These tanks are usually constructed of an oblong shape, of brick well cemented, with one or more divisions, and capable of containing at least ten times as many hogsheads as there are heads of cattle on the farm. They are vaulted over, having a small aperture, in which it pump is placed, sufficient to allow a man occasionally to clear out the sediment, when the liquid has been pumped imp. The form preferred is that of a cube, or rather that of several cubes in succession. A tank for a farm of 200 acres of amble land should be 15 feet wide, 15 deep, and 45 long, giving 3 cubes of 15 feet, or a cavity capable of containing upwards of 10,000 cubic feet of liquid. In this tank the urine is diluted with water to prevent too rapid decomposition, and also to retain the ammonia which is formed ; for which purpose gypsum and sulphate of copper are sometimes put, into the tanks. In very porous soils the bottom and sides must be puddled, to keep in the liquid ; and it may be advantageous to build the walls in cement altogether. The liquid from the yards and stables is carried into the tank by a main drain constructed of brick or stone, and which receives a number of smaller drains from every part of the yards and cattle-sheds. Thus the litter in the yard is always dry, and none of the richness of the manure is lost by evaporation.
Sometimes the tank is vaulted like a cellar under the cow-house and stables, which are washed out twice every day, and all the dung and water are swept into a cesspool communicating with the tank. A very diluted, but rich liquid soon fills the first division of the tank : sluice is then shut, and the next washings run into a second division, and when that is full, into a third. In the meantime the contents of the first tank have undergone a certain fermentation, by which the ammonia first evolved has become mild and impregnates tho water. It is then in a fit state to be carried on the land in tubs or water-carts. When properly diluted, It accelerates vegetation in a surprising degree; but if put on fresh, it burns the grass or any veget• able it touches, because the ammonia is in a caustic state. If a cow drop her urine in a field in a hot summer's day, all the grass it has touched becomes yellow and is burned up': but if the same happen in rainy weather, the spot soon becomes very green, and the grass luxuriant; because, in this case, the urine is amply diluted and its caustic nature corrected. Those who live near gas-works may collect
the ammoniacal gas-water in a tank, and, by the addition of sulphuric acid in very small quantities, they may produce a very fertilising liquid, which will stimulate vegetation, and be a very good manure.
The necessary concomitant of a tank, whether for water or manure, is a water-cart, that is, a large cask put upon wheels to bring water from some distance. When there are uo means of bringing water in pipes, a water-cart, is quite indispensable. It is simply a cask placed on the frame of a cart, with a plug-hole in the end or lower part, from which the water may be let out by a cock, or drop on a flat board or into a bucket with holes, so as to spread it about. The plug-hole is shut by a valve inside, which can be opened by means of a string, the pressure of the liquid keeping it close to the plug-hole.
Many of the artificial manures would make excellent liquids by merely mixing them up with water in a tank, and allowing a certain degree of fermentation to take place. Thus nothing is lost, and all volatile substances are taken up by the water. The soluble portions are dissolved and the earthy matters diffused, so as to be more equally spread over the land.
When a farm-yard is situated on a hill, and there are fields or pastures on a lower level, at no great distance from it, the liquid from the tank may be conducted by channels lined with clay, having small sluices to direct the streams to any particular field. It may thus be made to temporarily a considerable surface, which it will greatly It may be led into the common furrows between the lands or stitches in ploughed land, and allowed to soak in them, and then it can be spread with the earth of the furrow, by means of broad shovels, over the growing crops, and will greatly invigorate them.
Hitherto the experience in this country of liquid-manure tanks is of limited extent, but the general impression is growing, that by covered yards and box-feeding the litter may so absorb all the urine and excre ment of the animals, that tanks will be unnecessary.