160 On Calorkyand the Heat evolved during Comlustion, 



Other phjcnotncna might be adduced to the same purport; 

 but this is the strongest proof, the best known, and suffi- 

 cient for my purpose. It will, I presume, be seen, that though, 

 one part of I^voisier*s doctrine is probably just, yet the 

 other is as likely to be erroneous ; and, from a retrospect 

 of the success of various fallacious theories, from their being 

 always established on s«[ihistical reasoning from experi- 

 menia! proof, which is as liable to deceive mankind now as 

 aforetime, we shall be justified in this conclusion; that though 

 Lavoisier's theory appears to coincide with experimental 

 proof, yet it may not be just, and that, failing to account for 

 many phaenomena with which it is connected, it is at best 

 imperfect, if not materially erroneous. It indeed accounts 

 for the emission of heat and light in common cases of com- 

 bustion plausiblv enough, it i^iust be admitted; — But where 

 is tliep-QofP Plausible reasoning is often sophistical ; and 

 I cannot by any means think we have sufficient grounds for 

 believing that the caloric and light of common combustions 

 are produced agreeably to this doctrine. It appears to me that 

 the evidence thereof is mt^rely presumptive, and in many in- 

 stances it is evident that the heat and light nmst be derived 

 from another source. That the state of combustible, &c., and 

 product of combustion, before and after the process, must 

 have material influence in the quantity of heat and light 

 ciyen out_, is not to be denied ; b*ut in rapid combustions I 

 am disposed to think the effect is not great in proportion to 

 the quantity generated by the process. 



Since T perceived the deficiency of Lavoisier's theory, I 

 have been induced to pay particular attention to this subject. 

 Reflection soon taught me that oxygen and caloric must have 

 some remarkable relation to each other, as oxygen is the 

 only known supporter of combustion in nature : — what kind 

 of relation this can be, does not appear so ready to deter- 

 mine. Yet I am inclined to believe that it will be brought 

 to light before long, and that it will be discovered in the 

 new field of investigation opened by the" recent experiments 

 of Mr. Davy ; at least it is there I have looked for it. I 

 ju3t noted that there was a remarkable relation between oxy- 

 gpi and caloric, or rather between oxygen and the genera- 

 9 lion 



