file which includes the original illustrations4 ,see #ddafg-;h4htm or #ddafg-;h4zip3 7https3_/_/www4gutenberg4org_/cache_/epu b_/#ddafg_/pg#ddafg-;images4html7 or 7https3_/_/www4gutenberg4org_/files_/#dd afg_/ddafg-;h4zip7 ,images of the original pages are available through ,internet ,archive4 ,see https3_/_/archive4org_/details_/royalobs ervatory#jjmaun ,transcriber's note3 ,text enclosed by underscores is in italics 7italics74 ,small capital text has been replaced with all capitals4 ,the carat character 77 indicates that the following letter is superscripted 7example3 ,,iis74 ,if two or more letters are superscripted they are enclosed in curly brackets 7example3 ,d,,ni74 ,illustration3 ,,flamsteed1 ,,the ,,first ,,astronomer ,,royal4 7,from the portrait in the ',historia ,coelestis4'7 ,,the ,,royal ,,observatory ,,greenwich ,a ,glance at ,its ,history and ,work by ,e4 ,,walter ,,maunder1 ,f4,r4,a4,s4 ,with ,many ,portraits and ,illustrations from ,old ,prints and ,original ,photographs ,london ,the ,religious ,tract ,society #ef ,paternoster ,row1 and #fe ,st4 ,paul's ,churchyard #aijj ,london3 ,printed by ,william ,clowes and ,sons1 ,limited1 ,stamford ,street and ,charing ,cross4 ,,preface ,i was present on one occasion at a popular lecture delivered in ,greenwich1 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 places1 and yet entirely neglect places of at least equal importance in their own land4 ',ten minutes' walk from this hall1' he said1 'is ,greenwich ,observatory1 the most famous observatory in the world4 ,most of you see it every day of your lives1 and yet ,i dare say that not one in a hundred of you has ever been inside4' ,whether the lecturer was justified in the general scope of his stricture or not1 the particular instance he selected was certainly unfortunate4 ,it was not the fault of the majority of his audience that they had not entered ,greenwich ,observatory1 since the regulations by which it is governed forbade them doing so4 ,these rules are none too stringent1 for the efficiency of the institution would certainly suffer if it were made a 'show' place1 like a picture gallery or museum4 ,the work carried on therein is too continuous and important to allow of interruption by daily streams of sightseers4 ,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 history1 principal instruments1 and work4 ,to the far greater number who will never be able to enter it1 but who yet feel an interest in it1 ,i would trust that this little book may prove some sort of a substitute for a personal visit4 ,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 instruments4 ,i would also express my thanks to ,miss ,airy1 for permission to reproduce the photograph of ,sir ,g4 ,b4 ,airy2 to ,mr4 ,j4 ,nevil ,maskelyne1 ,f4,r4,a4,s41 for the portrait of ,dr4 ,maskelyne2 to ,mr4 ,bowyer1 for procuring the portraits of ,bliss and ,pond2 to ,messrs4 ,edney and ,lacey1 for many photographs of the ,royal ,observatory2 and to the ,editor of ,engineering1 for permission to copy two engravings of the ,astrographic telescope4 ,e4 ,w4 ,m4 ,,royal ,,observatory1 ,,greenwich1 ,august1 #aijj4 ,illustration3 ,,the ,,new ,,building4 7,from a photograph by ,mr4 ,lacey47 ,,contents ,,chapter ,,page ,i4 ,,introduction #ac ,,ii4 ,,flamsteed #be ,,iii4 ,,halley ,,and ,,his ,,successors #fj ,,iv4 ,,airy #ajb ,v4 ,,the ,,observatory ,,buildings #abd ,,vi4 ,,the ,,time ,,department #adf ,,vii4 ,,the ,,transit ,,and ,,circle ,,departments #aha ,,viii4 ,,the ,,altazimuth ,,department #bje ,,ix4 ,,the ,,magnetic ,,and ,,meteorological ,,departments #bbh ,x4 ,,the ,,heliographic ,,department #bea ,,xi4 ,,the ,,spectroscopic ,,department #bff ,,xii4 ,,the ,,astrographic ,,department #bhd ,,xiii4 ,,the ,,double-,,star ,,department #cjc ,,index #cag ,,list ,,of ,,illustrations ,,page ,,flamsteed1 ,,the ,,first ,,astronomer ,,royal ,frontispiece ,,the ,,new ,,building #g ,,general ,,view ,,of ,,the ,,observatory ,,buildings ,,from ,,the ,,new ,,dome #ab ,,flamsteed',s ,,sextant #cf ,,the ,,royal ,,observatory ,,in ,,flamsteed',s ,,time #dd ,,the ',,camera ,,stellata' ,,in ,,flamsteed',s ,,time #eb ,,edmund ,,halley #fa ,,halley',s ,,quadrant #fi ,,james ,,bradley #gb ,,graham',s ,,zenith ,,sector #gg ,,nathaniel ,,bliss #hc ,,nevil ,,maskelyne #hg ,,hadley',s ,,quadrant #ia ,,john ,,pond #if ,,george ,,biddell ,,airy1 ,,astronomer ,,royal #ajc ,,the ,,astronomer ,,royal',s ,,room #aaj ,,the ,,south-,,east ,,tower #aae ,w4 ,h4 ,m4 ,,christie1 ,,astronomer ,,royal #aba ,,the ,,astronomer ,,royal',s ,,house #abg ,,the ,,courtyard #acj ,,plan ,,of ,,observatory ,,at ,,present ,,time #acd ,,the ,,great ,,clock ,,and ,,porter',s ,,lodge #adg ,,the ,,chronograph #aeh ,,the ,,time-,,desk #afd ,,harrison',s ,,chronometer #afe ,,the ,,chronometer ,,room #afg ,,the ,,chronometer ,,oven #aga ,,the ,,transit ,,pavilion #agd ',,lost ,,in ,,the ,,birkenhead' #agi ,,the ,,transit ,,circle #ahi ,,the ,,mural ,,circle #aie ,,airy',s ,,altazimuth #bjh ,,new ,,altazimuth ,,building #baa ,,the ,,new ,,altazimuth #bac ,,the ,,new ,,observatory ,,as ,,seen ,,from ,,flamsteed',s ,,observatory #bai ,,the ,,self-,,registering ,,thermometers #bce ,,the ,,anemometer ,,room1 ,,north-,,west ,,turret #bdj ,,the ,,anemometer ,,trace #bdc ,,magnetic ,,pavilion--,,exterior #bdf ,,magnetic ,,pavilion--,,interior #bdh ,,the ,,dallmeyer ,,photo-,,heliograph #bed ,,photograph ,,of ,a ,,group ,,of ,,sun-,,spots #bei ,,the ,,great ,,nebula ,,in ,,orion #bfi ,,the ,,half-,,prism ,,spectroscope ,,on ,,the ,,south-,,east ,,equatorial #bgc ,,the ,,workshop #bgf ,,the #cj-;,,inch ,,reflector ,,with ,,the ,,new ,,spectroscope ,,attached #bgh ',,chart ,,plate' ,,of ,,the ,,pleiades #bhf ,,the ,,control ,,pendulum ,,and ,,the ,,base ,,of ,,the ,,thompson ,,telescope #bhi ,,the ,,astrographic ,,telescope #bia ,,the ,,driving ,,clock ,,of ,,the ,,astrographic ,,telescope #bid ,,the ,,thompson ,,telescope ,,in ,,the ,,new ,,dome #big ,,the ,,nebul ,,of ,,the ,,pleiades #cjj ,,double-,,star ,,observation ,,with ,,the ,,south-,,east ,,equatorial #cjh ,,the ,,south-,,east ,,dome ,,with ,,the ,,shutter ,,open #cad ,illustration3 ,,general ,,view ,,of ,,the ,,observatory ,,buildings ,,from ,,the ,,new ,,dome4 7,from a photograph by ,mr4 ,lacey47 ,,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 unknown4 ',who is that8' said the newcomer1 referring to me4 ,my friend replied that ,i was an astronomer from ,greenwich ,observatory4 ',indeed2 and what does he do there8' ,this question completely exhausted my friend's information1 for as his tastes did not lead him in the direction of astronomy1 he had at no time ever concerned himself to inquire as to the nature of my official duties4 ',oh--er--why--he observes1 don't you know8' and the answer1 vague as it was1 completely slaked the inquirer's thirst for knowledge4 ,it is not every one who has such exceedingly nebulous ideas of an astronomer's duties4 ,more frequently we find that the inquirer has already formed a vivid and highly-coloured picture of the astronomer at his 'soul-entrancing work4' ,resting on a comfortable couch1 fixed at a luxurious angle1 the eye-piece of some great and perfect instrument brought most conveniently to his eye1 there passes before him1 in grand procession1 a sight such as the winter nights1 when clear and frosty1 give to the ordinary gazer1 but increased ten thousand times in beauty1 brilliance1 and wonder by the power of his telescope4 ,for him ,jupiter reveals his wind-drifted clouds and sunset colours2 for him ,saturn spreads his rings2 for him the snows of ,mars fall and melt1 and a thousand lunar plains are ramparted with titanic crags2 his are the star-clusters1 where suns in their first warm youth swarm thicker than hiving bees2 his the faint veils of nebulous smoke1 the first hint of shape in worlds about to be1 or1 perchance1 the last relics of worlds for ever dead4 ,and beside the enjoyment of all this entrancing spectacle of celestial beauty1 the fortunate astronomer sits at his telescope and discovers--always he discovers4 ,this1 or something like it1 is a very popular conception of an astronomer's experiences and duty2 and consequently many1 when they are told that 'discoveries' are not made at ,greenwich1 are inclined to consider that the ,observatory has failed in its purpose4 ,an astronomer without 'discoveries' to his record is like an angler who casts all day and comes home without fish--obviously an idle or incompetent person4 ,again1 it is considered that astronomy is a most transcendental science4 ,it deals with infinite distances1 with numbers beyond all power of human intellect to appreciate1 and therefore it is supposed1 on the one hand1 that it is a most elevating study1 keeping the mind continually on the stretch of ecstasy1 and1 on the other hand1 that it is utterly removed from all connection with practical1 everyday1 ordinary life4 ,these ideas as to the ,royal ,observatory1 or ideas like them1 are very widely current1 and they are1 in every respect1 exactly and wholly wrong4 ,first of all1 ,greenwich ,observatory was originally founded1 and has been maintained to the present day1 for a strictly practical purpose4 ,next1 instead of leading a life of dreamy ecstasy or transcendental speculation1 the astronomer has1 perhaps1 more than any man1 to give the keenest attention to minute practical details4 ,his life1 on the one side1 approximates to that of the engineer2 on the other1 to that of the accountant4 ,thirdly1 the professional astronomer has hardly anything to do with the show places of the sky4 ,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 showman1 who may have seen more of these than an active astronomer in a lifetime2 while as to 'discoveries1' these lie no more within the scope of our national observatory than do geographical discoveries within that of the captain and officers of an ocean liner4 ,if it is not to afford the astronomer beautiful spectacles1 nor to enable him to make thrilling discoveries1 what is the purpose of ,greenwich ,observatory8 ,first and foremost1 it is to assist navigation4 ,the ease and certainty with which to-day thousands of miles of ocean are navigated have ceased to excite any wonder4 ,we do not even think about it4 ,we go down to the docks and see1 it may be1 one steamer bound for ,halifax1 another for ,new ,york1 a third for ,charleston1 a fourth for the ,west ,indies1 a fifth for ,rio de ,janeiro2 and we unhesitatingly go on board the one bound for our chosen destination1 without the faintest misgiving as to its direction4 ,we have no more doubt about the matter than we have in choosing our train at a railway station4 ,yet1 whilst the train is obliged to follow a narrow track already laid for it1 from which it cannot swerve an inch1 the steamer goes forth to traverse for many days an ocean without a single fixed mark or indication of direction2 and it is exposed1 moreover1 to the full force of winds and currents1 which may turn it from its desired path4 ,but for this facility of navigation1 ,great ,britain could never have obtained her present commercial position and world-wide empire4 ',for the ,lord our ,god most ,high1 ,he hath made the deep as dry2 ,he has smote for us a pathway1 ,to the ends of all the earth4' ,part of this facility is1 of course1 due to the invention of the steam engine1 but much less than is generally supposed4 ,even yet the clippers1 with their roods of white canvas1 are not entirely superseded2 and if we could conceive of all steamships being suddenly annihilated1 ere long the sailing vessels would again1 as of yore1 prove the ',swift shuttles of an empire's loom1 ,that weave us main to main4' ,but with the art of navigation thrust back into its condition of a hundred and fifty years ago1 it is doubtful whether a sufficient tide of commerce could be carried on to keep our home population supplied1 or to maintain a sufficiently close political connection between these islands and our colonies4 ,navigation was in a most primitive condition even as late as the middle of last century4 ,then the method of finding a ship's longitude at sea was the insufficient one of dead reckoning4 ,in other words1 the direction and speed of the ship were estimated as closely as possible1 and so the position was carried on from day to day4 ,the uncertainty of the method was very great1 and many terrible stories might be told of the disastrous consequences which might1 and often did1 follow in the train of this method by guess-work4 ,it will be sufficient1 however1 to cite the instance of ,commodore ,anson4 ,he wanted to make the island of ,juan ,fernandez1 where he hoped to obtain fresh water and provisions1 and to recruit his crew1 many of whom were suffering from that scourge of old-time navigators--scurvy4 ,he got into its latitude easily enough1 and ran eastward1 believing himself to be west of the island4 ,he was1 however1 really east of it1 and therefore made the mainland of ,america4 ,he had therefore to turn round and sail westwards1 losing many days1 during which the scurvy increased upon his crew1 many of whom died from the terrible disease before he reached the desired island4 ,the necessity for finding out a ship's place when at sea had not been very keenly felt until the end of the fifteenth century4 ,it was always possible for the sailor to ascertain his latitude pretty closely1 either by observing the height of the pole-star at night or the height of the sun at noonday2 and so long as voyages were chiefly confined to the ,mediterranean ,sea1 and the navigators were content for the most part to coast from point to point1 rarely losing sight of land1 the urgency of solving the second problem--the longitude of the ship--was not so keenly felt4 ,but immediately the discoveries of the great ,portuguese and ,spanish navigators brought a wider1 bolder navigation into vogue1 it became a matter of the first necessity4 ,to take1 for example1 the immortal voyage of ,christopher ,columbus4 ,his purpose in setting out into the west was to discover a new way to ,india4 ,the ,venetians and ,genoese practically possessed the overland route across the ,isthmus of ,suez and down the ,red ,sea4 ,vasco da ,gama had opened out the route eastward round the ,cape4 ,firmly convinced that the world was a globe1 ,columbus saw that a third route was possible1 namely1 one nearly due west2 and when1 therefore1 he reached the ,bahamas1 after traversing some #ff of longitude1 he believed that he was in the islands of the ,china ,sea1 some #bcj from ,spain4 ,those who followed him still laboured under the same impression1 and when they reached the mainland of ,america1 believed that they were close to the shores of ,india1 which was still distant from them by half the circumference of the globe4 ,little by little the intrepid sailors of the sixteenth century forced their way to a true knowledge of the size of the globe1 and of the relative position of the great continents4 ,but this knowledge was only attained after many disasters and terrible miseries2 and though a new kind of navigation was established--the navigation of the open ocean1 far away from any possible landmark1 a navigation as different as could be conceived from the old method of coasting--yet it remained terribly risky and uncertain throughout the sixteenth century4 ,therefore many mathematicians endeavoured to solve the problem of determining the position of a ship when at sea4 ,their suggestions1 however1 remained entirely fruitless at the time1 though in several instances they struck upon principles which are being employed at the present day4 ,the first country to profit by the discovery of ,america was ,spain1 and hence ,spain was the first to feel keenly the pinch of the problem4 ,in #aeih1 therefore1 ,philip ,,iii4 offered a prize of #ajj1jjj 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 land4 ,holland1 which had recently started on its national existence1 and which was challenging the colonial empire of ,spain1 followed very shortly after with the offer of a reward of #cj1jjj florins4 ,not very long after the offer of these rewards1 a master mind did work out a simple method for determining the longitude1 a method theoretically complete1 though practically it proved inapplicable4 ,this was ,galileo1 who1 with his newly invented telescope1 had discovered that ,jupiter was attended by four satellites4 ,at first sight such a discovery1 however interesting1 would seem to have not the slightest bearing upon the sailor's craft1 or upon the commercial progress of one nation or another4 ,but ,galileo quickly saw in it the promise of great practical usefulness4 ,the question of the determination of the place of a ship when in the open ocean really resolved itself into this3 ,how could the navigator ascertain at any time what was the true time1 say at the port from which he sailed8 ,as already pointed out1 it was possible1 by observing the height of the sun at noon1 or of the pole-star at night1 to infer the latitude of the ship4 ,the longitude was the point of difficulty4 ,now1 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 meridian4 ,the sailor could1 indeed1 obtain his own local time by observations of the height of the sun4 ,the sun reached its greatest height at local noon1 and a number of observations before and after noon would enable him to determine this with sufficient nicety4 ,but how was he to determine when he1 perhaps1 was half-way across the ,atlantic1 what was the local time at ,genoa1 ,cadiz1 ,lisbon1 ,bristol1 or ,amsterdam1 or whatever was the port from which he sailed8 ,galileo thought out a way by which the satellites of ,jupiter could give him this information4 ,for as they circle round their primary1 they pass in turn into its shadow1 and are eclipsed by it4 ,it needed1 then1 only that the satellites should be so carefully watched1 that their motions1 and1 consequently1 the times of their eclipses could be foretold4 ,it would follow1 then1 that if the mariner had in his almanac the local time of the standard city at which a given satellite would enter into eclipse1 and he were able to note from the deck of his vessel the disappearance of the tiny point1 he would ascertain the difference between the local times of the two places1 or1 in other words1 the difference of their longitudes4 ,the plan was simplicity itself1 but there were difficulties in carrying it out1 the greatest being the impossibility of satisfactorily making telescopic observations from the moving deck of a ship at sea4 ,nor were the observations sufficiently sharp to be of much help4 ,the entry of a satellite into the shadow of ,jupiter is in most cases a somewhat slow process1 and the moment of complete disappearance would vary according to the size of the telescope1 the keenness of the observer's sight1 and the transparency of the air4 ,as the power and commerce of ,spain declined1 two other nations entered into the contest for the sovereignty of the seas1 and with that sovereignty predominance in the ,new ,world of ,america--,france and ,england4 ,the problem of the longitude at sea1 or1 as already pointed out1 what amounts to the same thing1 the problem how to determine when at sea the local time at some standard place1 became1 in consequence1 of greater necessity to them4 ,the standard time would be easily known1 if a thoroughly good chronometer which did not change its rate1 and which was set to the standard time before starting1 was carried on board the ship4 ,this plan had been proposed by ,gemma ,frisius as early as #aebf1 but at the time was a mere suggestion1 as there were no chronometers or watches sufficiently good for the purpose4 ,there was1 however1 another method of ascertaining the standard time4 ,the moon moves pretty quickly amongst the stars1 and at the present time1 when its motions are well known1 it is possible to draw up a table of its distances from a number of given stars at definite times for long periods in advance4 ,this is actually done to-day in the ,nautical ,almanac1 the moon's distance from certain stars being given for every three hours of ,greenwich time4 ,it is possible1 then1 by measuring these distances1 and making1 as in the case of the latitude1 certain corrections1 to find out the time at ,greenwich4 ,in short1 the whole sky may be considered as a vast clock set to ,greenwich time1 the stars being the numbers on the dial face1 and the moon the hand 7for this clock has only one hand7 moving amongst them4 ,the local apparent time--that is1 the time at the place at which the ship itself was--is a simpler matter4 ,it is noon at any place when the sun is due south--or1 as we may put it a little differently1 when it culminates--that is1 when it reaches its highest point4 ,to find the longitude at sea1 therefore1 it was necessary to be able to predict precisely the apparent position of the moon in the sky for any time throughout the entire year1 and it was also necessary that the places of the stars themselves should be very accurately known4 ,it was therefore to gather the materials for a better knowledge of the motions of the moon and the position of the stars that ,greenwich ,observatory was founded1 whilst the ,nautical ,almanac was instituted to convey this information to mariners in a convenient form4 ,this proposal was actually made in the reign of ,charles ,,ii4 by a ,frenchman1 ,le ,sieur de ,saint-,pierre1 who1 having secured an introduction to the ,duchess of ,portsmouth1 endeavoured to obtain a reward for his scheme4 ,it would appear that he had simply borrowed the idea from a book which an eminent ,french mathematician brought out forty years before1 without having himself any real knowledge of the subject4 ,but when the matter was brought before the king's notice1 he desired some of the leading scientific men of the day to report upon its practicability1 and the ,rev4 ,john ,flamsteed was the man selected for the task4 ,he reported that the scheme in itself was a good one1 but impracticable in the then state of science4 ,the king1 who1 in spite of the evil reputation which he has earned for himself1 took a real interest in science1 was startled when this was reported to him1 and commanded the man who had drawn his attention to these deficiencies 'to apply himself1' as the king's astronomer1 'with the most exact care and diligence to the ,rectifying the ,tables of the ,motions of the ,heavens and the ,places of the ,fixed ,stars1 in order to find out the so much desired ,longitude at ,sea1 for the perfecting the ,art of ,navigation4' ,this man1 the ,rev4 ,john ,flamsteed1 was accordingly appointed first ,astronomer ,royal at the meagre salary of #ajj a year1 with full permission to provide himself with the instruments he might require1 at his own expense4 ,he followed out the task assigned to him with extreme devotion1 amidst many difficulties and annoyances1 until his death in #agai4 ,he has been succeeded by seven ,astronomers ,royal1 each of whom has made it his first object to carry out the original scheme of the institution2 and the chief purpose of ,greenwich ,observatory to-day1 as when it was founded in #afge1 is to observe the motions of the sun1 moon1 and planets1 and to issue accurate star catalogues4 ,it will be seen1 therefore1 that the establishment of ,greenwich ,observatory arose from the actual necessity of the nation4 ,it was an essential step in its progress towards its present position as the first commercial nation4 ,no thoughts of abstract science were in the minds of its founders2 there was no desire to watch the cloud-changes on ,jupiter1 or to find out what ,sirius was made of4 ,the ,observatory was founded for the benefit of the ,royal ,navy and of the general commerce of the realm2 and1 in essence1 that which was the sole object of its foundation at the beginning has continued to be its first object down to the present time4 ,it was impossible that the work of the ,observatory should be always confined within the above limits1 and it will be my purpose1 in the pages which follow1 to describe when and how the chief expansions of its programme have taken place4 ,but assistance to navigation is now1 and has always been1 the dominant note in its management4 ,,chapter ,,ii ,,flamsteed ,for the first century of its existence1 the lives of its ,astronomers ,royal formed practically the history of the ,royal ,observatory4 ,during this period1 the ,observatory was itself so small that the ,astronomer ,royal1 with a single assistant1 sufficed for the entire work4 ,everything1 therefore1 depended upon the ability1 energy1 and character of the actual director4 ,there was no large organized staff1 established routine1 or official tradition1 to keep the institution moving on certain lines1 irrespective of the personal qualities of the chief4 ,it was specially fortunate1 therefore1 that the first four ,astronomers ,royal1 ,flamsteed1 ,halley1 ,bradley1 and ,maskelyne 7for ,bliss1 the immediate successor of ,bradley1 reigned for so short a time that he may be practically left out of the count71 were all men of the most conspicuous ability4 ,it will be convenient to divide the history of the first seven ,astronomers ,royal into three sections4 ,in the first1 we have the founder1 ,john ,flamsteed1 a pathetic and interesting figure1 whom we seem to know with especial clearness1 from the fulness of the memorials which he has left to us4 ,he was succeeded by the man who was1 indeed1 best fitted to succeed him1 but whom he most hated4 ,the second to the sixth ,astronomers ,royal formed what we might almost speak of as a dynasty1 each in turn nominating his successor1 who had entered into more or less close connection with the ,observatory during the lifetime of the previous director2 and the lives of these five may well form the second section4 ,the line was interrupted after the resignation of the sixth ,astronomer ,royal1 and the third section will be devoted to the seventh director1 ,airy1 under whom the ,observatory entered upon its modern period of expansion4 ',god suffers not man to be idle1 although he swim in the midst of delights2 for when ,he had placed ,his own image 7,adam7 in a paradise so replenished 7of ,his goodness7 with varieties of all things1 conducing as well to his pleasure as sustenance1 that the earth produced of itself things convenient for both1--,he yet 7to keep him out of idleness7 commands him to till1 prune1 and dress his pleasant1 verdant habitation2 and to add 7if it might be7 some lustre1 grace1 or conveniency to that place1 which1 as well as he1 derived its original from his ,creator4' ,in these words ,,john ,,flamsteed begins the first of several autobiographies which he has handed down to us2 this particular one being written before he attained his majority1 'to keep myself from idleness and to recreate myself4' ',i was born1' he goes on1 'at ,denby1 in ,derbyshire1 in the year #afdf1 on the #aith day of ,august1 at #g hours #af minutes after noon4 ,my father1 named ,stephen1 was the third son of ,mr4 ,william ,flamsteed1 of ,little ,hallam2 my mother1 ,mary1 was the daughter of ,mr4 ,john ,spateman1 of ,derby1 ironmonger4 ,from these two ,i derived my beginning1 whose parents were of known integrity1 honesty1 and fortune1 as they were of equal extraction and ingenuity2 betwixt whom ,i was tenderly educated 7by reason of my natural weakness1 which required more than ordinary care7 till ,i was aged three years and a fortnight2 when my mother departed1 leaving my father a daughter1 then not a month old1 with me1 then weak1 to his fatherly care and provision4' ,the weakly1 motherless boy became at an early age a voracious reader4 ,at first1 he says-- ',i began to affect the volubility and ranting stories of romances2 and at twelve years of age ,i first left off the wild ones1 and betook myself to read the better sort of them1 which1 though they were not probable1 yet carried no seeming impossibility in the fiction4 ,afterwards1 as my reason increased1 ,i gathered other real histories2 and by the time ,i was fifteen years old ,i had read1 of the ancients1 ,plutarch's ,lives1 ,appian's and ,tacitus's ,roman ,histories1 ,holingshed's ,history of the ,kings of ,england1 ,davies's ,life of ,queen ,elizabeth1 ,saunderson's of ,king ,charles the ,first1 ,heyling's ,geography1 and many others of the moderns2 besides a company of romances and other stories1 of which ,i scarce remember a tenth at present4' ,flamsteed received his education at the free school at ,derby1 where he continued until the ,whitsuntide of #affb1 when he was nearly sixteen years of age4 ,two years earlier than this1 however1 a great misfortune fell upon him4 ',at fourteen years of age1' he writes1 'when ,i was nearly arrived to be the head of the free-school1 ,i was visited with a fit of sickness1 that was followed with a consumption and other distempers1 which yet did not so much hinder me in my learning1 but that ,i still kept my station till the form broke up1 and some of my fellows went to the ,universities2 for which1 though ,i was designed1 my father thought it not advisable to send me1 by reason of my distemper4' ,this was a keen disappointment to him1 but seems to have really been the means of determining his career4 ,the sickly1 suffering boy could not be idle1 though 'a day's short reading caused so violent a headache2' and a month or two after he had left school1 he had a book lent to him--,sacrobosco's ,de ,sphra1 in ,latin--which was the beginning of his mathematical studies4 ,a partial eclipse of the sun in ,september of the same year seems to have first drawn his attention to astronomical observation1 and during the winter his father1 who had himself a strong passion for arithmetic1 instructed him in that science4 ,it was astonishing how quickly his appetite for his new subjects grew4 ,the ,art of ,dialling1 the calculation of tables of the sun's altitudes for all hours of the day1 and for different latitudes1 and the construction of a quadrant--'of which ,i was not meanly joyful'--were the occupations of this winter of illness4 ,in #affd he made the acquaintanceship of two friends1 ,mr4 ,george ,linacre and ,mr4 ,william ,litchford2 the former of whom taught him to recognize many of the fixed stars1 whilst the latter was the means of his introduction to a knowledge of the motions of the planets4 ',i had now completed eighteen years1 when the winter came on1 and thrust me again into the chimney2 whence the heat and dryness of the preceding summer had happily once before withdrawn me4' ,the following year1 #affe1 was memorable to him 'for the appearance of the comet1' and for a journey which he made to ,ireland to be 'stroked' for his rheumatic disorder by ,valentine ,greatrackes1 a kind of mesmerist1 who had the repute of effecting wonderful cures4 ,the journey1 of which he gives a full and vivid account1 occupied a month2 but though he was a little better1 the following winter brought him no permanent benefit4 ,but1 ill or well1 he pressed on his astronomical studies4 ,a large partial eclipse of the sun was due the following ,june2 he computed the particulars of it for ,derby1 and observed the eclipse itself to the best of his ability4 ,he argued out for himself 'the equation of time'2 the difference1 that is1 between time as given by the actual sun1 or 'apparent time1' and that given by a perfect clock1 or 'mean time4' ,he drew up a catalogue of seventy stars1 computing their right ascensions1 declinations1 longitudes1 and latitudes for the year #agja2 he attempted to determine the inclination of the ecliptic1 the mean length of the tropical year1 and the actual distance of the earth from the sun4 ,and these were the recreations of a sickly1 suffering young man1 not yet twenty-one years of age1 and who had only begun the study of arithmetic1 such as fractions and the rule of three1 four years previously6 ,his next attempt was almanac-making1 in the which he improved considerably upon those current at the time4 ,his almanac for #afgj was rejected1 however1 and returned to him1 and1 not to lose his whole labour1 he sent his calculations of an eclipse of the sun1 and of five occultations of stars by the moon1 which he had undertaken for the almanac1 to the ,royal ,society4 ,he sent the paper anonymously1 or1 rather1 signed it with an anagram1 ',in mathesi a sole fundes1' for ',johannes ,flamsteedius4' ,his covering letter ends thus3-- ',excuse1 ,i pray you1 this juvenile heat for the concerns of science and want of better language1 from one who1 from the sixteenth year of his age to this instant1 hath only served one bare apprenticeship in these arts1 under the discouragement of friends1 the want of health1 and all other instructors except his better genius4' ,this letter was dated ,november #d1 #affi1 and on ,january #ad1 ,mr4 ,oldenburg1 the secretary of the ,society1 replied to him in a letter which the young man cannot but have felt encouraging and flattering to the highest degree4 ',though you did what you could to hide your name from us1' he writes1 'yet your ingenious and useful labours for the advancement of ,astronomy addressed to the noble ,president of the ,royal ,society1 and some others of that illustrious body1 did soon discover you to us1 upon our solicitous inquiries after their worthy author4' ,and after congratulating him upon his skill1 and encouraging him to furnish further similar papers1 he signs himself1 ',your very affectionate friend and real servant'--no unmeaning phrase1 for the friendship then commenced ceased only with ,oldenburg's life4 ,the following ,june1 his father1 pleased with the notice that some of the leading scientific men of the day were taking of his son1 sent him up to ,london1 that he might be personally acquainted with them2 and he then was introduced to ,sir ,jonas ,moore1 the ,surveyor of the ,ordnance1 who made him a present of ,townley's micrometer1 and promised to furnish him with object-glasses for telescopes at moderate rates4 ,on his return journey he called at ,cambridge1 where he visited ,dr4 ,barrow and ,newton1 and entered his name in ,jesus ,college4 ,it was not until the following year1 #afga1 that he was enabled to complete his own observatory1 as he had had to wait long for the lenses which ,sir ,jonas ,moore and ,collins had promised to procure for him4 ,he still laboured under several difficulties1 in that he had no good means for measuring time1 pendulum clocks not then being common4 ,he1 therefore1 with a practical good sense which was characteristic1 refrained from attempting anything which lay out of his power to do well1 and he devoted himself to such observations as did not require any very accurate knowledge of the time4 ,at the same time1 he was careful to ascertain the time of his observations as closely as possible1 by taking the altitudes of the stars4 ,the next four years seem to have passed exceedingly pleasantly to him4 ,the notes of ill-health are few4 ,he was making rapid progress in his acquaintanceship with the work of other astronomers1 particularly with those of the three marvellously gifted young men--,horrox1 ,crabtree1 and ,gascoigne--who had passed away shortly before his own birth4 ,he was making new friends in scientific circles1 and1 in particular1 ,sir ,jonas ,moore was evidently esteeming him more and more highly4 ,in #afgd he became more intimate with ,newton1 the occasion which led to this acquaintanceship being the amusing one1 that his assistance was asked by ,newton1 who had found himself unable to adjust a microscope1 having forgotten its object-glass--not the only instance of the great mathematician's absent-mindedness4 ,the same year he took his degree of ,a4,m4 at ,cambridge1 designing to enter the ,church2 but ,sir ,jonas ,moore was extremely anxious to give him official charge of an observatory1 and was urging the ,royal ,society to build an astronomical observatory at ,chelsea ,college1 which then belonged to that body4 ,he therefore came up to ,london1 and resided some months with ,sir ,jonas ,moore at the ,tower4 ,but shortly after his coming up to ,london1 'an accident happened1' to use his own expression1 that hastened1 if it did not occasion1 the building of ,greenwich ,observatory4 ',a ,frenchman that called himself ,le ,sieur de ,st4 ,pierre1 having some small skill in astronomy1 and made an interest with a ,french lady1 then in favour at ,court1 proposed no less than the discovery of the ,longitude1 and had procured a kind of ,commission from the ,king to the ,lord ,brouncker1 ,dr4 ,ward 7,bishop of ,salisbury71 ,sir ,christopher ,wren1 ,sir ,charles ,scarborough1 ,sir ,jonas ,moore1 ,colonel ,titus1 ,dr4 ,pell1 ,sir ,robert ,murray1 ,mr4 ,hook1 and some other ingenious gentlemen about the town and ,court1 to receive his proposals1 with power to elect1 and to receive into their number1 any other skilful persons2 and having heard them1 to give the ,king an account of them1 with their opinion whether or no they were practicable1 and would show what he pretended4 ,sir ,jonas ,moore carried me with him to one of their meetings1 where ,i was chosen into their number2 and1 after1 the ,frenchman's proposals were read1 which were3 '7#a7 ,to have the year and day of the observations4 '7#b7 ,the height of two stars1 and on which side of the meridian they appeared4 '7#c7 ,the height of the moon's two limbs4 '7#d7 ,the height of the pole--all to degrees and minutes4 ',it was easy to perceive1 from these demands1 that the sieur understood not that the best lunar tables differed from the heavens2 and that1 therefore1 his demands were not sufficient for determining the longitude of the place where such observations were1 or should be1 made1 from that to which the lunar tables were fitted1 which ,i represented immediately to the company4 ,but they1 considering the interests of his patroness at ,court1 desired to have him furnished according to his demands4 ,i undertook it2 and having gained the moon's true place by observations made at ,derby1 ,february #bc1 #afgb1 and ,november #ab1 #afgc1 gave him observations such as he demanded4 ,the half-skilled man did not think they could have been given him1 and cunningly answered ,they were feigned4 ,i delivered them to ,dr4 ,pell1 ,february #ai1 #afgd-e1 who1 returning me his answer some time after1 ,i wrote a letter in ,english to the commissioners1 and another in ,latin to the sieur1 to assure him they were not feigned1 and to show them that1 if they had been1 yet if we had astronomical tables that would give us the two places of the fixed stars and the moon's true places1 both in longitude and latitude1 nearer than to half a minute1 we might hope to find the longitude of places by lunar observations1 but not by such as he demanded4 ,but that we were so far from having the places of the fixed stars true1 that the ,tychonic ,catalogues often erred ten minutes or more2 that they were uncertain to three or four minutes1 by reason that ,tycho assumed a faulty obliquity of the ecliptic1 and had employed only plain sights in his observations3 and that the best lunar tables differ one-quarter1 if not one-third1 of a degree from the heavens2 and lastly1 that he might have learnt better methods than he proposed1 from his countryman ,morin1 whom he had best consult before he made any more demands of this nature4' ,this was in effect to tell ,st4 ,pierre that his proposal was neither original nor practicable4 ,if ,st4 ,pierre had but consulted ,morin's writings 7,morin himself had died more than eighteen years before71 he would have known that practically the same proposal had been laid before ,cardinal ,richelieu in #afcd1 and had been rejected1 as quite impracticable in the then state of astronomical knowledge4 ,possibly ,flamsteed meant further to intimate that ,st4 ,pierre had simply stolen his method from ,morin1 hoping to trade it off upon the government of another country2 in which case he would no doubt regard ,flamsteed's letter as a warning that he had been found out4 ,flamsteed continues3-- ',i heard no more of the ,frenchman after this2 but was told that1 my letters being shown ,king ,charles1 he startled at the assertion of the fixed stars' places being false in the catalogue2 said1 with some vehemence1 ,he must have them anew observed1 examined1 and corrected1 for the use of his seamen2 and further 7when 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 planets71 with the same earnestness1 he must have it done4 ,and when he was asked ,who could1 or who should do it8 ,the person 7says he7 that informs you of them4 ,whereupon ,i was appointed to it1 with the incompetent allowance aforementioned2 but with assurances1 at the same time1 of such further additions as thereafter should be found requisite for carrying on the work4' ,illustration3 ,,flamsteed',s ,,sextant4 7,from an engraving in the ',historia ,coelestis4'7 ,thus1 in his twenty-ninth year1 ,john ,flamsteed became the first ,astronomer ,royal4 ,in many ways he was an ideal man for the post4 ,in the twelve years which had passed since he left school he had accomplished an amazing amount of work4 ,despite his constant ill-health and severe sufferings1 and the circumstance--which may be inferred from many expressions in his autobiographies--that he assisted his father in his business1 he had made himself master1 perhaps more thoroughly than any of his contemporaries1 of the entire work of a practical astronomer as it was then understood4 ,he was an indefatigable computer2 the calculation of tables of the motions of the moon and planets1 which should as faithfully as possible represent their observed positions1 had had an especial attraction for him1 and1 as has been already mentioned1 some years before his appointment he had drawn up a catalogue of stars1 based upon the observations of ,tycho ,brahe4 ,more than that1 he had not been a merely theoretical worker1 he had been a practical observer of very considerable skill1 and1 in the dearth of suitable instruments1 had already made one or two for himself1 and had contemplated the making of others4 ,in his first letter to ,sir ,jonas ,moore he asks for instruction as to the making of object-glasses for telescopes1 for he was quite prepared to set about the task of making his own4 ,in addition to his tireless industry1 which neither illness nor suffering could abate1 he was a man of singularly exact and business-like habits4 ,the precision with which he preserves and records the dates of all letters received or sent is an illustration of this4 ,on the other hand1 he had the defects of his circumstances and character4 ,his numerous autobiographical sketches betray him1 not indeed as a conceited man1 in the ordinary sense of the word1 but as an exceedingly self-conscious one4 ,devout and high-principled he most assuredly was1 but1 on the other hand1 he shows in almost every line he wrote that he was one who could not brook anything like criticism or opposition4 ,such a man1 however efficient1 was little likely to be happy as the first incumbent of a new and important government post2 but there was another circumstance which was destined to cause him greater unhappiness still4 ,if we believe1 as surely we must1 that not only the moral and the physical progress of mankind is watched over and controlled by ,god's good ,providence1 but its intellectual progress as well1 then there can be no doubt that ,john ,flamsteed was raised up at this particular time1 not merely to found ,greenwich ,observatory1 and to assist the solution of the problem of the longitude at sea1 but also1 and chiefly1 to become the auxiliary to a far greater mind1 the journeyman to a true master-builder4 ,but for the founding of ,greenwich ,observatory1 and for ,john ,flamsteed's observations made therein1 the working out of ,newton's grand theory of gravitation must have been hindered1 and its acceptance by the men of science of his time immensely delayed4 ,we cannot regard as accidental the combination1 so fortunate for us1 of ,newton1 the great world-genius1 to work out the problem1 of ,flamsteed1 the painstaking observer1 to supply him with the materials for his work1 and of the newly-founded institution1 ,greenwich ,observatory1 where ,flamsteed was able to gather those materials together4 ,this is the true debt that we owe to ,flamsteed1 that1 little as he understood the position in which he had been placed from the standpoint from which we see it to-day1 yet1 to the extent of his ability1 and as far as he conceived it in accordance with his duty1 he gave ,newton such assistance as he could4 ,this is how we see the matter to-day4 ,it wore a very different aspect in ,flamsteed's eyes2 and the two following documents1 the one1 the warrant founding the ,observatory and making him ,astronomer ,royal2 the other1 the warrant granting him a salary1 will go far to explain his position in the matter4 ,he had a high-sounding1 official position1 which could not fail to impress him with a sense of importance2 whilst his salary was so insufficient that he naturally regarded himself as absolute owner of his own work4 ',warrant for the ,payment of ,mr4 ,flamsteed's ,salary4 ',charles ,rex4 ',whereas1 we have appointed our trusty and well-beloved ,john ,flamsteed1 ,master of ,arts1 our astronomical observator1 forthwith to apply himself with the most exact care and diligence to the rectifying the tables of the motions of the heavens1 and the places of the fixed stars1 so as to find out the so-much-desired longitude of places for the perfecting the art of navigation1 ,our will and pleasure is1 and we do hereby require and authorize you1 for the support and maintenance of the said ,john ,flamsteed1 of whose abilities in astronomy we have very good testimony1 and are well satisfied1 that from time to time you pay1 or cause to be paid1 unto him1 the said ,john ,flamsteed1 or his assigns1 the yearly salary or allowance of one hundred pounds per annum2 the same to be charged and borne upon the quarter-books of the ,office of the ,ordnance1 and paid to him quarterly1 by even and equal portions1 by the ,treasurer of our said office1 the first quarter to begin and be accompted from the feast of ,st4 ,michael the ,archangel last past1 and so to continue during our pleasure4 ,and for so doing1 this shall be as well unto you1 as to the ,auditors of the ,exchequer1 for allowing the same1 and all other our officers and ministers whom it may concern1 a full and sufficient warrant4 ',given at our ,court at ,whitehall1 the #dth day of ,march1 #afgd-e4 ',by his ,majesty's ,command1 ',j4 ,,williamson4 ',to our right-trusty and well-beloved ,counsellor1 ,sir ,thomas ,chichely1 ,knt41 ,master of our ,ordnance1 and to the ,lieutenant-,general of our ,ordnance1 and to the rest of the ,officers of our ,ordnance1 now and for the time being1 and to all and every of them4' ',warrant for ,building the ,observatory4 ',charles ,rex4 ',whereas1 in order to the finding out of the longitude of places for perfecting navigation and astronomy1 we have resolved to build a small observatory within our park at ,greenwich1 upon the highest ground1 at or near the place where the ,castle stood1 with lodging-rooms for our astronomical observator and assistant1 ,our will and pleasure is1 that according to such plot and design as shall be given you by our trusty and well-beloved ,sir ,christopher ,wren1 ,knight1 our surveyor-general of the place and scite of the said observatory1 you cause the same to be fenced in1 built and finished with all convenient speed1 by such artificers and workmen as you shall appoint thereto1 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 therein1 out of such monies as shall come to your hands for old and decayed powder1 which hath or shall be sold by our order of the #ast of ,january last1 provided that the whole sum1 so to be expended or paid1 shall not exceed five hundred pounds2 and our pleasure is1 that all our officers and servants belonging to our said park be assisting to those that you shall appoint1 for the doing thereof1 and for so doing1 this shall be to you1 and to all others whom it may concern1 a sufficient warrant4 ',given at our ,court at ,whitehall1 the #bbnd day of ,june1 #afge1 in the #bgth year of our reign4 ',by his ,majesty's ,command1 ',j4 ,,williamson4 ',to our right-trusty and well-beloved ,counsellor1 ,sir ,thomas ,chichely1 ,knt41 ,master-,general of our ,ordnance4' ,the first question that arose1 when it had been determined to found the new ,observatory1 was where it was to be placed4 ,hyde ,park was suggested1 and ,sir ,jonas ,moore recommended ,chelsea ,college1 where he had already thought of establishing ,flamsteed in a private observatory4 ,fortunately1 both these localities were set aside in favour of one recommended by ,sir ,christopher ,wren4 ,there was a small building on the top of the hill in the ,royal ,park of ,greenwich belonging to the ,crown1 and which was now of little or no use4 ,visible from the city1 and easily accessible by that which was then the best and most convenient roadway1 the river ,thames1 it was yet so completely out of town as to be entirely safe from the smoke of ,london4 ,in ,greenwich ,park1 too1 but on the more easterly hill1 ,charles ,i4 had contemplated setting up an observatory1 but the pressure of events had prevented him carrying out his intention4 ,a further practical advantage was that materials could be easily transported thither4 ,the management of public affairs under ,charles ,,ii4 left much to be desired in the matter of efficiency and economy1 and it was not very easy to procure what was wanted for the erection of a purely scientific building4 ,however1 the matter was arranged4 ,a gate-house demolished in the ,tower supplied wood2 iron1 and lead1 and bricks were supplied from ,tilbury ,fort1 and these could be easily brought by water to the selected site4 ,the sum of #ejj1 actually #ebj1 was further allotted from the results of a sale of spoilt gunpowder2 and with these limited resources ,greenwich ,observatory was built4 ,the foundation-stone was laid ,august #aj1 #afge1 and ,flamsteed amused himself by drawing the horoscope of the ,observatory1 a fact which--in spite of his having written across the face of the horoscope ,risum teneatis amici8 7,can you keep from laughter1 my friends871 and his having two or three years before written very severely against the imposture of astrology--has led some modern astrologers to claim him as a believer in their cult4 ,he actually entered into residence ,july #aj1 #afgf4 ,illustration3 ,,the ,,royal ,,observatory ,,in ,,flamsteed',s ,,day4 7,from an engraving in the ',historia ,coelestis4'7 ,his position was not a bright one4 ,the ,government had1 indeed1 provided him with a building for his observatory1 and a small house for his own residence1 but he had no instrument and no assistant4 ,the first difficulty was partly overcome for the moment by gifts or loans from ,sir ,jonas ,moore1 and by one or two small loans from the ,royal ,society4 ,the death of this great friend and patron1 four years after the founding of the ,observatory1 and only three years after his entering into residence1 deprived him of several of these2 it was with difficulty that he maintained against ,sir ,jonas' heirs his claim to the instruments which ,sir ,jonas had given him4 ,there was nothing for him to do but to make his instruments himself1 and in #afhc he built a mural quadrant of fifty inches radius4 ,his circumstances improved the following year1 when ,lord ,north gave him the living of ,burstow1 near ,horley1 ,surrey1 ,flamsteed having received ordination almost at the time of his appointment to the ,astronomer ,royalship4 ,we have little or no account of the way in which he fulfilled his duties as a clergyman4 ,evidently he considered that his position as ,astronomer ,royal had the first claim upon him4 ,at the same time1 comparatively early in life he had expressed his desire to fill the clerical office1 and he was a man too conscientious to neglect any duty that lay upon him4 ,that in spite of his feeble health he often journeyed to and fro between ,burstow and ,greenwich we know2 and we may take it as certain that at a time when the standard of clerical efficiency was extremely low1 he was not one of those who ',for their bellies' sake1 ,creep and intrude and climb into the fold4' ,his chief source of income1 however1 seems to have been the private pupils whom he took in mathematics and astronomy4 ,these numbered in the years #afgf to #agji no fewer than #adj2 and as many of them were of the very first and wealthiest families in the kingdom1 the gain to ,flamsteed in money and influence must have been considerable4 ,but it was most distasteful work4 ,it was in no sense that which he felt to be his duty1 and which he had at heart4 ,it was undertaken from sheer1 hard necessity1 and he grudged bitterly the time and strength which it diverted from his proper calling4 ,how faithfully he followed that1 one single circumstance will show4 ,in the thirteen years ending #afhi1 he made #bj1jjj observations1 and had revised single-handed the whole of the theories and tables of the heavenly bodies then in use4 ,in #afhh the death of his father brought him a considerable accession of means1 and1 far more important1 the assistance of ,abraham ,sharp1#a the first and most distinguished of the long list of ,greenwich assistants1 men who1 though far less well known than the ,astronomers ,royal1 have contributed scarcely less in their own field to the high reputation of the ,observatory4 #a ,abraham ,sharp had been with ,flamsteed earlier than this--in #afhd and #afhe4 ,sharp was not only a most careful and indefatigable calculator1 he was what was even more essential for ,flamsteed--a most skilful instrument-maker2 and he divided for him a new mural arc of #adj and seven feet radius1 with which he commenced operations on ,december #ab1 #afhi4 ,above all1 ,sharp became his faithful and devoted friend and adherent1 and no doubt his sympathy strengthened ,flamsteed to endure the trouble which was at hand4 ,that trouble began in #afid1 when ,newton visited the ,royal ,observatory4 ,at that time ,flamsteed1 though he had done so much1 had published nothing1 and ,newton1 who had made his discovery of the laws of gravitation some few years before1 was then employed in deducing from them a complete theory of the moon's motion4 ,this work was one of absolutely first importance4 ,in the first place and chiefly1 upon the success with which it could be carried out1 depended undoubtedly the acceptance of the greatest discovery which has yet been made in physical science4 ,secondarily--and this should1 and no doubt did1 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 ,royal4 ,newton was1 therefore1 anxious beyond everything to receive the best possible observations of the moon's places1 and he came to ,flamsteed1 as to the man from whom he had a right to expect to receive a supply of them4 ,at first ,flamsteed seems to have given these as fully as he was able2 but it is evident that ,newton chafed at the necessity for these frequent applications to ,flamsteed1 and to the constant need of putting pressure upon him4 ,flamsteed1 on the other hand1 as clearly evidently resented this continual demand4 ,feeling1 as he keenly did1 that1 though he had been named ,astronomer ,royal1 he had been left practically entirely without support2 his instruments were entirely his own1 either made or purchased by himself2 his nominal salary of #ajj was difficult to get1 and did not nearly cover the actual current expenses of his position1 he not unnaturally regarded his observations as his own exclusive property4 ,he had a most natural dislike for his observations to be published1 except after such reduction as he himself had carried through1 and in the manner which he himself had chosen4 ,the idea which was ever before him was that of carrying out a single great work that should not only be a monument to his own industry and skill1 but should also raise the name of ,england amongst scientific nations4 ,he complained of it1 therefore1 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 comet4 ,unknown to himself1 therefore1 he was called upon to decide a question that has proved fundamental to the policy of ,greenwich ,observatory1 and he decided it wrongly--the question of publication4 ,newton had urged upon him as early as #afia that he should not wait until he had formed an exhaustive catalogue of all the brighter stars1 but that he should publish at once a catalogue of a few1 which might serve as standards2 but ,flamsteed would not hear of it4 ,he failed to see that his office had been created for a definite practical purpose1 not for the execution of some great scheme1 however important to science4 ,all his work of thirty years had done nothing to forward navigation so long as he published nothing4 ,but if1 year by year1 he had published the places of the moon and of a few standard stars1 he would have advanced the art immensely and yet have not hindered himself from eventually bringing out a great catalogue4 ,no doubt the little incident of ,newton's difficulty with the microscope1 of which he had forgotten the object-glass1 had given ,flamsteed a low opinion of ,newton's qualifications as a practical astronomer4 ,if so1 he was wrong1 for ,newton's insight into practical matters was greater than ,flamsteed's own1 and his practical skill was no less1 though his absent-mindedness might occasionally lead him into an absurd mistake4 ,the following extract from ,flamsteed's own 'brief ,history of the ,observatory' gives an account of his view of ,newton's action towards him in desiring the publication of his star catalogue1 and at the same time it illustrates ,flamsteed's touchy and suspicious nature4 ',whilst ,mr4 ,flamsteed was busied in the laborious work of the catalogue of the fixed stars1 and forced often to watch and labour by night1 to fetch the materials for it from the heavens1 that were to be employed by day1 he often1 on ,sir ,isaac ,newton's instances1 furnished him with observations of the moon's places1 in order to carry on his correction of the lunar theory4 ,a civil correspondence was carried on between them2 only ,mr4 ,flamsteed could not but take notice that as ,sir ,isaac was advanced in place1 so he raised himself in his conversation and became more magisterial4 ,at last1 finding that ,mr4 ,flamsteed had advanced far in his designed catalogue by the help of his country calculators1 that he had made new lunar tables1 and was daily advancing on the other planets1 ,sir ,isaac ,newton came to see him 7,tuesday1 ,april #aa1 #agjd72 and desiring1 after dinner1 to be shown in what forwardness his work was1 had so much of the catalogue of the fixed stars laid before him as was then finished2 together with the maps of the constellations1 both those drawn by ,t4 ,weston and ,p4 ,van ,somer1 as also his collation of the observed places of ,saturn and ,jupiter1 with the ,rudolphine numbers4 ,having viewed them well1 he told ,mr4 ,flamsteed he would 7i4e4 he was desirous to7 recommend them to the ,prince privately4 ,mr4 ,flamsteed 7who had long been sensible of his partiality1 and heard how his two flatterers cried ,sir ,isaac's performances up1 was sensible of the snare in the word privately7 answered that would not do2 and 7upon ,sir ,isaac's demanding why not87 that then the ,prince's attendants would tell him these were but curiosities of no great use1 and persuade him to save that expense1 that there might be the more for them to beg of him3 and that the recommendation must be made publicly1 to prevent any such suggestions4 ,sir ,isaac apprehended right1 that he was understood1 and his designs defeated3 and so took his leave not well satisfied with the refusal4 ',it was ,november following ere ,mr4 ,flamsteed heard from him any more3 when1 considering with himself that what he had done was not well understood1 he set himself to examine how many folio pages his work when printed would fill2 and found upon an easy computation that they would at least take up #adjj4 ,being amazed at this1 he set himself to consider them more seriously2 drew up an estimate of them2 and1 to obviate the misrepresentations of ,dr4 ,sloane and some others1 who had given out that what he had was inconsiderable1 he delivered a copy of the estimate to ,mr4 ,hodgson1 then lately chosen a member of the ,royal ,society1 with directions to deliver it to a friend1 who he knew would do him justice2 and1 on this fair account1 obviate those unjust reports which had been studiously spread to his prejudice4 ,it happened soon after1 ,mr4 ,hodgson being at a meeting1 spied this person there1 at the other side of the room2 and therefore gave the paper to one that stood in some company betwixt them1 to be handed to him4 ,but the gentleman1 mistaking his request1 handed to the ,secretary ,dr4 ,sloane1 who1 being a ,physician1 and not acquainted with astronomical terms1 did not read it readily4 ,whereupon another in the company took it out of his hands2 and1 having read it distinctly1 desired that the works therein mentioned might be recommended to the ,prince2 the charge of printing them being too great either for the author or the ,royal ,society4 ,sir ,isaac closed in with this4' ,illustration3 ,,the ',,camera ,,stellata' ,,in ,,flamsteed',s ,,time4 7,from an engraving in the ',historia ,coelestis4'7 ,the work was in consequence recommended to ,prince ,george of ,denmark1 the ,queen's ,consort2 but it was not till ,november #aj1 #agje1 that the contract for the printing was signed4 ,two years later1 the observations which he had made with his sextant in his first thirteen years of office were printed4 ,then came the difficulty of the catalogue4 ,it was not complete to ,flamsteed's satisfaction1 and he was most unwilling to let it pass out of his hands4 ,however1 two manuscripts1 comprising some three-quarters of the whole1 were deposited with referees1 the first of these being sealed up4 ,the seal was broken with ,flamsteed's concurrence2 but the fact that it had been so broken was made by him the subject of bitter complaint later4 ,at this critical juncture ,prince ,george died1 and a stop was put to the progress of the printing4 ,two years more elapsed without any advance being made1 and then1 in order to check any further obstruction1 a committee of the ,royal ,society was appointed as a ,board of ,visitors to visit and inspect the ,observatory1 and so maintain a control over the ,astronomer ,royal4 ,this was naturally felt by so sensitive a man as ,flamsteed as a most intolerable wrong1 and when he found that the printing of his catalogue had been placed in the hands of ,halley as editor1 a man for whom he had conceived the most violent distrust1 he absolutely refused to furnish the ,visitors with any further material4 ,this led to1 perhaps1 the most painful scene in the lives either of ,newton or ,flamsteed4 ,flamsteed was summoned to meet the ,council of the ,royal ,society at their rooms in ,crane ,court4 ,a quorum was not present1 and so the interview was not official1 and no record of it is preserved in the archives4 ,flamsteed has himself described it with great particularity in more than one document1 and it is only too easy to understand the scene that took place4 ,newton was a man who had an absolutely morbid dread of anything like controversy1 and over and over again would have preferred to have buried his choicest researches1 rather than to have encountered the smallest conflict of the kind4 ,he was perhaps1 therefore1 the worst man to deal with a high-principled1 sensitive1 and obstinate man who was in the wrong1 and yet who had been so hardly dealt with that it was most natural for him to think himself wholly in the right4 ,flamsteed adhered absolutely to his position1 from which it is clear it would have been extremely difficult for the greatest tact and consideration to have dislodged him4 ,newton1 on his part1 simply exerted his authority1 and1 that failing1 was reduced to the miserable extremity of calling names4 ,the scene is described by ,flamsteed himself1 in a letter to ,abraham ,sharp1 as follows3-- ',i have had another contest with the ,president#b of the ,royal ,society1 who had formed a plot to make my instruments theirs2 and sent for me to a ,committee1 where only himself and two physicians 7,dr4 ,sloane1 and another as little skilful as himself7 were present4 ,the ,president ran himself into a great heat1 and very indecent passion4 ,i had resolved aforehand his kn--sh talk should not move me2 showed him that all the instruments in the ,observatory were my own2 the mural arch and voluble quadrant having been made at my own charge1 the rest purchased with my own money1 except the sextant and two clocks1 which were given me by ,sir ,jonas ,moore1 with ,mr4 ,towneley's micrometer1 his gift1 some years before ,i came to ,greenwich4 ,this nettled him2 for he has got a letter from the ,secretary of ,state for the ,royal ,society to be ,visitors of the ,observatory1 and he said1 as good have no observatory as no instruments4 ,i complained then of my catalogue being printed by ,raymer1 without my knowledge1 and that ,i was robbed of the fruit of my labours4 ,at this he fired1 and called me all the ill names1 puppy1 etc41 that he could think of4 ,all ,i returned was1 ,i put him in mind of his passion1 desired him to govern it1 and keep his temper3 this made him rage worse1 and he told me how much ,i had received from the ,government in thirty-six years ,i had served4 ,i asked what he had done for the #ejj per annum that he had received ever since he had settled in ,london4 ,this made him calmer2 but finding him going to burst out again1 ,i only told him my catalogue1 half finished1 was delivered into his hands1 on his own request1 sealed up4 ,he could not deny it1 but said ,dr4 ,arbuthnott had procured the ,queen's order for opening it4 ,this1 ,i am persuaded1 was false2 or it was got after it had been opened4 ,i said nothing to him in return2 but1 with a little more spirit than ,i had hitherto showed1 told them that ,god 7who was seldom spoken of with due reverence in that meeting7 had hitherto prospered all my labours1 and ,i doubted not would do so to a happy conclusion2 took my leave and left them4 ,dr4 ,sloane had said nothing all this while2 the other ,doctor told me ,i was proud1 and insulted the ,president1 and ran into the same passion with the ,president4 ,at my going out1 ,i called to ,dr4 ,sloane1 told him he had behaved himself civilly1 and thanked him for it4 ,i saw ,raymer after1 drank a dish of coffee with him1 and told him1 still calmly1 of the villany of his conduct1 and called it blockish4 ,since then they let me be quiet2 but how long they will do so ,i know not1 nor am ,i solicitous4' #b ,sir ,isaac ,newton4 ,the ,visitors continued the printing1 ,halley being the editor1 and the work appeared in #agab under the title of ,historia ,coelestis4 ,this seemed to ,flamsteed the greatest wrong of all4 ,the work as it appeared seemed to him so full of errors1 wilfully or accidentally inserted1 as to be the greatest blot upon his fair fame1 and he set himself1 though now an old man1 to work it out de novo and at his own expense4 ,to that purpose he devoted the remaining seven years of his life4 ,few things can be more pathetic than the letters which he wrote in that period referring to it4 ,he was subject to the attacks of one of the cruelest of all diseases--the stone2 he was at all times liable to distracting headaches4 ,he had been1 from his boyhood1 a great sufferer from rheumatism1 and yet1 in spite of all1 he resolutely pushed on his self-appointed task4 ,the following extract from one of his letters will give a more vivid idea of the brave old man than much description3-- ',i can still1 ,i praise ,god for it1 walk from my door to the ,blackheath gate and back1 with a little resting at some benches ,i have caused to be set up betwixt them4 ,but ,i found myself so tired with getting up the hill when ,i return from church1 that at last ,i have bought a sedan1 and am carried thither in state on ,sunday mornings and back2 ,i hope ,i may employ it in the afternoons1 though ,i have not hitherto1 by reason of the weather is too cold for me4' ,after the death of ,queen ,anne1 a change in the ministry enabled him to secure that three hundred copies of the total impression of four hundred of the ,historia ,coelestis were handed over to him4 ,these1 except the first volume1 containing his sextant observations 7which had received his own approval71 he burned1 'as a sacrifice to heavenly truth4' ,his own great work had advanced so far that the first volume was printed1 and much of the second1 when he himself died1 on the last day of #agai4 ,he was buried in the chancel of ,burstow ,church4 ,the completion of his work took ten years more2 a work of piety and regard on the part of his assistant1 ,joseph ,crosthwait4 ,when compared with the catalogues that have gone before1 it was a work of wonderful accuracy4 ,nevertheless1 as ,caroline ,herschel showed1 nearly a century later1 not a few errors had crept into it4 ,some of the stars are non-existent1 others have been catalogued in more than one constellation2 important stars have been altogether omitted4 ,perhaps the most serious fault arises from the neglect of ,flamsteed to accept from ,newton a practical hint1 namely1 to read the barometer and thermometer at the time of his observations4 ,nevertheless1 the work accomplished was not only wonderful under the untoward conditions in which ,flamsteed was placed2 it was wonderful in itself1 winning from ,airy the following high encomium3-- ',in regard not only to accuracy of observation1 and to detail in publication of the methods of observing1 but also to steadiness of system followed through many years1 and to completeness of calculation of the useful results deduced from the observations1 this work may shame any other collection of observations in this or any other country4' ,this catalogue was not ,flamsteed's only achievement4 ,he had determined the latitude of the ,observatory1 the obliquity of the ecliptic1 and the position of the equinoctial points4 ,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 equinoxes4 ,he had revised and improved ,horrox's theory of the lunar motions1 which was by far the best existing in ,flamsteed's day4 ,he showed the existence of the long inequality of ,jupiter and ,saturn2 that is to say1 the periodic influence which they exercise upon each other4 ,he determined the time in which the sun rotates on its axis1 and the position of that axis4 ,he observed an apparent movement of the stars in the course of a year1 which he ascribed1 though erroneously1 to the stellar parallax1 and which was explained by the third ,astronomer ,royal1 ,bradley4 ,flamsteed not only met with harsh treatment during his lifetime2 he has not yet received1 except from a few1 anything like the meed of appreciation which is his just due2 but1 at least1 his successors in the office have not forgotten him4 ,they have been proud that their official residence should be known as ,flamsteed ,house1 and his name is inscribed over the main entrance of the latest and finest of the ,observatory buildings1 and his bust looks forth from its front towards the home where he laboured so devotedly for nearly fifty years4 ,but he has received little honour1 save at ,greenwich1 and--in spite of the proverb--in his other home1 the village of ,burstow1 in ,surrey1 of which he was for many years the rector4 ,here a stained glass window representing1 appropriately1 the ,adoration of the ,magi1 has been recently set up to his memory1 largely through the interest taken in his history by an amateur astronomer of the neighbourhood1 ,mr4 ,w4 ,tebb1 ,f4,r4,a4,s4 ,no instrument of ,flamsteed's remains in the ,observatory1 his wife removing them after his death4 ,but we may consider his principal instrument1 the mural quadrant made for him by ,abraham ,sharp1 as represented by the remains of a quadrant by the same artist1 which was presented to the ,observatory by the ,rev4 ,n4 ,s4 ,heineken1 in #ahfe1 and now hangs over the door of the transit room4 ,,chapter ,,iii ,,halley ,,and ,,his ,,successors ,there is no need to give the lives of the succeeding ,astronomers ,royal so fully as that of ,flamsteed4 ,not that they were inferior men to him2 on the contrary1 there can be little doubt that we ought to reckon some of them as his superiors1 but1 in the case of several1 their best work was done apart from ,greenwich ,observatory1 and before they came to it4 ,this was particularly the case with ,,edmund ,,halley4 ,born on ,october #bi1 #afef1 he was ten years the junior of ,flamsteed4 ,like ,flamsteed1 he came of a ,derbyshire family1 though he was born at ,haggerston1 in the parish of ,st4 ,leonard's1 ,shoreditch4 ,he was educated at ,st4 ,paul's ,school1 where he made very rapid progress1 and already showed the bent of his mind4 ,he learnt to make dials2 he made himself so thoroughly acquainted with the heavens that it is said1 ',if a star were displaced in the globe he would presently find it out1' and he observed the changes in the direction of the mariner's compass4 ,in #afgc he went to ,queen's ,college1 ,oxford1 where he observed a sunspot in ,july and ,august1 #afgf1 and an occultation of ,mars4 ,this was not his first astronomical observation1 as1 in ,june1 #afge1 he had observed an eclipse of the moon from his father's house in ,winchester ,street4 ,illustration3 ,,edmund ,,halley4 7,from an old print47 ,a much wider scheme of work than such merely casual observations now entered his mind1 possibly suggested to him by ,flamsteed's appointment to the direction of the new ,royal ,observatory4 ,this was to make a catalogue of the southern stars4 ,tycho's places for the northern stars were defective enough1 but there was no catalogue at all of stars below the horizon of ,tycho's observatory4 ,here1 then1 was a field entirely unworked1 and young ,halley was so eager to enter upon it that he would not wait at ,oxford to obtain his degree1 but was anxious to start at once for the southern hemisphere4 ,his father1 who was wealthy and proud of his gifted son1 strongly supported him in his project4 ,the station he selected was ,st4 ,helena1 an unfortunate choice1 as the skies there were almost always more or less clouded1 and rain was frequent during his stay4 ,however1 he remained there a year and a half1 and succeeded in making a catalogue of #cda stars4 ,this catalogue was finally reduced by ,sharp1 and included in the third volume of ,flamsteed's ,historia ,coelestis4 ,in #afgh he was elected ,fellow of the ,royal ,society1 and the following year he was chosen to represent that society in a discussion with ,hevelius4 ,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 assistance1 or by the use of a telescope4 ,the next year he visited the ,paris ,observatory1 and1 later in the same tour1 the principal cities of the ,continent4 ,not long after his return from this tour1 ,halley was led to that undertaking for which we owe him the greatest debt of gratitude1 and which must be regarded as his greatest achievement4 ,some fifty years before1 the great ,kepler had brought out the third of his well-known laws of planetary motion4 ,these laws stated that the planets move round the sun in ellipses1 of which the sun occupies one of the foci2 that the straight line joining any planet with the sun moves over equal areas of space in equal periods of time2 and1 lastly1 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 it4 ,these three laws were deduced from actual examination of the movements of the planets4 ,kepler did not work out any underlying cause of which these three laws were the consequence4 ,but the desire to find such an underlying cause was keen amongst astronomers1 and had given rise to many researches4 ,amongst those at work on the subject was ,halley himself4 ,he had seen1 and been able to prove1 that if the planets moved in circles round the sun1 with the sun in the centre1 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 distance4 ,the actual case1 however1 of motion in an ellipse was too hard for him1 and he could not deal with it4 ,halley therefore went up to ,cambridge to consult ,newton1 and1 to his wonder and delight1 found that the latter had already completely solved the problem1 and had proved that ,kepler's three laws of planetary motion were summed up in one1 namely1 that the sun attracted the planets to it with a force inversely proportional to the square of the distance4 ,halley was most enthusiastic over this great discovery1 and he at once strongly urged ,newton to publish it4 ,newton's unwillingness to do so was great1 but at length ,halley overcame his reluctance2 and the ,royal ,society not being able at the time to afford the expense1 ,halley took the charges upon himself1 although his own resources had been recently seriously damaged by the death of his father4 ,the publication of ,newton's ,principia1 which1 but for him1 might never have seen the light1 and most certainly would have been long delayed1 is ,halley's highest claim to our gratitude4 ,but1 apart from this1 his record of scientific achievement is indeed a noble one4 ,always1 from boyhood1 he had taken a great interest in the behaviour of the magnetic compass1 and he now followed up the study of its variations with the greatest energy4 ,for this purpose it was necessary that he should travel1 in view of the great importance of the subject to navigation4 ,king ,william ,,iii4 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 'pink1' that is to say1 a small vessel with pointed stern1 named the ,paramour1 in which he proceeded to the southern ocean4 ,his first voyage was unfortunate1 but the ,paramour was recommissioned in #afii1 and he sailed in it as far as south latitude #eb4 ,in #agja and the succeeding year he made further voyages in the ,paramour1 surveying the tides and coasts of the ,british ,channel and of the ,adriatic1 and helping in the fortification of ,trieste4 ,he became ,savilian ,professor of ,geometry at ,oxford in #agjc1 having failed twelve years previously to secure the ,savilian ,professorship of ,astronomy1 mainly through the opposition of ,flamsteed1 who had already formed a strong prejudice against him1 which some writers have traced to ,halley's detection of several errors in one of ,flamsteed's tide-tables1 others to ,halley's supposed materialistic views4 ,probably the difference was innate in the two men4 ,there was likely to be but little sympathy between the strong1 masterful man of action and society and the secluded1 self-conscious1 suffering invalid4 ,at any rate1 in the contest between ,newton and ,flamsteed1 which has been already described1 ,halley took warmly the side of the former1 and was appointed to edit the publication of ,flamsteed's results1 and1 on the death of the latter1 to succeed him at the ,royal ,observatory4 ,the condition of things at ,greenwich when ,halley succeeded to the post of ,astronomer ,royal in #agbj was most discouraging4 ,the instruments there had all belonged to ,flamsteed1 and therefore1 most naturally1 had been removed by his widow4 ,the ,observatory had practically to be begun de novo1 and ,halley had now almost attained the age at which in the present day an ,astronomer ,royal would have to retire4 ,more fortunate1 however1 than his predecessor1 he was able to get a grant for instruments1 and he equipped the ,observatory as well as the resources of the time permitted1 and his transit instrument and great eight-foot quadrant still hang upon the ,observatory walls4 ,as ,astronomer ,royal his great work was the systematic observation of the positions of the moon through an entire saros4 ,as is well known1 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 period4 ,this period was well known to the ancient ,chaldeans1 who gave it its name1 since they had noticed that eclipses of the sun or eclipses of the moon recurred at intervals of the above length4 ,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 motion4 ,it was an ambitious scheme for a man so much over sixty to undertake1 nevertheless he carried it through successfully4 ,his desire to complete this scheme1 and to found upon it improved lunar tables1 hindered him from publishing his observations1 for he feared that others might make use of them before he was in a position to complete his work himself4 ,this omission to publish troubled ,newton1 who1 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 ,society1 ,march #b1 #agbg1 to ,halley's disobedience of the order issued under ,queen ,anne1 for the prompt communication of the ,observatory results4 ,that ,newton should thus have put public pressure upon ,halley1 the man to whom he was so much indebted1 and with whom there was so close an affection1 is sufficient proof that his similar attitude towards ,flamsteed was one of principle and not of arbitrariness4 ,halley1 on his side1 stood firm1 as ,flamsteed had done1 urging the danger that1 by publishing before he had completed his task1 he might give an opportunity to others to forestall his results4 ,it is said--probably without sufficient ground--that this refusal broke ,newton's heart and caused his death4 ,certainly ,halley's writings in that very year show his reverence and affection for ,newton to have been as keen and lively as ever4 ,halley's work at the ,observatory went on smoothly1 on the lines he had laid down for himself1 for ten years after ,newton's death2 but in #agcg he had a stroke of paralysis1 and his health1 which had been remarkably robust up to that time1 began to give way4 ,he died ,january #ad1 #agdb1 and was buried in the cemetery of ,lee ,church4 ,as an astronomer1 his services to the science rank higher than those of his predecessor2 but as ,astronomer ,royal1 as director1 that is to say1 of ,greenwich ,observatory1 he by no means accomplished as much as ,flamsteed had done4 ,professor ,grant1 in his ,history of ,physical ,astronomy1 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 observation4 ,he was far from being sufficiently careful as to the adjustment of his instruments1 the going of his clocks1 or the recording of his own observations4 ,the important feature of his administration was that under him the ,observatory was first supplied with instruments which belonged to it4 ,illustration3 ,,halley',s ,,quadrant4 7,from an old print47 ,his astronomical work apart from the ,observatory was of the first importance4 ,he practically inaugurated the study of terrestrial magnetism1 and his map giving the results of his observations during his voyage in the ,paramour introduced a new and most useful style of recording observations4 ,he joined together by smooth curves places of equal variation1 the result being that the chart shows at a glance1 not merely the general course of the variation over the earth's surface1 but its value at any spot within the limits of the chart4 ,another work which has justly made his name immortal was the prediction of the return of the comet which is called by his name1 to which reference will be made later4 ,another great scheme1 and one destined to bear much fruit1 was the working out of a plan to determine the distance of the sun by observations of the transit of ,venus4 ,of attractive appearance1 pleasing manners1 and ready wit1 loyal1 generous1 and free from self-seeking1 he probably was one of the most personally engaging men who ever held the office4 ,the salary of the ,astronomer ,royal remained under ,halley at the same inadequate rate which it had done under ,flamsteed--#ajj1 without provision for an assistant4 ,but in #agbi ,queen ,caroline1 learning that ,halley had actually had a captain's commission in the ,royal ,navy1 secured for him a post-captain's pay4 ,illustration3 ,,james ,,bradley4 7,from the painting by ,hudson47 ,halley's work is represented at the ,observatory by two of his instruments which are still preserved there1 and which hang on the west wall of the present transit room3 the ,iron ,quadrant afterwards made famous by the observations of ,bradley1 and ',halley's ,transit1' the first of the great series of instruments upon which the fame of ,greenwich chiefly rests4 ,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 ,terrace4 ,his quadrant was mounted on the pier which is now the base of the pier of the astrographic telescope4 ,this pier was the first extension which the ,observatory received from the original building4 ,on the breakdown of his health ,halley nominated as his successor1 ,james ,bradley2 indeed1 it is stated that he offered to resign in his favour4 ,he had known him then for over twenty years1 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 ability4 99 99 99 99 99 ,,james ,,bradley was born in #afib or #afic1 of an old ,north of ,england family4 ,his birthplace was ,sherbourne1 in ,gloucestershire1 and he was educated at ,north ,leach ,grammar ,school and at ,baliol ,college1 ,oxford4 ,during the years of his undergraduateship he resided much with his uncle1 the ,rev4 ,james ,pound1 ,rector of ,wanstead1 ,essex1 an ardent amateur astronomer1 a frequent visitor at the ,observatory in ,flamsteed's time1 and one of the most accurate observers in the country4 ,from him1 no doubt1 he derived his love of the science1 and possibly some of his skill in observation4 ,bradley's earliest observations seem to have been devoted to the phenomena of ,jupiter's satellites and to the measures of double stars4 ,the accuracy with which he followed up the first drew the attention of ,halley1 and so began a friendship which lasted through life4 ,his observations of double stars1 particularly of ,castor1 only just failed to show him the orbital movement of the pair1 because his attention was drawn to other subjects before it had become sufficiently obvious4 ,in #agai ,bradley and his uncle made an attempt to determine the distance of the sun through observations of ,mars when in opposition1 observations which were so accurate that they sufficed to show that the distance of the sun could not be greater than #abe millions of miles1 nor less than about #id millions4 ,the lower limit which they thus found has proved to be almost exactly correct1 our best modern determinations giving it as #ic millions4 ,the instrument with which the observations were made was a novel one1 being 'moved by a machine that made it to keep pace with the stars2' in other words1 it was the first1 or nearly the first1 example of what we should now call a clock-driven equatorial4 ,that same year he was offered the ,vicarage of ,bridstow1 near ,ross1 in ,monmouthshire1 where1 having by that time taken priest's orders1 he was duly installed1 ,july1 #agbj4 ,to this was added the sinecure ,rectory of ,llandewi-,velgry2 but he held both livings only a very short time4 ,in #agba the death of ,dr4 ,john ,keill rendered vacant the ,savilian ,professorship of ,astronomy at ,oxford1 for which ,bradley became a candidate1 and was duly elected1 and resigned his livings in consequence4 ,it was whilst he was ,savilian ,professor that ,bradley made that great discovery which will always be associated with his name4 ,though professor at ,oxford1 he had continued to assist his uncle1 ,mr4 ,pound1 at his observations at ,wanstead1 and after the death of the latter he still lived there as much as possible1 and continued his astronomical work4 ,but in #agbe he was invited by ,mr4 ,samuel ,molyneux1 who had set up a twenty-four-foot telescope made by ,graham as a zenith tube at his house on ,kew ,green1 to verify some observations which he was making4 ,these were of the star ,gamma ,draconis1 a star which passes through the zenith of ,london1 and which1 therefore1 had been much observed both by ,flamsteed and ,hooke1 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 star4 ,dr4 ,hooke had declared that there was such a change1 a change due to the motion of the earth in its orbit1 which would prove that the star was not an infinite distance from the earth1 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 it4 ,bradley found at once that there was such a change--a marked one4 ,it amounted to as much as #a of arc in three days2 but it was not in the direction in which the parallax of the star would have moved it1 but in the opposite4 ,whether1 therefore1 the star was near enough to show any parallax or not1 some other cause was giving rise to an apparent displacement of the star1 which entirely masked and overcame the effect of parallax4 ,so far1 ,bradley had but come to the same point which ,flamsteed had reached4 ,flamsteed had detected precisely the same apparent displacement of stars1 and1 like ,hooke1 had ascribed it to parallax4 ,cassini had shown that this could not be the case1 as the displacement was in the wrong direction2 and there the matter had rested4 ,bradley now set to follow the question up4 ,other stars beside ,gamma ,draconis were found to show a displacement of the same general character1 but the amount varied with their distance from the plane of the ecliptic1 the earth's orbit4 ,the first explanation suggested was that the axis of the earth1 which moves very nearly parallel to itself as the earth moves round the sun1 underwent a slight regular 'wobble' in the course of a year4 ,to check this1 a star was observed on the opposite side of the pole from ,gamma ,draconis2 then ,bradley investigated as to whether refraction might explain the difficulty1 but again without success4 ,he now was most keenly interested in the problem1 and he purchased a zenith telescope of his own1 made1 like that of ,molyneux1 by ,graham1 and mounted it in his aunt's house at ,wanstead1 and observed continuously with it4 ,the solution of the problem came at last to him as he was boating on the ,thames4 ,watching a vane at the top of the mast1 he saw with surprise that it shifted its direction every time that the boat was put about4 ,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 course1 they replied that there was no change in the wind at all1 and that the apparent change of the vane was simply due to the change of direction of the motion of the boat4 ,illustration3 ,,graham',s ,,zenith ,,sector4 7,from an old print47 ,this supplied ,bradley with a key to the solution of the mystery that had troubled him so long4 ,it had been discovered long before this that light does not travel instantaneously from place to place1 but takes an appreciable time to pass from one member of the solar system to another4 ,this had been discovered by ,rmer from observations of the satellites of ,jupiter4 ,he had noted that the eclipses of the satellites always fell late of the computed time1 when ,jupiter was at his greatest distance from the earth2 and ,bradley's own work in the observation of those satellites had brought the fact most intimately under his own acquaintance4 ,the result of the boating incident taught him1 then1 that he might look upon light as analogous to the wind blowing on the boat4 ,as the wind1 so long as it was steady1 would seem to blow from one fixed quarter so long as the boat was also in rest1 but as it seemed to shift its direction when the boat was moving and changed its direction1 so he saw that the light coming from a particular star must seem to slightly change the direction in which it came1 or1 in other words1 the apparent position of the star1 to correspond with the movement of the earth in its orbit round the sun4 ,this was the celebrated discovery of the ,aberration of ,light1 a triumph of exact observation and of clear insight4 ,as to the exactness of ,bradley's observations1 it is sufficient to say that his determination of the value of the ',constant of ,aberration' gave it as #bjci2 the value adopted to-day is #bjdg4 ,on the death of ,halley1 in #agdb1 ,bradley was appointed to succeed him4 ,he found the ,observatory in as utterly disheartening a condition as his predecessors had done4 ,as already mentioned1 ,halley had not the same qualifications as an observer that ,flamsteed had4 ,he was1 further1 an old man when appointed to the post1 he had no assistant provided for him1 and the last five years of his life his health and strength had entirely given way4 ,under these circumstances1 it was no wonder that ,bradley found the instruments of the ,observatory in a deplorable state4 ,nevertheless1 he set to work most energetically1 and in the year of his appointment he made #aejj observations in the last five months of the year4 ,he was particularly earnest in examining the condition and the errors of his instruments2 and as their defects became known to him1 he was more and more anxious for a better equipment4 ,he moved the ,royal ,society1 therefore1 to apply on his behalf for the instruments he required2 and a petition from that body1 in #agdh1 obtained what in those days must be considered the generous grant of #ajjj1 the proceeds of the sale of old ,admiralty stores4 ,the principal instruments purchased therewith were a mural quadrant and a transit instrument1 both eight feet in focal length1 still preserved on the walls of the transit-room4 ,it is interesting also to note that1 following in the steps of ,halley1 and forecasting1 as it were1 the magnetic observatory which ,airy would found1 he devoted #bj of the grant to purchasing magnetic instruments4 ,meantime he had continued his observations on aberration1 and had discovered that the aberration theory was not sufficient entirely to account for the apparent changes in places of stars which he had discovered4 ,a second cause was at work1 a movement of the earth's axis1 a 'wobble' in its inclination1 technically known as ,nutation1 which is due to the action of the moon1 and goes through its course in a period of nineteen years4 ,beside these two great discoveries of aberration and nutation1 ,bradley's reputation rests upon his magnificent observations of the places of more than three thousand stars4 ,this part of his work was done with such thoroughness1 that the star-places deduced from them form the basis of most of our knowledge as to the actual movements of individual stars4 ,in particular1 he was careful to investigate and to correct for the errors of his instrument1 and to determine the laws of refraction1 introducing corrections for changes in the readings of thermometer and barometer4 ,his tables of refraction were used1 indeed1 for seventy years after his death4 ,of his other labours it may be sufficient to refer to his determination of the longitudes of ,lisbon and of ,new ,york1 and to his effort to ascertain the parallax of the sun and moon1 in combination with ,la ,caille1 who was observing at the ,cape of ,good ,hope4 ,as ,astronomer ,royal1 ,bradley's great achievement was the high standard to which he raised the practical work of observation4 ,from his day onwards1 also1 there was always at least one assistant4 ,his first assistant was his own nephew1 ,john ,bradley1 who received the munificent salary of ten shillings a week4 ,still1 this was not out of proportion to the then salary of the ,astronomer ,royal1 which practically amounted only to #ij4 ,however1 in #ageb1 ,bradley was awarded a ,crown pension of #bej a year4 ,he refused the living of ,greenwich1 which was offered him in order to increase his emoluments1 on the ground that he could not suitably fulfil the double office4 ,bradley's later assistants were ,charles ,mason and ,charles ,green4 ,bradley's last work was the preparation for the observations of the transit of ,venus of #agfa1 according to the lines laid down by his predecessor1 ,halley4 ,his health gave way1 and he became subject to melancholia1 so that the actual observations were taken by the ,rev4 ,nathaniel ,bliss1 who succeeded him in his office after his death1 in #agfb4 ,he was buried at ,minchinhampton4 ,so far as we know ,bradley's character1 he seems to have been a gentle1 modest1 unassuming man1 entirely free from self-seeking1 and indifferent to personal gain4 ,he was in many ways an ideal astronomer1 exact1 methodical1 and conscientious to the last degree4 ,his skill as an observer was his chief characteristic2 and though his abilities were not equal as a mathematician or a mechanician1 yet1 on the one hand1 he had a very clear insight into the meaning of his observations1 and1 on the other1 he was skilful enough to himself adjust1 repair1 and improve his instruments4 ,of ,bradley's instruments1 there are still preserved his famous twelve-and-a-half-foot zenith sector1 with which he made his two great discoveries2 his brass quadrant1 which in #agej he substituted for ,halley's iron quadrant2 his transit instrument1 and equatorial sector4 ,bradley added to the buildings of the ,observatory that portion which is now represented by the upper and lower computing rooms1 and the chronometer room1 which adjoins the latter4 ,this room--the chronometer room--was his transit room1 and the position of the shutters is still marked by the window in the roof4 99 99 99 99 99 ,the ,rev4 ,,nathaniel ,,bliss1 who succeeded ,bradley1 only held the office for a couple of years1 and during that time was much at ,oxford4 ,he1 therefore1 has left no special mark behind him as ,astronomer ,royal4 ,he was born ,november #bh1 #agjj4 ,his father1 like himself1 ,nathaniel ,bliss1 was a gentleman1 of ,bisley1 ,gloucestershire4 ,illustration3 ,,nathaniel ,,bliss4 7,from an engraving on an old pewter flagon47 ,bliss graduated at ,pembroke ,college1 ,oxford1 as ,b4,a4 in #agbj1 and ,m4,a4 in #agbc4 ,he became the ,rector of ,st4 ,ebb's1 ,oxford1 in #agcf1 and on ,halley's death succeeded him as ,savilian ,professor of ,geometry4 ,he supplied ,bradley with his observations of ,jupiter's satellites1 and from time to time1 at his request1 rendered him some assistance at the ,royal ,observatory4 ,this was particularly the case1 as has been already mentioned1 with respect to the transit of ,venus of #agfa1 the observations of which were carried out by ,bliss1 owing to ,bradley's ill-health4 ,it was natural1 therefore1 that on ,bradley's death he should succeed to the vacant post2 but he held it too short a time to do any distinctive work4 ,such observations as he made seem to have been entirely in continuation of ,bradley's4 ,he took a great interest1 however1 in the improvement of clocks1 a department in which so much was being done at this time by ,graham1 ,ellicott1 and others4 99 99 99 99 99 ,,nevil ,,maskelyne1 the fifth ,astronomer ,royal1 was1 like ,bliss1 a close friend of ,bradley's4 ,he was the third son of a wealthy country gentleman1 ,edmund ,maskelyne1 of ,purton1 in ,wiltshire4 ,maskelyne was born in ,london1 ,october #f1 #agcb1 and was educated at ,westminster ,school4 ,thence he proceeded to ,cambridge1 where he graduated seventh ,wrangler in #aged4 ,he was ordained to the curacy of ,barnet in #agee1 and1 twenty years later1 was presented by his nephew1 ,lord ,clive1 to the living of ,shrawardine1 in ,shropshire4 ,in #aghb he was presented by his college to the ,rectory of ,north ,runcton1 ,norfolk4 ,the event which turned his thoughts in the direction of astronomy was the solar eclipse of ,july #be1 #agdh2 and about the time that he was appointed to the curacy of ,barnet he became acquainted with ,bradley1 then the ,astronomer ,royal1 to whom he gave great assistance in the preparation of his table of refractions4 ,like ,halley before him1 he made an astronomical expedition to the island of ,st4 ,helena4 ,this was for the special purpose of observing the transit of ,venus of ,june #f1 #agfa1 ,bradley having induced the ,royal ,society to send him out for that purpose4 ,here he stayed ten months1 and made many observations4 ,but though the transit of ,venus was his special object1 it was not the chief result of the expedition3 not because clouds hindered his observations1 but because the voyage gave him the especial bent of his life4 ,halley had actually held a captain's commission in the ,royal ,navy1 and commanded a ship2 ,maskelyne1 more than any of the ,astronomers ,royal before or since1 made the improvement of the practical business of navigation his chief aim4 ,none of all the incumbents of the office kept its original charter--',to find the so much desired ,longitude at ,sea1 for the perfecting the ,art of ,navigation1' so closely before him4 ,the solution of the problem was at hand at this time--its solution in two different ways4 ,on the one hand1 the offer by the ,government of a reward of #bj1jjj for a clock or watch which should go so perfectly at sea1 notwithstanding the tossing of the ship and the wide changes of temperature to which it might be exposed1 that the navigator might at any moment learn the true ,greenwich time from it1 had brought out the invention of ,harrison's time-keeper2 on the other hand1 the great improvement that had now taken place in the computation of tables of the moon's motion1 and the more accurate star-catalogues now procurable1 had made the method of 'lunars1' suggested a hundred and thirty years before by the ,frenchman1 ,morin1 and others1 a practicable one4 ,illustration3 ,,nevil ,,maskelyne4 ,in principle1 the method of finding the longitude from 'lunars1' that is to say1 from measurements of the distances between the moon and certain stars1 is an exceedingly simple one4 ,in actual practice1 it involves a very toilsome calculation1 beside exact and careful observation4 ,the principle1 as already mentioned1 is simply this3 ,the moon travels round the sky1 making a complete circuit of the heavens in between twenty-seven and twenty-eight days4 ,it thus moves amongst the stars1 roughly speaking1 its own diameter1 in about an hour4 ,when once its movements were sufficiently well known to be exactly predicted1 almanacs could be drawn up in which the ,greenwich time of its reaching any definite point of the sky could be predicted long beforehand2 or1 what comes to the same thing1 its distances from a number of suitable stars could be given for definite intervals of ,greenwich time4 ,it is only necessary1 then1 to measure the distances between the moon and some of these stars1 and by comparing them with the distances given in the almanac1 the exact time at ,greenwich can be inferred4 ,as has been already pointed out1 the determination of the latitude of the ship and of the local time at any place where the ship is1 is not by any means so difficult a matter2 but the local time being known and the ,greenwich time1 the difference between these gives the longitude2 and the latitude having been also ascertained1 the exact position of the ship is known4 ,there are1 of course1 difficulties in the way of working out this method4 ,one is1 that whilst it takes the sun but twenty-four hours to move round the sky from one noon to the next1 and consequently its movements1 from which the local time is inferred1 are fairly rapid1 the moon takes nearly twenty-eight days to move amongst the stars from the neighbourhood of one particular star round to that particular star again4 ,consequently1 it is much easier to determine the local time with a given degree of exactness than the ,greenwich time2 it is something like the difference of reading a clock from both hands and from the hour hand alone4 ,there are other difficulties in the case which make the computation a long and laborious one1 and difficult in that sense2 but they do not otherwise affect its practicability4 ,during this voyage to ,st4 ,helena1 both when outward bound and when returning1 ,maskelyne gave the method of 'lunars' a very thorough testing1 and convinced himself that it was capable of giving the information required4 ,for by this time the improvement of the sextant1 or quadrant as it then was1 by the introduction of a second mirror1 by ,hadley1 had rendered the actual observation at sea of lunar distances1 and of altitudes generally1 a much more exact operation4 ,this conclusion he put at once to practical effect1 and1 in #agfc1 he published the ,british ,mariner's ,guide1 a handbook for the determination of the longitude at sea by the method of lunars4 ,at the same time1 the other method1 that by the time-keeper or chronometer1 was practically tested by him4 ,the time-keeper constructed by ,john ,harrison had been tested by a voyage to ,jamaica in #agfa1 and now1 in #agfc1 another time-keeper was tested in a voyage to ,barbadoes4 ,charles ,green1 the assistant at ,greenwich ,observatory1 was sent in charge of the chronometer1 and ,maskelyne went with him to test its performance1 in the capacity of chaplain to his ,majesty's ship ,louisa4 ,illustration3 ,,hadley',s ,,quadrant4 7,from an old print47 ,the position which ,maskelyne had already won for himself as a practical astronomer1 and the intimate relations into which he had entered with ,bradley and ,bliss1 made his appointment to the ,astronomer ,royalship1 on the death of the latter1 most suitable4 ,at once he bent his mind to the completion of the revolution in nautical astronomy which his ,british ,mariner's ,guide had inaugurated1 and in the year after his appointment he published the first number of the ,nautical ,almanac1 together with a volume entitled1 ,tables ,requisite to be ,used with the ,nautical ,ephemeris1 the value of which was so instantly appreciated1 that #aj1jjj copies were sold at once4 ,the ,nautical ,almanac was ,maskelyne's greatest work1 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 staff4 ,the ,nautical ,almanac was1 however1 in the main not computed at the ,observatory2 the calculations were effected by computers living in different parts of the country1 the work being done in duplicate1 on the principle which ,flamsteed had inaugurated in the preparation of his ,historia ,coelestis4 ,maskelyne's next service to science was almost as important4 ,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 ,royal1 and he procured an arrangement by which a special fund was set apart by the ,royal ,society for printing them4 ,his observations covering the years #aggf to #ahaa fill four large folio volumes1 and though1 as already stated1 he had but one assistant1 they are #ij1jjj in number4 ,thus it was ,maskelyne who first rendered effective the design which ,charles ,,ii4 had in the establishment of the ,observatory4 ,flamsteed and ,halley had been too jealous of their own observations to publish2 ,bradley's observations--though he himself was entirely free from this jealousy--were made1 after his death1 the subject of litigation by his heirs and representatives1 who claimed an absolute property in them1 a claim which the ,government finally allowed4 ,none of the three1 however much their work ultimately tended to the improvement of the art of navigation1 made that their first object4 ,whereas ,maskelyne set this most eminently practical object in the forefront1 and so gave to the ,royal ,observatory1 which under his predecessors somewhat resembled a private observatory1 its distinctive characteristics of a public institution4 ,it fell to ,maskelyne to have to advise the ,government as to the assignment of their great reward of #bj1jjj for the discovery of the longitude at sea4 ,maskelyne1 while reporting favourably of the behaviour of ,harrison's time-keeper1 considered that the method of 'lunars' was far too important to be ignored1 and he therefore recommended that half the sum should be given to ,harrison for his watch1 whilst the other half was awarded for the lunar tables which ,mayer1 before his death1 had sent to the ,board of ,longitude4 ,this decision1 though there can be no doubt it was the right one1 led to much dissatisfaction on the part of ,harrison1 who urged his claim for the whole grant very vigorously2 and eventually the whole #bj1jjj was paid him4 ,the whole question of rewards to chronometer-makers must have been one which caused ,maskelyne much vexation4 ,he was made the subject of a bitter and most voluminous attack by ,thomas ,mudge1 for having preferred the work of ,arnold and ,earnshaw to his own4 ,otherwise his reign at the ,observatory seems to have been a singularly peaceful one1 and there is little to record about it beyond the patient prosecution1 year by year1 of an immense amount of sober1 practical work4 ,to ,maskelyne1 however1 we owe the practice of taking a transit of a star over five wires instead of over one1 and he provided the transit instrument with a sliding eye-piece1 to get over the difficulty of the displacement which might ensue if the star were observed askew when out of the centre of the field4 ,to ,maskelyne1 too1 we owe in a pre-eminent degree the orderly form of recording1 reducing1 and printing the observations4 ,much of the work in this direction which is generally ascribed to ,airy was really due to ,maskelyne4 ,indeed1 without a wonderful gift of organization1 it would have been impossible to plan and to carry the ,nautical ,almanac4 ,beside the editing of various works intended for use in nautical astronomy or in general computation1 the chief events of his long reign at ,greenwich were the transit of ,venus in #agfi1 which he himself observed1 and for which he issued instructions in the ,nautical ,almanac2 and his expedition in #aggd to ,scotland1 where he measured the deviation of the plumb-line from the vertical caused by the attraction of the mountain ,schiehallion1 deducing therefrom the mean density of the earth to be four and a half times that of water4 ,illustration3 ,,john ,,pond4 7,from an old engraving47 ,he died at the ,observatory1 ,february #i1 #ahaa1 aged #gi1 leaving but one child1 a daughter1 who married ,mr4 ,anthony ,mervin ,story1 to whom she brought the family estates in ,wiltshire1 inherited by ,maskelyne on the deaths of his elder brothers1 and1 in consequence1 ,mr4 ,story added the name of ,maskelyne to his own4 ,maskelyne's character and policy as ,astronomer ,royal have been sufficiently dwelt upon4 ,his private character was mild1 amiable1 and generous4 ',every astronomer1 every man of learning1 found in him a brother2' and1 in particular1 when the ,french ,revolution drove some ,french astronomers to this country to find a refuge1 they received from the ,astronomer ,royal the kindest reception and most delicate assistance4 ,maskelyne added no instrument to the ,observatory during his reign1 though he improved ,bradley's transit materially4 ,he designed the mural circle1 but it was not completed until after his death4 ,his additions to the ,observatory buildings consisted of three new rooms in the ,astronomer ,royal's house1 and the present transit circle room4 99 99 99 99 99 ,,john ,,pond was recommended by ,maskelyne as his successor at ,greenwich4 ,at the time of his succession he was forty-four years of age1 having been born in #agfg4 ,he was educated at ,trinity ,college1 ,cambridge1 and then spent some considerable time travelling in the south of ,europe and ,egypt4 ,on his return home he settled at ,westbury1 where he erected an altazimuth by ,troughton1 with a two-and-a-half-foot circle4 ,a born observer1 his observations of the declinations of some of the principal fixed stars showed that the instrument which ,maskelyne was using at ,greenwich--the quadrant by ,bird--could no longer be trusted4 ,maskelyne1 in consequence1 ordered a six-foot mural circle from ,troughton1 but did not live to see it installed1 and in #ahaf this was supplemented by ,troughton's transit instrument of five inches aperture and ten feet focal length4 ,the introduction of these two important instruments1 and of other new instruments1 together with new methods of observation1 form one of the chief characteristics of ,pond's administration4 ,under this head must be specially mentioned the introduction of the mercury trough1 both for determining the position of the vertical1 and for obtaining a check upon the flexure of the mural circle in different positions2 and the use in combination of a pair of mural circles for determining the declinations of stars4 ,another characteristic of his reign was that under him there was the first attempt to give the ,astronomer ,royal a salary somewhat higher than that of a mechanic1 and to support him with an adequate staff of assistants4 ,his salary was fixed at #fjj a year1 and the single assistant of ,maskelyne was increased to six4 ,this multiplication of assistants was for the purpose of multiplying observations1 for ,pond was the first astronomer to recognize the importance of greatly increasing the number of all observations upon which the fundamental data of astronomy were to be based4 ,in #ahcc he finished his standard catalogue of #aaac stars1 at that time the fullest of any catalogue prepared on the same scale of accuracy4 ',it is not too much to say1' was the verdict of the ,royal ,astronomical ,society1 'that meridian sidereal observation owes more to him than to all his countrymen put together since the time of ,bradley4' ,a yet higher testimony to the exactness of his work is given by his successor1 ,airy4 ',the points upon which1 in my opinion1 ,mr4 ,pond's claims to the gratitude of astronomers are founded1 are principally the following4 ,first and chief1 the accuracy which he introduced into all the principal observations4 ,this is a thing which1 from its nature1 it is extremely difficult to estimate now1 so long after the change has been made2 and ,i can only say that1 so far as ,i can ascertain from books1 the change is one of very great extent2 for certainty and accuracy1 astronomy is quite a different thing from what it was1 and this is mainly due to ,mr4 ,pond4' ,the same authority eulogizes him further for his laborious working out of every conceivable cause or indication of error in his declination instruments1 for the system which he introduced in the observation of transits1 for the thoroughness with which he determined all his fundamental data1 and for the regularity which he infused into the ,greenwich observations4 ,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 announced by ,brinkley1 ,royal ,astronomer for ,ireland4 ,but ,pond's administration was open1 in several particulars1 to serious censure1 and the ,board of ,visitors1 which had been for many years but a committee of the ,royal ,society1 but which had recently been reconstituted1 proved its value and efficiency by the remonstrances which it addressed to him1 and which eventually brought about his resignation4 ,his personal skill and insight as an observer were of the highest order2 but either from lack of interest or failing health1 he absented himself almost entirely from the ,observatory in later years1 visiting it only every ninth or tenth day4 ,he had caused the staff of assistants to be increased from one to six1 but had stipulated that the men supplied to him should be 'drudges4' ,his minute on the subject ran-- ',i want indefatigable1 hard-working1 and1 above all1 obedient drudges 7for so ,i must call them1 although they are drudges of a superior order71 men who will be contented to pass half their day in using their hands and eyes in the mechanical act of observing1 and the remainder of it in the dull process of calculation4' ,this was a fatal mistake1 and one which it is very hard to understand how any one with a real interest in the science could have made4 ,men who had the spirit of 'drudges1' to whom observation was a mere 'mechanical act1' and calculation a 'dull process1' were not likely to maintain the honour of the ,observatory1 particularly under an absentee ,astronomer ,royal4 ,pond tried to overcome the difficulty by devising rules for their guidance of iron rigidity4 ,the result was that after his resignation1 in #ahce1 the ,first ,lord and the ,secretary of the ,admiralty expressed their feeling to ,airy1 ,pond's successor1 'that the ,observatory had fallen into such a state of disrepute that the whole establishment should be cleared out4' ,a further evil was the excessive development of chronometer business1 so as practically to swamp the real work of the ,observatory1 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 administration4 ,with all his merits1 therefore1 as an observer1 the administration of ,pond was1 in some respects1 the least satisfactory of all that the ,observatory has known1 and he alone of all the ,astronomers ,royal retired under pressure4 ,he did not long survive his resignation1 dying in ,september1 #ahcf4 ,he was buried by the side of ,halley1 in the churchyard at ,lee4 ,of ,pond's instruments1 the ,observatory retains the fine transit instrument which was constructed by ,troughton at his direction1 and the mural circle1 designed by ,maskelyne1 but which ,pond was the first to use4 ,both of these have1 of course1 long been obsolete1 and now hang on the walls of the transit room4 ,the small equatorial1 called1 after its donor1 the ,shuckburgh equatorial1 was also added in ,pond's day1 and though practically never used1 still remains mounted in its special dome4 ,,chapter ,,iv ,,airy ,one hundred and sixty years from the day when ,flamsteed laid the foundation stone of the ,observatory1 the ,royal ,warrant under the sign manual was issued1 appointing the seventh and strongest of the ,astronomers ,royal1 ,august #aa1 #ahce4 ,he actually entered on his office in the following ,october1 but did not remove to the ,observatory until the end of the year4 ,,george ,,biddell ,,airy was born at ,alnwick1 in ,northumberland1 on ,july #bg1 #ahja4 ,his father was ,william ,airy1 of ,luddington1 in ,lincolnshire1 a collector of excise2 his mother was the daughter of ,george ,biddell1 a well-to-do farmer1 of ,playford1 near ,ipswich4 ,he was educated at the ,grammar ,school1 ,colchester1 and so distinguished himself there that although his father was at this time very straitened in his circumstances1 it was resolved that young ,airy should go to ,cambridge4 ,here he was entered as sizar at ,trinity ,college1 and his robust1 self-reliant character was seen in the promptness with which he rendered himself independent of all pecuniary help from his relatives4 ,in #ahbc he graduated as ,bachelor of ,arts1 being ,senior ,wrangler and ,smith's prizeman1 entirely distancing all other men of his year4 ,he had already begun to pay attention to astronomy1 at first from the side of optics1 to the study of which he had been very early attracted2 a paper of his on the achromatism of eye-pieces and microscopes1 written in #ahbd1 being one of especial value4 ,in #ahbf he attempted to determine 'the diminution of gravity in a deep mine'--that of ,dolcoath1 in ,cornwall4 ,in the winter of #ahbc-bd he was invited to ,london by ,mr4 7afterwards ,sir7 ,james ,south1 who took him1 amongst other places1 to ,greenwich ,observatory1 and gave him his first introduction to practical astronomy4 ,in #ahbf he was appointed ,lucasian ,professor at ,cambridge1 and in #ahbh1 ,plumian ,professor1 with the charge of the new ,university ,observatory4 ,prior to his election he had definitely told the electors that the salary proposed was not sufficient for him to undertake the responsibility of the ,observatory4 ,he followed this up by a formal application for an increase1 which created not a little commotion at the time1 the action being so unprecedented2 and after a delay of a little over a year he obtained what he had asked for4 ,the delay gave rise1 however1 to the remark of a local wit1 that the ,university had given 'to ,airy1 nothing1 a local habitation and a name4' ,illustration3 ,,george ,,biddell ,,airy4 ,the seven years which he spent in the ,cambridge ,observatory were the best possible preparation for that greater charge which he was to assume later4 ,when he entered on his duties the ,observatory had been completed four years1 but no observations had been published2 there was no assistant1 and the only instruments were a couple of good clocks and a transit instrument4 ,but ,airy set to work at once with so much energy that the observations for #ahbh were published early in the following year1 and he had very quickly worked out the best methods for correcting and reducing his observations4 ,in #ahbi an assistant was granted to him1 in #ahcc a second1 and in the latter year ,mr4 ,baldrey1 the senior assistant1 observed about #ejjj transits1 and ,mr4 ,glaisher1 the junior1 about the same number of zenith distances4 ,a syndicate had been appointed at ,cambridge for the purpose of visiting the ,observatory once in each term1 and making an annual report to the senate4 ,a smaller-minded and less acute man than ,airy might have resented such an arrangement4 ,he1 on the contrary1 threw himself heartily into it1 and made such formal written reports to the syndicate as best helped them in the performance of their duty1 and at the same time secured for the ,observatory the support and assistance which from time to time it required4 ,on his appointment to ,greenwich1 he at once entered into the same relations to the ,board of ,visitors of that ,observatory1 and from that time forth the friction that had occasionally existed between the ,board and the ,astronomer ,royal in the past entirely ceased4 ,the ,board was henceforth no longer a body whose chief function was to reprove1 to check1 or to quicken the ,astronomer ,royal1 but rather a company of experts1 before whom he might lay the necessities of the ,observatory1 that they in turn might present them to the ,government4 ,such representations were not likely to be in vain4 ,for1 as ,mr4 ,sheepshanks has left on record-- ',when ,mr4 ,airy wants to carry anything into effect by ,government assistance1 he states1 clearly and briefly1 why he wants it2 what advantages he expects from it2 and what is the probable expense4 ,he also engages to direct and superintend the execution1 making himself personally responsible1 and giving his labour gratis4 ,when he has obtained permission 7which is very seldom refused71 he arranges everything with extraordinary promptitude and foresight1 conquers his difficulties by storm1 and presents his results and his accounts in perfect order1 before men like 444 or myself would have made up our minds about the preliminaries4 ,now1 men in office naturally like persons of this stamp4 ,there is no trouble1 no responsibility1 no delay1 no inquiries in the ,house2 the matter is done1 paid for1 and published1 before the seekers of a grievance can find an opportunity to be heard4 ,this mode of proceeding is better relished by busy statesmen than recommendations from influential noblemen or fashionable ladies4' ,his first action towards the ,board was1 however1 a very bold and independent one4 ,he made strong representations on the subject of the growth of the chronometer business1 which proved displeasing to the ,hydrographer1 ,captain ,beaufort1 who was one of the official visitors1 and by his influence the report was not printed4 ,airy 'kept it1 and succeeding reports1 safe for three years1 and then the ,board of ,visitors agreed to print them1 and four reports were printed together1 and bound with the ,greenwich ,observations of #ahch4' ,with the completion of arrangements which put the chronometer business in proper subordination to the scientific charge of the ,observatory1 ,airy was free to push forward its development on the lines which he had already marked out for himself4 ,to go through these in detail is simply to describe the ,observatory as he left it4 ,little by little he entirely renovated the equipment4 ,greatly as ,pond had improved the instruments of the ,observatory1 ,airy carried that work much further still4 ,though he did not observe much himself1 and was not ,pond's equal in the actual handling of a telescope1 he had a great mechanical gift1 and the detail in its minutest degree of every telescope set up during his long reign was his own design4 ,in the work of reduction he introduced the use of printed skeleton forms1 to which ,pond had been a stranger4 ,the publication of the ,greenwich results was carried on with the utmost regularity2 and1 in striking contrast to the reluctance of ,flamsteed and ,halley1 he was always most prompt in communicating any observations to every applicant who could show cause for his request for them4 ,it is most difficult to give any adequate impression of his far-reaching ability and measureless activity4 ,perhaps the best idea of these qualities may be obtained from a study of his autobiography1 edited and published some four years after his death by his son4 ,the book1 to any one who was not personally acquainted with ,airy1 is heavy and monotonous1 chiefly for the reason that its #djj pages are little but a mere catalogue of the works which he undertook and carried through2 and catalogues1 except to the specialist1 are the dullest of reading4 ,to enter into the details of his work might fill a library4 ,illustration3 ,,the ,,astronomer ,,royal',s ,,room4 ,as ,astronomer ,royal he seems to have inherited and summed up all the great qualities of his predecessors3 ,flamsteed's methodical habits and unflagging industry2 ,halley's interest in the lunar theory2 ,bradley's devotion to star observation and catalogue making2 ,maskelyne's promptitude in publishing1 and keen interest in practical navigation2 ,pond's refinement of observation4 ,nor did he allow this inheritance to be merely metaphorical2 he made it an actual reality4 ,he discussed1 reduced1 and published1 in forms suitable for use and comparison to-day1 the whole vast mass of planetary and lunar observations made at the ,royal ,observatory from the year #agfj to his own accession1 a work of prodigious labour1 but of proportionate importance4 ,airy has been accused--and with some reason--of being a strong1 selfish1 aggressive man2 yet nothing can show more clearly than this great work how thoroughly he placed the fame and usefulness of the ,observatory before all personal considerations4 ,with far less labour he could have carried on a dozen investigations that would have brought him more fame than this great enterprise1 the purpose of which was to render the work of his predecessors of the highest possible use4 ,the light in which he regarded his office may best be expressed in his own words3-- ',the ,observatory was expressly built for the aid of astronomy and navigation1 for promoting methods of determining longitude at sea1 and 7as the circumstances that led to its foundation show7 more especially for determination of the moon's motions4 ,all these imply1 as their first step1 the formation of accurate catalogues of stars1 and the determination of the fundamental elements of the solar system4 ,these objects have been steadily pursued from the foundation of the ,observatory2 in one way by ,flamsteed2 in another way by ,halley1 and by ,bradley in the earlier part of his career2 in a third form by ,bradley in his later years2 by ,maskelyne 7who contributed most powerfully both to lunar and to chronometric nautical astronomy71 and for a time by ,pond2 then with improved instruments by ,pond1 and by myself for some years2 and subsequently1 with the instruments now in use4 ,it has been invariably my own intention to maintain the principles of the long-established system in perfect integrity2 varying the instruments1 the modes of employing them1 and the modes of utilizing the observations of calculation and publication1 as the progress of science might seem to require4' ,the result of this keen appreciation of the essential continuity of the ,astronomer ,royalship has been that it is to ,airy1 more than to any of his predecessors1 or than to all of them put together1 that the high reputation of ,greenwich ,observatory is due4 ,professor ,newcomb1 the greatest living authority on the subject outside our own land--and other great foreign astronomers have independently pronounced the same verdict--has said3-- ',the most useful branch of astronomy has hitherto been that which1 treating of the positions and motions of the heavenly bodies1 is practically applied to the determination of geographical positions on land and at sea4 ,the ,greenwich ,observatory has1 during the past century1 been so far the largest contributor in this direction as to give rise to the remark that1 if this branch of astronomy were entirely lost1 it could be reconstructed from the ,greenwich observations alone4' ,early in #ahcf ,airy proposed to the ,board of ,visitors the creation of the ,magnetic and ,meteorological department of the ,observatory1 and in #ahdj a system of regular two-hourly observations was set on foot4 ,this was the first great enlargement of programme for the ,observatory beyond the original one expressed in ,flamsteed's warrant4 ,it was followed in #ahgc with the formation of the ,solar ,photographic department1 to which the ,spectroscope was added a little later4 ,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 chronometers1 yet the perfecting of these instruments was one that he had much at heart1 and many recent appliances are either of his own invention or are due to suggestions which he threw out4 ,much work lying outside the ,observatory1 and yet intimately connected with it1 was carried out either by him or in accordance with his directions4 ,the transit of ,venus expeditions of #ahgd1 the delimitation of the boundary line between ,canada and the ,united ,states1 and1 later1 that of the ,oregon boundary2 the determination of the longitudes of ,valencia1 ,cambridge1 ,edinburgh1 ,brussels1 and ,paris2 assistance in the determination of the longitude of ,altona--all came under ,airy's direction4 ,nor did he neglect expeditions in connection with what we would now call the physical side of astronomy4 ,on three occasions1 #ahdb1 #ahea1 and #ahfj1 he himself personally took part in successful eclipse expeditions4 ,the determination of the increase of gravity observable in the descent of a deep mine was also the subject of another expedition1 to the ,harton ,colliery1 near ,south ,shields4 ,but with all these1 and many other inquiries--for he was the confidential adviser of the ,government in a vast number of subjects3 lighthouses1 railways1 standard weights and measures1 drainage1 bridges--he yet always kept the original objects of the ,observatory in the very first place4 ,it was in order to get more frequent observations of the moon that he had the altazimuth erected1 which was completed in ,may1 #ahdg4 ,this was followed1 in #ahea1 by the transit circle1 as he had long felt the need for more powerful light grasp in the fundamental instrument of the ,observatory4 ,the transit circle took the place both of the old transit instrument and of the mural circle4 ,above all1 he arranged for the observations of moon and stars to be carried out with practical continuity4 ,the observations were made and reduced at once1 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 commencement1 and could see precisely what had been done4 ,the greatest addition made to the equipment of the ,observatory in ,airy's day was the erection of the #ab-c_/d-;inch ,merz equatorial1 which proved of great service when spectroscopy became a department of the ,observatory4 ,illustration3 ,,the ,,south-,,east ,,tower4 7,from a photograph by ,mr4 ,lacey47 ,so strong and gifted a man as ,airy was bound to make enemies1 and at different times of his life bitter attacks were made on him from one quarter or another4 ,one of these1 curiously enough1 was from ,sir ,james ,south1 the man who1 as he said1 first introduced him to practical astronomy4 ,later came the discovery of ,neptune1 and ,airy was subjected to much bitter criticism1 since1 as it appeared on the surface1 it was owing to his supineness that ,adams missed being held the sole discoverer of the new planet1 and narrowly missed all credit for it altogether4 ,last of all was the vehement attack made upon him by ,richard ,anthony ,proctor1 in connection with his preparations for the transit of ,venus4 ,all such attacks1 however1 simply realized the old fable of the viper and the file4 ,attacks which would have agonized ,flamsteed's every nerve1 and have called forth full and dignified rejoinders from ,maskelyne1 were absolutely and entirely disregarded by ,airy4 ,he had done his duty1 and in his own estimation--and1 it should be added1 in the estimation of those best qualified to judge--had done it well4 ,he was perfectly satisfied with himself1 and what other people thought or said about him influenced him no more than the opinions of the inhabitants of ,saturn4 ,but great as ,airy was1 he had the defects of his qualities1 and some of these were serious4 ,his love of method and order was often carried to an absurd extreme1 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 well1 or better4 ,the story has often been told1 and it is exactly typical of him1 that on one occasion he devoted an entire afternoon to himself labelling a number of wooden cases 'empty1' it so happening that the routine of the establishment kept every one else engaged at the time4 ,his friend ,dr4 ,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 use1 and file it away amongst his papers4 ,his mind had that consummate grasp of detail which is characteristic of great organizers1 but the details acquired for him an importance almost equal to the great principles1 and the statement that he had put a new pane of glass into a window would figure as prominently in his annual report to the ,board of ,visitors as the construction of the new transit circle4 ,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 contents1' his system having grown with him from being a means to an end1 to becoming the end itself4 ,so1 too1 his regulation of his subordinates was1 especially in his earlier days1 despotic in the extreme--despotic to an extent which would scarcely be tolerated in the present day1 and which was the cause of not a little serious suffering to some of his staff1 whom1 at that time1 he looked upon in the true spirit of ,pond1 as mere mechanical 'drudges4' ,for thirty-five years of his administration the salaries of his assistants remained discreditably low1 and his treatment of the supernumerary members of his staff would now probably be characterized as 'remorseless sweating4' ,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 night1 without the slightest intermission1 except an hour at midday4 ,as an example of the extreme detail of the oversight which he exercised over his assistants1 it may be mentioned that he drew up for each one of those who took part in the ,harton ,colliery experiment1 instructions1 telling them by what trains to travel1 where to change1 and so forth1 with the same minuteness that one might for a child who was taking his first journey alone2 and he himself packed up soap and towels with the instruments1 lest his astronomers should find themselves1 in ,co4 ,durham1 out of reach of these necessaries of civilization4 ,a regime so essentially personal may indeed have been necessary after ,pond's administration1 and to give the ,observatory a fresh start4 ,but it would not have been to the advantage of the ,observatory1 had it become a permanent feature of its administration1 as it militated--was almost avowedly intended to militate--against the growth of real zeal and intelligence in the staff1 and necessarily occasioned labour and discomfort out of proportion to the results obtained4 ,fortunately1 in ,airy's later years1 the extension of the work of the ,observatory1 a slight failing in his own powers1 and the efforts he was devoting to the working out of the lunar theory1 compelled him to relax something of that microscopic imperiousness which had been the chief characteristic of his rule for so long4 ,airy had1 in the fullest degree1 the true spirit of the public servant2 his sense of duty to the ,state was very high4 ,he was always ready to undertake any duty which he felt to be of public usefulness1 and many of these he discharged without fee or reward4 ,so great an astronomer was necessarily most highly esteemed by astronomers4 ,he was ,president of the ,royal ,society for two years2 he was five times ,president of the ,royal ,astronomical ,society1 and twice received its gold medal1 beside a special testimonial for his reduction of the ,greenwich lunar observations4 ,from the ,royal ,society he received the ,copley medal and the ,royal medal1 beside honorary titles from the ,universities of ,oxford1 ,cambridge1 and ,edinburgh4 ,so invaluable a public servant1 he received the distinction of a ,knight ,commandership of the ,bath in #ahgb4 ,he had been repeatedly offered knighthood before1 but had not thought it well to receive it4 ,he was in the receipt of decorations also from a great number of foreign countries2 for1 for many years1 he was looked up to1 not only by ,english astronomers1 but by scientific men in all countries1 as the very head and representative of his science4 ,and he also received a more popular appreciation--and most justly so4 ,for whilst no one could have less of the arts of the ordinary popularizer about him1 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 men1 delivered at ,ipswich4 ,and we may count the bestowal upon him of the honorary freedom of the ,city of ,london1 in #ahge1 as one of the tokens that his services in this direction had not been unappreciated4 ,during the last seven years of his official career he undertook the working out of a lunar theory1 and1 to allow himself more leisure for its completion1 he resigned his position ,august #ae1 #ahha1 after forty-six years of office4 ,he was now eighty years of age1 and he took up his residence at the ,white ,house1 just outside ,greenwich ,park4 ,he resided there till his death1 more than ten years later--,january #b1 #ahib4 99 99 99 99 99 ,airy was succeeded in the ,astronomer ,royalship by the present and eighth holder of the office1 ,w4 ,h4 ,m4 ,,christie4 ,he was born at ,woolwich1 in #ahde1 his father having been ,professor ,samuel ,hunter ,christie1 ,f4,r4,s4 ,he was educated at ,king's ,college1 ,london1 and ,trinity ,college1 ,cambridge1 graduating as fourth ,wrangler in #ahfh4 ,in #ahgj he was appointed chief assistant at ,greenwich1 in succession to ,mr4 ,stone1 who had become her ,majesty's astronomer at the ,cape1 and in #ahha he succeeded ,airy as ,astronomer ,royal4 ,illustration3 ,w4 ,h4 ,m4 ,,christie1 ,,astronomer ,,royal4 7,from a photograph by ,elliott and ,fry47 ,during ,mr4 ,christie's office1 the two new departments of the ,astrographic ,chart and ,double-star observations have come into being4 ,the following buildings have been erected under his administration3 the great ,new ,observatory in the south ground1 the ,new ,altazimuth1 the ,new ,library1 nearly opposite to it1 the ,transit ,pavilion1 the porter's lodge1 and the ,magnetic ,pavilion out in the ,park4 ,whilst in the old buildings the ,astrographic dome has been added1 and the ,upper and ,lower ,computing rooms have been rebuilt and enlarged4 ,as to the instruments1 the #bh-;inch refractor1 the astrographic twin telescope1 the new altazimuth1 the #bf-;inch and #i-;inch ,thompson photographic refractors1 and the #cj-;inch reflector are all additions during the present reign4 ,roughly speaking1 therefore1 we may say that three-fourths of the present ,observatory has been added during the nineteen years of the present ,astronomer ,royal4 ,one exceedingly important improvement should not be overlooked4 ,airy observed little himself whilst at ,greenwich1 and had an inadequate idea of the necessity for room in a dome and breadth in a shutter-opening4 ,with the sole exception1 perhaps1 of the transit circle1 every instrument set up by ,airy was crammed into too small a dome or looked out through too narrow an opening4 ,the increase of shutter-opening of the newer domes may be well seen by contrasting1 say1 the old altazimuth or the ,sheepshanks dome with that of the astrographic4 ,this reform has had much to do with the success of later work4 ,,chapter ,v ,,the ,,observatory ,,buildings ,like a living organism1 ,greenwich ,observatory bears the record of its life-history in its structure4 ,it was not one of those favoured institutions that have sprung complete and fully equipped from the liberality of some great king or private millionaire4 ,as we have seen1 it was originally established on the most modest--not to say meagre--scale1 and has been enlarged just as it has been absolutely necessary4 ,to quote again from ,professor ,newcomb-- ',whenever any part of it was found insufficient for its purpose1 new rooms were built for the special object in view1 and thus it has been growing from the beginning by a process as natural and simple as that of the growth of a tree4 ,even now the very value of its structure is less than that of several other public observatories1 though it eclipses them all in the results of its work4' ,entering the courtyard--an enclosure some eighty feet deep by ninety feet in extreme breadth--by the great gate1 we see before us ,flamsteed ,house1 the original building of the ,observatory4 ,flamsteed's little domain was only some twenty-seven yards wide by fifty deep1 and for buildings comprised little beyond a small dwelling-house on the ground floor1 and one fine room above it4 ,this room--the original ,greenwich ,observatory--still remains1 and is used as a council room by the official ,board of ,visitors1 who come down to the ,observatory on the first ,saturday in ,june1 to examine into its condition and to receive the ,astronomer ,royal's report4 ,the room is called1 from its shape1 the ,octagon ,room1 and is well known to ,londoners from the great north window which looks out straight over the river between the twin domes of the ,hospital4 ,in ,bradley's time1 about #agdi1 the first extension of the domains of the ,observatory took place to the south and east of the original building1 the direction in which1 on the whole1 all subsequent extensions have taken place1 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 plateau1 from which the ground falls away very sharply on three sides and on part of the fourth4 ,the ,observatory domain at present is fully two hundred yards in greatest length1 with an average breadth of about sixty4 ,nearly the whole of this accession took place under the directorates of ,pond and ,airy4 ,the present instruments are1 therefore1 as a rule1 the more modern in direct proportion to their distance from the ,octagon ,room--the old original ,observatory4 ,there is one notable exception4 ,the very first extension of the ,observatory buildings1 made in the time of ,halley1 the second ,astronomer ,royal1 consisted in the setting up of a strong pier1 to carry two quadrant telescopes4 ,the pier still remains1 but now forms the base of the support of the twin telescopes devoted to the photographic survey of the heavens for the ,international ,chart4 ,standing just within the gate of the courtyard1 and looking westward1 that is toward ,flamsteed ,house1 we have immediately on our right hand the porter's lodge2 a little farther forward1 also on the right1 the ,transit ,pavilion1 a small building sheltering a portable transit instrument2 and farther forward1 still on the right1 the entrance to the ,chronograph ,room4 ,above the ,chronograph ,room is a little1 inconveniently-placed dome1 containing a small equatorially-mounted telescope1 known as the ,shuckburgh4 ,beyond the ,chronograph ,room a door opens on to the ,north ,terrace1 over which is seen the great north window of the ,octagon ,room4 ,close by the door of the ,chronograph ,room a great wooden staircase rises to the roof of the main building4 ,it is not an attractive-looking ascent1 as the steps overlap inconveniently4 ,still1 there is no record of an accident upon them1 and those who venture on the climb to the roof1 where are placed the anemometers and the turret carrying the time-ball1 which is dropped daily at #a p4m41 will be well repaid by the splendid view of the river which is there afforded to them4 ,passing under this staircase1 on the wall by its side is seen the following inscription3-- ,,carolus ,,ii,s ,,rex ,,optimus ,,astronomi ,,et ,,nautic ,,artis ,,patronus ,,maximus ,,speculam ,,hanc ,,in ,,utriusque ,,commodum ,,fecit ,,anno ,d,,ni ,,mdclxxvi4 ,,regni ,,sui ,,xxviii4 ,curante ,iona ,moore milite ,r4 ,t4 ,s4 ,g4 ,illustration3 ,,the ,,astronomer ,,royal',s ,,house4 7,from a photograph by ,mr4 ,lacey47 ,in the extreme angle of the courtyard is the entrance to the mean solar clock cupboard1 and to the staircase leading up to the ,octagon ,room4 ,at the head of this staircase in a small closet is the winch for winding up the time-ball4 ,coming back into the courtyard1 and crossing the face of the ,astronomer ,royal's private house1 the range of buildings is reached which form the left hand or south side of the enclosure4 ,entering the first of these1 we find ourselves in the ,lower ,computing ,room1 which is devoted to the ',time ,department4' ,the next room which opens out of it1 as we turn eastwards1 was ,bradley's ,transit ,room1 but is now used for the storage of chronometers4 ,passing through ,bradley's ,transit ,room1 we come to the present ,transit ,room1 which brings us close to the great gate4 ,the range of buildings is1 however1 continued somewhat farther1 containing on the ground floor some small sitting-rooms and a fire-proof room for records4 ,illustration3 ,,the ,,courtyard4 7,from a photograph by ,mr4 ,lacey47 ,turning back to the ,lower ,computing ,room1 we notice in it the stone pier1 already alluded to1 which was set up by ,halley1 and formed the first addition to the original ,observatory of ,flamsteed4 ,the ,lower ,computing ,room itself and ,bradley's ,transit ,room were due to the ,astronomer after which the latter is named4 ,an iron spiral staircase in the middle of the ,lower ,computing ,room leads up to the ,upper ,computing ,room1 and above that to the ,astrographic dome1 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 photography4 ,in this way it is intended to secure a record of the places of far more stars than could be done by the ordinary methods1 and in this project ,greenwich has necessarily taken a premier place4 ,this is a work which1 whilst it is the legitimate and natural outcome of the original purpose of the ,observatory1 is yet pushed beyond what is necessary for any mere utilitarian assistance to navigation4 ,for the sailor it will always be sufficient to know the places of a mere handful of the brightest stars1 and the vast majority of those in the great photographic map will never be visible in the little portable telescope of the sailor's sextant4 ,but it will be freely admitted that in the case of an enterprise of this nature1 in which the observatories of so many different nations were uniting1 and which was so precisely on the lines of its original charter1 though an extension of it1 it was impossible for ,greenwich to hold back on the plea that the work was not entirely utilitarian4 ,descending again to the ,lower ,computing ,room1 and passing through it1 not to the east1 into ,bradley's ,transit ,room1 but through a little lobby to the south1 we come upon an inconvenient wooden staircase winding round a great stone pillar with three rays4 ,this pillar is the support of ,airy's altazimuth1 and very nearly marks the place where ,flamsteed set up his original sextant4 ,returning again to the ,lower ,computing ,room1 and passing out to the east1 just in front of the ,time ,superintendent's desk1 we enter a small passage running along the back of ,bradley's ,transit ,room1 and from this passage enter the present ,transit ,room near its south end4 ,just before reaching the ,transit ,room1 however1 we pass the ,reflex ,zenith ,tube1 a telescope of a very special kind4 ,immediately outside the ,transit ,room is a staircase leading on the first floor to two rooms long used as libraries1 and to the leads above them1 on which is a small dome containing the ,sheepshanks equatorial4 ,these libraries are over the small sitting-rooms already referred to4 ,the fire-proof ,record ,rooms1 two stories in height1 terminate this range of buildings4 ,beyond the ,record ,rooms the boundary turns sharply south1 where stands a large octagonal building surmounted by a dome of oriental appearance1 a 'circular versatile roof1' as the ,visitors would have called it a hundred years ago4 ,this dome--which has been likened1 according to the school of sthetics in which its critics have been severally trained1 to the ,taj at ,agra1 a collapsed balloon1 or a mammoth ,spanish onion--houses the largest refractor in ,england1 the ',south-east ,equatorial' of twenty-eight inches aperture4 ,but1 though the largest that ,england possesses1 it would appear but as a pigmy beside some of the great telescopes for which ,america is famous4 ,beyond this dome the hollow devoted to the ,astronomer ,royal's private garden reduces the ,observatory ground to a mere 'wasp's waist1' a narrow1 inconvenient passage from the old and north observatory to the younger southern one4 ,the first building1 as the grounds begin to widen out to the south1 contains the ,new ,altazimuth1 a transit instrument which can be turned into any meridian4 ,a library of white brick and a low wooden cruciform building--the ,magnetic ,observatory--follow it closely4 ,this latter building houses the ,magnetic ,department1 a department which1 though it lies aside from the original purposes of the ,observatory1 as defined in the warrant given to ,flamsteed1 is yet intimately connected with navigation1 and was founded by ,airy very early in his period of office4 ,this deals with the observation of the changes in the force and direction of the earth's magnetism1 an inquiry which the greater delicacy of modern compasses1 and1 in more recent times1 the use of iron instead of wood in the construction of ships1 has rendered imperative4 ,closely associated with the ,magnetic ,department is the ,meteorological4 ,weather forecasts1 so necessary for the safety of shipping round our coasts1 are not issued from ,greenwich ,observatory1 any more than the ,nautical ,almanac is now issued from it4 ,but just as the ,observatory furnishes the astronomical data upon which the almanac is based1 so also a considerable department is set apart for furnishing observations to be used by the ,meteorological ,office at ,westminster for their daily predictions4 ,so far1 the development of the ,observatory had been along the central line of assistance to navigation4 ,but the ',magnetic ,department' led on to a new one1 which had but a secondary connection with it4 ,it had been discovered that the extent of the daily range of the magnetic needle1 and the amount of the disturbances to which it was subjected1 were in close connection with the numbers and size of the spots on the sun's surface4 ,this led to the institution of a daily photographic record of the state of the sun's surface1 a record of which ,greenwich has now the complete monopoly4 ,illustration3 ,,plan ,,of ,,observatory ,,at ,,present ,,time4 7,for key to plan1 see p4 #ace47 ,,key ,,to ,,the ,,plan ,,of ,,the ,,observatory ,,on ,,page #acd4 #a4 ,chronograph ,room4 #b4 ,old ,altazimuth ,dome4 #c4 ,safe ,room4 #d4 ,computing ,room4 #e4 ,bradley's ,transit ,room4 #f4 ,transit ,circle ,room4 #g4 ,assistants' ,room4 #h4 ,chief ,assistant's ,room4 #i4 ,computers' ,room4 #aj4 ,record ,rooms4 #aa4 ,chronometer ,rooms and ,south-east ,dome4 #ab4 ,greenhouse and ,outbuildings4 #ad4 ,new ,library4 #ae4 ,magnetic ,observatory4 #af4 ,offices4 #ai4 ,sheds4 #bc4 ,winch ,room for ,time-ball4 #bd4 ,porter's ,lodge4 #be4 ,new ,transit ,pavilion4 #bf4 ,new ,altazimuth ,pavilion4 #bg4 ,museum3 ,new ,building4 #bh4 ,south ,wing #bi4 ,north ,wing #cj4 ,west ,wing #ca4 ,east ,wing ,f4 ,rooms built for ,flamsteed4 ,h4 ,added by ,halley4 ,b4 ,bradley4 ,m4 ,maskelyne4 ,a4 ,airy4 ,f',f'4 ,flamsteed's boundaries4 ,m',m'4 ,maskelyne's #agij4 ,p',p'4 ,pond's #ahad4 ,a',a'4 ,airy's #ahcg4 ,a,a4 ,airy's #ahfh4 ,beyond the ,magnetic ,observatory the ground widens out into an area about equal to that of the northern part1 and the new building just completed1 and which is now emphatically ',the ,observatory1' stands clear before us4 ,the transfer to this stately building of the computing rooms1 libraries1 and store rooms has been aptly described as a shift in the latitude of ,greenwich ,observatory1 which still preserves its longitude4 ,it may be noted that the only two buildings of any architectural pretensions in the whole range are--,flamsteed's original observatory1 built by ,sir ,christopher ,wren1 and containing little beyond the octagon room1 in the extreme north2 and this newest building in the extreme south4 ,this ',new ,observatory1' like the old1 and like the great ,south-eastern tower1 is an octagon in its central portion4 ,but whilst the two other great buildings are simply octagonal1 here the octagon serves only as the centre from which radiate four great wings to the four points of the compass4 ,the building is by far the largest on the ground1 but in little accord with the popular idea of an astronomer as perpetually looking through a telescope1 carries but a single dome2 its best rooms being set apart as 'computing rooms1' for the use of those members of the staff who are employed in the calculations and other clerical work1 which form1 after all1 much the greater portion of the ,observatory routine4 ,an observer with the transit instrument1 for instance1 will take only three or four minutes to make a complete determination of the place of a single star4 ,but that observation will furnish work to the computers for many hours afterwards4 ,or1 to take a photograph of the sun will occupy about five minutes in setting the instrument1 whilst the actual exposure will take but the one-thousandth part of a second4 ,but the plate1 once exposed1 will have to be developed1 fixed1 and washed2 then measured1 and the measures reduced1 and1 on the average1 will provide one person with work for four days before the final results have been printed and published4 ,it is easy to see1 then1 that observing1 though the first duty of the ,observatory1 makes the smallest demand on its time4 ,the visitor who comes to the ,observatory by day 7and none are permitted to do so by night7 finds the official rooms not unlike those of ,somerset ,house or ,whitehall1 and its occupants for the most part similarly engaged in what is1 apparently1 merely clerical work4 ,an examination of the big folios would of course show that instead of being ledgers of sales of stamps1 or income-tax schedules1 they referred to stars1 planets1 and sun-spots2 but for one person actively engaged at a telescope1 the visitor would see a dozen writing or computing at a desk4 ,the staff1 like the building1 is the result of a gradual development1 and bears traces of its life history in its composition4 ,first comes the ,astronomer ,royal1 the representative and successor of the original ',king's ,astronomer1' the ,rev4 ,john ,flamsteed4 ,but the 'single surly and clumsy labourer1' which was all that the ',merry ,monarch' could grant for his assistance1 is now represented by a large and complex body of workers2 each varied class and rank of which is a relic of some stage in the progress of the ,observatory to its present condition4 ,the following extract from the ,annual ,report of the ,astronomer ,royal to the ,board of ,visitors1 ,june1 #aijj1 describes the present personnel of the establishment3-- ',the staff at the present time is thus constituted1 the names in each class being arranged in alphabetical order3-- ',chief assistants--,mr4 ,cowell1 ,mr4 ,dyson4 ',assistants--,mr4 ,hollis1 ,mr4 ,lewis1 ,mr4 ,maunder1 ,mr4 ,nash1 ,mr4 ,thackeray4 ',second-class assistants--,mr4 ,bryant1 ,mr4 ,crommelin4 ',clerical assistant--,mr4 ,outhwaite4 ',established computers--,mr4 ,bowyer1 ,mr4 ,davidson1 ,mr4 ,edney1 ,mr4 ,furner1 ,mr4 ,rendell1 and one vacancy4 ',the two second-class assistants will be replaced by higher grade established computers as vacancies occur4 ',mr4 ,dyson and ,mr4 ,cowell have the general superintendence of all the work of the ,observatory4 ,mr4 ,maunder is charged with the heliographic photography and reductions1 and with the preparation of the ,library ,catalogue4 ,mr4 ,lewis has charge of the time-signals and chronometers1 and of the #bh-;inch equatorial4 ,mr4 ,thackeray superintends the miscellaneous astronomical computations1 including the preparation of the new ,ten-,year ,catalogue4 ,mr4 ,hollis has charge of the photographic mapping of the heavens1 the measurement of the plates1 and the computations for the ,astrographic ,catalogue4 ,mr4 ,crommelin undertakes the altazimuth and ,sheepshanks equatorial reductions1 and ,mr4 ,bryant the transit and meridian zenith distance reductions and time-determinations4 ,in the magnetic and meteorological branch1 ,mr4 ,nash has charge of the whole of the work4 ,mr4 ,outhwaite acts as responsible accountant officer2 has charge of the library1 records1 manuscripts1 and stores1 and conducts the official correspondence4 ,as regards the established computers1 ,mr4 ,bowyer1 ,mr4 ,furner1 ,mr4 ,davidson1 and ,mr4 ,rendell assist ,mr4 ,lewis1 ,mr4 ,thackeray1 ,mr4 ,hollis1 and ,mr4 ,bryant respectively1 and ,mr4 ,edney assists ,mr4 ,nash4 ',there are at the present time twenty-four supernumerary computers employed at the ,observatory1 ten being attached to the astronomical branch1 two the chronometer branch1 six to the astrographic1 one to the heliographic1 four to the magnetic and meteorological1 and one to the clerical4 ',a foreman of works1 with two carpenters1 and two labourers2 a skilled mechanic with an assistant2 a gate porter1 two messengers1 a watchman1 a gardener1 and a charwoman1 are also attached to the ,observatory4 ',the whole number of persons regularly employed at the ,observatory is fifty-three4' ,the day work1 as said before1 is by far the greatest in amount1 the 'office hours' being from nine till half-past four1 with an hour's interval4 ,the arrangements for the night watches present some complications4 ,for many years the instruments in regular use were two only1 the transit circle and the altazimuth4 ,the arrangements for observing were simple4 ,four assistants divided the work between them thus3 an assistant was on duty with the transit circle one day1 his watch beginning about six a4m4 or a little later1 and ending about three the following morning2 a watch of twenty-one hours in maximum length4 ,the second day his duties were entirely computational1 and were only two or three hours in length4 ,the third day he had a full day's work on the calculations1 followed by a night duty with the altazimuth4 ,the latter instrument might give him a very easy watch or a terribly severe one4 ,if the moon were a young one it was easy1 especially if the night was clear1 as in that case an hour was enough to secure the observations required4 ,very different was the case with a full moon1 especially in the long1 often cloudy1 nights of winter4 ,then a vigilant watch had to be kept from sunset to sunrise1 so that in case of a short break in the clouds the moon might yet be observed4 ,such a watch was the severest 7with one exception7 that an assistant had to undergo4 ,his fourth day would then resemble his second1 and with the fifth day a second cycle of his quartan fever would commence1 the symptoms following each other in the same sequence as before4 ,such a routine carried on with iron inflexibility was exceedingly trying1 as it was absolutely impossible for an observer to keep any regularity in his hours of rest or times for meals4 ,this routine has been considerably modified by the present ,astronomer ,royal1 partly because the instruments now in regular daily use are five instead of two1 and partly because a less stringent system has proved not merely far less wearing to the observers1 but also much more prolific of results4 ,it was impossible for a man to be at his best for long under the old rgime1 and from forty-six to forty-seven has been an ordinary age for an assistant to break down under the strain4 ,one point in which the observing work has been lightened has been in the discontinuance of the altazimuth observations at the full of the moon1 another in the shortening of the hours of the transit circle watch2 and a further and most important one in the arrangement that the observers with the larger instruments should have help at their work4 ,the net result of these changes has been a most striking increase in the amount of work achieved4 ,thus1 whilst in the year ending ,may #bj1 #ahge1 #cghj transits were taken with the transit circle1 and #cfcf determinations of north polar distance2 in that ending ,may #aj1 #ahie1 the numbers had risen to #aa1bdj and #aa1jjf respectively1 the telescope remaining precisely the same4 ,one principle of ,airy's rule still remains4 ,so far as possible no observer is on duty for two consecutive days1 but a long day of desk work and observing is followed by a short day of desk work without observing4 ,it will be readily understood that with five principal telescopes in constant work and one or two minor ones1 some demanding two observers1 others only one1 each telescope having its special programme and its special hours of work1 whilst by no means every member of the staff is authorized to observe with all instruments indifferently1 it becomes a somewhat intricate matter to arrange the weekly rota in strict accordance with the foregoing principle1 and with the further one1 that whilst a considerable amount of ,sunday observing is inevitable1 the average duty of an observer should be three days a week1 not seven days a fortnight4 ,there is a story1 received with much reserve at ,cambridge1 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 clubs4 ,if so gifted a being ever existed1 he may be paralleled by the ,greenwich assistant who can predict for any future epoch the sequence of duties throughout the entire establishment4 ,at any rate1 one of the first items in the week's programme is the preparation of the rota for the week1 or rather1 to use an ecclesiastical term1 for the 'octave1' i4e4 from the ,monday to the ,monday following4 ,the special work to be carried out on any telescope is likewise a matter of programme4 ,for the transit circle a list of the most important objects to be observed is supplied for the observer's use1 and the general lines upon which the other stars are to be selected from a huge ',working ,catalogue' are well understood4 ,with some of the other telescopes the principles upon which the objects are to be selected are laid down1 but the actual choice is left to the discretion of the observer at the time4 ,there is no time for the watcher to spend in what the outsider would regard as 'discovery'2 such as sweeping for comets or asteroids1 hunting for variable stars1 sketching planets1 and so forth4 ,indeed1 there is a story current in the ,observatory that some fifty years ago1 when the tide of asteroid discovery first set in1 ,airy found an assistant1 since famous1 working with a telescope on his 'off-duty' night4 ,that stern disciplinarian asked what business the assistant had to be there on his free night1 and on being told he was 'searching for new planets1' he was severely reprimanded and ordered to discontinue at once4 ,a similar energy would not meet so gruff a discouragement to-day2 but the routine work so fully occupies both staff and telescopes that an assistant may be most thoroughly devoted to his science1 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 telescope4 ,for example1 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 glowing1 curdling1 emerald cloud--or the indescribable magnificence of the myriad suns that cluster like swarming bees or the grapes of ,eshcol in the constellation of ,hercules2 yet probably most of the staff have never seen either spectacle through it4 ,the professional astronomer who is worth his salt will find abundance of charm and interest in his work1 but he will not1 ',like a girl1 ,valuing the giddy pleasures of the eyes1' consider the charm to lie mainly in the occasional sight of wonderful beauty which his work may bring to him1 nor the interest in some chance phenomenon which may make his name known4 ,it is not every field of astronomy that is cultivated at ,greenwich4 ,the search for comets and for 'pocket planets' forms no part of its programme2 and the occupation so fascinating to those who take it up1 of drawing the details on the surfaces of the moon1 ,mars1 ,jupiter1 or ,saturn1 has been but little followed4 ,such work is here incidental1 not fundamental1 and the same may be said of certain spectroscopic observations of new or variable stars1 and of many similar subjects4 ,work such as this is most interesting to the general public1 and is followed with much devotion by many amateur astronomers4 ,for that very reason it does not form an integral part of the programme of our ,state observatory4 ,but work which is necessary for the general good1 or for the advancement of the science1 and which demands observations carried on continuously for many years1 and strict unity of instruments and methods1 cannot possibly be left to chance individual zeal1 and is therefore rightly made the first object at ,greenwich4 ,those striking discoveries which from time to time appeal strongly to the popular imagination1 and which have rendered so justly famous some of the great observatories of the sister continent1 have not often been made here4 ,its work has1 none the less1 been not only useful but essential4 ,a century ago1 when we were engaged in the hand-to-hand struggle with ,napoleon1 by far the most brilliant part of that naval war which we waged against the ,french1 and the most productive of prize-money1 was carried on by our cruisers1 who captured valuable prizes in every sea4 ,but a much greater service1 indeed an absolutely vital one1 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 refuge4 ,this was a work void of the excitement1 interest1 and profit of cruising4 ,it was monotonous1 wearing1 and almost inglorious1 but absolutely necessary to the very existence of ,england4 ,so the continuance for more than two centuries of daily observations of places of moon1 stars1 and planets is likewise 'monotonous1 wearing1 and almost inglorious2' the one compensation is that it is essential to the life of astronomy4 ,the eight ,astronomers ,royal have1 as already said1 kept the ,observatory strictly on the lines originally laid down for it1 subject1 of course1 to that enlargement which the growth of the science has inevitably brought4 ,but had they been inclined to change its course1 the ,board of ,visitors has been specially appointed to bring them back to the right way4 ,as already mentioned in the account of ,flamsteed1 the ,board dates from #agaj1 when it practically consisted of the ,president and ,council of the ,royal ,society4 ,its ,royal warrant lapsed on the death of ,queen ,anne1 and was not renewed at the accession of the two following sovereigns2 but in the reign of ,george ,,iii4 a new warrant was issued under date ,february #bb1 #agfe2 and this was renewed at the accession of ,george ,,iv4 ,when ,william ,,iv4 came to the throne1 the constitution of the ,board was extended1 so as to give a representation to the new ,royal ,astronomical ,society1 founded in #ahbj4 ,the ,president of the ,royal ,society is still chairman of the ,board1 but the ,admiralty1 of which the ,observatory is a department1 the two ,universities of ,oxford and ,cambridge1 and the ,royal ,astronomical ,society are all represented on it by ex officio members1 and twelve other members are contributed by the ,royal and ,royal ,astronomical ,societies respectively1 six by each4 ,the first ,saturday in ,june is the appointed day for the annual inspection by the ,board1 and for the presentation to it of the ,astronomer ,royal's ,report4 ,to this all-important business meeting has been added something of a social function1 by the invitation of many well-known astronomers and the leading men of the allied sciences to inspect the results of the year1 and to partake of the chocolate and cracknels1 which have been the traditional refreshments offered on these occasions for a period 'whereof the memory of man runneth not to the contrary4' ,,chapter ,,vi ,,the ,,time ,,department ,one day two ,scotchmen stood just outside the main entrance of ,greenwich ,observatory1 looking intently at the great twenty-four-hour clock1 which is such an object of attention to the passers through the ,park4 ',jock1' said one of them to the other1 'd'ye ken whaur ye are8' ,jock admitted his ignorance4 ',ye are at the vara ceentre of the airth4' ,geographers tell us that there is a sense in which this statement as it stands may be accepted as true4 ,for if the surface of the globe be divided into two hemispheres1 so related to each other that the one contains as much land as possible1 and the other as little1 then ,london will occupy the centre or thereabouts of the hemisphere with most land4 ,this was not1 however1 what the ,scotchman meant4 ,he meant to tell his companion that he was standing on the prime meridian of the world1 the imaginary base line from which all distances1 east or west1 are reckoned2 in short1 that he was on ',longitude ,nought4' ,he was not absolutely correct1 however1 for the great twenty-four-hour clock does not mark the exact meridian of ,greenwich4 ,to find the instrument which marks it out and defines it we must step inside the ,observatory precincts1 and just within the gate we see before us on the left hand a door which leads through a little lobby straight into the most important room of the whole ,observatory--the ,transit ,room4 ,illustration3 ,,the ,,great ,,clock ,,and ,,porter',s ,,lodge4 7,from a photograph by ,mr4 ,lacey47 ,this room is not well adapted for representation by artist or photographer4 ,four broad stone pillars occupy the greater part of the space1 and leave little more than mere passage room beside4 ,two of these pillars are tall1 as well as broad and massive1 and stand east and west of the centre of the room1 carrying between them the fundamental instrument of the ,observatory1 the transit circle4 ,the optical axis of this telescope marks ',longitude ,nought1' which is further continued by a pair of telescopes1 one to the north of it1 the other to the south1 mounted on the third and fourth of the pillars alluded to above4 ,this room has not always marked the meridian of ,greenwich1 for it stands outside the original boundary of the ,observatory4 ,but it is only a few feet to the east of the first transit instrument which was set up by ,halley1 the second ,astronomer ,royal1 in the extreme ,n4-,w4 corner of the ,observatory domain1 a distance equivalent to very much less than one-tenth of a second of time1 an utterly insensible quantity with the instruments of two hundred years ago4 ,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 earth4 ,the other1 the equator1 is fixed for us by the earth itself1 and is independent of any political considerations1 or of any effort or enterprise of man4 ,but of all the infinite number of great circles which could be drawn at right angles to the equator1 and passing through the north and south poles1 it was not easy to select one with such an overwhelming amount of argument in its favour as to obtain a practically universal acceptance4 ,the meridians of ,jerusalem and of ,rome have both been urged1 upon what we may call religious or sentimental grounds2 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 direction2 that of ,ferro1 in the ,canaries1 as being an oceanic station1 well to the west of the ,old ,world1 and as giving a base line without preference or distinction for one nation rather than another4 ,the actual decision has been made upon no such grounds as these4 ,it has been one of pure practical convenience1 and has resulted from the amazing growth of ,great ,britain as a naval and commercial power4 ,like ,tyre of old1 she is 'situate at the entry of the sea1 a merchant of the people for many isles1' and 'her merchants are the great men of the earth4' ,to tell in full1 therefore1 the steps by which the ,greenwich meridian has overcome all others is practically to tell again1 from a different standpoint1 the story of the 'expansion of ,england4' ,the need for a supreme navy1 the development of our empire beyond the seven seas1 the vast increase of our carrying trade--these have made it necessary that ,englishmen should be well supplied with maps and charts4 ,the hydrographic and geographic surveys carried on1 either officially by this country1 or by ,englishmen in their own private capacity1 have been so numerous1 complete1 and far-reaching as not only to outweigh those of all other countries put together1 but to induce the surveyors and explorers of not a few other countries to adopt in their work the same prime meridian as that which they found in the ,british charts of regions bordering on those which they were themselves studying4 ,naturally1 the meridian of ,greenwich has not only been adopted for ,great ,britain1 but also for the ,british possessions over-sea1 and1 from these1 for a large number of foreign countries2 whilst our ,american cousins retain it1 an historic relic of their former political connection with us4 ,the victories of ,clive at ,arcot and ,plassy1 of ,nelson at the ,nile and ,trafalgar1 the voyages and surveys of ,cook and ,flinders1 and many more2 the explorations of ,bruce1 ,park1 ,livingstone1 ,speke1 ,cameron1 and ,stanley2 these are some of the agencies which have tended to fix ',longitude ,nought' in the ,greenwich ,transit ,room4 ,there are two somewhat different senses in which the meridian of ,greenwich is the standard meridian for nearly the entire world4 ,the first is the sense about which we have already been speaking2 it constitutes the fundamental line whence distances east and west are measured1 just as distances north and south are measured from the equator4 ,but there is another1 though related sense1 in which it has become the standard4 ,it gives the time to the world4 ,there are few questions more frequently put than1 ',what time is it8' ',can you tell me the true time8' ,a stickler for exactitude might reply1 ',what kind of time do you mean8' ',do you mean solar or sidereal time8' ',apparent time or mean time8' ',local time or standard time8' ,there are all these six kinds of time1 but it is only within the last two generations1 within1 indeed1 the reign of our ,sovereign1 ,queen ,victoria1 that the subject of the differences of most of these kinds of time has become of pressing importance to any but theorists4 ,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 meridian4 ,this1 of course1 is the time of ,paris noon--apparent noon--but it would be exceedingly imprudent of any traveller through ,paris who wished1 say1 to catch the one o'clock express1 to set his watch by the gun4 ,for if it happened to be in ,february1 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 hour1 and that his train had gone2 whilst towards the end of ,october or the beginning of ,november1 he would find himself as much too soon4 ,until machines for accurately measuring time were invented1 apparent time--time1 that is to say1 given by the sun itself1 as by a sun-dial--was the only time about which men knew or cared4 ,but when reasonably good clocks and watches were made1 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 clock1 the reason being simply that the apparent rate of motion of the sun across the sky was not always quite the same1 whilst the movement of the clock was1 of course1 as regular as it could be made4 ,this difference between time as shown by the actual sun and by a perfect clock is known as the 'equation of time4' ,it is least about ,april #ae1 ,june #ae1 ,august #ca1 and ,december #be4 ,it is greatest1 the sun being after the clock1 about ,february #aa2 and the sun being before the clock1 about ,november #b4 ,flamsteed1 before he became ,astronomer ,royal1 investigated the question1 and so clearly demonstrated the existence1 cause1 and amount of the equation of time as entirely to put an end to controversy on the subject4 ,we had thus1 early in the century1 the two kinds of time in common use1 apparent time and mean time1 or clock time4 ,but as the sun can only be on one particular meridian at any given instant1 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 it4 ,it is thus noon at ,moscow #a hr4 #cf min4 before it is noon at ,berlin1 and noon at ,berlin #ed min4 before it is noon in ,london4 ,this was all well enough known1 but occasioned no inconvenience until the introduction of railway travelling2 then a curious difficulty arose4 ,suppose an express train was running at the rate of sixty miles an hour from ,london to ,bristol4 ,the guard of the train sets his watch to ,london time before he leaves ,paddington1 but if the various towns through which the train passes1 ,reading1 ,swindon1 etc41 each keep their own local time1 he will find his watch apparently fast at each place he reaches2 but on his return journey1 if he sets to ,bristol time before starting1 he will in a similar way find it apparently slow by the ,swindon1 ,reading1 and ,paddington clocks as he reaches them in succession4 ,it became at once necessary to settle upon one uniform system of time for use in the railway guides4 ,apart from this1 a passenger taking train1 say1 at ,swindon1 might have been very troubled to know whether the advertised time of his train was that of ,exeter1 the place whence it started1 or ,swindon1 the station where he was getting in1 or ,london1 its destination4 ',railway time1' therefore1 was very early fixed for the whole of ,great ,britain to be the same as ,london time1 which is1 of course1 time as determined at ,greenwich ,observatory4 ,at first it was the custom to keep at the various stations two clocks1 one showing local time1 the other 'railway1' or ,greenwich time1 or else the clocks would be provided with a double minute hand1 one branch of which pointed to the time of the place1 the other to the time of ,greenwich4 ,it was soon found1 however1 that there was no sufficient reason for keeping up local time4 ,even in the extreme ,west of ,england the difference between the two only amounted to twenty-three minutes1 and it was found that no practical inconvenience resulted from saying that the sun rose at twenty-three minutes past six on ,march #bb1 rather than at six o'clock4 ,the hours of work and business were practically put twenty-three minutes earlier in the day1 a change of which very few people took any notice4 ,other countries besides ,england felt the same difficulty1 and solved it in the same way1 each country as a rule taking as its standard time the time of its own chief city4 ,there were two countries for which this expedient was not sufficient--the ,united ,states and ,canada4 ,the question was of no importance until the iron road had linked the ,atlantic to the ,pacific in both countries4 ,then it became pressing4 ,no fewer than seventy different standards prevailed in the ,united ,states only some twenty years ago4 ,the case was a very different one here from that of ,england1 where east and west differed in local time by only a little over twenty minutes4 ,in ,north ,america1 in the extreme case1 the difference amounted to four hours1 and it seemed asking too much of men to call eight o'clock in their morning1 or it might be four o'clock in their afternoon1 their noonday4 ,the device was therefore adopted of keeping the minutes and seconds the same for all places right across the continent1 but of changing the hour at every #ae of longitude4 ,the question then arose what longitude should be adopted as the standard4 ,the ,americans might very naturally have taken their standard time from their great national observatory at ,washington1 or from that of their chief city1 ,new ,york1 or of their principal central city1 ,chicago4 ,but1 guided partly no doubt by a desire to have their standard times correspond directly to the longitudes of their maps1 and partly from a desire to fall in1 if possible1 with some universal time scheme1 if such could be brought forward1 they fixed upon the meridian of ,greenwich as their ultimate reference line1 and defined their various hour standards as being exactly so many hours slow of ,greenwich mean time4 ,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 ,europe2 and ,greenwich is not only ',longitude ,nought' for the bulk of the civilized world1 but ,greenwich mean time1 increased or decreased by an exact number of hours or half-hours1 is the standard time all over the planet4 ,no2 the statement requires correction4 ,two countries hold out1 both close to our own doors4 ,france1 instead of adopting ,greenwich time as such1 adopts ,paris time less #i m4 #ba s4 7that being the precise difference in longitude between the two national observatories74 ,ireland disdains even such a veiled surrender1 and ,dublin time is the only one recognized from the ,hill of ,howth to far ,valentia4 ,so the distressful country preserves her old grievance1 that she does not even get her time until after ,england has been served4 ,the alteration in national habits following on the adoption of this ,european system has had a very perceptible effect in some cases4 ,thus1 ,switzerland has adopted ,mid-,european time1 one hour fast of ,greenwich2 the true local time for ,berne being just half an hour later4 ,the result of putting the working hours this thirty minutes earlier in the day has had such a noticeable effect on the consumption of gas1 as to lead the gas company to contemplate agitating for a return to the old system4 ,thus1 ,greenwich time1 as well as the ,greenwich meridian1 has practically been adopted the world over4 ,it follows1 then1 that the determination of time is the most important duty of the ,royal ,observatory2 and the ,time ,department1 the one to which is entrusted the duty of determining1 keeping1 and distributing the time1 calls for the first attention4 ,entering the transit room1 the first thing that strikes the visitor is the extreme solidity with which the great telescope is mounted4 ,it turns but in one plane1 that of 'longitude nought1' 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 area1 and the foundations of which go deep down under the surface of the hill4 ,on the west side of the telescope1 and rigidly connected with it1 is a large wheel some six feet in diameter1 and with a number of wooden handles attached to it1 resembling the steering-wheel of a large steamer4 ,this wheel carries the setting circle1 which is engraved upon a band of silver let into its face near its circumference1 a similar circle being at the back of the wheel nearer the pillar4 ,eleven microscopes1 of which only seven are ordinarily used1 penetrate through the pier1 and are directed on to this second circle4 ,the present transit is the fourth which the ,observatory has possessed1 and its three predecessors1 known as ,halley's1 ,bradley's1 and ,troughton's1 respectively1 are still preserved and hang on the walls of the transit room1 affording by their comparison an interesting object-lesson in the evolution of a modern astronomical instrument4 ,the watcher who wishes to observe the passing of a star must note two things3 he must know in what direction to point his telescope1 and at what time to look for the star4 ,then1 about two minutes before the appointed time1 he takes his place at the eyepiece4 ,as he looks in he sees a number of vertical lines across his field of view4 ,these are spider-threads placed in the focus of the eye-piece4 ,presently1 as he looks1 a bright point of silver light1 often surrounded by little flashing1 vibrating rays of colour1 comes moving quickly1 steadily onward--'swims into his ken1' as the poet has it4 ,the watcher's hand seeks the side of the telescope till his finger finds a little button1 over which it poises itself to strike4 ,on comes the star1 'without haste1 without rest1' till it reaches one of the gleaming threads4 ,tap6 ,the watcher's finger falls sharply on the button4 ,some three or four seconds later and the star has reached another 'wire1' as the spider-threads are commonly called4 ,tap6 ,again the button is struck4 ,another brief interval and the third wire is reached1 and so on1 until ten wires have been passed1 and the transit is over4 ,the intervals are not1 however1 all the same1 the ten wires being grouped into three sets1 two of three apiece1 and the third of four4 ,illustration3 ,,the ,,chronograph4 ,each tap of the observer's finger completed for an instant an electric circuit1 and recorded a mark on the 'chronograph4' ,this is a large metal cylinder covered with paper1 and turned by a carefully-regulated clock once in every two minutes4 ,once in every two seconds a similar mark was made by a current sent by means of the standard sidereal clock of the ,observatory4 ,the paper cover of the chronograph after an hour's work shows a spiral trace of little dots encircling it some thirty times4 ,these dots are at regular intervals1 about an inch apart1 and are the marks made by the clock4 ,interspersed between them are certain other dots1 in sets of ten2 and these are the signals sent from the telescope by the transit observer4 ,if1 then1 one of the clock dots and one of the observer's dots come exactly side by side1 we know that the star was on one of the wires at a given precise second4 ,if the observer's dot comes between two clock dots1 it is easy1 by measuring its distance from them with a divided scale1 to tell the instant the star was on the wire to the tenth of a second1 or even to a smaller fraction4 ,whilst1 since the transit was taken over ten wires1 and the distance of each wire from the centre of the field of view is known1 we have practically ten separate observations1 and the average of these will give a much better determination of the time of transit than a single one would4 ,but let the watcher be ever so little too slow in setting his telescope1 or ever so little late in placing himself at his eye-piece1 and the star will have passed the wire1 and as it smoothly1 resistlessly moves on its inexorable way1 will tell the tardy watcher in a language there is no mistaking1 ',lost moments can never be recalled4' ,the opportunity let slip1 not until twenty-four hours have gone by will another chance come of observing that same star4 ,it is the stars that are chiefly used in this determination1 partly because the stars are so many1 whilst there is but one sun4 ,if1 therefore1 clouds cover the sun at the important moment of transit1 the astronomer may well exclaim1 so far as this observation is concerned1 ',i have lost a day6' ,the chance will not be offered him again until the following noon4 ,but if one star is lost by cloud1 there are many others1 and the chance is by no means utterly gone4 ,beside1 the sun enables us to tell the time only at noon2 the stars enable us to find it at various times throughout the entire night2 indeed1 throughout both day and night1 since the brighter stars can be observed in a large telescope even during the day4 ,there are two great standard clocks at the ,observatory3 the mean solar clock and the sidereal clock4 ,the latter registers twenty-four hours in the precise time that the earth rotates on its axis4 ,a 'day' in our ordinary use of the term is somewhat longer than this2 it is the average time from one noon to the next1 and as the earth whilst turning round on its axis is also travelling round the sun1 it has to rather more than complete a rotation in order to bring the sun again on to the same meridian4 ,a solar day is therefore some four minutes longer than an actual rotation of the earth1 i4e4 a sidereal day1 as it is called1 since such rotation brings a star back again to the same meridian4 ,the sidereal clock can therefore be readily checked by the observation of star transits1 for the time when the star ought to be on the meridian is known4 ,if1 therefore1 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 transit1 we know the clock must be so much fast or slow4 ,similarly1 the difference which should be shown between the sidereal and solar clocks at any moment is known2 and hence when the error of the sidereal clock is known1 that of the solar can be readily found4 ,it is often quite sufficient to know how much a clock is wrong without actually setting its hands right2 but it is not possible to treat the ,greenwich clock so1 for it controls a number of other clocks continually1 and sends hourly signals out over the whole country1 by which the clocks and watches all over the kingdom are set right4 ,in the lower computing room1 below the south window1 we find the ,time-,desk1 the head-quarters of the ,time ,department4 ,this is a very convenient place for the department1 since one of the chronometer rooms1 formerly ,bradley's transit room1 opens out of the lower computing room2 the transit instrument is just beyond2 it is close to the main gate of the ,observatory1 and so convenient for chronometer makers or naval officers bringing chronometers or coming for them1 whilst just across the courtyard is the chronograph room1 with the ,battery ,basement1 in which the batteries for the electric currents are kept1 and the ,mean ,solar ,clock lobby1 with the winch for the winding of the time-ball at the head of the stairs above it4 ,these rooms do not exhaust the territory of the department1 since it owns two other chronometer rooms on the ground floor and first floor respectively of the ,s4-,e4 tower4 ,at the time-desk means are provided for setting the clock right very easily and exactly4 ,just above the desk are a range of little dials and bright brass knobs1 that almost suggest the stops of a great organ4 ,two of these little dials are clock faces1 electrically connected with the solar and sidereal standard clocks1 so that1 though these clocks are themselves a good way off1 in entirely different parts of the ,observatory1 the time superintendent1 seated here at the time-desk1 can see at once what they are indicating4 ,between the two is a dial labelled ',commutator4' ,from this dial a little handle usually hangs vertically downwards1 but it can be turned either to the right or to the left1 and when thus switched hard over1 an electric current is sent through to the mean solar clock4 ,if now we leave the computing room and cross the courtyard to the extreme north-west corner1 we find the ,mean ,solar ,clock in a little lobby1 carefully guarded by double doors and double windows against rapid changes of temperature4 ,opening the door of the clock case1 we see that the pendulum carries on its side a long steel bar1 and that this bar as the pendulum swings passes just over the upper end of an electro-magnet4 ,when the current is switched on at the commutator1 this electro-magnet attracts or repels the steel bar according to the direction of the current1 and the action of the clock is accordingly quickened or retarded4 ,to put the commutator in action for one minute will alter the clock by the tenth of a second4 ,as the error of the clock is determined twice a day1 shortly before ten o'clock in the morning1 and shortly before one o'clock in the afternoon1 its error is always small1 usually only one or two tenths4 ,these two times are chosen because1 though time-signals are sent over the metropolitan area every hour from the ,greenwich clock through the medium of the ,post ,office1 at ten and at one o'clock signals are also sent to all the great provincial centres4 ,further1 at one o'clock the time balls at ,greenwich and at ,deal are dropped1 so that the captains of ships in the docks1 on the river1 or in the ,downs may check their chronometers4 ,the ,time-,ball is dropped directly by the mean solar clock itself4 ,it is raised by means of a windlass turned by hand-power to the top of its mast just before one o'clock4 ,connected with it is a piston working in a stout cylinder4 ,when the ball has reached the top of the mast1 the piston is lightly supported by a pair of catches4 ,these catches are pulled back by the hourly signal current1 and the piston at once falls sharply1 bringing the ball with it4 ,but after a fall of a few feet1 the air compressed by the piston acts as a cushion and checks the fall1 the ball then gently and slowly finishing its descent4 ,the instant of the beginning of the fall is1 of course1 the true moment to be noted4 ,the other dials on the time-desk are for various purposes connected with the signals4 ,one little needle in a continual state of agitation shows that the electric current connecting the various sympathetic clocks of the ,observatory is in full action4 ,another receives a return signal from various places after the despatch of the time-signal from ,greenwich1 and shows that the signal has been properly received at the distant station1 whilst all the many electric wires within the ,observatory or radiating from it are made to pass through the great key-board1 where they can be at once tested1 disconnected1 or joined up1 as may be required4 ,illustration3 ,,the ,,time-,,desk4 ,the distribution of ,greenwich time over the island in this way is thus a simple matter4 ,the far more important one of the distribution of ,greenwich time to ships at sea is more difficult4 ,the difficulty lay in the construction of a clock or watch1 the rate of which would not be altered by the uneasy motion of a ship1 or by the changes of temperature which are inevitable on a voyage4 ,two hundred years ago it was not deemed possible to construct a watch of anything like sufficient accuracy4 ,they would not even keep going whilst they were being wound1 and would lose or gain as much as a minute in the day for a fall or rise of #aj in temperature4 ,this was owing to the extreme sensitiveness of the balance spring--which takes the place in a watch of a pendulum in a clock--to the effects of temperature4 ,the ,british ,government1 therefore1 in #agad offered a prize of the amount of #bj1jjj for a means of finding the longitude at sea within half a degree1 or1 in other words1 for a watch that would keep ,greenwich time correct to two minutes in a voyage across the ,atlantic4 ,in #agce1 ,james ,harrison1 the son of a ,yorkshire carpenter1 succeeded in solving the problem4 ,his method was to attach a sort of automatic regulator to the spring which should push the regulator over in one direction as the temperature rose1 and bring it back as it fell4 ,this he effected by fastening together two strips of brass and steel4 ,the brass expanded with heat more rapidly than the steel1 and hence with a rise of temperature the strip bent over on the steel side4 ,this was the first germ of the idea of making watches 'compensated for temperature2' watches1 that is1 which maintain practically the same rate whether they are in heat or cold1 an idea now brought to great perfection in the modern chronometer4 ,illustration3 ,,harrison',s ,,chronometer4 ,the great reward the ,government had offered stimulated many men to endeavour to solve the problem4 ,of these1 ,dr4 ,halley1 the second ,astronomer ,royal1 and ,graham1 the inventor of the astronomical clock1 were the most celebrated4 ,but when ,harrison1 then poor and unknown1 came to ,london in #agce1 and laid his invention before them1 with an utter absence of self-seeking1 and in the true scientific spirit1 they gave him every assistance4 ,harrison's first four time-keepers are still preserved at the ,royal ,observatory4 ,he did not1 however1 receive his reward until a facsimile of the fourth had been made by his apprentice1 ,larcum ,kendall4 ,the latter is preserved at the ,royal ,observatory4 ,there is a ,larcum ,kendall at the ,royal ,institution which is said to have been used by ,captain ,cook4 ,harrison's chronometer was sent on a trial voyage to ,jamaica in #agfa1 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 stipulated4 ,since ,harrison's day the improvement of the chronometer has been carried on almost to perfection1 and now the care and rating of chronometers for the ,royal ,navy is one of the most important duties of the ,observatory4 ,illustration3 ,,the ,,chronometer ,,room4 ,a visitor who should make the attempt to compare a single chronometer with a standard clock would probably feel very disheartened when1 after many minutes of comparison1 he had got out its error to the nearest second1 were he told that it was his duty to compare the entire army here collected1 some five hundred or more1 and to do it not to the second1 but to the nearest tenth of a second4 ,practice and system make1 however1 the impossible easy1 and one assistant will quietly walk round the room calling out the error of each chronometer as he passes it1 as fast as a second assistant seated at the table can enter it at his dictation in the chronometer ledgers4 ,the seconds beat of a clock sympathetic with the solar standard1 rings out loud and clear above the insect-like chatter of the ticking of the hundreds of chronometers1 and wherever the assistant stands1 he has but to lift his eyes to see straight before him1 if not a complete clock-face1 at least a seconds dial moving in exact accordance with the solar standard4 ,the test to which chronometers are subjected is not merely one of rate1 but one of rate under carefully altered conditions4 ,thus they may be tried with the ,,xii pointing in succession to the four points of the compass1 or1 in the case of chronometer watches1 they may be laid flat down on the table or hung from the ring or pendant1 or with the ring right or left1 as it would be likely to be when carried in the waistcoat pocket4 ,but the chief test is the performance of a chronometer when subjected to considerable heat for a long period4 ,this is a matter of great consequence1 since a chronometer travelling from ,england to ,india1 ,australia1 or the ,cape1 would necessarily be subjected to very different conditions of temperature from those to which it would be exposed in ,england4 ,they are therefore kept for eight weeks in a closed stove at a temperature of about #he or #ij4 ,at one time a cold test was also applied1 and ,sir ,george ,airy1 the late ,astronomer ,royal1 in one of his popular lectures1 drew a humorous comparison between the unhappy chronometers thus doomed to trial1 now in heat and now in frost1 and the lost spirits whom ,dante describes as alternately plunged in flame and ice4 ,the cold test has1 however1 been done away with4 ,it is perfectly easy on the modern ship to keep the chronometer comfortably warm even on an ,arctic expedition4 ,the elaborate cold testing applied to ,sir ,george ,nares' chronometers before he started on his polar journey was found to have been practically quite superfluous2 the chronometers were1 if anything1 kept rather too warm4 ,the exposure of the chronometer in the cooling box1 moreover1 was found to be attended with a risk of rusting its springs4 ,illustration3 ,,the ,,chronometer ,,oven4 ,once the determination of the longitude at sea became possible1 it was clearly the next duty to fix with precision the position of the principal places1 cities1 ports1 capes1 islands1 the world over4 ,of all the work done in this department none has ever been done better1 in proportion to the means at command1 than that accomplished by ,captain ,cook in his celebrated three voyages4 ,as has already been pointed out1 it is the extent and thoroughness of the hydrographic surveys of the ,british ,admiralty which have largely contributed to the honour done to ,england by the international selection of the ,english meridian1 and of ,english standard time1 as in principle those for the whole civilized world4 ,the generosity and public spirit therefore which led the second ,astronomer ,royal to help forward and support his rival1 has almost directly led to this great distinction accruing to the ,observatory of which he was the head4 ,three different methods have successively been used in the determination of longitudes of distant places4 ,in each case the problem required was to ascertain the time at the standard place1 say ,greenwich1 at the same time that it was being determined in the ordinary way at the given station4 ,one method of ascertaining ,greenwich time when at a distance from it was1 as stated in ,chapter ,i41 to use the moon1 as it were1 as the hand of a vast clock1 of which the sky was the face and the stars the dial figures4 ,this is the method of 'lunar distances1' the distances of the moon from a certain number of bright stars being given in the ,nautical ,almanac for every three hours of ,greenwich time4 ,as chronometers were brought to a greater point of perfection1 it was found easier and better in many cases to use 'chronometer runs1' that is1 to carry backwards and forwards between the two stations a number of good chronometers1 and by constant comparison and re-comparison to get over the errors which might attach to any one of them4 ,illustration3 ,,the ,,transit ,,pavilion4 7,from a photograph by ,mr4 ,lacey47 ,but of late years another method has proved available4 ,distant nations are now woven together across thousands of miles of ocean by the submarine telegraph4 ,the ,american reads in his morning paper a summary of the debates of the previous night in the ,house of ,commons at ,westminster4 ,the ,londoner watches with interest the scores of the ,english cricket team in ,australia4 ,it is now therefore possible for an astronomer in ,england to record1 should he so desire1 the time of the transit of a star across the wires of his instrument1 not only on his own chronograph1 but upon that of another observatory1 it may be #bjjj miles away4 ,or1 much more conveniently1 each observer may independently determine the error of his own clock1 and then bring his clock into the current1 so that it may send a signal to the chronograph of the other station4 ,in one way or another this work of the determination of geographical longitudes has been an important part of the extra-routine work at ,greenwich1 part of the work which has built up and sustained its claim to define 'longitude nought'2 and many distinguished astronomers1 especially from the leading observatories of the ,continent1 have come here from time to time to obtain more accurately the longitude of their own cities4 ,the traces of their visits may be seen here and there about the ,observatory grounds in flat stones which lie level with the surface1 and bear a name and date like the gravestones in some old country churchyard4 ,these are not1 as one might suppose1 to mark the burial-places of deceased astronomers1 but record the sites where1 on their visits for longitude purposes1 different foreign astronomers have set up their transit instruments4 ,now1 however1 a permanent pier has been erected in the courtyard1 and a neat house--the ,transit ,pavilion--built over it1 so that in all probability no fresh additions will be made to these sepulchral-looking little monuments4 ,it might be asked1 ,what reason is there for a foreign observer to come over to ,england for such a purpose8 ,would it not be sufficient for the clock signals to be exchanged8 ,but a curious little fact has come out with the increase of accuracy of transit observation1 and that is1 that each observer has his own particular habit or method of observation4 ,a hundred years ago1 ,maskelyne1 the fifth ,astronomer ,royal1 was greatly disturbed to find that his assistant1 ,david ,kinnebrook1 constantly and regularly observed a star-transit a little later than he did himself4 ,the offender was scolded1 warned1 exhorted1 and finally1 when all proved useless to bring his observations into exact agreement with the ,astronomer ,royal's1 dismissed as an incompetent observer4 ,as a matter of fact1 poor ,kinnebrook has a right to be regarded as one of the martyrs of science1 and ,maskelyne1 by this most natural but mistaken judgment1 missed the chance of making an important discovery1 which was not made until some thirty years later4 ,astronomers now would be more cautious of concluding that observations were bad simply because they differed from what had been expected4 ,they have learnt by experience that these unexpected differences are the most likely hunting-ground in which to look for new discoveries4 ,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 chronograph1 he has to perceive with his eye that the star has reached the wire1 he has to mentally recognize the fact1 and consciously or unconsciously to exert the effort of will necessary to bring his finger down on the button4 ,a very slight knowledge of character will show that this will require different periods of time for different people4 ,it will be but a fraction of a second in any case1 but there will be a distinct difference1 a constant difference1 between the eager1 quick1 impulsive man who habitually anticipates1 as it were1 the instant when he sees star and wire together1 and the phlegmatic1 slow-and-sure man who carefully waits till he is quite sure that the contact has taken place1 and then deliberately and firmly records it4 ,these differences are so truly personal to the observer that it is quite possible to correct for them1 and after a given observer's habit has become known1 to reduce his transit times to those of some standard observer4 ,it must1 of course1 be remembered that this 'personal equation' is an exceedingly minute quantity1 and in most cases is rather a question of hundredths of seconds than of tenths4 ,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 ,department1 the most important of all the departments of the ,observatory4 ,the daily observation of sun and of many stars--selected from a carefully chosen list of some hundreds1 and known as 'clock stars'--the determination of the error of the standard clock to the hundredth of a second if possible1 and its correction twice a day1 the sending out of time signals to the ,general ,post ,office and other places1 whence they are distributed all over the country2 the care1 winding1 and rating of hundreds of chronometers and chronometer watches1 and from time to time the determination of the longitude of foreign or colonial cities1 make up a heavy1 ceaseless routine in which there is little opportunity for the realization of an astronomer's life as it is apt to be popularly conceived4 ,yet there is interest enough in the work4 ,there is the charm which always attaches to work of precision1 the delight of using delicate and exact instruments1 and of obtaining results of steadily increasing perfection4 ,it may be akin to the sporting passion for record-breaking1 but surely it is a noble form of it which has led the assistants1 in recent years1 to steadily increase the number of observations in a normal night's work up to the very limit1 taking care the while that their accuracy has in no degree suffered4 ,in longitude work also 'the better is the enemy of the good1' and there is the ambition that each fresh determination shall be markedly more precise than all that have preceded it4 ,the constant care of chronometers soon reveals a kind of individuality in them which forms a fresh source of interest1 whilst if a man has but a spark of imagination1 how easily he will wrap them round with a halo of romance6 ,glance through the ledgers1 and you will see how some of them have heard the guns at the siege of ,alexandria1 others have been carried far into the frozen north1 others have wandered with ,livingstone or ,cameron in the trackless forests of equatorial ,africa4 ,more striking still are those pages across which the closing line has been drawn2 never again will the time-keeper there scheduled return to the kindly inquisition of ,flamsteed ,hill4 ,this sailed away in the ,wasp1 and was swallowed up in the eastern typhoon2 that went down in the sudden squall that smote the ,eurydice off the ,isle of ,wight2 these foundered with the ,captain4 ,the last fatal journey of ,sir ,john ,franklin to find the ,north-,west ,passage leaves its record here2 the chronometers of the ,erebus and ,terror will never again appear on the ,greenwich muster roll4 ,land exploration claims its victims too4 ,sturt's ill-fated expedition across ,australia1 and ,livingstone's last wandering1 are represented4 ,illustration3 ',,lost ,,in ,,the ,,birkenhead4' ,sometimes an amusing entry interrupts the silent pathos of these closed pages4 ',lost by ,mr4 ,smith on the coast of ,africa1' reads at first sight like a rather thin attempt of some one to shift the responsibility of his own carelessness on to the broad shoulders of ,mr4 ,nobody4 ,in reality it probably gives a hint of the necessary1 dangerous1 and exciting work of slave-dhow chasing which gives employment to our ships on the ,african coast4 ',mr4 ,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 estuary4 ,probably the dhow was found1 and the ,arabs who manned it gave so stout a resistance that ',mr4 ,smith' and his men had other things to do than take care of chronometers before they could overcome them4 ,we may take it that the real story outlined here was one of courage and hard fighting1 not of carelessness and shirking4 ,stories of higher valour and nobler courage yet are also hinted3 the calm discipline of the crew of the ,victoria as she sank from the ram of the ,camperdown1 the yet nobler devotion of the men of the ,birkenhead1 as they formed up in line on deck and cheered the boats that bore away the women and children to safety1 whilst they themselves went down with the ship into the shark-crowded sea4 ',there rose no murmur from the ranks1 no thought ,by shameful strength1 unhonoured life to seek2 ,our post to quit we were not trained1 nor taught ,to trample down the weak4 ',what followed1 why recall8 ,the brave who died ,died without flinching in that bloody surf4 ,they sleep as well beneath that purple tide ,as others under turf4' ,,chapter ,,vii ,,the ,,transit ,,and ,,circle ,,departments ,the determination of time is a duty the importance of which readily commends itself to the general public4 ,it is easy to see that in any civilized country it is very necessary to have an accurate standard of time4 ,our railways and telegraphs make it quite impossible for us to be content with the rough-and-ready sun-dial which satisfied our forefathers4 ,but it should be remembered that it was neither to establish a 'longitude nought1' nor to create a system of standard time1 that ,greenwich ,observatory was founded in #afge4 ,it was for ',the ,rectifying the ,tables of the ,motions of the ,heavens and the ,places of the ,fixed ,stars1 in order to find out the so-much-desired ,longitude at ,sea for the perfecting the ,art of ,navigation4' ,the two related departments1 therefore1 those of the ,transit and the ,circle1 which are concerned in the work of making star-catalogues1 come next in order to the ,time ,department4 ,though both departments deal with the same instrument1 the transit circle1 they are at present placed at opposite ends of the ,observatory domain2 the ,circle ,department being lodged in the upper computing room of the old building2 the ,transit ,department in the south wing of the ,new ,observatory in the south ground4 ,it may be asked why1 if this were the purpose of the ,observatory at its foundation1 two and a quarter centuries ago2 if1 as was the case1 the work was set on foot from the beginning and was carried out with every possible care1 how comes it that it is still the fundamental work of the ,observatory1 and1 instead of being completed1 has assumed greater proportions at the present day than ever before8 ,the answer to this inquiry may be found in a special application of the old proverb1 originally directed against the discontent of man3 ',the more he has1 the more he wants4' ,for1 however paradoxical it may seem1 it is true that the fuller a star-catalogue is1 and the more accurate the places of the stars that it contains1 the greater is the need for a yet fuller catalogue1 with places more accurate still4 ,it is worth while following up this paradox in some detail1 as it affords a very instructive example of the way in which a work started on purely utilitarian grounds extends itself till it crosses the undefined boundary and enters the region of pure science4 ,we have no idea who made the earliest census of the sky4 ,it is written for us in no book2 it is not even engraved on any monument4 ,and yet no small portion of it is in our hands to-day1 and1 strangest of all1 we are able to fix fairly closely the time at which it was made1 and the latitude in which its compiler lived4 ,the catalogue is very unlike our star-catalogues of to-day4 ,the places of the stars are very roughly indicated2 and yet this catalogue has left a more enduring mark than all those that have succeeded it4 ,the catalogue simply consists of the star names4 ,an old lady who had attended a ,university ,extension lecture on astronomy was heard to exclaim3 ',what wonderful men these astronomers are6 ,i can understand how they can find out how far off the stars are1 how big they are1 and what they weigh--that is all easy enough2 and ,i think ,i can see how they find out what they are made of4 ,but there is one thing that ,i can't understand--,i don't know how they can find out what are their names6' ,this same difficulty1 though with a much deeper meaning than the old lady in her simplicity was able to grasp1 has occurred to many students of astronomy4 ,many have wished to know what was the meaning of1 and whence were derived1 the sonorous names which are found attached to all the brighter stars on our celestial globes3 ,adhara1 ,alderamin1 ,betelgeuse1 ,denebola1 ,schedar1 ,zubeneschamal1 and many more4 ,the explanation lies here4 ,some #ejjj years ago1 a man1 or college of men1 living in latitude #dj north1 in order that they might better remember the stars1 associated certain groups of them with certain fancied figures1 and the individual star names are simply ,arabic words designed to indicate whereabouts in its peculiar figure or constellation that special star was situated4 ,thus ,adhara means 'back1' and is the name of the bright star in the back of the great ,dog4 ,alderamin means 'right arm1' and is the brightest star in the right arm of ,cepheus1 the king4 ,betelgeuse is 'giant's shoulder1' the giant being ,orion2 ,denebola is 'lion's tail4' ,schedar is the star on the 'breast' of ,cassiopeia1 and ,zubeneschamal is 'northern claw1' that is1 of the ,scorpion4 ,so far is clear enough4 ,the names of the stars for the most part explain themselves2 but whence the constellations derived their names1 how it was that so many snakes and fishes and centaurs were pictured out in the sky1 is a much more difficult problem1 and one which does not concern us here4 ,one point1 however1 these old constellations do tell us1 and tell us plainly4 ,they show that the axis of the earth1 which1 as the earth travels round the sun1 moves parallel with itself1 yet1 in the course of ages1 itself rotates so as in a period of some #bf1jjj years to trace out a circle amongst the stars4 ,this is the cause of what is called 'precession1' and explains how it is that the star we call the pole-star to-day was not always the pole-star1 nor will always remain so4 ,we learn this fact from the circumstance that the old constellations do not cover the entire celestial sphere4 ,they leave a great circular space of #dj radius unmapped in the southern heavens4 ,this simply means that the originators of the constellations lived in #dj north latitude1 and stars within #dj of their south pole never rose above their horizon1 and consequently were never seen1 and could not be mapped1 by them4 ,in like manner1 the star census taken at ,greenwich ,observatory does not include the whole sky1 but leaves a space some #eb in radius round our south pole4 ,since the latitude of ,greenwich is nearly #eb north1 stars within that distance of the south pole do not rise above our horizon1 and are never seen here4 ,but if we compare the vacant space left by the old original constellations with the vacant space left by a ,greenwich catalogue of to-day1 we see that the centre of the first space1 which must have been the south pole of that time1 is a long way from the centre of the second space--our south pole of to-day4 ,the difference tells us how far the pole has moved since those old forgotten astronomers did their work4 ,we know the rate at which the pole appears to move1 by comparing our more modern catalogues one with another2 and so we are able to fix pretty nearly the time when lived those old first census-takers of the stars1 whose names have perished so completely1 but whose work has proved so immortal4 ,these old workers gave us the constellation groupings and names which still remain to us1 and are still in common1 every-day use4 ,their work affords us the most striking illustration of the result of precession1 but precession itself was not recognized till nearly #cjjj years after their day1 when a marvellous genius1 ,hipparchus1 established the fact1 and 'built himself an everlasting name' by the creation of a catalogue of over #ajjj stars prepared on modern principles4 ,that catalogue formed the basis of one which survives to us at the present time1 and was made some #agej years ago by ,claudius ,ptolemy1 the great astronomer of ,alexandria1 whose work1 which still bears the proud name of ,almagest1 ',the ,greatest1' remained for fourteen centuries the one universal astronomical text-book4 ,a modern catalogue contains1 like that of ,ptolemy1 four columns of entry4 ,the first gives the star's designation2 the second an indication of its brightness2 the third and fourth the determinations of its place4 ,these are expressed in two directions1 which1 in modern catalogues1 not in ,ptolemy's1 correspond on the celestial sphere to longitude and latitude on the terrestrial4 ,distance north or south of the celestial equator is termed 'declination1' corresponding to terrestrial latitude4 ,distance in a direction parallel to the equator is termed 'right ascension1' corresponding to terrestrial longitude4 ,for geographical purposes we conceive the earth to be encircled by two imaginary lines at right angles to each other--the one1 the equator1 marked out for us by the earth itself2 the other1 'longitude nought1' the meridian of ,greenwich1 fixed for us by general consent1 after the lapse of centuries1 by a kind of historical evolution4 ,on the celestial globe in like manner we have two fundamental lines--one1 the celestial equator1 marked out for us by nature2 the other at right angles to it1 and passing through the poles of the sky1 adopted as a matter of convenience4 ,but a difficulty at once confronts us--,where can we fix our 'right ascension nought'8 ,what star has the right to be considered the ,greenwich of the sky8 ,the difficulty is met in the following manner3 ,for six months of the year1 the summer months1 the sun is north of the celestial equator2 for the other six months of the year1 the months of winter1 it is south of it4 ,it crosses the equator1 therefore1 twice in the year--once when moving northward at the spring equinox2 once when moving southward at the equinox of autumn4 ,the point where it crosses the equator at the first of these times is taken as the fundamental point of the heavens1 and the first sign of the zodiac1 ,aries the ,ram1 is said to begin here1 and it is called1 therefore1 'the first point of ,aries4' ,one of the very first facts noticed in the very early days of astronomy was that1 as the stars seemed to move across the sky night by night1 they seemed to move in one solid piece1 as if they were lamps rigidly fixed in one and the same solid vault4 ,of course it has long been perfectly understood that this apparent movement was not in the least due to any motion of the stars1 but simply to the rotation of the earth on its axis4 ,this rotation is the smoothest1 most constant1 and regular movement of which we know4 ,it follows1 therefore1 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 same4 ,this interval of time is simply the difference of their right ascension4 ,if we are able1 then1 to turn our transit instrument to the sun1 and to a number of stars1 each in its proper turn1 and by pressing the tapping-piece on the instrument as the sun or star comes up to each of the ten wires in succession1 to record the times of its transit on the chronograph1 we shall have practically determined their right ascensions--one of the two elements of their places4 ,the other element1 that of declination1 is found in a different manner4 ,the celestial equator1 like the terrestrial1 is #ij from the pole4 ,the bright star ,polaris is not exactly at the north pole1 but describes a small circle round it4 ,twice in the twenty-four hours it transits across the meridian--once when going from east to west it passes above the pole1 once when going from west to east below the pole4 ,the mean between these two altitudes of ,polaris above the horizon gives the position of the true pole4 ,illustration3 ,,the ,,transit ,,circle4 ,a complete transit observation of a star consists therefore of two operations4 ,the observer1 as we have already described1 sees a star entering the field of the telescope1 and as it swims forward1 he presses the galvanic button1 which sends a signal to the chronograph as the star comes up to each of the ten vertical wires in succession4 ,but1 beside the ten wires1 there are others4 ,two vertical wires lie outside the ten of which we have already spoken1 and there is also a horizontal wire4 ,the latter can be moved by a graduated screw-head just above the eye-piece1 and as the star comes in succession to these two vertical wires1 this horizontal wire is moved by the screw-head1 so as to meet the star at the moment it is crossing the vertical wire1 and the observer presses a second little button1 which records the position of the horizontal wire on a small paper-covered drum4 ,then1 the transit over1 the observer leaves the telescope and comes round to the outside of the west pier4 ,here he finds seven large microscopes1 which pierce the whole thickness of the pier1 and are directed towards the circumference of a large wheel which is rigidly attached to the telescope and revolves with it4 ,this wheel is six feet in diameter1 and has a silver circle upon both faces4 ,each circle is divided extremely carefully into #dcbj divisions--these divisions1 therefore1 being about the one-twentieth of an inch apart4 ,there are1 therefore1 twelve divisions to every degree 7#ab #cfj #dcbj71 and each division equals five minutes of arc4 ,the lowest microscope is the least powerful1 and shows a large part of the circle1 enabling the observer to see at once to what degree and division of a degree the microscope is pointing4 ,the other six microscopes are very carefully placed #fj apart--as equally placed as they possibly can be4 ,these microscopes are all fitted with movable wires--wires moved by a very fine and delicate screw2 the screw-head having divisions upon it so that the exact amount of its movement can be told4 ,each of the six screw-heads will read to the one five-thousandth part of a division of the circle2 in other words1 to the one hundred thousandth part of an inch4 ,using all six microscopes1 and taking their mean1 we are able to read to the one-hundredth of a second of arc4 ,if1 therefore1 the observations could be made with perfect certainty down to the extremest nicety of reading which the instrument supplies1 we should be able to read the declination of a star to this degree of refinement4 ,it may be added that a halfpenny1 at a distance of three miles1 appears to be one second of arc in diameter2 at three hundred miles it would be one-hundredth of a second4 ,it need scarcely be said that we cannot observe with quite such refinement of exactness as this would indicate4 ,nevertheless1 this exactness is one after which the observer is constantly striving1 and tenths1 even hundredths1 of seconds of arc are quantities which the astronomer cannot now neglect4 ,the observer has then to read the heads of all these seven microscopes on the pier side1 and also two positions of the horizontal wire on the screw-head at the eye-piece4 ,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 wires4 ,there are1 therefore1 nine entries to make for one position of a star in declination1 and ten for one position of a star in right ascension4 ,the observer will also have to read the barometer to get the pressure of the air at the time of observation1 and one thermometer inside the transit room1 and another outside1 to get the temperature of the air4 ,in some cases thermometers at different heights in the room are also read4 ,a complete observation of a single star means1 therefore1 the entry of two-and-twenty different numbers4 ,it may be asked1 ,what is the use of reading the barometer and thermometer8 ,the answer to the question can only be given by contradicting a statement made above1 that the true pole lay midway between the position of the telescope when pointing to the pole-star at its upper transit1 and its position when pointing to it at its lower transit4 ,the pole being very high in the heavens in this country1 there are a great number of stars that1 like the pole-star1 cross the meridian twice in the twenty-four hours--once when they pass above the pole1 moving from east to west1 once when they pass below it1 moving from west to east ,as the real distance of a star from the true pole does not alter1 it follows that we ought to get the position of the pole from the mean of the two transits of any of these stars1 and they ought all to exactly agree with each other4 ,but they do not4 ,so1 too1 ,i said that the stars all appeared to move as in a single piece4 ,if1 then1 we constructed an instrument with its axis parallel to the axis of the earth1 and fixed a telescope to it1 pointing to any particular star1 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 equatorial1 that is to say--we ought to find that the star once in the centre of the field would remain there4 ,as a matter of fact1 when the star got near the horizon it would soon be a long way from the centre of the field4 ,sir ,george ,airy1 the seventh ,astronomer ,royal1 makes1 with reference to this very point1 the following remarks3 ',perhaps you may be surprised to hear me say the rule is established as true1 and yet there is a departure from it4 ,this is the way we go on in science1 as in everything else2 we have to make out that something is true1 then we find out under certain circumstances that it is not quite true2 and then we have to consider and find out how the departure can be explained4' ,in this particular case1 the disturbing cause is found in the action of our own atmosphere4 ,the rays of light from the star are bent out of a perfectly straight course as they pass through the various layers of that atmosphere1 layers which necessarily become denser the closer we get to the actual surface of the earth4 ,every celestial body therefore appears to be a little higher in the sky than it really is4 ,this action is most noticeable at the horizon1 where it amounts to about half a degree4 ,as both sun and moon are about half a degree in diameter1 it follows that when they have really just entirely sunk below the horizon they appear to be just entirely above it4 ,it happens1 in consequence1 on rare occasions1 that an eclipse of the moon will take place when both sun and moon are together seen above the horizon4 ,it was a great matter to discover this effect of refraction4 ,it was soon seen that it was not constant1 that it varied with both temperature and pressure4 ,it is1 indeed1 the most troublesome of all the hindrances to exact observation with which the astronomer has to contend2 partly because of its large amount--half a degree1 as has been already said1 in the extreme case--and partly because it is difficult in many cases to determine its exact effect4 ,the double observation with the transit circle gives us1 then1 the place in the sky where the star appeared to be at the moment of observation1 not its true place2 to find that true place we have to calculate how much refraction had displaced the star at the particular height in the sky1 and at the particular temperature and atmospheric pressure at which the observation was made4 ,illustration3 ,,the ,,mural ,,circle4 ,the transit circle is a comparatively recent instrument4 ,in earlier times the two observations of right ascension and declination were entrusted to perfectly separate instruments4 ,the transit instrument was mounted as the transit circle is1 between two solid stone piers1 and moved in precisely the same way4 ,but the great six-foot wheel1 which was made as stiff as it possibly could be1 was mounted on the face of a great stone pier or wall1 from which circumstance it was called the 'mural circle1' and a light telescope was attached to it which turned about its centre4 ,this arrangement had a double disadvantage--that the two observations had to be made separately1 and the mural circle1 not being a symmetrical instrument1 was liable to small errors which it was difficult to detect4 ,thus1 being supported on one side only1 a flexure or bending outwards of either telescope or circle1 or both1 might be feared4 ,it was for this reason that ,pond set up a pair of mural circles1 one on the east side of its supporting pier and the other on the west4#c ,his plan was not only to have each star observed simultaneously in the two instruments1 a plan by which1 at the cost of some additional labour1 he would have got rid1 to a large extent1 of the individual errors of the two separate instruments1 inasmuch as1 on the whole1 it might have been expected that the errors of the two instruments would have been very nearly equal in amount1 but of opposite character4 ,the differences1 too1 between the two instruments would have afforded the means for tracing these small errors to their respective causes1 and so ascertaining the laws to which they were subject4 #c ,the second circle was intended for the ,cape ,observatory1 but ,pond obtained leave to retain it4 ,in #ahea it was transferred to the ,observatory of ,queen's ,college1 ,belfast4 ,pond went further still4 ,he added to the mural circle a simple instrument1 the extreme value of which every astronomer recognizes to-day--the mercury trough4 ,not only was the star to be observed by both circles when the two telescopes were pointing directly to it1 it was also to be observed by reflection2 the telescopes were to be pointed down towards a basin of mercury1 in which the image of the star would be seen reflected4 ,the mercury being a liquid1 its surface is perfectly horizontal2 and1 since the law of reflection is that the angle of incidence is equal to the angle of reflection1 it follows that the telescope1 when pointed down toward the mercury trough1 points just at as great an angle below the horizon as1 when it is set directly on the star1 it points above it4 ,if the circle1 therefore1 be carefully read at both settings1 half the difference between the two readings will give the angular elevation of the star above the horizon4 ,a combination1 therefore1 of all four observations1 that is to say1 one reflection and one direct with each of the telescopes1 would give an exceedingly exact value for the star's altitude4 ,the conception of this method gives a striking idea of ,pond's thoroughness and skill as a practical observer1 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 office4 ,however1 in #ahea1 as already mentioned1 ,airy substituted for the two separate instruments--the transit and mural circle--the transit circle1 which1 unlike the mural circle1 is equally supported on both sides4 ,this1 however1 does not free it from the liability to some minute flexure in the direction of its length1 from the weight of its two ends1 and the mercury trough is used for the detection of such bending1 should it exist4 ,the present practice is to observe a star both by reflection and directly in the course of the same transit4 ,the observer sets the telescope carefully before ever the star comes into the field of view1 and reads his seven microscopes4 ,then he climbs up a narrow wooden staircase and watches the star transit nearly half across the field4 ,then comes a rush1 the observer swings himself down the ladder1 unclamps the telescope1 turns it rapidly up to the star itself1 clamps it again1 flings himself on his back on a bench below the telescope1 and does it so quickly that he is able to observe the star across the second half of the field4 ,there is no time for dawdling1 no room for making any mistakes2 the stars never forgive2 'they haste not1 they rest not2' and if the unfortunate observer is too slow1 or makes some slip in his second setting1 the star1 cold and inexorable1 takes no pity1 and moves regardless on4 ,it will be seen that a considerable amount of work is involved in taking a single observation of a star-place4 ,but in making a star-catalogue it is always deemed necessary to obtain at least three observations of each star2 and many are observed much more frequently4 ,a modern star-catalogue contains1 like ,ptolemy's1 four columns4 ,it contains also several more4 ,of these the principal are devoted to the effect of precession4 ,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 heavens1 it follows that the celestial poles1 and the celestial equator with them are slowly1 but continually1 changing their place with respect to the stars1 and therefore that the declinations of the stars are always undergoing change1 and as the equator changes1 the point where the sun crosses it in spring--the first point of ,aries--changes also1 and with it the stars' right ascensions4 ,to make one determination of a star's place comparable with another made at another time1 it is clear that we must correct for the effects of precession in the interval of time between the two observations1 and for the effects of refraction4 ,but observations made with the transit circle must also be corrected for errors in the instrument itself4 ,the astronomer will see to it that his instrument is made and is set up as perfectly as possible4 ,the pivots on which it turns must be exactly on the same level2 they must point exactly east and west1 and the axis of the telescope must be exactly at right angles to the line joining the pivots in all positions of the instrument4 ,these conditions are very nearly fulfilled1 but never absolutely4 ,day by day1 therefore1 the astronomer has to ascertain just how much his instrument is in error in each of these three matters4 ,were his instrument absolutely without error to-day1 he could not assume that it would remain so1 nor1 if he had measured the amount of its errors yesterday1 would it be safe to assume that those errors would not change to-day4 ,in the examination of these sources of error the mercury trough comes again into use4 ,the transit circle is turned directly downwards1 and the mercury trough brought below it4 ,a light is so arranged as to illuminate the field of the telescope1 and the observer1 looking in1 sees the ten transit wires and the one declination wire1 and also sees their images reflected from the surface of the mercury4 ,if the telescope be pointing exactly down towards the surface of the mercury1 then the image of the declination wire will fall exactly on the declination wire itself1 and by reading the circle we can tell where the zenith point of the circle is4 ,similarly1 if the pivots of the telescope are precisely on the same level1 the centre wire of the right ascension series would coincide with its reflected image4 ,a third point is determined by looking through the eye-piece of the north collimator telescope--that is to say1 the telescope mounted in a horizontal position at the north end of the room--at the spider lines in the focus of the south collimator4 ,in order to get this view1 the transit telescope has either to be lifted up out of its usual position1 or else the middle of the tube has to be opened4 ,the spider lines in the north collimator are then made to coincide with the image of the wires of the south collimator4 ,the transit telescope is then turned first to one collimator1 then to the other1 and the central wire of the right ascension series is turned till it coincides with the wire of the collimator2 the amount by which it has to be moved giving an index of the error of collimation2 that is to say1 of the deviation of the optical axis of the telescope from perpendicularity to the line joining the pivots4 ,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 afterwards1 before it is available for use4 ,but ,i have only mentioned some of the reductions and corrections which have to be made4 ,there are several more1 and it is a just pride of ,greenwich that her third ruler1 ,bradley1 as has been already told in the notice of his life1 discovered two of the most important4 ,the one1 aberration1 is due to the fact that light1 though it moves so swiftly--#ahf1jjj miles per second--yet does not move with an infinitely greater velocity than that of the earth4 ,the other1 nutation1 might be called a correction to precession1 inasmuch as1 moved by the moon's attraction1 the earth's axis does not swing round smoothly1 but with a slight nodding or staggering motion4 ,but when these observations of the places of a star have been made1 and have been properly 'reduced1' even then we do not find an exact correspondence between two different determinations4 ,little differences still remain4 ,some of these are to be accounted for by changes in the actual crust of the earth1 which1 solid and stable as we think it1 is yet always in motion4 ,professor ,milne1 our greatest authority on earth movements1 says1 ',the earth is so elastic that a comparatively small impetus will set it vibrating2 why1 even two hills tip together when there is a heavy load of moisture in the valley between them4 ,and then1 when the moisture evaporates in a hot sun1 they tip away from each other4' ,so there is a perceptible rocking to and fro even of the huge stone piers of a transit circle1 as seasons of rain and drought1 heat and cold1 follow each other4 ,more than that1 the earth is so sensitive to pressure that it was found1 at the ,oxford ,university ,observatory1 that there was a distinct swaying shown by a horizontal pendulum when the whole of a party of seventy-six undergraduates stood on one side of the instrument and close up to it1 from the position it had when the party stood ninety feet away4 ,more wonderful still1 a comparison of the star-places1 obtained at a number of observatories1 including ,greenwich1 has shown that the earth is continually changing her axis of rotation4 ,and so the star-places determined at ,greenwich have shown that the north pole of the earth1 #bfjj miles away1 moves about in an irregular curve about thirty feet in radius4 ,nothing is stable1 nothing is immovable1 nothing is constant4 ,the astronomer even finds that his own presence near the instrument is sufficient to disturb it4 ,the great interest attaching to transit-circle work is this striving after ever greater and greater precision1 with the result of bringing out fresh little discordances1 which1 at first sight1 appear purely accidental1 but which1 under further scrutiny1 show themselves to be subject to some law4 ,then comes the hunt for this new unknown law4 ,its discovery follows4 ,it explains much1 but when it is allowed for1 though the observations now come much closer together1 little deviations still remain1 to form the subject of a fresh inquiry4 ,astronomy has well been called the exact science1 and yet exactitude ever eludes its pursuer4 ,if it be asked1 ',what is the use of this ever-increasing refinement of observation8' no better answer can be given than the words of ,sir ,john ,herschel in one of his ,presidential addresses to the ,royal ,astronomical ,society3-- ',if we ask to what end magnificent establishments are maintained by ,states and sovereigns1 furnished with masterpieces of art1 and placed under the direction of men of first-rate talent and high-minded enthusiasm1 sought out for those qualities among the foremost in the ranks of science1 if we demand1 cui bono8 for what good a ,bradley has toiled1 or a ,maskelyne or a ,piazzi has worn out his venerable age in watching8--the answer is1 ,not to settle mere speculative points in the doctrine of the universe2 not to cater for the pride of man by refined inquiries into the remoter mysteries of nature2 not to trace the path of our system through space1 or its history through past and future eternities4 ,these1 indeed1 are noble ends1 and which ,i am far from any thought of depreciating2 the mind swells in their contemplation1 and attains in their pursuit an expansion and a hardihood which fit it for the boldest enterprise4 ,but the direct practical utility of such labours is fully worthy of their speculative grandeur4 ,the stars are the landmarks of the universe2 and1 amidst the endless and complicated fluctuations of our system1 seem placed by its ,creator as guides and records1 not merely to elevate our minds by the contemplation of what is vast1 but to teach us to direct our actions by reference to what is immutable in ,his works4 ,it is1 indeed1 hardly possible to over-appreciate their value in this point of view4 ,every well-determined star1 from the moment its place is registered1 becomes to the astronomer1 the geographer1 the navigator1 the surveyor1 a point of departure which can never deceive or fail him1 the same for ever and in all places2 of a delicacy so extreme as to be a test for every instrument yet invented by man1 yet equally adapted for the most ordinary purposes2 as available for regulating a town clock as for conducting a navy to the ,indies2 as effective for mapping down the intricacies of a petty barony as for adjusting the boundaries of ,transatlantic empires4 ,when once its place has been thoroughly ascertained and carefully recorded1 the brazen circle with which that useful work was done may moulder1 the marble pillar may totter on its base1 and the astronomer himself survive only in the gratitude of posterity2 but the record remains1 and transfuses all its own exactness into every determination which takes it for a groundwork1 giving to inferior instruments--nay1 even to temporary contrivances1 and to the observations of a few weeks or days--all the precision attained originally at the cost of so much time1 labour1 and expense4' ,but for these strictly utilitarian purposes a comparatively small number of stars would meet our every requisite4 ,in the narrow sense of which ,sir ,john ,herschel is here speaking1 we have no use for anything beyond the smallest of catalogues2 and if the question before us is1 ',why are we continually extending our catalogues8' the following words of a more recent writer#d on the subject will set forth the real explanation3-- ',a word in conclusion1 suggested by the history of star-catalogues4 ,we have no difficulty in understanding that it is necessary to study the planets1 and a reasonable number of the brighter stars1 for the purpose of determining the figure of the earth1 and the positions of points upon its surface2 but the use for a catalogue of ten thousand stars1 such as ,la ,caille compiled1 is not just so apparent4 ,nay1 what did ,ptolemy want with a thousand stars1 or ,tamerlane's grandson1 born1 reared1 and destined to die amidst a horde of savages1 however splendid in their trappings8 ,there is not1 and there never was1 any real1 practical use for the great volumes of star-catalogues that weigh down the shelves of our libraries4 ,the navigator and explorer need never see them at all4 ,why1 then1 were these pages compiled8 ,why have astronomers1 from ,hipparchus's time to the present1 spent their lives in the weary routine-work of observing the places of tiny points in the stellar depths8 ,does it not seem that there is something in the mind of man that impels him to seek after knowledge--truly--for its own sake8 something heaven-born1 heaven-nurtured1 ,god-given 444 that there is something in man common to him and his ,creator1 and therefore eternal 444 in beautiful accord with the plain statement that ,god made man in ,his own image8' #d ,mr4 ,thomas ,lindsay1 ,transactions of the ,astronomical and ,physical ,society of ,toronto1 #ahii1 p4 #ag4 ,,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 him4 ,the other half1 equally necessary for the solution of the problem of the longitude at sea1 was the ',rectifying the ,tables of the ,motions of the ,heavens4' ,this second duty was not less necessary than the other1 for1 if we may again use the old simile of the clock-face1 the fixed stars may be taken to represent the figures on the vast dial of the sky1 whilst the moon1 as it moves amongst them1 corresponds to the moving hand of the timepiece4 ,to know the places of the stars1 then1 without being able to predict the place of the moon1 would be much like having a clock without its hands4 ,but if not less necessary1 it was certainly more difficult4 ,the secret of the movements of the moon and planets had not then been grasped1 and the only tables which had been calculated were based upon observations made before the days of telescopes4 ,it is one of the most fortunate and remarkable coincidences in the whole history of science1 that at the very time that ,greenwich ,observatory was being called into existence1 the greatest of all astronomers was working out his demonstration of the great fundamental 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 distance4 ,several other of the great minds of that time1 in particular ,dr4 ,hooke1 the ,gresham ,professor of ,astronomy1 had seen that it was possible that some such law might supply the secret of planetary motion2 but it is one thing to make a suggestion1 and a very different matter indeed to be able to demonstrate it2 and the latter was in ,newton's power alone4 ,he did much more than demonstrate it--he brought out a whole series of most important and far-reaching consequences4 ,he showed that the ebb and flow of the tides was due to the attraction of both sun and moon1 especially the latter1 upon the waters of our oceans4 ,he pointed out certain irregularities which must take place in the motion of our moon1 due to the influence of the sun upon it4 ,he showed1 too1 what was the cause of that swinging of the axis of the earth which gives rise to precession4 ,he deduced the relative weights of the earth1 the sun1 and of ,jupiter and ,saturn1 the planets with satellites4 ,he proved also that comets1 which had seemed hitherto to men as perfectly lawless wanderers1 obeyed in their orbits the self-same law which governed the moon and planets4 ,the whole vast system of celestial movements1 which had long seemed to men irregular and uncontrolled1 now fell1 every one of them1 into its place1 as but the necessary manifestations of one grand1 simple order4 ,this great discovery gave a new and additional importance to the regular observation of the moon and planets4 ,they were needed now1 not only to assist in the practical work of navigation1 but for the development of questions of pure science4 ,halley1 the second ,astronomer ,royal1 and ,maskelyne1 the fifth1 devoted themselves chiefly to this department of work1 to the partial neglect of the observation of the places of stars4 ,airy1 the seventh1 whilst making catalogue-work a part of the regular routine of the ,observatory1 developed the observation of the members of the solar system1 and especially of the moon1 in a most marked degree1 and collected and completely reduced the vast mass of material which the industry of his predecessors had gathered4 ,it is pre-eminently of the work of ,airy that the memorable words quoted before of ,professor ,newcomb1 the great ,american mathematician and astronomer1 are applicable3 'that if this branch of astronomy were entirely lost1 it could be reconstructed from the ,greenwich observations alone4' ,a most important step taken by ,airy was the construction of an altazimuth4 ,an altazimuth is practically a theodolite on a large scale4 ,its purpose is to determine1 not the declination and right ascension of some celestial body1 as is the case with the transit circle1 but its altitude1 i4e4 its height above the horizon1 and its azimuth1 i4e4 the angle measured on the horizontal plane from the north point4 ,the altazimuth1 then1 like the transit circle1 consists of a telescope revolving on a horizontal axis1 but1 unlike the transit circle1 both the telescope and the piers which carry its pivots can be rotated so as to point not merely due north and south1 but in any direction whatsoever4 ,illustration3 ,,airy',s ,,altazimuth4 ,the observations with the altazimuth are rather more complicated than those with the transit circle4 ,looking in the telescope1 the observer sees a double set of spider threads or 'wires'2 and when a star or other heavenly body enters the field1 it will generally be observed to move obliquely across both sets of wires4 ,the observer usually determines to make an observation either in altitude or azimuth4 ,in the former case he presses the little contact button1 which1 as in the transit circle1 is provided close to the eyepiece1 as the star reaches each of the horizontal wires in succession4 ,if in azimuth1 it is the times of crossing the vertical wires that are in like manner telegraphed to the chronograph4 ,the transit over1 the appropriate circle is read2 for the telescope itself is rigidly attached to a vertical wheel having a carefully engraved circle on its face and read by four microscopes1 whilst the entire instrument carries another set of microscopes1 pointing to a fixed horizontal circle1 and upon which the azimuth can be read4 ,a complete observation involves four such transits and sets of circle readings1 two of altitude1 and two of azimuth2 for after one of altitude and one of azimuth the telescope is turned round1 and a second observation is taken in each element4 ,the observation gives us the altitude and azimuth of the star4 ,these particulars are of no direct value to us4 ,but it is a mere matter of computation1 though a long and laborious one1 to convert these elements into right ascension and declination4 ,the usefulness of the altazimuth will be seen at once4 ,it will be remembered that with the transit circle any particular object can only be observed as it crosses the meridian4 ,if the weather should be cloudy1 or the observer late1 the chance of observation is lost for four and twenty hours1 and in the case of the moon1 for which the altazimuth is specially used1 it is on the meridian only in broad daylight during that part of the month which immediately precedes and follows new moon4 ,at such times it is practically impossible to observe it with the transit circle2 with the altazimuth it may be caught in the twilight before sunrise or after sunset2 and at other times in the month1 if lost on the meridian in the transit circle1 the altazimuth still gives the observer a chance of catching it any time before it sets4 ,but for this instrument1 our observations of the moon would have been practically impossible over at least one-fourth of its orbit4 ,airy's altazimuth was but a small instrument of three and three-quarter inches aperture1 mounted in a high tower built on the site of ,flamsteed's mural arc2 and1 after a life history of about half a century1 has been succeeded by a far more powerful instrument4 ,the ',new ,altazimuth' has an aperture of eight inches1 and is housed in a very solidly constructed building of striking appearance1 the connection of the ,observatory with navigation being suggested by a row of circular lights which strongly recall a ship's portholes4 ,this building is at the southern end of the narrow passage1 'the wasp's waist1' which connects the older ,observatory domain with the newer4 ,it is the first building we come to in the south ground4 ,the computations of the department are carried on in the south wing of the new ,observatory4 ,it will be seen from the photograph that the instrument is much larger1 heavier1 and less easy to move in azimuth than the old altazimuth4 ,it is1 therefore1 not often moved in azimuth1 but is set in some particular direction1 not necessarily north and south1 in which it is used practically as a transit circle4 ,illustration3 ,,new ,,altazimuth ,,building4 ,there is quite another way of determining the place of the moon1 which is sometimes available1 and which offers one of the prettiest of observations to the astronomer4 ,as the moon travels across the sky1 moving amongst the stars from west to east1 it necessarily passes in front of some of them1 and hides them from us for a time4 ,such a passage1 or 'occultation1' offers two observations3 the 'disappearance1' as the moon comes up to the star and covers it2 the 'reappearance1' as it leaves it again1 and so discloses it4 ,illustration3 ,,the ,,new ,,altazimuth4 7,from a photograph by ,mr4 ,lacey47 ,except at the exact time of full moon1 we do not see the entire face of our satellite2 one edge or 'limb' is in darkness4 ,as the moon therefore passes over the star1 either the limb at which the star disappears1 or that at which it reappears1 is invisible to us4 ,to watch an occultation at the bright limb is pretty2 the moon1 with its shining craters and black hollows1 its mountain ranges in bright relief1 like a model in frosted silver1 slowly1 surely1 inevitably comes nearer and nearer to the little brilliant which it is going to eclipse4 ,the movement is most regular1 most smooth1 yet not rapid4 ,the observer glances at his clock1 and marks the minute as the two heavenly bodies come closer and closer to each other4 ,then he counts the clock beats3 'five1 six1 seven1' it may be1 as the star has been all but reached by the advancing moon4 ',eight1' it is still clear2 ere the beat of the clock rings to the 'nine1' perhaps the little diamond point has been touched by the wide arch of the moon's limb1 and has gone6 ,less easy to exactly time is a reappearance at the bright limb4 ,in this case the observer must ascertain from the ,nautical ,almanac precisely where the star will reappear2 then a little before the predicted time he takes his place at the telescope1 watches intently the moon's circumference at the point indicated1 and1 listening for the clock-beats1 counts the seconds as they fly4 ,suddenly1 without warning1 a pin-point of light flashes out at the edge of the moon1 and at once draws away from it4 ,the star has 'reappeared4' ,far more striking is a disappearance or reappearance at the 'dark limb4' ,in this case the limb of the moon is absolutely invisible1 and it may be that no part of the moon is visible in the field of the telescope4 ,in this case the observer sees a star shining brightly and alone in the middle of the field of his telescope4 ,he takes the time from his faithful clock1 counting beat after beat1 when suddenly the star is gone6 ,so sudden is the disappearance that the novice feels almost as astonished as if he had received a slap in the face1 and not unfrequently he loses all count or recollection of the clock beats4 ,the reappearance at the dark limb is quite as startling2 with a bright star it is almost as if a shell had burst in his very face1 and it would require no very great imagination to make him think that he had heard the explosion4 ,one moment nothing was visible2 now a great star is shining down serenely on the watcher4 ,a little practice soon enables the observer to accustom himself to these effects1 and an old hand finds no more difficulty in observing an occultation of any kind than in taking a transit4 ,such an observation is useful for more purposes than one4 ,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 was at the time of the observation4 ,then the time which the moon took to pass over the star enables us to calculate the diameter of our satellite2 the different positions of the moon relative to the star1 as seen from different observatories1 enable us to calculate its distance4 ,but if the disappearance takes place at the bright limb1 the reappearance usually takes place at the dark1 and vice vers2 and the two observations are not quite comparable4 ,there is one occasion1 however1 when both observations are made under similar circumstances1 namely1 at the full4 ,and if the moon happens also to be totally eclipsed1 the occultations of quite faint stars can be successfully observed1 much fainter than can ordinarily be seen close up to the moon4 ,total eclipses of the moon1 therefore1 have recently come to be looked upon as important events for the astronomer1 and observatories the world over usually co-operate in watching them4 ,october #d1 #ahhd1 was the first occasion when such an organised observation was made2 there have been several since1 and on these nights every available telescope and observer at ,greenwich is called into action4 ,it may be asked why these different modes of observing the moon are still kept up1 year in and year out4 ',do we not know the moon's orbit sufficiently well1 especially since the discovery of gravitation8' ,no2 we do not4 ,this simple and beautiful law--simple enough in itself1 gives rise to the most amazing complexity of calculation4 ,if the earth and moon were the only two bodies in the universe1 the problem would be a simple one4 ,but the earth1 sun1 and moon are members of a triple system1 each of which is always acting on both of the others4 ,more1 the planets1 too1 have an appreciable influence1 and the net result is a problem so intricate that our very greatest mathematicians have not thoroughly worked it out4 ,our calculations of the moon's motions need1 therefore1 to be continually compared with observation1 need even to be continually corrected by it4 ,there is a further reason for this continual observation1 not only in the case of the sun1 which is our great standard star1 since from it we derive the right ascensions of the stars1 and it is also our great timekeeper2 not only in that of the moon1 but also in the case of the planets4 ,their places as computed need continually to be compared with their places as observed1 and the discordances1 if any1 inquired into4 ,the great triumph which resulted to science from following this course--to pure science1 since ,uranus is too faint a planet to be any help to the sailor in navigation--is well known4 ,the observed movements of ,uranus proved not to be in accord with computation1 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 it1 as ,columbus saw ,america from ,spain4 ,its movements were felt by them trembling along the far-reaching line of their analysis1 with a certainty hardly inferior to that of ocular demonstration4'#e #e ,from ,sir ,john ,herschel's address to the ,british ,association1 ,september #aj1 #ahdf1 thirteen days before ,galle's first observation of the planet4 ,the discovery of ,neptune was not made at ,greenwich1 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 him1 and so allowed the ,french astronomer to engross so much of the honour of the exploit4 ,the controversy has been argued over and over again1 and we may be content to leave it alone here4 ,there is one point1 however1 which is hardly ever mentioned1 which must have had much effect in determining ,airy's conduct4 ,in #ahde1 the year in which ,adams sent his provisional elements of the unseen disturbing planet to ,airy1 the largest telescope available for the search at ,greenwich was an equatorial of only six and three-quarter inches aperture1 provided with small and insufficient circles for determining positions1 and housed in a very small and inconvenient dome2 whilst at ,cambridge1 within a mile or so of ,adams' own college1 was the ',northumberland' equatorial1 of nearly twelve inches aperture1 under the charge of the ,university ,professor of ,astronomy1 ,professor ,challis1 and which was then much the largest1 best mounted and housed equatorial in the entire country4 ,the ',northumberland' had been begun from ,airy's designs and under his own superintendence1 when he was ,professor of ,astronomy at ,cambridge4 ,naturally1 then1 knowing how much superior the ,cambridge telescope was to any which he had under his care1 he thought the search should be made with it4 ,he had no reason to believe that his own instrument was competent for the work4 ,illustration3 ,,the ,,new ,,observatory ,,as ,,seen ,,from ,,flamsteed',s ,,observatory4 ,on the other hand1 it is hard for the ordinary man to understand how it was that ,adams not only left unnoticed and unanswered for three-quarters of a year1 an inquiry of ,airy's with respect to his calculations1 but also never took the trouble to visit ,challis1 whom he knew well1 and who was so near at hand1 to stir him up to the search4 ,but1 in truth1 the whole interest of the matter for ,adams rested in the mathematical problem4 ,the irregularities in the motion of ,uranus were interesting to him simply for the splendid opportunity which they gave him for their analysis4 ,a purely imaginary case would have served his purpose nearly as well4 ,the actuality of the planet which he predicted was of very little moment2 the clat and popular reputation of the discovery was less than nothing2 the problem itself and the mental exercise in its solution1 were what he prized4 ,but it was not creditable to the nation that the ,royal ,observatory should have been so ill-provided with powerful telescopes2 and a few years later ,airy obtained the sanction of the ,government for the erection of an equatorial larger than the ',northumberland1' but on the same general plan and in a much more ample dome4 ,this was for thirty-four years the ',great' or ',south-,east' equatorial1 and the mounting still remains and bears the old name1 though the original telescope has been removed elsewhere4 ,the object-glass had an aperture of twelve and three-quarter inches and a focal length of eighteen feet1 and was made by ,merz of ,munich1 the engineering work by ,ransomes and ,sims of ,ipswich1 and the graduations and general optical work by ,simms1 now of ,charlton1 ,kent4 ,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 7with its counterpoises7 of many times the weight1 one made by ,sir ,howard ,grubb1 of ,dublin1 of twenty-eight inches aperture and twenty-eight feet focal length1 the largest refractor in the ,british ,empire1 though surpassed by several ,american and ,continental instruments4 ,the stability of the mounting was intended to render the telescope suitable for a special work4 ,this was the observation of 'minor planets4' ,on the first day of the present century the first of these little bodies was discovered by ,piazzi at ,palermo4 ,three more were discovered at no great interval afterwards1 and then there was an interval of thirty-eight years without any addition to their number4 ,but from ,december #h1 #ahde1 up to the present time1 the work of picking up fresh individuals of these 'pocket planets' has gone on without interruption1 until now more than #djj are known4 ,most of these are of no interest to us1 but a few come sufficiently near to the earth for their distance to be very accurately determined2 and when the distance of one member of the solar system is determined1 those of all the others can be calculated from the relations which the law of gravitation reveals to us4 ,it is a matter of importance1 therefore1 to continue the work of discovery1 since we may at any time come across an interesting or useful member of the family2 and that we may be able to distinguish between minor planets already discovered and new ones1 their orbits must be determined as they are discovered1 and some sort of watch kept on their movements4 ,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 cause1 has been recently supplied by the discovery of ,eros4 ,on ,august #ac1 #ahih1 ,herr ,witt1 of the ,urania ,observatory1 ,berlin1 discovered a very small planet that was moving much faster in the sky than is common with these small bodies4 ,the great majority are very much farther from the sun than the planet ,mars1 many of them twice as far1 and hence1 since the time of a planet's revolution round the sun increases1 in accordance with ,kepler's law1 more rapidly than does its distance1 it follows that they move much more slowly than ,mars4 ,but this new object was moving at almost the same speed as ,mars2 it must1 therefore1 be most unusually near to us4 ,further observations soon proved that this was the case1 and ,eros1 as the little stranger has been called1 comes nearer to us than any other body of which we are aware except the moon4 ,venus when in transit is #bd-a_/b millions of miles from us1 ,mars at its nearest is #cd-a_/b millions1 ,eros at its nearest approach is but little over #ac millions4 ,the use of such a body to us is1 of course1 quite apart from any purpose of navigation1 except very indirectly4 ,but it promises to be of the greatest value in the solution of a question in which astronomers must always feel an interest1 the determination of the distance of the earth from the sun4 ,we know the relative distances of the different planets1 and1 consequently if we could determine the absolute distance of any one1 we should know the distances of all4 ,as it is practically impossible to measure our distance from the sun directly1 several attempts have been made to determine the distances of ,venus1 ,mars1 or such of the minor planets as come the nearest to us4 ,three of these in particular1 the little planets ,iris1 ,victoria1 and ,sappho1 have given us the most accurate determinations of the sun's distance 7#ib1hgd1jjj miles7 which we have yet obtained2 but ,eros at its nearest approach will be six times as near to us as either of the three mentioned above1 and therefore should give us a value with only one-sixth of the uncertainty attaching to that just mentioned4 ,the discovery of minor planets has lain outside the scope of ,greenwich work1 but their observation has formed an integral part of it4 ,the general public is apt to lay stress rather on the first than on the second1 and to think it rather a reproach to ,greenwich that it has taken no part in such explorations4 ,experience has1 however1 shown that they may be safely left to amateur activity1 whilst the monotonous drudgery of the observation of minor planets can only be properly carried out in a permanent institution4 ,the observation of these minute bodies with the transit circle and altazimuth is attended with some difficulties2 but precise observations of various objects may be made with an equatorial2 indeed1 comets are usually observed by its means4 ,the most ordinary way of observing a comet with an equatorial is as follows3 ,two bars are placed in the eye-piece of the telescope1 at right angles to each other1 and at an angle of forty-five degrees to the direction of the apparent daily motion of the stars4 ,the telescope is turned to the neighbourhood of the comet1 and moved about until it is detected4 ,the telescope is then put a little in front of the comet1 and very firmly fixed4 ,the observer soon sees the comet entering his field1 and by pressing the contact button he telegraphs to the chronograph the time when the comet is exactly bisected by each of the bars successively4 ,he then waits until a bright star1 or it may be two or three1 have entered the telescope and been observed in like manner4 ,the telescope is then unclamped1 and moved forward until it is again ahead of the comet1 and the observations are repeated2 and this is done as often as is thought desirable4 ,the places of the stars have1 of course1 to be found out from catalogues1 or have to be observed with the transit circle1 but when they are known the position of the comet or minor planet can easily be inferred4 ,next to the glory of having been the means of bringing about the publication of ,newton's ,principia1 the greatest achievement of ,halley1 the second ,astronomer ,royal1 was that he was the first to predict the return of a comet4 ,newton had shown that comets were no lawless wanderers1 but were as obedient to gravitation as were the planets themselves1 and he also showed how the orbit of a comet could be determined from observations on three different dates4 ,following these principles1 ,halley computed the orbits of no fewer than twenty-four comets1 and found that three of them1 visible at intervals of about seventy-five years1 pursued practically the same path4 ,he concluded1 therefore1 that these were really different appearances of the same object1 and1 searching old records1 he found reason to believe that it had been observed frequently earlier still4 ,it seems1 in fact1 to have been the comet which is recorded to have been seen in #ajff in ,england at the time of the ,norman invasion2 in ,a4,d4 #ff1 shortly before the commencement of that war which ended in the destruction of ,jerusalem by ,titus2 and earlier still1 so far back as ,b4,c4 #ab4 ,halley1 however1 experienced a difficulty in his investigation4 ,the period of the comet's revolution was not always the same4 ,this1 he concluded1 must be due to the attraction of the planets near which the comet might chance to travel4 ,in the summer of #afha it had passed very close to ,jupiter1 for instance1 and in consequence he expected that instead of returning in ,august #ageg1 seventy-five years after its last appearance1 it would not return until the end of #ageh or the beginning of #agei4 ,it has returned twice since ,halley's day1 a triumphant verification of the law of gravitation2 and we are looking for it now for a third return some ten years hence1 in #aiaj4 ,halley's comet1 therefore1 is an integral member of our solar system1 as much so as the earth or ,neptune1 though it is utterly unlike them in appearance and constitution1 and though its path is so utterly unlike theirs that it approaches the sun nearer than our earth1 and recedes farther than ,neptune4 ,but there are other comets1 which are not permanent members of our system1 but only passing visitors4 ,from the unfathomed depths of space they come1 to those depths they go4 ,they obey the law of gravitation so far as our sight can follow them1 but what happens to them beyond8 ,do they come under some other law1 or1 perchance1 in outermost space is there still a region reserved to primeval ,chaos1 the ',anarch old1' where no law at all prevails8 ,gravitation is the bond of the solar system2 is it also the bond of the ,universe8 ,,chapter ,,ix ,,the ,,magnetic ,,and ,,meteorological ,,departments ,passing out of the south door of the new altazimuth building1 we come to a white cruciform erection1 constructed entirely of wood4 ,this is the ,magnet ,house or ,magnetic ,observatory1 the home of a double ,department1 the ,magnetic and ,meteorological4 ,this department does not1 indeed1 lie within the original purpose of the ,observatory as that was defined in the warrant given to ,flamsteed1 and yet is so intimately connected with it1 through its bearing on navigation1 that there can be no question as to its suitability at ,greenwich4 ,indeed1 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 race1 and of the keen insight with which he watched the new development of science4 ,the ,magnetic ,observatory1 therefore1 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 compasses1 and1 in more recent times1 the use of iron 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 office1 and was sanctioned in #ahcg4 ,the ,meteorological ,department has a double bearing on the purpose of the ,observatory4 ,on the one side1 a knowledge of the temperature and pressure of the atmosphere is1 as we have already seen1 necessary in order to correct astronomical observations for the effect of refraction4 ,on the other hand1 meteorology proper1 the study of the movements of the atmosphere1 the elucidation of the laws which regulate those movements1 leading to accurate forecasts of storms1 are of the very first necessity for the safety of our shipping4 ,it is true that weather forecasts are not issued from ,greenwich ,observatory1 any more than the ,nautical ,almanac is now issued from it2 but just as the ,observatory furnishes the astronomical data upon which the ,almanac is based1 so also it takes its part in furnishing observations to be used by the ,meteorological ,office at ,westminster for its daily predictions4 ,those predictions are often made the subject of much cheap ridicule2 but1 however far short they may fall of the exact and accurate predictions which we would like to have1 yet they mark an enormous advance upon the weather-lore of our immediate forefathers4 ',he that is weather wise ,is seldom other wise1' says the proverb1 and the saying is not without a shrewd amount of truth4 ,for perhaps nowhere can we find a more striking combination of imperfect observation and inconsequent deduction than in the saws which form the stock-in-trade of the ordinary would-be weather prophet4 ,how common it is to find men full of the conviction that the weather must change at the co-called 'changes of the moon1' forgetful that ',if we'd no moon at all-- ,and that may seem strange-- ,we still should have weather ,that's subject to change4' ,they will say1 truly enough1 no doubt1 that they have known the weather to change at 'new' or 'full1' as the case may be1 and they argue that it1 therefore1 must always do so4 ,but1 in fact1 they have only noted a few chance coincidences1 and have let the great number of discordances pass by unnoticed4 ,but observations of this kind seem scientific and respectable compared with those numerous weather proverbs which are based upon the mere jingle of a rhyme1 as ',if the ash is out before the oak1 ,you may expect a thorough soak'-- a proverb which is deftly inverted in some districts by making 'oak' rhyme to 'choke4' ,others1 again1 are based upon a mere childish fancy1 as1 for example1 when the young moon 'lying on her back' is supposed to bode a spell of dry weather1 because it looks like a cup1 and so might be thought of as able to hold the water4 ,during the present reign1 however1 a very different method of weather study has come into action1 and the foundations of a true weather wisdom have been laid4 ,these have been based1 not on fancied analogies or old wives' rhymes1 or a few forechosen coincidences1 but upon observations carried on for long periods of time and over wide areas of country1 and discussed in their entirety without selection and bias4 ,above all1 mathematical analysis has been applied to the motions of the air1 and ideas1 ever gaining in precision and exactness1 have been formulated of the general circulation of the atmosphere4 ,as compared with its sister science1 astronomy1 meteorology appears to be still in a very undeveloped state4 ,there is such a difference between the power of the astronomer to foretell the precise position of sun1 moon1 and planets for years1 even for centuries1 beforehand1 and the failure of the meteorologist to predict the weather for a single season ahead1 that the impression has been widely spread that there is yet no true meteorological science at all4 ,it is forgotten that astronomy offered us1 in the movements of the heavenly bodies1 the very simplest and easiest problem of related motion4 ,yet for how many thousands of years did men watch the planets1 and speculate concerning their motions1 before the labours of ,tycho1 ,kepler1 and ,newton culminated in the revelation of their meaning8 ,for countless generations it was supposed that their movements regulated the lives1 characters1 and private fortunes of individual men2 just as quite recently it was fancied that a new moon falling on a ,saturday1 or two full moons coming within the same calendar month1 brought bad weather6 ,it is still impossible to foresee the course of weather change for long ahead2 but the difference between the modern navigator1 surely and confidently making a 'bee-line' across thousands of miles of ocean to his destination1 and the timid sailor of old1 creeping from point to point of land1 is hardly greater than the contrast between the same two men1 the one watching his barometer1 the other trusting in the old wives' rhymes which afforded him his only indication as to coming storms4 ,it is still impossible to foresee the weather change for long ahead1 but in our own and in many other countries1 especially the ,united ,states1 it has been found possible to predict the weather of the coming four-and-twenty hours with very considerable exactness1 and often to forecast the coming of a great storm several days ahead4 ,this is the chief purpose of the two great observatories of the storm-swept ,indian and ,chinese seas1 ,hong ,kong and ,mauritius2 and the value of the work which they have done in preventing the loss of ships1 and the consequent loss of lives and property1 has been beyond all estimate4 ,the ,royal ,observatory1 ,greenwich1 is a meteorological as well as an astronomical observatory1 but1 as remarked above1 it does not itself issue any weather forecasts4 ,just as the ,greenwich observations of the places of the moon and stars are sent to the ,nautical ,almanac ,office1 for use in the preparation of that ephemeris2 just as the ,greenwich determinations of time are used for the issue of signals to the ,post ,office1 whence they are distributed over the kingdom1 so the ,greenwich observations of weather are sent to the ,meteorological ,office1 there to be combined with similar records from every part of the ,british ,isles1 to form the basis of the daily forecasts which the latter office publishes4 ,to each of these three offices1 therefore1 the ,royal ,observatory1 ,greenwich1 stands in the relation of purveyor4 ,it supplies them with the original observations more or less in reduced and corrected form1 without which they could not carry on most important portions of their work4 ,let it be noted how closely these three several departments1 the ,nautical ,almanac ,office1 the ,time ,department1 and the ,meteorological ,office1 are related to practical navigation4 ,whatever questions of pure science--of knowledge1 that is1 apart from its useful applications--may arise out of the following up of these several inquiries1 yet the first thought1 the first principle of each1 is to render navigation more sure and more safe4 ,the first of all meteorological instruments is the barometer1 which1 under its two chief forms of mercurial and aneroid1 is simply a means of measuring the pressure exerted by the atmosphere4 ,there are two important corrections to which its readings are subject4 ,the first is for the height of the station above the level of the sea2 the second is for the effect of temperature upon the mercury in the barometer itself1 lengthening the column4 ,to overcome these1 the height of the standard barometer at ,greenwich above sea-level has been most carefully ascertained1 and the heights relative to it of the other barometers of the ,observatory1 particularly those in rooms occupied by fundamental telescopes1 have also been determined1 whilst the self-recording barometer is mounted in a basement1 where it is almost completely protected from changes of temperature4 ,next in importance to the barometer as a meteorological instrument comes the thermometer4 ,the great difficulty in the ,observatory use of the thermometer is to secure a perfectly unexceptionable exposure1 so that the thermometer may be in free and perfect contact with the air1 and yet completely sheltered from any direct ray from the sun4 ,this is secured in the great thermometer shed at ,greenwich by a double series of 'louvre' boards1 on the east1 south1 and west sides of the shed1 the north side being open4 ,the shed itself is made a very roomy one1 in order to give access to a greater body of air4 ,a most important use of the thermometer is in the measurement of the amount of moisture in the air4 ,to obtain this1 a pair of thermometers are mounted close together1 the bulb of one being covered by damp muslin1 and the other being freely exposed4 ,if the air is completely saturated with moisture1 no evaporation can take place from the damp muslin1 and consequently the two thermometers will read the same4 ,but if the air be comparatively dry1 more or less evaporation will take place from the wet bulb1 and its temperature will sink to that at which the air would be fully saturated with the moisture which it already contained4 ,for the higher the temperature1 the greater is its power of containing moisture4 ,the difference of the reading of the two thermometers is1 therefore1 an index of humidity4 ,the greater the difference1 the greater the power of absorbing moisture1 or1 in other words1 the dryness of the air4 ,the great shed already alluded to is devoted to these companion thermometers4 ,illustration3 ,,the ,,self-,,registering ,,thermometers4 ,very closely connected with atmospheric pressure1 as shown us by the barometer1 is the study of the direction of winds4 ,if we take a map of the ,british ,isles and the neighbouring countries1 and put down upon them the barometer readings from a great number of observing stations1 and then join together the different places which show the same barometric pressure1 we shall find that these lines of equal pressure--technically called 'isobars'--are apt to run much nearer together in some places than in others4 ,clearly1 where the isobars are close together it means that in a very short distance of country we have a great difference of atmospheric pressure4 ,in this case we are likely to get a very strong wind blowing from the region of high pressure to the region of low pressure1 in order to restore the balance4 ,if1 further1 we had information from these various observing stations of the direction in which the wind was blowing1 we should soon perceive other relationships4 ,for instance1 if we found that the barometer read about the same in a line across the country from east to west1 but that it was higher in the north of the islands than in the south1 we should then have a general set of winds from the east1 and a similar relation would hold good if the barometer were highest in some other quarter2 that is1 the prevailing wind will come from a quarter at right angles to the region of highest barometer1 or1 as it is expressed in what is known as ',buys ,ballot's law1' 'stand with your back to the wind1 and the barometer will be lower on your left hand than on your right4' ,this law holds good for the northern hemisphere generally1 except near to the equator2 in the southern hemisphere the right hand is the side of low barometer4 ,the instruments for wind observation are of two classes3 vanes to show its direction1 and anemometers to show its speed and its pressure4 ,these may be regarded as two different modes in which the strength of the wind manifests itself4 ,pressure anemometers are usually of two forms3 one in which a heavy plate is allowed to swing by its upper edge in a position fronting the wind1 the amount of its deviation from the vertical being measured2 and the other in which the plate is supported by springs1 the degree of compression of the springs being the quantity registered in that case4 ,of the speed anemometers1 the best known form is the ',robinson1' in which four hemispherical cups are carried at the extremities of a couple of cross bars4 ,for the mounting of these wind instruments the old original ,observatory1 known as the ,octagon ,room1 has proved an excellent site1 with its flat roof surmounted by two turrets in the north-east and north-west corners1 and raised some two hundred feet above high-water mark4 ,illustration3 ,,the ,,anemometer ,,room1 ,,north-,,west ,,turret4 ,the two chief remaining instruments are those for measuring the amount of rainfall and of full sunshine4 ,the rain gauge consists essentially of a funnel to collect the rain1 and a graduated glass to measure it4 ,the sunshine recorder usually consists of a large glass globe arranged to throw an image of the sun on a piece of specially prepared paper4 ,this image1 as the sun moves in the sky1 moves along the paper1 charring it as it moves1 and at the end of the day it is easy to see1 from the broken1 burnt trace1 at what hours the sun was shining clear1 and when it was hidden by cloud4 ,an amusing difficulty was encountered in an attempt to set on foot another inquiry4 ,the ,superintendent of the ,meteorological ,department at the time wished to have a measure of the rate at which evaporation took place1 and therefore exposed carefully measured quantities of water in the open air in a shallow vessel4 ,for a few days the record seemed quite satisfactory4 ,then the evaporation showed a sudden increase1 and developed in the most erratic and inexplicable manner1 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 'tub1' and had made use of it accordingly4 ,a large proportion of the meteorological instruments at ,greenwich and other first-class observatories are arranged to be self-recording4 ,it was early felt that it was necessary that the records of the barometer and thermometer should be as nearly as possible continuous2 and at one time1 within the memory of members of the staff still living1 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 monotonous1 trying1 and distasteful of any that the ,observatory had to show4 ,the two-hour record was no doubt practically equivalent to a continuous one1 but it entailed a heavy amount of labour4 ,automatic registers were1 therefore1 introduced whenever they were available4 ,the earliest of these were mechanical1 and several still make their records in this manner4 ,on the roof of the ,octagon ,room we find1 beside the two turrets already referred to1 a small wooden cabin built on a platform several feet above the roof level4 ,this cabin and the north-western turret contain the wind-registering instruments4 ,opening the turret door1 we find ourselves in a tiny room which is nearly filled by a small table4 ,upon this table lies a graduated sheet of paper in a metal frame1 and as we look at it1 we see that a clock set up close to the table is slowly drawing the paper across it4 ,three little pencils rest lightly on the face of the paper at different points4 ,one of these1 and usually the most restless1 is connected with a spindle which comes down into the turret from the roof1 and which is1 in fact1 the spindle of the wind vane4 ,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 clock4 ,a second pencil is connected with the wind-pressure anemometer4 ,the third pencil indicates the amount of rain that has fallen since the last setting1 the pencil being moved by a float in the receiver of the rain gauge4 ,illustration3 ,,the ,,anemometer ,,trace4 ,an objection to all the mechanical methods of continuous registration is that1 however carefully the gearing between the instrument itself and the pencil is contrived1 however lightly the pencil moves over the paper1 yet some friction enters in and affects the record3 this is of no great moment in wind registration1 when we are dealing with so powerful an agent as the wind1 but it becomes a serious matter when the barometer is considered1 since its variations require to be registered with the greatest minuteness4 ,when photography1 therefore1 was invented1 meteorologists were very prompt to take advantage of this new ally4 ,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 hours1 and covered with a sheet of photographic paper4 ,in this case1 when the sensitive paper is developed1 we find its upper half blackened1 the lower edge of the blackened part showing an irregular curve according as the mercury in the thermometer or barometer rose or fell1 and admitted less or more light through the space above it4 ,here we have a very perfect means of registration3 the passage of the light exercises no friction or check on the free motion of the mercury in the tube1 or on the turning of the cylinder covered by the sensitive paper1 whilst it is easy to obtain a time scale on the register by cutting off the light for an instant--say at each hour4 ,in this way the wet and dry bulb thermometers in the great shed make their registers4 ,the supply of material to the ,meteorological ,office is not the only use of the ,greenwich meteorological observations4 ,two elements of meteorology1 the temperature and the pressure of the atmosphere1 have the very directest bearing upon astronomical work4 ,and this in two ways4 ,an instrument is sensible to heat and cold1 and undergoes changes of form1 size1 or scale1 which1 however absolutely minute1 yet become1 with the increased delicacy of modern work1 not merely appreciable1 but important4 ,so too with the density of the atmosphere3 the light from a distant star1 entering our atmosphere1 suffers refraction2 and being thus bent out of its path1 the star appears higher in the heavens than it really is4 ,the amount of this bending varies with the density of the layers of air through which the light has to pass4 ,the two great meteorological instruments1 the thermometer and barometer1 are therefore astronomical instruments as well4 ,in the arrangements at ,greenwich the ,magnetic ,department is closely connected with the ,meteorological1 and it is because the two departments have been associated together that the building devoted to both is constructed of wood1 not brick1 since ordinary bricks are made of clay which is apt to be more or less ferruginous4 ,copper nails have alone been employed in the construction of the buildings4 ,the fire-grates1 coal-scuttles1 and fire-irons are all of the same metal4 ,the growth of the ,observatory has1 however1 made it necessary to set up some of the new telescopes1 into the mounting of which much iron enters1 very close to the magnetic building4 ,the present ,astronomer-,royal has therefore erected a ,magnetic ,pavilion right out in the park at an ample distance from these disturbing causes4 ,the double department is1 therefore1 the most widely scattered in the whole ,observatory4 ,it is located for computing purposes in the west wing of the ,new ,observatory2 many of its magnetic instruments are in the old ,magnet ,house1 others are across the park in the new ,magnetic ,pavilion2 the anemometers are on the roof of the ,octagon ,room1 ,flamsteed's original observatory1 and the self-registering thermometers are in the south ground between the old ,magnet ,house and the ,new ,observatory4 ,illustration3 ,,magnetic ,,pavilion--,,exterior4 7,from a photograph by ,mr4 ,lacey47 ,the object of the ,magnetic ,observatory is to study the movements of the magnetic needle4 ,the quaintest answer that ,i ever received in an examination was in reply to the question1 ',what is meant by magnetic inclination and declination8' ,the examinee replied3 ',to make a magnet1 you take a needle1 and rub it on a lodestone4 ,if it refuses or declines to become a magnet1 that is magnetic declination2 if it is easily made a magnet1 or is inclined to become one1 that is magnetic inclination4' ,one greatly regretted that it was necessary to mark the reply according to its ignorance1 and not1 as one would have wished1 in proportion to its ingenuity4 ,magnetic declination1 however1 as everybody knows1 measures the deviation of the 'needle' from the true geographical north and south direction2 the inclination or dip is the angle which a 'needle' makes with the horizon4 ,at one time the only method of watching the movements of the magnetic needles was by direct observation1 just precisely as it was wont to be in the case of the barometer and thermometer4 ,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 movements4 ,in principle the arrangement is as follows3 ,a small light mirror is attached to the magnetic needle1 and a beam of light is arranged to fall upon the mirror1 and is reflected away from it to a drum covered with sensitive paper4 ,if1 then1 the needle is perfectly at rest1 a spot of light falls on the drum and blackens the paper at one particular point4 ,the drum is made to revolve by clockwork once in twenty-four hours1 and the black dot is therefore lengthened out into a straight line encircling the drum4 ,if1 however1 the needle moves1 then the spot of light travels up or down1 as the case may be4 ,now1 if we look at one of these sheets of photographic paper after it has been taken from the drum1 we shall see that the north pole of the magnet has moved a little1 a very little1 towards the west in the early part of the day1 say from sunrise to #b p4m41 and has swung backwards from that hour till about #aj p4m41 remaining fairly quiet during the night4 ,the extent of this daily swing is but small1 but it is greater in summer than in winter1 and it varies also from year to year4 ,illustration3 ,,magnetic ,,pavilion--,,interior4 7,from a photograph by ,mr4 ,lacey47 ,besides this daily swing1 there occasionally happen what are called 'magnetic storms2' great convulsive twitchings of the needle1 as if some unseen operator were endeavouring1 whilst in a state of intense excitement1 to telegraph a message of vast importance1 so rapid and so sharp are the movements of the needle to and fro4 ,these great storms are felt1 so far as we know1 simultaneously over the whole earth1 and the more characteristic begin with a single sharp twitch of the needle towards the east4 ,besides the movements of the magnetic needle1 the intensity of the currents of electricity which are always passing through the crust of the earth are also determined at ,greenwich2 but this work has been rendered practically useless for the last few years by the construction of the electric railway from ,stockwell to the ,city4 ,since it was opened1 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 night4 ,as an indication of the delicacy of modern instruments1 it may be mentioned that distinct indications of the current from this railway have been detected as far off as ,north ,walsham1 in ,norfolk1 a distance of more than a hundred miles4 ,a further illustration of the delicacy of the magnetic needles was afforded shortly after the opening of the railway referred to4 ,on one occasion the then ,superintendent of the ,magnetic ,department visited the ,generating ,station at ,stockwell1 and on his return it was noticed day after day that the traces from the magnets showed a curious deflection from #i a4m4 to #c p4m41 the hours of his attendance4 ,this gave rise to some speculation1 as it did not seem possible that the gentleman could himself have become magnetized4 ,eventually1 the happy accident of a fine day solved the mystery4 ,that morning the ,superintendent left his umbrella at home1 and the magnets were undisturbed4 ,the secret was out4 ,the umbrella had become a permanent magnet1 and its presence in the lobby of the magnetic house had been sufficient to influence the needles4 ,,chapter ,x ,,the ,,heliographic ,,department ,so far the development of the ,observatory had been along the central line of assistance to navigation4 ,but the ,magnetic ,department led on to one which had but a very secondary connection with it4 ,a greatly enhanced interest was given to the observations of earth magnetism1 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 away4 ,that the surface of the sun was occasionally diversified by the presence of dark spots1 had been known almost from the first invention of the telescope2 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 earth4 ,then two observers1 the one interesting himself entirely with the spots on the sun1 the other as wholly devoted to the study of the movements of the magnetic needle1 independently found that the particular phenomenon which each was watching was one which varied in a more or less regular cycle4 ,and further1 when the cycles were compared1 they proved to be the same4 ,whatever the secret of the connection1 it is now beyond dispute that as the spots on the sun become more and more numerous1 so the daily swing of the magnetic needle becomes stronger2 and1 on the other hand1 as the spots diminish1 so the magnetic needle moves more and more feebly4 ,this discovery has given a greatly increased significance to the study of the earth's magnetism4 ,the daily swing1 the occasional 'storms1' are seen to be something more than matters of merely local interest2 they have the closest connection with changes going on in the vast universe beyond2 they have an astronomical importance4 ,and it was soon felt to be necessary to supplement the ,magnetic ,observatory at ,greenwich by one devoted to the direct study of the solar surface2 and here again that invaluable servant of modern science1 photography1 was ready to lend its help4 ,just as1 by the means of photography1 the magnets recorded their own movements1 so even more directly the sun himself makes register of his changes by the same agency1 and gives us at once his portrait and his autograph4 ,this new department was again due to ,airy1 and in #ahgc the ',kew' photo-heliograph1 which had been designed by ,de la ,rue for this work1 was installed at ,greenwich4 ,illustration3 ,,the ,,dallmeyer ,,photo-,,heliograph4 ,in order to photograph so bright a body as the sun1 it is not in the least necessary to have a very large telescope4 ,the one in common use at ,greenwich from #ahge to #ahig1 is only four inches in aperture and even that is usually diminished by a cap to three inches1 and its focal length is but five feet4 ,this is not very much larger than what is commonly called a 'student's telescope1' but it is amply sufficient for its work4 ,this ',dallmeyer' telescope1 so called from the name of its maker1 is one of five identical instruments which were made for use in the observation of the transit of ,venus of #ahgd1 and which1 since they are designed for photographing the sun1 are called 'photo-heliographs4' ,the image of the sun in the principal focus of this telescope is about six-tenths of an inch in diameter2 but a magnifying lens is used1 so that the photograph actually obtained is about eight inches4 ,even with this great enlargement1 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 second4 ,this is managed by arranging a very narrow slit in a strip of brass4 ,the strip is made to run in a groove across the principal focus4 ,before the exposure1 it is fastened up so as to cut off all light from entering the camera part of the telescope4 ,when all is ready1 it is released and drawn down very rapidly by a powerful spring1 and the slit1 flying across the image of the sun1 gives exposure to the plate for a very minute fraction of a second--in midsummer for less than a thousandth of a second4 ,two of these photographs are taken every fine day at ,greenwich2 occasionally more1 if anything specially interesting appears to be going on4 ,but in our cloudy climate at least one day in three gives no good opportunity for taking photographs of the sun1 and in the winter time long weeks may pass without a chance4 ,the present ,astronomer-,royal1 ,mr4 ,christie1 has therefore arranged that photographs with precisely similar instruments should be taken in ,india and in the ,mauritius1 and these are sent over to ,greenwich as they are required1 to fill up the gaps in the ,greenwich series4 ,we have therefore at ,greenwich1 from one source or another1 practically a daily record of the state of the sun's surface4 ,more recently the ',dallmeyer' photo-heliograph1 though still retained for occasional use1 has been superseded generally by the ',thompson'2 a photographic refractor of nine inches aperture1 and nearly nine feet focal length1 presented to the ,observatory by ,sir ,henry ,thompson4 ,the image of the sun obtained after enlargement in the telescope1 with this instrument1 is seven and a half inches in diameter4 ,the ',thompson' is mounted below the great twenty-six-inch photographic refractor1--also presented to the ,observatory by ,sir ,henry ,thompson1--in the dome which crowns the centre of the ,new ,observatory4 ,a photograph of the sun taken1 it has next to be measured1 the four following particulars being determined for each spot3 ,first1 its distance from the centre of the image of the sun2 next1 the angle between it and the north point2 thirdly1 the size of the spot2 and fourthly1 the size of the umbra of the spot1 that is to say1 of its dark central portion4 ,the size or area of the spot is measured by placing a thin piece of glass1 on which a number of cross-lines have been ruled one-hundredth of an inch apart1 in contact with the photograph4 ,these cross-lines make up a number of small squares1 each the ten-thousandth 7#a_/ajjjj in47 part of a square inch in area4 ,when the photograph and the little engraved glass plate are nearly in contact1 the photograph is examined with a magnifying glass1 and the number of little squares covered by a given spot are counted4 ,it will give some idea of the vast scale of the sun when it is stated that a tiny spot1 so small that it only just covers one of these little squares1 and which is only one-millionth of the visible hemisphere of the sun in area1 yet covers in actual extent considerably more than one million of square miles4 ,the dark spots are not the only objects on the sun's surface4 ,here and there1 and especially near the edge of the sun1 are bright marks1 generally in long branching lines1 so bright as to appear bright even against the dazzling background of the sun itself4 ,these are called 'facul1' and they1 like the spots1 have their times of great abundance and of scarcity1 changing on the whole at the same time as the spots4 ,after the solar photographs have been measured1 the measures must be 'reduced1' and the positions of the spots as expressed in longitude and latitude on the sun computed4 ,there is no difficulty in doing this1 for the position of the sun's equator and poles have long been known approximately1 the sun revolving on its axis in a little more than twenty-five days1 and carrying of course the spots and facul round with him4 ,there are few studies in astronomy more engrossing than the watch on the growth and changes of the solar spots4 ,their strange shapes1 their rapid movements1 and striking alterations afford an unfailing interest4 ,for example1 the amazing spectacle is continually being afforded of a spot1 some two1 three1 or four hundred millions of square miles in area1 moving over the solar surface at a speed of three hundred miles an hour1 whilst other spots in the same group are remaining stationary4 ,but a higher interest attaches to the behaviour of the sun as a whole than to the changes of any particular single spot2 and the curious fact has been brought to light1 that not only do the spots increase and diminish in a regular cycle of about eleven years in length1 but they also affect different regions of the sun at different points of the cycle4 ,at the time when spots are most numerous and largest1 they are found occupying two broad belts1 the one with its centre about #ae north of the equator1 the other about as far south1 the equator itself being very nearly free from them4 ,but as the spots begin to diminish1 so they appear continually in lower and lower latitudes1 until instead of having two zones of spots there is only one1 and this one lies along the equator4 ,by this time the spots have become both few and small4 ,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 equator1 much farther than any were seen at the time of greatest activity4 ,there are then for a little time three sun-spot belts1 but the equatorial one soon dies out4 ,the two belts in high latitude1 on the other hand1 continually increase2 but as they increase1 so do they move downwards in latitude1 until at length they are again found in about latitude #ae north or south1 when the spots have attained their greatest development4 ,illustration3 ,,photograph ,,of ,a ,,group ,,of ,,sun-,,spots4 7,from a photograph taken at the ,royal ,observatory1 ,greenwich1 ,april1 #ahhb1 #bj d4 #aj h4 #f m47 ,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 time1 as1 for instance1 year by year4 ,but occasionally we have much more special instances of this connection4 ,some three or four times within the last twenty years an enormous spot has broken out on the sun1 a spot so vast that worlds as great as our own could lie in it like peas in a breakfast saucer1 and in each case there has been an immediate and a threefold answer from the earth4 ,one of the most remarkable of these occurred in ,november1 #ahhb4 ,a great spot was then seen covering an area of more than three thousand millions of square miles4 ,the weather in ,london happened to be somewhat foggy1 and the sun loomed1 a dull red ball1 through the haze1 a ball it was perfectly easy to look at without specially shading the eyes4 ,so large a spot under such circumstances was quite visible to the naked eye1 and it caught the attention of a great number of people1 many of whom knew nothing about the existence of spots on the sun4 ,this great disturbance1 evidently something of the nature of a storm in the solar atmosphere1 stretched over one hundred thousand miles on the surface of the sun4 ,the disturbance extended farther still1 even to nearly one hundred millions of miles4 ,for simultaneously with the appearance of the spot the magnetic needles at ,greenwich began to suffer from a strange excitement1 an excitement which grew from day to day until it had passed half-way across the sun's disc4 ,as the twitchings of the magnetic needle increased in frequency and violence1 other symptoms were noticed throughout the length of the ,british ,isles4 ,telegraphic communication was greatly interfered with4 ,the telegraph lines had other messages to carry more urgent than those of men4 ,the needles in the telegraph instruments twitched to and fro4 ,the signal bells on many of the railway lines were rung1 and some of the operators received shocks from their instruments4 ,lastly1 on ,november #ag1 a superb aurora was witnessed1 the culminating feature of which was the appearance1 at about six o'clock in the evening1 of a mysterious beam of greenish light1 in shape something like a cigar1 and many degrees in length1 which rose in the east and crossed the sky at a pace much quicker than but nearly as even as that of sun1 moon1 or stars1 till it set in the west two minutes after its rising4 ,so far we have been dealing only with effects4 ,their causes still rest hidden from us4 ,there is clearly a connection between the solar activity as shown by the spots and the agitation of the magnetic needles4 ,but many great spots find no answer in any magnetic vibration1 and not a few considerable magnetic storms occur when we can detect no great solar changes to correspond4 ,thus even in the simplest case before us we have still very much to explain4 ,two far more difficult problems are still offered us for solution4 ,what is the cause of these mysterious solar spots8 and have they any traceable connection with the fitful vagaries of earthly weather8 ,it was early suggested that probably the first problem might find an answer in the ever-varying combinations and configurations of the various planets1 and that the sun-spots in their turn might hold the key of our meteorology4 ,both ideas were eagerly followed up--not that there was much to support either1 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 advance4 ,so far1 however1 the first idea may be considered as completely discredited4 ,as to the second1 there would appear to be1 in the case of certain great tropical and continental countries like ,india1 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 sun4 ,dr4 ,meldrum1 the late veteran ,director of the great ,meteorological ,observatory in ,mauritius1 has expressed himself as confident that the years of most spots are the years of most violent cyclones in the ,indian ,ocean4 ,but this is about as far as real progress has been made1 and it may be taken as certain that many years more of observation will be required1 and the labours of many skilful investigators1 before we can hope to carry much farther our knowledge as to any connection between storm and sun4 ,a further relation of great interest has come to light within the last few years4 ,the year #ahfh opened a new epoch in the study of eclipses of the sun4 ,these1 perhaps1 scarcely lie within the scope of a book on the ,royal ,observatory1 since ,greenwich has seen but one in all its history4 ,that fell in the year #agae2 for the next it must wait many centuries4 ,yet1 as the late ,astronomer ,royal conducted three expeditions to see total eclipses1 and as the present ,astronomer ,royal has undertaken a like number1 and members of the staff have been sent on other occasions1 it may not be deemed quite a digression to refer to one feature which they have brought to light4 ,when the dark body of the moon has entirely hidden the sun1 we have revealed to us1 there and then only1 that strange and beautiful surrounding of the sun which we call the corona4 ,the earlier observations of the corona seem to reveal it as a body of the most weird and intricate form1 a form which seemed to change quite lawlessly from one eclipse to another4 ,but latterly it has been abundantly clear that the forms which it assumes may be grouped under a few well-defined types4 ,in #ahgh the corona was of a particularly simple and striking character4 ,two great wings shot out east and west in the direction of the sun's equator2 round either pole was a cluster of beautiful radiating 'plumes4' ,it was then recollected that the corona of #ahfg had been of precisely the same character1 both years being years when sun-spots were at their fewest4 ,the coron1 on the other hand1 seen at times when sun-spots are more abundant1 were of an altogether different character1 the streamers being irregularly distributed all round the sun4 ,other types also have been recognized1 and it is perfectly apparent that the corona changes its shape in close accordance with the eleven-year period4 ,the eclipses of #ahhi and #aijj1 for example1 showed coron that bore the very closest resemblance to those of #ahgh and #ahff1 the interval of eleven years bringing a return to the same form4 ,the further problem1 therefore1 now confronts us3 ,does the corona produce the sun-spots1 or do the sun-spots produce the corona1 or are both the result of some mysterious magnetic action of the sun1 an action powerful enough on occasion to thrill through and through this world of ours1 ninety-three millions of miles away8 ,,chapter ,,xi ,,the ,,spectroscopic ,,department ,another department was set on foot by ,airy at the same time as the ,heliographic ,department1 and in connection with it2 and it is the department which has the greatest of interest for the general public4 ,this deals with astronomical physics1 or astrophysics1 as it is sometimes more shortly called2 the astronomy1 that is1 which treats of the constitution and condition of the heavenly bodies1 not with their movements4 ,the older astronomy1 on the other hand1 confined itself to the movements of the heavens so entirely that ,bessel1 the man whose practical genius revolutionized the science of observation1 and whose influence may be traced throughout in ,airy's great reconstitution of ,greenwich ,observatory1 denied that anything but the study of the celestial movements had a right to the title of astronomy at all4 ,hardly more than sixty years ago he wrote3 ',what astronomy is expected to accomplish is evidently at all times the same4 ,it may lay down rules by which the movements of the celestial bodies1 as they appear to us upon the earth1 can be computed4 ,all else which we may learn respecting these bodies1 as1 for example1 their appearance1 and the character of their surfaces1 is1 indeed1 not undeserving of attention1 but possesses no proper astronomical interest4 ,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 others4 ,whether ,jupiter appears with dark stripes upon its surface1 or is uniformly illuminated1 pertains as little to the inquiries of the astronomer2 and its four moons are interesting to him only for the motions they have4 ,to learn so perfectly the motions of the celestial bodies that for any specified time an accurate computation of these can be given--that was1 and is1 the problem which astronomy has to solve4' ,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 advance4 ,bessel laid down his dictum as to the true subjects of astronomical inquiry1 ,comte declared that we could never learn what were the elements of which the stars were composed1 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 earth1 and should go on to prove itself a true astronomy1 even in ,bessel's restricted sense1 by supplying the means for determining motion in a direction which he would have thought impossible--that is to say1 directly to or from us4 ,the years that followed ,kirchhoff's application of the spectroscope to the study of the sun1 and his demonstration that sodium and iron existed in the solar atmosphere1 were crowded with a succession of brilliant discoveries in the same field4 ,kirchhoff1 ,bunsen1 ,angstrm1 ,thaln1 added element after element to the list of those recognized in the sun4 ,huggins and ,miller carried the same research into a far more difficult field1 and showed us the same elements in the stars4 ,rutherfurd and ,secchi grouped the stars according to the types of their spectra1 and so laid the foundations of what may be termed stellar comparative anatomy4 ,huggins discovered true gaseous nebul1 and so revived the nebular theory1 which had been supposed crushed when the great telescope of ,lord ,rosse appeared to have resolved several portions of the ,orion nebula into separate stars4 ,the great riddle of 'new stars'--which still remains a riddle--was at least attacked1 and glowing hydrogen was seen to be a feature in their constitution4 ,glowing hydrogen1 again1 was1 in the observation of total eclipses1 seen to be a principal constituent of those surroundings of our own sun which we now call prominences and chromosphere4 ,then the method was discovered of observing the prominences without an eclipse1 and they were found to wax and wane in more or less sympathy with the solar spots4 ,sun-spots1 planets1 comets1 meteors1 variable stars1 all were studied with the new instrument1 and all yielded to it fresh and valuable1 and often unexpected1 information4 ,illustration3 ,,the ,,great ,,nebula ,,in ,,orion4 7,from a photograph taken at the ,royal ,observatory ,greenwich1 ,december #a1 #ahii1 with an exposure of #b-a_/d hours47 ,in this activity ,greenwich ,observatory practically took no part4 ,airy1 ever mindful of the original purpose of the ,observatory1 and deeply imbued with views similar to those which we have quoted from ,bessel1 considered that the new science lay outside the scope of his duties1 until in ,mr41 now ,sir ,william1 ,huggins's skilful hands the spectroscope showed itself not only as a means for determining the condition and constitution of the stars1 but also their movements--until1 in short1 it had shown itself as an astronomical instrument even within ,bessel's narrow definition4 ,the principle of this inquiry is as follows3 ,if a source of light is approaching us very rapidly1 then the waves of light coming from it necessarily appear a little shorter than they really are1 or1 in other words1 that light appears to be slightly more blue--the blue waves being shorter than the red--than it really is4 ,a similar thing with regard to the waves of sound is often noticed in connection with a railway train4 ,if an express train1 the whistle of which is blowing the whole time1 dashes past us at full speed1 there is a perceptible drop in the note of the whistle after it has gone by4 ,the sound waves as it was coming were a little shortened1 and the whistle therefore appeared to have a sharper note than it had in reality4 ,and in the same way1 when it had gone by1 the sound waves were a little lengthened1 making the note of the whistle appear a very little flatter4 ,such a change of colour in a star could never have been detected without the spectroscope2 but since when light passes through a prism the shorter waves are refracted more strongly1 that is to say1 are more turned out of their course than the longer1 the spectroscope affords us the means of detecting and measuring this change4 ,let us suppose that the lines of hydrogen are recognized in a given star4 ,if we compare the spectrum of this star with the spectrum of a tube containing hydrogen and through which the electric spark is passing1 we shall be able to see whether any particular hydrogen line occupies the same place as shown by the two spectra4 ,if the line from the star is a little to the red of the line from the tube1 the star must be receding from us2 if to the blue1 approaching us4 ,the amount of displacement may be measured by a delicate micrometer1 and the rate of motion concluded from it4 ,illustration3 ,,the ,,half-,,prism ,,spectroscope ,,on ,,the ,,south-,,east ,,equatorial4 ,the principle is clear enough4 ,the actual working out of the observation was one of very great difficulty4 ,the movements of the stars towards us1 or away from us1 are1 in general1 extremely slow as compared with the speed of light itself2 and hence the apparent shift in the position of a line is only perceptible when a very powerful spectroscope is used4 ,this means that the feeble light of a star has to be spread out into a great length of spectrum1 and a very powerful telescope is necessary4 ,the work of observing the motions of stars in the line of sight was started at ,greenwich in #ahge1 the ',great ,equatorial' being devoted to it4 ,this telescope1 of #ab-c_/d inches aperture1 was not powerful enough to do much more than afford a general indication of the direction in which the principal stars were moving1 and to confirm in a general way the inference which various astronomers had found1 from discussing the proper motions of stars1 that the sun and the solar system were moving towards that part of the heavens where the constellations ,hercules and ,lyra are placed4 ,in #ahia1 therefore1 the work was discontinued1 and as already mentioned1 the #ab-c_/d telescope by ,merz was removed to make room for the present much larger instrument by ,sir ,howard ,grubb1 upon the same mounting4 ,the new telescope being much larger than the one for which mounting and observing room were originally built1 it was not possible to put the spectroscope in the usual position1 in the same straight line as the great telescope4 ,it was therefore mounted under it1 and parallel to it1 and the light of the star was brought into it after two reflections4 ,the observer therefore stood with his back to the object and looked down into the spectroscope4 ,it had1 however1 become apparent by this time that this most delicate field of work was one for which photography possessed several advantages1 and as ,sir ,henry ,thompson had made the munificent gift to the ,observatory of a great photographic equatorial1 it was resolved to devote the #bh-;inch telescope chiefly to double-star work1 and to transfer the spectroscope to the ',new ,building4' ,the ',new ,observatory' in the south ground is crowned indeed with the dome devoted to the great ,thompson photographic refractor1 but this is not its chief purpose4 ,its principal floor contains four fine rooms which are used as 'computing rooms'--for the office work1 that is to say1 of the ,observatory4 ,of these the principal is in the north wing1 where the main entrance is placed1 and is occupied by the ,astronomer ,royal and the two chief assistants4 ,the basement contains the libraries and the workshops of the mechanics and carpenters4 ,the upper floor will eventually be used for the storage of photographs and manuscripts1 and the terrace roofs of the four wings will be exceedingly convenient for occasional observations1 as1 for example1 of meteor showers4 ,the central dome1 which rises high above the level of the terraces1 is the only room in the building devoted to telescopic work4 ,as in the ,new ,altazimuth building1 a ring of circular lights just below the coping of the wall recalls the portholes of a ship1 and again reminds us of the connection of the ,observatory with navigation4 ,illustration3 ,,the ,,workshop4 ,here the spectroscope is now placed1 but not1 as it happens1 on the ,thompson refractor4 ,the equatorial mounting in this new dome is a modification of what is usually called the ',german' form of mounting--that is to say1 there is but one pier to support the telescope1 and the telescope rides on one side of the pier and a counterpoise balances it on the other ,the ',great ,equatorial1' on the other hand1 is an example of the ,english mounting1 and has two piers1 one north and the other south1 whilst the telescope swings in a frame between them4 ,in the new dome three telescopes are found rigidly connected with each other on one side of the pier1 the telescopes being 7#a7 the great ,thompson photographic telescope1 double the aperture and double the focal length of the standard astrographic telescope used for the ,international ,photographic ,survey2 7#b7 the #ab-c_/d telescope by ,merz1 that used to be in the great ,south-,east dome1 but which is now rigidly connected with the ,thompson refractor as a guide telescope2 and 7#c7 a photographic telescope of #i inches aperture1 already described as the ',thompson' photo-heliograph1 and used for photographing the sun or in eclipse expeditions4 ,the counterpoise to this collection of instruments is not a mere mass of lead1 but a powerful reflector of #cj inches' aperture1 and it is to this telescope that the spectroscope is now attached4 ,at the present time1 however 7,august1 #aijj71 regular work has not been commenced with it4 ,illustration3 ,,the #cj-;,,inch ,,reflector ,,with ,,the ,,new ,,spectroscope ,,attached4 ,beside this attempt to determine the motions of the stars as they approach us or retreat from us1 on rare occasions the spectroscope has been turned on the planets4 ,as these shine by reflected light1 their spectra are normally the same as that of the sun4 ,mars appeared to the writer1 as to ,huggins and others1 to show some slight indication of the presence of water vapour in its atmosphere4 ,jupiter and ,saturn show that their atmospheres contain some absorbing vapour unknown to ours4 ,and ,uranus and ,neptune1 faint and distant as they are1 not only show the same dark band given by the two nearer planets1 but several others4 ,more attractive has been the examination of the spectra of the brighter comets that have visited us4 ,the years #ahha and #ahhb were especially rich in these4 ,the two principal comets of #ahha were called after their respective discoverers1 ,tebbutt's and ,schaeberle's4 ,they were not bright enough to attract popular attention1 though they could be seen with the naked eye1 and both gave clear indications of the presence of carbon1 their spectra closely resembling that of the blue part of a gas or candle flame4 ,there was nothing particularly novel in these observations1 since comets usually show this carbon spectrum1 though why they should is still a matter for inquiry2 but the two comets of the following year were much more interesting4 ,both comets came very near indeed to the sun4 ,the earlier one1 called from its discoverer ,comet ,wells1 as it drew near to the sun1 began to grow more and more yellow1 until in the first week of ,june it looked as full an orange as even the so-called red planet1 ,mars4 ,the spectroscope showed the reason of this at a glance4 ,the comet had been rich in sodium4 ,so long as it was far from the sun the sodium made no sign1 but as it came close to it the sodium was turned into glowing vapour under the fierce solar heat4 ,and as the writer saw it in the early dawn of ,june #g1 the comet itself was a disc of much the same colour as ,mars1 whilst its spectrum resembled that of a spirit lamp that has been plentifully fed with carbonate of soda or common salt4 ,the ',great ,comet' of the autumn of the same year1 and which was so brilliant an object in the early morning1 came yet nearer to the sun1 and the heating process went on further4 ,the sodium lines blazed up as they had done with ,comet ,wells1 but under the fiercer stress of heat to which the ,great ,comet was subjected1 the lines of iron also flashed out1 a significant indication of the tremendous temperature to which it was exposed4 ,there are two other departments of spectroscopic work which it was attempted for a time to carry on as part of the ,greenwich routine4 ,these were the daily mapping of the prominences round the sun1 and the detailed examination of the spectra of sun-spots4 ,both are almost necessary complements of the work done in the heliographic department--that is to say1 the work of photographing the appearance of the sun day by day1 and of measuring the positions and areas of the spots4 ,for the spots afford but one index out of several1 of the changes in the sun's activity4 ,the prominences afford another1 nor can we at the present moment say authoritatively which is the more significant4 ,then again1 with regard to the spots themselves1 it is not certain that either their extent or their changes of appearance are the features which it is most important for us to study4 ,we want1 if possible1 to get down to the soul of the spot1 to find out what makes one spot differ from another2 and here the spectroscope can help us4 ,great sun-spots are often connected with violent agitation of the magnetic needles1 and with displays of auror4 ,but they are not always so1 and the inquiry1 ',what makes them to differ8' has been made again and again1 without as yet receiving any unmistakable answer4 ,the great spot of ,november1 #ahhb1 which was connected with so remarkable an aurora and so violent a magnetic storm1 was as singular in its spectrum as in its earthly effects4 ,the sun was only seen through much fog1 and the spectrum was therefore very faint1 but shooting up from almost every part of its area1 except the very darkest1 were great masses of intensely brilliant hydrogen1 evidently under great pressure4 ,the sodium lines were extremely broadened1 and on ,november #bj a broad bright flame of hydrogen was seen shooting up at an immense speed from one edge of the nucleus4 ,a similar effect--an outburst of intensely luminous hydrogen--has often been observed in spots which have been accompanied by great magnetic storms2 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 earth4 ,this sun-spot work was not carried on for very long1 as only one assistant could be spared for the entire solar work of whatever character4 ,yet in that time an interesting discovery was made by the writer--namely1 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 time1 and especially when sun-spots were increasing in number1 or were at their greatest development4 ,the prominence work had also to be dropped1 partly for the same reason1 but chiefly because the atmospheric conditions at ,greenwich are not suitable for these delicate astrophysical researches4 ,when the ,observatory was founded 'in the golden days' of ,charles ,,ii41 ,greenwich was a little country town far enough removed from the great capital1 and no interference from its smoke and dust had to be feared or was dreamt of4 ,now the 'great wen1' as ,cobbett called it1 has spread far around and beyond it1 and the days when the sky is sufficiently pure round the sun for successful spectrum work on the spots or prominences are few indeed4 ,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--,potsdam1 ,meudon1 the ,lick1 and the ,yerkes--we cannot say4 ,that would involve a very considerable departure from its original programme1 and probably also a departure from its original site4 ,for the conditions at ,greenwich tend to become steadily less favourable for such work1 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 town4 ,with the older work it is otherwise4 ,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 builder2 so long as no new railways burrow their tunnels in the neighbourhood of the ,observatory1 so long the fundamental duties laid upon ,flamsteed1 'of ,rectifying the ,tables of the ,motions of the ,heavens and the ,places of the ,fixed ,stars1' will be carried out by his successors on ,flamsteed ,hill4 ,,chapter ,,xii ,,the ,,astrographic ,,department ,the two last departments mentioned1 the heliographic and spectroscopic1 lie clearly and unmistakably outside the terms of the original warrant of the ,observatory1 though the progress of science has led naturally and inevitably to their being included in the ,greenwich programme4 ,but the ,astrographic ,department1 though it could no more have been conceived in the days of ,charles ,,ii4 than the spectroscopic1 does come within the terms of the warrant1 and is but an expansion of that work of ',rectifying the ,places of the ,fixed ,stars1' which formed part of the programme enjoined upon ,flamsteed1 the first ,astronomer ,royal1 at the first foundation of the ,observatory1 and which was so diligently carried out by him1 the first ,greenwich catalogue1 containing about #cjjj stars1 being due to his labours4 ,illustration3 ',,chart ,,plate' ,,of ,,the ,,pleiades4 7,from a photograph taken at the ,royal ,observatory1 ,greenwich1 with an exposure of forty minutes47 ,his immediate successors did much less in this field1 though ,bradley's observations were published1 long after his death1 as a catalogue of #cbbb stars1 in some aspects the most important ever issued4 ,pond1 the sixth ,astronomer ,royal1 restored catalogue-making to a prominent place in the ,greenwich routine1 and his precedent is sedulously followed to-day4 ,but each of these was confined to about #cjjj stars4 ,the necessity has long been felt for a much ampler census1 and ,argelander1 at the ,bonn ,observatory1 brought out a catalogue of #cbd1jjj stars north of ,south declination #b1 a work which has been completed by ,schnfeld1 who carried the census down to ,south declination #bc1 and by the two great astronomers of ,cordoba1 ,south ,america1 ,dr4 ,gould and ,dr4 ,thome1 by whom it was extended to the ,south ,pole4 ,these last three catalogues embrace stars of all magnitudes down to the #ith or #ajth2 but certain astronomers had endeavoured to go much lower1 and to make charts of limited portions of the sky down to even the #adth magnitude4 ,from the very earliest days that men observed the stars1 they could not help noticing that 'one star differeth from another star in glory1' and consequently they divided them into six classes1 according to their brightness--classes which are commonly spoken of now as magnitudes4 ,the ordinary #fth magnitude star is one which can be clearly seen by average sight on a good night1 and it gives us about one-hundredth the light of an average #ast magnitude star4 ,sirius1 the brightest of all the fixed stars1 is called a #ast magnitude star1 but is really some six or seven times as bright as the average4 ,it would take1 therefore1 more than two and a half million stars of the #adth magnitude to give as much light as ,sirius4 ,it is evident that so searching a census as to embrace stars of the #adth magnitude would involve a most gigantic chart4 ,but the work went on in more than one ,observatory for a considerable time1 until at last the observers entered on to the region of the ,milky ,way4 ,here the numbers of the stars presented to them were so great as to baffle all ordinary means of observation4 ,what could be done8 ,just at this time immense interest was caused in the astronomical world by the appearance of the great comet of #ahhb4 ,it was watched and observed and sketched by countless admirers1 but more important still1 it was photographed1 and some of its photographs1 taken at the ,royal ,observatory1 ,cape of ,good ,hope1 showed not only the comet with marvellous beauty of detail1 but also thousands of stars1 and the success of these photographs suggested to her ,majesty's ,astronomer at the ,cape1 ,dr4 ,gill1 that in photography we possessed the means for making a complete sky census even to the #adth magnitude4 ,the project was thought over in all its bearings1 and in #ahhg a great conference of astronomers at ,paris resolved upon an international scheme for photographing the entire heavens4 ,the work was to be divided between eighteen ,observatories of different nationalities4 ,it was to result in a photographic chart extending to the #adth magnitude1 and probably embracing some forty million stars1 and a catalogue made from measures of the photographs down to the #aath magnitude1 which would probably include between two and three million stars4 ,illustration3 ,,the ,,control ,,pendulum ,,and ,,the ,,base ,,of ,,the ,,thompson ,,telescope4 ,the eighteen ,observatories all undertook to use instruments of the same capacity4 ,this was to be a photographic refractor1 with an object-glass of #ac inches aperture and #aa feet focus4 ,at ,greenwich this telescope is mounted equatorially--that is1 so as to follow the stars in their courses--and is mounted on the top of the pier that once supported ,halley's quadrant4 ,the telescope is driven by a most efficient clock1 whose motive power is a heavy weight4 ,the rate of the weight in falling is regulated by an ingenious governor1 which brings its speed very nearly indeed to that of the star1 and any little irregularities in its motion are corrected by the following device4 ,a seconds pendulum is mounted in a glass case on the wall of the ,observatory1 and a needle at the lower end of the pendulum passes at each swing through a globule of mercury4 ,on one of the wheels of the clock are arranged a number of little brass points1 at such intervals apart that the wheel1 when going at the proper rate1 takes exactly one second to move through the distance between any pair4 ,a little spring is arranged above the wheel1 so that these points touch it as they pass4 ,if this occurs exactly as the pendulum point passes through the mercury nothing happens1 but if the clock is ever so little late or early1 the electric current from the pendulum brings into action a second wheel1 which accelerates or retards the driving of the clock1 as the case may be4 ,the total motion1 therefore1 is most beautifully even4 ,illustration3 ,,the ,,astrographic ,,telescope4 7,reproduced from ',engineering' by permission47 ,but even this is not quite sufficient1 especially as the plates for the great chart have to be exposed for at least forty minutes4 ,rigidly united with the #ac-;inch refractor1 so that the two look like the two barrels of a huge double-barrelled gun1 is a second telescope for the use of the observer4 ,in its eyepiece are fixed two pairs of cross spider lines1 commonly called wires1 and a bright star1 as near as possible to the centre of the field to be photographed1 is brought to the junction of two wires4 ,should the star appear to move away from the wire1 the observer has but to press one of two buttons on a little plate which he carries in his hand1 and which is connected by an electric wire with the driving clock1 to bring it back to its position4 ,the photographs taken with this instrument are of two kinds4 ,those for the great chart have but a single exposure1 but this lasts for forty minutes4 ,those for the great catalogue have three exposures on them1 the three images of a star being some #bj seconds of arc apart4 ,these exposures are of six minutes'1 three minutes'1 and twenty seconds' duration1 and the last exposure is given as a test1 since1 if stars of the #ith magnitude are visible with an exposure of twenty seconds1 stars of the #aath magnitude should be visible with three minutes' exposure4 ,thus it will be seen that in three minutes an impression is got of many scores of stars1 whose places it would require many hours to determine at the transit instrument4 ,but the positions of these stars on the plate still remain to be measured4 ,for this purpose a net-work of lines1 at right angles to each other1 is printed on the photograph before its development1 and1 after it has been developed1 washed and dried1 the distances of the stars from their nearest cross-lines are measured in the measuring machine4 ,illustration3 ,,the ,,driving ,,clock ,,of ,,the ,,astrographic ,,telescope4 7,reproduced from ',engineering' by permission47 ,the measuring machine is constructed to hold two plates1 one half its breadth higher than the other4 ,in fact1 in each of the two series of photographs the whole sky is taken twice1 but the two photographs of any region are not simply duplicates of each other4 ,the centre of each plate is at a corner of four other plates1 and in the micrometer the stars on the quarter common to two plates are measured simultaneously4 ,in this way will be carried out a great census of the sky that will exceed ,flamsteed's ten thousand fold4 ,and just as ,flamsteed's was but the first of many similar catalogues1 so1 no doubt1 will this be followed by others--not superseded1 for its value will increase with its age and the number of those that follow it1 by comparison with which it will prove an inexhaustible mine of information concerning the motions of the stars and the structure of the universe4 ,there is a great difference between the work of the observer with the ',astrographic ,telescope1' as this great twin photographic instrument is called1 and the work of the transit observer4 ,the latter sees the star gliding past him1 and telegraphs the instant that the star threads itself on each of the ten vertical wires in succession4 ,the astrographic observer1 on the other hand1 sees his star shining almost immovably in the centre of his field1 threaded on the two cross wires placed there1 for the driving-clock moves the telescope so as to almost exactly compensate for the rotation movement of the earth4 ,the observer's duty in this case is to telegraph to his driving-clock1 when it has in the least come short of or exceeded its duty1 and so to bring back the 'guiding star' to its exact proper place on the cross wires4 ,so far1 the work of the ,astrographic ,department has been1 as mentioned above1 a development on an extraordinary scale1 but a development still1 of the original programme of the ,observatory4 ,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 further4 ,sir ,henry ,thompson gave to the ,observatory1 not merely the photographic refractor of #i inches' aperture1 now used for solar photography1 and known as the ',thompson photo-heliograph1' but also one of #bf inches' aperture and #bb-a_/b feet focal length4 ,this instrument was specially designed of exactly double the dimensions of the standard astrographic telescope used for the ,international ,photographic ,survey1 the idea being that1 in the case of a field of special interest and importance1 a photograph could be obtained with the larger instrument on exactly double the scale given by the smaller4 ,it has rather1 however1 found its usefulness in a slightly different field4 ,the observation of the satellites of ,jupiter was suggested by ,galileo as a means of determining the longitude at sea4 ,as already pointed out1 the suggestion did not prove to be a practical one for that purpose1 but observations of the satellites have been made none the less with a view simply to improving our knowledge of their movements1 and of the mass of ,jupiter4 ,the utilitarian motive for the work having fallen through1 it has been carried on as a matter of pure science4 ,and the work has not stopped with the satellites of ,jupiter2 eight satellites were in due time discovered to ,saturn1 four to ,uranus1 and two to ,mars2 and though these could give not the remotest assistance to navigation1 they too have been made the subjects of observation for precisely the same reason as those of ,jupiter have been4 ,illustration3 ,,the ,,thompson ,,telescope ,,in ,,the ,,new ,,dome4 ,in just the same way1 when the discovery of ,neptune was followed by that of a solitary companion to it1 this also had to be followed4 ,the difficulties in the way of observing the fainter of all these satellites were considerable1 and the work has been mostly confined to two or three observatories possessing very large telescopes4 ,as the largest telescope at ,greenwich was only #g inches in aperture up to #ahei1 and only #ab-c_/d inches up to #ahic1 it is only very recently that it has been able to take any very substantial part in satellite measures4 ,but since the ,thompson photographic telescope was set up1 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 made1 whilst the photograph1 which can be measured at leisure during the day1 gives distinctly the more accurate results4 ,so1 too1 the places of the minor planets can be got more accurately and quickly by means of photographs with this great telescope than by direct observation1 and photographs of the most interesting of them all1 the little planet ,eros1 have been very successfully obtained4 ,so that1 though doing nothing directly to improve the art of navigation1 or to find the longitude at sea1 the great photographic refractor takes its share in the work of ',rectifying the ,tables of the ,planets4' ,illustration3 ,,the ,,nebul ,,of ,,the ,,pleiades4 7,from a photograph taken at the ,royal ,observatory1 ,greenwich1 ,december #c1 #ahii1 with an exposure of three hours47 ,the reflector of #cj inches' aperture1 which acts as a counterpoise to the sheaf of telescopes of the ,thompson1 is intended for use with the spectroscope1 the quality which mirrors possess of bringing all rays1 whatever their colour1 to the same focus being of great importance for spectroscopic work4 ,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 of the spectroscopic researches4 ,chief amongst these photographs are some good ones of the moon1 and more recently some exceedingly fine photographs of the principal nebul4 ,in no department of astronomy has photography brought us such striking results as in regard to the nebul4 ,dr4 ,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 rings2 and what had appeared a mere shapeless cloud was seen to be a vast symmetrical structure1 a great sidereal system in the making4 ,the great nebula in ,orion has grown in successive photographs in detail and extent1 until we have a large part of the constellation bound together in the convolutions of a single nebula of the most exquisite detail and most amazing complexity4 ,the group of the ,pleiades has had a more wonderful record still4 ,manifestly a single system even to the naked eye1 and showing some faint indications of nebulosity in the telescope1 the photographs have revealed its principal stars shining out from nebulous masses1 in appearance like carded wool1 and have shown smaller stars threaded on nebulous lines like pearls upon a string4 ,such photographs are1 of course1 of no utilitarian value1 and at present they lead us to no definite scientific conclusions4 ,they lie1 therefore1 doubly outside the limits of the purely practical1 but they attract us by their extreme beauty1 and by the amazing difficulty of the problems they suggest4 ,how are these weird masses of gas retained in such complex form over distances which must be reckoned by millions of millions of miles8 ,by what agency are they made to glow so as to be visible to us here8 ,what conceivable condition threads together suns on a line of nebula8 ,what universes are here in the making1 or perhaps it may be falling into ruin and decay8 ,,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 view1 yet the progress of science has caused many researches to be undertaken which overstep its boundaries4 ,thus in the present transit room1 beside the successive transit instruments we find upon the wall two long thin tubes1 labelled respectively ,alpha ,aquil and ,alpha ,cygni4 ,these were two telescopes set up by ,pond for a special purpose4 ,dr4 ,brinkley1 ,royal ,astronomer for ,ireland1 had announced that he had found that several stars shifted their apparent place in the sky in the course of a year1 due to the change in the position of the earth from which we view them1 by an amount which would show that they were only about six to nine billions of miles distant from us2 or1 in other words1 they showed a parallax of from two to three seconds of arc4 ,pond was not able to confirm these parallaxes from his observations1 and to decide the point he set up these two telescopes1 the ,alpha ,aquil telescope being rigidly fixed on the west side of the pier of ,troughton's mural circles2 the ,alpha ,cygni telescope on another pier1 the one which now forms the base of the pier of the astrographic telescope4 ,pond's method was to compare the position of these two stars with that of a star almost exactly the same distance from the pole1 but at a great distance from it in time of crossing the meridian2 in other words1 of almost the same declination1 but widely different right ascension4 ,the result proved that ,brinkley was wrong1 and vindicated the delicacy and accuracy of ,pond's observations4 ,these two telescopes1 therefore1 had their day and ceased to be4 ,others have followed them4 ,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 air4 ,or1 in other words1 if the aberration of light would give the same value as at present if we observed through water4 ,the water telescope1 as it was called1 is kept on the ground floor of the central octagon of the new observatory4 ,the observations obtained with it were hardly quite satisfactory1 but gave on the whole a negative result4 ,turning back to the transit room1 and leaving it by the south-west door1 we come into the little passage which leads at the back of ,bradley's transit room into the lower computing room4 ,just inside this passage1 on the left-hand side1 there is a little room of a most curious shape1 the 'reflex zenith room4' ,here is fixed a telescope pointing straight upwards1 the eye-piece being fixed by the side of the object-glass4 ,the light from a star--the star ,gamma ,draconis--which passes exactly over the zenith of ,greenwich1 enters the object-glass1 passes downwards to a basin of mercury1 and is reflected upwards from the surface of the mercury to a little prism placed over the centre of the object-glass1 from which it is reflected again into the eye-piece4 ,by means of this telescope the distance of the star ,gamma ,draconis from the zenith could be measured very exactly1 and1 consequently1 the changes in the apparent position of the star due to aberration1 parallax1 and other causes could be very exactly followed1 and the corrections to be applied on account of these causes precisely determined4 ,this particular telescope was devised by ,airy1 and the observations with it were continued to the end of his reign4 ,the germ of the idea may be traced back1 however1 to the time of ,flamsteed1 who would seem to have occasionally observed ,gamma ,draconis from the bottom of a deep well2 the precise position of the well is not1 however1 now known4 ,later1 ,bradley set up his celebrated #ab-a_/b-;foot zenith sector1 still preserved in the transit room1 first at ,wanstead and then at ,greenwich1 for the determination of the amount of aberration4 ,later1 a zenith tube by ,troughton1 of #be feet focus1 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 instrument4 ,these telescopes for special purposes have passed out of use4 ,observations with the spectroscope have been suspended for some years4 ,the work of the ,astrographic ,department will come to an end1 in the ordinary course of events1 when the programme assigned to ,greenwich in the ,international ,scheme is completed4 ,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 observatories1 but only recently here4 ,this is the ,department of ,double-,star ,observation4 ,the first double star1 ,zeta ,urs ,majoris1 was discovered #bej years ago4 ,bradley discovered two exceedingly famous double stars whilst still a young man observing with his uncle at ,wanstead--,gamma ,virginis and ,castor4 ,bradley made also other discoveries of double stars after his appointment to ,greenwich1 and ,maskelyne succeeded him in the same line1 but the great foundation of double-star astronomy was laid by ,sir ,william ,herschel4 ,at first it was supposed that double stars were double only in appearance2 one star comparatively near us 'happened' to lie in almost exactly the same direction as another star much further off4 ,it was1 indeed1 in the very expectation that this would prove to be the case1 that the elder ,herschel first took up their study4 ,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 double1 one star appearing by chance to be close to another with which it had no connection--but real double stars4 ,the discovery of these has led to the establishment of a new department of astronomy1 again scientific rather than utilitarian4 ,illustration3 ,,double-,,star ,,observation ,,with ,,the ,,south-,,east ,,equatorial4 7,from a photograph by ,mr4 ,edney47 ,as mentioned above1 it is only recently that ,greenwich has taken any appreciable part in this work4 ,under ,airy1 the largest equatorial of the time had been furnished with a good micrometer1 and observations of one or two double stars been made now and again2 but ,airy's programme of work was far too rigid1 and kept the staff too closely engaged for such observations to be anything but extremely rare4 ,and1 indeed1 when the micrometers of the equatorials were brought into use1 they were far more generally devoted to the satellites of ,saturn than to the companions of stars4 ,in the main1 double-star astronomy has been in the hands of amateurs1 at least in ,england4 ,but the discovery in recent years of many pairs so close that a telescope of the largest size is required for their successful observation1 has put an important section of double stars beyond the reach of most private observers1 and therefore the great telescope at ,greenwich is now mainly devoted to their study4 ,the ,astronomer ,royal1 therefore1 soon after the completion of the great equatorial of #bh-;inches aperture placed in the south-east dome1 added this work to the ,observatory programme4 ,the #bh-;inch equatorial is a remarkable-looking instrument1 its mounting being of an entirely different kind to that of the other equatorials in the ,observatory1 with the solitary exception of the ,shuckburgh1 which is set up in a little dome over the chronograph room4 ,the ,shuckburgh was presented to the ,observatory in the year #ahaa1 by ,sir ,g4 ,shuckburgh4 ,it was first intended to be mounted as an altazimuth1 but proved to be unsteady in that position1 and was then converted into an equatorial without clockwork1 and mounted in its present position4 ,the position is about as hopelessly bad a one as a telescope could well have1 completely overshadowed as it is by the trees and buildings close at hand4 ,the dome is a small one1 and the arrangements for the shutters and for turning the dome are as bad as they could possibly be4 ,it has practically been useless for the last forty years4 ,its only interest is that the method of mounting employed is a small scale model of that of the great telescope in the ,s4-,e4 dome4 ,in the ,german or ,fraunhofer form of mounting for an equatorial there is but a single pillar1 which carries a comparatively short polar axis4 ,at the upper end of the polar axis we find the declination axis1 and at one end of the declination axis is the telescope1 whilst at the other end is a heavy weight to counterpoise it4 ,the ,german mounting has the advantage that the telescope can easily point to the pole of the heavens2 its drawbacks are that1 except in certain special forms1 the telescope cannot travel very far when it is on the same side of the meridian as the star to which it is pointed1 the end of the telescope coming into contact under such circumstances with the central pier1 whilst the introduction of mere deadweight as the necessary counterpoise1 is not economical4 ,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 dome1 but has used a powerful reflector as a counterpoise to the sheaf of refractors at the other end of the declination axis4 ,the ,english equatorial requires two piers4 ,between these two piers is a long polar axis4 ,both in the little ,shuckburgh and in the great #bh-;inch equatorial the frame of the polar axis consists of six parallel rods disposed in two equilateral triangles1 with their bases parallel to each other1 the telescope swinging in the space between the two bases4 ,the construction of this form of equatorial1 therefore1 is expensive1 as it requires two piers4 ,it takes much more room than the ,german form1 and the telescope cannot be directed precisely to the pole4 ,but the instrument is symmetrical1 there is no deadweight1 and the telescope can follow a star from rising to setting without having to be reversed on crossing the meridian4 ,the great stability of the ,english form of mounting1 therefore1 commended it very highly to ,airy1 and he designed the great ,northumberland equatorial of the ,cambridge ,observatory on that plan1 as well as one for the ,liverpool ,observatory at ,bidston1 and in #aheh the ,s4-,e4 equatorial at ,greenwich4 ,the telescope at first mounted upon it had an object-glass of #ab-c_/d inches' aperture1 and #ah feet focal length4 ,that was dismounted in #ahia1 and is now used as the guiding telescope of the ,thompson #bf-;inch photographic refractor4 ,its place was taken by an immensely heavier instrument1 the present refractor of #bh inches' aperture1 and #bh feet focal length2 and that this change was effected safely was an eloquent testimony to the solidity of the original mounting4 ,the clock that drives this great instrument1 so that it can follow a star or other celestial object in its apparent daily motion across the sky1 is in the basement of the ,s4-,e4 tower4 ,it is a very simple looking instrument1 a conical pendulum in a glass case4 ,the pendulum makes a complete revolution once in two seconds4 ,below it in a closed case is a water turbine4 ,a cistern on the roof of the staircase supplies this turbine with water1 having a fall of about thirty feet4 ,the water rushing out of the arms of the turbine forces it backward1 and the turbine spins rapidly round1 driving a spindle which runs up into the dome1 and gears through one or two intermediate wheels with the great circle of the telescope2 the extremely rapid rotation of the spindle1 four times in a second1 being converted by these intermediate wheels into the exceedingly slow one of once in twenty-four hours4 ,just above the centre of motion of the turbine is a set of three small wheels1 all of exactly the same size1 and of the same number of teeth4 ,of these the bottom wheel is horizontal1 and is turned by the turbine4 ,the top wheel is also horizontal1 and is turned by the pendulum4 ,the third wheel gears into both these1 and is vertical4 ,if the top and bottom wheels are moving exactly at the same rate1 the intermediate wheel simply turns on its axis1 but does not travel2 but if the turbine and pendulum are moving at different rates1 then the vertical wheel is forced to run in one direction or the other1 and1 doing so1 it opens or closes a throttle valve1 which controls the supply of water to the turbine1 and so speedily brings the turbine into accord with the pendulum4 ,the control of the motion of the great telescope is therefore almost as perfect as that of the astrographic and ,thompson equatorials1 though the principle employed is very different4 ,and the control needs to be perfect1 for1 as said above1 the great telescope is mostly devoted to the observation of double stars1 and there can be no greater hindrance to this work than a telescope which does not move accurately with the star4 ,there is a striking contrast between the great telescope and all the massive machinery for its direction and movement1 and the objects on which it is directed--two little points of light separated by a delicate hair of darkness4 ,the observation is very unlike those of which we have hitherto spoken4 ,the object is not to ascertain the actual position in the sky of the two stars1 but their relative position to each other4 ,a spider's thread of the finest strands is moved from one star to the other by turning an exquisitely fine screw2 this enables us to measure their distance apart4 ,another spider thread at right angles to the first is laid through the centres of both stars1 and a divided circle enables us to read the angle which this line makes to the true east and west direction4 ,such observations repeated year after year on many stars have enabled the orbits of not a few to be laid down with remarkable precision2 and we find that their movements are completely consistent with the law of gravitation4 ,further1 just as ,neptune was pre-recognized and discovered from noting the irregularities in the motion of ,uranus1 so the discordances in the place of ,sirius led to the belief that it was attracted by a then unseen companion1 whose position with respect to the brighter star was predicted and afterwards seen4 ,illustration3 ,,the ,,south-,,east ,,dome ,,with ,,the ,,shutter ,,open4 ,gravitation thus appears1 indeed1 to be the ,bond of the ,universe1 yet it leaves us with several weighty problems4 ,the observation of the positions of stars shows that though we call them fixed they really have motions of their own4 ,of these motions1 a great part consists of a drift away from one portion of the heavens towards a point diametrically opposite to it1 a drift such as must be due1 not to a true motion of the individual stars1 but to a motion through space of our sun and its attendant system4 ,the elder ,herschel was the first to discover this mysterious solar motion4 ,sir ,george ,airy and ,mr4 ,edwin ,dunkin1 for forty-six years a member of the ,greenwich staff1 and from #ahha-ahhd the ,chief ,assistant1 contributed important determinations of its direction4 ,what is the cause of this motion1 what is the law of this motion1 is at present beyond our power to find out4 ,many years ago a ,german astronomer made the random suggestion that possibly we were revolving in an orbit round the ,pleiades as a centre4 ,the suggestion was entirely baseless1 but unfortunately has found its way into many popular works1 and still sometimes is brought forward as if it were one of the established truths of astronomy4 ,we can at present only say that this solar motion is a mystery4 ,there is a greater mystery still4 ,the stars have their own individual motions1 and in the case of a few these are of the most amazing swiftness4 ,the earth in its motion round the sun travels nearly nineteen miles in a second1 say one thousand times faster than the quickest rush of an express train4 ,the sun's rate of motion is probably not quite so swift1 but ,arcturus1 a sun far larger than our own1 has a pace some twenty times as swift as the orbital motion of the earth4 ,this is not a motion that we can conceive of as being brought about by gravitation1 for if there were some unseen body so vast as to draw ,arcturus with this swiftness1 other stars too would be hurtling across the sky as quickly4 ,such 'runaway stars' afford a problem to which we have as yet no key1 and1 like ,job of old1 we are speechless when the question comes to us from heaven1 ',canst thou guide ,arcturus and his sons8' ,it will be seen then that1 fundamentally1 ,greenwich ,observatory was founded and has been maintained for distinctly practical purposes1 chiefly for the improvement of the eminently practical science of navigation4 ,other inquiries relating to navigation1 as1 for instance1 terrestrial magnetism and meteorology1 have been added since4 ,the pursuit of these objects has of necessity meant that the ,observatory was equipped with powerful and accurate instruments1 and the possession of these again has led to their use in fields which lay outside the domain of the purely utilitarian1 fields from which the only harvest that could be reaped was that of the increase of our knowledge4 ,so we have been led step by step from the mere desire to help the mariner to find his way across the trackless ocean1 to the establishment of the secret law which rules the movements of every body of the universe1 till at length we stand face to face with the mysteries of vast systems in the making1 with the intimate structure of the stellar universe1 with the apparently aimless1 causeless wanderings of vast suns in lightning flight2 with problems that we cannot solve1 nor hope to solve1 yet cannot cease from attempting1 problems to which the only answer we can give is the confession of the magicians of ,egypt--',this is the finger of ,god4' ,,index ,aberration of light1 #gi ,adams1 ,john ,c41 his discovery of ,neptune1 #bag ,adhara1 #ahc ,airy1 ,george ,biddell1 seventh ,astronomer ,royal1 his early life1 #ajb2 his work at ,cambridge1 #aje2 comes to ,greenwich1 #aje2 his relations with the ,visitors1 #ajf2 his autobiography1 #ajh2 his character1 #aaa2 his labours1 #aac2 attacks on1 #aad2 his distinctions1 #aah2 his resignation1 #aai2 his death1 #abj2 anecdote of1 #adb2 his conduct re ,adams1 #bag2 his water telescope1 #cjd ,alderamin1 #ahc ,almagest1 #ahe ,almanac making1 #bi ,alpha ,aquil1 telescope for1 #cjc ---- ,cygni1 telescope for1 #cjc ,altazimuth the1 #aad2 description and work of1 #bjg1 et seq4 ,altazimuth ,department1 #bje1 et seq4 ,american time1 #aec ,andromeda nebula1 #cja ,anemometer1 use of1 #bch2 trace of1 #bdb ,angstrm1 #bfh ,anson1 ,commodore1 #ag ,apparent time1 #aeb ,arcturus1 motion of1 #cae ,argelander1 star catalogue of1 #bhg ,art of ,dialling1 the1 #bh ,assistants1 position of the1 #ih1 #ajj1 #aag1 #acg ,astrographic chart1 #abh ---- ,department1 #bhd1 et seq4 ---- dome1 #abh ---- telescope1 #bhi1 et seq4 ,astronomers ,royal1 the1 #be ,astrophysical researches1 #bhb ,auror1 #bha ,automatic register1 #bda ,axis of the earth1 precession of1 #ahd ,ball1 ,time1 #afb ,barometer1 use of the1 #aib1 #bcc ,battery basement1 #afa ,beaufort1 ,captain1 #ajg ,bessel quoted1 #bff ,betelgeuse1 #ahd ,birkenhead1 wreck of the1 #ahj ,bliss1 ,nathaniel1 fourth ,astronomer ,royal1 history of1 #hb ,bradley1 ,james1 third ,astronomer ,royal1 his life1 #gc2 his ordination1 #gd2 ,vicar of ,bridstow1 #gd2 ,savilian ,professor of ,astronomy1 #ge2 discovers ,aberration of ,light1 #ge1 et seq42 becomes ,astronomer ,royal1 #gi2 labours of1 #hj2 character of1 #ha ,bradley's transit room1 #abh ,brinkley1 ,dr41 #cjc ,british ,mariner's ,guide1 the1 #ij ,bunsen1 #bfh ,buys ,ballot's law1 #bcg ,canadian time1 #aec ,castor1 #gd1 #cjf ,catalogues1 star1 #ahb1 #ahe1 et seq41 #aih1 #bhd ,cepheus1 #ahc ,charles ,,ii41 warrants of1 #ci1 #dj ,christie1 ,w4 ,h4 ,m41 eighth ,astronomer ,royal1 work of1 #abj ,chromosphere of the sun1 #bfh ,chronograph1 the1 #aeg ---- room1 #abf ,chronometer business1 #aja1 #ajg ,chronometers1 ,harrison's improvements in1 #afe1 et seq42 tests of1 #afi2 'runs' of1 #agc2 romance of1 #agh ,circle ,department1 #aha1 et seq4 ,clock1 ,astrographic driving1 #bij2 driving #bh-;inch telescope1 #cab ,clocks1 standard1 #afj ,columbus1 aim of voyage of1 #ah ,comet1 appearance of a1 #bh ---- ,wells1 #bhj ,comets1 observation of1 #bbd2 spectra of1 #bhj ,commutator1 the1 #afb ,comte1 assertion of1 #bfg ,constant of ,aberration1 #gi ,cook1 ,captain1 work of1 #agj ,copper1 use of in ,observatory1 #bde ,corona of the sun1 #bfd ,crabtree1 ,james1 #ca ,crosthwait1 ,joseph1 #eg ,dallmeyer telescope1 #beb ,declination1 #ahf1 et seq4 ,denebola1 #ahd ,distances of planets1 #bbc2 of sun1 #bbd ,double-,star ,department1 #cjc1 et seq4 ,double ,stars1 #cjf ,dublin time1 #aee ,dunkin1 ,edwin1 #cae ,earth1 the1 movements of1 #bja ,eclipses of the moon1 #baf2 of the sun1 ,july #be1 #agdh444he2 other eclipses of the sun1 #bfc1 et seq4 ,electric ,railway1 influence of1 #bdi ,equation of ,time1 the1 #bi1 #aea ,equatorial1 ,shuckburgh's1 #aja ----1 the great #bh-;inch1 #bba ----1 the ,merz1 #ab-c_/d-;inch1 #aad ----1 #bh-;inch1 driving clock of1 #cji2 use of1 #cac ----1 clock-driven1 #gd ,eros1 discovery of1 #bbc2 photographs of1 #bih ,errors in observations1 noting of1 #aii1 et seq4 ,evaporation1 #bda ,facul of the sun1 #beg ,flamsteed1 ,john1 his report on ,saint-,pierre's proposal1 #bc1 #cb2 appointed first ,astronomer ,royal1 #bc1 #cd2 his autobiography1 #bf2 his studies1 #bi2 his almanac1 #bi2 sent to ,london1 #cj2 enters ,jesus ,college1 ,cambridge1 #ca2 completes his observatory1 #ca2 acquaintance with ,newton1 #ca2 takes his degree1 #cb2 his work1 #cd2 warrant for his salary1 #ci2 position of1 #db2 his ordination1 #de2 his pupils1 #de2 his trouble with ,newton1 #df1 et seq42 his catalogue1 #ec2 his letter to ,sharp1 #ed2 his death1 #ef2 his labours1 #eg ,flamsteed ,house1 #abf ,fraunhofer mounting1 #caj ,french time1 #aee ,galileo1 his discovery of ,jupiter's satellites1 #ai ,gamma ,draconis1 #ge1 #cjd ---- ,virginis1 #cjf ,gascoigne1 ,william1 #ca ,gemma ,frisius1 plan of1 #bb ,george of ,denmark1 ,prince1 #ej ,german mounting1 #bgf1 #caj ,gould1 ,dr41 #bhg ,graham1 #aff ,gravitation1 the bond of the universe1 #cac ,great comet of #ahhb1 the1 #bhj1 #bhh ,greatrackes1 ,valentine1 #bi ,green1 ,charles1 #ia ,greenwich time1 #aec2 distribution of1 #afc ,halley1 ,edmund1 his life1 #fj2 his early work1 #fj2 his catalogue of stars1 #fc2 elected ,f4,r4,s41 #fc2 his work on ,kepler's laws1 #fd2 becomes captain1 #fe2 ,savilian ,professor of ,geometry1 #ff2 ,astronomer ,royal1 #ff2 observations on saros of the moon1 #fg2 pressed by ,newton1 #fh2 his death1 #fh2 his services to science1 #fh2 his pay1 #gj2 nominates his successor1 #gc2 his transit instrument1 #gc ,halley's comet1 #bbe ,harrison1 ,james1 timekeepers of1 #hf1 #ia1 #ic1 #afe ,heineken1 ,rev4 ,n4 ,s41 #ei ,heineken quadrant1 #ei ,heliographic ,department1 #bea1 et seq4 ,herschel1 ,caroline1 #eg ,hipparchus1 catalogue of1 #ahe ,hodgson1 ,mr41 #ej ,hooke1 ,robert1 #ge1 #bjf ,horrox1 ,jeremiah1 #ca ,huggins1 ,sir ,w41 his use of spectroscope1 #bfh ,inscription1 an1 #abf ,international ,photographic ,survey1 #bif ,ireis1 #bbd ,iron quadrant1 #gc ,isobars1 #bcg ,jupiter1 satellites of1 #ai1 #bif2 atmosphere of1 #bgi ,keill1 ,john1 #gd ,kendall1 ,larcum1 #aff ,kepler1 laws of1 #fd ,kew1 photo-heliograph1 the1 #beb ,kinnebrook1 ,david1 #agf ,kirchhoff's use of spectroscope1 #bfg ,latitude1 finding the1 #ah ,ledgers1 chronometer1 romance of1 #agf ,leverrier1 his discovery of ,neptune1 #bag ,libraries1 #acb ,linacre1 ,g41 #bh ,lindsay1 ,thomas1 quoted1 #bjd ,litchford1 ,w41 #bh ,local apparent time1 #bb ,longitude1 finding the1 #ah2 at sea1 problem of1 #hf2 determination of1 #agc ,longitude nought1 #adh ,lower computing room1 #abh ,lunars1 method of1 #hf ,magnetic ,department1 work of1 #acc2 description of1 #bbh1 et seq4 ,magnetic inclination and declination1 #bdf ---- needles1 movements of1 #bdg1 #bfb ---- observatory1 #acb ---- pavilion1 #bde ---- storms1 #bdh1 #bfb ,mars1 distance of1 #bbc2 atmosphere of1 #bgi2 satellites of1 #bif ,maskelyne1 ,nevil1 fifth ,astronomer ,royal1 #he2 practical work of1 #hf2 ,astronomer ,royal1 #ia2 his work1 #ib2 his publications1 #ib2 his observations and work1 #ib1 et seq42 his death1 #id2 his character1 #ig2 recommends his successor1 #ig2 his mural circle1 #aja ,mean solar clock1 #afj ,mean time1 #aeb ,meldrum1 ,dr41 on sun spots1 #bfc ,meridian1 the1 #adi ,merz telescope1 #bgi ,meteorological ,department1 work of1 #acc2 description of1 #bbh1 et seq4 ,micrometers1 use of1 #cji ,microscopes1 use of1 #ahh ,milky ,way1 #bhh ,miller1 ,professor1 #bfh ,milne1 ,professor1 on earth movements1 #bja ,minor planets1 #bbb ,molyneux1 ,samuel1 #ge ,moon1 observation of the1 #bab1 et seq42 eclipses of1 #bff ,moore1 ,sir ,jonas1 #cj2 death of1 #db ,morin1 #cc ,mounting telescopes1 modes of1 #caj ,mudge1 ,thomas1 #id ,mural arc1 #g-;feet1 #df ,mural circles1 #aja1 #aif ,names of stars1 origin of1 #ahc ,nares1 ,sir ,george1 #agj ,nautical ,almanac1 the1 #bb1 #bc1 #ib ,navigation1 state of primitive1 #ag ,neptune1 discovery of1 #bag2 atmosphere of1 #bhj2 satellite of1 #bih ,new altazimuth1 the1 #acb1 #baj ,new ,observatory1 the1 #acf1 #bge ,new stars1 #bfh ,newcomb1 ,professor1 on growth of ,observatory1 #abd2 on ,greenwich observations1 #bjg ,newton1 ,sir ,i41 his absent-mindedness1 #ca2 his trouble with ,flamsteed1 #df1 et seq42 on ,kepler's laws1 #fe2 his ,principia1 #fe2 his pressure on ,halley1 #fh2 his discovery of gravitation1 #bjf ,north terrace1 the1 #abf ,northumberland equatorial1 #bah ,nutation of the earth1 #hj ,observation1 modes of1 #aef1 #agf1 #ahh2 by reflection1 #aif2 of comets1 #bbd ,observatory1 ,greenwich1 work of1 #ac2 foundation of1 #bc2 warrant for building1 #dj2 position of1 #da2 foundation stone laid1 #db2 condition of1 #gi2 enlargement of1 #aab2 recent extensions of1 #abj2 description of1 #abd1 et seq42 staff of1 #acg2 work of1 #aci1 et seq42 visitors to1 #age2 new altazimuth building1 #baa2 magnet house1 #bbh2 magnetic pavilion1 #bde2 new ,observatory1 #bge2 future of1 #bhc2 reflex zenith room1 #cjd2 objects of1 #caf ,occultations by the moon1 #bab1 et seq4 ,octagon room1 #abe1 #bch1 #bdb ,oldenburg1 ,mr41 #cj ,orion nebula1 #bfh1 #cja ,parallax of stars1 #cjc ,paramour1 the1 #fe ,paris1 conference at1 #bhh ----1 noon at1 #aea ,philip ,,iii41 offer of1 #ai ,photographic registration1 #bdd1 #bdg1 #beb1 #bee2 refractors1 #bhh ,photographs1 star1 #bij ,photo-heliographs1 #beb1 et seq41 #bgi ,piazzi1 discovery of1 #bbb ,pleiades1 the1 #cja ,polar plumes of the corona1 #bfd ,polaris1 #ahh ,pole-star1 variation of1 #ahd ,pond1 ,john1 sixth ,astronomer ,royal1 his life1 #ig2 his reign1 #ih2 his salary1 #ih2 his assistants1 #ih2 his observations1 #ii2 censured by ,visitors1 #ii2 his observations of stars1 #cjc ,pound1 ,james1 #gc ,precession of earth's axis1 #ahd ,principia1 publication of1 #fe ,proctor1 ,r4 ,a41 attack of1 #aaf ,ptolemy1 ,claudius1 catalogue of1 #ahe ,publication1 the problem of1 #dh1 #ib ,quadrant1 ,heineken1 #ei ----1 the iron1 #gc ,railway time1 #aeb ,rain gauge1 #bch ,record rooms1 #acb ,reflection1 observation by1 #aif ,reflex zenith room1 #cjd ---- ---- tube1 #aca ,refraction1 effects of1 #aid ,right ascension1 #ahf1 et seq4 ,roberts1 ,dr4 ,isaac1 #cja ,rmer1 discovery of1 #gh ,rosse1 ,lord1 #bfh ,royal ,society and ,flamsteed1 #df1 et seq4 ,saint-,pierre1 ,le ,sieur de1 proposal of1 #bc1 #cb ,sappho1 #bbd ,saros of the moon1 #fg ,satellites1 discovery of1 #bif ,saturn1 atmosphere of1 #bgi2 satellites of1 #bif ,schaeberle's comet1 #bhj ,schedar1 #ahd ,schiehallion1 attraction of1 #id ,schnfeld1 #bhg ,scotchmen1 anecdote of1 #adf ,sharp1 ,abraham1 #df ,sheepshanks1 ,rev4 ,james1 on ,airy1 #ajg ,shuckburgh equatorial1 #cji ,sidereal clock1 #afj ,sirius1 #bhg ,sloane1 ,dr41 #ej ',smith1 ,mr41' his chronometer1 #agi ,solar photographs1 #beg ---- storms1 #bfa1 #bhb ,sound waves1 #bga ,south1 ,sir ,james1 #aje1 #aad ,south-east equatorial1 the1 #acb1 #bba ,spectroscope1 use of1 #bfg ,spectroscopic ,department1 #bff1 et seq4 ,spots1 sun1 #bea1 et seq41 #bha ,staff of ,observatory1 #acg2 work of1 #aci1 et seq4 ,standard time1 #ba ,stars1 observations of1 #aef1 #agf1 #ahh2 origin of names of1 #ahc2 movements of1 #ahg2 catalogues of1 #aih1 #bhd1 et seq42 composition of1 #bfh1 et seq42 colour of1 #bga2 classes of1 #bhg2 census of1 #bhg2 photographs of1 #bhh1 et seq42 motions of1 #cjc1 #cae ,story1 ,mr4 ,a4 ,m41 #ig ,sun1 distance of the1 #gd1 #bbd2 spots on1 #bea1 et seq41 #bha2 eclipses of1 #bfc1 et seq42 chromosphere of1 #bfh2 motions of1 #cae ,sunshine recorder1 #bch ,swiss time1 #aee ,tebb1 ,mr4 ,w41 #eh ,tebbutt's comet1 #bhj ,telescope1 the great transit1 #aef ----1 #bh-;inch1 #bge ----1 astrographic1 #bhi ----1 ,shuckburgh1 #cji ----1 ,thompson1 #bef1 #bgi1 #bif ,thaln1 #bfh ,thermometer1 use of1 #aib1 #bcd ,thome1 ,dr41 #bhg ,thompson photo-heliograph1 #bef1 #bgi1 #bif ,time ball1 #afb ---- ,department1 the1 #adf1 et seq4 ---- desk1 #afa ----1 foreign1 #aec ---- signals1 #afb ---- standard1 #ba ,transit1 ,halley's1 #gc ,transit circle1 the1 #aad2 mode of observation with1 #ahh1 et seq4 ,transit circle1 ,troughton's1 #ih ---- ,department1 #aha1 et seq4 ---- observations1 number of1 #adj ---- pavilion1 #abf1 #age ---- room1 #abh1 #adg ,troughton's transit circle1 #ih ,uranus1 discovery of1 #bag2 atmosphere of1 #bgi2 satellites of1 #bif ,vanes1 use of1 #bch ,venus1 distance of1 #bbc ,victoria1 #bbd ,visitors1 the ,board of1 #ec2 censures ,pond1 #ii2 work of1 #ajf2 constitution of1 #add ,visitors to ,observatory1 #age ,warrant for ,flamsteed's salary1 #ci ,water telescope1 #cjd ,weather predictions1 #bbi1 et seq4 ,winds1 study of1 #bcg ,witt1 ,herr1 discovery of1 #bbc ,working ,catalogue1 the1 #adb ,zenith sector1 #hb1 #cje ---- tube1 #ge1 #cje ,zeta ,urs ,majoris1 #cjf ,zubeneschamal1 #ahd ,,the ,,end ,,london3 ,,printed ,,by ,,william ,,clowes ,,and ,,sons1 ,,limited1 ,,stamford ,,street ,,and ,,charing ,,cross4 99 99 99 99 99 ,transcriber's note3 ,minor typographical errors have been corrected without note4 ,irregularities and inconsistencies in the text have been retained as printed4 ,the illustrations have been moved so that they do not break up paragraphs4 ,mismatched quotation marks were not corrected if it was not clear where the missing quotation mark should be placed4