There is a morsel of Greenwich Park, which has, for now nearly two
centuries, been held sacred from intrusion. It is the portion inclosed
by the walls of the Observatory. Certainly a hundred thousand visitors
must ramble over the surrounding lawns, and look with curious eye upon
the towers and outer boundaries of that little citadel of science, for
one who finds admission to the interior of the building. Its brick
towers, with flanking turrets and picturesque roofs, perched on the side
of the gravelly hill, and sheltered round about by groups of fine old
trees, are as well known as Greenwich Hospital itself. But what work
goes on inside its carefully preserved boundary and under those
moveable, black-domed roofs, is a popular mystery. Many a
holiday-maker’s wonder has been excited by the fall, at one o’clock, of
the huge black ball, high up there, by the weather vane on the topmost
point of the eastern turret. He knows, or is told if he asks a loitering
pensioner, that the descent of the ball tells the time as truly as the
sun; and that all the ships in the river watch it to set their
chronometers by, before they sail; and that all the railway clocks, and
all the railway trains over the kingdom are arranged punctually by its
indications. But how the heavens are watched to secure this punctual
definition of the flight of time, and what other curious labours are
going on inside the Observatory, is a sealed book. The public have
always been, of necessity, excluded from the Observatory walls, for the
place is devoted to the prosecution of a science whose operations are
inconsistent with the bustle, the interruptions, the talk, and the
anxieties of popular curiosity and examination.
But when public information and instruction are the objects, the doors
are widely opened, and the press and its _attachés_ find a way into
this, as into many other sacred and forbidden spots. Only last week one
of ‘our own contributors’ was seen in a carriage on the Greenwich
railway, poring over the paper in the last Edinburgh Review that
describes our national astronomical establishment, and was known
afterwards to have climbed the Observatory hill, and to have rung and
gained admission at the little black mysterious gate in the Observatory
wall. Let us see what is told in his report of what he saw within that
sacred portal.
In the park on a fine day all seems life and gaiety—once within the
Observatory boundary, the first feeling is that of isolation. There is a
curious stillness about the place, and the footsteps of the old
pensioner, who closes the gate upon a visitor, echoes again on the
pavement as he goes away to wake up from his astronomical or
meteorological trance one of the officers of this sanctum. Soon, under
the guidance of the good genius so invoked, the secrets of the place
begin to reveal themselves.
The part of the Observatory so conspicuous from without is the portion
least used within. When it was designed by Christopher Wren, the general
belief was that such buildings should be lofty, that the observer might
be raised towards the heavenly bodies whose motions he was to watch.
More modern science has taught its disciples better; and in
Greenwich,—which is an eminently practical Observatory,—the working part
of the building is found crouching behind the loftier towers. These are
now occupied as subsidiary to the modern practical building. The ground
floor is used as a residence by the chief astronomer; above is the large
hall originally built to contain huge moveable telescopes and
quadrants—such as are not now employed. Now-a-days, this hall
occasionally becomes a sort of scientific counting-house—irreverent but
descriptive term—in which, from time to time, a band of scientific
clerks are congregated to post up the books, in which the daily business
of the planets has been jotted down by the astronomers who watch those
marvellous bodies. Another portion is a kind of museum of astronomical
curiosities. Flamstead and Halley, and their immediate successors,
worked in these towers, and here still rest some of the old, rude tools
with which their discoveries were completed, and their reputation, and
the reputation of Greenwich, were established. As time has gone on,
astronomers and opticians have invented new and more perfect and more
luxurious instruments. Greater accuracy is thus obtainable, at a less
expenditure of human patience and labour; and so the old tools are cast
aside. One of them belonged to Halley, and was put up by him a hundred
and thirty years ago; another is an old brazen quadrant, with which many
valuable observations were made in by-gone times; and another, an old
iron quadrant, still fixed in the stone pier to which it was first
attached. Some of the huge telescopes that once found place in this old
Observatory, have been sent away. One went to the Cape of Good Hope, and
has been useful there. Another of the unsatisfactory, and now unused,
instruments had a tube twenty-five feet long, whose cool and dark
interior was so pleasant to the spiders that, do what they would, the
astronomers could not altogether banish the persevering insects from it.
Spin they would; and, spite of dusting and cleaning, and spider-killing,
spin they did; and, at length, the savans got more instruments and less
patience, and the spiders were left in quiet possession. This has been
pleasantly spoken of as an instance of poetical justice. It is but fair
that spiders should, at times, have the best of astronomers, for
astronomers rob spiders for the completion of their choicest
instruments. No fabric of human construction is fine enough to strain
across the eye-piece of an important telescope, and opticians preserve a
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 comes 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, yet the Greenwich Tables have a world-wide reputation, and
some of them are used as the groundwork for calculations in all
Observatories at home and abroad. The astronomer does not want marble
halls or grand saloons for his work. Galileo used a bell-tower at
Venice, and Kepler stood on the bridge at Prague to watch the stars. The
men, not the buildings, do the work. No disappointment need be felt,
then, to find the modern Observatory a range of unadorned buildings
running east and west, with slits in the roof, and in some of the walls.
Within these simple buildings are the instruments now used, displaying
almost the perfection of mechanical skill in their construction and
finish—beautifully adapted to the object they have to fulfil, and in
perfect order. They are fixed on solid piers of masonry, deeply imbedded
in the earth, to secure freedom from vibration—a quality better obtained
when the foundations are on sand or gravel than when on rock.
To describe the instruments by their technical names, and to go into any
particulars of the instruments they have superseded, would take space,
only to do the work of a scientific treatise. Enough, therefore, to say
that there are the telescopes best adapted to the chief duty of the
place, which is, watching the moon whenever she is visible; watching the
_clock-stars_, by which the true time is calculated more exactly than it
could be from observations of the sun alone; and watching other
planetary bodies as they pass the meridian. Eclipses, occultations, and
other phenomena, of course, have their share of attention, and add to
the burden of the observer’s duties.
The staff of the Observatory includes a chief astronomer, Mr. Airy, with
a salary of 800_l._ a year; and six assistants who are paid, 470_l._,
290_l._, 240_l._, 150_l._, 130_l._, and 130_l._, respectively. This does
not include the officers of the Meteorological branch of the
establishment, to be spoken of hereafter; and which consists of Mr.
Glaisher, with 240_l._ a year, one assistant at 120_l._, and two
additional computers. At times, when these scientific labourers have
collected more observations than they are able to work out; additional
help is summoned, in shape of the body of scientific clerks before
spoken of; who, seated at desks, cast up the accounts the planetary
bodies, including such regular old friends as the moon and fixed stars,
but not forgetting those wandering celestial existences that rush, from
time to time, over the meridian, and may be fairly called the chance
customers of the astronomer.
Though the interior of the Observatory seems so still, the life of those
employed there has its excitements. Looking through telescopes forms a
small part only of their duty—and that duty cannot be done when the
weather is unfavourable. On cloudy days the observer is idle; in bright
weather he is busy; and a long continuance of clear days and nights
gives him more employment than he can well complete. Summer, therefore,
is his time of labour; winter his time of rest. It appears that in our
climate the nights, on the whole, are clearer than the days, and
evenings less cloudy than mornings. Every assistant takes his turn as an
observer, and a chain of duty is kept up night and day; at other
periods, the busiest portion of the twenty-four hours at the
Observatory, is between nine in the morning and two in the afternoon.
During this time they work in silence, the task being to complete the
records of the observations made, by filling in the requisite columns of
figures upon printed forms, and then adding and subtracting them as the
case requires. Whilst thus engaged, the assistant who has charge of an
instrument looks, from time to time, at his star-regulated clock, and
when it warns him that his expected planet is nearly due, he leaves his
companions, and quietly repairs to the room where the telescope is
ready. The adjustment of this has previously been arranged with the
greatest nicety. The shutter is moved from the slit in the roof, the
astronomer sits upon an easy chair with a moveable back. If the object
he seeks is high in the heavens, this chair-back is lowered till its
occupant almost lies down; if the star is lower, the chair-back is
raised in proportion. He has his note-book and metallic pencil in hand.
Across the eye-piece of the telescope are stretched seven lines of
spider-web, dividing the field of view. If his seat requires change, the
least motion arranges it to his satisfaction, for it rests upon a
railway of its own. Beside him is one of the star-clocks, and as the
moment approaches for the appearance of the planet, the excitement of
the moment increases. ‘The tremble of impatience for the entrance of the
star on the field of view,’ says an Edinburgh Reviewer, ‘is like that of
a sportsman whose dog has just made a full point, and who awaits the
rising of the game. When a star appears, the observer, in technical
language, _takes a second from the clock face_; that is, he reads the
second with his eye, and counts on by the ear the succeeding beats of
the clock, naming the seconds mentally. As the star passes each wire of
the transit, he marks down in his jotting-book with a metallic pencil
the second, _and the second only_, of his observation, with such a
fraction of a second as corresponds, in his judgment, to the interval of
time between the passage of the star, and the beat of the clock which
preceded such passage.’
An experienced observer will never commit an error in this mental
calculation, exceeding the tenth of a second, or six hundredth of a
minute. When the star has been thus watched over the seven cobweb lines
(or wires), the observer jots down the hour and minute, in addition to
the 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 marvellously 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-proof manuscript-room, and see how its volumes of observations have
been growing from the small beginnings of the days of Flamstead and
Halley, to those of our later and more liberal times, will have good
reason to acknowledge that the money devoted to this establishment has
been well employed.
One other spot must be noticed as amongst the notable things in this
astronomical sanctum. It is the Chronometer-room, to which, during the
first three Mondays in the year, the chief watchmakers of London send in
their choicest instruments for examination and trial. The watches remain
for a good portion of a year; their rates being noted, day by day, by
two persons; and then the makers of the best receive prizes, and their
instruments are purchased for the navy. Other competitors obtain
certificates of excellence, which bring customers from the merchant
service; whilst others pass unrewarded. To enter the room where these
admirable instruments are kept, suggests the idea of going into a
Brobdingnag Watch-factory. Round the place are ranged shelves, on which
the large watches are placed, all ticking in the most distinct and
formidable way one against another. When they first arrive, in January,
they are left to the ordinary atmospheric temperature for some months.
Their rates being taken under these circumstances, a large stove in the
centre of the apartment is lighted, and heat got up to a sort of
artificial East India or Gold Coast point. Tried under these influences,
they are placed in an iron tray over the stove, like so many watch-pies
in a baker’s dish, and the fire being encouraged, they are literally
kept baking, to see how their metal will stand that style of treatment.
Whilst thus hot, their rates are once more taken; and then, after this
fiery ordeal, such of them as their owners like to trust to an opposite
test, are put into freezing mixtures! Yet, so beautifully made are these
triumphs of human ingenuity—so well is their mechanism ‘corrected’ for
compensating the expansion caused by the heat, and the contraction
induced by the cold—that an even rate of going is established, so
nearly, that its variation under opposite circumstances becomes a matter
of close and certain estimate.
The rates of chronometers on trial for purchase by the Board of
Admiralty, at the Observatory, are posted up and printed in an official
form. Upon looking to the document for last year, we find a statement of
their performances during six months of 1849, with memoranda of the
exact weeks during which the chronometers were exposed to the open air
at a north window; the weeks the Chronometer-room was heated by a stove,
the chronometers being dispersed on the surrounding shelves; and the
weeks during which they were placed in the tray above the stove. The
rate given during the first week of trial is in every case omitted; like
newly entered schoolboys their early vagaries are not taken into
account; but after that, every merit and every fault is watched with
jealous care, and, when the day of judgment comes, the order of the
arrangement of the chronometers in the list is determined solely by
consideration of their irregularities of rate as expressed in the
columns, ‘Difference between greatest and least,’ and, ‘Greatest
difference between one week and the next.’
The Royal Observatory, according to a superstition not wholly extinct,
is the headquarters, not only of Astronomy, but of Astrology. The
structure is awfully regarded, by a small section of the community which
ignorance has still left amongst us, as a manufactory of horoscopes, and
a repository for magic mirrors and divining-rods. Not long ago a
well-dressed woman called at the Observatory gate to request a hint as
to the means of recovering a lost sum of money; and recently, somebody
at Brighton dispatched the liberal sum of five shillings in a
post-office order to the same place, with a request to have his nativity
cast in return! Another, only last year, wrote as follows:—‘I have been
informed that there are persons at the Observatory who will, by my
enclosing a remittance and the hour of my birth, give me to understand
_who is to be my wife_? An early answer, stating all particulars, will
oblige,’ &c.
This sketch descriptive of its real duties and uses are not necessary to
relieve the Greenwich Observatory from the charge of being an abode of
sorcerers and astrologers. A few only of the most ignorant can yet
entertain such notions of its character; but they are not wholly
unfounded. Magicians, whose symbols are the Arabic numerals, and whose
_arcana_ are mathematical computations, daily foretell events in that
building with unerring certainty. They pre-discover the future of the
stars down to their minutest evolution and eccentricity. From data
furnished from the Royal Observatory, is compiled an extraordinary
prophetic Almanack from which all other almanacs are copied. It
foretells to a second when and where each of the planets may be seen in
the heavens at any minute for the next three years. The current number
of the Nautical Almanack is for the Year of Grace 1853.
In this quiet sanctuary, then, the winds are made to register their own
course and force, and the rain to gauge its own quantity as it falls;
the planets are watched to help the mariner to steer more safely over
the seas; and the heavens themselves are investigated for materials from
which their future as well as their past history may be written.