GAS-LIGHT APPARATUS.

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Fig. 3. The Lime Machine, for purifying thecrude coal-gas, and to render it fit for use. Theconstruction of this machine will be explained inplate yii. It is put together of cast-iron plates.

Fig. 4. The Gasometer , for collecting and pre-serving the purified gas, and for distributing andapplying it as occasion may require. It consistsof two principal parts—namely, a large interiorvessel closed at the top and open at the bottom,made of sheet iron, designed to contain the gas,and an outer cistern or vessel, of rather greater ca-pacity, constructed of cast-iron plates, in which theformer vessel is suspended. The latter contains thewater by which the gas is confined. The interiorvessel which contains the gas is suspended by chainshung over wheels or pullies, to which weights areattached, so as to be just sufficient to balance theweight of the gasometer, all but a small difference,and allowing its slow descent in the manner whichis found as nearly adapted as can be to the propersupply of the lamps. The weight of the chains mustbe equal to the specific gravity of the material o iwhich the gasometer is composed, so as to compen-sate accurately for the quantity of water which thegasometer displaces, or what is the same, it must beequal to the loss of weight which the gasometersustains, when immersed in the water; and thecounterpoise weight must be equal (or nearly so) rto the absolute weight of the gasometer.

The action of these different parts of the appara-tus will be obvious from the following explanation :

a, a, are two iron retorts, placed horizontally,and side by side, in the furnace; the mouth of the