RESEARCH METHODS IX STUDY OF FOREST ENVIRONMENT. 129 
Considering only that which is particularly relevant to the prob- 
lem, it was found by Buckingham that considerably different types 
of soil show about the same capillary flow under the same con- 
ditions. A moist and a dry layer of soil were, in these experiments, 
placed one above the other in direct contact. The amount transferred 
from the moister to the drier soil in a given time was found to depend 
almost wholly on their original difference in moisture content; fur- 
thermore, the greater part of this transfer was accomplished in a 
very short time. 
A great manv methods have been devised for showing the rate of 
movement of water in soils; but none of these, so far as known, is 
readily standardized or will produce closely comparable results on 
duplication with the same soil. This is because the granulation of the 
soil has an important influence on the capillary forces set up. In 
view of this difficulty, no procedure can be suggested which is more 
likely to produce reliable comparative data than the following : 
After the completion of the moisture equivalent determination on 
the centrifugal machine, all water having been extracted which is 
subject to the force employed (whether this be 100 gravity or 3,000 
gravity), and the soil being then in a state of compactness which is 
somewhat close to a standard, add to the unit volume of soil a small 
standard amount of water, say 10 cubic centimeters; as soon as this 
has been absorbed in the surface centrifuge again for short periods 
until the amount added has been extracted, determining the time for 
this unit process. This should be a measure of the resistance offered 
by the soil to the passage of a unit amount of water through a unit 
distance (the distance may be somewhat variable, but correction may 
be made directly). 
It would be unwise to leave this very open subject without ref- 
erence to the possibilities of the electrical conductivity method: for, 
as Buckingham (116) has shown, there is a close correlation between 
the conditions affecting electrical conductivity and those affecting 
water conductivity in a given soil. It would seem that there is also 
a chance for correlation between heat conductivity and water con- 
ductivity. 
CHEMICAL ANALYSIS FOR NUTRIENTS. 
It may be said that almost nothing is known as to the quantitative 
requirements of most plants for the nutrient materials obtainable 
from the soil with the soil water, and little enough as to the elements 
which in greater or less quantity are essential for growth. The lack 
of knowledge with respect to trees is especially glaring, 20 little atten- 
*- , ° The writers do not consider the evidence obtained by the examination of leaf ash 
and other similarly crude methods, even as convincing evidence of qualitative require- 
ments. 
S2769— 22 9 
