It Appears To Me Probable, That The Singular Effects Of The Catia, And Of All Those Currents Of Air, To The Influence Of Which Popular Opinion Attaches So Much Importance, Must Be Looked For Rather In The Changes Of Humidity And Of Temperature, Than In Chemical Modifications.

We need not trace miasms to Caracas from the unhealthy shore on the coast:

It may be easily conceived that men accustomed to the drier air of the mountains and the interior, must be disagreeably affected when the very humid air of the sea, pressed through the gap of Tipe, reaches in an ascending current the high valley of Caracas, and, getting cooler by dilatation, and by contact with the adjacent strata, deposits a great portion of the water it contains. This inconstancy of climate, these somewhat rapid transitions from dry and transparent to humid and misty air, are inconveniences which Caracas shares in common with the whole temperate region of the tropics - with all places situated between four and eight hundred toises of elevation, either on table-lands of small extent, or on the slope of the Cordilleras, as at Xalapa in Mexico, and Guaduas in New Granada. A serenity, uninterrupted during a great part of the year, prevails only in the low regions at the level of the sea, and at considerable heights on those vast table-lands, where the uniform radiation of the soil seems to contribute to the perfect dissolution of vesicular vapours. The intermediate zone is at the same height as the first strata of clouds which surround the surface of the earth; and the climate of this zone, the temperature of which is so mild, is essentially misty and variable.

Notwithstanding the elevation of the spot, the sky is generally less blue at Caracas than at Cumana. The aqueous vapour is less perfectly dissolved; and here, as in our climates, a greater diffusion of light diminishes the intensity of the aerial colour, by introducing white into the blue of the air. This intensity, measured with the cyanometer of Saussure, was found from November to January generally 18, never above 20 degrees. On the coasts it was from 22 to 25 degrees. I remarked, in the village of Caracas, that the wind of Petare sometimes contributes singularly to give a pale tint to the celestial vault. On the 22nd of January, the blue of the sky was at noon in the zenith feebler than I ever saw it in the torrid zone.* (* At noon, thermometer in the shade 23.7 (in the sun, out of the wind, 30.4 degrees); De Luc's hygrometer, 36.2; cyanometer, at the zenith, 12, at the horizon 9 degrees. The wind ceased at three in the afternoon. Thermometer 21; hygrometer 39.3; cyanometer 16 degrees. At six o'clock, thermometer 20.2; hygrometer 39 degrees.) It corresponded only to 12 degrees of the cyanometer. The atmosphere was then remarkably transparent, without clouds, and of extraordinary dryness. The moment the wind of Petare ceased, the blue colour rose at the zenith as high as 16 degrees.

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