To write such a book upon any art as should be eminently useful to the professors of that art, as instructing them in methods whereby they may improve their practice, and avoid the difficulties they have to encounter, or gracefully evade them, would require the hand of a consummate artist, who, to great practice, should join large knowledge of his subject, and a minute acquaintance with the materials upon whose nature more of practical success depends, than enthusiasts in art are willing to own. Besides, he should possess sufficient learning to communicate the experience of past ages, for the improvement of this; and a good taste and acquaintance with general literature, to adorn his subject with the graces that all arts may borrow from each other, becoming always richer in proportion as they draw from their common treasury, Nature. To write a work of just criticism, upon a peculiar art, the author should no less be a professor, whose practice might exemplify his criticism, or at any rate might enable him justly to appreciate the merits and defects of the peculiar works which he should choose as subjects on which to found his criticisms. The lectures of Sir Joshua Reynolds made art popular in this country, less because they contained excellent precepts and well-chosen examples, than because, like Johnson’s criticism in the Lives of the Poets, they laid open the general principles applicable to all the arts. Poetry and music, painting and sculpture, architecture and landscape-gardening, may equally profit by them, the passages peculiarly appropriated to painters being far from the most numerous, though such as none but a painter could have written. Fuseli appears to be more exclusively a critic in his own art. He had prodigious practice in his own wild walk, wherein, however, even he often mistook the glare of caprice for the light of genius. He had great learning, the effect of which he injured by affectation and quaintness, yet there are exquisite passages in his lectures, which will always be read with profit and delight both by artists and lovers of art. The practical lectures delivered or published by other authors, some living, and some whose loss we have to lament, have not been popular, chiefly because they were most properly composed for the use of artists. And when we consider that they have been for the most part the works of men whose lives were passed in the most laborious department of a Profession that demands constant application, namely portrait painting, it is surprising how much they did in those hours which nature might have claimed as due to rest and relaxation. But such is the advantage possessed by a professor, when writing on the art be practises and understands.