FORCING AND FORCING STRUCTURES 79 



the top of the bench should be about even with a man's waist. 

 The center bench of a greenhouse is almost ideal when it is 7 feet 

 in width. This admits of working from each side 3!- feet and 

 thus the whole distance across the bench. Solid benches are usu- 

 ally much wider and the walks are made narrower. A common 

 method is to provide walks about 18 inches wide, next to the out- 

 side walls only. Sometimes a center walk only is provided, but in 

 wide houses the beds are often arranged 16 or 18 feet wide. As 



FIG. 25. Workmen cultivating plants on solid beds 



the ordinary length of lumber is 16 feet, a board of this length 

 placed on the heating or water pipes, which are distributed about 

 1 8 inches above the surface of the bed, enables the laborers to 

 work the soil in the bed by reclining upon the board, as shown 

 in figure 25. This is a common practice with solid benches. 



The solid bed is, of course, the most economical so far as con- 

 struction is concerned and is one of the most satisfactory for forcing 

 lettuce, cucumbers, and plants of this description which do not 

 require bottom heat. With roses, tomatoes, melons, and plants 

 which require bottom heat it is necessary to have raised benches, 



