Narrative of the surveying voyages of His Majesty's Ships Adventure and Beagle, Vol. 3 [of 3] · Charles Darwin
PASSAGE OF CORDILLERA.
It required little geological practice to interpret the marvellous story, which this scene at once unfolded; though I confess I was at first so much astonished that I could scarcely believe the plainest evidence of it. I saw the spot where a cluster of fine trees had once waved their branches on the shores of the Atlantic, when that ocean (now driven back 700 miles) approached the base of the Andes. I saw that they had sprung from a volcanic soil which had been raised above the level of the sea, and that this dry land, with its upright trees, had subsequently been let down to the depths of the ocean. There it was covered by sedimentary matter, and this again by enormous streams of submarine lava--one such mass alone attaining the thickness of a thousand feet; and these deluges of melted stone and aqueous deposits had been five times spread out alternately. The ocean which received such masses must have been deep; but again the subterranean forces exerted their power, and I now beheld the bed of that sea forming a chain of mountains more than seven thousand feet in altitude. Nor had those antagonist forces been dormant, which are always at work to wear down the surface of the land to one level: the great piles of strata had been intersected by many wide valleys; and the trees now changed into silex were exposed projecting from the volcanic soil now changed into rock, whence formerly in a green and budding state they had raised their lofty heads. Now, all is utterly irreclaimable and desert; even the lichen cannot adhere to the stony casts of former trees. Vast, and scarcely comprehensible as such changes must ever appear, yet they have all occurred within a period recent when compared with the history of the Cordillera; and that Cordillera itself is modern as compared with some other of the fossiliferous strata of South America.
APRIL 1ST.--We crossed the Uspallata range; and at night slept at the custom-house--the only inhabited spot on the plain. Shortly before leaving the mountains, there was a very extraordinary view: red, purple, green, and quite white sedimentary rocks, alternating with black lavas, were broken up and thrown into all kinds of disorder, by masses of porphyry, of every shade, from dark brown to the brightest lilac. It was the first view I ever saw, which really resembled those pretty sections which geologists make of the inside of the earth. The next day we crossed the plain, and followed the course of the same great mountain-stream which flows by Luxan. Here it was a furious torrent, quite impassable, and appearing larger than in the low country; as was the case with the rivulet of Villa Vincencio. On the evening of the succeeding day we reached the Rio de las Vacas, which is considered the worst stream in the Cordillera to cross. As all these rivers have a rapid and short course, and are due to the snow melted by the sun’s heat, the hour of the day makes a considerable difference in their volume. In the evening the stream is muddy and full, but about daybreak it becomes both clearer and much less impetuous. This we found to be the case with the Rio Vacas, and in the morning we crossed it with little difficulty.
The scenery thus far was very uninteresting, compared with that of the Portillo pass. Little can be seen beyond the bare walls of the one grand, flat-bottomed valley, which the road follows up to the highest crest. The valley and the huge rocky mountains were extremely barren: during the two previous nights the poor mules had absolutely nothing to eat; for excepting a few low resinous bushes, scarcely a plant could be seen. We went over in the course of this day some of the worst passes in the Cordillera. The degree of exaggeration concerning their danger and difficulty is very great. In Chile I was even told, that if I attempted to pass on foot my head would turn giddy, that there was no room to dismount, &c., but I did not see a place where any one might not have walked over backwards, or got off his mule on either side. One of the bad passes called _las Animas_ (the Souls), I had crossed, and did not find out till a day afterwards that it was one of the awful dangers.
No doubt there are many parts in which, if the mule should stumble, the rider would be hurled down a great precipice; but of such a catastrophe there is much less chance than with a man on foot. I dare say, in the spring, the “laderas,” or roads, which each year are formed anew across the piles of fallen detritus, are very bad; but from what I have seen, I suspect the real danger is nothing, and the apparent very little. With cargo mules the case is rather different; for the loads project so far, that the animals occasionally running against each other, or against a point of rock, lose their balance and are thrown down the precipice. With regard to crossing the rivers, I can well believe that the difficulty amounts to every degree, till they are impracticable. At this season there was little trouble, but in the summer they must be very bad. I can quite imagine, as Captain Head describes, the different expressions of those who _have_ passed the gulf, and those who _are_ passing. I never heard of any man being drowned, but with loaded mules this is of frequent occurrence. The arriero tells you to show your mule the best line, and then allow her to cross as she chooses; the cargo mule takes a bad line, and is often lost.
APRIL 4TH.--From the Rio de las Vacas to the Puente del Inca, half a day’s journey. As there was pasture for the mules, and geology for me, we bivouacked for the night. When one hears of a natural bridge, one pictures to oneself some deep and narrow ravine, across which a bold mass of rock has fallen; or a great arch hollowed out like the vault of a cavern. Instead of this, the Inca’s bridge consists of a crust of stratified shingle, cemented together by the deposits of the neighbouring hot springs. It appears as if the stream had scooped out a channel on one side, leaving an overhanging ledge, which was at last met by the earth and stones falling down from the opposite cliff. Certainly an oblique junction, as would happen in such case, was very distinct on one side. The bridge of the Incas is by no means worthy of the great monarchs whose name it bears.
Close by, there were some ruins of Indian buildings. These occur in several other places; the most perfect, which I saw, being the Ruinas de Tambillos. Small square rooms were there huddled together, but placed in distinct groups. Some of the doorways were yet standing: they were formed by a cross slab of stone, but only raised about three feet high. Ulloa, in his “Noticias Americanas,” remarks on the lowness of the doors in the ancient Peruvian dwellings. These houses, when perfect, must have been capable of containing a considerable number of persons. Tradition says, they were used as halting-places for the Incas, when they crossed these mountains. Traces of Indian habitations have been discovered in many parts of the Cordillera, where it does not appear probable, that they were constructed as mere resting-places; but yet where the land is as utterly unfit for any kind of cultivation as it is near the Tambillos or Puente del Inca. In the Portillo pass I saw one group of such ruins. In the ravine of Jajuel, near Aconcagua, where there is no pass, I heard of numerous remains situated at a great elevation, where it is both cold and extremely sterile. At first I imagined, that these houses were places of refuge built by the Indians on the first arrival of the Spaniards; but subsequently I have been almost inclined to speculate on the possibility of a small change of climate.
In the northern parts of Chile, within the Cordillera of Copiapó, old Indian houses are found in very many parts: by digging amongst the ruins, bits of woollen articles, instruments of precious metals, and heads of Indian corn, are not unfrequently discovered. I had likewise in my possession the head of an arrow, made of agate, of precisely the same figure as those now used in Tierra del Fuego. I am aware that the Peruvian Indians[13] frequently inhabit most lofty and bleak situations; but in these cases, I was assured by men, who had spent their lives in travelling the Andes, that very many (_muchisimas_) houses were found at elevations so great as almost to border on the perpetual snow, and in parts where there exist no passes, and where the land produces absolutely nothing, and what is still more extraordinary, where there is no water. Nevertheless it is the opinion of the people of the country (although they are much puzzled by the circumstance), that, from the appearance of the houses, the Indians must have used them as places of residence.
In the Despoblado (uninhabited valley), near Copiapó, at a spot called Punta Gorda, I saw the remains of seven or eight square little rooms, which were of a similar form with those at the Tambillos, but built chiefly of mud (which the present inhabitants cannot by any means imitate in durability[14]) instead of with stone. They were situated in the most conspicuous and defenceless position, at the bottom of a flat broad valley. There was no water nearer than three or four leagues, and that only in very small quantity, and bad: the soil was absolutely sterile;--I looked in vain even for a lichen adhering to the rocks. At the present day, with the advantage of beasts of burden, a mine, unless it were very rich, could scarcely be worked there with profit. Yet the Indians formerly chose it as a place of residence! If at the present time two or three showers of rain were to fall annually, instead of one during as many years, as now is the case, a small rill of water would in all probability be formed in this great valley, draining a mountainous country; and then, by irrigation (the method of which was formerly so well understood by the Indians), the soil might easily be rendered sufficiently productive to support a few families.
I have certain proofs that this part of the continent of South America has been elevated, near the coast, at least from four to five hundred feet, since the epoch of existing shells; and further inland the rise possibly may have been greater. As the peculiarly arid character of the climate is evidently a consequence of the height of the great range of mountains, we may feel almost sure, that prior to the latter elevations, the atmosphere was not so completely drained of its moisture as at the present day. At a remote geological era, it is probable that the Andes consisted of a chain of islands, which were covered by luxuriant forests; and many of the trees, in a silicified state, may now be seen embedded in the upper conglomerates. Of these I measured one which was cylindrical, with a circumference of fifteen feet. As it is nearly certain that the mountains have risen slowly, so would the climate likewise become deteriorated slowly. We need not feel greatly surprised at walls of stone and hardened mud here lasting for many ages, when we remember how many centuries the Druidical mounds have withstood even the climate of England. The only question is, whether the amount of change, since the introduction of man into South America, has been sufficient to cause a sensible effect on the atmospheric moisture, and therefore on the fertility of the valleys in the upper Cordillera. From the extreme slowness with which there is reason to believe the continent is rising, the longevity of man as a species, required to allow of sufficient change, is the most valid objection to the above speculations: for on the eastern shores of this continent, we have seen that several animals, belonging to the same class of mammalia with man, have passed away, while the change of level between land and water, in that part at least, has been so small, that it can scarcely have caused any sensible difference in the climate. I may add, however, that at Lima, the elevation, within the human epoch, certainly has amounted to between seventy and eighty feet.
When at Lima, I conversed on this subject[15] with Mr. Gill, a civil engineer, who had seen much of the interior country. He told me that a conjecture of a change of climate had sometimes crossed his mind; but that he thought that the greater portion of land now incapable of cultivation, but covered with Indian ruins, had been reduced to that condition, by neglect and subterranean movements injuring the water conduits, which the Indians formerly constructed on so wonderful a scale. I may here just mention that these people actually carried tunnels through hills of solid rock, when such were necessary to conduct the irrigating streams. Mr. Gill told me, he had been employed professionally to examine one; he found the passage low, narrow, crooked, and not of uniform breadth, but of very considerable length. Is it not most wonderful that any people should have attempted such operations without the aid of iron or of gunpowder!
Mr. Gill mentioned to me a most interesting, and as far as I am aware, quite unparalleled case, of the effect of subterranean disturbances in altering the drainage of a country. Travelling from Casma to Huaraz (not very far distant from Lima), he found a plain covered with ruins and marks of ancient cultivation, but now quite barren. Near it was the dry course of a considerable river, whence the water for irrigation had formerly been conducted. There was nothing in the appearance of the watercourse to indicate that the river had not flowed there a few years previously: in some parts beds of sand and gravel were scattered, and in others the solid rock had been worn into a broad channel.[16] It is self-evident that a person following up the course of a stream, will always ascend at a greater or less inclination. Mr. Gill was therefore very much astonished, when walking up the bed of this ancient river, to find himself suddenly going down hill. He imagined that the slope had a fall of about forty or fifty feet perpendicular. We here have the most unequivocal evidence, that a ridge or line of hills has been uplifted directly across the bed of a stream, which must have been flowing for many centuries. From the moment the river-course was thus arched, the water would necessarily be thrown back; and a new channel would be formed on one side some way above. From that time, also, the neighbouring plain would lose its fertilizing stream, and become converted into the desert which it now remains.
APRIL 5TH.--We had a long day’s ride across the central ridge, from the Inca’s bridge to the Ojos del Agua, which is situated near the lowest _casucha_ on the western slope. These casuchas are little round towers, with steps outside to reach the floor, which is elevated some feet above the ground on account of the snow-drifts. They are eight in number; and under the Spanish government, were kept during the winter well stored with food and charcoal, and each courier had a master-key. Now they only answer the purpose of caves, or rather dungeons. Seated on some little eminence, they are not, however, ill suited to the surrounding scene of desolation. The zigzag ascent of the Cumbre, or the partition of the waters, was very steep and tedious. The height, according to Mr. Pentland,[17] is 12,454 feet. The road did not pass over any perpetual snow, although there were patches on either hand. The wind on the summit was exceedingly cold, but it was impossible not to stop a few minutes to admire, again and again, the colour of the heavens, and the brilliant transparency of the atmosphere. The scenery, moreover, was grand. To the westward there was a fine chaos of mountains, divided by profound ravines. Generally some snow has fallen before this period of the season, and it has even happened that the Cordillera has been finally closed by this time. But we were most fortunate. The sky, by night and by day, was cloudless, excepting perhaps a few round little masses of vapour, that floated over the highest pinnacles. I have often seen these islets in the sky, marking the position of the Cordillera, when the mountains themselves have been hidden beneath the horizon.
APRIL 6TH.--In the morning we found some thief had stolen one of our mules, and the bell of the madrina. We therefore rode only two or three miles down the valley, and staid there the ensuing day in hopes of recovering the mule, which the arriero thought had been hidden in some ravine. The scenery in this part had assumed a Chilian character: the lower parts of the mountains, dotted over with the pale evergreen Quillay tree, and with the great candlestick cactus, certainly are more to be admired than any thing in the bare Eastern valleys; but I cannot quite agree with the admiration expressed by some travellers. The extreme pleasure, I suspect, is chiefly owing to the prospect of a good fire, after escaping from the cold regions above: and I am sure I most heartily participated in such feelings. 8TH.--We left the valley of the river of Aconcagua, by which we had descended, and reached in the evening a cottage near the Villa de St. Rosa. The fertility of the plain was extremely delightful. The autumn being well advanced, the leaves of many of the fruit-trees were falling; and of the labourers--some were busy in drying figs and peaches on the roofs of their cottages; while others were gathering the grapes from the vineyards. It was a pretty scene; but that pensive stillness was absent, which makes the autumn in England indeed the evening of the year. On the 10th we reached Santiago, where I experienced a very kind and hospitable reception from Mr. Caldcleugh. My excursion only cost me twenty-four days, and never did I more deeply enjoy an equal space of time. A few days afterwards I returned to Mr. Corfield’s house at Valparaiso.
Text from Project Gutenberg, public domain in the United States.