Q. How is the velocity of the wind determined?
A. By the anemometer. First take the reading of the discs on the anemometer and note the time. After six minutes have elapsed read the scales. Take the difference of the scales and multiply by 10, which gives the velocity. (See Fig. 73.)
For example: Suppose at 10:05 A.M. the reading is 62 miles, and at 10:11 A.M. the reading is 63 miles. If in six minutes it goes one mile, in sixty minutes it will go ten times, or ten miles per hour.
THE ANEMOMETER.
Fig. 73.
Q. How are the components of the wind in the direction of the line of fire and in a lateral direction determined? (See Fig. 74.)
A. First: Set the arrow on the disc to read the azimuth of the wind. (This is done automatically.)