st have resulted from a local eddy. In the
space of perhaps half-an-hour, the gentle breeze had carried this cloud
some miles to the East; and now its nature became obvious. That central
part which, seen from underneath, seemed simply a dense, confused part,
apparently no nearer than the rest, now, seen sideways, was obviously
much lower than the rest and rudely funnel-shaped--nipple-shaped one
might say; while the wide thin portion of cloud above it was
disk-shaped: the converging streaks of cloud being now, in perspective,
merged together. It thus became manifest that the cloud was produced by
a feeble whirlwind, perhaps a quarter to half-a-mile in diameter.
Further, the appearances made it clear that this feeble whirlwind was
limited to the lower stratum of air: the stratum of air above it was not
implicated in the cyclonic action. And then, lastly, there was the
striking fact that the upper stratum, though not involved in the whirl,
was, by its proximity to a region of diminished pressure, slightly
rarified; and that its precipitated vapour was, by the draught set up
towards the vortex below, drawn into converging streaks. Here, then, was
an action analogous to that which, as above suggested, happens around a
sun-spot, where the masses of illuminated vapour constituting the
photosphere are drawn towards the vortex of the cyclone, and
simultaneously elongated into striae: so forming the penumbra. At the
same time there was furnished an answer to the chief objection to the
cyclonic theory of solar spots. For if, as here seen, a cyclone in a
lower stratum may fail to communicate a vortical motion to the stratum
above it, we may comprehend how, in a solar cyclone, the photosphere
commonly fails to give any indication of the revolving currents below,
and is only occasionally so entangled in these currents as itself to
display a vortical motion.

Let me add that apart from the elucidations furnished by the phenomenon
above described, the probabilities are greatly in favour of the cyclonic
origin of the solar spots. That some of them exhibit clear marks of
vortical motion is undeniable; and if this is so, the question
arises--What is the degree of likelihood that there are two causes for
spots? Considering that they have so many characters in common, it is
extremely improbable that their common characters are in some cases the
concomitants of vortical motion and in other cases the concomitants of a
different kind of action