ON NINE BALLOON ASCENTS IN 1863 AND 1864. 



291 



Table VII. (continued.) 

 Setenteenth Ascext. 



January 12. — The temperature of the dew-point on leaving the earth was 

 36°, that of the air 41 1°, the degree of humidity was 80. The air gradually 

 became more moist on ascending till 1300 feet was reached, when the dif- 

 ference between the two temperatures was 3°-l ; a warm current was then 

 met with, but the difference between the two temperatures did not vary 

 much tin 2200 feet was passed, then it increased to 10|° at 4000 feet ; the 

 air again became moist, and at 6000 feet the difference of temperature 

 amounted to only 4|°, with 83 as the degree of humidity. The depression 

 of the wet thermometer below the dry greatly increased, tiU at 9300 feet it 

 was 20°-7, the degree of humidity being 38 ; and at 9800 feet cloud was 

 entered ; the difference decreased to 12°-2, and the degree of humidity in- 

 creased to 56; the air then became drier, and at 11,900 feet (the highest 

 point) the difference was 23°- 7, and the degree of humidity 42. On descend- 

 mg the ail- gradually became moist, till at 8600 feet it was nearly saturated, 

 then became somewhat drier, but was again nearly saturated at .5000 feet, 

 the degree of humidity being 93 ; again it became drier, but at 2000 feet the 

 au- was within 1° of saturation, after which it became slightly drier tiU the 

 ground was reached. 



■Cr2 



