WIND 75 
itats, but the chance of error is great, except when the breeze is steady. 
Anemographs alone give real satisfaction. Accurate results, however, are not 
obtainable without a series of two or more in different habitats, and it is 
still an open question whether the results obtained justify the expense. For 
a completely equipped base station, anemometer, anemograph, and wind 
vane are desirable instruments, but the study of the habitat has by no 
means reached the stage of precision in which their general use is 
necessary. 
109. The anemometer in its simplest form is adapted only to readings 
made under direct observation, as a sudden change in the direction of the 
wind reverses the move- 
ment of the indicator 
needle. This simple wind 
gauge, shown in figure 
23, has been used for in- 
structional purposes, and 
to a slight extent, also, in 
ascertaining the effect of 
cover. In constant winds, 
successive single readings 
are found to have value, 
but, ordinarily, the obser- 
vations must be simultane- 
ous. Careful tests of this 
simple instrument show that 
it is essentially accurate. 
It may be obtained from 
the C. H. Stoelting Com- 
pany, 31 W. Randolph St., 
Chicago, for $25. The 
standard anemometer 
(Fig. 24) is practically a 
recording instrument up to 1,000 miles, but as the dials run on without 
any indication of the total number of revolutions, it must be visited and 
read each day. This renders its use difficult for habitats which are some 
distance apart. When exact determinations of wind values become neces- 
sary, the most successful method is to establish a series of three standard 
anemometers. One of these should be placed upon the most exposed part 
of a typically open habitat, the second in the most protected part of the 
same habitat, while the third is located in the midst of a representative 
forest formation. If the two habitats are close together, the daily visits 
Fig. 24. Standard anemometer. 
