(5.) The sewers may be placed at the back of the houses, a great advantage which cannot be carried out under the combined system. (6.) The regularity in the amount of flow of sewage. (7.) The accuracy with which the quantity of sewage may be calculated and the sizes of sewers apportioned. (8.) Economy both to the general rates and also to individuals in carrying out their connections. (9.) Where old and defective sewers exist they are often fitted to carry surface water, but are quite inappropriate as sewers. No rules, however, can be laid down with regard to this question, as each town or district must be treated as the case requires. In conclusion, I will mention the different methods at present in vogue for the sewerage of towns. (1.) The combined system, where all sewage, surface water, manufacturers’ refuse, and subsoil waters are carried in the same sewer. (2.) Similar to the above, the subsoil water, however, being carefully excluded. (3.) The partially separate system. (4.) The absolutely separate system, where there are three sets of sewers, one for sewage proper, one for surface water, and one for subsoil water. (5.) The “Lieurner” system, which professes to remove all sewage by exhausting the air in the sewers and drains. (6.) “Shone’s” pneumatic ejector system, which is described as follows:-- “The ejectors are cast-iron receivers of a suitable form, placed underground at depths to suit the locality, into which ejectors the sewage flows through the ordinary pipe drains from the houses. As the liquid rises in the interior of the ejector, and when full, it lifts a valve and admits compressed air from an engine which supplies the entire district. The ejectors are thus emptied of their contents, which are blown out in about eighty seconds of time, and the sewage passes through cast-iron main pipes of suitable diameters to the land, or other outlet provided to receive it, or it may be distributed upon the waste land as it passes through.” (7.) The dry systems, which consist of-- (_a._) Earth closets; (_b._) Tubs, as the Goux, &c.; (_c._) Pails, as the Rochdale; (_d._) Middens. But all these dry systems require some system of sewers to carry off rain-water, slop-water, &c., and in my opinion are not suitable for very large communities. [174] If the sewers vested in and belonging to a local authority are allowed by their negligence to get out of repair, they are liable to an action for damages (_Vide_ ‘Fitzgerald’s Public Health Act,’ 3rd edition, p. 19). Keeping in repair does not, however, include construction of entirely new works. (_Ibid._)