Note: Project Gutenberg also has an HTML version of this
file which includes the original illustrations.
See 44167-h.htm or 44167-h.zip:
(https://www.gutenberg.org/cache/epub/44167/pg44167-images.html)
or
(https://www.gutenberg.org/files/44167/44167-h.zip)
Images of the original pages are available through
Internet Archive. See
https://archive.org/details/royalobservatory00maun
Transcriber's note:
Text enclosed by underscores is in italics (_italics_).
Small capital text has been replaced with all capitals.
The carat character (^) indicates that the following
letter is superscripted (example: II^s). If two or more
letters are superscripted they are enclosed in curly
brackets (example: D^{NI}).
[Illustration: FLAMSTEED, THE FIRST ASTRONOMER ROYAL.
(_From the portrait in the 'Historia Coelestis.'_)]
THE ROYAL OBSERVATORY GREENWICH
A Glance at Its History and Work
by
E. WALTER MAUNDER, F.R.A.S.
With Many Portraits and Illustrations from
Old Prints and Original Photographs
London
The Religious Tract Society
56 Paternoster Row, and 65 St. Paul's Churchyard
1900
London:
Printed by William Clowes and Sons, Limited,
Stamford Street and Charing Cross.
PREFACE
I was present on one occasion at a popular lecture delivered in
Greenwich, when the lecturer referred to the way in which so many
English people travel to the ends of the earth in order to see
interesting or wonderful places, and yet entirely neglect places
of at least equal importance in their own land. 'Ten minutes' walk
from this hall,' he said, 'is Greenwich Observatory, the most famous
observatory in the world. Most of you see it every day of your
lives, and yet I dare say that not one in a hundred of you has ever
been inside.'
Whether the lecturer was justified in the general scope of his
stricture or not, the particular instance he selected was certainly
unfortunate. It was not the fault of the majority of his audience
that they had not entered Greenwich Observatory, since the
regulations by which it is governed forbade them doing so. These
rules are none too stringent, for the efficiency of the institution
would certainly suffer if it were made a 'show' place, like a
picture gallery or museum. The work carried on therein is too
continuous and important to allow of interruption by daily streams
of sightseers.
To those who may at some time or other visit the Observatory it
may be of interest to have at hand a short account of its history,
principal instruments, and work. To the far greater number who
will never be able to enter it, but who yet feel an interest in
it, I would trust that this little book may prove some sort of a
substitute for a personal visit.
I would wish to take this opportunity of thanking the Astronomer
Royal for his kind permission to reproduce some of the astronomical
photographs taken at the Observatory and to photograph the domes
and instruments. I would also express my thanks to Miss Airy, for
permission to reproduce the photograph of Sir G. B. Airy; to Mr. J.
Nevil Maskelyne, F.R.A.S., for the portrait of Dr. Maskelyne; to Mr.
Bowyer, for procuring the portraits of Bliss and Pond; to Messrs.
Edney and Lacey, for many photographs of the Royal Observatory;
and to the Editor of _Engineering_, for permission to copy two
engravings of the Astrographic telescope.
E. W. M.
ROYAL OBSERVATORY, GREENWICH,
_August, 1900_.
[Illustration: THE NEW BUILDING.
(_From a photograph by Mr. Lacey._)]
CONTENTS
CHAPTER PAGE
I. INTRODUCTION 13
II. FLAMSTEED 25
III. HALLEY AND HIS SUCCESSORS 60
IV. AIRY 102
V. THE OBSERVATORY BUILDINGS 124
VI. THE TIME DEPARTMENT 146
VII. THE TRANSIT AND CIRCLE DEPARTMENTS 181
VIII. THE ALTAZIMUTH DEPARTMENT 205
IX. THE MAGNETIC AND METEOROLOGICAL DEPARTMENTS 228
X. THE HELIOGRAPHIC DEPARTMENT 251
XI. THE SPECTROSCOPIC DEPARTMENT 266
XII. THE ASTROGRAPHIC DEPARTMENT 284
XIII. THE DOUBLE-STAR DEPARTMENT 303
INDEX 317
LIST OF ILLUSTRATIONS
PAGE
FLAMSTEED, THE FIRST ASTRONOMER ROYAL _Frontispiece_
THE NEW BUILDING 7
GENERAL VIEW OF THE OBSERVATORY BUILDINGS FROM THE
NEW DOME 12
FLAMSTEED'S SEXTANT 36
THE ROYAL OBSERVATORY IN FLAMSTEED'S TIME 44
THE 'CAMERA STELLATA' IN FLAMSTEED'S TIME 52
EDMUND HALLEY 61
HALLEY'S QUADRANT 69
JAMES BRADLEY 72
GRAHAM'S ZENITH SECTOR 77
NATHANIEL BLISS 83
NEVIL MASKELYNE 87
HADLEY'S QUADRANT 91
JOHN POND 96
GEORGE BIDDELL AIRY, ASTRONOMER ROYAL 103
THE ASTRONOMER ROYAL'S ROOM 110
THE SOUTH-EAST TOWER 115
W. H. M. CHRISTIE, ASTRONOMER ROYAL 121
THE ASTRONOMER ROYAL'S HOUSE 127
THE COURTYARD 130
PLAN OF OBSERVATORY AT PRESENT TIME 134
THE GREAT CLOCK AND PORTER'S LODGE 147
THE CHRONOGRAPH 158
THE TIME-DESK 164
HARRISON'S CHRONOMETER 165
THE CHRONOMETER ROOM 167
THE CHRONOMETER OVEN 171
THE TRANSIT PAVILION 174
'LOST IN THE BIRKENHEAD' 179
THE TRANSIT CIRCLE 189
THE MURAL CIRCLE 195
AIRY'S ALTAZIMUTH 208
NEW ALTAZIMUTH BUILDING 211
THE NEW ALTAZIMUTH 213
THE NEW OBSERVATORY AS SEEN FROM FLAMSTEED'S OBSERVATORY 219
THE SELF-REGISTERING THERMOMETERS 235
THE ANEMOMETER ROOM, NORTH-WEST TURRET 240
THE ANEMOMETER TRACE 243
MAGNETIC PAVILION--EXTERIOR 246
MAGNETIC PAVILION--INTERIOR 248
THE DALLMEYER PHOTO-HELIOGRAPH 254
PHOTOGRAPH OF A GROUP OF SUN-SPOTS 259
THE GREAT NEBULA IN ORION 269
THE HALF-PRISM SPECTROSCOPE ON THE SOUTH-EAST EQUATORIAL 273
THE WORKSHOP 276
THE 30-INCH REFLECTOR WITH THE NEW SPECTROSCOPE
ATTACHED 278
'CHART PLATE' OF THE PLEIADES 286
THE CONTROL PENDULUM AND THE BASE OF THE THOMPSON
TELESCOPE 289
THE ASTROGRAPHIC TELESCOPE 291
THE DRIVING CLOCK OF THE ASTROGRAPHIC TELESCOPE 294
THE THOMPSON TELESCOPE IN THE NEW DOME 297
THE NEBULÆ OF THE PLEIADES 300
DOUBLE-STAR OBSERVATION WITH THE SOUTH-EAST EQUATORIAL 308
THE SOUTH-EAST DOME WITH THE SHUTTER OPEN 314
[Illustration: GENERAL VIEW OF THE OBSERVATORY BUILDINGS FROM THE
NEW DOME.
(_From a photograph by Mr. Lacey._)]
THE ROYAL OBSERVATORY
GREENWICH
CHAPTER I
INTRODUCTION
I had parted from a friend one day just as he met an acquaintance
of his to whom I was unknown. 'Who is that?' said the newcomer,
referring to me. My friend replied that I was an astronomer from
Greenwich Observatory.
'Indeed; and what does he do there?'
This question completely exhausted my friend's information, for as
his tastes did not lead him in the direction of astronomy, he had
at no time ever concerned himself to inquire as to the nature of my
official duties. 'Oh--er--why--he _observes_, don't you know?' and
the answer, vague as it was, completely slaked the inquirer's thirst
for knowledge.
It is not every one who has such exceedingly nebulous ideas of an
astronomer's duties. More frequently we find that the inquirer has
already formed a vivid and highly-coloured picture of the astronomer
at his 'soul-entrancing work.' Resting on a comfortable couch,
fixed at a luxurious angle, the eye-piece of some great and perfect
instrument brought most conveniently to his eye, there passes
before him, in grand procession, a sight such as the winter nights,
when clear and frosty, give to the ordinary gazer, but increased
ten thousand times in beauty, brilliance, and wonder by the power
of his telescope. For him Jupiter reveals his wind-drifted clouds
and sunset colours; for him Saturn spreads his rings; for him
the snows of Mars fall and melt, and a thousand lunar plains are
ramparted with titanic crags; his are the star-clusters, where suns
in their first warm youth swarm thicker than hiving bees; his the
faint veils of nebulous smoke, the first hint of shape in worlds
about to be, or, perchance, the last relics of worlds for ever
dead. And beside the enjoyment of all this entrancing spectacle of
celestial beauty, the fortunate astronomer sits at his telescope and
_discovers_--always he _discovers_.
This, or something like it, is a very popular conception of an
astronomer's experiences and duty; and consequently many, when they
are told that 'discoveries' are not made at Greenwich, are inclined
to consider that the Observatory has failed in its purpose. An
astronomer without 'discoveries' to his record is like an angler
who casts all day and comes home without fish--obviously an idle or
incompetent person.
Again, it is considered that astronomy is a most transcendental
science. It deals with infinite distances, with numbers beyond
all power of human intellect to appreciate, and therefore it is
supposed, on the one hand, that it is a most elevating study,
keeping the mind continually on the stretch of ecstasy, and, on the
other hand, that it is utterly removed from all connection with
practical, everyday, ordinary life.
These ideas as to the Royal Observatory, or ideas like them, are
very widely current, and they are, in every respect, exactly and
wholly wrong. First of all, Greenwich Observatory was originally
founded, and has been maintained to the present day, for a strictly
practical purpose. Next, instead of leading a life of dreamy ecstasy
or transcendental speculation, the astronomer has, perhaps, more
than any man, to give the keenest attention to minute practical
details. His life, on the one side, approximates to that of the
engineer; on the other, to that of the accountant. Thirdly, the
professional astronomer has hardly anything to do with the show
places of the sky. It is quite possible that there are many people
whose sole opportunity of looking through a telescope is the penny
peep through the instrument of some itinerant showman, who may have
seen more of these than an active astronomer in a lifetime; while as
to 'discoveries,' these lie no more within the scope of our national
observatory than do geographical discoveries within that of the
captain and officers of an ocean liner.
If it is not to afford the astronomer beautiful spectacles, nor to
enable him to make thrilling discoveries, what is the purpose of
Greenwich Observatory?
First and foremost, it is to assist navigation. The ease and
certainty with which to-day thousands of miles of ocean are
navigated have ceased to excite any wonder. We do not even think
about it. We go down to the docks and see, it may be, one steamer
bound for Halifax, another for New York, a third for Charleston,
a fourth for the West Indies, a fifth for Rio de Janeiro; and we
unhesitatingly go on board the one bound for our chosen destination,
without the faintest misgiving as to its direction. We have no more
doubt about the matter than we have in choosing our train at a
railway station. Yet, whilst the train is obliged to follow a narrow
track already laid for it, from which it cannot swerve an inch,
the steamer goes forth to traverse for many days an ocean without
a single fixed mark or indication of direction; and it is exposed,
moreover, to the full force of winds and currents, which may turn it
from its desired path.
But for this facility of navigation, Great Britain could never have
obtained her present commercial position and world-wide empire.
'For the Lord our God most High,
He hath made the deep as dry;
He has smote for us a pathway,
To the ends of all the earth.'
Part of this facility is, of course, due to the invention of the
steam engine, but much less than is generally supposed. Even yet
the clippers, with their roods of white canvas, are not entirely
superseded; and if we could conceive of all steamships being
suddenly annihilated, ere long the sailing vessels would again, as
of yore, prove the
'Swift shuttles of an empire's loom,
That weave us main to main.'
But with the art of navigation thrust back into its condition of a
hundred and fifty years ago, it is doubtful whether a sufficient
tide of commerce could be carried on to keep our home population
supplied, or to maintain a sufficiently close political connection
between these islands and our colonies.
Navigation was in a most primitive condition even as late as
the middle of last century. Then the method of finding a ship's
longitude at sea was the insufficient one of dead reckoning. In
other words, the direction and speed of the ship were estimated as
closely as possible, and so the position was carried on from day to
day. The uncertainty of the method was very great, and many terrible
stories might be told of the disastrous consequences which might,
and often did, follow in the train of this method by guess-work.
It will be sufficient, however, to cite the instance of Commodore
Anson. He wanted to make the island of Juan Fernandez, where he
hoped to obtain fresh water and provisions, and to recruit his
crew, many of whom were suffering from that scourge of old-time
navigators--scurvy. He got into its latitude easily enough, and
ran eastward, believing himself to be west of the island. He was,
however, really east of it, and therefore made the mainland of
America. He had therefore to turn round and sail westwards, losing
many days, during which the scurvy increased upon his crew, many of
whom died from the terrible disease before he reached the desired
island.
The necessity for finding out a ship's place when at sea had not
been very keenly felt until the end of the fifteenth century. It
was always possible for the sailor to ascertain his latitude pretty
closely, either by observing the height of the pole-star at night
or the height of the sun at noonday; and so long as voyages were
chiefly confined to the Mediterranean Sea, and the navigators were
content for the most part to coast from point to point, rarely
losing sight of land, the urgency of solving the second problem--the
longitude of the ship--was not so keenly felt. But immediately the
discoveries of the great Portuguese and Spanish navigators brought a
wider, bolder navigation into vogue, it became a matter of the first
necessity.
To take, for example, the immortal voyage of Christopher Columbus.
His purpose in setting out into the west was to discover a new
way to India. The Venetians and Genoese practically possessed the
overland route across the Isthmus of Suez and down the Red Sea.
Vasco da Gama had opened out the route eastward round the Cape.
Firmly convinced that the world was a globe, Columbus saw that a
third route was possible, namely, one nearly due west; and when,
therefore, he reached the Bahamas, after traversing some 66° of
longitude, he believed that he was in the islands of the China Sea,
some 230° from Spain. Those who followed him still laboured under
the same impression, and when they reached the mainland of America,
believed that they were close to the shores of India, which was
still distant from them by half the circumference of the globe.
Little by little the intrepid sailors of the sixteenth century
forced their way to a true knowledge of the size of the globe, and
of the relative position of the great continents. But this knowledge
was only attained after many disasters and terrible miseries; and
though a new kind of navigation was established--the navigation of
the open ocean, far away from any possible landmark, a navigation as
different as could be conceived from the old method of coasting--yet
it remained terribly risky and uncertain throughout the sixteenth
century. Therefore many mathematicians endeavoured to solve the
problem of determining the position of a ship when at sea. Their
suggestions, however, remained entirely fruitless at the time,
though in several instances they struck upon principles which are
being employed at the present day.
The first country to profit by the discovery of America was Spain,
and hence Spain was the first to feel keenly the pinch of the
problem. In 1598, therefore, Philip III. offered a prize of 100,000
crowns to any one who would devise a method by which a captain of
a vessel could determine his position when out of sight of land.
Holland, which had recently started on its national existence, and
which was challenging the colonial empire of Spain, followed very
shortly after with the offer of a reward of 30,000 florins. Not very
long after the offer of these rewards, a master mind did work out a
simple method for determining the longitude, a method theoretically
complete, though practically it proved inapplicable. This was
Galileo, who, with his newly invented telescope, had discovered that
Jupiter was attended by four satellites.
At first sight such a discovery, however interesting, would seem to
have not the slightest bearing upon the sailor's craft, or upon the
commercial progress of one nation or another. But Galileo quickly
saw in it the promise of great practical usefulness. The question
of the determination of the place of a ship when in the open ocean
really resolved itself into this: How could the navigator ascertain
at any time what was the true time, say at the port from which he
sailed? As already pointed out, it was possible, by observing the
height of the sun at noon, or of the pole-star at night, to infer
the latitude of the ship. The longitude was the point of difficulty.
Now, the longitude may be expressed as the difference between the
local time of the place of observation and the local time at the
place chosen as the standard meridian. The sailor could, indeed,
obtain his own local time by observations of the height of the sun.
The sun reached its greatest height at local noon, and a number of
observations before and after noon would enable him to determine
this with sufficient nicety.
But how was he to determine when he, perhaps, was half-way across
the Atlantic, what was the local time at Genoa, Cadiz, Lisbon,
Bristol, or Amsterdam, or whatever was the port from which he
sailed? Galileo thought out a way by which the satellites of Jupiter
could give him this information.
For as they circle round their primary, they pass in turn into its
shadow, and are eclipsed by it. It needed, then, only that the
satellites should be so carefully watched, that their motions,
and, consequently, the times of their eclipses could be foretold.
It would follow, then, that if the mariner had in his almanac the
local time of the standard city at which a given satellite would
enter into eclipse, and he were able to note from the deck of his
vessel the disappearance of the tiny point, he would ascertain the
difference between the local times of the two places, or, in other
words, the difference of their longitudes.
The plan was simplicity itself, but there were difficulties
in carrying it out, the greatest being the impossibility of
satisfactorily making telescopic observations from the moving deck
of a ship at sea. Nor were the observations sufficiently sharp to be
of much help. The entry of a satellite into the shadow of Jupiter is
in most cases a somewhat slow process, and the moment of complete
disappearance would vary according to the size of the telescope, the
keenness of the observer's sight, and the transparency of the air.
As the power and commerce of Spain declined, two other nations
entered into the contest for the sovereignty of the seas, and with
that sovereignty predominance in the New World of America--France
and England. The problem of the longitude at sea, or, as already
pointed out, what amounts to the same thing, the problem how to
determine when at sea the local time at some standard place, became,
in consequence, of greater necessity to them.
The standard time would be easily known, if a thoroughly good
chronometer which did not change its rate, and which was set to the
standard time before starting, was carried on board the ship. This
plan had been proposed by Gemma Frisius as early as 1526, but at the
time was a mere suggestion, as there were no chronometers or watches
sufficiently good for the purpose. There was, however, another
method of ascertaining the standard time. The moon moves pretty
quickly amongst the stars, and at the present time, when its motions
are well known, it is possible to draw up a table of its distances
from a number of given stars at definite times for long periods in
advance. This is actually done to-day in the _Nautical Almanac_,
the moon's distance from certain stars being given for every three
hours of Greenwich time. It is possible, then, by measuring these
distances, and making, as in the case of the latitude, certain
corrections, to find out the time at Greenwich. In short, the whole
sky may be considered as a vast clock set to Greenwich time, the
stars being the numbers on the dial face, and the moon the hand (for
this clock has only one hand) moving amongst them.
The local apparent time--that is, the time at the place at which the
ship itself was--is a simpler matter. It is noon at any place when
the sun is due south--or, as we may put it a little differently,
when it culminates--that is, when it reaches its highest point.
To find the longitude at sea, therefore, it was necessary to be
able to predict precisely the apparent position of the moon in
the sky for any time throughout the entire year, and it was also
necessary that the places of the stars themselves should be very
accurately known. It was therefore to gather the materials for a
better knowledge of the motions of the moon and the position of the
stars that Greenwich Observatory was founded, whilst the _Nautical
Almanac_ was instituted to convey this information to mariners in a
convenient form.
This proposal was actually made in the reign of Charles II. by
a Frenchman, Le Sieur de Saint-Pierre, who, having secured an
introduction to the Duchess of Portsmouth, endeavoured to obtain a
reward for his scheme. It would appear that he had simply borrowed
the idea from a book which an eminent French mathematician brought
out forty years before, without having himself any real knowledge
of the subject. But when the matter was brought before the king's
notice, he desired some of the leading scientific men of the day to
report upon its practicability, and the Rev. John Flamsteed was the
man selected for the task. He reported that the scheme in itself
was a good one, but impracticable in the then state of science. The
king, who, in spite of the evil reputation which he has earned for
himself, took a real interest in science, was startled when this was
reported to him, and commanded the man who had drawn his attention
to these deficiencies 'to apply himself,' as the king's astronomer,
'with the most exact care and diligence to the Rectifying the Tables
of the Motions of the Heavens and the Places of the Fixed Stars,
in order to find out the so much desired Longitude at Sea, for the
perfecting the Art of Navigation.'
This man, the Rev. John Flamsteed, was accordingly appointed first
Astronomer Royal at the meagre salary of £100 a year, with full
permission to provide himself with the instruments he might require,
at his own expense. He followed out the task assigned to him with
extreme devotion, amidst many difficulties and annoyances, until his
death in 1719. He has been succeeded by seven Astronomers Royal,
each of whom has made it his first object to carry out the original
scheme of the institution; and the chief purpose of Greenwich
Observatory to-day, as when it was founded in 1675, is to observe
the motions of the sun, moon, and planets, and to issue accurate
star catalogues.
It will be seen, therefore, that the establishment of Greenwich
Observatory arose from the actual necessity of the nation. It was
an essential step in its progress towards its present position as
the first commercial nation. No thoughts of abstract science were
in the minds of its founders; there was no desire to watch the
cloud-changes on Jupiter, or to find out what Sirius was made of.
The Observatory was founded for the benefit of the Royal Navy and of
the general commerce of the realm; and, in essence, that which was
the sole object of its foundation at the beginning has continued to
be its first object down to the present time.
It was impossible that the work of the Observatory should be always
confined within the above limits, and it will be my purpose, in the
pages which follow, to describe when and how the chief expansions of
its programme have taken place. But assistance to navigation is now,
and has always been, the dominant note in its management.