ll daily oscillations. It was found about fifty years ago by Lamont
(a Bavarian astronomer, but a native of Scotland) that the extent of
this daily oscillation increases and decreases regularly in a period
which he gave as 10-1/3 years, but which was subsequently found to be
11-1/10 years, exactly the same as the period of the spots on the sun.
From a diligent study of the records of magnetic observations it has
been found that the time of sun-spot maximum always coincides almost
exactly with that of maximum daily oscillation of the compass needle,
while the minima agree similarly. This close relationship between the
periodicity of sun-spots and the daily movements of the magnetic needle
is not the sole proof we possess that there is a connection of some sort
between solar phenomena and terrestrial magnetism. A time of maximum
sun-spots is a time of great magnetic activity, and there have even been
special cases in which a peculiar outbreak on the sun has been
associated with remarkable magnetic phenomena on the earth. A very
interesting instance of this kind is recorded by Professor Young, who,
when observing at Sherman on the 3rd August, 1872, perceived a very
violent disturbance of the sun's surface. He was told the same day by a
member of his party, who was engaged in magnetic observations and who
was quite in ignorance of what Professor Young had seen, that he had
been obliged to desist from his magnetic work in consequence of the
violent motion of his magnet. It was afterwards found from the
photographic records at Greenwich and Stonyhurst that the magnetic
"storm" observed in America had simultaneously been felt in England. A
similar connection between sun-spots and the aurora borealis has also
been noticed, this fact being a natural consequence of the well-known
connection between the aurora and magnetic disturbances. On the other
hand, it must be confessed that many striking magnetic storms have
occurred without any corresponding solar disturbance,[5] but even those
who are inclined to be sceptical as to the connection between these two
classes of phenomena in particular cases can hardly doubt the remarkable
parallelism between the general rise and fall in the number of sun-spots
and the extent of the daily movements of the compass needle.

[Illustration: Fig. 16.--The Texture of the Sun and a small Spot.]

We have now described the principal solar phenomena with which the
telescope has made us acquainted. But