LAND DRAINAGE BY MEANS OF PUMPS. 35 



as are under discussion it probably does not depend much upon the 

 length of time the plants are in operation each year. What amount 

 to allow for depreciation is a difficult matter to decide The length 

 of time before such machinery will wear out depends chiefly upon 

 the original quality of the installation and the care that is taken of 

 it afterwards. We can not safely assume that such machinery will 

 last more than 20 or 25 years. Much of it will be discarded sooner, 

 either because it is outgrown or worn out. With proper care it is 

 probable that such machinery may be made to endure twice as long 

 as it will last if it is carelessly treated. It is customary to include 

 with depreciation an item for repairs. This should be very small 

 during the first few years of the life of a well-constructed plant, but 

 will grow larger as the plant becomes older. 



The cost of fuel per year depends to a considerable extent upon the 

 kind of machinery used and also upon the amount of time the plant 

 is run. Whenever a steam plant starts there is a certain consumption 

 of fuel in preparation before starting, the heat value of which is lost 

 when the plant is stopped. Hence, since the operation of a pumping 

 plant is very intermittent, the fuel consumption is not strictly pro- 

 portionate to the time run. The amount of fuel used also depends 

 largely Upon the skill of the fireman. An unskillful man may easily 

 use 25 per cent more fuel than is really necessary. Different types of 

 equipment require different amounts of fuel to produce the same result; 

 that is, some types are more economical of fuel than others. The 

 cost of the labor at the pumping plant depends upon the class em- 

 ployed and the length of time it is required. The cost of electricity 

 per year depends on the type of pump and the care used in installa- 

 tion, as well as upon the total time the plant is run. The distance 

 from the transmission lines of the large power companies will influ- 

 ence the power rate. On the larger districts the power rate is usually 

 less than on the smaller ones. 



In general, in a given location, that type of pumping plant will be 

 best which requires the least annual cost, including all the elements 

 enumerated above. To a certain extent, variations in these different 

 elements tend to offset each other. For example, a highly efficient 

 plant from the point of view of fuel economy is complicated and 

 expensive, and hence will have a relatively high charge for interest 

 and depreciation. Likewise, it will require skillful and high-priced 

 attendance, but may, on the other hand, in a large plant, require 

 fewer men. If cheap labor is employed, tho coal and repair bills 

 will be increased and the deterioration of the plant will be more rapid. 

 The advantage of fuel economy is relatively more important in loca- 

 tions where f u<-J is especially high, and in a large plant than in a small 

 one, bul in any plant it diminishes in importance us the time of run- 

 JHU'j* per year den-eases or bryonies much interrupted. 



