arbault has a visible disc, within so limited an area of which the
sun is the centre, or rather within a narrow belt of that circle, we
should unhesitatingly declare that no such planet exists. But the
question assumes a very different aspect when it involves moral
considerations. If,' proceeds the Reviewer, writing in August 1860,
'after the severe scrutiny which the sun and its vicinity will undergo
before and after and during his total eclipse in July, no planet shall
be seen; and if no round black spot distinctly separable from the usual
solar spots shall be seen on the solar spots' (_sic_, presumably solar
disc was intended), 'we will not dare to say that it does not exist. We
cannot doubt the honesty of M. Lescarbault, and we can hardly believe
that he was mistaken. No solar spot, no floating scoria, could maintain
in its passage over the sun a circular and uniform shape, and we are
confident that no other hypothesis but that of an intra-mercurial planet
can explain the phenomena seen and measured by M. Lescarbault, a man of
high character, possessing excellent instruments, and in every way
competent to use them well, and to describe clearly and correctly the
results of his observations. Time, however, tries facts as well as
speculations. The phenomena observed by the French astronomer may never
be again seen, and the disturbance of Mercury which rendered it probable
may be otherwise explained. Should this be the case, we must refer the
round spot on the sun to some of those illusions of the eye or of the
brain which have sometimes disturbed the tranquillity of science.'

The evidence which has accumulated against Vulcan in the interval since
this was written is not negative only, but partly positive, as the
following instance, which I take from my own narrative at the time in a
weekly journal, serves to show:--After more than sixteen years of
fruitless watching, astronomers learned last August (1876) that in the
month of April Vulcan had been seen on the sun's disc in China. On April
4, it appeared, Herr Weber, an observer of considerable skill, stationed
at Pecheli, had seen a small round spot on the sun, looking very much as
a small planet might be expected to look. A few hours later he turned
his telescope upon the sun, and lo! the spot had vanished, precisely as
though the planet had passed away after the manner of planets in
transit. He forwarded the news of his observation to Europe. The
astronomer Wolff, we