it.'

"My answer was in the following terms:--

[Sidenote: Airy's scepticism.]

NO. 2.--G. B. AIRY _to the_ REV. T. J. HUSSEY.
[_Extract._]

"'OBSERVATORY, CAMBRIDGE, _1834, Nov. 23_.

"'I have often thought of the irregularity of _Uranus_, and since the
receipt of your letter have looked more carefully to it. It is a
puzzling subject, but I give it as my opinion, without hesitation,
that it is not yet in such a state as to give the smallest hope of
making out the nature of any external action on the planet ... if it
were certain that there were any extraneous action, I doubt much the
possibility of determining the place of a planet which produced it. I
am sure it could not be done till the nature of the irregularity was
well determined from several successive revolutions.'"

[Sidenote: Le Verrier's papers.]

[Sidenote: Planet to be detected by disc.]

[Sidenote: Galle's discovery of the planet.]

Although only a sentence or two have been selected from Airy's reply (he
was not yet Astronomer Royal), they are sufficient to show that the
problem of finding the place of such a possible disturbing body was
regarded at that time as one of extreme difficulty; and no one appears
seriously to have contemplated embarking upon its solution. It was not
until many years later that the solution was attempted. Of the first
attempt we shall speak presently, putting it aside for the moment because
it had no actual bearing on the discovery of the planet, for reasons which
form an extraordinary episode of this history. The attempt which led to
success dates from November 1845. The great French astronomer Le Verrier,
on November 10, 1845, read to the French Academy a paper on the Orbit of
Uranus, considering specially the disturbances produced by Jupiter and
Saturn, and showing clearly that with no possible orbit could the
observations be satisfied. On June 1, 1846, followed a second paper by the
same author, in which he considers all the possible explanations of the
discordance, and concludes that none is admissible except that of a
disturbing planet exterior to Uranus. And assuming, in accordance with
Bode's Law, that the distance of this new planet from the sun would be
about double that of Uranus (and it is important to note this
assumption), he proceeds to investigate the orbit of such a planet, and to
calculate the place where it must be looked for in