The minor ridges do not usually present such extraordinary forms as the principal ones. They are less exposed, and they are less broken up, and it is reasonable to assume that their annual degradation is less than that of the summit-ridges.
PART OF THE NORTHERN RIDGE OF THE GRAND CORNIER.
The wear and tear does not cease even in winter, for these great ridges are never completely covered up by snow,[[43]] and the sun has still power. The destruction is incessant, and increases as time goes on; for the greater the surfaces which are exposed to the practically inexhaustible powers of sun and frost, the greater ruin will be effected.
[43] I wrote in the Athenæum, August 29, 1863, to the same effect. “This action of the frost does not cease in winter, inasmuch as it is impossible for the Matterhorn to be entirely covered by snow. Less precipitous mountains may be entirely covered up during winter, and if they do not then actually gain height, the wear and tear is, at least, suspended. . . . We arrive, therefore, at the conclusion that, although such snow-peaks as Mont Blanc may in the course of ages grow higher, the Matterhorn must decrease in height.” These remarks have received confirmation.
The men who were left by M. Dollfus-Ausset in his observatory upon the summit of the Col Theodule, during the winter of 1865, remarked that the snow was partially melted upon the rocks in their vicinity upon 19th, 20th, 21st, 22d, 23d, 26th, 27th December of that year, and upon the 22d of December they entered in their Journal, “Nous avons vu au Matterhorn que la neige se fondait sur roches et qu’il s’en écoulait de l’eau.”—Matériaux pour l’étude des Glaciers, vol. viii. part i, p. 246, 1868; and vol. viii. part ii. p. 77, 1869.
The rock-falls which are continually occurring upon all rock-mountains 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: they 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.[[44]]
[44] 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.
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.”[[45]]