It is a fault in Mr. Witt's bath that the flue entirely surrounds the floor of the Calidarium, and consequently crosses the entrance door, rendering it necessary to the bather to step down from the seat to the floor of the apartment in going in, and to step upwards in going out. This arrangement leads to occasional slips, particularly when the floor is wet; and although unimportant to persons in the full vigour of health, calls for caution in all, and especially on the part of those who are in any degree infirm; and becomes a serious impediment where it is necessary to lift an invalid into the bath. Fortunately the inconvenience admits of an easy remedy; the flue, when it reaches the jamb of the doorway, may be carried over the door and so onwards along the side of the room; or it may be doubled back upon itself and made to return to the line from which it started, and then carried to any point of exit that may be suitable. A better material for the flue is brickwork; and as the intention of the flue is to afford a large surface for the radiation of heat, the plan has been adopted of making flues of large size, for example, three or four feet in height. A short length of a flue of these dimensions is equivalent to three or four times the length of a flue of one foot square, and its course along two or three sides of the room affords as much heat as can be required. I visited lately a small bath in Bell-street, Edgeware-road, in which a flue of this construction, about three feet in height and nine inches in width, ran along three sides of the room, and gave out a temperature of 160°. In the Turkish bath and in some of the modern British Thermæ the flues are carried under the floor, constituting a kind of Roman _Hypocaustum_, and are made to describe a series of parallel rows, which traverse from side to side and are connected at the ends. A very high degree of temperature is attained by this arrangement, as in the private bath of Mr. Stewart Rolland, of Victoria-street, Westminster; but it presents this manifest objection, namely, that the floor is so hot as to be unbearable to naked feet or to a naked skin, and is therefore not without danger to an invalid who may have accidentally fallen on the ground. Again, where very high temperatures are obtained, the woodwork of the seats becomes so hot as to render coverings of some kind necessary. The temperature of Mr. Stewart Rolland's Calidarium, when fully heated, ranges between 150° and 170°, while with the aid of a _Laconicum_ he is able to carry his temperature twenty degrees higher; his couches and seats are, therefore, covered with cotton sheets having a thick pile; and in place of wood he uses fibrous slabs, which have a lower conducting power and are less influenced by the heat. Moreover, in the construction of his walls he employs felt, on account of its non-conducting and non-inflammable properties, as an intermediate layer, in place of the sawdust used by Mr. Witt.