its height, the office
was, in the number of its scientific employees, nearly on an equality
with the three or four greatest observatories of the world.

One of my experiences has affected my judgment on the general morale
of the educated young men of our country. In not a single case did I
ever have an assistant who tried to shirk his duty to the government,
nor do I think there was more than a single case in which one tried
to contest my judgment of his own merits, or those of his work.
I adopted the principle that promotion should be by merit rather than
by seniority, and my decisions on that matter were always accepted
without complaint. I recall two men who voluntarily resigned when
they found that, through failure of health or strength, they were
unable to properly go on with their work. In frankness I must admit
that there was one case in which I had a very disagreeable contest in
getting rid of a learned gentleman whose practical powers were so far
inferior to his theoretical knowledge that he was almost useless in
the office. He made the fiercest and most determined fight in which
I was ever engaged, but I must, in justice to all concerned, say that
his defect was not in will to do his work but in the requisite power.
Officially I was not without fault, because, in the press of matters
requiring my attention, I had entrusted too much to him, and did
not discover his deficiencies until some mischief had been done.

Perhaps the most eminent and interesting man associated with me
during this period was Mr. George W. Hill, who will easily rank as
the greatest master of mathematical astronomy during the last quarter
of the nineteenth century. The only defect of his make-up of which
I have reason to complain is the lack of the teaching faculty.
Had this been developed in him, I could have learned very much
from him that would have been to my advantage. In saying this
I have one especial point in mind. In beginning my studies in
celestial mechanics, I lacked the guidance of some one conversant
with the subject on its practical side. Two systems of computing
planetary perturbations had been used, one by Leverrier, while the
other was invented by Hansen. The former method was, in principle,
of great simplicity, while the latter seemed to be very complex and
even clumsy. I naturally supposed that the man who computed the
direction of the planet Neptune before its existence was known, must
be a master of th