CONSTEUCTION OF THE ROMAN BATH. 99 



being taken to range the work with the outer face of the 

 uprights, by which means from half-an-inch to one inch of 

 each upright will project on the inner side of the work be- 

 yond the finish of the brick-work. Across these uprights the 

 laths are nailed, and the plastering finished in the usual way ; 

 the outer portion of the brick-work being either rough plas- 

 tered with a mixture of clay and lime or rough-cast. 



" The roof is constructed of a single joist laid flat from one 

 side to the other of the span of the building, cut 4 inches by 

 1 J, a sufficient fall for the rain being obtained by taking 

 from 1 to 1J inch off the outer edge of the roofing joist at 

 either side next the cave, this being gradually reduced to 

 nothing as the cut reaches the centre. Upon these thin 

 sheeting boards are nailed, and over them the ordinary roofing 

 calico, on which a coat of mineral paint or boiled tar is ap- 

 plied, which renders the work perfectly waterproof. The 

 whole is then ceiled with lath and plaster under the joists in 

 the usual way. On each of the sides of the hot room, oppo- 

 site each other, and as high up as the building will allow, 

 are placed two air holes or windows, through which a free 

 current of air always passes, thereby keeping the air in the 

 bath (no matter to what number of degrees heated) as pure 

 and fresh as the outside air. 



"The heating apparatus consists of an ordinary boiler 

 grate, with a flue carried back from it into the hot room, and 

 running three sides of it, returning along the opposite side 

 of the outer room, and carried up a chimney placed outside 

 the square of the building, as indicated on the plan. The 

 flue is constructed on the ordinary plan of a hothouse flue, 

 about 20 inches every way externally, the whole being raised 

 off the ground about 3 inches by bricks set as blocks, and the 

 bottom of the flue being formed of large tiles, bridged from 

 one brick to the adjoining one, placed about 18 or 20 inches 



