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diff --git a/44167-h/44167-h.htm b/44167-h/44167-h.htm new file mode 100644 index 0000000..d6c0f6c --- /dev/null +++ b/44167-h/44167-h.htm @@ -0,0 +1,9542 @@ +<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" + "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> +<html xmlns="http://www.w3.org/1999/xhtml"> +<head> +<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /> +<title>The Project Gutenberg eBook of The Royal Observatory Greenwich, by E. Walter (Edwared Walter) Maunder</title> + <link rel="coverpage" href="images/coverpage.jpg"/> + <style type="text/css"> + +body { + margin-left: 10%; + margin-right: 10%; +} + + h1,h2,h3,h4 { + text-align: center; /* all headings centered */ + clear: both; +} + +p { + margin-top: .51em; + text-align: justify; + margin-bottom: .49em; + text-indent: 1em; +} + +.noin {text-indent: 0em;} + + +.b13 {font-size:1.3em;} +.b12 {font-size:1.2em;} +.s08 {font-size:.8em;} + +hr { + width: 33%; + margin-top: 2em; + margin-bottom: 2em; + margin-left: auto; + margin-right: auto; + clear: both; +} + +hr.tb {width: 25%;} +hr.chap {width: 45%} + +table { + margin-left: auto; + margin-right: auto; +} + +.pagenum { /* uncomment the next line for invisible page numbers */ + /* visibility: hidden; */ + position: absolute; + left: 92%; + font-size: smaller; + font-style: normal; + text-align: right; +} /* page numbers */ + +.blockquot { + margin-left: 5%; + margin-right: 10%; +} + +.center {text-align: center;} + +.right {text-align: right;} + +.smcap {font-variant: small-caps;} + +.caption {font-weight: bold;} + +.space-above { margin-top: 3em; } + +.hanging {margin-left: 2em; text-indent: -2em; font-size: 15px;} + +.sig { text-align: right; margin-right: 5%; } + +/* Images */ +.figcenter { + margin: auto; + text-align: center; +} + +.bord img { padding: 1px; border: 2px solid black; } + + +/* Footnotes */ + +.footnote {margin-left: 10%; margin-right: 10%; font-size: 0.9em;} + +.footnote .label {position: absolute; right: 84%; text-align: right;} + +.fnanchor { + vertical-align: super; + font-size: 55%; + text-decoration: + none; +} + +/* Poetry */ +.poem { + margin-left:10%; + margin-right:10%; + text-align: left; +} + +.poem br {display: none;} + +.poem .stanza {margin: 1em 0em 1em 0em;} + +.poem span.i0 {display: block; margin-left: 0em; padding-left: 3em; text-indent: -3em;} +.poem span.i2 {display: block; margin-left: 1em; padding-left: 3em; text-indent: -3em;} +.poem span.i16 {display: block; margin-left: 8em; padding-left: 3em; text-indent: -3em;} + +@media handheld +{ + .poetry + { + display: block; + margin-left: 1.5em; + } +} + +/* Transcriber's notes */ +.tn {background-color: #E6E6FA; + color: black; + font-size:smaller; + border: dashed 1px; + padding:0.5em; + margin-bottom:5em; + font-family:sans-serif, serif; } + + hr.full { width: 100%; + margin-top: 3em; + margin-bottom: 0em; + margin-left: auto; + margin-right: auto; + height: 4px; + border-width: 4px 0 0 0; /* remove all borders except the top one */ + border-style: solid; + border-color: #000000; + clear: both; } + </style> +</head> +<body> +<div>*** START OF THE PROJECT GUTENBERG EBOOK 44167 ***</div> +<h1>The Project Gutenberg eBook, The Royal Observatory Greenwich, by E. Walter +(Edwared Walter) Maunder</h1> +<p> </p> +<p> </p> +<table border="0" style="background-color: #ccccff;margin: 0 auto;" cellpadding="10"> + <tr> + <td valign="top"> + Note: + </td> + <td> + Images of the original pages are available through + Internet Archive. See + <a href="https://archive.org/details/royalobservatory00maun"> + https://archive.org/details/royalobservatory00maun</a> + </td> + </tr> +</table> +<p> </p> +<hr class="full" /> +<p> </p> + +<p><span class="pagenum"><a name="Page_1" id="Page_1"> </a></span></p> + + +<div class="figcenter" style="width: 549px;"> +<img src="images/coverpage.jpg" width="549" height="784" alt="cover" /> +</div> + +<hr class="chap" /> + +<div class="figcenter bord" style="width: 380px;"> +<img src="images/title_page.jpg" width="380" height="600" alt="titlepage" /> +</div> + +<hr class="chap" /> + +<p><span class="pagenum"><a name="Page_2" id="Page_2"> </a></span></p> + +<div class="figcenter bord" style="width: 445px;"> +<img src="images/i_002.jpg" width="445" height="600" alt="Flamsteed" /> +<div class="caption"><p class="center">FLAMSTEED, THE FIRST ASTRONOMER ROYAL.<br /> + +(<em>From the portrait in the 'Historia Cœlestis.'</em>)</p></div> +</div> + +<hr class="chap" /> + +<p><span class="pagenum"><a name="Page_3" id="Page_3"> </a></span></p> + +<h1> +THE<br /> +ROYAL OBSERVATORY<br /> +GREENWICH<br /> +<br /> +<small>A GLANCE AT ITS HISTORY<br /> +AND WORK</small></h1> +<p class="center b12 space-above"> +BY</p> + +<h2>E. WALTER MAUNDER, F.R.A.S.</h2> + + +<p class="center space-above"> +<em>WITH MANY PORTRAITS AND ILLUSTRATIONS FROM<br /> +OLD PRINTS AND ORIGINAL PHOTOGRAPHS</em></p> +<p> </p> +<p> </p> + +<p class="center space-above">LONDON</p> + +<p class="center b13">THE RELIGIOUS TRACT SOCIETY</p> + +<p class="center"><span class="smcap">56 Paternoster Row, and 65 St. Paul's Churchyard</span><br /> +1900 +</p> + +<p><span class="pagenum"><a name="Page_4" id="Page_4"> </a></span></p> + + +<hr class="chap" /> + +<p class="center s08"> +LONDON:<br /> +PRINTED BY WILLIAM CLOWES AND SONS, LIMITED,<br /> +STAMFORD STREET AND CHARING CROSS. +</p> + +<hr class="chap" /> + +<p><span class="pagenum"><a name="Page_5" id="Page_5">[5]</a></span></p> + + + + +<h2>PREFACE</h2> + + +<p>I was present on one occasion at a popular lecture +delivered in Greenwich, when the lecturer referred +to the way in which so many English people travel +to the ends of the earth in order to see interesting +or wonderful places, and yet entirely neglect places +of at least equal importance in their own land. +'Ten minutes' walk from this hall,' he said, 'is +Greenwich Observatory, the most famous observatory +in the world. Most of you see it every day of +your lives, and yet I dare say that not one in a +hundred of you has ever been inside.'</p> + +<p>Whether the lecturer was justified in the general +scope of his stricture or not, the particular instance +he selected was certainly unfortunate. It was not +the fault of the majority of his audience that they +had not entered Greenwich Observatory, since the +regulations by which it is governed forbade them +doing so. These rules are none too stringent, for +the efficiency of the institution would certainly suffer +if it were made a 'show' place, like a picture<span class="pagenum"><a name="Page_6" id="Page_6">[6]</a></span> +gallery or museum. The work carried on therein +is too continuous and important to allow of interruption +by daily streams of sightseers.</p> + +<p>To those who may at some time or other visit +the Observatory it may be of interest to have at +hand a short account of its history, principal instruments, +and work. To the far greater number who +will never be able to enter it, but who yet feel an +interest in it, I would trust that this little book +may prove some sort of a substitute for a personal +visit.</p> + +<p>I would wish to take this opportunity of thanking +the Astronomer Royal for his kind permission to +reproduce some of the astronomical photographs +taken at the Observatory and to photograph the +domes and instruments. I would also express my +thanks to Miss Airy, for permission to reproduce the +photograph of Sir G. B. Airy; to Mr. J. Nevil +Maskelyne, F.R.A.S., for the portrait of Dr. Maskelyne; +to Mr. Bowyer, for procuring the portraits of +Bliss and Pond; to Messrs. Edney and Lacey, for +many photographs of the Royal Observatory; and +to the Editor of <cite>Engineering</cite>, for permission to copy +two engravings of the Astrographic telescope.</p> + +<p class="sig"> +E. W. M.</p> + +<p class="noin"><span class="smcap">Royal Observatory, Greenwich</span>,<br /> + <em>August, 1900</em>. +</p> + +<hr class="chap" /> + +<p><span class="pagenum"><a name="Page_7" id="Page_7">[7]</a></span></p> + +<div class="figcenter bord" style="width: 450px;"><a name="building" id="building"></a> +<img src="images/i_007.jpg" width="450" height="384" alt="new building" /> +<div class="caption"><p class="center">THE NEW BUILDING.<br /> + +(<em>From a photograph by Mr. Lacey.</em>)</p></div> +</div> + + +<hr class="chap" /> + +<h2>CONTENTS</h2> + +<div class="center"> +<table border="0" cellpadding="4" cellspacing="0" summary="contents"> +<tr><td align="left" colspan="2">CHAPTER</td><td align="right"><small>PAGE</small></td></tr> +<tr><td align="right">I.</td><td align="left"><span class="smcap">Introduction</span></td><td align="right"><a href="#Page_13">13</a></td></tr> +<tr><td align="right">II.</td><td align="left"><span class="smcap">Flamsteed</span></td><td align="right"><a href="#Page_25">25</a></td></tr> +<tr><td align="right">III.</td><td align="left"><span class="smcap">Halley and his Successors</span></td><td align="right"><a href="#Page_60">60</a></td></tr> +<tr><td align="right">IV.</td><td align="left"><span class="smcap">Airy</span></td><td align="right"><a href="#Page_102">102</a></td></tr> +<tr><td align="right">V.</td><td align="left"><span class="smcap">The Observatory Buildings</span></td><td align="right"><a href="#Page_124">124</a></td></tr> +<tr><td align="right"><span class="pagenum"><a name="Page_8" id="Page_8">[8]</a></span>VI.</td><td align="left"><span class="smcap">The Time Department</span></td><td align="right"><a href="#Page_146">146</a></td></tr> +<tr><td align="right">VII.</td><td align="left"><span class="smcap">The Transit and Circle Departments</span></td><td align="right"><a href="#Page_181">181</a></td></tr> +<tr><td align="right">VIII.</td><td align="left"><span class="smcap">The Altazimuth Department</span></td><td align="right"><a href="#Page_205">205</a></td></tr> +<tr><td align="right">IX.</td><td align="left"><span class="smcap">The Magnetic and Meteorological Departments</span></td><td align="right"><a href="#Page_228">228</a></td></tr> +<tr><td align="right">X.</td><td align="left"><span class="smcap">The Heliographic Department</span></td><td align="right"><a href="#Page_251">251</a></td></tr> +<tr><td align="right">XI.</td><td align="left"><span class="smcap">The Spectroscopic Department</span></td><td align="right"><a href="#Page_266">266</a></td></tr> +<tr><td align="right">XII.</td><td align="left"><span class="smcap">The Astrographic Department</span></td><td align="right"><a href="#Page_284">284</a></td></tr> +<tr><td align="right">XIII.</td><td align="left"><span class="smcap">The Double-Star Department</span></td><td align="right"><a href="#Page_303">303</a></td></tr> +<tr><td align="right"> </td><td align="left"><span class="smcap">Index</span></td><td align="right"><a href="#Page_317">317</a></td></tr> +</table></div> + +<hr class="chap" /> + +<p><span class="pagenum"><a name="Page_9" id="Page_9">[9]</a></span></p> + + + + +<h2>LIST OF ILLUSTRATIONS</h2> + +<div class="center"> +<table border="0" cellpadding="4" cellspacing="0" summary="illustrations"> +<tr><td align="left"> </td><td align="right"><small>PAGE</small></td></tr> +<tr><td align="left"><span class="smcap">Flamsteed, the First Astronomer Royal</span></td><td align="left"><a href="#Page_7"><em>Frontispiece</em></a></td></tr> +<tr><td align="left"><span class="smcap">The New Building</span></td><td align="right"><a href="#building">7</a></td></tr> +<tr><td align="left"><span class="smcap">General View of the Observatory Buildings from the New Dome</span></td><td align="right"><a href="#general">12</a></td></tr> +<tr><td align="left"><span class="smcap">Flamsteed's Sextant</span></td><td align="right"><a href="#sextant">36</a></td></tr> +<tr><td align="left"><span class="smcap">The Royal Observatory in Flamsteed's Time</span></td><td align="right"><a href="#engraving">44</a></td></tr> +<tr><td align="left"><span class="smcap">The 'Camera Stellata' in Flamsteed's Time</span></td><td align="right"><a href="#stellata">52</a></td></tr> +<tr><td align="left"><span class="smcap">Edmund Halley</span></td><td align="right"><a href="#halley">61</a></td></tr> +<tr><td align="left"><span class="smcap">Halley's Quadrant</span></td><td align="right"><a href="#quadrant">69</a></td></tr> +<tr><td align="left"><span class="smcap">James Bradley</span></td><td align="right"><a href="#bradley">72</a></td></tr> +<tr><td align="left"><span class="smcap">Graham's Zenith Sector</span></td><td align="right"><a href="#zenith">77</a></td></tr> +<tr><td align="left"><span class="smcap">Nathaniel Bliss</span></td><td align="right"><a href="#bliss">83</a></td></tr> +<tr><td align="left"><span class="smcap">Nevil Maskelyne</span></td><td align="right"><a href="#nevil">87</a></td></tr> +<tr><td align="left"><span class="smcap">Hadley's Quadrant</span></td><td align="right"><a href="#hadley">91</a></td></tr> +<tr><td align="left"><span class="smcap">John Pond</span></td><td align="right"><a href="#pond">96</a></td></tr> +<tr><td align="left"><span class="smcap">George Biddell Airy, Astronomer Royal</span></td><td align="right"><a href="#airy">103</a></td></tr> +<tr><td align="left"><span class="smcap">The Astronomer Royal's Room</span></td><td align="right"><a href="#royal">110</a></td></tr> +<tr><td align="left"><span class="smcap">The South-east Tower</span></td><td align="right"><a href="#tower">115</a></td></tr> +<tr><td align="left"><span class="smcap">W. H. M. Christie, Astronomer Royal</span></td><td align="right"><a href="#christie">121</a></td></tr> +<tr><td align="left"><span class="smcap">The Astronomer Royal's House</span></td><td align="right"><a href="#astro">127</a></td></tr> +<tr><td align="left"><span class="smcap">The Courtyard</span></td><td align="right"><a href="#court">130</a></td></tr> +<tr><td align="left"><span class="smcap">Plan of Observatory at Present Time</span></td><td align="right"><a href="#plan">134</a></td></tr> +<tr><td align="left"><span class="smcap">The Great Clock and Porter's Lodge</span></td><td align="right"><a href="#clock">147</a></td></tr> +<tr><td align="left"><span class="smcap">The Chronograph</span></td><td align="right"><a href="#graph">158</a></td></tr> +<tr><td align="left"><span class="smcap">The Time-desk</span></td><td align="right"><a href="#desk">164</a></td></tr> +<tr><td align="left"><span class="smcap">Harrison's Chronometer</span></td><td align="right"><a href="#harrison">165</a></td></tr> +<tr><td align="left"><span class="pagenum"><a name="Page_10" id="Page_10">[10]</a></span><span class="smcap">The Chronometer Room</span></td><td align="right"><a href="#room">167</a></td></tr> +<tr><td align="left"><span class="smcap">The Chronometer Oven</span></td><td align="right"><a href="#oven">171</a></td></tr> +<tr><td align="left"><span class="smcap">The Transit Pavilion</span></td><td align="right"><a href="#transit">174</a></td></tr> +<tr><td align="left"><span class="smcap">'Lost in the Birkenhead'</span></td><td align="right"><a href="#lost">179</a></td></tr> +<tr><td align="left"><span class="smcap">The Transit Circle</span></td><td align="right"><a href="#circle">189</a></td></tr> +<tr><td align="left"><span class="smcap">The Mural Circle</span></td><td align="right"><a href="#mural">195</a></td></tr> +<tr><td align="left"><span class="smcap">Airy's Altazimuth</span></td><td align="right"><a href="#alta">208</a></td></tr> +<tr><td align="left"><span class="smcap">New Altazimuth Building</span></td><td align="right"><a href="#zimuth">211</a></td></tr> +<tr><td align="left"><span class="smcap">The New Altazimuth</span></td><td align="right"><a href="#news">213</a></td></tr> +<tr><td align="left"><span class="smcap">The New Observatory as seen from Flamsteed's Observatory</span></td><td align="right"><a href="#observe">219</a></td></tr> +<tr><td align="left"><span class="smcap">The Self-registering Thermometers</span></td><td align="right"><a href="#self">235</a></td></tr> +<tr><td align="left"><span class="smcap">The Anemometer Room, North-west Turret</span></td><td align="right"><a href="#anemone">240</a></td></tr> +<tr><td align="left"><span class="smcap">The Anemometer Trace</span></td><td align="right"><a href="#trace">243</a></td></tr> +<tr><td align="left"><span class="smcap">Magnetic Pavilion—Exterior</span></td><td align="right"><a href="#ext">246</a></td></tr> +<tr><td align="left"><span class="smcap">Magnetic Pavilion—Interior</span></td><td align="right"><a href="#int">248</a></td></tr> +<tr><td align="left"><span class="smcap">The Dallmeyer Photo-heliograph</span></td><td align="right"><a href="#helio">254</a></td></tr> +<tr><td align="left"><span class="smcap">Photograph of a Group of Sun-spots</span></td><td align="right"><a href="#spots">259</a></td></tr> +<tr><td align="left"><span class="smcap">The Great Nebula in Orion</span></td><td align="right"><a href="#orion">269</a></td></tr> +<tr><td align="left"><span class="smcap">The Half-prism Spectroscope on the South-east Equatorial</span></td><td align="right"><a href="#prism">273</a></td></tr> +<tr><td align="left"><span class="smcap">The Workshop</span></td><td align="right"><a href="#workshop">276</a></td></tr> +<tr><td align="left"><span class="smcap">The 30-inch Reflector with the New Spectroscope attached</span></td><td align="right"><a href="#reflect">278</a></td></tr> +<tr><td align="left"><span class="smcap">'Chart Plate' of the Pleiades</span></td><td align="right"><a href="#plate">286</a></td></tr> +<tr><td align="left"><span class="smcap">The Control Pendulum and the Base of the Thompson Telescope</span></td><td align="right"><a href="#pendulum">289</a></td></tr> +<tr><td align="left"><span class="smcap">The Astrographic Telescope</span></td><td align="right"><a href="#telescope">291</a></td></tr> +<tr><td align="left"><span class="smcap">The Driving Clock of the Astrographic Telescope</span></td><td align="right"><a href="#driving">294</a></td></tr> +<tr><td align="left"><span class="smcap">The Thompson Telescope in the New Dome</span></td><td align="right"><a href="#thompson">297</a></td></tr> +<tr><td align="left"><span class="smcap">The Nebulæ of the Pleiades</span></td><td align="right"><a href="#neb">300</a></td></tr> +<tr><td align="left"><span class="smcap">Double-star Observation with the South-east Equatorial</span></td><td align="right"><a href="#star">308</a></td></tr> +<tr><td align="left"><span class="smcap">The South-east Dome with the Shutter Open</span></td><td align="right"><a href="#shutter">314</a></td></tr> +</table></div> +<hr class="chap" /> +<p><span class="pagenum"><a name="Page_11" id="Page_11"> </a><br /><a name="Page_12" id="Page_12"> </a></span></p> + +<div class="figcenter bord" style="width: 600px;"><a name="general" id="general"></a> +<img src="images/i_012.jpg" width="600" height="360" alt="general" /> +<div class="caption"><p class="center">GENERAL VIEW OF THE OBSERVATORY BUILDINGS FROM THE NEW DOME.<br /> + +(<em>From a photograph by Mr. Lacey.</em>)</p></div> +</div> + +<hr class="chap" /> + +<p><span class="pagenum"><a name="Page_13" id="Page_13">[13]</a></span></p> + + + + +<h2>THE ROYAL OBSERVATORY</h2> + +<h3>GREENWICH</h3> + + + +<hr class="chap" /> +<h2>CHAPTER I</h2> + +<h3>INTRODUCTION</h3> + + +<p>I had parted from a friend one day just as he met +an acquaintance of his to whom I was unknown. +'Who is that?' said the newcomer, referring to me. +My friend replied that I was an astronomer from +Greenwich Observatory.</p> + +<p>'Indeed; and what does he do there?'</p> + +<p>This question completely exhausted my friend's +information, for as his tastes did not lead him in +the direction of astronomy, he had at no time ever +concerned himself to inquire as to the nature of my +official duties. 'Oh—er—why—he <em>observes</em>, don't +you know?' and the answer, vague as it was, +completely slaked the inquirer's thirst for knowledge.</p> + +<p>It is not every one who has such exceedingly +nebulous ideas of an astronomer's duties. More +frequently we find that the inquirer has already +formed a vivid and highly-coloured picture of the +astronomer at his 'soul-entrancing work.' Resting<span class="pagenum"><a name="Page_14" id="Page_14">[14]</a></span> +on a comfortable couch, fixed at a luxurious angle, +the eye-piece of some great and perfect instrument +brought most conveniently to his eye, there passes +before him, in grand procession, a sight such as the +winter nights, when clear and frosty, give to the +ordinary gazer, but increased ten thousand times in +beauty, brilliance, and wonder by the power of his +telescope. For him Jupiter reveals his wind-drifted +clouds and sunset colours; for him Saturn spreads +his rings; for him the snows of Mars fall and melt, +and a thousand lunar plains are ramparted with +titanic crags; his are the star-clusters, where suns +in their first warm youth swarm thicker than hiving +bees; his the faint veils of nebulous smoke, the first +hint of shape in worlds about to be, or, perchance, +the last relics of worlds for ever dead. And beside +the enjoyment of all this entrancing spectacle of +celestial beauty, the fortunate astronomer sits at his +telescope and <em>discovers</em>—always he <em>discovers</em>.</p> + +<p>This, or something like it, is a very popular +conception of an astronomer's experiences and duty; +and consequently many, when they are told that +'discoveries' are not made at Greenwich, are inclined +to consider that the Observatory has failed in its +purpose. An astronomer without 'discoveries' to +his record is like an angler who casts all day and +comes home without fish—obviously an idle or incompetent +person.</p> + +<p>Again, it is considered that astronomy is a most +transcendental science. It deals with infinite distances, +with numbers beyond all power of human intellect +to appreciate, and therefore it is supposed, on the<span class="pagenum"><a name="Page_15" id="Page_15">[15]</a></span> +one hand, that it is a most elevating study, keeping +the mind continually on the stretch of ecstasy, and, +on the other hand, that it is utterly removed from all +connection with practical, everyday, ordinary life.</p> + +<p>These ideas as to the Royal Observatory, or ideas +like them, are very widely current, and they are, in +every respect, exactly and wholly wrong. First of +all, Greenwich Observatory was originally founded, +and has been maintained to the present day, for a +strictly practical purpose. Next, instead of leading +a life of dreamy ecstasy or transcendental speculation, +the astronomer has, perhaps, more than any man, to +give the keenest attention to minute practical details. +His life, on the one side, approximates to that of the +engineer; on the other, to that of the accountant. +Thirdly, the professional astronomer has hardly anything +to do with the show places of the sky. It is +quite possible that there are many people whose sole +opportunity of looking through a telescope is the +penny peep through the instrument of some itinerant +showman, who may have seen more of these than +an active astronomer in a lifetime; while as to 'discoveries,' +these lie no more within the scope of our +national observatory than do geographical discoveries +within that of the captain and officers of an ocean liner.</p> + +<p>If it is not to afford the astronomer beautiful +spectacles, nor to enable him to make thrilling +discoveries, what is the purpose of Greenwich Observatory?</p> + +<p>First and foremost, it is to assist navigation. The +ease and certainty with which to-day thousands of +miles of ocean are navigated have ceased to excite<span class="pagenum"><a name="Page_16" id="Page_16">[16]</a></span> +any wonder. We do not even think about it. We +go down to the docks and see, it may be, one steamer +bound for Halifax, another for New York, a third for +Charleston, a fourth for the West Indies, a fifth for +Rio de Janeiro; and we unhesitatingly go on board +the one bound for our chosen destination, without +the faintest misgiving as to its direction. We have +no more doubt about the matter than we have in +choosing our train at a railway station. Yet, whilst +the train is obliged to follow a narrow track already +laid for it, from which it cannot swerve an inch, the +steamer goes forth to traverse for many days an +ocean without a single fixed mark or indication of +direction; and it is exposed, moreover, to the full +force of winds and currents, which may turn it from +its desired path.</p> + +<p>But for this facility of navigation, Great Britain +could never have obtained her present commercial +position and world-wide empire.</p> + +<div class="poem"><div class="stanza"> +<span class="i0">'For the Lord our God most High,<br /></span> +<span class="i0">He hath made the deep as dry;<br /></span> +<span class="i0">He has smote for us a pathway,<br /></span> +<span class="i0">To the ends of all the earth.'<br /></span> +</div></div> + +<p>Part of this facility is, of course, due to the invention +of the steam engine, but much less than is +generally supposed. Even yet the clippers, with +their roods of white canvas, are not entirely superseded; +and if we could conceive of all steamships +being suddenly annihilated, ere long the sailing +vessels would again, as of yore, prove the</p> + +<div class="poem"><div class="stanza"> +<span class="i0">'Swift shuttles of an empire's loom,<br /></span> +<span class="i0">That weave us main to main.'<br /></span> +</div></div> +<p><span class="pagenum"><a name="Page_17" id="Page_17">[17]</a></span></p> +<p>But with the art of navigation thrust back into +its condition of a hundred and fifty years ago, it is +doubtful whether a sufficient tide of commerce could +be carried on to keep our home population supplied, +or to maintain a sufficiently close political connection +between these islands and our colonies.</p> + +<p>Navigation was in a most primitive condition even +as late as the middle of last century. Then the +method of finding a ship's longitude at sea was the +insufficient one of dead reckoning. In other words, +the direction and speed of the ship were estimated +as closely as possible, and so the position was carried +on from day to day. The uncertainty of the method +was very great, and many terrible stories might be +told of the disastrous consequences which might, and +often did, follow in the train of this method by +guess-work. It will be sufficient, however, to cite +the instance of Commodore Anson. He wanted to +make the island of Juan Fernandez, where he hoped +to obtain fresh water and provisions, and to recruit +his crew, many of whom were suffering from that +scourge of old-time navigators—scurvy. He got +into its latitude easily enough, and ran eastward, +believing himself to be west of the island. He was, +however, really east of it, and therefore made the +mainland of America. He had therefore to turn +round and sail westwards, losing many days, during +which the scurvy increased upon his crew, many of +whom died from the terrible disease before he +reached the desired island.</p> + +<p>The necessity for finding out a ship's place when +at sea had not been very keenly felt until the end<span class="pagenum"><a name="Page_18" id="Page_18">[18]</a></span> +of the fifteenth century. It was always possible for +the sailor to ascertain his latitude pretty closely, +either by observing the height of the pole-star at +night or the height of the sun at noonday; and so +long as voyages were chiefly confined to the Mediterranean +Sea, and the navigators were content for +the most part to coast from point to point, rarely +losing sight of land, the urgency of solving the +second problem—the longitude of the ship—was not +so keenly felt. But immediately the discoveries of +the great Portuguese and Spanish navigators brought +a wider, bolder navigation into vogue, it became a +matter of the first necessity.</p> + +<p>To take, for example, the immortal voyage of +Christopher Columbus. His purpose in setting out +into the west was to discover a new way to India. +The Venetians and Genoese practically possessed +the overland route across the Isthmus of Suez and +down the Red Sea. Vasco da Gama had opened +out the route eastward round the Cape. Firmly +convinced that the world was a globe, Columbus saw +that a third route was possible, namely, one nearly +due west; and when, therefore, he reached the +Bahamas, after traversing some 66° of longitude, he +believed that he was in the islands of the China Sea, +some 230° from Spain. Those who followed him +still laboured under the same impression, and when +they reached the mainland of America, believed that +they were close to the shores of India, which was +still distant from them by half the circumference of +the globe.</p> + +<p>Little by little the intrepid sailors of the sixteenth<span class="pagenum"><a name="Page_19" id="Page_19">[19]</a></span> +century forced their way to a true knowledge of the +size of the globe, and of the relative position of the +great continents. But this knowledge was only +attained after many disasters and terrible miseries; +and though a new kind of navigation was established—the +navigation of the open ocean, far away from any +possible landmark, a navigation as different as could +be conceived from the old method of coasting—yet it +remained terribly risky and uncertain throughout the +sixteenth century. Therefore many mathematicians +endeavoured to solve the problem of determining the +position of a ship when at sea. Their suggestions, +however, remained entirely fruitless at the time, +though in several instances they struck upon principles +which are being employed at the present day.</p> + +<p>The first country to profit by the discovery of +America was Spain, and hence Spain was the first +to feel keenly the pinch of the problem. In 1598, +therefore, Philip III. offered a prize of 100,000 +crowns to any one who would devise a method by +which a captain of a vessel could determine his +position when out of sight of land. Holland, which +had recently started on its national existence, and +which was challenging the colonial empire of Spain, +followed very shortly after with the offer of a reward +of 30,000 florins. Not very long after the offer of +these rewards, a master mind did work out a simple +method for determining the longitude, a method +theoretically complete, though practically it proved +inapplicable. This was Galileo, who, with his newly +invented telescope, had discovered that Jupiter was +attended by four satellites.</p> + +<p><span class="pagenum"><a name="Page_20" id="Page_20">[20]</a></span></p> + +<p>At first sight such a discovery, however interesting, +would seem to have not the slightest bearing +upon the sailor's craft, or upon the commercial +progress of one nation or another. But Galileo +quickly saw in it the promise of great practical +usefulness. The question of the determination of +the place of a ship when in the open ocean really +resolved itself into this: How could the navigator +ascertain at any time what was the true time, say at +the port from which he sailed? As already pointed +out, it was possible, by observing the height of the +sun at noon, or of the pole-star at night, to infer the +latitude of the ship. The longitude was the point +of difficulty. Now, the longitude may be expressed +as the difference between the local time of the place +of observation and the local time at the place chosen +as the standard meridian. The sailor could, indeed, +obtain his own local time by observations of the +height of the sun. The sun reached its greatest +height at local noon, and a number of observations +before and after noon would enable him to determine +this with sufficient nicety.</p> + +<p>But how was he to determine when he, perhaps, +was half-way across the Atlantic, what was the local +time at Genoa, Cadiz, Lisbon, Bristol, or Amsterdam, +or whatever was the port from which he sailed? +Galileo thought out a way by which the satellites of +Jupiter could give him this information.</p> + +<p>For as they circle round their primary, they +pass in turn into its shadow, and are eclipsed by it. +It needed, then, only that the satellites should be +so carefully watched, that their motions, and,<span class="pagenum"><a name="Page_21" id="Page_21">[21]</a></span> +consequently, the times of their eclipses could be +foretold. It would follow, then, that if the mariner +had in his almanac the local time of the standard city +at which a given satellite would enter into eclipse, +and he were able to note from the deck of his vessel +the disappearance of the tiny point, he would ascertain +the difference between the local times of the two +places, or, in other words, the difference of their +longitudes.</p> + +<p>The plan was simplicity itself, but there were +difficulties in carrying it out, the greatest being the +impossibility of satisfactorily making telescopic +observations from the moving deck of a ship at sea. +Nor were the observations sufficiently sharp to be of +much help. The entry of a satellite into the shadow +of Jupiter is in most cases a somewhat slow process, +and the moment of complete disappearance would +vary according to the size of the telescope, the keenness +of the observer's sight, and the transparency of +the air.</p> + +<p>As the power and commerce of Spain declined, +two other nations entered into the contest for the +sovereignty of the seas, and with that sovereignty +predominance in the New World of America—France +and England. The problem of the longitude at sea, +or, as already pointed out, what amounts to the same +thing, the problem how to determine when at sea +the local time at some standard place, became, in +consequence, of greater necessity to them.</p> + +<p>The standard time would be easily known, if a +thoroughly good chronometer which did not change +its rate, and which was set to the standard time before<span class="pagenum"><a name="Page_22" id="Page_22">[22]</a></span> +starting, was carried on board the ship. This plan +had been proposed by Gemma Frisius as early as +1526, but at the time was a mere suggestion, as there +were no chronometers or watches sufficiently good +for the purpose. There was, however, another method +of ascertaining the standard time. The moon moves +pretty quickly amongst the stars, and at the present +time, when its motions are well known, it is possible +to draw up a table of its distances from a number +of given stars at definite times for long periods in +advance. This is actually done to-day in the <cite>Nautical +Almanac</cite>, the moon's distance from certain stars +being given for every three hours of Greenwich time. +It is possible, then, by measuring these distances, +and making, as in the case of the latitude, certain +corrections, to find out the time at Greenwich. In +short, the whole sky may be considered as a vast +clock set to Greenwich time, the stars being the +numbers on the dial face, and the moon the hand +(for this clock has only one hand) moving amongst +them.</p> + +<p>The local apparent time—that is, the time at the +place at which the ship itself was—is a simpler matter. +It is noon at any place when the sun is due south—or, +as we may put it a little differently, when it +culminates—that is, when it reaches its highest point.</p> + +<p>To find the longitude at sea, therefore, it was +necessary to be able to predict precisely the apparent +position of the moon in the sky for any time throughout +the entire year, and it was also necessary that the +places of the stars themselves should be very accurately +known. It was therefore to gather the materials for<span class="pagenum"><a name="Page_23" id="Page_23">[23]</a></span> +a better knowledge of the motions of the moon and +the position of the stars that Greenwich Observatory +was founded, whilst the <cite>Nautical Almanac</cite> was +instituted to convey this information to mariners in +a convenient form.</p> + +<p>This proposal was actually made in the reign of +Charles II. by a Frenchman, Le Sieur de Saint-Pierre, +who, having secured an introduction to the +Duchess of Portsmouth, endeavoured to obtain a +reward for his scheme. It would appear that he had +simply borrowed the idea from a book which an +eminent French mathematician brought out forty +years before, without having himself any real knowledge +of the subject. But when the matter was +brought before the king's notice, he desired some +of the leading scientific men of the day to report +upon its practicability, and the Rev. John Flamsteed +was the man selected for the task. He reported that +the scheme in itself was a good one, but impracticable +in the then state of science. The king, who, in spite +of the evil reputation which he has earned for himself, +took a real interest in science, was startled when this +was reported to him, and commanded the man who +had drawn his attention to these deficiencies 'to +apply himself,' as the king's astronomer, 'with the +most exact care and diligence to the Rectifying the +Tables of the Motions of the Heavens and the Places +of the Fixed Stars, in order to find out the so much +desired Longitude at Sea, for the perfecting the Art +of Navigation.'</p> + +<p>This man, the Rev. John Flamsteed, was accordingly +appointed first Astronomer Royal at the meagre<span class="pagenum"><a name="Page_24" id="Page_24">[24]</a></span> +salary of £100 a year, with full permission to provide +himself with the instruments he might require, at his +own expense. He followed out the task assigned +to him with extreme devotion, amidst many difficulties +and annoyances, until his death in 1719. He has +been succeeded by seven Astronomers Royal, each +of whom has made it his first object to carry out +the original scheme of the institution; and the chief +purpose of Greenwich Observatory to-day, as when +it was founded in 1675, is to observe the motions +of the sun, moon, and planets, and to issue accurate +star catalogues.</p> + +<p>It will be seen, therefore, that the establishment +of Greenwich Observatory arose from the actual +necessity of the nation. It was an essential step in +its progress towards its present position as the first +commercial nation. No thoughts of abstract science +were in the minds of its founders; there was no +desire to watch the cloud-changes on Jupiter, or to +find out what Sirius was made of. The Observatory +was founded for the benefit of the Royal Navy and +of the general commerce of the realm; and, in essence, +that which was the sole object of its foundation at +the beginning has continued to be its first object +down to the present time.</p> + +<p>It was impossible that the work of the Observatory +should be always confined within the above limits, +and it will be my purpose, in the pages which follow, +to describe when and how the chief expansions of its +programme have taken place. But assistance to +navigation is now, and has always been, the dominant +note in its management.</p> + +<hr class="chap" /> + +<p><span class="pagenum"><a name="Page_25" id="Page_25">[25]</a></span></p> + + + + +<h2>CHAPTER II</h2> + +<h3>FLAMSTEED</h3> + + +<p>For the first century of its existence, the lives of its +Astronomers Royal formed practically the history +of the Royal Observatory. During this period, the +Observatory was itself so small that the Astronomer +Royal, with a single assistant, sufficed for the entire +work. Everything, therefore, depended upon the +ability, energy, and character of the actual director. +There was no large organized staff, established +routine, or official tradition, to keep the institution +moving on certain lines, irrespective of the personal +qualities of the chief. It was specially fortunate, +therefore, that the first four Astronomers Royal, +Flamsteed, Halley, Bradley, and Maskelyne (for Bliss, +the immediate successor of Bradley, reigned for so +short a time that he may be practically left out of the +count), were all men of the most conspicuous ability.</p> + +<p>It will be convenient to divide the history of the +first seven Astronomers Royal into three sections. +In the first, we have the founder, John Flamsteed, a +pathetic and interesting figure, whom we seem to +know with especial clearness, from the fulness of the +memorials which he has left to us. He was succeeded +by the man who was, indeed, best fitted to succeed<span class="pagenum"><a name="Page_26" id="Page_26">[26]</a></span> +him, but whom he most hated. The second to the +sixth Astronomers Royal formed what we might +almost speak of as a dynasty, each in turn nominating +his successor, who had entered into more or less +close connection with the Observatory during the +lifetime of the previous director; and the lives of +these five may well form the second section. The +line was interrupted after the resignation of the sixth +Astronomer Royal, and the third section will be +devoted to the seventh director, Airy, under whom +the Observatory entered upon its modern period of +expansion.</p> + +<blockquote> + +<p>'God suffers not man to be idle, although he swim in +the midst of delights; for when He had placed His own +image (Adam) in a paradise so replenished (of His goodness) +with varieties of all things, conducing as well to his +pleasure as sustenance, that the earth produced of itself +things convenient for both,—He yet (to keep him out of +idleness) commands him to till, prune, and dress his +pleasant, verdant habitation; and to add (if it might be) +some lustre, grace, or conveniency to that place, which, as +well as he, derived its original from his Creator.'</p></blockquote> + +<p>In these words <span class="smcap">John Flamsteed</span> begins the first +of several autobiographies which he has handed down +to us; this particular one being written before he +attained his majority, 'to keep myself from idleness +and to recreate myself.'</p> + +<blockquote> + +<p>'I was born,' he goes on, 'at Denby, in Derbyshire, in +the year 1646, on the 19th day of August, at 7 hours 16 +minutes after noon. My father, named Stephen, was the +third son of Mr. William Flamsteed, of Little Hallam; my +mother, Mary, was the daughter of Mr. John Spateman, of +Derby, ironmonger. From these two I derived my beginning, +whose parents were of known integrity, honesty, and<span class="pagenum"><a name="Page_27" id="Page_27">[27]</a></span> +fortune, as they [were] of equal extraction and ingenuity; +betwixt whom I [was] tenderly educated (by reason of my +natural weakness, which required more than ordinary care) +till I was aged three years and a fortnight; when my +mother departed, leaving my father a daughter, then not +a month old, with me, then weak, to his fatherly care and +provision.'</p></blockquote> + +<p>The weakly, motherless boy became at an early +age a voracious reader. At first, he says—</p> + +<blockquote> + +<p>'I began to affect the volubility and ranting stories of +romances; and at twelve years of age I first left off the +wild ones, and betook myself to read the better sort of +them, which, though they were not probable, yet carried no +seeming impossibility in the fiction. Afterwards, as my +reason increased, I gathered other real histories; and by +the time I was fifteen years old I had read, of the ancients, +Plutarch's <cite>Lives</cite>, Appian's and Tacitus's <cite>Roman Histories</cite>, +Holingshed's <cite>History of the Kings of England</cite>, Davies's +<cite>Life of Queen Elizabeth</cite>, Saunderson's of <cite>King Charles the +First</cite>, Heyling's <cite>Geography</cite>, and many others of the moderns; +besides a company of romances and other stories, of which +I scarce remember a tenth at present.'</p></blockquote> + +<p>Flamsteed received his education at the free school +at Derby, where he continued until the Whitsuntide +of 1662, when he was nearly sixteen years of age. +Two years earlier than this, however, a great misfortune +fell upon him.</p> + +<blockquote> + +<p>'At fourteen years of age,' he writes, 'when I was nearly +arrived to be the head of the free-school, [I was] visited +with a fit of sickness, that was followed with a consumption +and other distempers, which yet did not so much hinder me +in my learning, but that I still kept my station till the form +broke up, and some of my fellows went to the Universities; +for which, though I was designed, my father thought it +not advisable to send me, by reason of my distemper.'</p></blockquote> + +<p><span class="pagenum"><a name="Page_28" id="Page_28">[28]</a></span></p> + +<p>This was a keen disappointment to him, but +seems to have really been the means of determining +his career. The sickly, suffering boy could not be +idle, though 'a day's short reading caused so violent +a headache;' and a month or two after he had left +school, he had a book lent to him—Sacrobosco's +<cite>De Sphæra</cite>, in Latin—which was the beginning of +his mathematical studies. A partial eclipse of the +sun in September of the same year seems to have +first drawn his attention to astronomical observation, +and during the winter his father, who had himself a +strong passion for arithmetic, instructed him in that +science.</p> + +<p>It was astonishing how quickly his appetite for +his new subjects grew. The <cite>Art of Dialling</cite>, the +calculation of tables of the sun's altitudes for all +hours of the day, and for different latitudes, and the +construction of a quadrant—'of which I was not +meanly joyful'—were the occupations of this winter +of illness.</p> + +<p>In 1664 he made the acquaintanceship of two +friends, Mr. George Linacre and Mr. William +Litchford; the former of whom taught him to +recognize many of the fixed stars, whilst the latter +was the means of his introduction to a knowledge of +the motions of the planets.</p> + +<blockquote> + +<p>'I had now completed eighteen years, when the winter +came on, and thrust me again into the chimney; whence +the heat and dryness of the preceding summer had happily +once before withdrawn me.'</p></blockquote> + +<p>The following year, 1665, was memorable to him +'for the appearance of the comet,' and for a journey<span class="pagenum"><a name="Page_29" id="Page_29">[29]</a></span> +which he made to Ireland to be 'stroked' for his +rheumatic disorder by Valentine Greatrackes, a kind +of mesmerist, who had the repute of effecting wonderful +cures. The journey, of which he gives a full and +vivid account, occupied a month; but though he was +a little better, the following winter brought him no +permanent benefit.</p> + +<p>But, ill or well, he pressed on his astronomical +studies. A large partial eclipse of the sun was due +the following June; he computed the particulars of it +for Derby, and observed the eclipse itself to the best +of his ability. He argued out for himself 'the +equation of time'; the difference, that is, between +time as given by the actual sun, or 'apparent time,' +and that given by a perfect clock, or 'mean time.' +He drew up a catalogue of seventy stars, computing +their right ascensions, declinations, longitudes, and +latitudes for the year 1701; he attempted to determine +the inclination of the ecliptic, the mean length of the +tropical year, and the actual distance of the earth +from the sun. And these were the recreations of a +sickly, suffering young man, not yet twenty-one years +of age, and who had only begun the study of +arithmetic, such as fractions and the rule of three, +four years previously!</p> + +<p>His next attempt was almanac-making, in the +which he improved considerably upon those current +at the time. His almanac for 1670 was rejected, +however, and returned to him, and, not to lose his +whole labour, he sent his calculations of an eclipse of +the sun, and of five occultations of stars by the moon, +which he had undertaken for the almanac, to the<span class="pagenum"><a name="Page_30" id="Page_30">[30]</a></span> +Royal Society. He sent the paper anonymously, or, +rather, signed it with an anagram, 'In mathesi a sole +fundes,' for 'Johannes Flamsteedius.' His covering +letter ends thus:—</p> + +<blockquote> + +<p>'Excuse, I pray you, this juvenile heat for the concerns +of science and want of better language, from one who, from +the sixteenth year of his age to this instant, hath only +served one bare apprenticeship in these arts, under the discouragement +of friends, the want of health, and all other +instructors except his better genius.'</p></blockquote> + +<p>This letter was dated November 4, 1669, and on +January 14, Mr. Oldenburg, the secretary of the +Society, replied to him in a letter which the young +man cannot but have felt encouraging and flattering +to the highest degree.</p> + +<blockquote> + +<p>'Though you did what you could to hide your name from +us,' he writes, 'yet your ingenious and useful labours for +the advancement of Astronomy addressed to the noble +President of the Royal Society, and some others of that +illustrious body, did soon discover you to us, upon our +solicitous inquiries after their worthy author.'</p></blockquote> + +<p>And after congratulating him upon his skill, and +encouraging him to furnish further similar papers, +he signs himself, 'Your very affectionate friend and +real servant'—no unmeaning phrase, for the friendship +then commenced ceased only with Oldenburg's life.</p> + +<p>The following June, his father, pleased with the +notice that some of the leading scientific men of the +day were taking of his son, sent him up to London, +that he might be personally acquainted with them; +and he then was introduced to Sir Jonas Moore, the +Surveyor of the Ordnance, who made him a present<span class="pagenum"><a name="Page_31" id="Page_31">[31]</a></span> +of Townley's micrometer, and promised to furnish him +with object-glasses for telescopes at moderate rates.</p> + +<p>On his return journey he called at Cambridge, +where he visited Dr. Barrow and Newton, and +entered his name in Jesus College.</p> + +<p>It was not until the following year, 1671, that he +was enabled to complete his own observatory, as he +had had to wait long for the lenses which Sir Jonas +Moore and Collins had promised to procure for him. +He still laboured under several difficulties, in that he +had no good means for measuring time, pendulum +clocks not then being common. He, therefore, with +a practical good sense which was characteristic, +refrained from attempting anything which lay out of +his power to do well, and he devoted himself to such +observations as did not require any very accurate +knowledge of the time. At the same time, he was +careful to ascertain the time of his observations as +closely as possible, by taking the altitudes of the stars.</p> + +<p>The next four years seem to have passed +exceedingly pleasantly to him. The notes of ill-health +are few. He was making rapid progress in +his acquaintanceship with the work of other astronomers, +particularly with those of the three marvellously +gifted young men—Horrox, Crabtree, and Gascoigne—who +had passed away shortly before his own +birth. He was making new friends in scientific +circles, and, in particular, Sir Jonas Moore was evidently +esteeming him more and more highly. In +1674 he became more intimate with Newton, the +occasion which led to this acquaintanceship being +the amusing one, that his assistance was asked by<span class="pagenum"><a name="Page_32" id="Page_32">[32]</a></span> +Newton, who had found himself unable to adjust a +microscope, having forgotten its object-glass—not +the only instance of the great mathematician's +absent-mindedness.</p> + +<p>The same year he took his degree of A.M. at +Cambridge, designing to enter the Church; but Sir +Jonas Moore was extremely anxious to give him +official charge of an observatory, and was urging the +Royal Society to build an astronomical observatory +at Chelsea College, which then belonged to that body. +He therefore came up to London, and resided some +months with Sir Jonas Moore at the Tower. But +shortly after his coming up to London, 'an accident +happened,' to use his own expression, that hastened, +if it did not occasion, the building of Greenwich +Observatory.</p> + +<blockquote> + +<p>'A Frenchman that called himself Le Sieur de St. Pierre, +having some small skill in astronomy, and made an interest +with a French lady, then in favour at Court, proposed no +less than the discovery of the Longitude, and had procured +a kind of Commission from the King to the Lord Brouncker, +Dr. Ward (Bishop of Salisbury), Sir Christopher Wren, Sir +Charles Scarborough, Sir Jonas Moore, Colonel Titus, Dr. +Pell, Sir Robert Murray, Mr. Hook, and some other ingenious +gentlemen about the town and Court, to receive his +proposals, with power to elect, and to receive into their +number, any other skilful persons; and having heard them, +to give the King an account of them, with their opinion +whether or no they were practicable, and would show what +he pretended. Sir Jonas Moore carried me with him to one +of their meetings, where I was chosen into their number; +and, after, the Frenchman's proposals were read, which were:</p> + +<p>'(1) To have the year and day of the observations.</p> + +<p>'(2) The height of two stars, and on which side of the +meridian they appeared.</p> + +<p><span class="pagenum"><a name="Page_33" id="Page_33">[33]</a></span></p> + +<p>'(3) The height of the moon's two limbs.</p> + +<p>'(4) The height of the pole—all to degrees and minutes.</p> + +<p>'It was easy to perceive, from these demands, that the +sieur understood not that the best lunar tables differed from +the heavens; and that, therefore, his demands were not +sufficient for determining the longitude of the place where +such observations were, or should be, made, from that to +which the lunar tables were fitted, which I represented immediately +to the company. But they, considering the +interests of his patroness at Court, desired to have him +furnished according to his demands. I undertook it; and +having gained the moon's true place by observations made +at Derby, February 23, 1672, and November 12, 1673, gave +him observations such as he demanded. The half-skilled +man did not think they could have been given him, and +cunningly answered "<em>They were feigned</em>." I delivered them +to Dr. Pell, February 19, 1674-5, who, returning me his +answer some time after, I wrote a letter in English to the +commissioners, and another in Latin to the sieur, to assure +him they were not feigned, and to show them that, if they +had been, yet if we had astronomical tables that would give +us the two places of the fixed stars and the moon's true +places, both in longitude and latitude, nearer than to half +a minute, we might hope to find the longitude of places by +lunar observations, but not by such as he demanded. But +that we were so far from having the places of the fixed stars +true, that the Tychonic Catalogues often erred ten minutes +or more; that they were uncertain to three or four minutes, +by reason that Tycho assumed a faulty obliquity of the +ecliptic, and had employed only plain sights in his observations: +and that the best lunar tables differ one-quarter, +if not one-third, of a degree from the heavens; and lastly, +that he might have learnt better methods than he proposed, +from his countryman Morin, whom he had best +consult before he made any more demands of this nature.'</p></blockquote> + +<p>This was in effect to tell St. Pierre that his +proposal was neither original nor practicable. If +St. Pierre had but consulted Morin's writings (Morin<span class="pagenum"><a name="Page_34" id="Page_34">[34]</a></span> +himself had died more than eighteen years before), +he would have known that practically the same +proposal had been laid before Cardinal Richelieu +in 1634, and had been rejected, as quite impracticable +in the then state of astronomical knowledge. Possibly +Flamsteed meant further to intimate that St. Pierre +had simply stolen his method from Morin, hoping to +trade it off upon the government of another country; +in which case he would no doubt regard Flamsteed's +letter as a warning that he had been found out.</p> + +<p>Flamsteed continues:—</p> + +<blockquote> + +<p>'I heard no more of the Frenchman after this; but was +told that, my letters being shown King Charles, he startled +at the assertion of the fixed stars' places being false in the +catalogue; said, with some vehemence, "He must have +them anew observed, examined, and corrected, for the use +of his seamen;" and further (when it was urged to him how +necessary it was to have a good stock of observations taken +for correcting the motions of the moon and planets), with +the same earnestness, "he must have it done." And when +he was asked Who could, or who should do it? "The +person (says he) that informs you of them." Whereupon +I was appointed to it, with the incompetent allowance aforementioned; +but with assurances, at the same time, of such +further additions as thereafter should be found requisite for +carrying on the work.'</p></blockquote> + +<div class="figcenter bord" style="width: 600px;"><a name="sextant" id="sextant"></a> +<img src="images/i_036.jpg" width="600" height="369" alt="sextant" /> +<div class="caption"><p class="center">FLAMSTEED'S SEXTANT.<br /> + +(<em>From an engraving in the 'Historia Cœlestis.'</em>)</p></div> +</div> + +<p>Thus, in his twenty-ninth year, John Flamsteed +became the first Astronomer Royal. In many ways +he was an ideal man for the post. In the twelve +years which had passed since he left school he had +accomplished an amazing amount of work. Despite +his constant ill-health and severe sufferings, and the +circumstance—which may be inferred from many +expressions in his autobiographies—that he assisted<span class="pagenum"><a name="Page_35" id="Page_35"> </a><br /><a name="Page_36" id="Page_36"> </a><br /><a name="Page_37" id="Page_37">[37]</a></span> +his father in his business, he had made himself master, +perhaps more thoroughly than any of his contemporaries, +of the entire work of a practical astronomer +as it was then understood. He was an indefatigable +computer; the calculation of tables of the motions of +the moon and planets, which should as faithfully as +possible represent their observed positions, had had +an especial attraction for him, and, as has been +already mentioned, some years before his appointment +he had drawn up a catalogue of stars, based +upon the observations of Tycho Brahe. More than +that, he had not been a merely theoretical worker, +he had been a practical observer of very considerable +skill, and, in the dearth of suitable instruments, had +already made one or two for himself, and had contemplated +the making of others. In his first letter +to Sir Jonas Moore he asks for instruction as to the +making of object-glasses for telescopes, for he was +quite prepared to set about the task of making his own. +In addition to his tireless industry, which neither illness +nor suffering could abate, he was a man of singularly +exact and business-like habits. The precision +with which he preserves and records the dates of all +letters received or sent is an illustration of this. On +the other hand, he had the defects of his circumstances +and character. His numerous autobiographical +sketches betray him, not indeed as a conceited man, in +the ordinary sense of the word, but as an exceedingly +self-conscious one. Devout and high-principled he +most assuredly was, but, on the other hand, he shows +in almost every line he wrote that he was one who +could not brook anything like criticism or opposition.</p> + +<p><span class="pagenum"><a name="Page_38" id="Page_38">[38]</a></span></p> + +<p>Such a man, however efficient, was little likely to be +happy as the first incumbent of a new and important +government post; but there was another circumstance +which was destined to cause him greater unhappiness +still.</p> + +<p>If we believe, as surely we must, that not only +the moral and the physical progress of mankind is +watched over and controlled by God's good Providence, +but its intellectual progress as well, then there +can be no doubt that John Flamsteed was raised +up at this particular time, not merely to found +Greenwich Observatory, and to assist the solution +of the problem of the longitude at sea, but also, and +chiefly, to become the auxiliary to a far greater mind, +the journeyman to a true master-builder. But for the +founding of Greenwich Observatory, and for John +Flamsteed's observations made therein, the working +out of Newton's grand theory of gravitation must +have been hindered, and its acceptance by the men of +science of his time immensely delayed. We cannot +regard as accidental the combination, so fortunate for +us, of Newton, the great world-genius, to work out the +problem, of Flamsteed, the painstaking observer, to +supply him with the materials for his work, and of +the newly-founded institution, Greenwich Observatory, +where Flamsteed was able to gather those materials +together. This is the true debt that we owe to Flamsteed, +that, little as he understood the position in +which he had been placed from the standpoint from +which we see it to-day, yet, to the extent of his ability, +and as far as he conceived it in accordance with his +duty, he gave Newton such assistance as he could.</p> + +<p><span class="pagenum"><a name="Page_39" id="Page_39">[39]</a></span></p> + +<p>This is how we see the matter to-day. It wore +a very different aspect in Flamsteed's eyes; and the +two following documents, the one, the warrant founding +the Observatory and making him Astronomer +Royal; the other, the warrant granting him a salary, +will go far to explain his position in the matter. He +had a high-sounding, official position, which could +not fail to impress him with a sense of importance; +whilst his salary was so insufficient that he naturally +regarded himself as absolute owner of his own +work.</p> + + +<blockquote> + +<p class="center"><em>'Warrant for the Payment of Mr. Flamsteed's Salary.</em></p> + +<p class="center">'Charles Rex.</p> + +<p>'Whereas, we have appointed our trusty and well-beloved +John Flamsteed, Master of Arts, our astronomical +observator, forthwith to apply himself with the most exact +care and diligence to the rectifying the tables of the motions +of the heavens, and the places of the fixed stars, so as to +find out the so-much-desired longitude of places for the +perfecting the art of navigation, Our will and pleasure is, +and we do hereby require and authorize you, for the support +and maintenance of the said John Flamsteed, of whose +abilities in astronomy we have very good testimony, and +are well satisfied, that from time to time you pay, or cause +to be paid, unto him, the said John Flamsteed, or his +assigns, the yearly salary or allowance of one hundred +pounds per annum; the same to be charged and borne +upon the quarter-books of the Office of the Ordnance, and +paid to him quarterly, by even and equal portions, by the +Treasurer of our said office, the first quarter to begin and +be accompted from the feast of St. Michael the Archangel +last past, and so to continue during our pleasure. And for +so doing, this shall be as well unto you, as to the Auditors +of the Exchequer, for allowing the same, and all other our<span class="pagenum"><a name="Page_40" id="Page_40">[40]</a></span> +officers and ministers whom it may concern, a full and +sufficient warrant.</p> + +<p>'Given at our Court at Whitehall, the 4th day of March, +1674-5.</p> + +<p class="cenetr"> +'By his Majesty's Command,</p> +<p class="sig"> +'<span class="smcap">J. Williamson</span>. +</p> + +<p>'To our right-trusty and well-beloved Counsellor, +Sir Thomas Chichely, Knt., Master of our +Ordnance, and to the Lieutenant-General of our +Ordnance, and to the rest of the Officers of our +Ordnance, now and for the time being, and to all +and every of them.'</p></blockquote> + + +<blockquote> + +<p class="center"><em>'Warrant for Building the Observatory.</em></p> + +<p class="center">'Charles Rex.</p> + +<p>'Whereas, in order to the finding out of the longitude of +places for perfecting navigation and astronomy, we have +resolved to build a small observatory within our park at +Greenwich, upon the highest ground, at or near the place +where the Castle stood, with lodging-rooms for our +astronomical observator and assistant, Our will and pleasure +is, that according to such plot and design as shall be given +you by our trusty and well-beloved Sir Christopher Wren, +Knight, our surveyor-general of the place and scite of the +said observatory, you cause the same to be fenced in, built +and finished with all convenient speed, by such artificers +and workmen as you shall appoint thereto, and that you +give order unto our Treasurer of the Ordnance for the +paying of such materials and workmen as shall be used and +employed therein, out of such monies as shall come to your +hands for old and decayed powder, which hath or shall be +sold by our order of the 1st of January last, provided that +the whole sum, so to be expended or paid, shall not exceed +five hundred pounds; and our pleasure is, that all our +officers and servants belonging to our said park be assisting +to those that you shall appoint, for the doing thereof, and +for so doing, this shall be to you, and to all others whom it +may concern, a sufficient warrant.</p> + +<p><span class="pagenum"><a name="Page_41" id="Page_41">[41]</a></span></p> + +<p>'Given at our Court at Whitehall, the 22nd day of June, +1675, in the 27th year of our reign.</p> + +<p class="center"> +'By his Majesty's Command,</p> +<p class="sig"> +<span class="smcap">'J. Williamson</span>. +</p> + +<p>'To our right-trusty and well-beloved Counsellor, +Sir Thomas Chichely, Knt., Master-General of our +Ordnance.'</p></blockquote> + +<p>The first question that arose, when it had been +determined to found the new Observatory, was where +it was to be placed. Hyde Park was suggested, +and Sir Jonas Moore recommended Chelsea College, +where he had already thought of establishing +Flamsteed in a private observatory. Fortunately, +both these localities were set aside in favour of one +recommended by Sir Christopher Wren. There was +a small building on the top of the hill in the Royal +Park of Greenwich belonging to the Crown, and +which was now of little or no use. Visible from the +city, and easily accessible by that which was then +the best and most convenient roadway, the river +Thames, it was yet so completely out of town as +to be entirely safe from the smoke of London. In +Greenwich Park, too, but on the more easterly hill, +Charles I. had contemplated setting up an observatory, +but the pressure of events had prevented +him carrying out his intention. A further practical +advantage was that materials could be easily transported +thither. The management of public affairs +under Charles II. left much to be desired in the +matter of efficiency and economy, and it was not +very easy to procure what was wanted for the erection +of a purely scientific building. However, the matter<span class="pagenum"><a name="Page_42" id="Page_42">[42]</a></span> +was arranged. A gate-house demolished in the Tower +supplied wood; iron, and lead, and bricks were supplied +from Tilbury Fort, and these could be easily +brought by water to the selected site. The sum of +£500, actually £520, was further allotted from the +results of a sale of spoilt gunpowder; and with these +limited resources Greenwich Observatory was built.</p> + +<p>The foundation-stone was laid August 10, 1675, +and Flamsteed amused himself by drawing the horoscope +of the Observatory, a fact which—in spite of +his having written across the face of the horoscope +<i lang="la" xml:lang="la">Risum teneatis amici?</i> (Can you keep from laughter, +my friends?), 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 cult. He actually entered +into residence July 10, 1676.</p> + +<div class="figcenter bord" style="width: 600px;"><a name="engraving" id="engraving"></a> +<img src="images/i_044.jpg" width="600" height="335" alt="engraving" /> +<div class="caption"><p class="center">THE ROYAL OBSERVATORY IN FLAMSTEED'S DAY.<br /> +(<em>From an engraving in the 'Historia Cœlestis.'</em>)</p></div> +</div> + +<p>His position was not a bright one. The Government +had, indeed, provided him with a building for +his observatory, and a small house for his own +residence, but he had no instrument and no assistant. +The first difficulty was partly overcome for the +moment by gifts or loans from Sir Jonas Moore, and +by one or two small loans from the Royal Society. +The death of this great friend and patron, four years +after the founding of the Observatory, and only three +years after his entering into residence, deprived him +of several of these; it was with difficulty that he +maintained against Sir Jonas' heirs his claim to the +instruments which Sir Jonas had given him. There +was nothing for him to do but to make his instruments +himself, and in 1683 he built a mural quadrant<span class="pagenum"><a name="Page_43" id="Page_43"> </a><br /><a name="Page_44" id="Page_44"> </a><br /><a name="Page_45" id="Page_45">[45]</a></span> +of fifty inches radius. His circumstances improved +the following year, when Lord North gave him the +living of Burstow, near Horley, Surrey, Flamsteed +having received ordination almost at the time of his +appointment to the Astronomer Royalship. We +have little or no account of the way in which he +fulfilled his duties as a clergyman. Evidently he +considered that his position as Astronomer Royal +had the first claim upon him. At the same time, comparatively +early in life he had expressed his desire +to fill the clerical office, and he was a man too +conscientious to neglect any duty that lay upon him. +That in spite of his feeble health he often journeyed +to and fro between Burstow and Greenwich we know; +and we may take it as certain that at a time when +the standard of clerical efficiency was extremely low, +he was not one of those who</p> + +<div class="poem"><div class="stanza"> +<span class="i16">'For their bellies' sake,<br /></span> +<span class="i0">Creep and intrude and climb into the fold.'<br /></span> +</div></div> + +<p>His chief source of income, however, seems to +have been the private pupils whom he took in +mathematics and astronomy. These numbered in +the years 1676 to 1709 no fewer than 140; and as +many of them were of the very first and wealthiest +families in the kingdom, the gain to Flamsteed in +money and influence must have been considerable. +But it was most distasteful work. It was in no sense +that which he felt to be his duty, and which he had +at heart. It was undertaken from sheer, hard necessity, +and he grudged bitterly the time and strength +which it diverted from his proper calling.</p> + +<p><span class="pagenum"><a name="Page_46" id="Page_46">[46]</a></span></p> + +<p>How faithfully he followed that, one single circumstance +will show. In the thirteen years ending +1689, he made 20,000 observations, and had revised +single-handed the whole of the theories and tables of +the heavenly bodies then in use.</p> + +<p>In 1688 the death of his father brought him a +considerable accession of means, and, far more important, +the assistance of Abraham Sharp,<a name="FNanchor_1_1" id="FNanchor_1_1"></a><a href="#Footnote_1_1" class="fnanchor">[1]</a> the first +and most distinguished of the long list of Greenwich +assistants, men who, though far less well known than +the Astronomers Royal, have contributed scarcely +less in their own field to the high reputation of the +Observatory.</p> + +<p>Sharp was not only a most careful and indefatigable +calculator, he was what was even more +essential for Flamsteed—a most skilful instrument-maker; +and he divided for him a new mural arc of +140° and seven feet radius, with which he commenced +operations on December 12, 1689. Above all, Sharp +became his faithful and devoted friend and adherent, +and no doubt his sympathy strengthened Flamsteed +to endure the trouble which was at hand.</p> + +<p>That trouble began in 1694, when Newton visited +the Royal Observatory. At that time Flamsteed, +though he had done so much, had published nothing, +and Newton, who had made his discovery of the +laws of gravitation some few years before, was then +employed in deducing from them a complete theory +of the moon's motion. This work was one of +absolutely first importance. In the first place and<span class="pagenum"><a name="Page_47" id="Page_47">[47]</a></span> +chiefly, upon the success with which it could be +carried out, depended undoubtedly the acceptance +of the greatest discovery which has yet been made +in physical science. Secondarily—and this should, +and no doubt did, appeal to Flamsteed—the perfecting +of our knowledge of the movements of the moon +was a primary part of the very work which he was +commissioned to do as Astronomer Royal. Newton +was, therefore, anxious beyond everything to receive +the best possible observations of the moon's places, +and he came to Flamsteed, as to the man from whom +he had a right to expect to receive a supply of them. +At first Flamsteed seems to have given these as fully +as he was able; but it is evident that Newton +chafed at the necessity for these frequent applications +to Flamsteed, and to the constant need of putting +pressure upon him. Flamsteed, on the other hand, +as clearly evidently resented this continual demand. +Feeling, as he keenly did, that, though he had been +named Astronomer Royal, he had been left practically +entirely without support; his instruments +were entirely his own, either made or purchased by +himself; his nominal salary of £100 was difficult to +get, and did not nearly cover the actual current +expenses of his position, he not unnaturally regarded +his observations as his own exclusive property. He +had a most natural dislike for his observations to +be published, except after such reduction as he +himself had carried through, and in the manner +which he himself had chosen. The idea which was +ever before him was that of carrying out a single +great work that should not only be a monument to<span class="pagenum"><a name="Page_48" id="Page_48">[48]</a></span> +his own industry and skill, but should also raise the +name of England amongst scientific nations. He +complained of it, therefore, both as a personal wrong +and an injury to the country when some observations +of Cassini's were combined with some observations +of his own in order to deduce a better orbit for a +comet.</p> + +<p>Unknown to himself, therefore, he was called upon +to decide a question that has proved fundamental to +the policy of Greenwich Observatory, and he decided +it wrongly—the question of publication. Newton +had urged upon him as early as 1691 that he should +not wait until he had formed an exhaustive catalogue +of all the brighter stars, but that he should publish +at once a catalogue of a few, which might serve as +standards; but Flamsteed would not hear of it. He +failed to see that his office had been created for a +definite practical purpose, not for the execution of +some great scheme, however important to science. +All his work of thirty years had done nothing to +forward navigation so long as he published nothing. +But if, year by year, he had published the places of +the moon and of a few standard stars, he would have +advanced the art immensely and yet have not +hindered himself from eventually bringing out a +great catalogue. No doubt the little incident of +Newton's difficulty with the microscope, of which he +had forgotten the object-glass, had given Flamsteed +a low opinion of Newton's qualifications as a practical +astronomer. If so, he was wrong, for Newton's insight +into practical matters was greater than Flamsteed's +own, and his practical skill was no less, though<span class="pagenum"><a name="Page_49" id="Page_49">[49]</a></span> +his absent-mindedness might occasionally lead him +into an absurd mistake.</p> + +<p>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 catalogue, and +at the same time it illustrates Flamsteed's touchy +and suspicious nature.</p> + +<blockquote> + +<p>'Whilst Mr. Flamsteed was busied in the laborious work +of the catalogue of the fixed stars, and forced often to watch +and labour by night, to fetch the materials for it from the +heavens, that were to be employed by day, he often, on Sir +Isaac Newton's instances, furnished him with observations +of the moon's places, in order to carry on his correction of +the lunar theory. A civil correspondence was carried on +between them; only Mr. Flamsteed could not but take +notice that as Sir Isaac was advanced in place, so he raised +himself in his conversation and became more magisterial. +At last, finding that Mr. Flamsteed had advanced far in his +designed catalogue by the help of his country calculators, +that he had made new lunar tables, and was daily advancing +on the other planets, Sir Isaac Newton came to see him +(Tuesday, April 11, 1704); and desiring, after dinner, to be +shown in what forwardness his work was, had so much of +the catalogue of the fixed stars laid before him as was then +finished; together with the maps of the constellations, both +those drawn by T. Weston and P. Van Somer, as also his +collation of the observed places of Saturn and Jupiter, with +the Rudolphine numbers. Having viewed them well, he +told Mr. Flamsteed he would (<em>i.e.</em> he was desirous to) +recommend them to the Prince <em>privately</em>. Mr. Flamsteed +(who had long been sensible of his partiality, and heard +how his two flatterers cried Sir Isaac's performances up, +was sensible of the snare in the word <em>privately</em>) answered +that would not do; and (upon Sir Isaac's demanding "why +not?") that then the Prince's attendants would tell him +these were but curiosities of no great use, and persuade<span class="pagenum"><a name="Page_50" id="Page_50">[50]</a></span> +him to save that expense, that there might be the more for +them to beg of him: and that the recommendation must +be made <em>publicly</em>, to prevent any such suggestions. Sir +Isaac apprehended right, that he was understood, and his +designs defeated: and so took his leave not well satisfied +with the refusal.</p> + +<p>'It was November following ere Mr. Flamsteed heard +from him any more: when, considering with himself that +what he had done was not well understood, he set himself +to examine how many folio pages his work when printed +would fill; and found upon an easy computation that they +would at least take up 1400. Being amazed at this, he set +himself to consider them more seriously; drew up an +estimate of them; and, to obviate the misrepresentations +of Dr. S[loane] and some others, who had given out that +what he had was inconsiderable, he delivered a copy of the +estimate to Mr. Hodgson, then lately chosen a member of +the Royal Society, with directions to deliver it to a friend, +who he knew would do him justice; and, on this fair +account, obviate those unjust reports which had been +studiously spread to his prejudice. It happened soon after, +Mr. Hodgson being at a meeting, spied this person there, +at the other side of the room; and therefore gave the paper +to one that stood in some company betwixt them, to be +handed to him. But the gentleman, mistaking his request, +handed to the Secretary [Dr. Sloane], who, being a +Physician, and not acquainted with astronomical terms, +did not read it readily. Whereupon another in the +company took it out of his hands; and, having read it +distinctly, desired that the works therein mentioned might +be recommended to the Prince; the charge of printing +them being too great either for the author or the Royal +Society. Sir Isaac closed in with this.'</p></blockquote> + +<div class="figcenter bord" style="width: 600px;"><a name="stellata" id="stellata"></a> +<img src="images/i_052.jpg" width="600" height="382" alt="stellata" /> +<div class="caption"><p class="center">THE 'CAMERA STELLATA' IN FLAMSTEED'S TIME.<br />(<em>From an engraving in the 'Historia Cœlestis.'</em>)</p></div> +</div> + +<p>The work was in consequence recommended to +Prince George of Denmark, the Queen's Consort; +but it was not till November 10, 1705, that the +contract for the printing was signed. Two years +later, the observations which he had made with<span class="pagenum"><a name="Page_51" id="Page_51"> </a><br /><a name="Page_52" id="Page_52"> </a><br /><a name="Page_53" id="Page_53">[53]</a></span> +his sextant in his first thirteen years of office +were printed. Then came the difficulty of the +catalogue. It was not complete to Flamsteed's +satisfaction, and he was most unwilling to let it +pass out of his hands. However, two manuscripts, +comprising some three-quarters of the whole, were +deposited with referees, the first of these being sealed +up. The seal was broken with Flamsteed's concurrence; +but the fact that it had been so broken +was made by him the subject of bitter complaint +later. At this critical juncture Prince George died, +and a stop was put to the progress of the printing. +Two years more elapsed without any advance being +made, and then, in order to check any further +obstruction, a committee of the Royal Society was +appointed as a Board of Visitors to visit and inspect +the Observatory, and so maintain a control over the +Astronomer Royal. This was naturally felt by so +sensitive a man as Flamsteed as a most intolerable +wrong, and when he found that the printing of his +catalogue had been placed in the hands of Halley as +editor, a man for whom he had conceived the most +violent distrust, he absolutely refused to furnish the +Visitors with any further material. This led to, +perhaps, the most painful scene in the lives either +of Newton or Flamsteed. Flamsteed was summoned +to meet the Council of the Royal Society at their +rooms in Crane Court. A quorum was not present, +and so the interview was not official, and no record +of it is preserved in the archives. Flamsteed has +himself described it with great particularity in more +than one document, and it is only too easy to<span class="pagenum"><a name="Page_54" id="Page_54">[54]</a></span> +understand the scene that took place. Newton was +a man who had an absolutely morbid dread of +anything like controversy, and over and over again +would have preferred to have buried his choicest +researches, rather than to have encountered the +smallest conflict of the kind. He was perhaps, +therefore, the worst man to deal with a high-principled, +sensitive, and obstinate man who was +in the wrong, and yet who had been so hardly dealt +with that it was most natural for him to think himself +wholly in the right. Flamsteed adhered absolutely +to his position, from which it is clear it would have +been extremely difficult for the greatest tact and +consideration to have dislodged him. Newton, on +his part, simply exerted his authority, and, that +failing, was reduced to the miserable extremity of +calling names. The scene is described by Flamsteed +himself, in a letter to Abraham Sharp, as follows:—</p> + +<blockquote> + +<p>'I have had another contest with the President<a name="FNanchor_2_2" id="FNanchor_2_2"></a><a href="#Footnote_2_2" class="fnanchor">[2]</a> of the +Royal Society, who had formed a plot to make my +instruments theirs; and sent for me to a Committee, where +only himself and two physicians (Dr. Sloane, and another +as little skilful as himself) were present. The President +ran himself into a great heat, and very indecent passion. +I had resolved aforehand his kn—sh talk should not +move me; showed him that all the instruments in the +Observatory were my own; the mural arch and voluble +quadrant having been made at my own charge, the rest +purchased with my own money, except the sextant and +two clocks, which were given me by Sir Jonas Moore, with +Mr. Towneley's micrometer, his gift, some years before +I came to Greenwich. This nettled him; for he has got +a letter from the Secretary of State for the Royal Society<span class="pagenum"><a name="Page_55" id="Page_55">[55]</a></span> +to be Visitors of the Observatory, and he said, "<em>as good +have no observatory as no instruments</em>." I complained +then of my catalogue being printed by Raymer, without my +knowledge, and that I was <em>robbed of the fruit of my labours</em>. +At this he fired, and called me all the ill names, puppy, +etc., that he could think of. All I returned was, I put him +in mind of his passion, desired him to govern it, and keep +his temper: this made him rage worse, and he told me +how much I had received from the Government in thirty-six +years I had served. I asked what he had done for the +£500 per annum that he had received ever since he had +settled in London. This made him calmer; but finding +him going to burst out again, I only told him my catalogue, +half finished, was delivered into his hands, on his own +request, sealed up. He could not deny it, but said Dr. +Arbuthnott had procured the Queen's order for opening it. +This, I am persuaded, was false; or it was got after it had +been opened. I said nothing to him in return; but, with +a little more spirit than I had hitherto showed, told them +that God (who was seldom spoken of with due reverence in +that meeting) had hitherto prospered all my labours, and +I doubted not would do so to a happy conclusion; took +my leave and left them. Dr. Sloane had said nothing all +this while; the other Doctor told me I was proud, and +insulted the President, and ran into the same passion with +the President. At my going out, I called to Dr. Sloane, +told him he had behaved himself civilly, and thanked him +for it. I saw Raymer after, drank a dish of coffee with +him, and told him, still calmly, of the villany of his conduct, +and called it <em>blockish</em>. Since then they let me be quiet; +but how long they will do so I know not, nor am I +solicitous.'</p></blockquote> + +<p>The Visitors continued the printing, Halley being +the editor, and the work appeared in 1712 under the +title of <em>Historia Cœlestis</em>. This seemed to Flamsteed +the greatest wrong of all. The work as it appeared +seemed to him so full of errors, wilfully or accidentally +inserted, as to be the greatest blot upon his fair<span class="pagenum"><a name="Page_56" id="Page_56">[56]</a></span> +fame, and he set himself, though now an old man, to +work it out <i lang="la" xml:lang="la">de novo</i> and at his own expense. To +that purpose he devoted the remaining seven years +of his life. Few things can be more pathetic than +the letters which he wrote in that period referring to +it. He was subject to the attacks of one of the +cruelest of all diseases—the stone; he was at all +times liable to distracting headaches. He had been, +from his boyhood, a great sufferer from rheumatism, +and yet, in spite of all, he resolutely pushed on his +self-appointed task. The following extract from one +of his letters will give a more vivid idea of the brave +old man than much description:—</p> + +<blockquote> + +<p>'I can still, I praise God for it, walk from my door to +the Blackheath gate and back, with a little resting at some +benches I have caused to be set up betwixt them. But I +found myself so tired with getting up the hill when I return +from church, that at last I have bought a sedan, and am +carried thither in state on Sunday mornings and back; I +hope I may employ it in the afternoons, though I have not +hitherto, by reason of the weather is too cold for me.'</p></blockquote> + +<p>After the death of Queen Anne, a change in the +ministry enabled him to secure that three hundred +copies of the total impression of four hundred of the +<cite>Historia Cœlestis</cite> were handed over to him. These, +except the first volume, containing his sextant +observations (which had received his own approval), +he burned, 'as a sacrifice to heavenly truth.' His +own great work had advanced so far that the first +volume was printed, and much of the second, when +he himself died, on the last day of 1719. He was +buried in the chancel of Burstow Church.</p> + +<p><span class="pagenum"><a name="Page_57" id="Page_57">[57]</a></span></p> + +<p>The completion of his work took ten years more; +a work of piety and regard on the part of his assistant, +Joseph Crosthwait.</p> + +<p>When compared with the catalogues that have +gone before, it was a work of wonderful accuracy. +Nevertheless, as Caroline Herschel showed, nearly a +century later, not a few errors had crept into it. +Some of the stars are non-existent, others have been +catalogued in more than one constellation; important +stars have been altogether omitted. Perhaps the +most serious fault arises from the neglect of +Flamsteed to accept from Newton a practical hint, +namely, to read the barometer and thermometer at +the time of his observations. Nevertheless, the work +accomplished was not only wonderful under the +untoward conditions in which Flamsteed was placed; +it was wonderful in itself, winning from Airy the +following high encomium:—</p> + +<blockquote> + +<p>'In regard not only to accuracy of observation, and to +detail in publication of the methods of observing, but also +to steadiness of system followed through many years, and +to completeness of calculation of the useful results deduced +from the observations, this work may shame any other +collection of observations in this or any other country.'</p></blockquote> + +<p>This catalogue was not Flamsteed's only achievement. +He had determined the latitude of the Observatory, +the obliquity of the ecliptic, and the position of the +equinoctial points. He thought out an original +method of obtaining the absolute right ascensions of +stars by differential observations of the places of the +stars and the sun near to both equinoxes. He had +revised and improved Horrox's theory of the lunar<span class="pagenum"><a name="Page_58" id="Page_58">[58]</a></span> +motions, which was by far the best existing in +Flamsteed's day. He showed the existence of the +long inequality of Jupiter and Saturn; that is to say, +the periodic influence which they exercise upon each +other. He determined the time in which the sun +rotates on its axis, and the position of that axis. +He observed an apparent movement of the stars +in the course of a year, which he ascribed, though +erroneously, to the stellar parallax, and which +was explained by the third Astronomer Royal, +Bradley.</p> + +<p>Flamsteed not only met with harsh treatment +during his lifetime; he has not yet received, except +from a few, anything like the meed of appreciation +which is his just due; but, at least, his successors in +the office have not forgotten him. They have been +proud that their official residence should be known +as Flamsteed House, and his name is inscribed over +the main entrance of the latest and finest of the +Observatory buildings, and his bust looks forth from +its front towards the home where he laboured so +devotedly for nearly fifty years. But he has received +little honour, save at Greenwich, and—in spite of the +proverb—in his other home, the village of Burstow, +in Surrey, of which he was for many years the rector. +Here a stained glass window representing, appropriately, +the Adoration of the Magi, has been +recently set up to his memory, largely through +the interest taken in his history by an amateur +astronomer of the neighbourhood, Mr. W. Tebb, +F.R.A.S.</p> + +<p>No instrument of Flamsteed's remains in the<span class="pagenum"><a name="Page_59" id="Page_59">[59]</a></span> +Observatory, his wife removing them after his death. +But we may consider his principal instrument, the +mural quadrant made for him by Abraham Sharp, +as represented by the remains of a quadrant by the +same artist, which was presented to the Observatory +by the Rev. N. S. Heineken, in 1865, and now hangs +over the door of the transit room.</p> + +<hr class="chap" /> + +<p><span class="pagenum"><a name="Page_60" id="Page_60">[60]</a></span></p> + + + + +<h2>CHAPTER III</h2> + +<h3>HALLEY AND HIS SUCCESSORS</h3> + + +<blockquote> +<p>There is no need to give the lives of the succeeding +Astronomers Royal so fully as that of Flamsteed. +Not that they were inferior men to him; on the +contrary, there can be little doubt that we ought to +reckon some of them as his superiors, but, in the +case of several, their best work was done apart from +Greenwich Observatory, and before they came to it.</p></blockquote> + +<p>This was particularly the case with <span class="smcap">Edmund +Halley</span>. Born on October 29, 1656, he was ten +years the junior of Flamsteed. Like Flamsteed, he +came of a Derbyshire family, though he was born at +Haggerston, in the parish of St. Leonard's, Shoreditch. +He was educated at St. Paul's School, where +he made very rapid progress, and already showed +the bent of his mind. He learnt to make dials; he +made himself so thoroughly acquainted with the +heavens that it is said, 'If a star were displaced in +the globe he would presently find it out,' and he +observed the changes in the direction of the mariner's +compass. In 1673 he went to Queen's College, +Oxford, where he observed a sunspot in July and +August, 1676, and an occultation of Mars. This was +not his first astronomical observation, as, in June,<span class="pagenum"><a name="Page_61" id="Page_61"> </a><br /><a name="Page_62" id="Page_62"> </a><br /><a name="Page_63" id="Page_63">[63]</a></span> +1675, he had observed an eclipse of the moon from +his father's house in Winchester Street.</p> + +<div class="figcenter bord" style="width: 450px;"><a name="halley" id="halley"></a> +<img src="images/i_061.jpg" width="450" height="494" alt="halley" /> +<div class="caption"><p class="center">EDMUND HALLEY.<br /> +(<em>From an old print.</em>)</p></div> +</div> + +<p>A much wider scheme of work than such merely +casual observations now entered his mind, possibly +suggested to him by Flamsteed's appointment to the +direction of the new Royal Observatory. This was +to make a catalogue of the southern stars. Tycho's +places for the northern stars were defective enough, +but there was no catalogue at all of stars below the +horizon of Tycho's observatory. Here, then, was a +field entirely unworked, and young Halley was so +eager to enter upon it that he would not wait at +Oxford to obtain his degree, but was anxious to +start at once for the southern hemisphere.</p> + +<p>His father, who was wealthy and proud of his +gifted son, strongly supported him in his project. The +station he selected was St. Helena, an unfortunate +choice, as the skies there were almost always more +or less clouded, and rain was frequent during his stay. +However, he remained there a year and a half, and +succeeded in making a catalogue of 341 stars. This +catalogue was finally reduced by Sharp, and included +in the third volume of Flamsteed's <cite>Historia Cœlestis</cite>.</p> + +<p>In 1678 he was elected Fellow of the Royal +Society, and the following year he was chosen to +represent that society in a discussion with Hevelius. +The question at issue was as to whether more accurate +observations of the place of a star could be obtained +by the use of sights without optical assistance, or by +the use of a telescope. The next year he visited the +Paris Observatory, and, later in the same tour, the +principal cities of the Continent.</p> + +<p><span class="pagenum"><a name="Page_64" id="Page_64">[64]</a></span></p> + +<p>Not long after his return from this tour, Halley +was led to that undertaking for which we owe him +the greatest debt of gratitude, and which must be +regarded as his greatest achievement.</p> + +<p>Some fifty years before, the great Kepler had +brought out the third of his well-known laws of +planetary motion. These laws stated that the planets +move round the sun in ellipses, of which the sun +occupies one of the foci; that the straight line +joining any planet with the sun moves over equal +areas of space in equal periods of time; and, lastly, +that the squares of the times in which the several +planets complete a revolution round the sun are +proportional to the cubes of their mean distances +from it. These three laws were deduced from actual +examination of the movements of the planets. Kepler +did not work out any underlying cause of which these +three laws were the consequence.</p> + +<p>But the desire to find such an underlying cause +was keen amongst astronomers, and had given rise +to many researches. Amongst those at work on the +subject was Halley himself. He had seen, and been +able to prove, that if the planets moved in circles +round the sun, with the sun in the centre, then the +law of the relation between the times of revolution +and the distances of the planets would show that the +attractive force of the sun varied inversely as the +square of the distance. The actual case, however, of +motion in an ellipse was too hard for him, and he +could not deal with it. Halley therefore went up to +Cambridge to consult Newton, and, to his wonder and +delight, found that the latter had already completely<span class="pagenum"><a name="Page_65" id="Page_65">[65]</a></span> +solved the problem, and had proved that Kepler's +three laws of planetary motion were summed up in +one, namely, that the sun attracted the planets to it +with a force inversely proportional to the square of +the distance.</p> + +<p>Halley was most enthusiastic over this great discovery, +and he at once strongly urged Newton to +publish it. Newton's unwillingness to do so was +great, but at length Halley overcame his reluctance; +and the Royal Society not being able at the time +to afford the expense, Halley took the charges +upon himself, although his own resources had been +recently seriously damaged by the death of his +father.</p> + +<p>The publication of Newton's <cite>Principia</cite>, which, but +for him, might never have seen the light, and most +certainly would have been long delayed, is Halley's +highest claim to our gratitude. But, apart from this, +his record of scientific achievement is indeed a noble +one. Always, from boyhood, he had taken a great +interest in the behaviour of the magnetic compass, +and he now followed up the study of its variations +with the greatest energy. For this purpose it was +necessary that he should travel, in view of the great +importance of the subject to navigation. King +William III. gave him a captain's commission in the +Royal Navy—a curious and interesting illustration +of the close connection between astronomy and the +welfare of our navy—and placed him in command of +a 'pink,' that is to say, a small vessel with pointed +stern, named the Paramour, in which he proceeded to +the southern ocean. His first voyage was unfortunate,<span class="pagenum"><a name="Page_66" id="Page_66">[66]</a></span> +but the Paramour was recommissioned in 1699, and +he sailed in it as far as south latitude 52°.</p> + +<p>In 1701 and the succeeding year he made further +voyages in the Paramour, surveying the tides and +coasts of the British Channel and of the Adriatic, +and helping in the fortification of Trieste. He +became Savilian Professor of Geometry at Oxford in +1703, having failed twelve years previously to secure +the Savilian Professorship of Astronomy, mainly +through the opposition of Flamsteed, who had already +formed a strong prejudice against him, which some +writers have traced to Halley's detection of several +errors in one of Flamsteed's tide-tables, others to +Halley's supposed materialistic views. Probably the +difference was innate in the two men. There was +likely to be but little sympathy between the strong, +masterful man of action and society and the secluded, +self-conscious, suffering invalid. At any rate, in the +contest between Newton and Flamsteed, which has +been already described, Halley took warmly the +side of the former, and was appointed to edit the +publication of Flamsteed's results, and, on the death +of the latter, to succeed him at the Royal Observatory.</p> + +<p>The condition of things at Greenwich when +Halley succeeded to the post of Astronomer Royal +in 1720 was most discouraging. The instruments +there had all belonged to Flamsteed, and therefore, +most naturally, had been removed by his widow. +The Observatory had practically to be begun <i lang="la" xml:lang="la">de novo</i>, +and Halley had now almost attained the age at +which in the present day an Astronomer Royal +would have to retire. More fortunate, however, than<span class="pagenum"><a name="Page_67" id="Page_67">[67]</a></span> +his predecessor, he was able to get a grant for +instruments, and he equipped the Observatory as +well as the resources of the time permitted, and his +transit instrument and great eight-foot quadrant still +hang upon the Observatory walls.</p> + +<p>As Astronomer Royal his great work was the +systematic observation of the positions of the moon +through an entire <em>saros</em>. As is well known, a period +of eighteen years and ten or eleven days brings the +sun and moon very nearly into the same positions +relatively to the earth which they occupied at the +commencement of the period. This period was well +known to the ancient Chaldeans, who gave it its name, +since they had noticed that eclipses of the sun or +eclipses of the moon recurred at intervals of the above +length. It was Halley's desire to obtain such a set +of observations of the moon through an entire <em>saros</em> +period as to be able to deduce therefrom an improved +set of tables of the moon's motion. It was an +ambitious scheme for a man so much over sixty +to undertake, nevertheless he carried it through +successfully.</p> + +<p>His desire to complete this scheme, and to found +upon it improved lunar tables, hindered him from +publishing his observations, for he feared that others +might make use of them before he was in a position to +complete his work himself. This omission to publish +troubled Newton, who, as President of the Royal +Society—the Greenwich Board of Visitors having +lapsed at Queen Anne's death—drew attention at a +meeting of the Royal Society, March 2, 1727, to +Halley's disobedience of the order issued under Queen<span class="pagenum"><a name="Page_68" id="Page_68">[68]</a></span> +Anne, for the prompt communication of the Observatory +results. That Newton should thus have put +public pressure upon Halley, the man to whom he +was so much indebted, and with whom there was so +close an affection, is sufficient proof that his similar +attitude towards Flamsteed was one of principle and +not of arbitrariness. Halley, on his side, stood firm, +as Flamsteed had done, urging the danger that, by +publishing before he had completed his task, he +might give an opportunity to others to forestall his +results. It is said—probably without sufficient +ground—that this refusal broke Newton's heart and +caused his death. Certainly Halley's writings in +that very year show his reverence and affection for +Newton to have been as keen and lively as ever.</p> + +<p>Halley's work at the Observatory went on +smoothly, on the lines he had laid down for himself, +for ten years after Newton's death; but in 1737 he +had a stroke of paralysis, and his health, which had +been remarkably robust up to that time, began to +give way. He died January 14, 1742, and was buried +in the cemetery of Lee Church.</p> + +<p>As an astronomer, his services to the science +rank higher than those of his predecessor; but as +Astronomer Royal, as director, that is to say, of +Greenwich Observatory, he by no means accomplished +as much as Flamsteed had done. Professor Grant, in +his <cite>History of Physical Astronomy</cite>, says that he seems +to have undervalued those habits of minute attention +which are indispensable to the attainment of a high +degree of excellence in the practice of astronomical +observation. He was far from being sufficiently<span class="pagenum"><a name="Page_69" id="Page_69">[69]</a></span> +careful as to the adjustment of his instruments, +the going of his clocks, or the recording of his +own observations. The important feature of his<span class="pagenum"><a name="Page_70" id="Page_70">[70]</a></span> +administration was that under him the Observatory +was first supplied with instruments which belonged +to it.</p> + +<div class="figcenter bord" style="width: 450px;"><a name="quadrant" id="quadrant"></a> +<img src="images/i_069.jpg" width="450" height="591" alt="quadrant" /> +<div class="caption"><p class="center">HALLEY'S QUADRANT.<br /> +(<em>From an old print.</em>)</p></div> +</div> + +<p>His astronomical work apart from the Observatory +was of the first importance. He practically +inaugurated the study of terrestrial magnetism, and +his map giving the results of his observations during +his voyage in the Paramour introduced a new and +most useful style of recording observations. He +joined together by smooth curves places of equal +variation, the result being that the chart shows at +a glance, not merely the general course of the variation +over the earth's surface, but its value at any spot +within the limits of the chart.</p> + +<p>Another work which has justly made his name +immortal was the prediction of the return of the +comet which is called by his name, to which reference +will be made later. Another great scheme, and one +destined to bear much fruit, was the working out of +a plan to determine the distance of the sun by +observations of the transit of Venus.</p> + +<p>Of attractive appearance, pleasing manners, and +ready wit, loyal, generous, and free from self-seeking, +he probably was one of the most personally engaging +men who ever held the office.</p> + +<p>The salary of the Astronomer Royal remained +under Halley at the same inadequate rate which it +had done under Flamsteed—£100, without provision +for an assistant. But in 1729 Queen Caroline, learning +that Halley had actually had a captain's commission +in the Royal Navy, secured for him a post-captain's +pay.</p> + +<p><span class="pagenum"><a name="Page_71" id="Page_71"> </a><br /><a name="Page_72" id="Page_72"> </a></span></p> + +<div class="figcenter bord" style="width: 450px;"><a name="bradley" id="bradley"></a> +<img src="images/i_072.jpg" width="450" height="522" alt="bradley" /> +<div class="caption"><p class="center">JAMES BRADLEY.<br /> +(<em>From the painting by Hudson.</em>)</p></div> +</div> + +<p><span class="pagenum"><a name="Page_73" id="Page_73">[73]</a></span></p> + +<p>Halley's work is represented at the Observatory +by two of his instruments which are still preserved +there, and which hang on the west wall of the present +transit room: the Iron Quadrant afterwards made +famous by the observations of Bradley, and 'Halley's +Transit,' the first of the great series of instruments +upon which the fame of Greenwich chiefly rests. +This transit instrument seems to have been set up +in a small room at the west end of what is now known +as the North Terrace. His quadrant was mounted on +the pier which is now the base of the pier of the +astrographic telescope. This pier was the first extension +which the Observatory received from the original +building.</p> + +<p>On the breakdown of his health Halley nominated +as his successor, James Bradley; indeed, it is stated +that he offered to resign in his favour. He had +known him then for over twenty years, and that keen +and generous appreciation of merit in others which +was characteristic of Halley had led him very early +to recognize Bradley's singular ability.</p> + +<hr class="tb" /> + +<p><span class="smcap">James Bradley</span> was born in 1692 or 1693, of +an old North of England family. His birthplace was +Sherbourne, in Gloucestershire, and he was educated +at North Leach Grammar School and at Baliol +College, Oxford. During the years of his undergraduateship +he resided much with his uncle, the +Rev. James Pound, Rector of Wanstead, Essex, an +ardent amateur astronomer, a frequent visitor at the +Observatory in Flamsteed's time, and one of the +most accurate observers in the country. From him,<span class="pagenum"><a name="Page_74" id="Page_74">[74]</a></span> +no doubt, he derived his love of the science, and +possibly some of his skill in observation.</p> + +<p>Bradley's earliest observations seem to have been +devoted to the phenomena of Jupiter's satellites and +to the measures of double stars. The accuracy with +which he followed up the first drew the attention of +Halley, and so began a friendship which lasted +through life. His observations of double stars, +particularly of Castor, only just failed to show him +the orbital movement of the pair, because his attention +was drawn to other subjects before it had become +sufficiently obvious.</p> + +<p>In 1719 Bradley and his uncle made an attempt +to determine the distance of the sun through observations +of Mars when in opposition, observations which +were so accurate that they sufficed to show that the +distance of the sun could not be greater than 125 +millions of miles, nor less than about 94 millions. +The lower limit which they thus found has proved to +be almost exactly correct, our best modern determinations +giving it as 93 millions. The instrument +with which the observations were made was a novel +one, being 'moved by a machine that made it to +keep pace with the stars;' in other words, it was the +first, or nearly the first, example of what we should +now call a clock-driven equatorial.</p> + +<p>That same year he was offered the Vicarage of +Bridstow, near Ross, in Monmouthshire, where, having +by that time taken priest's orders, he was duly +installed, July, 1720. To this was added the sinecure +Rectory of Llandewi-Velgry; but he held both livings +only a very short time. In 1721 the death of Dr.<span class="pagenum"><a name="Page_75" id="Page_75">[75]</a></span> +John Keill rendered vacant the Savilian Professorship +of Astronomy at Oxford, for which Bradley became +a candidate, and was duly elected, and resigned his +livings in consequence.</p> + +<p>It was whilst he was Savilian Professor that +Bradley made that great discovery which will always +be associated with his name. Though professor at +Oxford, he had continued to assist his uncle, Mr. +Pound, at his observations at Wanstead, and after +the death of the latter he still lived there as much +as possible, and continued his astronomical work. +But in 1725 he was invited by Mr. Samuel Molyneux, +who had set up a twenty-four-foot telescope made by +Graham as a zenith tube at his house on Kew Green, +to verify some observations which he was making. +These were of the star Gamma Draconis, a star which +passes through the zenith of London, and which, +therefore, had been much observed both by Flamsteed +and Hooke, inasmuch as by fixing a telescope in an +absolutely vertical position—a position which could +be easily verified—it was easy to ascertain if there +was any minute change in the apparent position of +the star. Dr. Hooke had declared that there was +such a change, a change due to the motion of the +earth in its orbit, which would prove that the star +was not an infinite distance from the earth, the +seeming change of its place in the sky corresponding +to the change in the place of the earth from which +the observer was viewing it.</p> + +<p>Bradley found at once that there was such a +change—a marked one. It amounted to as much +as 1´´ of arc in three days; but it was not in the<span class="pagenum"><a name="Page_76" id="Page_76">[76]</a></span> +direction in which the parallax of the star would have +moved it, but in the opposite. Whether, therefore, +the star was near enough to show any parallax or not, +some other cause was giving rise to an apparent displacement +of the star, which entirely masked and +overcame the effect of parallax.</p> + +<p>So far, Bradley had but come to the same point +which Flamsteed had reached. Flamsteed had +detected precisely the same apparent displacement +of stars, and, like Hooke, had ascribed it to parallax. +Cassini had shown that this could not be the case, as +the displacement was in the wrong direction; and +there the matter had rested. Bradley now set to +follow the question up. Other stars beside Gamma +Draconis were found to show a displacement of the +same general character, but the amount varied with +their distance from the plane of the ecliptic, the +earth's orbit. The first explanation suggested was +that the axis of the earth, which moves very nearly +parallel to itself as the earth moves round the sun, +underwent a slight regular 'wobble' in the course of +a year. To check this, a star was observed on the +opposite side of the pole from Gamma Draconis; +then Bradley investigated as to whether refraction +might explain the difficulty, but again without +success. He now was most keenly interested in the +problem, and he purchased a zenith telescope of his +own, made, like that of Molyneux, by Graham, and +mounted it in his aunt's house at Wanstead, and +observed continuously with it. The solution of the +problem came at last to him as he was boating on the +Thames. Watching a vane at the top of the mast,<span class="pagenum"><a name="Page_77" id="Page_77"> </a><br /><a name="Page_78" id="Page_78">[78]</a></span> +he saw with surprise that it shifted its direction every +time that the boat was put about. Remarking to the +boatmen that it was very odd that the wind should +change just at the same moment that there was a +shift in the boat's course, they replied that there was +no change in the wind at all, and that the apparent +change of the vane was simply due to the change of +direction of the motion of the boat.</p> + +<div class="figcenter bord" style="width: 366px;"><a name="zenith" id="zenith"></a> +<img src="images/i_077.jpg" width="366" height="600" alt="zenith" /> +<div class="caption"><p class="center">GRAHAM'S ZENITH SECTOR.<br /> +(<em>From an old print.</em>)</p></div> +</div> + +<p>This supplied Bradley with a key to the solution +of the mystery that had troubled him so long. It +had been discovered long before this that light does +not travel instantaneously from place to place, but +takes an appreciable time to pass from one member +of the solar system to another. This had been discovered +by Römer from observations of the satellites +of Jupiter. He had noted that the eclipses of the +satellites always fell late of the computed time, when +Jupiter was at his greatest distance from the earth; +and Bradley's own work in the observation of those +satellites had brought the fact most intimately under +his own acquaintance. The result of the boating +incident taught him, then, that he might look upon +light as analogous to the wind blowing on the boat. +As the wind, so long as it was steady, would seem to +blow from one fixed quarter so long as the boat was +also in rest, but as it seemed to shift its direction +when the boat was moving and changed its direction, +so he saw that the light coming from a particular star +must seem to slightly change the direction in which +it came, or, in other words, the apparent position of +the star, to correspond with the movement of the +earth in its orbit round the sun.</p> + +<p><span class="pagenum"><a name="Page_79" id="Page_79">[79]</a></span></p> + +<p>This was the celebrated discovery of the Aberration +of Light, a triumph of exact observation and of +clear insight. As to the exactness of Bradley's +observations, it is sufficient to say that his determination +of the value of the 'Constant of Aberration' gave +it as 20·39´´; the value adopted to-day is 20·47´´.</p> + +<p>On the death of Halley, in 1742, Bradley was +appointed to succeed him. He found the Observatory +in as utterly disheartening a condition as his predecessors +had done. As already mentioned, Halley +had not the same qualifications as an observer that +Flamsteed had. He was, further, an old man when +appointed to the post, he had no assistant provided +for him, and the last five years of his life his health +and strength had entirely given way. Under these circumstances, +it was no wonder that Bradley found the +instruments of the Observatory in a deplorable state. +Nevertheless, he set to work most energetically, and +in the year of his appointment he made 1500 observations +in the last five months of the year. He was +particularly earnest in examining the condition and +the errors of his instruments; and as their defects +became known to him, he was more and more anxious +for a better equipment. He moved the Royal +Society, therefore, to apply on his behalf for the +instruments he required; and a petition from that +body, in 1748, obtained what in those days must +be considered the generous grant of £1000, the +proceeds of the sale of old Admiralty stores. The +principal instruments purchased therewith were a +mural quadrant and a transit instrument, both eight +feet in focal length, still preserved on the walls of the<span class="pagenum"><a name="Page_80" id="Page_80">[80]</a></span> +transit-room. It is interesting also to note that, +following in the steps of Halley, and forecasting, as it +were, the magnetic observatory which Airy would +found, he devoted £20 of the grant to purchasing +magnetic instruments.</p> + +<p>Meantime he had continued his observations on +aberration, and had discovered that the aberration +theory was not sufficient entirely to account for the +apparent changes in places of stars which he had +discovered. A second cause was at work, a movement +of the earth's axis, a 'wobble' in its inclination, +technically known as Nutation, which is due to the +action of the moon, and goes through its course in a +period of nineteen years.</p> + +<p>Beside these two great discoveries of aberration +and nutation, Bradley's reputation rests upon his +magnificent observations of the places of more than +three thousand stars. This part of his work was done +with such thoroughness, that the star-places deduced +from them form the basis of most of our knowledge +as to the actual movements of individual stars. In +particular, he was careful to investigate and to correct +for the errors of his instrument, and to determine +the laws of refraction, introducing corrections for +changes in the readings of thermometer and barometer. +His tables of refraction were used, indeed, +for seventy years after his death. Of his other labours +it may be sufficient to refer to his determination of +the longitudes of Lisbon and of New York, and to his +effort to ascertain the parallax of the sun and moon, +in combination with La Caille, who was observing at +the Cape of Good Hope.</p> + +<p><span class="pagenum"><a name="Page_81" id="Page_81">[81]</a></span></p> + +<p>As Astronomer Royal, Bradley's great achievement +was the high standard to which he raised the +practical work of observation. From his day onwards, +also, there was always at least one assistant. +His first assistant was his own nephew, John Bradley, +who received the munificent salary of ten shillings a +week. Still, this was not out of proportion to the +then salary of the Astronomer Royal, which practically +amounted only to £90. However, in 1752, +Bradley was awarded a Crown pension of £250 a +year. He refused the living of Greenwich, which was +offered him in order to increase his emoluments, on +the ground that he could not suitably fulfil the +double office. Bradley's later assistants were Charles +Mason and Charles Green.</p> + +<p>Bradley's last work was the preparation for the +observations of the transit of Venus of 1761, according +to the lines laid down by his predecessor, Halley. +His health gave way, and he became subject to +melancholia, so that the actual observations were +taken by the Rev. Nathaniel Bliss, who succeeded +him in his office after his death, in 1762. He was +buried at Minchinhampton.</p> + +<p>So far as we know Bradley's character, he seems +to have been a gentle, modest, unassuming man, +entirely free from self-seeking, and indifferent to +personal gain. He was in many ways an ideal +astronomer, exact, methodical, and conscientious to +the last degree. His skill as an observer was his +chief characteristic; and though his abilities were not +equal as a mathematician or a mechanician, yet, on +the one hand, he had a very clear insight into the<span class="pagenum"><a name="Page_82" id="Page_82">[82]</a></span> +meaning of his observations, and, on the other, he was +skilful enough to himself adjust, repair, and improve +his instruments.</p> + +<p>Of Bradley's instruments, there are still preserved +his famous twelve-and-a-half-foot zenith sector, with +which he made his two great discoveries; his brass +quadrant, which in 1750 he substituted for Halley's +iron quadrant; his transit instrument, and equatorial +sector. Bradley added to the buildings of the +Observatory that portion which is now represented +by the upper and lower computing rooms, and the +chronometer room, which adjoins the latter. This +room—the chronometer room—was his transit room, +and the position of the shutters is still marked by +the window in the roof.</p> + +<hr class="tb" /> + +<p>The Rev. <span class="smcap">Nathaniel Bliss</span>, who succeeded +Bradley, only held the office for a couple of years, +and during that time was much at Oxford. He, +therefore, has left no special mark behind him as +Astronomer Royal.</p> + +<p>He was born November 28, 1700. His father, +like himself, Nathaniel Bliss, was a gentleman, of +Bisley, Gloucestershire.</p> + +<div class="figcenter bord" style="width: 450px;"><a name="bliss" id="bliss"></a> +<img src="images/i_083.jpg" width="450" height="532" alt="bliss" /> +<div class="caption"><p class="center">NATHANIEL BLISS.<br /> +(<em>From an engraving on an old pewter flagon.</em>)</p></div> +</div> + +<p>Bliss graduated at Pembroke College, Oxford, as +B.A. in 1720, and M.A. in 1723. He became the +Rector of St. Ebb's, Oxford, in 1736, and on Halley's +death succeeded him as Savilian Professor of Geometry. +He supplied Bradley with his observations +of Jupiter's satellites, and from time to time, at his +request, rendered him some assistance at the Royal +Observatory. This was particularly the case, as has<span class="pagenum"><a name="Page_83" id="Page_83"> </a><br /><a name="Page_84" id="Page_84"> </a><br /><a name="Page_85" id="Page_85">[85]</a></span> +been already mentioned, with respect to the transit +of Venus of 1761, the observations of which were +carried out by Bliss, owing to Bradley's ill-health. +It was natural, therefore, that on Bradley's death he +should succeed to the vacant post; but he held it too +short a time to do any distinctive work. Such +observations as he made seem to have been entirely +in continuation of Bradley's. He took a great +interest, however, in the improvement of clocks, a +department in which so much was being done at this +time by Graham, Ellicott, and others.</p> + +<hr class="tb" /> + +<p><span class="smcap">Nevil Maskelyne</span>, the fifth Astronomer Royal, +was, like Bliss, a close friend of Bradley's. He was +the third son of a wealthy country gentleman, +Edmund Maskelyne, of Purton, in Wiltshire. Maskelyne +was born in London, October 6, 1732, and was +educated at Westminster School. Thence he proceeded +to Cambridge, where he graduated seventh +Wrangler in 1754. He was ordained to the curacy +of Barnet in 1755, and, twenty years later, was presented +by his nephew, Lord Clive, to the living of +Shrawardine, in Shropshire. In 1782 he was presented +by his college to the Rectory of North +Runcton, Norfolk.</p> + +<p>The event which turned his thoughts in the +direction of astronomy was the solar eclipse of July +25, 1748; and about the time that he was appointed +to the curacy of Barnet he became acquainted with +Bradley, then the Astronomer Royal, to whom he +gave great assistance in the preparation of his table +of refractions.</p> + +<p><span class="pagenum"><a name="Page_86" id="Page_86">[86]</a></span></p> + +<p>Like Halley before him, he made an astronomical +expedition to the island of St. Helena. This was +for the special purpose of observing the transit of +Venus of June 6, 1761, Bradley having induced the +Royal Society to send him out for that purpose. +Here he stayed ten months, and made many +observations. But though the transit of Venus was +his special object, it was not the chief result of +the expedition: not because clouds hindered his +observations, but because the voyage gave him the +especial bent of his life.</p> + +<p>Halley had actually held a captain's commission in +the Royal Navy, and commanded a ship; Maskelyne, +more than any of the Astronomers Royal before or +since, made the improvement of the practical business +of navigation his chief aim. None of all the incumbents +of the office kept its original charter—'To find the +so much desired Longitude at Sea, for the perfecting +the Art of Navigation,' so closely before him.</p> + +<p>The solution of the problem was at hand at this +time—its solution in two different ways. On the one +hand, the offer by the Government of a reward of +£20,000 for a clock or watch which should go so +perfectly at sea, notwithstanding the tossing of the +ship and the wide changes of temperature to which +it might be exposed, that the navigator might at any +moment learn the true Greenwich time from it, had +brought out the invention of Harrison's time-keeper; +on the other hand, the great improvement that had +now taken place in the computation of tables of the +moon's motion, and the more accurate star-catalogues +now procurable, had made the method of 'lunars,'<span class="pagenum"><a name="Page_87" id="Page_87"> </a><br /><a name="Page_88" id="Page_88"> </a><br /><a name="Page_89" id="Page_89">[89]</a></span> +suggested a hundred and thirty years before by the +Frenchman, Morin, and others, a practicable one.</p> + +<div class="figcenter bord" style="width: 450px;"><a name="nevil" id="nevil"></a> +<img src="images/i_087.jpg" width="450" height="557" alt="nevil" /> +<div class="caption"><p class="center">NEVIL MASKELYNE.</p></div> +</div> + +<p>In principle, the method of finding the longitude +from 'lunars,' that is to say, from measurements of +the distances between the moon and certain stars, is +an exceedingly simple one. In actual practice, it +involves a very toilsome calculation, beside exact +and careful observation. The principle, as already +mentioned, is simply this: The moon travels round +the sky, making a complete circuit of the heavens +in between twenty-seven and twenty-eight days. It +thus moves amongst the stars, roughly speaking, its +own diameter, in about an hour. When once its +movements were sufficiently well known to be exactly +predicted, almanacs could be drawn up in which the +Greenwich time of its reaching any definite point of +the sky could be predicted long beforehand; or, what +comes to the same thing, its distances from a number +of suitable stars could be given for definite intervals +of Greenwich time. It is only necessary, then, to +measure the distances between the moon and some of +these stars, and by comparing them with the distances +given in the almanac, the exact time at Greenwich +can be inferred. As has been already pointed out, +the determination of the latitude of the ship and of +the local time at any place where the ship is, is not +by any means so difficult a matter; but the local +time being known and the Greenwich time, the +difference between these gives the longitude; and +the latitude having been also ascertained, the exact +position of the ship is known.</p> + +<p>There are, of course, difficulties in the way of<span class="pagenum"><a name="Page_90" id="Page_90">[90]</a></span> +working out this method. One is, that whilst it takes +the sun but twenty-four hours to move round the sky +from one noon to the next, and consequently its +movements, from which the local time is inferred, are +fairly rapid, the moon takes nearly twenty-eight days +to move amongst the stars from the neighbourhood +of one particular star round to that particular star +again. Consequently, it is much easier to determine +the local time with a given degree of exactness than +the Greenwich time; it is something like the difference +of reading a clock from both hands and from the +hour hand alone.</p> + +<p>There are other difficulties in the case which +make the computation a long and laborious one, and +difficult in that sense; but they do not otherwise +affect its practicability.</p> + +<p>During this voyage to St. Helena, both when +outward bound and when returning, Maskelyne gave +the method of 'lunars' a very thorough testing, and +convinced himself that it was capable of giving the +information required. For by this time the improvement +of the sextant, or quadrant as it then was, by +the introduction of a second mirror, by Hadley, had +rendered the actual observation at sea of lunar distances, +and of altitudes generally, a much more exact +operation.</p> + +<p>This conclusion he put at once to practical effect, +and, in 1763, he published the <cite>British Mariner's +Guide</cite>, a handbook for the determination of the +longitude at sea by the method of lunars.</p> + +<p>At the same time, the other method, that by the +time-keeper or chronometer, was practically tested<span class="pagenum"><a name="Page_91" id="Page_91">[91]</a></span> +by him. The time-keeper constructed by John +Harrison had been tested by a voyage to Jamaica +in 1761, and now, in 1763, another time-keeper was +tested in a voyage to Barbadoes. Charles Green, the +assistant at Greenwich Observatory, was sent in +charge of the chronometer, and Maskelyne went with +him to test its performance, in the capacity of +chaplain to his Majesty's ship Louisa.</p> + +<div class="figcenter bord" style="width: 450px;"><a name="hadley" id="hadley"></a> +<img src="images/i_091.jpg" width="450" height="368" alt="hadley" /> +<div class="caption"><p class="center">HADLEY'S QUADRANT.<br /> +(<em>From an old print.</em>)</p></div> +</div> + +<p>The position which Maskelyne had already won +for himself as a practical astronomer, and the intimate +relations into which he had entered with Bradley +and Bliss, made his appointment to the Astronomer +Royalship, on the death of the latter, most suitable.<span class="pagenum"><a name="Page_92" id="Page_92">[92]</a></span> +At once he bent his mind to the completion of the +revolution in nautical astronomy which his <cite>British +Mariner's Guide</cite> had inaugurated, and in the year +after his appointment he published the first number +of the <cite>Nautical Almanac</cite>, together with a volume +entitled, <cite>Tables Requisite to be Used with the Nautical +Ephemeris</cite>, the value of which was so instantly +appreciated, that 10,000 copies were sold at once.</p> + +<p>The <cite>Nautical Almanac</cite> was Maskelyne's greatest +work, and it must be remembered that he carried +it on from this time up to the day of his death—truly +a formidable addition to the routine labours of an +Astronomer Royal who had but a single assistant on +his staff. The <cite>Nautical Almanac</cite> was, however, in +the main not computed at the Observatory; the +calculations were effected by computers living in +different parts of the country, the work being done +in duplicate, on the principle which Flamsteed had +inaugurated in the preparation of his <cite>Historia Cœlestis</cite>.</p> + +<p>Maskelyne's next service to science was almost +as important. He arranged that the regular and +systematic publication of the observations made at +Greenwich should be a distinct part of the duties of an +Astronomer Royal, and he procured an arrangement +by which a special fund was set apart by the Royal +Society for printing them. His observations covering +the years 1776 to 1811 fill four large folio volumes, +and though, as already stated, he had but one +assistant, they are 90,000 in number. Thus it was +Maskelyne who first rendered effective the design +which Charles II. had in the establishment of the +Observatory. Flamsteed and Halley had been too<span class="pagenum"><a name="Page_93" id="Page_93">[93]</a></span> +jealous of their own observations to publish; Bradley's +observations—though he himself was entirely free +from this jealousy—were made, after his death, the +subject of litigation by his heirs and representatives, +who claimed an absolute property in them, a claim +which the Government finally allowed. None of the +three, however much their work ultimately tended +to the improvement of the art of navigation, made +that their first object. Whereas Maskelyne set this +most eminently practical object in the forefront, and +so gave to the Royal Observatory, which under +his predecessors somewhat resembled a private +observatory, its distinctive characteristics of a public +institution.</p> + +<p>It fell to Maskelyne to have to advise the +Government as to the assignment of their great +reward of £20,000 for the discovery of the longitude +at sea. Maskelyne, while reporting favourably of +the behaviour of Harrison's time-keeper, considered +that the method of 'lunars' was far too important to +be ignored, and he therefore recommended that half +the sum should be given to Harrison for his watch, +whilst the other half was awarded for the lunar tables +which Mayer, before his death, had sent to the Board +of Longitude. This decision, though there can be +no doubt it was the right one, led to much dissatisfaction +on the part of Harrison, who urged his claim +for the whole grant very vigorously; and eventually +the whole £20,000 was paid him. The whole question +of rewards to chronometer-makers must have +been one which caused Maskelyne much vexation. +He was made the subject of a bitter and most<span class="pagenum"><a name="Page_94" id="Page_94">[94]</a></span> +voluminous attack by Thomas Mudge, for having preferred +the work of Arnold and Earnshaw to his own.</p> + +<p>Otherwise his reign at the Observatory seems to +have been a singularly peaceful one, and there is little +to record about it beyond the patient prosecution, +year by year, of an immense amount of sober, practical +work. To Maskelyne, however, we owe the practice +of taking a transit of a star over five wires instead +of over one, and he provided the transit instrument +with a sliding eye-piece, to get over the difficulty +of the displacement which might ensue if the star +were observed askew when out of the centre of the +field. To Maskelyne, too, we owe in a pre-eminent +degree the orderly form of recording, reducing, and +printing the observations. Much of the work in this +direction which is generally ascribed to Airy was +really due to Maskelyne. Indeed, without a wonderful +gift of organization, it would have been impossible +to plan and to carry the <cite>Nautical Almanac</cite>.</p> + +<p>Beside the editing of various works intended for +use in nautical astronomy or in general computation, +the chief events of his long reign at Greenwich were +the transit of Venus in 1769, which he himself +observed, and for which he issued instructions in the +<cite>Nautical Almanac</cite>; and his expedition in 1774 to +Scotland, where he measured the deviation of the +plumb-line from the vertical caused by the attraction +of the mountain Schiehallion, deducing therefrom +the mean density of the earth to be four and a half +times that of water.</p> + +<div class="figcenter bord" style="width: 450px;"><a name="pond" id="pond"></a> +<img src="images/i_096.jpg" width="450" height="523" alt="pond" /> +<div class="caption"><p class="center">JOHN POND.<br /> +(<em>From an old engraving.</em>)</p></div> +</div> + +<p>He died at the Observatory, February 9, 1811, +aged 79, leaving but one child, a daughter, who<span class="pagenum"><a name="Page_95" id="Page_95"> </a><br /><a name="Page_96" id="Page_96"> </a><br /><a name="Page_97" id="Page_97">[97]</a></span> +married Mr. Anthony Mervin Story, to whom she +brought the family estates in Wiltshire, inherited by +Maskelyne on the deaths of his elder brothers, and, +in consequence, Mr. Story added the name of +Maskelyne to his own.</p> + +<p>Maskelyne's character and policy as Astronomer +Royal have been sufficiently dwelt upon. His private +character was mild, amiable, and generous. 'Every +astronomer, every man of learning, found in him a +brother;' and, in particular, when the French Revolution +drove some French astronomers to this country +to find a refuge, they received from the Astronomer +Royal the kindest reception and most delicate +assistance.</p> + +<p>Maskelyne added no instrument to the Observatory +during his reign, though he improved Bradley's transit +materially. He designed the mural circle, but it was +not completed until after his death. His additions +to the Observatory buildings consisted of three new +rooms in the Astronomer Royal's house, and the +present transit circle room.</p> + +<hr class="tb" /> + +<p><span class="smcap">John Pond</span> was recommended by Maskelyne +as his successor at Greenwich. At the time of his +succession he was forty-four years of age, having +been born in 1767. He was educated at Trinity +College, Cambridge, and then spent some considerable +time travelling in the south of Europe and Egypt. +On his return home he settled at Westbury, where +he erected an altazimuth by Troughton, with a two-and-a-half-foot +circle. A born observer, his observations +of the declinations of some of the principal<span class="pagenum"><a name="Page_98" id="Page_98">[98]</a></span> +fixed stars showed that the instrument which +Maskelyne was using at Greenwich—the quadrant by +Bird—could no longer be trusted. Maskelyne, in +consequence, ordered a six-foot mural circle from +Troughton, but did not live to see it installed, and +in 1816 this was supplemented by Troughton's transit +instrument of five inches aperture and ten feet focal +length.</p> + +<p>The introduction of these two important instruments, +and of other new instruments, together with +new methods of observation, form one of the chief +characteristics of Pond's administration. Under this +head must be specially mentioned the introduction +of the mercury trough, both for determining the +position of the vertical, and for obtaining a check +upon the flexure of the mural circle in different +positions; and the use in combination of a pair of +mural circles for determining the declinations of +stars.</p> + +<p>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 +mechanic, and to support him with an adequate staff +of assistants. His salary was fixed at £600 a year, +and the single assistant of Maskelyne was increased +to six.</p> + +<p>This multiplication of assistants was for the purpose +of multiplying observations, 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 +based.</p> + +<p><span class="pagenum"><a name="Page_99" id="Page_99">[99]</a></span></p> + +<p>In 1833 he finished his standard catalogue of +1113 stars, at that time the fullest of any catalogue +prepared on the same scale of accuracy. 'It is not +too much to say,' was the verdict of the Royal +Astronomical Society, 'that meridian sidereal observation +owes more to him than to all his countrymen +put together since the time of Bradley.'</p> + +<p>A yet higher testimony to the exactness of his +work is given by his successor, Airy.</p> + +<blockquote> + +<p>'The points upon which, in my opinion, Mr. Pond's +claims to the gratitude of astronomers are founded, are +principally the following. <em>First</em> and chief, the accuracy +which he introduced into all the principal observations. +This is a thing which, from its nature, it is extremely difficult +to estimate now, so long after the change has been made; +and I can only say that, so far as I can ascertain from +books, the change is one of very great extent; for certainty +and accuracy, astronomy is quite a different thing from +what it was, and this is mainly due to Mr. Pond.'</p></blockquote> + +<p>The same authority eulogizes him further for his +laborious working out of every conceivable cause or +indication of error in his declination instruments, for +the system which he introduced in the observation +of transits, for the thoroughness with which he determined +all his fundamental data, and for the regularity +which he infused into the Greenwich observations.</p> + +<p>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 Brinkley, Royal Astronomer for Ireland.</p> + +<p>But Pond's administration was open, in several +particulars, to serious censure, and the Board of<span class="pagenum"><a name="Page_100" id="Page_100">[100]</a></span> +Visitors, which had been for many years but a committee +of the Royal Society, but which had recently +been reconstituted, proved its value and efficiency by +the remonstrances which it addressed to him, and +which eventually brought about his resignation. His +personal skill and insight as an observer were of the +highest order; but either from lack of interest or +failing health, he absented himself almost entirely +from the Observatory in later years, visiting it only +every ninth or tenth day. He had caused the staff +of assistants to be increased from one to six, but had +stipulated that the men supplied to him should be +'drudges.' His minute on the subject ran—</p> + +<blockquote> + +<p>'I want indefatigable, hard-working, and, above all, +obedient drudges (for so I must call them, although they +are drudges of a superior order), men who will be contented +to pass half their day in using their hands and eyes in the +mechanical act of observing, and the remainder of it in +the dull process of calculation.'</p></blockquote> + +<p>This was a fatal mistake, and one which it is very +hard to understand how any one with a real interest +in the science could have made. Men who had the +spirit of 'drudges,' to whom observation was a mere +'mechanical act,' and calculation a 'dull process,' +were not likely to maintain the honour of the Observatory, +particularly under an absentee Astronomer +Royal. Pond tried to overcome the difficulty by +devising rules for their guidance of iron rigidity. +The result was that after his resignation, in 1835, the +First Lord and the Secretary of the Admiralty expressed +their feeling to Airy, Pond's successor, 'that +the Observatory had fallen into such a state of<span class="pagenum"><a name="Page_101" id="Page_101">[101]</a></span> +disrepute that the whole establishment should be +cleared out.' A further evil was the excessive development +of chronometer business, so as practically to +swamp the real work of the Observatory, whilst the +prices paid for the chronometers at this time were +often much larger than would have been the case +under a more business-like administration.</p> + +<p>With all his merits, therefore, as an observer, the +administration of Pond was, in some respects, the least +satisfactory of all that the Observatory has known, +and he alone of all the Astronomers Royal retired +under pressure. He did not long survive his resignation, +dying in September, 1836. He was buried +by the side of Halley, in the churchyard at Lee.</p> + +<p>Of Pond's instruments, the Observatory retains +the fine transit instrument which was constructed by +Troughton at his direction, and the mural circle, +designed by Maskelyne, but which Pond was the +first to use. Both of these have, of course, long been +obsolete, and now hang on the walls of the transit +room. The small equatorial, called, after its donor, +the Shuckburgh equatorial, was also added in Pond's +day, and though practically never used, still remains +mounted in its special dome.</p> + +<hr class="chap" /> + +<p><span class="pagenum"><a name="Page_102" id="Page_102">[102]</a></span></p> + + + + +<h2>CHAPTER IV</h2> + +<h3>AIRY</h3> + +<blockquote> +<p>One hundred and sixty years from the day when +Flamsteed laid the foundation stone of the Observatory, +the Royal Warrant under the sign manual +was issued, appointing the seventh and strongest +of the Astronomers Royal, August 11, 1835. He +actually entered on his office in the following October, +but did not remove to the Observatory until the end +of the year.</p></blockquote> + + +<p><span class="smcap">George Biddell Airy</span> was born at Alnwick, in +Northumberland, on July 27, 1801. His father was +William Airy, of Luddington, in Lincolnshire, a +collector of excise; his mother was the daughter of +George Biddell, a well-to-do farmer, of Playford, near +Ipswich. He was educated at the Grammar School, +Colchester, and so distinguished himself there that +although his father was at this time very straitened +in his circumstances, it was resolved that young Airy +should go to Cambridge. Here he was entered as +sizar at Trinity College, and his robust, self-reliant +character was seen in the promptness with which he +rendered himself independent of all pecuniary help +from his relatives. In 1823 he graduated as Bachelor<span class="pagenum"><a name="Page_103" id="Page_103"> </a><br /><a name="Page_104" id="Page_104"> </a><br /><a name="Page_105" id="Page_105">[105]</a></span> +of Arts, being Senior Wrangler and Smith's prizeman, +entirely distancing all other men of his year. +He had already begun to pay attention to astronomy, +at first from the side of optics, to the study of which +he had been very early attracted; a paper of his +on the achromatism of eye-pieces and microscopes, +written in 1824, being one of especial value. In 1826 +he attempted to determine 'the diminution of gravity +in a deep mine'—that of Dolcoath, in Cornwall. +In the winter of 1823-24 he was invited to London +by Mr. (afterwards Sir) James South, who took him, +amongst other places, to Greenwich Observatory, +and gave him his first introduction to practical +astronomy. In 1826 he was appointed Lucasian +Professor at Cambridge, and in 1828, Plumian Professor, +with the charge of the new University Observatory. +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 +Observatory. He followed this up by a formal +application for an increase, which created not a little +commotion at the time, the action being so unprecedented; +and after a delay of a little over a year +he obtained what he had asked for. The delay gave +rise, however, to the remark of a local wit, that +the University had given 'to Airy, nothing, a local +habitation and a name.'</p> + +<div class="figcenter bord" style="width: 450px;"><a name="airy" id="airy"></a> +<img src="images/i_103.jpg" width="450" height="567" alt="airy" /> +<div class="caption"><p class="center">GEORGE BIDDELL AIRY.</p></div> +</div> + +<p>The seven years which he spent in the Cambridge +Observatory were the best possible preparation for +that greater charge which he was to assume later. +When he entered on his duties the Observatory had +been completed four years, but no observations had<span class="pagenum"><a name="Page_106" id="Page_106">[106]</a></span> +been published; there was no assistant, and the only +instruments were a couple of good clocks and a +transit instrument. But Airy set to work at once +with so much energy that the observations for 1828 +were published early in the following year, and he +had very quickly worked out the best methods for +correcting and reducing his observations. In 1829 an +assistant was granted to him, in 1833 a second, and +in the latter year Mr. Baldrey, the senior assistant, +observed about 5000 transits, and Mr. Glaisher, the +junior, about the same number of zenith distances.</p> + +<p>A syndicate had been appointed at Cambridge +for the purpose of visiting the Observatory once in +each term, and making an annual report to the +senate. A smaller-minded and less acute man than +Airy might have resented such an arrangement. He, +on the contrary, threw himself heartily into it, and +made such formal written reports to the syndicate as +best helped them in the performance of their duty, +and at the same time secured for the Observatory +the support and assistance which from time to time +it required. On his appointment to Greenwich, he +at once entered into the same relations to the Board +of Visitors of that Observatory, and from that time +forth the friction that had occasionally existed +between the Board and the Astronomer Royal in +the past entirely ceased. The Board was henceforth +no longer a body whose chief function was to reprove, +to check, or to quicken the Astronomer Royal, but +rather a company of experts, before whom he might +lay the necessities of the Observatory, that they in +turn might present them to the Government.</p> + +<p><span class="pagenum"><a name="Page_107" id="Page_107">[107]</a></span></p> + +<p>Such representations were not likely to be in +vain. For, as Mr. Sheepshanks has left on record—</p> + +<blockquote> + +<p>'When Mr. Airy wants to carry anything into effect by +Government assistance, he states, clearly and briefly, why +he wants it; what advantages he expects from it; and +what is the probable expense. He also engages to direct +and superintend the execution, making himself personally +responsible, and giving his labour gratis. When he has +obtained permission (which is very seldom refused), he +arranges everything with extraordinary promptitude and +foresight, conquers his difficulties by storm, and presents +his results and his accounts in perfect order, before men +like ... or myself would have made up our minds about +the preliminaries. Now, men in office naturally like persons +of this stamp. There is no trouble, no responsibility, no +delay, no inquiries in the House; the matter is done, paid +for, and published, before the seekers of a grievance can +find an opportunity to be heard. This mode of proceeding +is better relished by busy statesmen than recommendations +from influential noblemen or fashionable ladies.'</p></blockquote> + +<p>His first action towards the Board was, however, +a very bold and independent one. He made strong +representations on the subject of the growth of the +chronometer business, which proved displeasing to +the Hydrographer, Captain Beaufort, who was one of +the official visitors, and by his influence the report +was not printed. Airy 'kept it, and succeeding +reports, safe for three years, and then the Board of +Visitors agreed to print them, and four reports were +printed together, and bound with the Greenwich +Observations of 1838.'</p> + +<p>With the completion of arrangements which put +the chronometer business in proper subordination to +the scientific charge of the Observatory, Airy was<span class="pagenum"><a name="Page_108" id="Page_108">[108]</a></span> +free to push forward its development on the lines +which he had already marked out for himself. To +go through these in detail is simply to describe the +Observatory as he left it. Little by little he entirely +renovated the equipment. Greatly as Pond had +improved the instruments of the Observatory, Airy +carried that work much further still. Though he did +not observe much himself, and was not Pond's equal +in the actual handling of a telescope, he had a great +mechanical gift, and the detail in its minutest degree +of every telescope set up during his long reign was +his own design.</p> + +<p>In the work of reduction he introduced the use of +printed skeleton forms, to which Pond had been a +stranger. The publication of the Greenwich results +was carried on with the utmost regularity; and, in +striking contrast to the reluctance of Flamsteed and +Halley, he was always most prompt in communicating +any observations to every applicant who could show +cause for his request for them.</p> + +<p>It is most difficult to give any adequate impression +of his far-reaching ability and measureless activity. +Perhaps the best idea of these qualities may be +obtained from a study of his autobiography, edited +and published some four years after his death by his +son. The book, to any one who was not personally +acquainted with Airy, is heavy and monotonous, +chiefly for the reason that its 400 pages are little but +a mere catalogue of the works which he undertook +and carried through; and catalogues, except to the +specialist, are the dullest of reading. To enter into +the details of his work might fill a library.</p> + +<p><span class="pagenum"><a name="Page_109" id="Page_109"> </a><br /><a name="Page_110" id="Page_110"> </a></span></p> + +<div class="figcenter bord" style="width: 600px;"><a name="royal" id="royal"></a> +<img src="images/i_110.jpg" width="600" height="447" alt="royal" /> +<div class="caption"><p class="center">THE ASTRONOMER ROYAL'S ROOM.</p></div> +</div> + +<p><span class="pagenum"><a name="Page_111" id="Page_111">[111]</a></span></p> + +<p>As Astronomer Royal he seems to have inherited +and summed up all the great qualities of his predecessors: +Flamsteed's methodical habits and +unflagging industry; Halley's interest in the lunar +theory; Bradley's devotion to star observation and +catalogue making; Maskelyne's promptitude in +publishing, and keen interest in practical navigation; +Pond's refinement of observation. Nor did he allow +this inheritance to be merely metaphorical; he made +it an actual reality. He discussed, reduced, and +published, in forms suitable for use and comparison +to-day, the whole vast mass of planetary and lunar +observations made at the Royal Observatory from +the year 1760 to his own accession, a work of +prodigious labour, but of proportionate importance. +Airy has been accused—and with some reason—of +being a strong, selfish, aggressive man; yet nothing +can show more clearly than this great work how +thoroughly he placed the fame and usefulness of the +Observatory before all personal considerations. +With far less labour he could have carried on a dozen +investigations that would have brought him more +fame than this great enterprise, the purpose of which +was to render the work of his predecessors of the +highest possible use. The light in which he regarded +his office may best be expressed in his own words:—</p> + +<blockquote> + +<p>'The Observatory was expressly built for the aid of +astronomy and navigation, for promoting methods of +determining longitude at sea, and (as the circumstances +that led to its foundation show) more especially for determination +of the moon's motions. All these imply, as their +first step, the formation of accurate catalogues of stars, +and the determination of the fundamental elements of the<span class="pagenum"><a name="Page_112" id="Page_112">[112]</a></span> +solar system. These objects have been steadily pursued +from the foundation of the Observatory; in one way by +Flamsteed; in another way by Halley, and by Bradley in +the earlier part of his career; in a third form by Bradley +in his later years; by Maskelyne (who contributed most +powerfully both to lunar and to chronometric nautical +astronomy), and for a time by Pond; then with improved +instruments by Pond, and by myself for some years; and +subsequently, with the instruments now in use. It has +been invariably my own intention to maintain the principles +of the long-established system in perfect integrity; varying +the instruments, the modes of employing them, and the +modes of utilizing the observations of calculation and publication, +as the progress of science might seem to require.'</p></blockquote> + +<p>The result of this keen appreciation of the essential +continuity of the Astronomer Royalship has been +that it is to Airy, more than to any of his predecessors, +or than to all of them put together, that the high +reputation of Greenwich Observatory is due. Professor +Newcomb, the greatest living authority on the subject +outside our own land—and other great foreign +astronomers have independently pronounced the +same verdict—has said:—</p> + +<blockquote> + +<p>'The most useful branch of astronomy has hitherto been +that which, treating of the positions and motions of the +heavenly bodies, is practically applied to the determination +of geographical positions on land and at sea. The Greenwich +Observatory has, during the past century, been so far the +largest contributor in this direction as to give rise to the +remark that, if this branch of astronomy were entirely lost, +it could be reconstructed from the Greenwich observations +alone.'</p></blockquote> + +<p>Early in 1836 Airy proposed to the Board of +Visitors the creation of the Magnetic and Meteorological +department of the Observatory, and in 1840<span class="pagenum"><a name="Page_113" id="Page_113">[113]</a></span> +a system of regular two-hourly observations was set +on foot. This was the first great enlargement of +programme for the Observatory beyond the original +one expressed in Flamsteed's warrant. It was followed +in 1873 with the formation of the Solar Photographic +department, to which the Spectroscope was added a +little later.</p> + +<p>Though he had objected strongly on his first +coming to the Observatory to the excessive time +devoted to the merely commercial side of the care of +chronometers, yet the perfecting of these instruments +was one that he had much at heart, and many recent +appliances are either of his own invention or are due +to suggestions which he threw out.</p> + +<p>Much work lying outside the Observatory, and yet +intimately connected with it, was carried out either +by him or in accordance with his directions. The +transit of Venus expeditions of 1874, the delimitation +of the boundary line between Canada and the United +States, and, later, that of the Oregon boundary; the +determination of the longitudes of Valencia, Cambridge, +Edinburgh, Brussels, and Paris; assistance +in the determination of the longitude of Altona—all +came under Airy's direction. Nor did he neglect +expeditions in connection with what we would now +call the physical side of astronomy. On three +occasions, 1842, 1851, and 1860, he himself personally +took part in successful eclipse expeditions. The +determination of the increase of gravity observable +in the descent of a deep mine was also the subject +of another expedition, to the Harton Colliery, near +South Shields.</p> + +<p><span class="pagenum"><a name="Page_114" id="Page_114">[114]</a></span></p> + +<p>But with all these, and many other inquiries—for +he was the confidential adviser of the Government +in a vast number of subjects: lighthouses, railways, +standard weights and measures, drainage, bridges—he +yet always kept the original objects of the +Observatory in the very first place. It was in order +to get more frequent observations of the moon that +he had the altazimuth erected, which was completed +in May, 1847. This was followed, in 1851, by the +transit circle, as he had long felt the need for more +powerful light grasp in the fundamental instrument +of the Observatory. The transit circle took the +place both of the old transit instrument and of the +mural circle. Above all, he arranged for the observations +of moon and stars to be carried out with +practical continuity. The observations were made +and reduced at once, and published in such a way +that any one wishing to discuss them afresh could +for himself go over every step of the reduction from +the commencement, and could see precisely what +had been done.</p> + +<p>The greatest addition made to the equipment +of the Observatory in Airy's day was the erection of +the 12<small><sup>3</sup>/<sub>4</sub></small>-inch Merz equatorial, which proved of great +service when spectroscopy became a department of +the Observatory.</p> + +<div class="figcenter bord" style="width: 409px;"><a name="tower" id="tower"></a> +<img src="images/i_115.jpg" width="409" height="550" alt="tower" /> +<div class="caption"><p class="center">THE SOUTH-EAST TOWER.<br /> +(<em>From a photograph by Mr. Lacey.</em>)</p></div> +</div> + +<p>So strong and gifted a man as Airy was bound to +make enemies, and at different times of his life bitter +attacks were made on him from one quarter or +another. One of these, curiously enough, was from +Sir James South, the man who, as he said, first +introduced him to practical astronomy. Later came<span class="pagenum"><a name="Page_115" id="Page_115">[115]</a></span> +the discovery of Neptune, and Airy was subjected to +much bitter criticism, since, as it appeared on the +surface, it was owing to his supineness that Adams<span class="pagenum"><a name="Page_116" id="Page_116">[116]</a></span> +missed being held the sole discoverer of the new planet, +and narrowly missed all credit for it altogether. Last +of all was the vehement attack made upon him by +Richard Anthony Proctor, in connection with his +preparations for the transit of Venus. All such +attacks, however, simply realized the old fable of +the viper and the file. Attacks which would have +agonized Flamsteed's every nerve, and have called +forth full and dignified rejoinders from Maskelyne, +were absolutely and entirely disregarded by Airy. +He had done his duty, and in his own estimation—and, +it should be added, in the estimation of those +best qualified to judge—had done it well. He was +perfectly satisfied with himself, and what other +people thought or said about him influenced him +no more than the opinions of the inhabitants of +Saturn.</p> + +<p>But great as Airy was, he had the defects of his +qualities, and some of these were serious. His love +of method and order was often carried to an absurd +extreme, and much of the time of one of the greatest +intellects of the century was often devoted to doing +what a boy at fifteen shillings a week could have +done as well, or better. The story has often been +told, and it is exactly typical of him, that on one +occasion he devoted an entire afternoon to himself +labelling a number of wooden cases 'empty,' it so +happening that the routine of the establishment kept +every one else engaged at the time. His friend Dr. +Morgan jocularly said that if Airy wiped his pen on +a piece of blotting-paper he would duly endorse the +blotting-paper with the date and particulars of its<span class="pagenum"><a name="Page_117" id="Page_117">[117]</a></span> +use, and file it away amongst his papers. His mind +had that consummate grasp of detail which is characteristic +of great organizers, but the details acquired +for him an importance almost equal to the great +principles, and the statement that he had put a new +pane of glass into a window would figure as prominently +in his annual report to the Board of Visitors +as the construction of the new transit circle. His +son remarks of him that 'in his last days he seemed +to be more anxious to put letters which he received +into their proper place for reference than even to +master their contents,' his system having grown with +him from being a means to an end, to becoming the +end itself.</p> + +<p>So, too, his regulation of his subordinates was, +especially in his earlier days, despotic in the extreme—despotic +to an extent which would scarcely be +tolerated in the present day, and which was the +cause of not a little serious suffering to some of his +staff, whom, at that time, he looked upon in the true +spirit of Pond, as mere mechanical 'drudges.' For +thirty-five years of his administration the salaries of +his assistants remained discreditably low, and his +treatment of the supernumerary members of his staff +would now probably be characterized as 'remorseless +sweating.' The unfortunate boys who carried out +the computations of the great lunar reductions were +kept at their desks from eight in the morning till eight +at night, without the slightest intermission, except an +hour at midday. As an example of the extreme +detail of the oversight which he exercised over his +assistants, it may be mentioned that he drew up for<span class="pagenum"><a name="Page_118" id="Page_118">[118]</a></span> +each one of those who took part in the Harton +Colliery experiment, instructions, telling them by +what trains to travel, where to change, and so forth, +with the same minuteness that one might for a child +who was taking his first journey alone; and he himself +packed up soap and towels with the instruments, +lest his astronomers should find themselves, in Co. +Durham, out of reach of these necessaries of +civilization.</p> + +<p>A regime so essentially personal may indeed have +been necessary after Pond's administration, and to +give the Observatory a fresh start. But it would not +have been to the advantage of the Observatory, had +it become a permanent feature of its administration, +as it militated—was almost avowedly intended to +militate—against the growth of real zeal and intelligence +in the staff, and necessarily occasioned labour +and discomfort out of proportion to the results +obtained. Fortunately, in Airy's later years, the +extension of the work of the Observatory, a slight +failing in his own powers, and the efforts he was +devoting to the working out of the lunar theory, +compelled him to relax something of that microscopic +imperiousness which had been the chief characteristic +of his rule for so long.</p> + +<p>Airy had, in the fullest degree, the true spirit of +the public servant; his sense of duty to the State was +very high. He was always ready to undertake any +duty which he felt to be of public usefulness, and +many of these he discharged without fee or reward.</p> + +<p>So great an astronomer was necessarily most +highly esteemed by astronomers. He was President<span class="pagenum"><a name="Page_119" id="Page_119">[119]</a></span> +of the Royal Society for two years; he was five times +President of the Royal Astronomical Society, and +twice received its gold medal, beside a special testimonial +for his reduction of the Greenwich lunar +observations. From the Royal Society he received +the Copley medal and the Royal medal, beside +honorary titles from the Universities of Oxford, +Cambridge, and Edinburgh. So invaluable a public +servant, he received the distinction of a Knight +Commandership of the Bath in 1872. He had been +repeatedly offered knighthood before, but had not +thought it well to receive it. He was in the receipt +of decorations also from a great number of foreign +countries; for, for many years, he was looked up to, +not only by English astronomers, but by scientific +men in all countries, as the very head and representative +of his science.</p> + +<p>And he also received a more popular appreciation—and +most justly so. For whilst no one could +have less of the arts of the ordinary popularizer +about him, no one has ever given popular lectures +on astronomy which more fully corresponded to the +ideal of what such should be than Airy's six lectures +to working men, delivered at Ipswich. And we +may count the bestowal upon him of the honorary +freedom of the City of London, in 1875, as one of the +tokens that his services in this direction had not +been unappreciated.</p> + +<p>During the last seven years of his official career +he undertook the working out of a lunar theory, and, +to allow himself more leisure for its completion, he +resigned his position August 15, 1881, after forty-six<span class="pagenum"><a name="Page_120" id="Page_120">[120]</a></span> +years of office. He was now eighty years of age, +and he took up his residence at the White House, +just outside Greenwich Park. He resided there till +his death, more than ten years later—January 2, 1892.</p> + +<hr class="tb" /> + +<p>Airy was succeeded in the Astronomer Royalship +by the present and eighth holder of the office, +<span class="smcap">W. H. M. Christie</span>. He was born at Woolwich, in +1845, his father having been Professor Samuel Hunter +Christie, F.R.S. He was educated at King's College, +London, and Trinity College, Cambridge, graduating +as fourth Wrangler in 1868. In 1870 he was +appointed chief assistant at Greenwich, in succession +to Mr. Stone, who had become her Majesty's +astronomer at the Cape, and in 1881 he succeeded +Airy as Astronomer Royal.</p> + +<div class="figcenter bord" style="width: 417px;"><a name="christie" id="christie"></a> +<img src="images/i_121.jpg" width="417" height="600" alt="christie" /> +<div class="caption"><p class="center">W. H. M. CHRISTIE, ASTRONOMER ROYAL.<br /> +(<em>From a photograph by Elliott and Fry.</em>)</p></div> +</div> + +<p>During Mr. Christie's office, the two new departments +of the Astrographic Chart and Double-star +observations have come into being. The following +buildings have been erected under his administration: +the great New Observatory in the south +ground, the New Altazimuth, the New Library, +nearly opposite to it, the Transit Pavilion, the +porter's lodge, and the Magnetic Pavilion out in +the Park. Whilst in the old buildings the Astrographic +dome has been added, and the Upper and +Lower Computing rooms have been rebuilt and enlarged. +As to the instruments, the 28-inch refractor, +the astrographic twin telescope, the new altazimuth, +the 26-inch and 9-inch Thompson photographic refractors, +and the 30-inch reflector are all additions +during the present reign. Roughly speaking, therefore,<span class="pagenum"><a name="Page_121" id="Page_121"> </a><br /><a name="Page_122" id="Page_122"> </a><br /><a name="Page_123" id="Page_123">[123]</a></span> +we may say that three-fourths of the present Observatory +has been added during the nineteen years +of the present Astronomer Royal. One exceedingly +important improvement should not be overlooked. +Airy observed little himself whilst at Greenwich, +and had an inadequate idea of the necessity for +room in a dome and breadth in a shutter-opening. +With the sole exception, perhaps, of the +transit circle, every instrument set up by Airy was +crammed into too small a dome or looked out +through too narrow an opening. The increase of +shutter-opening of the newer domes may be well seen +by contrasting, say, the old altazimuth or the Sheepshanks +dome with that of the astrographic. This +reform has had much to do with the success of later +work.</p> + +<hr class="chap" /> + +<p><span class="pagenum"><a name="Page_124" id="Page_124">[124]</a></span></p> + + + + +<h2>CHAPTER V</h2> + +<h3>THE OBSERVATORY BUILDINGS</h3> + + +<p>Like a living organism, Greenwich Observatory bears +the record of its life-history in its structure. It was +not one of those favoured institutions that have sprung +complete and fully equipped from the liberality of +some great king or private millionaire. As we have +seen, it was originally established on the most modest—not +to say meagre—scale, and has been enlarged +just as it has been absolutely necessary. To quote +again from Professor Newcomb—</p> + +<blockquote> + +<p>'Whenever any part of it was found insufficient for its +purpose, new rooms were built for the special object in +view, and thus it has been growing from the beginning by +a process as natural and simple as that of the growth of a +tree. Even now the very value of its structure is less than +that of several other public observatories, though it eclipses +them all in the results of its work.'</p></blockquote> + +<p>Entering the courtyard—an enclosure some eighty +feet deep by ninety feet in extreme breadth—by the +great gate, we see before us Flamsteed House, the +original building of the Observatory. Flamsteed's +little domain was only some twenty-seven yards +wide by fifty deep, and for buildings comprised little +beyond a small dwelling-house on the ground floor, +and one fine room above it. This room—the original<span class="pagenum"><a name="Page_125" id="Page_125">[125]</a></span> +Greenwich Observatory—still remains, and is used +as a council room by the official Board of Visitors, +who come down to the Observatory on the first +Saturday in June, to examine into its condition and +to receive the Astronomer Royal's report. The room +is called, from its shape, the Octagon Room, and is +well known to Londoners from the great north +window which looks out straight over the river +between the twin domes of the Hospital.</p> + +<p>In Bradley's time, about 1749, the first extension +of the domains of the Observatory took place to the +south and east of the original building, the direction +in which, on the whole, all subsequent extensions +have taken place, owing to the fact that the original +building was constructed at the extremity of what +Sir George Airy was accustomed to call a 'peninsula'—a +projecting spur of the Blackheath plateau, from +which the ground falls away very sharply on three +sides and on part of the fourth.</p> + +<p>The Observatory domain at present is fully two +hundred yards in greatest length, with an average +breadth of about sixty. Nearly the whole of this +accession took place under the directorates of Pond +and Airy. The present instruments are, therefore, +as a rule, the more modern in direct proportion to +their distance from the Octagon Room—the old +original Observatory. There is one notable exception. +The very first extension of the Observatory buildings, +made in the time of Halley, the second Astronomer +Royal, consisted in the setting up of a strong pier, +to carry two quadrant telescopes. The pier still +remains, but now forms the base of the support of<span class="pagenum"><a name="Page_126" id="Page_126">[126]</a></span> +the twin telescopes devoted to the photographic +survey of the heavens for the International Chart.</p> + +<p>Standing just within the gate of the courtyard, +and looking westward, that is toward Flamsteed +House, we have immediately on our right hand the +porter's lodge; a little farther forward, also on the +right, the Transit Pavilion, a small building sheltering +a portable transit instrument; and farther forward, +still on the right, the entrance to the Chronograph +Room. Above the Chronograph Room is a little, +inconveniently-placed dome, containing a small equatorially-mounted +telescope, known as the Shuckburgh. +Beyond the Chronograph Room a door opens on to +the North Terrace, over which is seen the great north +window of the Octagon Room. Close by the door of the +Chronograph Room a great wooden staircase rises to +the roof of the main building. It is not an attractive-looking +ascent, as the steps overlap inconveniently. +Still, there is no record of an accident upon them, +and those who venture on the climb to the roof, +where are placed the anemometers and the turret +carrying the time-ball, which is dropped daily at +1 p.m., will be well repaid by the splendid view of +the river which is there afforded to them.</p> + +<p>Passing under this staircase, on the wall by its +side is seen the following inscription:—</p> + +<p class="center"> +<span class="smcap">Carolus II<sup>s</sup> Rex Optimus<br /> +Astronomiæ et Nauticæ artis<br /> +Patronus Maximus<br /> +Speculam hanc in utriusque commodum<br /> +fecit<br /> +Anno D<sup>NI</sup> MDCLXXVI. Regni sui XXVIII.</span><br /> +</p> + +<p class="sig"> +Curante Iona Moore milite<br /> +R. T. S. G. +</p> + +<p><span class="pagenum"><a name="Page_127" id="Page_127">[127]</a></span></p> + +<div class="figcenter bord" style="width: 400px;"><a name="astro" id="astro"></a> +<img src="images/i_127.jpg" width="400" height="469" alt="astro" /> +<div class="caption"><p class="center">THE ASTRONOMER ROYAL'S HOUSE.<br /> +(<em>From a photograph by Mr. Lacey.</em>)</p></div> +</div> + +<p>In the extreme angle of the courtyard is the +entrance to the mean solar clock cupboard, and to +the staircase leading up to the Octagon Room. At +the head of this staircase in a small closet is the +winch for winding up the time-ball.</p> + +<p><span class="pagenum"><a name="Page_128" id="Page_128">[128]</a></span></p> + +<p>Coming back into the courtyard, and crossing the +face of the Astronomer Royal's private house, the +range of buildings is reached which form the left +hand or south side of the enclosure. Entering the +first of these, we find ourselves in the Lower Computing +Room, which is devoted to the 'Time Department.' +The next room which opens out of it, as +we turn eastwards, was Bradley's Transit Room, but +is now used for the storage of chronometers. Passing +through Bradley's Transit Room, we come to the +present Transit Room, which brings us close to the +great gate. The range of buildings is, however, continued +somewhat farther, containing on the ground +floor some small sitting-rooms and a fire-proof room +for records.</p> + +<div class="figcenter bord" style="width: 600px;"><a name="court" id="court"></a> +<img src="images/i_130.jpg" width="600" height="443" alt="court" /> +<div class="caption"><p class="center">THE COURTYARD.<br /> +(<em>From a photograph by Mr. Lacey.</em>)</p></div> +</div> + +<p>Turning back to the Lower Computing Room, +we notice in it the stone pier, already alluded to, +which was set up by Halley, and formed the first +addition to the original Observatory of Flamsteed. +The Lower Computing Room itself and Bradley's +Transit Room were due to the Astronomer after +which the latter is named. An iron spiral staircase +in the middle of the Lower Computing Room leads +up to the Upper Computing Room, and above that +to the Astrographic dome, so called because the +twin telescope housed therein is devoted to the work +of the Astrographic Chart—a chart of the entire sky +to be made by eighteen co-operating observatories +by means of photography. In this way it is intended +to secure a record of the places of far more stars than +could be done by the ordinary methods, and in this +project Greenwich has necessarily taken a premier<span class="pagenum"><a name="Page_129" id="Page_129"> </a><br /><a name="Page_130" id="Page_130"> </a><br /><a name="Page_131" id="Page_131">[131]</a></span> +place. This is a work which, whilst it is the legitimate +and natural outcome of the original purpose of the +Observatory, is yet pushed beyond what is necessary +for any mere utilitarian assistance to navigation. For +the sailor it will always be sufficient to know the +places of a mere handful of the brightest stars, and +the vast majority of those in the great photographic +map will never be visible in the little portable telescope +of the sailor's sextant. But it will be freely +admitted that in the case of an enterprise of this +nature, in which the observatories of so many different +nations were uniting, and which was so precisely on +the lines of its original charter, though an extension +of it, it was impossible for Greenwich to hold back +on the plea that the work was not entirely utilitarian.</p> + +<p>Descending again to the Lower Computing Room, +and passing through it, not to the east, into Bradley's +Transit Room, but through a little lobby to the south, +we come upon an inconvenient wooden staircase +winding round a great stone pillar with three rays. +This pillar is the support of Airy's altazimuth, and +very nearly marks the place where Flamsteed set up +his original sextant.</p> + +<p>Returning again to the Lower Computing Room, +and passing out to the east, just in front of the Time +Superintendent's desk, we enter a small passage +running along the back of Bradley's Transit Room, +and from this passage enter the present Transit +Room near its south end. Just before reaching the +Transit Room, however, we pass the Reflex Zenith +Tube, a telescope of a very special kind.</p> + +<p><span class="pagenum"><a name="Page_132" id="Page_132">[132]</a></span></p> + +<p>Immediately outside the Transit Room is a staircase +leading on the first floor to two rooms long used +as libraries, and to the leads above them, on which +is a small dome containing the Sheepshanks equatorial. +These libraries are over the small sitting-rooms +already referred to. The fire-proof Record +Rooms, two stories in height, terminate this range +of buildings.</p> + +<p>Beyond the Record Rooms the boundary turns +sharply south, where stands a large octagonal building +surmounted by a dome of oriental appearance, a +'circular versatile roof,' as the Visitors would have +called it a hundred years ago. This dome—which +has been likened, according to the school of æsthetics +in which its critics have been severally trained, to +the Taj at Agra, a collapsed balloon, or a mammoth +Spanish onion—houses the largest refractor in England, +the 'South-east Equatorial' of twenty-eight +inches aperture. But, though the largest that England +possesses, it would appear but as a pigmy beside some +of the great telescopes for which America is famous.</p> + +<p>Beyond this dome the hollow devoted to the +Astronomer Royal's private garden reduces the +Observatory ground to a mere 'wasp's waist,' a +narrow, inconvenient passage from the old and north +observatory to the younger southern one.</p> + +<p>The first building, as the grounds begin to widen +out to the south, contains the New Altazimuth, a +transit instrument which can be turned into any +meridian. A library of white brick and a low wooden +cruciform building—the Magnetic Observatory—follow +it closely.</p> + +<p><span class="pagenum"><a name="Page_133" id="Page_133">[133]</a></span></p> + +<p>This latter building houses the Magnetic Department, +a department which, though it lies aside from +the original purposes of the Observatory, as defined +in the warrant given to Flamsteed, is yet intimately +connected with navigation, and was founded by Airy +very early in his period of office. This deals with +the observation of the changes in the force and +direction of the earth's magnetism, an inquiry which +the greater delicacy of modern compasses, and, in +more recent times, the use of iron instead of wood +in the construction of ships, has rendered imperative.</p> + +<p>Closely associated with the Magnetic Department +is the Meteorological. Weather forecasts, so necessary +for the safety of shipping round our coasts, are not +issued from Greenwich Observatory, any more than +the <cite>Nautical Almanac</cite> is now issued from it. But just +as the Observatory furnishes the astronomical data +upon which the almanac is based, so also a considerable +department is set apart for furnishing observations +to be used by the Meteorological Office at +Westminster for their daily predictions.</p> + +<p>So far, the development of the Observatory had +been along the central line of assistance to navigation. +But the 'Magnetic Department' led on to a new one, +which had but a secondary connection with it. It +had been discovered that the extent of the daily +range of the magnetic needle, and the amount of the +disturbances to which it was subjected, were in close +connection with the numbers and size of the spots +on the sun's surface. This led to the institution of +a daily photographic record of the state of the sun's<span class="pagenum"><a name="Page_134" id="Page_134"> </a><br /><a name="Page_135" id="Page_135">[135]</a></span> +surface, a record of which Greenwich has now the +complete monopoly.</p> + +<div class="figcenter bord" style="width: 421px;"><a name="plan" id="plan"></a> +<img src="images/i_134.jpg" width="421" height="600" alt="plan" /> +<div class="caption"><p class="center">PLAN OF OBSERVATORY AT PRESENT TIME.<br /> +(For key to plan, see p. 135.)</p></div> +</div> + +<p class="center"><span class="smcap">Key to the Plan of the Observatory on Page 134.</span></p> + +<p class="noin"> +<span style="margin-left: 0.5em;">1. Chronograph Room.</span><br /> +<span style="margin-left: 0.5em;">2. Old Altazimuth Dome.</span><br /> +<span style="margin-left: 0.5em;">3. Safe Room.</span><br /> +<span style="margin-left: 0.5em;">4. Computing Room.</span><br /> +<span style="margin-left: 0.5em;">5. Bradley's Transit Room.</span><br /> +<span style="margin-left: 0.5em;">6. Transit Circle Room.</span><br /> +<span style="margin-left: 0.5em;">7. Assistants' Room.</span><br /> +<span style="margin-left: 0.5em;">8. Chief Assistant's Room.</span><br /> +<span style="margin-left: 0.5em;">9. Computers' Room.</span><br /> +10. Record Rooms.<br /> +11. Chronometer Rooms and South-east Dome.<br /> +12. Greenhouse and Outbuildings.<br /> +14. New Library.<br /> +15. Magnetic Observatory.<br /> +16. Offices.<br /> +19. Sheds.<br /> +23. Winch Room for Time-ball.<br /> +24. Porter's Lodge.<br /> +25. New Transit Pavilion.<br /> +26. New Altazimuth Pavilion.<br /> +27. Museum: New Building.<br /> +28. South Wing "<br /> +29. North Wing "<br /> +30. West Wing "<br /> +31. East Wing "<br /> +<br /> +F. Rooms built for Flamsteed.<br /> +H. Added by Halley.<br /> +B. " Bradley.<br /> +M. " Maskelyne.<br /> +A. " Airy.<br /> +F'F'. Flamsteed's boundaries.<br /> +M'M'. Maskelyne's " 1790.<br /> +P'P'. Pond's " 1814.<br /> +A'A'. Airy's " 1837.<br /> +A"A". Airy's " 1868.<br /> +</p> + +<p>Beyond the Magnetic Observatory the ground +widens out into an area about equal to that of the +northern part, and the new building just completed, +and which is now emphatically 'The Observatory,' +stands clear before us. The transfer to this stately +building of the computing rooms, libraries, and store +rooms has been aptly described as a shift in the +latitude of Greenwich Observatory, which still preserves +its longitude. It may be noted that the only two +buildings of any architectural pretensions in the whole +range are—Flamsteed's original observatory, built +by Sir Christopher Wren, and containing little beyond +the octagon room, in the extreme north; and this +newest building in the extreme south.</p> +<p><span class="pagenum"><a name="Page_136" id="Page_136">[136]</a></span></p> +<p>This 'New Observatory,' like the old, and like +the great South-eastern tower, is an octagon in its +central portion. But whilst the two other great +buildings are simply octagonal, here the octagon +serves only as the centre from which radiate four +great wings to the four points of the compass. The +building is by far the largest on the ground, but in +little accord with the popular idea of an astronomer +as perpetually looking through a telescope, carries +but a single dome; its best rooms being set apart +as 'computing rooms,' for the use of those members +of the staff who are employed in the calculations and +other clerical work, which form, after all, much the +greater portion of the Observatory routine.</p> + +<p>An observer with the transit instrument, for +instance, will take only three or four minutes to make +a complete determination of the place of a single +star. But that observation will furnish work to the +computers for many hours afterwards. Or, to take +a photograph of the sun will occupy about five +minutes in setting the instrument, whilst the actual +exposure will take but the one-thousandth part of a +second. But the plate, once exposed, will have to +be developed, fixed, and washed; then measured, and +the measures reduced, and, <em>on the average</em>, will provide +one person with work for four days before the final +results have been printed and published.</p> + +<p>It is easy to see, then, that observing, though the +first duty of the Observatory, makes the smallest +demand on its time. The visitor who comes to the +Observatory by day (and none are permitted to do +so by night) finds the official rooms not unlike those<span class="pagenum"><a name="Page_137" id="Page_137">[137]</a></span> +of Somerset House or Whitehall, and its occupants +for the most part similarly engaged in what is, +apparently, merely clerical work. An examination +of the big folios would of course show that instead of +being ledgers of sales of stamps, or income-tax +schedules, they referred to stars, planets, and sun-spots; +but for one person actively engaged at a +telescope, the visitor would see a dozen writing or +computing at a desk.</p> + +<p>The staff, like the building, is the result of a +gradual development, and bears traces of its life +history in its composition. First comes the Astronomer +Royal, the representative and successor of the +original 'King's Astronomer,' the Rev. John Flamsteed. +But the 'single surly and clumsy labourer,' +which was all that the 'Merry Monarch' could grant +for his assistance, is now represented by a large and +complex body of workers; each varied class and +rank of which is a relic of some stage in the progress +of the Observatory to its present condition.</p> + +<p>The following extract from the Annual Report of +the Astronomer Royal to the Board of Visitors, June, +1900, describes the present <em>personnel</em> of the establishment:—</p> + +<blockquote> + +<p>'The staff at the present time is thus constituted, the +names in each class being arranged in alphabetical +order:—</p> + +<p>'Chief assistants—Mr. Cowell, Mr. Dyson.</p> + +<p>'Assistants—Mr. Hollis, Mr. Lewis, Mr. Maunder, Mr. +Nash, Mr. Thackeray.</p> + +<p>'Second-class assistants—Mr. Bryant, Mr. Crommelin.</p> + +<p>'Clerical assistant—Mr. Outhwaite.</p> + +<p>'Established computers—Mr. Bowyer, Mr. Davidson, +Mr. Edney, Mr. Furner, Mr. Rendell, and one vacancy.</p> + +<p><span class="pagenum"><a name="Page_138" id="Page_138">[138]</a></span></p> + +<p>'The two second-class assistants will be replaced by +higher grade established computers as vacancies occur.</p> + +<p>'Mr. Dyson and Mr. Cowell have the general superintendence +of all the work of the Observatory. Mr. Maunder +is charged with the heliographic photography and reductions, +and with the preparation of the Library Catalogue. +Mr. Lewis has charge of the time-signals and chronometers, +and of the 28-inch equatorial. Mr. Thackeray +superintends the miscellaneous astronomical computations, +including the preparation of the new Ten-Year +Catalogue. Mr. Hollis has charge of the photographic +mapping of the heavens, the measurement of the plates, +and the computations for the Astrographic Catalogue. +Mr. Crommelin undertakes the altazimuth and Sheepshanks +equatorial reductions, and Mr. Bryant the transit +and meridian zenith distance reductions and time-determinations. +In the magnetic and meteorological branch, +Mr. Nash has charge of the whole of the work. Mr. Outhwaite +acts as responsible accountant officer; has charge of +the library, records, manuscripts, and stores, and conducts +the official correspondence. As regards the established +computers, Mr. Bowyer, Mr. Furner, Mr. Davidson, and +Mr. Rendell assist Mr. Lewis, Mr. Thackeray, Mr. Hollis, +and Mr. Bryant respectively, and Mr. Edney assists Mr. +Nash.</p> + +<p>'There are at the present time twenty-four supernumerary +computers employed at the Observatory, ten being +attached to the astronomical branch, two the chronometer +branch, six to the astrographic, one to the heliographic, +four to the magnetic and meteorological, and one to the +clerical.</p> + +<p>'A foreman of works, with two carpenters, and two +labourers; a skilled mechanic with an assistant; a gate +porter, two messengers, a watchman, a gardener, and a +charwoman, are also attached to the Observatory.</p> + +<p>'The whole number of persons regularly employed at +the Observatory is fifty-three.'</p></blockquote> + +<p>The day work, as said before, is by far the +greatest in amount, the 'office hours' being from<span class="pagenum"><a name="Page_139" id="Page_139">[139]</a></span> +nine till half-past four, with an hour's interval. The +arrangements for the night watches present some +complications.</p> + +<p>For many years the instruments in regular use +were two only, the transit circle and the altazimuth. +The arrangements for observing were simple. Four +assistants divided the work between them thus: an +assistant was on duty with the transit circle one day, +his watch beginning about six a.m. or a little later, +and ending about three the following morning; +a watch of twenty-one hours in maximum length. +The second day his duties were entirely computational, +and were only two or three hours in length. +The third day he had a full day's work on the +calculations, followed by a night duty with the altazimuth. +The latter instrument might give him a very +easy watch or a terribly severe one. If the moon +were a young one it was easy, especially if the night +was clear, as in that case an hour was enough to +secure the observations required.</p> + +<p>Very different was the case with a full moon, +especially in the long, often cloudy, nights of winter. +Then a vigilant watch had to be kept from sunset to +sunrise, so that in case of a short break in the clouds +the moon might yet be observed. Such a watch was +the severest (with one exception) that an assistant +had to undergo.</p> + +<p>His fourth day would then resemble his second, +and with the fifth day a second cycle of his quartan +fever would commence, the symptoms following each +other in the same sequence as before.</p> + +<p>Such a routine carried on with iron inflexibility<span class="pagenum"><a name="Page_140" id="Page_140">[140]</a></span> +was exceedingly trying, as it was absolutely impossible +for an observer to keep any regularity in his +hours of rest or times for meals.</p> + +<p>This routine has been considerably modified by +the present Astronomer Royal, partly because the +instruments now in regular daily use are five instead +of two, and partly because a less stringent system has +proved not merely far less wearing to the observers, +but also much more prolific of results. It was impossible +for a man to be at his best for long under +the old <em>régime</em>, and from forty-six to forty-seven has +been an ordinary age for an assistant to break down +under the strain.</p> + +<p>One point in which the observing work has been +lightened has been in the discontinuance of the +altazimuth observations at the full of the moon, +another in the shortening of the hours of the transit +circle watch; and a further and most important one +in the arrangement that the observers with the larger +instruments should have help at their work. The +net result of these changes has been a most striking +increase in the amount of work achieved. Thus, +whilst in the year ending May 20, 1875, 3780 transits +were taken with the transit circle, and 3636 determinations +of north polar distance; in that ending +May 10, 1895, the numbers had risen to 11,240 and +11,006 respectively, the telescope remaining precisely +the same.</p> + +<p>One principle of Airy's rule still remains. So far +as possible no observer is on duty for two consecutive +days, but a long day of desk work and observing is +followed by a short day of desk work without +observing.</p> + +<p><span class="pagenum"><a name="Page_141" id="Page_141">[141]</a></span></p> + +<p>It will be readily understood that with five +principal telescopes in constant work and one or two +minor ones, some demanding two observers, others +only one, each telescope having its special programme +and its special hours of work, whilst by no means +every member of the staff is authorized to observe +with all instruments indifferently, it becomes a somewhat +intricate matter to arrange the weekly <i lang="la" xml:lang="la">rota</i> in +strict accordance with the foregoing principle, and +with the further one, that whilst a considerable +amount of Sunday observing is inevitable, the average +duty of an observer should be three days a week, +not seven days a fortnight. There is a story, received +with much reserve at Cambridge, that there +was once a man at that university who had mastered +all the colours and combinations of shades and +colours of the various colleges and clubs. If so +gifted a being ever existed, he may be paralleled by +the Greenwich assistant who can predict for any +future epoch the sequence of duties throughout the +entire establishment. At any rate, one of the first +items in the week's programme is the preparation of +the <i lang="la" xml:lang="la">rota</i> for the week, or rather, to use an ecclesiastical +term, for the 'octave,' <em>i.e.</em> from the Monday +to the Monday following.</p> + +<p>The special work to be carried out on any telescope +is likewise a matter of programme. For the +transit circle a list of the most important objects to +be observed is supplied for the observer's use, and +the general lines upon which the other stars are to +be selected from a huge 'Working Catalogue' are +well understood. With some of the other telescopes<span class="pagenum"><a name="Page_142" id="Page_142">[142]</a></span> +the principles upon which the objects are to be +selected are laid down, but the actual choice is left to +the discretion of the observer at the time. There is +no time for the watcher to spend in what the outsider +would regard as 'discovery'; such as sweeping +for comets or asteroids, hunting for variable stars, +sketching planets, and so forth. Indeed, there is a +story current in the Observatory that some fifty +years ago, when the tide of asteroid discovery +first set in, Airy found an assistant, since famous, +working with a telescope on his 'off-duty' night. +That stern disciplinarian asked what business the +assistant had to be there on his free night, and on +being told he was 'searching for new planets,' he +was severely reprimanded and ordered to discontinue +at once. A similar energy would not meet so gruff +a discouragement to-day; but the routine work so +fully occupies both staff and telescopes that an +assistant may be most thoroughly devoted to his +science, and yet pass a decade at the Observatory +without ever seeing those 'show places' of the sky +which an amateur would have run over in the first +week after receiving his telescope. For example, +there is no refractor in the British Isles so competent +to bring out the vivid green light of the great Orion +nebula—that marvellous mass of glowing, curdling, +emerald cloud—or the indescribable magnificence +of the myriad suns that cluster like swarming bees +or the grapes of Eshcol in the constellation of +Hercules; yet probably most of the staff have +never seen either spectacle through it. The professional +astronomer who is worth his salt will find<span class="pagenum"><a name="Page_143" id="Page_143">[143]</a></span> +abundance of charm and interest in his work, but he +will not,</p> + +<div class="poem"><div class="stanza"> +<span class="i16">'Like a girl,<br /></span> +<span class="i0">Valuing the giddy pleasures of the eyes,'<br /></span> +</div></div> + +<p class="noin">consider the charm to lie mainly in the occasional +sight of wonderful beauty which his work may bring +to him, nor the interest in some chance phenomenon +which may make his name known.</p> + +<p>It is not every field of astronomy that is cultivated +at Greenwich. The search for comets and for 'pocket +planets' forms no part of its programme; and the +occupation so fascinating to those who take it up, of +drawing the details on the surfaces of the moon, +Mars, Jupiter, or Saturn, has been but little followed. +Such work is here incidental, not fundamental, and +the same may be said of certain spectroscopic +observations of new or variable stars, and of many +similar subjects. Work such as this is most interesting +to the general public, and is followed with much +devotion by many amateur astronomers. For that +very reason it does not form an integral part of the +programme of our State observatory. But work +which is necessary for the general good, or for the +advancement of the science, and which demands +observations carried on continuously for many years, +and strict unity of instruments and methods, cannot +possibly be left to chance individual zeal, and is +therefore rightly made the first object at Greenwich.</p> + +<p>Those striking discoveries which from time to +time appeal strongly to the popular imagination,<span class="pagenum"><a name="Page_144" id="Page_144">[144]</a></span> +and which have rendered so justly famous some of +the great observatories of the sister continent, have +not often been made here.</p> + +<p>Its work has, none the less, been not only useful +but essential. A century ago, when we were engaged +in the hand-to-hand struggle with Napoleon, by far +the most brilliant part of that naval war which we +waged against the French, and the most productive +of prize-money, was carried on by our cruisers, who +captured valuable prizes in every sea. But a much +greater service, indeed an absolutely vital one, was +rendered to the State by those line-of-battle ships +which were told off to watch the harbours wherein +the French fleet was taking refuge. This was a +work void of the excitement, interest, and profit of +cruising. It was monotonous, wearing, and almost +inglorious, but absolutely necessary to the very +existence of England. So the continuance for more +than two centuries of daily observations of places +of moon, stars, and planets is likewise 'monotonous, +wearing, and almost inglorious;' the one compensation +is that it is essential to the life of astronomy.</p> + +<p>The eight Astronomers Royal have, as already +said, kept the Observatory strictly on the lines +originally laid down for it, subject, of course, to that +enlargement which the growth of the science has +inevitably brought. But had they been inclined to +change its course, the Board of Visitors has been +specially appointed to bring them back to the right +way. As already mentioned in the account of +Flamsteed, the Board dates from 1710, when it +practically consisted of the President and Council<span class="pagenum"><a name="Page_145" id="Page_145">[145]</a></span> +of the Royal Society. Its Royal warrant lapsed on +the death of Queen Anne, and was not renewed at +the accession of the two following sovereigns; but +in the reign of George III. a new warrant was issued +under date February 22, 1765; and this was renewed +at the accession of George IV. When William IV. +came to the throne, the constitution of the Board +was extended, so as to give a representation to the +new Royal Astronomical Society, founded in 1820. +The President of the Royal Society is still chairman +of the Board, but the Admiralty, of which the +Observatory is a department, the two Universities +of Oxford and Cambridge, and the Royal Astronomical +Society are all represented on it by <i lang="la" xml:lang="la">ex +officio</i> members, and twelve other members are +contributed by the Royal and Royal Astronomical +Societies respectively, six by each. The first Saturday +in June is the appointed day for the annual +inspection by the Board, and for the presentation +to it of the Astronomer Royal's Report. To this +all-important business meeting has been added +something of a social function, by the invitation of +many well-known astronomers and the leading men +of the allied sciences to inspect the results of the +year, and to partake of the chocolate and cracknels, +which have been the traditional refreshments offered +on these occasions for a period 'whereof the memory +of man runneth not to the contrary.'</p> + +<hr class="chap" /> + +<p><span class="pagenum"><a name="Page_146" id="Page_146">[146]</a></span></p> + + + + +<h2>CHAPTER VI</h2> + +<h3>THE TIME DEPARTMENT</h3> + + +<p>One day two Scotchmen stood just outside the main +entrance of Greenwich Observatory, looking intently +at the great twenty-four-hour clock, which is such an +object of attention to the passers through the Park. +'Jock,' said one of them to the other, 'd'ye ken whaur +ye are?' Jock admitted his ignorance. 'Ye are at +the vara ceentre of the airth.'</p> + +<p>Geographers tell us that there is a sense in which +this statement as it stands may be accepted as true. +For if the surface of the globe be divided into two +hemispheres, so related to each other that the one +contains as much land as possible, and the other as +little, then London will occupy the centre or thereabouts +of the hemisphere with most land.</p> + +<p>This was not, however, what the Scotchman +meant. He meant to tell his companion that he was +standing on the prime meridian of the world, the +imaginary base line from which all distances, east or +west, are reckoned; in short, that he was on 'Longitude +Nought.'</p> + +<p>He was not absolutely correct, however, for the +great twenty-four-hour clock does not mark the exact<span class="pagenum"><a name="Page_147" id="Page_147">[147]</a></span> +meridian of Greenwich. To find the instrument +which marks it out and defines it we must step inside +the Observatory precincts, and just within the gate +we see before us on the left hand a door which leads +through a little lobby straight into the most important +room of the whole Observatory—the Transit Room.</p> + +<div class="figcenter bord" style="width: 450px;"><a name="clock" id="clock"></a> +<img src="images/i_147.jpg" width="450" height="473" alt="clock" /> +<div class="caption"><p class="center">THE GREAT CLOCK AND PORTER'S LODGE.<br /> +(<em>From a photograph by Mr. Lacey.</em>)</p></div> +</div> + +<p>This room is not well adapted for representation +by artist or photographer. Four broad stone pillars<span class="pagenum"><a name="Page_148" id="Page_148">[148]</a></span> +occupy the greater part of the space, and leave little +more than mere passage room beside. Two of these +pillars are tall, as well as broad and massive, and +stand east and west of the centre of the room, +carrying between them the fundamental instrument +of the Observatory, the transit circle. The optical +axis of this telescope marks 'Longitude Nought,' +which is further continued by a pair of telescopes, +one to the north of it, the other to the south, mounted +on the third and fourth of the pillars alluded to +above.</p> + +<p>This room has not always marked the meridian +of Greenwich, for it stands outside the original +boundary of the Observatory. But it is only a few +feet to the east of the first transit instrument which +was set up by Halley, the second Astronomer Royal, +in the extreme N.-W. corner of the Observatory +domain, a distance equivalent to very much less than +one-tenth of a second of time, an utterly insensible +quantity with the instruments of two hundred years +ago.</p> + +<p>It would be a long story to tell in detail how the +Greenwich transit room has come to define one of +the two fundamental lines that encircle the earth. +The other, the equator, is fixed for us by the earth +itself, and is independent of any political considerations, +or of any effort or enterprise of man. But of +all the infinite number of great circles which could be +drawn at right angles to the equator, and passing +through the north and south poles, it was not easy to +select one with such an overwhelming amount of +argument in its favour as to obtain a practically<span class="pagenum"><a name="Page_149" id="Page_149">[149]</a></span> +universal acceptance. The meridians of Jerusalem +and of Rome have both been urged, upon what we +may call religious or sentimental grounds; that of +the Great Pyramid at Ghizeh has been pressed in +accordance with the fantastic delusion that the +Pyramid was erected under Divine inspiration and +direction; that of Ferro, in the Canaries, as being an +oceanic station, well to the west of the Old World, +and as giving a base line without preference or +distinction for one nation rather than another.</p> + +<p>The actual decision has been made upon no such +grounds as these. It has been one of pure practical +convenience, and has resulted from the amazing +growth of Great Britain as a naval and commercial +power. Like Tyre of old, she is 'situate at the entry +of the sea, a merchant of the people for many isles,' +and 'her merchants are the great men of the earth.' +To tell in full, therefore, the steps by which the +Greenwich meridian has overcome all others is +practically to tell again, from a different standpoint, +the story of the 'expansion of England.' The need +for a supreme navy, the development of our empire +beyond the seven seas, the vast increase of our +carrying trade—these have made it necessary that +Englishmen should be well supplied with maps and +charts. The hydrographic and geographic surveys +carried on, either officially by this country, or by +Englishmen in their own private capacity, have been +so numerous, complete, and far-reaching as not only +to outweigh those of all other countries put together, +but to induce the surveyors and explorers of not a +few other countries to adopt in their work the same<span class="pagenum"><a name="Page_150" id="Page_150">[150]</a></span> +prime meridian as that which they found in the +British charts of regions bordering on those which they +were themselves studying. Naturally, the meridian +of Greenwich has not only been adopted for Great +Britain, but also for the British possessions over-sea, +and, from these, for a large number of foreign countries; +whilst our American cousins retain it, an historic relic +of their former political connection with us. The +victories of Clive at Arcot and Plassy, of Nelson at +the Nile and Trafalgar, the voyages and surveys of +Cook and Flinders, and many more; the explorations +of Bruce, Park, Livingstone, Speke, Cameron, and +Stanley; these are some of the agencies which have +tended to fix 'Longitude Nought' in the Greenwich +Transit Room.</p> + +<p>There are two somewhat different senses in which +the meridian of Greenwich is the standard meridian +for nearly the entire world. The first is the sense +about which we have already been speaking; it +constitutes the fundamental line whence distances +east and west are measured, just as distances north +and south are measured from the equator. But there +is another, though related sense, in which it has +become the standard. <em>It gives the time to the world.</em></p> + +<p>There are few questions more frequently put than, +'What time is it?' 'Can you tell me the true +time?' A stickler for exactitude might reply, 'What +kind of time do you mean?' 'Do you mean solar +or sidereal time?' 'Apparent time or mean time?' +'Local time or standard time?' There are all these +six kinds of time, but it is only within the last two +generations, within, indeed, the reign of our Sovereign,<span class="pagenum"><a name="Page_151" id="Page_151">[151]</a></span> +Queen Victoria, that the subject of the differences of +most of these kinds of time has become of pressing +importance to any but theorists.</p> + +<p>In one of the public gardens of Paris a little +cannon is set up with a burning-glass attached to it +in such a manner that the sun itself fires the cannon +as it reaches the meridian. This, of course, is the +time of Paris noon—apparent noon—but it would be +exceedingly imprudent of any traveller through Paris +who wished, say, to catch the one o'clock express, +to set his watch by the gun. For if it happened to +be in February, he would find when he reached the +railway station that the station clock was faster than +the sun by nearly a full quarter of an hour, and that +his train had gone; whilst towards the end of October +or the beginning of November, he would find himself +as much too soon.</p> + +<p>Until machines for accurately measuring time +were invented, apparent time—time, that is to say, +given by the sun itself, as by a sun-dial—was the +only time about which men knew or cared. But +when reasonably good clocks and watches were made, +it was very soon seen that at different times in the +year there was a marked difference between sun-dial +time and that shown by the clock, the reason being +simply that the apparent rate of motion of the sun +across the sky was not always quite the same, whilst +the movement of the clock was, of course, as regular +as it could be made.</p> + +<p>This difference between time as shown by the +actual sun and by a perfect clock is known as the +'equation of time.' It is least about April 15, June 15,<span class="pagenum"><a name="Page_152" id="Page_152">[152]</a></span> +August 31, and December 25. It is greatest, the sun +being after the clock, about February 11; and the sun +being before the clock, about November 2. Flamsteed, +before he became Astronomer Royal, investigated the +question, and so clearly demonstrated the existence, +cause, and amount of the equation of time as entirely +to put an end to controversy on the subject.</p> + +<p>We had thus, early in the century, the two kinds +of time in common use, apparent time and mean time, +or clock time. But as the sun can only be on one +particular meridian at any given instant, the time as +shown by the clocks in one particular town will differ +from that of another town several miles to the east +or west of it. It is thus noon at Moscow 1 hr. 36 min. +before it is noon at Berlin, and noon at Berlin 54 min. +before it is noon in London.</p> + +<p>This was all well enough known, but occasioned +no inconvenience until the introduction of railway +travelling; then a curious difficulty arose. Suppose +an express train was running at the rate of sixty +miles an hour from London to Bristol. The guard +of the train sets his watch to London time before he +leaves Paddington, but if the various towns through +which the train passes, Reading, Swindon, etc., each +keep their own local time, he will find his watch +apparently fast at each place he reaches; but on his +return journey, if he sets to Bristol time before starting, +he will in a similar way find it apparently slow by +the Swindon, Reading, and Paddington clocks as he +reaches them in succession.</p> + +<p>It became at once necessary to settle upon one +uniform system of time for use in the railway guides.<span class="pagenum"><a name="Page_153" id="Page_153">[153]</a></span> +Apart from this, a passenger taking train, say, at +Swindon, might have been very troubled to know +whether the advertised time of his train was that of +Exeter, the place whence it started, or Swindon, the +station where he was getting in, or London, its +destination. 'Railway time,' therefore, was very +early fixed for the whole of Great Britain to be the +same as London time, which is, of course, time as +determined at Greenwich Observatory. At first it +was the custom to keep at the various stations two +clocks, one showing local time, the other 'railway,' or +Greenwich time, or else the clocks would be provided +with a double minute hand, one branch of which +pointed to the time of the place, the other to the time +of Greenwich.</p> + +<p>It was soon found, however, that there was no +sufficient reason for keeping up local time. Even in +the extreme West of England the difference between +the two only amounted to twenty-three minutes, and +it was found that no practical inconvenience resulted +from saying that the sun rose at twenty-three minutes +past six on March 22, rather than at six o'clock. +The hours of work and business were practically put +twenty-three minutes earlier in the day, a change of +which very few people took any notice.</p> + +<p>Other countries besides England felt the same +difficulty, and solved it in the same way, each country +as a rule taking as its standard time the time of its +own chief city.</p> + +<p>There were two countries for which this expedient +was not sufficient—the United States and Canada. +The question was of no importance until the iron<span class="pagenum"><a name="Page_154" id="Page_154">[154]</a></span> +road had linked the Atlantic to the Pacific in both +countries. Then it became pressing. No fewer than +seventy different standards prevailed in the United +States only some twenty years ago. The case was +a very different one here from that of England, where +east and west differed in local time by only a little +over twenty minutes. In North America, in the +extreme case, the difference amounted to four hours, +and it seemed asking too much of men to call eight +o'clock in their morning, or it might be four o'clock +in their afternoon, their noonday.</p> + +<p>The device was therefore adopted of keeping the +minutes and seconds the same for all places right +across the continent, but of changing the hour at +every 15° of longitude. The question then arose +what longitude should be adopted as the standard. +The Americans might very naturally have taken their +standard time from their great national observatory +at Washington, or from that of their chief city, New +York, or of their principal central city, Chicago. But, +guided partly no doubt by a desire to have their +standard times correspond directly to the longitudes +of their maps, and partly from a desire to fall in, if +possible, with some universal time scheme, if such +could be brought forward, they fixed upon the +meridian of Greenwich as their ultimate reference +line, and defined their various hour standards as +being exactly so many hours slow of Greenwich mean +time.</p> + +<p>The decision of the United States and of Canada +brought with it later a similar decision on the part of +all the principal States of Europe; and Greenwich is<span class="pagenum"><a name="Page_155" id="Page_155">[155]</a></span> +not only 'Longitude Nought' for the bulk of the +civilized world, but Greenwich mean time, increased +or decreased by an exact number of hours or half-hours, +is the standard time all over the planet.</p> + +<p>No; the statement requires correction. Two +countries hold out, both close to our own doors. +France, instead of adopting Greenwich time as such, +adopts <em>Paris time less</em> 9 m. 21 s. (that being the precise +difference in longitude between the two national +observatories). Ireland disdains even such a veiled +surrender, and Dublin time is the only one recognized +from the Hill of Howth to far Valentia. So the +distressful country preserves her old grievance, that +she does not even get her time until after England +has been served.</p> + +<p>The alteration in national habits following on the +adoption of this European system has had a very +perceptible effect in some cases. Thus, Switzerland +has adopted Mid-European time, one hour fast of +Greenwich; the true local time for Berne being just +half an hour later. The result of putting the working +hours this thirty minutes earlier in the day has had +such a noticeable effect on the consumption of gas, as +to lead the gas company to contemplate agitating for +a return to the old system.</p> + +<p>Thus, Greenwich time, as well as the Greenwich +meridian, has practically been adopted the world over.</p> + +<p>It follows, then, that the determination of time is +the most important duty of the Royal Observatory; +and the Time Department, the one to which is +entrusted the duty of determining, keeping, and +distributing the time, calls for the first attention.</p> + +<p><span class="pagenum"><a name="Page_156" id="Page_156">[156]</a></span></p> + +<p>Entering the transit room, the first thing that +strikes the visitor is the extreme solidity with which +the great telescope is mounted. It turns but in one +plane, that of 'longitude nought,' and its pivots are +supported by the pair of great stone pillars which we +have already spoken of as occupying the principal +part of the transit-room area, and the foundations +of which go deep down under the surface of the hill. +On the west side of the telescope, and rigidly +connected with it, is a large wheel some six feet in +diameter, and with a number of wooden handles +attached to it, resembling the steering-wheel of a large +steamer. This wheel carries the setting circle, which +is engraved upon a band of silver let into its face +near its circumference, a similar circle being at the +back of the wheel nearer the pillar. Eleven microscopes, +of which only seven are ordinarily used, +penetrate through the pier, and are directed on to +this second circle.</p> + +<p>The present transit is the fourth which the +Observatory has possessed, and its three predecessors, +known as Halley's, Bradley's, and Troughton's, +respectively, are still preserved and hang on the walls +of the transit room, affording by their comparison +an interesting object-lesson in the evolution of a +modern astronomical instrument.</p> + +<p>The watcher who wishes to observe the passing of +a star must note two things: he must know in what +direction to point his telescope, and at what time to +look for the star. Then, about two minutes before +the appointed time, he takes his place at the eyepiece. +As he looks in he sees a number of vertical<span class="pagenum"><a name="Page_157" id="Page_157">[157]</a></span> +lines across his field of view. These are spider-threads +placed in the focus of the eye-piece. Presently, +as he looks, a bright point of silver light, often +surrounded by little flashing, vibrating rays of colour, +comes moving quickly, steadily onward—'swims +into his ken,' as the poet has it. The watcher's hand +seeks the side of the telescope till his finger finds a +little button, over which it poises itself to strike. On +comes the star, 'without haste, without rest,' till it +reaches one of the gleaming threads. Tap! The +watcher's finger falls sharply on the button. Some +three or four seconds later and the star has reached +another 'wire,' as the spider-threads are commonly +called. Tap! Again the button is struck. Another +brief interval and the third wire is reached, and so on, +until ten wires have been passed, and the transit is +over. The intervals are not, however, all the same, +the ten wires being grouped into three sets, two of +three apiece, and the third of four.</p> + +<div class="figcenter bord" style="width: 428px;"><a name="graph" id="graph"></a> +<img src="images/i_158.jpg" width="428" height="600" alt="graph" /> +<div class="caption"><p class="center">THE CHRONOGRAPH.</p></div> +</div> + +<p>Each tap of the observer's finger completed for an +instant an electric circuit, and recorded a mark on the +'chronograph.' This is a large metal cylinder covered +with paper, and turned by a carefully-regulated clock +once in every two minutes. Once in every two +seconds a similar mark was made by a current sent +by means of the standard sidereal clock of the +Observatory. The paper cover of the chronograph +after an hour's work shows a spiral trace of little dots +encircling it some thirty times. These dots are at +regular intervals, about an inch apart, and are the +marks made by the clock. Interspersed between +them are certain other dots, in sets of ten; and these<span class="pagenum"><a name="Page_158" id="Page_158">[158]</a></span> +are the signals sent from the telescope by the transit +observer. If, then, one of the clock dots and one of +the observer's dots come exactly side by side, we<span class="pagenum"><a name="Page_159" id="Page_159">[159]</a></span> +know that the star was on one of the wires at a given +precise second. If the observer's dot comes between +two clock dots, it is easy, by measuring its distance +from them with a divided scale, to tell the instant the +star was on the wire to the tenth of a second, or even +to a smaller fraction. Whilst, since the transit was +taken over ten wires, and the distance of each wire +from the centre of the field of view is known, we have +practically ten separate observations, and the average +of these will give a much better determination of the +time of transit than a single one would.</p> + +<p>But let the watcher be ever so little too slow in +setting his telescope, or ever so little late in placing +himself at his eye-piece, and the star will have passed +the wire, and as it smoothly, resistlessly moves on its +inexorable way, will tell the tardy watcher in a +language there is no mistaking, 'Lost moments can +never be recalled.' The opportunity let slip, not +until twenty-four hours have gone by will another +chance come of observing that same star.</p> + +<p>It is the stars that are chiefly used in this determination, +partly because the stars are so many, whilst +there is but one sun. If, therefore, clouds cover the +sun at the important moment of transit, the astronomer +may well exclaim, so far as this observation is +concerned, 'I have lost a day!' The chance will not +be offered him again until the following noon. But +if one star is lost by cloud, there are many others, +and the chance is by no means utterly gone. Beside, +the sun enables us to tell the time only at noon; the +stars enable us to find it at various times throughout +the entire night; indeed, throughout both day and<span class="pagenum"><a name="Page_160" id="Page_160">[160]</a></span> +night, since the brighter stars can be observed in a +large telescope even during the day.</p> + +<p>There are two great standard clocks at the +Observatory: the mean solar clock and the sidereal +clock. The latter registers twenty-four hours in the +precise time that the earth rotates on its axis. A +'day' in our ordinary use of the term is somewhat +longer than this; it is the average time from one +noon to the next, and as the earth whilst turning +round on its axis is also travelling round the sun, it +has to rather more than complete a rotation in order +to bring the sun again on to the same meridian. A +solar day is therefore some four minutes longer than +an actual rotation of the earth, <em>i.e.</em> a sidereal day, as +it is called, since such rotation brings a star back +again to the same meridian.</p> + +<p>The sidereal clock can therefore be readily checked +by the observation of star transits, for the time when +the star ought to be on the meridian is known. If, +therefore, the comparison of the transit taps on the +chronograph with the taps of the sidereal clock show +that the clock was not indicating this time at the +instant of the transit, we know the clock must be so +much fast or slow. Similarly, the difference which +should be shown between the sidereal and solar +clocks at any moment is known; and hence when the +error of the sidereal clock is known, that of the solar +can be readily found.</p> + +<p>It is often quite sufficient to know how much a +clock is wrong without actually setting its hands +right; but it is not possible to treat the Greenwich +clock so, for it controls a number of other clocks<span class="pagenum"><a name="Page_161" id="Page_161">[161]</a></span> +continually, and sends hourly signals out over the +whole country, by which the clocks and watches all +over the kingdom are set right.</p> + +<p>In the lower computing room, below the south +window, we find the Time-Desk, the head-quarters of +the Time Department. This is a very convenient +place for the department, since one of the chronometer +rooms, formerly Bradley's transit room, opens +out of the lower computing room; the transit instrument +is just beyond; it is close to the main gate of +the Observatory, and so convenient for chronometer +makers or naval officers bringing chronometers or +coming for them, whilst just across the courtyard is +the chronograph room, with the Battery Basement, in +which the batteries for the electric currents are kept, +and the Mean Solar Clock lobby, with the winch for +the winding of the time-ball at the head of the stairs +above it. These rooms do not exhaust the territory +of the department, since it owns two other chronometer +rooms on the ground floor and first floor +respectively of the S.-E. tower.</p> + +<p>At the time-desk means are provided for setting +the clock right very easily and exactly. Just above +the desk are a range of little dials and bright brass +knobs, that almost suggest the stops of a great +organ.</p> + +<p>Two of these little dials are clock faces, electrically +connected with the solar and sidereal standard +clocks, so that, though these clocks are themselves a +good way off, in entirely different parts of the Observatory, +the time superintendent, seated here at the +time-desk, can see at once what they are indicating.<span class="pagenum"><a name="Page_162" id="Page_162">[162]</a></span> +Between the two is a dial labelled 'Commutator.' +From this dial a little handle usually hangs vertically +downwards, but it can be turned either to the right +or to the left, and when thus switched hard over, an +electric current is sent through to the mean solar +clock. If now we leave the computing room and +cross the courtyard to the extreme north-west corner, +we find the Mean Solar Clock in a little lobby, carefully +guarded by double doors and double windows +against rapid changes of temperature. Opening the +door of the clock case, we see that the pendulum +carries on its side a long steel bar, and that this bar +as the pendulum swings passes just over the upper +end of an electro-magnet. When the current is +switched on at the commutator, this electro-magnet +attracts or repels the steel bar according to the +direction of the current, and the action of the clock +is accordingly quickened or retarded. To put the +commutator in action for one minute will alter the +clock by the tenth of a second. As the error of the +clock is determined twice a day, shortly before ten +o'clock in the morning, and shortly before one o'clock +in the afternoon, its error is always small, usually +only one or two tenths. These two times are chosen +because, though time-signals are sent over the metropolitan +area every hour from the Greenwich clock +through the medium of the Post Office, at ten and at +one o'clock signals are also sent to all the great provincial +centres. Further, at one o'clock the time +balls at Greenwich and at Deal are dropped, so that +the captains of ships in the docks, on the river, or in +the Downs may check their chronometers.</p> + +<p><span class="pagenum"><a name="Page_163" id="Page_163">[163]</a></span></p> + +<p>The Time-Ball is dropped directly by the mean +solar clock itself. It is raised by means of a windlass +turned by hand-power to the top of its mast just +before one o'clock. Connected with it is a piston +working in a stout cylinder. When the ball has +reached the top of the mast, the piston is lightly +supported by a pair of catches. These catches are +pulled back by the hourly signal current, and the +piston at once falls sharply, bringing the ball with it. +But after a fall of a few feet, the air compressed by +the piston acts as a cushion and checks the fall, the +ball then gently and slowly finishing its descent. +The instant of the beginning of the fall is, of course, +the true moment to be noted.</p> + +<p>The other dials on the time-desk are for various +purposes connected with the signals. One little +needle in a continual state of agitation shows that +the electric current connecting the various sympathetic +clocks of the Observatory is in full action. +Another receives a return signal from various places +after the despatch of the time-signal from Greenwich, +and shows that the signal has been properly received +at the distant station, whilst all the many electric +wires within the Observatory or radiating from it are +made to pass through the great key-board, where +they can be at once tested, disconnected, or joined +up, as may be required.</p> + +<div class="figcenter bord" style="width: 450px;"><a name="desk" id="desk"></a> +<img src="images/i_164.jpg" width="450" height="403" alt="desk" /> +<div class="caption"><p class="center">THE TIME-DESK.</p></div> +</div> + +<p>The distribution of Greenwich time over the +island in this way is thus a simple matter. The far +more important one of the distribution of Greenwich +time to ships at sea is more difficult. The difficulty +lay in the construction of a clock or watch, the rate<span class="pagenum"><a name="Page_164" id="Page_164">[164]</a></span> +of which would not be altered by the uneasy motion +of a ship, or by the changes of temperature which are +inevitable on a voyage. Two hundred years ago it +was not deemed possible to construct a watch of +anything like sufficient accuracy. They would not +even keep going whilst they were being wound, and +would lose or gain as much as a minute in the day +for a fall or rise of 10° in temperature. 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 temperature. +The British Government, therefore, in 1714 offered a<span class="pagenum"><a name="Page_165" id="Page_165">[165]</a></span> +prize of the amount of £20,000 for a means of finding +the longitude at sea within half a degree, or, in other +words, for a watch that would keep Greenwich time +correct to two minutes in a voyage across the +Atlantic. In 1735, James Harrison, the son of a +Yorkshire carpenter, succeeded in solving the problem. +His method was to attach a sort of automatic +regulator to the spring which should push the +regulator over in one direction as the temperature +rose, and bring it back as it fell. This he effected by +fastening together two strips of brass and steel. The +brass expanded with heat more rapidly than the +steel, and hence with a rise of temperature the strip<span class="pagenum"><a name="Page_166" id="Page_166">[166]</a></span> +bent over on the steel side. This was the first germ +of the idea of making watches 'compensated for +temperature;' watches, that is, which maintain practically +the same rate whether they are in heat or +cold, an idea now brought to great perfection in the +modern chronometer.</p> + +<div class="figcenter bord" style="width: 400px;"><a name="harrison" id="harrison"></a> +<img src="images/i_165.jpg" width="400" height="438" alt="harrison" /> +<div class="caption"><p class="center">HARRISON'S CHRONOMETER.</p></div> +</div> + +<p>The great reward the Government had offered +stimulated many men to endeavour to solve the +problem. Of these, Dr. Halley, the second Astronomer +Royal, and Graham, the inventor of the +astronomical clock, were the most celebrated. But +when Harrison, then poor and unknown, came to +London in 1735, and laid his invention before them, +with an utter absence of self-seeking, and in the true +scientific spirit, they gave him every assistance.</p> + +<p>Harrison's first four time-keepers are still preserved +at the Royal Observatory. He did not, +however, receive his reward until a facsimile of the +fourth had been made by his apprentice, Larcum +Kendall. The latter is preserved at the Royal +Observatory. There is a Larcum Kendall at the +Royal Institution which is said to have been used by +Captain Cook. Harrison's chronometer was sent on +a trial voyage to Jamaica in 1761, and on its return +to Portsmouth in the following year it was found that +its complete variation was under the two minutes for +which the Government had stipulated.</p> + +<p>Since Harrison's day the improvement of the +chronometer has been carried on almost to perfection, +and now the care and rating of chronometers for the +Royal Navy is one of the most important duties of +the Observatory.</p> + +<p><span class="pagenum"><a name="Page_167" id="Page_167"> </a></span></p> + +<div class="figcenter bord" style="width: 600px;"><a name="room" id="room"></a> +<img src="images/i_167.jpg" width="600" height="397" alt="room" /> +<div class="caption"><p class="center">THE CHRONOMETER ROOM.</p></div> +</div> + +<p><span class="pagenum"><a name="Page_168" id="Page_168"> </a><br /><a name="Page_169" id="Page_169">[169]</a></span></p> + +<p>A visitor who should make the attempt to compare +a single chronometer with a standard clock +would probably feel very disheartened when, after +many minutes of comparison, he had got out its +error to the nearest second, were he told that it was +his duty to compare the entire army here collected, +some five hundred or more, and to do it not to +the second, but to the nearest tenth of a second. +Practice and system make, however, the impossible +easy, and one assistant will quietly walk round the +room calling out the error of each chronometer as he +passes it, as fast as a second assistant seated at the +table can enter it at his dictation in the chronometer +ledgers. The seconds beat of a clock sympathetic +with the solar standard, rings out loud and clear +above the insect-like chatter of the ticking of the +hundreds of chronometers, and wherever the assistant +stands, he has but to lift his eyes to see straight +before him, if not a complete clock-face, at least a +seconds dial moving in exact accordance with the +solar standard.</p> + +<p>The test to which chronometers are subjected is +not merely one of rate, but one of rate under carefully +altered conditions. Thus they may be tried +with the XII pointing in succession to the four +points of the compass, or, in the case of chronometer +watches, they may be laid flat down on the table or +hung from the ring or pendant, or with the ring right +or left, as it would be likely to be when carried in +the waistcoat pocket. But the chief test is the performance +of a chronometer when subjected to considerable +heat for a long period. This is a matter of<span class="pagenum"><a name="Page_170" id="Page_170">[170]</a></span> +great consequence, since a chronometer travelling +from England to India, Australia, or the Cape, would +necessarily be subjected to very different conditions +of temperature from those to which it would be exposed +in England. They are therefore kept for eight +weeks in a closed stove at a temperature of about +85° or 90°. At one time a cold test was also applied, +and Sir George Airy, the late Astronomer Royal, in +one of his popular lectures, drew a humorous comparison +between the unhappy chronometers thus +doomed to trial, now in heat and now in frost, and +the lost spirits whom Dante describes as alternately +plunged in flame and ice. The cold test has, however, +been done away with. It is perfectly easy +on the modern ship to keep the chronometer comfortably +warm even on an Arctic expedition. The +elaborate cold testing applied to Sir George Nares' +chronometers before he started on his polar journey +was found to have been practically quite superfluous; +the chronometers were, if anything, kept rather too +warm. The exposure of the chronometer in the +cooling box, moreover, was found to be attended +with a risk of rusting its springs.</p> + +<div class="figcenter bord" style="width: 600px;"><a name="oven" id="oven"></a> +<img src="images/i_171.jpg" width="600" height="429" alt="oven" /> +<div class="caption"><p class="center">THE CHRONOMETER OVEN.</p></div> +</div> + +<p>Once the determination of the longitude at sea +became possible, it was clearly the next duty to fix +with precision the position of the principal places, +cities, ports, capes, islands, the world over. Of all the +work done in this department none has ever been done +better, in proportion to the means at command, than +that accomplished by Captain Cook in his celebrated +three voyages. As has already been pointed out, it +is the extent and thoroughness of the hydrographic<span class="pagenum"><a name="Page_171" id="Page_171"> </a><br /><a name="Page_172" id="Page_172"> </a><br /><a name="Page_173" id="Page_173">[173]</a></span> +surveys of the British Admiralty which have largely +contributed to the honour done to England by the +international selection of the English meridian, and +of English standard time, as in principle those for the +whole civilized world. The generosity and public +spirit therefore which led the second Astronomer +Royal to help forward and support his rival, has +almost directly led to this great distinction accruing +to the Observatory of which he was the head.</p> + +<p>Three different methods have successively been +used in the determination of longitudes of distant +places. In each case the problem required was to +ascertain the time at the standard place, say Greenwich, +at the same time that it was being determined in the +ordinary way at the given station. One method of +ascertaining Greenwich time when at a distance from +it was, as stated in Chapter I., to use the moon, as it +were, as the hand of a vast clock, of which the sky +was the face and the stars the dial figures. This is +the method of 'lunar distances,' the distances of the +moon from a certain number of bright stars being +given in the <cite>Nautical Almanac</cite> for every three hours +of Greenwich time.</p> + +<p>As chronometers were brought to a greater point +of perfection, it was found easier and better in many +cases to use 'chronometer runs,' that is, to carry backwards +and forwards between the two stations a +number of good chronometers, and by constant comparison +and re-comparison to get over the errors +which might attach to any one of them.</p> + +<div class="figcenter bord" style="width: 450px;"><a name="transit" id="transit"></a> +<img src="images/i_174.jpg" width="450" height="359" alt="transit" /> +<div class="caption"><p class="center">THE TRANSIT PAVILION.<br /> +(<em>From a photograph by Mr. Lacey.</em>)</p></div> +</div> + +<p>But of late years another method has proved +available. Distant nations are now woven together<span class="pagenum"><a name="Page_174" id="Page_174">[174]</a></span> +across thousands of miles of ocean by the submarine +telegraph. The American reads in his morning paper +a summary of the debates of the previous night in +the House of Commons at Westminster. The +Londoner watches with interest the scores of the +English cricket team in Australia. It is now therefore +possible for an astronomer in England to record, +should he so desire, the time of the transit of a star +across the wires of his instrument, not only on his +own chronograph, but upon that of another observatory, +it may be 2000 miles away. Or, much more +conveniently, each observer may independently determine +the error of his own clock, and then bring his<span class="pagenum"><a name="Page_175" id="Page_175">[175]</a></span> +clock into the current, so that it may send a signal +to the chronograph of the other station.</p> + +<p>In one way or another this work of the determination +of geographical longitudes has been an +important part of the extra-routine work at Greenwich, +part of the work which has built up and sustained its +claim to define 'longitude nought'; and many +distinguished astronomers, especially from the leading +observatories of the Continent, have come here from +time to time to obtain more accurately the longitude +of their own cities. The traces of their visits may be +seen here and there about the Observatory grounds +in flat stones which lie level with the surface, and +bear a name and date like the gravestones in some +old country churchyard. These are not, as one might +suppose, to mark the burial-places of deceased astronomers, +but record the sites where, on their visits +for longitude purposes, different foreign astronomers +have set up their transit instruments. Now, however, +a permanent pier has been erected in the courtyard, +and a neat house—the Transit Pavilion—built +over it, so that in all probability no fresh additions +will be made to these sepulchral-looking little monuments.</p> + +<p>It might be asked, What reason is there for a +foreign observer to come over to England for such +a purpose? Would it not be sufficient for the clock +signals to be exchanged? But a curious little fact +has come out with the increase of accuracy of transit +observation, and that is, that each observer has his +own particular habit or method of observation. A +hundred years ago, Maskelyne, the fifth Astronomer<span class="pagenum"><a name="Page_176" id="Page_176">[176]</a></span> +Royal, was greatly disturbed to find that his assistant, +David Kinnebrook, constantly and regularly observed +a star-transit a little later than he did himself. The +offender was scolded, warned, exhorted, and finally, +when all proved useless to bring his observations into +exact agreement with the Astronomer Royal's, dismissed +as an incompetent observer. As a matter of +fact, poor Kinnebrook has a right to be regarded as +one of the martyrs of science, and Maskelyne, by this +most natural but mistaken judgment, missed the +chance of making an important discovery, which was +not made until some thirty years later. Astronomers +now would be more cautious of concluding that +observations were bad simply because they differed +from what had been expected. They have learnt +by experience that these unexpected differences are +the most likely hunting-ground in which to look for +new discoveries.</p> + +<p>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 chronograph, +he has to perceive with his eye that the star +has reached the wire, he has to mentally recognize +the fact, and consciously or unconsciously to exert +the effort of will necessary to bring his finger down +on the button. A very slight knowledge of character +will show that this will require different periods of +time for different people. It will be but a fraction +of a second in any case, but there will be a distinct +difference, a constant difference, between the eager, +quick, impulsive man who habitually anticipates, +as it were, the instant when he sees star and wire<span class="pagenum"><a name="Page_177" id="Page_177">[177]</a></span> +together, and the phlegmatic, slow-and-sure man who +carefully waits till he is quite sure that the contact +has taken place, and then deliberately and firmly +records it. These differences are so truly personal +to the observer that it is quite possible to correct +for them, and after a given observer's habit has +become known, to reduce his transit times to those +of some standard observer. It must, of course, be +remembered that this 'personal equation' is an +exceedingly minute quantity, and in most cases is +rather a question of hundredths of seconds than of +tenths.</p> + +<p>It will be seen from the foregoing description how +little of what may be termed the picturesque or +sensational side of astronomy enters into the routine +of the Time Department, the most important of all +the departments of the Observatory. The daily +observation of sun and of many stars—selected from +a carefully chosen list of some hundreds, and known +as 'clock stars'—the determination of the error of +the standard clock to the hundredth of a second if +possible, and its correction twice a day, the sending +out of time signals to the General Post Office and +other places, whence they are distributed all over the +country; the care, winding, and rating of hundreds +of chronometers and chronometer watches, and from +time to time the determination of the longitude of +foreign or colonial cities, make up a heavy, ceaseless +routine in which there is little opportunity for the +realization of an astronomer's life as it is apt to be +popularly conceived.</p> + +<p>Yet there is interest enough in the work. There<span class="pagenum"><a name="Page_178" id="Page_178">[178]</a></span> +is the charm which always attaches to work of +precision, the delight of using delicate and exact +instruments, and of obtaining results of steadily +increasing perfection. It may be akin to the sporting +passion for record-breaking, but surely it is a +noble form of it which has led the assistants, in +recent years, to steadily increase the number of +observations in a normal night's work up to the +very limit, taking care the while that their accuracy +has in no degree suffered. In longitude work also +'the better is the enemy of the good,' and there is +the ambition that each fresh determination shall be +markedly more precise than all that have preceded it. +The constant care of chronometers soon reveals a +kind of individuality in them which forms a fresh +source of interest, whilst if a man has but a spark +of imagination, how easily he will wrap them round +with a halo of romance!</p> + +<p>Glance through the ledgers, and you will see how +some of them have heard the guns at the siege of +Alexandria, others have been carried far into the +frozen north, others have wandered with Livingstone +or Cameron in the trackless forests of equatorial +Africa.</p> + +<p>More striking still are those pages across which +the closing line has been drawn; never again will the +time-keeper there scheduled return to the kindly +inquisition of Flamsteed Hill. This sailed away in +the Wasp, and was swallowed up in the eastern +typhoon; that went down in the sudden squall that +smote the Eurydice off the Isle of Wight; these +foundered with the Captain. The last fatal journey<span class="pagenum"><a name="Page_179" id="Page_179">[179]</a></span> +of Sir John Franklin to find the North-West Passage +leaves its record here; the chronometers of the +Erebus and Terror will never again appear on the +Greenwich muster roll. Land exploration claims +its victims too. Sturt's ill-fated expedition across +Australia, and Livingstone's last wandering, are +represented.</p> + +<div class="figcenter bord" style="width: 450px;"><a name="lost" id="lost"></a> +<img src="images/i_179.jpg" width="450" height="321" alt="lost" /> +<div class="caption"><p class="center">'LOST IN THE BIRKENHEAD.'</p></div> +</div> + +<p>Sometimes an amusing entry interrupts the silent +pathos of these closed pages. 'Lost by Mr. Smith +on the coast of Africa,' reads at first sight like a +rather thin attempt of some one to shift the responsibility +of his own carelessness on to the broad +shoulders of Mr. Nobody. In reality it probably +gives a hint of the necessary, dangerous, and exciting +work of slave-dhow chasing which gives employment<span class="pagenum"><a name="Page_180" id="Page_180">[180]</a></span> +to our ships on the African coast. 'Mr. Smith' was +no doubt a petty officer who was told off to carry +the chronometer for a boat's crew sent to search for +a slave-dhow up some equatorial estuary. Probably +the dhow was found, and the Arabs who manned it +gave so stout a resistance that 'Mr. Smith' and his +men had other things to do than take care of +chronometers before they could overcome them. +We may take it that the real story outlined here was +one of courage and hard fighting, not of carelessness +and shirking.</p> + +<p>Stories of higher valour and nobler courage yet +are also hinted: the calm discipline of the crew of +the Victoria as she sank from the ram of the Camperdown, +the yet nobler devotion of the men of the +Birkenhead, as they formed up in line on deck and +cheered the boats that bore away the women and +children to safety, whilst they themselves went down +with the ship into the shark-crowded sea.</p> + +<div class="poem"><div class="stanza"> +<span class="i0">'There rose no murmur from the ranks, no thought<br /></span> +<span class="i2">By shameful strength, unhonoured life to seek;<br /></span> +<span class="i0">Our post to quit we were not trained, nor taught<br /></span> +<span class="i2">To trample down the weak.<br /></span> +</div><div class="stanza"> +<span class="i0">'What followed, why recall? The brave who died<br /></span> +<span class="i2">Died without flinching in that bloody surf.<br /></span> +<span class="i0">They sleep as well beneath that purple tide<br /></span> +<span class="i2">As others under turf.'<br /></span> +</div></div> +<hr class="chap" /> + +<p><span class="pagenum"><a name="Page_181" id="Page_181">[181]</a></span></p> + + + +<h2>CHAPTER VII</h2> + +<h3>THE TRANSIT AND CIRCLE DEPARTMENTS</h3> + + +<p>The determination of time is a duty the importance +of which readily commends itself to the general +public. It is easy to see that in any civilized country +it is very necessary to have an accurate standard of +time. Our railways and telegraphs make it quite +impossible for us to be content with the rough-and-ready +sun-dial which satisfied our forefathers. But +it should be remembered that it was neither to +establish a 'longitude nought,' nor to create a system +of standard time, that Greenwich Observatory was +founded in 1675. It was for 'The Rectifying the +Tables of the Motions of the Heavens and the Places +of the Fixed Stars, in order to find out the so-much-desired +Longitude at Sea for the perfecting the Art +of Navigation.'</p> + +<p>The two related departments, therefore, those of +the Transit and the Circle, which are concerned in +the work of making star-catalogues, come next in +order to the Time Department. Though both +departments deal with the same instrument, the +transit circle, they are at present placed at opposite +ends of the Observatory domain; the Circle Department +being lodged in the upper computing room<span class="pagenum"><a name="Page_182" id="Page_182">[182]</a></span> +of the old building; the Transit Department in the +south wing of the New Observatory in the south +ground.</p> + +<p>It may be asked why, if this were the purpose of +the Observatory at its foundation, two and a quarter +centuries ago; if, as was the case, the work was set +on foot from the beginning and was carried out with +every possible care, how comes it that it is still the +fundamental work of the Observatory, and, instead of +being completed, has assumed greater proportions at +the present day than ever before?</p> + +<p>The answer to this inquiry may be found in a +special application of the old proverb, originally +directed against the discontent of man: 'The more +he has, the more he wants.' For, however paradoxical +it may seem, it is true that the fuller a star-catalogue +is, and the more accurate the places of the stars that +it contains, the greater is the need for a yet fuller +catalogue, with places more accurate still.</p> + +<p>It is worth while following up this paradox in +some detail, as it affords a very instructive example +of the way in which a work started on purely utilitarian +grounds extends itself till it crosses the undefined +boundary and enters the region of pure science.</p> + +<p>We have no idea who made the earliest census of +the sky. It is written for us in no book; it is not +even engraved on any monument. And yet no small +portion of it is in our hands to-day, and, strangest of +all, we are able to fix fairly closely the time at which +it was made, and the latitude in which its compiler +lived. The catalogue is very unlike our star-catalogues +of to-day. The places of the stars are very<span class="pagenum"><a name="Page_183" id="Page_183">[183]</a></span> +roughly indicated; and yet this catalogue has left a +more enduring mark than all those that have succeeded +it. The catalogue simply consists of the star +names.</p> + +<p>An old lady who had attended a University +Extension lecture on astronomy was heard to exclaim: +'What wonderful men these astronomers are! +I can understand how they can find out how far off +the stars are, how big they are, and what they weigh—that +is all easy enough; and I think I can see how +they find out what they are made of. But there is +one thing that I can't understand—I don't know how +they can find out what are their names!' This same +difficulty, though with a much deeper meaning than +the old lady in her simplicity was able to grasp, has +occurred to many students of astronomy. Many +have wished to know what was the meaning of, and +whence were derived, the sonorous names which are +found attached to all the brighter stars on our celestial +globes: Adhara, Alderamin, Betelgeuse, Denebola, +Schedar, Zubeneschamal, and many more. The +explanation lies here. Some 5000 years ago, a man, +or college of men, living in latitude 40° north, in +order that they might better remember the stars, +associated certain groups of them with certain fancied +figures, and the individual star names are simply +Arabic words designed to indicate whereabouts in +its peculiar figure or constellation that special star +was situated. Thus Adhara means 'back,' and is +the name of the bright star in the back of the great +Dog. Alderamin means 'right arm,' and is the +brightest star in the right arm of Cepheus, the king.<span class="pagenum"><a name="Page_184" id="Page_184">[184]</a></span> +Betelgeuse is 'giant's shoulder,' the giant being +Orion; Denebola is 'lion's tail.' Schedar is the +star on the 'breast' of Cassiopeia, and Zubeneschamal +is 'northern claw,' that is, of the Scorpion. So far is +clear enough. The names of the stars for the most +part explain themselves; but whence the constellations +derived their names, how it was that so many snakes +and fishes and centaurs were pictured out in +the sky, is a much more difficult problem, and one +which does not concern us here.</p> + +<p>One point, however, these old constellations do +tell us, and tell us plainly. They show that the axis +of the earth, which, as the earth travels round the sun, +moves parallel with itself, yet, in the course of ages, +itself rotates so as in a period of some 26,000 years +to trace out a circle amongst the stars. This is the +cause of what is called 'precession,' and explains how +it is that the star we call the pole-star to-day was +not always the pole-star, nor will always remain so. +We learn this fact from the circumstance that the +old constellations do not cover the entire celestial +sphere. They leave a great circular space of 40° +radius unmapped in the southern heavens. This +simply means that the originators of the constellations +lived in 40° north latitude, and stars within 40° +of their south pole never rose above their horizon, +and consequently were never seen, and could not be +mapped, by them. In like manner, the star census +taken at Greenwich Observatory does not include +the whole sky, but leaves a space some 52° in radius +round our south pole. Since the latitude of Greenwich +is nearly 52° north, stars within that distance of<span class="pagenum"><a name="Page_185" id="Page_185">[185]</a></span> +the south pole do not rise above our horizon, and are +never seen here. But if we compare the vacant space +left by the old original constellations with the vacant +space left by a Greenwich catalogue of to-day, we +see that the centre of the first space, which must +have been the south pole of that time, is a long way +from the centre of the second space—our south pole +of to-day. The difference tells us how far the pole +has moved since those old forgotten astronomers did +their work. We know the rate at which the pole +appears to move, by comparing our more modern +catalogues one with another; and so we are able +to fix pretty nearly the time when lived those old +first census-takers of the stars, whose names have +perished so completely, but whose work has proved +so immortal.</p> + +<p>These old workers gave us the constellation +groupings and names which still remain to us, and +are still in common, every-day use. Their work +affords us the most striking illustration of the result +of precession, but precession itself was not recognized +till nearly 3000 years after their day, when a marvellous +genius, Hipparchus, established the fact, and +'built himself an everlasting name' by the creation +of a catalogue of over 1000 stars prepared on modern +principles. That catalogue formed the basis of one +which survives to us at the present time, and was +made some 1750 years ago by Claudius Ptolemy, +the great astronomer of Alexandria, whose work, +which still bears the proud name of <cite>Almagest</cite>, 'The +Greatest,' remained for fourteen centuries the one +universal astronomical text-book.</p> + +<p><span class="pagenum"><a name="Page_186" id="Page_186">[186]</a></span></p> + +<p>A modern catalogue contains, like that of Ptolemy, +four columns of entry. The first gives the star's +designation; the second an indication of its brightness; +the third and fourth the determinations of its +place. These are expressed in two directions, which, +in modern catalogues, not in Ptolemy's, correspond +on the celestial sphere to longitude and latitude on +the terrestrial. Distance north or south of the +celestial equator is termed 'declination,' corresponding +to terrestrial latitude. Distance in a direction +parallel to the equator is termed 'right ascension,' +corresponding to terrestrial longitude. For geographical +purposes we conceive the earth to be +encircled by two imaginary lines at right angles to +each other—the one, the equator, marked out for us +by the earth itself; the other, 'longitude nought,' the +meridian of Greenwich, fixed for us by general consent, +after the lapse of centuries, by a kind of historical +evolution. On the celestial globe in like manner +we have two fundamental lines—one, the celestial +equator, marked out for us by nature; the other at +right angles to it, and passing through the poles of +the sky, adopted as a matter of convenience. But a +difficulty at once confronts us—Where can we fix +our 'right ascension nought'? What star has the +right to be considered the Greenwich of the sky?</p> + +<p>The difficulty is met in the following manner: +For six months of the year, the summer months, the +sun is north of the celestial equator; for the other +six months of the year, the months of winter, it is +south of it. It crosses the equator, therefore, twice +in the year—once when moving northward at the<span class="pagenum"><a name="Page_187" id="Page_187">[187]</a></span> +spring equinox; once when moving southward at +the equinox of autumn. The point where it crosses +the equator at the first of these times is taken as the +fundamental point of the heavens, and the first sign +of the zodiac, Aries the Ram, is said to begin here, +and it is called, therefore, 'the first point of Aries.'</p> + +<p>One of the very first facts noticed in the very +early days of astronomy was that, as the stars seemed +to move across the sky night by night, they seemed +to move in one solid piece, as if they were lamps +rigidly fixed in one and the same solid vault. Of +course it has long been perfectly understood that this +apparent movement was not in the least due to any +motion of the stars, but simply to the rotation of the +earth on its axis. This rotation is the smoothest, +most constant, and regular movement of which we +know. It follows, therefore, that the interval of time +between the passage of one star across the meridian +of Greenwich and that of any other given star is +always the same. This interval of time is simply the +difference of their right ascension. If we are able, +then, to turn our transit instrument to the sun, and +to a number of stars, each in its proper turn, and by +pressing the tapping-piece on the instrument as the +sun or star comes up to each of the ten wires in +succession, to record the times of its transit on the +chronograph, we shall have practically determined +their right ascensions—one of the two elements of +their places.</p> + +<p>The other element, that of declination, is found in +a different manner. The celestial equator, like the +terrestrial, is 90° from the pole. The bright star<span class="pagenum"><a name="Page_188" id="Page_188">[188]</a></span> +Polaris is not exactly at the north pole, but describes +a small circle round it. Twice in the twenty-four +hours it transits across the meridian—once when +going from east to west it passes above the pole, +once when going from west to east below the pole. +The mean between these two altitudes of Polaris +above the horizon gives the position of the true +pole.</p> + +<div class="figcenter bord" style="width: 357px;"><a name="circle" id="circle"></a> +<img src="images/i_189.jpg" width="357" height="600" alt="circle" /> +<div class="caption"><p class="center">THE TRANSIT CIRCLE.</p></div> +</div> + +<p>A complete transit observation of a star consists +therefore of two operations. The observer, as we +have already described, sees a star entering the field +of the telescope, and as it swims forward, he presses +the galvanic button, which sends a signal to the +chronograph as the star comes up to each of the ten +vertical wires in succession. But, beside the ten wires, +there are others. Two vertical wires lie outside the +ten of which we have already spoken, and there is +also a horizontal wire. The latter can be moved by +a graduated screw-head just above the eye-piece, and +as the star comes in succession to these two vertical +wires, this horizontal wire is moved by the screw-head, +so as to meet the star at the moment it is +crossing the vertical wire, and the observer presses +a second little button, which records the position of +the horizontal wire on a small paper-covered drum. +Then, the transit over, the observer leaves the telescope +and comes round to the outside of the west +pier. Here he finds seven large microscopes, which +pierce the whole thickness of the pier, and are directed +towards the circumference of a large wheel which is +rigidly attached to the telescope and revolves with it. +This wheel is six feet in diameter, and has a silver<span class="pagenum"><a name="Page_189" id="Page_189"> </a><br /><a name="Page_190" id="Page_190"> </a><br /><a name="Page_191" id="Page_191">[191]</a></span> +circle upon both faces. Each circle is divided +extremely carefully into 4320 divisions—these +divisions, therefore, being about the one-twentieth of +an inch apart. There are, therefore, twelve divisions +to every degree (12 × 360 = 4320), and each division +equals five minutes of arc. The lowest microscope is +the least powerful, and shows a large part of the +circle, enabling the observer to see at once to what +degree and division of a degree the microscope is +pointing. The other six microscopes are very carefully +placed 60° apart—as equally placed as they +possibly can be. These microscopes are all fitted +with movable wires—wires moved by a very fine and +delicate screw; the screw-head having divisions upon +it so that the exact amount of its movement can be +told. Each of the six screw-heads will read to the +one five-thousandth part of a division of the circle; +in other words, to the one hundred thousandth part +of an inch. Using all six microscopes, and taking +their mean, we are able to <em>read</em> to the one-hundredth +of a second of arc. If, therefore, the observations +could be made with perfect certainty down to the +extremest nicety of reading which the instrument +supplies, we should be able to read the declination of +a star to this degree of refinement. It may be added +that a halfpenny, at a distance of three miles, appears +to be one second of arc in diameter; at three hundred +miles it would be one-hundredth of a second. It +need scarcely be said that we cannot observe with +quite such refinement of exactness as this would +indicate. Nevertheless, this exactness is one after +which the observer is constantly striving, and tenths,<span class="pagenum"><a name="Page_192" id="Page_192">[192]</a></span> +even hundredths, of seconds of arc are quantities +which the astronomer cannot now neglect.</p> + +<p>The observer has then to read the heads of all +these seven microscopes on the pier side, and also +two positions of the horizontal wire on the screw-head +at the eye-piece. The following morning he will also +read off from the chronograph-sheet the times when +he made the ten taps as the star passed each of the +ten vertical wires. There are, therefore, nine entries +to make for one position of a star in declination, and +ten for one position of a star in right ascension. The +observer will also have to read the barometer to get +the pressure of the air at the time of observation, and +one thermometer inside the transit room, and another +outside, to get the temperature of the air. In some +cases thermometers at different heights in the room +are also read. A complete observation of a single +star means, therefore, the entry of two-and-twenty +different numbers.</p> + +<p>It may be asked, What is the use of reading the +barometer and thermometer? The answer to the +question can only be given by contradicting a statement +made above, that the true pole lay midway +between the position of the telescope when pointing +to the pole-star at its upper transit, and its position +when pointing to it at its lower transit. The pole +being very high in the heavens in this country, there +are a great number of stars that, like the pole-star, +cross the meridian twice in the twenty-four hours—once +when they pass above the pole, moving from +east to west, once when they pass below it, moving +from west to east As the real distance of a star<span class="pagenum"><a name="Page_193" id="Page_193">[193]</a></span> +from the true pole does not alter, it follows that we +ought to get the position of the pole from the mean +of the two transits of any of these stars, and they +ought all to exactly agree with each other. But +they do not. So, too, I said that the stars all appeared +to move as in a single piece. If, then, we constructed +an instrument with its axis parallel to the axis of the +earth, and fixed a telescope to it, pointing to any +particular star, if we turn the telescope round as fast +from east to west as the earth itself is turning from +west to east—if we built an equatorial, that is to +say—we ought to find that the star once in the centre +of the field would remain there. As a matter of fact, +when the star got near the horizon it would soon be +a long way from the centre of the field.</p> + +<p>Sir George Airy, the seventh Astronomer Royal, +makes, with reference to this very point, the following +remarks:</p> + +<blockquote> + +<p>'Perhaps you may be surprised to hear me say the rule +is established as true, and yet there is a departure from it. +This is the way we go on in science, as in everything else; +we have to make out that something is true, then we find +out under certain circumstances that it is not quite true; +and then we have to consider and find out how the +departure can be explained.'</p></blockquote> + +<p>In this particular case, the disturbing cause is +found in the action of our own atmosphere. The +rays of light from the star are bent out of a perfectly +straight course as they pass through the various +layers of that atmosphere, layers which necessarily +become denser the closer we get to the actual surface +of the earth. Every celestial body therefore appears<span class="pagenum"><a name="Page_194" id="Page_194">[194]</a></span> +to be a little higher in the sky than it really is. This +action is most noticeable at the horizon, where it +amounts to about half a degree. As both sun and +moon are about half a degree in diameter, it follows +that when they have really just entirely sunk below +the horizon they appear to be just entirely above it. +It happens, in consequence, on rare occasions, that an +eclipse of the moon will take place when both sun +and moon are together seen above the horizon.</p> + +<p>It was a great matter to discover this effect of +refraction. It was soon seen that it was not constant, +that it varied with both temperature and pressure. +It is, indeed, the most troublesome of all the hindrances +to exact observation with which the astronomer has +to contend; partly because of its large amount—half +a degree, as has been already said, in the extreme +case—and partly because it is difficult in many cases +to determine its exact effect.</p> + +<p>The double observation with the transit circle +gives us, then, the place in the sky where the star +<em>appeared</em> to be at the moment of observation, not its +true place; to find that true place we have to calculate +how much refraction had displaced the star +at the particular height in the sky, and at the +particular temperature and atmospheric pressure at +which the observation was made.</p> + +<div class="figcenter bord" style="width: 436px;"><a name="mural" id="mural"></a> +<img src="images/i_195.jpg" width="436" height="600" alt="mural" /> +<div class="caption"><p class="center">THE MURAL CIRCLE.</p></div> +</div> + +<p>The transit circle is a comparatively recent instrument. +In earlier times the two observations of right +ascension and declination were entrusted to perfectly +separate instruments. The transit instrument was +mounted as the transit circle is, between two solid +stone piers, and moved in precisely the same way.<span class="pagenum"><a name="Page_195" id="Page_195">[195]</a></span> +But the great six-foot wheel, which was made as stiff +as it possibly could be, was mounted on the face of +a great stone pier or wall, from which circumstance +it was called the 'mural circle,' and a light telescope +was attached to it which turned about its centre. +This arrangement had a double disadvantage—that +the two observations had to be made separately, and<span class="pagenum"><a name="Page_196" id="Page_196">[196]</a></span> +the mural circle, not being a symmetrical instrument, +was liable to small errors which it was difficult to +detect. Thus, being supported on one side only, a +flexure or bending outwards of either telescope or +circle, or both, might be feared.</p> + +<p>It was for this reason that Pond set up a pair of +mural circles, one on the east side of its supporting +pier and the other on the west.<a name="FNanchor_3_3" id="FNanchor_3_3"></a><a href="#Footnote_3_3" class="fnanchor">[3]</a> His plan was not +only to have each star observed simultaneously in +the two instruments, a plan by which, at the cost of +some additional labour, he would have got rid, to a +large extent, of the individual errors of the two +separate instruments, inasmuch as, on the whole, it +might have been expected that the errors of the two +instruments would have been very nearly equal in +amount, but of opposite character. The differences, +too, between the two instruments would have afforded +the means for tracing these small errors to their +respective causes, and so ascertaining the laws to +which they were subject.</p> + +<p>Pond went further still. He added to the mural +circle a simple instrument, the extreme value of +which every astronomer recognizes to-day—the mercury +trough. Not only was the star to be observed +by both circles when the two telescopes were pointing +directly to it, it was also to be observed by reflection; +the telescopes were to be pointed down towards a +basin of mercury, in which the image of the star +would be seen reflected. The mercury being a<span class="pagenum"><a name="Page_197" id="Page_197">[197]</a></span> +liquid, its surface is perfectly horizontal; and, since +the law of reflection is that the angle of incidence is +equal to the angle of reflection, it follows that the +telescope, when pointed down toward the mercury +trough, points just at as great an angle below the +horizon as, when it is set directly on the star, it +points above it. If the circle, therefore, be carefully +read at both settings, half the difference between the +two readings will give the angular elevation of the +star above the horizon. A combination, therefore, of +all four observations, that is to say, one reflection and +one direct with each of the telescopes, would give +an exceedingly exact value for the star's altitude. +The conception of this method gives a striking idea +of Pond's thoroughness and skill as a practical +observer, and it is a distinct blot upon Airy's justly +high reputation in the same line that he discontinued +the system upon his accession to office.</p> + +<p>However, in 1851, as already mentioned, Airy +substituted for the two separate instruments—the +transit and mural circle—the transit circle, which, +unlike the mural circle, is equally supported on both +sides. This, however, does not free it from the +liability to some minute flexure in the direction of +its length, from the weight of its two ends, and the +mercury trough is used for the detection of such +bending, should it exist. The present practice is to +observe a star both by reflection and directly in the +course of the same transit. The observer sets the +telescope carefully before ever the star comes into the +field of view, and reads his seven microscopes. Then +he climbs up a narrow wooden staircase and watches<span class="pagenum"><a name="Page_198" id="Page_198">[198]</a></span> +the star transit nearly half across the field. Then +comes a rush, the observer swings himself down the +ladder, unclamps the telescope, turns it rapidly up to +the star itself, clamps it again, flings himself on his +back on a bench below the telescope, and does it so +quickly that he is able to observe the star across the +second half of the field. There is no time for +dawdling, no room for making any mistakes; the +stars never forgive; 'they haste not, they rest not;' +and if the unfortunate observer is too slow, or makes +some slip in his second setting, the star, cold and +inexorable, takes no pity, and moves regardless on.</p> + +<p>It will be seen that a considerable amount of work +is involved in taking a single observation of a star-place. +But in making a star-catalogue it is always +deemed necessary to obtain at least three observations +of each star; and many are observed much more +frequently.</p> + +<p>A modern star-catalogue contains, like Ptolemy's, +four columns. It contains also several more. Of +these the principal are devoted to the effect of precession. +As precession is caused by a movement of +the earth's axis making the pole of the sky seem to +describe a circle in the heavens, it follows that the +celestial poles, and the celestial equator with them +are slowly, but continually, changing their place with +respect to the stars, and therefore that the declinations +of the stars are always undergoing change, and as +the equator changes, the point where the sun crosses +it in spring—the first point of Aries—changes also, +and with it the stars' right ascensions.</p> + +<p>To make one determination of a star's place<span class="pagenum"><a name="Page_199" id="Page_199">[199]</a></span> +comparable with another made at another time, it is +clear that we must correct for the effects of precession +in the interval of time between the two observations, +and for the effects of refraction. But observations +made with the transit circle must also be corrected +for errors in the instrument itself. The astronomer +will see to it that his instrument is made and is set +up as perfectly as possible. The pivots on which it +turns must be exactly on the same level; they must +point exactly east and west, and the axis of the +telescope must be exactly at right angles to the line +joining the pivots in all positions of the instrument. +These conditions are very nearly fulfilled, but never +absolutely. Day by day, therefore, the astronomer +has to ascertain just how much his instrument is in +error in each of these three matters. Were his +instrument absolutely without error to-day, he could +not assume that it would remain so, nor, if he had +measured the amount of its errors yesterday, would +it be safe to assume that those errors would not +change to-day.</p> + +<p>In the examination of these sources of error the +mercury trough comes again into use. The transit +circle is turned directly downwards, and the mercury +trough brought below it. A light is so arranged as +to illuminate the field of the telescope, and the +observer, looking in, sees the ten transit wires and +the one declination wire, and also sees their images +reflected from the surface of the mercury. If the +telescope be pointing <em>exactly</em> down towards the surface +of the mercury, then the image of the declination +wire will fall exactly on the declination wire itself,<span class="pagenum"><a name="Page_200" id="Page_200">[200]</a></span> +and by reading the circle we can tell where the +zenith point of the circle is. Similarly, if the pivots +of the telescope are precisely on the same level, the +centre wire of the right ascension series would +coincide with its reflected image. A third point is +determined by looking through the eye-piece of the +north collimator telescope—that is to say, the telescope +mounted in a horizontal position at the north +end of the room—at the spider lines in the focus of +the south collimator. In order to get this view, the +transit telescope has either to be lifted up out of its +usual position, or else the middle of the tube has to +be opened. The spider lines in the north collimator +are then made to coincide with the image of the +wires of the south collimator. The transit telescope +is then turned first to one collimator, then to the +other, and the central wire of the right ascension +series is turned till it coincides with the wire of the +collimator; the amount by which it has to be moved +giving an index of the error of collimation; that is +to say, of the deviation of the optical axis of the +telescope from perpendicularity to the line joining +the pivots.</p> + +<p>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 afterwards, +before it is available for use. But I have only +mentioned some of the reductions and corrections +which have to be made. There are several more, +and it is a just pride of Greenwich that her third +ruler, Bradley, as has been already told in the notice +of his life, discovered two of the most important.<span class="pagenum"><a name="Page_201" id="Page_201">[201]</a></span> +The one, aberration, is due to the fact that light, +though it moves so swiftly—186,000 miles per second—yet +does not move with an infinitely greater velocity +than that of the earth. The other, nutation, might +be called a correction to precession, inasmuch as, +moved by the moon's attraction, the earth's axis does +not swing round smoothly, but with a slight nodding +or staggering motion.</p> + +<p>But when these observations of the places of a star +have been made, and have been properly 'reduced,' +even then we do not find an exact correspondence +between two different determinations. Little differences +still remain. Some of these are to be accounted +for by changes in the actual crust of the earth, which, +solid and stable as we think it, is yet always in +motion. Professor Milne, our greatest authority on +earth movements, says, 'The earth is so elastic that +a comparatively small impetus will set it vibrating; +why, even two hills tip together when there is a +heavy load of moisture in the valley between them. +And then, when the moisture evaporates in a hot +sun, they tip away from each other.' So there is +a perceptible rocking to and fro even of the huge +stone piers of a transit circle, as seasons of rain and +drought, heat and cold, follow each other. More +than that, the earth is so sensitive to pressure that +it was found, at the Oxford University Observatory, +that there was a distinct swaying shown by a horizontal +pendulum when the whole of a party of +seventy-six undergraduates stood on one side of the +instrument and close up to it, from the position it +had when the party stood ninety feet away. More<span class="pagenum"><a name="Page_202" id="Page_202">[202]</a></span> +wonderful still, a comparison of the star-places, +obtained at a number of observatories, including +Greenwich, has shown that the earth is continually +changing her axis of rotation. And so the star-places +determined at Greenwich have shown that +the north pole of the earth, 2600 miles away, moves +about in an irregular curve about thirty feet in radius.</p> + +<p>Nothing is stable, nothing is immovable, nothing +is constant. The astronomer even finds that his +own presence near the instrument is sufficient to +disturb it.</p> + +<p>The great interest attaching to transit-circle work +is this striving after ever greater and greater precision, +with the result of bringing out fresh little discordances, +which, at first sight, appear purely accidental, but +which, under further scrutiny, show themselves to be +subject to some law. Then comes the hunt for this +new unknown law. Its discovery follows. It explains +much, but when it is allowed for, though the observations +now come much closer together, little deviations +still remain, to form the subject of a fresh inquiry. +Astronomy has well been called the exact science, +and yet exactitude ever eludes its pursuer.</p> + +<p>If it be asked, 'What is the use of this ever-increasing +refinement of observation?' no better +answer can be given than the words of Sir John +Herschel in one of his Presidential addresses to the +Royal Astronomical Society:—</p> + +<blockquote> + +<p>'If we ask to what end magnificent establishments are +maintained by States and sovereigns, furnished with masterpieces +of art, and placed under the direction of men of +first-rate talent and high-minded enthusiasm, sought out for +those qualities among the foremost in the ranks of science,<span class="pagenum"><a name="Page_203" id="Page_203">[203]</a></span> +if we demand, <i lang="la" xml:lang="la">cui bono?</i> for what good a Bradley has toiled, +or a Maskelyne or a Piazzi has worn out his venerable age +in watching?—the answer is, Not to settle mere speculative +points in the doctrine of the universe; not to cater for the +pride of man by refined inquiries into the remoter mysteries +of nature; not to trace the path of our system through +space, or its history through past and future eternities. +These, indeed, are noble ends, and which I am far from any +thought of depreciating; the mind swells in their contemplation, +and attains in their pursuit an expansion and a +hardihood which fit it for the boldest enterprise. But the +direct practical utility of such labours is fully worthy of +their speculative grandeur. The stars are the landmarks +of the universe; and, amidst the endless and complicated +fluctuations of our system, seem placed by its Creator as +guides and records, not merely to elevate our minds by the +contemplation of what is vast, but to teach us to direct our +actions by reference to what is immutable in His works. +It is, indeed, hardly possible to over-appreciate their value +in this point of view. Every well-determined star, from the +moment its place is registered, becomes to the astronomer, +the geographer, the navigator, the surveyor, a point of +departure which can never deceive or fail him, the same +for ever and in all places; of a delicacy so extreme as to +be a test for every instrument yet invented by man, yet +equally adapted for the most ordinary purposes; as +available for regulating a town clock as for conducting a +navy to the Indies; as effective for mapping down the +intricacies of a petty barony as for adjusting the boundaries +of Transatlantic empires. When once its place has been +thoroughly ascertained and carefully recorded, the brazen +circle with which that useful work was done may moulder, +the marble pillar may totter on its base, and the astronomer +himself survive only in the gratitude of posterity; but the +record remains, and transfuses all its own exactness into +every determination which takes it for a groundwork, +giving to inferior instruments—nay, even to temporary +contrivances, and to the observations of a few weeks or +days—all the precision attained originally at the cost of so +much time, labour, and expense.'</p></blockquote> + +<p><span class="pagenum"><a name="Page_204" id="Page_204">[204]</a></span></p> + +<p>But for these strictly utilitarian purposes a comparatively +small number of stars would meet our +every requisite. In the narrow sense of which Sir +John Herschel is here speaking, we have no use for +anything beyond the smallest of catalogues; and if +the question before us is, 'Why are we continually +extending our catalogues?' the following words of a +more recent writer<a name="FNanchor_4_4" id="FNanchor_4_4"></a><a href="#Footnote_4_4" class="fnanchor">[4]</a> on the subject will set forth the +real explanation:—</p> + +<blockquote> + +<p>'A word in conclusion, suggested by the history of star-catalogues. +We have no difficulty in understanding that it +is necessary to study the planets, and a reasonable number +of the brighter stars, for the purpose of determining the +figure of the earth, and the positions of points upon its +surface; but the use for a catalogue of ten thousand stars, +such as La Caille compiled, is not just so apparent. Nay, +what did Ptolemy want with a thousand stars, or Tamerlane's +grandson, born, reared, and destined to die amidst +a horde of savages, however splendid in their trappings? +There is not, and there never was, any real, practical use +for the great volumes of star-catalogues that weigh down +the shelves of our libraries. The navigator and explorer +need never see them at all. Why, then, were these pages +compiled? Why have astronomers, from Hipparchus's +time to the present, spent their lives in the weary routine-work +of observing the places of tiny points in the stellar +depths? Does it not seem that there is something in the +mind of man that impels him to seek after knowledge—truly—for +its own sake? something heaven-born, heaven-nurtured, +God-given ... that there is something in man +common to him and his Creator, and therefore eternal ... +in beautiful accord with the plain statement that "God +made man in His own image?"'</p></blockquote> +<hr class="chap" /> + +<p><span class="pagenum"><a name="Page_205" id="Page_205">[205]</a></span></p> + + + +<h2>CHAPTER VIII</h2> + +<h3>THE ALTAZIMUTH DEPARTMENT</h3> + + +<p>The determining of the places of the fixed stars +which Flamsteed carried out so efficiently in his +<cite>British Catalogue of Stars</cite>—the first 'Census of the +Sky' made with the aid of a telescope—was but half +of the work imposed upon him. The other half, +equally necessary for the solution of the problem of +the longitude at sea, was the 'Rectifying the Tables +of the Motions of the Heavens.'</p> + +<p>This second duty was not less necessary than the +other, for, if we may again use the old simile of the +clock-face, the fixed stars may be taken to represent +the figures on the vast dial of the sky, whilst the +moon, as it moves amongst them, corresponds to the +moving hand of the timepiece. To know the places +of the stars, then, without being able to predict the +place of the moon, would be much like having a clock +without its hands. But if not less necessary, it was +certainly more difficult. The secret of the movements +of the moon and planets had not then been +grasped, and the only tables which had been calculated +were based upon observations made before the +days of telescopes.</p> + +<p><span class="pagenum"><a name="Page_206" id="Page_206">[206]</a></span></p> + +<p>It is one of the most fortunate and remarkable +coincidences in the whole history of science, that at +the very time that Greenwich Observatory was being +called into existence, the greatest of all astronomers +was working out his demonstration of the great 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 distance.</p> + +<p>Several other of the great minds of that time, in +particular Dr. Hooke, the Gresham Professor of +Astronomy, had seen that it was possible that some +such law might supply the secret of planetary motion; +but it is one thing to make a suggestion, and a very +different matter indeed to be able to demonstrate it; +and the latter was in Newton's power alone. He did +much more than demonstrate it—he brought out a +whole series of most important and far-reaching consequences. +He showed that the ebb and flow of the +tides was due to the attraction of both sun and moon, +especially the latter, upon the waters of our oceans. +He pointed out certain irregularities which must take +place in the motion of our moon, due to the influence +of the sun upon it. He showed, too, what was the +cause of that swinging of the axis of the earth which +gives rise to precession. He deduced the relative +weights of the earth, the sun, and of Jupiter and +Saturn, the planets with satellites. He proved also +that comets, which had seemed hitherto to men as +perfectly lawless wanderers, obeyed in their orbits the +self-same law which governed the moon and planets. +The whole vast system of celestial movements, which<span class="pagenum"><a name="Page_207" id="Page_207">[207]</a></span> +had long seemed to men irregular and uncontrolled, +now fell, every one of them, into its place, as but +the necessary manifestations of one grand, simple +order.</p> + +<p>This great discovery gave a new and additional +importance to the regular observation of the moon +and planets. They were needed now, not only to +assist in the practical work of navigation, but for the +development of questions of pure science. Halley, +the second Astronomer Royal, and Maskelyne, the +fifth, devoted themselves chiefly to this department +of work, to the partial neglect of the observation of +the places of stars. Airy, the seventh, whilst making +catalogue-work a part of the regular routine of the +Observatory, developed the observation of the members +of the solar system, and especially of the moon, +in a most marked degree, and collected and completely +reduced the vast mass of material which the +industry of his predecessors had gathered. It is +pre-eminently of the work of Airy that the memorable +words quoted before of Professor Newcomb, the great +American mathematician and astronomer, are applicable: +'that if this branch of astronomy were entirely +lost, it could be reconstructed from the Greenwich +observations alone.'</p> + +<p>A most important step taken by Airy was the +construction of an altazimuth. An altazimuth is +practically a theodolite on a large scale. Its purpose +is to determine, not the declination and right ascension +of some celestial body, as is the case with the +transit circle, but its altitude, <em>i.e.</em> its height above the +horizon, and its azimuth, <em>i.e.</em> the angle measured on<span class="pagenum"><a name="Page_208" id="Page_208">[208]</a></span> +the horizontal plane from the north point. The +altazimuth, then, like the transit circle, consists of a +telescope revolving on a horizontal axis, but, unlike +the transit circle, both the telescope and the piers +which carry its pivots can be rotated so as to point +not merely due north and south, but in any direction +whatsoever.</p> + +<div class="figcenter bord" style="width: 450px;"><a name="alta" id="alta"></a> +<img src="images/i_208.jpg" width="450" height="454" alt="alta" /> +<div class="caption"><p class="center">AIRY'S ALTAZIMUTH.</p></div> +</div> + +<p>The observations with the altazimuth are rather +more complicated than those with the transit circle.<span class="pagenum"><a name="Page_209" id="Page_209">[209]</a></span> +Looking in the telescope, the observer sees a double +set of spider threads or 'wires'; and when a star or +other heavenly body enters the field, it will generally +be observed to move obliquely across both sets of +wires. The observer usually determines to make an +observation either in altitude or azimuth. In the +former case he presses the little contact button, which, +as in the transit circle, is provided close to the eyepiece, +as the star reaches each of the horizontal wires +in succession. If in azimuth, it is the times of crossing +the vertical wires that are in like manner telegraphed +to the chronograph. The transit over, the +appropriate circle is read; for the telescope itself is +rigidly attached to a vertical wheel having a carefully +engraved circle on its face and read by four microscopes, +whilst the entire instrument carries another +set of microscopes, pointing to a fixed horizontal +circle, and upon which the azimuth can be read. +A complete observation involves four such transits +and sets of circle readings, two of altitude, and two +of azimuth; for after one of altitude and one of +azimuth the telescope is turned round, and a second +observation is taken in each element.</p> + +<p>The observation gives us the altitude and azimuth +of the star. These particulars are of no direct value +to us. But it is a mere matter of computation, +though a long and laborious one, to convert these +elements into right ascension and declination.</p> + +<p>The usefulness of the altazimuth will be seen at +once. It will be remembered that with the transit +circle any particular object can only be observed as it +crosses the meridian. If the weather should be<span class="pagenum"><a name="Page_210" id="Page_210">[210]</a></span> +cloudy, or the observer late, the chance of observation +is lost for four and twenty hours, and in the case of +the moon, for which the altazimuth is specially used, +it is on the meridian only in broad daylight during +that part of the month which immediately precedes +and follows new moon. At such times it is practically +impossible to observe it with the transit circle; +with the altazimuth it may be caught in the twilight +before sunrise or after sunset; and at other times in +the month, if lost on the meridian in the transit circle, +the altazimuth still gives the observer a chance of +catching it any time before it sets. But for this +instrument, our observations of the moon would have +been practically impossible over at least one-fourth +of its orbit.</p> + +<p>Airy's altazimuth was but a small instrument of +three and three-quarter inches aperture, mounted in a +high tower built on the site of Flamsteed's mural +arc; and, after a life history of about half a century, +has been succeeded by a far more powerful instrument. +The 'New Altazimuth' has an aperture of eight +inches, and is housed in a very solidly constructed +building of striking appearance, the connection of the +Observatory with navigation being suggested by a +row of circular lights which strongly recall a ship's +portholes. This building is at the southern end of the +narrow passage, 'the wasp's waist,' which connects +the older Observatory domain with the newer. It is +the first building we come to in the south ground. +The computations of the department are carried on +in the south wing of the new Observatory.</p> + +<p>It will be seen from the photograph that the<span class="pagenum"><a name="Page_211" id="Page_211">[211]</a></span> +instrument is much larger, heavier, and less easy to +move in azimuth than the old altazimuth. It is, +therefore, not often moved in azimuth, but is set in +some particular direction, not necessarily north and +south, in which it is used practically as a transit +circle.</p> + +<div class="figcenter bord" style="width: 450px;"><a name="zimuth" id="zimuth"></a> +<img src="images/i_211.jpg" width="450" height="467" alt="zimuth" /> +<div class="caption"><p class="center">NEW ALTAZIMUTH BUILDING.</p></div> +</div> + +<p>There is quite another way of determining the +place of the moon, which is sometimes available, and +which offers one of the prettiest of observations to<span class="pagenum"><a name="Page_212" id="Page_212">[212]</a></span> +the astronomer. As the moon travels across the sky, +moving amongst the stars from west to east, it +necessarily passes in front of some of them, and +hides them from us for a time. Such a passage, +or 'occultation,' offers two observations: the 'disappearance,' +as the moon comes up to the star and +covers it; the 'reappearance,' as it leaves it again, +and so discloses it.</p> + +<div class="figcenter news" style="width: 600px;"><a name="news" id="news"></a> +<img src="images/i_213.jpg" width="600" height="449" alt="news" /> +<div class="caption"><p class="center">THE NEW ALTAZIMUTH.<br /> +(<em>From a photograph by Mr. Lacey.</em>)</p></div> +</div> + +<p>Except at the exact time of full moon, we do not +see the entire face of our satellite; one edge or 'limb' +is in darkness. As the moon therefore passes over +the star, either the limb at which the star disappears, +or that at which it reappears, is invisible to us. To +watch an occultation at the bright limb is pretty; the +moon, with its shining craters and black hollows, its +mountain ranges in bright relief, like a model in +frosted silver, slowly, surely, inevitably comes nearer +and nearer to the little brilliant which it is going to +eclipse. The movement is most regular, most smooth, +yet not rapid. The observer glances at his clock, +and marks the minute as the two heavenly bodies +come closer and closer to each other. Then he counts +the clock beats: 'five, six, seven,' it may be, as the +star has been all but reached by the advancing moon. +'Eight,' it is still clear; ere the beat of the clock rings +to the 'nine,' perhaps the little diamond point has +been touched by the wide arch of the moon's limb, +and has gone! Less easy to exactly time is a +reappearance at the bright limb. In this case the +observer must ascertain from the <cite>Nautical Almanac</cite> +precisely where the star will reappear; then a little +before the predicted time he takes his place at the<span class="pagenum"><a name="Page_213" id="Page_213"> </a><br /><a name="Page_214" id="Page_214"> </a><br /><a name="Page_215" id="Page_215">[215]</a></span> +telescope, watches intently the moon's circumference +at the point indicated, and, listening for the clock-beats, +counts the seconds as they fly. Suddenly, +without warning, a pin-point of light flashes out at +the edge of the moon, and at once draws away from +it. The star has 'reappeared.'</p> + +<p>Far more striking is a disappearance or reappearance +at the 'dark limb.' In this case the limb of the +moon is absolutely invisible, and it may be that no +part of the moon is visible in the field of the telescope. +In this case the observer sees a star shining brightly +and alone in the middle of the field of his telescope. +He takes the time from his faithful clock, counting +beat after beat, when suddenly the star is gone! So +sudden is the disappearance that the novice feels +almost as astonished as if he had received a slap in +the face, and not unfrequently he loses all count or +recollection of the clock beats. The reappearance at +the dark limb is quite as startling; with a bright star +it is almost as if a shell had burst in his very face, +and it would require no very great imagination to +make him think that he had heard the explosion. +One moment nothing was visible; now a great star +is shining down serenely on the watcher. A little +practice soon enables the observer to accustom +himself to these effects, and an old hand finds no +more difficulty in observing an occultation of any +kind than in taking a transit.</p> + +<p>Such an observation is useful for more purposes +than one. If the position of the star occulted is +known—and it can be determined at leisure afterwards—we +necessarily know where the limb of the moon<span class="pagenum"><a name="Page_216" id="Page_216">[216]</a></span> +was at the time of the observation. Then the time +which the moon took to pass over the star enables us +to calculate the diameter of our satellite; the different +positions of the moon relative to the star, as seen +from different observatories, enable us to calculate its +distance.</p> + +<p>But if the disappearance takes place at the bright +limb, the reappearance usually takes place at the +dark, and <i lang="la" xml:lang="la">vice versâ</i>; and the two observations are +not quite comparable. There is one occasion, however, +when both observations are made under similar +circumstances, namely, at the full. And if the moon +happens also to be totally eclipsed, the occultations +of quite faint stars can be successfully observed, much +fainter than can ordinarily be seen close up to the +moon. Total eclipses of the moon, therefore, have +recently come to be looked upon as important events +for the astronomer, and observatories the world over +usually co-operate in watching them. October 4, +1884, was the first occasion when such an organised +observation was made; there have been several since, +and on these nights every available telescope and +observer at Greenwich is called into action.</p> + +<p>It may be asked why these different modes of +observing the moon are still kept up, year in and +year out. 'Do we not know the moon's orbit +sufficiently well, especially since the discovery of +gravitation?' No; we do not. This simple and +beautiful law—simple enough in itself, gives rise to +the most amazing complexity of calculation. If the +earth and moon were the only two bodies in the +universe, the problem would be a simple one. But<span class="pagenum"><a name="Page_217" id="Page_217">[217]</a></span> +the earth, sun, and moon are members of a triple +system, each of which is always acting on both of the +others. More, the planets, too, have an appreciable +influence, and the net result is a problem so intricate +that our very greatest mathematicians have not +thoroughly worked it out. Our calculations of the +moon's motions need, therefore, to be continually +compared with observation, need even to be +continually corrected by it.</p> + +<p>There is a further reason for this continual +observation, not only in the case of the sun, which +is our great standard star, since from it we derive +the right ascensions of the stars, and it is also our +great timekeeper; not only in that of the moon, but +also in the case of the planets. Their places as computed +need continually to be compared with their +places as observed, and the discordances, if any, inquired +into. The great triumph which resulted to +science from following this course—to pure science, +since Uranus is too faint a planet to be any help to +the sailor in navigation—is well known. The observed +movements of Uranus proved not to be in +accord with computation, and from the discordances +between calculation and observation Adams and +Leverrier were able to predicate the existence of a +hitherto unseen planet beyond—</p> + +<blockquote> + +<p>'To see it, as Columbus saw America from Spain. Its +movements were felt by them trembling along the far-reaching +line of their analysis, with a certainty hardly +inferior to that of ocular demonstration.'<a name="FNanchor_5_5" id="FNanchor_5_5"></a><a href="#Footnote_5_5" class="fnanchor">[5]</a></p></blockquote> +<p><span class="pagenum"><a name="Page_218" id="Page_218">[218]</a></span></p> +<p>The discovery of Neptune was not made at +Greenwich, and Airy has been often and bitterly +attacked because he did not start on the search for +the predicted planet the moment Adams addressed +his first communication to him, and so allowed +the French astronomer to engross so much of the +honour of the exploit. The controversy has been +argued over and over again, and we may be content +to leave it alone here. There is one point, +however, which is hardly ever mentioned, which must +have had much effect in determining Airy's conduct. +In 1845, the year in which Adams sent his provisional +elements of the unseen disturbing planet to Airy, the +largest telescope available for the search at Greenwich +was an equatorial of only six and three-quarter inches +aperture, provided with small and insufficient circles +for determining positions, and housed in a very +small and inconvenient dome; whilst at Cambridge, +within a mile or so of Adams' own college, was the +'Northumberland' equatorial, of nearly twelve inches +aperture, under the charge of the University Professor +of Astronomy, Professor Challis, and which was then +much the largest, best mounted and housed equatorial +in the entire country. The 'Northumberland' had +been begun from Airy's designs and under his own +superintendence, when he was Professor of Astronomy +at Cambridge. Naturally, then, knowing how much +superior the Cambridge telescope was to any which +he had under his care, he thought the search should +be made with it. He had no reason to believe that +his own instrument was competent for the work.</p> + +<div class="figcenter bord" style="width: 600px;"><a name="observe" id="observe"></a> +<img src="images/i_219.jpg" width="600" height="395" alt="observe" /> +<div class="caption"><p class="center">THE NEW OBSERVATORY AS SEEN FROM FLAMSTEED'S OBSERVATORY.</p></div> +</div> + +<p>On the other hand, it is hard for the ordinary +<span class="pagenum"><a name="Page_219" id="Page_219"> </a><br /><a name="Page_220" id="Page_220"> </a><br /><a name="Page_221" id="Page_221">[221]</a></span>man to understand how it was that Adams not only +left unnoticed and unanswered for three-quarters of +a year, an inquiry of Airy's with respect to his +calculations, but also never took the trouble to visit +Challis, whom he knew well, and who was so near at +hand, to stir him up to the search. But, in truth, +the whole interest of the matter for Adams rested +in the mathematical problem. The irregularities in +the motion of Uranus were interesting to him simply +for the splendid opportunity which they gave him +for their analysis. A purely imaginary case would +have served his purpose nearly as well. The actuality +of the planet which he predicted was of very little +moment; the <i lang="fr" xml:lang="fr">éclat</i> and popular reputation of the +discovery was less than nothing; the problem itself +and the mental exercise in its solution, were what +he prized.</p> + +<p>But it was not creditable to the nation that the +Royal Observatory should have been so ill-provided +with powerful telescopes; and a few years later Airy +obtained the sanction of the Government for the +erection of an equatorial larger than the 'Northumberland,' +but on the same general plan and in a much +more ample dome. This was for thirty-four years the +'Great' or 'South-East' equatorial, and the mounting +still remains and bears the old name, though the +original telescope has been removed elsewhere. The +object-glass had an aperture of twelve and three-quarter +inches and a focal length of eighteen feet, +and was made by Merz of Munich, the engineering +work by Ransomes and Sims of Ipswich, and the +graduations and general optical work by Simms, now<span class="pagenum"><a name="Page_222" id="Page_222">[222]</a></span> +of Charlton, Kent. The mounting was so massive +and stable that the present Astronomer Royal has +found it quite practicable and safe to place upon it +a telescope (with its counterpoises) of many times +the weight, one made by Sir Howard Grubb, of +Dublin, of twenty-eight inches aperture and twenty-eight +feet focal length, the largest refractor in the +British Empire, though surpassed by several American +and Continental instruments.</p> + +<p>The stability of the mounting was intended to +render the telescope suitable for a special work. +This was the observation of 'minor planets.' On +the first day of the present century the first of these +little bodies was discovered by Piazzi at Palermo. +Three more were discovered at no great interval afterwards, +and then there was an interval of thirty-eight +years without any addition to their number. But +from December 8, 1845, up to the present time, the +work of picking up fresh individuals of these 'pocket +planets' has gone on without interruption, until now +more than 400 are known. Most of these are of no +interest to us, but a few come sufficiently near to +the earth for their distance to be very accurately +determined; and when the distance of one member +of the solar system is determined, those of all the +others can be calculated from the relations which +the law of gravitation reveals to us. It is a matter +of importance, therefore, to continue the work of +discovery, since we may at any time come across an +interesting or useful member of the family; and that +we may be able to distinguish between minor planets +already discovered and new ones, their orbits must<span class="pagenum"><a name="Page_223" id="Page_223">[223]</a></span> +be determined as they are discovered, and some sort +of watch kept on their movements.</p> + +<p>A striking example of the scientific prizes which +we may light upon in the process of the rather dreary +and most laborious work which the minor planets +cause, has been recently supplied by the discovery +of Eros. On August 13, 1898, Herr Witt, of the +Urania Observatory, Berlin, discovered a very small +planet that was moving much faster in the sky than +is common with these small bodies. The great +majority are very much farther from the sun than +the planet Mars, many of them twice as far, and +hence, since the time of a planet's revolution round +the sun increases, in accordance with Kepler's law, +more rapidly than does its distance, it follows that +they move much more slowly than Mars. But this +new object was moving at almost the same speed as +Mars; it must, therefore, be most unusually near to +us. Further observations soon proved that this was +the case, and Eros, as the little stranger has been +called, comes nearer to us than any other body of +which we are aware except the moon. Venus when +in transit is 24<small><sup>1</sup>/<sub>2</sub></small> millions of miles from us, Mars at +its nearest is 34<small><sup>1</sup>/<sub>2</sub></small> millions, Eros at its nearest approach +is but little over 13 millions.</p> + +<p>The use of such a body to us is, of course, quite +apart from any purpose of navigation, except very +indirectly. But it promises to be of the greatest +value in the solution of a question in which astronomers +must always feel an interest, the determination of +the distance of the earth from the sun. We know +the <em>relative</em> distances of the different planets, and,<span class="pagenum"><a name="Page_224" id="Page_224">[224]</a></span> +consequently if we could determine the absolute +distance of any one, we should know the distances +of all. As it is practically impossible to measure our +distance from the sun directly, several attempts have +been made to determine the distances of Venus, +Mars, or such of the minor planets as come the +nearest to us. Three of these in particular, the little +planets Iris, Victoria, and Sappho, have given us the +most accurate determinations of the sun's distance +(92,874,000 miles) which we have yet obtained; but +Eros at its nearest approach will be six times as near +to us as either of the three mentioned above, and +therefore should give us a value with only one-sixth +of the uncertainty attaching to that just mentioned.</p> + +<p>The discovery of minor planets has lain outside +the scope of Greenwich work, but their observation +has formed an integral part of it. The general +public is apt to lay stress rather on the first than +on the second, and to think it rather a reproach to +Greenwich that it has taken no part in such explorations. +Experience has, however, shown that they +may be safely left to amateur activity, whilst the +monotonous drudgery of the observation of minor +planets can only be properly carried out in a permanent +institution.</p> + +<p>The observation of these minute bodies with the +transit circle and altazimuth is attended with some +difficulties; but precise observations of various objects +may be made with an equatorial; indeed, comets are +usually observed by its means.</p> + +<p>The most ordinary way of observing a comet with +an equatorial is as follows: Two bars are placed in<span class="pagenum"><a name="Page_225" id="Page_225">[225]</a></span> +the eye-piece of the telescope, at right angles to each +other, and at an angle of forty-five degrees to the +direction of the apparent daily motion of the stars. +The telescope is turned to the neighbourhood of the +comet, and moved about until it is detected. The +telescope is then put a little in front of the comet, +and very firmly fixed. The observer soon sees the +comet entering his field, and by pressing the contact +button he telegraphs to the chronograph the time +when the comet is exactly bisected by each of the +bars successively. He then waits until a bright star, +or it may be two or three, have entered the telescope +and been observed in like manner. The telescope +is then unclamped, and moved forward until it is +again ahead of the comet, and the observations are +repeated; and this is done as often as is thought +desirable. The places of the stars have, of course, +to be found out from catalogues, or have to be +observed with the transit circle, but when they are +known the position of the comet or minor planet can +easily be inferred.</p> + +<p>Next to the glory of having been the means of +bringing about the publication of Newton's <cite>Principia</cite>, +the greatest achievement of Halley, the second +Astronomer Royal, was that he was the first to +predict the return of a comet. Newton had shown +that comets were no lawless wanderers, but were as +obedient to gravitation as were the planets themselves, +and he also showed how the orbit of a comet +could be determined from observations on three +different dates. Following these principles, Halley +computed the orbits of no fewer than twenty-four<span class="pagenum"><a name="Page_226" id="Page_226">[226]</a></span> +comets, and found that three of them, visible at +intervals of about seventy-five years, pursued practically +the same path. He concluded, therefore, that +these were really different appearances of the same +object, and, searching old records, he found reason +to believe that it had been observed frequently earlier +still. It seems, in fact, to have been the comet which +is recorded to have been seen in 1066 in England at +the time of the Norman invasion; in <small>A.D.</small> 66, shortly +before the commencement of that war which ended +in the destruction of Jerusalem by Titus; and earlier +still, so far back as <small>B.C.</small> 12. Halley, however, experienced +a difficulty in his investigation. The period +of the comet's revolution was not always the same. +This, he concluded, must be due to the attraction of +the planets near which the comet might chance to +travel. In the summer of 1681 it had passed very +close to Jupiter, for instance, and in consequence he +expected that instead of returning in August 1757, +seventy-five years after its last appearance, it would +not return until the end of 1758 or the beginning of +1759. It has returned twice since Halley's day, a +triumphant verification of the law of gravitation; and +we are looking for it now for a third return some +ten years hence, in 1910.</p> + +<p>Halley's comet, therefore, is an integral member +of our solar system, as much so as the earth or +Neptune, though it is utterly unlike them in appearance +and constitution, and though its path is so +utterly unlike theirs that it approaches the sun +nearer than our earth, and recedes farther than +Neptune. But there are other comets, which are<span class="pagenum"><a name="Page_227" id="Page_227">[227]</a></span> +not permanent members of our system, but only +passing visitors. From the unfathomed depths of +space they come, to those depths they go. They +obey the law of gravitation so far as our sight can +follow them, but what happens to them beyond? +Do they come under some other law, or, perchance, +in outermost space is there still a region reserved to +primeval Chaos, the 'Anarch old,' where no law at +all prevails? Gravitation is the bond of the solar +system; is it also the bond of the Universe?</p> + +<hr class="chap" /> + +<p><span class="pagenum"><a name="Page_228" id="Page_228">[228]</a></span></p> + + + + +<h2>CHAPTER IX</h2> + +<h3>THE MAGNETIC AND METEOROLOGICAL +DEPARTMENTS</h3> + + +<p>Passing out of the south door of the new altazimuth +building, we come to a white cruciform erection, +constructed entirely of wood. This is the Magnet +House or Magnetic Observatory, the home of a +double Department, the Magnetic and Meteorological.</p> + +<p>This department does not, indeed, lie within the +original purpose of the Observatory as that was +defined in the warrant given to Flamsteed, and yet +is so intimately connected with it, through its bearing +on navigation, that there can be no question as to +its suitability at Greenwich. Indeed, its creation is +a striking example of the thorough grasp which Airy +had upon the essential principles which should govern +the great national observatory of an essentially +naval race, and of the keen insight with which he +watched the new development of science. The +Magnetic Observatory, therefore, the purpose of which +was to deal with the observation of the changes in +the force and direction of the earth's magnetism—an +inquiry which the greater delicacy of modern compasses, +and, in more recent times, the use of iron<span class="pagenum"><a name="Page_229" id="Page_229">[229]</a></span> +instead of wood in the construction of ships has +rendered imperative—was suggested by Airy on the +first possible occasion after he entered on his office, +and was sanctioned in 1837. The Meteorological +Department has a double bearing on the purpose of +the Observatory. On the one side, a knowledge of +the temperature and pressure of the atmosphere is, as +we have already seen, necessary in order to correct +astronomical observations for the effect of refraction. +On the other hand, meteorology proper, the study of +the movements of the atmosphere, the elucidation of +the laws which regulate those movements, leading to +accurate forecasts of storms, are of the very first +necessity for the safety of our shipping. It is true +that weather forecasts are not issued from Greenwich +Observatory, any more than the <cite>Nautical Almanac</cite> is +now issued from it; but just as the Observatory +furnishes the astronomical data upon which the +Almanac is based, so also it takes its part in furnishing +observations to be used by the Meteorological +Office at Westminster for its daily predictions.</p> + +<p>Those predictions are often made the subject of +much cheap ridicule; but, however far short they +may fall of the exact and accurate predictions which +we would like to have, yet they mark an enormous +advance upon the weather-lore of our immediate +forefathers.</p> + +<div class="poem"><div class="stanza"> +<span class="i0">'He that is weather wise<br /></span> +<span class="i0">Is seldom other wise,'<br /></span> +</div></div> + +<p class="noin">says the proverb, and the saying is not without a +shrewd amount of truth. For perhaps nowhere can +we find a more striking combination of imperfect<span class="pagenum"><a name="Page_230" id="Page_230">[230]</a></span> +observation and inconsequent deduction than in the +saws which form the stock-in-trade of the ordinary +would-be weather prophet. How common it is to +find men full of the conviction that the weather must +change at the co-called 'changes of the moon,' +forgetful that</p> + +<div class="poem"><div class="stanza"> +<span class="i0">'If we'd no moon at all—<br /></span> +<span class="i2">And that may seem strange—<br /></span> +<span class="i0">We still should have weather<br /></span> +<span class="i2">That's subject to change.'<br /></span> +</div></div> + +<p>They will say, truly enough, no doubt, that they have +known the weather to change at 'new' or 'full,' as +the case may be, and they argue that it, therefore, +must always do so. But, in fact, they have only +noted a few chance coincidences, and have let the +great number of discordances pass by unnoticed.</p> + +<p>But observations of this kind seem scientific and +respectable compared with those numerous weather +proverbs which are based upon the mere jingle of +a rhyme, as</p> + +<div class="poem"><div class="stanza"> +<span class="i0">'If the ash is out before the oak,<br /></span> +<span class="i0">You may expect a thorough soak'—<br /></span> +</div></div> + +<p class="noin">a proverb which is deftly inverted in some districts +by making 'oak' rhyme to 'choke.'</p> + +<p>Others, again, are based upon a mere childish fancy, +as, for example, when the young moon 'lying on her +back' is supposed to bode a spell of dry weather, +because it looks like a cup, and so might be thought +of as able to hold the water.</p> + +<p>During the present reign, however, a very different +method of weather study has come into action, and<span class="pagenum"><a name="Page_231" id="Page_231">[231]</a></span> +the foundations of a true weather wisdom have been +laid. These have been based, not on fancied analogies +or old wives' rhymes, or a few forechosen coincidences, +but upon observations carried on for long periods +of time and over wide areas of country, and discussed +in their entirety without selection and bias. Above +all, mathematical analysis has been applied to the +motions of the air, and ideas, ever gaining in precision +and exactness, have been formulated of the general +circulation of the atmosphere.</p> + +<p>As compared with its sister science, astronomy, +meteorology appears to be still in a very undeveloped +state. There is such a difference between the power +of the astronomer to foretell the precise position of +sun, moon, and planets for years, even for centuries, +beforehand, and the failure of the meteorologist to +predict the weather for a single season ahead, that +the impression has been widely spread that there is +yet no true meteorological science at all. It is forgotten +that astronomy offered us, in the movements +of the heavenly bodies, the very simplest and easiest +problem of related motion. Yet for how many thousands +of years did men watch the planets, and speculate +concerning their motions, before the labours of +Tycho, Kepler, and Newton culminated in the revelation +of their meaning? For countless generations +it was supposed that their movements regulated the +lives, characters, and private fortunes of individual +men; just as quite recently it was fancied that a +new moon falling on a Saturday, or two full moons +coming within the same calendar month, brought +bad weather!</p> + +<p><span class="pagenum"><a name="Page_232" id="Page_232">[232]</a></span></p> + +<p>It is still impossible to foresee the course of weather +change for long ahead; but the difference between +the modern navigator, surely and confidently making +a 'bee-line' across thousands of miles of ocean to his +destination, and the timid sailor of old, creeping from +point to point of land, is hardly greater than the +contrast between the same two men, the one watching +his barometer, the other trusting in the old wives' +rhymes which afforded him his only indication as to +coming storms.</p> + +<p>It is still impossible to foresee the weather change +for long ahead, but in our own and in many other +countries, especially the United States, it has been +found possible to predict the weather of the coming +four-and-twenty hours with very considerable exactness, +and often to forecast the coming of a great +storm several days ahead. This is the chief purpose +of the two great observatories of the storm-swept +Indian and Chinese seas, Hong Kong and Mauritius; +and the value of the work which they have done in +preventing the loss of ships, and the consequent loss +of lives and property, has been beyond all estimate.</p> + +<p>The Royal Observatory, Greenwich, is a meteorological +as well as an astronomical observatory, but, as +remarked above, it does not itself issue any weather +forecasts. Just as the Greenwich observations of the +places of the moon and stars are sent to the <cite>Nautical +Almanac</cite> Office, for use in the preparation of that ephemeris; +just as the Greenwich determinations of time +are used for the issue of signals to the Post Office, +whence they are distributed over the kingdom, so the +Greenwich observations of weather are sent to the<span class="pagenum"><a name="Page_233" id="Page_233">[233]</a></span> +Meteorological Office, there to be combined with +similar records from every part of the British Isles, +to form the basis of the daily forecasts which the +latter office publishes. To each of these three offices, +therefore, the Royal Observatory, Greenwich, stands +in the relation of purveyor. It supplies them with +the original observations more or less in reduced and +corrected form, without which they could not carry +on most important portions of their work.</p> + +<p>Let it be noted how closely these three several +departments, the <cite>Nautical Almanac</cite> Office, the Time +Department, and the Meteorological Office, are related +to practical navigation. Whatever questions of pure +science—of knowledge, that is, apart from its useful +applications—may arise out of the following up of +these several inquiries, yet the first thought, the first +principle of each, is to render navigation more sure +and more safe.</p> + +<p>The first of all meteorological instruments is the +barometer, which, under its two chief forms of mercurial +and aneroid, is simply a means of measuring +the pressure exerted by the atmosphere.</p> + +<p>There are two important corrections to which its +readings are subject. The first is for the height of +the station above the level of the sea; the second is +for the effect of temperature upon the mercury in the +barometer itself, lengthening the column. To overcome +these, the height of the standard barometer at +Greenwich above sea-level has been most carefully +ascertained, and the heights relative to it of the other +barometers of the Observatory, particularly those in +rooms occupied by fundamental telescopes, have also<span class="pagenum"><a name="Page_234" id="Page_234">[234]</a></span> +been determined, whilst the self-recording barometer +is mounted in a basement, where it is almost +completely protected from changes of temperature.</p> + +<p>Next in importance to the barometer as a meteorological +instrument comes the thermometer. The great +difficulty in the Observatory use of the thermometer +is to secure a perfectly unexceptionable exposure, so +that the thermometer may be in free and perfect +contact with the air, and yet completely sheltered +from any direct ray from the sun. This is secured +in the great thermometer shed at Greenwich by a +double series of 'louvre' boards, on the east, south, +and west sides of the shed, the north side being open. +The shed itself is made a very roomy one, in order +to give access to a greater body of air.</p> + +<p>A most important use of the thermometer is in +the measurement of the amount of moisture in the air. +To obtain this, a pair of thermometers are mounted +close together, the bulb of one being covered by +damp muslin, and the other being freely exposed. +If the air is completely saturated with moisture, no +evaporation can take place from the damp muslin, +and consequently the two thermometers will read +the same. But if the air be comparatively dry, more +or less evaporation will take place from the wet bulb, +and its temperature will sink to that at which the +air would be fully saturated with the moisture which +it already contained. For the higher the temperature, +the greater is its power of containing moisture. The +difference of the reading of the two thermometers is, +therefore, an index of humidity. The greater the +difference, the greater the power of absorbing moisture, +<span class="pagenum"><a name="Page_235" id="Page_235"> </a><br /><a name="Page_236" id="Page_236"> </a><br /><a name="Page_237" id="Page_237">[237]</a></span>or, in other words, the dryness of the air. The great +shed already alluded to is devoted to these companion +thermometers.</p> + +<div class="figcenter bord" style="width: 396px;"><a name="self" id="self"></a> +<img src="images/i_235.jpg" width="396" height="600" alt="self" /> +<div class="caption"><p class="center">THE SELF-REGISTERING THERMOMETERS.</p></div> +</div> + +<p>Very closely connected with atmospheric pressure, +as shown us by the barometer, is the study of the +direction of winds. If we take a map of the British +Isles and the neighbouring countries, and put down +upon them the barometer readings from a great +number of observing stations, and then join together +the different places which show the same barometric +pressure, we shall find that these lines of equal +pressure—technically called 'isobars'—are apt to run +much nearer together in some places than in others. +Clearly, where the isobars are close together it means +that in a very short distance of country we have a +great difference of atmospheric pressure. In this +case we are likely to get a very strong wind blowing +from the region of high pressure to the region of low +pressure, in order to restore the balance.</p> + +<p>If, further, we had information from these various +observing stations of the direction in which the +wind was blowing, we should soon perceive other +relationships. For instance, if we found that the +barometer read about the same in a line across the +country from east to west, but that it was higher in +the north of the islands than in the south, we should +then have a general set of winds from the east, and +a similar relation would hold good if the barometer +were highest in some other quarter; that is, the +prevailing wind will come from a quarter at right +angles to the region of highest barometer, or, as it +is expressed in what is known as 'Buys Ballot's law,'<span class="pagenum"><a name="Page_238" id="Page_238">[238]</a></span> +'stand with your back to the wind, and the barometer +will be lower on your left hand than on your right.' +This law holds good for the northern hemisphere +generally, except near to the equator; in the southern +hemisphere the right hand is the side of low barometer.</p> + +<p>The instruments for wind observation are of two +classes: vanes to show its direction, and anemometers +to show its speed and its pressure. These may be +regarded as two different modes in which the strength +of the wind manifests itself. Pressure anemometers +are usually of two forms: one in which a heavy plate +is allowed to swing by its upper edge in a position +fronting the wind, the amount of its deviation from +the vertical being measured; and the other in which +the plate is supported by springs, the degree of +compression of the springs being the quantity +registered in that case. Of the speed anemometers, +the best known form is the 'Robinson,' in which four +hemispherical cups are carried at the extremities of +a couple of cross bars.</p> + +<p>For the mounting of these wind instruments the +old original Observatory, known as the Octagon +Room, has proved an excellent site, with its flat roof +surmounted by two turrets in the north-east and +north-west corners, and raised some two hundred +feet above high-water mark.</p> + +<div class="figcenter bord" style="width: 424px;"><a name="anemone" id="anemone"></a> +<img src="images/i_240.jpg" width="424" height="600" alt="anemone" /> +<div class="caption"><p class="center">THE ANEMOMETER ROOM, NORTH-WEST TURRET.</p></div> +</div> + +<p>The two chief remaining instruments are those +for measuring the amount of rainfall and of full +sunshine. The rain gauge consists essentially of a +funnel to collect the rain, and a graduated glass to +measure it. The sunshine recorder usually consists +of a large glass globe arranged to throw an image<span class="pagenum"><a name="Page_239" id="Page_239"> </a><br /><a name="Page_240" id="Page_240"> </a><br /><a name="Page_241" id="Page_241">[241]</a></span> +of the sun on a piece of specially prepared paper. +This image, as the sun moves in the sky, moves along +the paper, charring it as it moves, and at the end +of the day it is easy to see, from the broken, burnt +trace, at what hours the sun was shining clear, and +when it was hidden by cloud.</p> + +<p>An amusing difficulty was encountered in an +attempt to set on foot another inquiry. The +Superintendent of the Meteorological Department at +the time wished to have a measure of the rate at +which evaporation took place, and therefore exposed +carefully measured quantities of water in the open +air in a shallow vessel. For a few days the record +seemed quite satisfactory. Then the evaporation +showed a sudden increase, and developed in the most +erratic and inexplicable manner, until it was found +that some sparrows had come to the conclusion that +the saucer full of water was a kindly provision for +their morning 'tub,' and had made use of it accordingly.</p> + +<p>A large proportion of the meteorological instruments +at Greenwich and other first-class observatories +are arranged to be self-recording. It was early felt +that it was necessary that the records of the barometer +and thermometer should be as nearly as possible +continuous; and at one time, within the memory +of members of the staff still living, it was the duty +of the observer to read a certain set of instruments +at regular two-hour intervals during the whole +of the day and night—a work probably the most +monotonous, trying, and distasteful of any that the +Observatory had to show.</p> + +<p>The two-hour record was no doubt practically<span class="pagenum"><a name="Page_242" id="Page_242">[242]</a></span> +equivalent to a continuous one, but it entailed a +heavy amount of labour. Automatic registers were, +therefore, introduced whenever they were available. +The earliest of these were mechanical, and several +still make their records in this manner.</p> + +<p>On the roof of the Octagon Room we find, beside +the two turrets already referred to, a small wooden +cabin built on a platform several feet above the +roof level. This cabin and the north-western turret +contain the wind-registering instruments. Opening +the turret door, we find ourselves in a tiny room +which is nearly filled by a small table. Upon this +table lies a graduated sheet of paper in a metal frame, +and as we look at it, we see that a clock set up close +to the table is slowly drawing the paper across it. +Three little pencils rest lightly on the face of the +paper at different points. One of these, and usually +the most restless, is connected with a spindle which +comes down into the turret from the roof, and which +is, in fact, the spindle of the wind vane. The gearing +is so contrived that the motion on a pivot of the vane +is turned into motion in a straight line at right angles +to the direction in which the paper is drawn by the +clock. A second pencil is connected with the wind-pressure +anemometer. The third pencil indicates +the amount of rain that has fallen since the last +setting, the pencil being moved by a float in the +receiver of the rain gauge.</p> + +<div class="figcenter bord" style="width: 450px;"><a name="trace" id="trace"></a> +<img src="images/i_243.jpg" width="450" height="586" alt="trace" /> +<div class="caption"><p class="center">THE ANEMOMETER TRACE.</p></div> +</div> + +<p>An objection to all the mechanical methods of +continuous registration is that, however carefully the +gearing between the instrument itself and the pencil +is contrived, however lightly the pencil moves over<span class="pagenum"><a name="Page_243" id="Page_243">[243]</a></span> +the paper, yet some friction enters in and affects the +record: this is of no great moment in wind registration, +when we are dealing with so powerful an agent as +the wind, but it becomes a serious matter when the<span class="pagenum"><a name="Page_244" id="Page_244">[244]</a></span> +barometer is considered, since its variations require +to be registered with the greatest minuteness. When +photography, therefore, was invented, meteorologists +were very prompt to take advantage of this new ally. +A beam of light passing over the head of the column +of mercury in a thermometer or barometer could +easily be made to fall upon a drum revolving once in +the twenty-four hours, and covered with a sheet of +photographic paper. In this case, when the sensitive +paper is developed, we find its upper half blackened, +the lower edge of the blackened part showing an +irregular curve according as the mercury in the +thermometer or barometer rose or fell, and admitted +less or more light through the space above it.</p> + +<p>Here we have a very perfect means of registration: +the passage of the light exercises no friction or check +on the free motion of the mercury in the tube, or on +the turning of the cylinder covered by the sensitive +paper, whilst it is easy to obtain a time scale on the +register by cutting off the light for an instant—say +at each hour. In this way the wet and dry bulb +thermometers in the great shed make their registers.</p> + +<p>The supply of material to the Meteorological +Office is not the only use of the Greenwich meteorological +observations. Two elements of meteorology, +the temperature and the pressure of the atmosphere, +have the very directest bearing upon astronomical +work. And this in two ways. An instrument is +sensible to heat and cold, and undergoes changes of +form, size, or scale, which, however absolutely minute, +yet become, with the increased delicacy of modern +work, not merely appreciable, but important. So too<span class="pagenum"><a name="Page_245" id="Page_245">[245]</a></span> +with the density of the atmosphere: the light from a +distant star, entering our atmosphere, suffers refraction; +and being thus bent out of its path, the star appears +higher in the heavens than it really is. The amount +of this bending varies with the density of the layers +of air through which the light has to pass. The two +great meteorological instruments, the thermometer +and barometer, are therefore astronomical instruments +as well.</p> + +<p>In the arrangements at Greenwich the Magnetic +Department is closely connected with the Meteorological, +and it is because the two departments have +been associated together that the building devoted +to both is constructed of wood, not brick, since +ordinary bricks are made of clay which is apt to be +more or less ferruginous. Copper nails have alone +been employed in the construction of the buildings. +The fire-grates, coal-scuttles, and fire-irons are all of +the same metal.</p> + +<p>The growth of the Observatory has, however, +made it necessary to set up some of the new telescopes, +into the mounting of which much iron enters, +very close to the magnetic building. The present +Astronomer-Royal has therefore erected a Magnetic +Pavilion right out in the park at an ample distance +from these disturbing causes.</p> + +<p>The double department is, therefore, the most +widely scattered in the whole Observatory. It is +located for computing purposes in the west wing of +the New Observatory; many of its magnetic instruments +are in the old Magnet House, others are +across the park in the new Magnetic Pavilion; the<span class="pagenum"><a name="Page_246" id="Page_246">[246]</a></span> +anemometers are on the roof of the Octagon Room, +Flamsteed's original observatory, and the self-registering +thermometers are in the south ground between +the old Magnet House and the New Observatory.</p> + +<div class="figcenter bord" style="width: 450px;"><a name="ext" id="ext"></a> +<img src="images/i_246.jpg" width="450" height="410" alt="ext" /> +<div class="caption"><p class="center">MAGNETIC PAVILION—EXTERIOR.<br /> +(<em>From a photograph by Mr. Lacey.</em>)</p></div> +</div> + +<p>The object of the Magnetic Observatory is to +study the movements of the magnetic needle. The +quaintest answer that I ever received in an examination +was in reply to the question, 'What is meant by +magnetic inclination and declination?' The examinee +replied:</p> + +<p><span class="pagenum"><a name="Page_247" id="Page_247">[247]</a></span></p> + +<blockquote> + +<p>'To make a magnet, you take a needle, and rub it on a +lodestone. If it refuses or <em>declines</em> to become a magnet, +that is magnetic declination; if it is easily made a +magnet, or is <em>inclined</em> to become one, that is magnetic +inclination.'</p></blockquote> + +<p>One greatly regretted that it was necessary to +mark the reply according to its ignorance, and not, +as one would have wished, in proportion to its +ingenuity. Magnetic declination, however, as everybody +knows, measures the deviation of the 'needle' +from the true geographical north and south direction; +the inclination or dip is the angle which a 'needle' +makes with the horizon.</p> + +<p>At one time the only method of watching the +movements of the magnetic needles was by direct +observation, just precisely as it was wont to be in the +case of the barometer and thermometer. But the +same agent that has been called in to help in their +case has enabled the magnets also to give us a direct +and continuous record of their movements. In principle +the arrangement is as follows: A small light +mirror is attached to the magnetic needle, and a +beam of light is arranged to fall upon the mirror, +and is reflected away from it to a drum covered +with sensitive paper. If, then, the needle is perfectly +at rest, a spot of light falls on the drum and blackens +the paper at one particular point. The drum is made +to revolve by clockwork once in twenty-four hours, +and the black dot is therefore lengthened out into +a straight line encircling the drum. If, however, the +needle moves, then the spot of light travels up or +down, as the case may be.</p> + +<p><span class="pagenum"><a name="Page_248" id="Page_248">[248]</a></span></p> + +<p>Now, if we look at one of these sheets of photographic +paper after it has been taken from the drum, +we shall see that the north pole of the magnet has +moved a little, a very little, towards the west in the +early part of the day, say from sunrise to 2 p.m., and +has swung backwards from that hour till about 10 p.m., +remaining fairly quiet during the night. The extent +of this daily swing is but small, but it is greater in +summer than in winter, and it varies also from year +to year.</p> + +<div class="figcenter bord" style="width: 450px;"><a name="int" id="int"></a> +<img src="images/i_248.jpg" width="450" height="334" alt="int" /> +<div class="caption"><p class="center">MAGNETIC PAVILION—INTERIOR.<br /> +(<em>From a photograph by Mr. Lacey.</em>)</p></div> +</div> + +<p>Besides this daily swing, there occasionally happen +what are called 'magnetic storms;' great convulsive +twitchings of the needle, as if some unseen operator<span class="pagenum"><a name="Page_249" id="Page_249">[249]</a></span> +were endeavouring, whilst in a state of intense excitement, +to telegraph a message of vast importance, so +rapid and so sharp are the movements of the needle +to and fro. These great storms are felt, so far as we +know, simultaneously over the whole earth, and the +more characteristic begin with a single sharp twitch +of the needle towards the east.</p> + +<p>Besides the movements of the magnetic needle, +the intensity of the currents of electricity which are +always passing through the crust of the earth are also +determined at Greenwich; but this work has been +rendered practically useless for the last few years by +the construction of the electric railway from Stockwell +to the City. Since it was opened, the photographic +register of earth currents has shown a broad blurring +from the moment of the starting of the first train in +the morning to the stopping of the last train at night. +As an indication of the delicacy of modern instruments, +it may be mentioned that distinct indications +of the current from this railway have been detected +as far off as North Walsham, in Norfolk, a distance +of more than a hundred miles. A further illustration +of the delicacy of the magnetic needles was afforded +shortly after the opening of the railway referred to. +On one occasion the then Superintendent of the +Magnetic Department visited the Generating Station +at Stockwell, and on his return it was noticed +day after day that the traces from the magnets +showed a curious deflection from 9 a.m. to 3 p.m., +the hours of his attendance. This gave rise to some +speculation, as it did not seem possible that the +gentleman could himself have become magnetized.<span class="pagenum"><a name="Page_250" id="Page_250">[250]</a></span> +Eventually, the happy accident of a fine day solved +the mystery. That morning the Superintendent left +his umbrella at home, and the magnets were undisturbed. +The secret was out. The umbrella had +become a permanent magnet, and its presence in the +lobby of the magnetic house had been sufficient to +influence the needles.</p> + +<hr class="chap" /> + +<p><span class="pagenum"><a name="Page_251" id="Page_251">[251]</a></span></p> + + + + +<h2>CHAPTER X</h2> + +<h3>THE HELIOGRAPHIC DEPARTMENT</h3> + + +<p>So far the development of the Observatory had been +along the central line of assistance to navigation. +But the Magnetic Department led on to one which +had but a very secondary connection with it.</p> + +<p>A greatly enhanced interest was given to the +observations of earth magnetism, when it was found +that the intensity and frequency of its disturbances +were in close accord with changes that were in +progress many millions of miles away. That the +surface of the sun was occasionally diversified by the +presence of dark spots, had been known almost from +the first invention of the telescope; but it was not +until the middle of the present century that any +connection was established between these solar +changes and the changes which took place in the +magnetism of the earth. Then two observers, the +one interesting himself entirely with the spots on +the sun, the other as wholly devoted to the study of +the movements of the magnetic needle, independently +found that the particular phenomenon which each +was watching was one which varied in a more or less +regular cycle. And further, when the cycles were<span class="pagenum"><a name="Page_252" id="Page_252">[252]</a></span> +compared, they proved to be the same. Whatever +the secret of the connection, it is now beyond dispute +that as the spots on the sun become more and more +numerous, so the daily swing of the magnetic needle +becomes stronger; and, on the other hand, as the +spots diminish, so the magnetic needle moves more +and more feebly.</p> + +<p>This discovery has given a greatly increased +significance to the study of the earth's magnetism. +The daily swing, the occasional 'storms,' are seen to +be something more than matters of merely local +interest; they have the closest connection with +changes going on in the vast universe beyond; they +have an astronomical importance.</p> + +<p>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 surface; and +here again that invaluable servant of modern science, +photography, was ready to lend its help. Just as, +by the means of photography, the magnets recorded +their own movements, so even more directly the sun +himself makes register of his changes by the same +agency, and gives us at once his portrait and his +autograph.</p> + +<p>This new department was again due to Airy, and +in 1873 the 'Kew' photo-heliograph, which had been +designed by De la Rue for this work, was installed +at Greenwich.</p> + +<div class="figcenter bord" style="width: 600px;"><a name="helio" id="helio"></a> +<img src="images/i_254.jpg" width="600" height="389" alt="helio" /> +<div class="caption"><p class="center">THE DALLMEYER PHOTO-HELIOGRAPH.</p></div> +</div> + +<p>In order to photograph so bright a body as the +sun, it is not in the least necessary to have a very +large telescope. The one in common use at Greenwich +from 1875 to 1897, is only four inches in aperture<span class="pagenum"><a name="Page_253" id="Page_253"> </a><br /><a name="Page_254" id="Page_254"> </a><br /><a name="Page_255" id="Page_255">[255]</a></span> +and even that is usually diminished by a cap to three +inches, and its focal length is but five feet. This is +not very much larger than what is commonly called +a 'student's telescope,' but it is amply sufficient for +its work.</p> + +<p>This 'Dallmeyer' telescope, so called from the +name of its maker, is one of five identical instruments +which were made for use in the observation of the +transit of Venus of 1874, and which, since they are +designed for photographing the sun, are called 'photo-heliographs.'</p> + +<p>The image of the sun in the principal focus of this +telescope is about six-tenths of an inch in diameter; +but a magnifying lens is used, so that the photograph +actually obtained is about eight inches. Even with +this great enlargement, the light of the sun is so +intense that with the slowest photographic plates +that are made the exposure has to be for only a very +small fraction of a second. This is managed by +arranging a very narrow slit in a strip of brass. The +strip is made to run in a groove across the principal +focus. Before the exposure, it is fastened up so as to +cut off all light from entering the camera part of the +telescope. When all is ready, it is released and drawn +down very rapidly by a powerful spring, and the slit, +flying across the image of the sun, gives exposure to +the plate for a very minute fraction of a second—in +midsummer for less than a thousandth of a second.</p> + +<p>Two of these photographs are taken every fine +day at Greenwich; occasionally more, if anything +specially interesting appears to be going on. But in +our cloudy climate at least one day in three gives no<span class="pagenum"><a name="Page_256" id="Page_256">[256]</a></span> +good opportunity for taking photographs of the sun, +and in the winter time long weeks may pass without +a chance. The present Astronomer-Royal, Mr. +Christie, has therefore arranged that photographs +with precisely similar instruments should be taken in +India and in the Mauritius, and these are sent over +to Greenwich as they are required, to fill up the +gaps in the Greenwich series. We have therefore at +Greenwich, from one source or another, practically a +daily record of the state of the sun's surface.</p> + +<p>More recently the 'Dallmeyer' photo-heliograph, +though still retained for occasional use, has been +superseded generally by the 'Thompson'; a photographic +refractor of nine inches aperture, and nearly +nine feet focal length, presented to the Observatory +by Sir Henry Thompson. The image of the sun +obtained after enlargement in the telescope, with this +instrument, is seven and a half inches in diameter. +The 'Thompson' is mounted below the great twenty-six-inch +photographic refractor,—also presented to the +Observatory by Sir Henry Thompson,—in the dome +which crowns the centre of the New Observatory.</p> + +<p>A photograph of the sun taken, it has next to +be measured, the four following particulars being +determined for each spot: First, its distance from +the centre of the image of the sun; next, the angle +between it and the north point; thirdly, the size of +the spot; and fourthly, the size of the umbra of the +spot, that is to say, of its dark central portion. The +size or area of the spot is measured by placing a thin +piece of glass, on which a number of cross-lines have +been ruled one-hundredth of an inch apart, in contact<span class="pagenum"><a name="Page_257" id="Page_257">[257]</a></span> +with the photograph. These cross-lines make up a +number of small squares, each the ten-thousandth +(<small><sup>1</sup>/<sub>10000</sub></small> in.) part of a square inch in area. When the +photograph and the little engraved glass plate are +nearly in contact, the photograph is examined with +a magnifying glass, and the number of little squares +covered by a given spot are counted. It will give +some idea of the vast scale of the sun when it is +stated that a tiny spot, so small that it only just +covers one of these little squares, and which is only +one-millionth of the visible hemisphere of the sun in +area, yet covers in actual extent considerably more +than one million of square miles.</p> + +<p>The dark spots are not the only objects on the +sun's surface. Here and there, and especially near +the edge of the sun, are bright marks, generally in +long branching lines, so bright as to appear bright +even against the dazzling background of the sun itself. +These are called 'faculæ,' and they, like the spots, +have their times of great abundance and of scarcity, +changing on the whole at the same time as the spots.</p> + +<p>After the solar photographs have been measured, +the measures must be 'reduced,' and the positions +of the spots as expressed in longitude and latitude on +the sun computed. There is no difficulty in doing +this, for the position of the sun's equator and poles +have long been known approximately, the sun revolving +on its axis in a little more than twenty-five +days, and carrying of course the spots and faculæ +round with him.</p> + +<p>There are few studies in astronomy more engrossing +than the watch on the growth and changes of the<span class="pagenum"><a name="Page_258" id="Page_258">[258]</a></span> +solar spots. Their strange shapes, their rapid movements, +and striking alterations afford an unfailing +interest. For example, the amazing spectacle is +continually being afforded of a spot, some two, three, +or four hundred millions of square miles in area, +moving over the solar surface at a speed of three +hundred miles an hour, whilst other spots in the same +group are remaining stationary. But a higher interest +attaches to the behaviour of the sun as a whole than +to the changes of any particular single spot; and the +curious fact has been brought to light, that not only +do the spots increase and diminish in a regular cycle +of about eleven years in length, but they also affect +different regions of the sun at different points of the +cycle. At the time when spots are most numerous +and largest, they are found occupying two broad +belts, the one with its centre about 15° north of the +equator, the other about as far south, the equator +itself being very nearly free from them. But as the +spots begin to diminish, so they appear continually +in lower and lower latitudes, until instead of having +two zones of spots there is only one, and this one +lies along the equator. By this time the spots have +become both few and small. The next stage is that +a very few small spots are seen from time to time in +one hemisphere or the other at a great distance from +the equator, much farther than any were seen at the +time of greatest activity. There are then for a little +time three sun-spot belts, but the equatorial one soon +dies out. The two belts in high latitude, on the other +hand, continually increase; but as they increase, so +do they move downwards in latitude, until at length +<span class="pagenum"><a name="Page_259" id="Page_259"> </a><br /><a name="Page_260" id="Page_260"> </a><br /><a name="Page_261" id="Page_261">[261]</a></span>they are again found in about latitude 15° north or +south, when the spots have attained their greatest +development.</p> + +<div class="figcenter bord" style="width: 600px;"><a name="spots" id="spots"></a> +<img src="images/i_259.jpg" width="600" height="353" alt="spots" /> +<div class="caption"><p class="center">PHOTOGRAPH OF A GROUP OF SUN-SPOTS.<br /> +(<em>From a photograph taken at the Royal Observatory, Greenwich, April, 1882, 20 d. 10 h. 6 m.</em>)</p></div> +</div> + +<p>The clearest connection between the magnetic +movements and the sun-spot changes is seen when +we take the mean values of either for considerable +periods of time, as, for instance, year by year. But +occasionally we have much more special instances of +this connection. Some three or four times within the +last twenty years an enormous spot has broken out +on the sun, a spot so vast that worlds as great as our +own could lie in it like peas in a breakfast saucer, +and in each case there has been an immediate and a +threefold answer from the earth. One of the most +remarkable of these occurred in November, 1882. A +great spot was then seen covering an area of more +than three thousand millions of square miles. The +weather in London happened to be somewhat foggy, +and the sun loomed, a dull red ball, through the haze, +a ball it was perfectly easy to look at without specially +shading the eyes. So large a spot under such circumstances +was quite visible to the naked eye, and +it caught the attention of a great number of people, +many of whom knew nothing about the existence of +spots on the sun.</p> + +<p>This great disturbance, evidently something of +the nature of a storm in the solar atmosphere, +stretched over one hundred thousand miles on the +surface of the sun. The disturbance extended +farther still, even to nearly one hundred millions of +miles. For simultaneously with the appearance of +the spot the magnetic needles at Greenwich began<span class="pagenum"><a name="Page_262" id="Page_262">[262]</a></span> +to suffer from a strange excitement, an excitement +which grew from day to day until it had passed +half-way across the sun's disc. As the twitchings +of the magnetic needle increased in frequency and +violence, other symptoms were noticed throughout +the length of the British Isles. Telegraphic communication +was greatly interfered with. The telegraph +lines had other messages to carry more urgent +than those of men. The needles in the telegraph +instruments twitched to and fro. The signal bells +on many of the railway lines were rung, and some +of the operators received shocks from their instruments. +Lastly, on November 17, a superb aurora +was witnessed, the culminating feature of which was +the appearance, at about six o'clock in the evening, +of a mysterious beam of greenish light, in shape +something like a cigar, and many degrees in length, +which rose in the east and crossed the sky at a pace +much quicker than but nearly as even as that of sun, +moon, or stars, till it set in the west two minutes +after its rising.</p> + +<p>So far we have been dealing only with effects. +Their causes still rest hidden from us. There is +clearly a connection between the solar activity as +shown by the spots and the agitation of the magnetic +needles. But many great spots find no answer in +any magnetic vibration, and not a few considerable +magnetic storms occur when we can detect no great +solar changes to correspond.</p> + +<p>Thus even in the simplest case before us we have +still very much to explain. Two far more difficult +problems are still offered us for solution. What is<span class="pagenum"><a name="Page_263" id="Page_263">[263]</a></span> +the cause of these mysterious solar spots? and have +they any traceable connection with the fitful vagaries +of earthly weather? It was early suggested that +probably the first problem might find an answer in +the ever-varying combinations and configurations of +the various planets, and that the sun-spots in their +turn might hold the key of our meteorology. Both +ideas were eagerly followed up—not that there was +much to support either, but because they seemed to +offer the only possible hope of our being able to +foretell the general current of weather change for any +long period in advance. So far, however, the first +idea may be considered as completely discredited. +As to the second, there would appear to be, in the +case of certain great tropical and continental countries +like India, some slight but by no means conclusive +evidence of a connection between the changes in the +annual rainfall and the changes in the spotted surface +of the sun. Dr. Meldrum, the late veteran Director +of the great Meteorological Observatory in Mauritius, +has expressed himself as confident that the years of +most spots are the years of most violent cyclones in +the Indian Ocean. But this is about as far as real +progress has been made, and it may be taken as +certain that many years more of observation will be +required, and the labours of many skilful investigators, +before we can hope to carry much farther our knowledge +as to any connection between storm and sun.</p> + +<p>A further relation of great interest has come to +light within the last few years. The year 1868 +opened a new epoch in the study of eclipses of the +sun. These, perhaps, scarcely lie within the scope<span class="pagenum"><a name="Page_264" id="Page_264">[264]</a></span> +of a book on the Royal Observatory, since Greenwich +has seen but one in all its history. That fell in the +year 1715; for the next it must wait many centuries. +Yet, as the late Astronomer Royal conducted three +expeditions to see total eclipses, and as the present +Astronomer Royal has undertaken a like number, +and members of the staff have been sent on other +occasions, it may not be deemed quite a digression +to refer to one feature which they have brought to +light.</p> + +<p>When the dark body of the moon has entirely +hidden the sun, we have revealed to us, there and +then only, that strange and beautiful surrounding of +the sun which we call the corona. The earlier +observations of the corona seem to reveal it as a +body of the most weird and intricate form, a form +which seemed to change quite lawlessly from one +eclipse to another. But latterly it has been abundantly +clear that the forms which it assumes may be +grouped under a few well-defined types. In 1878 +the corona was of a particularly simple and striking +character. Two great wings shot out east and west +in the direction of the sun's equator; round either +pole was a cluster of beautiful radiating 'plumes.' +It was then recollected that the corona of 1867 had +been of precisely the same character, both years +being years when sun-spots were at their fewest. +The coronæ, on the other hand, seen at times when +sun-spots are more abundant, were of an altogether +different character, the streamers being irregularly +distributed all round the sun. Other types also have +been recognized, and it is perfectly apparent that the<span class="pagenum"><a name="Page_265" id="Page_265">[265]</a></span> +corona changes its shape in close accordance with +the eleven-year period. The eclipses of 1889 and +1900, for example, showed coronæ that bore the very +closest resemblance to those of 1878 and 1866, the +interval of eleven years bringing a return to the same +form.</p> + +<p>The further problem, therefore, now confronts us: +Does the corona produce the sun-spots, or do the +sun-spots produce the corona, or are both the result +of some mysterious magnetic action of the sun, an +action powerful enough on occasion to thrill through +and through this world of ours, ninety-three millions +of miles away?</p> + +<hr class="chap" /> + +<p><span class="pagenum"><a name="Page_266" id="Page_266">[266]</a></span></p> + + + + +<h2>CHAPTER XI</h2> + +<h3>THE SPECTROSCOPIC DEPARTMENT</h3> + + +<p>Another department was set on foot by Airy at the +same time as the Heliographic Department, and in +connection with it; and it is the department which +has the greatest of interest for the general public. +This deals with astronomical physics, or astrophysics, +as it is sometimes more shortly called; the astronomy, +that is, which treats of the constitution and condition +of the heavenly bodies, not with their movements.</p> + +<p>The older astronomy, on the other hand, confined +itself to the movements of the heavens so entirely +that Bessel, the man whose practical genius revolutionized +the science of observation, and whose +influence may be traced throughout in Airy's great +reconstitution of Greenwich Observatory, denied that +anything but the study of the celestial movements +had a right to the title of astronomy at all. Hardly +more than sixty years ago he wrote:</p> + +<blockquote> + +<p>'What astronomy is expected to accomplish is evidently +at all times the same. It may lay down rules by which +the movements of the celestial bodies, as they appear to +us upon the earth, can be computed. All else which we +may learn respecting these bodies, as, for example, their<span class="pagenum"><a name="Page_267" id="Page_267">[267]</a></span> +appearance, and the character of their surfaces, is, indeed, +not undeserving of attention, but possesses no proper astronomical +interest. Whether the mountains of the moon are +arranged in this way or in that is no further an object of +interest to astronomers than is a knowledge of the mountains +of the earth to others. Whether Jupiter appears with dark +stripes upon its surface, or is uniformly illuminated, pertains +as little to the inquiries of the astronomer; and its four +moons are interesting to him only for the motions they +have. To learn so perfectly the motions of the celestial +bodies that for any specified time an accurate computation +of these can be given—that was, and is, the problem which +astronomy has to solve.'</p></blockquote> + +<p>There is a curious irony of progress which seems +to delight in falsifying the predictions of even master +minds as to the limits beyond which it cannot +advance. Bessel laid down his dictum as to the true +subjects of astronomical inquiry, Comte declared that +we could never learn what were the elements of +which the stars were composed, at the very time that +the first steps were being taken towards the creation +of a research which should begin by demonstrating +the existence in the heavenly bodies of the elements +with which we are familiar on the earth, and should +go on to prove itself a true astronomy, even in +Bessel's restricted sense, by supplying the means for +determining motion in a direction which he would +have thought impossible—that is to say, directly to +or from us.</p> + +<p>The years that followed Kirchhoff's application +of the spectroscope to the study of the sun, and his +demonstration that sodium and iron existed in the +solar atmosphere, were crowded with a succession of +brilliant discoveries in the same field. Kirchhoff,<span class="pagenum"><a name="Page_268" id="Page_268">[268]</a></span> +Bunsen, Angström, Thal·n, added element after +element to the list of those recognized in the sun. +Huggins and Miller carried the same research into +a far more difficult field, and showed us the same +elements in the stars. Rutherfurd and Secchi grouped +the stars according to the types of their spectra, and +so laid the foundations of what may be termed stellar +comparative anatomy. Huggins discovered true +gaseous nebulæ, and so revived the nebular theory, +which had been supposed crushed when the great +telescope of Lord Rosse appeared to have resolved +several portions of the Orion nebula into separate +stars. The great riddle of 'new stars'—which still +remains a riddle—was at least attacked, and glowing +hydrogen was seen to be a feature in their constitution. +Glowing hydrogen, again, was, in the observation of +total eclipses, seen to be a principal constituent +of those surroundings of our own sun which we +now call prominences and chromosphere. Then the +method was discovered of observing the prominences +without an eclipse, and they were found to wax and +wane in more or less sympathy with the solar spots. +Sun-spots, planets, comets, meteors, variable stars, all +were studied with the new instrument, and all yielded +to it fresh and valuable, and often unexpected, +information.</p> + +<div class="figcenter bord" style="width: 352px;"><a name="orion" id="orion"></a> +<img src="images/i_269.jpg" width="352" height="600" alt="orion" /> +<div class="caption"><p class="center">THE GREAT NEBULA IN ORION.<br /> +(<em>From a photograph taken at the Royal Observatory Greenwich, +December 1, 1899, with an exposure of 2<small><sup>1</sup>/<sub>4</sub></small> hours.</em>)</p></div> +</div> + +<p>In this activity Greenwich Observatory practically +took no part. Airy, ever mindful of the original +purpose of the Observatory, and deeply imbued with +views similar to those which we have quoted from +Bessel, considered that the new science lay outside +the scope of his duties, until in Mr., now Sir William,<span class="pagenum"><a name="Page_269" id="Page_269"> </a><br /><a name="Page_270" id="Page_270"> </a><br /><a name="Page_271" id="Page_271">[271]</a></span> +Huggins's skilful hands the spectroscope showed itself +not only as a means for determining the condition +and constitution of the stars, but also their movements—until, +in short, it had shown itself as an astronomical +instrument even within Bessel's narrow definition.</p> + +<p>The principle of this inquiry is as follows: If a +source of light is approaching us very rapidly, then +the waves of light coming from it necessarily appear +a little shorter than they really are, or, in other words, +that light appears to be slightly more blue—the blue +waves being shorter than the red—than it really is. +A similar thing with regard to the waves of sound is +often noticed in connection with a railway train. If +an express train, the whistle of which is blowing the +whole time, dashes past us at full speed, there is a +perceptible drop in the note of the whistle after it has +gone by. The sound waves as it was coming were a +little shortened, and the whistle therefore appeared to +have a sharper note than it had in reality. And in +the same way, when it had gone by, the sound waves +were a little lengthened, making the note of the +whistle appear a very little flatter.</p> + +<p>Such a change of colour in a star could never +have been detected without the spectroscope; but +since when light passes through a prism the shorter +waves are refracted more strongly, that is to say, are +more turned out of their course than the longer, the +spectroscope affords us the means of detecting and +measuring this change. Let us suppose that the +lines of hydrogen are recognized in a given star. If +we compare the spectrum of this star with the +spectrum of a tube containing hydrogen and through<span class="pagenum"><a name="Page_272" id="Page_272">[272]</a></span> +which the electric spark is passing, we shall be able +to see whether any particular hydrogen line occupies +the same place as shown by the two spectra. If the +line from the star is a little to the red of the line from +the tube, the star must be receding from us; if to the +blue, approaching us. The amount of displacement +may be measured by a delicate micrometer, and the +rate of motion concluded from it.</p> + +<div class="figcenter bord" style="width: 600px;"><a name="prism" id="prism"></a> +<img src="images/i_273.jpg" width="600" height="389" alt="prism" /> +<div class="caption"><p class="center">THE HALF-PRISM SPECTROSCOPE ON THE SOUTH-EAST EQUATORIAL.</p></div> +</div> + +<p>The principle is clear enough. The actual working +out of the observation was one of very great difficulty. +The movements of the stars towards us, or away from +us, are, in general, extremely slow as compared with +the speed of light itself; and hence the apparent +shift in the position of a line is only perceptible when +a very powerful spectroscope is used. This means +that the feeble light of a star has to be spread out +into a great length of spectrum, and a very powerful +telescope is necessary. The work of observing the +motions of stars in the line of sight was started at +Greenwich in 1875, the 'Great Equatorial' being +devoted to it. This telescope, of 12<small><sup>3</sup>/<sub>4</sub></small> inches aperture, +was not powerful enough to do much more than +afford a general indication of the direction in which +the principal stars were moving, and to confirm in a +general way the inference which various astronomers +had found, from discussing the proper motions of +stars, that the sun and the solar system were moving +towards that part of the heavens where the constellations +Hercules and Lyra are placed. In 1891, +therefore, the work was discontinued, and as already +mentioned, the 12<small><sup>3</sup>/<sub>4</sub></small> telescope by Merz was removed +to make room for the present much larger instrument<span class="pagenum"><a name="Page_273" id="Page_273"> </a><br /><a name="Page_274" id="Page_274"> </a><br /><a name="Page_275" id="Page_275">[275]</a></span> +by Sir Howard Grubb, upon the same mounting. +The new telescope being much larger than the one +for which mounting and observing room were +originally built, it was not possible to put the +spectroscope in the usual position, in the same +straight line as the great telescope. It was therefore +mounted under it, and parallel to it, and the light of +the star was brought into it after two reflections. +The observer therefore stood with his back to the +object and looked down into the spectroscope. It +had, however, become apparent by this time that this +most delicate field of work was one for which photography +possessed several advantages, and as Sir +Henry Thompson had made the munificent gift to +the Observatory of a great photographic equatorial, it +was resolved to devote the 28-inch telescope chiefly +to double-star work, and to transfer the spectroscope +to the 'New Building.'</p> + +<p>The 'New Observatory' in the south ground is +crowned indeed with the dome devoted to the great +Thompson photographic refractor, but this is not its +chief purpose. Its principal floor contains four fine +rooms which are used as 'computing rooms'—for the +office work, that is to say, of the Observatory. Of +these the principal is in the north wing, where the +main entrance is placed, and is occupied by the +Astronomer Royal and the two chief assistants. +The basement contains the libraries and the workshops +of the mechanics and carpenters. The upper floor +will eventually be used for the storage of photographs +and manuscripts, and the terrace roofs of the four +wings will be exceedingly convenient for occasional<span class="pagenum"><a name="Page_276" id="Page_276">[276]</a></span> +observations, as, for example, of meteor showers. +The central dome, which rises high above the level of +the terraces, is the only room in the building devoted +to telescopic work. As in the New Altazimuth +building, a ring of circular lights just below the +coping of the wall recalls the portholes of a ship, and +again reminds us of the connection of the Observatory +with navigation.</p> + +<div class="figcenter bord" style="width: 450px;"><a name="workshop" id="workshop"></a> +<img src="images/i_276.jpg" width="450" height="319" alt="workshop" /> +<div class="caption"><p class="center">THE WORKSHOP.</p></div> +</div> + +<p>Here the spectroscope is now placed, but not, as +it happens, on the Thompson refractor. The equatorial +mounting in this new dome is a modification of +what is usually called the 'German' form of mounting—that +is to say, there is but one pier to support the +telescope, and the telescope rides on one side of the +pier and a counterpoise balances it on the other +<span class="pagenum"><a name="Page_277" id="Page_277"> </a><br /><a name="Page_278" id="Page_278"> </a><br /><a name="Page_279" id="Page_279">[279]</a></span>The 'Great Equatorial,' on the other hand, is an +example of the English mounting, and has two piers, +one north and the other south, whilst the telescope +swings in a frame between them. In the new dome +three telescopes are found rigidly connected with each +other on one side of the pier, the telescopes being (1) +the great Thompson photographic telescope, double +the aperture and double the focal length of the +standard astrographic telescope used for the International +Photographic Survey; (2) the 12<small><sup>3</sup>/<sub>4</sub></small> telescope by +Merz, that used to be in the great South-East dome, +but which is now rigidly connected with the Thompson +refractor as a guide telescope; and (3) a photographic +telescope of 9 inches aperture, already described as +the 'Thompson' photo-heliograph, and used for +photographing the sun or in eclipse expeditions. +The counterpoise to this collection of instruments is +not a mere mass of lead, but a powerful reflector of +30 inches' aperture, and it is to this telescope that the +spectroscope is now attached. At the present time, +however (August, 1900), regular work has not been +commenced with it.</p> + +<div class="figcenter bord" style="width: 449px;"><a name="reflect" id="reflect"></a> +<img src="images/i_278.jpg" width="449" height="600" alt="reflect" /> +<div class="caption"><p class="center">THE 30-INCH REFLECTOR WITH THE NEW SPECTROSCOPE +ATTACHED.</p></div> +</div> + +<p>Beside this attempt to determine the motions of +the stars as they approach us or retreat from us, +on rare occasions the spectroscope has been turned +on the planets. As these shine by reflected light, +their spectra are normally the same as that of the +sun. Mars appeared to the writer, as to Huggins +and others, to show some slight indication of the +presence of water vapour in its atmosphere. Jupiter +and Saturn show that their atmospheres contain some +absorbing vapour unknown to ours. And Uranus<span class="pagenum"><a name="Page_280" id="Page_280">[280]</a></span> +and Neptune, faint and distant as they are, not only +show the same dark band given by the two nearer +planets, but several others. More attractive has been +the examination of the spectra of the brighter comets +that have visited us. The years 1881 and 1882 were +especially rich in these. The two principal comets of +1881 were called after their respective discoverers, +Tebbutt's and Schaeberle's. They were not bright +enough to attract popular attention, though they +could be seen with the naked eye, and both gave +clear indications of the presence of carbon, their +spectra closely resembling that of the blue part of a +gas or candle flame. There was nothing particularly +novel in these observations, since comets usually show +this carbon spectrum, though why they should is still +a matter for inquiry; but the two comets of the +following year were much more interesting. Both +comets came very near indeed to the sun. The earlier +one, called from its discoverer Comet Wells, as it drew +near to the sun, began to grow more and more yellow, +until in the first week of June it looked as full an +orange as even the so-called red planet, Mars. The +spectroscope showed the reason of this at a glance. +The comet had been rich in sodium. So long as it +was far from the sun the sodium made no sign, but as +it came close to it the sodium was turned into glowing +vapour under the fierce solar heat. And as the writer +saw it in the early dawn of June 7, the comet itself +was a disc of much the same colour as Mars, whilst +its spectrum resembled that of a spirit lamp that has +been plentifully fed with carbonate of soda or common +salt. The 'Great Comet' of the autumn of the same<span class="pagenum"><a name="Page_281" id="Page_281">[281]</a></span> +year, and which was so brilliant an object in the early +morning, came yet nearer to the sun, and the heating +process went on further. The sodium lines blazed +up as they had done with Comet Wells, but under the +fiercer stress of heat to which the Great Comet was +subjected, the lines of iron also flashed out, a significant +indication of the tremendous temperature to which it +was exposed.</p> + +<p>There are two other departments of spectroscopic +work which it was attempted for a time to carry on as +part of the Greenwich routine. These were the daily +mapping of the prominences round the sun, and the +detailed examination of the spectra of sun-spots. +Both are almost necessary complements of the work +done in the heliographic department—that is to say, +the work of photographing the appearance of the +sun day by day, and of measuring the positions and +areas of the spots. For the spots afford but one index +out of several, of the changes in the sun's activity. +The prominences afford another, nor can we at the +present moment say authoritatively which is the more +significant. Then again, with regard to the spots +themselves, it is not certain that either their extent +or their changes of appearance are the features which +it is most important for us to study. We want, if +possible, to get down to the soul of the spot, to find +out what makes one spot differ from another; and +here the spectroscope can help us. Great sun-spots +are often connected with violent agitation of the +magnetic needles, and with displays of auroræ. But +they are not always so, and the inquiry, 'What makes +them to differ?' has been made again and again,<span class="pagenum"><a name="Page_282" id="Page_282">[282]</a></span> +without as yet receiving any unmistakable answer. The +great spot of November, 1882, which was connected with +so remarkable an aurora and so violent a magnetic +storm, was as singular in its spectrum as in its earthly +effects. The sun was only seen through much fog, +and the spectrum was therefore very faint, but shooting +up from almost every part of its area, except the +very darkest, were great masses of intensely brilliant +hydrogen, evidently under great pressure. The +sodium lines were extremely broadened, and on +November 20 a broad bright flame of hydrogen was +seen shooting up at an immense speed from one edge +of the nucleus. A similar effect—an outburst of +intensely luminous hydrogen—has often been observed +in spots which have been accompanied by great +magnetic storms; and it may even be that it is this +violent eruption of intensely heated gas which has +the directest connection with the magnetic and +auroral disturbances here upon earth.</p> + +<p>This sun-spot work was not carried on for very +long, as only one assistant could be spared for the +entire solar work of whatever character. Yet in that +time an interesting discovery was made by the writer—namely, +that in the green part of the spectrum of +certain spots a number of broad diffused lines or +narrow bands made their appearance from time to +time, and especially when sun-spots were increasing +in number, or were at their greatest development.</p> + +<p>The prominence work had also to be dropped, +partly for the same reason, but chiefly because the +atmospheric conditions at Greenwich are not suitable +for these delicate astrophysical researches. When<span class="pagenum"><a name="Page_283" id="Page_283">[283]</a></span> +the Observatory was founded 'in the golden days' +of Charles II., Greenwich was a little country town +far enough removed from the great capital, and no +interference from its smoke and dust had to be feared +or was dreamt of. Now the 'great wen,' as Cobbett +called it, has spread far around and beyond it, and +the days when the sky is sufficiently pure round the +sun for successful spectrum work on the spots or +prominences are few indeed.</p> + +<p>Whether in the future it will be thought advisable +for the Royal Observatory to enter into serious +competition in inquiries of this description with the +great 'astrophysical' observatories of the Continent +and of America—Potsdam, Meudon, the Lick, and +the Yerkes—we cannot say. That would involve a +very considerable departure from its original programme, +and probably also a departure from its +original site. For the conditions at Greenwich tend +to become steadily less favourable for such work, and +it would most probably be found that full efficiency +could only be secured by setting up a branch or +branches far from the monster town.</p> + +<p>With the older work it is otherwise. So long as +Greenwich Park and Blackheath are kept—as it is +to be hoped they always will be—sacred from the +invasion of the builder; so long as no new railways +burrow their tunnels in the neighbourhood of the +Observatory, so long the fundamental duties laid +upon Flamsteed, 'of Rectifying the Tables of the +Motions of the Heavens and the Places of the Fixed +Stars,' will be carried out by his successors on +Flamsteed Hill.</p> + +<hr class="chap" /> + +<p><span class="pagenum"><a name="Page_284" id="Page_284">[284]</a></span></p> + + + + +<h2>CHAPTER XII</h2> + +<h3>THE ASTROGRAPHIC DEPARTMENT</h3> + + +<p>The two last departments mentioned, the heliographic +and spectroscopic, lie clearly and unmistakably +outside the terms of the original warrant of the +Observatory, though the progress of science has led +naturally and inevitably to their being included in +the Greenwich programme. But the Astrographic +Department, though it could no more have been +conceived in the days of Charles II. than the +spectroscopic, does come within the terms of the +warrant, and is but an expansion of that work of +'Rectifying the Places of the Fixed Stars,' which +formed part of the programme enjoined upon Flamsteed, +the first Astronomer Royal, at the first foundation +of the Observatory, and which was so diligently +carried out by him, the first Greenwich catalogue, +containing about 3000 stars, being due to his labours.</p> + +<div class="figcenter bord" style="width: 431px;"><a name="plate" id="plate"></a> +<img src="images/i_286.jpg" width="431" height="600" alt="plate" /> +<div class="caption"><p class="center">'CHART PLATE' OF THE PLEIADES.<br /> +(<em>From a photograph taken at the Royal Observatory, Greenwich, with an +exposure of forty minutes.</em>)</p></div> +</div> + +<p>His immediate successors did much less in this +field, though Bradley's observations were published, +long after his death, as a catalogue of 3222 stars, in +some aspects the most important ever issued. Pond, +the sixth Astronomer Royal, restored catalogue-making +to a prominent place in the Greenwich routine,<span class="pagenum"><a name="Page_285" id="Page_285"> </a><br /><a name="Page_286" id="Page_286"> </a><br /><a name="Page_287" id="Page_287">[287]</a></span> +and his precedent is sedulously followed to-day. But +each of these was confined to about 3000 stars. The +necessity has long been felt for a much ampler census, +and Argelander, at the Bonn Observatory, brought +out a catalogue of 324,000 stars north of South +declination 2°, a work which has been completed by +Schönfeld, who carried the census down to South +declination 23°, and by the two great astronomers of +Cordoba, South America, Dr. Gould and Dr. Thome, +by whom it was extended to the South Pole.</p> + +<p>These last three catalogues embrace stars of all +magnitudes down to the 9th or 10th; but certain +astronomers had endeavoured to go much lower, and +to make charts of limited portions of the sky down to +even the 14th magnitude.</p> + +<p>From the very earliest days that men observed +the stars, they could not help noticing that 'one star +differeth from another star in glory,' and consequently +they divided them into six classes, according to their +brightness—classes which are commonly spoken of +now as magnitudes. The ordinary 6th magnitude +star is one which can be clearly seen by average sight +on a good night, and it gives us about one-hundredth +the light of an average 1st magnitude star. Sirius, +the brightest of all the fixed stars, is called a 1st +magnitude star, but is really some six or seven times +as bright as the average. It would take, therefore, +more than two and a half million stars of the 14th +magnitude to give as much light as Sirius.</p> + +<p>It is evident that so searching a census as to +embrace stars of the 14th magnitude would involve +a most gigantic chart. But the work went on in<span class="pagenum"><a name="Page_288" id="Page_288">[288]</a></span> +more than one Observatory for a considerable time, +until at last the observers entered on to the region +of the Milky Way. Here the numbers of the stars +presented to them were so great as to baffle all +ordinary means of observation. What could be +done?</p> + +<p>Just at this time immense interest was caused in +the astronomical world by the appearance of the great +comet of 1882. It was watched and observed and +sketched by countless admirers, but more important +still, it was photographed, and some of its photographs, +taken at the Royal Observatory, Cape of Good Hope, +showed not only the comet with marvellous beauty +of detail, but also thousands of stars, and the success +of these photographs suggested to her Majesty's +Astronomer at the Cape, Dr. Gill, that in photography +we possessed the means for making a complete sky +census even to the 14th magnitude.</p> + +<p>The project was thought over in all its bearings, +and in 1887 a great conference of astronomers at +Paris resolved upon an international scheme for +photographing the entire heavens. The work was to +be divided between eighteen Observatories of different +nationalities. It was to result in a photographic +chart extending to the 14th magnitude, and probably +embracing some forty million stars, and a catalogue +made from measures of the photographs down to +the 11th magnitude, which would probably include +between two and three million stars.</p> + +<div class="figcenter bord" style="width: 437px;"><a name="pendulum" id="pendulum"></a> +<img src="images/i_289.jpg" width="437" height="600" alt="pendulum" /> +<div class="caption"><p class="center">THE CONTROL PENDULUM AND THE BASE OF THE +THOMPSON TELESCOPE.</p></div> +</div> + +<p>The eighteen Observatories all undertook to use +instruments of the same capacity. This was to be +a photographic refractor, with an object-glass of 13<span class="pagenum"><a name="Page_289" id="Page_289">[289]</a><br /><a name="Page_290" id="Page_290">[290]</a></span> +inches aperture and 11 feet focus. At Greenwich +this telescope is mounted equatorially—that is, so as +to follow the stars in their courses—and is mounted +on the top of the pier that once supported Halley's +quadrant. The telescope is driven by a most efficient +clock, whose motive power is a heavy weight. The +rate of the weight in falling is regulated by an +ingenious governor, which brings its speed very nearly +indeed to that of the star, and any little irregularities +in its motion are corrected by the following device. +A seconds pendulum is mounted in a glass case on +the wall of the Observatory, and a needle at the +lower end of the pendulum passes at each swing +through a globule of mercury. On one of the wheels +of the clock are arranged a number of little brass +points, at such intervals apart that the wheel, when +going at the proper rate, takes exactly one second +to move through the distance between any pair. A +little spring is arranged above the wheel, so that +these points touch it as they pass. If this occurs +exactly as the pendulum point passes through the +mercury nothing happens, but if the clock is ever +so little late or early, the electric current from the +pendulum brings into action a second wheel, which +accelerates or retards the driving of the clock, as the +case may be. The total motion, therefore, is most +beautifully even.</p> + +<div class="figcenter bord" style="width: 450px;"><a name="telescope" id="telescope"></a> +<img src="images/i_291.jpg" width="450" height="530" alt="telescope" /> +<div class="caption"><p class="center">THE ASTROGRAPHIC TELESCOPE.<br /> +(<em>Reproduced from 'Engineering' by permission.</em>)</p></div> +</div> + +<p>But even this is not quite sufficient, especially as +the plates for the great chart have to be exposed +for at least forty minutes. Rigidly united with the +13-inch refractor, so that the two look like the two +barrels of a huge double-barrelled gun, is a second<span class="pagenum"><a name="Page_291" id="Page_291">[291]</a></span> +telescope for the use of the observer. In its eyepiece +are fixed two pairs of cross spider lines, +commonly called wires, and a bright star, as near as<span class="pagenum"><a name="Page_292" id="Page_292">[292]</a></span> +possible to the centre of the field to be photographed, +is brought to the junction of two wires. Should the +star appear to move away from the wire, the observer +has but to press one of two buttons on a little plate +which he carries in his hand, and which is connected +by an electric wire with the driving clock, to bring it +back to its position.</p> + +<p>The photographs taken with this instrument are +of two kinds. Those for the great chart have but +a single exposure, but this lasts for forty minutes. +Those for the great catalogue have three exposures +on them, the three images of a star being some +20 seconds of arc apart. These exposures are of +six minutes', three minutes', and twenty seconds' +duration, and the last exposure is given as a test, +since, if stars of the 9th magnitude are visible with +an exposure of twenty seconds, stars of the 11th +magnitude should be visible with three minutes' +exposure.</p> + +<p>Thus it will be seen that in three minutes an +impression is got of many scores of stars, whose +places it would require many hours to determine at +the transit instrument. But the positions of these +stars on the plate still remain to be measured. For +this purpose a net-work of lines, at right angles to +each other, is printed on the photograph before its +development, and, after it has been developed, washed +and dried, the distances of the stars from their +nearest cross-lines are measured in the measuring +machine.</p> + +<div class="figcenter bord" style="width: 358px;"><a name="driving" id="driving"></a> +<img src="images/i_294.jpg" width="358" height="600" alt="driving" /> +<div class="caption"><p class="center">THE DRIVING CLOCK OF THE ASTROGRAPHIC TELESCOPE.<br /> +(<em>Reproduced from 'Engineering' by permission.</em>)</p></div> +</div> + +<p>The measuring machine is constructed to hold +two plates, one half its breadth higher than the other.<span class="pagenum"><a name="Page_293" id="Page_293"> </a><br /><a name="Page_294" id="Page_294">[294]</a><br /><a name="Page_295" id="Page_295">[295]</a></span> +In fact, in each of the two series of photographs the +whole sky is taken twice, but the two photographs +of any region are not simply duplicates of each +other. The centre of each plate is at a corner of +four other plates, and in the micrometer the stars +on the quarter common to two plates are measured +simultaneously.</p> + +<p>In this way will be carried out a great census of +the sky that will exceed Flamsteed's ten thousand +fold. And just as Flamsteed's was but the first of +many similar catalogues, so, no doubt, will this be +followed by others—not superseded, for its value will +increase with its age and the number of those that +follow it, by comparison with which it will prove +an inexhaustible mine of information concerning +the motions of the stars and the structure of the +universe.</p> + +<p>There is a great difference between the work of +the observer with the 'Astrographic Telescope,' as +this great twin photographic instrument is called, +and the work of the transit observer. The latter +sees the star gliding past him, and telegraphs the +instant that the star threads itself on each of the +ten vertical wires in succession. The astrographic +observer, on the other hand, sees his star shining +almost immovably in the centre of his field, threaded +on the two cross wires placed there, for the driving-clock +moves the telescope so as to almost exactly +compensate for the rotation movement of the earth. +The observer's duty in this case is to telegraph to +his driving-clock, when it has in the least come short +of or exceeded its duty, and so to bring back the<span class="pagenum"><a name="Page_296" id="Page_296">[296]</a></span> +'guiding star' to its exact proper place on the cross +wires.</p> + +<p>So far, the work of the Astrographic Department +has been, as mentioned above, a development on an +extraordinary scale, but a development still, of the +original programme of the Observatory. But the +munificent gift of Sir Henry Thompson has put it +within the power of the Astronomer Royal to push +this work of sidereal photography a stage further. +Sir Henry Thompson gave to the Observatory, not +merely the photographic refractor of 9 inches' aperture, +now used for solar photography, and known as +the 'Thompson photo-heliograph,' but also one of 26 +inches' aperture and 22<small><sup>1</sup>/<sub>2</sub></small> feet focal length. This +instrument was specially designed of exactly double +the dimensions of the standard astrographic telescope +used for the International Photographic Survey, the +idea being that, in the case of a field of special interest +and importance, a photograph could be obtained +with the larger instrument on exactly double the +scale given by the smaller. It has rather, however, +found its usefulness in a slightly different field. The +observation of the satellites of Jupiter was suggested +by Galileo as a means of determining the longitude +at sea. As already pointed out, the suggestion did +not prove to be a practical one for that purpose, but +observations of the satellites have been made none +the less with a view simply to improving our knowledge +of their movements, and of the mass of Jupiter. +The utilitarian motive for the work having fallen +through, it has been carried on as a matter of pure +science.</p> + +<p><span class="pagenum"><a name="Page_297" id="Page_297">[297]</a></span></p> + +<p>And the work has not stopped with the satellites +of Jupiter; eight satellites were in due time discovered +to Saturn, four to Uranus, and two to Mars; and +though these could give not the remotest assistance +to navigation, they too have been made the subjects +of observation for precisely the same reason as those +of Jupiter have been.</p> + +<div class="figcenter bord" style="width: 450px;"><a name="thompson" id="thompson"></a> +<img src="images/i_297.jpg" width="450" height="364" alt="thompson" /> +<div class="caption"><p class="center">THE THOMPSON TELESCOPE IN THE NEW DOME.</p></div> +</div> + +<p>In just the same way, when the discovery +of Neptune was followed by that of a solitary +companion to it, this also had to be followed. The +difficulties in the way of observing the fainter of all +these satellites were considerable, and the work has<span class="pagenum"><a name="Page_298" id="Page_298">[298]</a></span> +been mostly confined to two or three observatories +possessing very large telescopes. As the largest +telescope at Greenwich was only 7 inches in aperture +up to 1859, and only 12<small><sup>3</sup>/<sub>4</sub></small> inches up to 1893, it is only +very recently that it has been able to take any very +substantial part in satellite measures. But since the +Thompson photographic telescope was set up, it has +been found that a photograph of Neptune and its +satellite can be taken in considerably less time than +a complete set of direct measures can be made, whilst +the photograph, which can be measured at leisure +during the day, gives distinctly the more accurate +results.</p> + +<p>So, too, the places of the minor planets can be +got more accurately and quickly by means of photographs +with this great telescope than by direct +observation, and photographs of the most interesting +of them all, the little planet Eros, have been very +successfully obtained. So that, though doing +nothing directly to improve the art of navigation, or +to find the longitude at sea, the great photographic +refractor takes its share in the work of 'Rectifying +the Tables of the Planets.'</p> + +<div class="figcenter bord" style="width: 600px;"><a name="neb" id="neb"></a> +<img src="images/i_300.jpg" width="600" height="359" alt="neb" /> +<div class="caption"><p class="center">THE NEBULÆ OF THE PLEIADES.<br /> +(<em>From a photograph taken at the Royal Observatory, Greenwich, December 3, 1899, with an exposure of three hours.</em>)</p></div> +</div> + +<p>The reflector of 30 inches' aperture, which acts +as a counterpoise to the sheaf of telescopes of the +Thompson, is intended for use with the spectroscope, +the quality which mirrors possess of bringing all +rays, whatever their colour, to the same focus being +of great importance for spectroscopic work. But the +experiments which have been made with it in celestial +photography have proved so extremely successful as +to cause the postponement of the recommencement<span class="pagenum"><a name="Page_299" id="Page_299"> </a><br /><a name="Page_300" id="Page_300"> </a><br /><a name="Page_301" id="Page_301">[301]</a></span> +of the spectroscopic researches. Chief amongst these +photographs are some good ones of the moon, and +more recently some exceedingly fine photographs +of the principal nebulæ.</p> + +<p>In no department of astronomy has photography +brought us such striking results as in regard to the +nebulæ. Dr. Roberts' photograph of the great +nebula in Andromeda converted the two or three +meaningless rifts—which some of the best drawings +had shown—into the divisions between concentric +rings; and what had appeared a mere shapeless cloud +was seen to be a vast symmetrical structure, a great +sidereal system in the making. The great nebula in +Orion has grown in successive photographs in detail +and extent, until we have a large part of the constellation +bound together in the convolutions of a +single nebula of the most exquisite detail and most +amazing complexity. The group of the Pleiades has +had a more wonderful record still. Manifestly a +single system even to the naked eye, and showing +some faint indications of nebulosity in the telescope, +the photographs have revealed its principal stars +shining out from nebulous masses, in appearance like +carded wool, and have shown smaller stars threaded +on nebulous lines like pearls upon a string.</p> + +<p>Such photographs are, of course, of no utilitarian +value, and at present they lead us to no definite +scientific conclusions. They lie, therefore, doubly +outside the limits of the purely practical, but they +attract us by their extreme beauty, and by the +amazing difficulty of the problems they suggest. +How are these weird masses of gas retained in such<span class="pagenum"><a name="Page_302" id="Page_302">[302]</a></span> +complex form over distances which must be reckoned +by millions of millions of miles? By what agency +are they made to glow so as to be visible to us here? +What conceivable condition threads together suns on +a line of nebula? What universes are here in the +making, or perhaps it may be falling into ruin and +decay?</p> + +<hr class="chap" /> + +<p><span class="pagenum"><a name="Page_303" id="Page_303">[303]</a></span></p> + + + + +<h2>CHAPTER XIII</h2> + +<h3>THE DOUBLE-STAR DEPARTMENT</h3> + + +<p>The foregoing chapters will have shown that though +the original purpose of the Observatory has always +been kept in view, yet the progress of science has +caused many researches to be undertaken which +overstep its boundaries. Thus in the present transit +room, beside the successive transit instruments we +find upon the wall two long thin tubes, labelled +respectively Alpha Aquilæ and Alpha Cygni. +These were two telescopes set up by Pond for a +special purpose. Dr. Brinkley, Royal Astronomer +for Ireland, had announced that he had found that +several stars shifted their apparent place in the sky +in the course of a year, due to the change in the +position of the earth from which we view them, by an +amount which would show that they were only about +six to nine billions of miles distant from us; or, in +other words, they showed a parallax of from two to +three seconds of arc. Pond was not able to confirm +these parallaxes from his observations, and to decide +the point he set up these two telescopes, the Alpha +Aquilæ telescope being rigidly fixed on the west side +of the pier of Troughton's mural circles; the Alpha<span class="pagenum"><a name="Page_304" id="Page_304">[304]</a></span> +Cygni telescope on another pier, the one which now +forms the base of the pier of the astrographic telescope. +Pond's method was to compare the position +of these two stars with that of a star almost exactly +the same distance from the pole, but at a great +distance from it in time of crossing the meridian; in +other words, of almost the same declination, but +widely different right ascension. The result proved +that Brinkley was wrong, and vindicated the delicacy +and accuracy of Pond's observations.</p> + +<p>These two telescopes, therefore, had their day and +ceased to be. Others have followed them. An +ingenious telescope was set up by Sir George Airy in +order to ascertain if the speed of light were different +when passing through water than when passing +through air. Or, in other words, if the aberration +of light would give the same value as at present if +we observed through water. The water telescope, as +it was called, is kept on the ground floor of the +central octagon of the new observatory. The observations +obtained with it were hardly quite satisfactory, +but gave on the whole a negative result.</p> + +<p>Turning back to the transit room, and leaving it +by the south-west door, we come into the little +passage which leads at the back of Bradley's transit +room into the lower computing room. Just inside +this passage, on the left-hand side, there is a little +room of a most curious shape, the 'reflex zenith +room.' Here is fixed a telescope pointing straight +upwards, the eye-piece being fixed by the side of the +object-glass. The light from a star—the star Gamma +Draconis—which passes exactly over the zenith of<span class="pagenum"><a name="Page_305" id="Page_305">[305]</a></span> +Greenwich, enters the object-glass, passes downwards +to a basin of mercury, and is reflected upwards from +the surface of the mercury to a little prism placed +over the centre of the object-glass, from which it is +reflected again into the eye-piece. By means of this +telescope the distance of the star Gamma Draconis +from the zenith could be measured very exactly, and, +consequently, the changes in the apparent position +of the star due to aberration, parallax, and other +causes could be very exactly followed, and the corrections +to be applied on account of these causes +precisely determined.</p> + +<p>This particular telescope was devised by Airy, and +the observations with it were continued to the end of +his reign. The germ of the idea may be traced back, +however, to the time of Flamsteed, who would seem +to have occasionally observed Gamma Draconis from +the bottom of a deep well; the precise position of the +well is not, however, now known. Later, Bradley set +up his celebrated 12<small><sup>1</sup>/<sub>2</sub></small>-foot zenith sector, still preserved +in the transit room, first at Wanstead and +then at Greenwich, for the determination of the +amount of aberration. Later, a zenith tube by +Troughton, of 25 feet focus, was used by Pond in +conjunction with the mural circle for observations of +Gamma Draconis in order to determine the zenith +point of the latter instrument.</p> + +<p>These telescopes for special purposes have passed +out of use. Observations with the spectroscope have +been suspended for some years. The work of the +Astrographic Department will come to an end, in the +ordinary course of events, when the programme<span class="pagenum"><a name="Page_306" id="Page_306">[306]</a></span> +assigned to Greenwich in the International Scheme +is completed.</p> + +<p>Within the last few years a new department +has come into being at Greenwich—a department +which has been steadily worked at many foreign +public observatories, but only recently here.</p> + +<p>This is the Department of Double-Star Observation. +The first double star, Zeta Ursæ Majoris, was +discovered 250 years ago. Bradley discovered two +exceedingly famous double stars whilst still a young +man observing with his uncle at Wanstead—Gamma +Virginis and Castor. Bradley made also other discoveries +of double stars after his appointment to +Greenwich, and Maskelyne succeeded him in the +same line, but the great foundation of double-star +astronomy was laid by Sir William Herschel.</p> + +<p>At first it was supposed that double stars were +double only in appearance; one star comparatively +near us 'happened' to lie in almost exactly the +same direction as another star much further off. It +was, indeed, in the very expectation that this would +prove to be the case, that the elder Herschel first +took up their study. But he was soon convinced +that many of the objects were true double stars—members +of the same system of which the smaller +revolved round the larger—not merely apparently +double, one star appearing by chance to be close to +another with which it had no connection—but real +double stars. The discovery of these has led to the +establishment of a new department of astronomy, +again scientific rather than utilitarian.</p> + +<div class="figcenter bord" style="width: 600px;"><a name="star" id="star"></a> +<img src="images/i_308.jpg" width="600" height="428" alt="star" /> +<div class="caption"><p class="center">DOUBLE-STAR OBSERVATION WITH THE SOUTH-EAST EQUATORIAL.<br /> +(<em>From a photograph by Mr. Edney.</em>)</p></div> +</div> + +<p>As mentioned above, it is only recently that +<span class="pagenum"><a name="Page_307" id="Page_307"> </a><br /><a name="Page_308" id="Page_308"> </a><br /><a name="Page_309" id="Page_309">[309]</a></span>Greenwich has taken any appreciable part in this +work. Under Airy, the largest equatorial of the +time had been furnished with a good micrometer, +and observations of one or two double stars been +made now and again; but Airy's programme of work +was far too rigid, and kept the staff too closely +engaged for such observations to be anything but +extremely rare. And, indeed, when the micrometers +of the equatorials were brought into use, they were +far more generally devoted to the satellites of Saturn +than to the companions of stars. In the main, double-star +astronomy has been in the hands of amateurs, at +least in England. But the discovery in recent years +of many pairs so close that a telescope of the largest +size is required for their successful observation, has +put an important section of double stars beyond the +reach of most private observers, and therefore the +great telescope at Greenwich is now mainly devoted +to their study. The Astronomer Royal, therefore, +soon after the completion of the great equatorial of +28-inches aperture placed in the south-east dome, +added this work to the Observatory programme.</p> + +<p>The 28-inch equatorial is a remarkable-looking +instrument, its mounting being of an entirely different +kind to that of the other equatorials in the Observatory, +with the solitary exception of the Shuckburgh, +which is set up in a little dome over the chronograph +room. The Shuckburgh was presented to the +Observatory in the year 1811, by Sir G. Shuckburgh. +It was first intended to be mounted as an altazimuth, +but proved to be unsteady in that position, and was +then converted into an equatorial without clockwork,<span class="pagenum"><a name="Page_310" id="Page_310">[310]</a></span> +and mounted in its present position. The position is +about as hopelessly bad a one as a telescope could well +have, completely overshadowed as it is by the trees +and buildings close at hand. The dome is a small +one, and the arrangements for the shutters and for +turning the dome are as bad as they could possibly be. +It has practically been useless for the last forty years.</p> + +<p>Its only interest is that the method of mounting +employed is a small scale model of that of the +great telescope in the S.-E. dome. In the German +or Fraunhofer form of mounting for an equatorial +there is but a single pillar, which carries a comparatively +short polar axis. At the upper end of the +polar axis we find the declination axis, and at one +end of the declination axis is the telescope, whilst at +the other end is a heavy weight to counterpoise it. +The German mounting has the advantage that the +telescope can easily point to the pole of the heavens; +its drawbacks are that, except in certain special forms, +the telescope cannot travel very far when it is on the +same side of the meridian as the star to which it is +pointed, the end of the telescope coming into contact +under such circumstances with the central pier, whilst +the introduction of mere deadweight as the necessary +counterpoise, is not economical. It has been already +pointed out that the present Astronomer Royal has +not only considerably modified the German mounting +in the great collection of telescopes in the Thompson +dome, but has used a powerful reflector as a counterpoise +to the sheaf of refractors at the other end of +the declination axis.</p> + +<p>The English equatorial requires two piers.<span class="pagenum"><a name="Page_311" id="Page_311">[311]</a></span> +Between these two piers is a long polar axis. Both +in the little Shuckburgh and in the great 28-inch +equatorial the frame of the polar axis consists of six +parallel rods disposed in two equilateral triangles, +with their bases parallel to each other, the telescope +swinging in the space between the two bases. The +construction of this form of equatorial, therefore, is +expensive, as it requires two piers. It takes much +more room than the German form, and the telescope +cannot be directed precisely to the pole. But the instrument +is symmetrical, there is no deadweight, and +the telescope can follow a star from rising to setting +without having to be reversed on crossing the meridian.</p> + +<p>The great stability of the English form of mounting, +therefore, commended it very highly to Airy, and +he designed the great Northumberland equatorial of +the Cambridge Observatory on that plan, as well as +one for the Liverpool Observatory at Bidston, and in +1858 the S.-E. equatorial at Greenwich.</p> + +<p>The telescope at first mounted upon it had an +object-glass of 12<small><sup>3</sup>/<sub>4</sub></small> inches' aperture, and 18 feet focal +length. That was dismounted in 1891, and is now +used as the guiding telescope of the Thompson 26-inch +photographic refractor. Its place was taken by an +immensely heavier instrument, the present refractor +of 28 inches' aperture, and 28 feet focal length; and +that this change was effected safely was an eloquent +testimony to the solidity of the original mounting.</p> + +<p>The clock that drives this great instrument, so +that it can follow a star or other celestial object in +its apparent daily motion across the sky, is in the +basement of the S.-E. tower. It is a very simple<span class="pagenum"><a name="Page_312" id="Page_312">[312]</a></span> +looking instrument, a conical pendulum in a glass +case. The pendulum makes a complete revolution +once in two seconds. Below it in a closed case is a +water turbine. A cistern on the roof of the staircase +supplies this turbine with water, having a fall of about +thirty feet. The water rushing out of the arms of the +turbine forces it backward, and the turbine spins +rapidly round, driving a spindle which runs up into +the dome, and gears through one or two intermediate +wheels with the great circle of the telescope; the +extremely rapid rotation of the spindle, four times +in a second, being converted by these intermediate +wheels into the exceedingly slow one of once in +twenty-four hours. Just above the centre of motion +of the turbine is a set of three small wheels, all of +exactly the same size, and of the same number of +teeth. Of these the bottom wheel is horizontal, and +is turned by the turbine. The top wheel is also +horizontal, and is turned by the pendulum. The +third wheel gears into both these, and is vertical. If +the top and bottom wheels are moving exactly at the +same rate, the intermediate wheel simply turns on its +axis, but does not travel; but if the turbine and +pendulum are moving at different rates, then the +vertical wheel is forced to run in one direction or +the other, and, doing so, it opens or closes a throttle +valve, which controls the supply of water to the +turbine, and so speedily brings the turbine into +accord with the pendulum. The control of the +motion of the great telescope is therefore almost as +perfect as that of the astrographic and Thompson +equatorials, though the principle employed is very<span class="pagenum"><a name="Page_313" id="Page_313">[313]</a></span> +different. And the control needs to be perfect, for, +as said above, the great telescope is mostly devoted +to the observation of double stars, and there can be +no greater hindrance to this work than a telescope +which does not move accurately with the star.</p> + +<p>There is a striking contrast between the great +telescope and all the massive machinery for its +direction and movement, and the objects on which +it is directed—two little points of light separated by +a delicate hair of darkness.</p> + +<p>The observation is very unlike those of which we +have hitherto spoken. The object is not to ascertain +the actual position in the sky of the two stars, but +their relative position to each other. A spider's +thread of the finest strands is moved from one star +to the other by turning an exquisitely fine screw; +this enables us to measure their distance apart. +Another spider thread at right angles to the first is +laid through the centres of both stars, and a divided +circle enables us to read the angle which this line +makes to the true east and west direction. Such +observations repeated year after year on many stars +have enabled the orbits of not a few to be laid down +with remarkable precision; and we find that their +movements are completely consistent with the law of +gravitation. Further, just as Neptune was pre-recognized +and discovered from noting the irregularities in +the motion of Uranus, so the discordances in the place +of Sirius led to the belief that it was attracted by a +then unseen companion, whose position with respect to +the brighter star was predicted and afterwards seen.</p> + +<div class="figcenter bord" style="width: 450px;"><a name="shutter" id="shutter"></a> +<img src="images/i_314.jpg" width="450" height="547" alt="shutter" /> +<div class="caption"><p class="center">THE SOUTH-EAST DOME WITH THE SHUTTER OPEN.</p></div> +</div> + +<p>Gravitation thus appears, indeed, to be the Bond<span class="pagenum"><a name="Page_314" id="Page_314">[314]</a></span> +of the Universe, yet it leaves us with several weighty +problems. The observation of the positions of stars +shows that though we call them fixed they really +have motions of their own. Of these motions, a great +part consists of a drift away from one portion of the<span class="pagenum"><a name="Page_315" id="Page_315">[315]</a></span> +heavens towards a point diametrically opposite to it, +a drift such as must be due, not to a true motion of +the individual stars, but to a motion through space +of our sun and its attendant system. The elder +Herschel was the first to discover this mysterious +solar motion. Sir George Airy and Mr. Edwin +Dunkin, for forty-six years a member of the Greenwich +staff, and from 1881-1884 the Chief Assistant, +contributed important determinations of its direction.</p> + +<p>What is the cause of this motion, what is the law +of this motion, is at present beyond our power to +find out. Many years ago a German astronomer +made the random suggestion that possibly we were +revolving in an orbit round the Pleiades as a centre. +The suggestion was entirely baseless, but unfortunately +has found its way into many popular works, +and still sometimes is brought forward as if it were +one of the established truths of astronomy. We can +at present only say that this solar motion is a mystery.</p> + +<p>There is a greater mystery still. The stars have +their own individual motions, and in the case of a +few these are of the most amazing swiftness. The +earth in its motion round the sun travels nearly +nineteen miles in a second, say one thousand times +faster than the quickest rush of an express train. +The sun's rate of motion is probably not quite so +swift, but Arcturus, a sun far larger than our own, +has a pace some twenty times as swift as the orbital +motion of the earth. This is not a motion that we +can conceive of as being brought about by gravitation, +for if there were some unseen body so vast as +to draw Arcturus with this swiftness, other stars too<span class="pagenum"><a name="Page_316" id="Page_316">[316]</a></span> +would be hurtling across the sky as quickly. Such +'runaway stars' afford a problem to which we have +as yet no key, and, like Job of old, we are speechless +when the question comes to us from heaven, 'Canst +thou guide Arcturus and his sons?'</p> + +<p>It will be seen then that, fundamentally, Greenwich +Observatory was founded and has been maintained +for distinctly practical purposes, chiefly for +the improvement of the eminently practical science +of navigation. Other inquiries relating to navigation, +as, for instance, terrestrial magnetism and +meteorology, have been added since. The pursuit +of these objects has of necessity meant that the +Observatory was equipped with powerful and accurate +instruments, and the possession of these again +has led to their use in fields which lay outside +the domain of the purely utilitarian, fields from +which the only harvest that could be reaped was that +of the increase of our knowledge. So we have been +led step by step from the mere desire to help the +mariner to find his way across the trackless ocean, to +the establishment of the secret law which rules the +movements of every body of the universe, till at +length we stand face to face with the mysteries +of vast systems in the making, with the intimate +structure of the stellar universe, with the apparently +aimless, causeless wanderings of vast suns in lightning +flight; with problems that we cannot solve, nor hope +to solve, yet cannot cease from attempting, problems +to which the only answer we can give is the confession +of the magicians of Egypt—'This is the +finger of God.'</p> + +<hr class="chap" /> + +<p><span class="pagenum"><a name="Page_317" id="Page_317">[317]</a></span></p> + + + + +<h2>INDEX</h2> + + +<div> +Aberration of light, <a href="#Page_79">79</a><br /> +<br /> +Adams, John C., his discovery of Neptune, <a href="#Page_217">217</a><br /> +<br /> +Adhara, <a href="#Page_183">183</a><br /> +<br /> +Airy, George Biddell, seventh Astronomer Royal, his early life, <a href="#Page_102">102</a>;<br /> +<span style="margin-left: 1em;">his work at Cambridge, <a href="#Page_105">105</a>;</span><br /> +<span style="margin-left: 1em;">comes to Greenwich, <a href="#Page_105">105</a>;</span><br /> +<span style="margin-left: 1em;">his relations with the Visitors, <a href="#Page_106">106</a>;</span><br /> +<span style="margin-left: 1em;">his autobiography, <a href="#Page_108">108</a>;</span><br /> +<span style="margin-left: 1em;">his character, <a href="#Page_111">111</a>;</span><br /> +<span style="margin-left: 1em;">his labours, <a href="#Page_113">113</a>;</span><br /> +<span style="margin-left: 1em;">attacks on, <a href="#Page_114">114</a>;</span><br /> +<span style="margin-left: 1em;">his distinctions, <a href="#Page_118">118</a>;</span><br /> +<span style="margin-left: 1em;">his resignation, <a href="#Page_119">119</a>;</span><br /> +<span style="margin-left: 1em;">his death, <a href="#Page_120">120</a>;</span><br /> +<span style="margin-left: 1em;">anecdote of, <a href="#Page_142">142</a>;</span><br /> +<span style="margin-left: 1em;">his conduct <em>re</em> Adams, <a href="#Page_217">217</a>;</span><br /> +<span style="margin-left: 1em;">his water telescope, <a href="#Page_304">304</a></span><br /> +<br /> +Alderamin, <a href="#Page_183">183</a><br /> +<br /> +<cite>Almagest</cite>, <a href="#Page_185">185</a><br /> +<br /> +Almanac making, <a href="#Page_29">29</a><br /> +<br /> +Alpha Aquilæ, telescope for, <a href="#Page_303">303</a><br /> +<br /> +—— Cygni, telescope for, <a href="#Page_303">303</a><br /> +<br /> +Altazimuth the, <a href="#Page_114">114</a>;<br /> +<span style="margin-left: 1em;">description and work of, <a href="#Page_207">207</a>, <em>et seq.</em></span><br /> +<br /> +Altazimuth Department, <a href="#Page_205">205</a>, <em>et seq.</em><br /> +<br /> +American time, <a href="#Page_153">153</a><br /> +<br /> +Andromeda nebula, <a href="#Page_301">301</a><br /> +<br /> +Anemometer, use of, <a href="#Page_238">238</a>;<br /> +<span style="margin-left: 1em;">trace of, <a href="#Page_242">242</a></span><br /> +<br /> +Angström, <a href="#Page_268">268</a><br /> +<br /> +Anson, Commodore, <a href="#Page_17">17</a><br /> +<br /> +Apparent time, <a href="#Page_152">152</a><br /> +<br /> +Arcturus, motion of, <a href="#Page_315">315</a><br /> +<br /> +Argelander, star catalogue of, <a href="#Page_287">287</a><br /> +<br /> +<cite>Art of Dialling</cite>, the, <a href="#Page_28">28</a><br /> +<br /> +Assistants, position of the, <a href="#Page_98">98</a>, <a href="#Page_100">100</a>, <a href="#Page_117">117</a>, <a href="#Page_137">137</a><br /> +<br /> +Astrographic chart, <a href="#Page_128">128</a><br /> +<br /> +—— Department, <a href="#Page_284">284</a>, <em>et seq.</em><br /> +<br /> +—— dome, <a href="#Page_128">128</a><br /> +<br /> +—— telescope, <a href="#Page_289">289</a>, <em>et seq.</em><br /> +<br /> +Astronomers Royal, the, <a href="#Page_25">25</a><br /> +<br /> +Astrophysical researches, <a href="#Page_282">282</a><br /> +<br /> +Auroræ, <a href="#Page_281">281</a><br /> +<br /> +Automatic register, <a href="#Page_241">241</a><br /> +<br /> +Axis of the earth, precession of, <a href="#Page_184">184</a><br /> +<br /> +<br /> +Ball, Time, <a href="#Page_162">162</a><br /> +<br /> +Barometer, use of the, <a href="#Page_192">192</a>, <a href="#Page_233">233</a><br /> +<br /> +Battery basement, <a href="#Page_161">161</a><br /> +<br /> +Beaufort, Captain, <a href="#Page_107">107</a><br /> +<br /> +Bessel quoted, <a href="#Page_266">266</a><br /> +<br /> +Betelgeuse, <a href="#Page_184">184</a><br /> +<br /> +Birkenhead, wreck of the, <a href="#Page_180">180</a><br /> +<br /> +Bliss, Nathaniel, fourth Astronomer Royal, history of, <a href="#Page_82">82</a><br /> +<br /> +Bradley, James, third Astronomer Royal, his life, <a href="#Page_73">73</a>;<br /> +<span style="margin-left: 1em;">his ordination, <a href="#Page_74">74</a>;</span><br /> +<span style="margin-left: 1em;">Vicar of Bridstow, <a href="#Page_74">74</a>;</span><br /> +<span style="margin-left: 1em;">Savilian Professor of Astronomy, <a href="#Page_75">75</a>;</span><br /> +<span style="margin-left: 1em;">discovers Aberration of Light, <a href="#Page_75">75</a>, <em>et seq.</em>;</span><br /> +<span style="margin-left: 1em;">becomes Astronomer Royal, <a href="#Page_79">79</a>;</span><br /> +<span style="margin-left: 1em;">labours of, <a href="#Page_80">80</a>;</span><br /> +<span style="margin-left: 1em;">character of, <a href="#Page_81">81</a></span><br /> +<br /> +Bradley's transit room, <a href="#Page_128">128</a><br /> +<br /> +Brinkley, Dr., <a href="#Page_303">303</a><br /> +<br /> +<cite>British Mariner's Guide</cite>, the, <a href="#Page_90">90</a><br /> +<br /> +Bunsen, <a href="#Page_268">268</a><br /> +<br /> +Buys Ballot's law, <a href="#Page_237">237</a><br /> +<br /> +<br /> +Canadian time, <a href="#Page_153">153</a><br /> +<br /> +Castor, <a href="#Page_74">74</a>, <a href="#Page_306">306</a><br /> +<br /> +Catalogues, star, <a href="#Page_182">182</a>, <a href="#Page_185">185</a>, <em>et seq.</em>, <a href="#Page_198">198</a>, <a href="#Page_284">284</a><br /> +<br /> +Cepheus, <a href="#Page_183">183</a><br /> +<br /> +Charles II., warrants of, <a href="#Page_39">39</a>, <a href="#Page_40">40</a><br /> +<br /> +Christie, W. H. M., eighth Astronomer Royal, work of, <a href="#Page_120">120</a><br /> +<br /> +Chromosphere of the sun, <a href="#Page_268">268</a><br /> +<br /> +Chronograph, the, <a href="#Page_157">157</a><br /> +<br /> +—— room, <a href="#Page_126">126</a><br /> +<br /> +Chronometer business, <a href="#Page_101">101</a>, <a href="#Page_107">107</a><br /> +<br /> +Chronometers, Harrison's improvements in, <a href="#Page_165">165</a>, <em>et seq.</em>;<br /> +<span style="margin-left: 1em;">tests of, <a href="#Page_169">169</a>;</span><br /> +<span style="margin-left: 1em;">'runs' of, <a href="#Page_173">173</a>;</span><br /> +<span style="margin-left: 1em;">romance of, <a href="#Page_178">178</a></span><br /> +<br /> +Circle Department, <a href="#Page_181">181</a>, <em>et seq.</em><br /> +<br /> +Clock, Astrographic driving, <a href="#Page_290">290</a>;<br /> +<span style="margin-left: 1em;">driving 28-inch telescope, <a href="#Page_312">312</a></span><br /> +<br /> +Clocks, standard, <a href="#Page_160">160</a><br /> +<br /> +Columbus, aim of voyage of, <a href="#Page_18">18</a><br /> +<br /> +Comet, appearance of a, <a href="#Page_28">28</a><br /> +<br /> +—— Wells, <a href="#Page_280">280</a><br /> +<br /> +Comets, observation of, <a href="#Page_224">224</a>;<br /> +<span style="margin-left: 1em;">spectra of, <a href="#Page_280">280</a></span><br /> +<br /> +Commutator, the, <a href="#Page_162">162</a><br /> +<br /> +Comte, assertion of, <a href="#Page_267">267</a><br /> +<br /> +Constant of Aberration, <a href="#Page_79">79</a><br /> +<br /> +Cook, Captain, work of, <a href="#Page_170">170</a><br /> +<br /> +Copper, use of in Observatory, <a href="#Page_245">245</a><br /> +<br /> +Corona of the sun, <a href="#Page_264">264</a><br /> +<br /> +Crabtree, James, <a href="#Page_31">31</a><br /> +<br /> +<span class="pagenum"><a name="Page_318" id="Page_318">[318]</a></span>Crosthwait, Joseph, <a href="#Page_57">57</a><br /> +<br /> +<br /> +Dallmeyer telescope, <a href="#Page_252">252</a><br /> +<br /> +Declination, <a href="#Page_186">186</a>, <em>et seq.</em><br /> +<br /> +Denebola, <a href="#Page_184">184</a><br /> +<br /> +Distances of planets, <a href="#Page_223">223</a>;<br /> +<span style="margin-left: 1em;">of sun, <a href="#Page_224">224</a></span><br /> +<br /> +Double-Star Department, <a href="#Page_303">303</a>, <em>et seq.</em><br /> +<br /> +Double Stars, <a href="#Page_306">306</a><br /> +<br /> +Dublin time, <a href="#Page_155">155</a><br /> +<br /> +Dunkin, Edwin, <a href="#Page_315">315</a><br /> +<br /> +<br /> +Earth, the, movements of, <a href="#Page_201">201</a><br /> +<br /> +Eclipses of the moon, <a href="#Page_216">216</a>;<br /> +<span style="margin-left: 1em;">of the sun, July 25, 1748...85;</span><br /> +<span style="margin-left: 1em;">other eclipses of the sun, <a href="#Page_263">263</a>, <em>et seq.</em></span><br /> +<br /> +Electric Railway, influence of, <a href="#Page_249">249</a><br /> +<br /> +Equation of Time, the, <a href="#Page_29">29</a>, <a href="#Page_151">151</a><br /> +<br /> +Equatorial, Shuckburgh's, <a href="#Page_101">101</a><br /> +<br /> +——, the great 28-inch, <a href="#Page_221">221</a><br /> +<br /> +——, the Merz, 12<small><sup>3</sup>/<sub>4</sub></small>-inch, <a href="#Page_114">114</a><br /> +<br /> +——, 28-inch, driving clock of, <a href="#Page_309">309</a>;<br /> +<span style="margin-left: 1em;">use of, <a href="#Page_313">313</a></span><br /> +<br /> +——, clock-driven, <a href="#Page_74">74</a><br /> +<br /> +Eros, discovery of, <a href="#Page_223">223</a>;<br /> +<span style="margin-left: 1em;">photographs of, <a href="#Page_298">298</a></span><br /> +<br /> +Errors in observations, noting of, <a href="#Page_199">199</a>, <em>et seq.</em><br /> +<br /> +Evaporation, <a href="#Page_241">241</a><br /> +<br /> +<br /> +Faculæ of the sun, <a href="#Page_257">257</a><br /> +<br /> +Flamsteed, John, his report on Saint-Pierre's proposal, <a href="#Page_23">23</a>, <a href="#Page_32">32</a>;<br /> +<span style="margin-left: 1em;">appointed first Astronomer Royal, <a href="#Page_23">23</a>, <a href="#Page_34">34</a>;</span><br /> +<span style="margin-left: 1em;">his autobiography, <a href="#Page_26">26</a>;</span><br /> +<span style="margin-left: 1em;">his studies, <a href="#Page_29">29</a>;</span><br /> +<span style="margin-left: 1em;">his almanac, <a href="#Page_29">29</a>;</span><br /> +<span style="margin-left: 1em;">sent to London, <a href="#Page_30">30</a>;</span><br /> +<span style="margin-left: 1em;">enters Jesus College, Cambridge, <a href="#Page_31">31</a>;</span><br /> +<span style="margin-left: 1em;">completes his observatory, <a href="#Page_31">31</a>;</span><br /> +<span style="margin-left: 1em;">acquaintance with Newton, <a href="#Page_31">31</a>;</span><br /> +<span style="margin-left: 1em;">takes his degree, <a href="#Page_32">32</a>;</span><br /> +<span style="margin-left: 1em;">his work, <a href="#Page_34">34</a>;</span><br /> +<span style="margin-left: 1em;">warrant for his salary, <a href="#Page_39">39</a>;</span><br /> +<span style="margin-left: 1em;">position of, <a href="#Page_42">42</a>;</span><br /> +<span style="margin-left: 1em;">his ordination, <a href="#Page_45">45</a>;</span><br /> +<span style="margin-left: 1em;">his pupils, <a href="#Page_45">45</a>;</span><br /> +<span style="margin-left: 1em;">his trouble with Newton, <a href="#Page_46">46</a>, <em>et seq.</em>;</span><br /> +<span style="margin-left: 1em;">his catalogue, <a href="#Page_53">53</a>;</span><br /> +<span style="margin-left: 1em;">his letter to Sharp, <a href="#Page_54">54</a>;</span><br /> +<span style="margin-left: 1em;">his death, <a href="#Page_56">56</a>;</span><br /> +<span style="margin-left: 1em;">his labours, <a href="#Page_57">57</a></span><br /> +<br /> +Flamsteed House, <a href="#Page_126">126</a><br /> +<br /> +Fraunhofer mounting, <a href="#Page_310">310</a><br /> +<br /> +French time, <a href="#Page_155">155</a><br /> +<br /> +<br /> +Galileo, his discovery of Jupiter's satellites, <a href="#Page_19">19</a><br /> +<br /> +Gamma Draconis, <a href="#Page_75">75</a>, <a href="#Page_304">304</a><br /> +<br /> +—— Virginis, <a href="#Page_306">306</a><br /> +<br /> +Gascoigne, William, <a href="#Page_31">31</a><br /> +<br /> +Gemma Frisius, plan of, <a href="#Page_22">22</a><br /> +<br /> +George of Denmark, Prince, <a href="#Page_50">50</a><br /> +<br /> +German mounting, <a href="#Page_276">276</a>, <a href="#Page_310">310</a><br /> +<br /> +Gould, Dr., <a href="#Page_287">287</a><br /> +<br /> +Graham, <a href="#Page_166">166</a><br /> +<br /> +Gravitation, the bond of the universe, <a href="#Page_313">313</a><br /> +<br /> +Great comet of 1882, the, <a href="#Page_280">280</a>, <a href="#Page_288">288</a><br /> +<br /> +Greatrackes, Valentine, <a href="#Page_29">29</a><br /> +<br /> +Green, Charles, <a href="#Page_91">91</a><br /> +<br /> +Greenwich time, <a href="#Page_153">153</a>;<br /> +<span style="margin-left: 1em;">distribution of, <a href="#Page_163">163</a></span><br /> +<br /> +<br /> +Halley, Edmund, his life, <a href="#Page_60">60</a>;<br /> +<span style="margin-left: 1em;">his early work, <a href="#Page_60">60</a>;</span><br /> +<span style="margin-left: 1em;">his catalogue of stars, <a href="#Page_63">63</a>;</span><br /> +<span style="margin-left: 1em;">elected F.R.S., <a href="#Page_63">63</a>;</span><br /> +<span style="margin-left: 1em;">his work on Kepler's laws, <a href="#Page_64">64</a>;</span><br /> +<span style="margin-left: 1em;">becomes captain, <a href="#Page_65">65</a>;</span><br /> +<span style="margin-left: 1em;">Savilian Professor of Geometry, <a href="#Page_66">66</a>;</span><br /> +<span style="margin-left: 1em;">Astronomer Royal, <a href="#Page_66">66</a>;</span><br /> +<span style="margin-left: 1em;">observations on saros of the moon, <a href="#Page_67">67</a>;</span><br /> +<span style="margin-left: 1em;">pressed by Newton, <a href="#Page_68">68</a>;</span><br /> +<span style="margin-left: 1em;">his death, <a href="#Page_68">68</a>;</span><br /> +<span style="margin-left: 1em;">his services to science, <a href="#Page_68">68</a>;</span><br /> +<span style="margin-left: 1em;">his pay, <a href="#Page_70">70</a>;</span><br /> +<span style="margin-left: 1em;">nominates his successor, <a href="#Page_73">73</a>;</span><br /> +<span style="margin-left: 1em;">his transit instrument, <a href="#Page_73">73</a></span><br /> +<br /> +Halley's comet, <a href="#Page_225">225</a><br /> +<br /> +Harrison, James, timekeepers of, <a href="#Page_86">86</a>, <a href="#Page_91">91</a>, <a href="#Page_93">93</a>, <a href="#Page_165">165</a><br /> +<br /> +Heineken, Rev. N. S., <a href="#Page_59">59</a><br /> +<br /> +Heineken quadrant, <a href="#Page_59">59</a><br /> +<br /> +Heliographic Department, <a href="#Page_251">251</a>, <em>et seq.</em><br /> +<br /> +Herschel, Caroline, <a href="#Page_57">57</a><br /> +<br /> +Hipparchus, catalogue of, <a href="#Page_185">185</a><br /> +<br /> +Hodgson, Mr., <a href="#Page_50">50</a><br /> +<br /> +Hooke, Robert, <a href="#Page_75">75</a>, <a href="#Page_206">206</a><br /> +<br /> +Horrox, Jeremiah, <a href="#Page_31">31</a><br /> +<br /> +Huggins, Sir W., his use of spectroscope, <a href="#Page_268">268</a><br /> +<br /> +<br /> +Inscription, an, <a href="#Page_126">126</a><br /> +<br /> +International Photographic Survey, <a href="#Page_296">296</a><br /> +<br /> +Ireis, <a href="#Page_224">224</a><br /> +<br /> +Iron quadrant, <a href="#Page_73">73</a><br /> +<br /> +Isobars, <a href="#Page_237">237</a><br /> +<br /> +<br /> +Jupiter, satellites of, <a href="#Page_19">19</a>, <a href="#Page_296">296</a>;<br /> +<span style="margin-left: 1em;">atmosphere of, <a href="#Page_279">279</a></span><br /> +<br /> +<br /> +Keill, John, <a href="#Page_74">74</a><br /> +<br /> +Kendall, Larcum, <a href="#Page_166">166</a><br /> +<br /> +Kepler, laws of, <a href="#Page_64">64</a><br /> +<br /> +Kew, photo-heliograph, the, <a href="#Page_252">252</a><br /> +<br /> +Kinnebrook, David, <a href="#Page_176">176</a><br /> +<br /> +Kirchhoff's use of spectroscope, <a href="#Page_267">267</a><br /> +<br /> +<br /> +Latitude, finding the, <a href="#Page_18">18</a><br /> +<br /> +Ledgers, chronometer, romance of, <a href="#Page_176">176</a><br /> +<br /> +Leverrier, his discovery of Neptune, <a href="#Page_217">217</a><br /> +<br /> +Libraries, <a href="#Page_132">132</a><br /> +<br /> +Linacre, G., <a href="#Page_28">28</a><br /> +<br /> +Lindsay, Thomas, quoted, <a href="#Page_204">204</a><br /> +<br /> +Litchford, W., <a href="#Page_28">28</a><br /> +<br /> +Local apparent time, <a href="#Page_22">22</a><br /> +<br /> +Longitude, finding the, <a href="#Page_18">18</a>;<br /> +<span style="margin-left: 1em;">at sea, problem of, <a href="#Page_86">86</a>;</span><br /> +<span style="margin-left: 1em;">determination of, <a href="#Page_173">173</a></span><br /> +<br /> +Longitude nought, <a href="#Page_148">148</a><br /> +<br /> +Lower computing room, <a href="#Page_128">128</a><br /> +<br /> +Lunars, method of, <a href="#Page_86">86</a><br /> +<br /> +<br /> +Magnetic Department, work of, <a href="#Page_133">133</a>;<br /> +<span style="margin-left: 1em;">description of, <a href="#Page_228">228</a>, <em>et seq.</em></span><br /> +<br /> +Magnetic inclination and declination, <a href="#Page_246">246</a><br /> +<br /> +—— needles, movements of, <a href="#Page_247">247</a>, <a href="#Page_262">262</a><br /> +<br /> +—— observatory, <a href="#Page_132">132</a><br /> +<br /> +—— pavilion, <a href="#Page_245">245</a><br /> +<br /> +—— storms, <a href="#Page_248">248</a>, <a href="#Page_262">262</a><br /> +<br /> +Mars, distance of, <a href="#Page_223">223</a>;<br /> +<span style="margin-left: 1em;">atmosphere of, <a href="#Page_279">279</a>;</span><br /> +<span class="pagenum"><a name="Page_319" id="Page_319">[319]</a></span><span style="margin-left: 1em;">satellites of, <a href="#Page_296">296</a></span><br /> +<br /> +Maskelyne, Nevil, fifth Astronomer Royal, <a href="#Page_85">85</a>;<br /> +<span style="margin-left: 1em;">practical work of, <a href="#Page_86">86</a>;</span><br /> +<span style="margin-left: 1em;">Astronomer Royal, <a href="#Page_91">91</a>;</span><br /> +<span style="margin-left: 1em;">his work, <a href="#Page_92">92</a>;</span><br /> +<span style="margin-left: 1em;">his publications, <a href="#Page_92">92</a>;</span><br /> +<span style="margin-left: 1em;">his observations and work, <a href="#Page_92">92</a>, <em>et seq.</em>;</span><br /> +<span style="margin-left: 1em;">his death, <a href="#Page_94">94</a>;</span><br /> +<span style="margin-left: 1em;">his character, <a href="#Page_97">97</a>;</span><br /> +<span style="margin-left: 1em;">recommends his successor, <a href="#Page_97">97</a>;</span><br /> +<span style="margin-left: 1em;">his mural circle, <a href="#Page_101">101</a></span><br /> +<br /> +Mean solar clock, <a href="#Page_160">160</a><br /> +<br /> +Mean time, <a href="#Page_152">152</a><br /> +<br /> +Meldrum, Dr., on sun spots, <a href="#Page_263">263</a><br /> +<br /> +Meridian, the, <a href="#Page_149">149</a><br /> +<br /> +Merz telescope, <a href="#Page_279">279</a><br /> +<br /> +Meteorological Department, work of, <a href="#Page_133">133</a>;<br /> +<span style="margin-left: 1em;">description of, <a href="#Page_228">228</a>, <em>et seq.</em></span><br /> +<br /> +Micrometers, use of, <a href="#Page_309">309</a><br /> +<br /> +Microscopes, use of, <a href="#Page_188">188</a><br /> +<br /> +Milky Way, <a href="#Page_288">288</a><br /> +<br /> +Miller, Professor, <a href="#Page_268">268</a><br /> +<br /> +Milne, Professor, on earth movements, <a href="#Page_201">201</a><br /> +<br /> +Minor planets, <a href="#Page_222">222</a><br /> +<br /> +Molyneux, Samuel, <a href="#Page_75">75</a><br /> +<br /> +Moon, observation of the, <a href="#Page_212">212</a>, <em>et seq.</em>;<br /> +<span style="margin-left: 1em;">eclipses of, <a href="#Page_266">266</a></span><br /> +<br /> +Moore, Sir Jonas, <a href="#Page_30">30</a>;<br /> +<span style="margin-left: 1em;">death of, <a href="#Page_42">42</a></span><br /> +<br /> +Morin, <a href="#Page_33">33</a><br /> +<br /> +Mounting telescopes, modes of, <a href="#Page_310">310</a><br /> +<br /> +Mudge, Thomas, <a href="#Page_94">94</a><br /> +<br /> +Mural arc, 7-feet, <a href="#Page_46">46</a><br /> +<br /> +Mural circles, <a href="#Page_101">101</a>, <a href="#Page_196">196</a><br /> +<br /> +<br /> +Names of stars, origin of, <a href="#Page_183">183</a><br /> +<br /> +Nares, Sir George, <a href="#Page_170">170</a><br /> +<br /> +<cite>Nautical Almanac</cite>, the, <a href="#Page_22">22</a>, <a href="#Page_23">23</a>, <a href="#Page_92">92</a><br /> +<br /> +Navigation, state of primitive, <a href="#Page_17">17</a><br /> +<br /> +Neptune, discovery of, <a href="#Page_217">217</a>;<br /> +<span style="margin-left: 1em;">atmosphere of, <a href="#Page_280">280</a>;</span><br /> +<span style="margin-left: 1em;">satellite of, <a href="#Page_298">298</a></span><br /> +<br /> +New altazimuth, the, <a href="#Page_132">132</a>, <a href="#Page_210">210</a><br /> +<br /> +New Observatory, the, <a href="#Page_136">136</a>, <a href="#Page_275">275</a><br /> +<br /> +New stars, <a href="#Page_268">268</a><br /> +<br /> +Newcomb, Professor, on growth of Observatory, <a href="#Page_124">124</a>;<br /> +<span style="margin-left: 1em;">on Greenwich observations, <a href="#Page_207">207</a></span><br /> +<br /> +Newton, Sir I., his absent-mindedness, <a href="#Page_31">31</a>;<br /> +<span style="margin-left: 1em;">his trouble with Flamsteed, <a href="#Page_46">46</a>, <em>et seq.</em>;</span><br /> +<span style="margin-left: 1em;">on Kepler's laws, <a href="#Page_65">65</a>;</span><br /> +<span style="margin-left: 1em;">his <cite>Principia</cite>, <a href="#Page_65">65</a>;</span><br /> +<span style="margin-left: 1em;">his pressure on Halley, <a href="#Page_68">68</a>;</span><br /> +<span style="margin-left: 1em;">his discovery of gravitation, <a href="#Page_206">206</a></span><br /> +<br /> +North terrace, the, <a href="#Page_126">126</a><br /> +<br /> +Northumberland equatorial, <a href="#Page_218">218</a><br /> +<br /> +Nutation of the earth, <a href="#Page_80">80</a><br /> +<br /> +<br /> +Observation, modes of, <a href="#Page_156">156</a>, <a href="#Page_176">176</a>, <a href="#Page_188">188</a>;<br /> +<span style="margin-left: 1em;">by reflection, <a href="#Page_196">196</a>;</span><br /> +<span style="margin-left: 1em;">of comets, <a href="#Page_224">224</a></span><br /> +<br /> +Observatory, Greenwich, work of, <a href="#Page_13">13</a>;<br /> +<span style="margin-left: 1em;">foundation of, <a href="#Page_23">23</a>;</span><br /> +<span style="margin-left: 1em;">warrant for building, <a href="#Page_40">40</a>;</span><br /> +<span style="margin-left: 1em;">position of, <a href="#Page_41">41</a>;</span><br /> +<span style="margin-left: 1em;">foundation stone laid, <a href="#Page_42">42</a>;</span><br /> +<span style="margin-left: 1em;">condition of, <a href="#Page_79">79</a>;</span><br /> +<span style="margin-left: 1em;">enlargement of, <a href="#Page_112">112</a>;</span><br /> +<span style="margin-left: 1em;">recent extensions of, <a href="#Page_120">120</a>;</span><br /> +<span style="margin-left: 1em;">description of, <a href="#Page_124">124</a>, <em>et seq.</em>;</span><br /> +<span style="margin-left: 1em;">staff of, <a href="#Page_137">137</a>;</span><br /> +<span style="margin-left: 1em;">work of, <a href="#Page_139">139</a>, <em>et seq.</em>;</span><br /> +<span style="margin-left: 1em;">visitors to, <a href="#Page_175">175</a>;</span><br /> +<span style="margin-left: 1em;">new altazimuth building, <a href="#Page_211">211</a>;</span><br /> +<span style="margin-left: 1em;">magnet house, <a href="#Page_228">228</a>;</span><br /> +<span style="margin-left: 1em;">magnetic pavilion, <a href="#Page_245">245</a>;</span><br /> +<span style="margin-left: 1em;">new Observatory, <a href="#Page_275">275</a>;</span><br /> +<span style="margin-left: 1em;">future of, <a href="#Page_283">283</a>;</span><br /> +<span style="margin-left: 1em;">reflex zenith room, <a href="#Page_304">304</a>;</span><br /> +<span style="margin-left: 1em;">objects of, <a href="#Page_316">316</a></span><br /> +<br /> +Occultations by the moon, <a href="#Page_212">212</a>, <em>et seq.</em><br /> +<br /> +Octagon room, <a href="#Page_125">125</a>, <a href="#Page_238">238</a>, <a href="#Page_242">242</a><br /> +<br /> +Oldenburg, Mr., <a href="#Page_30">30</a><br /> +<br /> +Orion nebula, <a href="#Page_268">268</a>, <a href="#Page_301">301</a><br /> +<br /> +<br /> +Parallax of stars, <a href="#Page_303">303</a><br /> +<br /> +Paramour, the, <a href="#Page_65">65</a><br /> +<br /> +Paris, conference at, <a href="#Page_288">288</a><br /> +<br /> +——, noon at, <a href="#Page_151">151</a><br /> +<br /> +Philip III., offer of, <a href="#Page_19">19</a><br /> +<br /> +Photographic registration, <a href="#Page_244">244</a>, <a href="#Page_247">247</a>, <a href="#Page_252">252</a>, <a href="#Page_255">255</a>;<br /> +<span style="margin-left: 1em;">refractors, <a href="#Page_288">288</a></span><br /> +<br /> +Photographs, star, <a href="#Page_290">290</a><br /> +<br /> +Photo-heliographs, <a href="#Page_252">252</a>, <em>et seq.</em>, <a href="#Page_279">279</a><br /> +<br /> +Piazzi, discovery of, <a href="#Page_222">222</a><br /> +<br /> +Pleiades, the, <a href="#Page_301">301</a><br /> +<br /> +Polar plumes of the corona, <a href="#Page_264">264</a><br /> +<br /> +Polaris, <a href="#Page_188">188</a><br /> +<br /> +Pole-star, variation of, <a href="#Page_184">184</a><br /> +<br /> +Pond, John, sixth Astronomer Royal, his life, <a href="#Page_97">97</a>;<br /> +<span style="margin-left: 1em;">his reign, <a href="#Page_98">98</a>;</span><br /> +<span style="margin-left: 1em;">his salary, <a href="#Page_98">98</a>;</span><br /> +<span style="margin-left: 1em;">his assistants, <a href="#Page_98">98</a>;</span><br /> +<span style="margin-left: 1em;">his observations, <a href="#Page_99">99</a>;</span><br /> +<span style="margin-left: 1em;">censured by Visitors, <a href="#Page_99">99</a>;</span><br /> +<span style="margin-left: 1em;">his observations of stars, <a href="#Page_303">303</a></span><br /> +<br /> +Pound, James, <a href="#Page_73">73</a><br /> +<br /> +Precession of earth's axis, <a href="#Page_184">184</a><br /> +<br /> +<cite>Principia</cite>, publication of, <a href="#Page_65">65</a><br /> +<br /> +Proctor, R. A., attack of, <a href="#Page_116">116</a><br /> +<br /> +Ptolemy, Claudius, catalogue of, <a href="#Page_185">185</a><br /> +<br /> +Publication, the problem of, <a href="#Page_48">48</a>, <a href="#Page_92">92</a><br /> +<br /> +<br /> +Quadrant, Heineken, <a href="#Page_59">59</a><br /> +<br /> +——, the iron, <a href="#Page_73">73</a><br /> +<br /> +<br /> +Railway time, <a href="#Page_152">152</a><br /> +<br /> +Rain gauge, <a href="#Page_238">238</a><br /> +<br /> +Record rooms, <a href="#Page_132">132</a><br /> +<br /> +Reflection, observation by, <a href="#Page_196">196</a><br /> +<br /> +Reflex zenith room, <a href="#Page_304">304</a><br /> +<br /> +—— —— tube, <a href="#Page_131">131</a><br /> +<br /> +Refraction, effects of, <a href="#Page_194">194</a><br /> +<br /> +Right ascension, <a href="#Page_186">186</a>, <em>et seq.</em><br /> +<br /> +Roberts, Dr. Isaac, <a href="#Page_301">301</a><br /> +<br /> +Römer, discovery of, <a href="#Page_78">78</a><br /> +<br /> +Rosse, Lord, <a href="#Page_268">268</a><br /> +<br /> +Royal Society and Flamsteed, <a href="#Page_46">46</a>, <em>et seq.</em><br /> +<br /> +<br /> +Saint-Pierre, Le Sieur de, proposal of, <a href="#Page_23">23</a>, <a href="#Page_32">32</a><br /> +<br /> +Sappho, <a href="#Page_224">224</a><br /> +<br /> +Saros of the moon, <a href="#Page_67">67</a><br /> +<br /> +Satellites, discovery of, <a href="#Page_296">296</a><br /> +<br /> +Saturn, atmosphere of, <a href="#Page_279">279</a>;<br /> +<span style="margin-left: 1em;">satellites of, <a href="#Page_296">296</a></span><br /> +<br /> +Schaeberle's comet, <a href="#Page_280">280</a><br /> +<br /> +Schedar, <a href="#Page_184">184</a><br /> +<br /> +Schiehallion, attraction of, <a href="#Page_94">94</a><br /> +<br /> +Schönfeld, <a href="#Page_287">287</a><br /> +<br /> +Scotchmen, anecdote of, <a href="#Page_146">146</a><br /> +<br /> +Sharp, Abraham, <a href="#Page_46">46</a><br /> +<br /> +Sheepshanks, Rev. James, on Airy, <a href="#Page_107">107</a><br /> +<br /> +Shuckburgh equatorial, <a href="#Page_309">309</a><br /> +<br /> +<span class="pagenum"><a name="Page_320" id="Page_320">[320]</a></span>Sidereal clock, <a href="#Page_160">160</a><br /> +<br /> +Sirius, <a href="#Page_287">287</a><br /> +<br /> +Sloane, Dr., <a href="#Page_50">50</a><br /> +<br /> +'Smith, Mr.,' his chronometer, <a href="#Page_179">179</a><br /> +<br /> +Solar photographs, <a href="#Page_257">257</a><br /> +<br /> +—— storms, <a href="#Page_261">261</a>, <a href="#Page_282">282</a><br /> +<br /> +Sound waves, <a href="#Page_271">271</a><br /> +<br /> +South, Sir James, <a href="#Page_105">105</a>, <a href="#Page_114">114</a><br /> +<br /> +South-east equatorial, the, <a href="#Page_132">132</a>, <a href="#Page_221">221</a><br /> +<br /> +Spectroscope, use of, <a href="#Page_267">267</a><br /> +<br /> +Spectroscopic Department, <a href="#Page_266">266</a>, <em>et seq.</em><br /> +<br /> +Spots, sun, <a href="#Page_251">251</a>, <em>et seq.</em>, <a href="#Page_281">281</a><br /> +<br /> +Staff of Observatory, <a href="#Page_137">137</a>;<br /> +<span style="margin-left: 1em;">work of, <a href="#Page_139">139</a>, <em>et seq.</em></span><br /> +<br /> +Standard time, <a href="#Page_21">21</a><br /> +<br /> +Stars, observations of, <a href="#Page_156">156</a>, <a href="#Page_176">176</a>, <a href="#Page_188">188</a>;<br /> +<span style="margin-left: 1em;">origin of names of, <a href="#Page_183">183</a>;</span><br /> +<span style="margin-left: 1em;">movements of, <a href="#Page_187">187</a>;</span><br /> +<span style="margin-left: 1em;">catalogues of, <a href="#Page_198">198</a>, <a href="#Page_284">284</a>, <em>et seq.</em>;</span><br /> +<span style="margin-left: 1em;">composition of, <a href="#Page_268">268</a>, <em>et seq.</em>;</span><br /> +<span style="margin-left: 1em;">colour of, <a href="#Page_271">271</a>;</span><br /> +<span style="margin-left: 1em;">classes of, <a href="#Page_287">287</a>;</span><br /> +<span style="margin-left: 1em;">census of, <a href="#Page_287">287</a>;</span><br /> +<span style="margin-left: 1em;">photographs of, <a href="#Page_288">288</a>, <em>et seq.</em>;</span><br /> +<span style="margin-left: 1em;">motions of, <a href="#Page_303">303</a>, <a href="#Page_315">315</a></span><br /> +<br /> +Story, Mr. A. M., <a href="#Page_97">97</a><br /> +<br /> +Sun, distance of the, <a href="#Page_74">74</a>, <a href="#Page_224">224</a>;<br /> +<span style="margin-left: 1em;">spots on, <a href="#Page_251">251</a>, <em>et seq.</em>, <a href="#Page_281">281</a>;</span><br /> +<span style="margin-left: 1em;">eclipses of, <a href="#Page_263">263</a>, <em>et seq.</em>;</span><br /> +<span style="margin-left: 1em;">chromosphere of, <a href="#Page_268">268</a>;</span><br /> +<span style="margin-left: 1em;">motions of, <a href="#Page_315">315</a></span><br /> +<br /> +Sunshine recorder, <a href="#Page_238">238</a><br /> +<br /> +Swiss time, <a href="#Page_155">155</a><br /> +<br /> +<br /> +Tebb, Mr. W., <a href="#Page_58">58</a><br /> +<br /> +Tebbutt's comet, <a href="#Page_280">280</a><br /> +<br /> +Telescope, the great transit, <a href="#Page_156">156</a><br /> +<br /> +——, 28-inch, <a href="#Page_275">275</a><br /> +<br /> +——, astrographic, <a href="#Page_289">289</a><br /> +<br /> +——, Shuckburgh, <a href="#Page_309">309</a><br /> +<br /> +——, Thompson, <a href="#Page_256">256</a>, <a href="#Page_279">279</a>, <a href="#Page_296">296</a><br /> +<br /> +Thalèn, <a href="#Page_268">268</a><br /> +<br /> +Thermometer, use of, <a href="#Page_192">192</a>, <a href="#Page_234">234</a><br /> +<br /> +Thome, Dr., <a href="#Page_287">287</a><br /> +<br /> +Thompson photo-heliograph, <a href="#Page_256">256</a>, <a href="#Page_279">279</a>, <a href="#Page_296">296</a><br /> +<br /> +Time ball, <a href="#Page_162">162</a><br /> +<br /> +—— Department, the, <a href="#Page_146">146</a>, <em>et seq.</em><br /> +<br /> +—— desk, <a href="#Page_161">161</a><br /> +<br /> +——, foreign, <a href="#Page_153">153</a><br /> +<br /> +—— signals, <a href="#Page_162">162</a><br /> +<br /> +—— standard, <a href="#Page_21">21</a><br /> +<br /> +Transit, Halley's, <a href="#Page_73">73</a><br /> +<br /> +Transit circle, the, <a href="#Page_114">114</a>;<br /> +<span style="margin-left: 1em;">mode of observation with, <a href="#Page_188">188</a>, <em>et seq.</em></span><br /> +<br /> +Transit circle, Troughton's, <a href="#Page_98">98</a><br /> +<br /> +—— Department, <a href="#Page_181">181</a>, <em>et seq.</em><br /> +<br /> +—— observations, number of, <a href="#Page_140">140</a><br /> +<br /> +—— pavilion, <a href="#Page_126">126</a>, <a href="#Page_175">175</a><br /> +<br /> +—— room, <a href="#Page_128">128</a>, <a href="#Page_147">147</a><br /> +<br /> +Troughton's transit circle, <a href="#Page_98">98</a><br /> +<br /> +<br /> +Uranus, discovery of, <a href="#Page_217">217</a>;<br /> +<span style="margin-left: 1em;">atmosphere of, <a href="#Page_279">279</a>;</span><br /> +<span style="margin-left: 1em;">satellites of, <a href="#Page_296">296</a></span><br /> +<br /> +<br /> +Vanes, use of, <a href="#Page_238">238</a><br /> +<br /> +Venus, distance of, <a href="#Page_223">223</a><br /> +<br /> +Victoria, <a href="#Page_224">224</a><br /> +<br /> +Visitors, the Board of, <a href="#Page_53">53</a>;<br /> +<span style="margin-left: 1em;">censures Pond, <a href="#Page_99">99</a>;</span><br /> +<span style="margin-left: 1em;">work of, <a href="#Page_106">106</a>;</span><br /> +<span style="margin-left: 1em;">constitution of, <a href="#Page_144">144</a></span><br /> +<br /> +Visitors to Observatory, <a href="#Page_175">175</a><br /> +<br /> +<br /> +Warrant for Flamsteed's salary, <a href="#Page_39">39</a><br /> +<br /> +Water telescope, <a href="#Page_304">304</a><br /> +<br /> +Weather predictions, <a href="#Page_229">229</a>, <em>et seq.</em><br /> +<br /> +Winds, study of, <a href="#Page_237">237</a><br /> +<br /> +Witt, Herr, discovery of, <a href="#Page_223">223</a><br /> +<br /> +Working Catalogue, the, <a href="#Page_142">142</a><br /> +<br /> +<br /> +Zenith sector, <a href="#Page_82">82</a>, <a href="#Page_305">305</a><br /> +<br /> +—— tube, <a href="#Page_75">75</a>, <a href="#Page_305">305</a><br /> +<br /> +Zeta Ursæ Majoris, <a href="#Page_306">306</a><br /> +<br /> +Zubeneschamal, <a href="#Page_184">184</a><br /> +</div> + +<hr class="chap" /> +<p> </p> + + +<p class="center space-above"> +LONDON: PRINTED BY WILLIAM CLOWES AND SONS, LIMITED,<br /> +STAMFORD STREET AND CHARING CROSS. +</p> + + +<hr class="chap" /> +<div class="footnotes"><h3>FOOTNOTES:</h3> + +<div class="footnote"> + +<p><a name="Footnote_1_1" id="Footnote_1_1"></a><a href="#FNanchor_1_1"><span class="label">[1]</span></a> Abraham Sharp had been with Flamsteed earlier than +this—in 1684 and 1685.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_2_2" id="Footnote_2_2"></a><a href="#FNanchor_2_2"><span class="label">[2]</span></a> Sir Isaac Newton.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_3_3" id="Footnote_3_3"></a><a href="#FNanchor_3_3"><span class="label">[3]</span></a> The second circle was intended for the Cape Observatory, +but Pond obtained leave to retain it. In 1851 it was transferred +to the Observatory of Queen's College, Belfast.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_4_4" id="Footnote_4_4"></a><a href="#FNanchor_4_4"><span class="label">[4]</span></a> Mr. Thomas Lindsay, <cite>Transactions of the Astronomical +and Physical Society of Toronto</cite>, 1899, p. 17.</p></div> + +<div class="footnote"> + +<p><a name="Footnote_5_5" id="Footnote_5_5"></a><a href="#FNanchor_5_5"><span class="label">[5]</span></a> From Sir John Herschel's address to the British Association, +September 10, 1846, thirteen days before Galle's first observation +of the planet.</p></div></div> +<p> </p> +<p> </p> + + +<div class="tn"><h3>Transcriber's note:</h3> + +<p>Minor typographical errors have been corrected without +note. Irregularities and inconsistencies in the text have been retained as printed.</p> + +<p>The illustrations have been moved so that they do not break up paragraphs, thus the page number of the illustration might not match the page number in the List of Illustrations.</p> + +<p>Mismatched quotation marks were not corrected if it was not clear +where the missing quotation mark should be placed.</p> + +<p>Missing page numbers are page numbers that were not shown +in the original text.</p> +</div> + +<p> </p> +<p> </p> +<div>*** END OF THE PROJECT GUTENBERG EBOOK 44167 ***</div> +</body> +</html> diff --git a/44167-h/images/coverpage.jpg b/44167-h/images/coverpage.jpg Binary files differnew file mode 100644 index 0000000..659ad21 --- /dev/null +++ b/44167-h/images/coverpage.jpg diff --git a/44167-h/images/i_002.jpg b/44167-h/images/i_002.jpg Binary files differnew file mode 100644 index 0000000..518811b --- /dev/null +++ b/44167-h/images/i_002.jpg diff --git a/44167-h/images/i_007.jpg 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