FORCING DKPAKT.MKNT. 



SUCCESSION PINE PIT. 



The annexed Plate, No. 22, is a representation of 

 the Ground Plan and Sections of the succession 

 Pine Pit, which was erected from the designs of 

 W. Atkinson, Esq., who has the merit of being the 

 first that constructed pits on this principle of double 

 walls, with a cavity between them, of four-inch 

 brick work. 



The back and ends are built in the honeycomb 

 manner, and have an inner four-inch wall carried up 

 from the floor level, to within two feet of the top ; 

 betwixt these walls there is a vacuum left from the 

 bottom, which is covered over at the top with a thin 

 slate, with apertures in it for the admission of steam, 

 that is communicated from the dung linings through 

 the pigeon hole work, in the back wall. The aper- 

 tures in the slates are furnished with small plugs, 

 whereby the steam can be excluded when in a 

 rancid state, and admitted at pleasure. These 

 walls are connected together by 14-inch piers, that 

 are built up at four feet apart, which strengthens 

 the back wall of the pit, and is a support for the 

 rafters, which come over the centre of each. The 

 top of the cavity being covered over, forms a very 

 useful shelf for placing pots of strawberries on, or 

 any other dwarf-growing plant, which it may seem 

 desirable to accelerate by artificial heat. The front 

 wall is, also, of a hollow, with 14-inch brick piers ; 



