Figs. 1361-2 show ao elevation partly in section, and a transverse section of one way of arranging the fitter. The apparatus consists of a central chamber a, to which the material to be treated is supplied by a pipe d, pressure being obtained by a pump, or by allowing the material to descend from an elevated cistern. The two sides of the chamber a are slotted, as shown at b, to allow the free escape of the mateiial on either side. The two faces of the ohamber a are also grooved all round, and the grooves are tilled with soft indiarubber c, as to project above the face of the chamber a. Against the face, is placed the filtering fabric, of such a size as to overlap the india rubber all around; holes are cut in it, corresponding to the slots b. Against the fabric, is plaeed a rectangular brass frame e, grooved and fitted with indiarubber in the same way as the faces of the chamber «. Another fabric is placed next, then another frame, and so on in succession. The alternating series of brass frames, filter-cloths, and indiasubber terminates in a cover-plate f.
The bolts h, fixed to the chamber a, hold the filter together. The outlet is at i. The material is admitted to the filter throughout its whole leng,th by a gutter leading from the feed-pipe. Filtration takes place, not through the fabric, which is woven so loosely as to be transparent, hut from its edges, the pure liquid traversing the fibres longitudinally till it escapes at the margin, while the solid matters are arrested, and range themselves concentrically upon the fabric around the indiarubber surface. A filter with plates 15 in. diam. and containing about 30 duplicate
surfaces of fabric, will pass 120 gal. per hour. The dirty fabrics need only a few minutes' rinsing in hot water to cleanse them from the adherent solids, and are at once ready for re-use. The action of tbe filter is purely mechanical, and it is not capable of removing impurities in chemical combination or solution.
Galvanism.—W. Eatborne Gill, of London, proposes a system of defecating by galvanism in conjunction with chemical agents and filtratkm. Galvanic and chemical actions are set up by the use of zinc strainers and strips, coated with a composition whose base is clean grease, the other ingredients consisting of charcoal, metallic sulphides, silica, alumina, and any. insoluble lime salt, reduced to powder, and inthnately blended. A zinc strainer receives the juice, which escapes by the orifices into a surrounding separator, where the lighter impurities rise, while the heavier pass into a bed of clean sand. It is claimed that the combined effect of the composition and the galvanic action set up in the juice is complete defecation, and prevention of all fermentation. But the only efficient part seems to be the sand-filter, which has long been known and appreciated.