Printing from letters engraved on blocks of wood is an ancient art, having had its origin in China many centuries before the Christian era. The Chinese method, which is still followed, was to write their characters with a brush on a sheet of paper, and while still wet, the piece of paper was laid face downward on a smooth piece of board to transfer the ink lines, and then all except the ink lines on the board was cut away. Thus they have one type plate for each book page. Printing with movable type, _i. e._, with a separate type for each letter, which may be repeatedly set up into forms of varying composition, is practically the beginning of the modern art of printing. This invention is usually ascribed to Johann Gutenberg, of Mentz, about 1436. [Illustration: FIG. 122.--BENJAMIN FRANKLIN’S PRESS, 1725.] In the earliest printing presses the form was locked up in a tray, and placed upon a platform, and the platen was then brought down upon it by turning a screw in a cross bar above. The first printing press of this type was made by Blaew, of Amsterdam, in 1620, which had a spring to cause the screw to fly back after the impression was taken. The press upon which Benjamin Franklin worked in London in 1725 is of this pattern, and is to be seen in the National Museum at Washington. It is almost entirely of wood, and is shown in Fig. 122. About the beginning of the Nineteenth Century Lord Stanhope invented a press entirely of cast iron, in which the oscillating handle operated a toggle to force down the platen in taking the impression. The bed traveled on guide ways, and the tympan and frisket were hinged to fold back and lay in elevated position. [Illustration: FIG. 123.--THE WASHINGTON PRESS.] The “Columbian” press was the first important American improvement. It was invented by George Clymer, of Philadelphia, and is shown in his British Pat. No. 4,174 of 1817. A compound lever was employed for applying the power. The “Washington” press was patented in the United States by Samuel Rust, April 17, 1829. In this press (see Fig. 123) the platen is forced downwardly by a compound lever applied to a toggle joint and is raised by springs on each side. The bed is run in and out by turning a crank on a shaft which has a pulley and belt passing around it.