Part ii

., 1837, p. 297. Other writers have given the ratio as 100:284.

The islands form scarcely 1/22d of the continental masses, which are so unequally divided that they consist of three times more land in the northern than in the southern hemisphere; the latter being, therefore, pre-eminently oceanic. From 40 degrees south latitude to the Antarctic pole the earth is almost entirely covered with water. The fluid element predominates in like manner between the eastern shores of the Old and the western shores of the New Continent, being only interspersed with some few insular groups. The learned hydrographer Fleurieu has very justly named this p 289 vast oceanic basis, which, under the tropics, extends over 145ºdegrees of longitude, the 'Great Ocean', in contradistinction to all other seas. The southern and western hemispheres (reckoning the latter from the meridian of Teneriffe) are therefore more rich in water than in any other region of the whole earth.

These are the main points involved in the consideration of the relative quantity of land and sea, a relation which exercises so important an influence on the distribution of temperature, the variations in atmospheric pressure, the direction of the winds, and the quantity of moisture contained in the air, with which the development of vegetation is so essentially connected. When we consider that nearly three fourths of the upper surface of our planet are covered with water,* we shall be less surprised at the imperfect condition of meteorology before the beginning of the present century, since it is only during the subsequent period that numerous accurate observations on the temperature of the sea at different latitudes and at different seasons have been made and numerically compared together.

[footnote] *In the Middle Ages, the opinion prevailed that the sea covered one seventh of the surface of the globe, an opinion which Cardinal d'Ailly ('Imago Mundi', cap. 8) founded on the fourth apocryphal book of Esdras. Columbus, who derived a great portion of his cosmographical knowledge from the cardinal's work, was much interested in upholding this idea of the smallness of the sea, to which the misunderstood expression of "the ocean stream" contributed not a little. See Humboldt, 'Examen Critique de l'Hist. de la Geographie', t. i., p. 186.

The horizontal configuration of continents in their general relations of extension was already made a subject of intellectual contemplation by the ancient Greeks. Conjectures were advanced regarding the maximum of the extension from west to east, and Dicaearchus placed it, according to the testimony of Agathemerus, in the latitude of Rhodes, in the direction of a line passing from the Pillars of Hercules to Thine. This line, which has been termed 'the parallel of the diaphragm of Dicaearchus', is laid down with an astronomical accuracy of position, which, as I have stated in another work, is well worthy of exciting surprise and admiration.*

[footnote] *Agathemerus, in Hudson, 'Geographi Minores', t. ii., p. 4. See Humboldt, 'Asie Centr.', t. i., p. 120-125.

Strabo, who was probably influenced by Eratosthenes, appears to have been so firmly convinced that this parallel of 36 degrees was the maximum of the extension of the then existing world, that he supposed it had some intimate connection with the form of the earth, and therefore places under this line the continent whose existence p 290 he divined in the northern hemisphere, between Theria and the coasts of Thine.*

[footnote] *Strabo, lib. i., p. 65, Casaub. See Humboldt, 'Examen Crit.', t. i., p. 152.

As we have already remarked, one hemisphere of the earth (whether we divide the sphere through the equator or through the meridian of Teneriffe) has a much greater expansion of elevated land than the opposite one: these two vast ocean-girt tracts of land, which we term the eastern and western, or the Old and New Continents, present, however, conjointly with the most striking contrasts of configuration and position of their axes, some similarities of form, especially with reference to the mutual relations of their opposite coasts. In the eastern continent, the predominating direction -- the position of the major axis -- inclines from east to west (or, more correctly speaking, from southwest to northeast), while in the western continent it inclines from south to north (or, rather, from south-southeast to north-northwest). Both terminate to the north at a parallel coinciding nearly with that of 70ºdegrees, while they extend to the south in pyramidal points, having submarine prolongations of islands and shoals. Such, for instance, are the Archipelago of Tierra del Fuego, the Lagullas Bank south of the Cape of Good Hope, and Van Diemen's Land, separated from New Holland by Bass's Straits. Northern Asia extends to the above parallel at Cape Taimura, which, according to Krusenstern, is 78 degrees 16', while it falls below it from the mouth of the Great Tschukotsehja River eastward to Behring's Straits, in the eastern extremity of Asia -- Cook's East Cape -- which, according to Beechey, is only 66 degrees E.*

[footnote] *On the mean latitude of the Northern Asiatic shores, and the true name of Cape Taimura (Cape Siewere-Wostotschnoi), and Cape Northeast (Schalagskoi Mys), see Humboldt, 'Asie Centrale', t. iii., p. 35, 37.

The northern shore of the New Continent follows with tolerable exactness the parallel of 70 degrees, since the lands to the north and south of Barrow's Strait, from Boothia Felix and Victoria Land, are merely detached islands.

The pyramidal configuration of all the southern extremities of continents belongs to the 'similtudines physicae in configuratione mundi', to which Bacon already called attention in his 'Novum Organon', and with which Reinhold Foster, one of Cook's companions in his second voyage of circumnavigation, connected some ingenious considerations. On looking eastward from the meridian of Teneriffe, we perceive that the southern extremities of the three continents, viz., Africa as the extreme p 291 of the Old World, Australia, and South America, successively approach nearer toward the south pole. New Zealand, whose length extends fully 12 degrees of latitude, forms an intermediate link between Australia and South America, likewise terminating in an island, New Leinster. It is also a remarkable circumstance that the greatest extension toward the south falls in the Old Continent, under the same meridian in which the extremest projection toward the north pole is manifested. This will be perceived on comparing the Cape of Good Hope and the Lagullas Bank with the North Cape of Europe, and the peninsula of Malacca with Cape Taimura in Siberia.*

[footnote] *Humboldt, 'Asie Centrale', t. i., p. 198-200. The southern point of America, and the Archipelago which we call Terra del Fuego, lie in the meridian of the northwestern part of Baffin's Bay, and of the great polar land, whose limits have not as yet been ascertained, and which, perhaps, belongs to West Greenland.

We know not whether the poles of the earth are surrounded by land or by a sea of ice. Toward the north pole the parallel of 82 degrees 55' has been reached, but toward the south pole only that of 78 degrees 10'.

The pyramidal terminations of the great continents are variously repeated on a smaller scale, not only in the Indian Ocean and in the peninsulas of Arabia, Hindostan, and Malacca, but also, as was remarked by Eratosthenes and Polybius, in the Mediterranean, where these writers had ingeniously compared together the forms of the Iberian, Italian, and Hellenic peninsulas.*

[footnote] *Strabo, lib. ii., p. 92, 108, Cassaub.

Europe, whose area is five times smaller than that of Asia, may almost be regarded as a multifariously articulated western peninsula of the more compact mass of the ontinent of Asia, the climatic relations of the former being to those of the latter as the peninsula of Brittany is to the rest of France.

[footnote] *Humboldt, 'Asie Centrale', t. iii., p. 25. As early as the year 1817, in my work 'De distributione Geographica Plantarum, secundum caels temperiem et altitudinem Montium', I directed attention to the important influence of compact and of deeply-articulated continents on climate and human civilization, "Regiones vel per sinus lunatos in longa cornua porrectae, angulois littorum recessibus quasi membratim discerptae, vel spatia patentia in immensum, quorum littora nullis incisa angulis ambit sine aufractu oceanus" (p. 81, 182). On the relations of the extent of coast to the area of a continent (considered in some degree as a measure of the accessibility of the interior), see the inquiries in Berghaus, 'Annalen der Erdkunde', bd. xii., 1835, s. 490, and 'Physikal. Atlas', 1839, No. iii., s. 69.

The influence exercised by the articulation and higher development of the form of a continent on the moral and intellectual condition of nations was remarked by Strabo,* who extols p 292 the varied form of our small continent as a special advantage.

[footnote] *Strabo, lib. ii., p. 92, 198. Casaub.

Africa* and South America, which manifest so great a resemblence in their configuration, are also the two continents that exhibit the simplest littoral outlines.

[footnote] *Of Africa, Pliny says (v. 1), "Nec alia pars terrarum paudiores recipit sinus." The small Indian peninsula on this side the Ganges present, in its triangular outline, a third analogous form. In ancient Greece there prevailed an opinion of the regular configuration of the dry land. There were four gulfs or bays, among which the Persian Gulf was placed in opposition to the Hyrcanian or Caspian Sea (Arrian, vii., 16; Plut., 'in vita Alexandri', cap. 44; Dionys. Perieg., v. 48 and 630, p. 11, 38, Bernh.). These four bays and the isthmuses were, according to the optical fancies of Agesianax, supposed to be reflected in the moon (Plut., 'de Facie in Orbem Lunae', p. 921, 19). Respecting the 'terra quadrifida', or four divisions of the dry land, of which two lay north and two south of the equator, see Macrobius, 'Comm. in Somnium Scipionis', ii., 9. I have submitted this portion of the geography of the ancients, regarding which great confusion prevails, to a new and careful examination, in my 'Examen Crit. de l'Hist. de la Geogr.', t. i., p. 119, 145, 180-185, as also in 'Asie Centr.', t. ii., p. 172-178.

It is only the eastern shores of Asia, which, broken as it were by the force of the currents of the ocean* ('fractas ex aequore terra'), exhibit a richly-variegated configuration, peninsulas and contiguous islands alternating from the equator to 60 degrees north latitude.

[footnote] *Fleurieu, in 'Voyage de Marchand autour du Monde', t. iv., p. 38-42.

Our Atlantic Ocean presents all the indications of a valley. It is as if a flow of eddying waters had been directed first toward the northeast, then toward the northwest, and back again to the northeast. The parallelism of the coasts north of 10 degrees south latitude, the projecting and receding angles, the convexity of Brazil opposite to the Gulf of Guinea, that of Africa under the same parallel, with the Gulf of the Antilles, all favor this apparently speculative view.*

[footnote] *Humboldt, in the 'Journal de Physique', liii., 1799, p. 33; and 'Rel. Hist.', t. ii., p. 19; t. iii., p. 189, 198.

In this Atlantic valley, as is almost every where the case in the configuration of large continental masses, coasts deeply indented, and rich in islands, are situated opposite to those possessing a different character. I long since drew attention to the geognostic importance of entering into a comparison of the western coast of Africa and of South America within the tropics. The deeply curved indentation of the African continent at Fernando Po, 4 degrees 30' north latitude, is repeated on the coast of the Pacific at 18 degrees 15' south latitude, between the Valley of Arica and the Morro de Juan Diaz, where the Peruvian coast suddenly changes the direction from wouth to north which it had previously followed, and inclines to the northwest. This change p 293 of direction extends in like manner to the chain of the Andes, which is divided into two parallel branches affecting not only the littoral portions,* but even the eastern Cordilleras.

[footnote] *Humboldt, in Poggendorf's 'Annalen der Physik', bd. xl., s. 171. On the remarkable fiord formation at the southeast end of America, see Darwin's Journal ('Narrative of the Voyages of the Adventure and Beagle', vol. iii.), 1839, p. 266. The parallelism of the two mountain chains is maintained from 5 degrees north latitude. The change in the direction of the coast at Arica appears to be in consequence of the altered course of the fissure, above which the Cordillera of the Andes has been upheaved.

In the latter, civilization had its earliest seat in the South American plateaux where the small Alpine lake of Titicaca bathes the feet of the colossal mountains of Sorata and Illimani. Further to the south, from Valdiva and Chiloë (40 degrees to 42 degrees south latitude), through the Archipelago 'de los Chonos' to 'Terra del Fuego', we find repeated that singular configuration of 'fiords' (a blending of narrow and deeply-indented bays), which in the Northern hemisphere characterizes the western shores of Norway and Scotland.

These are the most general considerations suggested by the study of the upper surface of our planet with reference to the form of continents, and their expansion in a horizontal direction. We have collected facts and brought forward some analogies of configuration in distant parts of the earth, but we do not venture to regard them as fixed laws of form. When the traveler on the declivity of an active volcano, as, for instance, of Vesuvius, examines the frequent partial elevations by which portions of the soil are often permanently upheaved several feet above their former level, either immediately precediing or during the continuance of an eruption, thus forming roof-like or flattened summits, he is taught how accidental conditions in the expression of the force of subterranean vapors, and in the resistance to be overcome, may modify the feeble perturbations in the equilibrium of the internal elastic forces of our planet may have inclined them more to its norther than to its southern direction, and caused the continent in the eastern part of the globe to present a broad mass, whose major axis is almost parallel with the equator, while in the western and more oceanic part the southern extremity is extremely narrow.

Very little can be empirically determined regarding the causal connection of the phenomena of the formation of continents, or of the analogies and contrasts presented by their p 294 configuration. All that we know regarding this subject resolves itself into this one point, that the active cause is subterranean; that continents did not arise at once in the form they now present, but were, as we have already observed, increased by degrees by means of numerous oscillatory elevations and depressions of the soil, or were formed by the fusion of separate smaller continental masses. Their present form is, therefore, the result of two causes, which have exercised a consecutive action the one on the other; the first is the expression of subterranean force, whose direction we term accidental, owing to our inability to defint it, from its removal from within the sphere of our comprehension, while the second is derived from forces acting on the surface, among which volcanic eruptions, the elevation of mountains, and currents of sea water play the principal parts. How totally different would be the condition of the temperature of the earth, and consequently, of the state of vegetation, husbandry, and human society, if the major axis of the New Continent had the same direction as that of the Old Continent; if, for instance, the Cordilleras, instead of having a southern direction, inclined from east to west; if there had been no radiating tropical continent, like Africa, to the south of Europe; and if the Mediterranean, which was once connected with the Caspian and Red Seas, and which has become so powerful a means of furthering the intercommunication of nations, had never existed, or if it had been elevated like the plains of Lombardy and Cyrene?

The changes of the reciprocal relations of height between the fluid and solid portions of the earth's surface (changes which, at the same time, determine the outlines of continents, and the greater or lesser submersion of low lands) are to be ascribed to numerous unequally working causes. The most powerful have incontestably been the force of elastic vapors inclosed in the interior of the earth, the sudden change of temperature of certain dense strata,* the unequal secular loss of p 295 heat experienced by the crust and nucleus of the earth, occasioning ridges in the solid surface, local modifications of gravitation,** and, as a consequence of these alterations, in the curvature of a portion of the liquid element.

[footnote] *De la Beche, 'Sections and Views illustrative of Geological Phenomena', 1830, tab. 40; Charles Babbage, 'Observations on the Temple of Serapis at Pozzuoli, near Naples, and on certain Causes which may produce Geological Cycles of great Extent', 1834. "If a stratum of sandstone five miles in thickness should have its temperature raised about 100 degrees, its surface would rise twenty-five feet. Heated beds of clay would, on the contrary, occasion a sinking of the ground by their contraction." See Bischof, 'Wurmelehre des Innern unseres Erdkorpers', s. 303, concerning the calculations for the secular elevation of Sweden, on the supposition of a rise by so small a quantity as 7 degrees in a stratum of about 155,000 feet in thickness, and heated to a state of fusion.

[footnote] **The opinion so implicitly entertained regarding the invariability of the force of gravity at any given point of the earth's surface, has in some degree been controverted by the gradual rise of large portions of the earth's surface. See Bessel, 'Ueber Maas und Gewicht', in Schumacher's 'Jahrbuch fur' 1840, s. 134.

According to the views generally adopted by geognosists in the present day and which are supported by the observation of a series of well-attested facts, no less than by analogy with the most important volcanic phenomena, it would appear that the elevation of continents is actual, and not merely apparent or owing to the configuration of the upper surface of the sea. The merit of having advanced this view beloongs to Leopold von Buch, the narrative of his memorable 'Travels through Norway and Sweden' in 1806 and 1807.*

[footnnote] *Th. ii. (1810), s. 389. See Hallstrom, in 'Kongl. Vetenskaps-Academiens Handlingar' (Stockh.), 1823, p. 30; Lyell in the 'Philos. Trans.' for 1835; Blom (Amtmann in Budskerud), 'Stat. Beschr. von Norwegen',1843, s. 89-116. If not before Von Buch's travels through Scandinavia, at any rate before their publication, Playfair, in 1802, in his illustrations of the Huttonian theory, § 393, and according to Keilhau ('Om Landjardens Stigning in Norge', in the 'Nyt Magazine fur Naturvidenskaberne'), and the Dane Jessen, even before the time of Playfair, had expressed the opinion that it was not the sea which was sinking, but the solid land of Sweden which was rising. Their ideas, however, were wholly unknown to our great geologist, and exerted no influence on 'Norge fremstillet efter dets naturlige og borgerlige Tilstand', Kjobenh., 1763, sought to explain the causes of the changes in the relative levels of the land and sea, basing his views on the early calculations of Celsius, Kalm, and Dalin. He broaches some confused ideas regarding the possibility of an internal growth of rocks, but finally declares himself in favor of an upheaval of the land by earthquakes, "although," he observes, "no such rising was apparent immediately after the earthquake of Egersund, yet the earthquake may have opened the way for other causes producing such an effect."

While the whole coast of Sweden and Finland, from Solvitzborg, on the limits of Northern Scania, past Gefle to Tornea, and from Tornea to Abo, experiences a gradual rise of four feet in a century, the southern part of Sweden is, according to Neilson, undergoing a simultaneous depression.*

[footnote] *See Berzelius, 'Jahrsbericht uber die Fortschritte der Physichen Wiss.', No. 18, s. 686. The islands of Saltholm, opposite to Copenhagen, and Bjornholm, however, rise but very little -- Bjornholm scarcely one foot in a century. See Forchhammer, in 'Philos. Magazine', 3d Series, vol. ii., p. 309.

The maximum of this elevating p 296 force appears to be in the north of Lapland, and to diminish gradually to the south toward Calmar and Solvitzborg. Lines marking the ancient level of the sea in pre-historic times are indicated throughout the whole of Norway,* from Cape Lindesnaes to the extremity of the North Cape, by banks of shells identical with those of the present seas, and which have lately been most accurately examined by Bravais during his long winter sojourn at Bosekop.

[footnote] *Keilhan, in 'Nyt Mag. fur Naturvid.', 1832, bd. i., p. 105-254; bd. ii., p. 57; Bravais, 'Surles Lignes d'ancien Niveau de la Mer', 1843, p. 15-40. See, also, Darwin, "on the Parallel Roads of Glen-Roy and Lochaber," in 'Philos. Trans. for' 1839, p. 60.

These banks lie nearly 650 feet above the present mean level of the sea, and reappear, according to Keilhau and Eugene Robert, in a north-northwest direction on the coasts of Spitzbergen, opposite the North Cape. Leopold von Buch, who was the first to draw attention to the high banks of shells at Tromsoe (latitude 69 degrees 40'), has, however, shown that the more ancient elevations on the North Sea appertain to a different class of phenomena, from the regular and gradual retrogressive elevations of the Swedish shores in the Gulf of Bothnia. This latter phenomenon, which is well attested by historical evidence, must not be confounded with the changes in the level of the soil occasioned by earthquakes, as on the shores of Chili and of Cutch, and which have recently given occasion to similar observations in other countries. It has been found that a perceptible sinking resulting from a disturbance of the strata of the upper surface sometimes occurs, corresponding with an elevation elsewhere, as, for instance, in West Greenland, according to Pingel and Graah, in Dalmatia and in Scania.

Since it is highly probable that the oscillatory movements of the soil, and the rising and sinking of the upper surface, were more strongly marked in the early periods of our planet than at present, we shall be less surprised to find in the interior of continents some few portions of the earth's surface lying below the general level of existing seas. Instances of this kind occur in the soda lakes described by General Andreossy, the small bitter lakes in the narrow Isthmus of Suez, the Caspian Sea, the Sea of Tiberias, and especially the Dead Sea.*

[footnote] *Humboldt, 'Asie Centrale', t. ii., p. 319-324; t. iii., p. 549-551. The depression of the Dead Sea has been successively determined by the barometrical measurements of Count Berton, by the more careful ones of Russegger, and by the trigonometrical survey of Lieutenant Symond, of the Royal Navy, who states that the difference of level between the surface of the Dead Sea and the highest houses of Jaffa is about 1605 feet. Mr. Alderson, who communicated this result to the Geographical Society of London in a letter, of the contents of which I was informed by my friend, Captain Washington, was of opinion (Nov. 28, 1841) that the Dead Sea lay about 1400 feet under the level of the Mediterranean. A more recent communication of Lieutenant Symond (Jameson's 'Edinburgh New Philosophical Journal', vol. xxxiv., 1843, p. 178) gives 1312 feet as the final result of two very accordant trigonometrical operations.

The level of the water in the two last-named seas is p 297 666 and 1312 feet below the level of the Mediterranean. If we could suddenly remove the alluvial soil which covers the rocky strata in many parts of the earth's surface, we should discover how great a portion of the rocky crust of the earth was then below the present level of the sea. The periodic, although irregularly alternating rise and fall of the water of the Caspian Sea, of which I have myself observed evident traces in the northern portions of its basin, appears to prove,* as do also the observations of Darwin on the coral seas,** that without earthquakes, properly so- called, the surface of the earth is capable of the same gentle and progressive oscillations as those which must have prevailed so generally in the earliest ages, when the surface of the hardening crust of the earth was less compact than at present.

[footnote] *'Sur la Mobilite du fond de la Mer Caspienne', in my 'Asie Centr.', t. ii., p. 283-294. The Imperial Academy of Sciences of St. Petersburgh in 1830, at my request, charged the learned physicist Lenz to place marks indicating the mean level of the sea, for definite epochs, in different places near Baku, in the peninsula of Abscheron. In the same manner, in an appendix to the instructions given to Captain (now Sir James C.) Ross for his Antarctic expedition, I urged the necessity of causing marks to be cut in the rocks of the southern hemisphere, as had already been done in Sweden and on the shores of the Caspian Sea. Had this measure been adopted in the early voyages of Bougainville and Cook, we should now know whether the secular relative changes in the level of the seas and land are to be considered as a general, or merely a local natural phenomenon, and whether a law of direction can be recognized in the points which have simultaneous elevation or depression.

[footnote] **On the elevation and depression of the bottom of the South Sea, and the diffrent areas of alternate movements, see Darwin's 'Journal', p. 557, 561-566.

The phenomena to which we would here direct attention remind us of the instability of the present order of things, and of the changes to which the outlines and configuration of continents are probably still subject at long intervals of time. That which may scarcely be perceptible in one generation, accumulates during periods of time, whose duration is revealed to us by the movement of remote heavenly bodies. The eastern coast of the Scandinavian peninsula has probably risen p 298 about 320 feet in the space of 8000 years; and in 12,000 years, if the movement be regular, parts of the bottom of the sea which lie nearest the shores, and are in the present day covered by nearly fifty fathoms of water, will come to the surface and constitute dry land. But what are such intervals of time compared to the length of the geognostic periods revealed to us in the stratified series of formations, and in the world of extinct and varying organisms! We have hitherto only considered the phenomena of elevation; but the analogies of observed facts lead us with equal justice to assume the possibility of the depression of whole tracts of land. The mean elevation of the non-mountainous parts of France amounts to less than 480 feet. It would not, therefore, require any long period of time, compared with the old geognostic periods, in which such great changes were brought about in the interior of the earth, to effect the permanent submersion of the northwestern part of Europe, and induce essential alterations in its littoral relations.

The depression and elevation of the solid or fluid parts of the earth -- phenomena which are so opposite in their action that the effect of elevation in one part is to produce an apparent depression in another -- are the causes of all the changes which occur in the configuration of continents. In a work of this general character, and in an impartial exposition of the phenomena of nature, we must not overlook the 'possibility' of a diminution of the quantity of water, and a constant depression of the level of seas. Thgere can scarcely be a doubt that, at the period when the temperature of the surface of the earth was higher, when the waters were inclosed in larger and deeper fissures, and when the atmosphere possessed a totally different character from what it does at present, great changes must have occurred in the level of seas, depending upon the increase and decrease of the liquid parts of the earth's surface. But in the actual condition of our planet, there is no direct evidence of a real continuous increase or decrease of the sea, and we have no proof of any gradual change in its level at certain definite points of observation, as indicated by the mean range of the barometer. According to experiments made by Daussy and Antonio Nobile, an increase in the height of the barometer would in itself be attended by a depression in the level of the sea. But as the mean pressure of the atmosphere at the level of the sea is not the same at all latitudes, owing to meteorological causes depending upon the direction of the wind and varying degrees of moisture, the p 299 barometer alone can not afford a certain evidence of the general change of level in the ocean. The remarkable fact that some of the ports in the Mediterranean were repeatedly left dry during several hours at the beginning of this century, appears to show that currents may by changes occurring in their direction and force, occasion a 'local'' retreat of the sea, and a permanent drying of a small portion of the shore, without being followed by any actual diminution of water, or any permanent depression of the ocean. We must, however, be very cautious in applying the knowledge which we have lately arrived at, regarding these involved phenomena, since we might otherwise be led to ascribe to water as the elder element, what ought to be referred to the two other elements, earth and air.

As the 'external' configuration of continents, which we have already described in their horizontal expansion, exercises, by their variously indented littoral outlines, a favorable influence on climate, trade, and the progress of civilization, so likewise does their internal articulation, or the vertical elevation of the soil (chains of mountains and elevated plateaux), give rise to equally important results. Whatever produces a polymorphic diversity of forms on the surface of our planetary habitation -- such as mountains, lakes, grassy savannas, or even deserts encircled by a band of forests -- impresses some peculiar character on the social condition of the inhabitants. Ridges of high land covered by snow impede intercourse; but a blending of low, discontinued mountain chains* and tracts of valleys, as we see so happily presented in the west and south of Europe, tends to the multiplication of meteorological processes and the products of vegetation, and, from the variety manifested in different kinds of cultivation in each district, even under the same degree of latitude, gives rise to wants that stimulate the activity of the inhabitants.

[footnote] *Humboldt, 'Rel. Hist.', t. iii., p. 232-234. See also, the able remarks on the configuration of the earth, and the position of its lines of elevation in Albrechts von Roon, 'Grundzugen der Erd Volker und Staatenkunde', Abth. i., 1837, s. 158, 270, 276.

Thus the awful revolutions, during which, by the action of the interior on the crust of the earth, great mountain chains have been elevated by the sudden upheaval of a portion of the oxydized exterior of our planet, have served, after the establishment of repose, and on the revival of organic life, to furnish a richer and more beautiful variety of individual forms, and in a great measure to remove from the earth that aspect of dreary p 300 uniformity which exercises so impoverishing an influence on the physical and intellectual powers of mankind.

According to the grand views of Elie de Beaumont, we must ascribe a relative age to each system of mountain chains* on the supposition that their elevation must necessarily have occurred between the period of the deposition of the vertically elevated strata and that of the horizontally inclined strata running at the base of the mountains.

[footnnote] *Leop. von Buch, 'Ueber die Geognostischen Systeme von Deutschland', in his 'Geogn. Briefen an Alexander von Humboldt', 1824, s. 265-271; Elie de Beaumont, 'Recherches sur les Revolutions de la Surface du Globe', 1829, p. 297-307.

The ridges of the Earth's crust -- elevations of strata which are of the same geognostic age -- appear, moreover, to follow one common direction. The line of strike of the horizontal strata is not always parallel with the axis of the chain, but intersects it, so that, according to my views,* the phenomenon of elevation of the strata, which is even found to be repeated in the neighboring plains, must be more ancient than the elevation of the chain.

[footnote] *Humboldt, 'Asie Centrale', t. i., p. 277-283. See, also my 'Essai sur le Gisement des Roches', 1822, p. 57, and 'Relat. Hist.', t. iii., p. 244-250.

The main direction of the whole continent of Europe (from southwest to northeast) is opposite to that of the great fissures which pass from northwest to southeast, from the mouths of the Rhine and Elbe, through the Adriatic and Red Seas, and through the mountain system of Putschi-Koh in Luristan, toward the Persian Gulf and the Indian Ocean. This almost rectangular intersection of geodesic lines exercises an important influence on the commercial relations of Europe, Asia, and the northwest of Africa, and on the progress of civilization on the formerly more flourishing shores of the Mediterranean.*

[footnote] *'Asie Centrale', t. i., p. 284, 286. The Adriatic Sea likewise follows a direction from S.E. to N.W.

Since grand and lofty mountain chains so strongly excite our imagination by the evidence they afford of great terrestrial revolutions, and when considered as the boundaries of climates, as lines of separation for waters, or as the site of a different form of vegetation, it is the more necessary to demonstrate, by a correct numerical estimation of their volume, how small is the quantity of their elevated mass when compared with the area of the adjacent continnents. The mass of the Pyrenees, for instance, the mean elevation of whose summits, and the real quantity of whose base have been ascertained by accurate measurements, would if scattered over p 301 the surface of France, only raise its mean level about 115 feet. The mass of the eastern and western Alps would in like manner only increase the height of Europe about 21 1/2 feet above its present level. I have found by a laborious investigation,* which from its nature, can only give a maximum limit, that the center of gravity of the volume of the land raised above the present level of the sea in Europe and North America is respectively situated at an elevation of 671 and 748 feet, while it is at 1132 and 1152 feet in Asia and South America.

[footnote] *'De la hauteur Moyenne des Continents', in my 'Asie Centrale', t. i., p. 82-90, 165-189. The results which I have obtained are to be regarded as the extreme value ('nombres-limites'). Laplace's estimate of the mean height of continents at 3280 feet is at least three times too high. The immortal author of the 'Mecanique Celeste' (t. v., p. 14) was led to this conclusion by hypothetical views as to the mean depth of the sea. I have shown ('Asie Centr.', t. i., p. 93) that the old Alexandrian mathematicians, on the testimony of Plutarch ('in Aemilio Paulo', cap. 15), believed this depth to depend on the height of the mountains. The height of the center of gravity of the volume of the continental masses is probably subject to slight variations in the course of many centuries.

These numbers show the low level of norther regions. In Asia the vast steppes of Siberia are compensated for by the great elevations of the land (between the Himalaya, the North Thibetian chain of Kuen-lun, and the Celestial Mountains), from 28 degrees 30' to 40 degrees north latitude. We may, to a certain extent, trace in these numbers the portions of the Earth in which the Plutonic forces were most intensely manifested in the interior by the upheaval of continental masses.

There are no reasons why these Plutonic forces may not, in future ages, add new mountain systems to those which Elie de Beaumont has shown to be of such different ages, and inclined in such different directions. Why should the crust of the Earth have lost its property of being elevated in the ridges? The recently-elevated mountain systems of the Alps and the Cordilleras exhibit in Mont Blanc and Monte Rosa, in Sorata, Illimani, and Chimborazo, colossal elevations which do not favor the assumption of a decrease in the intensity of the subterranean forces. All geognostic phenomena indicate the periodic alternation of activity and repose;* but the quiet we now enjoy is only apparent.

[footnote] *'Zweiter Geologischer Brief von Elie de Beaumont an Alexander von Humboldt', in Poggendorf's 'Annalen', bd. xxv., s. 1-58.

The tremblings which still agitate the surface under all latitudes, and in every species of rock, the elevation of Sweden, the appearance of new islands of eruption, are all conclusive as to the unquiet condition of our planet.

p 302 The two envelopes of the solid surface of our planet -- the liquid and the aeriform -- exhibit, owing to the mobility of their particles, their currents, and their atmospheric relations, many analogies combined with the contrasts which arise from the great difference in the condition of their aggregation and elasticity. The depths of ocean and of air are alike unknown to us. At some few places under the tropics no bottom has been found with soundings of 276,000 (or more than four miles), while in the air, if, according to Wollaston, we may assume that it has a limit from which waves of sound may be reverberated, the phenomenon of twilight would incline us to assume a height at least nine times as great.*

[footnote] *[See Wilson's Paper, 'On Wollaston's Argument from the Limitation of the Atmosphere as to the finite Divisibility of Matter.' -- 'Trans. of the Royal Society of Edinb.', vol. xvi., p. 1, 1845.] -- Tr.

The aërial ocean rests partly on the solid earth, whose mountain chains and elevated plateaux rise, as we have already seen, like green wooded shoals, and partly on the sea, whose surface forms a moving base, on which rest the lower, denser, and more saturated strata of air.

Proceeding upward and downward from the common limit of the aërial and liquid oceans, we find that the strata of air and water are subject to determinate laws of decrease of temperature. This decrease is much less rapid in the air than in the sea, which has a tendency under all latitudes to maintain its temperature in the strata of water most contiguous to the atmosphere, owing to the sinking of the heavier and more cooled particles. A large series of the most carefully conducted observations on temperature shows us that in the ordinary and mean condition of its surface, the ocean from the equator to the forty-eighth degree of north and south latitude is somewhat warmer than the adjacent strata of air.*

[footnnote[ *Hamboldt, 'Relation Hist.', t. iii., chap. xxix., p. 514-530.

Owing to this decrease of temperature at increasing depths, fishes and other inhabitants of the sea, the nature of whose digestive and respiratory organs fits them for living in deep water, may even, under the tropics, find the low degree of temperature and the coolness of climate characteristic of more temperate and more northern latitudes. This circumstance, which is analogous to the prevalence of a mild and even cold air on the elevated plains of the torrid zone, exercises a special influence on the migration and geographical distribution of many marine animals. Moreover, the depths at which fishes live, modify, by the increase of pressure, their cutaneous respiration, and the p 303 oxygenous and nitrogenous contents of the swimming bladders.

As fresh and salt water do not attain the maximum of their density at the same degree of temperature, and as the saltness of the sea lowers the thermometrical degree corresponding to this point, we can understand how the water drawn from breat depths of the sea during the voyages of the Kotzebue and Dupetit-Thouars could have been found to have only the temperature of 37 degrees and 36.5 degrees. This icy temperatureof sea water, which is likewise manifested at the depths of tropical seas, first led to a study of the lower polar currents, which move from both poles toward the equator. Without these submarine currents, the tropical seas at those depths could only have a temperature equal to the local maximum of cold possessed by the falling particles of water at the radiating and cooled surface of the tropical sea. In the Mediterranean, the cause of the absence of such a refrigeration of the lower strata is ingeniously explained by Arago, on the assumption that the entrance of the deeper polar currents into the Straits of Gibraltar, where the water at the surface flows in from the Atlantic Ocean from west to east, is hindered by the submariine counter-currents which move from east to west, from the Mediterranean into the Atlantic.

The ocean, which acts as a general equalizer and moderator of climates, exhibits a most remarkable uniformity and constancy of temperature, especially between 10 degrees north and 10 degrees south latitude,* over spaces of many thousands of square miles, at a distance from land where it is not penetrated by currents of cold and heated water.

[footnote] *See the series of observations made by me in the South Sea, from 8 degrees 5' to 13 degrees 16' N. lat., in my 'Asie Centrale', t. iii., p. 234.

It has therefore, been justly observed, that an exact and long-continued investigation of these thermic relations of the tropical seas might most easily afford a solution to the great and much-contested problem of the permanence of climates and terrestrial temperatures.*

[footnote] *We might (by means of the temperature of the ocean under the tropics) enter into the consideration of a question which has hitherto remained unanswered, namely, that of the constancy of terrestrial temperatures, without taking into account the very circumscribed local influences arising from the diminution of wood in the plains and on mountains, and the drying up of lakes and marshes. Each age might easily transmit to the succeeding one some few data, which would perhaps furnish the most simple, exact, and direct means of deciding whether the sun, which is almost the sole and exclusive source of the heat of our planet, changes its physical constitution and splendor, like the greater number of the stars, or whether, on the contrary, that luminary has attained to a permanent condition." -- Arago, in the 'Comptes Rendus des Seances de l'Acad. des Sciences', t. ii., p. 321, 327.

Great changes in the luminous disk of the sun would, p 304 if they were of long duration, be reflected with more certainty in the mean temperature of the sea than in that of the solid land.

The zones at which occur the maxima of the oceanic temperature and of the density (the saline contents) of its waters, do not correspond with the equator. The two maxima are separated from one another, and the waters of the highest temperature appear to form two nearly parallel lines north and south of the geographical equator. Lenz, in his voyage of circumnavigation, found in the Pacific the maxima of density in 22 degrees north and 17 degrees south latitude, while its minimum was situated a few degrees to the south of the equator. In the region of calms the solar heat can exercise but little influence on evaporation, because the stratum of air impregnated with saline aqueous vapor, which rests on the surface of the sea, remains still and unchanged.

The surface of all connected seas must be considered as having a general perfectly equal level with respect to their mean elevation. Local causes (probably prevailing winds and currents) may, however, produce permanent, although trifling changes in the level of some deeply indented bays, as for instance, the Red Sea. The highest level of the water at the Isthmus of Suez is at different hours of the day from 24 to 30 feet above that of the Mediterranean. The form of the Straits of Bab-el-Mandeb, through which the waters appear to find an easier ingress than egress, seems to contribute to this remarkable phenomenon, which was known to the ancients.*

[[footnote] *Humboldt, 'Asie Centrale', t. ii., p. 321, 327.

The admirable geodetic operations of Coraboeuf and Delcrois show that no perceptible difference of level exists between the upper surfaces of the Atlantic and the Mediterranean, along the chain of the Pyrenees, or between the coasts of northern Holland and Marseilles.*

[footnote] *See the numerical results in p. 328-333 of the volume just named. From the geodesical levelings which, at my request, my friend General Bolivar caused to be taken by Lloyd and Falmare, in the years 1828 and 1829, it was ascertained that the level of the Pacific is at the utmost 3 1/2 feet higher than that of the Caribbean Sea; and even that at different hours of the day each of the seas is in turn the higher, according to their respective hours of flood and ebb. If we reflect that in a distance of 64 miles, comprising 933 stations of observation, an error of three feet would be very apt to occur, we may say that in these new operations we have further confirmation of the equilibrium of the waters which communicate round Cape Horn. (Arago, in the 'Annuaire du Bureau des Longitudes pour' 1831, p. 319.) I had inferred from barometrical observations instituted in 1799 and 1804, that if there were any difference between the level of the Pacific and the Atlantic (Carribean Sea), it could not exceed three meters (nine feet three inches). See my 'Relat. Hist.', t. iii., p. 555-557, and 'Annales de Chimie', t. i., p. 55-64. The measurements, which appear to establish an excess of height for the waters of the Gulf of Mexico, and for those of the northern part of the Adriatic Sea, obtained by combining the trigonometrical operations of Delcrois and Choppin with those of the Swiss and Austrian engineers, are open to many doubts. Notwithstanding the form of the Adriatic, it is improbable that the level of its waters in its northern portion should be 28 feet higher than that of the Mediterranean at Marseilles, and 25 feet higher than the level of the Atlantic Ocean. See my 'Asie Centrale', t. ii., p. 332.

p 305 Disturbances of equilibrium and consequent movements of the waters are

## partly irregular and transitory, dependent upon winds, and producing waves

which sometimes, at a distance from the shore and during a storm, rise to a height of more than 35 feet; partly regular and periodic, occasioned by the position and attraction of the sun and moon, as the ebb and flow of the tides; and partly permanent, although less intense, occurring as oceanic currents. The phenomena of tides, which prevail in all seas (with the exception of the smaller ones that are completely closed in, and where the ebbing and flowing waves are scarcely or not at all perceptible), have been perfectly explained by the Newtonian doctrine, and thus brought "within the domain of necessary facts." Each of these periodically-recurring oscillations of the waters of the sea has a duration of somewhat more than half a day. Although in the open sea they scarcely attain an elevation of a few feet, they often rise considerably higher where the waves are opposed by the configuration of the shores, as for instance, at St. Malo and in Nova Scotia, where they reach the respective elevation of 50 feet, and of 65 to 70 feet. "It has been shown by the analysis of the great geometrician Laplace, that, supposing the depth to be wholly inconsiderable when compared with the radius of the earth, the stability of the equilibrium of the sea requires that the density of its fluid should be less than that of the earth; and, as we have already seen, the earth's density is in fact five times greater than that of water. The elevated parts of the land can not therefore be overflowed, nor can the remains of marine animals found on the summits of mountains have been conveyed to those localities by any previous high tides.*

[footnote] *Bessel, 'Ueber Fluth und Ebbe', in Schumacher's 'ahrbuch', 1838, s. 225.

It is no slight

This material taken from pages 305-362

COSMOS: A Sketch of the Physical Description of the Universe, Vol. 1 by Alexander von Humboldt

Translated by E C Otte

from the 1858 Harper & Brothers edition of Cosmos, volume 1 --------------------------------------------------

p 305 [balance of p 305 is in file "09 Humboldt"] It is no slight p 306 evidence of the importance of analysis, which is too often regarded with contempt among the unscientific, that Laplace's perfect theory of tides has enabled us, in our astronomical ephemerides, to predict the height of spring-tides at the periods of new and full moon, and thus put the inhabitants of the sea-shore on their guard against the increased danger attending these lunar revolutions.

Oceanic currents, which exercise so important an influence on the intercourse of nations and on the climatic relations of adjacent coasts, depend conjointly upon various causes, differing alike in nature and importance. Among these we may reckon the periods at which tides occur in their progress round the earth; the duration and intensity of prevailing winds; the modifications of density and specific gravity which the particles of water undergo in consequence of differences in the temperature and in the relative quantity of saline contents at different latitudes and depths;* and, lastly, the horary variations of the atmospheric pressure, successively propagated from east to west, and occurring with such regularity in the tropics.

[footnote] *The relative density of the particles of water depends simultaneously on the temperature and on the amount of the saline contents -- a circumstance that is not sufficiently borne in mind in considering the cause of currents. The submarine current, which brings the cold polar water to the equatorial regions, would follow an exactly opposite course, that is to say, from the equator toward the poles, if the difference in saline contents were alone concerned. In this view, the geographical distribution of temperature and of density in the water of the ocean, under the different zones of latitude and longitude, is of great importance. The numerous observations of Lenz (Poggendorf's 'Annalen', bd. xx., 1830, s. 129), and those of Captain Beechey, collected in his 'Voyage to the Pacific', vol. ii., p. 727, deserve particular attention. See Humboldt, 'Relat. Hist.', t. i., p. 74, and 'Asie Centrale', t. iii., p. 346.

These currents present a remarkable spectacle; like rivers of uniform breadth, they cross the sea in different directions, while the adjacent strata of water, which remain undisturbed, form, as it were, the banks of these moving streams. This diffrence between the moving waters and those at rest is most strikingly manifested where long lines of sea-weed, borne onward by the current, enable us to estimate its velocity. In the lower strata of the atmosphere, we may sometimes, during a storm, observe similar phenomena in the limited aerial current, which is indicated by a narrow line of trees, which are often found to be overthrown in the midst of a dense wood.

The general movement of the sea from east to west between p 307 the tropics (termed the equatorial or rotation currnt) is considered to be owing to the propagation of tides and to the trade winds. Its direction is changed by the resistance it experiences from the prominent eastern shores of continents. The results recently obtained by Daussy regarding the velocity of this current, estimated from observations made on the distances traversed by bottles that had purposely been thrown into the sea, agree within one eighteenth with the velocity of motion (10 French nautical miles, 952 toises each, in 24 hours) which I had found from a comparison with earlier experiments.*

[footnote] *Humboldt, 'Relat. Hist.', t. i., p. 67; 'Nouvelles Annales des Voyages', 1839, p. 255.

Christopher Columbus, during his third voyage, when he was seeking to enter the tropics in the meridian of Teneriffe, wrote in his journal as follows:* "I regard it as proved that the waters of the sea move from east to west, as do the heavens ('las aguas van con los cielos'), that is to say, like the apparent motion of the sun, moon, and stars."

[footnote] *Humboldt, 'Examen Crit. de l'Hist. de la Geogr.', t. iii., p. 100. Columbus adds shortly after (Navarrete, 'Coleccion de los Viages y Descubrimientos de los Espanoles', t. i., p. 260), that the movement is strongest in the Caribbean Sea. In fact, Rennell terms this region, "not a current, but a sea in motion". ('Investigation of Currents', p. 23). 66-74.

The narrow currents, or true oceanic rivers which traverse the sea, bring warm water into higher and cold water into lower latitudes. To the first class belongs the celebrated Gulf Stream,* which was known to Anghiera, and more especially to Sir Humphrey Gilbert in the sixteenth century.

[footnote] *Humboldt, 'Examen Critique', t. ii., p. 250; 'Relat. Hist.', t. i., p. 66-74.

[footnote] *Petrus Martyr de Anghiera, 'De Rebus Oceanicis et Orbe Novo', Bas., 1523, Dec. iii., lib. vi., p. 57. See Humboldt, 'Examen Critique', t. ii., p. 254-257, and t. iii., p. 108.

Its first impulse and origin is to be sought to the south of the Cape of Good Hope; after a long circuit it pours itself from the Caribbean Sea and the Mexican Gulf through the Straits of the Bahamas, and, following a course from south-southwest to north-northeast, continues to recede from the shores of the United States, until, further deflected to the eastward by the Banks of Newfoundland, it approaches the European coasts, frequently throwing a quantity of tropical seeds ('Mimosa scandens, Guilandina bonduc, Dolichos urens') on the shores of Ireland, the Hebrides, and Norway. The northeastern prolongation tends to mitigate the cold of the ocean, and to ameliorate the climate on the most northern extremity of Scandinavia. At the point where the Gulf Stream p 308 is deflected from the Banks of Newfoundland toward the east, it sends off branches to the south near the Azores.*

[footnote] *Humboldt, 'Examen Crit.', t. iii., p. 64-109

This is the situation of the Sargasso Sea, or that great bank of weeds which so vividly occupied the imagination of Christopher Columbus, and which Oviedo calls the sea-weed meadows ('Praderias de yerva'). A host of small marine animals inhabits these tently-moved and evergreen masses of 'Fucus natans', one of the most generally distributed of the social plants of the sea.

The counterpart of this current (which in the Atlantic Ocean, between Africa, America, and Europe, belongs almost exclusively to the northern hemisphere) is to be found in the South Pacific, where a current prevails, the effect of whose low temperature on the climate of the adjacent shores I had an opportunity of observing in the autumn of 1802. It brings the cold waters of the high southern latitudes to the coast of Chili, follows the shores of this continent and of Peru, first from south to north, and is then deflected from the Bay of Arica onward from south-southeast to north-northwest. At certain seasons of the year the temperature of this cold oceanic current is, in the tropics, only 60 degrees, while the undisturbed adjacent water exhibits a temperature of 81.5 degrees and 83.7 degrees. On that part of the shore of South America south of Payta, which inclines furthest westward, the current is suddenly deflected in the same direction from the shore, turning so sharply to the west that a ship sailing northward passes suddenly from cold into warm water.

It is not known to what depth cold and warm oceanic currents propagate their motion; but the deflection experienced by the South African current, from the Lagullas Bank, which is fully from 70 to 80 fathoms deep, would seem to imply the existence of a far-extending propagation. Sand banks and shoals lying beyond the line of these currents may, as was first discovered by the admirable Benjamin Franklin, be recognized by the coldness of the water over them. This depression of the temperature appears to me to depend upon the fact that, by the propagation of the motion of the sea, deep waters rise to the margin of the banks and mix with the upper strata. My lamented friend, Sir Humphrey Davy, ascribed this phenomenon (the knowledge of which is often of great practical utility in securing the safety of the navigator) to the descent of the particles of water that had been cooled by nocturnal radiation p 309 and which remain nearer to the surface, owing to the hinderance placed in the way of their greater descent by the intervention of sand-banks. By his observations Franklin may be said to have converted the thermometer into a sounding line. Mists are frequently found to rest over these depths, owing to the condensation of the vapor of the atmosphere by the cooled waters. I have seen such mists in the south of Jamaica, and also in the Pacific, defining with sharpness and clearness the form of the shoals below them, appearing to the eye as the aerial reflection of the bottom of the sea. A still more striking effect of the cooling produced by shoals is manifested in the higher strata of air, in a somewhat analogous manner to that observed in the case of flat coral reefs, or sand islands. In the open sea, far from the land, and when the air is calm, clouds are often observed to rest over the spots where shoals are situated, and their bearing may then be taken by the compass in the same manner as that of a high mountain or isolated peak.

Although the surface of the ocean is less rich in living forms than that of continents, it is not improbable that, on a further investigation of its depths, its interior may be found to possess a greater richness of organic life than any other portion of our planet. Charles Darwin, in the agreeable narrative of his extensive voyages, justly remarks that our forests do not conceal so many animals as the low woody regions of the ocean, where the sea-weed rooted to the bottom of the shoals, and the severed branches of fuci, loosened by the force of the waves and currents, and swimming free, unfold their delicate foliage, upborne by air-cells.*

[footnote] *[See 'Structure and Distribution of Coral Reefs', by Charles Darwin, London, 1842. Also, 'Narrative of the Surveying Voyage of H.M.S. "Fly" in the Eastern Archipelago, during the Years ' 1842-1846, by J. B. Jukes, Naturalist to the expedition, 1847.] -- Tr.

The application of the microscope increases, in the most striking manner, our impression of the rich luxuriance of animal life in the ocean, and reveals to the astonished senses a consciousness of the universality of life. In the oceanic depths, far exceeding the height of our loftiest mountain chains, every stratum of water is animated with polygastric sea-worms, Cyclidiae and Ophrydinae. The waters swarm with countless hosts of small luminiferous animalcules, Mammaria (of the order of Acalephae), Crustacea, Peridinea, and circling Nereides, which when attracted to the surface by peculiar meteorological conditions, convert every wave into a foaming band of flashing light.

p 310 The abundance of those marine animalcules, and the animal matter yielded by their rapid decomposition are so vast that the sea water itself becomes a nutrient fluid to many of the larger animals. However much this richness in animated forms, and this multitude of the most various and highly-developed microscopic organisms may agreeably excite the fancy, the imagination is even more seriously, and, I might say, more solemnly moved by the impression of boundlessness and immeasureability, which are presented to the mind by every sea voyage. All who possess an ordinary degree of mental activity, and delight to create to themselves an inner world of thought, must be penetrated with the sublime image of the infinite, when gazing around them on the vast and boundless sea, when involuntarily the glance is attracted to the distant horizon, where air and water blend together, and the stars continually rise and set before the eyes of the mariner. This contemplation of the eternal play of the elements is clouded, like every human joy, by a touch of sadness and of longing.

A peculiar predilection for the sea, and a grateful remenbrance of the impression which it has excited in my mind, when I have seen it in the tropics in the calm of nocturnal rest, or in the fury of the tempest, have alone induced me to speak of the individual enjoyment afforded by its aspect before I entered upon the consideration of the favorable influence which the proximity of the ocean has incontrovertibly exercised on the cultivation of the intellect and character of many nations, by the multiplication of those bands which ought to encircle the whole of humanity, by affording additional means of arriving at a knowledge of the configuration of the earth, and furthering the advancement of astronomy, and of all other mathematical and physical sciences. A portion of this influence was at first limited to the Mediterranean and the shores of southwestern Africa, but from the sixteenth century it has widely spread, extending to nations who live at a distance from the sea, in the interior of continents. Since Columbus was sent to "unchain the ocean"* (as the unknown voice whispered to him in a dream when he lay on a sick-bed near p 311 the River Belem), man has ever boldly ventured onward toward the discovery of unknown regions.

[footnote] *The voice addressed him in these words, "Maravillosamente Dios hizo sonar tu nombre en la tierra; de los atamientos de la mar Oceana, que estaban cerrados con cadenas tan fuertes, te dió las llaves" -- "God will cause thy name to be wonderfully resounded through the earth, and give thee the keys of the gates of the ocean, which are closed with strong chains." The dream of Columbus is related in the letter to the Catholic monarchs of July the 7th, 1503. (Humboldt, 'Examen Critique', t. iii., p. 234.)

The second external and general covering of our planet, the aerial ocean, in the lower strata, and on the shoals of which we live, presents six classes of natural phenomena, which manifest the most intimate connection with one another. They are dependent on the chemical composition of the atmosphere, the variations in its transparency, polarization, and color, its density or pressure, its temperature and humidity, and its electricity. The air contains in oxygen the first element of physical animal life, and besides this benefit, it possesses another, which may be said to be of a nearly equally high character, namely, that of conveying sound; a faculty by which it likewise becomes the conveying sound; a faculty by which it likewise becomes the conveyer of speech and the means of communicating thought, and consequently of maintaining social intercourse. If the Earth were deprived of an atmosphere, as we suppose our moon to be, it would present itself to our imagination as a soundless desert.

The relative quantities of the substances composing the strata of air accessible to us have, since the beginning of the nineteenth century, become the object of investigations, in which Gay-Lussac and myself have taken an

## active part; it is however, only very recently that the admirable labors of

Dumas and Boussingault have, by new and more accurate methods, brought the chemical analysis of the atmosphere to a high degree of perfection. According to this analysis, a volume of dry air contains 20.8 of oxygen, and 79.2 of nitrogen, besides from two to five thousandth parts of carbonic acid gas, a still smaller quantity of carbureted hydrogen gas,* and, according to the important experiments of Saussure and Liebig, traces of ammoniacal vapors,** from which plants derive their nitrogenous contents.

[footnote] *Boussingault, 'Recherches sur la Composition de l'Atmosphere', in the 'Annales de Chimie et de Physique', t. lvii., 1834, p. 171-173; and lxxi. 1839, p. 116. According to Boussingault and Lewy, the proportion of carbonic acid in the atmosphere at Audilly, at a distance, therefore, from the exhalations of a city, varied only between 0.00028 and 0.00031 in volume.

[footnote] **Liebig, in his important work, entitles 'Die Organische Chemie in ihrer Anwendung auf Agricultur und Physiologie', 1840, s. 62-72. On the influence of atmospheric electricity in the production of nitrate of ammonia, which, coming into contact with carbonate of lime, is changed into carbonate of ammonia, see Boussingault's 'Economie Rurale consideree dans ses Rapports avec la Chimie et la Meteorologie', 1844, t. ii., p. 247, 267, and t. i., p. 84.

Some observations of Lewy render it probable that the quantity of oxygen varies perceptibly p 312 but slightly, over the sea and in the interior of continents, according to local conditions or to the seasons of the year. We may easily conceive that changes in the oxygen held in solution in the sea, produced by microscopic animal organisms, may be attended by alterations in the strata of air in immediate contact with it.*

[footnote] *Lewy, in the 'Comptes Rendus de l'Acad. des Sciences', t. xvii.,