124 Proceedings of the Royal Society of Edinburgh. [Sess. 
experiments in the laboratory and in the soil itself. For comparison, I have 
given alongside them the values obtained in similar soils by well-known 
authorities. 
Table II. 
Constant. 
The author. 
E. J. Russell, Soil 
Conditions and Plant 
Growth. 
. 
Ingersoll and Zobel, 
Theory of 
Heat Conduction. 
A. D. Hall, The 
Soil. 
Hosier and Gustafson, 
Soil Physics and 
Management. 
True deusity of dry soil 
D = 2*5 
2-31 
i 
2*65 
2-62 
Apparent density of 
dry soil . 
D = l*25 
1-46 
1-22 
1-36 
Density of normal wet 
soil .... 
D = l-7 
1-65 
1 -55 (20% mois- 
Percentage volume : 
ture) 
(1) Solid . 
50% 
52-7%- 
50-8% 
52-9% 
(2) Water * 
45% 
40-0% 
49-2% 
47-1% 
(3) Air 
5% 
7-3% 
Specific heat wet soil . 
S = -46 
•45 
•36 (20% mois- 
Calories required to 
ture) 
raise 1 c.c. 1° C. 
C = -8 
•74 
•55 (20% mois- 
Latent heat of freezing 
ture) 
1 C.C.* 
L = 36 calories 
Conductivity * 
K = *004 
•0037 
DifFusivity * 
H 2 =*005 
•0049 
•005 
* During the past winter the soil has remained almost uniformly damp up to the 
beginning of April. If, however, the surface soil becomes dry, new values for these must 
be found by experiment. 
Throughout the paper the following notation will be used : — 
<f) m = mean of surface temperatures °F. during observations. 
<f>' m = mean of 4 in. depth „ „ „ 
6 m = 4>' m — = mean difference of surface and 4 in. depth temperatures 
°F. during observations. 
0 ' = fall of surface temperature °F. during observations. 
0" — fall of 4 in. depth „ „ „ 
0' F = fall of surface temperature °F. below 32° F. 
x — depth of soil frozen (in centimetres) at beginning of observations. 
x = depth of soil „ „ at end of observations. 
x m = mean depth „ „ during observations. 
h = hours during period of observations. 
R = mean rate of radiation in calories per square centimetre per minute 
during period of observations. 
The temperatures all through this paper are in degrees Fahrenheit. 
