The Co-Efficient of Humidity. 139 
Heather Moor (Callunetum vulgaris). 
Sub-Peats: at 2 to 5 inches from surface. 
No. 
Date. 
Moor. 
Water 
Loss 
at 15° 
% 
% of Air-dry Peat. 
Water. 
Loss at 
100° 
Humus. 
Mineral 
Residue. 
Humus. 
y 
X 
tn 
102 
Aug., 1910 
Broadhead 
36-6 
31 
14-3 
82-5 
2-5 
58 iii. 
June, 1906 
Bellhouse 
29-4 
1-6 
9-9 
88-5 
30 
206 ii. 
April, 1912 
Greetland 
250 
20 
8-3 
89-7 
3 0 
145 ii. 
June, 1911 
Bellhouse 
17-8 
1-5 
71 
91 -4 
2-5 
207 ii. 
April, 1912 
Greetland 
20-3 
1-3 
61 
92-6 
3-3 
205 ii. 
> » 
20-5 
1-2 
5-9 
92-8 
35 
105 
Aug., 1910 
Erringden 
22-2 
11 
5-7 
93-1 
3-85 
99 ii. 
Norland ... 
16-2 
0-9 
4-7 
94-4 
3-2 
205 iii. 
April, 1912 
Greetland 
140 
0-9 
4-2 
94-9 
3-36 
107 
Aug., 1910 
Erringden 
7-7 
0-7 
30 
96-3 
2-5 
Mean 
21-0 
P4 
6-9 
91-6 
317 
An inspection of the tables shows that the water-content falls 
steadily with diminution of the humus-content in spite of variation 
in season and locality. The coefficient of humidity, as expressed 
by the ratio water/humus, has a mean value of 2 f 3 in the case of 
the peats and 3'0 for the sub-peats. There is here a decided 
difference, which will be considered presently, but within either 
division there is no great departure from its mean value. The 
extreme range in either case is about 3 : 2 and this clearly represents 
the seasonal variation under the conditions already laid down, 
namely that soils are only sampled after a spell of dry weather. 
The range could certainly be extended by including more extreme 
conditions. Analyses made in August, 1911, during the prolonged 
drought of that summer, yield decidedly lower values for the Calluna 
habitat. But though valuable in determining the minimum value 
of the coefficient their inclusion here would confuse the general 
principle. 
VI.—Deduction of the Coefficient from the 
Individual Observations. 
Having obtained two series of numbers expressing the conditions 
of the Heather Moor as displayed in the peat and the sub-peat 
respectively, the question arises—what is the most suitable treatment 
of these experimental values to obtain a constant to express the 
humidity of the Calluna habitat ? Are the variations from the mean 
value such as have been already anticipated as inevitable, from the 
