r ones at all. It is a wonderful testimony to the care and sagacity of
Sir William Herschel, as was remarked in the last chapter, that Uranus was
found to have been observed, under the mistaken impression that it was an
ordinary star, by Flamsteed, Lemonnier, Bradley, and Mayer, all observers
of considerable ability. Flamsteed's five observations dated as far back
as 1690, 1712, and 1715; observations by others were in 1748, 1750, 1753,
1756, and so on up to 1771, and the body of testimony was so considerable
that there was no room for doubt as to the irreconcilability of the
observations with the orbit, such as might have been the case had there
been only one or two, possibly affected with some errors.

[Sidenote: Suspicion of perturbing planet.]

It is difficult to mention an exact date for the conversion into certainty
of the suspicion that no single orbit could be found to satisfy all the
observations; but we may certainly regard this fact as established in
1821, when Alexis Bouvard published some tables of the planet, and showed
fully in the introduction that when every correction for the disturbing
action of other planets had been applied, it was still impossible to
reconcile the old observations with the orbit calculated from the new
ones. The idea accordingly grew up that there might be some other body or
bodies attracting the planet and causing these discrepancies. Here again
it is not easy to say exactly when this notion arose, but it was certainly
existent in 1834, as the following letter to the Astronomer Royal will
show. I take it from his well-known "Account of some Circumstances
historically connected with the Discovery of the Planet exterior to
Uranus," which he gave to the Royal Astronomical Society at its first
meeting after that famous discovery (Monthly Notices of the R.A.S., vol.
iii., and Memoirs, vol. xvi.).

NO. 1.--_The_ REV. T. J. HUSSEY _to_ G. B. AIRY.
[_Extract._]

"'HAYES, KENT, _17th November 1834_.

"'With M. Alexis Bouvard I had some conversation upon a subject I had
often meditated, which will probably interest you, and your opinion
may determine mine. Having taken great pains last year with some
observations of _Uranus_, I was led to examine closely Bouvard's
tables of that planet. The apparently inexplicable discrepancies
between the ancient and modern observations suggested to me the
possibility of some disturbing body beyond _Ura