78: 



17th September, tne Hygrometer of Deluc, at 

 4 h in the morning, 44.7° (th. 17.9° R.). During 

 twilight, which lasts but some minutes, hygr. 

 45.5° (th. 17.5°). The evaporation caused by 

 the first unrefiected rays of the sun produces 

 cold. At 6 h , a little wind is felt, as in Europe ; 

 hygr. 44.5° (th. 17.8°) ; at 6i h , hygr. 38°. The 

 19th September, hygr. at midnight, 35° (th. 

 19.4°) ; at 4h in the morning, hygr. 39° (th, 

 19°) ; at 6 h in the morning, hygr. 41° (th. 22 a 

 R.). In examining the whole of my hygrome- 

 tric observations at Cumana, I find 22° R. 

 (27.5° cent.) of temperature. 



Mean of the day, July 47.6° of night 56.2o of 24 h 51.9° 

 Aug. 45.4 68.0 §1.7 



Oct. 46.7 *>5,7 51.4 



Mean of 3 months 46.6 56.7 51.7 Deluc. 



or 83.5 89.1 86.3 Sauss. 



At Geneva, the mean of 1796-1802 also yields 

 82.3° of the hygrometer of Saussure, but by 

 9.6° cent, of temperature. When the estimates 

 of the atmospheric humidity in degrees of the 

 hygrometer of Saussure, draw near each other 

 (between 83°-89°), the arithmetical mean differs 

 very little from the real hygrometrical mean. 

 The error would become serious between 70° 

 and 90°, as we may be convinced in examining 

 the table of the tension of the vapors, founded 



