The talent of Rupert's first imitators, like that of the originator himself, did not rise above mediocrity. Amongst their direct successors, and the successors of these, there are few of much account; but in the eighteenth century, when Sir Joshua Reynolds undertook, like Rubens at Antwerp, to himself direct the work of engraving, the number of good English mezzotint engravers became considerable. Earlom, Ardell, Smith, Dickinson, Green, Watson, and many others deserving of mention, greatly increased the resources of the process, by applying it to the reproduction of the master's works. Mezzotint, at first reserved for portraits, was used for subjects of every sort: flower pieces, genre, even history; and step by step it attained to practical perfection, of which, at the beginning of the present century, the English still had the monopoly. The methods of mezzotint differ completely from those of line engraving and etching. With the graver and the needle the shadows and half-tones are made out on copper by means of incised lines and touches; with the mezzotint tool, on the contrary, the lights are produced by scraping, the shadows by leaving intact the corresponding portions of the plate. Instead of offering a flat, smooth surface, like the plates in line engraving, a mezzotint copper must be first grained by a steel tool (called the "rocker"), shaped like a chisel, with a semicircular blade which is bevelled and toothed. Sometimes (and this is generally the case in the present day) the "rocking" of the surface, on which the engraver is to work, is produced, not by a tool, but by a special machine. When the drawing has been traced in the usual way on the prepared plate, the grain produced by the rocker is rubbed down with the burnisher wherever pure white or light tints are required. The parts that are not flattened by the burnisher print as darks; and these darks are all the deeper and more velvety as they result from the grain itself--that is to say, from a general preparation specially adapted to catch the ink--and are by no means composed, as in line engraving, of furrows more or less crowded or cross-hatched. Mezzotint engraving has, in this respect, the advantage of other processes; in all others it is decidedly inferior. The rough grain produced on a plate by the rocker, and the mere scraping by which it is obliterated or modified, are technical hindrances to decided drawing: only with graver or point is it possible to make outlines of perfect accuracy. Again, precision, delicacy of modelling, and perfect finish in detail are impossible to the scraper. Mezzotint, in fine, is suitable for the translation of pictures where the light is scarce and concentrated, but is powerless to render work quiet in aspect and smooth in effect.