[46] See directions to workmen, for adapting gas metres, [p. 229].
Nor do the various advantages which have now been detailed, form all the good that this important machine is capable of furnishing. The gas metre furnishes at its axis a power which has been ingeniously applied to put in motion the shaft of the lime machine, employed for purifying the gas, see fig. 3, [plate VII.][47] The importance of a power thus certain in its operation, and obtained free of expence, must at once be obvious, when it is considered that upon whatever plan the purifying apparatus or lime machine may be constructed, it is absolutely essential, that its contents be kept constantly in motion, in order to produce the desired effect upon the crude gas, which would otherwise pass away in an impure state.
[47] The upper axis communicates with the agitating shaft of the lime machine, and the lower axis is a continuation of the shaft of the gas metre. The two pullies are connected by a strap.
When the charge of keeping the agitating shaft of the lime machine in action, is intrusted to a workman, there is no positive security against his occasionally neglecting his duty, whereas by applying the gas metre to that purpose, the manufacturer is assured beyond the possibility of deception, that when gas is produced, that gas is as certainly purified, and a saving is effected in point of labour of the expence of two men, one during the day, and one during the night.
Description of the Gas Metre at the Royal Mint Gas Works.
Fig. 4, [plate II.], represents a perpendicular section of the gas metre. It is placed between the purifying apparatus or lime machine, and the gas holder fig. 8, [plate III.], exhibits a front elevation; fig. 1, [plate III.], a perspective view, and fig. 6, [plate III.], a transverse section of the machine.
It consists of a hollow wheel or cylinder, made of thin iron plate, revolving upon an horizontal axis, in the manner of a grindstone; this wheel is enclosed in a cast iron air tight case containing water.
The cylinder or wheel, is composed of two circular channels, 1 and 2, fig. 4, [plate II.], concentric to each other. The larger or outer channel 1, is divided into three equal compartments, by partition plates, marked a, as shewn in the design. The compartments are provided with hydraulic ducts or valves, made at the upper part of every partition plate a, a, a, and by means of them a communication is formed between the larger concentric channel 1, and the outer case in which the wheel revolves.
Similar valves are also placed at the foot of each partition plate, they are seen near the letters a, a, a, and by this means, a communication is established, between each compartment or chamber of the larger concentric channel 1, and the smaller interior circle 2, of the wheel.
On inspecting the design, it will be seen that the valves are situated in opposite directions to each other, hence there can be no communication either between the inner smaller concentric channel 2, and the larger compartment of the wheel 1, nor between the latter compartment, and the exterior case, in which the wheel revolves, except, through the valves a, a, a, which form the communicating ducts. It will be seen also, that these valves are carried from one chamber of the machine into another, but in opposite directions; the entry into one chamber, being in the opposite direction to the hydraulic duct, placed in the other chamber.