Considering The System Of The Mountains Of Brazil In Their Real Limits, We Find, Except Some Conglomerates, The Same Absence Of Secondary Formations As In The System Of The Mountains Of The Orinoco (Group Of Parime).

These secondary formations, which rise to considerable heights in the Cordillera of Venezuela and Cumana, belong only to the low regions of Brazil.

B. PLAINS (LLANOS) OR BASINS.

In that part of South America situated on the east of the Andes we have successively examined three systems of mountains, those of the shore of Venezuela, of the Parime and Brazil: we have seen that this mountainous region, which equals the Cordillera of the Andes, not in mass, but in area and horizontal section of surface, is three times less elevated, much less rich in precious metals adhering to the rock, destitute of recent traces of volcanic fire and, with the exception of the coast of Venezuela, little exposed to the violence of earthquakes. The average height of the three systems diminishes from north to south, from 750 to 400 toises; those of the culminant points (maxima of the height of each group) from 1350 to 1000 or 900 toises. Hence it results that the loftiest chain, with the exception of the small insulated system of the Sierra Nevada of Santa Marta, is the Cordillera of the shore of Venezuela, which is itself but a continuation of the Andes. Directing our attention northward, we find in Central America (latitude 12 to 30 degrees) and North America (latitude 30 to 70 degrees), on the east of the Andes of Guatimala, Mexico and Upper Louisiana, the same regular lowering which struck us towards the south. In this vast extent of land, from the Cordillera of Venezuela to the polar circle, eastern America presents two distinct systems, the group of the mountains of the West Indies (which in its eastern part is volcanic) and the chain of the Alleghenies. The former of these systems, partly covered by the ocean, may be compared, with respect to its relative position and form, to the Sierra Parime; the latter, to the Brazil chains, running also from south-west to north-east. The culminant points of those two systems rise to 1138 and 1040 toises. Such are the elements of this curve, of which the convex summit is in the littoral chain of Venezuela:

AMERICA, EAST OF THE ANDES.

COLUMN 1 : SYSTEMS OF MOUNTAINS.

COLUMN 2 : MAXIMA OF HEIGHTS IN TOISES.

Brazil Group : Itacolumi 900 (south latitude 20 1/2 degrees).

Parime Group : Duida 1300 (north latitude 3 1/4 degrees).

Littoral Chain of Venezuela : Silla of Caracas 1350 (north latitude 10 1/2 degrees).

Group of the West Indies : Blue Mountains 1138 (north latitude 18 1/5 degrees).

Chain of the Alleghenies : Mount Washington 1040 (north latitude 44 1/4 degrees).

I have preferred indicating in this table the culminant points of each system to the mean height of the line of elevation; the culminant points are the results of direct measures, while the mean height is an abstract idea somewhat vague, particularly when there is only one group of mountains, as in Brazil, Parime and the West Indies, and not a continued chain. Although it cannot be doubted that, among the five systems of mountains on the east of the Andes, of which one only belongs to the southern hemisphere, the littoral chain of Venezuela is the most elevated (having a culminant point of 1350 toises, and a mean height from the line of elevation of 750), we yet recognise with surprise that the mountains of eastern America (whether continental or insular) differ very inconsiderably in their height above the level of the sea. The five groups are all nearly of an average height of from 500 to 700 toises; and the culminant points (maxima of the lines of elevation) from 1000 to 1300 toises. That uniformity of structure, in an extent twice as great as Europe, appears to me a very remarkable phenomenon. No summit east of the Andes of Peru, Mexico and Upper Louisiana rises beyond the limit of perpetual snow.* (* Not even the White Mountains of the state of New Hampshire, to which Mount Washington belongs. Long before the accurate measurement of Captain Partridge I had proved (in 1804), by the laws of the decrement of heat, that no summit of the White Mountains could attain the height assigned to them by Mr. Cutler, of 1600 toises.) It may be added that, with the exception of the Alleghenies, no snow falls sporadically in any of the eastern systems which we have just examined. From these considerations it results, and above all, from the comparison of the New Continent with those parts of the old world which we know best, with Europe and Asia, that America, thrown into the aquatic hemisphere* of our planet, is still more remarkable for the continuity and extent of the depressions of its surface, than for the height and continuity of its longitudinal ridge. Beyond and within the isthmus of Panama, but eastward of the Cordillera of the Andes, the mountains scarcely attain, over an extent of 600,000 square leagues, the height of the Scandinavian Alps, the Carpathians, the Monts-Dores (in Auvergne) and the Jura. (* The southern hemisphere, owing to the unequal distribution of seas and continents, has long been marked as eminently aquatic; but the same inequality is found when we consider the globe as divided not according to the equator but by meridians. The great masses of land are stinted between the meridian of 10 degrees west, and 150 degrees east of Paris, while the hemisphere eminently aquatic begins westward of the meridian of the coast of Greenland, and ends on the east of the meridian of the eastern coast of New Holland and the Kurile Isles. This unequal distribution of land and water has the greatest influence on the distribution of heat over the surface of the globe, on the inflexions of the isothermal lines, and the climateric phenomena in general.

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