WYKEHAM MAETIN — HYPOCAUST-HEATING. 



18 



but has not been proved as to its power of standing fire-beat, nor 

 as to the shrinking of the joints. The next point to be considered 

 is the cost of fuel, the cheapness of the construction being abun- 

 dantly plain ; it is not easy to imagine anything much cheaper 

 than £6 or £7 for the heating of a greenhouse 20x10, in- 

 cluding an ornamental floor, every portion of which is pleasing 

 to the eye as well as available for use. The consumption of fuel 

 is equally moderate, and any kind of fuel can be used. I have 

 used cord-wood, uncleft faggots, and sawdust, and the chips out of 

 my wood yard, and I find, as I expected, that, excepting in the 

 depth of winter, it is quite unnecessary to keep up the fire during 

 the twenty-four hours. In the autumn four or five hours are 

 sufficient, the magazine of heated air in the lower chamber cooling 

 by very slow degrees, when the furnace-door is shut and the 

 damper of the chimney pushed in. Early in November a fire was 

 lighted at 4 o'clock and let to burn itself out ; nevertheless at 

 between 3 or 4 o'clock the following day a thermometer buried in an 

 inner border showed a heat of 71°. The fire had consisted of a faggot 

 of toppings of trees and about a bushel of sawdust ; and there is 

 no doubt that any loppings, prunings, cast off pea-sticks and other 

 garden rubbish will answer perfectly as fuel. Hence the working 

 is, in proportion, as cheap as the original construction. And it 

 should be kept in mind that in houses of this construction the 

 heat is not only provided cheaply, but it is given in a different 

 form from that usually supplied, namely as bottom-heat. This is 

 not the place for enumerating the various plants for which bottom- 

 heat is either indispensable or highly beneficial. They are nume- 

 rous, but persons conversant with gardening do not require in- 

 formation as to their number, and the experience of one season 

 proves but little. I may observe, however, that bottom-heat 

 in this form seems to be far superior to that supplied in a common 

 hotbed. I transplanted some thinnings of early carrots last spring 

 from a hotbed to my heated (external) border, expecting the 

 transplanted plants to form a succession crop to the original bed. 

 But to my great surprise, when they were fit for use, those in the 

 bed from which they were taken were less than half their size. 

 In trying to account for this, it immediately struck me that the 

 heat of the hotbed was daily exhausting itself, whilst, by the aid 

 of the sun, that of the heated border was daily increasing. And 

 although it was on the outside border, whilst the hotbed had a 

 glass frame, the result was, as I have stated, from the more 

 efficacious action of the fire-heat as compared with that from 



