usion
of recurring solar commotions within a cycle of fifty-five and a half
years was simultaneously pointed out; and Hermann Fritz showed soon
afterwards that the aurora borealis is subject to an identical double
periodicity.[489] The same inquirer has more recently detected both for
aurorae and sun-spots a "secular period" of 222 years,[490] and the Kew
observations indicate for the latter, oscillations accomplished within
twenty-six and twenty-four days,[491] depending, most likely, upon the
rotation of the sun. This is certainly reflected in magnetic, and
perhaps in auroral periodicity. The more closely, in fact,
spot-fluctuations are looked into, the more complex they prove. Maxima
of one order are superposed upon, or in part neutralised by, maxima of
another order;[492] originating causes are masked by modifying causes;
the larger waves of the commotion are indented with minor undulations,
and these again crisped with tiny ripples, while the whole rises and
falls with the swell of the great secular wave, scarcely perceptible in
its progress because so vast in scale.

The idea that solar maculation depends in some way upon the position of
the planets occurred to Galileo in 1612.[493] It has been industriously
sifted by a whole bevy of modern solar physicists. Wolf in 1859[494]
found reason to believe that the eleven-year curve is determined by the
action of Jupiter, modified by that of Saturn, and diversified by
influences proceeding from the earth and Venus. Its tempting approach to
agreement with Jupiter's period of revolution round the sun, indeed,
irresistibly suggested a causal connection; yet it does not seem that
the most skilful "coaxing" of figures can bring about a fundamental
harmony. Carrington pointed out in 1863, that while, during _eight
successive periods_, from 1770 downwards, there were approximate
coincidences between Jupiter's aphelion passages and sun-spot maxima,
the relation had been almost exactly reversed in the two periods
preceding that date;[495] and Wolf himself finally concluded that the
Jovian origin must be abandoned.[496] M. Duponchel's[497] prediction,
nevertheless, of an abnormal retardation of the maximum due in 1881
through certain peculiarities in the positions of Uranus and Neptune
about the time it fell due, was partially verified by the event, since,
after an abortive phase of agitation in April, 1882, the final outburst
was postponed to January, 1894. The interval was thus