THE GREEN-HOUSE AND CONSERVATORY. 27 



In this ash-pit door there is a small hole, to admit air 

 needful for combustion. This stove is on the principle of 

 the air-tight stove, and consumes but little fuel, a small 

 hod full keeping the fire for twenty-four hours. 



The fire is surrounded by two thicknesses of brick, the 

 inner one fire brick ; thus the heat given out is gradual, 

 and the plants are not injured, as is often the case with 

 our iron stoves. There is, of course, a small flue, running 

 back into a chimney, to carry off the smoke. The common 

 covering of this stove is a thick cast iron plate, c. 



If, however, a higher and more uniform temperature is 

 required, an iron boiler may be added to the stove. This 

 is cast in one piece ; the pipes are of wrought iron, and 

 screw on. It should be set directly over the fire chamber, 

 so that its bottom will be on a line with the top of the 

 door, a, and its top is covered by the iron plate, c. As the 

 water in this boiler becomes heated, it rises and flows 

 through the pipe, e, which is run to one end, or quite round 

 the house, and returning, enters the boiler again near its 

 bottom, y, as shown in the figure. 



As the boiler is tight, the water 

 of course makes the circuit of the 

 whole pipe, and keeps up a constant circulation. 



