20 MEXICO, CENTEIL AMEEICA, WEST INDIES. 



IL — Mexico Proper, North of the Isthmus of Tehua^tepec. 



Taken as a whole Mexico properly so called may be regarded as a lofty table- 

 land, on whicli stand mountain ranges and masses, which, despite Humboldt's oft- 

 repeated generalisation, have no kind of connection in their relief or general 

 trend with the Andean system of South America. They should be grouped 

 rather with that of California, though still with numerous interruptions. 



Mountains and Volcanoes. 



The mean altitude of the whole region is estimated at no less than 3,600 feet. 

 A plane passing at this elevation above the ocean would detach from the sustaining 

 pedestal an enormous triangular mass, whose apex would terminate in the south- 

 east above the Tehuantepec depression, and whose base would be prolonged by 

 two parallel horns projecting in the direction of the United States. 



The great central Mexican plateau is thus seen to be limited on the sides 

 facing the Atlantic and Pacific Oceans b}'^ border ranges, or at least by a succession 

 of heights or ridges forming a more or less continvious escarpment. Both of these 

 border ranges have received the designation of Sierra Mac/re, " Main Chain ; " a 

 term, however, which recurs in almost every part of Spanish xlmerica, where it is 

 freely applied to the dominating crests of the country. 



Like all border ranges, the Mexican sierras present striking contrasts between 

 their opposite sides, those facing inland falling somewhat gradually down to the 

 plateau, while those turned towards the oceans are far more abrupt, intersected by 

 scarps and cliffs, furrowed by deep crevasses, continually modified by landslips, 

 and scored by tremendous barrancas (chasms or gorges) . 



The whole region, which contracts gradually southwards between the two 

 border ranges, forms, so to say, a large avenue terminating in a labyrinth. The 

 successive waves of migratory populations coming from the north were attracted 

 from stage to stage towards the southern angle, that is, towards the basin of 

 Mexico and the plains of Puebla, which are bounded on the south by the Junta, 

 that is, the " Junction," or converging-point of the two sierras. 



To the triangular depression left between these sierras the expression Mexican 

 "plateau" is often applied ; it is also occasionally called the Anahuac plateau, or 

 simply Anahuac, terms borrowed from Clavigero and Humboldt. Nevertheless 

 the mesa or " table " of Mexico presents no continuous level surface, as might be 

 supposed from the current expressions. The depression viewed as a whole 

 presents rather a succession of basins, for the most part of lacustrine origin, which 

 follow at constantly diminishing altitudes in the direction from north to south. 

 But the separating barriers present such slight obstacles to migrations and travel 

 that during the last century a highway was easily constructed from the capital to 

 Santa Fé in New Mexico ; carriages could be driven from one city to the other 

 along this road, nearly J ,400 miles long. 



In the southern districts round about Mexico the basins are of relatively small 



