e second, and the task is done. Stars, not very near the sun, may be
seen in broad daylight, but, at night, it is requisite to direct a ray
of light from a lamp, so far to enlighten the field of the telescope, as
to permit the spider lines to be seen running across the brighter ground
on which the expected star is to be visible.

The adjustment of the instruments is a task of great nicety. If they are
out of trim only a shadow of a shade of a hair's-breadth, the desired
accuracy is interfered with, and they have to be re-adjusted.
Temperature is of course an important element in their condition, and a
slight sensibility may do mischief. The warmth of the observer's body,
when approaching the instruments, has been known to affect their
accuracy; and to avoid such sources of error, instruments have at times
been cased in flannel, that the non-conducting powers of that homely
fabric might screen the too-sensitive metal.

Sunday is a comparative holiday at the Observatory, for then, except
when any extraordinary phenomena are expected, the only duty done is to
drop the Time Ball, and observe the moon's place. The moon is never
neglected, and her motions have been here watched, during the last
hundred and seventy years, with the most pertinacious care--to the great
service of astronomy, and the great benefit of navigation.

The library should not pass unnoticed. It is small; but being devoted to
works upon astronomy, and the kindred sciences, there is ample room for
all that has hitherto been written on the subject, or that can, for many
generations, be produced. The observations of a lifetime spent in
watching the stars may be printed in marvelously few pages. A glance
through the Greenwich Astronomical Library gives a rough general idea of
what the world has done and is doing for the promotion of this science.
Russia contributes large, imperial-looking tomes, that tell of extended
observations made under the munificent patronage of a despot; Germany
sends from different points a variety of smaller, cheaper-looking, yet
valuable contributions; France gives proofs of her genius and her
discoveries; but _her_ forte is not in observation. The French are bad
observers. They have no such proofs of unremitting, patient toil in
search of facts, as those afforded in the records of the Greenwich
Tables of the Moon. Indeed, Greenwich, as we have already said, is a
working Observatory; and those who go into its library, and its
fire