Though, according to medical authorities, this does not form a _necessary_ appendage to the hot-air bath, it is yet a feature that _must_ be provided in the least pretentious of public establishments. Ever since, and long before, Cicero observed, in a letter to his brother Quintus, "Latiorem piscinam voluissem ubi jactata brachia non offenderentur," men who have taken the hot-air bath have loved the ample plunge. But although it should be sufficiently large for any bather to take a dive, and for an expert to take a true "header," it is a vast mistake to overdo it, and construct a small swimming bath, out of all proportion with the other features of the establishment. One does not look for such an adjunct: it is a great expense to keep up, requires a lot of space, and tempts many to stay too long in the cold water. All purposes will be served by a bath which will allow the bather to swim without touching the sides with his hands, and to dive along under water without danger of striking his head at the other end before he rises to the surface. Wherever possible, the bath should be quite 25 ft. in length and at least 7 ft. wide. In inferior institutions it may be as narrow as 4 ft. and proportionately shorter; but in such a bath one can only flounder about, and healthy bathers will go elsewhere. In deciding the position of the plunge bath there is one point to be strongly guarded against, and that is, that it be not stowed away in a damp, cold-looking, cellar-like place. Such a position may be all very well when the proprietor wishes to conceal dirty water; but from every other point of view it is highly objectionable. The wise man will bring his bath forward into the lightest possible position, where its clear, limpid waters will look enticing instead of repelling. For preference, it should be placed where the bather will take it naturally, _en route_ to the frigidarium, as at the Charing Cross baths, previously illustrated. In baths all on one level, it is convenient to place the bath partly in the lavatorium and partly in the frigidarium; but, to most persons, the necessity for passing under the inevitable partition and flap spoils the full enjoyment of the plunge. If placed within the frigidarium, and approached by a door from the lavatorium, some sort of a screen should be provided over the bath, as, at times, the apparition appearing at the above door, in full view of the occupants of the cooling-room, is somewhat ludicrous.