The Wind Of Petare Coming From The East And South-East, By The Eastern Extremity Of The Valley Of The Guayra, Brings From The Mountains And The Interior Of The Country, A Drier Air, Which Dissipates The Clouds, And The Summit Of The Silla Rises In All Its Beauty.

We know that the modifications produced by winds in the composition of the air in various places, entirely escape our eudiometrical experiments, the most precise of which can estimate only as far as .0003 degrees of oxygen.

Chemistry does not yet possess any means of distinguishing two jars of air, the one filled during the prevalence of the sirocco or the catia, and the other before these winds have commenced. 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.

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