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bottom of the generator, and blown with forced draught by the fan, A, until the coke is incandescent. The heat from the generator enters the carburetter at the top, and passes downwards, heating in its course the special bricks with which the carburetter is filled ; the heat then enters the bottom of the super-heater, c, which is also filled with chequer brick-work, and the waste heat passes out at the top of the super-heater, and away up the chimney. The carburetter and super-heater being sufficiently heated, the forced draught to the generator is stopped, the waste heat outlet at the top of the super-heater is closed, and the gasvalve at the top of the oil super-heater, D, is opened.

Steam is now admitted under the grate bars of the generator, and in passing through the incandescent coke in the generator it becomes decomposed, the oxygen of the steam combining with the carbon of the fuel, forming Co and H, as previously explained.

In order to render the water-gas thus produced luminous, crude oil or petroleum is forced by means of a small pump fixed to the wall into the top of the carburetter in the form

fine

spray. At this point it comes in contact with the water-gas, and is vaporized. There is thus a very intimate mixture of the particles of oil with the watergas, and in passing through the heated bricks in B and c, the oil vapour becomes permanently gasified and incorporated with the water gas; the gas passes onwards through the oil super-heater, D, and forward through the condensers and scrubbers, E and F.

The process of gas-making continues until the heat in B is not sufficient to decompose the steam. When this stage is reached, the oil and steam-valves are closed, and the gasvalve is changed to its former position, and the process of raising the heat in the generator, carburetter, aud superheaters by the forced draught is repeated.

The art of making this gas is to keep the heat in the

of a very

super-heater, c, at the proper temperature, to permanently combine the oil vapours and the non-luminous water-gas, for if the heat is not sufficient, the two gases separate on cooling, whereas, if it is too great, lampblack is formed.

The most successful method for enriching gas by means of oil-gas is that devised by Mr. Young, of Clippens, known as the Peebles process.

The principle of Young's process is dependent upon the washing of the oil-gas, which is produced by retorting the oil at a moderate temperature by means of oil of the same description before retorting, by which it is freed from all condensable vapours, and only permanent gases are allowed to escape to the purifiers. No loss takes place, as the olefines and other fixed gases, which are absorbed to a considerable extent by the oil during the washing of the gas, are again driven out by the action of heat during the retorting. The apparatus consists of two cast-iron retorts, about 10 feet in length, and set so as to have a downward slope to the back. The retorts are fitted with doors and ascension pipes in the usual manner, but in each door a small test cock is fixed, by opening which the colour of the gas can be seen. This should be of the palest lemon, as when any darker colour or approach to brown is produced, then tar is deposited. The oil is admitted by small cocks about 2 feet up

the ascension pipe, and falls down, meeting the stream of ascending gas, on to steel plates which extend to a distance of about 3 feet into the retort, so as, in a great measure, to prevent the direct impact of the oil on to the bottom of the retort. The temperature is kept about 1,400° to 1,600° F.

After passing up the ascension pipes, the gas flows to the hydraulic main, which is situated at the back of the retort bench; it then passes through a coil of condensing pipes, and so on to the scrubber. The oil cistern is situated

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