pipe gg, proceeding from the lower end of it, communicating with a small forcing-pump at h; this stands in an iron cistern H, which contains the water, and sustains the standard ii, for the centre of the handle G, with which the pump is worked by one or two men. The upper extremity of the standard guides the piston-rod of the pump, to confine it to a vertical motion; is a weight for counterbalancing the handle G of the pump. From what we have said before, the operation of this machine is evident; the power of the cylinder D is in proportion to its size compared with the size of the pump; but as it only acts through short limits, the pinion and drum B are necessary to raise the weight a sufficient height. The operation of lowering goods by this crane is extremely simple, as it is only necessary to open a cock at m, which suffers the water to escape from the cylinder into the cistern H, and the weight descends, but under the most perfect command of the person who regulates the opening of the cock; for by diminishing the aperture, he can increase the resistance at pleasure, or stop it altogether. Fig. 345 is a side elevation of a crane. The post is immovable, and is fixed on an iron frame, with arms extending in the form of a cross, the extremities of which are bolted down by strong screws to large blocks of stone sufficiently heavy to more than counterpoise the weight to be raised by the crane. In the top of the post is fixed a wrought-iron pivot, by which the weight is supported, and a strong cast-iron cap bears on the pivot, and has attached to it two iron frames, one on each side, that receive the pressure from the stay, as well as support the pull of the jib, which is formed of two bars of wrought-iron; the lateral pressure is borne by the bottom of the post, round which two friction-rollers turn to facilitate its motion. This crane will carry five tons with safety.

PRESSES.

THE press is a machine in most extensive use in the mechanic arts. It is usually made of wood, or iron, and serves to squeeze or compress any body very close.

Screw-presses generally consist of six members, or pieces; viz. two flat smooth tables of wood or metal, between which the substance to be pressed is placed; two screws, or worms, fastened to the lower plank, and passing through two holes in the upper; and two nuts, in form of an S, serving to drive the upper plank, which is movable, against the lower which is stable and without motion.

Presses used for expressing liquors, are of various kinds; some, in most respects, the same as the common presses, excepting that the under plank is perforated with a great number of holes, to let the juice run through into a tub or receiver underneath.

1. An improved cider-press, turned by a windlass, is shown in fig. 284.

AA is the base or foundation with its supporting parts; B B the cheeks or sisters; DD the cross-piece at top, through which the screw passes, and which consequently contains the female screw; E the screw with its appendages; FF the bridge or cross-piece which acts on the pommage; GG is the wide plank or vat on which the pulp rests in the hair bags, in which the mode of the liquor's passing off is seen.

This kind of press may be advantageously employed for packing cloth, paper, and other goods; as also in paper-mills, for flattening and rendering paper solid; and in the manufacture of woollen cloth, for glazing and setting a finish upon the article in its last stage.

2. Two elevations of a very good screw-press for a papermill are given in figs. 285 and 286.

A A is the bed, formed of an immense beam of oak; and each of the cheeks, B, consists of a long iron bar bb, fig. 286, the ends of which are welded together, so that it forms a long sink, one end of which receives the end of the bed A, and the other the end of a massive cast-iron bar D, through which the screw E is received, and its nut fixed fast therein. The open spaces of the long links or cheeks, b, b, are filled up by rails of wood C, which support the weight of parts of the press when it is not in action, but these bear nothing when the press has any articles under pressure in it; these articles are laid at H, on the bed, and the follower, G, is pressed upon them by the screw, when it is turned by a long lever put through the holes in the screw-head F.

The screws employed for paper-presses are generally formed with such coarse threads, and so rapid a spiral, that the elasticity of the paper is sufficient to force it to run back. To these a ratchet-wheel, a, is fixed, and a click e, fig. 287, is applied to its teeth; to prevent its return, the click is supported on a bar bd, which moves on a centre at B, but the other end is retained by a catch or lever fg. When the press is to be relieved, the

end f, of the catch, is driven back; this relieves the bar db, and the click no longer detaining the ratchet-wheel, the screw runs back.

3. A very ingenious and useful packing-press has been invented by Mr. John Peek. It is represented in fig. 288.

A A, the frame of the press; B B, the large screws, which, in this press, contrary to those in common use, is fixed and immovable; C, a circular iron bar, extending beyond the sides of the press, and having thereon two worms, or endless screws E E, which work in two toothed wheels fixed to the nuts, and, by turning the winch D, drive the nuts and bed up and down the screws as may be found necessary; F, a stage, suspended from the bed, and on which the men stand who work the press; such a stage may, if found necessary, be fixed at the other end of the bar, as shown by the square shoulder G. The bed of this press must be formed of two pieces of strong wood, which are held together by screws and nuts, passed through them, as shown at hhhh. The great utility of this press consists in its being capable of packing two sets of bales at once; thus answering the purpose of two presses, with more expedition.

4. The hydrostatic or water-press, or as it is sometimes called Bramah's Press, has, for a great number of purposes, superseded the use of the screw-press, over which it possesses great advantages, in all cases where a strong pressure is required. It is one among the many useful inventions of the late Mr. Joseph Bramah, of Piccadilly; and is ingeniously contrived for applying the quaqua versum pressure of fluids as a powerful agent in many kinds of machinery.

These contrivances consist in the application of water, or other dense fluids, to various engines, so as, in some instances, to cause them to act with immense force; in others, to communicate the motion and powers of one part of a machine to some other part of the same machine; and, lastly, to communicate the motion and force of one machine to another, where their local situations preclude the application of all other methods of connection.

The first and most material part of this invention will be clearly understood by an inspection of fig. 289, where A is a cylinder of iron, or other materials, sufficiently strong, and bored perfectly smooth and cylindrical; into which is fitted the piston B, which must be made perfectly water-tight, by leather or other materials, as used in pump-making. The bottom of the cylinder must also be made sufficiently strong with the other part of the surface, to be capable of resisting the greatest force or strain that may at any time be required. In the bottom of the cylinder is inserted the end of the tube C; the aperture of which communicates with the inside of the cylinder, under the piston B, where it is shut with the small valve D, the same as the suction-pipe of a common pump. The other end of the tube C communicates with the small forcing-pump or injector E, by means of which water or other dense fluids can be forced or injected into the cylinder A, under the piston B. Now, suppose the diameter of the cylinder A be 12 inches, and the diameter of the piston of the small pump or injector E only one quarter of an inch, the proportion between the two surfaces or ends of the said piston will be as 1 to 2304; and supposing the intermediate

space between them to be filled with water or other dense fluid capable of sufficient resistance, the force of one piston will act on the other just in the above proportion, viz. as 1 is to 2304. Suppose the small piston in the injector to be forced down when in the act of pumping or injecting water into the cylinder A, with the power of 20 cwt. which could easily be done by the lever H; the piston B would then be moved up with a force equal to 20 cwt. multiplied by 2304.

Thus is constructed a hydro-mechanical engine, whereby a weight amounting to 2304 tons can be raised by a simple lever, through equal space, in much less time than could be done by any apparatus .constructed on the known principles of mechanics; and it may be proper to observe, that the effect of all other mechanical combinations is counteracted by an accumulated complication of parts, which renders them incapable of being usefully extended beyond a certain degree; but in machines acted upon or constructed on this principle every difficulty of this kind is obviated, and their power subject to no finite restraint. To prove this, it will be only necessary to remark, that the force of any machine acting upon this principle can be increased ad infinitum, either by extending the proportion between the diameter of the cylinder A, or by applying greater power to the lever H.

Fig. 290 represents the section of an engine, by which very wonderful effects may be produced instantaneously by means of compressed air. A A is a cylinder with the piston B fitting air-tight, in the same manner as described in fig. 289. C is a globular vessel made of copper, iron, or other strong materials, capable of resisting immense force, similar to those of air-guns; D is a strong tube of small bore, in which is the stop-cock E. One of the ends of this tube communicates with the cylinder under the piston B, and the other with the globe C. Now, suppose the cylinder A to be the same diameter as that in fig. 289, and the tube D equal to one quarter of an inch diameter, which is the same as the injector, fig. 289; then, suppose that air is injected into the globe C (by the common method) till it presses against the cock E with a force equal to 20 cwt. which can easily be done; the consequence will be, that when the cock E is opened, the piston B will be moved in the cylinder A A with a power or force equal to 2304 tons; and it is obvious, as in the case fig. 289, that any other unlimited degree of force may be acquired by machines or engines thus constructed. Fig. 291 is a section, merely to show how the power and motion of one machine may, by means of fluids, be transferred or communicated to another, let their distance and local situation be what they may. A and B are two small tubes, smooth and cylindrical, in the inside of each of which is a piston, made water and air tight, as in figs. 288 and 289. CC is a tube conveyed under ground, or otherwise, from the bottom of one cylinder to the other, to form a communication between them, notwithstanding their distance be never so great, this tube being filled with water or other fluid, until it touch the bottom of the piston; then, by depressing the piston A, the piston B will be raised: The same effect will be produced vice versâ : thus bells may be rung, wheels turned, or other machinery put invisibly in motion, by a power being applied to either.

Fig. 292 is a section, showing another instance of communicating the action and force of one machine to another; and how water may be raised cut of wells of any depth, and at any distance from the place where the operating power is applied. A is a cylinder of any required dimensions, in which is the working piston B, as in the foregoing examples; into the bottom of this cylinder is inserted the tube C, which may be of less bore than the cylinder A. This tube is continued, in any required direction,

down to the pump cylinder D, supposed to be fixed in the deep well E E, and forms a junction therewith above the piston F; which piston has a rod G, working through the stuffing-box, as is usual in the common pump. To this rod G is connected, over a pulley or otherwise, a weight H, sufficient to overbalance the weight of water in the tube C, and to raise the piston F, when the piston B is lifted; thus, suppose the piston B is drawn up by its rod, there will be a vacuum made in the pump cylinder D, below the piston F; the vacuum will be filled with water through the suction pipe, by the pressure of the atmosphere, as in all pumps fixed in air. The return of the piston B, by being pressed downwards in the cylinder A, will make a stroke of the piston in the pump cylinder D, which may be repeated in the usual way by the motion of the piston B, and the action of the water in the tube C. The rod G of the piston F, and the weight H, are not necessary in wells of a depth where the atmosphere will overbalance the water in the suction of the pump cylinder D, and that in the tube C. The small tube and cock in the cistern I, are for the purpose of charging the tube C.

By these means it is obvious that the most commodious machines, of prodigious power, and susceptible of the greatest strength, inay readily be formed. If the same multiplication of power be attempted by toothed wheels, pinions, and racks, it is scarcely possible to give strength enough to the teeth of the racks, and the machine becomes very cumbersome and of great expense. But Mr. Bramah's machine may be made to possess great strength in very small compass. It only requires very accurate execution. Mr. Bramah, however, was greatly mistaken when he published it as the discovery of a new mechanic power. The principle on which it depends has been well known for nearly two centuries; and it is matter of surprise that it has never before been applied to any useful practical purpose.

5. The Stanhope printing-press is delineated in figs. 293 and 294, being elevations, and fig. 295, a plan.

AA is a massive frame of cast-iron formed in one piece; this is the body of the press, in the upper part of which a nut is fixed for the reception of the screw b, and its point operates upon the upper end of a slider d, which is fitted into a dove-tail groove formed between two vertical bars e e, of the frame. The slider has the platen DD firmly attached to the lower end of it; and being accurately fitted between the guides ee, the platen must rise and fall parallel to itself when the screw b is turned. The weight of the platen and the slider are counterbalanced by a heavy weight E, behind the press, which is suspended from the lever F, and this acts upon the slider to lift it up, and keep it always bearing against the point of the screw.

At G are two projecting pieces, cast all in one with the main frame, to support the carriage when the pull is made; to these the rails H are screwed, and placed truly horizontal, for the carriage I to run upon them, when it is carried under the press to receive the impression, or drawn out to remove the printed sheet. The carriage is moved by the rounce or handle K, with a spit and leather girts very similar to the wooden press. Upon the spit or axle, a wheel, L, is fixed, and round this leather belts are passed, one extending to the back of the carriage to draw it in, and two others, which pass round the wheel in an opposite direction, to draw it out.