Personal Narrative of Travels to the Equinoctial Regions of America, During the Years 1799-1804, Vol.3 — 39 - Chapter 3.32, Part 9

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.

For the inhabitants of the central parts of Europe the aquatic hemisphere may be called western, and the land hemisphere eastern; because in going to the west we reach the former sooner than the latter.

It is the division according to the meridians, which is intended in the text.

Till the end of the 15th century the western hemisphere was as much unknown to the nations of the eastern hemisphere, as one half of the lunar globe is to us at present, and will probably always remain.

) One system only, that of the Andes, comprises in America, over a long and narrow zone of 3000 leagues, all the summits exceeding 1400 toises high.

In Europe, on the contrary, even considering the Alps and the Pyrenees as one sole line of elevation, we still find summits far from this line or principal ridge, in the Sierra Nevada of Grenada, Sicily, Greece, the Apennines, perhaps also in Portugal, from 1500 to 1800 toises high.

* (* Culminant points; Malhacen of Grenada, 1826 toises; Etna, according to Captain William Henry Smith, 1700 toises; Monte Corno of the Apennines, 1489 toises.

If Mount Tomoros in Greece and the Serra Gaviarra of Portugal enter, as is alleged, into the limit of perpetual snow, those summits, according to their position in latitude, should attain from 1400 to 1600 toises.

Yet on the loftiest mountains of Greece, Tomoros, Olympus in Thessaly, Polyanos in Dolope and Mount Parnassus, M. Pouqueville saw, in the month of August, snow lying only in patches, and in cavities sheltered from the rays of the sun.

) The contrast between America and Europe, with respect to distribution of the culminant points, which attain from 1300 to 1500 toises, is the more striking, as the low eastern mountains of South America, of which the maximum of elevation is only from 1300 to 1400 toises, are situated beside a Cordillera of which the mean height exceeds 1800 toises, while the secondary system of the mountains of Europe rises to maxima of elevation of 1500 to 1800 toises, near a principal chain of at least 1200 toises of average height.

MAXIMA OF THE LINE OF ELEVATION IN THE SAME PARALLELS.

Andes of Chile, Upper Peru.

Knots of the mountains of Porco and Cuzco, 2500 toises.

: Group of the Brazil Mountains; a little lower than the Cevennes 900 to 1000 toises.

Andes of Popayan and Cundinamarca.

Chain of Guacas, Quindiu, and Antioquia.

More than 2800 toises.

: Group of Parime Mountains; little lower than the Carpathians; 1300 toises.

Insulated group of the Snowy Mountains of Santa Marta.

It is believed to be 3000 toises high.

: Littoral Chain of Venezuela; 80 toises lower than the Scandinavian Alps; 1350 toises.

Volcanic Andes of Guatimala, and primitive Andes of Oaxaca, from 1700 to 1800 toises.

: Group of the West Indies, 170 toises higher than the mountains of Auvergne, 1140 toises.

Andes of New Mexico and Upper Louisiana (Rocky Mountains) and further west.

The Maritime Alps of New Albion, 1600 to 1900 toises.

: Chain of the Alleghenies; 160 toises higher than the chains of Jura and the Gates of Malabar; 1040 toises.

This table contains the whole system of mountains of the New Continent; namely: the Andes, the maritime Alps of California or New Albion and the five groups of the east.

I may subjoin to the facts I have just stated an observation equally striking; in Europe the maxima of secondary systems, which exceed 1500 toises, are found solely on the south of the Alps and Pyrenees, that is, on the south of the principal continental ridge.

They are situated on the side where that ridge approaches nearest the shore, and where the Mediterranean has not overwhelmed the land.

On the north of the Alps and Pyrenees, on the contrary, the most elevated secondary systems, the Carpathian and the Scandinavian mountains* do not attain the height of 1300 toises.

(* The Lomnitzer Spitz of the Carpathians is, according to M. Wahlenberg, 1245 toises; Sneehattan, in the chain of Dovrefjeld in Norway (the highest summit of the old continent, north of the parallel of 55 degrees), is 1270. ) The depression of the line of elevation of the second order is consequently found in Europe as well as in America, where the principal ridge is farthest removed from the shore.

If we did not fear to subject great phenomena to too small a scale, we might compare the difference of the height of the Alps and the mountains of eastern America, with the difference of height observable between the Alps or the Pyrenees, and the Monts Dores, the Jura, the Vosges or the Black Forest.

We have just seen that the causes which upheaved the oxidated crust of the globe in ridges, or in groups of mountains, have not acted very powerfully in the vast extent of country stretching from the eastern part of the Andes towards the Old World; that depression and that continuity of plains are geologic facts, the more remarkable, as they extend nowhere else in other latitudes.

The five mountain systems of eastern America, of which we have stated the limits, divide that part of the continent into an equal number of basins of which only that of the Caribbean Sea remains submerged.

From north to south, from the polar circle to the Straits of Magellan, we see in succession: 1. THE BASIN OF THE MISSISSIPPI AND OF CANADA.

An able geologist, Mr. Edwin James, has recently shown that this basin is comprehended between the Andes of New Mexico, or Upper Louisiana, and the chains of the Alleghenies which stretch northward in crossing the rapids of Quebec.

It being quite as open northward as southward, it may be designated by the collective name of the basin of the Mississippi, the Missouri, the river St. Lawrence, the great lakes of Canada, the Mackenzie river, the Saskatchewan and the coast of Hudson's Bay.

The tributary streams of the lakes and those of the Mississippi are not separated by a chain of mountains running from east to west, as traced on several maps; the line of partition of the waters is marked by a slight ridge, a rising of two counter-slopes in the plain.

There is no chain between the sources of the Missouri and the Assineboine, which is a branch of the Red River and of Hudson's Bay.

The surface of these plains, almost all savannah, between the polar sea and the gulf of Mexico, is more than 270,000 square sea leagues, nearly equal to the area of the whole of Europe.

On the north of the parallel of 42 degrees the general slope of the land runs eastward; on the south of that parallel it inclines southward.

To form a precise idea how little abrupt are these slopes we must recollect that the level of Lake Superior is 100 toises; that of Lake Erie, 88 toises, and that of Lake Ontario, 36 toises above the level of the sea.

The plains around Cincinnati (latitude 39 degrees 6 minutes) are scarcely, according to Mr. Drake, 80 toises of absolute height.

Towards the west, between the Ozark mountains and the foot of the Andes of Upper Louisiana (Rocky Mountains, latitude 35 to 38 degrees), the basin of the Mississippi is considerably elevated in the vast desert described by Mr. Nuttal.

It presents a series of small table-lands, gradually rising one above another, and of which the most westerly (that nearest the Rocky Mountains, between the Arkansas and the Padouca), is more than 450 toises high.

Major Long measured a base to determine the position and height of James Peak.

In the great basin of the Mississippi the line that separates the forests and the savannahs runs, not, as may be supposed, in the manner of a parallel, but like the Atlantic coast, and the Allegheny mountains themselves, from north-east to south-west, from Pittsburg towards Saint Louis, and the Red River of Nachitoches, so that the northern part only of the state of Illinois is covered with gramina.

This line of demarcation is not only interesting for the geography of plants, but exerts, as we have said above, great influence in retarding culture and population north-west of the Lower Mississippi.

In the United States the prairie countries are more slowly colonized; and even the tribes of independent Indians are forced by the rigour of the climate to pass the winter on the banks of rivers, where poplars and willows are found.

The basins of the Mississippi, of the lakes of Canada and the St. Lawrence, are the largest in America; and though the total population does not rise at present beyond three millions, it may be considered as that in which, between latitude 29 and 45 degrees (longitude 74 to 94 degrees), civilization has made the greatest progress.

It may even be said that in the other basins (of the Orinoco, the Amazon and Buenos Ayres) agricultural life scarcely exists; it begins, on a small number of points only, to supersede pastoral life, and that of fishing and hunting nations.

The plains between the Alleghenies and the Andes of Upper Louisiana are of such vast extent that, like the Pampas of Choco and Buenos Ayres, bamboos (Ludolfia miega) and palm-trees grow at one extremity, while the other, during a great part of the year, is covered with ice and snow.

2. THE BASIN OF THE GULF OF MEXICO, AND OF THE CARIBBEAN SEA.

This is a continuation of the basin of the Mississippi, Louisiana and Hudson's Bay.

It may be said that all the low lands on the coast of Venezuela situated north of the littoral chain and of the Sierra Nevada de Merida belong to the submerged part of this basin.

If I treat here separately of the basin of the Caribbean Sea, it is to avoid confounding what, in the present state of the globe, is partly above and partly below the ocean.

The recent coincidence of the periods of earthquakes observed at Caracas and on the banks of the Mississippi, the Arkansas and the Ohio, justifies the geologic theories which regard as one basin the plains bounded on the south, by the littoral Cordillera of Venezuela; on the east, by the Alleghenies and the series of the volcanoes of the West Indies; and on the west, by the Rocky Mountains (Mexican Andes) and by the series of the volcanoes of Guatimala.

The basin of the West Indies forms, as we have already observed, a Mediterranean with several issues, the influence of which on the political destinies of the New Continent depends at once on its central position and the great fertility of its islands.

The outlets of the basin, of which the four largest* are 75 miles broad, are all on the eastern side, open towards Europe, and agitated by the current of the tropics.

(* Between Tobago and Grenada; Saint Martin and the Virgin Isles; Porto Rico and Saint Domingo; and between the Little Bank of Bahama and Cape Canaveral of Florida.

) In the same manner as we recognize, in our Mediterranean, the vestiges of three ancient basins by the proximity of Rhodes, Scarpanto, Candia, and Cerigo, as well as by that of Cape Sorello of Sicily, the island of Pantelaria and Cape Bon, in Africa; so the basin of the West India Islands, which exceeds the Mediterranean in extent, seems to present the remains of ancient dykes which join* Cape Catoche of Yucatan to Cape San Atonio of the island of Cuba (* I do not pretend that this hypothesis of the rupture and the ancient continuity of lands can be extended to the eastern foot of the basin of the West Indies, that is, to the series of the volcanic islands in a line from Trinidad to Porto Rico.

); and that island to Cape Tiburon of St. Domingo; Jamaica, the Bank of La Vibora and the rock of Serranilla to Cape Gracias a Dios on the Mosquito Shore.

From this situation of the most prominent islands and capes of the continent, there results a division into three partial basins.

The most northerly has long been distinguished by a particular denomination, that of the Gulf of Mexico; the intermediary or central basin may be called the Sea of Honduras, on account of the gulf of that name which makes a part of it; and the southern basin, comprehended between the Caribbean Islands and the coast of Venezuela, the isthmus of Panama, and the country of the Mosquito Indians, would form the Caribbean Sea.

The modern volcanic rocks distributed on the two opposite banks of the basin of the West Indies on the east and west, but not on the north and south, is also a phenomenon worthy of attention.

In the Caribbean Islands, a group of volcanoes, partly extinct and partly burning, stretches from 12 to 18 degrees; and in the Cordilleras of Guatimala and Mexico from latitude 9 to 19 1/2 degrees.

I noticed on the north-west extremity of the basin of the West Indies that the secondary formations dip towards south-east;

along the coast of Venezuela rocks of gneiss and primitive mica-slate dip to north-west.

The basalts, amygdaloids, and trachytes, which are often surmounted by tertiary limestones, appear only towards the eastern and western banks.