a moving body, it would not have been in the same place relatively to
the stars at the time when the map was constructed, as it occupied
some years later when the search was being made. If the body should
be situated in the spot which Le Verrier's calculations indicated in
the autumn of 1846, then it might be regarded as certain that it
would not be found in that same place on a map drawn some years
previously.

The search to be undertaken consisted in a comparison made point by
point between the bodies shown on the map, and those stars in the sky
which Dr. Galle's telescope revealed. In the course of this
comparison it presently appeared that a star-like object of the
eighth magnitude, which was quite a conspicuous body in the
telescope, was not represented in the map. This at once attracted
the earnest attention of the astronomer, and raised his hopes that
here was indeed the planet. Nor were these hopes destined to be
disappointed. It could not be supposed that a star of the eighth
magnitude would have been overlooked in the preparation of a chart
whereon stars of many lower degrees of brightness were set down. One
other supposition was of course conceivable. It might have been that
this suspicious object belonged to the class of variables, for there
are many such stars whose brightness fluctuates, and if it had
happened that the map was constructed at a time when the star in
question had but feeble brilliance, it might have escaped notice. It
is also well known that sometimes new stars suddenly develop, so that
the possibility that what Dr. Galle saw should have been a variable
star or should have been a totally new star had to be provided
against.

Fortunately a test was immediately available to decide whether the