Bath tubs are made of wood, or wood lined with galvanized sheet iron, or with zinc or heavy copper, tinned and planished, or nickel plated, of cast iron with porcelain enamel, and of stone ware. Any of these may be used, the selection depending chiefly upon their cost and upon the personal preference of house owners. For private residences copper bath tubs are used more than any others, the weight of the copper being from 16 to 20 oz. per sq. ft. for the best tubs. Enamelled iron tubs are also used extensively, especially in hospitals, asylums, etc. The porcelain bath tubs, although perfectly non-absorbent, most cleanly and attractive in appearance are not much in use, being very expensive, heavy and clumsy.

For bathing establishments enamelled iron and copper tubs are not to be recommended, the former losing their enamel by continued use, the hitter being easily knocked out of shape and requiring constant attention to keep on them a bright polish. In such places earthenware tubs will answer very well, being easily cleaned, and as they are used rapidly in succession they do not chill the water after the first bath, an objection raised sometimes against marble or porcelain tubs in private houses. Tubs in bathing establishments are often constructed of brickwork, lined with slate, or with white tiles or marble flags.

Many devices have been introduced to do away with the chain and plug arrangement of tubs, which device gets unclean from soapsuds here as in the case of wash bowls. Such improved bath wastes are, for instance. Weaver's, McFarland's, Foley's, H. C. Meyer's, Jenning's, Stidder's and others. None of these is preferable to the "standing overflow," a most simple and cleanly contrivance, consisting of a tube of same bore with the bath waste pipe, with a trumpet-shaped mouth at its top, which tube is inserted in place of the plug at the bottom of the bath tub. It renders a special overflow pipe unnecessary. The only objection, sometimes made against it, is that it may be in the way while bathing, especially with short, so-called "French "bath tubs.

While it is not my intention to consider the supply of hot and cold water to fixtures in general, nor to discuss the relative merits of ground cocks, compression bibbs and self-closing faucets, I must briefly touch, for reasons that will appear hereafter, upon the manner of supplying water to bath tubs.

If the hot and cold water faucets are placed near the top of the tub, the hot water speedily fills the bath room with steam (although this can be partly overcome by using a double bath cock with only one supply inlet); the noise of the falling water is also sometimes objected to. To avoid this inconvenience the supply has been made to enter the bath, hot and cold water mixed, through the same hole thai serves as an outlet for the foul water. Thus soapsuds and filth coating the waste pipe and left there from the time the bath was last used, mingle with the clean water. Such a device is unsanitary and must be utterly condemned.

If it is desirable to avoid the steam or noise in filling bath tubs, the supply inlet may be placed at the foot end of the tub, near its bottom. An advantage which this arrangement offers is that servants cannot draw water into pails or pitchers in a bath tub, a frequent cause of the chipping off of the enamel of iron tubs and the bruises made in the sides of copper tubs. It appears, however, that such a location of the supply inlet below the water line of the bath tubis, in certain cases, endangering the purity of the water supply. This risk always occurs wherever the bath tub is supplied directly from the rising main and the pressure of water is insufficient to supply at all times the upper stories of city houses. The American Architect of 1882, in calling attention to this danger (which danger is well known to exist in the case of water closets flushed directly from the service pipe), says, as follows:

" Thousands of fixtures are in daily use which are liable to have their supply fail altogether on certain days and hours, or to have it withdrawn temporarily by the opening of a faucet below. All such fixtures are exposed to the worst consequences of intermittent supply. If any person having access to fixtures so placed will try the experiment of opening a faucet at the time of low water, the rush of the air sucked back into the pipe will be plainly heard, or by placing the finger over the mouth of the faucet the inward pressure can be felt. Even where the head is considerable, an artificial lowering may be, and often is, caused by the opening of faucets in the lower stories, which will leave a vacuum in the pipe supplying the upper fixtures, and in such cases substances near the mouth of the upper faucets are liable to be sucked through them into the supply pipes. We have known the opening of a pantry cock in a lower story to siphon nut in tins way and discharge into the pantry sink tin- entire contents of a bath in a room above, much to the amazement of its occupant. The bath happened to be fitted with a bottom supply."

This may even happen with a supply from a tank in the attic, and the only means to prevent the occurrence would be to run special lines of hot and cold water from boiler and tank respectively to the bath inlet, or else to place a check valve in the cold water supply to the bath, which remedy, however, cannot be relied upon to work for ever.

There are many varieties of tubs, used for personal cleanliness, such as foot tubs, hip baths, bidets, shower baths, etc. They need no further explanation, as the principles for the sanitary construction of bath tubs apply equally well to them.

Bath tubs of wood, lined with metal, necessarily require some exterior finishing woodwork, which also serves to hide from view the supply pipes, the overflow, trap and waste pipe.

In Europe, metal bath tubs are made sufficiently heavy to stand without a casing. This method of fitting up bath tubs has much to recommend it from a sanitary point of view; such bath tubs stand free on the floor, perfectly accessible and with all pipes in sight, which seems entirely unobjectionable. Iron porcelain lined bath tubs are sometimes left without woodwork in our hospitals and asylums and give complete satisfaction.