Some gasometers have an enormous capacity. The record is at present held by that built for the South Metropolitan Gas Co., London, by Messrs. Clayton & Son of Leeds. This monster (of which we append an illustration, Fig. 196) is 300 feet in diameter and 180 feet high. When fully extended it holds 12,158,600 cubic feet of gas. Owing to its immense size, it is built on the telescopic principle in six "lifts," of 30 feet deep each. The sides of each lift, or ring, except the topmost, have a section shaped somewhat like the letter N. Two of the members form a deep, narrow cup to hold water, in which the "dip" member of the ring above it rises and falls. [Illustration: FIG. 197.--Drawing retorts. (_Photo by F. Marsh._)] AUTOMATIC STOKING. The labour of feeding the retorts with coal and removing the coke is exceedingly severe. In the illustration on p. 400 (made from a very fine photograph taken by Mr. F. Marsh of Clifton) we see a man engaged in "drawing" the retorts through the iron doors at their outer ends. Automatic machinery is now used in large gasworks for both operations. One of the most ingenious stokers is the De Brouwer, shown at work in Fig. 198. The machine is suspended from an overhead trolley running on rails along the face of the retorts. Coal falls into a funnel at the top of the telescopic pipe P from hoppers in the story above, which have openings, H H, controlled by shutters. The coal as it falls is caught by a rubber belt working round part of the circumference of the large wheel W and a number of pulleys, and is shot into the mouth of the retort. The operator is seen pulling the handle which opens the shutter of the hopper above the feed-tube, and switching on the 4 h.p. electric motor which drives the belt and moves the machine about. One of these feeders will charge a retort 20 feet long in twenty-two seconds. [Illustration: FIG. 198.--De Brouwer automatic retort charger.] A GAS GOVERNOR.