Notwithstanding the want of superficial water, the air is always charged with moisture; the consequence being a most equable temperature all the year round, and an extreme luxuriance of all vegetation. The climate is mild and comparatively healthy for a country situated within the tropics, and bathed by the waters of the Mexican Gulf. This mildness and healthiness may be attributed to the sea breezes that constantly pass over the peninsula, carrying the malaria and noxious gases that have not been absorbed by the forests, which cover the main portion of the land; and to the great abundance of oxygen exuded by the plants in return. This excessive moisture and the decomposition of dead vegetable matter is the cause of the intermittent fevers that prevail in all parts of the peninsula, where the yellow fever, under a mild form generally, is also endemic. When it appears, as this year, in an epidemic form, the natives themselves enjoy no immunity from its ravages, and fall victims to it as well as unacclimated foreigners.
These epidemics, those of smallpox and other diseases that at times make their appearance in Yucatan, generally present themselves after the rainy season, particularly if the rains have been excessive. The country being extremely flat, the drainage is necessarily very bad: and in places like Merida, for example, where a crowding of population exists, and the cleanliness of the streets is utterly disregarded by the proper authorities, the decomposition of vegetable and animal matter is very large; and the miasmas generated, being carried with the vapors arising from the constant evaporation of stagnant waters, are the origin of those scourges that decimate the inhabitants. Yucatan, isolated as it is, its small territory nearly surrounded by water, ought to be, if the laws of health were properly enforced, one of the most healthy countries on the earth; where, as in the Island of Cozumel, people should only die of old age or accident. The thermometer varies but little, averaging about 80° _Far_. True, it rises in the months of July and August as high as 96° in the shade, but it seldom falls below 65° in the month of December. In the dry season, from January to June, the trees become divested of their leaves, that fall more particularly in March and April. Then the sun, returning from the south on its way to the north, passes over the land and darts its scorching perpendicular rays on it, causing every living creature to thirst for a drop of cool water; the heat being increased by the burning of those parts of the forests that have been cut down to prepare fields for cultivation.