the materials of which the white lead is composed. It consists of a strong wooden tub, secured with iron hoops, the bottom of which is formed of blocks of hard stone, firmly cemented together, so as to present a level surface. Other larger blocks, of the same kind of stone, are carried round upon this bed, by machinery, 30 that any hard and brittle substances, when placed in the tub with water, are continually rubbed under it, until reduced to the finest powder.

This description of mill is employed, because it continually mixes, and rubs together, the materials submitted to its action. Care should be taken that no iron, employed in the construction of the mill, may be so situated as to be liable to act upon the bodies to be ground; and where metallic fastenings are required, copper may be used. Into a mill of this kind, twelve feet in diameter, and three feet deep, put twenty-one hundred weight of chloride of lead, and seven and a half hundred weight of carbonate of lime, in the form of the best washed chalk or whiting; then partly fill the tub with water, and put the mill in motion. After the materials have been ground from four to six hours, cease grinding, and add more water, until the tub is nearly full; then suffer the whole to stand till the next morning, when a white mass, consisting of carbonate of lead, mixed with undecomposed carbonate of lime and chloride of lead, will be found at the bottom of the tub, and above this, a clear liquor, which is a strong solution of chloride of calcium, nearly free from lead. This solution must be drawn off, by means of a syphon or plug, and as much fresh water added as the tub will conveniently hold; then the grinding is renewed for a few hours; and when stopped, the materials are allowed to settle as before, and the solution again drawn off, and fresh water added, the grinding being continued again for a few more hours. The process is continued, day after day, in this manner, the supernatant liquor becoming every day a weaker solution of calcium, nearly free from lead, until at the end of seven or fourteen days it is nearly tasteless, when the decomposition is considered to be complete, and the white mass, at the bottom of the tub, will have become very nearly a pure carbonate of lead; in which state it is removed from the tub, and dried and prepared for the market in the usual manner.

When the patentee uses water, impregnated with carbonic acid gas, instead of grinding the materials together, as above described, he employs the following apparatus:

A barrel, made of lead, wood, or copper, strongly hooped with iron, and of any convenient size, is mounted on gudgeons; to one of which, a fast and a loose pulley are connected, and rotary motion is communicated thereto from machinery, by means of a band. The other gudgeon is made hollow, and communicates with the interior of the barrel; it is also furnished with a stop-cock, and, by means of a screw-joint, may be connected to a force-pump, for the purpose of forcing carbonic acid gas into the barrel.

One hundred and forty pounds of chloride of lead, and fifty pounds of carbonate of lime, are introduced into the barrel, through an aperture made in the end thereof; then the barrel is nearly filled with pure water, and the aperture is closed by means of a screw-plate and

leather washer. Carbonic acid gas is then forced into the barrel, by means of the force-pump, until the water is saturated under a pressure of four or five atmospheres; after which, the barrel is made to revolve at the rate of twenty revolutions per minute, and the substances within immediately begin to act upon each other; the carbonic acid solution dissolving the carbonate of lime, and presenting it to the chloride of lead in a better form for decomposition than when solid, or nearly so. This operation is carried on for three or four days; at the expiration of which, the action has advanced so far, that very little chloride of lead, or carbonate of lime remains, and the liquid is a strong solution of chloride of calcium, which, when the insoluble. mass is settled, may be removed from the barrel in any convenient manner, and a further quantity of water, impregnated with carbonic acid, must be added, and the barrel set in motion for a day or two longer, until the decomposition is perfected.

When nitrate of lead is used the same process is adopted with the chloride, except that the exact chemical equivalent of the two substances is employed. In the grinding tub, twenty-four hundred weight and nine-tenths of nitrate of lead, and seven and a half hundred weight of carbonate of lime, are ground together; and in the barrel, one hundred and sixty-six pounds of nitrate of lead, and fifty pounds of carbonate of lime are introduced. In both cases, the two substances are allowed to re-act upon each other, until the decomposition is complete; after which the carbonate of lead is removed, and prepared for sale.

Lond. Jour. Arts & Sci.

Specification of a patent granted to JOHN HENRY LE KEUX, of Pentonville, for an Improvement in Line Engraving, and in producing impressions therefrom.

This improvement consists in engraving a subject on two plates, one portion of the subject on one plate, and the remainder on the other, so that when printed, the combination of the two impressions shall produce the effect required.

Two plates being prepared for engraving, on one of them is put a tracing of any given subject. The outline and dark shadows are then etched on this plate, and finished by the usual process of line engraving; this plate is called the subject plate.

A tracing, or transfer, from the above is then placed on the other plate, and a tint of lines is ruled all over the subject; the lights are then stopped out, and the under tints, or shadows, are produced by biting in; thus forming what is called the ground plate. The plates being marked with register lines are printed, one upon the impression of the other, so as to produce the effect sought.

The claim is to the ruling of a tint of lines, and then producing the required under tints, lights, or deep shadows, on a separate plate from that on which the general subject is engraved, and then taking impressions from the two plates so engraved in the manner described (both being engraved in the style called line engraving,) whereby an entirely novel effect is produced, with a considerable saving of labour. Mech. Mag. Sept., 1841.

Specification of a patent granted to RICHARD LAWRENCE STURTEVANT, of Bethnal Green, for Improvements in the Manufacture of Soap. Enrolled September 8, 1841.

These improvements consist in manufacturing hard soap at one operation in the ordinary boilers, without separation of lees, or precipitation of niger, which is effected by using some, or all, of the following ingredients, viz., cocoa-nut oil, palm oil, tallow oil, and potash lees. Also the muriates of soda and potash.

The specific gravity of the lees is measured by Beaumé's hydrometer, at a temperature of 62° Fahr.

The following is the mode of making white soap: 2,072 lbs. of cocoa-nut oil, (in its raw state, or deprived of its rancidity in the manner hereafter noticed;) 168 lbs of olive oil, sweet oil, or tallow; 375 gals. of soda lees at 24°, and 60 gals. of potash lees at 20°, are boiled together in the following order: The cocoa-nut, and other, oil, or tallow, are first put into the copper, which may be heated by fire or steam; 10 gals. of the soda lees are then added, and the mixture allowed to boil; the remainder of the soda lees is added from time to time in similar quantities, the mixture being kept boiling. In about ten minutes after the whole of the soda lees have been put into the copper, about 84 lbs. of muriate of soda, or potash, are slowly sprinkled over its surface, and the mixture boiled for half an hour, when the fire or steam is withdrawn, and the soap is finished, and is to be cleansed or framed, when cool, in the usual way.

A hard soap for fulling, and such like purposes, is composed of the following ingredients, viz., 1,792 lbs. of cocoa-nut oil; 336 lbs. of tallow; 224 lbs. olive oil; 112 lbs. of rape oil, or of colourless palm oil; 400 gals. of soda lees at 25°, and 80 gals. of potash lees at 20°.

All these ingredients being put into the copper, the heat is applied, and the operation conducted as above, except that the muriates of soda or potash are not used, but as soon as the soap is made, 2,240 lbs. of grained, or curd soap, made upon the old plan, is added, and the mixture boiled until the two soaps are thoroughly incorporated.

To remove the rancidity of cocoa-nut oil, 10 cwt. of it is boiled in a wooden vessel by steam, with three pounds of sulphuric acid, or six pounds of muriatic acid. Or the oil is boiled alone for a sufficient length of time in an iron pan, by means of a dry heat.

The claim is, 1. To the making of hard soap, at a single operation, without separation or removal of lees, or precipitation of niger.

2. To the use of cocoa-nut oil, in conjunction with other materials, in the manner, and for the purpose, described.

To the mode of depriving cocoa-nut oil of its rancid and unpleasant odour by the processes described.

4. To the use of potash lees for the purpose of improving the quality and appearance, and giving a greater tenacity to soap.

5. To the use of muriate of soda, and muriate of potash, for the purpose of giving greater tenacity and hardness to soap.

6. To the ascertainment with greater falicity and accuracy of the

quantities and proportions of alkaline lees requisite to be used with the other ingredients in the manufacture of soap.

7. To the mode of making a fulling soap, or soap for manufacturing purposes, in the manner described.

Ibid.

Specification of a patent granted to JOSEPH MAUDSLEY, of Lambeth, for an Improvement in the Arrangement and Combination of certain parts of Steam Engines, to be used for Steam Navigation. Enrolled September 16, 1841.

This improvement consists of an arrangement of marine steam engines. The steam cylinder has a small open topped cylinder placed concentrically within it; the piston is a broad rim, or annulus, which fits the space between the interior of the large, and exterior of the small cylinder. The piston is jointed to the lower end of the connecting rod in the following manner; two vertical piston rods rise from opposite sides of the piston, and passing up through stuffing boxes in the cover, are united to a T-shaped cross-head; the upright stems of this cross-head descend into the small cylinder, and the lower ends are attached to a guide block, to which the connecting rod is also attached by a joint pin; which pin, according to the length of the upright stems of the cross-head, may be placed either above or below the piston, or level with it. The cross-head is composed of two parallel plates, united at the extremities of the horizontal arms, a sufficient opening being left between them for the working of the connecting rod.

The claim is to the improvement in the arrangement and combination of the different parts of steam engines to be used for steam navigation. The distinguishing character of that improvement being, that the connecting rod,with its appurtenances, is situated, and works,within a small open topped cylinder, which is fixed in the central part of the steam cylinder, and within the central part of the annular piston.

Ibid.

Specification of a patent granted to JOHN DEANE, of Dover, for Improvements in Preparing Skins, and other animal substances, for obtaining gelatine, size, and glue, and in preparing skins for tanning. Enrolled August 23, 1841.

The hair is first removed from the skins, by placing them in a solution of lime, potass, or soda, in the proportion of from 8 to 26 lbs. of lime, and from 4 to 16 lbs. of potass or soda to every fifty gallons of water. The skins are then placed in a revolving cylinder formed of bars of wood or metal, or a perforated surface of wood may be used, and the cylinder being placed in a trough filled with any of the before mentioned solutions is caused to revolve until the action of the lime, &c., aided by friction, has removed all the hair. The skins are then taken out of the cylinder, fleshed or shaved, and washed until thoroughly cleansed. They are then steeped in a large vat of water,

until a slight putrescence is apparent, when they are removed to suitable vessels, and covered with water, into which is poured from 6 to 28 or 30 lbs. of hydrochloric acid from each cwt. of animal substance. The vessel is then covered over, and the skins left to the action of the acidulated water from eight to twenty-four hours, or until the skins. assume a white semi-transparent appearance, when they are taken out and thoroughly washed in cold water, and afterwards deposited for two or three days in a tank, through which a current of fresh water flows continually. Instead of the hydrochloric acid in solution, the skins may be treated with hydrochloric acid gas. Hides, &c., are subjected to the above processes, and then tanned in the ordinary way.

The claim is to the use of a rotating,perforated, or other, cylinder,for the purpose of unhairing the skins, hides, or pieces, to be used in the manufacture of gelatine, size, or glue; when used in combination with a solution of lime, potass, or soda, or combined portions of either. Also, the application of hydrochloric acid, or hydrochloric acid gas, or either of them diffused in water, in whatever manner they may be employed; when applied to hides, skins, or other animal substances, for the purpose of preparing them for the manufacture of gelatine, size, or glue. Also the sole application of the above mentioned acid and acid gas to hides and skins, for the purpose of preparing them for being tanned.

Ibid.