1822.] on Mr. Herapath's Theory. 363^ 



and much about the same time communicated their discoveries 

 to the Royal Society, exactly agreeing among themselves as to 

 those rules. Dr. Wallis indeed was something earlier in the 

 publication ; then followed Sir Christopher Wren ; and, lastly^ 

 Mr. Huygens. But Sir Christopher Wren confirmed the truth of 

 the thing before the Royal Society, by the experiment of pendu- 

 lums, which Mr. Mariotta soon after thought fit to explain in a 

 treatise entirely upon that subject.'^ Nothing can be plainer 

 than this ; and, therefore, nothing more evident than that the 

 theories of Wren and Huygens were those which the best philo- 

 sophers of Newton's time embraced, and which Newton himself 

 looked on as estabhshed by the experiments of Wren. Now it 

 unfortunately happens for C.'s assertions and objections, that 

 the two principal cases of Wren's theory for hard bodies ; namely, 

 that wherein the equal bodies meet with equal opposite momenta^ 

 and that wherein * one of them is at rest before collision, exactly 

 coincide with Mr. Herapath's. Mr. H., therefore, instead of 

 standing opposed to Newton and " the ablest mathematicians in 

 all ages," has in the two leading cases of his theory the 

 expressed testimony of no less than Wallis, Wren, Huygens, 

 and Newton ; besides Mariotte, and probably a number of other 

 respectable mathematicians. But the most extraordinary cir- 

 cumstance is, that the present doctrine of collision, which has 

 evidently crept into existence since the days of Huygens, New- 

 ton, See, C. unequivocally gives us to understand is that which 

 has been embraced by " the ablest mathematicians in all ages,^*' 

 notwithstanding here is indisputable evidence that a different 

 theory was mamtained not 100 years since by the first mathe- 

 maticians the world has yet produced. How would C. wish us 

 to dispose of this new article ? Shall we debit his accuracy or 

 his knowledge with it ? Shall we lay it to his insinuation that Mr. 

 H.'s theory cannot account for the pheenomena of latent heat ; 

 to his assertion that Mr. H. makes hardness and elasticity the 

 same ; to his parodying of Mr. H.'s theorems for the purpose of 

 misrepresenting them; to his charge that Mr. H. confounds pres- 

 sure with impulse? Or shall we add it to his knowledge of New- 

 ton's theory of heat ; of Hutton, Playfair, and Emerson's princi- 

 ples, and of WaUis, Wren, Huygens, and Newton's theories of 

 coUision? I will not, however, ^^ push C. to the wall" on this- 

 subject. 



1 have now replied in detail to C.'s objections, &:c. to Mr. 

 Herapath's theories of heat and coUision ; and I have shown that 

 he has not advanced a single circumstance tending to weaken, 

 much less to invalidate, any one of Mr. H.'s vievys. Indeed in 

 the whole that C. has said, there is not, one would imagine, even 



* I cannot speak positively as to this case; but unless the impression of it in my 

 mind has changed since I read it in tlie Phil. Trans, it is precisely as I have stated. 



Neio Series, vol. in. 2 b 



