196 



FIXED STRUCTURES FOR GROWING 



supply of dry heat will immediately be obtained, which may be rendered 

 moist at pleasure by pouring on water. Another mode of obtaining an imme- 

 diate extra supply of heat from a dung-bed, is, by sinking in it, when first 

 made, an iron pipe of three or four inches in diameter, with the two extremi- 

 ties turned up, and covered by flower-pot saucers. The length of the tube 

 may be nearly equal to that of the bed, and the one end must be sunk a few 

 inches deeper than the other, as in fig. 134. It is evident that by taking off 



the corners of this pipe 

 there will be a draught 

 created in it, in conse- 

 quence of its sides being 

 heated by the dung ; and 

 an extra degree of heat 

 will by this means be 

 brought into the atmo- 



Fig. 134. Section of a dung-bed, with a tube . air. ^^ Qf ^ ^ y^ 



plan might also be adopted for putting the air of a plant-bed in motion, 

 without the admission of the external air. 



490. Fermenting materials and fire-heat combined. In pits and low-forcing 

 houses heated chiefly by dung, provision is frequently made for the supply of 

 extra heat, by the addition of smoke-flues or hot- water pipes. Fig. 135 is a 



Fig. 135. Pinery' heated by dung linings. 



perspective elevation and section of a house, in which a bed of leaves within 

 is heated by a dung lining placed on the outside of a pigeon-holed wall, and 



extra heat is provided for by 

 three turns of a flue, one above 

 the other, in the back path : 

 o, is the pit in which the dung- 

 lining is placed and covered 

 with a hinged shutter ; 6, the 

 surface of the bed of leaves, 

 in which pine-apples, or cu- 

 cumbers, or melons may be 

 grown, or strawberry plants or 

 flowers forced; c, door; d, 

 flues; e, front pigeon-hole 

 wall ; and J\ end pigeon-hole 

 wall. Fig. ] 36 shows a mode 

 of applying dung under a bed 

 of soil without coining in im- 

 mediate contact with it, and 

 by which no heat whatever 



Fig. 136. Section of a vinery heate* by dung. Pduced by the dung is lost ; 



, is the bed of soil in which 



