_e_, up into the pipe _g_, and down the pipe _h_, (which is closed at the top) into the purifier _d_, is brought into contact with the liquor in that vessel, where it is opposed to a pressure in proportion to the perpendicular height of the column of liquid which it contains. The funnel in the compartment _c_, is considerably higher than the purifying apparatus, it therefore allows the liquid which it contains, when pressed upon by the gas, to ascend into it, without overflowing the apparatus, and to descend again as the pressure diminishes--_i_ is another wide-mouth funnel, by means of which the chamber _d_, is filled with the alcaline solution, or mixture of lime and water. The carbonic acid gas and sulphuretted hidrogen, evolved during the distillation of the coal, are thus made to combine with the alcali or lime, in the compartment _d_, of the purifier, forming carbonate and hidro-sulphuret of lime. The carburetted hidrogen, being left more or less pure, is conveyed through the pipe _k_, into the gasometer, fig. 3. The communication of the purifier, fig. 2, with the gasometer, is made by means of the well-known water-valve _l_, placed so that the communicating tube _k_, may be easily removed at pleasure--_m_, is a cock for drawing off the tar, &c. _n_, a gauge-cock for ascertaining the height of the liquid in the chamber _d_. The gasometer, fig. 3, the object of which is to store up the gas, consists of two principal parts--namely, a large interior vessel designed to contain the gas, and an outer cistern or vessel, of rather greater capacity, in which the former is suspended, designed to contain the water by which the gas is confined. The interior vessel which contains the gas is suspended by chains or cords hung over pullies, to which weights are attached, so as to nearly equipoise it. _o_ is a pipe, which communicates with the water-valve _l_, and by means of which the gas passes from the purifier, fig. 2, into the gasometer. The upper end of this pipe is covered, in the manner of a hood, by a cylindrical vessel _p_, open at bottom, but partially immersed beneath the surface of the water contained in the outer cistern of the gasometer, and perforated round near the lower edge with a number of small holes. The gas displaces the water from this receiver _p_, and escapes through the small holes, rising in bubbles through the water, so as to expose a large surface to its action, that it may be properly washed, &c. After rising through the water the gas enters the gasometer, which is suspended to move up and down by the chains, pullies, and balance-weights, _q_. From the centre of the gasometer a tube, _r_, descends, which includes a pipe, _s_, fixed perpendicular from the bottom of the cistern. The fixed pipe _r_, forms a guide to keep the gasometer always perpendicular. _t_ is also an iron pipe made fast in the centre of the inner vessel, and communicates with the upright tube, _s_, in the outer vessel. This contrivance obliges the