The action of these different parts of the apparatus will be obvious from the following explanation:
A, A, are two iron retorts, placed horizontally, and side by side, in the furnace; the mouth of the retorts where the coals are introduced, projects into an arched chamber, situated in front of the furnace, as shewn in the drawing by the broken down brick-work. The object of suffering the mouth of the retorts to project into a separate chamber, is merely to discharge with convenience the red hot coke from the retorts when the process is at an end; the coke being suffered to fall to the bottom of the chamber, where it cools, without becoming troublesome to the operator. It may be removed from this fire-safe chamber by the door represented at the end view of the furnace.
When the operation commences, the inner vessel of the gasometer, fig. 4 is sunk down, to expel the air which it contains to a level with the exterior vessel, or outer cistern, of the gasometer; and, consequently, becomes filled with water. As the distillation of the coal in the retorts proceeds, the liquid and gazeous products evolved from the coals are transmitted by means of the perpendicular syphon pipes B, B, into the horizontal pipe or main condenser C, with which they are connected. The liquid which is distilled, collects in the pipe, or main condenser, C, where it is retained until its quantity has risen so high as to discharge itself into the pipe D, which is connected with the upper part of one of the extremities of the condenser, C. One of the extremities of the pipes, B, B, therefore become immersed into the liquid contained in the main condenser or pipe C, whilst the vaporous or condensible fluid, after having overcome the pressure there opposed to it, is transported into the pipe E, which, after passing in a serpentine direction, E, E, &c. through the exterior vessel or cistern of the gasometer, terminates in the tar-vessel, fig. 2. Thus the vaporous fluids are condensed by passing through the serpentine pipe, E, E, &c. and become deposited in the tar-cistern, fig. 2; whilst the non-condensible or gazeous products are made to proceed by the pipe F, which branches off from the pipe E, into the lime machine, fig. 3. In this apparatus the gas, as it is evolved from the coals, comes into contact with slaked lime and water; the object of which is, to strip it of its sulphuretted hydrogen and carbonic acid gas with which it always abounds, and to render it fit for illumination. This being accomplished, the purified gas is conducted away out of the lime machine by means of the pipe G, into the perpendicular pipe H, which branches up through the bottom of the gasometer cistern. The upper extremity of this pipe is covered, in the manner of a hood, by a cylindrical vessel I, open at bottom, but partially immersed beneath the surface of the water contained in the outer cistern of the gasometer, it is also perforated round near the lower edge with a number of small holes. The gas, as it passes out of the pipe H, displaces the water from the receiver I, and escapes through the small holes, and is thus made to pass through the water in the cistern, in which the hood of the pipe I, is partly immersed, so as to expose a large surface to its action, that it may once more be washed, and deprived of all the foreign gazeous products which might have escaped the action of the lime, whilst it was agitated with this substance in the lime machine, fig. 3. After rising through the water in the gasometer cistern, it enters into the gasometer, which then ascends as the gas accumulates in it.