Page:Popular Science Monthly Volume 18.djvu/828

808 foreseen that the use of the water would not be uniform, and that in certain 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 objections by reports that Gennevilliers had become subject to infiltration 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 The project was withdrawn for a time, but was eventually renewed, with the feature of irrigation omitted.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 contemplated 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 determined 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 neighborhood 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 problem must provide for the purification of the sewage and the preservation of the river from contamination with it, and for the utilization of the rich manures which are contained in the waters. The former condition, in fact, is imposed as an absolute necessity; while the abandonment of the second would only constitute a certain economical loss. Irrigation 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 hundred 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, however, an essential difference in the conditions required for the two solutions which makes the combination impracticable. Ten or twenty times as much land would be required to utilize the waters by irrigation 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