Hence it is important that the chimney in which the flue terminates should be removed to a good distance from habitations, and, if it be practicable, should be erected on the summit of some neighbouring hill.

A method of condensation devised by Wilson and French is in use at the Sheffield Smelting Co/s Works. One great advantage it possesses is that it occupies little space. The principle of the condensation lies in this, namely, that the gases from the furnace carrying solid particles of fume with them are, after due cooling, forced through water in such a way that the water and fume are brought into very close contact and thoroughly - mixed; the solid element is thus effectually wetted and retained in the water, and the soluble gases are, as far as the dissolving power of the water permits, dissolved. Fig. 141 represents the condensing apparatus as it stands. The condenser consists of a wooden box or case a, having a shelving bottom where the solid matter arrested collects, and a tap b at the lowest point, by which the contents of the condenser are from time to time run off. The case is filled with water to the level of c. The box is fitted at d with a series of 3 or 4 - copper wire - gauze screens, which are supported in a horizontal position between f and e; f is a partition reaching from the top to a depth of 3 ft. 6 in., and the whole width of the box, so as to form, with the wall of the case a, a broad channel g, into which the gases first enter from the pipe A. From the lower part of this channel, a horizontal series of triangular wooden tubes . pass forwards beneath the screens, and are provided at the top surface with perforations through which the gases pass out from them, and then through the screens (which are immersed in the water) and water, to be finally discharged by the pipe j, which leads to the chimney of the works.

An open space ft, formed by the side of the case and the plank e which supports the triangular pipes and the screens, acts as a return or overflow channel for the water which is set in motion by the ascending current of gases: this promotes the subsidence of fume to the bottom of the box, and prevents at the fame time a considerable amount of saltation of the water above the gauze, which would tend to wear it out.

Fro. 111.

The cooling arrangement in use at these works is as follows: - The smoke from the furnace passes by a wide inclined flue to the bottom of the first of a series of 4 upright tubes, through which it passes in succession from the top of the first to the top of the second, and from this to the bottom of the third, and so on. The cooling tubes are made of boiler - plates (being simply old boiler - tubes), and they are placed vertically, merely with the object of saving space and to facilitate cleaning, since all the fume which settles there is found in cavities prepared for its reception at the bottom of the supporting brickwork. From the cooler, the smoke passes through a wrought - iron pipe to a blower or fan which is worked by a direct - action engine, and which forces the smoke into and through the condenser.

With respect to the working results of the apparatus, French says that the quantity of lead, silver, etc, arrested amounts to 95 to 98 Per cent. of that contained in the smoke as it leaves the furnace, and frequently even 95 to 98 Per cent. of the metallic contents as they enter the condenser, without taking into account that which deposits in the flue leading from the furnace to the condenser. These results are obtained when the smoke is made to pass through a depth of 8 1/2 in. of water and 3 wire - gauze screens. With greater depths of water and the same number of screens, as high percentages as 99 and 99.5 have been caught. With smaller depths, the results are lower, but still very satisfactory. The power required to work a condenser capable of condensing 95 to 98 Per cent. is about 2 h.-p. for each ore - hearth or reverberatory furnace. Bell was commissioned by the Sheffield Smelting Co. to test the capabilities of the condenser and its adaptability to their work. He tested the smoke immediately before it entered the con-denser (station 1 ) and as it left it (station 2), using the depth of water generally employed, viz., 7 in. above the perforations of the triangular pipes.

He found that with this depth of water, 93 to 93) Per cent. of the metallic lead was arrested; he took no account of the fume which was deposited in the flue between the furnace and the condenser, the quantity of which usually varies from 1/4 to 1/3 of the total amount of fume which leaves the furnace. In order to condense the remaining 5 percent. of fume (not arrested when 7 in. of water are used) a little extra depth of water (say 8 1/2 in.), and therefore an extra blowing power, would be requisite; but this would add only about Is. 6d. per 24 hours to the cost of working, and the extra cost would be in many cases repaid by the additional saving of fume. Bell also found that the condenser was effectual in arresting the sulphurous acid contained in the smoke. He says that a large proportion of the sulphurous acid gas was absorbed by the water in the condenser, and it was apparently not until this water was saturated that sulphurous acid began' to make its appearance at the second station. When the water in the condenser has become saturated with this gas, an event which would rapidly happen in cases where the condenser was used in ordinary lead smelting, the escape of sulphurous acid by the exit flue would recur.

French thinks that it might all be arrested by his condenser, if instead of charging it with a definite quantity of water, a constant stream of water were made to flow through it. But under this arrangement, settling - ponds for the fume suspended in the effluent water would have to be provided. Other modes of dealing with the sulphurous acid escaping after the saturation of the water in the condenser may be suggested. French thinks that the gas would be arrested if the smoke washed in the condenser were made to pass up a coke tower supplied with water at the top, and perhaps this might be effectual where the ore - hearth or any form of blast furnace'is in use. But it may be doubted if a coke - scrubber would arrest the acid when the smoke is so largely dilated with air as it is when proceeding from a reverberatory furnace. Still, the use of Wilson and French's condenser is calculated to facilitate subsequent disposal of the acid gases, and perhaps some chemical mode of dealing with them might be devised. French suggests that the waste gases might be propelled by means of a steam jet through a heating apparatus similar to the hot - blast heaters used in iron - smelting works, and the hot sulphurous acid, steam, and air passed through common salt, according to Hargreave's process.