A more material peculiarity in Mr. Perkins’ invention, and one which does not seem to have been approached by any preceding artist, was the contrivance of what are called _indenting cylinders_. These are rollers of two or three inches in diameter, and made of steel, decarbonized by the process above described, so as to be very soft. In this state they are made to roll backward and forward under a powerful pressure, over the surface of one of the hardened plates, until all the figures, letters, or indentations are communicated, with exquisite precision, in sharp relief upon the cylinder; which, being carefully hardened and tempered, becomes, by this means, fitted to communicate an impression to other plates, by an operation similar to that by which it was originally figured. It will be obvious that one advantage gained by this method must be the entire saving of the labour and expense of re-cutting in every case, on different plates, ornaments, borders, emblematical designs, &c., as these can now be impressed with little trouble on any number of plates, or in any part thereof, by the application of the cylinder. At first sight, the performance of such an operation as the one now alluded to may appear difficult, if not impracticable; and, indeed, many persons on its first announcement were disposed to doubt or deny its possibility altogether. With a proper and powerful apparatus, however, this method of transferring engravings from plates to cylinders, and _vice versa_, is every day performed with facility and success, not only in the production of bank notes, labels, &c., but in works exhibiting very elaborate engravings. LITHOGRAPHY. Lithography is the art of printing from stone, which claims for its author Aloys Senelfelder, a native of Munich, in the kingdom of Bavaria. The history of this useful art is recorded by the only person capable of assigning proper and correct motives, and of tracing the various means which were employed to arrive at the desired end, to ultimate success: had all other useful inventions, profitable and elegant arts, had the good fortune which this has happily experienced, we should not have had so much cause to regret deficiencies as we have frequently experienced in the course of our inquiries; then would the various illustrious authors of arts have had justice rendered to them, and still have remained possessed of that glorious immortality so justly the reward of transcendant merit; for the history of this meritorious invention is given by the author himself, thereby securing to it those advantages, which the erudite author of the preface congratulates the public upon, when in his concise epistle he uses that beautiful expression of his countryman, Klopstock, where he says, “Covered with eternal darkness are the great names of inventors.”