presses down the surface of the water sufficiently to make a passage for itself along and under the cover to the chamber at the exit end, and in doing so, is broken up into bubbles, which in struggling their way through, become partially washed by contact with the water, which slowly becomes. impregnated with ammonia, and is from time to time withdrawn and replaced with fresh water. An obvious objection to this form of washer, is the imperfect contact of the large globules of gas with the washing liquid, which ought, moreover, to be kept continually in an active state of agitation by some kind of stirring apparatus; but the greatest objection is the backward strain of pressure thrown on the retorts by the hydrostatic pressure exerted by the gas in forcing its way through the machine.

Various contrivances have been adopted for getting rid of this objection, and that now in general use consists of an elevated structure of iron, of 25 or 30 feet high, of a circular or rectangular shape, and from 3 to 6 or 7 feet wide. The gas being introduced into the bottom of the vertical vessel, passes upwards to the top, where it escapes by an outlet pipe, or, as the case may be, enters a second column, and descending, passes out at the bottom. Meantime large and powerful pumping apparatus is employed to force up to the top of the structure a constant stream of water, which, falling in a shower through the passing current of gas, generally effects the washing process satisfactorily. The same water is pumped over and over again, until it has been so impregnated with ammonia, that it is removed, and fresh water again introduced. This form of machine is not free of serious objections. The first of which is the difficulty of pumping up a sufficient volume of water to meet the greatly increased volume of gas that is passing the machine in winter, as compared with summer, which usually amounts to three or four times the quantity in the same time; and it is also a matter of wellknown experience, that all kinds of pumping machinery, requiring, as in a gas-work, to act day and night without intermission, is very liable to get out of order, and unless relays of apparatus are kept in readiness against accident, it is obvious that no stoppage for repairs can take place,

without allowing the gas meantime to pass without the washing process. I estimate that every 1000 feet of gas should be treated with 100 gallons of water (the water, of course, should never be below four or five degrees of saturation, otherwise it has a deteriorating effect on the illuminating power). The constant elevation of this body of water to the top of such a machine is expensive in engine power, and from the liability to get out of order for this work, it is a constant subject of care and anxiety in every large gas-work during the whole of the winter months.

Having experienced this with an apparatus such as now described, and being desirous, if possible, of getting rid of all the objections stated, I succeeded in contriving a machine on a new principle, by which the work is performed in the most satisfactory way that can be desired, and entirely free of all the objections attaching to those hitherto in use as above described. It has already been in constant operation day and night for nearly two years, and has never required to be stopt for repairs, or in any way gone out of the best working condition.

The leading idea of my improved washer, is to substitute a horizontal, instead of a vertical passage for the gas while being submitted to the action of the shower of water, whereby it should undergo a thorough shower-bath from a copious stream of water jets, falling some 20 inches, in an elongated horizontal chamber, instead of 30 feet in height; and that this should be effected without in any way presenting obstruction to its free passage, or throwing any back pressure on the retorts.

The apparatus consists of a cast-iron close cistern, with some external panelling and architectural ornament, measuring about 14 feet long, 12 feet wide, and 6 feet in depth, having a longitudinal vertical partition dividing its interior into two equal-sized chambers, 14 feet long, 6 feet wide, and 6 feet deep. In each chamber is fitted a revolving hollow cylinder, some 10 feet long, and 5 feet external diameter, with strong wrought-iron axles, and lignumvita bearings fitted inside the principal chest. The periphery of each cylinder is built all round with cast-iron buckets, twelve in

number, in the manner of a water wheel, with this difference, that with the exception of air-slits in the outside of each bucket, they are close all round the outside circumference. The interior surface of the buckets, about 10 inches less in diameter, is closed in with thin cast-iron plates, perforated with holes an inch apart, and one quarter inch diameter. Each cylinder is mounted at the front end with a spur wheel, actuated by pinions within the chest, for giving to each a

slow rotary motion, at about one-and-a-half revolution per minute. The pinion shafts pass by a stuffing-box to the outside, and are mounted with wheel gearing and driving pulleys, which are driven by engine power.

The chests being charged with water to the height of a few inches above the centre of the axles, and the cylinders being set in motion, in the direction of the arrow, fig. 1, which represents an end section of the cylinders, each bucket emerging from the water line CD, discharges a copious

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shower of water through the internal perforated plates, into the interior vacant space of each cylinder, and each bucket thus discharging its contents is nearly emptied by the time it reaches the surface of the water on the opposite side, as shown on fig. 1.

Fig. 2 is a front elevation of the machine, showing the outer driving gearing, and the inlet and outlet passages for the gas, AB.

Fig. 3 is a plan of the machine; the entrance for the gas being at A, and exit at B.

Fig. 4 is a cast-iron plate or screen, closely fitting the sides and top of the chest, and with a semicircular cavity accurately fitting the periphery of the front end of each cylinder, which is turned truly for this purpose, the two lower points of this plate, dipping a few inches into the water, compels the stream of gas entering at A to pass only through the interior of each revolving cylinder. On discharging at the back end of the first cylinder, a suitable aperture allows the gas to cross through the middle partition of the chest, and enter the interior of the second cylinder, and after passing forward through its interior it escapes by the outlet at B.

The volume of water thus brought up from the lower depths of the vessel amounts to 225 gallons per revolution. for each cylinder, being 450 gallons for the two, and the speed being 1 revolution per minute. There are 675 gallons, or

three tons, of water per minute showered by this apparatus upon the gas passing through it in that period of time.

To provide this copious shower in the ordinary washer would require appliances of a formidable character, in the way of pumps and other tackle. Here nothing of this kind.

is required; while the motive power requisite to lift the water about 18 or 20 inches in this machine is less than onetwelfth of that required to lift the water 30 feet in the old form of washer.

When the water is changed, it is only done partially, and