investigating the same problem. The place which Le Verrier assigned
to the hypothetical disturbing planet for the beginning of the year
1847, was within a degree of that to which Adams's computations
pointed, and which he had communicated to the Astronomer Royal seven
months before Le Verrier's work appeared. On July the 29th, 1846,
Professor Challis commenced to search for the unknown object with the
Northumberland telescope belonging to the Cambridge Observatory. He
confined his attention to a limited region in the heavens, extending
around that point to which Mr. Adams' calculations pointed. The
relative places of all the stars, or rather star-like objects within
this area, were to be carefully measured. When the same observations
were repeated a week or two later, then the distances of the several
pairs of stars from each other would be found unaltered, but any
planet which happened to lie among the objects measured would
disclose its existence by the alterations in distance due to its
motion in the interval. This method of search, though no doubt it
must ultimately have proved successful, was necessarily a very
tedious one, but to Professor Challis, unfortunately, no other method
was available. Thus it happened that, though Challis commenced his
search at Cambridge two months earlier than Galle at Berlin, yet, as
we have already explained, the possession of accurate star-maps by
Dr. Galle enabled him to discover the planet on the very first night
that he looked for it.

The rival claims of Adams and Le Verrier to the discovery of Neptune,
or rather, we should say, the claims put forward by their respective
champions, for neither of the illustrious investigators themselves
condescended to enter into the personal aspect of the question, need
not be further discussed here. The main points of the controversy
have been long since settled, and we cannot do better than quote the