National Geographic : 1953 Jan
102 Canadian National Film Board Samuel Hearne's Name, Carved in 1767, Calls to Mind a Famous Arctic Trek As a Hudson's Bay Company agent seeking copper mines reported by the Indians, this intrepid Englishman in 1770-72 roamed 1,000 miles northwest of Hudson Bay, discovered the Coppermine River, and followed it to the Arctic Ocean. He found copper deposits but no mines. Hearne later became governor of Fort Prince of Wales, built near the present site of Churchill, Manitoba, between 1733 and 1744 to protect the company's fur trade (page 113). He made the inscription at Sloop Cove, near Churchill, before his trip to the Arctic. since 1934. Some of the first photographs of cosmic-ray tracks recorded in the emulsions of photographic plates were made on the stratosphere flight of the balloon Explorer II in 1935.* This program has been supervised by Dr. W. F. G. Swann, director of the Bartol Foundation, and our Hudson Bay expeditions benefited much from his wise counsel and active support. Before our trips to Churchill, I myself had taken part in this program on the solar eclipse expedition of The Society and U. S. Army Air Forces to Brazil in 1947;t on the 14,260-foot summit of Mount Evans, Colorado; and on a series of research flights by a B-29 "flying laboratory" of the U. S. Army Air Forces measuring cosmic rays up to altitudes of 30,000 feet between Canada and Chile (page 101). Our immediate objective here at Churchill was to study how cosmic rays are deflected in their flight by the earth's field of magnetic force which makes the compass needle point north. This magnetic field extends for thou sands of miles out into space around our planet, far beyond the atmosphere. At the same time we planned to investigate the widely held theory that the sun has a similar magnetic field which would deflect some cosmic rays coming from far outside the solar system so that they could not reach the earth at all. Earth's Magnetic Field Deflects Rays The earth's magnetic field deflects cosmic rays approaching our planet in inverse pro portion to the energy they possess. This deflecting power is smallest at the north and south geomagnetic poles (not the same as the magnetic poles) located in Greenland and * See National Geographic Society CONTRIBUTED TECHNICAL PAPERS, Stratosphere Series Vol. 1, No. 2, p. 37 et seq. t See "Eclipse Hunting in Brazil's Ranchland," by F. Barrows Colton, NATIONAL GEOGRAPHIC MAGAZINE, September, 1947.