166 



HEATING AS APPLIED IN HORTICULTURE. 



raised in 4-inch work, level with the top 

 of the boiler, or as shown in our fig. : a 



Fig. 183. 



fin 



M 



i n n I 



O 



^ e „ — . 



9 _L 



1 



1 



1 



'1 



b 



\ 



■—<' ' e 



1 

 1 



1 

 1 





c 







a 





is the ash-pit ; b the boiler ; c the aper- 

 ture in front of the boiler, closed with 

 fire-brick ; e and d two bars, one for 

 supporting the fire-brick plug, and the 

 other fitting to the rim of the boiler, to 

 support a slate which encloses the front ; 

 f f is the chamber around the boiler, 

 filled with sawdust as a non-conductor of 

 heat; and a layer of sawdust extends 

 over the top of the boiler under the slate 

 slab g g, which is fitted over the brick- 

 work, an aperture being cut in it to allow 

 the throat of the furnace to pass through." 



The chimney rises from the top of the 

 boiler, in which is placed a small door for 

 supplying the fuel. " This chimney must 

 not exceed 4 or 5 feet in height, and its 

 area must in no case exceed the area of 

 the mouth of the furnace." A damper 

 is also placed in the chimney to regulate 

 the draught. " The aperture of the 

 boiler, which is closed with fire-brick, 

 and the front of the ash-pit, should also 

 be closed by a door or blower, having a 

 regulator to admit or exclude draught. 

 A blower is preferable to a door, as hinges 

 are always liable to rust, and then break 

 or strain ; and it is important to be able 

 to close the ash-pit pretty accurately." 



Fig. 182, already referred to, exhibits a 

 side view of the boiler and the connection 

 of the pipes. "In the first place," says 

 Mr Rogers, "the whole of the pipes should 

 if possible be above the boiler. One foot 

 is sufficient ; but, when convenient, the 

 higher the better. When 2 or 3-inch 

 pipe is used, the pipes may rise uniformly 



about 1 inch in 20 feet from a and b to c, 

 on which, being thus the highest point of 

 the pipes, an air-cock is placed. But if 

 4-inch pipes be employed, it is better that 

 a should be the highest point, and the air- 

 cock placed there ; and that the pipes 

 should fall uniformly 1 inch in 20 feet 

 from a to c, and from c to b ; indeed, this 

 is generally the best arrangement, where 

 not inconvenient." Why the position of 

 the pipes should be thus reversed because 

 they differ in size, will be found explained 

 in section Cause of Circulation. " From 

 b the return pipe r should descend either 

 perpendicularly, or with as steep an in- 

 clination as possible to the bottom of the 

 boiler. The supply cistern e must be so 

 placed, that its bottom is not lower than 

 the highest point of the pipes. The top 

 of the steam valve, v, should be level with 

 the supply cistern. Just below the valve 

 on the steam-pipe may be fixed a small 

 cock, k, connected with a pipe laid into 

 the house, by which, whenever the water 

 boils, the house may be steamed. In 

 small apparatuses this will happen pretty 

 frequently ; but in large houses, in order 

 to insure this advantage, a stop-cock or 

 sluice should be placed on the flow-pipe f, 

 by which the circulation being intercepted, 

 the water in the boiler may at any time 

 be raised to the boiling point in a few 

 minutes." This mode of heating has been 

 popular, and justly so; and one of its 

 most striking advantages is the long 

 duration of steady heat, rendering it 

 valuable to amateurs who do not keep 

 people for the purpose of attending to 

 their fires. It is adapted also to large 

 as well as small houses, or pits, and has 

 been known, when properly regulated, to 

 maintain its heat for twelve hours without 

 attention. The boilers are so constructed, 

 that they may be taken to pieces to be 

 thoroughly cleaned, which all boilers 

 require less or more according to the 

 purity and quality of the water used in 

 them. 



Hetties mode of heating. — The object here 

 aimed at is to combine the principles of 

 heating by hot air and hot water at the 

 same time. The figs. 184 and 185 will 

 show the construction, the former being an 

 elevation, and the latter an interior sec- 

 tion of the apparatus. Mr R. explains its 

 operation as follows : — " The inner casing 

 which contains the fire has a double or 



