The paper-mill consists of a water wheel, or other first mover, connected with a combination of toothed and other wheels, so arranged as to cause the cylinder in the washer, and the one in the beat* engine (which are nearly of a similar construction,) to make 150 or more revolutions per minute. On the same abaft, and of the same size as the water wheel, is a cogged wheel, which gives motion to a pinion, on whose axis is a two or three-throw crank, that works as many pumps, which raises a constant stream of water from the mill-dam ; this water is kept constantly running through the rage in the washing and beating engines. The building and machinery of a paper mill should be well constructed, other wise the great velocity of the wheels produces a tremor, which in time shakes it all to pieces. A washing engine, when it revolves at the rate of 120 revolu tions per minute, and has 40 teeth, each of which passes by 14 teeth in the block, produces 87,200 cuts in a minute, and makes a most horrible growling noise ; but in the beating engine, in which the cutters and teeth are smaller, and the revolution more rapid, the noise produced is one continued loud bum ming. The cuts made in the latter amount to nearly 200,000 per minute, which circumstance will account for the rapidity with which the rage are con verted into a pulpy mass In which the filaments are so minute as to be scarcely discernible. The washing engines of a mill are placed at a higher elevation than the beating engines, and they are actuated in the following manner. The large cogged wheel, before mentioned, drives a pinion upon a vertical axis; upon this axis are two horizontal spur-wheels, at different elevations; the upper one drives a pinion on the axis of the washing engine, and the lower one a pinion on the axis of the beating engine ; and as these engines are similar in their arrangement of parts, and differ only in certain proportions, we shall make the subject intelligible by the description of one only. The figure on the next page represents a plan of one of these engines. a a is a wooden vat or cistern, about 10 feet long, 4i wide, and 2& deep, the inside lined with lead; b is a longitudinal partition, also covered with lead ; c is a reticulated cylinder, fixed fast upon the revolving shaft d, extending across the engine, and put in motion through the medium of the pinion a, driven by a toothed wheel on the vertical shaft of the mill, as before mentioned. This cylinder is made of wood, and furnished with a number of parallel blades, fixed longitudinally around its circumference. Imme diately beneath this cylinder is a block of wood extending its length, and of the breadth of the space between the two dotted lines represented. The upper sur face of this block conforms to the curvature of the cylinder, and it is provided with teeth or blades, placed close together, so as to present so many acute cutting angles, which present themselves constantly to the teeth on the revolving cylinder, not in contact, but so near as to cut, chop, and tear the rags as they are forced between them by the action of the machine. The distance between these opposed series of teeth is always susceptible of regulation, by turning screws at f f, which raise or lower the bearings g g of the axis of the cylin der, which bearings are levers turning upon fulcrums at h A. The engine is served with water by a pipe i from a reservoir supplied by the pumps, which it delivers into a small cistern j, communicating with the engine. This pipe is provided with a cock, to stop or regulate the quantity of water; and to prevent any extraneous matter passing with the water into the engine, it has a hair or wire strainer k placed across it. When the engine is filled with water, and a quantity of rags put in, they are, by the revolution of the cylinder, drawn be tween its cutters and those on the block underneath. This cuts them into pieces ; then, by the rapid motion of the cylinder, the rags and water are thrown upwards over a breasting, which rises in the same curve with the toothed block, up to about the middle of the cylinder; from this point they descend an inclined plane, whose length is represented by the dotted line 1, and take a course round the vat, as indicated by the arrows; the whole contents of the vat are thus put into motion, which continues as long as the cylinder revolves ; that being of course determined by the uniform reduction of the rags into a pulpy consistency. The cutter block is made so as to slide into or out of its place from the outside of the machine, for the convenience of sharpening its teeth, &c. The cutters of the cylinder are fixed into grooves made in the wood of the cylinder, at equal distances from each other around its circumference, in a direction parallel to its axis ; the number of these grooves is twenty; and for the washer, each groove has two cutters or blades put in it ; then a fillet of wood is driven fast in between them, to hold them firm, and the fillets are nailed fast into the solid wood of the cylinder. The beater is made in the same manner, except that each groove contains three bars and two fillets.
In the operation of this cylinder, it is necessary it should be inclosed in a case, or its great velocity would throw all the rags and water out of the engine. The case is a wooden box, inclosed on all sides except the bottom ; one side of it rests on the edge of the vat, and the other upon the edge of the partition b. Inside this case are two hair or wire strainers, through which the foul water passes as it is dashed against them, and on the opposite side of these strainers the case is formed so as to conduct the foul water into two flat lead pipes, seen in section at o o, out of the machine. When the water is not required to be carried off, as in the beating engines, there are sliding shutters provided to these sieves, which pass through grooves on the top, and at the sides of the case, by which the water as well as the rags are returned into the engine.
When the rags have been about an hour in the first engine, if they require it, according to the modern practice, they are bleached. There are two ways of bleaching used at present ; one by the oxymuriatic acid gas, the other by the acid combined in the dry way with quicklime. In the that way, the rags are boiled in an alkaline solution of potash and lime for four or five hours, or it very coarse, for eight hours. The purpose of this is to destroy the coarse part of the hemp, commonly called shon or sheave, and which exists in a great degree in coarse linens, especially German rags. The solution is then washed out in the washing engine; the water being pressed out, they are exposed to the acid in the gaseous form, as linen is ; (see the article BLEACHING.) The gas is then washed out as carefully as possible ; this is of great importance, as, if any acid remain in the rags, it causes the paper, after some time, to putrefy and change its colour. In the other way, the oxymuriate of lime is diffined in water by agitation, the insoluble matter is thrown out, and the liquid, when clear, is diluted and put in the engine ; being thoroughly mixed with the rags, it is allowed to stand for an hour or more, and the acid carefully washed out. Bleaching is not now quite so much practised as formerly, on account of the low price of rags; indeed, we understand that unbleached papers are entirely used in the Oxford University Press, for the printing of bibles, testaments, &c., on account of their great durability. After the bleaching, (if that process is used at all,) the stuff is reduced for an hour or more in the washing engine, and is then put into the beating engine. When it has been beat, as it is called, for
about three hours and a half, it is generally fine enough, and a valve placed in the bottom of the engine being opened, the stuff escapes into the chest, or general reservoir, which supplies the vat or other machinery.
We shall now proceed to describe the mode of making paper by hand, with out the aid of machinery, (in the common acceptation of that term.) The vat is made of wood, and generally about five feet in diameter, and two and a half in depth. It is kept at the required temperature by means of a grate, introduced by a hole, and surrounded on the inside of the vat by a case of copper. For fuel to this grate, charcoal or wood is used; and frequently, to prevent smoke, the wall of the building comes in contact with one part of the vat, and the fire has no coinmunication with the place where the paper is made. Every vat is furnished on the upper part with planks, inclosed inwards, and even railed in with wood, to prevent any of the stuff from running over in the operation. Across the vat is a plank, which is called the trepan, pierced with holes at one of the extremities, and resting on the planks which surround the vat. The moulds are composed of wire cloth, and a movable frame. The wire cloth is varied in proportion to the fineness of the paper, and the nature of the stuff: A laid mould consists of a frame of wood, neatly joined at the corners. Wooden bars run across it, about an inch and a half distance from each other. Across these, and consequently along the mould, the wires run, from fifteen to twenty i in an inch. A strong raised wire is laid along each of the oross-bars, to which the other wires are fastened ; this gives the laid wire its ribbed appearance. The watermark is formed by sewing a raised piece of wire, in the form of letters, or any device that may be wished, on the wires of the mould, which makes the paper thinner in these places. The frame-work of a wove mould is nearly the same ; but, instead of swing on separate wires, the frame is covered with fine wire-cloth, of froth 48 to 84 wires in an inch. On both moulds a deckle, or movable raised edging, is used; this must fit very neatly, otherwise the edge of the paper will be rough. The felts are pieces of woollen cloth, spread over every sheet of paper, and upon which the sheets are laid, to detach them from the form, to prevent them from adhering together, to imbibe part of the water with which the stuff is charged, and to transmit the whole of it when placed under the action of the press. The two sides of the felt are differently raised ; that of which the hair is the longest is applied to the sheets which are laid down ; and any alteration of this disposition would produce a change in the texture of the paper. The stuff of which the felts are made should be suf ficiently strong, in order that it may be stretched exactly in the sheets without forming into folds; and, at the 'same time, sufficiently pliant to yield to every direction, without injury to the wet paper. As the felts have to resist the reiterated efforts of the press, it appears necessary that the warp be very strong, of combed wool, and well twisted. On the other hand, as they have to imbibe • certain quantity of water, and to return it, it ie necessary that the woof be of carded wool, and drawn out into a 'lack thread. After the stuff is ready, the workman takes one of the moulds, furnished with its frame, by the middle of the short sides, and fixing the frame round the wire-cloth with his thumbs, he plunges it obliquely four or five inches into the vat, beginning by the long side, which is nearest to him. After the immersion, he raises it to a level ; by these movements he fetches up on the mould a sufficient quantity of stuff; and as soon as the mould is raised, the water escapes through the wire-cloth, and the superfluity of the stuff over the sides of the frame. The fibrous parts of the stuff arrange themselves regularly on the wire-cloth, not only in proportion as the water escapes, but also as the workman favours this effect by gently shaking the mould ; afterwards, having placed the mould in a piece of board, the workman takes off the frame or deckle, and glides it towards the coucher, who, having previously laid his felt, places it with his left hand in an inclined situation, on a plank fixed in the edge of the vat, and full of holes. During .this operation the workman applies his frame, and begins a second sheet. The coucher seizes this instant, takes with his left hand the mould, now sufficiently dry, and laying the sheet of paper upon the felt, returns the mould, by gliding it along the trepan of the vat. They proceed in this manner, laying alternately a sheet and a felt till they have six quires of paper, which is called a post; and this they do with such swiftness, that in many sorts of paper two men make upwards of twenty posts in a day. When the last sheet of the post is covered with the last felt, the workmen about the vat unite together, and submit the whole heap to the action of the press. They begin at first to press it with a middling lever, and afterwards with a lever of great length. After this operation another person separates the sheets of paper from the felts, laying them in a heap; and several of these heaps collected together areagain put under the press. The stuff which forms a sheet of paper is received, as we have already said, in a form made of wire-cloth, which is more or less fine, in proportion to the stuff; surrounded with a wooden frame, and supported in the middle by many cross-bars of wood. In consequence of this construction, it is easy to perceive that the sheet of paper will take and preserve the impres sion of all the pieces which compose the form, and of the empty spaces between them. The traces of the wire-cloth are evidently perceived on the side of the sheet which was attached to the form, and on the opposite side they produce an assemblage of parallel and rounded risings. As in the paper which is most highly finished, the regularity of these impressions is still risible, it is evident that all the operations to which it is submitted have chiefly in view to soften these impressions without destroying them ; it is of consequence, therefore, to attend to the combination of labour which operates on these impressions. The coucher, in turning the form on the felt, flattens a little the rounded eminences which are in relievo on one of the surfaces, and occasions, at the same time, the hollow places made by the wire-cloth to be partly filled up; meanwhile, the effort which is made iu detaching the form produces an infinite number of email hairs on every protuberant part of the sheet. Under the action of the press, first with the felts, and then without them, the perfecting of the grain of the paper still goes on. The vestiges of the protuberances made by the wires are altogether flattened, and, of consequence, the hollows opposite to them dis appear also; but the traces formed by the interstices of the wire in consequence of their thickness, appear on both sides, and are rounded by the press. The paper, the grain of which is highly softened, is much fitter for thes of writing than that which is smoothed by the hammer; on the a coarse and unequal grain very much opposes the movements of the pen, as that which is beat renders them very uncertain. The art of making paper, there fore, should consist in preserving, and, at the same time, in highly softening the grain.