OF THE HYDROSTATIC PRESS. 133 



The thickness of metal ought never to be less than the 

 interior radius of the cylinder. 



By the first equation of class (104), it has been shown, that the 

 pressure on a square inch of the piston in Ibs. avoirdupois, is 



P 



~.7854D 8 ' 

 or by substituting the foregoing value of n, it is 



from which, by multiplication, we obtain 



8324 X .7854D 2 rz:P; 



but in order to express the pressure in tons, it is 

 6537.6696D* 



2240 (110). 



141. Therefore, when the diameter of the cylinder is given, the 

 entire pressure in tons is determined by the following very simple 



rule. 



RULE. Multiply the square of the diameter in inches, by 



the constant number 2.9186, and the product will be the 

 pressure in tons. 



And again, when the pressure in tons is given, the diameter of the 

 cylinder may be determined by reversing the process, or by the fol- 

 lowing rule. 



RULE. Divide the given pressure in tons by the constant 

 number 2.9186, and extract the square root of the quotient, 

 for the diameter of the cylinder in inches. 



142. The preceding theory, as we have developed it, unfolds every 

 particular connected with the Hydrostatic Press, and by paying 

 proper attention to the equations, rules, and examples, as we have 

 delivered them, every difficulty attending the construction of the 

 instrument will be removed ; to practical persons, however, that part 

 of the theory exhibited in the equations marked (109) and (110) 

 will be found the most valuable, as they do the more immediately 

 contain the particulars which direct their operations. The following 

 examples will prove the truth of these remarks. 



EXAMPLE 14. The diameter of the cylinder in a Hydrostatic Press, 

 is 10 inches ; what is its power, or what pressure does it transmit? 

 Here by the first rule above, we have 

 PzzlO 2 X 2.9186zz291. 86 tons. 



