Page:Polar Exploration - Bruce - 1911.djvu/228

224 the ice-bound North. More especially did the magnet appear to be affected when the aurora, rising in massive, thick arches from the eastward, and sending up streamers of beautifully coloured light, passed rapidly across our zenith and disappeared to the westward The magnet would oscillate wildly from side to side, or sometimes sheer rapidly to one side only, then as suddenly behave in a steady and normal manner." Armitage also noted that the most brilliant air effects took place during a "furious gale" or a "dead calm."

Buchan has pointed out that "Lemström has shown, by observations and experiments he made at Sodankylä, that auroræ are due to currents of positive electricity illuminating the atmosphere in their passage to the earth. Luminous appearances accompanied the setting in of a current towards the earth from the network of insulated wires with which he overspread the top of Mount Oratunturi, and this light was clearly auroral, giving the hitherto enigmatical citron line of Augström, which is the invariable constituent of aurora radiations. Other faint and indistinct lines are enumerated as present, and Lemström is of opinion that there is a tolerable agreement between some of these and the lines in the laboratory spectrum of rarefied air, but the whole subject demands further investigation."