VARIOUS METHODS OF HEATING DESCRIBED IN DETAIL. 243 



giving promise of a fair crop. The wall was covered with the 

 glass on the first of February, but no heat was applied to the 

 wall until the beginning of March. The sashes were fixed 

 exactly as we have described in the foregoing sketch. The wall 

 and fire-place were precisely the same, but no cavity was be- 

 neath the border. The result was, that the crop ripened five 

 weeks earlier than those on the same wall, uncovered, without 

 heat, and nearly four weeks earlier than those on the same wall, 

 with heat, and covered, in the usual way, with netting. Now 

 this was merely an experimental result, without much previous 

 preparation, save the covering up of the wall a month earlier 

 than the warming commenced, if, indeed, this can be called a 

 preparation, being an absolutely necessary prerequisite to suc- 

 cess, under any method of forcing. When the warm weather 

 set in, the sashes and rafters were taken away, and the enclosed 

 part received, during the season, the same treatment as the 

 other portions of the wall. 



In forming a hollow wall, there will be quite as much saved 

 by the internal cavity as will suffice to warm it, as only about 

 one half the quantity of bricks are required ; and even without 

 a heating apparatus, hollow walls are superior to solid ones, for 

 horticultural purposes ; for, under all circumstances, they are 

 found to be both warmer and drier. The addition of a heating 

 apparatus, however, will render the wall a very useful auxiliary 

 to the forcing-house, and the cost will be amply compensated by 

 the utility. By looking at the foregoing plan, it will be seen 

 that the furnace is placed in the foundation of the wall, with a 

 few steps to descend to it, the whole being covered with a trap- 

 door, leaving nothing unsightly open to the view of the visitor. 



In many parts of this country, grapes are frequently overtaken 

 by the autumn frosts, before they are ripened, and in many 

 others, they do not ripen at all. Now, it is obvious, that it is 

 neither owing to a deficiency of sun-light, nor a deficiency of 

 heat, for in Britain the quantity of both are much less, and the 

 quality of the latter less powerful for the maturation of fibre and 

 fruit ; and yet it is common enough to have good crops of (what 

 in America are called foreign) grapes, on the open walls. In 

 ordinary seasons, the black Hamburg, Muscadine, and Fron- 

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