« AnteriorContinuar »
The science of Geography is popularly understood as treating of the division of the lands upon the surface of the earth into various empires, kingdoms, and provinces, instituted by man; and this, doubtless, forms that important part of the science which is properly termed political, or moral, geography. But there is another, far more extensive, more important, and more really interesting division, which treats of the natural history of the earth; of its natural divisions by seas, mountain-chains, rivers, and valleys; of the constitution of its outer crust; of the laws which govern the climates of different portions; of its animate productions; this is called Physical Geography, and, as it is now understood, in the true sense of the word, partly comprises the various sciences of Geology, Zoology, Botany, Meteorology, &c.
It may be easily conceived, that there can be few studies more important to man than this of physical geography; every endeavour, therefore, to render some of its facts more intelligible to the general reader, must be a laudable task; nor does it require any profound knowledge or deep study to be able to comprehend many of its leading principles.
When we consider the numberless differences between countries, in regard to their climate, soil, and productions, animal and vegetable, it might seem almost impossible to investigate the causes of the great diversity which really exists: investigation, however, the object of the science in question, is daily extending; and all the peculiarities are found to be mutually dependent on a comparatively few great principles. Vol. V,
The necessarily intimate connexion between the organic productions of different countries and their climate, renders it important to explain the laws by which this connexion is governed. This is one object of the science of Meteorology, and in order to illustrate some parts of this paper, we must enter into a brief general notice on this subject.
If the whole surface of the earth were land, without any difference of soil, or any inequalities of level, the average temperature of the climates of different zones would decrease equably from the equator towards the poles, because the rays of the sun, by passing vertically through the atmosphere, would heat the tropical much more than the temperate regions, where the solar beams would lose some of their effect by having to traverse the air more obliquely, or to pass a greater distance through it. Temperate regions also would be much warmer than the polar, where little heat would be obtained at all from the sun, the great source of heat.
The first and most important cause of disturbance of this supposed regularity, arises from the irregular division of the surface into land and water. The ocean is of a more equal temperature throughout the globe than the land; partly because it is less easily heated by the sun's rays, and partly because of the constant mingling of its | waters by the currents and the motion of the waves, these being produced by the motion of the earth on its axis, and by the analogous currents, called Winds, in the aerial ocean, or atmosphere. From these two causes, the waters of the ocean, at more than 700 feet in depth, are found to be of the same temperature all over the globe.
An island in the middle of the ocean will hence have a cooler climate than the adjacent continents, if it be situated within the Tropics, and a warmer one if it lie more towards the Poles: because, in the first case, being surrounded by a body of water cooler than the land, the temperature of the island will be reduced; and, on the second supposition, the surrounding seas being warmer than the land under the same latitude, the temperature of the island will be raised.
Thus, the islands of the Atlantic, as Madeira, the Canaries, St. Helena, &c, enjoy a moderate climate, while the centre of the African continent parallel to them, is nearly uninhabitable, from its burning heat. On the other hand, England has a higher mean temperature* than the parts of the adjoining continent of Europe, under the same latitude: as Denmark, Sweden, and North Germany: this rule is, however, so far modified by other causes, that it Is by no means of constant application. In an island the atmosphere is more moist from the evaporation of the surrounding waters, and therefore more rain falls in the year; while in some vast inland plains the air is perfectly dry, and no rain ever falls.
That the general, or mean, .eniperature of any country depends chiefly on the prevailing winds, is well known. It is obvious, that if the wind blows more days in the year from the north, it will causo the place to be colder, generally, than it would naturally be; and the reverse, if the usual wind conies over a heated plain or over the ocean. The prevalent wind in England is from the south-west, and the mild damp climate of our country is greatly attributable to this wind, which comes over the Atlantic Ocean, loaded with moisture and raised in temperature.
A principal cause of the average tempei attire of the climate of any place, depends on its elevation above the level of the sea; or on its being at a greater or less distance from the centre of the earth. The lower part of the atmosphere is the warmest, and the heat decreases as we ascend in the air, so that in every part of the globe, there is an altitude where water is always frozen. This is called the line of perpetual snow, because the portions of mountains which riso ab.ive this height are always snow-clad. It is obvious, that the nearer the place is to the equator, the higher into the air must we ascend, to get into the temperature which is met with nearer the earth, at places situated at a greater distance from it. At the poles, and for a great distance from them, the water at the surface of the earth is always frozen t. Hence, a plain raised many thousand feet above the level of the sea, though under the tropics, may be as cold, or colder than England, or other places in the Temperate Zones.
Asia affords a striking illustration of these facts. The central Table-Land is the^highest part of the globe of any extent; and being surrounded with mountains covered with snow, has a temperature far below that of southern Europe on the same parallel; while on passing the southern, or Himalaya chain, the traveller descending into the peninsula of India enters a tropical climate. This partly arises from the nearer position of the country to the equator, but, chiefly, from its lower level; from its being sheltered to the North by the mountains just mentioned; and from the prevailing winds blowing from the south-east or south-west.
That the character as well as the temperature of a climate, must depend very much on the quantity of rain which falls, is also obvious, and this and the vegetation of a country mutually act on each other, as cause and effect. This very interesting fact we will explain by an example, which will be more intelligible than scientific speculations.
Let us consider an extended plain of sand in any tropical country, as Africa. The sun will heat the surface and the
• In all countries there is a summer and a winter, or a difference of seasons; the former being hotter dom the greater length of the •lay. or of thp time the sun is above the horizon, and therefore acting •n the land and air: the mean annual temperature is the average of ihc*e different temperatures, as found by repeated observations; and is that, nearly, of the spring or autumn of the year in each country. The summer-heat on the continents is greater, and the cold of winter more intense, than on an island; the former are said to have an excessive climate, and the latter an insular climate; yet the mean temperature of a place on the continent, may be the same as one on an *land in the same latitude. The reader must bear all these facts Mi mind, and he will perceive that it is impossible to give any general rule on this subject.
t It has been calculated, that the mean temperature of the equator round the globe is about 85°, and that at the poles is —10°, or ten degrees below zero, water freezing at 32° above zero. In the tropics, the line of perpetual snow is at about the height of 16,000 feet above the sea: in latitude 45°, (that of Venice and South Europe,) it is at about 6000 feet.
air, but the earth accumulating the heat more rapidly and more permanently, it will communicate to the lower portion of the air, a greater degree of temperature than it would otherwise have: and from a well-known law, this heated portion of air would rise, or ascend, and its place would be supplied with colder air coming from a distance, which would be heated in its turn, and rise, and so on, producing a constant current upwards of hot air. Now this current would prevent the clouds passing over the spot, from condensing by cold into rain, hence no rain would fall on the parched soil, and it is certain, that without moisture, little or no vegetation can be produced.
But if we suppose the same plain to consist, instead of barren sand, of some earth favourable for the growth of grass, or moss, or any verdure, this would screen the earth from the accumulating heat. Little or no upward current would arise, clouds would be condensed in the higher regions, and rain would fall, or at least, the vapours would be condensed by the colder vegetable clothing, and this dew would accelerate the growth of fresh plants, till in time, a forest might cover the former naked expanse. These trees would still further shado the earth, and preserve its moistened surface from evaporation, and would also attract moisture, and consequently keep down the temperature of such a country.
When, however, a sandy plain is surrounded by lofty mountains, a quantity of water is always collected from the atmosphere by their summits, and naturally descending their sides, irrigates the plain by rivers, which counteract the aridity that would otherwise accompany it; or if not abundant enough to form rivers, at least forms springs, as is the case with the Oases of Africa. (See p. 39.}
It is very difficult to ascertain or to be aware of the difference of level of adjacent countries, by simple ocular inspection. A valley intersecting a plain, is obvious to every one traversing it, but if a person ascend a chain of hills rising from a plain, on descending on the other side he cannot immediately tell whether he is come down to the same level as the plain, or whether he is above or below it.
We all know that the land, genorally, must be highei than the level of the sea, or the sea would overllow it and wo know that the land is not equally high, because we see it shelve down to the shore in some parts, or form very steep cliffs in others, while we see valleys and mountains varying it on all sides. Few persons, however, ore aware, that the difference in the level of extensive regions is so great, that while the Table-Land of Asia is raised 10,000 feet above the level of the sea, thero is a vast extent, of about 18,000 square miles, in the neighbourhood of the Caspian Sea, that is absolutely below the level of the ocean.
It is now known, that in the course of many ages, great revolutions in the surface of the globe are brought about by the slow, hut constant, wearing down of all the elevated parts, by the action of water, and also through the elevation of new islands and continents from the bottom of the deep by earthquakes J. There is conclusive evidence of the greater part of Europe having been raised from the deep, since the existence of other more ancient countries.
Now, if we suppose a large tract of the bed of the ocean to be gradually raised till it forms dry land, it will for many ages present the appearance of a level tract or plain, and such is probably the origin of most of those extensive deserts, steppes, plains, &c, which are found in different parts of the world.
We purpose, in this paper, to give a popular account of some of these, since they are less known from their being comparatively uninhabited, and little visited; and the varieties in their appearance and their productions, with the few common points of resemblance, will afford a useful and entertaining lesson, and enable us to judge of the inexhaustible fund of amusement and of know ledge which Physical Geography presents.
We shall commence with the plains in South America, called
At the foot of the lofty range of mountains in the province of Caraccas, thero lies a vast plain, stretching southwards
far beyond the limits of the visible horizon. The contrast presented on leaving the fertile, undulating valleys of that country, and the shores of the lake of Tacaragua, dotted over with islands covered with luxuriant vegetation, is indescribable. The traveller quits a beautiful tract, covered with the palms, sugar-canes, &c, of a tropical land, to enter on a barren desert. No hill, no elevation, disturbs the monotony of the scene, except here and there flat banks, so called by the natives, raised only a few feet above the general level, but, from their slight elevation and their great extent, hardly distinguishable. These are sometimes two hundred square mile's in extent, and appear like islands in a waveless sea.
That this plain was once the bottom of an ocean, tnere is conclusive evidence, from those facts which speak more decisively than any historic human records; and at that time the banks formed shoals analogous to those in our present seas. The observant and scientific traveller has his imagination carried back to this primaeval period, by an optical illusion presented to his view. When at night the eye ranges over the level tract to the extreme limit of vision, the level line which forms the horizon reminds him of that of a tranquil ocean*, and the stars as they rise or set, are absolutely reilected in the stratum of air that lies on the earth, as if seen in real water. This phenomenon arises from the same causes which produce the mirage of the desert, in flay time; that illusion which mocks the thirsty and fainting traveller with the appearance of lakes of water, when journeying over hot sandy plains,.
But the real ocean, with its associations, is a pleasing, though sublime object, while the "Llanos" of South America lie stretched out before the eye, like the naked ro;:ky crust of a worn-out planet. The interest they excite is of a peculiar kind, and arises only from their natural history. Unlike the deserts of Africa, they contain no Oases to recall the mind to earlier races of inhabitants; no carved monuments, no ruins, to suggest the idea of a past age of glory and renown; no fruit-trees run wild, to indicate that the diligence of past generations was exerted to provide food for their population. This portion of our globe seems estranged from all human interest; a wild arena for unfettered animal and vegetable existence.
The Llanos extend from the mountains on the coast of Caraccas to the forests of Guayana; from the snowy mountains of Merida to the great Delta of the Orinoco; in a south-westerly direction, they stretch, like an arm of the sea, from the rivers Mcta and Nichada, to the unfrequented sources of the Guaviare, comprising a surface of about sixteen thousand square miles. Though thus close to the equator, yet, from the physical geography of this continent, they do not resemble the Sahara of Africa in constant barrenness, but, during one half of the year, are covered with grass, like the Pampas of Buenos Aires, or the Table-Lands of central Asia.
The causes of the lower temperature and greater moisture of the climate of equinoctial America, compared with that of Africa, are to be found in the peculiar form of this part of the globe. Narrow, and much indented with seas and bays within the northern tropic, it presents but a comparatively small surface to the action of the sitn*s rays; while the great expanse towards the North Pole: an open ocean, over which the tropical winds come; the flatness of the eastern coast; the stream of cold sea-water which Hows from Terra del Fuego along the Peruvian coast; the number of mountain-chains rearing their snow-covered summits far above the clouds; the multitude of enormous
* That this effect of resemblance to a sea is not exaggerated, is proved by the evidence of Captain Hall, when speaking of another extensive plain,—a very conclusive authority on many subjects.
"Some of these singular places" (the prairies on the banks of the iMisaissippi,) are nearly level, others have a gently swelling or rolling surface. The grand prairie of the Illinois has specimens of both kinds, but its general character is level, with a few clumps of trees, and these far between. The resemblance to the sea which some of the prairies exhibited was really most singular. There is one spot in particular, near the middle of the grand prairie, where the ground happened to be of a rolling character, and where, excepting in the article of colour,—and that was not widely different from the tinge of some seas,—the similarity was so striking that I almost forgot *here I was. This deception was heightened by a circumstance krhich 1 had often heard mentioned, but the force of which none but a seaman could fully estimate; I mean the appearance of the distant insulated trees as they rose above the horizon, or receded from our view: they were so exactly like strange sails heaving in sight, that I am sure if two or three sailors had been present they would almost have agreed aa to what canvass these magical vessel! *r«r* carrying.——Xramfi in North America, vol, iii,
rivers; impenetrable forests, occupying the equatorial regions where the land is most extended; all concur to keep down the heat and aridity of America, compared with the African peninsula, which is diametrically opposed to it in all tl^ese characteristics. These peculiarities are sufficient to explain, why Africa and South America present the most opposito character of climates, aud the most different features of vegetation.
Though rhe Llanos are covered with a thin coating of fertile earth, and are periodically flooded by rains, so that they are decorated with luxuriant verdure; yet the neighbouring native tribes have never been enticed to leave the lovely valleys of the Caraccas and the coast, or the shores of the Orinoco, to settle in these wastes. On the first arrival of European and African settlers, these deserts were found nearly destitute of inhabitants. The Llanos are now especially appropriated to rearing cattle, though the management of animals yielding milk fit for human food was unknown to all the aborigines of the new continent.
Two kinds of native cattle pasture in the grass-plains of West Canada as well as in Mexico: the long-horned moufion, the original stem of the sheep, abounds on the dry, naked, calcareous rocks of California; and the camellike vikunnas, alpacas, and llamas, arc peculiar to the southern continent. Except the last, all these useful animals have preserved their natural freedom for thousands of years, the employment of milk and cheese as articles of food, like the culture of farinaceous grasses, being a characteristic distinction of the people of the old world.
Since, therefore, as it appears, the shepherd's life, that beneficial middle-state which fixes the wandering huntertnbes to the meadows, and prepares them for the pursuits of agriculture, was unknown to the original inhabitants of America, it is to this circumstance, that the absence of population in the Llanos, on their first discovery by Europeans, must be attributed. Hence appears also a variety of animal forms which have remained in a state of nature, uncontrolled by the presence of man.
Each continent of the globe has animals peculiar to it; many are only different species of genera found elsewhere; but there are many genera of animals peculiar to South America; though these are not sestrikingly different from the animals of the old world, as those of New Holland are from the animals i>f all the rest of the world.
In the Llanos are found, the agouti, of the same order as the guinea-pig, rabbit, porcupine, &c.; it is about the size of a hare, and has mauy of its habits. The armadillo, a singular animal, having a scaly hard shell, which is
flexible enough to give full scope to its motions, and is yet a secure defence from most enemies, belongs to the same order as the sloth, the ant-eater, &c, and lives on vegetable food, and burrows in the ground. The chiguire or capybara, another animal of the guinea-pig tribe, and the largest known; lives in herds on the banks of rivers, and feeds on fish and fruits. The chinchc, a species of marten, like our European pole-cat, possesses, but in a much greater degree, the power of defending itself, by emitting an odour, so intolerable, as seriously to affect men or animals exposed to it. Another, the mariputa, dwelling on tho banks of the Orinoco, is protected from the jaguar, its chief enemy, by the virulence and fcetidness of the effluvia which it emits.
Of the more formidable animals, the puma, or American lion, must be mentioned first; but both this, and the
jaguar, and other allied species, are well known to Europeans, from being seen in most menageries. These are but a few of the multitude of living creatures that swarm on these plains.
Nearly uninhabitable except to such animals, these plains would never have arrested the steps of those tribes who, Indian-like, prefer vegetable food, were not the Mauritia.or Fan-palm, found scattered over them here and there. The benefits of this important plant are widely! known: the stem attains a height of five and twenty feet, iii'about 120 or 150 years, and they form lovely groups of brilliant green in moist spots, something as our alders do. They preserve by their shade the humidity of the ground, and hence the Indians maintain, that the Mauritia myste- | riously attracts water to its roots*.
This tree alone supports the unsubdued nation of the Guaraunes, who dwell near the mouths of the Orinoco. They suspend mats made of the stalks of the leaves with great skill from stem to stem; and during the rainy season, when the Deltat is overflowed, they reside entirely in the trees by means of these mats, as completely as if they were apes. Those hanging huts are partly covered over with clay: the fires for domestic purposes are lighted on the lower story, which is always damp from the subjacent water, and the traveller by night, in sailing along the river, sees the flames in rows, suspended, as it were, in the air.
But besides a secure dwelling, the Mauritia affords them food also; before the blossoms J of the male tree burst their delicate spathes, or sheaths, and at that period alone, the pith of the stem contains a sago-like kind of meal, which, like Cassava, is dried in thin cakes. The sap, when fermented, becomes a sweet, intoxicating wine; the fruit, which is reddish, resembles a pine-cone in form, and affords, like the Pisang, and most fruits of the tropics, a varied nourishment in its different stages. Thus we find,
* By an analogous fallacy, mistaking cause and effect, they protest against the destroying of snakes; because they say the lagunes dry up when these leptiles are removed. The Mauritia thrives only where moisture collects, and the serpents only frequent the stagnant ponds.
t When a river empties itself into the sea by several mouths, these form a triangular figure, and the plain through which they run is called the Delta of the river, fiom the name of the Greek letter 1), which is of a triangular form.
t Many Palms are what botanists term iitteimu; that is, have the male and female flowers distinct from each other, on separate plants.
in the lowest scale of human cultivation, a whole race dependent on a single plant, as certain insects are confined to one part of a flower.
The discovery of the New World by the Europeans, has, of course, altered this scene; and these plains are now become inhabited. Towns are built, here and there, on the banks of the rivers, for the sake of facilitating the intercourse between the coast and Guayana, while others, in the interior, are the abodes of families who rear cattle, as is now every where done on these boundless wastes. These villages, for they deserve no higher denomination, lie sometimes several days" journeys apart, and consist of rude huts, constructed of stakes and reeds woven together, and covered with hides. Horses, mules, and cattle, left to run wild, in innumerable troops §, roam over the steppes. The incredible multiplication of these animals, since their introduction from the Old World, is the more astonishing, when the manifold dangers and privations to which they are exposed in that country, arc taken into consideration.
When the vertical rays of the ever-cloudless sun have withered up the grass to dust, the hardened earth opens as if shaken by an earthquake. If the surface is then acted on by opposing currents of air, a singular appearance is presented on the plain. Funnel-shaped clouds of sand rise from the ground, in the middle of the vortex, analogous to the water-spouts so formidable to the mariner on the ocean; a troubled straw-coloured light is thrown from the sky, which seems as if it had come down nearer the earth; the horizon appears to approach, and contributes still more to bewilder the traveller, caught in this commotion: the air, filled with sand, augments the usual heat, the east wind comes, heated by contact with the glowing earth, and brings anything but refreshment||. The small pools of water, hitherto protected from evaporation by the shade of the Fan-palm, are at length dried up; as, in the north, animals become torpid from excess of cold, here the contrary cause produces a similar effect, and the crocodile and the boa lie buried deep in the hardened earth. Here, also, the deceitful mirage allures the beguiled wanderer ■ the horses and cattle, tormented with burning thirst, and bewildered by the clouds of sand, run around neighing and bellowing with outstretched necks, snufling the wind, to detect, by the slightest moisture in the current, some distant pool, which has escaped the effects of the heat. The mules, with more apparent foresight, seek alleviation from the Melon-Cactus, which contains a juicy and refresh
ing interior beneath its hard and prickly bark; they strike aside the prickles with their fore-foot, and then with great
$ It has been computed that 1,200,000 oxen, 180,000 horses, and 90,000 mules, wander at large in the plains north of the Orinoco: and in the Pampas that there are 12,000,000 cattle and 3,000,000 horses;—all these sprang from the few individuals carried over by the Spaniards on their first settling I The horned cattle are principally valuable for their hides and tallow; 800,000 are annually exported from Buenos Aires and Monte Video alone.
|| These clouds of dust are especially frequent in the Peruvian sandy plains, between Amotape and Coquimbo; they would be very fatal to travellers, if not avoided when seen approaching. What appears remarkable is, that these partial whirlwinds always arise during a general calm; in this, also, the analogy between the ocean of air and the ocean of water is preserved; in the latter, small streams, in uliich the rippling is distinctly audible, are often observed ri,, ■ n a 4ead calm. Electricity is the primary cause of all these phr- ,0'-<
precaution apply their mouth to the plant. But so formiilable are the guards with which nature has furnished this reservoir, that animals are often seen lamed in the hoof from this cause.
When night comes on after the burning day, and brings a diminution of temperature, the persecuted animals are not allowed to enjoy this alleviation; enormous bats attack them during sleep, and suck their blood, or hang to their coats and form wounds, in which mosquitos, gad-Hies, and a multitude of insects, deposit their eggs, and convert them into festering sores. Thus, during the dry season, the larger quadrupeds lead a life of ceaseless misery in these regions.
On the approacn of the rainy season, the whole scene is quickly and strangely changed: the deep-blue of the evercloudless sky becomes lighter; at night, the black spot in the glorious southern constellation of the cross is hardly perceivable: the soft phosphorescent glimmer of the magellanic clouds is extinguished, and even the vertical stars of the eagle and ophiuchus, shine with a tremulous and less planet-like light *. A few solitary clouds first appear, like distant mountains in the south; vapours spread themselves like veils across the zenith, and the distant thunder announces the approach of the refreshing rain.
Scarcely is the surface of the earth moistened, when the reeking grounds are overspread with Kyllingia, Paspalum, and other sedges and grasses; herbaceous Mimosw unfold their leaves, and, together with the early song of birds, and the opening flowers of the water-plants, salute the rising sun. The horses and cattle now revel in the perfect enjoyment of existence, though the beautiful spotted jaguar lurks in the tall herbage, and darts, like the eastern tiger, on the unwary animal.
According to the natives, the moistened shores of the ponds are occasionally seen to rise and break into clods, which are cast, with a noise like that of a mud-volcano, into the air. The prudent spectator, aware of the cause, hastens from the place; for a gigantic water-snake or a fearful crocodile rises from the pit, aroused from their torpor by the first gush of rain.
By degrees, the rivers which form the southern boundary to the plains, the Arauca, the Apure, and the Payara, overflow their banks, and the same animals which, in the preceding half year, fainted from thirst on the parched and burning soil, are now compelled to live as amphibious: one part of the steppes becomes a vast lake, navigable for large vessels, which can sail ten or twelve miles together, straight across the country. The mares withdraw with their foals to the higher banks, which again resume their character of islands; but with each day these dry spots diminish, and at last, from want of pasture, the crowded horses are seen swimming about for hours together, seeking a scanty food from the flowering grasses which still rear their heads above the brown turbid waters. Many foals are drowned in consequence, and many are seized by crocodiles, or struck and disabled by their serrated tails: not unf'requently cattle and horses are afterwards seen, who have escaped from those monsters, and carry on their limbs the marks of the sharp teeth of these blood-thirsty lizards.
This appearance reminds the thoughtful observer of the power of conforming with exterior circumstances with which Nature has endowed, in common with man, certain species, both of animals and plants. The horse and the ox, like the farinaceous grasses, have been carried by him over the whole earth; from the Ganges to the Plata, from the
* These various appearances arc the results of increasing moisture in the air, and therefore precede the rain. The drier the atmosphere, the deeper the hlue of the sky; hence, the intense ;uure of that of tropical climates. English travellers are even struck with the great difference between their native sky and that of ltitly in this respect. An instrument has been contrived by which the depth of blue has been measured, and meteorological observations are made with it; it is called a Cyanometer, (blue measurer.) As the moisture increases, distant objects become more obscure and faint; and the heavenly bodies, therefore, are not so bright. The spot in the Cross is an astronomical phenomenon on which scientific men are not agreed; it appears much darker than the rest of the sky, and, therefore, just the reverse of those apparent clusters of stars which compose what are called Nebula;, the Milky-way, and the Magellanic clouds. Most of our readers are familiar with Capt. Hall's eloquent description of the effects of seeing the constellations of the southern hemisphere, as they gradually rise above the horizon, in sailing; and especially the feelings excited by the Cross, the sign of our salvation, planted by Ciod in the heavens as a beacon to man.—See Saturday Aia^aiHi*, Vol. 111., p. 139.
African Coast to the Plains of Antisana, which are higher above the level of the sea than the summit of the Peak of Teneriffeh Here the northern Birch, there the DatePalm. affords a shelter from the noon-day sun to the animals of which we have been speaking. The same genus which, in North-eastern Europe, combats with wolves and bears, is exposed in another hemisphere to the attacks of tigers and crocodiles I
But it is not only from these enemies that the herds and troops of cattle and horses are exposed to danger, they have a fearful foe among the fish. The stagnant lakes of Bera and Bastro are filled with innumerable electric eels%, which possess the power, at pleasure, of sending a very powerful shock from any part of their slimy yellow-spotted bodies; they are five or six feet long, and possess this extraordinary faculty in sufficient power to kill the largest animals if they can discharge their organs at once, and in the most favourable direction. At one time they existed in such numbers in one of the water-courses of the road from Uritucu, that every year many horses, stunned by their shocks, were drowned in crossing the ford. All other fish fly the neighbourhood of this formidable eel; and the angler, on the bank, is often startled by a shock conveyed to him along his moistened line $.
Thb comparative efficiency of the deserts and steppes of the globe, as barriers between the adjoining countries, is proved by the great difference which exists in the physical and moral characters of these contiguous lands.
Africa's northern deserts separate the two great human races, which, originating from a common home, have long been at vnriance, and whose discord has been the subject of mythology, under the fabled strife of Osiris and Typhon. North of Mount Atlas dwell the smooth, long-haired people, of tawny complexion and Caucasian features: southwards, on the contrary, from Senegal towards 45oudan, Negroes alone are found, in various stages of improvement.
In middle Asia, the steppes of Mongolia divide Siberian barbarism from the earliest seat of human cultivation in the Indian peninsula.
In South America, the Llanos and Pampas limit tho extent of European half-civilization, which has more recently been introduced there. North, between the mountain-chains of Venezuela and the Caribbean Sea, thriving towns and cheerful villages crowd on each other, and a taste for the arts and intellectual improvement, as well as their necessary result, the noble zeal for civil freedom, are now aroused. Towards the south, a gloomy wilderness surrounds the steppes; forests thousands of years old, an impenetrable thicket, fill the marshy territory between the Orinoco and the Amazon; mighty masses of granite narrow the bed of the foaming streams; mountain and forest re-echo the thunder of the cataract, combined with the roar of the tiger and the dead howl of the bearded ape. Where the shallower waters leave a sand-bank dry, the body of the lurking crocodile is seen lying, its jaws opened to seize its prey, and so motionless that it is often covered with birds, who perch on it. The spotted boa, with his tail wound round a branch of a tree, and his tong body doubled together, watches the opportunity and darts on some young bull, or a more feeble deer, as it approaches the bank, and, after smearing the body with its venomous saliva, sucks it in slowly and with effort through its distended throat and neck||; and then lies for weeks overcome with the mass of food, till it is digested, and hunger again compels it to seek a new meal.
t The pressure of the atmosphere is hence so much diminished on these plains, that when the wild cattle are baited by hounds, blood issues from their nose and mouth.
% Gymnotus Klectricus; it belongs to a very different section of the class, to that of the eel (JUuiYrim^ properly so called.—See Saturday Magazine, Vol. IV., p. 144.
§ The identity of Voltaism, or Galvanism, and electricity is well known, the action of the former species of these two divisions, is supposed to exist, in a latent state, in all organized matter, where dissimilarly constituted parts are in contact, and appears to bo intimately connected with the phenomenon of vitality, as well as with almost every one of the physical world.
|] The saliva with which this serpent covers its victim accelerates putrefaction, the muscular part becomes softened like jelly, and enables the reptile to swallow whole limbs at a time. When swimming in the Orinoco, they raise their head above the water like a dog: they occasionally attain a length of forty-five feet as it is said, but the largest skin ever brought to Europe has not exceeded tw o and twenty. The American serpent (a python,) is a distinct species from the East Indian,