72 CONSTRUCTION AND MANAGEMENT OP SMALL GASWORKS. 



and the coal that gives the higher factor is the one that 

 will give the better results, irrespective of cost. 



s. d. 



No. I. Gas, 10,000 cubic feet, at 2s. 6d. . .150 

 Coke, 14 cwts., at 9d o 10 6 



15 ) i 15 6 



No. 2. Gas, 9,000 cubic feet, at 2s. 6d. 

 Coke, 12 cwts., at gd. . 



14 ) i ii 6 



2-30 



No. i gives a higher factor, and is, therefore, the more 

 economical coal at the prices named. 



Frequently we require to know the value of No. 2 in 

 terms of No. i, i.e., the price that might be paid for No. 2 

 to make it as cheap as No. i. This is a simple proportion 

 sum. If x = value required, 



14 : 2-37 ::x : 2-30.'. #=135. ;d. 



The yields of gas and of coke are the chief, but not the 

 only, conditions that determine the comparative values of 

 coal. Questions such as the quality of gas and coke, 

 amount of impurities to be removed, proportion and 

 quantity of clinker, as affecting the proportion of coke 

 required for carbonizing, and other working conditions, 

 must have due consideration. Sometimes the works are so 

 located as to be dependent on one particular field or 

 district for a supply of coal, or even upon one or two col- 

 lieries. If there is only one line of delivery, either by rail or 

 water, the situation is in the hands of those collieries best 

 situated as regards delivery. At other places it is possible 



