172 



DISTRIBUTION OF GAS THROUGH MAINS. 



in the hour. The pressure in all the experiments was equal to a head of 

 water of five-tenths of an inch. 



The following Table will show how nearly the results of the experiments 

 agree with those found by calculation : 



It therefore follows that the quantities of the same gas discharged in equal 

 times by a horizontal pipe under the same pressure and for different lengths, 

 are to one another in the inverse ratio of the square roots of the lengths. 

 Hence, when we know the quantity of gas discharged from a given length of 

 pipe, we may find the quantity discharged by any other length with any 

 pressure, and of gas of any specific gravity. 



Example of the foregoing rule : It is required to find the number of cubic 

 feet that will be discharged from a horizontal pipe six inches diameter and 

 1760 yards long, the specific gravity of the gas being -420, and the pressure 

 equal to five-tenths of an inch perpendicular head of water. We know that 

 44,280 cubic feet will be discharged by a six-inch pipe 3'46 yards long ; 

 therefore, by inverse proportion, say, 



As \/1760 = 41-952, the required length, 

 Is to 44,280, the known quantity discharged, 

 So is 



^ = 1-860, the known length, 

 To 1963 - 2, the required quantity discharged. 



We therefore find that the loss by friction in a pipe a mile long is 44,1 16'8, 

 the initial velocity being equal to 46,080 by calculation. 



A horizontal main sixteen inches diameter and 1 760 yards long, is laid from 

 the works to the equilibrium cylinder : it is required to know how many 

 cubic feet of gas of the specific gravity -390 will be discharged with a press- 

 ure equal to a head of water of six-tenths of an inch. 



We have already found by the last example, that a six-inch pipe one mile 

 long, with a pressure of five-tenths of an inch, will deliver 1963 cubic feet of 



