When The Reddish Vapour Spreads Lightly Over The Sky, The Great Stars, Which In General, At Cumana, Scarcely Scintillate Below 20 Or 25 Degrees, Did Not Retain Even At The Zenith, Their Steady And Planetary Light.

They scintillated at all altitudes, as after a heavy storm of rain.* (* I have not observed any direct relation between the scintillation of the stars and the dryness of that part of the atmosphere open to our researches.

I have often seen at Cumana a great scintillation of the stars of Orion and Sagittarius, when Saussure's hygrometer was at 85 degrees. At other times, these same stars, considerably elevated above the horizon, emitted a steady and planetary light, the hygrometer being at 90 or 93 degrees. Probably it is not the quantity of vapour, but the manner in which it is diffused, and more or less dissolved in the air, which determines the scintillation. The latter is invariably attended with a coloration of light. It is remarkable enough, that, in northern countries, at a time when the atmosphere appears perfectly dry, the scintillation is most decided in very cold weather.) It was curious that the vapour did not affect the hygrometer at the surface of the earth. I remained a part of the night seated in a balcony, from which I had a view of a great part of the horizon. In every climate I feel a peculiar interest in fixing my eyes, when the sky is serene, on some great constellation, and seeing groups of vesicular vapours appear and augment, as around a central nucleus, then, disappearing, form themselves anew.

After the 28th of October, the reddish mist became thicker than it had previously been. The heat of the nights seemed stifling, though the thermometer rose only to 26 degrees. The breeze, which generally refreshed the air from eight or nine o'clock in the evening, was no longer felt. The atmosphere was burning hot, and the parched and dusty ground was cracked on every side. On the 4th of November, about two in the afternoon, large clouds of peculiar blackness enveloped the high mountains of the Brigantine and the Tataraqual. They extended by degrees as far as the zenith. About four in the afternoon thunder was heard over our heads, at an immense height, not regularly rolling, but with a hollow and often interrupted sound. At the moment of the strongest electric explosion, at 4 hours 12 minutes, there were two shocks of earthquake, which followed each other at the interval of fifteen seconds. The people ran into the streets, uttering loud cries. M. Bonpland, who was leaning over a table examining plants, was almost thrown on the floor. I felt the shock very strongly, though I was lying in a hammock. Its direction was from north to south, which is rare at Cumana. Slaves, who were drawing water from a well more than eighteen or twenty feet deep, near the river Manzanares, heard a noise like the explosion of a strong charge of gunpowder.

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