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gress 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 den pend 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 27507 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 § 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,
* 8413 feet. Trans. + 9021 feet. Trans. $ 13451 feet. Trans. § 1541 feet. Trans.
Quito, or Peru, do not exceed forty square leagues. Of difficult access, and separated from one another by rofound yallies, they are very unfavourable for the tran port of good and internal commerce, Crowning insulated suinmits, 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, w ere a suffocating h at prevails prejudicial 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 ap roximated 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. Iis length is equal to the distance from Lyons to the tropic of Cancer, which tra. verses the great African desert. This extraordinary plain appers 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 fiio Colorado. Th.ee sections accompany this essay, one longitudinal and direc.ed from south to north: it re
* Small islands.
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 Guanuxuato, we remain at first for ten leagu s in the valley of Tenochtitlan, elevated 2277 * metres above the level of the sea. The level of this beautiful valley 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) | lower than the valley of Tenochtitlan, and across which the great canal of evacuation of the lakes San Chris.' toval 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.
# 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 1420 feet. Trans.
lalpan, which is only 1379 metres * (2686 toisest) above the level of the sea, and is consequently less elevated than the city of Quito, though it appears the highest point of the whole road from Mexico to Chihuahua. To the north of this mountainous country the vast plains of S. Juan del Rio, Queretaro, and Zelaya begin, plains covered with villages and considerable cities. Their mean height equals Puy de Dôme in Auvergne, and they are near thirty leagues in length, extending to the foot of the metaliferous mountains of Guanaxuato. Those who have travelled into New Mexico assert that the rest of the way resembles what I have de. scribed and represented in a particular section. Immense plains, appearing like so many basins of old dried up lakes, follow one another, and are only separated by hills which hardly rise 200 or 250 f metres at most above the bottom of these basons. I shall exhibit in another work (in the Atlas to the historical account of my travels) the section of the four plains which surround the ca. pital of Mexico. The first, which comprehends the valley of Toluca, 2600 g metres (1940 toises); the second, or the valley of Tenochtitlan, 2274|| metres (1168 toises); the third, or the valley of Actopan, 1966 * metres (1009 toises); and the fourth, the valley of Istla, 981 7 metres (504 toises) of elevation. These four basins differ as much in their climate as in their elevation above the level of the sea; each exhibits a different cultivation : the first, and least elevated, is adapted for the cultivation of sugar; the second, cotton; the third, for European grain; and the fourth, for agava plantations, which may be considered as the vineyards of the Aztec Indians.
* 4522 feet. Trans.
+ This number, which does not correspond with the nietres, should evidently be 686. Trans. 1656 or 820 feet. Truns. § 8529 feet. Trans. #7459 feet. Trans.
The barometrical survey which I executed from Mexico to Guanaxato proves how much the configuration of the soil is favourable in New Spain for the transport of goods, navigation, and even the construction of canals. It is different in the transversal sections from the Atlantic to the South Sea. These sections show the difficulties opposed by nature to the communication between the interior of the kingdom and the coast. They every where exhibit an enormous difference of level and temperature, while from Mexico to New Biscay the plain preserves an equal elevation, and consequently a climate rather cold than temperate. From the capital of Mexico to Vera Cruz, the descent is shorter and more rapid than from the same point to Acapulco. We might almost say, that the country has a better military defence from na
* 8447 feet.
+ 3247 feet.