Page:Mexico (1829) Volumes 1 and 2.djvu/39

 formed to dispense moisture on their passage to the ocean. As the Eastern branch of the Cordillera disappears, or rather recedes towards the West, the space fertilized by these streams becomes more extensive; until in Texas, a country low, but well wooded, and rich in beautiful rivers, takes the place of the dreary steppes of the interior.

The Rio Grande de Sāntĭāgŏ, which traverses the Băxĭŏ, and empties itself into the Pacific near San Blas, and the Rio Bravo del Norte, which enters the Gulph of Mexico in 26 North lat., are the two principal rivers of the Table-land: the last, indeed, hardly merits that title, as it pursues its course over a part of the country where the Eastern Cordillera is lost; but the first rises in the very centre of Mexico, and the district through which it passes is amongst the richest of the known world.

Humboldt gives 25 degrees of the centigrade thermometer, (or 76 of Fahrenheit,) as the mean heat of the coast, and 17° centigrade (64 Farenheit) as that of the Tableland. But, in a country so extensive as Mexico, any general theory upon this subject must be liable to great exceptions. A situation, so sheltered as to give additional force to the reflected rays of the sun, or too much exposed to the winds of the Northwest, which sweep the country, at times, with incredible violence; a nearer approach to the Pacific side, (where the air is perceptibly milder;) the want, or abundance, of water; all these are circumstances which affect the temperature in the most opposite manner, even at the same height, and in the same parallel; and thus render it impossible, by the standard of elevation alone, to form any exact idea of the climate of the Table-land. Humboldt mentions the valley of Rio Verde, where sugar is raised with success at near four thousand feet above the degree of elevation which previous experiments had induced him to fix, as productive of the minimum of heat