18 



Improvements in heating hy hot Water. 



lation or retention of heat in the boiler, and a more immediate 

 and rapid circulation, than in the case of square, oblong. 



round, or any other description of boiler hitherto in use for 

 heating hot-houses. I shall not trouble you with descriptive 

 details of the returning pipes {d d), or of the fire-place and 

 ash-pit (ef) ; but I shall just observe, that the top of the 

 boiler {a) may be covered with a lid of wood, iron, or stone, 

 and that, where the circulation is extensive, as in the case of 

 heating several houses from one boiler, the motion of the 

 water will be promoted by leaving the lid loose, and by hav- 

 ing one or two openings, for the admission of the atmosphere, 

 in the conducting pipes. I have clearly proved, by experi- 

 ments with copper models, that these openings, or air-pipes, 

 increase the circulation ; and I have had cast-iron elbows 

 made with air-pipes ( ^g. 25.), which I 

 can introduce at pleasure, instead of 

 large reservoirs, or use with or without 

 them, according to the nature of the 

 house to be heated. 



I observe one of your correspondents 

 enquires if a green-house can be heated 

 from a library or a kitchen fire by hot 

 air. I have heated a conservatory from 

 a boiler placed behind the fii'e of an adjoining library with 

 complete success; and I agree in opinion with you, that if 

 any thing is to be done in the way of obtaining heat for extra 

 purposes from domestic fires, it is more likely to be effected 

 by the hot water system than by any other. It should never 



