MEASURE OF MOVING FORCE. 143 
If A = 2B, the part of the moving force lost, 
as here defined, would be one-third. 
It must be borne in mind that the moving force 
here described as lost is the vis viva. The quantity 
of it is otherwise expressed by Carnot’s theorem.* 
Mr. Ewart adduces, in his paper, several cases 
which he conceives not to be explicable according 
to the principles maintained by the advocates of the 
opposite measure of moving force to that which 
he adopted ; and if the difference between them 
had been as great in reality as it was in words, 
there is little doubt his conclusion would have 
been just. Both parties seemed to be right, and 
to obtain correct results, when they reasoned 
consistently with their hypothesis; but there 
required a little adjustment between them. The 
arguments for adopting, under some distinct de- 
* Putting « for the common velocity after collision, we 
have, from Carnot’s theorem, 
Ay’—(A+B) v=A (v—uy +B’, 
the vis viva lost by collision, which we will call L. 
From this equation we derive ua, 
SFr Cea Are) AB ig 
“, La Ad'— (A+B) aos = 443"? 
which is equal to 33x Av’, as obtained by Mr. Ewart. 
