her seem to predominate as part of its regular
internal economy.

The same kind of spectroscopic evidence tells heavily against a theory
of sun-spots started by Faye in 1872. He had been foremost in pointing
out that the observations of Carrington and Spoerer absolutely forbade
the supposition that any phenomenon at all resembling our trade-winds
exists in the sun. They showed, indeed, that beyond the parallels of 20
deg. there is a general tendency in spots to a slow poleward displacement,
while within that zone they incline to approach the equator; but their
"proper movements" gave no evidence of uniformly flowing currents in
latitude. The systematic drift of the photosphere is strictly a drift in
longitude; its direction is everywhere parallel to the equator. This
fact being once clearly recognised, the "solar tornado" hypothesis at
once fell to pieces; but M. Faye[466] perceived another source of
vorticose motion in the unequal rotating velocities of contiguous
portions of the photosphere. The "pores" with which the whole surface of
the sun is studded he took to be the smaller eddies resulting from these
inequalities; the spots to be such eddies developed into whirlpools. It
only needs to thrust a stick into a stream to produce the kind of effect
designated. And it happens that the differences of angular movement
adverted to attain a maximum just about the latitudes where spots are
most frequent and conspicuous.

There are, however, grave difficulties in identifying the two kinds of
phenomena. One (already mentioned) is the total absence of the regular
swirling motion--in a direction contrary to that of the hands of a watch
north of the solar equator, in the opposite sense south of it--which
should impress itself upon every lineament of a sun-spot if the cause
assigned were a primary producing, and not merely (as it possibly may
be) a secondary determining one. The other, pointed out by Young,[467]
is that the cause is inadequate to the effect. The difference of
movement, or _relative drift_, supposed to occasion such prodigious
disturbances, amounts, at the utmost, for two portions of the
photosphere 123 miles apart, to about five yards a minute. Thus the
friction of contiguous sections must be quite insignificant.

A view better justified by observation was urged by Secchi in and after
the year 1872, and was presented in an improved form by Professor Young
in his excellent little book on _The Sun_, published in