Bode's Law pointed to the existence of minor
planets, and might conceivably have helped in finding Uranus: but by
trusting to it in the case of Neptune, the investigators were perilously
near going astray. Sometimes it is better to follow resolutely the work in
hand whatever it may be, shutting one's ears to other calls; but Airy and
Challis lost their opportunities by just this course of action. The
history of science is full of such contradictory experiences; and the only
safe conclusion seems to be that there are no general rules of conduct for
discovery.

CHAPTER III

BRADLEY'S DISCOVERIES OF THE ABERRATION OF LIGHT AND OF THE NUTATION OF
THE EARTH'S AXIS

[Sidenote: Biographical method adopted.]

In examining different types of astronomical discovery, we shall find
certain advantages in varying to some extent the method of presentation.
In the two previous chapters our opportunities for learning anything of
the life and character of those who made the discoveries have been slight;
but I propose to adopt a more directly biographical method in dealing with
Bradley's discoveries, which are so bound up with the simple earnestness
of his character that we could scarcely appreciate their essential
features properly without some biographical study. But the record of his
life apart from his astronomical work is not in any way sensational;
indeed it is singularly devoid of incident. He had not even a scientific
quarrel. There was scarcely a man of science of that period who had not at
least one violent quarrel with some one, save only Bradley, whose gentle
nature seems to have kept him clear of them all. Judged by ordinary
standards his life was uneventful: and yet it may be doubted whether, to
him who lived it, that life contained one dull moment. Incident came for
him in his scientific work: in the preparation of apparatus, the making of
observations, above all in the hard-thinking which he did to get at the
clue which would explain them; and after reviewing his biography,[2] I
think we shall be inclined to admit that if ever there was a happy life,
albeit one of unremitting toil, it was that of James Bradley.

[Sidenote: Bradley's birth and early life.]

[Sidenote: Brief clerical career.]

He was born at Sherbourn, in Gloucestershire, in 1693. We know little of
his boyhood except that he went to the Grammar School at Northleach, and
that the memory of this fact was preserved at the school in 1832 when
Rig