10 



BOTTOM HEAT. 



passage of air through the soil, forced up through it 

 when heat expands that in the air-drains and interstices 

 amongst the brickbats, and down through it when the 

 air in the drains cools and contracts. 



When the difficulty of getting a boiler fixed at a 

 sufficiently low level to heat the pipes for warming the 

 border cannot be overcome, as must often be the case 

 where the country is level and the drainage bad, the 

 best substitute is, to make all the arrangements as to 

 air-drains I have described as necessary when pipes are 

 laid, and to connect these subsoil air-chambers with the 

 atmosphere of the interior of the vinery by a series of 

 drain-pipes along the front of the house near the hot- 

 water pipes. Along the back wall of the vinery con- 

 struct an underground air-chain, to be connected by a 

 series of pipes, 4 inches in diameter, with the general 

 underground air-chambers of the border. From this 

 drain another series of pipes should be carried up the 

 back wall some 7 or 8 feet, where they should have 

 openings into the interior of the vinery ; and if the flue 

 from the boiler is made to run along the back wall in 

 such a way as to heat the air in the upright air-drains, 

 it will become lighter, and escape into the general 

 atmosphere of the house ; while at the same time a 

 current of air will pass down the front air-pipes already 

 referred to, at a lower temperature than that escaping 

 from the outlets in the back wall, but sufficiently 

 warm to be of great benefit to the roots of the vines. 

 This arrangement has the additional advantage of keep- 

 ing: the air in the house in constant motion. There is 

 also the possibility of making such arrangements in 

 forming a vine-border as to admit of the application of 

 dung -linings for warming the soil. It is, however, 

 only necessary to have heat applied to the roots, as 



