430 Quinby on the Blowing Machinery of @ Furnace. 
But from the nature of the problem P x h =the momentunr 
of the piston in cubic feet of water raised one foot high per 
minute.* 
Therefore P x h=260.45 /pxd?p (IX) 
Whence p — 260.45 eet d? xp : 
Ree. j —260.45% yh x d* xp (xt 
. P 
= vPxk 
7860.45 x Vp XP ad 
(Pxhys (XI) 
P= (260.45 x d7)3 
‘ft is now easy to perceive how these formule are to be 
applied—it may, however, not be improper to remind the 
reader, that the value obtained for h, in equation (XI), by 
assuming values for d, and p, and P, is not the whole height 
of the fall, but merely the vertical height through which the 
water must act upon the wheel. To get the whole height of 
the fall, it will be necessary to add about one-fifth to the 
value obtained from the formule. his, however, can al- 
that in the formulz mome piston, the 
quantity P vanishes. This shows that when the friction and 
the inertia ef the piston are not reg , the result is inde- 
ertia of the piston. The only quantities that require to be 
corrected on account of friction, &c. are Peandh. If P be 
given, we must add.as much to the value of h, obtained from 
the formulze, as will be sufficient to overcome all the friction, 
&c. of the machinery. And if h be given, we must add as 
much to the value of P, cbtained from the formule, as will 
_ * Itis scarcely necessary to remark, that I have here referenee to my the- 
ery of water-yheels. : : 
