CONSTRUCTION OF HOT-HOUSES. 283 



dents have happened by furnaces having been thrust 

 into the house ; besides, too powerful a heat is 

 thereby excited at one place. 



It has been argued, that such a flue as the above 

 is too shallow ; that it would often require sweep- 

 ing, there being so little room to hold soot. But 

 the intention is to burn nothing but charcoal or cin- 

 ders, as mentioned above ; so that very little sbot 

 will accumulate, and sweeping oftener than once a- 

 year will seldom be found necessary. Even peat, 

 mixed half with cinders, make very little soot. But 

 small coals, uncharred, should not be used, as they 

 give out too much smoke, and too little heat. 



I come now to the consideration of the airjlue. 

 These flues, in my opinion, in the ordinary manner 

 in which they are constructed, notwithstanding the 

 encomiums bestowed upon them by certain theo- 

 rists, are quite useless in the hot-house. The 

 idea of collecting the heated air about a furnace, 

 and conducting it to the cold end of the house, 

 is just, and natural enough. But if this cannot be 

 done without conducting the tube or flue that shall 

 convey it, upon the fire flue, to the evident loss of 

 its surface, and of its best part, I would ask, what 

 is gained by the experiment ? or rather, what is lost 

 by it ? Evidently a great deal ; all the expence, and 

 double the quantity of heat that can be thus convey- 

 ed. The fact is, there is no heat comes to the far 

 end of the house, but just what is collected from the 

 fire-flue into the air-flue, as it travels along. None 

 of it conies from the furnace, 



