The principal feature of this invention consisted in the curving or bending of stereotype plates for the purpose of being printed in that form. A number of machines for printing in two colours, in exact register, was made for the Bank of England, and four millions of One Pound notes were printed before the Bank Directors determined to abolish their further issue. The regular mode of producing stereotype plates, from plaster of Paris moulds, took so much time, that they could not then be used for newspaper printing. Two years later, in 1818, Mr. Cowper invented and patented (No. 4194) his great improvements in printing. It may be mentioned that he was then himself a printer, in partnership with Mr. Applegath, his brother-in-law. His invention consisted in the perfect distribution of the ink, by giving end motion to the rollers, so as to get a distribution crossways, as well as lengthways. This principle is at the very foundation of good printing, and has been adopted in every machine since made. The very first experiment proved that the principle was right. Mr. Cowper was asked by Mr. Walter to alter Koenig's machine at The Times office, so as to obtain good distribution. He adopted two of Nicholson's single cylinders and flat formes of type. Two "drums" were placed betwixt the cylinders to ensure accuracy in the register,--over and under which the sheet was conveyed in it s progress from one cylinder to the other,--the sheet being at all times firmly held between two tapes, which bound it to the cylinders and drums. This is commonly called, in the trade, a "perfecting machine;" that is, it printed the paper on both sides simultaneously, and is still much used for "book-work," whilst single cylinder machines are often used for provincial newspapers. After this, Mr. Cowper designed the four cylinder machine for The Times,--by means of which from 4000 to 5000 sheets could be printed from one forme in the hour. In 1823, Mr. Applegath invented an improvement in the inking apparatus, by placing the distributing rollers at an angle across the distributing table, instead of forcing them endways by other means. Mr. Walter continued to devote the same unremitting attention to his business as before. He looked into all the details, was familiar with every department, and, on an emergency, was willing to lend a hand in any work requiring more than ordinary despatch.