Polmaise Method of Heating Greenhouses, ($*c. 245 



great admixture in most kinds of garden seeds, shows how 

 prone all kinds of plants are to variation, even from acci- 

 dental hybridization ; and it may be at once inferred, that 

 hybridization, effected with a view to the improvement of 

 the progeny, by a selection of suitable parents, must produce 

 good results. We would therefore invite particular attention 

 to the above article, and advise all who are interested in the 

 production of superior flowers, fruits, and vegetables, to com- 

 mence at once the process of hybridization. — Ed. 



Art. II. Polmaise Method of Heating Greenhouses and 

 Hothouses. By R. B. Leuchars, Gardener to J. Hopkins, 

 Esq., Clifton Park, Baltimore. 



Since the publication of my last article, (p. 145,) upon 

 this subject, I have had a communication from a friend who 

 says, " that for pits and small plant-houses Polmaise is supe- 

 rior to any other method of heating," and to demonstrate the 

 fact, he describes an apparatus he has erected, and which he 

 designates Polmaise ; which is nothing more than a common 

 flue, with a hot-air chamber over the furnace, and is partly 

 carrying out my suggestion, at page 150, of the April Maga- 

 zine, viz., to economize all the caloric, generated by com- 

 bustion, to the atmosphere of the house. If we take the 

 trouble to examine erections for heating hothouses, we will 

 find them so constructed that, of every 100° of heat gen- 

 erated by the fire, 35° are carried off by radiation from the 

 materials of which the furnace is constructed ; and I can at 

 this moment point out an illustration of this fact, where the 

 waste is as much as fifty per cent. Scarcely half the heat 

 generated goes to raise the temperature of the house. When 

 the furnace is situated inside the house, and the heat not 

 absorbed by materials under ground, this waste heat is in 

 some measure economized ; but who would have such a 

 bungling arrangement who could have it otherwise ? The 



