THE FORCING GROUND. Si 



nipt the progress of the heated air ; and that at the back 

 should be similar, that the descent may not be checked. By 

 this simple contrivance, which is by no means expensive, the 

 circulation of air in the house will be pretty nearly as com- 

 plete as it is in the open ground ; and as a proof that it is 

 healthy for plants, if you shut yourself up in the house, you 

 feel all the warmth, but none of the oppression, which we all 

 experience in a close stove. 



The admission of air may be at the back of the house near 

 the ground as well as anywhere, for it will make for the pipes 

 through the floor, and be warmed before it reaches the plants ; 

 but if you desire to cool the house, the opening of a top-light 

 a little, to let off the heated atmosphere, will be desirable. 

 A very small opening and a corresponding admission of fresh 

 air below will be found sufficient ; but when the doors are 

 frequently opened, the lights will seldom require to be re- 

 moved. This, however, depends much on what is to be done. 



In a pit like this, fruit-trees in pots, pine-apples, straw- 

 berries, and French beans may be forced in perfection ; grapes 

 or cucumbers can be forced upon the rafters ; and it will be 

 found more easily managed and controlled, as it were, than 

 any other construction that can be made ; nor is there any- 

 thing expensive about it. The glass of the roof may be six 

 inches wide, and any size from four inches upwards ; the top 

 light, or every alternate light, may be made to shde down : 

 everything about it is of the plainest work. The cheapest 

 of all boilers to buy, to fix, and to supply with fuel, is a com- 

 mon conical boiler, and the size must be in proportion to the 

 length of the pit, (which may be fifty or five hundred feet, 

 according to the work required to be done,) and whoever 

 supplies it will make it of a proper size according to the 

 length of pipe it has to heat. Whatever a house may be 

 destined for, the only difference we should make would be in 

 the internal arrangements. If for peaches, nectarines, or figs, 

 or apricots planted in the ground, the interior must form a 

 trellis on which the trees should be trained. If for vines, 

 especially, and to be brought in a season that admits of no 

 other forcing, the interior must have no stage, nor pit ; but 

 even then, mushrooms may be forced on the ground without 

 the least detriment to the fruit of the vines, the bed being 

 made on the floor of the house, and merely covered with 

 straw to keep the sun off. Many, however, get a stage, and 



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