Page:Popular Science Monthly Volume 23.djvu/177

This page has been validated.
165
RECENT MAGNETIC STORMS AND SUN-SPOTS.

17th, and 19th, accompanied by more or less magnetic disturbance. During that time a tremendous sun-spot, exceeding in size the largest of the April spots, was advancing from the edge of the disk to the center. In this country the principal auroral displays were on the nights of the 17th and 19th, and the chief force of the magnetic storm was felt on the 17th. On that day a storm of rain and snow prevailed over most of the Union, and simultaneously with this storm there raged a hurricane of magnetic forces. The effects were similar to those witnessed during the April storm, but more intense. As in April, some wires were worked without batteries, while others could not be worked at all. Cable communication was interrupted. Some startling phenomena occurred. Sparks of fire leaped from the wires and instruments. In the West, switch-boards were burned and PSM V23 D177 November 16 sunspot with accompanying magnetic disturbance.jpgFig. 1. keys melted. Operators received severe shocks. Practical telegraph men said they had never known such a powerful disturbance of the magnetic elements. In the evening, when the sky cleared at Chicago, a most magnificent sight was beheld in the heavens. The brilliancy of the aurora far exceeded that of the April display. A singular feature of this aurora, which was also noticed in Europe, was a splendid luminous arch spanning the sky from east to west and passing nearly through the zenith. Another feature that added brilliancy to the spectacle was the variety of color visible. The prevailing tints were rose-color and green, but in some places streamers and patches of violet, yellow, and orange light were seen. On the night of the 19th and morning of the 20th, the sky having cleared here, a splendid aurora was seen in New York. The magnetic disturbance also continued.

At the April meeting of the American Astronomical Society I exhibited some magic-lantern views representing the principal changes which took place in the great sun-spot during the magnetic storm of November. These views, copied from drawings of the spot made at the telescope, are reproduced in the accompanying cuts.

Fig. 1 represents the spot as it appeared on the 16th of November, the day before the culminating magnetic disturbance took place. Low magnifying powers, varying from sixty-five to a hundred and ten diameters, were used while making the drawings, as it was not desired to obtain pictures representing all the details. Consequently, only the