66 
Proceedings of the Royal Society of Edinburgh. [Sess. 
R 
The values of ^ 3 in ignited clay loam and sand have only varied between 
■54 and *57 during this time, while for clay loam the variation is from 
'13 
30 
MEAN 
SURFACE 
TEMP. 
fig. n 
CLAY LOAM 
0 
1 
o 
°c. 
CHANGE /N VALUE OF ^ W/TH 
I 
o • 
CHANGE OF MEAN SURFACE TEMPER f 
I 
0 
1 
0 
1 
o 
* 
if 
0 
0 
I 
# 
if 
if 
if =6 HOUR INTERVAL 
M/M. TO MAX.. 
m = 9 
o = // 
| | | ES 
II \ Ro 
•28 -30 -32 - 34 - 32 -38 -40 - 42 -44 - 46 
*40 to '48, according as the mean surface temperature was near 0° C. 
or 9° C. 
Now, ignition destroys the organic matter and soil colloids, so that the 
R 
similar small fluctuations of p^-in ignited clay loam and sand — neither of 
