292 



REPORT 1864. 



Table YII. (continued.') 

 Eighteenth Ascent. 



April 6. — The temperature of the dew-point on leaving the earth was 

 38°-5, and the degree of humidity 76, the difference between the temperature 

 of the air and that of the dew-point being 7°. 



This difference remained nearly stationaiy till about 1400 feet, where niist 

 was prevalent; the baUoou entered cloud at 2100 feet, and by the time 

 2470 feet was reached the difference had dechued to 2°. The air then 

 became rather drier, but by the time 3500 feet was attained, the difference 

 only equalled 1°, after which the air became several times moist and dry ; at 

 6900 feet the difference was 3°, then it suddenly became drier, and continued 

 to get so till 9400 feet, when it amounted to 19|°, and continued about the 

 same till 11,000 feet (the highest point), where it equalled 21°. On descend- 

 ing the air gradually became moist, and continued so till within 1400 feet 

 of "the earth, the difference being at that height 5°, after which it began to 

 increase, and continued to do so, till on the ground it amounted to 9°, these 

 respective values being 45°-8 and 36°'8. 



Juno 13.^The temperature of the dew-point was 44|° on the ground 



