_Irrigation._--The disposal of sewage by irrigation is by far the best method now within reach. Two methods are in use, viz, surface and subsoil irrigation. The first in its most complete form consists in carrying the liquid sewage to a piece of ground set apart for the purpose and carefully underdrained. The sewage is allowed to flow over the ground in shallow channels. The fluid slowly disappears in the soil and enters the drains as comparatively pure water, which may be allowed to flow into a stream. For villages this is the best means of disposing of sewage. Those who as village officials may be interested in this method will find plans of such sewage farms, together with faithful accounts of their operation and the results obtained, in the annual report of the State Board of Health of Massachusetts for 1892, page 559, and same report for 1893, page 563. Suggestions for its application to country houses are given farther on. For isolated rural homes, or village homes commanding a certain amount of ground around the house, the liquid sewage from water-closets, the kitchen and chamber slops may be disposed of by the simple means of subsoil irrigation, first described by Mr. Moule and subsequently elaborated by Colonel Waring. The system as used at present in its most successful form consists, outside of the house, of the following parts (see fig. 6): Two adjoining water-tight receptacles of brick. One of these receives the sewage from the house and is intended to act as a settling chamber for the coarser particles, paper, etc. This communicates with the second receptacle, which receives from it the fluid sewage. This chamber is called the flush tank and is provided with a siphon. When the fluid has reached a certain level, the siphon is set in operation and discharges the contents of the chamber at one time into the subsoil pipes. [Illustration: Fig. 7.--Subsurface irrigation of sewage: _a_, absorption tiles (Gerhard's "The Disposal of Household Wastes"); _b_ and _c_, lines of absorption tiles showing their relation to flush tank (From Waring's "Sewerage and Land Drainage").]