Quinby on the Blowing Machinery of a Furnace. 131 
be sufficient to overcome all the friction, &c. of the ma- 
chinery. 
n the subject of the proper diameter for the cylinder, it 
depeiids essentially on the quantity of blast which we wish to 
employ. If we wish to employ only 900 cubic feet of air 
per a eh the proper or svete of the cylinder will be about 
33 inches 
= To shew this, we will suppose that the pressure under 
which the air is discharged is 4 pounds per square inch ; 
then by applying formula (III,) the scale of the air-pipe 
is found =2 inches, (very nearly.) We must now assume a 
vali for N.—Suppose N =20: thereby taking D=33, and 
applying formula apie | we find L=3 feet 9 inches ; which 
about the proper length in proportion to the diameter 33. 
As, however, ee will always remain some compresse 
air in the cylinder, @ the end of each stroke,) it will be ne- 
cessary to increase the diameter, or the length of the cylin- 
der, a little beyond ee is given ‘by the formule. This isa 
matter that can only be estimated by sme and practieal 
men. Next, let us suppose that 4000 c air per 
minute, is the quantity of blast required ; ee let this be dis- 
charged under a pressure of 4 pounds per square inch: then 
by applying the formula, it is found that the diameter of the 
ot ae must be 43 inches. But this is essentially too 
We will now assume a diameter for the air-pipe. _ Suppose 
that the diameter of the air-pipe is 4 inches: then by apply- 
ing — = ,) the pressure per square inch i is found is be 
154 pound: 
And caicer L=5, and N=20, ant: a pplymagtie hae 
mulze we find the diameter of the cylinder 604 inches. If 
now we take 20 feet for the vertical space through which the 
water acts upon the wheel, and apply formula (X,) we shall 
obtain 7139 for'the number of cubic feet of water required 
per minute. 
From these results it is plain that when the quantity of the 
blast required per minute is great, it is better to employ two 
blast furnaces of New-Jersey and Pennsylvania, where charcoal on- 
ly is iit emplo 700 to 900 cubic feet r e 
largest es in ,* a much ‘greater blast 
t The &ir-pipes at some of the largest furnaces in Europe are from three 
and a half to four inches in diameter, In this country, where sherconk only 
is used, they are from two to two ‘ad a half inches in diamete 
