scenery are glens or passes, which, if seen from a height great enough to command them in all their relations, would be found in reality little more than trenches excavated through broad masses of elevated land, and expanding at intervals into the wide basins which are occupied by the glittering lake or smiling plain. [Illustration: FIG. 106.] [Illustration: J. Ruskin. J. H. Le Keux. 47. The Quarries of Carrara.] Sec. 49. All these facts had been entirely ignored by artists; nay, almost by geologists, before Turner's time. He saw them at once; fathomed them to the uttermost, and, partly owing to early association, partly, perhaps, to the natural pleasure of working a new mine discovered by himself, devoted his best powers to their illustration, passing by with somewhat less attention the conditions of broken-summited rock, which had previously been the only ones known. And if we now look back to his treatment of the crest of Mont Pilate, in the figure given at the close of the last chapter, we shall understand better the nature and strength of the instinct which compelled him to sacrifice the peaked summit, and to bring the whole mountain within a lower enclosing line. In that figure, however, the dotted peak interferes with the perception of the form finally determined upon, which therefore I repeat here (Fig. 106), as Turner gave it in color. The eye may not at first detect the law of ascent in the peaks, but if the height of any one of them were altered, the general form would instantly be perceived to be less agreeable. Fig. 107 shows that they are disposed within an infinite curve, A _c_, from which the last crag falls a little to conceal the law, while the terminal line at the other extremity, A _b_, is a minor echo of the whole contour. [Illustration: FIG. 107.]