We have already observed the mode of obtaining similar effects from wood and copper, are opposite to each other. The manner in which impressions from wood engravings are obtained, has likewise been noticed; and it remains that we observe the mode by which impressions are obtained from copper-plates. The plate is covered with appropriate ink; the surface is then carefully cleansed, leaving ink only in the excavations or lines in the copper. The plate and paper are passed through a roller press of great power, the roller being covered with a blanket, which presses the paper into all the crevices of the plate, and brings away the ink there deposited. ON STEEL. For several years steel has been used in great quantities, instead of copper-plates, by engravers. By this fortunate application of so durable, and it may be added, so economical a material, not only has a new field been discovered admirably suited to yield in perfection the richest and finest graphic productions, which the ingenuity of modern art can accomplish, but to do so through an amazingly numerous series of impressions without perceptible deterioration. The art of engraving on iron or steel for purposes of ornament, and even for printing, in certain cases, is by no means a discovery of modern times; but the substitution of the latter for copper, which has invited the superiority of the British burin to achievements hitherto unattempted by our artists, is entirely a modern practice. In the year 1810, Mr. Dyer, an American merchant, residing in London, obtained a patent for certain improvements in the construction and method of using plates and presses, &c., the principles of which were communicated to him by a foreigner residing abroad. This foreigner was Mr. Jacob Perkin, an ingenious artist of New England, and whose name has become subsequently so extensively known in this country, in connection with roller-press printing from hardened steel plates. The plates used by Mr. Perkins were, on the average, about five-eights of an inch thick; they were either of steel so tempered as to admit of the operation of the engraver, or, as was more generally the case, of steel decarbonated so as to become very pure soft iron, in which case, after they had received the work on the surface, they were case hardened by cementation.