ON DEW, &c. 



183 



when first placed on the board. At this last 

 observation, the wool, though 9i colder than 

 the air, was still without any increase in weight ; 

 but the swandown, which was 1 colder than 

 the wool, had gained \ a grain. My experi- 

 ments now properly ceased ; but having suffered 

 the thermometers, which had been placed on the 

 wool and swandown, and in the air, to remain 

 in those situations, I examined them again at 

 8h. 45m., that is, 2h. 0m. after they had 

 been first exposed. The wool, which was still 

 9j colder than the air, had gained somewhat 

 less than a grain ; and the swandown, which 

 was now llj colder than the air, had gained 

 2 grains, including the J grain already men- 

 tioned. When these last observations were 

 made, the sky was entirely cloudless, and the 



atmosphere very calm. 



< 



TABULAE VIEW OF OBSERVATIONS 



on the Evening of dugust 19, 1813. 



* In these experiments, contrary to what usually happens, 

 the grass was almost constantly colder than the filamentous 

 substances, although they were placed upon the raised board 



