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velling except on horseback, a-foot, or carried on the shoulders of Indians (called cargadores); but in the kingdom of New Spain carriages roll on to Santa Fe in the province of New Mexico, for a length of more than 1000 kilometres or 500 leagues. On the whole of this road there were few difficulties for art to surmount. The table-land of Mexico is in general so little interrupted by vallies, and its declivity is so genitle, that as far as the city of Durango, in New Biscay, 140 leagues from Mexico, the surface is continually elevated from 1700 to 2700 * metres above the level of the neighbouring ocean. This is equal to the height of Mount Cenis, St. Gothard, or the Great St Bernard. That I might examine this geological phenomenon with the attention which it deserves, I executed five barometrical surveys. The first was across the kingdom of New Spain, from the South Sea to the Mexican Gulf, from Acapulco to Mexico, and from Mexico to Vera Cruz. The second survey extended from Mexico by Tula, Queretaro, and Salamanca to Guanaxuato. The third comprehended the intendancy of Walladolid, from Guanaxuato to the volcano of Jorullo at Pascuaro. The fourth extended from Valladolid to Toluca, and from thence to Mexico. Lastly, the fifth in-. cluded the environs of Moran and Actopan. The number of points of which I determined the height,
* From 5576 to $850 feet. Trans.
either barometrically or trigonometrically, amounts to 208; and they are all distributed over a surface comprehended between the 16° 50' and 21° 0 of north latitude, and the 102°8' and 98° 28′ of west
longitude from Paris. Beyond these limits I know
but of one place of which the length was accurately ascertained, and that is the city of Durango, elevated, according to a deduction from a mean barometrical altitude, 2000 * metres above the level of the sea. Thus the table-land of Mexico preserves its extraordinary elevation much farther north than the tropic of Cancer. These measurements of heights, with the astronomical observations which I made on the same extent of ground, have enabled me to construct the physical maps which accompany this work. They contain a series of vertical sections. I have endeavoured to represent whole regions by a method which has hitherto been only employed for mines, or small portions of ground through which canals are intended to pass. In the statistics of the kingdom of New Spain, we must confine ourselves to plans likely to attract interest from views of political economy. The physiognomy of a country, grouping of mountains, extent of plains, elevation who haetermines its temperature; in short, whatever constitutes the construction of the globe, has the most essential influence on the progress of population and welfare of the inhabitants. It influences the state of agriculture, which must vary with the difference of climate, the means of internal commerce, the communications which depend on the nature of the territory, and the military defence on which the external security of the colony depends. In these relations alone extensive geological views can interest the statesman, when he calculates the force and territorial wealth of a nation. In South America, the Cordillera of the Andes exhibits at immense heights plains completely level. Such is the plain of 2565 * metres elevation on which the city of Santa Fe de Bogota is built. Wheat, potatoes, and chenopodium quinoa, are there carefully cultivated. Such is also the plain of Caxamarea, in Peru, the ancient residence of the unfortunate Atahualpa, of 2750f metres elevation. The great plains of Antisana, in the middle of which rises the part of the volcano which penetrates the region of perpetual snow, are 41001 metres higher than the level of the ocean. These plains exceed in length the summit of the Pic of Teneriffe by 389 y metres; and yet they are so level, that at the aspect of their natal soil, those who inhabit these countries have no suspicion of the extraordinary situation in which nature has placed them. But all the plains of New Grenada, Quito, or Peru, do not exceed forty square leagues. Of difficult access, and separated from one another by profound vallies, they are very unfavourable for the transport of goods and internal commerce, Crowning insulated summits, they form as it were islots * in the middle of the aerial ocean. Those who inhabit these frozen plains remain concentrated there, and dread to descend into the neighbouring regions, where a suffocating heat prevails prejudi. cial to the primitive inhabitants of the higher Andes. In Mexico, however, the soil assumes a different aspect. Plains of a great extent, but of a surface no less uniform, are so approximated to one another, that they form but a single plain on the lengthened ridge of the Cordillera; such is the plain which runs from the 18° to the 40° of north latitude. Its length is equal to the distance from Lyons to the tropic of Cancer, which traverses the great African desert. This extraordinary plain appears to decline insensibly towards the north. No measurement, as we have already remarked, was ever made in New Spain beyond the city of Durango; but travellers observe that the ground lowers visibly towards New Mexico, and towards the sources of the Rio Colorado. Three sections accompany this essay, one longitudinal and directed from south to north: it re
* 6561 feet. Trans.
presents the ridge of the mountains in their prolongation towards the Rio Bravo. The two others are transversal sections from the coast of the Pacific Ocean to the Gulf of Mexico. All three show at a glance the difficulty which the extraordinary configuration of the country opposes to the transport of productions from the interior to the commercial cities of the coast. In travelling from the capital of Mexico to the great mines of Guanaxuato, we remain at first for ten leagues in the valley of Tenochtitlan, elevated 2277 * metres above the level of the sea. The level of this beautiful valiey is so uniform, that the village of Gueguetoque, situated at the foot of the mountain of Sincoque, is only tent metres higher than Mexico. The hill of Barientos is merely a promontory which stretches into the valley. From Gueguetoque we ascend near Botas to Puerto de los Reyes, and from thence descend into the valley of Tula, which is 115 metres (222 toises) flower than the valley of Tenochtitlan, and across which the great canalof evacuation of the lakes San Christoval and Zumpango passes to the Rio de Moctezuma and the Gulf of Mexico. To arrive at the bottom of the valley of Tula, in the great plain of Queretaro, we must pass the mountain of Calpu
* 7468 feet. Trans. + 32.8 feet. Trans.
i Here there is evidently a mistake, for 115 metres do not correspond to 222 toises; the value of the first is 376 feet, and of the latter 1429 feet. Trans.