Chap. II.] Chemical Philosophy. 119 



particles of bodies; and that, from the generation, 

 communication, or abstraction, of this motion, all 

 the phenomena ascribed to caloric are to be ex- 

 plained*. 



This doctrine, however, has but few advocates. 

 The sultrages of modern philosophers are almost 

 unanimous in favour of the opinion that caloric, 

 or heat, is a distinct fluid. The latter opinion, in- 

 deed, seems to be confirmed, to a degree little short 

 of demonstration, by the late experiments of Dr. 

 Herschel on this subject ; who has shown, that the 

 rays o{ light, and the rays of heat, emitted from the 

 sun, are distinct and separable ; that the latter, as 

 w^ell as the former, are refracted by transparent 

 bodies, and r^ec^ec? by polished surfaces ; and that 

 both consist of particles which mutually repel 

 each other, and which produce no sensible eflect 

 upon the weight of other bodies f. 



It cannot be denied, indeed, that some difficulties 

 attend the doctrine of heat being a distinct and 

 positive substance. Nor is the following, which count 

 Rumford suggests, by any means one of the small- 

 est; viz. " that any thing which any insulated body, 

 or system of bodies, can continue to furnish, with- 

 (Hit limitation, cannot be a material substance." 

 Yet the electric fluid is granted, on all hands, to be 

 a distinct substance; and we know that this fluid 

 \?>cox\sX?int\yivivmshe{i,ivithout limitation, by means 

 of friction. On the whole, the old opinion scvms 

 still, with all its difiiculties, to stand on firmer 



* See numforcVs Essays; and Coniributions to Mcdiail uvd 

 PJit/sical Knoivltdgt. 



■\ riiilosoj^hical Transactions lor 1800. 



