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TANKS AND GAS-HOLDERS.

The following abstracts of specifications of iron tanks of various dimensions from thirty-three feet six inches to one hundred and one feet in diameter, which have been actuallymade and are now in use, will serve to show the mode of construction that has been foundto answer satisfactorily.

The first one is a tank made for the Chichester Gas Works in 1849, 33 feet in diameterinside and 15 feet high.

The lowest course of plates of the circumference f inch thick, and the top course 4 inch thick,and all other plates inch. No plate to be more than 4 feet in length or in width. All the platesexcept the top course to have diagonal ribs, and the flanges to be 3 inches wide, with bracketsbetween each bolt. The plates to be put together with iron cement, and the bolts and nuts to be notmore than 6 inches apart. The bolts of the bottom plates and of the lower two courses to bei inch, and all the others not less than ^ inch. Six hoops of 3 inches by flat iron to be fixedround the tank. The top plates to be east with a hollow chamber 2 inches by 24 inches, forming acondenser, and connected with the rest of the apparatus by two 6-inch pipes, with two siphous, twosocket-bends, and two flange-bends.

Six-inch inlet and outlet pipes, with four close carriage-valves, two tees and four bends, to be fixedin the most convenient manner for working into or out of eacli gas-holder separately, or both to-gether, with two tank-siphons and connections for pumping.

The next specification is that of a cast-iron tank for the Great Yarmouth Gas Company,made in 1847; the dimensions of which are 61 feet diameter and 17 feet deep inside mea-sure, exclusive of the flanges.

The bottom of the tank to be 1 inch thick throughout, with the exception of the outside row ofplates, which are to be 1 £ inch thick. The first row or lowest tier of side plates to be 1| inch thick ;the second tier 1 inch ; the third tier -i inch ; the fourth or upper tier, f inch thick. Each of theside plates to be of such width as to allow of 40 in the circumference of each plate, to be four deep,and to be numbered in the casting 1,2,3,4, beginning with the bottom tier. The tank to be boundtogether with four wrought-iron hoops with jaw's of strength proportioned to the hoops. The ironto be 3| inches wide and | inch thick. The tank to be bolted together with bolts made of S Ccrown-iron full f inch square, and not more than 7 inches from centre to centre of each bolt, andproperly cemented together with iron cement, well caulked. A bracket | inch thick to be castbetween every bolt-hole, and a bearing flange for the hoops to be cast on the inside of the 1, 2, and3, tiers of side plates. The flanges of the bottom of the tank to be cast inside, and those of thesides on the outside, and all of them to project 3 inches beyond the knees of the plates; all of theflanges to be at least f inch thick, and to have a strong fillet on the angles.

The third specification is of a tank 101 feet in diameter and 22| feet deep inside, exclu-sive of the flanges.

The flanges to the bottom to be on the inside, the others on the outside, and the whole of them toproject 3j inches at the least. The bottom of the tank to be 1 inch thick throughout, excepting theoutside row of plates and the row next to it; the ouside row to be lj inch thick, and the next rowto diminish in thickness from to 1 inch; the centre plate to be 1^ inch thick. The first tier ofside plates to be 1J inch; the second, lj inch ; the third inch; the fourth, 1 inch ; and the fifth,or top tier, 1 inch thick. Each of the side plates to be of such a width as to allow of 75 in thecircumference. Each plate to be 4 feet 6^ inches deep, and each tier of plates is to be numberedon the casting of them, such numbers to be 1, 2, 3, 4, and 5, beginning at the bottom tier.