Where an unobjectionable natural outflow cannot be provided, the irrigation of agricultural lands affords the best relief. The action of vegetation, the oxidation which takes in the upper and well-aerated layers of soil, and the well-known but not yet fully explained disinfecting qualities of common earth, are effective in removing the dangerous and offensive impurities, and in converting them into a more or less important source of fertility. Precisely how far this system may be available during winter, it is not easy to say. While the earth is locked with frost, there must be very little, if any, infiltration; but, as an offset, the action of a low temperature upon the sewage matters will clearly be antiseptic; and it is only necessary to provide against an undue washing away of the surface of the ground during thaws, and against the flowing of the sewage beyond the proper limits. Generally in the neighborhood of villages it will be easy to find lands over which the delivery may be carried on throughout the year without objection. The sewer, or some form of covered channel, should lead far enough from any public road to avoid offence. From this point it may be led by open gutters to the land over which it is to be spread,--or rather through such a system of surface gutters as will enable us to deliver it at different parts of the field, according to the requirements of the crops, and so as to use fresh land at frequent intervals, leaving that which has been saturated to the purifying processes of vegetation and atmospheric action.