442 



PITS AND FRAMES. 



found sufficient to exclude frost and damp. 

 In the other division, one side is provided 

 with a pavement platform c, under which 

 is placed a flow and return 4-inch pipe ; 

 the opposite side has a tank d, in which a 

 continuation of the 4-inch pipes is laid, 

 which warms the water around them ; the 

 tank is " covered with two layers of pan- 

 tiles, the upper tiles covering the joints of 

 the lower, which are laid on pieces of iron 

 placed 9 inches apart. The tiles are not 

 laid in mortar, so that there is always a 

 nice moisture in the plunging material. 

 In the event of too much moisture occur- 

 ring, the water is drawn off the tank, and 

 the heat arising from the pipes soon dries 

 it up ; in fact, the regulation of the 

 moisture is under perfect control, as the 

 pipe may be only half covered, or more or 

 less, as may seem advisable, and the 

 moisture will be in proportion. The 

 boiler is at the centre of one end, and 

 works one or both pits as may be re- 

 quired." — Gard. Chron. 



One essential fault occurs in this pit, 

 namely, having the pavement shelves let 

 into the side walls. This should not be, 

 as we have already more than once ob- 

 served both in regard to pits and green- 

 houses. The heat of the pipes or flues 

 placed under such shelves is prevented 

 from rising upwards at those very parts 

 where it is most required, namely, close 

 to the side walls. Such an arrangement 

 also conducts the cold in winter from the 

 side walls along the pavement, and not 

 unfrequently destroys the plants. All 

 shelving like the above should be kept 

 clear of the walls from two to three 

 inches ; yet, strange to say, this is an 

 error almost invariably fallen into by 

 builders. 



Roger £ pit. — The following plan has 

 been suggested by Mr Rogers, of Seven- 

 oaks, Kent, for a pit combining in itself 

 both top and bottom heat, accompanied 

 with the requisite degree of humidity 

 necessary for such structures. 



Fig. 616 is a section of the pit, sup- 

 posed to be built entirely above the 

 ground-level. The walls are hollow, and 

 formed of brick on edge, with a view to 

 economise material. 



Fig. 617 is the ground-plan, a b marking 

 the sectional line. 



The details are as follows :— Under each 

 rafter is carried up a hollow pillar, cccc, 



projecting only 4 inches within the pit, 

 and having no communication with the 



general cavities in the side walls : in these 

 a cavity is left both at top and bottom. 

 Along the centre of the pit a flue of brick 



Fig. 617. 



on bed, d, is carried, 2 feet broad, and 

 1^ feet in depth, with openings at its 

 bottom, e, corresponding with those in 

 the pillars along the front of the pit, and 

 also with those in the back, the openings 

 in the latter being just below the level 

 of the top of those in the front. These 

 openings are to be all connected by flues 

 or tile-drains. The hot-water pipes are 

 to be laid along the centre, as shown in 

 plan and section, but somewhat elevated 

 above the floor on which they are placed, 

 and covered over, about 9 inches above 

 their upper surface, with slate slabs 

 three quarters of an inch in thickness. 

 The communicating openings between 

 the flue in which the pipes are laid and 

 the hollow pillars of the back wall should 

 be 3 inches below the top of the said 

 flue, to act as chambers to retain heated 

 air. The boiler is to be placed at one 

 end of the pit, unless so situated as to be 



