Under the first of these four classes there are a number of arrangements which, when taken collectively, may be termed the dry system of collection.

The cess-pit and the midden were the first attempts at collecting excreta, not so much, however, for the purpose of profit as with the idea of preventing nuisance. The cess-pit need only be mentioned to be condemned. The ash-pit midden, or privy, has its advantages and its difficulties; of the difficulties, the education of the people to use them properly is chief-a difficulty, however, that applies quite as much to water-closets as to middens.

The general principle of the ash-pit midden, or privy system, is illustrated in Fig. 1. It consists of a common privy, with a small covered ash-pit, from the top of which a ventilating shaft is taken to the roof of the house to which it is attached. The floor of the ash-pit is of glazed earthenware, absolutely water-tight. The ashes used as an absorbent are emptied into the pit through the privy seat, whenever the closet is used. These pits are cleaned as often as may be necessary. This system is used at Hull, England.

The Manchester method, Fig. 2, consists of a common privy, outside the house, constructed with a sunken pit, in which stands a galvanized iron receptacle, placed under the seat of the closet.

The floor of the pit is of earthenware, and the ventilation is through the flue, as shown in the illustration. The door for removing the receptacle is at the side or back. In the absence of the receptacle, the ash-pit can be used. The receptacle is emptied weekly.

A, excrement pail. B, ash tub. C, seat cover (raised). D, iron collar below seat, reaching slightly into pail when cover is down. E, hinged upright of seat. G, door admitting from outside to excrement pail.

The Rochdale method is similar to the Manchester, except that the wooden pail, generally made from a kerosene barrel, is substituted for iron, and sits immediately beneath the closet seat and on the same level of the floor, instead of below the surface of the ground, which makes removal more difficult. Fig. 3 is an illustration of the Rochdale system.

FIG. 4.-DRY EARTH CLOSET.

The Goux system consists in lining the inside of the tub with absorbents, as charred sea-weed or dry earth, rammed in by a central core, so as to give a uniform lining to the tub, thus preventing splashing. This method necessitates the frequent removal of the excreta. The fæcal matter is received in the central cavity of the lining.

At Birmingham, where the galvanized pails are used to the extent of some 40,000, representing a population of 250,000, the contents are collected weekly. These are emptied into a

vat at the place of deposit, and some sulphuric acid added to fix the ammonia.

The object of these several methods is the conversion of the old and dangerous system of privy pits into receptacles calculated to promote health and decency, and keep out from sewers as much of the excremental matter as possible. There is no doubt whatever of the fact that either of these systems is infinitely more healthy and more reasonable in every way than the cesspool, and, personally, I am strongly inclined to think that a dry system of collection in villages and small towns, even if not in larger centres of population, is to be recommended in preference to the usual water-carriage sys

tem.

Lastly, we have among the dry systems of collection, Moule's dry earth closet, in which the deodorizing and absorbent power of the earth is applied to the treatment of excreta. This closet is illustrated in Fig. 4.

However efficient as a deodorizer and absorbent dry earth. may be, there are almost insuperable difficulties attendant upon its use, which have retarded its general introduction, even in country districts. About four and one-half pounds of dry earth per head per day are required to obtain a consolidated and inoffensive compost. A village of 1000 persons would need, therefore, about two tons of dry earth per day. Moreover, it is a sine qua non that no liquids are to be discharged into the closet, so that it is a system which does not provide for liquid excreta; or if the air is very damp, which is the normal condition in certain places, or if the contents get moist in any way, we have, to all intents and purposes, a cesspool without its advantages, or without the special precautions that are commonly taken with regard to cesspools.

We come now to consider the precipitating processes. A great number of these have been tried, but the general result seems not to have been satisfactory, since none have thus far been free from a feature which practically condemns the whole of them-viz., the employment of expensive chemicals in large quantities for the purpose of precipitating from the water certain matters which are therein suspended.

The third plan is that by which the great dilution of sewage

with water is proposed to be avoided by having two distinct sets of drains, one to convey away the household sewage alone to some water-course, or to be treated by precipitation or subsurface irrigation; the other set of drains to carry off storm and street water. This was first proposed half a century ago by Mr. F. O. Ward, of England, and was subsequently practically carried out by Mr. Menzes, at Eaton, and, more recently, by Colonel George E. Waring, at Memphis. There can be no doubt that if the rainfall could be excluded from the sewage proper, a vast step would be gained toward the practicability of usefully applying sewage to the soil, but even then the area of land required would be so great and the cost of preparation so immense that the suggestion has been considered by high authorities to be hardly practicable. Moreover, it has been pretty well established that the putrefactive decomposition of solid excretal matter in soils gives rise to the production of malarial and parasitic diseases, and that such solid organic matters, after a time, will form a crust or cake upon and in the interstices of the soil, which gives off offensive and dangerous effluvia. Again, the subsoil water from broad irrigation is charged with decomposing matters; and Petenkofer is not alone in his opinion that "there is no more fruitful source of disease than polluted subsoil water which is constantly changing its level."

The mere fact that the available land near large cities, at least, is insufficient for the disposal of sewage by irrigation, is sufficiently condemnatory of the process as an exclusive means of utilizing sewage. According to M. Lefeldt, an acre of land is required for the excreta of every 20 or 30 persons when applied by broad irrigation; while Mr. Henry Robertson, of England, in a paper on sewage disposal (Sanitary Record, 1884), contributed to the Sanitary Institute meeting at Dublin (1884), states that "open porous land with a good free subsoil drained six feet deep, will deal, per acre, with the sewage of 600 people," but the cost of preparing the land he estimates at from $4000 to $5000 per acre, so that, practically, it does not much matter which kind of irrigation be used.

The theory of purification by irrigation is that the fluid part of sewage gradually percolates through the land, and is finally