Texas is estimated to contain, 325,520 square miles. New Mexico " " 77,387 " " Upper California " 448,691 " " -------- 851,598 " "[4] If we, therefore, deduct from the preceding estimate of one million six hundred and fifty thousand square miles, the sum of eight hundred and fifty-one thousand five hundred and ninety-eight square miles, we shall have, as the best approximate calculation, that we can now make, seven hundred and ninety-eight thousand four hundred and two square miles, for the total superficial extent of the Republic of Mexico, as at present bounded since the ratification of our recent international treaty. By that negotiation it consequently appears that we have obtained one half the former territory of Mexico and twenty-six thousand five hundred and ninety-eight square miles besides. The geological structure or physiognomy of Mexico is peculiar. The great Cordillera of the Andes, which traverses the whole of South America, from its southernmost limit, is exceedingly depressed at the Isthmus of Panama, where its gentle swells serve merely to form a barrier between the union of the Pacific and Atlantic. But, as soon as this massive chain enters the broader portion of North America, it divides into two gigantic _arms_, to the east and west along the shores of the Gulf and of the Pacific, which support between them a continuous lofty platform, or series of table lands, crossed, broken, and intersected by innumerable and abrupt _sierras_, some of which rise to the height of seventeen thousand feet above the level of the sea. This geological structure prevails throughout the whole of Mexico, as now bounded; for, at the Rio Grande, the southern limit of Texas, the land sinks to comparative levels, and affords channels for the numerous and important streams with which, Louisiana, Florida and Texas are abundantly irrigated. Whilst this is the case on the _northern_ and _eastern_ confines of Mexico, the _western_ portion is still traversed by the main body of the gigantic Cordillera, which, penetrating California with its icy peaks of the Sierra Nevada, passes onward to the north until its rocky walls are lost, beyond Oregon, in the wilderness that bounds the Frozen Sea.[5]