ASTRONOMY 
 
 LIBRARY LIBRARY 
 
 UNIVERSITY OF CALIFORNIA, 
 
 Class 
 
CELESTIAL OBJECTS 
 
H> 
 
 HE 
 
 JNlVERSfTY 
 
 ASTRONOMY 
 LIBRARY 
 
C/W". Smart & Son. Leamington. Spa.Pholo. 
 
 7. 
 
CELESTIAL OBJECTS 
 
 FOR COMMON TELESCOPES 
 
 BY 
 
 THE REV. T. W. WEBB, M.A., F.K.A.S. 
 
 VICAB OF HABDWICK, HEBEFOBDSHIBB 
 
 NEW IMPRESSION 
 
 BEING A REPRINT OF THE FIFTH EDITION, REVISED AND 
 GREATLY ENLARGED (IN 1893) 
 
 BY itEV. T. E. ESP1N, M.A., F.K.A.S. 
 /R?^V 
 
 THE \ 
 
 IN TWO VOLUMES 
 
 VOL. I. 
 
 LONGMANS, GKEEN, AND CO. 
 
 39 PATERNOSTER ROW, LONDON 
 
 NEW YORK AND BOMBAY 
 
 1904 
 
 All right* reserved 
 
Xv\ 
 
 ASTRONOMY 
 LIBRARY 
 
 Many things, deemed invisible' tu secondary instruments, are plain 
 enough to one who ' knows bow to see tbeni ' SMYTH 
 
 \\ ben an object is once discovered by a superior power, an inferior 
 one will suffice to see it afterwards SIK W. HKKSCHBL 
 
 Inertia mors est j bilosopbiae vivamus nos et exerceamur 
 
 KEPLER 
 
 Pulchra sunt omnia faciente Te, et ecoe Tu inenarrabiliter pulchrior, 
 qni fecisti omnia S. AUGUSTINE 
 
 Sic enim magnalia sapientise sute decoravit Is, qui est ante speculum 
 ct usque in sseculuui ; nihil redundat, nibil deficit, nee locus est censura? 
 cujusquaiu. Quam desiderabilia opera ejua !***** et quis saturabitur 
 videns gloriam eoruui? - KEFLER. 
 
INTRODUCTION. 
 
 THE intention of the following treatise is to furnish 
 the possessors of ordinary telescopes with plain 
 directions for their use, and a list of objects for their 
 advantageous employment. 
 
 None but an eye-witness of the wonder and glory 
 of the heavens can thoroughly understand how much 
 they lose by description, or how inadequate an idea of 
 them can be gathered in the usual mode, from books 
 and lectures. It is but the narrative of the traveller 
 instead of the direct impression of the scene. To do 
 justice to this noble science, to appreciate as we ought 
 the magnificent testimony which it bears to the 
 eternal Power and Godhead of Him ' Who by His 
 excellent wisdom made the heavens/ we must study 
 it, as much as may be, not with the eyes of others, 
 but with our own. 
 
 This, however, is no easy matter: nor is the want 
 of a telescope the only difficulty. Instruments quite 
 sufficient for the student's purpose are far less expen- 
 sive than formerly ; a trifling outlay will often procure 
 VOL. L k 
 
 551)25 
 
vi INTRODUCTION. 
 
 them, of excellent quality, at second-hand ; and many 
 are only waiting to be called into action. But a 
 serious obstacle remains to the inexperienced possessor. 
 How is he to use his telescope in a really improving 
 way ? What is he to look for ? And how is he to 
 look for it? For want of an answer many a good 
 instrument is employed in a desultory and unin- 
 structive manner, or consigned to dust and inactivity. 
 
 Materials for his guidance exist, indeed, in pro- 
 fusion, but some of them are difficult of access ; some 3 
 not easy of interpretation; some, fragmentary and 
 incomplete: and the student would find it a dis- 
 couraging task to reduce them into a serviceable form. 
 This, then, is what has been attempted for him in 
 the following pages, by one who, during many years, 
 would have rejoiced to avail himself of some such 
 assistance, if he had known where to meet with it, 
 and who does not know where it is to be met with, 
 in a convenient shape, to the present day. 1 
 
 For the more advanced observer, the ' Cycle of 
 Celestial Objects/ published in 1844 by Captain, now 
 Vice-Admiral Smyth, will be found a treasury of 
 varied information, and of the highest value as the 
 companion of a first-rate telescope : but its very 
 superiority, to say nothing of its bulk and cost, 
 renders it more suitable for his purpose, than for 
 those humble beginnings which are now in view. It 
 
 1 The original edition was published in 1859. 
 
INTRODUCTION, vii 
 
 has, however, been of the most essential service in 
 the preparation of the present undertaking, which 
 without it would, in all probability, never have seen 
 the light, and which, as far as the sidereal portion is 
 concerned, is based upon it as the standard authority. 
 
 Nothing would have been easier than, on so fertile 
 a subject, to have expanded this treatise to a much 
 larger bulk : but it would thus, in some measure, have 
 defeated its own object. In order therefore to reduce 
 the size of the volume, without omitting such details 
 as may seem to be required by the present state of 
 Astronomy, the reader will have to excuse a condensed 
 mode of expression, the result of necessity rather than 
 of choice ; and, as considerable pains have been taken 
 in the verification of facts, a general list of authorities 
 will supersede references at the foot of the page. 1 
 
 Limited in extent, imperfect in execution, and in 
 parts only suggestive in character, this little book 
 may perhaps serve as a foundation on which students 
 of astronomy may raise the superstructure of their 
 own experience ; and in that case the author's inten- 
 tion will be fulfilled. He will be especially gratified, 
 if his endeavour to remove some difficulties may tend 
 to increase the number of those who ' consider the 
 heavens/ For he is convinced that in such a personal 
 examination of their wonders will be found an 
 
 1 Omitted in the present edition, as its bulk would have boon con- 
 siderably increased, with little correspondent advantage. 
 
vill INTRODUCTION. 
 
 interesting and delightful pursuit, diversifying agree- 
 ably and instructively the leisure hour, and capable 
 of a truly valuable application, as leading to the most 
 impressive thoughts of the littleness of man, and of 
 the unspeakable greatness and glory of the CREATOR. 
 To such a study, the impressive words of the late 
 Sir K. H. Inglis may be most suitably applied : ' Every 
 advance in our knowledge of the natural world will, 
 if rightly directed by the spirit of. true humility, and 
 with a prayer for GOD'S blessing, advance us in our 
 knowledge of Himself, and will prepare us to receive 
 His revelation of His Will with profounder reverence.' 1 
 
 1 Report of British Association, 1847. 
 
ADVERTISEMENT to the FIFTH EDITION. 
 
 BEFOKE commencing the work of editing a new 
 edition of ' Celestial Objects/ by the courtesy of 
 the editor of the English Mechanic, a request for 
 suggestions from amateurs was made in the columns 
 of that paper. The Astronomical and Physical Society 
 of Toronto appointed a Special Committee to draw 
 up a note of any improvements that might be made. 
 From these sources much valuable information was 
 derived, and in the following pages the suggestions 
 have been adopted as far as possible. The enormous 
 increase in the number of telescopes and observers 
 has led to the publication, in the last twelve years, 
 of innumerable observations in every branch of 
 Practical Astronomy, and has made it impossible for 
 any observer to follow up all the various branches of 
 Planetary and Stellar Astronomy. It seemed best, 
 therefore, to seek the help of specialists, and in the 
 following pages the additional matter has been 
 contributed by Miss Brown for the Sun, Mr. T. G. 
 Elger for the Moon, Mr. A. Stanley Williams for 
 
X ADVERTISEMENT TO THE FIFTH EDITION. 
 
 Mercury, Venus, Mars, Rev. W. R Waugh for Jupiter, 
 Rev. A. Freeman for Saturn, Mr. W. F. Denning for 
 Comets. Mr. Denning has also kindly contributed a 
 chapter on Meteorites. For this kind help and assist- 
 ance my sincere thanks are due. 
 
 The original text has been left unaltered as 
 far as possible, and the new matter added in foot- 
 notes. Since Parts I. and II. are used mainly for 
 reference, they have been placed in a volume by 
 themselves, while Part III., which would naturally be 
 in constant use in the Observatory, forms a volume 
 by itself. For Yolume II. I am entirely responsible, 
 and it has been re-written. The catalogue of Struve 
 has been used as a basis, instead of the 'Celestial 
 Cycle/ as the latter work has been republished by 
 Mr. Chambers, and has thus become generally available. 
 In selecting new objects it was thought best to go 
 down to a certain limiting magnitude. After careful 
 consideration, and consultation with those eminently 
 fitted to give an opinion, it was determined to insert 
 all double stars where the primary was above 
 mag. 6*5, and the distances less than 20". The double 
 stars in the old edition have been retained, with the 
 exception of one or two very wide pairs from Struve's 
 Appendix. It is thus hoped that the requirements of 
 telescopes of all sizes will have been met. ' 
 
 The objects have been arranged in order of R.A. 
 in each constellation, saving thereby the fifty pages 
 
ADVERTISEMENT TO THE FIFTH EDITION. xi 
 
 of Appendix II. in the fourth edition. The KA. has 
 been given to a decimal of a minute at the earnest 
 request of various observers, but with no idea of 
 attempting greater accuracy than in former editions. 
 Professors Burnham, Hall, Perrotin, Schiaparelli, 
 Messrs. Maw and Tarrant have kindly furnished me 
 with their double star measures, and where any 
 motion was mentioned in the last edition the later 
 measures from their lists have been added. While, 
 however, of some stars there are many measures, 
 others have rarely been observed since Dembouski's 
 remeasurement of the double stars of Struve. Mr. 
 Tarrant is at present engaged in the systematic work 
 of remeasuring all Struve's stars, and this will be 
 a valuable addition to our knowledge of Celestial 
 Motions. Some measures are my own, but want 
 of experience and suitable apparatus have caused 
 them to be few and incomplete. The latest orbits of 
 Binaries have been furnished me by Mr. Gore. 
 
 Under the heading of 'Stars with Remarkable 
 Spectra' will be found the most interesting stars of 
 the III, IV, and Y types, and all the variable stars at 
 present known. These have been taken from the 
 new edition of Birmingham's 'Red Stars/ and from 
 material kindly placed at my disposal by Professor 
 Pickering. This list has been made as complete as 
 possible, since so many of III and IV type stars are 
 variable, and work on stellar variation offers' one of 
 
xii ADVERTISEMENT TO THE FIFTH EDITION. 
 
 the most promising fields to the amateur. The 
 periods, etc., of the variable stars are taken from 
 Chandler's or Gore's catalogue. 
 
 Some additional matter will be found under 
 Nebulae and Clusters ; but, as a rule, it was felt that 
 the fourth edition was fairly complete in this respect, 
 and that the former objects are more suited for the 
 photographic plate than the eye. Some slight additions 
 have been made to the Southern Objects, but the 
 completion of this part must be left till a large 
 telescope has been erected in the south. Besides the 
 help already acknowledged, my thanks are due to Mr. 
 Mee, Mr. Knott, Captain Noble, Mr. Wesley, for 
 valuable assistance, and to Mr. Ranyard for the 
 engravings of "The Hercules Cluster/ etc. Mr. 
 Sadler has added various notes throughout the work. 
 
 In response to a generally expressed wish, two 
 notes have been inserted at the end of Part I. on 
 Celestial Photography and on the Spectroscope as 
 applied to the Telescope. The only omission of any 
 importance is the list of transits of strange bodies 
 over the Sun's disc, the general consensus of opinion 
 being against their retention. 
 
T. W. WEBB.A REMINISCENCE. 
 
 THOMAS WILLIAM WEBB was born Dec. 14, 1807, and 
 was the only son of a clergyman, the Rev. John Webb. 
 His mother died when he was still a child, and he 
 was educated by his father. From very early years 
 he showed a remarkable taste for experimental science. 
 In 1826 he entered at Magdalen Hall, Oxford, and in 
 1829 he took a second class in Mathematics. In the 
 same year he was ordained in Hereford Cathedral, 
 and in 1 843 he married Henrietta Montague, daughter 
 of Mr. Arthur Wyatt of Troy House, Monmouth. In 
 1852 he was appointed to the living of Hardwick. 
 In 1882 he was made one of the Prebendaries of 
 Hereford Cathedral. On Sept. 7, 1884, Mrs. Webb 
 died from apoplexy, a terrible blow to him, but borne 
 with that patient resignation and perfect faith which 
 was one of the marked features in his character. 
 From this time his health gradually failed, and he 
 died May 19, I885. 1 
 
 1 These particulars are taken from M.N. of the E.A.S., vol. xlvi.; 
 eee also a memoir in Mee's ' Observational Astronomy.' 
 
xiv T. W. WEBB. A REMINISCENCE. 
 
 His first telescope was a fluid achromatic, which 
 was replaced by a refractor of 3^ in., of 5 -ft. focal 
 length, by Tully ; in 1859 he obtained a 5^-in., of /-ft. 
 focal length, by Alvan Clark. In 1864 he was using 
 an 8-in. silver on glass reflector of 6-ft. focus by 
 With, and was engaged in trying this side by side 
 with the Alvan Clark Refractor. From 1866 to his 
 last observation (1885, March 19) he used a 9j-in. 
 silver on glass reflector, by With. This was mounted 
 equatorially on a Berthon stand with rough circles, 
 and in spite of several attempted improvements, the 
 positions obtained with it were never satisfactory. 
 The telescope was placed in a little observatory made 
 of wood and canvas, and stood a few yards SE. of 
 the vicarage front door. Mr. Webb left behind him 
 four large notebooks filled with observations, solar, 
 lunar, planetary, and stellar. The observations are 
 interspread with numerous exquisite drawings. The 
 manuscript observations are a model of neatness, 
 patience, and care. The stellar and nebula observa- 
 tions amount to 3463. Each page has a red line 
 ruled for a margin, and each observation is prefixed 
 with a number, entered in the margin. The rough 
 notes were made at the telescope, prefaced by the 
 state of the air, the powers used, etc., and written out 
 in full next day. The earliest recorded manuscript 
 observation is one on Jupiter, Dec. 2, 1834. From 
 1847 to 1856 Mr. Webb was engaged in observing the 
 
T. W. WEBB. A REMINISCENCE. XV 
 
 objects in the Bedford Cycle with the 3 1 7 -, and in 
 1859 he published the first edition of 'Celestial 
 Objects.' In later years, besides work in connection 
 with the four editions of his book, he gave considerable 
 time to the observation of Red Stars for the first 
 edition of Birmingham's Red Star Catalogue. Mr. 
 Webb discovered a considerable number of new ones, 
 and amongst them he detected, on Christmas Day, 
 1869, the variable S Orionis, which was also the last 
 star he observed, 1885, March 19. His sight, although 
 latterly slightly astigmatic, was remarkably good, 
 especially for planetary detail. A curious instance of 
 difference of vision was well illustrated one superb 
 evening, when Mr. Webb and the writer were observing 
 Saturn with the 9^ -in. reflector at Hard wick. Mr. 
 Webb saw distinctly the division in the outer ring 
 which the writer could not see a trace of, while the 
 writer picked up a faint point of light, which after- 
 wards turned out to be Enceladus, which Mr. Webb 
 could not see. 
 
 Mr. Webb was a father to all amateur astronomers, 
 and the post brought an appalling amount of corre- 
 spondence from them to Hardwick. All were care- 
 fully, kindly, and encouragingly answered in letters 
 charming alike for their elegant writing, and the 
 extraordinary amount of learning, and originality, 
 and witticism. Mr. Webb's versatility was one of 
 the features that struck every one who knew him 
 
XVI T. W. WEBB. A KEMINISCENCB. 
 
 intimately. Not only did he conduct researches into 
 each branch of Astronomy with untiring patience, 
 but he painted and sketched admirably, as did also 
 Mrs. Webb. Like Mr. Birmingham, he was fond 
 of music, and the talents he displayed in completing 
 his father's work, ' The Civil War in Herefordshire/ 
 showed an antiquarian of no mean order. Every- 
 thing, too, in Nature had a charm for him, and the 
 amount of knowledge and powers of observation in 
 this respect were well known to any one who had 
 the privilege of a country walk with him. Setting 
 out early in the afternoon, with a knapsack laden 
 with all kinds of little comforts for the sick, he 
 would walk with vigorous stride up the hills to see 
 some distant parishioner, and converse all the way, 
 handling the most difficult topics with keen logical 
 ability, at the same time with most unassuming 
 humility, and deference to the thoughts of others. 
 And then, when the cottage was reached, there was no 
 mistaking the warmth of welcome and the smile of 
 pleasure with which he was received. And there he 
 would sit, the children gathering round him, and 
 talk to his people of their everyday life, and local 
 matters, making himself one of themselves, and 
 imparting the sunshine of his life to theirs. 
 
 So passed his life at Hardwick a life of continuous 
 work, seeking neither offices in societies or Church 
 preferment, but working for work's sake, and that 
 
T. W, WEBB. A REMINISCENCE. xvii 
 
 from the highest motives, as is well shown by an 
 extract from his observation-book, with which these 
 few lines may well conclude. It well summarizes 
 his motives, and shows his guiding principle in life. 
 It runs : 
 
 ' Gratias D. 0. M. refero, qui servo suo indignissimo 
 per tot annos benignissime concesserit, ut opera Ejus 
 mirifica cum tanta voluptate contemplatus essem. 
 Quamobrem verba illustrissimi Kepleri mihimet 
 assumo, dicendo, " Quis saturabitur videns gloriam 
 eorum ? Qui lumine naturse desiderium in nobis 
 promoves luminis gratise, ut per id transferas nos in 
 lumen glorise, gratias ago Tibi, Creator, Domine, quia 
 delectasti me in factura Tua, et in operibus manuum 
 Tuarum exultavi " Amen.' 
 
CONTENTS. 
 
 INTRODUCTION 
 
 ADVERTISEMENT TO THE FIFTH EDITION 
 T. W. WEBB A REMINISCENCE . 
 
 f 4OE 
 V 
 
 ix 
 xiii 
 
 PART I. THE INSTRUMENT AND THE OBSERVER. 
 
 THE TELESCOPE . . . I 
 THE MODE OF OBSERVATION 10 
 NOTE I. ON CELESTIAL PHO- 
 TOGRAPHY . . 19 
 
 NOTE II. ON THE SPECTRO- 
 SCOPE APPLIED TO THE 
 
 TELESCOPE ... 22 
 
 PART II. THE SOLAR SYSTEM. 
 
 THE SUN . . . 
 
 MERCURY. . . . 
 VENUS .... 
 THE MOON 
 
 INDEX TO THE MAP OF THE 
 MOON .... 
 
 APPENDIX I. ADDITIONAL ! 
 II. BOOKS OF HE 
 
 25 
 
 MARS . . 
 
 . 150 
 
 47 
 
 JUPITER . 
 
 , 163 
 
 5i 
 
 SATURN . . . 
 
 . 188 
 
 66 
 
 URANUS AND NEPTUNE 
 
 . 204 
 
 
 COMETS . . . 
 
 . 205 
 
 40 
 
 METEORS . . , 
 
 . 222 
 
 )TES 
 REN< 
 
 
 . 2 3 I 
 
 PLATES. 
 
 PHOTOGRAPH OF KEV. T. W. WEBB . 
 MAP OF MOON .... 
 CHART OF MARS ... 
 
 To face Title-page 
 66 
 158 
 
4 
 
 OF THF 
 
 ( UNIVERSITY 1 
 V or / 
 
 XC4MrOR*\>^ 
 
 ^ - i: J^^""^ 
 
 PART L 
 
 THE INSTRUMENT AD THE OBSERVE K. 
 
 multiscium et quovis sceptro pretiosius Perspicillum ! an, qui te dextra 
 tenet, ille non rex, non dominus constituatur operum Dei? Vere tu 
 
 Quod supra caput est, magnos cum motibus orbes 
 Subjicis ingenio. KKPLEK. 
 
 THE TELESCOPE. 
 
 ALTHOUGH the professed design of this volume is to provide 
 a list of objects for common telescopes, it may not be out of 
 place to premise a few remarks upon the instruments so 
 designated. 
 
 By * common telescopes ' are here intended such as are 
 most frequently met with in private hands; achromatics 
 with apertures l of 3 to 5 inches ; or reflectors of somewhat 
 larger diameter, but, in consequence of the loss of light in 
 reflection, not greater brightness. 2 The original observations 
 
 1 'Aperture' always means the clear space which receives the 
 light of the object; the diameter of the object-glass in acbroniatics, 
 or the large speculum in reflectors, exclusive of its setting. 
 
 2 Maskelyne estimated the apertures of metallic reflectors and 
 achromatics of equal brightness as 8 to 5. Dawes gives this value 
 for Gregorians, but like Herschel II. rates Newtonians as 7 to 5. 
 Arago strangely asserted that no light was lost in achromatics; but 
 
 VOL. I. B 
 
2 THE INSTRUMENT AND THE OBSERVER. 
 
 In the following pages were chiefly made with such an 
 instrument an achromatic by the younger Tulley, 5^ feet 
 in focal length, 1 with an aperture of 3^ inches, and of fair 
 defining quality ; smaller instruments of course will do less, 
 especially with faint objects, but are often very perfect and 
 distinct : and even diminutive glasses, if good, are not to be 
 despised ; they will show something never seen without them. 
 I have a little hand telescope, 22^ inches long when fully 
 drawn out, with an object-glass of about 14 inches focus, and 
 i|~inch aperture : this, with an astronomical eye-piece, will 
 show the existence of the solar spots, the mountains in the 
 Moon, Jupiter's satellites, and Saturn's ring. Achromatics 
 of larger dimensions have become much less expensive than 
 formerly, and silvered specula of very considerable size are 
 now comparatively common ; even for these it is hoped that 
 this treatise, embodying some of the results of the finest 
 instruments, may not be found an inadequate companion as 
 far as it goes. 
 
 In judging of a telescope, we must not be led by appear- 
 ances. Inferior articles may be showily got up, and the 
 outside must go for nothing. Nor is the clearness of the 
 glass, or the polish of the mirror, any sign of excellence : these 
 
 the effects of absorption and reflection are so considerable, that with 
 very large apertures the advantage of ike achromatic disappears. 
 The silver- on-glass specula, invented by Foucault and Steinheil, but 
 perfected in England, take their place betAveeu the metal Newtonian 
 and the achromatic, approaching more nearly to the latter, especially 
 when the plane mirror is replaced by a prism (which, however, does 
 not always conduce to critical definition). Buffham assigns equal 
 light to silvered Newtonians of 9, 6|, and 4^, and achromatic^ of 
 8, 5f, and 4 inches respectively. Sa finds 6|-in. silv. refl. equal to 
 6-in. achr. 
 
 1 The focal length is measured from the object glass, or speculum, 
 to the spot where the rays cross and form a picture of the sun or any 
 celestial body. 
 
THE TELESCOPE. 3 
 
 may exist with bad * figure ' (i.e. irregular curvature), or bad 
 combination of curves, and the inevitable consequence, bad 
 performance. We need not regard bubbles, sand-holes, 
 scratches, in object-glass or speculum ; they merely obstruct 
 a very little light. Actual performance is the only adequate 
 test. The image should be neat and well-defined with the 
 highest power, and should come in and out of focus sharply ; 
 that is, become indistinct by a very slight motion on either 
 side of it. A proper test-object must be chosen ; the Moon 
 is too easy : Venus too severe except for first-rate glasses ; 
 large stars have too much glare ; Jupiter or Saturn are far 
 better ; a close double star is best of all for an experienced 
 eye ; but for general purposes a moderate-sized star will 
 suffice ; its image, in focus, with the highest power, should 
 be a very small disc, almost a point, accurately round, with- 
 out ' wings,' or rays, or mistiness, or false images, or append- 
 ages, except one or two narrow rings of light, regularly 
 circular, and concentric with the image ; l and in an uniformly 
 dark field ; a slight displacement of the focus either way 
 should enlarge the disc into a luminous circle. If this circle 
 is irregular in outline, or much brighter or fainter towards 
 the centre, 2 or much better defined on one side of the focus 
 
 1 The real diameter of a star in the telescope would be incon- 
 ceivably small. The apparent or 'spurious' disc, and rings, result 
 from the undulatory nature of light. They seem, however, to be 
 somewhat affected by atmospheric causes. Herschel II. speaks of 
 nights of extraordinary distinctness, in which 'the rings are but 
 traces of rings, all their light being absorbed into the discs.' I have 
 entered 1852, March 23, as 'a very fine night, though the rings and 
 appendages around the brighter stars were rather troublesome ; ' 
 1852, April i, 'an exceedingly fine night at first, with scarcely a 
 trace of rings or appendages.' See also the star 70 Ophiuchi, in the 
 following catalogue. 
 
 2 The small mirror in a reflector causes a central darkness out of 
 the focus, which should be nearly the same on either side of it. 
 
4 THE INSTRUMENT AND THE OBSERVER. 
 
 than the other, the telescope may be serviceable, but is not 
 of high excellence. The chances are many, however, against 
 any given night being fine enough for such a purpose, and a 
 fair judgment may be made by day from the figures on a 
 watch-face, or a minute white circle 011 a black ground, or 
 the image of the sun on a thermometer bulb, placed as far 
 off as possible. An achromatic, notwithstanding the deriva- 
 tion of its name, will show colour under high powers where 
 there is much contrast of light and darkness. This ' out- 
 standing ' or uncorrected colour results from the want of a 
 perfect balance between the optical properties of the two 
 kinds of glass of which the object-glass is constructed : it 
 cannot be entirely remedied, but it ought not to be obtrusive. 
 la the best instruments it forms a fringe of violet or blue 
 round luminous objects in focus under high powers, especially 
 Venus in a dark sky. A red or yellow border would be 
 bad; but before condemning an instrument from such a 
 cause, several eye-pieces should be tried, as the fault might 
 lie there, and be easily and cheaply remedied. Reflectors 
 are delightfully exempt from this defect ; and as now made 
 with specula of silvered glass, well deserve, from their com- 
 parative cheapness, combined with admirable defining power, 
 to regain much of the preference which has of late years been 
 accorded to achromatics. The horizontal view of objects at 
 all altitudes in a Newtonian reflector with rotating tube is ex- 
 tremely pleasant, when a little experience has been gained in 
 finding and following : the same advantage, however, attends 
 the use of a diagonal eye-piece with the achromatic, but with 
 loss of light. The chief disadvantage of reflectors is the greater 
 aperture, and consequently greater atmospheric disturbance, 
 corresponding with the same amount of light : and the occa- 
 sional renewal of the film causes a little expense or trouble. 
 The eye-piece, or ocular, is only a kind of microscope, 
 
THE TELESCOPE. 5 
 
 magnifying the image formed in the focus of tho object-glass 
 or speculum. The s ; ze of this image being in proportion to 
 its distance from the glass or mirror which forms it, the 
 power of the same eye-pieco in different telescopes varies as 
 the focal length. Hence the disadvantage of a short tele- 
 scope; to get high powers, we must employ minute and 
 deeply-curved lenses, which are much less pleasant in use ; 
 with a telescope twice as long, half the curvature in the eye- 
 piece produces an equal power. The magnified focal image, 
 as in the camera, is always inverted, and so in the astro- 
 nomical eye-piece it remains. 1 For terrestrial purposes it is 
 erected by two additional lenses ; but a loss of light is thus 
 incurred, and as the inversion of celestial objects is unimpor- 
 tant, erecting eye-pieces (always the longest of a set) should 
 never be employed for astronomy ; the eye soon becomes 
 accustomed to the inverted picture, and the hand to the 
 reversed motion in following the object. The lateral vision 
 in the Newtonian reflector interposes another difficulty, 
 easily mastered, however, by practice, and by attention to 
 the direction of motion through the field. A multitude of 
 eye-pieces is needless, but three at least are desirable ; ono 
 with low power and large field, for extended groups of stars, 
 nebulm, and cornets, supplying also, if necessary, the place of 
 a ' finder ' for deeper magnifiers ; a stronger one for general 
 purposes, especially the moon and planets ; and a third, as 
 powerful as the telescope will bear, for minuter objects, 
 especially double stars. A greater number of eye-pieces 
 admits, however, of what is often important an adaptation 
 of the power to the brightness of the object. Ordinary 
 
 1 It is erect in the Galilean eye-pieco and the Gregorian reflector. 
 But the use of the former is almost confined to opera-classes, as its 
 field \\ith high powers is exceedingly small; and the latter, an 
 inferior construction, is now little employed. 
 
6 THE INSTRUMENT AND THE OBSERVER. 
 
 astronomical eye-pieces are shorter in proportion to their 
 power. It is a better plan to change them by means of a 
 short tube, or * adapter,' than by a screw ; in which case they 
 are more liable to be dropped and injured. The power may 
 bo much increased by unscrewing and taking away the 
 'field-lens' that farthest from the eye; but the centre of 
 the field only will be distinct. The highest powers of large 
 telescopes are sometimes made thus, with single lenses for 
 the advantage of light; but the lens is then turned the 
 other way, convex towards the eye, as it gives sharper vision. 
 Sir W. Herschel used the double convex form, as having 
 shallower curves. The common kind, with two lenses, 
 having the flat side of each next the eye, is called the 
 Huygenian or negative eye-piece : the positive or Ramsden 
 eye-piece has a flatter field, but is not, like the other, 
 achromatic. The interposition of a combination called a 
 Barlow lens raises the power with little loss of light ; and as 
 one may be made to suit all the eye-pieces, it doubles the set 
 at a small expense. Browning's achromatic eye-piece, and 
 Home and Thornthwaite's aplanatic, and the Kellner con- 
 struction (for large fields) are all excellent in their way. 
 The brightness of the field varies inversely as the square of 
 the power: and hence minute stars are commonly more 
 visible with deep eye-pieces ; the reverse, however, for some 
 unknown reason, sometimes occurs. 
 
 If the power of our oculars has not been engraved upon 
 them, 1 we may get a fair approximation to it by viewing an 
 equally divided scale at a distance (for low powers, a brick 
 
 1 These figures are not, however, always to be depended upon, 
 and must be wrong if the eye-piece was made for an instrument of a 
 different focal length. The celebrated Short exaggerated the powers 
 of his reflectors : and those of the great achromatics of Dorput and 
 Berlin were found by Struve and Encke to be overrated. 
 
THE TELESCOPE. 7 
 
 wall will answer) with one eye through the telescope, and 
 with the other alongside of it, and noting how many 
 unmagnified divisions are covered by a single magnified 
 image. Or, better still, we may have recourse to the Berthou 
 Power-gauge, a little apparatus, the simple, efficient, and 
 inexpensive character of which entitles it to very warm 
 commendation. 1 
 
 The test of excellence in separating power has been fixed 
 by Dawes at the quotient, expressed in seconds, of 4-56 
 divided by aperture in inches. Thus a lo-inch object-glass 
 or speculum ought to separate double stars at o"*456 of 
 distance between their centres. This value practically 
 concurs with those given by Dallmeyer and Alvan Clark. 
 Reflectors somewhat surpass achromatics in this respect, as 
 theoretically they ought to do : but they are apt to be more 
 troubled by rings and flare, and scattered light. The best 
 telescopes of either kind will bear a power of 100 per inch 
 of aperture on stars: for planets, or the moon, half that 
 power will usually more than suffice. 
 
 An object-glass of inferior definition may sometimes be 
 improved by stopping out defects, or contracting the aper- 
 ture. Streaks or specks of unequal density are very in- 
 jurious : they may be detected by turning the telescope to a 
 bright light, taking out the eye-piece, and placing the eye 
 in the focus ; every irregularity will then be visible in the 
 illumination which overspreads the object-glass ; and, if of 
 small extent, may be stopped out by a bit of sticking-plaster. 
 If the performance is not thus improved, try a contracted 
 aperture : make a cap of pasteboard fitting over the object- 
 glass like the usual brass cap, but with a circular opening a 
 little less than the clear aperture ; if the indistinctness is 
 
 1 See English Mechanic March 5, 19, April 9, 1880, respecting 
 au excellent method of employing it. 
 
THE INSTRUMENT AND THE OBSERVER. 
 
 thus diminished, but not removed, try several discs of paste- 
 board placed successively within this cap, with progressively 
 contracted openings, till distinct vision is obtained ; there 
 we must stop, or valuable light will be lost. An excentric 
 opening in the pasteboard disc may sometimes be serviceable, 
 being turned round the axis so as to expose different parts 
 of the glass or mirror, till the best effect is produced : in 
 other cases, a central pasteboard disc, supported by narrow 
 arms from the sides, and leaving an open ring of light all 
 round, may be tried. But for comets or nebulae, it will be 
 best to restore the original aperture, as with faint and ill- 
 defined objects light is more essential than distinctness. The 
 centring of a reflector is more liable to derangement than 
 that of an achromatic ; it is, however, easily rectified by the 
 cautious use of the screws which are provided for the purpose. 
 When in correct adjustment, the eye-piece being removed, 
 a dark spot will be seen in the centre of the small mirror, 
 which is the image of that mirror reflected by the large 
 speculum: in proportion as it deviates from a central position, 
 the adjustment is incomplete, and the performance defective. 
 
 The definition of reflectors may often be greatly improved 
 by the use of a tube perforated with large and numerous 
 openings ; it is also desirable, where practicable, to interpose 
 between the observer and the instrument, in cold weather, a 
 moveable screen of felt or some non-conducting material. 
 
 A good stand is essential : if unsteady, it will spoil the 
 most distinct performance ; if awkward, it will annoy the 
 observer ; if limited in range, it may disappoint him at some 
 interesting juncture. It may be well left to a respectable 
 optician ; but where expense is a serious consideration, a 
 little mechanical ingenuity and knowledge of such contri- 
 vances will devise one which will answer sufficiently. The 
 old arrangement, with a vertical and horizontal, or ' altitude 
 
THE TELESCOPE. 9 
 
 and azimuth ' motion, is simple and manageable : the equa- 
 torial form, which makes the telescope revolve on an axis 
 parallel to that of the earth, has great advantages, in follow- 
 ing the object by a single motion, and where the expense 
 of divided circles and spirit-levels is admissible, in finding 
 planets and bright stars by day, and identifying minute 
 objects by night: but, to do its work, it must be placed 
 accurately in the meridian, and out of that position has little 
 superiority. The reflector, too, must rotate in a cradle, or the 
 ocular will assume very awkward inclinations. In any case, 
 if the stand is to be movable, let it be strong enough for 
 steadiness without being too heavy for portability. 1 
 
 A sidereal clock is often considered a necessary adjunct 
 to an equatorial mounting, in order to find objects invisible 
 to the naked eye. But it may be dispensed with by the 
 following method of ' differentiation ' in all cases, excepting 
 during the brief season of twilight, when neither sun nor 
 stars can be employed. Write down the difference of Eight 
 Ascension (taking particular notice whether additive or sub- 
 tractive) between the required and some known object the 
 sun by day, a neighbouring bright star by night. Seek the 
 known object by the finder, and place it in the centre of 
 your largest field : clamp the R. A. circle : set the telescope 
 to the declination of the object sought, and clamp it there : 
 unclamp in R. A. and move the telescope E. or W. as the 
 case requires, to the value of the ascertained difference in 
 
 1 A very cheap equatorial stand is described in Astron. Register, 
 No. 14, vol. ii. Franks observes that a common equatorial mounting 
 may be made very efficient at a trifling expense by the addition of 
 plain metal circles, on which slips of paper graduated with pen and 
 ink are fastened by glue dissolved in strong acetic acid, and after- 
 wards sized and varnished. A good pillar-stand may be made by 
 letting a 4-inch iron pipe deep into the ground, in which a small 
 tiible with a long foot revolves. 
 
10 THE INSTRUMENT AND THE OBSERVER. 
 
 R. A. and the object will be found in the field, somewhat "W. 
 of the centre, by a distance dependent on the duration of 
 the process. 
 
 An observatory is by no means essential, but it would 
 be difficult to over-estimate its advantage in point of comfort 
 as well as economy of time. It used to be an expensive 
 luxury; but a very simple and cheap 'telescope-house,' 
 combining shelter with open-air freedom, to the great merit 
 of which I can bear full testimony, has been devised by 
 the Rev. E. L. Berthon, and is described in the English 
 Mechanic, Oct. 13 and 20, 1871. The Eev. W. Conybeare 
 Bruce has also handled the subject very ably in the same 
 publication, Feb. 6 and 27, and April 2, 1880. 
 
 We will close this section with the encouraging words 
 of the Council of the Koyal Astronomical Society, in their 
 Report for 1828: 'Every one who possesses an instrument, 
 whose claims rise even not above a humble mediocrity, has 
 it in his power to chalk out for himself a useful and honour- 
 able line of occupation for leisure hours, in which his labour 
 shall be really valuable, if duly registered ; . . . those who 
 possess good instruments, have a field absolutely boundless 
 for their exertions.' 
 
 THE MODE OF OBSERVATION. 
 
 AN ordinary telescope may be easily prepared for use : to 
 fix it on its stand ; to point it by means of the finder ; to 
 adjust the focus to the eye (remembering that different eyes 
 require different adjustments), are processes scarcely requir- 
 ing instruction. But many mistakes may be made in detail ; 
 aiid in this, as in everything else, there are various methods 
 
THE MODE OF OBSERVATION. II 
 
 of doing the thing the wrong way. The present section will 
 therefore consist of negative rather than positive directions, 
 pointing out rather what should be avoided than what should 
 be done. 
 
 1. Do not begin by fixing the telescope in a warm room 
 and opening the window. A boarded floor is bad, as every 
 movement of the observer is liable to produce a tremor ; but 
 the mixture of warm and cool currents at the window is 
 worse; it is an artificial production of the fluttering and 
 wavering which, as naturally existing in the atmosphere, are 
 such an annoyance to astronomers. If a window must be 
 used, let it be opened as long beforehand as may be, and let 
 the object-glass be pushed as far as possible outside ; there 
 should be no fire in the room ; and any other windows, as 
 well as the door, should be shut before beginning to observe : 
 the nuisance may thus be sometimes abated ; but the right 
 place is unquestionably out of doors. 
 
 2. Do not wipe an object-glass or metallic speculum more 
 than can possibly be helped. Hard as the materials o.re, 
 scratching is a very easy process ; and the ultimate result of 
 ordinary wiping may be seen in an old spectacle-glass held 
 in the sunshine. The most valuable part of a good telescope 
 deserves much more careful treatment; and, if protected 
 from dust and damp, it will very seldom require to bo 
 touched. Nothing but great carelessness would expose it to 
 dust : and the dewing of the surface may be almost always 
 avoided. The object-glass or speculum, if kept in a cold 
 place, should not be uncovered, if possible, in a warmer air 
 till it has gained something of its temperature ; and it must 
 be invariably closed up in the air in which it has been used 
 before it is removed in-doors ; or, in either case, it may be 
 dewed like a glass of cold water brought into a heated room. 
 The object-glass, however, being much exposed to radiation, 
 
12 THE INSTRUMENT AND THE OBSERVER. 
 
 requires additional protection ; and this may be easily con- 
 trived. A tube of tin, pasteboard, or very thin wood, such 
 as is used for hat-boxes, or, best of all, calico stiffened with 
 shell-lac and varnished, fitting on to the place whence the 
 brass cap has been removed, and three or four times longer 
 than wide, will, in general, keep the object-glass bright. 
 This ' dew-cap ' must fit tight enough to stand firm, or it will 
 bend down and intercept the light ; but not so tight as to 
 cause trouble in removing it to put on the brass cap in the 
 open air. It is better to blacken its interior indeed, neces- 
 sary, if of tin ; this may be done with lamp-black mixed with 
 size or varnish, so as neither to show a gloss nor rub off; or 
 a piece of black cloth or velvet may be glued or pasted inside 
 it. A lining of blotting-paper is serviceable in heavy dew. 
 A dew-cap on the finder will often save much trouble. 
 Should it be necessary to leave the telescope for some time 
 in the cold, a clean handkerchief thrown over the end of the 
 dew-cap will be a complete safeguard. Should an object- 
 glass or speculum become damped after all, do not close it 
 up in that state ; if the cloud of dew is very slight, it may 
 quite disappear in a warm room, especially if exposed to a 
 fire ; if dense, however, it may leave a stain which ought to 
 be quickly removed, as well as any little specks of dirt or 
 dulness which will form, one knows not how. To do this, 
 dust the dried surface first with a soft camel's hair pencil or 
 varnishing brush, which will remove loose particles ; then 
 use, very cautiously, a very soft and even piece of chamois 
 leather, which has not been employed for any other purpose, 
 and must be always kept in a wide-mouthed stoppered bottle 
 or wrapped up from dust ; or a very soft silk handkerchief 
 (which Lassell uses for glass) preserved with similar care. 
 But the wiping must be as gentle as possible ; rubbing is 
 inadmissible in any case. Proctor advises sweeping from * 
 
THE MODE OF OBSERVATION. 13 
 
 small space near the edge as a centre. Any refractory stains 
 may be breathed upon, or touched with pure alcohol, and 
 wiped till dry : but if the glass has become discoloured, we 
 must put up with the defect ; and care should be taken not 
 to mistake specks in the substance of the glass for foreign 
 matters lodged on its surface. A slight tarnish may fre- 
 quently be removed from a metallic speculum by lemon-juice, 
 or a solution of citric acid, or spirit of hartshorn, carefully 
 wiped off in a short time : if this does not restore its bright- 
 ness, it is better to leave it alone : a slight loss of light is not 
 so great an injury as would result from strong friction. The 
 taking out or replacing of an object-glass or mirror is a deli- 
 cate operation, and hurry or carelessness may easily make it 
 a very dangerous one; speculum metal is nearly as brittle 
 as glass : but this material is rapidly going out of use, from 
 the superiority of the silver-on-glass mirrors, which are now 
 becoming appreciated as they deserve. The management 
 of these need not be described here, as special instructions 
 should always accompany them, such as will be found in 
 Browning's * Plea for Reflectors,' or Calver's * Hints for 
 Reflecting Telescopes.' 
 
 Dimness of vision often results from damp on the eye- 
 lens. This will rapidly disappear, without wiping, in a 
 warmer temperature. If the finder does not act well, this 
 may be suspected to be the cause. For these and many 
 other reasons, a small lamp, the light of which can be con- 
 cealed at pleasure, is a convenient adjunct to the telescope : 
 any glass surface held at a safe height over it will speedily 
 be cleared of moisture. A ground or papered glass front to 
 a lamp is advantageous for reading. 
 
 Eye-piece lenses lequire occasional wiping; the leather 
 may be pressed to their edges with a bit of soft wood. A 
 piece of blotting-paper rolled to a point, and aided by 
 
14 THE INSTRUMENT AND THE OBSERVER. 
 
 breathing, answers perfectly. Their flat faces are easily 
 scratched if laid downwards on a table. The screws demand 
 very gentle usage : a previous turn backwards, before screw- 
 ing in, causes the thread to fall with a snap into its place. 
 
 Brass-work should not be rubbed with polishing powder, 
 which might injure the lacquering. 
 
 3. If the telescope does not seem altogether right, not- 
 withstanding all the pains you can take in bringing it to 
 focus, do not meddle with screws or adjustments, unless you 
 thoroughly understand the construction, or can obtain good 
 directions. In most cases a screw-driver is a dangerous tool 
 in inexperienced hands. 
 
 4. Do not use any part of a telescope or stand roughly, 
 or expose it to any blow or strain. It is a delicate instru- 
 ment, and well deserves careful preservation. 
 
 5. Do not spare trouble in adjusting tho focus. It is 
 well known that different eyes require a change, sometimes 
 a great one : and the same observer's focus is not invariable, 
 being affected by the temperature of the tube and the state 
 of the eye, the adjustment of which, as Dawes has pointed 
 out, shortens with intense gazing, and is apt to vary with 
 the relative brightnesses of objects, besides being, to a certain 
 extent, under the observer's control. 
 
 6. Do not over-press magnifying power. Schroter long 
 ago warned observers against this natural practice, which is 
 likely to lead beginners into mistakes. A certain proportion 
 of light to size in the image is essential to distinctness ; and 
 though by using a deeper eye-piece we can readily enlarge 
 the size, we cannot increase the light so long as the aperture 
 is unchanged; while by higher magnifying we make the 
 inevitable imperfection of the telescope and the atmosphere 
 more visible. Hence the picture becomes dim and indistinct 
 beyond a certain amount of power, varying with the bright- 
 
THE MODE OF OBSERVATION. 15 
 
 ness of the object, the goodness of the telescope, and the 
 steadiness of the air. Comets and nebulas, generally speak- 
 ing, will bear but little magnifying. For the moon and 
 planets, the power should be high enough (if the weather is 
 suitable) to take off the glare, low enough to preserve suffi- 
 cient brightness and sharpness : the latter condition being 
 preserved, minute details are likely to come out better with 
 an increase of power. Stars bear much more magnifying, 
 from their intrinsic brilliancy ; and they are enlarged very 
 slightly in proportion : their images ought never, with any 
 power, to exceed the dimensions of minute discs, spurious 
 discs, as they are termed, arising from the undulatory nature 
 of light, and usually smallest in the best telescopes. A 
 very high power has, however, so many disadvantages, in the 
 difficulty of finding and keeping the object, the contraction 
 of the field, the rapid motion of the image (in reality, the 
 magnified motion of the earth), and the exaggeration of every 
 defect in the telescope, the stand, and the atmosphere, that 
 the student will soon learn to reserve it for special objects 
 and the finest weather, when it will sometimes tell admirably. 
 A very low power is apt to surround bright objects with 
 irradiation, or glare. Experience in all these matters is the 
 surest guide. 
 
 It may be very useful to know the diameter of the field 
 of each of our eye-pieces. This may be obtained from the 
 time which an object in or very ne*ir the equator takes in 
 passing centrally through it: any star having but little 
 declination will answer (y Virginia and 8 Orionis may be 
 especially mentioned), or the moon or a planet in a corre- 
 sponding position. Several trials may be made, and the 
 mean result in minutes and seconds of time multiplied by 
 1 5 will give the diameter of the field in minutes and seconds 
 of arc, or space, at the equator. 
 
1 6 THE INSTRUMENT AND THE OBSERVES. 
 
 7. Do not be dissatisfied with first impressions. When 
 people have been told that a telescope magnifies 200 or 300 
 times, they are often disappointed at not seeing the object 
 apparently larger. In viewing Jupiter in opposition with a 
 power of only 100, they will not believe that he appears 
 between two and three times as large as the moon to the 
 naked eye ; yet such is demonstrably the case. There may 
 be various causes for this illusion ; want of practice, of 
 sky-room, so to speak, of a standard of comparison. A 
 similar disappointment is frequently felt in the first impres- 
 sion of very large buildings ; St. Peter's at Rome is a well- 
 known instance. If au obstinate doubt remains, it may be 
 dissipated for ever when a large planet is near enough to 
 the moon to admit of both being viewed at once the planet 
 through the telescope, the moon with the naked eye. 
 
 8. Do not lose time in looking for objects under un- 
 favourable circumstances. A very brilliant night is often 
 worthless for planets or double stars, from its blurred or 
 tremulous definition ; it will serve, however, for grand 
 general views of bright groups or rich fields, or for irresolv- 
 able nebulae, which have no outlines to be deranged : a hazy 
 or foggy night will blot out nebula and minute stars, but 
 sometimes defines bright objects admirably ; never condemn 
 such a night untried. Twilight and moonlight 1 are often 
 advantageous, from the diminution of irradiation. Look for 
 nothing near the horizon; unless, indeed, it never rises 
 much above it ; nor over, or to the leeward of a chimney in 
 use, unless you wish to study the effect of a current of heated 
 air. If you catch a really favourable night, with sharp 
 
 1 Secclii has found the detail of the Great Nebula in Orion much 
 more visible in moonlight, which is also known not to obliterate even 
 such objects as the satellites of Mars and Uranus, or some of the 
 minuter comites of double stars. 
 
THE MODE OF OBSERVATION. 1 7 
 
 and steady vision, make the most of it ; you will not find 
 too many of them. Smyth, who thinks our climate has 
 been unfairly depreciated, says : * Where a person will look 
 out for opportunities in the mornings as well as evenings, 
 and especially between midnight and daybreak, he will find 
 that nearly half the nights in the year may be observed in, 
 and of these sixty or seventy may be expected to be splen- 
 did/ But ordinary students must of course take their 
 chance, with their fewer opportunities. With due precau- 
 tions as to dress, nothing need be feared from ' night-air : ' 
 that prejudice is fully confuted by the well-known longevity 
 of astronomers, even of such as have habitually protracted 
 their watchings 
 
 " Till the dappled dawn doth rise." 
 
 9. In examining faint objects, do not prepare the eye for 
 seeing nothing, by dazzling it immediately beforehand with 
 a lamp, or white paper. Give it a little previous rest in the 
 dark, if yon wish it to do its best. 1 
 
 i o. When a very minute star or faint nebula is not to 
 be seen at once, do not give it up without trying oblique or 
 averted vision, turning the eye towards the edge of the field, 
 but keeping the attention fixed on the centre, where the 
 object ought to appear ; this device, with which astronomers 
 are familiar, is often successful ; its principle depends pro- 
 bably on the greater sensitiveness of the sides of the retina. 
 
 ii. Do not avoid the trouble of recording regularly all 
 you see, under the impression that it is of no use. If it has 
 no other good effect, it tends to form a valuable habit of 
 accuracy ; and you might find it of unexpected importance. 
 
 1 Herscliel II., when about to verify his father's observations on 
 the satellites of Uranus, prepaied his eye with excellent effect, by 
 keeping it in utter darkness for a quarter of an hour. 
 
 VOL. !, 
 
1 8 THE INSTKUMENT AND THE OBSERVER. 
 
 And, like old Schroter, trust nothing to memory. If there 
 has been haste and sometimes if there has not it is sur- 
 prising what unforeseen doubts may arise the next day: 
 make at least rough notes at the time, and reduce them 
 speedily into form, before you forget their meaning. 
 
 1 2. Do not be discouraged, by ignorance of drawing, from 
 attempting to represent what you see. Everybody ought to 
 be able to draw ; it is the education of the eye, and greatly 
 increases its capacity and correctness; but even a rough 
 sketch may have its use ; taken on the spot, and compared 
 with the original, it will not be all untrue ; it may secure 
 something worth preserving, and lead to further improve- 
 ment. 
 
 In conclusion, may I be permitted to remind the young 
 observer not to lose sight of the immediate relation between 
 the wonderful and beautiful scenes which will be opened to 
 his gaze, and the great Author of their existence ? In look- 
 ing upon a splendid painting, we naturally refer its excel- 
 lence to the talent of the artist ; in admiring an ingenious 
 piece of mechanism, we cannot think of it as separate from 
 the resources and skill of its designer; still less should we 
 disconnect these magnificent and perfect creations, so far 
 transcending every imaginable work of art, from the remem- 
 brance of the Wisdom which devised them, and the Power 
 which called them into being. Such is eminently the right 
 use of the Telescope as an instrument, not of mere amuse- 
 ment or curiosity, but of a more extensive knowledge of the 
 works of the Almighty. So new an aspect as has thus been 
 given to the material universe so amazing a disclosure as 
 has thus been permitted to man, of the vastness of his 
 Maker's dominion can hardly be ascribed to blind accident 
 or human contrivance : in thus employing Galileo's invention, 
 we may well feel his grateful acknowledgment, that it was 
 
THE MODE OF OBSERVATION. 19 
 
 the result of the ' previous illumination of the Divine favour ' l 
 to have been not only beautiful, but true. 
 
 NOTK ON CELESTIAL PHOTOGRAPHY. 
 
 Celestial photography has been so largely undertaken since the last 
 edition that a few hints may be useful to the amateur. The moon 
 may be photographed in the focus of any telescope. It must be 
 remembered, however, that in the refractor the visual ami photo- 
 graphic images are not identical. In large telescopes a correcting lens 
 is applied, but the actinic focus of a lens may be readily obtained 
 by focussing the image through a violet screen of ghiss or gelatine 
 which alone transmits the chemical rays. For photographing the stars, 
 commercial lenses have been used with success by Gill, Pickering, Es, 
 Wolf, etc. It will be obvious that the space-penetrating power will 
 depend upon the aperture of the lens, its focal length, the sensitiveness 
 of the plate, the duration of exposure. For this work lenses with 
 large angular apertures are preferable, and short focal length, as the 
 shorter the focus the smaller the images ; the two largest at the 
 present time are the Bache telescope, at Harvard, and the Compton 
 telescope, 2 at the Wolsingham Observatory, each having an aperture 
 of 8 inches, and focal lengths of 44 and 42 inches respectively. The 
 Bache telescope is a doublet which allows of a larger field and better 
 definition. With these telescopes, stars of magnitude 14, Argelander's 
 pcale, are photographed with 60 minutes exposure. At the present 
 moment, single long-focussed lenses of 1 3-inch aperture are in use 
 at several observatories, and are employed in making a chart of the 
 heavens. From the great focal length of the lens, however, the field 
 is naturally small, and the whole sky has been covered meanwhile by 
 the energetic Director of the Harvard Observatory, who, after com- 
 pleting, the photo-survey of the northern heavens, sent the Bache 
 telescope to Arequipa. The focal lengths of the Bache and Compton 
 telescopes give plates on the same scale as Argelander's charts of the 
 Northern heavens, and hence the stars are readily identified. A 
 more powerful instrument, of 24-inch aperture, is at present in 
 course of erection at Harvard. The Bache telescope is driven by an 
 
 1 Divina prius llluminante gratia. 
 
 8 Made by Messrs. Hinton & Co., Bedford Street, Strand. 
 
2O THE IXSTRUMKNT AND THE OBSERVER. 
 
 ingenious electrically controlled clock, but the more usual methorl is 
 to fix the photo- telescope to a guide telescope. Admirable work has 
 thus been done by Wolf with a lens of eornewhat over 5-inch aper- 
 ture, and by Barnard and others, the camera being strapped to an 
 ordinary equatorial telescope. These photos have greatly increased 
 our knowledge of the heavens, for besides detecting new nebulae, and 
 remarkable groupings and configurations, they have shown that tho 
 milky way consists of stars intermingled with nebulous matter, and 
 suggest the possibility that the background of the milky way, and 
 perhaps of the whole heavens is one vast nebula. Photography gives 
 us a ready way of detecting variation in the light of the stars. Should 
 any star vary, plates taken at intervals will show it, and though tho 
 actual magnitude on either plate will be affected by the colour of 
 the star, red stars decreasing, bluish stars increasing in size, yet 
 the plates, when compared together, will at once show if there is 
 variation, both alike having the same colour equation. Probably the 
 best way of determining differences of magnitude, is by allowing the 
 stars to trail for a minute or more at the end of the exposure, thus 
 leaving for the brighter stars lines instead of round images, which are 
 frequently over exposed. As regards developers, there are so many 
 that it is difficult to choose. It must be remembered that the object is 
 to obtain the faintest detail. Therefore, the plates should be of the 
 most rapid kind, and the developer of the strongest. Most photo- 
 graphers have in stock a one-fluid developer, made of hydrokinone 
 and caustic potash. This is excellent, but care should be taken to 
 see that the plate is completely flooded by the developer. During 
 development the solution should be kept in motion. This may be 
 done by a clockwork rocker. The plate should be carefully shielded 
 from the light and left in the solution for fifteen or twenty minutes 
 at least, as the faintest detail must be got out. As soon as the surface 
 begins to turn dark development must be stopped. It should then be 
 washed, and immersed in the usual fixing solution of hyposulphite 
 of soda. Plates exposed to the action of caustic potash are liable to 
 frill. Should there be any signs of frilling the plate should be 
 immersed in a strong bath of alum and water. Finally, it should be 
 well washed in running water, and then placed aside to dry. As in 
 celestial photography, the exposure must be long compared with 
 daylight work, every precaution should be taken to insure success. 
 The dishes should be clearly marked, so that even in a dim light 
 there should be no confusion. Both dishes and bottles and hands 
 should be kept scrupulously clean. The lens should be well pro- 
 
THE MODE OP OBSERVATION. 21 
 
 tected so as not to become dewed over, and an examination of it 
 should be made between the exposures to see that no dew has been 
 deposited. A slight film of dew will ruin a whole night's work. 
 Plates should be invariably handled by the edges, and the film should 
 never be touched with the finger. Plates may frequently be inten- 
 sified with advantage. If the angular aperture of the lens is large, 
 moonlight will rapidly fog the plate, and no lengthy exposure should 
 be tried when there is any moon. Even on a dark night the plates 
 exposed for an hour in the Compton Telescope show a distinct 
 boundary between the part exposed to the sky and that shielded by 
 the edge of the carrier. If the focal length of the photo and visual 
 telescope are nearly the same, the star must be followed with a high 
 power, as a small error in the driving-clock will causo the stars to 
 shift on the plate. When the plate is examined under a magnifier 
 the stars should appear as round dots, the size varying with the 
 magnitude. With nebulae, the shorter the focal length the smaller 
 and brighter the image, consequently a small lens of short focus will 
 show greater extension than a large one of long focus. In photo- 
 graphing comets, the nucleus should be carefully followed with the 
 guide telescope, as comets generally have a rapid motion of their 
 own. Wolf and Charlois have detected a large number of asteroids 
 by photography. If an ecliptic star is accurately followed the 
 asteroids in the region will come out as lines on account of their motion 
 during the exposure. 
 
 The various results of focal length, aperture, and exposure may 
 be shown from the following table, condensed from one given in the 
 Harvard College Observatory Annals, vol. xviii. No. 7. 
 
 Aperture. Focal length. Exposure. Limiting 
 
 Inches. Inches. Minutes. Magnitude. 
 
 2'I ... 15 ... II'I 
 
 4 25 ... 115 
 
 8(Bache) ... 44 ... 25 ... 135 
 
 8 (Bache) ... 44 ... 61 ... 147 
 
 13 (Henry) ... 131 ... 180 ... 147 
 
 8 (Bache) ... 44 ... 82 ... 15-1 
 
 13 (Henry) ... 131 ... 240 ... 15-5 
 
 20 (Robert's reflector) 144 ... 120 ... 15-5 
 
 This table shows the great advantage of large aperture and short 
 focal length. 
 
22 THE INSTRUMENT AND THE OBSERVER. 
 
 II. 
 
 NOTE ON THE SPECTROSCOPE APPLIED TO THE TJKLESCOPE. 
 
 TJte Sun. To see the prominences the slit should be nearly closed 
 and placed tangentially to the edge of the sun's image. The instru- 
 ment should then be focussed on one of the hydrogen lines. Now 
 open the slit very gradually and the prominence will be seen on the 
 line. Clapham has seen the prominences with a 5-prism direct vision 
 on 3|-inch refractor; J. Evershed, jun., has done excellent work with 
 2j-inch achromatic and six small prisms, the observations being made 
 on the C line, which Mr. Evershed finds preferable to F. Sidgreaves 
 sees the prominences easily with a single dense glass prism of 60 on 
 5^-inch refi actor. 
 
 The Moon and Planets, as might be expected, give a solar spectrum 
 with some slight differences. In Mars there are evidences of aqueous 
 vapour ; as also in the case of the brighter asteroids. The spectrum 
 of Uranus is crossed by absorption bands of great intensity, which 
 may be easily observed without any slit, and Huggins, by photo- 
 graphy, finds solar lines, showing reflected sunlight. 
 
 Tlie Stars. Here we dispense with a slit, and substitute a cylindrical 
 lens. An elaborate instrument, however, is unnecessary. Huggins 
 long since showed that the stellar spectra may be well seen by holding 
 a small direct vision prism between the eye-piece and the eye. A 
 better plan is to mount the prisms, not less than five those of the 
 rainband spectroscope answer admirably in a sliding adapter before 
 the eye-piece. Some star with banded spectrum, such as a Oriouis and 
 a Herculis, should be focussed to a line, and then the spectroscope and 
 eye-piece moved slowly outwards till the bauds are distinctly seen. 
 By separating the distance between the prisms and the eye-piece 
 increased dispersion will be obtained. The observer should practise 
 on stars with banded spectra, like a Oriouis and a Herculis, till he has 
 thoroughly mastered the instrument. Stellar spectra were divided 
 by Secchi into four types, and the later researches of Pickering have 
 shown that this is the best division. Vogel, however, adopts only 
 three. Classification may be made as follows : 
 
 Type I. (a) The hydrogen lines and some other lines are dark, as in 
 
 Sirius and Vega. 
 
 (1) Lines are wanting, and the spectrum is perfectly con- 
 tinuous, 
 (c) The hydrogen lines are bright, as in 7 Cassiopeiao. 
 
THE MODE OF OBSERVATION. 23 
 
 Type II. The stars show a strong resemblance to the solar type ; as 
 in Aldebaran, Arcturus, etc. 
 
 Type III. The spectrum is columnar, the bands being sharply defined 
 on the more refrangible side and fading away on the less. In 
 some cases, as, for instance, in a Orionis, the bands are resolved 
 into innumerable fine lines. Most of the long-period variable 
 stars belong to this type, but have in addition bright lines of 
 hydrogen, etc., like Mira. 
 
 Type IV. The stars have large absorption bands, due to carbon; the 
 bands are sharply defined on the less refrangible side. 19 
 Piscium is the brightest of this class. The greater part are 
 irregularly variable to the extent of one magnitude, and some 
 are long-period variable stars, as U Cygni ; V Cygni ; T Cancri. 
 
 Type V. These stars consist of bright lines and bands and resemble 
 the nebular spectra. 
 
 The spectrum of Novae is a complex one, having bright lines flanked 
 with dark ones, and in some respects seems to resemble the spectra of 
 third-type variable stars. Motion in the line of sight displaces the 
 lines of the spectrum. If the body is moving towards the observer 
 the wave length is shortened, and the line moved towards the violet, 
 if it is moving away the wave length is increased and the line moved 
 towards the red. This is analogous in sound to a train passing 
 rapidly when the locomotive is whistling. It will be noticed that 
 the note is sharpened as it approaches and flattened as it recedes. 
 Whatever be the explanation of the duplicity of the lines in a nova, 
 the displacement clearly shows motion in the line of sight. Much 
 valuable information has been obtained as to motion of the stars 
 in the line of sight by this method. The doubling of the lines 
 shows that the star consists of two bodies in rapid revolution. The 
 first star of this class discovered was Ursae, the observers at Harvard 
 finding that the K line in the stellar photographs was doubled every 
 fifty-two days. Aurigae in the same way shows a period of revolu- 
 tion of four days. Professor Vogel has detected orbital motion in 
 Spica. Thus a new field is opened out, and when the telescope will 
 no longer separate stars on account of their proximity, the spectro- 
 scope comes in and shows us Binaries where the period is no longer of 
 years but of days, we may perhaps go further, and say of hours, since 
 photographs show that the displacement of the lines in Algol agree 
 wilh the period of variation, and some of the Algol stars have periods 
 of less than a day. For photographing the spectra of stars a prism 
 
24 THE INSTRUMENT AND THE OBSERVER. 
 
 before the O.G. is often used. This turns the star's image into a line, 
 and by slightly altering the rate of the driving-clock, the line is 
 expanded on the photographic plate into a band. 
 
 Nebulas. The spectra of nebulse usually consists of three pro- 
 minent lines grouped in the bluish green. One is the F line, the 
 line that is the brightest lias been referred to magnesium by Lockyer, 
 but this is denied by Huggins and Keeler. The third line Lockyer 
 finds due to iron. Other lines have been seen from time to time. 
 
 Comets. When the comet is a great distance from the sun, the 
 spectrum shows three bands due to hydro-carbon. At Perihelion many 
 other lines appear, notably those of sodium and iron. 
 
PART II. 
 
 THE SOLAR SYSTEM. 
 
 O domus luminopa et speciosa, dilexi decorem tuum, et locum habitations 
 glorise Domiui inci, fabricatoris et possessoris tui ! ST. AUGUSTINE. 
 
 THE SUN. 1 
 
 THE solar phenomena are specially wonderful. The un- 
 rivalled pre-eminence of that glorious sphere, the dependence 
 of our whole system upon the mysterious processes de- 
 veloped at its surface, the rapid and extensive disturbances of 
 which it is the scene, as well as (in fine weather) the daily 
 visibility of the object, all combine to invite research. But 
 the student had better not begin here : more than one astro- 
 nomer has suffered from that piercing blaze : Galileo pro- 
 bably thus blinded himself wholly, and Herschell I. in part. 
 With due precaution, there is no danger; but the eye and 
 hand had better first acquire experience elsewhere. Much 
 depends on the dark glass of the solar cap which is to be 
 screwed on the eye-piece ; red is often used, but is not 
 always dark enough, and transmits too much heat ; green 
 is cooler, but seldom sufficiently thick. The Germans have 
 employed deep yellow. Herschel I. adopted, with great 
 success, a trough containing a filtered mixture of ink and 
 
 1 The new matter is from manuscript notes furnished me by Miss 
 Brown. [EDITOR.] 
 
26 THE SOLAR SYSTEM. 
 
 water. Cooper, at Markree Castle, Ireland, used a ' drum ' 
 of alum water and dark spectacles, and could thus endure 
 the whole aperture, 13^ inches, of his great 25-foot achro- 
 matic. 1 With large apertures, a plane surface of unsilvered 
 glass placed diagonally, as originally suggested by Herschel 
 II., so as to reflect only a small fraction of the light and 
 heat, is found of eminent service. Merz, of Munich, has 
 so reduced the light by polarisation at four such surfaces, 
 that a dark glass, the tint of which is of course better dis- 
 pensed with, becomes unnecessary; and the same end is 
 attained in a very ingenious double-prism eye-piece devised 
 by Prof. Pickering : neither apparatus, however, is free from 
 accidental colour. An eye-piece constructed by Andrews 
 with two lenses of complementary tints, burnished in loosely 
 to avoid fracture from expansion, has succeeded with a small 
 aperture. In screen-glasses combinations of colour are 
 good. Red succeeds perfectly with green, or with green 
 and blue. Herschel II. used green and cobalt blue. 2 
 A Barlow lens, carefully silvered, is said to act admirably, 
 though a light screen might still be necessary. If there 
 is to be only one solar .cap, deep bluish grey, or neutral 
 tint, will be quite satisfactory ; if several, it would be worth 
 while to have different colours, Secchi's observations at 
 Rome seeming to show that the visibility of very delicate 
 details may depend on the tint. In the absence of a proper 
 screen, smoked glass may be used : it is said to intercept 
 heat very perfectly, by Prince, who places it within the eye- 
 
 1 Not, however, an example to be imitated. Dawes thought that 
 with a focus of 30 inches, 2 inches of aperture were enough for perfect 
 security. A 4f-inch silvered mirror is not safe for screen-glasses. 
 
 2 The value of complementary, or at any rate dissimilar, tints in 
 protecting the eye was known before the telescope. Fabricius ob- 
 served a solar eclipse in 1590 * per duplex diversi coloris vitrum; ' 
 and Apian speaks of them 50 years earlier. 
 
THE SUN. 27 
 
 piece, close to the * stop/ or circular opening, which bounds 
 the field ; but thus it can have only one degree of depth, 
 and must be taken out to view other objects. A strip of 
 glass may be smoked to different densities in different parts, 
 and held between the eye and eye-piece ; but it should be 
 protected from rubbing by a similar strip of glass placed 
 over it, and kept from touching by bits of card at the 
 corners, the edges of the two strips being bound round with 
 gummed slips of paper, or tape. 1 Where expense is not 
 regarded, an optician will provide a delightful graduated 
 screen with two wedges of glass, plain and coloured. A more 
 complete command may be obtained by two such wedges 
 sliding behind one another in a brass cap. In any case wo 
 should not begin with too faint a shade, but try the deepest 
 first, and change it if necessary. The thickness of any 
 external screen will contract the field much, unless the eye 
 is brought as close up as possible. A pleasanter view is 
 obtained by placing the screen within the adapter, but from 
 its larger surface it will require to be worked very true. 
 
 To bring the Sun into the field, do not attempt to look 
 for it with the finder unless it has a solar cap : point the 
 telescope till the finder shows it centrally on the hand, or on 
 a paper held behind it; or bring it to shine through the 
 eye-piece before the dark cap is screwed on. 
 
 With these precautions, there need be no fear for an 
 ordinary sight, though long and uninterrupted observation is 
 not desirable, from the heat of the screen so near the eye ; 
 on which account, when not in actual use, the telescope 
 should be pointed a little on one side. Should the light 
 or heat be still unpleasant, the aperture may be contracted 
 
 1 Gum-water or mucilage should always be made with cold 
 water. It is far btrouger, and keeps for a loug time without growing 
 mouldy. 
 
28 THE SOLAR SYSTEM. 
 
 as recommended for defective glasses, 1 or, for a very sensi- 
 tive eye, or a whole company at once, the image of the 
 Sun may be received direct from the eye-piece, without 
 any screen, on card. Choose a field large enough to take 
 in the whole disc, and alter the focus till the image on the 
 card is quite sharp, and at a convenient distance as to size ; 
 any spots then visible will be easily and, with due precau- 
 tion, very fairly seen. And so will specks of dirt in the 
 eye-piece ; but these may be detected by moving the tube, 
 is the true spots alone will keep their places in the image. 
 If the eye-piece includes only part of the Sun, do not mis- 
 take the edge of the field as shown on the card for the Sun's 
 limb ; both are circular, but the latter only will move so 
 long as the telescope is fixed. If a circle of suitable size is 
 drawn on the card, and crossed by lines forming small 
 squares, the image may be adjusted to coincide with it, and 
 the progress of the spots may be marked and recorded day 
 after day. 2 Noble has found that plaster of Paris, smoothed 
 
 1 Schwabo used a contracted aperture and light screen ; Her- 
 echel I. and Dawes preferred full apertures and deep screens, for 
 sharper definition. A small aperture ha?, however, one material 
 advantage in preserving the screens from cracking. I have known 
 a double screen demolished in a few seconds; partial fusion also, 
 or blistering, may be produced by a large aperture. 
 
 2 A simple method of determining the heliographic latitude and 
 longitude of spots has been invented by Professor Thompson. It 
 consists of a set of caidboard discs, 8 inches in diameter with lines 
 ruled on them to correspond with the varying positions of the sun's 
 axis at different times of the year. They require to be used with an 
 equatorially mounted telescope, and should be attached by a light 
 frame to the eye end of the instrument in order that the sun's image 
 may be projected on the disc, and made to coincide with the 8-inch 
 circle. The necessary data for reducing the Observations and finding 
 the position angle of the sun's axis, and its inclination to the ecliptic 
 are given in the " Companion to the Observatory" for every fifth day, 
 
THE SUN. 29 
 
 while wet on plate-glass, gives a most beautiful picture ; ho 
 fixes a disc of it inside the base of a pasteboard cone, black- 
 ened within, i foot long, and 6 inches across the large end : 
 the small end being opened so as to fit close on the eye- 
 piece, with a hole in the side of the cone to look at the 
 image. Hewlett prefers the projected picture to a direct 
 view. It has at any rate the advantage of avoiding the 
 tinge given by a screen-glass. In either mode of observa- 
 tion, if an achromatic is employed, it is an excellent plan to 
 shade the face in the one case, or the screen in the other, 
 by a large piece of pasteboard with a hole in it, through 
 which the tube passes. 
 
 All being arranged, we shall find four points especially 
 worthy of attention : i, the dark spots ; 2, the faculae ; 3, the 
 mottled appearance ; 4, the transparent atmosphere. 
 
 i. The Dark Spots. These are not always visible; the 
 disc is occasionally entirely free from them, but more fre- 
 quently one or more will be in sight. Unless very small, 
 they generally consist of two perfectly distinct parts a dark 
 ' umbra,' usually termed the ' nucleus ' by the older observers, 
 often very irregular in its outline, 1 which resembles, as Secchi 
 remarks, the creeping of a very dense luminous material over 
 an extremely rough surface ; and a surrounding * penumbra ' 
 (the * umbra ' of former days), a fainter shade with an equally 
 definite, but in general less angular boundary, usually, 
 according to Schwa be, in proportion to the umbra as 2 to i, 
 or as 7 to 3. The umbra appears black from contrast, but is 
 
 the intervening days being easily calculated. These discs may be 
 obtained from Miss E. Brown, of Cirencester, 28. 6d. the set. 
 
 1 A double flexure, like that of the letter S, is not unfrequent. 
 It was noticed by Messier in the great spot of 1759 (the colour of 
 which, he says was *brun fonce'') ; and in modern times by Chacor- 
 DMC and others. Howlott remarks this curve in the grouping of 
 famuli spots. 
 
30 THE SOLAR SYSTEM. 
 
 not quite so, as is evident when Mercury in transit, or the 
 limb of the Moon in an eclipse, passes near it. In such a 
 juxtaposition, during the eclipse of July 1860, Dembowski 
 found the lunar disc perfectly black, the umbra * brun fonce.' 
 Frequently the umbra is slightly and unequally illuminated, 
 as if partially overspread by a thin haze, which Secchi com- 
 pares to cirri, or mare's-tail clouds, and finds to be the 
 harbinger of its decrease and extinction; sometimes it is 
 intersected by narrow white veins, or bridges ; these Huggins 
 has occasionally found of especial brilliancy, and in one of 
 them Secchi detected by the spectroscope a different consti- 
 tution from that of the photosphere. In Dawes's very 
 ingenious solar eye-piece, 1 a sliding plate, or wheel, of 
 metal contains a series of holes gradually decreasing in size, 
 each of which may limit the field in turn, while the whole is 
 insulated by ivory, so as to prevent the eye-piece from getting 
 heated ; thus most of the luminous part may be shut off, and 
 the spot alone viewed with a very light screen-glass. In this 
 way, he detected in all large 2 and many small urnbne, a per- 
 fectly black spot, or opening, of much smaller size, which he 
 termed the * nucleus,' and the presence of which, he believed, 
 might point out an important difference in the origin of the 
 spots. Secchi, who concurs in this discovery, finds that holes 
 in a glazed visiting-card (which may be burnt with a red-hot 
 needle) answer well : the card, however, should be placed a 
 little way from the focus, or the edges of the hole may bo 
 
 A similar idea had been entertained by Professor Wilson, of 
 Glasgow, in the last century, who thought a screen would not be 
 necessary. But Langley says that even the darkest part would bo 
 insupportable to the naked eye. 
 
 2 He mentions, however, one large and unusually changeable 
 spot, in which he could detect no nucleus (1859). Brayley observes 
 that they had been already figured by Herschel II. at the Cape. 
 
THE SUN. 31 
 
 charred. A Barlow or even common concave lens, inter- 
 posed before the rays reach the focus, will divert a great 
 portion of the heat, and an excellent amateur arrangement 
 may be made by a combination of concave lens, card 
 diaphragm, and screen -glass. Howlett and others have 
 occasionally perceived the nuclei without any such assistance, 
 and Buffham has seen them frequently with a 2y^-in. object- 
 glass; often multiple ; once (1870, June 20) 5 in a single 
 umbra : Huggins finds frequently 3. The feeble illumination 
 of the umbra Dawes ascribed to the presence of a cloudy 
 stratum ' beneath the photosphere : this Secchi, with Merz's 
 polarising apparatus, finds tinged with a rosy hue. The most 
 diligent of solar observers, Schwabe of Dessau, has seen an 
 occasional reddish-brown colour in spots, whose immediate 
 contiguity to others of the ordinary greyish-black precluded 
 deception; in one instance, three telescopes, and several 
 by-standers, agreed as to this fact. Capocci, in 1826, 
 perceived a violet haze issuing from each side of the bright 
 central streak of a great double umbra : Secchi, during the 
 eclipse, i858,March 15, remarked a rose-coloured promontory 
 in a spot visible to the naked eye. Schmidt records many 
 tints, chiefly violet umbra) and yellowish penumbras, especially 
 as cast on paper ; Howlett and others have noticed brown, 
 and Lockyer copper-coloured and violet, tints in umbraB. 1 
 Birmingham has also seen a red cloud suspended, apparently, 
 across an umbra and nucleus. The penumbra which in 
 most cases encompasses considerable umbraB, occasionally 
 comprises a group of them, and frequently z outlasts them 
 
 1 Miss Brown sees red tints occnsionally, but never copper-colour 
 or violet. An * over-corrected ' object-glass might possibly cause a 
 violet tinge ; and the strong influence of contrast must, at least in 
 some cases, be taken into account. 
 
 8 Miss Brown's long series of careful observations do not confirm 
 this. 
 
32 THE SOLAR SYSTEM. 
 
 is made up, according to Schwabe, of a multitude of black 
 dots usually radiating in straight lines from the umbra. 
 Sccchi, with greater optical power, finds these radiations to 
 be alternate streaks of the bright light of the photosphere 
 and dark veins converging to the umbra. The penumbra, 
 Herschel II. observes, occasionally shows * definite spaces of 
 a second depth of shade;' it is generally darkest at the 
 outside ; l an appearance which is proved by photography to 
 be no illusion from contrast ; sometimes it includes brilliant 
 specks, or streaks, even close to the umbra. Schmidt 
 describes one of these insulated specks as the brightest 
 portion at that time visible. They have been frequently 
 seen to disappear in floating over the umbra. Sun-spots are 
 of all shapes and sizes, up to enormous dimensions, the 
 umbra frequently surpassing the earth greatly in magnitude. 
 The penumbra, especially of a group, is often much larger. 
 Herschel II., at the Cape of Good Hope, estimated the area 
 of one to be 3,780,000,000 square miles. Schwabe and 
 Schmidt speak of groups which have extended across more 
 than a quarter of the disc. The length of one, observed by 
 Hevel in 1643, is said to have occupied one-third of it. 
 Spots exceeding 50", Schwabe finds visible to the naked eye 
 through a fog, or dark glass: he has often recorded such 
 instances, sometimes repeatedly in 12 months; and Dawes 
 states that a year seldom, if ever, passes without them. 
 When thus perceptible they surpass the earth at least 3 
 times if conspicuous, much more. A gregarious tendency 
 ia obvious, and the groups are apt, especially in certain 
 seasons, to be nearly parallel with the solar equator. 
 
 ' This was figured by La Hire as far back as 1700. Dawes found 
 it to be the case with his cloudy stratum also, but only in opening 
 spots. Buff ham and Andrews have seen a nucleus encompassed by 
 a narrow grey ring. 
 
THE SUN. 33 
 
 Herschel II. says that, if they converge, it will be towards 
 the preceding side of the disc. They are absent from the 
 poles, and infrequent and of short duration for about 10 on 
 each side of the equator : beyond this region are two fertile 
 zones, reaching as far as 30 or 35 each way; sometimes 
 they exceed these bounds. Peters (U.S.) saw one (June, 
 1846) in 50 55', La Hire in 70, of solar latitude (if cor- 
 rectly reduced, which Carrington thinks questionable). The 
 observations of Peters and Carrington tend to unsettle 
 these limits, which may be subject to change: the latter 
 astronomer has ascertained that, previous to the minimum 
 epoch, the spots break out nearer to the equator, and the 
 reverse afterwards. 1 The numbers are said to be greater in 
 the N. than S. hemispheres. Schwabe finds that the W. 
 members of a group disappear first, and new ones are apt to 
 form on the other side, on which are the greatest number 
 of minute companions, and on which the spots themselves 
 generally increase, decreasing the opposite way ; also that 
 the small points are usually arranged in pairs; and that, 
 near the edge of the Sun, the penumbraB are much brighter 
 on the side next the limb. Herschel II. saw the penumbras 
 often best defined on the preceding side ; and Capocci found 
 that the principal spot of a group leads the way, and that 
 the umbrae are better defined in their increase than diminution. 
 Peters and Carrington observe a remarkable tendency to 
 divergence in adjacent umbras. 2 Groups are frequently 
 
 1 This is now an established fact, the spots not only breaking out, 
 but gradually approaching the equator as the minimum period draws 
 near. When it has passed they suddenly appear in high latitudes, 
 showing that a new cycle has commenced. So that after the minimum 
 there are for a time, as it were, two spot zones, one in the high 
 latitudes and one nearer the equator. 
 
 2 Miss Brown divides spots into eleven classes : (i) Normal ; (2) 
 VOL. I. D 
 
34 THE SOLAR SYSTEM. 
 
 elliptical, curvilinear, or bifurcated. The extraordinary 
 mutability of the spots will be obvious ; frequently they are 
 in continual change, varying from hour to hour, and even 
 more rapidly. Herschel I. lost a group while merely 
 turning away his eye for a moment : Biela has found spots 
 disappear while he looked at them : Krone has observed 
 them to form within a single minute: Schwabe saw a 
 penumbra increase from i' 3" to 5' 2'' in 24*. Lubbock has 
 seen spots with the naked eye, of which a telescope would 
 show no trace next day. Capocci noticed the temporary 
 reduction of an umbra, four times as large as the earth, to 
 the dimensions of Europe, ' under his eyes : ' an unfortunately 
 vague expression, as the Academic des Sciences has remarked, 
 but characteristic of that surprising fluctuation which must 
 strike every observer. Dawes has alluded to the probability 
 that the state of our own atmosphere may be concerned in 
 many of these apparent variations. 
 
 The inquiry into their nature is very perplexing, from the 
 absence of terrestrial analogies, the Sun evidently belonging 
 to a wholly different and entirely unknown class of bodies. 
 The theory of Professor Wilson of Glasgow, modified by 
 Herschel I., has been very generally adopted, that the spots 
 are openings l in a blazing envelope or * photosphere,' 2 
 through which we see, in the penumbra, a deeper and less 
 brilliant region ; at a still greater depth, in the interior of 
 the umbra, a feeble luminosity, marking the ' cloudy stratum ' 
 of Dawes (or ' cirri ' of Secchi) ; and below both these, in 
 
 Compound; (3) Pairs; (4) Clusters; (5) Trains; (6) Streams; (7) 
 Zigzags; (8) Elliptical; (9) Vertical; (10) Nebulous; (n) Dots. 
 
 1 According to Klein, this was first suggested by Schulen in 1770. 
 Lynn has, however, shown that Klein was mistaken. 
 
 2 Schroter used this very appropriate and now universally-admitted 
 term as far back as 1792. 
 
THE SUN. 35 
 
 the nucleus, the non-luminous body of the Sun. This view 
 rests on the perspective appearance of the penumbra, when 
 near the limb, which usually 1 is more contracted on the side 
 next the Sun's centre ; and the depression has been supposed 
 to be corroborated by several observations of actual notches 
 in the limb. 2 Herschel I. thought these openings might 
 be caused by invisible elastic vapour, rising from the dark 
 body of the Sun, and expanding in its ascent ; such is also 
 the view of Secchi, Chacornac, and Dawes, who refer the 
 brighter edges of the openings to their being * folded back,' 
 as it were, by the rush from beneath. On two occasions, in 
 1 86 1, Schwabe found the limb faint and indistinct beyond 
 spots recently entered. Herschel II. inclined to the idea 
 that a transparent atmosphere above the luminous stratum 
 may be subject near its equatorial regions, like that of the 
 earth, to hurricanes, forcing their way downwards to the 
 surface. Circular movements are occasionally traceable: 
 they were noticed by Silberschlag a century ago; Elvins 
 and Knobel observed them in 1867 ; and Dawes detected 
 them in two nuclei, one rotating through 100 in 6 d , the 
 
 1 De la Ruo, Stewart, and Loewy have found, in longitude, 75 
 cases having the penumbra equal on both sides, 456 giving tne per- 
 spective of depression, 74 the reverse; in latitude, 72 cases for, 17 
 against, depression, which they consider sufficiently established. It 
 has been said, however (Klein, Anleitung, 60), that larger instruments 
 and higher powers do not confirm the idea. 
 
 8 An indentation on a globe will disappear in profile, unless its 
 breadth and depth are considerable : hence such observations would 
 be rare; they have been recorded by La Hire, 1703; Cassini, 1719; 
 Herschel I., 1800; Dollond and others, 1846; Lowe, 1849; Newall, 
 1850, 1859; observers at Kew and Dessau, 1868; but some of these 
 may have been due to inferiority in optical means. If the spots were 
 masses suspended above the photosphere, as Kirchhoff and a few 
 others still maintain, they would, as Howlett well observes, be often 
 seen as notches in the limb. 
 
3<5 THE SOLAR SYSTEM. 
 
 other through 70 in 24**. Secchi has also perceived, besides 
 several cases of rotation, a spiral structure in the penumbne 
 and nuclei of certain spots. Something of the kind has 
 likewise been t \vic3 delineated by Birt, and noticed by 
 several other observers, especially Lohse in 1872; and, 
 though Sporer thinks it deceptive, it deserves careful atten- 
 tion. The excentricifcy or lateral deficiency occasionally 
 noticed in the penumbra seems to indicate an oblique 
 direction of disturbance. Secchi has revived Wilson's idea,, 
 that the penumbra may slope inwards : he calculates that 
 their depth is about ^ the semi-diameter of the earth, or 
 upwards of 1300 miles a depression which the subsequent 
 computations of Faye have extended through a space of 
 from 2000 to 3800 miles. From the nature of the photo- 
 sphere, we might conjecture that of the spots, were it not 
 equally unknown. Dawes, Huggins, and Schwabe, like 
 Herschel I., infer an irregular distribution of luminous 
 clonds: Arago's polariscope experiments were thought to 
 have shown that the light is that of flame, not of white-hot 
 solid or fluid matter ; but the result is questionable. Secchi 
 and Henry have shown that the spots are relatively cool. 
 Herschel II. deduced the partial removal of definite films, 
 floating on a dark or transparent ocean, rather than the 
 melting of mist or mutual dilution of gaseous media, and 
 the analogy of the Aurora Borealis has also been alluded to 
 by him and his father. At present, however, the idea seems 
 to be obtaining currency that the darkness results from the 
 absorption of the light of the photosphere in traversing 
 vapour below a certain degree of temperature, and that the 
 spots are produced by descending currents of gaseous 
 material which have become cooled from their propulsion 
 into a higher region. It is known at least that an intimate 
 connection exists between the number of spots and the 
 
THE SUN, 37 
 
 number and magnitude of the upward currents which cause 
 the prominences surrounding the solar limb. It does not 
 fall within our province to treat of these marvellous appen- 
 dages, at once beautiful in tint, fantastic in form, and 
 astonishing in mutability. The spectroscope, through which 
 alone they can be studied (excepting during a total solar 
 eclipse), is very seldom attached to ' common telescopes ; ' 
 and those inclined to pursue this most interesting branch 
 of research would find far better guidance than could be 
 given in these pages in Schellen's ' Spectrum Analysis ' 
 translated by Miss Lassell, Roscoe's ' Spectrum Analysis,' 
 Secchi's ' Le Soleil,' or Schellen's enlarged German edition 
 of it ' Die Soune,' or Proctor's ' Spectroscope.' 
 
 In confirmation of the theory last referred to, it is 
 observed that the prominences on the Sun's limb in the 
 vicinity of spots appear to curl over towards them; but 
 there is still much unexplained ; the prominences occur in 
 all latitudes, even in the neighbourhood of the poles ; but 
 the spots are chiefly confined, as we have seen, to much 
 narrower limits: and on the whole we are far from any 
 satisfactory knowledge of the processes by which they are 
 formed and maintained; our interest, however, in the 
 phaenomena is increasing, since there is now more than a 
 suspicion that they influence the whole dependent system. 
 The extraordinary perseverance of Schwabe l has shown that* 
 
 1 The late lamented President of the Astronomical Society, Mr. 
 Johnson, thus refers to the presentation of their Gold Medal to this 
 observer: 'It was not ... for any special difficulty attending the 
 research, that your Council has thought fit to confer on M. Schwabe 
 this highest tribute of the Society's applause. What they wish most 
 emphatically to exprc-s^ is their admiration of the indomitable zeal 
 and untiling energy which he has displayed in bringing that research 
 to a successful issue. Twelve years, as I have said, he spent to 
 satisfy himself six more years to satisfy, and still thirteen more to 
 
38 THE SOLAR SYSTEM. 
 
 the spots have regular maxima and minima, with a period 
 averaging about 10, or, according to Schmidt and Wolf 
 (from a much more extended comparison), 1 ii'ii years; 
 which corresponds so exactly with the period of all magnetic 
 variations, that both, as well as auroras and electrical earth- 
 currents, are now ascribed to the same unknown power, and 
 the spots are no longer objects of mere curiosity, but indica- 
 tions of a mighty force, one of the prime laws of the universe. 
 The revelations of the spectroscope, which, according to 
 Balfour Stewart, have indicated the existence of 23 terres- 
 trial elements in the Sun, are among the most surprising of 
 modern astronomical discoveries, and stand on evidence 
 which seems incontrovertible ; 2 but they still leave much to 
 
 convince, mankind. For thirty years never has the Sun exhibited 
 liis disc above the horizon of Dessau without being confronted by 
 Schwabe's imperturbable telescope, and that appears to have happened 
 on an average about 300 days a year. So, supposing that he observed 
 but once a day, he has made 9000 observations, in the course of 
 which he discovered about 4700 groups. This is, I believe, an 
 instance of devoted persistence (if the word were not equivocal, I 
 should say, pertinacity) unsurpassed in the annals of astronomy. The 
 energy of one man has revealed a phsenomenon that had eluded even 
 the suspicion of astronomers for 200 years 1 ' 
 
 1 An abstract of Dr. Wolfs results may be found in Memoirs of 
 the Eoyal Astronomical Society, vol. xliii., showing that though the 
 average length between successive maxima is irn years, a period 
 
 | of 1 6' i years is found between those of 1788 and 1804, while only 
 7 '3 years elapsed between those of 1829 and 1837. The intervals of 
 remarkable auroral displays correspond fairly with those of sun-spot 
 maxima, and Wolf finds evidence for a longer period, 56 years, in 
 the latter ; and that their increase is more rapid than their decrease, 
 with a second subsidiary maximum a year or two after their greatest 
 development. 
 
 2 The probability resulting from one or two coincidences in the 
 position of lines would of course be but slight, but it rises rapidly 
 with the multiplication of comparisons. Kirchhoff says, that about 
 60 lines are common to the \apour of iron and the light of the photo- 
 
THE SUN. 39 
 
 be investigated; much that we can never reasonably hope 
 to explain. 
 
 Concurrent authorities have justified our assuming that 
 the spots are at least depressions, if not openings ; yet 
 observations exist, looking another way ; and it may be well 
 to insert them from their curiosity, as well as their being 
 seldom referred to. Dr. Long, who published a Treatise on 
 Astronomy in 1764, states that he, 'many years since, while 
 he was viewing the image of the Sun, cast through a telescope 
 upon white paper, saw one roundish spot, by estimation not 
 much less in diameter than our earth, break into two, which 
 immediately receded from one another with a prodigious 
 velocity.' Dr. Wollaston says: 'Once I saw, with a 12 -inch 
 reflector, a spot burst to pieces while I was looking at it. I 
 could not expect such an event, and therefore cannot be 
 certain of the exact particulars ; but the appearance, as it 
 struck me at the time, was like that of a piece of ice when 
 dashed on a frozen pond, which breaks to pieces and slides 
 on the surface in various directions. I was then a very 
 young astronomer, but I think I may be sure of the fact.' 
 It is also stated that Bayley, who sailed twice with Captain 
 Cook, saw a spot split in two. 1 From such appearances, 
 an observer, unacquainted with the ordinary theory, might 
 easily have inferred the solidity, from the disruption, of the 
 dark object. On chemical grounds, connected (but not as a 
 necessary consequence) with spectrum analysis, Kirchhoff 
 and Bunsen have deduced a constitution analogous to floating 
 
 sphere, and the consequent chance in favour of its presence is more 
 tliuu I,OCK),OOO,OOO,OOO,OOO,OOO to one. Yet this is but one set out of 
 a combination of corresponding lines. 
 
 1 Some strange separations and oscillations of umbrae, recorded at 
 Lawson's observatory in 1849, were probably due to the unsteadiness 
 of our atmosphere ; but a better observer, Robinson of Armagh, saw a 
 luminous bridge shot across some thousands of miles of umbra in a 
 lew minutes. 
 
40 THE SOLAE SYSTEM. 
 
 clouds ; an opinion adopted by Donati and Sporer. Zollner 
 ascribes to them a scoriaccous character. Kaschig (1816), 
 Weiss (1864), Hallaschka, and Haag (1869), observed what 
 they considered a passage of one spot over another. 1 
 
 Notwithstanding their changeable nature, the larger spots 
 are possessed of some permanency. 2 After describing straight 
 lines about June n and Dec. i2, 8 but elliptical paths at 
 other times, in consequence of the position of the Sun's 
 equator towards our eye, 4 they go out of sight at the W. 
 limb, and, if not dissipated, return at the E. edge after about 
 i3 d to run the same course. Some have thus persisted 
 through many revolutions. 5 In 1779^ large spot continued 
 visible for 6 months, and in 1840 and 1841 Schwabe ob- 
 served 1 8 returns (though not consecutive) of the same group : 
 the most permanent, he says, arc usually round, of moderate 
 size, and not sharply denned. Carrington thinks there can 
 be no question of their occasional reappearance in the same 
 places ; as indeed had been supposed by La Hire as far back 
 as 1700: and this reduces within certain limits their proper 
 motion, which was perceived at an early period by Schroter 
 and others, and micrometrically established in a lateral 
 direction by Challis in 1857. Carrington has subsequently 
 made known his very interesting discovery that the period 
 of rotation varies with tho latitude ; the backward drift of 
 the photosphere in the higher latitudes causing a difference 
 of more than 2 days between the respective periods derived 
 
 1 Schellen, SpecJrum Analyst*, 273. 
 
 2 Hewlett has also found some of the smaller and more isolated 
 ones very persistent. 
 
 * So Herschel II., Outlines of Astronomy, 390. But in the next 
 paragraph they stand as July 12 and Dec. n. 
 
 4 Inclination 70 15', Carrington ; 6 57', Spore?. 
 
 5 Miss Brown, however, finds that it is the exception rather tliau 
 the rule for even large spots to return more than two or three times. 
 
THE SUN. 41 
 
 from spots in latitudes 50, and those situated near the 
 equator; so that the period of rotation of a spot may be 
 determined by its latitude, if unchanged : in this respect, 
 however, it may exhibit slight deviation. 1 With these 
 shifting landmarks, it is not surprising that the Sun's period 
 of rotation should have been variously estimated. Laugier's 
 value, 25* 8 h io m , was formerly adopted; Sporer has given 
 24 d i4 h 59 m , Carrington 24 d 23** i8 m 23% for spots in lati- 
 tude 15. Possibly, as the latter suggests, the anterior mass 
 may revolve with greater speed. Relative displacement in 
 groups would be an interesting study, requiring neither 
 micrometer nor clock, only careful drawing. The applica- 
 tion of photography to solar delineation, as at Kew and Ely, 
 is not likely to be within the reach of our readers : it is, how- 
 ever, too important to be passed over in silence. Hewlett 
 and several others have found that spots near the limb 
 require a different focus from those in the centre ; arising, 
 no doubt, as Dawes says, from the effect on the retina of 
 very different degrees of brightness. 
 
 2. The Faculse, or bright streaks. Less obvious than the 
 dark spots, and requiring more power, these are not difficult 
 objects, and were detected by Galileo : they are to be looked 
 for in the spot-bearing regions, but only near the limbs. 2 
 
 1 Peters (1846) ascribed to all the spots a set towards the equator; 
 Laugier, from it. Carrington's valuable results were the fruit of un- 
 wearied perseverance through n years in the use of a very simple 
 apparatus, consisting only of cross wires in an equatorially mounted 
 telescope, without driving-clock or micrometer. It is to be regretted 
 that his work has not been continued by some possessor of ' a common 
 telescope,' which, with the requisite command of time, would be quite 
 sufficient. A full account of his method is given in Carrington's 
 Observations of Solar Spots (1863) often to be met with second-hand. 
 
 2 They were observed by Carrington and Noble nearer the centre 
 than usual in 1870, a maximum spot-period. 
 
42 THE SOLAR SYSTEM. 
 
 They are irregular, curved, and branching, considerably more 
 luminous than their vicinity, but not, according to Secchi, 
 than the centre of the Sun. He observed one in 1858, at 
 least 60 in length. They are proved to be what they appear, 
 ridges in the photosphere, by an observation of Dawes, who 
 once saw a facula projecting above the limb as it turned 
 across it into the other hemisphere, and at another time the 
 luminous border of a large spot which had just entered, 
 forming an irregular low ridge upon the limb : Secchi also 
 has seen a similar appearance. We seldom, however, find 
 them visible close to the limb, 1 or far from it, as they are 
 changed in the centre into bright tufts and specks ; an effect, 
 as Secchi has pointed out, of perspective, if their height 
 much exceeds their breadth ; or of the elevation of their 
 crests above an absorbent atmosphere. Hewlett sees them 
 beautifully projected on a screen, and thus detects them in 
 the centre of the disc. They are nearly as variable as the 
 spots, and are probably connected with them, surrounding 
 them usually near the limb, and sometimes as they cross the 
 centre, attending their development, 2 and succeeding their 
 dissolution; as though they were temporary accumulations 
 of the displaced matter of the photosphere. Secchi com- 
 pares them to immense waves raised by the outburst of the 
 spots, of which they are commonly the harbingers. Schwabe 
 thinks them rather more obvious when spots are few, 3 and 
 suspects that one at least, consisting of 5 to 7 connected 
 ovals, and enclosing occasionally a great group of spots, may 
 
 1 Miss Brown sees them often very neaj the lirnb, but finds that 
 there is sometimes an intervening space without any. 
 
 2 The greatest authorities are now inclined to think that faculse do 
 not precede spots. 
 
 3 He has since adopted an opposite opinion. Monthly Notices, 
 xxvii. 286. 
 
THE SUN. 43 
 
 be a permanent or recurring feature. The authors of ' Solar 
 Physics' consider them (and probably the whole photo- 
 sphere) as consisting of solid or liquid bodies suspended or 
 slowly sinking in a gaseous medium. They find that on an 
 average they follow the accompanying spots, and infer that 
 they have probably been uplifted out of them, and have 
 fallen behind from being thrown up into a more swiftly 
 rotating region. 
 
 3. The Mottled Surface. An object-glass of only 2 inches 
 will exhibit a curdled or marbled appearance over the whole 
 disc, caused by the intermixture of spaces of different bright- 
 ness. The earliest mention I have noticed of this mottling 
 is during the solar eclipse, 1748, July 14 (O.S.), when it 
 was clearly described by Mr. J. Short (the eminent optician ?), 
 to whom it was quite new: since that time it has been a 
 familiar object ; and it must have been this coarser mottling 
 which Schwabe described in 1831, as showing itself strongest 
 in the spotted zones, like two freckled girdles round the Sun. 
 Should this marbled appearance not be at once detected, a 
 slight shaking of the image by tapping the telescope may 
 render it perceptible. Increase of magnifying power, how- 
 ever, brings out a far more delicate mottling overspreading 
 the coarser irregularity, and occasioned by the juxtaposition 
 of minute patches of greater brightness on a greyer ground. 
 This was first observed by Herschel I., and described in two 
 very valuable but not perhaps sufficiently known papers on 
 the Sun ('Phil. Trans.' 1795, 1801), in the former of which 
 the whole solar surface is said to have l the appearance of a 
 mixture of small points of an unequal light/ and in the 
 latter is described as f studded with nodules,' which are also 
 referred to a stratum of self-luminous clouds of unequal 
 thickness, of which the higher and lower regions tend 
 respectively to form faculae and penumbrse. It has more 
 
44 THE SOLAR SYSTEM. 
 
 recently been interpreted by Nasiuyth (1861) as the inter- 
 lacing of a multitude of lenticular masses resembling willow 
 leaves in form, the length of each being ten times its breadth. 
 Considerable discussion has arisen as to the point ; but the 
 supporters of this idea are few, and the prevalent opinion is 
 that of Daw83, who had been familiar with the phaenomenon 
 since 1830 ; and found, from very careful examination of the 
 photosphere, that it was composed of minute ( granules,' or 
 luminous clouds, irregular in form and size, and separated 
 by less brilliant interstices ; thus agreeing precisely with 
 the view given in 1792 by Herschel I. The less luminous 
 interstices are frequently stippled with dusky or nearly 
 black points, seldom circular and often arranged in rows. 
 In the faculoe and round the penumbrfe, where the photo- 
 sphere appears to be heaped up or rolled together, these 
 interstices usually disappear, and the compressed and 
 elongated granules, like very slender faculae, extend over 
 the penumbra, and often project, like irregular thatch, on to 
 the outer border of the umbra ; or, many being joined 
 together, cross the umbra and nucleus as luminous bridges. 
 The grey interstices were thought by Herschel I. to be 
 portions of a lower stratum ; but, as he remarked, the de- 
 pression must be very slight, since they are visible in 
 extreme foreshortening towards the limb. This view is 
 adopted by many of our best observers, including Fletcher, 
 Lockyer, Huggins, and Knott ; and is supported by 0. Struve, 
 Secchi, and Le Verrier. Huggins adds his impression, that 
 the general surface on which the granules are strewed is 
 itself ' corrugated into irregular ridges and vales,' not unlike 
 a stormy sea ; and coincides with the idea of Herschel IT. as 
 to ' a luminous medium intermixed but not confounded with 
 a transparent and non-luminous atmosphere.' In the use of 
 a i3-iuch achromatic of very fine definition, Langley hus 
 
THE SUN. 45 
 
 found that each of these granules is composed of a varying 
 number, 3 to 10, of brilliant points (his granules), which on 
 the whole occupy less than -^ of the Sun, and are the chief 
 source of its light. He thinks that they are the upper ends 
 of elongated filaments, the length of which is seen in an 
 inclined position in the penumbraB ; and he finds evidence 
 in the spots not only of cyclonic action, frequently right and 
 left-handed whirls in juxtaposition, but also of horizontal 
 currents. The same structure is also shown in some fine 
 photographs by Janssen. 
 
 4. The Transparent Atmosphere. 1 That this exists, and 
 is of far greater proportionate extent than planetary atmo- 
 spheres, is demonstrated in total eclipses by the red pro- 
 minences which then surprise the spectators, and which 
 may, as Janssen and Lockyer have discovered, be detected 
 at any time by the spectroscope : but the presence, and the 
 comparative shallowness, of an absorbent envelope forming 
 its interior stratum is at once evident from the faintness of 
 the limb compared with the centre of the disc. This was 
 early remarked at Rome by Luca Valerio, called by Galileo 
 the Archimedes of his time : it was denied by the inventor 
 of the telescope, but may be easily perceived when the 
 image is cast on paper; and its effect is evident in the 
 
 1 It may be well to note that astronomers divide this atmosphere 
 into the Corona, and Chromosphere. Professor Young thus describes 
 them. 'It (the atmosphere) is divided into two portions, separated by 
 a boundary as definite, though not so regular, as that which parts 
 them both from the photosphere. The outer, and far more extensive 
 portion, which, in texture and rarity, seems to resemble the tails of 
 <omets * * * * is known as the "coronal atmosphere" since to it is 
 chiefly due the corona or glory which surrounds the darkened sun 
 during an eclipse * * *. At its base and in contact with the photo- 
 sphere is what resembles a sheet of scarlet fire * * * *, this is the 
 chromosphere.' 
 
46 THE SOLAR SYSTEM. 
 
 Kew, and especially the Rutherfurd photographs. 1 By 
 means of a doubly refracting prism, Secchi has found the 
 limb not more luminous than the penumbras of spots in 
 the middle of the Sun that is, deprived of about half the 
 light; 2 and his previous discovery of a similar decrease of 
 heat confirms the existence of such an absorbent stratum. 
 Hence also may result the inferior distinctness of the solar 
 limb as compared with that of the Moon in eclipses : a fact 
 remarked by Airy, and exhibited by photography ; and 
 Secchi has observed that the occasional bad definition of 
 the spots may be due to the solar atmosphere instead of our 
 own. Some measures of his, and observations by Sporer, 
 seem to indicate a refractive power in this atmosphere, 
 producing an apparent displacement of the spots towards 
 the limb. 
 
 Something must be said of the Sun as a background for 
 the exhibition of intervening bodies. Partial solar eclipses 
 seldom gain much interest in the use of the telescope, 
 excepting from the occasional projection of mountains on 
 the Moon's limb. The total eclipse is so wonderful and so 
 fugitive as to require special preparation, and is too rare 
 in England to require notice here. The transits of Mercury 
 will be found under the head of that planet : those of Yenus 
 are too uncommon and distant to be admitted in our limited 
 space ; the next visible in England not occurring till 2004. 
 
 1 Arago's polariscope foiled to exhibit this difference; it has been 
 shown by the later observations of Schwabe, that it does not invari- 
 ably exist, and that when it is not perceptible, there is also an absence 
 of faculse, scars,' and pores. Sporer, however, is disposed to refer 
 such observations to dew or hoar-frost on the object-glass. 
 
 * He has subsequently reduced this to or J, and finds the limb 
 of a very decided smoky red tint. Elger has seen a portion of the 
 disc near the limb intensely brown, where large spots have dis- 
 appeared. 
 
MERCURY. 47 
 
 Comets, from the endless diversity of their paths, must 
 occasionally traverse the solar disc ; and the opportunity 
 of such a background would be most valuable for acquiring 
 more information as to their nature. If anything unusual 
 should ever be noticed on the disc, it should be carefully 
 watched; and should its rate of progress show that it is 
 not an ordinary spot, its appearance ought to be most 
 critically examined with various powers and screen-glasses, 
 and information telegraphed instantly, where practicable, 
 to some of our principal observatories. 
 
 It may never be granted to our readers to witness such 
 a wonderful outburst of light in front of the Sun as was 
 observed by Carrington and Hodgson, 1859, Sept. i ; and 
 repeated, according to Brodie, on a minor scale, 1864, Oct. i. 1 
 But should any of them be so fortunate, the propriety need 
 scarcely be mentioned of the greatest care in the record, and 
 readiness in the publication, of such an event. 
 
 MERCURY* 
 
 THIS planet, though at times readily visible 3 to the naked 
 eye, is but seldom seen from its nearness to the Sun, and 
 often lies too near the horizon for the telescope. A well- 
 adjusted equatorial stand will find it by day, but its small 
 diameter of about 3060 miles subtends at a mean only 7-5" ; 
 and it was sometimes missed, as well as once noticed extremely 
 faint, even by the experienced Schroter. 
 
 1 And to Hale and others, July 15, 1892. 
 
 9 The new matter is by Mr. A. Stanley Williams. 
 
 8 Often seen by Sehroter and Heis with the naked eye " luoenta 
 sole." Brightest from 10 to 14 days hefore greatest eastern (evening) 
 elongations, much fainter at actual elongations. 
 
48 THE SOLAR SYSTEM. 
 
 Ordinary observers will not see much, where professed 
 astronomers have usually found little ; but, as these pages 
 may possibly fall into the hands of some whose advantages 
 or enterprise may lead them to attack a neglected object, 
 the following points may be specified : 
 
 1. The Phases. These will be easily seen, and are only 
 remarkable because the breadth of the enlightened part has 
 been sometimes found loss than it should have been from 
 calculation. Schroter noticed this: Beer and Madler con- 
 firm it; but their explanation of a dense atmosphere en- 
 feebling the terminator, or boundary of light and darkness, 
 is inadequate, as their observation was before sunrise, when 
 even the dullest part of the disc would be very luminous. 
 See this again in Venus. 1 
 
 2. The Mountains. At the close of the last and begin- 
 ing of this century, Schroter, of Lilienthal in Hanover, a 
 most diligent observer, and his assistant Harding, obtained 
 what they deemed sufficient evidence of a mountainous 
 surface in the alternate blunting of the horns, 2 some minute 
 projections from the limb, and an irregular curve of the 
 terminator; they gave the inferred elevations a height of 
 nearly 1 1 miles. 
 
 3. The Atmosphere. The decrease of light towards the 
 terminator, and the occasional presence of dark streaks and 
 spots, indicated to the same astronomers a vaporous envelope, 
 
 1 According to Trouvelot the terminator becomes straight at eastern 
 elongations before, and at western elongations after the calculated 
 times, as is found in the case of Venus. 
 
 2 Noble also has suspected this (1864) as to S. horn, and Burton ; 
 and both saw an ill-defined terminator. Franks has seen (1877) 
 the S. cusp blunted. Trouvelot confirms (1876-81) the blunting of 
 tlie S. horn, and the irregular curve of the terminator. Guiot at 
 Soissons has observed the S. horn rounded with a 3f-in. refractor. 
 
MKHCURY. 49 
 
 where they even imagined traces of the action of winds. 
 From a combination of their observations Bessel deduced a 
 rotation in 24** o m 53" on an axis inclined about 70 to the 
 ecliptic of Mercury. A bright spot with faint lines diverg- 
 ing from it, NE. and S., was seen by Prince a little S. of the 
 centre, in unusually clear air, 1867, June n ; Birmingham 
 was pretty certain that there was a large white spot near E. 
 limb, 1870, March 13; and Vogel at Bothkamp observed 
 spots, 1871, April 14 and 22. In De La Hue's Newtonian, 
 ro-ft. focus, I3~in. aperture, constructed by himself, and now 
 at Oxford, the planet has a rosy tinge, noticed also by 
 Burton, and once by Harding; Franks, however, sees it 
 very white. Secchi has remarked that the disc is always 
 very ill-terminated, and very faint at the edges, but Burton's 
 admirable silvered specula give a sharply defined limb. 
 Venus in the same field appeared to Nasmyth fully twice as 
 reflective as Mercury. 1 
 
 1 Recent observations have added much to our knowledge of this 
 planet. In 1888 Denning published an important series of observa- 
 tions made with a loj-in. With-Browning reflector. In the autumn 
 of 1882 he obtained some good views of Mercury, and saw tha mark- 
 ings on the disc so pronounced as to suggest an analogy to those of 
 TMars. His observations also led this observer to conclude that the 
 rotation period of the planet must certainly be longer than that 
 usually accepted from Schroter's observations. Schiaparelli at Milan 
 has obtained even more decisive results. His observations were made 
 usually in the daytime, and chiefly with an 8^-m- refractor between 
 the years 1881-89. In the latter year he made the rather startling 
 announcement that the planet performs a rotation in the same time 
 that it completes a revolution round the sun (88 days). So that as 
 the axis of Mercury is apparently nearly perpendicular to his orbit, 
 the planet must always turn the same face to the sun. But owing 
 to a considerable motion of * libration,' resembling that which occurs 
 in the case of the Moon, as much as f of the planet's surface is at 
 times exposed to the sun's rays, the remaining | remaining for ever 
 in darkness. Schiaparelli also iound the markings on the disc so 
 
 VOL. I. E 
 
50 THE SOLAR SYSTEM. 
 
 Transits of Mercury are comparatively frequent; one 
 will be visible in Europe, 1894, Nov. 10. The planet 
 breaks in upon the Sun as a dark notch, sometimes preceded, 
 it is said, by a penumbral shade ; but the earliest impression 
 will be missed, unless the exact point of ingress is known, 
 and kept central in the field. As it advances, the part of 
 Mercury not yet entered may become visible by being pro- 
 jected upon the f corona/ which is so conspicuous in total 
 solar eclipses, and has been known to relieve dark bodies 
 in front of it, such as an inferior planet, or even a portion 
 of the Moon. (Pratt, 1873.) On finally entering the Sun, 
 or beginning to leave it, the planet has been seen lengthened 
 towards the limb from irradiation : fully on the disc, where 
 Mercury appears intensely black, some astronomers have 
 given it a slight dusky border, others a narrow luminous 
 ring: both, probably, deceptions from the violent contrast 
 and the fatigue of the eye, 1 especially as others have re- 
 marked nothing of the kind. A similar explanation may 
 be applied to a whitish or grey spot on the dark planet, 
 seen by Wurzelbauer, 1697 ; Schroter, Harding, and Kohler, 
 1799; Fritsch and others, 1802; Moll and his assistants, 
 1832 (when Harding clearly distinguished two spots, and 
 Gruithuisen suspected one); and recognised in England 
 and America, 1848, and by Huggins and Elger, 1868, when 
 Browning perceived two spots again. In 1878 also a bright 
 
 definite and of such a degree of permanency, that he was able to 
 construct a map of them. 
 
 According to Zollner's photometric researches the 'albedo,' or 
 reflecting power of Mercury is very low, only 13 per cent, of the 
 incident light being reflected. In 1890 the disc of Venus appeared 
 to Denning like newly-polished silver, whilst that of Mercury was of 
 a dull leaden hue. The planets were only 2 apart at the time. 
 
 1 Pratt, however, in 1868, saw the 'halo' finely by projection in 
 a darkened room. 
 
VENUS. 5 I 
 
 speck was noticed by several English and Belgian observers 
 (in one case, two specks), though others entirely failed to 
 detect it ; and every attempt to recognise it in America was 
 unsuccessful. No terrestrial analogy will explain a lumin- 
 osity thus visible close to the splendour of the Sun ; and 
 it seems natural to refer it to the exhausted state of tho 
 retina: an artificial disc, however, subsequently tried by 
 Huggins, showed nothing of the kind. And everything 
 that is seen, however improbable, should always be recorded : 
 an opposite procedure would have effectually precluded many 
 an important discovery. We may remark that Schroter 
 and Harding ascribed to these spots a motion corresponding 
 with the rotation which they subsequently inferred from 
 other indications. 1 
 
 VENUS* 
 
 Fairest of stars, last in the train of night, 
 
 If better thou belong not to the dawn, 
 
 Sure pledge of day, that erown'st the smiling morn 
 
 With thy bright circlet, praise HIM in thy sphere. 
 
 MILTON. 
 
 THE most beautiful of all the heavenly bodies to the unaided 
 eye is often a source of disappointment in the telescope. 
 For the most part it resists all questioning beyond that of 
 Galileo, to whom its phrases revealed the confirmation of 
 the Copernican theory ; an important discovery, which he 
 
 1 A similar phenomenon was observed on Venus in transit in 
 1761 (Append, ad. Ephem. Astron. 1766,62); and by some observers 
 in 1874. 
 
 8 The new matter is by Mr. A. Stanley Williams. 
 
52 THE SOLAK SYSTEM. 
 
 involved for a season in the following ingenious Latin 
 transposition 
 
 " Haec immatura & me jam frustra leguntur, o. y." 
 the letters in their original order forming the words 
 ( " Cynthia) figuras semulatur mater amorum." 
 
 Observers in general will subscribe to the experience of 
 Herschel II., who says it is the most difficult of all the 
 planets to define with telescopes. ' The intense lustre of its 
 illuminated part dazzles the sight, and exaggerates every 
 imperfection of the telescope : yet we see clearly that its 
 surface is not mottled over with permanent spots like the 
 Moon ; we notice in it neither mountains nor shadows, but 
 a uniform brightness, in which sometimes we may indeed 
 fancy, or perhaps more than fancy, brighter or obscurer 
 portions, but can seldom or never rest fully satisfied of the 
 fact ; ' and he infers, like his father, and Huygens long 
 before, that * we do not see, as in the Moon, the real surface 
 of these planets' (Venus and Mercury) 'but only their 
 atmospheres, much loaded with clouds, and which may serve 
 to mitigate the otherwise intense glare of their sunshine. 1 
 Notwithstanding, however, the authority of this opinion, 
 perseverance has of late years rendered it doubtful : mode- 
 rate-sized instruments have proved of service : and the 
 silvered reflector, from its colourless image, is here greatly 
 
 1 Chacornac was of the same opinion, from the absence of polarisa- 
 tion in the light of Venus. His apparatus showed her brightness to 
 be 10 times greater than that of the most luminous parts of the Moon. 
 The reduction of her light to 5^3 perceptibly diminished the image 
 from removal of irradiation. Jupiter the same. Zollner makes the 
 4 albedo ' of Venus 0*50, so that the planet reflects about half the light 
 that falls upon it. This high reflective power favours tks view of a 
 'lT) atraosphere. 
 
VENUS. 53 
 
 superior to the achromatic. The following are the chief 
 points to be noticed 
 
 i. The Phases. With a mean diameter of i8"'8, these 
 are of course easily seen, and very beautiful, excepting the 
 dull gibbous form in the superior or farther part of the orbit, 
 where the disc is also small ; near the greatest elongation 
 from the Sun towards the E. when she is an evening, or W. 
 when a morning star, Venus puts on a beautiful shape that 
 of the moon in quadrature ; between these points in the 
 inferior or nearer part of the orbit, she is a most elegant 
 crescent, larger, sharper, and thinner in proportion as she is 
 nearer really to the Earth and apparently to the Sun. This 
 crescent has been seen even with the naked eye in the sky of 
 Chile, 1 and with a dark glass in Persia, and a very small 
 telescope will show it. When quite slender it should not be 
 looked for after sunset or before sunrise, as it lies too low in 
 the vapour ; but an equatorial stand will find it in the 
 middle of the day an exquisite object ; and thus, or in a 
 transit instrument, it has been many times traced as a mere 
 curved thread extremely near the Sun. 2 Ordinary observers 
 may succeed without an equatorial mounting in seeing it a 
 very delicate crescent soon after it has passed its inferior 
 conjunction, by watching for its earliest appearance 
 
 " Under the opening eyelids of the morn," 
 
 setting the finder, or the telescope with the lowest power, 
 upon it, and following it at intervals sufficient to keep it in 
 the field, till it has cleared the vapours of the horizon ; in 
 this way it may be readily viewed for hours. In fact, the 
 
 1 Theodore Parker saw it in America when 12 years old, and 
 ignorant of its existence, and when no one else could perceive it. 
 
 2 Dawes considers that, with due precaution, Venus might be seen 
 in her upper conjunction within i' of the Sun's limb. 
 
54 THE SOLAK SYSTEM. 
 
 planet is best seen for many purposes in the day-time ; its 
 light, unpleasantly dazzling 1 in a dark sky, so as to bear a 
 screen-glass, is subdued by day to a beautiful pearly lustre. 
 Nor is it very difficult to find. For some time about its 
 greatest brightness, at 40 from the Sun in the inferior part 
 of the orbit, it not merely casts a shade by night, but is 
 visible to the naked eye at noon-day : if its position is pretty 
 well known, a little careful steady gazing will bring it out 
 as an intense white point, when in good air it will be a 
 charming telescopic object. At other seasons, a little hand- 
 telescope with a large field will show it much sooner in the 
 evening or later in the morning than might have been ex- 
 pected. 2 Like that of Mercury, the phasis often disagrees 
 with calculation ; at its greatest elongations it ought to be 
 exactly ' dichotomised ' as a half-moon ; but in August, 1793, 
 Schrotcr found the terminator slightly concave in that posi- 
 tion, and not straight till 8 days afterwards ; and Beer and 
 Miidlcr iully confirmed this by many observations in 1836, 
 proving that the apparent * half-moon ' takes place 6 days 
 earlier or later than the computed, according to the direction 
 of the planet's motion. They found also that there is a 
 similar defect in the breadth of the crescent-phasis. Neither 
 their explanation of this, through the shadows of mountains, 
 nor Schroter's, through the fading of light towards the termi- 
 nator, is satisfactory as far as night observations are con- 
 cerned. In 1839 De-Vico and his assistants at Rome found 
 
 1 Olbers at brightest 19 to 23 times above Aldebaran ; Bond 5 times 
 brighter than Jupiter at mean opposition ; Plummer 9 times brighter 
 than Sirius. 
 
 2 Trouvelot concludes that in the pure atmosphere of Cambridge, 
 U.S.A., Venus is visible to the naked eye in full sunshine in all parts 
 of its orbit, provided its angular distance from the sun is not lessi than 
 10 at inferior, or 5 at superior conjunction. 
 
VENUS. 55 
 
 a similar discrepancy of about 3 days. This curious phae- 
 nomenon is so easily seen, that I perceived it with an inferior 
 fluid achromatic, on Barlow's plan, 1833, March 6, before I 
 knew that it had been noticed by others. 1 
 
 2. The Mountainous Surface. La Hire, in 1700, with 
 an old i6-ft. refractor, power 90, professed to have seen on 
 several occasions in the crescent, when very narrow, 'des 
 iuegalitez beaucoup plus considerables quo celles de la 
 Lune ; ' and Briga not only described an indented termina- 
 tor, but unjustifiably altered Cassini's figures accordingly. 
 Fontana is also stated to have perceived it in earlier days. 
 But Schroter's observations at the end of the last century 
 are far more trustworthy. With several fine reflectors and 
 a very good achromatic, he and others found the boundary 
 sometimes slightly jagged, sometimes irregular in curvature, 
 so as to vary the relative thickness of the horns ; and the.se 
 would occasionally pass through such changes as to show a 
 rotation in 23*" 2i m 8 & . At the quadrature, the N. cusp would 
 frequently project, while the S. was blunted, with sometimes 
 a minute point cut off from it by a narrow black line, the 
 shadow apparently of a lofty ridge ; some of these mountains 
 Schroter supposed to be 27 or 28 miles high, but of course 
 with great uncertainty. Herschel L attacked these dis- 
 coveries in the 'Philosophical Transactions' for 1793, in 
 what Arago justly terms ' une critique fort vive, et, en 
 apparence du moins, quelque peu passionnee.' Schroter 
 calmly and satisfactorily vindicated himself through the 
 same medium in 1795 ; an< ^ Beer and Miidler, in 1833 and 
 1836, have fully established his accuracy as to an irregularly 
 curved terminator, causing great and rapid changes in the 
 
 1 From observations of 9 elongations, Trouvelot found that 
 ' dichotomy ' occurred at east elongation 4 to 8 days before, and at 
 west elongation 6 to 1 1 days after the time of greatest elongation. 
 
56 THE SOLAR SYSTEM. 
 
 shape of the cusps. They also saw an occasional bending 
 off oi the S. horn, corresponding with Schroter's flattening of 
 the limb in that direction, 1 as Langdon has done at the 
 other cusp. Gruithuisen in 1847 saw the S. horn blunted. 
 Fritsch, in 1799 an ^ 1801, witnessed several of these ap- 
 pearances with small telescopes. Gruithuisen and Pastorff 
 have drawn an indented terminator ; Flaugergues and Yalz 
 noticed its irregularity, but deny its changes. Breen, with 
 the great Northumberland telescope at Cambridge, of i9J-ft. 
 focus, and n^-in. aperture, has often seen the unequal curve 
 of the terminator, and the blunted S. horn, and so have 
 several recent observers : either cusp being at times blunted, 
 or nearly or quite cut off. Pratt especially with a fine 
 8|-in. ' With * mirror has fully confirmed Schroter's pro- 
 jections and indentations on the terminator. Safarik has 
 also seen them, 1868 ; and in 1876 Baron van Ertborn 
 repeatedly observed a bright point detached from the S. 
 horn. 2 But the most curious observations are those made 
 by De-Vico and his assistants at Rome, in April and May, 
 1841. An achromatic by Cauchoix, 6^-in. aperture, with 
 powers sometimes up to 1128, enabled them to trace the 
 approach towards the terminator, night after nighf, of a 
 valley surrounded by mountains like a lunar crater, 4^5 in 
 diameter. The crescent was narrow, and near the N. horn 
 
 1 It is a pity that the figures in their * Beitrage ' are BO bad. 
 Schroter's, though not good, are more intelligible. The Roman 
 observers also have noticed this strange temporary flattening of the 
 circular limb near the S. horn, and consider it a profile view of one of 
 the large grey spots, which, if so, must be deeply depressed. 
 
 2 In 1886 a bright narrow line of light, about fa of the diameter of 
 Venus in length, was observed by I. G. Lohse in prolongation of the 
 lower horn, but perfectly separated from it. Trouvelot, who between 
 the years 1876 and 1891 made 744 observations of the planet and 295 
 drawings, fully confirms the irregular curve of the terminator. 
 
VENUS. 57 
 
 they first saw an oblong black spot, which afterwards was 
 bordered with stronger light, in the sequel encroached with 
 half its ring upon the dark side, and ultimately formed a 
 black notch between two bright projections, giving the 
 appearance of a triply-pointed horn ; a longer black streak 
 was seen near the other cusp at the same time. Gruithuisen 
 and Pastorff seetn to have noticed in part the same irregu- 
 larity. Secchi, in 1857, with the 9 T 6 -in. Merz achr., when 
 the crescent was only o"'4 broad, observed it to be still 
 further contracted in one part. Safarik and Lyman have 
 seen two contractions ; Buckingham has found it when very 
 thin not merely irregular, but interrupted at 3 points ; and 
 Arcimis at Cadiz saw an indentation at the S. horn in 1876. 
 3. The Spots. These have occasioned much controversy, 
 from their indistinctness, which is such that the Virgiliau 
 'aut videt, aut vidisse putat* is often the observer's con- 
 clusion. There have been, however, many exceptions. In 
 1645 Foutaua detected a dark spot; 1 in 1666 and 1667 
 Domenico Cassini, at Bologna, repeatedly saw one bright 
 and several dusky spots, the former giving a rotation in 
 23 h 2i m ; 2 subsequently, in the air of France, he never could 
 recover them, nor were J. J. Cassini or Maraldi at Paris 
 more successful afterwards. In 1726 and 1727 Bianchini, 
 at Home, observed spots many times with a 66-ft. refractor, 
 aperture a little more than 21-in., power 112, like the 
 " seas " in the Moon to the naked eye, though less distinct ; 
 and not till after sunset, from want of light in his glass. 
 
 1 The spot observed by Fontana was however probably due to the 
 optical imperfections of the telescope used by him, as Flammariou 
 has pointed out. 
 
 2 So almost invariably stated, but Schiaparelli has pointed out 
 that the period of rotation actually found by Cassini himself from his 
 observations is 23 days. 
 
THE SOLAK SYSTEM. 
 
 His figures show them surrounding the equator of Venus, 
 forming, as it were, three oceans one tolerably circular, the 
 others much lengthened, and each of the latter subdivided into 
 three portions connected by narrower openings ; besides two 
 spots, one occupying the S. polar region, the other forming 
 a horse-shoe round the N. pole. He did his work well, but, 
 for want of sky-room, did not perceive the rapid motion of 
 the spots, and gave a wrong rotation of 24* 8 h . A copy of 
 this diagram is here given which the student may easily 
 transfer to a small globe. Schroter and Herschel I., half 
 a century later, with much finer instruments, but in less 
 pellucid skies, could only make out through many years a 
 few faint markings, with suspicions of motion. Bode saw 
 some dark spots in 1788 ; at last, 1801, Aug. 29, Schroter 
 
 360 330 300 270 240 210 l8o 150 120 
 
 360 33O 3OO 27O 240 2IO l8o 150 120 
 
 detected a dim oblique dusky streak, like one on Mercury, 
 giving a rotation in about 24**. Several other astronomers 
 had occasional glimpses of darker shado wings ; Gruithuisen 
 perceived repeatedly long vertical shales, and minute bril- 
 liant round specks, and Schumacher a dusky spot in the 
 twilight, which in half an hour was lust in increasing glare : 
 others, visible with a small telescope, he found effaced in a 
 
VENUS. 59 
 
 larger one a caution for future observers. Lamont failed 
 entirely with an n-in. achr. at Munich in 1836: but more 
 effective results were obtained at Eome, 1839-1841, by 
 De-Vico, who had been instigated by Schumacher to verify 
 Bianchini's assertions in the same atmosphere. He used 
 the Cauchoix achromatic chiefly by day, since in a dark sky 
 the glare overpowered the spots so much as to render the 
 micrometer useless, and account for Bianchini's erroneous 
 rotation : the drawings of the latter were, however, found, 
 save in the omission of one small spot, remarkably exact. 
 Of 6 observers, the most successful in seeing these faint 
 clouds were those who had most difficulty in catching very 
 minute companions of large stars ; l but all agreed in the 
 figures, and witnessed a progression, giving a rotation in 
 23 h 2i m 22 s on an axis greatly inclined, though less so than 
 B-ianchini had supposed.* They have given no less than 145 
 
 1 De-Vico assigns no reason, but it seems obvious enough, and 
 worthy of notice. A very sensitive eye, which would detect the 
 spots more readily, would be more easily overpowered by tho light 
 of a brilliant star, so as to miss a very minute one in its neighbour- 
 hood. There is abundant industry in these Roman observations : 
 Palomba, the assistant, made 11,800 measures in 1839, of which 
 10,000 were employed in determining tho rotation. But De- Vice's 
 style wants explicitness, and there are strange traces of inexperience 
 or inattention in the Jesuit College, rendering the memoirs of that 
 date far less satisfactory than those of the succeeding and now to be 
 lamented Director, Secchi. 
 
 2 The question of the duration of the rotation of Venus is still a 
 disputed one, and several very elaborate though contradictory investi- 
 gations upon the subject have been published within the last few 
 years. In 1890 Schiaparelli came to the conclusion after a very ex- 
 haustive discussion of all the existing material, including some 
 observations of his own, that the rotation of Venus is very slow; and 
 that whilst being very probably equal to the time taken by the planet 
 in making one revolution round the Sun (225 days), it is certainly 
 not less than 6 months or greater than 9 months. Perrotin confirms this 
 
60 THE SOLAR SYSTEM. 
 
 delineations ; many of these are very coarsely executed, but, 
 as they are little known in England, copies of a few of the 
 more characteristic are given here. Of late these spots, 
 invisible at Greenwich and to several of our first observers, 
 have been recognised by others De la Rue, Huggins, 
 Worthington with a I3~in. mirror, Seabroke with the 8^-in. 
 
 achr. belonging to Dawes, Terby, Denning, Safarik, Baron 
 van Ertborn, and others, and described as bright patches 
 and specks, and cloudy and crater-like markings of different 
 forms and sizes ; according to Ormesher, much like the spots 
 
 slow rotation from observations of the markings on the disc made by 
 him at Nice in 1890, and fixes it at from 195 to 225 days. In the same 
 year Terby published a number of observations made by him in 1887- 
 89, which appeared to him to still further confirm the slow duration 
 of the rotation. But in 1891 appeared an important memoir by 
 Niesten, giving the results of many observations made by himself and 
 Stuyvaert at Brussels between 1881 and 1890. These observers, 
 instead of supporting the slow rotation, strongly confirm the short 
 rotation period of De-Vico. They also found the markings so evident 
 and apparently permanent, that they were able to construct a map of 
 them. This map, however, does not bear the slightest resemblance 
 to that of Bianchini on p. 58. More recently still Trouvelot has dis- 
 cussed the subject, and decides that the rotation is performed in about 
 24 hours. His observations of a large dark spot are referred to on p. 
 61. With results so contradictory, and obtained too by some of our 
 very best observers, it is difficult to come to a satisfactory conclusion 
 upon the subject. The balance of the evidence appears at present, 
 however, to be in favour of a rotation in about 24 hours. 
 
VENUS. 6 1 
 
 of Mars. 1 With describes the disc (April 6, 1868) as 
 marbled or veined all over, and on the same occasion per- 
 ceived with a I2|-in. unsilvered mirror, a small bright 
 projection on the circular limb, 2 abont 40 from S. cusp : 
 this was confirmed by Key, at about 36, April 12 and 
 subsequent days, with granulations towards a terminator 
 more deeply serrated than that of the Moon: March 15, 
 Browning had seen a bright patch of some extent 80 from 
 that cusp, so luminous as to show projection like the snow 
 on Mars. Could we but see these features more readily, 
 what an interesting object would this lovely planet become, 
 especially as in point of size it is the only companion to the 
 Earth in the whole system ! 3 And the possessors of even 
 common telescopes need not despair, though their chances 
 may not be great : at Rome the spots have been seen even 
 with a little telescope of 2-in. aperture, and the following 
 recital shows that the chief difficulty lies in our own atmo- 
 sphere ; it is so curious that it must be given entire from 
 the 'Philosophical Transactions': 'January 23, 1749-50, 
 there was a splendid Aurora Borealis. About 6 h P.M., the 
 Rev. Dr. Miles, at Tooting, had been viewing Jupiter and 
 Venus, and showing them to some friends, with one of 
 Short's reflectors, greatest power 200, when a small red 
 
 1 Trouvclot recorded a number of greyish or whitish spots between 
 the years 1876 and 1891. They were usually of small size and little 
 permanence, and generally only visible near the terminator. But 
 in 1876, and again in 1891, he observed a large dark marking of com- 
 paratively well-defined nature and characteristic form, which remained 
 visible for a number of days. In 1891 the spot \\as observed to arrive 
 at the same position on the disc at a later and later hour on each 
 succeeding day. This circumstance indicates a rotation period slightly 
 longer than 24 hours. 
 
 2 Compare Schroter and Harding on Mercury, p. 48. 
 
 3 Diameter, 7850 miles. 
 
62 THE SOLAE SYSTEM. 
 
 cloud of the Aurora appeared, rising up from the SW. (as 
 one of a deeper red had done before), which proceeded in a 
 line with the planets, and soon surrounded both. Venus 
 appearing still in full lustre, he viewed her again with the 
 telescope, without altering the focus, and saw her much 
 more distinctly than ever he had done upon any occasion. 
 All his friends were of the same opinion as to the sight they 
 had of her on that occasion. They all saw her spots plain, 
 resembling those in the Moon, which he had never seen 
 before, and this while the cloud seemed to surround it as 
 much as ever; but whether the vapour might be rarer 
 nearer the planet, no judgment could be made, because of 
 her too powerful light.' In curious accordance with this, 
 Langdon saw the irregularity of the terminator beautifully 
 through an Aurora in 1873. 
 
 4. The Atmosphere. The bright border noticed by some 
 observers as attending the circular limb may be a deception ; 
 and so probably were the polar snows which Gruithuisen 
 imagined that he frequently saw ; l but there is very sufficient 
 proof of the existence of a vaporous envelope. Schroter's 
 dusky belt, already mentioned, indicates it. 2 He has ascribed 
 
 1 But Trouvelot, from a great many observations, confirms these 
 white polar spots, and has also pointed out that they have been seen 
 in some form or other by a great many observers. According to 
 Trouvelot they consist of brilliant white spots nearly always visible 
 close to the two cusps, and never departing much from these positions. 
 From their nearly invariable position he concludes that they mark 
 the poles of rotation, and that the equator is only inclined 10 or 12 
 to the plane of the planet's orbit. He considers them to be elevated 
 mountain masses, ice or snow covered ; and that to their presence 
 are due the deformations frequently observed in the horns. Under 
 favourable conditions the margins of these polar spots appear formed 
 of minute brilliant points, or detached mountain peaks. 
 
 2 Similar ones have been detected by Buffham, and a long, narrow 
 
VENUS. 63 
 
 to it the great decrease of light towards the terminator and 
 cusps ; and he and Herschel I. agreed as to the extension of 
 the horns beyond a semicircle, which may be due in part to 
 the penumbra, or additional daylight caused by the Sun's 
 not being a point but a great disc, but more to refraction 
 through an atmosphere. Schroter also perceived in 1790 
 a faint gleam along the limb beyond the horns, a true 
 twilight produced by an atmosphere which must be denser 
 than our own. In May, 1849, Madler at Dorpat found 
 the horns projecting to 200 and even to 240, showing a 
 refraction about ^ stronger than ours; and Lyman with a 
 9~in. achromatic in America obtained a similar result ; but 
 from the calculation of Neison, who detected an error in the 
 formula they employed, the true density comes out 1*892, 
 or nearly twice as great as that of our atmosphere. From 
 this cause Cassini in 1692, and Drew in 1854, found the 
 crescent too broad near the conjunction. Secchi, in 1857, 
 saw in that position the cusps much prolonged, and the 
 twilight extending 19^, even through our strongly illumi- 
 nated atmosphere. Noble has seen the whole disc so 
 bordered in almost every inferior conjunction ; it had been 
 recorded in the transit of 1769 ; and in 1864 and 1866, and 
 at the recent transit, in common with several other observers, 
 Lyman found the delicate ring complete, and considers that 
 it will always be so within i 50' from the Sun's centre ; a 
 segment only, of an extent proportioned to the distance, 
 being visible beyond that limit. When entering the Sun 
 in 1875, this light was especially conspicuous in one spot. 1 
 
 line, possibly atmospherical, by Do La Rue and Lord Rosse in the 
 great Melbourne Cassegrain reflector. 
 
 1 At the transit of 1882 the atmosphere very beautifully revealed 
 itself, when the planet was about half on the sun, in the form of a 
 brilliant half ring of light, marking the outline of that portion of 
 
64 THE SOLAR SYSTEM. 
 
 Tacchini considers that this atmosphere contains traces of 
 aqueous vapour. 
 
 5. The Phosphorescence of the Dark Side. This truly 
 unaccountable appearance l is remarkably well attested ; 
 though it is but fair to state that it has been questioned by 
 several good observers, even Dawes himself. It was noticed 
 as far back as 1715, in the 'Astro-Theology' of Derham, 
 who says that ' this sphaericity, or rotundity, is manifest in 
 our Moon, yea and in Venus too, in whose greatest Falcations 
 the dark part of their Globes may be perceived, exhibiting 
 themselves under the appearance of a dull, and rusty colour.' 
 1721, June 7, Kirch, junior, believed that he saw it, the 
 crescent being then extremely narrow ; and again, with two 
 others, 1726, March 8. Herschel I. perceived traces of it. In 
 1806 it displayed itself beautifully to Harding three times 
 (once with a companion), and to Schroter once, within five 
 weeks. Pastorff also witnessed it twice. Guthrie and others 
 noticed it in 1842, with small reflectors, in Scotland; 
 Purchas, at Ross, in England ; De-Vico and Palomba, many 
 times, in Italy. Berry at Liverpool saw it in 1862 with no 
 previous recollection of its visibility; it was remarked in 
 that year, and especially in 1863, by many observers in 
 England, and by one in 1865, as well as by four at Leipzig 
 with the 8~iri. achromatic. To these we may add Petty, 
 1868; Winnecke, 1871, Nov. 6; Elger, Erck, 1873; Banks, 
 
 Venus not yet entered on the sun. This semi-ring gleamed with a 
 beautiful silvery or pearly light, and was of uneven brightness and 
 breadth, probably owing to the planet's atmosphere being of varying 
 degrees of opacity at different parts of the limb. 
 
 1 Arago's 'negative visibility' is but a perplexing attempt at 
 solution. The faint illumination which renders some of our terrestrial 
 nights lighter than others, remarked by Schroter, Arago, and, I think, 
 by myself, scarcely affords an adequate comparison. Humboldt gives 
 a striking instance, Cosmos, I., 131 (Bohn). 
 
VENUS. 65 
 
 Grover, Arcimis, 1876; Mills, 1878. On Jan. 31 of that 
 year, after having many times looked for it in vain in former 
 years, I saw it, without specially thinking about it, with 
 powers of about 90 and 212 on my 9'38-in. mirror, coming 
 out at intervals rather paler and browner than the twilight 
 sky, and equally visible when the bright crescent was hidden 
 by a field-bar. Strange to say, it has been seen even in the 
 daytime, by Andreas Mayer, 1759, Oct. 20, through merely 
 a transit instrument, 44 after noon: 'etsi pars lucida 
 Veneris tennis admodum erat, nihilominns integer discus 
 apparuit, instar lunae crescentis, quse acceptum a terra lumen 
 reflectit:' and Winnecke records a similar observation, 
 though very faint, 1871, Sept. 25, a little before noon. 1 
 Von Hahn also says he made it out repeatedly, by day as 
 well as by night, and with several instruments; he was, 
 however, an inferior observer. Gruithuisen saw it once at 
 sunrise; Mad. Safarik in a broad crescent, 1871, Aug. 9, 
 n h A.M. ; Browning many times, 1870, Feb. and Mar. with 
 io^-in. silv. mirror, very distinct, brighter than the bright 
 
 1 LangJoii and several others perceived it by day a little before 
 inferior conjunction, 1870, Feb. 5; but this, as well as some other 
 instances, may have been merely the atmospheric ring of Lymaii and 
 Noble ; and such appears to have been the case in some day-observa- 
 tions of Baron van Ertborn in 1876. A curious observation of my 
 wife's may be cited here, made June 30, 1880, 7 h 30 A.M., between 
 the Lago Maggiore and Domo D'Ossola. The waning Moon, 2i h 
 past Last Quarter, was still at some height in W., but pale in the 
 strong sunshine, when she noticed that the circle appeared complete, 
 the dark side being smaller than the bright, of a more lilac tint than 
 the deep blue Italian sky, and irregularly shaded, being brighter 
 towards the SW. limb, as it would be, though she was not in the least 
 aware of it. The phenomenon was confirmed to her by a good 
 binocular glass; but neither I nor her servant could perceive it. She 
 was not thinking at the time of the lumiere cendrfe, and still less of 
 the dark side of Venus. 
 
 VOL. I. F 
 
66 THE SOLAR SYSTEM. 
 
 twilight of 5 b P.M., and even when gibbons Baron van Ertborn 
 saw it in 1876. The dark side is often too small in propor- 
 tion (as I saw it), like that of the crescent Moon to the 
 naked eye; and from the same cause, the irradiation of 
 the luminous part ; it is sometimes described as grey, some- 
 times reddish. It would be well worth looking for when 
 the crescent is narrow, but Venus should have high N. 
 latitude to clear the vaponrs of the horizon: the bright 
 part should be put behind a bar in the field ; and it should 
 be noted whether the dark side is lighter or darker than the 
 background. Noble has repeatedly seen the latter, projected, 
 perhaps, on the solar corona. 
 
 THE MOON. 1 
 
 (Abbreviations: Schr., Schroter. G., Gruithuisen. L., Lofirmann. 
 B. & M., Beer 2 Mddler. ; Ne., Neison. Schm., Schmidt. B.A. A., 
 Jlritish Astronomical Association. L.A.S., Liverpool Astronomical 
 Society. Sel. Journal., Selenographical Journal.) 
 
 THE comparatively small distance of our satellite, 240,000 
 miles, 3 renders it the easiest of telescopic objects. Its 
 shadowed and irregular surface, visible to the naked eye, 4 is 
 well brought out even with a low magnifier ; hence Galileo 
 
 1 The new matter is by Mr. Elger, who wishes it to be understood 
 that to bring this part up to date would have necessitated many 
 alterations and insertions in the text. 
 
 2 This name is retained, as originally associated with the work, 
 which, however, is known to have been chiefly executed by his colleague. 
 
 3 More accurately 238,840, varying, from its elliptical orbit, between 
 252,972 and 221,614 miles. 
 
 4 Klein observes that an immense amount of detail may be made 
 out in the Full Moon with the naked eye, especially if the light of a 
 flame enters it at the same time. 
 
THE MOON. 67 
 
 readily comprehended the nature of what his new and 
 imperfect invention disclosed to him, and the smallest 
 instrument will show that freckled aspect, arising from 
 numberless craters, which he compared to the eyes in a 
 peacock's tail. Many a pleasant hour awaits the student in 
 these wonderful regions ; only let him not expect that what 
 he sees so plainly will be equally intelligible, excepting in 
 its unquestionable relief from the effect of light and shade. 
 Greatly overstrained ideas, as to the possibility of making 
 out the minute details of the surface, have been entertained, 
 not much more reasonable than those of the islanders of 
 Teneriffe, whose simplicity led them to imagine that the 
 telescope of Piazzi Smyth would show their favourite goats 
 in our satellite; a very little consideration, however, will 
 detect the absurdity of such anticipations. The first 
 * Moon Committee ' of the British Association recommended 
 a power of 1000; few indeed are the instruments or the 
 nights that will bear it ; but when employed, what will be 
 the result ? Since increase of magnifying is equivalent to 
 decrease of distance, we shall see the Moon as large (though 
 not as distinct) as if it were 240 miles off, and any one can 
 judge what could be made of the grandest building on earth , 
 at that distance : very small objects, it is true, are discoverable 
 there with the finest instruments, possibly 150 feet broad, 
 or from their shadows one-third as much in height; but 
 their nature remains unknown. Much difficulty, too, arises 
 from the want of terrestrial analogies. It may be reasonably 
 supposed that Venus or Mars, at the like distance, might be 
 far more intelligible. We should certainly not find them 
 mere transcripts of our own planet, for the conditions of 
 existence as to temperature and air, if not in other respects, 
 are very different, and, as Schr. often remarks, variety of 
 detail in unity of design is characteristic of creation ; bntH 
 
 UNIVERSITY ) 
 
68 THE SOLAR SYSTEM. 
 
 we might have a fair chance of understanding something of 
 what we saw. It is quite otherwise with the Moon. It is, 
 in B. and M.'s words, no copy of the Earth ; the absence 
 of seas, rivers, atmosphere, vapours, and seasons l bespeaks 
 the absence of * the busy haunts of men ; ' indeed of all 
 terrestrial vitality, unless it be that of an insect or reptile. 
 Whatever may be the features of the averted hemisphere, on 
 which, as G. and Hansen have suggested, other relations 
 may exist, we perceive on this side a mere alternation of 
 level deserts and craggy wildernesses. The hope which 
 cheered on G. and others, of discovering the footsteps of 
 human intelligence, must be abandoned. 2 If it should be 
 thought probable, as it very reasonably may, that the lunar 
 surface is habitable in some way of its own, we have reason 
 to suppose that, where the conditions of life are so extremely 
 dissimilar, its traces would be as undecipherable by our 
 experience as a brief inscription in a character utterly 
 unknown. We ought not, in fact, to bo surprised at such a 
 difference between bodies belonging to distinct classes: it 
 would have been unreasonable to have looked for a duplicate 
 of a primary planet in its attendant. Waiving, then, any 
 disappointment from this cause, we shall find the Moon 
 a wonderful object of study. It presents to us a surface 
 
 1 This assertion must be limited to the subject in hand. It is not 
 intended to deny the possibility of some kind of atmosphere, or fluid; 
 and a trifling change of seasons would result from the slight inclina- 
 tion of the lunar axis (i 32' 9"). 
 
 2 The existence of many natural wonders on our own globe for 
 example, the canons, or river-gorges, of NW. America, one of which 
 has a length of 550 miles, an extreme depth of 7000 ft, and a closest 
 contraction of 100 ft. ; or the obelisk of limestone, near Lanslebourg, 
 360 ft. high with a base of 40 ft. (Weld., Auvergne, etc., 305), shows 
 how cautiously inferences should be drawn as to the artificial origin 
 of extraordinary appearances. 
 
THE MOON 69 
 
 convulsed, upturned, and desolated by forces of the highest 
 activity, the results of whose earliest outbreaks remain, not 
 like those of the Earth, levelled by the fury of tempests, 
 and smoothed by the flow of waters, but comparatively 
 undegraded from their primitive sharpness even to the 
 present hour. The ruggedness of the details, as old Hovel 
 anticipated, becomes more evident with each increase of 
 optical power, and we cannot doubt that we look upon the 
 unchanged results of those gigantic operations which have 
 stereotyped their record on nearly every region of the 
 lunar globe. 1 
 
 A brief general description of the phenomena of the 
 Moon will prepare us for an examination of its topography. 
 We have then 
 
 i. The Grey Plains, or Seas as they were formerly be- 
 lieved to be, and are still termed for convenience. 2 These 
 are evidently dry flats if the term 'flat' can be applied 
 to surfaces showing visibly the convexity of the globe 
 analogous to the deserts and prairies and pampas of the 
 Earth. B. and M. find that they do not form portions of 
 the same sphere, some lying deeper than others: they are 
 usually of a darker hue than the elevated regions which 
 bound them, but, with a strong general resemblance, each 
 has frequently some peculiar characteristic of its own. 
 
 1 This is sufficiently correct as a popular view of the subject ; but 
 ( unre careful examination may require it to be somewhat modified. 
 Tue varieties of colour, if not arising from vegetation, may indicate 
 an amount of 'weathering' which must bo great from the distance 
 at which it is perceptible: nor can we confidently affirm that with 
 powerful telescopes no traces can be detected of the hand of time. 
 
 2 Kiccioli, when he recast the lunar nomenclature, and substi- 
 tuted the names of philosophers for the feeble geographical analogies 
 of Hevel, retained the generic titles of ' seas,' though he altered their 
 designations. The reform attempted by G., who would have had 
 them called ; surfaces,' has never Ukeu effect. 
 
70 THE SOLAR SYSTEM. 
 
 2. The Mountain Chains, Hills, and Ridges. These are 
 of very various kiiids : some are of vast continuous height 
 and extent, some flattened into plateaux intersected by 
 ravines, some rough with clouds of hillocks, some sharpened 
 into detached and precipitous peaks. The common feature 
 of the mountain chains on the Earth a greater steepness 
 along one side is very perceptible here, as though the 
 strata had been tilted in a similar manner. Detached masses 
 and solitary pyramids are scattered here and there upon the 
 plains, frequently of a height and abruptness paralleled only 
 in the most craggy regions of the Earth. 1 Every gradation 
 of cliff and ridge and hillock succeeds : among them a large 
 number of narrow banks of comparatively slight elevation 
 but surprising length, 2 extending for vast distances through 
 level surfaces ; these so frequently form lines of communica- 
 tion between more important objects, uniting distant craters 
 or mountains, and crowned at intervals by insulated hills, 
 that Schr. formerly, and B. and M. in modern times, have 
 ascribed them to the horizontal working of an elastic force, 
 which, when it reached a weaker portion of the surface, 
 issued forth in a vertical upheaval or explosion. The fact 
 of the communication is more obvious than the probability of 
 the explanation. 
 
 1 Sehm. ascribes less rapidity to the gradients than is here 
 supposed ; very seldom exceeding 60, never attaining in any extent 
 90. Phillips was of an opposite opinion; but Ne. concurs with 
 Schin. 
 
 2 Schr. gives a length of 630 or 640 miles to a ridge connecting the 
 spots Copernicus and Kirch. The great serpentine ridge, traversing 
 the M. Serenitatis on the western side, is one of the most prominent 
 of these features, and is fully 300 miles in length. That they usually 
 appear to take the direction of the meridian is simply due to the 
 E. or W. projection of the shadows which make them prominently 
 visible. 
 
THE MOON. 71 
 
 3. The Crater-Mountains, comprising both the mound 
 or wall, and the included cavity. These are the grand 
 peculiarities of the Moon: commonly, and probably with 
 correctness, ascribed to volcanic agency : yet differing in 
 several respects from the foci of eruption on our own globe : 
 on the Earth, they are usually openings on the summits or 
 sides of mountains on the Moon, depressions below the 
 adjacent surface, even when it is a plain or valley ; on the 
 Earth, the mass of the cone usually far exceeds the capacity 
 of the crater on the Moon, they are much nearer equality ; 
 on the Earth, they are commonly the sources of long lava- 
 streams on the Moon, traces of such outpourings are rare ; 
 on the Earth, their number as well as dimensions are com- 
 paratively inconsiderable on the Moon, M. considers that 
 there are upwards of 1000 visible with a breadth of 9 miles, 
 and Schm. has drawn nearly 33,000 in all, so that they are 
 the greatest characteristic of its surface, and, the grey plains 
 excepted, among the largest of its features. When, however, 
 allowance has been made for the inferior power of gravity 
 on the- Moon, through which a six-fold displacement in 
 height or distance would be caused by the same amount of 
 force, 1 for the possible difference of materials, and for 
 the more rapid cooling produced by radiation in the absence 
 of an atmosphere, it is quite conceivable that volcanic force, 
 similar to that on the Earth, may have been the real agent, 
 though in a gently modified form. Any one may see, with 
 the ingenious Hooke, a strong resemblance to the rings 
 left by gaseous bubbles ; 2 but to this impression mechanical 
 
 1 Mount Tongariro in New Zealand was, in 1875, throwing stones 
 8 miles from the crater. 
 
 2 Scrope lias suggested a somewhat similar hypothesis. He thinks 
 that the lunar craters have derived their peculiar features * from the 
 explosions of vapour that produced them, breaking through a surface 
 
72 THE SOLAR SYSTEM. 
 
 difficulties arising from the cohesion of materials have been 
 opposed, and a more consistent explanation sought in the 
 idea that the larger craters may be the remains of molten 
 lakes; in these, left for a while unfrozen in the general 
 cooling and crusting over of the once-fiery globe, an alter- 
 nate shrinking and overflowing of lava, from a fluctuating 
 pressure from beneath, might gradually produce the existing 
 forms. This theory has been recently extended and advo- 
 cated with much ingenuity in the * Selenographical Journal ' 
 by Green, who would substitute erosive for eruptive agency, 
 even in the smaller craters; the undermining and re-dis- 
 solving power of fluid lava pressed upwards through the 
 surface, and subsequently in many cases receding, being 
 substituted for actual explosion. On this hypothesis the 
 brighter and more elevated parts of the globe would, as a 
 rule, date from a more ancient epoch than the darker and 
 once fluid plains. 1 
 
 We have nothing on the Earth to be compared with the 
 gigantic scale of the greater circles, though an extinct 
 crater-plain, 20 miles in diameter, with peaks on its 'ring, is 
 said to exist on the island of Mauritius: and the c aters 
 of the Sandwich Islands, Kirauea and Haleakala the one 
 a fused, the other a frozen, lake of lava, with the small 
 'blowing-cones' which eject only cinders and ashes afford 
 
 of soft and semi-liquid matter in successive bubbles, whose bursting 
 would throw off all round a concentric ridge formed of repeated layers 
 of this substance.' Volcanoes, 2nd Ed., 1872, p. 233. 
 
 1 Mr. S. E. Peal of Assam advocates, very ingeniously, 'A Theory 
 of Lunar Surfacing by Glaciation,' in which he contends that the 
 walled- plain s, ring-plains, etc., 'have all been lakes or lagoons left 
 for a time in a slowly glaciating crust, kept liquid by quasi- volcanic 
 orifices;' and that the aqueous vapour rising from these areas, forming 
 a local and dome-shaped atmosphere, ultimately condensed round the 
 margin as snow and formed the ring. 
 
THE MOON. 
 
 73 
 
 an analogy, 1 the striking nature of which will be apparent 
 from the following representation of the latter, taken from a 
 view in Elwes's ' Sketcher's Tour.' 2 Difficulties no doubt 
 remain ; but we can hardly wonder at them, while geologists 
 are still so little agreed about 'elevation-craters' and sub- 
 marine volcanoes on our own globe. The circular cavities 
 
 Extinct Crater of Haleakala. 
 
 of the Moon are arranged in three classes, Walled (or 
 Bulwark) Plains, Ring-Mountains, and Craters: a fourth 
 includes little pits without, or with scarcely a visible ring. 
 The second and third differ chiefly in size ; but the first 
 have a character of their own ; the perfect resemblance of 
 
 1 The craters of Java are also said to bear out this comparison. 
 
 2 Haleakala, ' the house of the Sun,' in E. Maui, is of an oblong 
 form, "with two great openings in the wall, more than 30 miles in 
 circumference, 10,000 feet above the sea, and about 2000 feet deep. 
 On the floor are 12 or 13 small red or yellow cones. The highest 
 summits in the view are the two snowy volcanoes of Hawaii, seen 
 over the clouds in a very faint distance: our sketch gives only the 
 general effect. 
 
74 THE SOLAR SYSTEM. 
 
 their interiors to the grey plains, as though they had been 
 originally deeper, but filled in subsequently with the same 
 material ; many of them, in fact, bearing evident marks of 
 having been broken down and overflowed from the outside. 
 Their colour is often suggestive of some kind of vegetation, 
 though it is difficult to reconcile this with the apparent 
 deficiency of air and water. It has been ingeniously sug- 
 gested that a low stratum of carbonic acid gas the frequent 
 product of volcanoes, and long surviving their activity may 
 in such situations support the life of some kind of plants : 
 and the idea deserves to be borne in mind in studying the 
 changes of relative brightness in some of these spots. 1 The 
 deeper are usually the more concave craters ; but the bottom 
 is often flat, sometimes convex ; and frequently shows sub- 
 sequent disturbance, in ridges, hillocks, minute craters, or 
 more generally, as the last effort of the eruption, central 
 hills of various heights, but seldom attaining that of the 
 wall, or even, according to Schni., the external level. The 
 ring is usually steepest within (as in terrestrial craters), 2 
 and many times built up in vast terraces, or in parallel 
 walls, frequently lying, Schm. says, in pairs divided by 
 narrow ravines. Nasmyth refers these terraces not very 
 probably to successively decreasing explosions ; in other 
 cases he more reasonably ascribes them to the slipping down 
 of materials piled up too steeply to stand, and undermined 
 
 1 The supposition, however, is said to be incompatible with the 
 law of the diffusion of gases. 
 
 G-. thought he perceived, in the grey tints of depressed surfaces, 
 gome of which vary with the amount of solar light, traces of several 
 kinds of vegetation, comprised between 65 N. and 55 S. latitude, 
 and preserving the correspondence observed on the Earth between 
 increasing latitude and elevation. 
 
 2 Schm. gives 4 to 15, and 20 to 50, as the respective average 
 inclinations without and within. 
 
THE MOON. 75 
 
 by lava at their base, leaving visible breaches in the wall 
 above : they would bo well explained on the supposition 
 just mentioned of fluctuating levels in a molten surface. 
 Small transverse ridges occasionally descend from the ring 
 chiefly on the outside : great peaks often spring up like 
 towers upon the wall ; gateways at times break through the 
 rampart, and in some cases are multiplied till the remaining 
 piers of wall resemble the stones of a huge megalithic 
 circle. 1 A succession of eruptions may be constantly traced, 
 in the repeated encroachment of rings on each other, where, 
 as Schm. says, the ejected materials seem to have been 
 disturbed before they had time to harden: the largest are 
 thus pointed out as the oldest craters, and the gradual 
 decay of the explosive force, like that of many terrestrial 
 volcanoes, becomes unquestionable. The peculiar whiteness 
 of the smaller craters may indicate something analogous to 
 the difference between the earlier and later lavas of the 
 Earth, or to the decomposition caused, as at Teneriffe, by 
 acid vapours : in the grey levels we thus perhaps obtain an 
 indication of the superficial character of their colouring. 2 
 
 4. Valleys, of ordinary character, are not infrequent ; 
 some of grand dimensions ; others mere gorges. The most 
 contracted of these latter are entitled to be classed apart as 
 
 5. Clefts (or Hills 8 ). These were discovered by Schr. : 
 G. and L. added to their number, which B. and M. raised to 
 90 in the text of their work ; but the latter astronomer, on 
 
 1 Or Druidical Avenue, as, for example, between Guerike and 
 Parry. 
 
 * In addition to these more prominent objects, traces of obscure 
 und ancient rings are found in almost every part of the lunar surface, 
 but perhaps more commonly on the Maria. 
 
 3 An incorrect term adopted from the German, in which it does 
 not imply, aa in English, the presence of \\ater. 
 
76 THE SOLAR SYSTEM. 
 
 taking charge of the noble Dorpat achromatic, Q^-in. aper- 
 ture, perceived more than 150, and thought it might be pos- 
 sible to descry 1000. Schm. published in 1866 a catalogue 
 of 425, the greater part discovered by himself; and has 
 since brought the number up to nearly icoo. These most 
 singular furrows pass chiefly through levels, intersect craters 
 (proving a more recent date), reappear occasionally beyond 
 obstructing mountains, as though carried through by a 
 tunnel, and commence and terminate with little reference to 
 any conspicuous feature of the neighbourhood. Ne. observes 
 that they are frequently connected with valley-systems open- 
 ing out of high lands, and often run down the centre of 
 valleys. Klein says they are not common in the great plains. 
 The idea of artificial formation is negatived by their magni- 
 tude ; l they have been more probably referred to cracks in 
 a shrinking surface ; a process which M. and others think 
 may even now be in operation. The observations of Ku- 
 nowsky, confirmed by M. at Dorpat and Schm., seem in 
 some instances to point to a less intelligible origin in rows 
 of minute contiguous craters ; but a more rigorous scrutiny 
 with the highest optical aid is yet required. 2 To these wo 
 may add 
 
 6. Faults, or closed, not open, cracks, sometimes of con- 
 
 1 Schm. gives them 1 8 to 92 miles long, mile to 2 T 4 5 miles broad, 
 and 100 to 430 yards deep. O., following out his strange theory 
 that the Moon was once surrounded by an immense ocean which has 
 wholly disappeared, considered the larger of thtse furrows as the 
 beds of dried-up rivers ; the smaller he referred to artificial clearings 
 in the forests, answering the purpose of roads. It is to be regretted 
 that the extravagance of his fancy should in many instances have 
 brought discredit upon the unquestionable precision of his sight. 
 
 2 Klein, with a very sharp image and power upwards of 400, finds 
 their breadth much more irregular than would be suspected with 
 inferior means. 
 
THE MOON. ' 77 
 
 siderable length, where the surface on one side is more ele- 
 vated than on the other. These familiar geological features 
 have been recognised in abundance by Birt and With, and 
 are more readily traced on the Moon than on the Earth, 
 from the absence of superincumbent alluvial deposits and 
 denudation. 
 
 Wonders are here in abundance for the student : but he 
 will find it impossible to pursue them far from the termi- 
 nator, they must be viewed under the oblique rays of a 
 rising or setting Sun. As the angle of illumination in- 
 creases, a fresh aspect of things creeps in, and extends itself 
 successively over the whole disc, and in its progress the 
 inexperienced observer will find himself astonished at the 
 change, and frequently bewildered in the attempt to trace out 
 the landmarks of the surface. Objects recently well recog- 
 nised under the relief of light and shade will become con- 
 fused by a novel effect of local illumination, and the eye 
 will wander over a wilderness of streaks and specks of light, 
 and spots and clouds of darkness, where it may sometimes 
 catch the whole, sometimes a portion, sometimes nothing, 
 of many a familiar feature ; while unknown configurations 
 will stand boldly out defying all scrutiny, and keeping their 
 post immovably till the decreasing angle of illumination 
 warns them to withdraw. Nothing can be more perplexing 
 than this optical metamorphosis, so complete in parts as 
 utterly to efface well-defined objects ; so capricious as in 
 some instances to obliterate one, and leave unaffected the 
 other, of two similar and adjacent forms. G., carrying out 
 an idea of Schr.'s, referred some of these changes to the 
 progress of vegetation which, if existing, will naturally, in 
 default of a change of seasons, run its whole course in a 
 single lunation : even the cautious B. and M. have admitted 
 that some variations of colour may possibly point in this 
 
78 THE SOLAE SYSTEM. 
 
 direction; and photographic results seem to indicate the 
 presence of green light not cognisable by the eye : but the 
 general change demands a more universal solution ; and 
 probably a wide range of colours in the soil may be con- 
 cerned in the effect. The subject calls for careful study, 
 but would involve much laborious application. 1 
 
 The most obvious features of the Moon under a high 
 illumination are the Systems of Bright Sir calf s which issue, 
 though in widely differing proportions, chiefly from seven 
 different centres: all craters, few inconsiderable, but none 
 of the very largest class. In some cases the streaks proceed 
 from a circular grey border surrounding the crater; in others 
 they cross irregularly at its centre. They pass alike over 
 mountain and valley, and even through the rings and cavi- 
 ties of craters, occasionally reach the terminator, 2 and seem 
 to defy all scrutiny. Nichol asserts that in some contiguous 
 systems, the order of formation may be detected from the 
 mode oiNtheir intersection ; 3 a statement well deserving the 
 notice of those whose telescopes will carry them through 
 the inquiry. But one thing is certain, that they are very 
 seldom accompanied by any visible deviation in the super- 
 ficial level ; a fact irreconcilable with Nasmyth's conjecture, 
 that they are cracks diverging from a central explosion, 
 filled up with molten matter from beneath ; trap-dykes on 
 the Earth are, indeed, apt to assume the form of the surface, 
 but the chances against so general and exact a restoration of 
 
 1 The polarisation of light by the Moon was found by Secchi to 
 be entirely different in the lowlands and in the mountainous parts. 
 Birt sees a greenish tint in the plains under very oblique lights. 
 
 2 Ne. remarks this, in opposition to B. and M., and says that some 
 of the Tycho streaks shift a little with varying libration. 
 
 3 The following, according to him, is the chronological order of 
 three great systems : Copernicus, Aristarchus, Kepler. 
 
THE MOON. 79 
 
 level, all along such multiplied and most irregular lines of 
 exposure, would be incalculable ; many of the rays are also 
 far too long and broad for this supposition, or for that of B 
 and M., that they may be stains arising from highly heated 
 subterraneous vapour on its way to the point of escape. 1 
 
 1 Schwabe suggests that they may be due to contrast: a shade 
 being formed in their intervals as the day increases by a multitude 
 of thin converging or parallel grey lines, which may be seen by a 
 good instrument, and which may possibly result from some kind of 
 vegetation. 
 
 In a paper recently published in the Attronomische Nachrichten, 
 Professor Pickering gives the results of his observations of the bright 
 streaks with a 13-inch telescope at Arequipa. He finds: (i) That 
 the streaks round Tycho do not radiate from the apparent centre of 
 this formation, but point towards a multitude of minute craterlets on 
 its SE. or N. rim. Similar craterlets occur on the rims of other 
 great craters, forming streak-centres. (2) Generally speaking, a 
 very minute and brilliant crater is located at the end of the streak 
 nearest the radiant point, the streak spreading out and becoming 
 fainter towards the other end. The great majority of lunar streaks 
 appear to issue from one or more of these minute craters, which rarely 
 exceed a mile in diameter. (3) The streaks which do not issue from 
 minute craters usually lie upon or across ridges, or in other similarly 
 exposed situations, sometimes apparently coming through notches in 
 the mountain walls. (4) Many of the Copernicus streaks start from 
 craterlets within the rim, flow up the inside and down the outside of 
 the walls. (5) Though there are similar craters within Tycho, the 
 streaks from them do not extend far beyond the walls of this forma- 
 tion. All the conspicuous streaks about Tycho originate outside its 
 walls. (6) The streak-systems of Copernicus, Kepler, and Aristarchus 
 are greyish in colour and much less white than that associated with 
 Tycho. Some white lines extending SE. from Aristarchus do not 
 apparently belong to the streak-system. In the case of craterlets 
 lying between Aristarchus and Copernicus, the streaks point away 
 from the latter. (7) There are no very long streaks. They vary 
 from 10 to 50 miles in length, and are rarely more than a quarter of a 
 mile in width at the crater. From this point they gradually widen 
 out and become fainter. Their width, however, at the end farthest 
 troni the crater is seldom more than 5 miles. 
 
80 THE SOLAR SYSTEM. 
 
 The extraordinary brilliancy of some portions of the Full 
 Moon is less difficult of explanation, when we bear in mind 
 the effect of chalky strata, or that peculiar kind of granite 
 which on the loftiest peaks of the Himalayas may readily 
 be confounded with the adjacent snow. In many cases the 
 form of the surface gives us no key to the distribution of 
 this vivid reflection; mothers it occupies a marked position, 
 as on the summit of rings and central mountains : the idea 
 of a mirror-like glaze reflecting an image of the Sun, though 
 entertained by such authorities as B. and M., seems difficult 
 to be reconciled with the ever-varying angle of illumination. 
 
 A scale of reflective power has been adopted from Schr. 
 by later selenographers, in which (blackness being o) the 
 darkest grey shades rank as i, the brightest portions 10. 
 This is of some use, though merely arbitrary. A more 
 reliable plan, especially in combination with such a scale, 
 would be the mode of comparative values, in which the light 
 of any given spot is referred to others above and below it in 
 brightness. Changes are more than suspected in the reflec- 
 tive power of portions of the lunar surface, and it would be 
 interesting to examine it in that aspect; but we have no 
 good map of the Full Moon, and if we bad, it never could 
 adequately express the various gradations of brightness, which 
 must be the object of topographical study. 
 
 A few peculiarities of arrangement deserve to be men- 
 tioned here. The remarkable tendency to circular forms, 1 
 even where explosive action seems not to have been con- 
 cerned, as in the bays of the so-called seas, is very obvious ; 
 
 1 It has recently been pointed out by Elger that the borders of 
 a large number of formations are polygonal in shape, and that many 
 exhibit a tendency to a hexagonal figure, e.g. Copernicus, Langrenus, 
 Vieta, Ptolemaus, Wargentin, Hevel, Hausteen, etc. (see Journal 
 B.A.A., vol. iii. p. 314). 
 
THE MOON. 8 1 
 
 and so are the horizontal lines of communication already 
 mentioned. The gigantic craters or walled-plains often 
 affect a meridional arrangement: three huge rows of this 
 kind are very conspicuous, near the centre, and the E. and 
 W. limb. A tendency to parallel direction has often a 
 curious influence on the position of smaller objects ; in many 
 regions these chiefly point to the same quarter, usually N. 
 and S. or NE. and SW. ; thus in one vicinity (between G, 
 L, and M on the accompanying map) B. and M. speak of 30 
 objects following a parallel arrangement, for one turned 
 any other way; even small craters entangled in such general 
 pressures (as round L) have been squeezed into an oval 
 form ; and the effect is like that of an oblique strain upon 
 the pattern of a loosely woven fabric : an instance (near 27, 
 28) of double parallelism, like that of a net, is mentioned, 
 with crossing lines from SSW. and SE. Local repetitions 
 frequently occur; one region (between 290 and 292) is 
 characterised by exaggerated central hills of craters; another 
 (A) is without them; in another (185), the walls themselves 
 fail. Incomplete rings are much more common towards the 
 N. than the S. pole ; the defect is usually in the N., seldom 
 in the W., part of the circle ; sometimes a cluster of craters 
 are all breached on the same side (near 23, 32). 1 Two 
 similar craters often lie N. and S. of each other, and near 
 them is frequently a corresponding duplicate. Two large 
 craters occasionally lie N. and S., of greatly resembling 
 character, S. usually of size of N. from 18 to 36 miles 
 apart, and connected by ridges pointing in a SW. direction 
 (20, 19: 78, 77: 83, 84: 102, 103: 208, 207, 204: 239, 
 242: 261, 260: 262, 263: 340, 345). Several of these 
 
 1 Compare Elwes's account of the small cones on the floor of the 
 ureat extinct crater Haleakala, some of them "broken down at the 
 side, nearly always on the NE." Sketcher's Tour, 214. 
 
 VOL. I. O 
 
82 THE SOLAR SYSTEM. 
 
 arrangements are the more remarkable, as we know of 
 nothing similar on the Earth. 
 
 The question as to the continuance of eruptive action on 
 the Moon is one of great interest. It is now well known 
 that the volcanos, which Herschel I. and others thought 
 they saw in activity on the dark side, were only the brighter 
 spots reflecting back to us the earth-shine of the lunar night 
 with the same proportional vivacity as the sunshine of the 
 day. No valid reason, indeed, has been assigned for the 
 fact, witnessed by many observers, especially Sm., that one 
 at least of these spots Aristarchus varies remarkably in 
 nightly luminosity at different periods, 1 nor for the specks 
 of light which more than once Schr, caught sight of on the 
 dark side for a short time : 2 but in these cases there has 
 been no subsequent perceptible alteration of surface ; and 
 they furnish no reply to the inquiry respecting present 
 changes. Such were abundantly recorded by Schr. in his 
 day, chiefly variations in the visibility or form of minute 
 objects ; but a great majority of them he, and subsequently 
 G., who witnessed many such appearances, referred to the 
 lunar atmosphere: and B. and M. are disposed to discard 
 them all as the result of inaccuracy or varying illumination. 
 
 1 Elger saw a spot on the dark side, apparently Aristarchus, 
 1867, April 12, 7 h 30 to 8 h 30, nearly as bright as a 7 m? star, with 
 a 4-in. aperture, and too conspicuous to be overlooked by the most 
 careless observer. It was much fainter during the last 15, and 
 scarcely perceptible at 9 h . The Moon was i d 5 h after I. Qu. He had 
 seen something similar on former occasions. Schr.'s conjecture that 
 the variations, which he observed in a minor degree in several parts 
 ef the disc, may be due to atmospheric condensation during the 
 lunar night, is more elegant than probable : it may, however, deserve 
 consideration. 
 
 8 Such a phenomenon, more extended, but very faint, was seen, 
 or fancied, by G. ; and witnessed in our own day, with great distinct- 
 ness, by Grover and by Williams. 
 
THE MOON. 83 
 
 The extraordinary influence of the latter upon the aspect of 
 distant and unknown objects may be estimated by any one 
 who will sketch the changed effects of light and shade on 
 any familiar terrestrial object at different times of day; 
 still there seems to be a residuum of minute variations not 
 thus disposed of, and in some cases possibly indicating actual 
 local change. Terrestrial analogy is in favour of the idea 
 that disturbing agency may have greatly diminished without 
 having become extinct : but observation, not assertion, must 
 decide the point, There are no traces of any grand convul- 
 sion since the date of the first lunar map ; and we are only 
 now becoming possessed of the means of detecting smaller 
 changes. Schr.'s drawings are very rough ; the much more 
 careful ones of L., and B. and M., would be too recent to 
 warrant great expectations, even were they more reliable 
 especially the latter as to minute details ; and they are sub- 
 ject to the same material drawback as the recently published 
 great map of Schm. admirable as it is in its own way 
 that of representing objects in only one aspect, and that a 
 conventional one. This defect is of course inherent in every 
 general map, and can only be supplied by topographical 
 sketches, after the manner of Schr., giving repeated views of 
 the same object under differing angles of illumination and 
 reflection. As yet, this has been only partially attempted. 
 We have no monograph representing any one spot for each 
 successive night of its visibility, and in varied conditions of 
 libration: but such a series would be very instructive, as 
 well as valuable for the future. But we must not omit to 
 do justice to the indefatigable as well as accurate labours 
 of Birt, continued through many years, and adding very 
 materially to our knowledge of lunar detail ; and much is to 
 be hoped from the researches of the Selenographical Society, 
 established in London in 1878, which, comprising many 
 
84 TFIE SOLAR SYSTEM. 
 
 eminent English and foreign astronomers, has for its object 
 the collection and preservation of observations, and the 
 indication of the most promising lines of research. 1 
 
 Little of a satisfactory nature can be said as to a Lunar 
 Atmosphere. That its density cannot amount to y^ of that 
 of our own is demonstrable from theory, and proved by 
 observation, which shows us a sharp outline, and detects no 
 change in the aspect of stars in contact with the limb : 2 
 and hence its entire absence has been maintained by great 
 astronomers : Schr. asserted its existence from many changes 
 of aspect in minute objects, and from a very dim twilight 
 which he traced through 9 years beyond the points of the 
 horns; his inferences are supported and in part exceeded 
 by G., who frequently saw or imagined fogs and clouds 
 
 rooting on tlic surface ; nor is Klein disposed to deny the 
 probability of such obscurations, especially in deep places. 
 The defined limb and the absence of refraction are accounted 
 
 1 This Society was dissolved at the close of the year, 1882, but its 
 work was subsequently resumed by the Liverpool Astronomical 
 Society, and is now being actively carried on by the Lunar Section of 
 the British Astronomical Association. 
 
 2 It has been ascertained of late years that the Moon's observed 
 diameter exceeds by 4" that computed from occultation of stara 
 This appears too much to be explained by irradiation. 
 
THE MOON. 85 
 
 for by Schr. by limiting the sensible atmosphere to the 
 inferior regions. B. and M., while explaining away not 
 very satisfactorily Schr.'s twilight, which they could never 
 distinctly find, do not deny the possibility of a very rarefied 
 gaseous envelope. 1 Those traces of twilight, which have 
 been confirmed by G. and recently by MM. Henry with a 
 large telescope at Paris, and which I imagined I saw, 1855, 
 June 20, but only doubtfully from want of better optical 
 means, might well engage the student's attention : in order 
 to assist him two figures are here given from among Schr.'s 
 numerous delineations. They represent the cusps of the 
 Moon as seen by him, 1792, Feb. 24, with a 7 -ft. reflector 
 by Herschel L, powers 74, 161. 
 
 Occultations of planets or stars, which are important to 
 the professed astronomer, are interesting to the amateur as 
 bringing out distances and motions of which the naked eye 
 takes little cognisance : the comparative nearness of our 
 satellite becomes self-evident, and its orbital movement is 
 made apparent from minute to minute. A grand effect is 
 produced by the visible sailing of this ponderous globe 
 through immeasurable space ; and it may well convey a 
 
 1 Some very curious photographic experiments by De la Rue 
 have been thought to tend the same way. It seems hardly probable 
 that oxygen, which forms of the weight of terrestrial earths, should 
 be entirely absent from the Moon; and the whiteness of the small 
 craters in the grey plains is a suggestive fact. Schm. has in a 
 few instances (to which he might have added one from Schr.) seen 
 a grey border to the black shadow in craters, but this he ascribes to 
 its being thrown from a very ragged edge. Schr. and other observers 
 have noted occasional want of definition in certain spots as compared 
 with others. In a few cases M. and Schm. have perceived a blue tint 
 round bright points on the terminator, probably, as Schm. says, due to 
 the * secondary spectrum' of all achromatics. De la Rue's remark is 
 important, that it is difficult to conceive any chemical formation of 
 matter without an atmosphere. 
 
86 THE SOLAR SYSTEM. 
 
 deep impression of the omnipotent Power and consummate 
 Wisdom which orders its undeviating course. The instan- 
 taneous extinction, too, and sudden flashing out of a large 
 star in these circumstances are very striking, though less 
 instructive than might have been expected as to the question 
 of an atmosphere : the immersion and emersion are usually 
 as sudden as if none existed ; but this may be accounted 
 for by the rapid motion of the Moon, or, on Schr.'s theory, 
 by the elevation of that portion of the limb : the gradual 
 extinction sometimes recorded may be only due to irregu- 
 larities on the edge : the distortions or flattenings occasion- 
 ally noticed in the shape of planets at occultation are too 
 extensive for any such cause, and must be referred to optical 
 illusion. 1 All occultations of importance are predicted in 
 the Nautical Almanac ; the most beautiful are immersions 
 behind the darJc limb when the latter receives a strong 
 earth-light, as between New Moon and I. Quarter. 2 
 
 The projection of a star upon the Moon, just before 
 immersion, as if it advanced in front of it, is very difficult 
 of explanation. South, after a careful examination of the 
 instances on record, was unable to come to any satisfactory 
 conclusion : it is an occurrence of the most capricious kind, 
 which can never be predicted for any star, eye, or telescope ; 
 and is evidently an optical, not astronomical, phenomenon. 
 
 Libration must be well understood, before proceeding to 
 topography. This is an apparent displacement of the spots 
 with respect to the limb (or centre), arising in one direction 
 (that of lunar longitude) from the equable rotation of the 
 
 1 See Proctor's very ingenious illustration of such deceptions 
 under the head of Saturn. 
 
 2 Kunovvsky has seen the dark liinb sharply defined 3 d 4" after 
 I. Quarter. G. professed that he was able to trace the larger suas 
 on the dark side with the naked eye. 
 
THE MOON. 87 
 
 Moon on its axis combined with its unequable velocity in 
 an elliptical orbit, in another direction (that of latitude) 
 from the inclination of its orbit to the ecliptic in conjunction 
 with a slight inclination of the axis to the plane of the orbit : 
 it completes its changes in about four weeks, though an 
 exact restoration of the position called ' mean (or medium) 
 libration' does not take place till the end of three years. 
 Hence, the usual statement that we see always the same 
 hemisphere is only approximately true. The spots are 
 constantly swinging a little backwards and forwards, and 
 those near the E. and W. limbs going alternately out of 
 sight ; while, as our eye rises successively above each pole, 
 a little more or less of those regions is seen, the whole 
 area thus concealed and exposed by turns amounting to T 2 T 
 of the surface of the globe. 1 No map of the Moon, there- 
 fore, can correctly represent its whole aspect on two follow- 
 ing nights, and they are of course constructed to correspond 
 with a state of mean libration. The displacement of tha 
 spots, which amounts at a maximum to 6 47' N. and S., 
 7 55' E. and W., and 10 24' from a concurrence of both, 
 in either direction from a normal position, produces little 
 effect upon the aspect of the central parts, which are merely 
 shifted with regard to the Moon's equator or I st meridian ; 
 but in the foreshortened neighbourhood of the limb its 
 results are very obvious. Fresh regions constantly take 
 the outline of the disc, and the mountainous projections of 
 to-night may be all out of sight to-morrow. One effect of 
 libration is, that the spots have no fixed position with respect 
 to the Moon's age, being sometimes earlier, sometimes later, 
 on the terminator, so that no precise instructions can be 
 given when to look for them ; it may be useful, however, to 
 know that, as Birt has pointed out, the terminator passes 
 1 Proctor, The Moon, 197. 
 
88 THE SOLAR SYSTEM. 
 
 through very nearly the same part of the surface at recurring 
 intervals of 59 d i h 28. A few approximations alone will 
 be found in these pages, especially as a little practice with 
 the map will render identification easy : the following con- 
 siderations, however, may be useful to the beginner: 
 
 The relief of the surface will be stronger as it is nearer 
 to the terminator, and all delicate and difficult objects are 
 best seen near the sunrise or sunset of the Moon, which, 
 like the corresponding times of the Earth, abound with grand 
 and beautiful effects of light and shade. Every little irregu- 
 larity then assumes temporary importance ; inconsiderable 
 hillocks, minute craters, low banks, narrow canals, become 
 visible in the horizontal ray ; rising grounds or soft valleys 
 seem to start into existence, the outer slopes of craters 
 advance into the surrounding levels, larger masses appear 
 in exaggerated prominence, 
 
 Majoresque cadunt de montibus umbrea. 
 
 These broad and deep shadows often taper off to such slender 
 points, that a caution may be requisite, not to infer anything 
 extravagant respecting the sharpness of the form which casts 
 them. It may be questioned whether anything in the Moon 
 exceeds the acuteness of the Swiss Finsteraarhorn, or the 
 abruptness of the Pic du Midi d'Ossau in the Pyrenees. An 
 oblique light cast upon a rough surface, modelled in clay 
 or dough, will show how disproportioned oftentimes is the 
 shadow to the reality ; and the same experiment will prove 
 to us that in many cases the true relief will be unknown till 
 the shadow on either side of the object has been examined. 
 The intense blackness of the lunar shadows gives an effect 
 which must be strangely contrasted with a distant prospect 
 of our Earth. Here, a highly reflective and vapour-charged 
 atmosphere surrounds all objects with a constant illumina- 
 
THE MOON. 89 
 
 tion, beginning before sunrise and outlasting sunset ; there, 
 the Sun goes up and down in noonday strength, and the 
 shadows are unrelieved by any reflection from a sky which 
 must be almost black all day: every mountain produces 
 utter darkness where it intercepts the Sun ; and every crater, 
 while its ring is glittering like snow in the rising or setting 
 beam, is filled with midnight shade. Dawes, alone, by em- 
 ploying the contracted field of his solar eye-piece, has 
 traced a very faint glimmering in these depths, produced 
 by reflection from the opposite sunlit cliffs. 1 The termi- 
 nator is, indeed, marked through the grey plains by a narrow 
 shadowy border, and the tops of the mountains just appear- 
 ing or vanishing in the night-side are somewhat deficient in 
 brightness ; but this is the ' penumbra,' or partial illumina- 
 tion, due to a portion of the Sun's disc, while the rest is 
 beneath the horizon. In other respects the glittering sharp- 
 ness of the Moon's sunrise, or sunset, is widely contrasted 
 with the softness of our own skies. But though it is then 
 that we must watch for minute details, for large objects we 
 shall find the relief too broad and partial ; unbroken night 
 conceals the greater cavities, and the shade of loftier summits 
 renders lower ranges invisible. Not till day descends 
 among the terraces of the one, or creeps down over the 
 shoulders and along the slopes of the other, does their true 
 structure come out; and their distinctness increases while 
 their minuter neighbours decline into insignificance. 
 
 L., 2 and B. and M., have done admirably well in their 
 
 1 Schm. twice saw the innermost cavity of the peculiarly shaped 
 crater 399 feebly illuminated at sunrise, as though filled with mist. 
 He prefers an explanation identical with that of Dawes; but qu. as 
 to its adequacy under the circumstances? Another large crater near 
 S. pole also twice showed a similar internal twilight. Compare 
 appearance of 132, Eng. Mech. 1871, Dec. 25 : 1872, Mar. 15. 
 
 3 His general map is valuable, and not expensive; but the scale. 
 
90 THE SOLAR SYSTEM. 
 
 delineations. Yet a little experience will show that they 
 have not represented all that may sometimes be seen with a 
 good common telescope. My own opportunities, even when 
 limited to a 3 r 7 -in. aperture, satisfied me, not only how 
 much remains to be done, but how much a little willing 
 perseverance might do, provided there were some knowledge 
 of the laws of perspective and shadow, and a due attention 
 to the direction of the incident and reflected light: some 
 facility in design would also be very desirable, and, if pro- 
 portion is tolerably preserved, a number of rough sketches 
 under varied lights taken at the eye-piece, and carefully 
 compared with the original, would be more serviceable than 
 one or two finished drawings. Detail being the great object, 
 a small portion only should be attempted at once ; this will 
 not merely be easier and more pleasant, but will avoid the 
 change in the shadows, which is considerable near the 
 terminator during a long-continued delineation. The record, 
 to be of value, must possess four data: i. Hour of Observa- 
 tion; 2. Moon's Aye, reckoned from or to the nearest 
 change ; 3. Position of Terminator referred to well-marked 
 spots, some nearly in tlie latitude of the observed region ; 
 others a good way N. and S. of it, so as to show the direction 
 of illumination, which is seldom exactly at right angles to 
 the lunar meridian ; 4. Libration, indicated (i.) in longitude, 
 by time reckoned to or from nearest perige or apoge; or 
 both may be specified ; (ii.) in latitude, by Moon's latitude 
 at the time ; these particulars being taken from ' Nautical 
 Almanac,' and the last reduced to the hour of observation. 
 
 15^ inches, is rather small, and the deviations from circularity in the 
 craters exaggerated. The discontinuance of his * Sections,' on a 3-ft. 
 (French) scale, from failing sight, was long a serious hindrance to 
 selenography ; but the missing portions have been recovered, and 
 recently published under the careful editorship of Schm. 
 
THE MOON. . QI 
 
 More than this cannot bo ascertained without a micrometer 
 or calculation; but this is enough for the comparison of 
 delineations. If the last two data are nearly coincident in 
 any observations, the angles under which the landscape is 
 illuminated and viewed differ so little that any variation 
 in its details must be referred to either (i) inadvertence or 
 mistake in the observer; (2) actual change in the Moon's 
 surface ; or (3) obscuration or deception in her atmosphere. 
 Schr. relates so many instances of the latter kind that, even 
 if we reject the confirmation of the keen-eyed but fanciful 
 G., it seems difficult to follow B. and M. in disposing of 
 them all as errors of observation ; nor does Klein, a very 
 accurate living observer, think the inquiry by any means 
 unworthy of special notice. One important caution seems 
 not to have occurred to Schr. : the change of lunar seasons, 
 slight as it is, somewhat affects the direction of the shadows ; 
 and the variations of foreshortening from libration may 
 make them more or less visible; and thus some apparent 
 discrepancies might be reconciled. With large apertures, a 
 lightly tinted screen-glass works well ; possibly the use of 
 different colours might bring out seme curious result. 1 
 
 A good popular Map of the Moon has been hitherto a 
 desideratum in England. B. and M.'s smaller map, though 
 very inexpensive, is scarcely known here ; and is rather 
 crowded. Russell's and Blunt's, striking as to general 
 effect, break down in details. Those in ordinary books of 
 astronomy are especially useless. The one here given will, 
 it is hoped, be found less defective : it makes no claim to 
 pictorial resemblance, and professes to be merely a guide to 
 such of the more interesting features as common telescopes 
 will reach. It is carefully reduced from the ' Mappa Sele- 
 
 1 See De la Kue, on increased distinctness during advance of 
 lunar eclipse, Monthly Notices, xxv 276. 
 
92 THE SOLAR SYSTEM. 
 
 nographica ' of B. and M., published in four sheets in 
 1834, and subsequently re-edited, on a scale of 3 ft. if in. 
 (3 French ft.), omitting an immense mass of detail accumu- 
 lated by their diligent perseverance, 1 which would only 
 serve to perplex the beginner. Selection was difficult in 
 such a crowd ; on the whole it seemed best to include every 
 object distinguished by an independent name, including the 
 recent additions ; many of little interest thus creep in, and 
 many sufficiently remarkable ones drop out ; but tho line 
 must have been drawn somewhere, and perhaps would have 
 been nowhere better chosen for the student. Other spots, 
 however, have been admitted from their conspicuousness, 
 to which B. and M. have given only a subordinate name ; 
 minuter details come in, in places, for ready identification ; 
 elsewhere, larger objects are passed by, as less useful for 
 the purpose of the map. The nomenclature is almost 
 identically that established by B. and M., as rectified and 
 extended by Neison. Hevel (or Hevelius), in the earliest 
 attempt, designated different regions of the Moon from 
 supposed geographical analogies ; but this system has long 
 been abandoned, except in the case of some mountain ranges. 
 Riccioli, a far inferior observer, adopted a more available 
 method, originally adopted by Langrenus, of affixing to the 
 larger spots the names of distinguished philosophers ; his 
 list was increased by Schr., who made each name include 
 the adjacent objects, by adding the letters of the alphabet ; 
 and this system, improved and generalised, has been applied 
 by B. and M. to the whole disc ; the name used alone dis- 
 tinguishes the principal object ; Greek or Roman letters 
 
 1 Some idea may be formed of this, from the 919 nricrometrical 
 measures of the position of spots, and 1095 of heights and depths, 
 contained in their work Der Mond. Schrn., however, has left them far 
 behind. 
 
THE MOON. 93 
 
 added to it signify respectively the elevations or hollows 
 in the vicinity. To avoid crowding our map, letters and 
 numbers are substituted for names; every object in the 
 descriptive notices will be thus referred to, but, as this selec- 
 tion is limited, a complete list of the names givon by Ne. is 
 subjoined, which will also secure, in all cases, the important 
 object of identification as far as it goes. The alphabetical 
 arrangement which follows it may be found convenient. 
 
 The remark is scarcely needed that the student who 
 aims at more than a superficial knowledge of this very 
 interesting subject will require furthor aid than he can 
 derive from these pages, or from the accompanying map. 
 The larger of the maps of B. and M. will help him greatly, 
 especially if, as a German student, he can avail himself of 
 their corresponding work, ' Der Mond ' ; l or, if economy is 
 an object, their own abridgment of it. In point of compre- 
 hensiveness, nothing can equal the magnificent map of 
 Schm., 6 French ft. in diameter, in 25 sections, published, 
 to their great honour, by the Prussian Government. It is 
 the fruit of 34 years' labour, and the surprising number 
 of 32,856 craters which it is said to contain sufficiently 
 bespeaks its minuteness. It has, indeed, one very serious 
 fault namely, the exaggeration of the importance of low 
 banks and ridges by a disproportioned depth of shade ; and 
 in this respect it is inferior to the map of B. and M. But 
 its mass of detail, unique as it is, cannot supersede the 
 necessity of verbal description ; and here the ' Moon ' of 
 Neison will render such invaluable service that it can hardly 
 be dispensed with. It is illustrated by a map in sections, 
 less minute than that of Schm., but quite sufficient for the 
 
 1 A little work by Schm. under the same title could not be sub- 
 stituted for it as a text-book, but is very pleasing and interesting, ami 
 well worthy of translation. 
 
94 THE SOLAE SYSTEM. 
 
 majority of students ; and our choice, if limited to a single 
 manual, would fall without hesitation on this eminently 
 careful and faithful work. 1 
 
 The points of the Lunar Compass must be mastered 
 before we can use the map. Astronomers have fixed these 
 from their relative, not intrinsic, position; that is, the 
 several portions of the disc are named from the adjacent 
 quarter of the sky when the moon is on the meridian. Hence 
 N. and S. occupy the top and bottom, but E. and W. are 
 reversed, as compared with terrestrial maps : the former 
 being to the left, the latter to the right. But maps of tho 
 Moon usually represent its telescopic that is, inverted 
 appearance, so that we shall find S. at top, N. at bottom, 
 E. to right, W. to left. The meridians and parallels of 
 latitude have been omitted, except the I st Meridian and 
 Equator, which divide it, like the original, into Four 
 Quadrants: these are called by B. and M., the i 8t or NW., 
 2 nd or NE., 3 rd or SE., 4 th or SW. Quadrant. A selection of 
 the most interesting objects in each follows, from materials 
 furnished by the ' Mond ' of these astronomers and retaining 
 their arrangement : additions are made from other sources ; 
 but all statements not otherwise authenticated depend upon 
 their authority. In the more remarkable instances, their 
 measures of height and depth are given ; these were ascer- 
 tained by the lengths of the shadows a method previously 
 employed with less accuracy by Schr. ; capable of much 
 precision on favourable ground, but elsewhere uncertain. 
 For our present purpose round numbers will be a fully 
 sufficient approximation. 2 
 
 1 A good map has recently been prepared by Gaudiberfc ; and, for 
 beginners, Mellor's " Handy Map," mounted on card, will be found 
 useful. 
 
 8 Minuteness of numerical detail in astronomical results should not 
 
THE MOOX (FIRST QUADRANT). 95 
 
 FIKST, OR NORTH-WEST, QUADRANT. 
 
 MARE CRISIUM (A on the map). We begin with a con- 
 spicuous dark plain, the most completely bounded on the 
 Moon, and visible to the naked eye : apparently elliptical 
 from foreshortening, but really oval the other way, being 
 about 28 im. from N. to S., 355 from E. to W., and contain- 
 ing about 66,000 square m., or -g^th part of the visible 
 hemisphere more than half as much again as the area of 
 England and Wales. Its grey hue has a trace of green 
 in the Full; this has also been represented by the late 
 talented Astronomer Royal for Scotland, C. Piazzi Smyth, 
 in two beautiful figures taken during the increase and wane. 
 On rare occasions it has been seen by Schr., and in part by 
 B. and M., speckled with mimite dots and streaks of light : 
 something of this kind I saw with a fluid achromatic, 1832, 
 July 4, near I. Quarter. A similar appearance was noticed 
 by Slack, and Ingall, 1865. It would be difficult to say 
 why, if these are permanent, they are so seldom visible a 
 suggestive, though at present unintelligible, phenomenon. 
 The surface is deeply depressed, lower than Mare Foecundi- 
 tatis and M. Tranquillitatis. Many low ridges cross it in a 
 N. and S. direction ; but in this, as in many other cases, it 
 must be remembered that those lying E. and W. would be 
 imperceptible for want of shadow. The boundary moun- 
 tains are in part very steep and lofty. The PROMONTORIUM 
 AGARUM (1) rises about 1 1,000 ft. ; a mountain SE. of Picard, 
 15,600 ft., rivalling our Mont Blanc. On W. edge, Schr. 
 delineated a crater called by him ALHAZEN, which he con- 
 stantly employed to measure the existing libration : he saw 
 
 be misunderstood. It represents no natural fact, but only the care 
 bestowed upon measurement. 
 
96 THE SOLAR SYSTEM. 
 
 in it after a time unaccountable changes, and since, it has 
 been said, it cannot be made out. B. and M. think he 
 confounded it with a crater (2) lying farther S. ; G., how- 
 ever, drew it in 1824; the question, which was debated 
 among Kunowsky, Kohler, and others, has been cleared up 
 by Birt, who has recovered Schr.'s crater, between two lofty 
 mountains ; the cause, however, of its greater obviousness in 
 Schr.'s earlier days still offers some difficulty. The plain 
 contains several moderate-sized craters the largest, PICARD 
 (4), S. of which G. saw some curious regular white- ridges 
 like ramparts : while on the W., Birt and Ingall have 
 pointed out a remarkable bright patch, which subsequently 
 faded to a great extent, and which, according to Espin, 
 marks a depression. The next crater N. (PEIRCE) has a 
 very minute interior craterlet, discovered by Schm. a test- 
 object. The next crater N. of this (PEIRCE A) Birt has 
 sometimes been unable to find. There are also several very 
 minute craters in the level. Near the E. edge where there 
 is a pass in the great surrounding ridge between 450 and 
 451, lie several small, but in part lofty mountains, 1 
 islands, as it were ; among these Schr. describes singular 
 changes, which he refers to an atmosphere; B. and M. 
 consider them merely varied illumination, or pass them by 
 as unworthy of attention. Succeeding observers may revise, 
 even if they ultimately acquiesce in, this summary decision. 
 Schr. was a bad draughtsman, used an inferior measuring 
 apparatus, and now and then made considerable mistakes ; 
 but I have never closed the simple and candid record of 
 his most zealous labours with any feeling approaching to 
 contempt ; and though there may be truth in the assertion 
 of B. and M., that he was biassed by the desire of discover- 
 
 1 These are ill-figured in the great map, and B. and M. have given 
 a separate representation of them in their Mond. 
 
THE MOON (FIRST QUADRANT). 97 
 
 ing changes, they, possibly, were not themselves free from 
 an opposite prepossession. 
 
 A long winding cleft is suspected to cross the centre 
 of A. 
 
 Central hills seldom occur in craters here. 
 
 A may be well seen about 5 a after New, or 3 d after Full ; 
 in the latter case it is a magnificent spectacle when crossed 
 by the terminator and partially covered in by the vast 
 shadows of the mountains, from which Schr. considered that 
 those on NE. side must be at least 16,000 or 17,000 ft. high. 
 
 This astronomer has inserted in his work a marvellous 
 observation by Eysenhard, a pupil of Lambert, 1774, July 
 25. The night being perfectly clear, he saw with a common 
 4-ft. refractor four bright spots in A, then intersected by 
 the terminator, two of which only those on the day-side 
 can be identified ; after noticing them at times for 2 h , he 
 found all at once that the part of the terminator in A had 
 a slow reciprocating motion, completed in 5 or 6 m , between 
 these pairs of spots, each pair being touched by it in turn. 
 Two other refractors of 7 and 12 ft. showed this appearance 
 with equal distinctness, and it was observed for 2 h , the 
 terminator in X remaining perfectly still. A very strange 
 story, yet Lambert seems to have believed it ; and perhaps 
 we cannot pronounce it wholly incredible in the face of an 
 equally wonderful and perfectly well-attested retrogression 
 in a satellite of Jupiter, to be described hereafter. 
 
 Between FIRMICUS (7) and the limb, halfway in mean 
 libration, are some curved dark streaks (Paludes Amarse, 
 Hevel), in which B. and M. found singular variations, re- 
 sulting, as they admit, possibly (not probably) from periodical 
 vegetation. 
 
 CLEOMEDES (12), a walled plain 78 m. in diameter, in- 
 cludes a small crater (Cleomedes A), brilliant, but not always 
 VOL. i. H 
 
98 THE SOLAR SYSTEM. 
 
 alike defined, in Full ; Schr. had found it not always equally 
 visible. He speaks of many variations in the interior level, 
 which he represents rather differently from B. and M. G. 
 found its W. part marked out into many rhomboids squares 
 in perspective, since confirmed in part by Ne. 
 
 BURCKHARDT (19), 35 m. in diameter, lies 12,700 ft. below 
 its E. wall. 
 
 GEMINUS (20), 54 m. broad, has a ring 12,300* ft. high 
 on E., 16,700 ft. on W. side. 2 
 
 BERNOUILLI (21), equally deep, is very precipitous. 
 
 GAUSS (22) is a walled plain, no m. long. B. and M. 
 describe the fine effect of sunset upon its ring. It has a 
 grand central mountain, which must at times command a 
 glorious view, across a plain of 50 m. covered with night, to 
 illuminated peaks all round the horizon, above which the 
 Sun on one side, and the Earth on the other, are slowly 
 coming into sight. 3 
 
 STRUVE (25), a slight depression, is remarkably dark in 
 Full. 
 
 ENDYMION (27), a walled plain 78 m. in diameter, is, in 
 some states of libration, very dark in Full ; the irregular 
 wall rises W. to more than 15,000 ft., overtopping all but the 
 very highest peaks of our Alps. I have seen it in grand 
 
 1 By a singular coincidence, in reducing as usual French io 
 English measure, the resulting number was i, 2, 3, 4, 5 with 6 in the 
 first place of decimals. The chances against such a sequence must 
 have been extremely great; but it exemplifies a principle, not always 
 kept in mind, that so long as a thing is possible, it must sometimes 
 occur. 
 
 2 And two distinct clefts traversing the inner slope of the SW. 
 and NE. walls respectively, and extending for some distance on the 
 floor. 
 
 8 There is a long range of hills running in a meridional direction 
 on the floor, and two large rings on the S. side of it. 
 
THE MOON (FIRST QUADRANT). 99 
 
 relief 3 d 7 h after New, 2 d Q h after Full. Between 27, 28, and 
 29 is a curious double parallelism, objects all ranging SSW. 
 or SE. 
 
 ATLAS (28), a superb amphitheatre 55 m. broad, 460 
 square m. in area ; its ring rich in terraces and towers, rising 
 1 1,000 ft. on N. ; a very dark speck in interior, where I have 
 also seen some clefts with Bird's i2-in. silvered reflector. 1 
 
 HERCULES (29), a worthy companion to it, 46 m. across. 
 The ring, in places double, includes a small crater of sub- 
 sequent date, and according to Schr. a central mountain, not 
 seen by others. Look for this pair 5 or 6 d after New, 3^ <l 
 after Full. 2 
 
 FRANKLIN (32). Several incomplete rings lie hereabout, 
 all open N. 
 
 DEMOCRITUS (38), a deep ring- plain, lies at the beginning 
 of a region remarkable for net-like and often quadrangular 
 forms. Craters and ring-plains are not, however, absent. 
 Among the latter the dark and level interior of MOIGNO 
 (408) bears a small but conspicuous crater. 
 
 MARE HUMBOLDTIANUM (B), discovered by B. and M., 3 is 
 
 1 There is a drawing of Atlas (and Hercules), showing these clefts 
 and other details on the floor, in Sel. Journal, vol. v. No. 53. 
 
 2 There are two small contiguous craters on the SE. wall, another 
 at the foot of the SW. wall, and many minute objects in the interior. 
 See Plate xxii. vol. vi. Journal L.A.S. 
 
 3 Part, however, is shown on Russell's Lunar Globe (1797), 
 beautiful as a work of art, poor in detail. A larger globe by the same 
 observer, in relief, is preserved in the S. Kensington Museum. Mme. 
 M'adler modelled a lunar globe in wax. Mme. Witte, a Hanoverian 
 lady, has completed a very perfect globe in relief, from B. and M.'s 
 observations and her own. There is at Bonn a magnificent relief of 
 the Moon, 18 Paris ft. in diameter, executed under Schm.'s direction by 
 Dickert (1854). Sir Chr. Wren, when Savilian Professor at Oxford, 
 made a lunar globe in relief at the request of the Royal Society and 
 
IOO THE SOLAR SYSTEM. 
 
 rather more than half as large as M. Crisium, but close to 
 the limb, above which the peaks of its W. border sometimes 
 appear in profile, in one part 16,000 ft. high. 
 
 In this region, in certain states of libration, occur two 
 singular flattenings of the limb, divided by a ridge. These, 
 with another, were discovered by Key, 1863. One of them 
 extends for 10. 
 
 GIOJA (44) is the nearest visible formation to N. Pole, 
 which, however, owing to foreshortening, is at some dis- 
 tance beyond it. 
 
 MOUNT TAURUS (51) is a lofty range, containing the ter- 
 raced crater ROZMER (52), 26 m. wide, 11,600 ft. deep. 
 
 POSIDONIUS (54). This walled plain, nearly 62m. across, 
 includes several small details, in which Schr. found repeated 
 changes : the shadow in the bright little crater was abnormal 
 in length, and once replaced by a grey veil. B. and M. never 
 saw anything unusual. Schm. found it once, but under 
 bad circumstances, 1849, Feb. n, shadowless: so G. 1821, 
 April 7. It has been finely drawn by Gaudibert, English 
 Mechanic, 1872, March i. It contains 7 clefts. A good 
 object about 6 d after New. 
 
 LITTROW (55) and MARALDI (56) show the SSW. paral- 
 lelism of the vicinity : VITRUVIUS (57), with a very dark in- 
 terior, lies in a mottled region, in one place slightly tinged 
 with blue. 
 
 MOUNT ARC.EUS (58), a small range gradually rising 
 from W. to a summit, ranked by Schr. as high as the loftiest 
 of our Pyrenees (N. gives 8400 ft.), and then sinking, on its 
 NE. face, in an amazing precipice, down to the wide plain. 
 It is remarkable for the spire of shade which it casts at sun- 
 rise ; but it has been unfairly treated by B. and M.. being 
 
 by command of Charles II., who placed it in his cabinet. We must 
 hope that it has been carefully preserved. 
 
THE MOON (FIRST QUADRANT). IOI 
 
 omitted from their nomenclature, which contains many very 
 inferior hills : as it is so interesting an object, I hope I am 
 not guilty of presumption in assigning a name to it, chosen 
 from its vicinity to 51. It requires close watching, as the 
 shadow rapidly loses its slender point ; look for it when the 
 ring of 61 just heaves in sight beyond the terminator. I 
 have seen it thus 4 d 2 i h after New. 
 
 MAC ROBIUS (59), nearly 42 m. broad, sinks almost 13,000 ft. 
 
 PROCLTJS (60) has a ring, next to 148 the most luminous 
 part of the Moon ; yet scarcely ever visible on the dark 
 side ; very much less so than many duller objects. B. and 
 M. ascribe this to the narrowness of the wall. It is the 
 centre of several bright streaks, not very easily seen. 
 
 PALUS SOMNII (F), an uneven, defined, always distinguish- 
 able surface, has a peculiar tint, perhaps yellowish-brown, 
 unlike the simple grey of MARE TRANQUILLITATIS (Gr). The 
 latter in Full is sometimes strewed with very small bright 
 points. 
 
 PLINIUS (61), a terraced ring, 32 m. in diameter, filled 
 with hillocks. N. lies a broad cleft, with a smaller one 
 farther out, and a very minute one between them. 1 
 
 MENELAUS (70), a very steep crater about 6600 ft. 
 deep ; with a ring very brilliant in Full. All the ridges 
 running from it trend SW., and this parallelism reaches 
 over a great district, including most of 85, 68, L, and the 
 vicinity. Several bright streaks issue from 70 one is a 
 continuation of a ray from 180, extending in all more than 
 1850 m. Here was one of Herschel I.'s pseudo-volcanoes. 
 
 MARE SERENITATIS (H). This wide and beautiful plain 
 is nearly circular, about 433 m. from N. to S., 424 from E. 
 to W. ; the interior appeared at Full to B. and M. of a clear 
 
 1 There is a sketch of Plinius and the associated clefts in the 
 Eng. Mec. 1882, Feb. 3. 
 
102 THE SOLAR SYSTEM. 
 
 light green, unnoticed by Schr. and L., and not easily seen 
 even by its discoverers ; it is set in a border of dark grey, 
 and bisected by a straight whitish streak, invisible, like most 
 of its class, near the terminator. Towards the W. edge of 
 the plain is a curious long low serpentine ridge, discovered 
 and figured by Schr., but only well seen from its shadow 
 near the terminator. I have found it thus between 5 and 
 6 d after New. A little E. of it I have seen a lower one 
 with reverse flexures. 
 
 LINNE (74). A small crater, described by L. as ' very 
 deep,' and by B. and M. as ' deep,' but discovered by Schm. 
 to have entirely lost that character, and to resemble a whitish 
 cloud, surrounding a most minute elliptic crater, which I have 
 seen beautifully on rare occasions with 9^-in. mirror. This 
 very interesting spot has undergone a rigorous scrutiny, and 
 opinions are still divided, owing to some want of explicit- 
 ness in the earlier records. The balance, however, seems 
 decidedly in favour of actual change: and this and many 
 other spots would have been more carefully observed, could 
 it have been foreseen that questions would subsequently bo 
 raised about them. 
 
 CAUCASUS (75). This grand mountain mass rises into 
 insulated peaks, suitably termed ' aiguilles ' by B. and M., 
 as lofty as any on the Moon, those on the limbs excepted, 
 and reaching 18,000 or 19,000 ft. Their narrow shadows 
 are drawn out into fine points a superb spectacle, which I 
 have seen about I. Quarter. Craters are very rare here. 
 
 EUDOXUS (77) and ARISTOTELES (78), a noble pair of 
 craters, not easily found in Full, in a region sprinkled as it 
 were with luminous dust. The terraced wall of 77, 1 1,300 ft. 
 above the W. interior, is on that side crowned by two turrets 
 of 15,000 ft. Etna, as Schr. observes, would stand in this 
 great cavity. 78 is more than 50 m. broad, nearly as deep 
 
THE MOON (FIRST QUADRANT). 103 
 
 as 77, but with a much richer wall. The interior of both 
 resembles the surrounding country more than is usual. I 
 have seen a row of 4 or 5 craterlets in 78, running SW. from 
 the central hill a test-object. 78 is very remarkable for 
 rows of minute hillocks lying NE., NW., and SW., in lines 
 pointing to the crater the finest specimen of this not un- 
 common arrangement: it is less .distinct round 77. It 
 requires very favourable light, and is difficult for the student. 
 I have seen it, with wide SW. libration, about I. Quarter. 
 S. and SW. of 77 the surface down to H is thronged with 
 hillocks, and W. especially, craterlets innumerable ; on E. 
 those mounds reach to 75. Many small craters and a little 
 cleft (crater-row, Schm.) NE. of 78 are omitted by B. and M. 
 
 GREAT VALLEY OF ALPS. An extraordinary cleft, figured 
 by Bianchini in his work on Venus ; a circumstance un- 
 noticed alike by Schr., B. and M., and Schm. About 83 m. 
 long, and from 3^ to 5! m. broad, it breaks in a straight line 
 through the very loftiest Alps, with precipitous sides and a 
 depth of at least 11,500 ft., in which Mont Perdu or the 
 Vignemale of the Pyrenees would disappear. The bottom 
 is very flat, but high powers according to Klein show land- 
 slips from the edges. It is always easily found. Between 
 this valley, 79 and I, lies a curious region all sprinkled with 
 hillocks: B. and M. estimated them at 700 or 800 at least. 
 I once saw them finely developed at I. Quarter, in a 2o-ft. 
 achr. by Slater, of 14^ -in. aperture. 1 
 
 ALPS (80), a lofty and exceedingly steep chain, rising 
 into separate peaks : one of the highest, the Mont Blanc of 
 Schr. (next to which our number stands), reaches, he says, to 
 14,000 ft. B. and M. reduce it below 1 2,000 ft. Close beneath 
 
 1 The valley is crossed about midway by a cleft which is easily 
 recognised, even under a high light. Detailed drawings of the forma- 
 tion will be found in the L.A.S. Journal, vol. iii. pp. 20 and 72. 
 
104 
 
 THE SOLAR SYSTEM. 
 
 its E. foot, Schr. perceived, 1789, Sept. 26, on the dark side 
 of the moon, a small speck of light, like a 5 m g . star to the 
 naked eye, which having been verified in position, and kept 
 in view for fully 15, disappeared irrecoverably: the round 
 shadow, sometimes black, at others grey, which he subse- 
 quently found in the day-side 
 in or near its place, was pro- 
 bably nothing new. A copy 
 of his figure is here given. 
 Strange to say, 1865, J an< J > 
 Grover recovered this bright 
 spot, or one very near its 
 site, with only 2 in. of aper- 
 ture, and saw it unchanged 
 like a 4 m*. star to the naked eye, but rather larger, for 
 fully 30. 
 
 PALUS NEBTJLARUM (I) and PALUS PUTREDINIS (K) are 
 for the most part so level, that mounds of 50 or 60 ft. would 
 be rendered visible by their shadows near the terminator. 
 
 CASSINI (81), a curious ring-plain ; the narrow wall 
 encloses a scarcely depressed space, and a deep ring-plain, 
 which has a considerable irregularity within, unnoticed by B. 
 and M., but not new, as I saw traces of it in I826. 1 The ring 
 casts long spires of shade about I. Quarter. An insulated 
 mountain E. of it in the plain (477, Mons Cliristi, Hevel), 
 usually very bright, was once seen by Sshm. near lunar sun- 
 set of a remarkable dark grey. G. had noted many changes 
 in its form and colour, which he ascribed to lunar clouds. 
 
 THE^TETUS (82) would take in Snowdon twice over, with 
 Btill depth to spare. 
 
 ARISTILLUS (83), a very magnificent crater, 34 m. broad, 
 
 1 There is also a conspicuous deep crater on the SE. side of the 
 floor. 
 
THE MOON (FIRST QUADRANT). 105 
 
 1 1,000 ft. deep on E. side, has a fine central mountain, which 
 I saw, with 5 J in. of aperture, as three parallel ridges. The 
 ring stands up nobly from the plain, and is flanked on all 
 sides (as Schr. perceived) by radiating banks resembling 
 lava-streams, or currents of ejected blocks or scoriaB, 1 evi- 
 dently posterior to the surrounding level: in suggestive 
 contrast to 120. I have seen them well about i d after 
 I. Quarter. 2 
 
 AUTOLYCUS (84), its smaller companion, is nearly as deep, 
 with a similar but less evident radiation. This pair of craters 
 illustrates a not uncommon arrangement, of two rings in the 
 same meridian ; very similar in every respect ; if unequal 
 in diameter as 3 to 4, and the smaller lying S. ; from 18 to 
 36m. apart ; and connected by low ridges running SW. 
 
 APENNINES (85). This very extensive chain is more like 
 the mountains of the Earth than is usually the case. 3 Its 
 length, according to Schr., is nearly 640 m., great part of it 
 lying in the next Quadrant. Its SW. side ascends gradually 
 the opposite aspect breaks down at once in awful preci- 
 pices of stupendous height, casting a shade through 83 m., 
 or losing the last ray as far beyond the terminator. Huy- 
 gens (90), the loftiest peak, rises, according to Schr., no bad 
 measurer, to 21,000 ft. B. and M. think he confounded 
 two adjacent summits, and give 18,000 ft.; Schm. prefers 
 18,500: in any case a superb elevation. On its apex is a 
 
 1 The volcanoes of Java have all ribbed sides ; but these are 
 ascribed to erosion by torrenta The grand volcano in the island of 
 Luzon ejects red-hot stones forced up over the edges of the crater, and 
 rolling down amid showers of fire on every side of the cone. 
 
 2 There is a large obscure ring a little N. of Aristillns, which is an 
 interesting object under a low sun. 
 
 3 Schm. considers the resemblance not striking, and notes the 
 absence of depressions similar to terrestrial river- valleys. Ne., how- 
 ever, asserts the reverse. 
 
[06 THE SOLAR SYSTEM. 
 
 minute crater. Other summits, though inferior, are yet of 
 extraordinary height and steepness : Hadley (87), facing 75, 
 15,000 ft. Bradley (89) 13,600 ft. Wolf (92) 11,000 ft. 
 The gradual entrance of the range into sunshine about 
 I. Quarter is a glorious spectacle ; and its projection into 
 the dark side, which may be seen without telescopic aid, 
 probably gave rise to the early idea mentioned by Plutarch, 
 that the Moon was mountainous: from its abruptness it 
 does not lose all real shadow till 3 d before Full. With very 
 few craters, it consists of ridges and peaks not to be num- 
 bered by thousands in large instruments: Schr. detected 
 this ; M. says it would take the opportunities of three or 
 four years to delineate all the details which a power of 800 
 or 1000 will show. 
 
 CLEFT OP HYGINUS. A fine specimen of these furrows 
 lies fortunately in an excellent position in the MARE VA- 
 PORUM (L), a tract of which the dusky streakiness has often 
 interested me about I. Quarter. The cleft is conspicuous 
 enough to yield to a power of 40 in a good telescope, under 
 any illumination. It begins from NE. at the foot of a long 
 low hill, as a flat valley about i J m. wide by 9 m. long, 
 where I have found (with 5i-in. aperture) that it receives a 
 branch from E. : having then contracted to about f m. with 
 precipitous sides and great proportionate depth, it passes 
 through 4 minute craters (or, as Ne. and Klein think, mere 
 enlargements), bends a little, receives another short branch 
 from E., and traverses Hyginus (93), but at a lower level, and 
 as a bank. B. and M. once saw, in the wane, its edges bridg- 
 ing the black cavity as two narrow bright lines ; and Schm.'s 
 large map represents it so : in this position I have not seen 
 it well, but repeatedly in the increase with 5^-in. achrom. 
 and 9j-in reflect., when the bank appears cut down before 
 reaching the E. side : once I saw the S. of those lines, but 
 
THE MOON (FIEST QUADRANT). 107 
 
 cut off at its E. end ; at another time the N., perhaps con- 
 tinuous, while a similar line diverged from the same point 
 W. to the NE. side of the crater. A bay at the N. end of 
 93, shown by L. and G., but missed by B. and M., seems the 
 result of a smaller explosion. This curious spot should be 
 well examined with the most powerful means. B. and M. 
 describe and figure a wall to 93 ; Schr., L., G., and myself 
 (even with reflector) see none. 1 The cleft then, after 
 touching on 5 very small craters and two broad hills, becomes 
 wider and shallower, and ends after about 106 m. much as 
 it began. S. of this cleft are two small dark spots, one 
 larger, and one of a greenish hue : on the N. side is a region 
 worthy of notice for its change of colour : in Full it is 
 tolerably luminous : at Quadratures, there is near 93 a large 
 blackish spot, covering two ranges of hills and the vale 
 between. Here B. and M., most unprejudiced if not oppo- 
 sitely-prejudiced witnesses, admit a variation of colour not 
 dependent merely on the angle of reflection, and possibly 
 connected with changes like those of our seasons. Of late 
 years a considerable depression, without ring, but full of 
 shadow at the terminator, has become visible in this region, 
 but is of difficult identification without the drawings in the 
 * Selenographical Journal.' It is called HYGINUS N. 
 
 CLEFT OF ARIADZEUS. This, discovered like the pre- 
 ceding by Schr., lies W. of it : it is longer, broader, and 
 probably deeper than its neighbour, with which, as I found, 
 1866, April 21, it is connected by a branch N. of 102. 2 It 
 seems to pass under the two mountains nearest its W. end, 
 
 1 Schm. drew it, and thinks there are no lunar craters without 
 banks. Such 'explosion-craters,' however, exist in Java, the Eifel, 
 and Auvergne. 
 
 2 This was discovered by G. a difficult object which Klein at 
 times found invisible, at others very distinct. 
 
108 THE SOLAR SYSTEM. 
 
 but others it cleaves visibly, though greatly narrowed by 
 one lofty hill. The accurate L. saw it passing through them 
 all, and traced it for 175 m. I have observed it interrupted, 
 but not exactly as B. and M. : I find it also double for a 
 short distance two halves not in the same line, with over- 
 lapping ends. G. detected a minute prolongation of it far 
 through Mare Tranquillitatis, subsequently seen by Kunow- 
 sky, Birtj and Freeman. This and the preceding cleft may 
 be looked for about I. Quarter. 1 
 
 TRIESNECKER (94) is surrounded by several minute clefts 
 intersecting and uniting with each other in a manner of 
 which only one other instance is known (near 228 ; Schm.) 2 
 L. detected some of them, but G. drew a surprising number. 
 With 5^-in. I found more than in B. and M. ; one cleft 
 double, with overlapping ends. Gaudibert has traced others. 
 E. of this spot L. found some curious streaks and markings 
 believed to be now changed in form. 3 
 
 MANILIUS (95), a beautiful cavity, 25 m. in diameter and 
 7700 ft. deep, has a broad luminous terraced crater- and 
 peak-besprinkled ring. Being visible on the night-side, it 
 was one of Herschel I.'s imaginary volcanoes in eruption. 
 Schr. has seen variations, not easily accounted for, in the 
 relative visibility of this and 70 in the earth-shine. 
 
 JULIUS C.ZESAR (96) 4 and BOSCOVICH (98) are very dark 
 
 1 Some ancient crater-rings have been seen on the site of this 
 cleft with the great Lick Telescope. 
 
 2 The interior of 232 may be added. 
 
 3 See drawing of Triesnecker and Hyginus clefts in Journal L. A.S., 
 vol. iii. p. 20. 
 
 4 The wide valley on the W. of this formation is very noteworthy 
 at sunrise. It probably represents a row of large depressions, the 
 division walls of which have been partially destroyed. The low 
 ridges and mounds a little E. of Sosigenes, forming in part the S. 
 boundary of Julius Csesar appear to exhibit indications of denudation. 
 
THE MOON (SECOND QUADBANT). 109 
 
 enclosures, DioNrsius (99) and SILBERSCHLAG (101) very 
 brilliant crater-rings. 
 
 Near the two fine craters AGRIPPA (102) and GODIN (103) l 
 (which exemplify the remark under 84), Schr. once saw for 
 a short time on the dark side, a minute point of light. 
 
 KH^TICUS (104), an irregular crater, marks exactly the 
 Moon's Equator, and is one of the few spots to which 
 the Sun and Earth may both be vertical. 2 (See another 
 Rhaeticus, in a note on 112.) 
 
 SECOND, OB NORTH-EAST QUADRANT. 
 
 SCHRODER (106). This imperfect crater in an intricate district 
 where the levels are bright, the hills and valleys very dark 
 grey, darkest at Full, is the guide to a remarkable spot a 
 little N., the number on the map standing between the two 
 objects. Here, in 1822, G. discovered the regular formation 
 which at first attracted so much attention, and subsequently, 
 from the fanciful character of the observer, fell into unmerited 
 oblivion. The object, which he called ' Schroter ' (a name 
 transferred by B. and M., when they could not find it, to the 
 nearest crater), and which some have maintained, notwith- 
 standing its size, to be a work of art, is described by him as 
 a collection of dark gigantic ramparts, visible only near the 
 terminator, extending about 23m. either way, and arranged 
 on each side of a principal meridional rampart in the centre, 
 
 1 There is a trumpet-shaped valley on the SW. flank of Godin 
 which is very conspicuous when the E. wall of the formation is on tho 
 moroing terminator. 
 
 2 A coarse cleft or narrow valley running round the outer slope of 
 the E. wall, and apparently connected with the Triesnecker rill-system, 
 is an easy object under a low morning sun. 
 
110 THE SOLAR SYSTEM. 
 
 from which they slope off SE. and SW. respectively, at an 
 angle of 45, like the ribs of an alder leaf; those to the SW. 
 abutting on a meridional side-wall, beyCnd which Schwabe 
 and himself subsequently perceived their continuation: 
 frequently, however, traces only of the figure could bo 
 discerned, as though it were obscured by clouds : from this 
 cause he supposed it had been quite misrepresented by the 
 careful L., though he had studied it for 6 months: some 
 years afterwards it appeared to have undergone a sudden 
 change, and subsequently G. himself could scarcely make it 
 out on some occasions, though at other times quite distinct : 
 B. and M., notwithstanding great pains, were altogether 
 unsuccessful, till in 1838, subsequently to the date of their 
 map, they surveyed and measured the region with the great 
 Berlin achromatic of 9 T 6 ^-in. aperture ; then at last, among 
 a number of curious labyrinthine details, of which their 
 ' Beitrage ' contains a view, 5 parallel valleys appeared side 
 by side, each about 9 m. by 3-^, sloping all to SW., with 
 prolongations in the same direction, giving very fairly half 
 of G.'s figure a remarkable attestation from an unfavourable 
 quarter. But he could call many earlier witnesses, having 
 shown it to several German philosophers ; Prince Metternich 
 at Vienna found it sooner than any one else from his 
 description, and it was beautifully seen by Schm. and 
 Schwabe. In England it does not seem to have been looked 
 for, as though to justify G.'s taunt, ' The scientific John Bull 
 here has gone empty away, and. behaved himself about it 
 just as his natural disposition led him.' This is, however, 
 no longer true. Knott saw it, 1861, March 19: I caught it 
 with 5^-in., 1862, Feb. 7, a long way from the terminator, 
 which passed through 121 ; and could even trace, it the 
 next day. I have several times seen it since, but never 
 on, or near, the terminator. It has been finely seen by 
 
THE MOON (SECOND QUADKANT). Ill 
 
 Whitley, 1870, June 7 and 8; and somewhat differently by 
 Birmingham, 1871, March 29. It is a curious specimen of 
 parallelism, but so coarse as to carry upon the face of it its 
 natural origin, and it can hardly be called a difficult object. 1 
 A line from 211, through 106, carried as far again, finds it 
 a little N. of its place in the map. An interesting drawing 
 by Gaudibert is in English Mechanic, 1874, March 13. 
 
 SINUS ^iEsTUUM (N). The absence of even the minutest 
 crater here is remarked as unique : but L. had shown one, 
 and M. subsequently picked out a few with the Dorpat 
 telescope. I have found two easy with 5^-in. 
 
 ERATOSTHENES (110) and STADIUS (111), neighbours, the 
 former more than 37 m. broad, the latter 5 m. broader, 
 connected by a steep mountain of 4500 ft. (higher than any 
 land in the British Isles), are curiously contrasted: 110 has 
 a fine central hill, 111 is nearly level. 110 has a widely- 
 terraced wall of very irregular height; the surrounding 
 ground is also very uneven ; so that on E. side it is 1 6,000 
 ft. above the inner, 7500 ft. above the outer surface; on W, 
 only 10,000 ft. and 3300 ft. Ill has such an insignificant 
 ring, about 130 ft. high, that B. and M. did not notice it 
 till after a three-years' search for Hiccioli's Stadius, which, 
 being only a spot of local colour, they missed after all. I 
 found, however, little difficulty with this ring. 2 Its interior, 
 as pointed out by Dobie, is curiously speckled, especially 
 S. and W., with minute craters, which have been supposed 
 to be on the increase. Schm. (1849) counted 50, and 
 with the i4-ft. Berlin achr. found this region perforated 
 with the minutest craterlets 'like a sieve.' 3 110 is about 
 
 1 Birt has referred to a similar formation in Auvergne, described 
 by Scrcpe, JSxtinct Volcanoes of Central France, 162 (2nd edit.). 
 
 2 It has been traced, together with some of the features it includes, 
 when the terminator has advanced as far E. as Herodotus. 
 
 3 Seventy craters within and about the border were detected in 
 
112 THE SOLAR SYSTEM. 
 
 as large as the county of Hereford, and lies intermediate 
 between most dissimilar regions. Its Full-Moon aspect is 
 very unlike the description of B. and M., and should be 
 drawn and watched. 
 
 COPERNICUS (112). One of the grandest craters, 56 m. 
 in diameter, it has a central mountain (2400 ft. Schm.), two 
 of whose 6 heads are conspicuous ; and a noble ring composed 
 not only of terraces, but distinct heights separated by ravines: 
 the summit, an arrow ridge, not quite circular, rises 1 1,000 ft. 
 above the bottom the height of Etna, after which Hevel 
 named it. Schm. gives it nearly 12,800 ft. with a peak of 
 13,500 ft. W., and an inclination in some few places of 60. 
 The shadow of this peak on the E. terraces he once saw 
 reddish-brown and obviously indistinct. Piazzi Smyth 
 observed remarkable resemblances between the conchoidal 
 cliffs of the interior and those of the great crater of Teneriffe. 
 A mass of ridges leans upon the wall, partly concentric, partly 
 radiating ; the latter are compared to lava, and the whole 
 is beautifully though anonymously figured in Herschel II.'s 
 ' Outlines of Astronomy.' There is also a much larger 
 drawing by Se. : but this grand object requires, and would 
 Avell reward, still closer study. It comes into sight a day 
 or two after I. Quarter. Vertical illumination brings out 
 a singular cloud of white streaks related to it as a centre. 
 It is then very brilliant, and Klein remarks that some 
 portions have a bluish tinge. The ring sometimes resembles 
 a string of pearls: B. and M. once counted more than 50 
 specks. Schm. found the whole neighbourhood, even as far 
 as 144, studded with the minutest craters. In the direction 
 of 113, a great number of blackish points come out under 
 a high light; and Klein remarks that processes may bo 
 
 the years 1885-86 with an 8J-in. Calver-Reflector. For notes re- 
 lating to these and other details see L.A.S. Journal, vol. v. p. 221. 
 
THE MOON (SECOND QUADRANT). 113 
 
 going on there, of which a superficial observation detects 
 nothing. 1 
 
 CRATER-RANGES NEAR COPERNICUS. Between 110 and 
 112 lies one of the most curious districts in the Moon. Here, 
 in strange contrast with the undisturbed Sinus ^Estuum, B. 
 and M. have shown 61 minute craters, believe that more 
 than twice that number might be seen, and question whether 
 any level ground is left : it is pierced ' like a sieve ' accord- 
 ing to Schm., who reckons about 300. The greater part are 
 arranged in ranges; one row is very evident, where they 
 stand so close that but for their partitions it would be a cleft, 
 which indeed its N. end resembles. The telescope at Dorpat 
 showed M., after his removal there, great part of the Hyginus 
 cleft as a chain of confluent openings, 2 thus strengthening 
 the idea that these forms may have had a common origin. 
 This region, strangely missed by Schr., was discovered by 
 G., who estimated its minute craters at 400 or 500 ft. iu 
 
 1 To the SW. of 112 Hevel has figured 3 contiguous round dark 
 spots under the name of 'Lacus Herculeus.' Of these the NW. 
 was named by Eiccioli 'Dominions Maria,' the SW. 'Stadius,' and 
 the E. * Rhseticus.' B. and M., puzzled in identification, owing pro- 
 bably to their being Full-Moon markings (though easy ones), dealt 
 summarily with this nomenclature ; ignoring Dom. Maria, notwith- 
 standing its claim of neighbourhood to the site 111; transferring 
 Stadius across it, without any intimation, per saltum, to that position ; 
 and removing Rhaeticus to 104, at some distance. The latter trans- 
 position led to a mistake in the first edition, which Knott has enabled 
 me to rectify. It is this original Rhaeticus, not 104, in which G. 
 discovered one of his curious* rampart-works;' and I should have 
 given a copy of his figure in Astr. Jahrb. 1828, had he not himself 
 condemned it. It was something like his 'Schroter;' a slightly 
 curved line, with a little crater at one end, and a mound at the other, 
 crossed by 4 shorter straight lines. A year later he complained that 
 it had been greatly obscured ' selenospherically,' and seldom visihle. 
 
 z W. of 93 I have, however, seen its bottom apparently quite flot 
 under high illumination, with Bird's 12-in. silvered reflector. 
 VOL. i. i 
 
114 THE SOLAR SYSTEM. 
 
 diameter ; B. and M. give them about 6 times that size. 
 They are easily seen, but the suitable illumination is 
 fugitive : they should be looked for while the sun is rising 
 on E. side of the wall of 112. 
 
 TOBIAS MATER (117), 9700 ft. deep towards W., has a 
 fine specimen of subsequent eruption by its side. 
 
 MILICHIUS (118). Remarkably luminous in Full. 
 
 MARE IMBRIUM (0). The largest of the circular plains, 
 ill-defined E., 5 times as large as M. Crisium : one half dark 
 and flat, the rest very irregular. 
 
 ARCHIMEDES (120). One of the most regular walled 
 plains, apparently more ancient than the surrounding level, 
 which seems to have nearly filled up its interior, and over- 
 flowed the lowest slope of its ring : though 50 m. in diameter, 
 it is depressed only about 650 ft. ; the wall, averaging 4200 ft. 
 above the interior, carries several towers, the highest nearly 
 7400 ft. The plain appears smooth as a mirror, according 
 to B. and M., but is divided into 7 nearly parallel stripes of 
 unequal brightness. Observations, however, by Knott in 
 1860, and Gray in 1880, indicate changes which deserve 
 special attention. There are minute craters in it : G. saw 
 one, Knott 6 or 7. The outer slope of the wall is very 
 complex ; a magnificent object against the rising or setting 
 sun. 1 
 
 LA HIRE (123), a small solitary mountain 4900 ft. high 
 (Schr.), inserted in the map of B. and M., and in the index 
 of their ' Mond,' but strangely omitted in the text. There 
 is nothing striking in its usual appearance, but it was twice 
 seen by Schr. under very different illumination so brilliant 
 as to glitter with rays like a star : he noticed also changes 
 
 1 More than 50 small objects have been detected on the floor by 
 Gray and others, including 4 crater-cones on the E. quarter of the 
 interior. 
 
THE MOON (SECOND QUADRANT). 115 
 
 in its form. G. never saw its radiant aspect, and thought its 
 shape entirely altered, and its size reduced, since Schr.'s 
 time. Schrn. detected a craterlet on the summit. I once 
 found it on the terminator, 2 d 7 h after I. Quarter, the 
 brightest object in sight, and radiating as described by Schr. 
 At another time I noticed a similar hill, about ^ of the 
 distance from 122 to 121, glittering on the terminator like a 
 star with rays. 1 Gerling (1844) found the same phenomenon 
 in a peaked hill on S. side of 80, and Brodie (1865) close to 
 149. I have also seen 131, and a hill S. of it, very brilliant 
 in the like circumstances. Future observation may decide 
 whether this depends upon a peculiar angle of reflection and 
 vision, or on some changes in a lunar atmosphere ; and on 
 this account these objects are especially recommended to the 
 student. 
 
 EULER (125), 19 m. across and nearly 6000 ft. deep, is 
 conspicuous for its bright streaks. 
 
 CARLINI (128). In this neighbourhood Williams and two 
 others observed for i^\ 1865, Nov. 24, on the dark side, a 
 distinct bright speck like an 8 m g . star with 4 T ^-in. aperture. 
 This region should be mapped with special care. 
 
 HELICON (129) and its neighbour Helicon A (now LE 
 VERRIER, 425) form a curious twin crater, each 13 m. in 
 diameter, and of vast depth. Schr. has given the latter of 
 them 13,600 ft. ; its complete disappearance in Full, 2 while 
 129 remains conspicuous, is a striking instance of this 
 peculiarity, and may account for the entire omission of one 
 of them in the maps of Hevel and Eiccioli. Did two small 
 craters, on the wall of 129 and the slope of 425, exist in B. 
 and M.'s time ? They are plainer than another which they 
 
 1 This has also been seen by Hunt, 1862. 
 
 2 Brodie finds (1865) that this is incorrect, and Gaudibert and 
 Dennett have seen 425 the brighter of the two. 
 
 
Il6 THE SOLAR SYSTEM. 
 
 have given here. I have seen with g-in. refl. a cratcilet in 
 the centre of 129, a test-object. 1 
 
 Pico (131) is a very fine specimen of an insulated pyra- 
 mid, rising from a narrow base to 9600 ft. according to Schr., 
 reduced by B. and M. to 7000 ft. (nearer 8000, Schm.) : on 
 any estimate a magnificent sight from the surrounding plain. 
 Schm., however, thinks the profile would not be very striking, 
 quite inferior to the steeper of the Swiss Alps, or even the 
 Niesen above the Lake of Thun. S. of 410, where that 
 number stands in our map, is a small crater Pico B. B. and 
 M. show a longish white spot S. of it, which Schm. could 
 never find. 
 
 PLATO (132). A slight magnifier shows this * steel-grey' 
 spot, lying as a lagoon at the edge of 0, and fore-shortened 
 into an oval whose proportions vary from (3 to 5) to (4 to 5) 
 in the extremes of N. or S. libration, its distance from the N. 
 limb being in one case half of its amount in the other : such 
 optical variations must always be allowed for in making or 
 comparing delineations of objects not far from the limb. 
 The rampart, not a very connected one, and failing, as Schm. 
 remarks, in terraces, averages 3800 ft. K, something less W., 
 where 3 towers crown it, the loftiest nearly 7000 ft., another 
 somewhat higher bulwark surmounting the E. side (Schm. 
 gives it 9000 ft.). A large winding cleft unnoticed by B. and 
 M. issues from a crater on the W. side, and runs for some 
 distance nearly parallel to the great valley of the Alps. 
 The very level interior, about 60 m. broad, and containing 
 2700 square miles, was described by B. and M. as crossed 
 by 4 lighter streaks from N. to S., and containing 3 or 4 
 specks ranking among the minutest of lunar objects. G. 
 
 1 Helicon is traversed by a ridge from N. to S., which has con- 
 siderably disturbed the walls, and rendered it a very interesting object 
 when it is on the morning terminator. 
 
THE MOON (SECOND QUADRANT). 117 
 
 detected 8. The central one is not difficult under a high 
 light, and, with at least 10 others, is evidently a craterlet. 
 Two are quite close, like a double star (Dawes) : to which 
 Pratt has added a third. A copy 
 from B. and M.'s map is given here, 1 
 as the local shading, considered 
 very variable by G., was found 
 greatly changed by me (1855), and 
 is so still. Bianchiui, Short, and 
 Elger have seen some longitu- 
 dinal bright streaks at lunar sunrise. The light-specks 
 have been of late years very carefully studied by Pratt, 
 Gledhill, Elger, and others. By the former observer 37 
 have been recorded (27 the greatest, 15 the average number 
 at once), as well as 30 or more streaks ; and Birt's most 
 accurate comparison of the whole series shows that the 
 visibility of many of them is affected at times by some local 
 cause. 2 The colour also of the interior, unlike almost all 
 other similar spots, is found to darken progressively with 
 the increasing angle of sunshine, and even beyond the lunar 
 noon, as though connected with heat. Klein saw several 
 times in 1878 something like fog in the E. portion. 8 There 
 is a large landslip at SE. end of ring, which Shaler (Cam- 
 bridge, U.S.) thinks may have resulted from the great 
 changes of temperature, possibly 1000, between noon and 
 midnight. 4 
 
 1 These streaks have been omitted in their 2nd edition. 
 
 2 Many additional light spots and streaks have been subsequently 
 recorded by Mr. A. S. Williams. 
 
 3 A similar observation was made by Ne. and Elger in 1871. 
 
 * Recent observations of Plato by Professor Pickering, at Arequipa, 
 tend to show that changes have taken place in the appearance of 
 some of the spots since they were systematically observed in tlie 
 years 1869 and 1870. See Observatory, vol. xv. 
 
Il8 THE SOLAR SYSTEM. 
 
 HARPALUS (133) has a wall rising 2800 ft. above the 
 plain, nearly 16,000 ft. above the chasm below. 
 
 SINUS IEIDUM (P), styled by B. and M. 'perhaps the 
 most magnificent of all lunar landscapes,' is a dark semi- 
 circular bay, level almost as water, wrinkled only by a few 
 slight ridges scarcely exceeding 100 ft. and encompassed by 
 abrupt and colossal cliffs, the promontories being upwards 
 of 140 m. apart. The ridge is crowded full of minute, 
 usually round summits, with numberless other objects : the 
 height is not conveniently measurable, but a point by no 
 means the loftiest, W. of SHARP (139), reaches about 15,000 ft., 
 and the great cape LAPLACE (134) rises some 9000 ft. abruptly 
 from the plain. Between it and 132 is a strong NW. paral- 
 Jelism. P is in noble projection 2 d or 3 d after I. Quarter. 
 
 KEPLER (144), nearly 22 m. in diameter, sinks 10,000 ft. 
 in the deepest part beneath a very low bright wall. It is 
 the centre of a great ray-system, connected with that of 112. 
 G. thought its aspect not always alike in the same illumi- 
 nation. 
 
 MARIUS (147). The interior of this cavity is both drawn 
 and described by B. and M. as quite uniform. It contains, 
 however, a minute white crater, seen by G. in 1825, and 
 rediscovered by me in 1864, conspicuous in the lunar morn- 
 ing, though invisible in the evening. There is also a trace 
 of some other object. A similar crater E. of the ring is not 
 in Schr.'s figure. More than 100 grey hillocks, the loftiest 
 little exceeding 1000 ft., lie in a narrow space NE. In the 
 plain S. is said to be a most curious winding cleft, like the 
 canons of NW. America. 1 
 
 ARISTARCHUS (148). The most brilliant crater in the 
 
 1 A drawing of this formation, showing four objects in the interior 
 (including ' the minute white crater '), and three depressions on the 
 S. border, will be found in the L.A.S. Journal, vol. vi. p. 278. 
 
THE MOON (SECOND QUADEANT). 1 19 
 
 Moon ; quite dazzling in a large telescope, the steep central 
 Lill being the most vivid part. The ring is 28 m. across, on 
 W. rising 7500 ft. above its inner, 2650 ft. above its outer 
 foot ; on E. it becomes a plateau, which connects it with a 
 smaller and steeper crater, HERODOTUS (149). A curious 
 serpentine valley will be noticed here, nowhere exceeding 
 2! m. in width (about ^ m. deep, Schna.), not unlike a dry 
 river-bed. 1 The reflective power of 148 is extraordinary, 
 rendering it visible even to the naked eye on the bright 
 side, and with the telescope on the dark: one of Her- 
 schel I.'s very few errors was his taking it for a volcano in 
 eruption. Schr. pointed out this, but the mistake has been 
 since repeated by others. There are, however, as already 
 mentioned, variations in its light, noticed by Schr., for 
 which Smyth, who has seen it of every size, from a 6 to a 
 10 m g . star, says it is difficult to account. 2 The bright 
 streaks around it in Full Moon are no more of the nature 
 of lava than they are elsewhere ; but I have seen it on the 
 terminator surrounded by wavy radiating streams. Schm. 
 has repeatedly found the * nimbus,' or darker space round 
 the wall, of a violet hue, a tint that he has seen also 
 occasionally in the interior of 272 as well as in other 
 places, and which I have independently noticed (1867), at 
 least a bluish glare, under high illumination, near 302 and 
 325. 3 About 45 m. WNW. begins a little group of 
 mountains (490), the highest nearly 7800 ft. : these coming 
 
 1 Ne. has seen the high mountain a little way N. of 149 blurred 
 and of a violet tint, when the surrounding objects were all sharp 
 and white. 
 
 8 See p. 82, antea. 
 
 3 There could be no suspicion of secondary spectrum, as the re- 
 flector was employed. Schm. has sometimes found blue light on the 
 peaks of mountains beyond the terminator, as well as in the interior 
 of 112 and 180, and in other situations. 
 
I2O THE SOLAR SYSTEM. 
 
 into light about 3 d after I. Quarter are the ' harbingers ' of 
 the great spot, conspicuous a day later. Birt remarks that 
 489, a mere ring in the map of B. and M,, wears a very 
 different aspect now. 
 
 HEVEL (154), a walled plain 70 m. across, contains a 
 straight ridge, and an extensive convexity of surface ; also 
 a small crater, considered by Schr., but on inadequate 
 ground, to be new. There are some remarkable cross clefts 
 on its floor and W. wall. 1 
 
 ANAXAGORAS (168), 31 m. broad, and very white, includes 
 a great mountain not in the middle. It is a streak-centre. 
 
 Between TIM^US (170) and FONTENELLE (171) is a good 
 deal of parallelism, and adjoining 171 on W. is one of the 
 most curious instances of it : a nearly square enclosure fore- 
 shortened into a lozenge, whose rampart-like boundaries, 
 according to B. and M., * throw the observer into the highest 
 astonishment.' They are very unequal in height, and one is 
 little more than a light-streak ; yet they are so regular that 
 it is scarcely possible to imagine them natural, till we find 
 that they are 64 m. long, 250 to 3200 ft. high, and i m. or 
 more thick. There are parallel ridges in the interior, and 
 in one place the form of a perfect cross : unfortunately, it 
 lies in such a position that years, as B. and M. observe, may 
 pass without a good view of it. I have often looked for it 
 in vain. Birmingham has been more successful. 
 
 E. of the table-land EOBINSON (413), are 3 curious dark 
 mountains, about 5900 ft. high. 
 
 PYTHAGORAS (176) is the deepest walled plain in the 
 Quadrant, nearly 17,000 ft. on SE. side. 
 
 1 These clefts are on the W. of Lohrmaim (153), a smaller ring 
 Mnraediately S. of Hevel. 
 
THE MOON (THIRD QUADRANT). 121 
 
 THIRD, OR SOUTH-EAST QUADRANT. 
 
 THIS includes the metropolitan crater of the Moon, TYCHO 
 (180), a most perfect specimen of the lunar volcano, visible 
 even to the naked eye in Full, and roughly figured by 
 Galileo in the earliest telescopic representations. Its dia- 
 meter is 54 m., its depth 17,000 ft. or nearly 3 m., so that 
 the summit of our Mont Blanc would drop beneath the ring : 
 the height of its fine central hill, 5000 ft. 1 (6000 Schm.), 
 ranging nearly with the terraces, from 3 to 5 rows of which 
 border the inner slope of the narrow wall. This noble 
 object lies among so many competitors that it is not always 
 immediately identified by an unpractised eye near the termi- 
 nator, a day or two after I. Quarter ; but as the Sun rises 
 higher upon it, its pre-eminence becomes more and more 
 evident. Its vicinity is thronged with hillocks and small 
 craters, so that for a long distance not the smallest level 
 spot can be found ; further off, the craters increase, till the 
 whole surface resembles a colossal honeycomb. At 180 
 commences the largest of the systems of rays, extending over 
 fully ^ of the visible hemisphere ; one ray passes through H, 
 almost to the opposite limb. Everywhere the visibility of 
 the streaks is the converse of that of the shadows, so that 
 many great ring-mountains which are overspread by these 
 rays become totally imperceptible under high illumination. 
 In photograms, however, they are less difficult of recognition 
 a singular fact. The streaks have no connection whatever 
 
 1 A smaller hill close to it on the W. is omitted by B. and M., 
 though readily seen. Birt rediscovered it, but it appears in D.'s 
 map. Gaudibert has detected a curious crevice passing along the 
 inner NE. slope, crossing the crest, and running down the outer SE. 
 face of the wall with a branch inside, and another outside the rampart. 
 Birt had at one time great difficulty in defining the interior of Tycho. 
 but subsequently found the mistiness disappear. 
 
122 THE SOLAR SYSTEM. 
 
 with the form of the surface, are not in the least elevated 
 or depressed, and resemble nothing on the Earth. In Full 
 the central hill and wall of 180 are brilliant, the interior 
 dark, as well as an exterior zone, beyond which a light cloud 
 forms the base of the streaks. Their appearance reminds 
 me of a vast net gathered up round a circular opening. 1 
 
 HESIODUS (187) guides the eye to a cleft E. of it, in the 
 M. NUBIUM (S). 2 
 
 CICHUS (189), a crater in table-land, lies 9000 ft. beneath 
 the plateau, 4000 ft. below the plain. In 1833 I perceived 
 r that the small crater on its ring was twice as 
 
 large as it had been represented 3 several 
 times by Schr. On becoming possessed of 
 the map of B. and M., I found it there also 
 enlarged. Schr., though a clumsy, was a faith- 
 ful draftsman ; his views have the appearance 
 of being each independently drawn, and they 
 are under different angles of illumination, 
 which often vary the apparent size of small 
 craters ; but, though the characteristic silence 
 of B. and M. may be disregarded, a longer 
 2 acquaintance with selenography leads to the 
 
 impression that such evidence of change is of little value. 
 The two figures here given, of which i is a copy of Schr.'s 
 design, 1792, Jan. 4, and 2 is taken from B. and M.'s map, 
 may serve as specimens of the respective modes of de- 
 lineation adopted by these observers. 
 
 1 A cleft on the inner slope of the SE. wall is easily traceable 
 under alow morning sun. 
 
 2 This object, which under favourable conditions is traceable in a 
 4-111. achromatic from the NE. of Hesiodus to the region SW. of 
 Ramsden, is an interesting example of a cleft striking across a moun- 
 tain-range (the Cichus Mercator range) nearly at right angles. 
 
THE MOON (THIRD QUADRANT). 123 
 
 LONGOMONTANUS (192), a great ring, 90 m. across, very 
 deep: a peak on W. wall measures nearly 15,000 ft. The 
 region is most wild and dislocated. 192, with HEINSIUS 
 (190), a triangle of craters each highest W., as is common 
 here, and WILHELM I. (191), are admitted by B. and M. to 
 be a little misplaced and ont of proportion in their map. 
 
 CLAVIUS (193). One of the grandest cavities in the 
 Moon, though ill-placed for observation ; tolerably circular, 
 and more than 142 m. broad; it is encompassed by a wall 
 damaged by successive explosions, but still portentously high 
 and steep, attaining 17,300 ft. in one of its W. peaks, and 
 covering the gulf with night amid surrounding day. On 
 and within the ring Schm. counts at least 90 craters. * In 
 a good telescope/ we are told by B. and M., { the prospect 
 of a sunrise upon the surface of Clavius is indescribably 
 magnificent/ The shaded side, they justly remark, cannot 
 bo in perfect darkness when exposed to the reflection of 
 such an enormous mass of enlightened cliffs. The bottom 
 of the small included crater lying farthest W. falls nearly 
 24,000 ft. below the peak already mentioned an interval 
 greater than the height of Chimborazo. Well may these 
 observers express their astonishment that of this gigantic 
 bulwark not a trace can be discovered in the Full Moon ! l 
 About i d after I. Quarter, Schr. remarks that its shadow- 
 blunts the S. horn to the naked eye. 
 
 MAGINUS (195). The ruin of a vast complex ring, with 
 an interior depressed 14,000 ft. Some minute hillocks and 
 a little hollow in its centre form a good test. There is an 
 admirable drawing of it in Ne.'s work. The Sun rises 
 grandly upon it a little after I. Quarter, but e the Full Moon 
 knows no Maginus ! ' S. of its W. side lies a hollow, the 
 only dark spot under high lights in all this wild region. 
 1 Scarcely to be taken literally, according to Ne. 
 
124 THE SOLAK SYSTEM. 
 
 SAUSSURE (196) bends into a curve one of the streaks of 
 180 a solitary instance, or nearly so, of such deviation. W. 
 of it the surface swarms with craterlets, some hardly o" '5 
 in diameter. 
 
 NASIREDDIN (198) and Nasireddin A, just N., are two fine 
 craters; the latter reaches 11,000 ft. The former I have 
 often wondered at, about I. Quarter, as the culminating 
 point of immense explosive energy. 
 
 The GREAT CRATER-RANGE of the I st Meridian comprises 
 5 vast walled plains in almost uninterrupted succession, 
 which, like two other series near each limb, seem to have 
 been formed upon a long cleft running N. and S. : similar 
 volcanic phsenomena occur on the Earth for example, the 
 Andes, and the Puys of Auvergne. The 5 lunar circles 
 greatly resemble each other in character. We begin at the 
 S. end : 
 
 1. WALTER (200) has lofty peaks on its ramparts. 1 
 
 2. PURBACH (202) is about 7500 ft. deep. NE. of it, out 
 of the main line, lies 
 
 THEBIT (203), 32 m. broad, 9800 ft. below one part of 
 its ring. The wall has been pierced by a smaller and deeper 
 crater, against the ring of which a yet lesser mine has been 
 sprung. 2 E. of it we find the 
 
 STRAIGHT WALL, a most curious formation, regular enough 
 for a work of art, but more than 60 m. long, and of a very 
 imiform height of about 1000 ft. (880, Schm.). To me it 
 appears brownish. Ne. finds slope exceedingly gradual on 
 W. side, and an irregular * ditch ' all along E. foot. At one 
 end is a small crater; at the other a branching mountain, 
 
 1 And a number of craters in the interior. One of these, nearly 
 central, casts a prominent spire of shadow at. sunrise. 
 
 2 This hns a central mountain, which is a good test for a 4-in. 
 achromatic. 
 
THE MOON (THIRD QUADRANT). 125 
 
 giving it, as B. and M. say, the appearance of a staff tipped 
 with a stag's horn. It may be well seen from i d to 2 d after 
 I. Quarter, or i d after III. Quarter. At a short distance E. 
 is a minute cleft of varying breadth and all the character of 
 a river, according to Klein, who considers it a test. We 
 now return to the centre of our series : 
 
 3. ARZACHEL (204), 65 m. across. On W. side of ring 
 is a peak of 13,600 ft. Its neighbour, 
 
 ALPETRAQIUS (205), is so deep on W. 12,000 ft. as to 
 be only 5 or 6 days free from shadow. It contains one of 
 the finest central peaks in the Moon drawn too small by 
 B. and M. 7000 ft. high (Schr.). E. of it, and close to 
 LASSELL (484), is a very brilliant little crater, Alpetra- 
 gius B, ' light-encompassed ' like 221. Farther E. in a line 
 through the S. ring of 205, and the centre of 484, is a small 
 round brilliant spot, described and drawn as a crater by B. 
 and M., but level now. 484 was difficult to them in Full, 
 but easy at present. 
 
 4. ALPHONSUS (207), 83 m. in diam., has a steep central 
 peak of 3900 ft. (4500 Schm.), about the height of Vesuvius ; 
 under a high light two bright specks, and several defined 
 blackish patches, vary the surface, in those places perfectly 
 level. L. drew 6 dark spots ; Schm. found but 3 dark and 
 
 1 faint. The latter sees 2 clefts in both 207 and 204. 
 
 5. PTOLEM^EUS (208) is the last and largest of the chain : 
 its breadth (over-stated by Schr.) is 115 m. a magnificent 
 lake, whose surface at sunrise or sunset is occasionally seen 
 all roughened with ridges like waves, not 100 ft. high. I 
 have seen the shadows of the W. boundary of it drawn out 
 into bundles of black filaments. Schr. on one occasion drew 
 4 deep pits in it, 2 of them equal to the obvious small crater : 
 he had never seen them before, and in their position are only 
 
 2 minute craterlets now. Schm. gives part of its rampart 
 
126 THE SOLAK SYSTEM. 
 
 12,800 ft., and counted, with the Berlin achromatic, at least 
 46 minute craters in its interior ; 1 2 in E. forming a chain. 1 
 He also found an innumerable multitude between this spot 
 and 203. 2 
 
 MOISTING (211) has a vast depth of 7500 ft. beneath a 
 wall only 1600 ft. high on the outside. A minute crater S., 
 Hosting A, is very luminous. HERSCHEL (212), 9500 ft. 
 deep, forms with 211 and 94 a triangle marking the Moon's 
 centre. 
 
 BULLIALDUS (213), a grand crater 38 m. across, 9000 ft. 
 deep, with a quadruple central hill of 3200 ft. bearing, 
 according to Schm., a minute crater-row, is connected by a 
 gorge with a little crater, and is the centre of a remarkable 
 group. I have seen a large radiation round it, as of ejected 
 matter. SW. of it Whitley has discovered several minute 
 crater-chains. 3 
 
 Three walled plains, of which one is PARRY (217), bear 
 evidence of extreme antiquity, and have their rings very 
 curiously split by as many clefts. 4 
 
 EUCLIDES (221) is the best specimen of an infrequent 
 variety, the * light-encompassed ' crater. There are 9 of 
 these all deep, regular, not large, bright, and closely sur- 
 rounded by a luminous cloud not resembling the white 
 streaks in character. Four of them lie near. 
 
 LANDSBERG (222), whose ring of 28 m., with a greatest 
 height of 9700 ft., must command a boundless prospect over 
 
 1 It is also traversed by a number of light streaks. 
 
 2 See paper on Ptolemaus, Journal B.A.A., vol. i. p. 305. 
 
 3 The fine ring-plain C, on the SE., is encircled by a silvery 
 glow. 
 
 4 The best view of the group (Parry, Bonpland, and Fra Mauro) 
 is obtained when the E. wall of Copernicus is on the morning 
 terminator. 
 
THE MOON (THIRD QU ABE ANT). 12? 
 
 the dead level W. of it : it rises very gradually without, but 
 is steep and terraced within. 1 
 
 FLAMSTEED (223) is a crater combined with a circle of 
 banks averaging only 320 ft. in height, which is complete in 
 Full, and looks like an overflowed ring. 
 
 MARE HUMORUM (T) is a small circular foreshortened 
 plain, about 280 m. across, which may be detected by a keen 
 unaided sight. The greater part is as distinctly green as H, 
 with, in most parts, a narrow grey border. It is sprinkled 
 with innumerable craterlets requiring power and very steady 
 air. 2 
 
 CAMP ANUS (226) contains an especially dark centre, and 
 2 minute craters not in B. and M. ; E. of it and W. of 
 HIPPALUS (225) is a most remarkable system of clefts: I 
 have seen 3 readily, 2 d 3 h after I. Quarter. 
 
 EAMSDEN (228) is surrounded by a very fine system of 
 branched and intersecting clefts discovered by Schm., having 
 strangely escaped previous notice. In this case the ring- 
 plain seems to have intercepted the clefts. 
 
 VITELLO (229) is almost unique in having, within a second 
 concentric rampart, a central peak overlooking the whole 
 ring. 
 
 GASSENDI (232), a conspicuous walled plain, 55m. across, 
 lies considerably higher than the M. Humorum. Its loftiest 
 point is 9600 ft. above the interior, which contains many 
 minute objects: one little hill shines brilliantly in Full. 
 Schr. noticed several changes here ; and there is a strange 
 diversity in the drawings by different hands; but it has 
 
 1 Among the seven conspicuous craters E. of this formation, four 
 are * light-encompassed.' 
 
 2 The long undulating ridges, which originate near Vitello (229), 
 and roughly follow the curvature of the W. side of the Mare, are 
 noteworthy objects at sunrise. 
 
128 THE SOLAR SYSTEM. 
 
 recently received much, careful study and delineation, and 
 would repay yet more. It must be remembered that its 
 proportions vary considerably according to libration. Many 
 curious clefts may be at times made out in it. Schm. men- 
 tions at least 14, Ne. 38. A monograph by the latter is 
 contained in Astronomical Register, 1873, May, August, 
 October. 
 
 MERSENIUS (231) has a convex interior, with several 
 minute craters, hills, and clefts ; L. gives but one craterlct ; 
 B. and M. omit everything : Schm.'s drawing is unsatisfac- 
 tory. This should be well studied. Two little craters, 
 Mersenius B (NE.) and c (NW.), are very luminous. Between 
 231 and 232 are two clefts, seen plainly by me 4 d 3 h after 
 I. Quarter. 
 
 HAINZEL (237) is of great depth and steepness : the ring 
 of CAPUANUS (238) is peculiarly irregular in height, and 
 contains at least 7 craterlets. 
 
 SCHICKARD (239), an enormous plain, exhibiting a fine 
 scene between 4 and 5 d after I. Quarter, is encircled by a 
 complex wall, 460 m. in compass. Chacornac observes, that 
 from the rapid rounding of the lunar globe, a spectator in 
 the centre would think himself in a boundless desert ; the 
 ring, though in the N. more than 10,500 ft. high, being in-- 
 visible in every direction. The interior is nearly level, but 
 its colour strongly varied a curious contrast to the mono- 
 tony of its neighbour, 1 PHOCYLTDES (242). The latter I have 
 frequently seen crossed by a grand shadow from a peak in 
 the ring. 
 
 WARGENTIN (243) is a singular formation ; a circular 
 
 1 There are a number of large depressions on the floor, and many 
 craterlets, which, under good conditions, may be seen in a 4-in. 
 achromatic. A well-marked dark area is conspicuous on the SW. 
 quarter of the interior. 
 
THE MOON (THIRD QUADRANT). 129 
 
 elevated plain 54m. across, which, excepting for a very slight 
 rampart, resembles a large thin cheese. G. and Sehwabe 
 have drawn a similar formation N. of it, and E. of 239. 1 
 
 BAILLY (245), like a small sea, lies near the limb ; its 
 wall, probably almost as high as that of 193, seems to run 
 back into the 
 
 DffiRFEL MOUNTAINS (246), a region of enormous eleva- 
 tion, whose 3 principal summits are occasionally visible in 
 grand profile. B. and M. admit that Schr. did not over- 
 estimate them at 25,000 or 26,000 ft. 
 
 Great craters lie between 242 and S. pole. KIRCHER 
 (252) is 18,000 ft. deep, among numberless small explosions. 
 CASATUS (254) is still deeper ; a dome upon its mighty wall 
 rises to about 22,300 ft. KLAPROTH (255) is a wonder of 
 flatness in these regions. 
 
 NEWTON S (256), an irregular crater, 142 m. long and 
 about half as broad, is the deepest known : the height of its 
 loftiest tower is probably about 23,900 ft. above the interior. 
 
 MALAPERT (258) is the nearest visible crater to S. Pole, 
 4 of lat. farther, among mountains where the sun never sets. 
 
 LEIBNITZ MOUNTAINS (259). Ranges of colossal eleva- 
 tion break up the limb here, more than rivalling 246, and 
 far exceeding anything within the disc : several of the peaks 
 measure nearly 30,000 ft.; and Ne. gives a probable height 
 of nearly 36,000 ft. to a huge mass, e on his map, lying a 
 little beyond the limb. They extend along a considerable 
 arc of the 3 rd and 4 th Quadrants. In the crescent their sum- 
 
 1 Low ridges on the floor are traceable when the E. wall is on the 
 morning terminator. 
 
 2 B. and M. transferred this name from a spot so called by Schr. 
 in close to 132, which they thought unworthy of the designation. 
 There was some inducement in this instance ; but the precedent should 
 not be followed, as liable to produce confusion. 
 
 VOL. I. K 
 
130 THE SOLAR SYSTEM. 
 
 mits frequently prolong the horn; in Full, with suitable 
 libration, they come out in striking projection on the sky, 1 
 while even their apparent bases may lie far above any lunar 
 " sea." Their outline is rather rounded : some long ridges 
 may be the profile of great rings. The E. extremity lies in 
 the direction of the bright streak running S. from 180. I 
 find a clear description and rough measure of them by 
 Cassini, in 1724. Schr., who did not know this, observed 
 them more correctly, and called them the LEIBNITZ MOUN- 
 TAINS. By some unwonted inadvertency, B. and M. have 
 interchanged the names of 246 and 259. 2 Ne. and myself 
 have preferred retaining them as given by the earlier dis- 
 coverer. These and other ranges sometimes roughen the 
 limb during a solar eclipse, but Schr. found that their peaks 
 then appear much sharper from the irradiation of the Sun. 
 
 BLANOANUS (260), a noble crater, 51 m. in diameter, with 
 a terraced and turreted ring, domineers ' like Etna over 
 Sicily,' bearing a peak of 18,000 ft. above the interior. 
 
 SCHEINER (261), larger and steeper, includes 10 craters 
 and a partition. 
 
 MOKETUS (262), a very fine object, is 78 m. broad, but of 
 unequal height, 15,000 ft. on W. side, widely terraced within, 
 with a bright central hill, the loftiest yet measured 6800 
 ft., by which it is easily identified. Its sunrise or sunset is 
 very fine : it may be seen in noble relief about i d after I. 
 Quarter. I have seen with 9-in. speculum a very minute 
 crater N. of central mountain. 
 
 1 We never see a real Full Moon; that is, she is never exactly 
 opposite to the Sun except when centrally eclipsed ; hence there is 
 always a small deficiency at one or the other pole; and libration 
 must be favourable, to show these mountains well, and on a circular 
 limb. 
 
 2 Their groundless complaint of Schr.'s want of explicitness here 
 shows superficial acquaintance with his work. 
 
THE MOON (THIRD QUADKANT). 131 
 
 GRUEMBERGER (265) lias a central crater, whose bottom 
 is probably more than 20,000 ft. below a great peak in the 
 wall. 
 
 ZUPUS (268), a valley, very dark in Full. SIESALIS 
 (270), a double ring, W. of which lies a very remarkable 
 cleft, figured by Gaudibert (Eng. Mech., 1873, Dec. 19), with 
 Schm.'s continuation probably more than 400 m. long ; the 
 longest known, but requiring favourable libration. 
 
 GRIMALDI (272). The S. link of a chain of great craters 
 lying in the meridian. This grand spot, 147 m. long by 129 
 wide, has a darker interior than any portion of the Moon of 
 equal size; it has sometimes been detected even without a 
 telescope. G. perceived here a regular formation somewhat 
 resembling the letter H much inclined. 
 
 EICCIOLI (273) is in part as dark ; its ring is grand 
 before the rising or setting Sun. 1 
 
 The CORDILLERAS (274) and D'ALEMBERT MOUNTAINS 
 (275), a series of great ranges, nearly 20,000 ft. in general 
 height much higher, according to Schr., in parts rise 
 along the E. limb. They extend far S., and this extremity 
 is called the ROOK MOUNTAINS (276). Two valleys were dis- 
 covered by Schr. in profile of this limb, of enormous depth, 
 rivalling the height of the mountains. They have not been 
 found by Ne. 
 
 BYRGIUS (279) has on its ring a small crater, Byrgins A, 
 remarkably brilliant, and a centre of streaks. NE. of it 
 stands a great mountain, of probably at least 13,000 ft. as 
 high as the Swiss Jungfrau. 
 
 1 The dark area is on the N. of the centre, and has been estimated 
 to be somewhat darker than any part of Grirualdi. There is a 
 remarkable cleft between Biccioli and Lohrmann. 
 
132 THE SOLAR SYSTEM. 
 
 FOURTH, OR SOUTH-WEST QUADRANT. 
 
 HirpARcnus (288), 92 m. across, contains all kinds of forma- 
 tions. Schr. has seen the shadow in its interior bordered 
 on SW. by a fringe of fine lines, indicating a row of sharp 
 and regular pinnacles on the wall. Three small craters, 
 Hipparchus E, o, and c (reckoned towards S.), in and near 
 W. wall, are very bright in Full. 
 
 ALBATEGNIUS (289). A walled plain, 64 m. wide, very 
 level. Its rampart, 14 to 18 m. bread, has been all torn by 
 explosions; B. and M. counted at least 33 of their results: 
 a peak in NE. attains 15,000 ft. Its central hill, piercing a 
 mass of shade, forms a noble spectacle, which I have seen 
 io h before I. Quarter. Close on NW. is 
 
 HALLEY (458), a 21 m. ring. Here, on NW. part of 
 floor, a photogram of 1865 shows a craterlet which Gaudibert 
 could hardly find when he saw another very distinctly SE. 
 not in the photogram, and, as he thinks, of subsequent for- 
 mation. There are several instances of craters omitted by 
 earlier observers, though now more obvious than others that 
 they have drawn : indications, possibly of modern activity, 
 but certainly of the great advantage of photography, in never 
 missing anything visible at the time. 
 
 Craters with irregular walls and very large central 
 mountains bend round from 259 through AIRY (291), to LA 
 CAILLE (292). This last, with a wall of 9700 ft., is almost 
 level. 
 
 WERNER (295), 45 m. across, is one of the loftiest rings ; 
 its narrow ridge ranging 13,000 ft. (the height of the Alpine 
 Eiger) above the depth, and rising on the E. to 16,500 ft., 
 nearly TOOO ft. loftier than our Mont Blanc. A spot on the 
 SE. side of it is very bright another, on the inner slope of 
 the NE. wall, is stated to be as brilliant as 148, and more 
 
THE MOON (FOURTH QUADRANT). 133 
 
 luminous than any other part of the Moon ; but this ' star- 
 like flashing point,' being only between 4 and 5 m. square, is 
 said to be easily overlooked with low powers. I have several 
 times readily seen it with two aehromatics of 3^ in., and 
 powers 75, 80, 144, but never of the specified brilliancy: 
 a careful study of it in 1864, with 5^ in., confirmed with 
 a Q-in. mirror in 1871, induces me to believe that it has 
 faded since the date of B. and M. The reflector lies shown 
 in it a minute black pit (Ne., crater-cone) and very narrow 
 ravine. It is not mentioned by Schr. 
 
 ALIACENSIS (296) is similar to 295, but larger. 
 
 THEON SEN. (297), THEON JUN. (298) ALFUAGANUS (300), 
 are all luminous. 
 
 ABULFEDA (305), nearly 40 m. across, and ALMANON 
 (306), have their walls united by a row of little craters like 
 a cleft, visible about I. Quarter. 
 
 ABENEZRA (310) sinks more than 14,500 ft. PONS (313) 
 has very dark spots in the ring. 
 
 ALTAI MOUNTAINS (315). This long range (name omitted 
 in B. and M.'s map) is almost the only high ground in this 
 Quadrant undisturbed by eruptive forces. Its rounded 
 summits lie awkwardly for measurement, but seem about 
 13,000 ft. I have often seen the NW. face as a bright line 
 of nearly 280 m. of cliffs, in the increasing Moon. 
 
 A group of 3 huge craters follows, forming a wild and 
 gigantic region, very difficult to delineate. The details occu- 
 pied B. and M. portions of more than 50 nights. It has 
 since been effectively sketched by Phillips. 
 
 THEOPHILUS (319) is the deepest of all visible craters, if 
 we regard the general line of the ring, which ranges from 
 14,000 to 18,000 ft. above the chasm, with a diameter of 64 m. 
 No scene in the least approaching to it exists on the Earth. 
 The central peak is 5200 ft. high (more than 6400, Schm., 
 
134 THE SOLAR SYSTEM. 
 
 who gives the wall but 3200 ft. outside height, and finds it 
 surrounded by radiating ridges: these I have seen with a 
 9 J-in. silvered speculum). CYKILLUS (320), equally large and 
 terraced, approaches to a square. A small crater, Cyrillus A, 
 on its E. side is very brilliant. CATHARINA (321) is rather 
 the largest of the three, and more than 1 6,000 ft. deep, but 
 irregular in character. Of this superb cluster, 319 first 
 catches the rising Sun, and I have seen it far beyond the 
 terminator, and even without the telescope, 5 d after New : 
 it is a grand object when filled with night, through which its 
 glittering central peak comes out like a star. A wide valley 
 connecting 320 and 321 is much better represented in the 
 beautiful old map of Tobias Mayer, and by .Russell, than by 
 B. andM. 1 
 
 ISIDOETJS (323) and CAPELLA (324) lie side by side, with 
 a peak more than 13,000 ft. between them ; a broad cleft 
 cuts down the ring of 324, open also in another direction. 
 Schr. here saw traces of a line of little confluent craters. 
 Double craters, too numerous not to have some special cause, 
 abound in this region. 
 
 CENSOKINUS (325), a minute crater, with its vicinity is 
 very brilliant in Full. 
 
 MESSIER (327) and Messier A, a pair of small deep craters, 
 exhibited to B. and M. such an entire similarity in size, 
 form, depth, brightness, and even the position of some peaks 
 upon the rings, that they say it must have been either a 
 wonderful coincidence, or the result of some, unknown 
 natural process. This similarity does not now exist, but the 
 evidence of physical change is not satisfactory. Two curious 
 white streaks, slightly divergent, extend from Messier A for 
 
 1 Between (319) and Beaumont (322) is a region which includes 
 crater-cones, considered by Klein to be analogous to terrestrial 
 volcanoes. 
 
THE MOON (FOURTH QUADRANT). 135 
 
 a long distance E., forming with the included shade not 
 always visible according to G. the picture of a comet's 
 tail. G., who imagined them to be artificial, states that they 
 are totally unlike any other lunar streaks, being composed 
 of a multitude of distinct lines, each possibly consisting 
 of minute points. In consequence of an observation by 
 Schr., who discovered this ' comet,' B. and M. examined the 
 streaks, and could scarcely have avoided including the craters, 
 more than 300 times, between 1829 and 1837, without 
 noticing any change. Strange to say, however, G., who 
 frequently examined this region, expressly states that on 
 several occasions in 1824 and 1825 the W. crater was ob- 
 served less distinct, or much the smaller, and in 1825 ex- 
 tended E. and W. : once only under very high illumination 
 did it appear to surpass its neighbour in size ; as, in fact, 
 Schr. had already drawn it in 1788. And without know- 
 ing anything of G.'s remarks, 1855, Nov. 14, I perceived 
 with my 3 T 7 -in. achr. that the E. crater appeared the larger 
 of the two; and 1856, March n, I found the W. crater not 
 only the lesser, but, ' lengthened obviously in an E. and W. 
 direction? I have since noted the dissimilarity with larger 
 instruments ; and, however difficult to be explained in accord- 
 ance with B. and M., it is a matter of very easy observation. 
 The figure is taken from a rough sketch, 1857, Feb. 28 : the 
 shadow is probably too broad in W. crater, which is that 
 to the left in the inverted diagram. 
 G. also found, on one occasion, the 2 
 craters not standing us usual in the 
 axis of the tail, but somewhat oblique ; 
 and at another time the interior of the W. crater bright, 
 and the wall open E., like a horse-shoe, while the E. crater 
 was perfect and shadowed. Klein twice found the W. ring 
 of the W. crater invisible, and ita interior foggily shaded. 
 
136 THE SOLAR SYSTEM. 
 
 GUTTEMBERG (330), like many of its neighbours, is pear- 
 shaped. NE. are 3 considerable clefts. E. and S. of it lie 
 the 
 
 PYRENEES 1 (331), two mountain masses, the N. portion 
 12,000 ft. high. 
 
 COLOMBO (333), a double crater : in the NE. cavity, 
 Schm. once found a central hill, not seen by B. and M., or 
 L., nor again by himself. 
 
 BOEDA (337) has a lofty range on its W. side ; a peak 
 (Borda a) lying in the direction of the centre of 340, rises at 
 one spring 1 1,000 ft., as abrupt as the Alpine Wetterhorn, or 
 the two great Pics du Midi in the terrestrial Pyrenees. 
 
 We come now to the last of the 3 great rows of craters 
 lying in the meridian, consisting of the 4 following objects, 
 which must be looked for in the crescent 3 d or 4 d old, or at 
 a shorter interval after Full : 
 
 1. LANGRENUS (338) is a superb object under oblique sun- 
 shine, with its terraced ring 9600 ft. high, raised in SE. to 
 more than 15,000 ft. by Schm., who gives 5800 ft. to its 
 brilliant central hill. 
 
 2. VENDELINUS (339) is unequal to 338, though on the 
 Earth it would be esteemed a wonder of magnificence : it 
 contains a very dark speck in Full. 
 
 3. PETAVIUS (340) is one of the finest spots in the Moon : 
 its grand double rampart, on E. side nearly 11,000 ft. high, 
 its terraces, and convex interior with central hill and cleft, 
 compose a magnificent landscape in the lunar morning or 
 evening, entirely vanishing beneath a Sun risen but half-way 
 to the meridian. Gaudibert has drawn it in Eng. Mechanic, 
 1874, May 8. This, as well as 338, is according to Schm. a 
 centre of radiating ridges, and he finds the E. walls of these 
 
 1 This name is omitted in the Mappa Selenographica. 
 
THE MOON (FOURTH QUADRANT). 137 
 
 3 great craters, as well as the neighbouring plain, all crowded 
 with craterlets and crater-rows. 1 
 
 4. FURNERIUS (345) has a central crater, N. of which I 
 have seen with 5^-in. a bent cleft: the deep little crater 
 Furnerius A at N. end of the wall is, in Full, a brilliant 
 point on a white streak, and with another streak E. of 
 STEVINUS (344) identifies this neighbourhood. 
 
 (NW. of K^STNER (347), in favourable libration, a large 
 grey plain conies out from the limb, resembling A, and little, 
 if at all, inferior to it in size. It was discovered, drawn, and 
 described bySchr., and named by him Kastner, but strangely 
 overlooked by B. and M., who appropriated his name to a 
 ring (347) connected with it. This interesting region has 
 received from the late Dr. Lee the appropriate name of 
 MARE SMYTHII, in remembrance of one whose services 
 to astronomy would, however, under no circumstances 
 have been forgotten. Its position in mean libration is 
 shown by a shaded space on the limb opposite W on the 
 Map.) 
 
 (In various parts of the W. limb [I think from 6 to 9, 
 and from n to 18^ S. lat., and on each side of 52 N. 
 lafc., towards E. for io], very remarkable flattenings are 
 visible in certain states of libration. Those to the S. lie be- 
 hind 347 and 424, with which one of them is identified by 
 Ne. They had been in part previously known to Dawes, but 
 were first described by Key, 1863, Sept. 21. Their most 
 striking appearance is very transient.) 
 
 WILHELM HUMBOLDT (352), one of several huge rings on 
 the limb, shows peaks of 16,000 ft. in profile. 
 
 STOEFLER (354), rising in one part to 12,000 ft., has a 
 
 1 Beautiful enlargements of Langrenus, Vendelinus, and Petavius, 
 from the Lick lunar photographs, have recently been made by Dr 
 L. Weinek of Prague. 
 
138 THE SOLAK SYSTEM. 
 
 very level interior, crossed by two of the rays from 180, and 
 containing at least 1 6 very minute craters. It is well seen 
 about I. Quarter. 
 
 MAUROLYCUS (358). A noble walled plain, sure to be 
 found in grand relief about I. Quarter, or 2 d before III. 
 Quarter. Its complex rampart is heaved up on E. side to 
 13,800 ft.; on W., though not according to B. and M. quite 
 so lofty, I have often seen it more conspicuous in the in- 
 creasing Moon ; and Schm. gives it here 1 8,000 ft. B. and 
 M. describe the plain as crossed by 1 2 diverging bright lines 
 in Full. 
 
 BACON (360) has a peak on E. ring nearly as high as 35S, 
 and on the top of SE. side a row of 5 minute craters. 
 
 LINDENAU (370), a perfect ring, rises on E. by 4 stages. 
 
 PICCOLOMINI (371), a noble circle 57 m. in diameter, has 
 a central hill and complex wall, bearing on E. a tower about 
 the height of our Mont Blanc. 
 
 FRACASTORIUS (372), a partially destroyed ring, which 
 has been seen complete by Birt and Simms, forms a bay of 
 the MARE NECTARIS (V): a little crater on E. headland is 
 brilliant in Full. There are good drawings of it in Eny. 
 Mechanic, 1873, Jan. 31, Feb. 14, April n ; 1876, June 30 ; 
 1883, Nov. 1 6. 
 
 From W. side of KEICHENBACH (375) towards EHEITA 
 
 (376) extends one of the gigantic valleys peculiar to this 
 region. 376 has a ring reaching 14,000 ft. Close under it 
 on the side next METIUS (384), is another valley 186 m. long, 
 and from 14 to 23 m. wide, bordered by steep walls; in one 
 spot more than 9000 ft. deep. Along W. side of FRAUNHOFEK 
 
 (377) is another valley 7 m. wide, which may be traced 
 through 345, though of very unequal depth, for 2 1 2 m. 
 
 STEINHEIL (385) is probably the deepest of the double 
 riiigs, in one place sinking to 12,000 ft. 
 
THE MOON (FOURTH QUADRANT). 139 
 
 VLACQ (388), the leader of a colossal group, is 57 in. 
 across. 
 
 A little crater E. of NICOLAI (393) called Nicolai A, is 
 very bright in Full. Minute insulated craters abound here 
 at the rate of 65,000 for the visible hemisphere. 
 
 ZACH (396), 13,000 ft. deep is magnificently terraced. 
 
 CURTIUS (404) has a very complex and unusually steep 
 wall, probably surpassing the elevation of our Chimborazo. 
 
 WEBB (456) marks very nearly the position of the lunar 
 equator. 
 
140 
 
 THE SOLAR SYSTEM. 
 
 INDEX TO THE MAP OF THE MOON. 
 
 GIJEY PLAINS, USUALLY CALLED SEAS. 
 
 A. Mare Crisium 
 
 I. Palus Nebula- 
 
 E. Sinus Roria 
 
 B. Huniboldti- 
 
 rum 
 
 S. Mare Nubiuin 
 
 anum 
 
 K. Putredinis 
 
 T. Humorum 
 
 C. Frigoris 
 
 I. Mare Vaporuin \S 
 
 'V, Nectar is 
 
 D. Lacus Mortis 
 
 M. SiuusMedii ix 
 
 OC, Fcecundi- 
 
 . Sonmiorum 
 
 N. -/Estuurn 
 
 tatis 
 
 F. Palus Somnii 
 
 "i). Mare Itnbrium 
 
 y. Smythii 
 
 G. Mare Tranquilli- 
 
 P. Sinus Iridum 
 
 Z. Australe 
 
 tatis 
 
 Q. Oceanus Procel- 
 
 
 H. Mare Serenitatis 
 
 larum 
 
 
 CRATERS 
 
 MOUNTAINS, AND OTHER 
 
 OBJECTS. 
 
 1. Promontorium 
 
 23. Messala 
 
 46. Archytas 
 
 Agarum 
 
 24. Schumacher 
 
 47. Plana 
 
 2. Alhazen 
 
 25. Struve 
 
 48. Mason 
 
 3. Eimmait 
 
 26. Mercurius 
 
 49. Baily 
 
 4. Picard 
 
 27. Endyniion 
 
 50. Burg 
 
 5. Condorcet 
 
 28. Atlas 
 
 01. Mt. Taurus 
 
 6. Azout 
 
 29. Hercules 
 
 52. Roraer 
 
 7. Firnncus 
 
 30. Oersted 
 
 53. Le Monnier 
 
 8. Apolloniua 
 
 31. Cepheus 
 
 54. Posidonius 
 
 9. Neper 
 
 32. Franklin 
 
 55. Littrow 
 
 10. Schubert 
 
 33. Berzeliud 
 
 56. Maraldi 
 
 11. Hansen 
 
 34. Hooke 
 
 57. Vitruvius 
 
 12. Cleoinedea 
 
 '35. Strabo 
 
 58. Mt. Argseus 
 
 13. Tralles 
 
 36. Thales 
 
 59. Macrobius 
 
 14. Oriani 
 
 37. Gartner 
 
 60. Proclus 
 
 15. Plutarch us 
 
 38. Democrltus 
 
 61. Plinius 
 
 16. Seneca 
 
 39. Arnold 
 
 62. Ross 
 
 17. Halm 
 
 40. Christian Mayer 
 
 63. Arago 
 
 18. Berosus 
 
 41. Meton 
 
 64. Ritter 
 
 19. Burckhardt 
 
 42. Euctemon 
 
 65. Sabiuo 
 
 20. Geminus 
 
 43. Scoresby 
 
 66. Jansen 
 
 21. Bernouilli 
 
 44. Gioja 
 
 67. Maskelyne 
 
 22. Gauss 
 
 45. Barrow 
 
 68. Mt. Haemua 
 
INDEX TO THE MAP OF THE MOON. 
 
 141 
 
 69. Promontorium 
 
 108. Pallas 
 
 148. Aristarchus 
 
 Acherusia 
 
 109. Ukert 
 
 149. Herodotus 
 
 70. Menelaus 
 
 110. Eratosthenes 
 
 150. Wollaston 
 
 71. Sulpicius Gallus 
 
 111. Stadius 
 
 151. Lichtenberg 
 
 72. Taquet 
 
 112. Copernicus 
 
 152. Harding 
 
 73. Bessel 
 
 113. Gambart 
 
 153. Lohrmann 
 
 74. Linne' 
 
 114. Reinhold 
 
 154. Hevel 
 
 75. Mt. Caucasus 
 
 115. Mt. Carpathus 
 
 155. Cavalerius 
 
 76. Calippus 
 
 116. Gay Lussac 
 
 156. Galileo 
 
 77. Eudoxus 
 
 117. Tobias Mayer 
 
 157. Cardanus 
 
 78. Aristoteles 
 
 118. Milichius . 
 
 158. Kraflft 
 
 79. Egede 
 
 119. Hortensius 
 
 159. Olbers 
 
 S 80. Alps 
 
 120. Archimedes 
 
 160. Vasco de Gama 
 
 81. .Cassini 
 
 121. Timocharis 
 
 161. Hercyniau Mts 
 
 82. Theaotetus 
 
 122. Lambert 
 
 162. Seleucus 
 
 83. Aristillus 
 
 123. La Hire 
 
 163. Briggs 
 
 84. Autolycus 
 
 124. Pytheas 
 
 164. Ulugh Beigh 
 
 '"^5. Apennines 
 
 125. Euler 
 
 165. Lavoisier 
 
 86. Aratus 
 
 128. Diophantus 
 
 166. Gerard 
 
 87. Mt, Had ley 
 
 127. Delisle 
 
 167. Repsold 
 
 88. Conon 
 
 128. Carlini 
 
 168. Anaxagoras 
 
 89. Mt. Bradley 
 
 129. Helicon 
 
 169. Epigenes 
 
 90. Mt. Huygens 
 
 130. Kirch 
 
 170. Timaeus 
 
 91. Marco Polo 
 
 131. Pico 
 
 171. Fontenelle 
 
 92. Mt. Wolf 
 
 132. Plato 
 
 172. Philolaus 
 
 93. Hyginus 
 
 133. Harpalus 
 
 173. Anaximenes 
 
 94. Triesnecker 
 
 134. Laplace 
 
 174. Anaximander 
 
 95. Manilius 
 
 135. Heraclides 
 
 175. Horrebow 
 
 98. Julius Caesar 
 
 136. Maupertuis 
 
 176. Pythagoras 
 
 97. Sosigeues 
 
 137. Condamine 
 
 177. CEnopides 
 
 98. Boscovich 
 
 138. Biauchini 
 
 178. Xenophanes 
 
 99. Dionysius 
 
 139. Sharp 
 
 179. Cleostratus 
 
 100. Ariadasus 
 
 140. Mairan 
 
 180. Tycho 
 
 101. Silberschlag 
 
 141. Louville 
 
 181. Pictet 
 
 102. Agrippa 
 
 142. Bouguer 
 
 182. Street 
 
 103. Godin 
 
 143. Encke 
 
 183. Sasserides 
 
 104. Rhaeticus 
 
 144. Kepler 
 
 " 184. Hell 
 
 105. Summering 
 
 145. Bessarion 
 
 185. Gauricufl 
 
 106. Sch'roter 
 
 146. Reiner 
 
 186. Pitatus 
 
 107. Bode 
 
 147. Marine 
 
 187. HesioduB 
 
THE SOLAR SYSTEM. 
 
 188. Wurzelbauer 
 
 189. Cichus 
 
 190. Heinsins 
 
 191. Wilhelm I. 
 
 192. Longomontanus 
 
 193. Clavius 
 
 194. Deluc 
 
 195. Maginus 
 
 196. Saussure 
 
 197. Orontius 
 
 198. Nasireddin 
 
 199. Lexell 
 
 200. Walter 
 
 201. Regiomontanus . 
 
 202. Purbach 
 
 203. Thebit 
 
 204. Arzachel 
 
 205. Alpetragius 
 
 206. Promontorium 
 
 JEnarium 
 
 207. Alphonsus 
 
 208. PtolemsBUS 
 
 209. Davy 
 
 210. Lalande 
 
 211. Hosting 
 
 212. Herschel 
 
 213. Bullialdus 
 
 214. Kies 
 
 215. Guerike 
 
 216. Lubiniczky 
 
 217. Parry 
 
 218. Bonpland 
 
 219. Fra Mauro 
 
 220. Riphrean Mts. 
 
 221. Euclides 
 
 222. Laudsberg 
 
 223. Flamsteed 
 
 224. Letroiine 
 
 225. Hippalus 
 
 226. Campanus 
 
 227. Mercator 
 
 228. Ramsden 
 
 229. Vitello 
 
 230. Doppelmayer 
 
 231. Mersenius 
 
 232. Gassendi 
 
 233. Agatharchides 
 
 234. Schiller 
 
 235. Bayer 
 
 236. Rost 
 
 237. Hainzel 
 
 238. Capuanus 
 
 239. Schickard 
 210. Drebbel 
 
 241. Lehmaim 
 
 242. Phocylides 
 
 243. Wargentin 
 
 244. Inghirami 
 
 245. Bailly 
 
 246. DorfelMts. 
 
 247. Hausen 
 
 248. Segner 
 
 249. Weigel 
 
 250. 'Zuchius 
 
 251. Betthms 
 
 252. Kircher 
 
 253. Wilson 
 
 254. Casatus 
 
 255. Klaproth 
 
 256. Newton 
 
 257. Cabeus 
 
 258. Malapert 
 
 259. Leibnitz Mts. 
 
 260. Blancanus 
 
 261. Scheiner 
 
 262. Moretus 
 
 263. Short 
 
 264. Cysatus 
 
 265. Gruemberger 
 
 266. Billy 
 
 267. Hansteen 
 
 268. Zupus 
 
 269. Fontana 
 
 270. Sirsalis 
 
 271. Damoiseau 
 
 272. Grimaldi 
 
 273. Riccioli 
 
 274. Cordilleras 
 
 275. D'AlembertMts. 
 
 276. Rook Mts. 
 
 277. Rocca 
 
 278. Cruger 
 
 279. Byrgius 
 
 280. Eichstadt 
 
 281. Lagrange 
 
 282. Piazzi 
 
 283. Bouvard 
 
 284. Vieta 
 
 285. Fourier 
 
 286. Cavendish 
 
 287. Reaumur 
 
 288. Hipparchus 
 
 289. Albategnius 
 
 290. Parrot 
 
 291. Airy 
 
 292. La Caille 
 
 293. Playfair 
 
 294. Apianus 
 
 295. Werner 
 
 296. Aliacensis 
 
 297. Theon, sen. 
 
 298. Theon, jun. 
 
 299. Taylor 
 
 300. Alfragauus 
 
 301. Delambre 
 
 302. Kant 
 
 303. Dollond 
 
 304. Descartes 
 
 305. Abulfeda 
 
 306. Almamo 
 
INDEX TO THE MAP OF THE MOON. 
 
 143 
 
 307. Tacitus 
 
 347. Kastner 
 
 386. Pitiscus 
 
 308. Geber 
 
 348. Lapeyrouse 
 
 387. Hommel 
 
 309. Azophi 
 
 349. Ansgarius 
 
 388. Vlacq 
 
 310. Aberiezra 
 
 350. Behaim 
 
 389. Kosenberger 
 
 311. Pontanus 
 
 351. Hecatseus 
 
 390. Nearohus 
 
 312. Sacrobosoo 
 
 352. Wilhelm Hum- 
 
 391. Hagecius 
 
 313. Pons 
 
 boldt . 
 
 392. Biela 
 
 314. Fermat 
 
 353. Legendre 
 
 393. Nicolai 
 
 315. Altai Mts. 
 
 354. Stofler 
 
 394. Lilius 
 
 316. Polybius 
 
 355. Licetus 
 
 395. Jacob! 
 
 317. Hypatia 
 
 356. Cuvier 
 
 396. Zach 
 
 318. Torricelli 
 
 357. Clairaut 
 
 397. Schomberger 
 
 319. Theophilus 
 
 358. Maurolycus 
 
 398. Boguslawsky 
 
 320. Cyrillus 
 
 359. Barocius 
 
 399. Boussingault 
 
 321. Catharina 
 
 360. Bacon 
 
 400. Mutus 
 
 322. Beaumont 
 
 361. Buch 
 
 401. Manzinus 
 
 323. Isidorus 
 
 362. Biisching 
 
 402. Pentland 
 
 324. Capella 
 
 363. Gemma Frisius 
 
 403. Simpelius 
 
 325. Censorinus 
 
 364. Poisson 
 
 404. Curtius 
 
 326. Taruntius 
 
 365. Nonius 
 
 405. Kinau 
 
 327. Messier 
 
 366. Fernelius 
 
 406. Pingre 
 
 328. Goclenius 
 
 367. Eiccius 
 
 407. Chevallier 
 
 329. Biot 
 
 368. Kabbi Levi 
 
 408. Moigno 
 
 330. Guttemberg 
 
 369. Zagut 
 
 409. Peters 
 
 331. Pyrenees 
 
 370. Lindenau 
 
 410. Teneriffe Mts. 
 
 332. Bohnenberger 
 
 371. Piccolomini 
 
 411. Smyth, Piazzi 
 
 333. Colombo 
 
 372. Fracastorius 
 
 412. Herschel, J. F. 
 
 334. Magelhaens 
 
 373. Neander 
 
 W. 
 
 335. Cook 
 
 374. Stiborius 
 
 413. Kobinson 
 
 336. Santbech 
 
 375. Keichenbach 
 
 414. South 
 
 337. Borda 
 
 376. Kheita 
 
 415. Babbage 
 
 338. Langrenus 
 
 377. Fraunhofer 
 
 416. Clausius 
 
 339. Vendelinus 
 
 378. Vega 
 
 417. Kosse 
 
 340. Petavius 
 
 379. Marinus 
 
 418. Cauchy 
 
 341. Palitzsch 
 
 380. Okeii 
 
 419. Crozier 
 
 342. Hase 
 
 381. Pontecoulant 
 
 420. McClure 
 
 343. Snellius 
 
 382. Hanno 
 
 421. Bellot 
 
 344. Stevinus 
 
 383. Fabricius 
 
 422. Wrottesley 
 
 345. Furnerius 
 
 384. Metius 
 
 423. Phillips 
 
 346. Maclaurin 
 
 385. Steinheil 
 
 424. Lubbock 
 
144 
 
 THE SOLAR SYSTEM. 
 
 425. Le Verrier 
 
 448. Le Gentil 
 
 470. Faye 
 
 426. Shuckburgh 
 
 449. Tannerus 
 
 471. Donati 
 
 427. Goldschmidt 
 
 450. Peirce 
 
 472. Alexander 
 
 428. Kunowsky 
 
 451. Birt 
 
 473. Janssen 
 
 429. Strove, Otto 
 
 452. Nicollet 
 
 474. Cassini, J. J. 
 
 430. Newoomb 
 
 453. Straight Range 
 
 475. Foucault 
 
 431. Gruitlmisen 
 
 454. Chacornac 
 
 476. Lee 
 
 432. Herigonius 
 
 455. De Vico 
 
 477. Piton 
 
 433. Lacroix 
 
 456. Webb 
 
 478. Herscliel, Caro 
 
 434. De la Rue 
 
 457. Hind 
 
 line 
 
 435. Challis 
 
 458. Halley 
 
 479. Brayley 
 
 436. Main 
 
 459. Faraday 
 
 480. Lockyer 
 
 437. Adams 
 
 460. Horrocks 
 
 481. Daniell 
 
 438. Wichrrmnn 
 
 461. Huggins 
 
 482. Grove 
 
 439. Bond, G. P. 
 
 462. Miller 
 
 483. Murchison 
 
 440. Maury 
 
 463. Birmingham 
 
 484. Lassell 
 
 441. Maclear 
 
 464. Ball 
 
 485. Hermann 
 
 442. Dawes 
 
 465. Bond, W. 0. 
 
 486. Manners 
 
 443. Cayley 
 
 468. Madler 
 
 487. Schmidt 
 
 444. Whewell 
 
 467. Argelamler 
 
 488. Secchi 
 
 445. De Morgan 
 
 468. Blanchiuus 
 
 489. Schiaparelli 
 
 446. Beer 
 
 469. Delaunay 
 
 490. Harbinger Mta. 
 
 447. Carrington 
 
 
 
INDEX TO THE MAP OF THE MOON. 
 
 ALPHABETICAL TABLE OP LUNAR NOMENCLATURE. 
 (The Roman Numerals indicate the Quadrant.) 
 
 Abenezra, 310. iv. 
 Abulfeda, 305. iv. 
 AcLims, 437. iv. 
 Agatharchides, 233. 
 
 iii. 
 
 Agrippa, 102. i. 
 Airy, 291. iv. 
 Albategnius, 289. iv. 
 Alexander, 4T2. i. 
 Alfraganus, 300. iv. 
 Alhazen, 2. i. 
 Aliacensis, 296. iv. 
 Almamon, 306. iv. 
 Alpetragius, 205. iii. 
 Alphonsus, 207. iii. 
 Alps, 80. i 
 Altai Mts., 315. iv. 
 Anaxagoras, 168. ii. 
 Anaximander, 174. ii. 
 Anaximenes, 173. ii. 
 Ansgarius, 349. iv. 
 Apennines, 85. i.-ii. 
 Apianus, 294. iv. 
 Apollonius, 8. i. 
 Arago, 63. i. 
 Aratus, 86. i. 
 Archimedes, 120. ii. 
 Archytas, 46. i. 
 Argzeus, Mt., 58. i. 
 Argelander, 467. iv. 
 Ariadaeus, 100. i. 
 Aristarchus, 148. ii. 
 Aristillus, 83. i. 
 
 VOL. I. 
 
 Aristoteles, 78. i. 
 Arnold, 39. i. 
 Arzachel, 201. iii. 
 Atlas, 28. i. 
 Autolycus, 84. i. 
 Azophi, 309. iv. 
 Azout, 6. i. 
 
 Babbage, 415. ii. 
 Bacon, 360. iv. 
 Bailly, 245. iii. 
 Baily, 49. i. 
 Ball, 464. iii. 
 Barocius, 359. iv. 
 Barrow, 45. i. 
 Bayer, 235. iii. 
 Beaumont, 322. iv. 
 Beer, 446. ii. 
 Behaim, 350. iv. 
 Bellot, 421. iv. 
 Bernouilli, 21. i. 
 Berosus, 18. i. 
 Berzelius, 33. i. 
 Bessarion, 145. ii. 
 Bessel, 73. i. 
 Bettinus, 251. iii. 
 Bianchirii, 138. ii. 
 Biela, 392. iv. 
 Billy, 266. iii. 
 Biot, 329. iv. 
 Birmingham, 463. ii. 
 Birt, 451. iii. 
 Blancanus, 260. iii. 
 
 Blanchimig, 468. iv. 
 Bode, 107. ii. 
 Boguslawsky, 398. iv. 
 Bohnenberger, 332. iv. 
 Bond, G. P., 439. i. 
 Bond, W. 0., 465. i.-ii. 
 Bonpland, 218. iii. 
 Borda, 337. iv. 
 Bngcovich, 98. i. 
 Bougiier, 142. ii. 
 Boussingault, 399. iv. 
 Bouvard, 283. iii. 
 Bradley, Mt., 89. i. 
 Brayley, 479. ii. 
 Briggs, 163. ii. 
 Buch, 361. iv. 
 Bullialdus, 213. iii. 
 Burckhardt, 19. i. 
 Burg, 50. i. 
 Busching, 362. iv. 
 Byrgius, 279. iii. 
 
 Cabeus, 257. iii. 
 Calippus, 76. i. 
 Campanus, 226. iii. 
 Capella, 324. iv. 
 Capuanus, 238. iii. 
 Cardanus, 157. ii. 
 Carliui, 128. ii. 
 Carpathus, Mt., 115. it 
 Carrington, 447. i. 
 Casatus, 254. iii. 
 Cassini, 81. i. 
 
 L 
 
146 
 
 THE SOLAK SYSTEM. 
 
 Cassini, J. J., 474. 
 
 De la Rue, 434. i. 
 
 Fra Mauro, 219. iii. 
 
 ii. 
 
 Delaunay, 469. iv. 
 
 Franklin, 32. i. 
 
 Catharina, 321. iv. 
 
 Delisle, 127. ii. 
 
 Fraunhofer, 377. iv. 
 
 Ca Valerius, 155. ii. 
 
 Deluc, 194. iii. 
 
 Furnerius, 345. iv. 
 
 Caucasus, Mt., 75. i. 
 
 Deraocritus, 38. i. 
 
 
 Cauchy, 418. i. 
 
 De Morgan, 445. i. 
 
 Galileo, 156. ii. 
 
 Cavendish, 286. iii. 
 
 Descartes, 304. iv. 
 
 Garabart, 113. ii. 
 
 Cay ley, 443. i. 
 
 De-Vico, 455. iii. 
 
 Gartner, 37. i. 
 
 Censorinus, 325. iv. 
 
 Dionysius, 99. i. 
 
 Gassendi, 232. iii. 
 
 Cepheus, 31. i. 
 
 Diophantus, 126. ii. 
 
 Gauricus, 185. iii. 
 
 Chacornac, 454. i. 
 
 Dollond, 303. iv. 
 
 Gauss, 22. i. 
 
 Challis, 435. i. 
 
 Donati, 471. iv. 
 
 Gay Lussac, 116. ii. 
 
 Chevallier, 407. i. 
 
 Doppelmayer, 320. 
 
 Geber, 308. iv. 
 
 Christian Mayer, 40. i. 
 
 iii. 
 
 Geminus, 20. i. 
 
 Cichus, 189. iii. 
 
 Dorfel Mts., 246. iii. 
 
 Gemma Frisius, 363. 
 
 Clairaut, 357. iv. 
 
 Drebbel, 240. iii. 
 
 iv. 
 
 Clausius, 416 iii. 
 
 
 Ge'rard, 166. ii. 
 
 Clavius, 193. Jii. 
 
 Egede, 79. i. 
 
 Gioja, 44. i.-ii. 
 
 Cleomedes, 12. i. 
 
 Eichstadt, 280. iii. 
 
 Goclenius, 328. iv. 
 
 Cleostratus, 179. iL 
 
 Eimmart, 3. i. 
 
 Godin, 103. i. 
 
 Colombo, 333. iv. 
 
 Encke, 143. ii. 
 
 Goldschmidt, 427. ii. 
 
 Condamine, 137. ii. 
 
 Endymion, 27. i. 
 
 Grimaldi, 272. iii. 
 
 Condorcet, 5. i. 
 
 Epigenes, 169. ii. 
 
 Grove, 482. i. 
 
 Conon, 88. i. 
 
 Eratosthenes, 110. ii. 
 
 Gruemberger, 265. iii. 
 
 Cook, 335. iv. 
 
 Euclides, 221. iii. 
 
 Gruithuisen, 431. ii. 
 
 Copernicus, 112. ii. 
 
 Euctemon, 42. i. 
 
 Guerike', 215. iii. 
 
 Cordilleras, 274. iii. 
 
 Eudoxus, 77. i. 
 
 Guttemberg, 330. iv. 
 
 Crozier, 419. iv. 
 
 Euler, 125. ii. 
 
 
 Crttger, 278. iii. 
 
 
 Hadley, Mt., 87. i. 
 
 Curtius, 404. iv. 
 
 Fabricius, 383. iv. 
 
 Haernus, Mt., 68. i. 
 
 Cuvier, 356. iv. 
 
 Faraday, 459. iv. 
 
 Hagecius, 391. iv. 
 
 Cyrillus, 320. iv. 
 
 Faye, 470. iv. 
 
 Hahn, 17. i. 
 
 Cysatus, 264. iii. 
 
 Fermat, 314. iv. 
 
 Hainzel, 237. iii. 
 
 
 Fernelius, 366. iv. 
 
 Halley, 458. iv. 
 
 D'Alembert Mts., 
 
 Firmicus, 7. i. 
 
 Hanno, 382. iv. 
 
 275. iii. 
 
 Flamsleed, 223. iii. 
 
 Hansen, 11. i. 
 
 Danioiseau, 271. iii. 
 
 Fontana, 269. iii. 
 
 Hansteen, 267. iii. 
 
 Daniell, 481. i. 
 
 Fontenelle, 171. ii. 
 
 Harbinger Mts., 490. ii. 
 
 Davy, 209. iii. 
 
 Foucault, 475. ii. 
 
 Harding, 152. ii. 
 
 Dawes, 442. i. 
 
 Fourier, 285. iii. 
 
 Harpalus, 133. ii. 
 
 Delambre, 301. iv. 
 
 Fracastorius, 372. iv 
 
 Hase, 342. iv. 
 
INDEX TO THE MAP OF THE MOON. 
 
 147 
 
 Hatisen, 247. iii. 
 HecatsBus, 351. iv. 
 Heinsius, 190. iii. 
 Helicon, 129. ii. 
 Hell, 184. iii. 
 Heraclides, 135. ii. 
 Hercules, 29. i. 
 Hercynian Mts., 161. 
 
 ii. 
 
 Herigonius, 432. iii. 
 Hermann, 485. iii. 
 Herodotus, 149. ii. 
 Herschel, 212. iii. 
 Herschel, J. F. W. 
 
 412. ii. 
 Herschel, Caroline, 
 
 478. ii. 
 
 Hesiodus, 187. iii. 
 Hevel, 154. ii. 
 Hind, 457. iv. 
 Hippalus, 225. iii. 
 Hipparchus, 288. iv. 
 Hommel, 387. iv. 
 Hooke, 34. i. 
 Horrebow, 175. ii. 
 Horrocks, 460. iv. 
 Hortensius, 119. ii. 
 Huggins, 461. iii. 
 Huygens, Mt., 90. ii. 
 Hyginus, 93. i. 
 Hypatia, 317. iv. 
 
 Inghirami, 244. iii. 
 Isidorus, 323. iv. 
 
 Jacobi, 395. iv. 
 Jansen, 66. i. 
 Janssen, 473. iv. 
 Julius Csesar, 96. i. 
 
 Kant, 302. iv. 
 
 Kastner, 347. iv. 
 Kepler, 144. ii. 
 Kies, 214. iii. 
 Kinau, 405. iv. 
 Kirch, 130. ii. 
 Kircher, 252. iii. 
 Klaproth, 255. iii. 
 Krafft, 158. ii. 
 Kuuowsky, 428. ii. 
 
 La Caille, 292. iii.-iv. 
 Lacroix, 433. iii. 
 Lagrange, 281. iii. 
 La Hire, 123. ii. 
 Lalande, 210. iii. 
 Lambert, 122. ii. 
 Landsberg, 222. iii. 
 Langrenus, 338. iv. 
 Lapeyrouse, 348. iv. 
 Laplace, 134. ii. 
 Lassell, 484. iii. 
 Lavoisier, 165. ii. 
 Lee, 476. iii. 
 Legendre, 353. iv. 
 Le Gentil, 448. iii. 
 Lehmann, 241. iii. 
 Leibnitz Mts., 259. iv. 
 Le Monnier, 53. i. 
 Letronne, 224. iii. 
 Le Verrier, 425. ii. 
 Lexcll, 199. iii. 
 Licetus, 355. iv. 
 Lichtenberg, 151. ii. 
 Liltus, 394. iv. 
 Lindenau, 370. iv. 
 Linne', 74. ii. 
 Littrow, 55. i. 
 Lockyer, 480. iv. 
 Lohrmann, 153. iii. 
 Longomontanus, 192. 
 
 Louville, 141. ii. 
 Lubbock, 424. iv. 
 Lubiniezky, 216. iii. 
 
 Maclaurin, 346. iv. 
 Maclear, 441/i. 
 Macrobius, 59. i. 
 Madler, 466. iv. 
 Magelhaens, 334. iv. 
 Maginus, 195. iii. 
 Main, 436. i. 
 Mairan, 140. ii. 
 Malapert, 258. iii.-iv. 
 Manilius, 95. i. 
 Manners, 486. i. 
 Manzinus, 401. iv. 
 Maraldi, 56. i. 
 Marco Polo, 91. ii. 
 Marinus, 379. iv. 
 Marius, 147. ii. 
 Maskelyne, 67. i. 
 Mason, 48. i. 
 Maupertuis, 136. ii. 
 Maurolycus, 358. iv. 
 Maury, 440. i. 
 McClure, 420. i. 
 Menelaus, 70. i. 
 Mercator, 227. iii. 
 Mercurius, 26. i. 
 Mersenius, 231. iii. 
 Messala, 23. i. 
 Messier, 327. iv. 
 Metius, 384. iv. 
 Meton, 41. i. 
 Milichius, 118. ii. 
 Miller, 462. iii.-iv. 
 Moigho, 408. i. 
 Moretus, 262. iii. 
 Mosting, 211. iii. 
 Murchison, 483. i.-ii. 
 Mutus, 400. iv. 
 
148 
 
 THE SOLAR SYSTEM. 
 
 Nasireddin, 198. iii.- 
 
 Plinius, 61. i. 
 
 Rosse, 417. iv. 
 
 iv. 
 
 Plutarchus, 15. i. 
 
 Rost, 236. iii. 
 
 Neander, 373. iv. 
 
 Poisson, 364. iv. 
 
 
 Nearchus, 390. iv. 
 
 Polybius, 316. iv. 
 
 Sabine, 65. i. 
 
 Neper, 9. i. 
 
 Pons, 313. iv. 
 
 Sacrobosco, 312. iv. 
 
 Newcomb, 430. i. 
 
 Pontanus, 311. iv. 
 
 Santbech, 336. iv. 
 
 Newton, 256. iii. 
 
 Ponte'coulant, 381. iv. 
 
 Sasserides, 183. iii. 
 
 Nicolai, 393. iv. 
 
 Posidonius, 54. i. 
 
 Saussure, 196. iii. 
 
 Nicollet, 452. iii. 
 
 Proclus, 60. i 
 
 Scheiner, 261. iii. 
 
 Nonius, 365. iv. 
 
 Prom. Acherusia, 69. i. 
 
 Schiaparelli, 489. ii. 
 
 
 Prom. JEnarium, 206. 
 
 Schickard, 239. iii. 
 
 (Enopides, 177. ii. 
 
 iii. 
 
 Schiller, 234. iii. 
 
 Oersted, 30. i. 
 
 Prom. Agarum, 1. i. 
 
 Schmidt, 487. i. 
 
 Oken,380. iv. 
 
 Ptolemseus, 208. iii. 
 
 Schomberger, 397. iv. 
 
 Olbers, 159. ii. 
 
 Purbach, 202, iii. 
 
 Schroter, 106. ii. 
 
 Oriani, 14, i. 
 
 Pyrenees, 331. iv. 
 
 Schubert, 10. i. 
 
 Orontius, 197, iii. 
 
 Pythagoras, 176. ii. 
 
 Schumacher, 24. i. 
 
 
 Pytkeas, 124. ii. 
 
 Scoresby, 43. i. 
 
 Palitzsch, 341. iv. 
 
 
 Secchi, 488. i. 
 
 Pallas, 108. ii. 
 
 Rabbi Levi, 368. iv. 
 
 Segner, 248. iii. 
 
 Parrot, 290. iv. 
 
 Ramsden, 228. iii. 
 
 Seleucus, 162. ii. 
 
 Parry, 217. iii. 
 
 Re'aumur, 287. iv. 
 
 Seneca, 16, i. 
 
 Peirce, 450. i. 
 
 Regiomontanus, 201. 
 
 Sharp, 139. ii. 
 
 Peutland, 402. iv. 
 
 iii.-iv. 
 
 Short, 263. iii. 
 
 Petavius, 340. iv. 
 
 Reichenbaeh, 375. iv. 
 
 Shuckburgh, 426. i. 
 
 Peters, 409. i. 
 
 Reiner, 146. ii. 
 
 Silberschlag, 101. i. 
 
 Phillips, 423. iv. 
 
 Reinhold, 114. ii. 
 
 Simpelius, 403. iv. 
 
 Philolaus, 172. ii. 
 
 Repsold, 167. ii. 
 
 Sirsalis, 270. iii. 
 
 Phocylides, 242. iii. 
 
 Rhseticus, 104. i.-iv. 
 
 Smyth, Piazzi, 411. ii. 
 
 Piazzi, 282. iii. 
 
 Rheita, 376. iv. 
 
 Snellius, 343. iv. 
 
 Picard, 4. i. 
 
 Riccioli, 273. iii. 
 
 Sommering, 105. ii. 
 
 Piccolomini, 371. iv. 
 
 Riccius, 367. iv. 
 
 Sosi genes, 97. i. 
 
 Pico, 131. ii. 
 
 RiphaBan Mts., 220. 
 
 South, 414. ii. 
 
 Pictet, 181. iii. 
 
 iii. 
 
 Stadius, 111. ii. 
 
 Pingre, 406, iii. 
 
 Ritter, 64. i. 
 
 Steinheil, 385. iv. 
 
 Pitatus, 186. iii. 
 
 Robinson, 413. ii. 
 
 Stevinus, 344. iv. 
 
 Pitiscus, 386. iv. 
 
 Rocca, 277. iii. 
 
 Stiborius, 374. iv. 
 
 Piton, 477. ii. 
 
 Romer, 52. i. 
 
 Stofler, 354. iv. 
 
 Plana, 47. i. 
 
 Rook Mts., 276. iii. 
 
 Strabo, 35. i. 
 
 Plato, 132. ii. 
 
 Rosenberger, 389. iv. 
 
 Straight Range, 453. ii. 
 
 Playfair, 293. iv. 
 
 Ross, 62. i. 
 
 Street, 182. iii. 
 
INDEX TO THE MAP OF THE MOON. 
 
 149 
 
 Struve, 25. i. 
 Struve, Otto, 429. ii. 
 Sulpicius Gallus, 71. i. 
 
 Tacitus, 307. iv. 
 Tannerus, 449. iv. 
 Taqnet, 72. i. 
 Taruntius, 326. i. 
 Taurus, Mt., 51. i. 
 Taylor, 299. iv, 
 Teneriffe Mis., 410. 
 
 ii. 
 
 Tliales, 36. i. 
 Thesetetus, 82. i. 
 Thebit, 203. iii. 
 Theon, sen., 237. iv. 
 Theon, jun., 298. iv. 
 Theophilus, 319. iv. 
 Timaeus, 170. ii. 
 Timocharis, 121. ii. 
 
 Tobias Mayer, 117. ii. 
 Torricelli, 318. iv. 
 Tralles, 13. i. 
 Tricsnecker, 94. i. 
 Tycho, 180. iii. 
 
 Ukert, 109. i. 
 Ulugh Beigh, 164. ii. 
 
 Vasco de Gaina, 160. 
 
 ii. 
 
 Vega, 378.iv 
 Yendelinus, 339. iv. 
 Viela, 284. iii. 
 Vitello, 229. iii. 
 Vitruvius, 57. i. 
 Vlacq, 388. iv. 
 
 Walter, 200. iii.-iv. 
 Wargentin, 243. iii. 
 
 Webb, 456. iv. 
 Weigel, 249. iii. 
 Werner, 295. iv. 
 Whewell, 444. i. 
 Wichmann, 438. iii. 
 Wilhelm Humbolclt, 
 
 352. iv. 
 
 Wilhelm I, 191. iii. 
 Wilson, 253. iii. 
 Wolf, Mt., 92. ii. 
 Wollaston, 150. ii. 
 Wrottesley, 422. i v. 
 Wurzelbauer, 188. iii 
 
 Xenopkanes, 173. ii. 
 
 Zach, 396. iv. 
 Zagut, 369. iv. 
 Zuchius, 25D. iii. 
 Zupus, 268. iii. 
 
I5O THE SOLAR SYSTEM. 
 
 MARS. 1 
 
 (Abbreviations, additional. D., Dawes ; , Herschel L; II., 
 Herscliel II. ; La., Lassell; Se., Secchi ; Sold., Scliiaparelli.) 
 
 THIS planet, with a diameter of 4210 miles, only about twice 
 the size of the Moon, and not much more than half as large 
 as our own globe, is yet peculiarly interesting to us, as 
 presenting the most intelligible features of any object within 
 our reach. In overtaking him about once in two years we 
 find, as he turns to us his broad round face, that this 
 supposed malignant aspect is changed into that of a minia- 
 ture Earth, which we might, without much extravagance, 
 imagine to be habitable by man. Not every opposition, how- 
 ever, as it is called, admits of an equally near prospect. 
 The orbits of the Earth and Mars are both elliptical, and 
 not fixed with respect to each other, and no two following 
 oppositions happen in the same part of either orbit, 2 so that 
 the most favourable possible juncture, when the earth is 
 furthest from the Sun and Mars nearest, occurs ordinarily 
 but once in 15 01-17 years, when the diameter of Mars, only 
 1 3" in reversed circumstances, may expand to nearly 30". The 
 presentation in 1909 will be more favourable than any 
 intervening one : 3 every opposition, however, should set the 
 telescope to work ; and we will proceed to describe what we 
 may expect to see. 
 
 i. The Phases. These are not remarkable : in opposition, 
 a full moon rising through ruddy haze, and, with sufficient 
 power, larger than our Moon to the naked eye : in other 
 
 1 The new matter is by Mr. A. Stanley Williams. 
 
 2 Pickering makes the mean opposition magnitude 2*25; that is 
 3-25 magnitudes brighter than a standard first mag. star, such as a 
 Aquilae. 
 
 3 But the opposition of 1894 will be a very favourable one. 
 
MARS. 151 
 
 situations a dnll gibbosity, never sinking to quadrature. M. 
 stated at one time, as Schr. had previously done, that this 
 phasis is always narrower than it should be by calculation ; 
 but in a subsequent publication the remark is not repeated. 
 Pastorff thought he saw a phosphorescence on the dark part ; 
 but this could hardly have been other than a deception. 1 
 
 2. The Dark Spots. The disc, when well seen, is usually 
 mapped out in a way which gives at once the impression of 
 land and water, the outlines, under the most favourable 
 circumstances, being extremely sharp: 2 the bright part is 
 orange, according to Se., sometimes dotted with red, brown, 
 and greenish points ; sometimes found by Schi. filled with 
 a complete network of thin lines and minute interspaces : 
 the darker regions, which vary greatly in depth of tone, are 
 in places brownish, but more generally of a grey-green, 3 or. 
 according to Se., bluish tint, possessing the aspect of a fluid 
 absorbent of the solar rays. If so, 4 the proportion of land 
 to water is considerably greater on Mars than on the Earth ; 
 
 1 Ou two occasions Schr. observed a partial flattening of the limb, 
 as on Venus. Schwabe also has seen it. Zellner makes the * albedo* 
 of Mars 0-27, so that a little more than \ of the sun's light falling on 
 the planet is reflected back. 
 
 Se.'s illustration is strikingly expressed: *fc tutto variegato 
 come una carta geografica.' 
 
 3 H. refers this colour to contrast. Jacob does not detect it. I 
 have seen it with a 9-in. mirror, beautifully blue. The accurate 
 Humboldt has puzzled himself about these colours. (Cosmos, iv. 503.) 
 
 4 On one occasion of very fine definition, Burton, with 900 on 3-ft. 
 Parsonstown refl., found a dusky space composed entirely of exceed- 
 ingly minute dark dots; Klein has seen something of the same 
 nature, and Pratt has remarked this stippled character, and seen 
 glimpses of a structure too complicated and delicate to be reproduced. 
 Frequently 'a broad hazy streak has been, by patient watching for 
 the best moments, resolved into several separate masses of shading 
 enclosing lighter portions full of very delicate markings,' occasionally 
 almost white. 
 
152 THE SOLAR SYSTEM. 
 
 so that the habitable area may possibly be much more alike 
 than the diameter of the planets. The water, however, if 
 such it be, is everywhere in communication, and long con- 
 necting straits are more common than on the Earth. Schi. 
 (1877-8) especially claims to be the discoverer of a multi- 
 plicity of dark narrow channels, splitting up the continents 
 into islands : they appear to have been partially seen by 
 others as far back as Dawes ; but the observation is of 
 peculiar difficulty, and Green considers some of them to be 
 merely the edges of faint tones, and of very questionable 
 permanency. 1 The dark spots were early seen, and a long 
 
 1 During the last few years, many of Schi.'s discoveries have been 
 confirmed by other observers, particularly the numerous narrow dark 
 streaks usually known by the name of 'Canals.' In 1881-2 Schi. 
 discovered that many of these canals were double, that is, consisting 
 of two narrow parallel streaks lying close together. This remarkable 
 peculiarity was long disputed, but now seems clearly established, the 
 duplication, or, as it has been termed, * gemination,' of the canals 
 having been seen by as many as 9 diSerent observers, and with 
 telescopes ranging in size up to the great Lick refractor of 36-in. 
 aperture. No satisfactory explanation either of the canals or of their 
 duplication has yet been given. Some of the canals appear certainly 
 to be variable, not only in intensity, but perhaps slightly in position, 
 and it has been thought that some of the variations are dependent 
 upon the Martial seasons, though this question requires further 
 investigation. The same canals may appear very dark and definite 
 during one opposition, and with the gemination well marked, whilst 
 at another they may be single, and only very faint or even invisible 
 altogether. According to Schi. the transition from the single to the 
 double aspect occasionally takes place with great rapidity, requiring 
 only a day or two. The canals are usually found connecting the dark 
 seas or lakes, and a dark spot or small lake is frequently found at the 
 point of intersection when two or more canals cross each other. In 
 1892 W. H. Pickering saw as many as 40 of these lakes, ranging from 
 30 to 100 miles in diameter, the smaller ones having the appearance 
 of minute black points. 
 
 It is necessary to bear in mind that the terms ' canal,' * lake,' and 
 
MARS. 1 5 3 
 
 series of drawings is extant, from Hooke, Cassini, and 
 Campani, in i666, 1 to a great number of the first observers 
 of the present day, with some general correspondence, 2 but 
 much difference of detail ; which seems due in part to 
 differences of telescopes, eyes, climates, and skill in delinea- 
 tion ; in part to altered perspective owing to the inclination 
 of the axis, 3 showing us sometimes more of N., sometimes 
 of S. hemisphere; and in part also to changes in the 
 planet's atmosphere. The older observers thought the spots 
 variable : 4 Ijl perhaps took the lead in supposing them to be 
 permanent an idea which Kunowsky, as late as 1822, 
 fancied was due to himself. Schr.'s work on Mars, the 
 ' Arcographische Fragmente,' which was to have contained 
 224 figures, left in MS. at his death in 1816, has been 
 
 'sea,' are merely convenient names by which to distinguish the 
 different features, and do not necessarily imply the existence of water. 
 Linsser, and more recently Schseberle, have supposed, indeed, that the 
 dark markings represent the continents rather than the oceans. The 
 latter observer states that, seen from the summit of Mount Hamilton 
 in California, the water of San Francisco Bay always appears lighter 
 than the neighbouring land surface. 
 
 1 Humboldt, following Delambre, says that Cassini does not seem 
 to have discovered the rotation of the spots till after 1670. He must 
 have overlooked the figures in Phil. Trans., No. 14. Kaiser has 
 shown, from the MS. Journal of Huygens, that the latter discovered 
 the rotation in 1659. 
 
 2 Ijl's combined figure in Phil. Trans., 1784, if reversed, as it 
 may have been in engraving, will be not unlike B. and M.'s polar 
 projections. 
 
 3 30 18', according to B. and M., and H. But is not this a mis- 
 take for the complementary angle? Hind gives, after IfL 61 18' for 
 inclination of axis to orbit of Mars ; 59 42' for do. to Earth's ecliptic ; 
 obliquity on Mars, 28 42' : but 90 59 42' = 30 18'. 
 
 4 Observations made in recent years by Schi. and others, appear 
 strongly to favour the actual variability of certain markings both in 
 form and intensity. Some of them have been ascribed to inundations 
 of low-lying flats. 
 
154 THE SOLAK SYSTEM. 
 
 recently examined by Dr. Terby, of Louvain, to whom the 
 accurate study of this planet is especially indebted. He 
 finds that Schr. considered the dark spots to be clouds, 
 among which he saw many rapid variations. 1 B. and M. 
 took up the subject with great spirit at the peculiarly 
 favourable opposition in 1830, recovered some of Kunowsky's 
 spots, and from their further observations in 1832, 1834, and 
 1837, though the same hemisphere was not always equally 
 visible, inferred their permanence. M., a little shaken as to 
 this in 1839, retrogrades still further at Dorpat in 1841 : 
 the drawings, however, of later observers exhibit substantially 
 many of the same forms, and, notwithstanding numerous 
 discrepancies, there can be no reasonable doubt that the 
 dark spots are really part of the surface. The distant view 
 of the Earth, indeed, might be much of this nature; its 
 features at one time distinct, at another confused or dis- 
 torted by clouds: besides, one affirmative the reappear- 
 ance of a spot proves more, where widespread atmospheric 
 obscuration seems to be frequent, than can be disproved by 
 many negatives. The existing maps of Mars, of which 
 there are several, can only be considered as approximations ; 
 nor shall we ever know the N. so well as the S. hemisphere, 
 as it is turned towards us in the planet's aphelion ; even 
 were its markings equally denned, which B. and M. deny. 
 
 1 Schr.'s complete work was published in 1881, under the editor- 
 ship of Bakhuyzen. A most complete monograph on the physical 
 aspect and condition of Mars has just been published by Flammarion 
 in the form of a large octavo volume of over 600 pages, and illustrated 
 by reproductions of 571 drawings and maps of the plauet, besides 
 many other illustrations bearing on the subject. The work gives a 
 complete account and discussion of all the observations that have 
 ever been made on Mars since the invention of the telescope, It is 
 published at a price very moderate for the size of the volume, and 
 should be in the hands of every studeut of the planet conversant with 
 the French language. 
 
MARS. 155 
 
 Under favourable circumstances the dusky spots are not 
 difficult objects ; I have repeatedly been able to draw them 
 with my 5^-ft. achromatic ; a much smaller instrument will 
 sometimes show the darker ones plainly ; while at other 
 times, and on other parts of the globe, they are feeble even 
 in large telescopes, and for delicate purposes require a long 
 and steady gaze. The presence of haze, or the use of a 
 light screen-glass, may be advantageous with a large aperture 
 in reducing the glare. The motion of the spots will soon 
 be evident, and as the rotation is completed, according to 
 Proctor, in 24 h 37 m 22735% tnev w ^l not varv g rea %" fr m 
 night to night at the same hour. Most of these remarkable 
 features are represented in a design for which I am indebted 
 to the kindness of Messrs. Burton and Dreyer : this, while 
 free from the conventional hardness that renders the elaborate 
 designs of Schi. so perplexing to the student, resembles in 
 all essential points the beautiful delineation of Green, com- 
 bining, however, many indications of the curious network of 
 narrow streaks, which the last-named observer considered 
 too uncertain or transitory to be introduced without further 
 confirmation, and the nature and permanence of which will 
 be an interesting object for future investigation by the 
 possessors of adequate optical means. 1 
 
 The nomenclature is at present in a state of confusion, 
 and can only be accepted as provisional, as well as to some 
 extent the representations to which it is applied. The old 
 one of B. and M. was soon found inapplicable, and was 
 superseded by others, based on the names of observers. Of 
 these the most received is that of Proctor, enlarged by 
 Green ; but this in turn has been laid aside by Schi. for one 
 
 1 Green employed, at Madeira, a 13-in. 'With' mirror; Schi., at 
 Milan, an 8 T 1 Merz. achr. of great perfection ; Burton, in Ireland, a 
 12-in. mirror of his own, with smaller instruments. 
 
1 5 6 
 
 THE SOLAR SYSTEM. 
 
 founded on ancient geography. Though by no means obtruded 
 by that unpretending observer, it is no doubt better suited 
 to his discoveries ; but these, again, though winning their 
 way among very high authorities, have yet to be confirmed 
 and corrected; and in the meanwhile, as ordinary students 
 are not likely to master his finer details, the few names that 
 they will require are derived from Green and Burton, and 
 are given here with a reference chart, to preserve the clear- 
 ness of the drawing. 1 The land is designated by letters, the 
 water by numbers. The expansion of the polar regions, 
 inseparable from Mercator's projection, must be mentally cor- 
 rected ; and in comparing the portrait with the original the 
 perspective of a sphere must be carefully borne in mind, where 
 the foreshortening is much greater than we are frequently 
 aware of, the eye being probably early biassed by maps of the 
 terrestrial hemisphere, in which it is artificially removed. 
 
 1 The nomenclature devised by Schi. is now in such general use, 
 that the following list giving his names for the chief markings of the 
 map will probably be found frequently useful : 
 
 A. Thymiamata 
 
 D. Chryse 
 
 E. Tharsis 
 G. Elysium 
 H. Hesperia 
 K. Ausonia 
 L. Hellas 
 M. Cydonia 
 
 N. Hammonis.Cornu 
 Q. Deucalionis Eegio 
 
 2. Acidalium Mare 
 
 3. Margaritifer Sinus 
 
 4. Indus 
 
 5. Erytrseum Mare 
 
 6. Auroras Sinus 
 
 7. Nectaris Fons 
 
 8. Solis Lacus 
 
 9. Tanais 
 
 10. Aouius Sinus 
 
 11. Mare Australe 
 
 12. Titanum Sinus 
 
 13. Propontis 
 
 14. Cimmerium Mare 
 16. Cyclops, Cerberus 
 
 18. Lethes 
 
 19. Tyrrhenum 
 
 Mare 
 
 20. Syrtis Minor 
 
 21. Lacus Moeris 
 
 22. Hadriaticum 
 
 Mare 
 
 23. Syrtis Major 
 
 24. Nilosyrtis 
 
 25. Protonilus 
 
 26. Hellespont ua 
 
 27. Sabaeus Sinus 
 
 There is no name corresponding to Dawes's Forked Bay, but Schi. 
 terms the peninsula forming the * fork ' Fastigium Aryn. In France 
 the Duwes Ocean is frequently called by the name 'Mer du Sablier* 
 jor Hour-glass Sea). 
 
MARS. 
 
 157 
 
 A. Leverrier Land 
 
 B. Jacob Land 
 
 C. Rosse Land 
 
 D. Aladlcr Continent 
 
 E. Secchi Continent 
 
 F. Noble Capo 
 
 0. Fontana Land 
 H. Burckliardt Land 
 t. Herschel I. Con- 
 tinent 
 
 K. Dreyer Island 
 L. Lockyer Land 
 M. Laplace Land 
 N. Banks Cape 
 0. Beer Continent 
 
 Q. Phillips Island 
 
 1. Dawes's Forked 
 
 Bay 
 
 2. Knobel Sea 
 
 3. Burton Bay 
 
 4. Dawes Strait 
 
 5. Do la Rue Ooean 
 
 6. Christie Bay 
 
 7. Schiaparelli Lake 
 
 8. Terby Sea 
 
 9. Catnpani Sea 
 
 10. Funchal Bay 
 
 11. Maunder Sea 
 
 12. TrouvelotBay 
 
 13. Oudemans Sea 
 
 14. Maraldi Sea 
 
 15. Schrotor Sea 
 
 16. Huggins Inlet 
 
 17. Huggins Bay 
 
 18. Gruithuisen 
 
 Inlet 
 
 19. Hook Sea 
 
 20. Gruithuisen Bay 
 
 21. Main Sea 
 
 22. Zollner Sea 
 
 23. Dawes Ocean 
 
 24. Kaiser Sea 
 
 25. Nasmyth Inlet 
 
 26. Lambert Sea 
 
 27. Herschel II. 
 
 Strait 
 
 28. Arago Strait 
 
 P. Kunowsky Land 
 
 3. The Polar Snows. A spot surrounding either pole is 
 so white and luminous as to have occasionally remained 
 visible when a cloud obscured the planet : and frequently to 
 seem, from irradiation, to project beyond the limb, as I have 
 myself noticed. These zones were figured by Maraldi in 
 1 704, who says they had been occasionally seen for 50 years; l 
 in fact, they could not long escape the telescope. They were 
 thought to resemble snow before IjFs time ; he gave consis- 
 tency to the idea by ascertaining that they decreased during 
 the summer, and increased during the winter of Mars, and 
 B. and M. have fully confirmed it, with the addition that the 
 S. polar spot has a greater variety of extent, corresponding 
 with its greater variety of climate from the excentricity of 
 the orbit. 2 Each pole comes alternately into sight, and both 
 
 1 B. and M. erroneously make him the discoverer in 1716. A 
 figure by Huygens, in 1656, may be meant as a rude representation 
 of them. 
 
 2 But Flammarion finds from a discussion of all available material 
 that both polar spots vary to nearly the same extent, and that the 
 excentricity of the orbit appears to cause no visible difference in tlip 
 climates of the two hemispheres. 
 
o tn, 
 
MAES. 159 
 
 are sometimes visible on the edge at once, when the opposi- 
 tion of Mars concurs with his equinox, fji found they were 
 not (or not always) opposite each other, both being sometimes 
 in or out of the disc at the same time. M., and Se. with 
 the admirable achromatic at Eome, of 9^-in. aperture 
 and I5~ft. focus, bearing ordinarily a power of 1000, found 
 the N. zone concentric with the axis, but the S. considerably 
 excentric ; according to Schi., always 5 or 6 from the pole. 
 It has been suggested by B. and M. that the poles of cold, 
 like those on the Earth, may not coincide with the poles of 
 rotation ; still, one would expect that they might have been 
 diametrically opposite; but in this case, as Schi. remarks, 
 the climate may be affected by the position of the neigh- 
 bouring land. B. and M. found in 1837 the N. pole sur- 
 rounded by a conspicuous dark zone, 1 the only well-marked 
 spot in sight, which they thought might possibly be a marsh 
 at the edge of the melting snow: in 1839 M. perceived it 
 had decreased ; in 1841 it was no longer visible. About the 
 opposition in 1856 I had interesting views of these zones, 
 which did not seem exactly opposite to each other : the S. 
 was surrounded by a very dark region, never seen by B. and 
 M. ; on the intervening limbs were occasionally luminous 
 spaces, so bright by contrast as to give the impression of 
 
 1 A narrow dark zone was seen by several observers surrounding 
 the S. polar spot in 1892, and so dark in parts as to appear nearly 
 black. In the same year the changes attending the melting and 
 breaking up of the southern ice cap were very great and complicated, 
 and the process of dissolution took place with great rapidity. 
 Photographs of Mars, taken on two successive nights in 1890, by 
 W. H. Pickering in California, show a large increase in the size of 
 the S. polar spot in the course of only 24 hours. The increase is said 
 to affect an area of 2,500,000 square miles (somewhat less than the 
 area of the United States), and the cause is ascribed to a fall of snow. 
 In 1888 a dark line was seen extending across the N. polar cap by 
 Perrotin, Schi. and Terby, dividing it into two parts. 
 
I6O THE SOLAR SYSTEM. 
 
 four patches of snow, as in one of Cassini's figures in 1666 : 
 these were also seen by Se. at the same time. April 4, 1871, 
 Crossley and Gledhill saw a very bright spot on SW. limb, 
 not far from, and closely resembling, the polar snow. In 
 1845 Mitchel with a great achromatic in America noticed 
 a very dark spot in the centre of the snow, which disappeared 
 the next night: 1 at another time he saw some movements in 
 a small bright spot at the edge of the snow. Such luminous 
 spots have been seen, though fixed in position, near the pole, 
 by Green. Se. in 1858 found the appearances at the poles 
 irreconcilable with the idea of circular caps, and was forced 
 to adopt the supposition of complicated and lobate forms. 
 Schi. alludes to the possibility of a mass of floating ice. 
 
 4. The Atmosphere. Such an appendage is implied in 
 the formation of snow, the varying outline or distinctness of 
 the dark spots, their usual disappearance towards the limb, 
 while they can be more readily traced to the terminator, and 
 their greater clearness noticed by B. and M., and Lockyer, 
 in the summer than the winter of Mars. Maraldi saw and 
 delineated a dusky belt for a considerable time in 1704; 
 possibly, however, only a bad view of some of the ' seas ; ' 
 something like it also appears in the designs of Schr., who, 
 from movements in these belts, inferred winds as rapid as 
 our own. Some of $ 's figures show white belts, and he says 
 that besides the permanent spots he often noticed occasional 
 changes of partial bright belts, and once a darkish one ; we 
 should, however, perhaps, have expected that clouds, viewed 
 from without, would always reflect a brighter light than 
 
 1 D. saw (1847, Nov. 9) a minute black point near the middle of 
 the disc, perhaps the Schiaparelli Lake. Ward has seen (1879, 
 Nov. 22) one of the dark lakes (the Terby Sea) as black and defined 
 as the shadow of a satellite on Jupiter, though the general defini- 
 tion on the planet was very bad. 
 
MARS. l6l 
 
 land or water. Some of the principal continents are occasion- 
 ally bordered with white, as though snow or clouds were 
 lying on lofty ground ; and ' Lockyer Land ' has been seen 
 by Schi. (who calls it Hellas) nearly as brilliant as the pole. 
 D. has at times noticed changeable white spots : one of these, 
 in the 'De la Rue Ocean,' seen by him 1865, Jan. 21, 22, 
 23, but invisible 1864, Nov. 10, 12, and looking 'precisely 
 like a large mass of snow,' has been called 'Dawes's Ice 
 Island,' but appears as ' Hall Island ' in the map of Green. 
 The same, or more probably a similar one, was seen by me 
 with 9~in. refl. 1871, April 4. 1 Browning frequently noticed 
 in 1867 the transit of faint white spots, becoming, as they 
 neared the limb, almost as brilliant as the polar snows; 
 similar changes were observed by Schi. in 1877. The bright 
 'menisci' or crescents which some observers have seen 
 illuminating the E. and W. borders of the disc may have 
 had an atmospheric cause, as well as numerous patches of 
 
 1 1842, Feb. 3, A.M., rain fell over nearly every part of the United 
 States, from the Gulf of Mexico to beyond Lake Superior, and from 
 the Mississippi to far out in the Atlantic. The upper side of this vast 
 cloud must have appeared as a great white spot if seen at the distance 
 of Mars. In 1892 W. H. Pickering saw a small conspicuous white 
 spot in the region just to the N. of the Terby Sea, which had 
 disappeared two days later. A similar spot was seen on one 
 night by Barnard in the same year in longitude 219 and latitude 30 
 or 40 N., which could not be recovered on subsequent nights. A 
 very curious feature was observed in 1890 by Hoi den, Keeler, and 
 Schseberle, with the Lick 36-in. refractor, in the form of a narrow 
 bright streak or arm projecting beyond the line of the terminator, and 
 curving round to meet another smaller arm about 2" further south. 
 The planet at the time shewed considerable phase, like the gibbous 
 moon, and at one time there was a nearly complete semicircle of light 
 projecting beyond the terminator. W. H. Pickering observed somewhat 
 similar projections in 1892. He ascribes them to clouds, and states 
 that some of them attained an Altitude of at least 20 miles above the 
 surface of the planet. 
 
 VOL. I. M 
 
1 62 THE SOLAR SYSTEM. 
 
 yellowish and bluish light upon the limb described by M., 
 at Dorpat in 1841, and a bright green patch seen by myself 
 on the E. limb, 1862, Oct. n. The atmosphere, according 
 to D., is only of moderate density ; and seems not to be the 
 cause of the ruddy tinge, as this is most decided in the centre 
 of the disc, while in 1864 he noticed patches of greenish 
 light near the limb. Huggins has also found the planet 
 reddest when its atmosphere was clearest, and remarks that 
 the colour does not affect the snow. His spectroscope showed 
 a vaporous envelope similar to, but probably not identical 
 with, our own : Janssen's, Vogel's, and Maunder's indicate 
 aqueous vapour. Cassini, and in this century Tralles, 
 exceeded all bounds in supposing that the atmosphere could 
 obscure small stars at some distance ; this effect, resulting 
 from the contraction of the pupil in a bright light, was 
 imperceptible in the great telescopes of ^[ , and the idea has 
 been overthrown by the experience of South, who has seen 
 one contact and two occultations of stars without change : in 
 the last, his great achromatic (now at the Dublin observatory), 
 n-|-in. aperture and nearly ig-it. focus, actually showed the 
 star neatly dichotomised in emerging. This is not surprising, 
 for the atmosphere, if in proportion to ours, would not extend 
 o"'4 beyond the limb when nearest to the Earth. ^ ascribed 
 a great ellipticity (-^) to this planetary globe; D. could detect 
 none ; Schr. made it less than -^ ; Hart wig gives it -g-^. 1 
 
 5. The Satellites, one of the most unexpected of modern 
 announcements, are not so utterly out of place in a work 
 like the present as might be supposed from their tardy dis- 
 covery. Deimos, the outermost, has been seen by Pratt, 
 
 1 W. H. Pickering found a distinct polar flattening in 1892, 
 amounting to at least fa. He considers that the differences found by 
 different observers may have really existed, and were due perhaps to 
 an equatorial cloud formation. 
 
JUPITER. 163 
 
 with an 8|-in. 'With' refl. Erck has seen it with 7^-in. 
 achr., and Common believes that whoever sees Enceladus 
 may catch both by hiding the planet ; of course at or near 
 their elongations: moonlight being no disadvantage. At 
 Harvard Observatory Deimos is thought to be brightening, 
 especially E. of Mars. Its diameter is supposed to be 6, 
 that of Phobos 7 miles. 
 
 The MINOR PLANETS hardly come within the design of 
 these pages, though the more conspicuous of them may some- 
 times be found by the ' Nautical Almanac ' with little trouble, 
 and Vesta, when nearest to us, is visible to the naked eye, 
 But any investigation respecting the discs, supposed nebulous 
 envelopes, and variable light of a few of these extremely 
 minute bodies, belongs only to first-rate instruments. 
 
 JUPITEE. 1 
 
 THIS magnificent planet is an excellent object, in view for 
 months together, and for some part of every year, shining 
 with a brilliancy which near opposition casts shadows in a 
 darkened room, and in the Earl of Rosse's reflector has been 
 compared to that of a coach-lamp ; 2 1J. is attended, too, by a 
 
 1 The new matter is by the Rev. W. E. Waugh. 
 
 2 Bond II. has often seen it with the naked eye in high and clear 
 sunshine : so Denning occasionally ; and it is recorded of Horrocks 
 and Humbolt. % visible to naked eye in sunshine every 12 years, 
 when opposition occurs at beginning of October, e.g., 1880, 1892, 1904. 
 
 Zollner's photometric experiments make the reflective power of 
 Jupiter very great. According to these as much as 63 per cent, of 
 the incident light is reflected. 
 
 The Kev. S. J. Johnson, M.A., speaks of the window frame of a 
 
1 64 THE SOLAR SYSTEM. 
 
 most interesting retinue. In the latter even a very moderate 
 telescope will show one of the most diversified scenes in the 
 heavens. Not only from night to night, but often from hour 
 to hour, incessant changes will catch the eye ; and since the 
 orbits of all the satellites lie nearly edgeways with respect 
 to the Earth, the retreating and advancing motions appear 
 to intersect one another, and these miniature planets are seen 
 overtaking, passing, meeting, hiding, and receding from one 
 another in most beautiful and endless mazes. We begin 
 with the features of the globe. 
 
 i. The Ellipticity. No heavenly body (except at times 
 Venus) shows a disc so readily as Jupiter ; a very low power 
 will bring out his noble face, 87,900 miles in diameter, or 
 1 1 times larger than our Earth ; 1 and with higher magnifiers 
 we shall soon perceive that it is not circular, but a little 
 flattened N. and S. 2 Obvious as this is, it was doubted at 
 one time by Cassini, and missed by Hooke, though he drew 
 the spots of Mars, and directed particular attention to the 
 
 room being distinctly illuminated during the apparition of 1891. 
 Pickering mean opposition Magnitude 2*52. 
 
 The question of inherent light has recently engaged the attention 
 of Jovian students, and the very probable high temperature of the 
 body, and the dense atmosphere would sanction a state of semi-incan- 
 descence. Capt. W. Noble, writing in '92 of the chocolate colour ot 
 the shadow of Sat. II. when in transit, says, 'The only feasible 
 explanation of this appearance which occurred to me was, that the 
 portion of the planet's disc from which all sunlight was shut off was 
 in a red-hot or glowing condition.' 
 
 1 1L would contain 1389 Earths. 
 
 Such is the great size of Jupiter that, mass for mass, he is larger 
 than all the other planets of the Solar system put together. 
 
 * The beginner may be reminded that the points of the celestial 
 compass only stand straight when the object is on the meridian ; but 
 at all times they may be verified by recollecting that the motion 
 through the field is always from E. to W. 
 
JUPITER. 165 
 
 polar flattening of the Earth. Astronomers differ as to its 
 amount; from many comparisons and observations Main 
 fixed it at a little more 
 than ^7 of the equatorial 
 diameter ; Se. gives -^ > 
 Engelmann, from a mean 
 of ii observers, y^-g-g-. 
 Once noticed, it is so evi- 
 dent that a correct eye will 
 not tolerate the circular 
 figures too often used to 
 represent this planet ; and 
 the student who wishes 
 to draw the belts should 
 prepare oval discs beforehand, which may be done thus 
 Make a rectangle 15 high, 16 wide, on any convenient scale 
 of equal parts ; find its centre by intersecting diagonals ; 
 from this describe a circle touching the top and bottom, and 
 then pull out as it were the sides of the circle to touch the 
 ends of the rectangle, altering the curves by eye and hand 
 till a tolerable ellipsis is produced : if many discs are wanted, 
 cut one out neatly in card, and draw the others by means 
 of its edge. The accompanying diagram may assist the 
 process. 
 
 On one occasion Schr. perceived a local flattening near 
 the S. pole, which was confirmed by other eyes and instru- 
 ments, but never returned ; an appearance similar to what he 
 noted in Mars and Venus. Birmingham and myself have 
 seen the limb deceptively flattened by the close proximity of 
 a satellite. 
 
 2. The Phaais. The orbit of Jupiter is so far external 
 to that of the Earth that there can be but little defalcation 
 of light ordinary books say none: a diminished breadth is, 
 
1 66 THE SOLAR SYSTEM. 
 
 however, measurable, if not visible, in our best instruments, 
 and a moderate telescope will show the approach of the 
 gibbous form about the time of Jupiter's quadrature, in a 
 slight shade along the limb furthest from the Sun. This 
 was recorded by myself as far back as 1838, May 30, but I 
 believe I had seen it previously, as often since, with the 5 J-ft. 
 achromatic : more recently, De la Rue, Se., and others have 
 mentioned it. I have thought it plainer in twilight than 
 darkness ; a fact in accordance with many similar observa- 
 tions by eminent astronomers. 1 At Adelaide (S. Australia), 
 II and III have been seen with an 8-in. achr. to emerge, in 
 consequence of phasis, at a sensible distance from the limb. 2 
 3. The Belts and Spots. Grey streaks across the disc, 
 unnoticed by Galileo, perhaps from their occasional faintness, 
 were soon detected by Torricelli, and by Zucchi in 1 630 ; and 
 it would be found that, though always lying in one equatorial 
 direction, they were not permanent in position, but subject 
 to sometimes very gradual, sometimes very rapid changes, 
 which, when we bear in mind the size of the planet, must 
 often be on an enormous scale. The equator is frequently 
 luminous, having on each side of it a broad dusky streak, 
 beyond which a series of apparently narrower stripes extend 
 to either pole. Here, however, perspective must be taken 
 into account. The planet appears so like a flat disc that we 
 
 1 The most perfect telescopic vision is sometimes attained undei 
 unlikely circumstances such as fog, twilight, and moonlight : every 
 object is best seen under certain proportions of light and powder and 
 contrast, which are matter of experience ; and in such experience lies 
 much of the observer's skill. Under certain atmospheric conditions, 
 not fully understood, a light mist certainly improves the definition of 
 Jovian markings similar to reducing the aperture by stops, thus cut- 
 ting off an excess of light. 
 
 2 With the larger instruments now in use such observations are 
 not now uncommon. 
 
JUPITER. 167 
 
 easily become unmindful of the spherical foreshortening in 
 every direction, counterbalanced, indeed, in its effect near 
 the equator by rotation, but irremediable towards either pole 
 where large tracts must ever remain almost unknown. In- 
 attention to this material point would be, and probably has 
 been, the cause of much unsatisfactory delineation. We can 
 easily perceive, however, that the visible arrangement of 
 details is very uncertain in all respects except that of a 
 general E. and W. direction; oblique, 1 curved, or ragged 
 streaks are sometimes seen, and dark spots of various sizes ; 
 and the belts are often interrupted, as well as varied by 
 notched or wavy outlines: but Green remarks that the 
 masses of dark and light, 2 large or small, usually balance one 
 another on the whole. Occasionally the belts 3 throw out 
 
 1 The change of inclination in one of these oblique belts in 1860 
 was very remarkable, and might be supposed to indicate that the 
 atmosphere revolved faster at the equator than at some distance of 
 N. latitude (Monthly Notices, xx. 243). 
 
 2 It is the opinion of Green that the light spots are higher in the 
 Jovian atmosphere than the darker ones. He speaks of them as lying 
 across and obscuring those of darker tint. His memoir published by 
 the K. A. S. contains some very beautiful drawings, and with the 
 accompanying descriptions gives a most interesting account of these 
 markings. 
 
 3 The belts or bands on the disc of Jupiter are usually denominated 
 as follows. North and South Equatorial North and South Temperate. 
 The equatorial light band, whose latitude is very near the Jovian 
 equator, being faint, requires a largo aperture, and good atmospheric 
 conditions to see it. It is thought by the most careful observers to be 
 variable. It is certainly sometimes much broken up, and sometimes 
 partially obscured by masses of dark matter apparently projected 
 from the north edge of the south equatorial belt. Professor Keeler's 
 beautiful drawings show this interesting feature as extending nearly 
 from limb to limb. The North and South Polar regions are the other 
 chief divisions of the planet's disc. Both these regions are frequently 
 though lightly banded, the bands being frequently broken in parts. 
 
1 68 THE SOLAK SYSTEM. 
 
 dusky loops or festoons, whose elliptical interiors, arranged 
 lengthways, and sometimes with great regularity, have the 
 aspect of a girdle of luminous egg-shaped clouds surrounding 
 the globe. These oval forms, which were very conspicuous 
 in the equatorial zone (as the interval of the belts may be 
 termed) in 1869-70, have been seen in other regions of the 
 planet, and are probably of frequent recurrence. Their 
 outlines were seen jagged in the great achr. at Bothkamp. 
 The earliest distinct representation of them is said to be that 
 by G. in 1838, followed by Lassell, 1850, and D., 1851, 
 March 8; but they are perhaps indicated in drawings of the 
 last century. It is by no means easy to assign a reason for 
 this prevalent configuration, which sometimes shows itself 
 in a solitary ellipse (Gledhill and Mayer, 1869-70 ; Gledhill 
 again, 187 1). Schwabe has observed the whole disc traversed 
 by minute parallel dark lines, most distinct in the dusky 
 belts, where also they have been recognised by the Earl of 
 Eosse, Jacob, and Burton. According to Schwabe the belts 
 fade off by the formation of longish white spots, or bays, and 
 return by a similar process; and in either case the two 
 principal streaks frequently show corresponding patches. 
 The edges nearest the equator are usually the darkest and 
 most permanent parts. The larger belts, especially, have 
 
 White and dark spots are often seen in these regions, and sometimes 
 the bands in the S. polar region are curved toward the pole. 
 
 Various observers have noted light spots on the equatorial zone 
 sometimes attached to the S. equatorial belt, and occasionally lying 
 partly over it producing the appearance of a rift in the belt. Keeler's 
 drawings, above referred to, show these rifts very plainly, as if there 
 were a drift of light matter over the surface of the belt. The S. 
 equatorial belt is frequently duplex, especially that portion following 
 the longitude of the Great Rod Spot. Small white spots are occasion- 
 ally seen on the light belt south of the S. equatorial one. At .the 
 latter end of 1892 several observers saw them, and recorded them in 
 their drawings. 
 
JUPITER. 169 
 
 at times a brownish, coppery, or purple hue : Se. (1860) calls 
 the principle belt red, with other alternate bands of green 
 and white ; but the more luminous equator sometimes exhibits 
 a remarkable ruddy, yellow, or brown tint : this, which had 
 formerly been noticed by $ (1790) and probably by G. 
 (1834?), was seen by Professor Herschel in 1860, Carpenter 
 in 1 86 1-2, and has been frequently remarked since 1 869. In 
 1870 Lord Eosse found it so conspicuous as to affect the 
 whole colour to the naked eye. Burton could not trace it, 
 however, in 1873. Airy and Browning suspect a periodical 
 return. Generally speaking, there is often ' something rich 
 and strange* in the colouring of the disc. Lord Kosse 
 describes yellow, brick-red, bluish, and even full-blue mark- 
 ings ; Hirst, a belt edged with crimson lake ; Miss Hirst, a 
 small sea-green patch near one of the poles : and the great 
 red spot of 1879 is still as conspicuous as ever. 1 Such spots 
 
 1 The Groat Red Spot has been very carefully observed by many, 
 pre-eminently by Messrs. Denning, Williams, and Green in England. 
 These observations extend from 1878 to 1892, and record its inten- 
 sifying in tint, and becoming clearer in outline, and its gradual decay 
 until it became so pale as to be well seen only in the larger apertures. 
 Mr. Offord speaks of it as of a beautiful pale orange tint in 1892. 
 Mr. Stanley Williams records it as being much paler in its central 
 portions, presenting therefore a ringed appearance. At the end of 
 '92 it was seen as very diff use, especially at its preceding end, making 
 it difficult to determine when that portion was passing the central 
 meridian. Its relative motion also became slightly retarded. Its 
 general appearance at this date was as if it was partially covered with 
 a veil of dense mist. 
 
 The colour and intensity of tint of the principal belts are evidently 
 very variable. Mr. MacEwen, in a careful drawing dated Dec. 12, 
 1892, gives the S. polar region as of a delicate madder brown. The 
 S. temperate bands as similar with a slight pinkish hue. The two 
 components of the S. equatorial belt as of a rich brownish yellow, 
 almost orange tinted. The darker portions being decidedly so. Tho 
 equatorial light band being somewhat redder. The N. equatorial 
 
I/O THE SOLAR SYSTEM. 
 
 are not uncommon, though seldom of so decided a hue. They 
 are occasionally luminous, more frequently very dark : one 
 of the latter, seen by Hooke in 1664, and Cassini in 1665, 
 was unusually permanent, having been observed, with many 
 interruptions, till 1715 ; it even seems to have reappeared 
 as late as I834, 1 always with the S. equatorial belt, though 
 the belt had often been seen without it. 2 G. once (1822) saw 
 
 belt of a rich brownish red. The N. temperate band similar, but 
 with a slight olive-green cast. The N. polar region and its band as 
 decidedly bluish in tone. Though there are considerable variations 
 in the drawings of other observers, the above may be regarded as 
 generally true and certainly almost wholly objective in character. 
 The colour apprehensive sense is diverse, hence some of the anomalies, 
 and some few scarcely detect colour at all. It has been noticed that 
 artists, as might be expected, detect planetary colour more readily 
 than those whose colour sense has been comparatively uneducated. 
 In this matter the ladies generally excel. 
 
 1 According to Hind, however, these spots were on opposite sides 
 of the equator. The spot, or rather spots, of 1834 had been seen by 
 Schwabe in 1828, and by myself with a fluid achromatic in 1831 and 
 1832. D. observed a very large black spot in 1843. Two were visible 
 at the close of 1858. 
 
 2 The general permanence of the appearance of the leading belts 
 is a well established fact, though minor changes of form and intensity 
 are common. A notable instance occurred during the autumn of 
 1891, when a portion of the S. temperate band gradually and greatly 
 thickened, so as to become a prominent marking. Its rotation period 
 was more rapid than most other spots on the disc. It was very care- 
 fully observed by many students, and various slight changes were 
 perceived, especially in tint. In large apertures it presented a duplex 
 appearance in latitude, and was sometimes seen to be accompanied by 
 light spots at both ends. The preceding end was more diffuse, and 
 seemed as if drifting away westerly. By the end of the year it had 
 become so faint as only to be seen in the best observing conditions. 
 In 1892, though much fainter, it was again observed. Disturbance 
 in the sub-atmosphere, or possibly in the body of the planet, is the 
 most probable cause of these changes, as they seem to be ejected 
 matter from the lower regions. In 1891, the N. temperate band 
 
JUPITER. I/I 
 
 and drew a small elliptical black speck close to the limb 
 near the S. pole. An observation by South affords a beauti- 
 ful illustration of the evanescent nature of some of these 
 objects. 'On June 3, 1839, at i3 h 45"' (sidereal time) I 
 saw with my large achromatic, immediately below the lowest 
 [? edge] of the principal belt of Jupiter, a spot larger than 
 I had seen before : it was of a dark colour, but certainly not 
 absolutely black. I estimated it at a fourth of the planet's 
 equatorial diameter. I showed it to some gentlemen who 
 were present: its enormous extent was such that on my 
 wishing to have a portrait of it, one of the gentlemen, who 
 was a good draftsman, kindly undertook to draw me one : 
 whilst I, on the other hand, extremely desirous that its 
 actual magnitude should not rest on estimation, proposed, 
 on account of the scandalous unsteadiness of the large in- 
 strument, to measure it tricometrically (sic) with my 5 -ft. 
 equatorial. Having obtained for my companion the necessary 
 drawing instruments, I went to work, he preparing himself 
 to commence his ; on my looking, however, into the telescope 
 of the 5 -ft. equatorial, at I3 h 45 (sic), I was astonished to 
 find that the large dark spot, except at its eastern and 
 western extremities, had become much whiter than any of 
 
 was in a very disturbed state, becoming as dark and nearly as broad 
 as tbe N. tropical belt. There were several well denned dark 
 spots on its southern edge. Four or five of these spots were often 
 seen at one time. Ephemerides were constructed of the time when 
 they severally passed the central meridian of the disc. Their motion 
 was found to be diverse to the rotation period of the Eed Spot, show- 
 ing probably that the Jovian atmospheric currents differed from the 
 rotation period usually received at least in some latitudes. In 1892 
 these interesting spots were comparatively few, and more difficult of 
 detection. Light spots were however frequently seen, and their rotation 
 period also varied. These spots and others of a similar type in the 
 southern portion of the planet excited considerable attention. 
 
172 THE SOLAK SYSTEM. 
 
 the other parts of the planet, and at i4 h 19 these miserable 
 scraps were the only remains of a spot which, but a few 
 minutes before, had extended over at least 22,000 miles.' 
 The speedy resolution of a spot into minute points was once 
 noticed by Schwabe, who also found that the large spots 
 were composed of smaller masses, surrounded in one case 
 by a general penumbra, like a sun-spot. A very different 
 kind of spots has recently been observed minute white 
 roundish specks, about the size of satellites, on the dark S. 
 belts. D. first saw them in 1849, Lassell in 1850, with his 
 Newtonian reflector, of 2-ft. aperture, 2O-ft. focus. D. has 
 since given several striking drawings of them in the ' Monthly 
 Notices of the Astronomical Society,' and they have been 
 subsequently seen by many observers. They are evidently 
 not permanent. Common telescopes will have little chance 
 with them, or with the similar traces which Lassell has 
 detected (1858) on the bright belts. All these phenomena 
 prove the existence of an envelope like that of the Earth in 
 instability, 1 without, however, necessarily inferring (as has 
 been done) perturbation by tempestuous winds : even in our 
 own atmosphere, when near the ' dew point,' or limit of 
 saturation with moisture, surprising changes sometimes occur 
 very quietly; a cloud-bank observed by H., 1827, April 19, 
 
 1 The spectroscopes of Huggiiis, Buckingham, Le Sueur, and 
 Vogel indicate an atmosphere similar to, but not identical with, our 
 own. Water could not exist there in a state of fluid or vapour, except 
 on the supposition of internal heat. The current opinion of later date 
 is that the atmosphere of 11 is not analagous to our own, but consists 
 very largely of metallic vapours, that its analogy to the Sun is closer 
 than to the earth; such condition rendering habitability very im- 
 probable except by creatures differently constituted to any with which 
 we are familiar. The recent observations with large apertures, suoh 
 as the 36-iu. Lick telescope, conjoined with spectroscopic reseurche.3, 
 corroborate this opinion. 
 
JUPITER. 173 
 
 was precipitated so rapidly that it crossed the whole sky 
 from E. to W. at the rate of at least 300 miles per hour ; 
 and alterations far more sudden are conceivable where every- 
 thing is on a gigantic scale. The ancient astronomers soon 
 recognised the signs of an atmosphere, and Huygens speaks 
 of clouds and winds on Jupiter ; but they seem to have 
 looked upon the dark as the cloudy belts, forgetting that to 
 an eye placed above them, vapours in sunshine would appear 
 whiter than the globe beneath. Schr. made the same mistake, 
 and ^[ for a time, though subsequently he perceived the 
 probability that the dusky belts may be the real body of 
 the planet. This is supposed to be established by the invisi- 
 bility of the darkest spots when near the limbs, and the 
 fading away of the grey streaks towards their ends; but 
 the argument is not conclusive : in the former case sufficient 
 allowance may not have been made for foreshortening ; and 
 the great red spot is seen on the limb : l the latter pheno- 
 menon is less evident than has been sometimes stated ; it is 
 not mentioned by ^ , though described and represented by 
 his son: greatly exaggerated in the clumsy figures of B. 
 and M., it does not appear in the elaborate design of De 
 la Hue: it comes out in Lohse's drawings at Bothkamp 
 with the n|-in. achr. ; in fine air it is questionable with 
 my 9|-in. mirror. Burton with i2-in. finds the darker 
 belts enfeebled only, the faint stripes effaced near the limb. 
 
 1 Though the Great Eed Spot was seen on the limb during the 
 period of its deepest intensity, during 1891 and 1892, it was barely 
 discernable when in that position. In some 50 drawings taken by 
 the members of the Jupiter section of the British Astronomical 
 Association its visibility is far more indefinite on the limb than mere 
 perspective demands. This corroborates the theory that the Bed 
 Spot is not atmospheric, but a glowing prominence on the body of 
 the planet itself, now somewhat fading, or possibly partially covered 
 with vapours. 
 
174 THE SOLAR SYSTEM. 
 
 However, it may be admitted as the likelier alternative that 
 what we call clouds are the more reflective portion of the 
 disc. That the atmosphere does not extend far enough 
 beyond the limb to affect the brightness or motion of the 
 satellites in passing behind the disc, was proved by D. with 
 his * solar eye-piece,' and theory demands great thinness for 
 an envelope exposed to such powerful central attraction; 
 but we have very little knowledge of the true constitution 
 of the apparent surface. Terrestrial analogies will be found 
 feeble in proportion as they are pressed. Vapours like our 
 own would reflect no such variety of colour ; and the very 
 inferior density of the planet, only that of the Earth, may 
 well lead us to anticipate startling discrepancies. The 
 equatorial direction of the streaks, and the swift rotation of 
 the globe, appear to be connected, though in what manner it 
 is not easy to explain, as the analogy of our trade-winds will 
 be found insufficient ; but the general aspect cannot be mis- 
 taken ; and Piazzi Smyth, in his charming book, ' Teneriffe,' 
 has described in the most graphic manner the appearance 
 of l a windy sky ' and the shapes of drifting and changing 
 vapours, 'most picturesque clouds,' seen with a 7i-in. achr. 
 on ' the peak of Teyde,' and beautifully delineated in his 
 more scientific ' Keport.' The great dark spots possess more 
 stability, as though some portions of the surface cleared the 
 sky above them for a considerable time ; yet these, or rather 
 the vapours around them, are liable to displacement, and do 
 not always give the same period of rotation. This, however, 
 appears to be very nearly 9 h 55 27*48 a for day and night ; l 
 so that the equator of this huge globe is flying 28,000 miles 
 
 1 Airy, from Cambridge observations in 1834, makes it 6'5 9 less. 
 Schmidt finds it different from dark and light spots. His mean> 
 1873, is 9 h 56 7'2 S . Cassini had thought that bright spots rotated 
 mere rapidly near the equator. 
 
JUPITER. 175 
 
 an hour, or between 7 and 8 miles every second 1 and a few 
 minutes show the movement of the spots, but puzzle the 
 draftsman. We must now proceed to 
 
 THE SATELLITES. * 
 
 Are these little moons visible to the naked eye ? The 
 question has been usually negatived, as, though I (i.e. the 
 first, or nearest) is about as far from Jupiter's surface as our 
 Moon from the Earth, they are very minute, and over- 
 powered by the planet's rays. Yet there have been excep- 
 tions. Benzenberg speaks of 16 correct observations by 3 
 independent observers. A tailor, named Schon, at Breslau, 
 who died in 1837, is said to have perceived I and III, when 
 sufficiently distant from Jupiter. The Marquis of Ormonde 
 is said to have seen them in the sky of Etna ; Jacob and 
 another have made out III at Madras : the missionary Stod- 
 dart at Oroomiah, in Persia, states that he could detect 
 some of them in twilight, before the glare of the planet came 
 out ; and under the same circumstances two are said to have 
 been more recently perceived by several persons at Devizes. 1 
 The keen eye of Heis could occasionally see two when close 
 together. Once (1832, Sept. i), III and IV being on the 
 same side, and far from Jupiter, I saw them, though not 
 separately, through the concave eye-glass which corrects 
 my near sight: so Denning, separate, 1874. Levander saw 
 I, 1859; officers of the 'Ajax,' II and III, 1860. Banks 
 has seen I and II as one; III often, and once a glimpse 
 of IV. II and III were seen separately by Boyd, 1860; 
 I, II, IV as one by Todd (U.S.A.), 1874. Mason saw III, 
 1863. Buffham has frequently detected it. To try this 
 
 1 This occurred about 20 before a remarkable crimson aurora, 
 1859, April 21. Compare the observation of Venus, p. 61. $ found 
 no perceptible effect on stars from auroral light. 
 
1 76 THK SOLAR SYSTEM. 
 
 experiment, the planet had better be just hid behind some 
 object, though I did not find it necessary. 1 Any small tele- 
 scope will bring them out, and a powerful instrument shows 
 them even in the day-time. 2 Like Galileo, we may not 
 at first perceivt all 4, as some are often invisible before or 
 behind Jupiter, or in his shadow; and this happened to 
 them all, 1681, Nov. 2; 1802, May 23; 1826, April 15; 
 1843, Sept. 27 ; but we shall soon recognise the whole train, 
 and must attend to the following particulars. 
 
 1. Their Identification, a matter of some importance. 
 Ill, if well situated, is usually brightest at first sight. IV 
 goes much further than the others ; but the best way is to 
 consult the daily configurations in the * Nautical Almanac,' 
 attending to the explanation of the symbols. 3 
 
 2. Their Magnitudes. Even a small instrument will 
 show that their light is steadier than that of stars; this 
 arises from their possessing real discs, which will soon be 
 ' raised ' or drawn out, with increase of aperture and power ; 
 and beautiful miniature full moons they will be found to be, 
 by no means, however, of one size. Engelmann, as a mean 
 from various observers, gives I, i"*o8i ; II, o"*9io; III, 
 i"'537; IV, i"'282, 4 corresponding respectively to about 
 
 1 Pickering finds their stellar magnitude 5-28; 5-31; 4-88; 5-98 
 respectively. 
 
 2 Grover has seen III, 45 before sunset, with only 2-in. 
 
 3 Their identification becomes easy to those familiar with observ- 
 ing them. Ill is unmistakable from its superior size and rosy orange 
 colour; IV from its steel-grey colour; II from its smallness compared 
 with the others, and its whiteness ; and I from its straw-colour, and 
 rapid motion. References to the N.A. are rarely needed for identity 
 to those who are constantly observing their phsenomena. A kind of 
 intuition born of practice is a great aid. 
 
 4 Se. made them o"'985, i"'o54, i"'6o9, i"'496; but the first two 
 measures were due to a single day : this anomaly will be again men- 
 tioned. With the Chicago i8J-in. achr. they have been measured 
 
JUPITER. 177 
 
 2500, 2100, 3S5 5 and 2960 miles. This accounts ill part 
 for their different brightness, but a difference of reflective 
 power (albedo) must be combined with it in the general 
 effect; and the individual light of each varies at different 
 times. From many comparisons ^ and Schr. considered 
 that, like our Moon, they always turn the same side to their 
 primary, and consequently different faces some of which 
 may be darkened by spots to us: this has been confirmed 
 by B. and M., but is still an inadequate explanation: its 
 results are not always uniform, and singular anomalies occur, 
 especially with IV. 1 As far back as 1707 Maraldi noticed 
 that, though usually faintest, it was sometimes brightest (a 
 variation which he ascribes to all the satellites), as Klein 
 has seen it at the present day; in 1711 Bianchini and another 
 once saw it for more than i h so feeble that it could hardly 
 be perceived; 1849, June ^jl'ft- made a similar observation 
 with far superior means ; Key once found it very small and 
 obscure for at least 48 h , and T. T. Smith and Denning have 
 noticed extraordinary faintness. Ill is more consistent, 
 usually taking the lead, yet Maraldi and Bond have some- 
 times observed the contrary : and many years ago, when I 
 paid some attention to this subject, I have seen it repeatedly 
 surpassed by IV. Engelmann thinks that, as a mean, II is 
 relatively the most, IV the least, luminous. In studying 
 these changes we should hide the planet behind a narrow 
 bar in the field, made by placing a thick wire, or strip of 
 
 i"'U4, o"9So, i"'778, i"'457. The mensures and the magnitudes 
 deduced from them will all be a little too large from the effect of 
 irradiation. These tiny discs are easily seen with a 4-in. aperture, 
 and their differences of diameter perceived by the practised observer. 
 A sharp definition of these discs is a good test for atmospheric and 
 optical excellence. 
 
 1 During the apparition of 1892, IV hrs frequently been seen 
 much brighter than its average. 
 
 VOL. 1. N 
 
1/8 THE SOLAE SYSTEM. 
 
 metal, or wood, or card, across the opening in the diaphragm 
 between the lenses of a Huygenian eye-piece; it is also 
 advantageous to throw the satellites a little out of focus, in 
 order to eliminate, as mathematicians say, or get rid of, the 
 impression of size, which might mislead the eye. ^ used 
 a convenient mode of expressing differences of light by 
 stops of different value ; thus III : I = II, IY would signify 
 that III was very much brighter than I and II, and both 
 these again a very little brighter than IV. Employing this 
 notation, Dennett, from a long series of observations in 
 1879, gives the mean reflective brightness III ; I, II, IV; 
 reflective power II, I, III ; IV : variability IV; 11 = I, III. 
 He thinks III is growing much darker and more variable, 
 IV slowly brighter. The distances from Jupiter must be 
 estimated in diameters of his disc, and the direction of each 
 satellite's motion noted, to avoid confusing the near and 
 remote halves of its orbit. The approximate periods here 
 given will be of use I, i d i8 b 28; II, 3 d i3 h i5 m ; III, 
 7 d 3 h 43 m ; IV, i6 d i6 h 32 m . Spots, as we shall presently 
 see, may easily cause this variable light: but a stranger 
 anomaly has been perceived; the discs themselves do not 
 always appear of the same size or form. $ noticed the 
 former fact and inferred the latter ; and both have been since 
 confirmed by others. B. and M., La., Se., and Buffham 
 have sometimes seen the disc of II larger than I, and La., 
 Se. and his assistant, and Burton have distinctly seen that of 
 III irregular and elliptical; and according to the Roman 
 observers, the ellipse does not always lie the same way; 
 Mitchel also, with n-in. achr., has observed this disc irre- 
 gular and hazy. Buffham has often found IV the smallest 
 of all, and irregular-looking. Phenomena so minute hardly 
 find a suitable place in these pages, but they seem too singular 
 to be omitted ; and in some cases possibly small instruments 
 
JUPITEB. 179 
 
 may indicate them ; at least, with an inferior fluid achr. 
 reduced to 3-in. aperture I have sometimes noticed differences 
 in the size of the discs which I thought were not imaginary. 
 3. Their Colours. Different eyes and instruments have 
 here given different results. $ makes I and III white, II 
 bluish or ash- coloured, IV dusky and ruddy. B. and M. 
 call I rather bluish, II and III yellowish, IV always bluish. 
 Se. finds III sometimes whitish, generally red. Engelmann 
 states that III is intensely yellow with low powers, and IV 
 in achromatics a distinct dusky blue : but D. considered IV 
 ruddy, as I have often thought ; especially with g-in. mirror. 1 
 One unfavourable night of very thin white haze (1832, 
 Oct. 8) I found with 3 T V-i n - tne colours of II, III, and IV 
 unusually contrasted, though the discs were not well seen. 
 Many times, both with the fluid and the 5^-ft. achr., I used 
 to fancy IV, when distant from Jupiter, and especially when 
 viewed obliquely, encompassed with a little scattered nebulous 
 light : but I have been unable to confirm this with better 
 instruments. It certainly is very unlike III when they are 
 near together ; but the difference perhaps arises from colour. 
 The* spectroscope of Vogel gives indications of atmospheres. 
 4. Their Eclipses. The fading away or breaking forth of 
 these little attendants as they pass into or out of the great 
 cone of shade which their monarch casts behind him for half 
 a hundred millions of miles, is always interesting, and, when 
 not too near the primary, within the reach of moderate in- 
 struments. The time being taken from the almanac, long 
 enough beforehand to be quietly prepared with the most 
 suitable eye-piece, a sharp look-out must be kept, as the 
 diminution or increase of light, though not instantaneous, is 
 speedy, especially with I and II. The planet had better be 
 concealed behind a bar. Both Immersion and Emersion may 
 1 Sa. sees I yelsh. wh., II yel., Ill ruddy yel., IV decided bl. . 
 
I So THE SOLAR SYSTEM. 
 
 be seen of III and IV, if not too near opposition ; this can 
 seldom be done with II (four instances only are on record), 
 never with I, as the disc of the primary interferes. As the 
 planes of their orbits pass so nearly through the Sun and 
 our eyes, it seems remarkable that though respective occul- 
 tations have been seen, there is only one recorded instance 
 of the eclipse of one satellite by the shadow of another. 
 
 5. Their Occultations by the globe of Jupiter: frequent, 
 but not usually of much interest, as they show no effect of 
 the planet's atmosphere. Occasionally, however, singular 
 appearances have been noticed. Schumacher once saw a 
 satellite hang on the limb, and seem to recede again, or make 
 an indentation in it; Gorton, 1863, April 26, found that II 
 appeared and disappeared several times before occultation, 
 perhaps from unsteady air; but at the same time Wray, 
 with an 8-in. object-glass, saw it projected distinctly within 
 the limb for nearly 20*. 1857, Jan. 3, Hodgson saw I pro- 
 jected on the disc for nearly i m with clear space round it. 
 Carlisle, at Stonyhurst, saw II within the limb for about 45" 
 after last contact in occultation, 1878, Sept. 20; and in the 
 same year Todd and Eingwood at Adelaide observed, with 
 an 8-in. achr. and splendid definition, 3 certain and 2 doubt- 
 ful cases of projection of I and II, as though seen ' through 
 the edge of the disc.' We are at once reminded of the pro- 
 jection of stars on the Moon ; but all such anomalies are 
 worth recording. Todd says that the satellites are visible 
 through the dusky, hidden by the bright, parts of the limb ; 
 but this might result from projection on a different back- 
 ground. Ne. is of opinion that they are seen through a 
 spurious limb produced by irradiation, and extending perhaps 
 o"'5 beyond the true. 1 A very singular occurrence was ob- 
 
 1 It is the current opinion of practised observers that the disap- 
 pearance is gradual, each satellite having been seen dichotomised on 
 
JUPITER. l8l 
 
 served at Melbourne, 1879, Sept. 14 : the occultation of the 
 star 64 Aquarii, which in the great reflector occupied about 
 35 s in disappearing, and could still be traced for io s longer 
 ' as a speck of light seen through ground glass ; this also 
 disappeared gradually;' it may be a question whether 
 through the irradiation-limb or the atmosphere. 
 
 6. Their Transits. The most beautiful phenomena of 
 this beautiful system ; often recurring, and not too difficult 
 for a moderate telescope : the first known instance having 
 been seen as early as 1658, with one of the old unwieldy 
 refractors, by its skilful maker Campani, and my fluid achr. 
 of 3-in. aperture having often given me a pleasing view of 
 the scene. When a satellite is seen rapidly approaching 
 Jupiter, on the /side (that is, the side following as the object 
 passes through the field), a transit is inevitable ; the satellite 
 will glide on to the disc like a ; brilliant bead, and remain 
 visible from its greater brightness for some distance accord- 
 ing to South, \ or \ of Jupiter's diameter till it is lost in 
 the luminous background, to reappear after a time, and pass 
 off in the same manner : or, if it traverses a dark belt, it 
 may be perceptible throughout. But this is not all. An 
 astronomer on Venus might witness a similar transit of our 
 Moon across the Earth at the time of one of our solar 
 eclipses, but he could scarcely if at all perceive the black dot 
 of shade which our attendant casts upon us, as, from our 
 comparative nearness to the Sun and the breadth of his disc, 
 the cone of lunar shadow tapers so rapidly that its end falls 
 short of the Earth in annular eclipses, and in total ones 
 covers so small a spot on the surface that it would be in- 
 visible at any considerable distance, 1 notwithstanding the 
 
 the edge of the primary when observing circumstances have been 
 highly favourable. 
 
 1 The greater axis of the elliptical dark spot (neglecting the 
 
1 82 THE SOLAE SYSTEM. 
 
 expansion due to the ' penumbra ' or border of fainter shade 
 extending over the region where the Sun's disc would be 
 deeply but not entirely obscured. But Jupiter is so much 
 further from the Sun that the shadows of his satellites form 
 much longer cones, and falling little diminished upon his 
 disc, traverse it as singular and conspicuous objects, perfectly 
 round and as black as ink, at varying distances p or / (that 
 is, preceding or following the satellites), according to the 
 relative positions of the Sun, Earth, and Jupiter. At oppo- 
 sition I has been seen projected on its shadow, which, en- 
 larged by penumbra, appeared as a dark ring. The sharpness 
 with which the entrance of the shadow can be traced has 
 been pointed out by Klein as a good test of defining power 
 in a telescope. When not near opposition, the shadow, 
 especially of III or IV, may be far within the disc, while 
 the satellite shines out in the dark sky. Occasionally two oi 
 these total solar eclipses may be seen at once on Jupiter, and 
 it will be interesting to mark their unequal velocities and 
 distances from the satellites to which they belong. Such is 
 
 penumbra) which traversed England (very nearly in the course of 
 the annular eclipse of 1858) during the last total eclipse, 1715, April 
 22, is given at 150 miles, from Dartford to Oswestry, in a curious 
 'Description' or map of its path, by Halley, formerly in my pos- 
 session, now in that of the Koyal Astronomical Society. It is 
 accompanied by the following characteristic notice : ' The like 
 Eclipse having not for many Ages been seen in the Southern Parts 
 of Great Britain, I thought it not improper to give the Publick an 
 Account thereof, that the suddain darkness, wherein the Starrs will 
 be visible about the Sun, may give no surprize to the People, who 
 would if .unadvertized, be apt to look upon it as Ominous, and to 
 interpret it as portending evill to our Sovereign Lord King George 
 and his Government, which God preserve. Hereby they will see 
 that there is nothing in it more than Natural, and no more than the 
 necessary result of the Motions of the Sun and Moon ; And how 
 well those are understood will appear by this Eclipsed 
 
JUPITER. 183 
 
 the regular mode of transit. But remarkable exceptions 
 are not uncommon, owing to the variable brightness of the 
 satellites, which sometimes cross the disc as dusky or even 
 black specks; when deepest, almost like their shadows. 
 This seems to have been first noticed by Cassini in 1665, but 
 was more fully described by Maraldi in 1707, and referred 
 to rotating or variable spots. After a long interval Schr. 
 and Harding reobserved the phenomenon in I796, 1 and per- 
 ceived that the spots were sometimes only partial. More 
 recently the great telescopes of La., Bond, D., and Se. have 
 shown that these little moons 2 are liable to the forma- 
 tion of spots, just dark enough to bo imperceptible in front 
 of the fainter limb of Jupiter, but to start out rapidly in 
 advancing upon the greater brightr.-BSS of his centre, where 
 they are generally dusky, irregular, and smaller than the 
 shadow. I have sometimes seen them thus readily with my 
 5^-ft. telescope. South, who once found, with his large achr., 
 two satellites of a light chocolate colour and their shadows 
 on the disc at once (which must have been, what he calls it, 
 'a glorious view'), says he never saw one black: but at 
 Cambridge, U.S., 1848, Jan. 28, when the shadows of I and 
 III were both in transit, III itself ' was seen with the great 
 refractor' 3 (Bond's) 'under very beautiful definition, as a 
 black spot between the two shadows, and not to be distin- 
 guished from them except by the place it occupied. It was 
 
 1 In 1785 and 1786 Schr. repeatedly saw round black spots tra- 
 versing Jupiter rapidly, like shadows of satellites, which M. says 
 could not have been dark transits. It is quite unaccountable that 
 $, and B. and M. in their Beitrdge should have passed by these 
 transits in silence. De Gasparis is said to have seen (1864, July 22) 
 a black point on the disc, which passed off it in i5 m . 
 
 2 With the exception of II, which D. finds always bright : the 
 brightest of all for its size. 
 
 * 22|-ft. focus, 14'95-in. aperture, by Merz, Fraunhofer's successc/ 
 
1 84 THE SOLAR SYSTEM. 
 
 smaller than its shadow in the proportion of 3 to 5, not 
 duskish simply, but quite black like the shadows.' Tebbutt 
 saw several dark transits of III in 1873. That of IV, 
 March 26 in that year, remarkable for its absolute blackness, 
 was seen by many observers in England ; among them the 
 late much-regretted Key, who noticed its very small appear- 
 ance afterwards. Sometimes these spots have been so 
 marked on III as actually to be visible to D., La., Se., 
 Burton and Sadler, when it was shining freely on a dark 
 sky ; the former has given the following figures, of which 
 
 cue ist represents what was seen both on and off the planet, 
 1860, Jan. 24, 31 : and the 2nd the appearance during 
 transit, 1849, Feb. n ; so as to imply in each instance an 
 unchanged position of the satellite towards the Earth. 1 
 1867, Aug. i, when Jupiter was without visible satellites 
 outside the disc, three being in transit at once, he again 
 saw the double spot, 2 but on the opposite or SW. side. The 
 3rd fig. represents IV as he has sometimes observed it, with 
 portions near the edge almost invisible from small reflective 
 power. Burton, too, has seen it polygonal. Se., who found 
 III reddish, and like the spotted face of Mars in a small glass, 
 luade designs during 1855, some of which are copied here, 
 
 1 G-. says that on two occasions he has seen the light of this 
 satellite reduced to a mere ring. Ingall, with a 5^-in. dialyte, saw 
 it (1870, Feb. 17) like a double star in contact. 
 
 3 Barneby also, who ascribes to it a ginger colour. 
 
JUPITER. 185 
 
 und from which he would infer a swift axial rotation ; if so, 
 these satellites must differ essentially from our Moon : that 
 they do so to some extent is clear from the ephemeral nature 
 
 Aug. 26. I9 h 20 m . Aug 26. 2i h io m - Aug. 27. Sept. 9. 
 
 of their obscurations, the same satellite often passing across 
 Jupiter bright and dark at the interval of a single revolution 
 in its orbit. An extract from my own observations, of a 
 date long anterior to those of La. and Se., may be per- 
 mitted as an encouragement to the possessors of ordinary 
 instruments. ( 1835, J an * 2 ^> i b 30, 250 [power of 5^-ft. 
 achr.] The 4th [a little past inferior conjunction] was very 
 pale, and rather ruddy ; its disc not only smaller than that 
 uf the ist or 2nd, but apparently imperfect as if spotted. 
 Had the night been more favourable, this might have been a 
 very interesting observation.' 
 
 From this change in the aspect of a satellite in dark 
 transit than which, as D. observes, no more delicate photo- 
 meter could be applied to the different parts of the disc we 
 must infer a far greater difference of brightness between the 
 centre and circumference of Jupiter than could have been 
 suspected : a white disc would not be converted into a black 
 one from mere contrast, unless the light of the background 
 varied in a corresponding manner : and it is very strange 
 that this variation is so little otherwise apparent to the eye. 
 Browning, however, has detected it, as I have since done, by 
 means of a graduated darkening glass. On optical grounds 
 we should hence deduce a very smooth surface for Jupiter, 
 
1 86 THE SOLAK SYSTEM. 
 
 and one not covered with vapour, since this, as we see in the 
 dense white clouds of our own sky, would not grow less 
 bright towards the edge. One of the apparent anomalies of 
 this system has been recently explained. The unexpected 
 magnitude of the shadows, especially of IV, in transit, 
 which had been noticed ever since Maraldi's time, has been 
 shown independently by Proctor and Buffham to be due to 
 enlargement from penumbra, into which, in consequence of 
 its distance from the primary, nearly the whole shadow of 
 IV is resolved, III being considerably affected by it, 
 throwing a smaller and blacker shadow from a larger disc, 
 and even I not exempt ; these diffused borders, the visible 
 extent of which will vary with the optical power employed, 
 have actually been detected on several occasions by La. 
 Buffham, Gorton, and others. An elliptical form which has 
 been seen by Burton in the shadows is not fully explicable 
 as the result of oblique projection, and seems rather to indi- 
 cate penetration through an imperfectly transparent and 
 not very shallow medium. Other appearances not easily 
 accounted for are on record. 1 Cassini once failed in finding 
 ihe shadow of I when it should have been on the disc. 
 Gorton saw it grey on one occasion. The shadow of II has 
 been seen especially indistinct by Buffham, Birt, and Grover ; 
 Terby and Flammarion found it grey, 1874, March. 25, when 
 that of III, very near it, was black. I saw it abnormally 
 
 1 Some time since it was authoritatively announced that Messrs. 
 Burnham and Barnard had seen Sat. I duplex. Full verification was 
 not forthcoming. There was much conjecture among astronomers 
 as to the cause of this appearance such as close conjunction with 
 spots in transit, markings on the surface of the satellite, optical 
 reflection due to special atmospheric conditions, etc. The above 
 eminent observers have indicated their belief that the form of the 
 satellite in question is elliptical which would to some extent account 
 for apparent duplicity. Vide Burton's observation on page 178. 
 
JUPITER. 187 
 
 email with gj-in. mirror, at the same time. The Melbourne 
 observers have seen the shadow of III flattened at its poles, 
 in mid-transit, in a high N. Lat ; and Grover has recorded 
 two somewhat similar observations of the same shadow. 
 South, many years ago, published in one of the public 
 journals a most interesting observation, which I greatly 
 regret that I cannot recover, but I am confident as to its 
 tenor, which was, that in his great achr. he perceived each 
 of two shadows of satellites on Jupiter to be attended by a 
 faint duplicate by its side ; traces of which could be just 
 detected with a smaller telescope (I believe) 5 ft. 1 But the 
 most surprising is a phenomenon which requires, and 
 possesses, the highest attestation. 1828, June 26, II, 
 having fairly entered on Jupiter, was found 12 or 13 after- 
 wards outside the limb, where it remained visible for at least 
 4 m , and then suddenly vanished. The authority of such an 
 observer as Smyth would alone have established this wonder- 
 ful fact; but it was recorded by two* other very competent 
 witnesses, and (what is especially remarkable) at consider- 
 able distances, Maclear at 12 miles and Pearson at 35 miles 
 from Smyth at Bedford. Explanation is here set at defiance ; 
 demonstrably neither in the atmosphere of the Earth nor 
 Jupiter, where, and what could have been the cause ? At 
 present we can get no answer. 2 
 
 1 Trouvelot saw the shadow of ist satellite double on April 24, 
 1887; and Sadler, May, 1874. 
 
 2 Gambart says that, at the immersion of I, 1823, Oct. 19, 'le 
 satellite a disparu et reparu plusieurs fois; ' but in this case qu. as to 
 the state of the air, or the eye ? Observations by Se. and Main, in 
 which the limb alternately approached and receded from a satellite 
 for 4 or 5, were obviously due to unsteady air. Grover on one 
 occasion saw the advance of II towards occultation entirely arrested 
 for i m when 3 or 4 of its own diameters from the limb: definition 
 splendid, and observation very certain. 
 
 One of the most important Jovian discoveries of the century is 
 
I 88 THE SOLAR SYSTEM. 
 
 SATURN. 1 
 
 FORTUNATELY for the student, a common telescope will ex- 
 hibit some part of the wonders of this superb planet, un- 
 paralleled in our own system, invisible elsewhere ; and they 
 whose expectations have not been unduly raised by designs 
 made with the best telescopes will be delighted with the 
 scene in their own. The minuter details require in general 
 great optical perfection ; but some of them may now and 
 then be reached, though with a feeble grasp, by ordinary 
 instruments, and our readers may have occasional access to 
 more powerful means ; it seems best, therefore, to be circum- 
 stantial. We shall describe the Globe, the Rings, and the 
 Satellites, in succession. 
 
 The Globe. Though about 69,200 m. 2 in equatorial 
 diameter, second only to Jupiter, and about 9 times larger 
 than the Earth, this noble ball has so little density that it 
 would float like oak on water, which is actually heavier, and 
 therefore, if any were found there, would sink to its centre ; 
 while on the probable supposition that the density of the 
 globe decreases outwards, its surface-material must be lighter 
 still, and the conditions of existence there so unlike our own 
 as to render conjecture hopeless. Seidel has shown that its 
 reflective power is only of that of Venus, Mars, or Jupiter. 3 
 Day and night, summer and winter, 4 and possibly clouds and 
 
 that by Professor Barnard, who, on the niglit of Sept, 9, 1892, detected 
 a fifth satellite revolving in a period of i i h 57 m 23-06". The distance 
 from Jupiter is about 67,000 miles, and its velocity per second 16*4 miles. 
 
 1 The new matter is by the Eev. A. Freeman. 
 
 2 Measurements differ a little ; this is the value given by Ne. as 
 freed from irradiation. 
 
 3 The mean opposition mag. is 0-93 according to Pickering. 
 
 4 The inclination of Saturn's equator to his orbit is found by 
 
SATURN. 189 
 
 winds, the only steps in the analogy, leave an immense dis- 
 tance to be overpassed ; and the tenfold nearer approach of 
 modern astronomers has not bridged over the chasm which 
 foiled the inquiries of Huygens, and kept him still in igaor- 
 ance of the wonders beyond it. 1 
 
 i. Ellipticity. There is no doubt of this compression, 
 but much uncertainty as to its amount : the inclination of 
 the axis, corresponding with that of the ring, causes some 
 difficulty ; the intersecting outlines of the ring occasion more 
 by deceiving the eye : and this has been the reason generally 
 assigned why $ and others in 1805 considered that the ball 
 was doubly flattened, at the equator as well as at the poles. 2 
 As, however, the great observer confirmed the appearance 
 with several instruments, by comparison with Jupiter, and 
 by actual measurement, the suspicion may recur that some- 
 thing is not altogether explained. The same peculiar outline 
 presented itself to G. in 1844. Others, especially Bond II., 
 have thought the two hemispheres not precisely alike in 
 flattening. The best values of the compression vary between 
 a little less than ^ and a little less than y 1 ^ : at any rate it is 
 very considerable. It is of course best seen during the dis- 
 appearance of the ring. 8 
 
 Mr. A. Martli to be 26 43' 23". The inclination of the orbit to the 
 ecliptic was 2 29' 34", in 1892. 
 
 1 * Ad loriginqua Saturni regna propius nunc quam antehac quis- 
 quam adivi, et usque eo progressus sum, ut vasti adeo itineris pars 
 una centesimatantummodoreliqua fuerit : quam si quo pacto superare 
 potuissem, quot, qualiaque . . . narranda hab.erem ! ' 
 
 2 Proctor has shown very ingeniously that remarkable illusions 
 are caused by the juxtaposition of lines 
 
 of different character. This will be 
 
 apparent from a diagram (taken from 
 
 his in Intellectual Observer, x. 23) in 
 
 which the two chords, though apparently curved, to most eyes at any 
 
 rate, are really straight lines. 
 
 * J. A. C. Oudemans obtains an apparent equatorial diameter of 
 
190 THE SOLAR SYSTEM. 
 
 2. Excentricity. Schwabe, though anticipated by Gallet, 
 1684, in perceiving that the globe is not accurately central 
 in the ring, first drew general attention to the fact, observed 
 by him in 1827 with a 3^-ft. achr. It has been doubted, but 
 seems established by measures which give the dark opening 
 a very little smaller on W. than E. side: 1 the Roman 
 observers as well as Schwabe considered it very evident, but 
 rapidly variable, in 1842 and 1843 : and I have sometimes 
 fancied it visible with the 5^-ft. achr. It has been thought 
 theoretically essential to the stability of the ring. 
 
 3. Belts and Spots. The globe is diversified by darker 
 and lighter bands, changeable, but usually parallel to the 
 equator, though T$L noticed occasional deviation. His ' quin- 
 tuple belt' of alternate light and shade is now seldom to 
 be seen : 2 usually there is a strong central whitish band, the 
 brightest part of the ball ; on each side of it a broad brown 
 or somewhat ruddy zone, with many streaks and markings, 
 generally parallel, and, according to some authorities, reach- 
 ing to the limb ; to the principal of which the Washington 
 achr. gives wavy edges : then a similar greenish or bluish 
 grey region extending to the poles, which are capped by a 
 darker patch of the same tint, with sometimes a pale central 
 space. $ found the brightness of the polar regions variable. 
 Browning describes the colours in 1868, with a i2^-in. 
 mirror, as light cinnamon and bright azure blue. Strange 
 to say, B. and M. missed these belts, which Huygens dis- 
 covered with his old refractor, and Grover has often seen 
 with only 2 in. of aperture. Spots or streaks are uncommon, 
 
 1 7" -3, and a polar diameter of I5"'4, at the mean distance of Saturn 
 from the Sun, with a resulting compression of l s . 
 
 1 Gallet reverses this position. 
 
 9 Seen by A. S. "Williams and Kev. A. Freeman in March, 1892, 
 on the N. part of the ball. 
 
SATURN. IQI 
 
 and the instances easily enumerated : Cassini and Fatio, two 
 bright streaks, 1683: $, 17 So, 1 1806; Schr. and Harding, 
 1796, 1797; Schwabe, 1847; Busch and Luther, a round 
 bright spot near S. limb, 1848. Bond I., in 1848 and 1854, 
 and De la Rue in 1856, figure some darker patches. La. 
 and Jacob, 1852 ; Coolidge and Bond II., 1856 ; D. and La., 
 1858; Se., 1 86 1. From the unequal strength of parts of 
 his quintuple belt $ found the rotation io b i6 m o*44 s . 
 Schr., from various spots, n h 51, n h 40"* 30", and rather 
 more than i2 h . But the best determination is that of Hall, 
 who, 1876, Dec. 7, observed with the great Washington 
 telescope, a well-defined white spot of 2" to 3" which was 
 seen at four other places, and continued for some weeks, 
 extending itself ultimately on one side into a streak. This 
 gave a period of io h I5" 1 . 2 An appearance which indicated 
 an atmosphere to ^ the hanging of the satellites on the 
 limb previous to passing behind it is as yet unconfirmed. 
 The spectroscope of Huggins shows the existence of an 
 atmosphere of similar quality to that of Jupiter ; Janssen's 
 indicates aqueous vapour in both. Vogel's shows more 
 atmospheric bands on the ball than the ring. From the 
 transit of Titan Chacornac found the reverse of Jupiter in 
 Saturn as to reflective power, the edges being brighter than 
 the centre. 8 
 
 1 The object figured by y in Phil. Trans., 1790, is called *a strong, 
 dark spot near the margin of the disk,' where even Bond's great achr. 
 fails to trace the belts, and where, on Jupiter, the darkest spots are 
 usually said to be imperceptible through his atmosphere. 
 
 2 From Mr. A. S. Williams' observations of bright spots on the 
 S. equatorial zone in 1891, a period of io h 14 2i*84 8 is obtained 
 by Marth. 
 
 8 But on March u, 1892, Titan entered bright upon the SSE. 
 limb of N., and became dark as it neared the central meridian, as 
 seen by Dr. Terby, Rev. A. Freeman, J. Guillaume, and others. 
 
192 THE SOLAR SYSTEM 
 
 The System of Rings, so far as has been ascertained, is 
 unique ; the only level surface, or rather collection of level 
 surfaces, that we know. From the combination of its 
 inclined position, its parallelism with itself, and the planet's 
 revolution round the sun, it will alternately show each side 
 to a distant spectator, and in two opposite points of the 
 orbit come into an edgeways position and disappear. The 
 whole revolution occupying nearly 29^ years, all the phae- 
 nomena of increasing and decreasing breadth will be gone 
 through in something less than 15 years for each side of 
 the ring: the widest opening, when the breadth almost 
 exactly equals half the length, will occur in 1899*7, whence 
 it will gradually contract to its edge-representation in 
 1907*6. To a spectator in the Sun, the ring would vanish 
 but once as it changed sides to him, being invisible, or 
 nearly so, from its thinness ; on the Earth, being neither in 
 the centre of Saturn's orbit, nor at rest, we may find it 
 disappear in 4 positions either edgeways to Sun and Earth 
 edgeways to Sun but not to Earth, when it will be too 
 faint, each side having only a very little horizontal light 
 edgeways to Earth but not to Sun, when, though enlight- 
 ened, it will be too narrow to be visible or edgeways to 
 neither, but having its dark side towards Earth : the motion 
 of Saturn, however, carries it before very long through all 
 these points, and the previously hidden side comes definitely 
 into view. We must now consider it as it will be in 1899*7, 
 with the ring at its greatest width projecting beyond each 
 pole of the globe : in this position it is brought out by a 
 very small power (I have seen it with about 20 on only 
 T^-in. aperture) the dark sky being visible on each side 
 through the 'ansaa' (or Jiandles), as the semi-ovals of light 
 are termed into which the ring is projected. Galileo's 
 telescope, though it magnified upwards of 30 times, could 
 
SATURN. 193 
 
 not define it thus, and he imagined that he saw a large 
 globe between two smaller ones : then followed a number of 
 queer-shaped misrepresentations by various hands, till in 
 1659 Christian Huygens made for himself a refractor of 
 23~ft. focus and 2j-in. aperture, which, bearing the power 
 of 100, solved the mystery. His exulting father celebrated 
 the discovery by a copy of verses, closed by a passage worthy 
 of preservation, in which he thus anticipates for his son a 
 fame as lasting as the firmament : 
 
 Gloria sideribus quam convenit esse cosevam, 
 Et tantum coelo comraoriente mori. 
 
 The telescope now improved rapidly, and the cumbrous 
 and troublesome refractor of those days was often exceed- 
 ingly good for the kind of thing. 1665, Oct. 13, two 
 brothers named Ball discovered, with a 38-ft. telescope, the 
 principal division in the ring, 1 which is frequently called 
 after their name: it was rediscovered by Cassini in 1675, 
 one of whose refractors, 20 ft. long, with not quite 2^-in. 
 aperture, bore a power of 90. A much lower power would 
 not show it all round, as Cassini seems to have seen it, even 
 in a modern achromatic. But we must proceed to details, 
 adopting Otto Strnve's designation of the three principal 
 rings, by the letters, A, B, C. 
 
 i. The Outermost Ring (A), about 154,500 miles outside 
 measure, 2 was perceived by Cassini, as early as 1675, to be 
 
 1 Humboldt was not aware of this fact. 
 
 2 According to J. A. C. Oudemans, a discussion of all the best 
 measures gave the following results for the apparent diameters of the 
 ring system, if seen from the mean distance of Saturn, namely, 
 9-53885 times the radius of the Earth's orbit : outer ring, exterior, 
 39"'5; inner ring, interior, 27"'5 ; dusky ring, interior, 2i"'8. To 
 which we may add the following measures of A. Hall : inner edge of 
 outer ring 34" 95, outer edge of inner ring 34"'ii. 
 
 VOL. I. 6 
 
194 THE SOLAK SYSTEM. 
 
 considerably fainter than the outer part of its neighbour ; a 
 small telescope will readily show the difference. There 
 seems reason to believe that its structure is either always, 
 or temporarily, multiple. Short in the last, Kater in this 
 century saw, on rare occasions, several concentric fine lines 
 upon its surface. The strongest of these, named after 
 Encke, who first drew attention to it in 1837, is perceived 
 from time to time rather outside the middle of the ring. 
 Jacob saw it constantly at Madras, and P. Smyth found it 
 very distinct in the pure sky of the Peak of Teneriffe ; La. 
 and Se. find only a dusky mark like a pencil line, D. and 
 De la Eue consider it a black division. 1 Immediately 
 within it, the latter observer represents a brighter streak 
 in the exquisite drawings taken in 1852 and 1856 with his 
 reflector of i3-in. aperture, now at the observatory of 
 Oxford. Se. has perceived another most minute line interior 
 to the first. With has seen several hair-lines upon A at once 
 with one of his own specula. D. and Coolidge (Bond's assis- 
 tant) have remarked a greater brightness at the inner edge, 
 La. (at Malta) at both edges of this ring. Common tele- 
 scopes of course break down here, yet I have once or twice 
 suspected a streaky aspect with the 5^-ft. achr. : but it is very 
 strange that these markings have escaped many of the best 
 telescopes, especially directed to Saturn, those of the two 
 Herschels, 2 Schr., Struve at Dorpat, and Mitchel at Cincin- 
 
 1 In 1851 and 1852 D. saw this line when Bond, Struve, and La., 
 with three of the finest telescopes in existence, missed it. It was 
 subsequently seen dusky in Bond's. 1858, April 17, during an un- 
 usual display of Saturn, La. could only detect a very slight shade. 
 Burton has recently seen it even across the ball, in the present imper- 
 fectly opened condition of the ring (Aug. 1880), which Trouvelot 
 failed to do with the great Washington achr. in a much more favour- 
 able position. I caught the line, 1880, Oct. 14, with g^-in. refl. 
 
 2 In an admirably perfect view of Saturn by H., 1830, April 4, with 
 
SATURN. 195 
 
 nati. Possibly they may be subject to obscuration or 
 change. Trouvelot has seen with the 26^-in. achr. at 
 Washington minute notches in the inner edge at each 
 apparent extremity. 
 
 2. The Ring B begins from its very sharp outer border 
 with a luminous region, sometimes the brightest part of the 
 whole system, though according to Schr. and Schwabe 
 variable a circumstance which I have also noticed, finding 
 it more conspicuous in 1853 and 1855 than in 1856 and 
 1857 : the inner edge is very obscure; Schumacher and D. 
 have seen it much better defined on one side of the ball. 
 From one rim to the other there is an increasing shade, 
 formerly considered regular, but : found by La., D., and Se. 
 to consist of 4 or 5 concentric and deepening bands, com- 
 pared by La. to the steps of an amphitheatre ; each may be 
 a separate ring, since fine black lines were at times traced 
 here by Encke, De-Vico, and Coolidge, 1 and Bond's telescope 
 showed markings like narrow waves of light and darkness. 
 De la Rue and D., in another year, have seen a lighter 
 central band. The innermost edge is sometimes brightened 
 up in other seasons it fades. I saw it in 1853 without any 
 previous knowledge, on one ansaj with only 3^-in. aperture : 
 in 1856 it was less visible, and went beyond my range in 
 
 1857- 
 
 3. The Ring C, the crape or gauze veil, is one of the 
 greatest marvels of our day. How it could have escaped so 
 long, while far minuter details were commonly seen, is a 
 mystery. Schr., in 1796, with his great reflector, 26 English 
 ft. focus iQ-in. aperture, particularly examined the space on 
 
 his 2o-ft. reflector, i8f-in. aperture, no subdivision could be traced 
 'with all possible attention and with all powers and apertures.' 
 
 1 $ saw such a line in June 1780, for a few days on one ansa only. 
 De-Vico's observations are not always satisfactory. 
 
196 THE SOLAR SYSTEM. 
 
 each side of the ball, and found it uniformly dark ; if any- 
 thing, darker than the sky. 1 Our great observers the two 
 Herschels never perceived it. Struve measured Saturn 
 repeatedly in 1826 with the superb Dorpat achromatic, i4-ft. 
 focus, 9 T Vin. aperture, but missed it, though he saw the 
 inner edge of B very feebly defined. In 1 82 8 a fine Cauchoix 
 achromatic of 6|-in. aperture having been placed in the 
 Roman observatory, it was seen, as an old assistant informed 
 Se., both in the ansse and across the ball, yet, strange to say, 
 and little to the credit of Roman science at that time, no 
 notice whatever was taken of it. Ten years later, in 1838, 
 the matter fell into worthier hands ; Galle of Berlin, with 
 a glass the counterpart of that at Dorpat, detected and 
 measured it very accurately, and published his observations ; 
 yet they somehow went on the shelf till, in Nov. 1850, Bond 
 in America, and our own D., had each the honour of an in- 
 dependent and original discovery ; and now everybody may 
 find it with a sufficient aperture : it has been well seen with 
 3-in. achr. by Ross ; I saw faint traces of it with my 3^-in. ; 
 anything larger, if good, is sure to bring it out. Where was 
 it for so many years ? Probably some change may have 
 rendered the part projected on the sky more luminous ; but 
 it is not a new formation, for where it crosses the ball it has 
 been seen ever since Campani's time, 1664: and it was even 
 repeatedly noticed that its outline did not suit the perspec- 
 tive of a belt on Saturn, as it was supposed to be, or that of 
 a shadow thrown by the ring : on this bright background it 
 is so easy that Grover has seen it with a 2-in. aperture. It 
 reaches half-way or rather more from the edge of B to 
 Saturn : at its first discovery D., and Otto Struve at 
 Poulkova (the Czar's observatory), with the superlative achr. 
 
 1 Bond's telescope shows tho same appearance between C and the 
 ball. It has been seen also by Whitley, 1870. 
 
SATURN. 197 
 
 by Merz, 22-ft. focus, i4 T 9 -in. aperture, considered it to be 
 divided in two by a dark line ; but this has not been seen 
 since ; nor is it certain whether there is a division between 
 it and B, or whether it is fainter towards its inner edge. 
 Its generally slaty hue has been at times found different on 
 the two sides of the planet, reddish and bluish ; and a re- 
 peated interchange of these tints, noticed by La. and D., 
 might indicate rotation ; its width and brightness in the two 
 ansaB have been occasionally seen different ; its narrowness 
 in front of the ball has induced an idea that it is not in the 
 same plane with the rings A and B ; and, in 1861-2, some 
 nebulous light attending the edge- view of the ring, on each 
 side of the globe, as observed by Struve II. and Wray, 
 might perhaps be the result of its perceptible thickness: 
 1863, Mar. 26, Carpenter at Greenwich found it almost as 
 bright as B, for part of which it might easily have been 
 mistaken. D., Jacob, and La. have concurred as to the very 
 curious fact of its partial transparency, permitting the limbs 
 of Saturn to be traced through it. 1 Trouvelot, with the 
 26^-in. achr., and Common, with his noble 36^-in. mirror, 
 have thought it speckled, as though consisting of separate 
 particles. Possibly a similar material may fill Ball's division, 
 as this has been sometimes seen not quite black, and Jacob 
 has even followed the shadow of Saturn across it. Many 
 slight variations lead to the inquiry whether this grand 
 system is really permanent in its detail. Se. thought the 
 bright rings might be clouds in an imperfectly transparent 
 atmosphere, 2 which is visible in the rings C and Ball's divi- 
 
 1 Perceived by Whitley (1870) with a 6|-in. silvered mirror. 
 Bond saw it transparent throughout ; but Trouvelot, in 1876, distinctly 
 found, with the Washington achr., the transparency gradually diminish 
 from the inner edge, till half-way across it disappeared. 
 
 2 The ring was suspected to have an atmosphere by y from the 
 
198 THE SOLAR SYSTEM. 
 
 sion ; and the American mathematician Pierce considers it 
 demonstrable that the ring is not solid, but may be a stream 
 or streams of a fluid rather denser than water, adding, in the 
 spirit of a true philosopher, { Man's speculations should be 
 subdued from all rashness and extravagance in the immediate 
 presence of the Creator.' An idea suggested by Cassini II., 
 that it may consist of a multitude of satellites, has been 
 earnestly advocated by Proctor, but would not be applicable 
 to C, excepting on Burton's ingenious suggestion, that the 
 separate particles, though brighter than the sky, may be 
 less luminous than the ball ; corresponding with the ' dark 
 transits ' of the satellites of Jupiter. The passage of the 
 rings over a considerable star might give us some further 
 information ; but such events are very infrequent. 1 Whiston 
 states that Dr. Samuel Clarke and his father, about 1707 or 
 1708, saw a star with a 17 -ft. refractor between the ring and 
 Saturn, but nothing of the kind has been since recorded. 
 D. alone has seen, but under unfavourable circumstances, a 
 star between 8 and 9 m g . pass behind the outer edge of A. 
 In such a case, all attention should be given to the visibility 
 of the star through at least Ball's division, and the dark 
 ring. The shadow 2 of the planet upon the rings is readily 
 
 apparent threading of the minutest satellites upon it when reduced 
 to extreme thinness. 
 
 1 The passage of the outer satellite lapetus through the shadow 
 of the crape ring was observed by E. E. Barnard with the 36-in. Lick 
 refractor. lapetus continued visible during the whole of its passage 
 through this shadow, but the absorption of sunlight became more and 
 more pronounced, until finally the satellite entered the shadow of the 
 bright inner ring, 1889, Nov. I, and then was eclipsed. 
 
 8 In April and May, 1892, the shadow of the outer ring upon the 
 ball was noticed to be concave to the south pole, though south of the 
 ring, which was, of course, convex to the same pole, by Rev. A. 
 Freeman, and H. MacEwen. This is a geometrical necessity when 
 the ring is nearly edgewise to the earth. 
 
SATUEN. 199 
 
 seen, except near the opposition, cutting off one of the four 
 arms of the ansse from apparent contact with the ball: 
 Grover has perceived it with a 2 -in. aperture. The outline 
 of this shadow has often been found curved the wrong way 
 for its perspective, or deviating on ring A from its line 
 on B ; 1 something of this kind has been noticed ever since 
 Cassini's time, and I have seen traces of it with the 5^-ft. 
 achr. ; the shadow of the ring on the ball has also been ob- 
 served notched by Schr., La., De la Rue, and Jacob. 2 Hence 
 an uneven surface would be inferred, and Se. finds that a re- 
 versed curvature would result from a slight convexity in the 
 ring ; but in each case we are at once confronted by its total 
 or nearly total disappearance when viewed edgeways, seeming 
 to demonstrate absolute flatness : it cannot however be quite 
 symmetrical, for not only do the opened ansce sometimes 
 show an unequal breadth of some or all of their lines and 
 markings E. and W., but about the time of their vanishing 
 or reappearance they have been repeatedly seen, ever since 
 1671, variable and unlike in length and thickness and con- 
 tinuity. When the light of the ring has been reduced to a 
 thread, knots of greater brightness have often been noticed 
 upon it. From the supposed motion of some of these in 
 
 1 Bond II. and Coolidge, in 1856-7, saw it strangely flattened 
 with a deep notch, like the eaves of a roof, and it was unequal in 
 depth of shade : it was also visible on each side of the ball at once, 
 and exhibited corners in crossing Ball's division ; several of these 
 strange anomalies have been confirmed by D., La., Se., Jacob, and 
 Trouvelot. "We must bear in mind the source of illusion mentioned 
 in p. 189, note 2; some of the phenomena, however, cannot be thus 
 explained. Grover has several times seen very distinctly a penumbra 
 to the shadow of the ball, as in the frontispiece to Kitchiner on the 
 Telescope. 
 
 s See also T. G. Elger's observations in 1888 (M.N. of K.A.S, 
 xlviii. pp. 368-9). 
 
200 THE SOLAK SYSTEM. 
 
 1789, $ deduced a rotation in io h 32 15", which an ex- 
 amination of the original observations will show to be with- 
 out foundation. Schr. and Harding (1802, 1803), Schwabo 
 (1833, 1848), Schm. and Bond (1848), and Se. (1862), 
 found them all immovable. 1 Schr. supposed that they were 
 mountains ; Olbers, more probably, that they were the per- 
 spective aspect of such parts of the ring as show the greatest 
 breadth of light. Bond finds this insufficient, as they are 
 not lost when the dark side is turned to us, and he thinks 
 that they may be explained by the reflection of light from 
 the interior edges, seen through the openings of the rings. 
 Yet many observations indicate too much irregularity to be 
 so readily accounted for. When it stands edgeways, or turns 
 its dark side to us slightly, the whole system totally vanishes 
 in ordinary instruments. $ seems to have kept hold of it, 
 probably in parts, and Bond did not quite lose it in 1848, 
 though it was seldom continuous: in 1862 Se. kept the 
 thread in sight, and the Greenwich equatorial showed an 
 interrupted line. The thinness of this enormous plane is 
 literally matter of astonishment; H. estimated it at 250 
 miles; Bond allowed it but o"*oi, or 40 miles about ^V?y 
 of its diameter! In 1848 and 1862 D. saw traces of the 
 dark side when turned to us, of a deep coppery tinge; 
 Huggins, 1862, dark blue. The reappearance in 1891 
 was watched with especial interest ; and the possessors 
 of ordinary instruments need not be disheartened; the 
 slender line of light is a beautiful spectacle ; and my fluid 
 achromatic of 4-in. aperture, but of which much of the 
 light went the wrong way, lost it in 1833 only one day 
 
 1 De-Vico saw on several consecutive nights in 1840, and once 
 in 1842, a fixed bright point attached to the open ansa. This, with 
 the instrument and eve of his successor Se., would alone have nega- 
 tived a rotation. 
 
SATURN. 201 
 
 sooner than Smyth's achr. of nearly 6-in., and but four days 
 sooner than H.'s i8-in. reflector. 1 Saturn at such times 
 shows usually a dark and very visible streak across his face, 
 which D., Schm., and Wray have divided lengthways, the 
 unenlightened side of the ring, and its shadow : the latter 
 has sometimes been invisible, when it ought to have been 
 seen ; D. thinks from an atmosphere. Schwabe and other 
 observers have thought the belts not exactly parallel to the 
 ring in this position. 
 
 The Satellites. The very confused way in which the 
 members of this numerous retinue were formerly designated, 
 by numbers counted in two different directions, has been 
 superseded by H.'s ingenious nomenclature, in which the 
 names reckoned towards Saturn are easily remembered in a 
 Latin pentameter and a half 
 
 lapetus, Tilan, Rhea, Dione, Tethys, 
 Enceladus, Mimas. 2 
 
 This arrangement has been since disturbed by the simul- 
 taneous discovery in 1848 by La. and Bond of an 8th, 
 Hyperion, extremely faint, between lapetus and Titan. The 
 lesser of them belong only to the highest instruments : the 
 innermost has never been seen certainly with anything 
 smaller than a 6J-in. object-glass, and with that only in the 
 purer skies of Paris, Rome, and Madras. Kitchiner and 
 Wray have seen it with a 7 -in. in England. The next, 
 though easier, is still very minute ; Ward, however, has 
 detected it with a 4 T ^j.-in. achr., Franks with 5-in. do. ; Perry 
 
 1 Lardner says, H. did not lose it: not a solitary instance of 
 inaccuracy. 
 
 2 The exact order of all the satellites, together with their classical 
 quantities, is indicated by the two hexameters 
 
 Ecce Mimas nitet, Enceladus, Tethysque, Dione, 
 Imle Rhea, et Titan, Hyperion, Tapetusque. 
 
202 THE SOLAR SYSTEM. 
 
 with a 6 T 6 (j-in., I with a 9Jj-in. mirror. But Titan, the 
 leader, is very conspicuous, being equal to an 8*5 m g . star, so 
 that it was discovered by Huygens in 1655, in which year it 
 was also seen, though not suspected to be a satellite, in 
 England, by Sir Paul Neil and Sir Christopher Wren. In 
 fact, this little point of light, which may be seen with i-in. 
 aperture, has in large telescopes a disc of about o""]5, 1 and 
 probably ranks in size between Mercury and Mars. Its 
 shadow was watched by $ in 1789 in transit across the disc 
 of Saturn; G. saw it in 1833; in 1862 it was observed by 
 D. 2 and several others, including myself ; it was seen twice 
 at Dun Echt in 1877, and once by Hunt in 1878. Gledhill, 
 Ward, and Bazley have also witnessed this curious but not 
 difficult phenomenon, which Banks saw with 2|-in. as easily 
 as the shadow of I on Jupiter. 3 lapetus is not small, though 
 
 1 W. H. Pickering's micrometric measures of Titan and Ehea in 
 1892, combined with the photometric measures of all the Satellites, 
 supposed all to have the same reflective power, give the following 
 dimensions at the mean distance of Saturn 
 
 Satellite. Miles. Diameter. Magnitude. 
 
 Mimas 600 o"-i5 12-5 
 
 Euceladus ... ... ... 800 -18 12-3 
 
 Tethys 1200 '28 11*4 
 
 Dione noo -27 11*5 
 
 Ehea 1600 -35 io-S 
 
 Titan 3000 70 9-4 
 
 Hyperion 400 'io 137 
 
 lapetus (maximum) ... 1200 o"-28 11-4 
 
 2 This observer also witnessed the immersion of Titan in the 
 planet's shadow. In 1892, January 4, an eclipse of Rhea was seen 
 with 6.^-in. refractor by Kev. A. Freeman. The close conjunctions of 
 pairs of the satellites are very pretty objects when the ring is nearly 
 edgewise ; sometimes one is then occulted by another. 
 
 3 The shadows of every satellite, except Hyperion and lapetus, 
 were observed several times each by Rev. A. Freeman and A. 8. 
 Williams in 1892 with refractor and reflector of e.|ual apertures, 6 in. 
 
SATURN. 203 
 
 probably, from a spotted surface and rotation like our Moon, 
 not always equally visible, being much brightest at his W. 
 elongation. 1 Rhea, Dione, and Tethys are more minute. 2 
 D. considers Tethys superior to Dione. 3 Kitchiner states, 
 from a friend, that, by hiding the planet, they have been 
 seen with 2 T 7 v -in. aperture; Capron has seen them with 
 3^-in. ; Banks has seen four with 2|-in. ; Grover two, with 
 only 2-in. ; 3! or 4 in. may be expected to show all five. 
 The three smaller are easier when further from the planet, 
 but they only depart from it respectively 9-6, 6-9. and 5*4 of 
 its radii. ^ could follow all then known up to the disc. 
 Schr. found them variable, like lapetus, but brightest to- 
 wards E. instead of W. $ has seen 7 brighter than 6. 
 The inclination of their orbits, nearly similar to that of the 
 ring, by spreading them over the sky, increases the difficulty 
 of distinguishing them from small stars in one night's obser- 
 vation ; and hence, probably, many mistakes have been 
 made. To a spectator placed on Mimas, revolving in less 
 tlian 23 h at a distance of only 32,000 miles from the edge of 
 A, the whole system of rings and the included globe would 
 float before the eye in such a spectacle of grandeur and 
 beauty as the imagination is wholly unequal to conceive. 
 
 1 The change, according to $, is equivalent to that from 2 to 5 m&. 
 Cassini had found it uncertain. So Banks, 1866. A confusion exists 
 in some writers as to the relative size and variable light of this 
 satellite and Titan. Pickering gives 11 '4 and 12*7 as the max. and 
 miu. m. of lapetus. 
 
 2 That Cassini with his inferior means should have not only dis- 
 covered them, but traced their periods, reflects great credit upon his 
 ability; it is gratifying to be able to subjoin the striking encomium 
 ofhisEloge: Les cieux qui racontent la gloire de leur Createur 
 n'en avoient jamais plus parle a personue qu'a lui, et n'avoient jauiais 
 uiieux persuade.' 
 
 3 Occasionally, though rarely, Dione is as bright as Tethys. 
 
204 THE SOLAR SYSTEM. 
 
 URANUS AND NEPTUNE. 
 
 THESE planets may be reached, but to no great purpose, with 
 ordinary means. URANUS, being visible in clear weather to 
 the naked eye, will be easily caught up in the finder by the 
 help of the almanac, and will be large and planetary-looking 
 in the telescope ; its disc indeed subtends less than 4", but 
 I never found the light of 3 T 7 ^-in. sufficient to define it 
 perfectly ; 5^-in. dealt far better with it : with Lawson's 7 -in. 
 object-glass, bequeathed to the Greenwich Naval School, I 
 have seen it beautifully, as a little Moon : no one has made 
 out much more : M. has seen it elliptical, and measured the 
 flattening : La. with his 2 -ft. speculum, and in the sky of 
 Malta, once thought it possible there might be a spot: 
 Buff ham (1870-1) considered that he succeeded in detecting, 
 with a 9~in. With mirror, white spots, portions probably of a 
 discontinuous belt, from which a rotation from N. to S. might 
 be imagined. The 26^-in. Washington achr. finds nothing, 
 but the Bothkamp n|-in. achr. has shown a lighter speck on 
 the N. limb of the sharp sea-green disc. 1 The two rings 
 suspected by $ have long been abandoned, and La. has 
 reduced the satellites to 4, which even the 5^ in. object- 
 glass of Smyth was incapable of reaching. Ward, however, 
 has glimpsed the two outer ones, Oberon and Titania, with a 
 4 T 3 -in. Wray achr., as Huggins has with 8-in. achr., and 
 Sadler with a 6^-in. mirror. My less acute eye has just 
 caught one with 9|-in. speculum. Marth has found their 
 visibility not affected by moonlight. Huggins and Se. differ 
 as to the details of its spectrum, but it is unquestionably a 
 very extraordinary one, crossed by 6 broad absorption-bands, 
 
 1 Young, with 23-rn. achr. at Princetown, and Perrotin with the 
 3o-in. at Nice, have seen belts. Henderson has seen a bright equa- 
 torial zone with io^-in. reflector. 
 
COMETS. 205 
 
 one corresponding with hydrogen, the rest of unknown 
 character. 
 
 NEPTUNE may be found in the same way, but will hardly 
 repay the search : I have several times seen him with my 
 5$- in. achr., but dull and ill-defined ; neither indeed would 
 the great instruments of Se. or Yogel give him a sharp con- 
 tour. His satellite, supposed by some to be the largest of its 
 class, and held by D. with 8-in. achr., no common telescope 
 of course would touch ; though Ward has glimpsed it with a 
 4^-in. achr. But who can say how grand a spectacle this 
 inconspicuous globe might present on a nearer approach ? or 
 what mysteries might be developed in a spectrum much 
 resembling, according to Se., that of Uranus ? or that he is 
 the most distant planet that obeys our central Sun ? or what 
 unexplored wonders may lie in still remoter space ? * Quis 
 unquain exhaustas dixerit coeli copias ? ' l The advance of 
 optical power may be expected either to open up fresh 
 marvels, or prove to us that, as far as the dominion of our 
 own Sun is concerned, we have reached the boundary of 
 our knowledge. 
 
 COMETS. 9 
 
 " Thou wondrous orb, that o'er the northern sky 
 Hold'st thy unwonted course with awful blaze ! 
 Unlike those heavenly lamps, whose steady light 
 Has cheered the sons of earth from age to age, 
 Thou, stranger, bursting from the realms of space 
 In radiant glory, through the silent night, 
 
 1 Bianchini. 
 
 9 The new matter and the chapter on Meteorites is by Mr. Denning. 
 
20(5 THE SOLAR SYSTEM. 
 
 Thy tresses streaming like the golden hair 
 Of Atalanta, or that beauteous maid 
 Pursued by Phoabus, upward shalt invite 
 Many a dull brow unus'd on heav'n to turn, 
 And many a bosom rend with deep alarm. 
 
 Where is tliy track throughout the vast expanse 
 
 Still onward hast thou urged thy bold career, 
 
 From that first hour when the Creator's hand 
 
 Impell'd thy fire along the fields of light, 
 
 Nor ever yet arriv'd within the verge 
 
 Of mortal ken, nor drank the distant beams 
 
 Of our inferior sun, unask'd by thee 
 
 To guide thee harmless on thy rapid way." 
 
 KEY. JOHN WEBB (1811). 
 
 WHEN Kepler stated his belief, not merely that comets in- 
 habited the aether as fishes the ocean, but that the ocean 
 was not fuller of fishes than the asther of comets, 1 his con- 
 temporaries probably amused themselves with his luxuriant 
 fancy. Yet Kepler was not so far wrong as regards number ; 
 for it is now believed that upwards of 10,000 2 have approached 
 the Sun within the orbit of Mars during the Christian aera. 3 
 A twelvemonth seldom passes by, in these days of telescopic 
 activity, without the announcement of several ; 1858 produced 
 
 1 * Nee minus setherem cometis refertum esse puto, quam oceanum 
 piscibus. Quod autem rari apparent nobis, ingens setheris vastitas in 
 causa est.' 
 
 2 Of late years new comets have been discovered at the rate of 
 nearly 5 annually. It is clear, therefore, that if we make an allow- 
 ance for those which have escaped observation, the rate per century 
 has been at least 600, and the aggregate number of comets during 
 1893 years, considerably upwards of 10,000. 
 
 3 The probable number of comets, it' we suppose the perihelia of 
 these bodies to be equally dispersed within the orbit of Neptune, has 
 been calculated as 17,558,424. An investigation by the late J. Kleiber 
 as to the mean number of comets always present in the solar system 
 gives the figures 5934 ! See AsL Nach., No. 3104. 
 
COMETS. 207 
 
 8, and sometimes 3 and even 4 (as in Feb. 1845) have been 
 in sight at once : l but conspicuous ones are far from 
 common. The generality are faint, and so much alike, at 
 least in ordinary telescopes, that they offer little attraction 
 beyond the curiosity of watching their progress : this, where 
 there are stars for sky-marks, may be sometimes traced from 
 hour to hour, and, in connection with the enormous distances 
 traversed, gives a grand idea of the majestic movements of 
 the universe. But larger comets are often equally imposing 
 to the naked eye and marvellous in the telescope ; of which 
 we had a splendid instance in * the Donati,' or, in astrono- 
 mical language, Comet VI, 1858 that is, the 6th in order of 
 that year and again in the less beautiful, but in some 
 respects more impressive, Comet II, 1861 : while Comets III, 
 1860, and II, 1862, were not less worthy of notice foi 
 peculiarity of structure; and the ' Coggia ' of 1874, by the 
 brilliancy of its star-like nucleus, and the complexity of 
 its intersecting envelopes, distinguished itself above its 
 congeners through many previous and successive years. 2 It 
 would lead us into too wide a field, as well as one already 
 cultivated by abler hands, 3 were we to describe separately 
 
 1 During the last week in November, 1892, no less than 7 were 
 visible ! 
 
 2 More recently Comet III, 1881, presented a fine effect in the N. 
 sky during the summer months of that year, and in the autumnal 
 mornings of 1882 a large comet, with a beaded nucleus and a tail of 
 22, formed an object of intense interest. At perihelion the latter 
 comet .may be said to have grazed the sun's surface (like the bright 
 comets of 1680, 1843, and 1880), and actually made a transit acros? 
 the solar disc on Sept. 16, but it was quite invisible in that position, 
 hence Pastorff's observation of 1819 is disproved. 
 
 3 See Hind's excellent treatise, The Comets (1852), and Bond's 
 Account of Donates Comet, Cambridge, U.S., 1858 ; but especially 
 his admirable Memoir in Annals of Observatory of Harvard College, 
 
208 THE SOLAK SYSTEM. 
 
 the more remarkable of these bodies ; it will be better, 
 therefore, to sketch a general outline, which may serve to 
 direct our expectations in future. First, however, we will 
 give directions for finding them, when invisible to the 
 naked eye. 
 
 If a comet is too faint to be readily perceived by moving 
 about, over the proper quarter of the sky, a hand telescope 
 with a large field (an opera glass may answer well), we must 
 take our larger instrument and ' sweep ' for it thus : ascertain 
 its probable position not, of course, at the date of discovery, 
 but at the time of the search, if the announcement gives a clue 
 to it ; put in the lowest eye-piece, point the telescope some 
 distance below, and on one side of, the supposed place of the 
 comet, and gently move it horizontally right or left, as the 
 case may be, till it points about as much on the other side. 
 When your first ' sweep ' has been thus completed, raise the 
 telescope vertically half the breaith of the field, or not much 
 more (as a faint object too near the top or bottom might be 
 missed), and sweep back again the same distance the reverse 
 way, ending pretty nearly where you began but of course 
 half a field higher ; raise again another half-field, and sweep 
 on, till either the comet sails across the field, or you are evi- 
 dently pointing much too high for it : in which case you may 
 conclude that it is too faint for you, or has gone away so far 
 as to make further search useless. The movement may, of 
 course, as well be begun above as below the supposed place 
 of the comet. This process of sweeping is equally available 
 for finding Mercury or Venus in the daytime, or minute stars 
 or nebulas at night ; the chief difficulty lies in so proportion- 
 ing the vertical movement that the object shall not escape 
 
 iii. Pingre consulted 616 authors for his Cometographie (1783) ; 
 and there were, in 1841, 382 works on the subject in the Poulkova 
 library. 
 
COMETS. 2O9 
 
 between the sweeps ; this is easy with rackwork, as the 
 breadth of the field, and the suitable number of turns of the 
 handle, may be previously ascertained by trial on a terrestrial 
 object ; with a plain stand there is little trouble in it where 
 stars occur frequently to guide the displacement of the field ; 
 but by day, or in twilight, or in barren tracts of sky, sweep- 
 ing without rackwork is less certain, and may require to be 
 repeated. 
 
 The light of most comets is too faint for high powers, and 
 demands a contrast with the dark sky which small fields do 
 not admit : to get the whole extent of head or tail the lowest 
 power should be chosen, and for the tail the naked eye will 
 be more effective than any glass, except the appropriate instru- 
 ment called a comet-finder : l high powers may be used for the 
 details of the nucleus, but the contraction of the field and the 
 want of contrast must always be allowed for. Small comets 
 are frequently nothing but luminous mists without trains, 
 sometimes without central condensation ; as we ascend in the 
 scale, nuclei, trains, envelopes, and various anomalous appear- 
 ances succeed, depending probably upon diversities in the 
 constitution of the comets themselves, as well as on their 
 degree of approach to the Sun; even Venus was thought 
 to have influenced the aspect of ' the Donati/ as it passed 
 near her. In common language, a comet consists of head 
 and tail ; but we have to make a telescopic analysis, and shall 
 begin with 
 
 i. The Nucleus: the most luminous part, occupying in a 
 general sense the centre of the head. It is sometimes absent 
 in telescopic comets, which are mere fogs, permitting the 
 minutest stars, even such as would be effaced by the slightest 
 terrestrial mist, to be seen through the very centre ; thus 
 
 1 An opera-glass is also strongly recommended for these 
 observations. 
 
 VOL. I. P 
 
210 THE SOLAK SYSTEM. 
 
 H. saw a group of 16 and 17 m g . stars throngli the heart 
 of the comet of Biela in 1832 : from this diffused state they 
 present every stage of condensation, including sometimes a 
 sparkling or granulated appearance, up to the aspect of a 
 star, which has occasionally, as in 1 744, equalled Venus in 
 brightness, and been visible to the naked eye in broad noon- 
 day, or, as in 1843, blazed out yet more splendidly like a 
 bright white cloud, close to the glowing meridian Sun. 1 
 High powers, however, usually dissolve any apparent solidity, 
 and different instruments may give very different sizes to 
 what looks like a planetary disc, throwing much doubt upon 
 its reality : sometimes a very minute point (as IjJ found in 
 1807 and 1811) holds out against any magnifying ; and such 
 was the case again in 1862, when it remained a point at 
 Poulkova, under a power of 1458 ; and this like broader 
 nuclei is not always central in the head. In some comets 
 (1618, 1652, 1661, 1707, Winnecke's 1869, III, 1882, etc.) 
 the nucleus seems to have been composed of separate masses, 
 a marvellous structure ; ' 2 would that we could often study 
 
 1 Other comets visible by clay (omitting some questionable 
 ones): A.C. 43, the star of 'the mightiest Julius,' which appeared 
 during the games held soon after his assassination, and gave rise 
 to the star on the forehead in his coins and statues; 1106, 1402, 
 1577 (Tycho's great comet), 1618. That of Feb. 1847 was seen by 
 Hind, and that of Aug. 1853 by Hartnup and Schmidt very near 
 the Sun ; but in each case with the telescope, in which they showed 
 planetary discs. Donati's comet was not visible, except with very 
 powerful instruments, by day. In 1882 two comets were observed 
 when close to the Sun. Comet Wells (I, 1882) was seen by Schmidt 
 on June 10, when only 2 0- 8 from the Sun's limb and the great comet 
 of the following autumn was watched until it entered upon the Sun's 
 disc on Sep. 16. In these cases telescopes were necessarily used. 
 
 2 There is a strange story of visible internal movement among 
 these subordinate nuclei in 1618 as if of coals stirred in a fire. 
 This seems like a bad telescope or an alarmed observer yet where 
 
COMETS. 211 
 
 it with modern advantages! Had 'the Donati's' nucleus 
 passed about 20' further N., it would have gone right over 
 Arcturus- and we might have obtained some negative in- 
 formation at any rate as to its composition. Miss Mitchell 
 alone seems to have caught what seemed the central transit 
 of a comet (1847) over a 5 m g . star, which shone through it 
 unchanged. Still, were the nucleus a mere point, it might 
 have been only a very close appulse ; and some minor ex- 
 amples are less conclusive. 1 Hirst, however, at Sydney, 
 witnessed what appeared a good instance, when Encke's 
 comet passed directly over one of two neighbouring 10 m g . 
 stars, affording an excellent criterion of absolutely un- 
 changed light. Were a denned phasis to show itself, a 
 certain amount of density might be inferred ; but if we 
 except ' the Donati ' as seen by D. in daylight, Oct. 8, this 
 has never been satisfactorily the case, as the retroverted form 
 often assumed by luminous sectors throws a doubt upon the 
 observations. The darkness close behind the nucleus in 
 1858, if not real shadow, seemed at least to prove that the 
 nucleus was not permeable to the solar energy, in whatever 
 way exerted, and that it had no rotation upon an axis. The 
 arrival of the next great comet will be a season of absorbing 
 interest, as we shall be much better prepared for its reception. 
 The spectrum analysis, first of Donati, subsequently of 
 Huggins, Se., and several others, has shown not only the 
 native light of the comets which have appeared since its 
 
 all is mystery, neither credulity nor its opposite is the part of 
 wisdom. 
 
 1 Donati saw a 7 m^. star enlarged so as to show a sensible disc, 
 when the nucleus of Comet III, 1860, passed very near it. Stars are 
 said to have started, or become tremulous, during occultation by 
 comets. Birmingham observed the comet of Encke illuminated by 
 a star over which it passed, 1868, Aug. 23; and Klein in 1861 re- 
 marked an exceptional twinkling in 5 ra^'. stars involved in the tail. 
 
212 THE SOLAR SYSTEM, 
 
 employment, bnt what had been little anticipated, theii 
 gaseous character, and the close resemblance of the majority 
 of their spectra to those of some of the compounds of carbon. 
 There can now be little doubt that such is the general con- 
 stitution of these bodies : but probably with much variety 
 in composition, as the acknowledged difference in colour 
 makes sufficiently evident ; and the nature of the nucleus is 
 still incomprehensible. 
 
 2. The Coma is the sphere of mist around the nucleus, 
 forming in popular language the head: this is sometimes of 
 considerable extent 2 40', or 5 times the Moon's diameter, 
 in 1770, when the nearest recorded approach of a comet to 
 the Earth took place, of i J million of miles. The coma fades 
 away into the surrounding sky, with an outline, including 
 that of the commencing tail, usually considered parabolic ; 
 Bond, however, found in 1858 that its section approached 
 much more nearly to a catenary curve. Its denser part, if 
 distinguishable by any set-off or outline, is called 
 
 3. The Envelope. This is an interior and brighter layer 
 of mist, suspended as an atmosphere around the nucleus, at 
 least where exposed to the sun : in Donati's comet some ob- 
 servers (amongst them myself) carried it a good way round 
 the back of , the nucleus ; but usually it turns straight off on 
 each side to form the commencement of the tail : within it is 
 sometimes a darker narrow band, separating it from another 
 interior and brighter envelope. 1 In 1858 no fewer than four 
 such dark spaces at once were sometimes shown by the great 
 achromatic at Cambridge, U.S., indicating the consecutive 
 rising of five shining waves, which had spread themselves in 
 succession outwards from the nucleus ; the latter seeming to 
 
 1 Huggins has made the important remark that these non- 
 luminous spaces may correspond to a condition of the vapour too 
 cool to emit light, and yet not condensed so as to reflect it. 
 
COMETS. 2 1 3 
 
 diminish in size and brightness after each of these emissions 
 of luminosity. M. at Dorpat noticed an actual increase of 
 one of these envelopes from 18" to 27" in 2 h . Occasionally, 
 as in 1861 and the * Coggia,' the nucleus appears not to 
 occupy the axis of some of these veils, which consequently 
 seem to cross one another in front of it. In 1811 the whole 
 coma and envelope were raised in one parabolic mass from 
 the nucleus, which was surrounded by clear dark sky on 
 every side: when the extreme diameter of the luminous 
 cloud amounted, according to Schr., to 947,000 miles, con- 
 siderably exceeding the bulk of the Sun, and almost doubling 
 the Moon's orbit. As this comet receded, the dark space 
 became indistinct, and the envelope sank finally down upon 
 the nucleus. Envelopes sometimes contain dark spots and 
 streaks (1858), and more frequently brushes or fans of light, 
 where the shining matter seems to stream out from circum- 
 scribed portions of the nucleus; these are rapidly variable, 
 and in Halley's comet at its return in 1835 showed such a 
 libration from side to side, traceable from hour to hour, that 
 Bessel inferred some powerful polar force unconnected with 
 gravity. Such a swinging was less distinctly recognised in 
 1858. In Comet II, 1862, in which these sectors or aigrettes 
 were very striking, Se. and Chacornac perceived, otherwise 
 than Schm. no motion of this kind, but thought that the jets 
 proceeded alternately from different parts of the nucleus. The 
 last observer found the light of the nucleus variable in- 
 versely as the breadth of the sector in 2*7 d., and that the 
 luminous matter ascended towards the Sun with a velocity 
 of nearly 2200 miles in a second. In Coggia's comet With 
 saw an evident oscillation one evening. The envelope and 
 coma together form the origin of 
 
 4. The Tail. This, when not greatly foreshortened, 
 appears as a long cylinder or more usually cone, widening 
 
214 THE SOLAE SYSTEM. 
 
 in general as it advances, and showing a hollow structure by 
 an interior darkness. There seems, however, a doubt of 
 the adequateness of the explanation ; * since the perspective 
 of 1858 required a very different proportion either of the 
 breadth or the intensity of the dark space : some other cause 
 may possibly be combined with vacancy to produce the 
 effect. This interval in the Donati was very dark close 
 behind the nucleus; Schwabe found it darker than the 
 twilight sky, and D. and Hartnup considered it a real 
 shadow: in 1811, however, such a vacancy surrounded the 
 nucleus on every side. The division into two streams 
 effected by it was seen with the naked eye in the great 
 comet of 1577, which astonished Tycho at his fishpond 
 before sunset, and it has been frequently noticed since the 
 discovery of the telescope; in 1843 ^ was absent; and a 
 brighter ray filled the middle when Halley's comet in 1835 
 was withdrawing from the Sun. The preceding stream 
 according to the comet's motion is usually brighter and 
 sharper defined, as well as curved backwards. Kepler 
 noticed this in 1618, and compared it in his own graphic 
 way to the appearance of a heap of corn swept over by the 
 wind in the threshing-floor : and no one will forget it who 
 saw the form of the Donati. 2 It has been usually referred 
 to motion through a resisting medium : but Pape, from an 
 elaborate investigation, finds that the curvature may be 
 explained by the combination of the comet's motion with 
 
 1 It appears probable, in the light of certain modern researches, 
 that the tail is due to electrical action. 
 
 2 Towards the close of its appearance, the American observers 
 noticed a reversal of the brightness and definition of the sides of this 
 comet's tail. They also found, contrary to the common opinion, that 
 the plane of its curvature was not identical with that of its motion : 
 Low this can be reconciled with Papc's theory does not appear. 
 
COMETS. 215 
 
 a repellant power in the Sun. The axis of the tail was 
 calculated by him to differ 6 18' from exact opposition to 
 the Sun, being left a little behind a -deviation of which 
 there have been previous examples. 1 The length of the tail 
 is sometimes enormous. According to Boguslawski, that of 
 the wonderful cornet which in 1843 nearly grazed the surface 
 of the Sun, and, as Se. expresses it, issued from it like a 
 dart of light, was cast away to the almost incredible extent 
 of 581 millions of miles 2 more than 6 times the distance 
 of the Earth from the Sun, and crossing the orbit of Jupiter ; 
 and this astounding stream, the longest object, as far as our 
 senses can reach, in all space, must have been shot out with 
 an equally inconceivable velocity after passing the perihelion ; 
 for, but a short time before, the head was on the other side 
 of the Sun, half round which it had been whirled in i^ h or 
 2 h , and under such circumstances the whole direction of the 
 same tail could not be supposed to have been reversed. 
 Even should the length be considered to be overstated, we 
 certainly have before us here one of the greatest marvels in 
 the universe. Minor trains are occasionally seen ; in some 
 cases (1769, 1811) the prolongations of an outer envelope; 
 in others apparently separate branches (1806, 1843); 
 according to Cheseaux, six of them, each hollow, formed a 
 glorious fan in 1744. A straight, long, narrow, and very 
 faint ray of this kind, directly opposite to the Sun, was seen 
 by several observers steadily preceding the great curved tail 
 in 1858.* The grand visitor of 1861 had a straight and a 
 curved tail, the latter of which probably swept over our 
 
 1 According to Schi., the tail of Comet III, 1862, was forced out 
 in a direction very different from that of the radius vector. The very 
 long train in 1769 was stated to have shown a double curvature 
 towards its end. 
 
 2 According to the then received solar parallax. 
 
2l6 THE SOLAR SYSTEM. 
 
 globe, or, according to Liais, buried it to a depth of 110,000 
 leagues. From certain periodical returns of lateral streams, 
 Dunlop in 1825 inferred a rotation of the tail 1 in 2o-| h , and 
 similar appearances were noticed in 1769, 1811, and 1862; 
 but the explanation is perhaps precarious, from the immense 
 velocity required. An additional stream has sometimes, 
 though rarely, been directed towards the Sun ; this extra- 
 ordinary phenomenon, called an anomalous tail, was noticed 
 in 1824, when it was longer and brighter, though narrower 
 and more tapering, than the usual one ; subsequently it was 
 found recorded that the grand comet of 1680 Newton's 
 comet had left a similar glowing wake upon the aether; 
 and it has since been noticed in 1845, 1848 (Encke's, 
 perhaps again in 1871), 1850, and i85i. 2 The principal 
 tail in 1858 was seen by the Americans crossed obliquely by 
 a number of brighter bands like auroral streamers, diverging 
 from a point between the nucleus and the Sun. 
 
 A few other details should be noticed. Coruscations or 
 flashings have been often remarked in the tail: that of 1556 
 was said to waver like the flame cf a torch in the wind ; and 
 numerous other instances might be given, before and since 
 the use of telescopes. The accurate Hooke took many pre- 
 cautions before he satisfied himself of their reality in 1680 
 and 1682, and Schr. stoutly maintained their existence in 
 1807, referring them to electricity or some analogous cause; 
 others negative them as too rapid for the progressive motion 
 of the light by which we should see them an objection, 
 however, applying only to foreshortened tails and treat 
 
 1 The details shown in Barnard's photographs of Swift's comet 
 (1892) appear to suggest that there was a rotation of the tail upon an 
 axis through the nucleus in a comparatively short period. 
 
 2 One of the three short rays, besides the tail, seen in 1577, may 
 possibly have been of this character 
 
COMETS. 217 
 
 them as illusions depending on our own atmosphere, or the 
 uncertainty of weary sight. Polarization experiments concur 
 with spectrum-analysis in discrediting their reality, by 
 showing that the denser portion of the tails, as well as comse, 
 shines in part by reflected light, owing probably, as Huggins 
 suggests, to the cooling of the incandescent material of the 
 nucleus. It would have added greatly to the interest of the 
 present pages, could they have embodied more satisfactory 
 results of spectroscopic research. But we are waiting for 
 favourable opportunities. 1 There seems no doubt, as we 
 
 1 These opportunities were afforded by the bright comets III, 1881, 
 IV, 1881 (Schseberle), I, 1882 (Wells), III, 1882, I, 1887, etc., and we 
 proceed to quote, chiefly from Mr. Plummet's reports, a few results of 
 spectrum analysis as given in the Monthly Notices and other publica- 
 tions: 'The spectrum of comet III, 1881, appeared to be continuous 
 with 3 bright bands in the yellow, green, and blue. Dr. Huggins 
 succeeded in photographing the spectrum of the comet which showed 
 2 groups of bright lines in the violet and a continuous spectrum. 
 IV, 1881, exhibited a spectrum consisting of 3 bright bands approxi- 
 mately coincident with the 3 brightest bands of the spectrum of the 
 Bunsen flame and a faint continuous spectrum. I, 1882, showed a 
 remarkable departure from the normal characteristics. Ever since 
 1864, when Donati first submitted a comet to this kind of examination, 
 the spectra of these bodies had revealed the bands of hydro-carbon, 
 but in this instance there was a striking deviation from the ordinary 
 type. This was indeed so marked on April 21 that the cometary 
 nature of the object would scarcely have been identified by its 
 spectrum. At the close of May a bright sodium line in the nucleus 
 and envelope was detected at Dun Echt. Early in June, when the 
 comet was at its brightest, this line tinder adequate dispersion was 
 seen to be louble, and the behaviour of the more refrangible line 
 indicated tc Professor Vogol that the density of the incandescent gas 
 was very great. Ill, 1882. It is curious to notice that while the 
 spectrum of I, 1882, was continuously observed as the comet approached 
 the Sun, and illustrate 1 the effects of great and increasing excitement, 
 the spectrum ;f III, 1882, could only be observed as it receded from 
 perihelion, and consequently the phamoinena that were observed in 
 regard U) I, 1882, might be expected to repeat themselves in III, 1882, 
 
218 THE SOL AH SYSTEM. 
 
 have said, that the materials of the smaller comets aro of a 
 gaseous nature, generally, though not invariably, affording 
 spectra analogous to those of compounds of carbon. This is 
 sufficiently marvellous; but the still more curious inquiry 
 into the nature of the nuclei in the grander specimens 
 remains unsolved. The chief instance, that of the ' Coggia,' 
 to which it has as yet been applicable, has only increased 
 the mystery. The spectrum of this resplendent stellar point 
 was so far continuous as to prove unborrowed light ; so far 
 interrupted, especially at the red end, as to indicate emission 
 or absorption by materials wholly unknown. Possibly some 
 more intelligible disclosures may be in store for us. But 
 even should we be permitted to lift partially in some special 
 instance the veil, we are still confronted by those differences 
 of colour which appear to indicate a difference of constitution. 
 * Omnia incerta ratione, et in naturae majestate abdita.' l 
 
 As regards colour, a wide margin must no doubt be left 
 for the superstition of the ancients, who dreaded the herald 
 
 but in the reversed order, and this to a great extent actually occurred. 
 When first examined on Sept. 18 the sodium lines were at once seen to 
 be distinctly double, both in the nucleus and outlying material, while 
 a number of other bright lines, coinciding with the more prominent 
 iron lines were visible. There was no indication of the usual banded 
 spectrum. When the comet had reached the Earth's distance from 
 the Sun, all trace of the sodium lines had vanished, and the 3 bands 
 of hydro-carbon were distinctly present. The full explanation of the 
 phenomena witnessed cannot be found in the simple increase or 
 decrease of temperature depending on the interval separating the 
 comet from the Sun, but a satisfactory solution may be found if we 
 suppose that cornetary light is to some extent due to electric discharges. 
 The spectrum of Holmes' s comet on Nov. 18, 1892, did not show the 
 ordinary bands, but appeared to be continuous through a considerable 
 portion of the green, and this would seem to indicate that the comet 
 shines by reflected sunlight only. 
 1 Seneca. 
 
COMETS. 219 
 
 of disaster, * terris mutantem rcgna cometen,' l and held it 
 as a malignant genius that 
 
 from his horrid hair 
 
 Shakes pestilence and war. 
 
 Those who noticed the fiery hue of the sabre-like comet that 
 passed to the E. at the commencement of the Crimean war 
 will understand with what feelings our fathers would have 
 gazed upon it, like the astonished spectators of the comet of 
 the Norman Conquest, represented in the Bayeux tapestry 
 with the inscription ' Isti mirantur stellam : ' nor will the 
 exaggeration of those beautiful lines seem unnatural, 
 
 Liquida si quando nocte cometae 
 
 Sanguine! lugubre rubent. 2 
 
 It is however certain, both from the Chinese and modern 
 observations, that there is much difference in respect to 
 colour : 3 $ even found the nucleus of the same comet 
 (1811) pale ruddy, the envelope greenish or bluish green: 
 and a similar contrast was noted by Struve in Halley's comet 
 in 1835, and by Winnecke in 1862. That the Sun induces 
 in them a polar force superior to that of gravitation the 
 hypothesis, in the main, of Olbers is most probable from 
 the form of the envelope and tail, as if repelled alike from 
 
 1 Lucan. The 'comet-dollars' still existing in Germany are a 
 curious evidence of this feeling as late as 1664. See Illustr. Lond. 
 Aew?s, July 20, 1861. 
 
 2 Virgil. 
 
 3 This comes out well chemieally. The *Donati' was photo- 
 graphed: with Comet II, 1861, it was found impossible even by De 
 la Kue. Several recent comets have been very successfully photo- 
 graphed. Jansen and Draper obtained some excellent photo- views 
 of III, 1 88 1, which exhibited many interesting features in the 
 structure of the envelope and tail. Some beautiful photographs 
 of Swift's comet of 1892, by Barnard, are reproduced in Knowledge 
 for December of that year. 
 
220 THE SOLAB SYSTEM. 
 
 the nucleus and Sun: and that a certain portion of the rarer 
 be disripatpd during the perihelion passage is 
 from the very aspect of a tail such as that of 1858, 
 whose restoration to the rapidly advancing nucleus is, to 
 our iinniitiiniiimij an impossibility. And in this, and in the 
 resistance which comets which, traverse the solar ffflinna may 
 be presumed to suffer, we find sufficient indications that our 
 system was not made to be eternal. The perfect balance of 
 its construction might at first lead to another impression, 
 and seem to countenance the old objection, that 'all things 
 maiinni* as they were from the beginning of the creation.' 
 But here is evidence to the contrary slight, but decisive 
 symptoms flat 'they all shall wax old as doth a garment;' 
 that they 'shafl be changed,' The traces of dissolution may 
 be perceived in the comet of Biela, whose separation into two 
 parts is one of the marvels of modem astronomy. 1 Single 
 in all previous observed returns (those of 1772, 1805, 18267 
 1832), in 1846 it became elongated, and then threw off a 
 portion which increased till it rivalled and even tat a short 
 tne iiiijiMird it* parent, each having at one period a starry 
 and short tail, while they were connected by faint 
 of Kgbt : and th*s they continued in sight for more 
 3 months, keeping a distance of something more than 
 the companion being the first to vanish. 
 1 852, the distance was more than 
 
 feittfcr ndwkwty i 
 to itedi*- 
 MM/vcd (ly Sefrttrkfty 
 
222 THE SOLAR SYSTEM. 
 
 METJEOES. 
 
 Their Cometary Relations. These phenomena have ac- 
 quired a special interest in recent years, and their astronomi- 
 cal origin and associations have been placed beyond doubt. 
 The identity of several well-known meteor-systems with 
 periodical comets was shown by the researches of Newton, 
 Schiaparelli, and others, about a quarter of a century ago, 
 and the singular behaviour of Biela's comet, and its resultant 
 meteor stream of Andromedes on November 27, 1872 and 
 1885, and November 23, 1892, form an interesting chapter 
 in the history of the subject. Four of the most brilliant 
 of the known meteor showers display a similarity of orbit 
 with the same number of well-observed comets, thus the 
 April Lyrids match with Comet 1, 1861, the August Perseids 
 with III, 1862, the November Leonids with I, 1866, and 
 the November Andromedes with Biela's lost comet. There 
 is also evidence of relationship between Halley's comet and 
 the May Aquarids, and a few other instances might be 
 quoted, though, it is perhaps surprising that comparatively 
 few such coincidences have been found among the very large 
 number of comets and meteor streams observed in past 
 years. 
 
 Difficulties of Observation. There is probably no other 
 department of astronomy standing in greater need of further 
 observational effort, and which requires more experience 
 and care on the part of those engaged in it. The practical 
 study of meteors brings us face to face with complications 
 and anomalies, which only the utmost accuracy and dis- 
 crimination can clear away. Apart, therefore, from the great 
 patience which the meteor-observer must exercise during 
 his prolonged vigils, he has to feel his way with extreme 
 
METEORS. 223 
 
 caution among a labyrinth of materials, and to weigh 
 every detail likely to assist him in gathering reliable results. 
 On every night of the year there are probably more than 
 100 feeble meteor showers in play, and many of these are 
 of such extreme tenuity that they may not yield individually 
 a single meteor in a continuous watch of 5 hours. Eadiant 
 points are sometimes thickly clustered together in the same 
 region of the heavens; and these facts require that an 
 observer, to be successful, must watch the sky during long 
 intervals, and that he must record the meteor flights with 
 invariable precision. If this is not done, pseudo-radiants 
 will be deduced, and the observations generally will be 
 almost worthless. Desirable accuracy can be attained after 
 a fair amount of practice, but one of the most difficult 
 features of the work is the apportionment of the individual 
 meteors to their respective radiants. It is necessary not 
 only to consider their directions of flight, but also their 
 traits of appearance, such as velocity, length of path, streaks 
 or trains. The meteors belonging to one and the same stream, 
 exhibit a family likeness which is often sufficiently pro- 
 nounced to enable them to be distinguished from other 
 systems. A vast amount of useful work remains* to be 
 accomplished in this field by ardent observers who will 
 gain, by experience, a just conception and knowledge of its 
 requirements. 
 
 Numbers Visible. Though the fall of meteors is incessant 
 it varies greatly in intensity. On the occasion of a periodical 
 shower, such as the Perseids with max. on August 10, 
 an observer may perhaps count about 100 meteors per hour 
 in a moonless sky. In the case of an exceptionally brilliant 
 and prolific display, such as that of the Leonids on November 
 12, 1833, 1000 meteors may be seen per minute. On 
 November 23, 1892, the Andromedes returned in such 
 
224 THE SOLAE SYSTEM. 
 
 abundance that an observer estimated the number falling as 
 1 08 per minute ! On ordinary nights, void of special showers, 
 the rate of appearance of these bodies is usually not more 
 than 10 per hour; and there are many dates, particularly 
 in the winter and spring months, which manifest a remark- 
 able scarcity, for the keenest watch will not reveal more 
 than 4 or 5 meteors per hour. The last half of the year 
 furnishes nearly double the number visible in the first half, 
 and in the morning hours at any season, the apparitions 
 greatly exceed those in the evening. 
 
 Their Velocities. The apparent velocity with which these 
 bodies enter our atmosphere varies between about 10 and 
 45 miles per second. The Andromedes of November 23 and 
 27 supply an example of the slow-moving class, while the 
 Leonids of November exemplify the swifter kind. The 
 former descend gradually, like snow-flakes in a calm, and 
 they generally throw off yellowish trains of sparks ; the 
 latter traverse their paths with terrific speed, and are 
 often too transient to be well seen, but they furrow the sky 
 with lines of phosphorescence, and these enable their paths 
 to be registered with great accuracy. Appendages, such as 
 trains, streaks, etc., doubtless represent the incandescent 
 and nearly exhausted material torn off from the nuclei 
 during their rapid combustion and flight through the air. 
 
 Elevation. The average heights of meteors during visible 
 combustion is about 76 miles at first appearance and 51 
 miles at disappearance. But large meteors (often termed 
 fireballs or bolides) generally penetrate much deeper into 
 the atmosphere than the ordinary shooting-stars, for while 
 the mean elevation of the former at extinction is only 30 
 miles, that of the latter is 54 miles. Occasionally the 
 material of a fireball is sufficiently large and compact to 
 resist total disruption, and falls upon the earth. Many 
 
METEOKS. 225 
 
 instances are on record, and the British Museum contains 
 numerous specimens of these aerolites. A few meteors 
 have been seen which were certainly more than 150 miles in 
 height at the earliest stages of their apparitions, and this 
 implies a far greater depth of atmosphere than what is 
 commonly supposed. 
 
 Stationary and Moving Radiant Points. There are some 
 anomalous facts concerning star-showers generally which 
 require much further study. The active duration of a large 
 proportion of the known radiant points appears to extend, 
 in possibly an intermittent manner, over several months, 
 during which they maintain an absolutely stationary position 
 amongst the stars ; and this is obviously incompatible with 
 theoretical views of the matter, which require a displacement 
 of about i per day to the eastwards. Such displacement 
 was discovered at Bristol in 1877 to affect the great 
 Perseid display of July-August, and the fact was strik- 
 ingly corroborated on mathematical grounds by the late 
 J. Kleiber, 1 whose early death is an irreparable loss to this 
 branch of astronomy. The radiant point of the Perseids is 
 in activity during a period of more than a month, for the 
 oncoming of the shower is usually announced by a few 
 brilliant streak-leaving meteors in the second week of July, 
 and the mobile focus of their divergence only attains 
 quiescence in the third week of August. The exact duration 
 of the shower is, however, not known, and further observa- 
 tions are required to determine it. There are many other 
 showers visible from Perseus and the region near in August, 
 and the meteors belonging to these are liable to be confused 
 with the true Perseids. The following ephemeris may 
 perhaps be useful as a guide and means of reference for 
 future observers of this rich annual shower : 
 1 Monthly Notices, March, 1892, p. 341. 
 
 Q 
 
226 
 
 THE SOLAR SYSTEM. 
 
 
 Radiant. 
 
 
 Radiant. 
 
 Date. 
 
 Degrees. 
 R.A. Dec. 
 
 Date. 
 
 Degrees. 
 R.A. Dec. 
 
 July 19 
 
 19 + 51 
 
 AugUbt 2 
 
 36 + 55 
 
 21 
 
 22 +52 
 
 4 
 
 38+ q6 
 
 23 
 
 25 + 52 
 
 6 
 
 40 + 56 
 
 25 
 
 27 + 53 
 
 s 
 
 4 2 + 57 
 
 , 27 
 
 30 + 54 
 
 IO 
 
 45 + 57 
 
 *. 29 
 
 32 + 54 
 
 12 
 
 47 + 57 
 
 v 31 
 
 24 + 55 
 
 H 
 
 50 + 57 
 
 Observations. Meteors should be recorded according to 
 the R.A. and Dec. of the points of their appearance and 
 disappearance. Their paths, as seen in the sky, should be 
 mentally noted with reference to the stars near, and then 
 on projecting them on a celestial globe or suitable star map, 
 the fundamental points may be read off and entered in a 
 MS. catalogue. When two observations of the same object 
 are secured at different stations, it becomes easy to determine 
 its real path, including its locality and height above the 
 earth's surface, its radiant point, etc. But it unfortunately 
 happens that multiple observations of bright meteors (such 
 as that seen on January 4, 1893, 6 h 30, which lit up the 
 sky and the country with a strikingly luminous effect) are 
 too loosely and imperfectly described to be of consequence. 
 Many fireballs are thus lost to science ; their transient glories 
 apparently serve no other end than that of startling spectators 
 who are fortunate enough to witness them. This is much 
 to be regretted, for the proper discussion of such phenomena 
 from reliable data would soon furnish significant evidence 
 as to the positions and durations of meteor showers. 
 What would accelerate the development of our knowledge 
 of fireballs more than perhaps any other circumstance, 
 
METEOKS. 227 
 
 would be the general attention of astronomical and meteoro- 
 logical observers, could we direct it, to the accurate descrip- 
 tion of the more salient features of these bodies. In a 
 word, if observers made it an invariable custom to record 
 objects of this kind, we should soon possess a store of 
 valuable facts to work upon, and the comparatively barren 
 record of the last few years might be succeeded by a chrono- 
 logical list of meteoric apparitions at the close of each year, 
 with all essential details given for comparison with past 
 and future records. 
 
 Catalogue of Eadiant Points. Subjoined is a list of 100 
 radiants selected from Mr. Denning's paper in Monthly 
 Notices, vol. 1. pp. 410-67. The table includes many of the 
 most important showers of the year, and the dates given are 
 those of the observed maxima. Some of these displays are of 
 extremely variable intensity. In one year they may yield 
 a plentiful supply of meteors and in the next be utterly 
 invisible. But the Perseids, Orionids, Geminids, and others 
 of similar type, are conspicuously numerous every year at 
 their appointed times, while others like the Andromedes 
 may be only seen once in 7 or 13 years, or, like the Leonids, 
 only reappear at their best at intervals of about 33 years. 
 In 1898, between November 23 and 27, there will probably 
 occur a splendid display of the Andromedes, while on 
 November 14, of 1899, 1900, we may expect magnificent 
 returns of the Leonids. The latter shower is really visible 
 every year ; a circumstance which proves that its meteors 
 are distributed throughout the ellipse of which the orbit is 
 composed. But the displays observed in the years inter- 
 mediate between the maximum epochs are seldom con- 
 spicuous, and offer no comparison with the brilliancy of 
 such returns witnessed in 1799, 1833, and 1866. 
 
228 
 
 THE SOLAR SYSTEM. 
 
 Ref. 
 
 No. 
 D. 
 
 Date of 
 Max. 
 
 Radiant 
 Point. 
 Degrees. 
 It. A. Dec. 
 
 Approx. 
 Star. 
 
 Aspect of 
 Meteors. 
 
 Other Dates of Activity, 
 Remarks, etc. 
 
 i 
 10 
 
 Jan. 2 
 Jan. 5 
 
 230+53 
 140+57 
 
 44 Bootis 
 6 Ursa? Maj. 
 
 M. Sw. B. 
 
 Sw. F. 
 
 lich annual shower. 
 Small short meteors. 
 
 16 
 
 Jan. ii 
 
 220+13 
 
 f Bootis 
 
 V. Sw. K. 
 
 ?ov. 28. Dec. 5. 
 
 25 
 
 Jan. 17 
 
 295 + 53 
 
 X Cygni 
 
 SI. B. 
 
 Veil observed, 1877. 
 
 2 7 
 
 Jan. 19 
 
 261 + 63 
 
 Draconis 
 
 M. SI. 
 
 March 28, April 22, etc. 
 
 3 
 
 Jan. 22 
 
 208 + 8 
 
 X Libra? 
 
 V. Sw. K. 
 
 ''eb. 15, April 16, 22, etc. 
 
 31 
 
 Jan. 25 
 
 131 + 32 
 
 i Cancri 
 
 M. Sw. 
 
 tfov. 10, 23, Dec. 2. 
 
 34 ' 
 
 Feb. i 
 
 211 + 69 
 
 a Draconis 
 
 SI. 
 
 Jan. 9, Dec. 8. 
 
 38 
 
 Feb. 7 
 Feb. 15 
 
 74 + 43 
 236 + 11 
 
 a Auriga? 
 a Serpentis 
 
 81. 
 
 V. Sw. 
 
 Aug. 21, Sept. 12 22. 
 April 27 May 4. 
 
 39 
 
 Feb. 15 
 
 261 + 4 
 
 ft Ophiuchi 
 
 Sw. K. 
 
 Compare No. 153. 
 
 4 
 
 Feb. 16 
 
 167 + 5 
 
 r Leonis 
 
 Sl.K. 
 
 ^ov. 27, Dec. 12. 
 
 41 
 
 Feb. 20 
 
 181 + 34 
 
 Piazzi XII. 29 
 
 V. Sw. B. 
 
 Well defined, 1877. 
 
 43 
 
 Feb. 20 
 
 263 + 36 
 
 p Herculis 
 
 Sw. 
 
 Visible before sunrise. 
 
 45 
 48 
 
 Mar. i 
 
 Mar. 14 
 
 47 + 45 
 175 + 10 
 
 a ft Persei 
 ft Leonis 
 
 V. SI. 
 81. B. 
 
 Showers here July to Dec. 
 March 3, 4, Dec. 12. 
 
 58 
 
 Mar. 18 
 
 316 + 76 
 
 X Cephei 
 
 SI. B. 
 
 Oct. 4-17. 
 
 59 
 
 Mar. 23 
 
 190 + 20 
 
 35 Coma? B. 
 
 Sw. 
 
 Also 175 + 20 March 25. 
 
 60 
 
 Mar. 24 
 
 161 + 58 
 
 ft Ursa? Maj. 
 
 Sw. 
 
 Dec. 2 9. Precise. 
 
 62 
 
 Mar. 27 
 
 229 + 32 
 
 n Corona? B. 
 
 Sw. F. 
 
 Observed in 1887. 
 
 63 
 
 Mar. 28 
 
 263 + 62 
 
 C Draconis 
 
 SI. 
 
 July 29, Aug. 24, etc. 
 
 69 
 
 April 17 
 
 165-6 
 
 e Crateris 
 
 V. SI. 
 
 Dec. 1221. 
 
 73 
 
 April 1 8 
 
 213 + 53 
 
 v Bootis 
 
 Sw. 
 
 Jan. 29, June 26. 
 
 74 
 
 April 1 8 
 
 231 + 17 
 
 ft Serpentis 
 
 Sw. F. 
 
 April 20, 1885. 
 
 79 
 
 April 19 
 
 228-2 
 
 /JL Serpentis 
 
 SI. 
 
 Jan. 2 and 20. 
 
 102 
 
 April 20 
 
 270+33 
 
 104 Herculis 
 
 V. Sw. 
 
 Lyrids. Rich shower. 
 
 119 
 
 April 25 
 
 272 + 21 
 
 102 Herculis 
 
 Sw. 
 
 July 13, Sept. 26. 
 
 127 
 
 May i 
 
 239 + 46 
 
 v Herculis 
 
 Sw. 
 
 March 14, June 25. 
 
 T 33 
 
 May 5 
 
 254-21 
 
 B Ophiuchi 
 
 SI. 
 
 Meteors with long paths. 
 
 135 
 
 May 6 
 
 338-2 
 
 n Aquarii 
 
 Sw. K. 
 
 Fine annual shower. 
 
 139 
 
 May ii 
 
 231 + 27 
 
 a Corona? B. 
 
 SI. F. 
 
 Well defined in 1885. 
 
 142 
 
 May 14 
 
 3M + I5 
 
 f Delphini 
 
 Sw. K. 
 
 July 28 Aug. 13. 
 
 147 
 
 May 29 
 
 264 + 64 
 
 f Draconis 
 
 SI. 
 
 See 27, 63, 147. 
 
 148 
 
 May 30 
 
 333 + 27 
 
 i Pegasi 
 
 Sw. K. 
 
 Well defined shower. 
 
 
 June 7 
 
 247 25 
 
 ft Herculis 
 
 SI. B. 
 
 A fireball radiant. 
 
 J 53 
 
 June 10 
 
 261 + 5 
 
 ft Ophiuchi 
 
 V. SI. 
 
 Feb. 15 = D. 39. 
 
 156 
 
 June 13 
 
 310+61 
 
 Cephei 
 
 Sw. K. 
 
 June 4, Oct. 6 16. 
 
 
 June 15 
 
 291 + 52 
 
 K Cygni 
 
 SwF. 
 
 July 27 Aug. ii. 
 
 158 
 
 June 15 
 
 285 + 23 
 
 
 SI. 
 
 April 20. 
 
 169 
 
 June 20 
 
 335 + 57 
 
 3 Cephei 
 
 Sw. 
 
 July 19, Aug. 25, etc. 
 
 176 
 
 June 28 
 
 294 + 39 
 
 a Cygni 
 
 SI. F. 
 
 April 21, s2. 
 
 179 
 
 July 4 
 
 303 + 24 
 
 24 Vulpecula? 
 
 Sw. 
 
 April 20, May 30, etc. 
 
 198 
 
 July ii 
 
 349+53 
 
 7 Andromeda? 
 
 Sw. 
 
 Aug. 17 = D. 410. 
 
 228 
 
 July 19 
 
 314 + 48 
 
 a Cygni 
 
 Sw. F. 
 
 Aug. 22. Cygnids. 
 
 236 
 
 July 22 
 
 16 + 31 
 
 ft Andromeda? 
 
 Sw. K. 
 
 Aug. 24, Nov. 5. 
 
 242 
 
 246 
 273 
 284 
 
 July 23 
 July 25 
 July 28 
 July 29 
 
 301-14 
 48 + 43 
 339-12 
 269 + 49 
 
 a Capricorni 
 a ft Persei 
 8 Aquarii 
 7 Draconis 
 
 V. SI. 
 Sw. B. K. 
 SI. B. 
 Sw. 
 
 July 17 and 28. 
 Aug. 4, Sept. 15, Nov. 13. 
 A conspicuous shower. 
 June 17, Sept. 18. 
 
 286 
 
 July 30 
 
 6 + 35 
 
 r Andromeda? 
 
 Sw. K. 
 
 Aug. 21, Oct. 5 8. 
 
 322 
 366 
 
 Aug. 4 
 Aug. 10 
 
 30+36 
 45 + 57 
 
 ft Trianguli 
 n Persei 
 
 Sw. K. 
 V. Sw. K. 
 
 Sept. 21, Dec. 4, etc. 
 Perseids. Fine shower. 
 
 403 
 
 Aug. 16 
 
 61+48 
 
 M Persei 
 
 V. Sw. K. 
 
 Aug. 24, Sept. 5, 21. 
 
 407 
 
 Aug. 17 
 
 292 + 52 
 
 K Cygni 
 
 Sw. B. 
 
 Jan. 17, Aug. 4, 5. 
 
 424 
 
 Aug. 21 
 
 73 + 41 
 
 a Auriga? 
 
 V. Sw. K. 
 
 Sept. 22, Oct. 2, etc. 
 
METEORS. 
 
 229 
 
 Kef. 
 No. 
 D. 
 
 Date of . 
 Max. 
 
 Radiant 
 Point. 
 Degrees. 
 R.A. Dec. 
 
 Approx. 
 
 Star. 
 
 Aspect of 
 Meteors. 
 
 Other Dates of Activity, 
 Remarks, etc. 
 
 435 
 
 Aug. 22 
 
 291+60 
 
 o Dracouis 
 
 SI. T. 
 
 Rich shower in 1879. 
 
 448 
 
 Aug. 23 
 
 70+50 
 
 a Aurigai 
 
 Sw. K. 
 
 July 31, Oct. 20. 
 
 465 
 
 Aug. 25 
 
 S + io 
 
 7 Pegasi 
 
 SI. B. 
 
 July 31, Sept. 1922. 
 
 479 
 
 Aug. 29 
 
 292 + 70 
 
 d Draconis 
 
 Sw. K. 
 
 Aug. i, Dec. 1829. 
 
 487 
 
 Sept. 3 
 
 354+38 
 
 v Andromedae 
 
 V. Sw. 
 
 July 28 Aug. 10. 
 
 505 
 
 Sept. 7 
 
 62 + 37 
 
 e Persei 
 
 V. Sw. K. 
 
 Aug. 25, Nov. 29. 
 
 533 
 
 Sept. 15 
 
 48 + 44 
 
 a ft Persei 
 
 V. Sw. 
 
 July 25, Nov. 13, etc. 
 
 537 
 
 Sept. 15 
 
 77 + 57 
 
 1 6 Camelop. 
 
 V. Sw. K. 
 
 Sept. 21, Oct. 15. 
 
 568 
 
 Sept. 21 
 
 3i + i9 
 
 a Arietis 
 
 SI. T. 
 
 Aug. 12, Oct. 7 , etc. 
 
 574 
 58i 
 
 Sept. 22 
 Sept. 22 
 
 7+io 
 335 + 58 
 
 7 Pegasi 
 3 Cephei 
 
 SI. 
 SI. 
 
 July 31, Aug. 25, etc. 
 July 19, Aug. 25, etc. 
 
 577 
 
 Sept. 22 
 
 63 + 22 
 
 K Tauri 
 
 V. Sw. K. 
 
 Aug. 425, Nov. 20. 
 
 599 
 611 
 
 Sept. 27 
 Oct. 2 
 
 75 + 15 
 225 + 52 
 
 15 Orionis 
 44 Bootis 
 
 V. Sw. K. 
 SI. B. T. 
 
 Aug. 25, Sept. 9, 15. 
 Active shower in 1877. 
 
 615 
 
 Oct. 4 
 
 x 33 + 79 
 
 Piazzi IX. 37 
 
 Sw. K. 
 
 Aug. 2024. 
 
 619 
 
 Oct. 4 
 
 310 + 77 
 
 X Cephei 
 
 SI. F. 
 
 March 18, Oct. 17. 
 
 638 
 
 Oct. 8 
 
 77 + 31 
 
 /3 Tauri 
 
 V. Sw. K. 
 
 Nov. 7, Dec. 2229. 
 
 643 
 
 Oct. ii 
 
 13 + 6 
 
 e Piscium 
 
 SI. B. 
 
 Sept. 15, 30, Oct. 21. 
 
 644 
 
 Oct. ii 
 
 29 + 72 
 
 50 Cassiopeia? 
 
 SI. F. 
 
 Aug. 23, Sept. 15, etc. 
 
 654 
 
 Oct. 14 
 
 40 + 20 
 
 e Arietis 
 
 M. Sw. 
 
 Rich shower in 1887. 
 
 664 
 73 
 
 Oct. 14 
 Oct. 1 8 
 
 135 + 68 
 9 2 +i5 
 
 a Ursae Maj. 
 f Orionia 
 
 Sw. 
 Sw. K. 
 
 Sept. 1318, Oct. 8. 
 Orionids. Fine shower. 
 
 708 
 
 Oct. 20 
 
 45 + 6 
 
 aCeti 
 
 SI. 
 
 Oct. 22. 
 
 714 
 
 Oct. 20 
 
 106+12 
 
 /3 Canis Maj. 
 
 V. Sw. K. 
 
 Oct. 8, Nov. 12. 
 
 727 
 
 Oct. 29 
 
 109 + 23 
 
 5 Geminorum 
 
 V. Sw. K. 
 
 Nov. 7, Dec. 4. 
 
 73i 
 
 Nov. i 
 
 43 + 22 
 
 e Arietis 
 
 SI. B. T. 
 
 Oct. 14, Nov. 13. 
 
 73 2 
 
 Nov. 2 
 
 55 + 9 
 
 e, Tauri 
 
 SI. B. T. 
 
 Rich shower in :886. 
 
 782 
 
 Nov. 13 
 
 150+22 
 
 7 Leonis 
 
 V. S*-. K. 
 
 Leonids. Brilliant shower. 
 
 789 
 
 Nov. 16 
 
 I54 + 4I 
 
 M Ursai Maj.. 
 
 V. Sw. K. 
 
 Sept. 15, Oct. 16, etc. 
 
 793 
 798 
 
 Nov. 17 
 Nov. 20 
 
 53 + 71 
 62 + 23 
 
 7 Camelop. 
 K Tauri 
 
 M. Sw. 
 SI. B. 
 
 A.U4. 21, Sept. 17. 
 Aug. 425, Sept. 22. 
 
 819 
 
 Nov. 27 
 
 25 + 44 
 
 7 Andromedae 
 
 SI. T. 
 
 Andromedes. Fine display. 
 
 840 
 
 Nov. 30 
 
 60 + 49 
 
 fj. Persei 
 
 V. Sw. 
 
 Aug. 16, Sept. 15, 21. 
 
 845 
 
 Nov. 30 
 
 190+58 
 
 e Ursae Maj. 
 
 Sw. K. 
 
 April 24, Nov. 13. 
 
 847 
 850 
 854 
 
 Dec. i 
 Dec. 4 
 Dec. 4 
 
 44+56 
 162 + 58 
 110 + 25 
 
 n Persei 
 /3 Ursae Maj. 
 6 Geminorum 
 
 SI. T. 
 V. Sw. K. 
 SI. 
 
 Oct. 14, Nov. 5, 29. 
 March 24, April 26, etc. 
 Oct. 29, Nov. 7. 
 
 857 
 
 Dec. 6 
 
 80+23 
 
 f Tauri 
 
 SI. B. 
 
 Active shower in 1876. 
 
 866 
 
 Dec. 8 
 
 J 45 + 7 
 
 it Leonis 
 
 Sw. K. 
 
 Jan. 9, Nor. 26. 
 
 867 
 
 Dec. 8 
 
 208 + 71 
 
 a Draconis 
 
 Sw. 
 
 Feb. i (? = Pons's comet). 
 
 876 
 
 Dec. 10 
 
 108 + 33 
 
 a Geminorum 
 
 Sw. 
 
 Geminids. Fine shower. 
 
 877 
 
 Dec. 10 
 
 117 + 32 
 
 /3 Geminorum 
 
 Sw. 
 
 Well observed 1885 & 1892. 
 
 896 
 
 Dec. 22 
 
 194 + 67 
 
 X Draconis 
 
 Sw. K. 
 
 Nov. 1423. 
 
 93 
 
 Dec. 24 
 
 218 + 36 
 
 7 Bootis 
 
 Sw. K. 
 
 March 14, April 10. 
 
 90S 
 
 Dec. 25 
 
 98 + 31 
 
 t* Geminorum 
 
 V. SI. 
 
 Oct. 2. 
 
 The abbreviations in Column 5 are V., very; M., moderately; Sw., swift; 
 SI., slow ; B., bright ; F., faint ; K., streaking meteors ; T., trained meteors. 
 
 Telescopic Meteors. These objects are far more numerous 
 than naked-eye meteors, but hitherto little attention appears 
 
230 THE SOLAR SYSTEM. 
 
 to have been given to their systematic study. With a comet 
 eye-piece magnifying 40 times, and having a field of about 
 i 5', on a lo-inch reflector, Mr. Denning has seen upwards 
 of 400 telescopic meteors, and finds the average rate of 
 appearance is i per hour with the eye-piece alluded to. He 
 considers that, judging from their features of appearance, 
 these bodies are at considerably greater elevations in the 
 atmosphere than ordinary bright meteors. The former often 
 exhibit a very slow movement across the field, and are so 
 diminutive that their great distance becomes an obvious 
 inference, though no actual determinations have yet been 
 made. Photography is beginning to play a part in these 
 observations, and we find that Dr. Wolf has recently 
 obtained several useful photographs of meteor trails. An 
 interesting effort on the part of future observers will be in 
 the direction of securing double observations of some of 
 these tiny meteoroids, either by photography or other means, 
 with the object of ascertaining definitely whether these 
 objects are really as distant as they seem. 
 
APPENDIX I. 
 
 ADDITIONS. 
 
 Tlie Telescope. Chloride of calcium, well dried from time to time, 
 has been recommended as a valuable absorbent of moisture in an 
 observatory, especially if silvered mirrors are used. The film should 
 on no account be touched when there is the least cloud of damp upon 
 it. A tin cap, fitting closely into the cell, and as near the face of the 
 mirror as possible, is a most effectual preservative. The following 
 directions for silvering mirrors may be useful ; they are not identical 
 with those published by Browning or Calver in their pamphlets, bnt 
 answer admirably in practice (Fr): 
 
 Prepare 4 solutions : A. 350 grs. silver nitrate in 10 oz. water ; B. 524 grs. nmmon, 
 nitrate in 10 oz. water ; C. 2 oz. caustic potash (pure by alcohol) in 10 oz. water; D. 
 i oz. lump sugar in 5 oz. water, add 32 grs. tart, acid, and boil for io m ; when cold, 
 add i oz. methylated spirit and sufficient water to make TO oz. All water used for 
 above must be' 'distilled. Clean mirror with nitric acid, rinse thoroughly, and place 
 face downwards in dish of dist. water Leave everything together, mirror, dishes, 
 chemicals, water, etc., in the room you intend silvering in, for 24 hours undisturbed; 
 this equalises temperature, which is of importance. When ready take a large beaker, 
 pour in silver sol., and then am. nit., in equal parts. Now slowly add the potash, 
 but stop directly there is a dark brown ppt., 1 which does not re-dissolve on stirring. 
 Clear with more am. nit., and add potash and am. nit. alternately until former is 
 exhausted. Add now a few drops of silver to get rid of free am., and allow ppt. to 
 subside before decanting into silvering vessel, which may be of white glazed earthen- 
 ware. Add sugar sol., and stir well. The colour of sol. will rapidly change, from 
 yellow, through various tints of brown, to inky black. \Vhen this stage is reached, 
 gently immerse the mirror, one edge first, and gradually lower the other until level, 
 thus avoiding air-bubbles. The mirror may be held by a strip of wood fastened with 
 pitch or cement to the back, and projecting at each end to rest upon rim of dish. 
 The face of mirror should be i inch from bottom of dish when in place. The silvering 
 being completed (which will take from 10 to so m , according to temperature) remove 
 mirror and rinse the brilliant film with plenty of water, finishing with distilled, and 
 set on its edge on blotting-paper to dry, afterwards polishing in the usual manner. 
 The quantities given are sufficient for a i2-in. speculum; and the above process was 
 communicated to the writer by Calver. 
 See also a letter by Brashear, English Mechanic, June n, 1880. 
 
 TJie Sun. Minute observation is often difficult from the agitation 
 caused by heat : hence large instruments lose much of their advan- 
 tage; and the time of day is not immaterial. Lohse with the great 
 Bothkamp achr. found the air becoming unsteady by n b . Definition 
 
 1 Precipiuie. 
 
232 APPENDIX. 
 
 is often excellent through a fog dense enough to answer as a screen 
 Where the expense of a second mirror would not be an objection, ai 
 imsilvered speculum would be admirable, especially if aided by i 
 similar * flat,' as suggested by D., the back of which might be workec 
 concave (an idea of H's) to avoid a double image. Sporer's later vului 
 of the rotation is 24- 54 d ; and from his own and Carrington's observa 
 tions he prefers a spot-period of 11-328 y. Vogel, 1873, gives the 
 limb but i light of centre. Langley finds the nuclei, when entirely 
 insulated from all surrounding light, ' not black, not even dark . . 
 but brilliant, with a violet-purple light . . . dazzliugly vivid . , 
 like that of a violet star.' Prof. Young, 1880, Oct. 7, observed a grea 
 prominence on SE. limb, which in less than i h ascended from 3' or 4 
 to 13', extending then beyond 350,000 miles, or more than f the Sun', 
 radius, from the limb. 
 
 Mercury. From the present position of its orbit, Fr. remarks tha 
 he is best observed in the autumn mornings and spring evenings. 
 Schr. is said to have seen him with naked eye in full daylight, am 
 the lumiere cendree on the dark side. Winnecke suspected dark spo 
 in quadrature, 1878. The transit of 1894, Nov. 10, begins about 20' 
 before sunset. 
 
 Venus. Elger saw dichotomy, 1873, Feb. 12, 9 d before greates 
 elongation ; and phosphorescence repeatedly, 1872 ; Sa., the latter ii 
 both years. 
 
 The Moon. The clefts near Triesneclter, p. 102, omitted in Lohr 
 niann's Topographie, are partially shown in his Map The terminato 
 returns nearly to the same position after 443 and 1447 days. Dennin; 
 has seen the crescent at 2O h 38. Ne. once witnessed an appearanc 
 in Plato (see p. no) resembling a fog, which covered the whol 
 interior at sunrise and gradually disappeared: it seemed like a haz; 
 border of perhaps 15" to the true shadow, hiding all beneath it till i 
 cleared away. Newcomb infers, from the occultation of stars, tha 
 the density of the lunar atmosphere cannot equal ^th part of our OWL 
 
 Mars.- Trouvelot has seen Deimos several times with 6$ in. achi 
 but only with the greatest attention ; brighter but less sharp thai 
 Enceladus, which he has glimpsed. 
 
 Jupiter. The Red Spot is still fainter, 1893. Satellites. Bond 
 1848, March 18, III entered disc very bright; 20 later hardly per 
 ceptible ; a little after as dark spot ; then for 2| h perfectly black am 
 nearly round. Prince, 1863, April 26, II projected on disc at leas 
 30 s before occultation. Kidd, 1872, Oct. 16, saw II through limb (o 
 possibly projected?); this was also observed at Stonyhurst with ] 
 
APPENDIX. 233 
 
 1880, Oct. 10 ; and at Greenwich with III, Nov. 28. Mrs. McCance, 
 
 1878, Oct. 12, saw II, III, IV with naked eye as one. At Stonyhurst, 
 
 1879, "Dec. 8, I was only just visible for more than h after transit, 
 though glare of planet cut off, and other sats. woll seen. Several 
 dark transits of I were recorded in 1880: at Stonyhurst, Nov. 3, its 
 shadow exceedingly faint; that of III very small. Noble and Camp- 
 bell, Oct. 1 8, shadow of I black, II brown ; Elger, II unusually light 
 then, but much lighter, hardly noticeable, Dec. 21. Pickering, from 
 observations at Arequipa, 1893, finds that I is egg-shaped, and rotates 
 round one of its minor axes. The other satellites occasionally showed 
 an elliptical disc, which appeara to be shortened equatorially. I 
 rotates in I3 h 3; II in 4i h 24"; III in the time of its revolution 
 round 11 . It has a distinct N. belt, and a doubtful S. one. IV has 
 also a period of rotation, equal to its orbital rotation. Surface mark- 
 ings are distinguished with great difficulty. Prof. Pickering makes 
 the conjecture that they each consist of a very much condensed swarm 
 of meteorites, like Saturn's ring. 
 
 Saturn.- -Hall's final value of the period of rotation is io h 14 23'8 S . 
 Encke's division is well shown (with another, if not two, on B) in 
 photographs of drawings taken at Parsonstown, 1860 ; though Mitchel 
 could never see it with most beautiful definition in the n-in. Cin- 
 cinnati achr. (since refigured and improved ; a suggestive circum- 
 stance with reference to such comparisons). Hall at Washington 
 was not more successful than Trouvelot. 
 
 Neptune. Sa. has caught the satellite with 9. 6|-in. silv. mirror : it 
 is far brighter p than / the planet. 
 
APPENDIX II. 
 
 BOOKS OF REFERENCE. 
 
 THE following list of works may be useful to the amateur who 
 desires more advanced information than is given by this little 
 work : 
 
 General Astronomy. The 'Celestial Cycle,' revised and enlarged 
 by F. Chambers. The amateur also should consult the Journal of the 
 British Astronomical Association; the Monthly Notices of the R.A.S., 
 etc. 
 
 Practical Astronomy. Loomis, or the more advanced book of 
 Chauvenet. 
 
 The Sun. Young ; one of the * International Scientific Series.' 
 
 The Moon. Neison's * Moon.' 
 
 Mars. Flammarion's ' Planet Mars.' 
 
 Jupiter. A. Stanley Williams's * Zenographical Fragments.' 
 
 Saturn. Proctor's ' Saturn and his System.' 
 
 Comets and Meteors. See text, p. 207. 
 
 Spectroscope. Schellen's 'Spectrum Analysis,' and Schemer's 
 * Spectrum Analysis of the Heavenly Bodies.' 
 
 General Sidereal Astronomy. Miss Clerke's ' System of the Stars ; ' 
 ' Gore's ' Visible Universe ; ' Flammarion's ' Les Etoiles.' 
 
 Double Stars. Crossley and Gledhill and Wilson's 'Handbook.' 
 
 Variable Stars. Gore's Catalogues of Variable and Suspected 
 Variable Stars, published by the Royal Irish Academy, containing a 
 mass of valuable information; Chandler's Catalogue in the Astron. 
 Journal, Nos. 179, 180. (New edition) 300. 
 
 Eed Stars. Birmingham's Catalogue. New edition. Cunning- 
 ham's ' Memoirs of the Royal Irish Academy,' No. V. 
 
 Nebulas. General Catalogue. Mem. R.A.S., vol. xlix. 
 
APPENDIX III. 
 
 7'Ae Sun, p. 29. In consequence of the death of Miss Brown, Thomp- 
 son's discs should be obtained from the director of the Solar Section 
 of the B.A.A. Of those who kindly assisted in the last Edition of 
 1 Celestial Objects,' I regret to record the deaths of T. G. Elger, Rev. 
 A. Freeman, and Miss Brown. 
 
 Mars, p. 150. The reports of the Mars Section of the B.A.A. of 
 the oppositions of 1894 and 1896, ' Memoirs,' vol. iv., part 4, and vol. vi., 
 part 3, are full of interesting details. The existence of Schiaparelli'd 
 canals seems to have been generally confirmed, but their germination 
 is put down by Antoniadi to imperfect focussing. The mystery as to 
 the conditions of things on Mars has been heightened by the spectro- 
 scopic observations of Keeler and Campbell, which show that there is 
 no water on the planet. The discovery by Herr Witt, in 1898, of a 
 planet between Mars and the Earth is of great interest. The planet 
 has a period of 643'! days, and has been named Eros. 
 
 Saturn, p. 198. Keeler has proved from spectroscopic observations 
 the meteoric constitution of the rings. 
 
 Page 201. A Qth Satellite has lately been announced. The dis- 
 covery was made by W. IJ. Pickering photographically. 
 
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