358 Description of a Pit for raising Cucumbers, 



recommend it to be made of sheet iron or copper (as the heat 

 is more readily transmitted through it than through cast iron) 

 in an oblong square form, two and a half feet wide, and three 

 and a half feet long, with a depth of one and a half foot. 

 The cover may be of cast iron, well fitted to the boiler. The 

 hole in the centre of the cover should be one foot in diame- 

 ter. The steam is to pass into the chambers through pipes 

 in the upper part of the sides of the boiler A ; the pipes 

 may be closed at pleasure with a throttle valve turning on its 

 centre, and having an external handle B. 



The annexed section of the proposed boiler will convey 

 a better idea of it than my description. 



In this mode of forcing, the gardener s chief care is, not to 

 excite too much steam, as I find a very moderate heat pre- 

 ferable, and more congenial to vegetation. In fact, the steam 

 which arises from water just at the boiling point is the most 

 proper for supplying that moist vapour, which, while it affords 

 a sufficiency of heat, is partially absorbed by the flooring at 

 the bottom of the bed, and communicates a moisture highly 

 beneficial to vegetation ; whereas if the steam was raised to a 



