One side of the lime-machine is provided with two large lenses, to admit light into the interior of the apparatus, so that by means of an eye-glass fixed in a proper place, the workman is enabled to see into the interior of the apparatus. And when the machine requires to be cleaned out, the manhole as it is called, is opened for the workmen to enter into the apparatus to remove any solid incrustation of carbonate of lime, or hydrosulphuret of lime that may happen to be formed in the lime trough, or any other part of the apparatus.
The wheel C, is loaded with a counter-weight, to balance the weight of the lime trough. To bring the lime trough again into a proper position, to be re-charged with a fresh portion of the purifying mixture, the workman turns the wheel C half round, the contrary way to that which caused the trough to be turned topside-down, and the trough may then be re-filled with a fresh portion of lime and water from the reservoir R, fig. 2, [plate II.], (or R, fig. 3, [plate VII.],) containing the mixture ready prepared. Y, is a pipe to bring water from a cistern into the lime reservoir R. The prepared lime which is to supply the machine is put into the vessel R, and a sufficiency of water being mixed with it, the mixture is stirred up to the consistence of a semi-fluid mass.
T, shows the pipe furnished with a sliding valve S, for conveying the purifying mixture of quicklime and water into the lime trough from the reservoir R, which is furnished with an agitator to stir up its contents.
To give motion to the shaft for stirring up the contents of the lime trough D, the inventor of this machine (Mr. Clegg,) has happily applied the gas, to act as a power for that purpose. This operation will be explained hereafter in describing the gas metre.
The pipe N, which conveys away the purified gas, proceeds from an hydraulic valve, to cut off the communication between the gas holder and the lime machine, if occasion should require it, and to prevent the gas from passing back from the gas holder into the lime machine.
It consists of a box containing water into which dips a small pipe, by means of which the gas passes out of the lime machine, and from thence into the pipe V, communicating with the gas metre. The box is furnished with a tube curved upwards to discharge the water when it accumulates above the required height, and to prevent any quantity being thrown out of the hydraulic valve, by the concussion of the fluid in the lime trough.
One cubic foot capacity of the lime trough is sufficient to purify 1000 cubic feet of gas obtained from Newcastle coal in twenty-four hours.
Test Apparatus, for certifying the purity of coal gas, and the proper manner of working the Lime Machine.
The proper purification of the gas being a matter of essential importance, as already illustrated [page 140], it becomes of great consequence to have some ready means of ascertaining whether the workman does his duty in this respect, by keeping the lime trough D, fig. 2, [plate II.], properly charged with the requisite quantity of lime and water necessary for the purification of the gas.
For this purpose an apparatus has been adapted by Mr. Clegg to the lime machine, which serves not only to indicate the quantity of fluid contained in the machine when gas is manufactured, but which also enables the workmen to appreciate the quantity of quick-lime necessary for the purification of the gas, and to ascertain its purity. The apparatus consists of a closed cup C, fig. 23, [plate IV.], partly filled with any coloured liquid. Into this cup is cemented, air-tight, a straight glass tube a, about 21⁄2 feet long and a 1⁄4 of an inch in the bore; the lower extremity of the tube nearly touches the bottom of the cup, and is therefore sealed by the fluid. d, d, is a small copper tube, which forms a communication between the air confined above the surface of the fluid in the guage cup C, and the gas which is proceeding into the lime-trough.