mountains (such as are referred to upon pp. 32, 92-3) are, of course, caused by these powers. No one doubts it; but one never believes it so thoroughly as when the quarries are seen from which their materials have been hewn; and when the germs, so to speak, of these avalanches have been seen actually starting from above.
These falls of rock take place from two causes. First, from the heat of the sun detaching small stones or rocks which have been arrested on ledges or slopes and bound together by snow or ice. I have seen such released many times when the sun has risen high; fall gently at first, gather strength, grow in volume, and at last rush down with a cloud trailing behind, like the dust after an express train. Secondly, from the freezing of the water which trickles, during the day, into the clefts, fissures, and crannies. This agency is naturally most active in the night, and then, or during very cold weather, the greatest falls take place.[1]
When one has continually seen and heard these falls, it is easily understood why the glaciers are laden with moraines. The wonder is, not that they are sometimes so great, but that they are not always greater. Irrespective of lithological considerations, one knows that this débris cannot have been excavated by the glaciers. The moraines are borne by glaciers, but they are born from the ridges. They are generated by the sun, and delivered by the frost. "Fire," it is well said in Plutarch's life of Camillus, "is the most active thing in nature, and all generation is motion, or at least, with motion; all other parts of matter without warmth lie sluggish and dead, and crave the influence of heat as their life, and when that comes upon them, they immediately acquire some active or passive qualities."[2]
- ↑ In each of the seven nights I passed upon the south-west ridge of the Matterhorn in 1861-3 (at heights varying from 11,844 to 12,992 feet above the level of the sea), the rocks fell incessantly in showers and avalanches. See p. 175.
- ↑ Tonson's Ed. of 1758. Bacon may have had this passage in mind when he wrote, "It must not be thought that heat generates motion, or motion heat (though in some respects this be true), but that the very essence of heat, or the substantial self of heat, is motion and nothing else."—Novum Organum, book ii. Devey's Translation.
