8 



BOTTOM HEAT. 



of the branches has always been. Where the expense 

 of stone pavement for covering the pipes is an objec- 

 tion to its use, the same end may be arrived at by first 

 laying the pipes on pieces of half-inch round iron, rest- 

 ing on a smooth stone surface, at intervals of 9 feet 

 apart. These bits of iron will act as rollers, and enable 

 the pipes to expand and contract without the risk 

 of " drawing" the joints. The pipes should then be 

 covered with a small brick drain full of loopholes on 

 each side, taking care that none of the covering bricks 

 rest on the pipes. From these loopholes hot-air drains 

 should be run right and left with dry bricks, or by 

 using common drain-tiles, on the top of which 6 inches 

 of brickbats should be laid, and then the turf, as 

 already recommended. I find that the application of 

 the bottom heat for eight days raises the temperature 

 of the border to 60°; and when this is indicated by the 

 underground thermometer, the heat may be shut off, 

 and will only have to be applied for a similar period 

 when the vines are setting. 



"While the present edition of this work is being pre- 

 pared for publication, a keen discussion, which origi- 

 nated in the columns of the ' Gardeners' Chronicle,' is 

 extending itself to the whole horticultural press, as to 

 the advantages or disadvantages of artificially supplied 

 bottom heat for vine -borders from hot -water pipes 

 placed under the borders, either in chambers or amongst 

 rubble. My own opinion, founded on experience, is, 

 that the subject scarcely admits of discussion, so evi- 

 dent are its advantages if used with discretion, as every 

 other appliance of the sort ought to be. A single 

 example of its beneficial influence may be seen in the 

 gardens here at this time, April 2d, and it is enough to 

 convince any unprejudiced mind. 



