Lamont, of Munich, in 1850, was the first to announce that these magnetic disturbances attain a maximum of frequency in about ten years. Two years later, Sabine, Wolf, and Gautier, noticed the coincidence of this period with that of the solar spots. And this coincidence was more than general. There was a coincidence of maximum spot-frequency with maximum of magnetic disturbance, and of minimum with minimum, which compelled them to assert a causal connection between the two periods. Wolf subsequently proved that the period of magnetic disturbance has the length of 11.11 years.
But there is still more striking evidence of this connection. On September 1, 1859, Mr. Carrington, an eminent English astronomer, happened to be intently engaged in observing and mapping a group of spots, when a sudden and most extraordinary outburst occurred, of so startling a nature that, having noted the exact moment by his chronometer, he hastily ran to call some one to see the exhibition with him;
Fig. 8.
Spiral Solar Spot, or Cyclone, observed by Secchi.
when upon returning, within 60 seconds, the whole spectacle had disappeared. "The spots had travelled considerably from their first position, and vanished as two rapidly-fading dots of white light. In the interval of five minutes, the two spots transvered a space of about 35,000 miles." He likens the appearance to that of a sudden conflagration. This was also independently seen at the same moment by Mr. Hodgson, who says: "I was suddenly surprised at the appearance of a very brilliant star of light, much brighter than the sun's surface, and most dazzling to the protected eye. It lasted some five minutes, and disappeared instantaneously."
At the moment when the sun was thus disturbed, the magnetic instruments at Kew exhibited the signs of great magnetic disturbance. "It was found," says Dr. Balfour Stewart, "that a magnetic storm had broken out at the very moment when this singular appearance had
