50 And 100 Years Ago; January 1994; Scientific American Magazine; by Staff Editor; 1 Page(s)

JANUARY 1944 Despite the wide-spread knowledge that forests cannot be indiscriminately logged indefinitely, many pulp-wood producers have been blithely continuing with little or no thought for the future. Result: There is little forestry reserve in the United States today and the vast timberlands of Canada are facing exhaustion. Add to this the other uses for wood that have been developed in recent years--in plastics, explosives, construction work, for examples--and it is obvious that unless something is done, and done vigorously and thoroughly, the paper industry is going to face an even greater crisis after the war than it is facing today.'--A. P. Peck, managing editor.

Two blind spots on the earth's surface totalling nearly 10,000,000 square miles have been opened up to air travel by one of the most dramatic scientific achievements to come out of the war. Anywhere within 1200 miles of either of Mother Earth's magnetic poles, magnetic compasses begin to jive and planes enter a shadowy no-man's-land; this no-man's-land includes most of Canada. Now, with the gyro flux gate compass, developed by engineers of the Bendix Aviation Corporation, the problem has been solved. The heart of the new compass is three double-wound electromagnets, forming the sides of an equilateral triangle. Different voltages are generated in each magnet, according to the angles at which the compass cuts the lines of force of the earth. Thus the basis of the indication on the compass dial is the combination of the angles and hence of the voltages generated. The resulting current, amplified by vacuum tubes, is stepped up to sufficient power to turn a motor, the shaft of which moves the needle of the dial.