"So hopeless and worthless did the enterprise seem, at one time," says M. F. Sweetser, "that Charles Turner, the engraver, used the proofs and trials of effect as kindling paper. Many years later, Colnaghi, the great print-dealer, caused him to hunt up the remaining proofs in his possession, and gave him fifteen hundred pounds for them. 'Good God!' cried the old engraver, 'I have been burning bank-notes all my life.'... In later days three thousand pounds had been paid for a single copy of the _Liber_." "The most obvious intention of the work," says Monkhouse, "was to show Turner's own power, and there never was, and perhaps never will be again, such an exhibition of genius in the same direction. No rhetoric can say for it as much as it says for itself in those ninety plates, twenty of which were never published. If he did not exhaust art or nature, he may be fairly said to have exhausted all that was then known of landscape art, and to have gone further than any one else in the interpretation of nature.... "Amongst his more obvious claims to the first place among landscape artists are his power of rendering atmospherical effects, and the structure and growth of things. He not only knew how a tree looked, but he showed how it grew. Others may have drawn foliage with more habitual fidelity, but none ever drew trunks and branches with such knowledge of their inner life.... Others have drawn the appearance of clouds, but Turner knew how they formed. Others have drawn rocks, but he could give their structure, consistency, and quality of surface, with a few deft lines and a wash; others could hide things in a mist, but he could reveal things through mist. Others could make something like a rainbow, but he, almost alone, and without color, could show it standing out, a bow of light arrested by vapor in mid-air, not flat upon a mountain, or printed on a cloud.... If we seek the books from which his imagination took fire, we have the Bible and Ovid; the first of small, the latter of great and almost solitary power. Jason, daring the huge glittering serpent; Syrinx, fleeing from Pan; Cephalus and Procris; Æsacus and Hesperia; Glaucus and Scylla; Narcissus and Echo. If we want to know the artists he most admired and imitated, or the places to which he had been, we shall find easily nearly all the former, and sufficient of the latter to show the wide range of his travel. In a word, one who has carefully studied the _Liber_ has indeed little to learn of the range and power of Turner's art and mind, except his color and his fatalism."