PLAN OF A PINE-PIT. 
397 
There is no necessity for the pipes, upon Mr. Knight’s system, to 
form a warm atmosphere for pines, as the heat will naturally rise 
through the bark ; hut in forcing cucumbers, melons, or rhubarb, 
there must be fourteen inches of earth upon the bark, through which 
the heat cannot easily penetrate. To remedy that defect, two or 
three wooden pipes, either square or round, three inches diameter, 
may be laid in the bark, with pipes communicating with the atmos¬ 
phere in which the plants are growing. Those pipes by being 
opened at pleasure are intended to regulate the heat. 
Heysham, Lancashire. 
50 
1. Pit filled with spent Bark. 
2. Dung. 
3. Covers of Wood. 
4. Pigeon Holes. 
5. Hot Air Chamber. 
6. Bricks on Edge. 
7. Bricks flat. 
8. Outside Walls. 
For other Particulars, see the 
Article, page 10, of the present 
Volume. 
■ 
