eee ee pe 797 SO IE AO es taht de Hee 7 2 Sate ee : a fA RNAS Sit BHC eRS OMe coe : as ree : : Pig nee ? $ : ‘ § “ ey tytish =a 916 : Aargitahaiae TE fe Aoritenaini ne fe eT oe YS east SS = sip at Sine t 2 ind eer wt - peo pe ee : ; tain ‘ ‘ e ‘ Taf Te fre te pA We hehe GFE sim SAREE A ag ins 4, ee : aS si Smee! x = : est te: oe aS a ore rea % f meters Z - een ermal RE an eres fe sr tge 3 ae MIN en enin A dniatn s ~ OY ete me iy SN tpt. it hn me “>: 4 pdt t P Teles Sneting Mapa Ghy NB ie! hee - ? . , ~ fon omic eet ataey nr au y : eas % c : Sir Ree Th ne neat . Ne ee ee ee et ‘ Veto « . . Pte : tae " eek ees aia ee natin: Boa 2 shar et Brg BP Ned 0 NM * - <4 oe es te edie = eee Sooty 2 Be iT Pam t_D ~~ " ; etter ae “ 5 Sa Wi i ME seas - pete Pal + aa : + . Pe 4 ~ ‘ * earn * ? - es Fe iad eta ees 3 es : Pen . cae : : Lies ° . oe ‘ : ai arse Peres utnenr : < nie ie aes “ Fe * r e a ' + % by tes ibn, oo deep Gtr tr wolse tes = eg rt “ , Me 4 Figd Z r “: ‘ Cte ee ee fem> Wome std My ore Togs ore ae ge ee F pe in é ofeawitan °* one eee hak dh Ae tnt tele, nal ae ee Yr ie tea) OR) ee . i ats, Bit y Wed T H EK M i) o - LONDON, EDINBURGH, ann DUBLIN PHILOSOPHICAL MAGAZINE AND JOURNAL OF SCIENCE. CONDUCTED BY SIR DAVID BREWSTER, K.H. LU.D.F.R.S. L. & E. &c. RICHARD TAYLOR, F.L.S.G.S. Astr.S. Nat.H. Mose. &c. RICHARD PHILLIPS, F.R.S. L.& E.F.G.S. &c. AND ROBERT KANE, M.D. M.R.LA. ‘‘Nec aranearum sane textus ideo melior quia ex se fila gignunt, nec noster vilior quia ex alienis libamus ut apes.’ Just. Lips. Monit. Polit. lib.i. cap. 1. VOL. XVII. NEW AND UNITED SERIES OF THE PHILOSOPHICAL MAGAZINE, ANNALS OF PHILOSOPHY, AND JOURNAL OF SCIENCE. JULY—DECEMBER, 1840. LONDOW: RICHARD AND JOHN E. TAYLOR, RED LION COURT, FLEET STREET, Printers and Publishers to the University of London ; SOLD BY LONGMAN, ORME, BROWN, GREEN, AND LONGMANS; CADELL; SIMPKIN AND MARSHALL}; S. HIGHLEY ; WHITTAKER AND CO.3 AND SHERWOOD, GILBERT, AND PIPER, LONDON: — BY ADAM AND CHARLES BLACK, AND THOMAS CLARK, EDINBURGH; SMITH AND SON, GLASGOW ; HODGES AND SMITH, DUBLIN: AND G. W. M. REYNOLDS, PARIS. Tue Conductors of the London, Edinburgh, and Dublin Philosophical Maga- zine, have to acknowledge the editorial assistance rendered them by their friend Mr. Enwarp W. Braytey, F.L.S., F.G.S., Assoc. Inst. C. E.; Corresp. Geol. Soc. of Cornwall, and Philos. Soc. of Basle; Hon. Mem. S. Afric. Inst.: Librarian to the London Institution. CONTENTS OF VOL. XVII. NUMBER CVII.—JULY, 1840. Prof. Johnston on the Iodide of a new Carbo-hydrogen...... Prof. Forbes on the Optical Characters of Greenockite (Sul- SE ANIACGE TG TLE TT EET) (ag rae rear maira i hier Peale Dr. Foville on fhe Anatomy oO. taccloisil. . 2... sss aoe ss: Dr. J. Reade’s Remarks on the permanent Soap Film and on MERE C so te Se be we eit soos are ain Saree Prof. Miller on the Form and Optical Constants of Nitre .... Mr. R. Rigg’s Observations on Mr. Smith’s Experiments on REMMI TULGER es cn Se wn are okt craggy vere ie eet Mr. C. Holthouse on Increasing the Light of a common Argand (ELIE D 2 sty Ree ma ial, Tete ig sci lang om a MR Dr. R. Hare’s Letter to Prof. Faraday, on certain Theoretical (LE ESR ae ac A a Bi a ho Ae eer Prof. Faraday’s Answer to Dr. Hare’s Letter on certain Theo- SUP MrG RHR ONPMEMES egal. w8e ss Geta once a Pe ek he eae ae New Books :—Dr. Meyen’s Report on the Progress of Vegeta- le Physiology during the year 18370 eee Proceedings of the Geological Society ye at the Friday-evening Meetings of the Royal In- SRMRTN otniecteee hoe oe eae ee ns sanyo ics AO ops ole ys ae Letter to Prof. Liebig on the Theory of Substitutions........ Memeeciearmation of Lampic Acid .... 2... ...0/.2. 508+. e's mamalysis of the Ashes of the SalsolaTragus ...........-+% Meecompined Eyposulphurous Acid. 2). 020s yews see eee ss On the Presence of Iodine in Cod Oil, by R. F. Marchand .. Mr. M’Cord’s Observations on the Solar and Terrestrial Ra- Meteorological Observations for May, 1840 .............. Meteorological Observations made at the Apartments of the Royal Society by the Assistant Secretary, Mr. Roberton ; by Mr. Thompson at the Garden of the Horticultural Society at Chiswick, near London; by Mr. Veall at Boston; and by Mr. Dunbar at Appiegarth Manse, Dumfries-shire : Table... NUMBER CVIII.—AUGUST. Rey. B. Powell on the Theory of the Dark Bands formed in the Spectrum from partial Interception by transparent Plates .. aZ 44 80 81 i a lv CONTENTS. Page Dr. J. Apjohn on the Potatoe-Spirit Oil of the French Che- : Mmistse 48.0.9. ge a! ae ahatenay eae piotearals'. ake’ sc se 86 _Observations on the Climate of Italy and other Countries in ) Sancient times i... 5.5204 eee 1 I 92 Mineralogical Notices. Communicated by Prof. Miller...... 102 Dr. Theodore Scheerer’s Observations on Hiaolith and Nephe- WNC ees Vie ORR ES WA eee er 105 Dr. Kane on the ‘Theoretical Constitution of the Compounds of AUTOM ONIA. ci'8..3 septa RO McA 5, ues = Ce SPs sie ne 120 Mr. E. A. Parnell on the Composition of Inulin............ 126 Mr. C. T. Coathupe on certain Effects of Temperature ...... 130 Mr. R. Thomas’s Remarks on some Tide Observations, published in the Transactions of the British Association....... oe 134 Mr. Gulliver’s Observations on the Blood Corpuscles, or Red Particles, of the Mammiferous Animals.................. 139 Froceedings.of the Royal Socetyy ..... .- is 4+ <<. «eee 142 — Geological Society =... > /.. +... 149 —_—————— _ Royal Irish Academy.................. 153 Cambridge Philosophical Society ........ 154 Urine, ofythe Wlephant ). <3). rs weeps de Sea eu oe 156 Wel ya Kae. ii! ak Ge dais cd abit. domain 156 On the Reduction of Potassio-chloride of Platina ....,..... 157 Dy. Barry, on the Corpuseles of the Blood... .... 2.5.:meeume 157 Acechior-platimayy yey. ee fs el le eos a 157 Nutrites,formed) by;direct Combination, 7)... 7)... > as) eee 159 Metecrological Observations for June, 1840 ............ 0 Soe UBIO 6 caspase sire Palvmnanceomeccas’ aetien Syst. tet eeee 160 NUMBER CIX.—SEPTEMBER=s Mr. Griffith’s Reply to that part of Mr. Weaver’s Paper re-~ lative to the Mineral Structure of the South of Ireland, which has appeared successively in the Numbers of the Philosophical Magazine for April, May, and June, 1840 .......,...... 161 M. Dumas’s Memoir on the Law of Substitutions, and the Wheory of Chemical Types (concluded). .. «1%. 9: an ee 179 Mr. A. Smee on the Ferrosesquicyanuret of Potassium........ 193 Mineralogical Notices. Communicated by Prof. Miller (con- BEOHEO esc). 5. ioe ataed Seed neeaminete s (= ete ul aac aye ane 202 Mr. R. Hunt on the Use of Hydriodic Salts as Photographic BNO OMNES oo bin ele glia die le city on 4 Sus piesa ee eins 202 Mr. S. Woods on the Anthracite Coal of South Wales ...... 211 Mr. A. Crosse on the Tension Spark from the Voltaic Battery 215 — Dr. Draper on the Process of Daguerreotype, and its appli- cation to taking Portraits fromthe Life, . ..... vsiclse.c pune Proceedings ut the Geological Society, ... 2.5.0.) 26 eee 226 CONTENTS. Vv Page Berenomens bf; Calefactian sss sid oie 'b tsi (eels Wl oye sels ie 230 emmemeneee OMe EMME SFP esos 5 Sof crate) ohh fe} of bye +, wo, v8 ol 231 Dee NG Pe ye ido slant -22) ep edbe el Ar Mey enendy 231 Composition of crystallized Phosphoric Acid ,............. 232 Detection of Alcohol in Essential Oils...........-.-.0060. 232 Ciconomical Preparation of Acetone. ....... 0600.0 02 en eee 233 BONN Ed OF ATTRA pcg. crs sat rin yids Shs stake Tosoaes: ean + Peaigoushase eS 234 UPC CATIONIC, 0). °4. yn, iet atm ccm «Poh aide me} ple “estes pee eke 235 See clienin, by: Mons.:C. Gerhardt, 3. on jee eed ai a aga dauns 236 Chemical and Contact Theories of Voltaic Electricity ...... 237 Hydromellonic Acid and Metallic Oxides.................. 238 aR ER ae Dy be airy lcd aie is wi wm aims es eer ese werent 239 Meteorological Observations for July, 1840................ 2389 —__-_—— ea oR ices vod orecatelenskenetaimearbyockish sim 4y'apete 240 NUMBER CX.—OCTOBER. M. Jacobi’s Comparative Measure of the Action of two Voltaic Pairs, the one Copper-zinc, the other Platina-zinc........ 241 Mr. R. Potter on the Application of Huyghens’s Principle in Ree ORO TGS soa os cepa Ae Sh alecais WUD 5 -svatemeneinete 243 fags Parnell:on Sulphocyanogen! 0) 4.2%)... 02 2s. yee - 249 Mr. R. Hunt cn the Use of Hydriodic Salts as Photographic ReER SON LCLIACU, Vice cic io we evant ele MIA, We ei ee, 260 fee ter on the Form of Ritilesch as inal. de ek 0). 268 Mr. C. W. Hamilton’s Note upon Mr. Griffith’s Paper ‘* upon the true Order of Succession of the Older Stratified Rocks Pe aieiatbey And. Dublin 2. e802. Seabee F nycededronn. 270 Mr. Lubbock on the Heat of Vapours and on Astronomical Refractions (continued from vol. xvi. p. 569) . EO ET 2 Dr. Faraday on Magneto-electric Induction; in a aibaeter its Bee esu ISSAC; nae tte ee A eee s CNIS S DUE ON Mat 281 Mr. J. D. Smith on the Detection and Estimation of Colophony (common Rosin) when dissolved in the Fixed Oils........ 289 Proccedimes- of the Royal Saciéty Ais. arte: tie SO OG 292 -~-~—— of the Geological Society .................. 303 — of the Royal Astronomical Society .......... 309 Detection of Iodate of Potash in Iodide of Potassium, by Mau- PRPCISCAMIAM LMNs! 2 aye 2 2 so yane woe a Se mkS seed oda eh ed 316 een Pepsin—tfhe Principle of Digestion. 7. Se 317 Decrepitating Salt of Wieliczka, by H. Rose .............. 318 Meteorological Observations for August, 1840 A) a RR eae OS a a Bieta ra eteheh wu) Mette 320 V1 CONTENTS. Page NUMBER CXI.—NOVEMBER. /The Rev. W. Whewell on the mean Level of the Sea ...... 321 * Mr. Gulliver’s Observations on certain Peculiarities of form in the Blood Corpuscles of the Mammiferous Animals ...... 325 Dr. T. Scheerer and Mr. W. Francis on some Combinations of Arsenic with Cobalt. . a). Dest Mr. W. Francis’s Examination of a cr ‘crystallized Nickel Ore .. 335 Mr. Lubbock on the Variation of the Semi-axis Major of the Moon's Orbitys 2 az: al Ao a ee ee 338 Dr. J. Davy’s Observations on the aqueous Solution of Car- bonate of Magnesia with excess of Carbonic Acid, and on the Salt which it affords by spontaneous Decomposition.... 346 An Abstract of Professor Daniell’s Papers on the Electrolysis of Secondary Compounds, in the Philosophical Transactions for 1SsGvand 1840.3) ye see S.. + ole cca 349 Dr. Faraday on Magneto-electric Induction; in a Letter to MM... Gay-Lussae (concluded) 3 ob. Pe 356 Prof. Dove onthe Law of Storms)... ........... . eee 366 Mr. W. G. Armstrong on the Electricity of a Jet of Steam issuing from a Boiler: in a Letter to Prof. Faraday ...... 370 Mr. H. L. Pattinson’s Experiments on the Electricity of High- Pressure Steam. o00). 00), a Vial oer 375 Prof. Sylvester's'Note ‘on Elimimation?1).../..40\) 0. 379 Procéeding’s ‘ofthe Royal’ Society vy eh. eda Peete ahs 380 ———— the Geological Society...........--+2 +00: 387 Note referred to in the Abstract of Professor Daniell’s Paper, DASE CT. PES OIL, 1 es), ea er 396 New-Compound of Platina 1. .%..4..2).... 10% eee 397 Bine Oxide of Titanrum in Scorive 5. hy oye ee tee 398 On the|Protem ‘of the Crystalline Humour....0.2.222.2. we 398 Meteorological Observations for September, 1840 .......... 399 oe Table. 0. ee 400, NUMBER CXII.—DECEMBER. Dr. 'T. Thomson on the Minerals found in the Neighbourhood OL GIaSPOW 66 oes alerzinl wile dope ee leheieee SR «os eee 401 Deductions from the first Year’s Observations at the Magnetic Observatory at Prague; in a Letter from Professor Kreil to Wrajor TSW ies cee so ia toh yn oon eyes Schacter ae 418 Mr. J. Tovey on Mr. Potter’s Application of Huyghens’s Prin- eiplesin PhysialiOpiies | vais pert 0.. 5 Specs a een 431 CONTENTS. Vil Pa Mr. J. Booth on the Focal Properties of Surfaces of the Second EY OA cag a le Be Rat an a Ae ant Bec 432 Address of the General Secretaries of the British Association, R. I. Murchison, Esq. and Major E. Sabine ............ 44] Dr. C. Schaf haeutl’s Remarks on the Electricity of Steam.... 449 Mr. W.G. Armstrong on the Electricity of Effluent Steam.... 452 Mr. H. L. Pattinson’s Further Experiments on the Electricity RUM So ere, Crh Taira Gok fa Ae Pa 457 The Rey. J. Challis on the Motion of a small Sphere vibrating Pe ePeSTSUIIS VEGOTUND Gre trs os yc cere ss) swe tee mole eters ahs 462 Mr. Lubbock on the Heat of Vapours and on Astronomical Reeerreniteis (eaNfennCl). 20. oh 5. Pe oa ee eee . 467 Proceedings of the Royal Geological Society of Cornwall Twenty-Seventh Annual Report of the Council. . Sees ae puemeteeetetic OF Garbo... ee Se eke se de eee eee ee b's 477 Peeroine—a new Mineral). >... 00.0.6 5- 0 SPA cat ec 478 Ee OW VL CT AL hy Tie ore Saha dow ols wien es ese ee alate 479 SELL I i een Arai et aii eA 479 Meteorological Observations for October, 1840 ............ 479 ESTE CES RTS Eat RMU es ee Ae MAL gi Pk gm a 480 NUMBER CXIII.—SUPPLEMENT TO VOL. XVII. G.B. Airy, Esq., Astronomer Royal, on Professor Challis’s Investigation of the Motion of a Small Sphere vibrating in SRM CIEE Se ee cist ieee Mae rics snare 48] Address of the General Secretaries of the British Association, R. I. Murchison, Esq. and Major E. Sabine (concluded). . 482 Mr. Lubbock on the Heat of Vapours and on Astronomical MAM MERIOHGH CONCIUNED ) oo. 3S nia. soe he « hap dh «Pine ne 488 eeecceainps of the Geological Society... ...25.00 0s. cece ee 508 fee Oxide of Titanium ............ si ails (atl a Ren Poet aed Na 542 Chelidonia and Pirropina ....,. diabrela nena Mapu eae GOS e 543 Bodex..... a pene ee rine ats, Sissons deve ay Sio"s2 aeeameits 545 PLATES. I. Illustrative of Mr. Grirritu’s Paper on the Mineral Structure -of the South of Ireland. II. Illustrative of Dr. Fanapay’s Letter to M. Gay-Lussac, on Magneto- electric Induction *. * This Plate will be given in one of the Number of the next Volume. OO Ene Errata, &c. P, 145, line 17 from the bottom: the following reference ought to have been inserted in this place: “ An abstract of Prof. Faraday’s Seventeenth Series of Researches in Electricity appeared in vol. xvi. p. 336.” P. 370, line 12; p. 372 line 15; and p. 374, line 8 from the bottom, for H. G. Armstrong, read W. G. Armstrone. - | <3 al Lond, & Edin Phil. Mag Nor NUP. __ GEOLOGICAL sTRUCTURE OF THE SOUTH OF Pr Niagra _ = . SESpEO@EE/ 2vaceenass ly ~ = = ————— = CF ; 5 — = p~ ov @ &’ Scale of Map es LEZ ‘S =e Z ay one “nah ee oe ST .-- : Le SDUNGARVAN Chloritic rock ¥fed lerglomeral SECTION FROM CLONEA CASTLE TO BALLYVOIL HEAD Oe Mangia ee sandastoy Ld Vo red AAG 8: LE @ BALLYVOIL - ~HUBBOCK ih a g te “ily limesto, LONEA CASTLE BALLYVO]L — louis FSA LD AO LIS . TR Teeth / A AF CALLA LSS corse SSRI \arborurerous Limestone SCPLes AA PEM SIFUSCONE St * x. % ZS Longuuamal_ 2 b00he8t to uch SCacles { gs he | MEY ig 9 Sa a SECTION FROM BALLINACOURTY 7O GLOUNDOLCAN > J ‘ Ay inde Us SHR, 0 Té S 7 Sadr. iy g KNOCKNACRANNY CLOUNDINE KILMINEEN y er ce Slate GLOUNDINE ee Carboniferous lunestone Carbonierous lumestone ] BALLINACOURTY {| PROSPECT g i. f LE rd Phan als Longuundina, one A mute to gi inch Vortuca SS A lo Bose h en ANOCKMEELDOWN . RANCE : ( quartz sandstone /}| tclay slate grey LEARCOR RIVE Teck’ Slate SANMASCONC e TCC ————_ SW md LF. ae may MII. 4 2 ~ puting = La af MIME, A ay hy hy 7S MUTT — su os Ty, } y ? iS ~ SILI: OMS SMLLLLLE on Why sus. ———= if LEVEL OF THE SEA SSS ‘Longiudina —___ 2,4 miles te dy Scales | 2079 us STARR (57 Se rock, red Sard store and. red Slate. ORRICNACOUR CROOKED BRIDCE hed sandstone & rea. slate quarts rock. And regs omerate Brownesh red guartx Dark red slatek re \, pnaglomerate Brownish read calamtues Bllowish ~ 0. Vellow SaNABTONE withy ih RIVER BLACKWATER Rk ved Cla MS Sellow LISMORE | Limestone Limestone XS CLOCHEEN J.B asuLre, uy oe meee ssa wey Atty Shea iver aia eas GA eae eRe i ! on Spee eG if FOR Crete es os aad Ra gear de sm se : Win 4 | Lona dBdin Prod MagNol.\PL R ———_ pooeneenmndhmn >. Fo pe Pode bee 4 O7'aA 94 THE LONDON ano EDINBURGH PHILOSOPHICAL MAGAZINE AND JOURNAL OF SCIENCE, [THIRD SERIES.) JUL Y 1840. I. On the Iodide of a new Carbo-hydrogen. | By James I. W. Jounston, F.R.S.* F coal gas be made to pass slowly and for a length of time over pure iodine, the latter substance moistens, and is partly changed into a dark-brown liquid, which effervesces with alkaline carbonates, showing the presence of hydriodic acid. After some hours, colourless prismatic crystals shoot out from the iodine, and clothe the interior of the vessel, and ultimately the whole is changed into a mixture of different compounds forming an olive-coloured substance, partly coating thickly the sides of the vessel, and partly constitu- ting an unctuous mass, with the dark fluid at the bottom. The liquid contains free iodine and hydriodic acid. When washed out from the solid portion by alcohol and neutralized by caustic potash, the solution givesa yellow precipitate, con- sisting of a mixture of Faraday’s iodide of carbo-hydrogen _ (H, C, It and of iodide of formyle (iodoform H C, I,). The solid product being exposed to the air loses its unctu- osity. If broken up and examined by the microscope it is seen to consist of a congeries of colourless prisms (H, C, I) mixed with another substance, which is amorphous, and of a dark green almost black colour. Alcohol separates the for- mer, or if the mixture be exposed to the air they volatilize, leaving the dark green substance nearly pure. The production of the hydriodic acid and of the iodides of formyle and of carbo-hydrogen is easily understood. Coal gas contains probably more than two equiatomic compounds of carbon and hydrogen ; at least two, C H, and C, H,, the * Communicated by the Author. [+ Mr. Faraday’s account of this substance will be found in Phil, Mag. First Series, vol. lix. p. 352. Eprr.] Phil, Mag. S, 3. Vol. 17, No, 107. July 1840, B 2 Prof. Johnston on the Iodide of a new Carbo-hydrogen. light carburetted and olefiant gases, are present. The latter would furnish the three compounds obtained in this experiment, as shown by the following formula: 2(C,H,) +51=H1+ C,H,1+C,HL that is to say, one atom of olefiant gas decomposes to form hydriodic acid and formyle, while another unites with iodine* directly. Still this does not represent the action quanti- tively, since the proportion of the C,H, I is much greater in actual experiment, and appears also to be variable. Such is the action in close vessels provided only with a small aperture to allow the current of gas to pass out very slowly; but since these three compounds are all volatile, it is easy to understand how only the solid dark green fixed sub- stance should be obtained when the iodine is placed in an open vessel and a current of coal gas is made to stream upon it. In this way it was first obtained by Mr. Kemp of Edin- burgh, to whom the discovery of this substance is due, and who several years ago presented me with a specimen prepared by exposing iodine for several days to the action of an open jet of coal gas. I am not aware how far Mr. Kemp has since studied the action in close vessels. I. This substance is of a dark olive green colour, is with- out taste, emits a slight odour of naphtha, is brittle, and has a density of about 0°95. Itis insoluble in water, and in boil- ing alcohol or ether. ‘Treated with hot nitric acid it becomes yellow and dissolves. With muriatic acid either in the form of gas or of liquid acid, it undergoes no change. Sulphuric acid aided by heat decomposes it. It blackens and gives off iodine vapour and sulphurous acid, leaving undissolved a very bulky charcoal. Dry chlorine slowly changes its colour to a dark brown. If previously moistened with alcohol it becomes * During the combination of chlorine with olefiant gas a portion of muriatic acid is formed, a fact inconsistent- with the idea of a direct union of the two substances to form H, C, Cl: may not an equivalent proportion of the volatile chloroform be produced, as in the above formula, substi- tuting Cl for 1? Felix d’Arcet (Ann. de Chim. et de Phys., \xvi. p. 108.) has stated, that during this action of chlorine on olefiant gas, a second oily liquid is formed, represented by C, H, Cl O, to which he gives the name of chloretheral, but which Berzelius with great probability I think, consi- ders to be a compound of the chloride with the oxide of elayle (C2 H, Cl + C,H, O). This explanation of the production of muriatic acid, how- ever, implies that the gases employed are always more or less moist. Re- gnault accounts for the presence of the acid by representing the oily com- pound by the rational formula (C. H,Cl + H Cl) part of which is decom- posed during the process, and H Cl evolved. But Lowig and Wiedman have shown that C, Hz (acetyle) does not preexist in the oil, though it may possibly be formed by its decomposition, See Poggendorft’s Annalen, xlix, p. 133, Prof. Johnston on the Iodide of a new Carbo-hydrogen. 3 yellow by the action of chlorine. In hot solutions of carbo- nated alkalies it is partly decomposed, iodine being separated, but its colour remains unchanged. Heated to 212° Fahr., it slowly but sensibly loses weight, evolving the odour of naphtha and a little iodine. At a higher temperature it gives off a volatile combustible liquid resembling naphtha, which burns with much smoke, and if the heat be still increased, iodine vapour appears in large quantity colouring the naph- tha (?) dark brown, and a bulky shining charcoal remains be- hind. It is not unlikely that hydriodic acid may also be among the products. : Burned with oxide of copper this substance gave the fol- lowing results : 1. 8°77 grs. gave C = 18°56 and H = 4°94 ers. 2. 8°77 grs. gave C = 1815 and H = 4855 ors. 3. 6°137 ers. gave C = 12'316 and H = 3°505 ors. These are equivalent, per cent., to As 2. 3. Carbon..... = 58°203 57°225 55°490 Hydrogen = 6°258 6151 6°346 Todine...... = 35°539 36°624 38164 100 100 100 It was not till I observed the discrepancy between the first and second analyses that I studied the action of a tempera- ture of 212° Fahr. on this compound, and found that it was slowly decomposed, and iodine expelled from it by this de- gree of heat. The third analysis therefore was made with more precaution, and care was taken to avoid decomposition by the application of heat while pumping out the moisture from the oxide of copper. In this analysis therefore the chances of error were least, and the result agrees very closely with the formula C,, H., 1, since Calculated. Experiment. 30 carbon... = 2293°110 55:667 55*490 20 hydrogen = 249°592 6°059 6°346 1 iodine.... = 1578°290 38274 38°164 4120°992 100 100 The excess of hydrogen is due to the more imperfect man- ner in which it was necessary to pump out the water in order to avoid the separation of iodine, as had probably been the 4 Prof. Johnston on the Iodide of a new Carbo-hydrogen. — case in the previous analysis*. ‘The experimental result however may be reconciled to the formula (C,, Ho) + H 1) which gives 6°340 of hydrogen per cent., a quantity so near to that found as to leave nothing for the ordinary error of analysis. ‘The action of chlorine hereafter described, if the results are to be depended upon, gives a probability to this formula, in addition to that which is derived from the rational formula, adopted by Liebig to represent the constitution of what by other chemists are still regarded as chlorides and iodides of olefiant gas (elayle) and some other carbo-hydro- gens. It has been already stated, that when boiled in carbonated alkaties the colour of this compound remains unchanged, and that it undergoes decomposition. ‘The decomposition however is only partial. 4°51 grs. boiled in a concentrated solution of carbenate of soda, and afterwards washed and dried at a gentle heat, still weighed 3°51 grs. having lost 22:17 per cent. ‘The whole of the iodine therefore is not separated oe. by this process; it may however be completely separated by mixture with pure carbonate of soda, and gradually heating over the lamp to a temperature below redness. In this way I obtained by means of nitrate of silver an ap- proximation to the quantity of iodine, which however was too rude to be worthy of insertion in the present paper. I was, at the time of making the experiment, unacquainted with the | more perfect method of estimating the quantity of iodine since published by Lassaigne. | II. Diffused through water and subjected to the action of | chlorine, the green colour of this compound is slowly changed | to brown, but the action is much more rapid and complete | when the iodide is reduced to fine powder, diffused through | alcohol, and submitted to a current of chlorine. Thus treated it speedily acquires a bright yellow colour, combining with chlorine and yielding the iodine to the supernatant liquid, in which it is readily recognised. I subjected to analysis a portion of the substance thus pre- pared, after washing with alcohol and drying at 212° Fahr. When heated in a close tube it gave off no iodine. a. 8°45 ers. gave C = 18°81 grs. and H = 4°545 grs. * 2.795 gers. heated to 212° for some time, lost 0°295 er., and at a subse- quent weighing the loss amounted to 0:485 gr. Still it seems possible to . preserve it for along time at ordinary temperatures and in close vessels without sensible decomposition. One cf the specimens employed in the above analysis was prepared by Mr. Kemp, and had been in my possession several years, Prof. Johnston on the Iodide of a new Carbo-hydrogen. 5 The water in the chloride of calcium tube reddened litmus, indicating the presence of muriatic acid, by which the weight of water would be in some measure incr reased. b. 7°61 gers. heated with dry carbonate of soda, gave 7:033 ers. of chloride of silver or 23°8 per cent. of chlorine. c. 4°462 ors. heated in like manner, but with more care, gave 4°517 ors. of chloride of silver or 24°12 per cent. of chlorine. These results give for the composition of the yellow matter A B erbone.. == Gibb = 30 atoms. Hydrogen 5°98 17°38 — Chlorine... 24°12 22°8 2:02 — Oxygen ... 8°35 3:11 — 100 This result indicates the irrational formula C,, H,, Cl, O.; which gives eO.carnon = 2294"1) = 62°13 per) cent. 20 hydrogen 212°15 5°75 — 2 chlorine 885'30 23°99 — 3 oxygen 300°00 8°13 a 3690°56 100° The elements contained in the above irrational formula are capable of being arranged in several rational positions. The green iodide being Cz) Ha) + I, The yellow substance may be (C5, Hn +Cl)+Cl (1), in which three of hydrogen are replaced by three of oxygen, the atom of iodine by one of chlorine, and the whole combined with another atom of chlorine—the oxygen being derived from the alcohol, which was undergoing a simultaneous decomposi-~ tion by the action of chlorine. tan may be Wen, 05 bt Cle ee Lee) H 30 C] Cl Grey ees) og Cdeblgs HET Oo: gv(8s) O 2 in both of which the principle of substitution is equally evident. Were we to represent the green compound by C., H., + HI, there would even be a conservation of the ori- ginal type of composition *. This type may also be supposed to be sufficiently preserved in the radical, and that it is owing [* See the memoir of M. Dumas, p. 442 of the last volume.—Enir. ] 6 Prof. Johnston on the Iodide of a new Carbo-hydrogen. to the presence of much muriatic acid in the solution, derived from the action of the chlorine on the alcohol, that this ra- dical 3° R unites with H Cl (2°) instead of simply with Cl, when it might have been represented by a formula * the exact counterpart of that which indicates the substance from which it is derived. | | There is, however, still another mode of representing the rational constitution of this substance, which while it is ac- cordant with the facts on which Dumas’s views are founded, is inconsistent with the principle of the conservation of types. The yellow compound may be (C)z H, O, + HO) + (C,. Hi, Cl.) ) aes consisting of equal atoms of an analogous oxide and chloride of the radical C,, Hg or C3, Hy, with the former of which is combined also an atom of water. This mode of representing it is accordant with the views of Berzelius, and is supported by many interesting and striking analogies. We ought indeed to distinguish carefully between the fact of the mutual substitution of hydrogen and chlorine, and the theory of the persistence of types, or the opinion that the element which replaces performs the same function in the organic compound as that which is replaced. Of the former there can be no doubt, while the adoption of the latter as a principle is as yet attended with many difficulties and appa- rent anomalies, which do not present themselves when we regard these altered compounds after the manner in which our yellow substance is represented in formula 4. New views all tend to hasten forward science, but a new view is not in itself necessarily an advance. It may often serveasa useful guide-post, when it does not directly help us on our way. Such good results are sure to follow from the discus- sion of the theory of substitutions, though all the views of its eminent author should not find a permanent place in the science. a I speak with the less confidence in regard to the above formula, because I am sensible that the examination of the two compounds described in this paper is by no means com- plete: a more careful research into the properties and che- mical relations, especially of the first of them, would be likely I think to lead to interesting results. The analyses above given were made as far back as 1838, and in February 1839, and the investigation was left unfinished till I should obtain a fresh supply of the compound. My * Cy OE Os + Ch Prof. Johnston on the Iodide of a new Carbo-hydrogen. 7 attention has recently been recalled to the subject by a paper on Hellenine, by M. Gerhardt (Ann. de Chim. et de Phys. vol. xxii. p. 163), in which he gives for this substance the for- mula C,; H,) O, or C3, Ho) Oy, containing apparently a ra- dical isomeric with the carbo-hydrogen C,, H.9, which exists in the iodide above described. By the action of chlorine, hel- lenine becomes (C, ; H,,O, + ©; Hy9 Cl,) according to Ber- zelius, or (C,,; Hy Cl O, + H Cl) according to Dumas, in which we see a considerable analogy with the formule for the oxichloride above described. By the action of anhydrous phosphoric acid on hellenine, a yellow liquid carbo-hydrogen is produced, to which M. Gerhardt gives the name of hel- lenene, and which is represented by the formula C,; H,,—~ the hypothetic radical which enters into the constitution of our oxichloride as it is represented in the formula (4). These interesting approximations indicate a series of com- parative experiments, to which the iodide described in the present paper might be subjected, with the hope of throwing new light on the nature of the ever-varying isomeric modifi- cations, of which the compounds of carbon and hydrogen are susceptible. I hope to be able soon to return to the subject with a view to this investigation. In regard to the presence of a carbo-hydrogen represented by the formula C,, H,, in coal gas, it need not excite our ‘surprise if many other such compounds should hereafter be met with among the volatile and gaseous products obtained from the distillation of coal. When we consider how many less volatile substances of this class have been extracted by Pelle- tier and Walter* from the products of the distillation of resin for the manufacture of gas, and how many more volatile ones have been separated by Couerbe+ from the gas thus produced when subjected to pressure, we shall be prepared to expect in coal gas also, the vapours of many other volatile substances in addition to those which have hitherto been detected. I have not as yet proposed any name for the supposed radical C,, H,,. It belongs to the same group as mesitylene (Enyl of Berzelius) = C, Hy, and retinyle C,, H,., in both of which the elements are in the ratio of 3to 2. It would be exceedingly desirable to adopt the system of nomenclature proposed by Berzelius for these compounds, in which the name is compounded of the Greek numerals expressive of the num- ber of atoms of each element which are contained in the compound. But that such names may be univerally adopted, it is necessary that the same atomic weights should also be * Poggendorft’s Annalen, vol. xliv. p. 81. + Ann. de Chim. et de Phys., vol. 1xix. p. 148. 8 Prof. Forbes on the Optical Characters of Greenockite. generally received. In the present case, for example, our green compound would be represented By C,, H,, + 1, according to Berzelius. By Cg Hy + I, according to Dumas. And by C,H.) + 1 according to British chemists. The compounds of carbon and hydrogen therefore, on the principle of Berzelius, which abstractedly is very valuable as a guide for general nomenclature, would receive in the works of different chemists at least two, and sometimes three differ- ent names of foreign origin. ‘Trivial names therefore derived as heretofore from different and various sources, will be likely in the present state of the science to create much less con- fusion in our rapidly extending, already exceedingly difficult and almost Protean nomenclature. Durham, May 16, 1840. II. On the Optical Characters of Greenockite (Sulphuret of Cadmium). By James D. Forbes, Lsq., F.R.SS. L. and fid., Professor of Natural Philosophy in the University of Eidinburgh.* [- appears from a late number of Professor Jameson’s Journal, that the crystallographic characters of this new mineral, as examined by Mr. Brooke, remain ambiguous, and that the crystals sent to him for examination do not enable him positively to say whether it belongs to the rhombohedral or to the prismatic system; it may therefore be interesting to state that I have discovered that it possesses only one axis of double refraction in the direction of the axis of the pyramid or prism in which it usually crystallizes, and consequently there can be no doubt that greenockite isa rhombohedrai cadmium blende. Edinburgh, May 18, 1840. III. On a new Species of Biliary Calculus. By 'THomas Taytor, ILR.CS. To the Editors of the Philosophical Magazine and Journal. GENTLEMEN, A er engaged in examining the extensive collection of calculi in the museum of the Royal College of Sur- geons, which had been entrusted to me for that purpose by the Board of Curators, I remarked, among those in the Hunterian collection, one, which from its extreme lightness and peculiar * Communicated by the Author. We were favoured with this article in the middle of May, but from an oversight which we regret its insertion was omitted. | Mr. T. Taylor on a new Species of Biliary Caleulus. 9 appearance, I was led to suspect had been incorrectly de- scribed in the manuscript catalogue as consisting of the mixed phosphates. This calculus was externally of a dirty white colour, and had the greasy feel of cholesterine calculi; it floated on water, and when applied to the tongue, left an impression of bitterness. It was of an oval figure slightly flattened, one inch and a half in length, rather better than an inch in thick- ness, and about one inch anda quarter in breadth, but being broken in this direction its exact measurement could not be ascertained. It readily yielded to the knife, and the cut sur- face presented a polished appearance: its structure was la- mellar, being composed of white and reddish-yellow layers arranged concentrically and alternating with each other. ‘The layers were easily separable: at its centre there was a small vacuity. When heated before the blowpipe it readily fused, then caught fire, burning with a clear flame and giving out the smell of animal matter, but nothing of a urinous character. It left a carbonaceous residue, which by raising the heat was converted into a white ash. ‘This ash was alkaline, dissolved in water and dilute acetic acid, and the solutions gave a white precipitate with oxalate of ammonia; it was therefore lime. When digested in boiling water, the water became slightly brown, but no apparent solution took place: the water on evaporation left a transparent yellowish-brown residue, which had a bitter taste and resembled inspissated bile. Boiling alcohol extracted from it only a minute quantity of white fatty matter, which was deposited on cooling. A solution of caustic potass removed the whole of the colouring matter, but the rest of the calculus was unacted on: the potass solution was dirty green, and when neutralized with muriatic acid deposited a scanty precipitate of the same tint. When digested in nitric acid, effervescence took place, with the escape of a little nitrous acid ; it then melted into a trans- parent oil, which on cooling concreted into a white fatt matter. This substance, when washed with distilled water, melted at a temperature much below that of boiling water. When, instead of nitric acid, muriatic or acetic acid was employed, the portion of calculus did not melt until it had been removed from the acid; it then presented similar ap- pearances to that obtained by the action of nitric acid; con- sequently this white fatty matter was not formed by the action _ of the nitric acid. 10 Mr. T. Taylor on a new Species of Biliary Calculus. In all these cases the acids retained lime in solution. The fatty matter separated by the action of acids was partially so- luble in boiling alcohol, and the solution on cooling deposited shining crystalline scales. With caustic potass it formed a ropy almost gelatinous solution, and was precipitated in white flakes on the addition of an acid. A small piece being placed upon the ball of a thermometer previously heated, began to solidify when the temperature had sunk to about 135° Fahr. From these experiments I concluded that this calculus consisted of margarate, or stearate of lime, mixed probably with the oleate of the same base and some of the other con- stituents of the bile. That the lime was in combination with the fatty acid, was indicated by the insolubility of the calculus either in alcohol or caustic alkaline solutions, until it had been previously digested in some acid. The minute quantities on which I had hitherto operated prevented me from determining whether only one or more of the fatty acids were present. ‘The following analysis was therefore made. Analysis.—12°80 grs. of the calculus previously dried zn vacuo over sulphuric acid were boiled in distilled water: a peculiar odour was given off, and the water acquired a yel- lowish-brown colour: being evaporated to dryness it left a transparent resinous-looking residue, which weighed 0°84. This residue when digested in alcohol left 0°24 in the form of dirty yellow flakes, which in distilled water swelled up and ultimately dissolved, forming a solution which in its chemical characters exactly resembled that of the mucus of the gall bladder. The alcoholic solution being evaporated to dryness, the re- sidue was redissolved in water; the solution was intensely bitter; with muriatic acid it gave a copious viscid precipi- tate: acetate of lead produced likewise a viscid precipitate, and the supernatant liquor when clear was again troubled by a solution of subacetate of lead. The 0°84 consisted therefore of mucus of the gall bladder 0:24; inspissated bile 0°60. After water had extracted from the calculus all that it was capable of dissolving, it was treated with successive portions of boiling alcohol sp. gr. *830. The first alcoholic solution on cooling deposited a white matter, which did not readily redissolve in hot alcohol or aether, but was acted upon by acetic acid. It appeared to be part of the calculus that had been dissolved unchanged; the quantity was however too minute to be estimated. The al- coholic solutions were filtered, and being mixed together, the Mr. T. Taylor on a new Species of Biliary Calculus. 11 whole was gently evaporated ; as the liquid became concen- trated, it deposited some white fatty matter and acquired a yellow tinge; a residuum was ultimately left, which had the appearance of a mixture of a fluid and concrete oleaginous substance. On the application of heat it became a yellow oil, which on cooling only partially solidified: it weighed 0°47. It strongly reddened litmus paper; dissolved readily in a cold solution of caustic potass; and was precipitated in soft flakes on the addition of an acid. This substance consisted therefore of oleic acid, mixed with margaric or stearic acid. Strong acetic acid diluted with twice its bulk of water was now poured over the calculus, and the action of the acid aided by a gentle heat. ‘The insoluble residue was collected on double filters, washed, and dried. The acetic solution with its washings was reduced to a small bulk, and a solution of ammonia added; after the lapse of several hours.no precipitate appearing, the excess of am- monia was nearly neutralized by a solution of oxalic acid: a white precipitate fell, which when washed, dried, and heated to dull redness in a platina crucible, left 2:09 carbonate of lime = 1°17 lime. The remaining liquid being evaporated to dryness and the ammoniacal salts expelled, a residuum was left which weighed 0°10: water dissolved a portion of this; the solution was al- kaline, and when evaporated minute crystals were formed, which slightly effervesced in acetic acid: their solution not precipitating chloride of platina, leaves little doubt of their being carbonate of soda: the small portion which remained undissolved proved to be carbonate of lime. The matter left upon the filter after the action of the acetic acid was again digested in boiling alcohol, a_ considerable portion dissolved, and the remainder had acquired a much deeper colour : it was collected on the same filters, which were repeatedly washed with boiling spirit; when dried and weighed against the outer filter it amounted to 0°86. This substance possessed a brownish-yellow colour. It dissolved in solutions of caustic and carbonate of potass, forming solutions having nearly the same colour. Muriatic acid rendered it green, and when added to its al- kaline solution threw down green flocks. With nitric acid it formed a red solution. This substance was therefore identical with the colouring matter of the bile, and which forms the principal constituent of the biliary calculi of oxen. The alcoholic solutions were concentrated by careful di- 12 Mr. T. Taylor on a new Species of Biliary Calculus. stillation in a small retort: the liquid remaining in the retort, when cold, formed a soft crystalline mass, composed of bril- liant plates and having a pearly lustre, very much resembling marearic acid. This substance, when fused and kept for some time 27 vacuo over sulphuric acid, weighed 8°88. It melted at 136° Fahr., and on cooling became a crystalline solid, red- dened litmus paper, and was easily soluble in a cold solu- tion of caustic potass; the solution when concentrated was ropy and gelatinous; when dilute it formed a slightly milky mixture with minute glistening particles floating in it; on the addition of an acid, the substance was thrown down in the form of white flakes, which possessed the same properties as before solution. When boiled with the alkaline carbonates, it was dissolved, with the escape of carbonic acid. By re- dissolving it in hot alcohol, crystalline plates were deposited on cooling, which after washing with cold spirit fused at about 140°. ‘The low fusing point of this substance evidently indicates the presence of oleic acid. In order to ascertain whether the crystals fusible at 140° were pure margaric acid or stearic acid rendered more fusible by an admixture of oleic acid, they were again dissolved in warm spirit, and the crystals as soon as formed dried by compression between folds of blotting paper; by repeating this process two or three times, the fusing point was raised to nearly 160°. ‘This must therefore be regarded as pure stearic acid; and as I find that both stearic and margaric acids require to be several times recrystallized from their alcoholic solutions to free them from even small quantities of oleic acid, and as no decided indi- cation of the presence of margaric acid could be detected in the mother liquors, I am inclined to believe that oleic acid had only been separated by the above treatment, and that con- sequently margaric acid did not enter into the composition of the calculus. It would however be impossible to speak de- cidedly on this point. . The result of the analysis is as follows: Stearic acid mixed with a small pro- portion of oleic Obs ee TIS Eee Teak s ATH DURE ade Leeledoer cons RieMn Soda with a trace of lime.....cecccsovssee 0°05 Yellow colouring matter of the bile...... 0°86 Inspissated bile ii. ilicccaw a iinote besides soe Om Mucus of the gall-bladder .,...sseseseses O°24 12°27 Loss sever aa 12°80 9°35 Mr. T. Taylor on a new Species of Biliary Calculus. 13 The greater part of the loss in this analysis should be added to the stearic acid, as owing to the sudden extrica- tion of vapour while under the receiver of the air-pump a small part of the acid was thrown out; but I prefer giving the quantities actually obtained to making any allowance for known sources of error. The composition of the calculus clearly points out its biliary origin, but whether taken from man or the brute must remain doubtful, as there is no history to guide us. Stearic, margaric, and oleic acids exist in the bile of oxen in combination with soda ; and according to Lecanu and Casa- seca*, stearic and oleic acid in that of man; the latter I have frequently detected, but I cannot find that these acids have ever been noticed as entering into the composition of biliary concretions, much less forming the prominent constituent. I was unable to detect the slightest trace of these acids in five specimens selected from about 200. From cholesterine calculi it is readily distinguished by the absence of any crystalline structure when broken, which un- less the quantity of colouring matter be very large is always more or less apparent in that variety; also by its insolubility in alcohol or ether and by readily dissolving in these men- strua, and in a cold solution of caustic potass after it has been acted upon by an acid. Before I conclude, I am anxious to rectify an error which I inadvertently committed in my paper on the calculi in the museum of St. Bartholomew’s Hospital+. I there stated that urate of ammonia had always been confounded with the uric acid variety in the tables that had been published on the relative frequency of the different species of calculus f. This was not, however, the case in a paper by Dr. Yelloly, in the Philosophical Transactions for 1829-30, containing the analysis of the Norwich collection, and I regret that I have not had an opportunity of making this acknowlegement sooner. April 8th, 1840, Tuomas Taytor, New Bridge Street, London. ' MLR.C.S. N.B. A notice of this calculus was sent to the Board of Curators in March 1839, but a variety of circumstances have delayed its publication. * Gmelin’s Handbuch der Chemie: Journal de Pharmacte, 12. + L. & E, Phil, Mag. vol. xii. p. 412. t Id. p. 414, Peds] IV. On the Anatomy of the Brain. By Dr. F ovitLe, M.D.Par* if is more than twelve years since Dr. Foville laid before the Royal Academy of Sciences of Paris some highly in- teresting discoveries respecting the anatomical structure of the brain. ‘They were the results of laborious researches in what at that period he had already been long engaged. At the time they attracted the careful attention of the anatomical members of the Institute, and more especially of the late Baron Cuvier, and of Professor Blainville, and an able and highly favourable report on the subject was presented to the Academy by the latter savant. ‘Translations of this Report and of Dr. Foville’s Memoir were published soon after in the Annals of Philosophy}. From that time to the present the Doctor has been pursuing his investigations, and has made new discoveries as well as confirmed his old ones, and has been engaged in preparing a detailed and extended work on the anatomy, physiology, and pathology of the brain and spinal cord. He laid a condensed view of the anatomical facts before the Medical Section of the British Association at its meeting in Birmingham, and has presented a further me- moir to the Academy of Sciences of Paris. ‘The Doctor has thrown the substance of both papers into the following de- scription. a Medical men in general are so well aware of the import- - ance, and at the same time of the difficulty of the study of the nervous system, that the physician who attempts to communi- cate to his professional brethren the result of his researches, may flatter himself that he is speaking on a subject which can- not fail to be interesting. Hence in desiring to communicate some results of my anatomical researches concerning the brain, I need not solicit the indulgence of the meeting for the subject itself, which has for many years engaged my attention, but I must apologise for the imperfect style of the present sketch. JI arrived in London only a few days ago in order to visit my friend Dr. Hodgkin, and had not anticipated his inviting me to join him at the meeting of the British Association for the Advancement of Science, and present to this meeting an abstract of my researches into the structure of the encephalon. Having left my manuscript, now nearly ready for publication, in France, and not having time and opportunity to procure new preparations from which I might write the present essay, I have been obliged to depend on * Communicated by Dr. Hodgkin. + Phil, Mag. and Annals, N.S, vol, v. p. 278,—Epit. Dr. Foville on the Anatomy of the Brain. 15 my memory for the description of some structural arrange- ments which have arrested my attention. When we look at the works which treat of the anatomy of the brain, we find that they may be distinguished into two classes. Some being designed to illustrate the form of the brain in general, and to indicate the particulars of its exter- nal surface as well as of its ventricular cavities, only exhibit its substance by sections, which destroy the arrangement of the parts without showing their structure. Others, being composed by authors aware of the imperfection of those processes by which nothing but superficial appearances and casual sections are exhibited, aim at elucidating the mysteries of the cerebral organization by studying the composition and arrangement of the substances constituting the encephalic masses, It is needless in speaking to so enlightened an assembly as this to draw any comparison between the advantages of these two different methods. Centuries have passed since the superiority of that which is designed to ascertain the intimate composition and structure of the parts was first recognised by some anatomists. The celebrated Willis has insisted as strongly as any modern writer on the advantages of the pro- cess alluded to; and Malpighi proved its excellence when he so accurately described the granular disposition of the gray matter and the fibrous structure of the white. Nevertheless in spite of these superior men, their improved views did not generally prevail in the schools; and when at the end of the last century, Reil, and at the beginning of the present, Gall, undertook to prove the fibrous structure of the white sub- stance of the brain, they thought they were announcing an anatomical discovery. Reil by his writings, and Gall by his lectures and publi- cations in which he was associated with Spurzheim, have pro- pagated their ardour for sound anatomical inquiries. But notwithstanding their efforts, the practice of cutting through the brain is not yet abandoned, though it is generally un- derstood that this old and imperfect method is insufficient of itself, and that it is by combining with it more appropriate means of investigation that facts which twenty years ago were controverted are now incontestably demonstrated. Thus, for example, all anatomists of the present day concur in the view that the white substance is fibrous, and the gray granular ; and at the same time, contrary to the views of Gall, a great many physiologists agree in thinking that the gray matter is the active part in the functions attributed to the nervous sy- stem, and that the white fibres are in the brain as in the. 16 Dr. Foville on the Anatomy of the Brain. nerves, inert conductors. It still remains to determine which of these substances is pre-existent to the other; in what or- der the development of the different parts which they com- pose takes place, and what are the most essential differences in the nervous systems in different animals. It is sufficient to mention the name of ‘Tiedemann to remind you of the light which has been thrown on these interesting and important questions. I will not undertake to enumerate the many points which are yet to be elucidated. I will merely, before exposing my own views on the structure of the encephalon, allude to those’ of the most eminent anatomists who have attempted to deter- mine the disposition of the two substances composing the encephalic masses. Willis, Malpighi, Reil, Gall, and Spurzheim are of opinion that the white fibres of the crura cerebri, after emerging from the medulla oblongata, penetrate into the hemispheres, di- verging in various directions till they meet the gray matter of the convolutions in which they terminate. ‘They believe that — the corpus callosum reaching from one hemisphere to the other is formed by the union on the median line of a new order of fibres, originating in that same gray matter of the convolutions, as that in which the fibres proceeding from the crura cerebri terminate. Gall clearly and distinctly ex- presses this opinion, when he says that the brain is formed of two different orders of fibres, the one of diverging, the other of converging fibres. Tiedemann does not admit these two orders of fibres. Ac- cording to his views, the fibres meeting in the corpus callosum are a continuation of those which proceed from the crura ce- rebri after they have gone through the entire circumference of the hemispheres. Which of these different views is consistent with the truth ? Is there no other difficulty than the choice between them? It is pretty generally admitted that the encephalic masses are, according to the poetic language of Reil, * an efflores- cence of the spinal marrow,” the cerebrum being developed at the summit.of its anterior, the cerebellum, at “the summit of its posterior columns. ‘The decussation between the two anterior pyramids belonging to the anterior columns is held to account for the effects of cerebral complaints being mani- fested on the side of the body opposed to their seat in the brain. For this last fact to be true, it is necessary that the decus- sation between the two pyramids should be at once in com- munication with all the muscular nerves in the body and with Dr. Foville on the Anatomy of the Brain. 17 all the parts of the brain, which being altered produce :sym- ptoms on the opposite side. Hence in our survey the necessity of tracing accurately the connexions between the pyramids and the other parts of the cerebro-spinal system. The spinal marrow situated below the decussation of the pyramids is composed of two symmetrical portions, which are united by a commissure of white matter. Without entering into the consideration of how many distinct columns are to be found in each half, I will now point out the different appear- ances belonging to the anterior and posterior surfaces of its commissure. Throughout its whole extent the anterior commissure is divided longitudinally by numerous small holes, which are never to be found absolutely on the median line, where there exists a kind of very small raphe. At its superior extremity this anterior surface of the commissure becomes more super- ficial, and gradually assumes something of the aspect belong- ing to the decussation of the pyramids; so much so, that it is not always easy to determine where the commissure ends and the decussation begins. The posterior surface of this commissure, which is visible at the bottom of the posterior fissure, does not present the Same appearance as the anterior surface. ‘The two surfaces are sonear each other that they seem at first to belong to the same fibrous layer; but a close examination demonstrates that this is not the case, for there is constantly a sensible in- terval between the two surfaces. On the median line, two small very fine parallel white layers pass from the one to the other. If this double commissure be compared to the corpus callosum and fornix, these white layers going from the one to the other bear some analogy to the septum lucidum in the brain. I think this cavity has already been noticed by Malpighi; and Dr. Hodgkin believes that he has more than once ob- served it. Gall described a longitudinal cavity on each side of the spinal cord, but it has been ascertained that they were pro- duced by blowing into the central longitudinal masses on each side of the marrow. ‘Thus we find in the commissure two transverse bands of white matter uniting the two halves of the spinal marrow, which bands are connected together on the median line by a delicate double band of white matter be- tween the layers, of which a natural cavity seems to exist. Let us now inquire what becomes of the two commissures when they penetrate on each side into the substance of the marrow. It seemsto me that they soon become united to- ‘gether so as to constitute a kind of axis, around which are attached the lateral fibrous columns by means of fibres ras Phil. Mag. 8, 3. Vol, 17. No. 107. July 1840, C 18 Dr. Foville on the Anatomy of the Brain. diating transversely from the former into the latter, It ap- pears also that a greater number of the fibres going to the roots of the spinal nerves proceed directly from the axis itself, This distribution is more evident with respect to the posterior than to the anterior roots. . Without attempting to describe the lateral columns of the spinal marrow, I must not omit to mention a remarkable dif- ference between the lateral parts of these columns and the anterior and posterior portions. If a portion of the spinal marrow be cut out transversely, freed from its membranes, and left to macerate in plain water for a few hours, the lateral parts of each half will assume, in consequence of the swelling of their fibrous fasciculi, an appearance something like that of a large nerve, whilst the anterior and posterior parts ad- joining these lateral columns are uniformly swelled without presenting any such appearance. Let us now see how the axes of the superficial columns of the spinal marrow are con- nected with the parts developed at their upper extremity, that is to say, in the medulla oblongata. The anterior part of the axis, in other words, the anterior part of the commissure, appears to go almost entirely into the decussation of the anterior pyramids, and into the pyra- mids themselves. A very fine commissure between the pyra- mids seems to be a continuation of the anterior commissure which exists throughout the whole length of the spinal mar- row. The posterior commissure ascending along the medulla oblongata comes very near to the surface, and when examined between the two lateral portions of the medulla, it seems to constitute a very delicate bond of union between the two sides of the calamus scriptorius. This union seems to be established by means of two slight fibrous columns, which are prolonga- tions of the posterior commissure of the spinal marrow. If these statements are correct, we see that when the pro- longations of the commissures or naked surfaces of the axis of the spinal marrow are examined in the medulla oblongata, instead of being very near each other on the median line, they are separated by all the interval existing between the anterior and posterior surfaces of the medulla oblongata. But so slight are the remains of the commissures when examined in the medulla oblongata, that it is very easy to overlook them. When the two halves of the medulla oblongata are separated, and this separation is easily produced by introducing and gently pressing a probe between the two anterior pyramids or the two halves of the calamus scriptorius, they present to our view fibres going from before backwards, and so dis- posed, that those on the right side correspond to the intervals Dr. Foville on the Anatomy of the Brain. 19 of those on the left. On each side they seem to pass from the pyramid before to some small columns which proceed from the posterior commissure behind. These two opposed layers of fibres passing from before to behind, correspond in the medulla oblongata to the double band having the same dis- position in the medulla spinalis. With the posterior bundles of the medulla oblongata, con- tinuous with the posterior commissure of the spinal marrow, are connected those white fibres seen on the surface of the calamus scriptorius, which are said to go to the auditory nerve. I must not forget to say, that from these same posterior ascending bundles ative radiating fibres, going to the su- perficial columns of the medulla oblongata, in like manner as there are found radiating fibres proceeding from the axis of the medulla spinalis and going to its superficial columns. These remarkable anatomical arrangements are not to be found in the spinal marrow and medulla oblongata alone; they exist still higher, in the crura cerebri. I must not now attempt to describe these connexions further, as I have several other points to notice, and shall therefore be glad if I have succeeded in conveying to you some idea of their character. Nor will I here undertake to describe the multifarious and highly complicated parts which are to be found in and above the medulla oblongata going to the cerebellum and cerebrum, into which many of them may be followed. I will merely remark, that among all these fibrous bundles those in communication with the anterior pyramids are the most simple and the most direct in their progress to the brain through the crus cerebri, for they constitute the inferior part. This inferior part of the crus cerebri, flattened a little transversely at its entrance into the brain, is received into a transverse cavity. The superior part of the same crus cerebri when entering the brain unites directly with the thalamus nervi optici, which Seems to be an enlargement and modification of this part. When attentively examined, the thalamus nervi optici is seen forming with its appendages, of which the nervus opticus emerging from it is the most remarkable, a complete circle, or at least a rounded mass, about the inferior part of the crus at its entrance into the brain. . It seems highly important to distinguish with exactness the further disposition of these two distinct prolongations of the crus cerebri. ; Internal to the fissure of Sylvius there is an elongated four- sided surface, of whitish colour, which is the only fibrous part of the external surface of the brain, This quadrangle is C2 20 Dr. Foville on the Anatomy of the Brain. perforated by a great number of vascular holes, and its greatest dimension is from within outwards and backwards. Its anterior margin is curved, and bears the external root of the olfactory nerve. Its posterior margin, equally curved, bears a part of the optic nerve, which is prolonged outwards and backwards from the commissure. At the anterior border of the same quadrangle is seen the base of the convolution which is in relation with the olfactory nerve. To the extreme limit of its posterior margin is attached in some sort by its base the great tuberosity of the most inter- nal convolution of the temporal lobe of the brain. ‘This con- volution is not less remarkable for its form and situation than for its surface, which appears invested by a whitish layer of matter perforated with holes like lace. Internally this quadrangle is inclined towards the inferior part of the septum lucidum, and presents a swelling corre- sponding to the commissure of the optic nerves. With the fibres composing the surface of this quadrangle are united all the roots of the olfactory nerve, except the anterior one, which is continued into the substance of the convolution on which this nerve rests. With the fibres of the same quadrangle are also combined a layer of nervous matter and some radicular prolongations given off from the optic nerve. The most internal portion of the quadrangle goes up under the septum lucidum to the base of the anterior part of the lateral ventricle. Its external portion, combined with the great tuberosity of the convolution of the cornu ammonis, or the convolution displaying the hippocampus major on its ventri- cular surface, corresponds with the deepest part of the de- scending cornu of the same ventricle in the temporal lobe. By its adherent surface this quadrangle covers a part of the inferior extra-ventricular portion of the corpus striatum and thalamus nervi optici, and also receives a delicate layer of fibres which come from the corpus striatum and optic thala- mus, in a line as distinct from that by which the fibrous planes proceed from the same parts to the internal surface of the convolutions, as that in which the anterior roots of the spinal nerves originate is distinct from that in which the posterior roots of the same nerves arise. Several radicular prolonga- tions of the olfactory nerve go into the slight fibrous layer which is observable in the substance of the corpus striatum. The anterior boundary of the fibrous quadrangle whose relations ] haye just now sketched, sends off a fibrous band, Dr. Foville on the Anatomy of the Brain. a) which connected at its origin with the base of the convolution of the olfactory nerve, ascends in front of the corpus callo- sum, to the side of which it\is applied, winds round its an- terior extremity, then follows its superior aspect, and descend- ing behind its posterior border into the convolution which bounds the fissure of Bichat, returns to the tuberosity si- tuated on the external edge of the quadrangle so often men- tioned. This fibrous band therefore, with the quadrangle in which it Ceases at its two opposite extremities, describes a large cir- cle in which the cerpus callosum is inscribed. The circumfe- rence of this fibrous band forms the base of a convolution whose remarkable disposition has engaged the attention of anatomists. It forms with the latter, on the edge of the corpus callosum contiguous to the hemispheres and the fissure of Bichat, a sort of listing, or border, in which the gray substance of the convolutions ends. I have thought it proper in an ex- tensive work on the anatomy of the brain to name this band cerebral border, and the corresponding convolution, convolu- tion of the border. Thus, without multiplying details, we find reaching all along the circumference, or if the term which I[ have proposed be approved of, along the contracted border forming the li- mit of the extensive gray membrane folded into convolutions on the surface of the brain, a fibrous cord, which forms along with the superficial quadrangle whence it is derived, a com- plete circle round the corpus callosum, and this quadrangle and its immediate dependence communicate on the other side with the sensorial nerves of the brain. Let us now take a rapid view of the fibrous parts of the hemispheres. They originate externally in a fasciculated fi- brous layer interposed between the gray masses of the corpus striatum and optic thalamus, and go to the internal surface of the cerebral convolutions, whilst the fibrous layer whence they issue is continued into the inferior part of the crus ce- rebri, and consequently into the anterior pyramids. On the outside of the corpus striatum and optic thalamus, these fi- brous planes of the hemisphere separate into two strata, upon which the cerebral convolutions are raised; and each of these strata or secondary planes becomes united to the external margin of the circular band forming the border of the hemi- spheres. One of these unions takes place in the hollow of the fissure of Sylvius ; the other in all the rest of the internal circumference or border of the gray substance of the convo- Jutions. Of these two orders of fibres thus differently disposed, the 22 Dr. Foville on the Anatomy of the Brain. one then communicates with the posterior part of the crus cerebri and the nerves of sensation; the other with the in- ferior part of the crus cerebri andthe anterior pyramids, which decussate like the effects of cerebral lesions bearing upon the powers of motion. ‘The first order of fibres are applied to the circumference of the convolutions very near the median line, and the circle which they form is on a vertical plane, di- rected antero-posteriorly; the second, radiating from within outwards towards the middle of the convex surface of the hemispheres, spread themselves out from thence towards the termination of the convolutions round the corpus callosum, and become connected here with the external margin of the circular band, which extends tothe same point of the conyo- lutions. This remark on the relation of the convoJutions to the two orders of fibrous parts, of which the one proceeds from the anterior pyramids and the anterior parts of the spinal mar- row, whilst the other is intimately connected with the sensorial nerve of the brain, and the posterior parts of the spinal mar- row, points out the manner in which the cerebral convolu- tions should be studied. If our description is confined to their forms, nothing of im- portance will be revealed. But if on the contrary we endea- vour accurately to determine their relation to the other parts of the system by means of the fibrous parts entering into their composition, the mind will be prepared to apprehend the different offices they are intended to fulfil. This is what I have endeavoured to accomplish in the first place in the human brain, and secondarily in that of a considerable num- ber of mammiferous animals. I shall subjoin here an abs- tract of my researches on this subject. Considered in reference to the different connexions of their fibrous parts, the convolutions may be distinguished into two principal classes: first, those clothing the prolongations in the brain of the fibrous bands connected with the olfactory lobes, optic nerves, and posterior parts of the medulla spinalis ; and second, those enveloping the cerebral terminations of the pyramidal fasciculus of the crus. The convolutions connected with the prolongations in the brain of the fibrous parts which proceed from the basilary quadrangle, or the common meeting-point of the sensorial nerves and the posterior parts of the medulla, constitute all the plain internal part of the hemisphere, the surface of the basilary cerebello-temporal zone, and the lobule of the insula. Those developed on the terminations of the pyramidal fas- ciculus of the crus, constitute all the external portion of the Dr. Foville on the Anatomy of the Brain. - 28 hemisphere and the concave surface of the orbital region of its base. ‘The respective limits of these two classes of convo- lutions are indicated on the one hand by a grand line of con- volutions which courses along in its whole extent the large circumference of the hemisphere, commencing in front at the anterior margin of the perforated quadrangle, and terminating behind at the posterior margin of the same quadrangle; and on the other hand by another line of convolutions, which forms the inclosure of the fissure of Sylvius, arising before and end- ing behind like the preceding grand line at the opposite mar- gins of the perforated quadrangle. Thus contiguous and united at their extremities, these two lines diverge from each other throughout the rest of their extent, the grand line traversing successively the internal border of the orbital region of the base of the brain, the great convex border of the hemisphere, and lastly, the external border of the basilary cerebello-temporal zone; whilst the convolutions of the inclosure of the fissure of Sylvius travels in succession along the anterior border, the superior bor- der, and lastly, the inferior border of the fissure which it bounds. All the principal divisions found by each of these two lines of convolutions correspond to those formed by the other. That part of the large circumference which forms the internal border of the orbital region corresponds to the convolution- ary inclosure of the fissure of Sylvius, forming the external limit of the same orbital region. ‘The great convex boundary of the hemisphere corresponds to the superior border of the fissure of Sylvius; and lastly, the external border of the ce- rebello-temporal zone answers to the inferior border of the fissure of Sylvius. The anterior angle formed by the union of the first and second parts of the inclosure of the fissure of ' Sylvius, answers to the angle formed at the anterior extremity of the brain by the union of the great convex border of the hemisphere with the external border of the orbital region. The posterior angle of the fissure of Sylvius, subtended by the line which forms its superior border, meeting with that which forms its inferior border, answers to the angle formed by the meeting of the great convex border of the hemisphere with the externa] border of the cerebello-temporal zone at the posterior extremity of the brain. Lastly, as these two lines meet at their extremities, in contact with the perforated qua- drangle, it is seen that the convolutions included in the in- terval between them occupying all the convex external aspect _ of the hemisphere and the orbital region of its inferior aspect, are quite distinct from those situated at the internal aspect 24 Dr. Foville on the Anatomy of the Brain. and at the basilary surface; and lastly, from those which in the fissure of Sylvius itself constitute the lobule of the insula. Of the convolutions of the regions which I have just pointed out, those of the internal aspect of the cerebello-temporal zone are included between the line of convolutions which tracks the large circumference of the hemisphere, and that part of the convolution of the border which extends from the anterior to the posterior margin of the perforated qua-~ drangle, following the curve from before to behind of the corpus callosum, and the fissure of Bichat. Lastly, the convolutions of the insula are included between the line of convolution forming the inclosure of the fissure of Sylvius, and that part of the convolution of the border, very short in man, on which is prolonged the external root of the olfactory nerve. If we dissect the convolutions of the plain internal surface of the hemisphere, those of the cerebello-temporal zone, and lastly, those of the insula, we can easily show that their fi- brous parts converge from the great circumference of -the hemisphere, and of the convolutionary inclosure of the fissure of Sylvius towards the corresponding regions of the convolu- tion of the border, and terminate at last in the fibrous band of the border itself, whose connexions with the perforated quadrangle, the sensorial nerves of the brain, and the posterior parts of the spinal marrow we are already acquainted with. On the contrary, dissection of the convolutions on the ex- ternal convex surface of the hemisphere included between the two grand lines of convolution which bound this aspect, one of these lines traversing the great circumference of the brain, the other following and forming the boundary of the fissure of Sylvius, shows that the fibrous twig of these convolutions terminates in the plane of the hemisphere which emanates from the pyramidal portion of the crus cerebri. As to the two lines of convolution situated on the limit of those convolutions which are united with the dependences of the border and of those which envelope the terminations of the plane of the hemisphere, they both pertain by one of their margins, to the productions of the border, and by the other to the productions of the plane of the hemisphere. ‘They form then a means of union between the two orders of con- volutions, of which the one is connected to the sensorial nerves and the posterior parts of the spinal marrow, and the other to the anterior pyramids and the anterior parts of the spinal marrow. Thus all the convolutions developed in the interval of the two spaces. between the external surface of the hemisphere Dr. Foville on the Anatomy of the Brain. 25 and the internal and external margins of the orbital region, are in exclusive relation with the prolongations of the pyra- midal fasciculus of the crus. All the conyolutions developed between the border, pro- perly speaking, and the great circumference of the hemi- sphere, pertain to the fibrous emanations from the perforated quadrangle. All the convolutions of the insula situated between the short region of the border which is traversed by the external root of the olfactory nerve, and the convolutionary inclosure of the fissure of Sylvius, belong peculiarly to the fibrous parts emanating from that region of the border to which belongs the external root of the olfactory nerve. Lastly, the great circumference in which are found the external surface of the convolutions belonging in particular to the terminations of the pyramidal fasciculus of the crus, and the internal surface of those which belong exclusively to the fibrous emanations from the perforated quadrangle, is destined by its double re- lations toa mixed purpose. It contains the anastomosis of the fibrous extremities of the pyramids and of the fibrous ex- tremities issuing from the perforated quadrangle. The convolutionary inclesure of the fissure of Svlvius, to the extra fissural margin of which are connected the convolu- tions developed upon the pyramidal termination of the crus, and with the fissural edge of which is combined the fibrous duplicature of the convolutions of the insula proceeding from that part of the border to which belongs the external root of the olfactory nerve, is destined, like the line of convolution which courses along the great circumference of the hemisphere, to contain the anastomosis of the fibrous parts belonging to the pyramidal convolutions with those which proceed from the border. They are thus in relation with the sensorial nerves of the brain, with the posterior parts of the crura, and with the medulla oblongata. We might proceed to describe the various groups formed by the two orders of convolutions which we have now esta- blished; but it must not be forgotten that our present object is merely to give a succinct idea of the principal results of our anatomical investigations. But I have as yet only pointed out a very trifling portion of the fibrous layers intermediate between the nerves of sen- sation of the brain, and I shall immediately proceed to men- tion the other parts which unite with the fibrous band and the superficial quadrangle previously described. tach of these parts forms, like the preceding, a circle which traverses . . be 5 = = the inferior part of the crus cerebri, some embracing this part 26 Dr. Foville on the Anatomy of the Brain. of the crus cerebri like a kind of bracelet, others separating from it in the greater part of their course, but always coming back to unite at their termination with the white quadrangle of the fissure of Sylvius. Setting off from the crus, the first of these parts is the white superficial covering of the optic thalamus, the fibres of which are circular. | The second is the teenia semicircularis, incomplete as a ring when considered alone, but completed by the quadrangle with which it directly unites in front, whilst behind it joins the great tuberosity of the convolution of the cornu ammonis, attached to the external part of the superficial quadrangle. Thirdly, the corpus striatum itself forms by its gray matter alone a complete circle, or rather an ellipse, the inferior ex- tra-ventricular part of which is covered by the quadrangle so often mentioned. Fourthly, to the outer side of the corpus striatum there is a fibrous circle, which surrounds it as the tenia semicircularis compasses the optic thalamus. So far as I know, this fi- brous ring has not hitherto been described. : Fifthly, the corpus fimbriatum and the corresponding half of the fornix form likewise a complete circle with the fibrous layer of the fissure of Sylvius. In the sixth place would come, if we had not before described it, the white band of the border. In the seventh and last place, the two little bands situated upon the corpus callosum close to the median line, termi- nate, like all the preceding parts, at the anterior and pos- terior limits of the white perforated surface internal to the fissure of Sylvius. The corpus callosum itself is in intimate relation with all these concentric circles. Its particular disposition was de- scribed in a memoir which I had the honour of reading be- fore the Academy of Medicine at Paris in 1825; but the death of Beclard, who was appointed to report on my paper, de- prived me of the judgement which that illustrious professor would have formed. There is not, I believe, any communication between the fibrous expansions of the inferior part of the crura of the op- posite sides of the brain. | It appears to me that in man the anterior commissure only unites those parts of the opposite sides which are connected with the nerves of sensation. ‘The well-known fact that in many mammifera this commissure only stands on each side to the olfactory nerves instead of reaching from one hemi- sphere to the other, adds force to the opinion I express, that Dr. Foville on the Anatomy of the Brain. BY the anterior commissure only unites parts devoted to sensa- tion. I shall not insist further on this anatomical proposition, but if you will allow me briefly to add a few physiological deductions, I would say that the fibrous parts intermediate between the internal surface of the convolutions and the an- terior pyramids, appear to me to be simple conductors, as well as those which unite the organs of sensation with the circumference of the gray substance of the convolutions; these transmitting to the muscles the influence of the gray substance which determines their contraction, whilst those convey from the organs of sense to the same gray substance impressions made on the surface of these organs. The grey substance of the convolutions appears to me to be the material substratum, by the intervention of which the will directs the movements of the body. For the last twenty years lesions of this substance have been pointed to as those most frequently occurring in the insane, by those physicians who expect to find in the brains of such patients alterations corresponding to the characteristic symptoms of their dis- orders. Atrophy of the convolutions, so frequently seen in de- mentia, appears to me to result from disuse of the functions of the gray substance; then the fibrous matter proceeding from this gray substance becomes atrophied also, just as the optic nerves fall into a state of atrophy in the blind. Pathological anatomy furnishes numerous examples of le- sions of the fibrous matter intermediate between the cortical substance of the convolutions and the anterior pyramids. Paralysis of the active organs of motion on the opposite side is generally the consequence. The information afforded by pathological anatomy, relative to the effects of lesions affecting the fibrous parts intermediate between the gray substance of the convolutions and the or- gans of sense, is not so clear. This is owing, I imagine, to the communication in the median line between these fibrous parts of opposite sides, and the great number of these parts rendering the complete obstruction of the impressions they - are meant to convey, difficult. Before summing up these conclusions, relative to the struc- ture and office of some parts of the brain, I should like to say a few words on the relations which the study of the cranium establishes between different regions of this bony case and the corresponding regions of the organ which it incloses. If the two frontal eminences are divided horizontally by sawing on a plane perpendicular to their centre, and this sec- 28 Dr. Foville on the Anatomy of the Brain. tion is carried to some depth in the brain, the lateral ventri- cles are opened by their anterior extremities, each of these extremities terminating in a cul-de-sac, answering to a frontal eminence. In the interval between these two cul-de-sacs of the anterior extremities of the ventricles we reach the anterior curve of the corpus callosum. If we saw in the same way the two superior occipital protuberances, we arrive at the pos- terior extremity of the two lateral ventricles, each of these extremities ending in a hollow cone, answering to one of the superior occipital depressions and eminences. ” Lastly, if the saw is made to divide the two parietal eminences at their sum- mits, and that portion of the long vault intermediate between them, it leads to that part of the lateral ventricles which is the most spacious and projects the most outwards. It is in this part of the ventricles that is situated, so to speak, the confluence of the anterior, posterior, and temporal regions of these cavities. The same section which leads from the pa- rietal eminences to that part of the lateral ventricles which is the most spacious and projects the most outwards, falls in the interval of the two eminences and of the corresponding por- tion of the ventricles upon the posterior margin of the corpus callosum. There exists on a level with the squamous portion of the temporal bone a depression in the interior of the cranium and a corresponding eminence, almost as considerable, on the outside. If we cut through this eminence and the contiguous part of the brain at the same time, we open the base of the temporal region of the ventricle. Now as there is nothing on the surface of the brain to ac- count for the cranial prominences of which I have just spoken, it appears to me that we may very fairly consider them as caused by the shape of the corresponding regions of the ven- tricles. This conclusion is strengthened by comparing the form of these eminences with that of the portions of the ven- tricles corresponding to them. The frontal eminences are round, like the two cul-de-sacs forming the anterior extre- mities of the ventricles. ‘The occipital protuberances, and especially the depressions answering to them in the interior of the skull, are sharper, if this language is applicable to pro- tuberances and depressions ; and the greater acuteness of the posterior extremities of the ‘ventricles in relation with these protuberances, is a fact sufficiently notorious. Lastly, the temporal eminences are oblique in the same direction as the corresponding part of the hollow of the ventricles. But the influence of the ventricular cavities, or of the serous sacs of the brain, is not confined to the formation of the different Dr. Foville on the Anatomy of the Brain. 29 pairs of eminences which I have just pointed out;it extends also to the form of the skull in general, which, in fact, it con- tributes to determine. The different transverse sections, which I have supposed to be made on a level with the centre of all these pairs of emi- nences on the median zone of the cranial vault, divide this me- dian zone into four regions, always perceptible during life, and each of them presenting an angular curve on the transverse line which separates it from the neighbouring regions. All of them display too an agreement in form and proportions with the corresponding region of the envelope of the ventricles, which seems to me incontestable. The first region, comprised between the frontal eminences and the inferior boundary of the forehead, answers exclusively to the convolutions developed in front of and beneath the cor- pus callosum, and presents but a small projection from above downwards, like the corresponding part of the ventricles. The lower projection on this part of the forehead does not always indicate a considerable development of the corresponding part of the brain. It may, in fact, be simply owing to the great size of the frontal eminences, and in this case the fact may be ascertained by percussion. The second region, included between the frontal and pa- rietal eminences, always forms the largest division of the median zone of the cranial vault; it is arched like the cor- pus callosum itself, and corresponds to the convolutions above this body. Its size, compared with that of the other regions of the bony arch, bears the same proportion to theirs, that the extent of the superior part of the corpus callosum does to the other fibrous parts enveloping the serous cavities of the brain. A considerable eminence is very often seen on the median line towards the centre of this region, in the upper part of the os frontis. This also appears to me, like all the other projections on the median line, to be owing to a thickening of the bones. The third region, intermediate between the transverse sec- tion of the parietal eminences and the superior occipitai pro- tuberances, is scarcely ever convex longitudinally. It is mostly straight or concave in this direction. Frequently even it presents on the median line a well-marked fossa. The complete separation for the two hemispheres at this part, the absence of the corpus callosum, lifted up as in the others by the fluid of the ventricles, and the superior concavity observed in passing from those parts of the ventricles covered by the corpus callosum, to those formed by a distinct fibrous cone 30 Dr. Foville on the Anatomy of the Brain. in each posterior half of the hemispheres, are in accordance with these peculiarities. To this region correspond the convolutions situated behind the posterior margin of the corpus callosum as far as the posterior termination of the ventricles. Lastly, the fourth region, situated in the interval between the superior occipital protuberances and the upper curved line of the occiput, divides the latter into a median convex quadrangle, and two lateral triangles, whose pointed summits terminate near the mastoid process. Now these triangles, instead of being convex like the rest of the median arch, al- most always present a plain or even concave surface. The depressed portions of these triangles correspond at their sharp summits to the insertion of the tentorium cerebelli and the external part of the lambdoidal suture. In the temporal regions of the cranial arch, we always re- mark, on a level with the great wing of the sphenoid bone, a depression running upwards and backwards in the same direction as the fissure of Sylvius, to which it corresponds. A right line drawn from the top of this depression towards the centre of the parietal eminence, marks the course of the fissure of Sylvius, and allows us to measure, on the living subject, the comparative volume of cerebral substance situated in front, and of that behind, this fissure. Now the fissure of Sylvius, and the cranial depression answering to it at the fore part of the temporal fossa, are variously modified according to the modifications of the ven- tricular hollow. The anterior and temporal regions of these cavities are separated by a large nervous mass which follows the crus cerebri. The fore part of the ventricle is enlarged above this mass and the temporal part of the ventricle be- low it. | The fissure of Sylvius, then, forms the interval between two regions of the ventricle, the frontal and the temporal, and consequently the interval between the convolutions co- vering in these two distinct regions of the serous cavity. It ceases above, at the part where these regions of the ventri- cular cavity unite into a common conflux. Its deepest part is below, at the bottom of the widest interval between the frontal and temporal extremities of the ventricle. Thus the form of the brain, and that of the skull also, would seem to be determined in their general character by the form of the serous sacs inclosed in the hemispheres, and constantly filled with the fluid peculiar to them. This is not meant to imply that the cerebral convolutions do not exert any influence on the secondary shape of the Dr. Foville on the Anatomy of the Brain. 31 skull. So far from that, observation proves that when the convolutions are greatly developed, the skull, though retain- ing the form that we have assigned to it, swells out in the intervening regions between the eminences corresponding to the extremities of the ventricles, so as almost to obliterate them; or if they still remain very prominent, they acquire a very great diameter. In this case, the head, modified by the development of the convolutions, acquires the cerebral forin, par excellence. On the contrary, when the convolutions are but very little developed, the prominences, and the regions separating them, are all exceedingly well marked, whilst, at the same time the projections corresponding to the ventricular extremities have avery small diameter. ‘The head then assumes, if I may be allowed to use such a term, the peculiarly ventricular form. The relations just now pointed out between the projecting points of the skull and the corresponding regions of the ven- tricles, appear still further confirmed by observing what takes place in chronic hydrocephalus. One of the first symptoms of this dropsy of the ventricles is the increased salience of these cranial tumours. But I shall not pursue the details of the relations between the skull and the brain any further at present. I consider them useful in reference to what is called surgical anatomy, and also for all those cases which call for an exact knowledge of the relations between the skull and the brain. The subject has been pursued in a work of some ex- tent, which I intend before long to lay before the public. To sum up, I consider that the fibrous parts of the brain are conductors; some from without to within, others from within to without. I believe that these conducting parts may be distinguished into afferentes and efferentes, and that the distinct course of both the one and the other may be demon- strated. ‘The first are inserted especially into the circum- ference of the gray substance, and the second into its internal surface. The gray substance of the convolutions intermediate be- tween the two preceding orders of fibrous parts, seems to me to be the material substratum, through the instrumentality of which the will directs the movements of the body. The prominences constantly seen coupled in pairs on the arch of the skull appear to me to be produced by the pro- jection of the corresponding regions of the ventricles. ‘The median eminences, not universally present, appear to be pro- _ duced by a thickening of the bones. The median zone of the cranial arch is naturally divided into four sections; one, anterior, corresponding to the fore part of the corpus callosum, and to the conyolutions de- 82 Dr. Reade on the permanent Soap Film, veloped before and beneath the level of the same part of that body. wire The second, more extensive, intermediate between the frontal and parietal eminences, is of a length proportioned to the extent from before to behind of the corpus callosum. It ceases behind on a level with the posterior margin of that body. 7 The third section, often concave from above to below, some- times even hollowed into a furrow on the median line, is pro- portionate in length to that of that part of the hemispheres completely separated, behind the corpus callosum. The fourth section, intermediate between the superior oc- cipital protuberances and the upper curved line of the os occipitis, displays in its middle a projecting quadrangle, corresponding to the hinder extremities of the ventricles, and to the conyolutions situated behind and beneath these ex- tremities *, March 30, 1840. V. Remarks on the permanent Soap Film and on Thin Plates. By JosepH Reape, M.D. “ Scilicet ut possem curvo dignoscere rectum, Atque inter silvas Academi queerere verum,””—Horace. To the Editors of the Philosophical Magazine and Journal, GENTLEMEN, A® the entire of the second book of Newton’s Optics is based on the theory first advanced by Dr. Hook, or rather by Mr. Boyle, “that colours are produced by the thicknesses of the plates,’’ supposing your scientific readers well acquainted with that great philosopher’s experiments, I shall immediately proceed with my own. Should these be capable of explanation according to the Newtonian theory, I shall be ever ready to alter my opinions, and what at pre- sent I conceive to be legitimate inferences. Aware of the difficulties I have to encounter, and of the prejudices against everything opposed to a doctrine stamped with the name of Newton, and advocated by the most celebrated characters, I hope for the indulgence of my scientific readers. Experiment 1. Having made a permanent soap film, as already described in your Journal}, and shown two years ago at the British Association at Liverpool, I placed the bottle on an inclined plane on the table until all the bands of colours * An able report on the subject of Dr. Foville’s researches has recently been presented to the Academy of Sciences by Professor Blainville. It contains further discoveries made by the Doctor with regard to the origin of the eighth pair of nerves. + [Lond, and Ed, Phil, Mag, vol, xi. p, 878.—Epit.] and on Thin Plates. 33 had evaporated and the entire film become of a black ap- pearance, what Newton likened to a hole in his bubble, transmitting almost the entire light. I now moved the bottle to and from me, and in a short time the entire film was clothed with silvery white, reflecting atoms, which soon formed into beautiful bands of colours by means of cohesive attraction; for, as they formed nearly simultaneously, they could not be produced by a descending fluid, causing relative thicknesses; but perhaps it may be said, that the film was thickened by evaporation of the saponaceous fluid. ‘To ob- viate this objection, I made the following new, and I presume to hope, conclusive experiment. Experiment 2. Having procured a cylindrical glass tube, about one inch in diameter, I dipped one end to the depth of three inches into a saponaceous solution and formed a film, which, when the tube was held perpendicularly, glided down three inches. I now corked the upper orifice, to prevent further descent, and laying the tube on the table, in a short time the bands were formed; when these disappeared, and the film was black, I shook the tube from side to side, and in a short time the black changed toa silvery white, and then formed into bands of different colours. On placing it again on the table the film appeared all over black. Here there could be no thickening of the plates by evaporation, as the air was at the bottom of the tube. This experiment, easy of manipulation, I hope may be esteemed conclusive, or, as Sir Isaac Newton calls it, an “‘experimentum crucis.” As my experiments are now shown in lecture-rooms, I am anxious that they should be accompanied by legitimate inferences, par- ticularly as some observations made by a Dublin Professor at Liverpool, prevented an explanation which I now give. Experiment 3. Having procured a plate of very deep blue glass, four inches square, I wiped it well, and then breathed on it through a narrow glass tube, forming a plate of vapour, which, by evaporation, went through all the relative thick- nesses measured by Newton, without any variety of colours. I now breathed a second time on this plate, and drew my _ finger across the middle so as to make furrows in the plate of vapour; immediately all the variety of colours in nature was formed, like threads of variegated silk. This experiment evidently shows that the atoms were relatively approximated, and that it was this approximation, and not any relative thick- ness of the plate of vapour, which caused the colours. Experiment 4. On repeating the experiments of the Abbé Mazéas, ‘Mémoires présentes,” with two pieces of plane glass, he justly remarks, that friction is necessary in the formation of Phil. Mag. 8. 3. Vol. 17. No. 107. July 1840. D 34 Dr. Reade on the Permanent Soap Films, coloured rings. Now it is evident that friction cannot alter the thickness of a plate of air, but must bring into view some sub- stances capable of condensation ; and there is nothing mixed with the air capable of such condensation, except vapour. I therefore must attribute the colours to this cause. Convinced that vapour was the cause, I improved on the Abbé Mazéas’s experiment: for, on washing one of the plates of glass with soap and water, and holding it before the fire, then breathing on the other, by means of a slight degree of friction I co- loured the entire glass, with a large black spot in’the centre more than an inch in diameter. When this black spot was formed, the glasses were so firmly united as to require a strong: force to separate them. This I attribute to the air being pressed out, and then the glasses acted in the same manner as a leather soaker used by school-boys, and not to any cohesive attraction of the surfaces, as supposed by chemists. I coated the glasses with a plate of water, and on pressing them together no co- lours appeared, until by a strong degree of friction I produced vapour. [also smeared the glasses with some candle-grease, and found no colours, until I held the glasses to the fire, when, on using friction, vapour and colours were produced. Atomic Theory of Colours. Having endeavoured to prove, I hope with effect, that colours are not produced by relative thicknesses of the plate, as advanced by Sir Isaac Newton in the second book of his Optics, I shall proceed to give what I conceive is the true explanation of this interesting phenomenon. Grimaldi and others maintained that light was capable of condensation and rarefaction. However, as they brought forward no experi- ments to prove it, I think it unfair to say that I took my theory from that celebrated philosopher. If we hold a candle before a black shade made with a pencil or any other slender and opake substance, and hold the paper sideways to the window, two shadows are formed, the one blue from the candle, the other brown from the daylight. Now this brown shadow can be changed to an orange by approximating the candle; at a yet nearer distance the orange becomes a perfect yellow, and when very close the colour entirely disappears, or the light of the shadow becomes rarefied into perfect trans- parency. ‘The blue in like manner undergoes rarefaction and change of colour, from a blue to a purple; and when the candle is very near the coil of paper, the shadow becomes black, because then there is but one light, that of the sun. To argue that the shadow is a mere privation, would be to say that brown, orange and yellow, blue and purple were privations;: and on Thin Plates. 35 (green was made by overlapping the blue and yellow shadows.) Surely, if it were a mere privation, the light of the candle: could only illuminate the black shadow and make it white. However, the fact is, that the black shadow is condensed light, and rarefied into different colours. If we suppose a number of grains of shot to represent the soap atoms, placed at different distances fron: one another, and represented by a, a*, a, a’, &c,, &c., the light passes through those and is reflected from the second surface, and gives, when variously condensed, this or that colour, according to the approximation of these atoms, and not the thickness of the plates*. Ascending and Descending Currents in a Soap Film. On making a soap film I placed it on an inclined plane, and perceived the coloured bands to descend slowly, and in- creasing in breadth, until at last the attraction of cohesion lost its influence, and the atoms became free and ascended in currents, particularly at the concave sides of the bottle ; as they rose generally white atoms, they passed through the coloured bands, until after passing through blue, red, green, &c. they fell into the ranks of their own colour. In boiling water we perceive currents by means of powdered resin, or other light substances, evidently caused by an addition of caloric. Here there is no such addition, and we must look to some other cause, perhaps electricity. Sometimes these atoms take an elliptical or circular motion; this is best seen by placing the bottle with the plane film on the table and surrounding it with the warm hand; as the room was at 60° and my hand at 80°, I threw 20° into the film. Here there can be no differences of thickness; however, almost simultaneously, the force of cohesive attraction forms the coloured bands, and when the film becomes white, then these beautiful and in- teresting movements take place. How far these laws may act on the solar system, I leave to the contemplation of the astronomer. ll fluids are in perpetual motion, from the broad Atlantic to the permanent soap film; and hereafter I shall be enabled, by some new experiments, to show that the same laws regulate the atmosphere. Colours of the Clouds and Complementary Colours. When the soap film was entirely black, after remaining perhaps an hour on the table, I placed the bottle in a basin of boiling water, and in a short time perceived the film to be * Count Rumford, as well as others, made many experiments on co- loured shadows, but entirely overlooked these changes; at last, in despair, he says, it was a deceptio oculi. : | D2 36 Dr. Reade on the Permanent Soap Films, clothed with white reflecting atoms; some of these soon changed to a purple, blue, orange, &c., and when the bottle was placed on an inclined plane the coloured bands were formed, broad and vivid. ‘To ascertain whether the bands of colour were similar by transmission and reflection, I held the film above a lighted candle, at an angle of about 45°, and perceived exactly the same coloured bands, and not any com- plementary colours, ‘*magnis componere parva.” We must attribute the colours of the clouds to the approximation of vaporific atoms, and not to different-sized globules of water. It is an interesting object of inquiry, to say why the black re- flecting atoms at great distances, should by heat or agitation, approximate to form white or bands of colour. We may, hypothetically, surmise that these atoms are spherical, and are enlarged by caloric, in the same manner as air in a bal- loon or bladder; or we may suppose that, by agitation, &c., they become oblate spheroids. Nothing is more surprising than the permanency of this soap film. In a few seconds Newton’s bubble bursts, and conse- quently hindered him from making deliberate observations ; but now that we have one which lasts for months, can be washed and renewed, an inferior mind may investigate the phzenomena of light and colours with more success than even that great philosopher, in the infancy of experimental science. Indeed, every new experiment opens a wider field for re- search, and I am sanguine enough to think that the perma- nent soap film and the newly invented iriscope may produce interesting discoveries. With intent to ascertain this perma- nency, I formed two films with a similar saponaceous mixture, in equally-sized bottles; the one was corked, the other open, and consequently exposed to the action of the atmosphere; in a short time the open one broke, the other remained for weeks. I therefore inferred that the film broke from the vaporific action of the atmosphere. ‘That it was not from pressure, I proved, by putting in a very long cork, so that the pressure might be increased; nor was it from agitation, as supposed by Newton, for in washing the film it was well shaken; neither could it proceed from any chemical action, as I made the film zz vacuo. I remarked that a film formed on the mouth of a wine glass remained a long time when the atmosphere was heavy and charged with vapour, whereas of a dry day it speedily burst. I hence infer that the air in a corked bottle becomes saturated with vapour, and thus that evaporation is diminished. I shall now sum up the foregoing arguments, to show that the colours do not proceed from re- lative thicknesses, and on Thin Plates. 37 1. The bands form simultaneously, or nearly so. 2. Plates of grease, water, vapour, go through all the thicknesses without colours; but as soon as friction forms vapour, or the finger approximates the atoms, colours appear. 8. By holding the bottle to the fire, or even by the heat of the hand, circular currents of red, white, blue, rise in a green field; and, at all times, coloured atoms are both as- cending and descending, contrary to gravity and thickness, the bands increase in breadth as they descend. 4.To end. Ihave succeeded in making a film sufficiently thick, with soap, as to counteract cohesive attraction, yet suf- ficiently thin to evaporate without undergoing any change of colour. The following diagrams give the different stages of the atomic theory of colours. Pro 1. Aches diss “blac, it Ne white. [—\ brown. pee ee | blue. aaat yellow EE A! red N ee SEE : Fig. 3. black. all black. white. In fig. 2, how can different thicknesses produce three- fourths of the film white? In fig. 3 there is a very small seoment of white at the bottom, and by shaking the bottle the entire film becomes white, and then forms into chromatic bands. The best method of seeing these minute saponaceous atoms forming colours, is to shake fig. 2, when atoms no larger than the point of a pin are diffused in the black, and after a time are seemingly dissolved in the black atoms, just as when a Jump of white sugar is dissolved in hot water; at first the solution is clouded, and then the saccharine atoms 38 On the Form and Optical Constants of Nitre. become as minute as those of the water, and equally semi- transparent. A candle held before fig. 3 is faintly reflected from the second surface, as there is no actual contact of atoms in nature; all substances, even the hardest metals, are porous. In my next communication I shall give a theory of the Iriscope, compared with Nobili’s rings. I remain, Gentlemen, Your obedient servant, London, June 8, 1840. J. Reape, M.D. VI. On the Form and Optical Constants of Nitre. By Professor M1LLER*. serie following values of the angles between normals to the several faces of nitrate of potash are calculated from means of the best measurements of a large number of crystals at a temperature of about 19° centigrade. ‘The close agreement of the results afforded by different crystals, renders it proba- ble that the errors of the concluded angles do not in any case exeeed half a minute. Fig. 2. pp 10°35 5's'\' 109 "0 hy 65 41 mm! 61 10 Ly 45 50 ea 38 88 oy 5b 1°5 In twin crystals having the twin axis perpendicular to one of the faces m (fig. 2). mm, 57° 40! Ai; Bic ee The parameters are respectively proportional to the num- bers 2°4285 3; 1°43523; 1°7023. The cleavage most easily obtained is parallel to the faces p. 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(THIRD SERIES.] AUGUS T 1840. XIII. On the Theory of the dark Bands formed inthe Spectrum from partial Interception by transparent Plates. By the Rev. Baven Power, M.A., F.RS., F.G.S., F.R.Ast.S., Savilian Professor of Geometry in the University of Oxford*. (1.) (PRE phenomenon of peculiar dark bands crossing the prismatic spectrum, when half the pupil of the eye (looking through the prism) is covered by a thin plate of any transparent substance, the edge being turned from the violet towards the red end of the spectrum, was first described b Mr. lox Talbot in 1837 (Lond. and Edinb. Phil. Mag. and Journal of Science, vol. x. p. 364.), who showed that these bands are due to the interference of the two halves of each primary pencil, one of which is retarded by the plate. (2.) Sir David Brewster has given various new modifications of these experiments (British Association Reports, vol. vil. Trans. of Sections, p. 13.), the most material of which tend to show that the effect is fully produced only when the plate is in the position just described, and diminishes and disappears as it revolves in its own plane; the same observation being also extended to the case of the spectra formed by inter- ference from grooved surfaces, or gratings. (3.) The explanation given by Mr. F. Talbot accounts for the production of the bands simply, but assigns no reason why the interception must take place on one szde more than the other. ‘That it does so, is considered by Sir David Brewster as indicating an entirely new properly of light; having refer- ence to the different sides of the pencil related to their posi- tion of greater or less refrangibility, and which he has not inexpressively termed a peculiar “ polarity.” — * Communicated by the Author. Phil. Mag. 8. 3. Vol. 17. No. 108. Aug. 1840. G 82 Prof. Powell on the Theory of the dark Bands (4.) My attention was drawn to the subject in the course of last summer, when I repeated the experiments, and devised several] new modifications with reference to an explanation which it appeared to me was supplied by the undulatory theory ; to these investigations I referred briefly at the Bir- mingham meeting of the British Association, 1839. For se- veral reasons (on which I need not here enter) I have delayed publishing any details; nor should Ido so now, but that ha- ving learned that Mr. Airy has recently pursued the research to many entirely new conclusions*, I am anxious to put on record the few points I have been able to establish, and to vindicate my views from misconceptions to which they have been exposed. . (5.) The following distinctions are important to be borne in mind with reference to the explanation of the phenomena. In these experiments we have to consider the different ele- mentary pencils of which the spectrum, as presented to the eye, is formed; and with respect to each of these, in the case of the prismatic spectrum it is easily seen that the edge of the plate intercepts that half which lies towards the EDGE of the prism. In the znterference-spectrum (according to Fraunhofer’s method), the spectra are formed one on each side of the axis, with their violet ends towards it. ‘The edge of the plate in this case must always intercept that half of each primary pencil, which after passing the focus lies NEAREST to the aais. (6.) I have found that with the same prism the intercept- ing plate must be within limits of thickness, which differ ac- cording to the substance of the plate, and with the same plate the character of the bands differs with the medium of which the prism is formed. ‘These differences appear to depend on the refractive and dispersive powers of the substances. (7.) With a prism of flint glass and a plate of mica, the greatest thickness which can be used may be about the ;25th of an inch. In this case the bands appear fine and numerous, and it seems only in consequence of their increase in number that they cease to be distinguishable when the thickness is increased beyond this. If we use less thicknesses (such as those into which mica is easily split) the bands become broader and fewer, and at length faint and ill-defined. It is perhaps not possible to distinguish them if fewer than four or five are formed through- out the spectrum. The bands are never very dark; show- ing that only a portion of the rays is concerned in their for- mation. [* A notice of Mr. Airy’s paper on this subject will be found in our re- port of the proceedings of the Royal Society for June 1S, 1840.—Ep1t. ] formed in the Prismatic Spectrum. 83 (8.) When the plate is very thin, another set of appear- ances presents itself. On splitting a piece of mica to such a tenuity that only a few indistinct broad bands were barely visible with a flint- glass prism, I observed at the same time another set of very Jine but extremely faint bands, evidently independent of the - former. (9.) When the film of mica was still thinner, the droad bands ceased to appear altogether, and only the jine set were visible. ‘To show ¢hese bands the films must be so thin as to be nearly iridescent : it is difficult to succeed in tearing them off sufficiently fine. 1 have sometimes used drops of water between glass plates pressed hard together. These bands are always very faint; but they are somewhat more conspicuous with prisms of the more dispersive oils, and always require a strong light to be seen. (10.) here is, however, a more remarkable circumstance connected with this set of bands; they continue to be formed when the edge of the thin film is towards the thicker side of the prism. (11.) In pursuing the theoretical explanation, we have to consider the conditions which may affect the rays situated towards the opposite sides of those primary homogeneous pencils, into which the incident beam of light is separated, and which converge in the eye to form the several points in the spectrum, both in the case of the prism, and of interfe- rence from grooves or gratings. Now in either case a distinction of this kind is deducible from the wave-theory, on comparing the length of undulatory route of the two extreme rays of any primary pencil; from which it appears that one of these rays is always more retarded than the other, as well in the prismatic as in the interference spectrum : that side of the pencil which is previously the least retarded, being that to which the plate is applied in the original form of the experiment. This distinction, combined with the general principles of explanation at first referred to, appear to me not only sufficiently to account for the ordinary phe- nomena, but in my modification of the experiment to assign a reason why a similar effect should be produced on the oppo- site side. (12.) With regard to the mathematical investigation, in the case of the prism, without going into a formal discussion, it is sufficient to observe, that on the principles of mathematical optics, when a diverging pencil of homogeneous light is re- fracted through a prism in the position of minimum deviation, G2 84 Prof. Powell on the Theory of the dark Bands the emergent pencil will originate from a geometrical focus, which is not a single point, but a caustic, whose convexity is towards the edge of the prism. Hence, on the principles of the wave-theory, it follows that the side of the pencil which lies towards the edge of the prism is that which undergoes less retardation, or has the shorter undulatory route; this dif- ference varies slightly for the different primary rays. I had arrived at this conclusion by a different approximate method, when in some correspondence the Astronomer Royal pointed out to me the above view of the problem, as con- nected with his investigations ‘‘ on the light in the neigh- bourhood of a caustic.” (Camb. Trans., vol. vi. part 3*.) (13.) With respect to the interference-spectrum, we have only to follow out the investigation given in Mr. Airy’s tract (Arts. 80, 83.) (as that gentleman has suggested to me) in the following manner. Taking the focus as the origin and the axis of the object- glass as the axis of x, let x y be the coordinates of any point in the wave, ab those of a point in the focal image on the same side of the axis, then the radius of the wave being ¢, we have | Gaythiyes and expanding and neglecting powers of y above the third, we find , 2 Lah A ae a2=C Das The distance g from xy to ab will be g= Vv ((e-a) + (y—8)’) 5 here performing the various expansions, and for brevity writing e® = (c—a)*? + 6%, we at length obtain (going to the third power of y) 2 a 1 pie BaEtcinll kee hit ttt nee —+26 a 2 ee: She odwie ade aan eS yt ay} 1 —26 z | BH e Y J The terms involving the second power of y have the same value on each side of the axis, and those depending on the third power are found to be [* See Lond. and Edin. Phil. Mag. vol. xii. p. 452,—En1r.] Jormed in the Prismatic Spectrum. 85 1, faba , years Y : ce _ bx fa ib : 9g 73 : : 2 e% ea) re? f +73 oo grail 9 ena yyndh Spay . Here, if —<-—, (which is the case, the image being form- tn nk ed in the focus, so that in fact we might assume a = 0Q,) it follows that when 0 and y have the same sign, this expression will be negative; that is, for the ray which has d and y on the same side, or is nearest the axis after passing the focus, the route will be the shortest. ‘The difference will be very small, and will vary slightly for the different rays of the spectrum. (14.) This difference of retardation in the several rays of each primary pencil, combined with the obvious principle laid down by Mr. F. Talbot, appears to me to supply an ex- planation of the phznomena. The whole effect in these experiments is made up of two parts, the original retardation, and that superinduced by the plate. If the previously Jeast retarded ray be intercepted, we take the difference, if the most retarded, the swum of the two effects. When we apply the plate, the whole resulting retardation may fall within the limits, (before mentioned, § 6.) or not, ac- cording to the magnitude of the two retardations, and accord- ing as we take their sum or difference. If it be beyond the limits for one portion of the pencil, it may be within them for another. In general, in the original form of the experiment, that is, for plates of ordinary thickness, the difference falls within the limits, though the swm is beyond them, for all portions of the pencil. But with a very thin plate, the sum may also be within the limits for those parts of the pencil whose difference of retardation is small: Or, in other words, with plates of a certain thickness, the retardation is too great to give bands with any portion of the pencils, when the plate is applied to the previously most retarded side: but it will give bands with some portion when applied to the previously east re- tarded side. On the other hand, if an extremely thin plate be applied to the most retarded side, it will still give bands with one portion of the pencils, as well as when applied to the least retarded side with other portions. Oxford, July 5, 1840. ie ey XIV. On the Potatoe Spirit Oil of the French Chemists. By James Apsoun, M.D., M.R.1.A., Professor of Chemistry in the Royal College of Surgeons, Dublin*. N December 1838, I received from my friend Mr. Scanlan a specimen of an oily fluid which had been given him by Mr. Bowerbank, an eminent London rectifier, and which the latter gentleman had found in small quantity in the faints or weak spirit drawn off towards the close of the rectification of common whisky. Shortly previous to this time, Mr. Coffey, the inventor of the celebrated patent still, had observed the same substance at the extensive distillery of Sir Felix Booth; and upon coming over to Dublin, and visiting the establish- ment of Mr. Busby at Blockpitts in this city, Mr. Scanlan had the satisfaction of recognizing this same oil in the faint vessel, constituting a thin stratum resting upon the surface of the re- mainder of the fluid. The oil obtained from Mr. Busby’s concern had a reddish- brown colour, owing to dissolved vegetable matter, and its specific gravity was ‘8401, that of the faints on which it rested being °9269. Shaken in a graduated tube with an equal bulk of water, its volume was reduced 20 per cent., and the water upon distillation yielded alcohol. To insulate the oil, there- fore, the following method was adopted. The fluid obtained from the faint receiver was first washed with an equal bulk of water ; then shaken in a bottle with an equal weight of pulverized and anhydrous carbonate of potash, and finally distilled from a glass retort, the condensation be- ing effected by Liebig’s tube refrigeratory. It began to boil at 262°, after which the temperature rose gradually until it became 268°, at which it continued until the whole of the oil was nearly over. The fluid first drawn off was set apart, as still containing alcohol, and that alone reserved for further purification which distilled over at 268°. This portion was redistilled. The ebullition commenced a little over 267°, and in less than a minute rose to 268°, at which point it continued until the rectification was nearly completed. The first and last portions being rejected, the middle portion, or that which came over at 268°, was set apart for experiment, The oil thus procured is a perfectly colourless liquid, de- stitute of all viscidity. ‘The specific gravity is -8138, and, as has been already observed, it boils steadily at 268°; cooled to —6° it does not congeal. With rectified spirit it is mis- cible in all proportions, its specific gravity being thus aug- * Communicated by the Author. On the Potatoe Spirit Oil of the French Chemists. 87 mented, and its boiling point lowered. It is immiscible with water, but nevertheless when agitated with this liquid, it ab- sorbs an appreciable quantity of it. It has a pungent and pe- culiar odour, and a sharp biting taste, somewhat similar to that of the oil of cloves. When gently heated it readily takes fire upon approaching to it a lighted taper, and burns with _ a clear flame unaccompanied by smoke. It is an excellent solvent for the fats, and also for resinous substances. Cain- phor, for example, is readily dissolved by it; and the same may be said even of copal, ifa gentle heat be applied. Potash is taken up by it in considerable quantity, oil of vitriol gives ita crimson colour. To determine its composition the follow- ing experiments were made: (1.) 4°24 grains of the oil burned in the usual manner with oxide of copper gave of water 5:06 grains, and of carbonic acid 10°42 grains. (2.) 7°71 grains gave of water 9:22 grains, and of carbonic acid 19°12 grains. (3.) 6°63 grains gave of water 8°05 grains, and of carbonic acid 16°26 grains. The following are the results deducible from these experi- ments : (1.) (2). (2,3 Carbon......-.. 67°96 68°59 67°84 Hydrogen .... 13°25 13°28 13°48 Oxygen ....000. 18°79 18°13 18°68 100 100 100 The means of the numbers yielded by the three experi- ments are given underneath in column (a.). The numbers in column (d.) are the quotients of the corresponding ones in (a.) divided by the respective atomic weights of carbon, hy- drogen, and oxygen, and those in column (c.) are others in the same ratio with the quotients. (a.) (d.) fc: Carbon ....... 68°13 11°132 4°804 Hydrogen ... 13°33 13°330 5°753 Oxygen ...... 18°54 sf Bie 1:00 100° The inspection of the latter shows that the most probable formula for the oil is C; Hg O,, which would give the follow- ing parts per cent. Carbon .....ceecees 68°60 Hydrogen......... 13°45 Oxygeneeveercesees 17°95 100. 88 Dr. Apjohn on the Potatoe Spirit Oil Assuming this formula as the true one, the deficiency in the carbon experimentally determined is not greater than what usually takes place; but the error in the hydrogen, though trifling in amount, being upon the opposite side to that on which it usually occurs, it became expedient to resort to some method of verification. ‘The specific gravity of the vapour of the oil was therefore taken according to the well- known method of Dumas. The weight of glass ball filled with dry air, the pressure being 30°324 and temperature 48°°5, was 914°86 ors. The ball was sealed at 364°, and then weighed 917°78 ers. Hence 917°78 — 91486 = 2°92 grains is the excess of the weight of vapour in ball over that of the air displaced. The capillary end of the beak attached to the ball having been broken under mercury, it was ascertained by the amount of this metal which flowed into the ball, that its capacity was 16°76 cubic inches, which, at a pressure = 30, and a temperature = 60°, will (supposing it air) become 16°76 448+60 _ 30°324 a7 Su i aeg Ae UUEE ae ae 17°333 cubic inches. From this must be subtracted *1 cubic inch which was found to remain in the balloon, so that the bulk of air excluded by the vapour, when reduced to the mean temperature and pressure, was 17°233 cubic inches, whose weight = 5°344 grains. Hence 2:92 + 5°344 = 10°264 is in grains the weight of the va- our. The capacity of the glass balloon at 48°-5 being 16°76 cubic inches, it will, owing to the expansion of glass, become at 364° 16°843 inches. ‘This therefore is the volume of the vapour and bubble of air at 364°. But the volume of the latter be- ing 0°1, it will at 364° become 0°16. Hence the true volume of the vapour at 364° = 16:843 — 0°16 = 16°683; so that e 448460 30°324 SO Oe WaRieOd 30 vapour reduced to a temperature = 60° and pressure = 30. But as this weighs 10°264 grains, 100 cubic inches of it would weigh 97°298 grains. ‘The specific gravity therefore of the OT 200 srorry = 213% Now if the composition of the oil be C; Hg Oj, the specific gravity got by adding together the products of the densities of the vapours of the different elements by the number of atoms of each would be 3:072. But we have here so close a correspondence between experiment and calculation, that no doubt can remain as to the correctness of the basis on which = 10'549 is the volume of the vapour is of the French Chemists. 89 the latter rests, or that the true formula for the oil is that al- ready assigned. These experiments were made in the winter of 1839, and at the time I had concluded them I was under the impression that the oil, to which they relate, was a new substance, or rather one which had not been previously described. In some © time after, however, upon looking over the second part of Mr. Graham’s Elements of Chemistry, which had been sent me by the author, I was much surprised at finding at page 134, in a table of the volumes of atoms in the gaseous state, mention made of a substance under the designation of * oil of the ardent spirit from potatoes,” to which he attributed the very same formula and density of vapour which I had found to belong to the oil found in grain-whisky, in the ex- amination of which I had been recently engaged. Anxious to investigate the matter further, and to ascertain if the two oils were certainly the same, I looked into Ber- zelius’s System, and the 5th volume of the Trazté de Chimie, appliquée aux Arts, by Dumas, devoted to the subject of or- ganic chemistry, but could not find any mention in either of the essential oil from potatoe spirit alluded to by Graham. Upon, however, turning to Dr. ‘Thomson’s recent volume on vegetable chemistry, I found, page 481, a notice of this fluid, and references to the 30th and 56th volumes of the Annales de Chim. et de Phys.in the former of which its origin and properties are described by Pelletier, and in the latter of whichits analysis is detailed by M. Dumas. ‘The properties I find ascribed by these chemists to the potatoe spirit oil are precisely those which belong to that which I have examined from corn-whisky, the only difference being that Pelletier represents its specific gra- vity as ‘821, whereas I have found that of the oil I obtained from Mr. Scanlan but ‘813, a difference, however, easily ex- plained by the circumstance of his not having taken the ne- cessary steps for rendering the fluid he examined perfectly free from water and alcohol. ‘The analytic results also of M. Dumas are nearly identical with mine, approaching how- ever more nearly, as might indeed be expected from his great skill in this department of chemistry, to the formula C, H, O, which he adopts, and which Professor Graham has taken trom his memoir. I may lastly mention, as a very unusual coinci- dence, that the specific gravity of its vapour, as obtained by Dumas, is 3°147, or but unity in the second place of decimals oreater than what has resulted for the corn-spirit oil from my experiments. We thus arrive at the conclusion, that the two fluids are identical, or that the oil which has hitherto been considered 90 Dr. Apjohn on the Potatoe Spirit Oil as peculiar to potatoe spirit, occurs also in that which is de- veloped during the fermentation of grain. From this latter source it admits of being procured in great quantity. When first observed by Mr. Coffey at Sir Felix Booth’s, there was an inch of it in the faint receiver, and from the diameter of the vessel he estimated its total amount at 50 gallons. ‘This is the quantity produced at that establishment every fortnight, the excise laws compelling the distiller to distil and brew alternately, and a week being generally consumed in each process. The whisky manufactured some years ago contained a considerable quantity of this oil, and owed to its presence a great deal of the pungency of taste by which it was distin- cuished. From its high boiling point, and the nature of the stills at present used, but a very small portion of this substance now passes over, and hence the reason why the spirit at present made is, as compared with the product of the old processes, less disagreeable to the palate, and probably less injurious to the constitution. It is no doubt owing to the same cause, viz. an improvement in the process of distillation, that this oil has at length been noticed in the distillers’ faints. Upon the old system of manufacture the greater portion of it was driven over, and was held dissolved by the spirit into which it was thus introduced ; but with the modern stills, particularly that devised by Mr. Coffey, nothing having so high a boiling point as this oil can by possibility pass into the part of the apparatus where the spirit is condensed. With respect to the manner in which the substance originates, whether it ex- ists ready-formed in the materials subjected to fermentation, or is a product of the process, 1 am not aware of any facts calculated to decide such a question. As, however, it is found in the fermented wash of both corn and potatoes, it may be presumed to be derived from the starchy principle, which is common to both. The potatoe spirit oil, as it has hitherto been called, has I find of late attracted much attention. Pelletier from some rough experiments upon it with acids, threw out the con- jecture that it was more analogous to alcohol than to the true volatile oils, and this opinion would seem to have been in some degree adopted by Dumas. More recently (Ann. de Chimie et de Phys., Jan., 1839) M. Auguste Cahours has revived this opinion, and concluded it to be one of the group including alcohol, pyroxylic spirit, and acetone, and has even succeeded in procuring from it a carbo-hydrogen, in which the elements are, as usual, associated in the ratio of atom and atom. M. of the French Chemists: 91 Cahours represents potatoe oil by the formula C,, H,, O, +H O, which makes it as to composition perfectly analogous to ordinary alcohol. The carbo-hydrogen C,) H,, he insu- lated by distilling the oil from anhydrous phosphoric acid. He calls it amylene, and finds the specific gravity of its vapour to be 4:904, so that an atom of it gives but one volume of - vapour, a circumstance in which, as Cahours observes, it agrees with Dr. Kane’s mesitylene, C, H;, but differs from the car- bohydrogens which occur in alcohol and pyroxylic spirit. By acting on potatoe oil with sulphuric acid and chlorine, Ca- hours obtained compounds corresponding perfectly with those yielded by alcohol when similarly treated. ‘These researches give additional interest to the discovery of this fluid in grain- fermented wash, and in such quantity as to be much more than adequate to meet any demand for it with a view to the interests of science. I may here observe, that I should have long since presented this notice to the Academy, but for the following reasons. There is another oily substance having, at common tem- peratures, the consistence of butter, which is long known to exist in the faints of grain spirit, and in smaller quantity in the spirit itself’ Upon looking through systematic treatises on chemistry, I found that this oil had been but very imper- fectly described, and that, in particular, no experiments had been made with the view of determining its composition. I had therefore resolved to submit it to an accurate examination and analysis, and to keep back what I had ascertained in reference to the fluid oil until I had completed my investigations into the nature and constitution of that which is a soft solid at common temperatures. In this investigation I had made some progress, when my attention was directed to a paper by Liebig and Pelouze, in the 63rd volume of the Ann. de Chim. et de Phys., in which, with their usual ability, they develope the nature of a butyraceous or fatty product which they had re- ceived from M. Deleschamps, and which comes over towards the close of the process of distilling wines with a view to the production of eau de vie or brandy. This oil they found to be a mixture of an acid which they called cenanthic acid, and of a compound of this acid with the oxide of zthyle, that is of cenan- thic acid and cenanthic ether. Upon perusing this paper I saw at once, from the experiments I had already made, that the fatty oil of grain spirit was identical with this mixture, with the exception that some third oleaginous material was present, which Liebig and Pelouze had not found in what they had operated upon. Upon this third substance I have made some experiments, the results of which I shall probably at some 92 Observations on the Climate of Italy future period submit to the Academy. I have resolved, how- ever, no longer to defer giving publicity to my experiments iden- tifying the fluid oils of grain and potatoe spirit, having had my attention drawn by Dr. Kane to a recent volume of Poggen- dorff’s Annalen, containing a paper by M. Mulder, in which I find myself anticipated on the other point; and the butter of corn spirit is satisfactorily shown to be what I had concluded it to be, not entirely from my own experiments, but from a comparison of them with the researches of Pelouze and Liebig. Mulder also notices the third principle which is associated with the cenanthic acid and cenanthic ether, and describes it under the name of oleum siticum. ‘The object therefore of the present communication is much more limited than it was originally intended to be, professing only to announce the de- tection of the potatoe-spirit oil of Pelletier and Dumas in fer- mented infusions of the mixed grains employed by the distil- ler. But as Mulder conceived his discovery of sufficient in- terest to justify him in giving it to the scientific world, I shall, I trust, be pardoned for bringing an analogous fact under the notice of the Academy. } XV. Observations on the Climate of Italy and other Countries an ancient times*. A VAGUE notion seems to have prevailed for some time past among persons conversant with ancient authors, that the climate of Europe in the classical ages of Greece and Rome must have been considerably colder than at the pre- sent day. Latterly this question has been taken up by two philosophers, who from a consideration of the vegetation have come to a different conclusion. Most persons probably have read the interesting essay by Arago in the Annuatre for 1834, who states that several of his facts have been borrowed from the writings of Schouw. ‘The conclusions drawn by these writers are probably in the main correct; but some of the facts stated by them appear to require modifications, which are more fully explained in the following pages. I. Vegetation of Ancient Italy: the beech, the date-palm, the olive. It has been said that Virgil speaks of the beech as growing in the neighbourhood of Rome; whereas now the climate is too hot for that tree, which is not found till we reach a con- siderable height on the Apennines. In fact, Tenore (Cenno * Communicated by the Author. and other Countries in ancient times. 93 sullo Geografia Fisica e Botanica del Regno di Napoli, p. 60*.) places the region of the beech in Southern Italy, at from 400 to 600 toises above the level of the sea. Virgil, however, in reality never speaks of the ‘ fagus,” generally supposed to be the beech, as growing near Rome. ‘That tree is mentioned twice in the Georgics (1. 173. and ii. 71.), but ina way from . which nothing can be concluded with regard to its locality ; and once in a similar way in the Kclogues (iii, 12.): there are, however, two other passages where the indication of the locality is more precise. ‘The first is the well-known passage of the first Eclogue. It is too obvious to require any discus- sion, that in this instance the scene is laid in the territory of Mantua. ‘The second passage (Kicl. ix. 9.) refers to the same country, and specifies the position of the beeches still more clearly as in the plain, but not far from the foot of the hills, e qua se subducere colles Incipiunt, mollique jugum demittere clivo, Usque ad aquam et veteres, jam fracta cacumina, fagos.” With the exception of a passage in the 2nd Eclogue (I. 3.), where the scene is laid ** Siculis in montibus,” these are, I be- lieve, the only occasions on which the “ fagus” is mentioned by Virgil ; nor in any of them is it connected with the neigh- bourhood of Rome. Still, however, it is remarkable that Virgil should speak of the “ fagus” as growing in the plains of Northern Italy, while in the present day we must ascend the adjacent mountains to a considerable height before we find it. ‘The lower limit of the beech on the southern side of the Alps (in the Valtelline and the Veronese) is placed by Schouw (Pflanzen-Geographie, p. 199.) at 2000 Parisian feet above the level of the sea, while the altitude of the plain of Lombardy is only 400. It would appear therefore that in Northern Italy the lower limit of the beech has ascended 1600 feet since the time of Virgil. The position of Virgil’s * fagi” in the plain near the foot of the hills, is in accordance with a passage of Pliny, where he puts the fagus among the mountain trees, that also descend into the plain. (Hist. Nat. xvi. 30.) In another passage (xvi. 15.) Pliny states that fagi formerly existed on the site of the temple of Jupiter Fagutalis within the precincts of the city of Rome. Brocchi, in his Physical Map of Rome, at the earliest period of its existence, lays down the Lucus Fagutalis on the Esquiline, not far from the Agger of Servius Tullius. The mean height of the Esquiline above the Mediterranean does not exceed 200 Parisian feet, and the highest point of the Agger only reaches 237, accord- [* See L. & E. Phil. Mag. vol. iv, p. 276.—Ep1t.] 94 Observations on the Climate of Italy ing to the measures of Schouw (Brocchi Swolo di Roma, p- 211.): consequently this grove of beeches must have ex- isted at a height of little more than 200 feet above the sea. I am aware that itis denied by some that the Fagus of Virgil is our beech: but even those persons admit that the Fagus of Pliny is the beech; and indeed in the description of that author (Hist. Nat. xvi. 7.), the triangular coat of the gland, the smoothness of the leaf, and the care with which the fagus, though bearing an edible and sweet gland, is distinguished from the trees bearing real “ glandes,” that is acorns, seems pretty decisive on this point. The only argument urged (Gardener’s Magazine for Ja- nuary, 1839, pages 10 and 19.) against the Fagus of Virgdl* being the beech (beyond the fact now under discussion of its not being found in the plains of modern Italy), is founded on an erroneous reading of a passage in the Georgics, according to which Virgil is made to speak of engrafting the fagus on the castanea or chestnut. But in the text of the best modern editions, Virgil says no such thing. ‘The passage (Georgie. ii, 69.) stands in Heyne thus: “Tnseritur vero et foetu nucis arbutus horrida; Et steriles platani malos gessere valentes ; Castanee fagus, ornusque incanuit albo Oe PUPtikie es scuconn cancer cnsiasls oanadnisseapcioneasaninseen || casaemcicncsnasnnapeaginn cle Uiqeis knee ita aaa Searesteoecoses: PPO e He eseeseeescases P, martini eeeteeeeseece @eotevleetees COaesreseeeeeeecsees Seat eooreeseseatenrees pene shidhs Sveichs apaeeawe| MUODEGITA Nate doce: ntaua scl cntaninna pa cinnamasice dodices cil unde Men naka naeceewae ke "| Lepteena ‘lata, "(Sow.) sesovessensessenseere(Spirifera attenuata......,Sp. attenuata ..... .|Sp. attenuata vsssemwes seneescreaceccseccsasseseesessesses| SPs DISUICALAsssreanersesss Sp. Deviate. sible paid ||Spitifera bisulcata. Sp. bisulcata...... occ e ene rseerecsccrsccaccccccstscsces Sp. lineata... wernccccsces eteccees ees eeeteccecenscens Sp. lineata, ..ocesacres sevesneree| SD. resupinata ..scccsccsle Raiasanpase ane enostsbennpecl lap cecuaenenpehasn ..|Sp. resupinata secs Spirifera glabra. sehecns savas Ps CLADE As canses casieuvers a¥| qsinaicsseseassiaesanains cpnen| |v cseskansnseneneaarensantneiaen cans saan ain Ss pewenens eacerresaaal SPs SYMMELTICA ceergeccclecsencncnncerasrvenensceson||escceseavasasccsocsossetsen)s cess ee eseseeens seeaenacecsvereeseesenseevee/ SPs CLEMISETIA yeereceeees/OPs CYEMISELIA oeseee||ecsseccecssareeneatecseesee|/ ODe crenistria sesvenees eee eee eeeseecsesseseusces Sp. semicircularis ...,.. eee ececenee||sesvecrececcsareccsensesces|seeces eeeocsces Cenesoonesvesgecesen Sp. FUT ANTAS| cs cncaeng tee cad Sp. pene eeeees||seceesseteas Besoorees eecroe Sp. filiaria... see seeenes ouola| vg braided cadevisens uv eedasedee creel Ope WAMMIMOSAs caceeuselteccasste cx tecmecctan erates teens seen eases te aneeeeesecs bisa UstegaUsaausionehiushegnaen cantnae ios arachnoidea , ask saeaes BPs arachnoidea seaeein SOAP OREO EHH SOREL ERE E EOE OE OST E EE HEE EE goede oee se SEH S OES EES OES HEH DER EDS RE SEO SOE SLE SEES ODS EES SES EDED Sp. imbricata’ wesensioe Stee erereetosaseesoenee UY evesacres||sonsorees snadacaconsaps and Sp. "cuspidata eenceeees Pleurorhynchus clon gatus.cccs}ssccccscrsecsscrcescceccvascacsesleccescnsevecsess PS YUM sash oinapins cgnaninan nn] as op ahs aves uns ee whe aaa camlale dl nase ds eaolmoplashies dermanes I bon neon ee dss at dass Ral eater sebsevtehus teabisbuseats NuCtila, GMA occ ceccecnlUNUCTUIA CUDTIMA casreccsclesccecsoasocnes eet anaies neal] kpieaacceavannasonacestseapnl tanren nentanvas beavbausneesccss Nita, UUM UT Stas was ecica aun Gaal co's mh Mein de us'clba oh autsb dik g Ldaee a Mls Ghueae idee momen a meean cancel Skene coeeeenebooebe dl cocontsuaiubncmssnshitenss ene snearscesescesccsecsssscorecverees| ASAPNUS SEMMULIFETUS]...ecarercerrossecssseeseee||socreseassnonennenses TAs. gemmuliferus . ~ anocccneseagudanschesetwiimaste) sal (Cie CLAMNCAUIULIS: Ades cine discs: suvccucccdedoxtrmbusmueall pias etchaduvedupspe acsasenl anus cbengebpsene ecacnse Seaver eee CO SHsesareseeseneerases AS. quadrilimbus SHOPS OLEH eH HEH EED SHES CEH TE SEH REEH S| CHES EHS TEESE SHR E EET EES SES [ee eRsseeeeeseeeseeseeResees * In the dark-gray clayslate of Blackball Head I found Spirifer semicir- cularis, Phillips. + Retepora membranacea occurs in the carboniferous slate at Roughty bridge above Kenmare, where it rests conformably on yellow sandstone con- taining calamites, . to the Mineral Structure of the South of Ireland. 175 I shall next advert to Mr. Weaver’s observations respecting my section which extends from Brandon bay, at the extremity of the peninsula of Dingle in the county of Kerry, in an east- ern direction across the Cahirconree or Slieve Meesh range of mountains, thence traversing the limestone valley of Castle island, and terminating in the great millstone grit of Munster*. Of this section, Mr. Weaver observes, ‘ ‘That the portion which more immediately claims attention, is that which ex- tends from the summit of the old red sandstone of the Slieve Meesh range, to the carboniferous limestone of Castle island. The former is represented as constituting nearly a cap or sheet, formed on an inclined plane, from west to east, the strata corresponding and succeeding each other in that di- rection to the junction with the carboniferous limestone.” Mr. Weaver further observes, that he ‘“‘ knows of no such arrangement; on the contrary, the strata of the old red sand- stone are accumulated toa great depth, and certainly, in some quarters, at least to the level of the sea, being disposed in a gently arched form from north to south.” -In the latter observation Mr. Weaver is perfectly correct : in fact, the Slieve Meesh or Cahirconree range may be com- pared to a semicone, having its base to the west and apex to the east; the western base presents a precipitous escarp- ment, the lower region of which is occupied by highly-in- clined strata, consisting of dark gray clayslate, which on the outer edges alternates with purple clayslate; the nearly up- right ends of these strata are covered by a series of uncon- formable beds of compact red sandstone and red conglomerate, alternating with coarse red slate; near the summit, these strata present a nearly horizontal arrangement, in a north and south direction, but they dzp to the eastward at a mode- rate angle. On approaching the declivities of the cone, both to the north and south, the conglomerate strata dip rapidly, on the one side, towards Tralee bay, and on the other, towards the bay of Castlemaine. From the summit, the eastern dip is continued towards the apex of the cone at Currens; but the lower bed, which rests on the ends of the transition slate, does not continue to form the surface, but dipping more ra- pidly to the eastward than the ridge of the hill, it is succeeded by a number of beds of conglomerates and coarse slate, each cropping out to the westward. At the eastern extremity of the range, or the apex of the cone, the upper portion of the red slate and conglomerate series is succeeded in a conform- able position by beds of fine-grained yellowish-gray sandstone * See Journal of the Geological Society of Dublin, vol. ii,, part 1, 176 Mr. R. Griffith on Mr. Weaver’s Paper relative of the carboniferous series, some of which contain calamites and many obscure casts of bivalves, one of which was named by Mr. Sowerby as the Avicula modiolaris*, The upper beds of the sandstone alternate with a dark-gray, and occa- sionally blueish-gray quartzose-rock, and they are succeeded by dark-gray clayslate, alternating with carboniferous lime- stone. ‘These strata, at Riversville quarry, which I have lately visited, dip to the east at an angle of 15°. It was here that Mr. Weaver could discover traces only of the graywacke formation; now the upper part of the quarry just mentioned contains thin beds of carboniferous limestone; and imme- diately to the south and east we have large quarries of that rock partaking of the same strike and dip as the schistose beds beneath it, which rest conformably on the strata belong- ing to the old red sandstone series of the Slieve Meesh range. How Mr. Weaver can consider beds in such a situation to belong to the transition series, I cannot understand ; for, as to his idea of there being a protrusion} of graywacke from be- neath the old red sandstone, it cannot be sustained, there being no reverse dip; on the contrary, the yellow sandstone and dark-gray slate rest conformably on the old red slate, and are succeeded by strata of limestone having the same strike and dip t. In regard to fossils in the yellow sandstone and carbonife- rous slate of this locality, as I mentioned in my paper which has been quoted by Mr. Weaver, they contain numerous im- perfect casts of Producta, Spirifera, Terebratula, Crinoidea, and Retepora; but though I lately sought, with much care, I did not discover any varieties of Orthzs or Favosites, supposed’ by Mr. Weaver to occur there. The foregoing description of the structure of the Cahir- conree, or Slieve Meesh range, is similar to that contained in my paper just alluded to, which has been verified by recent observations; but as Mr. Weaver was not convinced of the inaccuracy of his views respecting the carboniferous slate at the eastern base of the Slieve Meesh range, which, notwith- standing my section and description, he still considered to belong to the graywacke series, I do not expect that what I now repeat will have the effect of changing his opinion. But it should be observed, that this carboniferous slate, which un- * Journal of the Geological Society of Dublin, vol. ii., part 1. t+ See Lond. and Ed. Phil. Mag. for April, p. 291. { In my section already alluded to, the lithographer did not make an accurate copy of the original, and has made the limestone strata to rest un- conformably upon the carboniferous slate, while in nature these strata are conformable. se ee to the Mineral Structure of the South of Ireland. 177 derlies and alternates with the undoubted carboniferous lime- stone of the valley of Castle island, is precisely similar to the carboniferous slate which underlies and is interstratified with the lower beds of the carboniferous limestone at Clonea Castle, on the east coast of Waterford, near Dungarvan; it is likewise similar to the rock which alternates with the limestone of Cork harbour, of Killarney, of Kenmare, and of many other localities in the south of Ireland; consequently, as Mr. Weaver persists in the opinion that the limestone of Cork harbour, of Killarney, of Kenmare, &c., belongs to the transition series, it would be fatal to his argument to class the carboniferous slate of Clonea Castle, or of Currens, with the carboniferous limestone series. But I will observe, that in the localities just mentioned, beds of undoubted carboniferous limestone alternate with slate, pre- cisely similar in fossils, as well as in lithological character, to that of Cork harbour, &c. I do not think it necessary to pursue this argument further than to observe, that in endeavouring to form a distinction between the admitted carboniferous limestone of the valley of the river Laune, and that of Killarney, and also between the admitted carboniferous limestone of the valley of the Black- water, below Mallow, and that westward of Clonmeen Castle in the same valley, Mr. Weaver has involved himself in an untenable dilemma. There is no difference in geological position, in mineral character, or in fossils, between the lime- stone of Killarney, and that of the valley of the Laune between Beaufort bridge and Killorglin, which are all contained in the same valley, and all repose on the same base; and a similar statement may be made in regard to the limestone of the valley of the river Blackwater, above Clonmeen Castle, and that at and below Mallow; yet Mr. Weaver considers the limestone of Killarney and that above Clonmeen Castle to be transition, and that below Beaufort bridge and Mallow to be carboniferous. After what has been said, I hardly think it necessary to reply to the observations contained in the postscript to Mr. Weaver’s paper*, in which he endeavours to show that I am incorrect in considering the conglomerate and red sandstone of the Gap of Dunloe, and that to the south of the Lower Lake of Killarney generally, as identical with the red sand- stone, the conglomerate, and red slate of the Cahirconree or Slieve Meesh range. * Published in the Philosophical Magazine for June last. [L. and E, Phil. Mag. vol. xvi. p. 471.] Phil, Mag. S, 3. Vol. 17. No. 109. Sept, 1840, N 178 Onthe Mineral Structure of the South of Ireland. It should be observed, that the red conglomerates and red slates of the district of Killarney are situated on the south side of the carboniferous limestone valley of Castlemaine, while those of Cahirconree are on the north side; that the upper beds of both graduate into the carboniferous limestone series, at Currens on the north side, and at Brickeen island in the Lower Lake of Killarney on the south side of the valley. The unconformability of the conglomerate beds with the transition series on Cahirconree, and their conformability on McGilla- cuddy’s Reeks, the Purple Mountain, &c., is no proof that the rocks are not identical, as, in England, the old red sand- stone graduates both into the Silurian and mountain limestone series. | In respect to the fault described by me, the occurrence of which is doubted by Mr. Weaver, I shall observe, that it is clearly visible at the Gap of Dunloe and at Brickeen island ; and I will assert, that the positions of the old red sandstone strata on one side, and the chloritic rocks on the other, in both those places, are as clearly indicative of a fault as any I have ever seen, On the west side of the Gap of Dunloe, we have a perpendicular cliff upwards of 200 feet in height, which is traversed by a nearly upright cut or crack about 20 feet in breadth. On the south side of this cut we find strata of dark-green chloritic quartz-rock dipping to the south at an angle of 30°, while the strata on the north side dip to the west at an angle of 10°, and are composed of rather fine- grained conglomerate and a red quartzose-rock or compact sandstone identical with that which lies beneath the red con- elomerate of Cahirconree. I am of opinion that these ap- pearances do prove that there has been a fault. Figure No, 4 in the plate is an accurate representation of the fault as above described. Similar observations are applicable to the appearances at Brickeen island. ‘There also, the strata on the south side of the fault consist of green chloritic rock, having rather a slaty structure, which dip to the south ; while on the north side, we have in succession, red quartzose-sandstone and red slate, red limestone, and yellowish-green. slate containing calamites, abutting obliquely against the chloritic rock on the north side. ‘Towards the conclusion of his paper, Mr. Weaver observes, ** Proceeding now to the Dingle peninsula, the succession given also by Mr. Griffith from north to south, namely, from Brandon bay to Foylaturrive, is as follows: Ist, dark gray claysiate,” &c. The above sentence is a misquotation trom my paper. My words are, ‘If we make a section across the M. Dumas on the Law of Substitutions. 179 Dingle peninsula, from Foylaturrive on the south to Brandon bay on the north, we find that the strata consist of a base,of dark blackish-gray clayslate,” &c. Now by reversing the points, Mr. Weaver has made the dark gray clayslate to occur on the north side of the peninsula, namely, at Brandon bay, while it really occurs on the south: the misquotation was doubtless unintentional, but as Mr. Weaver’s argument was founded on this misconception, it is unnecessary to reply to it. In concluding my observations, I cannot avoid expressing my regret that Mr. Weaver was not present either at the meeting of the British Association at Newcastle, or at the Geological Society of London, when I communicated my views relative to the geological structure of the south of Ireland; for, viva voce discussion tends more to clear up geo- logical differences than lengthened written descriptions ; and where both parties are in search of truth there is little diffi- culty in attaining it. Dublin, July 8, 1840. cs eh TS STE OS Te ST LT OS ST TE STE TTL TE ae ae ca OF SSS a ee aa a ee 2 XXVI. Memoir on the Law of Substitutions, and the Theory of Chemical Types. By M. Dumas. [Continued from vol. xvi. p. 505, and concluded. ] Organic Radicals. OR some years organic chemistry has so frequently used what we call organic radicals, that it will appear sin- gular to see, if not their existence, at least the reality of the absolute function which they have been made to play, here put in doubt. We know that by the term organic radicals we mean to de- signate certain compound bodies which might fulfil their fune- tions in the manner of simple bodies, and which might enter, as they do, and following the same laws, into combination with the various bodies of nature. If by organic radicals, bodies analogous to cyanogen, to amidogen, to the oxalic or benzoic radical be intended, there is no doubt that there, in fact, compound bodies perform the function of simple bodies, like those analogous to them in mineral chemistry, the oxide of carbon, sulphuric acid, the binoxide of azote, and nitrous vapour. But if by the term organic radicals we must, as M. Berzelius wishes, designate certain invariable compounds which would fulfil the function of the metals, the theory of types, while ad- mitting their concurrence, cannot allow their permanency. N2 ‘ 180 M. Dumas on the Law of Substitutions, Thus to fix our ideas, in the theory of types the essence of bitter almonds is a type in which we can substitute for an equi- valent of hydrogen an equivalent of chlorine, of bromine, of iodine, of oxygen, or of amidogen, without the type being altered, | C28 Hl? O2 C28 FI10 Q2 Ch? (128 FT10 CE2 O C23 F190 CE? S C28 E10 C2 Az? H4. But whilst admitting that an element might be substituted for the system C*? H'? Q%, the theory of types does not con- sider it as an invariable group. It believes that hydrogen may be taken from that group, that chlorine may take its place, or that it may be made to undergo every other modifi- cation without its fundamental nature being altered by it. In a word, by a reciprocity easy to foresee, and which to receive all its development would require a detail of formule which I cannot enter upon here, we arrive at the conclusion, that in the same manner that it is possible in an organic com- pound to substitute sulphuric acid, which fulfils the same function for hydrogen, so we may in certain organic matters substitute a simple body for a group of molecules representing a compound body. To say that nitrous vapour takes the place of hydrogen in nitrobenzine, is the same as if we said that in ether potassium may take the place of zthyle. But we must not conclude from this that zthyle is a perma- nent, immutable (zmmuable), unchangeable compound, for ex- perience proves the contrary. Only by losing some hydrogen and gaining chlorine everything leads us to suppose that it preserves its character, as does the zther, of which it makes a art. ‘ But I admit that in a given type there are certain compound groups for which simple bodies may be substituted, and which in so far would deserve the name of radicals, They fulfil the same function as ammonium, which takes the place of the po- tassium in alum, for example. : Thus I cannot consider these groups as immutable bodies, for experience has pronounced the contrary, and every theory which would absolutely rest on this basis would go too far. Amongst the researches which contribute the most to mo- and the Theory of Chemical Types: Nomenclature. 181 dify the opinion on the function of the organic radicals, we should cite in the first place the important observations of M. Laurent on the essence of bitter almonds, and those not less remarkable of M. Piria on the hydruret of salicyle*. ‘To re- sume ; nothing hinders me from retaining the name of organic radicals for certain molecular groups capable of being substi- tuted for elementary bodies which may reciprocally be sub- stituted for them, but these groups may in their turn be mo- dified by substitution, like the other bodies which do not per- form this function. I had a memoir of M. Gehrardt put into my hands, but too late for me to make use of it in the present notice, in which these questions are examined in a manner which appeared to me very worthy the attention of chemists. | Nomenclature.— Amongst the questions which are presented to us as being the immediate consequence of the point of view which we have just set forth, there is one which deserves par- ticular attention; it has relation to the principle itself of our chemical nomenclature, and to the modifications which the progress of the science has led us to make it undergo. At the memorable period when the French Academicians, under the influence of the immortal discoveries of Lavoisier, conceived and unfolded the project of a reform in the old che- mical nomenclature, they grounded themselves upon the view which Lavoisier himself had just established, that is, upon the existence of those undecomposed substances which were recog- nized as the material elements of all bodies. Seeing that by the aid of these elements all the bodies of nature could be produced, that in associating them two and two binary bodies were formed, that in combining these one with another salts were produced, and that in combining these salts in their turn double salts were obtained, the nomencla- ture had to follow the philosophical principle in all its deve- lopments. It required that the names of the elements should be set forth in those of the binary compounds, that they should reappear in the names of simple salts, in those of double salts, &c. What strikes us in the chemistry of Lavoisier, and in the nomenclature which was the consequence and the expression of it, is the antagonism of the elements which combine to form the binary compounds; it is the antagonism of the acids and of the bases which combine to form salts; it is the antagonism of the salts which combine to form double salts, &c. * (See Lond. and Edinb. Phil. Mag., vol. xvi. p. 210, 211.-] 182 M. Dumas on the Law of Substitutions, and the . The chemistry of Lavoisier and its nomenclature seemed then tohave foreseen and prepared the electro-chemical theory, which has had nothing else to do than to call one of these an- tagonist bodies the positive element, and the other the nega- tive element. But let us not lose sight of the great discovery of Lavoisier ; it is the discovery of the elements. ‘This is the fundamental principle by which he revived chemistry and natural philoso- phy. Nota truth of this order is discovered without leaving its impress on all our thoughts; and for the same reason that Lavoisier had established that all the bodies of nature might be formed by means of some elements, he would be led to de- fine the compound bodies by the elements which compose them, and there, in fact, is the principle that our nomenclature has appropriated. 2 Now not only is the nomenclature of Lavoisier no longer sufficient for us, but it expresses a system of ideas quite con- trary to that which we seek to cause to prevail. It is no longer sufficient for us, because in organic che- mistry thousands of combinations are produced with three or four elements, and consequently those could not lend themselves to name all the compounds which result from them. It is positively contrary to the system of ideas explained aboye, in this, that it derives the notion of the bodies from the nature of its elements, whilst the latter have only what may be called a secondary interest in the classification. © Each type must have a name, and this name should be: found in the numerous modifications which it may undergo, so that it should never disappear so long as the type itself is not destroyed. It is on this principle that I have already formed the follow- ing names: acetic acid and chloracetic acid, ather and chlor- ether, olefant gas and chlorolefiant gas; names, the object of which is to set forth, as may be seen, the permanency of the types, notwithstanding the intervention of chlorine in the com- pounds. The theory of types views these bodies in some degree as casts from the same mould, with different materials, It would have the nomenclature always recal their fundamental molecu- lar arrangement, and that it should be put in the first line, whilst the nomenclature of Lavoisier applies itself to the ma- terial, brings out the nature of it, and places this notion first. The theory of types tells you, here is alum of chromium ; Theory of Chemical Types : Electro-chemical Theory. 183 the nomenclature of Lavoisier sees in it sulphate of potassa and of chromium under the form of alum. Alum is a type; all the alums are cast in the same mould ; their form is what the theory of types would set forth espe- cially; that which essentially defines each of them. It acts as an artist, who in seeing the statues consisting of different materials cast from the same mould, will say to you, ‘* Here is the Venus of Milo in brass, in lead, in plaster.” The art- istic type strikes him before he dreams of the material, and he will never think of saying that he is about to show you brass, plaster, or bronze in the form of the Venus of Milo. An entire reform of the organic nomenclature and of some parts of the mineral nomenclature, appears to me, then, both urgent and possible. Electro-chemical theory.— We just now saw how the princi- ple of dualism, introduced by the chemistry of Lavoisier in the definition of every chemical combination, was favourable to the conception of whatis called the electro-chemical theory. We have also understood how the theory of molecular types swerves from this.order of ideas, for it does not suppose two antagonist elements present in the bodies, acting as would two masses endowed with different electricities, and held in combi- nations by the mutual action of these two electricities. Does a chemical combination constitute a simple edifice or a double monument? this is the question. In the theory of types, the formulz combine, and are written without attending to the reduction (dédoubler) of each body into two others. In the electro-chemical theory they combine,- and are written in such a manner as always to paint to the mind these two prin- cipal divisions of the edifice which they represent. This is the manner in which the theory of types has been driven to separate itself from the electro-chemical theory, or rather that in which this latter has been led to combat the other from its first appearance. ‘The question, however, is given in the clearest way in the following letter from M. de la Rive. The skilful Genevese philosopher, whose name will al- ways be united with the history of electro-chemistry, wrote to me on the 25th of October last (1839) :— ‘¢ [ have read your researches on substitutions with very great interest. ‘They interested me the more as I have been occu- pied for more than a year upon a rather large work on the electro-chemical theories. I dare not, I must confess, go as far as you ; and without believing in the theory of Berzelius such as he has presented it, yet I cannot help thinking that there is something well-founded in the table of the relative chemical I i 184 | M. Dumas on the Law of Substitutions, and the powers of bodies. Now, that hydrogen can perform the func- tion of chlorine exactly, is what I can hardly admit. _ Allow me to ask you if chemists are not rather easy (facile) when they group their symbolsin every way. ‘There is in this facility of permutation something which does not completely satisfy us physicists, and which appears to lend itself rather too complacently to all combinations. Is there not something ar- bitrary in the manner in which chemists make these choices ? To attack the electro-chemical theory you group your formulee in a certain manner; immediately to defend this theory M. Berzelius groups them in another manner ; where is the law of nature ?”’* I shall be pardoned for quoting this letter ; it depicts the opinions of philosophers upon questions still new to many minds, and in all cases very obscure to those persons who have not followed them step by step in their development. Those who have taken a part in the experimental researches of which we are speaking, know well that the electro-chemical theory guided my first studies, that I professed and admitted it for a long time on the faith of its inventors. ‘They also know, * [It is proper to add here, that M. de la Rive, in the Bibliotheque Uni- verselle for February 1840, p. 193, after reciting the passage extracted from his letter by M. Dumas, as above, makes the following remarks on the sub- ject of it and the comments of M. Dumas :— | “In writing these lines to M. Dumas, I sought, as he himself remarked, to satisfy myself concerning a question which becomes every day more ob- scure. On the one hand, we cannot help recognizing that in organic chemistry, especially the electro-chemical theory, or rather the chemistry which connects the development cf electricity with the play of the affini- ties with which it is always accompanied, has on its side powerful argu- ments, even when we do not admit on this point all the views of M. Ber- zelius. On the other hand, there are certainly some phenomena, espe- cially in organic chemistry, in which the function of the same elements in the formation of compounds seems to change its nature in a manner so complete and so extraordinary, that we cannot admit of their possessing a previous predisposition to conduct themselves in such and such a chemical manner, or what comes to the same thing, an absolute electro-chemical power. Would not the result of this seem to be that the electro-negative - or electro-positive properties do not previously exist in bodies? That they do not exist until the bodies are presented to each other, and that from that time instead of being absolute they are relative, that is to say, depend for the same body on the relations which exist between its own nature and that of other bodies in the presence of which it is found ? This point of view can only be thoroughly examined by means of direct experiments. I shall return to it when I have finished bringing together a number of facts sufficiently considerable for its justification, if, as | pre- sume, I find it to be founded. TI shall be glad to try thus to reconcile, at least in part, the function which M. Berzelius attributes to electricity in the chemical phenomena with the very remarkable laws at which M. Dumas seems to have arrived.’’] Theory of Chemical Types: Electro-chemical Theory. 185 that it is the force of circumstances, that it is a clear and con- vincing experience, the production of chloracetic acid, which has led me to admit that hydrogen and chlorine perform the same function in certain compounds. I constructed my for- mula according to pure chemical experience, my mind being free and disengaged from every view of general theory. But to admit that chlorine may take the place of hydrogen and perform the same function, was to separate oneself from the chemists who would explain all the phenomena of com- binations by means of what is called the electro-chemical the- ory. I understood it thus, and I found it necessary to explain myself in a direct manner. Besides, how could we believe that this consequence would have escaped the penetration of M. Berzelius, when we see all the value he attaches to giving an immediate explanation, according to the electro-chemical theory, of each of the facts which daily enrich the theory of substitutions, and when we are able to appreciate the high ta- lent he displays in the combination of the formule which his theory requires ? It was not necessary to say to M. Berzelius, that in the views of electro-chemistry the nature of elementary particles should determine the fundamental properties of bodies, whilst in the theory of substitutions it is from the sz¢wation of these particles that the properties are especially derived. We have, however, on this head decisive facts in the domain of mineral chemistry itself. ‘Thus oxygen, sulphur, selenium, tellurium, chromium, iron, manganese, magnesium, and hydro- gen constitute a series of bodies capable of taking each other’s places, without the form or essential properties of the com- pounds being changed by it. Thus M. Berzelius attributes to the nature of the elements the function (réle) which I attri- bute to their position: this is the ground of our respective opinions: let us now come to the point where they separate in practice. Amongst the consequences of the electro-chemical theory, one of the most immediate consists in the necessity of viewing all chemical compounds as binary bodies. We must al- ways find in each of them the positive particle and the nega- tive particle, or the whole of the particles to which these two functions are attributed. Never was view more capable of shackling the progress of organic chemistry. All the diffi- — culties which we have felt for some years in the inquiry con- cerning the fundamental formule of bodies, the discussions, the misconceptions, the errors, spring from prepossessions which this view had given rise to in our minds, 186 M. Dumas on the Law of Substitutions, and the Some examples will make these two points of view easy of comprehension. Carbon can combine with oxygen, and thus form carbonic oxide and carbonic acid. In its turn carbonic oxide combines with chlorine, and produces the acid gas discovered by Dr. John Davy. The electro-chemical theory should see in this Jast an acid chloride of oxide of carbon. The theory of types views it, on the contrary, as carbonic acid, in which for half the oxygen chlorine is substituted. Thus the bodies CO, COCh, CS? are modifications of the same type*. Oxygenated water is a type, and one of the neatest and best- defined (nets) that chemistry possesses. Supply the place of the hydrogen by a metal, and you will have the binoxides of calcium, barium, strontium, and in general the simple (szmgu- liers) oxides. For these, substitute in its turn for half the oxy- gen, chlorine, as is the case in chloro-carbonic acid, and you will produce the decolorating chlorides. ‘Thus oxygenated water, the simple oxides and the decolorating chlorides, belong to the same type, to which must also be added the compounds which binoxide of azote forms with the alkaline oxides, so, for example, that we may have the following series: These compounds of oxides and of chlorine have received all kinds of definitions in the electro-chemical system. Chlo- rides of oxides, of chlorites, of hypochlorites, have been made of them, as people were guided by the pretended necessity of always putting together in the formula of a compound two an- tagonist bodies, the positive and the negative. This is precisely the character of the differences at the pre- * Here is what I said of phosgene gas in 1828 :—* It is easy to see that chloro-carbonic acid corresponds to carbonic acid itself. In fact, in all its combinations one volume of chlorine takes the place of one half-volume of oxygen; it is then as if the* oxide of carbon had been changed into acid, by substituting for the half-volume of oxygen which it was necessary to add, a volume of chlorine.””—See my T'raité de Chimie, vol. 1. p. 513. Theory of Chemical Types: Electro-chemical Theory. 187 sent time between the electro-chemical school and the school of molecular types. If acetic acid is deprived of all its hydrogen, and chlorine substituted for that hydrogen, we say that acetic acid and chloracetic acid possess the same molecular arrangement, and that they should possess the same general actions so long as their molecule is not destroyed. Urged by the convenient principles, the electro-chemical system, M. Berzelius, on the contrary, makes of chloracetic acid a separate body, in which he arranges the elements into two groups, which he supposes to be combined with each other. In his opinion the chlora- cetic acid becomes a compound of oxalic acid and chloride of carbon, a formula which is in no way justified, for chloracetic acid treated with potassa should give chloride of potassium and oxalate of potassa, whilst, according to my experience, it really gives carbonic acid and chloroform. It is just the same thing as when it was said that the bin- oxide of calcium and the chloride of lime belonged to the same type, that which the interesting and decisive experiments of M. Millon have so well proved; whilst M. Berzelius, relying on ingenious researches, was induced to assert that lime when uniting with chlorine gave rise to a chlorite. If M. Malaguti takes two equivalents of chlorine from ether, the theory of types foresees and explains that in their place there must have entered into the new product two equivalents of chlorine. It sees ether in the new product, as to the mo- lecular constitution and the fundamental properties. But M. Berzelius, on the contrary, as might have been sup- posed, disposes the elements of this new body, and_,those of the products of which it makes a part, in such a way as to make them constitute binary compounds, which according to these formulze would possess actions quite opposed to those which have been recognized by M. Malaguti. In all cases in which the theory of substitutions and the theory of types see single molecules losing some of their elements and substituting others for them, without the edifice being madi- fied in its form or its exterior actions, the electro-chemical theory reduces (dédouble) these same molecules, solely we must say to find those two antagonist groups which it afterwards supposes combined, in virtue of their reciprocal electrical ac- tion. Thus in my opinion the electro-chemical theory has been drawn out of the circle which experience traces for us, when it would have explained the new facts of organic chemistry. But is it to be asserted that the electrical properties of bodies are 188 M. Dumas on the Law of Substitutions, and the without influence on chemical phenomena? Unquestionably not: only it must be agreed, that it is at the moment when the combinations are made, at the moment when they are de- stroyed, that the function (76/e) of electricity may be observed. But when the elementary molecules have taken their equi- librium, we know not any longer how to define the influence that their electric properties may exercise, and no one has put forth views on this subject which agree with experience. I have then been induced to declare that the facts which I have just discovered were irreconcilable with the electro-che- mical theory of M. Berzelius, who considers hydrogen as al- ways positive and chlorine always negative, whilst we see them supply each other’s place, and perform the same function. But I am far from denying, on that account, that the che- mical and electrical forces may be the same, and there is no reason to take up the defence of the general function of elec- tricity in chemical phzenomena, when it is simply a particular electro-chemical theory which is under discussion. What I wished to say, what I said, is, that when we have endeavoured to represent the electric state of the combined molecules, pure hypotheses have been attained without any result for the sci- ence. When, on the contrary, as has been done so happily by our colleague M. Becquerel, an endeavour has been made to take advantage of this electricity which shows itself at the moment of chemical combinations or decompositions, results the most important and the most fruitful have been obtained. It is in this class of facts that the beautiful discoveries of Davy may be classed, those which M. Becquerel pursues with so much perseverance and success; in fact, the experimental law with which Mr. Faraday himself more recently enriched chemical philosophy. All the discoveries of these great physicists have reference to the phenomena of the chemical action, and are quite inde- pendent of the views which they may have expressed on the function of electricity in compound bodies. In the course of this memoir I have several times made use of the actions (réactions) of bodies, as being the only method quite proper for unfolding their real nature. ‘There is not- withstanding an objection in the experiments themselves, to which I have often referred the reader, thus :— A chemist who, without knowing the origin of it, had had to study the body C® H® Ch? O, seeing that under the influ- ence of potassa this body is changed into chloride of potassium and acetic acid, would certainly have seen in it either a chlo- Theory of Chemical Types; Electro-chemical Theory. 189 ride of the acetic radical, or acetic acid, in which for a por- tion of the oxygen chlorine had been substituted ; yet this body is nothing but the chlorinated ether of M. Malaguti. Just so, when I was occupied with the study of chloroform C* H? Ch H*, the manner in which it acts with the po- tassa, the formation of the chloride of potassium, and of the formic acid which result from it, led me to consider it as being formic acid, C* H? O%, in which equivalent quantities of chlorine supplied the place of the oxygen; yet M. Reenault has lately shown that chloroform is nothing but some hydro- chloric «ther of methylene, in which chlorine has supplied the place of a portion of the hydrogen, the body C* H® Ch? being changed by this substitution into C* H? Ch®%, The result of these examples, which might be multiplied, would be, that the actions of bodies are not a faithful guide, for they lead us to refer to acetic acid, a body derived from gether, and to formic acid, a body which represents hydro- chloric zther of methylene. But in looking nearer, we see, in fact, PRA MNGR axis woke save hy Jered SO Chlorinated zther C* H® O Acetic acid sé.s<.6é; C? HO OQ, belong really to the same molecular grouping, and that in saying that chlorinated ether is derived from zether, and that it produces acetic acid, nothing really contradictory has been affirmed. On the other hand, Methylic zether......... C* H®O HOpmicgiacidyy siindanceeas \) C* HAO Chloro-methylic zther C* H® Ch? Chiorofornt))2.i..20ia.000 | 4b? Che Ch‘, constitute bodies of the same molecular grouping, so that chloroform may be viewed as anhydrous formic acid, or as bichlorinated chloro-methylic ather, without these two ways of regarding it at ail contradicting each other. The result of this is, that chemical actions, without possess- ing the absolute character which has often. been given to them, deserve a confidence which may have been momentarily shaken, but which a profound examination again establishes in its true place in our minds. In fact, we have admitted that substitutions may unveil the molecular grouping of bodies by furnishing a set of equa- 190 M. Dumas on the Law of Substitutions, tions of condition which the general formula ought to satisfy. Now it is evident that the metamorphosing actions are often nothing but means for operating substitutions, by taking ad= vantage of affinities more complicated than those which are made use of in the ordinary:substitutions. It is therefore more than ever requisite to apply to the study of the actions of bodies, and not to trouble ourselves about the distance which often separates the point from which we started from that which we reach; for it may well happen, that these two points, so unlike in their properties, are really united to each other by the theory of substitutions, and belong to the same molecular grouping. | eee The law of substitutions expresses, then, a simple experi- mental relation; it is limited to the expression of a relation often observed between the hydrogen lost and the chlorine absorbed, by a hydrogenated body submitted to the action of chlorine. ‘This law establishes only, that if the substance loses 1, 2, 3 equivalents of hydrogen, it will gain 1, 2, 3 equi- valents of chlorine; but it does not explain this fact. The theory of types goes further; it explains what the law of substitutions is content to determine. It considers organic bodies as being formed of particles, which may be displaced and have their places supplied by others without the body being destroyed, so to speak. In the cases above-quoted, the molecule of acetic acid, that of ether, may lose hydrogen and take chlorine, without ceasing to constitute an acid or basic molecule, formed of the same number of equivalents and en- dowed with the same number of fundamental properties. It is then because, that on pain of being destroyed, the mo- lecule of acetic acid must take an equivalent of chlorine to stand for the equivalent of hydrogen which it loses, that this substitution, this remplacement is effected. ‘Thus it is that the theory of types explains the law of substitutions. The substitution of one element for another, equivalent for equivalent, is the effect; the preservation of the type is the cause. ‘The organic molecule, the organic type, constitute an edifice, in which a course (assise) of hydrogen can have its place supplied by a course of chlorine, of bromine, or of oxy- gen, without the exterior relations of that edifice being thereby modified. But it is necessary, when the course of hydrogen is taken away, to put something in its place; if not, the edifice crumbles or is transformed. The law of substitutions was hardly put forth before it be- came the subject of severe criticisms in Germany, to which I thought it useless to reply. If this law was just, it was for and the Theory of Chemical Types. 191 experience to teach us; if it was false, it was experience which would pronounce its falsity. In all cases it was necessary to leave time to determine its place in science. The theory of types was scarcely published when the same criticisms were reproduced, at least by M. Berzelius; and not- withstanding all my devotion to the interests of the science, I would again have left to time and experience the care of pronouncing on these debates. But when I reflected, it seemed quite evident to me, that as a consequence of the researches of organic chemistry, ge- neral chemistry had reached one of those periods of crisis, when every one owes to science the testimony of his convictions. We cannot conceal from ourselves that two systems of ideas are before us:—one, which is supported by all the au- thority of the past, the rights acquired by quiet possession now for nearly a century, the tacit assent of a great number of chemists, and which reckons amongst its defenders and at their head, a philosopher illustrious amongst the most illustrious, M. Berzelius; the other, which consists in asserting that the bodies formed of the same number of chemical equivalents placed in the same manner, belong to the same molecular type, and often to the same chemical type. This latter attributes to the number and arrangement of the particles an influence of the first order, which in the ideas of the received chemistry belongs especially to the nature of those particles. ‘The law of substitutions would be the ex- perimental demonstration of this new system, and would have led some of its partizans to adopt it. I do not claim its in- vention, for it does but reproduce and give precision to, under amore general form, opinions which are to be found in the writings of great chemists, and particularly MM. Robiquet, Mitscherlich, Liebig, Laurent, Persoz, Couerbe, &c. It is pre- cisely this coincidence between the numerous facts, to the dis- covery of which the law of substitutions has led, and the opi- nions already known relative to the influence of certain pre- existing molecular arrangements, that has given me the con- fidence necessary for their adoption in my turn when I pro- posed the admission of organic types. Here we have, then, before us two systems: one which at- tributes the principal agency to the nature of the elements, the other which reserves it for the number and arrangement of the equivalents. Pushed to an extreme, each of them in my judgement would be found to lead to an absurdity. . Regulated by ex- perience and kept by it within prudent limits, each of them must take a large share in the explanation of chemical phe- 192 M. Dumas on the Law of Substitutions. nomena; and to explain by a last word the meaning which I attach to their respective functions, I shall say that in chemistry the nature of the molecules, their weight, their form and their situation, must each exercise a real influence on the properties of bodies. It is the influence of the nature of molecules that Lavoisier has so well defined, it is that of their weight which Berzelius has characterized by his immortal labours. It might be said that the discoveries of Mitscherlich relate to the influence of their form, and the future will prove whether the present la- bours of the French chemists are destined to give us the key to the function which belongs to their position. . We subjoin to the preceding memoir by M. Dumas, a translation of an extract of a letter from M. Baudrimont, published in the Comptes Rendus, for March 16. ‘* M. Dumas says, that the law of substitutions, and the theory of chemical types, are unconcerned in the reclama~ tions of M. Baudrimont, who does not admit them. This re- quires an explanation from me. ‘¢ T cannot admit M. Dumas’s law of substitutions; first, because it has not the character of a physical law; secondly, because it is but the strict expression of an order of facts, much more extended than M. Dumas supposes; but I admit chemical substitutions; for substitution ts only one of the modes by which bodies may enter into combination. ‘¢ I should without doubt do more than M. Dumas in say- ing to the Academy : Chemical compounds are produced, either by direct combination or by displacement, or by substitution, or lastly, by several of these modes united. Substitution may be non-equivalent, equivalent, isotypic, isorhythmic, or isomor- phic ; let me be pardoned this neologism. But this formula, which is true, has not the character of a law; it is but the general expression of facts which are within the knowledge of all men, ever so little versed in chemistry ; for chemical substitutions have been known ever since we arrived at the knowledge that one metal can precipitate another, taking its place in a saline solution; ever since hydrogen was first ob- tained by displacing it by iron or zinc in the pretended sul- phuric and chlorhydric acids diluted with water; ever since we knew that chlorine displaces bromine and iodine; ever since we knew isomorphism by substitution; and ever since M. Beudant made more than a thousand applications of them to the calculation of the composition of minerals.... I admit, then, chemical substitution; but I repudiate the pretended law of M. Dumas, for the reasons I have just set forth, Mr. Smee on the Ferrosesquicyanuret of Potassium. 193 *‘ As to what relates to chemical types, which M. Dumas says I do not admit, I dare hope that the Academy, and all enlightened men will not participate in this opinion; for it will without doubt be allowed that he who first classed che- mical types, must necessarily have admitted them, even before M. Dumas had acquired any notion of them, as his memoir appears to show, since he makes this notion only go back to his experiments on chloracetic acid, the discovery of which is posterior to my thesis.” M. Dumas replies, that his memoir is conceived in such terms, that it should have spared the Academy all the recla- mations of which it has been the subject. In a historical note which he intends soon communicating to the Academy, he will show in what the views which are represented as identical differ, and to whom belongs the discovery of each of the prin- cipal points of the theory. XXVIII. On the Ferrosesquicyanuret of Potassium. By ALFRED SMEE, Lsq., Surgeon.* HE action of chlorine upon the ferrocyanate of potassium is a subject of much interest to the chemist, and has not been examined to any extent in this country. It therefore has been my endeavour to investigate this action carefully, and to see under what circumstances the change from the ferro- cyanate into the ferrosesquicyanuret takes place; and the methods which are here detailed to obtain this latter salt un- contaminated with impurities, will be found free from the dif- ficulties and uncertainties attending on the present mode of preparing it. When a current of chlorine is passed through a solution of ferrocyanate of potassa, or an aqueous solution of that gas is added to it in certain quantities, the persalts of iron are not precipitated. ‘This solution has no smell of chlorine, and is changed from a yellow colour to a dark red, and deposits on evaporation red crystals. A similar change takes place when bromine is added to the ferrocyanate, and in both cases the weight of the entire red mass is equal to that of the yellow ferrocyanate, plus the weight of the chlorine or bromine used, but minus the quantity of water which the yellow crystals are known to contain. ‘This indicates, first, that the red crystals are anhydrous; and secondly, that the chlorine or bromine is actually absorbed by the salt. The former fact is con- * Read before the Royal Society, June 18, 1840; and now communi- cated by the Author, Phil. Mag. §.3, Vol. 17, No, 109, Sepé, 1840, O 194 Mr. Smee on the Ferrosesquicyanuret of Potassium. firmed by heating the red precipitate in a test tube, when no water is given off; and the latter fact is also proved by the evo- lution of chlorine or bromine, on the addition of two or three — drops of strong heated sulphuric acid to a few grains of red salt. When heated alcohol is added to this red mass a small por- tion is dissolved, which is again deposited when the spirit is evaporated. ‘This salt by its characters is known to be either the bromide or the chloride of potassium. By this method the red ferrocyanate of potassa, which is insoluble in alcohol, becomes purified; but this is a troublesome and expensive process, as the bromide or chloride is but little soluble in the spirit, and therefore a large quantity must. be used. About half an equivalent of chlorine or bromine is required to effect this change, and great care must be employed to prevent excess of these substances, as they are apt to react upon a portion of the salt. ‘The liquid in this case contains Prussian blue dissolved, which materially discolours the salts, and it can only be precipitated from the solution by the ad- dition of neutral salts, as sulphate of soda, which renders the red ferrocyanate impure. In a similar manner, chloride of soda, as might be expected, forms the red ferrocyanate of po- tassa. | From the foregoing details a knowledge is obtained of the action of chlorine and bromine upon the ferrocyanate, for we have seen that chloride and bromide of potassium is formed, and that one half an equivalent of these substances is necessary for thischange. Now it is manifest that half an equivalent of potassium is removed from the ferrocyanate, so that the new salt, instead of consisting of iron one equivalent, potassium two equivalents, cyanogen three equivalents, contains iron one equivalent, potassium one and a half equivalent, cyanogen three equivalents; and therefore it is rightly named the ferrosesquicyanuret of potassium: that half. an equivalent of potassium has been removed from the salt, two or three experiments have verified. The acids as a class will not effect a similar change, be- cause as they combine not with potassium but with potassa, water must be decomposed, the oxygen uniting with the metal, and the hydrogen passing to the ferrocyanate, forming hydro- ferrocyanic acid. A question naturally arises whether the potassium may not be removed from the ferrocyanuret by other processes, and we are led to try the action of the anions, and of these I attempted to add oxygen to the salts by the use of nitric acid. Vhis acid, when added in small quantities to the yellow ferrocyanate, acts as the other acids by liberating hydroferro- Mr. Smee on the Ferrosesquicyanuret of Potassium. 195 cyanic acid, which is speedily decomposed into a pale blueish cyanuret of iron. When, however, further additions of this acid are made, the potassium takes oxygen, forms potassa, deutoxide of nitrogen is evolved, and the solution becomes dark coloured. This liquor, when neutralized with potassa, is found to give no precipitate with the persalts of iron, but forms Prussian blue with the protosalts of’ that metal. “The rapidity of this change depends upon the heat of the solution, for when warm the effect takes place immediately, whilst on the contrary, two or three days are required at a low tempera-~ ture. When evaporated, a large quantity of nitrate of potassa is deposited ; and lastly some red crystals are formed. When acid is more used, the ferrocyanate is totally decomposed ; the black mass which is the result has at first a sweet, but afterwards leaves a disagreeable metallic taste upon the palate, This process can never be used advantageously to form the ferro- sesquicyanuret, from the quantity of acid which is required, the degree of nicety which must be employed to effect the change, and the impurity of the salt when obtained. The next highly oxygenated acid which we have to examine is the iodic; this when added to ferrocyanate of petash becomes decomposed, the oxygen passes to the potassium to form potassa, free iodine is evolved, and the potassa passes to another portion of iodic acid, and is precipitated as the iodate of potassa. The free iodine can be readily removed by agi- tation with a little ether, and in this way a tolerably pure ferrosesquicyanuret of potassium can be extemporaneously obtained, for the solution contains but little iodate of potassa from its insolubility*. Chloric acid operates in the same way as iodic acid, but is more difficult of decomposition, and it requires the «ac- tion of heat before the smell of chlorine is exhaled and the red ferrocyanate formed. If chlorate of potassa be added to the ferrocyanate, and di- Jute sulphuric acid be dropped into the solution, red ferro- cyanate of potash will also be formed. Bromic acid will not act upon the ferrocyanate with the pro- duction of the ferrosesquicyanuret, but acts as other acids in forming Prussian blue. A great yariety of other oxyacids have been tried, but none were found to part with their oxygen. When a large quantity of peroxide of manganese in fine * This elegant process can be employed with advantage when a small quantity of the salt is suddenly wanted, as it scarcely requires a minute to effect. O2 196 Mr. Smee on the Ferrosesquicyanuret of Potassium. powder is added to a solution of the ferrocyanate of potash, and the mixture digested for a considerable time, the ferro- cyanate becomes converted into the ferrosesquicyanuret, and on evaporation crystals of the most beautiful ruby red are obtained. ‘The salt thus procured appears to be very pure. If a little dilute sulphuric acid be added to the solution in conjunction with the peroxide of manganese, the action takes place more quickly, but sulphate of potassa is formed, which is a great disadvantage. The last process in which nascent oxygen contributes to the formation of ferrosesquicyanuret of potassium, is, perhaps, one of the most elegant, efficient, and simple processes in the whole range of chemistry. This mode I was induced to follow from the consideration, that as nascent oxygen effects a change of the yellow to the red ferrocyanate of potassa, a similar change must be produced by its being subjected to a galvanic current. Accordingly some solution of the salt was placed in a tube bent like a syphon, and at-the bottom a piece of tow was thrust, in order that a separation might so far be effected, that the solution on one side could not readily pass to the solution on the other. Having thus completed the arrange- ment, a galvanic circuit was passed through the fluid ; when at the cathode, hydrogen was evolved, and at the anode no oxygen, on the contrary, was given off, but the solution be- came of a dark colour. The dark solution was found to pre- cipitate only the protosalts of iron, and on evaporation de- posited red crystals of the ferrosesquicyanuret, but at the ca- thode potash was discovered. The rationale of this change may be deduced from circumstances attending slight altera- tions of arrangement; for if on the zinc side of the bent tube a saturated solution of the ferrocyanate be placed, and on the platinum side distilled water, and then the galvanic circuit be completed, potash will appear at the platinode, and red ferrocyanate at the zincode. On the contrary, if the distilled water is placed at the zinc side and the ferrocyanate at the platinum side, potash is left at the platinode, whilst at the zincode no red ferrocyanate is found, but a substance which does not redden litmus paper, and which speedily decomposes into Prussian blue; this is probably ferrocyanogen. ‘Thus it appears that one equivalent of the yellow ferrocyanate is de- composed, the free potash travels one way and the hydro- ferrocyanic acid the other ; the oxygen unites with the hydro- gen of the acid and sets ferrocyanogen at liberty; this again unites with an equivalent of ferrocyanuret of potassium to form the ferrosesquicyanuret, Mr. Smee on the Ferrosesquicyanuret of Potassium. 197 Various other attempts were made to form the red ferro- cyanate by oxygen, such as heating it with nitrate of potassa, but the mixture exploded at a temperature below redness. When a mixture of powdered ferrocyanate and peroxide of manganese were heated together no ferrosesquicyanuret was formed. Several other oxides, as those of mercury, silver, tin, iron, &c. &c., were digested with ferrocyanate of potassa, but none that were tried, except the peroxide of manganese, formed the red ferrocyanate; many of them were converted into cyanurets. | A current of oxygen gas passed through the solution of the salt produces no alteratiou, showing that the gas must be in a nascent state to cause the change. The next substance we have to examine is phosphorus, and its action is somewhat remarkable; for little or no change is effected by the addition of an alcoholic or etherial solu- tion of phosphorus. When a piece of phosphorus is also placed in a solution of the ferrocyanate, or when phosphorus is heated with powdered ferrocyanate, the sesquicyanuret is not produced; but if a stick of phosphorus is placed in a bottle containing a solution of the salt, and only a portion of jt is covered with the liquor, the phosphorus gradually burns away, the solution becomes sour and red, and ceases to preci- pitate the persalts of iron. ‘This change takes place with a rapidity exactly proportionate to the wasting of the phospho- rus; for if the temperature is below 45°, but little action takes place, but above 60° the reddening is very speedily produced. The red solution is not to be tested with the salt of iron whilst it is acid, for in that case a copious greenish-white pre- cipitate is produced of phosphate of iron; but after it has been neutralized with potassa a solution of baryta is to be added, - to throw down the phosphate, and adrop of dilute sulphuric acid may then be added to remove any excess of baryta. The solution will now be found not to precipitate persalts of iron, but, on the contrary, a large quantity of Prussian blue is produced with the protosalts. ‘he actual combustion of the phosphorus seems essential to this change ; for if the water in which phosphorus has been allowed to burn, be added to the solution of the ferrocyanate, a similar change will not be produced. ‘The cause of this change appears paradoxical, for phosphorus has in other instances a deoxidizing agency, so that a piece placed in a solution of either gold, silver, pla- tinum, or copper, has the metal precipitated upon it. Per- haps it depends upon decomposition of water and the forma- tion of phosphuretted hydrogen ; for a narrow bottle, to which air has but limited access, is more favourable to the change 198 Mr. Smee on the Ferrosesquicyanuret of Potassium. than a wide vessel. If this explanation is correct, the action of phosphorus must be classed with the other oxygenating substances, for oxygen, and not phosphorus, removes the potassium”. No mode of abstracting the half equivalent of potassium by sulphur is known, for if half an equivalent of sulphur be heated with powdered ferrocyanuret, the ferrosesquicyanuret is not produced, and the alcoholic or terebinthine solution of sul- phur, added to a solution of the ferrocyanuret, also failed to produce this change. Even nascent sulphur arising from the decomposition of sulphuret of potash by an acid did not pro- duce any effect+. | A current of cyanogen gas passed through a solution of the salt is gradually absorbed, and it becomes of a very dark colour, but red ferrocyanate is not formed. Doubtless many may be surprised that the action of iodine has not been adverted to before, and more especially that it should not have been mentioned with chlorine and bromine, as to these it has a striking analogy in most of its properties; but in reality little resemblance exists between the action of iodine on the ferrocyanate of potassa, and that of chlorine and bremine, as we shall immediately see. If iodine is added to a solution of the salt it speedily becomes dissolved, the so- lution turning toa dark red, and gives a blue precipitate with salts of either oxide of iron. One equivalent of ferrocyanate of potash dissolves about one equivalent of iodine, which re- -mains in great part uncombined in solution. If the solution is allowed spontaneously to evaporate the free iodine passes off, and a whitish uncrystallized mass is obtained which has no free iodine, but hydriodate of potassa in its composition. This gives a precipitate with both oxides of iron. Now there is aready method of ascertaining how much iodine the ferro- cyanate will not only dissolve, but combine with, and for this purpose a definite quantity of the salt is to be dissolved in a small quantity of water, and then placed ina phial. Upon the solution ether is to be poured, then the iodine is to be added gradually, when as soon as the ether is discoloured the satu- ration is known to be effected. Brisk and continued agitation must follow each addition of the iodine, in order that the sether may part with any iodine previously to the point of saturation. When evaporated to dryness more of the iodine is evolved, but still hydriodate of potash may be abstracted from the mass by alcohol. When all the iodine 1s removed * No change takes place if the phosphorus is completely under the solu- tion of the salt. ; It is foreign to this page to describe the sulphocyanuret of potassium. Mr. Smee on the Ferrosesquicyanuret of Potassium. 199 from the mass, a result which is known by its not discolouring starch upon the addition of nitric acid, it still retains its power of forming Prussian blue with salts of either oxide of iron, and still presents the same indisposition to crystallize, for it neither shows itself as the yellow nor the red ferrocy- anate of potash, but as a compound having properties inter- mediate with both. When iodide of potassium is added to the ferrosesquicy- anuret, iodine is evolved, the solution loses its red colour, and the salt possesses the characters similar to the mass obtained by the action of iodine on the ferrocyanate of potash. ‘Thus it is evident that if a solution of persulphate of iron be treated with the red ferrocyanate whilst an iodide is present, Prussian blue will be formed. Whether this is really a mixture of the ferrocyanuret and ferrosesquicyanuret or a distinct compound, it is difficult to determine, but the latter is rendered probable from its ge- nerally presenting itself as an amorphous mass; yet, however, when the purified mixture is dissolved two or three times in water, a dark mass is deposited, and at last crystals of the yel- low salt are formed. Every method which has been discovered of converting the ferrocyanate of potassa into the ferrosesquicyanuret has now been detailed, and we have seen that they may each be re- ferred to the class of anions, for of the cathions the powerful agency of potassium was unable to effect this change. Upon the first formation of the ferrosesquicyanuret the colour wiil occasionally bea very dark red, but this is an ad- ventitious, not a necessary property; for when prepared by peroxide of manganese or chloride of soda, it does not possess this dark colour. If the red crystals be carefully picked and re-dissolved, in no instance is this seen, and in every case where the dark red exists it yields to liquor ammoniz or potassz, with the production of a small quantity of the ferrocyanate. The ferrosesquicyanuret, however prepared, has the same peculiar properties. It has been already mentioned that the protosalts are precipitated blue, whilst the persalts are not effected by this agent ; however, the solution in the latter case is always much darkened, and after a time a small quantity of dark-coloured substance is deposited. ‘The mode of pre- poration of the ferrosesquicyanuret does not influence this re- sult. With almost every acid, especially if heat be applied, Prussian blue is formed and hydrocyanic acid is given off, and thus - upon testing for minute quantities of metal, care must be taken to prevent any excess of acid, as in that case the chemist would 200 Mr. Smee on the Ferrosesquicyanuret of Potassium. find iron in everything he examines. With excess of alkali, on the contrary, no precipitate of Prussian blue is produced ; and therefore if search be made for that most useful of all metals, the experiment would declare that iron had no real existence; but if the golden mean be employed, or the solution be but very slightly acid, the ferrosesquicyanuret, as well as the ferrocyanuret, become most valuable and delicate tests, the one for the peroxide, the other for the protoxide of that metal. The change by chlorine and bromine has been shown to result from the abstraction of the half equivalent of potassium by the formation of chloride or bromide of that metal, and therefore the ferrosesquicyanuret is impure till that is removed by alcohol. We have seen also that the change may be ef- fected by the iodic, nitric, and chloric acids, but by these methods the salt is also contaminated to a great extent by the nitrate of potash, but to a much less extent with the chlorate, and scarcely at all with the iodate; with phosphorus the salt in a very impure state may still be made. With peroxide of manganese, however, and the galvanic current, it may be made of absolute purity. This last mode will probably supersede entirely every other mode of preparation, as with a galvanic battery a large quan- tity can be readily made. The battery which I have used for these experiments is the platinized silver, which from its simplicity is so well adapted for general purposes, and suit- able for long-continued action. Bank of England, Feb. 12, 1840. Table of Decompositions. By Chlorine and Bromine. 1 eq. F er eoenaeh 3 | Bbc oie of Potassa J | Potassa2 p= 1 eq. Red fer- pe ae 1. rocyanate % equivalent of chlorine J 3 equivalent chloride of potassium. - Bromine acts in the same way. By the Galvanic Current. Iron 1 Tron 1. 1 eq. Ferrocyanate : leq. Red ee Homies = } ; Cyanogen 3 = Feneyanitte } Cyanogen 3. Potassium 2 | Potassium 14. 3 eq. of Oxygen. | 4 eq. of Potassa. 4 eq. of Hydrogen from decomposition (| 4 eq. cf Hydrogen evolved. of water. The action of the acids, &c. have been already sufficiently adverted to. Mr. Smee on the Ferrosesquicyanuret of Potassium. 201 Table of Precipitates with the Iodo-ferrocyanate of Potassa pure. Gold ...... . Solution red, no precipitate. Platinum ..... a little white deposit. Mercury, bichloride white, becoming green. Lead”... ....)s + White, abundant. Silver ....... white, with a little reddish tinge. Bismuth .... white, afterwards yellow. ZAG) o) iyi6 serena White, Copper ...... dark brown. Iron protosalts. . . Prussian blue. Tron persalts. ... Prussian blue. Table of Precipitates with the Red Ferrocyanate of Potassm. Gold ... chloride ... solution darker, no precipitate. Platina. . . chloride ... solution darker, small crystals deposited. Palladium . nitrate... . red-brown precipitate. nitrate .... Silver. . . .< sulphate ... >deep orange. acetate .... Nickel ... nitrate ..... red brown. Copper act ... yellow brown. ** \ammoniuret . deep-greenish brown. Mercury . tierce. . atfirst yellow brown, then white, ichloride ... none. [then green. Bismuth. . nitrate. .... pale yellow brown. Tin .... protochloride white, gelatinous. protosulphate Prussian blue. ‘_persulphate . none, with iodide, potassium, Prussian blue. Antimony . Pol saien: 0 " bnone. Tron 183% tartrate ... Manganese _ chloride. ... sepia. Cobalt ... chloride. ... chocolate brown. Zine... sulphate? .. . buff. Cadmium . sulphate..... pale yellow. Curanium . nitrate. .... deep red brown. Lead ... acetate..... solution brownish, none. Alumina .. acetate. .... mone. Ra; ‘muriate ... ibe aryia oes | none. MILTALCH. 4) dias Strontia:. MNnitrate...... none. Lime ... muriate.... none. [ 202 ] XXVIII. Mineralogical Notices. Communicated by W. H. Miter, Lsq., Professor of Mineralogy in the University of Cambridge. | [Continued from p. 105.] ANALYSIS OF MONAZITE. [From Poggendorff's 4nnalen, vol. xlvii. p. 385. ] QE hundred parts of Monazite, the Mengite of Mr. Brooke, analysed by M. Carl Kersten, gave Oxide’ Of ‘Cerium site: ..4-scesapes 26°00 Oxide of lantanium ............ 23°40 THOrina sicsvesssesevcscessgeacnsis 17°95 Oxide Off ttn dog ane\ieces ss gene esti eo Protoxide of manganese ...... 1°86 LAME ssacvassecscctecovacdesevesess 1°68 Phosphoric acid .s....eseceeeee 28°50 Traces of potash and titanic acid. ANALYSES OF OCTAHEDRAL COPPER PYRITES. BYM.PLATTNER. [From Poggendorff’s Annalen, vol. xlvii. p. 351.] From Condurrow From the Woitzki From the Mar- Mine near Cam- Mine near the tan mountain borne, in Corn- White Sea. in Dalarne in wall. Sweden. Sulphur... 28°238 25°058 25°804 Copper ... 56°763 63°029 56°101 Lyon} jsceees) L4843) 34, 11°565 17°362 Silica... 0°120 From Lisleben. From Sange- Unknown locality. hausen. (Analysed by M. F’, Varrentrapp.) Sulphur... 22°648 22°584 26'981 Copper... 69°726 71:002 58°199 Tren iiscsce O20 6°406 ~ - 14°845 XXIX. On the Use of Hydriodic Salis as Photographic Agents. by Mr. Roserr Hunt.* . To the Editors of the Philosophical Magazine and Journal. GENTLEMEN, HAVE been engaged more than twelve months in study- ing the peculiarities of the salts of hydriodic acid, when used for the production of those photographic pictures which are formed by one operation, having their lights and shadows correct as in nature; and the results of my very numerous * Communicated by the Author, whose former papers on Photography will be found in vol. xvi. p. 138, 267: see also our report of the proceed- ings of the Royal Society for the past session. Mr. R. Hunt on Hydriodates as Photographic Agents. 203 experiments are, the establishment of fixed principles, which remove most of the uncertainty attending the use of the hy- driodates, an explanation of many of the anomalous results they give, and the discovery of some very remarkable pro- perties not before noticed. The uncertainty attending the application of the hydrio- dates, has greatly circumscribed their use, and it is the de- sire of forwarding the progress of a beautiful art, which now makes me solicit a few pages of your valuable Journal. SirJohn Herschel, in his very excellent memoir “On the Che- mical Action of the Rays of the Solar Spectrum,” &c.* particu- larly notices the inconstancy of the effects exhibited by the hydriodates. “ Nothing,” says that talented and indefatigable inquirer, ** can be more variable and capricious than the re- sults obtained according to the different intensities of the so- lutions applied; the qualities of the paper; the degree of darkening induced on the paper before the application of the ioduretted solution, the state of the paper as to moisture or dryness, and other circumstances.” That the various positions I wish to establish may be com- pletely understood, and to ensure the same results in other hands, it will be necessary to enter into a somewhat detailed account of several kinds of paper which have been used, and to give tolerably full directions for successfully using the same, either in the camera obscura, or for drawings by application. _ 1. The preparation of the paper —The variable texture of even the finest kinds of paper occasioning irregularities of im- bibition, is a constant source of annoyance, deforming the drawings with dark patches, which are very difficult to re- move ; consequently my first endeavours were directed to the formation of a surface on which the photographic prepara- tions might be spread with perfect uniformity. 2. A variety of sizes were tried with very variable results. Nearly all the animal glutens appear to possess a colorific property, which may render them available in many modifi- cations of the processes published by Mr. Talbot, but they all seem to protect the darkened silver from the action of the hydriodic solutions. 'The gums are acted on by the nitrate of silver and browned, independent of light, which browning considerably mars the effect of the finished picture. It is a singular fact that the tragacanth and acacia gums render the drawings much less permanent. I therefore found it ne- cessary for general practice to abandon the use of all sizes, except such as enter into the composition of the paper in the manufacture. [* An abstract of Sur J. Herschel’s paper appeared in vol. xvi. p. 331.] 204 Mr. R. Hunt on the Use of Hydriodic Salts 3. It occurred to me that it might be possible to saturate the paper with a metallic solution, which should be of itself entirely uninfluenced by light, on which the silver coating might be spread without suffering any material chemical change. ‘The results being curious, and illustrative of some peculiarities to be explained when the hydriodates come un- der our examination (65.), I shall record a few of them. 4. Sulphate and Muriate of Iron.—These salts, when used in certain proportions, overcame many of the first difficulties, but all the drawings on papers thus prepared faded out in the dark. ' 5. Acetate and Nitrate of Lead.—The salts of lead I have since perceived have been used by Sir John Herschel with success in some of his negative processes. I found a tolerably good result when I used a saturated solution of the above- named salts; but papers thus prepared required a stronger light than other kinds to give good results; when I used weaker solutions the drawing was covered with black patches. On these a little further explanation is required. When the strong solution has been used, the hydriodic salt which has not been expended in forming the iodide of silver, which, it is well known, is the lights of the photograph, goes to form an iodide of lead. ‘This iodide is soluble in boiling water, and is thus easily removed from the paper. When the weaker so- lution of lead has been used, instead of the formation of an iodide, the hydriodate exerts one of its peculiar functions in producing an oxide of the metal (65—67.). 6. Muriate and Nitrate of Copper.—These salts, in any quantities, rendered the action of the hydriodates very quick, and when used in small portions appeared to promise much assistance in quickening the process; but experience has shown their inapplicability, the edges of the parts in shadow being destroyed by chemical action. 7. Chloride of Gold.—I did not anticipate much from the use of this salt. On trial it was found to remain inactive until the picture was formed, when a very rapid oxidation of — the gold took place, and a consequent darkening of all the bright parts (5.) (65—67.). 8. Chloride of platina was found to act in all respects si- milarly to the chloride of gold, the re-darkening of the lights being much more rapid and intense (5. 7. 67.). 9, A very extensive variety of preparations were tried with like effects, and I was at length convinced, that the only plan by which a perfectly equal surface could be obtained, without impairing the sensitiveness of the paper, was careful manipu- lation with the muriated and silver solutions. we os as Photographic Agents. 205 By attention to the following directions, simple in their character, but arrived at by a long series of inquiries, any one may prepare photographic papers, on which the hydriodic solutions shall act with perfect uniformity. 10. Soak the paper for a few minutes in a muriated wash, removing with a soft brush any air-bubbles which may form on it. ‘The superfluous moisture must be wiped off with very clean cotton cloths, and the papers dried at common tem- peratures. When dry, the paper must be pinned out ona board, and the silver solution spread over it boldly but lightly, with a very soft sponge-brush. It is to be instantly exposed to sunshine, and, if practicable, carried into the open air; as the more speedily evaporation proceeds, the less does the silver penetrate the paper, and the more delicate it is. The first surface is very irregular, being made up of blue streaks, which are parts on which a true chloride is formed; and of brown ones, which appear to be the chloride of silver combined with a portion of undecomposed nitrate. As soon as the sur- face appears dry the silver solution must be again applied as before, and the exposure repeated. It must now be exposed until a fine chocolate-brown colour is produced equally on all parts of the surface, and then, until required for use, care- fully preserved from the further influence of light. | 11. In darkening these papers, the greatest possible atten- tion must be paid to the quantity of light to which they are submitted, everything depending on the rapidity of the black- ening process. ‘The morning sun should be chosen, it being very evident that some portion of the violet rays are absorbed by the atmosphere after the sun has passed the meridian, which permeated it freely before he had arrived at that point. A perfectly cloudless sky is of great advantage. ‘The in- jurious consequence of a cloud obscuring the sun during the last darkening process, is the formation of a surface which has the appearance of being washed with a dirty brush. This is with difficulty removed by the hydriodates, and the re- sulting pictures want that clearness which constitutes their beauty. Papers darkened by the diffused light of a cloudy day are scarcely, if at all acted on by these salts. 12. The kind of paper on which the silver is spread, is an object of much importance. A paper known to the trade as satin-post, double-glazed, bearing the mark of J. Whatman, Turkey Mill, is decidedly superior to every other kind I have tried. The demy printing papers are many of them bleached by chlorine, after an artificial substance has been given them by lime. These reverse the photographic process, yand the parts 206 Mr. R. Hunt on the Use of Hydriodic Salts on which the light acts with the most power become the darkest of the drawing, while the shaded parts are whitened. The dark specks which abound in some kinds of paper must be avoided, and the spots made by flies very carefully guarded against. These are of small consequence, indeed are not noticed during the darkening action; but when the hy- driodic wash is applied they form centres of chemical action, and the bleaching process goes on around them independent of light, deforming the drawing with small rings, which are continually extending their diameters. 13. The Muriated Solutions.—These saline washes may be considerably varied, and combined to an indefinite extent with a continued change of effect, which is singularly interesting. In their application I am invariably ‘guided by the combi- ning proportion of the salt; for having tried solutions of all strencths, I am at length satisfied no other proportions give such certain results; consequently I always work with my seale of equivalents at hand. ‘The following is a list of the salts I most frequently use, selected from upwards of seven hundred combinations which I have tried. They are placed in the order of sensitiveness they appear to maintain, when used under as nearly as possible the same circumstances. Colour of Picture. Red, changing to black in sunshine. 6. Chloride of sodium .... —_ Ditto. c. Muriate of strontia ..... Brown, changes but slightly. d A rich brown inclining to purple, darkens slightly. e. Sol. chloruret of lime . Very red. J. Sol. chloruret of soda . Red, changes a little. g. lodide of potassium .... Yellow brown. Variable, sometimes yellow- ish, often of a steel blue. 2. Phosphate of soda....... Mouse colour. k. Urate of soda.........0.. Yellow brown. 7. Muriate of iron ......... Deep brown, blackens. m. Bromide of sodium .... Red brown. a. Muriate of ammonia ... e Muriate of baryta.... eoe h. Chlorate of potassa «+. The change I mention in the colour of the finished pic- ture is that which arises from a fresh exposure to the solar rays; where no change is mentioned, it is too slight to be worth notice. ‘This phenomenon will, however, occupy our atten- tion presently (38.). In addition to the salts named I some- times use as Photographic Agents. 207 Colour of Picture. nm. Hydrochloric acid .... Red which blackens. o. Hydrochloric zther .... Black. p- Aqueous chlorine ....... Red, deepens a little. gq. Phosphoric acid ........ Very variable. 14. When papers prepared with any of the above, except 2 and g, are soaked for a little time in water, and dried in the sunshine, the picture produced—it matters not what hy- driodate is used—is rendered peculiarly red, and does not change by re-exposure: washing either of the papers 8, c, or d with weak solution of ammonia, occasions this peculiarity in a striking manner. 15. The Solution of Silver.—Take of crystallized nitrate of silver 120 grains, distilled water 12 fluid drachms; when the salt is dissolved, add of alcohol 4 fluid drachms, which ren- ders the solution opake. -After a few hours a minute quan- tity of a dark powder—oxide of silver ?—is deposited, and must be separated by the filter. 16. The addition of the alcohol to the solution was adopted from an observation I made of its influence in retarding the chemical action of the hydriodates on the salt of silver, which goes on in the shade. Its use is therefore to make the action depend more on luminous influence than would be the case without it. 17. Nitric ether and acetic zther not only check the bleaching process in the shade, but actually act with the hy- driodic salts in exalting the oxidation of the silver. In copying lace or feathers, they are very valuable agents, but for any other purposes they are useless, as all the faintly lighted parts are of the same tint. 18. The hydrochloric zether, which I use as the solvent of the silver, and apply without any saline wash, has a similar property to the nitric; but as it is readily affected by faint light, it is of greater value. However, papers prepared with it must be used within twenty-four hours, as after that they quickly lose their sensitiveness, and soon become nearly use- less. 19. The Hydriodic Solutions.—To fix with any degree of cer- tainty the strength of the solution of the hydriodic salts, which will in all cases produce the best effect, appears to me im- possible ; every variety of paper, either as regards its com- position, or the intensity of light to which it has been ex- posed to darken, requiring a solution of different specific gravity. 20. Hydriodates of Poiassa and Soda.—The former of these salts being more easily procured than any other of the 208 Mr. R. Hunt on the Use of Hydriodic Salts hydriodates, is the one generally employed. The strength at which I use these salts for most kinds of paper is thirty grains to an ounce of water. ‘The following résults will exhibit the different energies manifested by these solutions at several strengths, as tried on the same paper by the same light. 120 grains of salt to an ounce of water 5 | 12 minutes. took to whiten @eseseeseeseeoe ees Bee eeoggee 100 do. to do. 10 — 80 do. to do. 9 — 60. do. to do. 7 — 40 do. to do. 6 — 30. do. to do. 4 20 do. to do. 6 — 10 do. to do. 12 — The other hydriodic salts correspond nearly with these in their action; a certain point of dilution is necessary with all. 21. Hydriodate of ammonia, if used on unsized paper, has some advantage as to quickness over either the salts of potassa or soda. ‘This preparation is, however, so readily decom- posed, that the size of the paper occasions a liberation of iodine, and the consequent formation of yellow-brown spots. 22. Hydriodate of lron.—This metallic hydriodate acts with avidity on the darkened paper; but even in the shade its chemical energy is too great, destroying the sharpness of out- line and impairing the middle tints of the drawing. It also renders the paper very yellow. 23. Hydriodate of lime acts similarly to the iron, but less energetically, and the paper is not rendered yellow by it. 24. Hydriodate of manganese answers remarkably well when it can be procured absolutely free of iron. When the manganesic solution contains it, even in the smallest quantities, light and dark spots are formed over the picture, which give it a curious speckled appearance. 25. Hydriodic acid, if used on paper which will not decom- pose its aqueous solution, acts readily on the darkened silver. It is difficult, however, to procure a paper which does not li- berate the iodine. A portion of hydriodic acid, free, in any of the saline solutions, greatly quickens the action. 26. Hydriodate of baryta possesses advantages over every other simple hydriodic solution, both as it regards quickness of action, and the sharpness of the outline in the photograph. 27. I find, however, the quickness of this solution may be much increased. Forty grains of the hydriodate of baryta being dissolved in one ounce of distilled water, thereto should be added five grains of pure sulphate of iron, and allowed slowly to dissolve, Sulphate of baryta is precipitated, which as Photographic Agents. 209 should be separated by filtration, when the solution is com- posed of the hydriodate of baryta and iron. By now adding a drop or two of very dilute sulphuric acid, more baryta is precipitated and hydriodic acid left free. The clear solution must be decanted off, as the filtering through paper decom- poses the acid. By this means a photographic fluid of great value is formed. It should be prepared in small quantities, as it suffers decomposition under the influence of the atmo- sphere and of light. It is always easy to set hydriodic acid free by precipitating sulphate of baryta. 28. Directions for taking Photographs.—¥or drawings by application less care is required than for the camera obscura. With a very soft flat brush apply the hydriodic solution on both sides of the prepared paper until it appears equally ab- sorbed, place it in close contact with the object to be copied, and expose to sunshine. ‘The exposure should continue until the light parts of the picture (iodide of silver (54.)) are seen to brown. The observance of this simple rule will ‘be found of very great advantage in practice. Immersion for a short time in soft water removes the brown hue, and renders the bright parts of the picture more clear than they would other- wise have been. 29. If the paper is intended to be used in the camera, it is best to soak it in the hydriodic solution, until a slight change is apparent from the chemical action on the silver; it is then to be stretched on a frame, and not allowed to touch in any part but at the edges; placed in the dark chamber of the camera at the proper focus, and submitted to lumineus in- fluence. If the wetted: paper is placed upon any porous body, it will be found, owing to the capillary communication esta- blished between different points, that the solution is removed from some parts to others, and different states of sensitive- ness induced. Another advantage of the frame is, the paper being by the moisture rendered semi-transparent, the light penetrates and acts toa greater depth, thus cutting out fine lines which would otherwise be lost. However, if the camera is large, there is an objection to the frame ; the solution is apt to gather into drops, and act intensely on small spots to the injury of the general effect. When using a large sheet, the safest course is to spread it out when wetted upon a piece of very clean wet glass, great care being taken that the paper and glass are in every part in close contact. The picture is not formed so quickly when the glass is used as when the paper is extended on a frame, owing to the evaporation being slightly retarded; the additional time required, about one- Phil, Mag. S. 3. Vol.17, No. 109. Sept. 1840. P 210 Mr. R. Hunt on the Use of Hydriodic Salts. sixth longer, is however in most cases of small consequence. It is somewhat singular that if the glass plate is interposed between the paper and the lens, the action is not more re- tarded than if it had been placed behind it. The interfe- rence of a transparent plate is little felt in the hydriodic pro- cess. 30. On fixing these Photographs. — 'The picture being formed by the influence of light, it is required, to render it unchangeable by any further action of the luminous fluid, not only that the hydriodic salt be entirely removed from the paper, but that the iodide of silver which is formed be also dissolved out of the drawing. 31. By well washing the drawing in warm water the hy- driodate is removed, and the pictures thus prepared have been stated to be permanent; and if they are kept in a port- folio, and only occasionally exposed, they are really so; for I shall show presently (54.) that they have the property of being restored in the dark to the state in which they were prior to the destructive action of light. I have now before me the first drawing of this kind I ever executed, bearing the date June 17, 1839. This drawing has been kept loosely in my table drawer, and has often been exposed for many successive days to the action of the sun; yet the most delicate vena- tions of the rose leaves are as perfect as at first. ‘Thus pre- pared, however, these photographs will not bear continued exposure without injury, about three months in summer, or six weeks in winter being sufficient to destroy them. 32. For a long period I was under the impression that two iodides of silver existed, the one sensitive to solar influence, but the other not so; and in my paper published in your Ma- gazine for April, I stated such to be my opinion. I have, however, since that period seen reason sufficient to question the correctness of my conclusion. Under the former impres- sion, not being successful in removing the iodide from. the paper without also injuring the oxidized or dark portions, I endeavoured to effect a chemical change in the iodide of silver. Some of the results being curious, I shall give them. 33. By washing the photograph with a hot saturated so- lution of the acetate of lead, the yellowness of the lights was at first increased, but eventually considerably whitened, and the dark parts assumed a peculiar crimson hue. ‘The draw- ing faded out entirely by the action of light in three weeks. 34. When these drawings are dipped into a solution of the bichloride of mercury, they fade out in precisely the same manner as Sir John Herschel discovered the photographs on Mr, Talbot’s principle were obliterated, and in like manner ~~» Mr. Woods on the Anthracite Coal of South Wales. 211 are they restored by a liquid hyposulphite; the paper, in- stead of being completely white, being altogether of a full rich yellow. When these photographs are restored by the hyposulphite, they are even less permanent under the influence of light than those washed with the salt of lead. 35. The ferrocyanate of potassa exerts no action on these photographs in any way remarkable, unless they have been formed by the agency of the hydriodate of iron (22.) or of baryta and iron (27.). ‘They are then obliterated by it, but on exposure, the light parts of the picture are darkened, changing thus to a negative photograph, the originally dark parts being now a light blue. 36. With much attention, I have tried the hyposulphites of soda, ammonia and potassa. But I have failed to remove all the iodide of silver, without destroying at the same time the dark parts, and the minute portion which remains in the paper is very soon darkened by light to a tint similar to the lighter shades of Indian ink. When first done the drawing is much improved in appearance, but it is difficult to remove the hyposulphite so completely as is necessary to prevent the formation of the sulphuret of silver. 37. Sulphuretted hydrogen gas, which has the singular property of blackening the iodide of silver, when in that state which is easily darkened by light, but of bleaching it in the less susceptible state, acts on these photographs in a manner simi- Jar to the hyposulphites; but the oxidized portions of the picture are first destroyed and then restored by light. ‘The light parts are, however, rendered brown. I have tried a great variety of other agents, diversifying my method of using them in almost every possible way, but as yet I have discovered no material which effectually removes the iodide of silver alone; consequently I satisfy myself with well washing my photographs in hot water. {To be continued.] XXX. On the Anthracite Coal of South Wales. By SaMur. Woops, Hsq., #.G.S. To the Editors of the Philosophical Magazine and Journal. GENTLEMEN, PAYING received from a friend at Paris the accompany- ing analysis of some of the anthracite coal found abun- dantly in this neighbourhood, I transmit it to you in the belief that it may be worthy of record in your pages; and the quality and uses of this coal having lately excited so much ¥ 212 Mr. Woods on the Anthracite Coal of South Wales. attention and inquiry, a few preliminary observations may not prove unacceptable. This deposit of anthracite coal forms a part of the large Welsh coal basin extending from Brides-bay to Pontypool, —the western limit of the anthracite (or stone coal) deposit being the coast of Pembrokeshire, and its eastern terminating not far beyond the Neath Valley: the seams towards Merthyr and beyond, gradually losing their anthracetous and assuming the bituminous character, the width till it reaches Llandship- ping in Milford-haven is inconsiderable, from whence it slowly expands towards Tenby. In this district there do not appear to exist more than three or four distinct veins, all of which seem to have been exposed to intense heat, and to disturbing forces of great violence, these veins abounding in faults and tossed about in various directions, very difficult to follow, a large proportion being reduced into small particles known by the denomination of culm, employed chiefly in lime-burning: the larger pieces, however, possess a very uniform compact cha- racter and superior purity, and are in great reputation and demand for drying malt, for which purpose they have been long used. ‘The veins then appear to pass under Carmarthen- bay, and again to emerge in the Gwendraeth Valley beyond Kidwelly, where a vast quantity is procurable. From the southern edge of the basin from Pembrey to Swansea and Neath, the coal is chiefly bituminous, but occasionally of a mixed character, more or less approaching to anthracite, the latter becoming more pure and distinct as we advance north- ward through the collieries of Trimsaran, Brondyny, Llan- gennych and Pont-twrch in the Swansea Valley. To the north of all these points the quality rapidly improves, and all the coal north of a line drawn from Pont Yales to Aperpergwm, may be considered real anthracite. ‘The Gwendraeth Valley from near Pont Yales to the Big mountain, a distance of about eight miles trending N.E. is known to possess thirteen distinct veins, somewhat varying in purity and thickness, the latter in the aggregate amounting to about 40 feet, and the greatest depth hitherto worked, or in contemplation to work, about 65 fathoms; the dip from 30° to 45°. Seams of argil- Jaceous iron ore are also found between the coal veins. The use of this coal has hitherto been chiefly confined to — maltsters ; it has been more recently adopted for Dr. Arnott’s and other stoves, and is now successfully applied to the re-— duction of iron ores in the vicinity of Swansea; and its free- dom from smoke, joined to the durability of its heat, offer the strongest recommendations for its employment in locomotive engines either on land or water, and there is little doubt will Mr. Woods on the Anthracite Coal of South Wales. 213 be ultimately adopted for these purposes. ‘There seem at present some difficulties as to the best mode of using this combustible; since by sudden exposure to an incandescent furnace it is apt to split or exfoliate into minute fragments, which choke up the draught of air, or are thrown out like dust by any rapid motion. Dr. Ure assigns as the cause of this, I believe truly, that being a bad conductor of heat, the super- ficial parts expand and break off from the cooler internal portions; the remedy for which appears to be some contri- vance for gradually heating the coal before it comes into contact with the fire, and of supplying a constant current of hot air; these precautions are not required for common fires. Mr. Player has secured a patent for such a process, which is exhibited on the Thames in the steamer called the Anthracite, the action of which every one is disposed to praise, yet no one adopts: for this no reason appears but the difficulty of over- coming prejudices, or the fear of engaging in novelties in the first instance requiring some additional expenditure. With regard to its application to domestic use it has many and forcible recommendations; it gives out a clear, steady and durable heat; requires but little attention when once lighted ; and the absence of all annoyance from smoke, soot or dust, renders it very desirable for culinary purposes and for bed- rooms; in the parlour it may be thought deficient in the bright and cheerful character which belongs to the Newcastle coal; besides which, as the anthracite never cakes, it requires no aid from the poker, the employment of which on the con- trary extinguishes the fire, and therefore may be deemed ob- jectionable. Analysis of the vein of Anthracite coal called the Gwerdd (Green) vein from Coalbrook in Carmarthenshire near Pont y berem, in the vale of the Gwendraeth, the property of the Gwendraeth Anthracite Company; by Mons. Jac- quelain, of the Ecole des Arts at Paris. Ultimate analysis. Manufacturing analysis, Carbon ... 89°43 Carbon 89°80 Chik o9 Hydrogen 3°56 Ashes. yon oke 91°50 Oxygen... 3°66 Water 1:35 AZOLE ..0000 0:29 slightly car- - Volatile | buretted Mijas 4lisb dO sub- hydrogen, + 7°15 ygrome- stances ammonia tric moist- > 1°36 and oxygen ure. © eeesee ee 100 100 One gramme of the coal reduces 33°3 grammes of lead, con- sequently the heating power may be thus estimated: 1 kilo- 214 Mr. Woods on the Anthracite Coal of South Wales. gramme is capable of raising 76°54 kilogrammes of water (quere from 32°) to the boiling point, or of evaporating 11°55 kilogrammes. All the samples of coal placed in my hands were of a brilliant black, very compact, and of a lamellar structure; the cross fracture rough and uneven; they do not soil the fingers, and break easily under the hammer; the hardness is nevertheless considerable, and it is difficult so to reduce it to powder as to destroy its brilliancy. The double carbonate of lime and iron occurs between the laminze of this coal, and sometimes agglomerations of carbo- naceous matter possessing the appearance, lightness and fria- bility of wood charcoal. The specific gravity of this coal is 1:27; it burns in the furnace without flame; a small quantity reduced to powder consumes slowly without inflaming; ignited masses do not lose their form, but when separately exposed to the air become extinguished, whereas in mass the combustion succeeds well in the reverbatory furnace. I incinerated some of this coal reduced to powder in a muffle furnace charged with the same coal, and beginning with a stratum of lighted charcoal: the combustion continued for five hours, while every part of the interior of the furnace was incandescent. : The residue of this incineration upona small scale, consists of slightly ferruginous and calcareous ashes; that of combus- tion on the large scale is similar, but mixed with some small pieces of coal having suffered imcipient exfoliation. The ready combustion in mass is undoubtedly to be attributed to a slight separation of the laminze of the coal produced by the high temperature, and to the emission of a gas*. The quantity of gas which this coal is capable of supplying in close vessels has been found to be 24 litres for 100 grammes of coal, equivalent to 240 litres for a kilogramme. It will be seen that these results approach those obtained on the large scale in gas-works, where that quantity yields 180, 200, and 250 litres of gas; unfortunately the gas produced from this anthracite does not give more light than pure hydrogen; it is now well known that illuminating power may be communi- cated to hydrogen gas by causing it to circulate in reservoirs over the surface of oil of schist or of tar. From what has been stated, it is evident that coal having a uniform character similar to that which I have analysed, would be much in demand on account of its remarkable purity, both for domestic consumption and for blast furnaces, | * JT do not exactly comprehend how this separation of the laminz pro- motes combustion. I should have thought its tendency would have been to choke and check the fire—S. W. Mr. Crosse on the Tension Spark from the Voltaic Battery. 215 and especially for the latter, on account of the extremely high temperature it is capable of producing. I repeat, that if this combustible prove homogeneous and of equal quality in every part of the deposit, the discovery is one of great importance for the reduction of ores and the quality of the resulting products. Dr. Schafhaeutl of Munich, now or lately residing at Swansea, has analysed for the Kilgetty Company, two samples of the Pembrokeshire coal; the average specific gravity he states to be 1°413. | i ei. Carbon... eccoee 92°42 94°100 Hydrogen...... 3°37 2°390 Oxygenevercees 1°43 1°336 Nitrogen ....00. 1:05 874 Sulphur........ "12 Earthy matter 1°61 068 Alumina.....coee "478 SiNGR Sh. isakk wats "190 PVOH WU des esiinw. 264: IVWater aves end *300 100 100 Pembrey, Carmarthenshire. XXXI. On the Tension Spark from the Voltaic Battery. By ANDREW Crosse, sg. Communicated in a Letter to John P. Gassiot, F.R.S. To the Editors of the Philosophical Magazine and Journal. GENTLEMEN, ‘THE inclosed communication from my friend Andrew Crosse, Esq., may perhaps be interesting to the readers of the Philosophical Magazine; the paper he alludes to is one I communicated to the Royal Society, and which was ho- noured by a place in their Transactions of this year. I am, Gentlemen, yours, &c. Clapham Common, Aug. 3, 1840. Joun P. Gassior. My Dear Sir, I return you my best thanks for your paper on the voltaic spark, &c.; I have read it with attention, and was much inter-= ested by its perusal, particularly by that part which relates to Zamboni’s pile. I once had a cork ball kept vibrating be- tween the poles of four columns of De Luc’s pile, without cessation, for upwards of twelve years! Now for the possibi- 216 Mr.Crosse on the Tension Spark from the Voltaic Battery. lity of obtaining a spark between the poles of a voltaic battery before the circuit is completed. Were you to see the action of my unfinished water battery of 1626 pairs of zinc and copper cylinders, you would allow the question to be set at rest. I take a small glass stick, and tie on it, with waxed silk thread, very securely, two wires of platina, with the two extreme ends ready to be plunged into two cups of mercury connected with the opposite poles of the battery: the two other ends of the wires are brought to the distance of about ;45th of an inch from each other, as below. A | E F G H A B, CD, two platina wires secured on the glass stick EK, F, G, H atthe parts E, F, G, H. The two nearest ends of the wires approach each other at B, C to about the di- stance of ;1,th of an inch. I say about, for I have no in- strument to measure it with accuracy, nor is it of any conse- quence, as the cells of that battery are not by any means so well insulated, as that the above distance should be taken as a test of intensity of the battery. The moment the connexion is made with the poles of the battery, a small stream of fire takes place at the interval between B and C, which I have kept up for many minutes, nor did it appear inclined to cease. ‘This experiment never fails, but with a much greater number of plates, each pair not being separately insulated, it would never succeed. ‘To expect to produce a spark or visible current under similar circumstances with the above would be hopeless, except with a considerable number of pairs of plates, each pair being separately insulated. With 1200 pairs I have succeeded, and with 10,000 or 20,000 the distance at which it would strike would be very great, comparatively speaking. I showed a friend the other day about twelve inches of iron chain illuminated pretty strongly by the passage of repeated shocks of my large electrical battery through it, charged by the water battery alone. ‘The intensity was so great as to keep up a constant dance of pieces of silver-leaf between two plates connected with the opposite poles. ‘Lhe reason why Professor Daniell’s water battery, which you em- ployed in some of your experiments, failed, was first, that the cells were not separately insulated, and secondly, that they were too few in number. I presume it was the water battery which I once saw used at the Royal Institution, the intensity of which was very feeble. I do wish you could manage to pay me a visit, and see the Professor Draper on the Process of Daguerreotype. 217 action of my battery. I mean, as soon as I have time to add about 850 pairs of cylinders to it. Woe then to the unfor- tunate wretch who comes between the poles, when connected with the electrical battery ! | P. S. Please to observe, that when I procured the stream of electricity in the interval between the platina wires, I used the water battery alone, without other apparatus, and not connected with the electrical or any other battery. Broomfield, near Taunton, July 17, 1840. X X XII. On the Process of Daguerreotype, and its application to taking Portraits from the Life. By Joun Wit1iam Draver, M.D., Prof. Chemistry in the University of New York. MERY soon after M. Daguerre’s remarkable process for Photogenic Drawing was known in America, I made at- tempts to accomplish its application to the execution of por- traits from the life. MM. Arago had already stated, in his ad- dress to the Chamber of Deputies, that M. Daguerre expected, by a slight advance, to meet with success, but as yet no ac- count has reached us of that object being attained. More than one hundred instances are recordedin Berzelius’s chemistry, in which the agency of light brings about changes in bodies; these are of all kinds: formations of new com- pounds, re-arrangements of elements already in union, changes of crystallographic character, decompositions, and mechanical modifications. The process of the Daguerreotype is to expose a surface of pure silver to the action of the vapour of iodine, so as to give rise to a peculiar iodide of silver, which under certain circumstances is exceedingly sensitive to light. ‘The different operations of polishing, washing with nitric acid, exposure to heat, &c., are only to offer a pure silver surface; the operation of hyposulphite of soda, and the process, which I shall pre- sently describe, of galvanization, are to free the plate from its sensitive coating, and in no wise affect the depth of the sha- dows, as some of the French chemists at first supposed. There is but one part of the Daguerreotype which does not yield to theory: on one point alone there is obscurity. Why does the vapour of mercury condense in a white form on those portions of the film of iodide, which have been exposed to the influence of light ?—condense to an amount which is rigidly proportional to the quantity of incident light ? Even on this point there are facts which appear to have a bearing. (a.) It has long been known, that if a piece of soapstone or 218 Professor Draper on the Process of Daguerreotype, agalmatolite be made use of as a pencil to write with on glass, though the letters that may have been formed are invi- sible, and though the surface of the glass may subsequently have been well cleared, yet they will come into view as soon as the glass is breathed on. (d.) I have often noticed, that if a piece of very clear and cool glass, or what is better, a cold polished metallic reflector, has a little object, such as a piece of metal, laid upon it, and the surface be breathed over once, the object being then care- fully removed, as often as you breathe again on the surface, a spectral image of it may be seen, and this singular pheno- menon may be exhibited for many days after the first trial was made. (c.) Again, in the common experiment of engraving on glass by hydrofluoric acid, if the vapour has been very weak, no traces will be perceived on the glass after the wax has been removed; but on breathing over it, the moisture condenses in such a way, as to bring all the object into view. (d.) In a former number of this Journal I described a phe- nomenon which relates to the crystallization of camphor on surfaces of dry glass, on which moveable traces have been made by the pressure of a glass rod; this also appears to belong to the same class of effects. Berzelius (Traité, vol. ii. p. 186.) has attempted to explain (a.) and (c.) on this principle, that the changed and unchanged surfaces radiate heat unequally. ‘There may be strong doubts with some as to the correctness of this, but is not the Daguer- reotype due to the same cause, whatever it may be? We must separate carefully the chemical changes which iodide of silver undergoes in the sunbeam, from the mechanical changes which happen to the sensitive film: iodide of silver turns black in the solar ray, the whole success of the Daguer- reotype artist depends on his checking the process before that change shall have supervened. The coating of iodine is not zmmediately necessary to the production of images by the mercurial vapour. The con- dition seems to be traceable to the metallic surface. If you take a Daguerreotype, clean off the mercury, polish the plate thoroughly with rottenstone, wash it with nitric acid and bring it to a brilliant surface, yet if it has not been exposed to heat, the original picture will re-appear on exposure to the mercurial vapour. Is not this a result of the same kind as those just referred to? As a polishing material for the Daguerreotype plate, com- mon rottenstone and oil answer very well. ‘The plate having been planished by the workman, is to be rubbed down toa good surface, and as high a polish given to it as possible; and its application to taking Portraits from the Life. 219 it is to be heated and washed with nitric acid, as indicated in the French account, and finished by being rubbed with whiting (creta preparata), in the state of a very dry powder, going over it for the last time with a piece of clean dry cotton; this gives an intensely black lustre, which cannot be obtained by rottenstone alone, and thoroughly removes any film which nitric acid may have left. To coat with iodine, I make use of a box about two inches deep, in the bottom of which that substance in coarse flakes is deposited ; no cloth intervenes, but the silvered plate, with a temporary handle attached to it, is brought within half an inch of the crystals, and it becomes perfectly coated in the course of from one to three minutes; no metallic strips are necessary to ensure this effect; if the edges and corners are thoroughly clean, the golden hue will appear uniformly. M.Daguerre recommends, that the plate, after being iodized, shall be placed in the camera without loss of time. The longest interval, he says, ought not to exceed an hour. “ Be- yond this space the action of the iodine and silver no longer possesses the requisite photogenic properties.” There may be something peculiar in the preparation of the plate as I have described it, but it is certain that this obser- vation must be received with some limitation. A plate, which has been iodized, does not appear so quickly to lose its sen- sitiveness. On the other hand, by keeping it in the dark for twelve or twenty-four hours, its sensitiveness is often remark- ably increased. Other advantages also accrue. ‘Those who have made many of these photogenic experiments, will have had frequent occasion to remark, that the film of iodine is not equally sensitive all over, that there are spots or cloudy places which do not evolve any impression, and often the whole is in that condition, that the bright parts alone come out, while the parts that are in shadow do not evolve correspondingly, nor can they be well developed, except at the risk of solarizing the picture. Now, a plate that has been kept for several hours, is by no means so liable to these effects: I do not pretend to give any reason for this, but merely mention it as a fact, of considerable importance to the travelling daguerre- otyper; he will find that the iodine does not lose its sensi- tiveness in many days. In a paper read before the Royal Society, of which an abs- tract is given in the April number of this Journal for the present year (p. 333.), Sir John Herschel states, that there is an absolute necessity of a perfect achromaticity in the ob- ject-glass of a photographic camera. M. Daguerre appears to have been under the same impression, and recommends in his published account such an object-glass. ae 220 Professor Draper on the Process of Daguerreotype, All the rays of light, with perhaps the exception of the yel- low, leave an impression on the iodide of silver. ‘Uhe less refrangible rays, however, act much more slowly than those which are at the opposite end of the spectrum. In the com- mon kinds of glass, the most energetic action takes place in the indigo, or on the boundary of the blue. Now the retina receives an impression with equal facility from each of the different rays, the yellow light acting as quickly upon it as the red or the blue. Vision is therefore performed independently of time, the eye catching all the colours of the spectrum with equal facility and with equal speed. But it is not so with these photogenic preparations. In the action of light upon them, time enters as an element; the blue ray may have effected its. full change, whilst the red is yet only beginning slowly to act; and the red may have completed its change before the yellow has made any sensible impression. On these principles, it is plain that an achromatic object-glass is by no means essential for the production of fine photographs; for if the plate be withdrawn at a certain period, when the rays that have a maximum energy have just completed their action, those that are more dispersed but of slower effect, will not have had time to leave any stain. We work, in fact, with a temporary monochromatic light. Upon these principles I constructed the camera which I am in the habit of using, with a double convex non-achromatic lens. Some of the finest proofs were procured with a common spectacle lens, of fourteen inches focus, arranged at the end of a cigar-box as acamera; a lens of this diameter answers very well for plates four inches by three, reproducing the objects with the most admirable finish, copper-plate engravings being represented in the minutest particulars, and the marks of the tool becoming quite distinct under the magnifier. In this instance, it is true, owing to the magnitude of the focal length compared with the aperture, but little difficulty ensues from chromatic aberration; but when with the same focal length the aperture is increased to three or four inches, then the dispersion becomes very sensible, and yet good proofs can be procured, by working in the method here indicated, the chief difficulty then arising from spherical aberra- tion. It has already been stated, that the ray of maximum action for the Daguerreotype, when colourless French plate-glass is used, lies probably within the indigo space: it therefore fol- lows, that the length of the camera should be diminished, after arranging it to the luminous focus. ‘The importance of this is pointed out in a paper by Mr. Towson, inserted in this ,_ Journal last year ; I was, however, in the habit of using this ad- and its application to taking Portraits from the Life. 221 justment before reading the suggestions contained in that ex- cellent communication. The amount of shortening which should be given to the camera, where the lens is fifteen inches focus, does not commonly exceed three-tenths of an inch. If the luminous focus be used, the proof comes out indistinct. In the subsequent process of mercurializing, it is of little importance what is the angular position. Several experi- menters were for a time under the idea that an angle of 45° or 48° was a necessary inclination, in order that the plate should take the vapour; this arose from a misinterpretation of the printed account. Plates mercurialize equally well in a horizontal as in any other position ; perhaps a slight inclination may be of advantage, in allowing the vapour to flow with uni- formity over the iodized surface, but the chief use of an angle of 45°, is to allow the operator to inspect the process through the glass. Sometimes it is advantageous to heat the mercury a second time, when the proof is not distinctly evolved at first. Indeed, it occasionally happens, that a proof which did not evolve at all at first, will come out quite fairly on raising the tempera- ture of the mercury again. M. Daguerre recommends two methods of removing the sensitive coating from the plate, by washes of hyposulphite of soda, and a solution of common salt. The former answers perfectly, the second only indifferently well. ‘There is, how- ever, another process, which is very simple, and has an advan- tage over the former of these in cheapness. It adds nota little to the magic of the whole operation, in the eyes of those who are unaccustomed to chemical results. ‘The plate, having been dipped into cold water, is placed in a solution of common salt, of moderate strength; it lies without being acted upon at all; but if it be now touched on one corner with a piece of zinc, which has been scraped bright, the yellow coat of iodide moves off like a wave and disappears. It is a very pretty process. The zinc and silver forming together a voltaic couple, with the salt water intervening, oxidation of the zinc takes place, and the silver surface commences to evolve hydro-_ gen gas; whilst this is in a nascent condition it decomposes the film of iodide of silver, giving rise to the production of hydriodic acid, which is very soluble in water, and hence in- stantly removed, This process, therefore, differs from that with hyposulphite. The latter acts by dissolving the iodide of silver, the former by decomposing it. Itis necessary not to leave the zinc in contact too long, or it deposits stains, and in large plates the contact should be made at the four corners successively, to avoid this accident, 222 Professor Draper on the Process of Daguerreotype, After the proof is washed, all the defects in the preparation of the plate become apparent. Ifa film of mercury has ex- isted on it, due to its not having been burnt sufficiently long, there will be found a want of distinctness in the shadows; or if the plate has not been burnt at all, perhaps the former im- pressions which have been obtained will re-appear. This ac- cident frequently happened in my earlier trials, when care had not been taken to give a due exposure each time to the spirit flame. Spectral appearances of former objects, on dif- ferent parts of it, emerged,—an interior with Paul Pry coming | out, when the camera had been pointed at a church. There is no difficulty in procuring impressions of the moon by the Daguerreotype, beyond that which arises from her | motion. By the aid of a lens and a heliostat, I caused the moonbeams to converge on a plate, the lens being three inches in diameter. In half an hour a very strong impression was obtained. With another arrangement of lenses I obtained a stain nearly an inch in diameter, and of the general figure of the moon, in which the places of the dark spots might be in- distinctly traced. An iodized plate, being exposed for fifteen seconds only close to the flame of a gas light, was very distinctly stained ; in one minute there was a very strong impression. On receiving the image of a gas light, which was eight feet distant, in the camera, for half an hour, a good representation was obtained. The flame of a gas lamp was arranged within a magic lanthorn, and a portion of the image of a grotesque on one of the slides received on a plate; a very good representation was procured. With Drummond’s light, and the rays from a lime-pea in the oxy-hydrogen blowpipe, the same results were obtained. In the first experiments which I made for obtaining por- traits from the life, the face of the sitter was dusted with a white powder, under an idea that otherwise no impression could be obtained. A very few trials showed the error of this ; for even when the sun was only dimly shining, there was no difficulty in delineating the features. When the sun, the sitter, and the camera are situated in the same vertical plane, if a double convex non-achromatic lens of four inches diameter and fourteen inches focus be em- ployed, perfect miniatures can be procured, zm the open atr, in a period varying with the character of the light, from 20 to 90 seconds. ‘The dress also is admirably given, even if it should be black; the slight differences of illumination are Ti, and its application to taking Portraits from the Life. 223 sufficient to characterize it, as well as to show each button, button-hole, and every fold. Partly owing to the intensity of such light, which cannot be endured without a distortion of the features, but chiefly owing to the circumstance that the rays descend at too great an angle, such pictures have the disadvantage of not exhibit- ing the eyes with distinctness, the shadow from the eyebrows and forehead encroaching on them. To procure fine proofs, the best position is to have the line joining the head of the sitter and the camera so arranged as to make an angle with the incident rays of less than ten de- grees, so that all the space beneath the eyebrows shall be il- luminated, and a slight shadow cast from the nose. ‘This in- volves obviously the use of reflecting mirrors to direct the ray. A single mirror would answer, and would economise time, but in practice it is often convenient to employ two; one placed, with a suitable mechanism, to direct the rays in ver- tical lines ; and the second above it, to direct them in an inva- riable course towards the sitter. On a bright day, and with a sensitive plate, portraits can be obtained in the course of five or seven minutes, in the dif- fused daylight. ‘The advantages, however, which might be supposed to accrue from the features being more composed, and of a more natural aspect, are more than counterbalanced by the difficulty of retaining them so long in one constant mode of expression. But in the reflected sunshine, the eye cannot support the effulgence of the rays. It is therefore absolutely necessary to pass them through some blue medium, which shall abstract from them their heat, and take away their offensive brilliancy. I have used for this purpose blue glass, and also ammoniaco- sulphate of copper, contained in a large trough of plate glass, the interstice being about an inch thick, and the fluid diluted to such a point, as to permit the eye to bear the light, and yet to intercept no more than was necessary. It is not re- quisite, when coloured glass is employed, to make use of a large surface; for if the camera operation be carried on until the proof almost solarizes, no traces can be seen in the por- trait of its edges and boundaries; but if the process is stopped at an earlier interval, there will commonly be found a stain, corresponding to the figure of the glass. The camera I have used, though much better ones might be constructed, has for its objective two double convex lenses, the united focus of which for parallel rays is only eight inches; they are four inches in diameter in the clear, and are mounted in a barrel, in front of which the aperture is narrowed down to 34 inches, after the manner of Daguerre’s. 224 Professor Draper on the Process of Daguerreotype, The chair in which the sitter is placed, has a staff at its back, terminating in an iron ring, that supports the head, so arranged as to have motion in directions to suit any stature and any attitude. By simply resting the back or side of the head against this ring, it may be kept sufficiently still to allow the minutest marks on the face to be copied. The hands should never rest upon the chest, for the motion of respiration dis- turbs them so much, as to bring them out of a thick and clumsy appearance, destroying also the representation of the veins on the back, which, if they are held motionless, are co- pied with surprising beauty. It has already been stated, that certain pictorial advantages attend an arrangement in which the light is thrown upon the face at a small angle. This also allows us to get rid entirely of the shadow from the back-ground, or to compose it more gracefully in the picture ; for this, it is well that the chair should be brought forward from the back-ground, from three to six feet. Those who undertake Daguerreotype portraitures, will of course arrange the back-grounds of their pictures according to their own tastes. When one that is quite uniform is desired, a blanket, or a cloth of a drab colour, properly suspended, will be found to answer very well. Attention must be paid to the tint,—white, reflecting too much light, would solarize upon the proof before the face had had time to come out, and owing to its reflecting all the different rays, a blur or irradiation would appear on all edges, due to chromatic aberration. It will be readily understood, that if it be desired to introduce a vase, an urn, or other ornament, it must not be arranged against the back-ground, but brought forward until it appears perfectly distinct on the obscured glass of the camera. Different parts of the dress, for the same reason, require intervals, differing considerably, to be fairly copied; the white parts of a costume passing on to solarization before the yellow or black parts have made any decisive representation. We have therefore to make use of temporary expedients. A per- son dressed in a black coat, and open waistcoat of the same colour, must put on a temporary front of a drab or flesh co- lour, or by the time that his face and the fine shadows of his woollen clothing are evolved, his shirt will be solarized, and be blue, or even black, with a white halo around it. Where, however, the white parts of the dress do not expose much surface, or expose it obliquely, these precautions are not es- sential ; the white shirt collar will scarcely solarize until the face is passing into the same condition. Precautions of the same kind are necessary in ladies, dresses, which should not be selected of tints contrasting strongly, and its application to taking Portraits from the Life. 225 It will now be readily understood, that the whole art of taking Daguerreotype miniatures, consists in directing an almost hori- zontal beam of light, through a blue coloured medium, upon the face of the sitter, who is retained in an unconstrained posture, by an appropriate but simple mechanism, at such a distance from the back-ground, or so arranged with respect to the camera, that his shadow shall not be copied as a part of his body ; the aperture of the camera should be three and a half or four inches at least, indeed the larger the better, if the object be aplanatic. If two mirrors be made use of, the time actually occupied by the camera operation varies from forty seconds to two minutes, according to the intensity of the light. If only one mirror is employed, the time is about one-fourth shorter. In the direct sunshine, and out in the open air, the time varies from under half a minute. Looking-glasses, which are used to direct the solar rays, after a short time undergo a serious deterioration; the foil assuming a dull granular aspect, and losing its black brilliancy. Hence the time, in copying, becomes gradually prolonged. The arrangement of the camera, above-indicated, gives re- versed pictures, the right and left sides changing places. Mr. Woolcott, an ingenious mechanician of this city, has taken out a patent for the use of an elliptical mirror for por- traiture; it is about seven inches in aperture, and allows him to work conveniently with plates two inches square. ‘The concave mirror possesses this capital advantage over the con- vex lens, that the proof is given in its right position, that is to say, not reversed ; but it has the serious inconveniences of li- miting the size of the plate, and representing parts that are at all distant from the centre, in a very confused manner. With the lens, plates might be worked a foot square, or even larger. Y Miniatures procured in the manner here laid down, are in most cases striking likenesses, though not in all. They give of course all the individual peculiarities, a mole, a freckle, a wart. Owing to the circumstance, that yellow and yellowish browns are long before they impress the substance of the Daguerreotype, persons whose faces are freckled all over give rise to the most ludicrous results, a white, mottled with just as many black dots as the sitter had yellow ones. The eye appears beautifully; the iris with sharpness, and the white dot of light upon it, with such strength and so much of reality and life, as to surprise those who have never before seen it. Many are persuaded, that the pencil of the painter has been secretly employed to give this finishing touch. Phil. Mag. S. 3. Vol. 17. No. 109. Sept. 1840. Q [A226 44 XXXII. Proceedings of Learned Societies. GEOLOGICAL SOCIETY. [Continued from p. 153.] Dec. 18, PAPER was afterwards read, entitled, ‘‘ Observations 1839. on the locality of the Hyracotherium,” by William Richardson, Esq., F.G.S. In 1829, when Mr. Richardson first examined the coast from Whitstable to Herne Bay, it presented an uniform, geological struc- ture, composed of a capping of vegetable mould, under which was a stratum 3 or 4 feet thick of yellow brick earth, containing in the upper part rolled and angular flints, mammalian remains and fossils derived from secondary strata; and beneath, forming the mass of the cliff, was London clay of a dark brown colour, abounding im septaria, selenite, pyritous wood, teeth and vertebre of fishes, Nau- till with other characteristic marine testacea, Encrinital and Penta- crinital remains, and crustaceans. The whole of the line of coast undergoes rapid degradation in con- sequence of the encroachment of the sea and land springs ; and the changes thus annually produced, effect great alterations in the physical outline of the cliffs. ‘The geological structure, however, presented by them in 1829 remained for the greater part the same in the autumn of 1839, except at the part called Studd Hill. At this point, the dark brown incoherent clay had been removed, and a deep blue, tenacious one exposed. A change had also taken place in the character of the fossils, the marme remains having gradually become less promi- nent and been replaced by others of a fiuvio-marine character. In the autumn of last year, Mr. Richardson could not find a single ma- rine shell, and only a few fragments of crinoidal stems. Terrestrial vegetables have, however, become so prodigiously abundant, that he has obtained at different times above 500 fossil cones, fruits, and - other seed-vessels ; and fragments of small trees converted into py- rites occur in so great quantities, that they have been removed by barge loads for ceconomical purposes, and become a source of con- siderable profit to the neighbouring peasantry. These remains pre- sent no indications of having been transported from a distance. Neither land nor fresh-water shells have been observed. From the abundance of vegetables, and the knowledge that Nature ever directs her means as well in number as in fitness to particular ends, Mr. Richardson inferred, that remains either of quadrupeds or birds would be found in Studd Hill; and though his search was long fruitless, it was at last rewarded by the discovery of the portion of the Hyracotherium described by Mr. Owen in the preceding memoir. January 8, 1840. A paper was first read, on the carboniferous and transition rocks of Bohemia, by David T. Ansted, Esq., F.G.S. After alluding to the difficulties which beset the researches of a geologist in a country so little frequented as that visited by himself, and noticing the granite and gneiss mountains which constitute the Geological Society. 227 south-eastern and south-western boundaries of Bohemia, he proceeds to the main object of the memoir. The district described by Mr. Ansted is included within a triangle, having the country between Luditz and Pilsen for a base, and Prague for its apex; and its struc- ture is explained by a series of sections from Luditz to Pilsen— Radnitz to Rakonitz—Zebrak to Ginetz—and Przilep to Karlstein, all of them being more or less in the dip of the strata. The formations composing the district, are granite, gneiss, graywacke, coal mea- sures, trap rocks and accumulations of superficial debris. It is stated that a line drawn from Eger on the west to Prague on the east would completely separate the sedimentary deposits of a newer date than the carboniferous system from the coal measures and transi- tion rocks ; and that the latter occur only to the south of the line. Near Eger is a small local deposit of upper tertiary sandstone, men- tioned by Mr. Ansted on account of its containing myriads of fossil infusoria cases. Section 1. Luditz to Pilsen.—Luditz stands upon a range of round topped gneiss hills, but in a depression between two of them; and about 3 miles from the town, is a bed of thinly laminated micaceous sandstone, containing a few obscure vegetable markings, and believed by Mr. Ansted to be a recent deposit. Proceeding in the direction of Pilsen, the gneiss is succeeded bya hard cherty stone, considered by the author to belong to a rock which underlies the coal mea- sures in other parts of the country, but to have been protruded at this point by igneous agency. The next hill is formed of trap, and beyond it, is a bed of similar cherty sandstone, covered up towards the S.E. by the red conglomerate on which Manotin is built. To the south of this town, slate rocks are finely developed for several miles, forming precipitous cliffs, with the strata dipping to the S.E. They are covered in part by gravel, and are succeeded by rotten shales, assigned by Mr. Ansted to the graywacke system. ‘These shales are visible for only a short distance, being superficially replaced by a thick covering of gravel, which extends for ten miles. At the end of that distance, hills of sandstone commence, and contain near Pilsen workable seams of coal. The sandstone is coarsely grained and not very coherent; and the coal bands, which are accompanied by shales, are of variable thickness. The dip is very small, and to the S.E., but the stratification is totally unconformable with the gray- wacke. Pilsen is situated on a little stream, which unites close to the town with the Beraun; and the eastern limit of the sandstone seems to be a small tongue of coarse grit, which reaches the Beraun, and exposes a bed of coal on its western bank. At that point, how- a the graywacke comes in, having been brought up by a mass of trap. Section 2. Radnitz to Rakonitz—The direction of this section is nearly S. and N., Radnitz being about 12 miles east of Pilsen, and Rakonitz 20 miles east of Luditz. Radnitz stands upon an in- coherent coal measure sandstone; and two bands of coal are worked a little south of the town. Beyond the sandstone rises a hill of graywacke shale, protruded, Mr. Ansted believes, by the agency of a mass of trap visible a short way off. To the north of Radnitz is Q 2 228 Geological Society. an abrupt hill of the shale, considered to have been also brought up by a fault; and on its northern face commences a broad valley formed of coal measures, and bounded at its further extremity by another hill of graywacke, likewise thrown up by a fault. Coal is worked on three sides of this hill. The graywacke continues thence for six or seven miles, when the coal sandstone again constitutes the surface for a short distance (2 miles), and, after another interval occupied by graywacke, reappears forming the country around Ra- konitz. Section 3. Zebrak to Ginetz.— This section refers to a more southerly part of the district, and traverses a portion of the coal measures situated south of that line of graywacke which extends from Pilsen to Prague, and separates, except at one point, the coal field connected with the two first sections, from the district about to be noticed. At Zebrak, the point just mentioned, the coal measures intersect the graywacke range, in consequence apparently of a fault ; and the section commences at Zebrak in graywacke shale near the junction of the coal measures with the graywacke. These shales extend to Horzowitz, where they are overlaid unconformably by the coal sandstone, which constitutes the surface of the country for about two miles. At that point is a hill, on the summit of which occurs a cherty sandstone considered by Mr. Ansted to be the base of the coal measures and to have been forced up into its present position. The beds dip about 60° S.E., and rest apparently upon a very coarse, hard, red conglomerate, to which succeeds a vast de- velopment of shale, containing occasionally Trilobites. This divi- sion of the graywacke series, is at some distance, covered again by the conglomerate upon a change of dip, and then continues nearly three miles to Ginetz, with the strata moderately inclined to the N.E. At that town a band of limestone cccurs reported to be rich in Trilobites. ‘ Section 4. Przilep to Karlstein.—This section is parallel to the last, and crosses the line of country between Pilsen and Prague, Two or three tolerably thick beds of coal are worked near Przilep and supply Prague with fuel. Fossils also are not deficient. About 6 miles towards the north-west, other but inferior beds of coal are wrought; but towards the east, the coal thins out between lofty pre- cipices of shale, which form a narrow gorge. Pursuing the line of section towards the south-east, the direction of the dip, and at no great distance from Przilep, the coal basin is shut in by the steep face of a hill. At this point, Mr. Ansted believes, that the lower beds of the coal measures are not only brought up, but are bent over the upper, because, though the dip of the strata is to the S.E. or in the direction of the section, yet, on the summit of the hill above mentioned, is exposed an excellent natural surface of chert; and in a quarry near the top the inclination of the beds is about 25° S.E, or in the regular dip of the coal measures; and in a narrow valley at the bottom of a somewhat rapid descent, the lowest division of the graywacke is exposed dipping S. or actually overlying the coal measures, This inversion of superposition, Mr, Ansted explains by ‘ Geological Society. : 229 assuming, that the granite comes near the surface, and that by its agency the graywacke has been thrown into a trough, and its lowest beds so brought up as to be made to rest against inverted beds of the coal measures. Proceeding in the line of section, the author found in graywacke shale, portions of a Trinucleus, Trilobites or- natus. (Trans. Prague National Mus. Soc. 1833.*) The graywacke shell extends with contorted strata to an anti- clinal hill of limestone, beyond which occur broken and rotten shales, then limestone, next shales again, and lastly the picturesque limestone hill of Karlstein. Further south is a valley of graywacke bounded by an altered rock, which is succeeded by granite. The Karlstein limestone is stated to be identical with that at Ginetz, (see section 3) and the two other localities in the present line of section. It is ofa pale blue colour, very hard, contains several species of Orthocera and Trilobites, and is of great ceconomical importance. The recurrence of the same limestone at different points, Mr. Ansted explains, by supposing, that the granite in these cases, is also near the surface, and that a displacement of it bent the yielding shales, but snapt asunder a brittle band of limestone once continuous, the portions of which, not removed by subsequent operations, are ex- hibited at the points mentioned in the line of section ; and that the consequences of these operations have been, a disturbance in the re- gular succession, and an exhibition of the beds in the following order : granite, altered rocks, newest graywacke with limestone, oldest gray- wacke, coal measures. In conclusion, Mr. Ansted offers the following observations as thé results of his examination of this portion of Bohemia. The gray- wacke series is imperfectly developed, presenting at only one spot a passage upwards into the carboniferous series, and no passage down- wards into the graywacke, resting always unconformably upon it ; the secondary rocks are also very imperfectly developed, the mountain limestone being absolutely wanting, and the only indications of beds newer than the coal measures being a red conglomerate, into which they pass upwards. The flora of the coal measures is how- ever well known to be rich, and to have yielded near Radnitz the fossils described by Count Sternberg. A genus allied to Scorpio is also stated to have been found in them. ‘The fossils of the gray- wacke are said to be not very numerous; but the Trinucleus ap- pears to be abundant on the line of road between Prague and Pilsen ; and in a gorge near Lodentz, about fourteen miles from Prague, is a quarry which yields shells and other organic remains; and on the opposite side of the road, near the same spot, similar fossils may be obtained. Trilobites occur at Ginetz, and Orthocera at Karlstein ; and both these localities and the neighbourhood of Prague are men- tioned as rich in organic remains. The Trinucleus Caractaci is stated to occur near Zebrak.t * Impressions of shells were also found by the author in a grayish sand rock, a little nearer Prague; and the Trinucleus is found at Zebrak and Praskoles, on the south side of the high road about 10 miles south of Beraun. ¢ See the fossils of Caradoc sandstone, Silur. Syst. pl. 23, f. 1. 230 Intelligence and Miscellaneous Articles. A letter was afterwards read, addressed to Dr.Buckland, P.G.S. by the Rev. John Gunn, and dated Dec. 21st, 1839. This letter was accompanied by three paramoudras from the chalk near Norwich; and they had been selected by Mr. Gunn on account of one of them presenting a tuberculated exterior, a character which he states a paramoudra commonly assumes when it is in contact with horizontal lines of nodular flints; and the other two had been chosen because Belemnites and shells are imbedded in their sub- stance. The letter contains some observations on the irregularities in the surface of the Norfolk chalk, and on the pipes or sand galls by which it is penetrated. With reference ‘to these tubular hollows, Mr. Gunn refers to Mr. Lyell’s description of them, read at the meeting of the British Association at Birmingham, but he calls at- tention to their being constantly filled in the district examined by himself, with sand, gravel, or crag, to the total exclusion of all ma- terials belonging to the strata between the chalk and the crag; and he therefore infers, that the sand galls were not eroded during the eocene period, but that during that long period the Norfolk chalk was denudated. The letter was also accompanied by some specimens from the boulders contained in the diluvial (drift) strata of Norfolk and Suf- folk. Mr. Gunn is of opinion that these masses of rock indicate what were the strata that formed the shore against which the (so- called) diluvial waves washed; and that the masses were borne out to sea in a similar manner to the portions of cliff now annually de- stroyed by the waves. If the bottom of the present sea were raised, he says it would present features analogous to those of the crag and diluvial formations of Norfolk and Suffolk. XXXIV. Intelligence and Miscellaneous Articles. PHENOMENA OF CALEFACTION. M BOUTIGNY has read a paper before the Academy of Sci- ® ences on Calefaction, by which term he designates the singu- lar phenomenon presented by water when drops of it are thrown upon a very hot metallic surface. It has generally been supposed that this effect is produced only at a very high temperature, but M. Boutigny finds that it occurs in a lead crucible, and consequently below 612° Fahrenheit. M. Boutigny has observed also that «ther gradually dropped into a platina crucible nearly red-hot, calefies as well as water, that is to say, the mass becomes round, without the occurrence of any appear- ance of ebullition, is afterwards rapidly agitated, and does not seem to wet the crucible. The quantity, however, goes on dim:- nishing, but much less rapidly than if the vessel were cold. Du- ring this slow evaporation, a very irritating vapour arises, which does not at all resemble that of zther, but which in smell greatly resembles aldehyde, and of this the author supposes it to consist ; the presence of air appears to be necessary to the production of this vapour. ‘The commissioner to whom M. Boutigny’s paper was Intelligence and Miscellaneous Articles. 231 consigned, made an interesting observation: having immersed a piece of litmus paper into the crucible to try whether the vapour was acid, he observed that the part immersed retained its colour, whilst that which was even with the orifice of the crucible became evidently red. ‘The temperature was therefore higher in this place, and it is to be presumed that slow combustion took place analogous to that which occurs in the interesting experiments of Dobereiner. Anhydrous sulphurous acid presented M. Boutigny with pheno- mena still more remarkable than ether; he found that when a little of this acid dropped upon a platina capsule heated almost to redness, the drops were strongly agitated, became round, immoveable and opalescent, and seemed even to crystallize. The small spheroid when placed on the hand produced a sensation of cold. M. Boutigny was of opinion, that in this case the sulphurous acid suffered so great a diminution of temperature that it solidified. The commissioner rejects this explanation, and is satisfied with ad- mitting, that the acid under these circumstances evaporating more slowly than in the open air, produces nevertheless, by this slow eva- poration, so considerable a degree of cold as to congeal the moist- ure of the surrounding air, and to become hydrated. This explana- tion is apparently confirmed by the fact, that if the small solid globule be rapidly projected into a tube, and it be immediately corked, the globule disappears, but leaving in the place which it occupied a dew, that remains even when the tube is uncorked. M. Boutigny is of opinion that the phenomena described may be connected with the explosions in steam-boilers, and he is still occupied with the subject, and has made a great number of experi- ments with different liquids, and particularly with alcohol of dif- ferent degrees of strength, with xther, oil of turpentine and lemons, and with alkaline and acid solutions.—Journal de Pharm., Mai, 1840. HYDROMELLONIC ACID. Discovered by L. Gmelin. Prepared by dissolving mellonuret of potassium in boiling water, and adding to the solution hydrochloric, sulphuric, or nitric acid. A dirty white gelatinous precipitate which dries to a yellow powder, the hydrated hydromellonic acid. It is slightly soluble in cold, more freely in hot water, has a slightly acid reaction, and is not decomposéd by hydrochloric and nitric acids. Formula C,N, + H; eq. = 94°32. Turner’s Elements of Che- mistry, p. 796. CHROMIC ACID. M. J. Fritzche prepares chromic acid by the careful addition of concentrated sulphuric acid to a hot concentrated solution of bi- chromate of potash ; a crimson bulky precipitate is obtained, which is dried first by heat, and afterwards in vacuo. This is entirely chromic acid, which is to be washed to get rid of the mother water, and of the sulphuric acid which adheres to it. The author could 232 Intelligence and Miscellaneous Articles. not obtain the compound of sulphuric and chromic acids described by. M. Gay-Lussac in the 16th volume of the Ann: de Chim. et de Phys., and he is inclined to question its existence.—L’ Institut, No. 341. COMPOSITION OF CRYSTALLIZED PHOSPHORIC ACID. In the opinion of Prof. Graham, phosphoric acid may combine with water in three different proportions, and form a phosphate, biphosphate, triphosphate of water. The existence of these com- pounds has hitherto been hypothetical, except the first, which ap- pears to be vitrified phosphoric acid. The analysis of crystallized phosphoric acid has not yet been attempted, or at any rate not yet published. M. Peligot has attempted to supply this void in the history of phosphoric acid, by analysing crystals which slowly formed spontaneously in bottles filled with syrupy phosphoric acid. One of these bottles contamed two very distinct crystalline layers. The upper crystals were transparent and hard; the lower ones were soft, and had the appearance of sugar of honey. The crystals, separately collected, were dried in vacuo, on plates of absorbent porcelam ; the quantity of water was determined by cal- cining them with oxide of lead. According to M. Peligot’s analyses, the upper crystals contained from 27 to 28 per cent. of water, and the lower crystals 22 to 23 per cent. The extreme avidity of these crystals for water, renders a precise analysis of them very difficult; if, as theoretically supposed by M. Peligot, hydrated phosphoric acid containing three equivalents of water ought to contain 27°4 per cent., and the bihydrate 20:1 per cent., it will appear probable that the crystals examined were in fact these two hydrates. Their properties also corroborated this opinion; — for the most hydrated acid, when saturated with ammonia, precipt- tated silver of a yellow colour, while the second precipitated it white. —Journal de Pharm., Juin, 1840. DETECTION OF ALCOHOL IN ESSENTIAL OILS. For the above-purpose M. Borsarelli employs a small cylindrical tube closed at one end; this is two-thirds filled with the oil, and there are dropped into it small pieces of chloride of calcium, which are quite dry, and free from powder; the tube is then closed, and heated in a water-bath to 212° for four or five minutes, taking care to agi- tate it occasionally, and to allow it to cool slowly. If the essential oil contains a notable proportion of alcohol, the chloride dissolves entirely, and forms a Hquid stratum, which occu- pies the lower part of the tube, while the essential collects in the upper. If the oil contains only a very small portion of alcohol, the fragments of chloride of calcium effloresce, lose their form, and unite at the bottom of the tube into a white adhesive mass; when it is quite pure the pieces of chloride suffer no change, even in their form. Intelligence and Miscellaneous Articles. 233 It is proper to observe, that in trying an essential oil it is right to employ but a very small portion at first, and to add successive por- tions gradually ; otherwise, if the proportion of alcohol be very small, it may be absorbed by the chloride without sensibly altering it, and even without showing its presence. It is easy when the operation is over to determine the proportions of a mixture of alcohol and essential oil, by comparing its weight or volume with that of the pure oil which floats upon the alcoholic solution of the chloride. The same process, the author states, may be employed for deter- mining the quantity of alcohol which ether contains; but the tube should be longer, and not too perfectly closed.—Journal de Pharm., Juin, 1840. © (ECONOMICAL PREPARATION OF ACETONE. M. Zeise of Copenhagen observes, that when a considerable quan- tity of acetone is required, the methods usually employed are too ex- pensive, and he recommends the following process: mix thorough- ly one part of well-powdered quicklime with two parts of powdered crystals of acetate of lead. Soon after the mixture is made, the lime usually begins to heat violently ; but as no smell of acetone is perceptible, there is no sensible loss of it; it is better to put the mixture into the distillatory apparatus before this heating occurs, because afterwards the mass is so great that the introduction is more difficult. M. Zeise states that he has not found it advantageous to attempt getting rid of this circumstance by employing slacked lime ; for in this case dried acetate must be used to prevent the product from containing too much water, and the drying of the acetate is more troublesome than powdering the lime. The iron bottles in which mercury is imported, suit for this ope- ration extremely well; four pounds of the acetate may be operated upon at once; the bottle is placed almost horizontally in the fur- nace, but so that the opening is rather raised; to this a slightly curved short tube is adapted, and luted with a mixture of clay, chalk and salt, and this enters into a glass tube sufficiently large, properly curved and surrounded with a tin-plate pipe, in which an ascending current of water is kept up; and lastly, to this a receiver surrounded with ice is attached. The heat is slowly raised, and it is only towards the end of the operation that it is increased to red- ness. The product is a mixture of acetone, a small quantity cf water, two oily substances, which are less volatile than acetone, one of which is probably the dumasine of Kane. From this product pure acetone is obtained by dissolving chloride of calcium in it, distilling the solution in a water-bath, until at 212° nothing more passes over; the product is to be again treated with chloride of calcium, and three-fourths being distilled will be found to be pure acetone. On adding water to the residue, the oily bodies are separated from the acetone, which dissolves in the water and is separated from it by chloride of calcium. ep ena if Fa tr a bi t A ERS S SANS TRE ae tet cee ode Sac ecto 234 Intelligence and Miscellaneous Articles. From about 8 pounds of crystallized acetate of lead, M. Zeise ob- tained by the process now described from 10 to 113 ounces of per- fectly pure acetone.—Ann. de Chim. et de Phys., t. 1xxil. CARBURET OF PLATINA. M. Zeise observes that the formation of a compound of carbon and platina has been hitherto ineffectually attempted; he has, how- ever, succeeded in procuring by means of decomposing acechlor- platina by heat. When acechlor-platina is heated in a retort, to which a receiver is adapted, with a bent tube, it begins to decompose and yield a little gas at about 419°; at 464° the disengagement of gas is plenti- ful, and a brown liquid distils. This continues with the gradual increase of the heat up to 527°, a little colourless liquid coming over from time to time; at 572° much gas and liquid were pro- duced; when this heat ceased to produce any effect, the retort was heated to redness in the sand-bath; this occasioned a copious dis- engagement of gas; so that the quantity obtained at this period was greater than all previously procured, but the quantity of liquid was much smaller; when neither gas nor liquid was obtained, the operation was stopped, and the residue cooled out of contact with the air. The distilled liquid contained so much hydrochloric acid that it smoked in the air, and when mixed with water it gave an oily liquid which floated. Its odour was resinous and ethereal: the volume of the liquid was considerably diminished by treatment with water. The gas was a mixture of hydrochloric acid and an inflammable gas, which was probably protocarburet of hydrogen, and there were traces of carbonic acid. The residue was black, slightly coherent, and free from metallic particles. The slowness with which it burnt, indicated that it was a chemical compound of carbon and platina. In the first experiment 100 parts of acechlor-platina yielded 60°0107 of carburet of platina, and in the second 60°708 ; the mean — is 60°362. On the supposition that it is a bicarburet of platina, 100 parts of acechlor-platina ought to have yielded 60°347 parts of carburet. Then as 100 parts acechlor-platina, and consequently 60°362 of carburet of platina, contain 53°692 parts of platina, we have for 100 parts of carburet of platina, Garboi ss is cast ct tue 11°041 Platina bil ae rath uate 88°959 100 Calculation gives 11°029 carbon, and 88°971 platina; it retained scarcely a trace of chlorine. Carburet of platina may also be ob- tained by heating to redness a mixture of acechior-platina and hy- drate of lime.—Ann. de Chim. et de Phys., t. 1xxii. Intelligence and Miscellaneous Articles. 235 SULPHATE OF CARBYLE. M. E. Magnus states, that when anhydrous sulphuric acid is ab- sorbed by absolute alcohol, there are formed, under the influence of particular circumstances, white silky crystals in the alcohol; they are a sulphate of carburetted hydrogen, to which M. Magnus gives the name of sulphate of carbyle, from carbo and hydrogenium. The method adopted was that of exposing the alcohol in a small tube to anhydrous sulphuric acid in a stopped receiver. Crystals are rarely formed immediately ; the tube must be put into a second receiver containing sulphuric acid, and sometimes even into a third. For the sulphuric acid in the receiver also absorbs alcohol, which causes the cessation of the absorption of the acid by the alcohol which is contained in the tube. The formation goes on without the disen- gagement of sulphurous acid. The crystals which form in the alcohol tube are, it is true, sur- rounded with fuming acid, but M. Magnus succeeded in isolating them. In pouring off the liquid acid which filled the interstices, they yield abundant vapours: they rapidly attract humidity from the air and deliquesce; to dry them they were placed upon a plate of. baked clay, slightly heated in the air-pump over sulphuric acid until they yielded no more vapour. When ether was employed instead of alcohol, no crystals were obtained; it is possible, however, that under some circumstances they might be formed; the experiment confirms the previous state- ment of M. Magnus, that when ether is absorbed by anhydrous sulphuric acid, heavy oil of wine is always produced, which is never the case with absolute alcohol. This may be regarded as one of the strongest objections against the opinion that alcohol is a hy- drate of zther; for if this were the case, the sulphuric acid ought to remove the water, and then act upon it as if it were xther, which evidently does not occur. When these crystals are cautiously heated, they fuse without de- composition, and on cooling become a crystalline mass. They com- bine with water and alcohol with the disengagement of heat, and by evaporation they do not separate from the solution. The aqueous solution, saturated with barytes, yields soluble salts with a little sulphate of barytes. The quantity of sulphuric acid ob- tained was variable, and appeared to be eliminated by the action of the water. The soluble barytic salts are ethionate of barytes and a little isethionate, and it appears to be the conversion of ethionic into isethionic acid, which produces the sulphuric acid. By analysis sulphate of carbyle appears to be composed of Sulphuric acid...... 84°930 Carbon. os is,ss~, 4,0 40%), sbai90D FIFONOSEM ton.ins » oc ineillS 100 It is therefore a sulphate of carburetted hydrogen, or 1 equivalent 236 Intelligence and Miscellaneous Articles. of sulphuric acid 40+ 1 equivalent of carburetted hydrogen 7, si- milar to that formed by the action of anhydrous sulphuric acid on olefiant gas.—Ann. de Chim. et de Phys., t. Ixxii. ON HELLENIN. BY M. C. GERHARDT. This substance, obtained from Inula hellenium, is to be distin- guished from znulin yielded by the same root. It is readily obtained by treating the fresh root of the elecampane with alcohol of sp. gr. 0°837 ; when the excess of alcohol is separated by distillation, the concentrated liquor becomes milky by cooling, and deposits abun- dance of crystals. ‘They are purified by redissolving in alcohol and recrystallizing. When the root is distilled with water, downy flocculi, which are very white pure hellenin, are obtained in the receiver; but the quantity is so small that it is better to employ alcohol. Hellenin crystallizes in four-sided prisms; they are perfectly white, their smell and taste is extremely weak, and they are lighter than water. ‘They are insoluble in water, but very soluble in ether and alcohol, and these solutions are precipitated by water. It dis- solves also in all proportions, in essential oils and in creasote. It may readily be pulverized when it is rendered impure by the resin, which always exists with it in the root. Its fusing point is about 161° Fahr.; it boils at 527° to 536°, and volatilizes before it boils, exhaling a very weak odour. At this temperature, however, it is more or less altered, so that the density of its vapour cannot be ascertained. When hellenin is fused at a gentle heat, it recrystallizes in a mass on cooling; but if the heat be continued for some minutes, the mass on solidifying does not possess a crystalline texture, but resembles resin in appearance. The caustic alkalies do not decom- pose hellenin, even when heated, a property which it possesses in - common with several substances, such as camphor, the oil of ani- seed, mint, &c. On heating it in a solution of potash, it first fuses and eventually dissolves, and on the addition of hydrochloric acid the hellenin is precipitated without alteration. When heated with hydrate of potash, a great part of it is volatilized, whilst another portion is carbonized; on dissolving the mixture afterwards in water a slightly brown coloured liquid is obtained, which becomes slightly turbid on the addition of acids. Acids act upon hellenin as they do upon the greater part of the essential oils; concentrated sulphuric acid dissolves it at common temperatures, forming a red coloured solution, without the evolu- tion of any sulphurous acid, provided no heat be employed; never- theless after a considerable time the mixture becomes black, as if acted upon by heat. ‘The solution then contains a certain quantity of a peculiar acid, to which M. Gerhardt has given the name of sul- pho-hellenic acid. When hydrochloric acid gas is brought into contact with hellenin, it absorbs a large quantity of the gas, and a liquid of a violet co- Intelligence and Miscellaneous Articles, 237 lour is formed; when exposed to the air it exhales hydrochloric acid. Nitric acid of middling strength dissolves hellenin without the evolution of any hyponitrous acid, and water precipitates it unal- tered ; when the mixture is heated the hellenin is converted into what M. Gerhardt calls nitro-hellenin. Concentrated acetic acid dissolves hellenin ; the solution is colour- less, and deposits by evaporation unaltered crystals of this substance ; water precipitates the solution. Anhydrous phosphoric acid acts upon hellenin as it does upon camphor, converting it into a carburetted hydrogen, which M. Ger- hardt has named hellenene. Cold chlorine gas does not act upon hellenin, nor even when ex- posed to the direct rays of the sun; but when the mixture is heated, hydrochloric acid is disengaged and a resinous body is formed, in which a certain number of atoms of hydrogen are replaced by an equal number of atoms of chlorine ; a drop of bromine produces with hellenin an effervescence of hydrobromic acid; the product is of a yellow red, dissolves in alcohol, and is precipitated from it by water. It is probably a compound analogous to that formed with chlorine, and the author terms it hydrochloraie of chlorehellenin. Bichloride of tin and protochloride of antimony, the latter in a state of fusion, colour hellenin of a deep red colour, exactly like concentrated sulphuric acid. When distilled with lime, hellenin yields a yellow inflammable liquid ; it is neutral, does not mix with water, and in smell resembles acetone. The analysis of hellenin performed by M. Gerhardt agrees nearly with that of M. Dumas, and he considers it as constituted of 30 atoms of carbon,... 1146°6 77°92 20 atoms of hydrogen... 124°8 8°41 2 atoms of oxygen .. 200°0 13°67 1471-4 100 In composition it more nearly approaches creasote than any other substance, which, according to Ettling, contains CAEDOM loans ay Ge Hydrogen...... 8:12 Oxygen........ 14°46—100 Ann. de Chim. et de Phys., t. Ixxii. CHEMICAL AND CONTACT THEORIES OF VOLTAIC ELECTRICITY. After giving an extract from Professor Faraday’s Sixteenth Series of Researches, of which an abstract appeared in Lond. and Edinb. Phil. Mag., vol. xii. p. 122, M. de la Rive remarks, ‘“‘ The question of which Mr. Faraday treats in the memoir from which the fore- going extract is given, is the subject of a warm controversy at the present time, especially in Germany, where the partizans of the voltaic theory of contact are numerous. The authority of Mr. Faraday, and the clear and decisive manner in which he declares himself in favour of the chemical theory, are of great weight; the 238 Intelligence and Miscellaneous Articles. numerous investigations which this philosopher has made in elec- tricity, and his great practical acquaintance with voltaic apparatus, ‘give great value to his opinions on the origin of voltaic elec- tricity. ‘‘In beginning the memoir here alluded to, he has done me the honour to mention that I am one of those who have most strongly pleaded for fifteen years in favour of the chemical theory ; he has repeated most of the experiments upon which I have rested my opinion, and he has found them correct. I hope soon to be able, in like manner, to take up the experiments lately made in Germany in favour of the theory of contact, in order to show that they are in no way contrary to the chemical theory, and to add to this theory some new direct proofs. At the meeting of the Société de Phys. et d’ Hist. Nat. de Genéve, on the 21st of May last, I read a memoir on this subject, which will appear in one of our earliest Numbers.”— A. bE LA Rive, Bibliotheque Universelle. HYDROMELLONIC ACID AND METALLIC OXIDES. The hydromellonic acid is decomposed by metallic oxides into a metallic mellonuret and water ; 1t decomposes the carbonates both in the dry state and in solution, and the iodides and bromides on fusion. Its compounds with the alkaline metallic oxides and with the earths are insoluble in water. Mellonuret of Potassium.—Prepared by fusing sulphocyanuret of potassium in a porcelain crucible at a red heat, and adding mellon as long as an evolution of sulphuret of carbon and sulphur is re- marked. A brown opake glassy mass is obtained, which dissolved in boiling water yields, as the solution cools, hydrated crystals of mellonuret of potassium. It may also be formed by fusing 5 parts of chloride of antimony (butter of antimony) with 8 parts of sul- phocyanuret of potassium, and removing by boiling water the soluble portions of the residue after the escape of the sulphur and the sul- phuret of carbon. It is also formed as a secondary product in the process for the preparation of the sulphocyanuret of potassium; it is present in the solution in small, but in the residue in larger quan- tity, from which it may be removed by boiling water. Prop.—Crystallizes from water in colourless fine needles, which unite into dense flakes; a concentrated solution congeals to a soft white mass, which is with difficulty dissolved by cold water; the crystals contain water of crystallization, which they lose at a high temperature ; they then fuse without loss of weight to a clear yellow glass. The solution is tasteless, and precipitates all earthy and metallic salts. By fusing sulphocyanuret of potassium with mellon, the sulpho- cyanogen is liberated, and is instantly decomposed by the high tem- perature into sulphuret of carbon, sulphur, and mellon. By fusing 1 eq. chloride of antimony with 4 eq. sulphocyanuret of potassium, there are formed 3 eq. chloride of potassium 3 KCl, 1 eq. sulphuret of antimony Sb,8,, 2 eq. sulphuret of carbon 2 CS,, 1 eq. mellonuret of potassium KC,N,, and 1 eq. of free sulphur. By fusing ferrocy- Meteorological. Observations. 239 anuret of potassium with sulphur, the sulphocyanuret of potassium, and sulphocyanuret of iron, are formed; 4 eq. of the latter decom- pose into 4 eq. sulphuret of iron 4 Fe 8, 2 eq. sulphuret of carbon 2 CS,, and 1 eq. of mellon, which as soon as it is formed decomposes 1 eq. of sulphocyanuret of potassium into mellonuret of potassium and sulphocyanogen ; the latter is further decomposed into sulphur, sulphuret of carbon, and mellon. Formula K + C,N,; eq. = 182°47. Turner’s Elements of Che- mistry, pp. 797, 798. ————— CYANILIC ACID. By a long-continued boiling of mellon in dilute nitric acid, a so- lution is effected with the evolution of gaseous products, and the liquid yields on evaporation colourless, transparent, octohedral cry- stals ; by re-solution in hot water, hydrated cyanilic acid in soft tabu- lar crystals of a mother-of-pearl lustre are obtained. This acid has the same composition as the crystalline cyanuric acid ; contains, like the latter, 4 eq. water of crystallization, which it loses at 212°, when it becomes opake and falls to a white powder. By the destructive distillation it is converted into hydrated cyanic acid; by solution in sulphuric acid and caustic potassa into cyanuric acid. This acid has been but little examined. Its formation admits of explanation on the supposition that the elements of 1 eq. of mellon and 8 eq. of water give rise to 1 eq. cyanilic acid and 1 eq. ammonia, and the latter is in point of fact found combined with the nitric acid; ac- cording to this, its formation ought not to be dependent on the use of nitric acid alone.—Jbid. p. 798. METEOROLOGICAL OBSERVATIONS FOR JULY, 1840. Chiswick.—July 1. Overcast: boisterous. 2. Rain, with strong wind. 3. Cloudy and fine. 4. Very fine. 5. Cloudy: windy. 6, 7. Fine. 8 Fine: heavy rain, 9—12. Very fine. 13—17. Fine. 18. Overcast. 19. Cloudy : rain, 20. Heavy showers. 21. Very fine: rain. 22. Fine. 23. Cloudy. 24, Overcast and fine: rain. 25. Showery. 26. Cloudy: fine. 27. Fine. 28. Hazy. 29. Very fine. 30. Cloudy: rain. 31. Very fine. Boston.—July 1,2. Rain. 3. Stormy. 4, Fine: rain early a.m.: rain a.m. 5. Fine: rain a.m. 6. Cloudy: rainep.m. 7. Cloudy: rain early a.m. : rain ym. 8 Cloudy: rain p.m. 9. Cloudy. 10. Cloudy: rain pm. 11—13. Cloudy: rain sa.m.and p.m. 14,15. Fine. 16. Rain: rain early a.m. 17. Fine. 18,19. Cloudy: raine.m. 20. Fine, 21. Fine: rain p.m. 22. Fine. 23, 24. Cloudy. 25. Rain: thunder and lightning with rain p.m. 26. Cloudy. 27, Fine. 28. Cloudy: raina.m. 29. Fine. 30, Cloudy. 31. Fine. Applegarth Manse, Dumfries-shire.—July 1. Heavy rain a.m.: cleared up P.M. g. Drizzling all day. 3. Heavy rain all day. 4. Fair till 4 pe... then wet. 5. Showery: fair evening. 6. Rainy. 7, 8. Showery: thunder. 9, Fair all day. 10. Showery. 11. Warm: asingleshower: thunder. 12. Very wet. 13. Fine dry day. 14. Wet afternoon. 15. Very wet allday. 16, 17, Occasional showers. 18. Fair till afternoon, then wet. 19. Rainearly a.m.: cleared up. 20. Fair all day. 21. Heavy showers all day: thunder. 22. Fair all day. 23. Fair till evening, then rain. 24. Showery allday. 25. Showery afternoon. 26—30. Fair all day. 31. The same: a few drops p.m. Sun shone out 29 days. Rain fell 22 days. Thunder 3 days. Wind north 3 day. 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[THIRD SERIES.}] OCTOBER 1840. XXXV. Comparative Measure of the Action of two Voltaic Pairs, the one Copper-zinc, the other Platina-zinc. By M. Jacosi*, , HAVE the honour to communicate to the Imperial Aca- demy of Sciences, the result of my comparative experi- ments, concerning the force of two different voltaic pairs with partitions, the one copper-zinc, charged with sulphate of copper and sulphuric acid dilute with six parts by volume of water; the other platina-zinc, and charged, according to the recommendation of Mr. Grove, with concentrated nitric acid, and with the same diluted sulphuric acid. The first pair, copper-zinc, had 36 square inches of surface, the pair platina- zinc had only 2} square inches. ‘To measure the force of the current, I employed M. Becquerel’s electro-magnetic balance. This instrument is valuable for accurate measures, provided the helices be so disposed as to be able to fulfil the conditions of stable equilibrium, which necessarily ought to exist in a balance. ‘This is attained by making the repulsion only act between the magnetic bars and helices. For this purpose, one of the helices ought to be fixed below, the other above the said bars. This last helix is traversed by the rod, by which the bar is suspended from the beam of the balance. It is still necessary that a correction be adapted to the cur- rents measured by the balance. This correction, of which other synchronous investigations have shown the necessity, is in proportion to the square of the force of the current, Tor * Read before the Imperial Academy of Sciences of St. Petersburgh, on the 3lst of January, 1840. Phil, Mag. S. 3. Vol. 17, No. 110, Oct. 1840. Kt 242 On Copper-zine and Platina-zinc Voltaic Pairs. let X’ be the actual. current, & the current measured by the balance, we have the equation bib kal ~ yk, from which is deduced 4! = 35 (—WV1—4ky). For my balance I have found, by a series. of cbservations, y = 0°:00004228 (Bulletin Sc. de ? Acad. Sc. tom. v. p. 375.). The following table contains the experiments made with the voltaic combinations in question. ‘The first column con- tains the resistances, L, of the helices which serve as conjunc- tive wire, and which had been found by other experiments; the two other columns contain the forces of the effective currents, or of the currents measured in’ grammes, and cor- rected according to the formula above indicated. . Force of -| Force of 1B the pair, the pair, Copper-zinc.| Platina-zinc. q gr. faaeis)e 23°1 0°380 0°395 135°3 0:097 0:135 Let A, A! be the electro-motive forces, d, X! the resistances of the pair itself, we shall have, according to Ohm’s formula, the four following equations: | A is Al | raga ee Nees = 9 A Al ee Ce a N4+135°3 ge whence A = 14610, ~ = 15°35, A’ = 23000, 0! = 35; or taking 2 as the unit of surface, which is here 36 square inches, Ae OO ane Mom iitaagtT z the number of pairs, C the force of the current, L any re- zAs | 2rA+Ls find, that the maximum of force is obtained, if the pile be 27Xr = 24. Let s be the total surface ofa pile, sistance, we have C = From this equation we arranged so that = L, 1. e. that the total resistance of the pile shall be equal to the resistance of the conductor, what- ever its nature may be, this resistance being one which is in+ terposed in the circuit, and not belonging to the pile, As for On Huyghens’s Principle applied to Physical Optics. 243 other arrangements than those which correspond to the maxi- mum of effect, there is no constant relation between different voltaic combinations; we can only compare them, and judge of their relative preferableness by referring them to this maxi- mum ofaction. We have, by eliminating 2, the equations FE ge OR A 9. nh Ne Boat Mia! whence we deduce, by substituting the numerical values above round for A, Al, Ny Moved. wee A ee OS OY ONE and with reference to the number of pairs x = z.0°6; that is to say, zt requires only a pile of -6 square feet of platina to replace a pile of 100 square feet of copper ; or with reference to the number of pairs, 6 pairs of platina, each of a square foot of surface, will produce the same effect as 10 pairs of copper, each of ‘which presents a surface of 10 square feet. This eminent superiority of platina, as in Mr. Grove’s com- bination, is verified by many experiments on a large scale. C (max) = XXXVI. On the Application of Huyghens’s Principle in Physical Optics. By R. Potter, Lsg., B.A.* [N the present paper I propose to examine some of the con- sequences of the method at present followed in developing the results of the undulatory theory of light, which consists in considering elementary waves, having their origin in some previous positions of the main waves, as the cause of these latter in succeeding positions. In the Mémoires de ? Acad. for 1821 and 1822, Fresnel announces this method in the following terms :— *¢ Application du Principe d’ Huygens aux Phénomenes de la Diffraction. ** Ce principe que me parait une conséquence rigoureuse de Phypothése fondamentale, peut s’énoncer ainsi: Les vibra- tions d’une onde lumineuse dans chacun de ses points peuvent étre regardées comme la somme des mouvemens élémentatres qu’y enverraient au méme instant, en agissant isolément, toutes les parties de cette onde considérée dans une quelconque de ses positions antérieures.” Again, in speaking of the analytical process, he says, ** La recherche de la loi suivant laquelle leur intensité varie- rait autour de chaque centre d’ébranlement, présenterait sans doute de grandes difficultés ; mais heureusement nous n’avons pas besoin de la connaitre; car il est aisé de voir que les effets * Communicated by the Author, R 2 D244 Mr. R. Potter on the Application of produits par ces rayons se détruisent presque compléetement dés quils s’inclinent sensiblement sur la normale, en sorte que ceux qui influent d’une maniére appréciable sur la quantité de lumiere que recoit chaque point P peuvent étre regardés comme d’égale intensité.” In the application of the above principle, we take the origins of the elementary waves on any proposed surface as that of a reflecting or refracting substance, or an aperture, without its being necessary that this surface should coincide with any one wave surface as it arrives. . There are only a few cases in which the integration for the whole vibration of a particle can be effected directly; in the following, however, the integration involves no difficulty, and they suffice for proving the discordance of the results of the principle with acknowledged facts. ‘They show that the labour which has been expended in investigating more com- plicated cases, might with ordinary caution have been saved. The integration is readily performed when a series of plane waves fall on a plane reflector, or an aperture parallel to their surfaces, the reflector or aperture being of one of the circular forms enumerated below, and the particle whose vi- bration is required, being in the normal to such surfaces through the centre of the circular arcs. ‘These forms com- prise a circular aperture of any radius, an annulus contained between two circles, a circular sector, and the quadrilateral figure bounded by two radii, and two circular arcs: this latter form approximates to a rectilinear parallelogram, when the angle between the bounding radii is small, and the radii of the circular arcs are large. The integration for apertures or reflectors of the same forms, is readily performed also when light diverges from a luminous point in the normal line through the centre of the arcs; and the particle whose vibration is required is equally distant from the surface in the same line, and on the opposite or same side with the luminous point, according as an aper- ture or a reflector is considered. Let us commence with a series n M of plane waves falling directly on NZ a quadrilateral aperture K LMN, \ i bounded by the two concentric V4 circular arcs K N, L M, and the / radii C M, C L containing the ae angle M CL= @. Let B be the position of the particle whose vibration is re- quired situated anywhere in Huyghens’s Principle in Physical Optics. 245 the line BC which is perpendiculai to the plane of the aper- ture, and let CB = &, Let p Pq be any element of the aperture, whose breadth = 67, and distance P or Cg from C =7, therefore its di- stance from B = WV 7? + A? and its area == Or dr. Then, by the principle under discussion, we have the dis- placement of the particle at B caused by this element, pro- portional to area of element "distance B P sin { 37 (vi—B P) } fate Orédr. Qa —— aid) VAL Sin Xx (vi — V 72+ h?) 9 where a is some number. integrating for the whole vibration we have g PSA TS, _aé a De 5 it (ri —W 1? +h +R) \ + C between the limits ry '9 ™ sin oor (Vregt+te—Vv roti) } ; sin — (vi—4V re +h?—1 v 14H) \ is which gives the intensity of the light at B 2 922 | eee: ae sin? {2 (v Fh TaN 7TrP) } : 1h 2 Z ra i Q The intensity becomes a maximum and = » or equal to 4. a*d? when 6 = 27. esa 2 EEE Ee Zn + 1 If Vr +h? — Vri+h = Ca Pig. where 7 is any integer. This equation may be satisfied by an indefinite number of values of r, and 7,. When 1, and 7, are very great, and / small, we have Ne Yo?) + s(q-F + &e. aes = 1g — 7, nearly. 246 Mr. R. Potter on the Application of If now @ be not large and r,—r, be only a small odd num- ber of multiples of a the aperture will be nearly a parallelo- ‘ . A a’ OV? Mel 3 gram, and the maximum intensity = s—- But if in the 7/9 original expression we make 7, = 0, the aperture becomes the whole sector, and the maximum intensity, by giving 7, the a? 2>y 2 proper value, is . This shows that at however great a Yad distance from C such a quadrilateral aperture be situated, and however near to C the point B may be, the intensity ought to be the same as for the sector. . The result of the principle is therefore that light ought to bend into the shadows of bodies to an indefinite extent, as sound is known to pass through all apertures, and bend round all obstacles. It proves that the result Mr. Airy (Tract, page 270.) has obtained by an approximate method is not to be depended upon, and that the objection to the undulatory theory which was believed to have heen removed remains in full force. If it be said that these expressions involving )? as a multi- plier, must represent light of very feeble intensity, and there- fore insensible, or nearly so, we shall see that we have the same small quantity in the expression for a large circular aperture. If we make 0 = 27, 7, very large, and r, = 0, we have a large circular aperture, and the intensity = 4a)? sin? eae, iprIP—h) } ? | 2 s a i: and however great or small 2 may be, compared with 7,, we see that there will be a succession of maxima and minima values for different values of 2. This is at variance with the admitted properties of light, which it is allowed passes through large apertures without any change or diminution, or when diverging from a luminous point follows the law of the inverse square of the distance, except near the boundaries of the shadow. If we compare the maximum intensity from an annulus, however narrow it may be, and however large the radii, with that from a large circular aperture, we see that ¢éhey are the same; and the multiplier X* would either show that only a very small quantity of light could pass directly through any large oes 2 2 aa = 4.a?)? when VA ro? +h?—h = _Huyghens’s Principle in Physical Optics. 247 circular aperture ; or otherwise, if it were maintained that the constant @ may be very large; then our former conclusions will be free from any objection that they represent inappre- ciable quantities of light. A fact stated by M. Fresnel, which I have confirmed by a severe experimental examination, bears upon the point, of the effect of the limits of apertures. His experiments for the diffraction by a single edge of an opake plate (see the before- mentioned memoir, page 429.) were, in fact, made with an aperture generally of a centimeter in breadth, whilst his lu- minous point and micrometer were in some measures distant about seven metres from each other. Notwithstanding the small breadth of the aperture compared with its distances from the luminous point and micrometer, yet we find him stating that the fringes formed by one edge were not affected by the other edge, and that his measures might be taken as if made with a single edge. ‘The principle under discussion shows, that with the quadrilateral, sectorial or circular forms of apertures, the intensity should depend on the limits, how- ever distant. The same results arise when we take plane reflectors in place of apertures, only then the point B must be taken on the same side as that on which the waves are incident. To discuss the second case, let A be the luminous origin in the line AC B perpendicular A to the plane of the aperture, through the centre C. Let AC = BC = f, and the other parts as in the former figure. We have now for the displace- ment of the particle at B, due to the element p P g, | C agrér Qar AP+PB en i —(AP+PB))} and the whole displacement B fae r OP dacs Aig Bir 2 Pleo AS a), Vey 0 {= 12 VF +h) } “a@On Qo | Mee 008 | wt 2 VET} + C between the limits ¢ = "st ar ie oD ~*~ Soe Ses = Se hearse ae 4S ° 248 On Huyghens’s Principle applied to Physical Optics. TORE LI 2 |. eee UPC VELLS ao 423 V 12+ h—(V re + mb sin 452 (vt— Vre+Rh—V 72+ 7) b and the intensity =avPr ., ——. ry ier ae sin” 1 (V 72+ R— WV r+ ie). As in the former case, when we take # small and 7,, 79 very large, with 6 small, so as to form a quadrilateral aperture ap- proximating very nearly to a parallelogram, we arrive at the same conclusion, that light, according to the principle under discussion, ought to pass through apertures, however oblzquely situated with respect to its direction, and diverge into the shadow to an indefinite extent; the maximum intensity at B, being the same as if the aperture were the whole sector, and this holding, however near A and B may be to C. If we take A = 27 and take 7, very large, whilst 7, is small, we have the case of the intensity in the centre of the shadow of a small circular disc, which it was found by ap- proximate methods, ought to be the same as if the light passed uninterrupted; and M. Arago, having tried the eX- periment, found the result to accord. The complete investi- gation gives the intensity a” rn? é 2 fer Saeereiee) pede : = oa £28 EGR YS which goes through a series of maxima and minima values for different values of 2, when 7, and 7, are given; and not an uniform or slowly diminishing intensity along this line, as found by the approximate discussion. ; There is another case which places the absurdity of the principle in a very striking point of view, which is the case of a large circular aperture, then 7, = 0, and we have the in- tensity ie Ne hi 20 ene ane TE oR sin? eee as) hoi + 71) } = the maximum intensity is here dependent on / for its position, but not for its magnitude; that is, the maximum intensity at SPN B is —;-, however near A and B may be together, or how- 2 ever distant; contrary to the received and demonstrated prin- ciple, that the intensity of light diverging from a luminous origin varies as the inverse square of the distance. Queen’s College, Sept, 1840. | [ 249 ] XXXVII. On Sulphocyanogen. By Mr. EK. A. Parne.y*. 1. Its Composition. HILE engaged with an investigation of the action of alkalies on this substance (the results of which will be presently communicated), in which I was unable to account, in a satisfactory manner, for the production of a new acid, I was led to suspect the existence of hydrogen in sulphocyano- gen; more especially as M. Liebig had obtained traces of water in its combustion by oxide of copper, which he then attributed to hygrometric moisture. Before detailing my own results, I may state those which Liebig obtained with reference to this subject (Ann. de Chim. et de Phys., tom. xli. p. 200.). Three-tenths of a gramme of sulphocyanogen, dried with great care zm vacuo, afforded him in four combustions, 1. ‘O11 gramme of water, 2. °017 ae a 3. *009 Ga a 4. °016 — =e The mean of these gives 0°48 per cent. of hydrogen. In repeating the analysis I have invariably obtained a much larger proportion of hydrogen. ‘The sulphocyanogen ex- amined was precipitated from the sulphocyanide of potassium by chlorine, and possessed all the characters of a pure sub- stance: that used in the first and second analyses was kept on a sand-bath, at about 200°, for several hours, and afterwards for four hours in a water-bath at 212°. 1. 10°36 grains gave 0°85 grain of water equal to 0°91 per cent. of hydrogen. 2. 10°27 grains gave 7°49 carbonic acid, and 0°84 of water, or equal to 20°22 per cent. of carbon, and 0°90 of hydro- gen. ~ 'To avoid all chance of error from the presence of hygro- metric moisture, sulphocyanogen prepared by chlorine was dried in a Liebig’s drying tube for some hours, by a nitre- bath at 242°. At this temperature a faint odour of cyanogen was perceived, but no other change. 11°02 of this gave 7°93 carbonic acid, and 0:96 of water, equal to 19°91 per cent. of carbon and :96 of hydrogen. To estimate the sulphur 10°11 grains were ignited with eight times as much nitrate and carbonate of potash; after- wards treated with nitric acid, diluted, filtered, and nitrate of barytes added. ‘The sulphate of barytes amounted to 38°54 grains, which is equal to 52°59 per cent. of sulphur. If the received equivalent of sulphocyanogen be doubled, and * Communicated by the Author. 250 Mr. E. A. Parnell on Sulphocyanogen. one equivalent of hydrogen added to it, making the formula S, C, N, H, the hydrogen will amount to *84 per cent. My estimations of the carbon and sulphur are then below the theoretical quantities. But before deciding on its constitution, an important question presents itself,—is the substance ex- amined the radical of the sulphocyanides, or a product of the decomposition of that radical? ‘To settle this point, the basic sulphocyanide of lead (the double sulphocyanide and oxide of lead), was first examined for hydrogen. It gave me 0°39 per cent., together with 4°20 per cent. of carbon. Now the hy- drogen here is twice as much as it should be, supposing the salt to have the constitution S, C, N, H+ 2 Pb +2 PbQ, or the usual formula doubled, and one atom of hydrogen added to the radical. So it might be a hydrate of the above con- taining one equivalent of water; in which case it should con- tain 74°32 per cent. of lead. If, on the other hand, it be Pb Scy + Pb O. HO, it should contain 73°26 per cent. The carbon and hydrogen agree for either view. Liebig obtained (see memoir above-quoted) 74°958 per cent. of lead; two analyses gave me the following results. 1. 53°67 grains treated with nitric and a little sulphuric acid, gave 53°97 grains of sulphate of lead, equal to 39°58 of lead, or 73°74 per cent. 2. 59°98 gave 64°91 of sulphate, equal to 44°32 of lead, or 73°85 per cent. As from these analyses the question was still undecided, I took the sulphocyanide of silver, which gave 7:20 per cent. of carbon, and only ‘05 of hydrogen, which is evidently due to hygrometric moisture; for if hydrogen existed in the ra- dical, thus, S,C, N, H + 2 Aq, it should have contained °30 per cent. Thus it appears that the radical of the sulpho- cyanides does not contain hydrogen, and consequently, what has been regarded as sulphocyanogen, is a product of the de- composition of that radical. I will presently consider how it is produced. | | It also appears that the basic sulphocyanide of lead is a hydrate (forming one of those few substances which contain six elements); probably, according to the formula Pb Scy + PbO HO, containing Calculated. Found. Sulphur... 11°38 Garboncawiiuess | 4598 4°20 Nitrogen... 5°01 Hydrogen... 34 39 OXygen eeveseree 5°66 Leadieacsdcnsdasns/ 73° 2S 73°78 100°00 Mr. E. A. Parnell on Su/phocyanogen. 251 To return to the composition of * sulphocyanogen.” It is greatly to be regretted that we possess no data to decide on the formula of this substance, but its composition per cent. as given by ultimate analysis, which is far less satisfactory in an uncrystallized substance, as in the present instance, than in a crystallized body: and I do not know of any circumstance to guide us in fixing its equivalent. The constitution which first presents itself as most pro- bable, is to double the old formula, and add one equivalent of hydrogen to it, which would give sulphur 54°48, carbon 20°70, nitrogen 23:97, hydrogen 0:84 = 100. But this does not exactly accord with the results of analysis. Taking the mean, we shall have as its composition per cent., Sulphur.....ccsooee §2°59 Carbon) <..5.4ssase 80:06 Nitrogen (calc.).. 23°23 Hydrogen ecco *92 96°80 Here is then a deficiency of 3:2 per cent., which must be considered as oxygen. ‘The formula with which this best agrees, and which I would adopt provisionally, is S,. C\, Ne H, O, or ! 12 Sulphur...... 2414 53°27 12 Carbon.eesecse 917°22 20°24 6 Nitrogen...... 1062°24 23°45 3 Hydrogen... 37°43 "83 1 Oxygen «ee. 100°00 2°21 1 Equivalent... 4530°89 100°00 On this view of its composition, the reactions which occur in its production by chlorine may be explained in the follow- ing manner: % equiv. of water ec... = H, O, 6 — chlorine....s0008 = Ci, 6 — sulphocyanide . _ of seat ane Oe anaes be Taran H, O3 Si. Cig Ng Kg Cl?. Equal to 6 equivs. of chloride of K.C] potassium que 1— sulphocyanogen = H, O S,, C,,. N, Bice. ORYLAD uasecens) 4) O oii! Ml) Bic dt Sete PSE HO Sjo CigNe Ky Cle Or six equivalents of sulphocyanide of potassium, six of chlo- rine, and three of water, become one of sulphocyanogen, six 252 Mr. E. A. Parnell on Sulphocyanogen. of chloride of potassium, and two of oxygen. But what be- comes of this oxygen? I have observed, that however slowly the chlorine be passed through the solution of sulphocyanide of potassium, an oxidizing action on the sulphocyanogen al- ready formed takes place, even at the commencement of the operation ; sulphuric and cyanic acids being produced. It does not appear how this action can be satisfactorily ex- plained on the old view (a simple removal of potassium by chlorine), for it involves the decomposition of water by chlo- rine in a strong solution of sulphocyanide of potassium, or in fact, that water is more readily decomposed by chlorine than sulphocyanide of potassium. But on the view given above, an oxidizing action on sulphocyanogen already formed is easily explained; it is even essential, since no evolution of oxygen gas is to be noticed. The production of this substance by nitric acid can be ex- plained in a similar manner. Six equivalents of water, sul- phocyanide of potassium, and nitric acid, are equal to six of nitrate of potash and six of hydro-sulphocyanic acid, or Sie Cig Ng Hg, which with four equivalents of oxygen from the decomposition of another portion of nitric acid, become Si. Cy. Ng H; O, and 3 HO. Four equivalents of oxygen of the atmosphere acting on six of hydro-sulphocyanic acid, produce the same effect. With regard to the arrangement of the elements in this substance, it is obvious that many formule might with equal probability be selected. All that can be reasonably assumed on this subject is, that the carbon and nitrogen exist as cyano- gen: it is also probable that the cyanogen and sulphur are more intimately connected with each other than either of them is with the oxygen or hydrogen; in which case this sub- stance will be either a hydrate or an oxide of a hydruret of a sulphuret of cyanogen: but it appears probable that in all compounds which contain hydrogen united to a radical so as to form a hydruret, the hydrogen should be removed by chlorine, which in this instance is not the case. On another view the hydrogen (either wholly or in part) might be supposed to exist as an electro-positive or “ zincous” ele- ment, but we do not find that it is displaced by metals, which certainly ought to be the case if such is the true constitution. But instead of adopting views of its constitution on insuffi- cient data, it will be better in the present state of our know- ledge of this substance to be satisfied with its empirical formula alone. The name of the substance will obviously require change, but I shall leave this to him to whom we are indebted for its discovery; and although I have been led to Mr. E. A. Parnell on Sulphocyanogen. 258 observe an error in the conclusion at which he had arrived, it must not be forgotten that it is by his refined and beauti- fully simple method of analysis that I have been able to attain my results. — For convenience, I shall continue in the remainder of this paper to speak of the substance derived from the sulpho- cyanides as sulphocyanogen. 2. Action of Alkalies on Sulphocyanogen. We are indebted to Weehler and Liebig for all that is as yet known respecting the action of alkalies on this substance ; but this subject was not studied so completely by them as it appears to deserve, nor so satisfactorily as other points connected with the sulphocyanides in their remarkable re- searches. It appears from their experiments, that when sulphocyano- gen is digested in solution of potash, a small portion is dis- solved, and the remainder becomes redder, partly soluble in water, and partly in alcohol. After alcohol and water had been successively applied to this altered su!phocyanogen until nothing more was dissolved, a clear yellow substance re- mained, which Liebig considered as a higher degree of sul- phuration of cyanogen. But his analyses of this substance do not sufficiently accord with any theoretical numbers to decide its constitution. My own experiments certainly confirm the above as far as they go, but it would appear that heat had not been applied to the mixture ofsulphocyanogen and alkali, but that it had, on the contrary, been kept at common temperatures; for if sufficient potash had been present and a gentle heat applied, the whole of the sulphocyanogen would have been dissolved, and converted into other substances. When three parts of sulphocyanogen are digested with about four parts of potash and twenty or twenty-five of water, a portion is at once dissolved, the remainder, on the appli- cation of a gentle heat, forming a reddish yellow transparent solution, from which acids throw down a yellow precipitate, which is a mixture of two substances, one of a light lemon colour, the other brown, or almost black. The appearance of the changes which are here undergone, varies considerably with the manner of performing the operation. If, for in- stance, the sulphocyanogen be in excess, it is either not en- tirely dissolved, or if it is, the precipitate produced by acids contains unaltered sulphocyanogen: on the contrary, if the alkali be in excess, the decomposition is more complete, the precipitate has a much lighter colour, and does not appear 258 Mr. E, A. Parnell on Sulphocyanogen. so dense as in the former case. The length of digestion also considerably affects the result; the longer it is continued (within certain limits) the more complete is the action: and lastly, the method of preparation of sulphocyanogen likewise influences it; while that prepared by chlorine becomes red at the commencement of the action, that prepared by nitric acid becomes yellow. The cause of this difference will be imme- diately explained. Of the two substances precipitated by acids, the lemon- coloured one forms by far the largest portion ; and not having obtained the other pure, I have as yet paid little attention to it, although it appears intimately connected with the de- compositions which occur. ‘he last is insoluble in water and alcohol, while the lemon-coloured substance is soluble in both these liquids, which can consequently be used to se- parate them. I have found the following method of procedure to be the most convenient. ‘lake three parts of sulphocyanogen (that prepared by nitric acid is preferable) and four of potash, or one of sulphocyanogen, and 27 or 28 parts of solution of caustic potash in common use (sp. gr. 1:06), keep this mix- ture at a gentle heat (120°) for about three hours, and then boil for half an hour. It is then entirely dissolved, but on cooling a small quantity of the black matter separates, which must be removed by filtration. ‘To the filtered solution add hydro- chloric or dilute sulphuric acid, which throws down the mix- ture in question, sometimes of a bright lemon-colour, but more frequently darker. It must be collected on a filter and washed with cold water until all the chloride of potassium or sulphate of potash is removed. Boiling alcohol must be used to purify it, as hot water dissolves too minute a portion to be conveni- ently employed for this purpose: the filtered alcoholic solu- tion can be distilled nearly to dryness, which gives the sub- stance perfectly pure in the form of a flocculent lemon-yellow crystalline powder. Its taste is intensely bitter and acrid, but not immediately perceptible, on account ofits slight solubility: it thickens the saliva, and a minute portion of its dust inhaled causes sneezing. One part requires rather more than one thousand of cold water to effect its solution. Boiling water dissolves 2°36 per cent. Cold alcohol takes up 4 per cent., boiling alcohol about 14 per cent. Wood spirit possesses about the same solvent power on it as alcohol. When ignited in the air sulphur burns, and a brown sub- stance remains, which is entirely dissipated by a strong red heat: heated in a tube, sulphur, bisulphuret of carbon and Mr. -E. A. Parnell on Sulphocyanogen. 255 sulphuretted hydrogen are given off, leaving the same brown matter. It is soluble in concentrated sulphuric acid without change, and is again precipitated on the addition of water. Nitric acid completely decomposes it, giving rise to sulphuric, carboni¢ and nitrous acid. Hydrochloric acid dissolves a little without change. When its alcoholic solution is evaporated it appears to give crystals, but this is not the case. It is owing toa bright pel- licle which had been formed on the surface of the alcohol contracting, and presenting this appearance. The strong al- coholic and wood-spirit solutions are precipitated by water. All its solutions are yellow ; they redden litmus paper slightly, but some time is required to effect this; it would at first be said to be neutral. From its behaviour with metallic bases and the mode of its formation, it is manifestly entitled to be classed among acids; in short, it appears from my experi- ments, that as obtained by the above process it is a hydrate of an hydracid which is quadribasic, losing four atoms of hydrogen and acquiring four of a metal. All its salts that I have examined are coloured, being either yellow, brown, or black. They are uncrystallizable, and those which are so- Inble are partially decomposed by evaporation: for this reason, I have been unable to obtain any definite soluble salt in a state fit for analysis, and the insoluble salts that I have examined contain a large excess of acid. According to my experiments, its empirical formula will be S,, C,, N; H, O, its rational formula §,. Cy; , H, + 2 aq. The following are the results of my analyses. 11°01 grains of the pure substance (prepared by the above process), dried at 212°, gave 7:00 grains of carbonic acid and i*78 grains of water, or 17°58 of carbon and 1°79 of hydro- gen per cent. Other analyses have given a mean of 17°60 of carbon and 1°74 of hydrogen. ‘The mean of three estima- tions of the sulphur, (by heating with nitric acid which readily decomposes it, and precipitation of the sulphuric acid by ni- trate of barytes)is 55°16 per cent. ‘The nitrogen was esti- mated in the usual manner, by observing the relation between it, and the carbonic acid as produced by combustion by oxide of copper; but the product was collected in one receiver in- stead of several small tubes. ‘The results are as follows: Barometer 30°2 inches. 7 Mixture in receiver, 85 measures over ‘6 inch of mercury, equal to 83°3 measures, common pressure. After absorption of carbonic acid, there remained 32 mea- sures, over 3:4 inches of mercury, equal to 28°3 measures, common pressure, 256 Mr. E. A. Parnell on Sulphocyanogen. 83°3—28°3 = 55°0; therefore 83:3 of mixture contain 28°3 of nitrogen, and 55:0 of carbonic acid: and as 28°3: 55'0 >: 1: 1°94; or as 1 of nitrogen to 2 of carbon nearly. We have then for the per-centage, mul ple’ fel svetonis ay coal Carbone. ec. sick a) serpael aeae NIGOBER 60. je fy} ef elm Fiydrogem joie h sis ty Te Oxygen (loss) . . 5°12 100°00 which numbers closely correspond to Calculated. 12 Sulphur .... 2414° 55°64 10 Carbon .... 764°3 lot S NIGTGREN: (.\ 5 2 f CSO2 20°42 6 Hydrogen... 74°8 1°72 2 “Oxyoen ais. 2000 461 1 equivalent 4338°3 100:00 Since it appears to be a hydrated hydracid of a sulphuret of cyanogen, the name hydrothiocyanic acid will perhaps not be inapplicable. Its salts will then be thiocyanides, and its symbol may be Thcy H,. _ _Thiocyanides.—The alkaline reaction of potash, soda, am- monia, and barytes cannot be completely destroyed by any excess of this acid, although the pure salts are neutral. ‘The alkaline carbonates are not decomposed by it at common temperatures, but if boiled, carbonic acid is evolved, and a salt of the alkali formed. Its solutions in potash and soda give yel- low uncrystallized residues on evaporation. ‘The acid was digested some time with ammonia, filtered and evaporated over sulphuric acid zn vacuo: this gave a yellow uncrystallized salt, soluble in water, giving a solution neutral to test paper, and intensely bitter; but free acid had been deposited du- ring evaporation, notwithstanding it was at first highly al- kaline. Barytes.—The acid was digested with barytes, water, and carbonic acid gas passed through the solution to separate excess of barytes: a yellow solution remained, which on eva- poration gave a yellow salt, but mixed with crystals of hy- drate of barytes. | A solution of the acid produces no precipitate in solutions of salts of magnesia, both oxides of iron, manganese, zinc, or nickel. Copper.—A solution of the acid produces an ochre-brown Mr. E. A. Parnell on Sulphocyanogen. 257 precipitate in solution of sulphate of copper. The precipitate is decomposed by the hydrochloric, nitric and concentrated sul- phuric acids; also by sulphuretted hydrogen, the hydrothio- cyanic acid being liberated. It is blackened by alkalies, an al- kaline thiocyanide being produced: the black or brown sub- stance remaining appears to be a subsalt. When the thio- cyanide of copper is ignited in a tube, it gives off sulphur, hydrated cyanic acid, and bisulphuret of carbon, leaving a residue of sulphuret of copper. Lead.—Solutions of hydrothiocyanic acid produce a yellow precipitate in acetate and subacetate of lead, which is decom- posed by the stronger acids, and by sulphuretted hydrogen, the acid being reproduced unaltered in the last case. Nitric acid instantly produces sulphate of lead. On being heated in a tube, it gave rise to similar products as the copper salt ; hydrated cyanic acid, sulphur, bisulphuret of carbon, and sulphuret of lead. Like most insoluble salts of slightly solu- ble acids (when prepared from solutions of the acid), this is contaminated with a large excess of acid. ‘Iwo combustions by oxide of copper gave — 1. 8°62 per cent. of carbon 49 of hydrogen. 2. 8°72 °50 For the lead: 1. 12°3 grains treated with nitric acid gave nts grains of sulphate of lead, equal to 51°96 per cent. of ead. 2. 10°77 treated in the same manner, gave 8°19 of sulphate, or 51°93 per cent. Calculated according to the formula They 4 Pb + 4 aq, it should contain 7:90 of carbon, °51 of hydrogen, and 53°40 of lead per cent.; notwithstanding this difference, no other formula could have been selected, in accordance with the ulti- mate composition obtained for the acid. Like the copper salt, thiocyanide of lead is blackened by alkalies, a subsalt being produced. Szlver.—The behaviour of the solution of hydrothiocyanic acid with nitrate of silver is very peculiar and characteristic, forming a test sufficiently delicate to detect one part of the acid in 10°000 of water. On mixing the solutions a yellow flocculent precipitate is formed, which on standing a short time, or immediately on heating, aggregates, changing to a black colour, without any evolution of gas or odour of cy- anogen. ‘The change is not hastened: by solar light. When the black substance is treated with sulphuretted hydrogen, the acid is reproduced, and sulphuret of silver formed. Concen- trated sulphuric acid has no effect on it; if diluted, sulphate of silver is formed, and the acid is liberated. It is soluble Phil, Mag. 8. 3. Vol. 17, No. 110, Oct, 1840. S$ 258 Mr. E. A. Parnell on Sulphocyanogen. with decomposition in nitric acid, and by boiling in hydro- chloric acid, sulphuretted hydrogen being evolved in the latter case. ‘he affinity of silver for the radical of this acid ap- pears stronger than for chlorine; for if this acid and hydro- chloric acid be present in: the same solution, and nitrate of silver added, the thiocyanide of silver is first precipitated. It is insoluble in ammonia. 19°60 grains were treated with hot nitric acid, which dis- solved it; the silver was precipitated by hydrochloric acid, and nitrate of barytes added to the filtered solution to obtain the sulphuric acid. The chloride of silver amounted to 18°25 grains, or 13°747 of silver, equal to 70°14 per cent. The sulphate of baryta amounted to 21°24 grains, equal to 2°94 of sulphur: sulphur not converted into sulphuric acid, separated on a weighed filter, amounted to +20 grain, = 3°14 or 16:01 per cent. of sulphur. The proportion of silver here is just twice as great as the proportion of lead in the salt of that metal. In fact, it ap- pears to be a double thiocyanide and oxide of silver, or a sub- salt: thus They 4 Aq + 4AqQO, which by theory should contain | Found. Pulphur sas... 15:80 16°01 Silver (veteran) Fors 70°14 As the neutral thiocyanides are yellow and the subsalts black, so we have reason to believe that the yellow silver compound is the neutral thiocyanide; but this cannot be de- cided by analysis, on account of the rapid change which it undergoes. , Mercury.— Nitrate of protoxide and chloride of mercury are precipitated by the aqueous solution of this acid. ‘The pre- cipitate is at first white, but by heating it becomes yellow. In its properties it resembles the copper and lead salts; like them it is converted into a subsalt by alkalies, and it gives similar products on heating. Nitric acid instantly acts on it; a white compound is produced which undergoes no further change by nitric acid alone, but on the addition of hydrochloric acid it, is immediately dissolved. Nitrate of suboxide of mercury gives the black subthio- cyanide. Chloride of platinum and bichloride of tin are pre- cipitated yellow by solutions of the acid, but I have not ex- amined these precipitates. Such is the incomplete investigation I have had it in my power to make of these compounds, As the sulphocyanogen derived from the sulphocyanides does not appear to be what it was considered, but a highly complicated substance, the in- Mr. E. A. Parnell on Sulphocyanogen. 259 terest with which the products of its decomposition by alkalies will be viewed, is materially lessened. For this reason I have not pursued this subject so completely as I intended, nor, perhaps, as it deserves. Although I have been led by a point in this investigation, which I could not comprehend, to the discovery that sulphocyanogen, if not exactly so composed as I have represented it, is certainly not the radical of the sul- phocyanides, but a product of its decomposition; yet the point in question has not been ascertained, namely, the changes that sulphocyanogen undergoes by alkalies. At first I imagined the black substance which separated from the solution of sulphocyanogen in alkali, on cooling, and the brown or black substance precipitated by acids, znsoluble in water and alcohol, as accidental or merely secondary pro- ducts: I now look on these differently. When the last brown substance is digested again in an alkali, more hydrothiocyanic acid is separated; the remainder is quite black, and is evi- dently identical with the first black substance. It appears more to resemble paracyanogen than anything else with which I am acquainted ; but not having obtained it pure, and but in small quantity, I have not been able to decide this point. Sulphocyanide of potassium, and sulphite of potash, are likewise formed when sulphocyanogen is digested in pots ash, but the sulphite is in very small quantity, and I believe accidental. Hydrothiocyanic acid is not produced by potash and soda only; barytes, ammonia, and even the alkaline carbonates give birth to it. Its production by ammonia is remarkable. The sulphocyanogen becomes light yellow, but is not dis- solved; sulphocyanide of ammonium, with only a trace of thiocyanide, is formed. The yellow substance into which the sulphocyanogen is converted is, however, hydrothiocyanic acid. This proves that whatever may be the action of the alkali, it is not the affinity of its radical for the radical of the acid (or as it may be called, thiocyanogen) which is the leading cause; for if so, the whole of the acid should have existed as thiocyanide of ammonium. It is also probable that the action is an oxidizing one, for I find that the acid is produced by the action of chlorine and nitric acid on sulphocyanogen. Indeed, it is difficult to pre- pare sulphocyanogen by nitric acid without its production, and hence I have recommended that prepared by this means as preferable to that by chlorine for the preparation of this acid *. It has been observed, that when chlorine is passed into * If mixture of sulphocyanogen and hydrothiocyanic acid be digested 8 2 260 Mr. R. Hunt on the Use of Hydriodic Salts a dilute solution of sulphocyanide of potassium, the sulpho- cyanogen is precipitated of a light yellow colour, and does not subside readily. I have ascertained, by experiment, that this light yellow substance is not sulphocyanogen, but hydro- thiocyanic acid. It is, however, more difficult to convert sul- phocyanogen into this acid by chlorine, than by nitric acid ; chlorine consequently gives the purer substance. In conclusion, I would state, that these experiments have been performed in Prof. Graham’s laboratory, to whom and to his late assistant Mr: Fownes, I am happy in acknowledging myself indebted for their suggestions during this research. University College, June 25, 1840. XXXVIII. On the Use of Hydriodic Salts as Photographic Agents. By Mr, Ropert Hunt. [Continued from p. 211, and concluded. ] 38. On the darkening of the Photograph. ME: TALBOT first directed attention, at the last meeting of thie British Association, to a peculiarity possessed by some of these kinds of photographs, namely, that they were neither fixed nor otherwise; but that on exposure to sunshine they changed in their dark parts from a red to a black, the lights of the picture being unaffected by the light. 39. This singular effect I have proved to be entirely de- pendent on the influence exerted by the less refrangible rays of the solar spectrum in exalting the oxidation of the silver; but a brief statement of some effects produced by the dis- severed rays, will place the matter in a much clearer light. 40. By allowing a very intense prismatic spectrum, formed — by a flint-glass prism, to fall upon any of these photographs - which blacken by white light, it will be found that the dark- ening process commences in the red ray, at which point it goes on with the greatest intensity, and is gradually shaded off to the lowest edge of the extreme red; the shading is also continued through the orange and yellow rays being sharply cut off at that line of the spectrum where the pure green is. visible. 41. As it was not possible to pursue my inquiry on the effects of the spectrum with any degree of satisfaction without a heliostat, an instrument I have not the means of procuring, in alkali, the sulphocyanogen is first dissolved, leaving the acid. This ex- plains why sulphocyanogen prepared by nitric acid becomes yellow when treated with alkali, which is not the case with that prepared by chlorine. as Photographic Agents. 261 I turned my attention to the effects produced by the light which had permeated coloured media, the absorptive powers of which were carefully analysed. The media I was induced to adopt transmitted rays in the following order. Buiue.. Ammonia-Sulphate of Copper.—The whole of the most refrangible rays, from the edge of the green to the ex- tremity of the violet. Green. Nitro-muriate of Copper.—Those rays which have place between the extreme upper edge of the blue, and a line which would accurately divide the pure yellow. Yettow. Bi-chromate of Potassa.a—That portion of the spectrum which would lie between a line drawn below the orange, rather within the red ray, and through the lower edge of the pure green ray. Rep. A strong Solution of Carmine in Ammonia.—A por- tion of the orange and all the rays below it. 42. The most remarkable effects were produced upon the papers a, b, c, d, and n (13). ‘They have been subjected to similar influences, prepared with all the hydriodates I have mentioned (20—27); but I do not feel myself warranted in occupying your pages with any statement of the results on any, but those prepared with the pure hydriodate of iron and the hydriodate of baryta. These drawings were all well washed with hot water, and when quite dry, arranged under the different fluids, and exposed in a window which faces the south. I will name the papers from the salt used, and the colour shall indicate the rays. 43. Hydriodate of Iron, Muriate of Ammonia.—Buur. The picture nearly destroyed by the browning of the yellow lights, at the same time as the darker parts have much faded. Green. The dark parts nearly all faded out; the few re- maining spots much reddened, but no change in the yellow of the light parts. Ye.ttow. Looking through the paper, the lights appear darkened by a blueish-green tinge; the dark parts, originally a red brown, are changed to a blue-black. ‘toa The lights yellower than before; the darks a deep black. 44, Chloride of Sodium.—Buvr. The lights darkened, and the dark parts faded and reddened. Green. Picture entirely obliterated; the yellow unchanged. YeEtiow. The lights tinged a decided blue; shadows darkened. Rep. The lights of a green tinge; but I consider this to arise from the deepening of the yellow hue; the dark parts blackened. 262 Mr. R. Hunt on the Use of Hydriodic Salts 45. Muriate of Strontia.—Buve. These are more permanent than any other variety of the hydriodic photographs. Under this influence the shadows are browner than before; the lights scarcely changed. Gren. The yellow much increased in depth; the dark parts faded slightly and become very red. Yettow, The lights very little tinged with blue; the darks without any apparent change. Rep. The lights deepened; the shadows a fine black. a: 46. Muriate of Baryta.—Buvur. The yellow parts are be- come brown; the dark portions faded and reddened. GREEN, Lights unchanged; the dark parts very red. Yettow. Lights unchanged; shadows tinged green, over a very decided black- ening which has taken place. Rep, The yellow much height- ened; the dark parts much tinged with green. | 47. Hydrochloric Acid.—Buve. Faded out: lights dark- ened. GrerEn. Faded out; yellow much increased. YEL- Low. The lights rendered very yellow; darks unchanged. Rep. Yellow become very strong; the shadows are very much blackened. 48. FHydriodate of Baryta.—Under this head it will only be necessary to name the effects on three kinds of photo- a graphs, the others being very similar in all their changes to i those just mentioned. q 49. Muriate of Ammonia,—In my paper on the influence of coloured media, vol, xvi. p. 270 of your Journal, I have "i already mentioned the singular change which ensues upon ex~- i posing this kind of drawing to light under media such as we are now considering. ‘To that paper I refer you. ] 50. Muriate of Baryta.—Buver. Faded in the dark parts, which are become a brick red; the yellowness of the lights ; increased. Green. The lights unchanged; the shadows suf- fused with a pink hue. Yer iow. Lights unchanged; sha- q dows much darkened and strongly tinged with a light blue. | Rep. Lights unchanged; dark parts a deep blue. These sin- 1 gular effects, which, although they are traceable on nearly all \ those photographs which blacken by after exposure to sun-~ shine, are much more decided when the salts of baryta in one i or other of the processes have been used. I communicated | these facts with others to Sir John Herschel, who has paid | me a very high compliment by inserting my communication | in his valuable memoir ‘‘ On the Chemical Action of the Solar | Spectrum.” I the less regret my inability to pursue my obser- i vations on the effects of the pure prismatic rays on the hy- driodic preparations, finding that the subject is one which, among others equally curious and important, is engaging the H attention of this eminent philosopher. | | 51. Muriate of Strontia—Buvr. Lights but very little as Photographic Agents. 263 changed; darks faded and reddened. Green. Lights un- changed; shadows less faded, not so red. YELLow. Lights un- changed; dark parts a blue-black. Rep. Lights unchanged ; dark parts become very blaek. 52. From a careful perusal of these results it will appear that this curious darkening of the finished picture is most evi- dent under the influence of red light, but that this property extends up to the green rays, beyond which a different power is exercised ; the deoxidizing influence appearing to be great- est in the blue rays, whilst the yellow iodide of silver suffers decomposition in the most refrangible rays. . 53. The fading of Hydriodic Photographs.—I have before noticed (30.) the want of absolute permanence in these pictures. The study of the modus operandi of solar light in its action on them opens some very remarkable facts in relation to the iodide of silver, which when first observed, led me to believe the existence of two distinct salts, whereas I now entertain a different opinion. The drawing fades first in the dark parts, and as they are perceived to lose their definedness, the lights are seen to darken, until at last the contrast between light and _ shadow is very weak. 54. If a dark paper is washed with an hydriodate and ex- posed to sunshine, it is first bleached, becoming yellow; then the light again darkens it; if, when quite dry, it is put away in the dark, it will be found in a few days to be again restored to its original yellow, which may be again darkened, but not so easily as at first, and the yellow colour is again restored in the dark. The sensitiveness to the influence of light dimi- nishes after each exposure, but I have not been enabled to ar- rive at the point at which this entirely ceases. 55. If a dark paper, bleached by an hydriodate and light, be again darkened, and then placed in a bottle of water, the yellow is much more quickly restored, and bubbles of gas will. escape freely, which examination will show to be oxygen. 56. By inclosing pieces of hydriodated paper in a tube to darken, we discover, as might have been expected, some hy- drogen is given off. If the paper is then well dried and care- fully shut up in a warm dry tube, it remains dark; moisten. the tube or the paper, and the yellowness is speedily re- stored. 57. Take a photograph thus formed and place it in a vessel of water, in a few days it will fade out, and bubbles of oxygen will accumulate around the side. If the water is examined, there will be found no trace of either silver or iodine; thus it is evident the action has been confined to the paper. 58. We see that the iodide of silver has the power of sepa- 264 Mr. R. Hunt on the Use of Hydriodic Salts rating hydrogen from its combinations. I cannot regard this singular salt of silver as a definite compound: it appears to me to combine with iodine in uncertain proportions. In the process of darkening the liberation of hydrogen is certain; but I have not in any one instance been enabled to detect free iodine; of course it must exist either in the darkened surface, or in combination with the unaffected under layer; possibly this may be the iodide of silver, with iodine in simple mixture, which, when light acts no longer on the preparation, is libe- rated, combines with the hydrogen of that portion of moisture which the hygrometric nature of paper is sure to furnish, and | as an hydriodate again attacks the darkened surface, restoring i thus the iodide of silver. This is strikingly illustrative of the i fading of the photograph. ‘The picture is light iodide of sil- | ver and dark oxide of silver; as the yellow salt darkens under the influence of light it parts with its iodme, which immedi- | ately attacks the dark oxide, which is gradually converted into i - an iodide, oxygen, as I have shown, being liberated. The fol- ( lowing experiments go not only to prove this position, but also serve to illustrate in some measure the action of light on this compound. 59. Lodide of Silver. Precipitate with any hydriodate, silver from its nitrate in solution, and expose the vessel containing it, liquid and all, to sunshine, the exposed surfaces of the iodide will blacken; remove the vessel into the dark, and after a few hours all the blackness will disappear: we may thus continually restore and remove the blackness at pleasure. 60. If we well wash and then dry the precipitate it.blackens with difficulty, and if kept perfectly dry it continues dark; but moisten it and the yellow is restored after a little time. 61. In a watch-glass, or any capsule, place a little solution of silver; in another, some solution of any hydriodic salt; connect the two with a filament of cotton, and make up an electric circuit with a piece of platina wire, expose this little arrangement to the light, and in a very short time it will be seen that iodine is liberated in one vessel, and the yellow iodide of silver formed in the other, which blackens as quickly as it is formed. 62. Place a similar arrangement to the above (61.) in the dark, iodine is slowly liberated. No zodide of silver formed, but around the wire a beautiful crystallization of metallic silver. 63. vice versd, and it is to these parts that the collectors should be applied. It is precisely this which renders the revolving disc a new electrical machine (F’. 154.), and it is upon this point that Messrs Nobili and Antinori are so entirely mis- taken in their two memoirs. ‘This error is repeated through- out the whole of the memoir that Iam now comparing with my first paper, which, if] mistake not, contains the theory of Arago’s phenomenon in all its parts. At page 284 we find, that when a helix turns upon its axis concentrically with a magnetic pole, the result is absolutely nothing, and that the condition of rotation is unimportant. Now, though I have not made any experiments on the sub- ject, I venture to assert that there will be an effort in the elec- tric current to pass in a transverse direction to the helix, and that the circumstance of its rotation, instead of being unim- portant, is in these cases the only condition essentially re- quisite for the production of currents. The helix, in fact, may be considered as analogous to a cylinder which might occupy its place, but to which it is very inferior, as it consists of a long coil of wire. It may also be regarded as a simple in a Letter to M. Gay-Lussac. 287 wire placed in any situation occupied by a cylinder, and I have shown that they produce currents in their state of rota- tion, if their opposite extremities are connected with the gal- vallometer. It is said at page 284, that the formation of currents is “‘ wholly due to another condition, they being manifested: only at the moment when the spirals are brought near to the mag- nets, or removed from them. So long as the spirals are pre- sent, whether they move or not, there zs no current. So also there is none in the case of central rotation,” &c. Now in my first paper I showed that the essential condition was not the approximation or removal of the metal in movement, but simply that it should intersect the magnetic curves (I’. 101. 116. 118. &c.); and that consequently, ceteris paribus, the movement without change of distance is the most effective and powerful means of obtaining the current, instead of being the condition in which the result is absolutely nothing. In my second paper I proved that a movement through the mag- netic curves was the only condition necessary (I’. 217.); and that so far from the approximation or removal of the metal being necessary, currents may be produced in the magnet itself, merely by moving it in the proper direction (F. 220.). Lastly, when treating of this “ central arrangement,” and the supposed absence of effect when “the points of the disc remain constantly at the same distance from the magnetic pole,” Messrs, Nobili and Antinori say (p. 285.), ‘by thus renewing the combination of continued presence to which Mr. Faraday’s new laws in relation to currents do not assign any effect ;’ and in a note we read, “ These laws are reduced to three,” which are specified, at first fully, and then ina more condensed form, as follows: “ First Law. During gradual approximation: the current produced contrary to the current producing; repulsion between the two systems. SEcoND Law. The distance unvarying. No effect. Tuirp Law. During recession. ‘The current produced in the same direc- tion as the current producing. Attraction between the two systems.” Ihave never myself given these as the simple laws which govern the production of the currents that I was so fortunate as to discover; nor do I understand how Messrs. Nobili and Antinori can say that they are my laws, though at page 282 one of them is so called. But I described these three cases together in my first memoir (F. 26. 39. 53.), as well as in the notice, that is, in my letter to M. Hachette, as effects that I had observed. It has been established, by what I have already said, that they are not the laws of the action of magnetic electricity, for the simple fact that cur- 288 Mr. Faraday on Magneto-electric Induction. rents of electricity may be obtained by means of the re- volution of a cylinder (I. 219.), or of a disc in connection with a magnet (I". 218.), or of the magnet itself (F.220.), dis- proves each of them. One Law, which includes all the ef- fects, is given in my memoir (F'. 114. 116. &c.), and it simply expresses the direction in which the moving conductor in- tersects the magnetic curves. This law of direction being given, I endeavoured to recapitulate the whole in the terms that I shall here repeat (IF. 118.). ‘* All these results show that the power of inducing electric currents is circumferentially excited by a magnetic resultant or axis of power, just as circumferential magnetism is de- pendent upon and is exhibited by an electric current.” I have quoted this passage of the Italian physicists at full length, because it contains nearly all our points of difference, both as to fact and opinion, concerning this part of the sub- ject. Having thus shown all the errors included in it, I shall endeavour to be more concise, while I exhibit, with the assist- ance of the galvanometer, such others, derived from them, as are dispersed over the remainder of the memoir. It is in-= deed curious to remark, how, with galvanometrical indica- tions generally correct, these gentlemen have suffered them- selves to be led astray under the influence of preconceived opinions. For example, at page 287—288, and in fig. 2. plate ii. is shown the result of an examination by the gal- vanometer of the currents in a revolving disc. ‘These cur- rents are indicated nearly correctly by means of arrows; but the ¢wo consequences deduced from them agree with the theory enunciated, and are diametrically opposed to the facts. ‘¢ ‘The immediate inspection of the arrows which mark the currents in the two regions of the disc (fig. 2.) leads to one of these consequences (p. 287.), and it is that a system of cur- rents ts developed upon the parts that enter contrary to those produced on the other side. ‘The other consequence arises from comparing the currents produced upon the disc with the cur- rents of the producing cause, and it is that the direction of the currents upon the parts that enter is contrary to that of the producing currents, while on the other side the direction in the two systems ts zdentical.” But I showed in my first memoir (I. 119.), that * when a piece of metal is passed either before a single pole, or be- tween the two opposite poles of a magnet, or near electro- magnetic poles, whether ferruginous or not, electric currents are produced across the metal transverse to the direction of motion. This fact is proved by means of wires (F. 109.), plates (I. 101.) and discs (I. 92. &c.); and in all these cases 4 * Detection of Rosin when dissolved in the Fixed Oils. 289 the electric current was in the same direction, whether the metal were brought near to, or caused to recede from the magnet, provided that the direction of its movements were unaltered. In Arago’s revolving disc the electricity that I was able to obtain from one of these parts in a multitude of experiments always agreed with these results (F. 92. 95. 96.), and consequently (I. 119. &c.) I recapitulated them in a short description, as presented in Arago’s disc, establishing more particularly (F. 123.), that the currents produced near or under the poles are discharged or return into the parts of the metal situated on each side of and more distant from the place of the pole, where the magnetic induction is necessarily “* weaker.” [To be continued. ] XLII. On the Detection and Estimation of Colophony (common Rosin) when dissolved in the Fixed Oils. By J. DewnHam Smita, Esq. To Richard Phillips, Esq. F.RS., L. & E., &c. My pear Sir, QGOME samples of linseed oil were sent to me for analysis in July last, the bulks‘of which had been exported, but were found on their arrival to be unsaleable and perfectly useless, for when mixed with white-lead in the usual manner for making paint, the mixture became quite hard at the ex- piration of a few hours, it having set as plaster of Paris does when moistened with water. At first sight it was obvious that all these oils had been considerably adulterated ; for not only was their colour much deeper than that of ordinary linseed oil, but they were all extremely viscid, resembling castor oil, in this respect, much more than the comparatively thin and fluid commercial lin- seed oil. Suspecting both from smell and taste, particularly the latter, that the adulterant was common colophony' (black rosin), I endeavoured to ascertain whether my conjecture was well-founded, and if so, to determine the proportion of colophony contained in the several samples; especially as the adulterated oils were likely to become the subject of legal proceedings. I am not aware that there is any mode on record for se- parating, or even detecting common rosin when dissolved in the fixed oils, so that I was obliged to make numerous ex- periments, before a method was discovered which appeared Phil, Mag. S. 3. Vol. 17. No. 110. Oct. 1840. U 290 Mr. J. Denham Smith on the Detection and Estimation to offer satisfactory results. It would be useless to describe these unsuccessful trials; I therefore at once proceed to ex- plain the mode I ultimately adopted for detecting and esti- mating the proportion of colophony contained in the various specimens of oil. I found that when colophony was dissolved in pyroxylic spirit, the solution gave a bulky white precipitate, on the ad- dition of acetate of lead also dissolved in pyroxylic spirit; but that when unadulterated commercial linseed oil was digested with this solvent, the clear solution when cold was merely rendered turbid on the addition of the spirituous solution of acetate of lead. Discovering that pyroxylic spirit exerted a very marked solvent action on the precipitateabove-mentioned, and that the supernatant, or filtered solution, gradually de- posited more of this precipitate, after standing for some time or when gently evaporated, I had recourse to the common rectified spirit of wine, about sp. gr. ‘832, which although it is capable of dissolving this compound of resin and oxide of lead, yet does so in almost an inappreciable quantity, espe- cially if the spirit be cold. Having dissolved 30 grs. of common rosin in a small por- tion of linseed oil, by the assistance of heat, about 3 fluid ounces of rectified spirit of wine were poured upon the oil, and thoroughly mixed with it by agitation; this was boiled for two or three minutes, and then allowed to cool and the oil to subside; the next day the clear spirituous solution was poured off, about the same quantity of fresh spirit added to the residual oil, and the mixture agitated and boiled as be~ fore; when bright this solution was decanted and mixed with the former, the remaining oil again treated with about an ounce of spirit, and this solution added to the others; a fourth time spirit was added, but this solution gave no preci- pitate with acetate of lead; this agent merely rendering it turbid, as in the case of pure linseed oil when dissolved in spirit; from this I concluded that the whole of the resin, which the rectified spirit was capable of separating, was ex- tracted from the oil. ‘The three solutions when mixed were of a light yellow colour, and perfectly clear, when on the ad- dition of a freshly prepared solution of acetate of lead in rectified spirit the characteristic bulky white precipitate fell. At the expiration of four-and-twenty hours this was collected on a filter weighing 11:7 grs., and washed with cold rectified spirit until the washing left the merest perceptible stain when evaporated in a porcelain dish ; I then dried the precipitate on folds of bibulous paper, and finally with a gentle heat, until it suffered no decrease of weight, when the weight of the pre- of Colophony when dissolved in the Fixed Oils. 291 cipitate and filter was found to be 29°4 grs. —11°7 grs., weight of filter, = 17°7 grs. of the compound of resin and oxide of lead obtained from 30 grs. of common colophony, which would indicate that 59 gers. of this compound are equal to 100 grs. of rosin. This experiment was repeated with 40 grs. of rosin dis- solved in a little oil, and this mixture treated in the manner above described. In this instance 26:7 grs. of the precipitate were obtained, which is equal to 66°7 per cent. of the resin employed. It appears, from these experiments, that although this method is incapable of affording strictly accurate results, I presume from the slight solvent action of the spirit upon the precipitate, yet that an approximation to the quantity of colo- _ phony contained in oils adulterated with this substance, may be obtained, which perhaps by some subsequent modifications of and precautions in the process, may lead to a mode ca- pable of yielding not merely a tolerable approximation, but rigidly accurate results. When unadulterated commercial linseed oil is treated with rectified spirit in the manner described, the alcoholic solution affords no precipitate on the addition of a spirituous solution of acetate of lead, but it merely becomes turbid, exhibiting appearances very different from the bulky precipitate which is produced if colophony be present. ‘The samples of adul- terated oil when submitted to the process I have described, respectively afforded 27:7, 21 and 26:3 per cent. of this compound of resin and oxide of lead, which would indicate, according to the average of the two experiments with resin and oil already mentioned, 44°1, 33°4 and 41°7 per cent. of common rosin respectively contained in these specimens of oil. When this white precipitate is suspended in rectified spirit, and a current of hydrosulphuric acid gas passed through it, decomposition takes place, sulphuret of lead is formed, and a light yellow-coloured solution, which reddens litmus, is ob- tained ; this, on evaporation, leavesa brown and brittle resi- duum exactly resembling common rosin. For this mode of separating the acid resin from the oxide of lead, I am in- debted to my friend Dr. Brett. From the circumstance of this alcoholic solution affording no precipitate with nitrate of silver until the addition of a little ammonia, I conclude the resin acid which is combined with the oxide of lead in the precipitate obtained in the foregoing experiments, to be the sylvic acid. When ignited in a covered crucible, so as to avoid the access of atmospheric air, and consequent oxidation of the lead, 1 find that the precnitate, whether obtained from 2 292 | Royal Society. the two first experiments, or whether reduced from the pre- cipitates afforded by the adulterated oils submitted to ex- amination, produces precisely the same quantity of metallic lead, viz. 27: per cent. Both these precipitates also, when exposed to a moderate heat, fuse, affording a brown transpa- rent substance very much resembling common colophony, but which seems to be harder and more brittle than rosin is. Pure linseed oil, when mixed with the same quantity of rosin as analysis indicated in one of the samples of adulterated oil marked * Raw oil,” that containing 44°1 per cent., was ex- actly of the same density as the sample in question, both being 982, whilst pure linseed oil was considerably lighter, its den- sity being °9518; thus corroborating not merely the fact of adulteration, but also the close approximation to correct re- sults afforded by the mode of analysis adopted. I remain, my dear Sir, yours very truly, Duke-Street, Liverpool, J. DENHAM SMITH. Sept. 3, 1840. XLIV. Proceedings of Learned Societies. ROYAL SOCIETY. (Continued from p. 149.] April 30, fi ae following communications were read: — 1840.— 1. A Letter from Sir John Barrow, Bart., V.P., addressed to the President, accompanying a series of Magnetic Observations made on shore, and on board Her Majesty’s ships ‘ Erebus’ and ‘ Terror,’ under the direction of Captain James Clark Ross, R.N., together with a Series of Observations made on the temperature and specific gravity of the ocean at various depths, and at the surface, namely, ‘‘ Observations of the magnetic intensity on shore, and on board H.M.S. Erebus, with needle F. 1. ‘** Magnetic dip observations on shore, and on board H.M.S. Ere- bus, with needle F. 1. , “* Observations for the magnetic dip on shore, and on board H.M.S. Terror. ‘‘ Observations of the magnetic dip by needle F. C. 5. on shore, and on board H.M.S. Terror. id “‘ Observations in magnetic intensity by needle F. C. 5. on shore, and on board H.M.S. Terror.” The whole of these observations are up to the 31st December, 1839. They are transmitted to the Royal Society from the Lords Commissioners of the Admiralty. 2. Postscript to Major Sabine’s paper, entitled ‘‘ Contributions to Terrestrial Magnetism,’ which was read at the meeting of March 19th; (see p. 144), containing am extract from a letter from Capt. James Clark Ross, commanding the Antarctic expedition, dated from St. Helena, February 9th, 1840; noticing the success which had Royal Society. 293 attended the employment of Mr. Fox’s instrument, in observations of the magnetic dip and intensity on shipboard. 3. ‘A few remarks on a Rain Table and Map,” drawn’ up by Joseph Atkinson, Esq. Communicated by P. M. Roget, M.D., Sec. R.S. The table and map which accompany this paper exhibit the ave- rage annual depth of rain falling in different places in Great - Britain. 4, “* Extracts from a Meteorological Journal kept at Allenheads, in the county of Northumberland,” by the Rev. W. Walton, F.R.S. The general result of these observations, which were recorded twice each day, namely, at 9 a.m., and at 3 p.m., during the whole of the year 1839, is, that the mean temperature taken at those times was 44° 8’; the mean height of the barometer, corrected and re- duced to the temperature of 32°, was 28°401 inches, and the quan- tity of rain in the year was 55°71 inches. The author subjoins se- veral remarks on the conclusions deducible from an examination of the tables. 5. ‘‘ Description of an Astronomical Clock invented by the late Captain Henry Kater, F.R.S.,” drawn up from his own memoran- dums by his son Edward Kater, Esq. Communicated by Sir John F. W. Herschel, Bart., V.P.R.S. The great object aimed at by Captain Kater in the construction of the escapement of a chronometer, is to communicate equal impulses to the pendulum through some principle perfect in itself, and not dependent for its success on superior execution. In the escapement invented by him, the pendulum merely raises a weight, and is im- pelled by that weight through an increased space in its descent. It neither unlocks a detent, nor has anything to do with the train; and as the weight raised, and the spaces described, are constant quantities, this escapement is, in the strict meaning of the term, one of equal impulse. May 7.—A paper was read, entitled ‘‘ Researches in Embryology, Third Series: a Contribution to the Physiology of Cells.” By Martin Barry, M.D., F.R.S., F.R.S.E., Fellow of the Royal Col- lege of Physicians in Edinburgh. Of this paper an abstract was given in our number for June, vol. xvi., p. 526. A paper was also read, entitled ‘‘ On the Odour accompanying Electricity, and on the probability of its dependence on the presence of a new substance ;” by C. F. Scheenbein, Professor of Chemistry, Bale, communicated in a letter to Michael Faraday, Esq., D.C.L., Pais, cc. The author’s attention having been long directed to the remark- able fact, that odour, resembling that of phosphorus, is given off during the escape of positive electricity from the point of a con- ductor into air; and is likewise perceptible when lightning has struck any object, and also when water is electrolyzed, he has in- vestigated the circumstances attending these phenomena; and the results he has obtained will, he expects, afford a clue to the discovery of their cause. 294 Royal Society. The odour which accompanies the electrolyzation of water, he observes, is only disengaged at the positive electrode. He also finds that the odoriferous principle can be preserved in well-closed glass bottles for any length of time. The only metals which yield this odour are gold and platina; but dilute sulphuric, phosphoric, and nitric acids, and from aqueous solutions of several of the salts, also - disengage it. Raising the temperature of the fluid to the boiling point prevents the odour from arising; and the addition of com- paratively small quantities of powdered charcoal, iron, zine, tin, lead, antimony, bismuth or arsenic, or of a few drops of mercury, to the odorous principle contained in a bottle, immediately destroys the smell; and the same happens when platina or gold, heated red-hot, is introduced into the vessel containing that volatile substance. May i14.—A paper was read, entitled, ‘‘’Tables of the Variation, through a cycle of nine years, of the mean height of the Barometer, mean Temperature, and depth of Rain, as connected with the pre- vailing Winds, influenced in their direction by the occurrence of the Lunar Apsides, with some concluding observations on the result.’”’ By Luke Howard, Esq., F.R.S., &c. From the Tables here given, the author draws the following con- clusions :— . 1. The barometer is higher under the lunar apogee, than under the perigee ; the mean height in the former case being 29°84517, and in the latter, 29°75542. 2. The mean temperature is lower under the apogee than under the perigee; that of the former being 48°°7126, and of the latter, 49°-0356. The mean of the whole year was 48°7126. 3. The rain of the weeks following the apsis exceeds that under the perigee; but with two striking exceptions in the annual result of nine years, the one in the wettest, and the other in the driest year of the cycle. With regard to the winds, the author remarks that those from the north, north-east, and east, prevailed under the apogee on 38 days, under the perigee on 21 days; and those from the south, south-west, and west, prevailed under the apogee on 20 days, under the perigee on 38 days. It appears, therefore, that in the climate of London, the moon in her perigee brings over us the southern atmosphere, which tends to lower the density and raise the temperature of the air, occasioning also a larger precipitation of rain. In the apogee, on the contrary, there is a freer influx of air from the northward, a higher barometer, a lower temperature, and less rain; subject, however, to a large addition of rain under this apsis twice in a cycle of nine years, at the times when also the extremes of wet and dry take place on the whole amount of the year. A paper was also read entitled, ‘‘ Experimental Researches into the strength of Pillars of Cast Iron, and other materials.” By Eaton Hodgkinson, Esq. Communicated by Peter Barlow, Esq., F.R.S., &c. The author finds that in all long pillars of the same dimensions, Royal Society. 295 the resistance to crushing by flexure is about three times greater when the ends of the pillars are flat, than when they are rounded. A long uniform cast-iron pillar, with its ends firmly fixed, whether by means of disks or otherwise, has the same power to resist break- ing as a pillar of the same diameter, and half the length, with the ends rounded, or turned so that the force would pass through the axis. The strength of a pillar with one end round and the other flat, is the arithmetical mean between that of a pillar of the same dimen- sions with both ends round, and one with both ends flat. Some additional strength is given to a pillar by enlarging its diameter in the middle part. The author next inyestigated the strength of long cast-iron pillars with relation to their diameter and length. He concludes that the index of the power of the diameter, to which the strength is proportional, is 3°736. He then proceeds to determine, by a comparison of experimental results, the inverse power of the length to which the strength of the pillar is proportional. The highest value of this power is 1:914, the lowest, 1°537, the mean of all the comparisons, 1*7117. He thus deduces, first, approximate empirical formule for the breaking weight of solid pillars, and then proceeds to deduce more correct methods of determining their strength. Experiments on hollow pillars of cast iron are then described, and formule representing the strength of such pillars are deduced from these experiments. After giving some results of experiments still in progress for determining the power of cast-iron pillars to resist long-continued pressure, the author proceeds to determine from his experiments the strength of pillars of wrought iron and timber, as dependent on their dimensions. The conclusion for wrought iron is, that the strength varies inversely as the square of the pillar’s length, and directly as the power 3°75 of its diameter, the latter being nearly identical with the result obtained for cast iron; for timber, the strength varies nearly as the 4th power of the side of the square forming the section of the pillar. Experiments for determining the relation of the strength to the length in pillars of timber, were not instituted, as, from the great flexure of the material, it was consi- dered that no very satisfactory conclusions on this point could be derived experimentally. In conclusion, the author gives the relative strengths of long pillars of cast iron, wrought iron, steel, and timber. _ May 21.—The following papers were read, viz. : 1. ‘‘ Remarks on the Meteorological Observations made at Alten, Finmarken, by Mr. 8. H. Thomas in the years 1837, 1838, and 1839.” By Major Sabine, R.A., V.P.R.S., and Lieut. Col. Sykes, F.R.S.; being a Report from the Committee of Physics, including Meteorology, to the Council, and communicated by the Council to the Royal Society. These observations, made at Alten in lat. 69° 58! 3” N., and 23° 43' 10” east of Paris, would seem to have a claim to the atten- tion of the Royal Society, as they offer the experimentum crucis of 296 Royal Society. Professor Forbes’s empirical formula respecting the gradual diminu- tion of the daily oscillations of the barometer, within certain limit — hours, from the equator to the poles. Professor Forbes has laid down an assumed curve, in which the diurnal oscillation amounts to ‘1190 at the equator and 0 in lat. 64° 8’ N., and beyond that lati- tude the tide should occur with a contrary sign, plus becoming minus. Now Alten being nearly in lat. 70°, if Professor Forbes’s law hold good, the maxima of the diurnal oscillations should occur at the hour for the minima at the equator, and a similar inversion should take place with respect to the minima. Mr. Thomas has himself however modified the value his observations would otherwise have had, by adopting 2 p.m., instead of 3 p.m., for the hour of his ob- servations for the fall; and he has adapted his barometrical ob- servations to a mean temperature of 50° Fahr., instead of 32°. The first year’s observations commence on the 1st October, 1837, and terminate on the 30th September, 1838. ‘The barometer stood 66 feet 5 inches above low-water mark, and the thermometer hung _at 6 feet above the ground; but care was not always taken to pre- vent the sun shining on it. The mean height of the barometer for the year was 29°°771, and the mean of the thermometer al- most coincident with the freezing point, viz., 32°°017. The maximum height of the barometer was 30°°89 in January, and the minimum 28°71 in October. The mean of the barometer at 9 A.M. was 29°-764, therm. 33°°455; at 2p.m. 29°°765, therm. 33°°327; and at 9 p.m. 29°°784, therm. 29°-270. The diurnal observations would seem to support Professor Forbes’s theory ; but the 9 p.m. observations are entirely opposed to it, as they appear with the same maximum sign as at the equator, whereas the sign ought to have been the reverse; indeed, with respect to the diurnal observations, the mean of five months of the year at 9 a.m. gives ‘a plus sign, although the mean of the year at 2 p.m. only gives the trifling quantity of ‘001 plus. There is one remarkable feature in these observations that cannot fail to strike the meteorologist. M. Arago, from nine years’ observations at Paris, reduced to the level of the sea, makes the annual mean height 29°°9546 ; twenty-one years’ observations at Madras make it 29°°958 ; and three years’ observations at Calcutta, by Mr. James Prinsep, make it 29°°764; and Mr. Thomas brings out 29°°771. That there should be this coincidence between the observations at Calcutta and Alten is curious. Neither Mr. Thomas nor Mr. Prinsep state whether or not their means are reduced :to the level of the sea. It is to be suspected they are not. For the next year, that is to say, rd Oct. 1838 to Sept. 1839, both inclusive, Mr. Thomas uses a French barometer and French measurements, with centigrade thermometer attached to the baro- meter, and Fahrenheit’s for the detached thermometer. He changes his time of observation from 9 a.m. to 8a.m., 2P.m., and 8 P.Mm., and he reduces his barometrical observations to O centigrade. The results of the year are as follow:—mean annual pressure 29°'627 English ; thermometer Fahr. 38°36; greatest pressure Royal Society. 297 in April, least in January!! The mean of 8a.m. is 29°°620; therm. 33°°75. The mean of 2 p.m. is 29°°631; therm. 34°°78 ; and at 8 p.m. 29°°631; therm. 30°57. The diurnal observa- tions assist to support Professor Forbes’s theory ; but as in the pre- ceding year, the p.m. observation is at fault; and if the hour had been 9 o’clock instead of 8 o’clock, it would probably have been more so than it appears. ‘The low annual mean state of the baro- meter for the year 1837-38 is even increased in the last year’s ob- servations ; and as fresh instruments* appear to have been used, there is ground to believe that the fact is associated with the lo- cality, and it may be desirable not only to record in the Proceed- ings of the Royal Society the data already supplied, but to re- commend to Mr. Thomas more particular inquiry on the subject. The phenomena of the Aurora Borealis appear to have been ob- served by Mr. Thomas with great assiduity, and recorded with great care. On examining the register, with reference to M. Erman’s important remark, that ‘‘ in Siberia two kinds of aurora are distin- guished, one having its centre in the west, and the other in the east, the latter being the more brilliant,” it is found that twenty-two nights occur in the course of the two winters in which the formation of arches of the aurora is noticed and their direction recorded ; of these, ten are to the west, having their centres rather to the south- ward of west, the arches extending from N.W. to 8.S.E. and S.E.; seven are to the east, or more precisely to the southward of east, the arches extending from N.E. to S.E. and S.W. Of the five others, four are said to be from east to west across the zenith, and cannot therefore be classed with either of the preceding, and one is noticed generally as being to the north. The facts here recorded appear to afford an evidence of the same nature as those mentioned by M. Erman, as far as regards there being two centres of the phenomena. In respect to the relative brilliancy of the east- ern and western aurora, nothing very decided can be inferred from the register. If, as M. Erman supposes, they may be referred respectively to ‘‘les deux foyers magnétiques de l’hemisphére bo- réal,”’ it is proper to notice that the position of Alten is nearly mid- way between those localities. There can be no doubt that the frequent appearance of the aurora, and the peculiarities of the phenomena observed there, ren- der it a most desirable quarter for a magnetical and meteorological observatory. EpwarbD SaBINE. W.H. Sykes. 2. ‘* Second Letter on the Electrolysis of Secondary Compounds, addressed to Michael Faraday, Esq., D.C.L., F.R.S., &e.” By J. Frederic Daniell, Esq., For. Sec. R.S., Professor of Chemistry in King’s College, London. The author, in this letter, prosecutes the inquiry he had com- menced in the former one, [of which an abstract appeared in the * It appears that the barometer was compared before leaving France, and sub- sequently to its being taken back te that country. 298 Royal Soczety. L. & E. Phil. Mag., vol. xv., p. 317.—Epit.] into the mode in which the chemical elements group themselves together to consti- tute radicles, or proximate principles. He considers his experi- ments as establishing the principle that, considered as electrolytes, the inorganic oxy-acid salts must be regarded as compounds of me- tals, or of that extraordinary compound of nitrogen and four equi- valents of hydrogen to which Berzelius has given the name of ammonium, and compound anions, chlorine, iodine, &c., of the Ha- loide salts; and as showing that this evidence goes far to establish experimentally the hypothesis originally brought forward by Davy, of the general analogy in the constitution of all salts, whether de- rived from cxy-acids or hydro-acids. Some remarks are made on the subject of nomenclature, and the rest of the paper is occupied with the details of the experiments, all bearing on the important subject which he has undertaken to investigate. . May 28.—The following papers were read, viz. : 1. “ Meteorological Register kept at Port Arthur, Van Diemen’s Land, during the year 1838, and Register of Tides at Port Arthur, from August 1838 to July 1839, both inclusive.” By Deputy- Assistant-Commissary-General Lempriere. Communicated by Sir John Franklin, R.N., F.R.S., &c. 2. ‘* Notice relative to the form of the Blood-particles of the Ornithorhynchus hystrix.” By John Davy, M.D., F.R.S. A portion of the blood of the Ornithorhynchus hystrix, mixed when fresh with a strong solution of common salt, being examined by the author, exhibited a few globules of irregular shape. Another portion, preserved in syrup, contained numerous globules, most of which had an irregular form, but many were circular; none, how- ever, were elliptical, like those of birds. Hence the author con- cludes, that in form they accord more with those of Mammalia, 3. “‘ Researches on Electro-chemical equivalents, and on a sup- posed discrepancy between some of them and the atomic weight of the same bodies, as deduced from the theory of isomorphism,” By Lieut.-Colonel P. Yorke. Communicated by Michael Faraday, Esq., D.C.L., F.R.S., &e. The author describes various experiments made with a view to determine the electro-chemical equivalents of sodium and potassium. Three experiments gave, respectively, 22°3, 22°9, and 25, as the equivalent of the former; and two other experiments gave, respect- ively, 45 and 41°7, as the equivalent of the latter of these sub- stances. He then inquires what would be the result of the electro- lyzation of the aqueous solutions of soda and potash, on the hypo- thesis of these bodies being composed of two equivalents, or atoms, of metal, and one of oxygen. ‘To determine this question he em- ploys a solution of dichloride of copper in muriatic acid, as being a substance composed of two atoms of metal and one of an electro- negative element. Its electrolysis gave as the equivalent of copper, 52°8, 59°4, and 61°6, numbers approximating closely to 63:2, or double the atomic weight of copper. After a long train of investi- gation, he concludes that there is no reason deducible from the Royal Society. 299 theory of isomorphism for doubting the correctness of the received atomic weights of silver, sodium, &c., but that the difficulty, or anomaly, if it may be so called, should be considered as attaching itself to the di-compounds of copper; and that Faraday’s proposi- tions on this subject remain unimpeached. 4. “* Second series of Approximate Deductions made from about 50,000 observations taken during the years 1836, 1837, and 1838, at the Port Louis Observatory, Mauritius, four times each day ; namely, at 8 a.m., at noon, and at 4 and 8p.m.” By J. A. Lloyd, Esq., F.R.S. 5. * On the Solubility of Silica by Steam; with an account of an experiment on the subject, conducted in the East Indies by Julius Jeffreys, late of the Hon. East India Company’s Medical Establishment.” The inner surfaces of a flue built of siliceous bricks appeared to be deeply eroded by the passage over it of steam at a very high tem- perature, and fragments of siliceous materials laid in the course of the current were partially consumed. A siliceous crust was de- posited on several vessels of stone ware, coated with a micaceous glaze, placed in the upper part of the furnace, and this crust was re-dissolved when the vessels were removed to a hotter situation in the same furnace. The author notices the experiments of Dr. Turner* and others, which failed in showing the solubility of silica by steam, in consequence, as he conceives, of the heat having not been sufficiently great to effect the solution. June 4.—A paper was read, entitled, ‘‘ Contributions to the Che- mical History of Archil and of Litmus.” By Robert Kane, M.D., M.R.1.A. Communicated by Francis Baily, Esq., V.P.R.S. After a preliminary sketch of the labours of Heeren and of Robi- quet in investigating the origin of the beautiful colouring materials termed Archil and Litmus, obtained from different kinds of colourless lichens, and their detection of the two proximate principles termed erythrine and orceine, the author states the object of the inquiries de- tailed in the present paper to be threefold; viz. first, to ascertain the primitive form of the colour-making substance in a given species of lichen, and trace the stages through which it passes before the co- loured substance is developed; secondly, to determine the nature of the various colouring substances which exist in the archil of com- merce; and thirdly, to examine the colouring materials of ordinary litmus. He finds in the lichen Koccella tinctoria the following bodies, either pre-existing in the plant, or formed during the pro- cesses employed for its analysis: 1. Erythryline; 2. Erythrine (the Pseudo-erythrine of Heeren); 3. Erythrine bitter; 4. 'Telerythrine ; and 5. Roccelline (the Roccellic acid of Heeren). The properties and constitution of these substances are then described, and the che- mical formule given, which are deducible from their respective ana- lyses. The author finds the archil of commerce to consist essen- tially of three ingredients, namely, orceine, erythroleic acid, and [* See L. & E, Phil. Mag. vol. v. p. 297.—En1r.] 300 Royal Society: —Dr. Martin Barry azoerythrine ; of each of the two former there exist two modifications, and there is, in addition, a yellow matter. After comparing his re- sults with those obtained by Heeren, by an examination of the pro- ducts evolved by his erythrine in contact with air and with ammonia, and stating reasons for some changes in nomenclature, the author gives the chemical formule resulting from his own analysis of these different substances. His inquiries into the constitution of ordinary litmus, which form the last division of his subject, lead him to the conclusion that that substance contains the principles designated by him as Erythrolein, Erythrolitmine, Azolitmine, and Spaniolitmine ; and that the colour- ing constituents of litmus are, in their natural condition, red; the blue substances being produced by combination with a base, which bases in that of commerce are lime, potass, and ammonia; and there is mixed up-in the mass a considerable quantity of chalk and sand. The details of the analyses of these several substances, and the re- sulting chemical formule representing their constitution, are then given. The concluding section of the paper is occupied by an inquiry into the decoloration of the bodies which exist in archil and in litmus. The latter of these, the author concludes, is reddened by acids, in consequence of their removing the loosely combined ammonia by which the blue colour is produced ; and the so-called hydrogen acids liberate the colouring matter by their combining with the alkali to form bodies (either chlorides or iodides), with which the colouring matter has no tendency to unite. Hence it appears that the redden- ing of litmus is no proof that chloride of hydrogen is an acid, and that the double decomposition which occurs is the same in principle, whether hydrogen or a fixed metal come into play. After detailing the blanching effects of other deoxydizing agents on the colouring matter of litmus, and the action of chlorine on orceine and azolitmine, the author remarks, that in these actions chlorine is subjected to conditions different from those which determine the nature of the results with the generality of organic bodies, and that the displace- ment of hydrogen, so marked in other cases, does not exist in the class of substances under consideration; but that, im reality, the products of the bleaching energy of chlorine resemble in constitution the compounds of chlorine which possess bleaching powers. A paper was also read, entitled, ‘‘ On the Corpuscles of the Blood.” By Martin Barry, M.D., F.R.S. The author in the course of his researches in Embryology, detailed in his ‘‘ third series,’’ observed that some of the corpuscles of the blood undergo progressive alterations in their structure. The cor- puscles so altered he believes to be of the same kind as those de- scribed by Professor Owen; and having found that the alterations in question terminate in a separation of the corpuscles into globules, he thinks this fact confirms the idea of Professor Owen—that the blood-disc undergoes spontaneous subdivision. The author farther observed, that the corpuscles of the blood, in certain altered states, undergo rapid and incessant changes of form, which cannot be traced on the Corpuscles of the Blood. 301 to the action of neighbouring cilia. A corpuscle will sometimes as- sume the figure of an hour-glass, as if it were preparing to divide itself into two parts, but it instantaneously either regains its previ- ous form, or assumes a new one. ‘These motions are incessant, and so rapid, that it is not easy to catch and delineate any of the result- ing forms; they are compared to the writhings of an animal in pain. The author has seen them in a rabbit, as late as two hours and a half after death, and thinks it probable that they may continue for a longer time, although, when under the microscope, they gradually and in a short time cease; the rapid changes of form, which are at first apparent, passing into gentle undulations, and being succeeded by an alternation of rest and motion*. Should these facts be thought to confirm the opinion of John Hunter, that the blood ‘‘ has life within itself,” or ‘‘ acquires it in the act of forming organic bodies,” because its corpuscles in certain states exhibit “‘ vital actions,”’ still his assertion that ‘“ the red glo- bules”’ are the least important part of the blood, will appear to have no just foundation. The author finds that the phenomena attending what is called *‘ vital turgescence”’ of the blood-vessels, depend not merely on an accumulation and stagnation of blood, but on changes in the condi- tion of its corpuscles, which assume a more or less globular, or ellip- tical appearance resembling cells. Their interior is dark, from a great increase of red colouring matter which accumulates around a pellucid and colourless point, corresponding in situation to that of the central part of nuclei in other cases; and so completely do the corpuscles fill their vessels, that the fluid portion of the blood is ex- cluded, and the corpuscles are compressed into polyhedral forms. This condition of the blood-corpuscles during vital turgescence of the vessels, the author thinks deserving of consideration, in connexion with many of the phenomena attending local accumulations of blood, both in health and in disease; and more especially with reference to increased pulsation, the exudation of colourless fluid, and the heat and redness of inflamed parts. According to the views of the author, the formation and nourish- ment of organs is not effected merely by the fluid portion of the blood, for he has discovered that the cells which he showed in his ‘«‘ Third Series of Researches in Embryology+”’ form the chorion, are ‘altered blood-corpuscles ; and he has farther found that muscular fibre (that is, the future muscle-cylinder, not the fibril) is formed by the coalescence of cells, which also are derived from corpuscles of the blood. He has seen and figured every stage of transition, from the unaltered blood-corpuscle to the branched cells forming the chorion, on the one hand, and to the elliptical or oblong mus- cle-cells, on the other. The colour is not changed, except that the blood-corpuscles, when passing into cells for the formation of mus- * [See a note on this subject by Dr. Barry, p. 157 of the present volume.—Enpir. | t [See Lond. and Ed. Phil, Mag. vol. xvi. p. 526.—Enp1T. ] 302 Royal Society:—Dr. M. Barry on the Blood. cle, become of a much deeper red. There seems to occur in these an increase of red colouring matter. Valentin, in describing the mode of the formation of muscle, had stated that globules approach one another and coalesce to form threads, which in many places have the appearance of a necklace, but subsequently lose the traces of division, and become cylinders. Schwann had conjectured that the globules just referred to—as ha- ving been observed by Valentin—are cells, and that these cells coa- lesce to form a secondary cell, that is, the muscle-cylinder. The author confirms the observations of Valentin and the conjectures of Schwann, with the addition, that the globules coalescing to form the muscle-cylinder are blood-corpuscles which have become cells. The fibrils appear to be subsequently formed within the cylinder, which thus becomes the muscular fasciculus. The medullary portion of the cylinder appears to be composed of the pellucid objects, one of which is contained within each altered blood-corpuscle. Some of these pellucid objects, however, continue to occupy a peripheral situation. The author thinks it is not probable that muscular fibre and the chorion are the only tissues formed by the corpuscles of the blood ; he is disposed rather to inquire, how many are the tissues which they do not form? Nerves, for instance, are known to arise very much in the same manner as muscle-cylinders ; and epithelium-cells sometimes present appearances which have almost suggested to the author the idea that they were altered corpuscles of the blood. Schwann had previously shown that ‘‘ for all the elementary parts of organisms there is a common principle of development,’—the elementary parts of tissues having a like origin in cells, however different the functions of those tissues. The facts made known in the present memoir not only afford evidence of the justness of the views of Schwann, but they farther show that objects, such as the corpuscles of the blood, having all the same appearance, enter im- mediately into the formation of tissues which physiologically are extremely different. Some of these corpuscles arrange themselves into muscle, and others become metamorphosed into constituent parts of the chorion. But the author thinks it is not more difficult to conceive corpuscles having the same colour, form, and general appearance, undergoing transformations for very different purposes, than to admit the fact made known by two of his preceding me- moirs,—namely, that the nucleus of a cell, having a central situa- tion in the group which constitutes the germ, is developed into the whole embryo, while the nuclei of cells occupying less central situa- tions in the group, form no more than a minute portion of the am- nion. It is known that in the bee-hive a grub is taken—for a spe- cial purpose—from among those born as workers, which it perfectly resembles until nourished with peculiar food, when its development takes a different course from that of every other individual in the hive. The Society then adjourned over the Whitsun Recess, to meet again on the 18th of June, [ 303 ] GEOLOGICAL SOCIETY. Feb. 1, 1840.—Annual General Meeting. The President announced that the Wollaston Medal had been awarded to Prof. Dumont, of Liége, for his Memoir, Map, and Sections on the Geological Constitution of the Province of Liége, published in 1832; and one year’s interest of the Wollaston Fund to Mr. James De Carle Sowerby, in order to facilitate the continua- tion of his researches in Mineral Conchology ; Dr. Buckland, on presenting the Medal to Dr. Fitton, who had been requested by M. Dumont to receive it on his behalf, said :— Dr. Firron, I am highly gratified that it has become my duty on the present occasion, tocommit to your care as the Representative of our common friend, Professor Dumont, the Wollaston Gold Medal, which has been awarded to him by the Council of this Society for his Me- moir on the Geological Constitution of the province of Liége pub- lished at Brussels in 1832. The grounds of our tardy recognition in 1840, of the merits of a work published so long as eight years ago, are the same, that in 1830, prompted the Judges appointed by the Academy of Brussels, to select this Memoir as most worthy of the Prize then proposed by that Academy, for the best Geological description of the province which has formed the subject of M. Dumont’s successful labours. In the work thus doubly crowned, the Author has described the mineralogical and zoological characters of the rocks which occupy this district, and determined in minute detail, the relative places in order of succession, and the superficial extent of each subordinate division of the several formations. He has also illustrated the same by an accurately coloured Geological Map, and by coloured Sections, showing the general disposal of the strata in their original order of deposition, and the extraordinary derangements and dis- turbances that have subsequently thrown them into a state of almost inextricable confusion. In the execution of this work, M. Dumont has evidenced unusual powers of discriminating and accurate obser- vation, combined with a high capacity of reducing the minutiz of local details under the dominion of enlarged and masterly theo- _Yetical generalizations. Advancing at the early age of twenty one, to a task of gigantic labour, in a region where the unexampled dis- turbances, and almost incredible complexity of its component strata had baffled the sagacity of the most experienced geologists, this extraordinary youth at once withdraws the veil of confusion which had hitherto disguised the stratigraphical arrangements of his native province, and as it were, by an intuitive touch, reduces to order the entangled and almost incredible phenomena of dislocation, con- tortion, and inversion which had perplexed his predecessors in the same field of observation. In addition to the scientific value of M. Dumont’s exact and la- borious researches, in illustrating a high and difficult problem in positive geology, his work assumes a place of great statistical and 304 Geological Society: —Annual General Meeting, 1840. commercial importance, as describing the structure and contents of a rich and productive carboniferous district containing eighty-three beds of valuable coal; and its practical utility has been fully shown, by the fact of a second edition having been required to supply the demands of the landed proprietors, and persons practically interested in the operations and products of the coal mines. The geological tribunal of Brussels, including the highly distin- guished geologist Omalius d’Halloy, at once appreciated duly, and rewarded as they deserved, these brilliant discoveries ; but the phz- nomena represented on M. Dumont’s map and sections were so un- usually complex and improbable, that the geologists of England could not but forbear to admit their reality, until it was fully confirmed by our personal examination, with the aid of that new light which M. Dumont’s discoveries had thrown upon them. The result of such inquiry has been a full corroboration of M. Du- mont’s representations, and at this late hour we at length come for- ward with the homage of our tardy but sincere acknowledgements ; a duty too long delayed, from the exercise of precaution in its admi- nistration, but for this very reason now become more urgent, when the grounds for conscientiously discharging it have passed the or- deal of severe and critical investigation. It is for this great work then on the geological constitution of the Province of Liége, such as in 1832 it issued from the hands of a young, and then unknown individual, and apart from any more recent attempts to identify the Belgian formations with those of England, that our Society has awarded to M. André Hubert Dumont their Gold Wollaston Medal for the present year; in testimony of their admiration of the almost precocious talents then displayed by him, and of their sense of his worthiness to fill the distinguished scientific position to which he is now advanced, as Professor of Mineralogy and Geology in the Col- lege of Liége*. Dr. Fitton, on receiving the Medal from the hands of the Presi- dent, said, that he had been requested by M. Dumont to express his great regret that unavoidable duties prevented his appearing in person on this occasion. M. Dumont’s letter states with deep feeling his sense of the honour which the Geological Society of London has thus conferred upon him, and his hope that he may soon be enabled to come into England, for the purpose of extending his personal ac- quaintance with the members of this Society, and of being enabled, with the aid of their knowledge, to perfect the comparison of the ancient strata of Belgium with those of this country. The Society could not but anticipate great advantage to Geology from the ap- plication of M. Dumont’s talents to the comparative inquiries to which his letter alludes. On presenting the prize awarded to Mr. James De Carle Sowerby, Dr. Buckland said :— It is with no small pleasure that I rise to perform the duty of * [A paper by M. Dumont “On the Equivalents of the Cambrian and Silurian Systems in Belgium,” will be found in Lond. and Edinb. Phil, Mag,, vol. xv. p. 146,—Epz1t.] Presentation of the Wollaston Prizes. 805 placing into your hands the award that has been made to you by the Council of the Geological Society, of one year’s interest of the Wol- laston Fund, in order to facilitate the continuation of your researches in Mineral Conchology.—The services are great which have been rendered to Geology by the extremely useful and well-timed work on fossil shells, which was many years ago begun by your excellent father, and continued by him to the end of his life, and has been since conducted by yourself; and the association of his name with . that of Dr. Wollaston, recalls to my mind, as it must to the minds of most of my hearers, pleasing and grateful recollections of the bene- fits which during their lives they both conferred on this Society, and which theiv works will have extended to all our contemporaries and successors in this department of scientific inquiry. It was your father’s peculiar merit to be one of those accurate and enthu- siastic observers of nature, who have in modern times contributed so much to remove from science the rugged and austere aspect under which it used to be presented ; and who by facilitating to every one the means of advancing pleasantly in its pursuit, have, in an essential manner, promoted, and given popularity to the study of Botany and Conchology. It is to Mineral Conchology, which he so especially promoted, that we who are occupied with the investigation of the structure of the earth, have in modern times been mainly indebted for evidences which have led to the establishment of many of the most important stratigraphical distributions, that have been founded on the suc- cessive changes in animated nature which are made known to us by the study of fossil shells. It was on this foundation that Cuvier and Brongniart established their important divisions of the marine and freshwater strata of the Tertiary formations, which have since been more minutely distributed by Mr. Lyell into the eocene, pliocene, and miocene series, according to their relative numbers of extinct and recent species of fossil shells. It was on a similar foundation that Mr. William Smith rested his identification of the Secondary strata of England. It is on the same basis of conchological evidence that Mr. Murchison has founded his fourfold subdivisions of the Silurian portion of the Transition rocks; and it is chiefly to the illu- mination which this branch of Palzontology has shed upon the changes that took place on the surface of the earth, whilst its strata “were in process of formation, that we owe the rapid advances in geological knowledge which have been made since the commence- ment of the present century. To this rapid progress, arising from the introduction of the evidences of mineral Conchology, your own publications and those of your family have largely contributed ; you have further co-operated materially in advancing our inquiries by your personal assistance, at all times cheerfully and liberally ren- dered, to all your fellow labourers in the same fields of scientific research, who stood in need of your aid, for the elucidation of mi- nute distinctions in the characters of fossil organic remains, which have at this time become so important an element in geology. The volumes of the Transactions of this Society, and other publi- Phil. Mag. 8. 3. Vol. 17. No. 110. Oct. 1840. X 306 Geological Society:—Anniversary Address of the cations by many of its Members, including myself, bear further tes- timony to the importance of your labours, in illustrating our works with drawings and engravings of fossil shells and plants, expressing their characters with a degree of accuracy and truth, which no pencil or burine but those of a scientific artist could possibly accomplish ; and I am sure I give utterance to the feelings of all our fellows now around me, when I thus publicly acknowledge the services you have rendered both to ourselves, and to the science we cultivate; and ex- press the satisfaction with which we thus publicly recognise the va- lue of your exertions. Mr. Sowerby then expressed himself in the sige terms :— Sir, I hardly know what to say, so deeply do I feel the “unexpected and kind award bestowed upon me by this Society, but I must as- sure you, that I am extremely grateful for the honour done me. When, Sir, you spoke of my father, you excited feelings most dear to me, and I have long felt that I have experienced more consideration than I have deserved, in consequence of the esteem that has ever been attached to his memory. But I must have been a most un- grateful son had I not, after his persevering and kind instructions, done something for the advancement of Natural History. What little I have performed, especially for Members of this Society, has been for the love of Science; and I feel far more than amply re- warded by the honourable present I have just received at your hands. You have stated, Sir, that you take a pleasure in associating the name of Wollaston with that of Sowerby; I shall never forget the kindness and patience with which Dr. Wollaston communicated information. When the reflective goniometer was first completed by him, he spent several hours one morning with me in his study mea- suring the cleavages of various minerals related to hornblende and augite which I took to him for his opinion; and at another time he indulged me with an equally long lesson on the chemical exami- nation of minute portions of minerals. Little did I think at that time that I should ever share encouragement continued by his bounty, after his departure from this world; but I have lived to feel that his benevolence lives beyond the grave. Sir, I receive this award as a trust reposed in me, and hope that I shall not be found wanting in carrying out the object the Council has in view. I beg sincerely to thank the Society for the confidence placed in me. The following Fellows were declared to have been elected the Officers and Council for the ensuing year. President—Rev. W. Buckland, D.D. Professor of Geology and Mineralogy in the University of Oxford. Vice-Presidents—G. B. Greenough, Esq. F.R.S. & L.S.; Leo- nard Horner, Esq. F.R.S. L. & E.; Sir Woodbine Parish, K.C.H. F.R.S.; Rev. William Whewell, B.D. F.R.S. Professor of Casuistry in the University of Cambridge. Secretaries. —Charles Darwin, Esq. F.R.S.; William John Ha- milton, Esq. President, the Rev. Professor Buckland. 807 Foreign Secretary.—H. T. De la Beche, Esq. F.R.S. & L.S. Treasurer.—John Taylor, Esq. F.R.S. & LS. Council.—Arthur Aikin, Esq. F.L.S.; Francis Baily, Esq. F.R.S. L.S.; Viscount Cole, M.P. F.R.S.; W. H. Fitton, M.D. F.R.S. L.S. ; W. Hopkins, Esq. M.A. F.R.S.; R. Hutton, Esq. M.P. M.R.I.A. ; Charles Lyell, Esq. F.R.S. L.S.; William H. Miller, Esq. M.A. Pro- fessor of Mineralogy in the University of Cambridge; R. I. Mur- chison, Esq. F.R.S. L.S.; E. W. W. Pendarves, Esq. M.P. F.R.S.; — Philip Pusey, Esq. M.P. F.R.S.; George Rennie, Esq. F.R.S. ; Daniel Sharpe, Esq. F.L.S.; Rev. Adam Sedgwick, F.R.S. L.S. Woodwardian Professor in the University of Cambridge. Address to the Geological Society, delivered at the Anniversary, on the 2\st of February, 1840, by the Rev. Proressor BucKLAND, D.D., F.R.S., Corresponding Member of the Institute of France, President of the Society. GENTLEMEN, | By the Report just read, you have seen that the state of our Society is one of steady and salutary progression ; forty-three new Members have been added to the List of our Fellows, from which seventeen have been removed by death or resignation, leaving our actual number 768, with an increase of twenty-six during the last year. The vacancies that have occurred upon our foreign list have been supplied by three highly distinguished cultivators of science on the Continent, each pre-eminent for his successful labours in high departments of our subject, namely s Major Puillon de Boblaye, in Positive Geology, Professor Adolphe Brongniart, in Vegetable Paleontology, Professor Gustave Rose, in Crystallography and Mineral Analysis. We are rich in property, though our funds are, at this moment, low; but they will speedily be repaired by the sale of two large and costly parts which have been added to our Transactions. The Reports of the Library and Collections in our Museum are satisfactory. The chief additions to the former consist of presents from Authors and Members of the Society. Our principal bene- factor has been Mr. Greenough, who has given us a Collection of the older Authors,—supplying many of our deficiencies in the . Literature of Geology and Mineralogy. Considerable progress has been made in the arrangement of the Cabinets by our Sub-Curator, Mr. Woodward, under the superintendence and directions of Mr, Lonsdale; one hundred and sixty drawers of rock specimens and fossil remains having been labelled, and in part catalogued, since the meeting of last year. It is satisfactory to find that the number of persons who come to study our Collections has been much in- creased. Our entire establishment continues to receive the inestimable advantages it has long enjoyed, from the~zealous superintendence, and scientific acquirements of our Curator, Mr. Lonsdale. Our Wollaston Medal has been awarded to Professor Dumont, for his Map, Sections and Memoir on the Geological Constitution X 2 308 Geological Society: —Anniversary Address. of the Province of Liége, published in 1832; and one year’s interest of the Wollaston Fund has been presented to Mr. James De Carle Sowerby, to facilitate the continuation of his researches in Mineral Conchology. More than a quarter of a century has now elapsed since I became a Member of this Society ; and fifteen years have passed since I was first placed, by your kindness, in the honourable position of filling this Chair, at that important period of our history when we received the national recognition of a Royal Charter. I shall never cease to consider it one of the brightest rewards of my labours in geology, that my name is enrolled in that charter, as the first President of the Society in its corporate capacity. Since that important epoch, our chartered body has received from the Government of the country the valuable sanction and advantage of an establishment in the very convenient apartments of Somerset House, which we now occupy. The number and character of the scientific labourers who have joined our ranks, and the volumes added to our Transactions, since these events, show that such en- couragements have not been conferred on a society disposed to slumber under the sunshine of prosperity ; but that, aided by these advantages, we have endeavoured to maintain a steadily progressive course, in the great pen of illustrating the physical structure of the earth. It is not my site on the present occasion, to notice geological memoirs or subjects which belong to years preceding that wherein I entered upon my present office. The usual practice rather con- fines me to the most remarkable events of the last twelve months, during which I have had the honour to fill this chair. MUSEUM OF G2CONOMIC GEOLOGY. Among the most important of these events, we recognise with gratitude, and confident anticipation of great advantage, both to science and the arts, the establishment, by Her Majesty’s Govern- ment, of an institution hitherto unknown in England, namely, a Museum of Giconomic Grotocy. This is to be freely accessible to the public at stated periods, in the Department of Her Ma- jesty’s Woods and Forests, and Public Works, for the express object of exhibiting the practical application of geology tothe useful pur- ’ poses of life. In this Museum a large store of valuable materials has already been collected and arranged, chiefly by the exertions, and under the direction of Mr. De la Beche. In it will be exhi- bited examples of Metallic Ores, Ornamental Marbles, Building- stones and Limestones, Granites, Porphyries, Slates, Clays, Marls, Brickearths, and Minerals of every kind produced in this country, that are of pecuniary value, and applicable to the arts of life. Information upon such subjects, thus readily and gratui- tously accessible, will be of the utmost practical importance to the miner and the mechanic, the builder and the architect, the en- gineer, the whole mining interest, and the landed proprietors. The establishment will contain also examples of the results of Metallur- Royal Astronomical Society. 309 gic processes obtained from the furnace and the laboratory, with a collection of Models of the most improved machinery, chiefly em- ployed in mining. A well-stored Laboratory is attached to this department, conducted by the distinguished analytical chemist, Mr. Richard Phillips, whose duty it already is, at a fixed and mo- derate charge, to conduct the analysis of metallic ores, and cther minerals and soils submitted to him by the owners of mines or pro- prietors of land, who may wish for authentic information upon such matters. The pupils in this laboratory are already actively employed in learning the arts of mineral analysis, and the various metallurgic processes. A second department in the Giconomic Museum will be assigned to the promotion of improvements in Agriculture, and will contain sections of strata, with specimens of soils, sub-soils, and of the rocks from the decomposition of which they have been produced. To this last-mentioned collection proprietors of land are solicited to contribute from their estates labelled examples of soils, with their respective sub-soils ; and all persons who wish for an analysis of any sterile soil, for the purpose of giving it fertility, by the arti- ficial addition of ingredients with which nature had not supplied it, may here obtain, at a moderate cost, an exact knowledge of its composition, which may point out the corrective additions which it requires. This portion of the Museum will more especially exhibit the relations of geology to agriculture, in so far as a knowledge of the materials composing the sub-strata may afford extensive means of permanent improvement to the surface. [ To be continued. | ROYAL ASTRONOMICAL SOCIETY. [Continued from vol. xvi. p. 148.] Jan. 10, 1840.—The following communications were read :— Ephemeris of the Comet now visible. By Mr. C. Rumker, of Hamburg. Communicated by Dr. Lee. A Letter from Mr. Henry Lawson to the Secretary describing the appearance of the Comet, as seen at Hereford. . The comet was observed by Mr. Lawson on the mornings of the 23d and 29th of December, and of the 8th January instant. It had a tolerably well-defined nucleus, with a brushy tail on the side op- posite to the sun. The nucleus subtended an angle nearly equal to half the visual angle subtended by Jupiter; and the tail filled the whole field of view, the diameter of which was three minutes of time. Apparent Positions of the Comet observed at Edinburgh. By Pro- fessor Henderson. Observations of the Comet made at Ashurst and Dulwich. By Robert Snow, Esq. Mr. Snow found the comet on the 28th of December. The ob- served diameter of the head was then 58", and the tail extended beyond the field of view. It was again observed on the 29th, and 310 Royal Astronomical Society :—Mr. Snow’s and also on the 5th and 6th of the present month, when it was very bright and easily found. The nucleus was large, but not stellar. Occultations of Stars by the Moon to the end of 1839. By Ro- bert Snow, Esq. Catalogue of the Plesades. By Robert Snow, Esq. The author states that this catalogue does not lay claim to strict accuracy, but was constructed in order to form a chart, which might be consulted with advantage when occultations—of stars in the Pleiades by the moon take place. Piazzi’s stars fallimg within the limits of the chart were taken as standards, and the differences be- tween them and the other stars determined by a wire micrometer. For some stars, too faint to allow of illumination, the ring microme- ter was used; but they were more usually put down by estimation, which may be done with nicety when many are in the field together. This communication was accompanied by a chart. On the Variability of a Cassiopeie. By Robert Snow, Esq. In the Monthly Notice for May last (vol. iv. p. 195.), the atten- tion of the Society was directed to the supposed variability of this star; and it has, accordingly, been watched, with the naked eye, since June 9, 1839, up to the present time, January 8, 1840. The relative brightnesses of a, 6, y Cassiopeie have been registered on ‘sixty-eight evenings. The result at present is that y has been ge- nerally put down as brightest, and never faintest; 6 generally as faintest; a faintest twelve times out of sixty-eight, and generally so about the 5th day of the month. In the Society’s Catalogue, the order of magnitude is 6,a = y. Mr. Snow remarks that the star a appears to his eye at all times sharper and better defined than y or G; and it is also more readily obscured by fog or haze, although it is a reddish star. . Observations of a Cassiopeia in 1831 and 1832. By Mr. W. R. Birt, Librarian and Assistant Secretary to the Metropolitan Institution. Communicated by the President. These observations were commenced in April 1831, and extend to November 1832; and the earlier part of them, from April to December 1831, have already, with some others, been communicated to the Society. See Monthly Notices, vol. ii. No. 11. Ina letter to Sir John Herschel, Mr. Birt-states, that since 1832 his attention had not been directed to this star until he read the Monthly Notice for May last, when it immediately occurred to him that his obser- vations might probably assist in determining the period in which the brightness of the star completes the circle of its gradations. When Mr. Birt commenced observing the star in April 1831, the lustre appeared to be at its minimum. In December of the same year, he again observed it to be less than (3: His observations were then discontinued until June 1832, when it again appeared less than /3. Taking the extreme observations, we have thus two periods completed in about fifteen months, or one period in about 225 days. Assuming this as the period of the variation, and computing from April 26, 1831, the number of days elapsed until April 28, 1839, is 2924, which gives thirteen periods of about 225 days each. Sir John Herschel’s Mr. Birt’s Observations of « Cassiopeize. 311 observations give the maximum from November 12, 1838, to January 22, 1839; and calculating from July 7, 1831, twelve periods, the maximum would be obtained on December 4, 1838, On the whole, Mr. Birt concludes that the period of 225 days may be regarded as a first approximation, which may receive correction from a compari- son with the earlier observations of Sir William Herschel. On the Variability and Periodic Nature of the Star a Orionis. By Sir John F. W. Herschel, Bart. President. “In a communication which was read to this Society on the 10th of May last, I pointed out the star a Cassiopete as variable and periodical, That the fluctuations in splendour of this star should have escaped general notice is not extraordinary, since the difference between its greatest and least brightness can hardly be estimated at more than half a magnitude. But that a periodical variation to avery much greater extent, in so important and remarkable a star as a Orionis, should, up to this time, have been completely unnoticed by astronomers, does appear to me, I confess, not a little extraor- dinary, and might be taken as an argument to show, more than any thing, the comparatively neglected state of this highly interesting branch of Phyical Astronomy. Perhaps, however, in this, as in many other cases, the very prominence of the object has been the cause of its being neglected; as it might easily be supposed by any one entering on this research, that had a star so familiar to every practi- cal astronomer presented any striking peculiarity of this kind, it could not but have been obseryed. Hence, while the attention of observers has been directed, and with success, to much inferior stars, it seems to have been taken for granted, that among stars of the first magnitude nothing, in fact, remained to be discovered. ** Having bestowed much attention, during my residence at the Cape, on the estimation of the magnitudes of the southern stars, both by direct photometrical measurements, assigning numerical values to about sixty or seventy of them, selected as offering con- venient gradations of brightness, and also by very assiduous and often-repeated comparisons by the naked eye, with the view to com- pleting a graduated scale down to the fifth magnitude, at least, it became important to connect these magnitudes by similar compari- sons with those of the northern hemisphere, by means of stars in ‘the vicinity of the equator admitting of observation at both sta- tions. My method in these observations has been invariably on each night to establish, in the first instance, a sort of skeleton-scale, beginning with the stars of the first magnitude actually visible, and extending as far as was judged convenient for the occasion, then filling in this scale by the insertion of fresh stars between the mem- bers. The stars of the first magnitude actually above the horizon at the time of commencing observation were first arranged, and others of that magnitude inserted among them as they rose and gained altitude. *« On the very clear and brilliant night of the 26th November last, being engaged in a process of this kind, I was surprised, and I may almost say startled, by the extraordinary splendour of a Orionis, 312 Royal Astronomical Society :—Sir J. F. W. Herschel which far exceeded my idea at the moment of what was its natural state. Proceeding to compare it with other stars of the first magni- tude (Sirius being, of course, out of the question), their arrange- ment for the night was found to be as follows: Capella {] a Orionis | Rigel || Procyon ||| Aldebaran | Pollux. «‘In this and subsequent arrangements of the same sort, the number of vertical strokes between the names indicates the estimated amount of interval, or the grades or steps of magnitude by which the stars differ. Thus, the step from Capella to a Orionis is a great one; that from a Orionis to Rigel, a distinct but moderate one ; from Rigel to Procyon, a great one, admitting of the easy insertion of astar decidedly inferior to one, and superior to the other, between them ; from Procyon to Aldebaran, avery great step, admitting, at least, two such insertions of imaginary stars decidedly diverse in lustre between them; and soon. Now as I distinctly recollected having, on a great many occasions, placed a Orionis nearly on a par with Aldebaran, there could be no doubt of a change. Referring next morning to my father’s Catalogues of Comparative Brightness, I find that he makes the star in question slightly inferior, or at most equal, to Procyon, and much greater than Aldebaran. ““ In consequence of this observation, I proceeded forthwith to draw out in order all the comparisons of a Orionis with other stars made at the Cape, on the voyage homewards, and since my return. In so doing, I must confess I was hardly less surprised than at the sight of the star itself to find in my star-lists, containing the results of a partial reduction and arrangement of my Cape observations, a Orionis not merely marked as variable, but distinct entries made of it in that list at its maximum and minimum,—the maximum being stated as above Rigel, the minimum below Aldebaran. ‘This, however, had entirely escaped my memory, but being thus recalled, and so forcibly corroborated, I resolved to watch the star more nar- rowly in future; the more especially as it seemed to follow, from the tenour of the observations, that its diminution of brightness was likely to be rapid: and so, in fact, it has proved to be.” The author then proceeds to give the observations on which the evidence of the former changes of the star is grounded. They extend over the years 1836, 1837, 1838, and 1839, and are as follows (de- noting, for brevity, a Orionis by the word Orion) :— 1836. March 22. Rigel, Procyon, a Crucis, Orion, Regulus, Pollux. Nov. 12. on Procyon, Achernar, a Crucis, Aldebaran, Pollux. 13. Orion = Rigel. 26. Rigel, Orion, Achernar. Oct. 24. Orion (high), Achernar, Orion (low), Rigel, Aldebaran. Dec. 16. Rigel, Achernar, Orion. 29. Rigel, Achernar, Procyon, Orion, Aldebaran. on the Variability and Periodic Nature of « Orionis. 313 1838. Jan, Rigel, Procyon, Achernar, Orion, Pollux, a Crucis. Rigel, Procyon, Achernar, Orion, Aldebaran, a Crucis, Pollux. 18. Rigel, Procyon, Achernar, Orion, Aldebaran, a Crucis. Feb. 25. Rigel, Procyon, Orion, a Crucis, Pollux, Regulus. April 14. Procyon, Rigel, Orion, Aldebaran, Pollux, Regulus. D vo Jan. 17. Procyon, Aldebaran, Orion, Pollux, Regulus. 22. Rigel, Procyon, Aldebaran, Orion, Pollux, Regulus. Noy. 26. Orion, Rigel, Procyon, Aldebaran, Pollux. On examining the above series, the general order of arrangement (leaving out Orion) is found to be Rigel, Procyon, Achernar, Alde- baran, a Crucis, Pollux, Regulus; and the instances in which the arrangement is different are accounted for by some peculiar circum- stances connected with the observations. ‘Thus, with respect to the observation of October 24, 1837, the author states that the mis- placement of Achernar is accountable for by the circumstance of the two comparisons of Orion having been made (as appears by the notices high and low) first when rising with Achernar then high, and Rigel low; and ata later period of the night with Rigel then high, and, consequently, Achernar low. On January 2, 1838, a Crucis is set down as inferior to Pollux; but these two stars are difficult of comparison, both from situation and difference in colour, and from being, in fact, not very different in lustre. The trans- position of Procyon and Rigel in the observation of the 14th of April, 1838, is unaccountable, except from some unsuspected partial haziness in that part of the sky. This observation was made at sea. With regard to Orion, the observations evidently show three maxima, viz. in Nov. 1836, Oct. 1837, and Nov. 1839; and also three minima, viz. those of March 1836, Jan. 1838, and Jan. 1839. «Reasoning from this, the most obvious conclusion is that of an annual, or nearly annual period. But in that case, we must admit the decrease to be comparatively sudden, and the increase slow; whereas, if we admit of a period of about six months, this supposi- tion will not be necessary, and as the star cannot be observed (for this purpose) in the summer months, there is no primd facie reason against adopting the latter period; respecting which, however, further observation will soon enlighten us.” The observations subsequent to Nov. 26, 1839, confirmed the expected decrease of the star in a very decided manner :— 1839. Nov. 30. Rigel | Orion, Procyon || Aldebaran. Dec. 11. Rigel | Orion | Procyon || Aldebaran. 29. Rigel, Procyon, Orion, Aldebaran. 1840. Jan. 2. Rigel || Procyon | Orion || Aldebaran. 5. Rigel || Procyon | Orion || Aldebaran. 6. Rigel || Procyon || Orion || Aldebaran. In a note to this last observation, it is stated that “ the difference between Orion and Aldebaran is evidently and rapidly on the de- crease. ‘The stars are all high, at nearly equal altitudes, and ad- mirably arranged for comparison.” 314 Royal Astronomical Society :—Sir J. F. W. Herschel Jan. 7, 1840. ‘‘ Procyon, Orion, Aldebaran, form a succession by nearly equal steps.”—‘‘ Upon the whole, I think it may be stated, that in the interval from November 26 to the present date (January 8), Orion has sustained a loss of nearly half its light. It may easily be supposed that a diminution, thus evidently still in rapid progress, will, in no long time, carry down the rank of this star below that of Aldebaran, and that the confirmation or disap- pointment of this expectation is awaited with no small interest.” The author concludes with the following remarks :— ‘< The subject of variable and periodical stars has been of late rather unaccountably suffered to lie dormant; a state of neglect in which, as I have already observed, it ought not to be suffered to remain, and from which I have endeavoured to rescue it on two former recent occasions, by pointing out the stars a Hydre and a Cassiopeia, both large and conspicuous stars, as belonging to the latter class. A periodical change, however, existing to so great an extent in so large and brilliant a star as a Orionis, cannot fail to awaken attention to the subject, and to revive the consideration of those speculations respecting the possibility of a change in the lustre of our sun itself which were put forth by my father. If there really be a community of nature between the sun and fixed stars, every proof that we obtain of the extensive prevalence of such periodical changes in those remote bodies, adds to the probability of finding something of the kind nearer home. It is only in com- paratively very recent meteorological observations that we can ex- pect to find that precision in the determination of temperatures — which is necessary to establish the absence or presence of periodical change in the intensity of solar radiation; and if the period be not annual (as there is no reason why it should be), the usual mode of combining observations of temperature followed by meteorologists is altogether inappropriate to the research, which can only be carried on either analytically, by the introduction of a periodical term with unknown coefficiert, epoch, and period, or graphically, by projecting in a continuous curve the mean daily temperatures during a long series of years. For the detection of a period of great length, ex- tending over more than a year, the continued observation of the temperature of the water a few feet below the surface in open sea, under the equator, on the principles pointed out by M. Arago in his instructions for the voyage of the Bonite, would suffice. But we are far from possessing as yet sufficient records of such obser- vations to be worth discussing in this point of view. Such obser- vations must of their nature be casual. Even granting that in every ship which traversed the equator the requisite observations were made, the identity of their thermometric standards would be still open to question. “The assiduous observation in fixed physical observatories of the temperature of the earth, at several depths below the surface, extending from three to thirty feet—an element which we know to be (in its mean amount) solely dependent on solar radiation— would be in every respect more immediately and practically appli- cable to the inquiry, and we may expect to see it carried out into on the Variability and Periodic Nature of « Orionis. 315 effect. The direct measure of the solar radiation, too, by the actino- meter*, ought by no means to be neglected in this inquiry. «« M. Poisson, in a late memoir, has considered the possible con- sequences, in a geological point of view, of the sun and solar system having, in long by-gone ages, passed through a region in which the actual temperature of space should be much greater than in its present locality +. The great authority justly attributed to every idea thrown out by this philosopher, must render it a matter of dif- fidence and difficulty to maintain a contrary view. Without, how- ever, as a matter of abstract speculation, denying this possibility, I would observe that the temperature at any given point of space can arise only from two sources: Ist, That of the ether, as a fluid susceptible of increase and diminution of temperature ; and, 2ndly, The radiation of the stars. Of the temperature of the ether as a fluid, I confess I have no conception. Of the existence of such a fluid as the efficient cause of light, we have demonstrable evidence. But the properties of heat are so linked and interwoven with those of light, that it is asking more than can be granted to demand our admission that the ether is a fluid capable of being heated and cooled, while it is yet undecided (with a leaning to the affirmative side) whether it be not the efficient cause of heat itself. «* As regards the radiation of the stars.—There is a region in the heavens where starlight is decidedly more dense than elsewhere— the milky way. And we have, I may almost say, ocular evidence that our system is excentrically situated within that zone, and nearer to its southern than to its northern portion. Granting a perfect transparency of the celestial spaces, the brightness of any given region of the sky must be alike at all distances, whether we conceive that brightness to be uniformly diffused over its surface, or to emanate from a finite number of undistinguishably small points. Now, although the brightness of the southern regions of the milky way may, for argument’s sake, be admitted to be three or four times that of the northern, yet, as that light is almost com- pletely obliterated by the presence of a full moon in any part of the sky above the horizon, it follows that the brightness of the general firmament to a spectator placed within the brightest part of the milky way (supposing him not within the range of an individual sun), must be less than that of (not the full moon itself, but) that general illumination which the moon communicates to the whole sky by atmospheric reflexion ; i.e. an almost infinitesimal quantity compared to the direct light of the lunar disc, the intensity of which can hardly be to that of the sun in a higher ratio than one to half a million. “ The brightest regions in the sky—i.e. the brightest spaces * «< This instrument was devised by me for the dynamical measure of the solar radiation in the spring of 1824; and I have had it in use ever since, with continually increasing confidence in its indications.” [See p- 78 of the present volume.—Enir. (t A Translation of M. Poisson’s memoir will be found in the Scirn- tiric Memoirs, vol. i. p. 122.—Ep1r.] 316 Intelligence and Miscellaneous Articles. having a visible area—are those occupied by the planetary nebule. Of these, there is none which can be compared to Uranus in intrinsic brightness, to say nothing of the moon. Supposing, then, our system to be suddenly plunged into the bosom of one of these nebule, an increase of temperature would take place less than that which would arise from superadding to our own that which the surface of Uranus receives from the sun, or less than the 400th part of that which we actually receive from it; and this supposes Uranus to reflect all the light incident on it. ‘« Leaving to others to judge, however, how far these arguments are to be considered as militating against the view of climatological changes in remote antiquity above alluded to, I may remark that it is a matter of observed fact, that many stars have undergone in past ages, within the records of astronomical history, very extensive changes in apparent lustre, without a change of distance adequate to producing such an effect. If our sun were ever intrinsically much brighter than at present, the mean temperature of the surface of our globe would, of course, be proportionally greater. I speak now not of periodical, but of secular changes. But the argument is complicated with the consideration of the possibly imperfect transparency of the celestial spaces, and with the cause of that im- perfect transparency, which may be due to material non-luminous particles diffused irregularly in patches analogous to nebule, but of greater extent—to cosmical clouds, in short—of whose existence we have, I think, some indication in the singular and apparently ca- pricious phenomena of temporary stars, and perhaps in the recent extraordinary sudden increase and hardly less sudden diminution of n Argus.” Elements of the comet visible at this period, computed by Dr. Petersen, and received from Prof. Schumacher; and parabolic ele- ments of the same computed by Prof. Henderson, are given in the Monthly Notice for January. XLV. Intelligence and Miscellaneous Articles. DETECTION OF IODATE OF POTASH IN IODIDE OF POTASSIUM. BY MAURICE SCANLAN, ESQ. T appears that hydriodic acid is sometimes exhibited as a thera- peutic agent, and the method resorted to for its extemporane- ous preparation is that recommended by Dr. Andrew Buchanan, of Glasgow. It consists in mixing together, in proper proportion, iodide of potassium and tartaric acid, both in solution. Now, the quantity of free iodine liberated from this salt, which I have under examination, when treated with tartaric acid, in the way just mentioned, has led some dispensing chemists to suppose that it contains more iodine than other specimens of iodide of potassium, which, when treated in a similar way, afford a solution that is colourless, or, at most, of a very pale yellow colour; and hence, as I am informed, some actually look upon tartaric acid as a Intelligence and Miscellaneous Articles. $17 test of the value of commercial iodide of potassium, assuming the salt of which we are now speaking as a standard of comparison. How far it may be depended upon as a test, will appear from what follows. If tartaric acid in solution be added to a solution of pure iodide of potassium, the commixed solutions are at first colourless, but quickly become slightly yellow, owing to the action of atmospheric oxygen on the hydriodic acid which is thus generated. On making this experiment with the salt in question, I found, to my great astonishment, that free iodine, in quantity, was in- stantly developed. I was at first at a loss to account for so great a difference in the behaviour of this salt to that which I had prepared myself, and knew to be pure iodide of potassium; but from the ap- pearance of the crystals of this salt, and from the circumstance of its not being soluble in water to the extent that it should be, I Suspected the existence of iodate of potash in it, and I have since convinced myself of the fact of its presence. { find, if we add tartaric acid solution to a solution of iodate of potash, no change of colour takes place, but that bitartrate of potash is deposited in abundance, and, as a matter of course, iodic acid set at liberty : this solution instantly decomposes iodide of potassium in solution, giving rise to free iodine in great abundance ; or, if we add a drop of solution of tartaric acid to a solution of pure iodide of potassium, to which even a minute quantity of iodate of potash has been added, free iodine is instantly developed. Tartaric acid appears, then, from the experiments I have made, to be a very delicate test of the presence of iodate of potash in iodide of potassium, and will be found a very ready and useful one for this purpose in the hands of the dispensing chemist, showing him that any specimen of this salt in which free iodine is thus de- veloped, is actually of less value than one in which no trace of iodine appears on the instant of its application ; inasmuch as iodide of potassium, in a given weight, includes more iodine than iodate of potash does; as is seen at once by the atomic composition of these two salts. It is well known to every chemist, that one of the methods very commonly resorted to for the production of iodide of potassium is that of acting upon iodine with potash water. In this way we form lodate of potash at the same time; six atoms of potash and six atoms of "iodine giving birth to five atoms of iodide of potassium, and one atom of iodate of potash; which latter, if suffered to re- main mixed with the iodide, would increase the produce of the manufactured salt nearly five per cent., at the expense of its purity and crystalline beauty.—Lancet, Aug. 29, 1840. ON PEPSIN—THE PRINCIPLE OF DIGESTION, M. Wasmann has succeeded in isolating pepsin, the peculiar prin- ciple of the gastric juice, described by M. Schwann, in the follow- ing manner ;— The glandular membrane of the stomach is to be separated with- out cutting it; it is to be washed and digested in distilled water at 318 Intelligence and Miscellaneous Articles. a temperature of 86° to 95° Fahrenheit ; after some hours the liquid is to be poured off, the membrane is to be again similarly digested, and to be treated with cold water till it exhales a putrid odour; it is then to be filtered; the filtered liquor is transparent, slightly viscid, and exhibits a remarkable digestive power when a small quantity of hydrochloric acid is added to it. In order to extract the pepsin in a pure state, acetate of lead is to be added to this liquor; the precipitate is washed, diffused in water, and decomposed by a cur- rent of hydrosulphuric acid. The filtered liquor is ais and has an acid action, owing to the acetic acid. When this liquor is evaporated at 95° Fahrenheit, to the consist- ence of a syrup, and absolute alcohol is added to it, an abundant flocculent precipitate is formed, which on drying leaves a yellow gummy matter, which does not attract moisture, and is pure pepsin. This substance easily dissolves in water, and the solution, even though it contains only 1-5000, dissolves slightly acidulated white of egg, in about six or eight hours. The aqueous solution has an acid action owing to some acetic acid which remains intimately combined with it; it cannot be separated from the pepsinate of lead, even by repeated washings. By ebullition this liquor loses its di- gestive powers. If the free acid which it contains is cautiously saturated by potash, a small quantity only of which is requisite, flocculi are deposited, and the digestive power is also lost. The alkalies cautiously added to the solution of pepsin, till the free acid is saturated, occasion the formation of flocculi, and the li- quor has noacid action. Sulphuric acid in small quantity produces white flocculi, which redissolve in a slight excess of the acid; by the addition of a further quantity, fresh flocculi are produced; hy- drochloric and nitric acids produce the same effects. Perchloride of mercury occasions a precipitate which is redis- solved by an excess of it; the proto- and persulphates of iron and the sulphate of copper precipitate pepsin. Alcohol precipitates it from a concentrated solution. According to M. Pappenheim, this precipitate dissolves in hydrochloric acid, and dissolves boiled white of egg. M. Wasmann confirms this statement of the digestive power of the precipitate formed by alcohol, while, according to M. Schwann, alcohol destroys the digestive property of pepsin. * Pepsin is recognized by the precipitates which its solution gives with diluted acids, and which redissolve in an excess of the acids, and by its giving no precipitate with ferrocyanide of potassium. It is distinguished from albumen by the precipitates which its solution yields on the addition of water and hydrochloric acid; and from caseum, by its acid solutions yielding no precipitate with ferrocy= anide of potassium.—Journal de Chimie Médicale, Aout, 1840. DECREPITATING SALT OF WIELICZKA. BY H. ROSE. This salt was first noticed by M. Boué, who sent a specimen of it to M. Dumas; it is distinguished from common salt by decrepitating not only when it is heated, but when dissolved in water ; during so- lution decrepitation occurring with the disengagement of gas. It is evident that this gas was confined in the salt in a state of strong Meteorological Observations. 319 condensation ; and this is the cause which occasions the decrepitation both by heat and solution in water. M. Dumas found that the gas extricated from this variety of salt, when mixed with oxygen gas, detonated like hydrogen; nevertheless he supposed carbon to exist in it. He had not a sufficient quantity of the salt to examine more minutely the gas condensed in these crystals. M. H. Rose received from Professor Zeuschner of Krakaut, a con- siderable quantity of the detonating salt, and he has been enabled to repeat and verify the experiments of M. Dumas. The different portions of salt did not all give the same quantity of gas when dis- solved in water. The maximum, as stated by M. Dumas, amounted to about half the volume of the salt. The gas, when burnt with oxygen, gave nearly the same compo- sition as pond gas (CH). This product is probably so condensed as to exist as a liquid or solid in the interior of the salt, and resumes the state of an elastic fluid at common pressures. The property which this salt possesses ought in future to direct the attention to a great number of minerals which occur in nature, and which decrepitate in the fire without our being able to attri- bute it to the disengagement of moisture. It may be that the cause of the decrepitation is the disengagement of a gas condensed in the mineral.—Ann. de Chim. et de Phys., Mars, 1840. METEOROLOGICAL OBSERVATIONS FOR AUG. 1840. Chiswick. Aug. 1, 2. Very fine. 2—9. Hotanddry. 10. Very fine. 11. Showery. 12. Cloudy: rain. 13. Cloudy. 14. Rain. 15. Very fine: show- ery. 16. Fine. 17. Boisterous with heavy rain. 18. Cloudy. 19. Heavy rain: cloudy and fine. 20. Fine. 21. Foggy: very fine. 22. Foggy. 23— 26. Very fine. 27. Foggy: fine. 28. Slight fog: rain. 29. Foggy. 30, 31. Cloudy and fine. ‘The mean temperature of the month was nearly 2° above the average. Boston.— Aug. 1—3. Fine. 4. Cloudy. 5—10. Fine. 11. Rain, 19, 13. Fine, 14, Cloudy, 15. Stormy: raine.m. 16, Fine. 17. Stormy: rain early A.M.: rain with thunder and lightning p.m. 18. Stormy, 19, 20. Cloudy. 21. Fine: quarter past three p.m. thermometer 80°. 22. Cloudy: rain p.m. : lightning at night. 23,24. Fine. 25. Fine: rain pM. 26,27. Cloudy. 28. Fine. 29. Cloudy. 30. Fine: rain p.m. 31. Cloudy: rain a.m. N.B. The warmest August since 1826. Applegarth Manse, Dumfries-shire—Aug. 1,2. Very fine. 3. Mild: show- erya.M. 4. Fine. 5. Sultry. 6. Sultry: heat oppressive. 7—9, Sultry. 10, Wet and boisterous p.m. 11. Showery. 12—14. Occasional showers. 15. Fair throughout. 16. Much rainr.m. 17. Heavy rain: thunder: high flood. 18. Fine drying day. 19. Fine, with one slight shower. 20. Drizzling all day. 21. Fine: raine.m. 22, 23. Fine and fair allday. 24, 25, Showery. 26. Fair all day and clear sky. 27. Wetr.m. 28. Fair all day. 29. Drizzling all day. 30. Fine and fair all day. 31. Remarkably fine harvest day. Sun shone out 27 days. Rain fell 15 days. Thunder 1 day. Wind north-west 5days. Last-south-east 1 day. South-east 4i days. South 7 days. South-south-west 4 days. South-west 84 days. Variable 1 day. Calm 12 days. Moderate 11 days. Brisk 5 Ae Boisterous 2 days. Mean temperature of the month............ 57°60 Mean temperature of August, 1839 seven 55 *70 Mean temperature of spring water ..... ) SBi°8S ni oe 6S a9 09 19 6S 19 oc PUL’? G "a09 “AOY *"puo'yT yurod Mod SP ST AS rreee'nnn"w""ns | -ueayy | 69-€ | 2z-1] 29-1] ° OLOrt wing G.1S|L-19] &-F9'g9-25|00-9L] 6-LS | L-2 | €-9 |LSL-62 876-62 spi ne ae ame as | ee TY | to) 6a) ge) PL: op Ek Oe8.| SE 9IL.0€ | Pgt.0€ | “Ie Me ior mss fue] “Mm | "a FPS REQ] 69] gS | ZB | 0-8} 0-69) 8-99 | ST-0F €¢0.0€ | gzt-08 | "of OUTS) oe 0 | oes See spre %¢9 G-P9| LG | €L | 0.09] 0-2L | 6-09 | $6-6% OF1-0€ | Foz-0€ | °6z Be ee ee Ne ae to eo. 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OL), 98 | OBs| Oral Teh) Pak, 20-08 166-62 | 020-08 | *Z Dee | aes ee ae | oa SPN | POEL) goo + Vee) Ono DEO B0" Bb-08 696-62 | Pf0-08 | *9 ee eee ene ie Seep eas. GL| IL] SS | 28 |0-69| 9-89 | Z-L9 | 90-08 1g0-0€ | oST-o€ | “S © ec |g Oe IRIS) SA Se ih G94 OF |) OB) Cale reee G.L9 | $0.08 L1T-0€ | 881-08 | ‘V Pe ey leas as |e Ss Fed 260! Oli eP | -Le.| O90 | OE) ObiOF 191-08 | PPz-08 | *€ fe ee Tae pas eae tae) S| Bu 00) by . As Cu? f Cu? since beside 14 per cent. of arsenic, it contained 3 per cent. of sulphur. ‘The copper amounted to 7:86 per cent. How- ever, the iron and cobalt were separated in a defective manner, whence the former contained a considerable amount of cobalt. ‘The analysis needs therefore repetition; although, since iron and cobalt do not differ much in their atomic values, scarcely any essential change in the formula might ensue. XLIX. Examination of a crystallized Nickel Ore. By WituraM Francis, A.2.8.+ HE combination which is the subject of the present paper, although consisting mainly of arsenic and nickel, yet has to be distinguished from the kind of nickel ore analysed some time since by Professor Wohler. Whilst the latter is crystal- * T obtained of Dr. Marchand, who is at present engaged in very inter- esting experiments on alloys for fire arms, a piece cf dendritic copper bearing very great resemblance to the native.—Scu. + Communicated from Berlin by the Author, 336 Mr. W. Francis’s Examination of a crystallized Nickel Ore, lized in octahedrons, and is deposited from the smalt fur- naces ; the former is crystallized in large laminee, very similar to the second cobalt ore described in the preceding Article, and is evidently the product of a further process of purifica- tion: nor was it obtained directly from a smalt-work, but from the German silver manufactory of Mr. Henniger in Berlin. ‘This process of purification seems to resemble that which is practised at Modum with the cobalt ores. _ The analysis was performed in the laboratory of Professor Henry Rose; and the course pursued quite similar to that employed for combinations of arsenic. The nickel and iron, however, were not separated by succinate of ammonia, but determined according to Dr. Scheerer’s method. The result of the analysis was Sulphur ....cccccee 1°01 ATSENIC scvesesveree 34°07 NICKEL es wa vesteedass) ACI aG Cobalt. sscsaii se mae, (S28 TORS. b. cesecirsecse LOG 101°00. The peroxide of iron obtained was again dissolved in hy- drochloric acid, and precipitated by ammonia inexcess. Sul- phuret of ammonium produced no perceptible alteration in the filtered ammoniacal fluid. From the obtained oxide of nickel, however, 0:009 grammes of nickeliferous peroxide of iron were separated by solution and the addition of ammonia: which quantity had not been separated by the above method. In this separation, therefore, Dr. Scheerer’s method gave a better result than that with succinate of ammonia in the analysis of the cobalt ore described in the preceding Article. If it be admitted that the slight quantity of sulphur takes the place of a part of the arsenic, the atomic weight of the ar- senic is to that of the other metals as 7°74 + 18°10, therefore, exactly as in the combinations detailed in the pre- ceding Article. The formula for this nickel ore would ac» cordingly likewise be Ni? Co’ + As°® re: In this case the atomicproportion should be Gi 6 rie og Us coinciding, therefore, very nearly with that given by the ana- lysis. If, on the other hand, the formula Ni® Co® + As? Fe°® Mr. W. Francis’s Examination of a crystallized Nickel Ore. 337 were adopted, the proportion 743 19°35 would differ more from the result of the analysis. According to the first supposition, the combination, in 100 parts, should consist, admitting only nickel and arsenic as essential consti- tuents, of ATSeENIC ...02. 35°25 Miekelwceda0 GL*75 and with this the analysis agrees exceedingly well. According to the second formula (Ni° As*), on the contrary, the compo- sition should be FMPSEMMCH:. ocle a's GetOO INTE toc 4 eee 66°31. Now, whichever formula may be considered as most cor- rect, thus much is certain, that the combinations described in the preceding Paper, and in this, are by no means composed according to simple relations, as 1: 2, or 2: 3; nor will this appear at all extraordinary, in a metal such as arsenic, which forms an acid consisting of two atoms of radical and five atoms of oxygen. It is, indeed, questionable whether the formula Ni? As?, laid claim to by Prof. Wohler for the nickel ore analysed by him, does not likewise possess an atomic rejation similar to that of the combinations here treated of. Now the proportion 2: 3, 3: 5 approach one another very nearly, as the following calculation shows :— Ni? As? Ni? As? Nickel..... 54°15 6°75 Arsenic... 45°85 43°25. Professor Wohler, however, found the composition to be Nickel oS )3.07° 55 Arsenic ..... 44, approaching, therefore, nearer to the formula Ni? As? than to Ni? As’. It is therefore very probable that the number 5 also occurs in the atomic relation of the constituents in this combi- tion; and there would then have been found on the whole the following proportions between cobalt (or nickel) and arsenic: Third cobalt-combination Co® = (?) First and second do. as like- Nis Ast 04 Nh bas 3 wise purified nickel ore Common nickel ore ....... on As*. The middle combination will, according to theory, be re- garded as far more probably Co® As’; although the results of the analyses bring it nearer to the formula Co’ As’. Phil, Mag. S, 3. Vol. 17. No, 111, Nov. 1840, Z [368] L. On the Variation of the Semi-axis Major of the Moon’s Orbit, By Joun Witi1am Lussocx, Esq., Treas. RS. F.R.AS. and F.L.S., Vice-Chancellor of the University of London, &c. OISSON, in his Mémoire sur le Mouvement de la Lune autour de la Terre, has considered the following theorem, that the expres- sion for the variation of the semi-axis major contains no argument of long period, accompanied by a multiple of m less than m*. In this paper he has taken into account the terms which arise from the second approximation, or that in which the squares and pro- ducts of the quantities 6% da, Se, 80, dy and da may be neg- lected. It is evident that terms may arise in the next, and in- deed in every succeeding approximation of the order m°, which must be taken into account in order to prove the proposition with sufficient generality. Thus the variation of the eccentricity con- tains terms multiplied by m, as of the argument 9, (27 — 2); these, multiplied by others of the order m’, give in 8 e® terms of the order m*, and these multiplied by rn give in Te dz terms multiplied by m’*, which after integration become of the order m°; if the argument being of the kind under consideration, the divisor introduced by integration is of the order m*. It is true that Poisson refers to his Mémoire sur la Variation des Constants arbitraires Mém. de ? Academie, tom.i., for an extension to the third approxi- mation, that is, to terms depending upon the cube of the disturbing force. In this paper, however, expressions are employed, which take for granted that the disturbing force can be exhibited in the same form, developed in terms of the initiai values of the coordi- nates x, y, z, and of the initial values of their first differential co- efficients os . a This development has never been exe- cuted, nor has it been shown to be possible. When this system of constants is employed, the quantities which are equivalent to [ a, w], [a,e], &c., become equal to unity and rigorously constant, so that it is unnecessary to consider the effect produced by their variation. Even, however, with the simplifications which recourse to this pe- culiar system of constants affords, Poisson admits that this demon- stration would become too complicated to admit of its extension to the higher powers of the disturbing force. M.de Pontécoulant has made objections to the proof given by Poisson, but as he differen- tiates* in a manner at variance with that intended in the expressions of which Poisson makes use, and does not allude to the Memoir in question, in which a further approximation is attempted, these objections are not to be considered as exactly identical with those of that distinguished astronomer. * Conn. des Temps, 1840, p,21. Variation of the Semi-axis Major of the Moon’s Orbit. 339 In the Lunar Theory terms of the order m?%, and of the nature of those under consideration, may arise not only in the third but in every succeeding approximation, and hence it becomes absolutely necessary to seek some mode of proof which admits of unlimited extension, and I have therefore endeavoured to modify the proof given by Poisson, so as to include all terms of the order m°®, how- ever far the approximation be pushed, and without introducing any peculiar system of constants. For this purpose it is necessary to suppose the disturbing fune- tion & = (R) + (Sz)?s+ (Ga)? + (7) Se dR dR day TER + (Ge) e+ (qT) 2+ (S>) y+ (a) dk _ dR dt” de and to define 8f 8a, 8c, &c., to represent, not the total variation of the quantities % a, c, e, &c., as in Poisson’s paper, but that por- tion only which consists of arguments corresponding to those in- equalities which are not depressed by integration, as will be pre- sently explained. ‘The effect of the secular inequalities of the con- stants c, w and a, and_also that of all the other inequalities of which the arguments are independent of c, are supposed to be already included in the quantities (R), (52), (=). &e. As the constant c in Poisson’s notation always accompanies 7 ¢, all the arguments in the development of # may be properly repre- sented by an expression of the form (nt +c)+jmti+lti+ 6, _where z and 7 are whole numbers or zero, 7 a certain multiple of m? depending upon the secular variation of the angles c, , a, and Ba quantity rigorously constant, which accompanies /¢, but which I shall in future omit to write down. Whenever 7 = 0 without be- coming = 0 at the same time, the corresponding inequality in the expressions for the elliptic constants is necessarily a multiple of m at least, and only when z and 7 are both equal to zero the correspond- ing inequality in each of those expressions may no longer be mul- tiplied by m. dea =; ej Stay - (a, 0] $2 de + &e, Z2 f= ni WO? maa te 2 340 Mr. Lubbock on the Variation of ao = 16, a) det [oa] Sat + &e. The quantities between brackets may be considered as constant in the first approximation, and such that [e, a] = — [a, c] [w,c] = — [c, |. Similar theorems exist with respect to all the constants, and it is upon this property that the theorem in question may be said to de- pend. Ifa, e, y, c, w, «, have the same signification as in Poisson’s memoir (Mémozre de [ Institut, tom. xiii.) las'e] = 0 [a, y] ==.Q [e, ¥] = 0 [,e1=0 [ey =O [oa] =O} but these latter theorems do not appear to influence the proposition of which the proof is required. In differentiating the disturbing function with regard to c, as in- dicated in the expression a being the semieaxis major, R must be differentiated only with re- spect to c, inasmuch as it was contained in # primitively, and not as it is introduced in further approximations by the variations of the elliptic elements. As, however, the secular variations and those multiplied by m and m°, which I have already included in dk dk (f), Te) ( 4): &c., do not contain z or c, and as therefore c only occurs in the quanti- ties dk dk (ZR), aa) (a) &c.5 as it was introduced primitively *, dk _ d(k) d? R aude (= , iciancicke +(55 b+ (7-7) ea + dc? oi ad? k da? k d? Fk d° R i es BF +545 bat (7 1.) ?y*(aeae - 6%, da, be, &c., denoting here only that portion of the variations of & a, e, &c., which consists of periodical terms not independent of 7, and therefore multiplied by the square of m at least. * This remark applies solely to the constant c, and to no other. the Semi-axis Major of the Moon’s Orbit. 341 Bee 5" (ads, and it is sufficient to take da 1 a? R dk Tea ag (Sega f iadt— Fa) +21 (£# yea d? R Pek wi de oma) aig dc? i dedcan PR \ bo CR \ sy Fae bok Plehao isa) — This equation is similar in appearance only to the equation (A) of Poisson, p. 259, for the quantities 8 a, dc, de, &c., are here dif- ferently defined. I omit here all consideration of the terms 1 aR eal?" Te an because the proof which Poisson has given in his Mémoire sur le Mouvement de la Lune, is completely satisfactory with reference to them. dc de In the terms xs. &c., it is necessary to consider the va- a riation of the quantities [a, w|, [e, w], &c., and also that of the quantity d e contains the term dk [e, w | da o% which may be taken as a type of others ; a 11 (Fe marx f f esl (Sac ope (qe) a ~/'22) Bas 8% fon (HB) 342 Mr. Lubbock on the Variation of It must be recollected that in this expression no terms are included in de or [ [e, 0] = which are independent of c. If (Se ): as defined and limited in the expression for # in p-. 339, contains any term A cos (i (nt +c) +jsmnt+Int), d@ contains the term [a,w] 4 cos (Z (nt +c) +ymnt + ini); and considering now only the constant portion of [a, |, 3 con- tains the term A CAA epragrrareg en (2 (né +c) +ymnét + int). Similarly, if (S=) contains the term Bsin (i (nt +e) +ymnt+ Unt) de contains the term fo,e] Bsin (¢(nti+c) +ymnt+/ nt), &e contains the term B — [o, lar imudin eG c) +jmni+Tntz?), and these terms give, after well-known reductions, in 4 a pit Nae it AB SS n(itjmt+)l(itsm+?l) which is evidently of the order m+, 4 and B being each of the or- der m*, and z of necessity not equal to zero. ee I now proceed to consider the effect of the variation of the quan- lity cos (// — 1) Z, [e, @] an ’ which may be taken as the type of other similar quantities. Let [eel = C+ Deos(int+jmnt + Int) the Semi-axis Major of the Moon’s Orbit. 343 ade) = Acos (nt +j'mnt +1 nt) eel (oe =)= CAcos (int +jmni + lnt) + 7A cos (int —int +j'mnti—jgmnt+lnt—Int) + 24 cos (int + int+jimnt+jmnt+Uni+ ln?) Let (a) = Bsin (nt +3" mnt + l' nt) eal (5 ae CB sin (2""nt +7"mnt + l'nt) + s8 sin (2"nt —int+j"mnt—jmnt + l'nt —Int) +23 sin (int +int+j!"mntitjmnt+t l'nt+int). Red Ta) a an \dw cos (f/ nt +7” mnt+l” nt) aollaal 94 i +i m+l)\n _ DB cos’ nt—int+j’mnt —jmnt+l’n t —Int) 2 (4 —itjy’m —jm+l’—l\n _ DB cos (t’nt+int+j’mnt+jmnt+ l’nt+inte) 2 i +itj mtjm+l+in — fie, a) Stat sa s / baa pt os sin (/nt+jymnt+Unt) @+ym+l)n DA sin(/nt —int+j'mnt—jmnt+l nt — Int) 2 @—i+j’m—jgm+Ul—)n | _DAs sin (’nt+int+jy’mnt+jmnt+lnt+lnt) 2 @+itym+jnm4+l+))n 2 (7-4 a ;) = —7 Asin(/ nt +,/' mnt +n 344 Mr. Lubbock on the Variation of ( d?R | dwdc ) = 2" Boos (i! nt +9" mnt + l'né). These terms give in c (Peyee @R dw Acaciie Gale oes and therefore 5 2 a tS = " +2) Laas (a) oe —) - and hence the following terms : 7 CBAsin (nt +y'mnt + Unt) cos (2"nt +7" mné + int) + yj" m+tl\n iDBA + 3 sin (nt +7’ mnt + I nt) cos (7!nt —int +7" mnt —jmnt+ l'nt —Ind) (a —i+ y"m —jm+l'—l)n i! DBA te @ sin (2!n¢ + 7! mné + Int) cos (2"nt+int +7" mnt+ymni + l’nt+int) 42+ 7"m+7m+l'+1)n — 2! CBAcos (i'n +7" mnt + Unt) sin (’né + 7'!mnt +2 n2) (+ y'm + l)n a ad Fatt Big ("nt +7" mnt + l'nt) sin (7)nf—int+ 7! mnt —jmnt+Unt—lnt) (7) —i+jy'm—jn+l—l1)n — te ees ("nt +9" mnt +l" nt) sin(?néi+tint+y'mni+jgmni+l nt+ Int) (J+itym+jm+l+_l)n ; The terms multiplied by CB A, which arise from the constant portion of [e, w], have already been considered, the rest form four the Semi-axis Major of the Moon’s Orbit. 345 pairs, of which the following is one, and may be taken as a type of the rest: DBA 4 a An — t+ y"m —gmtl"—L f+i+y'm+ym4l+l sin (zn ¢+)' mnt+l' nt—i! nt+int—j"mni+jmni—l'ni+int). In order that this argument may be of the kind under considera- tion, we must have 7—7!'4+7=0 jim —j"m+jm = 0, and the term becomes in that case DBA q! 4n Lt" —i+y"m—gm+l'—1 ul in (dl el! —FETEFw aware y MM + Dae if 7 is not equal to zero, Dis of the order m, and the coefficient of sin (/ — 7?" + 1) nt, after a fresh integration, remains of the order a: th 2 = 0 gq = 7! the coefficient becomes Beas jim+tjm+U+l—j"mtjm—U 41 \ + jlm —jm tl —D) E+ ym tim t+ U4 D IDBALjn+U—U42 An{i + gy" m—gm +l" —l) a +7 m+jm+i— hy but unless 7 = 0, D is multiplied by m, and im either case, in con- sequence of the reductions which the numerator undergoes, the co- efficient after a fresh integration remains of the order m+. It remains now only to “consider the terms of which the following is the type: d?R : R tric) de Min ne: but as in 8e are here only included terms of the order m’, , fond?) S46 Dr. John Davy on the aqueous solution of is of the order m’, or at least such portion of it as is supposed D) tobeincludedin this expression; and as -—~— and —— are each dedc dc of the order m*, this term is of the order m®, which after a fresh integration remains of the order m?*. Hence we may conclude with safety, without having re-__ course to any peculiar system of constants, or to any preca- rious induction, that however far the approximation be car- ried, the variation of the semi-axis major in the Lunar Theory contains no term of long period multiplied by a power of m inferior to the fourth. a Sept. 21, 1840. LI. Some Observations on the aqueous Solution of Carbonate of Magnesia with excess of Carbonic Acid, and on the Salt which it affords by spontaneous Decomposition. By JoHn Davy, ID., F.BR.S.* T HAVE been induced to institute some experiments on the solution of carbonate of magnesia in water strongly im- pregnated with carbonic acid gas, in consequence of the high repute, on very questionable grounds, which it has lately ac- quired as a medicine. The solution I have used is that prepared and sold by Mr. Dinneford of New Bond-street, with the designation of Dinne- ford’s Solution of Magnesia, and with the following recom- mendation on the label: ‘* The great advantages of this elegant preparation are, that being in a flucd state and possessing all the properties of magnesia in general use, it is not likely to form dangerous concretions in the bowels; it corrects acidity and heart-burn effectually, without injuring the coats of the stomach, as carbonates of potash and soda are known to do; it prevents the food of infants turning sour, and in all cases it acts as a pleasing aperient, particularly adapted for fe-— males.”’ Such a recommendation I should not have thought it right to notice, were it an ordinary quack eulogy, and unsupported by certificates given by respectable medical men; and more- over were I not assured that great faith is placed by many persons in the asserted virtues of the preparation, and that the use of it is rapidly extending. The first trials I subjected the medicine to, were made with a view to test the permanence of the solution ; as by ex- * Communicated by Sir David Brewster. Carbonate of Magnesia with excess of Carbonic Acid. 347 osure to the air in an open vessel, exposure to a tempera- ture of 100° Fahrenheit, in a vessel loosely corked, and to the action of the air-pump under an exhausted receiver. The result in each instance was very similar; carbonic acid gas escaped, or was expelled, and a salt was deposited in the form of minute prismatic crystals. This separation of the magnesia in a solid form, on the disengagement of the excess of carbonic acid, was no more than might have been expected from the known nature of the compound, and the artificial manner in which it is form- ed by the condensation of the gaseous acid; and must be considered as quite incompatible with the declaration of its ‘fluid state” in the stomach and bowels, and sufficient ground to callin question the propriety of placing confidence in the preparation as a medicine, in preference to common carbonate of magnesia or calcined magnesia, than either of which it is so much more costly an article. The prismatic salt deposited on the escape of the excess of carbonic acid, has been examined by several chemists; rest- ing chiefly on the results of the experiments of Berzelius, and the late Dr. Henry, it has been considered as a hydrated carbonate of magnesia, composed of one proportion of mag- nesia, one of carbonic acid, and three of water, From the experiments which I have made onit, it appears to be composed as follows; viz. 29°61 Magnesia. 32:22 Carbonic acid. 10°27. Water expelled at 212° Fahrenheit. 27:90 Water expelled by a higher temperature, as by ignition. 100°00 or of one proportion and half of magnesia, and carbonic acid, one of water expelled at 212°, and three proportions of water expelled by a higher temperature. Compared with the common carbonate of magnesia, from the results which I have obtained operating on the latter, this appears to differ chiefly from the former in possessing half a proportion more of mag- nesia, and one proportion less of water, being composed of 41°52 Magnesia. 33°31 Carbonic acid. 17°47 Water expelled at 212°. 7°70 Water expelled at a higher temperature. 100:00 These results accord tolerably with those of other inquirers 348 On the aqueous solution of Carbonate of Magnesia. who have examined this compound ; the variation or want of perfect accordance, probably chiefly depends on the degree of dryness of the preparation examined, or on the quantity of water retained in the powder admitting of expulsion at 212°, which water being hygrometrical, at least in part, must vary with the degree of dryness of the atmosphere to which it is exposed. The method by which these two compounds of magnesia and carbonic acid were analysed was a simple one, admitting of considerable accuracy. The quantity of water expelled at a temperature of 212° was determined by exposure of an hour or more to the heat of a steam-bath; the quantity of carbonic acid, by acting on the compounds, very carefully weighed, by muriatic acid, saturated with carbonic acid, over mercury in a graduated tube; and the quantities of magnesia and of water expelled at a higher temperature than 212° by the action of a red heat, continued for two or three hours, till no further loss of weight was produced by a continuance of the high temperature. In estimating the proportion of carbonic acid, the calculation was made on the ground that 100 cubic inches of this gas weigh 47°262 grains. A few words relative to the properties of the first-men- tioned carbonate. Its tendency to crystallize is remarkable : however obtained, even when rapidly separated by the expul- sion of the excess of carbonic acid by heat, it has been de- posited in a crystalline form. This form is not obvious to the naked eye; but when the powder is examined by the micro- scope, each particle is found to be a distinct prismatic crystal. And the persistence of this form is no less remarkable; it is not destroyed by decomposition; the powder after ignition, after the expulsion of the whole of the water and carbonic acid, under the microscope shows no alteration; each particle is still prismatic, and when moistened with water is trans- parent. It is asserted that this carbonate readily loses the water with which it is combined. Ina dry atmosphere it loses a portion of the water, which perhaps may be considered as hygrometrical, and at the same time loses its transparency ; but I find, as has been already remarked, that a temperature of 212° expels only one portion, and that a high temperature is requisite to expel the three remaining proportions, and which are probably the strictly chemically combined water. It is also said that this compound is altered by the action of cold water, and by that of boiling water; that in one On the Electrolysis of Secondary Compounds. 349 instance a solution of bicarbonate of magnesia is formed, and an insoluble carbonate containing a smaller proportion of car- bonic acid; and in the other, that the same insoluble subcar- bonate is produced, but without the solution of bicarbonate, the proportion of carbonic acid required for this being ex- pelled in the form of gas. The results of the trials I have made have not confirmed either of these conclusions. It has appeared to me to dissolve both in hot and in cold water, without undergoing any decomposition. I have not been able to obtain an insoluble subcarbonate of magnesia by acting on the prismatic salt by cold water, or carbonic acid gas from it by boiling water,—for instance, boiling it in distilled water ina retort connected with a mercurial pneumatic apparatus. It is true, that when this carbonate is thrown into hot water, there is a disengagement of air, but the air is common air me- chanically entangled, not carbonic acid gas which had been chemically combined. Both the hot solution and the cold, on evaporation, yielded the prismatic compound. 1000 grains of water at the tempera- ture of 60° appear capable of holding in solution about four grains ; thus 326°6 grains of the solution of carbonate, after the excess of carbonic acid gas had been expelled by the air-pump, oe on spontaneous evaporation 1°5 grain of crystalline salt. Whether this slight degree of solubility can be useful, con- sidering the qualities of the compound as a medicine, or whether the crystalline spicular prismatic form which it as- sumes on separation of the excess of carbonic acid by which the carbonate was brought into solution can be injurious to the coats of the stomach, as a mechanical irritant, it is far from easy to determine; the probability is, reasoning analo- gically, that neither the one nor the other circumstance, me- dicinally considered, is of much consequence. Fort Pitt, Chatham, Oct. 1, 1840. LII. An Abstract of Professor Daniell’s Papers on the Electro- lysis of Secondary Compounds, in the Philosophical Trans- actions for 1839 and 1840. T has been long known that when a saline solution is sub- jected to the action of a galvanic current, both the water and the salt that it contains are resolved into their constitu- ents; oxygen and the acid being evolved at the zincode, whilst hydrogen and the base appear at the platinode. The primary object of these researches was the determination of the re- lative proportions of these decompositions, and their relation 350 : Professor Daniell on the to the amount of electrolytic force in action, with a view to increase our knowledge of the constitution of saline bodies in general, For this purpose an apparatus was constructed in the fol- lowing manner, which Mr, Daniell calls “ the double dia- phragm cell.” ** It consists of two cells formed of two glass cylinders, with collars at their lower ends, fitted by grinding to a stout glass tube bent into the form of the letter U, and firmly fixed on a wooden foot. The ends of this piece project a little into the interior of the two cylinders, the upper extremities of which are furnished with bent tubes for the collection of gases. A stout piece of platinum wire is ground to the upper part of each cell, to which an electrode of platinum or any other metal can be screwed on the inside, as occasion may require: the wires pass down upon the outside, and terminate in two mercury cups, by which connexion can be made, at pleasure, with the battery. Each cell will hold about seven cubic inches of liquid, and the connecting tube two inches. When the cell is charged, the connecting tube is filled with the liquid, and a piece of fine bladder tied over each end, so as perfectly to exclude the air. The bladders are firmly con- fined to their places by means of circular grooves ground round the ends of the glass tube. ‘The cylinders are then carefully fitted to their places, and filled with the proper quantities of the solutions to be acted upon, and after the operation their contents are easily decanted.” ‘The quantity of liquid in each cell during the experiment was about 4°5 cubic inches. ‘The power employed was that of a small con- stant battery of Mr. Daniell’s construction, containing thirty cells six inches in height, with tubes of porous earthenware, charged in the ordinary manner. (See Phil. Trans. for the year 1836.) : From this battery the current was made to pass through the apparatus just described, filled with a solution of the salt to be examined, say sulphate of soda. A common voltame- ter charged with dilute sulphuric acid, was also included in the circuit, so that the mixed gases evolved might be collected, in order to ascertain the exact amount of electrolytic force really in circulation. The gas given off from each side from the double dia- phragm cell was also collected, and the united bulk of the oxygen and hydrogen so evolved was found to be exactly equal to the volume of the mixed gases collected from the common voltameter. From numerous experiments it was found, that on decanting the saline liquid from each cell, and care- Electrolysis of Secondary Compounds. 351 fully neutralizing with acid or alkali, as the case might re- quire, the quantity of salt decomposed was almost, if not ex~ actly, equivalent to the gas evolved. (Thus if 11°8 cubic inches of oxygen had been evolved from the zincode, and 23°6 cubic inches of hydrogen from the platinode [the results of the decomposition of 4°5 grains of water], by neutralization it was found that the zincode cell contained about 20 grains of free sulphuric acid, and the platinode 16 grains of free soda, numbers which are equiva- lent to the quantity of water decomposed; meantime from the single voltameter 35:4 cubic inches of mixed gases [also the result of the decomposition of 4°5 grains of water] had been collected). These experiments were repeated upon sulphate of potass, phosphate of soda, sulphate of ammonia, showing the analogy of ammonia with metallic salts, and nztrate of potass, with corresponding results. The determination of the quantity of alkali in the latter instance was not possible, owing to the formation of a quantity of ammonia at the platinode, from the reaction of the disengaged hydrogen upon the nitric acid of the salt. The carbonates were examined in a similar manner with like results. Oxalate of ammonia yielded nothing but pure carbonic acid at the zincode, whilst hydrogen and ammonia appeared at the platinode. ‘The reason of this is evident from the following formula:— Oxalic acid. Carbonic acid. (2C +30) +0=2(C +20) the equivalent of oxygen afforded by the electrolytic decom- position of the salt being just sufficient to convert one equiva- lent of oxalic acid into two equivalents of carbonic acid. Sulphovinate of potassa was decomposed also in equivalent proportions, the acid and oxygen passing to the zincode whence the gas escaped uncombined—hydrogen and potassa being as usual developed at the platinode. From the preceding ex- periments it appears, ‘* that in the electrolysis of a solution of a neutral salt in water a current which is just sufficient to separate single equivalents of oxygen and hydrogen from a mixture of sulphuric acid and water, will separate single equi- valents of oxygen and hydrogen from the saline solution, while single equivalents of acid and alkali will make their appear- ance at the same time at the respective electrodes.” These relations were found equally to hold good, whether the oxygen was allowed to escape from the zincode of the double diaphragm cell, or whether it was absorbed by an 352 Professor Daniell on the electrode of copper, or of zinc, as in the ordinary cells of the battery. Further experiments showed that whenever dilute sul- phuric acid is used, there is a transfer of acid towards the zincode, and the determination of the proportions in which such a transfer occurs led to some curious results, to which we must presently revert. In order, however, to remove the ambiguity which might thus possibly be conceived to arise from the employment of dilute sulphuric acid as the measure of the electrolytic force, the following arrangement was substituted for the ordinary voltameter: a green glass tube (into the bottom of which, as platinode, was welded a weighed platinum wire) was filled with chloride of lead, maintained in a state of fusion by a spirit- lamp; the corresponding zincode was formed of plumbago. » At the termination of the experiment the tube was broken, the wire and adhering button of lead weighed ; and the result showed that ** the same current which is just sufficient to re- solve an equivalent of chloride of lead, which is a simple elec- trolyte unaffected by any associated composition, into its equi- valent ions, produces the apparent phenomena of the resolu- tion of water into its elements; and at the same time of an equivalent of sulphate of soda into its proximate principles.” Aqueous solutions of the chlorides were next tried, as the simple constitution of this class of salts promised to throw light upon the nature of the electrolysis of secondary compounds. A weighed plate of pure tin was made the zincode of the double cell, which was charged with a strong solution of chlorideof sodium, anda tube of fused chlorideof lead, as before, included in the circuit; not a bubble of gas appeared on the tin electrode, and no smell of chlorine was perceptible, but hydrogen in equivalent proportion to the quantity of tin dis- solved was given off at the platinode, and the cell contained an equivalent proportion of free soda. One equivalent of lead was reduced in the voltameter tube. Muriate of ammonia treated in the same way gave precisely similar results, proving it to be “an electrolyte, whose simple anion was chlorine, and compound cathion nitrogen with 4 equivalents of hydrogen. Its electrolytic symbol, therefore, instead of being (Cl + H) + (N + 3H), is Cl +(N + 4H).” Strikingly confirming the hypothesis of Berzelius of the base (N +4 H) called ammonium. In discussing the results of all these experiments, we must bear in mind the fundamental principle, * that the force which we have measured by its definite action at any one point of a~ Electrolysis of Secondary Compounds. 353 circuit cannot perform more than an equivalent proportion of work at any other point of the same circuit.” The sum of the forces which held together any number of ions in a com- pound electrolyte, could, moreover, only have been equal to the force which held together the elements of a single elec- trolyte, electrolyzed at the same moment in one circuit.” In the electrolysis of the solution of sulphate of soda, and many of the other salts, ** water seemed to be electrolyzed ; at the same time acid and alkali appeared in equivalent propor- tion with the oxygen and hydrogen atthe respective electrodes.” —‘** We must conclude,” from the above-mentioned principle, ** that the only electrolyte which yielded was the sulphate of soda, the ions of which, however, were not the acid and alkali of the salt, but an anion composed of an equivalent of sul- phur and four equivalents of oxygen and the metallic cathion sodium ; from the former, sulphuric acid was formed at the anode by the secondary action and evolution of one equiva- lent of oxygen ; and from the latter, soda at the cathode by the secondary action of the metal and the evolution of an equiva- lent of hydrogen.” : To avoid circumlocution (but only when speaking of elec- trolytic decomposition), Mr. Daniell proposes to adopt the word zon, introduced by Dr. Faraday, as a general termina- tion to denote the compounds which in the electrolysis of a salt pass to the zincode, and that they should be specifically distin- guished by prefixing the name of the acid slightly modified, as is shown in the following table :— Ordinary chemical formula. Electrolytic formula. Sulphate of copper (S+3 O)+(Cu+ O) = (S+40)+4Cu. eet of copper. Sulphate ofsoda (S+30)+ (Na+ 0) = (S+40)+Na. Oxysulph. of sodium. Nitrate of potassa (N+5 O)+(Ka +O) = (N+60)+ Ka. Oxynitrion of potassa. Phosphate of soda (P+33 O)+(Na+O) = (P+33 O)+Na. Oxyphosph. of soda. The following experiments seem to remove all doubt that the view just sketched is correct; they were, in fact, suggested to Prof. Daniell by the theory itself. ** A small glass bell, with an aperture at top, had its mouth closed by tying a piece of thin membrane over it. It was half filled with a dilute solution of caustic potassa, and suspended in a glass vessel containing a strong neutral solution of sul- phate of copper, below the surface of which it just dipped. A platinum electrode, connected with the last zinc rod of a large constant battery of twenty cells, was placed in the solution of potassa ; and another, connected with the copper of the first cell, was placed in the sulphate of copper immediately under Phil, Mag. S. 3. Vol. 17. No, 411, Nov. 1840. 2A 354 Professor Daniell on the the diaphragm which separated the two solutions. The cir- cuit conducted very readily, and the action was very energetic. Hydrogen was given off at the platinode in a solution of potassa, and oxygen at the zincode in the sulphate of copper. A small quantity of gas was also seen to rise from the surface of the diaphragm. In about ten minutes the lower surface of the membrane was found beautifully coated with metallic copper, interspersed with oxide of copper of a black colour, and hydrated oxide of copper of a light blue. ** The explanation of these pheenomena is obvious. Inthe experimental cell we have two electrolytes separated by a membrane, through both of which the current must pass to complete its circuit. ‘The sulphate of copper is resolved into its compound anion, sulphuric acid +oxygen (oxysulphion), and its simple cathion copper: the oxygen of the former escapes at the zincode, but the copper on its passage to the platinode is stopped at the surface of the second electrolyte, which for the present we may regard as water improved in its conduet- ing power by potassa. The metal here finds nothing by combining with which it can complete its course, but being forced to stop, yields up its charge to the hydrogen of the second electrolyte, which passes on to the platinode, and is evolved. | ‘‘ The corresponding oxygen stops also at the diaphragm, giving up its charge to the anion of the sulphate of copper. The copper and oxygen thus meeting at the intermediate point, partly enter into combination, and form the black oxide; but from the rapidity of the action, there is not time for the whole to combine, and a portion of the copper remains In the metallic state, and a portion of the gaseous oxygen escapes. The precipitation of blue hydrated oxide doubtless arose from the mixing of a small portion of the two solutions.” Nitrate of silver, nitrate of lead, proto-sulphate of iron, sul- phate of palladium, and proto-nitrate of mercury, were simi- larly treated, and afforded analogous results, somewhat modi- fied by the nature of the metallic base. Sulphate of magnesia was subjected to the same process, in hopes of finding mag- nesium, but magnesia alone was deposited, The theory of ammonium, as proposed by Berzelius, and the hypothesis of Davy developing the general analogy of all salts, whether derived from oxyacids or hydracids, may by this evi- dence, especially when taken in conjunction with the recent researches on the constitution of organic bodies, be considered as almost experimentally demonstrated*. The bisalts yield results which at first sight do not accord * See Ad itional Note at the end of the present Number among the Miscellaneous Notices, | Electrolysis of Secondary Compounds. 355 with the preceding deductions; a strong solution, for example, of pure crystallized bisulphate of potassa was made, and its neutralizing power carefully ascertained by the alkalimeter. Evaporation and ignition with carbonate of ammonia gave the quantity of neutral sulphate yielded by a certain measure of the solution. An equal measure was then placed in each arm of the double diaphragm cell, and the current passed through till 70°8 cubic inches of mixed gas were collected ; half the so- lutions from the zincode and platinode were then separately neutralized, and half evaporated and ignited in the vapour of carbonate of ammonia. It was then found that the zincode had gained 18 grains ; the platinode lost 19 of free acid: of potassa the zincode had lost 9°9 grains, and the platinode gained an equal quan- tity : thus, though the solution conducted very weil, not more than one-fifth of an equivalent of the potassa was transferred to the platinode, as compared with the hydrogen evolved, while half an equivalent of acid was transferred to the zincode when where a whole equivalent of oxygen was evolved. Mr. Daniell remarks upon this experiment,— ‘¢ T think we cannot hesitate to admit that, in this case, the current divided itself between two electrolytes, and that a part was conducted by the neutral sulphate of potassa, and a larger part by the sulphuric acid and water. It is a well- known fact that the voltaic current will divide itself between two or more metallic conductors in inverse proportion to the resistance which each may offer to its course; and that it does not in such cases choose ‘alone the path of least resistance. I am not aware that such a division of a current between two electrolytes in the same solution has ever before been pointed out, but analogy would lead me to expect it.” ‘These consi- derations enable us to explain some apparent anomalies in the electrolysis of diluted sulphuric acid and alkaline solutions. When diluted sulphuric acid was placed in the double diaphragm cell, and the current transmitted, some of the acid passed to the zincode; but from numberless experiments it appeared that this quantity scarcely ever exceeded the propor- tion of one-fourth of an equivalent as compared with the hy- drogen evolved. Mr. Daniell thought possibly this might be owing to the acid being mechanically carried back to the platinode, as in all cases there is a mechanical convection of the liquid from the zincode to the platinode, and this is the greater in proportion to the inferiority of its conducting _ power. If, however, this deficiency of acid were owing to a mechanical re-transfer, mechanical means, such as increasing the number of diaphragms, tt stop it; the proportion, 2A2 356 Mr. Faraday on Magneto-electric Induction ; however, was even under these circumstances still maintained. No difference was observed whether the oxygen was allowed to escape as from a zincode of platinum, or was absorbed by copper or zinc; the metals, of course, being dissolved in pro- portions equivalent to the hydrogen developed at the pla- tinode. Solution of potassa, baryta, or strontia, similarly treated, exhibited a transfer of about one-fourth of an equiva- lent towards the platinode. These curious results are easily explained by supposing that the solution is a mixture of two electrolytes; with sul- phuric acid they are H + (S + 4 O), oxysulphion of hydro- gen (H + O) water; the current so divides itself that three. equivalents of water are decomposed, and one equivalent of oxysulphion of hydrogen. Analogous changes occur with the alkaline solutions, the alkaline metal passing as usual to the platinode. LIII. On Magneto-electric Induction ; in a Letter to M. Gay- Lussac. By Micuart Farapay, D.C.L., F.R.S. [Continued from p. 289, and concluded. ] I REPRESENTED this state of things under a general form, in the figures 77 annexed to the memoir, which, as to the arrows, the designation of the parts, &c. &c., I have made to correspond, as well as I could, with fig. 2. plate iil. of the Italian philosophers’ memoir (plate ii.). I proceed to show how it agrees with the galvanometrical results obtained by them, and how far with their conclusions. With regard to the galvanometrical results, my figure might be used instead of theirs, without occasioning any dif- ference, and I have no reason to say that they are inexact, Relatively to ‘‘ one of those consequences,” which arises from ‘the immediate inspection of the arrows which mark the currents in the two regions of the disc,” or from any other attentive and experimental examination, we see that the cur- rents 7, 7, , on entering, instead of being in a contrary direc- tion to those which are in the parts s s s, which recede, fol- low exactly the same direction; that is, that as to the general movement near the pole they go from above below, or from the circumference towards the centre, transversely to the lines that the different parts describe in their course; and at a great distance (F. 92.) on each side of the pole they are in the contrary direction. In proportion to the nearness to the pole of a part of the line described by a point, it is traversed by a current, which commences, and increases in intensity in a Letter to M. Gay-Lussac. 857 until it reaches the shortest distance, or a little beyond, on account of time entering as an element into this effect. After- wards, by reason of the increasing distance, the current di- minishes in intensity without ever altering its direction rela- tively to its proper course. It is only when it arrives at the parts most distant, at which the electricity excited is dis- charged, that a current is manifested in an opposite direction, or in one more or less oblique. I apprehend that it is wholly useless to speak of the partial alterations in the direction of the currents through the parts that are the nearest to the centre, or to the circumference; two or three curves that I have rudely traced will show in what directions these altera- tions take place. The second consequence arising from the memoir of the Italian philosophers is, that ‘* the direction of the currents upon the parts that enter is contrary to that of the producing currents; (that is, of those that are considered as existing in the magnet) while on the other side the direction in the two systems is identical.” ‘This assertion is exactly contrary to the reality (F.117.). In figures 1. and 2. I have indicated, by means of arrows, the direction of the currents in the mag- netic pole, which is the same as the direction given by Messrs. Nobili and Antenori in fig. 1. pl. ili. But my figure 2, as well as the indications of the galvanometer, shows evidently that the currents in the parts that enter », , 2, when they approach the magnet, pass through in the same direction as the current in this side of the pole of the magnet; and that the currents in the parts that recede s, s, s, follow a direc- tion contrary to those supposed to exist in the side of the magnetic pole from which they recede. I may be mistaken, but it appears to me that Messrs. Nobili and Antenori suppose that circular currents are excited in the part of the metal adjacent to the pole, in absolutely the same manner as those formed in the helix, when it is made to approach the magnet, and that when this part of the disc re- cedes, the circular currents are somehow reversed, as occurs in the helix during its recession from the magnet. A passage in their first paper, and another at the end of page 284, ap- pear to imply that such is their opinion. ‘This idea occurred to me above a year ago, but I soon saw from numerous ex- periments, some of which I have just referred to, that it was by no means satisfactory; and when I had fully verified that the action of the helix in its approach to, and recession froin the pole was wholly explained (I. 42.) by the law as- signed (I. 114.), I was forced to abandon my previous ideas. The memoir afterwards proceeds (p. 288.) to explain the 358 Mr. Faraday on Magneto-electric Induction ; phenomena of Arago’s revolving disc; but as I have shown that the theory is in general based upon two conclusions con- trary to truth, it is unnecessary to make a minute examina- tion of it. It is impossible for it to exhibit the phenomena with exactitude. ‘Those who are anxious for full satisfaction on the subject, may decide, by means of a few experiments, whether the opinions which I put forth in the paper which first announced the discovery of these currents be true, or whether the Italian philosophers were justified in declaring that I was in error, and that they had published more just ideas on the subject. Everybody knows that when M. Arago published his re- markable discovery, he said the action of the disc upon the magnet was resolvable into three forces: the FIRST, perpen- dicular to the disc, which he found to be repulsive: the sE- conp, horizontal and perpendicular to the vertical plane con- taining the radius beneath the magnetic pole; this is a tan- gential force, and occasions the rotation of the pole with the metal: the THIRD, horizontal and parallel to the same radius; it becomes null at a certain point towards the circumference ; but when nearer the centre, it has a tendency to impel the pole towards the centre; and when nearer the circumference, to impel it in the contrary direction. At page 289, Messrs. Nobili and Antenori give an ex- planation of the first of these forces. As has been already said, these gentlemen consider that the parts adjacent to the magnet have currents contrary to those which are found near the pole to which they approach, and consequently they are repulsive ; and they consider that the parts that recede have currents identical in direction with those which are near the magnet from which they recede, and consequently these parts are attractive. The sum of each of these various forces is equal one to the other, but in what relates to the needle or magnet this distribution differs ; for ‘the repulsive forces being the nearest, invade the disc as far as the parts under the needle, and thus obtain a preponderance over the action of the contrary forces, which are exerted more obliquely, and at a greater distance. In short, it is only a part of the re- pulsive forces which is balanced by the attractive forces; the remainder meets with no opposition, and it is this remainder that produces the effect.” But I have shown in this letter, that the currents in the parts adjacent or distant are exactly contrary to what is sup- posed by Messrs. Nobili and Antenori; and that conse- quently where they expect attraction they would find repul- sion, and attraction where they expected repulsion; so that, in a Letter to M. Gay-Lussac. 359 following their opinion, corrected by experiment, the result should be aéfraction instead of repulsion. But Arago was right in saying that it is repulsion; and consequently the theory of the effect given cannot be the true one. My views upon the subject in question may be found in my first paper. I examined whether it were possible or probable (F. 125.) that time could be a necessary element for the de- velopment of the maximum current in the metal. In this case the resultant of all the forces would be in advance of the mag- net, when the plate was rotated, or in the rear of it, if it (the magnet) were rotated; and a line joining this resultant with the pole would be oblique to the plane of motion; then the force in the direction of this line might be resolved into two others, one parallel, the other perpendicular to the plane of movement or rotation; the latter would be a repulsive force, producing an effect analogous to that remarked by M. Arago. The second force is that which occasions the magnet and the disc mutually to follow each other. Referring to page 290, fig. 1. or 2. (my figure 2. may also be made use of,) we read, ‘** Forces of attraction exist in s, s, s, towards which it (the magnet) is attracted, and repulsive forces in n, n, 7, which impel it in the same direction;” consequently the magnet moves either after, or with the metal; but the currents, and conse- quently the forces, are exactly contrary to what has been sup- posed, as I have just shown; the magnet and the disc should therefore move in opposite directions, if the forces act in the manner that has been supposed. But as they do not move, in fact, in opposite directions, it is evident that the theory which explains their movement by reversing the facts must be itself erroneous. The third force is that which has a tendency to remove the magnetic pole either towards the centre or the circumference, on each side of a neutral point situated upon the radius above which the magnet is placed; this effect is described at page 281, and in fig. 4, which accompanies the memoir, and which I believe to be perfectly correct. ‘The memoir proceeds to explain the effect by referring to the repulsive force admitted (p. 289.) to account for the first effect observed by Arago, viz. the vertical repulsion of the disc; and supposing that this re- puisive force be distributed over a certain extent of the disc, beneath the magnet, it is established (p. 292. fig. 5.) that if the pole be situated very near the circumference, the portion of the body whence this force emanates will be lessened, being cut by the circumference itself; consequently the parts that are nearest to the centre are more powerful, and impel the pole in an outward direction; while if the pole be placed very near 360 Mr. Faraday on Magneto-electric Induction; the centre, the extent whence the force emanates will pass it; and as this part in excess is considered, though erroneously, as inactive, the portion situated towards the circumference is more powerful, and impels the pole towards the centre. Two or three slight objections present themselves to this opinion, but they are nothing, so to speak, in comparison with that which arises, when it is recollected, that in conformity with the author’s own ideas upon the action of currents, the error with respect to the direction of those which are excited near the pole obliges us to substitute attraction for repulsion, as Ihave already shown when treating of the first of these forces: consequently all the movements which are connected with the third force would be in a direction contrary to those that are actually presented; and the theory which, when cor- rected by experiments made with the galvanometer, indicates such movements, must be abandoned. Page 292 of the memoir refers to Mr. Faraday’s “ second law.” As I have already said, I never stated those three as- sertions as laws. I really regret extremely that a letter that was never intended to convey minute details, but merely a few facts, selected in haste from a multitude described previously in the memoir read before the Royal Society,—I regret that this letter, which 1 never expected to see in print, should have led the Italian philosophers into error. However, after having examined anew all the facts, I do not see that I am in any de- gree responsible for the error they have committed, as having advanced fallacious results; nor, as far as the memoir is con- cerned, for not having given to the scientific world the most complete details at the earliest period possible. I have not yet published my views as to the cause of the third force described by M. Arago; but as Messrs. Nobili and An- tenori, when giving the hypotheses, which I justly regard as inexact, say (p. 293.), ‘*In fact, what other hypothesis can reconcile the verticality that the needle preserves in the two positions 7, s, 7", s"', (fig. 4) with the fact of the repulsion from below, above which raises the needle in the second position s"', n!'?”,—I am induced to offer another hypothesis, premising, however, that the directions and forms that I shall trace, as those of the excited magneto-electric currents, are to be con- sidered only as general approximations. If a piece of metal, large enough to contain without distor- tion all the currents which may be excited in its whole extent by a magnetic pole placed above it, be moved in a rectilinear direction beneath the pole, then an electric current will move across the direction of its motion, in the parts immediately adjacent to the pole, and will return in the opposite direction Se in a Letter to M. Gay-Lussac. 361 on each side in the parts which, being more distant from the pole, are subject to a feebler inductive force: the current will thus be completed or discharged (see fig. 3.). Let ABCD represent a piece of copper moving in the direction of the ar- row E, and N the north end of the magnet placed above; currents of electricity will be produced in the piece of metal ; and though they undoubtedly extend from the part below the pole to a great distance around (F’. 92.), and at the same time diminish in intensity and alter in direction as they recede thence, yet the two circles may serve to represent the resultant of these currents; and it will be evident that the point of most intense action will be where they touch, and immediately under the magnetic pole, or, on account of the time required, a little in advance of it. Hence that portion of the forces which acts parallel to the plane of the metal will carry the pole forward in the direction of the arrow E, because the forces are equally powerful on the side of the pole A B, as on the side C D; and this portion, which on account of the time ne- cessary for the production of the currents excited is perpen- dicular to the direction of the metal, will be, as we have said, repulsive, and have a tendency to impel the pole upwards and away. But suppose that instead of the metal moving in a recti- linear direction, a circular disc revolving upon its axis be sub- stituted; and then let us consider, in the first place, the case of the magnetic pole placed upon its centre (fig. 4.); there is then no production of electric currents, not because there is no tendency to their formation, for I have stated in this letter, and shown in my memoirs (F. 149. 156. 217.), that from the time the disc begins to move, currents are also ready to move; but because they have a tendency to be formed in the direc- tion of radii from the circumference to the centre; and as all the parts are equally influenced, none of them having an ex- cess of power over the others, and all equally distant from the centre, no discharge can take place, and consequently no cur- rent can be developed. As no current can exist, no effect de- pendent on the action of a current upon the pole can be pro- duced, and consequently there is then neither revolution nor repulsion of the magnet. Hence the cause of the verticality without repulsion which occurs at this place. Let us now consider the case in which the pole of the mag- net, instead of being placed over the centre of the metal, is at one of its sides, as in N, figure 5. The tendency to form elec- tric currents is due to the movement of the parts of the disc through the magnetic curves (F. 116. 217.), and when these curves are of equal intensity, the electric currents increase in 362 Mr. Faraday on Magneto-electric Induction; force in proportion to the increase of rapidity in the motion of the parts of the disc that intersect the magnetic curves (F. 258.). Let us now trace a circle a 6 around a magnetic pole as a centre, and it will represent the projection of mag- netic curves of equal intensity upon the disc; a and 6 are points situated at an equal distance from the pole, in the pass- ing radius which is immediately under the pole; but as the part or point a passes by the pole with much greater velocity than the part J, the intensity of the electric current which is excited in this part a is proportionably greater. ‘This is also true for the points in any other radius of the revolving plate cutting the circle a 6, and true likewise for any other circle traced round .N as a centre, and representing consequently magnetic curves of equal intensity; with the exception, that when the circle extends beyond the centre C of the revolving disc, as to c d, instead of the existence of a feebler current at the point d than at the point c, there is then a tendency to produce an opposite current. The natural consequence of these actions of the different parts is, that as the sum of the forces tending to produce the electric current in the direction from ¢ to d is greater on the side c of the magnetic pole than on the side d, the curvature or return of these currents by the right and left also com- mences on this side; and then the two circles, which as be- fore may be considered as representing the resultants of these currents, do not come into contact exactly under the pole, but at a greater or less distance from it, towards the circumference, as in figure 6. ) This circumstance of itself would not occasion any move- ment in a pole restrained in its motion to the direction of the radius only; but being combined with that which results from the zime necessary for the development of the current, and to which reference has been already made, as explaining the first of the three forces by which M. Arago exhibits the action of the magnetic pole and disc, it will, I hope, fully elucidate all the effects that we are investigating, and will also prove the influence of time as an element. Let ¢ (fig. 7.) be the centre of a revolving disc, and 7 ¢ a part of the radius under the mag- netic pole p; the contact of the two circles representing the currents is, as we have just seen, on the side of the pole beyond the centre c; but on account of the element of time and the direction of the rotation R of the plate of metal, it is also a little to the left of the radius 7c; so that the pole is brought . under the action of the two orders of currents, not symmetric- ally but obliquely. The necessary consequence is, that if it be free to move in the direction of the radius, and in that di- in a Leiter to M. Gay-Lussac. 363 rection alone, it will move towards the centre c, for the cur- rents produced by a marked pole (north) are exactly such as by their action on the pole to impel it in that direction. This relation of the currents to the pole by which they are generated, may be proved by experiment as easily as by cal- culation. I have shown (F. 100.) that when a pole marked north is above a disc revolving in the direction of the arrows R, in the figures annexed either to Messrs. Nobili and Antenori’s memoir or to mine, the currents (indicated by the circles) are as is represented in figures 3, 6, or 7. Upon arranging a metal wire which would conduct the currents in this double direction (fig. 8.), and placing over it a marked pole (north) capable of moving only in a parallel direction to 7c, at any point in the line 7c, I found it had not any tendency to move. There was also another line perpendicular to the first, and which crosses it at the point of contact of the circles, in which the pole had no tendency to move. If piaced in any other si- tuation than upon these two lines, it moved either in one direc- tion or the other; and when placed in the positions marked 1, 2, 3, 4, it moved in the direction of the arrows represented at those points. Now the position of the pole, with regard to the currents in Arago’s experiment, when the magnet and the disc are arranged as in figures 5 and 7, is exactly that of the point 1 in fig. 8, and hence that pole has a tendency towards the centre C. We will now direct our attention to the result obtained if we gradually move the pole from the centre towards the cir- cumference. Let figure 9. represent this new condition at a given time, as figure 5. represented the first state; it is evi- dent that the velocity of the parts a 0 of the radius beneath the pole, will not differ from each other so much as they did previously, being only about 3:2 instead of 6:1; and the difference will also be less with all the curves of equal inten- sity comprised in this circle. ‘This occasions the situation of the pole, and the place of contact of the circles representing the currents (fig. 7.) mutually to approach in the direction of the line 7c, and necessarily carries the pole (fig. 8) nearer to the neutral line 7z. If we examine the second circle c d, fig. 9, of magnetic curves of equal intensity, it will be seen, that as the disc does not extend to c, or even beyond a, there is nothing to add to the force of the current upon that side of the pole, while at d the radius, by moving through the mag- -netic curves, adds to the intensity of the current excited at d, and everywhere else on that side of the pole, and may easily, according to the position of the pole upon the metal plate {that is, according as it is nearer or further from the edge), 364 Mr. Faraday on Magneto-electric Induction ; render their sum equal or greater than the sum of the forces on the other side, or that towards the circumference. If the sum of the forces be equal, then the pole will be somewhere in the line Zz, as at 5, fig. 8, and will have no tendency either towards the centre or the circumference, though its tendency to move with the disc or above it remains the same. Or if the sum of the forces be greater on the side d, fig. 9, than on the side c, then the pole will be in the position 2, fig.8, and will be impelled outwards in the direction of the radius, in conformity with Arago’s results. | Besides this cause of alteration in the motion of the pole parallel to the radius, and which is dependent on the position of the pole near the circumference, there is another cause that occurs, I apprehend, at the same time, and assists the action of the first. When the pole is placed towards the edge of the disc, the discharge of the currents excited behind is thrown against the side of the edge, from the absence of conducting matter; thus, in fig. 10, instead of having the regular form of the figures 7 and 8, the currents are deflected in their course towards the circumference, while they have all neces- sary latitude for their movement in the parts towards the cen- tre; this of itself would cause the point of greatest force to fall a little nearer the centre than the projection of the axis of the magnetic pole, and assist in placing the pole in the position 2, fig. 8. I have such confidence in this opinion, that though I have not had opportunity to make the experiment myself, yet I venture to predict, that if instead of employing a revolving disc, a lamina or plate of metal, five or six inches broad, as A, B, C, D, fig. 9, were caused to move in a rectilinear di- rection conformably to the arrow, under a magnetic pole si- tuated at a, the pole would have a tendency to move forward with the metal as well as above, but neither towards the right nor left; while if the pole were placed above the point 4, it would be directed towards the edge A B; or if it were placed above c, it would have a tendency to move towards the edge CD. Having thus replied to the question, “* What other hypo- thesis” ?, &c. proposed by the authors of the memoir at p. 293, I shall continue my examination of the memoir itself. At p. 294 the error relative to the nature of the currents, that is their supposed inversion, is repeated. The effect described is sure enough with a helix, and some particular forms of appa- ratus ; but the simple and elementary current generated by the. passage of a wire in front of a magnet is not reversed when the metal wire recedes. (F. 171.111. 92.) At p. 295 is the supposition that when the rotation is slow in a Letter to M. Gay-Lussac. 365 *¢ the revolution of the currents is circumscribed within narrow limits, and there is Zittle to add to the results that form the basis of the four] whole theory;” but that when the motion is rapid the currents envelope the whole disc, ‘‘ so as to become a species of labyrinth.” For my part I believe the currents have the same general direction as has been assigned to them in the figures, whether the rotation be slow or rapid; the only difference is an increase of velocity. A circumstance is then selected which is really simple, though it may at first appear complicated; namely, that in which the opposite poles are adjusted over a disc in one diameter, but towards the opposite edges on each side of the centre. This circumstance, with the direction of the movement and the cur- rent produced, is exhibited in fig.’7 of Messrs. Nobili and Antenori’s memoir. It is unnecessary to quote pages 296 and 297, which contain the explanation of this figure, but I shall refer to fig. 12, which corresponds to it, and is in conformity with my views and experiments, so that the two may be com- pared together. It is very satisfactory to me to find, that in this part of the memoir, as well as in the first, there is no im- portant result of experiment contrary to my published opi- nions, though I am very far from adopting the conclusions that have been drawn from them. If figure 12 be examined, it will be instantly seen that it results in the most simple manner from the action of the two poles. ‘Thus, as far as the upper or north pole only is con- cerned, the currents are asin figure6. But as with the north pole, the current determined by it moves from the circumfe- rence towards the centre, so with the south pole, in the same or corresponding position, the currents move from the centre to the circumference (I. 100.) ; and consequently in fig. 12 they are continued along the diameter N, S, through the centre of the plate, to return in the direction of the arrows upon the sides EK, O. The points upon which I find my views to dis- agree with the indications of the galvanometer obtained by Messrs Nobili and Antenori are, first, the direction of the cur- rents at N and S, which is contrary to what I obtained; and, secondly, the existence of any oblique axis of power, as P, Q, in their figure 7. The memoir concludes, at least as far as I am concerned, at page 298, by again mentioning the error (but not as an error) relative to the revolving disc, which becomes a new electrical machine. At the commencement, the authors being little conversant with the principles under the influence of which such a result is obtained, deny it; and though they say here, ** What shall we say after the new observations that 366 H. W. Dove on the Law of Storms. we have made during the continuation of our researches ?”—I am not disposed to alter anything that I have published; I have even more confidence than before in my own views; for had their observations been in agreement with the results which I had obtained, I should have had great reason, after my examination of their papers, to fear that my own ideas were erroneous. | I cannot conclude this letter without again expressing my regret at having been obliged to write it; but if it be recol- lected that Messrs. Nobili and Antenori’s memoirs were written and published after my original memoirs; that their last paper appeared even in the Annales de Chimie et de Phy- sique after mine; and that it had consequently the appear- ance of advancing the science further than I had done; that both papers accuse me of error in.experiment and theory, and also of dishonesty; that the last of these papers is dated in March, and though it is now December, has been followed by no correction or retractation on the part of the authors; and that I sent them several months ago (at the same time that I forwarded them to you and others,) copies of my ori- ginal memoirs, and of my notes to a translation of their first memoir; and if it be considered that, after all, I have not to reproach myself with the errors of which I am accused, and that these gentlemen’s memoirs are so framed as to compel me to reply to their objections ;—I hope that no one will say that I have written too hastily what might have been avoided ; or that I should have shown respect for the truth, and done justice to my own publications, or to this branch of science, if, being aware of such important errors, I had not called attention to them. I am, my dear Sir, yours very sincerely, M. Farapbay. LIV. On the Law of Storms. By H. W. Dove. To Richard T. aylor, Esq. Editor of the Philosophical Magazine and Journal. Dear Sir, i the year 1828, I published in Poggendorff’s Annalen, vol, xill, p. 596, a memoir “ On Barometric Minima,” in which I established the fact, that the storm which accom- panies a great depression of the barometric column is a vast whirlwind, which in the northern hemisphere proceeds from S.W. to N.E, ‘The example there more especially investigated is the storm of the 24th of December, 1821, the centre of H. W. Dove on the Law of Storms. 367 which travelled from Brest to Cap Lindenaes in Norway. The rotation in this whirlwind was in the direction S.E. N.W., consequently on the S.E. side of the storm, that is to © say, in France, Holland, Germany, Italy, Denmark, and Prussia the weather-vane veered from S.E. to S.W. and W. through south; on the contrary, towards the Atlantic coast of North America the direction was N.E. Atthe same timelI . observed in this memoir (p. 599.), that the greater number of hurricanes in the southern hemisphere, which I had examined, are whirlwinds rotating in the opposite direction. Three years later, Mr. Redfield of New York, arrived at the same result by independent observations, as appears from his memoir, entitled “* Remarks on the prevailing Storms of the Atlantic Coast of the North American States.” (Silliman’s Amer. Journ. of Sc., 1831. Avril.) Ina later memoir, how- ever, on the gales and hurricanes of the western Atlantic (2d. vol. xxxi.), Mr. Redfield has added a new and weighty fact to those already accumulated by me. From the storms, the course of which the American philosopher has there dis- cussed and delineated by a chart, it follows, that the hurri- canes taking their rise within the tropics, so long as they are confined between these limits, retain unaltered their original direction from §.E. to N.W.; sosoon, however, as they reach the temperate zones, they suddenly bend round almost at a right angle. and then travel from S.W. to N.E. Finally, Lieut.-Colonel Reid, in his valuable treatise ** On the Law of Storms,” published in 1838, confirms by new examples the results already obtained, and especially calls attention to the fact, that by this change in the direction of its course the whirlwind spreads itself out continually from the centre more and more. So long ago as the year 1735, Hadley proposed to solve the problem of the trade-winds, upon the principle, that air moving from the equator to the poles gradually acquires a westerly, and on the contrary air moving from the poles to the equator an easterly direction. A simple modification, or rather extension of this theory, gives a key to all the compli- cated phzenomena of the variable and apparently so irregular motions of the wind observed in our own and other extra-tro- pical latitudes. It is only necessary to take into considera- tion the two currents contending for and alternately obtaining the upper hand, in order to see that the origin of the current, which Hadley treated as fixed for a given place, is in fact variable ; wherefrom it follows, that the direction of the vane ought to be not stationary, but changeable, according to a law which I have named the law of rotation, From the same 368 H. W. Dove on the Law of Storms. fruitful principle I am now prepared to explain theoretically the phenomena of storms. . Let a b be a series of material points parallel to the equator, which are set in motion by a certain impulse in the direction at from south to north. The rotation of the earth combined with this impulse will produce a motion of a6 towards g h, if , the space d bh is void of matter. But if this space is filled by quiescent matter, the particles at 5 will, as they move, come into contact with particles in the space d 64, which rotate with less velocity; their motion in the direction of east will there- fore be retarded, and the point 4 will move not towards # but towards f/ The particles at a are, on the contrary, in juxta- c d e ip g h position with particles, which at first have an equal velocity of rotation, and consequently move as they would in a vacuum, that is, towards g. If, then, ab represent a mass of air im- pelled from south to north, the storm will have a more southerly direction at the east side, a more westerly one on the west side, and will thus acquire a tendency to whirl in the direction S.E. N.W. This tendency to whirl would not take place, were there no resisting matter in the space dbh, and will therefore increase in proportion as this resist- ance prevents the course of the storm from deviating towards the west. Now within the north tropical regions the space d bh is filled with air, which flows from N.E. to S.W. Here, therefore, the resistance is at a maximum, and the air at b has its westerly tendency so far checked, that it retains its original direction towards d almost unaltered, whilst, on the other hand, the air at a has acquired a tendency to move to- wards d. ‘The storm accordingly will whirl with the greatest intensity, but retains its initial direction and lateral magnitude. So soon, however, as it reaches the temperate zone, it finds itself in contact with air at dA, which is in motion from S.W. to N.E. The resistance, which the particles at 6 experience, will therefore be considerably diminished, or even almost vanish, that is to say, the direction 0d is transformed into the direction 6, and the storm bends round almost at a right H. W. Dove on the Law of Storms. 369 angle, and at the time grows wider and wider as it pro- gresses. ' The phenomena of storms south of the equator may easily be inferred from what has been said above of the opposite hemisphere. The rectilinear course within the tropics, the sudden curvature at the limits of the tropics and the tem- perate zones, the accompanying expansion of the whirls cen- stituting the storm; in a word, all the essential phenomena of storms, must clearly be the same for one hemisphere as for the other, with the sole exception, that in the one (the northern) the rotation is after the order of the letters S. KE. N. W., and in the other (the southern) after the order of the letters pW. N. E, a I take this opportunity to make, in my own vindication, a few remarks upon the manner in which my labours in this field have been brought under the notice of the English public. In the Lond. and Edinb. Phil. Mag., vol. xi. p. 390, a paper by Mr. Dalton has appeared, in which I am directly charged with claiming for myself a theory which he had already many years before made known, and which had still earlier been promulgated by the celebrated Hadley. Upon a dili- gent perusal of Mr. Dalton’s Meteorological Essays and Ob- servations, and of Hadley’s original Memoir (The Cause of the general Trade-wind, Phil. ‘Trans. 1735, p. 58), I have not succeeded in finding a single trace of, or bare allusion to, the existence of the law of rotation, which it was the principal object of my paper to establish by observations, and explain upon theoretical principles. And if your readers or Mr. Dalton should do me the honour to look into my Meteorolo- gical Essays, Berlin, 1837-38, pp. 244-250, it will be seen, that so far from attempting to usurp the credit so justly due to Hadley for the fundamental idea, upon which my own theory is founded, and which he had himself so successfully applied to the particular problem of the trade-winds, I have been anxious to acknowledge the full extent of my obligations to him, and to bring his merits as a discoverer prominently forward. In an article upon Lieut.-Colonel Reid’s law of storms in the Edinburgh Review, I find my meteorological researches again alluded to, but upon a distinct ground. The anony- mous Reviewer, in his patriotic anxiety to satisfy his readers of the purely British growth of this theory, allows that some remarkable passages upon the subject had previously ap- peared in the memoirs of the Berlin Professor, but that these are mere ingenious speculations, for they are no more. ‘The term passage, for a memoir (on barometric minima) of seven- Phil, Mag. S. 3. Vol.17. No. 111. Nov. 1840. 25 370 Mr. H. G. Armstrong on the Electricity teen closely printed pages, strikes me as a little extraordinary, but perhaps this arises from my imperfect acquaintance with the nice distinctions of your language. I leave it to my English | readers to determine, with what degree of justice results de- duced from a greater number of contemporary observations, aa than (as I believe) had ever previously or have even since i been brought together, can be represented as no more than ingenious speculations. I am, dear Sir, yours with much esteem, Berlin, Sept. 30, 1840. H. W. Dove. | LV. On the Electricity of a Jet of Steam issuing from a Boiler. By H. G. Armstrone, Lsg., in Letters to Professor Faraday*. SIR, A FEW days ago, I was informed that a very extraordinary electrical phenomenon, connected with the efflux of steam from the safety-valve of a steam-engine boiler, had been ob- | served at Seghill, about six miles from Newcastle. I there- i fore took an early opportunity of going over to that place, to | investigate the truth of what I had heard, and by so doing I have ascertained the precise facts of the case, which appear to me to possess so much novelty and importance, that I deem it right to transmit the particulars to you, believing that in your hands they will prove most conducive to the advance- IF ment of science. Without further preface, I shall proceed to i narrate what I saw and heard on the spot. Se eee vn Ld re 2 SROs 1 B @) 96 oO O O O a POS 50 GOO O900 OSM OS O 3 ) 6) = ® O Or @) O There is nothing remarkable in the construction of the boiler, which is supported upon brick-masonry in the usual way. The annexed sketch represents an end view of the * Communicated by Professor Faraday. of a Jet of Steam issuing from a Boiler. 871 boiler and safety-valve, by which it will be seen that the valve is placed on the top of a small cylinder, having a flange round the lower end, which is fastened by bolts to the summit of the boiler, between which and the flange, a cement, composed of chalk, oil and tow, is interposed for the purpose of making the joining steam-tight. About three weeks ago the steam began to escape at this joining, through a fissure in the cement, and has ever since continued to issue from the aperture in a copious horizontal jet. Soon after this took place, the engine-man, having one of his hands accidentally immersed in the issuing steam, presented the other to the lever of the valve, with the view of adjusting the weight, when he was greatly surprised by the appearance of a brilliant spark, which passed between the lever and his hand, and was accompanied by a violent wrench in his arms, wholly unlike what he had ever experienced be- fore. The same effect was repeated when he attempted to touch any part of the boiler, or any iron-work connected with it, provided his other hand was exposed to the steam. He next found that while he held one hand in the jet of steam, he com- municated a shock to every person whom he touched with the other, whether such person were in contact with the boiler, or merely standing on the brick-work which supports it; but that a person touching the boiler, received a much stronger shock than one who merely stood on the bricks. These singular effects were witnessed and experienced by a great many persons, and among others by two gentlemen with whom I am personally acquainted, and who fully corro- borate the above account, which I obtained from the engine- man. The boiler had been cleaned out the day before I saw it, and a thin incrustation of calcareous matter reaching as high as the water level had been removed, and the consequence was, that the indications of electricity, though still existing, were very much diminished. Still, however, what remained was very extraordinary; for when I placed one hand in the jet of steam and advanced the other within a small distance of the boiler, a distinct spark appeared, and was attended with a slight electrical shock. From the effect produced by the cleaning of the boiler, it appears pretty obvious that the phznomenon is in a great measure, though not wholly, dependent upon the existence of an incrustation within; and the reason why such effects do not in any degree attend the effluxion of a jet of steam from a boiler in ordinary cases, must, I apprehend, be sought for in the fact, that in the present instance the steam escapes 2582 372 — Mr. H. G. Armstrong on the Electricity through an aperture in a non-conducting material, while in a vast majority of cases the escape must take place through a metallic orifice. Can the explosion of boilers, respecting the cause of which so much uncertainty at present exists, have any connexion with the rapid production of electricity which thus appears to accompany the generation of steam? In the present case the incrustation in the boiler is very rapidly formed, and I therefore expect that in a few days the effects will have become as strong as they were at first. Whenever this takes place I shall again go over to witness them, and if you wish for any further information, I shall be glad to obtain it for you. In the mean time you are at liberty to make any use of this letter that you think fit. I am, Sir, very respectfully yours, Newcastle-upon-Tyne, Oet. 14, 1840. H. G. ARMSTRONG. Newcastle-upon-Tyne, Oct. 22, 1840. Dear Sir,—I yesterday revisited the boiler at Seghill, im company with some friends, and took with me such apparatus as I deemed necessary for experimenting on the electrical steam. The results of this second visit I now hasten to com- municate, and you will find in the following account of my proceedings, answers to all the queries you were kind enough to send me, for the purpose of directing my attention to the proper points of inquiry. | I found the boiler, and everything connected with it, pre- cisely in the state in which I have already described it, and on trying the steam in the same way as I did on the former occasion, the effect was very nearly the same; but when I placed myself on an insulating stool, the intensity of the sparks which passed between my hand and the boiler was greatly increased, as well as the twitching sensation in the knuckles and wrist, which accompanied the operation, and which in my former letter I designated a slight electrical shock. In pursuance of your instructions, I had provided myself with a brass plate, having a copper wire attached to it, which terminated ‘in a round brass knob. When this plate was held in the steam by means of an insulated handle, and the brass knob brought within about a quarter of an inch from the boiler, the number of sparks which passed in a minute was from sixty to seventy, as nearly as we could count; and when the knob was advanced about one-sixteenth of an inch nearer to the boiler, the stream of electricity be- came quite continuous. The greatest distance between the knob and the boiler, at which a spark would pass from one to of a Jet of Steam issuing from a Boiler. 373 the other, was fully an inch. A Florence flask, coated with brass filings on both surfaces, was charged to such a degree with the sparks from the knob, as to cause a spontaneous discharge through the glass; and several robust men received a severe shock from a small Leyden jar charged by the same process. ‘The strenvth of the sparks was quite as great when the ‘knob was presented to any conductor communica- ting with the ground, as when it was held to the boiler. It appeared to make very little difference in what part of the jet the plate attached to the conducting wire was held; but when a thick iron wire was substituted for the plate, the effect was greatest when the wire was held very near to the orifice. The valve was loaded at the rate of thirty-five pounds per square inch; but the pressure of the steam fluctuated consi- derably, which gave me an opportunity of observing that the quantity of electricity derived from the jet increased and di- minished with the pressure. ‘The electricity of the steam was positive ; for when the pith balls of the electrometer diverged upon an instrument connected with the steam, they were at- tracted by a piece of sealing-wax rubbed on woollen cloth; and when a pointed wire was held by the person on the stool, under the shade of a hat, a pencil, and not a star, of electrical light became visible. Besides the principal jet of steam which I operated upon, there were several small streams issuing from different parts of the boiler, and in each of these the electrometer indicated the presence of electricity. From the peculiar manner in which the steam blew off from the safety-valve when the weight on the lever was lifted, it was quite impossible to try any satis- factory experiment upon the steam which was allowed to escape by that means. I applied the gold-leaf electrometer to vari- ous parts of the boiler, which, I ought to observe, is in direct communication with the ground by means of the steam-pipes, oF could scarcely detect a trace of electricity in any part Of if. The engine has another boiler besides the one in question, and the two boilers lie immediately adjacent to each other. Having been informed that similar phenomena had been dis- covered in this second boiler, I proceeded to apply the elec- trometer to some small pencils of steam which were escaping in different parts, and found the same indications which I had observed under similar circumstances in the first boiler. I then raised the safety-valve, and the column of steam which escaped from it proved as highly charged with electricity as the horizontal jet which issued from the other boiler, and in which the phenomenon had first been observed. 374 Mr. H. G. Armstrong on the Electricity of a Jet of Steam. Upon inquiry, I found that the water used in the boilers was obtained from a neighbouring colliery, where it was pumped out of the mine, and that the same water was used for the boiler of a small high-pressure engine adjoining the colliery from which the water was procured. In order, there- fore, to form ‘an opinion whether or not the phenomenon in question was dependent upon the quality of the water from which the steain was generated, I proceeded to examine the steam evolved from the boiler to which I had been referred, and which proved to be a very small one. ‘The valve was loaded with only twenty pounds on the square inch, and I learned from the engine-man that no appearance of electricity had ever been noticed in the steam. Upon trial, however, | succeeded in obtaining very distinct sparks of electricity from the column of steam which issued from the safety-valve. The sparks were certainly weaker than those obtained at the other engine, but this may reasonably be ascribed to the inferior pressure of the steam, and smaller size of the boiler. I then repaired to another high-pressure engine, which belonged to the same establishment, and the boiler of which was supplied with razn water instead of that drawn from the mine. In this case the pressure of the steam was forty pounds on the square inch. The valve was inaccessible, but a powerful jet of steam was obtained from the upper gauge-cock; | could not, however, obtain any trace of electricity in the steam from this boiler, not even sufficient sensibly to affect the gold-leaf electrometer. The presumption, then, is exceedingly strong, that the phenomenon is in some way occasioned by the pe- culiar nature of the water from which the steam is produced. I inclose you a specimen of the incrustation*, of a month’s growth, deposited by the water from the mine in the boilers in which it is used. I shall be glad to receive any further instructions from you as to the proper mode of pursuing the investigation, and should be much gratified to hear your opinion as to the cause of this most curious phenomenon +. I am, dear sir, Very respectfully yours, H. G, ARMSTRONG, M. Faraday, Esq. * The incrustation is grey and hard; it contains traces of a soluble muriate and sulphate, but consists almost entirely of sulphate of lime, with a little oxide of iron and insoluble clayey matter, carried in probably by the water. There is hardly a trace of carbonate of lime in it.—M. F. + The evolution of electricity by vaporization, described by Mr. Arm- strong, is most likely the same as that already known to philosophers on hac at LVI. Ezperiments on the Electricity of High-Pressure Steam. By H. L. Partinson, Esq., F.G.S. Zo the Editors of the Philosophical Magazine and Journal. GENTLEMEN, VERY singular phenomenon, viz. the production of electricity by two steam-boilers, has been observed in this neighbourhood within the last few weeks, the particulars of which I have the pleasure of transmitting to you for publi- cation in your valuable Journal. The boilers in question are situated at Cramlington Colliery, eight miles north-east of Newcastle, where they supply steam to a high-pressure en- gine of 28-horse power, employed on the waggon-way to haul full and empty waggons to the top of two inclined planes, leading to the Colliery on the one hand, and to the river Tyne on the other. The boilers are cylindrical, with circu- lar ends, each twenty-one feet long, and five feet diameter. They are supplied with water from an adjacent pond by iron feed-pipes, four inches diameter, and the steam they produce is conveyed to the working cylinder by other iron pipes, six inches diameter, which pipes form also a direct metallic com- munication between the tops of the boilers. By means of ap- propriate valves the steam is supplied to the cylinder from one or other boiler at pleasure. A pipe, two inches diameter, leads from the bottom of one boiler on the outside of the brick-work to the ash-pit, through which the sediment deposited by the water is occasionally blown from one of Scott’s patent collect- ing cones, and a similar pipe is attached to the other boiler. The boilers are set in brick-work in the usual way, the fires below, with flues reaching all round, and passing into the chimney also in the usual manner. ‘The flues are covered with large flat bricks, and in the space between the boilers the two flues are necessarily separated by a brick wall. The safety-valves are attached to the boilers by flange joints; and between the flanges, to render them steam-tight, is placed a ring of plaited hemp covered with a cement of litharge, sand and linseed oil, mixed up together, and when applied of the consistence of glaziers’ putty. ‘This cement, as it soon becomes hard, is used about the engine for steam joints which occasionally fail; but all the joints of the pipes are made of iron borings and a much smaller scale, and about which there are as yet doubts whether it is to be referred to mere evaporation, as Harris says, or to chemical action, according to others. ‘This point it neither settles nor illustrates ; but it gives us the evolution of electricity during the conversion of water into vapour, upon an enormous scale, and therefore brings us much nearer to the electric phenomena of volcanos, water-spouts and thunder-storms, * than before.—M. F. 376 Mr. Pattinson on the sal-ammoniac, as ordinarily employed by engine-wrights. The steam is worked ata pressure of thirty-five pounds per inch. The joint between the top of one of the boilers and the seat of its safety-valve had given way, and steam was issuing forcibly through this aperture, when on Tuesday, September 29th last, the engine-man, William Patterson, while standing with this current of steam blowing upon his legs, took hold of the weight attached to the lever of the safety-valve, to try the strength of the steam, when he felt a peculiar pricking sen- sation in the ends of his fingers, but as the steam prevented him from seeing distinctly, he thought he had merely struck his fingers rather suddenly against the weight. On Friday, October 2nd, on taking hold of the lever, he again felt a sen- sation in his fingers of the same kind as before; and on Saturday, the 3rd, on touching the weight, this sensation was stronger, and more distinct; so much so, as to arrest his at- tention and Jead him to mention it to some other workmen employed about the engine, who all handled the weight, and convinced themselves that there was something about it very unusual. During the time they were thus-employed, Patterson applied his finger gently to the lever, and perceived a spark. This was repeated by the whole party, and they soon found that sparks could be obtained from any part of the end of the boiler, as far as the valve upon the steam-pipe connecting the two boilers, and also from the pipe through which the sediment is blown, as already described. ‘They observed further, that while standing in the volume of steam issuing from the joint, and touching the boiler, these sparks were always much stronger than when the boiler was touched by a person not in the current of steam. In one or two cases, according to their account, when the current of steam issuing from the joint was very strong, the person exposed to it being probably partially insulated by standing upon the dry and warm brick-work surrounding the boiler, gave strong sparks to others out of the current on bringing his hands to theirs; and once or twice they felt, under these circumstances, some- thing like a slight electrical shock. It may be observed, that at this time the weather was exceedingly fine and dry. It was not long before the engineer of the colliery, Mr. Marshall, be- came acquainted with these circumstances, and his first feeling was to apprehend that the boiler was in danger of exploding, for,as he said, ‘*when there wasfire on the outside of the boiler, he did not know what there might be within.” He accordingly sent to Messrs. Hawks’s, of Gateshead, who built the boiler, for a person toexamine it,and Mr. Golightly, their manager in that department, went out on Wednesday, the 7th inst., for that pur- pose. He gave his opinion as to the safety of the boiler, and Electricity of High-Pressure Steam. 377 returned much surprised at the phzenomena it presented. ‘The singular circumstance of a steam-boiler yielding electrical sparks, and giving shocks, now began to be noised abroad ; and my friend, Mr. Henry Smith, of Newcastle, who had heard the account both from Mr. Golightly and Mr. Marshall, wrote me a note acquainting me with the matter, and desiring me to go with him to see it, which I did on the 11th inst., and again on the following day, having with us the second time proper electrical apparatus. On our first visit, the boilers being unplugged and empty, we merely satisfied ourselves as to all the particulars of their setting, etc., already detailed. Next day, on our arrival, we found the engine at work, the steam up to a pressure of thirty-five pounds an inch, and blow- ing off strongly at the joint in the boiler. ‘The day was a little damp, but yet not unfavourable, and we were informed on alighting that the indications of electricity were very faint and weak; however, we proceeded to our examination, of which the following is the result. 1. On touching the boiler with the blunt point of a pen- knife anywhere about the circular end, the weight or the safety- valve itself, with the steam strongly blowing out of the joint, but with no part of the person exposed to the volume of steam, no spark could be perceived whatever. 2. On immersing one hand in the current of steam, and touching the parts of the boiler already named with the point of a penknife held in the other, a very minute but distinct spark was perceived, and this occurred equally on all parts of the boiler, or safety-valve, within reach. 3. By standing in the current of steam, so as to allow it to blow forcibly upon the person, the spark became larger; it was then one-eighth of an inch long. 4. On holding a large shovel in the current of steam with one hand, and touching the boiler with a penknife held in the other, a spark was obtained three-eighths of an inch long. 5. The cap of a gold-leaf electrometer, the bottom of which was held in the hand, was applied to the weight, the body of the operator being entirely out of the current of steam; and no divergence was produced whatever. 6. The electrometer held in the hand had its cap applied to the weight, the other hand of the operator being immersed in the current of steam: strong divergence was immediately produced. From this it was evident that the electricity proceeded from the steam ; but as the boiler-house was damp, so that insulation by glass could not well be preserved, a copper wire was at- tached to the shovel already mentioned, the end of which wire terminated in the engine-house, some yards distant from the ee 378 Mr. Pattinson on the Electricity of Steam. boiler-house, where was placed a table. The shovel was held by Mr. Smith in the current of steam, with its edge about an inch and a half from the aperture through which the steam issued, and the wire leading away from the shovel was insu- lated by being attached to sticks of sealing-wax held by assist- ants. Mr. Smith stood on an insulating stool. 7. On touching a pith-ball electrometer, the threads of which were five inches long, with the insulated wire leading from the shovel held as mentioned, the balls diverged four inches with positive electricity. 8. ‘The wire was attached to an insulated tin conductor, when it yielded sparks half an inch in length. F- 9. A pointed wire attached to this conductor exhibited the brush of light a quarter of an inch long, which always attends the escape of positive electricity from a point into the air. 10. A small jar was now charged so strongly as to give a rather disagreeable shock. By this time a large crowd of men, women and boys from the * Pit Raw,” -or pitmen’s re- sidences near the colliery, attracted by the novelty and singu- larity of the circumstances, had gathered about us, filling the engine-house and looking on with great curiosity and interest. A circle of sixteen of these men and women was formed, and they received together, much to their surprise and merriment, a powerful shock from the charged jar. This was several times repeated, the numbers receiving the shock varying each time from twelve to twenty. 11. A stout card was perforated by a discharge of the jar; and cotton wrapped round the end of a copper wire and dipped in pounded resin, readily set on fire. 12. When the edge of the shovel was made to approach the aperture through which the steam issued as near as three- quarters of an inch, very vivid and bright sparks of that length passed continually between it and the boiler. 13. The second boiler did not discharge steam through any fissure, but on lifting its valve by the hand it blew off in a strong current. When the shovel was held in one hand in this current of steam issuing from the safety-valve, and the boiler was touched with a penknife held in the other, a spark passed exactly, as under the same circumstances in the boiler subjected to the above experiments. From this it would appear that the steam of both boilers was in the same electrical condition. During the whole of these experiments the engine was doing its work as usual, occasionally going and occasionally standing ; but no difference was observed in the electricity given off by the steam. . I have been most careful to supply an exact account of the Professor Sylvester on Elimination. 379 facts of this extraordinary, and, as far as I know, unprecedented case, but I do not offer any theory to account for the phzno- mena. It is hardly possible to suppose that there is any local peculiarity about these boilers, or the place where they are situated, to occasion the highly electrical condition of the steam pr oduced in them; and yet it is as difficult to suppose the fact of high-pressure-steam being electrical, a general one; for if it were so, it could hardly, up to this time, have escaped observa- tion. The conditions, therefore, under which steam becomes electrical require to be investigated, and it is not unlikely that the investigation may lead to important results. I am, Gentlemen, Your obedient Servant, Bentham-Greve, Gateshead, H. L. Parrinson. October 19, 1840. LVII. Note on Elimination. By J. J. Svtvester, F.R.S., Professor of Natural Philosophy in University College, Lon- don*. "THE object of this brief note is to generalize Theorem 2. in my paper on Elimination which appeared in the last December Number of this Magazine. The Theorem so ge- neralized presents a symmetry which before was wanting. Here, as in so many other instances, the whole occupies in the memory a Jess space than the part. To avoid the ill-looking and slippery negative symbols, | warn my reader that I now use two rows of quantities written one over the other, to denote the product of the terms re- sulting from taking away each quantity in the under from each in the upper row. Let h, fy «+ h, be the roots of one equation of co- existence. o, fig seceny Ke, OF the Qther And let the prime derivative of the degree r be ReaUisee Take any two integer numbers p and gq, such that p + g = The derivative in question may be written, gpg Gn Gah a ie ex (rr eee es) ~ (Ga eee ie kg is ls Hy ‘ky ge ) Rainy Cia ae kigiaee Kin N.B. Whatever p and q be taken,‘so long only as p + q¢ * Communicated by the Author. 380 Royal Society. =r, the above expression changes nothing but its sign; which, therefore, upon transcendental grounds, it is easy to see is of one name or another, according as p is odd or even. - In the original paper, I asserted this theorem only for the case'of p = 0 or g = 0. | University College, London, Oct. 29, 1840. LVIil. Proceedings of Learned Societies. ROYAL SOCIETY. June 18, HE following letter was read from G. G. Anson, Esq., 1840. addressed to the President, enclosing a specimen of a deposit with which nine acres of land near Exeter, belonging to Lord Radnor, had been covered after the subsidence of a flood, and which was sent by H.R.H. Prince Albert, F.R.S. :— “« Buckingham Palace, June 8, 1840. «My pear Lorp, «His Royal Highness Prince Albert has commanded me to for- ward to you the enclosed specimen, which has been sent up to His Royal Highness from Lord Radnor’s place near Exeter, where nine acres of land were covered with this curious substance after a flood had subsided. His Royal Highness thinks it very probable that the subject may already have been brought before the Royal Society, but in case it should not have been, he sends the accompanying packet. It is said that a good deal of it has been applied to the purpose of making waistcoats for poor people. ‘« Believe me, «* My dear Lord, ** Yours very faithfully, “© G. G. Anson.” “ The Marquis of Northampton, President of the Royal Society.” The following description of the specimen referred to in the letter, drawn up by John Lindley, Ph. D. F.R.S., was also read : “‘ Description of the Specimen referred to in the preceding letter.” By John Lindley, Ph. D., F.R.S. The plant which overran Lord Radnor’s land is the Conferva crispa of Dillwyn, which is said to be the Conferva fluviatilis of Linnzeus. The species inhabits fresh water, and multiplies with great rapidity, forming entangled strata. ‘The green portion is the Conferva in its young state, the white portion is the plant old and bleached. The whole mass consists of articulated filaments, among which are frag- ments of grass-leaves. The following papers were then read, or their titles announced :— 1. An Account of Experiments on the Reflecting Telescope. By the Right Hon. Lord Oxmantown, F.R.S. This paper enters minutely into the details of the experiments, of the precautions requisite to ensure success, and of the manipulations a Royal Society. 381 ultimately adopted in forming a speculum three feet in diameter, subsequently applied to a telescope, mounted in a manner very si- milar to that of Sir John Herschel. ‘The author states, as the re- sults he arrived at, that specula can be made to act effectively, when cast of the finest speculum metal, in separate portions, and retained in their positions by an alloy of zinc and copper, as easily wrought as common brass, and that they can be executed in this manner of any required size; that castings of the finest speculum metal can be ex- ecuted of large dimensions, perfect, and not very liable to break ; that machinery can be employed with the greatest advantage in grinding and polishing specula; that to obtain the finest polish, it is not necessary that the speculum should become warm, and that any temperature may be fixed upon, and preserved uniform during the whole process; and that large specula can be polished as accurately as small ones, and be supported so as to be secured from flexure. 2. On the theoretical explanation of an apparently new Polarity in Light. By G. B. Airy, Esq., M.A., F.R.S., Astronomer Royal. The existence of a polarity in the rays of homogeneous light, ha- ving regard only to the sequence of colours in the spectrum, was in- ferred by Sir David Brewster from some experiments, of which he has given an account, contained in the Report of the Seventh Meeting of the British Association. The author states the results of his own observations of similar phenomena, and their theoretical explanation on the undulatory theory, together with the mathematical develop- ment of that explanation*. 3. On the Ferrosesquicyanuret of Potassium. By Alfred Smee, Esq. Communicated by P. M. Roget, M.D., Sec. R.S. The author examines, in this paper, the action of chlorine upon the ferrocyanate of potassa, and the conversion of the latter into ferrosesquicyanuret ; and proposes methods for obtaining this latter salt uncontaminated with impurities, and free from the difficulties and inconvenience attendant on the present mode of preparation +. 4. On the influence of Iodine in rendering several argentine com- pounds, spread on paper, sensitive to light; and on a new Method of producing, with greater distinctness, the Photogenic Image. By Mr. Robert Hunt. Communicated by Sir John Herschel, Bart., a P.BS. This paper contains various details of the results of a great number of experiments made with a view of rendering paper capable of being employed instead of metallic plates, in Daguerre’s photographic process. It is accompanied with 12 papers as spe- cimens. 5. Hourly Observations of the Barometer and Thermometer at sea, on the 21st of March, 1840. By Major-General A. Lindsay, H.E.I.C.S. Communicated by Sir John F. W. Herschel, Bart., V.P.R.S: These observations were made on board the ship Owen Glendower, on her voyage from Calcutta to London. * See our present volume, p. 31.—Epir. + Mr. Smee’s paper will be found in our present volume, 382 Royal Society: —Prof. Johnston on the Constitution 6. On the Constitution of Pigotite, and on the Mudesous and Mudesic Acids. By James F. W. Johnston, Esq., M.A., F.R.S. In this paper the author describes a substance, found by himself and by the Rev. M. Pigot, forming an incrustation on the sides of certain caves, occurring in the granitic cliffs on the east and west coast of Cornwall. This incrustation is in mass of a brown, and in powder of a yellow colour; is insoluble in water and alcohol; when heated, it gives off much water, blackens, yields empyreumatic pro- ducts, and leaves a black mass, having occasionally the lustre of graphite. In the air, at a bright red heat, this mass very slowly burns, leaving a grey or white ash, which consists of alumina, with some slight foreign admixtures. The organic constituent of this substance (pigotite), the author considers to be derived from the decay of the various plants which grow on the moist moorlands above, and which, being carried by the waters into the fissures of the granite beneath, combines with the alumina of the decomposed felspar; and when it reaches the air, deposits itself on the roof and sides of the caverns, in the form of layers, varying from a line to two or three inches in thickness. With reference to its supposed origin, the author has given to the organic constituent the name of mudesous acid (from pudnos, signifying decay through excess of moisture) ; and he mentions an observation, communicated to him by Dr. Boase, that the roots of the sea-pink (Statice Armeria) contain a colouring matter resembling, in appear- ance, the solutions of the mudesous acid. From numerous experiments and analyses detailed at length in his paper, the author derives the following general results : 1. That the native pigotite contains a dark-brown soluble, not deliquescent acid of vegetable origin, which, in the anhydrous state, is represented by C,, H, Og. 2. That this acid, the mudesous, is tribasic, the salt of silver (mudesite), being represented by (8 A, O + C,,H,O,), and pre- cipitates the salts of the metallic oxides of a brown colour. 3. That the native mudesite of alumina (Pigotite) is repre- sented as follows: a. Dried in the air by (4 Al + C,.H, 0, + 27H). 6, Dried at 212° F. by (4 Al + C,H, O, + 8 H O), losing 27 per cent. of water. c. Dried at 300° F. by (4 Al + C,,H, 0, + 8HO), losing 32 per cent. of water. 4, That this native mudesite, however, is more probably a com- pound of the organic tribasic salt, with a hydrate of alumina, and may be rationally represented thus : a. Dried in the air by (Al+ C,.H,O, + ,HO) + 3 (Al + 6HO). b. Dried at 212°F. by (Al+ C,,H,O, +4HO) + 3(Al+2HO). c. Dried at 300° F. by (Al+©,,H,O, + 2HO) + 3(Al+2HO). of Pigotite and the Resins. 383 5. That when treated with nitric acid, the native mudesite, as well as the mudesous acid itself, are oxidized and converted into a new brownish-yellow, soluble and deliquescent acid, containing more oxygen, and in the anhydrous state represented by C,. H; O,9. 6. That this new acid, the mudesic, combines readily with alu- mina and protoxide of mercury, giving salts of a yellow colour. Both the acids described in this paper are distinguished for their tendency to precipitate alumina and the protoxide of mercury. The mudesate of mercury dried at 300° F., is represented by (2H, O + Co H, O40). 7. That chlorine, when made to act on either of the acids, or their salts of alumina in contact with water, gradually deprives them of all colour, while, at the same time, muriatic acid is formed. Col- lected on the filter, boiled in water till the washings cease to pre- cipitate nitrate of silver, and dried, the white gelatinous, apparently altered mudesite or mudesate, is found on analysis to contain no atomic proportion of chlorine, but to have sensibly the constitution of the mudesic acid, or mudesates prepared by the direct action of nitric acid. The author thinks it not unlikely that a chloro-mudesic acid exists, and may be formed during this process, represented probably by C,, H,C1Oj,,, but which he has not succeeded in ob- taining in a separate state. The mudesous and mudesic acids are distinguished from each other by giving, the former brown, and the latter yellow precipitates with the neutral metallic salts—by being, the former unaltered, and the latter deliquescent in the air. Both form deliquescent salts with ammonia, and appear to undergo alteration by the long-continued action of hydrosulphuric, or of concentrated sulphuric and hydro- fluoric acids. 7. On the Constitution of the Resins, Part V. By James F. W. Johnston, Esq., M.A., F.R.S.* In this paper the author continues his examination of what are called the fetid resins, and from repeated analyses deduces for the resin of Sagapenum the formula C,,. H,, O,, and for that of Galbanum C,) H,, O,. He then compares the formule for the four resins : Opoponax = C,)H,,0,,, Assafoetida = Cy) Hog Ojo, Galbanum = C,, H,,O,., Sagapenum = C,, H,,0, ; and considers it probable “that, though no striking analogy among the irrational formule for these resins is perceptible, by which their analogy in physical properties can be accounted for, they may pos- sess an analogous rational constitution which future researches may disclose. Euphorbium consists of two resins, of which the more soluble, A, gave the formula C,,H,, O;. Elemi also consists of two resins, of which the more soluble, A, is represented by C4) H,. O,, and the less soluble, B, by Cyo H5. O,, as had previously been shown by Hess * Abstracts of the preceding series will be found in Lond. and Edinb. Phil. Mag., vol. xv. p. 3827, and present vol. p. 147.—Epir, 384 | Royal Soczety. and Rose. ‘The Bdellium of commerce contains much gum, and a resin C.. H,, O,. The resin of Benzoin presented peculiar difficulties when sub- mitted to investigation, from the ease with which it undergoes de- composition, even at temperatures much below that at which it melts. With regard to this resin, the author gives the following as the result of his numerous analyses :-— 1. That the colourless resin of benzoin is represented approxi- mately by Cyo Ho. Oo. 2. That by heat and dilute carbonated alkalies it is decomposed into water, benzoic acid, a little volatile oil, and a resin C49 Hy; Oy, or C4 Ha, O,. 3. That by boiling with quicklime, or concentrated carbonated alkalies, it gives two resins, one in large quantity = C,, H,, O,; and another in small quantity = C,) H5, O,. 4, That by caustic potash the crude resin is resolved into two re- sins represented respectively by C49 Ho. Oy, and Cyo H59 O,, of which the former is precipitated, and the latter remains in solution, when a saturated aqueous solution of caustic potash is added to an alcoholic solution of the crude resin. 5. And that by oxide of lead two resins are separated, for which analysis gave respectively the formule C,,H,.O,, and Cyg Hog Ojo. The author concludes by stating that such metamorphoses are by no means confined to this resin, though the more accurate know- ledge of their nature, obtained by the imperfect study he has made of the resin of benzoin, has explained many anomalies he had pre- viously observed, with regard to the relations of the resins to the al- kalies and metallic oxides. He considers the group of which dragon’s blood is the type, and which he represents by the expression Cyo Ha, ++ # O, to be peculiarly susceptible of modification (or decomposition?) by the action of bases; and he specifies among other results, with regard to which it is his intention to address the Society in a future paper, that dragon’s blood, of which the lump yanety == Cy, Ho, O,, and the drop variety (heated to 300° F.) == Opie Oa sives by the action of quicklime and oxide of lead, among other products, two resins represented approximately by C49 Hop Ojo and Cy Hy Og ?—that guiacum = Cyo Ho3 Ojo, with oxide of lead, gives a resin = C,. H,, O,,, the resin of jalap = C,)H,,0,,; by the action of the same oxide, a resin = C,)H,, O40; and that of assafoetida = C,, H,,O,., a new resin = C 49H, Oj;. These metamorphoses lead to the second great branch of inquiry respecting the nature and constitution of the resins. Certain results being established, at least approximately, with regard to the trrational constitution of the resins, and certain general irrational formule by which to express it, we are prepared for the study of their ratzonal constitution. ‘This part of the subject the author proposes to con- sider farther in subsequent communications. 8. Researches on the Tides. ‘Twelfth Series. On the Laws of the Rise and Fall of the Sea’s surface during each tide. By the Royal Society. 385 Rev. W. Whewell, B.D., F.R.S., Fellow of Trinity College, Cam- bridge*. The materials of the present investigation are five months’ tide observations made at Plymouth; three months’ observations made at Liverpool, under the direction of Captain Denham, R.N.; and twelve months’ observations made at Bristol, by Mr. Bunt, by means of his tide-gauge. According to the theory of the tides, the height of the surface of the water at a given place will increase as the sine, while the time increases as the arc. Hence if the time be made the abscissa, and the height the ordinate, the curve representing one tide would be the figure of signs. The author on making the com- parison of the empirical curve of the rise and fall of the water, de- duced from observation, with this theoretical curve, finds a general agreement between them; subject to certain deviations, consisting principally in the empirical curve indicating that both the rise and the fall are not symmetrical, like the theoretical curve, in conse- quence of the fall being generally more rapid than the rise, and thus occasioning a displacement of the summit of the curve towards that branch of it which corresponds to the fall. 9. Researches in Embryology. Third Series.—Additional Ob- servations. By Martin Barry, M.D., F.R.S.+ Having in the paper to which the present is supplementary made known the fact that the germinal spot in the mammiferous ovum re- solves itself into cells, with which the germinal vesicle becomes filled, the author has since directed his attention to the corresponding parts in the ova of birds, batrachian reptiles, and osseous fishes, which he finds to be the seat of precisely the same changes. The numerous spots in the germinal vesicle of batrachian reptiles and osseous fishes are no other than the nuclei of cells. The cells themselves, from their transparency, are at first not easily discerned, and appear to haye hitherto escaped notice; but after the observer has become aware of their presence, they are, in many instances, seen to be ar- ranged in the same manner, and to present the same interior them- selves as the corresponding cells in the ovum of mammalia. In the representations given by Professor Rudolph Wagner, the discoverer of the germinal spot, the author recognizes evidence of the same changes in ova throughout the animal kingdom. He con- firms and explains the observations of R. Wagner, that in the ova of certain animals an originally single spot divides into many, and that in the ova of other animals the number of spots increases as the ovum ripens. But he expresses also the opinion that in all ova there is originally but a single spot, this being the nucleus of the germinal vesicle or cell. The analogy between the ova of mammalia and the animal above- mentioned, extends also to the substance surrounding the germinal vesicle, which consists of nucleated cells. 10. Description of a Calculating Machine invented by Mr. Thomas * See Lond. and Edinb. Phil, Mag., vol. xv. p. 316.—Epir. t Ibid., vol. xvi. p. 526.—Epir. Phil. Mag. 8.3. Vol. 17. No. 111. Nov. 1840. 2C A OS ~ 386 Royal Society. Fowler, of Torrington in Devonshire. By Augustus De Morgan, Esq. Communicated by F. Baily, Esq., V.P.R.S. The arithmetical operations performed by the machine are those of multiplication and division; the factors and product in the for- mer case, and the quotient, dividend and divisor in the latter, being expressed in digits of the ternary scale of notation, every digit be- ing either — 1,0, or +1. In this system, unity being, in multi- plication, only an index, the rules for multiplication and division must consist entirely in directions for the management of the signs of unity; and it is on this principle that Mr. Fowler’s machine is made to act. A short account is given of the principal parts of the machine, and of the mode in which they bring out the final results. It is necessary, however, in applying it to use, to have recourse to tables, both for converting the factors and reconverting the result; operations which introduce both labour and risk of error. 11. On the Minute Structure and Movements of Voluntary Mus- cles, in a letter addressed to R. B. Todd, M.D., F.R.S., &c. By William Bowman, Esq., Demonstrator of Anatomy in King’s Col- lege, London, and Assistant Surgeon to King’s College Hospital. Communicated by Dr. Todd. The objects of the author, in this paper, are the following.—1st. To confirm, under some modifications, the view taken of the primi- tive fasciculi of voluntary muscles being composed of a solid bundle of fibrille : 2dly. To describe new parts entering into their com- position: and 3dly. To detail new observations on the mechanism of voluntary motion. He first shows that the primitive fasciculi are not oylindatintg but polygonal threads; their sides being more or less flattened where they are in contact with one another; he next records, in a tabular form, the results of his examination of their size in the different di- visions of the animal kingdom. It appears that the largest are met with in fish; they are smaller in reptiles, and their size continues to diminish in insects, in mammalia, and lastly, in birds, where they are the smallest of all. In all these instances, however, an extensive range of size is observable, not only in different species, but in the same animal, and even in the same muscle. He then shows that all the fibrille into which a primitive fasciculus may be split, are marked by alternate dark and light points, and that fibrille of this description exist throughout the whole thickness of the fasci- culus; that the apposition of the segments of contiguous fibrillz, so marked, must form transverse striz, and that such transverse striz do in fact exist throughout the whole interior of the fasciculus. He next inquires into the form of the segments composing the fibrille, and shows that their longitudinal adhesion constitutes fibrille, and their lateral adhesion discs, or plates, transverse to the length of the fasciculus ; each disc being, therefore, composed of a single segment from every one of the fibrille. He shows that these discs always exist quite as unequivocally as the fibrillz, and gives several exam- ples and figures of a natural cleavage of the fasciculus ito such discs. It follows that the transverse striz are the edges, or focal sections of hie Geological Society:— Anniversary Address. 387 these discs. Several varieties in the striz are then detailed, and the fact noticed that in all animals there is frequently more or less di- versity in the number of striz in a given space, not only on conti- guous fasciculi, but also on the same fasciculus at different parts. The author then proceeds to describe a tubular membranaceous sheath, of the most exquisite delicacy and transparency, investing each fasciculus from end to end, and isolating it from all other parts ; this sheath he terms Sarcolemma. Its existence and properties are shown by several modes of demonstration; and among others, by a specimen in which it is seen filled with parasitic worms (Trichine), which have removed all the fibrille. The adhesion of this sarco- lemma to the outermost fibrille is explained. It is also shown that there exist in all voluntary muscles a num- ber of minute corpuscles of definite form, which appear to be identi- cal with, or at least analogous to the nuclei of the cells from which the development of the fasciculi has originally proceeded. ‘These are shown to be analogous to similar bodies in the muscles of ors ganic life, and in other organic structures. The author next describes his observations on the mode of union between tendon and muscle; that is, on the extremities of the pri- mitive fasciculi. He shows that in fish and insects the tendinous fibrille become sometimes directly continuous with the extremities of the fasciculi, which are not taper, but have a perfect terminal disc. In other cases the extremities are shown to be obliquely trun- cated, where the fasciculi are attached to surfaces not at right angles to their direction. Lastly. He states his opinion, and gives new facts on which it is founded, that in muscular contraction the discs of the fasciculi ve- come approximated, flattened, and expanded; the fasciculi, of course, at the same time becoming shorter and thicker. He considers that in all contractions these phenomena occur; and he adduces argu- ments to show the improbability of the existence of any ruge or zigzags as a condition of contracting fasciculi in the living body. The paper is abundantly illustrated by drawings of microscopic ap- pearances. The Society then adjourned over the long vacation, to meet again on the 19th of November. GEOLOGICAL SOCIETY. [Continued from p. 309.1 MINING RECORDS OFFICE. A third department, which it is proposed to add to this establish- ment, is an office, for the preservation of such records and docu- ments relating to subterranean operations throughout the country as are important to be preserved for the information of future gene- rations. To the keeper of these records will be assigned the duty of ar- ranging the documents which may be transmitted to him from all parts of the kingdom, by any engineers, mineral surveyors, and proprietors of mines and coal works, who may be willing to ae OR’ 388 Geological Society: —Anniversary Address. send them; particularly maps, sections, and under-ground plans, which will record the state of each mine, when it is abandoned, for the information of those who at a future period may be disposed to bring it again into operation. This office will be accessible to all persons interested in obtaining the information it will afford. To this collection several engineers of most extensive experience in the mines of Newcastle and Cornwall have promised large con- tributions. The keeper will make copies of documents of this kind, which proprietors of mines, who cannot conveniently part with the ori- ginals, may lend, for the purpose of being preserved in this national collection. _ The public importance of such a records office was submitted to the Lords of Her Majesty’s Treasury by a Committee of the British Association for the Advancement of Science, assembled at New- castle in August, 1838; it being notorious that great losses of life and destruction of property have resulted both at Newcastle and in other coal mines throughout the kingdom, from the imperfect pre- servation of records of the operations previously conducted in them, and that still greater losses will inevitably ensue hereafter, unless ad- vantage be taken of the experience of living engineers and coal pro- prietors, who are willing to place ina public national repository copies of the documents they possess relating to their respective mines. In 1834, the attention of the public was called to this subject by Mr. T. Sopwith*, an eminent civil engineer and mine surveyor at Newcastle; and this gentleman is preparing a practical book of instructions on the subject of drawing geological and mining plans, the conducting of subterranean surveys, and examining mineral dis- tricts, with a view to the preservation of such information respecting the state of each mine at the period when it may be abandoned, as may be useful when further proceedings are afterwards commenced therein, or in its vicinity. A museum of ceconomic geology, comprehending institutions of this kind, demonstrates, even to the unlearned, the advantages that result from science in its application to the extraction of the trea- sures which Providence has laid up in the rich storehouses of the interior of the earth; and by exhibiting the results obtained from the elaboration of these materials, by the industry of man, in the workshop and at the forge, will afford a full and satisfactory reply to the question so often raised by persons to whom the value of the truths of pure science and philosophy, pursued for their own sake, are unintelligible,—and by whom everything is appreciated merely according to its immediate subserviency to the acquisition of wealth, or its ministration to the daily necessities or conveniences of human life. BUILDING-STONE COMMISSION. Another event which marks increasing attention to the practical importance of geology, is the publication of a Report to the Commis- * See Sopwith on Isometric Drawing, p. 50, ef seq. Building-Stone Commission. 389 sioners of Her Majesty’s Woods and Forests, from a Commission appointed by the Lords of the Treasury ; containing the results of an inquiry into the qualities and durability of the various Building- stones of this country, with a view to the selection of the best ma- terial to be employed in erecting the New Houses of Parliament. The results of this inquiry have been arranged in Tables, which represent the composition, colour, weight, size, cost, durability, &e., of all the most important kinds of stone that have been used in an- cient edifices in England; the Commissioners having judiciously appealed to that which is the most severe test of the durability of any stone, viz. the existing condition of the decorated architecture in our most ancient buildings. The Norman portions of the Church of Southwell, in Nottingbam- shire, constructed of magnesian limestone, in the twelfth century, have been found to afford an example of stone which combines strength and durability with applicability to ornamental carved work, in a degree surpassing all other kinds of stone that have been em- ployed in the most ancient fabrics of this country; the sharpest of the mouldings and carved enrichments of that church being throughout in as perfect a state as when first executed. The keep of Koningsburgh Castle, near Doncaster, built also of the magne- sian limestone in that vicinity, offers another proof of the durabi- _ lity of certain beds of this formation, exceeding that of any other building-stone in Great Britain, which is equally fit for ornamental purposes. But there are also varieties of magnesian limestone, such as that of which York Cathedral is built, which are in far advanced stages of decay, where they have been used for mouldings and ar- chitectural decorations. The general result of this elaborate inquiry into the durability of the different varieties of magnesian limestone is, that the stone re- sists decomposition in proportion as it is more perfectly crystalline ; a result, the cause of which is further illustrated by the experi- ments of Professor Daniell, which show that the nearer the magnesian compounds approach to equivalent proportions of carbonate of lime and carbonate of magnesia, the more crystalline they are. No investigation has been made by these Commissioners as to the capabilities of granite, porphyries, and other kinds of stone, which are inapplicable to the decoration of edifices without enor- mous expense. The Report is followed by valuable tabular lists of the most re- markable ancient fabrics in England, specifying the materials of which they are constructed, and their various conditions of preser- vation or decay, as they are respectively built of sandstone, or of Oolitic, shelly, or magnesian limestone. . To these are added tables of the chemical analysis, weight, cohe- sive power, specific gravity, and power of absorbing water, of many of the building stones most largely employed in England*. * [It may be added, as evincing the strong interest which this Report has excited, that its contents have been specially illustrated, by one of the Come | 390 Geological Society :—Anniversary Address. I consider this Report as of the highest value, in showing the general advantages which may be derived from connecting scientific knowledge with practical arts; and I trust we shall hear no more of such discreditable and unfounded assertions as, not, long ago, passed uncontradicted, at a meeting of an architectural society in London, that Stonehenge is made of statuary marble. GEOLOGICAL COMMITTEE OF ENGLISH AGRICULTURAL SOCIETY. The appointment of a Geological Committee, by the English Agricultural Society, at their meeting in Oxford, in July last, shows the sense entertained by that numerous body of landed proprietors, and cultivators of the soil of England, of the important services which may be rendered to them, by the application of geological knowledge to the improvement of the productive capabilities of the land. It is well known to geologists that an almost unbounded supply of mineral manure may be found in the sub-strata, which in very many districts are composed of ingredients different from those of the surface. So constant are the characters of many of the beds of the geological groups which pass in long and narrow bands from one side of England to the other, that a single experiment, carefully conducted, on any one stratum of each formation, with a view to ameliorate its soil, by an admixture of the ingredients of some other adjacent stratum, will afford an example which may be followed with similar results in distant parts of the kingdom, through which this same stratum passes, in its course across the island. Experiments, therefore, conducted by the owners and occupiers of land, under the advice of this Geological Committee, aided by the facilities for the analysis of soils now afforded by the laboratory of the Museum of Ciconomic Geology, may shortly enable us to realize at least some share of the success that attended Lavoisier’s application of chemistry to agriculture in France*. SCHOOLS OF CIVIL AND MINING ENGINEERING IN THE UNIVERSITIES OF DURHAM AND LONDON. The increasing demand for education in practical science has been recently provided for in the University of Durham, by the establish- ment of a course of instruction in Civil and Mining Engineering, with lectures in the Mathematical sciences, Chemistry, Metallurgy, Mineralogy, Geology, Surveying, Mapping, and Drawing, in addition to Ancient and Modern Languages. ‘To theoretical instruction in missioners, Mr. Charles Smith, in lectures delivered before the Society for the Encouragement of Arts, &c. and the Institute of British Architects ; and by Mr. Brayley,in a Course on the Mineralogy of the Arts, delivered before the Architectural Society, at one of the Friday-Evening Meetings of the members of the Royal Institution, and in two lectures expressly on the results arrived at by the Commissioners, given at the Russell Institution.— Eprr. } * It was said of Lavoisier, that in ten years he doubled the produce of his land in grain, while he quintupled the number of his flocks. No doubt this report is much exaggerated. Schools of Engineering and Mines. 391 such parts of these branches of knowledge as bear more especially on Practical Engineering, are added at Durham occasional survey- ing excursions, both in the field and underground, conducted by a practical civil engineer. More than thirty young men have, during the last year, been actively engaged in this new department of aca- demical study.* : The locality of Durham, upon the margin of the great Newcastle coal field, and in the vicinity of the lead mines of Alston Moor, and Weardale, is in a peculiar degree favourable for a school of mining and civil engineering; enjoying advantages of position similar to those of the great Saxon school at Freyberg, near the mining dis- tricts of the Ertzgebirge and the Hartz. The University of London also is taking measures to institute examinations of Candidates for certificates of proficiency in Civil Engineering, and the arts and sciences connected with Mining. In University College, London, courses of preparatory experi- mental lectures and exercises in Natural Philosophy have, during the last year, been provided for the students in that establishment, who are destined for the Profession of Civil Engineers. And in King’s College, London, a course of lectures in Civil En- gineering, and Sciences applied to Arts and Manufactures, is at this time attended by more than fifty students, who have the opportunity of adding practical to theoretical knowledge in a workshop and la- boratory established for their use. SCHOOL OF MINES IN CORNWALL. Another proof of the direction of public attention to the col- lateral branches of our science has, within the last twelve months, been afforded by the establishment in Cornwall, of a school for the instruction in Sciences and Arts connected with Mrnine, of young men who are to be engaged in conducting the important subterra- nean operations of that county. The want of such a school had been pointed out by Mr. John Taylor, in his Prospectus of a School of Mines in Cornwall, February 7, 1825,+ and in his Records of Mining, published in 1829. It has at length been instituted chiefly through the exertions and at the expense of Sir Charles Lemon. This incipient school, and the University of Durham, form almost solitary examples in England, of such scientific establishments as are nearly universal in the mining districts of the Continent. The experiment has begun in Cornwall with Courses of Lectures in Mathematics, Mechanics, Chemistry, and Mineralogy, by three pro- fessors ; and a course of instruction, by a practical surveyor, in Al- gebra, Drawing, and the Use of instruments: and during the next year, still further additions are contemplated. * See Durham University Calendar, 1839, p.10. [See also a communi- cation on this subject by the Rev. Pref. Chevallier and Prof. Johnston, in Lond. and Edinb. Phil. Mag., vol. xiii. p. 1.—Eb1r.] [+ The Prospectus here alluded to will be found in Phil. Mag., First Series, vol. Ixvi. p. 137.—En1r. | ae | ath 392 Geological Society :—Anniversary Address. POLYTECHNIC SOCIETY OF CORNWALL. To the zealous exertions of Sir Charles Lemon, and of many intelligent and active individuals at Falmouth, the county of Corn- wall is also indebted for the establishment of a Polytechnic Society, which, during the few years of its existence, has been attended with extraordinary success. One of its chief objects is to encou- rage, by rewards, the invention and improvement of machinery, of which so large an amount is essential to the working of the mines. Another object is to collect materials for expressing the quantity and value of the mineral and other produce of the county ; and to con- struct tables indicating the diminished longevity, and diseases, which, in a peculiar degree, affect the Cornish miners, and do not prevail amongst those employed in Collieries. It appears, from a paper published in the Sixth Annual Report of this Society (1839), that the average duration of a miner’s life is less, by many years, than that of the agricultural labourer in the same district; the ap- parent causes of this frightful evil being the inevitably imperfect ventilation of many of the veins or lodes in which the miner works ; and, partly, the extreme fatigue of ascending from great depths by ladders, instead of being lifted by machinery, as the workmen are from coal pits: these pits also are usually susceptible of more per- fect ventilation, than the metalliferous lodes in Cornwall. The attention of this Society is strenuously directed to the dis- covery of remedies for these tremendous evils, which affect no fewer than a population of 28,000 persons; that being the proportion of the inhabitants of Cornwall, who are occupied in working the mines. LOCAL MUSEUMS. Another circumstance which marks the progressive advance- ment of public feeling as to the value of geology, is the increasing disposition to form local museums in our provincial towns. At the meeting of the British Association, at Birmingham, in August last, after a strong expression of opinion, in the Section of Geology, as to the benefit likely to accrue to science from the esta- blishment of Provincial Museums, for the local productions of each neighbourhood, the justness of the suggestion was so fully recog- nised, that, in the adjacent town of Dudley, before five days had passed, a public museum had arisen from contributions, out of the ca- binets of private collectors in that town; presenting to the Asso- ciation a more perfect assemblage than was ever seen, of the exqui- site organic remains found in the limestone of that district, which has long been the classic type of a formation widely and abundantly distributed over the globe. About this time also a provincial museum was formed at Brap- FORD, in a district abounding in splendid examples of the vegetable remains which pervade the Yorkshire coal field; where the exten- sive collieries now wrought will furnish abundant materials for a collection, destined to illustrate the history of the extinct forms of vegetable life, which have produced the coal. The museum at LrEps, also, possesses a valuable collection of fossil ~ Royal Institution of South Wales, British Museum. 393 vegetables from the coal field in its neighbourhood ; and the West Ripinc GEOLOGICAL Society, formed under the auspices of Earl Fitzwilliam, on the plan of holding quarterly meetings at different towns of the Riding in succession, is diffusing a taste for Geology, and affording ground for appreciating its practical importance, to numbers of intelligent persons, whose local occupations, and property in the coal and iron mines, will enable them to enlarge the fossil Flora and Fauna of our country. ROYAL INSTITUTION OF SOUTH WALES. From the first Annual Report of the Royal Institution of South Wales, published during the last year, we learn that the Swansea Literary and Philosophical Institution, hitherto supported by the town and neighbourhood, has been expanded, under Royal patronage, to the whole southern division of the Principality ; and is now establish- ing its Museum and Lecture Rooms in a large and commodious edifice in the town of Swansea, under the presidentship of Lewis Weston Dillwyn, Esq. The position of this Institution, in the midst of a great mining and manufacturing district, is peculiarly favourable for collecting facts illustrative of geological phenomena, more especially those of the Coal formation ; and much has already been done by Mr. Logan, to develope, with extreme accuracy and minuteness of detail, the stratigraphical succession of the rocks composing this formation ; and to show the number and nature of the events which attended their original deposition, as well as the subsequent derangements that have affected them. Mr. L. W. Dillwyn, also, is attempting a classification of the coal plants of the South Wales Bason; with a view to ascertain, by means of a comparative collection in the Swan- sea Museum, whether there exists any specific difference between those of the upper and lower beds of the carboniferous series. BRITISH MUSEUM. The accessions lately made to the British Museum form another subject, of high importance in our Review of the Geological Pro- ceedings for the past year. At the head of these is the purchase, from Mr. T. Hawkins, of an additional series of the remains of fossil Saurians from the Lias formation; which, added to his former collec- tion, already placed in this national repository, present an unrivalled series of species in the extinct families of Lchthyosaurus and Plesio- saurus, once inhabitants of Britain. Equally important was the acquisition, in a former year, of the unique collection of still more gigantic and not less monstrous Reptiles, from the Wealden forma- tion of Kent and Sussex, obtained by purchase from Dr. Mantell. The possession of these several collections places the Museum, where it ought to stand, at the head of all existing repositories of organic remains, almost exclusively the productions of England ; and it is due to his late exertions, whilst Chancellor of the Exche- quer, that I should bear this public testimony to the services which Lord Monteagle has rendered to science, by supplying the means 394 Geological Society:— Anniversary Address. of placing these unrivalled collections in our national repository ; where their constant presentation to the view of its thousands of daily visitors cannot fail to attract increasing attention to the won- derful discoveries of Paleontology. These important public events, occurring beyond our walls, and having a direct and immediate tendency to enlarge the field of our labours, form an epoch in the history of our science, and place Geology before the country in a new and more widely popular aspect than it had occupied before. The past year has been also distinguished beyond all precedent, by the number and value of the GEOLOGICAL MAPS it has produced. GEOLOGICAL MAP OF CORNWALL AND DEVON. The first map which I shall mention, affords another example of the recognition by Government of the importance of our subject, by their having attached a geological department to the Ordnance Survey of England and Wales. ‘The first fruits of this appoint- ment are the splendid Maps of Devon and Cornwall, and a part of Somerset, coloured after the surveys of Mr. De la Beche; and it may be truly said of them, that they are more beautiful in their execution, more accurate in their details, and more instructive in the ceconomical and scientific information they give respecting imines, than any maps yet published by any government in the world ; affording documents to which we can at length with pride appeal, in reply to the reproach that has so long, with too much truth, been cast upon us, that England alone, of all the civilized nations, has abandoned to gratuitous individual exertions, and the liberality of amateurs in science, the great work of exploring and delineating the mineral structure of the country ; and ascertaining the nature and extent of the subterraneous produce, which lies at the foundation of the industry of its manufacturing population, and to which the nation owes no small portion of its wealth. The statistical importance of this first portion of the Ordnance Geological Map of England will be duly appreciated only by those, who know the extent of the property embarked in the mining inter- ests of the Western counties, and are aware that the annual value of the mineral produce of Cornwall and Devon alone has recently amounted to 1,34.0,0002. In the chapter on Ciconomic Geology, which forms part of the Memoir connected with his Map of Cornwall and Devon, Mr. De la Beche has placed, in a more prominent light than has ever yet appeared, the bearing of geological researches and mineral statistics upon political ceconomy; and proves, by tabular documents, the important fact, that the average value of the annual produce of the mines of the British Islands amounts to the enormous sum of 20,000,000/.*, of which about §8,000,000/. arise from iron, and 9,000,000/ from coal. * See Geological Report on Devon and Cornwall, p. 624, and note, 1839, In this estimate the value of the copper is taken in the ore, before fusion ; New Geological Maps. 595 Should this inquiry be extended through the endless departments of art, industry and commerce, which have their origin in the manufactories of metals, and in the power of steam, derived exclu- sively from the application of coal, the vast national importance of mineral statistics, and of models, maps and sections, on which alone their details can be effectually recorded, must be apparent to every one. Still more extensive will be the statistical and political importance of the next portion of this great work, now in progress by the same highly accomplished geologist, which is to comprehend the coal and iron districts of Monmouthshire and South Wales. GEOLOGICAL MAP OF ENGLAND. You have this day the satisfaction to see suspended in your meet- ing-room a new edition of Mr. Greenough’s Geological Map of Eng- land, which has for many years formed the glory of this Society. It is truly gratifying to observe how small a change this new edi- tion exhibits, either in the general dispositions, which it represented nearly a quarter of a century ago, or in the complicated details of the boundaries of the different formations. Some alterations appear in the Greensand series, the Wealden, the Lias, and the New red Sandstone. The principal additions are the introduction of the Si- lurian divisions made in the slate rocks, by Mr. Murchison, in the border districts of England and Wales; and the new distribution very recently assigned to the slate rocks of Devonshire and Corn- wall. A great improvement also has been made by the substitution of an entirely new Map of Wales and Siluria, founded on the Ordnance surveys of those regions, of which no accurate physical map ex- isted at the time of Mr. Greenough’s first publication. Another improvement in the execution consists in the union of linear shadows with the colours representing the superficial extent of the strata. The combined effects of these elements of expression, judiciously employed, has been to exhibit, more distinctly, the subdivisions of formations, without destroying the unity of the general mass to which they belong. By the frequent introduction also of conven- tional signs, and figures of reference, Mr. Greenough has produced a more condensed assemblage of scientific information, of varied kinds, than has been put together in any map of equal extent yet published. Extreme attention has also been paid to the physical features of the country, and in the orographic details more than 500 heights are given. The hydrographic features also are deli- neated with scrupulous exactness. GEOLOGICAL MAP OF IRELAND. The last summer has witnessed the production of Mr. Griffith’s large and splendid Geological Map of Ireland, containing the results that of the iron, lead, zinc, tin and silver, after fusion, in their first mar- ketable condition —as pigs, blocks and ingots. The coal is valued at the pit’s mouth. 396 Intelligence and Miscellaneous Articles. of nearly thirty years’ investigation, by that eminent geologist and civil engineer. Mr. Griffith had supplied an outline of this map published in the Report of the Railway Commissioners for Ireland, 1838. It is obvious that the information thus conveyed, as to the nature of the materials of which the island is composed, affords the most solid basis for sound calculation as to the future improvement of Ireland by the application of its natural resources. GEOLOGICAL MAP OF A LARGE PORTION OF EUROPE. During the last year we have also witnessed the publication of a beautifully coloured general Geological Map of Germany, France, and England, and parts of the adjoining countries, compiled from the larger original maps of Von Buch, Elie de Beaumont, and Greenough, by Professor Von Dechen, in one large sheet, published at Berlin.* This map exhibits the geological details of a larger continuous portion of the surface of the earth than has ever before been put together with so much exactness, and set forth on such eminent authority. It also presents to the statesman and political ceconomist the most important portions of central Europe, under the new aspect of the natural divisions of the mineral formations, of which each country is composed ; showing that in every region the nature and disposition of the substrata lie at the foundation, not only of its agricultural productiveness, but also of its capability of supplying the materials, which form the basis of its industry end arts. As an historical document, this map demonstrates the rapid progress of our science, and the state of maturity which it has attained. Thus far I have occupied your attention with external matters of extraordinary interest in the history of our science, which show that geological knowledge is spreading its salutary influence, more widely and rapidly than heretofore, over the practical business of the country. I now proceed to consider the communications made to the meetings of our Society during the past year. [To be continued. ] LIX. Intelligence and Miscellaneous Articles. NOTE REFERRED TO IN THE ABSTRACT OF PROFESSOR DANIELL’S PAPER, p. 354. Hi preceding considerations will furnish a satisfactory clue to the apparently anomalous origin of the currents in Becquerel’s circuits; when, for example, nitric acid is placed on one side of a diaphragm, and solution of potassa on the other, platinum electrodes being placed in either cell and the circuit completed, oxygen is evolved on the potassa side, and hydrogen shows itself in the acid by its secondary action. ‘‘ Nitrate of potassa is of course formed at the junction of the acid and alkali. Now let us recollect what ni- trate of potassa is in its electrical relations: it is an owinitrion of po- dassium (N+60)+P. Aqueo-nitric acid is also an owinitrion of * Schropp and Company, 1839. Intelligence and Miscellaneous Articles. 397 hydrogen (N +60) +H; and potassa is oxide of potassium (P +0). In their local action upon each other, the acid and the alkali are both decomposed; the oxinitrion of the former combines with the metal of the latter, and water is formed by the union of the hy- drogen and oxygen. ‘This water there is no difficulty in regarding as a separate and secondary product, inasmuch as the salt is inca~ pable of combining chemically with it. «When a circuit, however, is formed of proper conductors, the compositions and recompositions take place through a series of con- nected particles, as in the manner of all other electrolytic conduc- tion: and the oxygen and hydrogen, instead of combining together, as in the local action, are respectively evolved at the zincode and platinode. The following diagrams may perhaps assist in explain- ing my notion of the origin and connexion of the current :— Ie eae ge “ar oN meas aN OP OPOP|(N+60)H(N+60)H(N+60)H B as a eas « Let O P and (N + 60) H represent the two electrolytes on the opposite sides of the diaphragm A B before the action; after action has commenced they may be represented thus :— ~~ aS Zire OPOPOP|(N+60)H(N+60)H(N + 60)H.” B NEW COMPOUND OF PLATINA. Messrs. Rogers and Boyé have stated to the American Philoso- phical Society the existence of a new compound of platina. It is prepared by evaporating a solution of platina in aqua regia to dry- ness, and adding in small portions at a time a great excess of aqua regia. The compound may be thus readily obtained by filtration, and pressing the powder between folds of blotting-paper. If the concentration of the liquid be carried too far, it is necessary to add just as much water as is sufficient to keep the mass in a semifluid state, and to preyent the precipitation of the deutochloride of pla- tina. The salt is perfectly well characterized, and is composed of deuto- chloride of platina and nitric oxide. It is of a gamboge yellow co- lour, and crystallizes distinctly, though on account of the small- ness of the crystals, their form has not been yet determined; it is very deliquescent, and absorbs atmospheric moisture at common temperatures with great avidity. It is rapidly decomposed by the mere addition of water, which causes a brisk effervescence of nitric oxide, and deutochloride of platina remains in solution. When this compound is heated to 212°, it does not yield its com- bimed water. In order to determine the quantity of platina and chlorine, the salt was fused with carbonate of potash, and the platina thus obtained was weighed, the chlorme was then precipitated by a solution of nitrate of silver. ‘The quantity of nitric oxide was 398 Intelligence and Miscellaneous Articles. determined by introducing a portion of the salt into a graduated tube, inverted over mercury, and by decomposing it with water. The mean of experiments performed in different modes gave as the composition of this substance,— Ohlormeée* 28 es ee ik rem oe Nitric oxide ...... ee Ss Ae 4:98 Pretrerae 0 OP ae See ae 41°26 Water and 16s6. 22 eae fie: 9°87 100. BLUE OXIDE OF TITANIUM IN SCORIA. In analysing the blue scoriz of different countries, M. Kersten found sma!l quantities of titanic acid, and that these scorie possessed a blue colour similar to that of the blue oxide prepared in the dry way; he presumed, therefore, that this colour, instead of being derived from the protoxides of iron and manganese, which some- times occur in them, might be owing to titanic acid [oxide ?]. Ac- cording to the facts above stated, it is very probable that titanic acid, which occurs very often in the ores of iron, after having been dis- solved and scorified during the operations of the blast-furnace, is reduced to the state of oxide by the fused iron, similarly to what occurs in the humid way with solutions, and as has happened in se- veral preceding assays. If this assumption be well founded, it ought to be possible, with the substances usually contained in the scorie and with titanic acid, to reproduce blue glass on the small scale. M. Kersten succeeded, not only in fusing together silica, lime, alumina, titanic acid and iron, all of them pure, and in pro- ducing earthy glasses of a blue colour, resembling the blue scoriz of iron, but also succeeded in obtaining them with the same earths, titanic acid and zinc free from iron, or with pure tin. M. Kersten, therefore, concludes from these researches, that the blue colouring matter of many iron scorie is the blue oxide of ti- tanium. ‘This blue oxide deserves some attention from its applica- tion to the arts, and the author endeavoured to procure blue ena- mels upon porcelain by using it; and though they were not so fine as those of cobalt, they most nearly approach them.—L’/nstitut, No. 353. —_——— ON THE PROTEIN OF THE CRYSTALLINE HUMOUR. This substance was discovered by Berzelius, and according to him it constitutes 35°9 per cent. of the crystalline humour, and does not become, like albumen, a coherent mass by coagulation, but a granular one. In other respects its properties are similar. This new product may be obtained as follows :— The crystalline humour is to be carefully separated from fifty ox- eyes, they are to be washed, the cells torn, water is to be added and filtered. ‘The liquor heated in a water-bath soon coagulates and deposits clots. After drying, the pounded mass was subjected to the action of alcohol and water, and boiled; after this it was dried at 266° Fahrenheit. Meteorological Observations. 399 Thus obtained this substance is white, and’ possesses all the pro- perties of albumen, but is not easy to pulverise it. When it is put into a solution of potash in a silver vessel, the silver is blackened, which shows that it contains free sulphur : it contains no free phos- phorus. The composition of the crystalline humour [protein ?] is stated to be Hydrogen.... 6°94 or 62 atoms. Carbon :...,. 55°89 —.40 — Oxygen .... 21:16 — 12 — 2.0): a 16°54 — 10 — The quantity of sulphur is in the proportion of one atom to fifteen atoms of protein. The entire crystalline humour dissolved in nitric acid, mixed with a solution of nitrate of iron and precipitated by ammonia, furnishes the same quantity of phosphate of lime as a hydrochloric solution of the same substance. The phosphoric acid is derived from the phos- phate of lime; the substance therefore contains no free phosphorus. If the crystalline humour in a very dry state be put into sulphuric acid, it swells, and is converted into a transparent gelatinous mass, like the protein of caseum, fibrin, &c. By the addition of water it contracts and yields a hard powder. The author concludes that the principle of the crystalline humour is protein, for it possesses the same composition and atomic weight as the pure protein of albumen, fibrin, caseum, &c.—Journal de Chim. Médicale, Aott, 1840. METEOROLOGICAL OBSERVATIONS FOR SEPT. 1840. Chiswick.—Sept. 1, 2. Fine. 3. Rain. 4. Cloudy:rain. 5,6. Fine. 7, 8. Very fine. 9. Hazy. 10—13. Very fine. 14. Hazy: heavy rain. 15. Cloudy: rain at night. 16. Rain, with brisk S.W. wind: barometer exceedingly low. 17. Very fine: frosty at night. 18. Frosty haze: very fine. 19. Cloudy and cool. 20. Fine. 21. Fine: rain. 22. Heavy rain. 23. Rain: clear and fine at night. 24. Heavy showers. 25. Cold and wet. 26. Overcast: rain. 27. Cloudy and fine. 28. Heavy rain. 29, 30. Clear and fine. Boston.—Sept. 1. Cloudy. 2. Fine. 3. Rain: rain early am. 4—6. Fine, 7. Cloudy. 8. Fine. 9. Cloudy: rain early a.m. 10. Fine: rain early a.m. 11,12. Fine. 13. Fine: rainr.m. 14. Cloudy. 15. Fine. 16. Fine: rain early a.M.: rainer.m. 17. Cloudy: rainearly a.m. 18. Fine: rainr.m. 19, 20. Cloudy. 21. Cloudy: raine.m. 22. Stormy and rain: raina.M. 23. Rain: rain early a.m. 24. Fine: rainearly a.m. 25. Rain: rain early A.m.: rain a.M. 26. Fine: rainr.m. 27. Fine. 28. Cloudy. 29, Fine: rain p.m. 30. Fine. Applegarth Manse, Dumfries-shire.—Sept. 1. Fine harvest day: air electric. 2. Rain from midday. 3,4. Showery. 5. Fineand clear. 6. Fine but cloudy. 7. Fine: afew drops of rain. 8. Cloudy a.m.: rain r.m. 9. Wet: cleared up: wet again. 10, 11. Occasional heavy showers. 12. Moist, but moderate. 13. The same: oneshower. 14. Fineandclear. 15. Cold and showery. 16. Rain A.M. 17,18. Very fine. 19. Fine A.M.: moistr.m. 20. Fine a.m. 21. Fine A.Mm.: showery. 22. Fine and dry: thundera.m. 23. Rain. 24, Fine and fair. 25—27. Very wet. 28, 29. Moist. 30. Showery. Sun shone out 28 days, Rain fell 21 days. 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The monthly means gave the daily difference greatest in August, * We have now extended our observations so as to include some of the hours of the night. + As the ste dethtias of the absolute declination have not yet been made with the requisite exactness, the variations are here given in divi- sions of the scale, each division being 27-2261 seconds of arc, 2K2 420 Prof. Kreil’s Deductions from the first Year's Observations = 36°01; in April 33:01; and least in December, = 8°41, if the observations at 8 a.m. and 1 p.m. are compared, or 13°06 if those at 1 p.m. and 10 p.m. are compared. The secular decrease appears to have been unusually great this year; if the apparatus showed correctly, it amounted from July 1839 to June 1840, to no less than 17:70 divisions of the scale, = 8' 01"-9; but as in October, 1839, the thread by which the needle was suspended broke, this result may be inexact. The observations of the following month, however, show a still greater decrease. If we take the mean of all the observations from 5 a.m. to 10 p.m., we obtain the following declinations : 1839. November. Declination = 417°80 December; 5, —————— = 416'88 1840. January. — = 415°80 February. §.——— == 4a March. ee = A10:35 April. —— = 407°50 May. a = 402°87 June. _—_—_—~ = 399°30 The declination, therefore, decreased in these eight months 18°50 scale divisions, cr 8! 237. 2. The horizontal intensity observed with the bifilar had in the winter months its Minimum ......=544'42* at 11 a.m. Maximum ......=564°83 at 10 p.m. Difference ......== 20°41 In summer, its Minimum ......=443'63 at 10 a.m. Maximum ......=488°90 at § p.m. Difference,.....== 45°27 The minimum was earliest in August, when it took place at 9 a.m., and in June, when it occurred at 9" 30™ a.m.; it was latest in December, at 1 p.m.; and in January was at 11" 45™ a.m. ‘he maximum appears to fall in winter, 1. e. in December, January and February, during the hours of the night; it was earliest, at 8 p.m. in July, November, April and June. The following are the means of all the observations between 5 a.m. and 10 p.m. * A scule-division in this apparatus corresponds to 18°5757 seconds ofarc, or ,st>; of the whole horizontal intensity; but it should be re- marked, that since the instrument was set up in May, 1839, the magnetism ef a bar has not been examined, in order that the series might not be roken, at the Magnetic Observatory at Prague. 421 1839. July. Horizontal intensity = 532°41 August. ——— = 465°54 September. ———— = 488°85 October. ——— = 489°12 November. ———-— = 559:27 December. —-—-— = 598°58 1840, January. ——— = 58691 February. ——— = 552°68 March. —— = 560°01 April. —_—— = 498:00 May. —— AUST 17 June. — = 39601 The numbers here given are not corrected for the influence of temperature, because it appears to affect not only the in- tensity, but also the direction of the magnetic force, and we must wait for more certain data. ‘The continued and simul- taneous observations of the bifilar magnetometer and the in- clinatorium have shown, indeed, that changes of temperature are always accompanied by changes in the horizontal intensity; but they are also accompanied by corresponding alterations in the dip, which increases as the horizontal intensity de- creases, and vice versd. In some months of the year a decrease takes place in the horizontal intensity between 2 and 5 p.m., which may be ascribed to the maximum of inclination which occurs in those hours; this was previously recognized in the Milan observa- tions. 3. In winter the inclination attains its minimum at 6 a.m., and its maximum at 3 p.m. Minimum ....... 270°69* Maximum ...... 272°02 Difference ...... 135 In summer the minimum is at 5 a.m., and the maximum at 8 a.m. Minimum ...... 289°70 Maximum ...... 291'23 Difference...... 1°53 The several months show at all seasons a small minimum of the inclination about noon, whence we must conclude that * The value of a scale-division = 28°185 seconds of arc. The appa- ratus was set up in June, 1839, but was not sufficiently steady to give value to the observations with it until August; it continued, however, sub- ject to atremulous motion occasioned by passing carriages until February, 1840, when this disadvantage was remedied. 422 Prof. Kreil’s Deductions from the first Year’s Observations the two maxima, one in the forenoon and the other in the af- ternoon, always occur, though in the summer months the former is the most conspicuous, and in the winter the latter ; the observations which I had previously made at Milan were not sufficiently numerous to manifest the occurrence of this noon-minimum. Observations made in May and June,1840, at 2 and 4 a.m., show a maximum and minimumin the hours of the night, which sometimes exceed those above-mentioned. In May, at 11 p.m. the maximum ... ... at 2 a.m. the MINIMUM. ..oee wee 246°43 244°49 Difference se... 1:94 In June, at 11 p-m. the maximum ...... = 267°73 at 4a.m. the Minimum... ... «- = 266°53 Difference...... 1:20 The circumstance already noticed, that these maxima are in some months almost insensible, makes it difficult to recog- nize the dependence of the hour of their occurrence on the season of the year. . The following numbers, which are the monthly means of all the observations of the inclination made between 5 a.m. and 10 p.m., will show to what considerable alterations that element is subject in the course of a longer period. 1839. August. Inclination = 368°06 — September. = 374°42 October. = 366°42 November. = 336°40 December. ———— = 294°18 1840. January. eee tee Doane February. ———~—~ = 196'59 March. —— == 182°91 April. ———s- = _ 19747 May. ee = 245°59 June. —— 1° 966°70 If we compare these numbers with the means of the hori- zontal intensity, we shall not, it is true, see any perfectly par- allel march, which indeed we ought not to expect, as the horizontal component depends on the total intensity as well as on the dip; but it is sufficiently clear that there is a ge- neral accordance, the horizontal intensity increasing with the decrease of dip, and vice versd: therefore the changes of inclination indicated by the instrument are not to be ascri- bed to mere alterations of the centre of gravity in refer- ence to the point of suspension, but are, in part at least, at the Magnetic Observatory at Prague. 423 due to the altered direction of the force itself. It would seem then that the dip is subject to much greater alterations than has been hitherto recognized; and this is quite con- ceivable, if we suppose temperature to be one of the chief causes of the variation of the magnetic elements; for if the daily progress of the temperature from east to west produces the large diurnal variation in the declination, its annual march from south to north, and vice versé, ought in like manner to occasion an annual variation in the znclination. 4, The times of oscillation of the dipping needle showed during the winter,— S. Diff. At 8am. a maximum = 12°86978 j At 10a.m. a minimum = 12°8 5321 Spee : ; 0°01602 At 2p.m. a second maximum = 12:86923 0:02100 At 8 p.m. a second minimum = 12°84823 In summer, At midnight, a maximum. At 6 p.m. a minimum : es 12:50 79 0:02359 At 2 p.m. a second maximum = 12°57437 000832 At 9 p.m. a second minimum = 12°56605 The midnight maximum was shown by the night observa- tions of May and June. The dependence of the hours of maximum and minimum on the season could not be recognized with certainty from the observations of each month separately considered; it ap- peared, however, as if those of the forenoon observed in winter approached progressively nearer to noon. The following are the monthly means of all the observa- tions made from 5 a.m. to 10 p.m. s 12:02318 1839. August. Time of vibr. = September. = 11°86037 October. ———EE = 11°78188 November. + = 11°90803 December. —_——_ = 12°69148 1840. January. —— = 13°36133 February. = 13°40867 March. = 14°00672 April. ee = 13°76645 May. ane ae = 12°77688 June. — = 12°39025 From these numbers, which are not corrected for the in- fluence of temperature, or for any decrease in the magnetism of the bar, we cannot trace a connexion with the tempera- ‘ture, such as has been usually supposed to exist, viz. a de- 424 Prof. Kreil’s Deductions from the first Year's Observations creased force in increased temperature, and wice versd; but there is a correspondence between these numbers and the monthly means of the inclination; the inclination having de- creased aud the times of oscillation increased from October to March, whilst subsequently to March the inclination in- creased, and the times of oscillation decreased. Such obser- vations, continued with instruments somewhat differently con- structed, but having the same purpose in view, will soon show what part of this apparent connexion in the variations of the intensity and inclination is due to the instrument, and what to the phanomena themselves. 5. The influence of the moon on the magnetic condition of the earth was examined in the saine manner as was done in the case of the Milan observations. Having corrected approximately the observed horizontal intensities for tempera- ture and the loss of magnetism sustained by the bar, there appeared a confirmation of the results previously obtained, viz. that the magnetism of the earth is stronger at the time of the new moon than when the moon is full. The mean of the whole body of the observations showed an intensity During the last quarter = 549°99 At the new moon = 548°79 During the first quarter = 542°62 At the full moon = 541°11 6. The difficulty referred to in par. 2. of freeing the ob- servations of the horizontal intensity from the influence of temperature, and the uncertainty of the correction for the de- crease of magnetism in the bar, induced me to adopt a mode of arranging the observations in reference to the inquiry re- latively to the moon, by which the errors arising from both these causes might be avoided. Ifthe moon has an influence on the magnetic condition of the earth, it must produce a daily variation, masked by the greater effect produced by the sun, but recognisable when the latter is eliminated. I con- structed, therefore, tables, having for their argument the day of the month, and for the titles of the several columns the different distances of the moon from the magnetic meridian, i.e. her magnetic horary angles. To simplify the calcula- tion, I assumed that the moon passed the magnetic meridian an hour earlier than the true meridian. I deducted from each observation the monthly mean corresponding to the solar time of the observation; thus eliminating the influence of the sun, considered as the cause of the regular diurnal variation, ‘This deduction being made, the remainders repre- sent the sum of all other influences; but as these numbers were sometimes + and sometimes — I augmented each by a at the Magnetic Observatory at Prague. 4.25 constant quantity. The numbers thus obtained were entered in the tables, each in the column corresponding to the distance of the moon from the magnetic meridian at the time of the observation. Irom the great number of observations that were in this combination, it might be expected that the effects of other influences would disappear, and that of the moon alone would be visible. The two horizontal elements, the declina- tion and intensity, were thus treated, and the means obtained for the separate months were combined in a yearly mean, which is represented in the following table :— I. Declination in Scale-divisions, each = 27'-2261. Eastern : Western Horary Angles. et ae, HoraryAngles. 12 11:44 1]°21 1] | 13 10:96 | 10°79 10 14 11:14 11:01 9 15 10°78 10°64 8 16 10:76 10:24 i. LZ 10°55 10°69 6 ni ho: 10°51 10°42 5 19 10°52 10°15 4 20 10°66 10°16 3 21 10°48 10°32 2 22 10°54 10°46 1 23 10°97 | 10°62 0 From this table we may draw the following conclusions :— I. If we take the sums of the declinations during the eastern and during the western horary angles, we find the first sum to exceed the second by 2°60 scale-divisions = 70"-79; therefore the declination is greater when the moon is east of the meridian, as already shown by the Milan obser- vations. IJ. If we compare the sum of the declinations correspond- ing to the horary angles from 6% to 175 with those from 184 to 55, the first sum exceeds the second by 4°40 scale-divisions = 119"°79; the declination is therefore greater when the moon is in the neighbourhood of the inferior meridian : and the table shows that it is greatest at the hour when the moon is on the inferior meridian. III. From the comparison of the sums of the declinations corresponding to the horary angles from 21" to 2" with the sums of those from 18" to 20%, and 3" to 54, it results that the first sum exceeds the second by 0°97 scale-divisions = 26'*41 ; therefore it appears that at the time of the moon’s passin the superior meridian, a second maximum of the declination 426 Prof. Kreil’s Deductions from the first Year’s Observations does take place, though considerably less than the one indi- cated above. The results as to the horizontal intensity are contained in the following table :— II. Horizontal Intensity. Fastern ; . Western Hor. Angles. raed sini Hor. Angles. 12 32°92 34:15 1] 13 32°62 33°33 10 14 32°78 32°63 9 15 33°64 32°52 8 16 32°62 33°12 7 17 32°03 31:53 6 18 31°11 31°90 5 19 30°96 32°16 4 20 CO SENG 31:77 3 21 29°45 29:96 Q 22 29:07 30°31 1 23 29°92 30:04 0 From this table it appears :— I. That the intensity is stronger when the moon is west of the magnetic meridian, for the sum of the intensities corre- sponding to western horary angles exceeds by 5°14 scale-di- visions the sum of the intensities corresponding to eastern horary angles. II. The intensity is decidedly greater when the moon is in the neighbourhood of the inferior meridian than when she is near the superior meridian, for the horary angles from 6" to 175 give a sum greater by 28°08 scale-divisions than do the horary angles from 18} to 55. 7. The increased frequency and the greater number of the Prague observations enabled us to pursue the interesting phze- nomena of the magnetic perturbations with more exactness than we had been able to do at Milan. We proceeded in the following manner with both the horizontal elements. The changes were noted which had taken place between each observation and the next, and the sum of these (¢) was taken for each day without reference to their signs. ‘The monthly mean of these sums was taken and called >. Nowif on any day the quotient — was found greater than 2, that day was p> reckoned one of disturbance. It hence appeared that the magnetic elements frequently sustain a very considerable change of brief duration; though at the Magnetic Observatory at Prague. 427 during the remaining hours of the day, the perturbations may so little exceed the average, that on the whole it may not be a day of disturbance according to the above definition. This phenomenon, which may be called a magnetic shock, ought to be brought into notice, being, in fact, a perturbation of short duration, greater perturbations consisting only of several such shocks. As a definition of a magnetic shock, let g be the change in either of the magnetic elements be- tween two successive observations, and o the average change in the same month between every successive pair of observa- tions; then every change for which Es > 2, is to be regarded as a magnetic shock. The following table shows for each month the number of days of disturbance according to the above definition; and also the number of separate shocks which took place in addi- tion, namely, on days which were not those of disturbance. Table of Disturbances. Declination. Horizontal Intensity. Month. Days of Per- Days of Per- turbation. ets turbation. enous 1839. July. 1 1 5 2 Aug. 3 1 7 Z Sept. 5) 4 4 10 Oct. Z 15 10 3 Noy. 8 7 16 Bee Dec. 10 15 25 2 1840. Jan. 414 12 15 14 Feb. 7 8 9 bag March 5 ] 16 2 April 2 5 11 2 May 2 ] 13 ] June 1 ] 9 6 From this table we may infer :— I. That the perturbations are much more frequent in the winter than in the summer months; which may be caused, in part, by the force which produces the regular diurnal changes being much weaker in winter: but the very great perturba- tions which take place chiefly in the winter months, indicate that the disturbing forces have actually more intensity at that season of the year. ‘The greatest disturbances observed in the twelvemonth occurred on the following days:— 428 Prof. Kreil’s Deductions from the first Year's Observations 4th and 15th of September. 18th, 22nd, and 23rd of October. DOV tiie oes 8 aad ak »+eee0f November. 4th and 18th of January. 6th, 7th, and 9th of February. 29th and 30th of May. IJ. The days of disturbance are more numerous in the horizontal intensity than in the declination. III. In this year also several great perturbations were ob- served to occur on the same days on which the same phe- nomenon had taken place in preceding years. The days which particularly deserve notice in this respect, are about the 18th of January, from the 18th to the 22nd of February, and the 18th of October. Great disturbances were observed in 1837. January 16th. 1837. February 18th. 1838. 17th. 1838. * 16th ames 1839. 19th. 1839. 18th and 21st. 18th and 21st. 1840. 18th. 1840. 1836. February 17th. In February, 1840, the disturbance of the horizontal inten- sity was but feebly marked, probably in consequence of the very great perturbations which took place in the same month on the 6th, 7th, and 9th. The recurrence in October is a particularly marked one; ? 1836. October 18th. 1837. 18th. 1838. 17th. 1839. 18th. The two periods, February and October, are about equi- distant from the winter solstice. 8. If we put together, without respect to signs, the shocks which occur at the different hours of the day, both on the perturbation days and on others, we obtain as a final result the following table, exhibiting the number of scale-divisions by which the needles were displaced by disturbances. Sum of the Displacements. Hours. Declination. { Horizontal Intensity. Lf; "£6 419 536°44 1373°36 20 to 22 463:90 1746°14 Zoho so 497°95 1425°33 2to 4 697°76 1472°05 D tO any 1475°16 1911715 8 to 10 1481°17 296423 at the Magnetic Observatory at Prague. 4:29 This table shows that the least disturbance takes place in the declination from 8 to 10 a.m., and the greatest from 8 to 10 p.m., a result which had already appeared from the Milan observations. In the horizontal intensity also the disturbances are more frequent in the evening than in the morning. 9. If we now take the signs into account, and call an aug- mentation of either element +, and a diminution —, the fol- lowing table exhibits the remainders when the one sum is taken from the other. Direction of the Changes. Hours. Declination. | Horizontal Intensity. 17 to 19 — 0 92 —1219°69 20 to 22 + 224°56 Bo Sais) 23 to 1 + 203°34 — 120:13 2to 4 —405:36 — 104:75 5 to: 7 —654:°88 + 94°37 8 to 10 —556°19 = 29 are These numbers confirm for the declination the deduction already derived from the Milan observations, viz. that the declination is increased by the disturbances in the forenoon and middle of the day, and diminished by those occurring in the evening hours. In respect to the horizontal intensity, the negative signs are the prevailing ones, so that, in general, disturbances diminish this element, which is also in corre- spondence with the previous deductions; but it also appears from the numbers, that this occurs in a much higher degree during the hours of the night and morning than in the fore- noon and afternoon. - 10. During the greater disturbances we did not fail to ob- serve for several hours, from 5 minutes to 5 minutes, and to study the march of the phenomena in all the elements with as much exactness as possible. ‘Ten perturbations were thus observed, and the following circumstances were noticed as common to them all. ‘T’hese were before partly indicated by former observations, and appear to give a character of regu- larity to pheenomena which at first sight might be regarded as wholly irregular. I. Although the general effect of a disturbance is to weaken, on the whole, the horizontal intensity, considerable augmen- tations of that element do take place, but are of brief dura- tion, and always preceding the diminution. I]. The horizontal intensity remains weaker for some time 4.30 Prof. Kreil’s Deductions, Sc. after the great oscillations have ceased, and only gradually resumes its ordinary force. III. All the alterations of this element are accompanied by changes of the dip, and may chiefly be ascribed to them; an increase of dip, and a diminution of the horizontal inten- sity always taking place together, and vice versd. IV. The vibration of the dipping-needle is more rapid during disturbances, consequently the total force is increa- sed* ; and as we have seen that the horizontal intensity is weakened at such times, the influence of the increase of dip preponderates over the augmentation of the total intensity. In countries where the dip is much less than at Prague this may not always be the case, and the horizontal intensity may increase during a disturbance. V. The variations of the total intensity frequently occur simultaneously with those of the dip and horizontal force. In half the number of perturbations which were observed con- tinuously, the strongest total intensity coincided with the highest dip and least horizontal intensity, or the weakest total intensity with the smallest dip and greatest horizontal inten- sity; affording a further evidence that the variations of the horizontal component are chiefly due to the changes of dip. VI. In a strong disturbance all the three elements were usually affected, but in a variable degree, which may probably * This is in contradiction to the 23rd paragraph in my letter to M. Kupffer, (Phil. Mag., April 1840, p. 249), and I hope that it may prove a rectification. I consider the method applied to the Milan observations an unsafe one, as by it the daily means of the times of vibration on days of dis- turbance were compared with the average time of the whole month. Such a comparison cannot show with exactness the small effect which the pertur- bations produce in this element, because in the course of a month it is subs ject to too great changes, whether real or instrumental. The greater fre- quency of the observations in each day at Prague, enabled me to proceed in a different manner, namely by comparing the mean of a disturbed day with those of the preceding and following days. Occasionally, indeed, the observations of the same day evidenced the nature of the change produced by the dis- turbance; the times observed before the commencement of the perturbation being sensibly longer than those which were determined during its con- tinuance: thus the following times of vibration were cbserved on the 23rd of November. ; Before the disturbance. : After it had commenced. Peet 8. . mm, Ss. 3 30 Time of vibr. = 12:1569 9 0O Time of vibr. = 12°0724 4 30 = 12-1670 10 0 — = 12:0894 6 0 —_——_—. aoe Od OSL 11 0 = 12°0752 8 0 ———— = 121424 12 0.——— == 12:0624 13 0 = 12-0901 The following day the time of vibration returned to its previous dura- tion, Mr. Tovey’s Reply to Mr, Potter. 431 depend on the angle which the direction of the disturbing force makes with that of the regular force. By the hourly observa- tions, the 23rd. of March appeared to be a day of greater disturbance than any other in the month in respect to the hori- zontal intensity, although not a single shock was shown by the declination magnetometer. Had, however, the observations been continuous instead of hourly, the declination might also have been seen to have been disturbed. VII. The more these phenomena are studied the more strong becomes the impression of the importance of observing them at short intervals. Those of 5 minutes are too long, for the bar may alter its position many hundred scale-divisions in that interval, as we found by the Prague bifilar on the 22nd of October. On days of great disturbances, or when the aurora borealis is seen, we observe the two horizontal elements, here and at Gottingen, uninterruptedly for several hours at intervals of 15 or 20 seconds: it is much to be de- sired that this practice should become more general. In my letter to M. Kupffer, I noticed certain vertical vi- brations supposed to be produced by earthquakes. By a mistake of the pen these were said to have taken place in the dipping-needle, whereas it was in the declination magnetome- ter that they occurred. In Prague this instrument is sus- pended to a beam, which is supported by the principal walls of the house, and such vibrations only take place during very violent winds. In such cases there can be no doubt that they are due to this mechanical cause. In addition to the magnetic observations, we now note the temperature of the earth from one to five feet deep, and the height and temperature of the Moldau. I wish to add ob- servations on the temperature of the dew-point and the in- tensity of the sun’s rays, and shall be much obliged to you to inform me the price of the actinometer and the dew-point hygrometer, that I may request our government to purchase these instruments. I remain, with the highest esteem, &c. &c. Major Sabine, R.A. . Cart Krei. LXII. On Mr. Potter’s Application of Huyghens’s Principle in Physical Optics. By Joun Tovey, Esq. To the Editors of the Philosophical Magazine and Journal. GENTLEMEN, an your October Number, p. 243, Mr. Potter gives some examples of the application of the principle above-named; from which he contends that the result of this principle is 432 Professor Booth on the Focal Properties *‘ that light ought to bend into the shadows of bodies to an indefinite extent, as sound is known to pass through all aper- tures and to bend round all obstacles.” Consequently, ‘‘ that the result Mr. Airy (Tracts, p.270.) has obtained by an approximate method is not to be depended upon, and that the objection to the undulatory theory, which was believed to have been removed, remains in full force.” p. 246. I thought it possible that Mr. Airy might reply to this, but as he has not yet done so, I beg to be allowed to offer a few words, in order to point out the mistake which I conceive Mr. Potter has made. The expressions, which Mr. Potter obtains for the inten- sity of the light, have reference only to a certain line C B. He has not shown that there ought to be any light in the shadow except on this line. But a luminous line is merely a geometrical conception, from which no inference can be drawn as to the sensible intensity of the light in the shadow ‘where this line is found. It appears then that Mr. Potter has mistaken a luminous line for a luminous space; and, consequently, that his con- clusions have, in reality, no foundation. The meaning of what I have here stated may be illustrated by a fact which Mr. Potter has mentioned. The intensity of the light at certain points on a line in the centre of the shadow of a circular disc is, according to the theory, the same as if the light passed uninterruptedly. Now, when the disc is very small, and the light properly managed, a luminous spot may be observed in the centre of the shadow: when the disc is larger the spot vanishes; not from the diminution of its brightness, but from the diminution of its magnitude. Iam, Gentlemen, yours, &c. Littlemore, Clitheroe, Nov. 5, 1840. Joun Tovey. LXIII. On the Focal Properties of Surfaces of the Second Order. By James Bootu, A.M, of Trinity College, Dublin; Principal of and Professor of Mathematics in Bris- tol College. W/ BETHER properties of surfaces of the second degree exist, analogous to those of the foci of the conic sec- tions, has long been a subject of inquiry with the most distin- guished geometers; among whom may be mentioned as pre- eminent in researches of this nature M. Chasles and Professor MacCullagh, who have arrived independently at a series of discoveries, of which may be stated as the most im- portant and fundamental, the property, ‘ that in the prin- of Surfaces of the Second Order. 4.33 cipal planes of a surface of the second order, there exist conic sections, termed by him eccentric conics, confocal to the sections of the surface in the principal planes; possessing properties analogous to the foci of curves of the second order ; and cylinders perpendicular to those planes, bearing an ana- logy to the directrices of the same curves;” but this and other theorems of the same class, may be considered rather as the limiting relations of confocal surfaces, than as analogous to the well-known properties of curves of the second degree ; and this view of the subject is further confirmed by the consi- deration, that the theorems above alluded to fail in the very case most analogous to that of the conic sections, when the surface is one of revolution round the transverse axe. M. Chasles, indeed, in a very elegant memoir published now more than ten years ago *, has given several of the ana- logous theorems in the case of surfaces of revolution round the transverse axe, but has not hitherto extended his re- searches to the case of oblate spheroids, or to that of surfaces having three unequal axes, to do which is the object of the following pages. By a simple application of a new method, which has now been for some time published +, I have been led to the dis- covery of a very extensive class of properties of surfaces of the second degree, hitherto, I believe, entirely unknown ; from which may be easily deduced a series of theorems, relative to curves of the second order, none of which, so far as Iam aware, have been yet given to the public. The restricted limits of the present communication pre- clude the possibility of giving more than an outline of the theory, and the enunciations of several new theorems, the demonstrations of several of which being somewhat tedious, have been suppressed ; but this can cause no difficulty to any moderately expert analyst. (1.) Let a, 5, c, denote the three semiaxes in the order of magnitude of a surface of the second order, which for brevity may be represented by the symbol (=), and let the eccen- tricities of the three principal sections of the surface (>) be €, €, 7, so that a ee ie) pr 2 ee eer ie ae 2__ 72 Paste Loe a? sO (2.) Let « denote the semidiameter of the surface passing * * See the Nouveaux Mémoires del’ Académie Royale de Bruxelles, vol. vy. + See ashort treatise by the author, “On the application of a new Analytic Method to the theory of Curves and Curved Surfaces.” Dublin, Hodges and Smith, 1840. Phil, Mag. 8. 3. Vol. 17, No. 112, Dec. 1840, 2F 434. Professor Booth on the Focal Properties through one of its umbilicz, and let a point be assumed on this diameter, at the distance we from the centre; this point may be termed a focus of the surface. Hence in general a surface of the second order has fowr Foci, situated on the umbilical diameters. (3.) Let a plane be drawn parallel to one of the circular sections of the surface, meeting the umbilical diameter con- e . e o e ° Uu jugate to this circular section, at the distance —— from the € centre; this plane may be termed a directrix plane of the surface. This plane, and the focus of the surface, on the diameter of the surface, conjugate to this plane, are polar plane and pole, relative to the given surface. Hence in general a sur- face (>) has four piREcTRIx planes, parallel two by two, to its circular sections. Each pair of those planes intersect in the directrices of the principal section, whose semiaxes are a and 6; and these pairs may be termed conjugate directrix planes. The foci of the surface, which are the poles of the conju- gate directrix planes, may be called conjugate foci. The line joining a pair of conjugate foci is perpendicular to the plane of the principal section in the plane of «y, whose semiaxes are a and 6. (4.) Let the middle point of this line be called the ,focal centre of the surface. Hence in general a surface of the second order has four Foci and 7wo FOCAL CENTRES. Thus C is the centre of (&). G and G! are the umbilici, s and s' the conjugate foci of the surface; A D, A D’, the conjugate directrix planes ; O the focal centre of (=); or the focus of the principal section of of Surfaces of the Second Order. 435 (=) in the plane of zy, CG =u,CX =a,CZ=c,CY =}, CD = -, Os a5 CO=ae CA = =. (5.) Let 6 = DAC, be the angle which a directrix plane (or which a circular section of the surface as being parallel to it) makes with the plane of x y, or with the plane of the prin- cipal section, whose semiaxes are a and 4; then cos 9 = “. (6.) Let w be the angle which the umbilical diameter « makes with the corresponding directrix plane, then aC : AWA MN (@—0) (B—2)’ or sne = pai . Hence in two cases, the directrix plane is perpendicular to the diameter conjugate to it; either when the surface is one of revolution round the transverse axe, when 6 = c, or when (=) is an oblate spheroid, in which case a = 0. When the surface is an elliptic paraboloid, let 7 and /’ be the semiparameters of the parabolas in the planes of zy and xz ; }! 7° (7.) When (2) is a surface of revolution round the transverse axe, or the axis of X, y = 0; and in this case the conjugate directrix planes A D, A D! coincide and become perpendicu- tan?» = tan? CDI = then 6 = w, and sin? w = | : a Jar to the transverse axe C X, at the distance ey from the centre; and the foci of the surface coincide with the focal centre ; but when (=) is an oblate spheroid e = 0, and « = 9; in this case then 6 = 0, or the conjugate directrix planes be- come parallel to the plane of xy, distant from it by — and the focal centre coincides with the centre of the surface. (8.) When the surface is an elliptic paraboloid, one pair of conjugate directrix planes is infinitely distant, so that this surface has but ¢wo foci, and ¢wo directrix planes. (9.) When the surface is a cone, the conjugate directrix planes pass through the vertex, and are parallel to the circu- lar sections of the cone; the foci of the surface, and the focal centres all coincide with the vertex. (10.) The distance of a focus of the surface (=) from the focal centre, or from the plane of x y, is = ua : 2F2 436 Professor Booth on the Focal Properties (11.) The line OQ = I or the cord of (3) passing * through a pair of conjugate foci = ges : (12.) The length of the perpendicular from one of the». foci of the surface on the corresponding directrix plane, is Ae ee abe’ (13.) The length of the perpendicular from the centre on one of the directrix planes = rod : E (14.) ‘Che segment of the cord joining a pair of conjugate foci, intercepted between the plane of zy and one of the di- é cb rectrix planes, is = oR i . (15.) The length of the perpendicular from the focal centre on one of the conjugate directrix planes = aes : € We now proceed to give the enunciations of a very few theorems, merely as specimens of the results which flow from the preceding definitions, and the application of the method alluded to above; premising that neither the preceding de- finitions, nor the following theorems, are applicable either to the hyperboloid of one sheet, or to the hyperbolic parabo- Joid; and this may suggest a natural division of surfaces of the second order into two classes, the one containing the umbilical surfaces, the other those surfaces whose generatrices are right lines. Prop. —From any point t of a surface of the second order, let perpendiculars p, p’, be let fall on two conjugate di- rectrix planes; the rectangle under those perpendiculars is to the square of 7,—the distance of the point 7 from the focal centre O, relative to those conjugate directrix planes in a con- stant ratio, as the square of the perpendicular P from the centre on one of the directrix planes is to the square of the transverse axe a, or . ppl Pp ri Nae this constant ratio is one of equality, when the least semiaxis c of the surface is equal to the perpendicular let fall from the centre of the surface on the line joining the extremities of the semiaxes a and 0: this ratio of equality can never exist then when the surface is one of revolution round the trans- verse axes, except when (2) is an elliptic paraboloid. Generally when the ratio is one of equality, «° +4? = 1. of Surfaces of the Second Order. 4:3°7 When the surface is one of revolution round the transverse axe the conjugate directrix planes coalesce, p and p' there- ae _ fore coincide, and are equal, and P = —3 hence £ = wit “which is a fundamental property of surfaces of revolution and of the conic sections. When the surface is an oblate spheroid the conjugate di- rectrix planes become parallel to the plane of xy, and the focal centre coincides with the centre of the surface, the perpendiculars pp! are in the same right line but on opposite sides of r, hence in an oblate spheroid, if a right line is drawn perpendicular to the directrix planes meeting the surface in t, and the directrix planes in m and m’; the rectangle mr x tm! is to the square of the semidameter O fr, as the square of the distance between the directrix planes is to the square | of the diameter of the central circular section, or ms xtm mm re “a te tee When the surface is an elliptic paraboloid, let 7 and Jl! be the semiparameters of the parabolas in the planes of xy and x 2, then pp if w a Uh, When the surface is a cone, let « and § denote its semi- angles; « >6; then Pos smip re” tan? @’ or the square of the distance of any point on the surface of a cone from the vertex is to the rectangle under the perpendi- culars from the same point on two planes passing through the vertex parallel to the circular sections of the cone ina constant ratio. . Prop. II. -- The cone whose vertex is a focal centre of (>), and base any plane section of this surface, has its circular sections parallel to the planes passing through the vertex of the cone, and the right lines in which the base of the cone intersects the conjugate directrix planes. When the base of the cone passes through the right line, in which the conjugate directrix planes intersect, the planes parallel to the circular sections coincide, and the cene is therefore a surface of revolution. Hence the cone whose vertex is a focal centre of (>), and base any plane section of this surface, passing through the intersection of the conjugate directrix planes, is a surface of Jaime 438 Professor Booth on the Focal Properties revolution, its axis being the line joining the conjugate foci of the surface. When (2%) is a surface of revolution round the transverse ~ axe, the conjugate directrix planes coincide, therefore the - planes through the vertex of the cone and the intersections of the directrix planes by its base, coincide, hence the cone is™ a right cone, and we obtain the known theorem, that * the cone whose vertex is the focus, and base any plane section of a surface of revolution, round the transverse axe, is a right cone.” Hence also the cone whose vertex is the centre of an obe late spheroid and base any plane section of this surface, has its circular sections parallel to the diametral planes passing through the right lines in which the base of the cone inter- sects the parallel directrix planes. Prop. III].—The preceding theorem may be generalized thus: let a cone enveloping (>), having its vertex anywhere on the line QQ! joining the conjugate foci, be cut by any plane passing through the intersection of the conjugate di- rectrix planes in a conic section, the cone whose base is this section and vertex the focal centre of the surface, is a surface of revolution. . Prop. I1V.—Let a right line be drawn meeting a surface of the second order, in the points r and 7’, and the conjugate directrix planes in the points m and m’, the segments of this right line, mz and mz’, subtend equal angles at the focal centre. When the line is parallel to one of the directrix planes, it may be easily shown that the rectangle m+ x m7! = mO’s O being the focal centre, and m the point in which the right line meets the directrix plane to which it is no¢ parallel. Hence, if a tangent plane is drawn to a surface of the se- cond order at the umbilicus, meeting the other conjugate directrix plane (in a right line, the distances of any point in this right line from the umbilicus and focal centre are equal. When the surface is one of revolution round the transverse axe the points m and m! coincide, or the line O m bisects the supplement of the angle + Oz', which is a known property of such surfaces. Let a series of surfaces of the second order, having the same focal centre, and the same pair of conjugate directrix planes, be cut by any transversal; the segments of this right line, between each pair of surfaces, subtend equal angles at the common focal centre. When (3%) is a cone, if from m any point in one of the directrix planes a right line is drawn parallel to the other, of Surfaces of the Second Order. 439 meeting the cone in the points rz’, the rectangle mt x m/r = square of the distance of m from the vertex of the cone. Hence if a sphere is described through the circular base and vertex of a cone, the tangent plane to the sphere at the vertex of the cone is parallel to the second circular section of the Cone. Prop. V.—From the four foci of a surface of the second order, let fall perpendiculars on a tangent plane; multiplying together the perpendiculars from those foci which are situated on the same diameter and taking the sum, we have 19) Pa + Pip = 2 {B sin? y + —~ cos? vr}, v denoting the a? angle the perpendiculars make with the axis of Z. When (3%) is a surface of revolution round the transverse ae .p = pb = ¢ and u = a; hence Pp =p, When the surface is an elliptic paraboloid, P and P’ are infinite, and we obtain (p + p') cos = J sin? v + /' cos? v. X being the angle the perpendicular makes with the axis of X. Pror. VI.—Through any point of a surface of the second order, let two cords be drawn, passing through the extremities of the cord of the surface Q Q’, which joins a pair of conju- gate foci, and meeting one of the conjugate directrix planes in the points m, m', these points m, m', subtend at the focal centre a right anele, Prop. VII.—Let a plane quadrilateral be inscribed in a surface of the second order, whose sides, «, 6, y, 8, are pro- duced to meet one of the directrix planes in the points A, B,C, D. The sum of the angles which the points A, B and C, D subtend at the focal centre is equal to two right angles. Let two of the sides «, 3 of the quadrilateral be fixed, and let y,0 be variable; then A and B are fixed, and therefore the angle A OB is constant; hence also the angle C O D is constant, . Der.—The right line in which two tangent planes inter- sect, and the line joining the points of contact, are called conjugate polars relative to the given surface. Prov. VIII.—Two conjugate polars to a surface (2), meet one of the directrix planes in two points, which subtend a right angle at the focal centre. When the conjugate polars become conjugate tangents, the proposition still holds, and when the conjugate tangents are tangents to the lines of curvature they are at right angles. Hence if a tangent plane le drawn to any point of a surface, 440 Focal Properties_of Surfaces of the Second Order. meeting one of the directrix planes in a right line, and the tangents to the lines of curvature be produced to meet this line in the points m, m!, the sphere described on m m! as dia- meter will pass through the point of contact and the focal centre; hence may be given a new method of ererh oe the lines of curvature. Prop. [X.—Through the focal centre of a surface (>), let a right line and a plane be drawn perpendicular to each other ; the line meeting the surface in a point +r, and the plane meeting one of the directrix planes in a right line mm’; the plane m m’ 7 envelopes a surface of revolution, whose focus is the focal centre of (), and whose directrix plane passes through the intersection of the conjugate directrix planes of the given surface. Let the equation of the surface, the origin being placed at the focal centre, be i Be NRE FOI fe Tage coordinates of the point 7; let'& = wf + a, (b) v = v6+4+8, (b’) be the* tangential equations. of the line mm! in the direc- trix plane; and a &4+yu4 20=1 (c) the equation of the plane passing through the point (ay! 2') and the right line m mM. In the first place, as the line mm! is in a plane passing ! / through the origin, » = Fs y= oa ; and equations (b) (b’) (a); (2' zy! z') being the [2 I sh ei az Q / i are changed into = 5 C+ a ov =n t + B; and asithe line m m! is in the sale is ix place of which the tangential co- ordinates are = — OS Oe Oc oa these values of &, v, must satisfy the tangential equation of the right line mm; by these ‘substitutions the equations (b) (b’) are changed into zc(b?— +ae) = a! (bc f—aby) (d) 2 cb yu = y! (bc 2—aby) and we have now to eliminate 2’ y' 2! between the four equa- tions (a) (c) (d); from the three latter we get ce e—ace cr (P4+u+l) +aceE—abeys ae Gay J = Pe (++) +aceF—abcng * See the treatise quoted above, page 11. a Address of the Secretaries of the British Association. 441 ; cel —abcy — Pe +02 +0) 4+ ackek—abcyt’ Putting those values of x’ y/ 2! in (a), and making V = be? (+0? + &) + 2ackeeE—a® C7 we shall find for the resulting equation bcCalA2ben§—cee’—ae*}V = 0, which is satisfied by putting V = 0O,or Pe? (P+ 4+ C)42alek = ay? + c% the tangential equation of an ellipsoid of revolution whose focus coincides with the origin. It is easily shown that the tangential equation of the given surface referred to the same origin and axes is B(f + u)+ 004+ 2ack = 1. Hence if the given surface is a surface of revolution » = 0, and the locus found becomes identical with the given sur- face, as is otherwise known. When the given surface is an oblate spheroid e = 0,a = 4, and the locus becomes c® (£° + v? + ¢@) = 1, the tangential equation of a sphere described on the axis of revolution of the oblate spheroid as diameter. Similarly may it be shown, that if through any fixed point in space, a right line and a plane are always drawn at right angles to each other; the former meeting a fixed plane in a point 7, and the second intersecting another fixed plane in a right line mm; the plane mm!r envelopes a surface of re- volution of the second order, one of whose foci is at the fixed point. In a future Number, after treating of the general and numerous kindred properties of the two surfaces of the se- cond order, whuse generatrices are right lines, the author proposes resuming this subject, and developing briefly a general method, by the theory of reciprocal polars, of de- monstrating these and other similar theorems, many of which want of space has compelled him to omit in the present com- munication. | LXIV. Address of the General Secretaries of the British Associa- tion, RopeRIcK Impey Murcuison, F.R.S., F.G.S., and Major Eywarp Sazsine, V.P.RS.: read at the Meeting at Glasgow, September 1840. [* entering upon the duty assigned to us, we heartily con- gratulate our associates on this our second assembly in Scotland. As on our first visit we were sustained by the in- tellectual force of the metropolis of this kingdom, so now, by visiting the chief mart of Scottish commerce, and an ancient 442 Address of the General Secretaries seat of learning, we hope to double the numbers of our northern auxiliaries. Supported by a fresh accession of the property and intelli- gence of this land, we are now led on by a noble Marquis, who, disdaining not the fields we try to win, may be cited as the first Highland chieftain who, proclaiming that knowledge is power, is “proud to place himself at the head of the clans of science. If such be our chief, what is our chosen ground ?—raised through the industry and genius of her sons, to a pinnacle of commercial grandeur, well can this city estimate her obliga- tions to science! Happily as she is placed, and surrounded as she is by earth’s fairest gifts, she feels how much her pro- gress depends upon an acquaintance with the true structure of the rich deposits which form her subsoil; and great as they are, she clearly sees that her manufactures may at a mo- ' ment take a new flight by new mechanical discoveries. For she it is, you all know, who nurtured the man whose genius has changed the tide of human interests, by calling into active energy a power which (as wielded by him), in abridging time and space, has doubled the value of human life, and has esta- blished for his memory a lasting claim on the gratitude of the civilized world. ‘The names of Watt and Glasgow are united in imperishable records ! In such a city, then, surrounded by such recollections, en- couraged by an illustrious and time-honoured university, and fostered by the ancient leaders of the people, may we not augur that this Meeting of the British Association shall rival the most useful of our previous assemblies, and exhibit un- doubted proofs of the increasing prosperity of the British Association ? Not attempting an analysis of the general advance of sci- ence in the year that has passed since our meeting at Birming- ham, we shall restrict ourselves, on the present occasion, to a brief review of what the British Association has directly ef- fected in that interval of time, as recorded in the last published volume of our Transactions. From this straight path of our duty we shall only deviate in offering a few general remarks on subjects intimately connected with the well-being and dig- nity of our institution. One of the most important—perhaps the most important service to science—which it is the peculiar duty of the Asso- ciation to confer, is that which arises from its relation to the Government, —the right which it claims to make known the wants of science, and to demand for them that aid which it is beyond the power of any scientific body to bestow. In the of the British Association, to the meeting at Glasgow, 1840. 443 fulfilment of this important and responsible duty, the Asso- ciation has continued to act upon the principle already laid down in the Address of the General Secretaries at the meeting at Newcastle in 1838, namely, to seek the aid of Government in no case of doubtful or minor importance; and to seek it only when the resources of individuals, or of individual bodies, shall have proved unequal to the demand. The caution which it has observed in this respect has been eminently displayed in the part which it has taken with reference to the Antarctic expe- dition, and to the fixed magnetical observatories. It abstained from recommending the former to the Government until it had called for, and obtained from Major Sabine, by whom the importance of such an expedition was first urged, a report in which that importance was placed beyond all doubt; and it withheld from urging the latter, although its necessity was fully felt by some of its own members, until the letter of Baron Humboldt to the Duke of Sussex gave authority and force to its recommendation. ‘The delay which has in consequence occurred, has been productive of signal benefit to each branch of this great two- fold undertaking. Since the time alluded to, our views of the objects of investigation in terrestrial magnetism have been greatly enlarged, at the same time that they have become more distinct. Major Sabine’s memoir on the Intensity of Terrestrial Magnetism has served to point out the most in- teresting portion of the surface of the globe, as respects the distribution of the magnetic force, and has indicated, in the clearest manner, what still remained for observation to per- form; and the beautiful theory of M. Gauss, which has been partly built upon the data afforded by the same memoir,— while it has assigned the most probable configuration of the magnetic lines of declination, inclination, and intensity,—has done the same service with respect to all the three elements. In another point of view, also, delay has proved of great value to both branches of the undertaking, but mare especially to the fixed observatories. Our means of instrumental re- search have, since the time of their first projection, received great improvements, as well in their adequacy to the objects of inquiry, as in their precision; and finally, the two great lines of inquiry,—the research of the distribution of Terres- trial Magnetism on the earth’s surface,—and the investigation of its variations, secular, periodic, and irregular,—have been permitted to proceed pari passu. Last of ail, the prudent caution, and vigilant care, which the two great scientific bodies have exhibited, both in the origin and progress of the undertaking, have naturally in- 4.44 Address of the General Secretaries spired the Government with confidence; and while on the one hand science has not hesitated to demand of the country all that was requisite to give completeness to a great design, so on the other, the Government of the country has not hesi- © tated to yield, with a liberal and unsparing hand, every re- quest the importance of which was so well guaranteed. But while we thus enumerate the benefits which have re- sulted to magnetical science from the delay, it must be also acknowledged that something has been lost also, not to sci- ence, but to British glory. Although terrrestrial magnetism stood forward as the prominent object of the Antarctic expe- dition, yet it was also destined to advance our knowledge of the ‘* physzque du globe,” in ail its branches, and especially in that of geography. Had'the project of an Antarctic expedition been acceded to when it was first proposed, viz. at the meet- ing of the British Association, in Dublin, in 1835, there can be no reasonable doubt, that a discovery, which by its extent may almost be designated a Southern Continent, situated in the very region to which its efforts were to have been chiefly di- rected, must have fallen to its lot; and the flag of England been once more the first to wave over an unknown land. But while, as Britons, we mourn over the loss of a prize which it well became Britain and British seamen to have made their own, itis our part too as Britons, as well as men of science, to hail the great discovery—one of the very few great geographical discoveries which remained unmade ;—and to congratulate those by whom it has been achieved, those whom we are proud to acknowledge as fellow-labourers, and who have proved themselves in this instance our successful rivals in an honourable and generous emulation. The caution which has characterized the British Association in the origination of this great undertaking, has been followed up by the Royal Society in the manner in which it has plan- ned the details, and in the vigilant care with which it has watched over the execution. Of the success which has at- tended this portion of the work, the strongest proof has been already given in the unhesitating adoption of the same scheme of observation by many of the continental observers, and in the wide extension which it has already received in other quarters ofthe globe. All that yet remains is to provide for the speedy publication of the results. ‘The enormous mass of observa- tions which will be gathered in, in the course of three years, by the observatories established under British auspices, and by the Antarctic expedition, will render this part of the task one of great expense and labour. ‘To meet the former, we must again look to the Government, and to the East India of the British Association, to the meeting at Glasgow, 1840. 445 Company, who will certainly not fail to present the result of their munificence to the world in an accessible form. The latter can only be overcome by a well-organized system. The planning of this system, will, of course, be one of the first duties of the Royal Society; and it is important that it should be so arranged, that while every facility in the way of reduction _ may be given to those who shall hereafter engage in the theo- retical discussion of the observations, care is taken at the same time that the data are presented entire, without mutilation or abridgement. ‘The Council of the Royal Society, will, doubt- less, be greatly assisted in this duty by the eminent individual who has had in every way so large a share in the formation of these widely scattered magnetic establishments, and whose own observatory, founded by the munificence of the Dublin University, has nearly completed a twelve months’ magnetic observations on that enlarged and complete system of which it set the first example. | In referring, as we have done, to those most valuable ser- vices which the Royal Society have rendered, and are con- tinuing to render, in directing and superintending the details of this great undertaking, in both its branches, it is right that, on the part of the British Association, we should express the cordial satisfaction and delight with which we have witnessed their exertions, united with our own in this common cause; nor should we omit to recognize how much this desirable con- currence has been promoted by the influence of the noble president of the Royal Society, the Marquis of Northampton, whom, as on so many former occasions, we have the pleasure of seeing amongst us, as one of our warmest supporters and most active members. In the volume of our Transactions now under notice, is con- tained the memorial presented to Lord Melbourne by the Committee of the British Association, appointed to represent to Her Majesty’s Government the recommendations of the Association on the subject of terrestrial magnetism. This memorial is one of many services which have been rendered to our cause by Sir John Herschel, whose name, whose in- fluence, and whose exertions, since our meeting two years since at Newcastle, have largely contributed to place the subject where it now stands. ‘The devoted labour of other of our members has long been given to an object which they have had deeply at heart, viz. the advancement of the science of terrestrial mag- netism; but the sacrifice which Sir John Herschel has made of time, diverted from the great work, in which his ardent love of astronomy, his own personal fame, and his father’s memory are all deeply concerned, the more urgently demands 446 Address of the General Secretaries from our justice a grateful mention, because the science of magnetism had no claim on him, beyond the interest felt in every branch of science, by one to whom no part of its wide field is strange, and the regard which a national undertaking such as this deserved, from the person who occupies his di- stinguished station amongst the leaders of British science. The advancement of human knowledge, which may be reckoned upon as the certain consequence of the Antarctic expedition (should Providence crown it with success), and of the arrangements connected with it, is of so extensive a na- ture, and of such incalculable importance, that no juster title to real and lasting glory than it may be expected to confer, has been earned by any country at any period of time; no- thing has ever been attempted by England more worthy of the place which she occupies in the scale of nations. When much which now appears of magnitude in the eyes of politi- cians has passed into insignificance, the fruits of this underta- king will distinguish the age which gave it birth, and, engraved on the durable records of science, will for ever reflect honour on the scientific bodies which planned and promoted it, and on the Government which, with so much liberality, has car- ried it into effect. Were the value of this Association, Gentlemen, to be inea- sured only by the part which it has taken in suggesting and urging this one object, there might here be enough to satisfy the doubts of those who question its utility: to overlook such acts as these, and the power of public usefulness which they indicate, to scrutinize with microscopic view the minute de- fects incidental to every numerous assemblage of men, to _ watch with critical fastidiousness the taste of every word which might be uttered by individuals amongst us, instead of casting a master’s eye over the work which has been done, and is doing, at our meetings, is no mark of superior discern- ment and comprehensive wisdom, but is evidence rather of a confinement to narrow views, and an indulgence of vain and ignoble passions; But to proceed with our useful efforts,—one of the principal objects of our Annual Volumes, is the publication in the most authentic form of the results of special researches, under- taken by the request, and prosecuted in many instances at the cost, of the Association. It is a trite remark, that if a man of talent has but fair play, he will soon secure to himself his due place in public estimation. We fully admit the truth of this in many instances, and above all where the points of research are connected with commerce and the useful arts ; but many also are the subtile threads of knowledge, which, of the British Association, to the meeting at Glasgow, 1840. 447 destined at some future day to be woven into the great web in which all the sciences are knit together, are yet not appre- ciable to the vulgar eye, and if simply submitted to public judgement, would too often meet with silent neglect. Num- berless, we say, are the subjects (and if your Association ex- ceeds a centenary, still more numerous will they be) with which the retired and skilful man may wish to grapple, and still be deterred by his want of opportunity or of means. Then is it that, adopting the well-balanced recommendations of the men in whose capacity and rectitude you confide, you step forward with your aids, and bring about these recon- dite researches, the result of which in the volume under our notice; we now proceed to consider. The first of these inquiries to which we advert, you called for at the hands of Professor Owen, upon “ British Fossil Rep- tiles,” one of the branches of Natural History, on a correct knowledge of which the development of geology is intimately dependent. The merits of the author selected for this inquiry are now widely recognized; and he has, with justice, been approved as the worthy successor of John Hunter, that illustrious Scotch- man who laid the foundation of comparative anatomy in the British isles. ‘That this science is now taking a fresh spring, would, we are persuaded, be the opinion of Cuvier himself, could that eminent man view the progress which our young countryman is making towards the completion of the temple of which the French naturalist was the great architect. It is therefore a pleasing reflection, that when we solicited Pro- fessor Owen to work out this subject, we did not follow in the wake of Europe’s praise, but led the way (as this Association ought always to do), in drawing forth the man of genius and of worth; and the value of our choice has been since stamped by the approval of the French Institute. If Englishmen* first perceived something of the natural affinities of Palzeosaurians; it was reserved for Cuvier to com+ plete all such preliminary labour. The publication of his splendid chapters on the Osteology of the Crocodile and other Reptiles, drew new attention and more intelligent scrutiny to these remains; and it ought to be a subject of honest pride to us to reflect that the most interesting fruits of the researches of that great anatomist were early gathered by the English Palezontologists, Cliftand Hume. One of our leaders, whose report on Geology ornaments the volumes of this Associa- tion, formed the genus Pleszosaurus, on an enlarged view of the relation subsisting between the ancient and modern forms * Stukeley. 448 Address of the Secretaries of the British Association. of reptile life; while shortly after Buckland established the genus Megalosaurus, and Mantell, Zewanodon and Hyleosaurus, worthy rivals of the Geo-Saurz and Moso-Sauri of Cuvier. The other Englishmen who have best toiled in this field, are De la Beche, Hawkins, and Sir Philip Egerton. Yet although this report is on Bretish reptiles, we are fully alive to the great progress which this department has made, and is making, on the Continent, through the labours of Count Munster, Jager, and Hermann Von Meyer. The last-men- tioned naturalist has been for some time preparing a series of exquisite drawings of very many forms unknown to us in England, most of which have been detected in the Muschel- kalk, a formation not hitherto discovered in the British isles. Yet despite of all that had been accomplished in our own country or elsewhere, Professor Owen has thrown a new light of classification on this subject, founded on many newly discovered peculiarities of osseous structure, and has vastly augmented our acquaintance with new forms, by describing sixteen species of Plesiosaurz, three of which only had been recognisably described by other writers; and ten species of Ichthyosauri, five of which are new to science. Such results were not to be obtained without much labour; and previous to drawing up his report, Professor Owen had visited the principal depositories of Enaliosauri described by foreign wri- ters, as well as most of the public and private collections of Britain. This, the first part of Mr. Qwen’s report, concludes with a general review of the geological relations and extent of the strata through which he has traced the remains of Bri- tish Enaliosauri. ‘The materials which he has collected for the second and concluding portion of his report on the terrestrial and crocodilean Sauria, the Chelonia, Ophidian, and Batra- chian reptiles, are equally numerous, and the results of these researches will be laid before the Association at our next meeting. Deeply impressed as we are with the value of this report, we cannot conclude a notice of it, without again allu- ding to its origin, in the words of Professor Owen himself, ‘‘ IT could not,” says he, ‘‘ have ventured to have proposed to myself the British Fossil Reptilia as a subject of continuous — and systematic research, without the aid and encouragement which the British Association has liberally granted to me for that purpose.” Mr. Edward Forbes, whose labours in detecting the differ- ence of species and varieties among the existing marine testa- cea of our shores, have been most praiseworthy, has on this occasion given us a report on the pulmoniferous mollusca of the British isles. The variations in the distribution of the Dr. Schafhaeutl’s Remarks on the Electricity of Steam. #49 species in this class of animals, are shown by him to depend both upon climate and upon soil, the structure of the country (or geological conditions) having quite as much share in such varied distribution, as the greatest diversity of temperature. The Association has to thank the author for valuable tables, which show both the distribution of the pulmoniferous mol- lusca in our islands, and their relations to those of Europe generally. [To be continued. | LXV. Remarks on the Electricity of Steam. By Dr. CHARLES SCHAFHAEUTL*, sh lhioion discovery of a large quantity of free electricity in a jet of steam+ is decidedly of great interest, but the cir- cumstances under which this electricity is developed, are still involved in such great mystery, that I cannot omit to call the early attention of the experimenter to some points which appear to me of primary importance. Is the electricity in the jet of steam developed by the simple evaporation of water in the boiler, by the expansion of high- pressure steam in the air, or by the condensation of the steam, that is in its transition from the gaseous state to that in which it begins to become visible? It would of course be easy to decide the first question by cementing a glass tube containing a metallic wire into the boiler, the inner portion of which being of course in contact with the steam in the chamber, and precautions being taken to prevent the escape of steam either into the cylinder or. the open air. If I recollect right, during the process of evaporation, the evaporated part has been generally found to be negative elec- tric in respect to the remaining liquid; during condensation the reverse takes place. According to Mr. Armstrong’s ac- count, the electricity of the jet was positive, and seems there- fore to correspond with the electricity developed by the pro- cess of the condensation of steam. If we ascribe the elec- tricity contained in the jet of steam simply to the evapo- ration of the water in the boiler, the opposite electric state of the boiler seems difficult to be explained by the laws of common electricity, because there appears to me to be no reason why the steam in contact with the inside of the iron sheets of the boiler should not discharge its electricity the * Communicated by the Author. + See our last Number, pp. 370, 375. Phil. Mag. 8. 3. Vol. 17. No. 112. Dec. 1840. 2G 4.50 Dr. C. Schafhaeutl’s Remarks same as when it comes in contact with the outside, except the inside of the sheet iron, by a process of oxidation, becomes a non conductor of electricity in respect to the outside. An incrustation, according to Mr. Armstrong’s account, was found in the boiler only as high as the water reached ; but in boilers in which the water becomes very muddy, and which, there- fore, are apt to prime, a sort of thin incrustation is often spread over the whole interior of the boiler as well as the safety-valve, and therefore the state of the interior of the steam-chamber ought to be very closely examined. The number of sparks obtained by Mr. Armstrong from the boiler at a distance of a quarter of an inch, amounted to between 60 and 70 per minute. If we assume the quantity of water necessary for a 28-horse power high-pressure engine to be 2°47 cubic feet per minute, supplied by two boilers; one boiler evaporated, therefore, 1:23 cubic feet per minute, and the evaporation of 35°5 cubic inches of water with two ounces of Newcastle coal would be necessary to produce one spark of a quarter of an inch length per second, a quantity of elec- tricity which seems to bear no proportion with the small quantity of electricity produced during simple evaporation on a small scale. But Mr. Armstrong’s experiments seem distinctly to indi- cate that the electricity of the steam depends chiefly on its density, and the great quantity of free, electricity may, there- fore, perhaps, be made sensible by the rapid expansion of high-pressure steam, and may perhaps have some relation to the quantity of free caloric becoming latent during the ex- pansion of high-pressure steam. I scarcely need here mention the observation of Mr. Hare, that the operation of his defla- grator was entirely suspended by the operation of the com- mon galvanic trough apparatus; besides, all conductors of electricity during mutual friction develope caloric, whilst non-conductors of electricity, on the contrary, during mutual friction, develope, instead of caloric, electricity. It seems to me a great question whether the electricity of the steam was not in close connexion with the deposit, or the induration of the deposit upon the plates of the boiler. I have already shown in an article on steam-boiler explo- sions, published in the Mechanics’ Magazine, that those in- crustations were composed of a series of distinet layers, some- times very easily separable, and which proves that the indu- ration or crystallization of these layers, notwithstanding the continuous evaporation and feeding, must have been occasioned at certain intervals, and that one layer must have already on the Electricity of Steam. 451 been in an indurated state before the other was deposited. The layers assume a crystalline form only when they are in close contact with the iron plates. I have also shown in the above-mentioned treatise, that during the deposition of certain salts held in solution by the boiling water the ebullition became interrupted, taking place only at intervals, and always with a sort of explosion or sud- den development of steam, which often caused the glass flask to burst. During these sudden explosions the electricity of the escaping steam became so distinct, that it was readily indicated by a common gold-leaf electroscope; the electri- city ofthe steam, on thecontrary, escaping under ordinary cir- cuinstances being so feeble, that it cannot be detected without the aid of a condensator. The development of electricity during the crystallization of certain salts is very well known, and many chemical de- posits occur only under a certain pressure, to which the liquid containing them is subjected. ‘Thus the carbonaceous de- posits in common gas retorts are entirely obviated when the gas from the coals is evolved without pressure in the retorts, or even in a partial vacuum. The columns of vapour and smoke arising from the craters of volcanos generally discharge flashes of lightning in all di- rections, and it is obvious that the discharged electricity is owing tothe expansion or condensation of the escaping water gas, if not to a chemical separation in the column of smoke ascending from the crater with an immense force. The electricity in thunder-clJouds seems likewise to arise from condensation. I had once the good fortune to be im- mersed in a thunder-cloud hovering round the summit of Mount Brenner inthe Tyrol, having with me at the time a ba- rometer, thermometer, hygroscope, and an electroscope. I saw the clouds forming around me on the summit of the mountain into vaporous bodies of an irregular roundish shape, which seemed to retain their form by an attractive force arising from the centre of each individual cloud, as they had not the slightest tendency to amalgamate with each other. The hy- groscope close to the cloud was not at all affected, and only when immersed in the cloud, it turned first a few degrees, in- dicating after a few minutes the highest degree of moisture, and sinking gradually back to its first point. This fluctuation continued as long as I had time to observe it. ‘he electro- scope was likewise not affected at all outside the cloud. Im- mersed in the cloud the gold leaves began gradually to sepa- rate, the barometer at the same time slightly rising, and after each discharge of lightning both instruments returned to their ZG 2 452 Mr. W. G. Armstrong on the Electricity of Effluent Steam. original state. From these observations it would appear that with every flash of lightning the cloud became exhausted of its electricity and recharged itself for each succeeding flash. — The air in the cloud seems to move from the periphery to the centre, of the nature of a whirlwind, fluctuating with the leaves of the electroscope, and I had sufficient time to witness twenty-one electric discharges from the cloud in which I was immersed, when the wind became so violent, that the instruments were broken, and I was obliged to cling to the stump of a tree to save myself from being blown over the pre- cipice ; but the uproar around me was increasing and fluctu- ating with the electric discharges from the clouds, and the rapid alternations of wet and dry in the clouds, was during the whole time in exact coincidence with the electric dis- charges. LXVI. On the Electricity of Effluent Steam. By W. G. ArRmMstrone, Esq. To the Editors of the Philosophical Magazine and Journal. GENTLEMEN, h Y letters to Professor Faraday on the remarkable de- velopment of electricity which has recently been dis- covered in a jet of steam issuing from a steam-engine boiler in this neighbourhood, having already appeared in your pub- lication, it is, of course, unnecessary for me here to repeat the circumstances detailed in those letters. Ishall therefore take up the narrative of my proceedings, relative to this curious subject, at the point at which the second of those letters concludes. Having found electricity in all the three boilers I had ex- amined in which water from the neighbouring colliery was used, and not having discovered any indications of it in the boiler which was supplied with rain-water, I was naturally led to believe that the effects I have described were attribu- table to the peculiar nature of the water from which the electrical steam was produced; and, under this impression, I lost no time in visiting some other high-pressure boilers in the same district, which were also supplied with colliery water, strongly impregnated with lime and other mineral matter. The steam trom the safety-valves of these boilers also proved to be electrical, but not to such an extent as I had reason to anticipate from the similarity of the circumstances to those under which electricity was developed in such an extraordi- nary degree at Seghill. I then proceeded to try a number of boilers in this town and neighbourhood, in which steam was Mr. W. G. Armstrong on the Electricity of Effluent Steam. 453 propagated under different pressures, and from water of va- rious descriptions; and by insulating myself and holding a conducting-rod in the steam discharged from the safety- valves, I succeeded in every instance in obtaining electrical sparks, which varied in the different cases from about one- fourth to about half an inch in length. In company with Mr. Robert Nicholson, the engineer of the Newcastle and North Shields. railway, I next tried the boilers of the locomotive engines used on that railway, and finding electricity in great abundance in the ejected steam from these boilers, I determined, with Mr. Nicholson’s per- mission and assistance, to institute a set of experiments upon one of them, with a view to a fuller investigation of the sub- ject. I shall now briefly describe such of these experiments as have been the most marked in their results, and shall divide them into two classes, first taking those which were chiefly in- tended to exhibit the extent to which electricity existed in the issuing steam, and then proceeding with the experiments which were undertaken to ascertain the cause of the electric development. Nearly all the experiments were made at night, under cover of the engine-shed, and the atmosphere was generally humid; but when it happened to be otherwise, the quantity of electricity derived from the jet was greatly increased. Upon trying the steam in the first instance by the method adopted in the previous cases, that is to say, by standing on an insulated stool and holding with one hand a light iron rod immediately above the safety-valve, while the steam was freely escaping, and then advancing the other hand towards any conducting body, sparks of about an inch in length were obtained: but it was soon observed, that by elevating the rod in the steam the electricity was gradually increased, and that the maximum effect was not attained until the end of the rod was raised five or six feet above the valve, at which point the length of the sparks occasionally reached two inches. Small sparks were even obtained when the rod was wholly re- moved from the steam and held in the atmosphere at the distance of two or three feet from the jet, and the electricity thus drawn from the air was positive, like that of the steam. When the rod was extended into the cloud of vapour which accumulated in the upper part of the shed, electricity was drawn down as by a lightning-conductor from a thunder- cloud. I endeavoured to ascertain whether any precipitation of moisture, analogous to the formation of rain, accompanied 454 Mr. W.G. Armstrong on the Electricity of Effluent Steam. the abstraction of electricity from the steam, and a sprin- kling of wet was undoubiedly felt on the fase and hands by the person holding the rod, so long as he remained in- sulated, but the effect ceased as soon as the insulation was destroyed. After fully trying the steam with a simple iron rod, as a conductor, recourse was had to other conductors which pre- sented a larger surface to the steam, but the effect was not materially increased until a bunch of pointed wires of different lengths was attached to an iron rod and held in the issuing steam, with the points presented downwards. ‘The iron rod terminated ina round knob at the end next the hand, and from this knob sparks of the measured length of four inches were actually drawn, almost as rapidly as they could be counted, while a stream of electricity was at the same time passing off from the rod, at the part which most nearly ap- proached the chimney of the engine. Very perceptible sparks were also obtained when the points were held in a clear at- mosphere, at the distance of at least eight feet from the nearest part of the jet. In all the preceding experiments, the effect appeared to be proportionate to the quantity of steam discharged from the valve, when other things remained the same; and the elec- tricity became quite imperceptible when the escape was very inconsiderable. By abruptly raising the valve when the engine-shed was dark, the edges of fae lever and margin of the brass cup stile surrounded the valve, were rendered distinctly lumi- nous with rays of positive electricity which were strongest the instant the valve was lifted, and then quickly subsided, becoming very faint after the lapse of a second. In proceeding to investigate the cause of this extraordinary development of electricity, the first question which I] proposed for inquiry was, Whiere does the steam first become electri- cal, that is to say, is it electrical in the boiler, or if not, does it become»so. in passing through the orifice; or not till it escapes into the air? In order to determine which of these three suppositions was correct, the apparatus represented in the annexed figure, and of which the following is a de- scription, was employed. A is a glass tube passing into the steam chamber through the cock B, which was screwed into a hole in the top of the boiler, and was furnished with a stuffing-box to prevent escape between the outside of the tube and inner surface of the cock ; C is a stop-cock affixed to the upper end of the glass tube, Mr. W. G. Armstrong on the Electricity of Effluent Steam. 455 and upon which cock is screwed a second glass tube D_ ter- minating in another stop-cock E. The application of this apparatus will be easily understood. If the steam were in the same state of electricity in the boiler as when it issued into the air, it would necessarily com- municate positive electricity to the insulated cock C, in passing through the tube. Or, if the steam acquired its electricity by friction, or otherwise, in the channel through which it was discharged, it could only, in the present instance, do so at the expense of the cock C, which, being insulated, would in that case indicate negative electricity. Or, lastly, if the electricity were developed by condensation, expansion, or any other cause which came into operation after the steam escaped into the air, then the cock C would have neither positive nor negative elec- tricity. Previously to inserting the lower glass tube in the boiler, the steam was allowed to blow off through the large cock B, and the jet which issued from it proved, to the surprise of every one pre- sent, almost destitute of electricity. ‘This result completely vitiated the inference I had drawn from the circumstance of not finding electri- city in the steam from the rain-water boiler before alluded to, in which case, as I have al- ready stated in my second letter to Professor Faraday, the jet was obtained from the gauge cock. . The lower glass tube, without the upper one attached to it, was then passed into the boiler, and a highly electrical jet was obtained from it, which communicated positive electricity to the stop-cock C, from which the steam was discharged. The upper tube was accidentally broken in screwing it on to the lower one, leaving only about three inches of glass above the cock C. Under these circumstances the cock C still con- tinued highly charged with positive electricity, and a pale Jambent light flashed at short intervals down the inside of the tube from the cock towards the boiler. Having replaced the broken glass tube with a new one, the experiment was tried again on a subsequent evening, and the jet being now removed to a much greater distance than before from the cock C, no electricity whatever could be de- tected in that cock, while the one above it indicated positive 1} t] 456 Mr. W.G. Armstrong on the Electricity of Effluent Steam. electricity in a very high degree. It therefore became pretty evident that the electricity was not developed until the steam issued into the atmosphere, and that the upper stop-cock derived its electricity from its contiguity tothe jet. One cir- cumstance alone seemed in some degree to militate against this supposition, namely, that the electricity of the cock EB was greatly increased when the cock C was partially closed, as if the expansion which im that case took place in the upper tube rendered the steam electrical previously to its reaching the cock from which the jet was discharged. No negative electricity, however, could be discerned in any part of the apparatus, and without a development of negative electricity, I cannot see how positive electricity can possibly arise from expansion. ‘The more probable explanation of the effect ap- peared to be, that the partial closing of the middle cock. shortened the transparent or non-conducting part of the jet, and thereby caused the electricity to be more readily commu- nicated from the opake part of the jet. In consequence, no doubt, of increased accumulation of | electricity which was thus occasioned in the highest cock, together with the unavoidable dampness of the surrounding medium, the upper glass tube, and the cock above it, became illuminated in the most singular and beautiful manner. Flashes of wavering light flickered round the exterior surface of the glass, and darted from it to the distance of three or four inches, while strong rays of electrical light streamed from the angular parts of the cock, and the flashes from the glass were accompanied by a snapping noise which was distinctly audible amidst the hissing of the steam when the ear was advanced within a short distance from the tube. The upper glass tube was then removed, and as an additional test of the non-existence of free électricity i in the interior of the boiler, a pointed wire was thrust down through the cock C and tube A into the steam, and effectual means were used to prevent the escape which would otherwise take place at the cock C, in consequence of the tap remaining open to admit the wire. Now this wire being insulated by the glass tube and communicating with the insulated cock C, must have rendered that cock electrical, if the steam were eldelonitle ti in the boiler; but not the slightest indication of electricity could, under these cincdmstanaad be found in the cock. Having withdrawn the pointed wire from the tube, se glass tube, of which the sectional area was about ten times oreater than that of the one inserted in the boiler, was then. attached to the cock C, in the same manner as the tube D had been before. ‘The comparatively large bore of this tube Mr. Pattinson’s Experiments on the Electricity of Steam. 457 allowed the steam to expand in a very great degree before it issued into the air, and caused it to be discharged in the state of low-pressure steam ; but no diminution of electricity could be perceived in the jet, when thus attenuated; so that the elec- trical development does not appear to depend upon the de- gree of violence with which the steam comes in contact with the atmosphere. The entire absence of negative electricity seemed to pre- clude the possibility of the phznomena arising from expan- sion, and the only remaining supposition appeared to be, that the condensation which took place in the jet, set free the electricity which the steam had absorbed in the process of evaporation. ‘This supposition had been previously rendered probable, when it was discovered that the upper and most opake part of the jet yielded the most electricity, although I was at first inclined to attribute that circumstance to the dampness of the steam, in that part of the jet, rendering it a better conductor, and causing it to part more readily with its electricity. Experiments were next, therefore, commenced to ascertain the effect of insulating the boiler, and wholly con- densing the steam; but these require repetition before they can be much relied upon. ‘The great difficulty is to effect insulation amidst so much moisture, but I have no doubt that with a little perseverance this object will be accom- plished, and I trust I shall be able to furnish, in time for in- sertion in the next Number of the Philosophical Magazine, such further results as will set the question at rest. . I am, yours, &c. - Newcastle upon-Tyne, Nov. 18, 1840. Wm. Geo. ARMSTRONG. LXVIL. Further Experiments on the Electricity of Steam. By H. L. Parrinson, Esq., F.G.S. To the Editors of the Philosophical Magazine and Journal. GENTLEMEN, GQGINCE my last letter to you, dated the 19th ult. (pub- lished at p. 375 of this volume), relative to the electricity of steam issuing from two boilers at Cramlington Colliery, the subject has been further pursued both by myself and others, and sparks have been obtained from the steam of va~- rious boilers, in every direction. The mode of operating has generally been that described in my letter, viz. suffering the steam to escape from the safety-valve of the boiler tried, and testing its electricity by holding in it a shovel or an iron rod, the operator standing upon an insulating stool. Sometimes the indications have been very slight, and sometimes there 458 Mr. Pattinson’s further Experiments on the has hardly been any appearance of electricity in the steam ; but in such cases the trials have been generally made under unfavourable circumstances, and from all that has yet been done, the presumption is certainly that steam is always more or less electrical. It is not, however, always electrical to the same extent under the same pressure, as I shall. presently show. Mr. Armstrong was the first to experiment with a locomo- tive engine-boiler (one used on the Newcastle and’ North Shields railway), from which he obtained very striking re- sults. ‘lhe directors of the Newcastle and Carlisle railway, through their secretary, Mr. Adamson, gave me permission to experiment upon the boilers of the locomotive engines on that line, and I now beg to lay before you the results I have obtained. In preparing for, and performing these experi- ments, | have, as before, been assisted and accompanied by Mr. Henry Smith, and I have received the most willing and efficient aid from Mr. Anthony Hall of Blagdon, the mechani- cal engineer on the railway. 1. A copper rod, half an inch in diameter, and five feet long, was provided, made hollow for lightness; this was ter- minated at one end by a two-inch ball, and at the other (which was bent at aright angle) by ten or twelve sharp-pointed wires, spread out in every direction to collect the electricity more perfectly from the steam. 2. The Wellington locomotive engine, immediately after coming to the station with passengers, was first tried. At this time the steam was blowing forcibly out of the safety- valve, ata pressure of fifty-two pounds per inch. On hold- ing the pointed conductor in this current of steam, with its points downwards, the individual holding it standing at the time on an insulating stool, sparks three to four inches long were given off from his person to the boiler. The sparks were largest when the valve was held down a minute or two. and then suddenly lifted, so as to suffer a large volume of steam to escape with great rapidity. By this management the sparks were frequently four inches long, and occasioned considerable pain to the person on the stool, even when given from a brass ball held in his hand. ‘The sparks were largest when the points of the conductor were held in the steam about two feet above the valve; but larger sparks were ob- : Electricity of Steam. 459 tained when it was held much higher; and indeed sparks were obtained by holding the conductor entirely out of the cloud of steam, and at a distance from it, for the air in the wooden shed in which we operated became speedily electrical throughout. ‘The electricity was positive. | 3. The steam in the boiler was now gradually run down to see how the electrical condition would vary with the pressure. At forty pounds per inch the sparks became much less, the Jargest not reaching three inches. At thirty pounds the largest spark did not reach two inches; at twenty pounds it became barely an inch; at ten pounds not more than from one-fourth to one-half of an inch; and at five pounds per inch pressure the spark was hardly perceptible. But if at any pressure the valve was held down a few minutes so as to suffer the steam to accumulate and then suddenly opened, there was always a great increase, for an instant, of the electrical effects. 4. Another boiler, that of the Lightning engine, which had also just come in from a trip, and had its steam blowing off forcibly, at a pressure of fifty pounds per inch, was now tried in exactly the same way as the Wellington. On holding the pointed conductor in the steam, whether regularly blowing off at the valve or escaping with great rapidity from the sud- den lifting of the valve, it did not yield a spark more than one-fourth of an inch long. We then blew a quantity of water out of the boiler of the Lightning until it barely covered the tubes inside, and on afterwards testing its steam blowing off at fifty pounds per inch, the spark was found increased to nearly two inches in length. The steam of the Lightning was, however, much less electrical than the steam of the Wel- lington at the same pressure, under all the circumstances of our experiments. 5. The strong current of steam and water issuing from the boiler of the Lightning when the water was blown out of it as just stated, was tested for electricity, but no indications could be perceived whatever. 6. A very large conductor had been provided, made of zinc two-inch tubing, in this way,—three rings were made of this tubing, respectively three feet, two feet, and one foot diameter. ‘These rings were attached to each other a foot and a half apart by side pieces, so as to form a hollow frus- tum of a cone, three feet high, with ends three feet and one foot diameter respectively. ‘The inside of this cone was laced across with copper wire, and the whole bristled with pointed wires in every direction. By means of a long 460 Mr. Pattinson’s further Experiments on the iron bar, placed upright in a cask of rosin (both to insulate it and to serve as a foot), and a horizontal arm projecting from it, made to slide up and down on the vertical bar, the large conductor could be placed in any part of the cloud of steam issuing from the valve, and the electricity given off could be conveyed from it in any direction. Care was taken to round off all parts of this conductor, so as to avoid sharp points and angles as much as possible. On trying this large conductor in the current of steam from the Wellington, we were disap- pointed to find that it did not yield a longer spark than the small pointed copper rod with which we had previously ex- perimented. ‘The spark was larger in volume, but it did not possess greater intensity. It never struck through more than three inches of space, but its effect upon the person when taken was very violent and painful. Our intention was to have ascertained the rate at which large jars could be charged from the steam, in order to form some idea of the quantity of electricity given off; but the evening had become very damp, and the air was so moist, that we could not procure sufficient insulation, and were obliged to relinquish the attempt. 7. When the large conductor was held in the cloud of steam with its lower part or apex about two feet above the valve, it gave off numerous and powerful sparks; but if at this time the points of the small conductor were placed by a person connected with the ground in the steam below the large conductor a foot above the valve, the electricity given off by the large conductor was very materially dimi- nished. mai 8. By means of screws, the entire engine (the Wellington) was raised off the rails and placed upon blocks of baked wood, so as to insulate it entirely. ‘The steam being now blown off at the valve, the boiler and engine became strongly electrical with negative electricity ; points placed upon any part of the engine exhibiting the peculiar star of the negative element, and threads suspended from the engine being repelled by ex- cited sealing-wax. ‘The steam was at the same time strongly positive, and when a point connected with the conductor held in the steam was brought near a point attached to the insu- lated boiler, the pencil upon the former and star upon the latter were beautifully decisive as to the electrical states of each. 9. I repeated Volta’s experiment by placing a hot cinder upon the cap of a gold-leaf electrometer, and projecting a few drops of water upon it, when the leaves diverged strongly with negative electricity. I observed, that when the cinder was very hot, and the production of the steam consequently very rapid, the electricity given out was always most powerful. Electricity of Steam. 461 10. I then insulated an iron pan, twelve inches diameter and two inches deep, and attached to it a pith-ball electrometer, with balls three-eighths of an inch diameter, and threads five inches Jong, and also attached to the pan a metallic wire, the pointed extremity of which was placed about one-twentieth of an inch distant from the point of another wire connected with the ground. ‘The iron pan was then filled with cinders, very hot, from a wind-furnace, and on projecting upon them a few ounces of water, steam was evolved with great rapidity, and at the same moment the pith balls diverged to the di- stance of an inch, and sparks passed between the metallic wires. ‘This was several times repeated. These experiments enable us, I conceive, to give a clear explanation of the electrical phenomena presented by steam. There is no doubt whatever, as Dr. Faraday conjectures in his note to Mr. Armstrong’s paper in your last Number, ‘that this evolution of electricity by vaporization is the same as that already known to philosophers on a much smaller scale.” The electricity appears to originate at the instant of vaporization, and the steam as it collects within the boiler is electrified with positive electricity, the water and metallic boiler being at the same time negative. In this condition the electricity of both is latent, like the electricity of the two plates ofan excited electrophorus ; but the instant steam is suffered to escape, its positive electricity, being carried off aiong with it, and out of the influence of the equivalent quantity of ne- gative electricity in-the boiler, becomes free, and hence the steam is electrical with positive electricity. The same thing takes place with the boiler, in which negative electricity is set at liberty as the steam escapes, and which becomes evident on insulating the boiler. When steam much mixed with water, or what engine-men call ** wet steam,” escapes from a boiler, it evidently cannot be very highly electrical, for the negative water will tend to neutralize the positive steam, and this may perhaps in some measure account for the increased effect in the Lightning on lowering the water within its boiler, and for the increase of intensity in every boiler, observed when the valve has been forcibly held down and is suddenly opened; but it does not seem sufficient to account entirely for these variations of inten- sity, nor for the difference of intensity in different boilers at the same pressure. It is therefore probable that chemical action between the metal of the boiler and the water bas something to do with exalting the electrical condition of the steam at the moment it is generated; but this part of the subject certainly requires further investigation. By far the most powerful ef- 462 Rev. J. Challis on the Motzon of a small Sphere fects up to this time have been obtained from locomotive en- gines, in which water is heated in contact with brass tubes. How far this may influence the production of electricity, fur- ther experiments must determine. It is certainly somewhat cu- rious to consider the splendid locomotive engines we see daily in the light of enormous electrical machines; but this they un- doubtedly are; the steam is analogous to the glass plate of an ordinary machine, the boiler to the rubbers ; and a conductor properly exposed to the escaping steam gives out torrents of electricity. I am, Gentlemen, Your obedient Servant, Bentham-Grove, Gateshead, H. L. Partirnson. November 21, 1840. LXVIII. On the Motion of a small Sphere vibrating in a re- sisting Medium. By the Rev. J. Cuartis, Plumzan Pro- fessor of Astronomy tn the University of Cambridge*. 'N the London and Edinburgh Philosophical Magazine for September, 1833 (vol. iii. p.186.), I have given a solution of the problem of the resistance to the motion of a ball-pendulum vibrating in the air, by making use of the principle of the conservation of vis viva, and assuming that for slow vibra- tions the motion of the air surrounding the ball is the same as if the fluid were incompressible. [ have given another so- Jjution in the Cambridge Philosophical ‘Transactions (vol. v. part ii, p. 200.), by adopting the above assumption without using the principle of the conservation of vis viva; and in the latter solution it is not taken for granted, as in the other, that the same considerations apply to fluid motion directed to or from a moving centre, as to motion to or from a fixed centre. The two methods lead to the same result. In 1835, M. Plana published at Turin a Memoir (for a copy of which I am in- debted to the kindness of the author) containing a solution of the problem in question, the same in principle as that of Poisson in vol. xi. of the Mémozres of the Paris Academy of Sciences}, with the difference of treating separately the motions in a compressible and an incompressible fluid, and so obviating some objections to which Poisson’s. reasoning appeared liable. M. Plana adverts to my communication in the Philosophical Magazine, and subjoins a translation of it, but is unwilling to admit the correctness of the principle of the method | have employed, apparently for no other reason than that it leads to a result differing from his own. * Communicated by the Author. + Poisson’s memoir is also inserted in the Connaissance des Tems for 1834. vibrating in a resisting Medium. 463 The two methods are, in fact, so dissimilar in principle, and in their results, that if one is right the other must be wrong. But after the lapse of some years I am not able to discover any error either in the principle or the details of the method [ have employed in the Philosophical Magazine, nor of that in the Cambridge Philosophical ‘Transactions. ‘The object of mv present communication is to give a ¢hird solution, which applies expressly to vibrations of the ball in a compressible fluid. It will be proper to begin with proving generally that the same equations apply to the motion of the fluid when directed to or from a moving centre, as when directed to or from a fixed centre. Considering, first, the motion of the fluid to be in the di- rection of radii from a fixed centre, conceive two spherical surfaces described about this centre at the distances r and 7! differing very little from each other ; and let the ‘interior one pass through the point at which we consider the motion. Conceive also a conical surface, having its vertex at the centre of the spherical surfaces and its vertical angle indefi- nitely small, to intersect with its axis the interior spherical surface at that point. Let m* = the small portion of the in- terior spherical surface included by the conical surface ; then mera? : : 5— = the corresponding portion of the outer surface. It 2 will be assumed that during a very small time 6/, the velocity and density of the fluid which passes the area m? are uniformly v and p; and, similarly, that the velocity and density of the fluid passing in the same time the corresponding area of the other surface are uniformly vu! and p’.. Then the quantity of fluid which passes m? in the time O¢ is m?puédé; and that m? 72 which passes the other area in the same time, —.— - p! vu’ 6 ¢. r The increment of matter in the included space is, therefore, rl? pl vy! : —m? dt ( s- —/p v); the velocities v and v! being reckon- » ed positive when directed from the centre. The space itself is ultimately m* (7’—r). Hence the increment of density 5p m2 bt Ane p! yp! —72 p v) is equal to — m> (7'—r) Consequently, Sp . re plu'—r? pv te ear (7/—71) ‘ 464: Rev. J. Challis on the Motion of a small Sphere and passing from differences to differentials, ap “ad "7p 0 ait Pdr where, from the nature of the investigation, the differential coefficients are evidently partial. Now suppose the motion of the fluid to be directed to or from a moving centre, and let two spherical surfaces separated by a very small interval be described about this centre, the interior one always passing through the point of space at which we consider the motion. On account, therefore, of the motion of the centre, the spherical surfaces will not be sta- tionary. We may, however, conceive a conical surface, de- scribed as in the former case, to have its axis always passing through the moving centre and the point of space at which the motion is considered, and to include a given small por- tion m? of the interior spherical surface. ‘The velocity and density of the fluid passing the area m* may, as before, be considered uniform during a very small time 6¢; as may also, without entailing error, the velocity and density of the fluid passing the portion of the outer surface always included by the conical surface. Hence, using the same letters as in the case of a fixed centre, the quantity of fluid which passes m? in the time 6¢ is m?pudt. We have now to ascertain the quan- tity of fluid which in the same time passes the corresponding area of the exterior surface. Let 7 and 7’ be the radii of the two concentric surfaces at the beginning of the interval 67, and let « be the velocity of the centre resolved in the direction of ry. ‘Then after an interval 7, less than 62, the radii of the surfaces are 7 + at and 7! + a7 ultimately. Hence the area = Oi ley cecil oelt eee roy aoe of the outer surface corresponding to m? = m?. (Ee 1 ee ; AT AU ray ¢ meal iat aa*gp!? : = .| ———_ |} = » by neglecting terms that 7 ae aT rz ° may be neglected, since by hypothesis 7’ differs very little from 7, and az is very small. This result is independent of 7, and is the same as if the centre had been fixed. ‘The rest of the reasoning would consequently conduct to the equation (1.). Hence from this equation combined with the known dp du ; : 2 4 sea Val rw eS —_—\= equations Pp (the pressure) ee A: OG and p dr rie bay) 05 equations applicable to motion directed to or from either a vibrating in a resisting Medium. 465 fixed or a moving centre may be deduced, I will not stop to make the deduction, which presents no difficulty, but at once employ the equations given in the ‘Treatises on Hydro- dynamics for motion propagated Jrom a fixed centre. (Pro- pagation fowards the centre is excluded by the nature of the question.) ‘These equations are (putting 1+ for p), ae U =e Jiseeh) (2.), and as =e) 5, )y ahich as they contain niet y functions, apply immediately to the arbitrary disturbance given to the fluid. In the problem be- fore us they apply, therefore, to the motion given to the fluid by the vibrating sphere at zts surface. For as the sphere is supposed to be perfectly smooth and consequently to impress motion only ina direction normal to its surface, the motion at the surface is plainly directed to or from a moving centre. ' The arbitrary condition of the motion is that at a given di- stance (7), equal to the radius of the sphere from the centre regarded as fixed, and at a given point of the surface of the sphere, the velocity i impr essed follows either exactly or very approximately the law of a vibrating pendulum. _ Let the ve- locity of the centre of the sphere at any time ¢ be V sin dé. Then for any point the radius to which makes an angle 0 with the direction of the motion, we shall have the normal ca v equal to Vcos@sin 6¢. Hence, putting for brevity = f (r—at), and substituting in the equation (2.), it will be found that ae u+ Varcos @ sin bt = 0, an equation in which « and ¢ are the only variables, and which i is true whatever be ¢. ‘The integral of this equation is at u=Ce | — Vr*cos 6 cos ¢ sin (6¢—9), tan ¢ being put for Ae) The term involving C will be in- a sensible for all but very small values of ¢, on account of the factor e — and may therefore be omitted. Hence, by dif- paenvating and putting @ tan $ for br, - = — Var cos@ sin $ cos (bit— 9). Now the pressure at the point of the sphere Be ahs consi= dering is equal to a°s, or by equation (3.) a. LAC AS) or 1. du aie re Hence this pressure is V a cos@ sin ¢ cos (6¢—4). - Phil. Mag. S. 3. Vol. 17. No. 112..Dec. 1840. 2H a 466 Ona small Sphere vibrating in a resisting Medium. And by integrating in the usual way to obtain the. pressure on ; Arad bbe: AV are the whole sphere, it will be found to ber migyt . sin ¢ cos (bt—¢). This is reckoned positive in the direction con- trary to that of the motion of the sphere. Hence if = the ratio of the specific gravity of the fluid to that of the sphere, the accelerative force of the resistance in the positive direction 2) dois aN : | of the motion is _—_— .sing@cos(b¢—¢). If A = the di- stance to which motion is propagated in the fluid in the time : : 22a of one vibration of the sphere, 6 = , and consequently, r ee tang = = This is an exceedingly small quantity. Hence . : nr br very approximately sin ¢ = = = >> and the accelera- tive force of resistance = —Vbecosbt. Again, if z = the distance of the centre of the sphere at the time z from the ul mean place about which it is oscillating, o; = V sin bf, Gige , and — 3 = Vbcosbt. Hence the accelerative force of the istance = —o.-> The length of the pendplammle resistance = —o., WE e length of the pendulum being é and the force of gravity g, the accelerative force of gravity, taking account of the buoyancy of the fluid, is — a (1—o). Hence, a’? x Fi inge gut eo Ty Se agee and consequently Ct. £h, (l=s QE ea Meee This is the result I obtained by my two former methods. As it does not contain a, it is applicable to any resisting me- dium, supposing the vibrations to be slow. Putting the factor in brackets, under the form 1—2nc, we shall have ae For a brass ball of specific gravity 8, vibrating in air, 2 = 2 very nearly; and for the same vibrating in water, Mr. Lubbock on the Heat of Vapours, &c. 467 # = 1°78. The experiments of Bessel give for these two cases, 1-95 and 1°63. I do not consider the above solution of value for the nume- rical results to which it leads, so much as because it serves to establish the principles to be adopted in the treatment of another problem (perhaps the most important that could be proposed in the present state of physical science), the solu- tion of which has hitherto been unattempted, viz. 7f a minute spherical atom were subject to the mechanical action of the vi- brations of a very elastic medium, like those which take place in air, would it, in addition to a vibratory motion, receive also a permanent motion of translation? I propose at a fu- ture opportunity to state my reasons for considering this an important question, and to advance some ideas respecting the method in which I conceive it may be answered. Cambridge Observatory, Nov. 16, 1840. LXIX. On the Heat of Vapours and on Astronomical Re- Jractions. By Joun Wriutam Lussock, Esq., Treas. RS., FRAS. and F.LS., Vice-Chancellor of the University of London, §c. . [Continued from p. 280. ] On the Conditions of the Atmosphere, and on the Calculation of Heights by the Barometer. (Resumed.) . A® the expression which has served to calculate the tem- peratures evidently represents the state of the atmo- sphere far within the limits of the applicability of this or any other formula founded upon a state of repose to an atmo- sphere continually agitated by currents, it must of course serve to eliminate the density and to obtain an expression for the height in terms of the pressures and temperatures at the extremities of any atmospheric column. If z be the altitude of the place above any fixed point, a the distance of the fixed point from the centre of the earth, g the force of gravity, | aD. ga’ Ch Cee ie and putting the expression for g’, at vol. xvi. p. 440, k(1 + 26)(p?— E)dp' _ ga-dz! p (pl? — E) ar (a + ae 2H2 468 © Mr. Lubbock on the Heat of Vapours — This expression can be integrated, and I find, supposing z= 0, after a proper determination of the constants, ! es Bt 1 aa k (1+ #8) Clee Alipay ne Nap. log (~ ike ey o 1 ] a the variation of the force of gravity be deplete the pressures p, p' may be represented by the heights of the barometer /, h’. If M be the modulus or the quantity by which Naperian logarithms must be multiplied to give common logarithms, Laplace makes k a m-4.G, log M = 9:6377843. am 183374 og 6377843 In order to give an example of the use of this expression, I take the 21st observation of Gay Lussac, h = 76568 @= 30°75 h'= *3339 ’— — 7:00 log 18337°46 = 42633392 log (1 + a8) = 0:0474015 | | at) log. a Wat WING ae ye ae = 09696699 eye wal. ae p71 dake uhm Gee 1 bk ae 6’ , p log < log ee (>) == $°77627 76 (} — | 3°3566882 log B 9°5176049 3°8390833 = 6903: 7 2 hee etc log a = 6°8041168 in metres. z' = 6921°7 metres. and on Astronomical Refractions. 469 If = eal eg Y ee) =l1—q ae Pie = — Has before, vol. xvi. p. 440. P agat l1—Ep” The expression for z' may be put into the form a k(1 + «6) ee ge Nap: log (1! 4). | Oo If y = 149138 when p! = 0, g = 1, we get for the superiordimit of the atmosphere an altitude of about 24 miles, or 38918 metres. Ultimately the intensity of the cold deprives the air of its elasticity*. The density therefore requires in strictness to be re- presented by a discontinuous function ; for the formula suggested in this treatise is of course only applicable so long as the air exists in the state of an elastic vapour. ‘The freezing point of air is un- known, and we cannot decide when this condition ceases to obtain. Delambre estimates the height of the atmosphere as deduced from the phenomena of twilight + at 70,800 metres ; but this calculation is open to objection. See Conn. des Temps, 1841, p. 58. | I have given the example of the calculation of a height by an ob- servation of the barometer, in order to show how my formula for the density may be employed; but however inaccurate in principle the method in use may be, it is sufficiently exact for elevations ac- cessible to man. In all inquiries, however, connected with the con- dition of the higher regions of the atmosphere, and in the various hypetheses which may be made respecting the decrement of tem- perature, the corresponding height must be calculated by an ap- propriate formula, procured agreeably to the hypothesis which may be adopted. Our information respecting the state of the higher regions of the atmosphere is I think more likely to be improved by observations made in aéronautic ascents than by those made on the sides of mountains. : __ k(1 +28) zi yj = aru. (UeeneS a * See Poisson, Théorie de la Chaleur, p.460. ‘‘ On peut se représenter une colonne atmosphérique qui s’appuie sur la mer, par example, comme un fluide élastique terminé par deux liquides, dont l’un a une densité et une température ordinaires, et l’autre une température et une densité excessivement faibles.’’ See also Biot, Conn. des Temps, 1841. + See Delambre’s Astronomie, vol. i. p.337, and Lalande’s Ast., vol. il. art. 2270 ee 470 Mr. Lubbock on the Heat of Vapours At the summit of the atmosphere g = 1, if w’ be the corresponding value of u, . w= —Nap.log(1— H) c-“=1—4, c being the number of which the hyperbolic logarithm is unity. E p-8 4 1— Ep=8 = — H. See vol. xvi. p. 440. _ p being the pressure at the lower station; the pressure for *76568™ or 30°14 inches of mercury in the barometer being unity. I get, when 1 ie ey ae E = — 1:192, the following formula for calculating heights by observations of the barometer : fj : z= [47404605 | eee log (1 — Hq) in French metres, tape ime = [5°2564585| pee) log (1 — Hq) in English feet, = [i-ssssi95)\4 +49 log (1 — Hq) in English miles, the temperature @ at the lower station being reckoned from the freezing point. Log « = 7°3187588 for Fahrenheit’s scale. If we assume the 21st observation of Gay Lussac, and suppose y= 1°4, I find B = — ‘2857 E = — *8405 log H = 9°6596173. In Fahrenheit’s scale _ — [219935785] p® + +8405 Height in miles = [1°9885722] log (1 — Hq). If we suppose y = 1°5, I find — 448°, B= —°3338 E=—1:1920 log H= 9°7354232 ‘694832 - = 180694892] _ ago pP + 1:1920 Height in miles = [1°8457978] log (1 — Hq). If we suppose y = 1°6, I find B= — ‘375 E= —1°5112 log H = 9°7794573 and on Astronomical Refractions. 471 _ — [81285240] p + 1°5112 Height in miles = [1°7506111] log (1 — Hq). Mr. Russell has calculated for me the following table in order to show in what manner the density and temperature of the atmo- sphere vary in the higher regions under these three different sup- positions. — 448°, ae B= —-2857 oad a= —375 Bi ae ao ook Obi OF os m | p c ° Pp eth Iie P r e | m 0 |1-0000 |+ 87 |1-0000 |1-0000 |-4+ 87 {1-0000 |1-0000 |-+ 87 |1-0000| 0 4 | -4628|4 24 | -5248| -4630/4+ 24 | -5248| -4631/+ 25 | -5249| 4 8 | -1906|— 45 | 2534] -1902|— 48 | -2543| -1900/— 50 | -2553/ 8 12 | -0656 |—122 | -1076| -0645 |—130 | -1086| -0635 |—137 |--1093| 12 16 | -0167 |—206 | -0367| -0153|—223 | -0365| -0141|—240 | -0362| 16 20 | -0022|—298 | -0080| -0015 |—330 | -0068| -0009 |—361 | -0055 | 20 24 | -0000 |—399 | -0003 24 Limit 25°81 miles. 23°896 miles. 22-52 miles. By making y = 1°5, the expression for the density becomes ] ed simplified, — 2, eo = Ben *4 —1+ ca See vol. xvi. p. 440. / iff =1—o 1 -o=ayo te ee he. (1 Hye" | It must be recollected that the difficulty of determining the den- sities at different altitudes, and that of determining altitudes by ob- servations of the barometer, rest in finding the accurate law of the temperature. So that if the expression which I have here suggested for the temperature be adopted, the expression for the density, and those for finding the elevation by observations of the barometer, follow as a matter of course, and their accuracy is unquestionable. The employment of the formula in p. 467, for calculating heights, amounts to determining the constant H# from the observations themselves, and not from previous observations. But if the constants are supposed to be known, as in calculating a series of observations made under the same circumstances, it is more simple to employ the expression 472 Mr. Lubbock on the Heat of Vapours zg! == tw. ! 1+ = a _ The day on which M. Gay Lussac made his ascent was very warm, and the values of y and H determined from his observations may differ slightly from those mean values which will be obtained hereafter from more complete data. The preceding theory supposes implicitly that a given temperature at the earth’s surface always cor- responds in any given place to a given pressure; this, owing to the currents, the winds, and to other causes, is not the case; for the atmosphere is never in a state of repose, and its temperature and density are in a continual state of oscillation about their mean values. ‘The constants y and EZ may also be subject to variations from fluctuations in the quantity of aqueous vapour diffused through the atmosphere. If the decrements of temperature are the same for equal incre- ments of altitude, which observation shows is nearly the case at_ small elevations, § being the temperature at the lower station, 4 at the upper, and z' as before, the altitude of the latter reckoned from the former, l+ef=1+a(i—A2), and if the variation of the force of gravity be neglected Ul ge tt gds! p k{l+a(d— dz} ka A ar ie bos ee, (Plt a()-Ad)| mean orn is iy lta Jf p' being the pressure at the upper station, and p at the lower, (w | Mr. Ivory assumes, Phil. Trans., 1838, p. 192, Lea? ih (log £) aes oe Suse: Be robb Abe apy er WANE a vis oh gig 3 (log 5) Bi ch la Mi Ne we Besibs ae and on Astronomical Refractions. 473 But Mr. Ivory afterwards neglects the terms depending upon J'; f";, &c., so that he virtually assumes l+adi Q (log-$) | eee pe Bin EE ar a g ! ! ed 2 ad ae g g ey. (] ile ey gee gol) ; I Mr. Ivory makes the constant f = 97 P: 197, se that ! ! [2 PF =(9'8908555]£ + [(9:3467875] & - g ¢ d a! do! CSN i mh EE he met gods! fence (0% a é J f= aiut 20D hog £ 4 7 PS (1 — £) Bah 2 Se Binns 8 g a _A(1+e4) (1—/f) atic Diels te) 2 (1 -£) g cd g g ! = [09635418] log 7 + [0°3582881] (1 uy vi for 50° Fahr. at the lower station. As we cannot make direct observations of the temperature and density of the highest regions of the atmosphere, it becomes very important to avail of all indirect means of investigation. The pro- blem of Astronomical Refractions furnishes us with valuable data in this respect, and any hypothesis relative to the state of the atmo- sphere which will not satisfy the known phznomena of refraction, must of course be discarded. In any investigation of this kind it is indispensable to employ a formula for z in terms of the density consistent with the hypothesis, which may be made respecting the decrement of temperature; it is equally indispensable to carry the integral which affords the amount of refraction through limits which are in conformity with the same supposition. * aiu=o in Mr, Ivory’s notation. In this page p is the pressure and ¢ is the density at the earth’s surface. [To be continued. | ih ay [ 474, J} LXX. Proceedings of Learned Societies. ROYAL GEOLOGICAL SOCIETY OF CORNWALL. Twenty-Seventh Annual Report of the Council. es subject which naturally first presents itself to the Council in the preparation of their Report, is the irreparable loss the Society has sustained by the death of its illustrious and venerable President (Mr. Davies Gilbert) ; to whose early, active and liberal patronage, in conjunction with the efforts of Dr. Paris, it first owed its exist- ence, and by its connexion with his name its labours have been more extensively known, and far more generally acknowledged, than they might otherwise have been. The Council would fain have indulged in more grateful allusions, than a bare official form permits, to the numerous advantages and benefits the Society has owed to his kind and continued benefac- tions during the twenty-six years it was honoured by his presidence over its affairs—but that they have been anticipated by other pens —yet they cannot look back on his kind and considerate conduct without the feeling that every member of the Society has, by his loss, a friend less in the world. At the foundation of the Society, twenty-seven years ago, the value of, and necessity for scientific education among our practical miners was barely thought of; yet it was among the very first and most important objects of its founders: and to them it is the sin- cerest matter of gratulation that. a subject so often enforced from its chair, and recommended by its patrons and in its reports, is at length recognized as one of paramount utility and importance. This has been shown, not only by the foundation of Professor- ships for civil and mining engineering in the academic institutions of London and Durham, but by the institution of a Mining School in Cornwall, which, although first thought of as the result of a due appreciation of the public virtues of one of the earliest and most munificent friends of this Society (the late Lord de Dunstanville), has been carried into practical effect by the liberality of Sir Charles Lemon, by whose enlightened and patriotic exertions its permanent existence will, we trust, be secured. We look forward to the period when the result of the studies pursued in this institution, united to tle extensive practical knowledge to be derived from exploring the variety of our rocks,—the different characters of our “ lodes,” and the vast mechanical powers employed in working our mines,—will raise our miners far above their present position, although even now they bear the character (which they richly deserve) of the best and most useful practical miners in the world. Much has been said of a reception-room for plans,—and such a depository has from the foundation of the Society been opened here, and to some extent made useful by the liberality and intelligence of some of our mine agents. But when the labour of preparing them—highly valued as they are—and the want of adequate re- muneration, are considered, we need not wonder at the comparative 5 oe ae Royal Geological Society of Cornwall. 4.75 poverty of our archives in this respect. Mr. Henwood’s Survey of the Mines has probably brought together a larger collection of copies of mining plans than had ever before been obtained ; but unless simi- lar labeur be still devoted to their accumulation, it is vain to hope for them, unless at an expense which would perhaps but seldom be repaid by their value to any but practical miners. The rock formations of Cornwall had, until recently, been thought among the most ancient; but the late researches of Messrs. Sedg- wick and Murchison induce them to place our “‘ Ai//as”’ at an epoch not anterior to the old red sandstone, on zoological evidence of much force ; whilst to the granite and its congeners they ascribe a still more recent date. From the labours of these eminent philosophers, associated with the visit of Prof. Phillips (under the direction of the Government), and, in some humble degree, aided by the efforts of our own members, we hope this obscure portion of geological investigation will receive an elucidation equally luminous with that which Mr. Murchison’s herculean labours have shed on the closely- allied rocks of the ‘‘ Szlurian” region. The rapidly-accumulating collections of the Society are even now more than sufficient to fill every species of accommodation the pre- sent museum affords ; and it will be imperative on your new off- cers and Council to devise a method for rendering them more gene- rally available and useful than their present circumscribed premises will permit. It has been suggested, that with so much geological wealth as the Society possesses, the benefits it confers are but limited; and with a view to repeating an experiment which was unsuccessfully made by the late zealous and excellent Secretary (Dr. Boase), a few lectures will from time to time be given by one of the officers du- ring the ensuing winter; their periods will, however, be determined by engagements in which the Society has no part. It had been confidently anticipated that the Fifth Volume of the Society’s Transactions would, ere now, have been in the hands of the members: considerable progress has been made in it during the present year, but its completion has been delayed by professional engagements of the editor; the Council, however, believe that it will be published at an early period of the ensuing season. By order, W. J. Henwoop, October 9th, 1840. Secretary and Curator. The following papers have been read since the last Report :-— I. On some singular Metalliferous Deposits in the Mining district near St. Ives, called by the miners “Carbona.” By Joseph Carne, Esq., F.R.S., F.G.S., M.R.1LA., &c., &c., Treasurer of the Society. II. Remarks on the Land-slip between Axmouth and Lyme Re- gis. By the Rev. Canon Rogers, A.M., Member of the Society. ~ TII. Notes on the Geology of the Counties of Gloucester and Restigouche, in New Bruuswick, and the Canadian bank of the river Restigouche. By W. J. Henwood, C.E., F.R.S., F.G.SS. London 476 Royal Geological Society of Cornwall. and Paris, Hon. M.Y.P.S., Secretary of the Society, and Curator of the Museum. IV. Observations on a suite of Specimens from the neighbour- hood of Exeter. . By Joseph Parker, Jun., Esq., Corresponding Member of the Society. V. On the Age of the Shingle Beach at Pevensey, in Sussex. By John 8. Enys, Esq., F.G.S., &c., Member of the Society. VI. On the Organic Remains contained in the Slates and Lime- stones of South Devon. By J.C. Bellamy, Esq., Curator of the Devon and Cornwall Natural History Society. VII. On the Occurrence of Organic Remains in the Slate Rocks of the Southern Coasts of Cornwall. By Charles W. Peach, Esq., Associate of the Society. VIII. On the Sulphur Ores (iron pyrites) of the Vale of Ovoca, county of Wicklow. By W. J. Henwood, C.E., F.R.S., Correspond- ing Member of the Plymouth Institute. The Curator’s Report notices the following Donations to the Mu- seum :— Cinnabar, with hematite iron ore and copper pyrites from Bavaria, vitreous and purple copper ores and copper pyrites from Kenmare mine, county of Kerry, and metallic copper precipitated on the pumps of Connorree mine, county of Wicklow. By Thomas Cor- nish, Esq.—Specimens from the recent land-slip on the coast be- tween Axmouth and Lyme. By the Rev. Canon Rogers, A.M., Member of the Society.—Specimens from the trap dyke, and of the accompanying rocks, from Mr. Pennant’s slate quarry at Pen- rhyn, Caernarvonshire. By Joseph Carne, Esq., F.R.S., F.G.S, M.R.1.A., &c., Treasurer of the Society.—Wood-tin and garnets, from Polberrow mine, St. Agnes. By John T. Tregellas, Esq.— Pseudomorphous quartz, from Caradon, and crysocolla, from near Five Lanes. By Mr. George Jennings, Jun.—Stream-tin ore from Carnon mine. By Mr. Nicholas 8. Cloak.— Pearl spar and iron py- rites from Trevaskus mine. By Mr. — Joseph.—Galena, copper pyrites and sulphuret of antimony from Sicily. By — Floyd, Esq. —A suite of specimens from the neighbourhood of Exeter, and or- ganic remains resembling Alcyonia, from the new red sandstone of Devon. By Joseph Parker, Jun., Esq., Corresponding Member of the Society.—Organic remains from the slate series and limestones near Plymouth. By J.C. Bellamy, Esq., Curator of the Devon and Cornwall Natural History Society.—A fine specimen of Jew’s-house tin from St. Austell. By John Michell, Esq.—Chert from Halkin mountain, Flintshire. By Richard Thomas, Esq. (of London).— Organic remains from the summit of Snowdon, and carbonate of manganese from Caernarvonshire. By Henry Thomas, Esq., F.G.S., Associate of the Society.—A suite of specimens from the coast of Antrim and other parts of Ireland. By C. A. Johns, Esq.—Native copper, crystallized copper pyrites, and iron pyrites from Providence mines, near St. Ives; galena from North Wheal Alfred, with speci- mens from the copper and ‘sulphur (iron pyrites) ores of Wicklow. By Mr. Higgs, Member of the Society—Chalcedony, organic re- Intelligence and Miscellaneous Articles. 477 mains from the chalk, and conglomerates from near King’s Langley, Herts. By H. Campbell White, Esq., F.G.S., &c., &c., &e.—Quart- zose slickenside and purple copper ore from Carn Brea mines, cry- stals of the red oxide of copper, silicate of tin from Weald Coats, copper pyrites and carbonate of iron from Wheal Tolgus, and a new ore of copper from Great Saint George mine. By John Gar- by, Esq., Associate of the Society.—Crystalline quartz from Knock- mahon mine, county of Waterford. By John Petherick, Esq.— Acicular oxide of copper from Knockmahon mine. By Captain James Clemes.—Conglomerate from Slevnamann mountain, county of Tipperary, and sandstone from Mohir, county of Clare. By Day P. Le Grice, Esq., Member of the Society.—Specimens from vari- ous localities. By the Rev. Henry Holden.—Organic remains from Fowey and Caerhayse. By C. W. Peach, Esq., Associate of the Society.—Vitreous and purple copper ores, and copper pyrites from Kenmare mine, county of Kerry. By Dillon Croker, Esq.—Recent sandstone from Lelant. By the Rev. W. D. Longlands.—Wood from the diluvium at St. Erth stream. By Mr. Samuel Peters.— Hematite iron ore from Launceston, Van Diemen’s Land. By Richard Edmonds, Esq.—Specimens from the neighbourhood of Killarney, county of Kerry, from Knockmahon mine, county of Waterford, and from Cronebane, Tigrony, Connorree, Ballymur- tagh, and Ballygahn, in the Vale of Ovoca, county of Wicklow. “By W. J. Henwood, C.E., F.R.S., F.G.S., Secretary of the Society and Curator of the Museum. Officers and Council for the present year :— President.—Sir Charles Lemon, Bart., M.P., F.R.S., &c. Vice- Presidents.—Sir T. D. Acland, Bart., M.P., F.R.S.; John Paynter; John Taylor, F.R.S., &c.; Stephen Davey. Treasurer.—Joseph Carne, F.R.S. Joint Secretaries. Samuel Pidwell, Jun.; W. J. Henwood, F.R.S. Librarian.—Riehard Hocking. Council.—John Batten, John J. A. Boase, Thomas S. Bolitho, Samuel Borlase, Charles Fox, Thomas Lean, J. N. R. Millett, Rev. M. N. Peters, W. Petherick, N. Phillips, William Reynolds, W. M. Tweedy. LXXI. Intelligence and Miscellaneous Articles. ATOMIC WEIGHT OF CARBON. M.DUMAS and Stas haye, together, performed fourteen expe- riments relative to the atomic weight of carbon; the results all agree, and were obtained either by the combustion of pure charcoal or of highly carbonated and weli-known substances. The combustion was performed in oxygen, and care was taken to dry the gases obtained either by sulphuric acid or chloride of calcium. Thus dried, they were passed through two pieces of apparatus filled with solution of potash, and a third filled with potash in powder. The increased weight of the solutions and dry potash gave the weight of the car- bonic acid obtained. Thus the weight of the carbon burnt, and of the carbonic acid gas obtained, were known; and from these, with- 478 Intelligence and Miscellaneous Articles, out any hypothesis, the proportions in which the bodies combine could be deduced. According to M. Berzelius, the proportions are 200 of oxygen to 76°52 of carbon. According to the recent experiments, above-mentioned, by MM. Dumas and Stas, the result will be very different, for they gave by the combustion of naphthalin, four ex- - periments, 75°21, 75°01, 75°08, 75°07; by the combustion of cam- - phor, three experiments, 75°1, 75:1, 75-0; by the combustion of benzoic acid, two experiments, 75°09, 75°03; by that of the native graphite of Ceylon, three experiments, 74°91, 75°05, 74:99; by artificial graphite extracted from an iron which contained most of it, two experiments, 74°87, 74°90. <* All these numbers,’ M. Dumas remarks, ‘‘ agree in showing that the true atomic weight of carbon is 75, and not 76°52. ‘There is consequently an error in the indis- pensable elements in fixing the formule now employed in organic chemistry. That is to say, there will be many formule to modify, many analyses to repeat, especially of those substances which are rich in carbon, in which very considerable errors may have been committed.” M. Dumas adds, that the Academy will remark with interest, that this long and laborious series of experiments has brought us to the atomic weight indicated by Dr. Prout, who. had long supposed that the atomic weight of charcoal was exactly equal to six times that of hydrogen, or 12°5 x 6 = 75, which is the number given by the mean of our results. If, as believed by Prout, and as now ap- pears very probable, all atomic weights are multiples of that of hy- drogen by whole numbers, there will be many things to rectify in the atomic weights at present adopted. Future experiment will de- cide this point, but it is evident that they must be submitted to a serious verification. “The Academy,” continues M. Dumas, ‘ will remark also with interest, that the atomic weight-of carbon which results from these experiments agrees much better than the former with the old ana- lyses of Iceland spar, arragonite and marble, made by Thenard and Biot, as well as with the densities of oxygen and carbonic acid, de- termined either by MM. Biot and Arago, or by M. de Saussure, | whose results also approximate to ours with regard to the combus- tion of charcoal.” M. Boussingault has communicated some analyses of: bitumen, which entirely agree with our results.” —L’ Institut, No. 347. PYRRHITE-—-A NEW MINERAL. Only one example of this substance is known, and occurs in a splendid drusy cavity of felspar, which is in the possession of Vice- President Perowski, of Petersburgh. While the cavity chiefly con- tains felspar crystals several inches in size, finely defined, and of an ochre-yellow colour, it likewise includes six-sided tables of reddish- white, pearly lithion mica; white translucent crystals of albite ; crystals of clove-brown rock-crystal; andafew white topazes. The crystals of the new mineral are superimposed on the felspar, are Meteorological Observations. 479 eight in number, and are octahedrons of about three lines in length. Their surfaces are smooth, but possess little lustre, so that their angles cannot be measured with great accuracy; but from observa- tions made on several angles, the mean may be regarded as 109° 28’, so that we may probably assume that the crystals are regular octa- hedrons. No cleavage is observable. The colour is orange-yellow, and the lustre feebly vitreous. The substance is translucent on the edges, its hardness is that of felspar, but the specific gravity could not be determined. It occurs at Alabaschka, near Mursink, and on account of its yellow colour has been named Pyrrhite.—Jameson’s Journal, July 1840. PIHLITE—A NEW MINERAL. Sefstrom has discovered at Fahlun a new mineral which replaces mica in granite, and which he has termed Pihlite, in honour of the late M. Pihl, Director of Mines. It is an intermediate substance between talc and mica, and its composition is expressed by the fol- lowing formula : Lbid. DYSODIL. This mineral, arranged in systems of mineralogy under the name of Foltated Mineral Pitch, Ehrenberg has shown to consist of bitu- men, or mineral pitch, mixed with siliceous shells of infusoria, and occasionally with pollen of pines, &c. The wax-yellow variety found in Sicily, is made up of shells of Navicu/e and mineral pitch: the nearly black-brown coal of the Westerwalde, is a variety of dysodil; so _ also is the foliated leather-like bituminous coal of the Geistinger Busch at Rott and Siegburg in the Siebengebirge, and a foliated brown coal of the Vogelsberge. Hence the mineral species named dysodil appears to be a polir-slate impregnated with bitumen. ° Its colours are black-brown, or black. It never forms very thick beds, but sometimes widely-spread deposits. It is used as fuel.— Annals of Nat. History, April 1840. METEOROLOGICAL OBSERVATIONS FOR oct. 1840. Chiswick.—October 1. Overcast. 2,3. Very fine. 4. Rain. 5. Fine: rain, 6. Fine. 7. Frosty and foggy. 8. Very fine. 9. Hazy. 10. Dense fog: very fine. 11. Hazy. 12—15. Foggy in the mornings: fine. 16. Overcast. 18. Cloudy: rain. 19. Cloudy. 20. Clear. 21. Fine. 22. Hazy: rain. 23. Overcast: rain. 24, Overcast. 25. Very fine. 26. Overcast. 27. Heavy rain: clear. 28. Fine. 29. Foggy: rain: dense fog at night. 30. Cloudy and fine: clear. 31. Foggy: clear at night. Boston.—Oct. 1,2. Cloudy. 3, Fine. 4. Cloudy. 5. Cloudy: rain early A.M. 6,7. Fine. 8. Fine: rime frost this morning. 9. Cloudy. 10, 11. Fine. 12—14. Foggy. 15. Fine. 16. Cleudy. 17. Rain: rain early a.m. 18. Cloudy: raine.m. 19. Stormy. 20. Fine. 21. Cloudy. 22. Cloudy: rain early a.m. 23. Fine: raine.m. 24. Fine. 25. Fine: rain early a.m. 26. Fine. 27. Cloudy: rain early a.m. 28. Foggy. 29. Cloudy: rain a.m. and p.m. 30, 31. 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XVII. THIRD SERIES. LXXII. Remarks on Professor Challis’s Investigation of the Motion of a Small Sphere vibrating in a Resisting Medium. By Georce Bipvett Atry, Esq. M.A., F.R.S., Astronomer fioyal. Lo the Editors of the Philosophical Magazine and Journal. GENTLEMEN, : your Number for December there is a paper by my friend Professor Challis, on the theoretical resistance to the motion of a sphere vibrating in an elastic medium. ‘The problem is so difficult, and so important in its application to geodesy, and therefore of such general interest, that I have thought it best to state, in a public communication, the diffi- culty which I feel with regard to one step of the investigation, and to request Professor Challis to remove my difficulty by communication to your journal. I see nothing liable to objection in pages 463 and 464; but with the top of page 465 my difficulty commences. The differential equation, tacitly used by Professor Challis, is that SJ (r—at) f(r—at) r ee ate is perfectly correct for waves, diverging with equal intensity and with corresponding phase, in all directions from a centre ; or, if not in all directions, it is yet true if the waves diverge with equal intensity and corresponding phase through all the angular directions included in a spherical sector bounded by material planes, which (produced if necessary) would meet at the centre of the sphere. But it is not true in any other case. Thus we may have two such spherical sectors, separated only by a material partition, and with waves of different intensities and non-corresponding phases propagated in the two sectors, from the centre, or from the surface of a small concentric sphere; and the equation applies to egch sector separately ; but if the partition. be removed it no “longer applies to the whole compounded sector. For the pressures against the par- tition, produced by the fluids on the two sides, were different ; and, therefore, on removing the partition, a new motion of a Phil, Mag. 8.3. Vol. 17. No. 113. Suppl. Jan. 1841. 21 whose solution is v = ; which equation 482 Address of the General Secretaries totally different kind, modifying the old pressures, and there- fore modifying the old motions, will be introduced. ‘This remark applies even when the phases correspond, if the in- tensities are different. Now it appears to me, as far as I can follow the investiga- tion, that some such process has been used as adopting the solution above alluded to, and supposing it to hold with waves of different intensities in different parts of the surface of the small sphere. For the expressions in lines 25 and 28 contain the factor cos 0, which, as it is not differentiated in the : seh a AME , , operation for forming ie but remains still as a factor, seems to imply that the wave in each infinitesimal sector goes on just as if there were no other sector near it communicating lateral pressures. If I am correct in the view which I have taken of the con- nexion of these steps of the process, I conceive that the in- vestigation must be censidered faulty. Of the truth of my first remarks I have no doubt; but I am less confident as to the exact connexion of the different steps in Professor Challis’s investigation; and upon this point I am anxious to be informed. I am, Gentlemen, | Your very obedient servant, | Royal Observatory, Greenwich, December 9, 1840. G. B. Arry. LXXITi. Address of the General Secretaries of the British Associations RopERIcCK Impey Mourcuison, F.R.S., 2.G.S., and Major Enywarp SaBInE. V.P.R.S.: read at the Meet- ing at Glasgow, September 1840. | [Continued from p. 449, and concluded. | ROM Zoological researches let us now turn to Physical Geology. One of the most interesting fruits of modern experimental research is the knowledge of the fact, that elec- trical currents are in continual circulation below the surface of the earth. Whether these currents,. so powerful in developing magnetical and chemical phenomena, are confined to mineral veins and particular arrangements of metal and rock, or ge- nerally capable of detection by refined apparatus well applied, appeared a question of sufficient importance to deserve at least a trial on the part of the Association. Our present volume records the result of such a trial on the ancient and very re- cularly stratified rocks of Cumberland, consisting of limestone, sandstone, shale, and coal, so superimposed in many repeti- tions as to resemble not a little the common arrangement of a voltaic pile. Varied experiments, with a galvanometer of con- of the British Association to the meeting at Glasgow, 1840. 483 siderable delicacy, failed to detect, in these seemingly favour- able circumstances, any electrical current. The extensive and rapidly increasing applications of iron to public and private structures of a!l kinds in which durabi- lity of material is a first requisite, have made it highly desirable to possess accurate information respecting the nature of the chemical forces which effect the destruction of this hard and apparently intractable metal. ‘The preservation of iron from oxidation and cerrosion is indeed an object of paramount im- portance in civil engineering. ‘The Association was, therefore, anxious to direct inquiry to this subject, and gladly availed it- self of the assistance of Mr. Mallet, a gentleman peculiarly qualified for such investigations, both from his knowledge as a chemist, and from his opportunities of observation as a prac- tical engineer. An extensive series of experiments has ac- cordingly been instituted by him, with the support of the Association, on the action of sea and river water, in differ- ent circumstances as te purity and temperature, upon a large number of specimens of both cast and wrought iron of different kinds. These experiments are still in progress, and the effects are observed from time to time. ‘They will afford valuable data for the engineer, and form the principal object of the in- quiry ; but a period of a few years will be required for its completion. In the meantime, Mr. Mallet has furnished a report on the present state of our knowledge of the subject, drawn from various published sources, and from his own ex- tensive observations. In this report he examines very fully the general conditions of the oxidation of iron, and how this operation is greatly promoted, although modified in its results, by sea-water; also in what manner the tendency to corrosion is affected by the composition, the grain, porosity, and other mechanical properties of the different commercial varieties of iron. ‘The influence of minute quantities of other metals, in imparting durability to iron, is also considered. Mr. Mallet devotes much attention to the consequences of the galvanic as- sociation of different metals with iron, a subject of recent in- terest from the applications of zinc and other metals to protect iron, which are at present agitated. He concludes this, his first report, by recommending a series of inquiries, ten in number, which will supply the desiderata immediately required by the engineer and by the chemist. We have next to notice a report by Professor Powell, on the present state of our knowledge of refractive Indices for the standard rays of the solar spectrum in different media. The difficulty which the fact of the dispersion of light has offered to the universal aa HON of the undulatory theory, 212 484 Address of the General Secretaries has been in a great measure removed by the analysis of Cauchy and others, who have considered the distances of the undula- tory particles as quantities comparable to the length of a wave; velocities of propagation of the different rays of the spectrum are made to depend upon the length of wave which constitutes a ray of a given colour, and upon certain constants proper to the medium ; these constants being obtained from observations on refractive indices for certain definite rays (or dark lines) of the spectrum, the refrangibility ef any other definite ray (whose wave-length has been ascertained by examining an inter- ference-spectrum) becomes known, and may be compared with observation as a test of theory; such experiments have been made by Frauenhofer, Rudberg, and Professor Powell, who has given a tabular view of the various results, without, how- ever, instituting the comparison between theory and observa- tion, which it would be desirable to extend further than has yet been done. It would be important also to elucidate the — disturbing effect of temperature, which prevents even existing observations from being rigorously comparable. The calculations respecting the tides, which have been pro- secuted by the aid of the Association ever since its institution, have been continued this year by Mr. Bunt, under the direc- tions of Mr. Whewell. ‘These calculations have now reached such a point, that the mathematician, instead of being, as at the beginning of this period, content with the first rude approxima- tions, is now struggling to obtain the last degree of accuracy. The country in which we are now assembled, has always been conspicuous for attention to meteorology, a branch of physical science, in which the British Association, with its power of combining the efforts of many observers in distant quarters of the globe, may hope to be especially useful. In Scotland, Leslie opened a new train of inquiry, by ex- amining the earth’s temperature at different depths; and his successor in the University of Edinburgh, is now directing, at the request of the Association, a large and complete course of experiments on that interesting subject. Framed in conform- ity with the plans adopted for similar objects by Arago and Quetelet, these researches of Professor Forbes contain also the means of determining the power of conducting heat, which different sorts of rock possess; and may thus throw light on some of those peculiarities in the distribution of temperature at greater depths below the surface, which have become known by experience, but are not explained by theory. In Scotland, Sir David Brewster was the first to obtain an hourly meteorological journal for a series of years, and to draw from that fertile source new and important deductions, which of the British Association to the meeting at Glasgow, 1840. 485 have had a powerful influence on the progress of scientific metecrology. How gratifying to receive, through the same hands, after the lapse. of nearly 15 years, an additional con- tribution of the same kind, and from the same country 3 but embracing new conditions, on a new line of operations, in or- der to obtain new results! By the observations now in pro- gress at Inverness, and at Kingussie, the influence of elevation in modifying the laws which have been found to govern the hourly distribution of heat near the level of the sea, may be discovered, and thus a great addition be made to the experi- mental results, for which science has long been grateful to the distinguished philosopher we have named, and which have been described as of the highest value to meteorology, and as the only channel through which any specific practical in- formation can be obtained in this most interesting department of physics.” This is no ordinary praise. It is the just tribute of one who is worthy to offer it; one, who at the call of the British As- sociation, has conducted at Plymouth a still more extensive series of similar observations, and has added to them hourly comparisons of the temperature and moisture of the air, and an hourly record of barometric oscillations. Mr. Snow Har- ris has presented in a few pages of our last report, the precious results of (70,000) observations, and thus rendered them im- mediately available in the foundations of accurate meteorology. The documents thus patiently collected, are, however, not yet exhausted in value; they may be again and again called into the court of science, and made to yield testimony to other, and as yet, unsuspected truths. ‘They must not be lost. Shall we lay them by in manuscript among other unconsulted records of the past labours of men, or by under taking their publication, do justice to our workmen, and establish a new claim on the imi- tation of the present, and the gratitude of future days? This’ question is of seriousimport. Already, stimulated by success in thermometric registration, we have set to work on a more per- plexing problem; we have resolved to bind even the wandering winds in the magic of numbers. While we speak, the beautiful engines of our Whewells and Oslers are tr acing at every instant of time, the displacements of the atmosphere at Cambr idge, at Plymouth, at Birmingham, in Edinburgh, in Canada, in St. Helena, and at the Cape of Good Hope; and ere long we may hope to view associated in one diagram, the simultaneous movements of the air over Europe, Aetatics: Africa, India, and Australia, recorded with instruments which we have chosen, by men whom we have set to work. Among the causes which tend to retard the progress of 486 Address of the General Secretaries science, few, perhaps, operate more widely than the impedi- ment to a free and rapid communication of thought and of ex- periments, occasioned by difference of language. It appeared to the British Association, that this impediment might in some degree be removed, as far as regards our own country, by pro- curing, and causing to be published, translations of foreign scientific memoirs judiciously selected. Accordingly at each of the meetings at Newcastle and Birmingham a grant of 100/. was placed at the disposal of a committee appointed to carry this purpose into effect. Aided by the contributions of several translations which have been gratuitously presented to them, the committee have been enabled, in the two last years, to publish fourteen memoirs on subjects of prominent interest and importance in the mathematical and physical sciences, bearing the names of some of the most eminent of the conti- nental philosophers. Such, gentlemen, is an imperfect review of our recent pro- ceedings. In two essential respects the British Association differs from all the annual scientific meetings of the Continent, no one of which has printed transactions or employed money in aiding special researches. We also differ from them in the communications which, in the name of the representatives of science assembled from all parts of the United Kingdom, we feel ourselves authorized to make from time to time to the Government, on subjects connected with the scientific cha- racter of the nation. On our first visit to Scotland, for ex- ampie, we felt it to be an opprobrium that this enlightened kingdom should, in one essential feature of civilisation, be still behind many of the continental states, and we prepared an address to his late Majesty’s Government, urging strongly the necessity of the construction, without delay, of a map of Scot- land, founded on the trigonometrical survey. Representa- tions to the same effect have since been made by the Royal Society of Scotland, and by the Highland Society, and the subject has now engaged that attention, which will, we trust, soon procure for this country the first sheets of a large and complete map. If then it be asked, why are the men of highest station happy to associate and mingle with us in official duties >—why have the heads of the noble houses of Fitzwilliam, Lans- downe,* Northampton, Burlington, Northumberland, and Breadalbane, alternated in presiding over us, with our Buck- lands, our Sedgwicks, our Brisbanes, our Lloyds, and our * The Marquis of Lansdowne, who had accepted the office, was prevented from attending by deep domestic affliction, and the Marquis of Northamp- ton cheerfully supplied his place. ee of the British Association to the meeting at Glasgow, 1840. 487 Harcourts ?—why indeed, on this very occasion has Argyll himself, overlooking the claims due to his high position, and his ancient lineage, come forward to act with us, and even to serve in a subordinate office?—may we not reply, that it is, we helieve, a consequence of the just appreciation on the part of these patriotic and enlightened noblemen, of the beneficial influences which this Association exercises: in so many ways on the sources of the nation’s power and honour ? If we have hitherto dwelt almost exclusively on the value of our transactions, researches, recommendations, and the good application of our finances, let it not, however, be sup- posed, that we are not also fully alive to the advantages which flow from the social intercourse of these meetings, by bring- ing together, into friendly communion, from distant parts, those who are struggling on (often remote and unassisted) in advancing experimental science. If, indeed, this principle of union (which we are proud to have borrowed from our Ger- man brethren) has been hitherto found to work so well amongst our own countrymen, we cannot but doubly recognise its value when we see assembled so many distinguished per- sons from foreign countries. In the presence of these eminent men, we forbear to allude to individual distinctions, conscious that any brief attempt of our own would fall far short of a true estimate of merits, the high order of which is indeed known to every cultivator of science in Britain. Well, however, may we rejoice in having drawn such spirits to our Isle; valuable, we trust, will be the comparisons we shall be enabled to make between the steps which the different sciences are making in their countries and in our own. That advantages, indeed, of no mean order arise from such social intercourse, is a feeling now so prevalent, that foreign national associations for the promotion of natural knowledge have rapidly increased. Germany, France, and Italy have their annual Assemblies, and our allies of the Northern States hold their sittings beyond the Baltic. In all this there is doubtless much good, but an occasional more extensive inter- course of a similar nature, to be repeated at certain intervals, is greatly to be desired. It has therefore appeared to us (and we say it after con- sultation with many of our continental friends, who equally feel the disadvantage), that the formation of a general congress of science might be promoted at this meeting, which, not inter- fering with any assemblies yet fixed upon, or even contem- plated, may be so arranged, as to permit the attendance of the officers and active members of each national scientific institu- tion. ‘ 485 Mr. Lubbock on the Heat of Vapours If the British Association should take the first step in pro- _ posing a measure of this kind, and should solicit the ilustri- ous Humboldt to act as President, we are sure that scientific men of all nations would gladly unite in offering this homage to a man whose life and fortune have been spent in their cause, whose voice has been so instrumental in awakening Europe to the inquiry into the laws of terrestrial magnetism, and whose ardent search after nature’s truths has triumphed over the Andes and the Altai. If such be your suggestion, then will a fresh laurel be added to the wreath of this city. She who, through the power be- queathed to her by her illustrious offspring, conveys with rapid transit her inventions and her produce to the remotest lands, well can she estimate the value of an union of men whose labours can but tend to cement the bonds of general peace. Insuch a body the British representatives would, we trust, form no inconspicuous band; and with minds strength- ened by the infusion of fresh knowledge, they would, on re- assembling for our own national ends, the better sustain the permanent and successful career of the British Association. LXXIV. On the Heat of Vapours and on Astronomical Re- fractions. By Jonn Wiii1am Lupsock, Esq., Treas. RS., ERAS. and F.LS., Vice-Chancellor of the University of London, &c. [Continued from p. 473, and concluded. | F the constitution of the atmosphere be such as I have concluded, by proper substitutions in the differential equa- tions of refraction, an accurate table of refractions is to be procured, which may be-compared with that of M. Bessel obtained empirically. and on Astronomical Refractions. 489 Let SA ON be the trajectory described by light emanating from the star S in its passage through the atmosphere to the earth’s surface at O, § the apparent zenith distance, or the angle which the tangent to the trajectory makes with the line CO K at O, CH perpendicular to S A K, the direction of the ray before it enters the atmosphere = y, @ = C O, then Sponge att WOE By he a ysasin \/Tt2 et K p asin 9 Ci ee ees A Ye ——_—_—__ capa PT 4 Ca La haa rips ne I assume these equations, which are proved by Mr. Ivory in the Phil. Trans., 1838+, and which are equivalent to similar equations | given in the Méc. Céleste. a ie Ace asinddw e — Re ne Rar tg rrr a ke PP ene | (1 —2 aa) a/ cos*6 ai (= sia ) (1 —2aw) — 2aw -— =aiu,. 72 being a constant and ua certain function of the b+ _ density, which depends upon the constitution of the atmosphere, and which for the present may remain undefined. iz 2 : en = 2iu4+ 377u? 4+ &e. B ss asing6dw {1+ 2aw+ &c.} —- ©——s cos?6 + 22u+ B2eu + &e. — 2aw if e=u—— o, ZuU—a“wmier alae 971u+ 382u? + &.—2awe2r4 32% _ * The quantities rejected being plainly of no account relatively to those retained. Further, because w is always less than 1, : : “=k Ww is contained between « and « (1 + 2a), and it may be taken equal _ to a, or to the mean value «(1 + «){.” Thus we have (See Phil. _ Trans. 1838. p. 205.) * This quantity must not be confounded with the « which accompanies 6, {t Mr. Ivory’s paper here referred to has been reprinted in L. & E. Phil. Mag., be- ginning in vol. xv. p. 3, and concluding in vol. xvi.— Evir.] ¢ Laplace introduces the same simplification. Méc. Cél., vol. iv. p. 24. 490. _Mr. Lubbock on the Heat.of Vapours d.d6 = siné x son esa ys ee ila a W cos?) + 2224+ 37? 2 a(1+a)da af €08* 8) 2.2 %% [1] 3 sn te (l + ¢) ado = sind x ; + &c. (cos?6 + 2i.x)° [2] The refraction will thus consist of two terms, which I proceed to consider separately. ‘The second term is minute, not amounting to 2! sex. at the horizon. Throughout this treatise on Astronomical Refractions one accent will be affixed to any symbol that it may denote the particular value of the variable which obtains at the surface of the earth, and two accents will be affixed when the particular value which ‘obtains at the superior limit of the atmosphere is intended. | | The limits of 2, or a! and 2! corresponding to w! and uw", are z' =0, a! = yl! — , because wv! = 0, w= 1. 1 L=U— = omu— = fu; the function indicated by the letter f for the present may remain undefined. By Lagrange’s theorem i cee a Geer ea 4) umetltatoe deo 2.300 a . Hy t mi ay | Hence 2 2 2 3 Sole cre alle) ee (ta Qi dx 9-324 Ae Lette = 2! — X, u=u!'—U, w=1— FU, then | all a XK == ll — U~— {1—F U} X" =O X! = ye! X=U-——FU 2 U=X+—FX+ oe eet Be | 2 Q i ery 24K! ot EX 92 “dau D.o0 “dn and on Astronomical Refractions. 491 This series may be used if the atmosphere extends only to a finite altitude. : Let +>: A Joos?) + 2in_ , cos? § + 2Qiv=72? i z4 — 272° cos? 6 + cos* § 4 7? The integral of d.84@ is to be taken from dve=zdz , cos 4 HW cos? § + 22 2"! = 2, toz = ————___ —_——_ = ile Narits Vani —— n ! n Let (53) represent the value of (73) at the former of n ll : these limits, and (73) its value at the latter, then integrating continually by parts, hee i asin § dw A) piles he WV cos?§ + 2ie VW cos?§+ 2i4 Pozalee male uh d w\! 2 gp thoy = ae uae rol -${(f2)': Ged) z} me 1 " de os eae 28 — (55 73) * “yh &e. The second term is 3asin@ 72? 22? dw 2 (cos* § + i os Gabi ell g iz _ the integral of which is 3 a pas 1? 2 : cos‘ § 5a 1S = Bi zcost8 } 9 j2 3 2 492 Mr. Lubbock on the Heat of Vapours d2 wo £ 222° 272° cos? 4 A a ee ny ee dz? )3.5 3 he 3 +3156 507 13 ies ae 35 ae 4942 2 12 058 f zda So (hae i Ca CS dw waar cost§ +z pcos bi Tr [2] of pde,,, ay sane sa1- = Foi cost + 27-5 costo +95 = rae Tugel?) es d4 ‘ 7 ar Boa rate 2 cos’ 9 — 2 a4 cos?) — 73} In order to take this quantity between the proper limits, it is only necessary to write it first with two accents and then with one ac- cent, and take the difference of the quantities so expressed. Instead, however, of employing the preceding expressions, I shall now introduce the auxiliary quantity e employed by Mr. Ivory. Let = “FP fan 4M 2 ae é€ = tan — cos § 2 Ze tan & = ———___ "1 tee PM irre) Jere! Dippy ,. ex Vocos) +2ia = i \/ er a I assume with Mr. Ivory es a/ (1 — 2 + a 1 Pee a dx ( @aeagtdz V cos?0 + 2ia V2 7 al then ea Bea e227). Suppose dw contains any term of the form 4c¢~°* da, then asindédw —_ == will contain the term W/ cos? § + 2ie i and on Astronomical Refractions. 493 z Silt "Oo od og Gusubtce ed tes aldz, V Qi all which is to be integrated from z=0 to z=1. Thisintegral may be exhibited under two aspects; in the first, which is that given by Mr. Ivory, the coefficients of the different powers of e consist of a finite number of terms, In other forms of the integral, which will be given here, applicable to all atmospheres of finite altitude, the coefficients are composed of an infinite number of terms, conver- ging with rapidity and in a form suited for numerical computation. nee ? wll? 2 — ba! —— — &c. c 1 8 tage &c and the single term A c’* dx in dw will give in a (1 siné d } poe be greenies ” the term WV cos* 0+ 2iv 2Aa(1+a)siné 2 /2 3 fl3 ei oY {sae a getée beds ae 5 2 gIl4 93 $5(1 2) {a2 — 6282 $F ae hy z*+ &e. Lede 2 ll o4 «3 6 +8 (1a)? { 2/82 bat gs 4. o . ee a x 2 + &e. } edz oa eae +80 ee ee eS ee 0 (7 ++ 1) (7 + 2) ecoeee (m+ ” +1) Hence it will be seen that if d w contains any number of terms of the form Ac °" d x, the definite integral required 2 (1+) asin é at a3 (dw? x4 eee uw WV dia" it +55 -(32) +3 3 (45) + y.304 Ta) teebe g’/2 g!/3 4/44 2.3 iz) + 3.4 r=) teas Ta) tape (1] a!/4 d3 w as ae, a) (3) + 4.5.6 Ta) +5 5.6.7 ia) tae be +s. | Another expression for ?4 may be obtained in the following manner. Suppose dw contains any term A (a! —2)"da= A, X"dx 494 Mr. Lubbock on the Heat of Vapours a" — @ = au, (1 — 2) (1 + e2) An (a —2)'de 24, al™ Ty 4 62) 2 Aco? 6+ 2ix . 2 ix” ‘(—2)" mn m(m—1)(m—2)......1 : OE ets RY eee ee (n + m +1) m and m being whole numbers. Hence 2a(1+.«) sin9 > en rey 4 Aig ws + {Oo — a cine as Va 2.1 22% 3. 2 Ay a4 ee 5 4A, xf'6 5 +4 ae iy WL OR ee + &e. be [1] B21 Ayo 4.8.2 Aga! | 543 Age” 6.5.44 0"7 : . 1 4576 eee ae 73.919 + & fe +e} A,, A,, A., &c. are constants, the numerical value of which de- pends upon the constitution of the atmosphere. the first term is necessarily equal to unity, because when X = 0 w= 1, whenw=0, X = X' = 2", therefore generally A, 2! Ay e Sa he 2 + ae. 1. A, x" + Let w, be written for brevity instead of (52); d? w Oy ET A EE de, Gt Se Oa rr dP Ws ° ne ae a er i hea Mae 3) os d w da*\'.. then the quantities (5): (55) might be deduced from a, wes &c., in the mi manner, without having recourse to the series a d.(fa)? , a a. (fa)? onfets, tes ae + & and on Astronomical Refractions. — 495 Since ae dz) ad oy ea ia es du ‘ims die. i} dw _dw de du dxadw therefore dw _ W} dx mt 1] — cece similarly d2 w Wo ae 3 d ‘ ¢ -+%) 4 a 9° d3 w BY Ws 3— (W9)* daz a at a 5 C$)" OF) v7 — i (ota) a: ca .. dw da The quantities Tx? dx: &c., might also be deduced from iv aU” &c., by similar expressions, only changing the signs of those terms which are multiplied by uneven powers of = I have not, however, found it convenient to have recourse to this method of obtaining the development of » in terms of X. I have employed the series a d(FX)? Class AB ND, Qe oe eer: 4 LE ARTs DS and I have found = (F X)? by actual multiplication (FX°) 79, me Q,. 3 2 by multiplying — (FX?) by =: (F X), &c. This process, though somewhat tedious, is extremely easy. As it may be carried on sy- stematically, and the numbers follow each other, it is not liable to error. So far all is general; it now remains to make some supposition with regard to the function fz, upon which the constitution of the atmosphere depends. If we take, as in vol. xvi., p. 440, see also pres. vol. p. 279. 1 I w= 1— Hix" — 1+ afr 496 Mr. Lubbock on the Heat of Vapours w=u!—U. See p. 490. . - fi —— pee 7 = wo=1— Hi-vc" Cie ‘ ns Mt c “ = 1—4H, therefore Y 1— A)y-! a re ee eee Hy-! If we take, as in p. 274, y = 1'5, —4u 2 l—w= = 2 hae Dias ub = ae (l—Hq) H Hf fe=1— Sa dort 1 +H} p=p' (i-q)° _. AY? page i ow 3 cl ) fev 9e0 4 e¥l, H? a k(l+aé) == {- a) Pp 1 — agHB - See p.- 280, Jee i 6 poo rail a dnd = — HH, See vol. xvi, p. 440. vay l1—Hpy In page 470 I found H='54378 (from the observations of M. Gay Lussac) corresponding to the temperature 87°°35 of Fahren- heit, and to 30°145 inches of mercury in the barometer. As the uncertainty with respect to the values of y and # appertaining to the mean state of the atmosphere makes it useless to have recourse to reater refinement, I shall now suppose that this value of H will be sufficiently exact for the temperature 50° of Fahrenheit and for 30 inches of mercury in the barometer at the earth’s surface; the sequel will show that this hypothesis is admissible, and the calculation of 2 will stand thus: when y = 1°5 i log yg = 42633892 log B = 9°5228787 log M = 9°6377843 log H = 9°7354232 log (1+ #4!) = 0:0159881 a = 6°8041168 | 3°9171116 60624187 | 6:0624187 | _ log 7 = 78546929 i= ‘0071564 = °78478, ql! Nap, log —F and on Astronomical Refractions. 497 The following table shows the constitution of the atmosphere with this system rof constants. It should be recollected that in cal- culating this table, as well as those in p. 278 and p. 280, the law of Mariotte and Gay Lussac, p=ke(l + a6), is implicitly supposed to hold good at very low temperatures, which is -to a certain extent conjectural. For this reason, and for the reason that we have not at present sufficient data for determining with great precision the constants y and H, it is not intended to attach precision to the temperatures, densities and pressures given in the following table for the altitudes beyond 5 miles. The fol- lowing example will serve to show how the table was calculated : Calculation of the Pressure, Temperature, and Density for the height of 10 miles. log 10 = 1:0000000 — 78546929 log a = 3°5974758 in miles log M ie 6377843 74025242 82169086 002526 Ih 74025249 log 1:002526 = 0-0011364 152995 : eee 9°8470750 = log (1 — Hq) 74013878 703194 82169086 296806 = Hg 9°1844799 ; log ma = 9°4725517 log H = 9°7354232 9:7371285 54592 = 45408 =1—gy log (1—g) =9°6571324 9°6571324 1:2201080 9 3 log p = 0°4485185 93142648 89713972 16686265 98470750 1:4771213 log ¢ = 9'1613398 91613398 0°4485185 95072867 e= 14499 p=281 321°6 448:0 pe Te MOOR Se + = [1*2201080] : 448 ORE ey Phil. Mag. 8. 3. Vol. 17. Supplement, No. 113. Jan. 1841. 2K 498 Mr. Lubbock on the Heat of Vapours Table showing the constitution of the Atmosphere. Height | Pressure | Temp. Density in miles. Dp. Te @- Inch. Fahr, 0 30:00 | +50:0 | 1:00000 1 24°61 35:0 *84611 2 20:07 19:5 71294 3 16-25 | + 3:4 | -59798 4 13:06 | —13°3 49903 5 10°41 30°6 41403 10 2°31 126°4 14499 15 45 240°6 03573 BOGE A) diss —448°0 | oe According to this system of constants, the ascent for depressing Fahrenheit’s thermometer 1° is about 352 feet. If log « (in sex. sec.) = 1°7669538 a* = 00028348 (1 — if vg! = yl — = = °74514 log {aa ) t = 9'5066765. _ as F yaa 4 su angela 7h. See p. 473. — [95066765] U2 + [98077064] U3 + [9-8254352] U4 ++ [9°6827677] U® + [9:4289405] U6 + [9:0902531} U7 + [86829116] U8 + [82178251] U9 + [7:7028036] U9 +. (7°1436673] U1 + [65450488] U2 + [5-9104758] U3 + [52429802] U4 + [4-5449962] U™ + [38186763] U6 + &e. F Xis found by changing U into X in the above series. Although the development of » might be obtained by procuring the quan- dite oo eo eae ad © d XP ote cook age given in p. 492. I have preferred employing the series a d(FX)? a d?(k XP 27d M4. Bade dae decd XxX ied (Ay ad? (Fh Ae Guin X "9 82 d Xt eee 7 ee By involution from the expression for F X the following were ob- tained : & (FX)? =[7:3105250] x4 + [79125849] X> + [8-2225672] x6 + [8°3653575 | X7 + [8:3901249] X8 + [83259417] x9 through the expressions Giga it hye + &c. * T have adjusted the value of « so that the mean refraction at 45° might exactly agree with that of M. Bessel. and on Astronomical Refractions. 499 + [81894155] X! + [7:9925434] X"4 [7-7440827] xX! + [74492548] X18 + [7-1140008] X44 [6-7436508] X™ + [6°3433889] X16 + [5-9048724] X"7 + &e. 5 _ 3 (F X8) = [4-9382822] x6 + [5-7162512] x7 + [61990788] x° + [65124208] X° + [6-7058125] X+ [6-8073789] xX" + [68341245] X? + [6-7797954] X34 [67124763] X'4 + [6-5779048] X™ + [63758464] X16 + [6-1424833] X17 + [5-9091202]X8+4+&e. S2G X4) =[2-4411007] X8 + [3-3458338] X® + [3-9500667] x1 + [4-3853642] X" + [4-6996664] X24 [4-9204991] x13 + [5-0668412] X4-+4 [5-1470479] X® + [5-1817987] X16 + [5°1502344] X17 + [5-0587813] X'S [4-9792296] XY + &e. X®) =[9-8470092] X04 [01480392] X"+ [1-5496223] x” + [2-0850470] X134 [2-4878504] X14 + [2-8026972] Xx" + [3-0171128] X16 + [3-1689304] X17 + [3-2999429] X18 + [33830969] X19 + [3-4680509] X20 + &c, at 5.3.4.50(F The coefficients of the different powers of X in these series be- come very small, but they acquire large multipliers from the suc- cessive differentiations which are required to give the corresponding terms in the expression for . I find with this constitution of the atmosphere, A, being the : : d coefficient of X” in the expression for ——. da A, = 6422 A = 19268 + +0245 = 1:9513 A, = 2:6761+ +1635 -+ -0010 = 2°8406 A, = 24085 + -5008+ -0109 + -0001 — 2°9208 4,=1°6110+ -9741+ -0531 + -0007 = 2°6389 4,= ‘8617+ 13750+ -:1640 + -0045 = 2-4052 4,= °8854-+4 1552504 -3657 + :0192 +. -0003 = 22956 4, = ‘1486+ 139204 -6853 + -0595 + -0019 = 2°2373 A,= °0504 + 1:0812 + -9009 + -1428 + -0074...... = 2°1827 Ay= ‘0153 + +7322 + 1:0335 + -2802 + -0229 + -0007...... = 1:0848 4,,= *0042-+ 4389 + 1:1265 + -4596 + -0561 + :0029.,....= 2°6882 Ay.= ‘0010+ -2366 + 1:03829 + 6852 + 1094 + -0090...... = 2:0741 4;,= ‘0002+ -11638+ -8410+ ‘8072 + -2051 + -0226...... = 1:9924 2 SoS + 0529+ -5644 + °8410 + °3371 + -0492...... = 18466. dw ira 6422 X +. 1:9513 X? + 28406 X3 + 2-9203 x4 + 2°6389 X°4 2-4052 X° 4+ &c. Hence by substituting these values of 4,, A,, &c., in the ex- pression for 8 6 given in p. 491, I find the first term in the refraction 2K.2 36= —[1-3861838 | sind] 500 Mr. Lubbock on the Heat of Vapours = sin 0 {1132"8e + 639-9 & + 220!4 €§ 1] + 605 eT + 178 2 + 55 el + &e.} At the horizon e = 1, and this portion of the horizontal refraction = 2076!-9. The second term in the refraction is 8 sin daz? a2?da 2 aes (cos*@ + 222)? =. , dl a 3.4Viasin 6 x22? {1 —@2& + ez}? edz Q2V9g" {1 — 2% + 2x}? io 34M Ga sind a? edea 1. fan a a ae da + {522-22} e4 — Se. | Suppose dw contains any term A, (a! — a)" da a! — ge = a! (1 — 2) (1 + 2) 3.4V easing al? 3 ; ee ae == A,(1—2)"(1+ es)" edz 1—2zet4+ {522 —2z} e+ — xe. | Neglecting the higher powers of ¢ 3. es 2.1A,a4 9.1 Agall ane ARAN of 2.3.4 3.4.5 4.5.6 a se. b [2] With the same constants as before, y = 1:5, H = *54378 2.1 Aa! 2.1 A,al4 9.1 Agald 2.3.4 3.4.5 4.5.6 oI xe. | [2] == — ]''5 sin 6 €. This term thus amounts to only 1-5 at the horizon; according to Mr. Ivory it does not amount to more than 1". Hence, finally, the refraction is expressed by the following series :— Ref. = sin @ {1132"-8 e + 638""4 ¢3 + 220!"4 e® + 605 e' ++ 17'"8 e + 5!"5 ell + &e,} and on Astronomical Refractions. 501 = sin@ [30541728] e + [2°8051475] é + [2°3443834] e® + [1:7821564] e’ + [1:2501754] e9 + [0°7409070] e!! + &c.} __ [9°0139814] ish a Bee ag 6 RAD aps: Mr. Russell has calculated a table of refractions from the above formula; and the following comparative view has been drawn up, with Bessel’s table in the Tabule Regiomontane (which may be considered as the result of observations), with the table published annually in the Conn. des Temps, and with Mr. Ivory’s table, re- cently published in the Phil. Trans. 1838, p. 224. Tables of Mean Refractions. Bar. 30 inch. Therm., Fahr., 50°. Mean Refractions. | eo Calculated. Observed. eae Dist... |—HHAAANANV— __ _] —————_| Dist Conn.des Temps. Ivory. New Table*. Tab. Reg. fo) 4/ “4 4/ 4/ oO 10 10°30 10°30 10:30 10°30 10 20 21-26 21-26 21:26 21-26 20 30 33°72 33°72 vo's2 33°72 30 40 48-99 48:99 48-99 48°99 40 45 ° 58°36 58°36 58°36 58°36 45 50 69°52 69°52 69°51 69°52 50 55 83°25 83°25 83:24 83°24 | 55 60 100-86 100-85 100-85 100-85 60 65 124-65 124-65 124:63 124-62 65 70 159-22 159-16 159-16 159-11 70 qo 214-83 214-70 214:68 214:58 795 80 320-63 320°19 320-08 519-88 80 sl 394°33 353°79 353°64 393°38 $1 82 395°37 394:68 394-47 394-20 $2 83 445°87 445-42 445°11 444°86 $3 84 511-22 509°86 509-34 509-238 84 83 59580 593-96 593-13 593°38 85 855 648°34 646-21 645°15 647-10 853 86 710-07 707-43 706°04 707-15 86 865 783°07 779-92 77808 777°36 863 87 $70°37 866-76 864°30 86459 87 87% 975°89 971-93 968°84 972-21 873 88 1105-1 1101°35 1097°26 1101-40 85 885 1265-0 1262-6 1257°66 1265°5 8834 89 1464°9 1466°8 1461°49 1481°8 89 893 1716-4 1729-5 1725°70 1764:°9 893 90 2072-6 2075°4 90 * The constitution of the atmosphere is shown by the table in p. 498. = £ SS = Se ge en ne a 502 Mr. Lubbock on the Heat of Vapours The following table shows the errors of the table of the Conn. des Temps, of Mr. Ivory’s table, and of my table, assuming Bessel’s to be correct. : Error of Table | Error of : z Error of Table Error of Zenith of Error of || Zenith ra Error of : Mr. Ivory’s : o Mr. Ivory’s Dist. lconn.desTemps.| Table. |New Table.) Dist. loon desTemps.| Table. |New Table. — eee 4M Vd if {o) e e 70 preg" 4°05 | 4+ “05.|| 86.) + 312) |e) Soa 75 4 25 4+-12 | +4 -10 || sez} + 571 | 4+ 9256/4 +72 80 4-75 +31 | 4+ 20] 87 | + 578 | + a17/— +29 81 4. 95 +-41 | 4 -26]) 872| + 368 | — -28|— 3:37 82 aw ALAz 448 | 97") 88} 43-70 i 83 41-01 +56 |4 -25 || ssz| — 050 | — 2-90|— 7-80 84 4+ 1-99 4-63 | + 11 |) 89 | —1690 | — 15-00 | —20:30 85 4.249 458 | — -25 || 893] —4850 | — 35-40 | 39-20 85 | + 1-24 — 39 | — 1-95 I think that the discrepancies about 853, 86, 863, are caused by irrecularities in the refractions of the Zab. Reg. Groombridge, who made many observations for the purpose of determining the amount of the refraction near the horizon, makes the horizontal re- fraction, for barometer 30 inch, and therm. Fahr. 50°, 2075!-4.* There is, however, some uncertainty respecting this quantity, and generally respecting the amount of refractions near the horizon. Upon this point see Delambre, Ast., vol. i. p. 319. Mr. Ivory says “ There is great probability that the horizontal refraction is very near 2070", and does not exceed that quantity.” But for the irregularity in Bessel’s table, which is clearly seen in the diagram inserted in the annexed plate, my table of mean re- fractions would be identical with the table of that distinguished astronomer to within 3 degrees of the horizon. It may therefore be safely concluded that the refractions, which belong to the atmo- sphere, constituted as I have supposed, in conformity with my theory of the heat of steam and other vapours, are consistent with observation. The quantities denoted by w, (eg), s in the Mécanique Céleste correspond to the quantities, zw, g!, and =o f this treatise. ‘The equation er E “ a | =u, Méc. Cél., vol. iv. p. 262, corresponds to the equation uw = a of p. 498. * This curious coincidence, with my value of the horizontal refraction, is of course partly accidental. and on Astronomical Refractions. 503 Laplace assumes the relation between w and a. e=(e) [1+St]e ” or in the notation of this treatise _t2 ~ a= — Lac J and /' being arbitrary quantities, such that SF = *49042 l! = -000741816. A table, similar to that which I have given in p. 498, showing the constitution of the atmosphere, which Laplace has assumed, would be instructive, and would enable us to judge of the admissibility of the conditions attributed to the higher regions of the atmosphere by that ‘great philosopher. In this treatise I have obtained an expression* for the altitude in terms of the pressure, founded upon the conditions of elastic va- pours generally ; this gives the relation between wz and (see p. 471) from which a relation between 2x and w must afterwards be sought. When on the contrary the relation between w and x is assumed (as was done by Laplace) an advantage may be gained in the cal- culation of the refraction, at the expense, however, of a simple and intelligible definition of the constitution of the atmosphere; and such a relation is of course also unconnected with any considera- tions founded upon the nature of caloric. Mr. Ivory assumes the relation 28 AOU api cae i ade POG Pies p' denoting the pressure, and 9! the density of the atmosphere at the earth’s surface. From this relation it follows that (see p. 473) eT ee ai ihe a8) ( =) ei vee fe ee ee k, a, 6! are L, 8, 7’, in Mr. Ivory’s notation. aiu= * ~_ = —ailog(1— Hq). 1+ — a 504 Mr. Lubbock on the Heat of Vapours When w is a simple function of w, this value of « may be sub- stituted in the equation r=u— a (p. 489) and the value of » in terms of w may be found at once by the re- version of the series. kil + a9") as w= —log (1 — a) +flog(l—a) + 4 2f-> fe — log (1 — w) + f log (1 — ) ray This equation corresponds to the equation of Mr. Ivory d c—u Hy A d? c—u R, c~udu © crude pe 20%, when f= 0. Oh, = Tw See w=1—c-4, Mr. Ivory makes = 7, so that. ey A eee — &c. The table of mean refractions given by Mr. Ivory is founded upon the supposition that f', f", &c. = 0. bat fs & iA ese ae alge ¢ (1 —») ag + {ot 2a f- aha Ta ent do and let 2!’ = ————__~*—_ +" =(]—f) 2 ag h ct ———— =) = 2f— hs ae ae, ; h=2f—r a! = —log (l—a)+2'a z and / are identical with the quantities represented by those i ters by Mr. Ivory, if a = 0002835, i= "0012958, h = '22566, f= = then 7 = ‘0010078, h'= +29012. By Lagrange’s theorem I find * Mr.Ivory has the equivalent equation = = <. +aw=irtaw, p. 203, Mr. Ivory’s o is aéiw in the notation of this treatise, and on Astronomical Refractions. 505 12 2 h’ one oT On ene 3h Sh’ —Sx’ w=1l—e + hic = 7 5 ee rel hl? ah? 4a! — & 1 f 2 , ° XC. dw h’ .—a Qh’ .—24 3° hl Sh! .—S x2’ see ¢ °° — 2h” 6 ** + rama Ted d a! bape af - “ae NM i Bete The first part of the refraction is given by the expression OO Oe ial a (1 + a) siné echoes 0 “cos?6 +27 a! nis elge haa Let 2 n cos? 6 Q2dz OE Se ee paces dv= 27! 2 hs AP , (e) Cc ma d x! 9¢ (eS) Fa SS BS OTe — Z2 Voos64+ 27a! Val Vn ¢. de At the horizon cosé.= 0,. 2' =0 how) ewdat 9 OS aha ait Vaid ~ Vai Vn titer es 0 This part of the horizontal refraction a(l+a)Vn aie Qh c?™ 32 pia B® aes ae a? me ne rd na a(l+a) We 1 oh on Spank i | 3 h? 22 Bote. 3? hh? OY Jee ae or a 7a es Va 512 £238 4 Spt oy St a4.6 4, gf 2. 4 i ie = 2 P23 a 3 et See 23 13 “vin. Ps RRS i ae Ghee 77 33 43 506 Mr. Lubbock on the Heat of Vapours V8. See uh Bae 5.7 oid ogy CIE Gee +oag.8 t3 2.6% +Tena’! 130 ee 2 3 _ 2.8.5.7, p_ 2:527 as gs 2.7 V7 22.4.6 W224 V721.2.2 24 hi 32.5.7 33.7 34 1A V¥21.2.38 1-2V73.29.4 It voV752 "7 * T8275 1.2 43 7 bine” 43 = he f — Sy Bee a SS LaaVie 2 1.2 :3-4V7a 2 oe h3 f h4 +- &e. a 1 $a (VI-1)— (2 vz —3) 2 when the higher powers of f and / are rejected, and this expres- sion agrees with that given by Mr. Ivory, Phil. Trans., 1838, p. 207. be obs a ey ibe + i {4 _ ova tovah—Sasvz—y == ae In atmospheres which extend to an infinite distance m (or 2” in the notation of this treatise) is infinite and e always = 1, so that in this case the method employed by Mr. Ivory in p. 211 of his me- moir, Phil. Trans., 1838, would seem at least to require further elucidation.. Mr. Ivory has avoided this consideration, which would otherwise arise with the atmosphere which he has assumed, by imposing an arbitrary limit to the altitude of his atmosphere, while, however, if I am not mistaken, upon his own assumption, the density and the pressure are still finite. When z is large the numerators of the separate quantities of which the quantity 4, 41 in p. 211 is composed become large also. Ido not find in Mr. Ivory’s paper any remarks tending to prove that the quantities which he has discarded depending upon the higher powers of f and # are incapable of producing any sensible effect ; taken separately they are by no means insignificant. Nor do I think it follows as a matter of course, even if the positive and negative terms are numerically of equal value at the horizon, and so fortunately cut one another out, that the same thing will happen necessarily at ail other altitudes. Unless the approximation is pushed so far as to secure the retention of all the sensible terms, or those which fairly come within the limits of the errors of observa- tion, any comparison of the result with the valuable table of M. Bessel is illusory and only calculated to lead to incorrect conclu- - = and on Astronomical Refractions. 507 sions. It is also indispensable that the relation implied or ex- pressed between z and » should be in exact conformity with the conditions attributed to the atmosphere, and in this respect the table of mean refractions of the late Mr. Atkinson in the Memoirs of the Astronomical Society appears to me not to rest upon a solid foundation. Mr. Ivory cennects the pressure and the density by the relation | aS 3 Qe a 7777 4. +29999 ee M. Biot finds Q i -761909002718 7 + +238167190564 ©, 8 — ‘000076193282, when the coefficients are so taken as to apply as nearly as the ques- tion will admit of throughout the whole extent of the atmosphere. But, by a careful examination of the data, M. Biot finds that at the earth’s surface the following relation is more accurate. 2 3 = 956643870584 £. + *120146052460 a @ — 076789923044 a. 69.) and at the upper limit of the atmosphere 2 = = *6604978157646 a + *4159581823536 Ac — ‘00006605394115. According to my view this equation does not contain the true mathematical law which connects the density and pressure, but of course a parabola of this kind may always be found which will osculate the true curve at any given point. . In the Comptes Rendus des Séances de ? Académie des Sciences, tom. viii. p.95, M. Biot verified and adopted a calculation of Lambert, who found from the phenomena of twilight the altitude of the at- mosphere (hauteur des derniéres particules d’air réfléchissantes) to be 29,115 metres. It is unnecessary to dwell any further at present upon this sub- ject, because if my theory of the Heat of Vapours be correct, the calculation of Astronomical Refractions, founded upon conditions which are not in conformity with that theory, becomes a problem of mere curiosity. Pss0e 9 LXXV. Proceedings of Learned Societies. GEOLOGICAL SOCIETY. Anniversary Address of the Rev. Prof. Buckland, President, Feb. 21, 1840. [Continued from p. 396, and concluded.] POSITIVE GEOLOGY.—DEVONIAN SYSTEM. iB the Home Department of Positive Geology, the most striking circumstance has been an aunouncement by Professor Sedgwick and Mr. Murchison of the conclusion to which they were led by Mr. Lonsdale’s suggestion in December 1837, founded on the inter- mediate character of the fossils in the Plymouth and Torbay lime- stone—that the greater part of the slate rocks of the south of Devon and of Cornwall belong to the old red sandstone formation. _ The order of the observations which have led to this important result, is nearly as follows :— In a paper read at Cambridge, during the winter of 1836-37, Professor Sedgwick considered the fossiliferous slates on both sides of Cornwall to be of the same formation, and coeval, or nearly so, with the calcareous rocks that lie between the slates of South Devon. In 1836 and 1837 also*, Messrs. Sedgwick and Murchison pro- posed to transfer the culmiferous or anthracitic shale and grits (Shil- lot and Dunstone) of North Devon to the carboniferous system ; withdrawing them from the grauwacke in which they had before been included, and thus assigning a much more recent date than heretofore to the strata which occupy nearly one third part of the map of Devonshire. But the relations of the slates and limestones of South Devon still remained to be determined; the mineral characters of the former being different from those of the old red sandstone beneath the car- boniferous group, in many parts of South Wales and in Hereford- shire, while the true position of the limestones (e. g. those of Ply- mouth, Torbay, and Newton Bushell,) was doubtful. At this period (1837), the fossils of this district were examined by Mr. Lonsdale and Mr. Sowerby, to whom the organic remains, both of the car- boniferous and Silurian systems, were familiar. It was soon per- ceived, that while some of the South Devonshire fossils approached to those of the carboniferous strata, and others to those of Siluria, there were still many species which could not be assigned to either system ; the whole, taken together, exhibiting a peculiar and inter- mediate paleontological character. Mr. Lonsdale therefore sug- gested, that the difficulties which had perplexed this inquiry could be removed by regarding the limestones of South Devon as subor- dinate to slaty rocks, which represent the old red sandstones of Here- * In August 1836, at the Meeting of the British Association at Bristol; and in a paper read before the Geological Society, May and June, 1837. now published in the Geological Transactions, Second Series, vol. v., Part 3, Geological Society :—Anniversary Address. 509 ford, Wales, Scotland, and Ireland,—their true place in the series of Devonshire being intermediate between the culmiferous basin of North Devon, and the Silurian strata,—if the latter exist in that county. The value of this suggestion was not at first appreciated; but after the lapse of more than a year, Mr. Lonsdale’s views were adopted (March 1839) by Messrs. Sedgwick and Murchison*, who soon afterwards applied this new arrangement not only to the groups of Devonshire originally under review, but with a boldness which does credit to their sagacity, extended it to the whole of the slaty and calciferous strata of Cornwall, till then known only as grau- -wacke, clay-slate, or killas; assigning to those strata, likewise, the date of the old red sandstone, and resting this determination entirely on the character of the fossils. This change—the greatest ever made at one time in the classification of our English formations— was announced in a memoir read before the Geological Society in April 1839+; the authors then also proposing for the whole series (including both the old red sandstones of Herefordshire, and the fossiliferous slates and limestones of South Devon and Cornwall, ) the new name of “the Devonian system,” and expressing their belief, that many of the groups hitherto called grauwacke, in other parts of the British Islands and on the continent, would ere long be re- ferred to the same geological epoch. The proposed alteration, therefore, will terminate the perplexity hitherto arising from the circumstance, that the old red sandstone of Werner has been frequently confounded with the new red sandstone formation of English geologists. It also explains the cause of the English old red sandstone having been rarely recognised on the continent :—for if the Devonian slates afford the normal type of this formation, whilst the marly sandstones and conglomerates of Herefordshire are abnormal exceptions in it, we see the reason why their slaty continental equivalents, like the greater part of the South Devon slates, have been referred to the undivided Wernerian forma- tion of grauwacke. * Itis to be observed here, that Mr. Murchison, having previously shown that the fossils of the Silurian era are distinct from those of the carboni- ferous period, had also pointed out ‘‘ the vast accumulations” (in which few fossils had at that time been discovered) ‘‘ then known to separate the two systems.’ He mentions especially, that “the fishes of the old red sandstone—entirely distinct as to form and species—are as unlike those of the Silurian system, as they are to those of the overlying carboniferous system :” adding, “that he has no doubt, although at present unprovided with geological links to connect the whole series, that such proofs will be hereafter discovered, and that we shall then see in them as perfect evi- dence of a transition between the old red sandstone and carboniferous rocks, as we now trace from the Cambrian, through the Silurian, into the old red system.”—See Silurian System, p. 585, line 22, et seq. + [Abstracts of this and all the other papers referred to in this Address as having been read before the Geological Society during the year preceding its delivery, will be found in L, & &, Phil. Mag. vol. xiv. xv. xvi, and in the present yolume,—Epir. ] 510 Geological Society :—Anniversary Address. Mr. Austen, in a communication relating to the structure of the south of Devon, has identified the calcareous slate and limestone of the south of Cornwall with the limestones of this district, and con- siders that of Torbay among the newest deposits in the latter series. The Rev. D. Williams also has communicated two papers re- specting these disputed rocks, which he refers to the transition or grauwacke system, and endeavours to show that the strata of De- vonshire can be disting waned into certain groups by their litholo- gical characters. Mr. De la Beche in his map of Devon and Cornwall, published in 1839, has adopted divisions of the strata, similar to those of Pro- fessor Sedgwick and Mr. Murchison, as to their order of sequence ; applying, provisionally, to the culmiferous rocks the name of Car- bonaceous series, and to the Devonian and Cornish slates the appel- lation of G'reywacke. We know also on the authority of Mr. De la Beche that tin mines are worked in carbonaceous rocks at Owlescomb near Ashburton, on the east side of the Dartmoor granite, and on its west side at Wheal Jewel near Tavistock. He further informs us that one of the richest tin mines now worked in Cornwall, namely the Charles- town mine, east of St. Austle, is in a fossiliferous rock containing Encrinites and corals, and that the same corals occur also near tin mines at St. Just; and in the neighbourhood of Liskeard the Rey. D. Williams has found slates which contain vegetable impressions, dipping under other slates which are intersected by lodes of tin and copper. From these new facts, we learn that the killas and other slate rocks of Cornwall and the south of Devon do not possess the high antiquity which has till lately been imputed to them; and that tin occurs, as copper, lead and silver have long been known to do, not only in slate rocks that contain organic remains, but even in the coal formation. Soon after the publication of the views of Messrs. Sedgwick and Murchison, a similar change was applied by Mr. Griffith to the south-west portion of his geological map of Ireland. In a paper that accompanied the presentation of this map to us on 22nd of May last, he states that he has now coloured, as old red sandstone and carboniferous limestone, extensive districts of the counties of Kerry, Cork, and Waterford, previously considered of higher anti- quity ; imputing his former erroneous opinion to the identity in lithological character of the shales amd grits of the old red sand- stone and carboniferous systems, with the older rocks in the transi- tion series. Mr. Griffith has also demonstrated by sections the unconform- able position of the carboniferous and old red sandstone formations, which overlie older and more highly inclined slates in the counties of Kerry, Cork, Waterford, and Wexford. Mr. Charles William Hamilton has likewise adopted similar changes; and believes that the slates which occupy a large space between the Mourne Mountains and Dublin are equivalent to those near Cork, which he now transfers to the old red sandstone, Devonian System. | 511 Mr. Greenough, in the new edition of his map of England, repre- sents nearly the same boundaries and order of succession in Devon and Cornwall as we find in the maps of Mr. Dela Beche and Messrs. Sedgwick and Murchison ; but in his memoir connected with the map, adopting the name of Carbonaceous series for the culmife- rous rocks, he substitutes that of Upper killas for the Devonian system of Sedgwick and Murchison, (including under that term the old red sandstone of Herefordshire,) and Lower killas for the slates inferior to the Silurian system, which they have termed Cam- brian. Mr. Greenough, in his memoir, also shows by quotations from Dr. MacCulloch, that the undisputed old red sandstone of the north of Scotland exhibits, at intervals, the same great changes of mineral character, that occur in the strata intermediate between the Carbo- naceous and Silurian systems in the west of England and on the borders of Wales; and justly infers the inadequacy of any one term to characterize formations which vary so much in lithological com- position, that at one place they present the condition of a fine- grained silky slate, at another of sandstone, and at a third that of coarse gravel and conglomerate rock. Thus, with respect to the slate rocks of Devon, Cornwall and Wales, the difficulties are reduced to those of an unsettled nomen- clature ; whilst nearly all parties are in unison as to the fundamental fact of referring the slates of South Devon and Cornwall to the epoch of the old red sandstone formation. The term grauwacke, however, I rejoice to think, will not be condemned to the extirpation which has been threatened from the nomenclature of geology; it may still retain its place as a generic appellative, comprehending the entire transition series of the school of Freyberg, and divisible into three great subordinate formations:—the Devonian system of Sedgwick and Murchison being equivalent to the upper grauwacke, the Si- lurian to the middle grauwacke, and the Cambrian system to the lower. In this threefold distribution of the vast series of strata which have hitherto been indiscriminately designated by the common term grauwacke, we are, as it were, extending the progressive operations of a general inclosure act over the great common field of geology ; we propose a division, founded on measurements, surveys, and the study of organic remains, analogous to that of the secondary strata, from the chalk downwards to the coal formation, established by William Smith, and to the separations of the once undivided ter- ritory of the great tertiary system, effected by Cuvier and Brongniart, Desnoyers, Lyell, and Deshayes. To the uninitiated in geology, rectifications in the distribution of strata upon so large a scale may seem calculated to shake confi- dence in all the conclusions of our science ; but a contrary inference will be drawn by those who know that these corrections have never been applied to conclusions established on the sure foundation of organic remains, but to those rocks only of which the arrangement had been founded on the uncertain character of mineral compo- sition. 512 Geological Society :—Anniversary Address. COAL FORMATION. The Society has received from Professor Ansted a paper on the Carboniferous and Transition Rocks of Bohemia, a country which he visited last summer, directing especial attention to the district between Prague, Luditz and Pilsen, which he has illustrated by sec- tions made from personal observation. Above the fundamental granite and gneiss he found extensive deposits of grauwacke, on which lie, in unconformable superposition, disconnected patches of the coal formation. The age of this coal is well known, from the fossil Flora of Count Sternberg, who resided in the midst of it near Swina, to be identical with that of the great Coal formation of En- gland. Mr. Ansted gives information also as to the action of trap rocks in producing disturbances of the strata in this district ; and re- specting dislocations, by which the grauwacke is several times placed on a level with the coal measures, whilst in some cases the strata are inverted and the coal measures laid beneath the grauwacke. We have received an interesting communication from Mr. Hawk- shaw respecting a remarkable disclosure made in the Bolton Railway, six miles north of Manchester, of five fossil trees in a position vertical to the plane of the strata in which they stand. The roots are im- bedded in a soft argillaceous shale immediately under a thin bed of coal. Near the base of one tree, and beneath the coal, more than a bushel of hard clay nodules was found, each inclosing a cone of Lepidostrobus variabilis. The bark of the trees was converted to coal, from one quarter to three quarters of an inch thick; the sub- stance which has replaced the interior of the trees is shale; the cir- cumference of the largest of them is 154 feet at the base, 74 at the top, and its height 11 feet. One tree has spreading roots, four feet in circumference, solid and strong. By the care of Mr. Hawkshaw these trees have been preserved, and a covering is erected over them. The attendant phenomena seem to show that they grew - upon the strata that lie immediately beneath their roots*. Mr. Barber Beaumont, in a communication respecting these same trees, considers that no drifted plants occur in coal fields, and that all the vegetables which are now converted into coal, grew upon swampy islands covered with luxuriant vegetation, which accu- mulated in the manner of peat bogs; that these islands, having sunk beneath the sea, were there covered with sand, clay and shells, till they again became dry land, and that this operation was repeated in the formation of each bed of coal. In denying altogether the pre- sence of drifted plants, the opinion of the author seems erroneous ; universal negative propositions are in all cases dangerous, and more especially so in geology: that some of the trees which are found erect in the coal formation have not been drifted, is, I think, esta- blished on sufficient evidence; but there is equal evidence to show that other trees, and leaves innumerable which pervade the strata that alternate with the coal, have been removed by water to con [* See the abstract of this paper in L. & E. Phil. Mag. vol. xv. p. 539, and also that of a further communication from Mr. Hawkshaw, in the present number.—Ebir. | Secondary Series. 513 siderable distances from the spots on which they grew. Proofs are daily increasing in favour of both opinions: viz. that some of the ‘vegetables which formed our beds of coal grew on the identical banks of sand and silt and mud, which being now indurated to stone and shale, form the strata that accompany the coal; whilst other portions of these plants have been drifted, to various distances, from the swamps, savannahs, and forests that gave them birth, par- ticularly those that are dispersed through the sandstones, or mixed with fishes in the shale beds. The cases are very few in which I have ever seen fossil trees, or any smaller vegetables erect and petrified in their native place. The Cycadites and stumps of large Coniferous trees on the surface of the oolite in Portland, and the stems of Equisetaceous plants described by Mr. Murchison in the inferior oolite formation near Whitby, and erect plants which I have found in sandy strata of the latter formation near Alencon, are examples of stems and roots over- laid by sediment and subsequently petrified without removal from the spots in which they grew. At Balgray, three miles north of Glasgow, I saw in the year 1824, as there still may be seen, an un- equivocal example of the stumps of several stems of large trees stand- ing close together in their native place in a quarry of sandstone of the coal formation. In a paper on the sinking of the surface over coal mines, Mr. Bud- dle has shown that the depressions produced on the surface by the excavation of beds of coal near Newcastle-on-Tyne are regulated by the depth and thickness of the coal, the nature of the strata above it, and also the partial or total extraction of the beds of coal. The accumulation of water forming ponds in these superficial depressions, and the sinkings of a railway, have afforded accurate measures of the amount of the subsidences in question. WEALDEN AND PORTLAND FORMATIONS. In the north of Germany Mr. Roémer, of Hildesheim, has identified beneath the Cretaceous system, the Purbeck stone and beds of the Wealden formation, with nearly all its characteristic shells, and three minute species of Cypris. He has also found the Portland sand and the upper and lower Green sand and the Gault clay, in the north of Germany. He has, moreover, found the Wealden forma- tion near Bottingen in the High Alps. CHALK FORMATION. In extension of our knowledge of the Chalk formation, the Rev. J. Gunn has sent us a short communication, accompanied by a litho- graph representing the columnar disposition of some Paramoudras to the height of many feet one above another in the chalk of Norfolk. The history of these enormous urn-shaped flints, which were first noticed by Professor Buckland in an early volume of our Transactions, Ist series, vol. iv. p. 413. pl. 24., is still involved in much obscurity. Their form is most probably due to siliceous matter collected around and penetrating throughout the substance of gigantic spongiform bodies ; but we have yet to learn the reason why they are occasion- Phil. Mag, 8.3. Vol. 17. Supplement, No.113. Jan. 1841. 21 514 Geological Society: —Anniversary Address. ally placed in single vertical rows, almost like the joints of a basaltic column, sometimes nearly touching, but not articulating with one another. A paper has been read by Mr. Henry Lawes Long on the occur- rence of numerous subterraneous chasms or swallow-holes in the chalk on the west of Farnham, with observations on the drainage of the i | country near the west extremity of the highly-inclined ridge of chalk, VW called the Hog’s Back, between Guildford to Farnham. The land- i springs immediately on the north of Farnham descend southwards AT in open gulleys over tertiary strata, until they arrive at the narrow hea | band of chalk which passes under Farnham Park, where they are 1) suddenly engulphed in transverse fissures or swallow-holes, through Li which they pass under ground to a considerable distance, and again Hi) break forth on the southern side of the chalk. Seven of these iq swallow-holes occur near Farnham, from some of which the water emerges in sufficient force to turn a mill. They are probably con- nected with subterranean faults and transverse fractures, the origin i of which was coeval with the elevation of the narrow band of chalk, A all which forms the Hog’s Back, and which, near Farnham, is inclined at a high angle to the north. The water that now passes through 1 the Farnham swallow-holes may tend to enlarge the chasms through i which it takes its subterraneous course, by dissolving slowly the 11a chalk of their sides in the small quantities of carbonic acid which | rain-water usually contains. Similar transverse fractures, on a greater scale, have given origin Hi to the chasms, which, being enlarged by denudation into transverse i valleys, afford outlets through the high escarpment of the chalk to the rivers that, rising within the Weald, flow through the escarpment i of the north Downs into the valley of the Thames, and through the i escarpment of the south Downs into the sea, viz. to the Wey, the I Mole, the Darent, the Medway, and the Stour, through chasms in ii the north Downs; and to the Arun, the Aduz, the Ouse, and the Cuckmere, through chasms in the south Downs. Dr. Mitchell has ‘communicated a paper on Artesian and other wells, in the gravel and London clay in Essex, showing that water occurs under the London clay at various depths; the deepest at Foulness Island, being 460 feet. He attributes this inequality in i part to uneveness in the surface of the subjacent chalk. On it reaching the chalk a large volume of water usually rushes up. Ar- tesian wells are now general in Essex, where they are of the greatest utility in districts that have no natural springs. He also gives an in- teresting list of localities, both of constant and intermitting springs, | some of them very powerful, that burst out from the chalk. i Dr. Mitchell has also communicated an account of deleterious iW gases that occur in wells in the chalk and strata above it near Lon- i don. The most abundant of these, namely, carbonic acid gas, issues very partially and only from certain strata, and produces sometimes effects fatal to persons employed in digging wells. Sulphuretted hydrogen is occasionally met with in chalk ; and both sulphuretted hydrogen and carburetted hydrogen occur in beds immediately above the chalk. Supercretaceous formations. 515 SUPERCRETACEOUS FORMATIONS. In illustration of the history of the Eocene division of the tertiary strata, Mr. Bowerbank has concluded, from his personal observations at White cliff bay in the Isle of Wight, that there are no well-defined zoological distinctions between the London and plastic clays, but that in the cliffs of this bay the same shells are common to alternations of these clays with one another. At Alum bay also he found many: London clay fossils in beds of greenish grey sand and clay below the variegated sands and clays referred by Mr. Webster to the pla- stie clay. A similar rectification was sometime ago proposed by Professor Sedgwick. We have also witnessed during the past year the commencement of a valuable publication by Mr. Bowerbank on the fossil fruits and seeds of the London clay, illustrated with very numerous and accu rate engravings by Mr. James Sowerby. The great attention the author has long paid to the remains of fruits and seeds which occur in such vast abundance in the Isle of Sheppy, whence he has collected not less than 25,000 specimens, place him in a position peculiarly advantageous for the object before him. In this work drawings will be given of the anatomical structure of many of these fossils, as seen under the microscope. The simple ex- pedient Mr. Bowerbank has adopted of preserving these fruits in jars of water, has kept him in the entire possession of every specimen ever placed in his collection; whilst of the thousands of similar fossils that have been deposited in other collections, including that at the British Museum, nearly all have perished from the decompo- sition of the iron pyrites with which they are always penetrated. Mr. Lyeli has communicated to us a paper full of elaborate detail of facts, and of ingenious speculations respecting the Boulder forma- tion, or drift, associated with freshwater deposits, in the mud cliffs of Eastern Norfolk. These cliffs are in some places 400 feet high, and consist of chalk, crag, freshwater deposits, drift mud and sand, stratified and unstratified ;—with superficial accumulations of flint gravel. The centre of his observations is the town of Cro- mer; he considers the Boulder formation to have been accumulated on land permanently submerged, and not, by one or many, transient advances of water over dry land, and therefore proposes, as Mr Murchison and others have already done, to substitute the term of Drift for that of Diluvium, which many other writers have assigned to it. The Drift, or Diluvium, is of two kinds; one composed of sand, loam, clay, and gravel, all regularly stratified ; the other con- sisting of clay, not divided into beds, and containing boulders of granite, trap and other rocks. This clay is known on the east and north-east coast of Scotland by the name of Till. He considers the stratified Drift and Till to be contemporaneous formations, and compares the latter to moraines formed at the termination of glaciers. He imagines that drifted masses of ice, charged with earthy matter and fragments of rock, may have deposited the Till as they melted in still water, and the 2L2 516 Geological Society :—Anniversary Address. occasional intercalation or juxta-position of stratified materials is ascribed to the action of currents on materials also falling from melting icebergs. : Mr. Lyell refers the complicated bendings and tortuous foldings of many beds of this formation near Mundesley and Cromer to la- teral pressure from drifting ice, especially where extremely con- torted beds repose upon undisturbed and horizontal strata. But he admits that some of them may be due to landslips of ancient date, and which had no connection with the present line of cliffs. At — the bottom of the boulder formation, and immediately above the chalk, extensive remains of a buried forest occur, the stools of the trees being imbedded in black vegetable earth. From the position of this forest a vertical subsidence of several hundred feet and a subsequent rise of the land to the same amount is inferred. This forest and a bed of lignite are connected with fluviatile or lacustrine deposits, which occur about the level of low water below the drift; but at Mundesley they are partly above it, and the freshwater shells which they inclose being nearly all of British species, show that they, as well as the contemporaneous drift, all belong to the newer Plio- cene period. In an Address formerly delivered from this chair, in 1836, and in a subsequent edition of his “ Principles of Geology,” as well as in his “ Elements,” Mr. Lyell has called our attention to some differ- ences of opinion which had been expressed by several eminent con- chologists as to the number of fossil shells of the crag of Norfolk and Suffolk which could be identified with living species. So great was the discordance of the results at which M. Deshayes, Dr. Beck, and others seemed to have arrived, that their announcement was calculated materially to impair our confidence in the applicability of the chronological test so much relied on by Mr. Lyell for the clas- sification of the tertiary formations ; namely, that derived from the proportional number of recent and extinct species discoverable in each deposit. In the hope of arriving at some definite conclusion on this important point, Mr. Lyell visited Norfolk and Suffolk du- ring the last year, and having obtained a considerable collection from the crag near Norwich and Southwold, he instituted, with the assistance of Mr.Searles Wood and Mr. George Sowerby, a thorough comparison between them and recent species. The fossil shells of this formation, which the author calls the Norwich crag, are partly marine, and partly freshwater, and indicate a fluvio-marine origin, and the proportion of living species was found to be between 50 and 60 per cent. This deposit, therefore, the author refers to the older Pliocene period. A similar examination was then made of 230 species of shells from the Red Crag in Mr. Wood’s museum, and it was found that 69 agreed with living species, being in the proportion of about 30 per cent. This group therefore Mr. Lyell ascribes to the Miocene era. A collection of 345 species of Coralline Crag shells in Mr. Wood’s cabinet was then compared in like manner, and sixty-seven were determined to be identical with recent species, being about 19 per cent, Mr. Lyell, therefore, considers that the Coralling Crag is alsq _ Supercretaceous formations. 517 Miocene, although belonging to a more remote part of that period than the Red Crag. Having obtained from M. Dujardin a collection of 240 shells from the Faluns of Tour aine, he found with Mr. George Sowerby’s assistance that the recent shells were in the proportion of twenty-six per cent., so that he has now come round to the opinion long ago announced by M. Desnoyers, that upon the whole the Crag of Suffolk corresponds in age with the Faluns of Touraine, both be- ing Miocene, although the species in the two countries are almost entirely distinct, those of England having a northern and those of France a sub-tropical character. I am also informed by Mr. Lyell, that out of 400 marine and freshwater species, from the Eocene strata of the London and Hampshire basins, Mr. G. Sowerby was scarcely able to identify two per cent. with living shells. It is satisfactory therefore to observe that the test of age derived from the relative approach to the recent Fauna is in perfect accordance with the in- dependent evidence drawn from superposition. We ascertain for example by superposition that the freshwater strata of the mud cliffs of East Norfolk rest on Norwich crag, and are the newest forma- tion of all. They are then followed in the descending series by, Ist, the Norwich, 2ndly, the Red, and 3rdly, the Coralline Crag, beneath which is the London Clay. The same order of sequence is indi- cated by the organic remains considered independently, and simply with reference to the degree of cats este with the ex- isting Fauna. It has been known for many years, that near Bridlington, in York- shire, sand and clay containing marine tertiary shells had been ex- posed on the coast. Fron. an examination of the shells collected there by Mr. Bean, Mr. Lyell finds the deposit to agree in age with the Norwich Crag. I cannot conclude these remarks without observing, that some part of the confusion and apparent inconsistency of the opinions of different conchologists, respecting the age of the Crag, must have arisen from the intermixture of fossils derived equally from the Norfolk and Suffolk beds, or from strata, some of which now turn out to be referable to the Older Pliocene, others to the Miocene period. From an examination of some fossil shells, identical with recent species collected by Capt. Bayfield from the most modern deposit near the Gulf of St. Lawrence, and near Quebec, Mr. Lyell infers, that the climate of Canada was colder than now during the era im- mediately antecedent to our own times. Theshells, which were de- termined by Dr. Beck, differ in great part from those now living in the Gulf of St. Lawrence, agree more nearly with arctic genera and species, and resemble those which Mr. Lyell collected at Udde- valla, in Sweden; whereas, if the living shells most abundant in the Swedish and Canadian seas are contrasted, they differ almost en- tirely. From notes sent by Capt. Bayfield, it appears that at different depths in the stratified sand and clay containing the fossil shells, near Quebec, insulated boulders are numerous, which, it is presumed, have been brought down at distant intervals by 518 Geological Society :—Anniversary Address. drift ice, and have dropped to the bottom of the sea as the ice melted. While Mr. Lyell, by the aid of Dr. Beck’s determination of fos- sils, had adopted these views respecting the climate of Canada, Mr. James Smith, of Jordan Hill, had been led by independent observa- tions to a similar conclusion respecting the climate of Scotland during the Newer Pliocene era, arguing from the arctic character of the Testacea found in the raised beds of the valley of the Clyde, and other localities. In the first of two papers communicated by this author, he regarded all the deposits abounding in recent shells in Scotland and Ireland as belonging to one group; but in his second memoir he contends that there are two distinct formations on the Clyde, in the older of which there are from ten to fifteen per cent. of extinct or unknown species of shells, which he refers to the Newer Pliocene system of Lyell; whereas all the species found in the newer, which he calls Post-tertiary, exist also in the present seas. During this Post-tertiary period, which is considered to have been anterior to the human epoch, an elevation of at least forty feet took place on the shores of the Clyde. Mr. Smith affirms that the Till, or unstratified accumulation of clay and boulders, belongs not to the Post-tertiary, but to the older Pliocene division. . IGNEOUS ROCKS. The principal communication we have received on rocks of igne- ous origin has been from our Secretary, Mr. W. I. Hamilton, who has read an interesting paper on the north-west part of Asia Minor, from the Peninsula of Cyzicus to Koola, with a description of the Kata- kekaumene. Between Cyzicus and Koola the principal stratified rocks are schist, with saccharine marble, compact limestone resem- bling the scaglia of Italy and Greece, tertiary sandstones, and tertiary limestones. The igneous rocks are granite, peperite, trachyte and basalt. The tertiary limestones are referred to the great lacustrine formation which occupies so large a part of Asia Minor. Hot springs burst forth near Singerli from a porphyritic trap rock. The Katakekaumene is a volcanic region, extending about seven miles from north to south, and from eighteen to nineteen east and west. It presents two systems of volcanic craters and coulées: the older of them are placed on parallel ridges of gneiss and mica slate, and the newer in the intervening valleys; hence he argues, that when the latter eruptions took place, the lines of least resistance to subter- raneous expansion were in the valleys. The streams of lava from the more recent cones are bare and rugged, like the coulées in cen- tral France. Three periods of eruption are traced: the first, ha- ving produced basalt, which caps the plains of white limestone, and was ejected before the formation of the valleys; the second, marked by currents of lava from the more ancient system of voleanos in action since the formation of the valleys; the third resembling the coulées of Etna and Vesuvius, and mentioned by Strabo, but of which there is no historical tradition as to the period when they were in activity. Igneous Rocks—Paleontology. 519 We have a notice by the Rev. W. B. Clarke of a shower of ashes that fell on board the Roxburgh off the Cape de Verd islands in February, 1839, the cause of which was not apparent. The sails were covered with a fine powder, resembling the ashes of Vesuvius, which was probably derived from an eruption in the Cape de Verd group. PALEONTOLOGY. In the department of Paleontology Prof. Owen has, during the past year, contributed many papers, with his usual zeal and ability, to the elucidation of this most essential and perhaps most generally interesting branch of our subject. At the head of these we must place his determination of a tooth and part of a jaw of a fossil mon- key, of the genus macacus, with part of the jaw of an opossum, and the tooth of a bat, in Eocene strata of the English tertiary forma- tion. ‘These remains were found at Kingston, near Woodbridge in Suffolk, by Mr. Colchester, in strata which Mr. Lyell has referred to the London clay; thus proving the existence of quadrumanous, marsupial, and cheiropterous animals in this country during the Eocene period. We have now evidence of fossil Quadrumana in the tertiary formations, not only of India and Brazil, but also of France and England ; respecting which Mr. Owen has observed, that they appear under four of the existing modifications of the quadrumanous type: viz. the tailless ape (Hylobates), found fossil in the South of France; the gentle vegetable-feeding Semnopithecus, found fossil in India; the more petulant and omnivorous Macacus, found in Norfolk; and the platyrrhine Callithrizx, found in Brazil. This genus is peculiar to America, and its extinct species is of more than double the stature of any that exists at the present day This geographical distribution of Quadrumana adds further weight to the arguments derived from the tropical aspect of vegetable re- mains that abound in the London clay at Sheppy, showing that great heat prevailed in the European part of the world, as well as in India and South America, during the Eocene period. The probability of high temperature is further corroborated by Mr. Owen’s recent recognition of four petrified portions of a large serpent (Palgzophis Toliapicus), eleven feet long, and in several points resembling a boa, or python; and also of a bird allied to the vultures (Lithornis vulturinus), all from the London clay of the Isle of Sheppy; wherein the occurrence of fossil Crocodilians and Testudinata, and of fossil fruits, having a tropical aspect, allied to cocoa-nuts and many other fruits of palms, has been long known. Can we account for these curious facts without supposing that at the Eocene period of the tertiary epoch, the very clay on which London now stands was in the condition of a nascent spice-island, its shores covered with basking reptiles, and the adjacent lands waving with cardomums and palms, and thuias and cypresses, with monkeys vaulting and gamboling upon their branches, and gigantic serpents entwined around their trunks; the seas also swarming with sting-rays and saw-fishes, with chimeras and enormous sharks? for 520 Geological Society :—Anniversary Address. all these together with countless shells of pearly nautili occur among » the fossil remains of the numerous extinct species of fishes, which, during the early ages of the tertiary period, crowded the tepid seas of our now humid and chilling climate. Mr. Owen has also determined the character of a new genus of Pachydermatous animal (Hyracotherium) intermediate between the Hyrax, hog, and Cheropotamus, found in the London clay at Herne Bay, near Margate, by Mr. Richardson. _ Mr. Lyell having submitted to Mr. Owen some fossil teeth from the Red Crag of Newbourne in Suffolk, they proved to be refer- rible to the leopard, bear, hog, and a large kind of deer, and afford the first example of mammalian remains being found in England in any of those divisions of the Crag which Mr. Lyell, in a paper already alluded to, has ascribed to the Miocene period; these ge- nera are known to occur in the Miocene formations of France and Germany. The numerous Mammalia in the fluvio-marine crag of Norwich, are decidedly of a later date; among these Mr. Lyell enumerates the teeth and jaw of Mastodon longirostris, a tusk of an elephant with serpule attached, and bones of a horse, hog, and field- mouse ; there occur bones of birds, many fishes, and numerous shells, partly marine, and partly freshwater and terrestrial. The recent discoveries in Brazil by Dr. Lund of extinct Mam- malia, that probably lived in some late portion of the tertiary epochs, form a new and important chapter in Paleontology. The largest of these are referrible to more gigantic forms than at present exist of families now peculiar to South America—e. g.to Sloths and Armadillos; just as most of the fossil mammalia of New Holland belong to families and genera which are still peculiar to that country.* In a paper on one of these animals from Buenos Ayres, Mr. Owen has shown that the bony armour, which several authors have referred to the Megatherium, belongs to the Glyptodon, an animal allied to the Armadillo, and of which a head containing teeth, and attached to a tessellated bony covering of the body and tail, resembling those of an Armadillo, has been lately found near Buenos Ayres, and is figured by Sir Woodbine Parish in his interesting work on that country, 1838. The Glyptodon differed from the Megatherium in the structure and number of the teeth, and from all known Armadillos in the form of the lower jaw, and the presence of a long process descend- ing from the zygoma; and approached in both these respects to the Megatherium. The teeth differ from those of Armadillos, in ha- ving two deep grooves both on the outer and inner surface, are more complex than those of any known Edentate, and indicate a passage from that family into the Toxodon. The ungueal phalanges are wholly unlike those of the Megatherium, and most nearly resemble those of Dasypus, but are short broad and flat, and seem to have been covered with hoof-like claws. The form of the foot most nearly resembled that of the fore foot of the Mole. Having ap- (* On this subject see L. & E. Phil. Mag. vol. x. p. 405; vol. xi. p. 208 ; vol. xii. p.516.—Enir. ] Paleontology. 521 propriated to the. Glyptodon the armour supposed to belong to the Megatherium, Mr. Owen next proves that the latter animal was unprovided with any such bony covering, arguing from a compari- son of its vertebral column and pelvis with that of the Armadillo; and from the absence of the oblique processes, which in the lori- cated Edentata resemble as to form and use the ée-bearers in carpentry, that support the weight of a roof. The vertebral con- ditions of the Megatherium are nearer to those of the Sloths and Ant-eaters. We have accounts of twelve skeletons of Megatherium, not one of which was found to be accompanied by bony armour. Cuvier considered the Megatherium more nearly allied to the Ant- eaters and Sloths than to the Armadillos. Captain Martin has found that many parts of the bottom of the English Channel and German Ocean contain in deep water the bones and tusks of Elephants. They have been dredged up be- tween Boulogne and Dungeness, in the mid-sea between Dover and Calais, and at the back of the Goodwin Sands; also mid way between Yarmouth and the coast of Holland. In 1837 a fisherman enclo- sed in his net a vast mass of bones between the two shoals called Varn and Ridge, that form a line of submarine chalk-hills between Dover and Calais. Captain Martin says these bones do not occur on the top of banks or shoals, but in deep hollows or marine valleys. Sir John Trevelyan possesses the molars of a large Elephant from gravel in the bed of the Severn, near Watchet, and we have long known that the bones of Elephants occur in great abundance in the oyster grounds off Yarmouth. In subterranean Ornithology three important discoveries have been made during the past year; the first in the Eocene formation by Professor Owen, who has recognised the fossil Vulture before alluded to in the London clay of Sheppy ; the second, by Lord Cole and Sir P. Egerton, who have acquired from the chalk of Kent the hu- merus of a bird most like that of an Albatross, but of larger and longer dimensions; the third by Professor Agassiz, who has found in Switzerland a nearly entire skeleton of a small bird (not unlike a Swallow), at Glaris, in the indurated blue slate beds of the lower region of the chalk formation. We know that the bones of a Wader, larger than a Heron, have been found by Mr. Mantell in the Weal- den formation of Tilgate Forest; and that the Ornithichnites in the New Red Sandstone of Connecticut have been referred to seven species of birds. We have an interesting accession to our knowledge of the ana- tomy of the Ichthyosaurus in Mr. Owen’s description of the hinder fin of an Ichthyosaurus communis, discovered at Barrow-on-Soar by Sir Philip Egerton; this fin distinctly exhibits on its posterior margin the remains of cartilaginous rays that bifurcate as they approach the edge of the fin, showing in this respect a new approximation to the fin of a fish, and more fully justifying the propriety of the name Ichthyosaurus. ‘Traces are also preserved of scutiform compart- ments on the integument of the fin. It is singular that this struc- ture should never have been observed in any of the numerous spe- 522 Geological Society :—Anniversary Address. cimens from Dorset and Somerset that have come under our notice ; ‘whilst at Barrow-on-Soar, from whence the paddle in question was derived, even the fibres of the skin and folds of the epidermis are sometimes accurately retained *. Mr. Owen’s first part of his report on fossil Saurians, read at the British Association at Birmingham in August last, forms the com- mencement of a most important addition to the history of extinct reptiles. His recent investigations in Odontography have also sup- plied to the geologist a new and most efficient instrument of investi- gation, enabling him to distinguish genera of extinct animals by the microscopic structure of their teeth ; and as, of all fossil remains, the teeth are the parts most perfectly preserved, and in the case of cartila- ginous fishes the teeth and spines are generally the only parts that have escaped decomposition, this method assumes an especial im- portance in fossil Ichthyology, as affording exact characteristics of animals long swept from the surface of the earth, and whose very bones have been obliterated from among the fossil witnesses of the early conditions of life upon our planet. By this microscopic test applied to the family of Sharks, Mr. Owen has confirmed the views of Agassiz respecting the affinities between the living Cestracion and the extinct genera Acrodus, Ptychodus, Psammodus, Hybodus, Co- chliodus ; in the case of animals also of the higher orders, he has settled the much-disputed places of several extinct gigantic Mam- malia by the same unerring test. Thus he has shown the supposed reptile Basilosaurus to be a Cetaceous mammifer, allied to the Du- gong; the Megatherium to be, as Cuvier had considered it, more nearly allied to the Sloth than to the Armadillo; and the Sauro- cephalus to be, as Agassiz had supposed it, an osseous fish. Dr. Malcolmson, in amemoir on the Old Red Sandstone of the north of Scotland, has done important service in showing that the rocks composing that group are divided into three formations, the two lower of which are clearly distinguished from each other by their fossil fishes. The cornstone or central formation is charged with numerous remains of Ichthyolites, including Holoptychus nobilis- simus, a new species of Cephalaspis, and other forms not yet de- scribed. ‘The lower division, consisting in this region of conglome- rates, shales and sandstone, is characterized by the genera Dipterus, Diplopterus, Cheiracanthus, &c.,. of Agassiz, as well as by the occurrence of a singular Ichthyolite, which seems to offer close analogies to certain forms of Crustacea. By help of these Ich- thyolites, the author has been enabled to connect certain strata of Orkney and Caithness, and determine their relations to the beds of Old Red Sandstone containing fossil fishes in the basin of the Tay, and in the border counties of England and Wales, where they had been described by Mr. Murchison. Mr. Williams®n, in a notice on the fossil fishes of the coal-fields of York and Lancaster, says that these coal measures are very rich in Ichthyolites, which abound so much at Middleton colliery, near Leeds, that the workmen have given to one bed the name of fish * See Buckland’s Bridgewater Treatise, Pl. 10. Paleontology—Crustaceans— Worms. 523 coal ; they are usually in fine bituminous shale above and below the coal, and most frequent in the roof immediately above it, where, as at Burdie House, near Edinburgh, there is a thin seam of coprolitic matter ; they are rarely mixed with any great quantity of vegetable remains. In the lower measures of Lancashire they are associated with Goniatites and Pectens, and in the higher measures of Lan- cashire and Yorkshire with freshwater shells allied to Unio, and with Entomostraca. Exact observations as to facts of this kind are of inestimable importance, for it is only by careful induction from a sufficient number of such-like phenomena, and from similar de- tails as to the local distribution and condition of animal and vege- table remains in the marine and fluvio-marine and lacustrine depo- sits which compose the carboniferous series, that ,we shall arrive at a solution of the grand problem of the formation of coal. CRUSTACEANS. The Rev. T. B. Brodie has discovered in the Wealden formation near Dinton, in the vale of Wardour, the remains of Coleopterous and Hymenopterous insects, and a new genus of Lsopodous Crustacea in the family Cymothoide. The Isopods are clustered densely to- gether ; the lenses in their eyes are sometimes preserved ; there are also traces of legs, but of no antenne. With them he has found a large species of Cypris. The insects are chiefly small Coleoptera ; there are several species of Dipterous, and one Homopterous insect, and the wing of a Libellula. Mr. Brodie’s discovery is the first yet made of insects in the Wealden formation, and also the first example, in-a secondary formation, of Isopods that approximate in form to the Trilobites of the Transition series. WORMS. An addition has been made to fossil Helminthology by Mr. Atkin- son of Newcastle-on-Tyne, who has found in slabs of micaceous slaty sandstone, from the carbonaceous series near Haltwhistle, tortuous easts of vermiform bodies of various sizes, some almost an inch in diameter, and several feet in length ; the surface uf many of these is thickly marked by transverse rings and a longitudinal groove, similar to those in the largest recent marine sand worms, e.g. the Leodice gigantea. The integument of some of these worms con- taining chitine, like the covering of insects, seems to have endured long enough to fix impressions of the transverse rings upon the sand; and the habit of swallowing large quantities of earth and sand, which we observe in many recent worms, may explain the presence of the large portion of sand, now indurated to stone, which occupies the interior of the impression of the skin. Since many casts are found upon the same slab, these worms must have been very numerous at the bottom of the sea, when the sandstone was in pro- cess of formation. Similar impressions of Annelids on the Cam- brian rocks are figured by Mr. Murchison in Pl. 27 of his great work on the Silurian System. 524 Geological Society Anniversary Address. ICHNOLOGY. About twelve years ago we witnessed the creation of a new de- partment in geological investigations, viz. the science of Ichnology, founded on the evidence of footsteps made by the feet of animals upon the ancient strata of the earth; this new method commenced with the recognition of the footmarks of reptiles on the New Red Sandstone near Dumfries, and not long after (1834) was followed by most curious and unexpected discoveries in Saxony and Ame- rica. The Chirotherium of Hessberg and Ornithichnites of Con- necticut were among its early results. Our own country has during the last two years been abundantly productive of similar appearances in many localities. In recent excavations for making a dock at Pembray, near Llanelly, in Pembrokeshire, tracks of deer and of large oxen have been found on clay subjacent to a bed of peat, the lower peat being moulded into the footsteps ; similar impressions were also found upon the upper surface of the peat beneath a bed of silt, and bones both of deer and oxen in the peat itself. “ Footmarks of deer have been also noticed in Mr. Talbot's excavations for a harbour near Margam bur- rows on the east of Neath. Near Liverpool Mr. Cunningham has successfully continued his researches begun in 1838, respecting the footsteps of Chirotherium and other animals in the New Red Sandstone at Storeton Hill, on the west side of the Mersey. ‘These footsteps occur on five con- secutive beds of clay in the same quarry, the clay beds are very thin, and having received the impressions of the feet, afforded a series of moulds in which casts were taken by the succeeding depo- sits of sand, now converted into sandstone. ‘The casts of the feet are salient in high relief on the lower surfaces of the beds of sand- stone, giving exact models of the feet and toes and claws of these mysterious animals, of which scarcely a single bone or tooth has yet been found, although we are assured by the evidence before us of the certainty of their existence at the time when the New Red Sandstone was in process of deposition. Further discoveries of the footsteps of Chirotherium and five or six smaller reptiles in the New Red Sandstone of Cheshire, War- wickshire and Salop, have been brought before us by Sir P. Eger- ton, Mr. I. Taylor, jun., Mr. Strickland, and Dr. Ward. Mr. Cunningham, in a sequel to his paper on the footmarks at Storeton, has described impressions on the same slabs with them, derived from drops of rain that fell upon thin laminz of clay inter- posed between the beds of sand. The clay impressed with these prints of rain drops acted as a*mould, which transferred the form of every drop to the lower surface of the next bed of sand deposited upon it, so that entire surfaces of several strata in the same quarry are respectively covered with moulds and casts of drops of rain that fell whilst these strata were in process of formation. | On the surface of one stratum at Storeton, impressed with large footmarks of a Chirotherium, the depth of the holes formed by the Ichnology. 525 rain drops on different parts of the same footstep has varied with the unequal amount of pressure on the clay and sand, by the salient cushions and retiring hollows of the creature’s foot; and from the constancy of this phenomenon upon an entire series of footmarks in a long continuous track, we know that this rain fell after the animal had passed. The equable size of the casts of large drops that cover the entire surface of the slab, except in the parts im- pressed by the cushions of the feet, record the falling of a shower of heavy drops on the day in which this huge animal had marched along the ancient strand; hemispherical impressions of small drops, upon another stratum, show it to have been exposed to only a sprinkling of gentle rain that fell at a moment of calm. In one small slab of New Red Sandstone found by Dr. Ward near Shrewsbury, we have a combination of proofs as to meteoric, hydro- static, and locomotive phenomena, which occurred at a time inecal- culably remote, in the atmosphere, the water, and the movements of animals, and from which we infer with the certainty of cumulative cir- cumstantial evidence, the direction of the wind, the depth and course of the water, and the quarter towards which the animals were - passing ; the Jatter is indicated by the direction of the footsteps which form their tracks; the size and curvatures of the ripple-marks on the sand, now converted to sandstone, show the depth and direction of the current; the oblique impressions of the rain drops register the point from which the wind was blowing, at or about the time when the animals were passing. Demonstrations founded solely upon this kind of circumstantial evidence were duly appreciated, and are well exemplified, by the acute author of the story of Zadig ; who from marks he had noticed on the sand, of its long ears, and teats, and tail, and from irregular im- pressions of the feet, declared the size and sex, recent parturition and lameness of a bitch he had never seen; and who from the sweeping of the sand, and marks of horse-shoe nails, and a streak of silver on a pebble that lay at the bottom of a single footstep, and of gold upon a rock against which the animal had struck its bridle, inferred that a horse, of whose existence he had no other evidence, had recently passed along the shore, having a long switch tail, and shod with silver, with one nail wanting upon one shoe, and having a bridle studded with gold of twenty carats value. In addition to the commencement of Mr. Bowerbank’s publication on the Fossil Fruits and Seeds of the London Clay, before alluded to, we have hailed with satisfaction the announcement, by Professor Henslow and Mr. Hutton, of their intended continuation of the Fossil Flora of Great Britain, conducted for some years by Dr. Lindley and Mr. Hutton, and lately suspended. A Dictionary of the terms and language of geology has long been a desideratum to young students, to whose early progress the tech- nical terms of the science have hitherto presented formidable im- pediments. This want has been recently supplied by two publica- tions of this kind, one by Mr. George Roberts, author of the History of Lyme Regis; the other by Dr. Humble. Hh I 526 Geological Society:—Anniversary Address. During the last year the Society has received no communication on Mineralogy; and almost the only volume that has been published in England on this much-neglected subject, has been a small but highly elaborate treatise on Crystallography by Professor Miller, of the University of Cambridge. In this treatise the author has adopted - the crystallographic notation proposed by Professor Whewell in his paper on a General Method of calculating the Angles of Crystals, and the laws according to which they are formed, published in the Transactions of the Royal Society of London, 1825; and Professor Naumann’s method of indicating the positions of the faces of a ery- stal by the points in which radii, drawn perpendicular to the faces, meet the surface of a sphere. ‘The expressions which have been thus obtained are remarkable for their symmetry and simplicity, and are all adapted to logarithmic computation, and for the most part new. NOTICE OF DECEASED MEMBERS. - In proceeding to speak of the losses which, during the past year our science has sustained by death, I shall offer my first tribute of respect to the memory of one, whom a predecessor of mine in this chair has justly called the father of English geology; since to his discoveries we owe the first diffusion of exact knowledge as to the order of superposition of the secondary formations which occupy so large a portion of our island, and the first demonstration of that constancy of the organic remains, which he proved to be cha- racteristic of the component strata of each different formation. It was the especial merit of Mr. W1tLt1am SmiTH to establish a series of types of these groups, many of which have been adopted as classical, in such a manner as will perpetuate his name among the original discoverers of the age in which he lived. If, as it has been truly said, the honour of the first discoveries in tertiary geology belongs to France, where the labours of Cuvier and Brongniart gave to this great division of the strata of the earth a systematic arrangement before unknown, so the establishment of the types in secondary geology, from the chalk down to the new red sandstone, is due to England ; and the discovery of the leading natural divisions of that important portion of them which consti- tutes the oolite formations, was almost exclusively the work of Mr. William Smith. His earliest publication was a treatise on irrigation, 1806, a sub- ject on which his experiments gained him a medal from the Society of Arts. In 1801 he printed proposals for publishing accurate delineations and descriptions of the natural order of the various strata that are found in different parts of England and Wales, to be illustrated by a small geological map*. This work was never completed, but it led to the publication of his large map, in 1815, for which the Society * The original coloured copy of this map, dated 1801, was presented by Mr. Smith to our Society, and is now in the Museum, Deceased Members—Dr. W. Smith. 527 of Arts awarded him their medal and a premium of £50. In the same year also his stratigraphical collection of organic remains was purchased for the British Museum; this collection having formed the basis of his two separate volumes, entitled “ Strata identified by their Organized Fossils,” 1815, and “a Stratigraphical System of Organized Fossils,” 4to, 1817. | During the six years which followed the publication of his map of England, he put forth twenty geological maps of English coun- ties on a larger scale, and several coloured sections across the south of England, and a general Geological Section of England and Wales, from London to Snowdon. Among his unpublished papers were found unfinished and in part printed, an introductory work on geology, and preparations - for a volume on Ciconomic Geology, both illustrating the original- ity of his views. ‘ Mr. Wittt1aM SmirTH entered on the field of his honourable ex- ertions as a Civil Engineer and Mineral Surveyor at a time when his labours in geology were but little appreciated, and almost solitary. Amidst difficulties and discouragements, and at intervals snatched from the duties of a laborious profession, he accomplished the gi- gantic work of a general mineralogical survey of England, founded almost entirely on his own personal observations, which he ulti- mately recorded in a map of fifteen coloured, sheets, published by subscription in 1815. Inevitable delays retarded the appearance of this work nearly to the time when a more detailed and perfect map, by a distinguished president of this Society, eclipsed in some degree the fame which would have accrued to its author had it been published earlier, even in the less perfect form to which he had advanced it some years before. The sense entertained by this Society of the value of the scientific services of Mr. Smith, was marked by their award to him of their first Wollaston Medal, in 1831; and was accom- panied by the just and eloquent eulogium pronounced on that oc- easion by Professor Sedgwick. In the same year also the British Association assembled at York made successful application to go- vernment for a pension, which was settled upon Mr. Smith for life ; and at the meeting of this Association at Dublin, 1835, the Univer- sity conferred on him the honorary degree of Doctor of Civil Law. Mr. Smith was one of those remarkable persons whom strong natural sense and acute powers of observation occasionally enable to triumph over the disadvantages of a defective education. His attention was first called to physical inquiries, by the observing, when a boy, that a large stone which he was lifting under water in search of eels, could be moved with much more ease, than if the same stone had been on land. His juvenile curiosity was excited to learn the cause of an occurrence so surprising to him; and this first step led him, at the age of eighteen, to enter the profession of a surveyor and civil engineer. His early professional occupations from the year 1791 to 1799, whilst surveying collieries, constructing a part of the Somerset coal canal near Bath, and preparing reports 528 — Geological Society :—Annwersary Address. — respecting a supply of water for the Kennet and Avon Canal, and the trade it was likely to derive from carriage of stone and coal, &e., placed him in daily contact with geological phenomena espe- cially calculated to illustrate the order of superposition of the English strata, and laid the foundation of his future discoveries. By carefully noting the characters of the beds which he found in juxtaposition, and making comparative sections in various direc- tions in the vicinity of Bath, he ascertained that an uniform order of succession pervades the groups exposed in the escarpments of the hills in that part of England, and that this uniformity is attended by a similarity in the organic remains of certain beds, which differ entirely from those of the groups above and below them; by dili- gently collecting and collating these remains, he drew the inference, that each group of strata contains extraneous fossils peculiar to itself. His next step was to infer that the strata thus identified by himself in Somerset and Wiltshire were not of insulated and local occur- rence, but formed parts of the great system of deposits extending over England; and thus, after many years of intense labour and continual travel, he succeeded in extending the principles first caught sight of in the neighbourhood of Bath, into that philoso- phical generalization which became the basis of his geological map of England. ~ Before Mr. Smith had quitted his occupations in Somerset and his residence at Bath, he indicated on a coloured map the geologi- eal structure of that neighbourhood. This document, dated 1799, is in the museum of our Society. He had also arranged his col- lections of rocks and their organic remains in the order of succes- sion and continuity of the several strata; but neglecting to ap- propriate to himself the merit of these discoveries by immediate publication, he liberally imparted a knowledge of each, as it gra- dually arose, to his private friends, through whose oral communi- cations they obtained such general currency, that their real author was frequently lost sight of or unknown. I was myself indebted to Mr. Smith, though at that time a stranger to me, for my first know- ledge of the order of succession in the oolitic series. This I derived from information imparted to me by the late Rev. B. Richardson of Farley Castle, who had himself acquired it from Mr. Smith. A ta- bular view of the superposition of the English strata, written by Mr. Richardson, from the dictation of Smith in 1’799, at the house of the Rev. Joseph Townsend, in Bath, and since also presented to this So- ciety, forms a documentary proof of the extent of his discoveries be- fore the conclusion of the last century. In 1817 he planned the beautiful museum of Scarborough, in which he employed his original and instructive method of repre- senting, by sloping shelves passing one beneath another, the inclined position of the strata; each shelf bearing the fossils that are re- spectively characteristic of the stratum it is intended to represent. These works of William Smith undoubtedly place him in the position of an original discoverer, who was the first to establish, on an enlarged basis of evidence, the importatit facts of constancy Deceased Members—Dr. William Smith. | 529 in the order of superposition, and continuity in the horizontal ex- tension of the strata of this island; and to prove that each of these strata is characterized by organic remains peculiar to itself. But it must not be forgotten, that both in this country and on the conti- nent, other investigators, many of them no doubt unknown to him, were simultaneously collecting similar evidence in support of this great physical generalization. It only enhances the value and con- firms the accuracy of Mr. Smith’s conclusions, that the results of other independent inquiries were found to be in perfect harmony with his own. It is known to all who are acquainted with the productions of the school of Freyberg, that Werner had pointed out the importance of petrifactions as affording a basis for the ar- rangement of geological formations, the same in principle, though confirmed by less extensive details, than those which Mr. Smith elicited from the oolitic series in England. Professor Jameson has expressly stated that Werner was aware that petrifactions are com- paratively rare in the transition rocks, increasing in number in the newer series of that division, and becoming still more numerous in the Floetz formations: he had further remarked, that the animals of the earliest periods are of the lowest and most imperfect class, namely zoophytes; that in ascending through newer and newer formations, we meet with shells and fishes and marine plants, all different from any living animals and vegetables of the present earth ; that in the newest formations we find the remains of existing genera with those of land animals and land plants. Werner had also noted, in some detail, the order of succession of the strata of the Muschel-kalk of Germany, founding his divisions upon the changes he observed in the petrifactions it contains; and thus announcing the principle of making distinctions in strata upon the nature of their organic remains. The same principle had been previously caught sight of and par- tially elaborated by Lehman in Germany, and by other observers in France, where its application to tertiary strata received the fullest demonstration, in the great discoveries of Cuvier and Brongniart within the basin of Paris. In our just admiration of our country- man, therefore, we must not lose sight of the merits of his contem- porary labourers on the continent; and whilst we honour him as the father of English Geology, let us also pay just homage to those who had started before him in the same course, wherein it was his undisputed merit to have arrived first at the goal. Mr. W. Smith was born on the oolite formation at Churchill, in the county of Oxford, in 1769. When a child he was in the habit of collecting Terebratule from the oolite rocks in the fields of his native village, which he used as substitutes for marbles. As an engineer he was employed in works of irrigation and drain- age in many parts of England; as well as in stopping out the sea from breaches through which it had invaded the marshes of Norfolk, 1806, 1807, &c., and in the draining off the water of Mismer lake in Suffolk into the sea. He was the engineer also of the Ouse na- vigation in Sussex. In 1809 he was engaged in the restoration of Phil. Mag. S.3. Vol. 17. Supplement, No. 113. Jan.1841. 2M ee =o Se ee ee ee eee SE ee ee SS SS SSS EEE = SO SS SSS 530 Geological Society :—Anniversary Address. the hot springs at Bath. In 1821 he recommended to Col. Braddy] to search for coal (beneath the magnesian limestone) on an estate in which is now situated the great South Hetton Colliery. No colliery in Northumberland had been worked, at that time, under the magnesian limestone. Mr. Smith’s principles of drainage have been applied with much advantage near Bath, Woburn, and in Norfolk. Finding the town of Scarborough to be very ill supplied with water, he excavated in the interior of the hill of Falsgrave Moor, two.or three miles distant, a subterranean reservoir, in which he collected, from streamlets percolating that hill, sufficient water for the permanent supply of the town*. From his early days to the latest period of his life he tells us that he had the habit of looking on the groundf. Mr. Smith’s last public employment was in conjunction with Mr. De la Beche and Mr. Barry, in the Commission for reporting on the best building-stone for the new House of Commons{. During the later years of his life he resided near Scarborough superintending the estates of Sir John Johnson at Hackness ; and dying at North- ampton, in August 1839, aged seventy-one, after a few days’ ill- ness, at the house of his friend Mr. Baker, the historian of North- amptonshire, on his way to the Meeting of the British Association at Birmingham, was interred in the church-yard near the west end of the beautiful Norman church of St. Peter, in Northampton, which stands on the Oolite formation. He had often expressed a wish to be buried in this formation, on which he was born and educated, and the history of which he had so much elucidated. A monument will be erected to his memory in St. Peter’s Church by subscription of members of the Geological Society of London. | It was not the least of the services which have been rendered to our science by Mr. Smith, that he was during many years the geological preceptor of his accomplished nephew Mr. John Phillips, in whom he has bequeathed to us a pupil, who has shown, by pub- lications of the highest order in various departments of Geology, the soundness of the instructions received from his affectionate uncle. Mr. Davies GILBERT was one of the earliest members elected into this Society, at its formation in 1808. During two years he served as a Vice-President, and for six years was a member of our * An account of this curious work is published by himself in the Phi- losophical Magazine for June 1827. + See a paper by himself on Quartz in Soils, published in Charlesworth’s Magazine for July 1837. | { For more detailed accounts of the life of Mr. Smith, and of the amount and value of the services he rendered to Geology in England, I must refer to Dr. Fitton’s masterly and candid investigation of this question in the Edinburgh Review, Vol. XXIX, p. 310, &c. [reprinted, with additions, in L. & E. Phil. Mag., vol. i. p. 147, &c.]; to Mr. Conybeare’s Introduction to his Outlines of the Geology of England and Wales, 1822, p. 45; to the Address of Professor Sedgwick to this Society, 1831; and to a biographical notice by his nephew Professor John Phillips, in Charlesworth’s Magazine of Natural History, New Series, 1839, p. 213. Deceased Members—Mr. Davies Gilbert. 531 Council ; and though he communicated no papers, he took a lively interest in all our proceedings, and was ever prompt on all public occasions to promote the welfare and forward the great objects of our institution. His paternal name was Giddy: he was descended in the line of both his parents from very respectable families in Cornwall, and on the maternal side of Davies, allied to the noble family of Sandys; in 1817 he assumed the name of Gilbert, on succeeding te the property of his wife’s uncle, Mr. Charles Gilbert, of East Bourne, in Sussex. Having been privately educated in Cornwall, he became, in 1785, at the age of eighteen, a gentleman-commoner of Pembroke College, Oxford, where, being of more studious habits and more ma~ . ture attainments than is usual with students of his age, he associated chiefly with the senior members of his College. Dr. Parr, writing at this time to the late master of Pembroke, speaks of Mr. Giddy, then twenty-three years old, as “the Cornish philosopher,” and adds, that ‘“‘ he deserves that name.” To this College, as well as to the University, his affectionate and devoted attachment endured to his latest hour, and he became on several occasions a liberal benefactor towards improvements in Pembroke and its vicinity. During many years it was his great delight to pass a few days at Oxford, and he always considered the diploma Degree of Doctor of Laws, conferred on him by the Uni- versity in 1832, as one of the most gratifying events of his life. During his early residence his taste for chemistry and other branches of physical science had introduced him to the acquaint- ance of Dr. Beddoes, at that time a resident Member of Pembroke College, and who subsequently dedicated to him his pamphlet on mathematical evidence. This acquaintance* was the remote cause of the first step in the public life of Sir Humphry Davy; when Mr. Giddy, who had discovered young Davy’s genius for chemistry whilst yet a boy at Penzance, introduced him to Dr. Beddoes, to assist in his laboratory at Bristol, little dreaming that he should himself one day become the successor of this boy in the chair of the Royal Society. Mr. Davies Giddy was elected a fellow of the Royal Society in 1791, and subsequently of the Antiquarian, Linnean, Geological, and Astronomical Societies of London. He was also an honorary member of the Royal Society of Edinburgh, the Royal Irish Aca- demy, and of the New University of Durham. In 1814 he was elected first President of the Royal Geological Society of Cornwall, and afterwards Vice-Patron of the Cornwall Royal Polytechnic So- ciety, in both which offices he continued till the day of his death. He held the distinguished office of President of the Royal Society, during three years, from 1827 to 1830, and contributed several im- portant papers to their Transactions; one upon the Mathematical * [He also enjoyed the friendship of Dr. Priestley : and he was on his way to Birmingham on a visit to him, when, at a short distance from the town, he learnt that the residence of his venerable friend was in flames, and that a bigoted mob were in the act of destroying the library, manuscripts, and laboratory of that excellent man and distinguished philosopher.—Ep. | 2M2 532 Geological Society :—Anniversary Address. Theory of: Suspension Bridges (vol. 116, 1826, Part I., p. 202); also a Table for facilitating the Computations relative to Suspension Bridges (vol. 121, 1831, p. 341); a third paper, entitled Observa- tions on Steam Engines (vol. 117, 1827, p. 25); and a fourth on the Efficacy of Steam Engines in Cornwall, with Investigations of the Methods best adapted for imparting great Angular Velocity (vol. 120, 1830, Part I., p. 121); likewise a paper on the nature of Negative and Imaginary Quantities (vol. 121, 1831, p.91). He also printed three Addresses as President of the Royal Society, 1828, 1829, 1830*. In 1804 he was returned to parliament for the borough of Hel- ston; and in 1806 for Bodmin, which place he represented till 1832. During that time he was continually called on by the House of Com- mons to serve on committees of inquiry touching scientific and finan- cial questions, on which latter subject he published a letter, entitled ‘