sector cries cabeeer 3 HASSE eet Stee t ~- eatas Snel Steph tienes i tis stator dees 4 > ’ the Inteftines; by AtexanDER Monro » fer M.: De. and Profe efor of Anan re cra rH 968 KXIX. A Defeription of an American Ye/- cow Fever, in a Letter from Dr. Joun LINING, Phyfician at Charles-town’ zn South Carolina, to Dr. RoperT WuHYTT Profe efor of Medicine in the Univerfity of Edinburgh. 370 XXX. Anfwer to an Objettion againft Inocula- tion; by Esenezer Gitcurist M. D. _ Phyfician at Dumfries... «. - .. 396 XXXL. A: Propofal of a new Method yi curing obftrutted' Menfes ; by Dr. Arcuipatp HamiLTon Phyfici ician in Edinburgh. 403 XXXII. 44 Dropfy unexpectedly cured; by THomas LivINGsTon M. D. Phyfician at Aberdeen. 407 agers Hiftory of a Patient affected with > periedie nephritic Convulfions; by Corn- WELL ti €COrtEenwm bE ART. pag’ WELL TATHWELL M.D. Phyficianvat Stamford. “412 XXXIV. Hiftory of a Fever after Chitdebear- sang; bythefame >... 417 XXXV, Hiftory of a Fever with bad Gikiptéa 5 ; by the fame. “.420 XXXVI. Accounts of extraordinary Motions of the Waters in feveral Places of North’ Bri- tain, and of a Shock of an Earthquake Jelt.at Dunbarton. 2423 ERR. Ay TA Page 33. 1. wit. f. 5 r. 6. p. 127. from the-bottom of the ~ page, 1.4. r. 03190764. 1. 3. 7. 2.084857. 11. ry 50°51'.093797 that.is, 50°51'5".62782, p. 128. from the bottom, 1. 2. ¥. 50°51'.093797. p..264. from the top 1. 5. after Duguid dele late. p, 300. 1. ult. f. Jeraned t. learned. ESSAYS ES S A Y°S 7 A Wath otis MESERVATIONS PHYSICAL ann LITERARY. ARTICLE I. ° The Defcription of a new Plant ; by Dr. ALEX- ANDER GarveN, Phyfcian at Charlefton . 72 South Carolina. ] % OcTor GARDEN writes Doctor Whytt, that, in Summer 1754, he-met, about a mile from the town of New York in New England, with.a plant ; which, at firft, he took to be a bypericum, but, on examining 4 it, found it different: upon which -he took down its characters, and fent them, fome days after, to Mifs ‘Fenny Colden (daughter to the Honourable Caldwallader Colden), a very inge- nious young Lady and curious Botanift. In return to this, Mifs Colden fent Dr.Garden the characters of a plant which proves to be © Vox. Il. A . the , : ° 1/YCL4 2 ESSAYS ann OBSERVATIONS the fame: it is N° 153. of her colleétion ; and was firft found by her, Summer ¥753. Ufing the privilege of a firft difcoverer, fhe was pleafed to call this new plant Gardenia, in compliment to Dr. Garden. The Defcription of the GARDENIA, fent by Dr. Garden to Mi/s Colden. ANONYMOS. PoLYADELPHIA ENNEANDRIA. Raprx perpendicularis, in defcenfu fibras aliquot at plures cirros emittens, fen- fim attenuatur, fimplex, mollis. : Cautis fimplex, fruticofus, teres, rectus, ex alis foliorum internodiis fefquipol- licaribus laterales emittens -ramulos, —Jineam craffus, cubitum plus minus altus, cavus, annuus, glaber. Foxt1a fimplicia, feffilia, patula, bina ex op- pofito alternata, integerrima, obtufa, ovata, cordata in duo auricula, circa caulem fupra fe invicem expanfa, ad ‘bafin extenduntur, nitida, fuperné vi- ridia, inferné glauca, nervo medio in= . fra PHYSICAL ann LITERARY. 3 fra prominulo, pundtis lucidis) hyperict foliorum inftar perforata dimidium pollicis plus minus latitudine, -fefqui- pollicari fere longitudine.. — PepuNc. nunc alaris, nunc terminatrix, fili- formis, femiuntialis. Caxyx perianthium pentaphyllum perfiftens, _..» foliolis linearibus,. lanceolatis; ‘acutis. CoRoLEA pentapetala;pallidé rubra, bracteis lanceolatis, cum, calyce fitum alternan- tibus et longioribus. 3 STAMINA. Filamenta novem, leviter purpurea filiformia, inotria eorpora ad)bafin coa- fita.’, Fafciculi iti filamentorum, in- terpofitione trium corporum :meéfareis .fimilium, .4-fe invicem feparantur. Haecce corpora, colore funt bruneo- |, luteo, obtufa, crafla, breviora,; rece- ptaculo feffilia, hinc modice cava, in- i ade stbhofiauk Antherae {ubrotundae, par- vae, luteae. PISTILLUM germen, trigonum ;. ftyli_ tres, ‘ parum reflexi, teretes ; {tigma nullum, ~yel faltem nudis oculis imperceptibile. RECEPTAC. parvum cyathiforme excavatum. PericarpP. capfula oblonga, acuminata, ob- tufé triquetra, trilocularis, trivalvis, tribus 4 ESSAYS ann OBSERVATIONS tribus fulcis per longitudinem decur- rentibus. Semina plurima, parva, obtufé cylindrica, receptaculo proprio ‘per funem umbi- licalem breviffimum in duobus ordini- bus adhaerentia. ; 1. Hypericum inter polyadelphia polyan- dria collocat celeberrimus Linn us; - et optimo quidem jure: nam, in qua- cunque re variant inter fe diverfae hu- jus {pecies, conftanter tamen exiftunt filamenta numerofa ; at in hacce planta femper novem inveniuntur: filamenta, et femper in tria corpora vel ons tia concrefcunt. 2. In hyperico nunquam occurrunt neéfa- rea; at in anonymo femper exiftunt ‘ tria, confpicua, et ftamina ab invicem feparantia. 3, Germen et pericarpium figura fubro- tunda donantur; at in anonymo uter- que triquetra forma gaudet. 4. In'hyperico, calyx perianth. quinque- partitum ; at in anonymo, perianth, pentaphyllum. PHYSICAL ann LITERARY. 9 Myf Coxpen’s Defeription of the fame Plant, N13, GARDENIA, ‘Cover of the flower is a’cup, compofed of five lancet-{hap’d leaves continuing. Frowe is five “oval-fhap’d ‘leaves, longer than the cup, and {pread’out. g Curves are’nine, placed in :three bandleés ;- Hs ey three! are joined in‘one’ body for near -half their’ length; ~ ‘their upper lerpacts are fife threads ; they are a little filo fhortér than the flower-leaves. "The oo") gaps-aré'roundifh. °°" There are thifee fal! oval-fhap’d bodies, 0 ote ofa bright red colour,’ placed ‘on the °Vfeat of ‘the flower oa with the bundles of chives. PisTiLt. The feed-bud (germen) is of a long ovally fhape, with three deep furrows, ~\'""The jiiles are three threads of the “© fength'of the chives. The tips (ana ‘are plains © oats of the féed is a long oval-fhap'd box, of a dark red colour, with three deep furrows along it, and opening at three 6 ESSSAYS ann OBSERVATIONS three parts at top. Before the feeds are ripe, it contains three cells ; but when the feeds are ripe, the divifions feparate at the axis, and it contains but one cell. | Spat of the feed is three ridges (being the infide of the three furrows of the faid - box) each with two rows of feeds. SEEDS are numerous, fmall; and oval-fhap’d. Root is fibrous; but, tho’ fibrous, the:moft: of them, are about as thick as the ftalk; they are white and branched ; fome of them are like fine threads. . STALK grows fingle, is round and {mooth, and is branched out oppofitely an the arm-pits of the leaves... Leaves ftand thinly in pairs oncihell on the ftalk and branches, they have no leaf-ftalks, are oval-fhap’d, about half as long as they are broad, : broadeft.in the middle, are fmooth, have a rib a- long the middle, with fmall tranfpa- rent veins extending from it towards ‘the edges, and the edges are intire. The flowers are of a pale red colour ; they ftand in clufters on the top of the ftalk and PHYSICAL anv LITERARY: 7 and dranches, and fometimes in pairs at the arm-pits of the aves. This plant grows. in wet ground, and flowers in Augu/t. , OpservaTion. The three chives only in each bundle, and the three oval-fhap’d bo- dies on the feat of the flower, together with the feat to which the feeds adhere, diftin-" guifh this plant from the bypericums ; and, I think, not only make it a different genus, but likeways makes an order which an NUS has 0 not. dirs iii he ART. 8 ESSAYS anp OBSERVATIONS oA rorevilh A Defcription of the Matrix ‘or Ovary of the Buccinum’? Ampullatum*; dy Rosert Wuyttr M.D. F.R.S. Fellow. of the Royal College of Phyfictans, and Profeffor of Medicine in the Univerfity of Edin- burgh. 4 ATURALIsTs inform us that the buccina and purpura, the former towards the clofe of the Winter and the latter in the Spring, throw out a vifcid glutinous humor s which thickening and becoming dry, forms a congeries of cells or receptacles connected together, fomething refembling the cods of white vetches, and containing the nafcent buccina or purpura. This congeries of cells or pods is often found upon the fhore, and fometimes miftaken for the hardened froth of the fea. But whatever may be the manner in which thefe cells are formed, the matrix, ovary * The buccinum ampullatum is that in which the hermit- crab is found, gs i vey , PHYSICAL avn LITERARY. 9 vaty or receptacle, in which the nafcent buccina ampullata are found, has fomething remarkably curious in its ftructure. Tas. sh fig Is . depitediits the matrix, .as it is called, of the duccinum ampullatum, fent me from South-Carolina by Dr..Garden; the length of which was full two foot. aaaaa; &c. are.the cells, receptacles or pods, compofing this matrix, whofe number amounted to 94. Thefe pods, towards the extremity D, turned fmaller. ABCD, a band or ligament connecting the feveral cells or pods, of much the fame kind of fubftance with the fides of the cells, but thicker and tougher. Tue pods or cells are compofed of a thin, tough, tran{parent {kin or membrane, and contain in their cavities a confiderable num- ber of fimall duceina: Fig. 2. reprefents one of thefe cells intire, thro’ the tranfparent membrane of which ~ may be feen the Jueccina it contains. Fig. 3. thews one of thefe cells or pods o- pened, that its duccina may be diftin@ly feen. Vor. II,- B : Fug. ; ‘to ESSAYS ann OBSERVATIONS Fig. 4. exhibits feveral different views of the fmall ducezna, all of their natural fize. In fome of the pods or cells, I found 32, in others, only 28 duccina: but, as towards the fmall end of the matrix the pods were lefs, and had fewer duccina in them, we may fuppofe that each pod might contain 25 duc- cina; in which cafe, the number in the whole matrix muft have been 2350. _ART- ; / SICAL avo, LITERARY. — oy " \ ; ‘ ea ; me \ $: ! - 9 ara Te | + . —"e > nn = ve ree kw a 4 re ’ x t ’ - : i “ } » 7 , : - : s ra “ . > Ant eke ; 2 x 2 x \ a , q ‘ ss * oh ey s wi? 9 tag is i i¢ é ey a iy Mea ¥ heat . ‘ hd i ‘ Fi ¥ ; * . a . : at + v ‘ — : za ul s t = + " A y f f Gye * " ‘ mis : ‘ ay . Pe ‘3 Sune? ee > ori . +. . -) 4 i < . M y ¥ re F t i ; ! 4, : ; 7 P s P ¥ ? i 5 } ‘ te Ore fae oy ? AN es Shee te ; v . Ss ' 6 & 4 Pup 1e€,¥°9 i? ’ J yy ag # Fel me eye a a hy PHYSICAL ann. LITERARY. ee Arr. Ill. Drawings of fome very: large Bones ; by _ GEORGE CrerK Eg; is & aieag Il. fig. 1. reprefents the fcapula or fhoulder-bladé of ‘ah’ animal, found in a fhell mar]-pit near\the town of Drumfries, of a monftrous fize, | meafuring in length twenty one inches and eight tenths.’ : Fig. 2. is arib twenty three inches long, and two and two teliths broad. | > Fig. 3. and 4. are alfo pieces of broken ribs, found in the fame place; where the whole, or greateft part of the bones of the animal. were afterwards. difcovered, but lof or deftroyed by the country- -people who found them. As the. bones defcribed are at leaft one - third larger than thofe of oir biggeft oxen ‘or horfes, sthey are fuppofed to be the re- mains of an E/é or fome other animal not at prefent an inhabitant of this country. _ Tuey are juft now in the poffeffion of i; George Cathe ' ART, :2 ESSAYS ann OBSERVATIONS Arr. IV. Obfervations on Light and Colours; by Tuomas Metvirg M. A. * oe Oe ON haga F On the Mutual Penetration of Light. NE of the firft and greateft difficulties that occurs in reflecting on this fub- jet, is, to conceive how it is poflible that light * Read January 3. and February 7. 1752. Had the ingenious Author of this paper (who died De- cember 1153, at the age of 27) lived to put the finifhing hand to it, he would, probably, have added many things, and perhaps retrenched fome others, by which it would have been rendered ftill more deferying of the approbation of the public. Mr. Melvill ufed to obferve, that as, of all Sir Vfaac Newton" s difcoyeries, thofe relating to light and colours were perhaps the moft curious ; ; it was fomewhat remark- able, that few, if any, of his followers had gone one ftep beyond him on thefe fubjeéts, or attempted to compleat what 4e had left unfinifhed. Our Author, therefore, pro- pofed to have applied himfelf particularly to the further il- Juftration of the theory of light and colours. The follow- ing eflay is a fpecimen of what might have been expected from him, and fufliciently fhews the uncommon genius of its Author. cote EEE TE 2 i ¥ Ay fl i = \\ \ WS AY SS “PHYSICAL ann LITERARY, 743 fight can move thro’ light in all imaginable directions, without occafioning the leaft perceivable confufion or deviation from its rectilinear courfe. Many have been induced, from this confideration, to believe it incor. poteal ; and al¥ who have thoroughly weigh- ed the difficulty, have fee the neceffity of afcribing a fubtility to it inéomparably greater than we are led, by any phenomena, to afcribe to any other f{pecies of bodies in Nature, There is ‘no phyfical point in the vifible ‘ho- rizon which does not fend rays to every other point; no ftar in’ the heaven which docs — hot fend rays to every other ftar :\ the whole horizon ‘is filled with a fphere of rays from every point init; and the whole vifible uni- -_-verfe, with a fphere of rays from every ftar. In thort; for any thing we’ know,’ there are taysof light joining every two phyfical points _ ithe univerfe, and that in-contrary: dire@i- ni ons; except where aa bodies initer= een. 92. THosz who fuppofe shi High 3 is nothing elfe than vibrations or pulfes propegueed thro’ a fubtile elaftic medium from the vifible _ object to the eye, may perhaps remove the _ difficulty by a{cribing a {uffictent minute- nek 14 ESSAYS ann OBSERVATIONS nefs to the particles of that medium; fince we fee, by experience, that found in the air, and waves in the water, are conveyed in dif- ferent direGtions, without fenfibly. interfe- ring : but, .as that hypothefis feems infup- portable on other accounts “, we muft endea- your to accommodate our folution to the on- ly other conception we, can. frame of it; _ namely, that of particles actually projected from the luminous body... 3. Ir is manifeft, that, tho’ the mere ies tility of the particles of light may tend to ac- count for its eafy staan, in-all directions; thro’ denfe. tranfparent bodies, it. will not ferve to explain its eafy paflage thro’ other light equally fubtile: but, for this purpofe, it feems neceffary to fuppofe light incompa- rably rare when at the denfeft ; - that is, that the femi-diameters of two of the neareft particles in the fame or in different rays, foon after their emiffion, are. incomparably. lefs than their diftance. 4. Let us confider a little the courfe ofa particle of light from any of the remoter fixs ed * Newtont Principia, book 2. prop. 41. and 42, See alfo Newton's Optics, query 28. } | "PHYSICAL ann LITERARY. #3 ed ftars to the human eye; for inftancé} from the fmall one called the Rider in the tail of the Great Bear: ‘The. particles” by which we fee that ftar, have, in the firft place, paffed thro’ the fpace furrounding it, in which there ate probably feveral planets tevolving, and which muft be therefore fo filled’ with a fphere of rays from each of them that they may’ be vifible to an eye any where fituated in thofe fpaces ; after'that, they ~ have paffed laterally thro’ the whole’ torrent of light flowing from the ftar of the fecond magnitude which we fee befide it; and laft- ly, they have paffed likeways acrofs the whole ocean of the folar light, and all that light with which the {pace furrounding the fun is filled from all the comets, planets, and {atellites; and befides, in every phyfical point of their numerous journey from the Rider to our eye, they have paffed thro’ rays of light flowing in all direCtions from every fix- ed ftar in the vifible univerfe: and yet, du- ting the whole, they have never juftled a- eainft one particle of light; otherways they could not have arrived in their true direction _ to our eye. This reflection cannot fail to fuggeft a general notion of the rarity and te- Muity 16 ESSAYS ann OBSERVATIONS nuity of light, far furpaffing all the fuppo= fitions which are ufually made about it. _. 5. Tue chance which any one body has to juftle with others of like magnitude, is leffened in proportion to the bulk of the bo- dies with refpect to the fpace in which they move. It muft be therefore fuppofed, as we mentioned above, that the diftance of the neareft particles, flowing inthe fame and in different lines, muft exceed their diame- ter, not indeed infinitely, but.a number of times utterly incomparable with all our ordi- nary numbers, in order that a particle may efcape in one phyfical point of its progrefs: but, that it may pafs freely on thro’ the whole diftance of the remoteft fixed ftars, it is evident, that this proportion of .excefs mutt be multiplied bya number again incom- parable. But this excefs, fo increafed, muft be raifed'to a power whofe exponent is anum- ber equal to the number of all the fixed ftars, planets, and comets. And laftly, if there is an elaftic medium diffufed thro’ the mundane {pace, asthe propagation of heat™ and ma- ny other phenomena feem to.infinuate ; this laft number mutt be at leaft doubled, if we would .* Newt. Opt. queries. ad jizs | PHYSICAL any LITERARY. 17 would exprets the proportion in which the diftance of the neareft rays exceed the dia= meters of their particles: and yet this di- ftance of the neareft rays; flowing from the fame center; is fo incdmparably below our fmalleft meafiires; that théte is no poflibility of defining it. sa 6: Hav Euler confidered this extreme ra- - tity, as well as tenuity of light, which muft be acknowledged by all who fuppofe that its particles are actually projected from the’ lucid body, he would not have ‘alledged, that this opinion is inconfiftent with the freedom and perpetuity of the celeftial motions *. 7. Some have thought, that, if the parti- cles of light repel ‘one another, their’ mutual perturbation may be prevented: but the contrary is manifeft upon the leaft reflection; for tho’, by that means, the particles might |. be prevented from ftriking, they muft in- ftantly turn one another from their re¢tilinear courfes, as foon as they come, in different directions, within the reach of their mutual powers. Thus, we find by experience, it is impoffible to make one ftream of air pene- _ trate another without confufion ; for the two _ ftreams cither unite into a common one with tt.) Ui aivivindiniy 6 Giot * See his Nova theoria lucis et colorum. 18 ESSAYS ann OBSERVATIONS an intermediate direCtion, or produce irregu- lar eddies. 8. Hers, by the bye, we may fee that the ingenious fyftem of. Bofcovich,. the Roman Profeffor, .concerning the elements of mat= ter *, whatever may be faid for it from other confiderations, gives us no affliftance im com- prehending the mutual. penetration of light; for indivifible points, endued with an. infu- perable repulfive power, reaching to a finite diftance, are as fubject to interfere, as folid particles of a finite magnitude. Wg wD kw 9 Ox the Heating of Bodies by Light. 9. Ir appears, by Sir J/aac Newton's expe- riments on the inflexion of light, that, bo- dies Act upon it at fome diftance ; and that the fame power, varioufly exercifed in va- rious circumftances, is. the caufe, likeways, of refraGtion and reflexion. We know no inftance of any kind of attraction or repul- fion in Nature which is not mutual; we ob- ferve likeways that bodies are heated by the influence of the fun’s rays : it is therefore na- tural *See his Differt. de lumine et de viribus vivis. ° PAYSICAL ann’ LITERARY. 1g tural to look:uponthis:as the effed of the re- action jofight upon bodies, and: that, :at a diftance from them ;_ for,’ there is no-reafon to think:that light produces heat’ by actually ftriking the folid parts.of: bodies, «after we are fatisfied, that bodies produce the:reflexion and refraction of ‘light;- without: splenic? it to come into, contact | with theme !iu) iors ») 10. From thefe principles it follows, that light, in-pafling out ‘of one medzum into an- other of different denfityy muft>dlways | pro- duce fome degree oftheat ;, becaufe itis part- ly refracted and reflected at the common fur- face > fecondly, that, in» pafling’ forwards thro’»the fame homogeneous. or: -perfealy tranfparent medium, it can) produce no heat ; becaufe there is no reflexion ‘or refraction, no influenceof the body upon the light,’ -but every ray, purfues its own right-lined courfe, as if it moved in a perfec void *. _ \i1. Hence it appears, that, in water, glafs, and other tranfparent mediums, which | are * Sir Waac Newton, in the third book of his’ Principia, where he difputes concerning the tails of ‘cornet, ’ lays’ it down as an obvious principle, Quod radii folis non agitant media que permanant, nifi in reflexione et refractione. eo ESSAYS ann OBSERVATIONS are warmed by the fun’s rays, the heat mutt be propagated from their furfaces towards their central parts *. 12. Hence likeways we niideritand dite opaque bodies are fooner heated “by the fun- beams than tran{parent ones ; fince, there are innumerable reflexions and refractions within their fubftances, befides what happen’ in common with tranfparent bodies at their fu- perficial parts. As each colorific “particle of an opaque body, by the reaction of the par+ ticles-of light, muftbe fomewhat nioved whencthe light is reflefted backward and for- award between the fame: particles, “it is ma- nifeft:othat. they-likeways muft be driven backward and forward with a vibratory mo- tion 5. and the time of a vibration will be e- qual to that which light takes in moving thro’ a particle, or from one particle of a body to another adjoining. ‘This diftance in moft folid opaque bodies cannot be fuppofed greater than >:%55"" of an inch, © which {pace _ * Ihave found, by repeated’ trials, that the heat of wae fer in deep Jakes decreafes regularly from the farface down- wards, ‘PHYSICAL ann LITERARY: ay {pace a ‘particle of light »defecribes in pees eeees of afecond) With fo rapid a motion: (therefore may) the: inter- nal part of bodies be agitated by.the influence of dight, as to perform 125;000;000,000,000 vibrations: or\more ina fecondof time! The arrival of ‘different particles of olight:at the furface of the! fame: colorific; particle:in the fame-or differentrays, may difturb.the regu- larity of their, vibrations, but) will evidently increafe their, frequency, . orctaife fill mi- nuter vibrations among the parts which’ com= pofe thefe, particles ; . by: which: means the inteftine» motion: becomes! more :fubtile and thoroughly diffufed: If the quantity of light admitted into. the body be.increafed, the vi- brations ‘of the particles muft’ likeways in- creafe in magnitude and velocity ; till, at laft, they may be fo violent as to make all the _ component particles dafh ‘one another ta- | pieces by) their: mutual collifions: in which ‘cafe, the colour and texture:of the body muft be deftroyed, . Thus mayowe form, from known principles, fome imperfect conce- ption of the manner in which bodies are heated and burned by the ation of light : More than an imperfect notion’of thefe'fe- a cret 22 ESSAYS ann OBSERVATIONS cret operations of Nature is not to be expect- ed; for they certainly depend, in great meafure, upon laws and Son utterly un= known to us. 13. Ir one beam or ray of light). by sal fing ftraight onwards thro’ the fame pellucid fubftance, can communicate no heat to “its internal parts; neither will the» greateft quantity of rays, tho’ crowded into the nar- roweft fpacey by croffing one another.» From hence it follows, . that the portion of “air which lies inthe focus of the moft potent fpeculum is not at/all affected by the paflage lof light thro’ it, but continues of the fame temperature with the ambient air; altho’ any opaque body, or even. any tranfparent body denfer than air, when put in the fame place, would be intenfely heated: in an in ftant, 14. Turis confequence, esidenthy towing from the plaineft and moft certain principles, feems not to have been rightly underftood by many philofophers*: for which reafon, . q I * See Boerhaave element. chem. tom. 1. on fire, coroll. g- after exper. +4. and coroll. 1. and 7. after exper. 17. See allo Rutherforth’s fyftem of natural phildfophy, — prop. 366. PHYSICAL! any LITERARY. af I thought it'might be worth while to fay fomething in explication of it. The eafiett way to be fatisfied of. the matter experimen- tally, is, to hold.a hair or. down immediately above the focus of a lens or fpeculum, or, to blow.a ftream of fmoke from a pipe hori- zontally over it; for, if the air in the focus | were hotter than the furrounding fluid, it would, continually afcend upon account of its’ rarefaGtion, \and thereby fenfibly agitate thefe flender bodies. Or a /ens:may be fo placed as to form its focus within a body. of water or fome other tranfparent fubftance, the heat of which can be examined: from time to time with a thermometer: but care muft be taken in this experiment to hold the lens as near as poflible to the tranfparent bo- dy ; left the rays, by falling clofler than or- dinary on its: furface, fhould warm. it more than the.common fun-beams. _. 15. Ir is well known that the rays of light, by pafling -obliquely thro’ our’ atmofphere, Te toisw. are 366. of the aftronomital part; and Nolet lecons de phyfique, tom. 4. The filence of moft phyfical writers, con- cerning this paradoxical truth, —: it proba that ther were unacquainted with it, #4 ESSAYS ann OBSERVATIONS are inflected into a curve by the continued infra@ion arifing from the continual increafe of its denfity; therefore they muft produce fome degree of heat in every part of their progrefs thro’ it {N° ro.]. But, as the whole fucceflive refraction is “juft equal to the fingle refraction that would be made in paffing at once from the celeftial {paces into a medium as denfe -as the loweft ‘part of our atmofphere *, and all the fucceflive refle- xions that can be made from every different Jirctum, are but equal to ‘what would be made at once from the furface of 4 medium ‘of the fame denfity ; it eafily appears, by comparing the denfities of air and water, and their refpective figns of refraGion, that all the refra@tion and reflexion which the whole depth of our atmofphere produces is much lefs than what happens at one furface of wa- ter; and confequently, the heat produced in out atmofphere, by the immediate ation of light upon it; muft likeways “be much lefs than what is raifed in water. The air feems to have the greateft part of its heat communicated to it from the opaque vapours . _ which ~ * Neat. Opt. book 2. part 2. prop. 10. PHYSICAL awn LITERARY. 9 Which Aoat‘in it and the general furface of fea and land to which it is contiguous. tle 83H lg dl 5 5 Pal On the filcer-like Appeardace of Drops of ! 8 Water on the Leaves of Colewort. ; 16. It is commion to admire the volubility and laftre of drops of: rain that.tie..on the leaves of coleawort and fome other vegetables ; but no philofopher, as far as I know, has put himfelf to the trouble of explaining.this cu- tious phenomenon. Upon infpeGing them nar- rowly, i find, that fhe luftre of the drop — arifes from a copious reflexion of light from _ the flattened part ofvits furface contiguous to the plant : fe obferve’ further, that, when the drop, rolls. along ,a. part..which. has. been wetted,’ it immediately ‘lofes all its luftre ; _ the gteen plant being then feen clearly thro’ iki ‘abu aay in the other cafe, it Is hardly to be difcerned. he 17. From thefe two obfervations laid to- i gether, we may certainly conclude; Phat the drop does not really touch the plant” when it has the mercurial. appearance, but hangs Vou. II. D in 26 ESSAYS awn OBSERVATIONS in the-air at fome diftance from. it, by the force of a repulfive power; for, there) could: not be any copious reflexion of white light _ from its under furface, unlefs there were a real interval between it and the furface of the plant *, (See Tas. ili. Fig. 2.} | a8. Ir * Newt. Optics, query zo. Let AB, Tas. iii. Fig. 4. reprefent the'.extremity of any repulfive body immerfed in water, for inftance a flice of colewort leaf, CL and DM, the convex farfaces of water immediately furrounding it, and CD perpendicular | to AB, the common tangent of thefe curves, which: will be the’ continuation of the general furface of the water. The forces with which any two particles, E and F, ‘are - prefiled by the water in the dire&iions EG, FH perpendicular : to KB, are known to be as KG and KH, and the repulfive powers which balance them muft be in the fame proportion. | If therefore the relation between the ordinate and abfcifs in ' the curve DM could be any way found by experiment, the | law of the repulfive power might be determined, upon fup- , pofition that the particles are influenced by no force but the repulfive power of the line KB and the gravity of the fuper- incumbent fluid; but their mutual attration, which tends to lefien their lateral tendency, mutt be likeways taken into the account in order to an exact determination. Before I leave this fubje of attraction and repulfion, I beg leave to propofe to the Society, the fpontaneous motions of light bodies on the furfaces of fluids, as a thing worthy of being inquired into; for, tho’ it be manifeft in general that they depend upon the different figures of the furface, it is far from being an eafy matter to explain the particular cafes by mechanical or hydroftatical laws. The following account - of ‘PHYSICAL ANp LITERARY. 347 18. Ir that furface were perfectly fmooth, the under furface of the drop would be fo likeways 5 ; and would therefore fhow an image of. abe illuminating body by reflexion, like of the phenomena may be ufeful towards {uch .an enquiry. sa 1, Suppofe a fluid which is attraéted to the fide of its containing veflel, and confequently is elevated, at the fides, into a concave furface: If a body be immerfed which at- tracts the fluid, and is therefore furrounded likeways with a concave.elevation of the fluid ; as foon as the two elevations begin to join, the body will move towards the fide of the yeflel with an accelerated motion. Cafe 2. Suppofe a fluid which is formed into a convex furface, either by the! repul- five power of the containing veflel or cohefive force of ‘its own particles: Ifa light body be immerfed which attraéts the fluid ; as foon as its furrounding elevation begins to join with the lateral depreffion of the fluid, it will begin to move ~ towards the middle of the yeflel; and, if it be brought by force towards the fide, it will recede from it again with an accelerated motion. _An both the firft and fecond cafes, if the attrafting body be held faft, and the whole fluid made eafily moveable with its containing veffel, it will remoye to or from the at- tra€ting body in the fame manner as the attracting body did with refpect to it; 7.¢. in the firft cafe, the whole fluid will av move fo that the attraéting body may come to its edge; and i in the fecond, fo that it may recede from it. Cafe 3 If, in a fluid which is attraéed by the fides of its veffel, a body be. immerfed which repels the fluid, and is therefore f{urrounded with a ditch or convex depreffion of the fluid; as foon as that depreffion begins to join the elevation. of the ‘Quid at the fides, it will recede towards the middle; and, if isin. forcibly a8 ESSAYS awn OBSERVATIONS like a piece of polifhed filver: but, as it is confidetably rough and unequal, the wnder furface becomes rough likeways:; and fo, by . reflecting forcibly brought to the fide of the veffel, will fly from it with an accelerated motion. Ca/e 4. If, in a fluid which is formed into a convex furface at the fides, a repelling body be ime merfed; as foon as its depreflion begins to unite with the la- teral deprefiion of the fluid, it will move towards the fide with “an accelerated motion. In thefe two laft cafes, the fame obfervation holds as with refpe& to the fir and fecond, viz. that the whole flaid will move with correfpon- dent motions by the force of reaction, if the repelling body beheld faft. Cafe 5. Tf two bodies be immerfed in a fluid, which each of them attra&ts; as foon as their elevations begin to join, they will ruth towards one another with equal forces and accelerated motions, and continue to adhere to- gether. Cafe 6, IF two bodies be immerfed in a fluid which they repel; as foon as the two depreffions: that fur- round them begin to interfere, they will likeways ruth to- gether with an accelerated motion, Cafe 7. Tf two bodies be immerfed in a fluid, the one of which attraéts and the other repels it ; 3 as foon as the depreffian furrounding the one begins to join with the elevation of the other, they will mu-' tually fly from each other. La/ily, Ifa body be immerfed in a fluid which it attraéts in one part and repels in another, it will approach to or recede from other bodies and parts of the fluid, differently according to its fituaticn, by the rules above laid down. The different figures afcribed to the furface of the water in thefe feveral cafes are plainly difcernible by the fight : if the experiménts are made with candle-light, they are dif- al by the thadowy or luminous rings which they projet RHYSICAL snp LITERARY. ag tefleGing the light copioufly in different directions, aflumes the refplendent white coloyr of unpolithed filver.: 19. AFTER it is thus proved by an opti- cal argument \that the drop is really not in contact with the plant which fupports it, we ally: conceive’ whence its wonderful volu- bility projed on the bottom of the veflel, ce g as they are ‘eonvex or concave, Some writers have been fo inattentive as to atcha the, motions i in the firft cafe to an immediate attraftion between ‘the fwimming body and the fide of the veffel. Sve Helbam’s _ Leéiures, Before 1 had obferved the fourth and fixth cafes,- I thought the phenomena might be all explained from ‘this, rinciple, that thedight bodies always tend to the higheft arts of the water. Ithas been fuggefted to me by fome, that this tendency, combined with the greater of leffér im-. merfion of the bodies, upon account of .the ring of water. which they elevate or deprefs, may produce all the different cafes: and by others, that the whole is explicable from the fingle principle: of attraétion between the parts of water’ which caufes two drops to run into'ohe. I believe it will be found, on due confideration, that none of thefe accounts , : s fatisfaQory : but there is no reafon to defpair of coming to the bott om of thefe phenomena; fince other motions of a like kind have been fuccefsfully explained. Thus the. run- ning of a drop of oil towards the ;concourfe of two glafs- panes and the motion ofa bubble on the furface of liquors, when. the glafs is held obliquely towards that point, where the glafs is inclined to the liquor in the {mallet angle, are’ eafily underftood from the direftion of the compound force . with which the drop and bubble are acted. go ESSAYS ann OBSERVATIONS bility arifes, and why it leaves no tract of moifture where it rolls. 20. From the like reafoning,, we may conclude, That, when a f{mooth needle is made to fwim, it does not any where touch the water, but forms around.it, by its repul- five power, a ditch or bed, whofe concavity is mach larger than the bulk of the needle, [See Tas. ili. Fzg. 3.] And hence it is eafy to underftand how the needle {wims upon afluid lighter than itfelf; fince the quantity of water, difplaced by it, may be equal to the weight of the needle. Phenomena of this kind, inftead of being reduced to hydrofta- tical principles, are commonly attributed to the mere tenacity of water, and even ufed for meafuring its cohefive power. See Muff- chenbroeck, Elementa Phyfices, 21. Tuts inftance furnifhes us with a juft and neceflary correction of the common hy- , droftatical law, That « the whole {wimming ** body is equal in weight to a quantity of «the fluid whofe bulk is equal to that of “the part immerfed :” for, to comprehend this, as well as all ordinary cafes, it fhould be faid more generally, That « the whole weight of the fwimming body is equal to ce «© the PHYSICAL asp LITERARY: 38 *< the weight of the quantity of the fluid dif ‘placed by it. ; » 22. THese Phenomena appeared to me worthy of obfervation here: both becaufe they thew the fertility of optical: principles in Jeading to the knowledge of things other- ways inacceflible ; and becaufe they exhibit a clear {pecimen of a repulfive power, fimilar to that which we fuppofe neceflary for the reflexion of light from the anterior furface of adenfer medium. Nor do I fee how it is poflible to account for the fufpenfion of the drop: in the air by comparative attractions < into which fome other appearances of re pulfion have been, perhaps, not unfuccefs- fully, refolved *. . ; =n COE Te Ev: 4 On the Change which coloured Bodies undergo in different Lights. (23. Sir. Jfaac. Newton has abundantly proved, bya variety of arguments, that the ordinary colours of natural bodies arife folely from * See Furin on capillary attra&ion, at the end of Core’s , hydroflatical Lefures. , 44 ESSAYS anv OBSERVATIONS from the compounded colour of thofe rays which they reflect ; their colour being deno- minated by the fpecies of thofe primitive rays which they reflect in greateft plenty: but this part of ‘the Newtonian’ doGtrine will re+ eeive further confirmation by examining the different colours which. the fame body afflumes when illuminated by different lights; and which may ‘be called, in diftinGion - from the former, their extraordinary colours: 24: Bopres of ‘all the’ principal colours; wiz.red, yellow, green and blue, are very little altered when feen by the light of burfiing fpirits: but, if falts be continually mixed with them during the burning, agin changes enfue. ul 25. Wuen fal atmmon. siotath or alum are infufed, the colour of red bodies appears _ fomewhat faded and dirty: green and blue jf appear much the fame as’in candle-light ; both being faint and hardly diftinguifhible : white and’ yellow are {carcely at all affected. | 26. WHEN nitre or fea-falt are plentifully mixed with the burning ‘fpirits, and the . whole is ftirred about brifkly ; the brighteft ted bodies, feen by the light then emitted, are reduced..to a dirty tawny brown, that feenis PHYSICAL ‘ann LITERARY. 43 feerns'to’ have’ nothing of rednefs in it : ereen is transformed into another fort of , brown; only diftinguithable from the former _ by'a certain iulinedon to‘a livid olive-co- lout ; ‘when nitre is mixed with the ‘pirits, one may ftill fee fome remains of a greenith colour, ‘unlefs it be: poured in eeryriplentis fully :.dark: blue isshardly tobe. known’ from black, except that it appears the deeper® black ‘of the two? dight bluccis changed into'd very light brown of a peculiar kind: white affumes a livid -yellowifh-caft: ~ and! yellow: alone appears’ unaltered cand. ex- tremély ‘luminous; ‘Thefe “experiments I ‘made''with different forts of rich:coloured bodies,’ as filks, cloths and paints, Polifhed copper, which has. contracted from the air a high-flaming colour, is reduced by the fame light into: the ‘appearance of yellow brafs ; the’ faces and hands of {peCators appear like thofe of a dead corpfe ; and other mixed colours,’ which have’ red. or green in their compofition, undergo like chanives. a9: Having placed 4 pafte-board with a circular hole if'it between my eye and the flame of the fpirits, in order to diminith and circumfcribe my objedt, I examined the S eVox. Il. EB conttitution 34 ESSAYS ann OBSERVATIONS conftitution ‘of thefe different lights:with a prifm, (holding the refracting angle upwards) and found, that, in the firft cafe [N°.ag.], when. fal ammon. alum--of potafh fell into the {pirits, all forts of rays were emitted, but! not in- equal quantities ;- the yellow being vattly more copious than’ all the: reft. put together, sand -red mote. re than the: ye and blue. 28. In theclight of fpiiies mixed with niieet or fea-falt, I,could ftill obferve fome- blue, tho’ exceflively weak and diluted : with the latter, the ‘green was equally faint; but, with the former, pretty copious., But, when either of thefe falts were ufed, I could hardly fee any veftige of the red at all, .at-leaft when they were poured zz plentifully, and the {pirits conftantly agitated. At every little intermiffion indeed the red rays would fhow themfelves very manifeftly below. the hole, and red bodies feen by that light re- fumed fomewhat of their crdinary colour. =, and it was very entertaining to obferve how both would evanith again at once, as foon as the falting and ftirring were renewed. THE proportion in which the | bright yellow-exceeds the other colours in this light,. 1S “PHYSICAL ano LITERARY. ys s© fill . more extraordinary than in the former: infomuch that the hole feen thro’ the prifm appears uniformly of this yellow, and as ‘diftin@ly terminated as thro’a plain glafs; ex- cept that there is adjoining to it on the upper dide avery faint’ ftream) of green ‘and blue. White bodies illuminated with ‘it; appear alfo thro’ the prifm perfectly well defined ; both which are very furprizing phenomena to thofe who have been accuftomed to the ufe of the -prifm in‘ other heterogeneous lights, where it ‘never fails to throw confufion of the extre- _ mities of all vifible objects. ©°'29: Because -the hole appears thro’ the prifm quite circular and uniform ‘in colour 3 the bright yellow which prevails fo much -over the other colours, muft be of one de- termined degree of refrangibility ;) and the tranfition from ‘it to the fainter colour ad- joining; not gradual, but immediate. 30: Upon examining’ foap-waterifilms ‘in the fame light, 1 could only obferve lumi- nous bands feparated:bydark ones ; the green and blue: being too weak tovaffect my eye in this viewsn'Jt would be needlefs labour to enter here into a particular. detail of the rea- fons of ithe different transformations of co- 3} loured 36 ESSAYS ann OBSERVATIONS loured bodies, above related (N° 24, 25; and 26,1; fince, in general, it is evident enough, that they are owing to the different compo~- fitions of the lights with which. they.wete illuminated: the experiments, with ) the prifm [N° 27, 28.] are \ of | themfelves.a fufficient commentary upon the reft. Be he A Remark on Evxer’s Nova Theoria Lucis.et Colorum. 31. Eurer, in that. treatife, (publifhed lately along with fome other tracts, under the title of Opufcula Mathematica) endeavours to amend the Huygerzan hypothefis of vibra- tions, and fupport it againft the objections which made Newfon and his followers reje& it: we fhall not enter here upon the difcuf- fion of that queftion ; as it would require a difcourfe of confiderable length ; and the rather, that the Newtonian theory of light and colours depends not on any particular hypothetis with refpe& to the intimate nature of light (in like manner as his fyftem of u- niyerfal gravitation is independent of all hy- | pothefes PHYSICAL ax» LITERARY, gy pothefes. concerning the caufe of gravity), In, his Optics, he, lays down. his. difcoveries at-full length,, without ever inquiring whe- ther, light confifts. in vibrations, propagated thro’ .a fluid or .of. particles . proje@ted, in ftraight lines from. the luminous body : and, in. his queries, .where he touches this mat- ter *, he feems,to be more pofitive in rejea- ing the hypothefis. of vibrations, than in efta- blithing any other. 32, Bur Euler likeways : iL a new no-~ tion with refpec to the origin-of, colours in opaque bodies,» which is intirely inconfiftent with the principal part of Sir J/aac Newton’s dogtrine. He fuppofes, that cologred.bo- — dies reflect the:fun’s incident, white light from their anterior furface ; but, that the panticu- lar fpecies of light, by.which they appear coloured, is properly emitted by the parts of the body: . for inftance, he imagines, that vermilion does not appear red by a more co- | pious reflexion of red than of other,incident rays, but by, the new emifflion of red rays from. the particular velocity. of vibration which its elaftic parts are capable of concei- ying by the impulfe of the incident light. 33. It * Newt, Opt. quer. 28, and 29. | 38 ESSAYS ann OBSERVATIONS 33. Ir is a fufficient refutation of this fyftem, that no phenomena prove of require its exiftence: whereas Newton's theory not only folves the phenomena, but is dire@ly ‘drawn from a multitude of experiments. Ac- cording to Euler's hypothefis, a body of one ‘colour, placed in homogeneous light of an- ‘other, ought not to appear of the colour of the light, but of a middle one between that and itsown natural colour; which is contra~ = to experience *. 34. Ir it fhould be faid, That none of iti incident light is capable of qualifying the ‘body for emitting its proper colour, but rays ‘of the fame colour: that which ‘he calls new light emitted will be, in his fcheme;, more properly incident light reflected. 35. Tue chief or only fact which feems to have led him into that opinion, is, that there are many coloured bodies, fuch as metals, which dre capable of receiving a fine polith; and therefore of reflecting regularly the i- mages of other objects, and at the fame time retain their proper colour by which'they are {een in all pofitions. hat light by which we fee in them the images of other obje&s, he * Newt. Opt. book 1. parti2. prop. 10. PHYSICAL ‘and LITERARY. 3 he acknowledges to be incident light pro- perly reflected ; but the other, he f{uppofes, is properly. emitted from ‘the colorific, parts ,.of, the body. But what necefflity:is there of: re- curring to this fuppofition, when we know, previoufly, that thé:componentparts * of all opaque bodies are -tranfparent’; that, from’ every tranfparent body, there*is'a double re=: flexion ; part of the incident light being re fleGted at the firft furface, and apart of what’ paffes ‘thro’ the firtty tefleGed*ar the fecond?' and when we know, further, that very thin bodies; (as foap-bubbles, Mufcovy-elafs, and: _ ait inva fracture of glafs or ice, or between two /enfes) while they refle& fome rays of all: _ colour from the firft furface, refle&t only particular colours at the fecond-+? Do not thefe fats lead us naturally to fuppofe the: firftfort of light to: be only apart of the in- cident light reflected from the firft furface of the body; and the fecond, a part of what had paffed on, reflected from the pofterior farfaces of the fuperficial particles ? ) SEC T. _ * New?. Opt. book. 2. part 2. prop. 2. +f Ibid. book z. part 3. prop. 12. jo ESSAYS anv OBSERVATIONS si-tesde lan iia ce Concerning the Catife ‘of thé di ier Refrangis sole ee the Rays i. Se am £3 c fifi High IN feeder ta. sequent fon “? different; teikentn gibility of thedifferently-coloured, rays, Sir J/aae, Newtin-}rand feveral of his fallow-, ers have fuppofed,..that their particles aré.of different -magnitudes or denfities: . busy if. there be any. analogy between gravity andthe, refractive power; it-will produce equal..per= pendicular velocities in all particles, whate+ ver their magnitude or denfity be; andi fo all: forts of rays fosiedds be fill equally. re frangible. loo 37: Ir feems sscsclit a more probable: opinion, which others have advanced} that: the differently-coloured” rays: are projected: with, ~ * Altho” the dodrine contained in this feétion has been already publifhed in the Philofophical 'Tranfactions for 17535. (vid. vol. xlvili.cpart-1. p. 262,. &c.) having been communi- ° cated to the Royal Society, by the Author, in 4 letter to- the Reverend Dr. YFames Bradley D, D. F.R.S.3 yet it could not be omitted here, on account of its connexion with fome of the queries that follow; _befides that it contains fe- veral illuftrations not to be found in the Tranfactions, t+ Newt. Opt. query 29s PHYSICAL ann LITERARY. Af. with different velocities from the luminous body : the red, with the greateft; violet, with the leaft; and the intermediate colours, with intermediate degrees of velocity: for, upon this hypothefis, it is manifeft, that they will be differently refraéted in the prif- matic order ; according to obfervation. Since, according- to Sir. Waac Newton's doGrine of refraction how generally received, the velo- city of'a tay, afterentering any new medium; is, toits former velocity, as the fine of inci- dence-to the fine of-refraGtion*; if all the colouts move with equal fwiftnefs in any one medium, theit velocity will neceflarily be- come unequal, upon entering a denfer mediurns in the.inverfe proportion of their feveral fines of +efrangibility: tho’ we fuppofe, therefore, the fun’s.rays to be emitted with one. common velocity, it will follow that their velocities are unequal in air, glafs, wa- ter; or any tranfparent body, whofe refra- Give denfity differs from that of the folar at- mofphere +. This confideration is fufficient to take off the appearance of rg from our Aypothe/is. Vot. II. | F 38. Ou * Necwtoni Principia, lib. 1, prop. 95. + See below, query 3. a2 ESSAYS ann OBSERVATIONS 38. On -fuppofition that the different: re~ frangibility of the rays of light arifes folely from their different ‘velocities before imci- ‘dence; thefe velocities muft be, to one an~ other, nearly as their fines of refraction. 39. Sir IJfaac found’ their fines of refra- ction from glafs into air, beginning’ from the extreme violet, to be * as 78, 772, 772; 77% 77% 77% 77% 77% the fine: of in- cidence being 50: from whence their fines of refraction out of ‘air into glafs, © begin- ning from the extreme red; and ‘ending with the extreme°violet, are found to be a8 +P 78000, 77873, 77797) 77663, 77496, - 773,30, 77220, 77000 ; the fine ofineidence’ _ being 120120. Thefe numbers, therefore, nearly exprefs the velocities in air, of the feveral rays, before their incidence f. 40. HENCE * New?. Opt. book 1. part 2. prop. 3. + The extreme fines are plainly reciprocal to the former ; , and thofe of intermediate colours are fourth proportionals to the fine in Sir J/aac’s experiment, 77 and 78. t{ The quantities which give the accurate proportion of the velocities, before incidence, muft be in a conftant ratio: the fines of refraétion, by which the above calculations are tnade, have this condition: but, it is otherways manifeft, that they give only a grofs approximation to the truth. ~~ Bron PHYSICAL anps LITERARY. ~ 43. \.40. Hence. their velocities in any other medium, may be found ; for, they are, to thefe, , From what follows, perhaps, an exatter computation might be made, if a proper mean angle of incidence ‘were made ufe of, altho’ the quantities in the canon are really not in a conftant ratio. Tas. iii. fig. 1. Let two rays, falling in the fame line of Gncidence IC, with different velocities, upon AB the furface of a denfer medium, be refracted into different lines CR, CV. Taking any line CD in the perpendicular to reprefent the to- tal aétion of the refracting power on the lefs refrangible ‘ray, and CE on the more refrangible : If, thro’ D and E, parallels to IC be drawn, meeting the refracted rays in V, RandG; itis plain, that CR, CV will be, as their refpective velocities after refraction ; and DR, EV, as their velocities before incidence. Since the whole acceleration . which a given power produces ina body, is, ceteris paribus, as the time in which it operates; CD mutt be to CE near- ly as the time which the {wifter ray takes to pafs thro’ the refracting {pace, to that which the flower ray takes in paf- fing thro’ the fame, inverfely , as their velocities before inci- dence ; that is, as EV to DR: but CD is likeways to CE as DG to EV; therefore DR, EV and DG, are continued proportionals; therefore DR’ is to EV inthe fubduplicate ratio of DR to DG: but DR is to DG in a raizo compound- edof DR to DC, and DC to DG, that is, in the com- pounded ratio of S, DCR to S, DRC and of 8, DGC to 8, DCG; wherefore DR’is to EV in. the fubduplicate ra=- tio of S, DCR X S, DGC to S, DCG X S$, DRC; that is, ‘< The velocities before incidence are nearly in the dire&t ** {ubduplicate ratio of thefe fines and the reciprocal fub- # duplicate ratio of the fines of the excefles of the common _ ~ anole of incidence above the feveral angles of retraction,” 44 ESSAYS ann OBSERVATIONS thefe, as the fine of incidence to the fine of refraction, when a ray paffes from air into the given medium ™. 41. Wuite the differently-coloured rays are fuppofed to move with one common ve- locity, any pulfes, excited in the ethereal medium, muft overtake them at equal di- ftances; and therefore the intervals of re- flexion and tranfmiffion, if they arife in this manner, as Sir /fage Newton conjectures, would be allequal: but, if the red move {wifteft, the violet floweft, and the interme- diate colours with intermediate velocities ; it is plain, that the fame pulfes muft over- take the violet fooneft, the other colours in their order, and, laft- of all, the red ; that is, the intervals of the fits muft be leaft in violet, and gradually greater in the prifma- tic order; according to obfervation. 42. Asthe proportion between thefe inter; vals in red and violet can be affigned by ex- periment, and the proportion of their velo- cities in any medium likeways, by N° go. ; the velocity of the ethereal pulfes in any me- dium, and their diftance from one another, may be thence computed by the following rule: § Multiply # Newr, Princip, lib. 2, prop.'e. PHYSICAL ao LITERARY. 45 Multiply the product under the velocities ‘¢ of the red and violet rays by the difference «of the intervals of their fits; then divide «by the difference of the two products «which are formed by multiplying the in- terval of the fits in red by the velocity of the violet, and the interval of the fits «in violet by the velocity of red :” the quo- tient (hall exprefs the velocity of the ethereal pulfes *. - 43. Tue velocities of the red and violet in air, are, by the above eftimation, as 78: and 77 +; and the intervals of their fits are, by experiment t, as roo and 63: from whence, by the canon now laid down, the velocity of the ethereal pulfes is found to be. tothat of red light, as 79763 to 78000, ont As __* Let C denote the celerity of the ethereal pulfes, V the velocity of red light, and w that of violet, I and the in- tervals of their fits, and D the perpendicular diftance of two " faeceeding pulfes: itis plain, from the nature of the hypo- ‘thefis, that I isto Das Vto C—V, and again, D to: as C—wv to v; therefore, ex quo, Listoz as CV—Vv to Cu—Vv: from which arifes the aa ine ve = [kext y, + In the celeftial medium dity are lefs, [No 4o.] but very nearly i in the fame proportion. , News. Opt. book 2, p. 1, obfervat. T4e 46 ESSAYS anp OBSERVATIONS As light moves from the fun to us, by Dr.» Bradley's \ateft computation *, in 6, 12’) the pulfes of the ethereal duid will be: pro~ pagated thro’ the fame {pace in &y 1°. yl > 44. THE diftance between the ethereat pulfes, is, to +.the interval of the fits in-red, as the difference between the velocity of the ethereal pulfes.and that of. red light is to the velocity of red light ; that interval, there- fore, isnot much more than 2," of. the in= terval of the fits in red, and idvcreftife does not much exceed -774,5;, of an inch f.' 45. THE velocity of the: ethereal pulfes being determined, as above, from the inter- vals of the fits in the two extreme colours, as found by experiment, the intervals of the fits in the fix intermediate rays may be calcu- lated from theory; for the interval in any one colour muft be, to that in red, as a produ& under the velocity of the given colour and the excefs of the velocity of the ethereal pulfes above that of red, is to a produd under the velocity of red and the exeefs of the “* See Eames Abridg. tranfact. vol. vi. p. 157. + See note * to foregoing page. {See the table of the thicknefs of coloured plates in Newt. Opt. pate 2. book 2. “PHYSICAL avy LITERARY. the velocity of the ethereal pulfes above that of the givem colour: but, even upon the fup- pofition of the truth of our'theory, an exact coincidence between calculation and experi- ment is not to be expected till the velocities of the rays be moré’accurately determined.’ 46. Upon: the’ hypothefis of; the: different velocities of different colours, we may under-= ftand,, at leaft'in-general, whence it is, that the) intervals of the. fits® may beara propor- tion fome way. related, to the fpaces* occu- pied by the feveral,colours in the-fpectrum ; “an analogy otherways very unaccountable! Since, from the velocities of the feveral rays upon which the intervals of the feveral fits depend, arife likeways their feveral degrees of refrangibility, » which. determine the {pace occupied by each in the fpeGrum.: _,Ayp thus likeways we may conceive, how the different rays are qualified to produce different fenfations in the mind’: for, having different degrees. of impulfive force, they may caufe.vibrations of different magnitude or velocity in the optic nerve; by which, | deta vd. > > according + * Compare News, Opt. b.i. partz. prop. 3. with b.ii. _ Part 3. prop. 16th. . 48 ESSAYS ann OBSERVATIONS according to the laws of our conftitution, the ideas of different colours may be excited*; in like manneroas the ideas of different tones arife from different vibrations of the air com- fmunicated to the auditory-organ. It has been faid, That the different fenfations ex- _ cited in the mind cannot arife from the dif- ferent force of the particles of light; fince the colour of -homogeneal rays is not altered by paffing thro’ different media, tho’ their velocity be thereby always increafed or di- minifhed 4-. But it ought to be confidered, that everyoray; as it muft pafs at laft thro’ the humours of the eye in order to vifion, falls upon the-retzva with one given velocity; whatever number of refra€tions it ‘has pre- vioufly undergone: for the’ velocity of any ray in any one medium being, to its velocity in any other medium, in a conftant proportion, viz. the inverfe of the fines of incidence and refraction, when a ray paffes from the one into 'the other; it is manifeft, that each ray muft have a'certain determined velocity in any given medium, which cannot be either increafed: or diminifhed by making the ray pafs * Neavton’s Optics, query 13. ? + Mufchenbroeck, Elementa Phyfices, § 1261. PHYSICAL awe LITERARY. 99 ‘pals previoufly thro’ any number" of tran{pa- tent bodies any how difpofed*. Ir is inipoffible therefore to. know, - whe- ther‘ian alteration of ‘the’ fwiftnefs, \ with which a’hHomogeneal ray ftrikes the retina; would alter its colour ; I mean the fenfation of colour produced by it in the mind’: -fince it is impoffible to alter, at pleafure, the denfity .of that fluid —e determines its final velocity. One may diftinguith two different effects of the refractive power on the rays’ of light; viz. the’change of ‘dire&tion and change: of velocity. Sir Jfaac Newton has proved with tefpéct to the firft, That it is different ii the differentlyecolouted rays, and of a determined dégree in each: he has further proved; That refraction, confideréd in its firft effet, does not change the colour of any fimplé ray. But it appears, from what we have now faid; That none of his experiments prove the Wot. Il: G immutability * Here it is proper to obferve, that the Appothefis which fuppofes the intervals of the fits to be determined by the ve- locity of the ray, agreés well with a remarkable obfervatiow of Sir T/aac Newton (Optics, ~b. ii. part. 1: obfervs 21.) 2 iz. That thefe intervals in any medium, ata given angle of ° incidence, are of a given magnitude, without regard to the » denfity of the furrounding medium. 50 )6ESSAYS ann OBSERVATIONS immutability of fimple rays by the fecond effeéts of refraction. 47. As itis of great confequence in philo- fophy to diftinguifh between facts and -hypo+ thefes, however plaufible ; it ought to be ob- ferved, that the various refrangibility, reflexi- bility, and inflexibility of the feveral colours, and their alternate difpofitions at equal inter- vals to be. refleGted and tranfmitted, which are the whole ground-work of the New*o- nian fyftem, are to be confidered as certain facts deduced from experiment: but whether the velocities of the different rays are exactly equal, or different in the manner now de- {cribed, is no more than probable conjecture; and;.tho’ this point fhould be decided:by a method propofed afterwards, it would ftill continue uncertain, whether the fits of re- flexion and tran{miffion are occafioned by an alternate acceleration and retardation. of the motion of light, or in fome other manner *. ; And, _.* For inftance, it might be fuppofed, that every particle bf light has two contrary poles, like a load-ftone; the one of which is attracted by the parts of bodies, and the other repelled ; and that, befides their uniform reCtilineal motion, the particles of differently-coloured rays revolve in different periods round their center: for thus, their friendly and un- friendly PHYSICAL ann LITERARY. 5 And, after all, it is: no more than ‘probable conjecture, that fuch an alternate accelera- tion and» retardation is brought about by the influence ‘of pulfes excited in the ethereal medium: nay there are fome circumftances in thefe phenomena that feem hardly :intelli- gible by that hypothefis:alone ; as, why the intervals of the fits are lefs* Jin denfer mediums ; and why they increafe fo faft and in fointricate a proportion, according to the obliquity + of incidence. .. 48 AccorDING to Dr. Bradley’s beautiful theory of the aberration of light, the ftars appear to be removed from their true places to a certain diftance,: by the: proportion which the velocity/of the earth bears to the, velocity of light :It.is plain therefore, that, on our hypothefis,, a: ftar muft have a diffe- rent apparent place for every different colour; ww is, its apparent difk muft be extended >the aberration; into a longitudinal, form ring the prifmatic {pectrum, having Te its friendly poles being alternately turned towards the furfaces of bodies, they might be alternately difpofed to reflexion and tranfmifiion; and that at different intervals, in pro- portion to the periods of their rotation. _ * Newt. Optics, b. 2. part 3. PRPaS 17. + Prop. 1 5: ibidem. 52 ESSAYS axv OBSERVATIONS its red.extremity neareft to its true place. Ih the-ftars fituated near the pole of theeclis ptic,, its.length fhould continue always the fame, tho’ directed along all the different fecondaries of the ecliptic in the courfe of a year: but, in thoie whichilye in sor near the plane of the ecliptic, it fhould be greateit.at the limits of the eafterm and weftern aberrations ; the ftar recovering its colour and figure when the true and mean places coincide. But, there is no hope of difcovering, whether our hypothefis be true or falfe, by this confequence of it; for the greateft length of the dilated difk, being, to the whole aberration, as the difference of the velocity of red and violet to the: mean velocity of light, ze. as 1 to 77 nearly, (N° 39.) cannot much: exceed one fourth - part of a fecond ; for the greateft aberration is but about twenty feconds. | | 49. THE time which the extreme violet takes to move thro’ any fpace muft be, to that which the red takes, as 78 to 77. If ‘fupiter be fuppofed in a quadrate afpe@ with the fun, in which cafe the eclipfes of his fatellites are moft commodiouily obferved, his diftance from the earth being nearly equal -| to 2 PHYSICAL! Ann LITERARY. 53 to his diftance from the fun; light takes about forty one minutes of time in paffing from him to the earth; therefore the laft violet light which a fatellite reflects, before its total immerfion into the thadow of Yupiter, ought to continue, to affect the eye for a.77th part.of 41’; or 32”, after,the jred jrefleced _at the fame times gone: thatis, A fatellite, feen. from the earth, ought to change. its colour above half.a minute before its - total immerfion from white to, a livid, greenifh colour, thence into blue, .and.a¢ laft. evanith in violet, I need, f{carcely obferve, that.the fame phenomenon fhould take .place. in the time of emerfion, by a contrary fucceffion of colours, beginning with red.and ending in ; white. 50. Ir this ence fhould be aGually perceived by aftronomers, we fhall have a fufficient direct proof of the different velo- cities of the coloured rays, for I fee not to what other; caufe the phenomenon could. be rationally afcribed: If it be not, we may conclude that rays of all colours are emitted an reflected with one common veleetbycts ee dt $4 ESSAYS. and 08:5 ERMATLON S 6) Us sribhts . $,E.C TT. “VIL, ett 7 On the Inperfettion of our Knowledge’ corn ee 8 cerning the Inflexions e Fade a ‘gr. Sir Ifaac Newton went a very confi- usbalte length in examining: the inflexions of light, as well asits reflexions and refractions 3 but‘did not bring his inquiry on this head-to 4 conclufion. He tells us, that he intended once, if other ‘bufinefs had not called him off, to have made more experiments ; not for confirming him(felf in preconceived opinions, as many do; “but for difcovering the true manner in Which light is inflected, for pro- ducing: the: coloured fringes with black lines between them. He adds, however, fome queries which contain hints of What’ he had gathered: on this fubje& from his own obfervations, vz. that the rays of light differ according to their colour in their degrees of flexibility, and that they are bent feveral tines’ backwards and forwards with a fer: pentine motion in -pafling by the fharp edges of bodies: thefe'thoughts he threw out ‘in * order to incite others to a further fearch *.” | But, © Newt. Opt. p. 313. fee the firk two or three queries, °PHYSICAL ann LITERARY: 55 But,» fo’ far have’ his intentions» been difap- pointed hitherto, that few phyfical writers - feem to comprehend diftinétly the hints which he has left’concerning the manner of inflexions *;° and ‘none, as far. as I know, has BbH Ao eor oy * advanced * When any opaque body is held. at the diftance of three: or four inches from the eye, fo that a part of fome more ‘difant luminous object, fuch as the window or the flame of a candle, may be feen by rays pafling near its edge: If another opaque body, nearer to the eye, be brought acrofs from the oppofite fide; the edge of the firft body will feem to fwell outwards and meet the latter, and, in doing fo, will intercept a portion’ of the luminous pi that was feen before. © : pgarit > This phenomenon has been rafhly afcribed to the inflexion of light, by fuch as underftood not thoroughly the nature of ope nor obferved accurately the circumftances of the: faa. « Tet AB reprefent the Weaindas! ott (Tas. iii. Fig. 5:} - to which the fight is dire&ted, CD the more diftant opaque’ body,’ GH the nearer, and EF the diameter of the pupil; join ED, FD, EG, FG, and produce them till they meet __ ABoin-K, N, M and Ls Itis plain, ‘that the parts AN, MB of the Juminous obje€t cannot be feen. But, taking any~ ’ point! a between N and K, and drawing aDd@; fince the portion ¢F of the pupil is filled with light fowing from that point, it matt be vifible: any point 5 between a and’ K muft fill F a greater portion of the pupil, and’ therefore muft appear brighter. Again, any point c between 6 and K muft appear brighter than’ 4, ‘becaufe it fills a’ ‘greater portion gF with light. The pomt K itfelf, and every ether point in the fpace KL, muft appear with compleat luftre ; 56 ESSAYS anv OBSERVATIONS advanced one ftep beyond them. It is fur= prizing, that, before Sit) //aac Newton, «the world continued fo long entirely ignorant of the true theory of light and colours ; and it is no lefs. fo, that, fince he quitted the fub- ject, no further difcovery of any moment has yet been made amongft all the philofephical Societies in Europes , 52. Many luftte; fince they fend entire pencils of rays EKF, ELF to the eye: and the vifible brightnefs of every point from L towards M muft decreafe gradually as from K to N: #. ¢ The fpaces KN, LM will appear as dim fhadowy borders or fringes adjacent to the edges of the opaque bodies. When the edge G is brought to touch the right line KF, the pe- humbra’s unite; and, as foon as it reaches NDF, the above phenomenon begins: for it cannot pafs that right line without meeting fome line aDd drawn from a point between N and K, and, by intercepting all its rays that fell upon the pupil, render it invifible. In advancing gradually to the line KDE, it will meet other lines ED/, cDg, o&c.and therefore render the points 4; c, &%. from N to K facceflively invifible; and therefore the edge of the fixed opaque body CD muft feem to {well outwards, and cover the whole fpace NK, while GH by its motion covers MK. When GH is put to a greater diftance from the eye, CD continuing fixed; the fpace OP to be pafled over for intercepting NK is lefs; and therefore, with an equal motion of GH, the apparent fwel- ling of CD muft be quicker ; which is found true by expe- tience. If ML reprefents a luminous objeét, and REFQ_ any plane expofed to its light; the {pace FQ will be entirely ~ fhaded > PHYSICAL atv LITERARY. 49 g2. Many ingenious men have beftowed infinite thought’ and labour on the more complex.i.and aftonifhing «phenomena, of Nature, without arriving at any certain or definite difcoveries ; fuch as: earthquakes, thunder. and . other’ meteors, magneti{m, eleétricity,| vegetation, fermentation. and other chemiéal’ operations: .and the, fubtilty of thofe);matters will probably continue to clude the fearch of ldteft'pofterity. But, in the fimpler, fteadier; and, more regular fub- jects, fuch as light and colours, which. are capable of accurate menfuration and mathe- matical reafoning, a fagacious and induftri- ~ ous obferver can hardly fail of. making. fome progrefs ; efpecially ina branch of the in- quiry which is already pufhed to a confider~ able length. Difcoveries of this kind are capable of a particular fort of proof which is very beautiful and convincing, from the exact coincidence of the computed effects” Vor. Il. H | with fhaded from the rays, and the fpace FE will be occupied _ by a penumbra gradually darker from E to F: Let now GH continae fixed, and CD move parallel to the plane EF ; _ and, as foon as if is paffes the line LF, it is evident, that the f itadow QF will feem to fwell outwards, and when CD “teaches ME fo as to cover with its fhadow the fpace RE, QF by its extenfion will cover FE. This is found to hold | true likeways by experiment, 58 ESSAYS ann OBSERVATIONS with the real ones, as to quantity. Many mftances of this occur in Sir J/aac News ton’s writings, and in all mathematical philo- fophy: fuch as the calculation of | the moon’s irregularities; of the tides; of the preceffion cf the equinoxes; of the refiz ftance of fluids; and, in optics, his'compu- tation of the dimenfions of the rainbow ; of the aberration of colours ; ; of the inter- vals of the fits of reflexion and tranfmif= fion; and of the coloured rings reflected by thick tran{parent Speculums. ai further I have to offer cohcerning light and colours, confifting chiefly of doubts; . difficulties or loofe conjectures, fhall be pro< pofed under the form of queries. oO Tt. PHYSICAL ann LITERARY. 59 al oe Oe Ole WA's 118 Queries, confifing of Doubts, Difficulties, and Conjectures, concerning Light, Colours, and coloured Bodies. ° Qdery I. Are not the rays, emitted by all forts of luminous bodies, fimilar. to thofe of the fun, both as to colour and degrees of refrangibility ? And, do not luminous bo- dies differ from one another only according to'the colours which they emit moft. plenti- fully, in like manner as opaque bodies are _ diftinguifhed by the colours of incident light which they refle& in greateft abundance? _ (See N° 24, 25, 26, 27, 28, and 29.) But, to make our induction fufficiently ftrong, _ ought not experiments to be made with the ~ lights of a greater variety of ‘bodies? And would it not further conduce to the illuftra- tion of this queftion to form, by Sir J/aac’s method *, a beam of folar light, confifting of fuch colours and in fuch proportions as _ were feen.in the lights of falts and burning fpirits ; and then to obferve in it the appear- es ance * Newt. Opt. hook 1. part 2. prop. 11. 6o ESSAYS ann OBSERVATIONS ance of coloured bodies? Further, are not the intervals of the fits, inrays of any one colour, the fame in the fame medium, from whatever luminous body they are emitted ? For, if thefe intervals were different, would there not be changes in the colours of bodies not to be accounted for by the compofitions of the lights with which they are illuminated* ¢ ‘Quer. II, Do not all luminous bodies, the moft languid as well as moft bright, emit their lights of any one colour with one de- terminate velocity ; fince it is found by ex- perience that they are all equally refracted by the fame medium? And therefore, does not the different fplendor of luminous bodies proceed wholly from the different denfity of their light at equal diftances? And is not this confirmed by the equality of Bradley's aberration of light in fixed ftars of all mag- nitudes +? If this be fo, the comparative f{trength of different lights, fuch as of the fin, moon, a candle; Gc. may be eafily eftimated by finding the greateft diftances to which the fame opaque body is vifible when Yluminated by each of them, or the limits be- yond * See Art. + Zames's Abridg. of. tranfagt. vol. 6, p. 158. PHYSICAL ann LITERARY. 61 yond which it is invifible to a given eye ; for the denfities of the incident lights are nearly as the {quares of the diftances of thefe limits from the obje@ *. Does not all light move with the fame velocity after reflexion as before; fince the angle of reflexion is al- ways equal to the angle of incidence? The exception, made by fome, of electrical light is founded on no lefs a miftake than con- founding the luminous body with its light +. - But, the beft proof of this propofition is from the coincidence of the computations of the velocity of light, from the equation of the eclipfes of Supiter’s fatellites and the aber- ration of the fixed ftars f, QUER. * Let A and a (Tas. iii. fiz, 6.) denote the fame or two equal bodies of the fame colour ai with different jights, and B, 4, the limits. As we fuppofe the light re- ceived by the eye, at thefe points, is juft fufficient to affect _ it fenfibly and no more, the two lights at thefe different di- _ ‘ftances muft be nearly of the fame denfity ; .taking therefore gm AB a line Af equal to ab, the denfity of the light at @ muft be, to the denfity of the light at 4, nearly as AB? to Adz; and, it is evident, that thefe denfities, at equal diftances, muft be as the whole quantities of light reflected; and thefe again very nearly asthe whole quantities of light incident. TT Mufchenbroeck's Elementa Phyfices, late edition, in his chapter on eleétricity. | E Aames’s Tranfaa. vol. vi. &c, 62 ESSAYS ann OBSERVATIONS Quer. III. Is light emitted with the fame velocity, in whatever medium the luminous body be placed? Or, is it not rather emitted with greater velocity in denfer mediums, and - that in proportion to their refractive powers? The fame argument from. whence we gather in general the equal velocity of light emitted by all forts of luminous bodies, feems to prove the truth of the latter fuppofition. For, fince rays of any one colour, fromthe fun andacandle, for inftance, are equally refraied by a furface of glafs or water, we may conclude, that their velocities in air are equal. . Wherefore, if the denfity of the fun’s atmofphere, contiguous to his furface; be different from the denfity of our lower air, as may be fafely prefumed, his rays muft have been emitted with more or lefs yelocity than that of the candle; otherways, they could not have the fame velocity after- wards in any common medium: for, the ve- lecity with which any ray is emitted, is, by the laws of refraction, to its velocity in any given medium, as the fine of refraction to the fine of incidence, when a ray pafles from the PHYSICAL axp LITERARY: 63 the medium of emiffion into the given medium. >: Quer: lV. Ir the ntadafiliaere: is not much warmed ‘by the paflage of’ the fin’s light ‘thro’ it, ‘but ‘chiefly by its*conta& with the heated {urface: of the globe,’ as we’ fhewed above (N° 15.); may wenot hence ‘give one very fimple and plaufible reafon, why it is coldeft ‘in all climates on the tops of very high mountains; namely, becaufe they are removed to the greateft diftance from the general furface of the earth? For it is well- ‘known,’ that’a fluid heated by its - conta with a folid body decreafes' in heatfia forme inverfe proportion to the’ diftance’ from the body. - But, to have this ‘queftion fully de2 termined, the’ temperature ‘of the air inthe valley and on the mountain-top muft ‘be ob- ferved every hour both night and _ and " carefully compared together. | © Quer. V. From what has been Lad: down in Sect ii. concerning the manner of othe action of light in heating bodies, is it'not _ reafonable to fuppofe that the heat produced _ by a given number of. trays, in an opaque. | ad of a given aaa i muft be greater : when & 64 ESSAYS ann OBSERVATIONS when the rays are more inclined to one another, than when they are lefs fo? For the direction of the vibrations, raifed by the action of the light, whether in the colorific particles or thofe of. an inferior order, will more interfere with one another ; from whence the inteftine fhocks and colli- fions muft increafe : befides this, the colori- fic particles of opaque bodies being dif- pofed in various fituations, perhaps, upon the whole, the rays will fall more directly on.each, the more they are inclined to one another. Is not this the reafon-of what has been remarked by philofophers* +, That the heat of the fun’s light, colleGied into a cone, increafes in approaching the focus in a much higher proportion than according to its denfity? That the difference of the angle, in which the rays fall on any particle of a given magnitude placed at different diftances from the focus, is but {mall, is no proof that the phenomenon cannot be afcribed to it; fince we know not in what high proportion one or both the circumftances now mentioned may operate. However, that * Boerhaave, Element. chemic. de igne. + Mufchenbr, Elementa Phyfices, § 1040. PHYSICAL Asp LITERARY. 63 that it proceeds not from any. unknown action of the rays upon one another, as has been’ infinuated *, is evident from this, that each particular ray, after ‘pafling thro’ the focus, prefervés its;-own colour and ~ its own direGtion; ih the fame manner as if it were alone. Quer. VI. May-it not be ieerdeds shal the component parts of opaque bodies are greatet than thofe. of tranfparent ones, as _ theory requires +; from this fimple obferva- tion, that the former, fuch as metals, {tones; woods, €&c. when broken tran{verfely, fhew a vifible ,roughnefs and inequality at, the fra€ture ; whereas the latter, fuch:as glafs; _ chryftal, gems, ice, &c. appear ‘as fmooth; _ almoft; as when they are polifled ? Quer. VIL Do not Newton’s experitnents _ with the ifland and rock chryftal fufficiently prove, that the rays of light have different permanent properties in their different fides, relative to thefe two bodies?) Mutt we not therefore conceive each particle of light to _ preferve its pofition invariably while it moves forward, at leaft fo as not to revolve round -©Vor. Ik . I its * Muffchenbroeck’s Blementa phyfices, § 1040... + Newton's Opt. Book 2: part 3. props 4: 66 ESSAYS ann OBSERVATIONS its center perpendicularly to the direction of its motion? Would it not be proper to try how light is inflected in paffing clofely by the feveral angles and fides of thefe foffils? Quer. VIII. Is it not poffible to prove by experiment what Sir J/aac Newton takes for granted as a reafonable fuppofition, that thin tranfparent plates, of any uniform colour, divided into fmaller fragments, would com- pofe a powder of like colour *? And would not this tend to ftrengthen the analogy be- ° — tween the colours of fuch plates and thofe of natural bodies ? For this purpofe, I have tried to freeze foap-bubbles ; but could ne- ver make, any ftand till they were turned to ice, except fuch as were too thick to have lively colours : however, I doubt not, but; with due care, the thing. might be done ; efpecially, if the foap-water, inftead of be- ing blown with a pipe into bubbles,..were drawn out into a plain plate upon any wooden or metalline frame : for, the fides of a plain furface beating a greater proportion to its area, than a bafe of a fpherical fegment to its furface, the froft would be fooner com- municated: Newton's Opt. book 2. part 3. prop.'s. PHYSICAL anv LITERARY. 67 municated to the whole water in the former cafe than in the latter. There is this advan- tage too in ufing a plain furface of foap-wa- ter, that, before it freezes, the obferver may draw out’ any particular colour: or feries of colours, which he chufes, toa greater breadth, by ftroaking it along with a wet finger. For this reafon, amongft others, _ I have found it a more convenient fubje& for examining the various orders of colours; than fpherical bubbles adhering to a plane. Per- haps, melted rofin might be drawn out into a thin-coloured plate before it hardens’; for I have often blown it into bubbles with a to- bacco-pipe till it became coloured: I know no other ways in which the various orders of co- Jourscan be preferved for deliberate infpection, but either in a frozen plate of water or rofin, orin the permanent fcorza that appear on heated metals. I have counted, on the fide of a clean-polifhed: copper tea-kettle, the - fix firft orders of colours diftinGly and regu- larly ranged in the fame fucceflion in which they appear in the foap-bubbles ; the firft or- _ der being formed on that part of the kettle ? shat had been leaft heated. ear, 68 ESSAYS anp OBSERVATIONS ~ Quer. 1X. Wuar elfe is the inflexion of light towards the fine edges of bodies'than a particular cafe of refraction, in which the rays, after being bent by the attractive power, are carried beyond the) refracting {urface, and mifs entring it, becaufe of its fmall, extent? For, if the furface of the edge be produced, it will meet the inflected rays; and thus the» inflexion. will become properly refraction. »And, in like manner, we may confider the inflexion of light off from the edges of bodies, as a {pecies of re- flexion. f Quer. X. Is it not impoffible that an ani- mal can fee, if the diameter of its eye be much lefs than the interval between the fits of tranfmiffion and reflexion in water, that js, than --75>;"" of an inch? ) Quer. XI. Ture are many’experiments which thew that a yellow and blue ray mixed, make a-green one; a yellow and blue powder, a green powder; and a mixture of rays or paints of all the prifmatic colours, a white ray or paint : Now, do not the fame experiments equally demonftrate, that the idea of green is a confufion or mixture of the | | ideas PHYSICAL ano LITERARY. 69 ideas of yellow. and blue ; the idea of white, a mixture of the ideas of all the colours ; and, in general, the ideas of all compound colours, a mixture of the ideas of their conftituents? In the experiments which Sir J/aac Newton performed with the toothed inftrument, the component colours are not, indeed, prefented to the eye ¢ all at once; yet they follow one another in fo rapid a fucceflion, that their refpective impreffions remain in the eye till they are renewed, and therefore they muft affect the mind all at once*. Ifa piece of paper * It isin this manner that philofophers explain (Neaws. (Opt. Quer. 16.) the appearance of a fiery circle, which is made by a burning body whirled about fwiftly. We thall here give an account of fome other phenomena that flow from the f fame principle. If a white rod be moved rapidly backwards and forwards with an angular motion, the whole circular fpace which it uns over will appear whitifh; bur nor equally fo, being faintet and moft dilute in the middle, and brighter towards the two fides, which feem to be diftinfly terminated with two white rods interfe@ing each gther in the center of ro- tation. (See Tas. ili, Fig 7.) _ The total impreffion made upon the eye by equal fmall _ parts of the fe€lor muft be, as the quantity of light emitted from it and the frequency of the returns of the rod to it; i. @. inverfely, as the time between the returns of the rod. Let go ESSAYS ann OBSERVATIONS paper be daubed all over with fmall dots of blue and yellow, it will appear green to an eye which i is placed at too great a diftance to di- . ftinguifh “Let ABC erent the circular fe&tor, pe DC Apne be “feGting it; the rod always returns to DC after the time of of one vibration; and, to any other line EC between DC and AC or AB, the mean time of its return is the fame; for jt alternately returns in twice the time of defcribing AE, and twice the time of defcribing EB; fo that two fuc-’ ceeding intervals of its returns are equal to the time of two: vibrations : but the intervals of the returns to the lines AC. or CB are manifeftly equal to the time of two entire vibra- tions. ‘The brightnefs of the fefor therefore in DC, or any Hine between DC and AB or BC, muft be fimply as the quan- tity of light emitted from equal {mall portions of the fector ; that is, in the inverfe proportion of the velocities of the rod when in thefe lines... Tt is plain from this, that the feétor mutt be incomparably brighter in AC and BC, where it refts, than any where elfe, notwithftanding that the intervals of yeturn thither are double; that is, it will appear to be bounded diftinGly with a white rod on each fide. If the rod be agitated with {mall and quick vibrations of its own, by flicking it againft fome folid body immediately before it is hurried backwards and forwards with the angular motion, the fector appears divided, at equal intervals, by a great many diftin& rods, almoft as bright as the two Jateral ones (TAB. iii. Fig. 8.) refembling the {pokes of a f{pread fan. The reafon of which curious phenomenon is plainly this ; that its angular motion, being alternately in the fame and ina contrary direction to its particular vibrations, is alternately accelerated and retarded or ftopt. In the interval, where.it is accelerated, the feCtor muft appear very dilute ; and, where it “PHYSICAL avn LITERARY. 9% ftinguifh the feparate- points. In whatever manner fenfation be performed, it is certain; that the organs which receive the firft im- pulfe- from external objeGs' cannot convey to us any ideas, if they; or the impreffions made by them, be lefS ‘than of a certain definite magnitude. A numiber of things feparately intangible, if joined together, may be felt by the touch: A certain number of invifiblé points become fufficient to affe& the fight by their united rays ; and acertain number of founds too {mall to be heard feparately, at 95 form an audible found *. “Obait “Gtis ; greatly retarded or brought to reft, muft appear very Juminous or divided by white rods, for the fame reafon that they appear at the fides. * Some Sceptics have difputed apis the endlef divifis _. bility of quantity, becaufe the imagination foon arrives at 2 | minimum ; alledging from thence, that our idéa of extenfion “Gnvolves the notion of indivifibles, and’ is as it were com pounded of them. Nothing corporeal’ can be imagined or conceived at all which is not conceived as /een, Sandled, or otherways fenfibly perceived. Imaginative ideas are nothing. elfe than tranfcripts or images of fenfations, and therefore mutt be limited by the fame bounds and in the fame manner as fenfation. Now the. minimum /enfibile.is rather in all cafes a confufed, indiftin& and uncertain tranfition from pers _ eeivable to not perceivable, than the clear perception of a “point: indivifible in magnitude ; 3 for its magnitude depends on 72 ESSAYS ann OBSERVATIONS - Quer. XII. Since bodies derive’ their colours from the original and immutable qualities of thofe rays which they ‘reflect moft copioufly, ought they not to appear of the fame colour, whether viewed at the greateft or leaft diftances? Whence is it therefore, that the planets whofe folid parts are probably covered with vegetables, and muft therefore reflect a great fuperiority of green on the luftre of the objeét. That nothing can be conceived or imagined which is lefs than a certain bulk, is no more an argument againft the endlefs divifibility of quantity, than that nothing can be felt or feen below that fize ; which, it is ‘evident, from every magnifying glafs and from every diffe- rent diftance of an object, depends not at all on the confti- tution of the thing perceived, but on that of the-perceiver, or the means and circumftances of his perception. + Nor, tho’ it were granted that the minimum wifibile is di- flin@tly feen as an indivifible point, would it follow, that the idea of extenfion, received by fight; is made up of the ideas of indivifibles; for we receive the idea of extenfion by that motion of the eye which is neceflary to dire& its axis to different objeéts or parts of an obje&: and, it is well known, that the generation of quantity by motion is preferred by the beft writers, for this very reafon, that it neceffarily excludes the notion of indivifibles. It fhould be remembered likeways, that a vifible object is not divided by the eye into a number of contiguous minima vifibilia ; for; to whatever mathematical point in the objeét the eye is di- refted, a minimum wvifibile may be feen there by means of a ¢ertain portion of the objet immediately farrounding it, PHYSICAL any LITERARY. 93 green rays,” appear almoft intirely white when viewed from thé earth ?» May not this be accounted for, in the fame manner as the change of colour obfervable in earthly ob- jects feen thro’ a great tra ‘of ‘the atmo- fphere?) A mountain’ covered’ with ‘the frefheft verdute; at the diftance of twelve or fifteen milés, ‘lobks ‘Blueifh’; and'at twenty or thirty, efpecially if the’ air be ‘thickened; ; degenerates’ into’ a dim white,’ fo’ that “oné! can hardly diftinguith i it'from ‘the clouds that’ fkirt the horizon. With refpec: ‘to the pri-. mary planets, it! may bé likeways anfwered,' that perhaps we fee them chiefly ‘by light. reflected from the air i are that for round Racine ae RAO Quer. XIII. Why is it fo hard to aiftine } guith green bodies” from blue’ cf caridle-' | ee! ji ~ Quer. XIV. Whence proceeds lie blues: nefs of the fky?' Since it is certain that no: body affumes any particular colour, but be! _ eaufe it refleéts oné fort 6f rays more abun+ _ dantly than the reft'; and fince! it cannot be’ | fuppofed that the°conftituent «parts of /pure” _ air are grofs enough to feparate any colours of ete eee os ich we not conclude, | with Vor. I. K ’ Sir 74 ESSAYS ann OBSERVATIONS Sir Ifaac Newton™, that the violet and blue- making rays are refleCted more abundantly than the reft, by the finer vapours diffufed thro’ the atmofphere whofe parts are not big enough to give them the appearance of vifible opaque clouds? Do not thofe who fay +, that the ethereal blue proceeds from the mixture of the fun’s white light. reflect- ed faintly by the atmofphere with the perfect blacknefs of the celeftial {pace behind, re- vive, without any neceffity, the antient con- fufed notion, that all colours may be formed by certain. compofitions of light and fhade ?, Altho’ the atmofphere reflects more blue rays than what go to the formation of perfec white, it is eafy to conceive how coloured. bodies, illuminated by it, may not be fenfi- bly tincétured with blue. Let us fuppofe, that the atmofphere reflects + more of blue rays than of the other colours, and that ver- milion refle@ts 22 of the red rays incident upon it, and = of every ‘other colour; then, it isclear, that the red rays, reflected by the vermilion, will ftill exceed the blue reflected by it, as.1g exceeds r +2: fo that * Opt. book z. part 3. prop. 7. "+ Nature difplayed, vol.iv. And Jfu/chen. Phyf. § 1403. “PHYSICAL ann LITERARY. 73 that the purity of its red colour will not be fenfibly impaired. But, to thew that, in _ proper circumftances, the blueith colour of fky-light may be {een on bodies illuminated by it, ‘as it’is objected fhould always hap- pen*; expofe to the fun-beams, on 4 clear cloudlefs day, a fheet of white paper, and place on it any opaque body ; you will per- ceive that the fpace of the fhadow, which is illuminated only by the fky, appears remark- ably blueith, compared with the reft of the paper which receives the fun’s direct rays. If certain white and black paints mixed together produce blue, it is becaufe the black 1s not perfect thade, but a dark blue or purple + f- Any mixture of whitenefs and true black can only forma fainter white or grey, which has no more affinity with blue than with red or any other colour, ~ Quer. XV, Is not the opinion which Sir q Yfaac Newton feems to have had |], and, fince him, the generality of philofophers, con- cerning the caufe of the various colours re- flected - ¥ Mufchen. Phyf, § 1403." + Ibid. § 1172. Neat. Opt. book 2. part 3. prop. 7. {| Opt. book 2. part 3. prop. 5, near the end. 76 ESSAYS anp-OBSERVATIONS flected by the clouds at.fun-rifing and fetting, liable to great difficulties? For, why fhould the particles of the clouds become, .at that. particular ‘time and neyer at any other, of {uch magnitude as to feparate thefe colours? And.why, are they rarely, if ever, feen tin- tured with, blue and green, as well as red, orange and yellow? Is it. not more credi- ble that the feparation of rays is made in paf- fing thro’ the horizontal atmofphere?. and that the clouds only reflect and tranfmit the. fun’s light, as any half, tranfparent colourlefs. body would do in their. place ?. For, fince the atmofphere, .as was faid in the laft query, reflects a greater quantity of blue and violet rays than of the reft, the fun’s light, tranf> mitted thro’ it, qught to draw towards yel- low, orange, or red; efpecially when it, paffes thro’ the greateft tract of air: accord- ingly,,every one muft have remarked, that the fun’s horizontal light is fometimes fo deeply tinctured, that objects directly illuminated by it appear of a hi; ch orange ar even red ; at _ that inflant, is it any wonder that the colour- lefs clouds refle@ the fame rays in a more bright and lively manner? It is obfervable, that the clouds do not commonly “affame ow reriely : PHYSICAL: ayp LITERARY.: 77 their brighter dyes.till the fun .is fome mig. nutes fet ; and.that they pafs, from yellow to a flaming golden colour ; . and: thence, ; by degrees, to red; which turns deeper and deeper, tho’ Cae. till the fun leaves them altogether... Now, it is plain, that the clouds, at that time, receive the fun’s light thro’ a much longer. tract. of air. than we do at, the inftant of fetting, perhaps. by the diffe-. rence of a hundred miles or more ; as may. be, computed from their height or the duration of their colours. Is it not, therefore,’ na- tural to imagine, that, as the fun’ s light be- comes always. fomewhat yellowith or orange in paffing thro’ ‘the depth of the atmofphere horizontally, it ought to incline more and more from orange towards red, by pafling thro’ a till greater length of air; fo that the clouds, according to their different altitude, may aflume all the variety of colours, obfer-" _yed in them at fun-rifing and fetting, by barely reflecting the fun’s incident light ‘as they receive. a IT have often obferved with pleafure, when in Switzerland, that the’ {nowy fummits of the 4/fs turn more and ‘more reddifh after fun- fet; in the fame manner as the clouds. What makes the fame 78 ESSAYS ayp OBSERVATIONS fare colours much more rich and copious in the clouds, is their femi-tran{parency joined with the obliquity of their fituation, Doxs it not greatly confirm this explica- tion, that thefe coloured clouds immediately refume that dark leaden hue which they re- ceive from the fky as foon as the’fun’s direct rays ceafe to ftrike upon them? For, if their gaudy colours arofe, like thofe of the foap-bubble, from the particular fize of their parts, they would preferve nearly the fame colours, tho’ much fainter, when illumi- nated only by the atmofphere. About the time of fun-fet or alittle after, the lower part. of the fky, to fome diftance on each fide from the place of his fetting, feems to incline to a faint fea-green, by the mixture of his tran{mitted beams, which are then yellowith, with the ethereal blue : at greater diftances, this faint green gradually changes into a red- difh brown; becaufe the fun’s rays, by pafling ‘thro’ more air, begin to incline to orange: and, on the oppofite fide of the hemifphere, the colour of the horizontal fky inclines fenfibly to purple; becaufe his tranfmitted light which mixes with the azure, by pafling thro’ a fill greater length of PHYSICAL ann LITERARY. 79 of air, beanie reddifh ; as we have faid above. To underftand. diftin@ly why. the. Sais tays, by pafling thro’ a greater and greater quantity of air, change by, degrees. from white to yellow; thence to orange, and laftly to red, we have only to apply to the atmo- fphere, what Sir Jfaac fays (Book I. of his Optics, part 2. prop. 10.) concerning the colour of tranfparent liquors in general. Is it not. the fame coloured light of the tifing and fetting.fun which tin€tures the clouds, that, being thrown by the refraction of the atmofphere into the earth’s thadow, gives the moon fometimes, in total eclipfes, the obfcure reddith colour of brick? As the rays which pafs thro’ the greateft tract of ~ air, become reddifh; thofe which pafs thro’ the leaft, yellowifh; and the intermediate ones, orange: the red muft converge fafteft into the fhadow’; after them, the orange ; and laftly, the yellow: fo, that the whole {pace of the earth’s fhadew, from the point ef the cone to about — femidiameters from _ the earth, being filled with a faint light, _ whofe colours verge always more to red in eppe oaching the earth; the colour of the RES moon, 80 ESSAYS ann OBSERVATIONS - moon, in total eclipfes, muft needs vary likes ways, according to her diftance from the earth at the time of obfervation; and) if I miftake not, be always more inclined to red at entering arid leaving the thadow,. than in the middle. Let'Aftronomers determine, whether ‘the phenomena agree with ‘this theory. It is not furprizing, that this re- - fracted light is very-faint and obfcure at the diftance of the moon ; ‘-fince its mean denfity there, will be as much lefs than the denfity of the light of the fetting fun, as the annular {pace of the lower air thro’ which it paffes, drawn into the moon’s horizontal parallax, is lefs than the area of a great circle of the earth drawn into four times the excefs of the horizontal refra€tion of the atmofphere above the fame parallax; that is perhaps as i to or more. Quer. XVI. Ihave obferved, when at fea, that, tho’ I prefled my» body and head firmly to a corner of the cabin, fo as to be at teft in refpect of every object about me, the different irregular motions of the fhip, in rolling or pitching, were. ftill difcernible by the fight: How is this fact to be reconciled to optical principles? ~ Shall we conclude; that the eye, by the fudden motions of the vefiel, ; POR See — PHYSICAL awn LITERARY: 28% veffel, is rolled out of its due pofition? Or, if it retains a fixed fituation in the head, is the perception of the fhip’s motion owing to a vertigo in the brain, a deception of the imagination; or to what other caufe ? Quer. XVII. Has not gold been reduced, by beating, to a degree of thicknefs little exceeding that which mutt be afcribed to its colorific parts, according to Sir J/aac New- ton’s theory? But, how can it cohere into a continuous leaf, fo as to leave no vifible pores, unlefs there be many of its compo- nent particles contained in its thicknefs ? Quer. XVIII. Wuen one looks ftedfaft- ly at Szrzus or any bright ftar not much ele- vated above the horizon, its colour feems not _ to be conftantly white, but appears tinctured, at every twinkling, alternately with red and blue: To what is this appearance owing ? Is not the feparation of colours by the re fraction of the atmofphere too fmall to be perceived ? - Quer. XIX. Bopizs become black i burning; becaufe they are reduced* into very {mall parts: but, whence is it; that VoL. II. L moft. * Newt. Opt. Book iii, part 2. prop. 7. $2 ESSAYS ann OBSERVATIONS moft bodies, when further burned to afhes, affume a grey or whitifh colour? Quer. XX. Since the caufe of blacknefs in bodies is the fmallnefs of their tranfparent parts, which renders them incapable of re- flecting any colour ; how can black bodies, folid or fluid, be at the fame time opaque? Can light ‘be finally ftifled by the refractive powers of the particles alone? or, ought it not rather to make its way thro’ the body, if there be no reflexion, without any fenfible lofs, altho’ the feveral rays might iffue in various directions? And, may it not be de- manded, in like manner, concerning all co- toured opaque bodies, How ail forts of light ean be ftifled and ftopt within a body, whofe internal parts are fitted to reflect only one or two colours, and tranfmit all the reft? Quer. XXI. Ir the parts and pores of pellucid bodies be much lefs than the leaft interval between the fits of reflexion and tranfmiffion ; it is plain, that rays of light, entering a part or pore ina fit of tranfmiffion, will not be refleGted at its back furface: and thus it may be underftood, how all rays that enter the firft furface of a tranfparent body continue to be tranfmitted thro’ its fubftance to ; : \: PHYSICAL ann LITERARY. 83 to the greateft diftances, v/z. if the rays are always put into a new fit of moff cafy tran{- miffion at entering every new pore er particle, But is not that fuppofition contrary to what Sir J/aac.teaches elfewhere ; That the fits of reflexion and tran{miffion continue to return at equal intervals, after a ray has entered a tranfparent body, and are thus regularly pro- . pagatedto the greateft diftances*? And, if this be true, how can the rays be tran{mitted to any fenfible diftance, fince they muft often arrive in fits of eafy reflexion at the common furfaces of pores and particles? But, altho’ it could be underftood by the doctrine of the fits in light why there is no reflexion from the interior parts .of water and other pellucid mediums +, does not the rectilinear tranfmiffion of light thro’ thefe bodies in all direGions, and confequently in all degrees of obliquity; to their internal parts, prove, that thefe parts, upon account of their minutenets, lofe. their powers of refraction as well as. reflexion? And to what known property of light or bodies can this be attributed? ; QUER, * Newt. Opt. Book ii. part 2. prop. 12. ~ +f Ibid. Book ii. part 3. prop. 4. 84 ESSAYS ann OBSERVATIONS Quer. XXII. Ir the fits are produced by an alternate acceleration and retardation of the particles of light, fome of the particles, which are fwift enough to be tranfmitted at the firft furface of a tranfparent medium, muft overcome the reflecting power more eafily than others; namely, thofe that happen to be in their ‘point of greateft celerity or neareft to it: Now, muft not rays that are moving with different velocities be different- ly bent from their courfe, as we argued above with refpedt to fimple-coloured rays, by the fame refractive power? Why there- fore is not every beam of light, homogeneal or heterogeneal, diffufed by refraction into innumerable rays, according to the refpe- étive velocities with which they entered the refracting furface? Is it a fufficient anfwer to this query, That rays which are fartheft from their point of greateft {wiftnefs will be moft bent in a direction contrary to that of ~ refraction, by the reflecting power, and will therefore only return to the direction of {wifter rays by a greater degree of refraction? Quer. XXIII. Sir Yaac Newton juftly ar- gues, that light muft be reflected at a diftance from bodies; becaufe the moft polithed fur- face, PHYSICAL ann LITERARY. — ge face, being extremely rough and uneven in tefpect of the particles of light, would di- {fperfe them indifferently in all directions, if they rebounded from it by ftriking: But, will not the like difficulty ftill remain, viz. how light can be reflected or refracted regu- larly by the beft-polifhed furface, if the power of the body proceeds from an attra- ion or repulfion belonging ‘to each phyfical point? It might be perhaps fuppofed, that the repulfive power produces reflexion at a diftance fo great, in refpect of the inequa- lities that are left in polifhed bodies, : that the direction of force, refulting from their joint action, may be very nearly perpendicular to the general furface of the body ; and this might tend to account for the regular refle- xion from the anterior furface of a denfer _ medium. But, will this fuppofition fuffice for explaining the regularity of refra@tion, and of reflexion, from the pofterior furface of adenfer medium: in both which cafes, the light muft actually enter the pores of the attracting body, and therefore approach -much nearer to one inequality than another ; fince the pores, by which it enters, are cer- omg much lefs than thofe inequalities? In water s6. ESSAYS anv OBSERVATIONS water and other tranfparent liquors, this muft certainly be the cafe, if their globular particles touch one another, as is commonly concluded from their incompreffibility: for, as.a number of fpheres laid together leave no rectilinear paflages between them, the tran{- mitted light muft pafs thro’ the component particles ; and therefore the pores, by which it enters, muft be. much lefs than the whole hemifpherical furfaces of the particles which evidently conftitute the inequalities of the ge- neral furface of the liquor *. Quer. XXIV. How does light preferve its. reCtilinear courfe in pafling thro’ air, ether and other elaftic fluids? Will not the difh-. culty ftill continue, whatever fubtility or ra- rity is afcribed to thefe mediums; fince the. powers from whence their elafticity arifes, muft prevail thro’ all the free {paces that in- terveen their particles? Muft we not, there- - fore, fuppofe, that the rays of light are not fubjec& * We are certain, that the inequalities of a craggy rock er rough wall are much greater than the particles of air er their diftance from one another, by which their re- pulfive powers are probably terminated (Newz. Princip.): Why is found, therefore, reflected fo regularly from fuch bodies, that the echo is faintly heard, except at an angle of incidence equal to the angle of reflexion ? i > ae ene PHYSICAL ann LITERARY. 87 fubject to thefe repulfive powers, tho’ they pafs thro’ the fphere of their action?. Does not the refraction of light towards the per- pendicular, out of the celeftial {paces into air, even prove that it is attracted by the par- ticles of air? Would it not ‘be’ extravagant and incongruous beyond meafure, to imagine the ether fo fubtile, in refpet of light, that, tho’ it be driven out of the way by the rays, asair is by common projectiles, it is not ca- pable of retarding them fenfibly in their mo- tion from the moft diftant fixed ftars to our eye? Do not thefe and many other difficul- ties, in the phyfical part of Optics, whofe folution is fought for in vain from any prin- ciples hitherto difcovered, thew the necef- fity of éxtending our views and inlarging our ftock of principles by farther experi- - mental inquiry? Such objections are not to be confidered as demonftrations of the falle- hood of our prefent theory; but as proofs of its narrownefs, partiality and imperfe- ction. Des Cartes, contenting himfelf with a fuperficial and inaccurate knowledge of the laws of impulfe, vainly dreamed, that he had got poffeffion of the univerfal caufe from 88 ESSAYS ann OBSERVATIONS from whence all effeéts in Nature are deri» ved ; when, in truth, he was unable to de- duce from them the fimpleft cafes of colli- fion. Many in this age, who write and fpe- culate on phyfical fubjects, feem to fall inte a like error; while they employ their whole ftudy in endeavouring to reconcile all phe- nomena with the new principles difcovered by Sir Tfaac Newton: and, when they find, to their mortification, that this will not always fucceed ; phenomena muft be difguifed, and Nature tortured, to hide their ignorance: From the lazy method of philofophizing in the clofet, among books and diagrams, there never arofe, there never will arife, any dif- covery of confequence: Great inventors u- fually underftand the extent of their own principles too well, to leave much of the ap- plication of them to others. Tue difcovery of the different caine lity of the rays, was an ineftimable addition to natural knowledge; as it ferves, at once, for explaining innumerable phenomena in Na- ture which flow from it as immediate and neceffary confequences: and, if it fhall be demonftrated by the obfervation propofed in N° 49. that the differently-coloured rays really TPHYSICAL ayy LITERARY. 8g. really’ inove ; with different. velocities,.; our, theory of light will be/ftill farther improved ; as the different eofrangibility, can be thence - mechanically.explained. | . Tue whole fyftem ¢ of feeding is one .im- mente, feries of caufesand effects, whofe be-. ginning and end are equally hid, in. the depths of infinity, Only a fmall, a very fmall portion of it, comes under our imme- diate obfervation; being expofed alike to the fight and other fenfes of all mankind. Almoft every phenomenon is, at once, the caufe.of manifold effe€ts; and one effect, among many, of a fuperior caufe. The bu- - finefs of Science is to extend our views, by unfolding the latent caufes which exift in Nature; and thence explaining their mani- | feft effects. The difcovery of one fuch real caufe, unknown before, if it be of ge- neral or very extenfive influence, as that of “univerfal gravity, is to be efteemed a great advancement of natural philofophy. To. undervalue fuch a difcovery, as fome have _ done, becaufe the caufe of that caufe can- not ‘yet be affigned, is highly abfurd: fince the fame obje&tion muft for ever ly again e Vo. Il. M all go: ESSAYS an» OBSERVATIONS all caufes, except primary ones ;° which are cettainly removed: far beyond the reach of human inquiry... The proper office, and higheft boaft of true philofophy, ' ‘js, to bring us ftill nearer to the Derry, by lead- ing us upwards, ftep by ftep, in the — ty Teale of ‘Nature, | ART) wyes) CT eS Beal . yi uM é x 4 . 7 sw "pan eee Geter teat ear "> 5 % if a { YobuTab-si,p.o0 . nel x | PHYSICAL anpcLITERARY: 9 ART. Visi wa fn a Method. of computing the Barallgnet oi the. Moon* 5. by-—— A Bu lV. figs Ie.) <1, tr from. ©, the B., . center, of. the fun; a right. line ©W_ be carried round, always touching the earth’s fur- face, this line will form a conical furface ; which, being cut, by/a plane pafling through the center of the earth, at right angles to the line joining the centers of the fun and earths the fection; fo made; is the difk of the earth. 2. Fue fame conical furface will cut off a -eircular portion of the moon’s fphere, wz e535 within which, any arches, intercepted, by lines drawn from the center of the fun and ex- _ tended: to the difk of the earth, will be nearly, in the fame proportion to one another, asthe tefpective diftances intercepted on the difk. 3. Hence, ¢ being the center of the circular, portion, wee the ecliptic ; if the femidiameter i, of the difk be exprefled by the number of fe- 4 conds i in the arch! ‘¢ wor c.e= horizontal pa- ' tallax *N ovember 6th, 1755. ge ESSAYS ano OBSERVATIONS rallax of the moon from the fun, every line drawn on the difk will be expreffed by the fe- conds of its correfpondent arch of the moon’s {phere. | 4. Let C be the center of the difk, WE; NS, the projections of w é the ecliptic, and msa circle of latitude ; WNE being the up- per or northern femicircle, and WSE the lower‘or fouthern. Let V be the place of a- ny given vertex on the difk, and v the cor- refpondent point in the moon’s fphere ; VA, VB, perpendiculars to. NS, WE, and va, v 6 their correlatives. If the point v be the true place of the moon, 7. ¢. if the vifible pla- ces of the fun and moon be the fame, then will VA be the par. lon. » @©, and VB the par. lat. to a fpectator at the point V on | the difk, or at the given vertex on the furface of the earth. For the par, lon. ) ¢ @ is the difference of the vif. lon. » 2 © obferved at V and C= but the vif. long.» @ © obferved at C, is the fame as if feen from A; therefore the par. lon. > @ © is equal to the difference of the vif. lon. ) @ © obferved at V and A, which is equal to the arch va the meafure of V A. In like manner, V B may be proved te 7 » na STATOR PHYSICAL ann LITERARY. © 93 to be the par. lat. > 2 @;_ the vifvlat, being the fame when obferved at B or C. ' 5. In any other pofition of the moon, if its diftance from the point v exceeds not one de- gree, which it can never do inthe time ofan eclipfe ; the parallaxes, to a fpe€tator at the point V of the difk, will continue nearly the fame as before, without any fenfible alteration. Let / be the place of the moon, /d, /f, perpen- diculars tocm, ce, andlet f/, va, be pro- duced till they meet in the point g, and let /d meet with v4 in the point ¢; the vif. lon. » @©, will be nearly the Bint at the points g and /. Therefore the vif. long D 2 0, -ob- .ferved at V, is the angle viiaed which the arch vg is feen from that point. But the arch vg will be feen nearly under the fame angle from the points V and C ; and confequently it _ is the meafure of the vif. lon. D 2 ©. But the true lon.is d/= ag: therefore vg—ag = va isthe par. lon. ) ad ©. Again, ad=/g =vil. lat. » 2@; andcd=fl=tr. lat.: therefore vh—-acr=ad+dc=par. lat. » 2 ©. 6. BuT thefe parallaxes va, vb, and the vif. lon. and lat. ug, vt, fuppofe the {pectator at the point V on the difk ; whereas his true 94 ESSAYS anv OBSERVATIONS true, place is, at the.correfpondent point of the furface of the earth; , confequently, the vif. lon.;and..lat..>..4¢.0, vg, vt muft. be increafed. in the ratio of the. di- ftance of the point v from the {pe€tator’ s place on the furface, to its diftance.from, the point. V on the difk. But, as the horizontal femidiame- ter of the moon, fhould likewife, be. increafed in. the fame ratio,, it will equally anfwer the purpofe of finding the times.and phafis of an eclipfe, to. let thefe continue unaltered, and to diminifh the fun’s apparent femidiameter in the fame ratio. 7. Let. CP be the axis, of thevearth pros jected on the difk,’F MD. the ellipfe into . ' which the. parallel of the given place.is. pro-. jected, D.F its greater axis, OM its lefler fe. miaxis, VG perpendicular to.C.0; M Hy, GK, perpendicularsito CW, and MI, GL, at right angles to CN. and, for thortening the rules, put. CW, the femidiameter of the difk, or the horizontal parallel, >. 2-©, equal to the radius: of the-tables of fines and tan- gents. 8. For computing the parallaxes,V Ay V B, it will,be convenient firft to fuppofe the fun in the meridian, and the place of the ver- tex PHYSICAL ann LITERARY. 9 texat M; ‘then 'to compute ‘the variation of pa- rallaxes, for the’ given time, from noon. g. Tue meridian par. lon. } ¢ @is MI or CH; and the micridian par. lat’ > 2@© is MH or CI: for finding which. the requifites are, Sine P Cot of the lat, of thesplace, > hire bs elisa Cor of the declination of the fun, \ from the 4 Tables. Cof. i of feat kes the perianal a 7Ue —_~- Bae S; lat. ” x eoh decl. Q! North ‘if the lat, North. R. ‘South. pl. be South. om= Co lat. pl. x S, deci. e of a contr. fpec. to the decl. Q- oR Bee Dif » of oc an OM, ibe he fame? — Z omen Sum $ are of = te 2 Species, . Merid. par. lon. p62 Ho= MSE mean = Summer Winter © 2 folftice North. a 5 Homa Winter tothe Summer §if CMis.Q°\ South. CMxX 5S, merid.ang. § of -a contr. mpc. . par, lat. »42O= +e RR 2. fpee: to CM. 10. THE variations from the merid. parallaxes for the given hour from noon; may be conceived to be made up, each of two parts ; which are the Projections of MG and GV upon CW for the lon. and upon CN for the lat.; the former being HK, KB; 96 ESSAYS anp OBSERVATIONS K B; and the latter IL, LA. For finding which, belies the foregoing requifites there is required. ark wa of the degree from noon, MG= OM X spb noon © eS Cof. lat, pl. = deg, 2 noon” ya ia Variation of the Par. Lon. > a ©, o~ u? if Sa. ad MG x cof. ante aerid. ang. Welt wom 07 U Te Eat when the — is in ms BQ me 2 mz. ts GV x S, merid. ang. Ea ft AM, : 2d agate — ora ccas eel § Wek PM. Variatio of the Pan. Lar. > ao. “MGxS, aa ang.¢ South ift Parr = R North § mat it to the deci. ae “GV = iefid? ang. . R 2d Part = Forenoon 5 ae 2 when the fun is in * 4 5 is oe a Afternoon py: when the fun is in ; & 7 7 ‘i ‘ oe PHYSICAL ann LITERARY. 67 ir. By art. 6. the part to be fubtracted from the apparent femid. ©; muft bear the fame proportion to the whole, as the di- ftance of the vertex on the furface of the earth-from its point on the difk; tothe di- ftance of the points V,v; which is nearly the fame with the femidiameter of the moon’s orbit, and may always be expreffed by a conftant number, vz. that of the 2ds of a degree equal to the tadius of a’ circle. The diftance of the vertex from its point on the difk may be conceived to be made up of two parts, pofitive, or negative: the firft of which is the perpendicular diftance of the centre of the given parallel circle from the plane of the difk; the fecond part is the per pendicular diftance of the given vertex from a plane paffing thro’ the forefaid centre, and parallel to the difk. - Pag rie Sy lat. pl. x Sidecl.O§ Pof. 2when the lat. pl. if Part = R Neg. ea decl. © are the fame . of § different ; Species. Bea Pare OOS eS eT OR eee Pofitive 2. lefs 2 Ny osm : if the given hour from moon be Hots ‘ than 6. Vou, I. N 12. It 9% ESSAYS anv OBSERVATIONS 12. Ir would be eafy, from the foregoing rules, to conftruct tables of the parallaxes for any given latitude. -Such tables would be fufficiently exact, if calculated for every third degree. of the fun’s longitude, and e- very. quarter of an hour from noon to 6 hours; afluming 10000 for radius, or the ho- riz. par. )¢ ©. The equation to be fubtra- ted from the apparent femid. © needs only be calculated for every roth degree of longi- tude, and every half hour from noon to 6 hours, taking the mean femid. ©. 13. Ir the given time from noon be more than 6 hours, fubtract it from 12 hours, and the lon. © from 12 figns; and, for the re- maining time and longitude, feek the intire parallax, and the equation for the femid. ©, changing its fign. 14. Sucn tables, tho’ .conftructed for a particular latitude, may eafily be made to ferve for any other latitude. For the varia- tions from the meridian parallaxes are always proportional to the cofine of latitude. And the meridian parallax, whether of lon. or lat. is made up of the fum or difference of two parts; the firft of which is proportional to the fine, the fecond to the cofine of lat. Thefe - PHYSICAL ann LITERARY. © 99 Thefe two. parts for the tabular ‘latitude are found thus. To-the given lon.'@ add 6 figns ; and take out the merid. parallax. anfwering to each longitude.' Half the fum of 'thefe gives the 1ft part, and half their difference the 2d part, to be added to the firft when the merid. par. for the given lon. ©vis greater than the other; and to be fubtraGted when. lefs. In _ like manner, the equation for the femid. © confifts of two parts; the: 1ft of which is pro- portional to the fine, the 2d to the, cofine of lat. The 1ft part is the equation for the given lon. ©, and 6 hours from noon’; and this fubtracted from: the: equation) for the given lon, ©. and hour from aries ikea the ad part. tap ‘15. ‘Tue fame rites with Cécrie oe wig the moon’s parallaxes from a fixt ftaror pla- | net. If the femid. of the planet have no fenfible magnitude, there will be no place for the correction mentioned in art: 6. «But, as the requifites could not be found from the. common tables, if the ftar has latitude, it will be convenient, ‘firft, to fuppofe it ‘has none, and afterwards to apply a proper cor- _ rection. Befides, the proceeding in this way _ will make the tables already defcribed to be 4 ma of roo ESSAYS ann OBSERVATIONS of the fame ufe as in folar eclipfes, fubftitu- ting the lon. ¥ for the lon. ©, and, for the hour from-noon, the equatorial diftance of the ftar’s ecliptic place from the meridian; converted into time at the common rate of 15 degrees to an hour. 16. Ir the ftar have latitude, then the true lon. and lat. » 2 * are meafured by ar- ches, from the center of the moon, perpen- dicular to a circle of latitude, and to a great circle at right angles to it, both pafling thro’ the ftar. -Hence, As radius to cof. true lat. 3, fo tr. lon. » a ¥ tothe fame Projected. And,: As cof. tr. lon. » ¢ * to radius, -fo tan, tr. lat. D to the fame projected : without any fenfible error, {0 tr. aoe ) to the fame projected. 17. To find the correction of the paral- jaxes for the latitude of a ftar: let CW (fig. 2.) be the ecliptic on the earth’s fur- face, N its pole; CN acircle of latitude thro’ the ftar ; W its pole ; V the given ver- tex, CD, the lat.* ; WVA a great circle thro’ the vertex V, meeting with the circle of aa a - PHYSICAL ann LITERARY. to1 of latitude in A, WD another great circle ; VB, V4, arches perpendicular to WC, WD. Then WA is a quadrant, and the fine of VA is the par. lon. ) 2@* , whether the ftar has latitude, or not: the fine of VB is the par. 7 4 lat. if the ftar be in the ecliptic; but, if it is in the circle WD, the par. Jat. will be the fine of V4; which may be found from the parallaxes of lon. and lat. given for the ecli- ptic place of the-ftar: thus, S, WV = Cef. VA= WR -+ par. lon, * R—par. lon. | RS, VB (par. lat.) “ 5 8, VWB = S, WV ea rae + ; ¢ South. VWb= VWB ae ee if thelat x be $ Sout ‘Ss, Vi = par. lat. Dag 8, are er vwe 18. Since the radius of the tables of fines and tangents was all along taken for the ho- riz. ‘par. > @ 2@ or * ; the parallaxes and equation found muft be altered propor- tionally. EXAM- ‘you J 19066166 ozigShr'6 | a ho § Ff eH |v | icobleel6 Nt 61g25 = NO AD) | |13£6615°6 “s 06307 = NO | woou » “Sap “s P| |g6z9$z5"6 © ‘pap ‘s f id se] Joo J | | €golh62-6 1d “ae YOO J OW) jp) f1zSLog6 "nN 60462 =90 | WO ‘\¢lLovl6-6 © ‘Pep joo e . uoow » ‘Zap ig ‘AJ | O£r26g°6 “id ‘sey ‘g J 8 ee A of z$. 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( aed *ZWOPET gr LsSgq'v = Mayer — "re "09 ‘snipes UI Spz 15z65£g°6 ‘LESeq _— —_ — men “YIP 1290,1, ‘obzzy = Luvg a |eete929°6 L¢Lo61+'6 ‘Lyzgz = Luv Yl 920g259°6 uoou 2 “Bap ‘Jo g6z95z5'6 © ‘pap ‘g| |¢420726.6 © ‘pap joo 6frr569°6 4d “yey ‘g| |Egoeh6L'6 “1d 32] ‘JOO ‘SIG, 9qf wolf XILYIA “HiT PHYSICAL ano LITERARY. 105 é ART. VI. | A Sohition of Kepler’s Problem; by MaTTHEew -Srewart, Profeffor- of Mathematics in the Univerfity of Edinburgh *. * HO’ the problem propofed by the cele= brated Kepler has been folved by feve- tal Mathematicians. of. great note: yet, as this is of confiderable ufe in aftronomy, it is hoped the following folution maybe agree- able to fome; as it requires a lefs degree of knowledge in the more difficult parts of Ma- thematics, than the other methods do. ek OOP OL Tob eN, Bie. i: Let there be a ftreight line AB, and ‘CD. a portion of a curve wholly concave towards AB, and draw AC, BD parallel to each other, meeting the curve in C, D; let CE, a tan- — Vor. IL O Bent _ * December 4, 1755. ¥ . 106 ESSAYS anp OBSERVATIONS gent to the curve at C, meet BD in E; join AD, AE, BC, and let AE meet the curve in F: the tri- angle ABC will be greater than the feG@or ACF, but lefs than the fe- Gor ACD. Jorn CD. Becaufe AC, BE, are parallel, the triangles, ABC, AEC, will be equal: but the triangle AEC is greater than the fe&tor ACF; thetefore the triangle ABC is greater than the fector ACF. Again, be- caufe AC, BD, are parallel, the triangles, ABC, ADC, are equal: but the triangle ADC is lefs than the fettor ACD ; therefore © the triangle ABC is lefs than the fecter ACD. PROP. IL Fig 2. Let there be a curve AEB, wholly concave towards the ftreight line © AB, and let C, D, be two points in the line AB; draw DE to any point E PHYSICAL-ann LITERARY. 107 E in the curve, and draw CF paral- lel to DE, meeting the curve in F; let EG, a tangent to the curve at F, meet CF in G, andjoin DF, DG, and let DG meet the curve in H; let the point D be between the points, A, C: the feétor ACE will be greater than the fecétor ADH, but lefs than the fector ADF; and the fector BCE will be greater than the fector BDF, but lefs than the feGor BDH. Because the triangle DEC is greater than the fector EDH, let the fector ADE be added to both; and the fpace ACE will be greater than the fector ADH: and, becaufe the fie °°! angle DEC is lefs than the feGor EDF, let ¥ g os bu oe Le "gy the fe€tor ADE be added to both ; and the fe- &or ACE will be lefs than the fector ADF. Acain, becaufe the fector ACE together with the feGor BCE, is equal to the fector ADF together with the fector BDF, and the 3 fector 108 ESSAYS ann OBSERVATIONS fettor ACE is lefs than the feGtor ADF; therefore the fector BCE is greater than the fe&tor BDF: and, becaufe the feGtor ACE to- gether with the fector BCE, is equal to the fe&tor ADH together with the fector BDH, and the fector ACE is greater than the feGtor — ADH; therefore the fector BCE will be lefs than the fector BDH. / PROP. TM. PRoev. 1; Beas. Let there be a given circle AEB, and let D be a given point within the circle; and from D let there be drawn DE, DF, to two given ‘points, E, F, in the circle: granting the quadrature of the circle, it is _requifed to draw a line DG meeting -the arc FE inG; fo that the eae EDG may be to the fector GDF in _agiven ratio, fuppofe that of m to x, ; Ler C be the center of the circle, and join CE,CF; draw DH, DK, perpendicular ta ‘ iy i _ PHYSICAL ann LITERARY. frog CE, CF, meeting CE, CF in, K; and let _ EL, FM, be tangents to the circle at the 7 the fector DEG, and the triangle DFM equal + s. points, E, F. Because the points, D, E, F, are given, and the circle is given, the fe@tor DEF. will be given ; and, becaufe the fector EDG is to the fector GDF in the given ratio of m to. 2, the fectors; EDG, GDF, will, each of them, be given in magnitude. In the tangent EL take the point L towards I’; fo that, joining. HL, the triangle HEL may be equal to the fector EDG : again, in the tangent FM take the point M towards E ; fo that, joining KM, the triangle KFM will be equal to the fector FDG: it is evident, the points, L, M, will be given. Join DL, DM, meeting the circle in N, O; the point G will fall between the points, ‘'N, O. For, becaufe EL, FM, are tangents to the circle at E, F, the angles HEL, KFM, will be right; ‘and therefore DH, EL, will be pabaltele likeways DK, FM, will be parallel; therefore the triangles, DEL, HEL, will be equal, and likeways the triangles, DFM, KFM, will be equal : and therefore the triangle DEL will be equal to te 110 ESSAYS ann OBSERVATIONS to the fector DFG; therefore the feGtor DEG will be greater than the feCtor DEN, and the fector DFG greater than the fe@tor DFO; therefore the line DG will fall between the lines, DN, DO; therefore the point G will fall between the points, N, O. Acar, Becaufe the points, L, M are given, and the point D likeways given, the fectors, DEN, DFO, will be given ; and, be- caufe the fectors, DEG, DFG, are given, the feAors, DNG, DOG, will be given ; and therefore the fector NDG will be to the fe- ctor GDO in a given ratio, fuppofe that of ptog. The problem, therefore, will be re- duced to this again, To divide the fector NDO by the line DG, fo that the fector NDG may be to the feGtor GDO in the gi- ven ratio of p tog. And thus, repeating the operation, the point G will be found within a very narrow limit. N. B, Tue limit ON might have been found by taking in the tangents, EL, FM, the point L towards F, and the point M to- wards E; fo that, joining DL, DM, meeting the circle in N, O, the triangle DEL would be equal to the fector EDG, and the triangle DFM PHYSICAL anno LITERARY 114 DFM equal to the fector DFG: but the other way points out the method of cal- culation. PROP. IV. Prost.2. Fig. 4. - Let there be a femicircle whofe dia- meter is AB and center C, and let D be a+ point in the diameter: “granting the quadrature of the cir- cle, it is required to draw a line DE’ meeting the circle in E, fo that the femicircle may be to the fector BDE in a given ratio, fuppofe that of p to g. Suppose the problem folved. Let the fe- micircle be to the feétor BCF as p is to g;) join DF; draw CG parillel to DF, meeting _FG, a tangent to the circle at F, in G, and _ join DG meeting the circle inH; let CG meet the circle in K, and join DK, FK, CH. Because the femicircle is to the fector _ BDE asp tog, that is, as.the femicircle to the j fector ir2 ESSAYS ann OBSERVATIONS feGor BCF, the feGor BDE will be equal to the fector BCF:. but the fector BCF is [ Prop. 2.] greater than the fector BDK, but lefs than the fector BDH ; therefore the fector BDE is greater than the fector BDK, and lefs than the fector BDH ; therefore the line DE falls between the lines, DH, DK ; and there- fore the point E falls between the points, H, K. Again, 'becanfe the fector BDE is equal to the, fe¢tor BCF, and the feGor BCK is common to both, the {pace KCDEK will be equal to the fector KCF; and, becaufe the triangles, KCD, KCF, are equal, (becaufe KC, DF, are parallel), therefore the fector KDE is equal to the fpace KEFK.; and, be- caufe the triangles, GDK, GFK, are equal, taking the common fpace GHK from both, the fector KDH will be equal to the fpace KEFK together with the fpace GFHG; but the fector KDE is equal to the fpace KEFK, therefore the fector EDH is equal to the {pace GFHG. Because the femicircle is to the fector BCF asf to g, therefore the angle BCF is given, and therefore the angle FCD is like- ways given: and, in the triangle FCD, be- caufe the fides, CF, CD, are given, and like- ways PHYSICAL and LITERARY. riz ways the angle FCD, the angles CDF, CFD will be given; and therefore the - angles BCK, KCF will be BH therefore the arcs BK, KF are given: becaufe FG is a tangent to the citcle at the point ‘F, the angle CFG will bea tight angle: and be- caufe the angle FCG is Given and likeways the fide CF given, the fides CG, CF will be given :, in the triangle GCD, becaufe the fides GC, CD are given, and the angle GCD given, the angles CGD, CDG will be given: and-in the triangle: GCH, becaufe the fides . GC, CH and the angle, CGH is given, the angle GCH will be given ; and therefore the arc Hik will be given :. : ahd becaufe the arc FK is given, therefore the arc FH is given. Again, becaufe the are FK is given, the fector FCK will be given, and likeways the tri- angle’ FCK given, therefore the fpace KEFK will be given 5, and becaufe the triangles, GFC, GHC, are given, the fpacé GFCHG will be given 3 and becaufe the are _ FH is given, the feCtor FCH will be given ; _ therefore the fpace GFHG will be given. | Vor, I. p ae aia ESSAYS anv OBSERVATIONS From this, the following conftruction may be deduced, CONSTRUCTION. In the femicircle take the point F, and let the arc AFB be to the arc BF as pis tog; join CF, DF, and draw CG parallel to DF, meeting FG, a tangent to the circle, at F in G; and the circle in K; jom.DG meeting the circle in H, and join FK, DK; draw ‘the'line DE [Prop. 3.] meeting the circle in E, fo that'the fector KDE “may be to the feétor EDH as the {pace KEFK to, the {pace GFHG: the femicircle-will be to the fector BDE as 7 1s to g. Because the feGtor KDE is to the fector EDH, as the fpace KEFK to the {pace GFHG ; the fector EDH will ‘be to the fe&tor KDH, as the {pace KEFK to the fum of the fpaces KEFK, GFHG: but; becanfe the ‘PHYSICAL ann LITERARY. 119 the triangles, GDK, GFK are equal, and the {pace GHK common to both, the fector KDH will be equal to the fum of the {paces KEFK, GFHG ; therefore the fector KDE is equal to the fpace KEFK. And, becaufe the tri- angle KDC is equal to the triangle KFC, the {pace KCDE will be equal to the fector KCF; therefore (adding the fector BCK to both) _ the fector BDE will be equal to the feétor BCF..: Again, becaufe the arc AFB is to the arc BF as pis to g, the femicircle will be to the fector BCF as p is to 7; therefore the femicircle will be to the fector BDE as pis tog. QE. Dy * But, as this would require a 1 good deal af trigonometrical calculation, the following method may be ufed; which will give the point fought very nearly, when this problem is of ufe in the planetary fyftem. PROP. V.. Pros. 3, Fig. g. Let there be a femicircle whofe dia- _ meter is ABand centre C, and let 4q D si a point in the diameter not very y r ae. $Gr6 wea a, a * rT ae => ~ 116 ESSAYS anp OBSERVATIONS very excentric, granting the qua- drature of the circle, it is required to draw a line, DE, meeting the circle in FE, fo that the femicircle may be tothe fe&or BDE in a given ratio, fuppofe that of p to g, Suppose the problem folved ; and let the femicircle be to the fector BCF as p is to q3 join DF, and draw CG parallel to DF meet- ing FG a tangent to the circle at F in G; join DG, and let CG, DG meet the sitet in H, K: join DH, FH; draw €M parallel to DH meeting HM a tangent to the circle at Hin M; draw DL perpendicular to CH meeting CH in L; join LE, and let FN perpendicular to CH meet CH in N. Because the femicircle is to the feCtor BDE as is to 9, that is, as the femicircle ta the fector BCF, the fector BDE will be equal to the feétor BCF: and becaufe the fector BCH is common to both, the {pace HCDE will be equal to the fector HCF ; but be- caufe CH, DF are parallel, the triangle DCH is equal to the triangle FCH ; there- fore PHYSICAL awn LITERARY. y17 fore the fector EDH will be equal to the _ fpace contained by the arc HF and the chord FH. Again, -becaufe the fector BDE is equal to the fector BCF, and the feGtor BCF is [ Prop. 2.} greater than the fector BDH, and lefs than the feGtor BDK, the feGor _ BDE will be greater than the fector BDH, and lefs than the feGtor BDK: therefore the point E is in the arc HK between the points 4H, K.. [Let-thearc HK be called the limi- ting arc]. Becaufe the point D is not very excentric, the limiting arc will be little.” In the orbit of Mercury, the moft excentric of _ all the planets, the limiting arc will be lefs than fixteen minutes in that part of the orbit where it is greateft; therefore EH may be confidered as coinciding with the tangent to _ the circle at the point H ; and therefore the triangle ELH will be equal to the feétor _ EDH, that is, equal to the {pace contained _ by the arc FH and the chord FH; therefore the rectangle LHE will be double of the _ {pace contained: by the arc FH and the chord FH. Becaufe the rectangle contained by _ CH and the arc FH is double of the fe@or _ CFH, and the re¢tangle contained by CH, FN is double of the triangle CFH; the rectangle 118 ESSAYS ann OBSERVATIONS rectangle contained by CH and the excefs of the arc FH above FN will be double of the {pace contained by the arc FH and the chord FH; therefore the rectangle LHE will be equal to the rectangle: contained by CH and the excefs of the’ are FH above FN; therefore LH will be to HC as the excefs of the arc FH above FN to HE: but becaufe. the triangles DLH, CHM are fimilar, LH will be to HC as DL or FN to HM; therefore FN will be to HM as the excefs of the arc FH above FN to HE» From this, the following conftruction ‘may he deduced. : CONSTRUCTION. Let the femicircle be to the fectar - BCF as pistog; jon DF, draw CH parallel to DF meeting the circle in H; join DH, draw CM parallel to DH meeting HM a tangent to the circle at H in M; -and let FN perpendicular to CH meet CH in N ; im the. tangent | HM -PHYSICAL ann LITERARY. 11g _)-HM take HE towards F, fo that P &oFN may be to HM as theiexcefs. i ~ of the arc FH above FN to HE; indo DE: the femicircle will be. _to the fector BDE. as pe Is tO 4s ha: DL; Seipdidicular to CH; meet CH in.L; join FH, LE. Let CH meet FG;>a’ tangent to. the’ circle.at F, in G; He meeting the circle in K. oo » Because the:triangles DLH, CHM are _fimilar,..LH will be to HC as:DL or FN to- HM ; that is, asthe excefs of the arc FH: above FN to HE: therefore: the rectangle’ LHE. will be equal to thesrectangle -con- tained by HC and the excefs.of the arc HF . above FN : but, becaufe the rectangle con=' Re tained by CH and the arc HF is double: of ; 3 feCtor HCF, and the rectangle contained’ . ‘CH, FN is double of the triangle CFH ; refore the rectangle contained by CH and ae of the.arc FH above FN will be’ double of the {pace: contained by the are’ _FHand the chord FH ; therefore the re@- vy angle LHE will: be double of the fpace j eine’ by the arc FH and the chord FH; ae. ' and tgo0 ESSAYS ann OBSERVATIONS and therefore the triangle LHE will be equal ta the fpace contained by the are FH and the chord FH: but, becaufe DL, . HE are parallel, the triangles DHE, LHE are equal; therefore the triangle DHE is equal to the {pace contained by the arc FH and the chord FH: and, becaufe DF, CH are parallel, the triangles CDH, CFH are equal; therefore the fpace HCDE will be equal to the fector CFH.. Let the fe@or BCH be added to both, and the fector BDE will* be! ~ equal to the fector BCF : but, becaufe the fector BCF is greater than the fector BDH and lefs than the fe@tor BDK; therefore the. feGtor BDE is greater than the fector BDH and lefs than the fe@tor BDK, and therefore DE falls between DH, DK: and, becaufe’ the point D is not very excentric, the limi- ting arc HK will be little; therefore the tangent HE may be confidered as coinciding with the arc HK: becaufe the fe€Gtor BDE is equal to the fector BCF, the femicircle will be to the fector BDE as the femicircle | to the fector BCF : but the femicircle is to the fector BCF as pistog; therefore the femicircle is to the feétor BDE as # is to q Q. E. D. ‘ _ Kepler PHYSICAL anp LITERARY. i2f > Kepler firft of all difcovered that the pla- : Bets révolved in ellipfes round the fun placed ‘in one of the foci, and that they deferibed equal areas in equal times round the fon. Let the femi-ellipfe, [Fig. 6.] whofe greater axis is AP, focus S, and centre C, reprefent half the orbit of a planet round the fun in S; and ‘i fuppofe the planet at the point K in its orbit join SK + half the periodic time of the planet found the fun, is to the time the planet moves | Abin A to P, as the area of the femi-ellipfe to the area ASK; and therefore to find the place of the planet at any given time, it is fieceflary to find the pofition of the right ‘Jiné SK, which fhall cut off the area ASK eeeottional to thé time, that is, To draw thé line SK fo that the area of the feimi-ellipfe . imay be to the area ASK, as half the periodic time of the planet: round the fun to’ the a time. From K let fall KH pet pehdivatie to AP; meetinie the femicircle defcribed upon AP in G, and join SG: it is evident, from the na- _ ture of the ellipfe and circle, that the femi- -cifcle i is fo the feCtor ASG as the femi-ellipfe _ tothe feGtor ASK;; therefore the femicircle is to the feétor ASG as half the periodic time of B Vou, IL Q the 122 ESSAYS-anp OBSERVATIONS the planet round the fun to the time the planet moves, from A to K: the: problem therefore, is reduced to this, To draw the ‘ Jine SG meeting the femicircle in G, fo that the femicircle may be to, the fector ASG.as half the. periodic time of the planet round the fun to the given time. In the {emicircle, take the are AB, fo that the arc ABP may .be to the arc AB as half the periodic time of the planet round the fun to the given time. Join CB; the femicircle shorts will be.to the fedtor ACB as half the periodic time of the. planet round the fun to the given time, that. is, as the femicircle to the fector ASG ; there- fore the fectors ACB, ASG, are papa join. CG. | The sialic ACB is called by Kepler the mean anomaly, the angle ACG the anomaly of the excentric, and the angle ASK the co-, equate or true anomaly. The problemrthere-. fore is reduced to this: The mean anomaly of a.planet being given, to find the anomaly of the excentric and the coequate anomaly. “PROP. . fay ugigte: cs ‘AND LITERARY. 123! ae: : “PROP. Vi. -Promt: Iv. Fis 6. ' Let. AP. be, the; greater axis, of a pla-' onet’s orbit, “S the focus the place shale fun, ‘A the aphelion, P the’: ; ‘perihelion ; upon “AP let” the femi- ' eitcle ABP. be defcribed ; let C-be the center, andulet the angle ACB) “be the mean ‘anomaly of che planet’ vat “any. given time: it is required. to. find the anomaly of Phe excen, tic, sglgdh sit oid) “rahi $5 “Jon SB, ‘and. daw, -CD parallel to SB | meeting | ‘the circle in D: join SD in BD: | take the are DG, fo that the fine of the angle. | BCD, may be tothe tangent of the angle €DS,. as the excefs of the arc BD, above its, fine to the arc. DG; and join. CG: the angle ACG will be nearly the anomaly of the excentric. . Join. SG; _ draw BE petpendicular to CD | meeting CD in E, and draw CF parallel to. ‘ D meeting DF a tangent to the circle at D BECAUSE i124. ESSAYS ann OBSERVATIONS Because BE is the fine of the angle BCD, and DF the tangent of. the angle DCF, that is, of the angle SDC; BE will be to DF as the excefs of the arc BD aboye BE to the arc DG; therefore [ Prop. 5,] the fector ASG is equal to the fetor ACB; therefore the angle ACG is the anomaly of the excentric. ; THE computation is as follows: In the triangle BCS, as the fum of the fides BC, CS, is to the difference of the fides BC, CS, fois the tangent of half the angle -ACB to the. tangent fa half the difference of the angles, CSB, CBS; therefore the angles, CSB, CBS. will be given, that is, the angles, ACD, DCB, will be given, Again, in the triangle CSD, the fum of the fides, CD, CS, is to the difference of the fides CD, CS, as the tangent of half the angle ACD to the tangent of half the difference of the angles, CSD, CDS; therefore the angle CDS will be given. Again, becaufe as the fine of the angle BCD is to the tangent of the angle CDS, fo is the excefs of the arc BD aboveits fineto the arc GD; fayas the radius is to the fine of the angle BCD, fo is 57°. 2957795 Se, he number of degrees in an angle fubtended by PHYSICAL ann LITERARY. 12g: by an arc equal to’ the radius, tothe. number of degrees in an angle fubtended by an are equal to the fine of the angle BCD; [let. this angle be called A]. Again, as the fine. of the angle BCD to the tangent of the angle CDS, fo is the excefs of the angle BCD above the angle A, to the’angle GCD. Therefore the angle ACG, the vagy es ye the excentric, will be given. EX A:M. P.L E.,.1. In the orbit of Mercury, the mean diftance is to the excentricity as. 100000 ‘to 20589.) Suppofe the: mean anomaly from the apheli- on to be 60%, it is required to find the ana- maly of the excentric. In the triangle BCS, as 120589, the fum of BC, C$,.is to 79411 the difference of the fides BC, CS, fo .is the tangent of 39°, \half the fum of the angles, CSB, CBS, to the tangent of half the differ-: ence of the angles CSB, CBS, The log. tang, of 30° ig . 927614394 The log. of 79411 is 4.8998807 The fum is | 14.6613201 The log. of 120589 is 5.0813077 The difference 9. 5 Boat mri the log. 726: ESSAYS ann OBSERVATIONS log.’ tang. of 20° 4.9'.00894 half the difference: of the.angles CSB, CBS ; therefore the an— gle’ CSB or ACD is 50° 49'.00894, and the angle CBS: or, BCD is 9° 10’.99106. Again, in the triangle DCS, as 120589 the fum of: DC, CS,'isisto-79411 the difference of DC,) C8, fo isthestangent of ’25° 24'.50447 half the fum of the angles CSD, CDS, to the tan-. gent of half the difference of the angles CSD, CDS, | The log. tans6f-2 5° 2.4':504.47 is 9. 6767070 The log. oF 7 ha TiS Loe 4.8998807 The fam i ee Ih, 5765877. The log. of. IN is 5.0813077 The difference | 9:4952800 is the log. tang. of 17% 22'.21093 half the dif- ference GF the angles CSD, CDS ; therefore the angle CDS is 8° 2" 29354: Again, asthe | radius is to the ‘fine of 9° 10°.99106, fo is 57° .2957795)kec. the number of -dégrees in an~-angle,-fubtended by an are equal to the radius, to- the number of degrees and ‘minutes in an angle fubtended by an arc equal to the fine of 9° 10’ 99100. The PHYSICAL ann LITERARY. ‘ov The log: of 57.2957795 is, .1-7581226 The log. fine of 9° 10° diab ins is» 8 2030097 “Phe oie 10. ¥6:9611323 The log. of 'rad.is ° == 10.0000000 The difference. - im 0.961 1323 is the log. of.g° 8. 634.9999, . the number of degrees eal minutes .contained nan angle fubtended by an arc, equal to. the fine, of 9° 10'.99106. The angle A therefore _ is 9° 86349999; the excefs therefore of the, ‘angle BCD above the angle A is, 2'.3 5606. Again, as the fine of.9° 10'.99106: is to the. tangent of 8°. 2.29354, fois the angle 2 435606 to the angle DCG. The ai cei : 2 ‘it: 0.3721863, The log. tang. of 8° 2 1293 54 is, 9.1498998 © The fam is’ > 95220862! gre log. fine of 9° 10. 99106 is Q. ebsatie 8 The difference ©. 3190964. is the log. of ‘2’ 084953. the angle DCG, the angle ACG the anomaly of the excentric is 50° 51.093893, that. is 50°51 5:.63358. Ler, 128 ESSAYS ann OBSERVATIONS Ler SM, perpendicular to CG, meet CG in M: It is evident, becaufe the fe@or ACG is common to both the feétors ASG; ACB, _ that, if the fector ASG be equal to the feétor ACB, the-triangle SCG will be equal to the fe&tor BCG; and therefore the line SM will be equal to the arc BG: if the fe€tor ASG be greater than the fector ACB, the triangle SCG will be greater than the fecétor BCG ; and theréfore the line SM will be greater than the atc BG: and, if the féctor ASG be lefs than the fe€tor ACB, the triangle SCG will be lefs than the fector BCG ; and there- fore the line SM will be lefs than the arc BG: that is, if the are AG be greater, equal, or lefs, thah the true anomaly of the excentric, the line SM wilf be greater, equal, or lefs, than the are BG; and therefore, the lefs the difference is between the line SM and the arc. BG, the lefs will the difference ‘be between- the arc AG and the anomaly of the excenfric. Because the triangles GCH, CSM, are fimilar, CG is to GH as CS to SM ; that is, the radius’ is tothe fine of 50° 51'.093893 as 20589 to CM. 3 The PHYSICALManp LITERARY: 129 The log. of 20589 is -. 403136353 The log: fine of 50° 51’.0937.97 is.9: PIE IGI9O The fur “is 14. 2032243 The log. of rad. is ‘ 10. 9000000 The difference _ “a )iay Ae 2032243 is the log. of SM. Again, as CA to SM; fo is 57°» 2957795, &c. the number of eaicch in an angle fubtended by an arc equal to CA, the number of degrees in an angle a by an arc, equal to.SM. The log. of 57°.2967795, Ec. is I. 7681226 The log. of sM.j is Poiaanet 2032243 The fam is | 5.9613469 The log. of CA 5.000000 The difference O. 9613469 is the log. of 9° 8’.90625 the number of de- : grees and minutes in an angle fubtended by an arc equal to SM: ‘but, becaufe the arc AB is 60°, and the arc AG is 50° 51'.093797, the arc BG will be 9° 8’.906203; the difference therefore ‘between SM and the arc BG Vor. II. R is 1430 ESSAYS ano OBSERVATIONS is 0.000047 ; the difference therefore is lefs than the 354th part of a fecond. Mr. Machin, in his folution of this pro- blem in the Philofophical Tranfaétions, Number 447. makes the anomaly of the ex- centric to be 129°.14846, when the mean anomaly reckoned from the perihelion is 120°; and therefore, if the mean anomaly reckoned from the aphelion be 60°, the anomaly of _ the excentric will be 50°.85154, that is 50° 51’.0924. aa In order to determine the difference be- tween SH and the arc BG according to. this computation, ae The log. of 20589 is 4.31363 53 The log. fine of 50° 51.0924 is 9.8895888 The fum ts 14.2032241 The log. of rad. is 10.0000000 The difference 4.2032241 is the log. of SM. Again, as CA to SM, fo is © 57°. 2957795, Se. the number of degrees in an angle fubtended by an arc equal to CA, to the number of degrees in an angle fubtended by an arc equal to SM. : “ The PHYSICAL ann LITERARY. 135 The log. of 57°. 2957795» Ge. is 1.7581226 The log. of SM is - 4.2032241 The fum is ~ ibis §-9613467 The log. of CA is'' “° * ~ " ' 5.6000000 The gerence ; ©. Lie is the log. of 9° $’.905998, the number of degrees and minutes in an angle fubtended by an arc equal to SM: but, becaufe the arc AB is 60°, and the arc AG is 50° §1’.0924, the arc BG will be 9° 8’.9076 ; the difference there- fore between SM and the arc BG is 0’.001602; very nearly one tenth. of a fecond, and is more than thirty four times greater than the former, difference, BECAUSE AS is equal to the ee of BC, CS, and PS equal to the difference of BC, CS; it is evident, that, if, from the log. tang. of half the angle ACB, the difference of the logarithms of AS, SP be fubtracted, the remainder will. be the log. tang. of an angle, which, if added to half the angle ACB, will give the angle ASB or ACD; and, if fubtra@ted from half the angle ACB, will give the angle CBS or BCD. , E X- 132 ESSAYS ann OBSERVATIONS kX A MP Li Ed¢ hig . _ In the arbit of Mars, the mean. diftance is. to the excentricity as 152369 to 4100p Suppofing the mean anomaly to be 1°, it is required to find the anomaly of the excentric. The log, tang, of 3 AB half the t., «angle ACB, is...) 12 «. 719408584, The difference of A logs. ‘of ASa:ts bape POF cahn C e . 0,0806086 The difference “sieebs Se L - 8602298 is the log. tang. of 24’.9196814, half the dif- ference of the angles CSB, CBS; re the, angle CSB, that is the angle ACD, 54’.9196814; and the angle CBS, that is the angle BCD, is 5.0803 186. Again, to determine the angle CDS, | _ The log. tang. of half the angle Ais. 7:3958249 The difference of. the. logs. of AS, SP.. is 0,0806086 The difference | 7.8152169 is the log. ‘tang. of 22°.4641426, half the difference of the angles CSD, CDS; there- fore : PHYSICAL ann LITERARY. 133 _ fore the angle CDS; that is £0) angle DCR, is e 9956981. | AGAIN, as the fadiuscis to the fine of L% sai, fo “as. 57° he ce. the number of degrees in an angle fubtended by an arc equal to the radius, to. the number of degrees and (minutes ‘in an angle fubtended by an°arc equal’ tothe fine of 5’,0803 186... The log. of 57° 2957795 is 107581226 The log. fine of 5” te euekes is '7.1633313 — ——__. ——_— Sons | | 8.9214539 The log. of radius is “- 10.0000000 Be The difference ae 7 e?, 92 14539 is ‘the log. of 5 0073162, the number of minutes contained in the angle A; the excefs therefore of the angle BCD, above the angle A, is 0'.0930024. Again, as the fine of the angle BCD is to the tangent of the angle DCF, {0 is 0'.0930024 to the angle DCG. - The log. of o.cg30024 is © —2.9684941 The log. tang. of the ane DCF is 7.1622795 fee ihé fond AGAIN, im the fame orbit {uppofing itp --mean anomaly to be 100° degrees, it is re- quired to find the anomaly of the excentric. | The log. tang. of 50° half the angle ACB is 10.0761865 The difference of the logs.- of AS,-SP- is 0.0806086 The difference 99955779. ; is the log. tang. of 44° 42’.4982192, half the. difference of the angles CSB, CBS; there- fore the angle CSB, that is the angle ACD, is. 94° 42'.4982192; and the angie CBS, that is the angle BCD, is 5°17’ SOLTB AR Again, to determine the angle kes The log. tang. of half the angle ACD is to. 0557285 The difference of the logs. of AS, SP. is 0.0806086 The difference 9.9751199. is the log. tang. of 43° 21'.5819834, half the difference of. the angles CSD, CDS; therefore the angle CDS, that is the angle DCF, is 3° 59'.6671212. AGAIN; PHYSICAL ann LITERARY. 137 ‘ . Acatn, as’ the radius’ is to. the fine of 5° 27’.5017808 the angle BCD,, fo is if 57°. 2997795 to the angle A. The log. of 57°.2957795 is L.7581226 The log. fine of 5° 17’.5017808 is 8.9642381 The fum is | -10.7223607 The log. of radius is. 10.0000000 ‘The difference 0.7223607 is the log. of 5° 16’.600752 the number of degrees and minutes contained in.the angle A; the excefs therefore of the angle BCD above the angle A is o’.go10288. Again, as the fine of the angle BCD is to the tangent of the angle DCF, fo is o’ eee, to the _ angle DCG. | - The log. of 0’.9010288 is —I. 9547387 ’ The log. tang. of the angle DCF is 8. 8.844043 I Bie fam is 8. 8.7987818 The log. fine of the angle BCD is 8.964238t The difference —1.8345437 _ is the log. of 0'.6831934:; the angle DCG: therefore is) 0'.6831934,; therefore the angle ACG the anomaly of the excentric is é 94° 43'.1814126. ‘y » Vox. II. S ‘THE 1g8 ESSAYS ann. OBSERVATIONS | Tue three laft examples are taken from Dr. Keil’s aftronomical Lectures, Lecture 23d. and the numbers agree very nearly with his. In the orbits of Mercury and Mars, if the exce(s of the angle BCD above the angle A be added to the angle ACD, the fum will be nearly the anomaly of the excentric reckoned from the aphelion. In orbits of {mall excentricity, the angle ACD is nearly the anomaly of the excentric ; therefore the following rule will give the anomaly of the excentric very nearly. a From the logarithmic tangent of half the mean anomaly, fubtract the difference of the logarithms of the aphelion and perihelion’ diftances ; the remainder is the logarithmic tangent of an angle, which call B: to the angle B, add half the mean anomaly; the fds will give very nearly” si anomaly of the excentric. } BoA M*Pibwk uy, In the earth’s orbit, the mean diftance is to the excentricity as rooo0o to 1691. | Sup- pofe the mean anomaly from the aphelion to be 30°, it is required to find the anomaly of the excentric. | The PHYSICAL anp’ LITERARY. 139, The log. tang. of 15° is | 19:4280525 The diff. of the logs. of AS, SP is 0.0146892 _ The difference Fis 9:41 33633 is the log. tang. of 14° 31'.3670421, half the difference of the angles CSB, CBS; there- fore the angle CSB, et | is the apie ACD, is 29° 34'.367042; therefore the anomaly of, the excentric is nearly 29° 31’. ‘3670421, that is 29°-31'.22".022526, which agrees very nearly with Dr. Keil’s numbers im ‘the forefaid! Lecture. EXAMPLE Vi. es, in the earth’s, orbit, fico the mean anomaly to be 60° , it is required to find the anomaly of the excentric, The log. tang. of 30° is 9.7614394 The diff. of the logs. of AS, SP is o. Cranage : The difference 9. 7467 5c 502 is the log. tang. of 29° ro’ .081873, half the tcc of the angles CSB, CBS; there- _ fore the angle CSB, that is the angle ACD, : is 59° 10'.081873 ; therefore the anomaly of “the excentric is ahd 59° 10” eek Be, i. ) “EE Xs t40 ESSAYS ann OBSERVATIONS EcX A M°*P'L E © VIL In the orbit of Venus? the mean diftance is to the excentricity as 10000000 to 69855. Suppofe the mean .anomaly reckoned. from the aphelion to be 60°, it is required to find the anomaly of the excentric. The log. tang. of 30° is 9:°7614394 The diff. of the logs. of AS, SP is 0,0060677 -_-__ The difference sit 9:7553717 is the log. tang. of 29° 39'.27399595 half the difference of the angles CSC, CBS ; therefore the angle CSB, that is the angle ACD, is 59° 39 -2739959; therefore the anomaly of the excentric is nearly 59° 39°27 39959, that is 59° 39'.16".439754. Ir the mean anomaly aS from the perihelion be 120°, the anomaly of the ex- centric-would be nearly 120° 20.43°.560246, which ‘agtees very nearly with Mr. Machin’s numbers in the forecited tran{faction, Tue anomaly of the excentric being found, the coequate or true anomaly will be found by the refolution of the triangle GCS: Thus, from the log..tang. of half the anomaly of the excentric, fubtraét the difference of the : | logs, “PHYSICAL ann LITERARY. 141 logs. of the aphelion and perihelion diftances, _ the remainder ‘will be the Jog. tang. of an angle; to this angle add half the anomaly of the excentric; let the fum be called the angle C ; to: the log. tang. of the angle C, add half the fum of the logs. of the aphelion and perihelion diftances; from this fum, fub- tradthe log. of the mean diftance ; the re+ mainder will:be the log. tang. of the coequate or true anomaly. | Let CL be the leffer axis of the planet’s orbit. Becaufe, from the nature of the ellipfe, the’ {quare of CL is equal to the re- €angle ASP, the log. of CL will be equal to half the fum of the logs. of AS, SP: and, be- caufe the tangent of the angle KSH is to the _ tangent of the angle GSH as HK to HG; that is, from the nature of the ellipfe, as LC to CA; therefore, if to the log. tang. of _ the angle GSH, the log, of CL be added, MA nd from the fum the log. of AC be. fub- : racted, the remainder will be the log. tang, of the angle KSH. - AGarIn, the fine of the true anomaly is to the fine of the anomaly of the excentric, as _ the lefler axis of the orbit to the diftance of € planet from the fun, Pe BECAUSE m2 ESSAYS ann OBSERVATIONS Because CL is to HK as CG to GH, that is, as the radius to the fine of the ano- maly of the excentric, and HK is to KS as the fine of the true anomaly to the radius; therefore CL. is to KS as the fine of the true _ anomaly to the anomaly of the excentric. Tue place of a planet in an elliptic orbit [ granting the quadrature of the ellipfe} may be found at any given time within a {mall limit, by the following theorem. THEOREM. Fic. 7. Let the ellipfe, whofe greater axis is AP, foci S, K, and center. C, reprefent the orbit. of a planet round the fun at S; and, fuppofing the periodic time of the planet round the fun to be known, and likeways the time the planet paffed thro’ the aphelion A: As the pe- riodic time of the planet round the fun, is to the time elapfed fince the planet ae thro the point PHYSICAL any LITERARY. © 143: pee point A, fo let the area of the el- _ lipfe be to the fector ‘ACB; ' join - $B, and draw CD parallel to SB on. the fame fide of AP that SB is; . and let CD be equal to CA;, join’) ~ SD; let CD, SD, meet the ellipfein ~ E, F: the true place of the planet’ is between the points F, F; that is, the planet is paffed the point., — E, but not come to the point F. ¢* “el G be the place of the planet ; join; SG, and join BD meeting AP.in H, and join, KB; draw SL parallel | to KB meeting BD in L. Becaufe CD is parallel to. SB, CD will be to SB as CH to HS; therefore, twice CD will be to SB as twice CH to. HS.. gy But, becaufe twice CD is equal to AP, that "is, equal to KB together with BS, and twice CH is equal to KH together with HS; there- i foté KB together with BS will be to BS as _ KH together with HS is to HS; and there- » fore KB will be to BS as KH to HS, that is, as KB to SL; therefore BS, SL are equal : 4 th erefore the angle SBL is equal to the angle , oe SLB, | ~ 144. ESSAYS anv OBSERVATIONS SLB; that is, equal to the angle KBD ; and therefore, from a known property of the ellipfe, BD is a tangent to the ellipfe at the point B; and therefore [Prop. 2.} the feGtor ACB is greater than the fector ASE, and lefs than the fector ASF; but, becaufe G is the place of the planet, the area of the ellipfe will be to the fector ASG as the periodic time of the planet round the fun is to the time elapfed fince the planet paffed thro’ the point A, that is, as the area of the ellipfe to the feGtor ACB ; therefore the fecGtor ASG is equal to the fector ACB; and therefore the fector ASG is greater than the fector ASE, and lefs than the fector ASF ; there- fore the line SG falls between the lines SE, SF; and therefore G, the place of the planet, is between the points E, F; therefore the planet has paffed the point E, but not come to the point F. ArT. - ‘ i ee ie _ kh > ? , ® ~ ohh, 4 be oe re t : . \ 1 « s (>, . ‘ ve ® . 7 r . . ‘i ‘ . : i a ‘ ' i i ‘ ‘ ‘ f * os ‘ - } 7 t ° a f : een. ‘ + ’ 7 t : y a f 7 4 7 - f - yr a ey | 4 * * ‘ Fr ‘ ie La) v \ 2} -: a Ss 8 ‘J f ¥ 4 i. 5 Sea : ean tol “ 4 oe : . . : ‘ i . y PHYSICAL awd LITERARY. 14g Art. VII. Of the Cold produced by Evaporating Fluids, and of fome: ciber Means of producing Cold; by Dr: Wiitram Curren Profefor of Me- dicine in the Univerfity of Glafgow*. A Younc Gentleman one of my pupils, | . whom I had employed to examine the heat or cold that might be produced by the folution of certain fubftancés in fpirit of wine, obferved to me : That; when'a thermometer had been immerfed in fpirit of wine, tho’ the fpirit was exactly of the temperature of the furrounding air, of fomewhat colder; yet, upon taking the thermometer out of the {pirit, and fufpending it in the air, the mer- euty in the thermometer, which was of Fa- renbeit’s conftruCtion; always. funk two or “three degrees. This recalled to my mind fome experiments and obfervations of MM. de Mairan to the fame putpofe; which I had read fome timé before. See Differtation “fur la glace, edit. 1749. pag. 248, & feq. ev ov. 11. tT: ., -When tain ® May 1. 1755. | 146 ESSAYS ano OBSERVATIONS When I firft read the experiments of M. de Miaran in the place referred to, I fufpected, that water, and perhaps other fluids, in eva- - porating, produced, or, as the phrafe is, gene- rated fome degree of cold. The above ex- _ periment of my Pupil confirmed my fufpi- cion, and engaged me to verify it by a eae of new trials. T began by repeating the circa with fpirit of wine; and found, when I had taken the utmoft care to have the fpirit exactly of the temperature of the air, that ‘conftantly however, upon taking the thermometer out of the fpirit, the mercury funk feveral de- grees, and indeed continued to fink fo long as the ball of the thermometer continued wet with the fpirit of wine. I found alfo,, when the ball began to dry, and the mercury to rife again in the ftem of the thermometer, that, if the ball was again dipped into the {pirit’ and immediately taken out, the mer- cury in the thermometer might be again obferved to fink, and that thus, by repeated dippings, the cold produced might be ren- dered very remarkable. The cold produced was alfo obferved to be ftill greater, when, between cach dipping, the thermometer was - moved i NE I sl PHYSICAL ann LITERARY. 147 moved very nimbly to and fro in the air; or if, while ‘the ball was wet with fpirit of wine, it was blown upon by a pair of bellows; or indeed if the air’ about the ball’ was other- wife any how put ih motion. If any of thefe’ means for putting the’ aif in ‘motion ate em- ployed, ‘the ‘repeated moiftenings of the ball of the thermometer may be performed by dipping “it into. the ‘fpirit of wine. But, when ‘aocertain ‘degree of cold ‘has been produced by a firft dipping, that'is apt :to be diminifhed by dipping again into the warmer fpirit; and therefore the thermometer ought either to. be dipped into the fpirit and taken out again very quickly, ‘or, what is ‘fill better, the ball of the thermometer ought to be moift- ened by a feather that has been dipped into the fpirit of wine. \“By taking thefe methods, I have by fpirit of wine made‘the mercury in the thermometer fink from 44 degrees to ; below the freezing point ; and, by employing . fome’ other flnids to, ‘be mentioned. by and by, - T have produced « a finking of the thermo- meter much more ‘confidérable be » IN making experiments of this. kind;, it is to be obferved, that the cold produced i is ‘al very fhort duration. On this account it is 148 ESSAYS ann OBSERVATIONS is not proper to employ a thermometer in- clofed in a glafs tube; and it is neceflary ta employ one -having a {mall ball, which may. render it more fenfible.. But, as a/ {mall ball occafions. the divifions.of the fcale to, be the {maller, a thermometer filled with-‘quick- filver is not fo proper for thefe experiments, as one filled with {pirit of wine ;, having at the fame.time both a {mall ball anda flender ftem, What beft of all thews the cold cpro= duced, and is indeed, with refpect to feveral fluids, quiteneceflary, is an Air thermometer. This too will be sendered more convenient: by having the: upper part of the tube bent as in the. figure annexed, fo. that . the ball may be moiftened without the liquor’s. running. down | upon the ftem and feale, , Thave entered into this detail for the fake of thofe who may defire to repeat my, experi- ments. Having now faid enough on the man- ner of making them, I go on to obferye, that in this way I have examined a great variety of Alnids. Such as, _ The PHYSICAL asp LITERARY. 149, "The quick-lime Jpir it of fal. ammoniac, . The-ather of Frobenius, The nitrous ather, ~The volatile tinéture of filphurs Spirit of wine, Spirit of fal. ammoniac made with the fre ~ alkah, 2 . _ Brandy, « Wine, onli der riveq' bas re= turns to thestemperature of the air in the | chamber, and upon letting air again into:the receiver, the thermometer always rifes two: of three degrees above the temperature of the: external air. os _ Wen a veffel. containing fpitit of wine;: _ with a thermometer immerfed) in’ it, is fet __under the receiver of an air-pumps upon: % exhaufting the air, the mercury in the. ther- mometer finks feveral degrees.) It, becomes more efpecially remarkable when ‘the air in Wo. II. | J any -154, ESSAYS and OBSERVATIONS any plenty iffues out of the =f{pirit of wine. As the fpirit continues long to give out air, fo it.is long before the thermometer. im- merfed in it returns to the temperature of the external -aif.. But when after fome ‘time it appears ftationary, if it is then drawn up out of the fpirits and fufpended in the vacuum, the mercury finks very quickly eight or mine degrees; a good deal farther than ‘it would have: done in.the fame circumftances inthe air. In the fame manner as in: the air, the thermometer 7” vacuo may be made to fink lower by repeated dippings into the fpirit of wine: but here thefe repeated dippings have not fo remarkable an effect as in the air; becaufe the dipping cannot be: fo’ quickly performed, and the thermometer is therefore more affected by the warmth of the fpirit. It is fometimes alfo affected by a drop: of the fpirit’ which the ball takes up along with it, and which, as I fhould have obferved: above, ought al- ways to be taken away in the experiments made in the air. . This experiment with fpirit of wine was often enough repeated, to- thew clearly, that the evaporation of the fpirit | im x rad Se PHYSICAL any LITERARY. ‘t45 ‘gn vacuo prodaces‘a greater degree of cold than the evaporation of the fame’in the air. SATISFIED of this, I have tried alfo‘fome other fluids; as the ‘quick-lime{pirit° of fal. ammoniac, and thé ‘two.kinds’ of ether. Veflels | containing ‘thefe with a thermometer immierfed in the liqdor;" but {eparately aad at different ‘times, were fet under the receiver. ‘With regard to thé different fluids,’ the phe- Momena were much the fame.’-’ Upon ex- haufting the receiver, the fluid’ gavé out a great quantity of elaftic air; and ,while this happened, ‘the miercury in the’ immerfed thermometer funk -very faft and to a great Jength. In‘our trials, it generally fank below ‘the® fcale: applied fo ‘that’ we “eould not meafure vexatly “how “far. \ In one’ experi- -ment’ before :exhaufting the* receiver, the thermometer ‘had: ftood at 50 degrees, and, after exhaufting, we could judge very cer- ‘tainly that it funk to below 20.\\ Inanother experiment made with the nitrous ether, when the heat of the air was about 53 de- grees, we fet the veffel containing the ether in ‘another a little larger containing water. Upon exhaufting the receiver, and the veffel’s remaining for a few minutes 42 vacuo, we found .156 ESSAYS anp OBSERVATIONS found.the.moft part.of the water frozen, and _the veffel containing the ether furrounded with a thick and firm cruft of ice. » SucH.a means of producing cold, and to fo great a degree, has ‘not, fo far as: I know, been obferved before, and it feems to deferve -being . further) examined by experiments. Till that.is done, I do-not-chufe to give any account of fome other remarkable pheenomena that have occurred in the above experiments, nor to enter into the feveral fpeculations that the fubject feems to fuggeft. SiNCE writing the above, I have had occa- fion to obferve, that Mr. Richman of the A- cadamy of Peter/burg has taken notice of the effect. of evaporating fluids in’ producing cold; -but does. not impute it to the evaporation alone. His very exad&t account of the pheno- mena, and his theory with regard to them, may be feen in Nov. Comment. Acad. Petropor litane ad ann. 1747 & 1748. page 284, ART, . PHYSICAL ‘ann LITERARY. °157 “Agr. VIL... oa hale ‘upon Magnelia alba, Qyicklime, and fome other Alcaline Suifianees 4 by foszrs BLACK, M, D. ial. Bee 3 101: se8PARP L olen en (®) [ OFFMAN, in one “of ar Sbiervas tions, gives the hiftory . ‘of a. powder ‘called magnefia alba, which, had been long fed. and efteemed as, a. mild and taftelefs purgative ; but the method of, preparing. it ‘was not, generally known ‘before he made it public +. ri : ‘Ir was originally aden ‘from : a liquor % called the mother of nitre, which i is prods in the following manner: _ “SaLT-PETRE. is feparated from the tiene which firft affords it, or from the water with which it is wafhed out of nitrous earths, _ by the procefs commonly ufed in cryftallizing fats. In this procefs the brine is gradually sh diminifhed, and at length reduced to a {mall pugntity of. an unduous bitter faline liquor, affording ab June 5. 1755. OF ‘Hoff, op, T. iv. p, 479. 158 ESSAYS Ann OBSERVATIONS affording no more falt-petre by evaporation ; but, if urged with a brifk fire, drying up into a confufed mafs which’attratts water ftrongly, and becomes fluid. again when expofed to the ppa air. To this liquor the workmen have given the name of the mother of nitre; and Hoffman, finding it compofed of the magnefia united to an acid, obtained a feparation of thefe, either by expofing the compound to a ftrong fire in which the acid: was diffipated and the magne= fia remained behind, or ‘by t the addition of an alkali which attracted the acid to itfelf : and this Taft method he recommends as the beft. He likewife makes an inquiry into the nature and virtues of the powder thus prepared ; and obferves, ‘that it is an abforbent earth which jeins readily with all acids, and muft ne- ceflarily deftroy any acidity it meets in the ftomach ; but that its purgative power is un- certain, for fometimes it has not the leaft effe@ of that kind, As it is a mere infipid earth, he rationally concludes it to be pur- gative only when converted into a fort of neutral falt by an acid in the, ftomach, and ‘that its effeé is therefore proportional to the quantity of this acid. . ALTHQ’ ‘PHYSICAL anp LITERARY. 42 ALTHO’ magnefia appears from this hiftory of it to be avery innocent medicine,~ yet having obferved, that fome hypochondriaes who iufed it frequently, were! fubje& to flatu- lencies.and fpafms, he feemsito have fufpected it of fome noxious quality. » The circum- ftances however which gave rife to his fufpi= cion, may very poflibly have proceeded from the-imprudence of his) patiehts, .who, trufting too much to magnefia, (whichzis properly a palliative in that-difeafe,) and negleéting’the affiftance: of other: remedies, allowed their - diforder to increafe- upon them. « It may-in- deed:be alledged, that magnefia,. as a purga~ tive, is not the moft eligible. medicine for fuch conftitutions, as they agree, beft with thofe.-that: ftrengthen, ftimulate and warm ; which the faline:purges commonly ufed are not»obferved to do. | But there feems at leaft: - to be no objection to its ufe: when. children are troubled with: an acid in their ftomach; for gentle purging in this cafe is very proper, and it is often mote conveniently procured by _ means of magvefia than of any other medicine, _ of account of its being intirely infipid. Beli Die above-mentioned Author. obferving, . fome time after, that a bitter faline liquor, fimilar x60 ESSAYS anp OBSERVATIONS fimilar to that,,obtained from the brine’ of falt-petre, ... was likewife-- produced. by: the -evaporation of thofe waters which. contain common falt, had the curiofity to try if this would alfo: yield: a magnefia. The experi- ment fucceeded: and he thus found out another procefs for obtaining this powder, and at the fame time afflured himfelf by ex- periments, that the product from both ‘was exactly the fame*. My curiofity led me fome time ago to in= | quire more particularly into the nature of magnefia, and: efpecially to compare its pro- perties with thofe of the other abforbent earths, of which there plainly-appeared to me to be very different kinds, altho’ commonly confounded together under one name. — I was indeed led to this examination of the abforbent earths, partly by the hope of dif- covering a new fort of lime and lime-water, which might poflibly be*a more powerful folvent of the ftone than that commonly ufed; but was difappointed in my expecta- tions. I have had no opportunity of feeing Hof- man’s firtt magnefia or the liquor from which % it * Hoff. Op. T. iv. p. 500. “PHYSICAL and LITERARY. 168 it is prepared, and have therefore been obliged to make my experiments upon the fecond. ' | In order to prepare it, I at firtt employed the bitter faline liquor called drttern, which remains in the pans after the evaporation of fea water, But as ‘that Jiquor is not always eafily procured, FT afterwards: made ufé of a falt called epfom-falt, which is feparated from the bittern by cryftallization, and is evidently compofed of magnefia and the vitriolic acid. TuHereE is likewife a fpurious kind of Glauber falt, which yields plenty of magnefa, and feems to be no other than the epfom {alt of fea water reduced to’ cryftals of a larget fize. And common falt alfo affords 4 {mall quantity of this powder; becaufe being fepa- rated from the bittern by one hafty cryftalli- zation only, it siberene? contains a portion of that liquor. -'Tuose who would prepare a magnefia from one may ufe the following procefs. ' Dissorve equal quantities of epfom-falt, and of pearl afhes feparately in 4 fufficient quantity of water; purify each folution from its dregs, and mix. sa cia ig!) together 1-4 Vou. II. by 162 ESSAYS ann OBSERVATIONS by violent agitation: then make them juft to boil over a brifk fire. | | App now to the mixture three or four - times its quantity of hot water ; after a little agitation, allow the magnefia to fettle to the bottom, and decant off as much of the water as poflible. Pour on the fame quantity of cold water; and, after fettling, decant it off in the fame manner. Repeat this wafhing with the cold water ten or twelve times: or even oftner, if the magnefia be required per- fe€tly pure for chemical experiments. WHEN it is fufficiently wafhed, the water may be ftrained and fqueezed from it ina linen cloth ; for very little of the magnefia, paffes thro’. Tue alkali in the mixture uniting with the, acid, feparates it from the magnefia; which not being of itfelf foluble in water, muft confe- quently appear immediately under a folid form. But the powder which thus appears is not intirely magnefia; part of it is the neutral falt, formed from the union of the acid and alkali. This neutral falt is found, upon examination, to agree in all refpects with vitriolated tartar, and requires a large quantity of hot water to diffolve it. As much of it is therefore dif- folved PHYSICAL ann LITERARY. 163 ‘folved as the water can take up; the reft is difperfed thro’ the mixture in the form of a powder. Hence the necefflity of wafhing the magnefia with fo much trouble ; for the firft affufion’ of hot water is intended to diffolve _ the whole of the falt, and the fubfequent ad- ditions of cold water to wath away this fo- dution. | THE caution given of boiling the mixture is not unneceflary; if it be neglected, the whole of the magnefia is not accurately feparated at once; and by allowing it to reft for fome time, that powder concretes into “minute grains, which, when viewed with the mi- crofcope, appear to be affemblages of needles diverging from a point. This happens more efpecially when the folutions of the epfom- -falt and -of the alkali are diluted with too much water before they are mixed together. Thus, if a dram of epfom-falt and of falt of tartar be diflolved each in four ounces of water, and be mixed, and then allowed to reft three or four days, the whole of the magnefia . will be formed into thefe grains. - Or if we filtrate the mixture foon after it is made, and _ heat the clear liquor which’ paffes thro’; it will become turbid, and depofite a magnefia. J 164 ESSAYS ayp OBSERVATIONS I had the. curiofity to fatisfy myfelf of the purgative power of magnefia, and of Hoffman’s opinion concerning it, by the following eafy experiment. I madeaneutral falt of magnefia and diftilled vinegar; -choofing this acid as being, like that in weak ftomachs, the produc& of fermentation, Six drams of this I dif- folved in water, and gave to a middle-aged man, defiring him! to take it by degrees. After having taken about a third, he defifted, and purged four times In an eafy and -gentle manner. A woman of.a {trong conftitution got the remainder as a brifk purgative, and it operated ten times without caufing any un- eafinefs. The tafte of this falt is not dif- agreeable, and it appears to be rather of the | cooling than of the acrid kind. Havine thus given a thort fketch of the hiftory .and medical virtues of magnefia, I now proceed to an account of its chemical properties. By my firft experiments, -I in- tended to learn what fort of neutral falts might be obtained by joining it to each of the vulgar acids ; and the refult; was as follows. Macnesia. is quickly diffolved with vio- lent effervefcence, or explofion of air, by the acids PHYSICAL ann LITERARY. 165 acids of vitriol; nitre, and-of common: falt, and» by diftilled vinegar; the: neutral faline liquors thence produced having me wag peut properties. . Tuar iwhich is made aithy the vine acid; may be condenfed into pry lei Gipuitar in all refpects to epfom-falt, juoed « | Tuar, which» is) made .with the ‘nitrous is of, a yellow colour, - and yields» faline crydtals, which retain their form in»a: wony dry air, but melt in a moift-one. : \)Tuar whichiis produced by means ' vie fpitit of falt, -yields no cryftals; and if. eva- jorated to sas foon melts again when ex+ — to the-air; THAT which :i is obtained ‘from the union eit diftilled vinegar with magnefia, affords no . eryftals by evaporation, but is condenfed — into a faline mafs, which, while warm,’ is extremely tough and vifcid, very much re- fembling a ftrong glue both in colour and confiftence, and becomes brittle when cold. By thefe experiments magnefia appears to _ be a fubftance very different from thofe of the calcarious clafs; under which I would 7 be underftood to comprehend all thofe that @fe converted into a perfect quick-lime i in a , firong a66 ESSAYS ann OBSERVATIONS ftrong fire, fuch as iime-/tone, marble, chalk, thofe fpars and marles which effervefce with aqua fortis, all animal jfhells and the bodies called /thophyta. . All of thefe, by being joined: with acids, yield a fet of compounds which are very different from thofe we have juft now defcribed Thus, if a fmall quantity ‘of any calcarious matter be reduced to a fine: powder and. thrown: into {pirit .of vitriol, .it is “attacked by this -acid with a brifk effervefcence ;. but little or no diffolution enfues. It abforbs the acid, and remains united with it in the form: ofa white powder, at the bottom of the. veffel, while the liquor has hardly any tafte, and fhews only a very light cloud upon the addi- tion of an alkali¥, ri . Tue fame white powder is alfo formed when fpirit of. vitriol is added to a calca- carious earth diffolved in any other -acid ;. the vitriolic expelling the other acid, and joining * Mr. Margraaf has lately demonftrated, bya fet of curious and accurate experiments, that this powder is of the nature, and poffeffes the properties, of the gypfeous or felenitic fub- ftances. That fuch fubftances can be refolved into vitriolic acid and calcarious earth, and can be again compofed by joining thefe two ingredients together, Mem de l’Acad, de Berlin, an, 1750, p. 144, . : Hoff. Op. T. iv. p. 480 & 500. t PHYSICAL ann LITERARY. 16 joining itfelf to the earth by a ftronger /attra- ion ; and upon this account the magnefia of, fea-water feems to be different from either of thofe defcribed by Hoffman....He fays ex- prefsly, that the folutions of each. of his. pow-, ders, or, what is equivalent, that the liquors, from which , they.are obtained, formed,-a, _coagulum, and .depofited , a, white ,powder,, when he added the vitriolic acid *; , which. experiment ‘I -have often, tried) with, the marine bittern, but. without) fuccefs. .,..The. coagulum thus, formed in the mother, of, nitre may be owing’ to’a;quantity of quicks lime contained/in it ; for, quick-lime is,ufed in. extracting , the. falt-petre from, its matrix,, But itis more. difficult to account, for the dif, ference between Hoffman's, bittern and. ours, unlefs. we will. be fatisfied to refer. it to, this, that he got his from the waters of falt {prings;, which may, poflibly be different from nale of the fea. Macnesta is not lefs remarkably diftin: guithed from the calcarious barthe by j joining, ; te hie LT hale earths, sais cbiaitaaeh with fpirit of nitre, cannot be reduced to.a cryftalline ‘ ‘ Ke ESSAYS ayn OBSERVATIONS cryftalline form, ‘and if they ate diffolved in diftilled vinegar, the mixture fpontaneoutly dries: ‘up into‘a friable falt. ~“Havine thus found magnefia to differ from the common alkaline earths, the object f my next inquiry was its peculiar degree of attraction for acids, or what was the place due to’ it ‘in ‘Mr? Geogr oy’s table’ of elective attractions. Dia THREE drartié of rhdgnip @in ine scree 4n ouncé of ‘faléammioniae, ard’ fix ounces: of water were ‘mixed. together, » ‘and digefted fix days i ina retorfjéined. to'a receiver. Durine the whole time, the neck of the retort was pointed a little upwards, and the moft® watery: ‘part’ of the vapour, :which was condenfed there,’ fell back into its body. In the beginning’ of the experiment, a volatile falt was ihererare collected in a dry form in the -receiver; -and--afterwards diflolved into {pirit. ; ; 10 Wuen all was’ cool, I found in the retort a faline liquor, fome undiffolved magnefia, and’ fome falt ammoniae cryftallized:~ The faline liquor was fepatated from the other two, and c3 mixed withthe alkaline: fpirit. A coagulum PHYSICAL any LITERARY. 69 eoagulum was immediately fornied, and a magnef a precipitated from the mixture. Tite magnefia which had temained in the retort, wher well wathed and dried, weighed two fetuples and fifteen grains. © oe ‘We learn by the latter part of this experi ment, that the attradtidh of the volatile alkali for acids is ftrongér’ than that’ of magnefia, fince it feparated this powder from ‘the acid to which it was joined: But if aif: appears, that 4 geritle heat is capable of overcoming this fuperiority of attraction, and/of gradually elevating the alkali, while it leaves the lefs volatile acid with the waynsfid.° Dissorve a dram of “any ealeatious fetid - fkance in’ the acid of hitre of of common falty taking care that the folution be tendeted per? feGly neutral, of that no fuperfluous acid be added. Mix with this folution a dram of whagnéfia im fine powder, afid digett it in the heat of boiling water about twenty fout hours; then dilute thé mixture with double ite’ quantity of water, and filtrate. The greateft part of the earth mow left in the -filtre is vcalcarious, and the liquor which pafied thro’, if vane with a diffolved alkali, Mou. I ¥ os oyielda: i 370 ESSAYS anp- OBSERVATIONS yields a white powder, the largeft portion. of which is a true magnesia. From this experiment it appears, that an acid quits a calcarious earth to, join. itfelf to maghefia ; ‘but the exchange being performed flowly, feme of the magnefia is. ftill un- diffolved, and part of the calcarious earth remains yet,joined to the acid. WHEN. a {mall quantity of magnefia is thrown. into. a {olution of, the corrofive fubli- mate of mercury, it foon feparates part of the mercury inthe form of a dark red powder, and is itfelf diffolved. j . Imacrnine that I perceived fome ‘refem- blance between the properties of magué/fia and thofe of, alkalis, I was led to: try what change this fubftance would. fuffer from the addition of quick-lime, which alters in fuch a peculiar manner the alkaline falts.’ . Twenty feven, grains of magnefia in fine powder were mixed with eighteen ounces of lime-water in-a flafk, which, was corked clofe and fhaken frequently for four days. During this time, I frequently dipp’d into it little bits of paper;’ which were coloured with. the juice of violets; and thefe became green as foon. as they touched the water, until. the fourth ee ae “PHYSICAL! Ann LITERARY. i7} | fourth day, when their'colour ‘did not feém ~ to be altéred. » Thewater being now poured off, was intirely infipid, and agreed in every chemical trial with pure water. The-pow- der; after being perfectly well dried, weighed thirty feven grains. It did not diffolve intirely in fpirit of vitriol; but, after a brifk effer vefcence, part of it fubfided in the fame ‘man- ner as the calcarious ‘earths, when mixed _ with this acid. - Wuen T firft tried this experiment, I was at the trouble of digefting the’ mixture’in the heat of. boiling water, -and did ‘not then know that it would fucceed in ‘the’ heat of the air. But Dr. Aifon;? who has. obliged the world with many curious and‘ ufeful difco- — veries on the fubje& of quick-lime, having had occafion to repeat it, I learned from him that heat is not neceflary ; and he has more- over added an ufeful purpofe to which this property of magnefia may be applied; I mean the fweetening of water at fea, with which lime may have been mixed to prevent its pu- trefaction. THAT part of the gue powder: which B 3 Bines not diffolve in fpirit of vitriol, confitts oe - the lime feparated from the water.” Wed QUICK-LIME i72 ESSAYS ann OBSERVATIONS Quick-Lrmg itfelf is alfo rendered mild by magnefia, if thefe two are well rubbed together and infufed with a {mall quantity of water. By the following experiments, I propofed to know whether this {ubftance could be re- duced to a quick-lime. AN ounce of magnefiae was expofed in a erucible for about an hour to fych a heat as is fufficient to melt copper. When taken out, it weighed three drams and one fcruple, er had loft 7, of its former weight. I sepeated, with the wagnefia prepared in this manner, moft of thofe experiments I had already made ywpon it before calcina- tion, and the refult was as follows. Ir diffolves in all the acids, and with ‘sth compofes falts exactly fimilar to thofe de- {cribed in the firft fet of experiments: but what is particularly to be remarked, it is dif- folved without any the leaft degree of effer- vefcence. Ir flowly precipitates the corrofive fub- limate of mercury in the form of a black powder. Ir feparates the volatile alkali in falt am- moniac from the acid, when it is mixed with PHYSICAL ann LITERARY. 173 with a warm folution of that falt. But it does not feparate an acid from a calcarious earth, nor does it induce the leaft went upan lime-water, _ Lastiy, when a dram of it is digefted with an ounce of water in a bottle for fome hours, it does not make any the leaft change in the water. The magnefia, when dried, is found to have gained ten grains; but it nei- ther effervefces with acids, nor does it fen- fibly affect lime-water. OBsERVING magnefia to lofe fuch a ree markable proportion of its weight in the fire, my next attempts were direéted to the in- veftigation of this volatile part, and, among other experiments, the following feemed to throw fome light upon it. _ THREE ounces of magnefia were diftilled-in a glafs retort and receiver, the fire being gradually increafed until the magnefia was obfcurely red hot. When all was cool, I found only five drams. of a whitith water in the receiver, which had ‘a faint fmell of the fpirit of hartfhorn, gave a green colour to the : pice of violets, and rendered the folutions of “gorrofive fublimate and of filver very flightly _ turbid, 174 ESSAYS ann OBSERVATIONS turbid. But it did not fenfibly effervefce with acids. Tue magnefia, when taken out of the re- tort, weighed an ounce, three drams, and thirty grains, or had loft more than the half of its weight. It ftill effervefced pretty brifk- ly with acids, tho’ not fo: ftrongly as before this operation. Tue fire fhould have been raifed here to the degree requifite for the perfec calcinati- on of magnefia. But even from this imper- fect experiment, it 1s evident, that of the vo- latile parts contained in that powder, a {mall proportion only i is water; the reft cannot, it’ feems, be retained in veffels, under a vifible form. Chemifts have often obferved, in their diftillations, that part of a body has vanifhed from their fenfes, notwithftanding the utmoft care to retain it; and they have always found, upon further inquiry, that fubtile part to be air, which having been imprifoned in the body, under a folid form, was fet free and rendered fluid and elaftic by the fire. We may therefore fafely conclude, that the vola- . tile matter, loft in the calcination of magnefa, is moftly air; and hence the calcined mag~ nefia »PHYSICAL anv LITERARY. 175 nefia does, not emit air, or make, an effervef- cence, when mixed with acids. Psy Lae water, from its properties, feems_ to. contain a {mall. portion of? volatile. alkali, which. was probably formed from the earth, air, and water, or from fome of thefe com- bined together; and perhaps alfo from a fmall quantity of inflammable matter which adhered accidentally to the magnefia,. When- ever Chemifts. meet.with this falt, they are inclined to afcribe its origin to. fome animal, oat always done, when shes obtained it from the calcarious earths, all of which af- ford a {mall quantity of it. There) is, how- ever, no doubt that it.can fometimes be pro- duced, independently of any, fuch, mixture, fince. many freth vegetables and tartar afford a -confiderable quantity of it. And -how can -it,/in the prefent inftance, be fuppofed, that any animal or vegetable matter adhered to the magnefia, while it was diffolved by an acid, | feparated from this | by an alkali, and wafh- ed with fo much water? _ Two drams of magnef fa were calcined in a eearible, in the manner defcribed above, and : us reduced to two {cruples and twelve a; grains. ty6 ESSAYS anp OBSERVATIONS erains. This calcined magnefia was diffolved in a fufficient quantity of {pirit of vitriol, and then again feparated from the acid by the ad- dition of an alkali, of which a large quanti+ ty is neceflary for this purpofe. The mag- nefia being very well wathed and dryed, weighed one dram and fifty grains. It effer- vefced violently, or emitted a large quantity of air, when thrown into acids, formed a red powder when mixed with a folution of fub- limate, fepatated the calcarious earths from an acid, and fweetened lime-water: and had thus recovered all thofe properties which it had but juft now loft by caleimation : hor had it only recovered its original properties, but acquired befides an addition of weight nearly equal to what had been loft in the fire; and, as it is found to effervefce with acids, part of the addition muft certainly be air. Tuis air feems to have been furnifhed by the alkali from which it was feparated by the acid; for Dr. Hales has clearly proved, that alkaline falts contain a large quantity of fixed air, which they emit in great abundance when joined to a pure acid. In the prefent cafe, the alkali is really joined to an acid, but without any vifible emiffion of air 5 and yet the q PHYSICAL ann LITERARY.; 177 the air is not retained in it: '-for the neutral fait, into which it is converted, is the fame in quantity, and in every other refpect,: as if the acid employed had. not been. previoufly faturated with magnefia; ‘but offered to «the . alkali in its pure ftate,: and had driven the air out of it.in their confli@. -It feems there- fore evident, that the: air was forced from the alkali by the acid, and lodged itfelf in the “magnefia. Tuese confiderations led me to try a: ew experiments, whereby I-might know what quantity of air is expelled from an ‘alkali, or _ from magnefia, by acids.» Two drams of a pure fixed alkaline falt, and an ounce of water, were put into aFloren- tine flatk, which, together with its contents, weighed two ounces and two. drams. Some oil of vitriol diluted with water was dropt in, until the falt was exactly faturated ; which it was found tobe, when two drams, two feru- ples, and three grains of this acid had been added. The vial with its contents now weighed two ounces, four drams, and fif- teen grains. One ‘fcruple, ‘therefore, and eight grains were loft during the ebullition, _ of which a trifling portion may be water, or wo. II. Z fomething i178 ESSAYS ann OBSERVATIONS fomething of the fame kind. The reft is air. Tue celebrated Homberg has attempted to eftimate: the quantity of folid falt contained . in a determined portion of the feveral acids. He faturated equal quantities of an alkali with each of them ; and, obferving the weight which the alkali had gained, after being per- featly dryed, took this for the quantity of fo- id falt contained in that fhare of the acid which performed the faturation.. But we learn from the above experiment, that his efti- mate was not accurate, becaufe the alkali lofes weight as well as gains it. Two drams of magnefia, treated exactly as the alkali in the laft experiment, were juft diffolved by four drams, one fcruple, and fe- ven grains of the fame acid liquor, and loft one fcruple and fixteen grains by the ebulli- tion. Two drams of magnefia were reduced, by - the action of a violent fire, to two fcruples and twelve grains, with which the fame pro- cefs was repeated, asin the two laft expe- riments ; four drams, one fcruple, and two grains of the fame acid were required to com- pleat PHYSICAL ann LITERARY. 179, pleat the folution, and no weighty was loft.in, the experiment. ‘As-in the feparation of the pileaiie from the fixed parts of bodies,” by means,of heat,. a fmall.quantity of the latter is generally rai- fed with’ the former; fo the air and water, o- riginally contained’ in. the magnefia, and after- wards) diflipated by the:fire, feem to have carried off a {mall part, of the fixed. earth of this. fubftance. . This is probably, the rea- fon, why calcined magnefia is faturated with a quantity of acid; fomewhat lefs than what is required to difflolve: it before calcination : and the; fame may be afligned as one canfe which.hinders us from _reftoring the whole of its original asa Py. folution and Paseibltts tions 3! f5ic! I took care to alee veh iesiltec acid, in order. to avoid the heat and ebullition which _ it would.otherwife have excited in the water ; and I chofe a Florentine flafk, on. account of its lightnefs, capacity,» and fhape;, .which is peculiarly adapted to, the experiment ; for _ the vapours raifed by the ebullition;circulated for a fhort time, thro? the wide cavity of the vial, but were foon collected upon its fides, like dew, and none of them feemed to reach the 180 ESSAYS ann OBSERVATIONS the neck, which continued perfealy “ta to > end of the experiment. ‘ We now perceive the reafon, why: crude and calcined magnefia,° which differ if many refpets from one another, agree howevet in compofing the fame kind of falt,” when’ dif- folved in'any particular acid; for the crude magnefia feems to differ from the caleined chiefly by containing a’ confiderable quantity of ‘air, which air is unavoidably diffipated and loft during the diffolution. ; ' From out experiments, it feems probable, that the increafe of weight which fome. me- tals acquire, by being firft diffolved in acids, and then feparated from them again by alkalis, proceeds from air’ furnifhed by the: alkalis. And that in the aurum fulminans, which is pte- pared by the fame meatis, this air adheres to the gold in fuch a peculiar manner, that, in a moderate degree of “heat, the whole of it recovers its elafticity in the fame inftant of time i and-thus, by the’violent fhock which it givés to-the air around, produces the loud crack or fulmination of this powder. «Thofe who will imagine the explofion of fuch a mi- nute portion of fixed air, as can refide in the aurum fulminans, to be infufficient fot the excefliye PHYSICAL ann LITERARY. 181 _exceffive loudnefg of the noife, will confi- der, that it is not a large quantity of motion communicated to the air,- but rather a {mart ftroke which produces found, and that the.ex- plofion of bat:a few particles of fixed air may, be capable of caufing a loud noife,, provided they all recover their selec and in the fame inftanti - THE above experiments th us alii Pa conclude, that yolatile alkalis, and the com- mon abforbent,earths, which: lofe. their) air by being, joined to acids, but fhew evident figns of their having recovered it, when fe- parated from them by alkalis, received it from thefe alkalis which loft it in the inftant of their j joining with the acid. Tus following are a few experiments upon three of the abforbent earths, made in order to compare them with one another, and with magnesia. Sufpecting that magnefia might poftibly os no other than a common calcarious earth, which had changed its nature, by having been previoufly combined with an acid, I fatura- — ted a {mall quantity of chalk with the muria- tic acid, feparated the acid from it again by means 182 ESSAYS anno OBSERVATIONS: means of a fixed alkali, and carefully wafh- éd away the whole of the falt. Tue chalk when dryed was not found to have fuffered any alteration ; for it effervef- ced with the vitriolic acid, but did not diffolve in it; and when expofed to a violent fire, was converted into a quick-lime, in all re- {pects fimilar to that obtained from common chalk. In another experiment of the fame kind, I ufed the vitriolic acid with the fame event. Any calcarious matter reduced to a fine powder, and thrown into a warm folution of alum, immediately raifes a brifk effervefcence. But the powder is not diffolved ; it is rather increafed in bulk: and if the addition be re- peated until it is no longer accompanied with effervefcence, the liquor lofes all tafte of the alum, and yields only a very light cloud upon the admixture of an alkali. From this experiment we learn, that acids attract the calcarious earths more ftrongly than they do the earth of alum ; and as the acid in this falt is exactly the fame with the vitriolic, it compofes with the calcarious- earth a neutral fubftance, which is very diffi- cultly foluble in water, and therefore falls down PHYSICAL ano LITERARY. 183 down to the bottom of the veffel along with the earth of alum which is deprived of its acid. . The light cloud formed by the alkali proceeds from the minute portion of the calcarious compound which faturates the water. Tue earth of animal bones, when reduced toa fine powder and thrown into a diluted vitriolic acid, gradually abforbs the acid in the fame manner as the calcarious earths, but without any remarkable effervefcence. When it is added to the nitrous or to the muriatic acid, it is flowly diffolved. The compound liquor thence produced is ex- tremely acrid, and ftill changes the colour of the juice of violets toa red, even after it is fully faturated with the abforbent. Diftilled vinegar has little or no effeét upon this earth; _ for after along digeftion it ftill retains its four tafte, and gives only a light cloud upon the addition of an alkali. By dropping a diffolved fixed alkali. into a warm folution of alum, I obtained the earth of this falt, which, after being well wafhed _ and dried, was found to’ have the following — | properties. Ir 184 ESSAYS ann OBSERVATIONS . Ir is difflolved-in every acid but very. flowly, unlefs aflifted by heat.. The feveral folutions, when thoroughly faturated, are all aftringent with a flight degree of an acid tafte, and they alfo agree with a folution of alum in this, that they give a red colour to the infufion of turnfol. Nerruer this earth, nor that of animal bones, can be converted into quick-lime by the ftrongeft fire, nor do they fuffer any change worth notice. Both of them feem to attract acids but weakly, and to alter their properties lefs when united to them than the other abforbents. | Parr Ii. N reflecting afterwards upon thefe expe- riments, an explication of the nature of lime offered itfelf, which feemed to account, in an eafy manner, for moft of the proper- ties of that fubftance. Ir is fufficiently clear, that the calcarious ~ earths in their native ftate, and that the alkalis and magnefia in their ordinary condi- tion, contain a large quantity of fixed air, and this PHYSIC AL any LITERARY. 183 this air certainly adheres to them with confi- derable force, fince a ftrong fire is neceflary to feparate it from magnefia, and the ftrongeft is not fufficient to expell it entirely from fixed alkalis, or take away their power of effervef- _ cing with acid falts. . ’ Turse confiderations led me to conclude, that the relations between fixed air and al- kaline fubftances was fomewhat fimilar to the relation between thefe and acids ; that as the calcarious earths and alkalis attract acids ftrongly and can be faturated with them, fo they alfo attract fixed air, and are in their ordinary ftate faturated with it: and when we mix an acid with an alkali or with an abfor- bent earth, that the air is then fet at liberty, and breaks out with violence; becaufe the al- kaline body attracts it more weakly than it does the acid, and becaufe the acid and air cannot both be joined to the fame body at the fame time. 1 | _ I alfo imagined, that, when the calcarious earths are expofed to the action of a violent fire, and are thereby converted into quick- _ lime,. they fuffer no other change in their - compofition than the lofs. of a {mall. quantity of water and of their fixed air. The re- Vou II. Aa | markable 186 ESSAYS ann OBSERVATIONS markable: acrimony which we perceive in them after: this procefs, was not fuppofed to proceed from any additional matter received in the fire, but feemed to be an effential pro- perty of the pure earth, depending on an attraction for thofe feveral fubftances which it then became capable of corroding or dif- folving, which attraction had been infenfible as long as the air adhered to the earth, but difcovered itfelf upon the {eparation. Tuts fuppofition was founded upon an ob- fervation of the moft frequent confequences of combining bodies in chemiftry. -Com- monly when we’ join two bodies together, their acrimony or attraction for other fub- {tances becomes immediately either lefs per- ceivable or entirely infenfible ; altho’ it was fufficiently ftrong and remarkable before their union, and may be réndered evident again by disjoining them. A neutral falt, hich’ is compofed of an-acid and alkali, does not pofflefs the acrimony of either of its con- ftituent parts. It can eafily be feparated from water, has little or no effet upon metals, is incapable of being joined to inflammable bodies, and of corroding and diffolving ani- mals and vegetables; fo that the attraction both of the acid and alkali for thefe’ feveral fubftances. °PAYSICAL avo LITERARY. 187 -fabftances feems to be fufpended till ‘ili are again feparated from one another.) Crupe lime was therefore ‘confidered‘as a peculiar'yacrid .earth /rendered mild: “by its anion’ with fixed air’: and quick-lime as’ the fame earth, ii! which, by having’ feparated the air, we difcover that acrimony /orattra- Gtiion’ for water, for animal, vegetable, and for inflammable fabftances. Twa “the caléarious earths really lofe a fick quantity of air when they ate burnt to quick-lime, feems fufficiently proved: by an experiment of Mr. Margraaf*, an exceeding- ly acctirate and judicious’ Chemift) > He “fub- jected eight? ounces’ ‘of’ ofteocolla to diftilla- tion in an earthen’ retort; finithing his procefs with the mot violent fire of a reverberatory, and caught in the receiver only two drams of _ water, which by’ its {mell and properties fhewed itfelf to be flightly alkaline. He does ~ not tell. us the weight of the gfevcolla re- maining in the retort,/and only fays, that it was converted into quick-lime ; but as no cal- carious earth can be converted into quick-lime, _ or bear the heat which he applied without - lofing above a third i its weight, we may Wd. be it fafely 2 ~ Mem. de l’Acad, de Berlin. an. 1748, p- 57: 188 ESSAYS ann OBSERVATIONS fafely conclude, that the lofs in his experi- ment was proportional, and proceeded chiefly from the diffipation of fixed air. AccorDING to our theory, the relation of the calcarious earth to air and water appeared to agree with the relation of the fame earth to the vitriolic and vegetable acids.. As chalk for inftance has a ftronger attraction for the vitriolic than for the vegetable acid, and is diflolved with more difficulty when combined with the firft, than when joined to the fecond; fo it alfo attracts air . more ftrongly than water, and is ‘diflolved’ with more difficulty when faturated with air than when compounded with water only. A calcarious earth deprived of its air, or in the ftate of quick-lime, greedily abforbs a confiderable quantity of water, becomes fo- luble in that fluid, and is then faid to be flaked; but as foon as it meets with fixed air, it is fuppofed to quit the water and join itfelf to the air, for which it has a fuperior attraction, and is therefore reftored to its firt ftate of mildnefs and infolubility in water. Wuen flaked lime is mixed with water, the fixed air in the water is attracted by the PHYSICAL anp LITERARY. 189 the lime, and faturates a fmall. portion of it, _ which then ‘becomes again incapable of diffo- lution, but part of the remaining flaked lime is diflolyed and compofes lime-water. Ir this fluid be expofed to the open air, he particles of quick-lime which are neareft the furface gradually attract the particles of fixed air which float in the atmofphere. But at the fame time'that a particle of lime is thus | faturated with air, it is alfo. reftored to its native ftate of mildnefs and infolubility ; and as the whole of this change muft happen at the furface,° the: whole of the lime is fuc- ceffively colleéted there under its originah form of an infipid calcarious earth, called the cream or crufts of lime-water. ‘WHEN quick-lime itfelf is expofed'to the open. air, it abforbs the particles of water | and of fixed air which come within its {phere of attraction, as it meets with the firft of thefe in greateft plenty, the greateft part of it aflumes the form of flaked lime; the reft is reftored to its original ftate; and if it _ be expofed for a fufficient length of time, the whole of it is gradually faturated with air, to which the water as gradually yields its place. : We 190 ESSAYS ann OBSERVATIONS We have already fhewn by experiment, that magnefia alba is a compound of a pecu- liar earth and fixed air.’ When this fubftance is mixed with lime-water; the lime fhews a ftronger attraction for fixed air than that of the earth of magnefia; the air leaves this’ powder to join itfelf to the hme. And:as neither the lime when faturated with air, nor the magnefia’ when deprived of} it; /are foluble in water, the lime-water becomes per= fe&tly pure and infipid, the-lime which» ie contained being-mixed with the. magnefia. But if the magnefia be deprived of air by:cal=: Cination before it is mixed with the lime- water, this fluid fuffers no alteration. Ir quick-lime be mixed with a diffolved: alkali, it likeways fhews an attraction for fixed air fuperior to that of the alkali... Ie robs this falt of its air, and thereby becomes mild itfelf, while the alkali is confequently rendered more corrofive, or difcovers its na- tural degree of acrimony or ftrong attraction for water, and for bodies of the inflammable, and of the animal and vegetable kind; which attraction was lefs perceivable as long as it was faturated with air. And the; volatile alkali when deprived of its air, befides this attraction PHYSICAL ann LITERARY: t98 attraction for, various bodies, difcovers like- ways its natural degree of volatility, which was formerly fomewhat reprefled by the air - adhering to it,in the fame manner as it is re- prefled by the addition of an acid. Tuts account, of lime and alkalis recom- mended itfelf by its fimplicity, and by aftord- ing an eafy folution of many phenomena, but appeared upon a.nearer view:to be attended with confequences that were fo very{new and extraordinary, as to render fufpicious the principles from which they were drawn. I refolved however to examine, in a parti- cular manner, fuch of thefe confequences as were the moft unavoidable, and found, the greateft number of them might be reduced to the following propofitions : “kit _ I. Ir we only feparate a quantity of air from lime and alkalis, when we render them cauftic they will be found to lofe part of their weight in the operation, but will faturate the fame quantity of acid as before, and the fa~ _ turation will. be nerformed — effer- Beir PAN | NICV AS 192 ESSAYS ann OBSERVATIONS If. Ir quick-lime be no other than a cals carious earth deprived of its air, and whofe attraction for fixed air is ftronger than that of alkalis, it follows, that, by adding to it a fuf+ ficient quantity of alkali faturated with air, the lime will recover the whole of its air, and be entirely reftored to its original weight and con- dition: and it alfo follows, that the earth fe- parated from lime-water by an alkali, is the lime which was diffolved in the water now reftored to its original mild and infoluble ftate. Il]. Ir it be fuppofed that flaked lime does not contain any parts which are more firey, active or fubtile than others, and by which chiefly it communicates its virtues to water ; but that it is an uniform compound of lime and water: it follows, that, as part of it can be diffolved in water, the whole of it is alfo capable of being diffolved. IV. Ir the acrimony of the cauftic alkali does not depend on any part of the lime ad- hering to it, a cauftic or foap-ley will confe- quently be found to contain no: lime, unlefs the quantity of lime employed in making it P were greater than what is juft fufficient to ; extract the whole air of the alkali ; for then . . as PHYSICAL ann LITERARY... 193 ‘as much of the fuperfluous quick-lime might poflibly be: diffolved: by the ley as: would be diffolved by pure water, or the ley would contain as much lime as lime-water does. | V. We have fhewn in the former ‘experi- ments, that abforbent.earths lofe their air when, they are joined to an acid’ ; but recover it, if feparated again from that acid, by means of an ordinary alkali: the air paffing from the alkali to.the earth, at the fame time that the acid paffes from the earth: tothe alkali. Ir the cauftic alkali therefore be: deftitute of air, it will {eparate magnefia from.an acid under the form of a magnefia free:\of air, or which will not effervefce with.acids.;. and the fame cauftic alkali|will,alfo feparate-a cal- carious earth from acids under the; form of a calcarious, earth deftitute-of air, but fatu- rated with) water, or under tlie form of flaked lime.. _ Txese were all-neceffary conclufions from the above fuppofitions,, Many of them appeared too improbable to deferve any fur- ther attention : fome however, I found. upon reflection, ‘were. already. feconded by,.expe- ‘tience. Thus Ho oman, has .obferved,. that quicklime does not effervefce with “pao of Vou. II. Bob - © “vitriol, 194 ESSAYS ann OBSERVATIONS vitriol* ; and it is well known that the cauftic fpirit of urine, or of falt ammoniac, does not emit air, when mixed with acids. This con- fideration excited my curiofity, and determin- ed me to inquire into the truth of them all by way of experiment. I therefore engaged myfelf in a fet of trials; the hiftory of which is here fubjoined. Some new faéts are like- ways occafionally mentioned ; and here it will be proper to inform the reader, that I have never mentioned any without fatisfying myfelf of their truth by experiment, tho’ I have fometimes taken the liberty to negle& defcribing the experiments when iy feemed fufficiently obvious.’ Desir1NnG to know how much of an acid a calcarious earth will abforb, and ‘what quantity of air is expelled during the diffolu- tion, I faturated two drams of chalk with diluted fpirit of falt, and ufed the Florentine flafk, as related in a fimilar experiment upon magnefia. Seven drams and one grain of the acid finifhed the diffolution, and the chalk loft two fcruples and eight grains of air. Tus experiment was neceflary before the following, by which I Road a 6 to inquire inte _ * Hoff. Op. T. iv. p. 480. PHYSICAL ann LITERARY. 195 into the truth of the firft propofition fo far as it relates to quick-lime. Two drams of chalk were converted into a perfect quick-lime, and loft two {cruples and twelve grains in the fire. This quick- lime was flaked or reduced to a milky liquor with an ounce of water, and then diffolved in the fame manner, and with the fame acid, as the two drams of chalk in the preceding experiment. Six drams, two fcruples and fourteen grains of the acid finifhed the fatu- ration without any fenfible effervefcence or lofs of weight. Ir therefore appears from thefe experi- ments, that no air is feparated from quick- lime by an acid, and that chalk faturates nearly the fame quantity of acid after it is converted into quick-lime as before. ) Wiru refpect to the fecond propofition, I tried the following experiments. v _ A piece of perfect quick-lime made from two drams of chalk, and which weighed one dram and eight grains, was reduced to a very fine powder, and thrown into a filtrated mix- ture of an ounce of a fixed alkaline falt and two ounces’ of water. After a flight di- geftion, the powder being well wafhed and dried, 196 ESSAYS ann OBSERVATIONS dried; weighed one dram and fifty eight grains. It was fimilar in every trial to a fine powder of ordinary chalk, and was therefore faturated with air which muft have been fur- nifhed by the alkali. - ) A dram of pure falt of tartar was diffolved in fourteen pounds of Jime-watery andthe powder thereby precipitated, being carefully: collected and dried, weighed one and fifty grains.’ When expofed toa violent fire, it was converted into a true quick-lime, and had every other quality of a calcarious earth. » THIs experiment was repeated with the volatile alkali, and alfo with the foffil or al- kali of fea-falt, and exactly with the fame event. Tue third prepofition had lefs! appearance of probability than the foregoing; but; as an accurate experiment was the only teft of its truth, I reduced eight grains of. perfect: quick-lime made of chalk, to an exceedingly - fubtile powder, by flaking it in twoidrams of diftilled water boiling hot, and immediately threw the mixture into eighteen ounces of diftilled water in a flafk. After fhaking it, — a light fediment, which floated, thro’ the li- quor, was allowed to fubfide ; and this, when collected = PHYSICAL anp LITERARY. 107 colle@ted with the greateft care, and dryed, weighed, asnearly'as I could guefs, one third of a grains); The water tafted ftron gly of the lime, hadall the, qualities of lime-water, and yielded twelve grains of precipitate, upon the addition of falt-of tartary -In repeating this experiment, the: quantity,.of fediment was fometimes lefs than the above, and fometimes amounted to half a. grain. . It confifted,part- - ly of an earth which effervefced violently with agua fortis, and partly, of-an. ochry pow- der, which would not, diffolve, in that, acids The ochry powder, as it ufually appears in chalk to the eye, in the form of, veins ranning thro’ its fubftance, muft be .confidered., only as an accidental or foreign'admixture ;' and; with refpect tothe minute portion of alkaline earth which compofed the temainder of .the fediment,: it cannot be fuppofed.to have, been originally different from the reft, and incapas ble, from its nature, of being converted,,into quick-lime, or of being diffolved in water ; it feems rather to have confifted of a fmall ~ part of the chalk.in. its mild ftate, or fatu- rated with air, which had either remained, for want of a fufficient fire to drive it out entirely, or had been furnifhed by the diftilled water. lanky I 798 ESSAYS ann OBSERVATIONS -T indeed expected to fee a much larger quan- tity of fediment produced from the lime, on account of the air which water conftantly con- tains, and with a view to know whether wa- ter retains its air when fully faturated with lime, a lime-water was made.as ftrong as pof- fible ; four ounces of which were placed un- der the receiver of an air-pump, together with four ounces of common water ina vial of the fanie fize ; and, upon exhaufting the recei- ver, without heating the vials, the air arofe from each in nearly the fame quantity: from whence it is evident, that the air, which quick-lime attraéts, is of a different kind from that which is mixed with water. And that it is alfo different from ‘common elaftic air, is fufficiently proved by daily experience ; for lime-water, which foon attracts air, and forms a cruft when expofed in open and fhallow vef- fels, may be preferved, for any time, in bot- tles which are but flightly corked, or clofed in fuch a manner as would allow free accefs to elaftic air, were a vacuum formed in the bottle. Quick-lime therefore does not attract air when in its moft ordinary form, but is ca- pable of being joined to one particular {pecies only, which is difperfed thro’ the atmofphere, either -PHYSICAL ann LITERARY. 199 either in thé thape of an exceedingly fubtile powder, or more probably in that of an ela- {tic fluid. To this I have given the name of fixed air, and perhaps very improperly ; but . I thought it better to ufe a word already fa- miliar in philofophy, than to invent a new name, before we be more fully acquainted with the nature and properties of this fub- ftance, which will probably be the fubjeé& of my further inquiry. It is, perhaps, needlefs to mention here, that the calcarious fubftances ufed in making the above experiments fhould be of the pureft kind, and burnt with the utmoft violence of heat, if we would be fure of converting them into perfect quick-lime. I therefore made ufe of chalk burnt in a {mall covered crucible with the fierceft fire of a Black-{mith’s forge, for half an hour, and found it neceflary to employ, for this purpofe, a crucible of the Au/rian kind, which refemble black lead ; for if any calcarious fubftance be heated to fuch a degree in an ordinary or Heffan crucible, the whole. of it is melted down, together with part of the, | _ vefiel, into glafs. ___ I now prepared to inquire into the pro- I: perties of the cauftic alkali; in order to which, I 200 ESSAYS ann OBSERVATIONS I made a cauftic or foap ley in the following manner. . Twenty fix ounces of very ftrong quick- limie made of chalk, were flaked or reduced to a fort of fluid pafte; with eleven pounds of boiling water, and then mixed in a glafs veffel with eighteen ounces of a pure fixed alkaline falt, which had been firft diffolved in two pounds and a half of water. This mixture was fhaken frequently for two hours, when the action of the lime upon the alkali was fuppofed to be over, and nothing remain- ed but to feparate them again from one ano- ther. I therefore added 12 pounds of water, ftirred up the lime, and, after allowing it to fettle again, poured off as much of the clear ley as poffible. . Tue lime and alkali were mixed together under the form of a very thick milky liquor or fluid pafte ; becaufe they are thus kept in perpetual contact and equal mixture until they have acted fufficiently upon one another: whereas in the common way of ufing a larger quantity of water, the lime lies for the moft part at bottom, and, tho’ ftirred up ever fo often, cannot exert its influence fo fully upon the PHYSICAL ann LITERARY. 201 the alkali, which is, uniformly diffufed thro’ every part of the liquor. Tue above ley was found upon sriale toybe faturated by acids, without the leaft effervef- cence or diminution of weight. In was now proper to examine whether the alkali. fuffered any lofs in becoming cauftic, which I propofed to attempt by af- certaining the ftrength of the ley, or the quantity of falt which a given portion.of it contained; from. which by | computation fome imperfect knowledge might be obtained of the quantity of cauftic produced: from the eighteen ounces of mild falt. I therefore evaporated fome of my ley, but foon perceived that no certain. judgment could be formed of its ftrength in this way, becaufe it always abforbed a confiderable - quantity of air during ‘the evaporation, and the dried falt made a pretty brifk effervef- cence with acids, fo that the ley appeared ftrongsr than it really was; and yet, upon proceeding in the eftimate from this rude and unfair trial, it appeared that the falt had loft above a fixth ia becoming cauftic, and the quantity of acid faturated by two drams of t Vor. IT. Cec it coe ESSAYS ann OBSERVATIONS it was to the quantity of acid faturated by two drams of falt of tartar, nearly as fix to five. ‘Turse experiments are therefore agreeable to that part of the fecond propofition: which relates to the cauftic alkali. ~ Upon farther examining what creipeathn alkali had undergone, I found that the ley gave only an exceeding faint milky hue to Hime-water; becaufe the cauftic alkali wants that air by which falt of tartar precipitates the lime. When a few’ ounces of it’ were expofed in an open fhallow veflel for four and twenty hours, it imbibed a fmall quan- — tity of air, and made a flight effervefcence with acids. After a fortnight’s expofure in the fame manner, it became entirely mild, © effervefced as violently with acids, and had | the fame effet upon lime-water as a folution of an ordinary alkali. It likeways agrees with lime-water in ‘this refpeét, that it may. be kept in’ clofe veflels, or even ‘in bottles which are but flightly covered, for a canfide- rable time, without abforbing a ane ied * tity of air. In order to know how oti linte it con- tained, I whi cape ten ounces int a °C re “PHYSICAL asp LITERARY: 203 filver dith over a lamp, and melted the falt, after having diflipated the water™. Tue cauftic thus produced was. diflolved again in a fmall quantity of water, and de- pofited a trifling portion of fediment, which Timagined at firft to be limé; but. finding that it could eafily be diffolved in a little more water, concluded it to be a vitriolated tartar, which always accompanies the fixed alkali of vegetables. I then faturated the folution of the cauttic falt with fpirit of vitriol, expecting thus to detect the lime ;. becaufe that acid precipi- tates a calcarious earth from its ordinary folu- tions. During the faturation, a large quan- tity of white powder was formed; but this _ likeways turned out. to be a vitriolated tartar, which had appeared in the form of a _ powder, becaufe there was not enough of _ awater in the mixture to diffolve it. LASTLY * This evaporation was performed in a filver difh, on ac- count of the acrimony of the falt ; which is fo very great, _ that, having once evaporated a part of the faine ley in a bowl of Englifh earthen or ftone ware, and melted the cauftic avith a gentle heat, it corroded and diffolved a part of the wl, and left the infide of it pitted with {mall holes. 204 ESSAYS ann OBSERVATIONS - Lastry, I expofed a few ounces of the ley i in an open {hallow veffel fo long, that the alkali loft the whole of its cauftibity, and feemed entirely reftored to the’ ftate of an ordinary fixed alkali; but it did not however depofite a fingle atom of lime. And to aflure myfelf that my cauftic ley was not of a fingular kind, I repeated the fame ex- periments with an ordinary foap-ley, and with one made by mixing one part of a pure fixed alkaline falt with three parts of common ftone lime frefh flaked and fifted ; nor could I difcover any lime in either. The firft of thefe contained a fmall quantity of brimftone, and was far from being perfeCly cauftic, for it made a pretty brifk effervefcence with acids; but the laft was fo entirely deprived of its air, that it did not diminifh in the leaft the tran{parency of lime-water. THESE experiments feem therefore to fam: port the fourth propofition, and to fhew that the cauftic alkali does not contain any lime. As it feems probable, from the quicknefs and eafe wherewith the alkali was rendered cauttic, that more lime had been employed than what was juft fufficient to extract the whole of RCO MVST TYE Ss Sa. ‘ ‘PHYSICAL anv LITERARY. 205 of its air, we are furprifed to find that. little or none of the fuperfluous quick-lime was diffolved by the water. But this phenomenon will become lefs furprizing, by comparing it with fome fimilar inftances in chemiftry. Water may be made to depéfite a falt, by the admixture of a fubftance which it attracts more ftrongly than it does that falt; fuch as fpirit of wine; and quick-lime itfelf may be feparated from water upon the fame prin- ciple; for if that fpirit is added to an equal ‘quantity of lime-water, the mixture becomes turbid and depofites a fediment, which, when feparated and diffolved again in diftilled wa- _ ‘ter, compofes lime-water. We may there- - fore refer the above phenomenon, with refpect to the ley,: to the fame caufe with thefe, and fay, that the water did not diffolve the lime, becaufe it already contained a cauftic alkali, for which it has a fuperior attraction. > Talfo rendered the volatile alkali cauttic, in order to examine what change it fuffered in the operation, and obtained an exceedingly volatile and acrid {pirit, which neither effer- __vefced with acids, nor altered in the leaft the :s an {parency of lime- -water ; and, altho’ ve- or: 7 206 ESSAYS ann OBSERVATIONS ry ftrong, was lighter than water, and float- ed upon it like fpirit of wine. I next inquired into the truth of the fifth propofition, in the following manner. -. Two drams of epfom-falt were diffolved in a {mall quantity of water, and thrown into two ounces of the cauftic-ley ; the mixture in- ftantly became thick, like a decoétion of ftarch or barley, by the magnefia, which was precipitated. Ithen added fpirit of vi- triol by degrees, until the mixture became perfectly clear, or the whole of the:magnefia was again diffolved ; which happened with- eut any eftervefcence or emiflion of air. Hatr an ounce of chalk was diffolved in fpirit of falt, the quantity of which was fo adjufted, that the mixture was not acid in the leaft degree; and the folution was thrown ‘into twelve ounces of the cauftic ley ; which quantity I found, by experiment, to be fuffi- cient for precipitating almoft the whole of the - chalk. I now filtrated this turbid liquor, and jaid the powder remaining inthe paper upon a chalk-ftone, in order to draw as much of ‘the water from it as poflible, and thereby re- ‘duce it to the form of a more denfe and hea- vy powder, that it might fubfide the more perfectly PHYSICAL ann LITERARY. 207 perfectly in the following ‘part of the experi- ment. I then mixed it with about twenty _ ounces of pure water in a flafk, and, after al- lowing the powder to fubfide, poured off the water, which had ‘all the qualities of lime- water. And I fucceffively converted eight waters more into lime-water, feven of thefe in the fame quantity, and with the fame ma- -nagement, as thé firft. ‘The eighth was like- ‘ways in the fame quantity ; but I allowed it ‘to remain with the chalk, and fhook it fre= quently, for'two days. This, after being fil- trated, formed a cream or ¢ruft upon its fur. face when expofed to the air; changed the colour of the juice of violets into green ;) fe- _ parated an orange-coloured powder from a fo- - lution of corrofive fublimate ; became turbid upon the addition of an alkali ; was entirely fweetened by magnefia; and appeared fo ftrong to the tafte, that I could not have dif- tinguifhed it from ordinary lime-water. And when I threw fome falt ammotiiac into the ime which remained, the vapour of the vo- Jatile alkali immediately arofe from the mix- ture. ay ' “In this experiment therefore ‘beg air is firft driven out of the chalk by an acid, and hg in 208 ESSAYS ann OBSERVATIONS inorder to feparate this acid from it, we add an alkali which has been previoufly de- » prived of its air; by which means, the chalk itfelf is alfo obtained free of air, and in an a- crid form, or in the form of flaked lime. WE have alfo feveral proceffes for obtain- ing the volatile alkali in a cauftic form, which feem to be only fo many methods of obtain-. ing it in its pure ftate, and free of fixed air, The firft of thefe.is the feparation of the al- kali from an acid, merely by heat; an in- ftance of which we have from Mr. Mar- graaf *. He prepared from urine an ammo- niacal_falt, the acid of which is the bafis of the phofphorus, and is of fuch a peculiar na- ture, that it endures a red heat without being diffipated. ‘Sixteen ounces of the neutral fale were fubje&ted by him to diftillation. The acid remained in the retort, and he found in the receiver eight ounces of an alkaline {pirit, which, he tells us, was extremely volatile, very much refembling the fpirit of falt am- moniac diftilled with quick-lime; and no cryftals were formed in it, when expofed to the cold air. * Mem. de J’Acad, de Berlin, an. 1746, p. $7° : a ay at ° PHYSICAL ann LITERARY. 209 _ A cauttic volatile alkali may alfo be obtain- ed, by mixing falt ammoniac with half its weight of a cauftic fixed alkali, or of magne- fia which has been previoufly deprived of its air by fire; and then fubmitting thefe mix- tures to diftillation: -Or merely by adding a- ny ordinary volatile alkali to a proper quanti- ty of a cauftic ley; for in this cafe the air pafles from the volatile to the fixed alkali, by a fuperior attraction for the laft, and, by a gentle heat, the compound yields a fpirit fi- milar to that prepared from falt ammoniac and quick-lime. Ir is therefore probable, that, had se al- fo a method of feparating the fixed alkali from an acid, without, at the fame time, fa- turating it with air, we fhould then obtain it in a cauftic form; but I am not acquainted with an inftance of this feparation in chemi- ftry. ‘There are two indeed which, at firft fight, appear to be of this kind; thefe are © the feparation of the fixed alkali from the ni- trous.acid by means of inflamed charcoal, in the procefs for making nitrum fixatum, and of the fame alkali, from vegetable acids mere- ly by heat ; but, upon examining the pro- duct of each procefs, we find the alkali either Vor. II. Dd fully 210 ESSAYS ano OBSERVATIONS fully or nearly faturated with air. In the firft, either the charcoal or;the acid, or both to- gether, are; almoft wholly converted into air ; a part of which is probably joined to the al- kali. In the fecond, the acid is not properly feparated, but rather deftroyed by the fire: a confiderable portion of it is converted into an inflammable fubftance ;) and. we learn from Dr. Hales, that the bodies. of this clafs contain a large quantity off ;fixed air. Wuen we confider that the attraction of alkalis. for fixed air is weaker than that of ‘ the calcarious earths, and reflec upon the ef- fects of heat in chemiftry, we are led to:ima- gine, that alkalis might be entirely deprived of their air, or rendered perfeCly cauftic, by a fire fomewhat weaker than that which is fuf- ficient to produce the fame change upon lime; but this opinion does not feem agreeable to experience. Tue alkalis do,. however, acquire Kiige degree of caufticity in-a {trong fire, as ap- ‘pears from their being more eafily united with ‘{pirit of wine after having been kept in fur fion for fome time. For that fluid, which ‘cannot be tinctured by a mild falt of tartar, " will A PHYSICAL anmLITERARY. attr will foon- take a very deep.colour. from a few drops of 1a ftrong caufticley.... The circum- ftances which hindés us from rendering thefe falts, perfectly cauftic;by heat, are their pro- penfity. to diffipation in the, utmoft,violence of the fire, their extreme; acrimony, and the imperfection of. our,common yeflels.; . For before the heat becomes very intenfe, the al+ kalis either evaporate, or diffolve a partiof the crucibles in which they are contained,, and often, efcape thro’ their pores ;’, which hap- pens; efpecially.as foon as’-they have already acquired fome degree of additional. trarsche by the lofs of partof their air. ui? > Tue fufion alfo; which they fo cesar un= dergo, is well known by Chemitts, as arftrong obftacle to the feparationof the volatilefrom the fixed parts of a compound by fite ’;) according- ~ dy, infeveral procefles, weiaré directed to add to the fufible compound fome porousfubttance which ‘is incapable’ of fufion, and’ will retain the whole in a fpongy form, thereby to facili- tate the diffipation of the volatile parts. . In order to know whether an alkali would lofe a part of its air, and acquire’a degree of eaufticity, when expofed, with this precauti- on, to the action of a firong fire, 1 mixed an ounce 412. ESSAYS ann OBSERVATIONS éunce and a half of falt of tartar with three ounces of black-lead, a fubftance of any the moft urichangeable by chemical operations. This mixture I expofed, for feveral hours, in a covered crtcible, to a fire foméwhat ftrongeér than what is neceflary to keep falt of tartar in fufion, When allowed to cool, I found it ftill in the form of a loofe powder ; and taking out one half, I diluted it with wa- ter, and by filtration obtained a ley, which, when poured into a folution of white marble in aqua fortis, precipitated the marble under the form of a weak quick-lime: for the tur- bid mixture gave a green colour to the juice of violets, and threw upa cruft like that of lime-water ; and the precipitated powder col- lected and mixed with falt ammoniac imme- diately yielded the fcent of the volatile alkali, Lest it fhould here be fufpeted, that the alkaline qualities of this mixture, and of the precipitated marble, were not owing toa lime into which the marble was converted, but to the alkali itfelf which was added, it is pro- per to obferve, that I mixed fo {mall a propor- tion of the ley with the folution of marble as made me fure, from certain experiments, that the whole of the alkali was {pent in perform- ing ia PHYSICAL anp LITERARY. 212 ing the precipitation, and was confequently converted into a neutral falt by attracting the acid. The properties therefore of the mix- ture can only be referred to a lime, as is in- deed fufficiently evident from the cruft which is peculiar to lime-water. . I was therefore affured by this experiment, that an alkali does really lofe a part of its air, and acquire a degree of caufticity, by the pro- pet application of heat; but finding by feveral trials, that the degree of caufticity which; it had thus acquired was but weak, and that the quick-lime produced in this ex- periment was exhaufted and rendered mild by a fmall quantity of water, Iexpofed the crucible together with that half of the al- kali which remained in it to a ftronger fire, in order to expel a larger quantity of air, and render it more remarkably cauftic ; but the whole of it was diffipated by the force of the heat, and the black lead, which ftill retained ~ the form of a loofe and fubtile powder, yielded little or nothing to water. We learn then from the above experiment the reafon why the alkali newly obtained from the afhes of vegetables is generally of the more acrid kinds of that falt. It never appears gi4, ESSAYS ann OBSERVATIONS appears until the fubject be converted: into afhes, and is fuppofed to be:formed) by’ the fire, and to be the refult ofa particular com= bination of fome of the principles of the -ve- getable 5 one of which principles is air, which is contained in large quantity dn allvege+ table matters whatever. But as foon as the fmalleft part of a vegetable is converted: into afhes, and an alkali is thus formed, this fale neceflarily fuffers a calcination, during’ which it is kept i in a {fpongy form by the athes, and fhews a very confiderable degree of acrimony if immediately applied’ to the body of ‘an animal ; but if the afhes-are for any time expofed to the air, or if we feparate the alkali from them by the addition of a large quantity of water and fabfequent evaporation, the falt imbibes fixed air from the atmofphere, and becomes nearly faturated’ with it: tho’ even in this condition it is generally more acrid than falt of tartar, when this is pre- pared with a gentle heat. Borax hias fometimes been referred to the clafs of alkalis, on account of fome refem- blance it bears to thofe falts: but it has ‘been demonftrated by accurate experiments, that we fhould rather confider it-as a neutral falt ; that PHYSICAL and LITERARY: arg that it is compofed of an alkali and of a par+ ticular faline fubftance ;called the fedative falt, which adheres to the alkali in the! fame ‘manner asan acid, but can be feparated, by ' the addition-of any acid whatever, the added acid joining itfelf to the alkali-in the place of the. fedative falt., As this;conjunction of an acid with the alkali of borax happens without the leaft effervefcence, our principles lay us under a neceflity of allowing that-alkali to be perfectly free of air, which mutt proceed | from its being incapable of union. with fixed airand with the fedative falt at the fame time: whence it follows, that, were we to mix:the fedative {alt with an alkali faturated with air, the air ;would immediately, be expelled, or the two {alts in joining would produce an, effer- vefcence. This I’ found to be teally the cafe upon making the trial, by mixing a) {mall quantity of the fedative falt with an equal quantity of each of the three alkalis, rubbing ‘the mixtures well in a mortar, and adding’ a little water.. It is however- proper in. this place to obferve,.,that, if the experiments be i made in a different manner, they are attend- | -ed with a fingular circumftance. If a {mall quantity of the fedative falt be thrown into a r large 216 ESSAYS ann OBSERVATIONS large proportion of a diffolved fixed alkali, ‘the fedative falt gradually difappears, and is united to the alkali without any effervef- cence; but if the addition be repeated feveral times, it will at laft be accompanied with a brifk effervefcence, which will be- come more and more remarkable, until the alkali be entirely faturated with the fedative falt. Tus phenomenon may be explained: by confidering the fixed alkalis as not perfectly faturated with air: and the fuppofition will appear very reafonable, when we recolleé, that thofe falts are never produced without a confiderable degree of heat, which may ‘eafily be imagined to diffipate a fmall portion of fo volatile a body as air. Now, if a {mall quantity of the fedative falt be thrown into an alkaline liquor, as it is very flowly dif- folved by water, its particles are very gra- dually mixed with the atoms of the alkali. They are moft ftrongly attracted by fuch of thefe atoms as are deftitute of air, and therefore join with them without producing an effervefcence ; or, if they expel a {mall quantity of air from fome of the falt, this air is at the fame time abforbed by fuch of the contiguous PHYSICAL ayy LITERARY. 217 contiguous particles as are deftitute of it, and “no effervefcence appears until that part of the alkali, which was in a cauftic form or defti- tute of air, be nearly faturated with the fedative falt. But if, on the other hand, a large proportion of the fedative falt be per- feGtly and fuddenly mixed with the alkali, the whole, or a large part, of the air is as fuddenly expelled. | ) In the fame manner may we alfo ex- plain a fimilar phenomenon, which often prefents itfelf in faturating an alkali with the different acids: the effervefcence is lefs confiderable in the firft additions of acid, and becomes more violent as the “mixture approaches the point of faturation. This appears moft evidently in making the Jal diureticus or regenerated tartar: The particles of the vegetable acid here employed, being always diffufed thro’ a large quantity, of water, are more gradually applied to thofe of the alkali, and during the firft additions are chiefly united to thofe that are freeft of. air“. Vot. II. Phe, THAT * Boerh. Operat, Chem. procefs, LX XVI. 218 ESSAYS anv OBSERVATIONS: Tuat the fixed alkali, in its ordinary ftate,, is feldom entirely faturated with air, feems to be confirmed. by the following experiment. I expofed a {mall quantity of a pure vege- table fixed alkali to the air, in a broad and fhallow veffel, for the {pace of two months ; after which I found a. number of folid cryftals, which refembled a neutral falt fo much as to retain their form pretty well in the air, and to produce a confiderable degree of cold when diffolved in water. Their tafte was much milder than that of ordinary fale of tartar; and yet they feemed to be com- pofed only of the alkali, and of a larger quantity of air than is ufually contained in that falt, and which had been attracted from the atmofphere: for they ftill joined very readily with any acid, but with a more vio- lent effervefcence than ordinary; and they could not be mixed with the f{malleft portion of vinegar, or of the fedative falt, without e- mitting a fenfible quantity of air. - As it now appeared that feveral alkaline fubftances have an attraction for fixed air, I tried a few experiments to learn the relative ftrength of their feveral attractions. ~ TWENTY “PHYSICAL snp LITERARY. 219 ‘Twenty foiir grains of magnefia in fine _ powder ‘were mixed with five ounces’ of the cauftic ley ina fmiall vial, ‘which was imme- diately:corked and fhaken frequently for four hours. * The ley was then poured off, and the’ magnefia wafhed with repeated affufions of ‘watef, and dried.» It had loft about the half of its weight, and when “reduced toa fine powder was readily diffolved by acids with an effervefcence which was hardly per~’ ceivable : thevalkali had therefore extracted itsvair. I alfo threw fome’frefh magnefia into'the ley which had been poured off, and thereby rendered it perfectly mild and fimilar’ to afolution of falt’ of tartar;'fo that it ef- fervefced brifkly with acids. i _ Wir ian ounce of the mild fpirit of falt ammoniac, I mixed’a dram of magnefia in very fine powder which had been previoufly deprived.of its airiby fire ; and obferving that the magnefia had a tendency to concrete into a folid mafs, 1 hook the vial very frequently. After: fome days the powder was increafed to more than double its former bulk ; and _ when the vial was opened, the alkaline fpirit _ emitted a moft intolerably pungent {mell. It. likewife floated upon water, but was not perfectly 220 ESSAYS anp OBSERVATIONS perfectly cauftic ; for it ftill yielded fome air when mixed with acids, and alfo rendered lime-water turbid: neither of which would probably have happened if. I hadoufed. a greater quantity of magnefia, or had allowed the mixture to remain a longer time i: the vial. I now.wathed: out the whole of the mixture into a bowl, and dryed the magnefia until it loft all {mell.-of the alkalne odt weighed a dram and fifty eight grains, -effer- vefced viclently with acids, and therefore contained a large quantity of) ait, which: had been drawn from the alkali by a: ftronger: attraction, | _ Havine formerly fhewn, that magnefia’ faturated with air feparates an acid from a cal-. carious earth, which it is not able todo.after being deprived, of its ,air by fire; Inow fufpe@ted that the air was the caufe of this feparation, becaufe I found that it was joined » to the calcarious earth at the fame time ‘that! the acid was joined to the earth of maenefia ; and imagined that a pure calcarious earth might poffibl ly have a {tronger attraction for acids than a pure earth of mgnefia. I therefore diffolved two drams of magne- > fia. in the marine acid, and thus obtained a. compound PHYSICAL anp LITERARY.) 24 compound of anacid and of ithe pure earth: of this {ubftanee 5 for the air which was at firft. attached to it; was expelled during: the diffolution. I, thea. added: thirty grains’ of trong, quick-lime.in exceeding fine powder, fhook the mixture well, and filtrated it. The powder remaining ;in\the paper; after. being- well wafhed, was found tobe a magnefia, | which, \as I expected, was deftitute of air ; for itywas diffolved {by the vitriolic:acid) with- out, effervefcences;;;And:the filtrated liquor: contained the lime united to the acid’ ;’ for’ upon’ dropping fpirit of vitriol into it, a white® powder was immediately formed. » We mutt therefore: acknowledge aftron ger’ attraction between ithe: calcarious earths and acids than between) thefe and magnefia: but how does it then happen, that, -if magnefia faturated with air be mixed with a compound of acid and calcarious earth, thefe two laft, which attract one another the moft ftrongly, do not remain united; but the acid is joined _ tothe magnefia, and the calcarious earth to the air which it attracts much more weakly- } than it does theacid? Is it becaufe the fam _ of the forces which tend to join the magnefia » to the acid and the calcarious earth to the air 202, ESSAYS Ann OBSERVATIONS air, is greater than the fum of the “forces? which. tend to join the calcarious earth to” the acid, and the magnefia to the/air? and: becaufe there is a repulfion between the acid” and air, and between the two earths ; or they’ are fomehow kept afunder in fuch a manner as hinders sany three of them from wi united together ?. Wasi . Tue firft, part of this fappofition is favour=" _ ed by. our experiments, which feem to“fhew a greater difference between the “forces? wherewith the calcarious earth and magnefia ’ attract fixedjair, than between thofe which” difpofe them to unite »with the acid. The! repulfions.. however ; hinted in the fecond are perhaps more doubtful, tho’ they are fug- gefted. in many other inftances of decom- .pofition ; but the bounds of my prefent pur- pofe will not allow me ‘to enter upon this fubjeG@, which is one of:the moft soso in chemiftry. We meet alfo witha difficulty with re- fpe& to the volatile alkali fimilar to the above. Thus a calcarious earth that is pure or free of air has a much ftronger attraction for acids than a pure volatile alkali, as is evi- dent when we mix. quick-lime with falt ammoniac ; PHYSICAL ano LITERARY. 223 for the alkali is then immediately detached from the acid: and agreeably to this I found, | upon trial, that a pure or cauftic: volatile alkali-does not’ feparate a’ calcarious. earth from an acid. Yet, if we mix.a mild volatile alkali, which is. a compound of alkali-and air, with a compound of acid and calcarious - earth,: thefe two laft;: which attract .one’an- ¥ we other moft ftrongly; do not.remain united ; but the acid is joined to the alkali and the earth to the airyas happens) in’ the ‘precipi- tation. of a calcarious: éarth: from an acid;’ by means of the common or mild volatile alkali. I remember: likewife a parallel inftance with regard to quick-filver. This metal has) an-attraction for the vitriolic acid, and when joined to it appears-under the form of turbith * mineral: but this attraction is weaker than that of the fixed alkali for the fame acid ; for if we mix a diffolved falt of tartar with turbith mineral, the turbith is converted into a brown powder, and the alkali into vitrio-— lated tartar;. which change happens the fooner, if the pure or cauftic alkali is ufed, Yet, if toa compound of quick-filver and the nitrous acid, we add a compound of the fixed alkali 'g24 ESSAYS and OBSERVATIONS alkali and the vitriolic acid, or a vitriolated tartar, and digeft the mixture with a ftrong heat, the vitriolic acid does not remain with the alkali, bat is joined to the quick-filver which it attracts.more weakly, compofing with it a turbith mineral ; while the al- kali is joined to the nitrous acid which it likeways attracts more weakly than it does the vitriolic, and is converted into falt- petre. _ From fome of the above experiments, | it appears, that. a few alterations may be made in the column of acids in Mr. Geoffroy’s table of elective attractions, and that a new column may be added to that table, ac- cording to the following fcheme, where the alkaline fubftances are all confidered as. in their pure ftate and free of fixed air. - Acids. Fixed air. Fixed alkali, Calcarious earth. Calcarious earth, Fixed alkali. Volatile alkali and magnefia, Magnefia. eo Se ee _ Volatile alkali. AT PHYSICAL ann LITERARY. 223 Ar the foot of the firft column feveral _ of the metals might follow, and after thefe the earth of alum; but as I don’t know what number of the metals fhould precede that earth, I have left it to be determined by further experience. Tue volatile alkali and magnefia are placed in the fame line of this column; be- caufe their force of attraction feems pretty equal. When we commit a mixture of magnefia and falt ammoniac to diftillation, the alkali arifes and leaves the acid with the magnefia; becaufe this earth, by attracting the acid, reprefies its volatility, and it feems -alfo to diminith the cohefion of the acid and alkali, and to render them feparable by a gentle heat. If the magnefia be faturated with air, this likewife, on account of its volatile nature and attraction for the alkali, ‘ is driven up along with it, and makes it ap- pear under a mild form, and in the fame manner do the alkali and air arife from a mixture of falt ammoniac’and of a crude calcarious earth. F f ART. | 226 ESSAYS ann OBSERVATIONS Antu 1X. Of the Analyfis and Ufes of Peat, by ALEXAN~ DER Linp, Efquire *. The Analyfis of Peat. Ive ounces of peat, hard, dry, and of 2 deep brown colour, found fix or feven miles from Edinburgh, being diftilled with a gradual heat, gave firft an ounce and an half of clear water ; after which the oil began to come over, firft yellow, then darker colour- ed, till it became like tar, and along with it, a yellow or brown coloured acid oily liquor, ftrongly empyreumatic, to the quantity of fix. drams : this liquor, towards the laft, became alkaline: but of this there was onlya {mall quantity ; for the diftilled liquor that came over firft, was found to be confiderably acid, fo that it took more than a dram of o/. tart. per deliquium to faturate it ; if the diftillation had been continued with a very violent heat, there would have come over more alkaline fpirit with the pitchy oil: the quantity of oil * 1744s PHYSICAL ano LITERARY. 227 oil that came over was two drams and an half; it coagulates in the cold, and melts with a {mall heat. There remained in the _retort two ounces of coal; which being care- fully burnt in a crucible, left eleven drams and a few grains of fine yellow afhes. THAT it may appear how far the Scotch and Dutch peats agree, I fhall next give the analyfis of {ome Dutch peat made by Degner. He took twenty four ounces of peat, which being firft reduced to a powder; and then put in a retort, yielded, by a gentle diftillati- on, a good quantity of infipid phlegm, with an empyreumatical {mell. This-being taken away, there followed next a yellow {pirit,: and about the neck of the retort, remained fticking a certain white unQuous earth, re- - fembling a volatile falt. The degree of heat being increafed, there came forth a white {moke,, with ete a red oil rifing at the fame time, was collected in the receiver, in the form of a thick pitchy matter, fwiming upon the {pirit, and fticking ftrongly to. the fides-of the veffel. In the retort remained only a black coal, Havinec weighed each of thefe feparate- ly, the coal was nine ounces fix drams ; the ~ thick 228 ESSAYS ann OBSERVATIONS thick pitchy oil, an ounce and an half ; the volatile oily falt or fpirit four ounces ; the reft, the infipid phlegm received in an open receiver, Tue phlegm being firft examined, was nothing but a fimple clear watery liquor, without tafte or {mell. Tue redith yellow liquor that came next, was a liquid volatile unctuous falt, compofed of a watery phlegm, a volatile falt, anda little oil, which commonly goes under the name of fpirit. This mixt with fpirit of fea falt occafioned only a few bubbles; it raifed with oil of vitriol an effervefcence, and turned muddy ; it precipitated a folution of mercury in aqua fortis, into a black powder, turned fyrop of violets green, had no effet upon chalk, fpirit of falt ammoniae : fpirit of harts- horn made no other change upon it, but turning the liquor, which was before muddy, clear. From all which, he fays, it appears, this fpirit is of an alkaline nature ; and that except a little oil, contains chiefly a volatile alkaline falt. . Tue oil which was found fwiming upon the water or {pirit had a {trong empyreuma- tical fmel), tho’ not fo fetid as the diftilled oil of PHYSICAL ann LITERARY. 229 of animals. yet ftronger than that of oils di- ftilled from: bituminous mineral fubftances, and was infmell the moft like that of peat fmoke. In the cold, it congealed into a body of the confiftence of foap‘or honey, or rather into a pitchy fubftance of a redifh brown'co- lour, being of a cauftic pungent tafte; upon the fire it melted like waxy and when wae fooked like the foot of peat. Tuis oil eafily catches fire, but is foon a- gain extinguifhed: ©When kindled, it burns like weak fpirit of wine, but not fo intenfély. When put upon the fire in a {poon, if you ap- proach a lighted candle, itkindles into a flame ; and, upon the removal of the candle, is im- mediately extinguithed ; fo it muft be fre- quently kindled before it wholly confumes. Tue cinder that remained in the retort, being putin the fire, in’afhort time turn- ed red, and immediately, without fmoke or flame, fell into grey afhes, nothing different from ordinary peat-afhes, Thefe afhes contain lefs falt than thofe of wood. All peat-afhes da not yield the fame quantity of falt, but differ according to the quality of the peat. From a pound of Dutch athes, Degner, after boil- ing, ‘filtrating, and infpiffating in the ordi- nary \ 230 ESSAYS ann OBSERVATIONS nary way, obtained only half an ounce of a .redifh impure falt, mixt with much earth : from other peats that leave after burning a red afh, and that were taken from dryer ground, he had an ounce of a redifh im- pure falt. Tuis falt, he fays, has rather a faline than alkaline tafte; and when expofed to the o- pen air, runs flowly, after the manner of fuch faline lixivious falt.. Being diffolved in wa- ter and mixed with oil of vitriol, it becomes turbid, with a {mall bubbling up. With fix- ed falt, or f{pirit of harts-horn, it turns muddy ; . with fpirit of fea falt, there is no change, the liquor remaining clear, only a few bubbles. It coagulates foap when boiled with it, in the fame manner that fea falt does. This falt diffolved again in water, filtrated and infpif- fated until it begins to cryftallize, gathers, when fet in a cool place, into a falt of a cu- bical form, and when thrown into the fire, makes a noife like fea falt that is decrepitated, The liquor being further infpiffated and fet to cryftallize a fecond time, yielded a nitrous falt ; the remaining liquor was a pure lixi- vious alkaline falt; that made a {trong effer- vefcence with acids. From all which it ap- pears, “PHYSICAL ann LITERARY. 23 pears, that this falt is principally compofed of a falt like that of common fea falt, with a ~ fmall proportion of the alkaline kind. What remained after the falt was extract- ed out of the afhes, was only a ey earth and fome fand. To thefe analyfes, I fhall add two others. Dr. Smidberg a Phyfician at the Hague, ha- ving diftilled fome peat in a retort, obtain- ed from it a fpirit, an oil, a volatile falt, all of them much like that of hartshorn. Oft- man an Apothecary at Stutberg, from a Swa- bian peat, had a volatile fpirit, like that of fpirit of tartar, a fetid oil, but no volatile fals. The Ujes of Peat. Tue principal ufe of peat is burning, not only for the fervice of families, but likeways for that of a great many trades; fuch as brewers, . bakers, diftillers, making of lime, &e.: and, as there is a good deal of diffe- rence in peats, and fome kinds preferred to others, I hall here take notice of fome of the _ principal differences. THE 432 ESSAYS ann OBSERVATIONS Tue firft is, with refpe&t to the place out of which they are taken. Such as are got from brackifh grounds, near the fea, alfo fuch as are impregnated with vitriol or fulphur, have a difagreeable {mell, and are hurtful to the health. In Zealand, they have a kind of peat, which, when burning, makes eve- ry body in the room look like a dead perfon; and, when they fit long by the fire, grow faintifh : it alfo turns the bottom of their veffels white. Peats taken from moffes, free. of all minerals, have none of the above mentioned, or any other bad effec. As to the matter itfelf, that differs in ma- ny refpects ; fo that in the fame mofs, ac- cording to the different depth of it, there are three or four different kinds of peats found. In North Britain, inthe province of Gronin- gen, and in feveral other places, that which is uppermoft, is light and fpungy ; . further down, better; and at bottom, is a fubftance that is black, and makes a firm folid peat. In Holland, that which lies uppermoft is beft, being of a dark or black colour, ‘to which others fucceed of different colours and fubftances not fo good. That which is tight and fpungy, taken from a barren heathy ground, | PHYSICAL any LITERARY. 233 sround, or froma dry fandy foil; alfo fuch - mofs as is much mixed with pieces of rotten - wood, roots, mud, gravel, or fand, or which confuming quickly, leaves behind a great many impurities mixed with its afhes, is bad. ) Peats differ confiderably, according to | the pains beftowed in making them. Such as are perfectly freed from. all’ hetrogeneous matter, well knead and wrought, are the beft of all. Upon which account, - peats, made in the province of Holland, where no labour is {pared in the working them, are preferable to all others ; tho’, in other places, the fubftance may be equally good. A _ Dutch peat fix inches long and three or four thick, will weigh a pound; a peat made at _Nimiguen, of the fame dimenfions, will not _weigh above half a pound, often lefs. . It is a general obfervation, ‘that all peats made of mofs-mud, and well knead, are confiderably heavier than fuch as are‘only cut out of the ‘ mofs. tins PeatTs that are of a dark colour, and folid, that continue longeft in the fire without con- fuming, that have a good cinder, and fall into white afhes, are moft efteemed: on the Voz. II. Gg contrary, 234 ESSAYS ann OBSERVATIONS contrary, fuch asare light and porous, con- fume quickly in the fire, leave no cinder, but a great many impurities and afhes, are little valued. Tue afhes of peats differ alfo confiderably in colour, quantity, and weight ; as to which nothing certain can be determined. ~ Some- times the white, fometimes the grey, (and at other times! the red, are heavieft. 2: In: Friefland,, the. peat that leaves the red afhes, Degner fays, is heavieft; about Nimiguen thofe that are red are found lighter than the Dutch peat which leaves a grey ath. Tue Brewer, Diftiller, and other trades, prefer the peat that leaves red ath, which, tho’ it feldom has a firm cinder, yet burns. violently. The Baker makes choice of the light turf, and in North-Holland, where the inhabitants are extremely. cleanly, they ufe the peat that has red afhes, upon account of their being heavier'than the white, and therefore not fo apt. to fly about and fpoil their furniture. Besipes the ufes now commonly made of peats, there are two others in which, I think, they may be employed with great advantage. The firft is, the {melting iron ore, the only — fewel PHYSICAL ann LITERARY. (235 ’ fewel at prefent ufed in that operation is charcoal of oak, and other hard woods ; a- ny attempt made to do it with pit-coal, fo far as I can learn, has hitherto proved unfuccefs- ful ; and indeed from the nature of that fub- ftance, there feems little hopes of ever bring- ing it to anfwer the end, the bituminons or inflamable part of pit-coal having nearly the fame effe@ upon iron, which common ful- phur has. | It deftroys, as experience fhews, the malleability of iron and all other metals. Pit-coal has likeways another bad quality, which I have often found tomy coft. With a {trong heat it runs into a glafly fubftance, which in time, by its fticking fo clofely to- gether, and to the fides of the furnace, quite choaks it up, and, by its tenacity, hinders the metallic parts from finking downwards, as they would do. by their natural gravity. What is chiefly wanted’ in fmelting, is an o- ‘pen fire; the furnaces are-commonly fuffici- ently clogged with the ftony and other he- trogeneous bodies united with the ore, which run into glafs without the addition of any _ fuch foreign matter as has a tendency to vi- trification. The char’d wood, on the con- trary, keeps always an open fire, the in- flamable 236 ESSAYS ann OBSERVATIONS flamable part of which is fo far from hurt- ing metals, that it preferves their malleability, by fupplying with its own fulphur that which is deftroyed or carried off from the metal, by the intenfe heat employed in the {melt- ing ; and this is fo far true, that iron redu- ced to a calx or friable fubftance by calcina- tion, has its malleability reftored by being fluxed with powdered charcoal only. And this we may here obferve, by the bye, as an in- {tance of the difference of fubftituting a vege- table in place of a mineral fulphur. Tue peat then being intirely a vegetable fubftance, there feems nothing more requi- fite to make it a proper fewel for {melting iron, but the being able to .raife by its means a heat fufficient for that purpofe. This, ex- perience fhews, cannot be done with the peats we now have. The moft likely me- thod of obtaining this end, I think, is, to bring them to be as folid and compact a fub- ftance as poflible. The denfeft bodies, ca- teris paribus, when thoroughly heated, are, the hotteft: hence it is, that metals as they are the heavieft bodies, fo they reach the great- eft degree of heat. The fame holds in fewel ; the hardeft woods are made choice of, when es PHYSICAL ann LITERARY. 237 when a ftrong heat is wanted; and even in common peats, I have fhewn you how far _ preferable the hard and {olid are to the light and fpungy. By fome experiments which I have made, I find it to be no difficult mat- ter, to bring peat to a confiderable degree of folidity, as you yourfelves may fee by the _ fpecimen I now {how you. The fimple o-. peration of grinding, does the bufinefs ; and as a peat, when taken out of the mofs, isa foft body, and eafily grinded, a machine may be eafily contrived to grind, at a moderate ex- _ pence, feveral tuns ina day. The charge of digging peats, cutting them into fquares or the form of bricks, when of a proper dry- nefs, will be little different from that of ma- king peats in the ordinary way. The foli- _ dity of peat prepared in the manner menti- See oned is furprifing ; its {pecific gravity being fomewhat greater than that of pit-coal. I compared a peat of this kind with a piece of coal brought from Baron Cler’s coal-mines near Edimburgh, and by the hydroftatical ba- | lance, reckoning water 1000, their fpecific " gravities were nearly as follows, pit-coal 4287, folid peat 1303. From 238 ESSAYS ann OBSERVATIONS From what has been faid, it appears, that, if iron could be made with peat, it would be of great fervice, particularly in fome places of North Britain, where peat is to be had in plenty, along with iron, which now lies unwrought for want of wood: and even - where wood may be found, if peat brought to the confiftency I mention would do the - bufinefs, it would come cheaper than char’d wood. Another advantage of this kind of. peat, would be the fmelting of lead with it alone, which cannot well be done at prefent, without the help of pit-coal, which in fome places muft be brought from a confiderable diftance, and at no fmall charge. Tue other ufe I would propofe of peat, is the employing it as dung, for the fertilizing of ground, when prepared in the manner I fhall afterwards mention. I am not igno- rant, that the afhes of peats are ufed for that purpofe with great advantage, not only by themfelves, but likeways mixed with other dung; and even the duft of peat, that re- mains at the bottom of peat-ftacks; but in that ftate it has not the effects of dung, nor are its effets equal to what they would be, were it rightly prepared. To fet this matter ‘ 1p PHYSICAL and LITERARY. 239 in a proper light, I muft be allowed to fay fomething in’ general of vegetation, and of the ufe of dungs in promoting it. VeceTaBLes which increafe by feed, as is the cafe with by far the greateft part, if not all of them, are at firft plantulas wrapt up in a ‘very {mall bulk in the end of the feed ; which, when put in the ground, by the moifture they find there, extend themfelves, and are firft nourifhed by part of ithe feed itfelf, which does the fame office to the young plant, by affording it a finer nourifhment, as the placenta does to the embryo. When the plant becomes ftronger and fhoots forth its roots, it then draws its nourifhment from the earth. Thus it goes on growing until it has attained its utmoft perfection : after. which it gra- dually decays, dies, and at laft rots and pu- trefies. By putrefaction, the parts of which the vegetable was compofed, v7z. its falts, oils, phlegm and.earth, are feparated : part remains upon the ground where the plant falls ; but the far greateft part being volatile, | flies up into the air, from whence it defcends F again upon the earth and incorporates with it. The fame materials ferve to nourith new plants, there being no part of them, as we all . know, #40 ESSAYS ann OBSERVATIONS know, loft. What we call a vegetable mould, is an earth in which there is ftore of fuch parts of vegetables lodged, the ma- trix in which they lie, being a fine but bar- ren fand. As long as there isa fufficient ftock of fuch particles in any earth, that ground is fruitful ; but when this is exhauft- ed, which happens fooner or later, from the quantity of vegetables nourifhed by it, and - carried off for the ufes of life, it becomes barren. The only remedy, when no better can be had, is to allow it to reft, until it re- ceives a new recruit fromthe air, in which are perpetudlly floating, and falling down up- on the earth, particles of all kinds, proper for the nourifhment of plants. Butas this is a tedious way of recovering the fertility of ground, the better and more expeditious one, is by laying dung upon it, which being wholly made up of putrefied vegetables, or animals, equally proper for nourifhing plants, the parts, of which both are compofed, be- ing the fame, and the tranfition from the one to the other eafy ; the ground by this new acquifition becomes again fertile. Every ve- getable then whofe parts are fet loofe, by that laft fermentation of nature, putrefaction, affords PHYSICAL aNpOLITERARY: 24% affords:a proper pabulumfor vegetables ;. and the great diftinGion of plants, which :com- “monly lies: 'in'a very: {mall part, - and that'too the moft volatile, being taken: away 'by:pu-= trefaCtion, ‘all vegetables,) when reduced ta that ftate; feem to be:(pretty much upon a par for! that purpofe. Now;)' to return: to what I. intended to fay, ‘and to which what I have. mentioned was’ only a kind: of »pre- amble ;) Peat mofs, -being wholly'a vege- table matter, muft, if reduced toa thorough ftate, of -putrefaction, anfwer the: farne | pur- pofes for fertilizing ground as/other’putrefied _ vegetables. . While it lies:in the mofs, ‘there sh is too. great a quantity of ‘water,’ to raife a fufficient degree ‘of Heat, to bring) the ve- _ getables. of which peat-mofs. is compofed, _ whether actually growing, ‘decaying; ‘or de- cayed, to a compleat degree of. putrefaction. But if it were taken out of the mofs, and laid in heaps like other vegetables to rot, with a _ degree of moifture fuitable for that purpofe ; ph and if, to begin and alfo quicken the putrefa- ction, green frefh fucculent plants were em- ployed in a fufficient quantity firft to raife a Bic this I make no doubt would, bycommu- _ ‘hicating it to the moffy fubftance, in a fuirable — evox. II. Bh: time, 242 ESSAYS anp OBSERVATIONS time, and by right management, reduce the whole mafs to the ftate defired. This alrea- dy is in fome meafure practifed in Holland, where they mix the duft of peats with ordi- nary dung, in making of dung-hills. I fhall conclude this paper with only men- tioning two others ufes. of peat, which I had almoft forgot, viz. that peat-duft ftrawed up- on ground where peafe or other feeds are fown, in order to have an early crop, is an excellent prefervative of fuch vegetables from the froft; as it keeps the ground warm, by not allowing the cold to penetrate into it, And that there is nothing properer than peat to ftop water, and to confine it, in the making of fith-ponds, &c. This I learned from his Grace the Duke of Argyle, who I obferved ufed it with great fuccefs for that purpofe. ART. OS oa PHYSICAL ann LITERARY. 243 ART... . The Effects of Semen Hyofcyami’ albi, dy | Dr. ArcutzaLp HaMitTon Pies wie in ig it \ Student of sphinGitsl ofa thin habit of ree about twenty years of. \age, had been, for two years, in the ufe of taking | a {mall quantity of white. -henbane-feed-to make him fleep, and without any bad. effect. But on Friday March the 8th 1754, betwixt four and. five in the afternoon, he, in order to procure fleep, {wallowed about twice as much of this feed. as he could take up betwixt his _ fore-finger and thumb, 7.¢. nearly 25 grains. He felt himfelf half an hour after, very heavy and much inclined to fleep ; his eyes were opprefied, and {pirits dejected, with a general Jaffitude .and inactivity over his whole body. Thefe fymptoms ftill increafing, he went abroad and drank tea about fix o’clock, ; and with great difficulty could keep awake, ha- ving fometimes let fall the tea-fpoon infenfi- apy He complained of a great uneafinefs and as %. * May 1. 1755. ——- -____—_——_--- 844 ESSAYS anv OBSERVATIONS and drynefs of his throat, and that the tea in {wallowing was like to choak him. He had alfo fome gripes in his belly. After he drank;tea; he was foon feized with ‘convul- fions' and fo great a degree of infenfibility, that he did not know the people, who were in company with him. He {poke many in- coherent things, and atthe beginning-of-his illnefsifaid he was afraid he had taken’ poi- fon. 'The ‘people! who were with ‘him be- ing alarmed, ordered ‘him ‘to be carried! home, and (ent*for me.01 found him ‘incapable’ of giving any account °6f ‘this misfortane!> His eyes were open “and” ‘rolling, | now and: then he-was feized with tfémors;' ftartin gs, and convulfions, grapling ‘the ~bed-cloaths, ‘his head,’ face, nofe, and. other parts of ‘his *bo- dy, inthe manner’patients frequently do in nervous fevers. “His pulfe exceffively {mall and’ low with /uAfultus tendinum. The fenfe of feeling feemed ‘alfo impaired ; for when I pitichiea his {kin, he made no‘ complaint. He had no inclination to vomit, nor had any {tool from the time he took the feed. TI or- dered him immediately a vomit ; and’in the mean time Dr. Bo/awell was fent for. He {pit out the vomit as foon as it was poured in- to “PHYSICALcanp LITERARY. Yas tohis mouth 3{o that it appeated heowas:eil _ ther Not. deprived! of tafte,; orcould not | Tet the vomitoover! SA ‘fecond vomit) was) ain= Rantly given} which was alfonfpilt-or {pit out. A folution'of white \vitriolyiwas -afterdzards | given; the mot of which ke fwatlowed with- Gut 'the defitedeffea. Atrengelyfter with antimonial wine was adminiftred, whichche _ kept about twenty minutes. He got a fecond injection an hour after. As he continued in the fame miferable fituation, a blifter was applied tohis head, and finapifms to the foles of his feet. He pafied the night in the fame condition without fleeping, and was alternately feized with convulfions, ftartings, and catched with his hands at every thing about him. In the morning, he became more fenfible, and began to fpeak a little diftinétly, altho’ his head was yet very con- fufed and muddy. He told what quan- tity of the feed he had taken, and for what purpofe. His pulfe was now fomewhat ftronger. He got a purgative infufion, which operated four times that day. In the evening, he was ftill more diftina, his eyes continued heavy and his head 246 ESSAYS ann OBSERVATIONS head confufed. | His pulfe was’ now quick, full, and ftrong; and he complained. of a great pain and weight in his head. .. He was blooded about: twelve o’clock that night to the quantity) of twelve ounces.. He {weated plentifully, had. good fleep ;.. and was altogether fenfible and Siting. next morning, — , ART; “PHYSICAL ann LITERARY. 247 ’ Arr. XI. The Effects of the Thorn-Apple, by Dr. Apras _ . HAM Swaine: Phy/fician at Brentford *. Osert BurMmer, aman of a ftrong con- ftitution, 69 years of age, and who had enjoyed a good ftate of health all his life, _ till about two years before, when he was firft afflicted with the gravel ; in Odtober 1746, being advifed by a friend to take a decoction of the fruit of the common burdock, »as,a _temedy for his difeafe, by miftake gathered the fruit of the framonium or thorn-apple. After dividing three of thefe, each of which _ was as big as a fmall hen’s egg, into two parts, he boiled them in a pint of milk, which, when a little cooled, he drank off a- bout eight o'clock in the morning fafting. Prefently afterwards, he became vertiginous or giddy ; and therefore rofe from his chair -to take the air, with an intention to pluck ‘more fruit. In walking two or three hun- “dred yards from his houfe, he re as * i. oof 4 . * May I. 1755. 448 ESSAYS! Aun OBSERVATIONS if drunk, feared he fhould-fall on his head, and that he was about to lofe his fenfes; but had no ficknefs nor the ‘leaft inclination to vomit. As foon as he got home he went to bed, and complaining of an exceffive drynefs of. his tongue and throat, ‘a little water: mix- ed with wine was given him ;_ he alfo felt an odd: fenfation of :drynefs in :and: violent girding a-crofs the thorax.) In lefs than-half an hour he beganoto: faulter in his f{peech, became infenfible, reftlefs, and muttered: fre> quently ; in which condition I found him: His. extremities, “and -alfo: the trunk’ of /his body,. were: cold. His pulfeifmall and quick. He_ often « raifed:himfelf on his: knees, con- tinually ftretched: out his arms; and employ+ ed his hands as if fearching for fomething he wanted; his eyes were dull and:heavy:; « af- ter fome time, he became ‘dumb and more quiet, had almoft no pulfe ; and,, upon. his being taken: out-of bed, that. it might be put into: better order, his limbs, were, vifibly pa- ralytic. Altho’ he changed poftutes .a little, yet: he remained ftupid for fixior feven hours ; theniheraged: furioufly, requiring: two- per- . fons::to. hold- him in bed, notwithftanding § which, he raifed himfelf up, toffed greatly, and PHYSICAL Ano LITERARY. sug and feemed to catch at the byftanders with his hands, uttering incoherent fentences. At ‘aft he became fenfible and more quiet, reft- lefs and delirious by turns; and about ten o'clock if the evening of the fame: day “pers fectly recovered. After’ faking ‘a purgative, he flept well. all night, and fad ‘feveral ftoofs in the morning. For the fpace of fourteen hours he neither flept, vomited, nor difchar- _ged’any thing by ftool or tring; tho” he f7e- gaently’ paffes urine at other titnes, Being gfiet ere “capil 3 the i Beavel 02 £1900 ent 2338 . es ara = en ey eee ae S werys roariorm eee ‘908 wes Pik chs . As LI HIOU PssstLl, Gt . ' — ; t ; ‘i ° “ ~ eee rey! : ah 24h! ch i p glithtiiQsa Jiibs 9&b -ASI1 Vox. II Lj ArT; ‘ M © a | i ry fs ed * ~ OL, Bb sow orl 9 eae 4 fi. ) Be ART, lai \ : ~ , 20 i , ISM r by -y, + Al [eaten + VV ¥ boa i “~t - - e FUR], : 3SiO! ata Tae y ae ~~ a i . - GO? whos) * J) ; fl . r di, OSEe IO “Vu Si01V o aso, ESSAYS anv OBSERVATIONS ciiw . Agr. / RU. The Effet? of Misfe in curing “e Gout in the - Stomach ; by James PRINGLE. Efquire, late Surgeon ;.to the third. Hircanee oh _. Foot-Guards*, 25 abhreaianoneng te aged 43 years, natu-, rally of a delicate, conftitution, who has. been for feveral years, fubje&, to hyfteric, fits, attended with a a dry afthma, which her fhape much contributed to ; was frequently attack’d to a violent degree with the gout in her head and ftomach, as well as in all her extremities; and with which the was Jame'the moft part of Summer 1745. On the 3d of November following, fhe was violently feized with it in her ftomach, which occafioned violent hiccups and convulfions of the part. The defcription fhe gave of it was, that as foon as thefe fits feized her, there came on ~ a violent working of her ftomach, and fo great an agitation of her back, that her Maid was not able to keep her hand on it. By degrees * Aprile 3. 1746. PHYSICAL! ann LITERARY. 2518 degrees it rofe to her throat, when ithe! was almoft ftrangled. She: could by-no- means lie down, but was forced to fit night and day in an eafy chair ;. and even then if the lean’d her head to the one: fide or other, it gave her great pain; fo that {he was obliged _ torfit in an erect pofture.. Her legs were very much f{welled, which fubfided alittle en laying them on a chair; but:as foon as that happened, the afthma returned.: She did nothing all this while. but keep herfelf warm, now and then drinking a little of fome generous wine (as fhe faid, to keep it out of her ftomach), and once’ or twice took a little of the tnd. facra. On the 21 of November about 9 o'clock at night, a Lady of her acquaintance, whovhad {een her _ in this» condition, defired me to vifit’ her, tho’ fhe doubted if I fhould find her alive. Accordingly I went, andas 1 had feen fuch extraordinary effects of the tonguin medicine in the fgultus, and chad heard from) Mr. Read of its efficacy in other nervous cafes, I imagined it might be of fome fervice here: and therefore I fent her the following bolus. Re Cinnab. 242 ESSAYS anp OBSERVATIONS Ik. Cinnab. nativ: ; —— Antimon. aula gr. XXN. -. Mofch. opt. gr. xvi. dw Syr. balfg. fo Fe bolus. » Bur altho’ this is Mr. Read's common dofe, yet, as fhe -was: very weak, I ordered her-to take only the one half: of: it: amme- diately, drinking after it a cup of brandy, and the other half in fix hours after. ~ Next morning» I found her much better, having from the firft dofe no more convulfions in _ her ftomach. ‘I'then ventured, to give ‘her a whole bolus at g:o’clock in the’ morning, to be repeated. every. four ‘hours until fuch time as fhe fhould fleep or iweat: and not- withftanding the coldnefs of the weather, and her’ being obliged to fit in'a chair, yet, by the time fhe had taken four bolufes, a plentiful: fweat and fleep enfued, and then fhe was'able’to lic in a horizontal pofture on het couch without the return of her former fymptoms, ‘This fweat continued from the afternoon ‘of the 22d till the 24th at night, with very little intermiffion.. I gave over the bolufes and ordered her a julep, to eight ounces of which I] put twelve grains of mufk,- fQ /PHYSICAL asp LITERARY: 253 to be taken ad Iibitum. In this method the continued till the 27th, quite eafy and free from all her former fymptoms, and even the fwellings of her legs almoft gone : But as on this day ‘fhe fancied the gout in her’ ftomach was returning, I gave her another bolus. She aap lanes this time of the intolerable heat of the brandy, which was the firft’ ‘thing fhe had found warm in her ftomach during this illnefs. “On the 2oth, fhe: was- appre- henfive: of another attack,’ and ‘took another bolus; after which fhe’ found herfelf: very well, and’ walked about the room, the fwel- lings of her feet being quite: gone. | And on the 4th of December went out In a “chair: to thank the Lady who ‘fént me to her, ae continues to be one to this day. ° ArT. ‘254 ESSAYS avn OBSERVATIONS Arr... XIII. An Account of an- uncommon Effect of antimo= nial wine ; by Dr. James Wa ker. Sur- geon and. Agent Fen? the Wang at Edin- ga nere _ HE vinum benedittum is univerfally known to bea {trong emetic, when given in a large dofe ; and it has alfo been often prefcribed in fmaller quantities as an attenuant, fudorific,, and diuretic: but an accident lately difcovered to me a very diffe- rent effect of it, from any of the above ‘mentioned. | BEING one evening, in December 1755, a little hot and feverifh, with a quick and full pulfe, I went early to bed, and drank a full Englifh pint of fack-whey which I had order- ed one to make for me. Very foon after this, I fell afleep, and continued all night oppreffed with an unufual drowfinefs : at ten next morning, I with great difficulty got fo far the better of this lethargic difpofition, as to * February 5. 1756. ee ‘PHYSICAL any LITERARY.! 255 tb get out -of: bed ; when found myfelf till heavy and inclined to fleep,: with a laffitude: and numbnefs in my limbs; fo that I ,could fearce ftand.-, Being thus, incapable: to-go. a- bout. ‘bufines, I refolved to ride out on’ horfe= back); and:having mounted.with fome. diffi-. culty; found. my head, very. giddy, and-had, much ado,to keep myfelf:from fallingiafleep.' After having rode'three» hours, I returned: home much. .in» the fame fituation, ‘and! :was’ furprized,\to, find two,/appréentices: with, thei farhe; complaints I had:myfelf: . they-could: affign no edufe of their being! fo affected; hor: had they.éat'any thing but) their ufual:food,: except the curd of which I had got the whey. Being led iby this to fufpect fomething > un-: common‘in the wine with which the poffet was made’; J called for: it, pand had. a, bottle, brought me containing vinum benedictum, which had been made about a month before; and the bottle having been put in an impro- per place, was the reafon of its having been muftaken for Lifbon. IfoundI had drank in my whey about a gill and a half of this e- metic wine, and was furprized it had not vo- mited me ftrongly. Thinking, however, that the finely attenuated particles of the antimony might 256 ESSAYS And 'OBSERVAITIONS might be moftly {ufpended ‘in the ‘curd, I inquired particularly-at the two young Gen- tlemen who had eat it, whether they were affected with any naufea or vomiting ; but they told me they found no othet effe& buta heavinefs and great inclination to fleep. This drowfinefs. continued with them: ‘two days ; but I did not find myfelf quite free of it at the endof four days. - I do not know if it be worth while to obferve, that theday after I had drank: the above whey, my pulfe was'ten- in the minute! flower than it had:been the night before. It may be proper however to’ take notice, that the vinum benedittum-which was ufed, by miftake, inftead of Li/bon, was’ made exactly as is direéted in the Edinburgh. Difpenfatory ; and Vhave fince found half an ounce of it vomit a patient very well. Or £1 ART.’ PHYSICAL ann LIFERARY. 257 Raaty + SV: in obftinate Dyer ‘cured by, 1 EO ited ; “by James Grain GER M. D. Phyfician at _ London 7 upd a sly “middle aged, ‘but seiner foldier, was ferzed November 1751 with fhivering and: other fymptoms that precede an accute diforder: “The day fol- lowing, he went frequently to ftool, and e- vacuated blood to the quantity of a gill every quarter of an hour. Tho’ ‘the’ fever was' in- coffiderablé, yet, as he wasof a fanguitié ha- bit, the lancet was not fpared- He fwallow- ed fome ipecacuan vomits ; was gently pur- ged every third day with rhubarb ; and had fmall quantities of opiwm at bed-time to hin- der his rifine in the night: ‘The third week his fundament came down, attended with but little pain, unlefs when-he went to ftoolh. This fymptom, however, ‘was timeoufly re- moved by fomentations of'a decodtion of oak- bark, December ; his Kooks, tho’ lef frequent, Were’ mixed with blood and mnens. “Then mot. FET! O09 KO ge! othe 90% May 3. 1753. 258 ESSAYS arp OBSERVATIONS the gripes feized him in good earneft, fome- times fixed and torturing like a ftitch in the baftard ribs, at other times wandering with Lorborygmi, now as it were twifting his guts, then cutting him in two, as he expreffed it, and bending him forward. They. were al- ways moft fevere before ftool, eafier in the time of evacuation, but eafieft after. With thefe fymptoms were. complicated a dyfury and piles, greatly inflamed, but bleeding none. Thefe difmal complaints continued almoft equally violent for three months, altho’ V.S. emetics, vitr..antimon. cerat. mild an- tiphlogiftic purgatives, opiates, lubricating and aftringent remedies were ufed, as the fym- ptoms indicated. Opiates, tho’ they eafed him, feldom procured undifturbed repofe, and always aftected his head ; this confequence of Jeud. was more effectually prevented by balf. Jocatel. than any thing elfe.Vomits always relieved him, but increafed the pain — of the hemorroids. Aftringents, tho’ they bound him up for a little time, moft gene- rally brought on afterwards a more frequent inclination to ftool, . with increafed tormina. - Clyfters were impracticable on account of the piles, but he found confiderable fervice from the PHYSICAL anv LITERARY. 259 the milder purgatives, with calomel.; and when the {welling of his fundament was re- moved by fu/phur and emollient, difcutient applications, 'they became highly ufeful. In the 4th month, the region of the ftomach fwelled, with rednefs of his face, efpecially after food, and continued for fix months, al- tho’ its removal was attempted by bitters ; and the bark (cautioufly combined with pur- gatives), mulled claret, and camomile tea, while proper external applications were not forgotten. April and May, the hemorroids and dyfury left him; but his ftools became thinner, .more acrid, and intollerably fetid. Then he was feized with a hiccup, his face looked ghaftly, his extremities turned ‘cold, -his pulfe became quick, fmall, irregular, and his gripes were rather abated. . Evacuations © in thefe deplorable circumftances were: im- proper, but finapifms were applied to the foles of his feet; and epifpaftics to the region of the ftomach with feme fuccefs. A bolus of bark, ‘caftor, and camphire was given every third: hour, and wafhed down with a glafs of mulled claret; his guts too were fomented _ with anodyne, emollient, and antifeptic-cly- fiers. By thefe, his deadly fymptoms left “weed him, 260 ESSAYS ann OBSERVATIONS him, he could fit up at the fire, and had not above 12 {tools in the 24 hours, which were however ftill ichorous. I could not find from the nurfe that he ever paffed any of the villous coat of the guts, tho’ feybala were frequently evacuated. About the end ef May, he was able to walk round the ram- parts of Fort-William, and he told he thought he would recover, were he fent from Lach- aber. On this, he was carried, by water, to the Ifle of Muil, being provided with pro- per imedicines to forward his -recovery. Here, ‘tho’ the hiccup and facies hippocratica did not recur, yet his gripes did ; and he purged blood and worms almoft inceffantly. The latter end of ‘fuly, he was fent back to the Fort a perfect fkeleton; where, tho’ I am convinced the air is inferior to that of Cajtle-Dowart in Mull, yet, as great care was taken both of his diet and medicines, he paf- fed no more worms, his gripes only feized him at fiool, whither he went much more feldom than formerly ; what he pafled now appeared to be mucus mixed with pus and fireaks of blood. Very {mall dofes of ipeca- cuan, viz. eight grains three times a day were then adminiftred to him every third day ; bug ' PHYSICAL anp LITERARY. 261 but, tho’ they relieved by operating both up and down, yet they fickened him fo much, that I was obliged to fubftitute a bolus of calomel. over night, and a purging ptifannext morning, intheir place. » The difeafe, how- ever, did not yield ;:and:when the regiment was ordered to. march for Berwick upon Tweed, he. was put aboard: the vefiel that carried our baggage.«:‘Fhis was:a hardy ftep, confidering his weaknefs, and the length and danger of the voyage ; but he could not be carried with his comrades over the Black — mountain, and. he defired to die any where, tather than remain in Fort-Willam. Five or ‘fix weeks after he landed at: Berwick, his ftools were more numerous, jand ftill very painful. Sometimes blood, fometimes flime, fometimes ichor, and once he pafied a great quantity of hardened excrements, which re- lieved him of:.a dull. pain of his left. hypo- . chondre ; his legs too, at night, -fwelled: and pitted to the touch, and his ftomach was often inflated, . Bitters, with fieel, were preferibed, and camomile tea drank -for breakfaft, -while the utmoft regard was _hadto diet; the wtr.:antimon. was again bi nae alum poflet recommended. ‘The dyfentery 262 -EESSAYS ann OBSERVATIONS dyfentery baffled all our attempts’; and’now, defpairing of his recovery, I ordered him to drink lime-water, with a third part milk, to the quantity ofan Engi/h pint and a half every day: It was at the latter end of November 1752. In three days time, there was a fen- fible change to the better, ‘his ftools were lefs frequent, and his pains abated. -Encoura- ged by this happy beginning, he was ordered to drink 46. iii. of lime-water a-day.» This, in three weeks, made -him {o:coftive, that] was obliged to clyfter him, ‘and diminith the aq. calc,to the quantity firft ordered. ‘In fix weeks from his taking this medicine, he was fo thoroughly recovered, that he was difmif- fed the hofpital, and foon after marched to his company at Carlifle, where he ftill enjoys perfe@ health. The diforder was on him full 14. months ; and I have reafon to think his recovery was chiefly owing to the lime- water, after the moft celebrated antidyfen- terics had been ufed in vain. Tue dyfentery is endemic at Maryburgh, near Fort-Wiliam, and commonly attended with procedentia ant, piles, dyfury, .abdomi- nal inflations, ofdema’s, and hiccup. Many of the foldiers died, efpecially the more in- temperate ; PHYSICAL ann LITERARY. ‘263 temperate ; between the 2oth and 35th day, is the fatal period. Thofe who died had mortifications of the great’guts: it began with us about the latter end of Odfober ; autumn \however'is its ufual feafon; it rages commonly two months, tho’ many have it,all © the winter, and I always obferved them wortft in. rainy weather. It may be worth while to obferve, that of late lime-water principally conduced to cure an Officer of a dyfentery, while. another: was. effeCually, , cured. of_a weaknefs in the bladder, by the. fame re- medy, ah ; i bibine dyiee BMIVITION) ART. 864 ESSAYS snp OBSERVATIONS OaRT. XV. é be sriiheliishtte Piptue of ibe Bark it the wild -* Cabbage or Bialgelindtor Trees by the late Mr: PETER Ducurp late ‘Surzeon® in Jamaica, in a Letter to ALEXANDER Monro. fenior, MD. SE ae re ete ae NHE’ aytiters fixe on sie? ainsi ‘of the Wef-Indies generally take ‘litle notice of the Inhabitants of Yamaica, young and old, white and black, being much troubled with worms, efpecially the long round fort. They are however fo frequent, that every practifer ought to have regard to them in treating moft of his patients. I imagine thefe worms infeft the inhabitants here on account of their {weet vifcid bread-kind, to wit, plan- tains, yams, bananos, {weetifh potatoes, @c. which are fit nourifhment for thefe vermin. I was lately allowed to open a Gentleman’s child, that, at feven months of age, died of vomiting and convulfions. In its inteftines there were twelve large worms: one of them * May 1. 1755. PHYSICAL ann) LITERARY. .265 them filled the appendix vermiformis, and three of them were intertwifted in fuch a manner as to block up the opening at the valoule Tulpii, fo that nothing could. pafs from the fmall to the great guts. Nature’ has bountifally provided . the people here with a powerful. remedy -againft fo greatan evil. This is the bark of a tree growing plentifully in this Yand. Thei in- habitants call it aw#/d cabbage ot ‘bilke-water and from what I have feen, it appears ‘to be the moft powerful vermifuge yet ‘known for it frequently brings away as many. worms by ftool as would fill a large hat. “It is commonly given in” decoétion, but not in any regular quantity; the negroes being generally the preparers of this medicine, and therefore no wonder that it fomettimes has very violent effe@ts. “Iam now making experiments for afcertaining the dofe to pa- tients of different ages, and fhall foon fend you the refult of my trials, together’ Fade forte of the bark itfelf.” iioi., Wsvitbarat: Barkor-isibod of Pe Mxr. 266 ESSAYS ann OBSERVATIONS Art. XVI. The defcription of a monftrous Fatus ; by Mr. Joun Mowat Surgeon at Langholm, zz a Letter to ALEXANDER Mownro fenior, M.D.&S P.A*. Everat learned men having of late years difputed about the formation of mon- fters, it is probable the hiftories of them may be of ufe in accounting for fome phenomena in nature; on this account, I fend you the following defcription of one, which will be better underftood by the figures which young Profeffor Monro caufed to be drawn of it, of half the natural dimenfions. See plate VI. jig. I. | . when fix months with child, had this.abortion, which lived half an hour. Tas. VI. fg.1. AA The lower parts of the bodies of two female fwtu/es, with their low- er extremities in a natural ftate. _B The navel-ftring common to both /e- tufes. ' © The bodies joined immediately above the navel. DD The * May 1. 1755. ,. PHYSICAL ann LITERARY.» 267- D,D The fuperior extremities of the more | -compleat fetus, which is here apmpctented — moft in view. a d'The fuperior extremities of the other fetus. All the four being of a natural form. E The /lernum of the more compleat fetus which had clavicles joined to it in the com- mon way, as the other alfo had. _F One neck common in Appearance to both fetu/es. _The face and ears, being ial need. no letters of reference to their parts. iy _G The forehead had hair farther down than ordinary. . H The top of the head of an eeticiliaaty breadth, || IThe hairy {calp covering the parietal Bones. K The right temple of the fetus D D. _L The teguments covering the occipital bone. _M The ocezput of the other fetus. Fig. 2. The back view of thefe fatufes where the head, neck, and fore par of the: - thorax only are reprefented. -NWN The fcalp” over the four iy Biches. i! oOo— 268: ESSAYS. ann OBSERVATIONS “00 The two occipital bones.’ PP Two ears joined together. PQQ Fhe two meatus auditorit. Ro A paffage by which a saris could be put into the w/ophagus. 8 The neck of the fetusDD. “EP °Phe fernum. ~ -: UU The forepart of the atms. “THE back parts of neither fetus are drawn, having nothing preternatural. ‘Where the abiléinen of each fetus was diftin® at AA, the v/cera were ina natural ftate, and in thé wndivided cavity of the belly above CG there were two ftomachs, livers, fpleens, intePina dutdend, jejuna and ilum: but 1 faw. only one omentum and one pancreas. One. dia- phragm divided ‘the abdomen from the thorax,. but it was pierced by two vene cave and two afophagt, and two aorte defcendentes paffed be- | tween its appendices on each fide where the, vertebre were. THERE was a /fernum to the thorax of both fides F fiz. i.and T fiz. 2. From each flernum. a mediaftinum was extended to a ligamentous flefhy fubftance, which was continued tranf- verfely from ane fpine to the other. In each -—— PHYSICAL ann LITERARY. 269 each mediaffinum was a pericardium with its heart and veflels as in natural fatu/es, and on each fide of each .mediaflinum was a thorax with lungs. Thofe im the shorax of thexmore compleat\ child, the one, to- wit, with the face, being of a pale colour and {wimming when put into water, while the other lungs were of a redder colour and fank in water. ‘Tue. {pines gradually approached each) o- ther as they extended towards the neck; ‘at- the lower part of which the fides of the’ bo- dies of the vertebra feemed'to be contiguous $ but I. puthed.a probe up between eae as far as the fecond vertebra. Wirutn the head I faw a cerebellum on each fide divided from a common: cerebrum _ by amembranous plexus produced from the dura mater. 'The parts of the encephalon were too foft and tender for my diffection, and 1 examined the anatomy no further, but have the monfter in fpirits.with the three great ca- vities filled with lint and bran where the bowels were taken out. RT «jo ESSAYS ann OBSERVATIONS Arr. . XVII The Diffection of the fame Monfter continued ;) by ALEXANDER Monro junior, M. D. and’ Profeffor of Anatomy in the Univerfity of. Edinburgh *. FY father, having fhewed me Mr. VE Mowaz’s defcription of the mon- ftrous fetus, and a model of its form in wax, I was.curious to.know how the parts of the head and neck were formed. ~The prefer- ved fetus was obtained with difficulty, and: under a promife that no diflection fhould be made which might fpoil its form. The fub-> jet. was unfavourable, and the promife ren- dered the diffection difficult, and impoffible to be performed fo accurately as I wifhed. AFTER drawing afunder the two parietal bones of each fide I N N (fee Mr. Mowat’s Jig.) to take out the lint, &c. with which the fkull was filled, and having cleaned a- way the matter, membranes, &c. adhering to the bones, I faw the cramum of a natu- ral * May 1. 1755. ‘PITYSICAL and LITERARY. 271 ral form on that fide where the face is, fo far back as the fella turcica, behind which the ends of the cuneiform procefies of the two occipital bones united together. From each of thefe cuneiform procefies the’ occi- pital bones extended of a natural enough form to each fide; their fituation may be judged by confidering the figures at L, M, or O, O, having each a)foramen magnum for the fpinal marrow.» At the fide of each of ‘the occipital bones, neareft to» the conjoined preternatural ears, an os petrofum was placed, _ but without having any {quammous part of the temporal bones, fuch as were on the o- ther fide of each occipital. Between thefe offa petrofa there was a triangular little bone - which fuftained thefe preternatural ears, and was inftead of os ethmoides, fphenoides, and two fquammous bones. The fetus with the face had therefore allthe common nerves, but the fetus with only the conjoined ears wanted the 1, 2, 3, 4, 5, and 6 pairs. THE meatus Q, Q fig. 2. led into the organ of hearing. The orifice R was the entry to a paflage which opened into the efophagus of the fetus D D. eS THE 272 ESSAYS ann OBSERVATIONS Tue mouth of the more compleat ftus had all the ordinary parts, with the wvz/a, nares, larynx and pharynx. Behind this pha- rynx and the afophagus defcending from it, there was another /arynx and trachea. From the back part of the g/ottis of this laft menti- oned Jarynx, a little excrefcence refembling a tongue ftood out, and behind it a canal de- fcended of the form of one of the mares which joined with the one continued from R.to form another w/ophagus. I could not profecute the veffels and nerves placed on the neck and head without breach of promife, and therefore can give no ac- count of them. ‘Art. PHYSICAL ann LITERARY. 273 ART?” XVII. Bones found in the ovarium of a Woman ; by Dr. GeorGe Youn, and communicated | 0 the Society by Dr. Joun Boswe.t, Fe/- ~ bw of the Royal College of Phyficians in ‘Edinburgh *. ” Woman near fifty years of age, who had never had a child, being four months obftructed, thought fhe had con- ceived ; but the men/fes then returning, fhe had exceffive flooding, which was fometimes in great quantity, at other times was lefs, but fearce ever intermitted for a year and ‘a half. “It was then ftopped by fome medi- cine ; ; after which, her belly fwelled to fuch a degree in fix weeks, that her urine was almoft totally fappreffed ; fhe was very co- ftive unlefs when clyfters were given, and | fhe died in a few days more. On cutting the teguments of the abdomen, a large quantity of bloody water rufhed out; and when the containing parts were’ fully ) Vou. Il. Mm opened, .* November 1. 1737- f 274 ESSAYS ann OBSERVATIONS opened, all the cavity was bloody, and the vefiels were large and turgid with dark-co- loured blood. No bowel was now feen ; all that appeared in view being a great number of irregular flefhy lumps, which were blad- ders full of a red watery liquor. Some of — them were of the fize of the largeft apples I have feen,. others were as {mall as pigeon- eggs; and there were of all the interme- - diate fizes between thefe. Upon a ftricter examination, thefe veficles were found tobe all contained in one common cyft, of which Thad cut the fore-part with the teguments of the abdomen. ‘The large cyft filled. all the belly: when it was raifed, the bowels ap- peared in a natural flate ; except that, 1. ‘The left Fallopian tube was very large. 2. No ovarium of that fide could be feen unlefs the great cyft was that ovarium im- menfely diftended.. 3. The right ovarium was as big as the head of a new-born child. It contained a vifcid white-co- loured fubftance refembling mafhed brains, which run together like fuet when, put in- to water. In this ftuff I found the bones herewith fent. | THE PHYSICAL ann LITERARY. 275 _ Tue bone reprefented in plate V1. jig. 3. isa piece of a jaw with three firm dentes mo- f Jares, A, in it. Fag. .4.,and 5. are two views of a part of a jaw, in which are three dentes molares, B, irregularly fet, and an zn- oifor ©. ArT. eee | 276 ESSAYS ayn OBSERVATIONS Art. XIX. Proofs of the Contiguity of the Lungs and Pleura; by ALEXANDER Monro . fenior, M.D. and P. A.* HE experiment of opening the thorax without hurting the lungs of living animals, while the trunks of their bodies are immerfed in water, thro’ which no bubbles of air rife after the perforation, as propofed by the ingenious Lieberkubn and executed by the illuftrious Haller +, is a decifive one, if tightly performed, for proving no air be- tween the pleura and lungs. But, as an un- wary operator may wound the lungs in per- forating the thorax, when air would cer- tainly rife in the water, from which the exiftence of air in the thorax might be con-_— cluded, , and feveral other circumftances may, and have caufed the conclufion from this experiment to be difputed ; it may not be amifs to mention fome eafier ways of proving ¥ February 7..1754. . | t+ Opufc. de refpiyat. eR es ROR Seee ike \ Pas a re ae » rt ad oft al Wou.ILLAB.V1i. f. 976 io) PHYSICAL ann LITERARY. 277 proving the non-exiftence of air in this place. _ Such are the following : . 1, Dissecr the teguments.and intercoftal mufeles from the pura’ of:.cither a dead manor quadruped without wounding this membrane, »in. which there is no difficulty ; then. pull up and deprefs alternately the: ler num and ribs as often as you will, the lungs are feen contiguous all the while to. the pleura; but, on making: a: {mall punéture thro’ this membrane, the lungs, if | they are Not grown to the pleura, which is often'the cafe in the. human» fubje@,. fly from’ the pleura, and are no more feen. a » 4 Tuts, connection of the lungs. and pleura, more'ot.lefs of which is feen in. mot human _ bodies, - implies ftrongly a natural contiguity of thefe two parts): $08 on _ 3. Lay bare’the pleura, without wound-. ing it, between two ribs of any living quadru- ped, which requires no: great dexterity ; and then the contiguity of the lungs and pleura may be feen, tho’ the. lungs are. conftantly fliding and changing place along the pleura, and tho’ this membrane is in different flates: while the creature infpires, it is concave; hy during 278 ESSAYS ann OBSERVATIONS during ex{piration it is convex ‘and prominent outwards, for this plain reafon, that while in- {piration is performing, the air does not pafs fo quickly at the narrow glottis as to fill the lungs at once with air of denfity and weight equal to the atmofphere ; and during exfpiration; the air cannot efcape fo faft at the glottis as to prevent its more than ordinary condenfa- tion and expanfility in the samc than the'ex- ternal air has. Ir we were to find: accurately while weight ‘the pleura could raife when it’ is made convex during exfpiration in the pre- ceeding experiment ; would not this’ deter- mine how much more preffure, than that of the atmofphere; the part of the lungs within this ‘elevated pleura, on which this weight, is fuftained, is expofed to? Woutp not the preflure on the fame part of the lungs during infpiration be nearly as much lefs than the weight of the at- mofphere, as is the weight raifed in exfpi- yation; fince it is the fame .glotis which allows the air to pafs in both cafes? Is not the force, -by which the infpiratory organs, acting with the greateft energy of the mind, exceed the power of the exfpira- tory eS Pig “PHYSICAL ann LITERARY. 279 tory organs uninfluenced by the mind, con- - fiderably -lefs than the weight of the at- mofphere ;_ fince, if, after exfpiration, we prevent the entry of the air by the gittis, we eannot dilate the ¢horax as in in{piration, tho’ there is {till a good deal of rarefyin ga air inthe lungs } ? Do not the infpiratory organs, ahaa infpiration, overcome the refiftance of the expiratory organs, and likewife, that fhare of the preffure of the atmofphere, which the air; rufhing into the lungs, does not» ba- lance } ° _ Are not the ribs arched, and the een between them narrow, to prevent ill effects from that unbalanced part of the atmofphere | curing infpiration ? ART. 880 ESSAYS ann OBSERVATIONS | ArT. XX. An Account of fome Experiments made ith Opium on Living and Dying Animals; by RopertT Wuytt M.D. FE.R‘S. Fellow of the Royal College of Phyficians, and Profeffor of Medicine in the ent of Edinburgh *. HE ancient phyficians imagined that opium extinguifhed the flame of life in animals by its exceffive cold ; and in later times, there have not been wanting thofe who deduced its effects from a quite oppofi ite quality, whereby it was thought to rarefy the ‘ blood and to comprefs the brain or origin of the nerves. Thefe falfe notions, however, of the nature and action of opium, have been refuted by feveral of the moderns, whofe writings have thrown confiderable light upon this fubject. Tue following experiments were made with a view ftill further to illuftrate the man- ner in which this wonderful drug produces ‘its * Auguft 7. 1755. “PHYSICAL ano LITERARY. 281 its effe€ts, “and particularly to thew: its in» fluence upon’ the motion of the heart. 1.,.Havine injected a folution of: opium in water into the ftomach and guts of a frog, - TL obferyed, that in little more than: half art hour,,it feemed to have loft. all power of motion; as well as feelings for there was no contraction.‘ produced. in, the mufclés of its limbs .and, trank’ by irritating ;ithem. |) I opened the ¢horex an. hour after the in- jection, and found the heart, inftead of be- tween 60 and 70, making only 17 pulfations ina minute. The auricle, which was much diftended with blood, always Ponsratied firft; and, after it the ventricle, _ 2. A frog continued to move. its labo: and leap about.for above an hour after I had. cut out its. heart, and was,not quite dead after two hours and a half. _Five minutes. after taking out the heart of another frog, 1. injeed a folution of opium into its ftomach and guts. In lefs than half an hour, it feemed to be quite dead ; for neither pricking nor tearing ‘its initfefes 4 produced any contraction in them, or any “motion in the members to which. they be- = vot. Il. Nn Jonged 282 ESSAYS anp OBSERVATIONS longed... After, cutting off its head, a) probe puthed into'the {pinal marrow, made its fore+ legs contract feebly. 3 EIGHTEEN minutes paft ‘four! in. the afternoon, I injected a ftronger turbidfos lution :ofiepium in water than: that? fed “in the ‘preceeding’ experiments *, into the: o- mach’andeuts of aifrog; and as it fquirted out moft of the -folution injeCted bythe: anus, I threwinsfome' more in its place. At twenty four mifiutes paft five, I opened ‘this frog, and-obferved-the heart with‘its auricle. greatly diftended’ with blood and« beating very flowly, not above'feven times ina mit gute, “When? the heart'was touched: with the point of a pair of 4eiffars,-its motion was rendered quicker for two or three pulfations : after which it became‘ as flow as before. ‘4, IMMEDIATELY: after decollating a cae I deftroyed® its: fpinal marrow, by’ pufhing ‘a {mall probe down: thro’ its fpine, which occafioned ftrong convulfions of alf giok 4 bon. bits £198 the -* Kiz, half. an ounce of opium diffolved in ‘eight ounces of water ; which was alfo made ufe of in all the following ex- periments. The heat of the folution was nearly the fame in all the experiments; viz. about 60 degrees of Farenheit’s _ thermometer. PHYSICAL ayy LITERARY. 283 the’ mufeles, efpedially thofe of the inferior éxtremities)’ Ten. minutes after this, I opened the: Ahorax} and found the heart beating at the rate“of 1 AS times: ina minute. Sixteen mi- nutes after ‘decollation, it moved 40 times in 4 minute.“ After’ halfan® hour’ it: made 36, and! after°fifty minutes ‘only 30 “pulfations in the minute, which’ were now alfo Serene very’ fmall-and feeble. NBO Wun Topetied ‘the ‘thorax of another frog immediately: after ~ decollation, and deftroying ‘its: fpinal marrow, I obferved its vheart beating at thé rate of 60 ina mix nute, “whichis | four’ of five’ pulfations ' lefs than 2 have generally feen the ‘hearts of frogs make in*that time; when’ their thorae was’ opened ‘without decollation. “5. AT ‘nine minutes paft-elevén in ‘the forenoon, immediately after decollating an- other frog, I deftroyed its fpinal marrow- with aired. hot wire, which produ¢éd“ter- rible convulfions in allthe- mufcles, ‘as in’ the laft experiment. I opened the -rhorax°of' this frog ¢hirty five uiinutes after décollation, and obferved its heart beating 30 times!in a) minute. The contraction of thevauricle re- gularly seni: ipa a9 the: heart 23’the ‘i wauricle 284 ESSAYS ann OBSERVATIONS auricle was not near fo much diftended with blood, nor the heart fo much {welled..as in thofe frogs which had a folution of opium injeGted into their ftomach and guts*., At one o'clock (viz, an hour and fifty one mi- nutes after decollation), the heart of this frog made 20 pulfationsin a minute. At half an hour paft two, when the room, was, be- come warmer by the fhining of the fan, it beat 25 times in a minute; and when placed in the fun-beams, it performed, 31 contra- étions in that time. After this, I removed. the frog to an eaft window, where it. was. expofed to a cool breeze ; upon which the motion of its heart became flower, fo that in a fhort. time it only made 25: pulfes ina minute. I then expofed it anew to the fun- beams, by which its motion was foon quickened, fo that it beat 30 times in a minute. | AT) twenty five minutes patt five in the evening, (viz. fix hours and fixteen minutes after decollatton and the deftruction of its {pinal marrow) the auricle of this frog’s heart, which was ftill filled with blood, contra@- ed 4 See No. 3. above, and Effay on the Vital and other Involuntary Motions of Animals, p. 371 & 372. PHYSICAL ann LITERARY. 285 ed'twelve times ina minute; but the heart itfelf lay without motion;:.was {welled and very red: however, »when pricked with a _ pin, it performed two or three pulfations, and\then remained at)reft,: till roufed by'a new ftimulus. At. thirty: five: minutes paft five, the heart feemed to be: quite dead, but» the auricle continued its motion.; ‘nay, at half an hour paft eight, near three hours’ after)the heart had been without motion, the auricle, which was very neat \as much filled with blood as when I firft opened this frog, beat 11 or 12 times in the minute ; its pul- fations, however, were not now fo regular as to time, .as they had been before. _ ds it not probable, that the auricle of this frog’s heart beat longer ‘than ufual, becaufe it. continued, to the laft,:-to-be filled with _ blood ; whereas, generally, the auricles of frogs hearts, which are opened after decol- lation and the deftruction of their {pinal mar- row, expell, after fome time, the blood which they contain, and acquire the ap- pearance of a fmall pellucid bladder filled . with air? i, 6. 1 laid bare the abdominal mufcles and Deere of a frog,. by diffecting off the fkin, ' and 286 ESSAYS ann OBSERVATIONS andat twenty minutes before nine in’ thé morning, I immerfed the whole body of the frog in a turbid folution of opium in waters in-a {mall bafon, which I covered, to pre-) vent the frog from leaping out of it.> Dhir=: ty five minutes after immerfion, LE took it out: of the folution and opened: the thorax and: pericardium... The heart’sr auricle, » which! wasomuch diftended: with’ blood, beat 15° times in a minute, but the heart itfelf, ionly: 6 times. Forty minutes paft. nine (vize twenty five minutes after the frog was taken: out of the folution of opium) the heart feem~! ed to have recovered more life; \ for it per=: formed eight pulfations ina minute: the® contractions of the auricle now became feebler, and were f{carce more numerous — than thofe of the heart, but always preceeded them fome little time. Six minutes’ before ~ ten this heart moved only fix’times in the’ minute. Twenty four minutes paft ten it’ made only five pulfations in fixty five feconds,' the firft, third, and fifth of which pulfations » were after an interval of fifteen feconds, ‘and ’ the fecond and fourth after a paufe of ten’ feconds. Seventeen minutes-before twelve, and two hours and twenty eight minutes after the frog ePHYSICAL any LITERARY.( 287 frog’ was taken out of the folution of opium, its heart, moved Only thrice in ifeventy five feconds,’ and performed its’ fy/fole vety low-. ly. Before’ two} o’clock»afternoon the heart was quite dead 5. but how Jong, I cannot fay, not having had. lei{ure,to obferve ‘ date a quarter before twelve.to, near two. sw .7- AFTER cutting off a .frog’s ied ard, deftroying its fpinal marrow with a red:hot, wire, . I laidbare the abdominal mufcles and thorax, as in.the laft-experiment, and immer~. fed the whole body, of the frog.in'a, turbid, folution:of opium, at halfan hour paft nine. in; the morning.) ; Thirty jox, minutes. after)im= merfion I: took it-out of the, folution, and, opened..its. chorax, and pericardium. The _ heart and. its auricle.beat, each,, twenty fix’ times in 4 minute, ,and,|the,pulfations of the! auricle preceeded thofe. of the: héart tegu-, larly... The) heart did not appear to be more} {welled or redder) than -in.-a; natural tate,» and the auricle. was not near fo full of blood! asin Exp,.6. . Twelve minutes paft ten, vz.» fix. minutes after this frog was taken out.of _ the folution of opium, its heart beat 27 times ~ in a minute, . At eleven o'clock, it perform- ed 18 yibrations.in that time; and 16 at a rf quarter 288 ESSAYS anp OBSERVATIONS quater before twelve. At two o'clock afternoon, the auricle, which; having ex- pelled all its blood, was now only filled with air, continued its motions ; but the heart lay at reft. Ten minutes paft four, 7. 2. fue hours and forty four minutes after the frog was taken out of the folution, the auricle of its’ heart beat“ g times in sity wit’ fe- conds. 8. I laid bare the dideia wit valli and thorax of another frog, and at fourteen mi- nutes paft eight in the morning, immerfed. it as above in a turbid folution ‘of opitim. Fourteen minutes paft nine, I took it out ‘of the°folution, and laid open its thorax and pericardium ; after which the heart began to beat at the rate of nine times in a minute : _ but'the auricle, which was greatly diftended with blood, made no motion, except in fo far as it was agitated a little by the pulfation © of the heart: nor were the mufcles of the’ légs or thighs brought into contraction by cutting or tearing their fibres. “At half'an> hour paft nine the heart beat only 7 times” in aminute; and the auricle, which: was now pretty empty of blood, and, in place of it, filled with air, had a pulfation as well as : “PHYSICAL ad LITERARY. 289 as the heart) Thirteen minutes before ten, i. e. thirty three minutes after the ‘frog was taken out of the folution, the auricle*fhew- ed, at confiderable intervals, a very faint pulfation, but the heart lay without any ‘mo- tion. 9. Tue fame day, after cutting off the head and deftroying the {pinal marrow of an- other frog, I laid bare its abdominal mufcles and therax ; and, at eighteen minutes paft ten, immerfed it in a folution of op:um, as above. Eighteen minutes paft eleven, I took it out of the folution and opened its zhorax and pericardium, after which the heart began to move at the rate of 8 times in a minute. “Twenty five minutes paft eleven, the heart beat. 16 times in a minute; and at twelve o'clock it performed between 13 and 14 vi- rations in the fame time. At two o'clock, (viz. two hours and forty two minutes after. the frog was taken out of the folution) the au- ricle, which was now “filled with air, con- tinued to vibrate weakly, about 11 times in ‘the minute ; ; but the heart itfelf was without P ‘motion. __At ten minutes before four i in ‘the | “afternoon, the auricle _ ftill continued. ‘to wil 5 Vor. IT. ei” Oo move, ~ a90 ESSAYS any OBSERVATIONS move, but more feebly than the auricle BE; N°, 5. 10. [laid open the whole abdomen of a larger frog than any of the former ; and, at twenty two minutes patt ten in the morn- ing, immerfed it in a folution of opium, as above. Thirty five minutes after immerfion, I took it out of the folution, and opened its thorax and pericardium. The heart was vaftly red and much {welled, and its auricle greatly diftended with blood ; but both were without any motion: after two minutes, however, the heart began to vibrate at great leifure, fcarcely performing nine pulfations in a minute; but the overftretched auricle — made. not the fmalleft motion. During e- very /yftole, the heart was remarkably paler, and in the time of its relaxation became much redder; which phenomenon I obferved like- ways in all the frogs hearts in the above ex- periments, but more remarkably in thofe frogs who had been expofed to the action ‘of opium. Another thing, which I remark- ed in all thefe experiments, was, that the heart, during its /y/fole, became manifeftly fhorter, and was lengthened in the time of its aeaxation., But to return ; at fix minutes patt PHYSICAL ann LITERARY. 298 paft twelve, ( 7. €. an bour and nine tminutes after the frog was taken out of the folution) its heartmade only 6 pulfations in. the mi- nute ;, and at eleven minutes paft-twelve; obferving it without motion, I pricked it with.a pin, and breathed upon it, in order to renew, its pulfation; but to no purpofe. 11. TWENTY eight minutes. paft feven in the evening, I laid open.the whole abdomen and thorax of a frog, and immediately, after immerfed it..in.a folution of opzum-as above. Thirty eight minutes paft feven, when I prick- ed its, legs-with the point of a penknife, it made very little motion, ‘Two minutes.after this, I turned i it to its back, and obferved its heart moving.only, between. ten and eleven times ina: minute, , Having laid the 'frog:a- gain on its belly, that it,might be more ex- pofed, to the action of the, opium ; at, forty eight minutes paft feven, ,7..¢, ¢wenty minutes from the firtt immerfion, I turned it again to its back, and obferving, the heart»without motion, I; opened the pericardium: 3. which, producing no effed, I cut the heart, out of the body, .and laid it on. a plate, when it _ gave two or three pulfes, and never after Be moved, Ae «4 492 ESSAYS ann OBSERVATIONS moved, tho’ it was pricked once‘and) ‘again with a pin. No motion was. produced in any* of the other mufcles ee this frog, by pital. 4 them. 12, I cut offa feoe’ $ ‘ead and sieteoye the fpinal marrow with a hot wire, then laid open its thorax and abdomen, and immerfed it ina folution of opium at nineteen minutes paft eleven. Eight minutes before twelve, 2. e. thirty three minutes after’ immerfion, I obferved' its heart” beating very flowly': but two: minutes “before’ twelve, when I took it out of the folution of" opium, it had°io mo- tion’ After; this I opened the pericardium, and irritated the heart two or three times with the point of a fcalpel, which’ always produced a few pulfations. «I then’ put ‘the frog in the folution’ for’ five minutes’ more, and, wa taking it out, found its heart quite dead? 13) AFTER deans off a frog’s head and deftroying its {pinal marrow, I laid open its whole abdomen, and immerfed it in a folution - of opium, twenty three minutes before one. After it‘had lain fixteen minutes, T cut up its thorax and pericardium 5 and obferving the heart PHYSICAL ayo LITERARY. 208 heart beating very regularly ‘and pretty - ftrongly, 21 times in the minute, T immerfed it'again in-the folution, .which had now im- mediateaccefs ‘to the heart. After five mi- nutes, I took at out of the folution ;*-and - finding the heart withaut motion,’ I pricked it-with the:point ofa knife;:upon which it began to beat at the rate of r4>times in the minute, and .continued: its .motions; very languidly; and not without fome i cia il for about a quarter of an hour. (3 INO 14.1 cutout the heattiof axfrog, and: et it in fountain-water atsten minutes’ paft ten’s immediately after immerfion;:it beat about 28 times:in the minutes) Eighteen «minutes - paft ten, it made. 6:pulfations jin. thirty: fe. - conds. ‘Twenty minutes afterten, I:tookoit out of the: water and laid itcon'a.table, «and obferved, that as ‘often as :it: was gently touched with) any'thing,»it::made one -full and ftrong contraction, and no. \:more: however, in four or five’ minutes, it -be- gan to beat of its own accord, and, at twenty eight minutes after ten, performed 19 pulfations in a minute. Thirty five: mi- “Minutes paft ten, it beat.12 times in‘ami- ak 15. TWENTY 294 ESSAYS anp OBSERVATIONS 15. Twenty three minutes paft twelve, I cut out the heart of another frog, and put it in fountain-water. After twelve minutes immerfion, I took it out of the water, when it beat above 20 times in a minute. Having put it in the water for five minutes more, it ceafed from motion, and when taken out, did not move except when pricked, and then only performed: one pulfation. | 16. Ercur minutes paft eleven, I cut out the heart of a third frog, and put it-into fountain-water.. Eleven minutes after im- merfion its heart beat 8 times in the mi- nute; and four minutes after this it vibrated II times in thirty feconds; but the motion was confined to about one third part of the heart next its apex. Twenty minutes after immerfion, it continued to move: much in the fame way; but in two minutes more, obferving no motion in it, Ltook it out of the water, and laid it on a table, where it remained at reft, unlefs when touched. Soon after this, however, it began to move; and at twenty five minutes after immerfion, it made g pulfes in fixty three feconds. Four minutes after this, it moved only thrice in fifty feconds, and then ceafed altogether ; | unlefs ‘PHYSICAL ann LITERARY: 295 anlefs that, when pricked with the point of a knife, it gave one very faint pulfation. At forty feven minutes paft eleven, it was quite dead. 17. I cut out the heart. of a fourth frog, and at thirty minutes padt ten immerfed it in aturbid folution of opum in water of the fame degree of heat with the fountain-water ufed in the three laft experiments*. After this heart had been immerfed fen minutes, T took it out of the folution, and laid it on a ‘table, but it made not the {malleft motion ; and when pricked with the. point of a knife, tho’ it quickly recovered its fhape, yet it was not. excited into a proper contraction, as the heart of N° 14. I continued to obferve this heart from time to time for more than half an hour, but it never made the leaft motion. 18. I cut out the heart of a fifth frog, and put it into a folution of opium in water five minutes before eight. After feven mi- nutes. immerfion, Itook it out, and laid it on a plate, where it remained at reft.. When pricked with a knife, it did not perform a full pelgine like N° 14. but..feemed to feel a * Vie. Nearly. fixty degrees of Farenbeit’s thermometer. © aa 296 ESSAYS anv OBSERVATIONS a little, by a very faint kind of motion which was excited in fome of its fibres. 19. AT thirteen minutes before twelve, I cut out the heart of a fixth frog, and immer- fed it in a folution of opium. Six minutes after immerfion, it had nd motion; but when pricked, made one pulfation. After lying five minutes more in the folution, it was quite dead. 20. I cut out the heart of a feventh frog, and at thirty feven minutes paft nine in the morning, immerfed it in a folution of opzwm, as above. Forty two minutes after nine, ~ when I took it out of the folution, it was without motion: but when touched with the point of a knife or probe, it’ performed one contraction, but with -lefs vigour and more flowly than the heart of N° 14. Forty feven minutes paft nine, it began to beat of its own accord. Two minutes after this, it moved 6 times in the minute, but much more feebly than N° 14. Six minutes before ten, it beat only 4 times in a minute: after this, it began to beat much fafter ; but its motions foon returned to their former flownefs. At ten, after having lain near a minute’ without motion, it begin again, of its PHYSICAL atv-LITERARY. 497 fits own! accord,’ to beat oat. the: rate of ‘47 times in’ the’ minute, and continued, for : : eight or ten minutes after this to beat wery feeblyj-and: is in an: Hag (shane manner? as. to time.’ ~2r. Mr. Robert Ravelry. Student of ‘csarsis invthis place, having! diffolved two. feruples of opium in an ourice of water andia dram of liquid cwdanim;) injeGed it blood-warm into the zntefinum recium:of aivery {niall dog near fix months old: In lefs than a: minute. after the injection wasimade, ‘the dog: could’ not ftand on his hinder legs’ ;:.and in .3/0r 4. mi- nutes he had loft-the ufeiof them fo: much; that when they were ftrongly pinched,» he neither moved'théim, nor feemed in: the leaft degree'fenfible of pain. He could, however, | fill {cramble about with his fore-legs ; and when they or hisoears were: pinched,. he howled remarkably, and feemed to feel con- fiderable pain. ‘Ten minutes after the inje- tion, he lay ascif he had been quite ftupid ; only when a noife-was made by beating. on the ground, he opened his eyesa little and seed: but prefently after fell into a pro- found fleep. In ‘a’ few- minutes after this, j ‘he began to be convulfed ; upon which Mr. ‘Vor. Il. | P p Ramfay 298 ESSAYS ann OBSERVATIONS Ramfay inje&ted a ftrong folution of fea falt in water into his guts, which purged him fe- verely, and occafioned a prolapfus ant ; foon after this, he awaked from his fleep, and gradually recovered the ufe of his hinder legs:; fo that in lefs than an hour he could run a- bout the room, tho’ he often fell down, his legs bending under him. After three or four hours, he feemed to be quite well in every refpect ; but-altho’ the experiment was made at mid-day, he could tafte no meat till late at night. Whenvhe was inthe moft | ftupid ftate, he could make ufe of his fore+ — legs, and complained when his ears were pinched. | 22. THE fame young Gentleman, at my | defire, made the following experiment. On the gth of April 1755, after making an opening into the cavityof the abdomen of the dog on whom the laft experiment was made, he injected by the wound a dram of opium diffolved in two ounces and a half of water ; but before he could ftitch up the wound, about an ounce of the folution efcaped. The dog loft the power of his hinder limbs al- moft inftantaneoufly... Two minutes after the injection was made, he began to be convul- fed PHYSICAL ann LITERARY. 299. fed ; and, in two minutes more, after ha- ving raifed himfelf upon his fore-legs, he fell down fenfelefs. At this time Mr. Ramfay laid bare the thorax, by diffecting off the tegu- ments, which did not feem to give the dog any pain, and could plainly feel the. motion of his heart thro’ the pleura: it beat 76 times in a minute, but became gradually flower *. Immediately after counting the pulfe, Mr. Ramfay cut the ribs on each fide of the /fer- num, which he laid back in the. ufual way. The heart, which was thus brought in view, appeared quite turgid, and Garnet in mo- tion about five minutes ; during which time it perforfied only between 60 and 65 weak vibrations, for they were not compleat con- tractions. While the heart was thus moving, warm, /faliva was firft applied to it, then cold water, and laft of all oil of vitriol ;- which fhrivelled the parts it touched, almoft in the fame manner as a hot iron would have done; but none of them accelerated the heart’s vi- brations, which became gradually gee till they. ceafed altogether. THE % * The dog’s heart in a natural’ ftate, and before the in- _jeAtion of the folution of opium, beat 150 in the minute, 300. ESSAYS ayn OBSERVATIONS Tur fibres of fome.of the intercoftal mufcles on the right fide of the fernum continued to be agitated with a, weak tremulous motion:near half an hour, after the, injeCtion. was smade into the abdomen.;..but,the intercoftal muf- cles attached to the ribs on the fides,of. the thorax were ‘not obferved, to. move,’ nor did the diaphragm make.any motion when its fibres were pricked or, cut. NoTHING remarkable was feen in, the ad- domen ; only, altho’ it was opened ten mi-. nutes after making the injeGtion, the inte- | ftines had no motion ;_ whereas, in another. young dog, which had got no opium. Mr. Ramfay. obferved the periftaltic motion conti- nue half an hour after laying open the thorax, THE dog loft little or no blood in making the wound into his abdomen, nor were any of his bowels hurt by it. 23. A fmall dog into,whofe ftomach the late celebrated Dr. Mead had forced, at four different times, a folution of two drams of o- pium in water, lived above an hour and three © quarters after getting the firft dofe.. Vid. treatife on poifons, Effay IV. | 24. Ir may not be improper to add here an experiment related by Dr. 4/fon in his 3 leraned PHYSICAL ann LITERARY- 303 ined differtation on opium™. Into the, ‘crural vein of an old dog forty two. pounds: weight, he caufed be injected,at three different times, half an ounce of opium. diffolveds, in four: ounces, of water, filtrated; and of the, fame warmth, with the blood of ‘the animal. The firft time, about fifteen. drams were, _ thrown in, and.very flowly. ,. It had no obfer-, vable effect. Aboutyan hour after, eight drams, more were-injected flowly, and immediately the dog was feized with ftrong convulfions ;. the pulfe was frequent and fmall, and after fome ‘time: he foamed. atthe mouth. | But there appearing no figins of immediate death, after waiting an hour more,, the. laft nine drams were.thrown in quickly. upon which the pulfe became full and flow, and in.a mi- nute or fo, the dog expired.»’) _ From ‘the preceeding, experiments, we ae I think, fairly draw the’ pate con= clufions. (a) Opium biosletin to the ftomach, guts, cavity of the abdomen and thorax and abdo- | minal mufcles, foon leffens, and after fome time intirely deftroys all feeling and power * wry of 1: ® Edinburgh Med, Effays, vol. v. p. 1. art. xii. goz ESSAYS ann"OBSERVATIONS of motion, not only in the parts to which, it is applied, but thro’ the whole Na Pr; 2,9) Cras 22. (6) Opium produces thefe effects nite more quickly in animals which are foon killed by want of food and air, than in thofe which can live long without them, and the parts of whofe bodies preferve a power of motion and appearances, of life for a confiderable time after they are feparated from each other. N°r, 3, Ge. compared with N° 21, 42 & 23. : (c) Since a folution of ofium injeGted into the ftomach and guts deftroys the fenfibility and moving power of frogs, fully as foon when they are deprived of their heart,as when this organ remains untouched ; it follows, that opium applied to thefe parts, does not produce its effects by entering the blood, and being, by its means, conveyed to the brain, as fome have imagined, but by its imme- diate action on the organs and parts which it touches. N°r. compared with N°2. See alfo Edinburgh Medical Effays, edit. 3. vol. 5. part I. page I40. : (d) Since, after decollation and the de- fteuction of the fpinal marrow, opium ope- rates | PHYSICAL ano LITERARY? 303 rates much more flowly in’ deftroying the — -heart’s motion in frogs, than, it does when the animals are intire (N° 6. compared with N°7.); it follows, that.it muft, produce-its effects chiefly, if not wholly, by its ation on the brain, fpinal marrow, and nervous fyftem. The heart of the. frog N°7., whofe brain and fpinal marrow had. been deftroyed, beat 27 times in a minute, after the- animal had lain thirty fix minutes in a folution of: opium ; which was only three pulfations lefs than the heart of the frog N° 5. performed thirty five minutes after the deftruction of. its brain and {pinal marrow, altho’ it was not.expofed’ to the action of opium. - 7 (ce) WHEN opium injected into the veins, and. thus’ mixed with the blood, leffens or deftroys the fenfibility and moving power of animals much in the fame way as when it is applied to their ftomach, guts, or cavity of the abdomen (N° 24); isit not probable, that it produces thefe effects by its action on the extremities of the nerves which termi- nate upon the internal furface of the heart and whole vafcular fyftem ; and_ perhaps, _alfo, by affecting immediately the medulla cerebri itfelf? And when a {olution of opium Fk applied 304 ESSAYS anv OBSERVATIONS applied to the bare abdominal mufcles of 4 frog deprived of its brain and fpinal marrow, does, aftera long time, confiderably impair the heart’s motion; is it not reafonable to think, that this is owing to the finer-parts of the opium being abforbéd by the bibulous veins and carried to the°heart, and thus brought into éontact with the nerves of this ee N° 7. compared with N° g. (f). Since’ opium, without entering the blood or being carried to the feveral parts of the body, deftroys the power of feeling t in animals merely by aéting on the nerves to. which it is'applied (c) (d), it follows, that the nerves are the inftruments of fenfa- tion, or, at leatt, neceflary to it. Nor is it fufficient to deftroy this’ conclufion, that there have been inftances of animals endow- ed with feeling whofe brains were fo greatly difeafed, as to feem incapable of performing their functions. It is far from being fafe to build theories in phyfic ‘upon a few mon- ftrous appearances in nature. (zg) It appears from N° 4. and 5. com: pared with N° 3, 6, 8, 10 and 11. that de- collation and the deftruction of the {pinal marrow does not weaken or deftroy the heart's _ hl” PHYSICAL atp LITERARY. 305 héart’s motion in frogs, near fo foon as cprwm injected into their ftomach and guts,” or ap- plied to the mufcles and bowels of the lower belly and thorax.) f10 (b) Avtuo’ a folution of opium xpplied to the opened thorax and abdomen of a frog, after decollation and’ the deftructidn of its fpinal marrow, foon weakens or deftroys the ‘motion of the heart's” yet it does not ‘pro- duce’ thefe ‘effects ‘fo fpeedily as when: the “‘prain‘and. fpinal’ marrow are intite, N® ry. and'12. In the former cafe; the opidin can only ‘affect the heart by its topical influences in the jatter, it not only acts this ‘way, but -alfo exerts its powers upon the’ ‘brain,’ fpi- nal marrow, arid whole nervous fyftem ; and therefore sexu produice ” more tg effects. - (i) Iv appears, beyond doubt, from’ the preceeding experiments, that the heartis not | exempted from the’ power Of opium, ‘as the learned “Dr. Haller‘has affirmed *, ‘but has ‘its motion deftroyed by it, as well ds ‘the o- ther mufeles, only not fo'foon. “See N°'4. and ¢. compared with N° 3. 6. 8. & To. Vor. II. Qq and * A&. Gotting. vol. ii. p- 147 & 154. 306 ESSAYS ann OBSERVATIONS cand N° 14. 15. & 16. compared with N° 17. 18. 19. & 20. ’Tis true, that the fibres of the interco- ftals on the right fide of the /fernum of the — dog N° 22. continued to be agitated with a ‘tremulous motion confiderably longer than the heart, and when the intercoftal mufcles attached to the ribs were quite dead. But did not this happen becaufe, after feparating the fernum from the ribs, and thus cutting off all communication between it and the fpinal marrow, the mufcles attached to it, could be no more affeéted by the opium, which had been injeéted into the cavity of the abdomen ; while the heart and other muf- cles whofe communication, by means of the nerves, with the brain and {pinal marrow, was intire, continued to be expofed to its action? _ () As Dr. Langrifh has obferved, that the diftilled water of laurel-leaves injected in- to the cavity of the abdomen, kills dogs fooner than when it is taken into the ftomach * ; fo N° 21.and 23. compared with N° 22. fhew that opium injected into the ftomach and great \ * Phyfical experiments on brutes, p. 64. PHYSICAL any LITERARY. 307: “great guts of dogs, does not produce either - fuch fpeedy or powerful effects, as whem thrown into the cavity of the abdomen. And N° 6..compared with N° ro. fhews, that a . folution of opzum applied. to the abdominal: mufcles, does not kill frogs fo foon as, when all the vi/cera of the lower belly are expofed, to its action. (J) AuTuo’ it feems probable, from N° 22. compared with N° 24..that a folution of o-: pium inje&ted into the veins of dogs does not kill them fo foon as when thrown into. the cavity of the abdomen ; yet this cannot be cer- tainly concluded, fince the dog of, N°.24. was much older and above ten times heavier than the other. (m) Iv appears, that a folution of opium injected into the great guts of a dog, affects the inferior part of the f{pinal marrow much more remarkably than its fuperior part, or the brain ; fince the dogs of N° a1. and 22, not only loft the power of motion fooner in their hinder legs than in their fore ones, but alfo were infenfible of any pain.in them, and yet howl’'d ftrongly when their ears were pinched, “ : (n) A gos ESSAYS ann OBSERVATIONS. (x) A folution of op:um injected into the cavity of the abdomen or great guts of dogs, ‘does not. deftroy the feeling ‘and power of motion oftheir hinder limbs, by fending any effuvia to their mufcles'; otherways it could not produce thefe effeéts fo inftantane+ oufly, (N° 21, & 22:) Befides, fince opium thrown into the ftomach and guts of a’ frog after being deprived ‘of its heart, deftroys the fenfibility and moving power of its muf- cles equally foon, asif the animal had been intire’ (N° 2.) ; ’tis plain, that thefe’ ef- ~ feéts cannot he owing to the finer parts of the opium being received into the blood, and by its means carried to the feveral mufcles and organs. | (0) Nor does a folution of opium inje€ted into the: great guts or cavity of the abdomen in dogs produce its effects by tran{mitting through the nerves any fubtile effuvza to the fpinal marrow ; otherways its operation could not have been fo inftantaneous (N® 21. & 22.); nor could the fpinal marrow and its nerves have recovered their functions fo foon, after the opium was evacuated by a. purgative clyfter, N° 21. (p) It _PHYSICAL-ann LITERARY. 349 »(p) Ir remains; therefore, that op:um, by affecting the extremities ofthe nervesvof the. parts to which) itis applied,» does, by means of their connexion and :fympathy withthe brain and {pinal marrow, deftroy or prevent,! through the whole nervous «fyftem, . the o» ration of ithat power upon , which depends aoe and. motion in the bodies es ani~ midlsac- eoidit.ons « AG) Since: thie ae to the abelohats iedsnandilon of a frog, deprived of its brain) and {pinal marrow, does not deftroy the mo- tion of the heart fo foon, as when it is ap- plied tothe abdominal “mufcles of ‘2 frog whofe brain’ and’ {pinal marrow are intire, (N° 6. ando7.), it follows, that the brain and: fpinal marrow, and confequently the nerves derived from them, have a greater influence’ than any other ‘part of the aninnal fyftem, upon the motion of the heart © ; ‘(r) Opium: does not ‘only deftroy’the moving power of the mufcles of animals by intercepting the influence of the brain. and {pinal marrow, but alfo by unfitting the! mufcular fibres themfelves, or the nervous | power lodged in them for performing its of- fee: otherways a folution of opium, when applied .3t0 ' ESSAYS ann OBSERVATIONS applied to the abdominal mufcles or wvi/cera of a frog, would not put a ftop to the heart's motion fooner,) or indeed fo foon, as decol- lation and the deftruction of its f{pinal mar- row, (N° 4. & 5..compared with Ne 8. &> ro.). Opzum therefore does not produce: its .effects, jolely, by putting a ftop:to the function of the: brain and fpinal marrow,) but its influence reaches to the fibres of the: mufcles themfelvés, or to the: extremities of the nervous flneneints which terminate in. them. 1B _-Wuen I fay. the influence of opium reaches) . to. the nervous filaments which terminate in, the mufcular, fibres, it is not meant, that. any efiuvia or f{ubtile parts of the opium are tran{mitted to them (See 2 & o above), but that it deftroys their powers, by means of that fympathy which they have, through the brain or fpinal marrow, with the nerves to which the apum is immediately ap- plied. _({) From the above experiments we may. infer, that not-only the power of voluntary. motion in the mufcles, but alfo their irrita- bility or power of motion, when ftimulated, proceeds from the nerves, or is at leaft im- mediately *PHYSICAL asp LITERARY: gu mediately dependent on their - influence’; -fince opium, which produces its effects, /olely, by affecting . the nervous fyftem (m0 & 0), deftroys thofe powers fo fuddenly. I know it has been lately argued by a cele- brated author, that the irritability of the mufcles muft be independent of: the nerves, becaufe the smufcles of animals: preferve a power of moving when irritated, for fome time after the communication between them and the brain, by means of the nerves, is cut off *.» But fince a folution of opium applied to the abdominal mufcles of frogs, merely by ‘its aGtion'on the nerves, puts a ftop to the irritability or moving power of the heart, much fooner than the deftruction of the brain and fpinal marrow (g) ; © is it not reafonable to conclude, that the tremulous motions of irritated mufcles after their nerves are’ tied, | proceed from the integrity of the nervous filaments below the ligature, and the ner- vous power ftill, remaining in them or in the mufcular fibres themfelves* : THE tying. or cutting of a nerve,» only prevents the derivation of any new znfliuence oY | | from Rec. - ® Aéta Gotting. vol. ii. p. 134, &c. ¥f ESSAYS Ann OBSERVATIONS from the brain,? tothe parts to-which it be- longs ; but does not immediately, deftroy the power. or influence remaining in the nerve*it- felf. Opium applied in fufficient quantity to the fenfible: parts of animals; not only quick- ly puts a ftop to the funtion of the’ brain and fpinal marrow, and thus produces in the © mufcles all the effects of a ligature on theit — nerves, but alfo deftroys the power of every nervous filament.in the body (r), and there- fore puts. a ftop to the motion. of the | heart in frogs fooner than the deftruction of the _ brain and fpinal: marrow. = » (t) Tue almoft inftantaneous palfy essiie on the hinder legs of a dog, by injecting a fo- ution of opfwm into the cavity of its abdomen (N° 22.); and the effects of the fame folution injected into the ftomach and guts of a frog deprived of its heart (N° 2.), where no part of the opium could be conveyed to the -muf- cles, nor be conceived to alter the nature of their gluten ; thew, that the zritability of the mufcles has not its feat in this g/ve, as fome have lately imagined*. But if the} motions of irritated mufcles be owing toa difagreeable fenfation excited in them or their * Aét. Gotting. vol. il, p. 152. PHYSICAL ato LITERARY: 319 their nerves; as we have elfewhere endea- -vouted to fhew*, ’tis eafy to fee that opzum muft, by deftroying the jfenfibilty of the mufcles, of confequence alfo deftroy their irritability. (uw) in animals which have got. a large dofe of opium, the veins, efpecially thofe of the membranes of the brain, are obferved to be much {welled ; whence it has been thought, that ofzwm produces its effects in the bodies of animals, partly, at leaft, by rarefying the blood and comprefiing the brain : but this diftenfion of the veins feems to be no more than a confequence of the ve- ty flow motion of the blood through the heart, on account of the infenfibility with ost this organ is affected +-. _ (v) Since opium {oon puts a ftop to the vital motions of animals, which yet continue ‘Vor. I. Rr in | _ * Effay on the vital and other involuntary motions of a- nimals, fect. ix. and Phyfiological Effays, p. 188, &c. + In frogs, into whofe ftomach and guts I had inje&ted a folution of opium, I not only found the heart’s auricle, but alfo the great veins leading to it, much diftended with blood. Vid. Effay on vital motions, &c. p. 371. an@ 37 2. 314 ESSAYS anv’: OBSERVATIONS in time of fleep with little or no diminutiom of their vigour; fince it often eafes pain without bringing on fleep, and fince, by its topical action on the heart, it deftroys the motion of this organ after all communication between /it and the origin of the merves is cut off * ; it follows, that the effects of opium are not owing, as fome have thought, to its producing fleep: on the contrary, the fleep which it occafions, feems to be only a con- fequence of its impairing the fenfibility of the whole nervous fyftem: | Tue other effects of opzum may be alfo de- . duced from the fame: caufe, particularly its reftraining all evacuations that are owing to an unufual irritation of the parts of the bo- dy, and at the fame time promoting thofe natural fecretions which have been diminifh- ed or ftopt by fpafmodic ftrictures of the vef- fels, from fome uncommon /imulus affecting them. (w) Lastxy, does not opium kill animals by rendering their feveral organs wholly in- fenfible of the /#muli, which are deftined — by nature to excite them into aétion ; whence — not * Vid. N° 12. 13. 17. 18. 19. & 20. above. PHYSICAL anp LITERARY. 319 rot only a ftop is put to the periftaltic 'mo-. 7 _ tion of the guts, and to-the spropulfion: of the chylé*, “but ‘the’ fluids -alfo: begin’ to ftagnate firft in the fmaller and afterwards in the larger veflels +; while the heart be- coming gradually lefs fenfible of the /fmu- lus ON 104 LO83.02 YiittT .2mwo munis TO!) Spop * In a {mall dog, which Dr. Kazu Boerbaave's opened; after having given him three grains of) opium, he» obfer= ved fcarce any periftaltic motion-in ithe guts: ‘the flo: mach was much diftended; the pylorus was fhut;. and the bread and milk, which the dog had taken with the opium about ten hours before, ‘was indigefted. There was no- thing like chyle in the duodenum, nor any latteal veftels to be feen in the mefentery. The bladder of urine and great guts were much filled, nor had the animal eva- cuated either urine or feces from the time he fwallowed the opium. Impetum faciens Hippocrati dittum, p. 402. & 403. The learned Dr. Haller has alfo obferved, that opium puts a ftop to the periftaltic motion of the guts in frogs and other animals, Aé. Gotting. yol. ii. p. 154. + This my worthy Collegue Dr. Ajfon obferved with a microfcope in frogs into whofe flomach he had conveyed a few drops of a folution of opium in water. Vid. Me- dical Effays, vol. v. part 1. art. xii. And indeed the great diftenfion of the heart and its auricle in frogs kill- ed with opium (N° 5. compared with N° 3. 6. & 10. above) indicates a more than ordinary refiftance to the blood’s motion in the arteries, as well as a lefs degree of irrita- bility in the heart. Further, is not the flow, full pulfe, and dry parched mouth in thofe who have got an over-- dofe 316 ESSAYS ann OBSERVATIONS. lus of the blood with which it is diftended, contracts more feebly and at greater intervals, till at laft it ceafes from motion altagether ? - ART. dofe of opium, owing, partly to the flower motion of the @uids in'the {mall arteries|and fecretory veffels of the glands ? ho’ it muft be confeffed, that the drynefs of the mouth may bein fome meafure owing to the perfpiration being greatly increafed by the opium. . PHYSICAL ann LITERARY. 319. Art. XXI. The Hiftory of a compleat Luxation of the, Thigh, ina Letter to Dr. Joun RuTHER- FooRD, Prefident of the Royal College of. Phyficians, and.Profeffor of Medicine in the Univerfity of Edinburgh ; by James Mac- KenzIE, M. D. late Phyfician at Wor- cefter *.: oe ee se Feb. 10. 1755. fe HE account which I gave you of a " compleat luxation of the thigh re- ** duced at the Worcefler Infirmary, I now *« fend in writing, agreeably to your requeft. ** T fend you alfo DoCtor Wall’s Letter vouch- “s ing this diflocation ; and Mr. Fefferys's *‘ narrative of the fame cafe. Ifyou think ‘any further proof neceflary, there are ftill ** two Phyficians and two Surgeons more, ‘alive and well, who were prefent at the ** reduction, and will bear witnefs (if requi- ** red) to the truth of this accident, as well ** as the two Gentlemen above named, and *myfelf, who am, &c.” WILLIAM ® March 6. 1755, ‘ g18 ESSAYS ann OBSERVATIONS Irt1amM Jones, a tall, robuft, ‘heal- thy Butcher, fifty fix years old, was carried to the Worcefer Infirmary on the feventeenth of Auguft 1747, lame, and in grievous pain. His account of himfelf was, That he happened unfortunately, fome hours before, to ride an unruly horfe, which ran away with him; and that, making an ef- fort to check him, juft as he was-galloping over a {tone bridge, the animal reared himfelf upon his hinder feet; and immediately fell backward on his rider... The man was ftun» ned with the fall ; but the horfe quickly re-’ coveted himfelf, and went off full f{peed;’ dragging poor ‘fones after him, by his leg’ which was engaged in the ftirrup. | The: horfe was.foon providentially ftopped, - and the man fet at liberty, but unable to move his thigh, which he believed was broken. » Tue Surgeon in waiting, (for four Phyfi- cians and three Surgeons gave their atten-" dance in rotation, namely, Doétors Attwood, Mackenzie, Cameron, and Wall; and Meff. Edwards, Ruffel, and “fefferys) having tho- roughly examined the fituation and figure of the PHYSICAL ano LITERARY. 319 the parts difabled and in pain, came to one. ef the Phyficians, and told him, that the poor man’s thigh was diflocated; that the head .of the bone was ftruck quite out of the acetabulum, and lay fairly in the ‘groin. The Phyfician having, in his younger. days, attended Boerbaave (who, furely, underftood phyfic and furgery as well as any man ever did), and knowing that, from the prodigious ftrength of the ligaments, and depth of the focket in that articulation, this learned Profef= for was of opinion, that the thigh-bone was never diflocated by external violence, but fre- quently broken near the head: which was the _ true reafon why fuch accidents were feldom, or never, cured: the Phyfician, I fay, perfua- ded, that his preceptor was in the right, -obferved to the Surgeon, that there muft be a miftake fomewhere, and that there was no inftance on record, which could be depend- ed upon, of fuch a luxation as he defcribed : to which the Surgeon replied, “ Sir, if you «* will not believe me, you will believe your ‘< own eyes and fingers prefently.” TuE novelty of the cafe brought all the ; _ Phyficians and Surgeons to the. Infirmary. A Skeleton was fetched, and great care ta~ ken g20 ESSAYS ann OBSERVATIONS ken, by a ftri&t inquiry into circumftances, to fatisfy all prefent, that the bone was not broken, but really and fairly diflocated. There is no reafoning againft facts: the toes and knee were turned outwards, the difabled limb was longer than the found, the hip-joint utterly inflexible, and the round large head of the bone lay obvious to the fight and touch in the groin. THE next inquiry was, how this difloca- tion fhould be reduced. All were called to confultation ; not one of the Phyficians or Surgeons had ever feen the cafe before. Some of the principal books of modern fur- gery were looked into; but one and all de- fcribed the reduction, and recommended extenfion in fuch a general, languid, hear- fay, manner, that it was plain they were as unpractifed in the cafe, as the Gentlemen prefent: nor was any better fuccefs to be expected from Galen’s * method of reducing a * Vid. Gal. in librum Hipp. de artic. commentarior. lib. 4. aph. 42. And indeed the antients feem to have been acquainted with luxations of the hip-joint only in children, or diftem- pered bodies; wnlefs we fhall except Paulus Agineta, whofe | ‘PHYSICAL anp LITERARY. 321 ‘e luxation of this joint by hanging the pa- tient to a ftrong beam by the heels with his head near the ground. Arter mature deliberation, it was agreed, that, in cafe the ufual extenfion did not fuc- ceed, the vis percuffionis (which is well known to increafe the force to a furprifing degree by accelerating the motion) fhould next be ‘tried. In order to both, therefore, we provi- ded a large ftrong table, of a proper length | and height, which we faftened with {crews to the floor, and covered with fuch blankets and bolfters as we wanted; a piece of ftrong cloth alfo was laid upon the blankets, un- der the patient’s back, of length fufficient _ to turn up between his thighs, and pafs over his fhoulders down to the floor, where both ends were fecurely fixed, with a view to refift or counteradt the neceffary extenfion. We provided alfo two towels of a conve- nient length and thicknefs ; one of which, at the middle, was tied with a tight, but eafy knot above the patient’s ankle, and the two ends twifted together, were given to three Bor. TT. i ftrong whofe various methods of extenfion, in this cafe, whether “real or fuppofed, fome of the moderns have copied, and: fome have altered. g22 ESSAYS avn OBSERVATIONS ftrong’ ‘men to hold. ~The other towel» was in the fame manner faftened above the knee; and the double end given to three more ; while the Surgeons ftood ready, one with his hand on the ball of the diflocated bone to direct it into the focket, one at the knee, and another at the foot to turn them inwards. When all things were ready, the exten- fion was begun, in the common, method, by the towel-men ; but tho’ they exerted their utmoft ftrength, the head of the bone was not moved in the leaft, and their effort ferved only to increafe the poor man’s: tor- ture to an intolerable degree. Finpine thus-the extenfion of no figni- ficancy ; and the patient’s courage reviving after fome refpite ; the v/s percuffionis was was carried into execution: after the follow- ing manner. ‘The towel-men were direéted to flacken their towels to a certain point, to ftand with their feet firm; their arms freight, and their bodies bending a little forward and, upon a certain fignal agreed on, were — ordered to pull with a vehement and quick jerk, throwing themfelyes back with, all their ‘might. AFTER baw . 24 PHYSICAL ato LITERARY: 323 . AFTER every thing was in good order, vand the affiftants apprifed of the nature and meceflity of the ;operation-which they were about to perform ; the fignal agreed on was atlaft given. .'The \towel-men pulled in.a moment.with a firong and. fudden' {pring 5 ; the. Surgeons. performed: sheir parts. dexte- ‘roully ; ; and inftantly there was aloud crath heard, which made one of the Phyficians call out, Alas! the tables is broken.¢ But at that yery moment the’ patient, ‘.with a thundering voice,.., cried,, It’s, in, it’s.in, ‘it’s in, ,.And.fo it really was; for.we imme- diately- found the limb, reftored’.to,its natural pofition, length, , and | flexibility, .., The pa- tient. was put, to, bed >and, by a proper. diet and:care, , recoyered his: former, health,.and ~ could, walk perfealy,, -vetel in» 'three,.-weeks. ‘4 One of the Phyficians often met him after- h wards on foot driving cattle; ,..and., always : afked, How he, did?..; To ;which his con- ftant an{wer was, Very, well; thank-God and the Gentlemen. And he can now, upon oc _ cafion, walk twenty miles;in a-day, owithout ih fatigne or pain, tho’ the injured limb ftill re- mains.néar a quarter,of an inch longer than _ the other. 1p dou DART ‘i 324 ESSAYS ayn OBSERVATIONS: ATRY XXII. Some Obfervations on the new Method of cus ring the Cataratt, by extratting the Cryfal- ~ Fine Humour ; by THomas Yours Bar geen in Bainburgh 7" O: reftore loft fight, is recovering one of the moft ufeful of all the fenfes, and the couching of the cataract, would be one of the moft valuable operations, could it always be done with fafety ; but the bad fuccefs, and. dreadful confequences which often attend it, have deterred many good Surgeons from performing this operation, and thrown it much into the hands of em- pyrics. | [have couched but few in the old way, and thofe with fuch bad fuccefs, that I was fully determined to operate no more on the eyes ; nor did the fuccefs of the new method performed by the ingenious M. Daviel, alter my refolution for a confiderable time, till, at the importunity of fome of my beft friends, ) I * March 4. 1756. "PHYSICAL asp’ LITERARY 325 Tconfented to try this new operation. » Six cataracts. luckily caft up Jatt’ fummerin» the Royal. Infirmary at’ Edinburgh, which Iex- tracted in the following manner. ./THE patient, being feated in,a chair, with an affiftant at his back, to fupport his head, and keep up’ his eye-lid, asin the old ope+ ration; the operator may ftand. or fit ina chair, as he finds moft convenient. » He fhould keep down the under-eye-lid with two fingers of the one hand, while with the other, he takes the fmall knife A (Plate VIIL.. Fig. 3.) with which he pierces the tranf- parent cornea atothe external angle of. the eye, near to where the; corvea joins with the Jelerotica, taking )great care: not» to ‘wound the zr#s. Run the knife in:a horizontal di- rection acrofs the anterior chamber, and bring it out: about the fame: diftance from the white of the eye, as where it entered ; then cut that part of thee.cornea which lies below the two orifices, as'much in the form _ of acrefcent as poffible, this makes the in- cifion larger, and keeps the cicatrice more _ off the fight; lift up the flap of the cut - cornea with the feoop B (Fig. 4.) or any other convenient inftrument; introduce at the fame = ‘p26 ESSAYS ann CBSERVATIONS fame time a_common couching needle»C; (Fig: 5:) thro’ the pupil, ‘to open the eapfada of the-eryftalline Jens, that’ the’ latter! amay - come the more’ eafily out. A‘ {malbaper= ture’ generally ferves this’ purpofe ;\ ‘if the lenssis of a firm confiftence, it!*often. fticks to the point of the needle; fo'that when the — inftrumentois withdrawn the cryftalline comes along with’it;° if it does not, avery gentle preflure- upon the eye forces it out. “The operation may ibe frequently performed) with the knife alone,|'the! capfula'of : the cryftal- line being-fometimes fo thin, that, after. the cornea is cut, ai {mall preffure on wes pei makes the dens come away.” (273 b¢Purs anethod> of operating ‘is anil hia, fame with that practifed by:M. Daviel, which $ou'll find at largein the Memoirs of the A= cademy ‘of ‘Surgery, vol. ii. p. 337. Ihave followed thes example of the famous Mr. Sharp, ‘and {hunned the great multiplicity: of inftruments M. Daviel makes ufe of, which renders this operation more fimple, lefs tedi- ous, and lefs dangerous. I fhall next*mention the fuccefs of atl vw in the. order they were performed., 1 RoBERT PHYSICAL anv LITERARY: 327 ./a.Rozert Laurie, aged about 30. years, was admitted into the Royal, Infirmary with a ‘cataract in both eyes. I operated onthe left eye. the 23d. of Fuly 175 5- _ As foon as I had pafled the knife into” the anterior chamber, he turned his eyes fo much upwards, that the cornea. was, quite out of fight ; I waited till the eye-returned to ‘its ‘former, pofition, when I found the point ‘of the inftrument in the zis, which I imme- diately difengaged, and finifhed the or without any other accident.) I expected a great inflammation. filein’ the iris being. bewelieids but was: agreeably- difap- ‘pointed, finding the man recover with little “pain, no fever,and the inflammation incon- fiderable. ERG: ‘AsouT three weeks after the operation, che could diftinguith colours, and large ob- jects tolerably well; but could not bear much light. His eye ‘continued weak’ and watery for about three weeks more, when -he,could eafily fee a pin inthe fleeve-of~ his own coat; his eye was clear, but the pupil - not quite round,. which was weeeey owing to the 7ris being hurt, (CIRO : 25. eee 328 ESSAYS anp OBSERVATIONS 2, was admitted into the Royal Infirmary about the middle of Septem- ber, with a cataract in the one eye, and the cornea of the other quite opaque. Tue pupil of the cataracted eye was con- tracted to above the fize of a large pin head, but quite immoveable. He was vifited by feveral Surgeons in town, who were of opinion, that the dif- eafe was incurable; and that the bottom of the eye was affected, as well as the cryftal- line dens. I propofed trying the new operation, be- fe fore he fhould be difmiffed incurable; to which they very readily confented. I performed it without any accident, and the man recovered in a few days, without any fever, pain, or inflammation. He was difmiffed the houfe about a fortnight after the operation, when his eye was quite clear, but the pupil ftill immoveable ; and he could only perceive a glimmering of light, which is more than was expected from the ap- pearance of the pupil before the opera- tion. 3. & 4. Joun Crartc, aged about 40 years, was admitted into the Royal Infirmary with PHYSICAL ano LITERARY. 329°: with a catara&t in-both eyes, which. had much: of the milky appearance. ( I operated on both eyes the | 28th of Sepe: tember 756, and nothing extraordinary oc- curred during the operation ;- only, “upon? dividing ‘the capfula of ‘the cryftalline, "4" fort of milky liquor came? out; and the/exs was’ of a datk-brown colour. He had va very {peedy recovery ; fix days/after the operation,’ Tuncovered his -eye';‘he! was’ capable of dif- tinguifhing ‘colours.’ T looked agaim into his: eyes om the 013th day; when I fotnd his fight: till obetter, sand! his ‘eyes more able to ‘look : vat a objedts, ‘without —— i in g- \ i} He was difimiffed the Sort the; rly of 5 Meenas when he could «read ssa me _ affiftance of glaffes. 5.. RopertT Laurie, | bdehdear'l bail ea ready mentioned, had the operation perform- ed on the right eye-ithe rath of Odétaber, when nothing extraordinary happened ; he _had a very good recovery, with: {carce’ any pain or inflammation } "he was difmiffed from the houfe the 19th of: November,’ when’ ‘he faw very diftin@ly with ‘both eyes. u Be vor. if. EAT goss 30) 6 NAGASE 2,30 ESSAYS anv OBSERVATIONS 6: Acnes BaRRowMAN, aged,.about 30. years, was admitted. into the Royal, Infir- mary, with cataracts in both eyes. _ I, operated on, the left exis the 26th of Odtober 17.55. Tue {pace betwixt her eye-lids, whem rai- fed up; was fo fmall, that I could! with dif- ficulty fee all the cornea, which, in this pa- tient;- was remarkably flat. | - As foon as I had: paffed:the Las ite into the anterior chamber,'. fhe was feized with a fit of coughing, which obliged me °to cut the cornea in a very great hurry. The opening © in the cornea was but fmall, which gave me more difficulty in extracting the cryftalline, than I-had in any of the former. NotwiTHsTanpine this unlucky acci- dent, fhe had a tolerably good recovery; her eye was-pained, and fomewhat inflamed, for fometime after the operation, but never vio- lently. » She was. difmiffed the houfe about fix weeks after the operation, being then , able to diftinguifh very {mall objects... - N. By Some -eyes are more proper for this operation than others ; the larger the eye, and the more convex the cornea, the opera- tion will be the eafier. This woman had a remarkably PHYSICAL any LITERARY: 331 rematkably bad’ eye in this refpect ; it was fmall, the cornea flat, and the diftance be- tween the eye-lids, when open, was very little: perhaps ‘the /peculum ocul: would ‘be of ufe to help all thefe faults while the cornea is cutting, but no longer, for fear of. prefling out the vitreous humour. Re ree Tuere was nothing particular in the treat- ment of thefe patients after the operation 5 it confifted chiefly in blooding, {pare diet, now and then a gentle laxative, and cloths dipt in vinegar and water applied frequently to theéyes ;“they were not confined to their beds above a day or'two, and none of them required’fomentations. 9 T do not pretend, ~from the above cafes, to make a comparifon betwixt the fuccefs of _ couching, and the new method; this requires _ more cafes than I have had occafion to fee. - Accorpr1ne to the trials made by fome of - the French Surgeons, which you'll find in the Memoirs of the Academy of Surgery, v0/. ul. p. 578. the couching was the moft fuccefsful. Mr. Morand couched fix patients. 3 of them faw diftinctly. j 3 of the cataracts rofe again. 332 ESSAYS anv OBSERVATIONS ML: /a Faye extracted fx cataraéts. in the new way. it 2 of the. patients { fave diftinaly.. 2. of them faw lefs diftinély. 2 of them were quite blind. bit tic) M. Poyet extradted feven cataracts after the new method. 2. of his patients faw ditindly. 2 of them lefs diftinGly. 1 could diftinguifh light. 2 of them were quite blind, . Were I to judge from my own experience in both operations, the new method certain- ly claims the. preference ;. fince I have. only operated upon fix cataracts, and all of them have fucceeded, tho’ {ome were not. very pro- mifing. _ ’ This, I hope, will excite others to re further trials and improvements in this ope- ration. ART. PHYSICAL anp>LITER ARYs 333 A il XXII, A Hernia. from the, Omentum falling down, data the Scrotum ;. . dy Tuomas Liyine~ ston, M. D.. Phyfician. at. Aberdeen *. | eae man, aged about. 28,: of, avery. _. thin habit of body, .and. naturally of a. healthy conftitution, .was.feized' with a pain and uneafinefs about the region of the’ ftomach ; for which -complaints, (without any regular advice) he tookia vomit, which. operated in, the ufual. ‘manner, but without! . alleviating -his former uneafinefs. In’ the evening of that day, about fix hours) after the operation of the vomit, he was -feized: _ with fharp.pains over all his belly, for which, _ by the advice of a Phyfician, -he was ordered f an emollient clyfter, and an anodyne at bed- time.. The clyfter operated gently, and he paffed the night pretty free of pain, till, to- wards morning that the pain returned more violent than ever; particularly in the left _ fide of the umbilical region, . and in the left — tefticle. “ February 5. 1755. 334 ESSAYS ann OBSERVATIONS tefticle. Iwas called to vifit him that fore- noon, and upon examination found a {cro- tal hernia on the left fide, about the fize of a large fift, extremely hard over all its fur- face, and very painful on the flighteft touch. He had a hard frequent pulfe, intenfe thirft, and all the other fymptoms of inflammation. He was immediately blooded to a confider- able quantity, warm ftupes wrung out of an emollient decoction were alternately applied upon his /crotum and belly, and an emol- lient purgative clyfter was injetted. The application of the warm ftupes gave him fome {mall relief, and he imagined the parts were fofter ; but, upon ufing the taxzs, the pain was intolerable, and it was in vain to endea-: \vour to reduce the fernia. He continued in this ftate till the evening, when his fever demanded a fecond blooding, which was ac-" cordingly performed; another -ftimulating’ clyfter was thrown up, and foon after he had two or three copious dejections of in- durated faces. The operation of the clyfter 3 gave him fome eafe ; but the ftate of the hernia was not in the leaft altered. He'con- tinued reftlefs and much pained all night,- andin the morning he drank the decoé?. ta- marindor . PHYSICAL any LITERARY: 339 marindor. cum dupl. fenne, which gave him {e- veral loofe ftools. throughout.the day, the, hernia continuing as hare and painful as for-, merly. He would not agree to have the operation. of the dubonocele performed,’and in the’even- ing his pulfe became feeble ; he had. fre= quent returns’ of a /imgultus, and died next morning. “It may be neceflary to mention, that foon after the vomit he cried out, that fomething was tearing his ftomach and guts: towards the bottom of his belly. | Dorino.his illnefs I was\much perplexed about the nature.of the Jerma,, As the’ cly- fters and ptifan had operated very naturally, I could not: imagine that, it,was any. por-. tion of the inteftines; and as he was of a remarkably thin habit of body, I could fcarcely imagine that is/was the omen- tum ; however, as his friends gave me the r Bbersy of examining the, body, my doubts and {cruples were foon fatisfied. I firft look- ed the ftate of the abdomen, where the fol- lowing appearances were very obvious. The omentum fallen down, greatly ftretched, and _ fo tenfe, that one fhould have imagined it would have broke, The ftomach much dif- tended 436. ESSAYS avo OBSERVATIONS tended with air, the great curvature of it much lower down than its natural ‘fituation ;’ the great arch of the colon quite out of its place, and lying as low as the middle of the -fmall’ guts; the jefuvnum and ileum eonfiderably in- flamed and much diftended with air, and’ the mefenteric -veffels much more turgid than ufual. Thefe were the principal things to be obferved in the abdomen. Upon ma- king an incifion through the teguments of the /crotum, (in the fame’ direction as is ordered in the ‘operation ‘for the bubono- cele) 1 foon difcovered the “hernial fac, which was very thin, tenfe; and rigid ; and, upon laying the fac’ ‘open, there was nothing “to be® found but the ‘omentum, which was compleatly mortified as high as the ring of the mufcle. Upon dilating the ring itfelf, I found a convolution of the ¢/eum fticking in the very mouth of the’ opening, but the one half of the tranfverfe diameter of the canal was only engaged, and that part of it which was {trangulated’ was in a mortified ftate. ~The remaining part of the gut betwixt that and the ca- fut coli was much fmallerthan ufual, con- fiderably inflamed, -and contained a little putrid .) | PHYSICAL awp LITERARY 337 putrid vifcid chyle. Upon taking out the omentum, 1 found a refiftance towards the ~ lower part of the /erotum, which I imagined _ was owing to fome adhefion ; but, upon u- fing a very gentle force, it was. eafily ex- tracted, and plainly came out of the tunica va- ginalis teftis, in which there. was a pretty large hole or perforation. ~The. tefticle appeared to be quite found. That portion of the o- mentum which was contained. in. the Scrotum, weighed fix ounces and a half, Vou. Il. Un ie ART. mos 15 ° 338 ESSAYS ann OBSERVATIONS Art. XXIV. Al Child brought forth at a Rent of the Belly *. YEN Lpril 1736, Elfpet Grant, in the'parith | of Moy, being with child, took ‘her la- — bour-pains’ After they had continued three days with the child in the birth, two cracks, as if the rafters of the ‘houfe’ had “broke, were heard about the fick wife, and her bel- ly was rent from near’ the navel, witha , {quaint downwards and to the left fide, to near the fhare-bone. At this rent the child €ame into the world, the after-burthen was brought away, and the intrails were feen. Tue rent was cured without any other ap- plication, than that of butter mixed with white fugar, and its fcar was only as the fcratch of a big pin. Turse facts are attefted by the judicial oaths of una Kennedy a midwife, and Mary Ogilvie a neighbour, who were prefent when the rent was made and the child came out of it; of Margaret Dallas, who affifted to. bring * May 1..1755. PHYSICAL AND LITERARY. 339. bring away the after-burthen ; = of Robert Smith who faw the rent and intrails imme- diately after this ; and.of /obel Tarrel, who. afterwards examined ,the fcar: taken and fubfcribed by ‘fames , Macqueen younger. of Corribrough, Bailie to the Laird of Mackintoft-, at Moyball, November 22.1738; of which the original fubfcribed copies are kept by the Secretaries of the Philofophical Society. of Edinburgh. A Child efcaping at a Rent of the Womb in- to the Abdomen ; dy ALEXANDER Monro, Senior, WDD, uid oe N March 1744, 1 was defired by Mr. Ramfay Surgeon here, to witnefs the exa- ‘mination of the body of a woman who died ~ 4n child-labour without being delivered. The account given me of this woman was, that fhe was about 35 years of age, and had born two dead children, and a living one. Being at her full reckoning, her pains had begun on - Tuefday morning, and continved in a natural i. ‘way, the child advancing towards the birth, i and oe g4o. ESSAYS ayv OBSERVATIONS and fome of the waters coming away all that day and Wednefday, till Wednefday evening, - when fitting in a chair in labour, fhe: gave a fudden {pring from the chair, complaining of violent pain in her belly. The child ne- ver was felt afterwards by thofe who attempt- ed to affift her delivery. She conftantly complained of violent pain in her belly, with her fenfes and judgment intire, till Frzday morning, when fhe died. On Saturday her body was opened. ArTer cleaning away with {punges a con- fiderable quantity of blood floating in the abdomen, we faw a ripe child and its fecun- dines lying in the lower part of it, a little to the right fide... The child, placenta, and um- bilical rope were intire, and the membranes ‘were as ufual after birth. ‘The woman’s w/e- rus had its fundus raifed as high as the navel, with its fubftance foft and {pongy-as 1s com- mon in pregnants, nothing preternatural appearing in its fore-fide; but when the jundus was turned down and forwards to- wards the ofa pubis, a large rent four inches Jong was feen towards the neck of the womb; which being again put into its natural fitua- tion, was opened its whole length, in the © middle PHYSICAL anv LITERARY. 341 middle of its forepart, when we had a bet- ter view of the rent, extending from very near the os uteri’ upwards, a little obliquely to the right fide. The os ufert was then ve- ry little open. The cervix which is diftin- guifhable plainly from the fundus ina woman | not with child, was here extended into the . fame common fac with it. The inner furface of the womb was all fmooth, feeming to be covered with a fine villous membrane. From the larger fize of the finufes at the back and upper part of the womb, I judged the plz- centa to have been formerly applied there. ART, 342 ESSAYS anp OBSERVATIONS © Art. XXV. A preternatural Collection of Waters in the Womb with Twins; by STEPHEN FELL Surgeon in Ulverftone *. Fr November 1747, 1 was called to Hannah Salthoufe, mother of feveral children, then, according to her reckoning, in the firft week of the eighth month of her preg- nancy. She had obferved her belly increa- fing in bulk very faft during the preceeding - month, and particularly in the two laft weeks, in every day of which a fenfible difference was faid to have been obferved, At my firft vifit ‘her abdomen appeared to me much more diftended than ever I had feen in a wo- man with child, efpecially from the navel to the upper part of the epigaftric region, where it was more tenfe than towards the offa pubis, and the moft ftretched part had little fenfe of feeling. Her pulfe was high and quick, her breathing was difficult, her face * February 6. 1755. “PHYSICAL ann LITERARY. 343 fice was ehdavireds, and fhe had conti- nued “unnatural labour- -paifisy with much thirft and little ‘urine. The os t2nce was a little opened, but without any ‘forming of water that could be felt. « I ordered clyftérs and an ee at night, which made her pafs it quietly. » A Next day the pains were more natu- ral, and fhe was tolerably eafy. In the . evening, fhe took an opiate with two fcruples of pulv. ad partum, after which, there were intervals between her pains; but at four in the morning, fhe became delirious, and appeared like one who had not ‘an hour to live. On taking rich hot negus, thefe fymptoms went off ; and then having felt a child’s head floating in wa- ter, I broke the membranes, and brought away two male children, who were fcarce half the fize of children born at the u- fual time. One of them was dead, fwell’d and livid ; the other lived 64 hours, but without taking food, or making any dif- charge by ftool or urine. The quantity _ of water voided in this delivery was com- | puted by all prefent not lefs than fix wine gallons, 48 or 50 iid. My 344 ESSAYS anny OBSERVATIONS _ My 'patient’s belly fubfiding to the natu- ral dimenfions, was fwathed immediately af- ter the after-burthen was brought, aways She had . ftrengthening cordials and) ano- dynes given her, with a proper diet, and fometimes clyfters.. Now, on the 12th day after her delivery, fhe appears out of danger. ART. PHYSICAL ann LITERARY. 349 Arr. XXVI. Hiftories of tophaceous Concretions in the ah= mentary Canal; by ALEXANDER Monro Senior, M. D. F.R.S. and Profeffor of Anatomy in the Univerfity of inhi = sa HE number of hiftories of pietidconi concretions in the alimentary canal is not: fo great, but that your collection might, in my opinion, admit of fome few, efpecially if there is a variety in them. Hift. 1. A healthy boy, about twelve years of age, began to complain of colic pains, _ which increafing with frequent gripes, Jdor- _borygmi and vomiting, had fuch an effea, _ that his parents afferted, he was fcarce of fo large ftature after fix years of his difeafe as he was at the beginning of it. Vomits, purges, vermifuges, attenuants, and a vari- ety of other medicines had been given in that time without any benefit. _ His father,” one of the town-officers or -ferjeants, having then afked my worthy friend vor. II. - Rx and *® February 6. 1755. 346 ESSA¥S ann _ OBSERVATIONS and collegue Dr. Plummer’s advice, he defi- | red my afliftance. We were told by the lad, who was greatly emaciated and very weak, that fome years paft he had not had the vo- iting, but found a hard painful tamar above the left groin, which fometimes.fhifted place a little, where he fancied often he felt fome- — thing like the ftriking of two hard bodies on each other. He had been of late much fa- tigued with fenef/mus. Sometimes he had no excretion of feces for feveral days, and often he could. fearce make any water; and that only ia drops.. During two-days before our vifit, the éene/mus was conftant, and he felt fomething hard within the’ rectum near to the anus, which he and feveral’ others had endeavoured in vain.to siege away. with. their fingers. On extracting this fubftance with a fonts ceps, fuch as is ufed for extracting ftones from the bladder, he was much eafier than © he had been of aconfiderable time. Next — day, he paffed two other balls, and on each of — the two following days, a ball, which he could not force out at the aus, was extracted with the forceps. After this, he had no uneafi- nefs, PHYSICAL ann LITERARY. 349 nefs, and foon cpa ‘a heal sche Ga man. THE largeft of thefe five balls which was the frft extracted, ‘is five inches in circum ferente and fomething globular, but with feveral prominences and flat farfaces. Mott of the flat parts hada fmooth fhining tar-. tarous thin coat, the reft of it was more rough and of a fpongy appearance. . The two laft brought away, are lefs in’bulk, and with- out fo much tartarous cruft. ‘The two fmall ones aré all’ covered over with the fhining tar- tarous cruft, ‘which in feveral places is pret+_ tily variegated with different’ fhades of an afhy colour. OnéOf them has fome refem- blance in its fhape to the fhell of a tortoife: The other or fmalléft may be compared to two pyramids joined by a: common bafe. Tue fecond in fizé’and the fmalleft are cut thro’ near! to the middle; where there” is a fmall flat bone, ‘that probably has been: ‘the’ the mucleus about which thefe balls were formed, tho’ they are’ not of ‘the’ fame fhape. LaySh bes We were informed by the parents,’ that _ they ‘had often chid their fon for {wallowing - the fmall bones of iii ia ‘and lambs feet, the | -finewy 348 ESSAYS ann OBSERVATIONS finewy parts of which, when boil’d, the fa- mily frequently took for food. Hifi. 2.. A man who had been long tor- tured with a painful hard {welling in his belly a little above the right groin, which frequently caufed vomiting and diarrhea, tho’ at other times he was very coftive,afk- ~ ed my advice, when he. was very weak and emaciated. The feat.of this tumor, the kind of feel it had thro’ the..containing parts, and itstumbling, as the patient faid, from) one place to another, when. he changed. poftures, made me fufpe.a concretion to be lodged in ‘the great fac of the colon. | In hope to puth it forwards in. the colon, 1 caufed his great guts to be: filled with whey injeted by the anus, and then directed him- felf and affiftants to prefs repeatedly the ¢u- mor upwards. This maneuvre being feveral times renewed without fuccefs, I prefcribed a brifk purgative, and ordered the injections with the prefiure to be repeated as foon as the cathartic began to operate. But, this and feveral other fuch operations failing, my patient. died, Havine obtained leave to examine his body, miy conjeCture proved to be right ; for in ePHYSICAL; anp LITERARY. 349 in the caput coli;there was a ball of more than feven inches circumference, with a de- preffion at oppofite.ends. . The inteftine shad contracted fo. much.at the fide of the ball nexe to the cavity of the colon, that I could. not . force it thro’ the aperture there, ‘but was obliged to.cut the faciin which it was ee to take it out... Ene ball ie no tartarous th on its For be and when-it was cut! thro’, its nucleus was a chalky or limy fubftance about the fize of a common pea, - Elift; 3. DR. Fohn Stevenfon Phyfician gave me a concretion fix. inches in circumference, the nucleus. of which is a plumftone, taken out of the inteftines of a boy of five years. old. Tho’ the ftone had been {wallowed long be- fore the boy’s death, the kernel of it: was Fs frefh when, the ftone was taken from the _ middle ofthe ball.. A clyfter had brought away feveral other plumftones from this. boy fome months after the plums had been eat. , _ Fift..4. Dr. Stevenfon alfo gave me ano-~ ther fuch concretion, which has four flat fides with feveral depreffions in them, mea- foring about five inches in circumference, formed 350 ESSAYS ann OBSERVATIONS formed alfo on a burnet plumftone,’ which he took out of the inteftine of a girl. . Hit. 5. From the fame Gentleman I like- ways had a third concretion pretty like to, but a little larger than, the one defcribed and painted by Dr. Simfon in Med. Eff. vols ic art. 32. which, with three fuch others, he — took out of the inteftines of another patient.’ Each ‘of them had a fmall ftone in the mid- dle, the patient having formerly fwallowed {mall ftones and pebbles, for what he called a colic in his ftomach. a B10 Tue Dr. tells me, that all thefe three pa- tients wafted, without ‘being fick or lofing! their ‘appetite. They were fond of fleth for’ food, and were averfe to flops... They feldony were free of borborygmi, which made the abdomen to change ‘almoft conftantly its ap- pearance, the parts of it rifing’ and finking as the air went from one place to another. Hift. 6. Ix a ball of this kind eight inches’ one’ way and fix the other, taken from a Gentleman’s inteftines, whofe hiftory I -do not know, the nucleus is a little round piece of wood about the fize of a common hazle nut. None PHYSICAL ann LITERARY. 358 None of the) balls mentioned in thefe four laft hiftories have any tartarous .cruft, but they and all the other cut) ones have the appearance. of being compofed of /rata furrounding the nucleus, their colour dif- _ fering in fhades from a dark rufty to. a pale afhy colour. Their fubftance, except where there is tartarous cruft, refembles a fine hat or chamois-leather when cut. Hift. 7. In the colle@tion of curiofities kept by the Surgeons of this place, there is a ball taken out of the ftomach of a horfe, which is nearly fpherical, and Nineteen inches in circumference. Its furface has fomething of the mulberry form, being compofed of agreat number _ of hemifpherical knobs, about a quarter of an inch diameter contiguous to each i other. Their outward fhell looks like a thin cruft of fandy clay; but within this the fubftance has the fame matted appear- ance as the human concretions have. Hit. 8. Baus are alfo frequently form- ed in the ftomachs of cows. Three of them which were given to me, are al- -moft exact fpheres of a black colour, com- a pofed 352 ESSAYS ann OBSERVATIONS pofed of .an external hard ~ tartarous cruft, which is about =} of an inch thick. Within this there is nothing but fhort black hairs matted compactly together. The circumference of the largeft is 9 inches ; of the fecond, 6's ; and that of the third, is 54. ART. PHYSICAL asp LITERARY. 353 Arr. XXVII. Remarks on Procidentie Ani, Intufufceptio, Inflammation, and Volvulus of the Inte- frines ; by ArsxanperR Monro fenior, LES DA a ata San “T ftool more or lefs of the infide of the rectum is generally thruft out be- yond the verge of the anus, which afcends when the preflure of the diaphragm and ab- dominal mufcles ceafes. If the protruded inteftine is not then retracted, it is {queezed by the /phinéter ani, fo that the return of li- quors from the part of it which is beyond ~ this ftricture, muft be rendered difficult ; on which account, this part fwells, becomes of acolour more red than natural, anda larger than ordinary quantity of flime flows from the ends of the veffels that open on its inverted villous furface.. This ftate is called procidentia ani; a difeafe, to which chil- ppren, old people, thofe weakened by difeafes, fuch as are attacked by ¢eve/mus, from "Vou. I. Y y whatever * February 6. 1755. 354 ESSAYS ann OBSERVATIONS whatever irritating caufe, are more fubje& than others. Tue fpeedy reduction of the inverted pro- truded part of the inteftine, is the effectual | | cure ; nor fhould time be loft, as is often ad- © vifed, in trying to diminith the fwelling by © warm fomentations and poultices, which re- | lax the veffels, and. rarify the liquors, and | therefore produce an effet very different | from what they are intended to have. »If the prolapfed inteftine is fo much fwelled, | that it cannot be made to pafs thro’ the con- tracting /phindter, incifions may be made in , its furface, by which part of the flime and blood contained in. the cellular membranes, may be {queezed out, to diminifh its volume, and thus to make it capable of returning a- gain within the body. Tue practice of the nurfes and other good women, in making the reduction of a pro- cidentia, is very faulty. They apply a warm ° cloth to the protruded part of the gut, and prefling on it, endeavour to thruft it all up at once. Before the inteftine {wells, this o- peration fometimes fucceeds with children whole /phinéfer is weak. But dry cloths or fingers are liable to adhere to the villous-coat and PHYSICAL.anp LITERARY. 355 and give great pain in taking themvoff. The: cloths or fingers applied here ought. always to be befmeared with oil; unfalted butter or axunge, to prevent-this adhefion. VThe’ bulk of the prolapfed part -is often fo’ great, that it is impoflible to make it all pafs? at once thro’ the /pbinéter, anda fruitlefs at-: tempt of reduction generally increafes the- fwelling. The reduction ought to be made: by preffing a {mall‘part’of the fides of the orifice, with a greafy finger; and when that part is thruft within the orifice, another fin-’ ger is applied to what is then the verge of the orifice to pufh it upwards, while the firft applied finger is withdrawn: by fuch an al- ternate fucceffion of two fingers, the «whole - may be introduced in moft cafes without in- _cifions,: fo that this difeafe is feldom fatal ; j and for that reafon, the patient is generally too “much neglected after the reduction is made, which is sigan attended with bad con- fequences. Ir, after the reduction, the part continues to be pained and the patient’s pulfe is quick, blood-letting, and alow cooling diet, are ne- _ceffary to prevent inflammation and its confe- quences. In all cafes, too much coftivenefs and 356 ESSAYS ann OBSERVATIONS and its contrary a diarrhea, efpecially with tenefmus, are equally to be guarded againft ; feeing a return of the procidentia may be cau- fed by cither of them. The relaxed parts are to be braced by ftrengthening topical me- dicines, In the aftringents commonly pre- {cribed, I can have no confidence; their ef- fe&t.goes no deeper than the fkin ; but. fti- mulants, fuch as ardent f{pirits or tin@tures of the aromatic refins made with them, give a {pring to all the parts, and excite a glow- ing heat whenever they are applied, fo as to touch any part of the extremity of the gut, which they can always be made to do. I have faid, that this difeafe, the prociden- tia ani, is feldom fata] ; and the redu@ion of the prolapfed part of the inteftine into the body, is generally regarded as a cute of — it; but that this is not true, when the — doubling of the inteftine is high up, will ap- — pear from the following hiftory. A large-fized ftrong healthy boy, a year and an half old, after a darrhwa of fome days, with ¢enefmus, was obferyed to have 4 procidentia ani, which was treated two days by the women who attended him; after which’ _ Mr, Adam Drummond, Surgeon in this place, wag ~ PHYSICAL ann LITERARY. 357 wras called to his afliftance. He reduced the _ procidentia frequently ; but it foon returned, which made him defire I fhould be con- fulted. THE inverted inteftine. ftood out four inches from the anus, without being much fwelled or of a deep red colour, and the child feemed to haye no other difeafe. Mr. Drum- mond mot eafily introduced all the tumor in- to the body; but foon after it was puthed out again, upon the child’s having .a defire to ftool, notwithftanding a fervant’s keeping 4 finger on gach fide of the gus near to each. other, while fome liquid excrement was pafied. After the reduction was again made, I put my finger, which is long, up the rectum, puthing the orifice of the inverted gut on _.the point of it, and then found the orifice _ of the inverted gut refembling the feel of the os tince of an unimpregnated womb refting on it, which I could throw up fome way further with a fudden jirk of the laft joint of f the finger, but without being able to invert it. We then caufed a large quantity of milk and water to be injected with force, while the two fides of the anus were prefled firmly re on the pipe of the fyringe introduced by the anus: 358 ESSAYS anv OBSERVATIONS anus into the rectum, to prevent the liquor’s ~ recoiling, in hope that the liquor would car- ry the inverted gut before it, to caufe its: return to the natural fituation. ‘This opera- tion being repeated feveral times in vain, the procidentia always returning with the sene/- mus, a very long probe of whale-bone was made, a fponge was faftened round the probe, this was wet in oil, the probe was in- troduced into the orifice, which, I faid, -re~ fembled an os tince, the fides of which reft- ed on the fpunge; and with this the inte- {tine was puthed a great way up into the bo- dy in the direction of the reéfum, but with- . 4 out fuccefs. Several attempts of the: fame kind failing, we defpaired of a cure ; and the child, fometime after, being attacked with fevere vomiting and seer tenefmus, died in few days. Mr. Drummond, who opened the body, told me, that the inverfion began a little below the upper part of the figmoid flexure of ‘the colon’; aid that the mefcolon was torn away from the inverted part. Wuen a doubled part of an inteftine-is extefided into the cavity of this alimentary canal, PHYSICAL anp LITERARY 359 canal; without appearing externally at the anus, it 1s called intufufceptio, which, I am - perfuaded, is a much more frequent dif- eafe than is generally thought. I have feen feveral whom I judged to have died by it, and fhall now relate the cafes of four people whofe bodies were examined after death. 1. A middle aged woman, during fixteen months before, her death, f{uffered greatly _from,.colic-pains, diftenfion of her belly, “vomiting, and fenefmus. » In the latter part of her life, when I firft faw her, fhe had ho ceflation from me except by the force of eit In the great arch of the colon was.a doubled mt of that gut) feven inches long. The containing inteftine had a very flight adhe- fion to the inverted doubled part contiguous toit. .The doubled part’ was of a dark red colour, but not very hard. The paffage for the feces thro’ it was very narrow, not al- _ lowing a finger puthed with force to pafs. | 2. A woman about fifty years of age lived two years with fuch {ymptoms as were nar- tated in the preceeding cafe. We found 2 doubled part of the colon! four inches long in the 360 ESSAYS ann OBSERVATIONS the left loin, with the fame appearance as de- {cribed in the former hiftory. 3. Agirl feven year old, after eating a carrot and fome curren-berries, had a colic which continued with a diftended belly, vo- miting, and pafling little feces, from ‘uly till the middle of December, notwithftand- ing various medicines were given. Mr. Malcolm Surgeon in Dalkeith, whofe patient fhe was, being allowed to open her corpfe, cut out the affected part of the in- teftine, and fent itto me. ‘The end of the ilium, valvula Tulpii, caput colt, and appen-: — dix vermiformis, were raifed twelve inches within the colon, to which they had a flight adhefion. ‘The outer furface of the con- tained inteftines was dark-coloured, and very unequal. The orifice of the prolapfed part Was not at its end, but at one fide an inch and a half from the end, with a foft flexible prominence at each fide of the aperture, which I judge to have been Tulpius’s valve. The doubled parts were fo grown together, that I could not diftinguith one from the o- ther. The paffage within them was fo fmall and crooked, that Teroukd not pufh a probe thro’ PHYSICAL ann LITERARY. 364 thro’ it; but cutting it open gradually, I ‘found it was ftill pervious. 4. Dr. Cullen, Profefior of Medicine in the Univerfity of Gla/gow, communicated the following ‘cafe to me. A. boy about twelve years of age com-, plained of wandering colic-pains, which he imputed to blows received on his belly from fome of his companions. -Thefe pains re- turned frequently with diarrhea, and fome- times bloody ftools, for near a year, when his parents. confulted Mr. ‘ames Muir Sur- geon in Glafgow about him. The boy was ‘then much emaciated, hada quick pulfe, and was fo weak as to be confined» to his bed. Two weeks after this, .a livid membranous fubftance, pafled by the boy at ftool, was brought to Mr. Muir; who obferving it to _ be tubular, tied one end of it, and blowing into the other, diftended it into fuch a con- - _yoluted tube thirteen inches long, as you fee reprefented A BC, Bg. 1. of Tab. VII. which I .caufed to be drawn from the origi- nal which was fent me. As it has the mefen- Btery D. conneéted to all its concave fide, it "appears to have been an intire piece of gut, and not the villous coat only. Befides this p) You. II. Zz large 362 ESSAYS anp OBSERVATIONS large portion of inteftine, there were fevera? fhreds and fmaller pieces paffed bythe patient ; notwithftanding which, Mr. Mu:r faw after- wards, among the boy’s feces, fkins of po- tatoes which he had eat after thefe parts of the inteftine came away, fo that they had not made any difcontinuity in the alimentary canal. The fymptoms continuing, the boy died in fix weeks. Mr. Muir opened the body of his patient,. in prefence of feveral Gentlemen of the fa- culty, who faw what I am now to defcribe, with the affiftance of a figure, which Icau- | fed to be taken'of the dried preparation of the inteftine fent me. . Tue folds of the inteftines and omentum were all glued together by a fatty curdy matter. Within four inches of the valve of the colon, the zhum ABC, Fig. 2. Tab. VII. formed into the ufual curve by the me- fentery D, fuddenly rofe perpendicularly at E, where it was much contracted and had the appearance of a cicatrice. When the inte- ftine was opened, this contracted part of it was found much thicker and harder than it was any where elfe, efpecially on one fide, where : : - PHYSICAL ann LITERARY.’ 363 where it ftood fo far into the cayity, as to leave a very fmall paflage for the aliment. Along this contracted part, the mefentery F was firm and thick.) After) this, the inte- ftine G became of a natural enough i and make. Tue Gentlemen in Gla/gow were, 1 think, jaftly of opinion, thatthe part of the inte- ftine. inflated, by Mr. Muir,. delineated in fig. 1. was an intufufcepted part fallen away by gangrene from the inteftine at Ein Fig. 22 where, if theré- was a concretion, as is res lated in cafe 3. it might have feparated with out leaving any difcontinuity in the alimen- tary canal. if [have feveral -times obi an sil infceptio in the fmall guts of children} a little below which I obferved feveral worms ;. but the inverted .part was neither fwelled nor dif- coloured;. which made me think this dif order had. happened foon, before, death. Ini ‘one of them a lumbricus teres had patfed the ' half of its length thro’ a hole made in the gut; but; as thete was no rednefs or other mark of inflammation at this part, I judged _ the perforation to have been made by: the ‘ worm after the death of the fubject. THERE "364 ESSAYS anv OBSERVATIONS _'Tuere is little difficulty in conceiving how a piece of a gut fhould enter doubled — into the part below it, and how it may be gradually protruded downwards to :a confi- derable extent by the food or feces, in their defcent towards the aus ; but it is not eafy, when this difeafe begins, to diftinguith it from a variety of other diforders which hap- pen in the alimentary canal, or to find a re- medy when it is fufpected, efpecially if the intufufceptio is in the {mall guts ; and’ from the obfervation above narrated of the. child with the fatal procidentia ani, it would ap- pear difficult to cure it; nay, if the doubled parts of the inteftine are grown together, as in moft.of the hiftories,:a reduction: of it. is impoffible.. » Nature feldom will perform what I imagine the did ‘in the laft cafe, fe- parate the doubled ‘part, and unite what con- tained it. Nor dovd believe any will be fo hardy as to advife the amputation of the af> feGted part of the gut. Tis furprfing how the people in the pre- ceeding hiftories lived fo long as they did, with fuch large doublings of the inteftine, - and its mefentery prefled together within an- other —— Si NN —S PHYSICAL ann LITERARY. 365 other piece of inteftine, when the common inflammation of the inteftine often kills foon thofe it attacks; of which I could give nu- merous examples, but fhall relate only one. A Gentleman of weak nerves, and fubjeé to flatusand pain in his ftomach, was feized with a colic-pain about ten o'clock at night, for which he fwallowed)a {mall quantity of an’ ardent ‘fpirit. - At three .in the morning, twelve or fourtéen'ounces of blood were let from a vein-in his arm, and a laxative cly- - fter was injected, and operated well) “At eleven that forenoon I firft faw him, when’ his friends thought him much better,’ being free of pain ; bat as his'belly was greatly: fwelled andivery'tenfe, his pulfe quick, {mall and intermitting, “his eyes languid, this coun-' tenance faded, and a cold clammy {weat was over all his’body; I made the progvofis of his having very few hours to live. He died before five of the afternoon, fo that his’ _ difeafe killed him‘ in eighteen hours ; and I have heard of ‘others who died in lefs than twelve hours after the firft gh sis ‘of ‘, ‘idisuriaionnietil THE 366 ESSAYS anv OBSERVATIONS THE common practice of taking fpiritu- ous liquors, or the warm carminatives, when people feel colic-pains, is often unlucky, and public warning fhould be given againft it; for tho’ relief is found from fuch things in the windy or fpafmodic colics, which is not a deadly difeafe, yet they hurry on the inflammatory ones fo faft,) that they foon prove mortal. I muft likeways think, that writers on the inflammation of the in-, teftines don’t reprefent ftrongly enough -the languor and low {mall pulfe which fuch pa- tients. generally have more than in moft, other difeafes. Itis fuch, that I have feen feveral cafes, where people. of. fkill, decei-. ved by thefe fymptoms, have been afraid to order blood-letting, left the patient had not, ftrength to bear it, and thereby neglected this evacuation till it was too late. When there is a fixed pain in the ftomach or in-: teftines, with a quick tho’ {mall pulfe, no time is to be loft ; blood ought immediately to be let plentifully, and venefection fhould be repeated till the pulfe becomes full and free, which isa hopeful fign of a cure’s be- ing made, tho’ neither pain nor fever have yet ceafed. | Tre * PHYSICAL ann LITERARY. 369 Tue intufufceptio or inflammation, but e- {pecially the latter, is generally the caufe of what is commonly called the. iliac paffion or miferere; for the volvulus or twifting a part of the inteftines into a knot, which was formerly faid to be the cafe, is generally thought now, when anatomy is more culti- vated, and infpeétion of morbid bodies is more univerfally allowed, to be an imaginary evil. It is very rare, but not impoffible, as will appear from the hiftory fubjoined to this, and communicated to me by my Son. — ART. 368 ESSAYS ann OBSERVATIONS ArT. XXVIII. A Hyiftory of a genuine Volvulus of the In- teflines; by ALEXANDER Mowro junior; M. D. and Profeffor of Anatomy *. N old man complained of acolic, which . was neglected more than two days ; when Mr. William Wood Surgeon in Edin- | burgh being called, found him in the ago- nies of death. Next day I obtained leave to open his abdomen, in prefence of feveral ftudents of phyfic. We faw fourteen inches long of the zute/linum ium hanging in a finus down in the fe/vis, all black and mortified, occafioned by a ftrangulation at the upper part of the two pieces of the zum which formed the fnus. The firm ftricture there was made by the appendix vermiforms, the body of which lay behind the conftricted parts of the ium, while the end of it paf- fing over and before them, had funk back again into a plica of the mefentery, from which, with great difficulty, I could draw It ® February 6. 1755. PHYSICAL anp LITERARY 369 it out, for it was there extended into a glo- | bular fhape of three fourths of an inch dia- meter, by a glairy liquor, and was lodged in a depreffion of the mefentery, the entry to which was fmaller than the cavity where _ the globular end. of. the a had been lodged: Vo. Il. ey Aaa ‘ite | | Arr. 370, ESSAYS and OBSERVATIONS boi / KKK. J A Deleription i the eres Yellow Tee 0 in\ aLetter from at:thatoperiod, by which. the urinary veflels, become at the fame. time fullerand moreftraitened) t010g _2. Ir is, remarkable . thefe sistas ib iicas accompanied with’ any fymptom of the nephritic kind till the pain and dy/ury plainly appeared fo, after the third fit, which the intermediate means feem to have contributed to make much flighter than the two former. Turis will lead us, efpecially in nervous cafes, which are often found to be fym- pathic, to be more particularly attentive to, even, the fmaller fymptoms, which are fometimes a better clue to guide us to the origin of the diforder, than thofe violent ac- cidents that are more apt to engrofs our at- tention. 8. Tue diarrhea preceeding the fits, was probably only an effect of the irritation of the urinary paflages by confent of parts : fince the keeping of her open afterwards feemed of fervice, inftead of bringing on a relapfe. Whence I fhall only beg leave to obferve, how neceffary it is in practice to diftinguifh ai6 ESSAYS ann OBSERVATIONS diftinguith fymptoms ‘that ‘only’ precedéo= thers from thofe that produce others: in fhort, of what confequence it is ‘not to: mif- take'that fora caufe which’ is only priof in point of time; efpecially as’ this, I’ fear; is too common a cafe, and often requires our. utmoft care, in obferving the» Reso _ edentia; to avoid it. £2 ART. 5 PHYSICAL ano LITERARY. 419 \ Arr. XXXIV. Hijory. of a iia after Cie arin % ie a fhe, fame". ) ) Delicate young woman (who, for two years before fhe was married,.. had; from a fright, been, fubject, at times, to a kind of hyfteric epilepfy, efpecially at the approach of the catamenia) about four days after being {afely delivered of her firft child, had a milk-fever, which came on attended with languor, catchings and reftlefsnefs. She was carefully treated with mild diaphoretic and antifpamodic remedies both internally and externally. A miliary eruption came out upon her arms; the Jochia flowed regularly, and the belly was kept moderately open : _ yet fhe got no reft, was delirious, her tongue dry and black, and her pulfe quick and fall. A blifter was applied over her head, _ which, without any pain or ftrangury, pro- » duced a very large difcharge.,, The next : day, being the ninth from the beginning of S VoL.. 11. Ggeg “ the : oe May 1. 1755. 6 418 ESSAYS ann OBSERVATIONS the fever, the got fome fleep, and became more fenfible. A gentle perfpiration was promoted by fp. mindereri in diluents, and hot bricks applied occafionally to her feet. The pulfe was more quiet and regular, the tongue moifter, and a white cloud fubfided in the urine. On the 12th day, thefe flatter- ing fymptoms vanifhed—the delirium rofe higher than ever: fhe was perpetually co- matous of convulfed; breathed with diffi- culty; often rubbed her hands together, and’ picked thé bed-cloaths ; and the pulfe could fcarce be felt. A ftimulant clyfter was not retained, veficatories would not rife upon her, yet fhe was excoriated with in- voluntary urine. In this deplorable extre- mity, /2 napifins raifed a blifter on her feet, anda large flux was promoted from them by an emollient cataplafm, to which wnguent. ad veficator, was added pro re natd. As no medicine could be got down by the mouth, pulv. cort. Peruv. unc. fs. in decoét. capit. papav. alb. unc. vi. was thrown up by way of clyfter, and repeated twice the next day with fix drams. each. Thefe three, containing in all two ounces of bark, were retained for a week; in which time the bad fymptoms 8 4 4 : 4 PHYSICAL até LITERARY.’ 419 fymptoms went off by degrees, and fhe took . freely of both whey and other nourifhment. Her feet ftill. continued. running, and were drefied with unguent. alb. Three more of the clyfters with \/crup: vi. each. were given - in as many days. She now refted well, and her. pulfe was become regular, was much emaciated, and'fo weak, fhe could {carce be raifed without :bringing on fome hyfteric fymptoms. » By degrees fhe began to recover her ftrength : the clyfters were repeated | now and then, increafing the quantity of bark in each to wac.i. Her \appetite re- turned: “ina fortnight fhe could be got outof bed: in another week, inftead of the ¢lyfters, fhe took extr. cort: Peruv: fcrup. ii. twice-a-day," ‘occafionally interpofing fome rhubarb ; in about’ ten days more fhe was | got pretty well. ©The ext month fhe had a flight fit of the kind: fhe had been ufed to before marriage ; but, by the he!p of fome volatile fetid tin@ture im bitter wine, fhe:got rid of thefe, and ‘has continued free from them ever fince,;tho’ «fhe has had feveral more children. ART. 420 ESSAYS ano OBSERVATIONS ArT. XXXV. Hiftory of a Fever with bad Symptoms; - by the fame *. Middle-aged man, generally employ- ed in a malt-kiln, about the latter end of July 1749, fometime after having fatigued himfelf, and got into: a quarrel: in a crowd at a public diverfion, was feized with a fever; inthe beginning of which, he was blooded, then had: a vomit, and af+ terwards a great variety of diaphoretic me- dicines were tried with him. He was kept fweating, and feveral crops of eruptions fuc- ceeded each other, without any relief. Bli- fters were applied in feveral places, yet ftill a delirium and vigilie continued. Mutk, and even the bark in fubftance, was given him; but all without any effeé for above a month. The Apothecary who attended him in the mean time often urged the necef- fity of further advice ; but his friends would not confent to it, till, at laft, I was called in. | I * ~ May 1.1755: PHYSICAL ann LITERARY! 421 1. found him in‘continual tremors and fibfuls tus tendinum; Jjhis pulfe was fmall and ob- fcure; his tongue-foul and dufky ; and his urine had only.a-flight cloud in it. His eyes were fo dim,: he could farce diftinguith the perfons about him ;.and it was very difficult to make him: hear, .efpecially on the right fide. He. was reftlefs, , languid, and deli- rious; often groaned and fighed, and was ftill bathed in a perpetual {weat.... Some red {pots appeared upon his breaft, pen many purple and livid ones on his back, . _ As:he had been coftive for fome days, fift a ftooh or two was procured by a warm cly- fter, fome antimonial, drops (which I have often experienced to deferve very juftly the encomiums Dr. Huxham * has beftowed upon them as an excellent deobftruent) were given ~ now and then in red wine. Elixir of vitriol and volatile tincture of bark were admini- ftred, firft in faline draughts, and afterwards in tin@ure of rofes. Within three days, his _ fweats were gradually checked, the red pa- _ pule came to a kindly fuppuration, the livid fpots difappeared, the tremors, /ubfultus, and delirium went off. An abfcefs (which I had foretold * Obf. de acre, vol. i. p. 141. 422 ESSAYS ann OBSERVATIONS foretold from the particularcdeafnef$ on-that fide) broke in his’ right; ear, andj together. with a blifter behind it,: was‘kept! conftantly running. Ina day or'two'more, all the bad fymptoms' were vanifhed’; *-his’ pulfe erew fuller and ftronger, a ¢00d fediment appeared in his urine, and his tongue regained its“na- tural colour. ''The volatile tin@ure was foon changed for a much ee proportion of ‘the fimple tinGture of bark. “In a week, not'on= ly his fenfes returned, but an appetite ; and he began to recover his ftrength. A ftrong decoction of bark was added to the laft men- tioned tinéture, by which, with a few dofes of rhubarb interpofed occafionally, the cure was compleated. yatt Art. . ; : _ PHYSICALIAND LITERARY! 429 no 5id $SOIDEWVWIOV,. 9a VATE hey bo FO Soitom xD a XXXVL. mprorst Mee grere| f; ath! - i + souborg dliw. isisw Lo ath * Aecounts it *fooner. The tafk you impofe upon me, *‘ qiz, the giving an account of the commo- “tion that was obferved in the waters of ‘© Loch-lomond on the 1ft of November, is al- « ready executed by Mr. Macfarlane the Mi- “ nifter. of Arrochar, according to the beft “accounts he could get of it from the {pe- “ Gators; as Iwas not an eye-witnefs of © ‘« this uncommon phenomenon, and as the ac- * count he gives of it is perfectly agreeable ‘to the relations of all thofe who faw it, Lee | * Lochlomond lies upwards of fifty Engli/> miles welt of Edinbargh, about the 56th degree of north latitude. PHYSICAL anp LITERARY. 43% « J will write you an exact ‘copy of his re- “lation, which, I think, is as full and dif- “* tinct an account as can be got of it. «On the 1ft day of November laft, Loch- ‘< Jomond, all of a fudden, and without any * guft of wind, rofe againft its banks with “‘ great rapidity, and immediately retired ; “Cand in five minutes time fubfided, till it *¢ was as low in appearance as any body then © “© prefent had ever feen. it in time of the “* sreateft fummer drought, and then it in- « ftantly returned toward the fhoré, and ‘in «© five minutes time rofe as” high as it was «before ; and the agitation continued at «¢ this rate from half an hour paft nine fore- «noon till fifteen minutes paft ten, taking “five minutes to rife and as many to fub- “fide ; and from fifteen minutes after ten, «till eleven, every rife came fomewhat fhort _ “in height of the immediately preceeding « rife, taking five minutes to flow, and five « ¢o ebb, until the water fettled as it was _ « Before the agitation: After the agitation _ «was over, the height to which the water _ “had rofe was meafured, and found to be _ “2 feet 4 inches perpendicular. Loch-long «held si neem: were agitated on the fame cc day 432, ESSAYS anv. OBSERVATIONS « day; and about the fame time ;.. but: the << phenomenon was not fo minutely obferved *‘as that any.exact account canbe got of it. “<< Turs relation.of Mr. Macfarlane’s of the “ phenomenon, contains in it evety thing re- «© markable I. have as yet, heard concern “* ing it. 4. Letter from Mr. Marx. M‘Cauium: to _ Georce Cierx, Efg; concerning an-un= ; ufual motion. of the Waters. of the Frith of ‘Forth af Queens-ferry, feven miles weft of ..Edinburgh, ' on tbe 1/f of November 1759: SAR, ee ‘T° the beft of my remembrance, on . Saturday the firft of November, a- ‘‘ bout ten o'clock before’noon, being then «© on the pier at Queens-Ferry, I obferved the ‘“‘ water torife very fuddenly, and return “aoain with the fame velocity about a “< foot or eighteen inches perpendicular, . as “‘ near as | can remember; the barks and ‘boats then afloat ran forwards and back- ‘« wards with great fapidity, and this conti- “nued for the fpace of three or four mi+ «nutes ; but.after the fecond or third rufh cc of PHYSICAL and LITERARY. 433 * of the water, it gradually abated. There ‘“* was no wind at the time the waters were *< agitated as above.” 6. An Account of an unufial Motion in thé Waters of Clofeburn-Loch in Dumfries- Shire, on Sunday the 1/f of February 1756, in a Letter to GEoRGE CLERK, Bq; SIR, Crosesurn, February 4. 1756. uM sour a quarter before nine on Sunday morning, we were alarmed with an “ ynufual motion in the waters of Clofeburn- _.“Loch. The firft thing that appeared to me in this wonderful fcene, was a ftrong ** convulfion and agitation of the waters from «‘ the weft fide towards the middle, where * they toffed and wheeled in a terrible man- “ner. From thence proceeded two large “currents, or more propefly rivers, which «ran with a fwiftnefs and rapidity beyond «© all defcription quite contrary ways; one “from the middle to the fouth-eaft, and Vou. il. a “ the & 4. #1 may not be amifs to obferve, that, on the ft of 3 February 1756, according to advices from abroad, a confi- derable earthquake happened at Oporto in Portugal. 434. ESSAYS avn OBSERVATIONS “the other! to the north-caft points of the *© Loch. . There. they were ftopped® fhort, *‘as the banks are pretty high, and ob- «‘liged to turn; which occafioned a pro- ““digious’ tumbling and, agitation at. both «ends of this body of water. . There was ‘likeways a current, which rofe.fome- - ** times.confiderably above the furface; near “the weft fide, that I frequently obfer- ‘ved .running with great velocity a hun- «‘dred yards to the fouthward,. and. re- ‘turning in a moment. with as, great ve- “locity the other way. | What I obferved “in the next place, was the toffing of ‘‘the waters in the ponds, which were «more or lefs moved as the agitation of “the Loch came near this fide, .or kept “at a greater diftance from it. But, as ‘it is beyond my capacity to give a particu- ‘lar defcription of all that happened on this “< occafion, I fhall conclude with telling you, * that the agitations and currents above men- « tioned continued, without intermiflion, for «© at leaft three hours and an half, jor four «‘ hours, when they began to abate a little in ‘‘ their violence, tho’ the toffings and cur- “* rents were not quite over at funfet.. I had “« almoft PHYSICALManp LITERARY! 435 © almoft: forgot Ito-tell: you; that this pheno» ** menon' was renewed on Monday-morning a * little beforé nine}; .and lafted,for»an hour ‘and anchalf ;> but the motion of the waters; “© ey were not) {oO violent.as’ the day before: ¢* What:is very remarkable, there|,was . not *¢ the leatt gale of wind, on Sunday till one £< o'clock, which: help ys us not, a aelca in our ‘“ obfervations,””: | davos Sniwodriaien sly Yo 6. Letter from Mr. Panton relating to the Earthquake felt at Dunbarton. . STR, Dunzarton, Faruary 17. 1756. yp an{wer to your’s relative to the earth- quake here, there happened but one «« fhock, and that very moderate, before one «© of the clock December 31ft 1755; it con- “tinued for a very fmall fpace of time. It _ ‘agitated fome people in bed very percepti- «bly, and wasfelt by Mrs. Wezr and fome «others, who were not’ gone to bed. It ‘had a fenfible effet upon tame birds in ee cages, and fowls: it fo alarmed both, as - “to make the former flutter prodigioufly, _ and the latter to croak in a frightful man- - “ner: it thook the board out of one cage, ete ; “ and 436 ESSAYS ano OBSERVATIONS << and fpilt the water in the glafs thereof. It * was equally felt by thofe who lived in “ ground-ftoreys, as by thofe in fecond and third ftoreys. There were fome fconces © in Mrs. Colguhoun’s houfe obferved to vi- *‘ brate during the fhock. er more « happened worth noticing. N. B. This earthquake was felt at the! fame time in Glafgow, Greenock, and other places of the neighbouring country. End of the fecond Volume, : {? a om oh ; TO py ee ne. A. Acids, their attraction of fixed alcalis, calcarious earths, &e, e (Pag. 224. > (i the quantity of air expelled. fous alcalis by them, 177. Air (fixed) attra€ted by calcarious earth, fixed alcali, &c. 224. Air, the feparation jof it from ih turns them ine to quick-lime, 185.. ‘. chalk deprived of it Ms affords lime- water, 206. Air-pump, the cold produced in its exhaufted receiver, 153.) Alcalis, the quantity of air expelled from them by acids, 177, Alcali (cauftic) contains no.jime, 192..and 200. Alcaline fubftances, _experiments on them, 1 57- Antimonial wine, an uncommon “effect of i it, 254 Ani (procidentia) remarks on it, 353. B. Belly, a child efcaping bya rent in it, 340. Brack (Dr. Josepu) his experiments on magzefia alba, quick- lime, &e. 157. Bodies, the reflexion of light from their furfaces, 84. light ones their fpontaneous motions on the furfaces of fluids, 26. -———coloured ones, the changes they ee in different lights, 32, doubts, difficulties, and conjectures con- cerning them, 59. Bones, drawings of very large ones, 11. Bosweut (Dr. Joun) his account of bones found in the ova- rium of a woman, 273. Bulge-water tree, its hark cures worms, 264. Cc, ho D REV es Catara&, obfervations on the new method of curing it, 324, Chalk, deprived of its air, becomes lime, 206. Chryftalline’ humour, extracted fuccefsfully after the new method, 327, &e. Crerx (Georce Efgq;) his drawings of very large bones, 11. Clouds, their various colours at fun- n-tlig and Setar inet eed ac- counted for, 75..° ° ‘ CLosesurn (Loch) anyuncommon motion of its waters, 433. Coipen (Mifs Jenny)! her erage) of the rina anew plant, 5. Cold,, produced by evaporating\fluids, and by other rend, 145. Colewort, of the filver-like appearance of the drops” of water on its leaves, 25. isis uA Colours, obfervations on them, 12, \ queries, doubts, and conjectures concerning raya 59 Convulfions, periodic nephritic ones, 412. . Concretions, hilorifs of tophigecous ones in the alimentaty canal, 345: Cows, large balls found in their ftomachs, 351. Cuxen (Dr. Witt1am) of the cold produced by evaporating fluids, and by other means, 145. _ D. Dogs, experiments made on them with opium, ‘297. Dropfy, a hiftory of one cured’ unexpeétedly, 407.: Dyfentery, an obftinate one cured by lime-water, Lz: Dvuevip (Peer) on the anthelminitic virtue of the bark of the bulge-water tree, 264. ! Dunbarton, an account of an earthquake felt there, 435. farth, calcarious, its relation to air and water, 188. when deprived of its air, is converted into quick- lime, 185. Earthquake, one felt at Dunbarton, 435. 4 Ever, Serie ye. s gp ww | i Ever, a miftake ofthis, 17. a remark on his nova theoria lucis, &e. 36. Evaporation of fluids, produces cold, 145. F. “ (Sterne) his hiftory of a erecnotaral collection of water with twins, 342. Fever, after child-bearing, 417. with bad fymptoms, 420. Fever ( American yellow) a defcription of it, 372. its fymptoms, 376. its prognofis, 391. Fluids, the fpontaneous motions of light bodies on their fur- ot ———— —____ im faces, 26. Ai ae cold hy jam by the evaporation of different ones, 149. Focus, of a fpeculum, not heated by the pete of light thro’ it, 22. Fetus, a defcription be a monftrous one, 226. _ Frogs, experiments on them with opium, 281. a hte Garven (Dr. ArexanpeEr) his defcription of a new plant, 1. Giccukist (Dr. Epenezer) his anfwer to an objection a- _ gainft inoculation, 396. ‘Gout in the ftomach, cured by mufk, 250. Guts, remarks on their éntu/ufceptio and inflammation, 353. > Graincer (Dr. James) his account of a dyfentery cured by 4 lime-water, 257. Oi -Hauuer (Dr. Atzeret) a miftake of his, 306. bi /Hamizton (Dr. Ancurpatp) his account of the effects of - femen hyofiyami, 243. , ————his propofal for curing obftructed men/es, 403. eart, its power of motion deftroyed by opium, 306. —in NI Di ost BO in frogs becomes fhorter and paler during its #ffole, and longer arid redder in its diaftole, 290. Henbane, feed, its effets when taken ina large dofe, 243. Hernia, a hiftory of one, 333. . =x | L Inoculation (of the {mall-pox) an objeétion againft it anfwered, 396. —the moft proper time for it, 401. ; Intufufceptio of the guts, remarks on it, 359. Inflammation of the guts, remarks on it, 365. K. Kerxer’s problem, a folution of it, 105. L. Light, obfervations on it, 12. its mutual penetration, ibid. its amazing fubtility, 13, &&e. ————on the heating of bodies by it, 18. ——— its reflexion from the furfaces of bodies, 84. ——— its rays projected with different velocities, 41. the caufe of the different refrangibility of itsrays, 40. ———the imperfeCtion of our knowledge concerning its in- flexions, 54. queries, doubts, and conjectures about it, 59. Lights, different ones produce many changes in coloured bo- dies, 31. Lime-water procured from chalk without calcination, 206. —cures the dyfentery, 257. Linp (Arexanper Efq;) on the analyfis and ufes of peat, 226. ' y Linine (Dr. Joun) his hiftory of the American yellow fever, 370. , Livineston (Dr, Tuomas) his hiftory of ahernia, 333- —his account of a dropfy, 407. eet Loch-lomond Ix Na Ik Bw Xz Eath-lomond and. Lach-ne/s, an. unufual agitation of their. wa- ters, 424. and 430. . fo ‘sit te ‘ Lungs, always contiguous to the shade 296i) | shinee Luxation, a compleat one of the thigh, 317. > M. a (Dr. Joss) his hiftory of a complet luxation _ of the thigh, 317. , Magne: fa alba, experiments on it, 1 ey . —————— its hiftory and medical virtues, 1 58. ee. ——-+—-——-— it deftroys quick-lime and lime-water,, 170. —__—_—_—_ ———-cannot be reduced 4 calcination to quick- -lime, ee " abr Zl ee ic queperr oe air ‘expelled from it by acids, “he ; i ones Cara A tans ~ Mexvitz (THomas) his “aad Nee on light a and colours; .12. Menjes,, a. new method of curing an obftrnétion of them, 403.. -Moon, .an eafy method of computing its, parallaxes, 91, Monro (Dr. ArExanpeEr fenior) his proofs of the. contiguity of the lungs and. plewra, 276. > : “his hiftory of a. child cfeaping iy a rent in 1 the womb, 341. his hiftory of tophaceous concretions in the ali- _ mentary canal, 345. ——his obfervations on 1 procidentice ani, intufis /eptio, and inflammation of the inteftines, 353, ox Monro (Dr. ALEXANDER junior) his diffeétion ne mon- ftrous fetus, 270. his account of a true volwulus of the inteftines. 268, Mowar (James) his defcription ofa monftrous 5 fetus, 206... Mokk, cures the gout in the Komach, 250. N. Needle, a fmooth one does not touch the furface of the water / __ on which fwims, 30. . cs Kkk f° _ Newron wil pU BM x Newron (Sir Tsaac) miftaken in his conjeture concerning the colours of the clouds at fasriting and Sinbesi rig 75- Nephritic oa Se O. Opium, experiments made with it on animals, 280. deftroys all feeling and power of motion in animals, 301. does not produce its effects by comprefling a brain or bringing on fleep, 313. its effects, not owing to any fubtile effuviafent to the brain or mufcles, but //e to its a@tion on the nerves to which it is applied, 302. and 308. ; ———kills frogs fooner than the deftru€tion of their brain and ‘f{pinal marrow, 304. . aie —kills dogs foonelt when sa. riage into the cavity of their ‘abdomen,’ 306." : oe ———deftroys the jrritable power of the fete Tes ‘310. ——retards and® at ‘laft’ puts a ftop to the motion of the heart; 305. *° the way in which it kills animals, 314. { of3 to Ovarium, of a woman, bones fowhd'in it, 273. a dmovw = ; zf01 O39 ” Pp. Parallaxes of the moon, ; an ealy method’ of eoeipuane them, gl. Peat, its analyfis, 226. its ufes, 231. Philofopers, a miftake of many- lof them, 22. Planets, why they appear white, 72.. Plant, a defcription of a new one, 1. Prince (JAMES E{q;) on the effects of mufk in the gout in the ftomach, 250. Procidentia ani, remarks on its cure, 354. Quantity, its endlefs divifibility afferted againft fome Sceptics, 71. j Queries concerning light, colours, and coloured bodies, 59. — Quick. YNZ DC Ei xX Quick-lime, experiments on it, ‘157. *. -only an acrid earth deprived of itsair, 187. ———produced without the affiftance of fire, 206, —_—