Aquatint proper consists entirely of gradations of tone produced by biting with aquafortis into the copper through a resinous ground broken into a multitude of fine granules, that render the personal touch practically negligible, and in consideration of this we can appreciate the exceptionally skillful use Havell, Junior, made of the difficult process. The graining of the aquatint grounds is produced by allowing fine dust particles to settle upon the freshly prepared plate. It is to these grainings of different degrees of fineness that the engraver must look for the subtlety of the tonal surfaces, but strength is obtained usually through the use of the etched line. The chief limitation of the aquatint process lies in the great difficulty of getting more than a few differences of shade, as the ground goes to pieces rather rapidly under successive bitings, and the transitions from one tone to another are very few, so that half tones are not readily obtainable. It is in the economical use of these half tones that Havell, Junior, achieved so much and thereby produced a chiaroscuro seldom, if ever, equaled in aquatint. Artists have sometimes frowned upon this combination of aquatint with other forms of engraving, especially when executed with the burin, for "like the permanent misery of a quarrelling married couple, they may ruin everything with discord"; but any such lack of harmony, when not overcome by Havell's skill, was usually completely subdued by the color which was subsequently applied to the printed sheet. This is seen by a comparison of the plain proof of such an elaborate plate as that of the rattlesnake attacking the mocking birds (Plate xxi) with the result attained in the finished impression. In replying to a criticism of Havell's work in 1830, Audubon expressed his conviction that "no birds were ever so beautifully and softly represented on copper," and any hardness, which his plates rarely showed, was not due to aquatinting, the inherent quality of which is softness. To quote our authority again: In Havell's hands aquatint gave the essential structure of forms by a judicious use of the process called "feathering." This he often did upon the bare copper plate without a ground, allowing the acid to bite its own granular surface. In this way he produced the soft gradations and telling accents so necessary to the portrayal of birds, but by a further judicious use of line the accurate forms of both bird and plant life were given with great force and delicacy. When Audubon first proposed to present the Congressional Library at Washington with a copy of his _Birds_, he asked Havell to do all the coloring himself; Havell