194 IIOW CROPS FEED. 
have least effect on light-colored soils. (See the table on 
p. 196.) 
The Rapidity of Change of Temperature independently 
of color or moisture has been determined on a number of 
soils by Schiibler. A given volume of dry soil was heat- 
ed to 145°, a thermometer was placed in it, and the time 
was observed which it required to cool down to 70°, the 
temperature of the atmosphere being 61°. The subjoined 
table gives his results. In one column are stated the 
times of cooling, in another the relative power of retaining 
heat or capacity for heat, that of lime sand being assumed 
as 100. 
HUMCISAN oo:s.csds sama wceancasdee ands 83 hours 80 min...... 100 
Quarts GANA: « sascoenass Aeees esse ee Be A Oe ede a vial 95.6 
POUheL 6 2C1IY siacsied Nea tanvees avniniess Ae ee) Oe 6.9 
APY URN nee one ea dgia Bea ha ee eS Bi SE BE ane weet 3.8 
TAT TOs cao asd etakedinwanceuaaws Br BEY 280) is dias ae 71.8 
Chey lew Lit esas cake densi coeveues DQ OT Mesias et 70.1 
Cav Clay: cacihins stones sean saiss ee eer en 68.4 
Pureeray clays. ees caove case caonsedsix TDS aaseterssareld 66.7 
Garden earth... eee cece eee eee eee Dior 88! NG Sse adensd 64.8 
Fine carb. limescses scenes ecdes sauat eID ys ewenad 61.3 
HUB cec3o se bSiemdiciee de eioecie scien LOS Bo Be wenus 49.0 
MAGN eS 10. scie cs wee i syris eis ow oe'e’ steers Be OE Re Eo eeisncle 38.0 
It is seen that the sandy soils cool most slowly, then 
follow clays and heavy soils, and lastly comes humus. 
The order of cooling above given is in all respects 
identical with that of warming, provided the circumstances 
are alike. In other words these soils, containing no moist- 
ure, or but little, and exposed to heat of low intensity, 
would be raised through a given range of temperature in 
the same relative times that they fall through a given 
number of degrees. 
It is to be particularly noticed that dark humus and white 
magnesia are very closely alike in their rate of cooling, 
and cool rapidly; while white lime sand stands at the op- 
posite extreme, requiring twice as long to cool to the same 
extent. These facts strikingly illustrate the great differ. 
