On the Resistance of Fluids. Ill 



Art. VII. — On the Resistance of Fluids, in reply to Mr. Blake; 

 by Geo. W. Keely, Prof, of Natural Philosophy, Waterville 

 College. 



TO PROFESSOR SILLIMAN. 



Sir — ^When I saw Mr. Blake's first communication in Vol. xxix, 

 No. 2, of this Journal, in which among other novelties, he attacked 

 the Newtonian demonstration of the law of resistance on direct im- 

 pulse of a fluid, I did give it a very careful and attentive perusal, 

 his repeated insinuation to the contrary notwithstanding. I observ- 

 ed that his argument against that demonstration wore two aspects, 

 one bad for Mr. Blake, the other worse, according as his term " force 

 of resistance" meant the action in an indefinitely short time, or in 

 no time. The had is bad enough, as your readers must have per- 

 ceived from my last communication, if not before ; but bad as it is, 

 the worse is, as will presently appear, so very much worse, that 

 common courtesy forbade that I should, in that communication, even 

 state the alternative. Mr. Blake, however, has eagerly vindicated 

 his right to the worse, and thereby has, with some probably, gained 

 a temporary advantage : of how much real value this is, shall soon 

 be shewn. 



Understanding now that Mr. Blake, by " force of resistance," or 

 " force," means action in no time, I propose to prove. 



First, That Mr. B. has misunderstood the meaning of the demon- 

 stration he has attacked. 



To do this, I will first quote the demonstration as given by Pro- 

 fessor Olmsted, in bis Natural Philosophy. 



"Both the number of particles which meet the plane, and the 

 force of each, are as their velocity : hence the resistance is propor- 

 tional to the square of the velocity." This is also the argument of 

 Newton and all his followers. 



Now, your readers will remember that In Mr. Blake's first com- 

 munication, he undertakes to demonstrate that his "force of resist- 

 ance," or " force," is as the square of the velocity. Then follow the 

 two annexed sentences. 



" Since the area of the plane is given, the number of particles in 

 action at any moment is given, and consequently the force of each, 

 at any instant, is as the square of the velocity of the plane." 



" We may now note a fundamental error in the received theory, 

 which assumes, usually without argument, that the force of each 



