9. DISCOVERY OF NEW PLANETS--HERSCHEL, PIAZZI, ADAMS, AND LE VERRIER.


It would be very interesting, but quite impossible in these pages, to
discuss all the exquisite researches of the mathematical astronomers,
and to inspire a reverence for the names connected with these
researches, which for two hundred years have been establishing the
universality of Newton's law. The lunar and planetary theories, the
beautiful theory of Jupiter's satellites, the figure of the earth, and
the tides, were mathematically treated by Maclaurin, D'Alembert,
Legendre, Clairaut, Euler, Lagrange, Laplace, Walmsley, Bailly,
Lalande, Delambre, Mayer, Hansen, Burchardt, Binet, Damoiseau, Plana,
Poisson, Gauss, Bessel, Bouvard, Airy, Ivory, Delaunay, Le Verrier,
Adams, and others of later date.

By passing over these important developments it is possible to trace
some of the steps in the crowning triumph of the Newtonian theory, by
which the planet Neptune was added to the known members of the solar
system by the independent researches of Professor J.C. Adams and of
M. Le Verrier, in 1846.

It will be best to introduce this subject by relating how the
eighteenth century increased the number of known planets, which was
then only six, including the earth.

On March 13th, 1781, Sir William Herschel was, as usual, engaged on
examining some small stars, and, noticing that one of them appeared to
be larger than the fixed stars, suspected that it might be a comet.