[ 94 ] • 



duced. That the velocity with which the water is difcharged is 

 really fuch as the theory gives, is fufHciently confirmed by the 

 well-known experiment that water fpouts to the level of the 

 refervoir, except fo far as it is impeded by external caufes. But 

 though the velocity with which water, unrefifted in its paflage, 

 iflues through the aperture may be thus afcertained by the 

 height or diftance to which it fpouts, yet the mean velocity of 

 the whole body of effluent water, taking in all caufes obftruding 

 its difcharge which feem to lie beyond the reach of calculation, 

 will be confiderably lefs than this, and can be eftimated in general 

 by the analogy of experiment only. 



The manner of making this eftimate is to find by experiment the 

 quantity difcharged, in agiven time,in any particular cafe,and reduc- 

 ing it to a column whofe bafe is equal to the aperture, the height of 

 that column will be the fpace which would be defcribed in the pro- 

 pofed time by all the particles moving with a common velocity. The 

 height of a column difcharged in any number of feconds / is equal" to 

 Zt¥</IY), F denoting the area of the aperture in fquare inches, 

 / the fpace which a body defcribes in one fecond, falling freely 

 from a ftate of reft, and D the height from which a heavy body 

 muft fall in order to acquire the velocity of the effluent fluid. 

 A cubic inch of Water weighs ,52746 parts of a troy ounce j 



tnererore 



I 



. _ = D, the height from which a body muft fall 

 14,65 /F ^ ■' 



to acquire the mean velocity with which the water fpouts out, 

 W denoting the weight of the water in troy ounces. Thus fup- 

 pofe a cylinder 20 inches high, kept conftantly filled with water, 

 is found to difcharge 20 ounces troy through a circular aperture 



of 



