VARIOUS METHODS OF HEATING DESCRIBED IN DETAIL. 237 



instead of shutters, I would decidedly prefer glass ; and where 

 there are plenty of spare sashes about the place, they might be 

 used in this way, with much advantage, just as spare sashes are 

 used for covering peach and apricot wall-trees in England. But 

 suppose that sashes of sufficient length were provided for the 

 purpose ; the expense would probably be counterbalanced by the 

 advantage gained. For a house 100 feet long, 25 sashes would 

 be required, which, at 3 dollars each, would be 75 dollars; a 

 very trifling sum when a desirable object is to be attained by the 

 judicious expenditure of it. And, in this case, although it may 

 appear injudicious to some, the object is, in my opinion, suf- 

 ficiently important to justify this expense. Light absorbed is 

 productive of heat, especially if the absorbing body be of a dark 

 color, for then it is absorbed without being again reflected upon 

 the transparent medium. Hence we see the advantage of hav- 

 ing the border covered with a body admitting light, and the soil 

 of which the surface of the border is composed, of a dark color, 

 that the heat which falls upon it may be absorbed and retained. 



For winter forcing, small houses are decidedly preferable to 

 large ones. Houses about 25 or 30 {eet long are sufficiently 

 large, and are more easily heated, and more convenient to man- 

 age. Even in the milder climate of England, small vineries 

 are preferred to large ones, and are found to be more profitably 

 worked. Above all things, loftiness should be guarded against, 

 as being the very worst feature in a forcing-house, as the heated 

 air continues to ascend upwards; and, unless the external 

 atmosphere can be admitted at the top, the vines at that portion 

 of the house will always be in a state of vegetable suffocation; 

 a fact of too frequent occurrence, in lofty houses, even in sum- 

 mer, and which is rendered still more injurious by the present 

 defective methods of ventilation. 



A few words more regarding the permanency of these borders. 

 Assuming that a proper command of heat, both for the atmos- 

 phere and the soil, is obtained, the question has been asked, How 

 long will borders, so circumscribed, continue to supply a house of 

 grape-vines with the requisite nourishment ? This question has 

 hitherto proved a drawback to the adoption of these borders by 

 many who have, in every other respect, the highest opinion of 



