Forest Patrols
Collier's New Encyclopedia (1921)
AERIAL. (See AERONAUTICS: FOREST PATROLS.) FOUR-POWER TREATY. (See WASHINGTON CONFERENCE.) FRANCE. Leygues ministry succeeded Aristide (Jan. 16, 1921) by that that of succeeded by Briand. Premier Briand Raymond Poincaré (Jan. 15, 1922). FROSTS AND FROST PROTECTION. The term frost, in agricultural usage, means the occurrence of a temperature low enough to kill or injure vegetation. Such a temperature is usually about the freezing point of water, being being a little under 32° Fahrenheit in the case of ordinary fruits and vegetables. The temperature of a plant may be affected by other conditions than the atmospheric temperature considered by itself. Thus a clear, calm night is more conducive to frosts than a moist, disturbed night, since the absence of clouds facilitates the radiation of heat from the earth; evaporation of moisture goes on more rapidly, and the surface of pla plants is accordingly chilled; while the absence of disturbing winds or breezes allows the colder, heavier layers of air to settle stagnantly to the ground. For the same reason, frosts are more apt to occur in valleys than at points higher up on hillsides, the cold air settling undisturbed in the valley. Moisture in the atmosphere retards evaporation, and thus is one of the preventives of frost. The U. S. Weather Bureau classifies frosts as light, heavy, and killing. This bureau has made an extensive study of the subject and maintains the most thorough frostprotection service in the world. In addition to the regular publication of frost charts and special forecasts, it distributes warnings by telegraph, by telephone, and, more recently, through the agency of radio broadcasting stations. Frostprotection methods include the covering
What Has Changed in the Last Century
When Collier's printed this cross-reference in 1921, aerial forest patrol was barely two years old: Army pilots had begun flying over California's timber in 1919, spotting smoke and dropping written messages to rangers below. The airplane's role has since gone far beyond spotting — smokejumpers began parachuting to fires in 1940, and water- and retardant-dropping air tankers became standard after the 1950s. Detection itself has largely left the cockpit: infrared line-scanning aircraft, lightning-strike detection networks and weather satellites now do the watching, and most of the staffed fire lookout towers of the 1920s have been abandoned. Uncrewed drones now fly night mapping missions over large fires, work no 1919 patrol pilot could have attempted.
Written for this edition, 2026.