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SLOW ELEVATION OF MOUNTAIN-CHAINS.

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may confidently come to the conclusion that the forces which slowly and by little starts uplift continents, and those which at successive periods pour forth volcanic matter from open orifices, are identical. From many reasons, I believe that the frequent quakings of the earth on this line of coast are caused 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 (and we know that earthquakes repeatedly affect the same areas in the same manner), form a chain of hills; and the linear island of St. Mary, which was upraised thrice the height of the neighbouring country, seems to be undergoing this process. I believe that the solid axis

of a mountain differs in its manner of formation from a volcanic hill only in the molten stone having been repeatedly injected, instead of having been repeatedly ejected. Moreover, I believe that it is impossible to explain the structure of great mountain-chains, such as that of the Cordillera, where the strata, capping the injected axis of plutonic rock, have been thrown on their edges along several parallel and neighbouring lines of elevation, except on this view of the rock of the axis having been repeatedly injected after intervals sufficiently long to allow the upper parts or wedges to cool and become solid; for if the strata had been thrown into their present highly-inclined, vertical, and even inverted positions, by a single blow, the very bowels of the earth. would have gushed out, and instead of beholding abrupt mountain-axes of rock solidified under great pressure, deluges of lava would have flowed out at innumerable points on every line of elevation.*

* For a full account of the volcanic phenomena which accompanied the earthquake of the 20th, and for the conclusions deducible from them, I must refer to vol. v. of the Geological Transactions.

CHAPTER XV.

PASSAGE OF THE CORDILLERA.

Valparaiso Portillo Pass-Sagacity of mules-Mountain-torrents-Mines, how discovered-Proofs of the gradual elevation of the Cordillera-Effect of snow on rocks-Geological structure of the two main ranges: their distinct origin and upheaval-Great subsidence-Red snow-Winds— Pinnacles of snow-Dry and clear atmosphere-Electricity-Pampas— Zoology of the opposite sides of the Andes-Locusts--Great bugsMendoza-Uspallata Pass-Silicified trees buried as they grew-Incas Bridge-Badness of the passes exaggerated-Cumbre-Casuchas-Valparaiso.

March 7th, 1835.-We stayed three days at Concepcion, and then sailed for Valparaiso. The wind being northerly, we only reached the mouth of the harbour of Concepcion before it was dark. Being very near the land, and a fog coming on, the anchor was dropped. Presently a large American whaler appeared close alongside of us, and we heard the Yankee swearing at his men to keep quiet whilst he listened for the breakers. Captain Fitz Roy hailed him, in a loud clear voice, to anchor where he then was. The poor man must have thought the voice came from the shore, such a Babel of cries issued at once from the ship, every one hallooing out, "Let go the anchor! veer cable! shorten sail!" It was the most laughable thing I ever heard. If the ship's crew had been all captains and no men there could not have been a greater uproar of orders. We afterwards found that the mate stuttered. I suppose all hands were assisting him in giving his orders.

THE PORTILLO PASS.

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On the 11th we anchored at Valparaiso, and two days afterwards I set out to cross the Cordillera. I proceeded to Santiago, where Mr. Caldcleugh most kindly assisted me in every possible way in making the little preparations which were necessary. In this part of Chili there are two passes across the Andes to Mendoza: the one most commonly used —namely, that of Aconcagua or Uspallata-is situated some way to the north; the other, called the Portillo, is to the south, and nearer, but more lofty and dangerous.

There are

March 18th. We set out for the Portillo Pass. Leaving Santiago we crossed the wide burnt-up plain on which that city stands, and in the afternoon arrived at the Maypu, one of the principal rivers in Chili. The valley, at the point where it enters the first Cordillera, is bounded on each side by lofty barren mountains, and although not broad it is very fertile. Numerous cottages were surrounded by vines, and by orchards of apple, nectarine, and peach trees-their boughs breaking with the weight of the beautiful ripe fruit. In the evening we passed the custom-house, where our luggage was examined. The frontier of Chili is better guarded by the Cordillera than by the waters of the sea. very few valleys which lead to the central ranges, and the mountains are quite impassable in other parts by beasts of burden. The custom-house officers were very civil, which was perhaps partly owing to the passport which the President of the Republic had given me; but I must express my admiration at the natural politeness of almost every Chileno. In this instance the contrast with the same class of men in most other countries was strongly marked. I may mention an anecdote with which I was at the time much pleased. We met near Mendoza a little and very fat negress riding astride on a mule. She had a goitre so enormous that it was scarcely possible to avoid gazing at her for a moment; but my two companions almost instantly, by way of apology, made the common salute of the country by taking off their

hats. Where would one of the lower or higher classes in Europe have shown such feeling politeness to a poor and miserable object of a degraded race?

Our manner of travelling In the inhabited parts we

At night we slept at a cottage. was delightfully independent. bought a little firewood, hired pasture for the animals, and bivouacked in the corner of the same field with them. Carry

ing an iron pot, we cooked and ate our supper under a cloudless sky, and knew no trouble. My companions were Mariano Gonzales, who had formerly accompanied me in Chili, and an arriero, with his ten mules and a madrina. The madrina (or godmother) is a most important personage: she is an old steady mare, with a little bell round her neck; and wherever she goes, the mules, like good children, follow her. The affection of these animals for their madrinas saves infinite trouble. If several large troops are turned into one field to graze, in the morning the muleteers have only to lead the madrinas a little apart and tinkle their bells; and although there may be two or three hundred together, each mule immediately knows the bell of its own madrina and comes to her. It is nearly impossible to lose an old mule; for if detained for several hours by force, she will, by the power of smell, like a dog, track out her companions, or rather the madrina, for, according to the muleteer, she is the chief object of affection. The feeling, however, is not of an individual nature; for I believe I am right in saying that any animal with a bell will serve as a madrina. In a troop each animal carries on a level road a cargo weighing four hundred and sixteen pounds (more than twenty-nine stone), but in a mountainous country one hundred pounds less; yet with what delicate slim limbs, without any proportional bulk of muscle, these animals support so great a burden! The mule always appears to me a most surprising animal. That a hybrid should possess more reason, memory, obstinacy, social affection, powers of muscular endurance, and length of life, than either of its parents, seems

TERRACES OF SHINGLE.

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to indicate that art has here outdone nature. Of our ten animals, six were intended for riding and four for carrying cargoes, each taking turn about. We carried a good deal of food, in case we should be snowed up, as the season was rather late for passing the Portillo.

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March 19th. We rode during this day to the last, and therefore most elevated, house in the valley. The number of inhabitants became scanty; but wherever water could be brought on the land, it was very fertile. All the main valleys in the Cordillera are characterized by having on both sides a fringe or terrace of shingle and sand, rudely stratified, and generally of considerable thickness. fringes evidently once extended across the valleys, and were united; and the bottoms of the valleys in northern Chili, where there are no streams, are thus smoothly filled up.. On these fringes the roads are generally carried, for their surfaces are even, and they rise with a very gentle slope up the valleys; hence, also, they are easily cultivated by irrigation. They may be traced up to a height of between seven and nine thousand feet, where they become hidden by the irregular piles of débris. At the lower end or mouths of the valleys they are continuously united to those land-locked plains (also formed of shingle) at the foot of the main Cordillera which I have described in a former chapter as characteristic of the scenery of Chili, and which were undoubtedly deposited when the sea penetrated Chili, as it now does the more southern coasts. No one fact in the geology of South America interested me more than these terraces of rudelystratified shingle. They precisely resemble in composition the matter which the torrents in each valley would deposit if they were checked in their course by any cause, such as entering a lake or arm of the sea; but the torrents, instead of depositing matter, are now steadily at work wearing away both the solid rock and these alluvial deposits along the whole line of every main valley and side valley. It is im

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