Horn-shavings, hoofs, hair, wool, fish-scales and fish-bones, &c., and other animal substances not decomposing readily. The manuring value of these kinds of refuse depends partly on the quantity of nitrogen contained, and partly on the greater or less degree of subdivision in which they are applied. In regard to the former, it may be assumed from numerous investigations, that these substances, in the impure condition in which they are rejected from dwelling-houses and manufactories, contain in an air-dried condition about

The mineral substances accompanying this are only of importance in bones, these consisting to a full half of earthy phosphates. In the other materials named, the amount of such substances (ash) is so small that it may be disregarded in estimating their manuring value.

These substances have this character in common, that from their great firmness and toughness, they very strongly resist decomposition if alone, except when powdered or cut fine, as is the case in bone-dust, bone-charcoal, and turners' horn-shavings, which therefore may be applied directly as manures. With rags, feathers, bristles, leather, &c., reduction into small fragments, which moreover would be impracticable on farms, would not alone be sufficient, and therefore these substances must be subjected to the process of putrefaction,-best with the assistance of dissolving, materials, such as lime, wood-ashes, soda, &c.-until they have

by an analysis of the composition. Simple dried blood should contain, according to Prof. Way's analysis, from 6 to 8 per cent. of water and from 14 to 13 per cent. of nitrogen. Great variations may exist in samples, either from their not being sufficiently dried, when the per-centage of nitrogen will be proportionately lower, or from careless drying, overheating and carbonizing the blood. Good samples of the above character may be valued at £8 or £9 per ton, or perhaps even more now.-A. H.

become decomposed and so soft that they may be rubbed to pieces and mixed uniformly with the soil*. They then have double the worth, to the farmer, than they can claim in the fresh condition. Woollen rags may be at present obtained at the comparatively low price of 2s. 6d. to 38. per cwt..; and we may assign about the same value to the other rough refuse, while fine horn-dust or shavings may be estimated at twice as much.

Bone-charcoal, as now sold from the sugar-refineries, contains, as chief constituent, some 60 per cent. of phosphate of lime, with to 1 per cent. of very firmly combined nitrogen; it will therefore have a manuring value of 3s. to 3s. 9d. To exert a certain effect in the first year, it must be mixed with nitrogenous stable-manure, guano, &c. It also acts very powerfully alone on newly broken-up, fresh land.

May-bugs (wire-worms), snails, maggots, caterpillars, &c.— Since, among these animals, as they occur saturated with moisture in their natural condition, the may-bug contains 3 per cent., the rest about 1 to 12 per cent. of nitrogen, and all a considerable quantity of phosphoric acid besides, it needs no special demonstration to show that they must act as powerful manures, if, as is readily effected, they have been converted in and under the soil into a uniform friable

mass.

Refuse of prussiate of potash manufactories.-Yellow prussiate of potash is produced by heating animal substances with potash; the residue after the extraction with water contains animal charcoal, with a little very firmly combined nitrogen, and mostly also a small residue of potash-salts. As an unmixed manure it cannot be recommended, but it is a good addition to other manures rich in nitrogen, and to compost-mixtures, provided it can be obtained at a correspondingly low price.

Finally, we have to mention here human excrements, which are brought into a manageable form in the simplest and most convenient way, and without loss, by incorporation in compost-heaps.

*Or they may be subjected to the process of distillation (as described at page 176) Woollen rags are used in this country chiefly by the hopgrowers. They form the principal manure applied to the olive and lemon trees in northern Italy, where a trench is dug round the tree, the rags buried in this (about 20lbs. to each lemon tree) and left to decay..

4. Liquid Refuse of other kinds.

Soapsuds and wash-water.-Many and powerful manuring substances are not indeed present in these liquids, but still always enough to repay the little trouble of conveying them to an adjacent compost heap. The constituents chiefly acting are alkaline substances, soda and common salt; but besides these, the particles of dirt, from perspiration, dust, &c., are not without some action, and the dirtiest water is therefore to be regarded as the best. Far more active is the wash-water of cloth-factories, especially that which contains urine, and has been used for the first cleansing of the wool. The lye which is used in the preparation of flax or of linen for bleaching, contains alkaline substances, and besides these, nitrogenous matters out of the flax. In like manner the water in which flax is steeped would promise a very good effect, if it were not mostly too much diluted.

Kitchen-slops and brine. The same holds good of these liquids as of the foregoing; they contain common salt and small quantities of animal, or only of vegetable substances, derived from the remnants of food, or left behind in cooking. The solid refuse of the kitchen is a still more valuable addition to the compost-heap, provided it is not applicable for feeding the stock.

Acid-water from oil-refineries, &c.-In purifying oil for illuminating purposes, the raw oil is mixed with sulphuric acid, which carbonizes the slimy and albuminous substances expressed with the oil, so that when water is subsequently added, these settle down with the sulphuric acid and may be drawn off. This residuary liquid therefore contains sulphuric acid and carbonaceous, nitrogenous mud, and may find a useful application as a fixer of ammonia, to be added to urine, rotten dung or decaying compost. Mixed with marl or other calcareous substances, it causes the production of a quantity of gypsum corresponding to the amount of sulphuric acid present. The acid liquids of bleaching works, &c. contain free sulphuric acid and gypsum.

Acid-liquor from starch-works. In the old method of preparing wheat-starch, still in use in Germany, the gluten is separated from the starch by producing a fermentation, which is at first alcoholic, and then advances to the acid, finally to the commencement of the putrefactive, under which

treatment the greater part of the gluten becomes dissolved. The acid liquid thus produced contains consequently a tolerable quantity of nitrogen, in the dissolved gluten, and also of ammoniacal salts produced from this; it is therefore capable of producing the same effect in manuring as strong urine.

Under-lye of soap-boilers. In soap-boiling, common salt is finally added to the mass in such quantity that the water present becomes strong brine, in which the soap can no longer remain dissolved; as it cools therefore the soap comes to the top and the salt water or under-lye settles to the bottom. The under-lye contains in addition the excess of the alkaline lye of the mass of soap, is therefore rich in common salt and soda, always containing also sulphate of soda, and therefore, when diluted with 3 to 4 parts of water, it may be used as a solvent and promoter of fermentation, also as a neutralizing material for watering compost-heaps. In soft-soap works, soda and common salt, or manuring salt, are prepared from it. 1 cwt. of the latter may fetch about 3s., provided it be not mixed with worthless substances.

Gas-liquor from gas-works.-Coal always contains some nitrogen, from which, on the heating in close vessels, is formed carbonate of ammonia; this passes off with the illuminating gas and is dissolved in the water or milk of lime through which the gas is passed. The water of this kind rejected from the Saxon gas-works contains 4th to ths per cent. of nitrogen, and hence 1 cwt. of it, omitting the cost of transport, would have a manuring value of 2d. to 6d.* It was for a long time sold at the price of 23d. per cwt. to manufacturers, who profitably prepared from it sulphate of ammonia or sal-ammoniac, by adding sulphuric or hydrochloric acid and evaporating. As a manure, it may be placed on a level with the best putrid urine: in compost-heaps it will prove especially useful when these contain peaty or moory substances. If these are not present, it is advantageous to add previously to the gas-liquor so much sulphuric acid as suffices to remove the pungent odour (to 1 cwt., according to the strength of the liquor, 1 to 4 lbs.), to prevent the loss of the volatile ammonia.

The conversion of the kinds of refuse just described, into compost-manures, forms the subject of the following section.

*London gas-liquor appears to be about twice this strength, therefore proportionately more valuable.-A. H.

CONVERSION OF REFUSE INTO COMPOST.

255

XV. CONVERSION OF REFUSE INTO COMPOST.

THE kinds of refuse treated in the preceding section are by no means to be regarded as all suitable and complete manu ring substances in the condition in which they are ordinarily met with. In some the outward, in others the internal condition, requires a preliminary alteration, on the one hand to allow them to be mixed easily and uniformly with the soil, on the other that they may be expected to exert a rapid and powerful action. This alteration is achieved in the simplest manner and cheapest way, by converting the refuse into compost, that is, by mixing it with earth and allowing it to rot away into a crumbling mass by slow decomposition.

The high value of such composts or mixed manures, and the care with which all refuse and residuary substances of every kind fit for preparing composts are therefore sought for and collected, is especially taught us by the Belgian farmers. As they manure their land afresh every year, since otherwise the preponderating culture of corn would soon diminish the fertility of their partly middling, partly bad soil, they are compelled to apply the utmost care to the increase and advantageous treatment of their stores of manure, although from the large quantity of stock ordinarily kept, much stable-manure is produced.

Hence on the larger farms one especial man is always kept, as manure-bailiff, who hunts up all refuse and attends to its subsequent management. The mud accumulated in sewers and the ditches of the fields, or the mud from standing pools and canals, weeds, turf, with a certain amount of fresh stable-dung, as also the dust produced on the highroads and lanes, &c., are mixed, in layers, with lime, with ash from soap-boiling, peat-ashes, coal-ashes, as well as the dung of fowls, pigeons and geese, the whole being turned over several times, and urine always poured in at the same time. This manure is not put upon the land until completely rotten.

In the towns the cleansing of the streets is the business of the paupers, which at the same time opens a source of