Aprit 19, 1872. THE BUILDING NEWS. 311 ——— ee ee —————eEeEeeEE———EEE either to be deposited in the box or caught jn the deodorising materials which form the packing of the strainer. ‘The fluid which passes through the strainer flows away by the sewer. As this apparatus forms the key to the whole system, it may be well to describe in general terms what it consists of. It may be said to be a strainer within a strainer, the inner one of which contains a manure box, This inner strainer with its manure box is removed daily, and replaced with a fresh one, The outer and larger strainer is not removed so often. The sewage enters through the bottom of the strainers, and the manure box is so arranged as to catch the solid matters. The strainer consists of cocoa-nut fibre matting, like a double sack, the space between the sides of which is packed with one of several substances. First, burnt clay, with about one-tenth part of crushed bones and a small quantity of silicate of soda, or (2) with cocoa-nut fibre and the same quantities of crushed bones and silicate ; or (5) with a mix- ture of cocoa-nut fibre and sea-weed charcoal, with the same quantities of crushed bonesand silicate. The sewage afterwards passes through a pile mat and two or three copper- wire gauze screens with fibre packing between them, and lastly it passes into the chamber through two thicknesses of ordinary passage floor coir matting. An examination of the results of passing the sewage through these various kinds of packing shows that the strainer, when packed with cocoa-nut fibre, reduces the amount of organic carbon in solution from 100 to 52, or nearly to one-half, and the amount of albumenoid ammonia from 100 to 85; but with sea-weed charcoal pack- ing neither is reduced considerably. They show also that the reduction of the organic carbon generates free ammonia; and finally that the greater part of the purification effected is performed by the simple mechani- cal action of the strainer, irrespective of precipitants. Mr. Austin argues that no such expensive constructions as those recently proposed by the Thames Valley Sewerage Commission are necessary, seeing that if the solids are removed (as, for instance, by his process) not more than 9 grains of organic matter to the gallon would be found in the effluent water, which would be removed by irrigation over and through a comparatively very small por- tion of land; and that such a quantity of land may generally be obtained. But, he thinks, in most cases the Water would be purified with greater economy in passing, as before said, through tanks or ponds filled with fish, such as chub, carp, and barbel, and plants, such as brooklime, reeds, flags, bulrushes, and watercresses. The space re- quired for these tanks would be considerably less than that required for irrigation, because the water would be more quickly purified by the animal and succulent vegetable life at work in them, and might consequently run off with greater velocity. These fish and water plants, it is said with truth, are the natural instruments for the extraction of organic matter from all river water, and would perform the operation of purifying much more economically than crops of rye grass, or any other crop which was not in- digenous to water. He argues that while the Rivers Pollution Commission came to one conclusion from the facts brought before them—viz., that the oxidation of organic matter in sewage when thrown into a river proceeds with extreme slowness, and that it is impossible to say how far such contaminated water must flow hefore the sewage matter becomes thoroughly oxidised—it would appear that those facts are open to another inference, and he pro- ceeds to show by figures that the absorption of -organic matter by the river water and whatever ‘it contains is much more rapid than the Commission had stated. _ The conclusion Mr, Austin draws is that, in order to purify the effluent water of sulli-
age by any economical process, the extraction of its solid ingredients must he effected at the earliest possible moment; the sooner they are extracted the more economical the process of purification required; and that if the solids were so extracted the quantity of organic matter in solution would be speedily absorbed or oxidised, and, therefore, that it would seem politic and reasonable to require nothing more than the extraction of all sus- pended organic matter, limiting the adultera- tions to such a quantity of organic matter in solution as would, in conjunction with all discharged from any subjacent towns, be dispersed or absorbed before any of it could reach the nearest populous district below. —————<>—__—_ DECORATIVE PROCESSES. GRAINING, STAINING, AND INLAYING OF GRANITES AND MARBLES, By AN EXPreRreNceD WORKMAN, (Concluded from page 272. HIE sponges made as described in our last are useful for imitating all granites, English serpentines, Egyptian porphyry, and as a groundwork for several marbles, notably verd antique, Egyptian green,.&c. As an illustration of the system, we will take the red Aberdeen or Peterhead granite. The distinguishing features of all granites are a broken or granular appearance, as if the parts had been at one time broken up into small pieces, and in course of time again cemented together by petrifying matter in a fluid state, and solidified by superincumbent pressure, forming an exceedingly hard sub- stance, coloured by the chemical colouring matter peculiar to the locality in which it is found; and thus we get the red granite and the gray, each varying in depth and bril- lianey according to the quarry from which it is obtained. Our English serpentines par- take in a great measure of the form and character of the granites; but they differ in colour, and have fine white and coloured veins crossing the slabs, which are absent in almost all granites. In imitating granites by the aid of sponges, we first mix a ground colour of the exact shade of the medium tint of the granite we are about to imitate. For the red granite we mix this colour with light red—ze., burnt Oxford ochre, with a little Indian red added, lightened to the required shade with white. We prefer this colour to be flat, as it forms a key for all the subsequent colour to rest upon without danger of running. It will be found the best to get up the ground white before painting with the ground colour of the granite. We now paint over the part we are about to operate upon with the medium tint, and let it seta little; we then dip an open sponge into a mixture of drop or ivory black and turps, adding sufficient japanner’s gold-size to fasten it. We have a piece of board by us to dab the sponge upon in order to take off any superfluous colour ; then we go over the whole of the work with this, using the sponge without pressure ; and giv- ing the hand a slight twist while the sponge is in contact with the work. If the black is thin enough with turps, but not too thin, this motion of the hand will partially remove a portion of the medium colour, and allow a little of the white underground to appear through the thin black, and serve to give depth and transparency to the work. We now take another sponge, and a thin mixture of blue gray, and go over again with this lightly as before. ‘Then we do the same with a thin white, using some little discretion as to the quantity of each we put on the work, or else we shall be very liable to make muddy, dirty work. We now mix a tint of solid colour—that is, body colour of the same tint as the dark- est tint of the prevailing or general colour of the granite. This red may be tinted with light red or Venetian red and Indian red.
We take a large open sponge, and with this colour we go over the whole of the work, and in working we turn the sponge round so that the marks or forms left by it every time it comes in contact with the work shall be as varied as possible. We also use a piece of stiff crumpled paper to dab or break up the work after the sponge. By this method, the whole of the black, white, and gray, which are partially transparent, appear to be underneath the last colour, and the paper being used breaks up the large ‘‘ splatches” of colour left by the sponge, and gives depth and unity to the whole. We may now spurt in a few fine spots of pure white, which finishes the process. Our English serpentines may all be imi- tated in exactly the same manner, using dif- ferent colours, of course, according to the kind or colour we are imitating, and adding the fine white veins peculiar to these marbles after the sponge work is dry. Another method of imitating granites, but which is not so good as the one before described, is done by splashing or throwing the colours on to the work in round splashes or dots. We may get a very pretty effect by this method, but it is utterly devoid of that broken, irregular appearance the sponge work has, and which is, in fact, the natural appearance of the real marble. The splashed granites aredone as follows: The ground colour and the working colours are the same as those used in the sponge granites. The ground is laid in, and while wet, a short-haired pound brush is dipped into the black, and the operator holds in his left hand a strong stick or piece of wood. Having this in a convenient position he strikes the brush against the wood witha sharp blow, the force of the concussion causes the black contained in the brush to fly out with considerable force, and in their passage through the air which intervenes between the brush and the work the particles or drops of colour become rounded and fall upon the work, forming, when they strike, round dots of various sizes, according to the amount of colour contained in each indi- vidual drop. Some workmen are very expert at this work, and will cover a large wall with exceeding regularity as to size and uniformity of shade; but it is at best but an imperfect method, resulting in failure in nine cases out of ten, Another method of splashing is by using a short, stiff, flat hog-hair brush, something like a large mottler in shape, but with less hair in it and five or six inches in breadth. We wantnow a flat piece of wood with a strip of wood fastened to one edge, and standing above thesurface of the board about halfaninch. We now dip the brush into the colour we are about to use ; then, holding the board in the left hand and the brush in the right, we place the ends of the bristles on the board and press the brush against the half-inch strip, so that the bristles will spring over it ; in the act of springing the bristles will throw the colour in spots on to the work. Of course, one colour is followed on after another, same as in the other methods described. There are machines made to perform this operation, in which the bristles are fixed upon a reyolying cylinder, turned by a handle, and fed with colour from a reservoir beneath, on a similar principle to those used by paper- stainers for effecting the same purpose on wall papers. ea! Egyptian porphyry may be imitated partly by the sponge and partly by splashing. ‘There are several colours of this marble ; but the marble we mean is of a dark rich red-brown colour. We first mix a rich dark ground colour with Indian red and black, On this we sponge the black and a little thin blue- gray with a fine sponge. We then splash in pure vermilion in minute spots, and follow with small spots of solid white. Another shade of porphyry is of a deep rich yellow- brown colour. The ground colour for imitating this marble is made from burnt umber, orange
