Then, if not before, it was clear that the earth was a great
globular magnet, having its poles of opposite magnetism, and that the
auroral lights, whatever their precise cause might be, were
manifestations of the magnetic activity of our planet. After the
invention of magnetic telegraphy it was found that whenever a great
Aurora occurred the telegraph lines were interrupted in their
operation, and the ocean cables ceased to work. Such a phenomenon is
called a ``magnetic storm.''
The interest excited by the Aurora in scientific circles was greatly
stimulated when, in the last half of the nineteenth century, it was
discovered that it is a phenomenon intimately associated with
disturbances on the sun. The ancient ``Zurich Chronicles,'' extending
from the year 1000 to the year 1800, in which both sun-spots visible
to the naked eye and great displays of the auroral lights were
recorded, first set Rudolf Wolf on the track of this discovery. The
first notable proof of the suspected connection was furnished with
dramatic emphasis by an occurrence which happened on September 1,
1859. Near noon on that day two intensely brilliant points suddenly
broke out in a group of sun-spots which were under observation by Mr
R. C. Carrington at his observatory at Redhill, England.
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