Electric currents have been reported as produced in telegraph wires during Auroræ. Though transient they are said to be often very powerful, and to interrupt the ordinary signals. Loomis (Sillim. Journ. vol. xxxii.) mentions cases where wires have been ignited, brilliant flashes produced, and combustible materials kindled by their discharge.
Here, too, we may note the account of electric phenomena in the case of the Aurora Australis described (antè, p. 28) by Mr. Proctor.
Mr. George Draper’s report as to disturbed condition of the Indian Submarine and other cables during Aurora of February 4, 1872.
Mr. George Draper, of the British-Indian Submarine Telegraph Company, speaking of the Aurora of February 4, 1872 (and writing to the ‘Times’ under date February 5th), states that the Aurora visible in London was also visible at Bombay, Suez, and Malta, and that the Company’s electrician at Suez reported that the earth-currents there were equal to 170 cells (Daniell’s battery), and that sparks came from the cable. The electrical disturbances lasted until midnight, and interrupted the working of both sections of the British Indian Cable between Suez and Aden, and Aden and Bombay. For some days previously the signals on the British Indian cables had been much interfered with by electrical and atmospheric disturbances.
At Malta there was a severe storm on the morning of the 4th, so that it was necessary to join the cable to earth for some hours, and the Aurora was very large and brilliant there.
The electrical disturbances on the cables in the Mediterranean and on those between Lisbon and Gibraltar, and Gibraltar and the Guadiana, were also very great. The signals on the land line between London and the Land’s End were interrupted for several hours on the night of the 4th by atmospheric currents. Similar effects accompanied the displays of Oct. 24 and 25, 1870.
Aurora and Meteoric Dust.
Aurora and meteoric dust. Theories of Dr. Zeyfuss and M. Gröneman.
A theory has been propounded independently by Dr. Zeyfuss and by M. Gröneman, of Gröningen, according to which the light of the Aurora is caused by clouds of ferruginous meteoric dust ignited by friction with the atmosphere. Gröneman shows that these might be arranged along the magnetic curves by the action of the earth’s magnetic force during their descent, and that their influence might produce the observed magnetic disturbances.
Ferruginous dust in the Polar Regions.