COAL

is obtained by the a nj till at i on of coal In large chambers di retorts. Tho distillation proceeds | ¢ | about four hours under a great beat, a is| the products are broadly, coke, gas, a S| coal-tar. The gas is then cooled, wash >. | with water, and treated with slaked li: djto remove impurities. The large cyl d | drical ve els so prominent in al! ges-wos are the gas holders, from which the hee it |icsnes to the consumers. These of | rise and sink in a tank of water by th le | own weight and the upward pre ure y | the gas inside. It will be observed tt 3 | this movement is made on pulleys —_ «| opon the uprights that support dj holder. The gas is conveyed from t n | holder by mains, and from the mains tot 3 |} consumer by service pipes. At the low point in the level of the main a trap h Pp, | takes off any deposit of water that m s.| form in the pipes. Meters are used n | the consumer to measure the gas suppli. pa oy ha varieties a le me — recen e penny-in-theiot meters. tuieon d } for consumer to regulate the sup] 0 | of gas to the burner, and this can alws D Heder Bnet heey yom pa 3. coal gas is used rj with air. tt produces a smokele bi dj|fiame of high temperature, but cook i d | stoves ought to be provided with chimne wr} to carry off fumes. Tho idea of burn i d | gas probably arose from the in flamm a 6 | streams of gas cmitted from coal beds of i the mining districts, The Royal Sock ee ce oe [s. 153]