458 



into the blue* of the air. This intensity, mea- 

 sured with the cyanometer of Saussure, was 

 found from November to January generally 18°, 

 never above 20°. On the coasts it was from 

 22° to 25°. I remarked in the village of Carac- 

 cas, that the wind of Petare sometimes contri- 

 butes singularly to give a pale tint to the celes- 

 tial vault. On the 22d of January the blue of 

 the sky was at noon in the zenith feebler than 

 I ever saw it in the torrid zone -J*. It corres- 

 ponded only to 12° 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°. 

 I have often observed at sea, but in a smaller 

 degree, a similar effect of the wind on the colour 

 of the serenestsky. 



We know less exactly the mean temperature 

 of Caraccas, than that of Santa Fe de Bogota, 

 and of Mexico. I believe however I can de- 

 monstrate, that it cannot be very distant from 

 twenty or twenty-two degrees. I found by my 

 own observations during the three very cool 



* See ch. iii, vol. ii, p. 101 and foil. 



t At noon, thermometer in the shade 23*7° (in the sun, 

 out of the wind, 30'4°) ; Deluc's hygrometer, 36*2° j cyano- 

 meter at the zenith, 12°, at the horizon 9°. The wind ceased 

 at three in the forenoon. Th. 21° 5 hygr. 39*3° ; cyan. 16°. 

 At six o'clock, therm. 20 2° ; hygr. 39°. 



