In Britain very little paper is now made by hand, the paper-machine having changed the character the manufacture. It is usually stated that Louis Robert, a Frenchman, "invented thd paper-machine, and that it was brought to this country by Didot of Paris in an imperfect state, but received improvements from Fourdrinier. But it must not be overlooked that Brantalt took out a patent in 1805, rather more than a year before Fourdrinier, for very similar improvements to those de scribed in Fourdrinier's specification. The object of all was to cause an equal supply of the pulp to flow upon an endless wire-gauze apron, which would revolve and carry on the paper until it is received on an endless sheet of felt, passing around and between large couching cylinders. These machines have now been brought to such perfection, that paper can be made in one continuous web of any length; and, before leaving the machine, is sized, dried, calcudered, hot-pressed, and cut into sheets. Different. engineers have contrived variations of constructions in the paper-machine, but the general principles of all are the same. We therefore select for illustration the machine which was exhibited by Mr. George Bertram of Edinburgh, and which was universally acknowledged to be by far the most complete and perfect which was presented in the in ternational exhibition of 1862. Since then no very impor tant improvemetits have been made in the main part of the machine, but the drying portion has been greatly ex tended.
Fig. 2 is a side view of the machine. The principle of the, machine is very simple; it, contains a pulp vat, A, with a hog or wheel inside to agitate the pulp and an arrangement for pouring the pulp over the wire-gauze: mold, B, B, B, B, which instead of being in single squares, as in the hand process, is an endless sheet mov ing round two rollers, a, b, which keep it stretched . out and revolving when in operation. Under the part which receives the pulp there is a series of small brass rollers, d, these, being nearly close together, keep it perfectly level, which is a most necessary condition; besides which, there is a shallow trough, ee, called the save all, which catches and retains the water, which always escapes with some pulp in suspension; and an \arrangement of suction boxes and tubes, f, f, f, worked by air-pumps, which draw much of the water out as the pulp passes over them. The pulp is kept from running over the sides by straps called the deckles, which are also endless bands, usually of vul canized India-rubber, carried round moving rollers, se that they travel with the wire-gauze, and therefore offer no resistance to it. In addition to all this, the frame-work on which the surface of the wire-gauze rests has a shog ging motion, or side-shake, which has an important effect m working the fibers together before the pulp finally set tles down. When it reaches the couching roils, which press out most of the remaining moisture, and carry it forward to the first and second series of press-rolls by means of an endless web of felt which passes round them, the speed of these rollers and the traveling sheet of felt, CC, is nicely calculated, so as to prevent a strain upon the still very tender web of paper. Sometimes the upper rollers of
these two series are filled with steam, in order to com mence drying the web. The paper is now trusted to itself, and passes on, as indicated by the arrows, from the second to the first set of drying cyliners, D, where it. again meets with a felt sheet, which keeps it in close con tact with the drying cylinders, which are of large size, and filled with steam. Around these it passes, drying as. it goes; is then received between the two smoothing rolls, or calenders, which press both surfaces, and remove the marks of the Wire and felt, which are until then visi ble on the paper. This is necessarily done before the drying. is quite completed; and from the smoothing-rolls it passes to the second series of drying cylinders, where the drying is finished, and thence to the calenders, which are polished rollers of .hard cast-iron, so adjusted as to give a considerable pressure to the paper, and at the same time a glossiness of surface. For writing papers, the paper passes through a shallow trough of size after leaving the drying cylinders, and then passes over another series of skeleton cylinders, with fans moving inside, by which it is again dried without beat, and afterwards passes through the calenders. Printing and other papers are usually sized by mixing the size in the pulp, in which stage the coloring materials— such as ultramarine for the blue tint of foolscap—are also introduced. Still following the paper web in the drawing, it is seen to pass from the calenders to another machine, F; this slits the web into widths, which are again cross cut into sheets, the size of is regulated at will. The water-mark is impressed on machine-made paper by means of a fine light-wire cylinder with a wire-woven pattern: this is placed over the wire gauze sheet upon which the pulp is spread, but near the other end of it, so that the light impression of the marker may act upon the paper just when it ceases to be pulp, and this remains all through its course. There are many other interesting points about the paper-machine, but their introduction here would rather tend to confuse the reader. Its productive power is very great; it moves at a rate of from 30 to 70 ft. per minute, spreading pulp, couching, drying, and calendering as it goes, so that the stream of pulp flowing in at one end is in 2 minutes passing out finished paper at the other. It has been computed that an ordinary machine, making webs of paper 64 in. wide, will turn out 4 miles a day, and that the total production of all the mills in Britain is not less than 6,000,000 of yards, or 3,400 miles daily.