Cavendish

1. Three Papers, containing Experiments on Fac titious Air. (Phil. Trans. 1766, p. 141.) It bad been observed by Boyle, that some kinds of air were un fit for respiration ; and Hook and Mayow look ed still further forwards into futurity with prophetic glances, which seem to have been soon lost and by the inattention or want of candour of their successors. • Hales had made many experiments on gases, but without sufficiently distinguishing their. different kinds, or even being fully aware that fixed air was essentially different from the common atmo sphere. Sir James Lowther, in 1788, had sent to the Royal -Society some bladders filled with coal damp, which remained inflammable for 'many weeks; little imagining the extent of the advantages which were one day to result to his posterity from the la bours of that society, by the prevention of the lb. tal mischiefs which this substance so frequently oc casioned. Dr Seip had soon after suggested, that the gas which stagnated. in some caverns near Pyr mont was the cause of the briskness of the water ; Dr Brownrigg of Whitehaven had confirmed this opinion by experiments in 1741; and Dr Black, in 1755, bad explained the operation of this fluid in rendering the earths and alkalis mild. Such was the state of pneumatic chemistry when Mr Caven dish began these experimental researches : He first describes the apparatus. now commonly used in pro cesses of this kind, a part of which had been before employed by Hales and others, but which he had rendered far more perfect, by the occasional em ployment of mercury. He next relates the experi ments, by which he found the specific gravity of in flammable air to be about of that of common air, whether it was produced from zinc or otherwise : first weighing a bladder filled with a known bulk of the gas, and then in a state of collapse ; and alsoax amining the loss of weight during the solution of zinc in an acid, having taken care to absorb all the su perfluous moisture of the gas by means of dry potato. He also observed, that the gas obtained during the solution of copper in muriatic acid was rapidly ab sorbed by water, but he did not inquire further into its nature. The second paper relates to fixed air, which was found to undergo no alteration in its elasticity when kept a year over mercury ; to be ab sorbed by an equal bulk of water or of olive oil, and by less than half its bulk of spirit of wine; to exceed the in specific gravity by more than one half, and to render this fluid unfit for supporting combustion, even when added to it in the propor tion of 1 to 9 only. Mr Cavendish ascertained the quantity of this gas contained in marble and in the alkalies ; but his numbers fell somewhat short of those which have been determined by later experiments : he also observed the solubility of the supercarbonate of magnesia. In the third part, the air produced by fermentation and putrefaction is examined : Mac bride had shown thetas part of it was fixed air ; and .our author finds that sugar and water, thrown into fermentation by yeast, emit this gas, without alter ing the quantity or quality of the common air pre viously contained in the vessel, which retains its power of exploding with hydrogen, exactly like com mon air: he also shows that the gas thus emitted is identical with the fixed air obtained from marble ; and that the inflammable air, extricated during pu trefaction, resembles that which is procured from zinc, although it appeared to be a little heavier.

2. .Experiments on Rathbone Place Water. Phil.

Thirds. 1767 P. Oge paper Mt 'Cavesdith obsess the solubility of the oupercarbonale of lime, which is found io several waters about London, and is decomposed by the process of boiling, the simple maisenate being deposited in the form a cruet • the addition of pare lime water also causes a pre cipitation of a greater quantity of lime than it con. terns. These conclusions are manfinned by epithet&

ad experiments, in which thenupercarbonate is form ed, and remains in sobition.

8.

Ali .4tOs to seplain avast v the principal Paessesnessa of F.1,-riotyby mecum gran Elastic Fluid.

rrane.

1771. P. 884. Oar author's theory of elentricity agrees with that *hick had been puhrtsh. ed a' few yews before by &pion, but he thee eater. . ed mere minutely Imo the details of nation, showing the manner in Which the supposed fluid Aug he distributed in a -cif cases, and me Fielding "the phesemena of electrified and dnargel abstain:es, as they are actually Observed. There is ' some degree • of unnecessary complication from the great generality of the determinations the law of electlic ameaction and repulsion not hawing been sit that time filly ascertained,- although Mr Caves. dish declines to the tree suppositioa, of daces eery. in inereesely as the slow of the distance : 4148 de ficiency he proposes to supply by future expels. menu, and leaves . it to more 'skilful nuithemeticians **render some other parts •of due theory eta more complete. He probably foiled, that the amenity of Ihe experiments, which he intended to pursies, was allarwords superseded by theme -of Lord Stanhope pd. Coulomb; but he. had maned the methe• meticel investigadon someudiet -farther a s latter peeled of fah life, though be did me palish his pa• parse aireasission, however, which is the.leas to be regretted. as M. 'Poisson, assisted by all the improve• mead' of tnedern-analysis, has lately treated the same subject hi a very masterly manner. The aolotrow• 'edged imperfections, 'in sense parts '01 Mr 'Caren. dish's •demosetratiee reasoning, have served to play the strength of e judgment and sagacity, still mom admitable than the plodding labours of an an• menatical calculator. One of the corollaries seems at drat eight to lead to a made Of distinguishing pan thee from negative electricity, stair* is sat justified by arperieeest ; but the fallacy swears to be refer. *Me to the very •comprehensive oharader au thor's hypothesis, which requires some litde moat& estion to accommodate it to threctuolcircammences of ate ishromic fluid, as it must le supposed to mist in 4 d Report V the Committee oppoiated brae lord Society, to consider fly' es Afetionifer securing the Boulder at Peek*. Pliil..rrasu. 1773.

P. 48. drfaitsonal Letter. P. 66. Mt Cavendish, sod mast of his• colleagues on thesommitme, rectum= mended the adoption •of pointed (modem:yrs ; hie Woos protested, sued preferaed idant 'conductors; hut the comutittee persisted in their opinion. Late' ofporiaseata, beamed, hose eitown, that the ptin is despete between them was of ihtlemetnnest.

S. dos desinnit.of sons sitdompts to imitate Ate RA Toped* by • Iskatoscity. Phil. Thor& LW& The Ineeliarity of these deco it shown to depend is some magma on the pupas tional conducting powers of the substances comes ed, and on the quantity of electricity, as distisgoish. ed from its intensity. Iron is found to midget 404 million them as well as pure water, and sea min IMO tines as well: and the path, chosen by the elm Vic fluid, depending on the nature of sU the sub. names within its reach, an animal, not immediately sheeted in the circuit, will often be affected, ea ac. coast of the facility with which animal substances it general conduct the duid. The shock of a torpedo, posh/deg a strong sensation. but incapable of beim/ ommeyed by a chain, was imitoted by the effect of s weak chaige of a very large battery: and an mi. Mal torpedo esf wood being made a part of the cirosit, tinesisook diffused itself very perceptibly through the water in which s was placed; tut the a:perms succeeded better, when the issugusent was male of wes Mather, which conducts rather better then wood, the battery being manse highly charged, in propoetin to the increase of 000dueting power.