ELECTRIC CURRENTS

Evening Star, Issue 20023, 14 November 1928, Page 9

ELECTRIC CURRENTS

LECTURE BY DR FOCKEH ‘ Electric Currents in Nature ’ was the subject of an address by Dr C. M. Focken, B.Sc., 8.M.E.; under the auspices of the Otago Institute in the physics lecture room of the University last night. Mr H. D. Skinner presided. At the outset Dr Focken pointed out that his lecture would be limited to a discussion of the effects and I nature of some forms of free dec- j tricity; the electric currents in the earth itself; the electricity in the atmosphere; the important contribution of electricity received from the sun, and another contribution received from somewhere much farther away than the sun. The lecturer showed by means of simple experiments that the earth behaved like a huge magnet, and' that magnetism and i electricity were intimately connected. The methods adopted and some results obtained in the general magnetic survejr of the globe, which was being undertaken by the Carnegie Institution of Washington, were illustrated by lantern slides. These raised problems of how to account for the earth’s permanent magnetic field and for the variations in' it. The explanation of the former was still far from completed, but promising hypotheses had helped to elucidate some of the variations. The two solar ionising agents—-nltr-. violet light and the clouds of charged corpuscles emanating from particular areas on the sun—went a long way towards explaining the normal diurnal variation and the phenomenon of magnetic storms respective! v. Modern theories. of the sun’s atmosphere rendered it likely that the corpusclar emissions were due to a local and temporary rise in the radiation pressure arising from an unusually bright region of the surface. Consequently the magnetic character of any day was likely to be associated not necessarily with the presence ot sun spots but the presence of 4 blight regions near the centre of the sun s of the causes, demonstrations, and results of the electricity m the atmosphere were next discussed by the lecturer He pointed , out that the normal condition existed in hue weather regions," and showed a current carrying positive electricity from the air to the earth. Since,. despite tins current, the earth maintained a negative surface charge, the problem was to find a compensating current rroni earth to air adequate to neutralise the air-earth current of the Imoweather regions. The explanation or it was probably concerned with tic solar corpuscular radiation or with the electrical phenomena at regions other than those of fine weather. By pioducing a beam of cathode rays by electric discharge from an induction cod the lecturer experimentally demonstrated how moving electrons were deviated by a magnetic field. The lecturer dealt at some length with the subject of the very penetrating radiation thought to be or cosmic origin, which had greatly interested scientists in recent years, it was not until 1925 that conclusive and unambiguous evidence was obtamec. proving the existence. of these very penetrating rays and indicating their nature and origin. Observations made both by day and by night showed that the rays came apparently as much from one direction as from any other, and certainly no more plentifully from the direction of the sun or from the direction ot the Milky Way- Since it was not to the stars they must look for the origin,, the birthplace of cosmic rays was either in the great spiral nebulic or in that very rarefied matter whicli pervaded all space. The Irequencies of the cosmic rays, were limited to three bands, which it was calculated corresponded to the anmmlation of mass accompanying the formation of magnesium and silicon from hydrogen, oxygen, and nitrogen from 'hydrogen, and helium from hydrogen. The ■ cosmic rays were raining down continually from all directions, and no one knew all their elfccts. They might be shortening or lengthening our lives, killing bacteria, or causing mvstcrious diseases. These results were full of interest and stimulating in a degree to the imagination. Heie again they had a subject where a. careful watch on Nature’s laboratories in the heavens enabled them td* supplement the obvious deficiencies in their own. . , , Dr Focken was accorded a vote ot thanks for his interesting lecture.