592 



GAS, COAL 



forced more rapidly along the remoter and smaller ramifications of the pipes. Thus it 

 happens, however, that the gas will bo discharged from the orifices near the gasholder 

 with superfluous velocity. It is therefore advisable to lay the pipes in such a manner, 



1054 



that in every point of their length, the velocity of discharge may be nearly equal. 

 This may be nearly effected as follows : 



From experiment it appears that the magnitude of the friction, or the resistance 

 which the air suffers in moving along the pipes, under a like primary pressure, that is 

 for equal initial velocity, varies with the square root of the length. The volume of gas 

 discharged from the end of a pipe is directly proportional to the square of its diameter, 

 and inversely as the square root of its length ; or, cr.!lfc the length L, the diameter D, 



D 2 

 the cubic feet of gas discharged in an hour 7c; then k=z~. Experience likewise 



shows, that for a pipe 250 feet long, which transmits in an hour 200 cubic feet of gas, 

 one inch is a sufficient diameter. 



Consequently, 200 I k : : 



455,000 



From this formula the following table of proportions is calculated : 



