Elizabeth Cary Agassiz, Louis Agassiz: his life and correspondence, third edition

Chapter 23: 1871-1872: Aet. 64-65.

• Sailing of the Hassler.
-- Sargassum fields.-dredging at Barbadoes. -- from the West Indies to Rio de Janeiro. -- Monte Video. -- quarantine. -- glacial traces in the Bay of Monte Video. -- the Gulf of Mathias. -- dredging off Gulf of St. George. -- dredging off Cape Virgens. -- possession Bay. -- salt pool. -- moraine. -- Sandy point. -- cruise through the straits. -- scenery. -- wind storm. -- Borja Bay. -- glacier Bay. -- visit to the glacier. -- Chorocua Bay.

This whole investigation was of the greatest interest to Agassiz, and, coming so early in [703] the voyage, seemed a pleasant promise of its farther opportunities. The whole ship's company soon shared his enthusiasm, and the very sailors gathered about him in the intervals of their work, or hung on the outskirts of the scientific circle. A pause of a few days was made at one or two of the West Indian islands, at St. Thomas and Barbadoes. At the latter, the first cast of the large dredge was made on a ledge of shoals in a depth of eighty fathoms, and, among countless other things, a number of stemmed crinoids and comatulae were brought up. An ardent student of the early fossil echinoderms, it was a great pleasure to Agassiz to gather their fresh and living representatives. It was like turning a leaf of the past and finding the subtle thread which connects it with the present.

Little can be said of the voyage from the West Indies to Rio de Janeiro. It had the usual vicissitudes of weather, with here and there a flight (so it might justly be called) of flying-fish, a school of porpoises or dog-fish, or a sail in the distance, to break the monotony. At Rio de Janeiro it became evident that the plan of the voyage must be somewhat curtailed. This was made necessary partly by the delays in starting,—in consequence of which the season would be less favorable than had been anticipated along certain portions of the proposed route,—and partly by the defective machinery, which had already given some trouble to the Captain. The Falkland Islands, the Rio Negro, and the Santa Cruz rivers were therefore renounced; with what regret will be understood by those who know how hard it is to be forced to break up a scheme of work, which was originally connected in all its parts. The next pause was at Monte Video; but as there was a strict [712] quarantine, Agassiz was only allowed to land at the Mount, a hill on the western side of the bay, the geology of which he was anxious to examine. He found true erratics—loose pebbles, granite, gneiss, and granitic sandstone, having no resemblance to any native rock in the vicinity—scattered over the whole surface of the hill to its very summit. The hill itself had also the character of the ‘roches moutonees’ modeled by ice in the northern hemisphere. As these were the most northern erratics and glaciated surfaces reported in the southern hemisphere, the facts there were very interesting to him.

With dredgings off the Rio de la Plata, and along the coast between that and the Rio Negro, the vessel held on her way to the Gulf of Mathias, a deep, broad bay running some hundred miles inland, and situated a little south of the Rio Negro. Here some necessary repairs enforced a pause, of which Agassiz took advantage for dredging and for studying the geology of the cliffs along the north side of the bay. As seen from the vessel, they seemed to be stratified with extraordinary evenness and regularity to within a few feet of the top, the summit being crowned with loose sand. Farther on, they sank to sand [713] dunes piled into rounded banks and softly moulded ledges, like snow-drifts. Landing the next day at a bold bluff marked Cliff End on the charts, he found the lower stratum to consist of a solid mass of tertiary fossils, chiefly immense oysters, mingled, however, with sea-urchins. Superb specimens were secured,— large boulders crowded with colossal shells and perfectly preserved echini. From the top of the cliff, looking inland, only a level plain was seen, stretching as far as the eye could reach, broken by no undulations, and covered with low, scrubby growth. The seine was drawn on the beach, and yielded a good harvest for the fish collection. At evening the vessel anchored at the head of the bay, off the Port of San Antonio. The name would seem to imply some settlement; but a more lonely spot cannot be imagined. More than thirty years ago, Fitzroy had sailed up this bay, partially surveyed it, and marked this harbor on his chart. If any vessel has broken the loneliness of its waters since, no record of any such event has been kept. Of the presence of man, there was no sign. Yet the few days passed there were among the pleasantest of the voyage to Agassiz. The work of the dredge and seine was extremely successful, and the [714] rambles inland were geological excursions of great interest. Here he had the first sight of the guanaco of the Patagonian plains. The weather was fine, and at night-fall, to the golden light of sunset succeeded the fitful glow, over land and water, of the bonfires built by the sailors on the beach. Returning to the ship after dark, the various parties assembled in the wardroom, to talk over the events of the day and lay out plans for the morrow. These are the brightest hours in such a voyage, when the novelty of the locality gives a zest to every walk or row, and all are full of interest in a new and exciting life. One is more tolerant even of monotonous natural features in a country so isolated, so withdrawn from human life and occupation. The very barrenness seems in harmony with the intense solitude.

The Hassler left her anchorage on this desolate shore on an evening of singular beauty. It was difficult to tell when she was on her way, so quietly did she move through the glassy waters, over which the sun went down in burnished gold, leaving the sky without a cloud. The light of the beach fires followed her till they too faded, and only the phosphorescence of the sea attended her into the [715] night. Rough and stormy weather followed this fair start, and only two more dredgings were possible before reaching the Strait of Magellan. One was off the Gulf of St. George, where gigantic star-fishes seemed to have their home. One of them, a superb basket-fish, was not less than a foot and a half in diameter; and another, like a huge sunflower of reddish purple tint, with straight arms, thirty-seven in number, radiating from the disk, was of about the same size. Many beautiful little sea-urchins came up in the same dredging. About fifty miles north of Cape Virgens, in tolerably calm weather, another haul was tried, and this time the dredge returned literally solid with Ophiurans.

On Wednesday, March 13th, on a beautifully clear morning, like the best October weather in New England, the Hassler rounded Cape Virgens and entered the Strait of Magellan. The tide was just on the flood, and all the conditions favorable for her run to her first anchorage in the Strait at Possession Bay. Here the working force divided, to form two shore parties, one of which, under Agassiz's direction, the reader may follow. The land above the first shore bluff at Possession Bay rises to a height of some four hundred [716] feet above the sea-level, in a succession of regular horizontal terraces, of which Agassiz counted eight. On these terraces, all of which are built, like the shore-bluffs, of tertiary deposits, were two curious remnants of a past state of things. The first was a salt-pool lying in a depression on the second terrace, some one hundred and fifty feet above the sea. This pool contained living marine shells, identical with those now found along the shore. Among them were Fusus, Mytilus, Buccinum, Fissurella, Patella, and Voluta, all found in the same numeric relations as those in which they now exist upon the beach below. This pool is altogether too high to be reached by any tidal influence, and undoubtedly indicates an old sea-level, and a comparatively recent upheaval of the shore. The second was a genuine moraine, corresponding in every respect to those which occur all over the northern hemisphere. Agassiz came upon it in ascending to the third terrace above the salt-pool and a little farther inland. It had all the character of a terminal moraine in contact with an actual glacier. It was composed of heterogeneous materials,—large and small pebbles and boulders impacted together in a paste of clayey gravel and sand. The ice had evidently [717] advanced from the south, for the mass had been pushed steeply up on the southern side, and retained so sharp an inclination on that face that but little vegetation had accumulated upon it. The northern side, on the contrary, was covered with soil and overgrown; it sloped gently off,—pebbles and larger stones being scattered beyond it. The pebbles and boulders of this moraine were polished, scratched, and grooved, and bore, in short, all the usual marks of glacial action. Agassiz was naturally delighted with this discovery. It was a new link in the chain of evidence, showing that the drift phenomena are connected at the south as well as at the north with the action of ice, and that the frozen Arctic and Antarctic fields are but remnants of a sheet of ice, which has retreated from the temperate zones of both hemispheres to the polar regions. The party pushed on beyond the moraine to a hill of considerable height, which gave a fine view of the country toward Mount Aymon and the so-called Asses' Ears. They brought back a variety of game, but their most interesting scientific acquisitions were boulders from the moraine scored with glacial characters, and shells from the salt-pool, [718]

Still accompanied by beautiful weather, the Hassler anchored at the Elizabeth Islands and at San Magdalena. Here Agassiz had an opportunity of examining the haunts and rookeries of the penguins and cormorants, and obtaining fine specimens of both. As the breeding places and the modes of life of these animals have been described by other travelers, there is nothing new to add from his impressions, until the vessel anchored, on the 16th March, before Sandy Point, the only permanent settlement in the Strait.

Here there was a pause of several days, which gave Agassiz an opportunity to draw the seine with large results for his marine collections. By the courtesy of the Governor, he had also an opportunity of making an excursion along the road leading to the coalmines. The wooded cliffs, as one ascends the hills toward the mines, are often bold and picturesque, and Agassiz found that portions of them were completely built of fossil shells. There is an oyster-bank, some one hundred feet high, overhanging the road in massive ledges that consist wholly of oyster-valves, with only earth enough to bind them together. He was inclined, from the character of the shells, to believe that the coal must be cretaceous rather than tertiary. [719]

On Tuesday, the 19th March, the Hassler left Sandy Point. The weather was beautiful, —a mellow autumn day with a reminiscence of summer in its genial warmth. The cleft summit of Sarmiento was clear against the sky, and the snow-fields, swept over by alternate light and shadow, seemed full of soft undulations. The evening anchorage was in the Bay of Port Famine, a name which marks the site of Sarmiento's ill-fated colony, and recalls the story of the men who watched and waited there for the help that never came. The stay here was short, and Agassiz spent the time almost wholly in studying the singularly regular, but completely upturned strata which line the beach, with edges so worn down as to be almost completely even with each other.

For many days after this, the Hassler pursued her course, past a seemingly endless panorama of mountains and forests rising into the pale regions of snow and ice, where lay glaciers in which every rift and crevasse, as well as the many cascades flowing down to join the waters beneath, could be counted as she steamed by them. Every night she anchored in the sheltered harbors formed by the inlets and fiords which break the base of the [720] rocky walls, and often lead into narrower ocean defiles penetrating, one knows not whither, into the deeper heart of these great mountain masses.

These were weeks of exquisite delight to Agassiz. The vessel often skirted the shore so closely that its geology could be studied from the deck. The rounded shoulders of the mountains, in marked contrast to their peaked and jagged crests, the general character of the snow-fields and glaciers, not crowded into narrow valleys as in Switzerland, but spread out on the open slopes of the loftier ranges, or, dome like, capping their summits, —all this afforded data for comparison with his past experience, and with the knowledge he had accumulated upon like phenomena in other regions. Here, as in the Alps, the abrupt line, where the rounded and worn surfaces of the mountains (moutonees, as the Swiss say) yield to their sharply cut, jagged crests, showed him the ancient and highest line reached by the glacial action. The long, serrated edge of Mount Tarn, for instance, is like a gigantic saw, while the lower shoulders of the mass are hummocked into a succession of rounded hills. In like manner the two beautiful valleys, separated by a bold bluff [721] called Bachelor's Peak, are symmetrically rounded on their slopes, while their summits are jagged and rough.

On one occasion the Hassler encountered one of those sudden and startling flaws of wind common to the Strait. The breeze, which had been strong all day, increased with sudden fury just as the vessel was passing through a rather narrow channel, which gave the wind the additional force of compression. In an inconceivably short time, the channel was lashed into a white foam; the roar of wind and water was so great you could not hear yourself speak, though the hoarse shout of command and the answering cry of the sailors rose above the storm. To add to the confusion, a loose sail slatted as if it would tear itself in pieces, with that sharp, angry, rending sound which only a broad spread of loose canvas can make. It became impossible to hold the vessel against the amazing power of the blast, and the Captain turned her round with the intention of putting her into Borja Bay, not far from which, by good fortune, she chanced to be. As she came broadside to the wind in turning, it seemed as if she must be blown over, so violently did she careen. Once safely round, she flew before the [722] wind, which now became her ally instead of her enemy, and by its aid she was soon abreast of Borja Bay. Never was there a more sudden transition from chaos to peace than that which ensued as she turned in from the tumult in the main channel to the quiet waters of the bay. The Hassler almost filled the tiny harbor shut in between mountains. She lay there safe and sheltered in breathless calm, while the storm raged and howled outside. These frequent, almost land-locked coves, are the safety of navigators in these straits; but after this day's experience, it was easy to understand how sailing vessels may be kept waiting for months between two such harbors, struggling vainly to make a few miles and constantly driven back by sudden squalls.

In this exquisite mountain-locked harbor, the vessel was weather-bound for a couple of days. Count Pourtales availed himself of this opportunity to ascend one of the summits. Up to a height of fifteen hundred feet, the rock was characterized by the smoothed, rounded surfaces which Agassiz had observed along his whole route in the Strait. Above that height all was broken and rugged, the line of separation being as defined as on any valley wall in Switzerland. It was again impossible [723] to decide, on such short observation, whether these effects were due to local glacial action, or whether they belonged to an earlier general ice-period. But Agassiz became satisfied, as he advanced, that the two sets of phenomena existed together, as in the northern hemisphere. The general aspect of the opposite walls of the Strait confirmed him in the idea that the sheet of ice in its former extension had advanced from south to north, grinding its way against and over the southern wall to the plains beyond. In short, he was convinced that, as a sheet of ice has covered the northern portion of the globe, so a sheet of ice has covered also the southern portion, advancing, in both instances, far toward the equatorial regions. His observations in Europe, in North America, and in Brazil seemed here to have their closing chapter.

With these facts in his mind, he did not fail to pause before Glacier Bay, noted for its immense glacier, which seems, as seen from the main channel, to plunge sheer down into the waters of the bay. A boat party was soon formed to accompany him to the glacier. It proved less easy of access than it looked at a distance. A broad belt of wood, growing, as Agassiz afterward found, on an accumulation [724] of old terminal moraines, spanned the lower valley from side to side. Through this wood there poured a glacial river, emptying itself into the bay. Strange to say, this glacier-washed forest, touching the ice on one side and the sea on the other, was full of flowers. The red bells of the glossy leaved Desfontainia, the lovely pink blossoms of the Phylesia, the crimson berries of the Pennetia, stood out in bright relief from a background of mossy tree-trunks and rocks. After an hour's walking, made laborious by the spongy character of the ground,—a mixture of loose soil and decaying vegetation, in which one sank knee-deep,—the gleam of the ice began to shimmer through the trees; and issuing from the wood, the party found themselves in front of a glacier wall, stretching across the whole valley and broken into deep rifts, caves, and crevasses of dark blue ice. The glacier was actually about a mile wide; but as the central portion was pressed forward in advance of the sides, the whole front was not presented at once. It formed a sharp crescent, with the curve turned outward. One of the caves in this front wall was some thirty or forty feet high, about a hundred feet deep, and two or three yards wide at the entrance. At the [725] further end it narrowed to a mere gallery, where the roof was pierced by a circular window, quite symmetrical in shape, through which one looked up to the blue sky and drifting clouds. There must be strange effects in this ice-cavern, when the sun is high and sends a shaft of light through its one window to illuminate the interior.

This first excursion was a mere reconnaissance. An approximate idea of the dimensions of the glacier, and some details of its structure, were obtained on a second visit the following day. The anchorage for the night was in Playa Parda Cove, one of the most beautiful of the many beautiful harbors of the Magellan Strait. It is entered by a deep, narrow slit, cut into the mountains on the northern side of the Strait, and widening at its farther end into a kind of pocket or basin, hemmed in between rocky walls bordered by forests, and overhung by snow and ice-fields. The next morning at half-past 3 o'clock, just as moonlight was fading before the dawn, and the mountains were touched with the coming day, the reveille was sounded for those who were to return to Glacier Bay. This time Agassiz divided his force so that they could act independently of each other, [726] though under a general plan laid out by him. M. de Pourtales and Dr. Steindachner ascended the mountain to the left of the valley, following its ridge, in the hope of reaching a position from which they could discover the source and the full length of the glacier. In this they did not succeed, though M. de Pourtales estimated its length, as far as he could see from any one point, to be about three miles, beyond which it was lost in the higher range. It made part of a net-work of glaciers running back into a large massif of mountains, and fed by many a neve on their upper slopes. The depth as well as the length of this glacier remains somewhat problematical, and indeed all the estimates in so cursory a survey must be considered as approximations rather than positive results. The glazed surface of the ice is an impediment to any examination from the upper side. It would be impossible to spring from brink to brink of a crevasse, as is so constantly done by explorers of Alpine glaciers where the edges of the cracks are often snowy or granular. Here the edges of the crevasses are sharp and hard, and to spring across one of any size would be almost certain death. There is no hold for an Alpine stock, no grappling point for hands [727] or feet. Any investigation from the upper surface would, therefore, require special apparatus, and much more time than Agassiz and his party could give. Neither was an approach from the side very easy. The glacier arches so much in the centre, and slopes away so steeply, that when one is in the lateral depression between it and the mountain, one faces an almost perpendicular wall of ice, which blocks the vision completely. M. de Pourtales measured one of the crevasses in this wall, and found that it had a depth of some seventy feet. Judging from the remarkable convexity of the glacier, it can hardly be less in the centre than two or three times its thickness on the edges,—something over two hundred feet, therefore. Probably none of these glaciers of the Strait of Magellan are as thick as those of Switzerland, though they are often much broader. The mountains are not so high, the valleys not so deep, as in the Alps; the ice is consequently not packed into such confined troughs. By some of the party an attempt was made to ascertain the rate of movement, signals having been adjusted the day before for its measurement. During the middle of the day, it advanced at the rate of ten inches and a fraction [728] in five hours. One such isolated observation is of course of little comparative value. For himself, Agassiz reserved the study of the bay, the ancient bed of the glacier in its former extension. He spent the day in cruising about the bay in the steam-launch, landing at every point he wished to investigate. His first care was to examine minutely the valley walls over which the glacier must once have moved. Every characteristic feature, known in the Alps as the work of the glaciers, was not only easily recognizable here, but as perfectly preserved as anywhere in Switzerland. The rounded knolls to which De Saussure first gave the name of roches moutonees were smoothed, polished, scratched, and grooved in the direction of the ice movement, the marks running mostly from south to north, or nearly so. The general trend of the scratches and furrows showed them to have been continuous from one knoll to another. The furrows were of various dimensions, sometimes shallow and several inches broad, sometimes narrow with more defined limits, gradually passing into mere lines on a very smoothly-polished surface. Even the curious notches scooped out of the even surfaces, and technically called ‘coups de gouge,’ were not [729] wanting. In some places the seams of harder rock stood out for a quarter of an inch or so above adjoining decomposed surfaces; in such instances the dike alone retained the glacial marks, which had been worn away from the softer rock.

The old moraines were numerous and admirably well preserved. Agassiz examined with especial care one colossal lateral moraine, standing about two miles below the present terminus of the ice and five hundred feet above the sea-level. It consisted of the same rocks as those found on the present terminal moraine, part of them being rounded and worn, while large, angular boulders rested above the smaller materials. This moraine forms a dam across a trough in the valley wall, and holds back the waters of a beautiful lake, about a thousand feet in length and five hundred in width, shutting it in just as the Lake of Meril in Switzerland is held in its basin by the glacier of Aletsch. There are erratics some two or three hundred feet above this great moraine, showing that the glacier must have been more than five hundred feet thick when it left this accumulation of loose materials at such a height. It then united, however, with a large glacier more to the [730] west. Its greatest thickness, as an independent glacier, is no doubt marked, not by the boulders lying higher up, but by the large moraine which shuts in the lake. The direct connection of this moraine with the glacier in its former extension is still further shown by two other moraines, on lower levels and less perfect, but having the same relation to the present terminus of the ice. The lower of these is only one hundred and fifty feet above the actual level of the glacier. These three moraines occur on the western slope of the bay. The eastern slope is more broken, and while the rounded knolls are quite as distinct and characteristic, the erratics are more loosely scattered over the surface. In mineralogical character they agree with those on the western wall of the bay. Upon the summits of some small islands at the entrance of the bay, there are also some remnants of terminal moraines, formed by the glacier when it reached the main channel; that is, when it was some three miles longer than now.

The more recent oscillations, marking the advance and retreat of the glacier within certain limits, are shown by the successive moraines heaped up in advance of the present terminal wall. The central motion here, as in [731] all the Swiss glaciers, is greater than the lateral, the ice being pushed forward in the middle faster than on the sides. But there would seem to be more than one axis of progression in this broad mass of ice; for though the centre is pushed out beyond the rest, the terminal wall does not present one uniform curve, but forms a number of more or less projecting angles or folds. A few feet in front of this wall is a ridge of loose materials, stones, pebbles, and boulders, repeating exactly the outline of the ice where it now stands; a few feet in advance of this, again, is another ridge precisely like it; still a few feet beyond, another; and so on, for four or five concentric zigzag crescent-shaped moraines, followed by two others more or less marked, till they fade into the larger morainic mass, upon which stands the belt of wood dividing the present glacier from the bay. Agassiz counted eight distinct moraines between the glacier and the belt of wood, and four concentric moraines in the wood itself. It is plain that the glacier has ploughed into the forest within some not very remote period, for the trees along its margin are loosened and half uprooted, though not yet altogether decayed. In the presence of the glacier [732] one ceases to wonder at the effects produced by so powerful an agent. This sheet of ice, even in its present reduced extent, is about a mile in width, several miles in length, and at least two hundred feet in depth. Moving forward as it does ceaselessly, and armed below with a gigantic file, consisting of stones, pebbles, and gravel, firmly set in the ice, who can wonder that it should grind, furrow, round, and polish the surfaces over which it slowly drags its huge weight. At once destroyer and fertilizer, it uproots and blights hundreds of trees in its progress, yet feeds a forest at its feet with countless streams; it grinds the rocks to powder in its merciless mill, and then sends them down, a fructifying soil, to the wooded shore below.

Agassiz would gladly have stayed longer in the neighborhood of Glacier Bay, and have made it the central point of a more detailed examination of the glacial phenomena in the Strait. But the southern winter was opening, and already gave signs of its approach. At dawn on the 26th of March, therefore, the Hassler left her beautiful anchorage in Playa Parda Cove, six large glaciers being in sight from her deck as she came out. The scenery during the morning had a new scientific interest [733] for Agassiz, because the vessel kept along the northern side of the Strait, while the course hitherto had been nearer the southern shore. He could thus better compare the differences between the two walls of the Strait. The fact that the northern wall is more evenly worn, more rounded than the southern, had a special significance for him, as corresponding with like facts in Switzerland, and showing that the ice-sheet had advanced across the Strait with greater force in its ascending than in its descending path. The north side being the strike side, the ice would have pushed against it with greater force. Such a difference between the two sides of any hollow or depression in the direct path of the ice is well known in Switzerland.

Later in the day, a pause was made in Chorocua Bay, where Captain Mayne's chart makes mention of a glacier descending into the water. There is, indeed, a large glacier on its western side, but so inaccessible, that any examination of it would have required days rather than hours. No one, however, regretted the afternoon spent here, for the bay was singularly beautiful. On either side, deep gorges, bordered by richly-wooded cliffs and overhung by ice and snow-fields, were cut into [734] the mountains. Where these channels might lead, into what dim recesses of ocean and mountain, could only be conjectured. The bay, with all its inlets and fiords, was still as a church. Voices and laughter seemed an intrusion, and a louder shout came back in echoes from far-off hidden retreats. Only the swift steamer-ducks, as they shot across, broke the glassy surface of the water with their arrow-like wake. From this point the Hassler crossed to Sholl Bay, and anchored at the entrance of Smythe's Channel. As sunset faded over the snow mountains opposite her anchorage, their white reflection lay like marble in the water.