144 
W. B. Crump. 
and then the remaining water is a function of the humus. Not 
only is it a function, but it is the same function as in the case of the 
peats, for the value of the coefficient is the same in each group. 
The question naturally arises whether this residual water (b) is 
itself a constant, or whether it is not a variable depending upon the 
percentage of earthy (i.e., non-humous) matter in the soil sample. 
Practically it may he regarded as a constant because it only has to 
be taken into account when the soils contain upwards of 80 or 85% 
of earthy matter, so that any variation of the amount is too small to 
affect the quantity of residual water so long as that is itself as low 
as the value arrived at above. The nature of the soil particles is 
likely to have a much greater influence on its magnitude. The sub¬ 
peats examined are all coarse sands composed largely of quartz- 
grains and free, or nearly so, from clay. In this case the residual 
water does not exceed 5 % of the air-dry soil. What it may amount 
to in the case of clay soils is still unknown. 
Accepting 5% as a sufficiently accurate allowance, in each case 
it is now possible to deduct this from the total water-content of the 
sub-peats tabulated above and so obtain the true coefficient of 
humidity for each sample. The improvement affected by this 
deduction is apparent on comparing the values of the coefficient in 
the samples that include both peats and sub-peats. 
Coefficient of Soil-Humidity in successive layers after deduction 
of Residual Water (5%). 
Soil No. 
58 i. 
m 
2-4 
Soil No. 
205 i. 
rn 
2-2 
ii. 
• • • 
2-1 
ii. 
(3-5) 
2-6 
iii. 
(3-0) 
2-4 
iii. 
(3-4) 
21 
99 i. 
• • • 
21 
206 i. 
• • • 
216 
ii. 
(3-2) 
2-4 
ii. 
(3-0) 
2-4 
145 i. 
• • • 
1-7 
207 i. 
• • • 
2-4 
ii. 
(2-5) 
1-8 
ii. 
(3-3) 
2-5 
The uncorrected values of in for the sub-peats are placed within 
brackets. 
Before finishing with the humidity equations it is perhaps worth 
while to enquire what values would be obtained in the case of the 
peats if the equation y=b + tnx applied to them. Using equations 
3 and 4 the method of least squares gives the following results:— 
Peats. 
Residual Water ( b) ... ... —1*5% 
Coefficient of Humidity (in) ... 2'35 
