94 THE SOIL OF THE FARM. 



tons per acre. The usual practice is to spread it on the 

 soil and plow it in ; but it is occasionally formed into a 

 compost with earth and dung. The neighborhood of the 

 coast is in some districts a distinct element in the value 

 of the land, on account of the sea- weed as a manure, 

 which is thus more cheaply obtained. 



Sewage as a Manure. — The difficulty in the way of its 



use is its enormous bulk in proportion to its valuable 

 constituents. A ton of city sewage ordinarily contams 

 only three pounds of solid matter — viz., one jDound of 

 organic and two pounds of mineral constituents, the 

 former vieldino^ less than three ounces of ammonia, and 

 the latter half an ounce of phosphoric acid and one and a 

 half ounces of potash ; so that in a ton or sewage there is 

 only about five ounces of fertilizing matter. One ton of 

 guano may thus contain as much of the food of plants as 

 twelve hundred tons of sewage. According to the mar- 

 ket price of the former the theoretical value of the sewage 

 ought thus to be about five cents per ton. Practically, 

 however, there is no comparison between the values of the 

 two manures ; because it is found that ten or even twenty 

 times the theoretic equivalent of sewage is required to 

 produce the effect of guauo ; and considering the far 

 greater cost of utilizing the sewage, only a nominal price 

 can be put upon it. 



There are several methods of utilizins: sewasfe : — 

 Irrigation is the method which has been most largely 

 practised. It consists in distributing the sewage over the 

 surface of well-drained fields, from reservoirs into which 

 the sewers empty, or into which their contents are 

 pum]ied. 



In the dry-earth system the sewage nuisance is dealt 

 with house by house. Dry pulverized earth in movable 

 boxes in privies is made the receptacle in which excreta 

 arc covered and rendered harmless, being still serviceable 



