GLASS STRUCTUEES AND APPLIANCES. 



223 



frequent intervals, they are not suiiiciently strong- to 

 bear the wear-and-tear of pit-management ; and be- 

 sides, four-inch cannot be trusted to exclude twenty 

 or thirty degrees of frost. The lower portions of the 

 walls of pits are also very generally pigeon-holed, 

 that is, a certain number of the headers are left out, 

 and thus any quantity of four-inch openings are left 

 right through the walls. Other pits rest on pillars, 

 fourteen inches or more square, and from two to f our 

 feet high ; or wood or iron pillars are placed at in- 

 tervals of four feet or so along the front and back 

 walls, and York or other slab-stones, or slates, are 

 carried along from one to the other. These may be 

 a foot or more wide, and the upper wall of the pit is 



These may or may not differ greatly in size, form, 

 or structure. They must differ in temperature, and 

 with the object of enabling them so to- differ with 

 greater facility and despatch, certain structural pecu- 

 liarities are introduced. For example, the oldest 

 plan of heating pits — some practitioners would still 

 call it the best — viz., by the use of fermenting ma- 

 terials, while possessing many elements of danger 

 and uncertainty, had at least the merit of keeping 

 them warm for a long time without attention, and of 

 giving out moisture as well as heat. This, however, 

 was associated with one very constant and consider- 

 able drawback. In the further decomposition of the 

 heating materials they lost bulk as well as caloric. 

 Now in all pits this was an evil — the deeper the i^it 

 the greater the evil. In pits a vard or four feet 



Fig. 15.— Pit Built on Pillars. 



Showing wooden battens covered with brushwood, over hot- 

 air chamber, a, chamber ; b, battening ; c, brushwood ; 

 d, space for soil ; e, space for Melon or other plants. 



Fig. 16.— Pit with Stages. 



Showing how the stages are arranged near the glass for the 

 storage of plants, or the culture of Kidnf'y Beans, Straw- 

 berries, &c. 



built along the centre of the slab, leaving a projec- 

 tion on either side for the reception of a temporary 

 bottom to the pit, and a covering for the lining or 

 space all around it. 



Instead of the pillars and stones, some turn 

 arches of brick along the front and back walls, 

 which save material and afford equally free access 

 as the pillars to the chamber underneath the pit. 

 These methods of building have other merits, 

 besides the economising of material. They divide 

 the upper and lower portions of the pit into separate 

 parts ; atford facilities for reaching the base at any 

 season without disturbing the upper portion ; and 

 keep the growing plants all the year round within 

 almost the same distance of the glass, the last being 

 a matter of the highest cultural importance. 



With the object of treating each subject as much 

 as possible on its merits and by itself, it is thought 

 best to add as little as possible here about the heat- 

 ing or warming of pits. Every one, however, knows 

 that there are cold pits, dung-pits, Pine-pits, &c. 



deep the loss of bulk did not matter much ; but in 

 pits double those depths the loss of bulk carried the 

 plants so far from the glass as to seriously injure 

 and weaken them. Hence chiefly the origin of pits 

 with second or false bottoms. These, as already 

 stated, divided the depth of the pit into two equal or 

 unequal portions, and kept the plants at a uniform 

 distance, or nearly so, from the glass through all 

 their stages. These false bottoms are formed of 

 slabs of stone or slate, wood, or bars of iron ; but the 

 simplest, best, and most efiicient are those formed 

 of rough wooden battens, with a layer of brush- 

 wood on the top of them (Fig. 15). These will last 

 one or two seasons, according to quality, and afford 

 thorough drainage to the plunging material, such as 

 cinder-ashes, in which the pots are plunged, or to 

 the soil in which Melons, Cucumbers, or other plants 

 grow. Such a porous bottom is also most favourable 

 for the passage of heat from the bottom chambers or 

 lining into the upper portion of the pits. The stout 

 battens rest on the inner projections of the slabs 



