Moving Force. 245 
case in practice, the velocity at which the 
maximum of effect is produced, may be found 
as follows. It should first be ascertained by 
experiment how near the issuing velocity can 
be brought to that which is due to the pres-" 
sure. From the experiments which I have 
made, I have been Jed to conclude that no 
greater issuing velocity can possibly be ob- 
tained from a machine of this kind than what 
is due to .8 of the pressure. If this conclusion 
be correct, it follows that, whatever may be 
the issuing velocity of the water, a moving 
force, equal to 7 of the moving force which is 
necessary to generate that velocity in the 
water, when falling freely, is expended in 
. producing change of figure ; that is, in forcing 
the water through the tubes and through the 
or ifice C ; and if the velocity of the machine 
be such that PC=5AB, the i issuing velocity 
will be equal to the velocity of the orifice, and 
the whole moving force of the water in 
descending from A to B will be expended ia 
producing change of figure. ) 
For, the head due to V, the issuing velocity, 
will in this case be PR, which is also the head 
due to v, the velocity of the orifice. We shall 
therefore have V=v ; and if CP represent the 
total moying force necessary to raise the 
4A 
