230

TANKS AND GAS-HOLDERS.

and tooled stone for the cap of the main pier, 6 feet by 2 feet by 1 foot, with a portion cut out toallow the balance-weights to pass, and holes for the foundation-bolts, and cases for the foundation-bolts, and case of columns. At each of the two secondary points also squared and tooled stone caps3 feet by 2 feet 6 inches and 1 foot thick, with holes for the foundation-bolts and the case ofcolumns.

The preceding form is the cheapest in which a tank can be constructed, when not ex-cavated out of the solid rock.

The following is the estimated cost of a tank 36 feet diameter and 12 feet deep :—

£. s. d.

752!j cubic yards of excavation, @ Is.. . . . . . . 37 12 8

107 cubic yards of puddling at the bottom of tank, @ Is. Crf. . . 8 0 6

246 superficial feet of York flagging under wall, @ Is. 9d. . . . 21 10 6

rods of brickwork in mortar, @ £12. 10s. . . . . . 68 15 0

119 cubic yards of puddling, and filling-in behind wall, @ Is. 6d. . 8 18 6

30 cubic feet of Bramley Fall stone for base of tripods, fa) 4s. 3d. . 6 7 6

374 cubic yards of earth carted away, @ 2s. 2d .37 1 10

£188 6 6

Fig. 2 shows the section of a tank 15 feet deep, similarly constructed to that representedin Fig. 1, with walls of sufficient strength for a gas-holder of 60 feet diameter. In tanks ofthis size the earth may be left in a mound in the centre with slopes as before stated andrepresented in Plate XXIV.

The following is an estimate for a tank 18 feet deep, for a gas-holder 55 feet in dia-

meter :—

£. s. d.

1890 cubic yards of excavation, @ lOrf.78 15 0

176 cubic yards of puddling at the bottom, @ Is. 6d. . . . 13 4 0

334 superficial feet of York binding at bottom of wall, @ Is. 9 d. . 29 4 6

12£ rods of stock brickwork in mortar, @ £13 .... 162 10 0

238 cubic yards of puddling and filling-in behind wall of tank, @

Is. Gd .17 17 0

70 cubic feet of Bramley Fall stone for tripods, @ 4s. 3d. . . 14 7 6

£316 8 0

The section of the wall of a tank at the Brighton Gas Works, 20 feet deep and S3 feet2 inches in diameter, constructed without clay puddle, is shown in Fig. 3. The excava-tion in this case was in solid chalk, which could be excavated almost vertically, so thatthe sides could be dug out of the exact external diameter of the tank. The brickworkwas laid nearly entirely in cement and clean, sharp sand, in equal proportions; and theinterior was formed of two half-brick rings breaking joint with each other. In the specifi-cation of this tank it was stated that none of the joints should exceed one-quarter of an inchthick, except the vertical joints between the two half-brick rings, which were to be three-quarters of an inch thick. The tank walls and piers were carried up of the several thick-