Sec. 18. I have thought it worth while, for the sake of these lessons, and the other interests connected with them, to lead the reader thus far into the examination of the principal precipices among the Alps, although, so far as our immediate purposes are concerned, the inquiry cannot be very fruitful or helpful to us. For rocks of this kind, being found only in the midst of the higher snow fields, are not only out of the general track of the landscape painter, but are for the most part quite beyond his power--even beyond Turner's. The waves of snow, when it becomes a principal element in mountain form, are at once so subtle in tone, and so complicated in curve and fold, that no skill will express them, so as to keep the whole luminous mass in anything like a true relation to the rock darkness. For the distant rocks of the upper peaks are themselves, when in light, paler than white paper, and their true size and relation to near objects cannot be exhibited unless they are painted in the palest tones. Yet, as compared with their snow, they are so dark that a daguerreotype taken for the proper number of seconds to draw the snow shadows rightly, will always represent the rocks as _coal-black_. In order, therefore, to paint a snowy mountain properly, we should need a light as much brighter than white paper as white paper is brighter than charcoal. So that although it is possible, with deep blue sky, and purple rocks, and blue shadows, to obtain a very interesting resemblance of snow effect, and a true one up to a certain point (as in the best examples of the body-color drawings sold so extensively in Switzerland) it is not possible to obtain any of those refinements of form and gradation which a great artist's eye requires. Turner felt that, among these highest hills, no serious or perfect work could be done; and although in one or two of his vignettes (already referred to in the first volume) he showed his knowledge of them, his practice, in larger works, was always to treat the snowy mountains merely as a far-away white cloud, concentrating the interest of his picture on nearer and more tractable objects.