intercepts the Weisshorn; and which, when we face the valley of the Rhone from the Bel Alp, falls steeply at our right to the promontory called the Nessel. Viewed from this promontory, the Dom finds its match, and more than its match, in its mighty neighbour, whose hugeness is here displayed from top to bottom. On the lower reaches of the Aletschhorn also the Dom maintains its superiority; the Weisshorn being for a time wholly unseen, and the Matterhorn but imperfectly. As we rise, however, the Dom steadily loses its individuality, until from the ridge of the Aletschhorn it is jumbled to a single leviathan heap with the mass of Monte Rosa. The Weisshorn meanwhile as steadily gains in grandeur, rising like a mountain Saul amid the congregated hills, until from the arête it distances all competitors. In comparison with this kingly peak, the Matterhorn looks small and mean. It has neither the mass nor the form which would enable it to compete, from a distant point of view, with the Weisshorn.

The ridge of the Aletschhorn is of schistose gneiss, in many places smooth, in all places steep, and sometimes demanding skill and strength on the part of the climber. I thought we could scale it with greater ease if untied, so I flung the rope away from me. My guide was in front, and I carefully watched his action among the rocks. For some time there was nothing to cause anxiety for his safety. There was no likelihood of a slip, and if a slip occurred there was opportunity for recovery. But after a time this ceased to be the case. The rock had been scaled away by weathering parallel to the planes of foliation, the surfaces left behind being excessively smooth, and in many cases flanked by slopes and couloirs of perilous steepness. I saw that a slip might occur here, and that its consequences would be serious. The rope was therefore resumed. A fair amount of skill and an absence of all precipitancy rendered our progress perfectly secure. In every place of danger one of us planted himself as securely as the rock on which he stood, and remained thus fixed until the danger was passed by the other. Both of us were never exposed to peril at the same moment. The bestowal of a little extra time renders this arrangement possible along the entire ridge of the Aletschhorn; in fact, the dangers of the Alps can be almost reduced to the level of the dangers of the street by the exercise of skill and caution. For rashness, ignorance, or carelessness the mountains leave no margin; and to rashness, ignorance, or carelessness three-fourths of the catastrophes which shock us are to be traced. Even those whose faculties are ever awake in danger are sometimes caught napping when danger seems remote; they receive accordingly the punishment of a tyro for a tyro's neglect.

While ascending the lower glacier we found the air in general crisp and cool; but we were visited at intervals by gusts of Föhn

warm breathings of the unexplained Alpine sirocco, which passed over our cheeks like puffs from a gently-heated stove. On the arête we encountered no Föhn; but the rocks were so hot as to render contact with them painful. I left my coat among them, and went upward in my shirt sleeves. At our last bivouac my guide had allowed two hours for the remaining ascent. We accomplished it in one, and I was surprised by the shout which announced the passage of the last difficulty, and the proximity of the crest of the mountain. This we reached precisely eight hours after starting-an ascent of fair rapidity, and unalloyed by a single mishap from beginning to end.

Rock, weathered to fragments, constitutes the crown of the Aletschhorn; but against this and above it is heaped a buttress of snow, which tapers to a pinnacle of surpassing beauty, as seen from the Eggischhorn. This snow was firm, and we readily attained its highest point. Over this I leaned for ten minutes, looking along the face of the pyramid, which fell for thousands of feet to the névés at its base. We looked down upon the Jungfrau, and upon every other peak for miles around us, one only excepted. The exception was the Finsteraarhorn, the highest of the Oberland Mountains. I could clearly track the course pursued by Bennen and myself eleven years previously; the spurs of rock and slopes of snow; the steep and weathered crest of the mountain, and the line of our swift glissade, as we returned. Bennen lived heroically by the sword, and he perished by it. Round about the dominant peak of the Oberland was grouped a crowd of other peaks, retreating eastward to Graubünden and the distant Engadin; retreating southward over Italy, and blending ultimately with the atmosphere. At hand were the Jungfrau, Mönch, and Eiger. A little further off the Blumlis Alp, the Weisse Frau, and the Great and Little Nesthorn. In the distance the grim precipices of Mont Blanc, rising darkly from the Allée Blanche, and lifting to the firmament the snow-crown of the mountain. The Combin and its neighbours were distinct; and then came that trinity of grandeur, with which the reader is so well acquainted-the Weisshorn, the Matterhorn, and the Dom-supported by the Alphubel, the Allaleinhorn, the Rympfischhorn, the Strahlhorn, and the mighty Monte Rosa. From no other point in the Alps have I had a greater command of their magnificence -perhaps from none so great; while the blessedness of perfect health rounded off within me the external splendour. The sun, moreover, seemed to take a pleasure in bringing out the glory of the hills. The intermixture of light and shade was astonishing; while to the whole scene a mystic air was imparted by a belt of haze, in which the furthest outlines disappeared, as if infinite distance had rendered them impalpable.

Two concentric shells of atmosphere, perfectly distinct in character, clasped the earth this morning. That which hugged the surface was of a deep neutral tint, too shallow to reach more than midway up the loftier mountains. Upon this, as upon an ocean, rested the luminous higher atmospheric layer, both being separated along the horizon by a perfectly definite line. This higher region was without a cloud; the arrowy streamer that had shot across the firmament during our ascent, first reduced to feathery streaks, had long since melted utterly away. Blue was supreme above; while all round the horizon the intrinsic brilliance of the upper air was enhanced by contrast with the dusky ground on which it rested. But this gloomier portion of the atmosphere was also transparent. It was not a cloud-stratum cutting off the view of things below it, but an attenuated mist, through which were seen as through a glass darkly the lower mountains, and out of which the higher peaks and ridges sprung into sudden glory.

But the pomp of peak and crag has already palled upon the public mind; why, then, dwell upon it? I do so because my own enjoyment of it was fresh, notwithstanding the number of times that I had seen it. We will now, however, quit this region of the sublime and beautiful. The emotions excited by natural grandeur are all very well in their way, but they are evanescent, and something is needed to fill the vacuity created by their departure. Here the action of the intellect comes to our aid, and fills the shores of life after the feelings have retreated.

The vision of an object always implies a differential action on the retina of the observer. The object is distinguished from surrounding space by its excess or defect of light in relation to that space. By altering the illumination, either of the object itself or of its environment, we alter the appearance of the object. Take the case of clouds floating in the atmosphere with patches of blue between them. Anything that changes the illumination of either alters the appearance of both, that appearance depending, as stated, upon differential action. Now the light of the sky, being polarised, may, as the reader of this Review already knows, be in great part quenched by a Nicol's prism, while the light of a cloud, being unpolarised, cannot be thus extinguished. Hence the possibility of very remarkable variations, not only in the aspect of the firmament, which is really changed, but also in the aspect of the clouds which have that firmament as a background. It is possible, for example, to choose clouds of such a depth of shade that when the Nicol quenches the light behind them, they shall vanish, being undistinguishable from the residual dull tint which outlives the extinction of the brilliance of the sky. A cloud less deeply shaded, but still deep enough, when viewed with the naked eye, to appear dark on a

bright ground, is suddenly changed to a white cloud on a dark ground by the quenching of the sky behind it. This was the case to-day with the lower atmospheric stratum above referred to. When the light of the upper firmament was removed it no longer appeared dark, but whitish; being changed into a milky haze by contrast with the superjacent darkness. When a reddish cloud at sunset chances to float in the region of maximum polarisation, the quenching of the sky behind it causes it to flash with a brighter crimson. Last Easter eve the Dartmoor sky, which had just been cleansed by a snow storm, wore a very wild appearance. Round the horizon it was of steely brilliancy, while reddish cumuli and cirri floated southwards. When the sky was quenched behind them these floating masses seemed like dull embers suddenly blown upon, brightening into fire. In the Alps we have the most magnificent examples of crimson clouds and snows, so that the effects just referred to may be here studied under the best possible conditions. On the 23rd of August the evening Alpen-glow was very fine, though it did not reach its maximum depth and splendour. Towards sunset I walked up the slopes to obtain a better view of the Weisshorn. The side of the peak seen from the Bel Alp, being turned from the sun, was tinted mauve; but I wished to see one of the rose-coloured buttresses of the mountain. Such was visible from a point a few hundred feet above the hotel. The Matterhorn also, though for the most part in shade, had a crimson projection, while a deep ruddy red lingered along its western shoulder. Four distinct peaks and buttresses of the Dom, in addition to its dominant head-all covered with pure snow-were reddened by the light of sunset. The shoulder of the Alphubel was similarly coloured, while the great mass of the Fletschorn was all aglow, and so was the snowy spine of the Monte Leone.

Looking at the Weisshorn through the Nicol, the glow of its protuberance was strong or weak according to the position of the prism. The summit also underwent a change. In one position of the prism it exhibited a pale white against a dark background; in the rectangular position, it was a dark mauve against a light background. The red of the Matterhorn changed in a similar manner; but the whole mountain also passed through striking changes of definition. The air at the time was highly opalescent-filled in fact with a silvery haze, in which the Matterhorn almost disappeared. This could be wholly quenched by the Nicol, and then the mountain sprang forth with astonishing solidity and detachment from the surrounding air. The changes of the Dom were still more wonderful. A vast amount of light could be removed from the sky behind it, for it occupied the position of maximum polarisation. By a little practice with the Nicol it was easy to render the extinction of the light or its restoration almost instantaneous. When the sky was quenched, the

four minor peaks and buttresses and the summit of the Dom, together with the shoulder of the Alphubel, glowed as if set suddenly on fire. This was immediately dimmed by turning the Nicol through an angle of 90°. It was not the stoppage of the light of the sky alone which produced this startling effect; the air between the Bel Alp and the Dom was, as I have said, highly opalescent, and the quenching of this intermediate glare augmented remarkably the distinctness of the mountain.

On the morning of the 24th of August similar effects were finely shown. At 10 A.M. all three mountains, the Dom, the Matterhorn, and the Weisshorn, were powerfully affected by the Nicol. But in this instance also the line drawn to the Dom being accurately perpendicular to the direction of the solar shadows, and consequently very nearly perpendicular to the solar beams, the effects on this mountain were most striking. The grey summit of the Matterhorn at the same time could scarcely be distinguished from the opalescent haze around it; but when the Nicol quenched the haze, the summit became instantly isolated, and stood out in bold definition. It is to be remembered that in the production of these effects the only things changed are the sky behind and the luminous haze in front of the mountains; that these are changed because the light emitted from the sky and from the haze is plane polarised light,' and that the light from the snows and from the mountains being sensibly unpolarised, is not directly affected by the Nicol. It will also be understood that it is not the interposition of the haze as an opaque body that renders the mountains indistinct, but that it is the light of the haze which dims and bewilders the eye, and thus weakens the definition of objects seen through it.

These results have a direct bearing upon what artists call "aërial perspective." As we look from the summit of the Aletschhorn, or from a lower elevation, at the serried crowd of peaks, especially if the mountains be darkly coloured-covered with pines, for exampleevery peak and ridge is separated from the mountains behind it by a thin blue haze which renders the relations of the mountains as to distance unmistakable. When this haze is regarded through the Nicol perpendicular to the sun's rays, it is in many cases wholly quenched, because the light which it emits in this direction is wholly polarised. When this happens, aërial perspective is abolished, and mountains very differently distant appear to rise in the same vertical plane. Close to the Bel Alp, for instance, is the gorge of the Massa, a river produced by the ablation of the Aletsch glacier, and beyond the gorge is a high ridge darkened by pines. This ridge may be projected upon the dark slopes at the opposite side of the Rhone valley, and between both we have the blue haze referred to, throwing (1) See FORTNIGHTLY REVIEW, February, 1869, p. 239.