DISTRIBUTION 57 



such questions as breakfast pressure, dinner pressure, 

 Sunday morning cooking, or engine pressure. But apart 

 and beyond these, there are variations that cannot be fore- 

 cast. A large gas engine may be started and stopped at 

 any hour in the twenty-four; and the same as regards appa- 

 ratus for special technical purposes, now so generally used. 



The considerations that should govern the selection 

 of the diameters of main pipes are something more than 

 the delightfully simple plan of making them as large as 

 you can for the money. From the way in which 

 this point is sometimes discussed, one might almost 

 imagine that the skill of a gas engineer was to be 

 judged by the size of his pipes, and that one who lays a 

 6-inch pipe is more up to date than one who chooses a 

 4-inch. Taking up an existing main is a troublesome 

 and costly business that cannot come on every year, 

 or once in five years. But conservatism in respect to 

 mains can be carried too far. After they have been in 

 regular use for sixty to seventy years, the question of 

 re-laying may well be considered. In the course of that 

 period they will have accumulated a considerable amount 

 of rust and naphthalene deposit, and many of the joints 

 will be weak and unsound. There are hundreds of miles 

 of old main in use throughout the country that might be 

 replaced or relaid, with advantage to the company. 



The pressure at the outlet of the governor is used or 

 dispersed in three ways : (a) in carrying the gas to the 

 consumer's meter ; (3) in carrying the gas from the meter to 

 the burner ; (c) in supplying the requisite pressure to feed 

 the burner. It should be clearly understood that a very 

 appreciable portion of the governor pressure is required to 

 do the work of carrying the gas to the burner. We can put 

 any desired pressure, up to the full weight of the holder, at 



