224 VARIOUS METHODS OF HEATING DESCRIBED IN DETAIL. 



means of effecting this purpose, and are, not only on the score 

 of simplicity and economy, but, also, in an ammoniacal and 

 hygrometrical point of view, the best methods of producing heat 

 with which I am acquainted. 



The principal kind of structures to which the tank system of 

 heating has yet been applied, to any extent, in England, are 

 what are termed forcing-pits ; and in these it has been exten- 

 sively used, with much success. In this department of forcing, 

 it has proved one of the greatest improvements of modern times. 

 In England it is used on a large scale, in the culture of pines, 

 vines, melons, cucumbers, &c., during winter ; and, although 

 in this point of view, it may not be deemed of equal importance 

 in this country, where early forced fruits and vegetables are less 

 demanded, it is, nevertheless, calculated to be of immense value 

 to horticulturists in general, and plant-growers in particular. 

 There is little doubt, but, ere long, an increasing demand for 

 early forced fruits and vegetables, fresh from the forcing-house, 

 will stimulate enterprising individuals to the erection of those 

 cheap and simple structures, which could scarcely fail of being 

 a profitable investment. A given space, covered with a glass 

 roof, and otherwise protected, requires a comparatively small 

 amount of fuel to maintain a tolerable degree of warmth in the 

 soil, much less than is generally supposed. It is not my pur- 

 pose to enter, at present, into the details of this question, and I 

 merely notice it in connection with the subject of heating. By 

 many it may be regarded as a mere speculative theory, which 

 it certainly is, yet I think it worthy of more serious considera- 

 tion. 



In many of the English nurseries, tanks are used for stimu- 

 lating the growth of their young stock, and in many kinds the 

 annual growths are indeed remarkable. We have seen camellias, 

 one year from the graft, as strong and vigorous as plants three 

 or four years old under the old method of culture. Almost all 

 kinds of green-house plants are benefited by being kept in tank 

 pits, and we are inclined to think, if tank pits were more gener- 

 ally used by the nursery-men of this country, they would have 

 their plants easier got ready for market, and they would require 

 much less time to do so than is generally the case. 



