196 HOW CROPS FEED. 
from ever acquiring the temperature it shortly attains 
when dry. 
From this cause the difference in temperature between 
dry and wet soil may often amount to from 10° to 18°. 
On this point, again, Schtibler furnishes us with the re- 
sults of his experiments. Columns 4 and 5 in the table 
below give the temperatures which the thermometer at- 
tained when its bulb was immersed in various soils, both 
wet and dry, each having its natural color, (Columns 1 
and 2 are referred to on p. 191.) 
1 2 3 4 5 6 
Surface. Surface. 
Whit-|Black- Differ- Differ- 
ened. ened. | ence. Wet. | Dry. ence. 
Magnesia, pure white................ 108.7°} 121.3°) 12.6° | 95.2°} 108.77) 13.5° 
Fine carbonate of lime, white......... 109.2°| 122.9°] 13.7° | 96.1°| 109.4°| 13.3° 
Gypsum, bright white-gray............ 110.3°| 124.3°| 14.0° | 97.3°] 110.5°] 13.2° 
Plow' land, @rayi: 5 icceaunwis deci ve 107.6°} 122.0°| 14.4° | 97.7°| 111.7°| 14.0° 
Sandy clay, yellowish. ............. 0. 108.3°| 121.6°) 13.3° | 93.2°] 111.4°) 13.2° 
Quartz sand, bright yellowish-gray... [109.9°| 123.6°; 13.7° | 99.1°| 112.6°| 13.5° 
Loam, yellowish, .............2-2 0 ee 107.8°} 121.1°} 13.3° | 99.1°/ 112.1°) 13.0° 
Lime sand, whitish-gray.,............ 109.9°} 124.0°| 14.1° | 99.3°} 112.1°] 12.8° 
Heavy clay soil, yellowish-gray........ '107.4°| 120.4°} 13.0° | 99.37) 112.8°| 13.0° 
Pure clay, bluish-gray................. 106.3°) 120.0°} 13.7° | 99.5°] 113.07} 13.5° 
Garden mould, blackish-gray.......... |108.3°| 122.5°) 14.2° | 99.5°| 113.5°| 14.0° 
Slaty marl, brownish-red............. /108.3°] 123.4°) 15.1° }101.8°] 115.3°| 13.5° 
Humns, brownish-black............... 1108 .5°! 120.9°! 12.4° (103.6°| 117.3°| 13.7° 
We note that the difference in favor of the dry earth is 
almost uniformly 18° to 14°. This difference is the same 
as observed between the whitened and blackened speci- 
mens of the same soils, (Column 3.) 
We observe, however, that the wet soil in no case be- 
comes as warm as the same soil whitened. We notice 
further that of the wet soils, the dark-colored ones, humus 
and marl, are most highly heated, Further it is seen that 
coarse lime sand (carbonate of lime) acquires 3° higher 
temperature than fine carbonate of lime, both wet, prob- 
ably because evaporation proceeded more slowly from the 
coarse than from the fine materials. Again it is plain on 
comparing columns 1, 2, and 5, that the gray to yellowish 
brown and black colors of all the soils, save the first three, 
assist the elevation of temperature, which rises nearly 
