illustrates his perception of the lower aqueous and other curvatures. If the reader will look back to the etching of the entire subject, Plate +21+, he will now discern, I believe, without the necessity of my lettering them for him, the lines of fall, rounded down from the crests until they plunge into the overhanging precipices; the lines of projection, where the fallen stones extend the long concave sweep from the couloir, pushing the torrent against the bank on the other side; in the opening of the ravine he will perceive the oblique and parallel inclination of its sides, following the cleavage of the beds in the diagonal line A B of the reference figure; and, finally, in the great slope and precipice on the right of it, he will recognize one of the grandest types of the peculiar mountain mass which Turner always chose by preference to illustrate, the "slope above wall" of _d_ in Fig. 13, p. 148; compare also the last chapter, Sec.Sec. 26, 27. It will be seen, by reference to my sketch of the spot, Plate +20+, that this conformation does actually exist there with great definiteness: Turner has only enlarged and thrown it into more numerous alternations of light and shade. As these could not be shown in the etching, I have given, in the frontispiece, this passage nearly of its real size: the exquisite greys and blues by which Turner has rounded and thrown it back are necessarily lost in the plate; but the grandeur of his simple cliff and soft curves of sloping bank above is in some degree rendered. We must yet dwell for a moment on the detail of the rocks on the left in Plate +37+, as they approach nearer the eye, turning at the same time from the light. It cost me trouble to etch this passage, and yet half its refinements are still missed; for Turner has put his whole strength into it, and wrought out the curving of the gneiss beds with a subtlety which could not be at all approached in the time I had to spare for this plate. Enough, however, is expressed to illustrate the points in question. Sec. 44. We have first, observe, a rounded bank, broken, at its edges, into cleavages by inclined beds. I thought it would be well, lest the reader should think I dwelt too much on this particular scene, to give an instance of similar structure from another spot; and therefore I daguerreotyped the cleavages of a slope of gneiss just above the Cascade des Pelerins, Chamouni, corresponding in position to this bank of Turner's. Plate +48+ (facing p. 303), copied by Mr. Armytage from the daguerreotype, represents, necessarily in a quite unprejudiced and impartial way, the structure at present in question; and the reader may form a sufficient idea, from this plate, of the complexity of descending curve and foliated rent, in even a small piece of mountain foreground,[95] where the gneiss beds are tolerably continuous. But Turner had to add to such general complexity the expression of a more than ordinary undulation in the beds of the St. Gothard gneiss.