Mr Hart on Heating Apartments. 173 



Plate III. Fig. 1. Section of the building, shewing the pipes laid 

 inclined, the lower ends projecting through the wall of the furnace 

 into the aperture or tunnel which communicates with the external 

 air, while the other end of the tubes reaches about a foot beyond 

 the opposite end of the furnace, before it enters the heated air 

 flue in the wall of the buildings. A spiral of sheet iron, sup- 

 ported on studs, is introduced into the centre of each lube to 

 give the air a gyratory or sweeping motion, along the sur- 

 face of the heated metal. The tubes are placed about one inch 

 asunder, and a row of fire-tile is laid above them, leaving a 

 space of nine inches at the end uncovered, as seen in Plate III. 

 figs 2. and 3. ; by this arrangement, the flame and heat gets 

 completely round them, and is made to sweep along their sur- 

 face, till it finds a passage through the openings left between 

 the tubes and the side-walls up to the next tier : it then passes 

 along them in the same manner, when it finds similar openings 

 at their other extremities up into the vent. The furnace used 

 for heating these tubes is of the same construction as those used 

 by the potters, as it consumes the smoke ; the space for the 

 fuel is fourteen inches wide by twenty-four deep ; and the arch 

 or opening for the admission of the flame is six inches in 

 height. To prevent smoking the house from carelessness, when 

 kindling the fire, or adding fresh fuel, the mouth of this furnace 

 is provided with a lid or cast-iron cover : The air, therefore, for 

 supplying the fire, enters by a side tube left in the brick-work, 

 the opening of which is below the level of the arch of the fur- 

 nace, and the aperture for the admission of the air has a regis- 

 ter to regulate the draught ; the furnace likewise is provided 

 with a door in front to withdraw the ashes. The flame, after 

 passing through the arch, is made to turn upward, and spread 

 itself upon the tubes by means of the dwarf wall A ; and the 

 tubes being placed about two feet above the opening for admit- 

 ting the flame, they never become red-hot. The external air 

 enters the passage B by a grate in the wall ; from thence it 

 passes through the heated tubes, where it is rarified ; it then 

 ascends the heated air-flue, and escapes by the registers into 

 the different apartments. The combined area of the pipes con- 

 tains about 280 superficial inches of free space for the passage 

 of the air, while the heated air-flue is two superficial feet, or 288 



