A country extending from the sixteenth to the thirty-seventh degree of latitude, and presenting a great variety of surface, necessarily affords numerous modifications of climate. Such is the admirable distribution of heat on the globe, that the strata of the atmosphere become colder as we ascend, while those of the sea are warmest near the surface. Hence, under the tropics, on the declivities of the Cordilleras, and in the depths of the ocean, the plants and marine animals of the polar regions find a temperature suited to their development. It may easily be conceived that, in a mountainous country like Mexico, having so great a diversity of elevation, temperature, and soil, the variety of indigenous productions must be immense; and that most of the plants cultivated in other parts of the globe may there find situations adapted to their nature.

There, however, the principal objects of agriculture are not the productions which European luxury draws from the West India Islands, but the grasses, nutritive roots, and the agave. The appearance of the land proclaims to the traveller that the natives are nourished by the soil, and that they are independent of foreign commerce. Yet agriculture is by no means so flourishing as might be expected from its natural resources, although considerable improvement has been effected of late years. The depressed state of cultivation, it is true, has been attributed to the existence of numerous rich mines; but Humboldt, on the contrary, maintains that the working of these ores has been beneficial in causing many places to be improved which would otherwise have remained steril.