From the salt Steppes of Asia, from the European Heaths smiling in summer with their purple blossoms rich in honey, and from the arid Deserts of Africa devoid of all vegetation, let us now return to those South American plains of which I have already began to trace the picture, albeit in rude outlines.
The interest which this picture can offer to the beholder is, however, exclusively that of pure nature. Here no Oasis recalls the memory of earlier inhabitants; no carved stone,[12] no ruined building, no fruit tree once the care of the cultivator but now wild, speaks of the art or industry of former generations. As if estranged from the destinies of mankind, and riveting attention solely to the present moment, this corner of the earth appears as a wild theatre for the free development of animal and vegetable life.
The Steppe extends from the Caraccas coast chain to the forests of Guiana, and from the snowy mountains of Merida (on the slope of which the Natron Lake Urao is an object of superstitious veneration to the natives,) to the great delta formed by the Orinoco at its mouth. To the south-west a branch is prolonged, like an arm of the sea,[13] beyond the banks of the Meta and Vichada to the unvisited sources of the Guaviare, and to the lonely mountain to which the excited fancy of the Spanish soldiery gave the name of Paramo de la Suma Paz—the seat of perfect peace.
This Steppe occupies a space of 16,000 (256,000 English) square miles. It has often been erroneously described as running uninterruptedly, and with an equal breadth, to the straits of Magellan, forgetting the forest-covered plain of the Amazons which intervenes between the grassy Steppes of the Apure and those of the river Plate. The Andes of Cochabamba, and the Brazilian group of mountains, send forth, between the province of Chiquitos and the isthmus of Villabella, some detached spurs, which advance, as it were, to meet each other.[14] A narrow plain connects the forest lands of the Amazons with the Pampas of Buenos Ayres. The latter far surpass the Llanos of Venezuela in area; and their extent is so great that while their northern margin is bordered by palm trees, their southern extremity is almost continually covered with ice.
The Tuyu, which resembles the Cassowary (the Struthio rhea), is peculiar to these Pampas, which are also the haunt of troops of dogs[15] descended from those introduced by the colonists, but which have become completely wild, dwelling together in subterranean hollows, and often attacking with blood-thirsty rage the human race whom their progenitors served and defended.
Like the greater portion of the desert of Sahara,[16] the northernmost of the South American plains, the Llanos, are in the torrid zone: during one half of the year they are desolate, like the Lybian sandy waste; during the other, they appear as a grassy plain, resembling many of the Steppes of Central Asia.[17]
It is a highly interesting though difficult task of general geography to compare the natural conditions of distant regions, and to represent by a few traits the results of this comparison. The causes which lessen both heat and dryness in the New World[18] are manifold, and in some respects as yet only partially understood. Amongst these may be classed the narrowness and deep indentation of the American land in the northern part of the torrid zone, where consequently the atmosphere, resting on a liquid base, does not present so heated an ascending current;—the extension of the continent towards the poles;—the expanse of ocean over which the trade-winds sweep freely, acquiring thereby a cooler temperature;—the flatness of the eastern coasts;—currents of cold sea-water from the antarctic regions, which, coming from the south-west to the north-east, first strike the coast of Chili in the parallel of 35° south latitude, and advance along the coast of Peru as far north as Cape Pariña, and then turn suddenly to the west;—the numerous lofty mountain chains rich in springs, and whose snow-clad summits, rising high above all the strata of clouds, cause descending currents of cold air to roll down their declivities;—the abundance of rivers of enormous breadth, which, after many windings, seek the most distant coast;—Steppes which from not being sandy are less susceptible of acquiring a high degree of heat,—impenetrable forests occupying the alluvial plains situated immediately beneath the equator, protecting with their shade the soil beneath from the direct influence of the sunbeams, and exhaling in the interior of the country at a great distance from the mountains and from the ocean vast quantities of moisture, partly imbibed and partly elaborated:—all these circumstances afford to the flat part of America a climate which by its humidity and coolness contrasts wonderfully with that of Africa. It is to the same causes that we are to attribute the luxuriant vegetation, the magnificent forests, and that abundant leafiness by which the new continent is peculiarly characterised.
If, therefore, one side of our planet has a moister atmosphere than the other, the consideration of the present condition of things is amply sufficient to explain the problem presented by this inequality. The physical inquirer needs not to clothe the explanation of these phenomena in a mantle of geological myths. He needs not to assume that on our planet the harmonious reconciliation of the destructive conflict of the elements took place at different epochs in the eastern and the western hemispheres; or that America emerged later than the other parts of the globe from the chaotic watery covering,[19] as an island of swamps and marshes tenanted by alligators and serpents.
There is, indeed, a striking similarity between South America and the southern peninsula of the old continent in the form of the outline and in the direction of the coasts; but the nature of the soil, and the relative position of the neighbouring masses of land, produce in Africa that extraordinary aridity which over an immense area checks the development of organic life. Four-fifths of South America are situated on the southern side of the equator; or in a hemisphere which from the greater proportion of sea and from other causes is cooler and moister than our northern half of the globe,[20] to which the larger part of Africa belongs. The breadth of the South American Steppe, measured from east to west, is only a third of that of the African Desert. The Llanos receive the influence of the tropical sea wind, while the African Deserts, being situated in the same zone of latitude as Arabia and the south of Persia, are in contact with strata of air which have blown over warm heat-radiating continents. The venerable and only lately appreciated father of history, Herodotus, in the true spirit of an enlarged view of nature, described the Deserts of northern Africa, of Yemen, of Kerman and Mekran (the Gedrosia of the Greeks), and even as far as Moultan, as forming a single connected sea of sand.[21]
In addition to the action of these hot winds, there is (so far as we know) an absence or comparative paucity in Africa of large rivers, of widely extended forests producing coolness and exhaling moisture, and of lofty mountains. Of mountains covered with perpetual snow, we know only the western part of the Atlas,[22] whose narrow range, seen in profile from the Atlantic, appeared to the ancient navigators when sailing along the coast as a single detached lofty sky-supporting mount. The eastern prolongation of the chain extends nearly to Dakul, where Carthage, once mistress of the seas, now lies in mouldering ruins. As forming a long extended coast-chain, or Gætulian rampart, the effect of the Atlas range is to intercept the cool north breezes, and the vapours which ascend from the Mediterranean.