Mexico is a country reaching from the Gulf on its eastern coast to the Pacific Ocean, almost 2,000 miles, with a breadth varying from 140 to 750 miles. The whole territory of Montezuma, at the time of the Spanish conquest, was not less than 1,600,000 square miles, more than one half of which has been obtained by the United States by purchase, enforced treaties, or otherwise. The plains on the coast are low, marshy, and in the summer and autumn malarial diseases are very prevalent. Strangers can visit the place with safety only about four months in the year, when severe northern gales cool the heated atmosphere and dissipate the seeds of disease. There are 6,000 miles of coast line, but, considering its extent, it does not furnish many good harbors. The main body of the land is an elevated plateau, traversed by chains of mountains, some of which are of extraordinary height. The eastern Cordillera, or chain, that runs nearly north from the initial point has an elevation of 6,000 feet, the western nearly 10,000. Traversing the longitudinal range, there are several cross ranges containing some of the highest volcanoes on the continent. They are all quiescent now, and none of them have been active during the present century. There are not many lakes, and none that are very large. The basins of some, though of sufficient extent, are so arid, and evaporation is carried on so rapidly that the water in them has, at times, quite disappeared. Neither are the rivers of much importance as thoroughfares. The Rio Grande, forming the boundary between Mexico and Texas, is the longest (1,500 miles), but navigable only for a short distance. Those in the mountain region are impetuous torrents, larger near their source than afterward, as they lose more by absorption, in passing through arid portions of the table-lands, than they gain by drainage, except in the rainy season. After plowing deep furrows, and cutting out immense ravines among the foot hills of the mountains, some are partly exhausted, drawn into reservoirs and canals constructed for purposes of irrigation, and spread out into sluggish bayous, of no great depth, before they reach the sea. The lack of navigable streams has been seriously felt.