290 2>.'a" Second Ih-plj/ to C. 



confidence to wliich C.'s quotations and observations are en- 

 titled; and perhaps enough to enable the reader to form a pretty 

 good notion of the laudable course C. has taken, as well as of 

 the value of those unusual associations of words, or if C will 

 liave it so of ideas, which he would dignify with the name 

 of mathematical arguments. That he might not however have 

 to complain of unequal attention to different parts of his per- 

 formance, I will just take the trouble to show that his reason- 

 ing is an elegant counterpart of his charges and quotations. 



C. attempted to raise an objection, in his first paper, against 

 Mr. Herapath's theory of heat on the supposition that the ve- 

 locity of the particles in bodies of equal temperature being 

 " m an mverse proportion " to their masses, the less particles 

 may overtake and strike the larger, whilst the larger can never 

 overtake the smaller. To answer this, wliich is evidently as- 

 suming that the motions of collision are the mean motions 

 (though C. has the " modesty " to say, in his reply, that no 

 such an idea of mean motion can be founded on his), I ex- 

 amined the case when the particles are supposed to be divested 

 of that corpuscular attraction which would affect the uni- 

 formity of their motion. With this supposition, which, as I 

 said, corresponds to the " mean circumstances of the case," I 

 clearly demonstrated the futility of C.'s objection. After this 

 I briefly considered the irregularity occasioned in the motions 

 of the particles by their mutual attractions ; and hence showed 

 that the larger particles may sometimes overtake and strike 

 the less, which consequently disproved C.'s superficial asser- 

 tion to the contrary. C.'s refutation of my arguments to this 

 effect, consists in avoiding their force, and making a round 

 declaration, that supposing the particles to have no attraction 

 " is directly contrary to the other supposition that the parti- 

 cles" would " have limited paths," did they attract one another ; 

 and that without attraction " the particles would altogether 

 fly oft" and be dissipated." These discoveries of the difference 

 between attraction and no attraction, must, the reader will 

 perceive, considering their connexion with heat and collision, 

 have great weight against what I had said ; and the difficulties 

 under which they were made, their novelty, and their import- 

 ance, would fully eatitle C. to say, 



" Dicam insigne, recens, adhuc 

 Indictum ore alio." 



This being the substance of C.'s reply to my exposure of 

 his absurd objections to the theory of heat embraced by New- 

 ton, I think it unnecessary to dwell upon them any longer; 

 and I shall therefore proceed to consider his notions of col- 

 lision. «' If;" 



