1920-21.] Relation of Soil Colloids to Conductivity of Soil. 65 
The expected values for for a mean surface temperature of 10° C. 
K 0 
would be *45 in clay loam, and ’55 in sand ; it happened that the ignited clay 
20 
I 
o o 
19 
MEAN 
SURFACE 
TEMP. 
17 
FIG. I * 
SAND 
CHANGE /N VALUE OF ■— iV/TH • 
CHANGE OF MEAN SURFACE TEMPER f 
o 
o 
16 
o 
15 
14 
13 
12 
10 
* 
9 
8 
I » 
I 
o 
o 
7 
6 
5 
4 
3 
2 
•30 -32 
*- I • 
* t 
* 
*- 
l 
•34 -36 -38 -40 -42 -44 
I 
I 
I 
1 
I 
t 
1 
•46 -48 
= 6 HOUR /NTERZAL 
MIN. TO MAX. 
@ - 9 
0 — 1 / 
1 
•50 -52 
AV 
Ro 
•54 -56 
loam had a value of ^ equal to '55 also, and the curves for it and sand have 
run together faithfully day by day for over two months, during which the 
mean surface temperature has fluctuated between 9° C. and just above 0° C. 
VOL. xli. 5 
