but copper, copper, pure copper. This
suggests an anecdote. When the operations in
this Compass Observatory were first
commenced, there was found to be a small
variation in the magnet. The instruments were
re-adjusted; their character was investigated, their
construction re-examined; other observations
were made—but still the variation continued.
Pockets were searched for knives; the garden
looked over to see that no stray spade or
rake had been left outside the building, yet
near enough for mischief. Nothing could be
discovered. At length the brass bolt on the
window was suspected; and though brass had
a good character, not being thought capable
of coaxing the magnet from its truth, it was,
in despair of finding any other delinquent,
unscrewed from its position. No sooner was
this done, than the wayward needle returned
to its true position; the brass bolt was
ejected in disgrace, and no morsel of the
brazen metal has since been allowed to show
itself within the precincts of the building
sacred to the mysterious fluid that draws the
iron needle to the North.

Once inside the Observatory, the first
impression is one of isolation and quietude.
Look up to the wooden roof, and you see two
shutters, to be opened when an observation is
to be made upon a star. Through the floor
rise three pedestals of masonry, built solidly
from the earth, and isolated from the Observatory
floor, so that no vibration may be
communicated to them. All three stand in a row,
running north and south. The object of two
of them is to support with complete steadiness
and truth two instruments for determining,
at any moment of time, the exact magnetic
north, whilst the third pedestal holds one by
one the compasses brought there to be tested.
The most northern of these three narrow
stone tables is, in fact, a bed of trial—a place
of ordeal—whilst the other two support the
instrumental judges, who are to pass
sentence upon the fluttering needles brought
under their unyielding gaze. The test is a
severe one. It is easy, with proper means, to
get the true magnetic north with a fixed
instrument on shore, but to make something
that shall tell it with equal truth upon the
deck of a ship, as it heaves and tosses, and
plunges on the sea, is a very different thing.
Yet, instruments equal to such triumphs of
skill are obtained, and in this place it is that
their qualities are first investigated. The
south pedestal has upon it a tall tube of glass,
within which there hang some long fibres of
untwisted silk, supporting a magnetic tube so
beautifully poised, that it obeys without let
or hindrance its natural tendency towards
the magnetic north. This tubular magnet
has at one end a glass on which a scale
and figures are engraved, but so fine and
small as to be with difficulty seen by the naked
eye. The second pedestal supports a
telescope, with which the observer looks down
the tubular throat of the magnet towards this
tiny scale on the glass at its extremity. Our
friends, the ''spiders," have contributed some
lines to the telescope, and the centre one of
these crosses the exact figure showing the
magnetic position at the moment.

With this figure in his mind, the telescope
and the observer's eye are poised in the
opposite direction, through the window of
the Observatory, towards a spot some half
mile to the north, called Cox's Mount; an
eminence on which a wall has been raised to
bear a numbered scale similar to that on the
magnet—with this difference—that the one is
very minute, and the other very large. To
the corresponding figure on the distant wall
the instrument is directed, and being thus
pointed towards the true magnetic north, it is
brought to bear upon the pivot of the compass
—which by this time occupies a place on the
top of the third pedestal to be tested. Without
a complex description, and the free use of
scientific terms, it would be perhaps impossible
to convey a thoroughly exact conception of the
steps of the whole process. Such a detail would
be not only too technical, but unnecessary,
here. It will be enough in general terms to
say, therefore, that the indication obtained
from a star, or from the instrument on the
south pedestal, called the collimator, is, by
means of the instrument in the centre,
combined with a mark upon a distant object, and
then brought down to prove the true powers
of the compass placed on the third pedestal.
It is a beautifully exact operation. The
silence of isolation, the steadiness of stone
tables and practised operators, the most
beautifully constructed instruments, are combined
to ensure accurate realities as a result. The
tests are so varied, and so often repeated, that
no error can escape, and the compass, when it
leaves the building to begin its adventures
afloat, commences its career with an
irreproachable character as a Standard Compass
of the Royal Navy—to be, on board the ship
of war to which it is sent, a kind of master
instrument of reference, by which ruder and
cheaper compasses may be checked and
regulated.

Just as the history of the stars and of the
variations of the magnet is registered and
posted up at the Greenwich Observatory, so is
that of the compasses entered up here. Every
compass that passes its examination may be
said to receive its commission, and be appointed
to a ship. Its number is taken; its vessel
and destination are noted, and, subsequently,
its length of service. On its return home from
successive trips, it comes back to this place,
when its character is again investigated and
note made of any loss of magnetic power, of
any deviations it may have exhibited, how it
may have lost and how gained, and of any
other circumstances showing either improvement
or deterioration. Now and then one is
blacklisted, but this seldom happens; the
greatest loss yet noted being 30 minutes. The
Standard Compasses cost, when made new,