The wire cloth moves at the rate of from 25 to 40 feet per minute, and such a machine would consequently make at least 10 yards of paper in that time, which is equal to a mile in three hours. The width of the paper is usually about 4½ feet, therefore each machine will make 10,450 square yards of paper in twelve hours; and there are upwards of three hundred of such machines at work in this country. The value of the paper thus produced is calculated to exceed two millions sterling.
Numerous improvements have been made in Fourdrinier's original machine, but the principle of its construction remains essentially the same, and it is by this means that most of the paper now used for writing or printing is manufactured. A paper-making machine, on a different principle, has, however, been invented by Mr. Dickinson, and has been carried by him to great perfection. Instead of allowing the pulp to fall on to a flat surface of wire gauze, a polished hollow brass cylinder, perforated with holes and covered with wire cloth, revolves in contact with the prepared pulp, and a partial vacuum being produced within the cylinder, the pulp adheres to the gauze, and its fibres cohere sufficiently, before the cylinder has completed a revolution, to be turned off on to another cylinder covered with felt, on which it is subjected to pressure by rollers, and is thence delivered to the drying cylinders.
Mr. Dickinson afterwards obtained a patent, in 1855, for making a union paper, consisting of a thin sheet of that made by his own machine, and a similar sheet made by a Fourdrinier machine united together. For this purpose the two sheets were brought together, as they passed from the machines, whilst still wet and in an unfinished state, and were pressed together between rollers, by which means they were completely incorporated. The object of this contrivance was to combine, in a single sheet, the different kinds of surface which paper made by those two modes of manufacture present. It is also employed economically for engravings, to give a fine surface to a thick sheet of coarser material. The threads in postage envelopes and in bankers' cheques, are introduced by this process of plating two surfaces together.