We will now consider the sanitary arrangements in houses, and to a certain extent in towns also.

I will first say a few words about water cisterns.

With the system of constant service there is no need to have cisterns for drinking water, and that is one of the great advantages of the constant service. But with the system of intermittent service the drinking water must be stored in cisterns.

The first thing to be considered is the material of which the cisterns are made-wood, stone, slate, lead, or iron. Wooden ones are clearly open to many objections and not veiy much used. In some houses of the poorer classes casks and tubs of wood are often used for water.

Stone cisterns are too heavy for use, in any other situation than in the basement of a house, and though they are excellent cisterns, they are useless for general purposes above the ground floor.

Slate cisterns are often used, and were much recommended some time ago. They have some disadvantages : the first is their weight, the second is that the joints aje apt to become leaky, and I believe, although several reasons are given for this, the true reason is that more or less vibration is continually going on from the traffic in the streets, and perhaps proximity to railroads, which is sufficient to weaken the joints of these heavy slate cisterns, and they always leak after a time When this happens, the man sent for is the plumber, and he very naturally empties the cistern, gets into it, and fills up the joints with red lead.

Leaden cisterns and leaden pipes are very largely used-I think even more largely used than any other kind. Some time ago there was a considerable outcry against leaden cisterns and pipes, because certain waters dissolved the lead and became poisonous ; the outcry was perfectly just, because we are not justified in running the risk attached to leaden cisterns and pipes, unless we know that the water we are to have in them will not dissolve the lead. I said that they are very largely used, and the reason is that it is found that the majority of waters supplied for drinking purposes do not affect lead, or if they do affect it, only do so for a short time, and an insoluble coating is formed on the surface of the lead inside the cisterns and pipes, which renders them proof against further attacks of the water, so practically as a matter of fact we are not poisoned, although nine out of ten people drink water out of pipes or cisterns made of lead. Waters that attack lead best are very soft pure waters; rain water, for instance, attacks it with great rapidity; that is not the kind of water we are supplied with for drinking purposes.

Waters containing certain salts have very little action on leaden pipes and cisterns, but it is clearly wise if any other material can be found which possesses most of the advantages of lead, and not the disadvantage, to use it.

The advantages of lead must be clear to everybody. It is a material very easily worked, extremely lasting, and, as far as pipes are concerned, can be bent in any direction with the greatest facility, and joined with a perfectly water-tight joint.

The material that is now replacing lead for the purposes of cisterns and pipes is wrought-iron. Some years ago the use of wrought-iron pipes for conveying water came into fashion, and they are being used more and more. They have the advantage of being cheaper than lead, and are very durable. The disadvantage they have is, that the iron is not so easily jointed, and bends have to be made of every kind, because the metal cannot be bent Wrought-iron cisterns, especially galvanised wrought-iron-that is to say coated with a layer of zinc-are becoming very much used indeed for water cisterns, and they are the best kind of cisterns we have at present. It is quite possible that Professor Barffs invention of indestructible iron, a process by which the iron is coated with an absolutely unalterable layer of oxide, will come into use for cisterns and water-pipes, as well as for many other things.

Excellent glazed stoneware cisterns are now made cheaply enough for use in the poorest dwellings.

We assume, then, that it is necessary to have a cistern to supply the drinking water of the houses, and the first thing to be careful about with a cistern is, that it must not be used for any other purpose. You must not have one cistern to supply the water for drinking, and for every other purpose for which water is required in a house. That is an exceedingly important thing, because, in some way or another, if the cistern is used for the closets as well, the water may get contaminated, and become unfit to drink. It has been argued that by a proper arrangement of taps and pipes, you can make it almost impossible that this shall take place, but if you cannot prove an instance to the contrary, you may always meet such an argument of that kind by the assertion that it is going upon a wrong principle alto-, gether. Even if you cannot see how the water can be contaminated, that may be because you are not sufficiently experienced ; but, however great your experience, you are perfectly safe in asserting the belief that it is going upon a wrong principle.

The water-closets may, however, be supplied by subsidiary cisterns, fed from the one main, cistern. Cisterns are supplied with water by means of a tap, which goes by the name of the ball-cock or ball-valve, from having attached to it a hollow copper-ball filled with air. The water, as it comes into the cistern, raises up the ball, and the cistern is filled to a certain height As soon as it has reached a certain point, the ball rising closes the valve. Supposing that this ball-valve does not act for some reason or another (and you must always, in all contrivances, provide for their getting out of order), as from rust, which prevents the ball rising easily, the water rises, and the ball remains sunk, then the valve does not get closed, and you have the house flooded, unless you have some contrivance by which the water can get away. So, too, suppose the ball does float, and does rise, and from the tap having become worn out the water does not get quite turned off, or if turned off, yet the water continues running, then you will have the water overflowing into the house, unless you have some arrangement to prevent such a disaster. Well, that contrivance is provided by means of a waste-pipe, or overflow pipe, as it is called. It «is generally placed near one corner of the cistern, beginning just above the level of the water when the cistern is full, and it comes down through the bottom of the cistern, so that whenever the water goes on running, as soon as it gets up to the level of the top of the waste-pipe, it flows over and runs away.