or V\ 
118 On the Measure of 
vibrate about the fixed fulcrum F, the quantity 
of motion of m, will be equal to the quantity of 
motion of n. Let CD be another balance 
beam, and let CG and GD be each equal to 
AF, and the weights of o and p be each 
equal to that of m, and let A and C move with 
equal velocities. If the quantity of motion 
of m be equal to that of », the quantity of 
‘motion of p must also be equal to that of n; 
a 1 the sum of the quantities of motion of 
9 and p must be equal to the sum of the 
quantities of motion of m and x. But let 
both beams be at rest, and let the pressure of 
2 be applied for a given time to C, to generate 
velocity in o and p; a pressure of 3 will be 
required to be applied to A for an equal time, 
and through an equal space, to generate an 
equal velocity inm. The generating forces, 
therefore, are as 2 to 3, although the quan- 
tities of motion generated by these forces are 
equal. 
5. Let G (fig. 5.) be the centre of gravity 
of two bodies, A and B, connected by an 
elastic rod, at rest, but free to move in any 
direction ; and let a given quantity of motion 
be communicated at any point, D, ina direc- 
tion at right angles to the rod, Mr. Vince has 
demonstrated that the velocity of G will be 
_ the same wherever the motion is communi- 
