194 WOW 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 fer heat, that of lime sand being assumed 
as 100. 
Lime sand... cc... wees be ces cet MOMIES enone 100 
atts eind 52. 1403h0. taurine ae 3 . *o Ga eee 95.6 
POOP OLN 6d ooo cans ela ai eee 2 St. Aiea 76.9 
EV OMEN on cc Gh ose ee eek oe ee 2. Sa eee eee 73.8 
ay tiie ce ote ee che eee 2 #0 eee 71.8 
Clay plow land:.........,..2.9250 228) 0? Se 70.1 
Heavy Clay .2.0 cine od sib da nascteaecdeeee, oe sn 68.4 
Pre Sy Cle es oor mts pie see 2 OS. oe ae 66.7 
EPOCH CAVE 2. .o° sc Lbs cae ee ebro we 9 8. 62 Se ee 64.8 
Fine carb. lime....................,2 < e 61.5 
PP TEAIEN dre cas oasis bad Lad a ok ee 1 haa eee ee 49.0 
EON Se eos UF daa ie Badia aha ae Ll 8 20. coe 338.0 
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. 
