Royal Insitlution. 133 



The formation of elastic fluids arising from the decompo- 

 siliou of vegetable and animal matters, proceeds very slowly 

 uiuler pressure: in illustrating this principle Mr. Davy re- 

 ferred to the method lately adopted by M. Appert for pre- 

 serving meat or vegetables, which consists of enclosing 

 tUcm m close tin plate vessels, excluded from the contact 

 of air. Putrefaction cannot proceed unless aeriform fluids 

 escape. Mr. Daw conceives that this method may be im- 

 proved by using stronger vessels, and compressing into 

 them a quantity of fixed air, which by its pressure and 

 chemical jiropcrties would prevent decomposition. 



in illusirating the effects of combustion, Mr. Davy no- 

 ticed some recent experiments made by Count Rumford, 

 who conceives that the liaht emitted is proportional to the 

 heat of the flame, and that it may be greatly increased by 

 brujging several parallel wicks near each other. A model 

 of what the Count calls a polyflame light was exhibited. 

 It had four wicks, and the Count states that a lamp of this 

 kind, when properly constructed, will afford as much light 

 as 50 wax candles. 



Mr. Davy ct)ncluded his lecture by explaining the phas- 

 nomena of heat on the mechanical hypothesis of its being 

 a vibratory motion of the particles of bodies ; and accounted 

 for latent heat, when solids are converted into fluids, by 

 supposing that the motion is employed to make the par- 

 ticles revolve round their axis. He offered this view, merely 

 for the j)urpose of comparison with the idea of a specific 

 fluid, ihe existence of which had often been too confidently 

 advanced by some philosophers. On such a subject it was 

 proper to dou!)l. The facts of science should be kept per- 

 fectly distinct from the hypothetical opinions advanced to 

 explain them. 



" 'I'hc truly philosoj>hical inquirer into nature," says Mr. 

 Davv, " wdl not consider it as a disgrace that he is unable 

 to exphin every thing. lie will feel that truth is more 

 promoteti bv the minute and accurate examination of a few 

 objects, than bv any premature attempts to form grand and 

 universal theories." 



Mr. Davy delivered his 3d Lecture on Saturday, Feb. 8, 

 (it was upon cheniical attraction). After stating that the 

 most important phamoraena of chemical change depend 

 upon the operation of chemical atiraction, and on the 

 agencies of heat, the Professor said it would be necessary 

 to enter into a discu^siun of the laws of attraction, and to 

 illustrate them by experiments. 'I'his discussicni, he said, 

 migi)t appear minute and tedious; but it was essential, as 

 the subject was the scafl'olding by which the edifice of ehe- 



I 3 niical 



