of the plate unstopped in order to gauge the result of the various bitings. The method subsequently pursued is very similar to that used by etchers (described p. 61), and a series of bitings and stoppings-out develop the design towards its completion. To know the exact number of minutes to allow the acid to bite is one of the greatest difficulties in aquatint engraving. It varies very surprisingly even under apparently the same conditions of temperature and requires long experience. During its various stages the stronger portions of the foliage and the dark portions standing against the sky are painted over to preserve their form and facilitate the stopping of the sky. Sometimes a plate is completed with one ground after a dozen bitings, but not infrequently a second ground is laid on parts requiring deeper biting, and etching is resorted to in the case of the strongest black lines. In practice aquatint engraving resembles drawing in Indian ink. Each time the aquafortis is put on the plate a new tint is produced, and as each part of the design is considered dark enough it is stopped out. By the use of a brush dipped in aquafortis the finishing touches are given to darken certain lightly-bitten parts, and this "feathering" has to be most delicately performed, or a false touch will ruin the whole plate. To lighten other portions they are burnished. It will thus be seen how complicated a process aquatint engraving is, and its wider use was no doubt restricted by its technical difficulties which no amateur could attempt.
Jean Baptiste Le Prince, a French painter and
