the process completed. This was, after all, the real tug of war. Many
unknown quantities existed: its mass, its distance, its eccentricity,
the obliquity of its orbit, its position--nothing was known, in fact,
about the planet except the microscopic disturbance it caused in Uranus,
several thousand million miles away from it. Without going into further
detail, suffice it to say that in June, 1846, he published his last
paper, and in it announced to the world his theory as to the situation
of the planet.

Professor Airy received a copy of this paper before the end of the
month, and was astonished to find that Leverrier's theoretical place for
the planet was within 1° of the place Adams had assigned to it eight
months before. So striking a coincidence seemed sufficient to justify a
Herschelian sweep for a week or two. But a sweep for so distant a planet
would be no easy matter. When seen through a large telescope it would
still only look like a star, and it would require considerable labor and
watching to sift it out from the other stars surrounding it. We know
that Uranus had been seen twenty times, and thought to be a star, before
its true nature was discovered by Herschel; and Uranus is only about
half as far away as Neptune.

Neither at Paris nor at Greenwich was any optical search undertaken; but
Professor Airy wrote to ask M. Leverrier the same old question that he
had fruitlessly put to Adams: Did the new theory explain the errors of
the radius vector or not? The reply of Leverrier was both prompt and
satisfactory--these errors were explained, as well as all the others.
The existence of the object was then for the first time officially
believed in. The British Association met that year at Southampton, and
Sir John Herschel was one of its sectional presidents. In his inaugural
address, on September 10, 1846, he called attention to the researches of