III.—In the Extreme South
From the Rio Plata the course of the Beagle was directed to the mouth of the Santa Cruz river, on the coast of Patagonia. One evening, when we were about ten miles from the bay of San Blas, vast numbers of butterflies, in bands and flocks of countless myriads, extended as far as the eye could range. One dark night, with a fresh breeze, the foam and every part of the surface of the waves glowed with a pale light. The vessel drove before her bows two billows of liquid phosphorus, and in her wake she was followed by a milky train. I am inclined to consider that the phosphorescence is the result of organic particles, by which process (one is tempted almost to call it a kind of respiration) the ocean becomes purified.
The geology of Patagonia is interesting. For hundreds of miles of coast there is one great deposit composed of shells—a white pumiceous stone like chalk, including gypsum and infusoria. At Port St. Julian it is eight hundred feet thick, and is capped by a mass of gravel forming probably one of the largest beds of shingle in the world, extending to the foot of the Cordilleras. For 1,200 miles from the Rio Plata to Tierra del Fuego the land has been raised by many hundred feet, and the uprising movement has been interrupted by at least eight long periods of rest, during which the sea ate deep back into the land, forming at successive levels the long lines of cliffs, or escarpments, which separate the different plains as they rise like steps one behind the other. What a history of geological change does the simply constructed coast of Patagonia reveal! In some red mud, capping the gravel, I discovered fossil bones which showed the wonderful relationship in the same continent between the dead and the living, and will, I have no doubt, hereafter throw more light on the appearance of organic beings on our earth and their disappearance from it than any other class of facts. Patagonia is sterile, but is possessed of a greater stock of rodents than any other country in the world. The principal animals are the llamas, in herds up to 500, and the puma, which, with the condor and other carrion hawks, preys upon them.
From the Strait of Magellan, the Beagle twice made a compass of the Falkland Islands, and archipelago in nearly the same latitude. It is a delicate and wretched land, everywhere covered by a peaty soil and wiry grass of one monotonous colour. The only native quadruped is a large wolf-like fox, which will soon be as extinct as the dodo. The birds embrace enormous numbers of sea-fowl, especially geese and penguins. The wings of a great logger-headed duck called the "steamer" are too weak for flight; but, by their aid, partly by swimming, partly flapping, they move very quickly. Thus we found in South America three birds who use their wings for other purposes besides flight—the penguins as fins, the "steamers" as paddles, and the ostrich as sails.
Tierra del Fuego may be described as a mountainous land, separated from the South American continent by the Strait of Magellan, partly submerged in the sea, so that deep inlets and bays occupy the place where valleys should exist. The mountain-sides, except on the exposed western coasts, are covered from the water's edge upwards to the perpetual snow-line by one great forest, chiefly of beeches. Viewing the stunted natives on the west coast, one can hardly conceive that they are fellow-creatures and inhabitants of the same world; and I believe that in this extreme part of South America man exists in a lower state of improvement than in any other part of the globe. The zoology of Tierra del Fuego is very poor. In the gloomy woods there are few birds, but where flowers grow there are humming birds, a few parrots and insects, but no reptiles.
IV.—The Wonders of the Cordilleras
After encountering many adventures in these Antarctic seas, among which was a narrow escape from shipwreck in a fierce gale off Cape Horn, and amidst hitherto unexplored Antarctic islands, the Beagle set a course northward in the open Pacific for Valparaiso, the chief seaport of Chile, which was reached on July 23, 1834. Chile is a narrow strip of land between the Cordilleras and the Pacific, and this strip itself is traversed by many mountain lines which run parallel to the great range. Between these outer lines and the main Cordilleras a succession of level basins, generally opening into each other by narrow passages, extend far to the southward. These basins, no doubt, are the bottoms of ancient inlets and deep bays such as at the present day intersect every part of Tierra del Fuego.
From November, 1834, to March, 1835, the Beagle was employed in surveying the island of Chiloe and the broken line called the Chonos Archipelago. This archipelago is covered by one dense forest, resembling that of Tierra del Fuego, but incomparably more beautiful. There are few parts of the world within the temperate regions where so much rain falls. The winds are very boisterous, and the sky almost always clouded. Fortunately, for once, while we were on the east side of Chiloe the day rose splendidly clear, and we could see the great range of the Andes on the mainland with three active volcanoes, each 7,000 feet high.
While at Valdivia, on the mainland, on February 20, 1835, the worst earthquake ever recorded in Chile occurred, and it was followed for twelve days by no less than 300 tremblings. A bad earthquake at once destroys our oldest associations; the earth, the very emblem of solidity, has moved beneath our feet like a thin crust over a fluid. One second of time has created in the mind a strange idea of insecurity which hours of reflection would not have produced. The most remarkable effect was the permanent elevation of the land round the Bay of Concepcion by several feet. The convulsion was more effectual in lessening the size of the island of Quiriquina off the coast than the ordinary wear and tear of the sea and weather during the course of a whole century; but on the other hand, on the Island of St. Maria putrid mussel-shells, still adhering to the rocks, were found ten feet above high-water mark. Near Juan Fernandez Island a volcano uprose from under the water close to the shore, and at the same instant two volcanoes in the far-off Cordilleras bust forth into action.
The space from which volcanic matter was actually erupted is 720 miles in one line and 400 miles in another line at right-angles from the first; hence, in all probability, a subterranean lake of lava is here stretched out of nearly double the area of the Black Sea. The frequent quakings of the earth on this line of coast are caused, I believe, by the rending of the strata, necessarily consequent on the tension of the land when upraised, and their injection by fluidified rock. This rending and injection would, if repeated often enough, form a chain of hills.