The following engraving, Fig. 1, rerresents an apparatus of a convenient form, by Mr. James, of Knightsbridge. It consists of two vessels (A and B,) of stone ware, upon a strong stand c. The upper vessel, which is covered, receives the impure water in a chamber d, at the lower part of which there is a large aperture, stopped by a sponge e, which detains the grosser impurities : hence the water passes through a finely perforated earthenware plate into a layer of six inches of prepared charcoal, through which the water filters, and is thereby purified from any noxious smells, as well as any floating impurities; it then passes through another perforated plate g, and is received at k into the separate vessel, which is a stone ware cask, from which it may be drawn off at pleasure by the cock.
A very convenient filtering machine, from its portability, is Wiss•s patent filter, which is shown in the prcceding cut, Fig. 2. a is a force pump; b • suction pipe, to be inserted in a pail or other vessel of water ; c the pipe which conducts the water out of the pump to the top of the vessel d; e is a receiver for the purified water; f a cock for drawin* it off; g g g, screws for separating the receiver from the machine when required. The filtering substances used in this apparatus are of the same description as in the foregoing ones. The upper portion of the filter down to the letter d in the engraving, is left vacant for the dirty water which first passes through a thin bed of charcoal, and then through a bed of sand occupying the remainder of the vessel, and supported by a perforated metal plate, covered with a few layers of flannel.
A very simple method of freeing water from its impurities by means of the capillary attraction of fibrous substances is represented in the annexed engraving. a is the reservoir, b the lower com partment, c an open tube soldered into the bottom of the reservoir, in which is put a wick of cotton or wool, (the latter is best,) with one end immersed in the bottom of the reservoir, whilst the other end hangs down a little below it, forming a kind of syphon. The water in rising by the capillary attraction between the filaments deposits the gross matter floating therein, and descends in a compara tively pure state into the vessel b, or into a jug placed therein.
The figures represented in page 502, are a portion of Mr. Suwerkrop's appa ratus for filtering and beating water. , Fq. 1 shows a side elevation of the vessels in question; and Fig. 2 is a vertical section of the same. The letters have refer ence to similar parts in each figure. The water is supposed to be conveyed by
the pipe a from a reservoir situated upon a higher level than the cask b, which is divided by the partition c into two equal parts, forming thereby a double fil tering machine. In each of these divisions, the filtering substances and the arrangement of them are the same. As the water flows from a higher level, it will of course ascend through the filtering substances, and flow out at the part. The first substance which it has to pass through is a circular mat made by coiling up and sewing together a rope of platted horse-hair, which detains the grossest of the impurities; from this it passes through a floor or false bottom of wood, e, pierced throughout with numerous small holes ; upon the wooden bottom is laid first a stratum of coarse gravel or small pebbles, over this is put a layer of finer, then a layer of finer still, and lastly, a bed of sand f, about six or seven inches thick ; from this the water rises in a tolerably pure state ; if not sufficiently purified, instead of drawing it off for use, it may be allowed to pass through the curved pipe h into the upper division i of the cask. The water continuing to rise, then percolates successively through the horse-hair mat j, the perforated floor k, and the various strata of the sand and gravel 1, finally flowing out of the cask, and through the pipe eh into the heating vat n. The vat is constructed with a furnace o, and flue p p inside of it, all made of copper, except the grating for the fuel, which is made of cast iron as usual ; copper being preferred for the flue on account of its oxidating less rapidly than iron or other cheap materials. The heated air or gases first rise up the neck q into the hollow sphere r, which becomes soon occupied with intensely heated air, from whence it has little disposition to descend and escape by means of the spiral tubes, which finally become flues for the grosser products of the combustion ; as these tubes, however, make a long circuitous course through the tub of water, the heat is almost wholly absorbed by it. The furnace and flues are supported and kept in their positions by stays fixed to the sides of the vat, as shown. The three closed apertures in the cask b, FIg. I, are for the several purposes of washing the bottoms of the horse-hair mats, by pasting water through them downwards ; and for taking out and refreshing the layers of sand and gravel when they have become foul by deposition from the water.