MAGNETIC POLES

Evening Post, Volume CVII, Issue 129, 5 June 1929, Page 13

MAGNETIC POLES

VAGARIES OF NEEDLE

CANADA SEEKING SOLUTION

(From "The Post's" Representative.) VANCOtrVEE, Ist May.

A radip message iudicates'that Major Burwash, Canadi/i explorer, is now in the vicinity of the spot where Sir John.Franklin disappeared. Major Burwash is spending tho winter on Boothia Peninsula, where he intends to conduct a series of tests in an effort to solve vagaries of the Magnetic Pole. He is associated with the Northwest Territories branch of the Federal Government. Details of his observations are being transmitted to Ottawa by wireless from the steamer Fort James, which is wintering at Boothia. The magnetic compass has long been recognised as inaccurate on account of the wandering propensities of the magnetic pole. During the last few years, mariners and aviators, have turned to more modern devices, such as the gyroscopic, sun, and radio compasses, but the magnetic compass is still widely used. ■■'"..'■'"'.'

Besides the recognised variation from true north of nearly 50 degrees. from coast to coast in Canada which the magnetic compass shows, there' is a 'further range of error from the fact 1 that the magnetic pole moves.eac,h year approximately two-thirds of a mile. For several years it marches to the'west, then turns back and maches east again. Thus at Fort Churchill, oh Hudson Bay, the needle pointed "24 deg. west of north in 1700, 1 deg. west in 1800, and 10 deg. west in 1900.

A knowledge of this march of the needle is of great practical value, for most of the original land surveys in the older provinces were made by compass, and nowadays, when it is desired to retrace an old lost boundary line, it is necessary to know the change in the needle direction that has occurred in the interval; Moreover, such information is necessary for the purpose, of keeping up-to-date all the needle declination measurements made in the* past, and for correlating surveys made by compass at different dates.

. The practical value of compass information in such a large territory as Canada was well recognised by the earliest explorers, for the declination was measured in the Gulf of St. Lawrence by Jacques Cartier in 1543 and Samuel de Champlain in 1604; in the interior by Sir John Franklin in 1819, and on the Pacific by Sir Francis Drake in 1579, Captain Cook in 1778, and Captain Vancouver in 1792.

Since 1880 the Topographical Survey of the Department of the Interior has been making measurements of the declination and the annual change of the needle in conjunction with its other work. Such measurements may. be taken by the surveyor in a few minutes, at very little additional expense, when he is already on the ground with the. necessary instruments. About 25,000 such measurements have been obtained to date. The survey has used these, together with the results of the early explorers, the meteorological service, the Dominion Observatory, the Canadian Hydrographic Service, the Carnegie Institute of Washington, the . provincial Governments, and various individuals, to compile and publish at intervals .* maps of Canada showing the true direction of needle and tables during: the march of the needle, or how it changes its direction from, year to year. ' .

While the reason for the needle pointing in different directions at each place is known to be due to ,the magnetic poles not -with the geographical poles, the reason :,for the needle changing direction from year to year has never received a satisfactory explanation. For many years the most popular theory was that such changes in the needle direction were caused by the magnetic poles marching around the geographical poles, and such eminent physicists as. Lord Kelvin and others computed'that it too,k the.magnetic poles 1000, years to' perform a complete march or journey around the geographical poles.. But this theory had to be abandoned after Captain Amundsen found the North Magnetic Pole in 1903-5 to be .within 50 miles of the place where it was first discovered by Sir James Boss in- 1831. \ In other words, the march of the magnetic poles was then seen to be altogether too small to explain the. yearly -change in direction of the compass needle.. Becent researches of the Geographical Survey Department indicate that tho yearly change in direction is due to the action of magnetic forces within the earth. It has been felt that additional magnetic data in the Tar North, especially in regard to the march of the North Magnetic Pole, would afford additional information in this intricate, question. However, a special expedition for that sole purpose would .have been expensive.