224 Description of a Melon and Pine Pit. 



hollow wall, similar, in every respect, as to construction, to 

 that described by Mr. Silver lock in the Transactions of the 

 Society ;* and I cannot describe it better than by using his 

 words : " It is built nine inches thick, with sound even-sized 

 bricks, placed edgeways, the joints being carefully made, 

 and laid with the very best mortar. The bricks are placed 

 with their faces and ends alternately to the outside, so that 

 those which have their ends exposed become ties to the sur- 

 faces of the wall. In each succeeding course, as the wall is 

 built, the bricks with their ends outwards are placed on the 

 centre of the bricks which are laid lengthways in the course 

 below. Thus a hollow space is formed in the middle of the 

 wall, of four inches in width, which is only interrupted where 

 the tying bricks cross it, but there is a free passage for air 

 from top to bottom of the wall." 



My front wall is four feet, and my back wall five feet six 

 inches high, enclosing a space of six feet wide and fifteen feet 

 long, and the walls are covered with a wall plate, and with 

 sliding lights, as in ordinary hot-beds. 



The space included may be filled to a proper depth with 

 leaves, or tan, when it is wished to promote the rapid growth 

 of plants ; but at present it contains only nine large pots, in 

 which the Melon plants grow, and the stems of these are 

 supported by a trellis at a proper distance from the glass. 

 The wall is externally surrounded by a hot-bed composed of 

 leaves and horse dung, by which it is kept warm, and the 

 warm air contained in its cavity is permitted to pass into the 

 inclosed space through many small perforations in the bricks 

 At each of the lower corners is a passage, which extends 



* See Vol. iv. page 224. 



