140 ON MR. EWART’S PAPER ON THE 
resist equal pressures during the same time. The 
other party took into consideration the spaces 
through which the same moving force was exerted; 
and as these were as 2 to 1, or as the product of 
the weight of each striking body and the square 
of its velocity, they concluded that the vis viva, 
to which this is proportional, was the proper 
measure of the effect of a body in motion. 
The main object of Mr. Ewart’s paper (in 
accordance with the conclusions of Smeaton 
(Phil. Trans. 1776), Dr. Wollaston and others) 
was to show that if a constant pressure applied 
by any agent were multiplied by the space through 
which it acted, the result, being in a given pro- 
portion to the vis viva, was the most natural 
measure of moving force. He urged that if the 
effects of pressures were estimated with regard 
to the spaces through which they passed, instead 
of the velocities for a certain time, they would 
apply, as a measure of work done, in all the cases 
of practical mechanics ; and would, he contended, 
remove many inconsistencies and errors, from the 
reasonings upon questions occurring in them. He 
gives illustrations of his statements from almost 
every branch of practical mechanics aud hydrau- 
lics; pointing out discrepancies, and solving 
