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XI

FLOATING ICEBERGS

261

effect of a severe shock (and such occur here 1) on a body like a glacier, already in motion, and traversed by fissures! I can readily believe that the water would be fairly beaten back out of the deepest channel, and then returning with an overwhelming force, would whirl about huge masses of rock like so much. chaff. In Eyre's Sound, in the latitude of Paris, there are immense glaciers, and yet the loftiest neighbouring mountain is only 6200 feet high. In this Sound, about fifty icebergs were seen at one time floating outwards, and one of them must have been at least 168 feet in total height. Some of the icebergs were loaded with blocks of no inconsiderable size, of granite

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and other rocks, different from the clay-slate of the surrounding mountains. The glacier farthest from the Pole, surveyed during the voyages of the Adventure and Beagle, is in lat. 46° 50', in the Gulf of Penas. It is 15 miles long, and in one. part 7 broad, and descends to the sea-coast. But even a few miles northward of this glacier, in the Laguna de San Rafael, some Spanish missionaries2 encountered "many icebergs, some great, some small, and others middle-sized," in a narrow arm of the sea, on the 22nd of the month corresponding with our

1 Bulkeley's and Cummin's Faithful Narrative of the Loss of the Wager. The earthquake happened August 25, 1741.

2 Agüeros, Desc. Hist. de Chiloe, p. 227.

June, and in a latitude corresponding with that of the Lake of Geneva !

In Europe, the most southern glacier which comes down to the sea is met with, according to Von Buch, on the coast of Norway, in lat. 67°. Now this is more than 20° of latitude, or 1230 miles, nearer the pole than the Laguna de San Rafael. The position of the glaciers at this place and in the Gulf of Penas may be put even in a more striking point of view, for they descend to the sea-coast, within 7° of latitude, or 450 miles, of a harbour, where three species of Oliva, a Voluta, and a Terebra, are the commonest shells, within less than 9° from where palms grow, within 4° of a region where the jaguar and puma range over the plains, less than 21° from arborescent grasses, and (looking to the westward in the same hemisphere) less than 2° from orchideous parasites, and within a single degree of tree-ferns!

These facts are of high geological interest with respect to the climate of the northern hemisphere, at the period when boulders were transported. I will not here detail how simply the theory of icebergs being charged with fragments of rock explains the origin and position of the gigantic boulders of eastern Tierra del Fuego, on the high plain of Santa Cruz, and on the island of Chiloe. In Tierra del Fuego the greater number of boulders lie on the lines of old sea-channels, now converted into dry valleys by the elevation of the land. They are associated with a great unstratified formation of mud and sand, containing rounded and angular fragments of all sizes, which has originated in the repeated ploughing up of the sea-bottom by the stranding of icebergs, and by the matter transported on them. Few geologists now doubt that those erratic boulders which lie near lofty mountains have been pushed forward by the glaciers themselves, and that those distant from mountains, and embedded in subaqueous deposits, have been conveyed thither either on icebergs, or frozen in coast-ice. The connection between the transportal of boulders and the presence of ice in some form, is strikingly shown by their geographical distribution over the earth. In South America they are not found farther than 48° of latitude, measured from the southern pole; in North America it appears

1 Geological Transactions, vol. vi. p. 415.

ΧΙ

CLIMATE OF ANTARCTIC ISLANDS

263

that the limit of their transportal extends to 53° from the northern pole; but in Europe to not more than 40° of latitude, measured from the same point. On the other hand, in the intertropical parts of America, Asia, and Africa, they have never been observed; nor at the Cape of Good Hope, nor in Australia.1

On the Climate and Proauctions of the Antarctic Islands.Considering the rankness of the vegetation in Tierra del Fuego, and on the coast northward of it, the condition of the islands south and south-west of America is truly surprising. Sandwich Land, in the latitude of the north part of Scotland, was found by Cook, during the hottest month of the year, “covered many fathoms thick with everlasting snow;" and there seems to be scarcely any vegetation. Georgia, an island 96 miles long and 10 broad, in the latitude of Yorkshire, "in the very height of summer, is in a manner wholly covered with frozen snow." It can boast only of moss, some tufts of grass, and wild burnet; it has only one land-bird (Anthus correndera), yet Iceland, which is 10° nearer the pole, has, according to Mackenzie, fifteen land-birds. The South Shetland Islands, in the same latitude as the southern half of Norway, possess only some lichens, moss, and a little grass; and Lieut. Kendall 2 found the bay, in which he was at anchor, beginning to freeze at a period corresponding with our 8th of September. The soil here consists of ice and volcanic ashes interstratified; and at a little depth beneath the surface it must remain perpetually congealed, for Lieut. Kendall found the body of a foreign sailor which had long been buried, with the flesh and all the features perfectly preserved. It is a singular fact that on the two great continents in the northern hemisphere (but not in the broken land of Europe between them) we have the zone of perpetually frozen under-soil in a low latitude-namely, in 56° in North America at the depth of three feet, and in 62°

3

1 I have given details (the first, I believe, published) on this subject in the first edition, and in the Appendix to it. I have there shown that the apparent exceptions to the absence of erratic boulders in certain hot countries are due to erroneous observations; several statements there given I have since found confirmed by various authors.

2 Geographical Journal, 1830, pp. 65, 66.

3 Richardson's Append. to Back's Exped. and Humboldt's Fragm. Asiat. tom. ii. p. 386.

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