315 



struck with this effect of a fog, which 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 

 find a particular attraction in fixing my eyes, 

 when the sky is serene, on some great constel- 

 lation, and seeing groups of vesicular vapours 

 appear and augment, as around a central nu- 

 cleus, and then disappear, and form themselves 

 anew. 



From the 28th of October to the 3d of No- 

 vember, the reddish fog was thicker than it had 

 yet been. The heat of the nights seemed stif- 

 ling, though the thermometer rose only to 26°. 

 The breeze, which generally cooled the air 

 from eight or nine o'clock in the evening, was 

 no longer felt. The atmosphere appeared as if 

 it were on fire. The ground, parched and dusty, 



atmosphere open to our researches. I have often seen at Cu- 

 mana a great twinkling of the stars of Orion and Sagittarius, 

 when Saussure's hygrometer was at 85°. At other times 

 these same stars, considerably elevated above the horizon, 

 emitted a steady and planetary light, the hygrometer being 

 at 90° or 93°. It is probably not the quantity of vapour, but 

 the manner in which it is diffused, and more or less dissolved 

 in the air, that determines the twinkling, 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 twinkling is stronger in very cold 

 weather. 



