302 



SCIENCE OF GARDENING. 



PART II. 



of this pit, we would suggest the perforation of the whole of the side walls (Jig- 231. ) 

 in order to admit the steam more readily than it can find admittance by a single range of 

 openings adopted by West. Where pits on West's plan are already built, a substitute for 

 this preparation in the side walls may be found in the application of a wattled hurdle 

 against them (Jig. 231. 6), as has been adopted in the Cointe de Vande's garden at 

 Bayswater. On wet soils a hollow bottom is an obvious improvement. 



1549. The pillar-pit, or Alderstone pit (Jig. 232.), is constructed with cast-iron pillars of 



232 



three feet in height (a, a), which being joined by plates of that metal, form a support to the 

 wall on which the sashes rest. Above ground, this wall (b, b, b, 6), of four or nine inches in 

 thickness, is built on the iron plates, and carried the usual height of a cucumber-frame. 

 On this, a coping, or plate, either of wood or iron, is placed, to which is fixed cross rafters 

 either of wood or iron (c, c, c, c), to hold the sashes (d, d). Around the pit is a trench (e, e) 

 of the same depth as the cast-iron pillars, and its exterior sides supported by a brick wall. 

 The centre of the bed, under the sashes, is filled with dung or bark in the usual manner, 

 and the surrounding trench is destined for linings, which being protected by the wall, and 

 covered by boards (f, f,f,f), supported on cross pieces of iron, retain their heat longer, and 

 are less influenced by changes in the atmosphere. The chief advantage alleged in favor 

 of this frame, is the greater durability of the brick walls, than of frames of wood, and its 

 more elegant appearance in a garden. 



1550. Of adapted frames there are M'Phail's, or the frame with dung-flues, the pit with 

 rising frame, and the frame with props. 



1551. M'PhaiTs frame (Jig. 233.) consists of two parts, the frame (a, a) and lights (6), 

 which are of wood, and not different from those used for growing cucumbers, and 

 the basement (c, d} on which the frame is placed, which is flues of brick- work, with 

 the outer wall uniformly perforated. Against these perforated flues, linings of 

 dung are formed, the steam of which enters the flue and heats the earth (e, e,e] in the 

 centre of each light. The chief objections to this plan are the first cost, and the greater 

 consumption of dung, which some allege is required to keep up the proper heat. Its 

 advantages are, that hot dung may be used without any preparation, by which much 

 heat is gained ; and in the winter months, when a powerful artificial heat is required, 

 and (in the case of common hot-beds) is apt to burn the plants, they are here in the 

 coldest part of the soil, and cannot possibly be injured by any degree of heat which can 

 be communicated by dung. 



233 6 



a 



1552. The pit with rising frame (Jig. 234.) contains a basement-wall of brick-work of 

 the height of the dung or bark (a, a), and in this is a perpendicular vacuity (b, b} in which 

 a common frame (c, c) is placed, and by a spindle, pinion, &c. (rf) may be raised or 

 lowered at pleasure. Its object is the same as that of Weeks's frame already described, 

 and which it attains with less risk to the plants, but at a great comparative expense. 

 This variety of pit is the invention of John Nairn, (Hort. Trans, vol. iii.) who has had 

 it executed, and heated by surrounding tubes (<?, e, e). filled with steam. 



