It was not very long after the discovery of the
sun-spot cycle that the curious observation was made that a striking
coincidence existed between the period of the sun-spots and another
period affecting the general magnetic condition of the earth. When a
curved line representing the varying number of sun-spots was compared
with another curve showing the variations in the magnetic state of the
earth the two were seen to be in almost exact accord, a rise in one
curve corresponding to a rise in the other, and a fall to a fall.
Continued observation has proved that this is a real coincidence and
not an accidental one, so that the connection, although as yet
unexplained, is accepted as established. But does the influence extend
further, and directly affect the weather and the seasons as well as
the magnetic elements of the earth? A final answer to this question
cannot yet be given, for the evidence is contradictory, and the
interpretations put upon it depend largely on the predilections of the
judges.
But, in a broad sense, the sun-spots and the phenomena connected with
them must have a relation to terrestial meteorology, for they prove
the sun to be a variable star. Reference was made, a few lines above,
to the resemblance of the spectra of sun-spots to those of certain
stars which seem to be failing through age.
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