1822.] Mr. Herapath*s Reply to X. 29 



Article VI. 



Reply to X. By John Herapath, Esq. 



(To the Editor of the Annals of Philosophy.) 



DEAR SIR, Cranford, Dec. 14, 1821. 



X. informs us that he wishes the objections he has advanced 

 against my theory, or rather the difficulties he has met with in 

 the perusal of it, " to be received without offence." I assure 

 him that any observations on my works published in the same 

 friendly spirit in which his appear to be, whether 1 reply to them 

 or not, I shall always respect ; and however much they may 

 differ from my ideas, shall uniformly regard them as the candid 

 effusions of a hberal mind. It is, therefore, my request, that X. 

 receive this reply to his ^* Remarks " with the same feeling of 

 friendly good will with which I can assure him it is dictated ; 

 and should my observations in any place appear harsh, which I 

 trust they will not, I hope this preface will be admitted a suffi- 

 cient apology for what is not the effect of intention. 



X. acknowledges in his second paper, in the Annals for Nov. 

 that he has " found'' in his first, '* some observations'* (misre- 

 presentations) " v/hich he would wish to retract ; " but adds, 

 that they are '* only one or two of little or no importance." In 

 this, I must beg to differ from him both as to number and im- 

 portance. However, as he has made so candid an acknowledg- 

 ment, I will not press the matter. 



In his first paper, p. 224, Annals for Sept. he suspects me of 

 having argued falsely from my principles ; and in his second, 

 repeats the charge. He says : " We may certainly grant that 

 the elasticity varies as the action of the particles against a given 

 portion of the surface containing the gas, but it may fairly he 

 questionedj whether this action can be measured by the momen- 

 tum X the number of returns." Does X. perceive that this is 

 not demonstrating, but merely surmising, that I am wrong? The 

 only reply 1 should, perhaps, make to such an observation is, 

 " Lay aside surmise ; endeavour to show I am wrong ; and I will 

 try to prove I am right." However, if X. will consult p. 341 and 

 342, Annals for May, I think he will find I am not mistaken in 

 th^ conclusion I have drawn. My object is to compare the effect 

 of a gaseous body so constituted as I have described, with a 

 pressive force. Now a pressive force is an incessant and a per- 

 petual kind of action. All opposing forces, therefore, which are 

 to be equated with pressure, must be such as, under equal cir- 

 cumstances, would produce the same effects, whether these 

 effects be estimated for a moment, for an hour, for a day, 

 or for any time indefinitely. Hence the necessity of taking 

 time into account; and of computing the elasticity by the 



