st the possibility of any direct magnetic
action by the sun upon the earth, on the ground of its involving an
extravagant output of energy; but the fact is unquestionable that--in
Professor Bigelow's words--"abnormal agitations affect the sun and the
earth as a whole and at the same time."[482]

The nearer approach to the event of September 1, 1859, was
photographically observed by Professor George E. Hale at Chicago, July
15, 1892.[483] An active spot in the southern hemisphere was the scene
of this curiously sudden manifestation. During an interval of 12m.
between two successive exposures, a bridge of dazzling light was found
to have spanned the boundary-line dividing the twin-nuclei of the spot;
and these, after another 27m., were themselves almost obliterated by an
overflow of far-spreading brilliancy. Yet two hours later, no trace of
the outburst remained, the spot and its attendant faculae remaining just
as they had been previously to its occurrence. Unlike that seen by
Carrington, it was accompanied by no exceptional magnetic phenomena,
although a "storm" set in next day.[484] Possibly a terrestrial analogue
to the former might be discovered in the "auroral beam" which traversed
the heavens during a vivid display of polar lights, November 17, 1882,
and shared, there is every reason to believe, their electrical origin
and character.[485]

Meantime M. Rudolf Wolf, transferred to the direction of the Zurich
Observatory, where he died, December 6, 1893, had relaxed none of his
zeal in the investigation of sun-spot periodicity. A laborious revision
of the entire subject with the aid of fresh materials led him, in
1859,[486] to the conclusion that while the _mean_ period differed
little from that arrived at in 1852 of 11.11 years, very considerable
fluctuations on either side of that mean were rather the rule than the
exception. Indeed, the phrase "sun-spot period" must be understood as
fitting very loosely the great fact it is taken to represent; so
loosely, that the interval between two maxima may rise to sixteen and a
half or sink below seven and a half years.[487] In 1861[488] Wolf
showed, and the remark was fully confirmed at Kew, that the shortest
periods brought the most acute crises, and _vice versa_; as if for each
wave of disturbance a strictly equal amount of energy were available,
which might spend itself lavishly and rapidly, or slowly and
parsimoniously, but could in no case be exceeded. The further incl