Narrative of the surveying voyages of His Majesty's Ships Adventure and Beagle, Vol. 3 [of 3] · Charles Darwin
SANTA CRUZ--PATAGONIA.
APRIL 13TH.--The Beagle anchored within the mouth of the Santa Cruz. This river is situated about sixty miles south of Port St. Julian. During the last voyage, Captain Stokes proceeded thirty miles up, but then, from the want of provisions, was obliged to return. Excepting what was discovered at that time, scarcely any thing was known about this large river. Captain FitzRoy now determined to follow its course as far as time would allow. On the 18th, three whale-boats started, carrying three weeks’ provisions; and the party consisted of twenty-five souls--a force which would have been sufficient to have defied a host of Indians. With a strong flood-tide, and a fine day, we made a good run, soon drank some of the fresh water, and were at night nearly above the tidal influence. The river here assumed a size and appearance, which, even at the highest point we ultimately reached, was scarcely diminished. It was generally from three to four hundred yards broad, and in the middle about seventeen feet deep. The rapidity of the current, which in its whole course runs at the rate of from four to six knots an hour, is perhaps its most remarkable feature. The water is of a fine blue colour, but with a slight milky tinge, and not so transparent as at first sight would have been expected. It flows over a bed of pebbles, like those which compose the beach and surrounding plains. Although its course is winding, it runs through a valley which extends in a direct line to the westward. This valley varies from five to ten miles in breadth; it is bounded by step-formed terraces, which rise in most parts one above the other to the height of five hundred feet, and have on the opposite sides a remarkable correspondence.
APRIL 19TH.--Against so strong a current, it was of course quite impossible to row or sail. Consequently the three boats were fastened together head and stern, two hands left in each, and the rest came on shore to track. As the general arrangements, made by Captain FitzRoy, were very good for facilitating the work of all, and as all had a share of it, I will describe the system. The party, including every one, was divided into two spells, each of which hauled at the tracking line alternately for an hour and a half. The officers of each boat lived with, ate the same food, and slept in the same tent with their crew, so that each boat was quite independent of the others. After sunset, the first level spot where any bushes were growing, was chosen for our night’s lodging. Each of the crew took it in turns to be cook. Immediately the boat was hauled up, the cook made his fire; two others pitched the tent; the coxswain handed the things out of the boat; the rest carried them up to the tents, and collected firewood. By this order, in half an hour, every thing was ready for the night. A watch of two men and an officer was always kept, whose duty it was to look after the boats, keep up the fire, and guard against Indians. Each in the party had his one hour every night.
During this day we tracked but a short distance, for there were many islets, covered by thorny bushes, and the channels between them were shallow. APRIL 20TH.--We passed the islands and set to work. Our regular day’s march, although it was hard enough, carried us on an average only ten miles in a straight line, and perhaps fifteen or twenty altogether. Beyond the place where we slept last night the country is completely _terra incognita_, for it was there that Captain Stokes turned back. We saw in the distance a great smoke, and found the skeleton of a horse, so we knew that Indians were in the neighbourhood. On the next morning (21st) tracks of a party of horse, and marks left by the trailing of the chuzos were observed on the ground. It was generally thought they must have reconnoitred us during the night. Shortly afterwards we came to a spot, where from the fresh footsteps of men, children, and horses, it was evident the party had crossed the river. APRIL 22D.--The country remained the same, and was extremely uninteresting. The complete similarity of the productions throughout Patagonia, is one of its most striking characters. The level plains of arid shingle support the same stunted and dwarf plants; and in the valleys the same thorn-bearing bushes grow. Every where we see the same birds and insects. Even the very banks of the river, and of the clear streamlets which entered it, were scarcely enlivened by a brighter tint of green. The curse of sterility is on the land, and the water flowing over a bed of pebbles partakes of the same curse. Hence the number of waterfowl is very scanty; for what is there to support life in the stream of this barren river?
Patagonia, poor as she is in some respects, can, however, boast of a greater stock of small rodents[1] than, perhaps, any other country in the world. Several species of mice are externally characterized by large thin ears and a very fine fur. These little animals swarm amongst the thickets in the valleys, where they cannot for months together taste a drop of water. They all seem to be cannibals, for no sooner was a mouse caught in one of my traps than it was devoured by others. A small and delicately-shaped fox, which is likewise very abundant, probably derives its entire support from these small animals. The guanaco is also in his proper district; herds of fifty or a hundred were common; and, as I have said, we saw one which must have contained at least five hundred. The puma with the condor in its train, follows and preys upon these animals. The footsteps of the former were to be seen almost every where on the banks of the river; and the remains of several guanaco, with their necks dislocated, and bones broken, showed how they had met their death. APRIL 24TH.--Like the navigators of old when approaching an unknown land, we examined and watched for the most trivial sign of a change. The drifted trunk of a tree, or a boulder of primitive rock, was hailed with joy, as if we had seen a forest growing on the flanks of the Cordillera. The top, however, of a heavy bank of clouds, which remained almost constantly in one position, was the most promising sign, and eventually turned out true. At first the clouds were mistaken for the mountains themselves, instead of the masses of vapour condensed by their icy summits.
26TH.--We this day met with a marked change in the geological structure of the plains. From the first starting I had carefully examined the gravel in the river, and for the two last days had noticed the presence of a few small pebbles of a very cellular basalt. These gradually increased in number and in size, but none equalled in dimensions a man’s head. This morning, however, pebbles of the same rock, but more compact, suddenly became abundant, and in the course of half an hour, we saw at the distance of five or six miles the angular edge of a great basaltic platform. When we arrived at its base we found the stream bubbling among the fallen blocks. For the next twenty-eight miles, the river-course was encumbered with these basaltic masses. Above that limit, immense fragments belonging to a primitive formation, but derived from the surrounding alluvium, were equally numerous. In both cases no fragments at all remarkable in size or number had been washed down the stream, more than three or four miles below either the parent rock, or the mass of alluvium from which they were derived. Considering the singular rapidity of the great body of water in the St. Cruz, and that no still reaches occur in any part, these examples are most striking of the inefficiency of rivers in transporting even moderately-sized fragments.
The basaltic cliffs are obscurely divided by lines of more cellular or amygdaloidal varieties, and the strata appear to the eye perfectly horizontal. They overlie the great tertiary deposits, and are covered (except where denuded in some of the lower terraces) by the usual beds of gravel. The basalt is clearly nothing more than lava, which has flowed beneath the sea; but the eruptions must have been on the grandest scale. At the point where we first met this formation, the mass was about 120 feet in thickness; following the river-course, it imperceptibly rose and became thicker, so that at forty miles above the first station it was 320 feet. What the thickness may be close to the Cordillera, I have no means of knowing, but the platform there attains an elevation between two and three thousand feet above the level of the sea: we must therefore look to the mountains of that great chain for its source; and worthy of such a source are streams, that have flowed over the bed of an ocean to a distance of one hundred miles.
A fine section of the basaltic platform is presented by the cliffs on both sides of the valley. At the first glance it is evident the strata must at one time have been united. What power then has removed along a whole line of country, a solid mass of very hard rock, which had an average thickness of about three hundred feet, and a breadth varying from rather less than two to four miles? The river, though it has so little power in transporting even inconsiderable fragments, yet in the lapse of ages might produce an effect by its gradual erosion, of which it is difficult to judge the limit. But in this case, independently of the insignificance of such agency, good reasons can be assigned for believing that this valley was formerly occupied by an arm of the sea. It is needless in this work to detail arguments, which chiefly rest on the form and nature of the banks, on the manner in which the valley near the foot of the Andes expands into a great bay, and on the occurrence of a few sea-shells lying in the bed of the river.
If I had space I could prove that South America was formerly here cut off by a strait joining the Atlantic and Pacific oceans, like that of Magellan. But it may yet be asked, how has the solid basalt been removed? Geologists formerly would have brought into play, the violent action of some overwhelming debacle; but in this case such a supposition would have been quite inadmissible; because the same step-like terraces, that front the Patagonian coast, sweep up on each side of the valley. No possible action of any flood could have thus modelled the land in these two situations; and by the formation of such terraces the valley itself has been hollowed out. Although we know that there are tides, which run within the narrows of the Strait of Magellan at the rate of eight knots an hour, yet we must confess it makes the head almost giddy to reflect on the number of years, century after century, which the tides unaided by a heavy surf, must have required to have corroded so vast an area and thickness of solid rock. Nevertheless, we must believe that the strata undermined by the waters of this ancient strait, were broken up into huge fragments, and there lying scattered on the beach, were reduced to smaller blocks, then to pebbles, and lastly to the most impalpable mud, which the tides drifted into the bed, either of the Eastern or Western Ocean.
With the change in the geological structure of the plains the character of the landscape likewise altered. While rambling up some of the narrow and rocky defiles, I could almost have fancied myself transported back again to the barren valleys of St. Jago. Among the basaltic cliffs, I found some plants which I had seen nowhere else, but others I recognised as being wanderers from Tierra del Fuego. These porous rocks serve as a reservoir for the scanty rain-water, and consequently on the line where the igneous and sedimentary formations unite, several small springs (most rare occurrences in Patagonia) burst forth; and they could lie distinguished at a distance by the circumscribed patch of bright green herbage. APRIL 27TH.--The bed of the river became rather narrower, and hence the stream more rapid. It here ran at the rate of six knots an hour. From this cause, and from the many great angular fragments, tracking the boats became both dangerous and laborious.
This day I shot a condor. It measured from tip to tip of the wings, eight and a half feet, and from beak to tail, four feet. It is a magnificent spectacle to behold several of these great birds seated on the edge of some steep precipice. I will here describe all I have observed respecting their habits. The condor is known to have a wide geographical range, being found on the west coast of South America, from the Strait of Magellan throughout the entire range of the Cordillera. On the Patagonian shore, the steep cliff near the mouth of the Rio Negro in lat. 41°, was the most northern point where I saw these birds, or heard of their existence. They have there wandered about four hundred miles from the great central line of their habitation in the Andes. Further south, among the bold precipices which form the head of Port Desire, they are not uncommon; yet only a few stragglers occasionally visit the sea-coast. A line of cliff near the mouth of St. Cruz, is frequented by these birds, and about eighty miles up the river, where first the sides of the valley were formed by steep basaltic precipices, the condor again appeared, although in the intermediate space not one had been seen. From these and similar facts, the presence of this bird seems chiefly to be determined by the occurrence of perpendicular cliffs. In Patagonia, the condors either by pairs or many together, both sleep and breed on the same overhanging ledges. In Chile, during the greater part of the year, they haunt the lower country near the shores of the Pacific, and at night several roost in one tree; but in the early part of summer, they retire to the most inaccessible parts of the inner Cordillera, there to breed in peace.
With respect to their propagation, I was told by the country people in Chile, that the condor makes no sort of nest, but in the months of November and December lays two large white eggs on a shelf of bare rock. On the Patagonian coast I could not see any sort of nest among the cliffs, where the young ones were standing. It is said the young condors cannot fly for an entire year. At Concepcion, on the fifth of March (corresponding to our September), I saw a young bird, which, though in size little inferior to an old one, was completely covered by down like that of a gosling, but of a blackish colour. I feel sure this bird could not have used its wings for flight for many months. After the period when the young condors can fly, and apparently as well as the old birds, they yet remain both roosting at night on the same ledge, and hunting by day with their parents. Before, however, the young bird has the ruff round its neck turned white, it may often be seen hunting by itself. At the mouth of the St. Cruz, during part of April and May, a pair of old birds might be seen every day either perched on a certain ledge, or sailing about in company with a single young one, which latter though full fledged, had not its ruff white. I should think, especially when recollecting the state in which the Concepcion bird was on the previous month, that this young condor had not been hatched from an egg of that summer. As there were no other young birds, it seems probable that the condor only lays once in two years.
These birds generally live by pairs; but among the inland basaltic cliffs of the St. Cruz, I found a spot, where scores most usually haunt. On coming suddenly to the brow of the precipice, it was a fine sight to see between twenty and thirty of these great birds start heavily from their resting-place, and wheel away in majestic circles. From the quantity of dung on the rocks, they must long have frequented this cliff, and probably they both roost and breed there. Having gorged themselves with carrion on the plains below, they retire to these favourite ledges, to digest their food. From these facts, the condor must to a certain degree, like the gallinazo, be considered a gregarious bird. In this part of the country they live altogether on the guanacoes, which either have died a natural death, or, as more commonly happens, have been killed by the pumas. I believe, from what I saw in Patagonia, that they do not on ordinary occasions extend their daily excursions to any great distance from their regular sleeping-places.
The condors may oftentimes be seen at a great height, soaring over a certain spot in the most graceful spires and circles. On some occasions I am sure that they do this for sport, but on others, the Chileno countrymen tell you that they are watching a dying animal, or the puma devouring its prey. If the condors glide down, and then suddenly all rise together, the Chileno knows that it is the puma which, watching the carcass, has sprung out to drive away the robbers. Besides feeding on carrion, the condors will frequently attack young goats and lambs. Hence the shepherd dogs are trained, the moment the enemy passes over, to run out, and looking upwards, to bark violently. The Chilenos destroy and catch numbers. Two methods are used; one is to place a carcass within an enclosure of sticks on a level piece of ground, and when the condors are gorged, to gallop up on horseback to the entrance, and thus enclose them: for when this bird has not space to run, it cannot give its body sufficient momentum to rise from the ground. The second method is to mark the trees in which, frequently to the number of five or six, they roost together, and then at night to climb up and noose them.
They are such heavy sleepers, as I have myself witnessed, that this is not a difficult task. At Valparaiso, I have seen a living condor sold for sixpence, but the common price is eight or ten shillings. One which I saw brought in, had been lashed with rope, and was much injured; yet, the moment the line was cut by which its bill was secured, although surrounded by people, it began ravenously to tear a piece of carrion. In a garden at the same place, between twenty and thirty were kept alive. They were fed only once a week, but they appeared in pretty good health.[2] The Chileno countrymen assert that the condor will live and retain its powers, between five and six weeks without eating. I cannot answer for the truth of this, but it is a cruel experiment, which very likely has been tried.
When an animal is killed in the country, it is well known that the condors, like other carrion vultures, soon gain intelligence of it, and congregate in an inexplicable manner. In most cases it must not be overlooked, that the birds have discovered their prey, and have picked the skeleton clean, before the flesh is in the least tainted. Remembering the opinions of M. Audubon, on the little smelling powers of such birds,[3] I tried in the above-mentioned garden the following experiment: The condors were tied, each by a rope, in a long row at the bottom of a wall. Having folded up a piece of meat in white paper, I walked backwards and forwards, carrying it in my hand at the distance of about three yards, but no notice whatever was taken. I then threw it on the ground, within one yard of an old cock bird; he looked at it for a moment with attention, but then regarded it no more. With a stick I pushed it closer and closer, until at last he touched it with his beak; the paper was then instantly torn off with fury, and at the same moment, every bird in the long row began struggling and flapping its wings. Under the same circumstances, it would not have been possible to have deceived a dog.
I may remark, that oftentimes when lying down to rest on the open plains, and on looking upwards, I have seen carrion hawks, sailing through the air at a great height. Where the country is level I do not believe a space of the heavens, of more than 15° above the horizon, is commonly viewed with any attention by a person either walking or on horseback. If such is the case, and the vulture is on the wing at a height of between three and four thousand feet, before it could come within the above range of vision, its distance in a straight line from the beholder’s eye, would be rather more than two British miles. Might it not thus readily be overlooked? When an animal is killed by the sportsman in a lonely valley, may he not all the while be watched from above by the sharp-sighted bird? And will not the manner of its descent proclaim throughout the district to the whole family of carrion-feeders, that their prey is at hand?
When the condors in a flock are wheeling round and round any spot, their flight is beautiful. Except when rising from the ground, I do not recollect ever having seen one of these birds flap its wings. Near Lima, I watched several for nearly half an hour, without once taking off my eyes. They moved in large curves, sweeping in circles, descending and ascending without once flapping. As they glided close over my head, I intently watched, from an oblique position, the outlines of the separate and terminal feathers of the wing, if there had been the least vibratory movement, these would have been blended together, but they were seen distinct against the blue sky. The head and neck were moved frequently, and apparently with force, and it appeared as if the extended wings formed the fulcrum on which the movements of the neck, body, and tail, acted. If the bird wished to descend, the wings were for a moment collapsed; and then when again expanded with an altered inclination, the momentum gained by the rapid descent seemed to urge the bird upwards, with the even and steady movement of a paper kite. In the case of any bird _soaring_, its motion must be sufficiently rapid, so that the action of the inclined surface of its body on the atmosphere, may counterbalance its gravity. The force to keep up the momentum of a body moving in a horizontal plane in that fluid (in which there is so little friction) cannot be great, and this force is all that is wanted. The movement of the neck and body of the condor, we must suppose, is sufficient for this. However this may be, it is truly wonderful and beautiful to see so great a bird, hour after hour, without any apparent exertion, wheeling and gliding over mountain and river.
APRIL 29TH.--From some high land we hailed with joy the white summits of the Cordillera, as they were seen occasionally peeping through their dusky envelope of clouds. During the few succeeding days, we continued to get on slowly, for we found the river-course very tortuous, and strewed with immense fragments of various ancient slaty rocks, and of granite. The plain bordering the valley had here attained an elevation of about 1100 feet, and its character was much altered. The well-rounded pebbles of porphyry were in this part mingled with many immense angular fragments of basalt and of the rocks above mentioned. The first of these erratic blocks which I noticed, was sixty-seven miles distant from the nearest mountain; another which had been transported to rather a less distance, measured five yards square, and projected five feet above the gravel. Its edges were so angular, and its size so great, that I at first mistook it for a rock _in situ_, and took out my compass to observe the direction of its cleavage. The plains here were not quite so level as those nearer the coast, but yet, they betrayed little signs of any violent action. Under these circumstances, it would be difficult, as it appears to me, to explain this phenomenon on any theory, excepting through that of transport by ice while the country was under water. But this is a subject to which I shall again recur.
Text from Project Gutenberg, public domain in the United States.