ter no vacancy in the grade of professors of mathematics
in the navy shall be filled."

In 1873 this provision was annulled by a law, again providing
for a corps of twelve professors, three of whom should have the
relative rank of captain, four of commander, and the remainder of
lieutenant-commander or lieutenant.

Up to 1878 the Secretary of the Navy was placed under no restrictions
as to his choice of a professor. He could appoint any citizen whom
he supposed to possess the necessary qualifications. Then it was
enacted that, before appointment, a candidate should pass a medical
and a professional examination.

I have said that the main cause of hesitation in making my
application arose from my aversion to very late night work. It soon
became evident that there was less ground than I had supposed for
apprehension on this point. There was a free and easy way of carrying
on work which was surprising to one who had supposed it all arranged
on strict plans, and done according to rule and discipline. Professor
Yarnall, whose assistant I was, was an extremely pleasant gentleman
to be associated with. Although one of the most industrious workers
at the observatory, there was nothing of the martinet about him.
He showed me how to handle the instrument and record my observations.
There was a Nautical Almanac and a Catalogue of Stars. Out of these
each of us could select what he thought best to observe.

The custom was that one of us should come on every clear evening,
make observations as long as he chose, and then go home. The transit
instrument was at one end of the building and the mural circle, in
charge of Professor Hubbard, at the other. He was weak in health,
and unable to do much continuous work of any kind, especially the
hard work of observing. He and I arranged to observe on the same
nights; but I soon found that there was no concerted plan between
the two sets of observers. The instruments were old-fashioned
ones, of which mine could determine only the right ascension of a
star and his only its declination; hence to completely determine
the position of a celestial body, observations must be made on the
same object with both instruments. But I soon found that there was
no concert of action of this kind. Hubbard, on the mural circle,
had his plan of work; Yarnall and myself, on the transit, had ours.
When either Hubbard or myself got tired, we could "vote it cloudy"
and go out for a plate of oysters