Physical Notes

Abstract

PROF. LEMSTRÖM, of Helingsfors, has recently described to the Physical Society of St. Petersburg a singular experiment which, unless otherwise explained by some of the circumstances of the experiment not yet published, must be regarded as a fundamental fact in the physical theory of electricity. He finds that a ring of insulating material when rotated about its axis of symmetry with a high velocity acts like a galvanic circuit, and produces a magnetic “field” in the space within it. Prof. Lemström is a disciple of Edlund, and regards this experiment as confirmatory of Edlund's theoretical views on the nature of electricity. According to Lemström, the ether in the insulator, being dragged along by the ring, produces vortical motion of the ether in the central space, which vortical motion he conceives to be the essential condition of a magnetic field. Arguing from these premises, Lemström proceeds to build up an ingenious theory of terrestrial magnetism. The converse operation of rotating an iron bar within a hollow insulating body or insulating medium ought also to produce magnetism in the bar. The earth being a magnetic body rotating in an insulating medium, ought to be magnetised by rotation about its axis, the axis being the axis also of magnetisation, unless the irregular internal disposition of the magnetic constituents produced an irregular distribution of the magnetism, or unless the distribution were affected by the induced magnetism due to movements of electricity in the atmosphere, as in the aurora, or by the magnetism which would, on Lemström's theory, be generated by the revolution of the earth round the sun, and by the motion of the solar system through space.