238

TANKS AND GAS-HOLDERS.

take a J-inch bolt square under head ; the bolt-holes not to be more than 7 nor less than 6 inchesapart from centre to centre ; between each bolt-hole a bracket is to he cast. The ring to be 5 feetwide, and the ends to be turned up so as to receive the flanges of the side plates. The flanges to be3 inches wide.

Side Plates .—On the inner diameter of the ring a row of side plates to be fixed 4 feet high, 66 innumber, and to be bolted down to the bottom plates by f-inch bolts and nuts. The plates to be finch thick, with the flanges and brackets the same as for the bottom plates, and, in addition, on theside next the centre of the tank two flanges are to be cast on, £ inch thick, with 3 brackets on theunder side. On the other side of the plates 2 brackets to be cast from top to bottom, to be 9 incheswide at the bottom, diminishing to nothing at the top. The bracket to be £ inch thick, and to havea foot cast on the bottom 6 inches wide by £ inch thick. The bolt-holes and brackets to be of thesame size as for the bottom plates. The outer circle of side plates to consist of five tiers, each tiercontaining 66 plates.

The bottom tiers to be l£ inch thick.

Second „ 1 ,,

Third „ | „

Fourth and fifth J ,,

Flanges. —The bottom row of side plates to have flanges 3 inches wide clear of the plate, and 1 inchthick, with bolt-holes of the same size and distance apart as those already described. Two hoop-flanges to be cast on each, 3 inches wide by 1 inch thick, with two brackets § inch thick. Thesecond, third, and fourth tiers to have the flanges f inch thick, and the bolt-holes of the samesize and distance apart as for the bottom tier.

Brackets .—The brackets to be J inch thick. Each row of plates to have 2 hoop-flanges f-inchthick, with 2 brackets for the support of the hoops. The fifth tier of plates to have the flanges, thebolt-holes, and brackets, the same as the other rows, but to have only 1 hoop-flange f inch thick,with 2 brackets cast on to carry the hoop.

Bolts and Nuts .—The whole of the bolts and nuts to be f inch diameter, square under head, andto be made of the best |-inch iron.

Hoops .—Nine wrought-iron hoops, to be made of the best iron; those for the bottom tier of platesto be 4$ inches wide by f inch thick. The remainder of the hoops to be 4£ inches wide by f inchthick. The jaws for connecting them together to have a sectional area of twice the area of the hoop.The hoops to be secured together by wrought-iron keys made of the best iron.

Joints .—The whole of the joints to be made of the best iron cement. The joints in no part tobe more than £ inch thick. The whole of the bolts and nuts to be well lapped with iron cementprevious to being screwed up.

The third annular tank, for the Bristol and Clifton Gas Company, to which the next spe-cification applies, was 110 feet diameter inside and 24 feet deep to the top of the flanges ofthe bottom plates. The excavation for this tank was to such depth that the top of it mightbe six feet above the level of the yard. The ground was supposed to consist of good clay ;the core of the tank was to be left in, but all the vegetable mould was to be removed and allother spongy parts to the depth of 20 inches, and the whole to be replaced with the bestclay well beaten and incorporated with the natural stratum, so as to form a perfectly water-tight surface of puddle. On the top of the core was to be a support for the roof of the gas-holder, formed of 16 standards of home fir, 6 inches diameter, driven in sufficiently to ensurestability and to form a circle of 36 feet diameter; the standards to be connected by runnersproperly secured by bolts and straps. The following are the particulars of the ironwork:—