86 THE MANURE HEAP AND SEWAGE 
In the first place it is evident that sewage contains material that 
is very valuable if it can be used upon the soil. The large amounts 
of nitrogen in the urea alone from a large city would be worth mil- 
lions of dollars yearly if it could be utilized. The nitrogen was 
taken originally from the soil by the crops, and the continued fer- 
tility of the soil is dependent upon its being in some way replaced. 
It requires no argument to show the wastefulness of throwing this 
valuable material away without attempting to utilizeit. In China 
careful attention is paid to prevent the loss of such material, and 
as a result the soil remains fertile; while in our country a constantly 
decreasing fertility has followed the practice of wasting it. The 
only methods yet devised of utilizing city sewage on a large scale is 
by what is called sewage farming. 
Sewage Farming.—This method of disposing of sewage has 
been established as a means of at once disposing of and utilizing 
the sewage of large cities. These farms, necessarily located as 
near as possible to the city, receive its sewage and distribute it over 
the fields by conduits, thus furnishing the crops at the same time 
with nourishment and water. Upon such soils crops are raised, 
mostly garden crops, since these are sure of a ready market in the 
city. This plan of utilizing sewage has been very vigorously urged, 
and many such farms have been organized in England, in contin- 
ental Europe, and somein this country. Enormous sewage farms 
are cultivated near the cities of Paris and Berlin, the latter city 
having thousands of acres under cultivation. In some of the arid 
western sections of United States, where water is especially valua- 
ble, sewage farming has also become very profitable. 
There can be no doubt that this method of disposing of sewage 
is, theoretically, the proper one. It has two distinct advantages: 
(1) Economic. It puts back into the soil the great quantities of 
nitrogen and other materials taken from it by the crops. (2) 
Sanitary. ‘The sewage ingredients, after being incorporated into 
the soil, undergo the various types of bacterial decompositions 
which have been described in recent chapters. The organic 
