PITS AND FRAMES. 



Fig. 646. 



Fig. 647. 



late the opening, and to which the lights 

 are secured by a bolt, which can easily be 

 removed ; / wooden ventilator, closed ; 



g the same, open. 

 Fig. 646 is plan 

 of rafter, under each 

 pair of lights, with a 

 concave centre to carry 

 off the water, and small 

 gutters, a a, on each 

 side of the rafter, to 

 carry off water caused 

 by co ndensation. Fig. 

 647, plan of hinge." 

 Behind Mr Allcard's 

 pit is a small pit for alpine plants, which we 

 think rather an objection, and have, there- 

 fore, omitted it in our figure, because, as his 

 pit is arranged, many of the operations of 

 culture are performed from without; conse- 

 quently the pit behind must be in the way 

 of the operator, and must prevent his reach- 

 ing the plants standing at the back part of 

 the pit. In Mr Allcard's pit, melons and 

 cucumbers are cultivated during summer 

 upon beds of fermenting material; and in 

 winter a boarded flooring is placed in it, 

 upon which are set plants to be pre- 

 served till spring. By referring to our 

 section, fig. 648, it will be seen that we 

 have made some alterations, which may be 

 perhaps considered improvements ; at least 

 they represent such an arrangement as we 

 would adopt for ourselves. We have pro- 

 vided head room along the back of the pit 

 by sinking a narrow passage, (a in fig. 

 648;) and instead of employing fermenting 



Fig. 648. 



materials, we have introduced a tank, b b, 

 for bottom heat, and two 3-inch hot-water 

 pipes, c, between the tank and the front 



wall for atmospheric heat, to be used to- 

 gether with the tank or not according to 

 circumstances — that is, according as a dry 

 or moist heat is required. Under the tank, 

 sea-kale or rhubarb may be forced, or 

 mushrooms grown, as in the Dalkeith 

 pits. Such pits, upon the whole, we 

 consider excellent; but with the ample 

 provision which can be made in the back 

 and front walls for ventilation, we would 

 prefer to have the whole roof fixed, except- 

 ing the openings in the pediments, as 

 being more economical in the erection, 

 and less liable to accidents and leakage. 

 With the convenience of having a passage 

 within, we would increase the breadth by 

 the extent of the width of the passage, 

 which could be done at very little addi- 

 tional expense, and would afford much 

 more accommodation. However, where 

 there is no access required to the interior, 

 the breadth of Mr Allcard's pit is quite 

 sufficient, and the movable roof may also 

 be retained. 



Pine or melon pit. — Fig. 649 — a very use- 

 ful pine or melon pit may be constructed 



Fig. 649. 



upon the following principle : — The walls 

 are built hollow, to prevent the escape of 

 heat ; and may be either partly under- 

 ground or above it, according to circum- 

 stances and the dryness of the soil. The 

 bottom is to be heated by a tank a, extend- 

 ing under the whole floor of the bed, over 

 which a stratum of drainage b should be 

 placed ; and over that the bed of earth c, 

 if for melons, or gravel if for plunging 

 pines in. For admitting moist heat from 

 the tank into the pit above, iron or 

 earthenware tubes should be set upright, 

 communicating with the tank below and 

 the pit above. These tubes are to be 



