178 ANNUAL KEPORT 



1. SIMPLE SUBSIDENCE. 



This plan is that of emptying the liquid sewage into large tanks or 

 vats, in which the solid matter settles and the liquid overflow passes 

 into the nearest stream or tidewater. 



Such is the condition of some English rivers that this effluent 

 water, although loaded with deadly organic poison, is actually purer 

 than the stream into which it nay issue. This was the case at Leeds 

 where a costlier plan of sewage disposal was abandoned because it 

 turned out the v. aste water cleaner than the river. 



Under this system the solid matter called the "sludge," is carted or 

 barged off to some place of deposit on land or water. This plan may 

 serve well as a temporary one for small cities. 



2. IRRIGATION. 



As the word indicates, this system disposes of sewage by discharging 

 it by means of suitable piping over areas of agricultural lands, being 

 itself purified while enriching the soil. The plan is not new. 



The town of Bunzlow, in Germany, has had a sewage farm in op- 

 eration for three hundred years. 



The Craigentinny meadows, near Edinburgh, of four hundred acres, 

 have received a good share of the s^-wage of that city for a hundred 

 years, and that to great profit. 



A number of English towns, among them Croydon, Cheltenham 

 and Blackburn have adopted the irrigation system. 



The city of Berlin, built on a sandy plain, has of late years intro- 

 duced this plan on a great scale. Still later Paris has begun disposing 

 of a portion of her sewage on land lying west of the Seine. 



A drawback to this plan is that lands do not always need irrigation, 

 while sewage flows incessantly. If no other remedy is devised the 

 surplus must flow off by some waterwa3r The experience of Berlin 

 and other North German cities shows that the cold of northern win- 

 ters does not preclude the discharge of sewage upon land. 



[n mild climates and in the warm season anywhere, a modified form 

 of the irrigation system promises to serve as a useful adjunct for dis- 

 posing of sewage when not needed for irrigating. This modifica 

 tioQ consists in flowing the sewage off the fields on to small areas of 

 land thoroughly underdrained to a depth of six feet or more. The 

 soil to the depth of the drainage becomes a great filterbed, holding solid 

 and suspended matter, leaving the filtered water to escape by the 

 drains. 



