AND PORTO SANTO. 129 



The mean of thirty-eight observations in the month of Novem- 

 ber in Funchal, 154 feet above the sea, at 8^ a.m. 2 p.m. and sun- 

 set, by Leslie's hygrometer was 3.2 ; of 41 by de Saussiire's, 65.1 ; 

 of 24 observations in December, by Leslie, 3. 1 ; of 37 by De Saussure, 

 75.3; of 31 by De Saussure in January, 83.3. During a very 

 strong wind in the month of November De Saussure's fell from 

 71 to 50 within five hours: its maximum of dryness during my 

 observations was 41° (in the morning of the 22d of November) 

 the thermometer being at 19 C. or 66,2 F., and a correspondent 

 observation with Leslie's hygrometer giving 5.3 '. De Saussure's 

 stood at 57° on the Peak of Euivo, before the clouds had ascended, 

 the thermometer being at 49 F., at which time (10. a.m.) Leslie's 

 descended to 2.4 at Funchal, (equal to 85° of De Saussure's, from 

 a comparison of numerous coincident observations,) the ther- 

 mometer being at 68|° : now if we reduce the former observation 

 to the same temperature as the latter, taking the results of the 

 experiments of De Saussure for ascertaining the weight of moisture 

 contained in the air at different degrees of the thermometer and 

 hygrometer, for the data of our calculation §, the 57° of Kuivo 

 becomes 46f° which gives but 162 feet to each degree for the 

 decrease of humidity in this region ^. Snow descends in Madeira 



' Lieutenant Colonel Franzinl informed me, that no hygrometrical observations had 

 been made in Lisbon. I made the following, during my stay therein September: 

 8. a.m. mean of 21, Saussure, 71.3 ; of 19, Leslie, 3.7 ; of 19, Thermometer 71. F. ; 

 2. p.m. mean of 19, S. 61 ; of 20, L. 6 ; of 18 Thermometer 75.6: 9. p.m. mean of 

 17, S. 67: of 16, L. 5.6; of 16 Thermometer 71.8. The minimum of my obser- 

 vations was 23.5 S. a corresponding observation of Leslie giving 11^ ; Temperature 

 80|, September 4th, at 2. p.m. 



^Essais sur VHygrometrie. Neuchatel, 1783. p. 181. 



^ I endeavoured to procure De Saussure's cyanometer through professor Pictet, but 

 unsuccessfully, the inventor's standard being lost ; the accurate degradation of blue 

 over the whole circumference of the apparatus, and the absolute similarity of the tint 

 or shade of a given division of the copy with that of the same number in the original, 



S 



