RESEARCH METHODS IN STUDY OF FOREST ENVIRONMENT. 147 
Bates (145) in discussing the actual measure of heat available for 
use in the plant. The first of these influences may be practically 
ignored, as was the case with humidity, if there is available a record 
which has integrated all the factors in evaporation. It is believed, 
however, that most ecological studies will be found deficient if the 
record of wind movement is not obtained. 
To obtain a record of wind movement in the forest which may cause 
mechanical injury, the anemometer should undoubtedly be placed 
almost at the tops of the tree crowns, where the most severe winds 
will be encountered. A strong support is needed to prevent loss of 
record at the most critical times. 
In the study of reproduction and of other shall plants, it may even 
be necessary to dig a pit for the stem of the anemometer in order that 
the cups may be close to the ground surface. 
The standard Eobinson anemometer is the most practical instru- 
ment for all outside work. Because of a friction factor, it underrates 
wind of low velocity such as is often characteristic of the forest floor, 
and slightly overrates the high velocities. The amount of wind move- 
ment may be read on the dial of the instrument to tenths of miles, 
and the anemometer may also be electrically connected to a register 
so as to give a record of each mile of wind movement. Because it 
records no less than a mile of wind movement, the Robinson ane- 
mometer is not wholly satisfactory from the standpoint of mechani- 
cal injury to trees. It is possibly more true in mountainous regions 
than elsewhere that the winds of greatest velocity are gusty, and it 
seems likely that the gusts of only a few seconds' duration may have 
at least twice the mean velocity recorded for whole miles. While 
daily or more frequent readings of the anemometer dial may be suffi- 
cient where a definite use of the wind record can not be foreseen, in 
many cases the occurrence of maximum and minimum velocities, the 
movement by day and by night, etc., as obtainable from the electri- 
cally operated register, will be desired. Since the current required 
for operation is only 2 or 3 volts, connection with the anemometer in 
the field may be made with the crudest sort of conductors, using wire 
fences, or insulated wire laid on the ground. In this way the register 
may be in a protected place and receive due attention. 
Apparently the only apparatus capable of recording momentary 
high velocities is the Dines pressure-tube anemometer, the use of 
which in the forest is hardly feasible. 
Wind vanes with connections and registering device are obtain- 
able, and may possibly be desired at one station in a locality. There 
is, however, no ecological significance in wind direction : and if there 
were, it is probable that a single observation on prevailing direction 
each day and night would be amply sufficient. 
