C *3 3 
II. The Bakerian Lecture on the Force of Percussion, By William 
Hyde Wollaston, M. D. Sec. R. S. 
Read November 14, 1805. 
When different bodies move with the same velocity, it is 
universally agreed that the forces, which they can exert 
against any obstacle opposed to them, are in proportion to 
the quantities of matter contained in the bodies respectively. 
But, when equal bodies move with unequal velocities, the 
estimation of their forces has been a subject of dispute be- 
tween different classes of philosophers. Leibnitz and his 
followers have maintained that the forces of bodies are as the 
masses multiplied into the squares of their velocities, (a 
multiple to which I shall for conciseness give the name of 
impetus); while those, who are considered as Newtonians, 
conceive that the forces are in the simple ratio of the velocities, 
and consequently as the momentum or quantitas motus, a name 
given by Newton to the multiple of the velocity of a body 
simply taken into its quantity of matter. 
It cannot be expected that at this time any new experiment 
should be thought of, by which the controversy can be de- 
cided, since the most simple experiments that have already 
been appealed to by either party have received different in- 
terpretations from their opponents, although the facts were 
admitted. 
