TANKS AND GAS-HOLDERS.

237

The tank to be bound together with five wrought-iron hoops, each hoop to be 5 inches wide and]£ inch thick. The tank to be bolted together with full 1-iuch bolts of wrought-iron, not more than7 inches asunder from centre to centre of each bolt, and to be properly cemented together with ironcement. A flange column to be fixed on the centre plate of the tank, so as to support the roof ofthe gas-holder when down. The plates of the tank, exclusive of the bolts, cement, hoops, and centrecolumn, to weigh 350 tons.

ANNULAR OR RING TANKS.

In situations where the natural foundation is bad, and it would be costly to make an arti-ficial foundation over the whole surface by means of concrete or piles, a ring of artificialfoundation is made, upon which the iron sides of the tank and a short internal cylinder areerected, and the other parts of the bottom are covered with clay puddle. In tanks of thisdescription the earth is usually excavated either to the entire depth of the tank, leaving aninternal mound or core, or the excavation is only carried to a part of the depth of the tank,and the iron sides rise for the remaining part above the level of the ground.

The following abstracts of specifications for tanks of this kind of various sizes, made forthe Venice Gas Company, for the station of the Chartered Gas Company’s Works at BrickLane, and for the Bristol and Clifton Gas Company, will show the mode of constructionadopted in sncli cases. The first one was for a tank 75 feet internal diameter and 19 feetdeep.

The castings consist of—

40 inner cylinder plates, 1 inch thick.

40 bottom plates, 1 inch thick.

40 lower side plates for outer cylinder, 1 inch thick.

40 second tier plates, £ inch.

40 third tier plates, £ inch.

40 fourth tier plates, £ inch.

240 plates in the cylinder and bottom.

The flanges of all the plates to be 3| inches wide on the face, J inch in thickness at the junctionwith the plates, tapering to £ inch thick at the edge. Half an inch to be allowed for the thicknessof each joint. The bolt-holes to be £ square in the clear. The brackets to be § inch thick on the edge,tapering to half an inch at the base or root. The bead or astragal to be one inch. The anglesformed by the flanges round the plates to be filled with an angle-fillet £ of an inch on the angle.

The annular tank for the Chartered Gas Company’s station in Brick Lane, constructed in1848, is 103 feet diameter and 22 feet deep, inside measure. The following is an abstractof the specification for the various parts :—

Bottom Plates .—The bottom to consist of one ring, containing 66 plates, each plate to be 1 inchthick, and the flanges and brackets to be £ inch thick. The bolt-holes to be f inch square, and to