170 



DISTRIBUTION OF GAS THROUGH MAINS. 



In this last instance the square root of 5 being 2'236, 



As x/50 = 707 : 80 : : 2"236 : 253'0 ; 



and so for any other pressure, the specific gravity and aperture heing the 

 same. 



The velocities of different gases under the same pressure will be to one 

 another, inversely, as the square roots of their specific gravities ; there- 

 fore a heavy gas will be discharged through the same opening with a less 

 velocity than that due to a lighter gas. For example, if coal-gas of the 

 specific gravity '420, and with a pressure of five-tenths of an inch, flows 

 through a circular orifice one-fourth of an inch in diameter at the rate of 

 eighty cubic feet per hour, gas having the specific gravity "400 will flow 

 through the same opening at the rate of 81 '9 per hour, pressure remaining 

 the same. For by inverse proportion. 



As v/406= 20-000 



Is to 80, the quantity discharged of the heavy gas, 



So is x/420 = 20-493 



To 81 '9, the quantity of lighter gas discharged. 



The discharges of the same gas through different openings and under the same 

 pressure, are proportional to the areas of the orifices in circular inches, or to 

 the squares of their diameters. Allowing an excess in the larger openings for 

 the difference of the friction, the results of the following experiments will 

 agree very nearly with this law* : 



* Allowance must also be made for slight and unavoidable errors, always attendant upon experi- 

 ments conducted even with the nicest care. 



