28 Mr. Davies Gilbert oji the expediency of assigning 
the space in English feet through which a 
body freely descends in one second of time, 
the velocity acquired. 
the length of the perpendicular tube, or the 
actual height of the head, 
the velocity due to the head, 
the length of either arm from the centre to 
the orifice. 
the velocity with which that point moves in 
revolving, expressed by feet in a second, 
the centrifugal force at the orifice. 
And since the force exerted by each particle of 
the fluid varies as its distance from the centre 
= the whole pressure from centrifugal 
force. An expression independent of the 
length of the arm ; and the slightest reflec- 
Let/ = 
Then 2 / = 
Then 2 ^hi = 
Let R = 
Then^ = 
R 
2^R ^2 - 
