of arms, the error might be changed in the
opposite direction; so that the deviation in
one vessel was not a guide to its amount or
direction in another; and that there was no
other remedy but ascertaining the fact by
direct experiment in each ship." These facts
were recognised by a committee of English
officers, appointed to investigate the matter,
one of whom was the Captain Johnson whom
we have already quoted, and of whose
subsequent labours we shall have further presently
to speak.

With these words of explanatory preface,
let us set out on a visit to the establishment
where the dangers of those afloat are sought
to be lessened by scientific investigations on
shore.

About two miles and a half eastwards from
the Greenwich Observatory, in the picturesque
parish of Charlton, and on the extreme corner
of the high land that runs from Blackheath,
till it juts out close upon the banks of the
Thames—stands the building we are in
search of. Those who may try to discover it
will probably find some little difficulty in the
task, for the place is unpretending in outward
aspect, and is little known in the neighbourhood;
has never before been publicly described
—except, perhaps, in those unread publications
called Blue Books, and in the technical
volume of the naval officer who has charge of
this sanctum of science.

It is called the Compass Observatory; and
its locality may probably be more completely
indicated by saying that it is not very distant
from, though on a far higher level than that
corner of the Woolwich Dockyard whence the
great chimney soars up like a rival monument
to that on Fish Street Hill, and where the
engine that sets the Dockyard Machines in
motion hums like a bee of forty-horse power.
When the place is reached, those who expect
to see "a public building," will be
disappointed; those who like to find that Science
may abide in small and humble places,
will be pleased. A long strip of newly-
reclaimed land, a detached brick house, and in
its rear, an octagonal wooden structure of
little greater outward pretensions than a
citizen's "summer house," make up the whole
establishment.

Passing under the pleasant shade of two
fine oak trees, and then between a collection
of very promising roses, we enter the
house. Once inside, we see that the spirit of
order, regularity, and neatness, is there
paramount. The exactitude requisite for
scientific observation, gives a habit of exactness
in other things. In one room we perceive
a galvanic battery ready for experiments; a
disc of iron for showing a now defunct mode
of steadying the vibrations of the compass; a
specimen of the mixed iron and wood braced
together as they are now employed in the
construction of first-class ships of the Royal
Navy, like the Queen's Yacht; and more
interesting than all the rest, a copper bowl.
contrived by Arago, for stilling the irritability
(so to speak) of the magnetic needle.

The French astronomer and ex-minister of
the Provisional Government here claims our
admiration of his scientific skill, and his work
suggests the reflexion how much more
pleasant the calm pursuit of nature's laws must
be to such a man, than the turbulent effort
to enact rules and constitutions for an
impetuous and changeable people. Passing from
this room to another, we find books, and
charts, and maps, on which are laid down the
magnetic currents over the great oceans, and
amongst its instrumental relics, a magnetic
needle that belonged to poor Captain Cook.
It is a plain small bar of steel in a rough
wooden case, but to the mariner who loves
his craft and its heroes, this morsel of iron
has an interest greater than the most perfect
of nautical inventions—for Cook was a seaman
who achieved great ends with humble means
and from humble beginnings. A third room
is full of compasses of all sorts, sizes, and
kinds, from China, from Denmark, from
France; from the most rude and simple, to
the most complex and finished. All the
schemes and plans ever proposed for
improving this useful invention are here
preserved. Many of the contrivances have been
discovered more than once. A sanguine
theorist completes what to him is perfectly
new. Certain that he is to be immortalised
and enriched, he sets off to the Observatory
with his treasure, to reveal his grand secret,
and receive the anticipated reward. He is
shown into the compass-room, and there,—
horror of horrors,—upon the table, amidst a
host of others, there is an old discarded,
instrument the very counterpart of his own!
It was made, and tried, and discarded, years
ago.

From the main brick building we pass
through another line of roses, and under a
bower, boasting some fifty different varieties
of that charming flower, to the wooden
structure in the rear, which is, in fact, the
Observatory.

This building is entirely free from iron.
It is approached by stone steps; the door has
a pure copper lock, which being opened by a
copper key, swings on copper hinges to admit
the visitor after he has first cleared the dirt
from his shoes upon a copper scraper. Nearly
facing the door is a stove to keep up the
temperature in cold weather. It looks black
enough, and has a black funnel. When the
visitor is told that Captain Johnson has his
coat-buttons carefully made without any iron
shank concealed under their silken cover;
and that his assistant, Mr. Brunton, repudiates
buttons to his jacket altogether, and has
pockets guiltless of a knife; he is apt to turn
to the stove, and hint the presence there of
the forbidden metal.

"Ah, ah!" is the reply, it looks like iron
sure enough; but the fireplace, the chimney,
the poker, the shovel, are all alike. Nothing