6. The best kind of water-closet for general use is probably some form of what are known as the wash-out closets. They are made in one piece of earthenware, have no machinery inside them, have a quantity of water in the basin into which the excreta drop, and do not require a separate trap beneath them. Each closet must, however, be carefully tested by itself: a very small warp or twist produced in the baking may so interfere with the siphonage as to make it practically worthless, and the basin cannot be altered or repaired. For use in public places some of the hopper closets are very satisfactory, the best which I have examined being the Rhoads Hopper and the Hellyer Hoppers. Where there are no {192} children, and it is certain that the fixtures will be used with reasonable care, valve closets may be used. No form of pan closet can be considered as satisfactory, nor have I found any form of plunger closet that I would specially recommend. 7. Water-closets should always be flushed from a special tank provided for the purpose, and never direct from the main system of water-pipes. The flush must be large and rapid, and this requires a large supply-pipe, and for many forms of closets a flushing rim. Whatever be the form of closet, it should not be encased in a wooden box or closet, as is usually done, but it should stand freely exposed to light and air. Sanitarians commonly advise that water-closets should be located in outer walls and have an open window for ventilation. Such a position is usually impossible, and is not specially desirable in our climate. The open window acts as an inlet quite as often as it does as an outlet, and the air of the closet is thus swept into the house. The room should be ventilated in such a way that the tendency of the air at the door shall always be from the house into it. This is to be effected by a shaft passing through the room up and through the roof; and it is well to have this shaft take its air-supply from just behind the closet or from beneath the seat. It is best made of galvanized iron, and at a convenient point should be expanded into a lantern and have a gas-jet placed in it. The air-supply for the closet is to be taken at the bottom of the door or through a transom or louvres. Ventilating pipes from a water-closet should never be run into a brick flue. While it is not so important as many writers seem to think that a water-closet should be placed on an outer wall, it is very important that it should be as light as possible, and the placing it in a dark corner in the basement or under the stairs is very objectionable. 8. No overflow-pipe from any cistern or tank, except the one used for flushing water-closets, should be connected with the soil-pipe or sewer. Trapping such an overflow-pipe does not prevent the danger. The same rule applies to waste-pipes from refrigerators and to the waste-pipes from the safes which are commonly placed beneath fixtures.