under suitable circumstances. It is useful for temporary large gatherings of people at flower shows, cattle shows, race meetings, volunteer reviews, &c., especially where there is supervision, and where persons can be told off to attend to the distribution of the earth. Earth-closets are suitable for use in villages and country houses in the open air, but they ought not, in my opinion to be placed indoors even in the country. Where the earth can be collected and dried on the spot, and the compost afterwards used upon the garden, the plan has been found very useful if only sufficient care be exercised, and no nuisance need be produced,

To sum up with regard to the conservancy plans, their very name condemns them one and all, for use in large towns at any rate, or in the interior of houses. One of the most important of sanitary principles is, that the refuse matters should be removed as speedily and as continuously as possible from the neighbourhood of habitations, and the principle of all conservancy systems is that the refuse matters are to be kept in and about the house, at any rate as long as they are not a nuisance, which of course means that, in a large number of cases, they become a serious nuisance. It is also obvious that the carriage of the refuse matters entails considerable cost under any of these systems, and so the less frequently they are removed the less does it cost, and what is detrimental to the life of the population becomes advantageous to the ratepayers. If the manure so collected were valuable, it might, of course, be made to pay the cost of collecting, but this is not the case as a rule, the only instance in which any of these

systems have been made to pay being where the excretal matters have been collected in pails or tubs, unmixed with anything which would lessen their value. With all these systems, too, it is necessary to have some method for disposing of the slops and foul water generally, which cannot be allowed to run into the water-courses, as it would contaminate them, and so it is necessary to have sewers, the construction of which will be described in the next lecture.

As opposed to the conservancy systems, we have the water-carriage system, by means of which the refuse excretal matters are conveyed away in the foul water by gravitation through the sewers, and are thus removed from the houses as speedily and cheaply as possible by means of the pipes, which must in any case be provided in towns, to get rid of the foul water. The sewage is increased in bulk, but is not rendered perceptibly fouler by this admixture. Indeed, as a rule, the sewage of a town supplied with water-closets is less foul than that of a town supplied with middens. Although, however, sewers are necessary in towns to carry the foul water away, in country places the slop water may be allowed. to run into the surface drains, provided they do not pass near wells, and this is best managed by means of a contrivance which I shall describe in another chapter.

The water-carriage system has disadvantages of its own, and requires special precautions to be taken, which so far as they are connected with dwellinghouses, will be described in the next two chapters.

CHAPTER V.

Sewerage-Main Sewers and House Branches, Traps, Ventilation, &c.

EVEN where conservancy systems are used for the removal of refuse excretal matters, it is necessary to have some contrivance by means of which the foul water can be got rid of. In country places, it may be discharged into ordinary agricultural drains laid beneath the garden. It then percolates into the soil and serves to fertilise the crops. If, however, such waste water is thrown gradually down the traps and into the drains a small quantity at a time, the water escapes through the junctions of the first few pipes, and the fat and other solid matters become deposited in them, and soon choke up the pipes; so that it is necessary to collect the slop-water, and discharge it at intervals. The best contrivance for this purpose is Mr. Rogers Field's flush tank; the slop-water is discharged over a loose iron grating at the top, and passes through a funnel-shaped aperture with a syphon bend at the bottom of it, which can also be lifted out, into the tank below. The discharge-pipe from this tank does not start from the top of it, but very near the bottom, is carried upwards to the top and turns over and passes downwards to its outlet, which is at a lower level than the point from which the pipe began. This pipe is made in the earthenware end of the tank itself. Thus it will be seen

F

that a syphon is produced, so that when the tank is filled to the top, and the shorter limb of the syphon also filled up to the bend, a sufficient quantity of water thrown in suddenly will start the syphon, and so empty the tank of its contents to the level from which the lower limb starts inside the tank. The discharge end of the syphon has a weir placed across it with a notch in it. By means of these contrivances, not only will a smaller quantity of water start the syphon, but a false action which was found occasionally to take place, and which caused the water to dribble away without the tank being emptied, is prevented. Thus the whole body of water contained in the tank is made to rush through the drains, and the difficulty spoken of above is avoided. The tank also acts as a very good fat trap. In towns, however, it is necessary to have sewers for the removal of the foul water. Sewers ought to be impervious to water, so that their contents may not percolate into the soil around, and so drains which are made to dry the soil are obviously not fitted to be used as sewers. The larger sewers are usually made of bricks, and built with an oval section, this being preferable to the circular, and of course far better than any rectangular section. The bricks should be of the very hardest kind, and set in cement, and it is advisable to build the "invert" or lower part of the sewer, upon invert blocks made of stoneware. For smallersized sewers stoneware pipes are the best. They should always be used for sewers not greater than 18 inches in diameter. Larger sewers than these are cheaper made with bricks set in cement. Stoneware pipe

sewers would be much more used than they are in towns, but for the fact that the estimated size of the sewers generally is usually larger than is required, and much larger than would be required if the rain and surface water were carried away by separate drains. The pipe of the sewer only requires to be large enough to carry away the water that can be discharged into it, and anything beyond that size is an absolute disadvantage, as it makes it more difficult to flush the sewers properly, for a larger pipe is insufficiently flushed by a quantity of water that would easily flush a smaller one. For flushing purposes it is best to have an arrangement by which a considerable quantity of water is delivered into the sewer at once, so that it may fill it, or nearly So. The same quantity of water delivered more gradually does not produce by any means the same effect. In laying sewers whether main or house sewers, provision should always be made for making new connections without cutting into the pipes. This may be done by putting in junctions at various points-a plan especially suited for private estates, where the points at which junction may be wanted will suggest themselves. With street mains more ample provision should be made. Mr. Jennings's pipes, which allow the sewers to be opened at any point without cutting the pipes, may be used. The pipes in fact, have no sockets, the place of the socket being supplied by divided rings, in one half of which the pipes are laid at their junction while the other half covers the upper part of the junction. With ordinary socket pipes, Messrs. Doulton's lidded pipes may be used with advantage. In these a third

F2