Chap. VIII.
BRITAIN.
615
easily rises, and the vacuum is filled from the adjoining foul air-flues, which derive theirsupply from the cells, the cells in return receiving a corresponding supply of fresh air to
replace ttiat winch has Deen drawn up the vertical shalt. Une hundred weight of coal perday for each wing, containing 130 cells, has been the consumption. The principle here
Fig. 580. PLAN OP VENTILATING FLIES.
adopted is similar to that used in deep mines, the ventilating chimney serving the purposeof the upcast shaft.
Warming is effected by an apparatus where the whole radiating surface derives its heatfrom the circulation of hot water, and it is calculated that the area of the whole is sufficientto maintain a temperature of 60 degrees, when the external air is at 32. There is aprovision for increasing the radiating surface in the main flues as its temperature becomeslowered by an increased distance from the boiler, so that the most remote cells arc equallywarmed.
The apparatus consists of a double iron case; the space between being filled with waterbecomes the boiler ; the fire is lighted in the interior, but is not brought in contact witheither the sides or top : from the top of the boiler a rising main communicates with thevarious circulating pipes, and the return pipes are introduced at the bottom. The externalcase of the boiler is covered with vertical plates 7 inches deep, and g of an inch thick, placedabout 5 inches apart, and disposed in zigzag lines over the whole surface. The apparatusis set in brickwork, and the plates occupy the interior of the air-flue which surroundsthe boiler; they are useful both as radiators and keeping the air longer in contact withit. A slide valve placed in the main flue-pipe regulates the circulation, and lowers thetemperature if required. The pipes being disposed in flues formed of brick, they can onlybe moderately heated, and impart in consequence a genial warmth to the current of airpassing through them.
The cost of erection of the Pentonville model prison was as follows : —
Messrs. Grissell and Peto’s contract, &c. for the buildingAsphalte for cells, roads, and pathsWater-closets, fittings, basins, cocks, &c.
Locks, fastenings, bells, &c. -
Superintendence -
Sundries -
machinery, heating and cooking apparatus
Besides the prison the following are to be added : -
Detached residence for seven families, completeArchway and terrace wallWall enclosing garden -Stables and road -
£
s.
d.
; - 70,115
14
6
2,503
8
9
1,154
10
9
941
5
9
689
4
11
361
10
9
75,765
15
4
i well and
8,402
12
2
£84,168
12
o
each 161/. 17s. 2j
£
S.
d.
- 1,892
7
3
- 2,856
5
2
739
10
7
415
0
0
£5,903 2 10
R R 4