(PLATE 53. PATAGONIAN BOLAS.)
(PLATE 54. PATAGONIAN SPURS AND PIPE.)
During our stay at Port Famine, the Fuegians twice came and plagued us. As there were many instruments, clothes, and men on sh.o.r.e, it was thought necessary to frighten them away. The first time a few great guns were fired, when they were far distant. It was most ludicrous to watch through a gla.s.s the Indians, as often as the shot struck the water, take up stones, and, as a bold defiance, throw them towards the ship, though about a mile and a half distant! A boat was then sent with orders to fire a few musket-shots wide of them. The Fuegians hid themselves behind the trees, and for every discharge of the muskets they fired their arrows; all, however, fell short of the boat, and the officer as he pointed at them laughed. This made the Fuegians frantic with pa.s.sion, and they shook their mantles in vain rage. At last, seeing the b.a.l.l.s cut and strike the trees, they ran away, and we were left in peace and quietness. During the former voyage the Fuegians were here very troublesome, and to frighten them a rocket was fired at night over their wigwams; it answered effectually, and one of the officers told me that the clamour first raised, and the barking of the dogs, was quite ludicrous in contrast with the profound silence which in a minute or two afterwards prevailed. The next morning not a single Fuegian was in the neighbourhood.
When the "Beagle" was here in the month of February, I started one morning at four o"clock to ascend Mount Tarn, which is 2600 feet high, and is the most elevated point in this immediate district. We went in a boat to the foot of the mountain (but unluckily not to the best part), and then began our ascent. The forest commences at the line of high-water mark, and during the first two hours I gave over all hopes of reaching the summit. So thick was the wood, that it was necessary to have constant recourse to the compa.s.s; for every landmark, though in a mountainous country, was completely shut out. In the deep ravines the death-like scene of desolation exceeded all description; outside it was blowing a gale, but in these hollows not even a breath of wind stirred the leaves of the tallest trees. So gloomy, cold, and wet was every part, that not even the fungi, mosses, or ferns could flourish. In the valleys it was scarcely possible to crawl along, they were so completely barricaded by great mouldering trunks, which had fallen down in every direction. When pa.s.sing over these natural bridges, one"s course was often arrested by sinking knee deep into the rotten wood; at other times, when attempting to lean against a firm tree, one was startled by finding a ma.s.s of decayed matter ready to fall at the slightest touch. We at last found ourselves among the stunted trees, and then soon reached the bare ridge, which conducted us to the summit. Here was a view characteristic of Tierra del Fuego; irregular chains of hills, mottled with patches of snow, deep yellowish-green valleys, and arms of the sea intersecting the land in many directions. The strong wind was piercingly cold, and the atmosphere rather hazy, so that we did not stay long on the top of the mountain. Our descent was not quite so laborious as our ascent, for the weight of the body forced a pa.s.sage, and all the slips and falls were in the right direction.
I have already mentioned the sombre and dull character of the evergreen forests, in which two or three species of trees grow, to the exclusion of all others. (11/3. Captain Fitz Roy informs me that in April (our October) the leaves of those trees which grow near the base of the mountains change colour, but not those on the more elevated parts. I remember having read some observations, showing that in England the leaves fall earlier in a warm and fine autumn than in a late and cold one. The change in the colour being here r.e.t.a.r.ded in the more elevated, and therefore colder situations, must be owing to the same general law of vegetation.
The trees of Tierra del Fuego during no part of the year entirely shed their leaves.) Above the forest land there are many dwarf alpine plants, which all spring from the ma.s.s of peat, and help to compose it: these plants are very remarkable from their close alliance with the species growing on the mountains of Europe, though so many thousand miles distant. The central part of Tierra del Fuego, where the clay-slate formation occurs, is most favourable to the growth of trees; on the outer coast the poorer granitic soil, and a situation more exposed to the violent winds, do not allow of their attaining any great size. Near Port Famine I have seen more large trees than anywhere else: I measured a Winter"s Bark which was four feet six inches in girth, and several of the beech were as much as thirteen feet. Captain King also mentions a beech which was seven feet in diameter seventeen feet above the roots.
(PLATE 55. CYTTARIA DARWINII.)
There is one vegetable production deserving notice from its importance as an article of food to the Fuegians. It is a globular, bright-yellow fungus, which grows in vast numbers on the beech-trees. When young it is elastic and turgid, with a smooth surface; but when mature, it shrinks, becomes tougher, and has its entire surface deeply pitted or honeycombed, as represented in Plate 55. This fungus belongs to a new and curious genus (11/4.
Described from my specimens and notes by the Reverend J.M. Berkeley in the "Linnean Transactions" volume 19 page 37, under the name of Cyttaria Darwinii: the Chilean species is the C. Berteroii. This genus is allied to Bulgaria.); I found a second species on another species of beech in Chile: and Dr. Hooker informs me that just lately a third species has been discovered on a third species of beech in Van Dieman"s Land. How singular is this relationship between parasitical fungi and the trees on which they grow, in distant parts of the world! In Tierra del Fuego the fungus in its tough and mature state is collected in large quant.i.ties by the women and children, and is eaten un-cooked. It has a mucilaginous, slightly sweet taste, with a faint smell like that of a mushroom.
With the exception of a few berries, chiefly of a dwarf arbutus, the natives eat no vegetable food besides this fungus. In New Zealand, before the introduction of the potato, the roots of the fern were largely consumed; at the present time, I believe, Tierra del Fuego is the only country in the world where a cryptogamic plant affords a staple article of food.
The zoology of Tierra del Fuego, as might have been expected from the nature of its climate and vegetation, is very poor. Of mammalia, besides whales and seals, there is one bat, a kind of mouse (Reithrodon chinchilloides), two true mice, a ctenomys allied to or identical with the tucutuco, two foxes (Canis Magellanicus and C. Azarae), a sea-otter, the guanaco, and a deer. Most of these animals inhabit only the drier eastern parts of the country; and the deer has never been seen south of the Strait of Magellan.
Observing the general correspondence of the cliffs of soft sandstone, mud, and shingle, on the opposite sides of the Strait, and on some intervening islands, one is strongly tempted to believe that the land was once joined, and thus allowed animals so delicate and helpless as the tucutuco and Reithrodon to pa.s.s over. The correspondence of the cliffs is far from proving any junction; because such cliffs generally are formed by the intersection of sloping deposits, which, before the elevation of the land, had been acc.u.mulated near the then existing sh.o.r.es. It is, however, a remarkable coincidence, that in the two large islands cut off by the Beagle Channel from the rest of Tierra del Fuego, one has cliffs composed of matter that may be called stratified alluvium, which front similar ones on the opposite side of the channel,--while the other is exclusively bordered by old crystalline rocks; in the former, called Navarin Island, both foxes and guanacos occur; but in the latter, Hoste Island, although similar in every respect, and only separated by a channel a little more than half a mile wide, I have the word of Jemmy b.u.t.ton for saying that neither of these animals is found.
The gloomy woods are inhabited by few birds: occasionally the plaintive note of a white-tufted tyrant-flycatcher (Myiobius albiceps) may be heard, concealed near the summit of the most lofty trees; and more rarely the loud strange cry of a black woodp.e.c.k.e.r, with a fine scarlet crest on its head. A little, dusky-coloured wren (Scytalopus Magellanicus) hops in a skulking manner among the entangled ma.s.s of the fallen and decaying trunks. But the creeper (Oxyurus tupinieri) is the commonest bird in the country.
Throughout the beech forests, high up and low down, in the most gloomy, wet, and impenetrable ravines, it may be met with. This little bird no doubt appears more numerous than it really is, from its habit of following with seeming curiosity any person who enters these silent woods: continually uttering a harsh twitter, it flutters from tree to tree, within a few feet of the intruder"s face. It is far from wishing for the modest concealment of the true creeper (Certhia familiaris); nor does it, like that bird, run up the trunks of trees, but industriously, after the manner of a willow-wren, hops about, and searches for insects on every twig and branch. In the more open parts, three or four species of finches, a thrush, a starling (or Icterus), two Opetiorhynchi, and several hawks and owls occur.
The absence of any species whatever in the whole cla.s.s of Reptiles is a marked feature in the zoology of this country, as well as in that of the Falkland Islands. I do not ground this statement merely on my own observation, but I heard it from the Spanish inhabitants of the latter place, and from Jemmy b.u.t.ton with regard to Tierra del Fuego. On the banks of the Santa Cruz, in 50 degrees south, I saw a frog; and it is not improbable that these animals, as well as lizards, may be found as far south as the Strait of Magellan, where the country retains the character of Patagonia; but within the damp and cold limit of Tierra del Fuego not one occurs. That the climate would not have suited some of the orders, such as lizards, might have been foreseen; but with respect to frogs, this was not so obvious.
Beetles occur in very small numbers: it was long before I could believe that a country as large as Scotland, covered with vegetable productions and with a variety of stations, could be so unproductive. The few which I found were alpine species (Harpalidae and Heteromidae) living under stones. The vegetable-feeding Chrysomelidae, so eminently characteristic of the Tropics, are here almost entirely absent (11/5. I believe I must except one alpine Haltica, and a single specimen of a Melasoma. Mr. Waterhouse informs me, that of the Harpalidae there are eight or nine species--the forms of the greater number being very peculiar; of Heteromera, four or five species; of Rhyncophora, six or seven; and of the following families one species in each: Staphylinidae, Elateridae, Cebrionidae, Melolonthidae. The species in the other orders are even fewer. In all the orders, the scarcity of the individuals is even more remarkable than that of the species. Most of the Coleoptera have been carefully described by Mr. Waterhouse in the "Annals of Natural History."); I saw very few flies, b.u.t.terflies, or bees, and no crickets or Orthoptera. In the pools of water I found but few aquatic beetles, and not any fresh-water sh.e.l.ls: Succinea at first appears an exception; but here it must be called a terrestrial sh.e.l.l, for it lives on the damp herbage far from water. Land-sh.e.l.ls could be procured only in the same alpine situations with the beetles. I have already contrasted the climate as well as the general appearance of Tierra del Fuego with that of Patagonia; and the difference is strongly exemplified in the entomology. I do not believe they have one species in common; certainly the general character of the insects is widely different.
If we turn from the land to the sea, we shall find the latter as abundantly stocked with living creatures as the former is poorly so. In all parts of the world a rocky and partially protected sh.o.r.e perhaps supports, in a given s.p.a.ce, a greater number of individual animals than any other station. There is one marine production which, from its importance, is worthy of a particular history. It is the kelp, or Macrocystis pyrifera. This plant grows on every rock from low-water mark to a great depth, both on the outer coast and within the channels. (11/6. Its geographical range is remarkably wide; it is found from the extreme southern islets near Cape Horn, as far north on the eastern coast (according to information given me by Mr. Stokes) as lat.i.tude 43 degrees,--but on the western coast, as Dr. Hooker tells me, it extends to the R. San Francisco in California, and perhaps even to Kamtschatka. We thus have an immense range in lat.i.tude; and as Cook, who must have been well acquainted with the species, found it at Kerguelen Land, no less than 140 degrees in longitude.) I believe, during the voyages of the "Adventure" and "Beagle," not one rock near the surface was discovered which was not buoyed by this floating weed. The good service it thus affords to vessels navigating near this stormy land is evident; and it certainly has saved many a one from being wrecked. I know few things more surprising than to see this plant growing and flourishing amidst those great breakers of the western ocean, which no ma.s.s of rock, let it be ever so hard, can long resist. The stem is round, slimy, and smooth, and seldom has a diameter of so much as an inch. A few taken together are sufficiently strong to support the weight of the large loose stones, to which in the inland channels they grow attached; and yet some of these stones were so heavy that when drawn to the surface, they could scarcely be lifted into a boat by one person. Captain Cook, in his second voyage, says that this plant at Kerguelen Land rises from a greater depth than twenty-four fathoms; "and as it does not grow in a perpendicular direction, but makes a very acute angle with the bottom, and much of it afterwards spreads many fathoms on the surface of the sea, I am well warranted to say that some of it grows to the length of sixty fathoms and upwards." I do not suppose the stem of any other plant attains so great a length as three hundred and sixty feet, as stated by Captain Cook. Captain Fitz Roy, moreover, found it growing up from the greater depth of forty-five fathoms. (11/7. "Voyages of the "Adventure" and "Beagle"" volume 1 page 363. It appears that seaweed grows extremely quick. Mr. Stephenson found Wilson"s "Voyage round Scotland" volume 2 page 228, that a rock uncovered only at spring-tides, which had been chiselled smooth in November, on the following May, that is, within six months afterwards, was thickly covered with Fucus digitatus two feet, and F. esculentus six feet, in length.) The beds of this sea-weed, even when of not great breadth, make excellent natural floating breakwaters. It is quite curious to see, in an exposed harbour, how soon the waves from the open sea, as they travel through the straggling stems, sink in height, and pa.s.s into smooth water.
The number of living creatures of all Orders, whose existence intimately depends on the kelp, is wonderful. A great volume might be written, describing the inhabitants of one of these beds of seaweed. Almost all the leaves, excepting those that float on the surface, are so thickly incrusted with corallines as to be of a white colour. We find exquisitely delicate structures, some inhabited by simple hydra-like polypi, others by more organised kinds, and beautiful compound Ascidiae. On the leaves, also, various patelliform sh.e.l.ls, Trochi, uncovered molluscs, and some bivalves are attached. Innumerable crustacea frequent every part of the plant. On shaking the great entangled roots, a pile of small fish, sh.e.l.ls, cuttlefish, crabs of all orders, sea-eggs, starfish, beautiful Holothuriae, Planariae, and crawling nereidous animals of a mult.i.tude of forms, all fall out together. Often as I recurred to a branch of the kelp, I never failed to discover animals of new and curious structures. In Chiloe, where the kelp does not thrive very well, the numerous sh.e.l.ls, corallines, and crustacea are absent; but there yet remain a few of the Fl.u.s.traceae, and some compound Ascidiae; the latter, however, are of different species from those in Tierra del Fuego; we see here the fucus possessing a wider range than the animals which use it as an abode. I can only compare these great aquatic forests of the southern hemisphere with the terrestrial ones in the intertropical regions. Yet if in any country a forest was destroyed, I do not believe nearly so many species of animals would perish as would here, from the destruction of the kelp. Amidst the leaves of this plant numerous species of fish live, which nowhere else could find food or shelter; with their destruction the many cormorants and other fishing birds, the otters, seals, and porpoises, would soon perish also; and lastly, the Fuegian savage, the miserable lord of this miserable land, would redouble his cannibal feast, decrease in numbers, and perhaps cease to exist.
JUNE 8, 1834.
We weighed anchor early in the morning and left Port Famine.
Captain Fitz Roy determined to leave the Strait of Magellan by the Magdalen Channel, which had not long been discovered. Our course lay due south, down that gloomy pa.s.sage which I have before alluded to as appearing to lead to another and worse world. The wind was fair, but the atmosphere was very thick; so that we missed much curious scenery. The dark ragged clouds were rapidly driven over the mountains, from their summits nearly down to their bases. The glimpses which we caught through the dusky ma.s.s were highly interesting; jagged points, cones of snow, blue glaciers, strong outlines, marked on a lurid sky, were seen at different distances and heights. In the midst of such scenery we anch.o.r.ed at Cape Turn, close to Mount Sarmiento, which was then hidden in the clouds. At the base of the lofty and almost perpendicular sides of our little cove there was one deserted wigwam, and it alone reminded us that man sometimes wandered into these desolate regions. But it would be difficult to imagine a scene where he seemed to have fewer claims or less authority. The inanimate works of nature--rock, ice, snow, wind, and water, all warring with each other, yet combined against man--here reigned in absolute sovereignty.
JUNE 9, 1834.
In the morning we were delighted by seeing the veil of mist gradually rise from Sarmiento, and display it to our view. This mountain, which is one of the highest in Tierra del Fuego, has an alt.i.tude of 6800 feet. Its base, for about an eighth of its total height, is clothed by dusky woods, and above this a field of snow extends to the summit. These vast piles of snow, which never melt, and seem destined to last as long as the world holds together, present a n.o.ble and even sublime spectacle. The outline of the mountain was admirably clear and defined. Owing to the abundance of light reflected from the white and glittering surface, no shadows were cast on any part; and those lines which intersected the sky could alone be distinguished: hence the ma.s.s stood out in the boldest relief. Several glaciers descended in a winding course from the upper great expanse of snow to the sea-coast: they may be likened to great frozen Niagaras; and perhaps these cataracts of blue ice are full as beautiful as the moving ones of water. By night we reached the western part of the channel; but the water was so deep that no anchorage could be found. We were in consequence obliged to stand off and on in this narrow arm of the sea, during a pitch-dark night of fourteen hours long.
JUNE 10, 1834.
In the morning we made the best of our way into the open Pacific.
The western coast generally consists of low, rounded, quite barren hills of granite and greenstone. Sir J. Narborough called one part South Desolation, because it is "so desolate a land to behold:" and well indeed might he say so. Outside the main islands there are numberless scattered rocks on which the long swell of the open ocean incessantly rages. We pa.s.sed out between the East and West Furies; and a little farther northward there are so many breakers that the sea is called the Milky Way. One sight of such a coast is enough to make a landsman dream for a week about shipwrecks, peril, and death; and with this sight we bade farewell for ever to Tierra del Fuego.
The following discussion on the climate of the southern parts of the continent with relation to its productions, on the snow-line, on the extraordinarily low descent of the glaciers, and on the zone of perpetual congelation in the antarctic islands, may be pa.s.sed over by any one not interested in these curious subjects, or the final recapitulation alone may be read. I shall, however, here give only an abstract, and must refer for details to the Thirteenth Chapter and the Appendix of the former edition of this work.
ON THE CLIMATE AND PRODUCTIONS OF TIERRA DEL FUEGO AND OF THE SOUTH-WEST COAST.
The following table gives the mean temperature of Tierra del Fuego, the Falkland Islands, and, for comparison, that of Dublin:--
Lat.i.tude Summer Winter Mean of Summer degrees " Temp. Temp. and Winter deg. F. deg. F. deg. F.
--------------------------------------------------------------- Tierra del Fuego 53 38 S. 50 33.08 41.54 Falkland Islands 51 38 S. 51 -- -- Dublin 53 21 N. 59.54 39.2 49.37
Hence we see that the central part of Tierra del Fuego is colder in winter, and no less than 9 1/2 degrees less hot in summer, than Dublin. According to von Buch the mean temperature of July (not the hottest month in the year) at Saltenfiord in Norway, is as high as 57.8 degrees, and this place is actually 13 degrees nearer the pole than Port Famine! (11/8. With respect to Tierra del Fuego, the results are deduced from the observations of Captain King "Geographical Journal" 1830, and those taken on board the "Beagle."
For the Falkland Islands, I am indebted to Captain Sulivan for the mean of the mean temperature (reduced from careful observation at midnight, 8 A.M., noon, and 8 P.M.) of the three hottest months, namely, December, January, and February. The temperature of Dublin is taken from Barton.) Inhospitable as this climate appears to our feelings, evergreen trees flourish luxuriantly under it.
Humming-birds may be seen sucking the flowers, and parrots feeding on the seeds of the Winter"s Bark, in lat.i.tude 55 degrees south. I have already remarked to what a degree the sea swarms with living creatures; and the sh.e.l.ls (such as the Patellae, Fissurellae, Chitons, and Barnacles), according to Mr. G.B. Sowerby, are of a much larger size, and of a more vigorous growth, than the a.n.a.logous species in the northern hemisphere. A large Voluta is abundant in southern Tierra del Fuego and the Falkland Islands. At Bahia Blanca, in lat.i.tude 39 degrees south, the most abundant sh.e.l.ls were three species of Oliva (one of large size), one or two Volutas, and a Terebra. Now these are amongst the best characterised tropical forms. It is doubtful whether even one small species of Oliva exists on the southern sh.o.r.es of Europe, and there are no species of the two other genera. If a geologist were to find in lat.i.tude 39 degrees on the coast of Portugal a bed containing numerous sh.e.l.ls belonging to three species of Oliva, to a Voluta, and Terebra, he would probably a.s.sert that the climate at the period of their existence must have been tropical; but, judging from South America, such an inference might be erroneous.
The equable, humid, and windy climate of Tierra del Fuego extends, with only a small increase of heat, for many degrees along the west coast of the continent. The forests for 600 miles northward of Cape Horn, have a very similar aspect. As a proof of the equable climate, even for 300 or 400 miles still farther northward, I may mention that in Chiloe (corresponding in lat.i.tude with the northern parts of Spain) the peach seldom produces fruit, whilst strawberries and apples thrive to perfection. Even the crops of barley and wheat are often brought into the houses to be dried and ripened. (11/9. Agueeros "Descrip. Hist. de la Prov. de Chiloe" 1791 page 94.) At Valdivia (in the same lat.i.tude of 40 degrees with Madrid) grapes and figs ripen, but are not common; olives seldom ripen even partially, and oranges not at all. These fruits, in corresponding lat.i.tudes in Europe, are well known to succeed to perfection; and even in this continent, at the Rio Negro, under nearly the same parallel with Valdivia, sweet potatoes (convolvulus) are cultivated; and grapes, figs, olives, oranges, water and musk melons, produce abundant fruit. Although the humid and equable climate of Chiloe, and of the coast northward and southward of it, is so unfavourable to our fruits, yet the native forests, from lat.i.tude 45 to 38 degrees, almost rival in luxuriance those of the glowing intertropical regions. Stately trees of many kinds, with smooth and highly coloured barks, are loaded by parasitical monocotyledonous plants; large and elegant ferns are numerous, and arborescent gra.s.ses entwine the trees into one entangled ma.s.s to the height of thirty or forty feet above the ground. Palm-trees grow in lat.i.tude 37 degrees; an arborescent gra.s.s, very like a bamboo, in 40 degrees; and another closely allied kind, of great length, but not erect, flourishes even as far south as 45 degrees south.
ON THE HEIGHT OF THE SNOW-LINE, AND ON THE DESCENT OF THE GLACIERS, IN SOUTH AMERICA.
For the detailed authorities for the following table, I must refer to the former edition:--
Height in feet Lat.i.tude of Snow-line Observer ---------------------------------------------------------------- Equatorial region; mean result 15,748 Humboldt.
Bolivia, lat.i.tude 16 to 18 degrees south 17,000 Pentland.
Central Chile, lat.i.tude 33 degrees south 14,500 to 15,000 Gillies and the Author.
Chiloe, lat.i.tude 41 to 43 degrees south 6,000 Officers of the "Beagle" and the Author.
Tierra del Fuego 54 degrees south 3,500 - 4,000 King.
An equable climate, evidently due to the large area of sea compared with the land, seems to extend over the greater part of the southern hemisphere; and as a consequence, the vegetation partakes of a semi-tropical character. Tree-ferns thrive luxuriantly in Van Diemen"s Land (lat.i.tude 45 degrees), and I measured one trunk no less than six feet in circ.u.mference. An arborescent fern was found by Forster in New Zealand in 46 degrees, where orchideous plants are parasitical on the trees. In the Auckland Islands, ferns, according to Dr. Dieffenbach have trunks so thick and high that they may be almost called tree-ferns; and in these islands, and even as far south as lat.i.tude 55 degrees in the Macquarie Islands, parrots abound. (11/10. See the German Translation of this Journal; and for the other facts Mr. Brown"s Appendix to Flinders"s "Voyage.")
As the height of the plane of perpetual snow seems chiefly to be determined by the extreme heat of the summer, rather than by the mean temperature of the year, we ought not to be surprised at its descent in the Strait of Magellan, where the summer is so cool, to only 3500 or 4000 feet above the level of the sea; although in Norway, we must travel to between lat.i.tude 67 and 70 degrees north, that is, about 14 degrees nearer the pole, to meet with perpetual snow at this low level. The difference in height, namely, about 9000 feet, between the snow-line on the Cordillera behind Chiloe (with its highest points ranging from only 5600 to 7500 feet) and in central Chile (a distance of only 9 degrees of lat.i.tude), is truly wonderful. (11/11. On the Cordillera of central Chile, I believe the snow-line varies exceedingly in height in different summers. I was a.s.sured that during one very dry and long summer, all the snow disappeared from Aconcagua, although it attains the prodigious height of 23,000 feet. It is probable that much of the snow at these great heights is evaporated, rather than thawed.) The land from the southward of Chiloe to near Concepcion (lat.i.tude 37 degrees) is hidden by one dense forest dripping with moisture. The sky is cloudy, and we have seen how badly the fruits of southern Europe succeed. In central Chile, on the other hand, a little northward of Concepcion, the sky is generally clear, rain does not fall for the seven summer months, and southern European fruits succeed admirably; and even the sugar-cane has been cultivated.
(11/12. Miers"s "Chile" volume 1 page 415. It is said that the sugar-cane grew at Ingenio, lat.i.tude 32 to 33 degrees, but not in sufficient quant.i.ty to make the manufacture profitable. In the valley of Quillota, south of Ingenio, I saw some large date-palm trees.) No doubt the plane of perpetual snow undergoes the above remarkable flexure of 9000 feet, unparalleled in other parts of the world, not far from the lat.i.tude of Concepcion, where the land ceases to be covered with forest-trees; for trees in South America indicate a rainy climate, and rain a clouded sky and little heat in summer.
(PLATE 56. EYRE SOUND.)
The descent of glaciers to the sea must, I conceive, mainly depend (subject, of course, to a proper supply of snow in the upper region) on the lowness of the line of perpetual snow on steep mountains near the coast. As the snow-line is so low in Tierra del Fuego, we might have expected that many of the glaciers would have reached the sea. Nevertheless I was astonished when I first saw a range, only from 3000 to 4000 feet in height, in the lat.i.tude of c.u.mberland, with every valley filled with streams of ice descending to the sea-coast. Almost every arm of the sea, which penetrates to the interior higher chain, not only in Tierra del Fuego, but on the coast for 650 miles northwards, is terminated by "tremendous and astonishing glaciers," as described by one of the officers on the survey. Great ma.s.ses of ice frequently fall from these icy cliffs, and the crash reverberates like the broadside of a man-of-war through the lonely channels. These falls, as noticed in the last chapter, produce great waves which break on the adjoining coasts.
It is known that earthquakes frequently cause ma.s.ses of earth to fall from sea-cliffs: how terrific, then, would be the effect of a severe shock (and such occur here (11/13. Bulkeley"s and c.u.mmin"s "Faithful Narrative of the Loss of the Wager." The earthquake happened August 25, 1741.)) on a body like a glacier, already in motion, and traversed by fissures! I can readily believe that the water would be fairly beaten back out of the deepest channel, and then, returning with an overwhelming force, would whirl about huge ma.s.ses of rock like so much chaff. In Eyre"s Sound, in the lat.i.tude of Paris, there are immense glaciers, and yet the loftiest neighbouring mountain is only 6200 feet high. In this Sound, about fifty icebergs were seen at one time floating outwards, and one of them must have been AT LEAST 168 feet in total height. Some of the icebergs were loaded with blocks of no inconsiderable size, of granite and other rocks, different from the clay-slate of the surrounding mountains.
(PLATE 57. GLACIER IN GULF OF PENAS.)
The glacier farthest from the Pole, surveyed during the voyages of the "Adventure" and "Beagle," is in lat.i.tude 46 degrees 50", in the Gulf of Penas. It is 15 miles long, and in one part 7 broad, and descends to the sea-coast. But even a few miles northward of this glacier, in the Laguna de San Rafael, some Spanish missionaries encountered "many icebergs, some great, some small, and others middle-sized," in a narrow arm of the sea, on the 22 of the month corresponding with our June, and in a lat.i.tude corresponding with that of the Lake of Geneva! (11/14. Agueeros "Desc. Hist. de Chiloe"
page 227.)
In Europe, the most southern glacier which comes down to the sea is met with, according to Von Buch, on the coast of Norway, in lat.i.tude 67 degrees. Now, this is more than 20 degrees of lat.i.tude, or 1230 miles, nearer the pole than the Laguna de San Rafael. The position of the glaciers at this place and in the Gulf of Penas may be put even in a more striking point of view, for they descend to the sea-coast within 7 1/2 degrees of lat.i.tude, or 450 miles, of a harbour, where three species of Oliva, a Voluta, and a Terebra, are the commonest sh.e.l.ls, within less than 9 degrees from where palms grow, within 4 1/2 degrees of a region where the jaguar and puma range over the plains, less than 2 1/2 degrees from arborescent gra.s.ses, and (looking to the westward in the same hemisphere) less than 2 degrees from orchideous parasites, and within a single degree of tree-ferns!
These facts are of high geological interest with respect to the climate of the northern hemisphere, at the period when boulders were transported. I will not here detail how simply the theory of icebergs being charged with fragments of rock explains the origin and position of the gigantic boulders of eastern Tierra del Fuego, on the high plain of Santa Cruz, and on the island of Chiloe. In Tierra del Fuego the greater number of boulders lie on the lines of old sea-channels, now converted into dry valleys by the elevation of the land. They are a.s.sociated with a great unstratified formation of mud and sand, containing rounded and angular fragments of all sizes, which has originated in the repeated ploughing up of the sea-bottom by the stranding of icebergs, and by the matter transported on them. (11/15. "Geological Transactions" volume 6 page 415.) Few geologists now doubt that those erratic boulders which lie near lofty mountains have been pushed forward by the glaciers themselves, and that those distant from mountains, and embedded in subaqueous deposits, have been conveyed thither either on icebergs, or frozen in coast-ice. The connection between the transportal of boulders and the presence of ice in some form, is strikingly shown by their geographical distribution over the earth.
In South America they are not found farther than 48 degrees of lat.i.tude, measured from the southern pole; in North America it appears that the limit of their transportal extends to 53 1/2 degrees from the northern pole; but in Europe to not more than 40 degrees of lat.i.tude, measured from the same point. On the other hand, in the intertropical parts of America, Asia, and Africa, they have never been observed; nor at the Cape of Good Hope, nor in Australia. (11/16. I have given details (the first, I believe, published) on this subject in the first edition, and in the Appendix to it. I have there shown that the apparent exceptions to the absence of erratic boulders in certain hot countries are due to erroneous observations; several statements there given I have since found confirmed by various authors.)
ON THE CLIMATE AND PRODUCTIONS OF THE ANTARCTIC ISLANDS.