A TREATISE ON GAS-TIGHT.

85

before described, rising through the water intothe gasometer, and raising it up : the gas thenpasses away to the burners, u 11. In this man*ner the process proceeds until the whole of thevolatile products of the coal in the retort isevaporated. The use of the gasometer is, toequalize the emission of the gas which comesfrom the retort more quickly at some timethan others. When this happens, the interiorvessel rises up to receive it, and when thestream from the retort diminishes, the weightof the gasometer expels its contents. Whenthe process is finished, the retort is suffered tocool, and its ground stopper is then removedto replenish it with coal. The residue found inthe retort is coke, v v are cocks to let off anyliquid that may collect in the pipe o or t; forif the smallest portion of liquid were to ob-struct the free passage of the gas to the bur-ners, the consequence would be, that thelights would not burn steadily—they would,as it is called, dance , or become extinguished.x is the main stop-cock which communicateswith the burners—these, of course, may beplaced as convenience may require, z z aretwo projecting parts in the top of the gasome^