The distribution of light and shade in clouds is most striking. The watery particles of which they are composed, yielding constantly to changes in temperature and moisture, are always changing; so that a most beautiful cloud may alter in figure and appearance in an instant of time; the light parts may suddenly become dark, and those that were shaded may all at once glow in the rays of the sun. Again, the appearance of a cloud, with respect to the sun, may entirely alter its character. The same cloud, to one observer, may appear entirely in shade, to another tipped with silver; to a third it may present brilliant points and various degrees of shade, or one of its edges only may appear illuminated; sometimes the middle parts may appear in shadow, while the margin may be partially luminous, rendering the middle parts all the more obscure by the contrast.
A wonderful variety may also be produced by the shadow of one cloud falling upon another. The accompanying sketch furnishes an example of this. Sometimes the whole of a cloud projects a shadow through the air upon some other far
distant cloud, and this again upon another, until at length it reaches the ground. The shadows of moving clouds may often be traced upon the ground, and they contribute greatly to modify the appearance of the landscape. A large number of small flickering clouds produce broken lights and shades which have an unpleasant jarring effect; but when the clouds are massive, or properly distributed,
the shadows often produce a high degree of repose.
Clouds are often seen to advantage in mountainous countries. Here the aspect of the heavens may be entirely different at different elevations. A single cloud in the valley may conceal the whole of the upper sky from an observer; but as he ascends he may gradually get above this and other layers or bands of cloud, and see a beautifully variegated sky above him, while the clouds which conceal the valley may be rolling at his feet. Evelyn, in his Memoirs, notices a scene of this kind. He says,—“Next morning we rode by Monte Pientio, or, as vulgarly called, Monte Mantumiato, which is of an excessive height, ever and anon peeping above airy clouds with its snowy head, till we had climbed to the inn at Radicofany, built by Ferdinand the greate Duke for the necessary refreshment of travellers in so inhospitable a place. As we ascended we entered a very thick, solid, and dark body of cloudes, which looked like rocks at a little distance, which lasted neare a mile in going up; they were dry, misty vapours, hanging undissolved for a vast thicknesse, and obscuring both sun and earth, so that we
seemed to be in the sea rather than in the cloudes, till, having pierced through it, we came into a most serene heaven, as if we had been above all human conversation, the mountain appearing more like a great island than joyn’d to any other hills, for we could perceive nothing but a sea of very thick cloudes rowling under our feete like huge waves, every now and then suffering the top of some other mountain to peepe through, which we could discover many miles off: and betweene some breaches of the cloudes we could see landskips and villages of the subjacent country. This was one of the most pleasant, newe, and altogether surprising objects that I had ever beheld.”
In the following interesting account of the ascent of the Peak of Teneriffe by Captain Basil Hall, it will be seen that heavy rain clouds may skirt the mountain, while its summit is in a pure and dry air.
“On the 24th of August,” he says, “we left Oratava to ascend the Peak. The day was the worst possible for our purpose, as it rained hard; and was so very foggy that we could not see the Peak, or indeed any object beyond one hundred yards distant.
“After riding slowly up a rugged path for four hours, it became extremely cold, and, as the rain never ceased for an instant, we were by this time drenched to the skin, and looked with no very agreeable feelings to the prospect of passing the night in wet clothes. At length the night began to close in, and the guides talked of the improbability of reaching the English station before night. It was still raining hard; but we dismounted, and took our dinner as cheerfully as possible, and hoping for clearer weather the next day. On remounting, we soon discovered that the road was no longer so steep as it had been heretofore, and the surface was comparatively smooth: we discovered, in short, that we had reached a sort of table-land, along which we rode with ease. Presently we thought the fog less dense, and the drops of rain not so large, and the air less chilling. In about half an hour we got an occasional glimpse of the blue sky; and as we ascended, (for our road, though comparatively level, was still upon the rise,) these symptoms became more manifest. The moon was at the full, and her light now became distinct, and we could see the stars in the zenith. By this time we had reached the Llano de los Remenos, or Retamos Plain, which is many thousand feet above the sea; and we could distinctly see that during the day we had merely been in a cloud, above which having now ascended, the upper surface lay beneath us like a country covered with snow. It was evident, on looking round, that no rain had fallen on the pumice gravel over which we were travelling. The mules were much fatigued, and we got off to walk. In a few minutes our stockings and shoes were completely dried, and in less than half an hour all our clothes were thoroughly dried. The air was sharp and clear, like that of a cold frosty morning in England; and though the extreme dryness, and the consequent rapid evaporation, caused considerable cold, we were enabled by quick exercise to keep ourselves comfortable. I had various instruments with me, but no regular hygrometer: accident, however, furnished me with one sufficiently indicative of the dry state of the air. My gloves, which I kept on while mounted, were completely soaked with the rain; and I took them off during this walk, and, without considering what was likely to happen, rolled them up, and carried them in my hand. When, at the end of an hour, or somewhat less, we came to remount our mules, I found the gloves as thoroughly dried and shrivelled up as if they had been placed in an oven. During all the time we were at the Peak itself, on the 26th, the sky was clear, the air quite dry, and we could distinguish, several thousand feet below us, the upper and level surface of the stratum of clouds through which we had passed the day before, and into which we again entered on going down, and found precisely in the same state as when we started.”
It is not uncommon to observe an effect quite contrary to the one given in the last two examples, the high summits of mountains being frequently concealed by heavy clouds of mist, while at a very short distance below them the air is clear and pure. In ascending to the Port of Venasque, one of the mountain passes of the Pyrenees, Mr. Murray found the mists so dense that he despaired of getting above them, or of their clearing away. But fortunately the wind freshened, and the mist, broken by it, “came sweeping,” he says, “over our heads, sometimes enveloping us in darkness, sometimes exposing the blue sky, and a part of the mountains. Section after section of the bald and towering masses which rose above the path