The Captain determined to take the boats no further; the mountain were between 20 & 30 miles distant & the river very serpentine. Its apparent dimensions & depth nearly the same; its current equally strong. The country & its productions remained equally uninteresting. In addition to all this our provisions were running short; we had been for some days on half allowance of biscuit. This same half allowance, although really sufficient, was very unpleasant after our hard work; & those who have not tried it will alone exclaim about the comfort of a light stomach & an easy digestion. It was very ridiculous how invariably the conversation in the evening turned upon all sorts, qualities & kinds of food.
The Captain & a large party set off to walk a few miles to the Westward. We crossed a desert plain which forms the head of the valley of S. Cruz, but could not see the base of the mountains. On the North side, there is a great break in the elevated lava plain, as if of the valley of a river. It is thought probable that the main branch of the S Cruz bends up in that direction & perhaps drains many miles of the Eastern slope of the chain. We took a farewell look at the Cordilleras which probably in this part had never been viewed by other European eyes, & then returned to the tents. At the furthest point we were about 140 miles from the Atlantic, & 60 from the nearest inlet of the Pacific.
Our provisions being almost exhausted, and the river as large as it was beyond the lava country, our allotted time being out, and every one weary and foot-sore, I decided upon walking overland to the westward, as far as we could go in one day, and then setting out on our return to the Beagle. I was the more inclined to this step, because the river here made a southerly bend, to follow which would have required at least a day, without making much westing, and because I thought that some of our party might walk in that time at least twice as far as they could track the boats, and then return before night. To have followed the course of the river two days longer, we should have needed all the small remainder of our provisions, and probably without being enabled to see further than we might by one day's walk directly westward. Leaving those who were the most tired to take care of the boats, a party set out early, in light marching order. A large plain lay before us, over which shrubs, very small trees, and bushes were sparingly scattered; yet parts of this plain might be called fertile and woody, by comparison with the tracts between us and the eastern sea-coast.
At noon we halted on a rising ground, made observations for time, latitude, and bearing; rested and eat our meal; on a spot which we found to be only sixty miles from the nearest water of the Pacific Ocean. The Cordillera of the Andes extended along the western side of our view; the weather was very clear, enabling us to discern snow-covered mountains far in the north, and also a long way southward; hence much of the range was visible, but of the river we could discern nothing. Only from the form of the land could we conclude that at the end of the southerly reach I have mentioned, the direction of the river is nearly east and west for a few miles, and that then it may turn northward, or rather come from the north along the base of the Cordillera.
There are many reasons for inducing one to suppose that it comes not only from the north, but from a considerable distance northward. At the place where we ceased to ascend the stream, the Santa Cruz was almost as large as at the places where we passed the first and second nights near the estuary. The velocity of the current was still at least six knots an hour; though the depth remained undiminished. The temperature of the water was 45°, while that of the air was seldom so high, even in the day-time, and at night was usually below the freezing point. Trees, or rather the trunks of trees, were found lying upon the banks, whose water-worn appearance indicated that they had been carried far by the stream. The water was very free from sediment, though of a whitish blue colour, which induces me to suppose that it has been chiefly produced by melted snow, or that it has passed through lakes in which the sediment it might have brought so far was deposited. If filled from the waters of the nearer mountains only, its temperature would surely be lower, approaching that of melted snow: it would also, in all probability, bring much sediment, and would therefore be muddier, and less pure in colour.
When one considers how large an extent of country there is between the River Negro and the Strait of Magalhaens, and that through that extensive region only one river of magnitude flows, it may be difficult to account for the manner in which the drainage of the eastern side of the great Cordillera is carried off, or where the melted snow and occasional heavy rains disappear.
The Gallegos is small, though it runs into a large estuary. The Chupat river is very small: that at Port Desire is scarcely more than a brook. At times, it is true, these smaller rivers are flooded, but their floods (added to their usual streams) seem unequal to carrying off the continual drainage of the Andes. South of the Negro only the Santa Cruz flows with a full and strong stream throughout the whole year, and my idea is that the sources of the river Santa Cruz are not far from those of the southern branch of the Negro, near the forty-fifth degree of latitude; and that it runs at the foot of the Andes, southward, through several lakes, until it turns to the eastward in the parallel of fifty degrees.
In Viedma's Diary I find that he heard from the Indians at Port San Julian (in 1782) that the river Santa Cruz flowed from a large lake near the Cordillera of the Andes, and that there was abundance of wood on its banks. In consequence of this information, he went, in November, with a party of Spaniards and Indians on horseback, to explore this lake. In his way, Viedma crossed the river Chico, which flows into the estuary of the Santa Cruz, just above Weddell Bluff. The Chico, though small at times and then fordable, was subject, the Indians said, to great floods in the spring, when the melting snows of the Cordillera over-filled a lake, far in the north-west, whence this river ran. Afterwards, Viedma crossed the river Chalia, which they told him rose in another lake near the Cordillera, was likewise subject to floods, and emptied itself into the Santa Cruz: when he passed, it was only up to the horses' knees (after searching many leagues, however, for a ford), but at his return it was deeper. This Chalia can be no other than the stream which flows through Basalt Glen, a mere brook when we saw it in the dryest season of the year. Viedma reached the lake,* and found every thing correspond to the description; for it was deep and large, surrounded by snow-covered mountains, on which were many forests.
Some persons have doubted whether there is ever much drainage to be carried off from the eastern side of the Andes, between the parallels of forty and fifty; but if they will take the trouble to read Viedma's Diary, and some other notices to be found in the work of Don Pedro de Angelis, I think they will be convinced that there is always a considerable drainage, and that at times there are heavy floods to be carried off.
Reference to the accompanying plan will shew our position when we halted, and I decided to return, not having explored, I should think, more than one-third of its course. At that place the level of the river was found to be four hundred feet higher than that of the sea at the entrance; and as the distance is about two hundred miles, the average descent or fall of the water must be near two feet in a mile, which, I apprehend, is unusually great. I could not, indeed, believe that the computation and data were correct, until after repeated examination. Two barometers were used at the river-side, and a very good one was carefully watched on board the Beagle. Certainly, the rapid descent of the river, in many places, was such, that even to the eye it appeared to be running down-hill; and this remark was often made in the course of our journey.
Two days before we reached our westernmost point, many traces of an old Indian encampment were seen; but excepting at that place and at the spot which we passed on the 22d, no signs of inhabitants were any where found. Scarcity of pasture, and the badness of the ground for their horses' feet, must deter Indians from remaining in this neighbourhood; but that they frequently cross the river, when travelling, is well known.
The quantities of bones heaped together, or scattered near the river, in so many places which we passed, excited conjectures as to what had collected them. Do guanacoes approach the river to drink when they are dying? or are the bones remains of animals eaten by lions or by Indians? or are they washed together by floods? Certain it is they are remarkably numerous near the banks of the river; but not so elsewhere.
I can hardly think that the guanaco is often allowed to die a natural death; for pumas are always on the alert to seize invalid stragglers from the herd. At night the guanacoes choose the clearest places for sleeping, lying down together like sheep; and in the day they avoid thickets, and all such places as might shelter their ever-watchful enemy. Condors, also, and fierce little wild cats* help to prevent too great an increase of this beautiful, inoffensive, and useful animal.
Late on the 4th we returned to our tents, thoroughly tired by a daily succession of hard work, and long walks. At this bivouac we were about one hundred and forty miles, in a straight line, from the estuary of Santa Cruz, or from Weddell Bluff; and about two hundred and forty-five miles distant by the course of the river. Our station at noon on the 4th, was eight miles in a straight line farther westward, and about thirty miles from the Cordillera of the Andes. The height of those mountains was from five to seven thousand feet above our level, by angular measurement with a theodolite.