particular race of spiders, that their webs may
be taken for that purpose. The spider lines
are strained across the best instruments at
Greenwich and elsewhere; and when the spinners                                                                 of these beautifully fine threads disturbed
the accuracy of the tube in the western wing
of the old Observatory, it was said to be but
fair retaliation for the robberies the                                                                                   industrious insects had endured.

A narrow stair leads from the unused
rooms of the old Observatory to its leaded roof,
whence a magnificent view is obtained; the
park, the hospital, the town of Greenwich, and
the windings of the Thames, and, gazing
further, London itself comes grandly into the
prospect. The most inveterate astronomer
could scarcely fail to turn for a moment from
the wonders of the heavens to admire these
glories of the earth. From the leads, two
turrets are reached, where the first constantly
active operations in this portion of the building,
are in progress.

At the present time, indeed, these turrets
are the most useful portions of the old                                                                              building. In one is placed the well-known                                                                               contrivance for registering, hour after hour, and
day after day, the force and direction of the
wind. To keep such a watch by human
vigilance, and to make such a register by
human labour, would be a tedious, expensive,
and irksome task; and human ingenuity
taxed itself to make a machine for perfecting
such work. The wind turns a weather-cock,
and, by aid of cog-wheels the motion is                                                                            transferred to a lead pencil fixed over a sheet of
paper, and thus the wind is made to write
down the direction which itself is blowing.
Not far distant is a piece of metal, the flat side
of which is ever turned by the weather-cock to
meet the full force of the wind, which, blowing
upon it, drives it back against a spring. To this
spring is affixed a chain passing over pullies
towards another pencil, fixed above a sheet of
paper, and moving faithfully, more or less, as
the wind blows harder or softer. And thus
the 'gentle zephyr' and the fresh breeze, and
the heavy gale, and, when it comes, the furious
hurricane, are made to note down their
character and force. The sheets of paper on
which the uncertain element, the wind, is
bearing witness against itself, is fixed upon a
frame moved by clockwork. Steady as the
progress of time, this ingenious mechanism
draws the paper under the suspended pencils.
Thus each minute and each hour has its
written record, without human help or inspection.                                                               Once a day only, an assistant come to put                                                                              a new blank sheet in the place of that which                                                                         has been covered by the moving pencils, and                                                                      the latter is taken away to be bound up in a                                                                    volume. The book might with truth be lettered 'The                                                          History of the Wind; written by Itself,'-- an Æolian
autobiography.

Close by is another contrivance for registering
in decimals of an inch the quantity of rain
that falls. The drops are caught, and passing                                                                        down a tube, a permanent mark is made by
which the quantity is determined.

The eastern turret is devoted to the Time
Ball and its mechanism. Far out at sea-- away
from all sources of information but those to
be asked of the planets, his compass, his
quadrant, his chronometer, and his almanack,
the mariner feels the value of time in a way
which the landsman can scarcely conceive.
If his chronometer is right, he may feel safe;
let him have reason to doubt its accuracy, and
he knows how the perils surrounding him
are increased. An error of a few seconds in
his time may place him in danger-- an error
of a few minutes may lead him to steer
blindly to his certain wreck. Hence his
desire when he is leaving port to have his
time-pieces right to a second; and hence the
expenditure of thought, and labour, and
money, at the Greenwich Observatory, to
afford the shipping of the great port of
London, and the English navy, the exact time                                                                   — true to the tenth of a second, or six hundredth                                                                       of a minute-- and to afford them also a book,                                                                        the Nautical Almanack, containing a mass of                                                              astronomical facts, on which they may
base their calculations, with full reliance as to
their accuracy. Every day for the last seventeen
years, at five minutes before one o'clock, the
black ball five feet across and stuffed with cork,
is raised halfway up its shaft above the eastern
turret of the Observatory,  -- at two-and-a-half
minutes before that hour, it rises to the top.
Telescopes from many a point, both up and
down the river, are now pointed to this
dark spot above the Greenwich trees, and many
an anxious mariner has his time-pieces beside
him, that their indications may be made true.
Watch the Ball as you stand in the Park. It
is now just raised. You must wait two
minutes and a half, and as you do so, you
feel what a minute may be. It seems a long,
palpable, appreciable time, indeed. In the
turret below, stands a clock telling the true
time, gained by a laborious watching of the
clock-stars; and beside the clock, is a man with
a practised hand upon a trigger, and a                                                                                practised eye upon the face of the dial. One
minute-- two minutes pass. Thirty seconds
more, and the trigger has released the Ball.
As it leaves the top of the shaft, it is one
o'clock to the tenth of a second. By the
time it has reached the bottom it is some
five seconds later.

Leaving the Ball Turret, and the old building                                                                      which it surmounts, the new Observatory,
where the chief work of the establishment is
done, claims our notice. This attention would
scarcely be given to its outward appearance
for it is a long low building, scarcely seen
beyond its own boundaries. The Greenwich
Observatory is not a show place, but an                                                                             eminently practical establishment. St. Petersburg
and other cities have much more gorgeous
buildings devoted to astronomical purposes,
and Russia and other countries spend much
more money on astronomy than England does,