In fact, aqueous vapour is without a parallel in these particulars; it is not only the lightest of all vapours, in the common acceptation of that term, but the lightest of all gases except hydrogen and ammonia. To this circumstance the soft and tender beauty of the clouds of our atmosphere is mainly to be ascribed.
The _sphericity_ of the cloud-particles may be immediately inferred from their deportment under the luminous beams. The light which they shed when spherical is _continuous_: but clouds may also be precipitated in solid flakes; and then the incessant sparkling of the cloud shows that its particles are _plates_, and not spheres. Some portions of the same cloud may be composed of spherical particles, others of flakes, the difference being at once manifested through the _calmness_ of the one portion of the cloud, and the _uneasiness_ of the other. The sparkling of such flakes reminded me of the plates of mica in the River Rhone at its entrance into the Lake of Geneva when shone upon by a strong sun.--_Proceedings of the Royal Society_, vol. xvii. p. 317.
Clouds are so often referred to in these pages that I thought it might be of interest to note the latest remarks on their formation.
On Tuesday the 13th I accompanied a party of friends to the Märjelin See, skirted the lake, struck in upon the glacier, and having heard much of the position and the comfort of a new hotel upon the Bel Alp, I resolved to descend the glacier and pay the place a visit. The Valais range had been covered before we quitted the Æggischhorn; and, though the sun rode unimpeded in the higher heavens, vast masses of cloud continued to thrust themselves forth like tree-branches into the upper air.
The clouds extended, becoming ever blacker, until finally they were unlocked by thunder, and shook themselves down upon us in furious rain. The glacier is here cut up into oblique valleys of ice, subdivided by sharp-edged crevasses. We advanced swiftly along the ridges, but these finally abutted against the mountain, and we were compelled to cross from ridge to ridge. Hirst followed Bennen, and I trusted to my own devices. Joyously we struck our axes into the crumbling crests, and made our way rapidly between the chasms. The sunshine gushed down upon us, and partially dried our drenched clothes. At some distance to our left we observed upon the ice a group of persons, consisting of two men, a boy, and an old woman, engaged beside a crevasse; a thrill of horror shot through me, at the thought of a man being possibly between its jaws. We quickly joined them, and found an unfortunate cow firmly jammed between the frozen sides of the fissure, and groaning piteously. The men seemed very helpless; their means were inadequate, and their efforts ill-directed. 'Give the brute space, cut away the ice which presses the ribs, and _you_ step upon that block which stops the chasm, and apply your shoulders to the creature's buttocks.' The ice splinters fly aloft, under the vigorous strokes of Bennen. Hirst suggests that a rope should be passed round the horns, so as to enable all hands to join in the pull. This is done. Another rope is passed between the hind legs. Bennen has loosened the ice which held the ribs in bondage, and now, like mariners heaving an anchor, we all join in a tug, timing our efforts by an appropriate exclamation. The weight moves, but extremely little; again the cry, and again the heave--it moves a little more. This is repeated several times till the fore-legs are extricated and thrown forward on the ice. We now lift the hinder parts, and succeed in placing the animal upon the glacier, panting and trembling all over. Folding our rope, we went onward. The day again darkened. Again the thunder rang, being now preceded by lightning, which was thrown into my eyes from the polished surface of my axe. Flash followed flash and peal succeeded peal with terrific grandeur, and the loaded clouds sent down from all their fringes dusky streamers of rain. They looked like waterspouts, so dense was their texture. Furious as was the descending shower, hard as we were hit by the mixed pellets of ice and water, I enjoyed the scene. Grandly the cloud-besom swept the mountains, their colossal outlines looming at intervals like overpowered Titans struggling against their doom.