13.5 instead of
11.1 years; and it is noticeable that the delay affected chiefly the
southern hemisphere. Alternations of activity in the solar hemispheres
were indeed a marked feature of the maximum of 1884, which, in M. Faye's
view,[498] derived thence its indecisive character, while sharp, strong
crises arise with the simultaneous advance of agitation north and south
of the solar equator. The curve of magnetic disturbance followed with
its usual strict fidelity the anomalous fluctuations of the sun-spot
curve. The ensuing minimum occurred early in 1889, and was succeeded in
1894 by a maximum slightly less feeble than its predecessor.[499]

It cannot be said that much progress has been made towards the
disclosure of the cause, or causes, of the sun-spot cycle. No external
influence adequate to the effect has, at any rate, yet been pointed out.
Most thinkers on this difficult subject provide a quasi-explanation of
the periodicity in question through certain assumed vicissitudes
affecting internal processes;[500] Sir Norman Lockyer and E. von
Oppolzer reach the same end by establishing self-compensatory
fluctuations in the solar atmospheric circulation; Dr. Schuster resorts
to changes in the electrical conductivity of space near the sun.[501] In
all these theories, however, the course of transition is arbitrarily
arranged to suit a period, which imposes itself as a fact peremptorily
claiming admittance, while obstinately defying explanation.

The question so much discussed, as to the influence of sun-spots on
weather, does not admit of a satisfactory answer. The facts of
meteorology are too complex for easy or certain classification. Effects
owning dependence on one cause often wear the livery of another; the
meaning of observed particulars may be inverted by situation; and yet it
is only by the collection and collocation of particulars that we can
hope to reach any general law. There is, however, a good deal of
evidence to support the opinion--the grounds for which were primarily
derived from the labours of Dr. Meldrum at Mauritius--that increased
rainfall and atmospheric agitation attend spot-maxima; while Herschel's
conjecture of a more copious emission of light and heat about the same
epochs has recently obtained some countenance from Savelieff's measures
showing a gain in the strength of the sun's radiation _pari passu_ with
increase in the number of spots visible on his surface.[502]

The examination of what we