Magnetic observations on board the ‘Tegetchoff.’
Payer, in his ‘New Lands within the Arctic Circle’ (vol. i. pp. 327, 328), gives the result of the magnetic observations on board the Austrian ship ‘Tegetchoff’ in the years 1872-74, made by means of a magnetic theodolite, a dipping-needle, and three variation instruments. The extraordinary disturbances of the needle rendered the determination of exact mean values for the magnetic constants impossible. The following were the principal results of these observations:—
Disturbances great.
(1) The magnetic disturbances were of extraordinary magnitude and frequency.
Greater as the rays were rapid. Quiescent arches exercised no influence.
(2) They were closely connected with the Aurora, and they were greater as the motion of the rays was more rapid and fitful and the prismatic colours more intense. Quiescent and regular arches, without changing rays or streamers, exercised mostly no influence on the needle.
Declination-needle, effects on.
(3) In all the disturbances the declination-needle moved towards the east, and the horizontal intensity decreased while the inclination increased.
Sir John Franklin sums up his information as to the needle to much the same effect, viz. that brilliant and active coruscations cause a deflection almost invariably if they appear through a hazy atmosphere and if the prismatic colours are exhibited in the beams or arches. On the contrary, when the air is clear and the Aurora presents a steady dense light of a yellow colour and without motion, the needle is often unaffected by its appearance.
Parry’s experience.