from the beaten track, getting into a chaos of crags which had been shaken from the heights. My ascent was quick, and I soon found myself upon the crest of broken rocks which caps the mountain. The peak and those adjacent, which are similarly shattered, exhibit a striking picture of the ruin which nature inflicts upon her own creations. She buildeth up and taketh down. She lifts the mountains by her subterranean energies, and then blasts them by her lightnings and her frost. Thus grandly she rushes along the grooves of change' to her unattainable repose. Is it unattainable? The incessant tendency of material forces is toward final equilibrium; and if the quantity of this tendency be finite, a time of repose must come at last. If one portion of the universe be hotter than another, a flux instantly sets in to equalise the temperatures; while winds blow and rivers roll in search of a stable equilibrium. Matter longs for rest; when is this longing to be fully satisfied? If satisfied, what then? Rest is not perfection; it is death. Life is only compatible with mutation; when equilibrium sets in life ceases, and the world thenceforward is locked in everlasting sleep.

A wooden cross bleached by many storms surmounts the pinnacle of the Æggischhorn, and at the base of it I now take my place and scan the surrounding scene. Down from its birthplace in

the mountains comes that noblest of ice-streams the Great Aletsch glacier. Its arms are thrown round the shoulders of the Jungfrau, while from the Monk and the Trugberg, the Gletscherhorn, the Breithorn, the Aletschhorn, and many another noble pile, the tributary snows descend and thicken into ice. The mountains are well protected by their wintry coats, and hence the quantity of débris upon the glacier is comparatively small; still, along it can be noticed dark longitudinal streaks, which are incipient moraines. Right and left from these longitudinal bands sweep finer curves, twisted here and there into complex windings, which mark the lamination of the subjacent ice. The glacier lies in a curved valley, the side towards which its convex curvature is turned is thrown into a state of strain, the ice breaks across the line of tension, a curious system of oblique glacier ravines being thus produced. From the snow-line which crosses the glacier above the Faulberg a pure snow-field stretches upward to the Col de la Jungfrau, which unites the Maiden to the Monk. Skies and summits are to-day without a cloud, and no mist or turbidity interferes with the sharpness of the outlines. Jungfrau, Monk, Eiger, Trugberg, cliffy Strahlgrat, stately, lady-like Aletschhorn, all grandly pierce the empyrean. Like a Saul of mountains, the Finsteraarhorn overtops all his neighbours; then we have the Oberaarhorn, with the riven

glacier of Viesch rolling from his shoulders. Below is the Märjelin See, with its crystal precipices and its floating icebergs, snowy white, sailing on a bluegreen sea. Beyond is the range which divides the Valais from Italy. Sweeping round, the vision meets an aggregate of peaks which look, as fledglings to their mother, towards the mighty Dom. Then come the repellent crags of Mont Cervin, the idea of moral savagery, of wild untameable ferocity, mingling involuntarily with our contemplation of the gloomy pile. Next comes an object scarcely less grand, conveying it may be even a deeper impression of majesty and might than the Matterhorn itselfthe Weisshorn, perhaps the most splendid object in the Alps. But beauty is associated with its force, and we think of it, not as cruel, but as grand and strong. Further to the right is the Great Combin; other peaks crowd around him, while at the extremity of the curve along which the gaze has swept rises the sovran crown of Mont Blanc. And now,

as the day sinks, scrolls of pearly clouds form around. the mountain-crests, and are wafted from them into the distant air. They are without colour of any kind; but their grace of form and lustre are not to be described.

G

NOTE ON CLOUDS.

It is well known that when a receiver filled with ordinary undried air is exhausted, a cloudiness, due to the precipitation of the aqueous vapour diffused in the air, is produced by the first few strokes of the pump. It is, as might be expected, possible to produce clouds in this way with the vapours of other liquids than water.

In the course of some experiments on the chemical action of light on vapours which have been communicated to the Royal Society, I had frequent occasion to observe the precipitation of such clouds; indeed, several days at a time have been devoted solely to the generation and examination of clouds formed by the sudden dilatation of mixed air and vapours in the experimental tubes.

The clouds were generated in two ways: one mode consisted in opening the passage between the filled experimental tube and the air-pump, and then simply dilating the air by working the pump. In the other, the experimental tube was connected with a vessel of suitable size, the passage between which and the experimental tube could be closed by a stopcock. This vessel was first exhausted ; on turning the cock the air rushed from the experimental tube into the vessel, the precipitation of a cloud within the tube being a consequence of the transfer. Instead of a special vessel, the cylinders of the air-pump itself were usually employed for this purpose.

It was found possible, by shutting off the residue of air and vapour after each act of precipitation, and again exhausting the cylinders of the pump, to obtain with some

substances, and without refilling the experimental tube, fifteen or twenty clouds in succession.

The clouds thus precipitated differed from each other in luminous energy, some shedding forth a mild white light, others flashing out with sudden and surprising brilliancy. This difference of action is, of course, to be referred to the different reflective energies of the particles of the clouds, which were produced by substances of very different refractive indices.

Different clouds, moreover, possess very different degrees of stability: some melt away rapidly, while others linger for minutes in the experimental tube, resting, as they slowly dissolve, upon its bottom like a heap of snow. The particles of other clouds are trailed through the experimental tube as if they were moving through a viscous medium.

Nothing can exceed the splendour of the diffraction phenomena exhibited by some of these clouds; the colours are best seen by looking along the experimental tube from a point above it, the face being turned towards the source of illumination. The differential motions introduced by friction against the interior surface of the tube often cause the colours to arrange themselves in distinct layers.

The difference in texture exhibited by different clouds caused me to look a little more closely than I had previously done into the mechanism of cloud-formation. A certain expansion is necessary to bring down the cloud; the moment just before precipitation the cooling air and vapour may be regarded as divided into a number of polyhedra, the particles along the bounding surfaces of which move in opposite directions when precipitation actually sets

Every cloud-particle has consumed a polyhedron of vapour in its formation; and it is manifest that the size of the particle must depend, not only on the size of the vapour