Description of the Process of Manufacturing Coal Gas, for the Lighting of Streets Houses, and Public Buildings / With Elevations, Sections, and Plans of the Most Improved Sorts of Apparatus Now Employed at the Gas Works in London and the Principal Provincial Towns of Great Britain; Accompanied With Comparative Estimates, Exhibiting the Most Economical Mode of Procuring This Species of Light

by Friedrich Christian Accum

From these particulars the action of the machine will be obvious.

Let us suppose that the outer case (which is marked in the sketch by a black tint,) in which the wheel revolves, be filled with water, to about an inch above the axis of the wheel, and that gas is conveyed into the interior small channel, by a pipe, passing along the axis, so as to allow the wheel to turn freely round, and that the pipe is turned up at right angles in the inner chamber, and projects a little way above the surface of the water, as shewn in the design. The gas then must enter into the interior chamber of the wheel above the surface of the water, and must press against the adjacent partition; it will therefore cause the wheel to turn round, and in consequence of this motion, the next partition plate will press the gas against the surface of the water, and cause it to pass through the hydraulic opening, in an equal quantity to that, which is introduced into the exterior chamber.

This alternate filling, and discharging, of the contents of each chamber, will take place once during every revolution of the wheel, and hence the number of times each particular chamber has been filled, and emptied of gas, may be known.

In fact this machine performs the office of three revolving gas holders, fixed on an horizontal axis, and moving in a cistern, which is the outer case of the machine. One gas holder, or one compartment of the machine, is always in the act of becoming filled with gas, another is emptying its contents into the outer case, from which it passes into the reservoir, where it is to be stored up, or to the lamps, where it is to be burned, and the third compartment is stationary, or in an equilibrium. The wheel in any situation will therefore always have one of its receiving, and one of its discharging valves open, and consequently it will revolve.

Now to ascertain the quantity of gas discharged by one revolution of the wheel, we need only to know the capacity of the chambers, and add them together. Let us for example suppose, that each chamber contains 576 cubic inches, then one revolution of the wheel, discharges a cubic foot of gas. To register the total number of revolutions which the wheel makes in a certain time, a train of wheel-work is connected with the axis of the metre, see fig. 8, [plate III.]; it consists of a pinion impelling a common train of wheel-work, composed of any number of wheels. The pinion on the axis of one wheel, acts into the circumference of the next wheel, and the circumference of the wheel being as ten to one, it is obvious whilst the metre makes 100,000 revolutions, if the series consists of six wheels, the last wheel of the series, will only have made one revolution. Each axis of the wheels is provided with a finger and dial plate, divided into ten parts, therefore any number of revolutions may be read off at any time by inspection betwixt 10,000,000 and one.

The velocity with which the metre acts, is of course in proportion to the quantity of gas passing through it. Thus suppose there is a burner or gas lamp connected with the machine, of one foot capacity lighted, which consumes four cubic feet of gas in an hour, the gas metre performs four revolutions per hour, and so on for every number of burners or lamps, not exceeding the number which the machine is calculated to supply.

To render the construction of the gas metre more obvious, we have at fig. 6, [plate III.], exhibited a transverse section of the machine; a, is the outer case of the machine in which the wheel revolves. B, B, the outer or larger concentric chamber, (marked 1, in fig. 4, [plate II.]) L, the inner or smaller concentric chamber, (marked 2, in fig. 4, [plate II.]) d, the index on the axis which passes through a stuffing box in front of the machine. 5, 5, 5, 5, are stays or braces for supporting the wheel; they are likewise seen in fig. 4, [plate II.] A, is the inlet pipe for the gas to enter into the machine. The gas passes through the pipe h, and from thence into the curved pipe i, into the interior chamber L, of the metre. The pipe h, is surrounded by a second pipe K, which has a small aperture at x, the office of which is, to act as a siphon, in order to preserve the proper level of the water in the machine. The water is poured into the machine, through the small funnel at the back of the entrance pipe A. y, is a float, which stops the performance of the metre altogether, if a fraudulent attempt should be made, to stop the registering of the metre, by drawing off the water with which it is charged. In fig. 1, [plate III.], a, is the inlet pipe; b, the outlet pipe of the gas; and fig. 2, shows the interior chamber.

The registering wheel work, may be adapted to any part of the machine, and the motion may be communicated by a mitre wheel, from the shaft of the machine to the index.

The gas metre at the Royal Mint measures and registers 30,000 cubic feet of gas every twenty-four hours.[48]

[48] The gas metre at the Bristol gas works registers 60,000 cubic feet of gas every twenty-four hours. The metre at the Chester gas works registers 40,000 cubic feet every twenty-four hours.—One of the metres at the Birmingham gas works registers 40,000 cubic feet, and the other (now erecting) will register 100,000 cubic feet every twenty-four hours.