Fully admitting the extraordinary execution of the engravings, every ornithologist may perceive that as portraits of the birds they are of very unequal merit.
The engravings which these volumes contain are mostly bad copies, often of bad figures, though many are piracies from Bewick, and the whole is a most unsatisfactory performance.
The objection that a copper plate shows signs of wear after a thousand impressions have been taken has been removed, since duplicate plates are readily produced by electrotyping, while transfers of copper engravings, on stone, zinc or aluminium, make it possible to turn out large editions in a printing-machine, which thus supersedes the slow-working hand-press.
A very curious fresco, found in the cemetery of Calixtus, preserved by the engravings of the earlier investigators (Bottari, torn.
So few examples of glass vessels of this period which have been painted in enamel have come down to us that it has been questioned whether that art was then practised; but several specimens have been described which can leave no doubt on the point; decisive examples are afforded by two cups found at Vaspelev, in Denmark, engravings of which are published in the Annaler for Nordisk Oldkyndeghed for 1861, p. 305.