457. On the central portions of the cascades, moreover, there are no signs of the veins. At the bases they first appear, reaching in each case their maximum development a little below the base. As you and I stood upon the heights above the Zäsenberg and scrutinised the cascade of the Strahleck branch of the Grindelwald glacier, we could not doubt that the base of the fall was the birthplace of the veins. We called this portion of the glacier a "Structure Mill," intimating that here, and not on the névé, the veined structure was manufactured.
SECTION OF ICEFALL, AND GLACIER BELOW IT, SHOWING ORIGIN OF VEINED STRUCTURE.
458. This, however, is, at bottom, the language of strong opinion merely, not that of demonstration; and in science opinion ought to content us only so long as positive proof is unattainable. The love of repose must not prevent us from seeking this proof. There is no sterner conscience than the scientific conscience, and it demands, in every possible case, the substitution for private conviction of demonstration which shall be conclusive to all.
459. Let us, for example, be shown a case in which the stratification of the névé is prolonged into the glacier; let us see the planes of bedding and the planes of lamination existing side by side, and still indubitably distinct. Such an observation would effectually exclude stratification from the problem of the veined structure, and through the removal of this tempting source of error, we should be rendered more free to pursue the truth.
460. We sought for this conclusive test upon the Mer de Glace, but did not find it. We sought it on the Grindelwald, and the Aar glaciers,[J] with an equal want of success. On the Aletsch glacier, for the first time, we observed the apparent coexistence of bedding and structure, the one cutting the other upon the walls of the same crevasse. Still the case was not sufficiently pronounced to produce entire conviction, and we visited the Görner glacier with the view of following up our quest.
[J] M. Agassiz, however, reports a case of the kind upon the glacier of the Aar.
STRUCTURE AND BEDDING ON ALETSCH GLACIER.
461. Here day after day added to the conviction that the bedding and the structure were two different things. Still day after day passed without revealing to us the final proof. Surely we have not let our own ease stand in the way of its attainment, and if we retire baffled we shall do so with the consciousness of having done our best. Yonder, however, at the base of the Matterhorn, is the Furgge glacier that we have not yet explored. Upon it our final attempt must be made.