The gas producer, which is represented in vertical section in Fig. 2, is a cylinder of brickwork inclosed in a casing of malleable iron. It is 7 ft. 6 in. deep, and 3 ft. in diameter, which becomes reduced to 20 in. above, where it is closed by means of a cast-iron lid, which is continuous with the floor of the retort house. There are no firebars at the bottom, so that the fuel rests on a floor of firebrick. At the bottom of the walls of the producer there are several holes about 1 ft. in length by 6 in. in height. By means of these openings any clinker that may form and the ashes of the spent fuel can readily be withdrawn. They also allow of the admission of air to maintain the combustion in the lower portion of the mass of fuel; and at each opening there is a malleable iron tube for delivering a jet of steam direct from a steam boiler. We shall subsequently explain the functions performed by the steam. The fuel employed is the coke or char resulting from cannel coal when it has yielded up its hydrocarbons and other gases during the process of carbonization in the gas retorts. Being entirely made from Scotch cannel the coke is very poor in quality, as it contains a large percentage of mineral matter or ash relatively to its fixed carbon. The retorts are worked with three-hour charges, but the producer is only charged once in every six hours For each set of eight retorts the charge of raw cannel is about 18 cwt., and it is found in practice that the coke drawn from five of the retorts is quite sufficient to fill up the producer to the top. Formerly a set of seven retorts fired in the ordinary way from a furnace underneath, required from 60 to 75 per cent. of the coke made, but now, with eight retorts in each oven, the quantity has been reduced to about 30 per cent., or less than one-half of what it formerly was. Before the retorts are drawn the lid is removed from the top of the producer, and any fuel still remaining unconsumed is touched up a bit by way of leveling it on the surface, and as soon as it has been filled up to the constricted portion a shovelful of soft luting is spread over the top of the coke, and the lid is laid upon it and driven home, thereby making a perfectly air-tight joint. The contents of the other three retorts, as also the contents of the whole of the retorts at each alternate drawing, are taken to the coke heap in the yard. We have already spoken of a charge of cannel as being about 18 cwt. for each set of eight retorts, but in connection with that matter we should mention that it was formerly about 13 cwt. per oven containing seven retorts, and that there is every prospect of it being increased without increasing the length of time occupied in carbonizing the cannel of each charge.