COPYING MACHINES. The various con trivances for procuring- duplicates of manu scripts without the labor of transcribing them may be reduced to two classes. In the one, the writing is first made, and then copied: in the other, the copy and the original are produced at the same time. The essence of the first method is this: In writing the original, an ink is used that is made for the purpose, or common ink is thickened by the addition of a little sugar. When the writing is dry, a damped sheet of thin unsized paper is laid upon it. and over this 'a piece of oiled paper. The whole is then subject ed to pressure, and the damped paper is found to have received an impression of the writing. It is of course the reverse of the original, but the thinness and transparency of the paper allows it to be read right on the other side. The machines for communicating the pressure are of various kinds. Some pass the sheets between rollers like the copper-plate press; others act on the princi ple of the simple screw-press. A simple plan is to wrap the sheets around a wooden roller of about an inch diameter, lay this upon a table. and roll it under a fiat board, pressing all the while. In the second method of copying, pre pared blackened or carbon paper is laid between two sheets of thin writing-paper. The writing is traced firmly on the upper sheet, with a steel or agate point, or common black-lead pencil, and the lines are found transferred in black from the blackened sheet to the paper adjacent. By having several of these blackened leaves, a number of copies may he produced at once, so that the method can be employed in duplicating invoices, newspaper- copy, and telegraph messages. The blackened paper is prepared by saturating it with a mixture of lard and lampblack. The manifold writer of Wedgewood, invented in 1806, was on this plan.
The first suggestion for a copying press is said to have been made by Benjamin Franklin, who sanded the yet wet ink of his manuscript with emery and then passed the manuscript between rollers in contact with a soft, highly polished pewter plate. This received the impression from
the emery. from which numerous copies could be made by the copper-plate printing process. In 1780. :lames Watt adopted the simple plan of copying by pressing transparent, bibulous paper against the damp manuscript, so that the writ ing would be transferred as on a blotter and then read from the other side.
In the papyrograph a speeially prepared paper is used, upon which words are written with a common pen. hilt with a special ink. The sheet is then soaked in water, and the ink corrodes the fabric of the wet paper, leaving open lines in place of the writing. The sheet is then used as a stencil, like that prepared by the electric pen. The mimeograph is an apparatus invented by Thomas A. Edison, by which stencils of written pages are obtained for the purpose of producing an indefinite number of copies. It consists of a fine-pointed steel stylus, moving over the sur face of a sheet of tissue paper, coated on one side with a film of sensitive material. This paper is placed on a plate of steel, known as the base board, upon which are cut intersecting corruga tions. numbering 200 to the inch. As the stylus moves over the paper it presses. it down upon the steel plate, and the fine sharp points puncture the paper from the under side in the line of the writing. This paper. or stencil - plate, is then fastened into a frame, which stretches it tight and smooth, again placed upon the baseboard with a sheet of paper between. and an ink-roller of peculiar construetion is passed over its sur face. forcing the ink through the perforations upon the paper beneath, thus making a print. The patent for this instrument was applied for in 1878, and there have been numerous improve ments since, the apparatus being used exten sively in connection with the typewriter, where the stencil is made by the type bars striking a sheet of paper laid against a piece of gauze.