174 ESSAY 



above it, had precisely the same heat. The 

 depth of the snow was 4 inches. 



My next experiment took place on the even- 

 ing of the 6th, the intervening day having been 

 snowy. The sky was clear, but the air had a 

 considerable motion. The heat of the atmo- 

 sphere, at the height of 4 feet, was at 9% h. 26; 

 while that of the surface of the snow, and of 

 swandowri lying upon it, was 22. The depth 

 of the snow was now about 5 inches. 



On the 7th, a little after sunset, the heat of 

 the air in the garden was 23, that of the surface 

 of snow 19, but that of swaridown lying upon 

 the snow only 15. There was then a gentle 

 breeze ; some parts of the sky were covered with 

 clouds, and the lower atmosphere was a little 

 obscure. While the exposed surface of the 

 snow was 19> a part of its surface, which had 

 been covered, about 20 minutes, with a piece 

 of pasteboard, was 22. Grass, at the bottom 

 of the snow, was 31, and the earth an inch be- 

 neath the grass 32. 



After this, there was no fit time for observa- 

 tion until the 13th. The thermometers were 

 exposed at 8 h. on the evening of that day, the 

 sky being then without clouds ; but the stars 

 were not bright, and there was a perceptible 

 motion in the air. At 83- h. the temperature of 

 the air was 22^, that of the surface of the snow 



