§ 12. And yet, if we examine the crest structure closely, we shall find that nearly all these curvatures are obtained by Nature's skilful handling of perfectly straight beds,--only the meeting of those two waves of crest is indeed indicative of the meeting of two masses of different rocks; it marks that junction of the slaty with the compact crystallines, which has before been noticed as the principal mystery of rock structure. To this junction my attention was chiefly directed during my stay at Chamouni, as I found it was always at that point that Nature produced the loveliest mountain forms. Perhaps the time I gave to the study of it may have exaggerated its interest in my eyes; and the reader who does not care for these geological questions, except in their direct bearing upon art, may, without much harm, miss the next seven paragraphs, and go on at the twenty-first. Yet there is one point, in a Turner drawing presently to be examined, which I cannot explain without inflicting the tediousness even of these seven upon him.
[Illustration: J. Ruskin. R. P. Cuff. 33. Leading Contours of Aiguille Bouchard.]
§ 13. First, then, the right of the Aiguille Bouchard to be called a crest at all depends, not on the slope from _a_ to _b_, Plate +33+, but on that from _a_ to _h_. The slope from _a_ to _b_ is a perspective deception; _b_ is much the highest point of the two. Seen from the village of Chamouni, the range presents itself under the outline Fig. 54, the same points in each figure being indicated by the same letters. From the end of the valley the supremacy of the mass _b c_ is still more notable. It is altogether with mountains as with human spirits, you never know which is greatest till they are far away.
§ 14. It will be observed also, that the beauty of the crest, in both Plate +33+ and Fig. 54, depends on the gradually increasing steepness of the lines of slope between _a_ and _b_. This is in great part deceptive, being obtained by the receding of the crest into a great mountain crater, or basin, as explained in § 11. But this very recession is a matter of interest, for it takes place exactly on the line above spoken of, where the slaty crystallines of the crest join the compact crystallines of the aiguilles; at which junction a correspondent chasm or recession, of some kind or another, takes place along the whole front of Mont Blanc.