GAS-HOLDERS.
239
Bottom Ring .—The bottom ring to be 3 feet 10 inches wide and $ inch thick, composed of 66plates radiating from the centre; the flanges for joining them to be 3 inches deep, and to have holescast in them for f-iuch bolts, square under the head, and 6 inches from centre to centre. The outerand inner edges of the plates to be turned up for receiving the sides of the tank.
Inner Side Plates .—Upon the inner circumference of the bottom ring to be fixed one tier of 66plates 4 feet high and f inch thick, breaking joint with the bottom plates, and these plates to havetop and bottom and end flanges 3 inches broad and | inch thick, and to be secured to each otherwith J-inch bolts and nuts, square under the head. The plates to be strengthened on the side nextthe centre with horizontal ribs 21 inches by f inch. On the other side each plate to have twobrackets; the whole depth of the plate 9 inches wide at the bottom and diminishing to nothing atthe top, and f inch thick. Each of these brackets to have a foot cast on it 9 inches by 6 inches byJ inch.
Outer Side of the Tank, to consist of 5 tiers, each composed of 66 plates, breaking joint with thoseabove and below. The bottom tier of plates to be 1J inch thick, with flanges 3 inches broad andclear of the plate, and 1 \ inch thick, having holes cast for and to be secured with lj-inch bolts andnuts 6 inches between the centres. The second tier with its flanges to be 1 inch thick, secured with1-inch bolts and nuts. The third tier and its flanges to be | inch thick, secured with |-inch boltsand nuts. The fourth and fifth tiers and flanges to be f inch thick, with f-inch bolts and nuts. Allthe flanges of the tank to be strengthened with brackets | inch thick and 6 inches apart, and all thebolts to be 6 inches between the centres. The fourth and fifth tiers of plates to be panel-moulded.
Hoop-ribs .—The top tier of plates to have one hoop-rib, and the other tiers to have each two hoop-ribs flush with the flanges; to be J inch thick, and each to have two brackets in the length of theplate cast underneath for supporting the hoops.
Hoops .—Nine wrought-iron hoops; the two for the bottom tier to be each 4^ inches broad and Jthick. All the others to be 4J inches broad and $ inch thick. The ends to be connected by jawsand keys; the sectional area of the jaws to be twice that of the hoops.
Joints to be made with the best iron cement. No joint to exceed \ inch in thickness. The boltsand nuts to be lapped with cement before being screwed up.
A tank of this description 170 feet in diameter and 25 feet deep for a telescopic gas-holder,has been recently constructed from the designs of Mr. F. J. Evans, at the works of theChartered Company at Westminster, which affords an excellent example of this method ofconstruction. Plate XXVI. represents a section of this tank with the dry well for the in-let pipe. The low level of the works near the river would not permit a much deeper exca-vation than 12 feet. The dimensions of the various parts are shown in the plate, from whichthe mode of construction may be clearly seen.
GAS-HOLDERS.
The gas-holder is, strictly speaking, the inverted cover which contains the gas, and whichrises and falls above the level of the water in the tank in proportion to the quantity of gas itcontains, though the tank and the cover are commonly spoken of as one. These vesselswere formerly called “ Gasometers,” but as they do not now usually serve to measure the