236 VARIOUS METHODS OF HEATING DESCRIBED IN DETAIL. 



words, the manure required for one year costs more than the 

 making of this border, by $220. Then, if we estimate the an- 

 nual expenditure on account of the border, for heating, repairs, 

 etc., to be $25, we have $700, the cost of manure, minus 

 $25, the cost of the tank border, which gives an annual saving 

 of no less than $675 by this method of heating. 



It may be supposed that a body thus situated over a hot- 

 water tank, might be too rapidly dried by the ascending heat. 

 But this is only a supposition ; and in practice it amounts to 

 nothing more, for the warmth generated by the tank is so grad- 

 ual, and spread over so large a surface, that the heat is equally 

 distributed, and no part of the mass is overheated, or one part 

 heated above another. And, indeed, one would scarcely believe, 

 from the small quantity of heat thus generated, that so striking 

 an effect would be produced ; of course, the border must not be 

 allowed to get too dry. Nor will this be a matter of so much 

 difficulty as may appear, as two or three good soakings with 

 water, or, what is better, weak liquid manure, will generally 

 suffice, until the weather permits you to uncover the border 

 during the middle of a wet day, covering it up again before 

 evening. The operation of watering will be much facilitated 

 by having a hose fitted to the tap of a cistern containing rain- 

 water inside the house ; and no hot-house of any kind should be 

 without such an appendage. If the mechanical texture of the 

 soil be good, the water soon finds its way through. The larger 

 portion of the moisture being held in suspension by the lower 

 stratum of soil, becomes gradually warmed by the tank, and is 

 again carried upwards by the heated air ; so that the roots of 

 the vines have the full advantage, not only of the heat, but of 

 the moisture. The abstraction of heat may be in a great meas- 

 ure prevented, in excessively frosty weather, by laying a few 

 inches thick of straw, or stable litter, immediately over the soil 

 beneath the covering. This is merely a precautionary expedient, 

 and, though useful, will seldom be necessary. 



In the formation of a chambered border many alterations and 

 improvements will suggest themselves to the mind of the practi- 

 cal man, which could not be very conveniently represented in 

 the accompanying sketches. For instance, as a covering, 



