140 



Torcing-Pit heated hy Jiot Water. 



Section of proposed Pit on the line a b of Jig. 30. 

 The arrows indicate the course of the circulating current. 



siderable value. There is nothing in the plan which lays claim 

 to novelty; it professes merely to be a combination of various 

 expedients, already severally in use, but which have not, it is 

 believed, been hitherto applied to any very efficient purpose. 



Fig. 29. is a section of the proposed pit, which is supposed to 

 be built entirely above ground ; brick on edge with hollow walls. 

 This mode of construction is not essential to the plan, but its 

 economy recommends it whenever a pit is to be built anew. 



Fig. 30. is a plan of the same, and ab \s the line of the section 

 shown in^-. 29. The following details will be best understood 

 by keeping both plan and section in sight. 



At certain intervals, say every 3 ft. 8 in. or 4 ft., corresponding 

 with the rafters which support the lights, a hollow pilaster {p p 

 y^Jig. 30.) is carried up inside the pit, projecting from the wall, 

 the thickness of one brick only, and so constructed as to have 

 no communication with the general cavity of the wall ; and an 

 aperture is left in each of these pilasters, both at top and bottom, 

 inside the pit. Along the centre of the pit, also above ground, 

 is constructed a flue of 4-inch work, 2 ft. wide, and 18 in. deep, 

 having an aperture at bottom corresponding with each aperture 

 of the pilasters on the front, or lower, side of the pit, and an 

 aperture just below its upper edge corresponding with each 

 pilaster along the back ; and these apertures are respectively to 

 be connected by means of small brick flues, or, cheaper and better, 

 by 6-inch draining-tiles, with the apertures in the pilasters with 

 which they correspond. The space between the flue and the 

 back wall may be filled up with earth or rubbish, and trodden 

 firm before the cross flues are laid ; that between the flue and 

 the front wall should be filled with brickbats, stones, or with 



