RELATIONS OF THE SOIL TO HEAT. 19] 
Schiibler made observations on the temperatures at: 
tained by various dry soils exposed to the sun’s rays, 
according as their surfaces were blackened by a thin 
sprinkling of lamp-black or whitened by magnesia. His 
_ results are given in columns 1 and 2 of the following table 
(vide p. 196,) from which it is seen that the dark surface 
was warmed 13° to 14° more than the white. We like- 
wise notice that the character of the very surface deter- 
mines the degree of warmth, for, under a sprinkling of 
lamp-black or magnesia, all the soils experimented with 
became as good as identical in their absorbing power for 
the sun’s heat. 
The observations of Malaguti and Durocher prove that 
the peculiar temperature of the soil is not always so 
closely related to color as to other qualities. They studied 
the thermometric characters of the following soils, viz. : 
Garden earth of dark gray color,—a mixture of sand and 
gravel with about five per cent of humus; a grayish- 
white quartz sand; a grayish-brown granite sand; a fine 
light-gray clay (pipe clay); a yellow sandy clay; and, 
finally, four lime soils of different physical qualities. 
It was found that when the exposure was alike, the 
‘dark-gray granite sand became the warmest, and next to 
this the grayish-white quartz sand. The latter, notwith- 
standing its lighter color, often acquired a higher temper- 
ature at a depth of four inches than the former, a fact to 
be ascribed to its better conducting power. The black 
soils never became so warm as the two just mentioned. 
After the black soils, the others came in the following or- 
_ der: garden soil; yellow sandy clay; pipe clay; lime 
soils having crystalline grains; and, lastly, a pulverulent 
chalk soil. 
To show what different degrees of warmth soils may 
acquire, under the same circumstances, the following max- 
imum temperatures may be adduced: At noon of a July 
day, when the temperature of the air was 90°, a thermom- 
