8o8 THE POPULAR SCIENCE MONTHLY. 



foreseen that the use of the water would not be uniform, and that in cer- 

 tain weathers and seasons the cultivators would be as anxious to keep 

 it off from their lands as they would be at other times to draw it on. 

 This proposition brought out a general protest. The region which it 

 was proposed to irrigate was largely occupied with country-seats whose 

 proprietors did not at all relish the introduction of the objectionable 

 matter so near their homes. Additional force was given to their ob- 

 jections by reports that Gennevilliers had become subject to infiltra- 

 tion of the waters, and afflicted with fevers generated by them. The 

 project was withdrawn for a time, but was eventually renewed, with 

 the feature of irrigation omitted. In its modified form, it contem- 

 plated only the employment of the 1,500 hectares of the forest of St. 

 Germain as a reservoir, on which the sewage-matter should be turned 

 to be absorbed in the ground. This proposition aroused a more deter- 

 mined resistance than the others. Those who lived along the line of 

 the proposed conduit apprehended that the foul waters might at some 

 time be turned upon their own land ; the residents of the neighbor- 

 hood of the forest regarded with dismay the establishment at their 

 doors of a vast cesspool in the shape of a tract of land which should be 

 covered daily with nearly 200 cubic metres of water, with 60,000 or 

 70,000 cubic metres of nastiness in a year. The plan is, moreover, 

 defective, for it is not capable of satisfying either of the conditions 

 which are had in view. 



The conditions which are essential to a complete solution of the prob- 

 lem must provide for the purification of the sewage and the preserva- 

 tion of the river from contamination with it, and for the utilization of 

 the rich manures which ai'e contained in the waters. The former con- 

 dition, in fact, is imposed as an absolute necessity ; while the aban- 

 donment of the second would only constitute a certain economical loss. 

 Ii-rigation is really contemplated only as one of the means to the end ; 

 but it is a very inadequate means, for its successful adaptation to the 

 chief purpose would require the employment of a larger quantity of 

 land than it is practicable to obtain for the disposal of the sewage of a 

 large city. A city of ten or twenty thousand inhabitants might with 

 comparatively little trouble find the three hundi'ed or five hundred 

 acres in its vicinity which would be requisite for this purpose ; but, 

 with a city twice as large, the problem is more complicated, while, in 

 a metropolis, it becomes impossible of solution. 



Sewage-water, when used for irrigation, is undoubtedly rendered 

 innocuous. It might seem at first sight feasible to combine the two 

 operations, so as to accomplish both objects at once. There is, how- 

 ever, an essential difference in the conditions required for the two solu- 

 tions which makes the combination impracticable. Ten or twenty 

 times as much land would be required to utilize the waters by irriga- 

 tion as would be needed simply to absorb the foul matter and cause it 

 to be destroyed by slow oxidation. Thus, the 1,500 hectares of the 



