Jacques Wardlaw Redway

“ Various devices are used to ascertain wind direction in times of very low velocity. A thread flown at the end of a stick fastened near the wind vane will often enable an observer to discover the direction of the wind when other evidence is absent. An ascending smoke column is swayed by a breeze too light to move a thread. The human face is exceedingly sensitive to the wind. ”

“ Several types of magnet recorders are used with the Robinson anemometer. In the type most commonly used, an arm carrying the recording pen is attached to the armature of the magnet. The revolving disk carries the studs representing miles of wind movement against the spring which acts as a circuit closer; the recording pen thereupon makes an offset from the straight line on the record sheet. Each offset represents theoretically a mile of wind. As soon as the stud passes the contact spring—a matter of from five to ten seconds—the pen is drawn back to its normal position. ”

“ Rather more uncertain is the movement of foliage. In many instances a wind vane whittled from a very thin strip of wood and perforated so as to whirl on a pin as an axis has been pretty nearly as serviceable as an expensive vane. Small vanes made of thin aluminium sheet metal, spread-tail in pattern, have answered every purpose required for ascertaining wind direction. ”

“ For the greater part, the mean hourly velocity of the wind at the various stations provided with anemometers varies from 5 miles to 15 miles per hour. On sea and lake coasts it is materi- ally higher; and in a few mountain valleys it is lower than 3 miles.
Throughout the prairie region and the great plains, the wind is apt to be steady, its velocity varying but little during the daylight period. In regions where land breezes alternate with those from the sea, a short period of calm precedes each change. ”

“ Until recently Weather Bureau stations have been equipped with instruments for the study of surface winds only. The research laboratories, however, have made great advances in the study of air conditions at considerable heights, using kites and pilot balloons carrying recording instruments. Ordinarily the observer must depend on wind vanes, smoke columns, flags, dust movements and clouds for the determination of wind conditions. ”

“ If the wiring is situated where contact with electric light wires is possible, heavily insulated wires, such as are prescribed by local regulations, should be used. All permanent wire joints and splices should be snugly twisted a length of 2 inches—or, better, soldered—and wrapped with tape. All outside wires should be held by insulators. ”

“ Robinson anemometer, electrically connected with recording apparatus, P. 239.
The Wind Vane.—The wind vane of the spread-tail pattern, used by the Weather Bureau, is probably the most practical form in use. It holds steadily to the wind; it is sensitive enough to respond to a breeze of 2 miles an hour. The regulation vane is 6 feet over all. The tail is made of very thin board strips, thoroughly weather-proofed; the metal work is rust-proof; the bearings are constructed so that friction is reduced to the minimum. This is the general service vane designed to show wind direction only. ”