and a connection has been further traced between violent outbursts of
solar activity and simultaneous magnetic storms.

The frequency of the Aurora Borealis was found by Wolf to follow the
same period. In fact, it is closely allied in its cause to terrestrial
magnetism. Wolf also collected old observations tracing the
periodicity of sun-spots back to about 1700 A.D.

Spoerer deduced a law of dependence of the average latitude of
sun-spots on the phase of the sun-spot period.

All modern total solar eclipse observations seem to show that the
shape of the luminous corona surrounding the moon at the moment of
totality has a special distinct character during the time of a
sun-spot maximum, and another, totally different, during a sun-spot
minimum.

A suspicion is entertained that the total quantity of heat received by
the earth from the sun is subject to the same period. This would have
far-reaching effects on storms, harvests, vintages, floods, and
droughts; but it is not safe to draw conclusions of this kind except
from a very long period of observations.

Solar photography has deprived astronomers of the type of Carrington
of the delight in devoting a life's work to collecting data. It has
now become part of the routine work of an observatory.

In 1845 Foucault and Fizeau took a daguerreotype photograph of the
sun. In 1850 Bond produced one of the moon of great beauty, Draper
having made some attempts at an even earlier date. But astronomical