with another portion of the products referred to, in a liquid form, whilst the gas will pass into No. 3 chamber; when, as in the two former cases, it will be finally saturated with steam; and, passing from thence into No. 3 condenser, will deposit the remaining ammonia and its compounds, together with a portion of sulphuretted hydrogen: all of these liquid products, it is important to observe, should flow from the aforesaid condensers, as fast as they are deposited, into a suitable receiver or receivers ; each being sealed by an hydraulic joint, in order to prevent the gaseous vapours and gases from again returning and combining with the gas from which they had been extracted. From this apparatus the gas will pass, freed from the impurities, consisting of condensable vapours and gaseous compounds, into the lime machines; which, being charged with "dry lime," in the usual way, will be found (owing to the state in which the gas is previous to entering the lime machines) to purify a much larger volume of gas than can be accomplished with a given quantity of lime by the present processes, and also to avoid any inconveniences which arise on opening the purifiers and removing the "refuse lime" from the sieves, preparatory to recharging with fresh lime. As a further means of obviating such inconveniences, atmospheric air, heated or otherwise (the former being more rapid in its purifying operation), is blown through the materials employed for purifying the gas: the air, after being so blown through, may be discharged into, or through, the furnace-bars or chimney-shaft; the inflammable gas, contained in the lime-purifier, having being first blown out and discharged into the atmosphere. The apparatus employed for this purpose may be a centrifugal bellows, or other suitable pneumatic apparatus; the blast-pipe being connected to the exit-pipe of the purifier, and thus blowing out the contaminated atmospheric air, and the vapours and gases combined. therewith, through the pipe by which the gas enters the purifying vessel; an extra pipe and valve being attached to the entrance and exit pipes of each lime machine for this purpose. The reason why the atmospheric air is made to take the opposite course in its passage through the purifier is, to ensure the air coming in contact, in the first instance, with the less con

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taminated lime or other product, and vice versa. This injection of air into the lime purifier, when out of action, may be employed with advantage in the manufacture of gas, preparatory to removing the lime and other refuse materials, whether such manufacture be carried on according to the improved process, or the processes of manufacture hitherto adopted. The now purified gas goes into the gas-holder; and in its transit from the gas-holder to the mains, for the supply of the consumer, may be naphthalized, if required. For this purpose, apparatus may be employed, similar to that already described as the ammoniacal filtering-towers, by simply substituting naphtha for the liquid ammonia, and permitting it to descend through the atmosphere of gas to be naphthalized. In carrying out this plan, one or more filtering-towers may be employed, according to the volume of gas to be naphthalized, or the rapidity with which the naphtha is pumped up and passed through the gas; but, in all cases, the gas, previous to its being naphthalized, must be at a temperature not exceeding the lowest to which it will be subject in the mains, otherwise a portion of the atmosphere of naphtha supplied to the gas will be deposited during the transit to the consumer. In case the gas should be of too high an illuminating power, or that the naphtha contained in the gas is of more commercial value when extracted, than when left in the gas and employed for the purpose of illumination, a given portion of that naphtha may be extracted from the gas by the application of animal or vegetable oils, or purified tar, as a solvent, applied by means of the apparatus already described as the filtering-towers ;-the solvent employed being pumped up to the vessel supplying the perforated plates or diaphragms, until the denaphthalizing process has been carried to the requisite extent, or until the solvent employed has become saturated with the naphtha, when it must be removed and a fresh supply furnished. It will be obvious, that the apparatus herein before referred to, and hereinafter more particularly described, as the mechanical precipitator, may be employed with advantage for the separation of other gaseous compounds, in which the separation will be facilitated by subdi2 ૨

VOL. XXXII.

vision and agitation of the particles, combined with reduction of temperature.

The following is a detailed description of the apparatus employed in carrying out the invention :—

In Plate XIII., figs. 1, to 6, inclusive, shew the mode of setting and heating the retorts and regenerators; fig. 1, being a sectional elevation; fig. 2, a longitudinal section; fig. 3, a plan of one of the lower retorts, shewing the opening through which the flame rises; fig. 4, a sectional plan of the regenerators, shewing the manner of setting and heating the same; fig. 5, a sectional plan of the top retort; and fig. 6, a front elevation of retorts and regenerators, shewing the sights and flue-plugs. a, b, c, are the retorts; d, e, f, the regenerators, shewing the plates or metallic clippings contained therein, which are intended to increase the surface of heating medium, over which the gas flows from the retorts below; g, g, the furnaces; and h, h, the blow-holes, through which the flame rises from the furnaces. The flames or products of combustion first pass over the two lower retorts, and then ascend through the flues i, i, into the flue of the regenerators d, and f, where they combine and pass over the top retort c; they then proceed to heat the regenerator e, and, finally, escape into the flues above, in their course to the chimney-shaft, as shewn by the arrows in the figs. 1, and 2. m, m, are the pockets into which the solid depositions are received, and from which they are discharged at the flue-plugs 1, 1, which letters also designate all the other plugs and sights shewn in fig. 6. k, k, shew the protecting tiles, covering the retorts where the flame rises. In this method of setting the retorts, the furnace-bridge is altogether abandoned, and the flame is made to rise direct from the furnaces in front of the retorts, through the two side openings h, h; and, in order to ensure the bottom of the lower retorts being at the required temperature, they are raised by means of cross bricks about three inches, thus leaving ample space for the flame to act upon their bottoms. It will be observed, on reference to the drawings (see fig. 6), that each retort is furnished with a separate regenerator, into which the gas passes, immediately

from the retort with which it is connected, as previously explained.

Fig. 7, is a vertical section of the mechanical precipitator, and fig. 8, is the plan of the same. a, a, are the perforated revolving fans intended to agitate the gas in the chamber b, b, in which they revolve. The shaft being stepped into the lower chamber, is passed through an inclined plane d, d, under which the gas blows through the tar in its passage from the pipe x, x.-e, e, is a chamber, connected with the aforesaid, containing a convoluted worm or refrigerating pipe g, g, intended to cool the gas after it has escaped from the chamber b, through the curved pipe f; for which purpose the pipe is kept cool by a constant supply of water passing through the chamber e, e, provided by the pipe h, h, entering at the top of the chamber, and discharged through the pipe j, connected to the bottom. These pipes h, and j, are the short and long legs of a syphon; the chamber e, e, being also a part of the said syphon. The legs of the syphon are each furnished with a cock or valve, to open a communication with, or to cut off, the supply of water to the body e, of the syphon. The top of the pipe h, is furnished with a water-feed, in order to fill the body of the syphon previous to its being put into action; the valves or cocks p, p, being shut during the process of filling, and the air being discharged through the pipe s.—m, is an air-pump, affixed to the top of the chamber e, as shewn in fig. 8; which pump, as well as the perforated agitating apparatus, will be worked by the descent of the water flowing from the long legj, of the syphon, which gives motion to a small water-wheel, in connection with the bevilwheels, riggers, and band. This air-pump is employed for the purpose of removing the small quantity of air which would otherwise collect and stop the action of the syphon. Or motion may be given to the air-pump piston, and the shaft driving the vertical revolving fan, by a steam-engine, or any other available power. All the condensable products collected in the refrigerating pipe g, flow therefrom through the pipe n, into the chamber c, as do the like products precipitated in the agitating chamber b, b; which products finally pass off at the opening r, and at the level of the dotted

line, into a suitable receiver provided for that purpose. To prevent the gas blowing through the aperture in the inclined plane, where the fan-shaft passes, the shaft is inserted in a pipe z, bolted to the said inclined plane, being of an altitude sufficient to overcome the pressure of the gas. Instead of the usual stuffing-box, for the agitating shaft to work in, the patentee employs an hydraulic seal, consisting of an inverted cup t, affixed to the said shaft, dipping into water or any other liquid contained in the concentric space of the circular vessel v.

Fig. 9, is a plan, and fig. 10, a sectional elevation of the ammoniacal filtering towers, steam-chambers, and condensers, shewn combined in one apparatus; but which may be separated if thought more convenient. The operation is as follows:-The gas takes the course of the arrows in the ammoniacal towers 1, 2, and 3, entering each at the bottom, and making its exit at the top; from whence it proceeds into the steam-chambers 4, 5, and 6, and undergoes the processes of steaming and condensing, as before fully explained. a, a, are the steam-pipes, with cocks to regulate the volume of steam to be combined with the gas in each of the chambers; b, is the entrance from the boiler; c, c, c, are the three separate condensers before explained, shewing the entrance and exit pipes leading to and from the steam-chambers and condensers; and d, is a tank, into which the ammoniacal liquor is pumped through the pipe e. This tank has two divisional plates f, f, affixed to the top and sides, and descending to within a few inches of the bottom of the tank, and is sealed, to the level of the dotted line, by liquid ammonia. To ensure the gas flowing from one tower to another, as before detailed, each tower is furnished with a pipe g, connecting it to the aforesaid tank, and rising in the latter to the height of the dotted line; at which level the liquid ammonia flows through the pipe g, into its particular tower; where, falling through the perforated plate n, to the bottom of each tower, it washes and extracts the ammonia, as before described. In order to ensure an equalization of pressure in each compartment of the feed-tank, air-pipes h, h, h, connect the said towers and feed-chambers. Instead of the arrangement of

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