Page:Darwin Journal of Researches.djvu/266

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244
[CHAP. XI.
HEIGHT OF SNOW-LINE.

not at all. These fruits, in corresponding latitudes in Europe, are well known to succeed to perfection; and even in this continent, at the Rio Negro, under nearly the same parallel with Valdivia, sweet potatoes (convolvulus) are cultivated; and grapes, figs, olives, oranges, water and musk melons, produce abundant fruit. Although the humid and equable climate of Chiloe, and of the coast northward and southward of it, is so unfavourable to our fruits, yet the native forests, from lat. 45° to 38°, almost rival in luxuriance those of the glowing intertropical regions. Stately trees of many kinds, with smooth and highly coloured barks, are loaded by parasitical monocotyledonous plants; large and elegant ferns are numerous, and arborescent grasses entwine the trees into one entangled mass to the height of thirty or forty feet above the ground. Palm-trees grow in lat. 37°; an arborescent grass, very like a bamboo, in 40°; and another closely allied kind, of great length, but not erect, flourishes even as far south as 45° S.

An equable climate, evidently due to the large area of sea compared with the land, seems to extend over the greater part of the southern hemisphere; and as a consequence, the vegetation partakes of a semi-tropical character. Tree-ferns thrive luxuriantly in Van Diemen's Land (lat. 45°), and I measured one trunk no less than six feet in circumference. An arborescent fern was found by Forster in New Zealand in 46°, where orchideous plants are parasitical on the trees. In the Auckland Islands, ferns, according to Dr. Dieffenbach,[1] have trunks so thick and high that they may be almost called tree-ferns; and in these islands, and even as far south as lat. 55° in the Macquarrie Islands, parrots abound.

On the Height of the Snow-line, and on the Descent of the Glaciers, in South America.—For the detailed authorities for the following table, I must refer to the former edition:—

Latitude. Height in feet
of Snow-line.
Observer.
Equatorial region; mean result 15,748 Humboldt.
Bolivia, lat. 16° to 18° S. 17,000 Pentland.
Central Chile, lat. 33° S. 14,500 to 15,000 Gillies, and the Author.
Chiloe, lat. 41° to 43° S. 6,000 Officers of the Beagle, and the Author.
Tierra del Fuego, 54° S. 3,500 to 4,000 King.

As the height of the plane of perpetual snow seems chiefly to

  1. See the German Translation of this Journal: and for the other facts Mr. Brown's Appendix to Flinders's Voyage.