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ARTICLE V.THE GLACIERS OF THE ALPS.

[BY CHESTER DEWEY, D.D., LL.D., OF THE UNIVERSITY OF Rochester.]

The Glaciers of the Alps: The Origin and Phenomena of Glaciers. By JOHN TYNDALL, F. R. S. Boston. 1860.

Suppose yourself standing upon one of the higher summits of that great cluster of mountains, the Alps. Take your position on Mt. Rosa, 15,208 feet above the ocean, in lat. 46 deg. 15 min. about, and long. 7 deg. 40 min. east; or on Mt. Cervin, 14,837 feet, ten miles west of the former; or on Mt. Blanc, 15,712 feet, lat. 45, deg. 50 min., and long. 7 deg. 20 min. east, nearly south of the east end of Lake Geneva, about 40 miles distant, and nearly as far south-east of the city, Geneva. On the last the eye is above all visible summits, and all the higher points of the Alps are in the field of view. The whole scene is one wide waste of interminable snow, except where the perpendicular ledges of the mountain sides darken the prospect. The same view is repeated on all the lower but still high mountains, only on a scale less grand and magnificent. On these snow falls in great quantity. This is the source from which the glaciers are chiefly supplied, and forms the immense fields, called the névé, or snow. At about 9000 feet this snowfield forms the line of perpetual congelation, or the snow-line on the Alps. On the Andes this line is about 15 or 16,000 feet, under or near the Equator; on the Himalayas, 18,000 feet above the sea-Himalaya meaning the "abode of frost or snow." The name Mt. Blanc reveals to us the snow and ice; and even the name Alps may be only a slightly changed derivation from the Latin albus, white. The glacier of Grindenwald is named Eis-meer, Ice-Sea.

The word Glacier is from the French glacier, and this from the French glace, ice.

The Alps extend from Mt. Blanc north-eastwardly to the Tyrol, but higher in the southern part; presenting numerous high summits, between which the snows descend till they become the ice which forms the glaciers at the lower part, and of which it is said there are more than four hundred. Many of these glaciers are from 12 to 20 miles long, and some a mile or more broad. The glaciers extend below the line of perpetual congelation, and their termination is about 6,000 feet above the sea-some are less-nearly stationary, that is, the melting of the lower part is equal to the annual descent; some are becoming shorter; and two are stated to be extending downwards, and covering a valley once inhabited.

The direction of the glaciers depends upon the opening of the valleys, and may be towards any point of the compass. That of Chamouni, the Mer de Glace, descends northwards, others eastwards, and so on. As several valleys may descend in different directions so as to unite in one, so a glacier may be composed of several united. Thus Tyndall describes the union of five to form the great glacier which descends from the lower mountains on the north side of Mt. Blanc, like the several united streams to form one noble river. These united constitute the Mer de Glace, or Sea of Ice.

The inquiry has often been made, why those familiar with this glacier should call it a Sea of Ice, when the length and breadth made it much more resemble a river, or, if it were not for its palpable descent, an arm of the sea. From the naturally winding course of the valleys in which a glacier lies, a river of ice would be its pertinent designation. The surface of the glacier is not even and smooth, but far different. The following beautiful and adequate reason is given by an author who visited the Mer de Glace in 1814: "At first sight," says he," this immense field of ice, about six miles long and one and a half wide, has the same appearance as if a tumultuous and highly agitated sea had been suddenly frozen." He then remarks, that the glacier is "intersected

with numerous chasms and ravines, some of which are 100 feet deep." Tyndall gives the same appearance of the glacier, as “of a sea, which, after it had been tossed by a storm, had sufficiently stiffened into rest. The ridges upon its surface accurately resemble waves in shape." For this he gives the following obvious solution. The deep fissures by rents have between them a ridge of ice, sharp and angular at first. As this glacier moves towards the north, the edges of the ridge towards the sun are "sculptured (melted) off," and "converted into slopes which represent the back of a wave, while the opposite (northern) side of the ridges" is protected from the sun's action, and remains steep like the "front of the wave."

It is obvious that difference in the direction, magnitude of rents and ridges, as well as width of the glacier, may make Mer de Glace worthy of being confined to the glacier of Chamouni alone.

This account prepares us to believe the description that follows from the first mentioned author: "The whole of this frozen sea is surrounded with bare and lofty summits. The black desolation which presented itself on every side; the dreary and unbroken silence which reigned around; and the sublimity and novelty with which every object was marked," made the whole most impressive and indescribable. He remarked also on the noise of the waters rushing below, the crashing noise of falling masses from the rocky sides of the mountains into chasms, and the loud explosions from the bursting of the ice in the formation of chasms and crevasses deep and large. Tyndall says, the crevasses have rarely been seen to form, though the explosions are common and often terrific; and in a known case it began with a mere long fracture not the tenth of an inch in width.

Yet it is obvious that the broken ridges, hollows or deep chasms, and projecting portions, which result from the descent and very unequal pressure of the parts of the glaciers, must present in a cross view the appearance of waves of the sea suddenly" stiffened into rest," though a less complete resemnblance, doubtless, than that of the Mer de Glace.

As the glaciers lie in the valleys whose sides are mountain

ous tracts and steep ledges, there must be a constant falling of rocks and stones, sand and gravel, from the action of atmos pheric agencies. Many of these will be large masses of rock. "Thus the glacier," says Tyndall, “is incessantly loaded along its borders with the ruins of the mountains that limit it." It follows that" as the glacier moves downard, it carries with it the load deposited upon it. Long ridges of débris thus flank the glacier, and these ridges are called lateral moraines. By "moraines," then, is meant this mass of rock, sand, &c.— the débris deposited on the glacier. When two glaciers unite to form a larger glacier, "their adjacent lateral moraines are laid side by side at the place of confluence, thus constituting a ridge which runs along the middle of the trunk-glacier," and it is named a medial moraine.' It is evident that two glaciers united will have two lateral and one medial moraine; that three glaciers joined in one, will have two lateral, and two medial moraines; and that four must have two lateral and three medial moraines, and so on. When the moraine of a glacier is deposited at the lower extremity," it is called “a terminal moraine."

If a glacier lessens in width, it may leave "its lateral moraines stranded on the flanks of the valleys." This has occurred, and "a succession of old lateral moraines is the consequence," as seen at the Mer de Glace. So, if the glacier "diminish in length at distant intervals, the result will be a "succession of more or less concentric terminal moraines," as shown on the Rhone Glacier, as well as at the Mer de Glace. (p. 264.)

If the observers are correct in their statements of mounds of rock and sand, now covered with earth, as terminal moraines, far lower down than found at present, as is commonly admitted, the Alps must have been far colder in earlier times than at present, so that the glaciers were far more extensive.

The large rocks that fall from the mountain sides upon a glacier often roll upon it a considerable distance from its edge or side. A mass of granite 24 feet high was measured among these blocks. By the side of such a mass Professor Agassiz pitched his tent for his summer observations on the

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