t a young and unknown man should have successfully
solved so extremely difficult a problem? It was altogether unlikely.
Still, he would test him: he would ask for further explanations
concerning some of the perturbations which he himself had specially
noticed, and see if Mr. Adams could explain these also by his
hypothesis. If he could, there might be something in his theory. If he
failed--well, there was an end of it. The questions were not difficult.
They concerned the error of the radius vector. Mr. Adams could have
answered them with perfect ease; but sad to say, though a brilliant
mathematician, he was not a man of business. He did not answer Professor
Airy's letter.

It may to many seem a pity that the Greenwich Equatoreal was not pointed
to the place, just to see whether any foreign object did happen to be in
that neighbourhood; but it is no light matter to derange the work of an
Observatory, and alter the work mapped out for the staff into a sudden
sweep for a new planet, on the strength of a mathematical investigation
just received by post. If observatories were conducted on these
unsystematic and spasmodic principles, they would not be the calm,
accurate, satisfactory places they are.

Of course, if any one could have known that a new planet was to be had
for the looking, _any_ course would have been justified; but no one
could know this. I do not suppose that Mr. Adams himself could feel all
that confidence in his attempted prediction. So there the matter
dropped. Mr. Adams's communication was pigeon-holed, and remained in
seclusion for eight or nine months.

Meanwhile, and quite independently, something of the same sort was going
on in France. A brilliant young mathematician, born in Normandy in 1811,
had accepted the post of Astronomical Professor at the Ecole
Polytechnique, then recently founded by Napoleon. His first published
papers directed attention to his wonderful powers; and the official head
of astronomy in France, the famous Arago, suggested to him the
unexplained perturbations of Uranus as a worthy object for his fresh and
well-armed vigour.

At once he set to work in a thorough and systematic way. He first
considered whether the discrepancies could be due to errors in the
tables or errors in the old observations. He discussed them with minute
care, and came to the conclusion that they were not thus to be explained
away. This part of the work he published in November, 1845.

He then set to