traction of the metal. Great elasticity and strength may also be given to bars or strips of wrought-iron, thus casehardened; and carriage and other springs may be made in this manner.

The patentee claims the method or process of casehardening iron, by coating, covering, or combining wroughtiron with cast-iron, as herein set forth.-[Inrolled at the Petty Bag Office, May, 1841.]

Specification drawn by Messrs. Newton and Berry.

To JOSEPH APSEY, of Cornwall-road, Lambeth, engineer, for improvements in the construction of flues for steamengine boiler and other furnaces.—[Sealed 6th April, 1841.]

THESE improvements consist in making the flues surround nearly the whole outer surface of the boiler, the outlet into the chimney being at a point below the water-line of the boiler; by which means, although the flues are above that line, the rush of the flame, heated gases, &c., will not be higher than the outlet into the chimney, all above that outlet being a stagnant heated atmosphere. Thus, any injury that the metal of the boiler, above the water-line, would sustain, if the rush of flame to the chimney was above that line, is prevented.

The patentee claims the mode of constructing flues of steam-engine and other boiler furnaces, whereby the same are carried above the water-line of the boilers, and the outlet into the chimney is found below the water-line of the boilers, as above described. [Inrolled in the Inrolment Office, October, 1841.]

To JOHN BETHELL, of Mecklenburgh-square, in the parish of St. Pancras and county of Middlesex, Gent., for certain improvements in rendering wood, cork, leather, woven and felted fabrics, ropes and cordage, stone and plasters or compositions, either more durable, less pervious to water, or less inflammable, as may be required for various useful purposes.—[Sealed 11th July, 1838.]

THIS invention of improvements in rendering wood, cork, leather, woven and felted fabrics, ropes and cordage, stone and plaster, or compositions, either more durable, less pervious to water, or less inflammable, as may be required, consists in impregnating such articles with various mixtures or solutions, so that they may be saturated throughout, and thus rendered either more durable, less pervious to water, or less inflammable, according to the different mixture or solution with which they are impregnated.

The apparatus used for this purpose, is an air and watertight vessel or tank, made of strong metal, of any form that may be preferred, (one made like the circular wrought-iron boilers for high-pressure steam-engines answers very well,) strong enough to withstand an internal pressure of two hundred pounds to the square inch, having a lid or door to it, which is made to screw on air-tight. The tank is fitted on the top with a common steam-boiler safety-valve; and it is connected by one pipe, having a stop-cock or valve in it, with an exhausting air-pump, and by another pipe, likewise fitted with a stop-cock, with a pump for forcing liquids into the tank, made like the pumps for forcing water into hydrostatic presses.

The articles to be impregnated are put into the tank, and the lid screwed on air-tight; the cocks in the pipes, leading to the pumps, being shut, the tank is then filled

with the desired mixture or solution, through a pipe, having a stop-cock in it, which is then shut, and the cock, in the pipe leading to the air-pump, being opened, that pump is set to work for the purpose of exhausting the air from the tank, and also out of the pores of the various articles placed therein; after which the liquid mixture or solution will penetrate into and fill up those pores, more particularly if the tank is kept heated, which may be done in any convenient manner; but for some articles this may not be found sufficient; and, in such cases, the air-pump, after having exhausted the tank, is stopped, the cock or valve shut, and the liquid force-pump set to work, (its cock being previously opened,) to force some of the same mixture or solution into the tank, until the required degree of pressure is obtained.

The working of the liquid forcing pump must be repeated every one or two hours, as the articles, by absorbing the mixture or solution, cause the pressure to diminish. The degree of pressure, to which it is determined to work up to, is regulated by loading the safety-valve with the appropriate weights, and as soon as the pressure of the condensed liquor exceeds the weight on the valve, the liquid is forced out of the valve, and the pressure within reduced.

In impregnating wood, by this apparatus, the process is much expedited by placing the logs of wood in the tank, in a perpendicular or slanting position, so that the butt ends of the logs may be at the bottom of the tank, and their upper ends a little above the surface of the liquid. In this case, as soon as the exhausting process is commenced with the air-pump, the air travels freely up the longitudinal pores of the wood, and the liquid follows it, entering into the bottom or butt end of the log, and following the air, as it is drawn out of them at the top by the air-pump.

It may not be necessary, with some very porous articles, to use both the processes of exhausting the tank of air, by the air-pump, and forcing in the liquids by the hydrostatic force-pump; but either one or the other of the processes, as is most convenient, may be used, and will be found to impregnate the articles sufficiently.

The form of apparatus, above described, is that which is most preferred; but it is evident, that the pressing or forcing the liquid mixtures or solutions into the articles, by means of pneumatic or hydrostatic pressure, may be obtained in various other modes; the following are examples :-Steam, at very high pressure, may be let into the tank, through a pipe, over the surface of the liquid within, thereby pressing on it with considerable force; or condensed air might be pumped in for the same purpose; or an hydrostatic force may be obtained, in the closed tank, by connecting it with a cistern placed at a considerable height above the level of the tank, by means of a pipe, having a stop-cock in it; when, upon the cock being opened, the pressure of the liquid through the pipe, from the elevated cistern, will be increased in the tank in proportion to the altitude of the eistern over the tank.

Another mode of impregnating wood, is by means of bags, made of sheet caoutchouc, or air and water-proof cloth, large enough to hold about two gallons, which are made open at one end, into which the butt ends of the pieces of wood are placed, and the edges of the bags tied very firm and close to the pieces of wood, by means of small lines, wound several times round the outside edges of the bags, over the pieces of wood; and to the other ends of the bags are fitted small pipes, furnished with stop-cocks, which proceed either to an elevated cistern, containing the liquid with which it is desired to impregnate the wood, as above described, or else to a liquid forcing-pump, as above

VOL. XX.

mentioned. When the cock in the pipe is opened, the liquid in the cistern, by its greater altitude, will force its way into the pores of the wood; or when the pipe is connected with the pump, the hydrostatic pressure, caused by the pump when worked, will force the liquid into the pores of the wood. One cistern or pump will thus be sufficient to impregnate many pieces of wood at once.

Trees that have just been cut down, may be rapidly impregnated in this manner, and many such new fallen trees will be thoroughly impregnated in a few days, with the solutions of the first class, hereafter mentioned, by merely placing the butt ends in troughs or open tanks, filled with the solutions, which will circulate with the sap throughout the whole tree.

Skins of leather, and fabrics of any kind, may be impregnated in a similar manner, by sewing them together in the form of bags, having pipes leading to an elevated cistern or pump, as above described, through which the solutions or mixtures may be forced into the bags and through every pore of the skins or fabrics.

Pipes, made of leather, or of folds of thick canvass, can, in this manner, be made less pervious to water, with the mixtures or solutions hereafter mentioned, for that purpose, by closing one end of the pipes and forcing the liquid mixtures in at the other end. Any of the articles may also be impregnated by placing them in the tank above described, exhausting the air therefrom by the air-pump, and then applying heat, in any convenient manner, to the tank, until the solution or mixture therein is made to boil, which is commonly called boiling in vacuo.

The mixtures or solutions, to be used with either of the above form of apparatus, for impregnating the various articles, are divided into three classes; the first class containing such as are applicable to render certain of the arti