The Extreme Purity Of The Atmosphere Which Constantly Prevails In The Low Regions During The Dry Season, Counterbalances The Elevation Of Site And The Rarity Of The Air On The Table-Lands. The Elevated Strata Of The Atmosphere, When They Envelope The Ridges Of Mountains, Undergo Rapid Changes In Their Transparency.

The night of the 11th of November was cool and extremely fine.

From half after two in the morning, the most extraordinary luminous meteors were seen in the direction of the east. M. Bonpland, who had risen to enjoy the freshness of the air, perceived them first. Thousands of bolides and falling stars succeeded each other during the space of four hours. Their direction was very regular from north to south. They filled a space in the sky extending from due east 30 degrees to north and south. In an amplitude of 60 degrees the meteors were seen to rise above the horizon at east-north-east and at east, to describe arcs more or less extended, and to fall towards the south, after having followed the direction of the meridian. Some of them attained a height of 40 degrees, and all exceeded 25 or 30 degrees. There was very little wind in the low regions of the atmosphere, and that little blew from the east. No trace of clouds was to be seen. M. Bonpland states that, from the first appearance of the phenomenon, there was not in the firmament a space equal in extent to three diameters of the moon, which was not filled every instant with bolides and falling stars. The first were fewer in number, but as they were of different sizes, it was impossible to fix the limit between these two classes of phenomena. All these meteors left luminous traces from five to ten degrees in length, as often happens in the equinoctial regions. The phosphorescence of these traces, or luminous bands, lasted seven or eight seconds. Many of the falling stars had a very distinct nucleus, as large as the disk of Jupiter, from which darted sparks of vivid light. The bolides seem to burst as by explosion; but the largest, those from 1 to 1 degree 15 minutes in diameter, disappeared without scintillation, leaving behind them phosphorescent bands (trabes) exceeding in breadth fifteen or twenty minutes. The light of these meteors was white, and not reddish, which must doubtless be attributed to the absence of vapour and the extreme transparency of the air. For the same reason, within the tropics, the stars of the first magnitude have, at their rising, a light decidedly whiter than in Europe.

Almost all the inhabitants of Cumana witnessed this phenomenon, because they had left their houses before four o'clock, to attend the early morning mass. They did not behold these bolides with indifference; the oldest among them remembered that the great earthquakes of 1766 were preceded by similar phenomena. The Guaiqueries in the Indian suburb alleged "that the bolides began to appear at one o'clock; and that as they returned from fishing in the gulf, they had perceived very small falling stars towards the east." They assured us that igneous meteors were extremely rare on those coasts after two o'clock in the morning.

The phenomenon ceased by degrees after four o'clock, and the bolides and falling stars became less frequent; but we still distinguished some to north-east by their whitish light, and the rapidity of their movement, a quarter of an hour after sunrise. This circumstance will appear less extraordinary, when I mention that in broad daylight, in 1788, the interior of the houses in the town of Popayan was brightly illumined by an aerolite of immense magnitude. It passed over the town, when the sun was shining clearly, about one o'clock. M. Bonpland and myself, during our second residence at Cumana, after having observed, on the 26th of September, 1800, the immersion of the first satellite of Jupiter, succeeded in seeing the planet distinctly with the naked eye, eighteen minutes after the disk of the sun had appeared in the horizon. There was a very slight vapour in the east, but Jupiter appeared on an azure sky. These facts bear evidence of the extreme purity and transparency of the atmosphere in the torrid zone. The mass of diffused light is the less, in proportion as the vapours are more perfectly dissolved. The same cause which checks the diffusion of the solar light, diminishes the extinction of that which emanates either from bolides from Jupiter, or from the moon, seen on the second day after its conjunction. The 12th of November was an extremely hot day, and the hygrometer indicated a very considerable degree of dryness for those climates. The reddish vapour clouded the horizon anew, and rose to the height of 14 degrees. This was the last time it appeared that year; and I must here observe, that it is no less rare under the fine sky of Cumana, than it is common at Acapulco, on the western coast of Mexico.

We did not neglect, during the course of our journey from Caracas to the Rio Negro, to enquire everywhere, whether the meteors of the 12th of November had been perceived. In a wild country, where the greater number of the inhabitants sleep in the open air, so extraordinary a phenomenon could not fail to be remarked, unless it had been concealed from observation by clouds. The Capuchin missionary at San Fernando de Apure,* (* North latitude 7 degrees 53 minutes 12 seconds; west longitude 70 degrees 20 minutes.), a village situated amid the savannahs of the province of Varinas; the Franciscan monks stationed near the cataracts of the Orinoco and at Maroa,* (* North latitude 2 degrees 42 minutes 0 seconds; west longitude 70 degrees 21 minutes.) on the banks of the Rio Negro; had seen numberless falling-stars and bolides illumine the heavens. Maroa is south-west of Cumana, at one hundred and seventy-four leagues distance. All these observers compared the phenomenon to brilliant fireworks; and it lasted from three till six in the morning.

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