraction would have taken place. And, laftly, the difference be= tween the expenditure of fluid, through an orifice made in a thin plate, and that which is ‘obferved through an additional tube, does not take place in vacuo. The influence of the weight of the atmofphere on the horizontal or afcending flux being thus eftablifhed, the author confiders it as a fecondary caufe, referable to, and explicable by, his principle of the lateral communication of motion in fluids. In conical divergent tubes, for example, the effect of this Jateral communication is, that the central cylindrical jet, hav-- ing for its bafis the feClion of the contracted vein, carries with it the lateral fluid which would have remained ftagnant in the enlarged part of the cone. Hence a vacuum tends to be produced in this enlarged part which furrounds the central cylindric ftream ; the preflure of the atmofphere becomes active to fupply the void, and is exerted on the furface of the re- fervoir, fo as to increafe the velocity of the fluid at the interior extremity of the tube. The author proves, that the velocity or total‘expenditure of fluid through an aper- ture of given dimenfions, may be increafed by a proper adjutage in the proportion of 24, to 10: he applies ‘this refult to the conftruction of the funnels of chimneys. He determines the lofs of emitted fluid, which may be fuftained by finuofity in pipes. He fhews by experiment, that a pipe which is enlarged in any part, affords a much lefs quan- tity of fluid than if it were throughout of a diameter equal to that of its fmallett feétion. This, as he remarks, is acircumftance to which fufhcient attention has not been paid in the conftruGtion of hydraulic machines. It is not enough to avoid elbows and contraétions ; for it fometimes happens, that by an intermediate enlargement the whole of the advantage arifing from other judicious difpofitions of the parts of the machine is loft. ‘There are two caufes of the increafe of expenditure through defcending pipes. The firft is owing to the lateral communication of motion which takes place in defcending pipes, in the fame manner as in thofe which poffefs an horizontal fituation; the fecond arifes from: the acceleration by gravity which takes place in the fluid while it falls through the defcend- ing 526 Accounts of Books. ing tube. This fecond kind of augmentation was known to the ancients, though they pof- fefféd. no good theory nor decilive experiments refpecting it. “The author endeavours to eflablith a theory on the principle of virtual afcenfion combined with the preffure of the at- mofphere. His dedudtions are confirmed by experiment, im which he has fucceeded fo. far as to feparate thé two caufes of augmentation, and afligned to each their refpective de- gree of influence; ; Citizen Venturi then proceeds to different objects of enquiry, to which his principle feemed applicable... He gives the theory of the water-blowing * machine, and he deter- mines by calculation the quantity of air which one of thefe machines can afford i in a given time. He obferves, that the natural falls of water in the mountains always produce a local wind ; and he eyen thinks, that the falling {treams in the internal parts of mountains are in fome inftances the caufe of the winds which iffue from caves. He proves, by the facts, that it is poflible in certain inflances to carry off, without any machinery, the waters from a fpot of ground, though it may be fituated on a lower level than that of the channel which is to receive the water. The whirlpools, or circular eddies of water fo frequent i in rivers, are, Pete to the theory of our author, the effect of motion communicated from the parts of the current which are moft rapid, to thofe lateral parts which are leaft fo. In the application of this principle, he points out the circumftances adapted to produce fuch eddies at the furface or at the bot- tom of rivers. He concludes, that every movement of this kind deftroys a part of the force of the current, and that in a channel through which water conftantly flows, the eight of this fluid will be greater than it would have been if the dimenfions of the channel had been uniformly reduced to the meafure of its fmalleft feAiion. There is another kind of whirling motion fomewhat different in its nature from thefe laft. It is produced in the water of a refervoir, when it is fuffered to flow through an hori- zontal orifice. The author deduces the theory of thefe vortices from the do€trine of cen- tral forces. The form of the hollow-funnel, which in this cafe opens through the fluid of the refervoir, is a curve of the 64th {pecies of the lines of the third order, enumerated by Newton. Theory and experiment both unite here in proving, that it is not only poffible, but that there really exifts in nature a vortex, the concavity of which is convex towards the axis, and of which the revolutions of its different parts follow the ratio of the fquare of the dif- tance from the centre. Daniel Bernoulli was in the wrong, in his Hydrodynamics, to re- proach Newton for having fuppofed a vortex to be moved according to this law. In the laft place, the author confiders that lateral communication of motion which takes place in the air as well as inthe water. This is the-caufe of fuch local and partial * Souffiet d'eau. Yt is alfo called trompe, but we have no appropriate name for this engine in Englifh. The reader may confult Lewis’s Philofophical Commerce of Arts, and Chaptal’s Elements of Chemiftry, for de- feriptions. It confifts of an upright pipe, through which a fhower of water is made to fall. This fhower carries ' down a mafs of air with it, which is received beneath a kind of tub, and conduéted to the furnace by means of a pipe. The moft remarkable natural phenomenon of this kind is the fquall at fea. When a cloud fuddenly falls in the form of rain, it drives down a portion of the atmofphere, which glides rapidly along the furface of the fea, and is capable of fuddenly overfetting veffels, or carrying away their mais. It may eafily be imagined, that feamen are very attentive to look out for this phenomenon, and to guard againft it in time by lowering — fails, &c. N. winds Accounts of Books, 527 winds as fometimes blow contrary to the direction of the general wind. It is by virtue of the fame principle, that the refonant vibration, excired laterally in the extremity of an ore £an-pipe, is communicated to the whole column of air contained in the pipe itfelf. From the fame principle, the author deduces the augmentation of force which found re- ceives in conical divergent tubes, compared with thofe of a cylindrical form. On this occa- fion, he points out the remarkable differences which appear to take place between the refo- nant vibrations of air contained in a tube, and the fonorous pulfations propagated through the open atmofphere. In an Appendix, Citizen Venturi relates different experiments which he has made to de- termine the convergence and velocity of the fluid filaments which prefs forward to iffie out of a refervoir by an orifice through a thin plate. He Proves, by a very clear experi- ment, that the contra€tion of the vein is made at a greater diftance from the orifice: under ftrong than under weak preffures. He explains, why in a right-lined orifice, the fides of the contracted vein correfpond with the angles of the orifice and the angles with the fides. He examines the expenditure through a tube, the extremity of which is thruft into the re- fervoir itfelf, according to the method of Borda in the Memoirs of the Academy of Sciences for the year 1766. t . The Commiffaries of the Inftitute appointed to examine this work of Citizen Venturi, without undertaking to decide refpe€ting all the applications of his principle, give him full credit for the acutenefs and fagacity he has difplayed in this curious experimental courfe. The author himfelf is indeed fufficiently candid to admit that every thing’ of this nature, which is not confirmed by direct experiment, ought to form a fubject of difcuffion and en- “quiry. “ I have not,” fays he, page 9, *‘infifted upon theoretical confiderations, excepting fo: “ far as they combine with the fas, and fo far as it was neceflary to unite thofe facts in a “fingle point of view. The reader may, if he pleafes, even omit the fmall portion of “ theory, and confider my propofitions fimply as the refult of experiment.” There is no doubt but that the whole work will tend to confirm the reputation of its au- thor asa fkilful experimentalift, and enlightened obferver. Confiderations on the Doétrine of Phlogifton and the Decompofition of Water. By Jofeph Prieflley, LL. D. F.R.S. &c: Philadelphia printed, 1796. Obfervations on the Do&rine of Phlogifton and the Compofition of Water. Part II, By Jofeph Prieftley, LL.D. F. R.S. Philadelphia printed, 1797. “Two LeGtures on Combuttion. Supplementary to a Courfe of Le@ures on Chemiftry, read at Naflau Hall, containing an Examination of Dr: Prieftley’s Confiderations on the Doétrine of Phlogifton and the Decompofition of Water. By John Macleati, Profeftér of Mathematics and Natural'Philofophy in’ the College of New Jerfey. Philadelphia printed, 1797. As Thope to give a fuller account in future of Dr. Prieftley’s obfervations in favour of the old chemical fyftem, I fhall for the prefent. content myfelf with announcing the titles of the three laft works, 4 The 528 Account of Bocks.—Corre/pondence. The Medical Repofitory, Vol. I, Nos. I. and If. octavo. The two numbers contain 287 pages; clofely printed. New-York, printed for T. and J. Swords. The authors and editors of this work are Doctors Samuel L. Mitchill, Member of the Legiflative Aflembly of the State of New-York, F.R.S. Edin. Profeffor of Chemiftry in Co- lumbia College, and Dodors Edward Miller, and E. H. Smith, of New-York. The firft Number appeared in July 1797, and the fecond in the month of November laft. It is in- tended to be publifhed in quarterly numbers of at leaft 100 o€tavo pages cach, at the price of half a dollar per number. It confifts of medical effays or communications, a review of new publications, not only fuch as are ftri€ly medical, but alfo thofe which relate to agri- culture and other branches of natural hiftory, philofophy, &c. or may be in any manner related to the objects contemplated in the plan of a medical repofitory 5 and laftly, medi- cal fadls, hints, enquiries, and news. i. It is a well known faét, that the public will not affift in any periodical work until they have received proof, fora certain length of time, of the accuracy, fpirit, and ability, with which the conduétors are able from their own fources, whether original or derivative, to fupport it. A work of the kind before us is peculiarly calculated for the diffufion of know- ledge in a country like America, where; from various circumftances, the written’fources of intelle€tual acquifition are much more limited than in Europe. It is equally calcula- ted to accelerate improvement in the whole of that confiderable part of the globe, wherein the language of England is current. The prefent numbers fhew no want either of ability or induftry on the ee of the authors, and will, it is to be hoped, meet the fuccefs they merit. ——E—— ah MY young correfpondent from Liverpool has fhewn confiderable abilit in his medita- tions and conje¢tures on the many important chemical fats he mentions. When facts can be fo difpofed as by mutual illuftration to prove an entire theory, the individual who makes the arrangement, may, perhaps, do more for the advancement of fcience, than the performer of many folitary experiments: but when this cannot be done, the chief ufe of imperfe& conclufions or conje€tures muft be to point out new and decifive experiments. W.S. may fupport the hope of making fuch experiments, by reflecting that the greateft difcoveries have been made by men who did not poffefs the means of acquiring much ap- paratus. Apothecaries’ phials, Florence flafks, bafons, cups, faucers, a blow-pipe and charcoal, common tobacco-pipes and garden-pots, as fubftitutes for crucibles and a fur- nace, and the ordinary bellows, together with a few chemical materials, would con- ftitute no mean apparatus for philofophical experiment. When he fhall turn his thoughts towards the experimental refearches, to which his obfervations evidently lead, I am confident he will be of opinion, that the publication of his conjectures, in their prefent ftate, would not be defirable. = oe — Philos. Journal. Vol L PLXL. facing pws. : ads | 2 2 ri : DO yA LO HU, Wali; frecring (Srocfars ust ‘ Y ¢ / Lig.* 2. ‘ ‘ C awda. me A TA Wo ecavellegeall, vA Shh . % 4 » ye so Ae . ; wrtatyth ev aR Fak aRE SS me © fab Er 7. thea Thee ‘20> Ng RG TPS. RS - . - - ‘ Philos. Jourrial PLL facir ug Pp.528 . = lima ; ES : : Be M, Pearsons flortalte € lechucal Mere, bine? Fig. 1. Jcale of Inches. Barlow seulp a SSS a errr pe setter re, . A POU OR ON ALOT NATURAL PHILOSOPHY, CHEMISTRY, AND THE ARTS; ARTICLE I. By Citizen Pecxetrer. Read to the Natwnal In/ftitute 30th April, 1796. [Concluded from p. 222.] Habitudes of the Carbonates of Barytes and Strontian. Obfervations on Strontian. ~ With muriatic acid. ih DISSOLVED too grains of native carbonate of barytes in mu- riatic acid, and obtained 22 grains of carbonic acid gas. The folution being evaporated afforded cryftals in the form of fhort flattened prifms, or hexagonal plates, the weight of which was 138 grains. I alfo diffolved in the fame acid 100 grains of carbonate of barytes, obtained by the decompofition of barytic fulphate: the difengagement of carbonic acid gas alfo amounted to 22 grains, and the muriate cryftallized like the preceding, fo that there was not any difference in their appearance *. It * The fuccefs which Dr. Crawford met with in the internal ufe of muriate of barytes, in the treatment of fcrophulous difeafes, begins to be known in France; and feveral phyficians already preferibe this new medicine. As, however, it is very active, and fometimes even dangerous, it cannot be too ftrongly recommended that it be given at firft only in a very fimall dofe, and that the effeéts which it may produce during its adminiftration be accurately obferved. The Society of Health is at prefent engaged in a general work, in which itis intended to determine what advantages medicine may derive from the ufe of muriate of barytes. They have alfo appointed commiffaries to obferve its effeéts in the treatment of horfes; and Cit. Hufard and Biron, who are intrufted with chefe latser experiments, have already given both the muriate and carbonate of barytestohorfes {eized with the forcy [farcin]. Both thefo medicines given to different horfes in the quantity of two drachms a day feem-— ed fora while to have effeéted a perfeét cure: they were even confidercd as cured at the end of a fortnight; Vou. I, —Mancn 1798, as when “ . Se Obfervations on Strontian. It is not the fame with the carbonate of ftrontian : this was totally diffolved by muriatie acid, but the difengagement of carbonic acid gas amounted to thirty hundredths, and the falt obtained from this combination was in long needles or very flender rhomboidal cryftals, terminated by a pyramid with two faces: the prifms are fometimes hexahedral. This falt is alfo more foluble than muriate of barytes. I obtained 176 grains of the muriate from 100 grains of the carbonate. Dr. Crawford’ was one of the firft who obferved the great difference which there was in the form of the cryftals of the muriates of barytes and ftrontian, as well as their different degrees of folubility in water, and thence fufpected that thefe two fubftances could not be of the fame nature. - With fulphuric acid. Native carbonate of barytes reduced to powder is decompofed by fulphuric acid, with difengagement of carbonic acid gas. ‘The refult of this —- is fulphate of barytes, infoluble in water. Carbonate of {trontian is alfo decompofed by fulphuric acid, with aifengagement of car- bonic acid gas; and the compound which is obtained is alfo but little foluble i in water. Dr. Hope has obferved that four ounces of diftilled water only diffolved half a grain of it, and that if muriate of barytes be added to this folution, a precipitation of fulphate of ba- rytes takes place: fulphate of ftrontian is therefore more foluble than that pf barytes. With acetous acid. The acetous acid difengages the carbonic acid from carbonate of barytes. The fame acid alfo decompofes carbonate of ftrontian. The falts which refult from thefe combinations, viz. the acetites of barytes and ftrontian, are obtained in a cryftalline form, and are not deliquefcent. Red Flame of Alcohol, holding in felution Nitrate or Muriate of Strontian or Lime. ‘ AMONGST the charaters by which Mefirs. Hope, Klaproth, and others have diftinguifhed {trontian from barytes, there is one which they agree in confidering as peculiarly diftinétive. Chemifts have obferved that alcohol, in which either nitrate or muriate of barytes is dif- folved, burns with a flame of a white yellow, whilft alcohol holding in’ folution nitrate or muriate of ftrontian burns with a flame of acarmine red. Dr. Hope relates in his memoir that Dr. Ath had fo long fince as 1787 obferved the particular colour which muriate of flrontian gives to the flame of alcohol. ‘The experiments repeated before the pupils of the polytechnic {chool prefented the fame refults ; but as the nitrate and muriate of lime alfo communicate to alcohol the property of burning with a red flame, I thought it right to afcertain whether the nitrate and muriate of ftrontian did not contain lime. For this pur- pofe I tried the following experiments : when the one to which the muriate of barytes had been given died without any apparent circumftance to indi- cate his death: the fecond, that which had taken the artificial carbonate of barytes, alfo died fuddenly fome days afteravards. The two horfes having been opened, all the vifcera were found in a found ftate, and exhibited no indication, either of the effect of the barytic preparations, or of the repercuffion of the diftafe. The experi- ments are continued on other horfes. Sinec this article has been compiled, I have been informed, that a third horfe Which was under a courfe of earbonate of barytes, alfo died fuddenly. It feems, therefore, more and more evident, that the carbonates of barytes, whether native or artificial, may prove mortal when taken internally. P, 2 Expe- Obfervaiions on Sirontian a Experiments to afcertain whether Strontian contains Lime. 1. TO a folution of nitrate of barytes Tadded fluoric acid, perfeétly pure and free from fulphuric acid ; the mixture took place without precipitation. 2. Toa folution of nitrate of ftrontian I added the fame fluoric acid: the mixture alfo took place without precipitation. : 3- To folutions of the nitrates of barytes and flrontian put into feparate veflels I added two or three drops of nitrate of lime, and afterwards fome fluoric acid: this acid then very foon produced a white precipitate, which was fluate of lime. It follows, from thefe comparative experiments, that the nitrate of ftrontian did not con- tain lime; for, if it had contained ever fo little, the fluoric acid would have occafioned a pre- cipitation. This acid has fo ftrong an affinity with lime that it takes it from the fulpl{uric acid, when fulphate of lime is holden in folution in water; fo that when a few drops of fluoric gcid are added to a felenitic water, a precipitation takes place as readily as when the “oxalic acid is ufed. The fluoric acid prefents therefore an excellent means of detecting the prefence of lime. Very pure fluate of ammoniac may alfo be ufed ; for, if this be mixed with the nitrate, muriate, or fulphate of lime, a eeeompentaa takes place by double affinity, and the precipitate is fluate of lime. Nitrate of Strontian ts not precipitated, as Nitrate of Barytes is, by the Pruffiates of Pot-afh or Lime. WE have feen, that the charaéters of ftrontian in which it appears moft fimilar to ‘barytes, exhibit, neverthelefs, differences fufficiently well marked, when they are fubjected to a rigorous examination. ‘The following experiment, which is owing to the obfervations ‘of Dr. Hope, prefents a more ftriking diftin€tion between the two earths. Kk was known that nitrate of barytes is totally precipitated by the pruffiates of pot-ath and lime. ‘Dr. Hope having added pruffiate of pot-ath to a folution of nitrate of ftrontian, perceived only a flight precipitation, occafioned by the iron which accompanies the carbonate of ftron- tian, I had a mind to afcertain this myfelf, and therefore prepared three folutions, viz. r. A folution of native carbonate of barytes in nitric acid: 2. A folution in the fame acid of carbonate of barytes, prepared by the decompofition of barytic fulphate: 3. A folution of carbonate of ftrontian in the fame acid. Thefe three folutions being placed in feparate weffels, I added a fufficient quantity of pruffiate of pot-afh, to decompofe them entirely. There was in effect an abundant precipitate in the nitrates of barytes, and the fupernatant liquors being tried with carbonate of pot-afh gave no fign of further precipitation. The nitrate of ftrontian, on the contrary, gave only a weak blue precipitation, in confequence of the iron which it contained ; and an excefs of pruffiate of pot-ath precipitated nothing more: but the fupernatant liquor, tried with carbonate of pot-ath, afforded a very abundant white precipitate, which was carbonate of ftrontian. Thus it appears manifeft, that pruffiate of pot-afh does not at all decompofe the nitrate of ftrontian, whereas it totally decompofes the nitrate of barytes. ‘This method points out, therefore, a diftinétive charatter between the two earths. I fhall not here examine the na- ture of the precipitate which is obtained from the nitrate of barytes when decompofed by pruffiate of pot-afh, nor whether the decompofition takes place in i of the forma- a2 tion $32 Obfervations on Sirontian, tion of a trifule, or of a mixture of fulphuric acid, which the pruMate of pot-ath may fometimes contain, The comparative experiments which I have ftated having been made with the fame pruMiate of pot-ath, the nitrate of ftrontian ought to have been’ decompofed, as well as that of barytes, if thefe earths had been of the fame nature. Conftituent Parts of the Native Carbonates of Strontian and Barytes. TO detail at large the different experiments which I haye made to determine the contti- tuent parts of the native carbonates of ftrontian and barytes, would be too prolix: I fhall therefore only fay, that it was by folution in muriatic acid that I determined the quantity of carbonic acid gas, and by calcination that of the earth. The mean refult which I ob- tained was, In 1¢o grains of native carbonate of ba-; In 100 grains of carbonate of ftrontian, rytes, or witherite, PRISE i * Barytes, = Kinar wrg 62 Strontian, Se re - 62 Carbonic acid, - 3 22 Carbonic acid, Bp - 30 Water, = - - b 16 Water © eA Tw Bite ie ' 10 > ainridey a attic od thew - - ' ‘ , fs fac! Sarai sit 4 Kyigty aaa Conclufion. ; _ [HAVE not been able to carry my refearches further refpecting ftrontian, not haying any more.to fubmit to new experiments: as foon as I can procure fome, I fhall continue them, as I perceive that it will be advantageous to eftablith the difference between it and barytes by more numerous and more ftriking characters. The refults of my examination, and that of Mefirs. Hope and Klaproth, are : iat’ 4g ift, That the carbonate of ftrontian is neither hie ot nor emetic, as oth the, mative _and_artificial carbonates of barytes are; ar _ adly, That the carbonate of ftrontian is fpecifically lighter than that of. barytes 5 Tee! ‘3dly, That it more eafily parts with it’s carbonic acid, and contains. alfo a alates Propor- tion of it than carbonate of barytes does ; 4thly, That calcined ftrontian is foluble in cold and hot water, but more e abundantly in the latter, fo as to afford cryftals by cooling;—a property, indeed, which it poffefles i in ‘common with barytes ; sthly, That the muriate and other falts of ftrontian are more foluble than the homo- logous barytic falts ; and the nitrate and muriate communicate to alcohol the property of burning with a red flame, whereas the fame barytic falts tinge the flame of their alcoholic folution with a yellowifh blue ; éthly, That ftrontian does not contain lime 5 : qthly and laftly, That the nitrate of ftrontian is not decompofed ‘ pruffiate of pot-afh, which decompofes the nitrate of barytes. All thefe chara&ters already eftablifh a fufficiently diftinguifhable difference between ftron- tian and barytes, and a ftill greater between it and all other known earths, fo that it may be confidered as a peculiar earth. 4 CON- OBfervations on Strontian, 533 CONTINUATION, IN the memoir which I read to the Inftitute the 3oth of April laft, on the earth Known by the name of ftrontian, I remarked, that this earth was, when calcined, very foluble in boiling water, and that a portion became feparated in a cryftalline form by cooling. I alfo remarked, that barytes acquired by calcination the property of becoming foluble in boiling water, and alfo affording cryftals by cooling. It is in this ftate of cryftallization that ftron- tian and barytes 1 muft be found pure; and if they are of the fame nature, as fome chemifts conceive, they ought to give fimilar refults when fubmitted to comparative experiments. Tt has been thought that the properties which this earth exhibits in its combinations with the acids might be attributed to the prefence of carbonate of lime in the carbonate of ftron- tian ; but calcined ftrontian diffolved in water cannot be fufpeéted to contain lime, and it is therefore i in this {tate that I have thought proper to procure fome, in order to examine it comparatively with barytes, which I have alfo taken the pains to prepare in like manner in ‘cryftals, and perfeétly deprived of carbonic acid. I fhall here relate to the Inftitute the i ; which I have made on this fubjec. . I firft put into a fmall capfule fixteen grains of pure cryftallized barytes, with thirty- yer grains, [demi-gros] of pure nitric acid of 124°. The combination took place with dif- ‘engagement of caloric, and the cryftals of barytes without being diffolved foon prefented opaque cryftals, which were nitrate of barytes. I added 144 grains [deux gros] of dif- tilled water, and the’ whole was diffolved. ; (2 _ Sixteen grains of cryftals of ftrontian were treated with thirty-fix grains of the fame “Seid The combination took place with difengagement of caloric, but! the cryflals were ‘diffolved, and. ‘did not become opaque as in the preceding experiment. I added 144. grains, of water, in order to have a folution fimilar in {trength to the former. 3: A portion: of the’ folution, No. 1, or that of nitrate of barytes prepared with pure barytes, being pur into a glafs, ‘Tadded to it a pretty confiderable quantity of pruffiate of pot-ath. A precipitation took place, and bin: liquor was not oi ipetoaw precipitated by the addition of carbonate of potath. ' ‘The other portion of oe nitrate being evaporated, afforded cryftals of barytic nitrate in ottahedrons. 4. A portion of the folution, No. 2, or of the nitrate of pure {trontian, tried in like man- “ner with pruffiate of pot- -afh, afforded a flight precipitation ; but, although I added} an ex- cefs of the prufliate, the “bts Si ret {till yieldeda pretty abundant precipitate with carbonate of pot-ath. © The other portion of the folution of nitrate of ftrontian being evaporated, afforded ogta- “hedral’ cryftals, which were more foluble than thofe of the barytic nitrate. 5. Fifty-four grains of barytes, pure and in cryftals, being treated with 144 grains [deux gros] ‘of weak nitric acid, the folution took place with) heat, but without effervefcence. I added 144 grains of diftilled water, and placed, the folution to evaporate in a fand-bath fightly heated ; and when a portion of the water was evaporated, there were formed cryf- tals in hexagonal plates fimilar to thofe of muriate of barytes. Their weight was thirty- two grains. Twelve grains of this muriate, triturated in a glafs mortar with half an ounce of alcohol, were 534 Obfervations on Strontian, were entirely diffolved. I put the whole into a matrafs, and endeavoured to favour the folution by means of heat; a portion of the falt remained, however, undiffolved at the bottom of the matrafs. | Having fet the folution on fire, the alcohol burned with a yellowifh flame. 6. Fifty-four grains of cryftals of flrontian being treated comparatively with the fame muriatic.acid, the folution alfo took place with heat. “he liquor being evaporated in an equak degree with that of the muriate of barytes (which, although upon the fire, had already cryf- tallized) {till remained fluid ; but, on being taken off the fire, it cryftallized in a mafs, and in needles like muriate of frontian. This falt is therefore more foluble in water than the mu- riate of berytes. The weight of the muriate of ftrontian obtained in this experiment was thirty-eight grains. . This muriate is alfo more foluble in alcohol ; for, having triturated twelve grains in a glafs mortar with feventy-two grains of alcohol, they were entirely diffolyed,. 1 added, how- ever, afufficient quantity of alcohol to make the whole half an ounce, asin the Preceding experiment ; and having then fet it on fire, it burned with a flame of a beaytiful red. tas; 7. A faturated [aqueous] folution of pure barytes affords by the addition of a few drops of malic acid a white precipitate, which is malate of barytes; but the fame acid does not produce any precipitation in a faturated folution of ftrontian: it follows, therefore, that malate of ftrontian is more foluble than malate of barytes. » Wi het Thefe experiments continue, therefore, to eftablith a difference between pure barytes and pure ftrontian. , TILeMe Carbonate of ftrontian has hitherto been found only in one place ; Strontian in Argyle- fhire: but M. Meyer, apothecary at Stettin, has lately announced that this earth is found in combination with fulphuric acid in the fulphate of barytes at Freyberg in Saxony. Jn c¢onfequence of this obfervation I analyfed a piece of barytic fulphate from Saxony, but the earth which I obtained from it was only barytes, and not ftrontian. I prefume that the ful- phate which I affayed was different from that of which M. Meyer {peaks 3 but I have, at alt events, reafon to know that ftrontian exifts in other places as well as Argylethire. _ Citizen Guyot, who travelled into Scotland with the Citizen Deleffere, fent_me fome years ince fevera! fpecimens of minerals which he had himfelf procured on the fpot, among{t which there is one which is labelled inthe handwriting of Citizen Guyot “ Barytes from Leade pills” in Scotland. I have examined this fpecimen, and find that it is carbonate of ftron- tian. Its colour is a greenith white, and it feems formed by the union of a number of prifms, which gives it a ftriated appearance. Its fpecific gravity is 3.6195. This carbonate, treated with muriatic acid, yields 314 per cent. of carbonic acid gas, and affords a muriate which cryftallizes in needles, and which, when diffolyed in alcohol, communicates to it the property of burning with ared flame: in fhort, this muriateappears to me perfectly fimilar to muriate of ftrontian. Ihave alfo treated the {tone from Leadhills with the other acids, and the produéts which I have obtained demonftrate that the bafe of this carbonate differs in no refpeét from ftrontian: here, therefore, we have this earth as well as at Strontian, and very probably the refearches of mineralogifts will difcover it in many other places, Il. Abra Objervations on Strontian. 535 Tl. Abjivad of Two Memoirs on a New Method of obtaining Barytes pure, and on the Properties of this Earth compared with thofe of Strontian. By Citizens Fourcror and VAUQUELIN. Read to the National Inftitutes 30h April and 21ff September 1796*. "Tus difficulty of obtaining barytes pure, and the almoft total impofhibility of feparating this earth from the carbonic acid by calcination of its carbonate, are already fufficiently ‘known. In a courfe of Experiments undertaken jointly by Citizens Fourcroy and Vauquelin, to determine the characters and. diftinétive properties of the falts and com- pounds formed by barytes, one of the points which they were moft defirous of attaining, was of courfe to obtain this earth in a real ftate of purity. Citizen Vauquelin having at length difcovered a means of effe€ting this purpofe by the decompofition of nitrate of ba- rytes by the action of fire, it became more eafy to thofe chemifts to examine fuch pro- perties of this earth as had hitherto been unknown to them. The two memoirs of which we are here about to give an abftract, fhow the moft remarkable properties which charac= terize both this earth and ftrontian. 1. Nitrate of barytes in o¢tahedral cryftals, being expofed to the aétion of fire ina por- celain retort, melts, fwells, and gives out much oxygenous and azotic gis, with fearcely any nitrous vapour ; and the retort being fuffered to cool when no more elaftic fluid is dif- engaged, there is found on breaking it a grey, folid, but fomewhat porous, mafs of a harfh- tafte, and more cauftic than quick-lime, which is pure barytes. ' 2. Expofed to the blow-pipe on a piece of charcoal, this earth fufes, bubbles up, and runs - into globules which quickly penetrate into the charcoal. 3. In the air it efflorefces, cracks, bur{ts, {wells up, heats and whitens, and, becoming thus rapidly flaked, it abforbs 0.22 ofits weight of water and carbonje acid. 4. It abforbs water with extreme avidity, melts with hifling, heats confiderably, folidifies the water, and cryftallizes and hardens with it in fuch a manner as to become a very tena- cious cement, capable of adhering very ftrongly to glafs. A little more water changes it into a very bulky white powder. If it be entirely covered with water, it diffolves in it with a violent hiffing, and then cryftallizes in tranfparent needles, which adhere together, and form compages like the particles of beaten plafter. 5- Cold water diffolvesa twenty-fifth part of its weight ; boiling water more than half: the latter by cooling depofits very beautiful tranfparent prifms, which efflorefce and become pulverulent when expofed to the air. 6. A {olution of barytes has its furface more readily incrufted with a pellicle by expofure to the air, and depofits amore abundant precipitate by carbonic acid than lime-water. _ 4. The oxalic, citric, phofphoric, and phofphorous acids precipitate this folution, and the precipitates are re-diflolved by the addition of an excefs of the acids by which they are formed. 8, This folution decompofes thofe of foap, and of the nitrates of mercury, lead, and * Tranflated from Annales de Chimie, XX1, p. 276, by J. F-——y, filver, §36 Offervations on Strontian. filver, precipitating the firft black, the fecond white, and the laft of a fawn-colour. An excels of the barytic folution renders the oxides of Jead and filver foluble. 9. Barytes thus prepared is foluble in alcohol. It is dreadfully poifonous, and kills ani- mals. Its moft remarkable and moft charaéteriftic properties are its extreme cryftallizabi- lity, which diftinguifhes- it from/all the a hitherto known in chemiftry, — its great folubjlity in water. The difcovery by Meffrs Hope and Klaproth of thefe two latter properties in ftrontian induced us however to think for a while, with Citizens Pelletier and Coquebert, that barytes was fo fimilar to it as that they could not but be confidered as very nearly allied, and per- haps even one and the fame earth; but having received fome fragments of ftrontianite, of which we had not before been enabled to inveltigate the properties ourfelves, we were eager to examine this new earth comparatively with barytes ; and the yefult of this’ exami- nation, as related in the fecond memoir, which we are now abftracting, fhewed us that, notwithftanding fome very ftrong analogies, thefe two earthy fubftances are really different, as Citizen Pelletier has concluded from his own refearches relative to this fubject. The following are the principal facts fated in this fecond memoir. Native carbonate of ftrontian has a fhade of light green, which that of barytes has not; it requires a little more muriatic acid for its folution, and contains more carbonic acid. Mu- riate of ftrontian cryftallizes by cooling, whilft that of barytes cryftallizes by evaporation : the former in hexagonal prifms, the latter in inclined plates. — The folution of muriate of ftrontian thickens into a jelly by evaporation, whilft that of muriate of barytes dries in eryf- talline plates : the former, which is yery foluble in alcohol, makes it burn with a flame of a beautiful purple; the latter, which is almoft infoluble in this liquid, gives ita yellow flame. ‘The greateft and mpft remarkable difference which exifts between ftrontian and barytes is, that ftrontian has lefs affinity with acids than barytes, and even than the fixed alkalies; a that a folution of barytes precipitates muriate of ftrontian in white flocks. — Nitrate of ftrontian differs from that of barytes ; ; iftly,, in giving more nitrous atu when decompofed by fire, in confequence of its retaining the nitric acid lefs ftrongly than barytes ; and, 2dly, in being three times as foluble in water. Strontian obtained from its nitrate by the adtion of fire is lefs harfh than barytes 3 it does not fufe in like manner by the blow-pipe, but glitters with a phofphoric flame ; itis almott ten times lefs foluble in water 5 and it feems to be lefs powerful in its attraétions than lime, which it does not feparate from acids, When precipitated by the oxalic acid, it is not re-diffolved by an excefs of this acid, as barytes is ; but the fulphate of ftrontian is on the elke refoluble by an excefs of fulphuric acid, which that of barytes is not. © The aqueous folution of flrontian is not precipitated. by the ‘gallic acid, whereas that’ of barytes affords with this acid a greenifh precipitate, © The authors of thefe memoirs ¢onclude from the Experiments (the refults GE which are here ftated) that ftrontian exhibits more properties which are'different from thofe of barytes than of fuch as are analogous to them ; and that, flriking as are the latter, it muft never- thelefs beconcluded, fromthe whole of the phanomena, that thefe earths are really two different fubltances ; a conclufion which is more particularly evident in refpect of their dif+ ferent degrees of affinity, and of ftrontian not being a poifon, whereas barytes is a very aétive and violent one. Several Strontian. Salts of Platina. $37 Several of the properties which they have defcribed had been before obferved by Meflis. Klaproth, Hope, and Pelletier ; but feveral alfo are of their own difcovery. We have not here fpoken of fuch of the refults afforded by the two earths in their combinations, as were perfectly fimilar to each other; it having been our principal obje& to point out thofe fpecific charaéters by which they are to be diftinguifhed. It is clear that we may reafonably entertain a hope, that more extenfive experiments fhall one day point out ufes both of barytes and ftrontian, as well as of their combinations, of great importance in refpect of the arts, when they fhall have been found more abundantly in na- ture, and when the progrels of fcience fhall have perfe€ted the means of obtaining them in a ftate of purity. The extreme folidity which barytes afflumes when flaked, may lead us to prefume that it may be of ufe for making very hard and durable cements, or perhaps even mordants for the application of different matters on flone, glafs, pottery and other fub- flances of a like nature. III. . Extrait of a Letter from Count Mussin PuscuKxin, Vice-Prefident of the Department of Mines at Peterfburg. On the Salts, Precipitates, and Amalgam of Platina ; on Cobalt ; on Antimonial Soap ; and on the Decompofition of Soap by the Acid Extracts of Colouring Matters*. I. On the Salts and Precipitates of Platina. Tue brick-coloured falt, which is obtained by pouring muriate of ammoniac into a fo- lution of platina, is totally foluble in water, and depofits, when difiolved in boiling water, a black matter, which M. Fourcroy believes to be iron; but, in my opinion, it feems rather to be plumbago, though I have not yet made the requifite experiments to afcertain this fact. A fpecimen of this fubftance accompanies this letter. In order that the whole of the falt may diffolve, it is neceflary to boil it for a long time with water ; and when it is perceived that no more of the falt is taken up, the water muft be decanted, and frefh water poured into the veflel. An ounce of the falt required upon the whole between eight and nine pounds of water poured on and decanted at five different , times. By this means the whole of the falt was not only diflolved, but its colour imme- diately became a beautiful orange ; and by thefe cryftallizations, by evaporation on the water-bath and new folutions, after which the fluid was left to a very flow evaporation, the orange-colour of the cryftals became converted into a moft brilliant topaz-colour, and by new ebullitions was found no longer to depofit any black matter. I haye not yet fucceeded in obtaining larger cryftals than thofe which Werner calls verry /mal/ ; but, by the afliftance of a good Englith microfcope, all thofe which the topaz-coloured falt afforded were ob- ferved to be perfectly tranfparent, and with fcarcely any exception affected the form either of an oétahedral pyramid, or that of a polyhedron compofed of fix perfe€l hexagons united together by eight ifofceles triangles. ‘There were fome lefs regular cry{tals, which partook of the nature of both thefe figures. * Annales de Chimie, XXIJV. 205. Vou. 1.—Maren, 1798. 32 The 538 The alkalis precipitated (though with difficulty) from the aqueous folutions a fmall’ quantity of yellow powder, refembling Naples-yellow. I fuppofe, however, that this pre- cipitate was compofed of cryftals, though none could be difcerned with the magnifier : and it did not appear to be foluble in water; for the nitrous acid, by remaining upon it for forty-eight hours, did not appear to have affe@ted it in the leaft.. The light yellow pre- cipitate which is obtained by vegetable alkali, after fal-ammoniac has thrown down the whole of the brick-coloured precipitate, was feparated by the filter, and fubmitted without edulcoration to the aétion of nitrous acid in the proportion of nearly half an ounce of the acid to one dram of the precipitate, in conical veflels, fuch, for example, as a wine-glafs, in which the precipitate occupied the fmalleft-poflible {pace, and the acid covered it a finger’s depth, and prefented a confiderable furface to the air. In three or four days the acid takes. up more or lefs, according to the temperature, and affumes the confiftence of a jelly, at firft yellow, but afterwards of a chryfolite green more or lefs confiftent, but always in a certain degree moift. Before the blow-pipe this jelly becomes converted into a black fubftance, probably the imperfeé oxide of platina. This experiment appeared furprifing to me at firlt 5 but I recolle€ted that Margraff, by detonating faltpetre upon platina, and then wafhing and filtering, had likewife obtained a jelly which may have been of the fame nature as mine. I mutt obferve that I fatisfied myfelf in the moft convincing manner, that the acid and alkali I made ufe of were abfolutely pure, and that the platina alone, that is to fay in the metallic ftate, did not convert the nitrous acid into a jelly. Urine, whether frefh or putrid, precipitates platina in the form of. a fuper-compound” falt, at the fame time that a grey yellow precipitate is formed, which is neither faline nor foluble in water. Part of this precipitate is formed a few moments after the urine is poured’ into the folution of platina: the falt is formed afterwards. In‘order to obtain this falt, it is neceflary that the folution of platina fhould be very concentrated, and carry with it an abundant portion of the firft precipitate. Ihave not yet attempted to diffolve this falt in boiling water, but I think it would exhibit a yery beautiful topaz-yellow ; for fome of the cryftals, when obferved in the microfcope, were femi-tranfparent, and had not the red co-. lour of the falt precipitated by the muriate of ammoniac. With refpeét to the grey-yellow precipitate, I fuppofe it to be phofphate of iron contaminated with fome foreign fubftance, and perhaps mixed with a fmall quantity of the precipitate of platina. , When urine is poured into a folution of the red falt in water, a beautiful lemon-yellow precipitate is formed, and the grey matter afterwards falls down flowly. “This may per- haps afford a new method of feparating iron from platina, if this grey precipitate fhould in faét prove to be the phofphate of iron. ; . Salts, Precipitates and Amalgam of Platina: IL. On the Amalgam of Platina. ; REFLECTING on the facility with which the fuper-compound falts of platina are re~. duced in the fire, I thought that an amalgam of platina might perhaps be obtained by tritu- rating thefe falts with mercury. To afcertain this, I took a dram of the orange-coloured . ° falt of platina, and triturated it with an equal weight of mercury in a mortar of chalcedony. 7 : da Singular Phenomena of the Amalgam of Platina. 339° Ina few minutes the falt loft its colour, hecoming at firlt brown, and afterwards greenith- brown ; the matter was reduced to a very fine powder. Another dram of mercury was then) added and the trituration continued, when the powder became grey; a third dram of mercury began to form an amalgam, and when the quantity amounted to fix drams the amalgam was perfeét. The whole operation fcarcely employed twenty minutes. Ladded mercury to the quantity of nine times the weight of the falt, notwithftanding which the amalgam was very tenacious; a fact which is indeed furprifing, when it is confidered that the falt contains no more than about 40 parts of platina in the hundred. In my Experi- ment therefore 24 grains of platina were fufficient to give confiftence to 540 grains of mer- cury. This amalgam was eafily fpread out under the peftle ; it perfedtly well received the impreflions of the moft delicate feals 3 its grain was very clofe and brilliant, and in no refpect inferiot to that of the beft amalgam of tin. Though the fight of a perfea: amalgam of platina made in a few minutes, the produc- tion of which had coft Lewis feveral weeks, and Sickingen feveral days, gave me pleafure, I had not lefs fatisfa€tion in obferving the fingular phenomenon I thall proceed to defcribe : Being defirous of clearing my amalgam of its faline parts by wafhing, I triturated it in water in a glafs mortar, and had {carcely given a few ftrokes of the pettle before I obferved the furface of the amalgam to be covered with a black powder, mixed with fome yellow particles. In lefs than ten minutes the whole of the amalgam difappeared, inftead of which I had this black powder. The yellow matter, which confifted of undecompofed falt of platina, having likewife difappeared by trituration ; the black powder was feen, upon de- canting the water, in extremely brilliant maffes (parcelles), which probably were platina. The mercury had therefore paffed with the greateft facility to the ftate of black oxide, nearly approaching the metallic ftate. A portion of running mercury was found beneath, in the quantity of about two drams. Having taken a portion of the amalgam in the palm ‘of my hand, and rubbed it with my finger, the fame decompofition took place in a few in- ftants, and left a black powder interfperfed with brilliant particles. On the fuppofition that this oxide would eafily pafs to the ftate of cinnabar in the humid way, I poured the fulphate of ammoniac (Beguin’s volatile liver of fulphur) upon it, and in lefs than 24 hours the powder became of a dull red, intermixed with metallic particles, which were evidently platina. I afcertained afterwards by fome experiments, that various metallic fubftances, and all the animal matters which I tried, decompofe this amalgam by fimple conta&t. For thefe reafons it is abfolutely neceffary to ufe a glafs or filiceous peflle and mortar in the compo-~ fition of the amalgam. In what manner are we to explain the fpeedy reduction of the platina without oxidation of the mercury during the formation of the amalgam, as well as the much more fpeedy oxi- dation of the mercury when brought into contaét with water, or metallic or animal mat- ters? This appears to me to be a very difficult queftion, of which I expect the folution ‘from more enlightened chemifts. For the {mall quantity of oxygene in the falt of platina is furely infufficient to deprive fo large a portion of mercury of its metallic ftate ; befides which, in the dry trituration, fuch as that which is made in the hollow of the hand, the acid is not diffolved, Is it likely that there may be a decompofition of atmofpheric air, and 3Z2 a dif- 540 Platina. —Cobalt.—Decompofitions of Soap. a difengagement of caloric from the vital air*? This muft be determined by new experi- ments, which I have good reafon to expec from the illuftrious philofopher to whom I have the honour to addrefs myfelf. Ifublimed the oxided powder of mercury in a {mall glafs re- tort. It afforded metallic mercury, and the muriate of mercury. The fub{tance which remained at the bottom of the retort was friable, light, and of a colour inclining to a deep grey yellow. The {mall quantity of the powder of amalgam which I fubjected to experiment was not fufficient to admit of an examination of this refidue. I fhall not fail to repeat the experiment more at large, and acquaint you with the refults. In the mean time I requeft that the contents of this letter may ferve as a fupplement to the hiftory of platina, and beg that you will give ita place i in your Annals under that title. Ill. Concerning Cobalt. WITH regard to the experiments Lhave made on cobalt, I muft fufpend my informa- tion until I fhall have been able to procure the regulus of cobalt in a quantity fomewhat confiderable, for the purpofe of repeating my experiments in the large way. Thofe which { have already made have afforded feveral interefting phenomena, particularly with regard to the effeéts of cold as a chemical agent.. At prefent, I fhall only remark, that the oxides of cobalt, which have hitherto been fuppofed, after the methods of the beft chemifts, to be abfolutely pure, are neverthelefs contaminated with much foreign matters. IV. On the Antimonial Soap. PROFESSOR RUDOLPH has made an antimonial foap, after my method of preparing the mercurial foap, He finds it very active. ‘ V. On the Decompofition of Soaps by the Acid Extraéts of Colouring Matters. 1 HAVE obferved, in decompofing foaps, that the acid extra€ts of colouring matter, fuch, for example, as that of Brazil wood by the diluted acetous acid, perfe&tly decompofe foaps, whether made with oil or wax. ‘The oleo-colorant or cero-colorant compounds thus ob- tained are abfolutely infoluble in water, and afford extremely brilliant colours, which may perhaps be advantageoufly ufedin painting, Aint aphe! encauttic }. It would be likewife interefting * The author thinks, and with reafon, that the oxygene united to the platina is far from being fufficient to oxide fo large a quantity of mercury ; but he has not perhaps fufficiently attended to the facility with which the lealt oxidable metals pafs to the ftate of oxide, when they are rendered fluid, and their parts difengaged by their affinity with mercury. This has long been obferved with regard to the amalgam of gold, which foon becomes eovered with a purple oxide by mere expofure to the air. Citizen Guyton, in a memoir on certain properties of platina, read tothe National Inftitute the firft Meffidor, in the year 4, has exhibited a new proof of this prin- ciple in the oxidation of an amalgam Of platina, obtained by the direét combination of the two metals, by means of an clevated temperature, and by the fimple effeét of the affinity which was announced by the rank which platina occupies in the fcale of adhefions to mercury. Note of the Editors of the Annales. 4 Citizen Chauffier has already communicated, in his leffons to the Polytechnic School, feveral experiments of this kind, whieb have perfectly fucceeded. The foap of copper afforded a yery brilliant green, which it is prefume Demonftrations of the Fundamental Property of the Lever enumerated. 541 interefting to afcertain precifely whether the colouring matter has not more analogy with earths than has hitherto been thought, and whether it would not be advantageous, particu- larly in red dies, to employ the foaps of tin and of cochineal. t IV. Obfervations on the Fundamental Property of the Lever ; with a Proof of the Principle affiuined by Archimedes-in his Demonftration. . By the Rev, 8. VINCE *, AM. ERS. Tue want of a demonftration of the property of the lever upon clear and felf-evident principles has juftly been confidered as a great defideratum (defect) in the fcienceof mechanics, as the moft important parts of that branch of natural philofophy are founded upon it. Archimedes was, I believe, the firft who attempted it. He fuppofes, that if two equal bo- dies be placed upon a lever, their effect to turn it about any point is the fame as if they were placed in the middle point between them. This propofition is by no means felf-evi- dent, and therefore the inveftigation which is founded upon it has been rejected as imper- feet. Huygens obferves, that fome mathematicians, not fatisfied with the principle here taken for granted, have, by altering the form of the demonftration, endeayoured to render its defects lefs fenfible, but without fuccefs. He then attempts a demonftration of his own, in which he takes for granted, that if the fame weight be removed to a greater diftance from the fulcrum, the effect to turn about the lever will be greater: this is a prin- ciple by no means to be admitted, when we are fuppofed to be totally ignorant of the effects of weights upon a lever at different diftances from the fulcrum. Moreover, if it were felf-evident, his demonftration only holds when the lengths of the arms are commen: furable. Sir I. Newton has given a demonftration,, in which it is {uppofed, that if 4 given, weight aét in any direétion, and any radii be drawn from the fulcrum to the line of di- rection, the effect to turn the lever will be the fame, on whichever of the radii it acts, But fome of the moft eminent mathematicians fince his time have objected to- this prin- ciple, as being far from felf-evidént ; and, in confequence thereof, have attempted.to de- monftrate the propofition upon more clear and fatisfaCtory principles. The demonftration by M‘Laurin, as far as it goes, is certainly very fatisfaftory ; but as he collects the truth of the propofition only from induétion, and has not extended it to the cafe where the arms are incommenturable, his demontftration is imperfe&t. The demontftration given by Dr, Hamilton, in his Effays, depends upon this propofition, that when a body is at reft, and acted upon by three forces, they will be as the three fides. of a triangle parallel to the di- redlions of the forces. Now this is true when the three forces act at any point of a body ; whereas, confidering the lever as the body, the three forces act at different: points, and prefumed was known to the ancient mafters. On this fubjeét, confult the 3d cahier of the Journal of the Polytechnic School, p. 426 and 427. © Phil. Tranf, m.pec.xery, 33+ 2 therefore $42 Demenfirations of the Fundamental Property of the Lever, therefore the principle, as applied by the author, is certainly not applicable. If in this des monftration we fuppofe a plane body, in which; the three forces act, inftcad of fimply a lever, then the three forces being a€lually dire&ted tothe fame point of the body, the body ' would be at reft. But in reafoning from this to the. cafe of the lever, the fame difficulties would arife as in the proof of Sir I. Newton. But admitting that all other objections could be removed, the demonftration fails when any two of the forces are parallel. Another demonttration is founded upon this principle, that if two non-elaftic bodies meet with equal quantities of motion, they will, after impact, continue at teft; and hence it is concluded, that if a lever which is in équilibrio be put in motion, the motions of the twe bodies muft be equal; and therefore the preflures.of thefe bodies upon the lever at reft to put it in motion, muft be as their motions. Now in the firft place, this is comparing the effects of preffure and motion, the relation of the meafures of which, or whether they ad- mit of any relation, we are totally unacquaintéd ‘with. Moreover, they aét under very different.circumftances 5 for in the former cafe the bodies a€ted immediately on each other, and in the latter.they a& by means of a lever, the properties of which we are fuppofed to be ignorant.of. When forces aét on a body confidered as a ‘point, or direétly againft the fame point of any. body, we only eftimate the effeét of thefe forces to move the body out © of its place, and no rotatory motion is either generated, or any caufes to produce it confi- dered in the inveftigation. When we therefore apply the fame propofition to inveftigate the effeé& of forces to generate 2 rotatory motion, we manifeftly apply it to a cafe which is not contained in it, nor to which there is a fingle principle in the propofition applicable. The demonttration given by Mr. Landen, in his Memoirs, is founded upon felf-evident principles ; nor do I fee any objections to his reafoning upon them. But as his inveftiga- tion confifts of feveral cafes, and is befides very long and tedious, fomething more fimple ds ftill much to be ree: for, proper to be introduced in an elementary treatife of me- chanics, fo as not to perplex the young ftudent, either by the length of the demonftration or want of evidence in its principles. What I here propofe to offer will, I hope, render the whole bufinefs not only very fimple, but alfo perfectly fatisfactory. . The demonftration given by Archimedes would be very fatisfactory and elegant, pro- vided the principle on which it is founded could be clearly proved, viz. that two equal powers at the extremities, or their fum at the middfe, of a lever, would have equal effects to move about any point. Now, that the effects will be the fame, fo far as refpects any progreffive motion being communicated to the lever when at liberty to move freely, is fufficiently clear; but there is no evidence whatever that the effeéts will be the fame to give the lever a rotatory motion about any point, becaufe a very different motion is there produced, and we are fuppofed to know nothing about the efficacy of a force at different diftances from the fulcrum to produce fuch a motion. Befides, the two motions are not only different, but the /ame forces are known to produce diffrent effets in the two cafes; fo that in the former cafe the two equal powers, as the extremities of the arms, produce equal effects in generating a progr efive motion; but in the latter cafe, they do not produce equal effects in generating a rotatory motion. We cannot, therefore, reafon from one to the other. The principle, however, may be thus proved : y Let x Fundamental Property of the Lever.— Acid of Tins 543° Let AC, Pl. XXII. Fig. 1. be two equal bodies on a {traight lever, A P moveable about P. Bifet A CinB: poder P Ato Q and take B Q=B P, and fuppofe the end Q to be fuf- tained by-a prop. Then as A and Care fimilarly fituated in refpeét to each end of the lever, that is, AP=C Q, and AQ=CP, the prop and fulcrum muft. bear equal parts of the whole weight ; and therefore the prop at Q will be prefled with a weight equalto A. Now’ take away the weights A andC, and put a weight at B equal to their fum; and then the- weight at B being equally diftant from Q and P, the prop and fulcrum mutt fuftain equal parts of the whole weight, and therefore the prop will now alfo fuftain a weight equal to A. Hence, if the prop Q be taken away, the moving force to turn the lever about P in both cafes muft evidently be the fame ; therefore the effects of A and C upon the lever to turn it about any point, are the fame as when they are both placed in the middle point between them. And the fame is manifeftly true if A and C be placed without the fulcrum and: prop. Iftherefore A C be a cylindrical lever of uniform denfity, its effect to turn itfel£ about any point will be the fame as if the whole were collected into the middle point Bs: which follows from what has been already proved, by conceiving the whole cylinder to be divided into an infinite number of laminz perpendicular to its axis of equal thicknefles. The principle therefore aflumed by Archimedes is thus eftablifhed upon the moft.felf- evident principles, that is, that equal bodies at equal diftances muft produce equal effedts ; which is manifeft from this confideration, that when all the circumftances in the caufe are equal, the effects muft be equal. Thus the whole demonftration of Archimedes is rendered perfectly complete, and at the fame time it is very fhort and fimple. The other part of the demonftration we fhall here infert for the ufe of thofe who may not be acquainted with it. Let KY, Fig. 2. be a cylinder, which bifec&t in A, on which point: it- would manifeftly reft. Take, any. point Z, and bifect ZX in B, and Z Yin C; then, from what has been proved, the effects of the two parts ZX, ZY, to turn the lever about A, are the fame as if the weight of each part were colle€ted into B and C refpectively, which weights are manifeftly as Z X, ZY, and which therefore conceive to be placed at B and C. Now A B=A X—X B=iX Y—i XZ, = ¥, Z; and A C=A WE Nees =i KY—2 ZY=1 XZ; confequently AB: AC::iY¥Z aXe, 233: Y2Z: XZ :: the weight at C: the weight at B. The property of the ftraight lever, being thus eftablifhed, every thing relative to the bent lever immediately follows. V. Obfervations on the Acid of Tin, and the Analy/is of its Ores. Read at the Sitting of the Clafe of Mathematical and Philofophical Sciences of the National Inftitute of France, the Sitf) of Meffidor, in.the Year 5. By Citizen Gurzon *. T has long been obferved that the nitric acid calcines tin inftead of diffolying it, and the phlogiftic hypothefis was incapable of explaining this phenomenon. It remained among # Inferted in the XXIVth volume of the Annales de Chimie, . the 544 Acid of Tin, and Analyfs of its Ores. the number of facts for which the moft fruitful imagination could not afford a probable fo- lution, This difficulty has vanifhed fince it has been difcovered that the metals are capa- ble of being converted into acids by a fufficient quantity of oxygene. Tin is one of the metals which muft have moft effeflually contributed to fix the attention of chemifts upon this combination. In this manner it is {een that the precipitation of gold by tin in the form of a purple oxide is fimply, as I have announced in the Elements of Chemiftry of the Aca- demy of Dijon, the refult of the ation of the ftannic acid upon gold. This oxigenation of tin is much more evidently feen in the operation which I have defcribed in the firft vo- lume of the Chemical Digtionary of the Encyclopedia, p. 632 ; an operation which feems well calculated to exhibit at the fame inftant every fundamental principle of the pneumatic chemiftry. For when the diluted nitric acid and tin are treated fimply in the retort, the refult is oxide of tin and nitrate of ammoniac, the latter of which is formed by the azote or bafis of the acid, and the hydrogene of the water, without the appearance of nitrous gas at any period of the operation. No further difficulty remained therefore with refpeét to the oxidation of tin by the nitric. acid, asit is evidently effected by the decompofition of the acid and the affinity of the tin for oxygene. But no account has yet been given of the ftate in which this metal exifts in its ores, particularly in the cryftals of tin (zinn-graupen, zinnftein, of the Germans), nor of the caufes which oppole their folution in acids. This queftion prefented itfelf to my confideration on reading the publication of Mr. Klaproth on the ores of tin in the fecond volume of Analyfes with which he has enriched chemiftry and mineralogy. He begins by comparing the produéts of the fame ore ‘treated with alkaline reducing fluxes, and with charcoal alone. The difference convinced him, that in the firft procefs the alkali retains a confiderable portion of the metal in the ftate of oxide. He afterwards en- deavoured to complete the analyfis in the humid way. For this purpofe he followed Berg- man’s procefs, which confifts in digefting the powdered ore in concentrated fulphuric acid ; adding muriatic acid after the cooling, and precipitating the folution by foda. By this treat- ment 131 parts of precipitate ought to be afforded for every 100 parts of metal contained inthe ore. Mr. Klaproth, in fa&t, obtained a folution of about 0,19 of that rather fearce tin ore which the Englith call wood-tin ; but he could not fucceed in charging the muri- atic acid with any perceptible quantity of tin, by fubje€ting the other more common va- rieties to the fame treatment. Refleéting on the nature of the obftacle which might probably oppofe the action of the muriatic acid on a fubftance which he eftimated to contain 0,99 of oxide of tin, he ima- gined that it could be nothing but an excefs of oxygene. To remove this excefs, he firft attempted to treat the ore in the retort with a mixture of fulphur. “Moft of the fulphur wasfublimed, and the refidue, lightly agglutinated, had ftill’ the fame grey whitifh appearance as after the pulverization, excepting that fome brilliant gold-coloured fpecks were feen; namely, fulphate of tin, or aurum-mufivum. The mi- neral, however, was not more foluble in the muriatic acid than before. After many other trials equally unfuccefsful, the celebrated chemift of Berlin had re- courfe to that fubftance which in his hands has become fo powerful an inftrument of ana- lyfis. Analy fis of Tin Ores, 543 iyfis. He treated his ores with fix parts of potafh in a crucible of filver, and the feccets was beyond his expectations. _ By the firft operation, 0,91 were rendered foluble in w iter, precipitated and afterwards taken up by the muriatic acid. The muriate of tin being then de- compofed by carbonate of foda, a pure oxide was obrained, which was eafily re. diffolved in the Jame acid, and precipitated by zine. This precipitate, fufed in a crucible with tal- low, afforded a button of the fame weight as had been obtained from the fime kind of ore in the dry way. — ; ___ By this means he was authorifed to conclude as follows, with regard to the brown ore af Schlackenwald; ; as LS ToS ae aie Gi: . =i ola ba O55 Salexe. i= = - 0,95 In 100 parts i Oxygene = “ 23,75 \ 100 I have treated in the fame manner a cryflal of tin ore of this kind, alfo from Schiact- enwald ; not becaufe I had any doubt. of the fuccefs announced by a chemift who has fo Jeng been in_pofleffion of well-earned confidence; but this fuccefs feemed to be a con- firmation of the conjecture on which Mr. Klaproth bad founded his experiments, and { fuppofed that there was good reafon to donbt whether the complete faturation or {uper{a- turation of tin by oxygene were the true caufe of its infolubility in the muriatic acid. Fer I could not at any period of the operation difcern either the fubftance which might feize this excefs of oxygene, or any trace of the phenomena which muft have accompanied its difengagement. nat Gn order to obferve the circumftances with more facility, I operated in a-fmall crucible of platina over a reverberatory lamp of Argand (fur une lampe d’Argand 4 réchaut*). Fifty-five centigrammes of the brown cryfhals of tin, reduced into fine powder, were well mixed with 4x times the quantity of potafh purified by alcohol, and dried. The mixture “was moiftened with a few drops of water, then evaporated to drynefs, and afterwards Jeated to the commencement of fufion... After the firtt operation, hot water was poured. on the mafs, and took up more than half the mineral. Muriatic acid firft precipitated it, and afterwards diflolved it with the greateft facility. The precipitate or metallic oxide, reproduced by carbonate of potafh, was in fa completely foluble by the fame acid, as Mr, Klaproth had affirmed. 2 But aftcr having thus witneffed the facts, my firft doubt concerning the direc folubility of this ore was rather ftrengthened than removed. For it cannot be affirmed that the exeefs of oxygene was diflipated during the fufion with potafh, becaufe the metal could not form a foluble combination with the alkali, but in confequence of its oxidation to the la degree, or, to {peak more correcily, its acidification ; fo that the lixivium of the filtered refidue is a true ftannate, or perhaps a {tannite +, of tin (potath). 2 * The author intends foon to give a defcription of thiy lamps ¢ Mr, Hatchet in his paper on the molybdate of lead and the molybdic acid, inferted in the Pinlofophicat Trantaétions of London for 1796, compares precifely the aétion of the nitric acid on molybdena, to {uperosy~ genate ity tothat which produces the fame effeét on tin. Tt may converfdy be inferred that tin ty acidified like molytdena, G, Vor. L—Marcnt 1798. aA 546 Analyfis of Tin Ore—Fair ry Rings. In the mean time, as we are forced to admit that all the oxygene of the: ore is found 3 in the alkaline folution, the more effe€tual aétion of the acid upon the metal cannot be fup- pofed to arife from the lofs of a portion of this principle, becaufe it continues {till in the fame ftate of faturation ; neither is there any fign of oxygenated muriatic acid gas; and it would likewife be difficult to conceive, why in this circumftance there fhould rather be a difengagement of the gas than when the acid is digefted on the ore, as is obferved i in the oxides of manganefe and of lead. To eftablith this point of theory on a more decifive nuatat I diffolved fix grammes of tin in the nitric acid, and evaporated feveral times to drynefs the new acid which was fucceflively poured on. I fuppofe it cannot be doubted but that the tin in this ftate had combined with as much oxygene as it is capable of fixing.. Neverthelefs, the mafs of white -oxide, wafhed until the water which came off cauled no further change in vegetable colours, was very foluble in muriatic acid. What therefore is the caufe of the infolubility of the ore, which confifts alfo of tin and oxygene with {carce one hundredth part of foreign matter? This caufe is to be found on- ly in the ftate of aggregation of the latter. This affertion cannot be thought ftrange, ex- cept on account of the little. regard which has hitherto. beeh paid to its energy. If com- binations be the refult of affinity or éleétive ' attragtion, i is ndt this attraction itfelfa power which may be rendered ineffe€tual by the fum of the forces which a& in the contrary ‘di- reGtion? Thefe truths furely cannot appear repulfive ‘to Mr. ‘Klaproth, who has ren- déred them fo evident, by fhewing that the ruby, the fapphire ‘and the adamantine fpar, of which the elements are in their own nature fo eafily foluble, do not refift the ordinary methods of analyfis but in confequence of the aggregation of their integral parts. VI. Terris Bi , On Fairy Rings. afi Tue appearance in the grals, commonly. called Fairy Rings, is well known. It ‘con- fiits either of a ring of grafs of. more luxuriant vegetation than the reft, or ‘a kind of cir- cular path in which the vegetation is more defeétive than elfewhere. “It appears to’ be pretty well afcertained, that the latter fate precedes the former. Two caufes are affigned © for this phenomenon : the one, which cannot be controverted, is the running of a fungus ; the other, witich has been confidered as an effufion of theory, i is grounded on a fuppofition that the explofion of lightning may produce effects of the fame kind on the ground "as Dr. Prieftley’s battery was found to produce on the polithed furface of a plate of metal, that is to fay, a feries of concentric rings. Some obfervations, whith I find'in my com- mon-place book, appear to fhew that this laft effeét uray; in certain circumstances, take place. . 4 On Tuefday the roth of June,. 1781, a very powerful thunder-ftorm. pafled over the weftern extremity of London. I was then‘at Batterfeay'and made no other remark on the phenomena than that the explofions, which were very marked and ‘diftin&, were in many inftances forked a 'the lower end, but never at the top; whence it follows, that the clouds were in the pofitiv © fate for the moft part. On the following Sunday, namely the 24th, I happened Egfedts of Lightning ona Grove of Trees. 547. I happened to bein Kenfington Gardens, in every part of which extenfive piece of ground the lightning had left fome marks of its agency, chiefly by difcoloration of the grafs in zigzag ftreaks, fome of which were fifty or fixty yards in length. _ Inflances of this fuper- ficial courfe of the lightning along the ground before it enters the earth are fufficiently frequent. Bui the circumftance which attracted my attention the moft was feen in a final! grove of trees at the angular point of one of the walks. Plate XXII. figure 3. exhibits a fketch of part of.the gardens, in which the angular point is denoted by the letter A. Figure 4. reprefents the pofition of the trees. The numbers exprefs the diftances be- tween the trees in feet. Clofe to the ftem of the tree A was a hole in the ground four inches long and two wide, proceeding to the fouthward ; and at two feet further to the fouth was another fimilar hole. Between thefe two holes the ground was torn away. This appearance is reprefented in figure 3, in which the letter A reprefents the trunk of the tree. The grafs was very much feorched to the diflance of about three feet in ev ery dire€tion from the trunk, and in this burned {pace there were feveral other fmaller holes. ‘ Clofe to the trunk of B, on the fouth fide, there was a hole in the ground. Near the tree C there was alfo a hole in the ground, and it was furrounded with a faint ; ring « of burnt grafs at a little diftance ; but as the grafs was grown again, it feemed pro- bable, that the ring was occafioned by fome earlier ftroke than that on Tuefday. ‘The tree D was furrounded by a ring of 6 feet radius, and 18 inches broad. Within | the ring the grafs was frefh ; but on the furface of the ring the grafs and the ground were” much Or “To the 1 yy of the tree upon the ring itfelf were two holes, in which * the ground had the appearance of afhes. The tree E had half a faint ring to the weift- ward. t The tree F was furrounded by a faint ring of twoy ards radius. Within the ring the - grafs was unhurt. To the weftward, at about three! feet diftance from the inner ring, Was part of another fimilar ring, of much the fame appearance ; the verdure being unhurt in. the interval between the rings. I imagined the leaves of the trees were alittle curled, but could obferve no blafted boughs; a circumftance which, together with the other facts, appears to indicate that thefe appear- ances were produced by the recent ftorm of the roth. —oEaaoaEaEaEEaEaEaEaeEeEeEeEeEeEeEeEeEeEeEeEeEoEoUoUIUIUIUIUIoIUIUIUIUIUIUIyIyayayeyyyy———y—————>——————— VI. Experimental Refearches to afcertain the Nature of the Prece/s by which the Eye ai of itelf to yt id diftin® Pifon. (Concluded from page. 4.79. ] si In: the eel there is a tranfparent horny convex covering at fome diftance before the eyc, to, defend it from external accidents. This covering to an eye fitted to fee in air, would en- tirely take off the effects arifing from change of figure in the cornea; but in water, wheré’ no fuch change could be attended with advantage, fuch a covering is employed as an fis ternal defence. . 37 ’ , 442 — hy 548 Peculicvities of Vi ifion in Fifbes, Se. In the eyes of fifhes the ciliary proceffes are entirely wanting. The cryftalline lens is {pherical and imbedded in the vitreous humours, which is inclofed in cells of a ftronger tek- ture than in other animals. The iris does not admit of motion; this 33 taken notice of by Haller; and the reafor probably is, that the light in water is never too ftrong for the eye to bear. There is a mule fituated between the retina and the {clerotic coat, which is, as Mr. Home thinks, common to all fifh. "Chis mufele is particularly defcribed by Mr. Haller; and its ufe is Rated to be that of bringing the retina nearer the cryftalline lens for the purpofe of fee- ing objeéls at a greater diftance.. Mr. Hunters called it the choroide mufele, and has pre- ferved feveral preparations of it. This mufcle has a tendinous centre round the optic.nerve, at which part it is attached to the felerotic coat; the mufcular fibres are fhort, and go off from the central tendon in all. dire€tions ; the fhape of the mufcle is nearly that of a horfe-fhoe ; anteriorly it is attached. to the choroide coats, and by means of that to the felerotic. Its a(tion tends evidently ta bring the retina forwards; and in general the optic nerve in fifhes makes a bend where it cn- ters the eye, to admit of this motion without the nerve being ftretched. J In thofe fithes that have the fclerotic coat completely covered with bone, the whole adjuft- ment to great diftances muft be produced by the aétion of the choroide mufcle ; but in rhe others, which are by far the greater number, this effeét will be much affifted - the action of the ftrait mufcles pulling the eye-ball againft the focket, and comprelling the pofterior part, which, asit is the only membraneous part in many fifhes, would appear to be formed fo for that purpofe. In fithes, the eye in its natural bly ftate appears to be adjufted to near objeds, requiring fome change to alapt it to fee diftant ones ; in this refpect differing entirely from the bird, the quadruped, and the human. The preceding’obfervations, on the ftruéture of the eye, indicate two methods oF adjufting the eye ; one for feeing in air, the other for feeing in water ; and that the cryftalline lens, as the moft confpicuous part, appears to have engrofled the whole attention of formes enquirers, who in general do not feem to have paid fufficient attention to the elongation of the axis and change of curvature in the cornea. That the axis of vifion is really lengthened, and the lens moved forward, appears highly probable from the whole of the faéts; and fince the elonga- tion of the eye, the change of pofition of the cryftalline, or the alteration of curvature in the. cornea, have feverally appeared to be the caufe of the requifite adjuftment, the combination of all thrve muft undoubtedly be fufficient to effect the purpofe. In the Philofophical Tranfactions for 1797, page 1, Mr. Home explains certain morbid affections of the ftrait mufcles and cornea of the eye, and confiders their treatment. He {tates the ufes of the mufcles'to be ; firft, that ‘af moving the eyc-balls in different direQtions ; fecondly, that of caufing the two eyes to correfpond’; and thirdly, that of producing ad- juftment by their Jateral preflure. Imperfeétion in any one of thefe different ations muft be confidered as a difeafe. ‘T hree different cafes occur in pradtice ; namely, indiftina vifiony double vifion, and fquinting, . Indiftiné vifion is explained to confit of an inability in the mufcles to fupport that. de- gree of tenfion which is requifite to adjuft the eye to near objects. In this morbid affection of the firaight mufcles they may be capable of performing all the intermediate re kt as ’ ' ‘py On the Imperfetions of Fiffon. 549 as ufual, but not the extreme degrees without confiderable pain. As thefe fymptoms have not been accounted for before in this way, the author adduces fome curious inftances of* fimilar affeCtions of other mufcles, and concludes that bad effeéts mutt neceffarily arife from every thing which irritates or weakens the parts themfelves, or the generat habit ; and that fuch means ought to be adopted as may foothe the parts in their fenfations, and. quiet and ftrengthen their actions, fince in that way only the mufcular fibres can poflibly Tecover their tone. On the fubject of double vifion the pp a remarks, that many opinions have been ad vanced to’ accoufit for the fingle appearance of objects contemplated by both eyes. The opinion of Dr. Reid of Glafgow, that vifion is fingle when the impreffions are made on correfpondent parts of the retina in the two eyes, and double when this is not the cafe, appears to him to be ftrongly confirmed by the facts. This want of correfpondence may. be produced by fome change in the refraéting media of one of the eyes, or elfe by a want. of Tuhilar actions ia the mufcles of both eyes refpeftively. The former takes place after the cryftalline lens of one or both eyes has been extracted, and the convex Iens made ufe- of to produce the requifite focal adjuftment is not duly placed. ‘The latter is more parti- cularly the object of medical treatment. Mr. Home advifes repofe, that is to fay, that the difordered eye fhould be covered for a time. For, as he remarks, the firft obje& of atten= tion, with regard to ftrained or over-fatigued mufcles, muft be to put them into an ealy Hate, and confine them from motion; and this practice is no lefs ne dae to the mufcles of the eye than thofe of other parts. As double vifion is produced by a moderate derangement of the optic axes, {quinting is effected bya much greater derangement. In the cafe of fquinting, the author proves that the object is not feen by both eyes; but that one eye, more or lefs perfe&, is dire€ted to the object, while the other, which in fuch cafes is imperfect, is drawn afide by habit, in order that its operation may not difturb the perception received by the other eye. The greater ftrength, fhortnefs and ftraitnefs of the adductor mufcle caufes the deviation to be made towards the nofe, ‘{hefe doftrines are illuftrated by appofite cafes. Squinting takes place in three different circumftances ; that is to fay, where one eye has only an indiftinét vifion ; where both eyes are capable of feeing objects, but the one is lefs perfeét than the other ; and where ‘the mufcles of one eye have, from pra€tice, as in the cafe of frequently. looking through telefcopes, acquired a power of moving it independently of the other. When f{quinting arifes from abfolute imperfeétion in the eyes there is no cure. Where it arifes from weaknefs ‘only inthe fight of one eye, it may in fome inftances be got the better.of by confining the perfon to the ufe of one eye by covering the other; in this way the mufcles, from conflant ufe, become perfe@ in the habit of direéting the organ, and acquire ftrength and power of adjaftment. The time required muft depend upon the weaknefs of the fight, and length of time during which the mufcles-haye. been left to themfelyes, The Author fhews, that he cornea is not, like the cuticle, devoid of life ; though, like tendons and ligaments, it is neither fupplied with red blood nor pofleffes fenfibility, but is made up of membraneous ligaments, which are continuations of the tunica conjunétiva and the tendons of the four ftrait muféles. When wounded, it commonly unites, like other 2 living 55° Treatment of Difeafes of the Cornea. living parts, by the.firft intention, and) in fome. cafes with inflammation exceeding the limits of adhefion ;,and.the whale; internal. cayity of the eye proceeds. tora ftate of fuppuran tion. . ‘Lhefe ftages,of inflammation are.only met with in parts, poffeffed. of life. Ae‘ zelic ‘From thg opinion of the, cornea being void of life,, the opacities which are found, m8 take place;on it have been fuppofed. to arife,.from. inanimate matter laid over its furface. And under that, notion. acrid, and inritating applications, have been ufed. to, remoye, it, fach, as powdered glafs, powdered fugar, &c. Such APNEA en jPeine of fervigey have. ,con» -firmed.the opinion. +5 yee: sede .etremer » ots + 0 oqr- Home: confiders the, cornea Soop ligamentous party nat as fagb.: Bet in. its vital powers... This arifes from fuch_ parts having. no veilels carrying. red blood... When. they in- flame, which is a ftate of increafed adtion, they therefore require rN different mode. of treat- ment from the other parts of the body, whofe vital powers are ftrong in confequence of being largely fupplied with red. blood. , ! The truly healthy. inflammation requires an increafed adtion i in the parts: affedled ; And if this, either from weaknefs or indolen¢e, i is, not ‘kept UP, ‘the inflammation does, not £9. rapidly through its ftages, but remains ina ftate between refolution and fuppuration. . In ligamentous ftruatures the actions, mutt therefore be roufed and fupported, when, under j in- flammation, to promote, refolution, and to prevent. the. parts from falling into an indolent difeafed fate. This is howev cr, attended, w with difficulty, a and they. t9 too often ecome ¢ on derably thickened by,a a _decompolition. ° coagulating Apes during d the -adhebiv e : ftate of ine ammation, whe 3 in ‘the cornea renders: te opake. he th ick nin Of the parts remains after. the anflaomaten is gone, and, can Sis be removed a ie 2 which is is a a Hfh, : as related in fo apocryphal book which, bears se name ; 3 , with’ other circumftances of like practice among the Arabians; and alfo. certain facts and obfervations, which occurred in his own ‘practice, are related as proofs of the ‘advantage < of ftimulating applica- tions | to ‘the cornea, In fome old cafes of Opacity, ‘he found gall the beft application. ‘He ufed it pure, and Ifo diluted. ‘The gall of. _quadrupeds, in, thefe ‘trials gave: more pain than the gall of fith. ‘The painful fenfation w was very fevere ae an ‘hour or two, and then went of its application. “The obje& of his obfervations having been to explain. the principle upon which thofe effets depend, this knowledge may, as he obferves, regulate the praétice fuitable-to be adopted i in fuch gales. It will fhew the i impropriety. ‘of “uling fuch | medicines ‘while’ the inflammatory ation is increafing, and will point out their adoption the moment the inflammation appears to be at a ftand, inftead of poftponing thefe remedies till an in- dolent unhedlthy ftate takes place, which too prea terminates i in opacities not to be after- wards removed by any application. : marie VII. Expe- - tof ? ) f On the Properties of Light, 55u Vil. Experiments and Obfervations on the Infloxion, Reflexion, and Calours of Light: By Henrr Broucuam, Fun. Efy.* iG has.always appeared wonderful to me, fince nature feems to delight in thofe clofe analogies which enable her to preferve fimplicity, and even uniformity in variety, that there fhould be no difpofitions in the parts of light with refpe@ to inflexion and reflexion ana- logous or fimilar to their different refrangibility. In order to afcertain the exiltence: of fuch properties; I began a courfe of Experiments and Obfervations, a fhort account of which forms the fubftance of this paper. For the fake of perfpicuity I fhall begin wich the janalytical branch of the fubject, comprehending my obferyations under two’ parts : flexion, orjthe bending of the-rays in their paflage by bodies, and reflexion. And I thall _ conclude by applying the principles there eftablifhed to. the explanation of phenomena, in «the way. of fynthefis. «, As in every experimental enquiry much depends on. the attention paid to the minuteft: .circumftances, in juftice to myfelf I ought to mention that each experiment was fet down- as particularly as poflible, immediately after it was made; that they were all repeated »eyery. favourable day for nearly a year, and before various perfons ; and as anything like a wPreconceived opinion with refpeé to matter of theory that is in. difpute, will, it is more than probable, influence us in the manner of drawing our conclufions, and even in. the manner of,recording the experiments that lead to thefe, I haye endeavoured, as much as pollible, to keep in, view the faying of the Brahmin, “that he who obftinately adheres to- »“ any,fet of opinions, may bring himfelf at laft to believe that the freth /andal-wood is-a ‘fame, of fre 8.0. Nagy dali ra S0T | UasbOhise® Baz 4 Parr. Of Flexion. ; _. TN order to fix our ideas on a fubje& which has never been treated of with mathematical precifion, we thall {uppofe, for the prefent, that all the parts of Tight are equally ated : upon in, their paflage by bodies, and deduce feveral of the moft important propofitions awhich,occur, without.mentioning the demonftrations. Hens od P Def. i, lf pray pafles within /ajcertain diftance of any body, it is bent inwards ; this we fhall call inflexion. 2. If it paffes at a ftill greater diftance,, it is turned away ; this may be \termed deflexion. 3. The angle of inflexion is that which the infleed ray makes with. - the, line drawn parallel to the edge of the inflecting body; and the angle of incidence is that- made by the ray before inflexion, at the point where it meets the parallel, And fo of the vanglejof deflexion. Tae ab ape Peet cae eee ; ly Propofition I. The force by which bodies inflec& and, deflect)the rays, acts in lines per- | pendicular, totheir furfaceses. oo iiw oo) sich dialy toni yd. bad 7 {., Prop. IL, The fines.of inflexion and deflexion are.cach of them to: the fine of incidence _ina given ratio—(and what this Tatio,is, we thall afterwards fhew). Prop Ml, The bending force is to the) propelling force of light as the fine of the dif ference ; between the angles of inflexion, (or deflexion, and incidence to the cofine of the angle of inflexion or deflexion). # Philofophical Tranfaétions, m.Dccxevn ¥. + Afiatic Refearches, vol! i, p. 224. 7 Prop. a 552 Propefitions concerning the Ajpedigns gf Light. Prop. 1V. The rays of light may be made to revolve round a centre in a fpiral orbit. Prop.V. lf the infle€ting furface be of confiderable extent, and a plane, then the curve cefcribed may be found by help of the Prop. XLA. Book 1, of Principia ; provided only the yiroportion of the force to the diftance be given. ‘Thus, if the bending force be inverfely as the diftance, the curve cannot be found ; for, in order to obtain i its equation, a curvilinear “area muft be fquared, which, in this‘cafe, is a conic hyperbola ; the relation, however, be- tween its ordinates and abfciffe may be obtained in fluxions, thas: y ¥ + by = att, Ifthe forte (which is moft probable) be inverfely as the fquare of the diftance, the ctitve to be fquared is the cubic hyperbola ; fpecies LXV. genustll. of Newton's Enumeration; and this being quadrable, the curve defcribed by the light will ‘We the parabola pon pe Hie . pura; Species LXIX. of Newton. If the force be inv erfely as the cube of the diftance, the curve is a circular arch, and that of deflexion {s a conichyperbola*. If the inflecting body be @ globe or cylinder, and the force be inverfely as the fquare of the diftance from’ the furfice ; then, by’ Prop. LXXI. Book I. of Principia, the attraction to the centre is inverfely as the fquare of the diftatice from. that centre; and therefore, ‘by Prop. Xf. and XTEf. of the fame Book, the ray moves in an ellipfe by the infleéting, and in an hyperbola by the deflecting force ; each having one focus in the centre of the body. ‘he truth of thefethings mathematicians will eafily determine. Pop. VI. If a ray fall on a {pecular furface, it will be bent before incidence into a curve having two points of contrary flexure, and then will be bent back the fie way into ~» equal and fimilar curve, as in Fig: 1. Pi. XXII. ~ Corollary to thefe propofitions. If a pencil of rays fall converging on an tetpore pody, the fhadow will be lefsthan the body by twice the fine of inflexion. And if a pencil fall diverging on the body, the fhadow will be greater than the body by twice the fine of inflexion; but lefs than it fhoyld be, if the rays had paffed without bend. ing, by twice the fine of the difference between the angles of inflection and incidence. The ‘fine or angle of incidence is greater than the fine or angle of inflexion, when the incident rays make an acute angle with the body ; but, when they make an obtufe or right angle, then the fine or angle of inflexion is lefs than that of incidence. The fine of incidence is greater than tlmt of deflexion, if the angle made by the incident ray with the’ body is ob- tufe ; but lefs, if that angle be acute or right. If a globe or circle be held in a beam of light, the rays may be made to converge to a focus. Hitherto it has been fuppofed that the parts of which light confifts ave all the fame dif- pofition to be aéted upon by bodies which infleét and deflect them; but we fhall now fee that this is by no means the cafe. Obfervation I. Into my darkened chamber I let a beam of the fun’s light through a hole in a metal plate (fixed in the window-fhut) of ;4, of an inch diameter ; and all other light being abforbed by black cloth hung before the window and in the room, at the holé I placed a prifm of glafs, whofe refraéting angle was 45 degrees, and which was covered all over with black paper, except a fmall part on each fide, which was free from impurities, and through which the light was refraéted, fo as to form a diftin& and tolerably homoge- neous peeavih on a chart at fix feet from the window. In the rays, at two fect from the \ * Principia, Lib, i. Prop, 8. prifm, On the Inflexion, Reflexion, and Colours of Light. 553 prifm, I placed a black unpolifhed pin (whofe diameter was everywhere one tenth of an inch) parallel to the chart and ina vertical pofition. Its fhadow was formed in the fpec- trum on the chart, and had aconfiderable penumbra, efpecially in the brighteft red, for it was by no means of the fame thicknefs in all its parts; that inviolet was broadeft and moft diftin@ ; that in the red narroweft and moft confufed; and that in the intermediate co- lours was of an intermediate thicknefs and degree of diftinétnefs. - It was not bounded by ftraight but by curvilinear fides, convex towards the axis, to which they approached as to an afymptote, and that neareft in the leaft refrangible rays, as is reprefented in Fig. 2, where AB is the axis, [IK L MN A, and HGF EDA the two outlines. Nor could this be owing, to any irregularity in the pin, for the fame thing happened in all forts of bodies that were ufed ; and alfo if the prifm was moved on its axis, fo that the colours might afcend and defcend on thefe bodies ; {till, wherever the red fell, it made the leaft, and the violet the greateft fhadow. 1 Ob/. Il. In the place of the pin I fixed a fcreen, having in it a large hole, on which was a brafs plate pierced with a fmall hole 4d of an inch in diameter. Then caufing an afliftant to meve the prifm flowly on its axis, I obferved the round image made by the different rays pafling through the hole to the chart ; that made by the red was greateft, by the violet leaft, and by the intermediate rays, of an intermediate fize. Alfo, when at the back of the hole, [held a fharp blade of a knife, fo as to produce the fringes mentioned by Grimaldo and Newton; thofe fringes in the red were broadeft and moft moved inwards towards- the fhadow, and moft dilated when the knife was moved over the hole, and the hole itfelf on the chart was more dilated during the motion when illuminated by the red, than when illuminated by any other of the rays, and leaft of all when illuminated by the violet. Now in Obfervation I. the angle of incidence of the red rays was equal to that of the violet and all the reft, and yet the angle of inflexion was greateft and leaft in the violet; and in- deed the difference between the two was greater than appesrs at firft from the experiment ; for that part of the fhadow which was formed by the violet, fell at a greater diftance from the point of incidence than did that part which was formed by the red, from the diyer- gency of the different rays upwards by the refra€tion, as appears in Fig. 3, where D E is the window, IG the beam propagated through the hole F, refraéted by the prifm K IH and pointing on the chart O P qs; the fpectrum v r, being feparated in Lr, the red rays incident on the pin C D at C; and My, the violet incident at D; the fhadow of DC being formed inv r, fo that v being farther from D, than r is from C, therefore (by the propofitions formerly laid down) the fhadow in v fhould be confiderably lefs than in r, if the rays were equally infleled. Laftly, in Obf. II. the angle of the red’s incidence was nearly equal to that of the violet’s, by the motion of the prifm, and the confequent motion of the colours; only that if there was any difference it was on the fide of the violet: and yet the violet was leaft infleed, and the red moft inflected ; and fo of the fecond inflexion by the knife-blade : wherefore I conclude that the rays of the fun’s light differ in degree of inflexibility, and that thofe which are leaft refrangible are moft inflexible. ‘Of. MI. My room being darkened as before, anda conical beam propagated through the {mall hole in the window fhut ; at this hole I placed a hollow prifm made of broken plates of mirror, and of fuch an angle that, when filled with diftilled water, it caft a fpec- Vos. Il.—Marca 1798. 4B trum, 554: On the Inflewion, Reflex ions and Colours of Light, trum onan horizontal table, and was:there received on @ chart ifeven feet from the windaws; I then placed on the fame table, and in the rays; between the chart and the; prifiny.atythtee: inches from’ the chart, two fharp, knife-blades, with eveh edges, and fixedsto.2 board with: wax, {6 as to-make an angle! withone another); moving theninearer:and nearer, till di fayw -the fringes appear in’ the red:light on the chart; and then» inthe orange and other colours, fucceflively.’ then. withdrew one, and the fringes became faint andmarrow, andinotvalli ~ within the fhadow of the remaining knife, butiatvits edge, and even imthey light of \the. fpedttum. Laftly, when I flowly. approached theiother, | they: moved into the thadow,‘and: became broadet“and»farther feparatéd one [from avothen;: there’ being the like ftingeslint both fhadows. This; repeated in all the rays, andyplainly daw, that atithe:approach of the! knife the fringés Became broader and farther removed from one Jat gia and — the! light, ‘in the red than inthe violet, or any of the other rays. 19 te girs 01/.1V. In repeating the foregoing Experiment, | obferved' a very curious s phenome=. noni When the angle of the ‘knife-blades was fo: held'in any of the-rays,>.as to miakeithe hyperbolic fringes defcribed by Newton*, ‘and thefe being always ofithe colour iti) which» they were held 5 moving the angle ailittle, fois to make the fringes out oftthe lightthat’ went to the top of any one divifion of the fpe€trum, and: alfo’out of that which went near: the bottom of the next, the fringes were made of two colours’; 3 one partiwas ofthe’ highett colour, and the other of the loweft ; but both were on the proud of the highett. Thus, | if held on the confine of” the gréen and blue, the upper’ half of each fringe was bhi¢, the under green, but both parts in the blue divifion of the fpe@trams and ‘trying the fame. in’ all the rays, it was evident that the red was moved farther into the: orarige, and the orange’i into the yellow, than the blue was into the indigo, or the indigo ‘into the violet. Now in: Obf. Wi. the fringes were formed by the inflexion of one knife, and were moved'into its thadow, and feparated and dilated by the deflexion of the other ; and this moft in the red, and Jeaft in the violet. Likewife in Obf. IV. the fringes of one colour were defieéted into the region of the next, and this moft in the red, and ‘leat in the violet ;) although in*both obfervations the violet, from the pofition of'the chart, was fartheft from the angle, “and confequeiitly, | had the rays been equally deflected, the violet fhould have been fartheft moved, and moft dilated bythe deflexion : but, feeing that, at equal angles of incidence in the third, and at lefs in the fourth Obfervation, the red was moft, andthe violet tig ene iti is “Sines that the moft inflexible rays are alfo moft deflexible. Having thus found that the parts of light differ iit’ ‘flexibility, T withéd next’ to learn two things ; in what proportion the angle of inflexion is to that’ of deflexion at equal incidences 5 and fecondly, what proportion the different’ flexibilities of the different rays bear to one another. But the nature of the coloured fringes mutt firft be underftood ; fo that T defer this enquiry till after I have made ufe of the prineiples™ how Taid' down WE ite explination of natural phenomena, and preceed in tHe micah’ time to’ rit af Parr H, or Of aigeiissy: ae THAT bodies refleé& light by a repulfive power extending to fome difandt fail ie secret tt has never been denied’ fince the time of Sir lfaac Newton t ‘Now this sat aya j f axaln # Optics, Book 1 lls » Of. &. df hia! Bock tt Part im, Prop. 38. ra pMond gi On the InfleXiin, Reflexion, and ‘Osbuurs of Light. 55 5 tends to’a diflaneé mitich greater that that’ of apparent contaét, at which an attraction again begins: ftilk at'a’diftance; though lefs thaw "that'at which’ Before ‘there was a repulfion 5 as will appear bythe following demonftration, which occurs to me,'and which is general with -repect to'the ‘theory of Bofcovich*.’ In’Fig. 4, let the body A have for P an attra@ion which at thie diftanice 6f AP is proportional to PM; then Jet P move towards A,. fo as to come to the fituation’P’, and let the attra€tion Here be P’ M7’; as it ‘is continual during the’ motion of’ P ‘to’ P4°M M“is'a‘cutve line. “Now in the cafe of the attraétion of bodies for light, and'for one another,'P M is lefs than P/ MW’; 3 and confequently MM’ does nat ever return into itfelf, and therefore it muft £0 ad infinitum, having its arc between AB and A C, to which it approaches as afymptotes, the ab{cifla always reprefenting the “dif- ‘tance, and the ordinate the attraction at that diftance:, Let P’ now continue its motion to P”, and M’ will” move M”; and if P’’ meets A, or the bodies come into perfect, contact, peng M” will be infinite 5 ; fo that the attr action being changed into cohefion will be infinite, ‘and the bodies’ infeparable, contrary to univerfal experience ; fo that, P can never come nearer toA than a given, diftance. In the cafe of grav ity PM is inverfely as the {quare of ‘A P, fo that the curve NM M”’is the cubic hyperbola ; but the demonftrarion holds, what- ever be the proportion of the force to the diftaace. It appears then, that flexion, refraction, and reflexion, are performed by a force aéting at a definite diftance ; and it is reafonable to think even a priori, that, as this fame force i in other circum{tances is exerted to a different degree on the different parts. of light i in refracting, infleéting, and. deflecting them, it fhould alfo be exercifed with the like variations in refle€ting them, , Let.us attend to the proof which enables. us to change conjeéture into conyiction. OL. I. The fun J thining into. my, darkened chamber through a fmall hale esis an. inch_ in diameter, | I placed a pin of sath of an inch diameter i in, the cone of light (one half inch from | the hole) inclined. to the Tays, at an angle of about 45°5 and:.its fhadow, was received on a hart. parallel to it, . at the diftance of two Feet. The fhadow was furrounded by the ree fringes on ) eaclt fide, difcovered by Grimaldo ; beyond thefe there were two ftreaks of white light. diverging from ¢ the fhadow, and wapraledt with bright colours, . very inregularly feattered up and down; b on. ulin, another. pin, whofe furface was) well polithedy and placing, it, nearer the hole, the an before, the. colours in. the ftreaks became much - brighter (and the ftreaks themfelves narrower), being extended. from, ene fide to. the; jother, fo that, except in a very few. points, here, and there, no white was now. to re feens ‘and, on. moving the pin, the colours moved alfo. But they difappeared if the pin was, deprived of its ‘po- lith by; being held in the flame, of a candle, or if a:roll of paper was ufedjinfleadiof the ping allo they, were much brighter i in divedt, than inpr¢fected Jight, and tint thellight of the Sanat the, ifoculs 9 of a lens, than in his direct unrefracted light. Placing,«, piece, of: paper xound the hole in the, window-thut, I obferved ther colours continued theres and inclining the chart to, the point where they left off; Ipfaw them. continued dn’ ity arid then proceed as before, tothe thadow, . If the pin was held: horizontally, or nearly fo, they were feen of a great fize on the floor the walls rand roof of the, room, forming a large cirele;, and if the ghart was, Jaid horizontally,2 and the pin held between the,hale, and it, in a-venficak pofition, theircle was feen on the chart, and became an, oyal bydneliding the pit acdittleto thé ho- w, 3 Rag « Nova Tacoria Philofophiae Naturalis, 4B2 Ov. 556 On the Inftexion, Reflexian, and Colours of Light. O4/. Il. Having produced a clear fet of colours, as in the laft Obfervation, I viewed them as attentively as poflible, and found that they were divided into fets, fometimes feparated by a gleam of white light, fometimes by a line of fhadow, and fometimes contiguous, or even running a little into one another. They were fpeétra or images of the fun, for they varied with the luminous body by whofe rays they were formed, and with the fize of the beam in which the pin was held 5; and when by placing it between my eye and the candle alittle to one fide Ilet the colours fall on my retina, I plainly faw that they refembled the candle in fhape and fize (though a little diftended), and alfo in motion, fince, if the flame was blown upon, they had the like agitation, The colours, therefore, which fell on the chart were images of the fun: they had parallel fides pretty diftin@tly defined, but the ends were confufed and femicircular, like thofe of the prifmatic fpe@rum. Like it, too, they were oblong, and in fome the length exceeded the breadth fix, even eight, times. ‘The breadth was, as I found by meafurement, exaétly equal to that of the fun’s image received on a chart as far from the pin as the image was, and the length was always to the breadth at all diftances in the fame ratio, but not in all pofitions of the pin ; for, ifit was moved on its axis, the images moved towards the fhadow on one fide, and from it on the other, be- coming longer and longer (the breadth remaining the fame) the nearer they came to the fhadow on the one fide, and fhorter in the fame proportion the farther they went from it on the other. ' Ob/. Il. Having picked out an image that appeared very bright and well defined, I let it through a hole with moveable fides in the upper part of a fort of defk, which moved to any opening by hinges, and had a chart for its under fide, on which the ane fell, and I fhut the hole fo clofe as to prevent any of the others from coming through. I then had a full opportunity of examining it in all refpeéts, and I counted in it diftinétly the feven. prifma- tic colours ; the red was fartheft from the fhadow of the pin, and from the pin itfelf; then the orange; then the yellow, green, blue, and indigo; and the violet neareft of all: in fhort, it was exa€tly fimilar to a prifmatic fpetrum much diminifhed in length and breadth, and turned horizontally on the wall oppofite to the prifm, with the red fartheft ' away. In figure 5, s¢ is the pin refle€ting the rays C P and CO, which pafs through PO the hole in the defk ED, to the chart or bottom of the defk RTS; and from there the fpeétrum I K divided into its colours, I being violet, and K red. On moving the hole in the defk, and letting through other images, the colours were not in all arranged the fame way: but I moved the-pin on its axis, and obferved thofe where the order was inverted, to move, not only with refpeét to the pin, but alfo with refpeét to the contiguous images ; and I was furprifed to fee them affume the order of colours firft mentioned, namely the red outer- moft, and the violet innermoft. In like manner, the images which before the motion were regular, on moving into the places left by the others had always the order of their colours inverted, fo that the thing muft be owing to fome irregularities in the pin’s fur- face; for thofe which were made bya fmall glafs tube filled with quickfilver, and freed from fcratches by a blow-pipe, preferved during the motion the proper order of colours. Another irregularity in the arrangement was alfo obfervable even in the glafs tube; for two contiguous images, by mixing one with another for two or three fucceflions, appeared each to have outermoft a dull colour between red and violet, and innermoft a green; but here unlefg On the Inflexion, Reflexion, and Colours of Light. 557 unlefs the fucceffion continued through all the images, the outermoft of all was red, and the innermoft image had univerfally violet in the infide. OL/. IV.I placed at a hole in the window-{hut a prifm to refra€l the rays, and received the {pe€trum at the diftance of fix feet from the window on a chart; then at the diftance of two feet I placed a fcreen with a hole in the middle of it, through which I Jet pafs fuc- ceflively the different rays. At the diftance of one inch from the hole, between it and the chart, I placed the refle€ting cylindrical body; the images were found on the chart and walls of the room round to the fides of the hole on the fcreen, and were always wholly of the colour in which they were formed, except in the confines of the green, where a fmall quantity of white light fell, and made them of all the feven colours ; but this was almoft wholly prevented by uling a prifm with a greater refracting angle, and holding the pin and fcreen farther from it. I then removed the f{creen, and left the refeétor in its place, fo a3 it might reach through the rays; and thus there were formed images having in them, from top to bottom, the feven colours, one after another, the lowelt divifion being red, the higheft violet. They were inclined confiderably towards their tops, and were much broader at the bottom or red parts than at the tops or violet parts. And laftly, the refle€tor being moved fo that the images might be difturbed (as in the former experiment made in the white light), the red was moft, the violet leaft dilated. In cafe thefe effects. might be owing to any peculiarities in the fhape or pofition of the refle€tor, I placed at three feet from the prifm a lens of four inches breadth, to colleét the rays to a focus, fix feet be-. yond which I held a chart, and there received the fpe@trum inverted, the red being upper- moft, and the violet undermoft ; holding the refleCtor at two feet from the focus and four from the chart, the images were formed juft as before, only inverted, inclining towards the violet, of greater breadth towards the red, and more diftended towards the fame quarter when the refleor was moved. ; O4/. V. ‘Things remaining as in the laft part of the laft Experiment; at the focus of the Jens I placed a fecond prifm, which refracted the rays into a white beam *, and this I re- ceived on a fereen with a hole in the middle, through which a finall part of it paffed, and falling on the refle€tor placed behind was formed by it into images after the manner of the firft Experiment, each having in regular order the feven prifmatic colours. One of the brighteft and moft diftin& I let pafs through a hole in the fecond fcreen, and it fell on the chart. I then caufed an affiftant to intercept the red rays between the firft prifm. and the lens, and immediately the red part-of the image vanifhed; and when the violet was inter- cepted, the violet of the image vanifhed ; and if the green was intercepted, the green was wanting in the image. In fhort, whatever colours were ftopped, the fame were miffing in the image. In Fig. 6. the rays pafling through the hole C of the window, A Bare re- fracted by the prifm P MN, and feparated into D V, D G, and D R, violet, green and red; which, being colleéted into a focus F by the Jens L, are there again refraéted by a prifm P’ M’N’, and formed into a white’beam a b m n, part of which is intercepted by. the fereen SS’, and part paffes through the hole h, as h H to H on the chart X Y Z W, and part is reflected: by the body og into a fet of images which are received on a fereen T U, andone of them, rg v, let pafs to W XY Z; but when an obftacle E ftops DR, r the red va- * Optics, Book ii. Part {1. Prop, 2 P Pr nifhes ; 558 Ox the Inflexion, Reflexion, and’ Colours of Light. nifhes ; and if DG be ftopped, g the green vanifhes; and if D V be ftopped,, mdifappedte Laftly, if DR and DG be ftopped, g andr yanith, Ot/. VI. Having produced a fet of fateh images, I let one pals through tHe defk deferibed in the third Experiment, and received it ona fmall lens 2 inch broad to colle& the rays into a focus, which I received on the chart by moving it-a little on its hinge ;.and by all. the obs fervations I could make, and all the tefts I could think of, it was white inclining to yellow, and of the fame nature and conftitution with the fun’s dire&t light: but if any, ray was ftopped before coming to the lens, the focus was a mixture of the remaining rays; and the chart being moved a little farther round, the image was formed on it, the colours being in an inyerted order. At the focus I held a refleCtor, and there were formed images of all the feven colours, as in the fun’s direct light (Exp. 1.) ; if the light was fufficiéntly ftrong, and the defk near the window-fhut hole, one of thefe could even be colleéted by a fecond lens into.a white focus. This experiment is rendered more uniform by fubftituting for the lens a concave metallic mirror, and placing at the focus another mirror to reduce the rays into ‘a beam which may be made of any compofition we pleafe by ftopping one or more of the colours at the hole in the defk. I obferved in the courfe of thefe experiments a phe- nomenon worth mentioning; if a comb (as in Newton’s experiment *) be very {wiftly moved before one of the images or more, a fenfation of white is produced: but this i is fill more evident if the pin be fwiftly moved round i its axis ; for then the i images move alfo, and, running into one another, caufe a fenfation of nae whitenefs. Ob. VIL [let an image through the hole in the defk, and viewed it through a glafs her holding its axis parallel to the fides of the image, and its refra@ting angle upwards. I found that if the image was bright, and free from white light, the colours were not changed by the refraction; but if it was mixed and diluted with white, the prifm, decom- pounding the white, caufed the image to appear violet at one fide, and red‘at the other ; yet ftill this only confufed the colours of the image without changing t them. Farther,, if the prifm, was moved on its axis, the violet was lifted higher than the red or any of the other colours. Nor was the conftitution of the colours at all. changed by reflexion from a~ pia or mirror, except in fo far as they were mixed by a concave one, as mentioned in the lat experiment. If a pin was held behind the hole to refle the colours, it formed other images of the colour in which it was held, and as far as I could judge threw the red to the greateft diftance and breadth and inclination, Nor were the colours of the image, changed by reflexion from natural. bodies, for thefe were all of the colours in which they were held, but brighteft in that which they were difpofed to refle@ moft. copioufly. Like- wife the rings of colour made by thin plates were broadeft in the red, and narrowelt in the violet ; and the like happened to the fringes that furround the fhadows of bodies. Laftly, the thadows of bodies were themfelyes broadeft in the violet, and narrowe(t in the red. Ob/. VIL I filled with water a glafs tube, whofe diameter was 3th of an inch, and confe~ quently the radius of curvature e ant : ww . ; fot ee : P i Sindee he ge ATA ue eet ests = Fy ‘ ¥ | a, ey i a aN deste i : 4 Sr ae Ts Tuilos Journal VoL LPLXBML taing ps7 Peortw ail A fee: R: Ny ARE. OF NATURAL PHILOSOPHY, CHEMISTRY, AND DEA RTS, rs MARCH 1708.—SUPPLEMENT. ARTICLE I. Objervations on Water-Spouts fen from Nice. By M. Mrcuavn, Correfpondent with the Royal Academy of Sciences at Turin *. V V A T E R-fpouts, as Mr. Senebier remarks, are phenomena which arife too feldom, and are too difficult of obfervation, to admit of our forming an accurate notion of their cirs cumftances, or pointing out the means by which their caufes may be inveftigated. Yet, as nature is never more difpofed to explain her fecret operations than in fuch as are performed on a great feale, there is no doubt but that thefe phenomena, if well explained, would lead te ufeful refults +. , Ido not flatter myfelf with the hope of giving a complete explanation of the caufe of water-{pouts, fuch as M. Senebier appears to-defire ; but as the true explanation can only be had by careful and frequent obfervation, I hope my work will not be totally ufelefs if it fhould afford an additional ftep towards the defired end. My obfervations did not in ftri€tnefs commence till the 6th of January 1789, but it ap- pears neceflary, for the fatisfaQion and information of my readers, to mention fome facts of an earlier date. I muft therefore remark, that after a mild feafon for the greateft part of the month of December 1788, at Nice, where the winter is not in general feyere, with clear weather in the day-time, our atmofphere underwent a total change on the day of the new moon, which was the 27th of that month. On that day avery violent ftorm of wind arofe, attended with a degree of cold as acute as ever was known in the memory of man. ‘The fky became covered with clouds, and {now fell to the depth of more than eight inches. * Turin Mem. VI. 4, Senebier fur les Moyens de perfeétionner la Météorologie, Journal de Rozier, Mai 1787. Vor. .—Marcn 1798,—Surri. 7 4k As 578 Obfervations on the Formation and As the fame-effeets are produced’by the fame cawfes, f have-littie doubt but that water fpouts were formed near us on the night berween the 27th and 28th.’ But, as I did not fee them, it becomes unneceilary for me io enlarge upon any which I did not myfelf clearly obferve. ; ' The fevere cold had frogen thefnow, and rendered jt foompaét that, notwithftanding the influence of feveral days of clear weather foon afterwards, in which the heat of the fun was very perceptible, there was not the leaft drop of water fell from the eaves of the houfe in which 1 dwell, which is expofed to the fun in winter for eight hours, and, being fituated near the feay isy perfectly fheltcred on the-north-lide-by the eminence, of the rock of the. cattle. ‘This fact appeared very furprifing tome, after a refidence of about forty years in this town. Several old perfons remarked, that this fnow would wait for another fall before it melted, and I found by the refult that tlie obfervation was true. On Sunday the fourth of January 1789, at the phafis of the firft quarter of the moon, the cold vas again renewed, and continued feyere,on the Monday and Tuefday. At eight in the morning | firft obferved an immenfe mafs of clouds towering upwards, and extending from north-eaft to feuth, whichrofe-towards-the-zenith, by-advancing-to the weitward. Ac- cuftomed as I am fo confider thefe-clouds according\ to the fyftém of my old Profeffor of Natural Philofophy, Father Beccaria*; concluded that they would proceed to defolate our fields, the fruits of which, particularly the oranges and lemons, had already perifhed by the antecedent cold. Andas a ftrong wind ‘then-prevailéd over the face of the fea, I foretold to.my two eldeft fons, thatit was, very probable we might difcoyer fome water-fpout in the. courfe of the day. In faét, about five -minutes,afser ten in the morning, I obferved on the fea, at the diflance of not more than a mufket-fhot from the fhore, a round fpace of ten or. twelve toifes in.diaméeter,cim whichithe water,didmetréally:beilsi bat feemediready to boil. Plate XLV. © Ror:theresappearediall:round, | anddfometimes withinothe circle, vapours in, the form of miftsy eight : tiles; and:more, iny heights haying -the appearance, though.on.a. {eale incomparably larger, of thofe: vapours which-rifefromothe furface, of water beginning, to immer. Lfaweclearly-that this was, ifIumay fo.exprefs:myfelf, the, embryo.of the foot. of a water-{pout driven along by the wind, while the clouds were not fufficiently-adyauced.. to afford the’ ftema body. It continued. therefore. to move before the,wind. from eaft to welty keeping, to-my very. great -furprife, its {urrounding. vapours, elevated like fails, note. - withftanding the-extreme-force/of impulfion: whichndrove it towards the fhore, As foon ag, it came near the land, the circle was contracted, the mais of vapour became of. lefs dimen- fons, and at the moment it touched’ the land/it, was: at once overfet, by the wind, un- der the appearance of along train of mit, figs 15 by whichowas {peedily diffipated. I then per= ceived that the hope [ kind formed of feeing:water-fpouts during the day, was on the point of being realized : but as’ my occupations: demanded my attendance elfewhere, I charged my two eldeft*fons’to watch alternately at the window,:in order that-the phenomenon might not pafs unobferved.” ' | . Atlaft, about eight minutes before noon, my fecond foncame tome, exclaiming, ‘ Fa-~ ther, here is’ a very’ fuperb water-fpout.” His earneftnef.was equal to that of a failor, %* Elegtricifme Atmofpherique. Wejhave a tranflation in Englith. : who, Lippearanees of Water-Sponts, \ - 579 who, after a Jong and tedious voyage, ‘firft difeovers the land. J followed him'to the win- dow, and beheld an immenfe water-fpout pafling majeitically before Nice, as reprefented in fig. 2. The clouds‘had already occupied not only the upper and fouthern’part of the at- mofphere, but they had proceeded towards the weft, fo a3 to cover the whole extent with- in my view; with this circumftance neverthelefs, that they had left uncovered beneath and towards the fouth a part in the form of a fegment of a circle, ‘through which, at an extreme diftance, fome clouds were difcerned, upon which the fun threw the colours of the morning. The foot ‘of this water-fpout, which was in every refpect infinitely fuperior to that which Mefirs. Papacin, Renaud, and myfelf, obferved in 1780, was fo ample, that a man of war of 100 guns, with all its fails, might have been enveloped and even concealed init. For we are, from daily practice, fufficiently accuftomed to judge of the fize of ob- jects at different diftances by that of the image formed upon the retina, aflifted by our ha- bitual reafoning. And hence, from the circular form of the foot of this water-fpout, fome judgment may be made of the volume of vapour it afforded. Inftead of the tranquillity it exhibited at its firlt appearance, this lower part affumed the refemblance of the crater of a volcano, with this exception, that it ‘threw out nothing but large ftreams of cloud and fpouts of fea-water. But it threw thefe in parabolic ftreams from the centre to the circumference, and all around, with fuch impetuofi ity and violence as to render it very evident to us, that an inexpreflible effervefcence muft have prevailed in the interior bafon, though the great diflance and the opacity of the furrounding vapour prevented us from feeing the Sb ie as diftinctly as we faw the ‘ebullition of the wa- ter-fpout of 1780*. ‘The diameter of the water-fpout, and that of its expanded upper part, were large in pro- “portion. Its‘colour was a very deep indigo, the fame as that of the clouds, which extended from eaft to weft. It was impoffible for us to obferve the afcent of the Vapours of frefh water ; but the obfervation of 1780, in’ Which this was clearly feen, fupplies this defe&t. It will alfo be fhewn that the afcenfion was again {een in a moft complete manner. While we were looking at this extraordinary appearance, which my fons beheld for the firt time, and which feemed to have concentrated all their fenfes in one, on a fudden an impetuous fhower of hail difcharged itfelf again ft the windows in grains of the fize of pif- tol and mufket balls. ‘We immediately fafpended our obfervations, in order ‘to’ tlofe the fades of both {tories of the hoafe, in which the whole family alfiited, for feat Of having the windows abfolutely broken to pieces, as happened a few years before. But I foon pet- ceived that this precaution was abfolutely ufelefs, or at leaft unneceffary. For the hail, though i in a few minutes it covered the grourid to the height of four inchés, did not in the leaft damage the treés in the garden behind oar houfe. It confifted merely of large flakes of fnow roundeéd by the wind in their fall, and poffelling neither the Weight nor the hard- nefs of hail. Upon opening fome of the pieces I found them to confit of a thin compact fhell, nearly empty within, excepting a few rays from the centre to the circumference. ® See the Journal’ de Phyfique, XXX. Part I. 24. for Obfervation furune Trotbe de Mer, faite 2 Nice de Provence en) 1790, et addreflée & M, Faujas de St. Fond, par M, Michaud. The fagts are lefs minutely Bated, but nearly agree with the prefent memoir, N. 4E2 The 580 Objervations on the Formation and The degree of congelation in thefe balls was fo flight that they began to melt the moment they touched the ground, and accelerated the fufion of the {now which had fallen before. , This frozen fnow, which during its fall had obfcured the air fufficiently to prevent our feeing the water-fpout through the blinds, having ceafed, we refumed our obfervations with all pofible diligence, and beheld another water-fpout fomewhat inferior in magni- tude to the former which had difappeared. It followed nearly the fame courfe as the other. By the account of time employed by each in its fucceflive pafiage, I eftimated that the one before us muft have been the third ; neverthelefs, by confining my narration to what I really faw, it muft be confidered as the fecond only. This water-{pout having continued its courfe towards Antibes, we obferved that it began to contractin all its dimenfions, fome time before it arrived at the fhore, and that the foot was reduced to nothing when it touched the ground. It contraéted infenfibly upwards, the expanded conical part became broader and more rare, and the whole joined the mafs of clouds in the fame manner as one mift incorporates with another. There muft confequently be fome error in the account of the obfervation of 1780, where I fay that the fpout withdrew upwards as quick as light- ning. This expreflion gives too precipitate an idea of the diffolution of the water-fpout. Having thus kept fight of it until its total extin@tion, I returned towards the place where Thad difcovered the firft water-{pout, and was greatly furprifed at difcovering a new foot ready formed, without any defcending {pout a, fig. 3, Plate XXV. My aftonifhment was owt? on thefe three circumftances: The exiftence of the foot of the water-fpout without its {tem or body. For before shin <2} ata bt and from the fa&ts in 1780, I confidered it as indubitable that the enve- loping matter of the foot or recipient was a production of the body of the water-fpout. it- felf, or an expanfion of its proper fubftance. Now I faw clearly enough in this phenome- non the identity of the fubftance which compofes clouds and mifts, and that it was not fup- plied by the water-fpout. The embryo of the fpout which I had feen at ten o’clock, ap- peared to fhow that it was probably produced by the fea. 2. I was furprifed to fee that this foot was ftationary at the place of its formation, where- as thofe which I had before feen were carried {wiftly along by the wind. For though it was not impoffible but that this foot might be carried by a motion along the line of fight, and confequently notjperceptible by me ; it was at leaft certain that it gained nothing from eaft to weft, that is to fay, from my left to my right, the ‘dire€tion in which the fea, the clouds, and the other water-fpouts which had travelled fo far in fo fhort a {pace of time, were carried, 3- I was aftonithed, that the body of the water-fpout being wanting, which, according to my notions, might increafe the intenfity of the power by which this appearance is pro- duced, it was neverthelefs poflible that this envelope fhould be capable of remaining up-— xight and ftationary. In this uncertainty I fufpended my reflexions to obferve the refult. I remarked a kind of teat or protuberance, b, fig. 3, projecting obliquely from the lower part of the clouds which arrived from the eaft. The foot continued motionlefs, and the protuberance preferved its oblique dire€tion, till the moment when by the ation of the wind it arrived at the foot; at which inftant we all three obferved the protuberance dire&t. itfelf perpendicularly towards the foot, and like an immenfe fack of gauze unroll itfelf 6 from Appearances of W ater-Spouts. 581 from the extremity ¢, fig. 3; when the folds of this fack difappeared, and the body of the water-fpout, which was grey and tranfparent, fixed itfelf in the bottom of the foot, af- fumed the vertical pofition, and became larger in diameter. My fecond fon, who, as well : as his elder brother, pofleffes a very clear fight, immediately exclaimed, ¢ See, father, how rapidly the vapours fly up through the bag.” I faw, in fa&, that they feemed to expand it with a kind of tenfion, at the fame time giving ita deep indigo colour, whlch was commu- nicated to the cloud. At the fame inftant the colour of the whole water-fpout became fo deep that we could diftinguifh no motion in its expanded part. We obferved only that the whole phenomenon moved from eatt to welt, and was deftroyed on the coaft of Pro= vence. Laftly, a fourth was formed, which was deftroyed in the fame manner, without any fuch reproduétion, beyond the hills of Antibes, as I obferved in 1780, becaufe, their courfe being more oblique towards the north, they could not meet the gulph Jean, and the prolongation of their track was altogether over land. A fall of fnow fucceeded imme= diately afterwards, which was of the ufual denfity and configuration, It lafted all the ref of the afternoon and the following night, fo that on the following day there was as much fnow on the ground as before. It afterwards rained for a long time, which cleared the country of the fnow that had accumulated. As the impetuous wind of the preceding day continued with undiminithed force through the whole night, and the other acceflary cir cumftances were likewife prefent, I think there is reafon to conclude that new water-{pouts mutt have been formed in the afternoon, and perhaps in the night of the 6th; but the ob- {curity of the atmofphere, from the fall of {now, did not permit me to obferve them. I dhall therefore proceed to make fome remarks on the wind which caufed this phenomenon. ‘Though the velocity of this wind was nearly equal to that of the greateft ftorms in our feas, the waves were not proportionally deep. Two circumftances appeared to concur in producing this effe& ; the firft, that by the form of our coaft an eaft wind cannot have paffed over fo great an extent of fea as a wind from the fouth-weft, from which quarter our greateft ftormscome. This caufe is conftant with regard to our local fituation. The other circumftance was, that the wind did not blow obliquely downwards, but moved parallel to the furface of the fea. This fuppofition, which is the only one that requires proof, was confirmed at the time of obfervation by the appearance of a fmall Catalan veflel, which the wind of the 6th of January blew afhore near Nice. I faw her pafs before my windows, driven by a force fhe was incapable of refifting. She did not labour much, but came to an anchor at a little diitance, from which, however, the violence of the wind drove her on fhore, though without confiderable damage, fince fhe was got off a few days after, and purfued her voyage. The force of this wind was feen not only in the inftance of this veffel, but in a confiderable number of others which were loft on the neighbouring fhores, = [t is an obfervation very agreeable to the opinion of Profeffor Toaldo, and at the fame time well eftablithed by every obfervation I have made fince I direted my attention to the phenomena of water-fpouts, from the beginning of 1789 to the 19th of March in the fame year, on which day we obferved thofe which I fhall prefently defcribe: it is a confirmed obfervation, I fay, that the phafes of the moon are accompanied with a change of weather, It gh2 Obfervntions-on the Formation and Je is certain that the cold weather which fuddenly came.on with the new'moon of the 27th of December, recurred again exactly at each new phatis. I cannot be deceived in this re- feet, becaufe the.chimney of my apartment fmoked each time, and did not fmoke but during this accidental cold. "Two days afterwards, when the weather became milder, this chimney acted as ufual, and did not fmoke ‘again until'the following change. I could urge many other circumftances in favour of the opinion of Mr. Toaldo ; but I forbear, becaufe they are foreign to my prefent fubject, Laftly, on the 1gth of March the wind, which had begun the preceding evening, blew with a degree of impetuofity lefs than that of the 6th of January. The clouds were accu- mulated from the ealt towards the welt, but they were much lefs condenfed than at that time. At forty minutes after eleven inthe miorning, we obferved two water-{fpouts, a, b, Plate XXV-fig. 4, which moved at the fame time, the one after the other. The moft re- markable circumftances in thefe water-fpouts were: 1. The prodigious enlargement of the protuberance d, fig. 4, from the.extremity of which hung the effective {pout b, which was incomparably thinner ; butthe wonder difappears, when we refleét that the following fpout, which maintained itfelf in the fame ftate as thofe we had before obferved, robbed the preceding one in fome meafure of its fupport ; fo that this enlargement was, as it were, a commencement of diffolution, and the thinnefs of b was a proof of the little intenfity of eleGtric power then acting 5 a conclufion which is alfo confirmed by the following circum- ~ftances. 2. ‘Che incapacity in the feet of thefe two water-{pouts to elevate their fur- rounding plumes. Itisfeen, ab, fig. 4, that they were reverfed by a force which pre- yented their rifing in a perpendicular direétion, like thofe of the preceding water-fpouts. At the extremities of the plumes here defcribed, as.well as at the centre of the circle near the furface of the fea, there was formed a fmall atmofphere : but as it was not extenfive, the vapours were fo few that we had very little fnow, which continued for about half an hour; when the weather cleared up. ‘During the tranfition of thefe water-{pouts very dif- tant thunder was heard five or fix times. In the interval between the obfervations of the 6th of January and the 19th of March, other water-{pouts muft have been formed on the coafts of Provence. It is certain, at leaft, that I faw the appendices proje€ting from the clouds, and that the product-of frozen fnow reached our firft hills on this fide of the Var; but as my profpect, being limited by the mountains of Provence, did not allow me to fee thefe water-fpouts in fuch a manner as to make any drawing or defcription, I fhall here conclude my. obfervations, and attend to the refults. I don’t know whether Iam mifled by partiality for my own obfervations, when I ex- prefs my opinion that the faéts noted by me on the 12th of April 1780 are of great value in natural philofophy, as well becaufe.of the vicinity of the water-fpout which appeared that day, as of the tranfparency of the furrounding vapours.of the foot, which exhibited the interior ebullition with fcarcely any obf{curity. Whence it follows, . That there is a real ebullition in i fea, at the place circum{cribed by the foot of the sasha 8) 2. That the vapours of the water which muft arife, are the produdt of an evaporation which Appearances of Water-Spouts.. + te 583. which muft feparate freth. water from: the falt ;, it. being afcertained by experiment, that, diftillation is the only method_by which. fea-water can be rendered. completely freth. I fhall, take. the liberty in this place to make ufe of a.comparifon, by way of explaining, miore, perfectly the phenomenon we at that time beheld. It will not probably be unac~. ‘ceptable to fuch:as have never feen a:water-{pout, at leaftim fo favourable a pofition, Sup- pofe the chimney of a baker’s oven, fuchas we have. at. Nice, in which the fuel commonly burned confifts of branches of pine recently broken from the tree, aud fufficient to bake large quantities-of bread ; Jet this chimney bé imagined to be in the ftate-of throwing out immente clouds of. vapounand fmoke: Suppofe a funnel) of glals to” be adapted to the aperture at the Jower part, and to have its. diameter enlarged upwards, until it terminates ina yery extended veficl.. It. may eafily be conceived that the afcending vapours will be fo preffed together in the narrow neck of the glafs, as-to render it opake, without permitting the fucceflive undulations, of the vapour to be difcerned. But in proportion as they pro- ceed further-from the caufe of motion, which is the fire of the oven, and arrive at a part of the glals where they have.room to expand, the vapours; being lefs condenfed, will exhi- bit their peouliar. motions, and the fucceflive eruptions of the fmoke will indubitably be feen. Inthis imaginary experiment, let the foot be fuppofed to be abftraéted ; let the af- cending vapour, be fimply that of boiling water, and the conical tube of glafs here con- templated, will afford a,nafural reprefentation of the phenomenon obferved in 1780, and confirmed on the, 6th.of January 1789. It may perhaps-be objected, that, thefe facts do not at all agree with Profeffor Mufchen- broek’s theory.of water-fpouts, given in chis Eflaide Phyfique. This‘objection was ftarted by all my. philofophical acquaintance, againit the report’ of our obfervation ia 1780, and ‘en- gaged me to fufpend the publication,of my memoir for feveral years, becaufe it was not polible to reconcile the, means employed by nature in the produétion.of water-{pouts, nor their ufe, with the ideas of the celebrated Dutch Profeflor., Befides' which, having only one obfervation to offer, though well fupported by the teftimony of two refpectable perfons, I flattered myfelf that I might remove all the difficulties by reprefenting a water-f{pout in the fame manner as lightning and thunder are imitated by the. eleétrical machine. For it feemed to me at that time, and ftill appears to be, a thing very pra¢licable. But at pre- fent, by a new ‘feries of obfervations in confirmation of that of 1780, I fee clearly that the procefles of nature are. very different from thofe pointed out by Profeflor Mufchenbroek. That enlightened and moft accurate obferver had no opportunity of examining this pheno- menon in a fayourable pofition himfelf, and has been equally unfortunate in the explanation of the fuppofed defcent of water, which really afcends in water-fpouts, as well as in the for- mation of the foot, which according to his theory ‘is a miafs of fea-water in its natural ftate. I can affirm without fear of contradiction by experience, that this foot or atmo- {phere as it may be called is nothing but the matter of clouds and mifts. Tt muft moreover be remarked, that in the time of Mufchenbrock the theory of eleAtri- city had made fo little progrefs, that he did not avail himfelf of it in the account of fi fiery meteors. It is therefore lefs wonderful that he fhould not have recurred to it in his theory of water-fpouts. What then is the agent, it may be afked, which caufes this ebullition in the fea, and raifes 584 Obfervations on the Formation and raifes the vapours through the water-fpout to the cloud? Simply to affirm that this agent is cle€tricity, without further proof, is in fa& to fay nothing. To this queflion I muft anfwer, that I have exhibited the produéts of obfervation : Ihave related what I have moft clearly feen. I think I can difcern the caufe without being able to exhibit proof: but I thall be happy to be anticipated by philofophers of greater fkill in this theory, and think it better to fufpend my judgment than yield to the fedudtive pleafure of explaining every thing by adding to the mals of error in natural philofophy. The fecond faét which prefents itfelf in our obfervations is, that two caufes unite in the formation of water-fpouts, or rather two different modifications of the fame caufe. When the foot appears without the water-fpout, it isnot the productive caufe, but rather an effer- vefcence which prevails in the fea at that place. But how many interefting queftions might be afked refpeéting this part of the phenomenon! What caufe is it fo powerful as to retain the foot a, fig. 3, and keep it motionlefs, notwithftanding an impetuous eafterly wind, until the projection in the cloud which is to form the water-{pout fhall arrive direétly over it? Was the apparent bag which developed itfelf from the cloud, pre-exiftent in the projecting part? As I can make no fatisfactory reply to thefe and other queftions which might be propofed, I fhall proceed to the third remarkable fact. 3. When the foot of a water-fpout begins to approach the earth, its diameter contracts, its height is diminifhed, and its volume becomes lefs and lefs ; fo that the foot is reduced to nothing at the inflant it touches the fhore. From the attentive examination I have made, it has appeared that the foot even of the greateft water-fpouts began to diminifh when the depth of the fea beneath became lefs than the elevation of the foot itfelf above the furface. | If this be true, as I think it is, it may be concluded that the effervefcence which fupplies the fpout with water, and forms the furrounding vapours of the foot, extends itfelf in depth nearly as much as the foot itfelf rifes above the fea, and that materials for the fupply of vapour become defective in quantity in proportion to the fhallownefs of the water. - Explanation of the Drawing. : FIG. 1. Plate XXIV. reprefents the imperfe&t foot a of the water-fpout feen on the 6th of January 178g, at five minutes after ten in the morning. On the left hand are feen the clouds which rife towards the zenith, but ftill confiderably diftant. ‘This foot had plumes elevated nearly like fails, and was driven towards the fhore by the wind. In proportion as it came near the land it contracted, and was reduced into a column of mitt, which the wind overfet on the land the moment the fupply of water was wanting. Fig. 2 reprefents, letter a, the enormous water-fpout obferved on the fame day at eight minutes before noon. Nothing could more nearly refemble a fhip of war on fire than this phenomenon, excepting that no flames appeared. Ihave endeavoured to fhew the con- tinual jets of its furrounding vapour, and of the water which iffued from the centre. Atb are feen the remains of a water-fpout after it has been deftroyed by the foot having touched the ground. Fig. 3. Plate XXV. a reprefents the foot of the fecond water-{pout ready formed, which was probably the third. It has yet no fpout. Atb is feena protuberance tending obliquely © towards the eaft, and advancing to the weft with the cloud to which it is fufpended, At the : Water-Spouts. Hobitudes of Light 585 the letter ¢ it may be obferved how the protuberance b having arrived over the foot 2 be- came vertical, and unrolled itfelf inftantly in a kind of large bag, of the figure of an inverted tone, nearly tranfparent, like gauze. As foon as this bag compofed of the matter of the cloud had developed itfelf, which occupied the time of three or four feconds, and had fixed its fmall extremity in the bottom of the foot d, it became {traight, without folds. A vapour like that feen in 1780 immediately rofe up the tube, extended it in the form of a water-fpout, deprived it of its tranfparency, gave it a deep indigo-colour, like that of the clouds, and at the fame inftant the foot and the fpout were moved from eaft to welt, and followed the courfe which the impulfe of the wind gave to the clouds to which the fpout was attached. This {pout being deflroyed, the following {pout exhibited the fame phenomena as the others. Tt muft be remarked, that the diftance of the protuberance b from the foot already formed at a could not be augmented in the fignre ; but this protuberance, when firft obferved, was at more than a league diftant from a, which remained motionlefs till its arrival. It is pro- bable that it may have arrived from 2 {till greater diftance. It is alfo to be noted, that the f{pouts 2 and 3 were fomewhat lefs in all their dimenfions than the firft. » Fig. 4. exhibits two water-fpouts, which were feen following each other on the rgth of March. ‘The wind was lefs {trong than on the 6th of January, the fea lefs agitated, the clouds lefs accumulated, and lefs deep in colour. The intenfity of the phenemenon was alfo proportionally lefs. It may be feen at a and b that the furrounding plumes of the foot had not the power to raife themfelves up, as in the preceding figures, but were kept down by the wind. The enlargement of the upper part of the fpout d appeared to be a commencement of diffolution, fuch as was obferved at b fig. 2. Thefe two water-fpouts proceeded to the point of N. Dame de la Garde, beyond Antibes. Thofe of the 6th of January reached the fhore between the town of Antibes and the mouth of the Var. The line they defcribed from the time we firft faw them to that of reaching the fhore may be ¢eftimated at five er fix common leagues. Advertifement vefpecting the Figures. THE. magnitude of fig. 1. in thefe drawings mutt not be confidered as proportional to thofe of the figures 2, 3,4. The firfl water-fpout paffed at no greater diftance than a mufket-thot from our windows; the others were at the diftance of two or three leagues. It is neceflary to make allowance for what the firft gained by its nearnefs, and the others loft by their remote fituation, in order to form a judgment of the refpective fize of cach fuppofed to be at the fame diftance. SSS Il. Experiments and Objervations on the Inflexion, Reflexion, and Colours of Light. By Henry BroucHam, Fun. Efy. [Concluded from page 563.] Have endeavoured to unfold the property of flexibility, as varied in inflexion, de- flexion and reflexion ; and alfo the phyfical caufe of this property; and having indulged in a {peculation depending on this caufe, I flatter myfelf neither altogether ufelefs nor unim- VoL. L—Makcu 1798,—Surrz. 4f portant ; 586 On the Inflexion, Reflexion, and Colours of Light. portant; I haften now to the natural phesomena, the explanation of which, depends. on the property whofe e iflence and nature we have juit now been inveltigating ; and, that we, may treat this part of the fubject with concifenefs and order, we fhall rank the phenomena under a divifion fimilar to that under which we laid down the principles, beginning with thofe appearances which are explicable on the principles of flexion. 1. It is obfervable, that when a body is expofed in the fun’s light fo as to caft a fhadow,, and another body is a} pproached to it, either between the fun and it, or the fhadow and it, or in the fame line with it, the fhadow of the oneé body. comes out a eonfiderable ' way, and meets that of the other. “Now itis evident, that when the bodies are held at a fufficient dif- tance from one another, a penumbra is formed round the” thadow of each, making it lefs than it fhould be were there no inflexion; but when the bodies are brought fo clofe to one another that the edge of the one is within the {phere of the other’s inflexion, the light being already bent by this laft, the former can have none to bend, and confequently no penum- bra in the part of the fhadow Correfponding to that part of the body which is within the éther’s fphére of inflexion ; and the reft’ of the fhadow having a penumbra, this part that has none will be larger than it, and increafé as the bodies approach, till at laft it meets the other fhadow: the like appearance happening when the fhadows are thrown on the éye.. Mr. Metvill. has endeavoured to fhew that it belongs fimply to a cafe of vifion*. However, we have now feen that it has no reference to the tte: or pofition of the ICS but only to the/comnron nature of all fhadows+.: d yarn 37 <2. 1f-we fhut ‘out all the light coming’ into’ a room from external objeds, eickpe what may pafs through a fmall hole of 4 or ith of an inch in diameter, the i images’ of the external objects, as clouds, houfes, trees, will be painted on the oppofite wall by the rays: of light crofling at the hole; but if apiece of rough -glafs or of very fine paper be’ held fo? as to cover it all over, the light does not pafs through; then if the paper be wetted with oil, or the glefs with water, fo as togive either a {mall degree of tranfparency, the firft'rays: that come through are thofe from red and orange. objects, and. laft.from blueiand violete Now it is evident that tranfparency in general, and this particular fact, are explicable by what was before laid down. It was found by Newton, that a _body tranfmits the light inci- dent on it more or lefs according to the continuity of its particles; and’ that a ftrong Te- flexion takes place on the confines of a vacuum}: How does: this: happen ? The initial velocity of lighti is fuflicient to carry it through the firft furface or fet of particles 5 “but it is fo much diminifhed that it is refleéted by the repulfive power ‘of the: ‘back fide of thefe parti- cles, unlefs there be others behind at a’ certain diftance, namely, that at which inflexion or attraction acts, that is, apparent contaét: this attraétion renews the impetus of light, and’ tranfmits it to another fet, and fo on. Now this aétion being ftrongeft on the largeft-and red particles, and weakeft on the blue and violet, if the continuity be diminifhed, the former will be tranfmitted, and n not the latter; which is conformable to the Fag juft now men- tioned. © A fia ‘ 3. The doétrine of flexibility furnifhes an “ealy: and fatishattory Shen of the different colours which are afflumed by flame. Whether we fuppofe the light to come from the burning body or the oxygenous gas, the largeft or red particles have the ftrongeft attrace ~ | * Edinburgh Literary Effays, Vol. 11. ‘ +See, yeni acu Journ.’ I oe $ Optics, Book ii, Part Ill, Prop, 39 fs * 5 ; Di .Dus a i si % ‘On the Inflexion, Reflexion, and Colours of Light. ‘587 tion for bodies, the violet the weakeft ; when therefore the gas andthe body combine, the precipitation of light mult be in the reverfe order of the affinity between the particles of light and thofe of the bodies. If then the combination take place flowly, the violet and blue pat- ticles will be firft emitted, and laft of all the red: and this is confiftent with fa&t ; for any inflammable body whatever, on being lighted, burns at firft with a blue or violet flame, and afterwards has its flame of two or three difiin& colours, blue, white, red, &c. as is feen re- markably in the cafe of a candle. Nay, 1 have obferved in the flame of a blow-pipe, all the feven primary colours at once. When indeed a body is burnt in pure oxygenous gas, the combination is fo rapid, that white light alone is precipitated undecompofed ; but in com- mon air, where the azotic gas impedes the combuftion, the above phenomena are obyious. 4. A curious phenomenon has often furprifed philofophers, namely, blue fhadows. Thefe I have obferved at all times when the paper on which I received them was illuminated by the fky and any other light; and the reafon of them I take to be this: that the fhadow made by one light is illuminated by the blue rays from the fky; for I have often obferved purple, and even reddifh ones, when the {ky or clouds happened to be of thofe colours; and this account of the matter is confirmed by an experiment. Having received the coloured fpe&trum made by a prifm with a large refracting angle, on a fheet of rough white paper, and held above it another fheet ; I {topped all the rays that illuminated the firft, except the blue, and violet, and red; and if I held a body between the blue and the fecond paper, its fhadow was red; and if I held a body between the red and the paper, its fhadow was blue; and fo of other colours. This I take to amount to.a demonttration of the thing *. 5. Paffing over other phenomena of lefs note, | come now to,one that has divided op- ticians more than any other; 1 mean the coloured fringes that furround the fhadows of bodies. I made feveral obfervations on thefe, which enable-me to conclude that each fringe is an image of the luminous body; for, holding between my, eye and a candle two knife- blades, as I approached the one to the other, the edge of the candle feemed multiplied, and foon became coloured, coming wholly away from the candle; and, as the knives approached {till nearer, became diftin& dilated images, highly tin@ured with the prifmatic colours 5 and juft before the knives met, the candle, whofe edges had been all along coloured with red and yellow, became much diftended, till at laft it was divided in the;middle, one half feeming to be drawn away by each knife, and then) it wholly difappeareds I have ob- ferved three kinds of thefe images, two without, and one within the fhadow : the firft had its colours in the order from the fhadow, red outermoft, and violet innermoft; the fecond and third had the colours in the contrary order; but the fecond was fo very faint that I could never perceive it, unlefs when let fall on my eye. All this is eafily explained by the different flexibility of the rays. In fig. 9, Plate XXIII. let AD be a body by which the rays SDT and S'D'T’ pafs, and let SD be within A D's {phere of inflexion, and S'D ‘within its {phere of de-, flexion ; then. SD will be bent into DG: but becaufe of the different inflexibility of its parts, the red will be bent into DR, and the violet into DV, and the intermediate rays will fall between R and V; the whole forming an image RGYV, feparated into the feven primary * Since writing the above, I find the fame explanation of the matter giyen by Mr, Melvill and fome-of the French academicians, particularly Meffrs. Buffon and Biguelin ; alfoCount Rumford (Philof Journal I. 101); put I have thought fr wo keep it!in, on account of the éxperiment that oceviried to me in illufration of it. 4F 2 colours 5 588 On the Inflexion, Reflexionyand Colours of Light. colours; and in like manner by the different deflexibility of the parts whereof $’D’ confifts, an image without the fhadow, as V’G‘R’‘, will be formed, fimilar to VGR, R/ being red, and V' violet, all which is both theory and experience ; and the fame explanation may be extended to the other cafes. Now in all thefe, the bending power ftretching toa very fmall definite diftance, and being of different degrees of ftrength at different diftances from the body, feveral pencils or {mall beams, pafling through different parts of the fpheres, will be acted upon by the power in its different ftates of ftrength, and each beam will be difpofed: into an image in the way before defcribed. Of thefe images [ have fometimes obferved four, and even, by ufing great care, the faint lineaments ofa fifth. In forming them, the power acts ftrongeft at the fmalleft diftances, and of confequence bends the mean flexible rays that pafs near, farther inwards or outwards than thofe that pafs farther off; fo that the extreme rays will in the former cafe be more feparated from the mean than in the latter; and the nearer image will always be the iargeft and moft highly coloured ; which is confiftent with faét. This explains fully the celebrated experiment of Sir Ifaac Newton with the knives, and the explanation is confirmed by the experiments which I related above on flexibility, where the bending force a&ted moft ftrongly on thofe images formed out of red light, and leaft ftrongly on thofe formed out of violet and blue light. A number, of ether phenomena are explicable on the fame principles, being only particular cafes,/as it were, of the coloured fringes or images: I fhall here mention a few of the moft remarkable. 6. When making fome of the experiments which I have ‘related-in the courfe of this paper, I obferved, that when the fun was furrounded, but not covered, by clear white clouds, the white image on the chart (the hole being 1 inch in diameter).was furrounded. by two rainbows pretty broad and bright; in the colours were red om the outfide, and violet next the white of the image. Thefe bows muft not be confounded with one which fome- times appears wholly of a dull red and yellow, when the fun or moon fhines through 2. cloud, and which is owing to the dire tranfmiffion of the red rays, and reflexion ‘of the others; for not only are the colours different in {pecies, in brightnefs, and in number, in. the phenomena under difcuffion, but likewife they are formed by the hole in the window, as I knew by altering its fhape into an oblong; and the colours now were not difpofed in circles, but in broad lines of the fame breadth as the bows had been, running along the fhadow of the hole’s Gdes, and in the fame pofition of colours as before. It is evident that. their caufe is the inflexion of the light which comes from the clouds by the fides of the hole (for if the fky have no clouds the colours do not appear) which feparate the white light into the parts of which it is compofed. 7- It is obfervable, that when we look at any luminous bedy at a diftance greater than one or two feet, its flame appears furrounded by two bows of faint colours, the inner— moft of them terminating in a white which continues to the flame; and the colours are red outermoft, and green and blue innermoft : the appearance is moft remarkable if we look at a {mall hole in the window-fhur, the room being otherwife dark; and if the eye be preffed. upon, ana then opened, the colours are more lively than before, as Defcartes obferved * ;- from which both he and Newton concluded that the appearance was owing entirely. to wrinkles formed on the furface of the eye by the preffure +. But this could neither form. * De Mcteoribus, + Leé&. Optic. Seék. III. ad finem, the On the Inflexion, Reflexion, and Colours of Light. 589 the bows with the regularity in which they always appear, nor could the colours be in the order above mentioned from the different refrangibility of the rays: it will alfo be obvious to any one who tries the thing, that the preflure only increafes the brightnefs and breadth of the bows, but does not form them. The true folution of the difficulty feems to be this : The rays which enter the pupil are infle€ted in their paflage through the fibres which extend’ over the cornea, and which are very minute, but opake; by thefe they are decompounded into fringes, having the red outermoft and the violet innermott 3 and the fringes formed by each fibre, being joined:together, form the bow. How then does the preffure enlarge and vivify them? The fibres are naturally extended over the furface of a {pherical fegment : when this furface is comprefled into a plane circle, they are condenfed into a much lefs fpace, and confequently brought nearer to one another; the rays are therefore more in- flected and feparated than before. If this explanation be true, it will follow that the like bows may be produced by fmall'hairs like fibres placed near one another ; and this I found perfectly confiftent with fa@: the bows are in this cafe brighter than in the other; and the fmall hairs on a hat or the hand made them brighter than. any other I have tried: A circumftance which I obferved in both cafes feems to thew clearly the identity of the eaufes; the white fpace which reached from the interior bow to the flame, was fpeckled or mottled ina manner which cannot be ‘eafily defcribed;, but which any one will perceive. upon trying the experiment. 8. The laft of thefe phenomena which I fhall mention is the celebrated one obferved by Sir Ifaac Newton, namely the rings of colours with which the focus of a concave glafs mir- ror is furrounded. Sir Ifaac made feveral ‘moft ingenious and accurate experiments to inveftigate their nature *; and finding their breadth to be in the inverfe fubduplicate: fatio of the mirror’s thicknefs, he concluded that they. were of the fame nature and original with thofe of thin plates defcribed’by him +. ‘The Duc de Chaulnes purfued thefe expe- riments with confiderable fuccefs : he found that the tings were brighter, the nearer to the: perpendicular the rays-were incident ;: and that if, inftead of a concave glafs mirror, ametal - one was ufed, with a {mall piece of fine cambric, or reticulated:filver wire, firetched before it, the colours were no longer difpofed in rings, but in flreaks.of the fame thape with the intervals between the threads : hence he concludes that they are owing to inflexion; that in pafling through the firft {urface they are infleéted, and condenfed by the fecond +, Iam not, 1 own, quite fatisfied with this account of the matter: that they are produced by ine flexion the Duke’s experiments put beyond doubt ; but that they fhould be formed in pafl- ing through the: firit furface, and refleed by the fecond, is quite inconfiftent with the ratio obferved by their breadth, this being greater in the thinneft glafs, and alfo with the order of the colours. Befides, all the coloured images, which fall:on the back fide of the: mirror, will be (by what we before found, when fpeaking of flexibility §) refleted into a: white focus ;. fo that, upon the whole, there appears every reafon to believe that, the rings are formed by the firit furface, out of the light'which, after reflexion from the fecond fur- face, is {cattered, and:pafleson tothe chart. It will. follow, 1ft, that a plane mirror makes. them not ; for the regularly reflected light, not being thrown. to a focus, mixes with the. *-Optics, Book ii. Part IV. + Book ii. Parts I. and If, $, Mein, de MAcademie pour Année 1755. § Pact U1, Obf, 6 of this paper, decom. 59° Ou the Inflesion, Reflexion, and Colours of Light. decompounded feattered light, and dilutes it. 2d, That the nearer to the perpendicular the rays are incident, the more light will be-refle&ted to the focus, and confequently the lefs will dilute and weaken the rings. 3d, That the thinuer the mirror is, or the nearer the two furfaces are, the broader will the rings be. 4th, That the rings farther from the focus will be broader. And laftly, that when homogeneous light is reflected the ‘fringes or images will be larger, and farther from ‘one another in red than in any other primary colour. All which is perfectly confiftent with the experiments of Newton and Chaulnes. There is only one difficulty that may be ftarted to this explanation : How happens it that the colours (made by the mirror) are always circular ?, We anfwer, It is owing to the manner of po- lifhing the concave mirror, which is laid. between a convex and concave plate, and then turned round (with putty, or melted pitch) in the very dire€lion’ in which. the rings: are. If it fiould be asked, Why doesithe thicknefs of the mirrorinfluence the breadth of the rings exactly in the inverfe.fubduplicate ratio? we anfwer, That toa certain diftance from the point of incidence (and the rays are never‘ feattered) far from it) this is demonftrable to hold as a property of mathematical lines in general. ; Having found that the fringes by flexion are images/of, the luminous ee *, [thought that from this confideration a'method of determining the different degrees of flexibility of the different rays might be deduced, fimilar to that which I had formerly ufed for deter= mining their degrees of reflexibility +. Itherefore made the following experiment: | ~ '; . Obf.12.$ Having let into my darkened chamber a {trong beam of the fun’s light, through a hole {{,th of an inch in diameter, I held a hair at four feet from the hole; and receiving the thadow at. two feet from the hair, I drew a line acrofs the middle of the coloured images, and pointed off in each the divifions of the colours, as nearly as I could obferve ; and repeating the obfervation feyeral times, and at different diftances, 1 found, by the fame way I had formerly done in my experiment on reflexibility,, that the axis, or, line drawn through the middle of each, was divided inverfely according to the intervals, of the chords’ which found the notes in an o¢tave, ut, re, imi, fal, lay fa, fi, ut. Butas the meafures in thefe experiments were very minute,and the operations of confequence liable to inaccus . racy, I thought proper to try the thing by another teft. - Ob/. 13, Thefun fhining into the room, as before, I placed’ at the hole an hollow prifm made of fine plate glafs and filled with pure water, its refracting angle being 55 degrees, T he fpeGtrum was thrown! on’ an horizontal chart eight feet from the window ; and ar four feet from the prifm there was placed in the raysia rough black pin =‘:th of an inch in diameter. ‘fie fhadow in the fpe&trum*was bounded by hyperbolic fides, as before defcribed; and drawing a line, which might be the axis of the thadow, and pafs precifely through its middle, I marked on one fide fix or eight points of’ the fhadow’s outline in each-fet of rays 5 and this being often repeated at different diftances and in different {hadows, the pofition of the-axis remaiting the fame, the curves) formed by joining the points, were all parallel; which fhows that*each fine of inflexion taken apart has.a given ratio to the fine of incidence; [afterwards divided the*dxis according torthe mufical intervals, and: thus found where eacli colour of the fpectrum had terminated, in what coloureach»part of the thadows had been; ® Page 539. bas -I |. 4 APage t60. t paint satsts invtlie original; N. ‘ : cbs I sald : , , +8 : and : On the Inflexion, Reflexion, and Colours of Light. 5or and: by what rays formed. Then ¥ joined the parts that I) had marked, and ‘obtained a earve, which I took to be, either nearly or accurately, an hyperbola of the fourth order. I next meafured the ordinates (the axis of the fpectrum and fhadow being the axis of the curve) at the confines of each colour; firft, the ordinate at the extremity of the rectilinear red, then that at the confine of the red and orange, and fo on to that at the extreme recti- linear violet. ‘Lo each of thefe ordinates I added the greateft one, or that in the violet, which (in fig. 10) is VV’; that is, 1 produced vV to V4, fo that VV is equal to-vV 5 and through V’ I drew VR’ parallel to the axis VR, and produced gG to G’, and rR to R/; then from VI fet off V’g’ equal to Gg, and V‘r’ equal to R/r, and the other ordinates in like manner; and I found, according to the method before defcribed*, that WV’ was di- vided inverfely, after the manner of the muficalintervals. It is therefore evident that the inflexibilities of the rays are dire€tly as their deflexibilities and reflexibilities, but inverfely as their refrangibilities. The fame may be proved by meafuring and dividing the images made in the infide of the fhadows. Thefel have found to be at equal incidences: and-dif= tances, equal to the images on the outfide, both in breadth, in-diftance from the edge of the fhadow, and in the relation which their divifions bear to one another ; wherefore what: ever be the ratio of the angle of inflexion to that of incidence, the fame is the ratio of the angle of deflexion to that of incidence ; fo that the angle of deflexion is equal to the angle of inflexion. | If farther proof of this propofition be defired, the following experiment and obfervations, which from the importance of the thing I do not fcruple to nasi man be fufficient. Ot/. 14. When two knife blades were placed by one another in a beam of light iol entered the dark room, fo that the one might form and the other diftend the images, I ‘made in one of-the blades (with a file) a {mall dent, which, om the chart, ‘caft an elliptic or femicircular outline’; then I obferved that the images of both blades were difturbed by it, and wound round the edges of the femicircle; and they were all affeled in precifely the fame manner and degree: So then the firft knife defleéted the images formed by the fecond in precifély the fame degree that it inflected thofe images which itfelf formed, and fo of the other knife; otherwife the effect of the dent would have been different upon the two fets of images. “We may therefore conclude that the angles, or fines of inflexion and de- flexion, bear the fame ratio to the angle or fine of incidence, and that they are equal to one another. My next objeét was to determine this ratio in one of thefe ‘cafes, arid confe- quently in both ; and it was very agreeable to find data for the folution of this problem in | Newton’s meafurement of the i images and fhadow ; fince this philofopher’s well-known ac- ‘curacy in fuch matters, befides the fingular ingenuity of the methods he employed, made me more fatisfied with thefe than any experiment I could make on the fubject. In fig. 17. CS is the line perpendicular to the chart‘SU, ‘and pafling through the’ centre of the body; whofe half is CD or SE.’ EB is: parallel to-'CS, and AT a ‘ray incident’ at D.. AD or EDI is the angle of incidence, EDR that of the red’s deflexion, EDV that of the violet’s, and EDG that of the interniediates.| According to Newton +, CD was'y1,th of aniitich; DE fix inches, SI ,4.,th of an inch, RV +}:th, and ‘confequently. RG ° fethyy GSo wis 7oths 5 esting the angles IDE, rk EDG, and DEY will be found to be 4% 30°35 5.7',and * Page hs, 4 Opes Book ILI. Obf. 3. F fe i [or an pertongs! 9’, refpec- A $92 On the Inflexion, Reflexion, and Colours of Light. 9’, refpeétively. Now the natural fines of 4’, 30"5 §’3 7’ andig’, areas the numbers) 1309, 1454, 20353, and 2617, which are as the fines of incidence, deflexion, and inflexion, of the violet green, and red. Thus the angles of flexion of the extreme and mean rays being given, thofe of the other rays are found by dividing the difference between 1454. and 2617 in the harmonical ratio; for then the red will be equal to 145}, the orange 87,2, the yel-. low 155y's) the green 193%, the blue 1935, the indigo 1293, and the violet 25845 and by adding to the number 1454 the violet, and to their fum the indigo, and fo on, we get the flexibility ‘of the red from 2617 to 24714, of the orange from 24713 to 23843, of the yellow from 2334% to 22294, of the green from 2229} to 20354, of the blue from 2035 + to 18412, of the indigo from 1841} to 1712$, and of the violet from 1712} to 1454, the common ‘fine of incidence being 1309. It is therefore evident that the flexibility of the yed is not to that of the violet as the refrangibility of the violet to that-of the red; and a little attention will convince us that we had no reafon to expeé the analogy fhould be kept up in this refpe&; forthe refrangibility of the rays depends on the {pecies of the re- fraéting medium, and follows no general rule; whereas our calculation has been made concerning the aétion of the bending power at a certain diftance, greater than that whereat the particles of media aét on the rays in refraQting them. It was obferved in the mathe- matical propofitions prefixed to this paper, that the angle of flexion is lefs than that of incidence, when in the cafe of inflexion the angle made by the ray and the body is acute, and when in the cafe of deflexion that angle is obtufe ; and when the ray is perpendicular, or parallel, the angle of incidence vanifhes in both cafes. It is evident therefore, that in both thefe fituations of things the ratio of 1309 to 2036 being that of a lefs to a greater, will not enable us to find the angle of flexion, although it ferves very well when the ray before inflexion makes an obtufe, and before the deflexion an acute angle. 1 have there- fore mentioned the angle made by the bent ray with the incident, which gives a general formula; for let the angle of incidence’ be I, and that which the bent ray makes withthe incident B, then F being the angle of flexion, we have F = B +1; fo thatifI =O, F=B, or if the incident makes an obtufe angle with the body in the cafe of deflexion, and au acute in that of inflexion, then F = I — B, and in the remaining cafe F = 1 + B. Thefe obfervations enable us to give a very fhort fummary of optical feience. When partictes of light pafs at a certain diftance from any body, a repulfive power drives them off; at a diftance a little lefs this power becomes attractive: at a ftill lefs diftance it again becomes repulfive ; and at the leaft diftance it becomes attractive, as before, always acting in the fame direCtion, Thefe things hold, whatever be the direction of the particles; but if, when produced, it pafles through the body, then the neareft repulfive force drives the particles back, and the neareft attrative force either tranfmits them or turns them out of their courfe during tranfmiflion. Farther, \the particles differ in their difpofitions to be ated upon by this power in all thefe varieties of exertion ; and thofe which are moft ftrongly affeSted by its exertion in one cafe, are alfo moft ftrongly affected by that exertion when varied, except in the cafes of refragtion, of which we before {poke ; and'thefe difpofitions of the parts are in all the cafes in the fame harmonical ratio. Laftly, the caufe of thefe dif- ferent difpofitions is the magnitude of the 'particles being various. All that remains now to be done on this part of the fubject, is to explain one or two phenomena relating to reflexibility. 2 1. It 7 \ On the Iuftexion, Reflexion, and Colours of Light, 593 1. It has been remarked, that if we look at a candle, or other luminous body, with our eyes almoft fhut, bright ftreaks feem to dart. upwards and downwards from it. Newton* explains this by refraction through the humours adhering to the eyelids; Rohault # and Mr. Young ¢ afcribe them to refléxions; Defcartes makes them arife from wrinklesion the eye’s furface ; De la Hire from refraGtion through the moifture on tlre eyelids, as through a concave lens; and Prieftley || from inflexion through the lafhes. The truth of Sir Ifaac’s obfervation is obvious, becaufe the ftreaks which dart from the top of the luminous ‘body are formed by the under eyelid, or at leaft by the moifture adhering to the under ciliary procefs, and thofe which appear from the bottom of the body by the upper eyelid; which could not be, either if they were formed by reflexion from the procefles, or by inflexion through the lafhes. I have however obferved another kind of ftreaks, mottled with broken colours of all kinds, and formed by reflexion from the moifture on the proceffés. ‘In thefe the under freak correfponds to the under procefs, and wice verfa. They may be formed by any po- lifhed body held in the proper pefition between the pupil and luminous body. The colours are very beautiful when made by the fun, and refemble, in form and irregularity of arrange- ment, fome of the ftreaks made by large half-polifhed bodies, as deferibed in Part If. of this paper. ; 2. The next obje& of attention is one of the greateft importance to our theory, namely, the formation of images by reflexion. Three things here require explanation : the nuitber of the images, their colours, and their variations in point of fize. - 0b/: 15. I have uniformly found that no refle€ting furface forms them except it be curve, _ and (its furface) of a ftru€ture fomewhat fibrous. A plain mirror, nor a concave, nor a ‘convex one, do not make them; unlefs they are of that ftru€ture; and for the fame reafon ‘quickfilver, when held fo as to reflect the light incident upon it, forms them not ; but by tri- turating it, fo as to divide it into fmall particles, and by placing thefe in the beam of the fun’s light, each particle formed an image with the colours in the regular order, and very bright. On holding a cylinder in the rays, and obferving the lengths of the images, I found that if the curvature was increafed, the images were alfo increafed in fize, being more diftended and highly coloured. Thefe things immediately fuggeft the explanation, Each of the {mall fibres forms an image, which, from the different reflexibility of the rays, is divided into the feven primary colours. But why does not a plain mirror form one of thefe upon the fame principles? In fig. 12. let AE be the curve furface of a very convex mirror, that is of a {mall fibre, GC a ray reflected by the {mall furface DC. It will be fe- parated into CI red, and CK violet, by the unequal ation of FC on its parts. But if DC is continued to L ina ftraight line, then LC’s {phere of reflexion extending a little way be- yond it to KC, the part neareft to C, and not to IC, will drive KC, and alfo the indigo and part of the blue, nearer to the perpendicular ; then IC being within LC’s {phere of inflexion, will, together with the orange, yellow, and part of the green, be brought nearer to KC; fothat IC and KC will both be brought to an angle equal to that of incidence, and will be reflected in a parallel white beam, If LC is removed a little, or the furface becomes more convex, * V.c&. Opts Scét. IIT. ad finem. + Phyfica, p. 249. Clark’s edit. t Phil. Tranf. 1793. |] On Vifion, vol. ii. Vou. L—Marcu 1798,—Surrr. 4G Ic $94 Phenomena dependent on the Reflexion of Light. IC is attraéted, and KC repelled, but not fo much as to reduce them to parallelifm and whitenefs ,; an image being formed narrower, and lefs coloured, than when LC is moved fo far round that KC is attracted, and IC deflefted or repelled. If LC is moved round, fo that the mirror is concave, then KC is repelled and IC attracted, as before, unlefs the curvature be confiderable ; and then KC and IC are both repelled, and an image formed in the cauflic by reflexion. In Oé/. 3. we found that certain irregularities in the furface of the refleCtor caufed the images to be in the inverted order of colours. How does this hap- pen? In fig. 13. letg f, fe, er, ri, and ih, reprefent the fe€tions of the convex fibres on the furface of the reflector, and let the ray AB be reflected from ef, feparated into Br red and Bv violet ; then if AB was fo inclined to ef, that Br and Bw fell upon er, the fide of the fibre next to ef, and a little larger than éf, it is evident that Bv will be refleted into vV, and Br into rR, and an image VR will be formed, having the violet outermoft, and the red innermoft, the intermediate colours being in their order from V to R. Laftly, it is evident that the greater the angle of incidence is, the longer will be the image, and the farther fe- parated its colours ; for which reafon the farther the images are from the fhadow, the lefs dilated and coloured will they be. Nor will they have the fame appearance at all diftances from the point of incidence. Very near it they will be all in the form of fringes acrofs the ftreak, the breadth being greater than the length (if I may ufe the expreffion) ; but as we recede from it they will become diftended, as before defcribed, the length increafing fafter than the breadth, and at one point or diftance they will be juft as long as broad ; all which agrees with experiment. And it is needlefs to fhow by particular demonftration, the manner in which one image is divided from another, the reafon obvioufly being the manner in which the fibres on the refleGting furface are arranged and inclined to one another. ' 3: A number of phenomena involved in that of the images are explicable by what has been faid on them. If a piece of metal be fcratched, and then expofed in the funfhine, a number of broken colours will be formed by the fcratches, as may be feen either by let- ting them fall on the eye, or by receiving them on a white obje&t. This is evidently owing to the different reflexibility of the rays incident on the fcratches, which are fo many irregu- lar fpecula, of great curvature ; the images are therefore diftorted and broken, juft as a can- dle, &c. appears broken and coloured when viewed through a piece of irregular cryftal, fuch as the bottom of a wine glafs. If we look attentively at any object expofed in the light of the fun, provided it be not polifhed, we fhall fee its furface mottled with various points of colours from the fpecular nature of its minute particles. If we look towards the fun with a hat on our head, held down, fo that the fun’s dire& light may not fall on our eyes, but on the hairs of the hat, and be refle€ted, we fhall fee a variety of lively colours darting in all dire€tions from thofe hairs ; and we may eafily fatisfy ourfelves that they are not the confequence of flexion, by trying the fame thing with unpolifhed threads ; in which cafe they do not appear, provided the threads be not very fmall. In the fame manner we may account for the colours of {pider’s webs, of different cloths which change their colours when their pofition is altered, and of fome foffils which appear of different ftreaks of ca- lours when held in the light ; fuch as the fire marble of Saxony, &c. All thefe bodies hay- ing furfaces of a fibrous ftru€ture, each fibre reflects and decompounds the rays. 4. The confideration of the foregoing phenomena inclined me to think that, upon the 3 principles Error of the common Doftrine of the various Reflewibility of Light. 595 Principles which have been laid down, the colours of natural bodies may be explained. The celebrated difcovery of Newton, that thefe depend on the thicknefs of their parts, is de- graded by a comparifon with his hypothefis of the fits of rays and waves of ether. De- lighted and aftonifhed by the former, we gladly turn from the latter; and unwilling to in- volve in the fmoke of unintelligible theory fo fair a fabric, founded on ftri&t industion, we with to find fome continuation of experiments and obfervations, which may relieve us from the necefity of the fuppofition. My fpeculations on this fubje&t have by no means been completed, as I have not yet finifhed the demonftrations and experiments into which it has engaged me to enters but in order to complete my plan I fhall offer a few hints on the fub- je&t :—The parts of light are affirmed in Prop. III. Book I. Part I. of the Optics to be dif- ferent in reflexibility ; that is, according to the author’s definition, in difpofition to be turned back, and not tranfmitted at the confines of two tranfparent media. That the demonftra- tion involves a logical error, appears pretty evident. When the rays, by refraction through the bafe of the prifm ufed in the experiment, are feparated into their parts, thefe become divergent, the violet and red emerging at very different angles, and thefe were alfo incident on the bafe, at different angles from the refra€tion of the fide at which they entered : when therefore the prifm is moved round on its axis, as defcribed in the propofition, the bafe is neareft the violet, from the pofition of the rays by refraétion, and meets it firft; fo that the violet being reflected as foon as it meets the bafe, it is refleted before any of the other rays, not from a different difpofition to be fo, but merely from its different refrangibility. Although then this experiment is a complete proof of the different refrangibility of the rays, it proves nothing elfe ; and indeed an experiment will convince us that the rays all have the fame difpofition to be reflected, provided the angle of incidence be the fame. For I held a prifm vertically, and let the fpectrum of another prifm be reflected by the bale of the former, fo that the rays had all the fame angle of incidence ; then turning round the vertical prifm on its axis when one fort of rays was tranfmitted or refle€ted, all were tranfmitted or refleted. We cannot therefore apply the different reflexibility of light to the explanation of the colours of bodies, fince this property has no exiftence. But we have fhewn that the rays differ in reflexibility, taking the word in the new fenfe, as explained above. Let us fee whether this principle will not folve the important problem. It is evident that the particles of bodies are fpecular. Now, I take the colours of bodies to depend not on the fize, but on the pofition, of thefe particles, or at leaft on only the fize in as far as it ine fluences their pofition ; an idea perfelly familiar to mathematicians. . Obf: 16. In making fome of the experiments which I related above, on the reflexibility of light, I obferved, among the regular images made by moft of the pins which I ufed, one or two all of the fame colour, as red, blue, &c.; and when the pin was moved thefe moved alfo, becoming of other colours in regular order like the reft ; which fhows plainly that their being of one colour at firft was owing to fome fibre in the furface jutting out, or ra- ther to feveral of thefe, which {topped the red and all the reft but the blue of feveral images, or the blue and all the reft but the red. Farther, I produced feveral regular images by two or three very {mall pins, and with confiderable trouble. I at laft contrived to place them in fuch a pofition, as that one blue colour of confiderable fize might be produced, then a red, and fo on, by altering the pofture of the pins. Now whether the pofture or the fize be al- tered it matters not, for the one affects the other. Is it not evident that this experiment, 4G2 and 596 Cart of the Colours of Natural Bodies. and the conclufion to which it evidently leads, may be transferred to the colours of natural bodies, as feen by reflexion? For, the parts being fpecular and {pherical, each will form an image of the luminous body ; and by the pofition of the fides of the neighbouring ones, any fix of the colours may be {topped while the feventh emerges; and if this happens in one part it will happen in all, fince, that the texture and fize of the parts is the fame throughout has never been called in queftion. But it will be afked, How are the particles to reflec a mixture of different colours? We anfwer, That a particle having its fide concave and front convex will produce the effeét; for the colours will be thus mixed in a proportion deter- mined by the pofition of the others. How can whitenefs and blacknefs be produced? If the particles be large, then the whole light incident on each will be reflected and feparated, and all the images being compounded and mixed together, a confufed fenfation, or a fen- fation of white, will be the refult. For, the parts being tranfparent, and the images formed by the convex furface of the fecond row of particles, thefe will be larger in proportion to the thicknefs of the particles or plates through which they have to pafs before they meet with obftru€tion, and confequently will not be {topped by other particles; and in like manner: the colour will be red if the particles are a little lefs, and fo on. If the particles be very fmall, the light will be feparated into images alfo fmall; with which and with one another the particles interfering, the light by many reflexions and obftruCtions will be totally loft. How do bodies appear of their proper colours, though no luminous body be fhining whofe image may be formed by a reflexion? They refle&t images of the clouds which refle& the fun’s white light ; for if we hold between our eye and a hole in the window illuminated by the light of the clouds a refle€ting body, as a pin, &c. coloured images are formed of the hole diftended, like thofe of the fun, as I have often found; and the fame holds of inflexion. Why does cutting a body to pieces not Alter its colours? This only changes the pofition of mafles of particles, not of the particles themfelves ; but if by bruifing them we change their magnitude and. pofition, we change alfo their colonr : thus the leaves of vegetables bruifed in a mortar, many paints powdered, &c. Why do many bodies change colours when viewed in different pofitions ? Becaufe they refle&t two colours or more of each image to different quarters; and it matters not whether their pofition with refpeé to us, or our pofition with refpect to them, be changed. How do bodies become coloured by tranf- mitted light ? Becaufe the foregoing reafonings apply alfo to the flexion of the rays in their paflage through the parts of bodies. Thefe obfervations appear to me to furnith a very fimple folution of the problem. I fhall endeavour in a future communication to confirm what has been faid by other remarks and experiments; for it would be tedious, and per- haps fuperfluous, to illuftrate what has been faid by figures and demonftrarions *. Purfuant to thefe remarks, it will not be difficult to account for the rings of colours of thin plates by reflexion, as we before did thofe of thick plates by flexion +. Indeed, thofe formed in the experiment of the two lenfes, fuppofed by Newton to be owing to the plates. * It is obvious that the different refrangibility of the rays-will not account for the bright and diftiué colour of bodies. If the refraéting angle of a prifm be continually diminithed, till, for example, it is equal to one of a minute, the refraction will produce no fenfible colour. Indeed, almoft every piece of plane glafs has its fides in a fmall degree inclined to one another, and yet no colours are formed. Much lefs then will refraétion through the infinitely fmaller parts-of bodies produce feparation of the rays. t Page 589. of ~ Habitudes of Light—Chemical Nomenclature, 597 of air between them, appear to have a different caufe, as may be without mueh reafoning gathered from the curious experiments of the Abbé Mazeas*, and even from one or two of Sir Ifaac’s own, in which he fuppofes fome medium more fubtle than air to be between the glaffes+. But at prefent I forbear entering into the fubjeé&t any farther, This paper has already been extended to a greater length than was at firft intended. And I haften to conclude by a fhort fummary of propofitions, containing the principal things which have been demonftrated in the courfe of it. Prop. I. 'The angles of inflexion and deflexion are equal at equal incidences, Prop. Ul. The fine of inflexion is to that of incidence in a given ratio (which i deter- mined in the paper). ; Prop. Ml. The fun’s light confifts of parts which differ in degree of inflexibility and de- flexibility, thofe which are moft refrangible being leaft flexible. Prop. WV. The flexibilities of the rays are inverfely as their refrangibilities; and sie {pec- trum by flexion is divided by the harmonical ratio, like the fpe€trum by refraCtion. Prop. V. The angle of reflexion is not equal to that of incidence, except in particular (though common) combinations of circumftances, and in the mean rays of the fpeétram. Prop. Vi. The rays which are moft refrangible are leaft reflexible, or make the leat angle of reflexion. Prop. Vit. The reflexibilities of the different rays are inverfely as their refrangibilities, and the fpe€trum by reflexion is divided in the harmonical ratio, like that by refraétion. Prop. VIL. The fines of reflexion of the different rays are in given ratios to thofe of incidence (which are determined in the paper). Prop. 1X. The ratio of the fizes of the different parts of light are found. Prop. X. The colours of natural bodies are found to depend on the different reflexibilities / of the rays, and fometimes on their flexibilities. Prop. XI. The rays of light-are reflected, refra&ted, infleéted, and deflected, by one and the fame power varioufly exerted in different circumftances. —aaaeeS=qreoouoanuunuu LL e—————————E— Ill. On certain Points of Nomenclature. By a Correfpondent, To Mr. NicHozson, SIR, -T appears to me, that the new name fartarin, propofed to defignate thefubftance com- monly called vegetable alkali, is more objectionable than fome of the number of names which are in ufe. 1. Becaufe the word tartar is familiarly known to always denote a falt of acid propertics, which confifts of nearly three parts of tartareous acid, and one of vegetable alkali. 2. The word tartareous acid, which is already employed to denote the acid contained in tartar (and for which fub{tance there is no other name), fo nearly refembles the word fartarin . as to make this name an improper one for the alkali of tartar and of vegetables in general. # Mem, de l’Academie pour l’Année 1738, + Optics, Book ii, Part T. Obf, x. and xi. 3: But 598 On the Nomenclature of Alkalis, °c. 3. But a very fmall proportion of alkali is obtained from tartar comparatively with ‘that got from other fources ; and it feems at leaft as improper to call it ¢artarin becaufe it is gotten from tartar, as it would be to call it fern alkali, wormwood alkali, beech alkali, &c. I agree thatthe name fot-a/h is very objeGtionable, and I with that another could be thought of that is appropriate, efpecially becaufe this word is commonly underftood in commerce and in the arts to denote the vegetable alkali in its ordinary mild but impure ftate, as ufed in manufatories ; in which ftate the alkali is only partially faturated with carbonic acid, and which therefore fhould be called, according to the new nomenclature, fub-carbonate of pot-afb ; whereas, in the new fyftem, the name pot-afh is intended to fignify the alkali in its pure or cauftic ftate. Confidering, sft. That the alkali called pot-afh is very generally diffufed through the whole vegetable kingdom, which neither of the other fpecies of alkali are—2. That the other fixed alkali, commonly called foffil alkali, or foda, exifts principally in the mineral kingdom—3. That the volatile alkali or ammoniac is obtained almoft entirely from the animal kingdom —4, That the denomination vegetable alkali is {till very generally employed, and has been fo for a very long time—5. That the three alkaline falts refemble one another in fo many properties as to form a natural genus which may continue to be denominated alkali :—\fay, from thefe confiderations it feems beft to retain the former f{pecific terms veges table, foffil, and volatile alkali; but abbreviated, as propofed fome years ago by Mr. Chriftie, and accordingly to employ the names vegalkali, fofkali, and volkali, till more appofite names be fuggefted. Give me leave to remark, that Englifh writers are not uniform in their online of feveral terms of the new fyftem, and I apprehend fome of them write improperly for inftance : We hear alfo fometimes erroneous profody, for inftance ca/aric for caloric. Oxigen and oxygene for oxygen. Hidrogen and hidrogene for Aydrogen. Oxid and oxyde for oxide. Sulpha¢ and fulfate for /u/phate. Sulphi# and fulfite for /u/phite. Muriat, &c. &c. &c. for muriate. Calorique for caloric. The French writers uniformly write gaz, and the Englifh generally gas. In the Englifh, either mode may be employed; but the French probably prefer their orthography gaz on account of the word gas founding too much like another word in their language which excites an jndelicate idea, Feb. 175 1798- I am, Sir, your fincere friend, A VERY HUMBLE PHILOLOGER. NEW Account of Books. 599 NEW PUBLICATIONS. Effai fur les Ouvrages Phyfico-mathématiques de Léonard de Vinci, avec de Fragmens tirés. de fes Manufcrits apportés de Italie. Lu & la premiére Claffe de I’Inftitut National des ' Sciences et Arts. Par J. B. Venturi,-Profefleur de Phyfique 4 Modéne, de I’Inftitut de Bologne, &c. A Paris, chez Duprat,1797.—Or, An Effay on the Phyfico-mathematical Works of Leonardo da Vinci, with Extra&ts from his Manufcripts brought from Italy. Read before the Firft Clafs of the National Inftitute of Sciences and Arts. By J. B. Venturi, Profeffor of Natural Philofophy at Modena, Member of the Inftitute at Bo- Jogna, &c. Quarto, 56 pages, with one plate, Aone the treafures of fcience and art which the French have lately brought from: Ttaly, are thirteen manufcript volumes written by Leonardo da Vinci, whofe extraordinary powers as a painter, fculptor, mufician, geometer, philofopher, and engineer, are well known. Citizen Venturi, who refided in France during the war in his own country, has obtained the communication of thefe manufcripts, aud has felected fuch parts as appear deferving of pub- lication, which he purpofes to print in three feparate and complete treatifes, on mechanics, hydraulics, and optics. The fragments in the prefent work are for the moft part difting. and feparate from thofe principal matters, and are enriched with notes by the editor. Leonardo was born in 1452. He was the natural fon of a notary, whofe family poffeffes. at this day at Vinci in Tufcany the fituation of refpe€table mediocrity. Nature, which, as C. Venturi obferves, is not actuated by confiderations of birth, was prodigal of her gifts to this man.. His perfon was beautiful ; his difpofition animated and lively, and the powers of his mind wonderful. He applied to geometry, mufic, and painting, and in each of thefe purfuits he foon excelled his teachers. He was called to Milan to caft an eque(trian ftatue in bronze, which Louis Sforza confecrated to the memory of his father. He offered his fervices to the Duke in every undertaking relating to military machines, water-works, {culpture, mechanics, and painting, with a defiance to any one who fhould pretend to excel him ; a boaft which indeed he had the means of fupporting. When France took poffefion- of the Milanefe at the end of the rsth century, he paffed feveral years at Florence; not becaufe he was in any refpect prejudiced again{t the French, as is reported ; on the con- trary, Louis the XIIth gave him a penfion, together with certain duties on the Milanefe canals, where Leonardo was employed under the French government. While he was at Florence he fele€ted two of the moft beautiful ladies of the country, with the intention: of drawing their portraits, and prefented them to Louis the XIIth. He left Milan, and ree. "paired to Rome in 1513, after Sforza had again entered the Milanefe; after which he went to France on the invitation.of Francis 1, where he died, as it is faid, in. the arms of. that prince. I fhall forbear at prefent to enter into any detail refpeCting the contents of this interefting work, in which this great genius, who preceded Chancellor Bacon in the true method of. philofophifing near a century, has the peculiar felicity of an editor and commentator,. whofe valuable annotations befpeak him a complete mafter of the fubjects of fcience and yefearch he has undertaken to publifh and elucidate. On a future occafion I fhall prefent, my readers with fome extracts of the moft curious parts, ‘ Phyflology ; 600 New Publications. * Phyficlogy ; ; or, An Attempt to explain the Funétions and Laws of the Nervous S tte the Contra€tion of Mafcular Fibres, and the ¢onftane and involuntary AGlions of t Heart, the Stomach and Organs of Refpiration,.by Means of fimple, univerfal, and varying Principles. ‘To which are added, Obfervations on the intelle&ual Oneal of the Brain; and on the Diverfity of Seafations; with Remarks on the Effe&ts of Poifons, and an Explanation of the Experiments of Galvani and others on Animal Elec- tricity. By E. Peart, M.D. &e. 8vo. 327 pages. W. Miller, 1798. Lhave juft received this work; for which reafon I can at prefent only announce its publication, and fay that. the author's explanation of the phenomena mentioned in the title'appears to be founded upon the fyftem which he offered to the world in his Lle- mentary Principles of Nature publithed in 1789. Travels inthe Two Sicilies, and fome Parts of the Apennines. , Tranflated from the origi« nal Italian of the Abbé Lazzaro Spalianzani, Profeffor Royal of Natural Hillory in the Univerfity of Pavia, F.R.S. &c.&c. In Four Volumes 8vo. 1500 pages, wie - x1 Plates. Robinfons, 1798. . This célebrated philofopher had the good fortune to obtain a clear and diftin@ view of three out of the four craters whic ave ftill burning in the volcanized countries through which he travelled, namely, Etna, Stromboli, and Vulcano, of which he ‘has-given defipns; — but at Vefuvius his with could not be gratified. The Lipari Iflands have been the fubjedt of his afiduous examination, as well with regard to their igneous produ€tions, as the’ ftatey charater, and occupations of the inhabitants ; and the environs of the unfortunate city of Meffina afforded much information, from the variety of natural’ objets they préfenteds Scylla and Charybdis; the fitheries in the Straits of Meflina for the fword-fifh, the ravenous fhark, and for coral, with various other interefting: abjedds, ‘alfo enpaeee his ate” tention during his excurfion in the year "1788-89... i gpekigrd § bs “To fay that thefe volunies contain a treafure of . geological, and chemical information 423 is fecarcely neceflary to thofe who are acquainted — with the former labours of the Profeffor. I muft therefore more particularly obferve, that he has'traverfed thefe intereft- ing diftri€ts, contemplated and compared the volcanic produdls: with a particular regard to local circumftances, and the inferences to which thofe circumftances lead; exe amined the feveral fubftances with every precaution which the difficulties of fixing the external chara&ters and obvious properties could fuggeft ; fubmitted them to the action of fire before the blow-pipe, and in the furnace, with the pyrometer of Wedgwood and pneumatic apparatus ; and laftly, that in fuch fpecimens as could not from their external characters be referred to known earths already analyfed by chemifts of reputation, he has had recourfe to the methods of humid analyfis. Where his experimental enquiries have proved concife, he has frequently incorporated them with the account of his journeys ; but where otherwife, he has placed them with fuch fubjects of general difcuffion as could not form a part of his narrative in the order of time. From this rapid fketch of his method of proceeding, the reader, who may be acquainted. swith the advantages which the modern improvements of Chemiftry mutt afford in the hands of an enlightened obferver, will be able to form fome eftimate of the value of the work. END OF THE FIRST VOLUME, @Dilout ve {ty iba Philos. Journal, TLL PLAX facing p.600. 7 oe Fg i ? re NC: Rea ppt gi Valery eJuuls 7 ‘ eh’ * SA) Journal VAl IT PLNXV Facing p.600. , ue “ = He eSevwowicrur of Wilby « Ynorrls, a7 % choa siz Sa3 ni i ae ous ee Mitte,