rated red marl, and it is superinduced by a bed of gravel, The thickness of the entire stratum of the said earth is from four inches to one foot; and its general position is very even, regular, and level. When first taken out of the earth its colours are very fine, particularly the lilac, which on exposure to the sun's rays, or to the influence of frost, soon becomes white. It has considerable weight, part of which it loses by drying, but in the manufacturing state its weight is very nearly that of the crude earth. Very little symmetry appears in its form or fracture. Its texture is very fine, with scarcely any exhibition of sandy or silicious matter, when pressed between the teeth. The chemical examination to which it has hitherto been subjected, has shewn that it contains clay, siliceous sand, and the oxide of iron; but a more studied examination would no doubt shew the existence of certain peculiarities in its component parts, or in the order of their combination, or the minuteness of its integrant parts, from which the detergent property of this earth might be found to arise. The processes for manufacturing the said earth are performed as follow. After digging it out of the vein, it is dried by means of stoves, or otherwise; then pulverized and sifted through fine sieves, or such other apparatus as is commonly used for sifting meal or other powders, A size is then prepared (in preference) from the white shreds of leather, and the dry sifted earth is beaten up or pounded or kneaded together with the said size, either by hand or by rammers, rollers, or such other machines or apparatus as are commonly used for the like purposes; after which operation it is formed into convenient parcels or cakes resembling those of soap, and of such sizes, figures, and dimensions, as are best adapted to the purposes of its intended application. The use of the size is to keep

the

the parts of the earth together, and to moderate the effect of its absorbent quality, which is so extreme, as to cause it to become pulverulent like quick lime when water is added to the dried earth; and accordingly I do not confine myself in the said manufacturing processes to the use of size made of leather, but I do apply other animal and vegetable mucilages to the same purpose, giving the preference to such, as by their cheapness and adhesive quality are best adapted to the purposes of the manufacture: and I consider the present instruction with regard to the use of one of the said mucilages as sufficient to enable any person to execute any processes in that respect. Lastly, I do observe that the leading and most distinctive property of the said earth, is that of cleansing wool in a manner much superior to soap; because, it makes it equally white and clean, without robbing it of what manufacturers call its nature, as soap does. To explain these effects I must state the well-known fact, that when wool is washed with coarse soap, it undergoes some change, either in the polish of its surface, or in the elasticity of its fibres, or in some other respects, which cause it to feel less full in the hand, so that it will not rise and spring up after pressure in the same manner as it did before such washing. Whereas, on the contrary, wool, when treated with the washing earth, becomes equally white and clean, at the same time that it remains in possession of all its original fulness and elasticity, which are of great consequence and value in the manufacture of this important article of national produce.

In witness whereof, &c.

Description

Description of an Instrument for breaking up Logs of Wood for the Purposes of Fuel, by blasting them with Gunpowder. Ry Mr. RICHARD KNIGHT, Ironmonger, Foster Lane, Cheapside.

With a Plate.

From the TRANSACTIONS of the SOCIETY for the Encouragement of ARTS, MANUFACTURES, and COMMERCE.

The Silver Medal was presented to Mr. KNIGHT for this Invention.

I HAVE frequently observed the great difficulty, la

bour, and loss of time, experienced in breaking up logs of wood, particularly for the purpose of fuel; such as the stumps and roots of large trees, which remain after the felling of timber, many of which, especially such as consist of the harder and more knotty kind, as oaks, elms, yews, &c. are frequently left to rot in the ground, in order to avoid the necessary expense of breaking them to pieces in the common way, which is generally effected by the axe, and driving a succession of iron wedges with a sledge hammer; a laborious and tedious process. Sometimes gunpowder is used, by setting a blast in a similar way to that in mines or stone-quarries. This method, though less laborious than the former, is tedious, is attended with several difficulties, and requires considerable experience and dexterity, or the plug will be more frequently blown out than the block rent by the explosion. With a view, therefore, to obviate these difficulties, I have constructed an instrument. The simplicity of its construction and application is such as almost to preclude an idea of its originality; but as it has hitherto appeared entirely