36 BOAED OF AGRICULTURE. 



Disposal of Subsurface Irrigation, 



The buildings usually have two drains, one for liquids and 

 the other for more solid matter, which, after passing through 

 a flush tank, unites wnth the first mentioned, and both dis- 

 charsre in a tiffht settlino; basin, which overflows into a her- 

 ring-bone system of two-inch porous tile pipe, laid with 

 open joints twelve or fourteen inches below the surface, five 

 feet apart. Dependent on the character of the soil and the 

 volume of water, a subsoil system for efiluent drainage five 

 feet deep may or may not be necessary. 



Fourteen inches below the surface is beyond the reach of 

 many forms of vegetation. Although capillary attraction 

 may raise some of the liquid to grass roots, most of it 

 must go by gravitation to the subsoil water. You would 

 not expect much benefit from manure turned under fourteen 

 inches. As a fertilizer it has little or no value, even if the 

 roots should reach as deep. Until the nitrogenous matter 

 becomes ammoniacal by decomposition, a process which does 

 not take place without free exposure to air and the presence 

 of micro-organisms or infusoriaj it is absolutely worthless as 

 a fertilizer, a fact recognized by every farmer in working 

 over his manure heap when he washes to receive immediate 

 benefit from its use. The continued presence of water re- 

 tards oxidation. Timber put in the Thames at the time of 

 the Roman invasion of England, nearly two thousand years 

 ago, is still in a good state of preservation. It is at or near 

 the surface of the land, where organic matter decays, and 

 thus becomes food for plants. 



Schloessing records an interesting experiment, showing the 

 influence of the infusoria in the process of purifying sewage 

 when used in irriijation. 



A hollow column six feet in height was filled with earth in 

 a manner to reproduce exactly the soil as found at Genne- 

 villicrs. Through this was passed sewage in a relative 

 quantity to that employed in irrigation, and at equal intervals 

 with its use on the land. Epuration took place as com- 

 pletely as in the natural earth. Chloroform was then passed 

 through the column, which at once arrested epuration, and 

 the sewage traversed the column without being purified. 



