GAS, COAL 



591 



pipes is regulated by the governor. From the magnitude of this pressure, and 

 the quantity of gas which in a given time, as an hour, must be transmitted through 

 a certain length of pipes, depends the width or the diameter that the latter should 



1052 f 



have, in order that the motion may not be retarded by the friction which the gas, like 

 all other fluids, experiences in tubes, whereby the gas might be prevented from 



1053 



issuing with the velocity required for the jets of flame. The velocity of the gas in 

 the main pipe increases in the ratio of the square root of the pressing column of 

 water upon the gasholder, and therefore by increasing this pressure the gas may be 



