d
at the Lick Observatory, it is understood that Burnham and Barnard,
whose eyes are of the keenest, looked in vain for the companion
of Procyon. Yet, in 1895, it was found with the same instrument
by Schaeberle, and has since been observed with the great Yerkes
telescope, as well as by the observers at Mount Hamilton, so that the
reality of the discovery is beyond a doubt. The explanation of the
failure of Burnham and Barnard to see it is very simple: the object
moves in an eccentric orbit, so that it is nearer the planet at some
points of its orbit than at others. It was therefore lost in the
rays of the bright star during the years 1887-94. Is it possible
that it could have been far enough away to be visible in 1873-74?
I need scarcely add that this question must be answered in the
negative, yet it may be worthy of consideration, when the exact
orbit of the body is worked out twenty or thirty years hence.

In my work with the telescope I had a more definite end in view
than merely the possession of a great instrument. The work of
reconstructing the tables of the planets, which I had long before
mapped out as the greatest one in which I should engage, required
as exact a knowledge as could be obtained of the masses of all
the planets. In the case of Uranus and Neptune, the two outer
planets, this knowledge could best be obtained by observations on
their satellites. To the latter my attention was therefore directed.
In the case of Neptune, which has only one satellite yet revealed
to human vision, and that one so close to the planet that the
observations are necessarily affected by some uncertainty, it was
very desirable that a more distant one should be found if it existed.
I therefore during the summer and autumn of 1874 made most careful
search under the most favorable conditions. But no second satellite
was found. I was not surprised to learn that the observers with
the great Lick telescope were equally unsuccessful. My observations
with the instrument during two years were worked up and published,
and I turned the instrument over to Professor Hall in 1875.

The discovery of the satellites of Mars was made two years later,
in August, 1877. As no statement that I took any interest in the
discovery has ever been made in any official publication, I venture,
with the discoverer's permission, to mention the part that I took
in verifying it.

One morning Professor Hall confidentially showed me his first
o