Inftnft Ht«t mi (Itfeernihlt by tit Stti/h, Uft* i<fs 



peraturcj theefRftsof heat an4 cold introduced into the fyftem in liquid foodj, with various 

 other phyfiological events, are adduced by our author in fupport of the probability of that 

 dcj£lrine which he recommends to the attention of philpfophers. 



Chap. III. In the third chapter, the Count proceeds to point out a variety of ftrjkiiyg con- 

 fcquences and obfervations which flow from the imperfe£l conducing power of fluids. One 

 of the inoft immediate of thefe is the very great degree of heat which may exifl: at a fmall 

 diftance from other bodies intenfely cold. Thus it is found that ite evaporates while expofed 

 to an atmofphere in which the thermometer ftaads far below 32 degrees ; an event which he 

 rationally accounts for, by fuppoflng that foine of the particles of air which come into con- 

 tact with the ice are fo hot as not only to melt thofe particles of ice which they happen to 

 touch, but alfo to reduce part of the generated water to fteam before it has time to freeze 

 again ; or otherwife by fuppofing. the fame efil-6l to be^produced by the intenfe heat generated 

 from the abforptionof light by fmall projeding points of the ice. He even thinks the metals 

 would evaporate if they were bad condu^ors of heat, inftead of being very good con- 

 duftors as in fa£l; they are ; and in proof of this he urges the fad, that mercury, which from 

 its fluidity is what he would call a non-condu£lor, is known to evaporate by the mere heat of 

 the atmofphere. 



That the rnoft intenfe heat is often excited in the midft of maffes of cold liquids, is not to 

 be doubted. The fun's rays generate heat of extreme intenfity ; but when circumftances are 

 not favourable to its accumulation it is foon difperfed, and leaves no traces of its exiftencc- 

 which can be meafured either by inftruments or the organs of fenfe. Ths Count does not 

 think it improper to infer, that the heat excited by a ray of light in an indefinitely fmall par- 

 ticle of folid and opaque matter floating in a mafs of cold water, may be equally intenfe with 

 that which is generated in the focus of the mofl powerful burning mirror or lens. Hence 

 he accounts for various efFedts of the fun's lights which gradually produce changes of the 

 fame nature as thofe which arife from very elevated temperatures. Thus wood.is rendered 

 brown or fuperficially charred, luna cornea is ren'dereJ black, or as may be fuppofed fuperfi— 

 cially reduced, metallic oxyds are deprived of oxygen, the green leaves of vegetables emit 

 the fame fluid, &c. 



Among other familiar inftances of, intenfe heat, in circumftaiKes where no vifible figns^ 

 appear, the Count adduces that of the afcending current of air from a candle. Iron is fully 

 red hot at the temperature of about iooa° of Fahrenheit's fcale ; brafs melts at 3807°, copper 

 at 4587°, filver at 47 17°, and gold at 5237*; and itmuft be obvious that this laft: temperature: 

 obtains where gold undergoes fuilon. But fine gold, filver, or copper wire flatted, fuch as is 

 ufed to cover thread to make lace, melts inftantly on being held in the flame of a candle, or 

 even if held for a few feconds over the flame at the diftance of an inch, where there is no- 

 appearance of fire or ignition. The air, or many of its particles, mufl therefore be heated 

 to this intenfity, though thfir number may be infufEcient to caufe any very elevated degree 

 cf temperature in a large mafs of metal or a thermometer. 



From this hypothefis of intenfe heat in the fmall parts of fluids, or bodies fufpended in them 

 it will follow that chemical foluttons and precipitations are or may be effected by the fole 

 agency of heat, and will not differ from fufion and congelation j — that the points of tempe- 

 rature at whicli bodies aflume the folid, the fliid and the gafcous ftates will be of the utmoft. 

 <Bonfe<iuence with regard to thefe events,, and that perhaps there may be no other eflTcntial-, 



difiercnce 



