786 



Some delicate experiments which I tried, to 

 verify the point of extreme humidity of my 

 whalebone hygrometer, at the moment of my 

 departure from Cumana for Caraccas, led me 

 to suspect that towards the end of October, 

 that instrument indicated 1.8° of too great hu- 

 midity. The 50th degree of my hygrometer of 

 Deluc, was perhaps equal only to 84.7° of the 

 hair hygrometer, while the 50° of an hygrometer 

 of Deluc, well rectified in those extreme points, 

 make 85.5° of the hair hygrometer of Saussure. 

 The 5th of September, at 3 h in the afternoon 

 (th. 23° R. ; hygr. 36° Del.), I saw large drops 

 of rain fall from a sky quite blue, and without 

 any traces of clouds. The same day, between 

 noon and 3 h , the thermometer rose, in the 

 streets of Cumana, in the shade, but exposed to 

 the reflection of the edifices, five feet above the 

 soil, to 29° R. (36.2° cent.). The inhabitants 

 of Cumana are exposed to that heat during the 

 greater part of the year, in the open air, in the 

 streets, and great squares, on a white and pow 

 dery soil. When the mean temperature of the 

 day (from sun-rise to sun-set, without reckon- 

 ing the night), is 22°-24° R., great coolness is 

 enjoyed between 17°- 19° R. (21.8°-23.7° cent.). 

 In the driest time, during the night, (at 19° 

 R.), the hygrometer of Deluc often keeps up at 

 30° (65.3° Saussure). Sunrise makes the hygro- 

 meter move to humidity, but very slowly. The 



