112 On the Resistance of Fluids. 



particle is as the velocity of the plane, instead of the square of the 

 velocity, as we have now shown it to be." 



Now who does not see that in these sentences, Mr. Blake identi- 

 fies his " force" of a particle, with the force of a particle as the 

 term is understood in the common theory, and if we take as the 

 meaning of his " force," what he insists upon, viz. the action at a 

 point of time, i. e. in no time, is it not obvious that he has commit- 

 ted an error? Does not Mr. B. know that the force of a particle 

 in the common theory, is the vis motrix, the momentum, in short, 

 the whole force of a particle, and has he not expressly said, in his 

 last paper, •' when I determined the force of a particle, I determined 

 not its whole action, but only its action at any instant ?" Any com- 

 ment is unnecessary. There is not even the consolation of a dilem- 

 ma. I do not pretend to knoiv whether this will " amuse^' your 

 readers, but coming as it does from a professed reformer of the abuse 

 of compounding terms, it is sufficiently amusing. 



But secondly, is it not most clear that Mr. Blake has entirely 

 failed in his attack upon the demonstration of the received theory ? 

 The only argument he pretends to bring against it is this. It is " a 

 fundamental error," in that demonstration that the force of a particle 

 is as the volocity, because I prove that the force of a particle is as 

 the square of the velocity ; which, in the light of his definition is 

 just this : it is a fundamental error in that demonstration that the 

 whole force of a particle is as the velocity, because I prove that that 

 force of a particle which is not the whole action, but the action in 

 no time, is as the square of the velocity. 



The above is, in substance, the argument I should have given in 

 my last, could 1 have thought that Mr. Blake could have overlooked 

 a point so essential to even an appearance of success. Here, there- 

 fore, I might close, for my whole object has been to defend the ar- 

 guments and conclusions of the common theory, and your readers 

 must have perceived it. That theory was attacked by Professor 

 Wallace ; I showed that his objection to it rested on an unwarranta- 

 ble assumption : it was again attacked by Mr. Blake. I have now 

 shown that his objection to it rests on an error. With your permis- 

 . sion, however, Mr. Editor, I will make a few additional remarks. 

 And first, if any of your readers suppose that, having regard to Mr. 

 Blake's formal definitions of " force of resistance," or " force," viz. 

 " irrespective of duration," " at any indivisible instant." I ought 

 to have understood, in spite of the evidently consequent error, that he 



