HEATING BY HOT-WATER PIPES. 



159 



to the coiled pipe, and thus forms an 

 endless pipe. At the highest point of 

 Fig. 169. 



a 



the heating-pipe / is another pipe d, of a 

 larger diameter. This is called the ex- 

 pansion-pipe, into which the water rises 

 as it expands in heating, to prevent the 

 apparatus bursting. The filling-pipe o 

 rises to the level, and no higher, of the 

 lower part of the expansion or safety pipe. 



" The tubes being thus arranged, the 

 whole series, except the expansion-pipe, 

 is filled with water by means of a force- 

 pump applied to the filling-pipe o ; and 

 as it is of importance to free the endless 

 pipe thoroughly from air, the water is 

 pumped several times through the tube 

 until this is accomplished. The endless 

 pipe being thus filled with water, and the 

 expansion-pipe empty, every part of the 

 apparatus is strongly and hermetically 

 closed. The endless pipe having a bore 

 of about half-an-inch, and being a quarter 

 of an inch thick, is capable of sustaining 

 a very great pressure. 



Fig. 170 is a plan of the furnace taken 

 above the grate. 



Fig. 170. 



" Fig. 171 is a longitudinal section taken 

 through the centre of the furnace. 

 Fig. 171. 



" Fig. 172 is a section, supposing the 

 front wall of the furnace to be removed ; 

 Fig. 172. 



z X 



rra, wall of common bricks, 9 inches thick, 

 which encloses the furnace on its four 

 sides ; b b a wall 9 inches thick, formed 

 of Welsh fire-lumps, that enclose the fire- 

 chamber on three sides. From the face 

 and ends of this wall fire-bricks project, to 

 support the coiled pipe a, placed in the 

 flue. The intention of this wall is to pre- 

 vent the too rapid abstraction, by the coil, 

 of the heat from the fire, which comes in 

 contact with it at the opening in front 

 only, where the hot gases turn into the 

 back and side flues in which three-fourths 

 of the furnace or boiler coil is placed. 

 The roof of the furnace is formed of 

 Welsh lumps, in which is an opening m 

 fitted with a movable cover, for supply- 

 ing the furnace with fuel, (coke or an- 

 thracite coal being preferred.) The ash- 

 pit o is enclosed with a door n, in which 

 there is a register ; k is a double fire-door 

 to an opening in the wall, for clearing the 

 fire-place and furnace bars from dust and 

 scoria. This has a dead plate, to separate 

 the ash-pit from the heating flues ; x, 

 heating-pipe, rising from the boiler coil 

 which passes round the internal wall in 



