An excursion to the summit of the North Dome was exceedingly interesting. From the rear of our camp we entered immediately a dense forest of conifers, which stretched southward along the summit of the ridge until solid granite, arresting erosion, afforded but little foothold. As usual, among the cracks, and clinging around the bases of bowlders, a few hardy pines manage to live, almost to thrive; but as we walked groups became scarcer, trees less healthy, all at last giving way to bare, solid stone. The North Dome itself, which is easily reached, affords an impressive view up the Illilluette and across upon the fissured front of the Half-Dome. It is also one of the most interesting specimens of conoidal structure, since not only is its mass divided by large, spherical shells, but each of these is subdivided by a number of lesser, divisional planes. No lithological change is, however, noticeable between the different shells. The granite is composed chiefly of orthoclase, transparent vitreous quartz, and about an equal proportion of black mica and hornblende. Here and there adularia occurs, and, very sparingly, albite.
With no difficulty, but some actual danger, I climbed down a smooth granite roof-slope to where the precipice of Royal Arches makes off, and where, lying upon a sharp, neatly fractured edge, I was able to look down and study those purple markings which are vertically striped upon so many of these granite cliffs. I found them to be bands of lichen growth which follow the curves of occasional water-flow. During any great rain-storm, and when snow upon the uplands is suddenly melted, innumerable streams, many of them of considerable volume, find their way to the precipice-edge, and pour down its front. Wherever this is the case, a deep purple lichen spreads itself upon the granite, and forms those dark cloudings which add so greatly to the variety and interest of the cliffs.
I found it extremest pleasure to lie there alone on the dizzy brink, studying the fine sculpture of cliff and crag, overlooking the arrangement of débris piles, and watching that slow, grand growth of afternoon shadows. Sunset found me there, still disinclined to stir, and repaid my laziness by a glorious spectacle of color. At this hour there is no more splendid contrast of light and shade than one sees upon the western gateway itself,—dark-shadowed Capitan upon one side profiled against the sunset sky, and the yellow mass of Cathedral Rocks rising opposite in full light, while the valley is divided equally between sunshine and shade. Pine groves and oaks, almost black in the shadow, are brightened up to clear red-browns where they pass out upon the lighted plain. The Merced, upon its mirror-like expanses, here reflects deep blue from Capitan, and there the warm Cathedral gold. The last sunlight reflected from some curious, smooth surfaces upon rocks east of the Sentinel, and about a thousand feet above the valley. I at once suspected them to be glacier marks, and booked them for further observation.
My next excursion was up to Mount Hoffmann, among a group of snow-fields, whose drainage gathers at last through lakes and brooklets to a single brook (the Yosemite), and flows twelve miles in a broad arc to its plunge over into the valley. From the summit, which is of a remarkably bedded, conoidal mass of granite, sharply cut down in precipices fronting the north, is obtained a broad, commanding view of the Sierras from afar, by the heads of several San Joaquin branches, up to the ragged volcanic piles about Silver Mountain.
From the top I climbed along slopes, and down by a wide détour among frozen snow-banks and many little basins of transparent blue water, amid black shapes of stunted fir, and over the confused wreck of rock and tree-trunk thrown rudely in piles by avalanches whose tracks were fresh enough to be of interest.
Upon reaching the bottom of a broad, open glacier-valley, through whose middle flows the Yosemite Creek and its branches, I was surprised to find the streams nearly all dry; that the snow itself, under influence of cold, was a solid ice mass, and the Yosemite Creek, even after I had followed it down for miles, had entirely ceased to flow. At intervals the course of the stream was carried over slopes of glacier-worn granite, ending almost uniformly in shallow rock basins, where were considerable ponds of water, in one or two instances expanding to the dignity of lakelets.
The valley describes an arc whose convexity is in the main turned to the west, the stream running nearly due west for about four miles, turning gradually to the southward, and, having crossed the Mono trail, bending again to the southeast, after which it discharges over the verge of the cliff. An average breadth of this valley is about half a mile; its form a shallow, elliptical trough, rendered unusually smooth by the erosive action of old glaciers. Roches moutonnées break its surface here and there, but in general the granite has been planed down into remarkable smoothness. All along its course a varying rubbish of angular bowlders has been left by the retiring ice, whose material, like that of the whole country, is of granite; but I recognized prominently black sienitic granite from the summit of Mount Hoffmann, which, from superior hardness, has withstood disintegration, and is perhaps the most frequent material of glacier-blocks. The surface modelling is often of the most finished type; especially is this the case wherever the granite is highly silicious, its polish becoming then as brilliant as a marble mantel. In very feldspathic portions, and particularly where orthoclase predominates, the polished surface becomes a crust, usually about three-quarters of an inch thick, in which the ordinary appearance of the minerals has been somewhat changed, the rock-surface, by long pressure, rendered extremely dense, and in a measure separated from the underlying material. This smooth crust is constantly breaking off in broad flakes. The polishing extended up the valley sides to a height of about seven hundred feet.
The average section of the old glacier was perhaps six hundred feet thick by half a mile in width. I followed its course from Mount Hoffmann down as far as I could ride, and then, tying my horse only a little way from the brink of the cliff, I continued downward on foot, walking upon the dry stream-bed. I found here and there a deep pit-hole, sometimes twenty feet deep, carved in mid-channel, and often full of water. Just before reaching the cliff verge the stream enters a narrow, sharp cut about one hundred and twenty feet in depth, and probably not over thirty feet wide. The bottom and sides of this granite lip, here and there, are evidently glacier-polished, but the greater part of the scorings have been worn away by the attrition of sands. A peculiar, brilliant polish, which may be seen there to-day, is wholly the result of recent sand friction.
It was noon when I reached the actual lip, and crept with extreme caution down over smooth, rounded granite, between towering walls, to where the Yosemite Fall makes its wonderful leap. Polished rock curved over too dangerously for me to lean out and look down over the cliff-front itself. A stone gate dazzlingly gilded with sunlight formed the frame through which I looked down upon that lovely valley.
Contrast with the strength of yellow rock and severe adamantine sculpture threw over the landscape beyond a strange unreality, a soft, aërial depth of purple tone quite as new to me as it was beautiful beyond description. There, twenty-six hundred feet below, lay meadow and river, oak and pine, and a broad shadow-zone cast by the opposite wall. Over it all, even through the dark sky overhead, there seemed to be poured some absolute color, some purple air, hiding details, and veiling with its soft, amethystine obscurity all that hard, broken roughness of the Sentinel cliffs. In this strange, vacant, stone corridor, this pathway for the great Yosemite torrent, this sounding-gallery of thunderous tumult, it was a strange sensation to stand, looking in vain for a drop of water, listening vainly, too, for the faintest whisper of sound, and I found myself constantly expecting some sign of the returning flood.