\\lien the pieces have received the proper fold, the last operation previous to packing them, is the pressing. This is commonly performed by placing a certain num ber of pieces divided by thin smooth boards of wood in a common screw press, similar to those used by printers for taking out the impression left by the types in the printing press. Besides the wooden boards, a piece of glazed pasteboard is placed above and below every piece of cloth, that the outer folds may be as smooth and glossy as possible. The operation of the common screw press being found tedious and laborious, a very simple and efficacious method has been lately introduced of effecting the pressure by a column of water, which is so easy and expeditious, that the strength of a child is sufficient for the operation ; and its power may be rendered much greater than what could be produced by almost any exertion of human force. These presses are used with great success in different extensive works ; but as their discovery is recent, the application of the hydrostatical principle is also various. In Plate CVIII. Fig. 6, will be found a very simple mode of applying them to use, which it is hoped will sufficiently illustrate the general principle of their action, and may safely be adopted, with any judicious alteration which may render them more serviceable for the particular purpose in view. At present their novelty confines them to a few large works.
The water press may be made as to the frame work, very similar to any other kind of press ; hut it is to be observed, that as the pressure is upwards, it must be very strongly secured to the floor upon which it stands, and which must he equal to the whole mechanical reaction, or be sufficiently strong to resist the whole force of the pressure. In the Figure the frame work is dis tinguished by the letter A ; the upper press board by (I, and the under board by F. The board G is sup posed to be fixed and immoveable in the two upright posts ; but it would be very convenient that it should be made to slide up and down as required, and it may be stopped above by blocks of wood, or any of the means by which the sole of the common screw press is usually made up to the height wanted. It may also be coun terpoised with weights, for case in the management. The lower press hoard F, must slide freely up and down, like the upper board of the common press. Under this board is the receiver 13, for the water, which is here sup posed to be a hollow tube of leather, or any other soft substance which can be rendered impervious to water, and which must be sufficiently strong to resist a very great pressure. Let the leather tube therefore be stretched upon very strong hoops or iron, at two or three inches distance from each other, and again hooped out, immediately above those in the ilisidt... The
within will then keep the tube always lisle nded, and those without will counteract the lateral pressure of the water within. To the bottom of this receiver is attached a tube, branching from the main tube 11, for admitting the water into the receiver, and C, C arc two stop cocks in the main tube, the right hand one for admitting, and the left hand one for discharging the water. The pressure of the column of water in the main pipe 1), will then be in the direct ratio of the square of its altitude, and the pipe, according to the pressure required, may be of any length. The goods to he pressed being placed between the press boards (i and F, if the admitting cock be opened and the discharging cock shut, the with'• press board will be forced up by the pressure of the whole weight of the column of water in the main pipe I); which, at 33 feet height, will give 15 it pressure on every square inch. When the press is to be opened, it may be done in an instant by shutting the receiving and opening the discharging cock, which will discharge the water in the receiver into the drain at E. The simplicity of this press, and its immense power, render it one of the greatest improvements which have been lately applied to the practical purposes of manufacture, and whet e there is a command of water sufficiently elevated to fill the mutant pipe, it is wrought with no trouble or ex pence. Indeed, the waste of water is so very small, that the quantity may be easily collected from rain in a cis tern, or may be sent up by means of a small forcing pump. A well bored iron cylinder, with a close filled piston, would be a safer and more durable receiver than the leather tube represented. But front the innnense pressure, the piston would require much care in the packing.
For lawns and muslins of a light texture, the opera tion of smoothing requires a different process in some respects than close heavy fabric. Tnev only require to be slightly smoothed, to remove any marks which they may have received at the bleaching ; and as their beauty depends rather on their transparency than their close ness, the more the cylindrical form of the yarn is pre served the better. ']'hey are therefore put through a small machine, consisting of three rollers or cylinders ; and as the power required to move this is small, the person who attends it generally drives it by a small winch. It is represented by Plate CVIII. Fig. 7. A being the frame, B the winch or handle, and the rollers 1, 2, and 3. The mid roller 2 is of smoothly turned iron, the other two of wood. It is always wrought cold. Bonk and nnill muslins, Which arc finished with starch at the bleachlield to give them a clear wiry appearance, receive no other finishing at the calender than foaling and pressing.