THE PURIFICATION OF SEWER-WATERS. 807 



kilogrammes of solid matter, of which one kilogramme and a half is 

 merely in suspension. This stuff, flowing into the Seine, causes an 

 accumulation of 110,000 cubic metres of mud in a year at the mouths 

 of the conduits, and makes necessary for its removal an annual expendi- 

 ture of nearly 200,000 francs. Even this sum is not adequate for the 

 purpose. Far from securing the removal of the obstruction, it is not 

 even sufficient to prevent a continued accumulation, and the muddy 

 deposits are constantly extending farther down the river, and at the 

 same time becoming thicker. Since 1875 they have become about a 

 yard thick, and occupy nearly a quarter of the bed of the river from 

 Asnieres to beyond Chatou. The Seine has, moreover, been made foul, 

 and its waters have become unfit for domestic use, poisonous to fishes, 

 and a source of fetid emanations. 



The authorities of Paris have been for many years considering 

 measures to remove these sources of impurity from the river. As they 

 are rich in fertilizing matters, the thought was suggested that they 

 might be turned to good account for purposes of agriculture. It was 

 therefore resolved to apply them to works of irrigation in the peninsula 

 of Gennevilliers, where, passing through the thin soil of red earth un- 

 derlaid with gravel, they might leave their rich manures on the arid 

 land, and be returned to the Seine purified. Five hectares (twelve and 

 a half acres) of land were chosen to be irrigated by the sewer-water, 

 which was conducted in trenches around garden-beds. These lands 

 in return produced abundant crops of the coarser vegetables. Three 

 years afterward, in 18G9, independent gardeners began to take in the 

 sewer-water, and the demand for it increased, so that, in 187G, 115 

 hectares were irrigated, and in 1880 more than 300 hectares. Had the 

 use of the sewage-water as a fertilizing material been the only condi- 

 tion to be fulfilled, the success might have been pronounced complete. 

 The principal object, however, was the purification of the Seine, and 

 in this only the most insignificant result was obtained ; for the gardens 

 were capable of taking only a minute fraction of the sewage that had 

 to be disposed of. Complaints of bad effects upon health were in- 

 creased rather than diminished, so that, in 1875, the Minister of Pub- 

 lic Works appointed a commission to devise some means of remedying 

 the unpleasant situation. 



A plan was submitted by eminent engineers, under which it was 

 believed the Seine could be definitely relieved of the noxious sub- 

 stances which were defiling it. This plan contemplated the convec- 

 tion, by means of new machinery and conduits which were to be con- 

 structed for the purpose, of the foul waters to the peninsula of St. Ger- 

 main, where it was thought 6,300 hectares of land might be applied to 

 the reception and disposition of them. Of this tract, 1,500 hectares f 

 denuded and sterile land in the forest of St. Germain misfht be em- 

 ployed as a place of deposit, where the sewage that was not used in 

 irrigation could be turned on and absorbed into the ground, for it was 



