The invention of Alois Senefelder, at the close of the 18th century, of printing from chemically prepared slabs of argillaceous, slaty limestone, is one of those few which was perfect at tho flrgt, or susceptible of few improvements, either in the principle or the details. Lithographic printing per se and lithographic printing machinery have experienced no notable change during this century. The superiority of specimens now produced, over, those of Senefeldei and his iawae-diate successors is due mainlyj if not wholly, to the expert ness and skill of experienced workmen, the principle and the made of operation being the same. The art may be called a branch of engraving as in some cases the stone is engraved by hand, as is a steel or copper plate. It also, partakeapf the character cf drawing or designing, for. usually the figure is drawn on the stone with crayon, pen, or brush. Sometimes, however, the design is transferred from cfiimicaily prepared paper. For engraving, tho stone is finished to a fine face and its surface washed with a weak dilution of nitric acid. The artist then uBes his burin until the design is completed1. The engraving is merely a slight scratching sufficient to reach beyond the influence of the acid, which is only superficial. The ink is of an oily nature and, is spread over the engraving by a hand dabbef, leaving its substance only in the lines, which are untouched by the acid. When the figure is drawn on the stone by crayon, the surface is slightly roughened by rubbing two stones together with a small amount of fine silicious sand and water between the faces. The crayons and drawing ink (the latter dissolved in water, are composed of tallow, wax, shellac, common soap, and PariftoriSfeunswick blapk, or similar substances, the proportions varying in different establishments. The artist makes his design with this crayon oil, and when finished the acid is washed over the stone, when it dissolves out the alkali of the ink, leaving the insoluble portion to harden upon the stone; it attacks also the calcareous material of the stone, thus lowering the clean portions slightly and correspondingly raising the inked portions. These take readily the ink from the roller as it is passed over the stone, while those clean portions of stone, not having the design upon them, are prevented from receiving any ink by the interposition of moisture. In transferring from paper, the ink and paper must be specially adapted to the purpose. The ink is similar to that used for printing from the stone and after the transfer is made the treatment is similar. In printing, the stone is secured on a movable table or bed, the roller, charged with ink, is passed over its face and an application of gum arabic and water is made, which fixes the ink. This must be allowed to thoroughly dry before the stone is ready for printing, when a damp sponge is passed over the stone, removing the gum from all portions. The stone is dampened and the ink applied, which adheres only to the prepared lines of the design. This deposition of the ink, although apparently simple, is a process requiring the exercise of good judgment and the experience acquired only by long practice. The paper is then laid on the stone and the tympan, of some flexible material, as rubber, brought down over it. The stone is then traversed by means of a crank pressure being applied to the tympan and stone by an edge of wood—appletree being preferred—that is brought down by a powerful leverage. This method sometimes requires the services of two persons. By the press represented in the engraving, however, only one person is required, the pressure being obtained by a weight. A is the, table, and B the frame. C is the stone, supported on bearers adjusted by screws, as seen. D is the roller to which are suspended weights, E, connected with guides, F, the weights bearing on the roller, D, by means of i friction rollers in each guide. Q is the tympan over which the roller runs, in this machine made of leather and rubber. The stone in this machine is stationary and the roller passes over it. It is designed for office use in multiplying duplicates of letters, notes, circulars, etc., for merchants, bankers, companies, architects, lawyers, schools, copyists, artists, clergymen, and others. The inventor says the press can print one hundred copies per hour of writings or drawings. Patented through the Scientific American Patent Agency, February 28, 1868. Orders should be addressed to C. C. Maurice & Co., No. 10 North William street, New York.