Изображения страниц
PDF
EPUB
[graphic][merged small][merged small]

Valparaiso The Portillo Pass-Land of the Red Snow-Electrical Conditions-A Swarm of Locusts-Experiments with the Reduvius-A Forest of Stone-Valley of the Copiapó-Ruins at Old Callao Antiquity of Man.

[graphic][subsumed]

HE Beagle reached Valparaiso on March 11th, from which place Darwin started on a trip across the Cordillera Mountains. The party went by the Portillo, a lofty and dangerous pass which led across the Andes to Mendoza. The scenery was grand in the extreme, and

offered a wide and varied

field for geological investigation. As they ascended the flora changed, and the gradual replacement of tropical forms by those of an alpine character was observed. The vast mountains spread away on all sides, offering every inducement to the geological hammer of the naturalist; and that a well-defined idea

of the geological structure of the entire region was obtained by him is evident. He found shells, that formerly lived in the ocean, in beds fourteen thousand feet above the sea. Here was a bed which he surmised was of the age of the chalk cliff of England.

The altitude affected Darwin not a little, especially in walking rapidly, but he entirely forgot it in the delight of collecting fossils, with which the region abounded. The natives called shortness of breath "puna," and suggested various remedies, having singular and original ideas of the cause.

The upper peaks here have been called the land of the red snow, and Darwin was constantly on the lookout for its appearance. One day as he was walking behind the mules he noticed in the track of one a reddish line, and then another, until finally the tint was very distinct, and the famous red snow was discovered a very common phenomenon in this lofty altitude. At first Darwin thought the pale red hue came from the dust, blown from neighbouring mountains, of red porphyry. The colour was most distinct when the snow was thawing, and if some of the latter was rubbed on a paper a faint red hue was seen, while under the microscope were found groups of minute spheres in colourless cases, each about a thousandth part of an inch in diameter. The red snow was, in reality, a microscopic plant, Protococcus nivalis, and in the Arctic regions especially it often produces wonderful displays.

Crossing the mountains the party descended on the other side into a deep valley between the two ranges, and into the republic of Mendoza, The

Electrical Conditions of the Atmosphere. 99

altitude was still over two miles, and vegetation. extremely scant. Here the night was passed, in a locality that, from the possibility of a heavy snow, was extremely dangerous, a cave being the only retreat in case of a storm. There was scarcity of fuel, and, owing to the altitude, it required four or five hours to boil potatoes; indeed, Darwin boiled his two days, and found them as hard as at first.

The electrical condition of the atmosphere was very noticeable, as well as its transparency. In referring to this, he says: "The increased brilliancy of the moon and stars at this elevation, owing to the perfect transparency of the atmosphere, was very remarkable. Travellers having observed the difficulty of judging heights and distances amidst lofty mountains, have generally attributed it to the absence of objects of comparison. It appears to me that it is fully as much owing to the transparency of the air confounding objects at different distances, and likewise partly to the novelty of an unusual degree of fatigue arising from a little exertion, habit being thus opposed to the evidence of the senses. I am sure that this extreme clearness of the air gives a peculiar character to the landscape, all objects appearing to be brought nearly into one plane, as in a drawing or panorama. The transparency is, I presume, owing to the equable and high state of atmospheric dryness. This dryness was shown by the manner in which woodwork shrank (as I soon found by the trouble my geological hammer gave me); by articles of food, such as bread and sugar, becoming extremely hard; and by the preservation of the skin

and parts of the flesh of the beasts which had perished on the road. To the same cause we must attribute the singular facility with which electricity is excited. My flannel waistcoat, when rubbed in the dark, ap peared as if it had been washed with phosphorus ; every hair on a dog's back crackled; even the linen sheets, and leathern straps of the saddle, when handled, emitted sparks."

The descent was made on the east side of the Cordilleras, where a magnificent view of the pampas was obtained. An immediate difference between the vegetation was apparent, though the soil and climate were materially like that of the country recently passed. The same was true of the fauna, many Patagonian forms being seen, among them the Agouti, Biscacha, three species of armadillo, and ostrich.

As they descended into the valley Darwin had his first experience with the locust. He was near the village of Luxan, when he noticed a large ragged cloud, reddish brown in colour. It was at first supposed to be smoke from a pampas fire, but soon developed into a swarm of locusts. The vast congregation was moving to the north at a rate of fifteen miles an hour. They completely filled the air from a height of twenty feet from the ground to nearly half a mile above it, and made a noise as they flew like the rustling of a mighty wind, or, as Darwin said, of a breeze through the rigging of a ship. Where they were the thickest the sky was wholly obscured. They occasionally alighted upon the ground, so completely covering it that it changed

A Forest of Stone.

ΙΟΙ

before the observer's eye from green to brown. The locusts were a common pest here, and often threatened the crops of the natives, their only salvation being to wage a war of fire against them.

Crossing the Luxan, the village of that name was reached, where the night was spent in repelling the attacks of the reduvius-a black bug that is a most courageous blood-sucker. To test the pugnacity of this creature Darwin placed one upon a table, where, if a finger was pointed at it, the blood-thirsty insect would protrude its sucker and charge at it.

Of the people of Mendoza Darwin quotes the description of Sir F. Head: "They eat their dinners, and it is so very hot they go to sleep-and could they do better?" Darwin adds: "I quite agree with Sir F. Head: the happy doom of the Mendozinos is to eat, sleep, and be idle.”

Darwin returned to Chili by the Pass of Uspallata, and here also he made careful geological studies. To show his prescience, upon discovering a layer of tertiary beds resembling some in which he had found fossil trees, he began to search for them here with most satisfactory results, as in the central portion of the range, a mile above the sea, he noticed numbers of snow-white columns projecting from a cliff. Here was a forest of stone, one of the most interesting finds he made, the trees extending in every direction, some silicified, and others coarsely crystallised white calcareous spar. Nearly all were broken off near the ground, and were from four to five feet in circumference. Darwin took sections of them as specimens, and found that they were firs, or

« ПредыдущаяПродолжить »