THE SUN COMPASS

Waipa Post, Volume XXIV, Issue 1577, 22 November 1924, Page 2

THE SUN COMPASS

AMUNDSEN’S POLAR GUIDE.

When Captain Amundsen was getting ready last year to fly across the Noith Pole, writes a correspondent of the Manchester Guardian, a mishap to his aeroplane necessitated an eleventh-hour postponement of the expedition, and so prevented almost certain catastrophe; for though in every other respect he had made most careful preparations for his voyage of discovery, he had greatly underrated the peculiar difficulties of aerial navigation in Polar (regions. He has ito. thank Captain Boykow, on the scientific stair of Messrs C. P. Goerz, for drawing attention to those difficulties and helping him to overcome them.

The airman in normal latitudes can generally find his way by the ground below him, with the help of a good map. If clouds temporarily bar his outlook, his magnetic compass will at any moment prove a safe emergency guide, though there is still a chance of error through any oscillation imparted to the compass dial by the acceleration of the aeroplane. But in the unmapped and unexplored Arctic regions to be traversed by Amundsen nothing but a sea of compact and monotonous pack ice is to be anticipated. The airman must rely exclusively on his compass. And it is precisely in the high Polar latitudes that the compass .becomes entirely unreliable. The magnetic needle either performs violent oscillations to left and right or gyrates rapidly on its axis. The sun saves the situation. During the long Polar day it remains at practically constant height above the horizon/ travelling round the sky once every 24 hours. The airman need only know the local time in order at any moment to be able to calculate the correct angle of his course at the moment with regard to the sun. Only the calculation is not such a simple matter as to be possible is actual practice. At the beginning of this year Mr Hammer, Amundsen’s friend and travelling companion, asked Captain Bovkow whether an instrument to obviate this calculation could be perfected by the beginning of the summer. The reply was an unhestitating “Certainly,” and two days later a working model of a sun’s compass was shown him.

The little instrument is of remarkably simple construction. It is designed to follow the daily rotation of the sun, and in the case of a constant course to project an image of the sun at a fixed place on a fronted glass plate. It is only about eight inches high, and is fitted into the aeroplane in front of the piljt, who will adjust the lens before smarting to the course actually desired and at the same time will set a clockwork mechanism going. He then has simply to keep the miniature sun on the frosted glass accurately on the cross lines to be sure keeping his course. While the sun moves around the firmament* its miniature replica remains fixed on the frosted glass. Only in the event of an occasional change of course necessitated by a sudden gale or for some other reason will the lens need adjustment.