As the lines of an engraved block of wood are prominent or in relief, while those of a copper-plate are, as has been previously explained, _intagliate_ or hollowed, the mode of taking an impression from the former is precisely the reverse of that which has just been described. The usual mode of taking impressions from an engraved block of wood is by means of the printing-press, either from the block separately, or wedged up in a _chase_ with types. The block is inked by being beat with a roller on the surface, in the same manner as type; and the paper being turned over upon it from the _tympan_, it is then run in under the _platen_; which being acted on by the lever, presses the paper _on to_ the raised lines of the block, and thus produces the impression. Impressions from wood are thus obtained by the _on-pression_ of the paper against the raised or prominent lines; while impressions from copper-plates are obtained by the _in-pression_ of the paper into hollowed ones. In consequence of this difference in the process, the inked lines impressed on paper from a copper-plate appear prominent when viewed direct; while the lines communicated from an engraved wood-block are indented in the front of the impression, and appear raised at the back. [Illustration: PRINTED FROM A WOOD-BLOCK.] [Illustration: PRINTED FROM A COPPER-PLATE.] The above impressions--the one from a wood-block, and the other from an etched copper-plate--will perhaps render what has been already said, explanatory of the difference between copper-plate printing from hollowed lines, and _surface printing_ by means of the common press from prominent lines, still more intelligible. The subject is a representation of the copper-plate or rolling press. Both the preceding impressions are produced in the same manner by means of the common printing-press. One is from wood; the other, where the white lines are seen on a black ground, is from copper;--the hollowed lines, which in copper-plate printing yield the impression, receiving no ink from the printer’s balls or rollers; while the surface, which in copper-plate printing is wiped clean after the lines are filled with ink, is perfectly covered with it. It is, therefore, evident, that if this etching were printed in the same manner as other copper-plates, the impression would be a fac-simile of the one from wood. It has been judged necessary to be thus minute in explaining the difference between copper-plate and wood engraving, as the difference in the mode of obtaining impressions does not appear to have been previously pointed out with sufficient precision.