thin paper is used, or where narrow margins are desired—this system of masking is best, as the whole of the operation is entirely automatic. The layer-on may devote the whole of his attention to removing impressions and inserting fresh paper. =Another System= of masking frequently made use of is one in which an aperture of suitable size is cut in a piece of cardboard, such aperture being, say, 2 mm. larger than the print. The portion removed is reduced in size by 2 mm. all round, leaving it exactly the size of the impression desired. This piece is utilised for packing by attaching to the cylinder as previously described. The cardboard mask, presenting the exact appearance of a sunk mount, is affixed by means of a bar to the cylinder, and when folded down upon the latter, the “cut out” used as packing exactly occupies the centre of the mask, leaving a marginal space all round of 2 mm. Before printing, the mask must be varnished with negative varnish, bitumen in benzol, or otherwise waterproofed, to prevent adhesion to the print layer. The mask has to be turned back by hand at the insertion of each sheet—a considerable disadvantage when compared with the automatic frame. On the other hand, its advantages are simplicity of preparation, and the possibility it allows of masking and printing several irregularly-disposed pictures on one sheet. =Damping the Plate.=—The use of the cylinder pressure has further advantages than merely prolonging the life of the plate—the operation of damping is much less needed than on the hand-press. The printing paper does not come in contact with the plate before the instant of printing or remain upon it after the operation, but is held to the cylinder by the grippers and mask, and so carried over the inked plate, consequently little opportunity is afforded for absorption of the etching fluid. With chalk paper and a new plate damping may be necessary every twenty-five impressions, but as the plate becomes older fifty or even one hundred may be printed between the etchings. On plain paper of hard surface much longer numbers may be expected.