The effect of elevation on the temperature is most marked, and it is no uncommon thing to be shivering on one side of the street in the city of Mexico, and to be literally scorched by the rays of the sun on the other. Changes are upon record of 55° of Fahrenheit within three hours, on one of the mountain-plains at the same height with the valley of Mexico. Notwithstanding the volcanic character of Mexico, earthquakes are by no means so frequent there as in some of the neighbouring countries. One of the most memorable on record occurred on the 14th of September, 1759, when the volcano of Jorullo, with several smaller cones, forced the surface of the soil, destroying all before it. The infinite variety of climate and soil fits this country for the production of the fruits of all regions, from those of the hottest within the tropics to those of the severest cold, where cultivation can be carried on. But the want of ports, and of navigable rivers on the Atlantic, opposes the advantages that might result from this variety of production, though on the Pacific there are a few admirable ports, such as Acapulco. The prevalence of the "Nortes," or northerly winds, at certain seasons, seriously affects the navigation on one side, while that of the "papagallos" is as inconvenient on the other. The Mexican population is commonly divided into seven classes:--1. European Spaniards, commonly called "_gachupines_." 2. White Creoles. 3. Mestizos, descendants of Whites and Indians. 4. Mulattoes, descendants of Whites and Blacks. 5. Zambos, from Indians and Negroes. 6. Pure Indians. 7. African Blacks. But this classification may be reduced to four:--1. Whites. 2. Indians. 3. Blacks. 4. Mixed Races, the various gradations of which may be considered almost infinite.