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FLAMSTEED, THE FIRST ASTRONOMER ROYAL. 
{From the portrait in the ' Historia Calestis.') 



r 



THE 

ROYAL OBSERVATORY 
GREENWICH 

A GLANCE AT ITS HISTORY 
AND WORK 



E. WALTER MAUNDER F.RA.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 
I9OO 



LONDON : 

PRINTED nV WILLIAM CLOWES AND SONS, LIMITED, 

STAMFORD STREET AND CHARING CROSS. 



22 



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 

5 



6 PREFACE 

gallery or museum. The work carried on therein 
is too continuous and important to allow of inter- 
ruption 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 instru- 
ments, 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. Maske- 
lyne ; 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, 
Aicgust) 1900. 











7 


liilP 


" 





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 

7 



CONTENTS 



CHAPTER 

VI. The Time Department 



PAGE 
I46 



. I8l 



VII. The Transit and Circle Departments 

VIII. The Altazimuth Department .... 205 

IX. The Magnetic and Meteorological Departments 228 

X. The Heliographic Department . . . .251 

XL The Spectroscopic Department . 

XII. The Astrographic Department 

XIII. The Double-Star Department 

Index 



266 
284 
303 
3i7 



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 

H alley'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 no 

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 

9 



io LIST OF ILLUSTRATIONS 



PAGE 



The Chronometer Room 167 

The Chronometer Oven 171 

The Transit Pavilion 174 

1 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' Obser- 
vatory ... 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 Equa- 
torial 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 Nebula of the Pleiades. 300 

Double-star Observation with the South-east Equa- 
torial 308 

The South-east Dome with the Shutter Open . . 314 



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. 

1 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 

13 



14 THE ROYAL OBSERVATORY 

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 
1 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 in- 
competent 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 



INTRODUCTION 15 

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 any- 
thing 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 ' dis- 
coveries/ these lie no more within the scope of our 
national observatory than do geographical discoveiies 
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 Ob- 
servatory ? 

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 



16 THE ROYAL OBSERVATORY 

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. 

1 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 inven- 
tion of the steam engine, but much less than is 
generally supposed. Even yet the clippers, with 
their roods of white canvas, are not entirely super- 
seded ; 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.' 



INTRODUCTION 17 

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 

B 



18 THE ROYAL OBSERVATORY 

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 Medi- 
terranean 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 



INTRODUCTION 19 

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 princi- 
ples 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. 



20 THE ROYAL OBSERVATORY 

At first sight such a discovery, however interest- 
ing, 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, 



INTRODUCTION 21 

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 ascer- 
tain 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 keen- 
ness 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 



22 THE ROYAL OBSERVATORY 

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 



INTRODUCTION 23 

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 know- 
ledge 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 accord- 
ingly appointed first Astronomer Royal at the meagre 



24 THE ROYAL OBSERVATORY 

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 17 19. 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. 



CHAPTER II 

FLAMSTEED 

For the first century of its existence, the lives of its 
Astronomers Royal formed practically the history 
of the Royal Observatory. During this period, the 
Observatory was itself so small that the Astronomer 
Royal, with a single assistant, sufficed for the entire 
work. Everything, therefore, depended upon the 
ability, energy, and character of the actual director. 
There was no large organized stafif, established 
routine, or official tradition, to keep the institution 
moving on certain lines, irrespective of the personal 
qualities of the chief. It was specially fortunate, 
therefore, that the first four Astronomers Royal, 
Flamsteed, Halley, Bradley, and Maskelyne (for Bliss, 
the immediate successor of Bradley, reigned for so 
short a time that he may be practically left out of the 
count), were all men of the most conspicuous ability. 
It will be convenient to divide the history of the 
first seven Astronomers Royal into three sections. 
In the first, we have the founder, John Flamsteed, a 
pathetic and interesting figure, whom we seem to 
know with especial clearness, from the fulness of the 
memorials which he has left to us. He was succeeded 
by the man who was, indeed, best fitted to succeed 

25 



26 THE ROYAL OBSERVATORY 

him, but whom he most hated. The second to the 
sixth Astronomers Royal formed what we might 
almost speak of as a dynasty, each in turn nominating 
his successor, who had entered into more or less 
close connection with the Observatory during the 
lifetime of the previous director ; and the lives of 
these five may well form the second section. The 
line was interrupted after the resignation of the sixth 
Astronomer Royal, and the third section will be 
devoted to the seventh director, Airy, under whom 
the Observatory entered upon its modern period of 
expansion. 

' God suffers not man to be idle, although he swim in 
the midst of delights ; for when He had placed His own 
image (Adam) in a paradise so replenished (of His good- 
ness) with varieties of all things, conducing as well to his 
pleasure as sustenance, that the earth produced of itself 
things convenient for both, He yet (to keep him out of 
idleness) commands him to till, prune, and dress his 
pleasant, verdant habitation ; and to add (if it might be) 
some lustre, grace, or conveniency to that place, which, as 
well as he, derived its original from his Creator.' 

In these words JOHN FLAMSTEED begins the first 
of several autobiographies which he has handed down 
to us ; this particular one being written before he 
attained his majority, * to keep myself from idleness 
and to recreate myself.' 

' I was born, 5 he goes on, ' at Denby, in Derbyshire, in 
the year 1646, on the 19th day of August, at 7 hours 16 
minutes after noon. My father, named Stephen, was the 
third son of Mr. William Flamsteed, of Little Hallam ; my 
mothei, Mary, was the daughter of Mr. John Spateman, of 
Derby, ironmonger. From these two I derived my begin- 
ning, whose parents were of known integrity, honesty, and 



FLAMSTEED 27 

fortune, as they [were] of equal extraction and ingenuity ; 
betwixt whom I [was] tenderly educated (by reason of my 
natural weakness, which required more than ordinary care) 
till I was aged three years and a fortnight ; when my 
mother departed, leaving my father a daughter, then not 
a month old, with me, then weak, to his fatherly care and 
provision.' 

The weakly, motherless boy became at an early 
age a voracious reader. At first, he says 

1 1 began to affect the volubility and ranting stories of 
romances ; and at twelve years of age I first left off the 
wild ones, and betook myself to read the better sort of 
them, which, though they were not probable, yet carried no 
seeming impossibility in the fiction. Afterwards, as my 
reason increased, I gathered other real histories ; and by 
the time I was fifteen years old I had read, of the ancients, 
Plutarch's Lives, Appian's and Tacitus's Roman Histories, 
Holingshed's History of the Kings of England, Davies's 
Life of Queen Elizabeth, Saunderson's of King Charles the 
First, Heyling's Geography, and many others of the moderns ; 
besides a company of romances and other stories, of which 
I scarce remember a tenth at present.' 

Flamsteed received his education at the free school 
at Derby, where he continued until the Whitsuntide 
of 1662, when he was nearly sixteen years of age. 
Two years earlier than this, however, a great mis- 
fortune fell upon him. 

1 At fourteen years of age,' he writes, ' u hen I was nearly 
arrived to be the head of the free-school, [I was] visited 
with a fit of sickness, that was followed with a consumption 
and other distempers, which yet did not so much hinder me 
in my learning, but that I still kept my station till the form 
broke up, and some of my fellows went to the Universities ; 
for which, though I was designed, my father thought it 
not advisable to send me, by reason of my distemper.' 



28 THE ROYAL OBSERVATORY 

This was a keen disappointment to him, but 
seems to have really been the means of determining 
his career. The sickly, suffering boy could not be 
idle, though ' a day's short reading caused so violent 
a headache ; ' and a month or two after he had left 
school, he had a book lent to him Sacrobosco's 
De Sphcera, in Latin which was the beginning of 
his mathematical studies. A partial eclipse of the 
sun in September of the same year seems to have 
first drawn his attention to astronomical observation, 
and during the winter his father, who had himself a 
strong passion for arithmetic, instructed him in that 
science. 

It was astonishing how quickly his appetite for 
his new subjects grew. The Art of Dialling, the 
calculation of tables of the sun's altitudes for all 
hours of the day, and for different latitudes, and the 
construction of a quadrant ' of which I was not 
meanly joyful' were the occupations of this winter 
of illness. 

In 1664 he made the acquaintanceship of two 
friends, Mr. George Linacre and Mr. William 
Litchford ; the former of whom taught him to 
recognize many of the fixed stars, whilst the latter 
was the means of his introduction to a knowledge of 
the motions of the planets. 

1 1 had now completed eighteen years, when the winter 
came on, and thrust me again into the chimney ; whence 
the heat and dryness of the preceding summer had happily 
once before withdrawn me.' 

The following year, 1665, was memorable to him 
'for the appearance of the comet,' and for a journey 



FLAMSTEED 29 

which he made to Ireland to be 'stroked' for his 
rheumatic disorder by Valentine Greatrackes, a kind 
of mesmerist, who had the repute of effecting wonderful 
cures. The journey, of which he gives a full and 
vivid account, occupied a month ; but though he was 
a little better, the following winter brought him no 
permanent benefit. 

But, ill or well, he pressed on his astronomical 
studies. A large partial eclipse of the sun was due 
the following June ; he computed the particulars of it 
for Derby, and observed the eclipse itself to the best 
of his ability. He argued out for himself ' the 
equation of time ' ; the difference, that is, between 
time as given by the actual sun, or ' apparent time,' 
and that given by a perfect clock, or 'mean time.' 
He drew up a catalogue of seventy stars, computing 
their right ascensions, declinations, longitudes, and 
latitudes for the year 1701 ; he attempted to determine 
the inclination of the ecliptic, the mean length of the 
tropical year, and the actual distance of the earth 
from the sun. And these were the recreations of a 
sickly, suffering young man, not yet twenty-one years 
of age, and who had only begun the study of 
arithmetic, such as fractions and the rule of three, 
four years previously ! 

His next attempt was almanac-making, in the 
which he improved considerably upon those current 
at the time. His almanac for 1670 was rejected, 
however, and returned to him, and, not to lose his 
whole labour, he sent his calculations of an eclipse of 
the sun, and of five occultations of stars by the moon, 
which he had undertaken for the almanac, to the 



3 o THE ROYAL OBSERVATORY 

Royal Society. He sent the paper anonymously, or, 
rather, signed it with an anagram, ' In mathesi a sole 
fundes,' for 'Johannes Flamsteedius.' His covering 
letter ends thus : 

1 Excuse, I pray you, this juvenile heat for the concerns 
of science and want of better language, from one who, from 
the sixteenth year of his age to this instant, hath only 
served one bare apprenticeship in these arts, under the dis- 
couragement of friends, the want of health, and all other 
instructors except his better genius.' 

This letter was dated November 4, 1669, and on 
January 14, Mr. Oldenburg, the secretary of the 
Society, replied to him in a letter which the young 
man cannot but have felt encouraging and flattering 
to the highest degree. 

' Though you did what you could to hide your name from 
us,' he writes, 'yet your ingenious and useful labours for 
the advancement of Astronomy addressed to the noble 
President of the Royal Society, and some others of that 
illustrious body, did soon discover you to us, upon our 
solicitous inquiries after their worthy author.' 

And after congratulating him upon his skill, and 
encouraging him to furnish further similar papers, 
he signs himself, ' Your very affectionate friend and 
real servant ' no unmeaning phrase, for the friendship 
then commenced ceased only with Oldenburg's life. 

The following June, his father, pleased with the 
notice that some of the leading scientific men of the 
day were taking of his son, sent him up to London, 
that he might be personally acquainted with them ; 
and he then was introduced to Sir Jonas Moore, the 
Surveyor of the Ordnance, who made him a present 



FLAMSTEED 31 

of Townley's micrometer, and promised to furnish him 
with object-glasses for telescopes at moderate rates. 

On his return journey he called at Cambridge, 
where he visited Dr. Barrow and Newton, and 
entered his name in Jesus College. 

It was not until the following year, 1671, that he 
was enabled to complete his own observatory, as he 
had had to wait long for the lenses which Sir Jonas 
Moore and Collins had promised to procure for him. 
He still laboured under several difficulties, in that he 
had no good means for measuring time, pendulum 
clocks not then being common. He, therefore, with 
a practical good sense which was characteristic, 
refrained from attempting anything which lay out of 
his power to do well, and he devoted himself to such 
observations as did not require any very accurate 
knowledge of the time. At the same time, he was 
careful to ascertain the time of his observations as 
closely as possible, by taking the altitudes of the stars. 

The next four years seem to have passed 
exceedingly pleasantly to him. The notes of ill- 
health are few. He was making rapid progress in 
his acquaintanceship with the work of other astrono- 
mers, particularly with those of the three marvellously 
gifted young men Horrox, Crabtree, and Gascoigne 
who had passed away shortly before his own 
birth. He was making new friends in scientific 
circles, and, in particular, Sir Jonas Moore was evi- 
dently esteeming him more and more highly. In 
1674 he became more intimate with Newton, the 
occasion which led to this acquaintanceship being 
the amusing one, that his assistance was asked by 



32 THE ROYAL OBSERVATORY 

Newton, who had found himself unable to adjust a 
microscope, having forgotten its object-glass not 
the only instance of the great mathematician's 
absent-mindedness. 

The same year he took his degree of A.M. at 
Cambridge, designing to enter the Church ; but Sir 
Jonas Moore was extremely anxious to give him 
official charge of an observatory, and was urging the 
Royal Society to build an astronomical observatory 
at Chelsea College, which then belonged to that body. 
He therefore came up to London, and resided, some 
months with Sir Jonas Moore at the Tower. But 
shortly after his coming up to London, ' an accident 
happened,' to use his own expression, that hastened, 
if it did not occasion, the building of Greenwich 
Observatory. 

' A Frenchman that called himself Le Sieur de St. Pierre, 
having some small skill in astronomy, and made an interest 
with a French lady, then in favour at Court, proposed no 
less than the discovery of the Longitude, and had procured 
a kind of Commission from the King to the Lord Brouncker, 
Dr. Ward (Bishop of Salisbury), Sir Christopher Wren, Sir 
Charles Scarborough, Sir Jonas Moore, Colonel Titus, Dr. 
Pell, Sir Robert Murray, Mr. Hook, and some other in- 
genious gentlemen about the town and Court, to receive his 
proposals, with power to elect, and to receive into their 
number, any other skilful persons ; and having heard them, 
to give the King an account of them, with their opinion 
whether or no they were practicable, and would show what 
he pretended. Sir Jonas Moore carried me with him to one 
of their meetings, where I was chosen into their number ; 
and, after, the Frenchman's proposals were read, which were: 

1 (i) To have the year and day of the observations. 

1 (2) The height of two stars, and on which side of the 
meridian they appeared. 



FLAMSTEED 



33 



1 (3) The height of the moon's two limbs. 

' (4) The height of the pole all to degrees and minutes. 

' It was easy to perceive, from these demands, that the 
sieur Understood not that the best lunar tables differed from 
the heavens; and that, therefore, his demands were not 
sufficient for determining the longitude of the place where 
such observations were, or should be, made, from that to 
which the lunar tables were fitted, which I represented im- 
mediately to the company. But they, considering the 
interests of his patroness at Court, desired to have him 
furnished according to his demands. I undertook it ; and 
having gained the moon's true place by observations made 
at Derby, February 23, 1672, and November 12, 1673, gave 
him observations such as he demanded. The half-skilled 
man did not think they could have been given him, and 
cunningly answered " They were feigned." I delivered them 
to Dr. Pell, February 19, 1674-5, wno > returning me his 
answer some time after, I wrote a letter in English to the 
commissioners, and another in Latin to the sieur, to assure 
him they were not feigned, and to show them that, if they 
had been, yet if we had astronomical tables that would give 
us the two places of the fixed stars and the moon's true 
places, both in longitude and latitude, nearer than to half 
a minute, we might hope to find the longitude of places by 
lunar observations, but not by such as he demanded. But 
that we were so far from having the places of the fixed stars 
true, that the Tychonic Catalogues often erred ten minutes 
or more ; that they were uncertain to three or four minutes, 
by reason that Tycho assumed a faulty obliquity of the 
ecliptic, and had employed only plain sights in his obser- 
vations : and that the best lunar tables differ one-quarter, 
if not one-third, of a degree from the heavens ; and lastly, 
that he might have learnt better methods than he pro- 
posed, from his countryman Morin, whom he had best 
consult before he made any more demands of this nature.' 

This was in effect to tell St. Pierre that his 
proposal was neither original nor practicable. If 
St. Pierre had but consulted Morin's writings (Morin 

c 



34 THE ROYAL OBSERVATORY 

himself had died more than eighteen years before), 
he would have known that practically the same 
proposal had been laid before Cardinal Richelieu 
in 1634, and had been rejected, as quite impracticable 
in the then state of astronomical knowledge. Possibly 
Flamsteed meant further to intimate that St. Pierre 
had simply stolen his method from Morin, hoping to 
trade it off upon the government of another country ; 
in which case he would no doubt regard Flamsteed's 
letter as a warning that he had been found out. 
Flamsteed continues : 

' I heard no more of the Frenchman after this ; but was 
told that, my letters being shown King Charles, he startled 
at the assertion of the fixed stars' places being false in the 
catalogue ; said, with some vehemence, " He must have 
them anew observed, examined, and corrected, for the use 
of his seamen ; " and further (when it was urged to him how 
necessary it was to have a good stock of observations taken 
for correcting the motions of the moon and planets), with 
the same earnestness, "he must have it done." And when 
he was asked Who could, or who should do it ? " The 
person (says he) that informs you of them." Whereupon 
I was appointed to it, with the incompetent allowance afore- 
mentioned ; but with assurances, at the same time, of such 
further additions as thereafter should be found requisite for 
carrying on the work.' 

Thus, in his twenty-ninth year, John Flamsteed 
became the first Astronomer Royal. In many ways 
he was an ideal man for the post. In the twelve 
years which had passed since he left school he had 
accomplished an amazing amount of work. Despite 
his constant ill-health and severe sufferings, and the 
circumstance which may be inferred from many 
expressions in his autobiographies that he assisted 



FLAMSTEED 37 

his father in his business, he had made himself master, 
perhaps more thoroughly than any of his contem- 
poraries, of the entire work of a practical astronomer 
as it was then understood. He was an indefatigable 
computer ; the calculation of tables of the motions of 
the moon and planets, which should as faithfully as 
possible represent their observed positions, had had 
an especial attraction for him, and, as has been 
already mentioned, some years before his appoint- 
ment he had drawn up a catalogue of stars, based 
upon the observations of Tycho Brahe. More than 
that, he had not been a merely theoretical worker, 
he had been a practical observer of very considerable 
skill, and, in the dearth of suitable instruments, had 
already made one or two for himself, and had con- 
templated the making of others. In his first letter 
to Sir Jonas Moore he asks for instruction as to the 
making of object-glasses for telescopes, for he was 
quite prepared to set about the task of making his own. 
In addition to his tireless industry, which neither ill- 
ness nor suffering could abate, he was a man of sin- 
gularly exact and business-like habits. The precision 
with which he preserves and records the dates of all 
letters received or sent is an illustration of this. On 
the other hand, he had the defects of his circum- 
stances and character. His numerous autobiographical 
sketches betray him, not indeed as a conceited man, in 
the ordinary sense of the word, but as an exceedingly 
self-conscious one. Devout and high-principled he 
most assuredly was, but, on the other hand, he shows 
in almost every line he wrote that he was one who 
could not brook anything like criticism or opposition. 



38 THE ROYAL OBSERVATORY 

Such a man, however efficient, was little likely to be 
happy as the first incumbent of a new and important 
government post ; but there was another circumstance 
which was destined to cause him greater unhappiness 
still. 

If we believe, as surely we must, that not only 
the moral and the physical progress of mankind is 
watched over and controlled by God's good Provi- 
dence, but its intellectual progress as well, then there 
can be no doubt that John Flamsteed was raised 
up at this particular time, not merely to found 
Greenwich Observatory, and to assist the solution 
of the problem of the longitude at sea, but also, and 
chiefly, to become the auxiliary to a far greater mind, 
the journeyman to a true master-builder. But for the 
founding of Greenwich Observatory, and for John 
Flamsteed's observations made therein, the working 
out of Newton's grand theory of gravitation must 
have been hindered, and its acceptance by the men of 
science of his time immensely delayed. We cannot 
regard as accidental the combination, so fortunate for 
us, of Newton, the great world-genius, to work out the 
problem, of Flamsteed, the painstaking observer, to 
supply him with the materials for his work, and of 
the newly- founded institution, Greenwich Observatory, 
where Flamsteed was able to gather those materials 
together. This is the true debt that we owe to Flam- 
steed, that, little as he understood the position in 
which he had been placed from the standpoint from 
which we see it to-day, yet, to the extent of his ability, 
and as far as he conceived it in accordance with his 
duty, he gave Newton such assistance as he could.- 






FLAMSTEED 39 

This is how we see the matter to-day. It wore 
a very different aspect in Flamsteed's eyes ; and the 
two following documents, the one, the warrant found- 
ing the Observatory and making him Astronomer 
Royal ; the other, the warrant granting him a salary, 
will go far to explain his position in the matter. He 
had a high-sounding, official position, which could 
not fail to impress him with a sense of importance ; 
whilst his salary was so insufficient that he naturally 
regarded himself as absolute owner of his own 
work. 

1 Warrant for the Payment of Mr. Flamsteed's Salary. 

' Charles Rex. 

1 Whereas, we have appointed our trusty and well-beloved 
John Flamsteed, Master of Arts, our astronomical 
observator, forthwith to apply himself 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, so as to 
find out the so-much-desired longitude of places for the 
perfecting the art of navigation, Our will and pleasure is, 
and we do hereby require and authorize you, for the support 
and maintenance of the said John Flamsteed, of whose 
abilities in astronomy we have very good testimony, and 
are well satisfied, that from time to time you pay, or cause 
to be paid, unto him, the said John Flamsteed, or his 
assigns, the yearly salary or allowance of one hundred 
pounds per annum ; the same to be charged and borne 
upon the quarter-books of the Office of the Ordnance, and 
paid to him quarterly, by even and equal portions, by the 
Treasurer of our said office, the first quarter to begin and 
be accompted from the feast of St. Michael the Archangel 
last past, and so to continue during our pleasure. And for 
so doing, this shall be as well unto you, as to the Auditors 
of the Exchequer, for allowing the same, and all other our 



40 THE ROYAL OBSERVATORY 

officers and ministers whom it may concern, a full and 
sufficient warrant. 

' Given at our Court at Whitehall, the 4th day of March, 

1674-5- 

'By his Majesty's Command, 

'J. Williamson. 

'To our right-trusty and well-beloved Counsellor, 
Sir Thomas Chichely, Knt., Master of our 
Ordnance, and to the Lieutenant-General of our 
Ordnance, and to the rest of the Officers of our 
Ordnance, now and for the time being, and to all 
and every of them.' 

' Warrant for Building the Observatory. 
' Charles Rex. 

' Whereas, in order to the finding out of the longitude of 
places for perfecting navigation and astronomy, we have 
resolved to build a small observatory within our park at 
Greenwich, upon the highest ground, at or near the place 
where the Castle stood, with lodging-rooms for our 
astronomical observator and assistant, Our will and pleasure 
is, that according to such plot and design as shall be given 
you by our trusty and well-beloved Sir Christopher Wren, 
Knight, our surveyor-general of the place and scite of the 
said observatory, you cause the same to be fenced in, built 
and finished with all convenient speed, by such artificers 
and workmen as you shall appoint thereto, and that you 
give order unto our Treasurer of the Ordnance for the 
paying of such materials and workmen as shall be used and 
employed therein, out of such monies as shall come to your 
hands for old and decayed powder, which hath or shall be 
sold by our order of the 1st of January last, provided that 
the whole sum, so to be expended or paid, shall not exceed 
five hundred pounds ; and our pleasure is, that all our 
officers and servants belonging to our said park be assisting 
to those that you shall appoint, for the doing thereof, and 
for so doing, this shall be to you, and to all others whom it 
may concern, a sufficient warrant. 



FLAMSTEED 41 

1 Given at our Court at Whitehall, the 22nd day of June, 

1675, m tne 2 7 tn y ear f our re >g n - 

' By his Majesty's Command, 

'J. Williamson. 

'To our right-trusty and well-beloved Counsellor, 
Sir Thomas Chichely, Knt., Master-General of our 
Ordnance.' 

The first question that arose, when it had been 
determined to found the new Observatory, was where 
it was to be placed. Hyde Park was suggested, 
and Sir Jonas Moore recommended Chelsea Col- 
lege, where he had already thought of establishing 
Flamsteed in a private observatory. Fortunately, 
both these localities were set aside in favour of one 
recommended by Sir Christopher Wren. There was 
a small building on the top of the hill in the Royal 
Park of Greenwich belonging to the Crown, and 
which was now of little or no use. Visible from the 
city, and easily accessible by that which was then 
the best and most convenient roadway, the river 
Thames, it was yet so completely out of town as 
to be entirely safe from the smoke of London. In 
Greenwich Park, too, but on the more easterly hill, 
Charles I. had contemplated setting up an obser- 
vatory, but the pressure of events had prevented 
him carrying out his intention. A further practical 
advantage was that materials could be easily trans- 
ported thither. The management of public affairs 
under Charles II. left much to be desired in the 
matter of efficiency and economy, and it was not 
very easy to procure what was wanted for the erection 
of a purely scientific building. However, the matter 



42 THE ROYAL OBSERVATORY 

was arranged. A gate-house demolished in the Tower 
supplied wood ; iron, and lead, and bricks were sup- 
plied from Tilbury Fort, and these could be easily- 
brought by water to the selected site. The sum of 
^"500, actually 520, was further allotted from the 
results of a sale of spoilt gunpowder ; and with these 
limited resources Greenwich Observatory was built. 

The foundation-stone was laid August 10, 1675, 
and Flamsteed amused himself by drawing the horo- 
scope of the Observatory, a fact which in spite of 
his having written across the face of the horoscope 
Risum teneatis amici? (Can you keep from laughter, 
my friends ?), and his having two or three years before 
written very severely against the imposture of as- 
trology has led some modern astrologers to claim 
him as a believer in their cult. He actually entered 
into residence July 10, 1676. 

His position was not a bright one. The Govern- 
ment had, indeed, provided him with a building for 
his observatory, and a small house for his own 
residence, but he had no instrument and no assistant. 
The first difficulty was partly overcome for the 
moment by gifts or loans from Sir Jonas Moore, and 
by one or two small loans from the Royal Society. 
The death of this great friend and patron, four years 
after the founding of the Observatory, and only three 
years after his entering into residence, deprived him 
of several of these ; it was with difficulty that he 
maintained against Sir Jonas' heirs his claim to the 
instruments which Sir Jonas had given him. There 
was nothing for him to do but to make his instru- 
ments himself, and in 1683 he built a mural quadrant 










& J! 



lc 



5 



FLAMSTEED 



45 



of fifty inches radius. His circumstances improved 
the following year, when Lord North gave him the 
living of Burstow, near Horley, Surrey, Flamsteed 
having received ordination almost at the time of his 
appointment to the Astronomer Royalship. We 
have little or no account of the way in which he 
fulfilled his duties as a clergyman. Evidently he 
considered that his position as Astronomer Royal 
had the first claim upon him. At the same time, com- 
paratively early in life he had expressed his desire 
to fill the clerical office, and he was a man too 
conscientious to neglect any duty that lay upon him. 
That in spite of his feeble health he often journeyed 
to and fro between Burstow and Greenwich we know ; 
and we may take it as certain that at a time when 
the standard of clerical efficiency was extremely low, 
he was not one of those who 

1 For their bellies' sake, 
Creep and intrude and climb into the fold.' 

His chief source of income, however, seems to 
have been the private pupils whom he took in 
mathematics and astronomy. These numbered in 
the years 1676 to 1709 no fewer than 140; and as 
many of them were of the very first and wealthiest 
families in the kingdom, the gain to FJamsteed in 
money and influence must have been considerable. 
But it was most distasteful work. It was in no sense 
that which he felt to be his duty, and which he had 
at heart. It was undertaken from sheer, hard neces- 
sity, and he grudged bitterly the time and strength 
which it diverted from his proper calling. 



46 THE ROYAL OBSERVATORY 

How faithfully he followed that, one single cir- 
cumstance will show. In the thirteen years ending 
1689, he made 20,000 observations, and had revised 
single-handed the whole of the theories and tables of 
the heavenly bodies then in use. 

In 1688 the death of his father brought him a 
considerable accession of means, and, far more im- 
portant, the assistance of Abraham Sharp, 1 the first 
and most distinguished of the long list of Greenwich 
assistants, men who, though far less well known than 
the Astronomers Royal, have contributed scarcely 
less in their own field to the high reputation of the 
Observatory. 

Sharp was not only a most careful and inde- 
fatigable calculator, he was what was even more 
essential for Flamsteed a most skilful instrument- 
maker ; and he divided for him a new mural arc of 
140 and seven feet radius, with which he commenced 
operations on December 12, 1689. Above all, Sharp 
became his faithful and devoted friend and adherent, 
and no doubt his sympathy strengthened Flamsteed 
to endure the trouble which was at hand. 

That trouble began in 1694, when Newton visited 
the Royal Observatory. At that time Flamsteed, 
though he had done so much, had published nothing, 
and Newton, who had made his discovery of the 
laws of gravitation some few years before, was then 
employed in deducing from them a complete theory 
of the moon's motion. This work was one of 
absolutely first importance. In the first place and 

1 Abraham Sharp had been with Flamsteed earlier than 
this in 1684 and 1685. 



FLAMSTEED 47 

chiefly, upon the success with which it could be 
carried out, depended undoubtedly the acceptance 
of the greatest discovery which has yet been made 
in physical science. Secondarily and this should, 
and no doubt did, appeal to Flamsteed the perfecting 
of our knowledge of the movements of the moon 
was a primary part of the very work which he was 
commissioned to do as Astronomer Royal. Newton 
was, therefore, anxious beyond everything to receive 
the best possible observations of the moon's places, 
and he came to Flamsteed, as to the man from whom 
he had a right to expect to receive a supply of them. 
At first Flamsteed seems to have given these as fully 
as he was able ; but it is evident that Newton 
chafed at the necessity for these frequent applications 
to Flamsteed, and to the constant need of putting 
pressure upon him. Flamsteed, on the other hand, 
as clearly evidently resented this continual demand. 
Feeling, as he keenly did, that, though he had been 
named Astronomer Royal, he had been left prac- 
tically entirely without support ; his instruments 
were entirely his own, either made or purchased by 
himself; his nominal salary of ;ioo was difficult to 
get, and did not nearly cover the actual current 
expenses of his position, he not unnaturally regarded 
his observations as his own exclusive property. He 
had a most natural dislike for his observations to 
be published, except after such reduction as he 
himself had carried through, arrd in the manner 
which he himself had chosen. The idea which was 
ever before him was that of carrying out a single 
great work that should not only be a monument to 



48 THE ROYAL OBSERVATORY 

his own industry and skill, but should also raise the 
name of England amongst scientific nations. He 
complained of it, therefore, both as a personal wrong 
and an injury to the country when some observations 
of Cassini's were combined with some observations 
of his own in order to deduce a better orbit for a 
comet. 

Unknown to himself, therefore, he was called upon 
to decide a question that has proved fundamental to 
the policy of Greenwich Observatory, and he decided 
it wrongly the question of publication. Newton 
had urged upon him as early as 1691 that he should 
not wait until he had formed an exhaustive catalogue 
of all the brighter stars, but that he should publish 
at once a catalogue of a few, which might serve as 
standards ; but Flamsteed would not hear of it. He 
failed to see that his office had been created for a 
definite practical purpose, not for the execution of 
some great scheme, however important to science. 
All his work of thirty years had done nothing to 
forward navigation so long as he published nothing. 
But if, year by year, he had published the places of 
the moon and of a few standard stars, he would have 
advanced the art immensely and yet have not 
hindered himself from eventually bringing out a 
great catalogue. No doubt the little incident of 
Newton's difficulty with the microscope, of which he 
had forgotten the object-glass, had given Flamsteed 
a low opinion of Newton's qualifications as a practical 
astronomer. If so, he was wrong, for Newton's in^ 
sight into practical matters was greater than Flam- 
steed's own, and his practical skill was no less, though 



FLAMSTEED 



49 



his absent-mindedness might occasionally lead him 
into an absurd mistake. 

The following extract from Flamsteed's own 
1 brief History of the Observatory ' gives an account 
of his view of Newton's action towards him in 
desiring the publication of his star catalogue, and 
at the same time it illustrates Flamsteed's touchy 
and suspicious nature. 

1 Whilst Mr. Flamsteed was busied in the laborious work 
of the catalogue of the fixed stars, and forced often to watch 
and labour by night, to fetch the materials for it from the 
heavens, that were to be employed by day, he often, on Sir 
Isaac Newton's instances, furnished him with observations 
of the moon's places, in order to carry on his correction of 
the lunar theory. A civil correspondence was carried on 
between them ; only Mr. Flamsteed could not but take 
notice that as Sir Isaac was advanced in place, so he raised 
himself in his conversation and became more magisterial. 
At last, finding that Mr. Flamsteed had advanced far in his 
designed catalogue by the help of his country calculators, 
that he had made new lunar tables, and was daily advancing 
on the other planets, Sir Isaac Newton came to see him 
(Tuesday, April n, 1704) ; and desiring, after dinner, to be 
shown in what forwardness his work was, had so much of 
the catalogue of the fixed stars laid before him as was then 
finished ; together with the maps of the constellations, both 
those drawn by T. Weston and P. Van Somer, as also his 
collation of the observed places of Saturn and Jupiter, with 
the Rudolphine numbers. Having viewed them well, he 
told Mr. Flamsteed he would {i.e. he was desirous to) 
recommend them to the Prince privately. Mr. Flamsteed 
(who had long been sensible of his partiality, and heard 
how his two flatterers cried Sir Isaac's performances up, 
was sensible of the snare in the word privately) answered 
that would not do ; and (upon Sir Isaac's demanding " why 
not?") that then the Prince's attendants would tell him 
these were but curiosities of no great use, and persuade 

D 



50 THE ROYAL OBSERVATORY 

him to save that expense, that there might be the more for 
them to beg of him : and that the recommendation must 
be made publicly, to prevent any such suggestions. Sir 
Isaac apprehended right, that he was understood, and his 
designs defeated : and so took his leave not well satisfied 
with the refusal. 

1 It was November following ere Mr. Flamsteed heard 
from him any more : when, considering with himself that 
what he had done was not well understood, he set himself 
to examine how many folio pages his work when printed 
would fill ; and found upon an easy computation that they 
would at least take up 1400. Being amazed at this, he set 
himself to consider them more seriously ; drew up an 
estimate of them ; and, to obviate the misrepresentations 
of Dr. S[loane] and some others, who had given out that 
what he had was inconsiderable, he delivered a copy of the 
estimate to Mr. Hodgson, then lately chosen a member of 
the Royal Society, with directions to deliver it to a friend, 
who he knew would do him justice ; and, on this fair 
account, obviate those unjust reports which had been 
studiously spread to his prejudice. It happened soon after, 
Mr. Hodgson being at a meeting, spied this person there, 
at the other side of the room ; and therefore gave the paper 
to one that stood in some company betwixt them, to be 
handed to him. But the gentleman, mistaking his request, 
handed to the Secretary [Dr. Sloane], who, being a 
Physician, and not acquainted with astronomical terms, 
did not read it readily. Whereupon another in the 
company took it out of his hands ; and, having read it 
distinctly, desired that the works therein mentioned might 
be recommended to the Prince ; the charge of printing 
them being too great either for the author or the Royal 
Society. Sir Isaac closed in with this.' 

The work was in consequence recommended to 
Prince George of Denmark, the Queen's Consort ; 
but it was not till November 10, 1705, that the 
contract for the printing was signed. Two years 
later, the observations which he had made with 







2 ~ 



i a 



H .* 



< * 



FLAMSTEED 53 

his sextant in his first thirteen years of office 
were printed. Then came the difficulty of the 
catalogue. It was not complete to Flamsteed's 
satisfaction, and he was most unwilling to let it 
pass out of his hands. However, two manuscripts, 
comprising some three-quarters of the whole, were 
deposited with referees, the first of these being sealed 
up. The seal was broken with Flamsteed's con- 
currence ; but the fact that it had been so broken 
was made by him the subject of bitter complaint 
later. At this critical juncture Prince George died, 
and a stop was put to the progress of the printing. 
Two years more elapsed without any advance being 
made, and then, in order to check any further 
obstruction, a committee of the Royal Society was 
appointed as a Board of Visitors to visit and inspect 
the Observatory, and so maintain a control over the 
Astronomer Royal. This was naturally felt by so 
sensitive a man as Flamsteed as a most intolerable 
wrong, and when he found that the printing of his 
catalogue had been placed in the hands of Halley as 
editor, a man for whom he had conceived the most 
violent distrust, he absolutely refused to furnish the 
Visitors with any further material. This led to, 
perhaps, the most painful scene in the lives either 
of Newton or Flamsteed. Flamsteed was summoned 
to meet the Council of the Royal Society at their 
rooms in Crane Court. A quorum was not present, 
and so the interview was not official, and no record 
of it is preserved in the archives. Flamsteed has 
himself described it with great particularity in more 
than one document, and it is only too easy to 



54 THE ROYAL OBSERVATORY 

understand the scene that took place. Newton was 
a man who had an absolutely morbid dread of 
anything like controversy, and over and over again 
would have preferred to have buried his choicest 
researches, rather than to have encountered the 
smallest conflict of the kind. He was perhaps, 
therefore, the worst man to deal with a high- 
principled, sensitive, and obstinate man who was 
in the wrong, and yet who had been so hardly deall 
with that it was most natural for him to think himseli 
wholly in the right. Flamsteed adhered absolutely 
to his position, from which it is clear it would have 
been extremely difficult for the greatest tact and 
consideration to have dislodged him. Newton, on 
his part, simply exerted his authority, and, that 
failing, was reduced to the miserable extremity of 
calling names. The scene is described by Flamsteed 
himself, in a letter to Abraham Sharp, as follows : 

1 1 have had another contest with the President ! of the 
Royal Society, who had formed a plot to make my 
instruments theirs ; and sent for me to a Committee, where 
only himself and two physicians (Dr. Sloane, and another 
as little skilful as himself) were present. The President 
ran himself into a great heat, and very indecent passion. 
I had resolved aforehand his kn sh talk should not 
move me ; showed him that all the instruments in the 
Observatory were my own ; the mural arch and voluble 
quadrant having been made at my own charge, the rest 
purchased with my own money, except the sextant and 
two clocks, which were given me by Sir Jonas Moore, with 
Mr. Towneley's micrometer, his gift, some years before 
I came to Greenwich. This nettled him ; for he has got 
a letter from the Secretary of State for the Royal Society 

1 Sir Isaac Newton. 



FLAMSTEED 55 

to be Visitors of the Observatory, and he said, " as good 
have 710 observatory as ?io instruments? I complained 
then of my catalogue being printed by Raymer, without my 
knowledge, and that I was robbed of the fruit of my labours. 
At this he fired, and called me all the ill names, puppy, 
etc., that he could think of. All I returned was, I put him 
in mind of his passion, desired him to govern it, and keep 
his temper : this made him rage worse, and he told me 
how much I had received from the Government in thirty- 
six years I had served. I asked what he had done for the 
^500 per annum that he had received ever since he had 
settled in London. This made him calmer ; but finding 
him going to burst out again, I only told him my catalogue, 
half finished, was delivered into his hands, on his own 
request, sealed up. He could not deny it, but said Dr. 
Arbuthnott had procured the Queen's order for opening it. 
This, I am persuaded, was false ; or it was got after it had 
been opened. I said nothing to him in return ; but, with 
a little more spirit than I had hitherto showed, told them 
that God (who was seldom spoken of with due reverence in 
that meeting) had hitherto prospered all my labours, and 
I doubted not would do so to a happy conclusion; took 
my leave and left them. Dr. Sloane had said nothing all 
this while ; the other Doctor told me I was proud, and 
insulted the President, and ran into the same passion with 
the President. At my going out, I called to Dr. Sloane, 
told him he had behaved himself civilly, and thanked him 
for it. I saw Raymer after, drank a dish of coffee with 
him, and told him, still calmly, of the villany of his conduct, 
and called it blockish. Since then they let me be quiet ; 
but how long they will do so I know not, nor am I 
solicitous.' 

The Visitors continued the printing, Halley being 
the editor, and the work appeared in 17 12 under the 
title of Historia Ccelestis. This seemed to Flamsteed 
the greatest wrong of all. The work as it appeared 
seemed to him so full of errors, wilfully or acciden- 
tally inserted, as to be the greatest blot upon his fair 



56 THE ROYAL OBSERVATORY 

fame, and he set himself, though now an old man, to 
work it out de novo and at his own expense. To 
that purpose he devoted the remaining seven years 
of his life. Few things can be more pathetic than 
the letters which he wrote in that period referring to 
it. He was subject to the attacks of one of the 
crudest of all diseases the stone ; he was at all 
times liable to distracting headaches. He had been, 
from his boyhood, a great sufferer from rheumatism, 
and yet, in spite of all, he resolutely pushed on his 
self-appointed task. The following extract from one 
of his letters will give a more vivid idea of the brave 
old man than much description : 

' I can still, I praise God for it, walk from my door to 
the Blackheath gate and back, with a little resting at some 
benches I have caused to be set up betwixt them. But I 
found myself so tired with getting up the hill when I return 
from church, that at last I have bought a sedan, and am 
carried thither in state on Sunday mornings and back ; I 
hope I may employ it in the afternoons, though I have not 
hitherto, by reason of the weather is too cold for me.' 

After the death of Queen Anne, a change in the 
ministry enabled him to secure that three hundred 
copies of the total impression of four hundred of the 
Historia Ccelestis were handed over to him. These, 
except the first volume, containing his sextant 
observations (which had received his own approval), 
he urned, 'as a sacrifice to heavenly truth.' His 
own great work had advanced so far that the first 
volume was printed, and much of the second, when 
he himself died, on the last day of 17 19. He was 
buried in the chancel of Burstow Church. 



FLAMSTEED 



57 



The completion of his work took ten years more ; 
a work of piety and regard on the part of his assistant, 
Joseph Crosthwait. 

When compared with the catalogues that have 
gone before, it was a work of wonderful accuracy. 
Nevertheless, as Caroline Herschel showed, nearly a 
century later, not a few errors had crept into it. 
Some of the stars are non-existent, others have been 
catalogued in more than one constellation ; important 
stars have been altogether omitted. Perhaps the 
most serious fault arises from the neglect of 
Flamsteed to accept from Newton a practical hint, 
namely, to read the barometer and thermometer at 
the time of his observations. Nevertheless, the work 
accomplished was not only wonderful under the 
untoward conditions in which Flamsteed was placed ; 
it was wonderful in itself, winning from Airy the 
following high encomium : 

1 In regard not only to accuracy of observa ion, and to 
detail in publication of the methods of observing, but also 
to steadiness of system followed through many years, and 
to completeness of calculation of the useful results deduced 
from the observations, this work may shame any other 
collection of observations in this or any other country.' 

This catalogue was not Flamsteed's only achievement. 
He had determined the latitude of the Observatory, 
the obliquity of the ecliptic, and the position of the 
equinoctial points. He thought out an original 
method of obtaining the absolute right ascensions of 
stars by differential observations of the places of the 
stars and the sun near to both equinoxes. He had 
revised and improved Horrox's theory of the lunar 



58 THE ROYAL OBSERVATORY 

motions, which was by far the best existing in 
Flamsteed's day. He showed the existence of the 
long inequality of Jupiter and Saturn ; that is to say, 
the periodic influence which they exercise upon each 
other. He determined the time in which the sun 
rotates on its axis, and the position of that axis. 
He observed an apparent movement of the stars 
in the course of a year, which he ascribed, though 
erroneously, to the stellar parallax, and which 
was explained by the third Astronomer Royal, 
Bradley. 

Flamsteed not only met with harsh treatment 
during his lifetime ; he has not yet received, except 
from a few, anything like the meed of appreciation 
which is his just due ; but, at least, his successors in 
the office have not forgotten him. They have been 
proud that their official residence should be known 
as Flamsteed House, and his name is inscribed over 
the main entrance of the latest and finest of the 
Observatory buildings, and his bust looks forth from 
its front towards the home where he laboured so 
devotedly for nearly fifty years. But he has received 
little honour, save at Greenwich, and in spite of the 
proverb in his other home, the village of Burstow, 
in Surrey, of which he was for many years the rector. 
Here a stained glass window representing, appro- 
priately, the Adoration of the Magi, has been 
recently set up to his memory, largely through 
the interest taken in his history by an amateur 
astronomer of the neighbourhood, Mr. W. Tebb, 
F.R.A.S. 

No instrument of Flamsteed's remains in the 



FLAMSTEED 59 

Observatory, his wife removing them after his death. 
But we may consider his principal instrument, the 
mural quadrant made for him by Abraham Sharp, 
as represented by the remains of a quadrant by the 
same artist, which was presented to the Observatory 
by the Rev. N. S. Heineken, in 1865, and now hangs 
over the door of the transit room. 



CHAPTER III 

HALLEY AND HIS SUCCESSORS 

THERE is no need to give the lives of the succeeding 
Astronomers Royal so fully as that of Flamsteed. 
Not that they were inferior men to him ; on the 
contrary, there can be little doubt that we ought to 
reckon some of them as his superiors, but, in the 
case of several, their best work was done apart from 
Greenwich Observatory, and before they came to it. 

This was particularly the case with Edmund 
H ALLEY. Born on October 29, 1656, he was ten 
years the junior of Flamsteed. Like Flamsteed, he 
came of a Derbyshire family, though he was born at 
Haggerston, in the parish of St. Leonard's, Shore- 
ditch. He was educated at St. Paul's School, where 
he made very rapid progress, and already showed 
the bent of his mind. He learnt to make dials ; he 
made himself so thoroughly acquainted with the 
heavens that it is said, ' If a star were displaced in 
the globe he would presently find it out,' and he 
observed the changes in the direction of the mariner's 
compass. In 1673 he went to Queen's College, 
Oxford, where he observed a sunspot in July and 
August, 1676, and an occupation of Mars. This was 
not his first astronomical observation, as, in June, 

60 




EDMUND HALLEY. 

{From an old print.) 



HALLEY AND HIS SUCCESSORS 63 

1675, he had observed an eclipse of the moon from 
his father's house in Winchester Street. 

A much wider scheme of work than such merely 
casual observations now entered his mind, possibly 
suggested to him by Flamsteed's appointment to the 
direction of the new Royal Observatory. This was 
to make a catalogue of the southern stars. Tycho's 
places for the northern stars were defective enough, 
but there was no catalogue at all of stars below the 
horizon of Tycho's observatory. Here, then, was a 
field entirely un worked, and young Halley was so 
eager to enter upon it that he would not wait at 
Oxford to obtain his degree, but was anxious to 
start at once for the southern hemisphere. 

His father, who was wealthy and proud of his 
gifted son, strongly supported him in his project. The 
station he selected was St. Helena, an unfortunate 
choice, as the skies there were almost always more 
or less clouded., and rain was frequent during his stay. 
However, he remained there a year and a half, and 
succeeded in making a catalogue of 341 stars. This 
catalogue was finally reduced by Sharp, and included 
in the third volume of Flamsteed's Historia Ccelestis. 

In 1678 he was elected Fellow of the Royal 
Society, and the following year he was chosen to 
represent that society in a discussion with Hevelius. 
The question at issue was as to whether more accurate 
observations of the place of a star could be obtained 
by the use of sights without optical assistance, or by 
the use of a telescope. The next year he visited the 
Paris Observatory, and, later in the same tour, the 
principal cities of the Continent. 



64 THE ROYAL OBSERVATORY 

Not long after his return from this tour, Halley 
was led to that undertaking for which we owe him 
the greatest debt of gratitude, and which must be 
regarded as his greatest achievement. 

Some fifty years before, the great Kepler had 
brought out the third of his well-known laws of 
planetary motion. These laws stated that the planets 
move round the sun in ellipses, of which the sun 
occupies one of the foci ; that the straight line 
joining any planet with the sun moves over equal 
areas of space in equal periods of time ; and, lastly, 
that the squares of the" times in which the several 
planets complete a revolution round the sun are 
proportional to the cubes of their mean distances 
from it. These three laws were deduced from actual 
examination of the movements of the planets. Kepler 
did not work out any underlying cause of which these 
three laws were the consequence. 

But the desire to find such an underlying cause 
was keen amongst astronomers, and had given rise 
to many researches. Amongst those at work on the 
subject was Halley himself. He had seen, and been 
able to prove, that if the planets moved in circles 
round the sun, with the sun in the centre, then the 
law of the relation between the times of revolution 
and the distances of the planets would show that the 
attractive force of the sun varied inversely as the 
square of the distance. The actual case, however, of 
motion in an ellipse was too hard for him, and he 
could not deal with it. Halley therefore went up to 
Cambridge to consult Newton, and, to his wonder and 
delight, found . that the latter had already completely 



HALLEY AND HIS SUCCESSORS 65 

solved the problem, and had proved that Kepler's 
three laws of planetary motion were summed up in 
one, namely, that the sun attracted the planets to it 
with a force inversely proportional to the square of 
the distance. 

Halley was most enthusiastic over this great dis- 
covery, and he at once strongly urged Newton to 
publish it. Newton's unwillingness to do so was 
great, but at length Halley overcame his reluctance ; 
and the Royal Society not being able at the time 
to afford the expense, Halley took the charges 
upon himself, although his own resources had been 
recently seriously damaged by the death of his 
father. 

The publication of Newton's Principia, which, but 
for him, might never have seen the light, and most 
certainly would have been long delayed, is Halley's 
highest claim to our gratitude. But, apart from this, 
his record of scientific achievement is indeed a noble 
one. Always, from boyhood, he had taken a great 
interest in the behaviour of the magnetic compass, 
and he now followed up the study of its variations 
with the greatest energy. For this purpose it was 
necessary that he should travel, in view of the great 
importance of the subject to navigation. King 
William III. gave him a captain's commission in the 
Royal Navy a curious and interesting illustration 
of the close connection between astronomy and the 
welfare of our navy and placed him in command of 
a 'pink,' that is to say, a small vessel with pointed 
stern, named the Paramour, in which he proceeded to 
the southern ocean. His first voyage was unfortunate, 





66 THE ROYAL OBSERVATORY 

but the Paramour was recom missioned in 1699, an d 
he sailed in it as far as south latitude 52 . 

In 1 70 1 and the succeeding year he made further 
voyages in the Paramour, surveying the tides and 
coasts of the British Channel and of the Adriatic, 
and helping in the fortification of Trieste. He 
became Savilian Professor of Geometry at Oxford in 
1703, having failed twelve years previously to secure 
the Savilian Professorship of Astronomy, mainly 
through the opposition of Flamsteed, who had already 
formed a strong prejudice against him, which some 
writers have traced to Halley's detection of several 
errors in one of Flamsteed's tide-tables, others to 
Halley's supposed materialistic views. Probably the 
difference was innate in the two men. There was 
likely to be but little sympathy between the strong, 
masterful man of action and society and the secluded, 
self-conscious, suffering invalid. At any rate, in the 
contest between Newton and Flamsteed, which has 
been already described, Halley took warmly the 
side of the former, and was appointed to edit the 
publication of Flamsteed's results, and, on the death 
of the latter, to succeed him at the Royal Observatory. 

The condition of things at Greenwich when 
Halley succeeded to the post of Astronomer Royal 
in 1720 was most discouraging. The instruments 
there had all belonged to Flamsteed, and therefore, 
most naturally, had been removed by his widow. 
The Observatory had practically to be begun de novo, 
and Halley had now almost attained the age at 
which in the present day an Astronomer Royal 
would have to retire. More fortunate, however, than 



HALLEY AND HIS SUCCESSORS 67 

his predecessor, he was able to get a grant for 
instruments, and he equipped the Observatory as 
well as the resources of the time permitted, and his 
transit instrument and great eight-foot quadrant still 
hang upon the Observatory walls. 

As Astronomer Royal his great work was the 
systematic observation of the positions of the moon 
through an entire saros. As is well known, a period 
of eighteen years and ten or eleven days brings the 
sun and moon very nearly into the same positions 
relatively to the earth which they occupied at the 
commencement of the period. This period was well 
known to the ancient Chaldeans, who gave it its name, 
since they had noticed that eclipses of the sun or 
eclipses of the moon recurred at intervals of the above 
length. It was Halley's desire to obtain such a set 
of observations of the moon through an entire saros 
period as to be able to deduce therefrom an improved 
set of tables of the moon's motion. It was an 
ambitious scheme for a man so much over sixty 
to undertake, nevertheless he carried it through 
successfully. 

His desire to complete this scheme, and to found 
upon it improved lunar tables, hindered him from 
publishing his observations, for he feared that others 
might make use of them before he was in a position to 
complete his work himself. This omission to publish 
troubled Newton, who, as President of the Royal 
Society the Greenwich Board of Visitors having 
lapsed at Queen Anne's death drew attention at a 
meeting of the Royal Society, March 2, 1727, to 
Halley's disobedience of the order issued under Queen 



68 THE ROYAL OBSERVATORY 

Anne, for the prompt communication of the Obser- 
vatory results. That Newton should thus have put 
public pressure upon Halley, the man to whom he 
was so much indebted, and with whom there was so 
close an affection, is sufficient proof that his similar 
attitude towards Flamsteed was one of principle and 
not of arbitrariness. Halley, on his side, stood firm, 
as Flamsteed had done, urging the danger that, by 
publishing before he had completed his task, he 
might give an opportunity to others to forestall his 
results. It is said probably without sufficient 
ground that this refusal broke Newton's heart and 
caused his death. Certainly Halley's writings in 
that very year show his reverence and affection for 
Newton to have been as keen and lively as ever. 

Halley's work at the Observatory went on 
smoothly, on the lines he had laid down for himself, 
for ten years after Newton's death; but in 1737 he 
had a stroke of paralysis, and his health, which had 
been remarkably robust up to that time, began to 
give way. He died January 14, 1742, and was buried 
in the cemetery of Lee Church. 

As an astronomer, his services to the science 
rank higher than those of his predecessor ; but as 
Astronomer Royal, as director, that is to say, of 
Greenwich Observatory, he by no means accomplished 
as much as Flamsteed had done. Professor Grant, in 
his History of Physical Astronomy, says that he seems 
to have undervalued those habits of minute attention 
which are indispensable to the attainment of a high 
degree of excellence in the practice of astronomical 
observation. He was far from being sufficiently 



HALLEY AND HIS SUCCESSORS 



69 



careful as to the adjustment of his instruments, 
the going of his clocks, or the recording of his 
own observations. The important feature of his 




halley's quadrant. 
{From an old print.) 



70 THE ROYAL OBSERVATORY 

administration was that under him the Observatory 
was first supplied with instruments which belonged 
to it. 

His astronomical work apart from the Obser- 
vatory was of the first importance. He practically 
inaugurated the study of terrestrial magnetism, and 
his map giving the results of his observations during 
his voyage in the Paramour introduced a new and 
most useful style of recording observations. He 
joined together by smooth curves places of equal 
variation, the result being that the chart shows at 
a glance, not merely the general course of the variation 
over the earth's surface, but its value at any spot 
within the limits of the chart. 

Another work which has justly made his name 
immortal was the prediction of the return of the 
comet which is called by his name, to which reference 
will be made later. Another great scheme, and one 
destined to bear much fruit, was the working out of 
a plan to determine the distance of the sun by 
observations of the transit of Venus. 

Of attractive appearance, pleasing manners, and 
ready wit, loyal, generous, and free from self-seeking, 
he probably was one of the most personally engaging 
men who ever held the office. 

The salary of the Astronomer Royal remained 
under Halley at the same inadequate rate which it 
had done under Flamsteed 100, without provision 
for an assistant. But in 1729 Queen Caroline, learning 
that Halley had actually had a captain's commission 
in the Royal Navy, secured for him a post-captain's 
pay. 




JAMES BRADLEY. 
[From the painting by Hudson.) 



HALLEY AND HIS SUCCESSORS 73 

Halley's work is represented at the Observatory 
by two of his instruments which are still preserved 
there, and which hang on the west wall of the present 
transit room : the Iron Quadrant afterwards made 
famous by the observations of Bradley, and ' Halley's 
Transit,' the first of the great series of instruments 
upon which the fame of Greenwich chiefly rests. 
This transit instrument seems to have been set up 
in a small room at the west end of what is now known 
as the North Terrace. His quadrant was mounted on 
the pier which is now the base of the pier of the 
astrbgraphic telescope. This pier was the first exten- 
sion which the Observatory received from the original 
building. 

On the breakdown of his health Halley nominated 
as his successor, James Bradley ; indeed, it is stated 
that he offered to resign in his favour. He had 
known him then for over twenty years, and that keen 
and generous appreciation of merit in others which 
was characteristic of Halley had led him very early 
to recognize Bradley's singular ability. 

James Bradley was born in 1692 or 1693, of 
an old North of England family. His birthplace was 
Sherbourne, in Gloucestershire, and he was educated 
at North Leach Grammar School and at Baliol 
College, Oxford. During the years of his under- 
graduateship he resided much with his uncle, the 
Rev. James Pound, Rector of Wanstead, Essex, an 
ardent amateur astronomer, a frequent visitor at the 
Observatory in Flamsteed's time, and one of the 
most accurate observers in the country. From him, 



74 THE ROYAL OBSERVATORY 

no doubt, he derived his love of the science, and 
possibly some of his skill in observation. 

Bradley's earliest observations seem to have been 
devoted to the phenomena of Jupiter's satellites and 
to the measures of double stars. The accuracy with 
which he followed up the first drew the attention of 
Halley, and so began a friendship which lasted 
through life. His observations of double stars, 
particularly of Castor, only just failed to show him 
the orbital movement of the pair, because his attention 
was drawn to other subjects before it had become 
sufficiently obvious. 

In 17 19 Bradley and his uncle made an attempt 
to determine the distance of the sun through observa- 
tions of Mars when in opposition, observations which 
were so accurate that they sufficed to show that the 
distance of the sun could not be greater than 125 
millions of miles, nor less than about 94 millions. 
The lower limit which they thus found has proved to 
be almost exactly correct, our best modern deter- 
minations giving it as 93 millions. The instrument 
with which the observations were made was a novel 
one, being * moved by a machine that made it to 
keep pace with the stars ; ' in other words, it was the 
first, or nearly the first, example of what we should 
now call a clock-driven equatorial. 

That same year he was offered the Vicarage of 
Bridstow, near Ross, in Monmouthshire, where, having 
by that time taken priest's orders, he was duly 
installed, July, 1720. To this was added the sinecure 
Rectory of Llandewi-Velgry ; but he held both livings 
only a very short time. In 172 1 the death of Dr. 



H ALLEY AND HIS SUCCESSORS 75 

John Keill rendered vacant the Savilian Professorship 
of Astronomy at Oxford, for which Bradley became 
a candidate, and was duly elected, and resigned his 
livings in consequence. 

It was whilst he was Savilian Professor that 
Bradley made that great discovery which will always 
be associated with his name. Though professor at 
Oxford, he had continued to assist his uncle, Mr. 
Pound, at his observations at Wanstead, and after 
the death of the latter he still lived there as much 
as possible, and continued his astronomical work. 
But in 1725 he was invited by Mr. Samuel Molyneux, 
who had set up a twenty-four-foot telescope made by 
Graham as a zenith tube at his house on Kew Green, 
to verify some observations which he was making. 
These were of the star Gamma Draconis, a star which 
passes through the zenith of London, and which, 
therefore, had been much observed both by Flamsteed 
and Hooke, inasmuch as by fixing a telescope in an 
absolutely vertical position a position which could , 
be easily verified it was easy to ascertain if there 
was any minute change in the apparent position of 
the star. Dr. Hooke had declared that there was 
such a change, a change due to the motion of the 
earth in its orbit, which would prove that the star 
was not an infinite distance from the earth, the 
seeming change of its place in the sky corresponding 
to the change in the place of the earth from which 
the observer was viewing it. 

Bradley found at once that there was such a 
change a marked one. It amounted to as much 
as 1" of arc in three days ; but it was not in the 



76 THE ROYAL OBSERVATORY 

direction in which the parallax of the star would have 
moved it, but in the opposite. Whether, therefore, 
the star was near enough to show any parallax or not, 
some other cause was giving rise to an apparent dis- 
placement of the star, which entirely masked and 
overcame the effect of parallax. 

So far, Bradley had but come to the same point 
which Flamsteed had reached. Flamsteed had 
detected precisely the same apparent displacement 
of stars, and, like Hooke, had ascribed it to parallax. 
Cassini had shown that this could not be the case, as 
the displacement was in the wrong direction ; and 
there the matter had rested. Bradley now set to 
follow the question up. Other stars beside Gamma 
Draconis were found to show a displacement of the 
same general character, but the amount varied with 
their distance from the plane of the ecliptic, the 
earth's orbit. The first explanation suggested was 
that the axis of the earth, which moves very nearly 
parallel to itself as the earth moves round the sun, 
underwent a slight regular ' wobble ' in the course of 
a year. To check this, a star was observed on the 
opposite side of the pole from Gamma Draconis ; 
then Bradley investigated as to whether refraction 
might explain the difficulty, but again without 
success. He now was most keenly interested in the 
problem, and he purchased a zenith telescope of his 
own, made, like that of Molyneux, by Graham, and 
mounted it in his aunt's house at Wanstead, and 
observed continuously with it. The solution of the 
problem came at last to him as he was boating on the 
Thames. Watching a vane at the top of the mast, 




GRAHAM'S ZENITH SECTOR. 

{From an old print.) 



78 THE ROYAL OBSERVATORY 

he saw with surprise that it shifted its direction every 
time that the boat was put about. Remarking to the 
boatmen that it was very odd that the wind should 
change just at the same moment that there was a 
shift in the boat's course, they replied that there was 
no change in the wind at all, and that the apparent 
change of the vane was simply due to the change of 
direction of the motion of the boat. 

This supplied Bradley with a key to the solution 
of the mystery that had troubled him so long. It 
had been discovered long before this that light does 
not travel instantaneously from place to place, but 
takes an appreciable time to pass from one member 
of the solar system to another. This had been dis- 
covered by Romer from observations of the satellites 
of Jupiter. He had noted that the eclipses of the 
satellites always fell late of the computed time, when 
Jupiter was at his greatest distance from the earth ; 
and Bradley's own work in the observation of those 
satellites had brought the fact most intimately under 
his own acquaintance. The result of the boating 
incident taught him, then, that he might look upon 
light as analogous to the wind blowing on the boat. 
As the wind, so long as it was steady, would seem to 
blow from one fixed quarter so long as the boat was 
also in rest, but as it seemed to shift its direction 
when the boat was moving and changed its direction, 
so he saw that the light coming from a particular star 
must seem to slightly change the direction in which 
it came, or, in other words, the apparent position of 
the star, to correspond with the movement of the 
earth in its orbit round the sun. 



HALLEY AND HIS SUCCESSORS 79 

This was the celebrated discovery of the Aberra- 
tion of Light, a triumph of exact observation and of 
clear insight. As to the exactness of Bradley's 
observations, it is sufficient to say that his determina- 
tion of the value of the ' Constant of Aberration ' gave 
it as 20'39" \ tne value adopted to-day is 20'47". 

On the death of Halley, in 1742, Bradley was 
appointed to succeed him. He found the Observatory 
in as utterly disheartening a condition as his prede- 
cessors had done. As already mentioned, Halley 
had not the same qualifications as an observer that 
Flamsteed had. He was, further, an old man when 
appointed to the post, he had no assistant provided 
for him, and the last five years of his life his health 
and strength had entirely given way. Under these cir- 
cumstances, it was no wonder that Bradley found the 
instruments of the Observatory in a deplorable state. 
Nevertheless, he set to work most energetically, and 
in the year of his appointment he made 1500 observa- 
tions in the last five months of the year. He was 
particularly earnest in examining the condition and 
the errors of his instruments ; and as their defects 
became known to him, he was more and more anxious 
for a better equipment. He moved the Royal 
Society, therefore, to apply on his behalf for the 
instruments he required ; and a petition from that 
body, in 1748, obtained what in those days must 
be considered the generous grant of ;iooo, the 
proceeds of the sale of old Admiralty stores. The 
principal instruments purchased therewith were a 
mural quadrant and a transit instrument, both eight 
feet in focal length, still preserved on the walls of the 



So THE ROYAL OBSERVATORY 

transit- room. It is interesting also to note that, 
following in the steps of Halley, and forecasting, as it 
were, the magnetic observatory which Airy would 
found, he devoted ^"20 of the grant to purchasing 
magnetic instruments. 

Meantime he had continued his observations on 
aberration, and had discovered that the aberration 
theory was not sufficient entirely to account for the 
apparent changes in places of stars which he had 
discovered. A second cause was at work, a move- 
ment of the earth's axis, a * wobble ' in its inclination, 
technically known as Nutation, which is due to the 
action of the moon, and goes through its course in a 
period of nineteen years. 

Beside these two great discoveries of aberration 
and nutation, Bradley's reputation rests upon his 
magnificent observations of the places of more than 
three thousand stars. This part of his work was done 
with such thoroughness, that the star-places deduced 
from them form the basis of most of our knowledge 
as to the actual movements of individual stars. In 
particular, he was careful to investigate and to correct 
for the errors of his instrument, and to determine 
the laws of refraction, introducing corrections for 
changes in the readings of thermometer and baro- 
meter. His tables of refraction were used, indeed, 
for seventy years after his death. Of his other labours 
it may be sufficient to refer to his determination of 
the longitudes of Lisbon and of New York, and to his 
effort to ascertain the parallax of the sun and moon, 
in combination with La Caille, who was observing at 
the Cape of Good Hope. 



HALLEY AND HIS SUCCESSORS 81 

As Astronomer Royal, Bradley's great achieve- 
ment was the high standard to which he raised the 
practical work of observation. From his day on- 
wards, also, there was always at least one assistant. 
His first assistant was his own nephew, John Bradley, 
who received the munificent salary of ten shillings a 
week. Still, this was not out of proportion to the 
then salary of the Astronomer Royal, which practi- 
cally amounted only to go. However, in 1752, 
Bradley was awarded a Crown pension of 250 a 
year. He refused the living of Greenwich, which was 
offered him in order to increase his emoluments, on 
the ground that he could not suitably fulfil the 
double office. Bradley's later assistants were Charles 
Mason and Charles Green. 

Bradley's last work was the preparation for the 
observations of the transit of Venus of 1761, according 
to the lines laid down by his predecessor, Halley. 
His health gave way, and he became subject, to 
melancholia, so that the actual observations were 
taken by the Rev. Nathaniel Bliss, who succeeded 
him in his office after his death, in 1762. He was 
buried at Minchinhampton. 

So far as we know Bradley's character, he seems 
to have been a gentle, modest, unassuming man, 
entirely free from self-seeking, and indifferent to 
personal gain. He was in many ways an ideal 
astronomer, exact, methodical, and conscientious to 
the last degree. His skill as an observer was his 
chief characteristic ; and though his abilities were not 
equal as a mathematician or a mechanician, yet, on 
the one hand, he had a very clear insight into the 

F 



82 THE ROYAL OBSERVATORY 

meaning of his observations, and, on the other, he was 
skilful enough to himself adjust, repair, and improve 
his instruments. 

Of Bradley's instruments, there are still preserved 
his famous twelve-and-a-half-foot zenith sector, with 
which he made his two great discoveries ; his brass 
quadrant, which in 1750 he substituted for Halley's 
iron quadrant ; his transit instrument, and equatorial 
sector. Bradley added to the buildings of the 
Observatory that portion which is now represented 
by the upper and lower computing rooms, and the 
chronometer room, which adjoins the latter. This 
room the chronometer room was his transit room, 
and the position of the shutters is still marked by 
the window in the roof. 

The Rev. Nathaniel Bliss, who succeeded 
Bradley, only held the office for a couple of years, 
and during that time was much at Oxford. He, 
therefore, has left no special mark behind him as 
Astronomer Royal. 

He was born November 28, 1700. His father, 
like himself, Nathaniel Bliss, was a gentleman, of 
Bisley, Gloucestershire. 

Bliss graduated at Pembroke College, Oxford, as 
B.A. in 1720, and M.A. in 1723. He became the 
Rector of St. Ebb's, Oxford, in 1736, and on Halley's 
death succeeded him as Savilian Professor of Geo- 
metry. He supplied Bradley with his observations 
of Jupiter's satellites, and from time to time, at his 
request, rendered him some assistance at the Royal 
Observatory. This was particularly the case, as has 



wt 



"<* 













NATHANIEL BLISS. 
{From an engraving on an old pewter flagon.) 



HALLEY AND HIS SUCCESSORS 85 

been already mentioned, with respect to the transit 
of Venus of 1761, the observations of which were 
carried out by Bliss, owing to Bradley's ill-health. 
It was natural, therefore, that on Bradley's death he 
should succeed to the vacant post ; but he held it too 
short a time to do any distinctive work. Such 
observations as he made seem to have been entirely 
in continuation of Bradley's. He took a great 
interest, however, in the improvement of clocks, a 
department in which so much was being done at this 
time by Graham, Ellicott, and others. 

Nevil Maskelyne, the fifth Astronomer Royal, 
was, like Bliss, a close friend of Bradley's. He was 
the third son of a wealthy country gentleman, 
Edmund Maskelyne, of Purton, in Wiltshire. Maske- 
lyne was born in London, October 6, 1732, and was 
educated at Westminster School. Thence he pro- 
ceeded to Cambridge, where he graduated seventh 
Wrangler in 1754. He was ordained to the curacy 
of Barnet in 1755, and, twenty years later, was pre- 
sented by his nephew, Lord Clive, to the living of 
Shrawardine, in Shropshire. In 1782 he was pre- 
sented by his college to the Rectory of North 
Runcton, Norfolk. 

The event which turned his thoughts in the 
direction of astronomy was the solar eclipse of July 
25, 1748 ; and about the time that he was appointed 
to the curacy of Barnet he became acquainted with 
Bradley, then the Astronomer Royal, to whom he 
gave great assistance in the preparation of his table 
of refractions. 



86 THE ROYAL OBSERVATORY 

Like Halley before him, he made an astronomical 
expedition to the island of St. Helena. This was 
for the special purpose of observing the transit of 
Venus of June 6, 1761, Bradley having induced the 
Royal Society to send him out for that purpose. 
Here he stayed ten months, and made many 
observations. But though the transit of Venus was 
his special object, it was not the chief result of 
the expedition : not because clouds hindered his 
observations, but because the voyage gave him the 
especial bent of his life. 

Halley had actually held a captain's commission in 
the Royal Navy, and commanded a ship ; Maskelyne, 
more than any of the Astronomers Royal before or 
since, made the improvement of the practical business 
of navigation his chief aim. None of all the incumbents 
of the office kept its original charter ' To find the 
so much desired Longitude at Sea, for the perfecting 
the Art of Navigation,' so closely before him. 

The solution of the problem was at hand at this 
time its solution in two different ways. On the one 
hand, the offer by the Government of a reward of 
20,000 for a clock or watch which should go so 
perfectly at sea, notwithstanding the tossing of the 
ship and the wide changes of temperature to which 
it might be exposed, that the navigator might at any 
moment learn the true Greenwich time from it, had 
brought out the invention of Harrison's time-keeper ; 
on the other hand, the great improvement that had 
now taken place in the computation of tables of the 
moon's motion, and the more accurate star-catalogues 
now procurable, had made the method of ' lunars,' 



NEVIL MASKELYNE. 



HALLEY AND HIS SUCCESSORS 89 

suggested a hundred and thirty years before by the 
Frenchman, Morin, and others, a practicable one. 

In principle, the method of finding the longitude 
from 'lunars,' that is to say, from measurements of 
the distances between the moon and certain stars, is 
an exceedingly simple one. In actual practice, it 
involves a very toilsome calculation, beside exact 
and careful observation. The principle, as already 
mentioned, is simply this : The moon travels round 
the sky, making a complete circuit of the heavens 
in between twenty-seven and twenty-eight days. It 
thus moves amongst the stars, roughly speaking, its 
own diameter, in about an hour. When once its 
movements were sufficiently well known to be exactly 
predicted, almanacs could be drawn up in which the 
Greenwich time of its reaching any definite point of 
the sky could be predicted long beforehand ; or, what 
comes to the same thing, its distances from a number 
of suitable stars could be given for definite intervals 
of Greenwich time. It is only necessary, then, to 
measure the distances between the moon and some of 
these stars, and by comparing them with the distances 
given in the almanac, the exact time at Greenwich 
can be inferred. As has been already pointed out, 
the determination of the latitude of the ship and of 
the local time at any place where the ship is, is not 
by any means so difficult a matter ; but the local 
time being known and the Greenwich time, the 
difference between these gives the longitude ; and 
the latitude having been also ascertained, the exact 
position of the ship is known. 

There are, of course, difficulties in the way of 



90 THE ROYAL OBSERVATORY 

working out this method. One is, that whilst it takes 
the sun but twenty-four hours to move round the sky 
from one noon to the next, and consequently its 
movements, from which the local time is inferred, are 
fairly rapid, the moon takes nearly twenty-eight days 
to move amongst the stars from the neighbourhood 
of one particular star round to that particular star 
again. Consequently, it is much easier to determine 
the local time with a given degree of exactness than 
the Greenwich time ; it is something like the difference 
of reading a clock from both hands and from the 
hour hand alone. 

There are other difficulties in the case which 
make the computation a long and laborious one, and 
difficult in that sense ; but they do not otherwise 
affect its practicability. 

During this voyage to St. Helena, both when 
outward bound and when returning, Maskelyne gave 
the method of ' lunars ' a very thorough testing, and 
convinced himself that it was capable of giving the 
information required. For by this time the improve- 
ment of the sextant, or quadrant as it then was, by 
the introduction of a second mirror, by Hadley, had 
rendered the actual observation at sea of lunar dis- 
tances, and of altitudes generally, a much more exact 
operation. 

This conclusion he put at once to practical effect, 
and, in 1763, he published the British Mariners 
Guide, a handbook for the determination of the 
longitude at sea by the method of lunars. 

At the same time, the other method, that by the 
time-keeper or chronometer, was practically tested 



HALLEY AND HIS SUCCESSORS 



9' 



by him. The time-keeper constructed by John 
Harrison had been tested by a voyage to Jamaica 
in 1761, and now, in 1763, another time-keeper was 
tested in a voyage to Barbadoes. Charles Green, the 
assistant at Greenwich Observatory, was sent in 
charge of the chronometer, and Maskelyne went with 




hadley's quadrant. 
{From an old print.) 

him to test its performance, in the capacity of 
chaplain to his Majesty's ship Louisa. 

The position which Maskelyne had already won 
for himself as a practical astronomer, and the intimate 
relations into which he had entered with Bradley 
and Bliss, made his appointment to the Astronomer 
Royalship, on the death of the latter, most suitable. 



92 THE ROYAL OBSERVATORY 

At once he bent his mind to the completion of the 
revolution in nautical astronomy which his British 
Mariner s Guide had inaugurated, and in the year 
after his appointment he published the first number 
of the Nautical Almanac, together with a volume 
entitled, Tables Requisite to be Used with the Nautical 
Ephemeris, the value of which was so instantly 
appreciated, that 10,000 copies were sold at once. 

The Nautical Almanac was Maskelyne's greatest 
work, and it must be remembered that he carried 
it on from this time up to the day of his death truly 
a formidable addition to the routine labours of an 
Astronomer Royal who had but a single assistant on 
his staff. The Nautical Almanac was, however, in 
the main not computed at the Observatory ; the 
calculations were effected by computers living in 
different parts of the country, the work being done 
in duplicate, on the principle which Flamsteed had 
inaugurated in the preparation of his Historia Ccelestis. 

Maskelyne's next service to science was almost 
as important. He arranged that the regular and 
systematic publication of the observations made at 
Greenwich should be a distinct part of the duties of an 
Astronomer Royal, and he procured an arrangement 
by which a special fund was set apart by the Royal 
Society for printing them. His observations covering 
the years 1776 to 181 1 fill four large folio volumes, 
and though, as already stated, he had but one 
assistant, they are 90,000 in number. Thus it was 
Maskelyne who first rendered effective the design 
which Charles II. had in the establishment of the 
Observatory. Flamsteed and Halley had been too 



HALLEY AND HIS SUCCESSORS 93 

jealous of their own observations to publish ; Bradley's 
observations though he himself was entirely free 
from this jealousy were made, after his death, the 
subject of litigation by his heirs and representatives, 
who claimed an absolute property in them, a claim 
which the Government finally allowed. None of the 
three, however much their work ultimately tended 
to the improvement of the art of navigation, made 
that their first object Whereas Maskelyne set this 
most eminently practical object in the forefront, and 
so gave to the Royal Observatory, which under 
his predecessors somewhat resembled a private 
observatory, its distinctive characteristics of a public 
institution. 

It fell to Maskelyne to have to advise the 
Government as to the assignment of their great 
reward of ^20,000 for the discovery of the longitude 
at sea. Maskelyne, while reporting favourably of 
the behaviour of Harrison's time-keeper, considered 
that the method of ' lunars ' was far too important to 
be ignored, and he therefore recommended that half 
the sum should be given to Harrison for his watch, 
whilst the other half was awarded for the lunar tables 
which Mayer, before his death, had sent to the Board 
of Longitude. This decision, though there can be 
no doubt it was the right one, led to much dissatis- 
faction on the part of Harrison, who urged his claim 
for the whole grant very vigorously ; and eventually 
the whole ^"20,000 was paid him. The whole ques- 
tion of rewards to chronometer-makers must have 
been one which caused Maskelyne much vexation. 
He was made the subject of a bitter and most 



94 THE ROYAL OBSERVATORY 

voluminous attack by Thomas Mudge, for having pre- 
ferred the work of Arnold and Earnshaw to his own. 

Otherwise his reign at the Observatory seems to 
have been a singularly peaceful one, and there is little 
to record about it beyond the patient prosecution, 
year by year, of an immense amount of sober, practical 
work. To Maskelyne, however, we owe the practic 
of taking a transit of a star over five wires instea 
of over one, and he provided the transit instrumen 
with a sliding eye-piece, to get over the difficulty 
of the displacement which might ensue if the star 
were observed askew when out of the centre of the 
field. To Maskelyne, too, we owe in a pre-eminent 
degree the orderly form of recording, reducing, and 
printing the observations. Much of the work in this 
direction which is generally ascribed to Airy was 
really due to Maskelyne. Indeed, without a wonderful 
gift of organization, it would have been impossibl 
to plan and to carry the Nautical Almanac. 

Beside the editing of various works intended for 
use in nautical astronomy or in general computation, 
the chief events of his long reign at Greenwich were 
the transit of Venus in 1769, which he himself 
observed, and for which he issued instructions in the 
Nautical Almanac ; and his expedition in 1774 to 
Scotland, where he measured the deviation of the 
plumb-line from the vertical caused by the attraction 
of the mountain Schiehallion, deducing therefrom 
the mean density of the earth to be four and a half 
times that of water. 

He died at the Observatory, February 9, 181 r, 
aged 79, leaving but one child, a daughter, who 



s 



JOHN POND. 
( From an old engraving. ) 



HALLEY AND HIS SUCCESSORS 97 

married Mr. Anthony Mervin Story, to whom she 
brought the family estates in Wiltshire, inherited by 
Maskelyne on the deaths of his elder brothers, and, 
in consequence, Mr. Story added the name of 
Maskelyne to his own. 

Maskelyne's character and policy as Astronomer 
Royal have been sufficiently dwelt upon. His private 
character was mild, amiable, and generous. ' Every 
astronomer, every man of learning, found in him a 
brother ; ' and, in particular, when the French Revo- 
lution drove some French astronomers to this country 
to find a refuge, they received from the Astronomer 
Royal the kindest reception and most delicate 
assistance. 

Maskelyne added no instrument to the Observatory 
during his reign, though he improved Bradley's transit 
materially. He designed the mural circle, but it was 
not completed until after his death. His additions 
to the Observatory buildings consisted of three new 
rooms in the Astronomer Royal's house, and the 
present transit circle room. 

John Pond was recommended by Maskelyne 
as his successor at Greenwich. At the time of his 
succession he was forty-four years of age, having 
been born in 1767. He was educated at Trinity 
College, Cambridge, and then spent some considerable 
time travelling in the south of Europe and Egypt. 
On his return home he settled at Westbury, where 
he erected an altazimuth by Troughton, with a two- 
and-a-half-foot circle. A born observer, his observa- 
tions of the declinations of some of the principal 

G 



9 8 THE ROYAL OBSERVATORY 

fixed stars showed that the instrument which 
Maskelyne was using at Greenwich the quadrant by 
Bird could no longer be trusted. Maskelyne, in 
consequence, ordered a six-foot mural circle from 
Troughton, but did not live to see it installed, and 
in 1816 this was supplemented by Troughton's transit 
instrument of five inches aperture and ten feet focal 
length. 

. The introduction of these two important instru- 
ments, and of other new instruments, together with 
new methods of observation, form one of the chief 
characteristics of Pond's administration. Under this 
head must be specially mentioned the introduction 
of the mercury trough, both for determining the 
position of the vertical, and for obtaining a check 
upon the flexure of the mural circle in different 
positions ; and the use in combination of a pair of 
mural circles for determining the declinations of 
stars. 

Another characteristic of his reign was that under 
him there was the first attempt to give the Astronomei 
Royal a salary somewhat higher than that of 
mechanic, and to support him with an adequate stal 
of assistants. His salary was fixed at 600 a year, 
and the single assistant of Maskelyne was increase* 
to six. 

This multiplication of assistants was for the pur- 
pose of multiplying observations, for Pond was the 
first astronomer to recognize the importance of greatly 
increasing the number of all observations upon whicl 
the fundamental data of astronomy were to be 
based. 



HALLEY AND HIS SUCCESSORS 99 

In 1833 he finished his standard catalogue of 
1 113 stars, at that time the fullest of any catalogue 
prepared on the same scale of accuracy. ' It is not 
too much to say/ was the verdict of the Royal 
Astronomical Society, 'that meridian sidereal obser- 
vation owes more to him than to all his countrymen 
put together since the time of Bradley.' 

A yet higher testimony to the exactness of his 
work is given by his successor, Airy. 

1 The points upon which, in my opinion, Mr. Pond's 
claims to the gratitude of astronomers are founded, are 
principally the following. First and chief, the accuracy 
which he introduced into all the principal observations. 
This is a thing which, from its nature, it is extremely difficult 
to estimate now, so long after the change has been made ; 
and I can only say that, so far as I can ascertain from 
books, the change is one of very great extent ; for certainty 
and accuracy, astronomy is quite a different thing from 
what it was, and this is mainly due to Mr. Pond.' 

The same authority eulogizes him further for his 
laborious working out of every conceivable cause or 
indication of error in his declination instruments, for 
the system which he introduced in the observation 
of transits, for the thoroughness with which he deter- 
mined all his fundamental data, and for the regularity 
which he infused into the Greenwich observations. 

One result of this great increase of accuracy was 
that Pond was able at once authoritatively to discard 
the erroneous stellar parallaxes that had been an- 
nounced by Brinkley, Royal Astronomer for Ireland. 

But Pond's administration was open, in several 
particulars, to serious censure, and the Board of 



i oo THE ROYAL OBSERVATORY 

Visitors, which had been for many years but a com- 
mittee of the Royal Society, but which had recently 
been reconstituted, proved its value and efficiency by 
the remonstrances which it addressed to him, and 
which eventually brought about his resignation. His 
personal skill and insight as an observer were of the 
highest order ; but either from lack of interest or 
failing health, he absented himself almost entirely 
from the Observatory in later years, visiting it only 
every ninth or tenth day. He had caused the staff 
of assistants to be increased from one to six, but had 
stipulated that the men supplied to him should be 
1 drudges.' His minute on the subject ran 

' I want indefatigable, hard-working, and, above all, 
obedient drudges (for so I must call them, although they 
are drudges of a superior order), men who will be contented 
to pass half their day in using their hands and eyes in the 
mechanical act of observing, and the remainder of it in 
the dull process of calculation.' 

This was a fatal mistake, and one which it is very 
hard to understand how any one with a real interest 
in the science could have made. Men who had the 
spirit of ' drudges,' to whom observation was a mere 
1 mechanical act,' and calculation a ' dull process,' 
were not likely to maintain the honour of the Obser- 
vatory, particularly under an absentee Astronomer 
Royal. Pond tried to overcome the difficulty by 
devising rules for their guidance of iron rigidity. 
The result was that after his resignation, in 1835, the 
First Lord and the Secretary of the Admiralty ex- 
pressed their feeling to Airy, Pond's successor, 'that 
the Observatory had fallen into such a state of 



HALLEY AND HIS SUCCESSORS 101 

disrepute that the whole establishment should be 
cleared out.' A further evil was the excessive develop- 
ment of chronometer business, so as practically to 
swamp the real work of the Observatory, whilst the 
prices paid for the chronometers at this time were 
often much larger than would have been the case 
under a more business-like administration. 

With all his merits, therefore, as an observer, the 
administration of Pond was, in some respects, the least 
satisfactory of all that the Observatory has known, 
and he alone of all the Astronomers Royal retired 
under pressure. He did not long survive his resig- 
nation, dying in September, 1836. He was buried 
by the side of Halley, in the churchyard at Lee. 

Of Pond's instruments, the Observatory retains 
the fine transit instrument which was constructed by 
Troughton at his direction, and the mural circle, 
designed by Maskelyne, but which Pond was the 
first to use. Both of these have, of course, long been 
obsolete, and now hang on the walls of the transit 
room. The small equatorial, called, after its donor, 
the Shuckburgh equatorial, was also added in Pond's 
day, and though practically never used, still remains 
mounted in its special dome. 



CHAPTER IV 

AIRY 

ONE hundred and sixty years from the day when 
Flamsteed laid the foundation stone of the Obser- 
vatory, the Royal Warrant under the sign manual 
was issued, appointing the seventh and strongest 
of the Astronomers Royal, August 1 1, 1835. He 
actually entered on his office in the following October, 
but did not remove to the Observatory until the end 
of the year. 

George Biddell Airy was born at Alnwick, in 
Northumberland, on July 27, 1801. His father was 
William Airy, of Luddington, in Lincolnshire, a 
collector of excise ; his mother was the daughter of 
George Biddell, a well-to-do farmer, of Playford, near 
Ipswich. He was educated at the Grammar School, 
Colchester, and so distinguished himself there that 
although his father was at this time very straitened 
in his circumstances, it was resolved that young Airy 
should go to Cambridge. Here he was entered as 
sizar at Trinity College, and his robust, self-reliant 
character was seen in the promptness with which he 
rendered himself independent of all pecuniary help 
from his relatives. In 1823 he graduated as Bachelor 

102 



GEORGE BIDDELL AIRY. 



AIRY 



I0 5 



of Arts, being Senior Wrangler and Smith's prize- 
man, entirely distancing all other men of his year. 
He had already begun to pay attention to astronomy, 
at first from the side of optics, to the study of which 
he had been very early attracted ; a paper of his 
on the achromatism of eye-pieces and microscopes, 
written in 1824, being one of especial value. In 1826 
he attempted to determine ' the diminution of gravity 
in a deep mine' that of Dolcoath, in Cornwall. 
In the winter of 1823-24 he was invited to London 
by Mr. (afterwards Sir) James South, who took him, 
amongst other places, to Greenwich Observatory, 
and gave him his first introduction to practical 
astronomy. In 1826 he was appointed Lucasian 
Professor at Cambridge, and in 1828, Plumian Pro- 
fessor, with the charge of the new University Obser- 
vatory. Prior to his election he had definitely told 
the electors that the salary proposed was not suffi- 
cient for him to undertake the responsibility of the 
Observatory. He followed this up by a formal 
application for an increase, which created not a little 
commotion at the time, the action being so unpre- 
cedented ; and after a delay of a little over a year 
he obtained what he had asked for. The delay gave 
rise, however, to the remark of a local wit, that 
the University had given 'to Airy, nothing, a local 
habitation and a name.' 

The seven years which he spent in the Cambridge 
Observatory were the best possible preparation for 
that greater charge which he was to assume later. 
When he entered on his duties the Observatory had 
been completed four years, but no observations had 



106 THE ROYAL OBSERVATORY 

been published ; there was no assistant, and the only 
instruments were a couple of good clocks and a 
transit instrument. But Airy set to work at once 
with so much energy that the observations for 1828 
were published early in the following year, and he 
had very quickly worked out the best methods for 
correcting and reducing his observations. In 1829 an 
assistant was granted to him, in 1833 a second, and 
in the latter year Mr. Baldrey, the senior assistant, 
observed about 5000 transits, and Mr. Glaisher, the 
junior, about the same number of zenith distances. 

A syndicate had been appointed at Cambridge 
for the purpose of visiting the Observatory once in 
each term, and making an annual report to the 
senate. A smaller-minded and less acute man than 
Airy might have resented such an arrangement. He, 
on the contrary, threw himself heartily into it, and 
made such formal written reports to the syndicate as 
best helped them in the performance of their duty, 
and at the same time secured for the Observatory 
the support and assistance which from time to time 
it required. On his appointment to Greenwich, he 
at once entered into the same relations to the Board 
of Visitors of that Observatory, and from that time 
forth the friction that had occasionally existed 
between the Board and the Astronomer Royal in 
the past entirely ceased. The Board was henceforth 
no longer a body whose chief function was to reprove, 
to check, or to quicken the Astronomer Royal, but 
rather a company of experts, before whom he might 
lay the necessities of the Observatory, that they in 
turn might present them to the Government. 



AIRY 107 

Such representations were not likely to be in 
vain. For, as Mr. Sheepshanks has left on record 

'When Mr. Airy wants to carry anything into effect by 
Government assistance, he states, clearly and briefly, why 
he wants it ; what advantages he expects from it ; and 
what is the probable expense. He also engages to direct 
and superintend the execution, making himself personally 
responsible, and giving his labour gratis. When he has 
obtained permission (which is very seldom refused), he 
arranges everything with extraordinary promptitude and 
foresight, conquers his difficulties by storm, and presents 
his results and his accounts in perfect order, before men 
like ... or myself would have made up our minds about 
the preliminaries. Now, men in office naturally like persons 
of this stamp. There is no trouble, no responsibility, no 
delay, no inquiries in the House ; the matter is done, paid 
for, and published, before the seekers of a grievance can 
find an opportunity to be heard. This mode of proceeding 
is better relished by busy statesmen than recommendations 
from influential noblemen or fashionable ladies.' 

His first action towards the Board was, however, 
a very bold and independent one. He made strong 
representations on the subject: of the growth of the 
chronometer business, which proved displeasing to 
the Hydrographer, Captain Beaufort, who was one of 
the official visitors, and by his influence the report 
was not printed. Airy 'kept it, and succeeding 
reports, safe for three years, and then the Board of 
Visitors agreed to print them, and four reports were 
printed together, and bound with the Greenwich 
Observations of 1838.' 

With the completion of arrangements which put 
the chronometer business in proper subordination to 
the scientific charge of the Observatory, Airy was 



108 THE ROYAL OBSERVATORY 

free to push forward its development on the lines 
which he had already marked out for himself. To 
go through these in detail is simply to describe the 
Observatory as he left it. Little by little he entirely 
renovated the equipment. Greatly as Pond had 
improved the instruments of the Observatory, Airy 
carried that work much further still. Though he did 
not observe much himself, and was not Pond's equal 
in the actual handling of a telescope, he had a great 
mechanical gift, and the detail in its minutest degree 
of every telescope set up during his long reign was 
his own design. 

In the work of reduction he introduced the use of 
printed skeleton forms, to which Pond had been a 
stranger. The publication of the Greenwich results 
was carried on with the utmost regularity ; and, in 
striking contrast to the reluctance of Flamsteed and 
Halley, he was always most prompt in communicating 
any observations to every applicant who could show 
cause for his request for them. 

It is most difficult to give any adequate impression 
of his far-reaching ability and measureless activity. 
Perhaps the best idea of these qualities may be 
obtained from a study of his autobiography, edited 
and published some four years after his death by his 
son. The book, to any one who was not personally 
acquainted with Airy, is heavy and monotonous, 
chiefly for the reason that its 400 pages are little but 
a mere catalogue of the works which he undertook 
and carried through ; and catalogues, except to the 
specialist, are the dullest of reading. To enter into 
the details of his work might fill a library. 






AIRY in 

As Astronomer Royal he seems to have inherited 
and summed up all the great qualities of his pre- 
decessors : Flamsteed's methodical habits and 
unflagging industry ; Halley's interest in the lunar 
theory ; Bradley's devotion to star observation and 
catalogue making; Maskelyne's promptitude in 
publishing, and keen interest in practical navigation ; 
Pond's refinement of observation. Nor did he allow 
this inheritance to be merely metaphorical ; he made 
it an actual reality. He discussed, reduced, and 
published, in forms suitable for use and comparison 
to-day, the whole vast mass of planetary and lunar 
observations made at the Royal Observatory from 
the year 1760 to his own accession, a work of 
prodigious labour, but of proportionate importance. 
Airy has been accused and with some reason of 
being a strong, selfish, aggressive man ; yet nothing 
can show more clearly than this great work how 
thoroughly he placed the fame and usefulness of the 
Observatory before all personal considerations. 
With far less labour he could have carried on a dozen 
investigations that would have brought him more 
fame than this great enterprise, the purpose of which 
was to render the work of his predecessors of the 
highest possible use. The light in which he regarded 
his office may best be expressed in his own words : 

'The Observatory was expressly built for the aid of 
astronomy and navigation, for promoting methods of 
determining longitude at sea, and (as the circumstances 
that led to its foundation show) more especially for deter- 
mination of the moon's motions. All these imply, as their 
first step, the formation of accurate catalogues of stars, 
and the determination of the fundamental elements of the 



Ti2 THE ROYAL OBSERVATORY 

solar system. These objects have been steadily pursued 
from the foundation of the Observatory ; in one way by 
Flamsteed ; in another way by Halley, and by Bradley in 
the earlier part of his career ; in a third form by Bradley 
in his later years ; by Maskelyne (who contributed most 
powerfully both to lunar and to chronometric nautical 
astronomy), and for a time by Pond ; then with improved 
instruments by Pond, and by myself for some years ; and 
subsequently, with the instruments now in use. It has 
been invariably my own intention to maintain the principles 
of the long-established system in perfect integrity ; varying 
the instruments, the modes of employing them, and the 
modes of utilizing the observations of calculation and publi- 
cation, as the progress of science might seem to require.' 

The result of this keen appreciation of the essential 
continuity of the Astronomer Royalship has been 
that it is to Airy, more than to any of his predecessors, 
or than to all of them put together, that the high 
reputation of Greenwich Observatory is due. Professor 
Newcomb, the greatest living authority on the subject 
outside our own land and other great foreign 
astronomers have independently pronounced the 
same verdict has said : 

' The most useful branch of astronomy has hitherto been 
that which, treating of the positions and motions of the 
heavenly bodies, is practically applied to the determination 
of geographical positions on land and at sea. The Greenwich 
Observatory has, during the past century, been so far the 
largest contributor in this direction as to give rise to the 
remark that, if this branch of astronomy were entirely lost, 
it could be reconstructed from the Greenwich observations 
alone.' 

Early in 1836 Airy proposed to the Board of 
Visitors the creation of the Magnetic and Meteoro- 
logical department of the Observatory, and in 1840 



AIRY 113 

a system of regular two-hourly observations was set 
on foot. This was the first great enlargement of 
programme for the Observatory beyond the original 
one expressed in Flamsteed's warrant. It was followed 
in 1873 with the formation of the Solar Photographic 
department, to which the Spectroscope was added a 
little later. 

Though he had objected strongly on his first 
coming to the Observatory to the excessive time 
devoted to the merely commercial side of the care of 
chronometers, yet the perfecting of these instruments 
was one that he had much at heart, and many recent 
appliances are either of his own invention or are due 
to suggestions which he threw out. 

Much work lying outside the Observatory, and yet 
intimately connected with it, was carried out either 
by him or in accordance with his directions. The 
transit of Venus expeditions of 1874, the delimitation 
of the boundary line between Canada and the United 
States, and, later, that of the Oregon boundary ; the 
determination of the longitudes of Valencia, Cam- 
bridge, Edinburgh, Brussels, and Paris ; assistance 
in the determination of the longitude of Altona all 
came under Airy's direction. Nor did he neglect 
expeditions in connection with what we would now 
call the physical side of astronomy. On three 
occasions, 1842, 185 1, and i860, he himself personally 
took part in successful eclipse expeditions. The 
determination of the increase of gravity observable 
in the descent of a deep mine was also the subject 
of another expedition, to the Harton Colliery, near 
South Shields. 

II 



ii4 THE ROYAL OBSERVATORY 

But with all these, and many other inquiries for 
he was the confidential adviser of the Government 
in a vast number of subjects : lighthouses, railways, 
standard weights and measures, drainage, bridges- 
he yet always kept the original objects of the 
Observatory in the very first place. It was in order 
to get more frequent observations of the moon that 
he had the altazimuth erected, which was completed 
in May, 1847. This was followed, in 185 1, by the 
transit circle, as he had long felt the need for more 
powerful light grasp in the fundamental instrument 
of the Observatory. The transit circle took the 
place both of the old transit instrument and of the 
mural circle. Above all, he arranged for the observa- 
tions of moon and stars to be carried out with 
practical continuity. The observations were made 
and reduced at once, and published in such a way 
that any one wishing to discuss them afresh could 
for himself go over every step of the reduction from 
the commencement, and could see precisely what 
had been done. 

The greatest addition made to the equipment 
of the Observatory in Airy's day was the erection of 
the I2|-inch Merz equatorial, which proved of great 
service when spectroscopy became a department of 
the Observatory. 

So strong and gifted a man as Airy was bound to 
make enemies, and at different times of his life bitter 
attacks were made on him from one quarter or 
another. One of these, curiously enough, was from 
Sir James South, the man who, as he said, first 
introduced him to practical astronomy. Later came 



Airy 



"5 



the discovery of Neptune, and Airy was subjected to 




THE SOUTH-EAST TOWER. 
{From a -photograph by Mr. Lacey.) 

much bitter criticism, since, as it appeared on the 
surface, it was owing to his supineness that Adams 



n6 THE ROYAL OBSERVATORY 

missed being held the sole discoverer of the new planet, 
and narrowly missed all credit for it altogether. Last 
of all was the vehement attack made upon him by 
Richard Anthony Proctor, in connection with his 
preparations for the transit of Venus. All such 
attacks, however, simply realized the old fable of 
the viper and the file. Attacks which would have 
agonized Flamsteed's every nerve, and have called 
forth full and dignified rejoinders from Maskelyne, 
were absolutely and entirely disregarded by Airy. 
He had done his duty, and in his own estimation 
and, it should be added, in the estimation of those 
best qualified to judge had done it well. He was 
perfectly satisfied with himself, and what other 
people thought or said about him influenced him 
no more than the opinions of the inhabitants of 
Saturn. 

But great as Airy was, he had the defects of his 
qualities, and some of these were serious. His love 
of method and order was often carried to an absurd 
extreme, and much of the time of one of the greatest 
intellects of the century was often devoted to doing 
what a boy at fifteen shillings a week could have 
done as well, or better. The story has often been 
told, and it is exactly typical of him, that on one 
occasion he devoted an entire afternoon to himself 
labelling a number of wooden cases ' empty,' it so 
happening that the routine of the establishment kept 
every one else engaged at the time. His friend Dr. 
Morgan jocularly said that if Airy wiped his pen on 
a piece of blotting-paper he would duly endorse the 
blotting-paper with the date and particulars of its 






AIRY i, 7 

use, and file it away amongst his papers. His mind 
had that consummate grasp of detail which is charac- 
teristic of great organizers, but the details acquired 
for him an importance almost equal to the great 
principles, and the statement that he had put a new 
pane of glass into a window would figure as promi- 
nently in his annual report to the Board of Visitors 
as the construction of the new transit circle. His 
son remarks of him that ' in his last days he seemed 
to be more anxious to put letters which he received 
into their proper place for reference than even to 
master their contents,' his system having grown with 
him from being a means to an end, to becoming the 
end itself. 

So, too, his regulation of his subordinates was, 
especially in his earlier days, despotic in the extreme 
despotic to an extent which would scarcely be 
tolerated in the present day, and which was the 
cause of not a little serious suffering to some of his 
staff, whom, at that time, he looked upon in the true 
spirit of Pond, as mere mechanical ' drudges.' For 
thirty-five years of his administration the salaries of 
his assistants remained discreditably low, and his 
treatment of the supernumerary members of his staff 
would now probably be characterized as ' remorseless 
sweating.' The unfortunate boys who carried out 
the computations of the great lunar reductions were 
kept at their desks from eight in the morning till eight 
at night, without the slightest intermission, except an 
hour at midday. As an example of the extreme 
detail of the oversight which he exercised over his 
assistants, it may be mentioned that he drew up for 



1x8 THE ROYAL OBSERVATORY 

each one of those who took part in the Harton 
Colliery experiment, instructions, telling them by 
what trains to travel, where to change, and so forth, 
with the same minuteness that one might for a child 
who was taking his first journey alone ; and he him- 
self packed up soap and towels with the instruments, 
lest his astronomers should find themselves, in Co. 
Durham, out of reach of these necessaries of 
civilization. 

A regime so essentially personal may indeed have 
been necessary after Pond's administration, and to 
give the Observatory a fresh start. But it would not 
have been to the advantage of the Observatory, had 
it become a permanent feature of its administration, 
as it militated was almost avowedly intended to 
militate against the growth of real zeal and intelli- 
gence in the staff, and necessarily occasioned labour 
and discomfort out of proportion to the results 
obtained. Fortunately, in Airy's later years, the 
extension of the work of the Observatory, a slight 
failing in his own powers, and the efforts he was 
devoting to the working out of the lunar theory, 
compelled him to relax something of that microscopic 
imperiousness which had been the chief characteristic 
of his rule for so long. 

Airy had, in the fullest degree, the true spirit of 
the public servant ; his sense of duty to the State was 
very high. He was always ready to undertake any 
duty which he felt to be of public usefulness, and 
many of these he discharged without fee or reward. 

So great an astronomer was necessarily most 
highly esteemed by astronomers. He was President 



AIRY 119 

of the Royal Society for two years ; he was five times 
President of the Royal Astronomical Society, and 
twice received its gold medal, beside a special testi- 
monial for his reduction of the Greenwich lunar 
observations. From the Royal Society he received 
the Copley medal and the Royal medal, beside 
honorary titles from the Universities of Oxford, 
Cambridge, and Edinburgh. So invaluable a public 
servant, he received the distinction of a Knight 
Commandership of the Bath in 1872. He had been 
repeatedly offered knighthood before, but had not 
thought it well to receive it. He was in the receipt 
of decorations also from a great number of foreign 
countries ; for, for many years, he was looked up to, 
not only by English astronomers, but by scientific 
men in all countries, as the very head and representa- 
tive of his science. 

And he also received a more popular apprecia- 
tion and most justly so. For whilst no one could 
have less of the arts of the ordinary popularizer 
about him, no one has ever given popular lectures 
on astronomy which more fully corresponded to the 
ideal of what such should be than Airy's six lectures 
to working men, delivered at Ipswich. And we 
may count the bestowal upon him of the honorary 
freedom of the City of London, in 1875, as one of the 
tokens that his services in this direction had not 
been unappreciated. 

During the last seven years of his official career 
he undertook the working out of a lunar theory, and, 
to allow himself more leisure for its completion, he 
resigned his position August 15, 1881, after forty-six 



i2o THE ROYAL OBSERVATORY 

years of office. He was now eighty years of age, 
and he took up his residence at the White House, 
just outside Greenwich Park. He resided there till 
his death, more than ten years later January 2, 1892. 

Airy was succeeded in the Astronomer Royalship 
by the present and eighth holder of the office, 
W. H. M. CHRISTIE. He was born at Woolwich, in 
1845, his father having been Professor Samuel Hunter 
Christie, F.R S. He was educated at King's College, 
London, and Trinity College, Cambridge, graduating 
as fourth Wrangler in 1868. In 1870 he was 
appointed chief assistant at Greenwich, in succession 
to Mr. Stone, who had become her Majesty's 
astronomer at the Cape, and in 1881 he succeeded 
Airy as Astronomer Royal. 

During Mr. Christie's office, the two new depart- 
ments of the Astrographic Chart and Double-star 
observations have come into being. The following 
buildings have been erected under his administra- 
tion : the great New Observatory in the south 
ground, the New Altazimuth, the New Library, 
nearly opposite to it, the Transit Pavilion, the 
porter's lodge, and the Magnetic Pavilion out in 
the Park. Whilst in the old buildings the Astro- 
graphic dome has been added, and the Upper and 
Lower Computing rooms have been rebuilt and en- 
larged. As to the instruments, the 28-inch refractor, 
the astrographic twin telescope, the new altazimuth, 
the 26-inch and 9-inch Thompson photographic re- 
fractors, and the 30-inch reflector are all additions 
during the present reign. Roughly speaking, therefore, 




W. H. M. CHRISTIE, ASTRONOMER ROYAL 
( From a photograph by Elliott and Fry. ) 



AIRY I23 

we may say that three-fourths of the present Obser- 
vatory has been added during the nineteen years 
of the present Astronomer Royal. One exceedingly 
important improvement should not be overlooked. 
Airy observed little himself whilst at Greenwich, 
and had an inadequate idea of the necessity for 
room in a dome and breadth in a shutter-open- 
ing. With the sole exception, perhaps, of the 
transit circle, every instrument set up by Airy was 
crammed into too small a dome or looked out 
through too narrow an opening. The increase of 
shutter-opening of the newer domes may be well seen 
by contrasting, say, the old altazimuth or the Sheep- 
shanks dome with that of the astrographic. This 
reform has had much to do with the success of later 
work. 



CHAPTER V 

THE OBSERVATORY BUILDINGS 

LIKE a living organism, Greenwich Observatory bears 
the record of its life-history in its structure. It was 
not one of those favoured institutions that have sprung 
complete and fully equipped from the liberality of 
some great king or private millionaire. As we have 
seen, it was originally established on the most modest 
not to say meagre scale, and has been enlarged 
just as it has been absolutely necessary. To quote 
again from Professor Newcomb 

1 Whenever any part of it was found insufficient for its 
purpose, new rooms were built for the special object in 
view, and thus it has been growing from the beginning by 
a process as natural and simple as that of the growth of a 
tree. Even now the very value of its structure is less than 
that of several other public observatories, though it eclipses 
them all in the results of its work.' 

Entering the courtyard an enclosure some eighty 
feet deep by ninety feet in extreme breadth by the 
great gate, we see before us Flamsteed House, the 
original building of the Observatory. Flamsteed's 
little domain was only some twenty-seven yards 
wide by fifty deep, and for buildings comprised little 
beyond a small dwelling-house on the ground floor, 

and one fine room above it. This room the original 

124 



THE OBSERVATORY BUILDINGS 125 

Greenwich Observatory still remains, and is used 
as a council room by the official Board of Visitors, 
who come down to the Observatory on the first 
Saturday in June, to examine into its condition and 
to receive the Astronomer Royal's report. The room 
is called, from its shape, the Octagon Room, and is 
well known to Londoners from the great north 
window which looks out straight over the river 
between the twin domes of the Hospital. 

In Bradley's time, about 1749, the first extension 
of the domains of the Observatory took place to the 
south and east of the original building, the direction 
in which, on the whole, all subsequent extensions 
have taken place, owing to the fact that the original 
building was constructed at the extremity of what 
Sir George Airy was accustomed to call a ' peninsula ' 
a projecting spur of the Blackheath plateau, from 
which the ground falls away very sharply on three 
sides and on part of the fourth. 

The Observatory domain at present is fully two 
hundred yards in greatest length, with an average 
breadth of about sixty. Nearly the whole of this 
accession took place under the directorates of Pond 
and Airy. The present instruments are, therefore, 
as a rule, the more modern in direct proportion to 
their distance from the Octagon Room the old 
original Observatory. There is one notable exception. 
The very first extension of the Observatory buildings, 
made in the time of Halley, the second Astronomer 
Royal, consisted in the setting up of a strong pier, 
to carry two quadrant telescopes. The pier still 
remains, but now forms the base of the support of 



i 2 6 THE ROYAL OBSERVATORY 

the twin telescopes devoted to the photographic 
survey of the heavens for the International Chart. 

Standing just within the gate of the courtyard, 
and looking westward, that is toward Flamsteed 
House, we have immediately on our right hand the 
porter's lodge ; a little farther forward, also on the 
right, the Transit Pavilion, a small building sheltering 
a portable transit instrument ; and farther forward, 
still on the right, the entrance to the Chronograph 
Room. Above the Chronograph Room is a little, 
inconveniently-placed dome, containing a small equa- 
torially-mounted telescope, known as the Shuckburgh. 
Beyond the Chronograph Room a door opens on to 
the North Terrace, over which is seen the great north 
window of the Octagon Room. Close by the door of the 
Chronograph Room a great wooden staircase rises to 
the roof of the main building. It is not an attractive- 
looking ascent, as the steps overlap inconveniently. 
Still, there is no record of an accident upon them, 
and those who venture on the climb to the roof, 
where are placed the anemometers and the turret 
carrying the time-ball, which is dropped daily at 
I p.m., will be well repaid by the splendid view of" 
the river which is there afforded to them. 

Passing under this staircase, on the wall by its 
side is seen the following inscription : 

Carolus II s Rex Optimus 

Astronomic et Nautioe artis 

Patronus Maximus 

Speculam hanc in utriusque commodum 

FECIT 

Anno D ni MDCLXXVI. Regni sui XXVIII. 

Curante Iona Moore milite 

R. T. S. G. 



THE OBSERVATORY BUILDINGS 



127 



In the extreme angle of the courtyard is the 
entrance to the mean solar clock cupboard, and to 




THE ASTRONOMER ROYAL'S HOUSE. 
{From a photograph by Mr. Lacey. ) 

the staircase leading up to the Octagon Room. At 
the head of this staircase in a small closet is the 
winch for winding up the time-ball. 



i28 THE ROYAL OBSERVATORY 

Coming back into the courtyard, and crossing the 
face of the Astronomer Royal's private house, the 
range of buildings is reached which form the left 
hand or south side of the enclosure. Entering the 
first of these, we find ourselves in the Lower Com- 
puting Room, which is devoted to the ' Time Depart- 
ment.' The next room which opens out of it, as 
we turn eastwards, was Bradley's Transit Room, but 
is now used for the storage of chronometers. Passing 
through Bradley's Transit Room, we come to the 
present Transit Room, which brings us close to the 
great gate. The range of buildings is, however, con- 
tinued somewhat farther, containing on the ground 
floor some small sitting-rooms and a fire-proof room 
for records. 

Turning back to the Lower Computing Room, 
we notice in it the stone pier, already alluded to, 
which was set up by Halley, and formed the first 
addition to the original Observatory of Flamsteed. 
The Lower Computing Room itself and Bradley's 
Transit Room were due to the Astronomer after 
which the latter is named. An iron spiral staircase 
in the middle of the Lower Computing Room leads 
up to the Upper Computing Room, and above that 
to the Astrographic dome, so called because the 
twin telescope housed therein is devoted to the work 
of the Astrographic Chart a chart of the entire sky 
to be made by eighteen co-operating observatories 
by means of photography. In this way it is intended 
to secure a record of the places of far more stars than 
could be done by the ordinary methods, and in this 
project Greenwich has necessarily taken a premier 



THE OBSERVATORY BUILDINGS 131 

place. This is a work which, whilst it is the legitimate 
and natural outcome of the original purpose of the 
Observatory, is yet pushed beyond what is necessary 
for any mere utilitarian assistance to navigation. For 
the sailor it will always be sufficient to know the 
places of a mere handful of the brightest stars, and 
the vast majority of those in the great photographic 
map will never be visible in the little portable tele- 
scope of the sailor's sextant. But it will be freely 
admitted that in the case of an enterprise of this 
nature, in which the observatories of so many different 
nations were uniting, and which was so precisely on 
the lines of its original charter, though an extension 
of it, it was impossible for Greenwich to hold back 
on the plea that the work was not entirely utili- 
tarian. 

Descending again to the Lower Computing Room, 
and passing through it, not to the east, into Bradley's 
Transit Room, but through a little lobby to the south, 
we come upon an inconvenient wooden staircase 
winding round a great stone pillar with three rays. 
This pillar is the support of Airy's altazimuth, and 
very nearly marks the place where Flamsteed set up 
his original sextant. 

Returning again to the Lower Computing Room, 
and passing out to the east, just in front of the Time 
Superintendent's desk, we enter a small passage 
running along the back of Bradley's Transit Room, 
and from this passage enter the present Transit 
Room near its south end. Just before reaching the 
Transit Room, however, we pass the Reflex Zenith 
Tube, a telescope of a very special kind. 



i 3 2 THE ROYAL OBSERVATORY 

Immediately outside the Transit Room is a stair- 
case leading on the first floor to two rooms long used 
as libraries, and to the leads above them, on which 
is a small dome containing the Sheepshanks equa- 
torial. These libraries are over the small sitting- 
rooms already referred to. The fire-proof Record 
Rooms, two stories in height, terminate this range 
of buildings. 

Beyond the Record Rooms the boundary turns 
sharply south, where stands a large octagonal building 
surmounted by a dome of oriental appearance, a 
1 circular versatile roof,' as the Visitors would have 
called it a hundred years ago. This dome which 
has been likened, according to the school of aesthetics 
in which its critics have been severally trained, to 
the Taj at Agra, a collapsed balloon, or a mammoth 
Spanish onion houses the largest refractor in Eng- 
land, the 'South-east Equatorial' of twenty- eight 
inches aperture. But, though the largest that England 
possesses, it would appear but as a pigmy beside some 
of the great telescopes for which America is famous. 

Beyond this dome the hollow devoted to the 
Astronomer Royal's private garden reduces the 
Observatory ground to a mere 'wasp's waist,' a 
narrow, inconvenient passage from the old and north 
observatory to the younger southern one. 

The first building, as the grounds begin to widen 
out to the south, contains the New Altazimuth, a 
transit instrument which can be turned into any 
meridian. A library of white brick and a low wooden 
cruciform building the Magnetic Observatory 
follow it closely. 



THE OBSERVATORY BUILDINGS 133 

This latter building houses the Magnetic Depart- 
ment, a department which, though it lies aside from 
the original purposes of the Observatory, as defined 
in the warrant given to Flamsteed, is yet intimately 
connected with navigation, and was founded by Airy 
very early in his period of office. This deals with 
the observation of the changes in the force and 
direction of the earth's magnetism, an inquiry which 
the greater delicacy of modern compasses, and, in 
more recent times, the use of iron instead of wood 
in the construction of ships, has rendered impera- 
tive. 

Closely associated with the Magnetic Department 
is the Meteorological. Weather forecasts, so necessary 
for the safety of shipping round our coasts, are not 
issued from Greenwich Observatory, any more than 
the Nautical Almanac is now issued from it. But just 
as the Observatory furnishes the astronomical data 
upon which the almanac is based, so also a consider- 
able department is set apart for furnishing observa- 
tions to be used by the Meteorological Orifice at 
Westminster for their daily predictions. 

So far, the development of the Observatory had 
been along the central line of assistance to navigation. 
But the ' Magnetic Department ' led on to a new one, 
which had but a secondary connection with it. It 
had been discovered that the extent of the daily 
range of the magnetic needle, and the amount of the 
disturbances to which it was subjected, were in close 
connection with the numbers and size of the spots 
on the sun's surface. This led to the institution of 
a daily photographic record of the state of the sun's 




PLAN OF OBSERVATORY AT PRESENT TIME. 
(For key to plan, see p. 135.) 



THE OBSERVATORY BUILDINGS 135 

surface, a record of which Greenwich has now the 
complete monopoly. 

Beyond the Magnetic Observatory the ground 
widens out into an area about equal to that of the 
northern part, and the new building just completed, 
and which is now emphatically 'The Observatory,' 
stands clear before us. The transfer to this stately 
building of the computing rooms, libraries, and store 
rooms has been aptly described as a shift in the 
latitude of Greenwich Observatory, which still preserves 
its longitude. It may be noted that the only two 
buildings of any architectural pretensions in the whole 
range are Flamsteed's original observatory, built 
by Sir Christopher Wren, and containing little beyond 
the octagon room, in the extreme north ; and this 
newest building in the extreme south. 

Key to the Plan of the Observatory on Page 134. 

1. Chronograph Room. 24. Porter's Lodge. 

2. Old Altazimuth Dome. 25. New Transit Pavilion. 

3. Safe Room. 26. New Altazimuth Pavilion. 

4. Computing Room. 27. Museum : New Building. 

5. Bradley's Transit Room. 28. South Wing 

6. Transit Circle Room. 29. North Wing 

7. Assistants' Room. 30. West Wing 

8. Chief Assistant's Room. 31. East Wing 

9. Computers' Room. 

10. Record Rooms. F. Rooms built for Flamsteed. 

11. Chronometer Rooms and H. Added by H alley. 

South-east Dome. B. Bradley. 

12. Greenhouse and Outbuild- M. Maskelyne. 

ings. A. Airy. 

14. New Library. F'F'. Flamsteed's boundaries. 

15. Magnetic Observatory. M'M'. Maskelyne's 1790. 

16. Offices. P'P'. Pond's 1814. 
19. Sheds. A'A'. Airy's 1837. 
23. Winch Room for Time- A" A". Airy's 1868. 

ball. 



136 THE ROYAL OBSERVATORY 

This * New Observatory/ like the old, and like 
the great South-eastern tower, is an octagon in its 
central portion. But whilst the two other great 
buildings are simply octagonal, here the octagon 
serves only as the centre from which radiate four 
great wings to the four points of the compass. The 
building is by far the largest on the ground, but in 
little accord with the popular idea of an astronomer 
as perpetually looking through a telescope, carries 
but a single dome ; its best rooms being set apart 
as ' computing rooms,' for the use of those members 
of the staff who are employed in the calculations and 
other clerical work, which form, after all, much the 
greater portion of the Observatory routine. 

An observer with the transit instrument, for 
instance, will take only three or four minutes to make 
a complete determination of the place of a single 
star. But that observation will furnish work to the 
computers for many hours afterwards. Or, to take 
a photograph of the sun will occupy about five 
minutes in setting the instrument, whilst the actual 
exposure will take but the one-thousandth part of a 
second. But the plate, once exposed, will have to 
be developed, fixed, and washed ; then measured, and 
the measures reduced, and, on the average, will provide 
one person with work for four days before the final 
results have been printed and published. 

It is easy to see, then, that observing, though the 
first duty of the Observatory, makes the smallest 
demand on its time. The visitor who comes to the 
Observatory by day (and none are permitted to do 
so by night) finds the official rooms not unlike those 



THE OBSERVATORY BUILDINGS 137 

of Somerset House or Whitehall, and its occupants 
for the most part similarly engaged in what is, 
apparently, merely clerical work. An examination 
of the big folios would of course show that instead of 
being ledgers of sales of stamps, or income-tax 
schedules, they referred to stars, planets, and sun- 
spots ; but for one person actively engaged at a 
telescope, the visitor would see a dozen writing or 
computing at a desk. 

The staff, like the building, is the result of a 
gradual development, and bears traces of its life 
history in its composition. First comes the Astrono- 
mer Royal, the representative and successor of the 
original ' King's Astronomer/ the Rev. John Flam- 
steed. But the 'single surly and clumsy labourer/ 
which was all that the ' Merry Monarch* could grant 
for his assistance, is now represented by a large and 
complex body of workers ; each varied class and 
rank of which is a relic of some stage in the progress 
of the Observatory to its present condition. 

The following extract from the Annual Report of 
the Astronomer Royal to the Board of Visitors, June, 
1900, describes the present personnel of the establish- 
ment : 

1 The staff at the present time is thus constituted, the 
names in each class being arranged in alphabetical 
order : 

1 Chief assistants Mr. Cowell, Mr. Dyson. 

1 Assistants Mr. Hollis, Mr. Lewis, Mr. Maunder, Mr. 
Nash, Mr. Thackeray. 

' Second-class assistants Mr. Bryant, Mr. Crommelin. 

1 Clerical assistant Mr. Outhwaite. 

* Established computers Mr. Bovvyer, Mr. Davidson 
Mr. Edney, Mr. Furner, Mr. Rendell, and one vacancy. 



i 3 8 THE ROYAL OBSERVATORY 

1 The two second-class assistants will be replaced by- 
higher grade established computers as vacancies occur. 

* Mr. Dyson and Mr. Cowell have the general superin- 
tendence of all the work of the Observatory. Mr. Maunder 
is charged with the heliographic photography and reduc- 
tions, and with the preparation of the Library Catalogue. 
Mr. Lewis has charge of the time-signals and chrono- 
meters, and of the 28-inch equatorial. Mr. Thackeray 
superintends the miscellaneous astronomical computa- 
tions, including the preparation of the new Ten- Year 
Catalogue. Mr. Hollis has charge of the photographic 
mapping of the heavens, the measurement of the plates, 
and the computations for the Astrographic Catalogue. 
Mr. Crommelin undertakes the altazimuth and Sheep- 
shanks equatorial reductions, and Mr. Bryant the transit 
and meridian zenith distance reductions and time-deter- 
minations. In the magnetic and meteorological branch, 
Mr. Nash has charge of the whole of the work. Mr. Outh- 
waite acts as responsible accountant officer ; has charge of 
the library, records, manuscripts, and stores, and conducts 
the official correspondence. As regards the established 
computers, Mr. Bowyer, Mr. Furner, Mr. Davidson, and 
Mr. Rendell assist Mr. Lewis, Mr. Thackeray, Mr. Hollis, 
and Mr. Bryant respectively, and Mr. Edney assists Mr. 
Nash. 

1 There are at the present time twenty-four supernume- 
rary computers employed at the Observatory, ten being 
attached to the astronomical branch, two the chronometer 
branch, six to the astrographic, one to the heliographic, 
four to the magnetic and meteorological, and one to the 
clerical. 

'A foreman of works, with two carpenters, and two 
labourers ; a skilled mechanic with an assistant ; a gate 
porter, two messengers, a watchman, a gardener, and a 
charwoman, are also attached to the Observatory. 

1 The whole number of persons regularly employed at 
the Observatory is fifty-three.' 

The day work, as said before, is by far the 
greatest in amount, the 'office hours' being from 



THE OBSERVATORY BUILDINGS 139 

nine till half-past four, with an hour's interval. The 
arrangements for the night watches present some 
complications. 

For many years the instruments in regular use 
were two only, the transit circle and the altazimuth. 
The arrangements for observing were simple. Four 
assistants divided the work between them thus : an 
assistant was on duty with the transit circle one day, 
his watch beginning about six a.m. or a little later, 
and ending about three the following morning ; 
a watch of twenty-one hours in maximum length. 
The second day his duties were entirely computa- 
tional, and were only two or three hours in length. 
The third day he had a full day's work on the 
calculations, followed by a night duty with the altazi- 
muth. The latter instrument might give him a very 
easy watch or a terribly severe one. If the moon 
were a young one it was easy, especially if the night 
was clear, as in that case an hour was enough to 
secure the observations required. 

Very different was the case with a full moon, 
especially in the long, often cloudy, nights of winter. 
Then a vigilant watch had to be kept from sunset to 
sunrise, so that in case of a short break in the clouds 
the moon might yet be observed. Such a watch was 
the severest (with one exception) that an assistant 
had to undergo. 

His fourth day would then resemble his second, 
and with the fifth day a second cycle of his quartan 
fever would commence, the symptoms following each 
other in the same sequence as before. 

Such a routine carried on with iron inflexibility 



i 4 o THE ROYAL OBSERVATORY 

was exceedingly trying, as it was absolutely im- 
possible for an observer to keep any regularity in his 
hours of rest or times for meals. 

This routine has been considerably modified by 
the present Astronomer Royal, partly because the 
instruments now in regular daily use are five instead 
of two, and partly because a less stringent system has 
proved not merely far less wearing to the observers, 
but also much more prolific of results. It was im- 
possible for a man to be at his best for long under 
the old regime, and from forty- six to forty-seven has 
been an ordinary age for an assistant to break down 
under the strain. 

One point in which the observing work has been 
lightened has been in the discontinuance of the 
altazimuth observations at the full of the moon, 
another in the shortening of the hours of the transit 
circle watch ; and a further and most important one 
in the arrangement that the observers with the larger 
instruments should have help at their work. The 
net result of these changes has been a most striking 
increase in the amount of work achieved. Thus, 
whilst in the year ending May 20, 1875, 3780 transits 
were taken with the transit circle, and 3636 deter- 
minations of north polar distance ; in that ending- 
May 10, 1895, the numbers had risen to 11,240 and 
11,006 respectively, the telescope remaining precisely 
the same. 

One principle of Airy's rule still remains. So far 
as possible no observer is on duty for two consecutive 
days, but a long day of desk work and observing is 
followed by a short day of desk work without 
observing. 



THE OBSERVATORY BUILDINGS 141 

It will be readily understood that with five 
principal telescopes in constant work and one or two 
minor ones, some demanding two observers, others 
only one, each telescope having its special programme 
and its special hours of work, whilst by no means 
every member of the staff is authorized to observe 
with all instruments indifferently, it becomes a some- 
what intricate matter to arrange the weekly rota in 
strict accordance with the foregoing principle, and 
with the further one, that whilst a considerable 
amount of Sunday observing is inevitable, the average 
duty of an observer should be three days a week, 
not seven days a fortnight. There is a story, re- 
ceived with much reserve at Cambridge, that there 
was once a man at that university who had mastered 
all the colours and combinations of shades and 
colours of the various colleges and clubs. If so 
gifted a being ever existed, he may be paralleled by 
the Greenwich assistant who can predict for any 
future epoch the sequence of duties throughout the 
entire establishment. At any rate, one of the first 
items in the week's programme is the preparation of 
the rota for the week, or rather, to use an ecclesi- 
astical term, for the ' octave,' i.e. from the Monday 
to the Monday following. 

The special work to be carried out on any tele- 
scope is likewise a matter of programme. For the 
transit circle a list of the most important objects to 
be observed is supplied for the observer's use, and 
the general lines upon which the other stars are to 
be selected from a huge ' Working Catalogue ' are 
well understood. With some of the other telescopes 



142 THE ROYAL OBSERVATORY 

the principles upon which the objects are to be 
selected are laid down, but the actual choice is left to 
the discretion of the observer at the time. There is 
no time for the watcher to spend in what the out- 
sider would regard as ' discovery ' ; such as sweeping 
for comets or asteroids, hunting for variable stars, 
sketching planets, and so forth. Indeed, there is a 
story current in the Observatory that some fifty 
years ago, when the tide of asteroid discovery 
first set in, Airy found an assistant, since famous, 
working with a telescope on his ' off-duty ' night. 
That stern disciplinarian asked what business the 
assistant had to be there on his free night, and on 
being told he was 'searching for new planets/ he 
was severely reprimanded and ordered to discontinue 
at once. A similar energy would not meet so gruff 
a discouragement to-day ; but the routine work so 
fully occupies both staff and telescopes that an 
assistant may be most thoroughly devoted to his 
science, and yet pass a decade at the Observatory 
without ever seeing those show places ' of the sky 
which an amateur would have run over in the first 
week after receiving his telescope. For example, 
there is no refractor in the British Isles so competent 
to bring out the vivid green light of the great Orion 
nebula that marvellous mass of glowing, curdling, 
emerald cloud or the indescribable magnificence 
of the myriad suns that cluster like swarming bees 
or the grapes of Eshcol in the constellation of 
Hercules ; yet probably most of the staff have 
never seen either spectacle through it. The pro- 
fessional astronomer who is worth his salt will find 



THE OBSERVATORY BUILDINGS 143 

abundance of charm and interest in his work, but he 
will not, 

' Like a girl, 
Valuing the giddy pleasures of the eyes,' 

consider the charm to lie mainly in the occasional 
sight of wonderful beauty which his work may bring 
to him, nor the interest in some chance phenomenon 
which may make his name known. 

It is not every field of astronomy that is cultivated 
at Greenwich. The search for comets and for * pocket 
planets ' forms no part of its programme ; and the 
occupation so fascinating to those who take it up, of 
drawing the details on the surfaces of the moon, 
Mars, Jupiter, or Saturn, has been but little followed. 
Such work is here incidental, not fundamental, and 
the same may be said of certain spectroscopic 
observations of new or variable stars, and of many 
similar subjects. Work such as this is most interest- 
ing to the general public, and is followed with much 
devotion by many amateur astronomers. For that 
very reason it does not form an integral part of the 
programme of our State observatory. But work 
which is necessary for the general good, or for the 
advancement of the science, and which demands 
observations carried on continuously for many years, 
and strict unity of instruments and methods, cannot 
possibly be left to chance individual zeal, and is 
therefore rightly made the first object at Green- 
wich. 

Those striking discoveries which from time to 
time appeal strongly to the popular imagination, 



144 THE ROYAL OBSERVATORY 

and which have rendered so justly famous some of 
the great observatories of the sister continent, have 
not often been made here. 

Its work has, none the less, been not only useful 
but essential. A century ago, when we were engaged 
in the hand-to-hand struggle with Napoleon, by far 
the most brilliant part of that naval war which we 
waged against the French, and the most productive 
of prize-money, was carried on by our cruisers, who 
captured valuable prizes in every sea. But a much 
greater service, indeed an absolutely vital one, was 
rendered to the State by those line-of-battle ships 
which were told off to watch the harbours wherein 
the French fleet was taking refuge. This was a 
work void of the excitement, interest, and profit of 
cruising. It was monotonous, wearing, and almost 
inglorious, but absolutely necessary to the very 
existence of England. So the continuance for more 
than two centuries of daily observations of places 
of moon, stars, and planets is likewise monotonous, 
wearing, and almost inglorious ; ' the one compensa- 
tion is that it is essential to the life of astronomy. 

The eight Astronomers Royal have, as already 
said, kept the Observatory strictly on the lines 
originally laid down for it, subject, of course, to that 
enlargement which the growth of the science has 
inevitably brought. But had they been inclined to 
change its course, the Board of Visitors has been 
specially appointed to bring them back to the right 
way. As already mentioned in the account of 
Flamsteed, the Board dates from 1710, when it 
practically consisted of the President and Council 



THE OBSERVATORY BUILDINGS 145 

of the Royal Society. Its Royal warrant lapsed on 
the death of Queen Anne, and was not renewed at 
the accession of the two following sovereigns ; but 
in the reign of George III. a new warrant was issued 
under date February 22, 1765 ; and this was renewed 
at the accession of George IV. When William IV. 
came to the throne, the constitution of the Board 
was extended, so as to give a representation to the 
new Royal Astronomical Society, founded in 1820. 
The President of the Royal Society is still chair- 
man of the Board, but the Admiralty, of which the 
Observatory is a department, the two Universities 
of Oxford and Cambridge, and the Royal Astro- 
nomical Society are all represented on it by ex 
officio members, and twelve other members are 
contributed by the Royal and Royal Astronomical 
Societies respectively, six by each. The first Satur- 
day in June is the appointed day for the annual 
inspection by the Board, and for the presentation 
to it of the Astronomer Royal's Report. To this 
all-important business meeting has been added 
something of a social function, by the invitation of 
many well-known astronomers and the leading men 
of the allied sciences to inspect the results of the 
year, and to partake of the chocolate and cracknels, 
which have been the traditional refreshments offered 
on these occasions for a period ' whereof the memory 
of man runneth not to the contrary.' 



CHAPTER VI 

THE TIME DEPARTMENT 

One day two Scotchmen stood just outside the main 
entrance of Greenwich Observatory, looking intently 
at the great twenty-four-hour clock, which is such an 
object of attention to the passers through the Park. 
4 Jock,' said one of them to the other, 'd'ye ken whaur 
ye are?' Jock admitted his ignorance. 'Ye are at 
the vara ceentre of the airth.' 

Geographers tell us that there is a sense in which 
this statement as it stands may be accepted as true. 
For if the surface of the globe be divided into two 
hemispheres, so related to each other that the one 
contains as much land as possible, and the other as 
little, then London will occupy the centre or there- 
abouts of the hemisphere with most land. 

This was not, however, what the Scotchman 
meant. He meant to tell his companion that he was 
standing on the prime meridian of the world, the 
imaginary base line from which all distances, east or 
west, are reckoned ; in short, that he was on ' Longi- 
tude Nought.' 

He was not absolutely correct, however, for the 
great twenty-four-hour clock does not mark the exact 

146 



THE TIME DEPARTMENT 



M7 



meridian of Greenwich. To find the instrument 
which marks it out and defines it we must step inside 
the Observatory precincts, and just within the gate 
we see before us on the left hand a door which leads 




THE GREAT CLOCK AND PORTER'S LODGE. 

{From a photograph by Mr. Lacey.) 



through a little lobby straight into the most important 
room of the whole Observatory the Transit Room. 

This room is not well adapted for representation 
by artist or photographer. Four broad stone pillars 



148 THE ROYAL OBSERVATORY 

occupy the greater part of the space, and leave little 
more than mere passage room beside. Two of these 
pillars are tall, as well as broad and massive, and 
stand east and west of the centre of the room, 
carrying between them the fundamental instrument 
of the Observatory, the transit circle. The optical 
axis of this telescope marks ' Longitude Nought,' 
which is further continued by a pair of telescopes, 
one to the north of it, the other to the south, mounted 
on the third and fourth of the pillars alluded to 
above. 

This room has not always marked the meridian 
of Greenwich, for it stands outside the original 
boundary of the Observatory. But it is only a few 
feet to the east of the first transit instrument which 
was set up by Halley, the second Astronomer Royal, 
in the extreme N.-W. corner of the Observatory 
domain, a distance equivalent to very much less than 
one-tenth of a second of time, an utterly insensible 
quantity with the instruments of two hundred years 
ago. 

It would be a long story to tell in detail how the 
Greenwich transit room has come to define one of 
the two fundamental lines that encircle the earth. 
The other, the equator, is fixed for us by the earth 
itself, and is independent of any political considera- 
tions, or of any effort or enterprise of man. But of 
all the infinite number of great circles which could be 
drawn at right angles to the equator, and passing 
through the north and south poles, it was not easy to 
select one with such an overwhelming amount of 
argument in its favour as to obtain a practically 



THE TIME DEPARTMENT 149 

universal acceptance. The meridians of Jerusalem 
and of Rome have both been urged, upon what we 
may call religious or sentimental grounds ; that of 
the Great Pyramid at Ghizeh has been pressed in 
accordance with the fantastic delusion that the 
Pyramid was erected under Divine inspiration and 
direction ; that of Ferro, in the Canaries, as being an 
oceanic station, well to the west of the Old World, 
and as giving a base line without preference or 
distinction for one nation rather than another. 

The actual decision has been made upon no such 
grounds as these. It has been one of pure practical 
convenience, and has resulted from the amazing 
growth of Great Britain as a naval and commercial 
power. Like Tyre of old, she is situate at the entry 
of the sea, a merchant of the people for many isles/ 
and ' her merchants are the great men of the earth.' 
To tell in full, therefore, the. steps by which the 
Greenwich meridian has overcome all others is 
practically to tell again, from a different standpoint, 
the story of the expansion of England.' The need 
for a supreme navy, the development of our empire 
beyond the seven seas, the vast increase of our 
carrying trade these have made it necessary that 
Englishmen should be well supplied with maps and 
charts. The hydrographic and geographic surveys 
carried on, either officially by this country, or by 
Englishmen in their own private capacity, have been 
so numerous, complete, and far-reaching as not only 
to outweigh those of all other countries put together, 
but to induce the surveyors and explorers of not a 
few other countries to adopt in their work the same 



150 THE ROYAL OBSERVATORY 

prime meridian as that which they found in the 
British charts of regions bordering on those which they 
were themselves studying. Naturally, the meridian 
of Greenwich has not only been adopted for Great 
Britain, but also for the British possessions over-sea, 
and, from these, for a large number of foreign countries; 
whilst our American cousins retain it, an historic relic 
of their former political connection with us. The 
victories of Clive at Arcot and Plassy, of Nelson at 
the Nile and Trafalgar, the voyages and surveys of 
Cook and Flinders, and many more ; the explorations 
of Bruce, Park, Livingstone, Speke, Cameron, and 
Stanley ; these are some of the agencies which have 
tended to fix 'Longitude Nought' in the Greenwich 
Transit Room. 

There are two somewhat different senses in which 
the meridian of Greenwich is the standard meridian 
for nearly the entire world. The first is the sense 
about which we have already been speaking ; it 
constitutes the fundamental line whence distances 
east and west are measured, just as distances north 
and south are measured from the equator. But there 
is another, though related sense, in which it has 
become the standard. It gives the time to the world. 

There are few questions more frequently put than, 
* What time is it ? ' Can you tell me the true 
time ? ' A stickler for exactitude might reply, ' What 
kind of time do you mean ? ' ' Do you mean solar 
or sidereal time ? ' 'Apparent time or mean time ? ' 
' Local time or standard time ? ' There are all these 
six kinds of time, but it is only within the last two 
generations, within, indeed, the reign of our Sovereign, 



THE TIME DEPARTMENT 151 

Queen Victoria, that the subject of the differences of 
most of these kinds of time has become of pressing 
importance to any but theorists. 

In one of the public gardens of Paris a little 
cannon is set up with a burning-glass attached to it 
in such a manner that the sun itself fires the cannon 
as it reaches the meridian. This, of course, is the 
time of Paris noon apparent noon but it would be 
exceedingly imprudent of any traveller through Paris 
who wished, say, to catch the one o'clock express, 
to set his watch by the gun. For if it happened to 
be in February, he would find when he reached the 
railway station that the station clock was faster than 
the sun by nearly a full quarter of an hour, and that 
his train had gone ; whilst towards the end of October 
or the beginning of November, he would find himself 
as much too soon. 

Until machines for accurately measuring time 
were invented, apparent time time, that is to say, 
given by the sun itself, as by a sun-dial was the 
only time about which men knew or cared. But 
when reasonably good clocks and watches were made, 
it was very soon seen that at different times in the 
year there was a marked difference between sun-dial 
time and that shown by the clock, the reason being 
simply that the apparent rate of motion of the sun 
across the sky was not always quite the same, whilst 
the movement of the clock was, of course, as regular 
as it could be made. 

This difference between time as shown by the 
actual sun and by a perfect clock is known as the 
1 equation of time.' It is least about April 1 5, June 15. 



152 THE ROYAL OBSERVATORY 

August 31, and December 25. It is greatest, the sun 
being after the clock, about February 1 1 ; and the sun 
being before the clock, about November 2. Flamsteed, 
before he became Astronomer Royal, investigated the 
question, and so clearly demonstrated the existence, 
cause, and amount of the equation of time as entirely 
to put an end to controversy on the subject. 

We had thus, early in the century, the two kinds 
of time in common use, apparent time and mean time, 
or clock time. But as the sun can only be on one 
particular meridian at any given instant, the time as 
shown by the clocks in one particular town will differ 
from that of another town several miles to the east 
or west of it. It is thus noon at Moscow 1 hr. 36 min. 
before it is noon at Berlin, and noon at Berlin 54 min. 
before it is noon in London. 

This was all well enough known, but occasioned 
no inconvenience until the introduction of railway 
travelling ; then a curious difficulty arose. Suppose 
an express train was running at the rate of sixty 
miles an hour from London to Bristol. The guard 
of the train sets his watch to London time before he 
leaves Paddington, but if the various towns through 
which the train passes, Reading, Swindon, etc., each 
keep their own local time, he will find his watch 
apparently fast at each place he reaches ; but on his 
return journey, if he sets to Bristol time before starting, 
he will in a similar way find it apparently slow by 
the Swindon, Reading, and Paddington clocks as he 
reaches them in succession. 

It became at once necessary to settle upon one 
uniform system of time for use in the railway guides. 



THE TIME DEPARTMENT 153 

Apart from this, a passenger taking train, say, at 
Swindon, might have been very troubled to know 
whether the advertised time of his train was that of 
Exeter, the place whence it started, or Swindon, the 
station where he was getting in, or London, its 
destination. ' Railway time/ therefore, was very 
early fixed for the whole of Great Britain to be the 
same as London time, which is, of course, time as 
determined at Greenwich Observatory. At first it 
was the custom to keep at the various stations two 
clocks, one showing local time, the other l railway,' or 
Greenwich time, or else the clocks would be provided 
with a double minute hand, one branch of which 
pointed to the time of the place, the other to the time 
of Greenwich. 

It was soon found, however, that there was no 
sufficient reason for keeping up local time. Even in 
the extreme West of England the difference between 
the two only amounted to twenty-three minutes, and 
it was found that no practical inconvenience resulted 
from saying that the sun rose at twenty-three minutes 
past six on March 22, rather than at six o'clock. 
The hours of work and business were practically put 
twenty-three minutes earlier in the day, a change of 
which very few people took any notice. 

Other countries besides England felt the same 
difficulty, and solved it in the same way, each country 
as a rule taking as its standard time the time of its 
own chief city. 

There were two countries for which this expedient 
was not sufficient the United States and Canada. 
The question was of no importance until the iron 



154 THE ROYAL OBSERVATORY 

road had linked the Atlantic to the Pacific in both 
countries. Then it became pressing. No fewer than 
seventy different standards prevailed in the United 
States only some twenty years ago. The case was 
a very different one here from that of England, where 
east and west differed in local time by only a little 
over twenty minutes. In North America, in the 
extreme case, the difference amounted to four hours, 
and it seemed asking too much of men to call eight 
o'clock in their morning, or it might be four o'clock 
in their afternoon, their noonday. 

The device was therefore adopted of keeping the 
minutes and seconds the same for all places right 
across the continent, but of changing the hour at 
every 15 of longitude. The question then arose 
what longitude should be adopted as the standard. 
The Americans might very naturally have taken their 
standard time from their great national observatory 
at Washington, or from that of their chief city, New 
York, or of their principal central city, Chicago. But, 
guided partly no doubt by a desire to have their 
standard times correspond directly to the longitudes 
of their maps, and partly from a desire to fall in, if 
possible, with some universal time scheme, if such 
could be brought forward, they fixed upon the 
meridian of Greenwich as their ultimate reference 
line, and defined their various hour standards as 
being exactly so many hours slow of Greenwich mean 
time. 

The decision of the United States and of Canada 
brought with it later a similar decision on the part of 
all the principal States of Europe ; and Greenwich is 



THE TIME DEPARTMENT 



155 



not only 'Longitude Nought' for the bulk of the 
civilized world, but Greenwich mean time, increased 
or decreased by an exact number of hours or half- 
hours, is the standard time all over the planet. 

No ; the statement requires correction. Two 
countries hold out, both close to our own doors. 
France, instead of adopting Greenwich time as such, 
adopts Paris timeless 9 m. 21 s. (that being the precise 
difference in longitude between the two national 
observatories). Ireland disdains even such a veiled 
surrender, and Dublin time is the only one recognized 
from the Hill of Howth to far Valentia. So the 
distressful country preserves her old grievance, that 
she does not even get her time until after England 
has been served. 

The alteration in national habits following on the 
adoption of this European system has had a very 
perceptible effect in some cases. Thus, Switzerland 
has adopted Mid-European time, one hour fast of 
Greenwich ; the true local time for Berne being just 
half an hour later. The result of putting the working 
hours this thirty minutes earlier in the day has had 
such a noticeable effect on the consumption of gas, as 
to lead the gas company to contemplate agitating for 
a return to the old system. 

Thus, Greenwich time, as well as the Greenwich 
meridian, has practically been adopted the world over. 

It follows, then, that the determination of time is 
the most important duty of the Royal Observatory ; 
and the Time Department, the one to which is 
entrusted the duty of determining, keeping, and 
distributing the time, calls for the first attention. 



156 THE ROYAL OBSERVATORY 

Entering the transit room, the first thing that 
strikes the visitor is the extreme solidity with which 
the great telescope is mounted. It turns but in one 
plane, that of ' longitude nought/ and its pivots are 
supported by the pair of great stone pillars which we 
have already spoken of as occupying the principal 
part of the transit-room area, and the foundations 
of which go deep down under the surface of the hill. 
On the west side of the telescope, and rigidly 
connected with it, is a large wheel some six feet in 
diameter, and with a number of wooden handles 
attached to it, resembling the steering-wheel of a large 
steamer. This wheel carries the setting circle, which 
is engraved upon a band of silver let into its face 
near its circumference, a similar circle being at the 
back of the wheel nearer the pillar. Eleven micro- 
scopes, of which only seven are ordinarily used, 
penetrate through the pier, and are directed on to 
this second circle. 

The present transit is the fourth which the 
Observatory has possessed, and its three predecessors, 
known as Halley's, Bradley's, and Troughton's, 
respectively, are still preserved and hang on the walls 
of the transit room, affording by their comparison 
an interesting object-lesson in the evolution of a 
modern astronomical instrument. 

The watcher who wishes to observe the passing of 
a star must note two things : he must know in what 
direction to point his telescope, and at what time to 
look for the star. Then, about two minutes before 
the appointed time, he takes his place at the eye- 
piece. As he looks in he sees a number of vertical 



THE TIME DEPARTMENT 157 

lines across his field of view. These are spider- 
threads placed in the focus of the eye-piece. Pre- 
sently, as he looks, a bright point of silver light, often 
surrounded by little flashing, vibrating rays of colour, 
comes moving quickly, steadily onward * swims 
into his ken,' as the poet has it. The watcher's hand 
seeks the side of the telescope till his finger finds a 
little button, over which it poises itself to strike. On 
comes the star, 'without haste, without rest/ till it 
reaches one of the gleaming threads. Tap ! The 
watcher's finger falls sharply on the button. Some 
three or four seconds later and the star has reached 
another 'wire/ as the spider-threads are commonly 
called. Tap ! Again the button is struck. Another 
brief interval and the third wire is reached, and so on, 
until ten wires have been passed, and the transit is 
over. The intervals are not, however, all the same, 
the ten wires being grouped into three sets, two of 
three apiece, and the third of four. 

Each tap of the observer's finger completed for an 
instant an electric circuit, and recorded a mark on the 
1 chronograph.' This is a large metal cylinder covered 
with paper, and turned by a carefully-regulated clock 
once in every two minutes. Once in every two 
seconds a similar mark was made by a current sent 
by means of the standard sidereal clock of the 
Observatory. The paper cover of the chronograph 
after an hour's work shows a spiral trace of little dots 
encircling it some thirty times. These dots are at 
regular intervals, about an inch apart, and are the 
marks made by the clock. Interspersed between 
them are certain other dots, in sets of ten ; and these 



158 THE ROYAL OBSERVATORY 

are the signals sent from the telescope by the transit 




THE CHRONOGRAPH. 



observer. If, then, one of the clock dots and one of 
the observer's dots come exactly side by side, we 



THE TIME DEPARTMENT 159 

know that the star was on one of the wires at a given 
precise second. If the observer's dot comes between 
two clock dots, it is easy, by measuring its distance 
from them with a divided scale, to tell the instant the 
star was on the wire to the tenth of a second, or even 
to a smaller fraction. Whilst, since the transit was 
taken over ten wires, and the distance of each wire 
from the centre of the field of view is known, we have 
practically ten separate observations, and the average 
of these will give a much better determination of the 
time of transit than a single one would. 

But let the watcher be ever so little too slow in 
setting his telescope, or ever so little late in placing 
himself at his eye-piece, and the star will have passed 
the wire, and as it smoothly, resistlessly moves on its 
inexorable way, will tell the tardy watcher in a 
language there is no mistaking, * Lost moments can 
never be recalled.' The opportunity let slip, not 
until twenty-four hours have gone by will another 
chance come of observing that same star. 

It is the stars that are chiefly used in this deter- 
mination, partly because the stars are so many, whilst 
there is but one sun. If, therefore, clouds cover the 
sun at the important moment of transit, the astronomer 
may well exclaim, so far as this observation is 
concerned, * I have lost a day ! ' The chance will not 
be offered him again until the following noon. But 
if one star is lost by cloud, there are many others, 
and the chance is by no means utterly gone. Beside, 
the sun enables us to tell the time only at noon ; the 
stars enable us to find it at various times throughout 
the entire night ; indeed, throughout both day and 



160 THE ROYAL OBSERVATORY 

night, since the brighter stars can be observed in a 
large telescope even during the day. 

There are two great standard clocks at the 
Observatory : the mean solar clock and the sidereal 
clock. The latter registers twenty-four hours in the 
precise time that the earth rotates on its axis. A 
* day ' in our ordinary use of the term is somewhat 
longer than this ; it is the average time from one 
noon to the next, and as the earth whilst turning 
round on its axis is also travelling round the sun, it 
has to rather more than complete a rotation in order 
to bring the sun again on to the same meridian. A 
solar day is therefore some four minutes longer than 
an actual rotation of the earth, i.e. a sidereal day, as 
it is called, since such rotation brings a star back 
again to the same meridian. 

The sidereal clock can therefore be readily checked 
by the observation of star transits, for the time when 
the star ought to be on the meridian is known. If, 
therefore, the comparison of the transit taps on the 
chronograph with the taps of the sidereal clock show 
that the clock was not indicating this time at the 
instant of the transit, we know the clock must be so 
much fast or slow. Similarly, the difference which 
should be shown between the sidereal and solar 
clocks at any moment is known ; and hence when the 
error of the sidereal clock is known, that of the solar 
can be readily found. 

It is often quite sufficient to know how much a 
clock is wrong without actually setting its hands 
right ; but it is not possible to treat the Greenwich 
clock so, for it controls a number of other clocks 



THE TIME DEPARTMENT 161 

continually, and sends hourly signals out over the 
whole country, by which the clocks and watches all 
over the kingdom are set right. 

In the lower computing room, below the south 
window, we find the Time-Desk, the head-quarters of 
the Time Department. This is a very convenient 
place for the department, since one of the chrono- 
meter rooms, formerly Bradley's transit room, opens 
out of the lower computing room ; the transit instru- 
ment is just beyond ; it is close to the main gate of 
the Observatory, and so convenient for chronometer 
makers or naval officers bringing chronometers or 
coming for them, whilst just across the courtyard is 
the chronograph room, with the Battery Basement, in 
which the batteries for the electric currents are kept, 
and the Mean Solar Clock lobby, with the winch for 
the winding of the time-ball at the head of the stairs 
above it. These rooms do not exhaust the territory 
of the department, since it owns two other chrono- 
meter rooms on the ground floor and first floor 
respectively of the S.-E. tower. 

At the time-desk means are provided for setting 
the clock right very easily and exactly. Just above 
the desk are a range of little dials and bright brass 
knobs, that almost suggest the stops of a great 
organ. 

Two of these little dials are clock faces, electri- 
cally connected with the solar and sidereal standard 
clocks, so that, though these clocks are themselves a 
good way off, in entirely different parts of the Obser- 
vatory, the time superintendent, seated here at the 
time-desk, can see at once what they are indicating. 

L 



1 62 THE ROYAL OBSERVATORY 

Between the two is a dial labelled ' Commutator.' 
From this dial a little handle usually hangs vertically 
downwards, but it can be turned either to the right 
or to the left, and when thus switched hard over, an 
electric current is sent through to the mean solar 
clock. If now we leave the computing room and 
cross the courtyard to the extreme north-west corner, 
we find the Mean Solar Clock in a little lobby, care- 
fully guarded by double doors and double windows 
against rapid changes of temperature. Opening the 
door of the clock case, we see that the pendulum 
carries on its side a long steel bar, and that this bar 
as the pendulum swings passes just over the upper 
end of an electro-magnet. When the current is 
switched on at the commutator, this electro-magnet 
attracts or repels the steel bar according to the 
direction of the current, and the action of the clock 
is accordingly quickened or retarded. To put the 
commutator in action for one minute will alter the 
clock by the tenth of a second. As the error of the 
clock is determined twice a day, shortly before ten 
o'clock in the morning, and shortly before one o'clock 
in the afternoon, its error is always small, usually 
only one or two tenths. These two times are chosen 
because, though time-signals are sent over the metro- 
politan area every hour from the Greenwich clock 
through the medium of the Post Office, at ten and at 
one o'clock signals are also sent to all the great pro- 
vincial centres. Further, at one o'clock the time 
balls at Greenwich and at Deal are dropped, so that 
the captains of ships in the docks, on the river, or in 
the Downs may check their chronometers. 



THE TIME DEPARTMENT 163 

The Time-Ball is dropped directly by the mean 
solar clock itself. It is raised by means of a windlass 
turned by hand-power to the top of its mast just 
before one o'clock. Connected with it is a piston 
working in a stout cylinder. When the ball has 
reached the top of the mast, the piston is lightly 
supported by a pair of catches. These catches are 
pulled back by the hourly signal current, and the 
piston at once falls sharply, bringing the ball with it. 
But after a fall of a few feet, the air compressed by 
the piston acts as a cushion and checks the fall, the 
ball then gently and slowly finishing its descent. 
The instant of the beginning of the fall is, of course, 
the true moment to be noted. 

The other dials on the time-desk are for various 
purposes connected with the signals. One little 
needle in a continual state of agitation shows that 
the electric current connecting the various sympa- 
thetic clocks of the Observatory is in full action. 
Another receives a return signal from various places 
after the despatch of the time-signal from Greenwich, 
and shows that the signal has been properly received 
at the distant station, whilst all the many electric 
wires within the Observatory or radiating from it are 
made to pass through the great key-board, where 
they can be at once tested, disconnected, or joined 
up, as may be required. 

The distribution of Greenwich time over the 
island in this way is thus a simple matter. The far 
more important one of the distribution of Greenwich 
time to ships at sea is more difficult. The difficulty 
lay in the construction of a clock or watch, the rate 



164 



THE ROYAL OBSERVATORY 



of which would not be altered by the uneasy motion 
of a ship, or by the changes of temperature which are 
inevitable on a voyage. Two hundred years ago it 
was not deemed possible to construct a watch of 
anything like sufficient accuracy. They would not 
even keep going whilst they were being wound, and 




THE TIME-DESK. 



would lose or gain as much as a minute in the day 
for a fall or rise of io in temperature. This was 
owing to the extreme sensitiveness of the balance 
spring which takes the place in a watch of a pen- 
dulum in a clock to the effects of temperature. 
The British Government, therefore, in 17 14 offered a 



THE TIME DEPARTMENT 165 

prize of the amount of 20,000 for a means of finding 
the longitude at sea within half a degree, or, in other 
words, for a watch that would keep Greenwich time 
correct to two minutes in a voyage across the 
Atlantic. In 1735, James Harrison, the son of a 
Yorkshire carpenter, succeeded in solving the problem. 
His method was to attach a sort of automatic 




HARRISON'S CHRONOMETER. 



regulator to the spring which should push the 
regulator over in one direction as the temperature 
rose, and bring it back as it fell. This he effected by 
fastening together two strips of brass and steel. The 
brass expanded with heat more rapidly than the 
steel, and hence with a rise of temperature the strip 



166 THE ROYAL OBSERVATORY 

bent over on the steel side. This was the first germ 
of the idea of making watches 'compensated for 
temperature ; ' watches, that is, which maintain prac- 
tically the same rate whether they are in heat or 
cold, an idea now brought to great perfection in the 
modern chronometer. 

The great reward the Government had offered 
stimulated many men to endeavour to solve the 
problem. Of these, Dr. Halley, the second As- 
tronomer Royal, and Graham, the inventor of the 
astronomical clock, were the most celebrated. But 
when Harrison, then poor and unknown, came to 
London in 1735, and laid his invention before them, 
with an utter absence of self-seeking, and in the true 
scientific spirit, they gave him every assistance, 

Harrison's first four time-keepers are still pre- 
served at the Royal Observatory. He did not, 
however, receive his reward until a facsimile of the 
fourth had been made by his apprentice, Larcum 
Kendall. The latter is preserved at the Royal 
Observatory. There is a Larcum Kendall at the 
Royal Institution which is said to have been used by 
Captain Cook. Harrison's chronometer was sent on 
a trial voyage to Jamaica in 1761, and on its return 
to Portsmouth in the following year it was found that 
its complete variation was under the two minutes for 
which the Government had stipulated. 

Since Harrison's day the improvement of the 
chronometer has been carried on almost to perfection, 
and now the care and rating of chronometers for the 
Royal Navy is one of the most important duties of 
the Observatory. 



THE TIME DEPARTMENT 169 

A visitor who should make the attempt to com- 
pare a single chronometer with a standard clock 
would probably feel very disheartened when, after 
many minutes of comparison, he had got out its 
error to the nearest second, were he told that it was 
his duty to compare the entire army here collected, 
some five hundred or more, and to do it not to 
the second, but to the nearest tenth of a second. 
Practice and system make, however, the impossible 
easy, and one assistant will quietly walk round the 
room calling out the error of each chronometer as he 
passes it, as fast as a second assistant seated at the 
table can enter it at his dictation in the chronometer 
ledgers. The seconds beat of a clock sympathetic 
with the solar standard, rings out loud and clear 
above the insect-like chatter of the ticking of the 
hundreds of chronometers, and wherever the assistant 
stands, he has but to lift his eyes to see straight 
before him, if not a complete clock-face, at least a 
seconds dial moving in exact accordance with the 
solar standard. 

The test to which chronometers are subjected is 
not merely one of rate, but one of rate under care- 
fully altered conditions. Thus they may be tried 
with the XII pointing in succession to the four 
points of the compass, or, in the case of chronometer 
watches, they may be laid flat down on the table or 
hung from the ring or pendant, or with the ring right 
or left, as it would be likely to be when carried in 
the waistcoat pocket. But the chief test is the per- 
formance of a chronometer when subjected to con- 
siderable heat for a long period. This is a matter of 



170 THE ROYAL OBSERVATORY 

great consequence, since a chronometer travelling 
from England to India, Australia, or the Cape, would 
necessarily be subjected to very different conditions 
of temperature from those to which it would be ex- 
posed in England. They are therefore kept for eight 
weeks in a closed stove at a temperature of about 
8 5 or 90 . At one time a cold test was also applied, 
and Sir George Airy, the late Astronomer Royal, in 
one of his popular lectures, drew a humorous com- 
parison between the unhappy chronometers thus 
doomed to trial, now in heat and now in frost, and 
the lost spirits whom Dante describes as alternately 
plunged in flame and ice. The cold test has, how- 
ever, been done away with. It is perfectly easy 
on the modern ship to keep the chronometer com- 
fortably warm even on an Arctic expedition. The 
elaborate cold testing applied to Sir George Nares' 
chronometers before he started on his polar journey 
was found to have been practically quite superfluous ; 
the chronometers were, if anything, kept rather too 
warm. The exposure of the chronometer in the 
cooling box, moreover, was found to be attended 
with a risk of rusting its springs. 

Once the determination of the longitude at sea 
became possible, it was clearly the next duty to fix 
with precision the position of the principal places, 
cities, ports, capes, islands, the world over. Of all the 
work done in this department none has ever been done 
better, in proportion to the means at command, than 
that accomplished by Captain Cook in his celebrated 
three voyages. As has already been pointed out, it 
is the extent and thoroughness of the hydrographic 



THE TIME DEPARTMENT 173 

surveys of the British Admiralty which have largely 
contributed to the honour done to England by the 
international selection of the English meridian, and 
of English standard time, as in principle those for the 
whole civilized world. The generosity and public 
spirit therefore which led the second Astronomer 
Royal to help forward and support his rival, has 
almost directly led to this great distinction accruing 
to the Observatory of which he was the head. 

Three different methods have successively been 
used in the determination of longitudes of distant 
places. In each case the problem required was to 
ascertain the time at the standard place, say Greenwich, 
at the same time that it was being determined in the 
ordinary way at the given station. One method of 
ascertaining Greenwich time when at a distance from 
it was, as stated in Chapter I., to use the moon, as it 
were, as the hand of a vast clock, of which the sky 
was the face and the stars the dial figures. This is 
the method of ' lunar distances,' the distances of the 
moon from a certain number of bright stars being 
given in the Nautical Almanac for every three hours 
of Greenwich time. 

As chronometers were brought to a greater point 
of perfection, it was found easier and better in many 
cases to use ' chronometer runs,' that is, to carry back- 
wards and forwards between the two stations a 
number of good chronometers, and by constant com- 
parison and re-comparison to get over the errors 
which might attach to any one of them. 

But of late years another method has proved 
available. Distant nations are now woven together 



174 



THE ROYAL OBSERVATORY 



across thousands of miles of ocean by the submarine 
telegraph. The American reads in his morning paper 
a summary of the debates of the previous night in 
the House of Commons at Westminster. The 
Londoner watches with interest the scores of the 
English cricket team in Australia. It is now there- 
fore possible for an astronomer in England to record, 




THE TRANSIT PAVILION. 

{From a photograph by Mr. Lacey.) 

should he so desire, the time of the transit of a star 
across the wires of his instrument, not only on his 
own chronograph, but upon that of another observa- 
tory, it may be 2000 miles away. Or, much more 
conveniently, each observer may independently deter- 
mine the error of his own clock, and then bring his 



THE TIME DEPARTMENT 175 

clock into the current, so that it may send a signal 
to the chronograph of the other station. 

In one way or another this work of the deter- 
mination of geographical longitudes has been an 
important part of the extra-routine work at Greenwich, 
part of the work which has built up and sustained its 
claim to define ' longitude nought ' ; and many 
distinguished astronomers, especially from the leading 
observatories of the Continent, have come here from 
time to time to obtain more accurately the longitude 
of their own cities. The traces of their visits may be 
seen here and there about the Observatory grounds 
in flat stones which lie level with the surface, and 
bear a name and date like the gravestones in some 
old country churchyard. These are not, as one might 
suppose, to mark the burial-places of deceased as- 
tronomers, but record the sites where, on their visits 
for longitude purposes, different foreign astronomers 
have set up their transit instruments. Now^ how- 
ever, a permanent pier has been erected in the court- 
yard, and a neat house the Transit Pavilion built 
over it, so that in all probability no fresh additions 
will be made to these sepulchral-looking little monu- 
ments. 

It might be asked, What reason is there for a 
foreign observer to come over to England for such 
a purpose? Would it not be sufficient for the clock 
signals to be exchanged ? But a curious little fact 
has come out with the increase of accuracy of transit 
observation, and that is, that each observer has his 
own particular habit or method of observation. A 
hundred years ago, Maskelyne, the fifth Astronomer 



T76 THE ROYAL OBSERVATORY 

Royal, was greatly disturbed to find that his assistant, 
David Kinnebrook, constantly and regularly observed 
a star-transit a little later than he did himself. The 
offender was scolded, warned, exhorted, and finally, 
when all proved useless to bring his observations into 
exact agreement with the Astronomer Royal's, dis- 
missed as an incompetent observer. As a matter of 
fact, poor Kinnebrook has a right to be regarded as 
one of the martyrs of science, and Maskelyne, by this 
most natural but mistaken judgment, missed the 
chance of making an important discovery, which was 
not made until some thirty years later. Astronomers 
now would be more cautious of concluding that 
observations were bad simply because they differed 
from what had been expected. They have learnt 
by experience that these unexpected differences are 
the most likely hunting-ground in which to look for 
new discoveries. 

In a modern transit observation with the use of 
the chronograph it will be seen at once that before 
the observer can register a star-transit on the chrono- 
graph, he has to perceive with his eye that the star 
has reached the wire, he has to mentally recognize 
the fact, and consciously or unconsciously to exert 
the effort of will necessary to bring his finger down 
on the button. A very slight knowledge of character 
will show that this will require different periods of 
time for different people. It will be but a fraction 
of a second in any case, but there will be a distinct 
difference, a constant difference, between the eager, 
quick, impulsive man who habitually anticipates, 
as it were, the instant when he sees star and wire 



THE TIME DEPARTMENT 177 

together, and the phlegmatic, slow-and-sure man who 
carefully waits till he is quite sure that the contact 
has taken place, and then deliberately and firmly 
records it. These differences are so truly personal 
to the observer that it is quite possible to correct 
for them, and after a given observer's habit has 
become known, to reduce his transit times to those 
of some standard observer. It must, of course, be 
remembered that this ' personal equation ' is an 
exceedingly minute quantity, and in most cases is 
rather a question of hundredths of seconds than of 
tenths. 

It will be seen from the foregoing description how 
little of what may be termed the picturesque or 
sensational side of astronomy enters into the routine 
of the Time Department, the most important of all 
the departments of the Observatory. The daily 
observation of sun and of many stars selected from 
a carefully chosen list of some hundreds, and known 
as 'clock stars' the determination of the error of 
the standard clock to the hundredth of a second if 
possible, and its correction twice a day, the sending 
out of time signals to the General Post Office and 
other places, whence they are distributed all over the 
country ; the care, winding, and rating of hundreds 
of chronometers and chronometer watches, and from 
time to time the determination of the longitude of 
foreign or colonial cities, make up a heavy, ceaseless 
routine in which there is little opportunity for the 
realization of an astronomer's life as it is apt to be 
popularly conceived. 

Yet there is interest enough in the work. There 

M 



178 THE ROYAL OBSERVATORY 

is the charm which always attaches to work of 
precision, the delight of using delicate and exact 
instruments, and of obtaining results of steadily 
increasing perfection. It may be akin to the sport- 
ing passion for record-breaking, but surely it is a 
noble form of it which has led the assistants, in 
recent years, to steadily increase the number of 
observations in a normal night's work up to the 
very limit, taking care the while that their accuracy 
has in no degree suffered. In longitude work also 
'the better is the enemy of the good,' and there is 
the ambition that each fresh determination shall be 
markedly more precise than all that have preceded it. 
The constant care of chronometers soon reveals a 
kind of individuality in them which forms a fresh 
source of interest, whilst if a man has but a spark 
of imagination, how easily he will wrap them round 
with a halo of romance ! 

Glance through the ledgers, and you will see how 
some of them have heard the guns at the siege of 
Alexandria, others have been carried far into the 
frozen north, others have wandered with Livingstone 
or Cameron in the trackless forests of equatorial 
Africa. 

More striking still are those pages across which 
the closing line has been drawn ; never again will the 
time-keeper there scheduled return to the kindly 
inquisition of Flamsteed Hill. This sailed away in 
the Wasp, and was swallowed up in the eastern 
typhoon ; that went down in the sudden squall that 
smote the Eurydice off the Isle of Wight ; these 
foundered with the Captain. The last fatal journey 



THE TIME DEPARTMENT 



179 



of Sir John Franklin to find the North- West Passage 
leaves its record here ; the chronometers of the 
Erebus and Terror will never again appear on the 
Greenwich muster roll. Land exploration claims 
its victims too. Sturt's ill-fated expedition across 
Australia, and Livingstone's last wandering, are 
represented. 

Sometimes an amusing entry interrupts the silent 



I * 



^-y** 



\-. ... -\ 




















4. 




,,,..,..^ 






5 - 


' 




U./ -/ 


'* 


'^.. 


,/ " 


| 



//Atf A 



LOST IN THE BIRKENHEAD. 



pathos of these closed pages. ' Lost by Mr. Smith 
on the coast of Africa/ reads at first sight like a 
rather thin attempt of some one to shift the responsi- 
bility of his own carelessness on to the broad 
shoulders of Mr. Nobody. In reality it probably 
gives a hint of the necessary, dangerous, and exciting 
work of slave-dhow chasing which gives employment 



180 THE ROYAL OBSERVATORY 

to our ships on the African coast. ' Mr. Smith ' was 
no doubt a petty officer who was told off to carry 
the chronometer for a boat's crew sent to search for 
a slave-dhow up some equatorial estuary. Probably 
the dhow was found, and the Arabs who manned it 
gave so stout a resistance that Mr, Smith ' and his 
men had other things to do than take care of 
chronometers before they could overcome them. 
We may take it that the real story outlined here was 
one of courage and hard fighting, not of carelessness 
and shirking. 

Stories of higher valour and nobler courage yet 
are also hinted : the calm discipline of the crew of 
the Victoria as she sank from the ram of the Camper- 
down, the yet nobler devotion of the men of the 
Birkenhead, as they formed up in line on deck and 
cheered the boats that bore away the women and 
children to safety, whilst they themselves went down 
with the ship into the shark-crowded sea. 

1 There rose no murmur from the ranks, no thought 

By shameful strength, unhonoured life to seek ; 
Our post to quit we were not trained, nor taught 
To trample down the weak. 

' What followed, why recall ? The brave who died 

Died without flinching in that bloody surf. 
They sleep as well beneath that purple tide 
As others under turf.' 



CHAPTER VII 

THE TRANSIT AND CIRCLE DEPARTMENTS 

The determination of time is a duty the importance 
of which readily commends itself to the general 
public. It is easy to see that in any civilized country 
it is very necessary to have an accurate standard of 
time. Our railways and telegraphs make it quite 
impossible for us to be content with the rough-and- 
ready sun-dial which satisfied our forefathers. But 
it should be remembered that it was neither to 
establish a ' longitude nought,' nor to create a system 
of standard time, that Greenwich Observatory was 
founded in 1675. It was for ' 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.' 

The two related departments, therefore, those of 
the Transit and the Circle, which are concerned in 
the work of making star-catalogues, come next in 
order to the Time Department. Though both 
departments deal with the same instrument, the 
transit circle, they are at present placed at opposite 
ends of the Observatory domain ; the Circle Depart- 
ment being lodged in the upper computing room 

181 



i8 2 THE ROYAL OBSERVATORY 

of the old building ; the Transit Department in the 
south wing of the New Observatory in the south 
ground. 

It may be asked why, if this were the purpose of 
the Observatory at its foundation, two and a quarter 
centuries ago ; if, as was the case, the work was set 
on foot from the beginning and was carried out with 
every possible care, how comes it that it is still the 
fundamental work of the Observatory, and, instead of 
being completed, has assumed greater proportions at 
the present day than ever before ? 

The answer to this inquiry may be found in a 
special application of the old proverb, originally 
directed against the discontent of man : ' The more 
he has, the more he wants.' For, however paradoxical 
it may seem, it is true that the fuller a star-catalogue 
is, and the more accurate the places of the stars that 
it contains, the greater is the need for a yet fuller 
catalogue, with places more accurate still. 

It is worth while following up this paradox in 
some detail, as it affords a very instructive example 
of the way in which a work started on purely utili- 
tarian grounds extends itself till it crosses the unde- 
fined boundary and enters the region of pure science. 

We have no idea who made the earliest census of 
the sky. It is written for us in no book ; it is not 
even engraved on any monument. And yet no small 
portion of it is in our hands to-day, and, strangest of 
all, we are able to fix fairly closely the time at which 
it was made, and the latitude in which its compiler 
lived. The catalogue is very unlike our star-cata- 
logues of to-day. The places of the stars are very 



TRANSIT AND CIRCLE DEPARTMENTS 183 

roughly indicated ; and yet this catalogue has left a 
more enduring mark than all those that have suc- 
ceeded it. The catalogue simply consists of the star 
names. 

An old lady who had attended a University 
Extension lecture on astronomy was heard to ex- 
claim : ' What wonderful men these astronomers are ! 
I can understand how they can find out how far off 
the stars are, how big they are, and what they weigh 
that is all easy enough ; and I think I can see how 
they find out what they are made of. But there is 
one thing that I can't understand I don't know how 
they can find out what are their names ! ' This same 
difficulty, though with a much deeper meaning than 
the old lady in her simplicity was able to grasp, has 
occurred to many students of astronomy. Many 
have wished to know what was the meaning of, and 
whence were derived, the sonorous names which are 
found attached to all the brighter stars on our celestial 
globes : Adhara, Alderamin, Betelgeuse, Denebola, 
Schedar, Zubeneschamal, and many more. The 
explanation lies here. Some 5000 years ago, a man, 
or college of men, living in latitude 40 north, in 
order that they might better remember the stars, 
associated certain groups of them with certain fancied 
figures, and the individual star names are simply 
Arabic words designed to indicate whereabouts in 
its peculiar figure or constellation that special star 
was situated. Thus Adhara means 'back,' and is 
the name of the bright star in the back of the great 
Dog. Alderamin means ' right arm,' and is the 
brightest star in the right arm of Cepheus, the king. 



1 84 THE ROYAL OBSERVATORY 

Betelgeuse is 'giant's shoulder,' the giant being 
Orion ; Denebola is [ lion's tail.' Schedar is the 
star on the ' breast ' of Cassiopeia, and Zubeneschamal 
is ' northern claw,' that is, of the Scorpion. So far is 
clear enough. The names of the stars for the most 
part explain themselves ; but whence the constella- 
tions derived their names, how it was that so many- 
snakes and fishes and centaurs were pictured out in 
the sky, is a much more difficult problem, and one 
which does not concern us here. 

One point, however, these old constellations do 
tell us, and tell us plainly. They show that the axis 
of the earth, which, as the earth travels round the sun, 
moves parallel with itself, yet, in the course of ages, 
itself rotates so as in a period of some 26,000 years 
to trace out a circle amongst the stars. This is the 
cause of what is called 'precession,' and explains how 
it is that the star we call the pole-star to-day was 
not always the pole-star, nor will always remain so. 
We learn this fact from the circumstance that the 
old constellations do not cover the entire celestial 
sphere. They leave a great circular space of 40 
radius unmapped in the southern heavens. This 
simply means that the originators of the constella- 
tions lived in 40 north latitude, and stars within 40 
of their south pole never rose above their horizon, 
and consequently were never seen, and could not be 
mapped, by them. In like manner, the star census 
taken at Greenwich Observatory does not include 
the whole sky, but leaves a space some 5 2 in radius 
round our south pole. Since the latitude of Green- 
wich is nearly 5 2 north, stars within that distance of 



TRANSIT AND CIRCLE DEPARTMENTS 185 

the south pole do not rise above our horizon, and are 
never seen here. But if we compare the vacant space 
left by the old original constellations with the vacant 
space left by a Greenwich catalogue of to-day, we 
see that the centre of the first space, which must 
have been the south pole of that time, is a long way 
from the centre of the second space our south pole 
of to-day. The difference tells us how far the pole 
has moved since those old forgotten astronomers did 
their work. We know the rate at which the pole 
appears to move, by comparing our more modern 
catalogues one with another ; and so we are able 
to fix pretty nearly the time when lived those old 
first census-takers of the stars, whose names have 
perished so completely, but whose work has proved 
so immortal. 

These old workers gave us the constellation 
groupings and names which still remain to us, and 
are still in common, every-day use. Their work 
affords us the most striking illustration of the result 
of precession, but precession itself was not recognized 
till nearly 3000 years after their day, when a marvel- 
lous genius, Hipparchus, established the fact, and 
1 built himself an everlasting name ' by the creation 
of a catalogue of over 1000 stars prepared on modern 
principles. That catalogue formed the basis of one 
which survives to us at the present time, and was 
made some 1750 years ago by Claudius Ptolemy, 
the great astronomer of Alexandria, whose work, 
which still bears the proud name of Almagest, 'The 
Greatest,' remained for fourteen centuries the one 
universal astronomical text-book. 



186 THE ROYAL OBSERVATORY 

A modern catalogue contains, like that of Ptolemy, 
four columns of entry. The first gives the star's 
designation ; the second an indication of its bright- 
ness ; the third and fourth the determinations of its 
place. These are expressed in two directions, which, 
in modern catalogues, not in Ptolemy's, correspond 
on the celestial sphere to longitude and latitude on 
the terrestrial. Distance north or south of the 
celestial equator is termed 'declination,' correspond- 
ing to terrestrial latitude. Distance in a direction 
parallel to the equator is termed 'right ascension,' 
corresponding to terrestrial longitude. For geo- 
graphical purposes we conceive the earth to be 
encircled by two imaginary lines at right angles to 
each other the one, the equator, marked out for us 
by the earth itself; the other, ' longitude nought,' the 
meridian of Greenwich, fixed for us by general con- 
sent, after the lapse of centuries, by a kind of historical 
evolution. On the celestial globe in like manner 
we have two fundamental lines one, the celestial 
equator, marked out for us by nature ; the other at 
right angles to it, and passing through the poles of 
the sky, adopted as a matter of convenience. But a 
difficulty at once confronts us Where can we fix 
our ' right ascension nought ' ? What star has the 
right to be considered the Greenwich of the sky ? 

The difficulty is met in the following manner : 
For six months of the year, the summer months, the 
sun is north of the celestial equator ; for the other 
six months of the year, the months of winter, it is 
south of it. It crosses the equator, therefore, twice 
in the year once when moving northward at the 



TRANSIT AND CIRCLE DEPARTMENTS 187 

spring equinox ; once when moving southward at 
the equinox of autumn. The point where it crosses 
the equator at the first of these times is taken as the 
fundamental point of the heavens, and the first sign 
of the zodiac, Aries the Ram, is said to begin here, 
and it is called, therefore, ' the first point of Aries.' 

One of the very first facts noticed in the very- 
early days of astronomy was that, as the stars seemed 
to move across the sky night by night, they seemed 
to move in one solid piece, as if they were lamps 
rigidly fixed in one and the same solid vault. Of 
course it has long been perfectly understood that this 
apparent movement was not in the least due to any 
motion of the stars, but simply to the rotation of the 
earth on its axis. This rotation is the smoothest, 
most constant, and regular movement of which we 
know. It follows, therefore, that the interval of time 
between the passage of one star across the meridian 
of Greenwich and that of any other given star is 
always the same. This interval of time is simply the 
difference of their right ascension. If we are able, 
then, to turn our transit instrument to the sun, and 
to a number of stars, each in its proper turn, and by 
pressing the tapping-piece on the instrument as the 
sun or star comes up to each of the ten wires in 
succession, to record the times of its transit on the 
chronograph, we shall have practically determined 
their right ascensions one of the two elements of 
their places. 

The other element, that of declination, is found in 
a different manner. The celestial equator, like the 
terrestrial, is 90 from the pole. The bright star 



188 THE ROYAL OBSERVATORY 

Polaris is not exactly at the north pole, but describes 
a small circle round it. Twice in the twenty-four 
hours it transits across the meridian once when 
going from east to west it passes above the pole, 
once when going from west to east below the pole. 
The mean between these two altitudes of Polaris 
above the horizon gives the position of the true 
pole. 

A complete transit observation of a star consists 
therefore of two operations. The observer, as we 
have already described, sees a star entering the field 
of the telescope, and as it swims forward, he presses 
the galvanic button, which sends a signal to the 
chronograph as the star comes up to each of the ten 
vertical wires in succession. But, beside the ten wires, 
there are others. Two vertical wires lie outside the 
ten of which we have already spoken, and there is 
also a horizontal wire. The latter can be moved by 
a graduated screw-head just above the eye-piece, and 
as the star comes in succession to these two vertical 
wires, this horizontal wire is moved by the screw- 
head, so as to meet the star at the moment it is 
crossing the vertical wire, and the observer presses 
a second little button, which records the position of 
the horizontal wire on a small paper-covered drum. 
Then, the transit over, the observer leaves the tele- 
scope and comes round to the outside of the west 
pier. Here he finds seven large microscopes, which 
pierce the whole thickness of the pier, and are directed 
towards the circumference of a large wheel which is 
rigidly attached to the telescope and revolves with it. 
This whefel is six feet in diameter, and has a silver 




J % 

ml ft 



THE TRANSIT CIRCLE. 




TRANSIT AND CIRCLE DEPARTMENTS 191 

circle upon both faces. Each circle is divided 
extremely carefully into 4320 divisions these 
divisions, therefore, being about the one-twentieth of 
an inch apart. There are, therefore, twelve divisions 
to every degree (12 x 360 = 4320), and each division 
equals five minutes of arc. The lowest microscope is 
the least powerful, and shows a large part of the 
circle, enabling the observer to see at once to what 
degree and division of a degree the microscope is 
pointing. The other six microscopes are very care- 
fully placed 6o apart as equally placed as they 
possibly can be. These microscopes are all fitted 
with movable wires wires moved by a very fine and 
delicate screw ; the screw-head having divisions upon 
it so that the exact amount of its movement can be 
told. Each of the six screw-heads will read to the 
one five-thousandth part of a division of the circle ; 
in other words, to the one hundred thousandth part 
of an inch. Using all six microscopes, and taking 
their mean, we are able to read to the one-hundredth 
of a second of arc. If, therefore, the observations 
could be made with perfect certainty down to the 
extremest nicety of reading which the instrument 
supplies, we should be able to read the declination of 
a star to this degree of refinement. It may be added 
that a halfpenny, at a distance of three miles, appears 
to be one second of arc in diameter ; at three hundred 
miles it would be one-hundredth of a second. It 
need scarcely be said that we cannot observe with 
quite such refinement of exactness as this would 
indicate. Nevertheless, this exactness is one after 
which the observer is constantly striving, and tenths, 



192 THE ROYAL OBSERVATORY 

even hundredths, of seconds of arc are quantities 
which the astronomer cannot now neglect. 

The observer has then to read the heads of all 
these seven microscopes on the pier side, and also 
two positions of the horizontal wire on the screw-head 
at the eye-piece. The following morning he will also 
read off from the chronograph-sheet the times when 
he made the ten taps as the star passed each of the 
ten vertical wires. There are, therefore, nine entries 
to make for one position of a star in declination, and 
ten for one position of a star in right ascension. The 
observer will also have to read the barometer to get 
the pressure of the air at the time of observation, and 
one thermometer inside the transit room, and another 
outside, to get the temperature of the air. In some 
cases thermometers at different heights in the room 
are also read. A complete observation of a single 
star means, therefore, the entry of two-and-twenty 
different numbers. 

It may be asked, What is the use of reading the 
barometer and thermometer? The answer to the 
question can only be given by contradicting a state- 
ment made above, that the true pole lay midway 
between the position of the telescope when pointing 
to the pole-star at its upper transit, and its position 
when pointing to it at its lower transit. The pole 
being very high in the heavens in this country, there 
are a great number of stars that, like the pole-star, 
cross the meridian twice in the twenty-four hours 
once when they pass above the pole, moving from 
east to west, once when they pass below it, moving 
from west to east. As the real distance of a star 



TRANSIT AND CIRCLE DEPARTMENTS 193 

from the true pole does not alter, it follows that we 
ought to get the position of the pole from the mean 
of the two transits of any of these stars, and they 
ought all to exactly agree with each other. But 
they do not. So, too, I said that the stars all appeared 
to move as in a single piece. If, then, we constructed 
an instrument with its axis parallel to the axis of the 
earth, and fixed a telescope to it, pointing to any 
particular star, if we turn the telescope round as fast 
from east to west as the earth itself is turning from 
west to east if we built an equatorial, that is to 
say we ought to find that the star once in the centre 
of the field would remain there. As a matter of fact, 
when the star got near the horizon it would soon be 
a long way from the centre of the field. 

Sir George Airy, the seventh Astronomer Royal, 
makes, with reference to this very point, the following 
remarks : 

' Perhaps you may be surprised to hear me say the rule 
is established as true, and yet there is a departure from it. 
This is the way we go on in science, as in everything else ; 
we have to make out that something is true, then we find 
out under certain circumstances that it is not quite true ; 
and then we have to consider and find out how the 
departure can be explained.' 

In this particular case, the disturbing cause is 
found in the action of our own atmosphere. The 
rays of light from the star are bent out of a perfectly 
straight course as they pass through the various 
layers of that atmosphere, layers which necessarily 
become denser the closer we get to the actual surface 
of the earth. Every celestial body therefore appears 

N 



194 THE ROYAL OBSERVATORY 

to be a little higher in the sky than it really is. This 
action is most noticeable at the horizon, where it 
amounts to about half a degree. As both sun and 
moon are about half a degree in diameter, it follows 
that when they have really just entirely sunk below 
the horizon they appear to be just entirely above it. 
It happens, in consequence, on rare occasions, that an 
eclipse of the moon will take place when both sun 
and moon are together seen above the horizon. 

It was a great matter to discover this effect of 
refraction. It was soon seen that it was not constant, 
that it varied with both temperature and pressure. 
It is, indeed, the most troublesome of all the hindrances 
to exact observation with which the astronomer has 
to contend ; partly because of its large amount half 
a degree, as has been already said, in the extreme 
case and partly because it is difficult in many cases 
to determine its exact effect. 

The double observation with the transit circle 
gives us, then, the place in the sky where the star 
appeared to be at the moment of observation, not its 
true place ; to find that true place we have to cal- 
culate how much refraction had displaced the star 
at the particular height in the sky, and at the 
particular temperature and atmospheric pressure at 
which the observation was made. 

The transit circle is a comparatively recent instru- 
ment. In earlier times the two observations of right 
ascension and declination were entrusted to perfectly 
separate instruments. The transit instrument was 
mounted as the transit circle is, between two solid 
stone piers, and moved in precisely the same way. 



TRANSIT AND CIRCLE DEPARTMENTS 195 

But the great six-foot wheel, which was made as stiff 
as it possibly could be, was mounted on the face of 
a great stone pier or wall, from which circumstance 
it was called the ' mural circle/ and a light telescope 




THE MURAL CIRCLE. 



was attached to it which turned about its centre. 
This arrangement had a double disadvantage that 
the two observations had to be made separately, and 



196 THE ROYAL OBSERVATORY 

the mural circle, not being a symmetrical instrument, 
was liable to small errors which it was difficult to 
detect. Thus, being supported on one side only, a 
flexure or bending outwards of either telescope or 
circle, or both, might be feared. 

It was for this reason that Pond set up a pair of 
mural circles, one on the east side of its supporting 
pier and the other on the west. 1 His plan was not 
only to have each star observed simultaneously in 
the two instruments, a plan by which, at the cost of 
some additional labour, he would have got rid, to a 
large extent, of the individual errors of the two 
separate instruments, inasmuch as, on the whole, it 
might have been expected that the errors of the two 
instruments would have been very nearly equal in 
amount, but of opposite character. The differences, 
too, between the two instruments would have afforded 
the means for tracing these small errors to their 
respective causes, and so ascertaining the laws to 
which they were subject. 

Pond went further still. He added to the mural 
circle a simple instrument, the extreme value of 
which every astronomer recognizes to-day the mer- 
cury trough. Not only was the star to be observed 
by both circles when the two telescopes were pointing 
directly to it, it was also to be observed by reflection ; 
the telescopes were to be pointed down towards a 
basin of mercury, in which the image of the star 
would be seen reflected. The mercury being a 

1 The second circle was intended for the Cape Observatory, 
but Pond obtained leave to retain it. In 185 1 it was transferred 
to the Observatory of Queen's College, Belfast. 



TRANSIT AND CIRCLE DEPARTMENTS 197 

liquid, its surface is perfectly horizontal ; and, since 
the law of reflection is that the angle of incidence is 
equal to the angle of reflection, it follows that the 
telescope, when pointed down toward the mercury 
trough, points just at as great an angle below the 
horizon as, when it is set directly on the star, it 
points above it. If the circle, therefore, be carefully 
read at both settings, half the difference between the 
two readings will give the angular elevation of the 
star above the horizon. A combination, therefore, of 
all four observations, that is to say, one reflection and 
one direct with each of the telescopes, would give 
an exceedingly exact value for the star's altitude. 
The conception of this method gives a striking idea 
of Pond's thoroughness and skill as a practical 
observer, and it is a distinct blot upon Airy's justly 
high reputation in the same line that he discontinued 
the system upon his accession to office. 

However, in 185 1, as already mentioned, Airy 
substituted for the two separate instruments the 
transit and muial circle the transit circle, which, 
unlike the mural circle, is equally supported on both 
sides. This, however, does not free it from the 
liability to some minute flexure in the direction of 
its length, from the weight of its two ends, and the 
mercury trough is used for the detection of such 
bending, should it exist. The present practice is to 
observe a star both by reflection and directly in the 
course of the same transit. The observer sets the 
telescope carefully before ever the star comes into the 
field of view, and reads his seven microscopes. Then 
he climbs up a narrow wooden staircase and watches 



198 THE ROYAL OBSERVATORY 

the star transit nearly half across the field. Then 
comes a rush, the observer swings himself down the 
ladder, unclamps the telescope, turns it rapidly up to 
the star itself, clamps it again, flings himself on his 
back on a bench below the telescope, and does it so 
quickly that he is able to observe the star across the 
second half of the field. There is no time for 
dawdling, no room for making any mistakes ; the 
stars never forgive ; ' they haste not, they rest not ; ' 
and if the unfortunate observer is too slow, or makes 
some slip in his second setting, the star, cold and 
inexorable, takes no pity, and moves regardless on. 

It will be seen that a considerable amount of work 
is involved in taking a single observation of a star- 
place. But in making a star-catalogue it is always 
deemed necessary to obtain at least three observa- 
tions of each star ; and many are observed much more 
frequently. 

A modern star-catalogue contains, like Ptolemy's, 
four columns. It contains also several more. Of 
these the principal are devoted to the effect of pre- 
cession. As precession is caused by a movement of 
the earth's axis making the pole of the sky seem to 
describe a circle in the heavens, it follows that the 
celestial poles, and the celestial equator with them 
are slowly, but continually, changing their place with 
respect to the stars, and therefore that the declinations 
of the stars are always undergoing change, and as 
the equator changes, the point where the sun crosses 
it in spring the first point of Aries changes also, 
and with it the stars' right ascensions. 

To make one determination of a star's place 



TRANSIT AND CIRCLE DEPARTMENTS 199 

comparable with another made at another time, it is 
clear that we must correct for the effects of precession 
in the interval of time between the two observations, 
and for the effects of refraction. But observations 
made with the transit circle must also be corrected 
for errors in the instrument itself. The astronomer 
will see to it that his instrument is made and is set 
up as perfectly as possible. The pivots on which it 
turns must be exactly on the same level ; they must 
point exactly east and west, and the axis of the 
telescope must be exactly at right angles to the line 
joining the pivots in all positions of the instrument. 
These conditions are very nearly fulfilled, but never 
absolutely. Day by day, therefore, the astronomer 
has to ascertain just how much his instrument is in 
error in each of these three matters. Were his 
instrument absolutely without error to-day, he could 
not assume that it would remain so, nor, if he had 
measured the amount of its errors yesterday, would 
it be safe to assume that those errors would not 
change to-day. 

In the examination of these sources of error the 
mercury trough comes again into use. The transit 
circle is turned directly downwards, and the mercury 
trough brought below it. A light is so arranged as 
to illuminate the field of the telescope, and the 
observer, looking in, sees the ten transit wires and 
the one declination wire, and also sees their images 
reflected from the surface of the mercury. If the 
telescope be pointing exactly down towards the surface 
of the mercury, then the image of the declination 
wire will fall exactly on the declination wire itself, 



200 THE ROYAL OBSERVATORY 

and by reading the circle we can tell where the 
zenith point of the circle is. Similarly, if the pivots 
of the telescope are precisely on the same level, the 
centre wire of the right ascension series would 
coincide with its reflected image. A third point is 
determined by looking through the eye-piece of the 
north collimator telescope that is to say, the tele- 
scope mounted in a horizontal position at the north 
end of the room at the spider lines in the focus of 
the south collimator. In order to get this view, the 
transit telescope has either to be lifted up out of its 
usual position, or else the middle of the tube has to 
be opened. The spider lines in the north collimator 
are then made to coincide with the image of the 
wires of the south collimator. The transit telescope 
is then turned first to one collimator, then to the 
other, and the central wire of the right ascension 
series is turned till it coincides with the wire of the 
collimator ; the amount by which it has to be moved 
giving an index of the error of collimation ; that is 
to say, of the deviation of the optical axis of the 
telescope from perpendicularity to the line joining 
the pivots. 

I have said enough to show that the making of 
an observation is a small matter as compared with 
those corrections which have to be made to it after- 
wards, before it is available for use. But I have only 
mentioned some of the reductions and corrections 
which have to be made. There are several more, 
and it is a just pride of Greenwich that her third 
ruler, Bradley, as has been already told in the notice 
of his life, discovered two of the most important. 



TRANSIT AND CIRCLE DEPARTMENTS 201 

The one, aberration, is due to the fact that light, 
though it moves so swiftly 186,000 miles per second 
yet does not move with an infinitely greater velocity 
than that of the earth. The other, nutation, might 
be called a correction to precession, inasmuch as, 
moved by the moon's attraction, the earth's axis does 
not swing round smoothly, but with a slight nodding 
or staggering motion. 

But when these observations of the places of a star 
have been made, and have been properly reduced,' 
even then we do not find an exact correspondence 
between two different determinations. Little differ- 
ences still remain. Some of these are to be accounted 
for by changes in the actual crust of the earth, which, 
solid and stable as we think it, is yet always in 
motion. Professor Milne, our greatest authority on 
earth movements, says, ' The earth is so elastic that 
a comparatively small impetus will set it vibrating ; 
why, even two hills tip together when there is a 
heavy load of moisture in the valley between them. 
And then, when the moisture evaporates in a hot 
sun, they tip away from each other.' So there is 
a perceptible rocking to and fro even of the huge 
stone piers of a transit circle, as seasons of rain and 
drought, heat and cold, follow each other. More 
than that, the earth is so sensitive to pressure that 
it was found, at the Oxford University Observatory, 
that there was a distinct swaying shown by a hori- 
zontal pendulum when the whole of a party of 
seventy-six undergraduates stood on one side of the 
instrument and close up to it, from the position it 
had when the party stood ninety feet away. More 



202 THE ROYAL OBSERVATORY 

wonderful still, a comparison of the star-places, 
obtained at a number of observatories, including 
Greenwich, has shown that the earth is continually 
changing her axis of rotation. And so the star- 
places determined at Greenwich have shown that 
the north pole of the earth, 2600 miles away, moves 
about in an irregular curve about thirty feet in radius. 

Nothing is stable, nothing is immovable, nothing 
is constant. The astronomer even finds that his 
own presence near the instrument is sufficient to 
disturb it. 

The great interest attaching to transit-circle work 
is this striving after ever greater and greater precision, 
with the result of bringing out fresh little discordances, 
which, at first sight, appear purely accidental, but 
which, under further scrutiny, show themselves to be 
subject to some law. Then comes the hunt for this 
new unknown law. Its discovery follows. It explains 
much, but when it is allowed for, though the observa- 
tions now come much closer together, little deviations 
still remain, to form the subject of a fresh inquiry. 
Astronomy has well been called the exact science, 
and yet exactitude ever eludes its pursuer. 

If it be asked, What is the use of this ever- 
increasing refinement of observation ? ' no better 
answer can be given than the words of Sir John 
Herschel in one of his Presidential addresses to the 
Royal Astronomical Society : 

1 If we ask to what end magnificent establishments are 
maintained by States and sovereigns, furnished with master- 
pieces of art, and placed under the direction of men of 
first-rate talent and high-minded enthusiasm, sought out for 
those qualities among the foremost in the ranks of science, 



TRANSIT AND CIRCLE DEPARTMENTS 203 

if we demand, cut bono t for what good a Bradley has toiled, 
or a Maskelyne or a Piazzi has worn out his venerable age 
in watching ? the answer is, Not to settle mere speculative 
points in the doctrine of the universe ; not to cater for the 
pride of man by refined inquiries into the remoter mysteries 
of nature ; not to trace the path of our system through 
space, or its history through past and future eternities. 
These, indeed, are noble ends, and which I am far from any 
thought of depreciating ; the mind swells in their contem- 
plation, and attains in their pursuit an expansion and a 
hardihood which fit it for the boldest enterprise. But the 
direct practical utility of such labours is fully worthy of 
their speculative grandeur. The stars are the landmarks 
of the universe ; and, amidst the endless and complicated 
fluctuations of our system, seem placed by its Creator as 
guides and records, not merely to elevate our -minds by the 
contemplation of what is vast, but to teach us to direct our 
actions by reference to what is immutable in His works. 
It is, indeed, hardly possible to over-appreciate their value 
in this point of view. Every well-determined star, from the 
moment its place is registered, becomes to the astronomer, 
the geographer, the navigator, the surveyor, a point of 
departure which can never deceive or fail him, the same 
for ever and in all places ; of a delicacy so extreme as to 
be a test for every instrument yet invented by man, yet 
equally adapted for the most ordinary purposes ; as 
available for regulating a town clock as for conducting a 
navy to the Indies ; as effective for mapping down the 
intricacies of a petty barony as for adjusting the boundaries 
of Transatlantic empires. When once its place has been 
thoroughly ascertained and carefully recorded, the brazen 
circle with which that useful work was done may moulder, 
the marble pillar may totter on its base, and the astronomer 
himself survive only in the gratitude of posterity ; but the 
record remains, and transfuses all its own exactness into 
every determination which takes it for a groundwork, 
giving to inferior instruments nay, even to temporary 
contrivances, and to the observations of a few weeks or 
days all the precision attained originally at the cost of so 
much time, labour, and expense.' 



204 THE ROYAL OBSERVATORY 

But for these strictly utilitarian purposes a com- 
paratively small number of stars would meet our 
every requisite. In the narrow sense of which Sir 
John Herschel is here speaking, we have no use for 
anything beyond the smallest of catalogues ; and if 
the question before us is, 'Why are we continually 
extending our catalogues ? ' the following words of a 
more recent writer 1 on the subject will set forth the 
real explanation : 

1 A word in conclusion, suggested by the history of star- 
catalogues. We have no difficulty in understanding that it 
is necessary to study the planets, and a reasonable number 
of the brighter stars, for the purpose of determining the 
figure of the earth, and the positions of points upon its 
surface ; but the use for a catalogue of ten thousand stars, 
such as La Caille compiled, is not just so apparent. Nay, 
what did Ptolemy want with a thousand stars, or Tamer- 
lane's grandson, born, reared, and destined to die amidst 
a horde of savages, however splendid in their trappings ? 
There is not, and there never was, any real, practical use 
for the great volumes of star-catalogues that weigh down 
the shelves of our libraries. The navigator and explorer 
need never see them at all. Why, then, were these pages 
compiled? Why have astronomers, from Hipparchus's 
time to the present, spent their lives in the weary routine- 
work of observing the places of tiny points in the stellar 
depths? Does it not seem that there is something in the 
mind of man that impels him to seek after knowledge 
truly for its own sake ? something heaven-born, heaven- 
nurtured, God-given . . . that there is something in man 
common to him and his Creator, and therefore eternal . . . 
in beautiful accord with the plain statement that " God 
made man in His own image? '" 

1 Mr. Thomas Lindsay, Transactions of the Astronomical 
and Physical Society of Toronto, 1899, p. 17. 



CHAPTER VIII 

THE ALTAZIMUTH DEPARTMENT 

The determining of the places of the fixed stars 
which Flamsteed carried out so efficiently in his 
British Catalogue of Stars the first ' Census of the 
Sky ' made with the aid of a telescope was but half 
of the work imposed upon him. The other half, 
equally necessary for the^ solution of the problem of 
the longitude at sea, was the ' Rectifying the Tables 
of the Motions of the Heavens.' 

This second duty was not less necessary than the 
other, for, if we may again use the old simile of the 
clock-face, the fixed stars may be taken to represent 
the figures on the vast dial of the sky, whilst the 
moon, as it moves amongst them, corresponds to the 
moving hand of the timepiece. To know the places 
of the stars, then, without being able to predict the 
place of the moon, would be much like having a clock 
without its hands. But if not less necessary, it was 
certainly more difficult. The secret of the move- 
ments of the moon and planets had not then been 
grasped, and the only tables which had been calcu- 
lated were based upon observations made before the 
days of telescopes. 

205 



206 THE ROYAL OBSERVATORY 

It is one of the most fortunate and remarkable 
coincidences in the whole history of science, that at 
the very time that Greenwich Observatory was being 
called into existence, the greatest of all astronomers 
was working out his demonstration of the great funda- 
mental law of the material universe the law that 
every particle of matter attracts every other particle 
with a force which varies directly with the mass and 
inversely with the square of the distance. 

Several other of the great minds of that time, in 
particular Dr. Hooke, the Gresham Professor of 
Astronomy, had seen that it was possible that some 
such law might supply the secret of planetary motion ; 
but it is one thing to make a suggestion, and a very 
different matter indeed to be able to demonstrate it ; 
and the latter was in Newton's power alone. He did 
much more than demonstrate it he brought out a 
whole series of most important and far-reaching con- 
sequences. He showed that the ebb and flow of the 
tides was due to the attraction of both sun and moon, 
especially the latter, upon the waters of our oceans. 
He pointed out certain irregularities which must take 
place in the motion of our moon, due to the influence 
of the sun upon it. He showed, too, what was the 
cause of that swinging of the axis of the earth which 
gives rise to precession. He deduced the relative 
weights of the earth, the sun, and of Jupiter and 
Saturn, the planets with satellites. He proved also 
that comets, which had seemed hitherto to men as 
perfectly lawless wanderers, obeyed in their orbits the 
self-same law which governed the moon and planets. 
The whole vast system of celestial movements, which 



THE ALTAZIMUTH DEPARTMENT 207 

had long seemed to men irregular and uncontrolled, 
now fell, every one of them, into its place, as but 
the necessary manifestations of one grand, simple 
order. 

This great discovery gave a new and additional 
importance to the regular observation of the moon 
and planets. They were needed now, not only to 
assist in the practical work of navigation, but for the 
development of questions of pure science. Halley, 
the second Astronomer Royal, and Maskelyne, the 
fifth, devoted themselves chiefly to this department 
of work, to the partial neglect of the' observation of 
the places of stars. Airy, the seventh, whilst making 
catalogue-work a part of the regular routine of the 
Observatory, developed the observation of the mem- 
bers of the solar system, and especially of the moon, 
in a most marked degree, and collected and com- 
pletely reduced the vast mass of material which the 
industry of his predecessors had gathered. It is 
pre-eminently of the work of Airy that the memorable 
words quoted before of Professor Newcomb, the great 
American mathematician and astronomer, are appli- 
cable : ' that if this branch of astronomy were entirely 
lost, it could be reconstructed from the Greenwich 
observations alone.' 

A most important step taken by Airy was the 
construction of an altazimuth. An altazimuth is 
practically a theodolite on a large scale. Its purpose 
is to determine, not the declination and right ascen- 
sion of some celestial body, as is the case with the 
transit circle, but its altitude, i.e. its height above the 
horizon, and its azimuth, i.e. the angle measured on 



208 



THE ROYAL OBSERVATORY 



the horizontal plane from the north point. The 
altazimuth, then, like the transit circle, consists of a 
telescope revolving on a horizontal axis, but, unlike 
the transit circle, both the telescope and the piers 
which carry its pivots can be rotated so as to point 




airy's altazimuth. 



not merely due north and south, but in any direction 
whatsoever. 

The observations with the altazimuth are rather 
more complicated than those with the transit circle. 



THE ALTAZIMUTH DEPARTMENT 209 

Looking in the telescope, the observer sees a double 
set of spider threads or ' wires ' ; and when a star or 
other heavenly body enters the field, it will generally 
be observed to move obliquely across both sets of 
wires. The observer usually determines to make an 
observation either in altitude or azimuth. In the 
former case he presses the little contact button, which, 
as in the transit circle, is provided close to the eye- 
piece, as the star reaches each of the horizontal wires 
in succession. If in azimuth, it is the times of cross- 
ing the vertical wires that are in like manner tele- 
graphed to the chronograph. The transit over, the 
appropriate circle is read ; for the telescope itself is 
rigidly attached to a vertical wheel having a carefully 
engraved circle on its face and read by four micro- 
scopes, whilst the entire instrument carries another 
set of microscopes, pointing to a fixed horizontal 
circle, and upon which the azimuth can be read. 
A complete observation involves four such transits 
and sets of circle readings, two of altitude, and two 
of azimuth ; for after one of altitude and one of 
azimuth the telescope is turned round, and a second 
observation is taken in each element. 

The observation gives us the altitude and azimuth 
of the star. These particulars are of no direct value 
to us. But it is a mere matter of computation, 
though a long and laborious one, to convert these 
elements into right ascension and declination. 

The usefulness of the altazimuth will be seen at 
once. It will be remembered that with the transit 
circle any particular object can only be observed as it 
crosses the meridian. If the weather should be 

O 



210 THE ROYAL OBSERVATORY 

cloudy, or the observer late, the chance of observation 
is lost for four and twenty hours, and in the case of 
the moon, for which the altazimuth is specially used, 
it is on the meridian only in broad daylight during 
that part of the month which immediately precedes 
and follows new moon. At such times it is practi- 
cally impossible to observe it with the transit circle ; 
with the altazimuth it may be caught in the twilight 
before sunrise or after sunset ; and at other times in 
the month, if lost on the meridian in the transit circle, 
the altazimuth still gives the observer a chance of 
catching it any time before it sets. But for this 
instrument, our observations of the moon would have 
been practically impossible over at least one-fourth 
of its orbit. 

Airy's altazimuth was but a small instrument of 
three and three-quarter inches aperture, mounted in a 
high tower built on the site of Flamsteed's mural 
arc ; and, after a life history of about half a century, 
has been succeeded by a far more powerful instrument. 
The ( New Altazimuth ' has an aperture of eight 
inches, and is housed in a very solidly constructed 
building of striking appearance, the connection of the 
Observatory with navigation being suggested by a 
row of circular lights which strongly recall a ship's 
portholes. This building is at the southern end of the 
narrow passage, 'the wasp's waist,' which connects 
the older Observatory domain with the newer. It is 
the first building we come to in the south ground. 
The computations of the department are carried on 
in the south wing of the new Observatory. 

It will be seen from the photograph that the 



THE ALTAZIMUTH DEPARTMENT 211 

instrument is much larger, heavier, and less easy to 
move in azimuth than the old altazimuth. It is, 
therefore, not often moved in azimuth, but is set in 
some particular direction, not necessarily north and 




NEW ALTAZIMUTH BUILDING. 



south, in which it is used practically as a transit 
circle. 

There is quite another way of determining the 
place of the moon, which is sometimes available, and 
which offers one of the prettiest of observations to 



212 THE ROYAL OBSERVATORY 

the astronomer. As the moon travels across the sky, 
moving amongst the stars from west to east, it 
necessarily passes in front of some of them, and 
hides them from us for a time. Such a passage, 
or ' occupation, ' offers two observations : the 4 dis- 
appearance,' as the moon comes up to the star and 
covers it ; the ' reappearance,' as it leaves it again, 
and so discloses it. 

Except at the exact time of full moon, we do not 
see the entire face of our satellite ; one edge or 'limb ' 
is in darkness. As the moon therefore passes over 
the star, either the limb at which the star disappears, 
or that at which it reappears, is invisible to us. To 
watch an occultation at the bright limb is pretty ; the 
moon, with its shining craters and black hollows, its 
mountain ranges in bright relief, like a model in 
frosted silver, slowly, surely, inevitably comes nearer 
and nearer to the little brilliant which it is going to 
eclipse. The movement is most regular, most smooth, 
yet not rapid. The observer glances at his clock, 
and marks the minute as the two heavenly bodies 
come closer and closer to each other. Then he counts 
the clock beats : ' five, six, seven,' it may be, as the 
star has been all but reached by the advancing moon. 
1 Eight,' it is still clear ; ere the beat of the clock rings 
to the 'nine,' perhaps the little diamond point has 
been touched by the wide arch of the moon's limb, 
and has gone ! Less easy to exactly time is a 
reappearance at the bright limb. In this case the 
observer must ascertain from the Nautical Almanac 
precisely where the star will reappear ; then a little 
before the predicted time he takes his place at the 




S 

i 

* 

I 

i 

i, 



W 5 



THE ALTAZIMUTH DEPARTMENT 215 

telescope, watches intently the moon's circumference 
at the point indicated, and, listening for the clock- 
beats, counts the seconds as they fly. Suddenly, 
without warning, a pin-point of light flashes out at 
the edge of the moon, and at once draws away from 
it. The star has ' reappeared.' 

Far more striking is a disappearance or reappear- 
ance at the 'dark limb.' In this case the limb of the 
moon is absolutely invisible, and it may be that no 
part of the moon is visible in the field of the telescope. 
In this case the observer sees a star shining brightly 
and alone in the middle of the field of his telescope. 
He takes the time from his faithful clock, counting 
beat after beat, when suddenly the star is gone ! So 
sudden is the disappearance that the novice feels 
almost as astonished as if he had received a slap in 
the face, and not unfrequently he loses all count or 
recollection of the clock beats. The reappearance at 
the dark limb is quite as startling ; with a bright star 
it is almost as if a shell had burst in his very face, 
and it would require no very great imagination to 
make him think that he had heard the explosion. 
One moment nothing was visible ; now a great star 
is shining down serenely on the watcher. A little 
practice soon enables the observer to accustom 
himself to these effects, and an old hand finds no 
more difficulty in observing an occultation of any 
kind than in taking a transit. 

Such an observation is useful for more purposes 
than one. If the position of the star occulted is 
known and it can be determined at leisure afterwards 
we necessarily know where the limb of the moon 



216 THE ROYAL OBSERVATORY 

was at the time of the observation. Then the time 
which the moon took to pass over the star enables us 
to calculate the diameter of our satellite ; the different 
positions of the moon relative to the star, as seen 
from different observatories, enable us to calculate its 
distance. 

But if the disappearance takes place at the bright 
limb, the reappearance usually takes place at the 
dark, and vice versa; and the two observations are 
not quite comparable. There is one occasion, however, 
when both observations are made under similar 
circumstances, namely, at the full. And if the moon 
happens also to be totally eclipsed, the occultations 
of quite faint stars can be successfully observed, much 
fainter than can ordinarily be seen close up to the 
moon. Total eclipses of the moon, therefore, have 
recently come to be looked upon as important events 
for the astronomer, and observatories the world over 
usually co-operate in watching them. October 4, 
1 884, was the first occasion when such an organised 
observation was made ; there have been several since, 
and on these nights every available telescope and 
observer at Greenwich is called into action. 

It may be asked why these different modes of 
observing the moon are still kept up, year in and 
year out. 'Do we not know the moon's orbit 
sufficiently well, especially since the discovery of 
gravitation?' No; we do not. This simple and 
beautiful law simple enough in itself, gives rise to 
the most amazing complexity of calculation. If the 
earth and moon were the only two bodies in the 
universe, the problem would be a simple one. But 



THE ALTAZIMUTH DEPARTMENT 217 

the earth, sun, and moon are members of a triple 
system, each of which is always acting on both of the 
others. More, the planets, too, have an appreciable 
influence, and the net result is a problem so intricate 
that our very greatest mathematicians have not 
thoroughly worked it out. Our calculations of the 
moon's motions need, therefore, to be continually 
compared with observation, need even to be 
continually corrected by it. 

There is a further reason for this continual 
observation, not only in the case of the sun, which 
is our great standard star, since from it we derive 
the right ascensions of the stars, and it is also our 
great timekeeper; not only in that of the moon, but 
also in the case of the planets. Their places as com- 
puted need continually to be compared with their 
places as observed, and the discordances, if any, in- 
quired into. The great triumph which resulted to 
science from following this course to pure science, 
since Uranus is too faint a planet to be any help to 
the sailor in navigation is well known. The ob- 
served movements of Uranus proved not to be in 
accord with computation, and from the discordances 
between calculation and observation Adams and 
Leverrier were able to predicate the existence of a 
hitherto unseen planet beyond 

' To see it, as Columbus saw America from Spain. Its 
movements were felt by them trembling along the far- 
reaching line of their analysis, with a certainty hardly 
inferior to that of ocular demonstration.' * 

1 From Sir John Herschel's address to the British Association, 
September 10, 1846, thirteen days before Galle's first obser- 
vation of the planet. 



218 THE ROYAL OBSERVATORY 

The discovery of Neptune was not made at 
Greenwich, and Airy has been often and bitterly 
attacked because he did not start on the search for 
the predicted planet the moment Adams addressed 
his first communication to him, and so allowed 
the French astronomer to engross so much of the 
honour of the exploit. The controversy has been 
argued over and over again, and we may be con- 
tent to leave it alone here. There is one point, 
however, which is hardly ever mentioned, which must 
have had much effect in determining Airy's conduct. 
In 1845, the year in which Adams sent his provisional 
elements of the unseen disturbing planet to Airy, the 
largest telescope available for the search at Greenwich 
was an equatorial of only six and three-quarter inches 
aperture, provided with small and insufficient circles 
for determining positions, and housed in a very 
small and inconvenient dome ; whilst at Cambridge, 
within a mile or so of Adams' own college, was the 
1 Northumberland ' equatorial, of nearly twelve inches 
aperture, under the charge of the University Professor 
of Astronomy, Professor Challis, and which was then 
much the largest, best mounted and housed equatorial 
in the entire country. The ' Northumberland ' had 
been begun from Airy's designs and under his own 
superintendence, when he was Professor of Astronomy 
at Cambridge. Naturally, then, knowing how much 
superior the Cambridge telescope was to any which 
he had under his care, he thought the search should 
be made with it. He had no reason to believe that 
his own instrument was competent for the work. 

On the other hand, it is hard for the ordinary 



THE ALTAZIMUTH DEPARTMENT 221 

man to understand how it was that Adams not only- 
left unnoticed and unanswered for three-quarters of 
a year, an inquiry of Airy's with respect to his 
calculations, but also never took the trouble to visit 
Challis, whom he knew well, and who was so near at 
hand, to stir him up to the search. But, in truth, 
the whole interest of the matter for Adams rested 
in the mathematical problem. The irregularities in 
the motion of Uranus were interesting to him simply 
for the splendid opportunity which they gave him 
for their analysis. A purely imaginary case would 
have served his purpose nearly as well. The actuality 
of the planet which he predicted was of very little 
moment ; the eclat and popular reputation of the 
discovery was less than nothing ; the problem itself 
and the mental exercise in its solution, were what 
he prized. 

But it was not creditable to the nation that the 
Royal Observatory should have been so ill-provided 
with powerful telescopes ; and a few years later Airy 
obtained the sanction of the Government for the 
erection of an equatorial larger than the 4 Northumber- 
land,' but on the same general plan and in a much 
more ample dome. This was for thirty-four years the 
'Great' or 'South-East' equatorial, and the mount- 
ing still remains and bears the old name, though the 
original telescope has been removed elsewhere. The 
object-glass had an aperture of twelve and three- 
quarter inches and a focal length of eighteen feet, 
and was made by Merz of Munich, the engineering 
work by Ransomes and Sims of Ipswich, and the 
graduations and general optical work by Simms, now 



222 THE ROYAL OBSERVATORY 

of Charlton, Kent. The mounting was so massive 
and stable that the present Astronomer Royal has 
found it quite practicable and safe to place upon it 
a telescope (with its counterpoises) of many times 
the weight, one made by Sir Howard Grubb, of 
Dublin, of twenty-eight inches aperture and twenty- 
eight feet focal length, the largest refractor in the 
British Empire, though surpassed by several American 
and Continental instruments. 

The stability of the mounting was intended to 
render the telescope suitable for a special work. 
This was the observation of 'minor planets.' On 
the first day of the present century the first of these 
little bodies was discovered by Piazzi at Palermo. 
Three more were discovered at no great interval after- 
wards, and then there was an interval of thirty- eight 
years without any addition to their number. But 
from December 8, 1845, up to the present time, the 
work of picking up fresh individuals of these 'pocket 
planets ' has gone on without interruption, until now 
more than 400 are known. Most of these are of no 
interest to us, but a few come sufficiently near to 
the earth for their distance to be very accurately 
determined ; and when the distance of one member 
of the solar system is determined, those of all the 
others can be calculated from the relations which 
the law of gravitation reveals to us. It is a matter 
of importance, therefore, to continue the work of 
discovery, since we may at any time come across an 
interesting or useful member of the family ; and that 
we may be able to distinguish between minor planets 
already discovered and new ones, their orbits must 



THE ALTAZIMUTH DEPARTMENT 223 

be determined as they are discovered, and some sort 
of watch kept on their movements. 

A striking example of the scientific prizes which 
we may light upon in the process of the rather dreary 
and most laborious work which the minor planets 
cause, has been recently supplied by the discovery 
of Eros. On August 13, 1898, Herr Witt, of the 
Urania Observatory, Berlin, discovered a very small 
planet that was moving much faster in the sky than 
is common with these small bodies. The great 
majority are very much farther from the sun than 
the planet Mars, many of them twice as far, and 
hence, since the time of a planet's revolution round 
the sun increases, in accordance with Kepler's law, 
more rapidly than does its distance, it follows that 
they move much more slowly than Mars. But this 
new object was moving at almost the same speed as 
Mars ; it must, therefore, be most unusually near to 
us. Further observations soon proved that this was 
the case, and Eros, as the little stranger has been 
called, comes nearer to us than any other body of 
which we are aware except the moon. Venus when 
in transit is 24J millions of miles from us, Mars at 
its nearest is 34^ millions, Eros at its nearest approach 
is but little over 13 millions. 

The use of such a body to us is, of course, quite 
apart from any purpose of navigation, except very 
indirectly. But it promises to be of the greatest 
value in the solution of a question in which astronomers 
must always feel an interest, the determination of 
the distance of the earth from the sun. We know 
the relative distances of the different planets, and, 



224 THE ROYAL OBSERVATORY 

consequently if we could determine the absolute 
distance of any one, we should know the distances 
of all. As it is practically impossible to measure our 
distance from the sun directly, several attempts have 
been made to determine the distances of Venus, 
Mars, or such of the minor planets as come the 
nearest to us. Three of these in particular, the little 
planets Iris, Victoria, and Sappho, have given us the 
most accurate determinations of the sun's distance 
(92,874,000 miles) which we have yet obtained ; but 
Eros at its nearest approach will be six times as near 
to us as either of the three mentioned above, and 
therefore should give us a value with only one-sixth 
of the uncertainty attaching to that just mentioned. 

The discovery of minor planets has lain outside 
the scope of Greenwich work, but their observation 
has formed an integral part of it. The general 
public is apt to lay stress rather on the first than 
on the second, and to think it rather a reproach to 
Greenwich that it has taken no part in such explora- 
tions. Experience has, however, shown that they 
may be safely left to amateur activity, whilst the 
monotonous drudgery of the observation of minor 
planets can only be properly carried out in a per- 
manent institution. 

The observation of these minute bodies with the 
transit circle and altazimuth is attended with some 
difficulties ; T but precise observations of various objects 
may be made with an equatorial ; indeed, comets are 
usually observed by its means. 

The most ordinary way of observing a comet with 
an equatorial is as follows : Two bars are placed in 



THE ALTAZIMUTH DEPARTMENT 225 

the eye-piece of the telescope, at right angles to each 
other, and at an angle of forty-five degrees to the 
direction of the apparent daily motion of the stars. 
The telescope is turned to the neighbourhood of the 
comet, and moved about until it is detected. The 
telescope is then put a little in front of the comet, 
and very firmly fixed. The observer soon sees the 
comet entering his field, and by pressing the contact 
button he telegraphs to the chronograph the time 
when the comet is exactly bisected by each of the 
bars successively. He then waits until a bright star, 
or it may be two or three, have entered the telescope 
and been observed in like manner. The telescope 
is then undamped, and moved forward until it is 
again ahead of the comet, and the observations are 
repeated ; and this is done as often as is thought 
desirable. The places of the stars have, of course, 
to be found out from catalogues, or have to be 
observed with the transit circle, but when they are 
known the position of the comet or minor planet can 
easily be inferred. 

Next to the glory of having been the means of 
bringing about the publication of Newton's Principia, 
the greatest achievement of Halley, the second 
Astronomer Royal, was that he was the first to 
predict the return of a comet. Newton had shown 
that comets were no lawless wanderers, but were as 
obedient to gravitation as were the planets them- 
selves, and he also showed how the orbit of a comet 
could be determined from observations on three 
different dates. Following these principles, Halley 
computed the orbits of no fewer than twenty-four 

P 



226 THE ROYAL OBSERVATORY 

comets, and found that three of them, visible at 
intervals of about seventy-five years, pursued practi- 
cally the same path. He concluded, therefore, that 
these were really different appearances of the same 
object, and, searching old records, he found reason 
to believe that it had been observed frequently earlier 
still. It seems, in fact, to have been the comet which 
is recorded to have been seen in 1066 in England at 
the time of the Norman invasion ; in A.D. 66, shortly 
before the commencement of that war which ended 
in the destruction of Jerusalem by Titus ; and earlier 
still, so far back as B.C. 12. Halley, however, ex- 
perienced a difficulty in his investigation. The period 
of the comet's revolution was not always the same. 
This, he concluded, must be due to the attraction of 
the planets near which the comet might chance to 
travel. In the summer of 1681 it had passed very 
close to Jupiter, for instance, and in consequence he 
expected that instead of returning in August 1757, 
seventy-five years after its last appearance, it would 
not return until the end of 1758 or the beginning of 
1759. It has returned twice since Halley's day, a 
triumphant verification of the law of gravitation ; and 
we are looking for it now for a third return some 
ten years hence, in 19 10. 

Halley's comet, therefore, is an integral member 
of our solar system, as much so as the earth or 
Neptune, though it is utterly unlike them in appear- 
ance and constitution, and though its path is so 
utterly unlike theirs that it approaches the sun 
nearer than our earth, and recedes farther than 
Neptune. But there are other comets, which are 



THE ALTAZIMUTH DEPARTMENT 227 

not permanent members of our system, but only 
passing visitors. From the unfathomed depths of 
space they come, to those depths they go. They 
obey the law of gravitation so far as our sight can 
follow them, but what happens to them beyond ? 
Do they come under some other law, or, perchance, 
in outermost space is there still a region reserved to 
primeval Chaos, the ' Anarch old/ where no law at 
all prevails ? Gravitation is the bond of the solar 
system ; is it also the bond of the Universe ? 



CHAPTER IX 

THE MAGNETIC AND METEOROLOGICAL 
DEPARTMENTS 

Passing out of the south door of the new altazimuth 
building, we come to a white cruciform erection, 
constructed entirely of wood. This is the Magnet 
House or Magnetic Observatory, the home of a 
double Department, the Magnetic and Meteorological. 
This department does not, indeed, lie within the 
original purpose of the Observatory as that was 
defined in the warrant given to Flamsteed, and yet 
is so intimately connected with it, through its bearing 
on navigation, that there can be no question as to 
its suitability at Greenwich. Indeed, its creation is 
a striking example of the thorough grasp which Airy 
had upon the essential principles which should govern 
the great national observatory of an essentially 
naval race, and of the keen insight with which he 
watched the new development of science. The 
Magnetic Observatory, therefore, the purpose of which 
was to deal with the observation of the changes in 
the force and direction of the earth's magnetism an 
inquiry which the greater delicacy of modern com- 
passes, and, in more recent times, the use of iron 

228 



THE METEOROLOGICAL DEPARTMENT 229 

instead of wood in the construction of ships has 
rendered imperative was suggested by Airy on the 
first possible occasion after he entered on his office, 
and was sanctioned in 1837. The Meteorological 
Department has a double bearing on the purpose of 
the Observatory. On the one side, a knowledge of 
the temperature and pressure of the atmosphere is, as 
we have already seen, necessary in order to correct 
astronomical observations for the effect of refraction. 
On the other hand, meteorology proper, the study of 
the movements of the atmosphere, the elucidation of 
the laws which regulate those movements, leading to 
accurate forecasts of storms, are of the very first 
necessity for the safety of our shipping. It is true 
that weather forecasts are not issued from Greenwich 
Observatory, any more than the Nautical Almanac is 
now issued from it; but just as the Observatory 
furnishes the astronomical data upon which the 
Almanac is based, so also it takes its part in furnish- 
ing observations to be used by the Meteorological 
Office at Westminster for its daily predictions. 

Those predictions are often made the subject of 
much cheap ridicule ; but, however far short they 
may fall of the exact and accurate predictions which 
we would like to have, yet they mark an enormous 
advance upon the weather-lore of our immediate 
forefathers. 

1 He that is weather wise 
Is seldom other wise,' 

says the proverb, and the saying is not without a 
shrewd amount of truth. For perhaps nowhere can 
we find a more striking combination of imperfect 



230 THE ROYAL OBSERVATORY 

observation and inconsequent deduction than in the 
saws which form the stock-in-trade of the ordinary 
would-be weather prophet. How common it is to 
find men full of the conviction that the weather must 
change at the co-called ' changes of the moon/ 
forgetful that 

'If we'd no moon at all 

And that may seem strange 
We still should have weather 
That's subject to change.' 

They will say, truly enough, no doubt, that they have 
known the weather to change at ' new ' or ' full,' as 
the case may be, and they argue that it, therefore, 
must always do so. But, in fact, they have only 
noted a few chance coincidences, and have let the 
great number of discordances pass by unnoticed. 

But observations of this kind seem scientific and 
respectable compared with those numerous weather 
proverbs which are based upon the mere jingle of 
a rhyme, as 

4 If the ash is out before the oak, 
You may expect a thorough soak ' 

a proverb which is deftly inverted in some districts 
by making oak ' rhyme to ' choke.' 

Others, again, are based upon a mere childish fancy, 
as, for example, when the young moon ' lying on her 
back ' is supposed to bode a spell of dry weather, 
because it looks like a cup, and so might be thought 
of as able to hold the water. 

During the present reign, however, a very different 
method of weather study has come into action, and 



THE METEOROLOGICAL DEPARTMENT 231 

the foundations of a true weather wisdom have been 
laid. These have been based, not on fancied analogies 
or old wives' rhymes, or a few forechosen coincidences, 
but upon observations carried on for long periods 
of time and over wide areas of country, and discussed 
in their entirety without selection and bias. Above 
all, mathematical analysis has been applied to the 
motions of the air, and ideas, ever gaining in precision 
and exactness, have been formulated of the general 
circulation of the atmosphere. 

As compared with its sister science, astronomy, 
meteorology appears to be still in a very undeveloped 
state. There is such a difference between the power 
of the astronomer to foretell the precise position of 
sun, moon, and planets for years, even for centuries, 
beforehand, and the failure of the meteorologist to 
predict the weather for a single season ahead, that 
the impression has been widely spread that there is 
yet no true meteorological science at all. It is for- 
gotten that astronomy offered us, in the movements 
of the heavenly bodies, the very simplest and easiest 
problem of related motion. Yet for how many thou- 
sands of years did men watch the planets, and specu- 
late concerning their motions, before the labours of 
Tycho, Kepler, and Newton culminated in the reve- 
lation of their meaning ? For countless generations 
it was supposed that their movements regulated the 
lives, characters, and private fortunes of individual 
men ; just as quite recently it was fancied that a 
new moon falling on a Saturday, or two full moons 
coming within the same calendar month, brought 
bad weather ! 



232 THE ROYAL OBSERVATORY 

It is still impossible to foresee the course of weather 
change for long ahead ; but the difference between 
the modern navigator, surely and confidently making 
a ' bee-line \ across thousands of miles of ocean to his 
destination, and the timid sailor of old, creeping from 
point to point of land, is hardly greater than the 
contrast between the same two men, the one watching 
his barometer, the other trusting in the old wives' 
rhymes which afforded him his only indication as to 
coming storms. 

It is still impossible to foresee the weather change 
for long ahead, but in our own and in many other 
countries, especially the United States, it has been 
found possible to predict the weather of the coming 
four-and-twenty hours with very considerable exact- 
ness, and often to forecast the coming of a great 
storm several days ahead. This is the chief purpose 
of the two great observatories of the storm-swept 
Indian and Chinese seas, Hong Kong and Mauritius ; 
and the value of the work which they have done in 
preventing the loss of ships, and the consequent loss 
of lives and property, has been beyond all estimate. 

The Royal Observatory, Greenwich, is a meteoro- 
logical as well as an astronomical observatory, but, as 
remarked above, it does not itself issue any weather 
forecasts. Just as the Greenwich observations of the 
places of the moon and stars are sent to the Nautical 
Almanac Office, for use in the preparation of that ephe- 
meris ; just as the Greenwich determinations of time 
are used for the issue of signals to the Post Office, 
whence they are distributed over the kingdom, so the 
Greenwich observations of weather are sent to the 



THE METEOROLOGICAL DEPARTMENT 233 

Meteorological Office, there to be combined with 
similar records from every part of the British Isles, 
to form the basis of the daily forecasts which the 
latter office publishes. To each of these three offices, 
therefore, the Royal Observatory, Greenwich, stands 
in the relation of purveyor. It supplies them with 
the original observations more or less in reduced and 
corrected form, without which they could not carry 
on most important portions of their work. 

Let it be noted how closely these three several 
departments, the Nautical Almanac Office, the Time 
Department, and the Meteorological Office, are related 
to practical navigation. Whatever questions of pure 
science of knowledge, that is, apart from its useful 
applications may arise out of the following up of 
these several inquiries, yet the first thought, the first 
principle of each, is to render navigation more sure 
and more safe. 

The first of all meteorological instruments is the 
barometer, which, under its two chief forms of mer- 
curial and aneroid, is simply a means of measuring 
the pressure exerted by the atmosphere. 

There are two important corrections to which its 
readings are subject. The first is for the height of 
the station above the level of the sea ; the second is 
for the effect of temperature upon the mercury in the 
barometer itself, lengthening the column. To over- 
come these, the height of the standard barometer at 
Greenwich above sea-level has been most carefully 
ascertained, and the heights relative to it of the other 
barometers of the Observatory, particularly those in 
rooms occupied by fundamental telescopes, have also 



234 THE ROYAL OBSERVATORY 

been determined, whilst the self-recording barometer 
is mounted in a basement, where it is almost 
completely protected from changes of temperature. 

Next in importance to the barometer as a meteoro- 
logical instrument comes the thermometer. The great 
difficulty in the Observatory use of the thermometer 
is to secure a perfectly unexceptionable exposure, so 
that the thermometer may be in free and perfect 
contact with the air, and yet completely sheltered 
from any direct ray from the sun. This is secured 
in the great thermometer shed at Greenwich by a 
double series of \ louvre ' boards, on the east, south, 
and west sides of the shed, the north side being open. 
The shed itself is made a very roomy one, in order 
to give access to a greater body of air. 

A most important use of the thermometer is in 
the measurement of the amount of moisture in the air. 
To obtain this, a pair of thermometers are mounted 
close together, the bulb of one being covered by 
damp muslin, and the other being freely exposed. 
If the air is completely saturated with moisture, no 
evaporation can take place from the damp muslin, 
and consequently the two thermometers will read 
the same. But if the air be comparatively dry, more 
or less evaporation will take place from the wet bulb, 
and its temperature will sink to that at which the 
air would be fully saturated with the moisture which 
it already contained. For the higher the temperature, 
the greater is its power of containing moisture. The 
difference of the reading of the two thermometers is, 
therefore, an index of humidity. The greater the 
difference, the greater the power of absorbing moisture, 




THE SELF-REGISTERING THERMOMETERS. 



THE METEOROLOGICAL DEPARTMENT 237 

or, in other words, the dryness of the air. The great 
shed already alluded to is devoted to these companion 
thermometers. 

Very closely connected with atmospheric pressure, 
as shown us by the barometer, is the study of the 
direction of winds. If we take a map of the British 
Isles and the neighbouring countries, and put down 
upon them the barometer readings from a great 
number of observing stations, and then join together 
the different places which show the same barometric 
pressure, we shall find that these lines of equal 
pressure technically called ' isobars ' are apt to run 
much nearer together in some places than in others. 
Clearly, where the isobars are close together it means 
that in a very short distance of country we have a 
great difference of atmospheric pressure. In this 
case we are likely to get a very strong wind blowing 
from the region of high pressure to the region of low 
pressure, in order to restore the balance. 

If, further, we had information from these various 
observing stations of the direction in which the 
wind was blowing, we should soon perceive other 
relationships. For instance, if we found that the 
barometer read about the same in a line across the 
country from east to west, but that it was higher in 
the north of the islands than in the south, we should 
then have a general set of winds from the east, and 
a similar relation would hold good if the barometer 
were highest in some other quarter ; that is, the 
prevailing wind will come from a quarter at right 
angles to the region of highest barometer, or, as it 
is expressed in what is known as ' Buys Ballot's law,' 



238 THE ROYAL OBSERVATORY 

' stand with your back to the wind, and the barometer 
will be lower on your left hand than on your right.' 
This law holds good for the northern hemisphere 
generally, except near to the equator ; in the southern 
hemisphere the right hand is the side of low barometer. 

The instruments for wind observation are of two 
classes : vanes to show its direction, and anemometers 
to show its speed and its pressure. These may be 
regarded as two different modes in which the strength 
of the wind manifests itself. Pressure anemometers 
are usually of two forms : one in which a heavy plate 
is allowed to swing by its upper edge in a position 
fronting the wind, the amount of its deviation from 
the vertical being measured ; and the other in which 
the plate is supported by springs, the degree of 
compression of the springs being the quantity 
registered in that case. Of the speed anemometers, 
the best known form is the * Robinson,' in which four 
hemispherical cups are carried at the extremities of 
a couple of cross bars. 

For the mounting of these wind instruments the 
old original Observatory, known as the Octagon 
Room, has proved an excellent site, with its flat roof 
surmounted by two turrets in the north-east and 
north-west corners, and raised some two hundred 
feet above high-water mark. 

The two chief remaining instruments are those 
for measuring the amount of rainfall and of full 
sunshine. The rain gauge consists essentially of a 
funnel to collect the rain, and a graduated glass to 
measure it. The sunshine recorder usually consists 
of a large glass globe arranged to throw an image 




THE ANEMOMETER ROOM, NORTH-WEST TURRET. 



THE METEOROLOGICAL DEPARTMENT 241 

of the sun on a piece of specially prepared paper. 
This image, as the sun moves in the sky, moves along 
the paper, charring it as it moves, and at the end 
of the day it is easy to see, from the broken, burnt 
trace, at what hours the sun was shining clear, and 
when it was hidden by cloud. 

An amusing difficulty was encountered in an 
attempt to set on foot another inquiry. The 
Superintendent of the Meteorological Department at 
the time wished to have a measure of the rate at 
which evaporation took place, and therefore exposed 
carefully measured quantities of water in the open 
air in a shallow vessel. For a few days the record 
seemed quite satisfactory. Then the evaporation 
showed a sudden increase, and developed in the most 
erratic and inexplicable manner, until it was found 
that some sparrows had come to the conclusion that 
the saucer full of water was a kindly provision for 
their morning c tub,' and had made use of it accordingly. 

A large proportion of the meteorological instru- 
ments at Greenwich and other first-class observatories 
are arranged to be self-recording. It was early felt 
that it was necessary that the records of the barometer 
and thermometer should be as nearly as possible 
continuous ; and at one time, within the memory 
of members of the staff still living, it was the duty 
of the observer to read a certain set of instruments 
at regular two-hour intervals during the whole 
of the day and night a work probably the most 
monotonous, trying, and distasteful of any that the 
Observatory had to show. 

The two-hour record was no doubt practically 

Q 



242 THE ROYAL OBSERVATORY 

equivalent to a continuous one, but it entailed a 
heavy amount of labour. Automatic registers were, 
therefore, introduced whenever they were available. 
The earliest of these were mechanical, and several 
still make their records in this manner. 

'On the roof of the Octagon Room we find, beside 
the two turrets already referred to, a small wooden 
cabin built on a platform several feet above the 
roof level. This cabin and the north-western turret 
contain the wind-registering instruments. Opening 
the turret door, we find ourselves in a tiny room 
which is nearly filled by a small table. Upon this 
table lies a graduated sheet of paper in a metal frame, 
and as we look at it, we see that a clock set up close 
to the table is slowly drawing the paper across it. 
Three little pencils rest lightly on the face of the 
paper at different points. One of these, and usually 
the most restless, is connected with a spindle which 
comes down into the turret from the roof, and which 
is, in fact, the spindle of the wind vane. The gearing 
is so contrived that the motion on a pivot of the vane 
is turned into motion in a straight line at right angles 
to the direction in which the paper is drawn by the 
clock. A second pencil is connected with the wind- 
pressure anemometer. The third pencil indicates 
the amount of rain that has fallen since the last 
setting, the pencil being moved by a float in the 
receiver of the rain gauge. 

An objection to all the mechanical methods of 
continuous registration is that, however carefully the 
gearing between the instrument itself and the pencil 
is contrived, however lightly the pencil moves over 



THE METEOROLOGICAL DEPARTMENT 243 

the paper, yet some friction enters in and affects the 
record : this is of no great moment in wind registration, 




THE ANEMOMETER TRACE. 



when we are dealing with so powerful an agent as 
the wind, but it becomes a serious matter when the 



244 THE ROYAL OBSERVATORY 

barometer is considered, since its variations require 
to be registered with the greatest minuteness. When 
photography, therefore, was invented, meteorologists 
were very prompt to take advantage of this new ally. 
A beam of light passing over the head of the column 
of mercury in a thermometer or barometer could 
easily be made to fall upon a drum revolving once in 
the twenty-four hours, and covered with a sheet of 
photographic paper. In this case, when the sensitive 
paper is developed, we find its upper half blackened, 
the lower edge of the blackened part showing an 
irregular curve according as the mercury in the 
thermometer or barometer rose or fell, and admitted 
less or more light through the space above it. 

Here we have a very perfect means of registration : 
the passage of the light exercises no friction or check 
on the free motion of the mercury in the tube, or on 
the turning of the cylinder covered by the sensitive 
paper, whilst it is easy to obtain a time scale on the 
register by cutting off the light for an instant say 
at each hour. In this way the wet and dry bulb 
thermometers in the great shed make their registers. 

The supply of material to the Meteorological 
Orifice is not the only use of the Greenwich meteoro- 
logical observations. Two elements of meteorology, 
the temperature and the pressure of the atmosphere, 
have the very directest bearing upon astronomical 
work. And this in two ways. An instrument is 
sensible to heat and cold, and undergoes changes of 
form, size, or scale, which, however absolutely minute, 
yet become, with the increased delicacy of modern 
work, not merely appreciable, but important. So too 



THE METEOROLOGICAL DEPARTMENT 245 

with the density of the atmosphere : the light from a 
distant star, entering our atmosphere, suffers refraction ; 
and being thus bent out of its path, the star appears 
higher in the heavens than it really is. The amount 
of this bending varies with the density of the layers 
of air through which the light has to pass. The two 
great meteorological instruments, the thermometer 
and barometer, are therefore astronomical instruments 
as well. 

In the arrangements at Greenwich the Magnetic 
Department is closely connected with the Meteoro- 
logical, and it is because the two departments have 
been associated together that the building devoted 
to both is constructed of wood, not brick, since 
ordinary bricks are made of clay which is apt to be 
more or less ferruginous. Copper nails have alone 
been employed in the construction of the buildings. 
The fire-grates, coal-scuttles, and fire-irons are all of 
the same metal. 

The growth of the Observatory has, however, 
made it necessary to set up some of the new tele- 
scopes, into the mounting of which much iron enters, 
very close to the magnetic building. The present 
Astronomer-Royal has therefore erected a Magnetic 
Pavilion right out in the park at an ample distance 
from these disturbing causes. 

The double department is, therefore, the most 
widely scattered in the whole Observatory. It is 
located for computing purposes in the west wing of 
the New Observatory ; many of its magnetic instru- 
ments are in the old Magnet House, others are 
across the park in the new Magnetic Pavilion ; the 



2 4 6 THE ROYAL OBSERVATORY 

anemometers are on the roof of the Octagon Room, 
Flamsteed's original observatory, and the self-regis- 
tering thermometers are in the south ground between 
the old Magnet House and the New Observatory. 
The object of the Magnetic Observatory is to 




MAGNETIC PAVILION EXTERIOR. 
{From a photograph by Mr. Lacey.) 

study the movements of the magnetic needle. The 
quaintest answer that I ever received in an examina- 
tion was in reply to the question, ' What is meant by 
magnetic inclination and declination ? ' The examinee 
replied : 



THE METEOROLOGICAL DEPARTMENT 247 

1 To make a magnet, you take a needle, and rub it on a 
lodestone. If it refuses or declines to become a magnet, 
that is magnetic declination ; if it is easily made a 
magnet, or is inclined to become one, that is magnetic 
inclination.' 

One greatly regretted that it was necessary to 
mark the reply according to its ignorance, and not, 
as one would have wished, in proportion to its 
ingenuity. Magnetic declination, however, as every- 
body knows, measures the deviation of the ' needle ' 
from the true geographical north and south direction ; 
the inclination or dip is the angle which a ' needle ' 
makes with the horizon. 

At one time the only method of watching the 
movements of the magnetic needles was by direct 
observation, just precisely as it was wont to be in the 
case of the barometer and thermometer. But the 
same agent that has been called in to help in their 
case has enabled the magnets also to give us a direct 
and continuous record of their movements. In prin- 
ciple the arrangement is as follows : A small light 
mirror is attached to the magnetic needle, and a 
beam of light is arranged to fall upon the mirror, 
and is reflected away from it to a drum covered 
with sensitive paper. If, then, the needle is perfectly 
at rest, a spot of light falls on the drum and blackens 
the paper at one particular point. The drum is made 
to revolve by clockwork once in twenty-four hours, 
and the black dot is therefore lengthened out into 
a straight line encircling the drum. If, however, the 
needle moves, then the spot of light travels up or 
down, as the case may be. 



248 



THE ROYAL OBSERVATORY 



Now, if we look at one of these sheets of photo- 
graphic paper after it has been taken from the drum, 
we shall see that the north pole of the magnet has 
moved a little, a very little, towards the west in the 
early part of the day, say from sunrise to 2 p.m., and 
has swung backwards from that hour till about 10 p.m., 
remaining fairly quiet during the night. The extent 




MAGNETIC PAVILION INTERIOR. 
{From a photograph by Mr. Lacey.) 



of this daily swing is but small, but it is greater in 
summer than in winter, and it varies also from year 
to year. 

Besides this daily swing, there occasionally happen 
what are called ' magnetic storms ; ' great convulsive 
twitchings of the needle, as if some unseen operator 



THE METEOROLOGICAL DEPARTMENT 249 

were endeavouring, whilst in a state of intense excite- 
ment, to telegraph a message of vast importance, so 
rapid and so sharp are the movements of the needle 
to and fro. These great storms are felt, so far as we 
know, simultaneously over the whole earth, and the 
more characteristic begin with a single sharp twitch 
of the needle towards the east. 

Besides the movements of the magnetic needle, 
the intensity of the currents of electricity which are 
always passing through the crust of the earth are also 
determined at Greenwich ; but this work has been 
rendered practically useless for the last few years by 
the construction of the electric railway from Stockwell 
to the City. Since it was opened, the photographic 
register of earth currents has shown a broad blurring 
from the moment of the starting of the first train in 
the morning to the stopping of the last train at night. 
As an indication of the delicacy of modern instru- 
ments, it may be mentioned that distinct indications 
of the current from this railway have been detected 
as far of! as North Walsham, in Norfolk, a distance 
of more than a hundred miles. A further illustration 
of the delicacy of the magnetic needles was afforded 
shortly after the opening of the railway referred to. 
On one occasion the then Superintendent of the 
Magnetic Department visited the Generating Station 
at Stockwell, and on his return it was noticed 
day after day that the traces from the magnets 
showed a curious deflection from 9 a.m. to 3 p.m., 
the hours of his attendance. This gave rise to some 
speculation, as it did not seem possible that the 
gentleman could himself have become magnetized. 



250 THE ROYAL OBSERVATORY 

Eventually, the happy accident of a fine day solved 
the mystery. That morning the Superintendent left 
his umbrella at home, and the magnets were undis- 
turbed. The secret was out. The umbrella had 
become a permanent magnet, and its presence in the 
lobby of the magnetic house had been sufficient to 
influence the needles. 









CHAPTER X 

THE HELIOGRAPHIC DEPARTMENT 

So far the development of the Observatory had been 
along the central line of assistance to navigation. 
But the Magnetic Department led on to one which 
had but a very secondary connection with it. 

A greatly enhanced interest was given to the 
observations of earth magnetism, when it was found 
that the intensity and frequency of its disturbances 
were in close accord with changes that were in 
progress many millions of miles away. That the 
surface of the sun was occasionally diversified by the 
presence of dark spots, had been known almost from 
the first invention of the telescope ; but it was not 
until the middle of the present century that any 
connection was established between these solar 
changes and the changes which took place in the 
magnetism of the earth. Then two observers, the 
one interesting himself entirely with the spots on 
the sun, the other as wholly devoted to the study of 
the movements of the magnetic needle, independently 
found that the particular phenomenon which each 
was watching was one which varied in a more or less 
regular cycle. And further, when the cycles were 

251 



252 THE ROYAL OBSERVATORY 

compared, they proved to be the same. Whatever 
the secret of the connection, it is now beyond dispute 
that as the spots on the sun become more and more 
numerous, so the daily swing of the magnetic needle 
becomes stronger ; and, on the other hand, as the 
spots diminish, so the magnetic needle moves more 
and more feebly. 

This discovery has given a greatly increased 
significance to the study of the earth's magnetism. 
The daily swing, the occasional storms,' are seen to 
be something more than matters of merely local 
interest ; they have the closest connection with 
changes going on in the vast universe beyond ; they 
have an astronomxal importance. 

And it was soon felt to be necessary to supple- 
ment the Magnetic Observatory at Greenwich by one 
devoted to the direct study of the solar surface ; and 
here again that invaluable servant of modern science, 
photography, was ready to lend its help. Just as, 
by the means of photography, the magnets recorded 
their own movements, so even more directly the sun 
himself makes register of his changes by the same 
agency, and gives us at once his portrait and his 
autograph. 

This new department was again due to Airy, and 
in 1873 the 'Kew ' photo-heliograph, which had been 
designed by De la Rue for this work, was installed 
at Greenwich. 

In order to photograph so bright a body as the 
sun, it is not in the least necessary to have a very 
large telescope. The one in common use at Greenwich 
from 1875 to 1897, is only four inches in aperture 



THE HELIOGRAPHIC DEPARTMENT 255 

and even that is usually diminished by a cap to three 
inches, and its focal length is but five feet. This is 
not very much larger than what is commonly called 
a ' student's telescope/ but it is amply sufficient for 
its work. 

This 'Dallmeyer' telescope, so called from the 
name of its maker, is one of five identical instruments 
which were made for use in the observation of the 
transit of Venus of 1874, and which, since they are 
designed for photographing the sun, are called ' photo- 
heliographs.' 

The image of the sun in the principal focus of this 
telescope is about six-tenths of an inch in diameter ; 
but a magnifying lens is used, so that the photograph 
actually obtained is about eight inches. Even with 
this great enlargement, the light of the sun is so 
intense that with the slowest photographic plates 
that are made the exposure has to be for only a very 
small fraction of a second. This is managed by 
arranging a very narrow slit in a strip of brass. The 
strip is made to run in a groove across the principal 
focus. Before the exposure, it is fastened up so as to 
cut off all light from entering the camera part of the 
telescope. When all is ready, it is released and drawn 
down very rapidly by a powerful spring, and the slit, 
flying across the image of the sun, gives exposure to 
the plate for a very minute fraction of a second in 
midsummer for less than a thousandth of a second. 

Two of these photographs are taken every fine 
day at Greenwich ; occasionally more, if anything 
specially interesting appears to be going on. But in 
our cloudy climate at least one day in three gives no 



256 THE ROYAL OBSERVATORY 

good opportunity for taking photographs of the sun, 
and in the winter time long weeks may pass without 
a chance. The present Astronomer-Royal, Mr. 
Christie, has therefore arranged that photographs 
with precisely similar instruments should be taken in 
India and in the Mauritius, and these are sent over 
to Greenwich as they are required, to fill up the 
gaps in the Greenwich series. We have therefore at 
Greenwich, from one source or another, practically a 
daily record of the state of the sun's surface. 

More recently the ' Dallmeyer' photo-heliograph, 
though still retained for occasional use, has been 
superseded generally by the ' Thompson ' ; a photo- 
graphic refractor of nine inches aperture, and nearly 
nine feet focal length, presented to the Observatory 
by Sir Henry Thompson. The image of the sun 
obtained after enlargement in the telescope, with this 
instrument, is seven and a half inches in diameter. 
The Thompson ' is mounted below the great twenty- 
six-inch photographic refractor, also presented to the 
Observatory by Sir Henry Thompson, in the dome 
which crowns the centre of the New Observatory. 

A photograph of the sun taken, it has next to 
be measured, the four following particulars being 
determined for each spot : First, its distance from 
the centre of the image of the sun ; next, the angle 
between it and the north point ; thirdly, the size of 
the spot ; and fourthly, the size of the umbra of the 
spot, that is to say, of its dark central portion. The 
size or area of the spot is measured by placing a thin 
piece of glass, on which a number of cross-lines have 
been ruled one-hundredth of an inch apart, in contact 



THE HELIOGRAPHIC DEPARTMENT 257 

with the photograph. These cross-lines make up a 
number of small squares, each the ten-thousandth 
(xoioa m P art f a sc l uare inch in area. When the 
photograph and the little engraved glass plate are 
nearly in contact, the photograph is examined with 
a magnifying glass, and the number of little squares 
covered by a given spot are counted. It will give 
some idea of the vast scale of the sun when it is 
stated that a tiny spot, so small that it only just 
covers one of these little squares, and which is only 
one- millionth of the visible hemisphere of the sun in 
area, yet covers in actual extent considerably more 
than one million of square miles. 

The dark spots are not the only objects on the 
sun's surface. Here and there, and especially near 
the edge of the sun, are bright marks, generally in 
long branching lines, so bright as to appear bright 
even against the dazzling background of the sun itself. 
These are called 'faculae,' and they, like the spots, 
have their times of great abundance and of scarcity, 
changing on the whole at the same time as the spots. 
After the solar photographs have been measured, 
the measures must be 'reduced/ and the positions 
of the spots as expressed in longitude and latitude on 
the sun computed. There is no difficulty in doing 
this, for the position of the sun's equator and poles 
have long been known approximately, the sun re- 
volving on its axis in a little more than twenty-five 
days, and carrying of course the spots and faculae 
round with him. 

There are few studies in astronomy more engross- 
ing than the watch on the growth and changes of the 

R 



258 THE ROYAL OBSERVATORY 

solar spots. Their strange shapes, their rapid move- 
ments, and striking alterations afford an unfailing 
interest. For example, the amazing spectacle is 
continually being afforded of a spot, some two, three, 
or four hundred millions of square miles in area, 
moving over the solar surface at a speed of three 
hundred miles an hour, whilst other spots in the same 
group are remaining stationary. But a higher interest 
attaches to the behaviour of the sun as a whole than 
to the changes of any particular single spot ; and the 
curious fact has been brought to light, that not only 
do the spots increase and diminish in a regular cycle 
of about eleven years in length, but they also affect 
different regions of the sun at different points of the 
cycle. At the time when spots are most numerous 
and largest, they are found occupying two broad 
belts, the one with its centre about 15 north of the 
equator, the other about as far south, the equator 
itself being very nearly free from them. But as the 
spots begin to diminish, so they appear continually 
in lower and lower latitudes, until instead of having 
two zones of spots there is only one, and this one 
lies along the equator. By this time the spots have 
become both few and small. The next stage is that 
a very few small spots are seen from time to time in 
one hemisphere or the other at a great distance from 
the equator, much farther than any were seen at the 
time of greatest activity. There are then for a little 
time three sun-spot belts, but the equatorial one soon 
dies out. The two belts in high latitude, on the other 
hand, continually increase ; but as they increase, so 
do they move downwards in latitude, until at length 







$ 

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* 

5 S 



- 4 

<3 



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THE HELIOGRAPHIC DEPARTMENT 261 

they are again found in about latitude 15 north or 
south, when the spots have attained their greatest 
development. 

The clearest connection between the magnetic 
movements and the sun-spot changes is seen when 
we take the mean values of either for considerable 
periods of time, as, for instance, year by year. But 
occasionally we have much more special instances of 
this connection. Some three or four times within the 
last twenty years an enormous spot has broken out 
on the sun, a spot so vast that worlds as great as our 
own could lie in it like peas in a breakfast saucer, 
and in each case there has been an immediate and a 
threefold answer from the earth. One of the most 
remarkable of these occurred in November, 1882. A 
great spot was then seen covering an area of more 
than three thousand millions of square miles. The 
weather in London happened to be somewhat foggy, 
and the sun loomed, a dull red ball, through the haze, 
a ball it was perfectly easy to look at without specially 
shading the eyes. So large a spot under such cir- 
cumstances was quite visible to the naked eye, and 
it caught the attention of a great number of people, 
many of whom knew nothing about the existence of 
spots on the sun. 

This great disturbance, evidently something of 
the nature of a storm in the solar atmosphere, 
stretched over one hundred thousand miles on the 
surface of the sun. The disturbance extended 
farther still, even to nearly one hundred millions of 
miles. For simultaneously with the appearance of 
the spot the magnetic needles at Greenwich began 



262 THE ROYAL OBSERVATORY 

to suffer from a strange excitement, an excitement 
which grew from day to day until it had passed 
half-way across the sun's disc. As the twitchings 
of the magnetic needle increased in frequency and 
violence, other symptoms were noticed throughout 
the length of the British Isles. Telegraphic com- 
munication was greatly interfered with. The tele- 
graph lines had other messages to carry more urgent 
than those of men. The needles in the telegraph 
instruments twitched to and fro. The signal bells 
on many of the railway lines were rung, and some 
of the operators received shocks from their instru- 
ments. Lastly, on November 17, a superb aurora 
was witnessed, the culminating feature of which was 
the appearance, at about six o'clock in the evening, 
of a mysterious beam of greenish light, in shape 
something like a cigar, and many degrees in length, 
which rose in the east and crossed the sky at a pace 
much quicker than but nearly as even as that of sun, 
moon, or stars, till it set in the west two minutes 
after its rising. 

So far we have been dealing only with effects. 
Their causes still rest hidden from us. There is 
clearly a connection between the solar activity as 
shown by the spots and the agitation of the magnetic 
needles. But many great spots find no answer in 
any magnetic vibration, and not a few considerable 
magnetic storms occur when we can detect no great 
solar changes to correspond. 

Thus even in the simplest case before us we have 
still very much to explain. Two far more difficult 
problems are still offered us for solution. What is 



THE HELIOGRAPHIC DEPARTMENT 263 

the cause of these mysterious solar spots ? and have 
they any traceable connection with the fitful vagaries 
of earthly weather ? It was early suggested that 
probably the first problem might find an answer in 
the ever-varying combinations and configurations of 
the various planets, and that the sun-spots in their 
turn might hold the key of our meteorology. Both 
ideas were eagerly followed up not that there was 
much to support either, but because they seemed to 
offer the only possible hope of our being able to 
foretell the general current of weather change for any 
long period in advance. So far, however, the first 
idea may be considered as completely discredited. 
As to the second, there would appear to be, in the 
case of certain great tropical and continental countries 
like India, some slight but by no means conclusive 
evidence of a connection between the changes in the 
annual rainfall and the changes in the spotted surface 
of the sun. Dr. Meldrum, the late veteran Director 
of the great Meteorological Observatory in Mauritius, 
has expressed himself as confident that the years of 
most spots are the years of most violent cyclones in 
the Indian Ocean. But this is about as far as real 
progress has been made, and it may be taken as 
certain that many years more of observation will be 
required, and the labours of many skilful investigators, 
before we can hope to carry much farther our know- 
ledge as to any connection between storm and sun. 

A further relation of great interest has come to 
light within the last few years. The year 1868 
opened a new epoch in the study of eclipses of the 
sun. These, perhaps, scarcely lie within the scope 



264 THE ROYAL OBSERVATORY 

of a book on the Royal Observatory, since Greenwich 
has seen but one in all its history. That fell in the 
year 171 5 ; for the next it must wait many centuries. 
Yet, as the late Astronomer Royal conducted three 
expeditions to see total eclipses, and as the present 
Astronomer Royal has undertaken a like number, 
and members of the staff have been sent on other 
occasions, it may not be deemed quite a digression 
to refer to one feature which they have brought to 
light. 

When the dark body of the moon has entirely 
hidden the sun, we have revealed to us, there and 
then only, that strange and beautiful surrounding of 
the sun which we call the corona. The earlier 
observations of the corona seem to reveal it as a 
body of the most weird and intricate form, a form 
which seemed to change quite lawlessly from one 
eclipse to another. But latterly it has been abun- 
dantly clear that the forms which it assumes may be 
grouped under a few well-defined types. In 1878 
the corona was of a particularly simple and striking 
character. Two great wings shot out east and west 
in the direction of the sun's equator ; round either 
pole was a cluster of beautiful radiating 'plumes.' 
It was then recollected that the corona of 1867 had 
been of precisely the same character, both years 
being years when sun-spots were at their fewest. 
The coronae, on the other hand, seen at times when 
sun-spots are more abundant, were of an altogether 
different character, the streamers being irregularly 
distributed all round the sun. Other types also have 
been recognized, and it is perfectly apparent that the 



THE HELIOGRAPHIC DEPARTMENT 265 

corona changes its shape in close accordance with 
the eleven-year period. The eclipses of 1889 and 
1900, for example, showed coronae that bore the very 
closest resemblance to those of 1878 and 1866, the 
interval of eleven years bringing a return to the same 
form. 

The further problem, therefore, now confronts us : 
Does the corona produce the sun-spots, or do the 
sun-spots produce the corona, or are both the result 
of some mysterious magnetic action of the sun, an 
action powerful enough on occasion to thrill through 
and through this world of ours, ninety-three millions 
of miles away ? 



CHAPTER XI 

THE SPECTROSCOPIC DEPARTMENT 

Another department was set on foot by Aiiy at the 
same time as the Heliographic Department, and in 
connection with it ; and it is the department which 
has the greatest of interest for the general public. 
This deals with astronomical physics, or astrophysics, 
as it is sometimes more shortly called ; the astronomy, 
that is, which treats of the constitution and condition 
of the heavenly bodies, not with their movements. 

The older astronomy, on the other hand, confined 
itself to the movements of the heavens so entirely 
that Bessel, the man whose practical genius revo- 
lutionized the science of observation, and whose 
influence may be traced throughout in Airy's great 
reconstitution of Greenwich Observatory, denied that 
anything but the study of the celestial movements 
had a right to the title of astronomy at all. Hardly 
more than sixty years ago he wrote : 

1 What astronomy is expected to accomplish is evidently 
at all times the same. It may lay down rules by which 
the movements of the celestial bodies, as they appear to 
us upon the earth, can be computed. All else which we 
may learn respecting these bodies, as, for example, their 
266 



THE SPECTROSCOPIC DEPARTMENT 267 

appearance, and the character of their surfaces, is, indeed, 
not undeserving of attention, but possesses no proper astro- 
nomical interest. Whether the mountains of the moon are 
arranged in this way or in that is no further an object of 
interest to astronomers than is a knowledge of the mountains 
of the earth to others. Whether Jupiter appears with dark 
stripes upon its surface, or is uniformly illuminated, pertains 
as little to the inquiries of the astronomer ; and its four 
moons are interesting to him only for the motions they 
have. To learn so perfectly the motions of the celestial 
bodies that for any specified time an accurate computation 
of these can be given that was, and is, the problem which 
astronomy has to solve.' 

There is a curious irony of progress which seems 
to delight in falsifying the predictions of even master 
minds as to the limits beyond which it cannot 
advance. Bessel laid down his dictum as to the true 
subjects of astronomical inquiry, Comte declared that 
we could never learn what were the elements of 
which the stars were composed, at the very time that 
the first steps were being taken towards the creation 
of a research which should begin by demonstrating 
the existence in the heavenly bodies of the elements 
with which we are familiar on the earth, and should 
go on to prove itself a true astronomy, even in 
Bessel's restricted sense, by supplying the means for 
determining motion in a direction which he would 
have thought impossible that is to say, directly to 
or from us. 

The years that followed Kirchhoff's application 
of the spectroscope to the study of the sun, and his 
demonstration that sodium and iron existed in the 
solar atmosphere, were crowded with a succession of 
brilliant discoveries in the same field. Kirchhoff, 



268 THE ROYAL OBSERVATORY 

Bunsen, Angstrom, Thalen, added element after 
element to the list of those recognized in the sun. 
Huggins and Miller carried the same research into 
a far more difficult field, and showed us the same 
elements in the stars. Rutherfurd and Secchi grouped 
the stars according to the types of their spectra, and 
so laid the foundations of what may be termed stellar 
comparative anatomy. Huggins discovered true 
gaseous nebulae, and so revived the nebular theory, 
which had been supposed crushed when the great 
telescope of Lord Rosse appeared to have resolved 
several portions of the Orion nebula into separate 
stars. The great riddle of 'new stars' which still 
remains a riddle was at least attacked, and glowing 
hydrogen was seen to be a feature in their constitution. 
Glowing hydrogen, again, was, in the observation of 
total eclipses, seen to be a principal constituent 
of those surroundings of our own sun which we 
now call prominences and chromosphere. Then the 
method was discovered of observing the prominences 
without an eclipse, and they were found to wax and 
wane in more or less sympathy with the solar spots. 
Sun-spots, planets, comets, meteors, variable stars, all 
were studied with the new instrument, and all yielded 
to it fresh and valuable, and often unexpected, 
information. 

In this activity Greenwich Observatory practically 
took no part. Airy, ever mindful of the original 
purpose of the Observatory, and deeply imbued with 
views similar to those which we have quoted from 
Bessel, considered that the new science lay outside 
the scope of his duties, until in Mr., now Sir William, 




THE GREAT NEBULA IN ORION. 

{From a photograph taken at the Royal Observatory, Greenwich , 
December I, 1899, with an exposure of 2\ hours.) 



THE SPECTROSCOPIC DEPARTMENT 271 

Huggins's skilful hands the spectroscope showed itself 
not only as a means for determining the condition 
and constitution of the stars, but also their movements 
until, in short, it had shown itself as an astronomical 
instrument even within Bessel's narrow definition. 

The principle of this inquiry is as follows : If a 
source of light is approaching us very rapidly, then 
the waves of light coming from it necessarily appear 
a little shorter than they really are, or, in other words, 
that light appears to be slightly more blue the blue 
waves being shorter than the red than it really is. 
A similar thing with regard to the waves of sound is 
often noticed in connection with a railway train. If 
an express train, the whistle of which is blowing the 
whole time, dashes past us at full speed, there is a 
perceptible drop in the note of the whistle after it has 
gone by. The sound waves as it was coming were a 
little shortened, and the whistle therefore appeared to 
have a sharper note than it had in reality. And in 
the same way, when it had gone by, the sound waves 
were a little lengthened, making the note of the 
whistle appear a very little flatter. 

Such a change of colour in a star could never 
have been detected without the spectroscope ; but 
since when light passes through a prism the shorter 
waves are refracted more strongly, that is to say, are 
more turned out of their course than the longer, the 
spectroscope affords us the means of detecting and 
measuring this change. Let us suppose that the 
lines of hydrogen are recognized in a given star. If 
we compare the spectrum of this star with the 
spectrum of a tube containing hydrogen and through 



272 THE ROYAL OBSERVATORY 

which the electric spark is passing, we shall be able 
to see whether any particular hydrogen line occupies 
the same place as shown by the two spectra. If the 
line from the star is a little to the red of the line from 
the tube, the star must be receding from us ; if to the 
blue, approaching us. The amount of displacement 
may be measured by a delicate micrometer, and the 
rate of motion concluded from it. 

The principle is clear enough. The actual working 
out of the observation was one of very great difficulty. 
The movements of the stars towards us, or away from 
us, are, in general, extremely slow as compared with 
the speed of light itself; and hence the apparent 
shift in the position of a line is only perceptible when 
a very powerful spectroscope is used. This means 
that the feeble light of a star has to be spread out 
into a great length of spectrum, and a very powerful 
telescope is necessary. The work of observing the 
motions of stars in the line of sight was started at 
Greenwich in 1875, the 'Great Equatorial' being 
devoted to it. This telescope, of \2\ inches aperture, 
was not powerful enough to do much more than 
afford a general indication of the direction in which 
the principal stars were moving, and to confirm in a 
general way the inference which various astronomers 
had found, from discussing the proper motions of 
stars, that the sun and the solar system were moving 
towards that part of the heavens where the constella- 
tions Hercules and Lyra are placed. In 1891, 
therefore, the work was discontinued, and as already 
mentioned, the 12 J telescope by Merz was removed 
to make room for the present much larger instrument 



THE SPECTROSCOPIC DEPARTMENT 275 

by Sir Howard Grubb, upon the same mounting. 
The new telescope being much larger than the one 
for which mounting and observing room were 
originally built, it was not possible to put the 
spectroscope in the usual position, in the same 
straight line as the great telescope. It was therefore 
mounted under it, and parallel to it, and the light of 
the star was brought into it after two reflections. 
The observer therefore stood with his back to the 
object and looked down into the spectroscope. It 
had, however, become apparent by this time that this 
most delicate field of work was one for which photo- 
graphy possessed several advantages, and as Sir 
Henry Thompson had made the munificent gift to 
the Observatory of a great photographic equatorial, it 
was resolved to devote the 28-inch telescope chiefly 
to double-star work, and to transfer the spectroscope 
to the 'New Building.' 

The * New Observatory ' in the south ground is 
crowned indeed with the dome devoted to the great 
Thompson photographic refractor, but this is not its 
chief purpose. Its principal floor contains four fine 
rooms which are used as i computing rooms ' for the 
office work, that is to say, of the Observatory. Of 
these the principal is in the nOrth wing, where the 
main entrance is placed, and is occupied by the 
Astronomer Royal and the two chief assistants. 
The basement contains the libraries and the workshops 
of the mechanics and carpenters. The upper floor 
will eventually be used for the storage of photographs 
and manuscripts, and the terrace roofs of the four 
wings will be exceedingly convenient for occasional 



276 THE ROYAL OBSERVATORY 

observations, as, for example, of meteor showers. 
The central dome, which rises high above the level of 
the terraces, is the only room in the building devoted 
to telescopic work. As in the New Altazimuth 
building, a ring of circular lights just below the 
coping of the wall recalls the portholes of a ship, and 
again reminds us of the connection of the Observatory 
with navigation. 




THE WORKSHOP. 



Here the spectroscope is now placed, but not, as 
it happens, on the Thompson refractor. The equa- 
torial mounting in this new dome is a modification of 
what is usually called the * German ' form of mounting 
that is to say, there is but one pier to support the 
telescope, and the telescope rides on one side of the, 
pier and a counterpoise balances it on the other 




THE 30-TNCH REFLECTOR WITH THE NEW SPECTROSCOPE 
ATTACHED. 



THE SPECTROSCOPIC DEPARTMENT 279 

The 'Great Equatorial,' on the other hand, is an 
example of the English mounting, and has two piers, 
one north and the other south, whilst the telescope 
swings in a frame between them. In the new dome 
three telescopes are found rigidly connected with each 
other on one side of the pier, the telescopes being (1) 
the great Thompson photographic telescope, double 
the aperture and double the focal length of the 
standard astrographic telescope used for the Interna- 
tional Photographic Survey ; (2) the I2f telescope by 
Merz, that used to be in the great South-East dome, 
but which is now rigidly connected with the Thompson 
refractor as a guide telescope ; and (3) a photographic 
telescope of 9 inches aperture, already described as 
the Thompson ' photo-heliograph, and used for 
photographing the sun or in eclipse expeditions. 
The counterpoise to this collection of instruments is 
not a mere mass of lead, but a powerful reflector of 
30 inches' aperture, and it is to this telescope that the 
spectroscope is now attached. At the present time, 
however (August, 1900), regular work has not been 
commenced with it. 

Beside this attempt to determine the motions of 
the stars as they approach us or retreat from us, 
on rare occasions the spectroscope has been turned 
on the planets. As these shine by reflected light, 
their spectra are normally the same as that of the 
sun. Mars appeared to the writer, as to Huggins 
and others, to show some slight indication of the 
presence of water vapour in its atmosphere. Jupiter 
and Saturn show that their atmospheres contain some 
absorbing vapour unknown to ours. And Uranus 



28o THE ROYAL OBSERVATORY 

and Neptune, faint and distant as they are, not only 
show the same dark band given by the two nearer 
planets, but several others. More attractive has been 
the examination of the spectra of the brighter comets 
that have visited us. The years 1881 and 1882 were 
especially rich in these. The two principal comets of 
1 88 1 were called after their respective discoverers, 
Tebbutt's and Schaeberle's. They were not bright 
enough to attract popular attention, though they 
could be seen with the naked eye, and both gave 
clear indications of the presence of carbon, their 
spectra closely resembling that of the blue part of a 
gas or candle flame. There was nothing particularly 
novel in these observations, since comets usually show 
this carbon spectrum, though why they should is still 
a matter for inquiry ; but the two comets of the 
following year were much more interesting. Both 
comets came very near indeed to the sun. The earlier 
one, called from its discoverer Comet Wells, as it drew 
near to the sun, began to grow more and more yellow, 
until in the first week of June it looked as full an 
orange as even the so-called red planet, Mars. The 
spectroscope showed the reason of this at a glance. 
The comet had been rich in sodium. So long as it 
was far from the sun the sodium made no sign, but as 
it came close to it the sodium was turned into glowing 
vapour under the fierce solar heat. And as the writer 
saw it in the early dawn of June 7, the comet itself 
was a disc of much the same colour as Mars, whilst 
its spectrum resembled that of a spirit lamp that has 
been plentifully fed with carbonate of soda or common 
salt. The ' Great Comet ' of the autumn of the same 



THE SPECTROSCOPIC DEPARTMENT 281 

year, and which was so brilliant an object in the early 
morning, came yet nearer to the sun, and the heating 
process went on further. The sodium lines blazed 
up as they had done with Comet Wells, but under the 
fiercer stress of heat to which the Great Comet was 
subjected, the lines of iron also flashed out, a significant 
indication of the tremendous temperature to which it 
was exposed. 

There are two other departments of spectroscopic 
work which it was attempted for a time td carry on as 
part of the Greenwich routine. These were the daily 
mapping of the prominences round the sun, and the 
detailed examination of the spectra of sun-spots. 
Both are almost necessary complements of the work 
done in the heliographic department that is to say, 
the work of photographing the appearance of the 
sun day by day, and of measuring the positions and 
areas of the spots. For the spots afford but one index 
out of several, of the changes in the sun's activity. 
The prominences afford another, nor can we at the 
present moment say authoritatively which is the more 
significant. Then again, with regard to the spots 
themselves, it is not certain that either their extent 
or their changes of appearance are the features which 
it is most important for us to study. We want, if 
possible, to get down to the soul of the spot, to find 
out what makes one spot differ from another; and 
here the spectroscope can help us. Great sun-spots 
are often connected with violent agitation of the 
magnetic needles, and with displays of aurorae. But 
they are not always so, and the inquiry, * What makes 
them to differ ? ' has been made again and again, 



282 THE ROYAL OBSERVATORY 

without as yet receiving any unmistakable answer. The 
great spot of November, 1882, which was connected with 
so remarkable an aurora and so violent a magnetic 
storm, was as singular in its spectrum as in its earthly 
effects. The sun was only seen through much fog, 
and the spectrum was therefore very faint, but shooting 
up from almost every part of its area, except the 
very darkest, were great masses of intensely brilliant 
hydrogen, evidently under great pressure. The 
sodium lines were extremely broadened, and on 
November 20 a broad bright flame of hydrogen was 
seen shooting up at an immense speed from one edge 
of the nucleus. A similar effect an outburst of 
intensely luminous hydrogen has often been observed 
in spots which have been accompanied by great 
magnetic storms ; and it may even be that it is this 
violent eruption of intensely heated gas which has 
the directest connection with the magnetic and 
auroral disturbances here upon earth. 

This sun-spot work was not carried on for very 
long, as only one assistant could be spared for the 
entire solar work of whatever character. Yet in that 
time an interesting discovery was made by the writer 
namely, that in the green part of the spectrum of 
certain spots a number of broad diffused lines or 
narrow bands made their appearance from time to 
time, and especially when sun-spots were increasing 
in number, or were at their greatest development. 

The prominence work had also to be dropped, 
partly for the same reason, but chiefly because the 
atmospheric conditions at Greenwich are not suitable 
for these delicate astrophysical researches. When 



THE SPECTROSCOPIC DEPARTMENT 283 

the Observatory was founded ' in the golden days ' 
of Charles II., Greenwich was a little country town 
far enough removed from the great capital, and no 
interference from its smoke and dust had to be feared 
or was dreamt of. Now the ' great wen/ as Cobbett 
called it, has spread far around and beyond it, and 
the days when the sky is sufficiently pure round the 
sun for successful spectrum work on the spots or 
prominences are few indeed. 

Whether in the future it will be thought advisable 
for the Royal Observatory to enter into serious 
competition in inquiries of this description with the 
great ' astrophysical ' observatories of the Continent 
and of America Potsdam, Meudon, the Lick, and 
the Yerkes we cannot say. That would involve a 
very considerable departure from its original pro- 
gramme, and probably also a departure from its 
original site. For the conditions at Greenwich tend 
to become steadily less favourable for such work, and 
it would most probably be found that full efficiency 
could only be secured by setting up a branch or 
branches far from the monster town. 

With the older work it is otherwise. So long as 
Greenwich Park and Blackheath are kept as it is 
to be hoped they always will be sacred from the 
invasion of the builder ; so long as no new railways 
burrow their tunnels in the neighbourhood of the 
Observatory, so long the fundamental duties laid 
upon Flamsteed, 'of Rectifying the Tables of the 
Motions of the Heavens and the Places of the Fixed 
Stars,' will be carried out by his successors on 
Flamsteed Hill. 



CHAPTER XII 

THE ASTROGRAPHIC DEPARTMENT 

The two last departments mentioned, the heliographic 
and spectroscopic, lie clearly and unmistakably 
outside the terms of the original warrant of the 
Observatory, though the progress of science has led 
naturally and inevitably to their being included in 
the Greenwich programme. But the Astrographic 
Department, though it could no more have been 
conceived in the days of Charles II. than the 
spectroscopic, does come within the terms of the 
warrant, and is but an expansion of that work of 
4 Rectifying the Places of the Fixed Stars/ which 
formed part of the programme enjoined upon Flam- 
steed, the first Astronomer Royal, at the first founda- 
tion of the Observatory, and which was so diligently 
carried out by him, the first Greenwich catalogue, 
containing about 3000 stars, being due to his labours. 
His immediate successors did much less in this 
field, though Bradley's observations were published, 
long after his death, as a catalogue of 3222 stars, in 
some aspects the most important ever issued. Pond, 
the sixth Astronomer Royal, restored catalogue- 
making to a prominent place in the Greenwich routine, 

284 




'CHART PLATE' OF THE PLEIADES. 

{From a photograph taken at the Royal Observatory ', Greemvich, with an 
exposure of forty mimites. ) 



THE ASTROGRAPHIC DEPARTMENT 287 

and his precedent is sedulously followed to-day. But 
each of these was confined to about 3000 stars. The 
necessity has long been felt for a much ampler census, 
and Argelander, at the Bonn Observatory, brought 
out a catalogue of 324,000 stars north of South 
declination 2, a work which has been completed by 
Schonfeld, who carried the census down to South 
declination 23 , and by the two great astronomers of 
Cordoba, South America, Dr. Gould and Dr. Thome, 
by whom it was extended to the South Pole. 

These last three catalogues embrace stars of all 
magnitudes down to the 9th or 10th ; but certain 
astronomers had endeavoured to go much lower, and 
to make charts of limited portions of the sky down to 
even the 14th magnitude. 

From the very earliest days that men observed 
the stars, they could not help noticing that 'one star 
dififereth from another star in glory/ and consequently 
they divided them into six classes, according to their 
brightness classes which are commonly spoken of 
now as magnitudes. The ordinary 6th magnitude 
star is one which can be clearly seen by average sight 
on a good night, and it gives us about one-hundredth 
the light of an average 1st magnitude star. Sirius, 
the brightest of all the fixed stars, is called a 1st 
magnitude star, but is really some six or seven times 
as bright as the average. It would take, therefore, 
more than two and a half million stars of the 14th 
magnitude to give as much light as Sirius. 

It is evident that so searching a census as to 
embrace stars of the 14th magnitude would involve 
a most gigantic chart. But the work went on in 



288 THE ROYAL OBSERVATORY 

more than one Observatory for a considerable time, 
until at last the observers entered on to the region 
of the Milky Way. Here the numbers of the stars 
presented to them were so great as to baffle all 
ordinary means of observation. What could be 
done ? 

Just at this time immense interest was caused in 
the astronomical world by the appearance of the great 
comet of 1882. It was watched and observed and 
sketched by countless admirers, but more important 
still, it was photographed, and some of its photographs, 
taken at the Royal Observatory, Cape of Good Hope, 
showed not only the comet with marvellous beauty 
of detail, but also thousands of stars, and the success 
of these photographs suggested to her Majesty's 
Astronomer at the Cape, Dr. Gill, that in photography 
we possessed the means for making a complete sky 
census even to the 14th magnitude. 

The project was thought over in all its bearings, 
and in 1887 a great conference of astronomers at 
Paris resolved upon an international scheme for 
photographing the entire heavens. The work was to 
be divided between eighteen Observatories of different 
nationalities. It was to result in a photographic 
chart extending to the 14th magnitude, and probably 
embracing some forty million stars, and a catalogue 
made from measures of the photographs down to 
the nth magnitude, which would probably include 
between two and three million stars. 

The eighteen Observatories all undertook to use 
instruments of the same capacity. This was to be 
a photographic refractor, with an object-glass of 13 




THE CONTROL PENDULUM AND THE BASE OF THE 
THOMPSON TELESCOPE. 



2 9 o THE ROYAL OBSERVATORY 

inches aperture and u feet focus. At Greenwich 
this telescope is mounted equatorially that is, so as 
to follow the stars in their courses and is mounted 
on the top of the pier that once supported Halley's 
quadrant. The telescope is driven by a most efficient 
clock, whose motive power is a heavy weight. The 
rate of the weight in falling is regulated by an 
ingenious governor, which brings its speed very nearly 
indeed to that of the star, and any little irregularities 
in its motion are corrected by the following device. 
A seconds pendulum is mounted in a glass case on 
the wall of the Observatory, and a needle at the 
lower end of the pendulum passes at each swing 
through a globule of mercury. On one of the wheels 
of the clock are arranged a number of little brass 
points, at such intervals apart that the wheel, when 
going at the proper rate, takes exactly one second 
to move through the distance between any pair. A 
little spring is arranged above the wheel, so that 
these points touch it as they pass. If this occurs 
exactly as the pendulum point passes through the 
mercury nothing happens, but if the clock is ever 
so little late* or early, the electric current from the 
pendulum brings into action a second wheel, which 
accelerates or retards the driving of the clock, as the 
case may be. The total motion, therefore, is most 
beautifully even. 

But even this is not quite sufficient, especially as 
the plates for the great chart have to be exposed 
for at least forty minutes. Rigidly united with the 
13-inch refractor, so that the two look like the two 
barrels of a huge double-barrelled gun, is a second 



THE ASTROGRAPHIC DEPARTMENT 291 
telescope for the use of the observer. In its eye- 




THE ASTROGRAPHIC TELESCOPE. 

{Reproduced from 'Engineering'' by permission.) 

piece are fixed two pairs of cross spider lines, 
commonly called wires, and a bright star, as near as 



292 THE ROYAL OBSERVATORY 

possible to the centre of the field to be photographed, 
is brought to the junction of two wires. Should the 
star appear to move away from the wire, the observer 
has but to press one of two buttons on a little plate 
which he carries in his hand, and which is connected 
by an electric wire with the driving clock, to bring it 
back to its position. 

The photographs taken with this instrument are 
of two kinds. Those for the great chart have but 
a single exposure, but this lasts for forty minutes. 
Those for the great catalogue have three exposures 
on them, the three images of a star being some 
20 seconds of arc apart. These exposures are of 
six minutes', three minutes', and twenty seconds' 
duration, and the last exposure is given as a test, 
since, if stars of the 9th magnitude are visible with 
an exposure of twenty seconds, stars of the nth 
magnitude should be visible with three minutes' 
exposure. 

Thus it will be seen that in three minutes an 
impression is got of many scores of stars, whose 
places it would require many hours to determine at 
the transit instrument. But the positions of these 
stars on the plate still remain to be measured. For 
this purpose a net-work of lines, at right angles to 
each other, is printed on the photograph before its 
development, and, after it has been developed, washed 
and dried, the distances of the stars from their 
nearest cross-lines are measured in the measuring 
machine. 

The measuring machine is constructed to hold 
two plates, one half its breadth higher than the other. 




THE DRIVING CLOCK OF THE ASTROGRAPHIC TELESCOPE. 
{Reproduced from 'Engineering'' by pei-mission.) 



THE ASTROGRAPHIC DEPARTMENT 295 

In fact, in each of the two series of photographs the 
whole sky is taken twice, but the two photographs 
of any region are not simply duplicates of each 
other. The centre of each plate is at a corner of 
four other plates, and in the micrometer the stars 
on the quarter common to two plates are measured 
simultaneously. 

In this way will be carried out a great census of 
the sky that will exceed Flamsteed's ten thousand 
fold. And just as Flamsteed's was but the first of 
many similar catalogues, so, no doubt, will this be 
followed by others not superseded, for its value will 
increase with its age and the number of those that 
follow it, by comparison with which it will prove 
an inexhaustible mine of information concerning 
the motions of the stars and the structure of the 
universe. 

There is a great difference between the work of 
the observer with the ' Astrographic Telescope,' as 
this great twin photographic instrument is called, 
and the work of the transit observer. The latter 
sees the star gliding past him, and telegraphs the 
instant that the star threads itself on each of the 
ten vertical wires in succession. The astrographic 
observer, on the other hand, sees his star shining 
almost immovably in the centre of his field, threaded 
on the two cross wires placed there, for the driving- 
clock moves the telescope so as to almost exactly 
compensate for the rotation movement of the earth. 
The observer's duty in this case is to telegraph to 
his driving-clock, when it has in the least come short 
of or exceeded its duty, and so to bring back the 



296 THE ROYAL OBSERVATORY 

* guiding star ' to its exact proper place on the cross 
wires. 

So far, the work of the Astrographic Department 
has been, as mentioned above, a development on an 
extraordinary scale, but a development still, of the 
original programme of the Observatory. But the 
munificent gift of Sir Henry Thompson has put it 
within the power of the Astronomer Royal to push 
this work of sidereal photography a stage further. 
Sir Henry Thompson gave to the Observatory, not 
merely the photographic refractor of 9 inches' aper- 
ture, now used for solar photography, and known as 
the ' Thompson photo-heliograph,' but also one of 26 
inches' aperture and 22J feet focal length. This 
instrument was specially designed of exactly double 
the dimensions of the standard astrographic telescope 
used for the International Photographic Survey, the 
idea being that, in the case of a field of special interest 
and importance, a photograph could be obtained 
with the larger instrument on exactly double the 
scale given by the smaller. It has rather, however, 
found its usefulness in a slightly different field. The 
observation of the satellites of Jupiter was suggested 
by Galileo as a means of determining the longitude 
at sea. As already pointed out, the suggestion did 
not prove to be a practical one for that purpose, but 
observations of the satellites have been made none 
the less with a view simply to improving our know- 
ledge of their movements, and of the mass of Jupiter. 
The utilitarian motive for the work having fallen 
through, it has been carried on as a matter of pure 
science. 



THE ASTROGRAPHIC DEPARTMENT 297 

And the work has not stopped with the satellites 
of Jupiter ; eight satellites were in due time discovered 
to Saturn, four to Uranus, and two to Mars ; and 
though these could give not the remotest assistance 
to navigation, they too have been made the subjects 
of observation for precisely the same reason as those 
of Jupiter have been. 




THE THOMPSON TELESCOPE IN THE NEW DOME. 



In just the same way, when the discovery 
of Neptune was followed by that of a solitary 
companion to it, this also had to be followed. The 
difficulties in the way of observing the fainter of all 
these satellites were considerable, and the work has 



298 THE ROYAL OBSERVATORY 

been mostly confined to two or three observatories 
possessing very large telescopes. As the largest 
telescope at Greenwich was only 7 inches in aperture 
up to 1859, an d only I2 inches up to 1893, it is only 
very recently that it has been able to take any very 
substantial part in satellite measures. But since the 
Thompson photographic telescope was set up, it has 
been found that a photograph of Neptune and its 
satellite can be taken in considerably less time than 
a complete set of direct measures can be made, whilst 
the photograph, which can be measured at leisure 
during the day, gives distinctly the more accurate 
results. 

So, too, the places of the minor planets can be 
got more accurately and quickly by means of photo- 
graphs with this great telescope than by direct 
observation, and photographs of the most interesting 
of them all, the little planet Eros, have been very 
successfully obtained. So that, though doing 
nothing directly to improve the art of navigation, or 
to find the longitude at sea, the great photographic 
refractor takes its share in the work of ' Rectifying 
the Tables of the Planets.' 

The reflector of 30 inches' aperture, which acts 
as a counterpoise to the sheaf of telescopes of the 
Thompson, is intended for use with the spectroscope, 
the quality which mirrors possess of bringing all 
rays, whatever their colour, to the same focus being 
of great importance for spectroscopic work. But the 
experiments which have been made with it in celestial 
photography have proved so extremely successful as 
to cause the postponement of the recommencement 




* 



s .^ 



THE ASTR0GRAPH1C DEPARTMENT 301 

of the spectroscopic researches. Chief amongst these 
photographs are some good ones of the moon, and 
more recently some exceedingly fine photographs 
of the principal nebulae. 

In no department of astronomy has photography 
brought us such striking results as in regard to the 
nebulae. Dr. Roberts' photograph of the great 
nebula in Andromeda converted the two or three 
meaningless rifts which some of the best drawings 
had shown into the divisions between concentric 
rings ; and what had appeared a mere shapeless cloud 
was seen to be a vast symmetrical structure, a great 
sidereal system in the making. The great nebula in 
Orion has grown in successive photographs in detail 
and extent, until we have a large part of the con- 
stellation bound together in the convolutions of a 
single nebula of the most exquisite detail and most 
amazing complexity. The group of the Pleiades has 
had a more wonderful record still. Manifestly a 
single system even to the naked eye, and showing 
some faint indications of nebulosity in the telescope, 
the photographs have revealed its principal stars 
shining out from nebulous masses, in appearance like 
carded wool, and have shown smaller stars threaded 
on nebulous lines like pearls upon a string. 

Such photographs are, of course, of no utilitarian 
value, and at present they lead us to no definite 
scientific conclusions. They lie, therefore, doubly 
outside the limits of the purely practical, but they 
attract us by their extreme beauty, and by the 
amazing difficulty of the problems they suggest. 
How are these weird masses of gas retained in such 



302 THE ROYAL OBSERVATORY 

complex form over distances which must be reckoned 
by millions of millions of miles? By what agency 
are they made to glow so as to be visible to us here ? 
What conceivable condition threads together suns on 
a line of nebula ? What universes are here in the 
making, or perhaps it may be falling into ruin and 
decay ? 



CHAPTER XIII 

THE DOUBLE-STAR DEPARTMENT 

The foregoing chapters will have shown that though 
the original purpose of the Observatory has always 
been kept in view, yet the progress of science has 
caused many researches to be undertaken which 
overstep its boundaries. Thus in the present transit 
room, beside the successive transit instruments we 
find upon the wall two long thin tubes, labelled 
respectively Alpha Aquilae and Alpha Cygni. 
These were two telescopes set up by Pond for a 
special purpose. Dr. Brinkley, Royal Astronomer 
for Ireland, had announced that he had found that 
several stars shifted their apparent place in the sky 
in the course of a year, due to the change in the 
position of the earth from which we view them, by an 
amount which would show that they were only about 
six to nine billions of miles distant from us ; or, in 
other words, they showed a parallax of from two to 
three seconds of arc. Pond was not able to confirm 
these parallaxes from his observations, and to decide 
the point he set up these two telescopes, the Alpha 
Aquilae telescope being rigidly fixed on the west side 
of the pier of Troughton's mural circles ; the Alpha 

303 



3o 4 THE ROYAL OBSERVATORY 

Cygni telescope on another pier, the one which now 
forms the base of the pier of the astrographic tele- 
scope. Pond's method was to compare the position 
of these two stars with that of a star almost exactly 
the same distance from the pole, but at a great 
distance from it in time of crossing the meridian ; in 
other words, of almost the same declination, but 
widely different right ascension. The result proved 
that Brinkley was wrong, and vindicated the delicacy 
and accuracy of Pond's observations. 

These two telescopes, therefore, had their day and 
ceased to be. Others have followed them. An 
ingenious telescope was set up by Sir George Airy in 
order to ascertain if the speed of light were different 
when passing through water than when passing 
through air. Or, in other words, if the aberration 
of light would give the same value as at present if 
we observed through water. The water telescope, as 
it was called, is kept on the ground floor of the 
central octagon of the new observatory. The obser- 
vations obtained with it were hardly quite satisfac- 
tory, but gave on the whole a negative result. 

Turning back to the transit room, and leaving it 
by the south-west door, we come into the little 
passage which leads at the back of Bradley's transit 
room into the lower computing room. Just inside 
this passage, on the left-hand side, there is a little 
room of a most curious shape, the ' reflex zenith 
room.' Here is fixed a telescope pointing straight 
upwards, the eye-piece being fixed by the side of the 
object-glass. The light from a star the star Gamma 
Draconis which passes exactly over the zenith of 



THE DOUBLE-STAR DEPARTMENT 305 

Greenwich, enters the object-glass, passes downwards 
to a basin of mercury, and is reflected upwards from 
the surface of the mercury to a little prism placed 
over the centre of the object-glass, from which it is 
reflected again into the eye-piece. By means of this 
telescope the distance of the star Gamma Draconis 
from the zenith could be measured very exactly, and, 
consequently, the changes in the apparent position 
of the star due to aberration, parallax, and other 
causes could be very exactly followed, and the cor- 
rections to be applied on account of these causes 
precisely determined. 

This particular telescope was devised by Airy, and 
the observations with it were continued to the end of 
his reign. The germ of the idea may be traced back, 
however, to the time of Flamsteed, who would seem 
to have occasionally observed Gamma Draconis from 
the bottom of a deep well ; the precise position of the 
well is not, however, now known. Later, Bradley set 
up his celebrated i2i-foot zenith sector, still pre- 
served in the transit room, first at Wanstead and 
then at Greenwich, for the determination of the 
amount of aberration. Later, a zenith tube by 
Troughton, of 25 feet focus, was used by Pond in 
conjunction with the mural circle for observations of 
Gamma Draconis in order to determine the zenith 
point of the latter instrument. 

These, telescopes for special purposes have passed 
out of use. Observations with the spectroscope have 
been suspended for some years. The work of the 
Astrographic Department will come to an end, in the 
ordinary course of events, when the programme 

U 



3 o6 THE ROYAL OBSERVATORY 

assigned to Greenwich in the International Scheme 
is completed. 

Within the last few years a new department 
has come into being at Greenwich a department 
which has been steadily worked at many foreign 
public observatories, but only recently here. 

This is the Department of Double-Star Observa- 
tion. The first double star, Zeta Ursse Majoris, was 
discovered 250 years ago. Bradley discovered two 
exceedingly famous double stars whilst still a young 
man observing with his uncle at Wanstead Gamma 
Virginis and Castor. Bradley made also other dis- 
coveries of double stars after his appointment to 
Greenwich, and Maskelyne succeeded him in the 
same line, but the great foundation of double-star 
astronomy was laid by Sir William Herschel. 

At first it was supposed that double stars were 
double only in appearance ; one star comparatively 
near us * happened ' to lie in almost exactly the 
same direction as another star much further off. It 
was, indeed, in the very expectation that this would 
prove to be the case, that the elder Herschel first 
took up their study. But he was soon convinced 
that many of the objects were true double stars 
members of the same system of which the smaller 
revolved round the larger not merely apparently 
double, one star appearing by chance to be close to 
another with which it had no connection but real 
double stars. The discovery of these has led to the 
establishment of a new department of astronomy, 
again scientific rather than utilitarian. 

As mentioned above, it is only recently that 



THE DOUBLE-STAR DEPARTMENT 309 

Greenwich has taken any appreciable part in this 
work. Under Airy, the largest equatorial of the 
time had been furnished with a good micrometer, 
and observations of one or two double stars been 
made now and again ; but Airy's programme of work 
was far too rigid, and kept the staff too closely 
engaged for such observations to be anything but 
extremely rare. And, indeed, when the micrometers 
of the equatorials were brought into use, they were 
far more generally devoted to the satellites of Saturn 
than to the companions of stars. In the main, double- 
star astronomy has been in the hands of amateurs, at 
least in England. But the discovery in recent years 
of many pairs so close that a telescope of the largest 
size is required for their successful observation, has 
put an important section of double stars beyond the 
reach of most private observers, and therefore the 
great telescope at Greenwich is now mainly devoted 
to their study. The Astronomer Royal, therefore, 
soon after the completion of the great equatorial of 
28-inches aperture placed in the south-east dome, 
added this work to the Observatory programme. 

The 28-inch equatorial is a remarkable-looking 
instrument, its mounting being of an entirely different 
kind to that of the other equatorials in the Obser- 
vatory, with the solitary exception of the Shuckburgh, 
which is set up in a little dome over the chrono- 
graph room. The Shuckburgh was presented to the 
Observatory in the year 181 1, by Sir G. Shuckburgh. 
It was first intended to be mounted as an altazimuth, 
but proved to be unsteady in that position, and was 
then converted into an equatorial without clockwork, 



310 THE ROYAL OBSERVATORY 

and mounted in its present position. The position is 
about as hopelessly bad a one as a telescope could well 
have, completely overshadowed as it is by the trees 
and buildings close at hand. The dome is a small 
one, and the arrangements for the shutters and for 
turning the dome are as bad as they could possibly be. 
It has practically been useless for the last forty years. 
Its only interest is that the method of mount- 
ing employed is a small scale model of that of the 
great telescope in the S.-E. dome. In the German 
or Fraunhofer form of mounting for an equatorial 
there is but a single pillar, which carries a compara- 
tively short polar axis. At the upper end of the 
polar axis we find the declination axis, and at one 
end of the declination axis is the telescope, whilst at 
the other end is a heavy weight to counterpoise it. 
The German mounting has the advantage that the 
telescope can easily point to the pole of the heavens ; 
its drawbacks are that, except in certain special forms, 
the telescope cannot travel very far when it is on the 
same side of the meridian as the star to which it is 
pointed, the end of the telescope coming into contact 
under such circumstances with the central pier, whilst 
the introduction of mere deadweight as the necessary 
counterpoise, is not economical. It has been already 
pointed out that the present Astronomer Royal has 
not only considerably modified the German mounting 
in the great collection of telescopes in the Thompson 
dome, but has used a powerful reflector as a counter- 
poise to the sheaf of refractors at the other end of 
the declination axis. 

The English equatorial requires two piers. 



THE DOUBLE-STAR DEPARTMENT 311 

Between these two piers is a long polar axis. Both 
in the little Shuckburgh and in the great 28-inch 
equatorial the frame of the polar axis consists of six 
parallel rods disposed in two equilateral triangles, 
with their bases parallel to each other, the telescope 
swinging in the space between the two bases. The 
construction of this form of equatorial, therefore, is 
expensive, as it requires two piers. It takes much 
more room than the German form, and the telescope 
cannot be directed precisely to the pole. But the in- 
strument is symmetrical, there is no deadweight, and 
the telescope can follow a star from rising to setting 
without having to be reversed on crossing the meridian. 

The great stability of the English form of mount- 
ing, therefore, commended it very highly to Airy, and 
he designed the great Northumberland equatorial of 
the Cambridge Observatory on that plan, as well as 
one for the Liverpool Observatory at Bidston, and in 
1858 the S.-E. equatorial at Greenwich. 

The telescope at first mounted upon it had an 
object-glass of I2f inches' aperture, and 18 feet focal 
length. That was dismounted in 1891, and is now 
used as the guiding telescope of the Thompson 26-inch 
photographic refractor. Its place was taken by an 
immensely heavier instrument, the present refractor 
of 28 inches' aperture, and 28 feet focal length ; and 
that this change was effected safely was an eloquent 
testimony to the solidity of the original mounting. 

The clock that drives this great instrument, so 
that it can follow a star or other celestial object in 
its apparent daily motion across the sky, is in the 
basement of the S.-E. tower. It is a very simple 



3 i2 THE ROYAL OBSERVATORY 

looking instrument, a conical pendulum in a glass 
case. The pendulum makes a complete revolution 
once in two seconds. Below it in a closed case is a 
water turbine. A cistern on the roof of the staircase 
supplies this turbine with water, having a fall of about 
thirty feet. The water rushing out of the arms of the 
turbine forces it backward, and the turbine spins 
rapidly round, driving a spindle which runs up into 
the dome, and gears through one or two intermediate 
wheels with the great circle of the telescope ; the 
extremely rapid rotation of the spindle, four times 
in a second, being converted by these intermediate 
wheels into the exceedingly slow one of once in 
twenty-four hours. Just above the centre of motion 
of the turbine is a set of three small wheels, all of 
exactly the same size, and of the same number of 
teeth. Of these the bottom wheel is horizontal, and 
is turned by the turbine. The top wheel is also 
horizontal, and is turned by the pendulum. The 
third wheel gears into both these, and is vertical. If 
the top and bottom wheels are moving exactly at the 
same rate, the intermediate wheel simply turns on its 
axis, but does not travel ; but if the turbine and 
pendulum are moving at different rates, then the 
vertical wheel is forced to run in one direction or 
the other, and, doing so, it opens or closes a throttle 
valve, which controls the supply of water to the 
turbine, and so speedily brings the turbine into 
accord with the pendulum. The control of the 
motion of the great telescope is therefore almost as 
perfect as that of the astrographic and Thompson 
equatorials, though the principle employed is very 



THE DOUBLE-STAR DEPARTMENT 313 

different. And the control needs to be perfect, for, 
as said above, the great telescope is mostly devoted 
to the observation of double stars, and there can be 
no greater hindrance to this work than a telescope 
which does not move accurately with the star. 

There is a striking contrast between the great 
telescope and all the massive machinery for its 
direction and movement, and the objects on which 
it is directed two little points of light separated by 
a delicate hair of darkness. 

The observation is very unlike those of which we 
have hitherto spoken. The object is not to ascertain 
the actual position in the sky of the two stars, but 
their relative position to each other. A spider's 
thread of the finest strands is moved from one star 
to the other by turning an exquisitely fine screw ; 
this enables us to measure their distance apart. 
Another spider thread at right angles to the first is 
laid through the centres of both stars, and a divided 
circle enables us to read the angle which this line 
makes to the true east and west direction. Such 
observations repeated year after year on many stars 
have enabled the orbits of not a few to be laid down 
with remarkable precision ; and we find that their 
movements are completely consistent with the law of 
gravitation. Further, just as Neptune was pre- recog- 
nized and discovered from noting the irregularities in 
the motion of Uranus, so the discordances in the place 
of Sirius led to the belief that it was attracted by a 
then unseen companion, whose position with respect to 
the brighter star was predicted and afterwards seen. 

Gravitation thus appears, indeed, to be the Bond 



314 THE ROYAL OBSERVATORY 

of the Universe, yet it leaves us with several weighty 
problems. The observation of the positions of stars 
shows that though we call them fixed they really 





A 


1 .^A 


w 


J ^ 


mfmmmmM___ 


Ik 


III 



THE SOUTH-EAST DOME WITH THE SHUTTER OPEN. 

have motions of their own. Of these motions, a great 
part consists of a drift away from one portion of the 



THE DOUBLE-STAR DEPARTMENT 315 

heavens towards a point diametrically opposite to it, 
a drift such as must be due, not to a true motion of 
the individual stars, but to a motion through space 
of our sun and its attendant system. The elder 
Herschel was the first to discover this mysterious 
solar motion. Sir George Airy and Mr. Edwin 
Dunkin, for forty-six years a member of the Green- 
wich staff, and from 1 881-1884 the Chief Assistant, 
contributed important determinations of its direction. 

What is the cause of this motion, what is the law 
of this motion, is at present beyond our power to 
find out. Many years ago a German astronomer 
made the random suggestion that possibly we were 
revolving in an orbit round the Pleiades as a centre. 
The suggestion was entirely baseless, but unfortu- 
nately has found its way into many popular works, 
and still sometimes is brought forward as if it were 
one of the established truths of astronomy. We can 
at present only say that this solar motion is a mystery. 

There is a greater mystery still. The stars have 
their own individual motions, and in the case of a 
few these are of the most amazing swiftness. The 
earth in its motion round the sun travels nearly 
nineteen miles in a second, say one thousand times 
faster than the quickest rush of an express train. 
The sun's rate of motion is probably not quite so 
swift, but Arcturus, a sun far larger than our own, 
has a pace some twenty times as swift as the orbital 
motion of the earth. This is not a motion that we 
can conceive of as being brought about by gravita- 
tion, for if there were some unseen body so vast as 
to draw Arcturus with this swiftness, other stars too 



3 i6 THE ROYAL OBSERVATORY 

would be hurtling across the sky as quickly. Such 
1 runaway stars ' afford a problem to which we have 
as yet no key, and, like Job of old, we are speechless 
when the question comes to us from heaven, ' Canst 
thou guide Arcturus and his sons ? ' 

It will be seen then that, fundamentally, Green- 
wich Observatory was founded and has been main- 
tained for distinctly practical purposes, chiefly for 
the improvement of the eminently practical science 
of navigation. Other inquiries relating to naviga- 
tion, as, for instance, terrestrial magnetism and 
meteorology, have been added since. The pursuit 
of these objects has of necessity meant that the 
Observatory was equipped with powerful and ac- 
curate instruments, and the possession of these again 
has led to their use in fields which lay outside 
the domain of the purely utilitarian, fields from 
which the only harvest that could be reaped was that 
of the increase of our knowledge. So we have been 
led step by step from the mere desire to help the 
mariner to find his way across the trackless ocean, to 
the establishment of the secret law which rules the 
movements of every body of the universe, till at 
length we stand face to face with the mysteries 
of vast systems in the making, with the intimate 
structure of the stellar universe, with the apparently 
aimless, causeless wanderings of vast suns in lightning 
flight ; with problems that we cannot solve, nor hope 
to solve, yet cannot cease from attempting, problems 
to which the only answer we can give is the con- 
fession of the magicians of Egypt ' This is the 
finger of God.' 



INDEX 



Aberration of light, 79 

Adams, John C, his discovery of Nep- 
tune, 217 

Adhara, 183 

Airy, George Biddell, seventh Astro- 
nomer Royal, his early life, 102 ; his 
work at Cambridge, 105 ; comes to 
Greenwich, 105 ; his relations with the 
Visitors, 106 ; his autobiography, 108 
his character, in ; his labours, 113 
attacks on, 114; his distinctions, 118 
his resignation, 119 ; his death, 120 
anecdote of, 142 ; his conduct re 
Adams, 217 ; his water telescope, 304 

Alderamin, 183 

Almagest, 185 

Almanac making, 29 

Alpha Aquilae, telescope for, 303 

Cygni, telescope for, 303 

Altazimuth the, 114 ; description and 
work of, 207, et seq. 

Altazimuth Department, 205, et seq. 

American time, 153 

Andromeda nebula, 301 

Anemometer, use of, 238 ; trace of, 242 

Angstrom, 268 

Anson, Commodore, 17 

Apparent time, 152 

Arcturus, motion of, 315 

Argelander, star catalogue of, 287 

Art of Dialling, the, 28 

Assistants, position of the, 98, 100, 117, 

Astrographic chart, 128 

Department, 284, et seq. 

dome, 128 

telescope, 289, et seq. 

Astronomers Royal, the, 25 

Astrophysical researches, 282 

Aurorae, 281 

Automatic register, 241 

Axis of the earth, precession of, 1S4 

Ball, Time, 162 
Barometer, use of the, 192, 233 
Battery basement, 161 
Beaufort, Captain, 107 
Bessel quoted, 266 
Betelgeuse, 184 



Birkenhead, wreck of the, 180 

Bliss, Nathaniel, fourth Astronomer 
Royal, history of, 82 

Bradley, James, third Astronomer Royal, 
his life, 73 ; his ordination, 74 ; Vicar 
of Bridstow, 74 ; Savilian Professor 
of Astronomy, 75 ; discovers Aberra- 
tion of Light, 75, et seq. ; becomes 
Astronomer Royal, 79 ; labours of, 
80 : character of, 81 

Bradley's transit room, 128 

Brinkley, Dr., 303 

British Mariners Guide, the, 90 

Bunsen, 268 

Buys Ballot's law, 237 



Canadian time, 153 

Castor, 74, 306 

Catalogues, star, 182, 185, et seq. 198, 

284 
Cepheus, 1S3 

Charles II., warrants of, 39, 40 
Christie, W. H. M., eighth Astronomer 

Royal, work of, 120 
Chromosphere of the sun, 268 
Chronograph, the, 157 

room, 126 

Chronometer business, 101, 107 
Chronometers, Harrison's improvements 

in, 165, et seq.; tests of, 169 ; ' runs ' 

of, 173 ; romance of, 178 
Circle Department, 181, et seq. 
Clock, Astrographic driving, 290 ; 

driving 28-inch telescope, 312 
Clocks, standard, 160 
Columbus, aim of voyage of, 18 
Comet, appearance of a, 28 

Wells, 280 

Comets, observation of, 224 ; spectra of, 

280 
Commutator, the, 162 
Comte, assertion of, 267 
Constant of Aberration, 79 
Cook, Captain, work of, 170 
Copper, use of in Observatory, 245 
Corona of the sun, 264 
Crabtree, James, 31 
Crosthwait, Joseph, 57 



317 



3i8 



INDEX 



Dallmeyer telescope, 252 
Declination, 186, et seq. 
Denebola, 184 

Distances of planets, 223 ; of sun, 224 
Double-Star Department, 303, et seq. 
Double Stars, 306 
Dublin time, 155 
Dunkin, Edwin, 315 

Earth, the, movements of, 201 
Eclipses of the moon, 216 ; of the sun, 

July 25, 1748. ..85 ; other eclipses of 

the sun, 263, et seq. 
Electric Railway, influence of, 249 
Equation of Time, the, 29, 151 
Equatorial, Shuckburgh's, 101 

, the great 28-inch, 221 

, the Merz, i2|-inch, 114 

, 28-inch, driving clock of, 309 ; use 

of, 313 

, clock-driven, 74 

Eros, discovery of, 223 ; photographs of, 

2 98 . 

Errors in observations, noting of, 199, 

et seq. 
Evaporation, 241 

Facula; of the sun, 257 

Flamsteed, John, his report on Saint- 
Pierre's proposal, 23, 32 ; appointed 
first Astronomer Royal, 23, 34; his 
autobiography, 26 ; his studies, 29 ; 
his almanac, 29; sent to London, 30 ; 
enters Jesus College, Cambridge, 31 ; 
completes his observatory, 31 ; ac- 
quaintance with Newton, 31 ; takes 
his degree, 32 ; his work, 34 ; warrant 
for his salary, 39 ; position of, 42 ; his 
ordination, 45 ; his pupils, 45 ; his 
trouble with Newton, 46, et seq. ; his 
catalogue, 53 ; his letter to Sharp, 54 ; 
his death, 56 ; his labours, 57 

Flamsteed House, 126 

Fraunhofer mounting, 310 

French time, 155 

Galileo, his discovery of Jupiter's 

satellites, 19 
Gamma Draconis, 75, 304 

Virginis, 306 

Gascoigne, William, 31 

Gemma Frisius, plan of, 22 

George of Denmark, Prince, 50 

German mounting, 276, 310 

Gould, Dr., 287 

Graham, 166 

Gravitation, the bond of the universe, 

313 
Great comet of 1882, the, 280, 288 
Greatrackes, Valentine, 29 
Green, Charles, 91 
Greenwich time, 153; distribution of, 

163 



Hallev, Edmund, his life, 60 ; his early 
work, 60 ; his catalogue of stars, 63 ; 
elected F.R.S., 63 ; his work on 
Kepler's laws, 64 ; becomes captain, 
65 ; Savilian Professor of Geometry, 
66; Astronomer Royal, 66; observa- 
tions on saros of the moon, 67 ; pressed 
by Newton, 68 ; his death, 68 ; his 
services to science, 68 ; his pay, 70 ; 
nominates his successor, 73 ; his tran- 
sit instrument, 73 

Halley's comet, 225 

Harrison, James, timekeepers of, 86, 91, 
93, 165 

Heineken, Rev. N. S., 59 

Heineken quadrant, 59 

Heliographic Department, 251, et seq. 

Herschel, Caroline, 57 

Hipparchus, catalogue of, 185 

Hodgson, Mr., 50 

Hooke, Robert, 75, 206 

Horrox, Jeremiah. 31 

Huggins, Sir W., his use of spectroscope, 
268 

Inscription, an, 126 

International Photographic Survey, 296 

Ireis, 224 

Iron quadrant, 73 

Isobars, 237 

Jupiter, satellites of, 19, 296 ; atmo- 
sphere of, 279 

Keill, John, 74 

Kendall, Larcum. 166 

Kepler, laws of, 64 

Kew, photo-heliograph, the, 252 

Kinnebrook, David, 176 

Kirchhoffs use of spectroscope, 267 

I Latitude, finding the, 18 

! Ledgers, chronometer, romance of, 176 

Leverrier, his discovery of Neptune, 217 

Libraries, 132 

Linacre, G., 28 

Lindsay, Thomas, quoted, 204 

Litchford, W., 28 

Local apparent time, 22 

Longitude, finding the, 18 ; at sea, 
problem of, 86; determination of, 173 

Longitude nought, 148 

Lower computing room, 128 

Lunars, method of, 86 

Magnetic Department, work of, 133 ; 

description of, 228, et seq. 
Magnetic inclination and declination, 

246 

needles, movements of, 247, 262 

observatory, 132 

pavilion, 245 

storms, 248. 262 

Mars, distance of, 223 ; atmosphere of, 

279 ; satellites of, 296 



INDEX 



3 T 9 



Maskelyne, Nevil, fifth Astronomer 
Royal, 85 ; practical work of, 86 ; 
Astronomer Royal, 91 ; his work, 92 ; 
his publications, 92 ; his observations 
and work, 92, et seq. ; his death, 94 ; 
his character, 97 ; recommends his 
successor, 97 ; his mural circle, 101 

Mean solar clock, 160 

Mean time, 152 

Meldrum, Dr., on sun spots, 263 

Meridian, the, 149 

Merz telescope, 279 

Meteorological Department, work of, 
133 ; description of, 228, et seq. 

Micrometers, use of, 309 

Microscopes, use of, 188 

Milky Way, 288 

Miller, Professor, 268 

Milne, Professor, on earth movements, 
201 

Minor planets, 222 

Molyneux, Samuel, 75 

Moon, observation of the, 212,^ seq. ; 
eclipses of, 266 

Moore, Sir Jonas, 30 ; death of, 42 

Morin, 33 

Mounting telescopes, modes of, 310 

Mudge, Thomas, 94 

Mural arc, 7-feet, 46 

Mural circles, 101, 196 

Names of stars, origin of, 183 

Nares, Sir George, 170 

Nautical Almanac, the, 22, 23, 92 

Navigation, state of primitive, 17 

Neptune, discovery of, 217 ; atmosphere 
of, 280 ; satellite of, 298 

New altazimuth, the, 132, 210 

New Observatory, the, 136, 275 

New stars, 268 

Newcomb, Professor, on growth of Ob- 
servatory, 124 ; on Greenwich obser- 
vations, 207 

Newton, Sir I., his absent-mindedness, 
31 ; his trouble with Flamsteed, 46, et 
seq. ; on Kepler's laws, 65 ; his Prin- 
cipia, 65 ; his pressure on Halley, 68 ; 
his discovery of gravitation, 206 

North terrace, the, 126 

Northumberland equatorial, 218 

Nutation of the earth, 80 

Observation, modes of, 156, 176, 188; 
by reflection, 196 ; of comets, 224 

Observatory, Greenwich, work of, 13 ; 
foundation of, 23 ; warrant for build- 
ing, 40 ; position of, 41 ; foundation 
stone laid, 42 ; condition of, 79 ; en- 
largement of, 112; recent extensions 
of, 120 ; description of, 124, et seq. ; 
staff of, 137; work of, 139, et seq.; 
visitors to, 175 ; new altazimuth 
building, 211 ; magnet house, 228 ; 
magnetic pavilion, 245 ; new Obser- 



| vatory, 275 ; future of, 283 ; reflex 
zenith room, 304 ; objects of, 316 

Occultations by the moon, 212, et seq. 
I Octagon room, 125, 238, 242 

Oldenburg, Mr., 30 

Orion nebula, 268, 301 

, Parallax of stars, 303 

Paramour, the, 65 

Paris, conference at, 288 

, noon at, 151 

Philip III., offer of, 19. 

Photographic registration, 244, 247, 252, 
255 ; refractors, 288 

Photographs, star, 290 

Photo-heliographs, 252, et seq., 279 

Piazzi, discovery of, 222 

Pleiades, the, 301 

Polar plumes of the corona, 264 

Polaris, 188 

Pole-star, variation of, 184 

Pond, John, sixth Astronomer Royal, his 
life, 97 ; his reign, 98 ; his salary, 98 ; 
his assistants, 98 ; his observations, 
99 ; censured by Visitors, 99 ; his 
observations of stars, 303 
; Pound, James, 73 
! Precession of earth's axis, 184 

Frincipia, publication of, 65 
' Proctor, R. A., attack of, 116 
' Ptolemy, Claudius, catalogue of, 185 
I Publication, the problem of, 48, 92 

I Quadrant, Heineken, 59 
, the iron, 73 

Railway time, 152 
Rain gauge, 238 
Record rooms, 132 
Reflection, observation by, 196 
Reflex zenith room, 304 

tube, 131 

Refraction, effects of, 194 

Right ascension, 186, et seg. 

Roberts, Dr. Isaac, 301 

Romer, discovery of, 78 

Rosse, Lord, 268 

Royal Society and Flamsteed, 46, et seq. 

Saint-Pierre, Le Sieur de, proposal of, 
23, 32 

Sappho, 224 

Saros of the moon, 67 

Satellites, discovery of, 296 

Saturn, atmosphere of, 279 ; satellites 
of, 296 
j Schaeberle's comet, 280 

Schedar, 184 

Schiehallion, attraction of, 94 

Schonfeld, 287 
j Scotchmen, anecdote of, 146 

Sharp, Abraham, 46 

Sheepshanks, Rev. James, on Airy, 107 

Shuckburgh equatorial, 309 

Sidereal clock 160 



320 



INDEX 



Sirius, 287 

Sloane, Dr., 50 

' Smith, Mr.,' his chronometer, 179 

Solar photographs, 257 

storms, 261, 282 

Sound waves, 271 

South, Sir James, 105, 114 

South-east equatorial, the, 132, 221 

Spectroscope, use of, 267 

Spectroscopic Department, 266, et seq. 

Spots, sun, 251, et seq., 281 

Staff of Observatory, 137 ; work of, 139, 

et seq. 
Standard time, 21 
Stars, observations of, 156, 1/6, 188 ; 

origin of names of, 183 ; movements 

of, 187 ; catalogues of, 198, 284, etseq.; 

composition of, 268, et seq. ; colour of, 

271; classes of, 287; census of, 287; 

photographs of, 288, et seq ; motions 

of, 3^3, 3i5 
Story, Mr. A. M., 97 
Sun, distance of the, 74, 224; spots on, 

251, et seq., 281 ; eclipses of, 263, et 

seq. ; chromosphere of, 268 ; motions 

of, 315 
Sunshine recorder, 238 
Swiss time, 155 



Tebb, Mr. W., 58 
Tebbutt's comet, 280 
Telescope, the great transit, 156 

, 28-inch, 275 

, astrographic, 289 

, Shuckburgh, 30^ 

, Thompson, 256, 279, 296 

Thalen, 268 

Thermometer, use of, 192, 234 

Thome, Dr., 287 



Thompson photo-heliograph, 256, 279, 
296 

Time ball, 162 

Department, the, 146, et seq. 

desk, 161 

, foreign, 153 

signals, 162 

standard, 21 

Transit, Halley's, 73 

Transit circle, the, 114; mode of obser- 
vation with, 188, et seq. 

Transit circle, Troughton's, 98 

Department, 181, et seq. 

observations, number of, 140 

pavilion, 126, 175 

room, 128, 147 

Troughton's transit circle, 98 

Uranus, discovery of, 217 ; atmosphere 
of, 279 ; satellites of, 296 

Vanes, use of, 238 

Venus, distance of, 223 

Victoria, 224 

Visitors, the Board of, 53 ; censures 

Pond, 99 ; work of, 106 ; constitution 

of, 144 
Visitors to Observatory, 175 

Warrant for Flamsteed's salary, 39 

Water telescope, 304 

Weather predictions, 229, et seq. 

Winds, study of, 237 

Witt, Herr, discovery of, 223 

Working Catalogue, the, 142 

Zenith sector, 82, 305 

tube, 75, 305 

Zeta Ursae Majoris, 306 
Zubeneschamal, 184 



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