A DAY IN THE MOON
 
 From a drawing by the Abbi Morcitx. 
 
 THE EARTH AS SEEN FROM THE MOON. 
 
 (The landscape shows part of the range of the I,unar Alps.) 
 
 [Fronlispixe.
 
 A DAY IN THE MOON 
 
 BY THE ABBE TH. MOREUX 
 
 Director of the Bourges Observatory 
 
 WITH 40 ILLUSTRATIONS FROM PHOTOGRAPHS 
 AND DRAWINGS 
 
 Mew 
 FREDERICK A. STOKES COMPANY 
 
 PUBLISHERS
 
 PRINTED IN ENGLAND
 
 ANNtA 
 
 CONTENTS 
 
 CHAPTER t f PAGE 
 
 I. THE MOON . . :';'' . . I 
 
 II. OBSERVATIONS OF THE ANCIENTS 4 8 
 
 III. THE MOON AS SEEN BY THE NAKED 
 
 EYE . y, . . . 27 
 
 IV. WITH THE EYE AT THE TELESCOPE . 45 
 V. ON THE WAY . , . . 66 
 
 VI. LUNAR LANDSCAPES . ." . . 82 
 
 VII. ON THE MOON . . ,"j . . 103 
 
 VIII. THE MOON, THE TIDES, AND THE 
 
 CHANGES OF THE WEATHER . JAi 1 2O 
 
 IX. THE MOON, VEGETATION, AND ORGANIC 
 
 LIFE ? . " . . . 137 
 
 X. ASTRAL INFLUENCES AND ASTROLOGERS 153 
 
 XI. THE ACTION OF THE MOON ON MEN 
 
 AND ANIMALS . . '. . , . 1!
 
 vi CONTENTS 
 
 PAGE 
 
 LIST OF 348 OBJECTS SHOWN ON THE MAP OF 
 THE MOON DRAWN BY THE ABBE MOREUX 
 (CRATERS, MOUNTAINS, AND INEQUALITIES 
 OF THE SURFACE) ..... 184 
 
 OBJECTS TO BE STUDIED ON EACH DAY OF 
 
 THE LUNATION ..... 190 
 
 LUNAR ELEMENTS ..... 192 
 LIST OF THE PRINCIPAL LUNAR <e SEAS " . 195 
 CHIEF CHAINS OF LUNAR MOUNTAINS . . 196 
 
 INDEX ....... 197
 
 ILLUSTRATIONS 
 
 The Publishers are indebted to the kindness of the Author for the loa of many 
 of his original drawings for reproduction in this English translation. 
 
 THE EARTH AS SEEN FROM THE MOON . . Frontispiece 
 
 FACING PAGE 
 
 THE NORTH HORN OF THE MOON ..... l6 
 
 EARTH-LIT NEW MOON . . . 30 
 
 THE MOON AT THE FIRST QUARTER (AGED 7 DAYS 3 HOURS) . 34 
 
 THE PHASES OF THE MOON ...... 36 
 
 THE MOON (AGED 8 DAYS 23^ HOURS) 38 
 
 THE FULL MOON (AGED 14 DAYS I HOUR) . 40 
 
 THE MOON (AGED 20 DAYS 19 HOURS) . . 42 
 
 THE MOON AT THE LAST QUARTER (AGED 23 DAYS 8 HOURS) . 44 
 
 SUNRISE ON THE MOUNTAIN RING " WALTER " . . 48 
 
 HEVELIUS AND HIS WIFE OBSERVING T!!E POSITIONS OF THE 
 
 HEAVENLY BODIES ....... 58 
 
 THE MOON ......... 60 
 
 COMPARATIVE SIZE OF THE EARTH AND THE MOON . . 76 
 
 A GAP IN THE MOUNTAIN RAMPART OF COPERNICUS . . 82 
 
 OUTLYING BUTTRESSES OF THE LUNAR ALPS ... 84 
 
 COPERNICUS ......... 92 
 
 PERSPECTIVE VIEW OF A LUNAR MOUNTAIN-RING . . . IO2 
 
 REGION OF THE LUNAR APENNINES ..... IO6 
 
 RF.GION OF THE " MARE SERENITATIS " 1O8 
 
 vn
 
 viii ILLUSTRATIONS 
 
 FACING PAOB 
 
 EXAMPLE OF THE CREVASSING OF A HARD SURFACE CLEFTS 
 
 NEAR TR.IESNECKER . . . . . . .112 
 
 THE "STRAIGHT RANGE" PRESENTING THE APPEARANCE OF A SWORD 114 
 ASPECT OF THE " MURUS RECTUS " (THE " STRAIGHT RANGE ") 
 
 OF THE MOON . . . . . . . .Il6 
 
 CONJECTURAL FORMATION OF THE UNSEEN SIDE OF THE MOON Il8 
 DIAGRAM TO ILLUSTRATE THE ACTION OF THE MOON ON THE TIDES I2O 
 REGION OF THE " MARE VAPORUM " . . . . 12<f 
 
 INTERIOR OF A LUNAR VOLCANO . . . . 130 
 
 A CLEFT IN THE MOON*S SURFACE NEAR HYGINUS . .136 
 
 THE NORTHERN HORN OF THE MOON . . . .138 
 
 THE EDGE OF THE MOON LIGHTED UP BY THE SETTING SUN . 142 
 
 THE MOON'S SURFACE ....... 148 
 
 REGION BETWEEN THE " MARE IMBRIUM " AND THE NORTH 
 
 POLE OF THE MOON . . . . . .154 
 
 THEOPHILUS, CYRILLUS, AND CATHERINE . . . l6o 
 
 IN THE TEXT 
 
 GALILEO GALILEI (AFTER THE PORTRAIT BY LEON l) . . . II 
 
 THE FIRST PICTURE OF THE MOON DRAWN BY GALILEO . . 14 
 
 METHOD OF MEASURING THE HEIGHT OF A LUNAR MOUNTAIN . l6 
 
 DE RHEITA'S MAP OF THE MOON (A.D. 1645) . . . 51 
 
 CYRANO DE BERGERAC's FLIGHT TO THE MOON ... 67 
 DIAGRAM ILLUSTRATING THE DISTANCE OF THE MOON FROM THE 
 
 EARTH . . . . . . . .79 
 
 SKETCH-MAP SHOWING THE SIZE OF " COPERNICUS " AND " MAURI- 
 
 LYCUS " . . . . ... . . .87
 
 A DAY IN THE MOON 
 
 i 
 
 THE MOON 
 
 To launch out into space, to rise ever upwards, to 
 leave the Earth far away and fly on strong wings 
 to the Moon, to descend upon its silvery surface, 
 traverse its unknown plains and valleys, examine 
 in detail the structure of that globe which we see 
 suspended above our heads, and at last to come 
 back and tell the people of the Earth the daring 
 adventures of that distant journey . . . what a dream ! 
 
 We have all had such dreams on some autumn 
 evening when, as we returned in thoughtful mood 
 from some long walk in the country, the thin 
 crescent of the new Moon rose on the background 
 of the sky, still tinted with the twilight glow. 
 
 And this reminds me of an evening in one of 
 the vacations I spent in the Sologne, my native 
 i
 
 2 A DAY IN THE MOON 
 
 district. I had accompanied my father on one of 
 those walks of which he was particularly fond, and 
 during which he never missed an opportunity of 
 developing my interest in the various phenomena 
 that Nature is each moment placing before our 
 eyes. 
 
 Behind us the sun had set and night was coming 
 on with a perfectly clear sky. We were walking 
 along a footpath among clumps of heath and furze. 
 A herdsman was singing as he slowly brought back 
 his cattle to their shed, and gradually as the 
 night came on the thousand sounds of Earth were 
 hushed. One might have said that Nature was 
 assuming a recollected silence the better to prepare 
 man to feel the charm of the heavens that were 
 soon all studded with stars. 
 
 And now, as the tints of the landscape faded away, 
 my childish imagination was full of delight. 
 
 The wide unbroken plain extended to the hori- 
 zon, which it seemed to touch, and I thought that 
 the sea must present much the same appearance. 
 Here and there the thickets of high-growing 
 shrubs stood out in dark patches on the ground, and 
 I imagined they were like great waves. The clumps 
 of pines scattered here and there farther off, black,
 
 THE MOON 3 
 
 ill-defined masses rising over all else, seemed to me 
 to be big ships with their masts swaying gently in 
 the light evening breeze. 
 
 Suddenly a glow like that of a fire gleamed out 
 beyond them, the ruddy disc of the full Moon rose 
 above all the things of Earth, and immediately my 
 mind was prompted to other thoughts. 
 
 Why is it that the Moon does not always appear 
 to be round ? 
 
 What is the explanation of its phases ? 
 
 I knew that with the naked eye one could only 
 have a very rough idea of its aspect, and I had 
 often levelled at its shining disc a telescope of 
 very moderate power, the only astronomical instru- 
 ment then in my possession. 
 
 Those greyish spots that one sees with the 
 naked eye appeared more clearly defined even with a 
 magnifying power of only ten, but my telescope was 
 hardly powerful enough to show me the lunar craters 
 and mountain-walled plains. I thought indeed that 
 I could catch glimpses of them, but nevertheless I 
 was always ambitiously dreaming already of more 
 powerful instruments. 
 
 I used often to ask myself at that time if it was 
 true that the Moon was strewn with giant mountains,
 
 4 A DAY IN THE MOON 
 
 that a man could walk and stand on its surface and 
 photograph its landscapes ? And those " craters " 
 that had been discovered in our satellite, had they 
 really been volcanoes in earlier ages ? 
 
 If man had existed in the times of the Brontosaurs 
 and the Iguanodons, would he have been able to 
 make out the jets of fire and smoke in lunar 
 eruptions ? 
 
 Why did this heavenly body revolving around us 
 always present the same appearance since man first 
 observed its enigmatical surface ? 
 
 On our Earth generations succeed each other. 
 Man has spread over and peopled the globe. And 
 each evening the tillers of the soil returning to their 
 farms look up to the sky. 
 
 At the hour when in the cities of civilised lands 
 artificial light blots out the stars and deprives the 
 town-dweller of that spectacle of the universe, the 
 countryman can gaze on the starry sky, and he 
 always asks himself the same questions without 
 making any attempt to solve them. At school 
 he is taught to divide up the Earth into 
 separate compartments. He learns by heart the 
 exploits of blood-stained heroes. He knows the 
 date of the battle of Crecy, when for the first time
 
 THE MOON 5 
 
 cannon made their appearance hurling their deadly 
 bolts. He is told of the properties of explosives 
 and the principle of the bullet in the modern rifle. 
 
 And those who possess riches no longer live in 
 contact with Nature. Fashionable gatherings, plays, 
 race-courses, theatres, are the chief interest of their 
 aimless and unprofitable pursuits. 
 
 The literature of the day reflects this idle and use- 
 less life. Most of our works of fiction display in 
 the full light of day the blemishes of a decadent 
 Society, and under the pretext of psychological 
 analysis describe the disorderly outburst of passion. 
 
 There is material and industrial progress every- 
 where, and this is a good thing, but moral progress 
 does not keep pace with it. Men neglect the study 
 of Nature, and lose touch with its manifestations, 
 which are capable of leading them infallibly to a 
 consideration of the great questions of science and 
 philosophy. 
 
 Since the days of the Egyptians and Greeks and 
 the other peoples of antiquity with whom our civili- 
 sation began, the mass of men have remained quite 
 ignorant of the great questions which are alone 
 worthy to occupy a thoughtful mind. 
 
 Man, bowed to the Earth, no longer looks upon
 
 6 A DAY IN THE MOON 
 
 the Heavens and no longer pays homage to his 
 Maker. 
 
 Question a thousand of the inhabitants of our 
 planet and ask them where they are in the universe, 
 speak to them of the Solar System, of Jupiter, of 
 Saturn, or of the stars hardly one, at most, will 
 understand you and grasp the fact that there are 
 other subjects of interest beyond that of our trifling 
 daily occupations. 
 
 From the astronomical point of view nearly all of 
 them have remained, so far as this goes, not at the 
 epoch of Pericles or Augustus, but at that of the 
 Stone Age. 
 
 And meanwhile what wonderful progress has been 
 made by all the physical sciences in'general progress 
 by which Astronomy has been the first to benefit. 
 
 We can now answer questions of which the 
 solution once seemed to be a thing of insurmountable 
 difficulty. 
 
 The discoveries in physical Astronomy have told 
 us more and more of the marvels of far-off" worlds. 
 
 And as for those that lie nearer to this Earth of 
 ours, we are able to examine them with magnificent 
 instruments. They are part of our own system, and 
 are linked with our lot in the universe, and, to adapt
 
 THE MOON 7 
 
 the saying of an ancient philosopher, " nothing that 
 concerns them ought to be without interest for us." 
 
 Science has in a measure realised that dream of 
 visiting worlds so different from our own, thanks 
 to the penetrating power of the instruments it places 
 at our disposal. 
 
 We can now enter on detailed studies of each of 
 the planetary bodies, and as the Moon is of all the 
 lights of the firmament the one nearest to us, it is 
 natural to begin our excursions in the heavens with 
 this neighbouring world, which the laws of attraction 
 link with our planet by bonds as subtle as they are 
 mysterious.
 
 II 
 
 OBSERVATIONS OF THE ANCIENTS 
 
 WHATEVER may be said to the contrary, it is not 
 at all certain that the powers of the human intelli- 
 gence have made any very notable progress since 
 the first appearance of man on the Earth. 
 
 We have no doubt that there were among the 
 ancients men of superior intelligence from every 
 point of view, and the study of their writings, 
 their pursuits, their theories, is well calculated to 
 throw a new light on our recent discoveries and 
 at the same time help us to realise the imperfection 
 of our knowledge. 
 
 When it is a question of studying a science, the 
 only acceptable method is that of following its 
 development and its evolution through the various 
 periods of history. Such a method will at once 
 show us that each science grows like a living 
 creature. Each important step of progress is always 
 the outcome of long preparation, and never comes
 
 OBSERVATIONS OF THE ANCIENTS 9 
 
 suddenly, just as in the living organism the useless 
 elements are got rid of and give place to new 
 substances. 
 
 We shall have many examples of this in the 
 course of our familiar talk about the science of 
 the Moon, or as it has been called, Selenography. 
 
 Without speaking of the dreams of mythology, 
 that assigned to the Moon the personality of Selene 
 or Diana, and told how the Nemean lion came 
 from our bright neighbour to terrify mortal men, 
 it is very interesting to examine the opinions of 
 the ancient world about our satellite in times when 
 the telescope was a completely unknown instrument. 
 
 Achilles Tatius, who wrote three centuries after 
 Christ, has recorded for us the opinions of his 
 immediate predecessors. For some of them the 
 Moon was merely a detached fragment of the Sun 
 in days nearer our own Laplace could find no 
 better theory. According to others, it was formed 
 of exhalations from the earth which took fire in 
 the upper regions of the heavens. 
 
 In a passage of his translation of Plutarch, Amyot 
 tells, quoting a disciple of Aristotle, how the latter 
 held that "the forms and images of the great sea 
 of the Ocean appeared in the Moon as in a mirror."
 
 io A DAY IN THE MOON 
 
 Many of the ancient philosophers had remarked the 
 connection between the phases of the Moon and 
 its position with respect to the Sun, and this idea 
 of comparing the Moon to a mirror had become 
 current among them. So the author just quoted 
 says that " in its polished brightness it is the most 
 beautiful and clearest mirror in the world." 
 
 All these fancies were very far from reality, and 
 the first astronomical telescopes were destined to give 
 some astounding surprises to the old astronomers. 
 
 The telescope was not, it is true, first invented 
 by Galileo, but it is to this man of science that the 
 honour belongs of having been the first to apply 
 the instrument to the study of the heavens. 
 
 There can be no doubt of this, and Galileo him- 
 self tells the story in his Sidereus Nuntius^ which 
 appeared in March 1610 : 
 
 "About ten months ago I was informed that a 
 certain Dutchman had devised a telescope, by means 
 of which he saw distant objects as plainly as if they 
 were near at hand. This instrument had already 
 been used to make a number of experiments, to 
 the results of which some gave credit while others 
 denied them. 
 
 " And this was confirmed for me some days later
 
 OBSERVATIONS OF THE ANCIENTS n 
 
 by a letter which the Frenchman, Jacques Badovere, 
 addressed to me from Paris. All this finally led 
 me to devote myself entirely to studying the means 
 
 GALILEI GALILEO 
 (1564-1642). 
 
 After the portrait painted and engraved in 1624 by Ottavio L.eoni. 
 
 of arriving at the application of a similar device ; 
 and I, in fact, succeeded therein shortly after, with 
 the help of the theory of refraction. First of all, 
 then, I made a leaden tube, to the ends of which
 
 12 A DAY IN THE MOON 
 
 I fitted lenses, both of which had one plane surface, 
 while the other side of one of them was convex and 
 that of the other concave. Then bringing my eye 
 to the concave lens, I saw objects looking near 
 enough ; these objects appeared three times nearer 
 and nine times larger than with the unassisted 
 sight. 
 
 " I then made a more carefully finished instru- 
 ment, which magnified the objects more than sixty 
 times. 
 
 "Finally, sparing neither trouble nor expense, I 
 succeeded in making for myself an instrument so 
 excellent that it enabled me to see objects a thou- 
 sand times larger than with the unassisted sight." 
 
 With regard to the magnifying powers of which 
 Galileo here speaks, we must go into some details 
 that are necessary for the understanding of this 
 somewhat ambiguous passage, and which will make 
 clear the meaning of an expression that frequently 
 recurs in dealing with astronomical subjects. 
 
 Take a square of which each side is an inch in 
 length and double these linear dimensions. What 
 shall we have ? 
 
 Each side of the new square will be two inches 
 in length, and the surface, which originally measured
 
 OBSERVATIONS OF THE ANCIENTS 13 
 
 one square inch, will have become 2x2 = 4 square 
 inches. 
 
 Thus, in doubling the linear dimensions one 
 quadruples the surface ; if one lengthens the sides 
 threefold, the surface becomes 3x3 = 9 times 
 larger. 
 
 It has now been long an established rule in 
 physics that the magnifying power of instruments 
 is always to be stated in linear units. When we 
 speak of a microscope magnifying twelve times, we 
 mean that in the object under examination each 
 dimension appears twelve times longer. 
 
 Galileo, doubtless to strike the imagination of 
 his contemporaries, purposely had recourse to the 
 method adopted by certain dealers in optical in- 
 struments, who advertise microscopes magnifying 
 1 44 times, but carefully omit to add " super- 
 ficially " the corresponding linear magnification 
 being only twelve times. 
 
 This principle applies to objects of other forms 
 than a square, as, for instance, a polygon or a 
 circle. 
 
 Galileo's first telescope magnified the surface nine 
 times ; that is to say, three times, estimating by 
 linear units.
 
 A DAY IN THE MOON 
 
 Later, it is true, he constructed instruments 
 magnifying the diameter of celestial objects thirty- 
 two times ; that is to say, 32 x 32 = 1,024 times 
 superficially. 
 
 These instruments are now kept in one of the 
 
 museums of 
 Florence. 
 
 Galileo was 
 at Venice when 
 he heard of 
 the discovery 
 of the tele- 
 scope. He at 
 once returned 
 to Padua, 
 where he held 
 a professorship 
 of Mathema- 
 tics, and it was there that he constructed his first 
 instrument with lenses that he happened to have 
 in his possession. 
 
 Later on he presented a telescope magnifying 
 thirty-two times to the Doge Leonardo Donati, and 
 then another of the same kind to the Grand Duke 
 of Tuscany. 
 
 THE FIRST PICTURE OF THE MOON. 
 DRAWN BY GALILEO IN 1610.
 
 OBSERVATIONS OF THE ANCIENTS 15 
 
 The Venetian Senate, in its admiration for his 
 invention, confirmed him for life in his professor- 
 ship at a salary of i ,000 florins a year ; and the 
 Grand Duke of Tuscany lavished gifts upon him. 
 
 " It would be superfluous," continues Galileo, in 
 the passage already quoted, "to reckon up the 
 advantages to be obtained by the use of this instru- 
 ment on land as well as at sea. But leaving aside 
 these terrestrial things, I have directed my researches 
 towards the heavens, beginning with the Moon." 
 
 And what Galileo saw might well excite the 
 wonder of his contemporaries. 
 
 He first of all discovered mountains, more or 
 less brilliant spots and circular hollows, which he 
 compared to the eyes in a peacock's tail. 
 
 At the moment of the phases the boundary be- 
 tween the dark part and the light appeared to him 
 under the form of an irregular, uneven line, and he 
 drew from this the logical conclusion that the Moon 
 was far from being a perfectly smooth sphere. But 
 then, how was one to explain the fact that at the 
 moment of Full Moon the margin showed neither 
 projections nor hollows ? 
 
 For this question Galileo found two answers 
 which were incorrect. He said that either the Moon
 
 i6 
 
 A DAY IN THE MOON 
 
 had an atmosphere which enlarged the apparent 
 size of its disc and made its marginal irregularities 
 disappear, or else the mountains seen in perspective 
 concealed each other. 
 
 In reality he ought to have noted that only when 
 an object is illuminated from the side it throws a 
 shadow that makes its summits stand out and 
 
 reveals its irregularities. 
 
 With our actual tele- 
 scopes the outer edges- of 
 the Moon are far from being 
 as regular as they appeared 
 with the telescopes of 
 moderate power in use at 
 the beginning of the seven- 
 teenth century. We have, 
 however, to thank Galileo 
 for having noted another 
 and a very important phenomenon, which put him 
 on the track of an ingenious method of measuring 
 the height of the lunar mountains. 
 
 On account of the surface of the Moon being 
 convex, when the sun rises upon one of its regions 
 the rays first light up the lofty summits of the 
 mountains. An astronomer looking from the 
 
 METHOD OF MEASURING THE 
 HEIGHT OF A LUNAR 
 MOUNTAIN.
 
 THE NORTH HORN OF THE MOON. 
 
 (Reversed image.) 
 
 16]
 
 OBSERVATIONS OF THE ANCIENTS 17 
 
 Earth sees, therefore, a luminous spot separated 
 from the bright part of the Moon by a dark 
 band corresponding to the valleys still plunged in 
 shadow. 
 
 But under these conditions it is easy to take the 
 line of a solar ray as a tangent to the curved 
 surface of the Moon ; this straight line touching 
 the mountain summit forms with two lines drawn 
 to the centre of the moon (one vertically through 
 the summit, the other from the point where the 
 ray first touches the curved outline of the moon) 
 a right-angled triangle, of which the length of the 
 sides can be ascertained. Then a simple calcula- 
 tion gives at once the height of the illuminated 
 summit (which is equal to the difference between 
 the two lines drawn to the centre of the moon). 
 
 The study of the shadow thrown by a lofty 
 peak would lead to the same conclusions, and 
 since the time of Galileo astronomers have not 
 failed to improve and perfect these methods. 
 
 But however this may be, it is certain that in 
 1610 there was a complete revolution in accepted 
 ideas as to the nature of the Moon. Thanks to 
 Galileo's discoveries, it became impossible to deny 
 that our satellite presented the appearances of a
 
 1 8 A DAY IN THE MOON 
 
 world in many ways resembling the Earth, and 
 with a surface standing out in higher relief in 
 certain regions. 
 
 But did this miniature of our planet possess seas, 
 rivers, and forests ? Was it inhabited ? 
 
 This was something that could not yet be de- 
 cided by observation, and the savants of the time 
 could give free rein to all the fancies we permit 
 to romancists and poets. Such a fine chance was 
 not lost, and voyages to the Moon supplied to 
 authors a subject all the easier to dilate upon 
 because there was a complete absence of positive 
 facts. 
 
 But was Galileo, as is so frequently stated, the 
 first to distinguish the mountains of the Moon ? 
 
 History, as has often been said, is nothing but 
 a perpetual beginning again. Was this compara- 
 tively recent invention of instruments, that make 
 objects appear nearer, anything more than a re- 
 discovery, and are we to believe that the ancients 
 were entirely ignorant of the use of magnifying 
 glasses and even of some kind of telescope ? This 
 is a question that we may examine together before 
 closing the chapter. 
 
 Anaxagoras, according to the account of Diogenes
 
 OBSERVATIONS OF THE ANCIENTS 19 
 
 Laertius, asserted that there were mountains, valleys, 
 and inhabitants in the Moon. 
 
 This passage has generally been regarded as a 
 piece of mere fancy, but who can say whether, 
 when he wrote these lines, the author of the Orphic 
 poems was not echoing an old tradition that came 
 from Egypt, Phoenicia, or Chaldaea ? 
 
 The best-established scientific ideas can be lost 
 as the old civilisations were ; and it seems to me 
 interesting to give here the results of a study I 
 made some time ago of this little-known chapter 
 in the history of Optics among the ancients. 
 
 First of all, was glass known to the peoples 
 of antiquity ? This point appears open to no 
 doubt. 
 
 There is a passage in the writings of Aris- 
 tophanes in which he relates that in his time globes 
 of glass were sold by the grocers in Athens. At a 
 later date Pliny tells how the immense theatre 
 erected at Rome by Scaurus, the son-in-law of 
 Sylla, which could hold 80,000 spectators, had 
 three sets of seats rising above each other, and 
 those of the second series were entirely covered 
 with mosaics in glass. 
 
 In the seventh book of his Recognitions the
 
 20 A DAY IN THE MOON 
 
 pseudo-Clement relates a legend of St. Peter having 
 gone to the island of Aradus and seen there a temple 
 with columns of glass of extraordinary height and 
 thickness, which excited his wonder even more than 
 the splendid statues by Phidias with which this 
 temple was adorned. 
 
 Seneca, in his Questions on Nature? speaks of the 
 phenomena of the colours seen when one looks 
 slant-wise through the projecting angles of a 
 piece of glass. At this time, therefore, the prism and 
 the production of colours by refraction were known. 
 
 In] the reign of Nero cups of cut rock-crystal 
 were in use. The tear bottles found in the tombs 
 are also made of glass, and at this period it was on 
 glass globes that the celestial spheres and the con- 
 stellations were marked out. 
 
 In his Optics, Ptolemy inserts a table of the 
 refraction of a ray of light in passing through glass. 
 Now, the indices of refraction given in our modern 
 works on Physics approximate so nearly to his, 
 that we must conclude that the glass of his time 
 differed very little from that which we make nowa- 
 days. 
 
 1 Quastionum naturalium, libri vii., the only surviving Roman 
 treatise on physics. Translator's Note.
 
 OBSERVATIONS OF THE ANCIENTS 21 
 
 All these are certain facts. But it will be said 
 that they do not prove that the learned of antiquity 
 knew the properties of lenses. 
 
 Granted ; but here is some other evidence. 
 
 Everyone has heard of the emerald through 
 which Nero watched the games of the amphitheatre. 
 Aristophanes in his comedy of the Clouds makes a 
 curious jest. In the play Strepsiades explains to 
 Socrates the possibility of setting fire to com- 
 bustibles by means of a glass globe. And this 
 ingenious person tells how he has found a way of 
 avoiding the payment of his debts by thus, from a 
 distance, destroying the acknowledgments in the 
 hands of his creditors, without their being able to 
 find him out. 
 
 The Romans, who had learned science from the 
 Greeks, instead of caustic, used globes of glass ex- 
 posed to the sun for cauterising flesh. And if the 
 Vestals negligently allowed the sacred fire to 
 become extinguished, it was their duty to rekindle 
 it by means of the heat of the sun concentrated 
 through little glass spheres. 
 
 When in 1 905 I was sent by the French Govern- 
 ment to Tunisia to observe the total eclipse of the 
 Sun, I took advantage of my stay at Tunis to pay
 
 22 A DAY IN THE MOON 
 
 a visit to Pere Delattre, who, as is well known, has 
 with admirable patience brought together in a 
 museum, that is unique in the world, the materials 
 for a reconstruction of Carthaginian civilisation. 
 
 My colleagues and myself were not a little sur- 
 prised at being shown, amongst other remarkable 
 objects, a cameo carved as an intaglio, with a design 
 of singular perfection. It represented a horse scratch- 
 ing its head with its hind hoof. The minute 
 details of the mane suggested to me the idea that 
 the artist must have used a magnifying glass when 
 carving it. And it actually was with a plano- 
 convex lens of rock-crystal, found in a tomb of 
 the same period, that we were able to examine the 
 cameo in detail. I have since learned that this is 
 not the only instance of the same kind. 
 
 There is in the French Cabinet des Medailles a 
 seal attributed to Michel Angelo, but which is 
 really of much earlier date. Fifteen figures are 
 engraved on it in a circle of a radius of only 
 7 millimetres. 1 These figures are not all visible 
 to the naked eye. 
 
 Cicero relates a still more extraordinary fact. 
 
 1 A little more than a quarter of an inch (0*275 *") The diameter 
 would thus be about half an inch (0-55 in.).
 
 OBSERVATIONS OF THE ANCIENTS 23 
 
 He tells of an artist having written out the whole 
 of Homer's Iliad in microscopic characters. 
 
 One may judge of the minuteness of the work, 
 when it is added that, according to the same 
 author, the piece of parchment could be contained 
 in a nutshell. 
 
 Pliny also relates that Mymecides had sculptured 
 in ivory the representation of a four-horse chariot 
 so small that a fly could have covered it with its 
 wings. 
 
 The Greeks and Romans must therefore have 
 known the magnifying power of optical lenses. 
 
 If there were any doubt of this, we need only 
 recall the story of that magnifying glass in the 
 Carthage Museum. In the same cases of the 
 museum one can see similar lenses made of glass, 
 but these have become opaque with the lapse of 
 time. 
 
 But as long ago as 1852 Sir David Brewster 
 exhibited, at a meeting of the British Association, 
 a lens of rock-crystal, which had lately been found 
 in the excavations of Nineveh. 
 
 It is therefore quite natural to suppose that the 
 ancients might very well have reached a knowledge 
 of optical instruments such as microscopes and
 
 24 A DAY IN THE MOON 
 
 telescopes, all the more because what is essentially 
 required for such instruments is only the placing 
 together of a couple of magnifying lenses. 
 
 There is all the more to be said for this theory 
 because if we deny to the peoples of antiquity this 
 useful knowledge, it is impossible to explain a 
 good many statements they make amongst others, 
 this which I take from Democritus. This philo- 
 sopher affirmed that the Milky Way was made up 
 of a countless number of stars, and that it was 
 the confused mingling of their light that was the 
 cause of its phosphorescent whiteness. How could 
 Democritus have imagined such an explanation at a 
 period when the nations of his time still believed 
 in the legend of the drops of milk from the breasts 
 of Juno ? 
 
 It may be that the ancients even knew something 
 of the reflecting telescope, the instrument made with 
 a concave mirror. And this supposition is not more 
 unlikely than the other. 
 
 Some writers appeal in support of this idea to 
 the burning mirrors that Archimedes used at the 
 siege of Syracuse to set on fire the ships of 
 Marcellus. 
 
 But it seems to be now fairly well ascertained
 
 OBSERVATIONS OF THE ANCIENTS 25 
 
 that the mirrors in question were not concave, or 
 of a single piece, but formed of a great number of 
 flat reflecting surfaces at various angles concentrating 
 the solar rays on the same point. 
 
 Such an arrangement can produce the same 
 concentration of heat as the concave mirror of a 
 telescope, and BufFon, by means of 148 plane 
 mirrors, once succeeded in setting fire to a deal 
 board at a distance of 49 metres (about 160 ft.). 
 
 Critics have, however, always been very reserved 
 when it comes to the question of explaining a 
 statement made by serious historical writers re- 
 garding vision by means of some unknown 
 apparatus. 
 
 Ptolemy Euergetes, the brother of King Ptolemy 
 Philadelphus, who lived in the third century before 
 Christ, had caused to be fixed on the summit of the 
 lighthouse of Alexandria an instrument with which 
 ships could be seen at a great distance. Many 
 authors have suggested that this may have been a 
 concave mirror. 
 
 The thing is quite possible, but it must be added 
 that a mirror of this kind could be of no use 
 whatever for bringing distant objects near without 
 the addition of a lens. But there is no reason
 
 26 A DAY IN THE MOON 
 
 why such an optical device should not have been 
 adopted at this period. This is shown by the 
 evidence already cited. 
 
 When therefore Galileo directed his telescope at 
 the Moon, it was perhaps not the first time that 
 man had made celestial objects seem nearer to him, 
 and who can say if the priests of old Egypt may 
 not have watched from the summits of their 
 observatories the last eruptions of the lunar 
 volcanoes ?
 
 Ill 
 
 THE MOON AS SEEN BY THE 
 NAKED EYE 
 
 ONE September day some years ago I was in Paris 
 taking a quiet walk along the quays by the Seine, 
 when there suddenly came to me the idea of making 
 a long journey. I had three weeks in front of me, 
 more than is necessary for getting far away from 
 the capital. 
 
 On one point only I was embarrassed. Where 
 was I to go ? 
 
 But two hours later I was in the express on my 
 way to Amsterdam. I had taken the first train 1 
 found starting from the Gare du Nord. 
 
 And this was how I came to visit Holland. 
 
 But I would not now advise anyone to adopt 
 this way of setting out on a journey. 
 
 Those who study in advance the regions they 
 are about to visit (and there are many who do so) 
 
 seem to me to be much better advised. 
 
 27
 
 28 A DAY IN THE MOON 
 
 Let us imitate those serious and sensible people, 
 and before setting out for the Moon let us study 
 together the facts that are essential for the under- 
 standing of the celestial phenomena connected with 
 our satellite. 
 
 And, first of all, what is a satellite ? What is 
 the meaning of this word that we so often apply 
 to the Moon ? 
 
 You know that the Solar System is composed 
 of a great central body round which revolve certain 
 planets, smaller than itself. 
 
 Now, these planets are in several cases accom- 
 panied in their stately movement of revolution by 
 other stars smaller than themselves, as a kind of 
 bodyguard. 
 
 The number with each planet varies. Mars has 
 two of them, Jupiter eight, and a telescope of very 
 moderate power will show you the four largest of 
 these. 
 
 If we could go away some hundreds of thousands 
 of miles from our Earth, we should see that it 
 was, in the same way, accompanied in its rapid 
 course by a single satellite. This only child of our 
 dear mother Earth is the Moon. 
 
 Let us go back in imagination several thousand
 
 29 
 
 centuries to the time when the Earth, a vast 
 globular mass of gas at a high temperature, shone 
 like a miniature sun. 
 
 Beside this relatively small star there would be 
 not a trace of a satellite, but around it an immense 
 ring of diffused matter resembling, though of more 
 restricted dimensions, that which we see in the 
 nebula of the constellation Lyra. 
 
 Ages pass by, and the spectacle has gradually 
 changed. There has been a movement of the 
 Earth's axis, and now all the material of its primi- 
 tive ring, instead of lying in spirals around it, has 
 concentrated into a single compact mass. The 
 ring has been the origin of a very small luminous 
 body revolving round that star the Earth. 
 
 Earth and Moon at this epoch shone with a 
 brightness that was all their own. They formed 
 in the heavens one of the lesser double stars, of 
 which the component units are linked together by 
 the laws of attraction. 
 
 To analyse what must have taken place under 
 these new conditions of existence is a problem of 
 celestial mechanics that is easy of solution. 
 
 First of all, like all the heavenly bodies, the 
 Moon turned on its own axis that is to say, to
 
 30 A DAY IN THE MOON 
 
 its movement of revolution, making it follow an 
 orbit round the Earth, there was added a movement 
 of rotation on itself completed in the course of a 
 few hours. 
 
 But when two bodies in a fluid state are in 
 presence of each other at a moderate distance, an 
 elongation of their shape is produced, a kind of 
 spreading out in the direction of the line joining 
 them together ; it is the same phenomenon as 
 that of the tides, and each region as it passes 
 before the attracting body is in turn influenced 
 by it. 
 
 Now, the mass of the Earth is enormous in 
 comparison with that of the Moon, and accord- 
 ingly at this remote period the tides of the 
 satellite must have been produced with extra- 
 ordinary intensity. 
 
 Thus at each turn of its rotation the convex 
 distortion of the lunar mass under the attraction 
 of our globe would act just like a brake applied 
 to the Moon, generally retarding its motion, so 
 that the final result of this phenomenon would be 
 that the time of its rotation on its axis and its 
 revolution round the earth would gradually become 
 equal.
 
 From a photograph. 
 
 EARTH-LIT NEW MOON. 
 
 30]
 
 AS SEEN BY THE NAKED EYE 31 
 
 At present things go on just as if the Moon 
 were fixed to the Earth by an enormous arm keeping 
 it in the same relative position, and checking any 
 deviation to right or left. 
 
 And this is why we always see the same side of 
 the Moon. 
 
 The ancients had long ago noticed this fact, 
 which you yourself can test by observation with 
 the naked eye, especially at the time of the Full 
 Moon, when you will see that the spots are always 
 arranged in the same way. 
 
 From remote times the peoples of antiquity 
 traced in it a kind of human face with two eyes, 
 a mouth, and 'a nose. Sometimes, as nowadays, 
 men took the appearance to be that of a man 
 bending under a burden. 
 
 Albertus Magnus has left us a description of 
 the Moon which is extremely precise for a time 
 when the human eye was not aided by magnifying 
 instruments. Well, this description corresponds very 
 exactly with what an astronomer of to-day would 
 say. 
 
 So the Moon, since man appeared on the Earth, 
 has always presented the same side to us. 
 
 Are we to conclude from this that it does not
 
 32 A DAY IN THE MOON 
 
 rotate upon itself? If you please, do not jump 
 to hasty conclusions, but let us examine the question 
 more closely. 
 
 Walk round a table in the middle of which you 
 have placed something, and don't take your eyes 
 off this object, which will represent the Earth, 
 while you are playing the part of the Moon. 
 
 When you have gone half-way round, it is 
 evident that you will be facing the wall of the 
 room that was behind you at the beginning of 
 the experiment. Thus, without paying attention 
 to it, you will have already yourself turned half- 
 round. 
 
 Finally, by the time you have come back to the 
 point you started from, you will have completed 
 one round " of your orbit," and at the same time 
 you yourself will have turned completely round, 
 just as if you had made a slow pirouette on your feet. 
 
 There would be just the same sort of thing if 
 a balloon could go all round the world. When 
 they reached the Antipodes the aeronauts, compared 
 with ourselves in the north, would be head down- 
 wards, and by the time they returned to our regions 
 they would have slowly made a regular somersault, 
 like the clowns in a circus.
 
 AS SEEN BY THE NAKED EYE 33 
 
 And nevertheless during all this voyage men 
 remaining below on the Earth would see only the 
 lower part of the balloon, which would always keep 
 the same side towards them, just as the moon does. 
 
 " Well, then," you will say, " we are condemned 
 never to have a sight of the other hemisphere of 
 the Moon ? " 
 
 " Evidently." 
 
 " Has it the same structure as that which we 
 can see craters, mountains, valleys, etc. ? " 
 
 This is a point to which we shall return later on. 
 
 The other side of the Moon, precisely because we 
 cannot see it, and shall never see it at least unless 
 we go there has always, like all unknown things, 
 exercised a mysterious attraction on selenographers, 
 and we shall refer to it again. 
 
 Let us come back, then, to the subject of the 
 appearance of the Moon. 
 
 I have met many persons who do not even 
 yet understand why the Moon does not always 
 appear under the form of a perfectly circular disc. 
 They have remained in the same state of knowledge 
 as was that of remote antiquity, or rather they 
 have no ideas on the subject. They don't know, 
 and they are not anxious to know. 
 3
 
 34 A DAY IN THE MOON 
 
 The Chaldasan astronomer Berosus, to explain 
 the phenomenon, supposed that the Moon was a 
 globe half alight and half dark, and that in turning 
 upon its axis it showed us these different regions 
 in succession. 
 
 However, there were, even before Berosus, 
 philosophers who knew better, and had found 
 out the true explanation. 
 
 Thales had perfectly well noted that the Moon 
 received its light from the Sun, and later Aristarchus 
 rightly remarked that at the moment when the 
 Moon was half lighted up, the Earth was exactly 
 opposite the dividing line between light and 
 darkness, while the direction of the Sun was at 
 right angles with the line between Earth and Moon. 
 
 Make the experiment yourself with a white 
 ball hanging by a string in a room lighted by a 
 single lamp, and you will soon succeed in working 
 out the position of which Aristarchus speaks. 
 
 This able mathematician did even better. From 
 this observation he deduced a method of measuring 
 the distance of the Sun, and he found that it was 
 nineteen times greater than the space that separates 
 us from the Moon. 
 
 He had made a mistake in the application of
 
 Photograph by the Lick Observatory. 
 
 THE MOON AT THE FIRST QUARTER 
 
 (Aged 7 days 3 hours). 
 
 34]
 
 AS SEEN BY THE NAKED EYE 35 
 
 his idea, but in principle it was right enough, and 
 Kepler more than once recommended this method. 
 
 Vendelinus and Riccioli made use of it, but with- 
 out any more success. In a telescope the Moon 
 in fact does not appear as a perfectly even sphere, 
 and the irregularities of its surface make it hopeless 
 to fix any precise moment when the line between 
 light and shadow is really a straight one. 
 
 But, on the other hand, the invention of the 
 telescope in 1610 removed all possible doubt as 
 to the explanation of the Moon's phases. 
 
 In the field of view of the instrument it was 
 in fact easy to follow hour by hour the flooding of 
 new regions of the Moon by the Sun's light. 
 
 And, nevertheless, though one can hardly 
 believe it, in 1613 Albergotti still taught, as a 
 professor of Astronomy, that the Moon gave a light 
 of its own, and to prove this he appealed to 
 Biblical texts which he interpreted in his own way. 
 This mania for mixing, without any reason, Holy 
 Scripture and scientific theory (from which, by the 
 way, Galileo himself was not exempt) seems to us 
 nowadays extraordinary. And, nevertheless, I have 
 come across it more than once, as is shown by 
 many letters I have received on the subject.
 
 36 A DAY IN THE MOON 
 
 A little reflection, seasoned with some extremely 
 simple experiments, will show us the real mechanism 
 of the phases of the Moon. 
 
 Let us take once more our white ball, hanging 
 on a string and held at arm's length, with a lamp 
 placed on a table on a level with the eye, and, 
 without moving from the spot where you stand, 
 carry the ball in a circle round your head, which 
 will represent the Earth. 
 
 Only you must take care to keep the ball a 
 little above the level of the eye, for the Moon 
 moves in an orbit slightly inclined to the path 
 followed by the Earth. 
 
 Let us begin with the position of Full Moon. 
 
 The ball is at the other side of your head from 
 the lamp. Facing it, you see that it presents a 
 disc entirely illuminated. 
 
 As you move it from this position you begin to 
 perceive a narrow segment of shadow, cutting ofF 
 a little of the illuminated circle. As you continue 
 the movement in the same direction you arrive at 
 the Last Quarter, and the boundary line between 
 the shadow and the light will divide the disc into 
 two equal parts, the lighted part being to the left. 
 
 Again a slight movement, and the shadow will
 
 Direction, of Sun, 
 
 Full Z Moon 
 
 THE PHASES OF THE MOON. 
 
 361
 
 AS SEEN BY THE NAKED EYE 37 
 
 gain further ground, and soon leave only quite a 
 thin crescent. As soon as the Moon is in the same 
 direction as the Sun, above or below it, it turns its 
 dark side to us and the disc entirely disappears. 
 This is the Old Moon. 
 
 Starting from this position we have the phases in 
 reversed order, and we come to the First Quarter, 
 and then the Full Moon, and so on. 
 
 If the experiment is reversed, going round the 
 ball held at arm's length so that your head re- 
 presents the Moon, you will see that our Earth 
 would present to the Selenites 1 as we might call 
 the inhabitants of the Moon, if there were any 
 similar phases, but in the opposite order. 
 
 In other words, when, for instance, after the New 
 Moon the people of the Earth see their satellite 
 under the form of a crescent, the Selenites would 
 see the Earth in its last quarter, that is to say 
 three-fourths illuminated. 
 
 And this remark will explain to you why at this 
 period of the lunar month we see not only a thin 
 and very bright crescent, but sometimes the rest of 
 the Moon dimly illuminated by the diffused reflec- 
 tion from the Earth. 
 
 From Selene, the Greek name for the Moon. Translator's Note.
 
 38 A DAY IN THE MOON 
 
 This is what is called the " earth-shine " on the 
 Moon. 
 
 We have said that the Moon revolves in an 
 orbit obliquely inclined to the plane of our own. 
 The inclination is slight only 5 8' but it is 
 nearly constant. The result is that the Moon does 
 not always pass precisely between us and the Sun. 
 If it passes at a point where it hides that brilliant 
 disc from us, there is an eclipse of the Sun. If, on 
 the other hand, when passing on the opposite side of 
 the Earth, it is hidden in the shadow of our planet, 
 there is an eclipse of the Moon. 
 
 These two phenomena therefore take place only 
 at the time of New or Full Moon, and they recur 
 in a series that extends over about eighteen years. 
 
 These are extremely interesting topics from the 
 astronomical point of view, and we shall return to 
 them. But we shall end this chapter with an 
 attempt to solve a question which has caused the 
 expenditure of floods of ink since first men became 
 interested in it. 
 
 Why does the Moon appear larger on the horizon 
 than when at its highest point ? 
 
 I have said " appear larger," because this is cer- 
 tainly a mere optical illusion.
 
 Photograph by P. Puiseuz, Paris. 
 
 THE MOON 
 (Aged 8 days 23$ hours. February 6th, 1903, 4.3 a.m.). 
 
 38]
 
 AS SEEN BY THE NAKED EYE 39 
 
 In reality its disc is larger when in the zenith, 
 the highest point of the sky, than it is near the 
 horizon, as is shown by measurements made with a 
 micrometer fitted to a telescope. And this is what 
 theory should lead us to expect, for the Moon in 
 the zenith is slightly nearer the observer. But this 
 very small difference is quite unappreciable to the 
 naked eye, and we may say, still keeping close to 
 the exact truth, that as seen by us the Moon always 
 occupies precisely the same amount of space in the 
 heavens. 
 
 Then why does it seem to us larger when it is 
 near the horizon, and apparently therefore near the 
 Earth ? 
 
 And remember that this phenomenon is not 
 something special to the Moon. The Sun in the 
 same position also appears larger to us, and finally 
 the constellations themselves seem to occupy more 
 space when they are to all appearance nearer the 
 ground. The most humble student of the heavens 
 can see this for himself any evening if he will 
 observe the Great Bear at different hours of the night. 
 
 There are plenty of theories to explain such 
 appearances. One of them is based on the fact 
 that we cannot avoid mistakes in judging distances
 
 40 A DAY IN THE MOON 
 
 accordingly as the background, on which the object 
 is seen, is bright or dark. And a fog makes 
 objects seem larger because it makes them seem 
 farther off. Here is an instance of such a mistake 
 from my own personal experience. 
 
 One summer day about dawn I was taking a 
 walk with a friend in a country that neither of us 
 knew well. The road rose steeply in front of us, 
 and where its highest point met the sky-line we 
 saw, coming into sight over the crest, what looked 
 like someone in a rather short dress, such as the 
 countrywomen wear in many parts of the province 
 of Berry. We were for a moment in doubt as to 
 what kind of person we were about to meet. I bet 
 that it was an ecclesiastic in a soutane, my friend 
 that it was a peasant woman. But the distance 
 between us and the subject of our wager was not 
 at all as great as we imagined. We were soon close 
 up to the " person " in question. We had both 
 lost our wager. For a goose was walking in stately 
 fashion down the middle of the road, with its head 
 directly towards us. The twilight haze had de- 
 ceived us as to the real distance, and the object, 
 projected against what we thought to be a far-off 
 background, had assumed an enormous size.
 
 From a photograph. 
 
 THE FULL MOON. 
 (Aged 14 days i hour). 
 
 40]
 
 AS SEEN BY THE NAKED EYE 41 
 
 It is true that at the moment when one of the 
 heavenly bodies is rising its rays reach us after 
 traversing a denser layer of the atmosphere than 
 when it is nearer the zenith ; its brightness is 
 diminished and it appears larger to us. But this is 
 only an imperfect solution of the problem. For, 
 as a matter of fact, when the bright disc shows dull 
 and grey through a dense fog it never gives us the 
 same impression of size as the broad sunset Sun. 
 Fog and haze, therefore, do not explain every- 
 thing. 
 
 Another theory is based on the absence of points 
 of comparison, when the Sun or Moon are at the 
 highest points of their course. 
 
 As it rises, the Moon is seen as a part of the 
 landscape, and we have objects close by with which 
 to compare it. There are none of these as it 
 approaches the zenith. It seems to be nearer us, 
 and though its apparent diameter has not really 
 changed, we think it looks smaller. 
 
 But here again we have not the real key to the 
 riddle. For at sea in calm weather, especially in 
 the evening, though there are absolutely no objects 
 with which to compare the size of the setting Sun, 
 the illusion remains just as strong. It is the same
 
 42 A DAY IN THE MOON 
 
 on a plain, where there is not a tree or a house to 
 help the observer's estimate. 
 
 We must therefore, as I have shown long before 
 this, have recourse to a theory based on psycho- 
 logical principles, and my explanation rests upon 
 two optical illusions that it is easy to test. 
 
 In the first place, the firmament that is to say, 
 the ideal vault to which, whether we will or not, we 
 attach in imagination all the stars, as if they were 
 equally distant seems to us a flattened curve and 
 not spherical. 
 
 The reason is very simple. For us the Earth 
 seems always flat, though we well know the con- 
 trary, and the masses of cloud carried overhead by 
 the wind appear some hours later to touch the 
 horizon. 
 
 Now, above the clouds we place the stars, and 
 we instinctively imagine the vault of the clouds 
 and the stellar vault as parallel curves, and thus 
 both are for us flattened arches bending down to 
 the horizon, so that there the heavenly bodies would 
 be farther off than at the zenith. 
 
 If I am met with the objection that even with 
 a clear sky there is the impression of the vault of 
 the heavens being flattened in the same way, I find
 
 Photograph by P. Puiseux, Paris. 
 
 THE MOON 
 (Aged 20 days 19 hours. September izth, 1903, 3.13 a.m.). 
 
 42]
 
 AS SEEN BY THE NAKED EYE 43 
 
 an explanation in the fact that we have no means 
 of estimating distance in the sky, and, whatever be 
 the explanation accepted, the error and illusion 
 persist. The arch appears to us flattened at its 
 upper part. 
 
 In the second place, it is undeniable that the 
 apparent dimensions of an object are greater when 
 we project it upon a more distant background. 
 
 Do you want an example ? In the evening look 
 fixedly at the incandescent filament of an electric 
 light close to you. Then suddenly cast your eyes 
 on a more distant object, the front of the opposite 
 house seen through the window, or something still 
 farther off". The image of the lamp, still seen by 
 your eye, will seem enormous, and will occupy a 
 considerable surface of the dark background. 
 
 Here is the whole solution of the problem, and 
 I sum it up in a single phrase : the Moon seems 
 to us larger on the horizon simply on account of 
 the apparently flattened or elliptic form of the 
 sky. 
 
 Since I first stated this theory some astronomers 
 have sought for other explanations, and I have 
 found a better proof of my hypothesis. 
 
 When the Sun is setting in a clear sky and your
 
 44 A DAY IN THE MOON 
 
 eyes can easily endure its brightness, fix them for 
 a few moments on its still brilliant orb, then look 
 at another point of the horizon. Your retina will 
 present to you a dark spot, green, bluish, or black, 
 and you will be able to keep sight of it if you 
 take care frequently to wink your eyes. 
 
 Note attentively the apparent size of this sub- 
 jective image. It will naturally appear to you of 
 the same size as the solar disc, but and here we 
 have a complete confirmation of my theory if at 
 this moment you turn your gaze towards higher 
 and higher points of the sky, the same image will 
 appear to be diminished in size, and it will reach its 
 minimum surface when you see it at the zenith. 
 
 Here we have the solution of all difficulties, and 
 we may conclude with a somewhat picturesque 
 passage from the letters of Euler to a German 
 Princess : 
 
 " I believe," he said, with reference to the subject 
 that has occupied us, " that I have placed in its 
 true light the difficulty with which we have had 
 to deal in this matter, so as to make your Highness 
 the better appreciate the importance of the true 
 solution of this great problem."
 
 Photograph by the Lick Observatory. 
 
 THE MOON AT THE LAST QUARTER 
 
 (Aged 23 days 8 hours). 
 
 44]
 
 IV 
 WITH THE EYE AT THE TELESCOPE 
 
 HERE we are at our fourth chat about " lunar 
 matters," and we have already made serious progress 
 in the study of our satellite, from the mechanical 
 point of view. 
 
 Let us sum up rapidly what we have learned ; 
 this will help us not to forget, and give us the 
 opportunity of adding something to it. 
 
 At the outset the materials which were later on 
 to form the Moon were distributed in the shape 
 of an immense ring encircling the Earth at a 
 distance. The Moon was therefore never a part 
 of the Earth as the celebrated Laplace believed, 
 and as is held by a good number of his still living 
 followers. 
 
 We have even better reason for not falling into 
 the exaggerations of that American philosopher 
 
 who, in good faith, supposed that the Moon 
 
 45
 
 46 A DAY IN THE MOON 
 
 detached itself one fine day from the Earth, at 
 a period when the latter was already completely 
 formed. 
 
 "This enormous sphere rolling in space and 
 illuminating the landscapes of our Earth, what is 
 it in reality," he said recently, " but a fragment of 
 our planet, that once filled the gap left on our 
 maps by the great depression of the Pacific ? " 
 
 Astronomy, being now really a science, cannot 
 give its support to such fantastic theories. 
 
 When the ring, of which we have just traced 
 the history, had concentrated into a single mass to 
 form the Moon, the latter continued to revolve 
 around us, and Newton was the first to show that 
 in so doing it simply obeys the laws of gravitation. 
 It is only in virtue of its first impulsive force that 
 it does not fall directly towards the Earth. But 
 let us suppose that force suddenly vanishes ; im- 
 mediately the light of our nights would, just like 
 a mere stone, begin to move towards our globe, 
 and would reach it in less than five days of twenty- 
 four hours. 
 
 We have, for the sake of greater simplicity, 
 assumed that the Moon goes round us in a circle. 
 In reality, obeying the laws of motion discovered
 
 WITH THE EYE AT THE TELESCOPE 47 
 
 by Kepler, her orbit is slightly flattened in the form 
 of an ellipse. 
 
 And the Earth not being situated in the centre 
 of a circular orbit, it follows that the Moon is now 
 a little nearer, now a little farther off. 
 
 At its mean distance it is only 238,833 miles 
 distant. Its movement round the Earth is at the 
 rate of a little more than a thousand yards a second, 1 
 but at the same time it shares in the movement of 
 our globe round the Sun. 
 
 The figure which it describes in space is not then 
 in reality a circle, or even an ellipse, but a curve 
 that it is easier to represent than to define. 
 
 The perturbations in our own movement, which 
 are caused by this ball of 2, 1 60 miles in diameter, 
 are beyond imagination. 
 
 At the time of Full Moon it diminishes the 
 attraction of the Sun ; about New Moon, when it 
 is passing between us and the Sun, its attraction 
 unites with that of the latter in very slightly altering 
 the shape of the Earth's orbit. If the Moon is 
 behind the Earth in its path through space, it 
 diminishes our velocity, whilst it accelerates it as 
 it passes it front of us. 
 1 The average velocity is 3,334 ft. per second. Translates Note.
 
 48 A DAY IN THE MOON 
 
 All this might very easily be reduced to calcula- 
 tion, but, alas ! its orbit does not lie in the same 
 plane as ours, and we have seen that the mean 
 angle between the two planes is 5 8', and our 
 having to speak of a " mean " inclination tells us 
 that this also varies, so that altogether astronomers 
 have no easy task in making their way through 
 this labyrinth of masses, positions, distances, and 
 the rest. 
 
 Add to this that the ideal ellipse traced out by 
 the course of the Moon is itself deformed by the 
 attraction of the Earth ; that the flattening of its 
 curve becomes more marked for a certain time, and 
 then again diminishes, and you have a feeble idea 
 of the Chinese puzzle the Moon inflicts on students 
 of the mechanism of the heavens. 
 
 The period of its revolution that is to say, the 
 time it takes to come back to the same apparent 
 point among the stars is known to the hundredth 
 of a second, but it also is variable. 
 
 Actually it is about 27 days, 7 hours, 43 minutes, 
 1 1 '5 5 seconds. 
 
 During this time it appears to make a complete 
 circuit of the heavens ; it changes its place therefore 
 each day to a very perceptible extent.
 
 w 
 
 H 
 
 4 . 
 < X 
 
 3 
 
 o oo
 
 WITH THE EYE AT THE TELESCOPE 49 
 
 And, in fact, if on a fine night you note the 
 apparent distance from the Moon to a star in its 
 neighbourhood, you will see that at the end of a 
 few hours there has been a considerable change 
 of place. It amounts to a little more than 
 13 in the twenty-four hours, and this in the 
 contrary direction to the movement of the celestial 
 sphere. 
 
 It follows from this that each evening the Moon 
 is about three-quarters of an hour behind its place 
 of the evening before. 
 
 The solar day being itself a little variable, one 
 can understand that it is impossible to base our 
 calendar on the observation of the Moon. 
 
 We shall have occasion later on to return to 
 some other points bearing on this matter, in order 
 to complete our account of the movements of the 
 Moon. For the moment we have something better 
 to do. Do you see from the window the Full 
 Moon rising slowly in the sky ? 
 
 Let us go quickly up to our observatory. 
 
 The night is perfectly clear. The breeze ha 
 fallen to a calm, and if there is no disturbance in 
 the upper regions of the atmosphere the sight to 
 be seen with the telescope will be wonderful. 
 4
 
 50 A DAY IN THE MOON 
 
 However, we must not be in a hurry, but go to 
 work in a systematic way. 
 
 Take first this opera-glass, which has a magni- 
 fying power of only three times. 
 
 Look through it ; according to what we have 
 already said, the disc of the Moon ought to appear 
 to you to have a surface nine times greater than 
 when seen with the naked eye. You see precisely 
 what Galileo saw the first time he directed a 
 telescope of this same power towards the Moon 
 that is to say, " precisely the same " so far as size 
 goes, for in the year 1610 he did not first observe 
 the Full Moon, but one of its phases. 
 
 At that moment certain details which now to 
 you seem drowned in the solar light would be more 
 marked, and so it was he compared them to the 
 eyes of a peacock's tail, thus linking the graces of 
 Diana and the charms of Juno's bird. 
 
 But what you can now see much more plainly than 
 with the naked eye are the dark, irregularly dis- 
 tributed spots. 
 
 You no longer recognise the face you have been 
 used to find there, and which the ancients saw there 
 more than two thousand years ago, as is proved by 
 these verses of Amyot, a translation from the Greek
 
 .. 
 
 s\1 ' ' J* 
 
 Oesenianhit rt am en j 
 et 
 
 DE RHEITA'S MAP OF THE MOON, 
 A.D. 1645.
 
 WITH THE EYE AT THE TELESCOPE 53 
 
 of Plutarch, who himself was quoting the poet 
 Agesianax : 
 
 "De feu luisant elle est environnee 
 Tout a 1'entour; la face enlumine 
 D'une pucelle apparaist au milieu, 
 De qui 1'oeil semble etre plus rouge que bleu, 
 La joue un peu du rouge coloree." * 
 
 All these sombre surfaces were a great puzzle to 
 the old astronomers, who at last took them to be 
 vast seas. 
 
 After all, it was not such a bad guess, and Pere 
 de Rheita gives us an explanation of it in a book 
 he published at Antwerp in 1645. 
 
 11 Not only," he says, c< the aspect of the Full 
 Moon is not different from that which the Earth 
 presents when seen in very fine weather from the 
 top of a high mountain, but it greatly resembles 
 it. In fact, as one has often been able to verify 
 by actual experience, the meadows and fields, the 
 mountains and the valleys, illuminated by the light 
 of the sun and bathed in it, are plainly visible 
 from the summit of a mountain, while the waters, 
 the lakes, rivers, and seas really look darker. 
 
 " She is environed all round with gleaming fire ; in the midst 
 appears the illumined face of a maiden, whose eye seems to be red 
 rather than blue, and her cheek slightly tinted with red."
 
 54 A DAY IN THE MOON 
 
 " But if one were raised above the Earth a 
 thousand, ten thousand, or twenty thousand leagues, 
 or the whole distance that separates us from the 
 Moon, and if one then observed the Earth with 
 an excellent telescope, I have no doubt that it 
 would appear to present a great resemblance to the 
 face of the Moon." 
 
 It was therefore admitted at this period that the 
 dark spots were seas, to which names were given ; 
 and although it is now proved that the Moon does 
 not contain a single drop of water, astronomers 
 have been so lazy, as to make no practical protest 
 against this deplorable system of names. 
 
 Kepler and Scheiner indeed made maps of our 
 satellite, but the first map worthy of the name was 
 engraved by Michael Florentins van Langren, 
 generally known by the name of Langrenus. This 
 map was completed and published in 1645. 
 
 Its author was probably the first to apply the 
 names of celebrated men to the features of the 
 Moon. 
 
 At the same time Peyresc and Canon Gassendi 
 of Digne also set to work on a complete map, 
 but they abandoned their task when they heard 
 that Hevelius had the same idea.
 
 WITH THE EYE AT THE TELESCOPE 55 
 
 But put away your opera-glass, and be so good 
 as to look through this telescope of moderate 
 power, which magnifies thirty diameters. The 
 fresh details you can now make out will give you 
 an idea of the complex spectacle the disc of the 
 Full Moon presented to the astronomers of 1650, 
 when they made up their minds to set it down 
 in a drawing. 
 
 The lunar mountains appearing in brilliant light ; 
 certain craters and circles showing their darker 
 interior ; whitish streaks radiating from the sides of 
 some of them ; and the greyish surface of the 
 " seas " which are nothing of the kind all to- 
 gether present a variety of aspects that is somewhat 
 confusing. 
 
 One would think it would have opened the 
 eyes of the first selenographers to the real facts 
 of the case. 
 
 Not at all. Hevelius did like his predecessors 
 and even exaggerated their nomenclature. 
 
 This Hevelius, whose real name was Hovel, was 
 a most enthusiastic student of the Moon. 
 
 He was born at Dantzig in 1 6 1 1 . His father, 
 a rich brewer in that city, intended him for 
 business, but Hevelius had other plans. When
 
 56 A DAY IN THE MOON 
 
 still young, he set off to London to complete his 
 studies, and then he went to Paris, where he formed 
 a friendship with Pere Mersenne, Boulliaud, and 
 Gassendi, then a professor at the College de France. 
 
 Till then he had been specially devoted to 
 mathematics, but an eclipse of the Sun, which 
 'took place on June i, 1631, keenly interested 
 him in Astronomy. 
 
 Returning to his native city in 1634, he succeeded 
 to the brewery, but his one real interest was the 
 study of the Moon. The observations which he 
 made at night he himself engraved on copper 
 next day. 
 
 He thus obtained plates of singular beauty, 
 which for more than a century were recognised 
 as authoritative in the world of selenography. 
 
 When it came to giving names to the points 
 shown on his chart he found himself in a difficulty. 
 
 He would have liked to place " up there " the 
 names of famous men, but, as he himself tells us, 
 he abandoned the idea, for fear of making enemies 
 of those who were left out, or who might think 
 their share too small. 
 
 He therefore decided to transfer to the Moon 
 the names of our seas, cities, and mountains.
 
 WITH THE EYE AT THE TELESCOPE 57 
 
 But of all this system of names, which was just 
 as good as any other, and which was published after 
 five years of arduous observation in his Seleno- 
 graphia, there remain now on our lunar maps 
 out of 250 names only those of the Alps, the 
 Apennines, and of four " promontories." 
 
 The Jesuit Riccioli of Bologna had not the 
 same fears as Hevelius. 
 
 He knew men, and, making use of the obser- 
 vations of his colleague Grimaldi, he did not 
 hesitate to place the names of learned men on the 
 map of the Moon. 
 
 These, flattered in their self-love, were sure to 
 buy copies, and this is how since 1651 the Moon 
 has become the " cemetery of astronomers " and 
 the " Pantheon of savants." 
 
 It is true that certain discontented spirits made 
 some small protests, and accused Riccioli of having 
 given more than their due share to his illustrious 
 colleagues of the Society of Jesus ; but the fear of 
 being struck out of the list carried the day, and 
 everyone was satisfied. 
 
 Besides, the learned of earlier days were not 
 forgotten, and there were seen rising above the 
 surface of the Moon famous craters and mountain-
 
 58 A DAY IN THE MOON 
 
 walled plains bearing the names of Archimedes, 
 Plato, Aristarchus, Ptolemy, Copernicus, Tycho, 
 Kepler, and the rest. 
 
 The names of the seas adopted by Hevelius, the 
 Caspian, the Mediterranean, the Euxine, etc., were 
 replaced by such names as the Sea of Storms, the 
 Sea of Humours, of Rains, of Fecundity, of Cold, 
 and other equally fanciful titles. 
 
 We must go on to 1680 before we find another 
 interesting attempt to produce a map of the Moon. 
 The Italian Domenico Cassini had received letters 
 of naturalisation in France, and was the first 
 director of the Observatory of Paris. Beginning 
 in 1673, he arranged for drawings of the phases 
 of the Moon to be made day after day by Patigny. 
 For this work the artist made use of a large 34-feet 
 telescope, which still exists. 
 
 The drawings were not published, but Cassini 
 prepared from them a map, including also his 
 own observations. It appeared in 1692, and 
 the copper-plate was long kept at the Royal 
 Printing Office ; but one fine day the director of 
 this State institution thought it was time to 
 get rid of some of the material that was piled 
 up in his storehouses, and the map of Cassini
 
 Facsimile of an engraving in the " Machina Ccelestis." 
 
 HEVELIUS AND HIS WIFE OBSERVING THE POSITIONS OF THE 
 HEAVENLY BODIES. 
 
 58]
 
 WITH THE EYE AT THE TELESCOPE 59 
 
 was included in a lot of copper-plates sold to a 
 boiler-maker. 
 
 And it was a great pity, for though we still 
 possess some reduced copies of this fine piece of 
 work, not one example of the original has come 
 down to us. 
 
 Arago, who tells the story, which he heard from 
 Bouvard, adds rather naively, " This director was 
 not, one may presume, a lover of Astronomy." 
 We can well believe it. 
 
 Cassini's plate was rather more than a foot and 
 a half in diameter. La Hire soon after undertook 
 the production of a globe of the Moon, and then 
 a map 4 metres in diameter, which was long dis- 
 played in a black frame on the staircase of the 
 library of Sainte-Genevieve. 
 
 Then came (1762) the reduced map of Tobias 
 Mayer (20 centimetres in diameter *), which remained 
 the only exact one till 1824. 
 
 Sir William Herschel paid much attention to 
 lunar studies, but he has left us no drawings of 
 his observations. Nevertheless, he indirectly con- 
 tributed to a deeper knowledge of our satellite, 
 and this in a rather unexpected way. 
 1 I.e. not quite 8 inches.
 
 60 A DAY IN THE MOON 
 
 As he had concave mirrors for telescopes con- 
 structed by hundreds in order to choose the best 
 of them for his own observations, and as at the 
 same time the salary he received was insufficient 
 for his expenses, he had the idea of selling to his 
 brother astronomers the mirrors he did not use. 
 
 Soon he had a European fame as an optician. 
 Everywhere his telescopes were appreciated at their 
 true value, and for once the proverb which says 
 that " Astronomy does not feed its adepts " was 
 found to be incorrect. 
 
 The sale of his mirrors was for Herschel a 
 source of almost unlimited profit. 
 
 The King of England ordered from him four 
 telescopes of lo-feet focus. Herschel let him have 
 them for ,660 a mere nothing. The King of 
 Spain was more generous, and paid him .3,150 
 for a telescope of 25-feet focal length. Two smaller 
 instruments were bought by Lucien Bonaparte in 
 1814 at the price of 2,310. 
 
 The regular scale of prices began at 228 for 
 a reflector of y-feet focus, and went up to 2,600 
 for an instrument of 20 feet. The orders were 
 numberless. 
 
 One might at first sight think that the distribu-
 
 THE MOON. 
 
 60]
 
 WITH THE EYE AT THE TELESCOPE 61 
 
 tion throughout the learned world of these powerful 
 telescopes, far superior to those that had been con- 
 structed before Herschel's time, would result in 
 enormous progress in Astronomy. 
 
 But there was nothing of the kind ; and this 
 once more proves the assertion that " The most 
 essential part of an optical instrument is the eye 
 that looks through the eye-piece." 
 
 To do useful work in Physical Astronomy, what 
 is wanted is, in fact, the skilled eye guided by a 
 brain. Hence the need of a long and patient 
 training of the sense of sight, attentive and reason- 
 ing observation of the phenomena to which it is 
 directed ; perfect sincerity, the entire abandonment 
 of preconceived ideas all united to a passionate 
 love for science and truth. 
 
 The numerous possessors of Herschel's telescopes 
 were doubtless lacking in the required qualities, for 
 most of them made no new observation of any 
 particular value. 
 
 Nevertheless, two of them, Schroeter and Pond, 
 were exceptions, and thus the efforts of the cele- 
 brated Hanoverian astronomer in this direction 
 were not useless. 
 
 Schroeter studied the Moon for many years,
 
 62 A DAY IN THE MOON 
 
 and published his interesting Fragmenta Seleno- 
 graphica. 
 
 " He was," says Goodacre, " a poor draughtsman, 
 but, notwithstanding this defect, his sketches have 
 considerable value." 
 
 At the beginning of the nineteenth century we find 
 Lohrmann and Gruithuisen at work, but the latter 
 was haunted by absurd ideas which he tried to set 
 forth in his drawings. He was convinced that signs 
 of life and civilisation were to be seen in the Moon. 
 
 It was then that Beer and Madler showed by 
 the colossal work which they brought to a successful 
 completion what a student of the heavens can accom- 
 plish with the help of an instrument of very 
 moderate power. 
 
 Their telescope had an aperture of not quite 
 4 inches ; and, nevertheless, it was sufficient for 
 them to accumulate on a map 90 centimetres 1 in 
 diameter such a number of details that the other 
 selenographers confessed they had not the courage 
 to compete with them. 
 
 However, in 1 8 64 the British Association formed 
 a committee with the chief object of popularising 
 the study of the Moon. 
 
 1 35 -4 inches.
 
 WITH THE EYE AT THE TELESCOPE 63 
 
 In 1874 Nasmyth and Carpenter published a 
 magnificently illustrated volume representing the 
 features of the Moon's surface from models made 
 by the former of these observers. 
 
 From the artistic point of view no previous 
 representation could give a better idea of what one 
 sees in the telescope than those relief-pictures by 
 Nasmyth. 
 
 Direct photographs are more exact, but they are 
 far from having the charm of this work, which one 
 never tires of examining. 
 
 Neison's book, published two years later, pays 
 special attention to precision of detail, and adds 
 several thousand new objects. 
 
 From this date we decidedly enter upon a new 
 phase of Selenography. The work of Beer and 
 Madler is surpassed by these later productions, to 
 which was added in 1878 the largest map yet 
 published. 
 
 For thirty-five years Schmidt had been spending 
 his time in studying and drawing the Moon. 
 Making use of Lohrmann's measurements for the 
 positions of the objects, he collected together the 
 details contained in more than three thousand 
 original drawings, in a large map 1^87 metres in
 
 64 A DAY IN THE MOON 
 
 diameter, 1 which was published by the Prussian 
 Government. 
 
 Unfortunately, no second edition of this map 
 was issued, and it is now not to be had. It con- 
 tains no less than 32,856 "craters." 
 
 The British Association, when it founded its 
 committee, proposed the publication of a map 
 5 metres in diameter. 2 But this ambitious project 
 has not been carried out. 
 
 Though we have to do without this regular 
 " ordnance map " of our satellite, we can mean- 
 while content ourselves with the works of Neison 
 and Elger, the drawings of the French pasteur 
 Gaudibert, and finally Goodacre's map, which 
 measures nearly 2 metres 3 in diameter. The author 
 has made use of the wonderful photographs obtained 
 in America, and above all, those of the Observatory 
 of Paris, to fix the form of the principal ranges 
 and peaks, using special drawings for the minute 
 details that are only to be seen with the most 
 powerful instruments. 
 
 I suppose you would like to see these fine details 
 with your eye at the eyepiece of a telescope. 
 
 1 73-62 inches, just over 6 feet. 
 
 2 A little over 16 feet. z About 6 feet.
 
 WITH THE EYE AT THE TELESCOPE 65 
 
 But you should know, my dear reader, that, for 
 this, one must choose one's date ; never make 
 the experiment at the time of Full Moon, but on 
 some evening about the First Quarter, for instance, 
 at the moment when the Sun is just lighting up 
 with his first rays the high summits of the lunar 
 Alps and Apennines. 
 
 Oh ! then I promise you a splendid sight, of 
 which you can never tire. 
 
 No photograph, no drawing, can give a real idea 
 of the sight of the Moon through a powerful 
 telescope. 
 
 If we could accomplish this distant journey, we 
 should make it at one of these exceptional moments, 
 so as to be able to watch the sunrise and see the 
 day-star rise slowly in the sky, lighting up step 
 by step the towering peaks, and penetrating with 
 its rays the hollows of the yawning craters and the 
 black pits that are scattered over the surface of our 
 satellite, while its cold light traces on the boundless 
 plains shadows that stretch away beyond the reach 
 of sight.
 
 V 
 ON THE WAY 
 
 A WEEK has passed since the moment when the 
 crescent of the New Moon first showed itself in the 
 twilight. If we were of the Mohammedan religion 
 we would be careful to note the exact hour of its 
 appearance, which at certain periods of the year 
 fixes the end of the fast of Ramadan. 
 
 Some days after we noticed the " earth-shine " on 
 the moon, "the Old Moon in the arms of the 
 New," to use a picturesque expression well-known 
 to astronomers. Then, as the boundary between 
 shadow and light advances little by little, a half of 
 the disc of our satellite is at length illuminating 
 with its uncertain radiance the landscapes of 
 our Earth. Now is the favourable moment for 
 making the long journey to which I have invited 
 you. 
 
 But what about the means of making it ? It is 
 here the difficulty begins, and ancient and modern 
 
 66
 
 
 CYRANO DE BERGERAC'S FLIGHT TO THE MOON 
 (From an old engraving).
 
 ON THE WAY 69 
 
 romancers (including Cyrano de Bergerac) have in- 
 vented only improbabilities. 
 
 Perhaps some centuries to come the problem will 
 be solved, and solved in the simplest way in the 
 world, so let us not worry about such a trifle. 
 
 Before the invention of balloons and aeroplanes 
 no one thought seriously of being able to rise in 
 the air. 
 
 Whoever finds out a means of suppressing or 
 even diminishing the force of gravitation, that 
 mysterious power which holds the heavenly bodies 
 together and keeps us fixed to the earth, will thus 
 enable men to leave their planet and launch out 
 upon the conquest of neighbouring worlds. And 
 the Moon will be the first stage of these inter- 
 planetary voyages. 
 
 I grant that it seems a daring supposition, but it 
 is in no way an absurd one from the point of view 
 of mechanics and physics. 
 
 But as to the physiological question that is 
 another matter. 
 
 The temperature of interplanetary space is near 
 absolute zero that is to say that during all its 
 course a machine moving towards the Moon or a 
 shell fired at that distant target would remain
 
 70 A DAY IN THE MOON 
 
 constantly at about 450 degrees (Fahrenheit) below 
 zero. 
 
 Unless indeed radium or some similar substance 
 should give us the means of bottling up heat, or 
 that .... 
 
 But no ! Let us stop ! This is not a romance that 
 we have to relate in detail. And at the present 
 moment science need not trouble about your means 
 of travelling to the Moon, and every day astrono- 
 mers explore this distant region more easily than 
 the pioneers of our globe explore the Antarctic. 
 
 The conditions of existence over there are as well 
 known as those here on the Earth, and with one 
 leap we can take the selenographers for our guides 
 and come down into the middle of a lunar land- 
 scape, more easily than you go from London to 
 Paris. 
 
 So we make our start. 
 
 At about six miles above the surface of the earth 
 respiration becomes painful ; at about twelve miles 
 the air is so rarefied that no animal " worthy of the 
 name " could live there even for the briefest 
 moment. Organic germs like bacteria and vibrios 
 would, however, survive. Carried to those lofty 
 regions by whirlwinds (which, by the way, are not
 
 ON THE WAY 71 
 
 very frequent events), they would come down again 
 uninjured from their perilous ascent. 
 
 At 1 60 miles there is proof that there is still an 
 atmosphere, but so attenuated, so slight, that it is 
 almost an abuse of language to give the name to 
 even the sum-total of the molecules to be found there. 
 
 At a little over 8,000 miles that is to say, when 
 we have traversed a distance about equal to the 
 diameter of the earth the great globe that we have 
 left, seen from this distance, would occupy about 
 40 degrees of the heavens. 
 
 We pass the space of another terrestrial diameter ; 
 we continually increase our distance till it is three, 
 four, five . . . nine diameters, the Earth steadily 
 diminishing in apparent size. At ten times this dis- 
 tance it is still a magnificent object in the sky with 
 an apparent diameter of more than 5 degrees, and 
 with a hundred times a greater surface than that 
 of the Full Moon seen from the Earth. 
 
 At the same time the size of our satellite is 
 visibly increasing. 
 
 When we have arrived, what will be the apparent 
 diameter of the Earth in the heavens ? 
 
 Here is a problem in geometry that is easy 
 enough to solve.
 
 72 A DAY IN THE MOON 
 
 Let us suppose, first of all, that two astronomers 
 are at two places the distance between which is just 
 equal to the radius (half-diameter) of the earth. 
 This condition, moreover, is easy to realise, as you 
 shall see for yourself. 
 
 If you want to divide a circle, representing the 
 earth's circumference, into six exactly equal parts, 
 all you need do is to take a compass opened 
 out to the length of the radius, and starting 
 from any point of the circumference, mark off 
 in succession round the circle, six points each the 
 length of the radius apart. The sixth will bring 
 you back to your starting-point. Join all these 
 points together and to the centre, and you will have 
 six triangles, of which all the sides will be equal 
 and therefore all the angles also equal to each other. 
 Each angle at the centre is clearly equal to one-sixth 
 of 360 degrees (the angular measurement of the 
 whole circumference), and thus it will be 60 degrees 
 exactly. 
 
 It follows that two observers placed 60 degrees 
 apart on the Earth are separated, in a straight 
 line, by a distance just equal to the Earth's radius. 
 
 In practice it will be understood that one can 
 take into account the flattening of the Earth's shape,
 
 ON THE WAY 73 
 
 and even make the observations from any two points 
 of which the position is exactly known, the rest 
 being only a matter of calculation and the principle 
 being the same. 
 
 Let us suppose, then, our two astronomers are 
 posted at the ends of a line equal to the radius 
 of the Earth. You will grant that it will be easy 
 for each of them, just at the same moment, to direct 
 his instrument at the centre of the Moon and 
 measure the angle at the base of the long triangle 
 thus formed, the base being the line between them 
 on the Earth, and the sides the lines joining each 
 observer to the centre of the Moon, the line of 
 sight of the observation. 
 
 Very well. But now our problem is solved, for 
 every one knows that if one adds together the 
 three angles of a triangle the total is 180 degrees. 
 
 Let us take an example. Our two astronomers 
 have obtained for their base angles, one 100, the 
 other 79. 
 
 100 4- 79 = 179 ; and 179 taken from 180 = 
 i degree. The angle at the summit of the long 
 triangle would in this case have exactly the value 
 of one degree. 
 
 Well, this experiment has been made in several
 
 74 A DAY IN THE MOON 
 
 different ways, and astronomers have always found 
 a value nearly equal to one degree, or exactly 
 57 minutes and 2 seconds. 
 
 As early as the beginning of the eighteenth 
 century Baron Krosigk spent considerable sums in 
 determining, by the method we have outlined, the 
 distance of the Moon from the Earth. 
 
 It was he who first had the idea of choosing the 
 Cape of Good Hope and the city of Berlin as the 
 bases of operations. 
 
 These two points of observation are situated just 
 over 86 degrees of latitude apart, and nearly on the 
 same meridian. It was perfect. 
 
 It was therefore decided that William Wagner 
 should remain in Europe, while Peter Kolbe went 
 to the Cape. Unfortunately, the former of these 
 two observers did his part of the business very badly, 
 and the affair had to be put off to a later occasion. 
 
 In 1751 the Paris Academy of Sciences took up 
 the project again. The Abbe Lacaille was sent to 
 the Cape, and Lalande to Berlin. This time the 
 operation was completely successful. It was the 
 first serious determination of the distance between 
 the Earth and our satellite. Man had at last made 
 the first step in the conquest of the heavens.
 
 ON THE WAY 75 
 
 We may be allowed to go a little farther into 
 this matter, which, though it is really so simple, 
 is often misunderstood even by educated persons. 
 
 Let us return to the problem we have already 
 discussed. From the solution we gather that an 
 observer placed in the Moon would see the radius 
 of the Earth under an angle of 57 minutes. Our 
 planet would of course appear to him under double 
 this angle, for as two radii equal one diameter, we 
 have 57' x 2 = 114 minutes or, what comes to 
 the same thing, i 54'. 
 
 Now, as many times as the angle i 54' is con- 
 tained in 360 degrees, so many times could a 
 Selenite place Earths, one touching the other, round 
 a whole circumference of the sky. 
 
 Let us work out the calculation this time. It 
 will only take a moment. 360 degrees, or 21,600 
 minutes, divided by 114 minutes (or i 54') will 
 give us the figure 189. 
 
 If we suppose the orbit of the Moon to 
 be exactly circular, it will therefore be equal 
 to 189 times the diameter of the Earth at the 
 equator. 
 
 The radius of this orbit, or the distance of the 
 Earth from the Moon, will now be obtained easily
 
 76 A DAY IN THE MOON 
 
 by dividing this value by twice 3* 14 16,* or 6'28 in 
 round numbers. 
 
 Now, 189 divided by 6' 2 8 =30, nearly exactly. 
 
 From which we must conclude that the distance to 
 the Moon could be filled up with only thirty Earths. 
 
 Taking the equatorial diameter of our Earth 
 according to recent measurements as 7,926*6 miles, 
 we have for the approximate distance 237,798 miles. 
 
 To simplify our calculation we have left certain 
 figures out of account. Bringing into our reckoning 
 the latest valuations, and not neglecting tenths of a 
 second, we get for the measurement 238,833 miles. 
 
 Even the error of a second would not make a 
 difference of 28 leagues in the result. One can see 
 very well by this example the precision obtained 
 by the methods of modern Astronomy. We actually 
 know the distance of our satellite to within a few 
 miles. 
 
 To determine the size of the Moon is now mere 
 child's play. It is easy for us to measure the 
 apparent angular diameter of the Moon. It is just 
 over 31 minutes. 
 
 At the same distance the Earth would appear 
 
 1 Non-mathematical readers may be reminded that 3'i4i6 is the 
 value of the circumference of a circle whose diameter is I. Trans- 
 lator's Note.
 
 S o 
 
 1
 
 ON THE WAY 77 
 
 about four times larger, for we have found its 
 diameter to be 114 minutes. 
 
 Taking the diameter of the Earth as the starting- 
 point, work it out by the Rule of Three, and you 
 will find for that of the Moon about 2,155 miles, 
 which will give you its volume as 49 times smaller 
 than that of our globe. 
 
 It remains to determine the mass and weight of 
 the Moon, but this question would take some time, 
 and we shall soon have occasion to refer to it again. 
 
 Besides, during this long talk we have made 
 serious progress towards our satellite. 
 
 A distance of 238,833 miles to traverse : but 
 that is not a very great affair only 30 times the 
 diameter of the terrestrial globe. 
 
 A country postman who makes a daily round of 
 over 1 8 miles would walk in 35 years as far as the 
 whole distance between Earth and Moon. 
 
 Our express engine-drivers have to their credit 
 much longer totals of travel. 
 
 An aviator who has any respect for himself easily 
 does 100 kilometres 1 an hour. At this rate, and 
 supposing he could keep up the same speed, he 
 would reach the Moon after a flight of 1 60 days. 
 1 62^ miles.
 
 78 A DAY IN THE MOON 
 
 On the day when men have at their disposal an 
 explosive powerful enough to give to a shell an 
 initial velocity of 12 kilometres 2 per second, the 
 shell shot into the air would never come back to 
 Earth. The so-called civilised nations could then 
 find in the exercise of " shooting the Moon " a 
 strong counter-attraction to the folly of mutually 
 bombarding each other. Under such conditions 
 the shots. sent from the Earth might serve as mail- 
 coaches, and take letters to our brethren the 
 Selenites in less than a working day of twelve hours. 
 
 A despatch handed in at the central office of the 
 Paris-Moon post at 6 a.m. would reach our satellite 
 at 3 in the afternoon of the same day . . . always 
 provided the State did not lay hands on the monopoly 
 of the new line. 
 
 The slightest delay would have the most disas- 
 trous results. The Moon would have passed on, 
 and the mail, finding no one to receive it, would 
 carry on its despatches to " an unknown destina- 
 tion." 
 
 But the best way to realise how near the Moon 
 is to us is to compare the time taken by light to 
 reach us from that suburb of the Earth, and that 
 * 7j miles.
 
 DIAGRAM ILLUSTRATING THE DISTANCE OF THE MOON FROM THE 
 
 EARTH. 
 79
 
 ON THE WAY 81 
 
 which it takes to pass across the spaces that separate 
 us from the Sun, the planets, and, above all, the stars. 
 
 While a ray of light from the Pole Star reaches 
 us after a long journey of 46 years, and takes 
 more than four years to "work off" the tre- 
 mendous distance that divides us from our neigh- 
 bour Alpha Centauri, we know that the luminous 
 vibrations from the Sun certainly do not take 
 more than 9 minutes to arrive here. 
 
 Now, light, as you know, moves at the rate of 
 186,000 miles a second. In a little more than 
 one second say about the time it takes to count 
 " two " it crosses the abyss that separates us 
 from the Moon. 
 
 This neighbouring globe, 49 times smaller than 
 our own, is therefore really at arm's length. It 
 moves in our wake, and shares, up to a certain point, 
 our destiny in the universe. A politician might say 
 that it is within our " sphere of influence " ; and this 
 nearness is enough to explain why astronomers in 
 general study it so little, and yet know it so well. 
 
 But we have arrived. Our imaginary vehicle 
 sets us down. 
 
 Let us open our eyes and lose nothing of the 
 
 strange spectacle presented to our gaze. 
 6
 
 VI 
 LUNAR LANDSCAPES 
 
 IT is still night in the region in which we have 
 landed on the surface of the Moon. 
 
 The sky sparkles with incomparable splendour. 
 The eye can distinguish in it thousands and thousands 
 of stars. Not even the glories of a tropical night 
 can give any idea of what night on the Moon 
 must be. 
 
 But soon the Sun will appear. There is no dawn 
 to herald it, but already there is rising in the east 
 a long, spindle-shaped trail of whiteness it is the 
 zodiacal light, ten times more brilliant than with us. 
 
 For hours this false dawn rises higher in the sky; 
 its tints of phosphorescent colours are brighter 
 and brighter from the summit to the base ; in the 
 midst of the enormous cone, all aglow with green 
 and opal, there gleams a resplendent star : it is the 
 beautiful Venus, hardly recognisable amid its mantle 
 
 of light. 
 
 82
 
 <
 
 LUNAR LANDSCAPES 83 
 
 But already the fine rays of the Sun's corona 
 are heralding the day-star. For a few minutes the 
 chromosphere is in sight, marking with a red glow 
 the summits of the high mountain peaks. 
 
 Then all of a sudden blue rays of light, so 
 strong that the eye cannot endure them, dart from 
 the distant horizon. And now on all sides isles of 
 brightness seem to rise up around us as the summits 
 catch the sunlight. The day has come. 
 
 Where have we landed ? 
 
 Let us look attentively at our surroundings. 
 Here aerial perspective is unknown, and the isles 
 of light seem to mark out a large ellipse on the 
 background of a black expanse. 
 
 Evidently we are looking down on the summits 
 of a vast circuit of heights, nearly hexagonal, if we 
 may judge by the arrangement of the outstanding 
 spots of brightness. We are watching the dawn 
 of the lunar day from the lofty rampart of a " crater" 
 known as Copernicus. 
 
 " What ! Do you mean to say this enormous 
 circle of fifty miles in diameter could be the crater 
 of a volcano ? " Well, this clearly goes beyond all 
 probability, but the old astronomers did not look 
 at things quite so closely.
 
 84 A DAY IN THE MOON 
 
 So long as there was a roughly circular rampart, 
 generally resembling in appearance our terrestrial 
 volcanoes, the comparison was inevitable ; and as it 
 is natural for the human mind to assign a cause to 
 the effects it observes without waiting long over it, 
 an explanation was soon found for those huge 
 mountain systems, of which the smallest telescope 
 will show you specimens by hundreds. 
 
 Provide yourself with higher powers, and you 
 will soon remark that a good many of these lunar 
 " craters " have a central mountain inside of them. 
 
 This peculiarity did not escape the notice of the 
 first selenographers, and here is how they reasoned 
 with regard to it : 
 
 We know by calculation that the intensity of 
 gravitation is about six times less on the Moon 
 than it is with us. Let us suppose, which is indeed 
 quite likely, that the explosive effects of interior 
 gases are as violent there as on the Earth. It follows 
 that volcanic debris would be thrown six times 
 farther. The central mountain was thus originally 
 the active cone of the volcano, and everything is 
 explained. 
 
 Thus, when the course of ages had not yet 
 thickened the surface crust, and when the liquid or
 
 LUNAR LANDSCAPES 85 
 
 molten interior communicated with the outside by 
 the blow-holes of the central fire, these eruptive 
 openings vomited into space and to prodigious 
 heights the inner substances of the Moon. Rocks, 
 volcanic matter of all kinds, vitrified minerals, dust 
 and hot ashes all this came from the underlying 
 beds through the central vent, and was deposited 
 in a huge circle at a greater or less distance from 
 the volcano. 
 
 That there are in the Moon some small craters 
 * formed in this way seems beyond doubt, but the 
 volcanic theory of the lunar circles does not explain 
 everything. 
 
 One might, first of all, object that it is very 
 strange that we generally do not find in the interior 
 of these great circles any serious inequalities of the 
 ground, any mountain resembling those of the outer 
 rampart. One would expect to find regular con- 
 centric rings at various distances from the centre, 
 marking the progressive decrease of the eruptive 
 phenomena in the course of geological time. 
 
 But there is nothing of the kind ! And, what 
 is still more to the purpose, the central peak has 
 not often a form reminding us of the mouths of 
 our volcanoes.
 
 86 A DAY IN THE MOON 
 
 And then, who can believe that this elevation in 
 the interior, always of lower height than the moun- 
 tains around it, could have thrown out masses of 
 matter to such a distance that they are piled up 
 into these enormous circular ramparts, the height 
 of which often exceeds that of the loftiest summits 
 of the Alps ? 
 
 And an example of this is before our eyes. 
 Copernicus is the monarch of the ring-shaped 
 mountains of our satellite, the king of the ringed 
 plainSy to use a favourite expression of English 
 selenographers, an expression greatly to be preferred 
 to the old grotesque and fanciful terminology of 
 the " craters." 
 
 There are more than twenty-five miles between us 
 and its centre, as we stand perched on a point of 
 its rampart towering some 13,000 feet above its 
 interior plain. 
 
 Including its external slopes, the diameter of this 
 circular mountain is nearly sixty miles. From one 
 side of Copernicus to the other there is about the 
 same distance as from Paris to Orleans. 1 
 
 An attentive observer might pass all his life in 
 studying Copernicus. He would every day find 
 1 Or from London to Portsmouth. Translator's Note.
 
 LUNAR LANDSCAPES 
 
 new details in it, and this marvellous object includes 
 all the interesting characteristics of the other moun- 
 tain rings, several of which, however, exceed it in 
 extent. 
 
 Petavius, for example, measures 100 miles from 
 one side to the other, and Manginus and Lagrange 
 show the same dimensions. Herschel presents a 
 diameter of 90 miles; Gauss is still larger no
 
 88 A DAY IN THE MOON 
 
 miles ; Humboldt is 112^ miles across, and Clavius 
 exceeds this width by more than 1 1 miles. 
 
 And then there are the giant circles of Grimaldi, 
 Stoefler and Maurolycus, of which the mean diameter 
 reaches 150 miles. 
 
 If one could transfer Maurolycus to France, placing 
 its centre at Orleans, the circular ramparts that 
 form its boundary would pass near Le Mans, Tours, 
 Nevers, and Saint-Denis. Paris, Melun, Sens, La 
 Charite, Bourges, Blois, and Chartres would be 
 hidden away in its interior. 1 
 
 A strange kind of crater indeed, the bottom of 
 which is so very like the great plains of the Beauce 
 and the Sologne, where one might walk for hours and 
 hours without seeing any mountain on the horizon. 
 
 1 It may help the English reader to note that similarly if the 
 centre of Maurolycus were placed at Oxford, its rampart of mountains 
 would run in a huge circle which to the north-west would lie just 
 beyond Wolverhampton and the Potteries, and would sweep round 
 by Burton-on-Trent to Peterborough, pass a few miles east of 
 Cambridge and through Chelmsford, cross the Thames below 
 London, about Gravesend, pass through Ashdown Forest, in Kent, 
 and reach the sea at Littlehampton ; then pass through the middle 
 of the Isle of Wight, reach the mainland again near Christchurch, 
 take in the whole of Salisbury Plain, and by the Mendip Hills 
 reach the shore of the Bristol Channel opposite Newport, and then 
 curve through the south-east borders of Wales and back to the 
 Pottery district. Among the places within its mountain ring would 
 be London, Birmingham, Bristol, Southampton, and Portsmouth. 
 Translator's Note.
 
 LUNAR LANDSCAPES 89 
 
 Through their having failed to make any exact 
 measurement of these enormous formations, the old 
 astronomers allowed themselves to be misled by 
 appearances. 
 
 But while we are making these explanations the 
 Sun has entirely risen. On our earth in latitudes 
 about half-way between Pole and Equator, the time 
 the Sun takes to show his complete disc, from the 
 appearance of its upper margin till its lower edge 
 just touches the horizon, is only 2|- minutes. On 
 the Moon it takes no less than an hour for the 
 same thing to take place . . . and you can see the 
 reason of this. 
 
 Our satellite turns on its axis about 28 times 
 less quickly than the Earth, and everything is in 
 proportion to this slow rotation. 
 
 From the time of sunrise a period of 354 hours 
 of light goes by, and then comes a night of equal 
 duration. 
 
 Such is the length of the lunar days. It has always 
 seemed to me an excellent illustration of the rela- 
 tive nature of time. 
 
 Our divisions of it into hours, minutes, and 
 seconds are obviously arbitrary, and based upon the 
 return of the Sun to the same point in the heavens.
 
 90 A DAY IN THE MOON 
 
 Now, this interval between two of its passages 
 across the meridian depends on our movement of 
 rotation. And just as we do not think of basing 
 our measures of time and our calendar on the 
 rotation and revolution of Jupiter, so the Selenites 
 would have no reason for founding theirs on our 
 terrestrial calendar. 
 
 Thus, when I promised to let you pass a day 
 on the Moon, I meant to speak of a true lunar 
 day, so we have more than three hundred hours 
 before us, in which to visit our satellite and carry 
 out excursions that a terrestrial explorer might 
 envy. 
 
 It is not, however, the fact that days as long as 
 this are entirely unknown in our world. Our polar 
 regions give us some that last even longer, but the 
 Sun of these far northern lands is a smoky torch 
 compared to that which shines like an electric arc 
 light in the lunar skies. 
 
 You can see for yourself that, though the Sun 
 is hardly risen above the horizon, you can already 
 distinguish all the details of this fantastic natural 
 scenery that seems created for Titans. 
 
 Now we notice the five central mountains of the 
 great ring, imposing masses whose summits gleam
 
 LUNAR LANDSCAPES 91 
 
 with a harsh glare, while their bases are still plunged 
 in the shadows of a night that is never absolutely 
 black but is illuminated by the earth-shine. 
 
 Over there, on the horizon, are the glittering 
 higher summits of the opposite rampart, and the 
 loftiest of them rears its terminal cone to the height 
 of more than 13,000 feet I nearly said "into the 
 air." 
 
 But here we have to change our terminology 
 and our literary phrases. The absence of air, or 
 of any gas that can be breathed, completely alters 
 our way of looking at things. 
 
 On the Moon there is no aerial perspective. 
 Everything glitters with dazzling light. Its rays 
 strike on the projecting rocks with an absence of 
 all gradation that gives them an unreal look. 
 Things near and far seem confusingly alike, and 
 the eye is not guided in its judgment of distance 
 by any variation of tint. 
 
 The clouds which temper the effect of the sun- 
 light, which rise from the valleys, assume definite 
 shapes, float hither and thither in the ocean of air 
 carrying with them the dreams of poetic souls, and 
 which shroud the mountain crests and give varia- 
 tions of dull grey or bright colour to the sky all
 
 92 A DAY IN THE MOON 
 
 this is unknown in the lunar landscape. And this 
 only half-surprises us, for as soon as ever we reach 
 the Moon we recognise that air and water are 
 alike unknown to the lands on which we have set 
 foot. 
 
 But the first selenographers were far from 
 suspecting this. Otherwise they would not have 
 given to these vast desolate plains such ill-chosen 
 names as " sea," " ocean," and " marsh." 
 
 The stony desert in front of us out of which 
 Copernicus rises is known as the " Ocean of 
 Storms." l We shall traverse the extremity of it, 
 its borders, as we continue our journey northwards. 
 
 The absence of any atmosphere a fact definitely 
 established by modern astronomers explains another 
 very characteristic peculiarity of this world that is 
 so unlike our own. 
 
 On the Earth the Sun's rays reach us after a 
 long passage through the layers of the atmosphere. 
 There is thus what we may call a selective absorp- 
 tion of some of them, a winnowing out, so to say, 
 of the different colour rays, many of which are 
 lost in the meshes of this new kind of sieve. 
 
 The shortest light- waves, those of violet and 
 1 Oceanus Procellarura.
 
 COPERNICUS. 
 
 92!
 
 LUNAR LANDSCAPES 93 
 
 blue, are delayed on the way, and only the longer 
 radiations near the red end of the spectrum reach 
 us easily. 
 
 Do you want a palpable proof of this ? Watch 
 the sunrise and notice the general tone of the land- 
 scape up to midday. 
 
 At dawn the east is bright with the rosy tint of 
 which the poets sing. The clouds are edged with 
 lines of scarlet. All white surfaces reflect the same 
 colours. Then the day-star appears and the red is 
 mingled with other parts of the spectrum, giving at 
 first violet tints and later on more yellow tones. 
 
 As the rays of the sun rising above the horizon 
 pass through a less dense body of air, the shorter 
 light-waves reach us more easily, and it is towards 
 midday that we receive the most of them. 
 
 At that time of day, especially in tropical 
 countries, the shadows of things assume quite plainly 
 the complementary tints of these rays. 
 
 Such of my readers as live in Algeria or Tunisia, 
 or in Egypt or India, can see this for themselves 
 with the help of a photographic apparatus. Let 
 them look at the image of a landscape on the dull 
 surface of the focussing glass, and they will see that 
 the shadows are all quite blue.
 
 94 A DAY IN THE MOON 
 
 On the Moon, where there is not even the 
 slightest trace of an atmosphere, the Sun's rays do 
 not pass through any filtering screen before reach- 
 ing the ground, and it is this blue colour that gives 
 its dominant note to the landscape. And this is 
 why the Sun seen thence looks like an electric arc, 
 a gigantic lamp of glittering blue ; a gleaming mass 
 whose fierce blinding light adds all the more to the 
 impression of coldness produced by the sight of a 
 world rigid in death unreal and yet existing, 
 gloomy yet full of light, blue and black at the 
 same time. 
 
 Nevertheless if we look more closely we shall 
 find there, as on the Earth, a whole scale of colours. 
 In the midst of this mountain-ring now partly 
 bathed in the Sun's rays, besides the dominant note 
 of blue, and half drowned in it, you can make out 
 the various shades of minerals and rocks like those 
 of our Earth. 
 
 And here we may remark how little is the worth 
 of the assertions made by certain astronomers who 
 repeat the follies of their predecessors, and tell us 
 that on the Moon there is no medium, that every- 
 thing is either black or full of light, accordingly a 
 the Sun is absent or darts its rays upon it.
 
 LUNAR LANDSCAPES 95 
 
 No ! Objects on the Moon must keep their 
 own colours, tinged with blue of course, for that 
 is the general tone of the sunlight on these wild 
 landscapes. The angle of the precipices on which 
 it falls, the slopes of the ground, the height of the 
 Sun all these causes combine to produce half-tints, 
 diversified tones, and changing effects as on the 
 Earth. 
 
 During the night on the hemisphere of the Moon 
 that is constantly turned towards us, our planet 
 serves as a moon to its satellite an enormous disc 
 reflecting a light fourteen times more intense than 
 that with which fair Diana's orb illuminates our 
 landscapes, even when at the full and at its maxi- 
 mum brightness it passes through the zenith and 
 sends down its soft light into the smallest clefts of 
 our deep valleys. 
 
 When the " Full Earth " sends back to the Moon 
 the reflection of the sunlight and our own atmo- 
 sphere adds to the effect of this fierce glare, it is 
 like broad day on the surface of our satellite. The 
 intense shadows of the mountains are less dark, 
 and absolute blackness can find a refuge only in 
 the deepest chasms. 
 
 Even in the midst of the long lunar day Sun
 
 96 A DAY IN THE MOON 
 
 and Earth act as allies and combine their light to 
 soften the crudity of tones and colours. 
 
 This is a point that we, men of the Earth, had 
 not till now realised, but which our first excursion 
 shows us in the clearest fashion. 
 
 And nevertheless there can be no possible com- 
 parison with the landscapes of the Earth. Cast 
 your eyes over and beyond these frightful preci- 
 pices, those steep declivities broken only by two or 
 three terrace-like slopes of debris, and what presents 
 itself to your dazzled eyes is above all a spectacle 
 of the most awful desolation. There is not a patch 
 of moss, not a heath-grown ledge, to soften the 
 rocky ridges and sharp-cut edges of these abrupt 
 surfaces ; not even the lowest form of plant-life, 
 not a lichen, to attenuate the wild aspect of the 
 landscape and give it even the slightest appearance 
 of life. 
 
 And now we can better understand that passage 
 in which Nasmyth, most enthusiastic of seleno- 
 graphers, tells us how the whole landscape as far 
 as the eye can reach is the realisation of a dream 
 of the most awful desolation and of nature without 
 life. It is not even a dream of death, but it is the 
 vision of a world where life has never existed.
 
 LUNAR LANDSCAPES 97 
 
 And yet who can assert that in the far-off times 
 of the Earth's first ages the Moon was not the 
 abode of living beings ? 
 
 If we had at our disposal the " time machine " 
 of Mr. H. G. Wells, the romancer who deals in 
 the most astounding of improbabilities, we might 
 witness a spectacle of much the same kind . . . 
 while looking at our Earth. 
 
 One or two turns of a crank and the flywheel 
 of the machine begins to revolve. 
 
 Ten million years have passed by with the speed 
 of lightning ; twenty millions ; fifty ; eighty ; a 
 hundred million years. 
 
 Let us stop the machine and take a look. 
 In the sky the day-star has become pale. The 
 last fires of our glorious Sun are burning down. 
 
 Its ruddy rays still reach the Earth, but alas ! 
 it is only to light up the most mournful of 
 pictures. 
 
 The Earth's atmosphere exists no longer. The 
 rocks and minerals and calcareous compounds have 
 absorbed it little by little. The waters of the 
 oceans have permeated the underlying strata, and 
 the cold of interplanetary space has frozen up the 
 last traces of moisture. On the desert ground no 
 7
 
 98 A DAY IN THE MOON 
 
 crop any longer ripens. The Earth has become 
 sterile. Forests and prairies have all disappeared. 
 
 At the beginning of this slow but continuous 
 cooling down of the earth the human race in a 
 body had taken refuge in the equatorial zone, 
 where a dwarfed vegetation had replaced the 
 abundant flora of the tropics. 
 
 Some millions of years more and only a vegeta- 
 tion like that of the polar regions could withstand 
 the glacial climate. 
 
 One by one most species of animals became 
 extinct. To hold out somewhat longer the last 
 families of the human race dug into shafts and 
 deep-lying underground tunnels, and it is there 
 that in the last of these catacombs their frozen 
 bones are now lying. 
 
 Ten million years more and an explorer traversing 
 this silent desolation might well believe he had 
 good reason to think of the Earth as Nasmyth does 
 of the Moon. 
 
 Every trace of organic life would, in fact, have 
 disappeared. Our monuments, our powerful 
 machines, all the products of our industry and 
 civilisation, would have been reduced to dust and 
 gone back to the earth, and not one particle would
 
 LUNAR LANDSCAPES 99 
 
 remain to reveal the previous existence of life on 
 our planet. 
 
 Such an end of the Earth and its inhabitants 
 is the normal manner of death for the worlds in 
 stellar space. But poor humanity may vanish 
 hence in some frightful catastrophe, and science, 
 even in the guise of the Wells machine, is power- 
 less to reveal to us the lot that awaits us. 
 
 However this may be, this account of the end 
 of our planet seems to apply very well to the 
 lunar world. Our satellite is 49 times smaller 
 than the Earth. It has therefore cooled down more 
 quickly ; and though its days are materially longer, 
 the phases of its life among the heavenly bodies 
 have been hurried through more rapidly than ours. 
 
 At the present time there is nothing to justify 
 us in believing that life exists on the surface of 
 the Moon, and the astronomers of our Earth have 
 explored every corner of it. 
 
 The smallest angular space that the human eye 
 can appreciate is about half a minute. A magni- 
 fying power of 30 diameters enables us to see 
 a spot a second in diameter. Now an angular 
 distance of a second on the Moon represents about 
 1,960 yards. This is the limit of visibility for
 
 ioo A DAY IN THE MOON 
 
 small telescopes. But when one adapts to a 
 more powerful instrument a magnifier of 300 
 diameters, the eye can distinguish details measuring 
 only 197 yards. With the power of 600 one can 
 perceive an object measuring 98^ yards. This 
 would be reduced to 59 yards and 29^- yards if 
 we used powers of 1,000 and 2,000 diameters. 
 
 In practice we have unfortunately to reckon 
 with an element of some importance, the atmo- 
 spheric waves, of which our telescopes also magnify 
 the effects in the most distressing fashion. The 
 training of the observer, the practice of the eye, 
 and the diameter of the objective have also to be 
 taken into account. There has often been talk of 
 powers of 2,000 being adapted to large telescopes. 
 But in the opinion of all selenographers these 
 high powers give no result when applied to the 
 study of the Moon, and as a rule we have to 
 content ourselves with a magnifying power of 400. 
 
 But here another question arises, and we must be- 
 ware of falling into the mistake of certain popular 
 astronomers who reproduce an argument of Arago. 
 
 This astronomer tried to make out that to 
 magnify a portion of the Moon's surface 2,000 
 times was the same thing as to bring it 2,000
 
 LUNAR LANDSCAPES 101 
 
 times nearer, and consequently to see it just as we 
 see an object on earth 120 miles distant from us 
 in the same way, for instance, as a tourist sees 
 the mountains of Corsica from the heights above 
 Monaco (distance, 1 90 kilometres = 1 1 8 J miles.) 
 
 Well, this reasoning loses all its force as soon as we 
 try to apply it to an object in the heavens elevated 
 above the horizon and anywhere near the zenith. 
 
 In this case, as a matter of fact, our line of 
 sight passes through a depth of air equivalent only 
 to that which separates us from an object placed 
 at a distance of about 6 miles on the earth, whilst 
 when we look at Corsica from Monaco or the 
 cone of Etna from Malta the rays of light come 
 to us weakened by passing through a mass of air 
 that is twenty times denser. This more or less 
 opaque screen, agitated by strong currents, in con- 
 tinual movement and laden with dust and vapour, 
 deadens the tints and blots out the details so 
 that the comparison is worthless. 
 
 What should be said is that with a magnifying 
 power of 400 and experience is there to prove it 
 a trained eye can distinguish on the Moon an object 
 135 metres (or 443 feet) in diameter, and this 
 magnifying power is ordinarily used by astronomers.
 
 102 A DAY IN THE MOON 
 
 In exceptional cases with an abnormally clear 
 and calm atmosphere we can use powers of 600 
 and observe on the Moon spots and objects only 
 90 metres ( = 295 feet) in diameter, whilst, accord- 
 ing to Dr. Weineck, in the case of our photo- 
 graphic maps of the Moon we have to be content 
 with making out spots of 700 metres (= 2,296 
 feet) in diameter. 
 
 The superiority of telescopic vision over photo- 
 graphy is still more marked when it is a matter 
 of revealing a long narrow object such as a 
 geological fault or a crack in the ground. With 
 a magnifying power of 400 we can distinguish 
 clefts in the surface that are only 40 to 50 metres 
 wide (i.e. 131 to 1 64 feet). 
 
 A great building like one of our cathedrals, a 
 railway-station, a village, a regiment on the march, 
 would therefore be quite visible. But no one 
 has ever observed such signs of civilisation. We 
 are, however, thus in a good position for studying 
 the question of changes in the surface formation 
 of the Moon, and astronomers have not failed to 
 do this. . . . But time is running on, and this 
 question will come up naturally in the course of 
 our intended excursions.
 
 VII 
 ON THE MOON 
 
 BUT we must see about leaving this elevated point 
 of observation overlooking the mountain crests of 
 this circle of Copernicus, and making our way down 
 to visit the great plains that the sunlight is now 
 bathing in its slanting rays. 
 
 It is not easy to fix upon the line of easiest 
 descent. Everywhere the mountain sides go down 
 abruptly at a startling angle of inclination, then 
 rising up to minor outlying summits they join on to 
 subsidiary ranges or folds of the surface that are 
 arranged round Copernicus like the spokes of an 
 enormous wheel. 
 
 We cannot dream of reaching the region to the 
 south, of which you can distinguish the deep 
 gorges and frightful precipices where the rocks fall 
 noiselessly and the avalanches of stones awake no echo. 
 
 Let us rather make our way to the north side ; 
 
 the ground there looks more practicable. 
 
 103
 
 io 4 A DAY IN THE MOON 
 
 But take note of this you will recollect that the 
 lunar globe has an attraction six times less than that 
 of our terrestrial globe. Here is the explanation 
 of that sense of lightness which is so thoroughly 
 characteristic of the place. 
 
 Have you ever thought about the cause of 
 weight ? It is essentially only a variety of attrac- 
 tion. It seems that the fall of an apple was enough 
 to start a train of thought that put the great 
 mathematician and philosopher Newton on the 
 track of the discovery that the heavenly bodies 
 attract each other in the same way that the Earth 
 draws falling bodies to its surface. Later on he 
 was enabled by a study of the movement of the 
 Moon in its orbit definitely to establish those great 
 laws of attraction which are the basis of the 
 mechanism of the heavens. " Things work out," 
 said Newton, " as though bodies attracted each other 
 according to their mass, that is to say, according to 
 the quantity of matter they contain." 
 
 The weight of a body is not therefore an inherent 
 quality of matter. 
 
 Let us, for instance, imagine a single atom existing 
 by itself in the world and in space. There is 
 nothing that attracts this atom. Therefore it has
 
 ON THE MOON 105 
 
 no weight. Place in its presence a small mass of 
 other atoms. Immediately the two unequal masses 
 tend to approach each other, and weight comes into 
 existence. 
 
 This attracting force of weight is therefore in the 
 highest degree something variable according to the 
 masses of bodies. The mass of the Moon being 
 much less than that of the terrestrial globe, one can 
 very easily see that a stone transferred to our 
 satellite would there be less strongly attracted, and 
 would therefore weigh less. 
 
 Take, for instance, a rock which you would judge 
 to weigh exactly 100 pounds here on the earth. 
 Lift it in your arms on the Moon, and you would 
 feel as if you were holding up barely 20 pounds. 
 
 And, wonderful to say, there was no need for 
 astronomers to make an excursion to the Moon in 
 order to determine the weight of bodies on its 
 surface and even to weigh the Moon itself. There 
 are plenty of ways of doing this, and the most simple 
 to grasp is one that can be easily understood by 
 everybody. 
 
 If the Moon were as heavy as the Earth, the two 
 bodies would equally attract each other, and both 
 would begin to revolve round their common centre
 
 io6 A DAY IN THE MOON 
 
 of gravity, that is to say, round a point situated 
 just half-way between the Earth and the Moon. 
 
 But as a matter of fact their masses are unequal, 
 and at the moment when the Moon is before the 
 Earth on its orbit it is easy to discover by observa- 
 tion that we are drawn forward just a little by our 
 satellite. The amount of this displacement, cal- 
 culated by the apparent displacement of the Sun 
 in the heavens, is about 2,300 miles, or nearly the 
 eighty-first part of our distance from the Moon. 
 Hence it can be inferred that the mass of the Earth 
 is 8 1 times greater than that of the Moon ; at any 
 rate, it is most certainly something between the 
 numbers 80 and 83. 
 
 Let us follow out the consequences of this line of 
 reasoning. Newton has shown under his second 
 law that attraction diminishes in proportion to 
 distance. We can show this even here on our 
 Earth where bodies weigh less the farther they are 
 from its centre. 1 If, then, the Earth and the Moon 
 were the same size, a stone on our satellite would 
 weigh 8 1 times less than here on earth. But this 
 
 1 Such experiments are of course made not by balancing weight 
 against weight in scales, but by the use of spring balances. 
 Translator's Note. 

 
 REGION OF THE LUNAR APENNINES. 
 
 The diagonal range is that of the Apennines ; the great mountain ring in the lower'patt 
 of the photo is " Archimedes."
 
 ON THE MOON 107 
 
 conclusion does not hold good as matters actually 
 are, for the stone on the Moon is much nearer 
 its attracting centre. The figure just given is there- 
 fore far from expressing the reality, and making all 
 necessary calculations, as we know the radius (or 
 semi-diameter) of the Moon, we find that the force 
 of gravity, or weight, on our satellite is only 
 one-sixth of the average of that same force at the 
 surface of the Earth. 
 
 And there is another consequence if you weigh 
 here on the Moon what would be 60 pounds with 
 us, a spring balance would indicate only a weight of 
 10 pounds, and as your muscular force remains 
 the same as ever, you now understand how here 
 you can succeed in easily lifting an enormous block 
 of stone. 
 
 In the same way, before jumping over an ob- 
 stacle, or leaping across a mass of sloping debris 
 or an open crevasse, you will do well to be careful, 
 and to remind yourself that an effort which would 
 enable you " in your own country " to make a 
 jump of 6 feet would carry you to a distance of 
 36 feet on the surface of the Moon. 
 
 But if we take certain precautions this diminution 
 of jweight is just what will give us an unexpected
 
 108 A DAY IN THE MOON 
 
 means of reaching without difficulty the base of this 
 tremendous declivity, and rapidly making our way 
 to the outlying hill-buttresses of the great chain 
 of the lunar Apennines. 
 
 Isolated peaks rearing their crests above a vast 
 desert, numbers of great tumuli in the summits of 
 which open yawning craters whose depth the eye 
 cannot fathom, low hills, parallel furrows, some 
 basin-shaped hollows, and here and there enormous 
 crevasses such is the appearance of the wide tract 
 that we traverse to the north of Copernicus in order 
 to reach the great " Sea of Rains " (the Mare 
 Imbrmni]. 
 
 We might thus make a march of hundreds of 
 miles always in the midst of this desert-like steppe 
 with its overheated surface burned up by the blaze 
 of an unendurably tropic sun. 
 
 At the lunar noon that is to say, when the Sun 
 has completed half its course across the sky the 
 ground will be heated to such a degree that it 
 would immediately roast any organic substance 
 placed upon its surface. The temperature would 
 be above 212 degrees, and during the long lunar 
 night of about two weeks a gas thermometer would 
 indicate a cold of some 300 degrees below zero.
 
 REGION OF THE " MARE SERENITATIS." 
 
 The great plain is the so-called " Sea of Serenity." The isolated crater in 
 its upper part is " Bessel." The large crater near the end of the range forming 
 its upper boundary is " Plinius." 
 
 108]
 
 ON THE MOON 109 
 
 What plants, what animals could survive such 
 extremes and such variations of temperature ? 
 
 But already the Apennines are in sight. For 
 400 miles this mountain range, the most beautiful 
 in our satellite, will close in our horizon to the 
 eastward. 
 
 It has, however, no resemblance to the mountain 
 masses of our own Alps. Here we have a titanic 
 piling up of rocky material, heaped together with 
 a breadth that in some places is as much as 160 
 miles, especially where the chain appproaches the 
 " Sea of Vapours." 
 
 From this shapeless mass there rise up slender 
 peaks of which you can see the long shadows on 
 our right, forests of rocky steeples, columns, 
 minarets, gigantic obelisks, crowding together their 
 impossible-looking shapes to form a panorama that 
 seems something unreal, masses of dazzling blue 
 on a black background all spangled with stars. 
 
 Behind us the great mountain ring of Eratos- 
 thenes stands out strongly from the monotonous 
 plain that marks the beginning of the " Sea of 
 Rains." 
 
 Let us press on continually to the northwards. 
 We salute as we pass it by the square-shaped mass
 
 i io A DAY IN THE MOON 
 
 of the Wolf Mountains, of which the loftiest 
 summit reaches a height of 12,000 feet, and Mount 
 Huyghens with its tall peak, whose summit goes up 
 to an altitude of 18,000 feet. 
 
 Now in front of us and a little to our left, 
 an enormous mass rises the mountain ring of 
 Archimedes, the interior diameter of which is not 
 less than 50 miles. We are now in the " Marsh 
 of Fogs." Cast a glance as we pass by at Thea- 
 tetus, the little volcano near which certain 
 astronomers think they have made out a trail of 
 smoke. We have now reached the first buttresses 
 of the lunar Alps. Once more we see great peaks 
 rising before us, but they are less numerous than 
 those in the Apennine chain, where selenographers 
 have counted up more than 3,000. 
 
 Here the eye distinguishes only some hundreds, 
 of which the most remarkable is " Mont Blanc,'* 
 with its height of nearly 12,000 feet. 
 
 At the base of its precipitous sides a wide valley 
 opens out, a fantastic gap stretching away in a 
 straight line as far as the eye can reach, a giant 
 furrow that underground forces have formed in 
 the midst of this impenetrable scene of mountain 
 chaos.
 
 ON THE MOON in 
 
 Not far from here rises the huge circle of Plato, 
 a vast arena 60 miles across. 
 
 But the hours are going by, and the Sun is 
 inclining towards the west. Let us hasten our 
 steps towards the " Sea of Serenity," and continue 
 our excursion so as to reach the southern part of 
 the Moon. 
 
 We are now nearing Linnee, a small crater which 
 for years has been raising amongst astronomers the 
 question of changes in the Moon. 
 
 Linnee was very closely observed by earlier 
 selenographers. Now modern descriptions do not 
 at all correspond to those given by Lohrmann, 
 Schroeter, Huggins, and several others. 
 
 It would seem that in the first half of the nine- 
 teenth century important changes took place in the 
 appearance of this curious object, and that in 1866 
 its interior was filled up with some kind of white 
 matter, very likely lava. 
 
 The two little craters of Messier show also very 
 curious changes of appearance ; now they are visible, 
 now they are hidden by a screen that looks like 
 smoke. 
 
 We may also take note of the observations of 
 MM. Charbonneaux and Millochau, who remarked
 
 ii2 A DAY IN THE MOON 
 
 similar appearances whitish patches some 4 miles 
 long, showing themselves over a little crater situated 
 near Theatetus, which we remarked as we passed 
 by it. 
 
 The study of all these facts, and of a number of 
 others which have not been so fully investigated, 
 raises therefore once more the problem of the 
 internal activity of a central fire in our satellite. 
 It is very difficult to admit the possibility of the 
 presence in the Moon of appearances due to any 
 vegetation surviving even on the low-lying plains, 
 but we have yet to find some explanation for certain 
 changes of colour that recur with each lunation, 
 and for a number of variations that fit in very 
 well with the supposition that internal forces are 
 still reshaping the topography of the Moon's 
 surface. 
 
 Besides, the geology of this land so near our own 
 is well calculated to puzzle even the most learned. 
 The surface crust of our satellite has been subjected 
 to the action of powerful forces that have no 
 analogy with those which appear to have determined 
 the surface features of our Earth. 
 
 It is probable that at the outset that is to say, 
 at the period when the Moon was in a viscous
 
 o 
 
 W
 
 ON THE MOON 113 
 
 state the gases imprisoned in the interior of its 
 mass raised here and there enormous domes, a kind 
 of gigantic bubble, thus leading up to the falling in 
 of the surface on a vast scale and in circular or 
 elliptic shapes. 
 
 This would be the origin of such great depres- 
 sions as the " Sea of Crises," the " Sea of Serenity," 
 the " Sea of Rains," etc. All these are in fact 
 bounded by mountain masses, of which the steepest 
 side is always turned to the part that has fallen in. 
 
 Later on, as the crust gradually became thicker, 
 these swellings of the surface were localised within 
 narrower limits ; the consequent collapse of the 
 surface resulting in the formation of mountain rings 
 like Tycho, Ptolemy, Theophilus, etc. . . . The 
 presence of central mountains in these rings is also 
 fairly well explained by this theory for want of 
 room certain parts of the falling dome were forced 
 to pile themselves up one on the other. 
 
 In some cases the rise of floods of lava has more 
 or less filled up the inner arena, and overflowed 
 in metallic streams through gaps in the encircling 
 walls. 
 
 Finally, when the outer crust could no longer, 
 on account of its want of elasticity, bend to the 
 8
 
 1 1 4 A DAY IN THE MOON 
 
 upward force of the interior gases, the envelope 
 cracked and split around the points of pressure, 
 and we might thus account for those broad rays 
 that seem to radiate from certain mountain rings, 
 such as those of Tycho, Kepler, and Copernicus. 
 Sometimes the breaks resulting from this upward 
 pressure from within have formed long yawning 
 chasms, as in the ineighbourhood of Triesnecker or 
 Hyginus ; sometimes they have been filled up by 
 metallic lavas, as in the case of the rays around 
 Tycho, where we see them glittering more and 
 more brightly as the Sun rises higher above the 
 horizon. 
 
 The southern part of the Moon that which we 
 see at the top in an astronomical telescope which 
 reverses the object is not at all like the regions 
 we have just visited. 
 
 To get an idea of it, let us rise above the surface 
 of the Moon and continue our journey so as to 
 have a bird's-eye view from an aeroplane, if you 
 like. 
 
 Your first impression at the sight of this wild 
 landscape will make you think of a huge volcanic 
 region, but as you look more closely you will 
 soon find out your mistake.
 
 O X 
 ."= H 
 
 i o
 
 ON THE MOON 115 
 
 The real lunar volcanoes are hardly visible with 
 our most powerful telescopes. 
 
 The great circles displayed before your eyes are 
 all vast plains surrounded by mountain ramparts. 
 
 First of all there are Hipparchus and Ptolemy, 
 measuring about 125 miles in diameter. Their 
 inner arena is full of eruptive mouths that we 
 cannot count. Broad valleys open to the south of 
 Ptolemy, towards Alphonso and Arzachel, and there 
 is nothing on earth that can give us an idea of 
 such a confused mountain upheaval. Peaks of 
 6,500, 10,000, 13,000 feet overhang yawning 
 hollows 12 miles across ; volcanic cones have risen 
 by hundreds on the bare abrupt slopes ; then over 
 vast extents of ground the crust has fallen, pro- 
 ducing gigantic cracks as in that region of the 
 " Sea of Mists," 1 where the arena of an old mountain 
 ring is split in two. 
 
 A good half of it has sunk down, and the two 
 edges of the "fault" have actually a difference of 
 level amounting to 2,300 or 2,600 feet ; this is 
 the "Straight Range" to be seen near "Birt," 
 and which in certain lights takes the form of a 
 sword. 
 
 1 The Mare Vaporum.
 
 n6 A DAY IN THE MOON 
 
 Farther south the elevations become still higher 
 in the direction of Tycho and Maginus. 
 
 Then there is Clavius, with its boldly shaped 
 rampart, a deep cavity overhung by mountains 
 more than 16,000 feet high, with a vast arena 142 
 miles in diameter. 
 
 Behind us Maurolycus and Stoefler, already 
 shrouded in night, show only the shining tips of 
 their fantastic summits. 
 
 But the south pole of the Moon has a greater 
 surprise in store for us. Against the dark sky 
 there stands out a gigantic mountain chain, higher 
 in proportion than our Himalayas, for the Leibnitz 
 Mountains probably rise above the level of 25,000 
 feet. Beside these lunar giants the Doerfel Moun- 
 tains show up their imposing masses, amongst which 
 Schroeter and Madler have measured summits 
 26,000 feet high. 
 
 Here the eye of the astronomer can go no 
 farther. The Moon, as we have seen, always 
 presents the same side to the Earth. What kind 
 is the other side ? It is a mystery. And no human 
 being will ever be able to solve it. Certain learned 
 men of the past tried to make out that, as a result 
 of the Earth's attraction, the Moon must have
 
 55 
 O =. 
 
 O *i 
 
 W s 
 K o 
 H :S 
 
 H M 
 
 1! 
 
 H O 
 
 S 
 
 5. <H 
 
 o 
 
 -
 
 ON THE MOON 117 
 
 taken an irregular form, that of an egg, of which 
 the longer end is turned towards us. 
 
 On the other hand, it has been an easy matter 
 for us to assure ourselves of the absence of any 
 atmosphere on the visible part of the Moon. We 
 know that every ray of light is bent by refraction 
 in passing through the layers of our atmosphere, 
 and this is why the Sun is visible a little before 
 its time of rising and a little after its setting. 
 
 In the same way, in the case of an " occultation," 
 when the Moon passes between us and a star, if 
 there were refraction and therefore a lunar atmo- 
 sphere the star would not disappear at the exact 
 moment given by calculation, and the time it was 
 hidden from us would be shortened. 
 
 Well, on this point observation has never been 
 in disagreement with theory, and so the partisans 
 of a lunar atmosphere, obliged to abandon this 
 point, have not quite given up the game as lost. 
 " If the Moon," they say, " is more elongated on 
 our side of it, the opposite side is nearer the 
 centre, therefore lower, and it is precisely in that 
 region the air has accumulated." 
 
 Unfortunately for them, measurements taken from 
 contour lines drawn for the Moon by Dr. Franz
 
 n8 A DAY IN THE MOON 
 
 have not confirmed this way of looking at the 
 matter. The Moon is indeed a practically spherical 
 body. The most one can grant is that subsidences 
 of the crust which, however, are of no great 
 importance have taken place there as on the Earth. 
 These are the result of a law which we shall study 
 in a future volume a law that points to the 
 opposite side of the Moon roughly resembling the 
 drawing we give here. 
 
 However, it is not quite strictly correct to say 
 that we can see only one side of the Moon. 
 
 Our satellite indeed completes its movement of 
 rotation and revolution in the same time, but the 
 orbit it follows is an ellipse. 
 
 When the Moon has gone through a quarter of 
 its orbital movement it has revolved a little more 
 than a quarter on its own axis. An astronomer 
 on the Earth therefore sees in each lunation a 
 border or lateral segment that he would never 
 have a sight of if the Moon described an exact 
 circle in its movement round the Earth. 
 
 Thanks to this phenomenon of libration (as it is 
 called), the Moon seems to possess a sort of 
 swaying movement, in consequence of which we 
 know a little more than the half of its surface.
 
 H jj 
 
 X 2 
 
 1 11 
 
 W M fl 
 
 S 1 
 
 W *- ja 
 K s-ti 
 
 o 
 
 ? 
 O '.2 
 
 Si 
 
 s - 
 * s 
 
 o 
 
 H . 
 
 ^ I 
 
 1
 
 ON THE MOON 119 
 
 Similar phenomena, due to other causes, allow us 
 to get sight of a narrow border at the north and 
 south. Well, all we thus get a glimpse of points 
 to the supposition that the other side of the 
 Moon has a similar constitution to that which 
 we see. 
 
 But it is time to return to the Earth, which 
 we can see all this time high in the sky. The 
 Sun is already setting, and its last blue margin will 
 soon disappear below the horizon. The lengthening 
 shadows already warn us of the approach of the 
 lunar night. The cold begins to assail us. Let 
 us fly from those endless plains, those monstrous 
 peaks, those countries of death and desolation, those 
 silent landscapes, those frightful solitudes, those 
 black tomb-like chasms, those granite precipices, 
 those awful summits where no gust of wind any 
 longer goes by, those slender spires of rock whose 
 balance there is no longer anything to alter, those 
 deserts that life has quitted for ever ; let us fly 
 from this region of eternal silence, with its 
 apocalyptic visions and its sepulchres that the angel 
 of death has closed with his icy wings.
 
 VIII 
 
 THE MOON, THE TIDES, AND THE 
 CHANGES OF THE WEATHER 
 
 WE have seen in the preceding chapters that the 
 Moon attracts the Earth, just as the latter exerts 
 an attraction on its satellite. The intensity is 
 obviously not the same, seeing that their masses 
 are in the proportion of I to 81-5. 
 
 This attraction of the Moon influences also terres- 
 trial objects, and this is easy to understand. If you 
 strew iron filings on the surface of a magnet, the 
 particles will attach themselves to the magnetised 
 metal ; and if you bring another powerful magnet 
 near it, you understand quite well that the action 
 of this second magnet has the effect of diminishing 
 the attraction of the first for the filings. 
 
 When, for instance, the Moon passes between 
 the Sun and the Earth, it must add its effect to 
 that of the Sun, and terrestrial objects must be 
 attracted to some small extent by the mass of the 
 
 120
 
 MOON, TIDES, AND WEATHER 121 
 
 two globes, but above all by that of the Moon, 
 which is much the nearer. 
 
 Very delicate observations are required to measure 
 this diminution in the intensity of gravitation or 
 weight, but nevertheless the phenomenon takes 
 forms that render measurement easy when we con- 
 sider it in the total effect of the action it exercises 
 on the oceans that envelop the Earth. It causes 
 a periodical rise in them, which we know by the 
 name of the tide. 
 
 Every time, in fact, that the Moon passes over 
 a region of our globe, the particles of water, being 
 less attracted by the Earth, are raised towards the 
 Moon, the whole mass moving towards the precise 
 point where the attraction of the Moon is strongest, 
 and the phenomenon changing its place according 
 to the course of our satellite and its progress in 
 the heavens. 
 
 At first sight it is more difficult to understand 
 why this kind of swelling of the ocean, this rising 
 up of the waters under the Moon, should take 
 place also in the opposite region of the Earth 
 that is to say, at the Antipodes. And nevertheless, 
 theoretically it must be so. 
 
 At the antipodes of the place at which the Moon
 
 122 A DAY IN THE MOON 
 
 is on the meridian, all the particles of the ocean 
 that are situated farther from our satellite than the 
 centre of the Earth are subjected to a weaker 
 attraction. They have thus less tendency to draw 
 nearer to the Moon, and consequently they rather 
 tend to a delay in moving towards it ; there should 
 therefore be a high tide. 
 
 If this explanation seems to you difficult to 
 grasp, take at least this much of it : Every molecule 
 of water situated on the farther side of the Earth 
 as regards the Moon, by this fact is subject to a 
 minimum attraction on the part of the Moon ; 
 therefore, on the part of the Earth farthest from 
 the Moon the liquid element is less heavy than in 
 the regions at both sides of it. Now, physical 
 science demonstrates that if one puts liquids of 
 different density into the two branches of a tube 
 bent into the form of the letter U, in order to be 
 at equilibrium the less heavy liquid must stand at a 
 higher level. And this is precisely what happens 
 in the ocean on the opposite side from the 
 Moon. 
 
 This simple explanation, however, was not known 
 to the ancients. It would, indeed, have been enough 
 for them to have remarked that the phenomenon
 
 MOON, TIDES, AND WEATHER 123 
 
 of the tides has an evident connection with the 
 passage of the Moon across the meridian, for the 
 tide, like the Moon in the sky, is about three- 
 quarters of an hour later each day. 
 
 It is, however, true that, though there are two 
 periods of ebb and flow in a day, the moment 
 of high water does not actually occur till after the 
 passage of the Moon across the meridian of the 
 place, and one must take into account the position 
 of the points of observation and the configuration 
 of the coast. 
 
 It was Kepler who first suspected the true cause 
 of the tide and attributed it to the action of the 
 Moon ; but it was the fate of this remarkable 
 genius that his theories had no chance of success 
 in his lifetime. 
 
 In 1 63 i one of his contemporaries in connection 
 with this very subject called him a visionary, and 
 as his opponent was a scientific man I was going 
 to say an official one poor Kepler could only bow 
 his head. 
 
 And all the same, he who thus took to task 
 the illustrious Kepler was not exactly a partisan of 
 Aristotelian philosophy ; he was always claiming 
 for himself the right of freedom of thought, and
 
 124 A DAY IN THE MOON 
 
 if I did not tell you his name you would be quite 
 unable to guess it. 
 
 This learned man had already shown himself 
 much the weaker of the two in a discussion on 
 physics with Torricelli, and his name was . . . 
 Galileo ! 
 
 As the Moon has an action upon the oceans 
 that is to say, on the liquid envelope of the globe 
 one might expect a -priori that in studying the 
 general laws of our atmosphere we would find in 
 it a tide somewhat similar to that to which the 
 liquid mass is subject. 
 
 It is an interesting problem, because it might 
 lead us to practical results from the meteorological 
 point of view. 
 
 With the idea that a tide in the atmosphere could 
 not take place without causing widespread dis- 
 turbances, more than one builder of theories has 
 already suggested a possible relation between the 
 phases of the Moon and the changes of the 
 weather. 
 
 Simple in appearance as the problem is, it is 
 nevertheless one of the most complex that men of 
 science have had to solve. So they have attacked 
 it from several different sides at once.
 
 Photo taken at the Paris Observatory. 
 
 REGION OF THE 
 
 MARE VAPORUM." 
 
 At the base of the photograph is the Mare Vaporum ; above this is seen 
 Triesnecker with its long clefts or crevasses. The great mountain ring at the top 
 and to the right is Ptolemy, 117 miles in diameter. 
 
 124]
 
 MOON, TIDES, AND WEATHER 125 
 
 In some countries experience has shown that 
 there is more rain during the time the Moon is 
 increasing than when it is waning. This is clearly 
 the case in the north of France and Germany, and 
 our meteorological records supply good evidence of 
 this fact. 
 
 However, we must not exaggerate the importance 
 of the relation between the number of rainy days 
 of the first period and those of the second ; the 
 difference is extremely slight. 
 
 But in the south of France this law does not 
 hold good : it is even reversed. 
 
 And besides, theoretically it is easy to fix by 
 calculation the amount of this lunar tide of the 
 atmosphere. It works out in tenths of millimetres 
 at its maximum, and thus comes within the range 
 of mere errors of observation ; that is to say, it 
 does not appreciably affect our barometers. 
 
 The explanation is perhaps to be sought elsewhere. 
 
 We know that the variations of the barometer, 
 especially notable falls of it, are not essentially 
 connected with changes of weather. 
 
 France and Western Europe are in a somewhat 
 exceptional position for profiting by the indications 
 of the barometer.
 
 126 A DAY IN THE MOON 
 
 The southern regions are much less subject to 
 the influences of the Gulf Stream than those of 
 the north, and conditions such as bring rainy 
 weather in one place do not produce the same 
 effect in other districts. 
 
 Is there any meteorologist of to-day who can 
 flatter himself that he knows thoroughly the 
 conditions that bring rain ? 
 
 It may very well be that the Moon by its 
 presence above the horizon has some connection 
 with rainfall through chemical action, electric action, 
 or the effect of ionisation, and through slight 
 mechanical action. 
 
 It is therefore most prudent to hesitate before 
 making any pronouncement, and it is, above all, 
 our duty not to deny the facts under the pretext 
 that we cannot see any explanation for them. 
 
 Here, as elsewhere, it may be that popular 
 belief knows better than the men of science. 
 
 Moveover, there is something to be said for 
 the truth of the theory from another point of view. 
 In recent years mathematicians have approached 
 the question by another way, that seems likely to 
 give more results. 
 
 We have already noted that the Moon is not
 
 MOON, TIDES, AND WEATHER 127 
 
 always at the same distance from the equator of 
 the heavens. Its movements, considered in relation 
 with the plane of the elliptic, to which the Earth's 
 axis is inclined, give rise to a phenomenon that 
 everybody can observe for himself. 
 
 There are times when it passes the meridian 
 at a great height in the sky, tracing a very large 
 arc of a circle above the horizon. At others, on 
 the contrary, it remains confined to the regions 
 towards the south, does not rise high, and sends 
 us its rays very obliquely. 
 
 So the depth of atmosphere on which it exerts 
 its action is continually varying. Our satellite thus 
 produces displacements of the air, a kind of 
 enormous swelling outwards, that passes slowly 
 from the tropical regions to higher latitudes. 
 
 This is what calculation proves. What has 
 observation to tell us on the subject ? 
 
 Exactly the same thing. The limit of the region 
 of the trade winds is subject to a periodical move- 
 ment backwards and forwards corresponding to 
 the declination of the Moon. This movement, 
 or rather this swaying of the zones of high and 
 low pressures, which is radically linked with 
 a unique phenomenon, may therefore bring fine
 
 128 A DAY IN THE MOON 
 
 weather and rain simultaneously but in different 
 regions. 
 
 The combination of this effect with the Full 
 Moon or the New Moon is perhaps in more than 
 one instance an additional element in modifying the 
 weather, so that, all things considered, I do not 
 despair of seeing men of science gradually coming to 
 a proof of what all the world admitted long since, 
 namely, that our satellite really counts for something 
 in certain atmospheric changes. 
 
 But we must take care not to exaggerate or push 
 things to extremes. The intermediate phases be- 
 tween Full Moon and New Moon do not seem to 
 be so chargeable with the bad results popularly attri- 
 buted to them. 
 
 "But," you say, "what about the 'Rust 
 Moon ' ? " 
 
 Patience ! We are coming to that. 
 
 First of all, do you know the meaning of the 
 word ? and at what period the Rust Moon 
 appears ? l 
 
 Towards the end of April, or rather during the 
 
 1 The popular belief which the author here discusses is common 
 among the French peasantry, but does not seem to be current among 
 country folk in England. Translator's Note.
 
 MOON, TIDES, AND WEATHER 129 
 
 month of May, when the temperature of the day 
 begins to increase perceptibly, and thus conditions 
 are favourable for the rising of sap in plants, a 
 somewhat curious phenomenon occurs every year. 
 
 Put out a minimum thermometer a little above 
 the ground, and you will find that even during 
 nights in which the indicator has not gone down 
 to freezing-point some plants have been frost-bitten, 
 and the affected buds are a sort of rust colour. 
 Now, this occurs always under a clear, cloudless sky. 
 If the Moon is above the horizon, it is of course 
 quite visible ; hence the accusation brought against 
 it by the peasants of " rusting " the plants. 
 
 The " Rust Moon " has been known from time 
 immemorial. Market gardeners and vine growers 
 are afraid of it, and they attribute its ravages to a 
 special cold-producing power in the rays of our 
 satellite. Let us see if there is any basis for this 
 accusation. In any case the " Rust Moon " has 
 been officially known to men of science only for 
 a century, as is shown by this story related by 
 Arago : 
 
 " * 1 am pleased to see you gathered around me,' 
 said Louis XVIII one day to the members of a 
 deputation of the Bureau des Longitudes, who had 
 9
 
 130 A DAY IN THE MOON 
 
 come to present to him their Almanac and Annual, 
 4 for you will clearly explain to me what is the Rust 
 Moon and how it acts upon the crops.' 
 
 " Laplace, to whom these words were specially 
 addressed, seemed dumbfounded : though he had 
 written so much about the Moon, he had in fact 
 never dreamed of such a thing as the Rust Moon. 
 He appealed with a look to all his colleagues, but 
 as no one seemed inclined to speak, he decided to 
 reply himself : 
 
 " ' Sire, the Rust Moon has no place in astro- 
 nomical theory. We are not in a position, therefore, 
 to satisfy the curiosity of your Majesty.' 
 
 " That evening, when at the card-table, the King 
 made very merry over the embarrassment into which 
 he had thrown his Bureau of Longitudes. Laplace 
 heard of it, and went to see Arago at the Ob- 
 servatory in order to ask him if he could throw any 
 light on this famous ' Rust Moon ' that had given 
 rise to such a disagreeable incident. Arago knew 
 no more about it than Laplace, but he promised the 
 illustrious astronomer that he would make inquiries 
 of the gardeners of the Jardin des Plantes and other 
 horticulturists. 
 
 " As the result of his investigation, Arago settled
 
 From a drawing by the Abbe Moreus. 
 
 INTERIOR OF A LUNAR VOLCANO. 
 
 130]
 
 MOON, TIDES, AND WEATHER 131 
 
 that henceforth the ' Rust Moon ' would be taken to 
 be that which beginning in April reaches the Full 
 either at the end of that month or oftener in the 
 course of the month of May." 
 
 I do not know if the definition is perfect. It has 
 often given rise to excited discussions, which how- 
 ever seem to me very puerile. 
 
 The gardeners settle it each year in their own 
 way. Sometimes their plants are touched by the 
 frost, sometimes they don't do very badly, and the 
 " Rust Moon " does not always " rust " them. But 
 however this may be, we have here the popular 
 account of a fact that we may look into more closely. 
 
 Agriculturists, as we have said, assert that at 
 night with a clear sky leaves and buds exposed to 
 the moonlight are " rusted," in other words are 
 frost-bitten, although the thermometer exposed to 
 the air remains several degrees above freezing-point. 
 On the other hand, if, as the result of the presence 
 of clouds in the sky, the rays of the Moon do 
 not reach the plants, these effects are not observed, 
 although the general temperature of the air remains 
 the same. 
 
 It would seem then, at first sight, that the lunar 
 rays are the cause of this chilling.
 
 132 A DAY IN THE MOON 
 
 Nevertheless, if at the time of New Moon, when 
 our satellite is not above the horizon, the sky clears, 
 you will find that the young shoots, especially those 
 of the vine, freeze and " rust " just the same. 
 
 The Moon has therefore nothing to do with the 
 matter, and the explanation of it must be looked for 
 elsewhere. 
 
 The cold of the night was specially studied long 
 ago by Wilson, and here is what that physicist 
 observed in 1783 : 
 
 After having placed a thermometer on the snow 
 and noted that it indicated about 22 below zero, 
 while the temperature shown by another 4 feet 
 from the ground was 14, he saw the lower ther- 
 mometer suddenly rise some 8 as clouds came 
 over the sky. 
 
 When the night is fine and clear, therefore, 
 bodies lose their heat by the simple process of 
 radiation. The presence of a screen or cloud, or 
 a covering of canvas or of straw, slight though it 
 may be, at once neutralises this effect. 
 
 All our readers can easily repeat Wilson's ex- 
 periments. They will find that in still, cloudless 
 nights the grass has always a lower temperature 
 than the air six feet above it. We must not, there-
 
 MOON, TIDES, AND WEATHER 133 
 
 fore, judge of the cold that affects a plant during 
 the night merely by the readings of a thermometer 
 hanging in the air. 
 
 This phenomenon is perfectly well known, and 
 has been taken advantage of from time imme- 
 morial in India, for instance for making ice. 
 Shallow vessels filled with water are arranged in an 
 excavation filled with maize straw. A bank of 
 earth runs round it to keep the cooled air from 
 disturbance. When the sky is clear and the air 
 calm without too much humidity, and the tempera- 
 ture falls below 50, the water freezes, even when 
 a thermometer laid on the straw indicates 40. 
 One hears of ice-makers who employ in this way 
 hundreds of workmen, and the process was used 
 for the same purpose by the physicist Wells, who 
 repeated the experiment in England during the 
 summer. 
 
 But to succeed one must have a clear night ; in 
 cloudy weather there is no radiation, and the dif- 
 ference of temperature becomes imperceptible. 
 
 Now, all this helps us to understand what happens 
 at the time of the " Rust Moon." In the nights 
 of April and May the temperature of the air is 
 often not more than 8 to 9 above freezing-point.
 
 134 A DAY IN THE MOON 
 
 Then, as the result of nocturnal radiation, the 
 ground may cool down to one or more degrees 
 below freezing-point. The plants are subjected to 
 the same cooling process, and are frost-bitten. Now 
 when this takes place, it is under a clear sky, and 
 if the Moon is above the horizon it shines in all 
 its splendour. If, on the contrary, the weather is 
 cloudy, the Moon will not be visible, and there 
 will be no frost on the ground unless, of course, 
 the general temperature of the air falls below 
 freezing-point. 
 
 It is therefore true, as the gardeners assert, that 
 with the same general conditions of temperature, a 
 plant may be frozen or not frozen according as 
 the Moon is visible or hidden behind the clouds. 
 But once more, the moonlight is here only an 
 indication of the fact that the sky is clear, and it 
 is on account of this clear sky that the night cools 
 down ; but this freezing takes place just the same 
 when the Moon is not above the horizon. We 
 may say, then, with Arago : " The observation of 
 the gardeners was therefore incomplete, but it would 
 be wrong to make out that it was false." 
 
 And now may we ask why these nightly frosts 
 take place in spring, at the end of April and the
 
 MOON, TIDES, AND WEATHER 135 
 
 beginning of May, and not in summer or autumn ? 
 
 The first reason is, that at that time of the year 
 winter is hardly ended, and the Sun has not had 
 the time to warm the Earth, whilst later on, the 
 loss of heat by cooling down in the night does not 
 equal the excess of heat stored up during the day. 
 
 To this chief reason another must be added. 
 We know what an important part water, in a 
 vaporised state, plays in maintaining and equalising 
 the temperature of our atmosphere. Well, the 
 quantity of this vapour is always varying, and we 
 have proof of this every day in the changing indica- 
 tions of the hygrometer. 
 
 Since the invention of that instrument physicists 
 and meteorologists have studied its tabulated results, 
 and this is what they find. 
 
 The total amount of vapour in the air increases 
 constantly from spring till the month of August, 
 usually the hottest time of the year. But from 
 September it decreases, and reaches its minimum 
 precisely in the month of April, the very time when 
 it is most necessary for counterbalancing nocturnal 
 radiation. 
 
 So in spring everything combines to give us 
 chilly nights and to make the Moon fall under
 
 136 A DAY IN THE MOON 
 
 the suspicion of having a cooling effect, of which 
 it is quite innocent. 
 
 But does this mean that the Moon has no effect 
 on plants ? 
 
 It would be very rash to make such a statement 
 after merely examining the theory of the " Rust 
 Moon." 
 
 We must look at the problem from another point 
 of view, and this is what we are going to do.
 
 3 H
 
 IX 
 
 THE MOON, VEGETATION, AND 
 ORGANIC LIFE 
 
 THE question of the influence of the Moon on 
 plants is as old as the world, and about every 
 twenty-five years we find some bold spirit who 
 does not disdain to break a lance in its defence. 
 
 In a little book on Meteorology that is very 
 popular in the province of Berry, M. Larcheveque 
 writes that, according to his investigations, there is 
 among the people of central France a very strong 
 belief in the influence of the Moon on planting, 
 sowing, etc. For instance, it is held that one 
 should plant and sow and prune trees at the New 
 Moon. The first growth from the seed and the 
 subsequent progress of the plant will be more 
 rapid and vigorous if these operations are carried 
 out at the New Moon. 
 
 This is the theory. From inquiries I have made 
 in a good many places I find that it may be taken
 
 138 A DAY IN THE MOON 
 
 to be a very widespread opinion. One comes across 
 it in much the same form in all the countries of the 
 world. 
 
 But and this is the main point of the matter 
 this same theory has been knocked to pieces by 
 a fair number of men of science, and the popular 
 exponents of learning have boldly taken up the 
 cry. 
 
 " These are," they say, " nothing but old women's 
 stories, to which we need pay no attention." 
 
 Have you remarked that often the savants are 
 just those who know Nature the least ? 
 
 I have met with mathematicians who could hardly 
 distinguish a maize plant from a leek ; physicists 
 ignorant of the most elementary principles of 
 physiology ; and geologists who, on the other 
 hand, had not opened a book on physics for twenty 
 years. 
 
 This exaggerated specialism, with its disregard 
 for all that is outside its scope, produces the most 
 deplorable results. 
 
 Men of science who boast, as they have a right 
 to do, of the experimental method, and sometimes 
 practise it, are too often mere " men of the labora- 
 tory," and lose sight of Nature.
 
 From the Lunar Atlas of Lavy and Puiseux. 
 
 NORTHERN HORN OF THE MOON. 
 
 (Reversed image.) 
 
 138!
 
 MOON, VEGETATION, ORGANIC LIFE 139 
 
 Astronomers in general treat with contempt any 
 possible influence of the Moon on vegetation, and 
 the meteorologists do much the same. 
 
 If the explanation of a fact is not available, men 
 refuse to accept it as authentic. The whole history 
 of science supplies us with many instances of this. 
 
 Remember how the Academicians of a former 
 day denied that stones could fall from the sky ; 
 denied the facts of somnambulism and hypnosis at a 
 time when these phenomena were not accurately 
 studied ; denied the very real fact of lightning 
 coming down in the form of a ball of fire, etc. 
 
 It seems to me that there is something of the 
 same kind going on with regard to the Moon ; 
 instead of having recourse to the experimental 
 method, people are content to deliver dissertations, 
 and imitate the very methods of the Aristotelians 
 and Scholastics that they rail at ! 
 
 A series of scientific experiments might be carried 
 out under due supervision, but I know of no 
 astronomers or meteorologists who have " resigned 
 themselves " to such labours in order to study the 
 subject with which we are occupied. 
 
 Without taking one side or the other as to this 
 alleged influence of the Moon, I thought the best
 
 1 40 A DAY IN THE MOON 
 
 plan would be to hear the evidence of the rival 
 camps. 
 
 Let us listen first to M. Henri Ayme, the 
 Secretary of the Agricultural Syndicate of Lagnes 
 in the department of Vaucluse : 
 
 " I am not one of those who think that science 
 has discovered everything, and that one should 
 reject without examination whatever it cannot ex- 
 plain. But if something that cannot be explained 
 is to be taken as certain, I consider that it ought 
 to be supported by serious proofs from experience. 
 So if I am convinced of the absence of any influence 
 from the Moon in the region of vegetable physiology, 
 this is not because such an influence would be 
 inexplicable, but it is above all because during 
 twenty-five years of agricultural practice I have 
 never found any seriously established fact to support 
 this belief, and because I can bring very precise 
 facts against it. 
 
 " In our country the belief in the influence of 
 the Moon is far from having the force of an axiom, 
 witness the farmer who said to me : 
 
 " ' We know the Moon can do nothing to our 
 crops, but one hears it so much talked about that 
 it always has some effect on the imagination.'
 
 MOON, VEGETATION, ORGANIC LIFE 141 
 
 " The facts cited in support of it cannot be taken 
 as indisputable. Let us see how this is. 
 
 "There is a widespread belief that trees pruned 
 at the Old Moon grow less strongly than if the 
 pruning is done during the New Moon ; but at 
 the same time, according to the popular belief, 
 there is a day that is specially unlucky for such 
 work. It is the last Wednesday of the lunar 
 month ; so it is an accepted idea that a tree cut 
 on that day will not send out a new shoot, and 
 this to such a point that one is recommended to 
 choose the day for cutting away brambles and 
 noxious plants. Here is what a farmer told me : 
 
 " ( One year, being very pressed with work, I 
 began to prune six young mulberry trees, without 
 taking much thought about the day or the Moon. 
 When I had pruned three of them it occurred to 
 me that it was the last Wednesday of the Moon. 
 I left my work unfinished, feeling quite sure that 
 I had killed my three trees, and at the New Moon 
 I came back to them and pruned the three remaining 
 ones. But afterwards I could not see the least 
 difference between those that ought to die, and 
 those that, according to the popular belief, ought 
 to grow vigorously.'
 
 142 A DAY IN THE MOON 
 
 " ' That,' I replied, ' is an experience that ought 
 really to make you lose all your wonderful con- 
 fidence in the Moon.' 
 
 " And here are several other instances of which 
 I have been a witness : 
 
 " One day we were busy planting potatoes. A 
 neighbour passed by and addressed us thus : 
 " ' So you want to have a crop of little beads ? ' 
 " ' How is that ? ' 
 
 " ' The Moon is no good to-day for the work 
 you are doing. You will have for your crop a 
 lot of potatoes, but they will be very small ; the 
 Moon has no force.' 
 
 " You see, he spoke very confidently. When 
 we dug the potatoes there was nothing out of 
 the way in their number, but they were of splendid 
 size ; and this made us say that if the Moon had 
 had all its force on the day we planted them, they 
 would have been as big as pumpkins. 
 
 " One day I was engaged in grafting an apricot tree, 
 when a professional grafter noticed what I was doing. 
 " ' What ! grafting to-day ! But the Moon ? ' 
 " 1 1 must tell you I have not consulted her.' 
 " The professional, with a smile of pity for my 
 ignorance, was so good as to say to me :
 
 H IS 
 H > 
 
 R S 
 
 w J 
 
 H 
 
 a * 
 
 o 
 
 o a 
 o - 
 
 - 
 
 I 
 
 Q W 
 W S 
 
 w 
 
 w 
 
 H
 
 " ' The graft will take, but the tree will not 
 bear fruit the Moon is New, but that is no good 
 for grafting ! ' 
 
 " My graft was a success, and still better, the 
 following year it gave me six fruits. Twenty years 
 have gone by. In that time my apricot has become 
 a fine tree, which has always been very fruitful, 
 despite the prophecy that condemned it to sterility. 
 
 " As to wood being liable to be worm-eaten 
 according to the state of the Moon when it is 
 cut, I have no belief in it, for I have always had 
 my woodcutting done during the wane of the 
 Moon, and this has been no obstacle to the 
 worms attacking it. 
 
 " As for the story of wood floating or going 
 to the bottom of the water according as the Moon 
 was Old or New when it was cut, this is the first 
 time I have heard of it. I should like to witness 
 the experiment, as to the success of which I have 
 plenty of reasons for doubt. 
 
 " Many gardeners take no notice of the phases 
 of the Moon. They are content to do their 
 sowing at the most convenient times, and succeed 
 just as well as those who consult the Moon on 
 every occasion.
 
 144 A DAY IN THE MOON 
 
 " I might quote many more examples to show 
 that this belief in the influence of the Moon 
 rests on no serious facts, that it is only a popular 
 prejudice very difficult to uproot, and based on 
 the agricultural knowledge, or rather ignorance, 
 of two hundred years ago. 
 
 " I remember having read La Maison rustique 
 du XVII e Siecle, a big folio of 1,200 pages, in which 
 this belief in the Moon has the place of honour, 
 and is made to explain how to be successful, just 
 as one explains a chess opening. 
 
 "At that time it was not only agriculture that 
 was subject to the Moon, all knowledge was derived 
 from the science of the stars. To give only one 
 instance, doctors had a day of the Moon for 
 giving medicine to, or bleeding, those of phlegmatic, 
 sanguine, or hypochondriac temperaments. 
 
 " To-day medical science has got rid of these 
 prejudices. 
 
 " Let us hope that, to its great advantage, agricul- 
 ture will do the same." 
 
 So speaks M. Ay me. 
 
 Is it exactly " to the great advantage " of 
 agriculture that it should deny the existence of any 
 lunar influence on vegetation ?
 
 MOON, VEGETATION, ORGANIC LIFE 145 
 
 That is precisely the point of the difficulty, 
 and we shall see other and as serious combatants 
 entering into the debate on the opposite side. 
 
 In an extremely interesting paper written by a 
 horticulturist, under the title of Action mtale de la 
 Lune, M. Galle-Defond (of Port-de-Piles, Vienne) 
 has put together some notes that, to my mind, 
 meet in very clear and precise language the 
 objections above stated. 
 
 Here are the rules which he deduces from 
 numerous experiments. 
 
 He first of all remarks that the New Moon 
 appears to be favourable to the ascent of the sap 
 in plants, which therefore grow more vigorously 
 at this period of the lunar month. 
 
 From this he believes he can deduce different 
 methods of treatment for various kinds of plants, 
 according to the results he wishes to obtain. 
 
 In the case of carrots, radishes, salsifies, turnips, 
 leeks, and beet, all belonging to the class of plants 
 cultivated for their roots, the sowing should be 
 done from the 5th to the I5th day of the lunation. 
 
 But aubergines, chervil, chicory, cabbages, lettuces, 
 onions, parsley, tomatoes, haricots, green peas, 
 etc., and finally cucurbitaceous plants, melons and 
 10
 
 146 A DAY IN THE MOON 
 
 cucumbers, should be sown and planted during 
 the period of the waning Moon. 
 
 According to this observer, the cucurbitaceous 
 plants in particular have been the subject of con- 
 clusive experiments. 
 
 All this goes to confirm the old saying : " If 
 the Moon is lost the beans are spoilt." 
 
 Popular wisdom would thus have some good 
 in it. 
 
 It will be seen that here there is no question of 
 sowing on a Wednesday rather than any other 
 day ; one must not exaggerate anything. 
 
 If the Moon exerts any influence on vegetation 
 it would therefore be by being favourable to the 
 rise of the sap during the first part of the 
 lunation. 
 
 This principle once admitted, it is easy to under- 
 stand the method used by M. Galle-Defond, who 
 varies the times of sowing according to the results 
 to be obtained. 
 
 But does the sap between the time of New Moon 
 and Full Moon rise more abundantly than during 
 the following days ? This is the whole problem. 
 
 There seems no doubt that the question can be 
 solved when reduced to this form, but the experi-
 
 MOON, VEGETATION, ORGANIC LIFE 147 
 
 ments must be carried out with method and 
 precision. Certain plants seem to be specially 
 adapted for the test. 
 
 " In the cultivation of mushroom beds," says 
 M. Cordier, a gardener of Luneville, " I have 
 always remarked that there was as abundant a crop 
 between the 8th and the I5th day of the lunation 
 as during all the rest of the month put together, 
 and as the development of the mushroom takes 
 4 to 6 days, the rise of the sap would thus 
 correspond to the first days of the Moon. 
 
 " A second observation refers to the cultivation 
 of the melon. I believe I have very often re- 
 marked that the fruit formed much better during 
 the Old Moon than during the New ; and as to 
 obtain well-formed fruit, one must avoid producing 
 an excessive supply of sap, whether by watering 
 or by heat it would seem that the New Moon 
 produces this excess of sap, which in normal times 
 one can avoid." 
 
 With regard to the cultivation of the beetroot, 
 M. Compiegne and his sons, at Cremarest (Pas-de- 
 Calais), have remarked a point that confirms the 
 preceding observations. If one cuts a beet across, 
 one can count concentric circular rings around its
 
 148 A DAY IN THE MOON 
 
 core ; now the number of these rings is equal to 
 that of the revolutions of the Moon since the 
 springing up of the plant. 
 
 These extremely interesting points may be com- 
 pared with others that are less known. 
 
 M. Galle-Defond tells us that one of his friends, 
 a planter in America, has declared to him that 
 some kinds of trees have marked on their cross 
 sections not only the rings indicating the years 
 of growth, but also what really are concentric lunar 
 circles. 
 
 The same remark is made by M. Jacques, a 
 landed proprietor in New Caledonia, where for 
 several years he has been exploiting great tracts of 
 forest. 
 
 " In France," he tells us, " trees are only cut 
 in winter, for the excellent reason that if the thinning 
 is done in the winter, when the circulation of the 
 sap is least active, the trees continue to grow better, 
 while those that are thinned out in summer, in 
 June or July, for instance, either grow badly or 
 not at all. Further, it has undoubtedly been shown 
 that wood cut in summer does not keep well, 
 and soon after it is felled is attacked by mushroom 
 growths and insects, which cause it to rot quickly
 
 Photograph by G. E. Hale. 
 
 THE MOON'S SURFACE. 
 
 148]
 
 MOON, VEGETATION, ORGANIC LIFE 149 
 
 and make it useless for any purpose. This can 
 be very well explained by a kind of fermentation 
 taking place in the tree if it is cut down at the 
 
 D i 
 
 moment when it contains an abundance of sap. 
 
 "Here the Moon is not to blame, for it is the 
 Sun that favours this great production of sap, that 
 afterwards leads to decay. 
 
 " But in New Caledonia, where the temperature 
 is from 73 to 77 in winter and from 77 to 86 
 in summer, the rapid decomposition of wood cut 
 during the New Moon cannot be attributed to 
 the same causes, unless it is admitted that in tropical 
 countries the sap circulates in greater abundance 
 during the New than during the Old Moon. 
 
 " I must tell you that at the outset I had no 
 belief whatever in any influence of the Moon on 
 the preservation of wood. It was all very well 
 for the natives to say to me, * Him not good to 
 cut at present, him wait to cut till good.' I paid 
 no attention, and I had a costly experience of it. 
 
 " For all the woods, even those of the hardest 
 structure, that were cut during the New Moon, 
 were very soon worm-eaten, while those felled 
 during the Old Moon remained, even after the 
 lapse of many years, in an excellent state of
 
 1 50 A DAY IN THE MOON 
 
 preservation. And this was not in any one month 
 rather than another, for I had the curiosity to 
 repeat the experiment during every lunar month of 
 the year, and the result was always the same. 
 
 " The Bancoulier tree, for instance, which is very 
 soft wooded, if felled and cut up in the New Moon 
 literally went to dust in six months ; the same 
 wood felled and cut up during the Old Moon kept 
 without change for years. 
 
 "It does not follow from this that the Moon 
 exerts a direct action on timber cut during this or 
 that phase, but I simply note the fact that wood 
 cut during a certain period of the lunar month 
 rapidly deteriorates, while that cut in another period 
 of the Moon keeps in the normal way." 
 
 We might quote here M. Galle-Defond's experi- 
 ments on the cultivation of fruit trees. We shall 
 content ourselves merely with noting that, according 
 to him, it is most important not to plant any fruit 
 tree or shrub during the first fortnight of the 
 Moon if one wants to have a good supply of fruit 
 from it. 
 
 To sum up, it would seem that the Moon exerts 
 some influence upon vegetable life, and if in our lands 
 the experiments are not all conclusive, it is because
 
 MOON, VEGETATION, ORGANIC LIFE 151 
 
 frequently the lunar action, perhaps a very slight 
 one, is counteracted by changes of the weather which 
 diminish its effect or neutralise it altogether. 
 
 And the best proof of it is afforded us by facts 
 observed in tropical countries, where there is nothing 
 to disturb the action of our satellite. 
 
 If these conclusions are justified, we ought to be 
 able to note this lunar influence all the more clearly 
 as we turn our attention to vegetable phenomena 
 of a more rudimentary class. 
 
 And this is precisely what is shown by the 
 experiments of M. Carbonnier on cryptogamic 
 vegetation, principally that which grows in stagnant 
 waters. 
 
 The maximum intensity of growth of this kind 
 always corresponds to the time of the Full Moon. 
 
 These are undoubted facts ; whatever be the 
 explanation, they will remain none the less certain. 
 
 To whatever theory we may appeal, it is a fact 
 known to all botanists that the growth of plants 
 depends on the carbonic acid diffused in the atmo- 
 sphere ; now this phenomenon takes place above 
 all under the action of light. No light, no pro- 
 duction of chlorophyll, and therefore no vegetable 
 growth.
 
 152 A DAY IN THE MOON 
 
 One might thus explain why seeds sown at the 
 New Moon develop more rapidly than if they 
 had been placed in the ground at the Full 
 Moon. 
 
 In the former case, when the seedlings push 
 through the surface of the ground the Moon gives 
 them some of the light they need to absorb carbon 
 and grow ; in the second case they come out of 
 the ground when the Moon is below the horizon, 
 and are thus deprived of its luminous rays during 
 the nights. 
 
 And then, who can tell us what is the inner 
 mechanism of vegetable growth, presiding over the 
 life of the microbe as well as that of more highly 
 organised structures ? What is the action of the 
 rays of the spectrum, of chemical radiations, and of 
 unknown vibrations ? 
 
 Truly, instead of denying facts, we would do 
 better to study them more closely. The explanation 
 will come after that.
 
 ASTRAL INFLUENCES AND 
 ASTROLOGERS 
 
 THE search for the causes of things is most cer- 
 tainly a deep-seated tendency, a law of the mind 
 a law that dominates it forcibly and inevitably for 
 through all time we see humanity seeking to find 
 behind the effects it has observed a reason capable 
 of giving a logical explanation of them. 
 
 If those causes eluded his search through his 
 invincible ignorance, man very often sought for an 
 explanation of the phenomena around him in the 
 forces of Nature personified for the purpose, and 
 endowed by his imagination with the most ex- 
 travagant powers. 
 
 Thus, as the vault of the skies attracted the 
 attention of primitive peoples, the constellations 
 were soon supposed to play a preponderating part 
 in human destinies and in all the actions of life. 
 
 Virgil tells us how Orion was associated with
 
 i 5 4 A DAY IN THE MOON 
 
 the coming of rain, and the Pleiades forecasted 
 stormy weather. 
 
 But the presence of the Sun and Moon or the 
 planets above the horizon, and later on the calcu- 
 lated positions of the heavenly bodies, became, in 
 the hands of the astrologers, the basis of a complete 
 science for the prediction of the future. 
 
 The Sun, as we know, in the course of the year 
 pays a visit to each of the twelve constellations of 
 the zodiac. An individual born in such or such a 
 month was therefore supposed to be under the 
 influence of this or that constellation. Thus 
 fatalism had a fine field. 
 
 Don't smile at all this. Why, even to-day there 
 are plenty of almanac-makers that would think they 
 were not living up to their reputation if they did 
 not give horoscopes taken from the position of the 
 Sun in each sign of the zodiac. 
 
 Were you born under the sign of the Bull or 
 the Ram ? You are assured of material prosperity. 
 The Scorpion predicts a contrary destiny for you ; 
 the Lion presages heroes ; the Virgin forecasts a 
 pure-minded disposition ; Capricorn brings riches 
 and so forth. 
 
 Unfortunately the diversity of the life -destinies
 
 From the Photographic Atlas of the Paris Observatory. 
 
 REGION BETWEEN THE "MARE IMBRIUM " AND THE NORTH POLB 
 OF THE MOON. 
 
 At the top are the Mare Imbrium (Sea of Rains), I,aplace~ Promontory and 
 the Sinus Iridum (Gulf of Rainbows). I^wer down, the large mountain ring 
 with a dark interior is Plato. Below this is the Mare Frigoris (Sea of Cold) and 
 then the North Pole of the Moon with the mountainous region around it. 
 . (Reversed image.) 
 
 154]
 
 ASTRAL INFLUENCES, ASTROLOGERS 155 
 
 of men born under this or that sign has always 
 been so great that the astrologers soon found the 
 need of additional explanations. 
 
 It was then that they brought in the action of 
 the Moon and the planets. 
 
 Mercury was the patron of the arts ; Mars 
 inspired to war ; Venus could only keep to her 
 mythological character ; Jupiter indicated to mortals 
 born under its influence that they were destined to 
 the greatest triumphs ; witness this passage from a 
 book on Astrology of the days of Louis XIII : 
 <c Jupiter in the first sign of the zodiac makes 
 nobles, men of power, bishops, rulers, sages, 
 philosophers, merchants, bankers." 
 
 Saturn was associated with the greatest sorrows ; 
 it was considered an unlucky star. What would 
 they have said of Uranus and Neptune ? But 
 they were unknown at that time. 
 
 All this seemed quite natural, and no one was 
 tempted to laugh at it ; nevertheless, one thinks 
 one must be dreaming as one reads some of the 
 manuscripts of the Middle Ages and the extra- 
 ordinary horoscopes they contain. 
 
 The doctrines of the astrologers were held in 
 high honour among the Arabs, and from them
 
 156 A DAY IN THE MOON 
 
 passed into Spain ; but it was especially on the 
 return of the Crusaders from the East that they 
 spread over Western Europe. 
 
 Then kings and princes had their official astro- 
 logers, and these poor people had too often reason 
 to repeat the words of Scripture " No lite confidere 
 in prindpibus " (" Put not your trust in princes "). 
 
 Flattery, generally so successful with the great, 
 was often no help to the astrologers, and they had 
 to rack their brains to find something better. 
 
 Thus one day, when he was in a bad humour, 
 Louis XI sent for his astrologer Galeotti, and put 
 a very embarrassing question to him. 
 
 " As by your own claim you know everything," 
 said the king to him, " tell me when you will 
 die." 
 
 Alas for Galeotti ! He knew the king had told 
 his people that as soon as they had a sign from 
 him they were to put the astrologer into a sack and 
 throw him into the river. 
 
 But his ready wit saved him from this awkward 
 situation. 
 
 " Sire," he replied at once, " I have carefully 
 consulted the stars on this subject, and they tell 
 me I shall die just three days before your Majesty."
 
 ASTRAL INFLUENCES, ASTROLOGERS 157 
 
 The king was very superstitious, but perhaps he 
 did not believe this ; nevertheless, he took care not 
 to carry out his plan. " After all," he thought, 
 " one can never be certain." 
 
 Strange to say, and to a certain point this is an 
 excuse for the almost universal belief in Astrology 
 at a time when modern Astronomy had not yet 
 revealed the mechanism of the heavens, the 
 astronomers themselves gave the example, and most 
 of them united the professions of astrologer and 
 astronomer. 
 
 It is true that many of them regarded Astrology 
 as only a necessary expedient for earning their daily 
 bread and an indirect means of enabling them to 
 devote themselves to more serious work. 
 
 In his Ephemerides for 1469 Johann Miiller, 
 who is better known under the name of 
 " Regiomontanus," investigates the question of the 
 aspects of the Moon under which it is best to 
 perform the operation of blood-letting, and on 
 what parts of the human body the various signs of 
 the zodiac have a special influence. 
 
 We find, indeed, such indications in an old 
 drawing in a manuscript in the library of Bourges. 
 
 Taurus the Bull influences the neck and the upper
 
 158 A DAY IN THE MOON 
 
 part of the throat ; Cancer, the chest, lungs, 
 stomach, etc. 
 
 Stoefler, an able mathematician, who was a pro- 
 fessor at Tubingen, believed in the influence of the 
 heavenly bodies on events here on Earth. 
 
 Having calculated that there would be a con- 
 junction of the planets Mars, Jupiter, and Saturn in 
 the month of February 1 524, he predicted a universal 
 deluge at that date. 
 
 Could it be otherwise, seeing that this heavenly 
 phenomenon would take place in the sign of the 
 Fishes ? 
 
 The prophecy made a great stir, and a doctor of 
 Toulouse, named Auriol, took it so seriously that 
 he immediately had a great vessel constructed on 
 the plan of Noah's ark. 
 
 February came and it was the driest month of 
 the year. 
 
 It is said that Jerome Cardan drew a horoscope 
 for Edward VI. 
 
 But he piled up such a series of unsuccessful 
 prophecies that at last, disgusted with his failures, 
 he ended by predicting his own death for the 
 year 1570. 
 
 As if he meant to show that, once in a way,
 
 ASTRAL INFLUENCES, ASTROLOGERS 159 
 
 his prophecies could be correct, he starved himself 
 to death. 
 
 Tycho Brahe (15461601) did not, as a rule, 
 make any distinction between Astrology and As- 
 tronomy ; these two sciences were only one at 
 that time, or rather the true Astronomy had not 
 yet come into existence. 
 
 Though he had something like a real vocation 
 for the study of the stars, Tycho had all the trouble 
 in the world to accomplish his plans. 
 
 His father, Otho Brah, Lord of Knudstrup, in 
 Scania, had been brought up in the complete 
 ignorance that then befitted a nobleman. How- 
 ever, he consented to let his son go first to 
 Copenhagen, and then to Leipsic, to study law, 
 but Tycho eluded his tutor's vigilance and spent 
 all his nights in the study of the skies. 
 
 Though of a kindly and generous character, and 
 endowed with the noblest feelings, he had a hasty 
 and violent temper. This was the source of end- 
 less trouble for him that followed him through 
 all his life. 
 
 It appears that while he was a student at Leipsic 
 he drew his own horoscope, and was startled to 
 find that the scheme, where the influence of the
 
 160 A DAY IN THE MOON 
 
 planet Mars came into it, presaged for him a dis- 
 figurement in the face. 
 
 There was nothing to justify this indication, 
 till one fine day he picked a quarrel with one of 
 his fellow-students over a theorem in geometry. 
 
 A duel was arranged. On a dark night by the 
 light of a smoky torch the two opponents attacked 
 each other furiously, and after they had crossed 
 weapons several times, a sword-cut took offTycho 
 Brahe's nose. 
 
 The horoscope was fulfilled. 
 
 Tycho was not too downcast at his unfortunate 
 adventure ; his wound healed, and he made him- 
 self an artificial nose of gold, silver, and wax. 
 Contemporaries tell us that the imitation was so 
 perfect that no one ever noticed his loss. 
 
 Even Kepler, who was to make himself famous 
 by the discovery of his immortal laws, was obliged 
 to play the astrologer. 
 
 At every turn his works refer to the wonderful 
 properties of numbers, to disturbing influences, 
 the conjunction of planets, etc., etc. 
 
 He was only twenty-four years old when, in 
 1594, he was appointed professor at Gratz, in 
 Styria. Besides his work as a teacher he was en-
 
 THE THREE CHIEF MOUNTAIN RINGS ARE (FROM TOP TO 
 BOTTOM) THEOPHILUS, CYRILLUS, AND CATHERINE. 
 
 (Erect image.)
 
 ASTRAL INFLUENCES, ASTROLOGERS 161 
 
 trusted with the making of almanacs predictions 
 as to the weather, horoscopes, all that kind of 
 thing was then very closely connected with the 
 astronomical figures relating to the positions of the 
 stars. 
 
 Later on he had to continue the practice of this 
 wretched profession in order to support his large 
 family, and he often drew the horoscopes of princes, 
 who summoned him to their courts " to know 
 their fate by the stars." 
 
 Kepler, in reality, had no belief in these practices, 
 and we have the proof of this very clearly in a 
 passage in his writings : " What have you to 
 complain of, you over-scrupulous philosophers, if 
 a daughter (Astrology), whom you think foolish, 
 supports a wise, though poor, mother (Astronomy) ; 
 if this mother is tolerated among men more foolish 
 still, only for the sake of these same follies ? If 
 men had not had the credulous hope of reading 
 the future in the heavens, would you ever have 
 been wise enough to study Astronomy for its own 
 sake ? " 
 
 And in fact, in Kepler's days, alchemists, astrolo- 
 gers, and magicians swarmed to such a degree that 
 L'Estoile wrote in his Journal de Henri III: 
 1 1
 
 1 62 A DAY IN THE MOON 
 
 " In the time of Charles IX these vermin had 
 secured such immunity in Paris, that there were 
 as many as 30,000 of them, as the chief of them 
 admitted in 1572." 
 
 Henri II of France often consulted the famous 
 Nostradamus, who wrote his Centuries, a collection 
 of prophecies in which no one ever understood 
 anything very likely not even their author. 
 
 This work, of which Henri II accepted the 
 dedication, was, however, of this much service to 
 Nostradamus, that it led to his being summoned 
 by the King, who gave him 100 crowns in gold 
 and sent him to Blois to draw the horoscopes of 
 his sons, the young princes. 
 
 New honours were lavished on Nostradamus as 
 the result of this mission, and later Charles IX 
 and Catharine de* Medici attached him to their 
 service. 
 
 The latter soon began to set the very highest 
 value on Astrology. She spent absurd amounts 
 of money on building observatories merely for 
 the purpose of being herself able to consult the 
 stars. 
 
 One of the most famous of these was that of 
 the Hotel de Soissons. It consisted of a column
 
 ASTRAL INFLUENCES, ASTROLOGERS 163 
 
 nearly 100 feet high, which the pickaxe of the 
 town improver has spared to our day. 
 
 This Hotel de Soissons has a whole curious story 
 of its own connected with Astrology. 
 
 We shall let Dulaure himself tell it to us : 
 " Why did this queen after having built the 
 palace of the Tuileries, expended considerable sums 
 upon it, and adorned it with the work of the 
 most famous artists and all that luxury could desire 
 in the way of comfort and elegance leave the 
 place for good and all soon after the building 
 was completed ? Why did she take a dislike to 
 the palace, and, at a time when the finances were 
 exhausted, buy the Abbey of Saint-Maur des Fosses 
 to erect a residence there for herself? Why did 
 she then abandon this project, only to take up 
 another, and buy the convent of the Filles 
 Penitentes ? Why did she disturb the nuns who 
 lived there by transferring them to the Abbey of 
 Saint-Maur, and secularise the monks of the latter 
 abbey in order to transfer them to the Hospital of 
 Saint-Jacques du Haut Pas ? Why was she obliged 
 to ask of her son, the king, the permission to 
 carry out these changes, and of the Pope bulls to 
 ratify these transfers and secularisations, and of 

 
 1 64 A DAY IN THE MOON 
 
 the Parlement de Paris the registration of all these 
 acts ? Why, finally, did she order all these changes, 
 and especially give up the Tuileries, to build 
 and go to live in a new residence? Here is the 
 reason Catharine de' Medici was frightened at 
 the prediction of an astrologer, who foretold that 
 she would die in a place called Saint-Germain. Now 
 the Tuileries were situated in the parish of Saint- 
 Germain 1'Auxerrois. ' It was at once noticed,' 
 says Mezeray, ' that she superstitiously avoided all 
 the places and churches that bore that name. She 
 would not again go to Saint-Germain-en-Laye, and 
 because her palace of the Tuileries was in the 
 parish of Saint-Germain in 1'Auxerrois, she even had 
 another built, namely, the H6tel de Soissons near 
 Saint-Eustache.' 
 
 " There is something satisfying to self-love 
 when one sees ridiculous actions on the part of 
 powerful people who have aspired to celebrity. 
 This queen, so powerful, so feared, so imperious, 
 debased herself by her stupid credulity to the level 
 of the very lowest class of society. She believed what 
 to-day the old women of the most out-of-the-way 
 villages would blush to believe ; she believed 
 in the predictions of magicians, and she, who
 
 ASTRAL INFLUENCES, ASTROLOGERS 165 
 
 struck terror into the hearts of so many, was 
 herself terrified at the oracles of the wretched 
 astrologer. 
 
 "This hotel, which in the fourteenth century 
 had borne in succession the names of de Nesle, 
 de Boheme, and de Behaigne, and in the fifteenth 
 that of d'Orleans, then that of the Filles 
 Penitentes ' when the nuns of that order occupied 
 it, was called the H6tel de la Reine in 1571, 
 when it became the property of Catharine de' 
 Medici. After the death of the queen it was 
 called the Hotel des Princesses, and finally the 
 Hotel de Soissons as at present. 
 
 "Catharine de' Medici had had erected there, 
 after the plans of Bullant, and in the angle of a 
 side court, a fluted Doric column of great height, 
 to be used by herself as an observatory. It adjoined 
 and was in communication with the Hotel de la 
 Reine. This column is the only structure belonging 
 to the Hotel de Soissons that survives. It is still 
 to be seen close to the buildings of the Halles ; 
 it has a winding stair in its interior. The queen 
 used to ascend it to consult the stars, and seek to 
 find in their positions the promise of a happiness that 
 those who reign amid crimes never find on this earth."
 
 1 66 A DAY IN THE MOON 
 
 The favourite astrologers of Catharine de' Medici 
 were R6gnier, and a certain Cosmo Ruggieri, a 
 native of Florence. It was the latter who made 
 the prediction as to the place of the princess's death. 
 
 But notwithstanding all the precautions she took, 
 this is what happened. At least it is what certain 
 historians tell us. 
 
 After having fled from all the Saint-Germains 
 in the world, one day, when Catharine was at Blois, 
 she had a severe attack of fever on hearing the 
 news of the assassination of the Duke of Guise. 
 At once she sent in terror for a priest and asked 
 his name. 
 
 " The Pere Saint-Germain, preacher to the King," 
 was the reply. 
 
 " Ah ! " exclaimed Catharine, "I am a dead 
 woman ! " 
 
 And in fact she died next day, January 5, 1589. 
 
 In the following reigns there were perhaps fewer 
 astrologers, but their influence did not diminish. 
 
 At the moment when his son was born Henri IV 
 desired his doctor and the astrologer Lariviere 
 to draw the horoscope of the royal child. 
 
 The astrologer got very well out of the business 
 by declaring that the young prince was born under
 
 ASTRAL INFLUENCES, ASTROLOGERS 167 
 
 the sign of the Balance, and this was why 
 Louis XIII, from his very cradle, was surnamed 
 " the Just." 
 
 So it was a very simple business ! 
 
 An astrologer was also on duty at the birth 
 of Louis XIV and drew his horoscope with equal 
 success. 
 
 How could it have been otherwise, since 
 even the astronomers lent themselves to these 
 practices ? 
 
 Many of them even believed in their forecasts 
 for instance, the famous Morinus, who did not 
 hesitate to predict to people, on all manner of 
 occasions, what would happen to them at an early 
 date. 
 
 Thus it was that he announced to his colleague 
 Gassendi as the time of his death the end of the 
 coming July of 1650. "But," the famous 
 Canon of Digne used to delight in telling his 
 friends, " I was never better than at the fatal 
 epoch marked out by the prediction of Morinus." 
 
 And a little later have we not the Comte de 
 Boulainvilliers in concert with the Italian astrologer 
 Colonna predicting the death of Voltaire at the 
 age of thirty-two. " Everyone knows," remarks
 
 1 68 A DAY IN THE MOON 
 
 Arago when relating the fact, " how that prediction 
 was fulfilled ! " 
 
 Gradually, however, the fashion seemed to 
 change and we see the " most excellent mathema- 
 ticians and extractors of quintessences," of whom 
 Rabelais had made sport, turning their attention 
 to almanacs or " prognostications." 
 
 Thus in this connection we read in the second 
 edition of the Astronomic de M. Lalande, printed 
 in 1771, this characteristic passage : 
 
 " It is not without difficulty that at last the 
 philosophic spirit has dissipated these errors ; at 
 the beginning of this century people at times came 
 to consult the astronomers of the Academic as to 
 the future, and in 1705 M. Lieutaud thought 
 it well to print as a preface to the Comaissance 
 de Temps : c No predictions will be found here, 
 because the Academy has never recognised the 
 solidity of the rules given by the Ancients for 
 predicting the future by the relative positions of 
 the stars/ 
 
 " If one reads a letter in the Mercure de France 
 of 1763, in which I told of the anxiety of the 
 Sultan of Turkey to obtain all the works published 
 by the astronomers of the Academy, it will be
 
 ASTRAL INFLUENCES, ASTROLOGERS 169 
 
 remarked that he asked especially for any 
 predictions made as to the future by the science 
 of the stars. Perhaps his Highness only wanted 
 our books of astronomy in the hope of finding 
 in them the fate of the Powers, who seemed intent 
 on mutual destruction." 
 
 Nowadays no one any longer ventures to 
 consult men of science as to reading the future in 
 the stars, but the bent of the popular mind has not 
 altered. 
 
 Did not Napoleon go to have " his good fortune " 
 told by the celebrated card-reader Mademoiselle 
 Lenormand ? 
 
 It is not long since I had proposals from more 
 than one contemporary astrologer to draw my 
 horoscope. 
 
 The card-readers and the necromancers of 
 spirit-seances find each year Paris newspapers 
 ready to publish their ambiguous and grotesque 
 predictions. 
 
 The fortunes they make for themselves in this 
 " noble profession " are one more proof of the 
 ignorance and insurmountable credulity of the 
 public. 
 
 But let us stop, for one might write volumes
 
 i yo A DAY IN THE MOON 
 
 on such a subject, and probably without advantage 
 to anyone. 
 
 Let us leave the astrologers to draw their 
 horoscopes. The planets are too far off to exert 
 an influence on the life of any one of us. Even 
 the perturbations they cause in the earth's move- 
 ments are infinitesimal. 
 
 But we cannot say as much of the Moon, and 
 I confess that here those who take an interest in 
 the influence of the heavenly bodies have a better 
 case. 
 
 What effect can the Moon have on the develop- 
 ment of the animal organism, and what influences 
 come from it ? This is what it remains for us to 
 examine.
 
 XI 
 
 THE ACTION OF THE MOON ON MEN 
 AND ANIMALS 
 
 IF it may be admitted that the Moon exerts some 
 action on the phenomena of vegetation, one cannot 
 see a priori any reason why animal growth should 
 not be, up to a certain point, dependent on the 
 same influence. 
 
 Everyone knows the effects of spring on the 
 animal organism, and, as far as I know, no one has 
 found a complete explanation for it. 
 
 At the moment when the sap begins to rise 
 freely in the plants, it seems as if at the same 
 time a " revival " comes over men and animals. 
 
 If, then, the Moon promotes by its action the rise 
 of the sap, or the chemical combinations of the 
 vegetable cell, one can imagine the possibility of 
 a similar action on the animal cell, which in its 
 inner structure differs very little from the former. 
 
 And in fact there is no lack of observations 
 171
 
 172 A DAY IN THE MOON 
 
 bearing on this point. One would want whole 
 volumes to classify them all. 
 
 M. Latourte of Dieppe wrote recently : 
 
 " I keep some hens, and during forty years I 
 have reared a good number. 
 
 " Now, each time that I put eggs to be hatched, 
 the chickens hatched out during the period from 
 the First Quarter to the Full Moon break through 
 the shell more easily, and are more vigorous than 
 their fellows who come out in the period from the 
 Last Quarter to the New Moon." 
 
 This confirms the observations of M. Galle- 
 Defond, who is a poultry farmer as well as a 
 horticulturist : 
 
 " The Moon," he writes, " is not without some 
 influence on the success or failure of the hatching 
 out of chickens or goslings." 
 
 The growth of animals born at the beginning 
 of the lunation follows the same rule as that of 
 plants. It appears to be more rapid than that of 
 animals born in the waning of the Moon. 
 
 So perhaps our ancestors were not so foolish 
 when they preached their plan of having their 
 hair cut and their beards trimmed at the New 
 Moon.
 
 ACTION ON MEN AND ANIMALS 173 
 
 Even the wine industry has the benefit of these 
 prescriptions. So we are told that the racking of 
 the wine should never be done towards the end of 
 the lunar month. 
 
 It is now known that the fermentation of wine 
 depends on the development of a micro-organism 
 of a cell and if we admit the influence of the 
 Moon on organic beings, it will be easily under- 
 stood that here too its influence would come under 
 a general law. 
 
 So we can only repeat what we have said in previous 
 chapters : Light is only a form of energy, and we 
 are very far from having analysed all its radiations. 
 
 Perhaps it is in this mysterious influence which 
 promotes the development of the cell, and is 
 favourable to the general activity of the human body, 
 that we must look for the explanation and origin 
 of the word lunatic \ applied to persons subject inter- 
 mittently to loss of reason and attacks of madness. 
 
 With the ancients there was no doubt as to the 
 action of the Moon on the mental state of certain 
 subjects. 
 
 In a book of 1399, a learned history of the 
 madness of Charles VI of France, we read : 
 
 " The King, who had recovered his health, kept
 
 174 A DAY IN THE MOON 
 
 the feast of Easter in his royal residence of Saint- 
 Paul. . . . Every one was rejoicing at his recovery, 
 but this happy state of things did not last long. That 
 same year he relapsed six times into madness, either 
 at the New or at the Full Moon." 
 
 If this were an isolated fact, evidently it would 
 prove nothing, but we shall see that it is corro- 
 borated by other testimony of the same kind. 
 
 In a work on medicine published in 1578 by 
 Dr. Joubert of Montpellier, the falling sickness, 
 or epilepsy, as well as melancholy, are classed among 
 the illnesses that quite evidently depend upon the 
 course and phases of the Moon. Menuret con- 
 siders skin diseases to be those the recurrences 
 of which are most indisputably connected with the 
 lunar phases. He asserts that he himself had 
 observed in 1760 a cutaneous attack of a patient 
 increasing continually during the waning of the 
 Moon, and reaching its maximum of intensity 
 towards the time of New Moon, when it covered 
 all the face and chest and caused unbearable irrita- 
 tion. After this epoch all the symptoms gradually 
 disappeared, and the face became clear, but the 
 same symptoms were seen to begin again as soon 
 as the Full Moon had passed.
 
 ACTION ON MEN AND ANIMALS 175 
 
 In another disease of this class the same doctor 
 noticed that a similar series of phenomena appeared 
 in a reversed order. 
 
 Whatever be the opinion one may profess on 
 the mechanism of the development of such maladies, 
 it would not be absurd to compare them to those 
 nervous phenomena that to a certain degree are 
 dependent on lunar influences. Mead has cited the 
 case of a child that always suffered from convulsions 
 at the time of the Full Moon, and Piso observed 
 that an attack of paralysis recurred with every New 
 Moon, that is to say, at the periods of least activity. 
 
 According to Menuret, with some epileptics the 
 attacks recur at the moment of the Full Moon. 
 
 One does not at first sight see very well how 
 our satellite can act in such a way, but we may at 
 least point out that all nervous maladies, and in 
 certain cases those that affect the terminations of 
 the nerves in certain skin diseases, appear to be 
 directly dependent on electrical influences. Now, 
 there can be no doubt that, especially in the higher 
 regions of the atmosphere, the charge of atmo- 
 spheric electricity can vary under the influence of 
 the Moon's light, and one might, strictly speaking, 
 connect the two kinds of phenomena.
 
 i y6 A DAY IN THE MOON 
 
 What further appears to corroborate these some- 
 what daring views is the mass of organic facts 
 observed long since in hospitals in the cases of 
 patients suffering clearly and exclusively from 
 nervous troubles vertigo, hysteria, somnambulism, 
 etc. in a way more or less in relation with the 
 phases of the Moon. 
 
 This was the opinion of the celebrated Gall, who 
 declared that he had recorded, in the case of weakly 
 persons, two epochs of irritability corresponding to 
 the New Moon and the Full Moon. 
 
 The celebrated physician and astronomer Olbers 
 attempted to make an experimental verification of 
 these facts, and after having been long in medical 
 practice, he denied them all absolutely. 
 
 Those who are of the opposite opinion object to 
 this way of looking at the matter that the instances 
 observed in our countries are much less numerous 
 than those of tropical lands. 
 
 But however this may be, Balfour felt satisfied 
 that in Bengal the progress of certain maladies, and 
 particularly that of intermittent fevers, follows the 
 course of the Moon. 
 
 Bruce asserts that more than once he observed 
 that the Moon exercises such an influence on
 
 ACTION ON MEN AND ANIMALS 177 
 
 epileptics, and with such regularity that it is 
 always on the third day of the Full Moon that 
 the paroxysm of the illness ended in an intermittent 
 fever. 
 
 It was, besides, a generally received opinion among 
 Orientals that epileptics were agitated by the Moon, 
 and it was on account of this opinion that they 
 were given the name of lunatics, a term after- 
 wards applied to the insane. 
 
 The observations of Fontana bearing on the same 
 subject were also made in hot countries, but the 
 case that most clearly points to lunar influence is 
 that reported in the first volume of the Memoirs 
 of the Royal Academy of Madrid. The patient in 
 question was attacked periodically with a difficulty 
 of breathing, which became more marked at the 
 approach of New and Full Moon. 
 
 This singular illness lasted for several years in 
 succession. 
 
 It is probably to the fewness of such observa- 
 tions in the hospitals of France and Europe that 
 one must attribute the opinion of pathologists, 
 who are little disposed to accept the theory of 
 lunar influences on their patients. 
 
 Nevertheless it is the opinion of several alienists 
 12
 
 iy8 A DAY IN THE MOON 
 
 of our own day that their patients are more 
 agitated at the period of the Full Moon than at 
 that of New Moon. 
 
 It might be well to take up the question 
 again both here at home and in our tropical 
 possessions. 
 
 It would be a fine subject for a thesis for the 
 doctor's degree for such of my pupils as are short 
 of suggestions or of material. 
 
 Experience alone can decide the question. What 
 we must, however, insist upon is that our organism 
 is infinitely more sensitive to outside influences 
 than much of the apparatus invented by modern 
 physicists, and that, besides, the human body must 
 be a receiver for wonderfully synchronised waves 
 of radiations still unknown to us ; that we have 
 an electric or magnetic sense, which permits us 
 to perceive variations of this kind, though of 
 infinitesimal amount ; and that the learned men of 
 our day, when they talk of " nervous influx," are 
 hiding under this term their profound ignorance 
 of the mechanism that regulates all our organic 
 actions. 
 
 We conclude that we should continually study 
 matters, and not rashly cast aside the opinions of
 
 ACTION ON MEN AND ANIMALS 179 
 
 our ancestors, especially when we find them 
 supported by facts of which the authenticity cannot 
 be called in question. 
 
 The Moon, that great satellite, so near our 
 earth, which from the mechanical point of view 
 causes such enormous perturbations to our world, 
 should not be treated as a negligible factor from 
 whatever point of view we consider it. 
 
 There seems no doubt about its having some 
 influence on life, but to what degree is this 
 exerted ? That is the new question that appeals 
 to learned and ignorant, physicist and physician, 
 physiologist and astronomer. 
 
 These serious considerations are, it seems to me, 
 calculated to restore to their due place certain 
 branches of lunar research, which have been too 
 much neglected by students of the heavens. 
 Perhaps they will, moreover, avail to merit for me 
 the forgiveness of the astrologers, of whom I have 
 said so many hard things in the course of this 
 
 work. 
 
 * * * * * 
 
 It is not generally known that the study of 
 the Moon is within the reach of low-powered in- 
 struments.
 
 i8o A DAY IN THE MOON 
 
 One need only have a comparatively small tele- 
 scope to make very interesting observations. 
 
 We have seen that many selenographers had at 
 their disposal only instruments of small aperture 
 and short focal distance. They have, all the same, 
 done useful work in exploring the surface of our 
 satellite. 
 
 Why should not a good many of my readers 
 do the same. 
 
 And here one must take care not to fall into 
 a very widespread error. When one sets about 
 the study of Physical Astronomy one imagines that 
 one will see much better by using high magnifying 
 powers. It is a great mistake. 
 
 With telescopes of low power, objects are always 
 seen very sharply defined, and it is thus one should 
 begin to observe. 
 
 First of all, train your eyes ; the faculty of 
 penetrating vision will come later. 
 
 It is rather a long task, but the trouble is well 
 repaid. 
 
 Throughout you will be able to see enough of 
 detail to take a great interest in it, and so much 
 that you will be embarrassed when you have to 
 reproduce what you see in a sketch.
 
 ACTION ON MEN AND ANIMALS 181 
 
 Since the application of photography to the 
 study of the Moon, there has been too much 
 neglect of direct vision and the study of detail ; 
 this should be taken up again, unless we are 
 merely to mark time and make no progress. 
 
 Lunar photographs are useful in the sense that 
 they fix the topography of our satellite in a 
 definite way, better than this can be done by 
 micrometer measurements. But when it comes to 
 observing fissures, small craters, passing shadows, 
 and elevations of no great height, nothing is 
 equal to direct observation with the eye. 
 
 A telescope of 108 millimetres shows far more 
 objects than the best photographs. 
 
 Finally, there are regions which should be 
 specially studied. They are those that present 
 certain curious peculiarities from the geological 
 and volcanic point of view ; others may be recom- 
 mended by their picturesque character, as, for 
 instance, the " Straight Range " of the Moon, of 
 which we have already spoken, or the famous 
 woman's head in the Moon so well known to the 
 old selenographers. 
 
 In his first maps Cassini had, in fact, drawn 
 at the western end of the " Sinus Iridum " the
 
 1 82 A DAY IN THE MOON 
 
 promontory of the Heraclides in the form of the 
 head of a young woman. It was long believed 
 that the famous astronomer merely intended by 
 this means to distinguish his map from those that 
 preceded it, and thus to sign it, so to say. 
 
 And it was not till long after that this strange 
 appearance was again seen. In the drawing of 
 Schroeter the form shown by Cassini is not to 
 be recognised. That of M. Mabire gives it, how- 
 ever, but with the appearance of an aged woman. 
 
 One evening, when I was studying the Moon, 
 I saw the same promontory once more under 
 a form very like that in Cassini's drawings. The 
 apparition with its extended wings looked rather 
 like a nymph or a na'iad. 
 
 There is really here, then, a mere question of 
 lighting. When closely surveying the surface of 
 the Moon, it sometimes happens that one grasps 
 details that only present themselves on rare 
 occasions, as the result of libration varying to an 
 endless extent the angle at which the solar rays 
 fall. 
 
 One can also with the help of a telescope of 
 low power secure interesting photographs of our 
 satellite.
 
 ACTION ON MEN AND ANIMALS 183 
 
 As is well known, all that is necessary is to 
 replace the ordinary eye-piece by that of the 
 instrument, or, better still, fit the camera to the 
 telescope, leaving the eye-piece in position. 
 
 In an instrument of small aperture the difference 
 between the optical and chemical focus is almost 
 inappreciable, and one soon succeeds in finding 
 the right position after a few trials. 
 
 This method is of the greatest service when it 
 is a matter of photographing the phases of an 
 eclipse of the Moon or the Sun, and I have often 
 used it successfully on these occasions. An 
 exposure of a fraction of a second gives excellent 
 results. 
 
 With these practical hints I close the volume. 
 I shall be happy if I have succeeded in developing 
 in some of my readers a taste for those lunar 
 studies that are within the reach of anyone who is 
 in earnest about them.
 
 LIST OF 348 OBJECTS SHOWN ON THE 
 
 MAP OF THE MOON, DRAWN BY 
 
 THE ABfi MOREUX 
 
 (CRATERS, MOUNTAINS, AND INEQUALITIES 
 OF THE SURFACE) 
 
 The letters N.E., S.E., N.W. t S.W., signify North-east, South-east, 
 North-west, South-west, and indicate in -which quarter oj the Moon 
 the objects art to be sought for. 
 
 S.W. 
 N.W. 
 N.W. 
 N.W. 
 
 N.E. 
 
 N.W. 
 
 S.W. 
 
 N.E. 
 
 N.W. 
 
 N.W. 
 
 S.E. 
 
 N.W. 
 
 N.W. 
 
 S.W. 
 
 N.W. 
 
 S.W. 
 S.E. 
 
 Abenezra 
 
 S.W. 
 
 Apian . 
 
 Abulfeda 
 
 S.W. 
 
 Apollo 
 
 JEnarium (promontory) 
 
 S.E. 
 
 Arago . 
 
 Agatharchides 
 
 S.E. 
 
 Aratus 
 
 Agrippa 
 
 N.W. 
 
 Archimedes 
 
 Airy . 
 
 S.W. 
 
 Archytas 
 
 Albategnius 
 
 S.W. 
 
 Argelander . 
 
 Alexander . . . 
 
 S.W. 
 
 Ari starch us . 
 
 Alhazen 
 
 N.W. 
 
 Aristillus 
 
 Almanon 
 
 S.W. 
 
 Aristotle 
 
 Alpetrages . 
 
 S.E. 
 
 Arzachel 
 
 Alps (Mts.) . 
 
 South 
 
 Atlas . 
 
 Alps (Valley of) . 
 
 S.W. 
 
 Autolycus . 
 
 Altai (Mts.) 
 
 S.W. 
 
 Azophi 
 
 Anaximander 
 
 N.E. 
 
 Azout . 
 
 Anaximenes 
 
 N.E. 
 
 
 Ansgar 
 
 S.W. 
 
 Bacon . 
 
 Apennines (Mts.) 
 
 N.E. 
 
 Bailly . 
 
 184
 
 OBJECTS ON MAP OF MOON 185 
 
 Baily . 
 
 . S.W. 
 
 Cardan 
 
 . N.E. 
 
 Ball . ,. 
 
 . S.E. 
 
 Carlini 
 
 . N.E. 
 
 Barocius . . 
 
 . S.W. 
 
 Carpathians (Mts.) 
 
 . N.E. 
 
 Bayer . . . 
 
 . S.E. 
 
 Cassini . . 
 
 . N.W. 
 
 Beaumont . 
 
 . S.W. 
 
 Catherine . . 
 
 . S.W. 
 
 Behaim 
 
 . S.W. 
 
 Caucasus (Mts.) . 
 
 . N.W. 
 
 Berosus 
 
 . N.W. 
 
 Cavendish . 
 
 . S.E. 
 
 Bessarion . . 
 
 . N.E. 
 
 Cepheus . . 
 
 . N.W. 
 
 Bessel . 
 
 . N.W. 
 
 Chacornac . 
 
 . N.W. 
 
 Bianchini . 
 
 . N.E. 
 
 Chevallier . . 
 
 . N.W. 
 
 Biela . . ' 
 
 . S.W. 
 
 Cichus. . . 
 
 . S.E. 
 
 Birt . 
 
 . S.E. 
 
 Clairaut . 
 
 . S.W. 
 
 Boguslawski - . 
 
 . S.W. 
 
 Clavius , . 
 
 . S.W. 
 
 Bohnenberger 
 
 . S.W. 
 
 Cleomedes . -. 
 
 . N.W. 
 
 Bond . 
 
 . S.W. 
 
 Colombo . . 
 
 . S.W. 
 
 Bonpland . 
 
 . S.E. 
 
 Condamine . : . 
 
 . N.E. 
 
 Borda . 
 
 . S.W. 
 
 Condorcet . . 
 
 . N.W. 
 
 Boscovitch . 
 
 . N.W. 
 
 Cook . . 
 
 . S.W. 
 
 Bouguer 
 
 . N.E. 
 
 Copernicus . . 
 
 . N.E. 
 
 Boulliaud . 
 
 . S.E. 
 
 Cruger . 
 
 . S.E. 
 
 Boussingault 
 
 . S.W. 
 
 Curtius 
 
 . S.W. 
 
 Bouvard 
 
 . S.E. 
 
 Cuvier. 
 
 . S.W. 
 
 Bradley (Mts.) . 
 
 . N.W. 
 
 Cyrillus . ..- 
 
 . S.W. 
 
 Briggs. ^ , . . 
 
 . N.E. 
 
 Cysatus 
 
 . S.W. 
 
 Buch . 
 
 . S.W. 
 
 
 
 Burckhardt . 
 
 . N.W. 
 
 D'Alembert (Mts.) 
 
 . S.E. 
 
 Burg . 
 
 . N.W. 
 
 Damoiseau . 
 
 . S.E. 
 
 Busching . 
 
 . S.W. 
 
 Davy . 
 
 . S.E. 
 
 
 
 Dawes . 
 
 . N.W. 
 
 Calippus . 
 
 . N.W. 
 
 Delambre . 
 
 . S.W. 
 
 Campanus . . 
 
 . S.E. 
 
 De la Rue . 
 
 . N.W. 
 
 Canon . .-- 
 
 . N.W. 
 
 Delisle 
 
 . N.E. 
 
 Capella 
 
 . S.W. 
 
 Democritus . . 
 
 . N.W. 
 
 Capuanus . 
 
 . S.E. 
 
 Descartes . '. 
 
 . S.W.
 
 i86 
 
 A DAY IN THE MOON 
 
 Diophantes . 
 
 . N.E. 
 
 Gauss . 
 
 . N.W. 
 
 Doerfel (Mts.) 
 
 . S.E. 
 
 Gay-Lussac . 
 
 . N.E. 
 
 Donati 
 
 . S.W. 
 
 Geminus 
 
 . N.W. 
 
 Doppelmayer 
 
 . S.E. 
 
 Gerard 
 
 . N.E. 
 
 Drebbel . 
 
 . S.E. 
 
 Goclenius . 
 
 . S.W. 
 
 
 
 Godin . 
 
 . N.W. 
 
 Egede 
 
 . N.W. 
 
 Grimaldi 
 
 . S.E. 
 
 Eichstadt . 
 
 . S.E. 
 
 Gruemberger 
 
 . S.E. 
 
 Eimmart 
 
 . N.W. 
 
 Gruithuisen 
 
 . N.E. 
 
 Encke 
 
 . N.E. 
 
 Guerike 
 
 . N.E. 
 
 Endymion . 
 
 . N.W. 
 
 Guttenberg . 
 
 . S.W. 
 
 Eratosthenes 
 
 . N.E. 
 
 
 
 Euclid 
 
 . S.E. 
 
 Hadley (Mts.) . 
 
 . S.W. 
 
 Eudoxus 
 
 . N.W. 
 
 Rasmus (Mts.) 
 
 . N.W. 
 
 
 
 Hagecius 
 
 . s.w. 
 
 Fabricius 
 
 . s.w. 
 
 Hainzell 
 
 . S.E. 
 
 Fermat 
 
 . s.w. 
 
 Halley 
 
 . S.W. 
 
 Fernel 
 
 . s.w. 
 
 Halm . 
 
 . N.W. 
 
 Firmicus 
 
 . N.W. 
 
 Hansen 
 
 . N.W. 
 
 Flamsteed . 
 
 . S.E. 
 
 Hansteen . 
 
 . S.E. 
 
 Fontana 
 
 . S.E. 
 
 Harbinger . 
 
 . N.E. 
 
 Fontenelle . 
 
 . N.E. 
 
 Harding 
 
 . N.E. 
 
 Fourier 
 
 . S.E. 
 
 Harpalus 
 
 . N.E. 
 
 Fournier 
 
 . S.W. 
 
 Hecatseus . 
 
 . S.W. 
 
 Fracastorius 
 
 . S.W. 
 
 Heinsius 
 
 . S.E. 
 
 Fra Mauro . 
 
 . S.E. 
 
 Helicon 
 
 . N.E. 
 
 Franklin % 
 
 . N.W. 
 
 Hell . 
 
 . S.E. 
 
 Fraunhofer . 
 
 . S.W. 
 
 Hercules 
 
 . N.E. 
 
 Frisius (Gemma) . 
 
 . S.W. 
 
 Hercynian (Mts.) 
 
 . S.E. 
 
 
 
 Herigonius . 
 
 . S.E. 
 
 Galileo 
 
 . N.E. 
 
 Herodotus . 
 
 . N.E. 
 
 Gambart 
 
 . N.E. 
 
 Herschel 
 
 . N.E. 
 
 Gartner 
 
 . N.W. 
 
 Herschel, C. 
 
 . N.E. 
 
 Gauricus 
 
 . S.E. 
 
 Herschel, J. 
 
 . N.E.
 
 OBJECTS ON MAP OF MOON 187 
 
 Hesiod 
 
 . N.E. 
 
 Leibnitz (Mts.) . 
 
 . S.W. 
 
 Hevelius 
 
 . N.E. 
 
 Lemonnier . 
 
 . N.W. 
 
 Hind . 
 
 . s.w. 
 
 Letronne 
 
 . S.E. 
 
 Hipparchus . 
 
 . S.W. 
 
 Leverrier 
 
 . N.E. 
 
 Hypatia 
 
 . s.w. 
 
 Lexell 
 
 . S.E. 
 
 
 
 Licetus 
 
 . S.W. 
 
 Inghirami . 
 
 . S.E. 
 
 Lichtenberg 
 
 . N.E. 
 
 Isidore 
 
 . S.W. 
 
 Lilius . 
 
 . S.W. 
 
 
 
 Lindenau . 
 
 . S.W. 
 
 Jacobi 
 
 . s.w. 
 
 Linnee 
 
 . N.W. 
 
 Janssen 
 
 . N.W. 
 
 Longomontanus . 
 
 . S.E. 
 
 Julius Caesar 
 
 . N.W. 
 
 Lubiniezky . 
 
 . S.E. 
 
 Kant . 
 
 . S.W. 
 
 Maclaurin . 
 
 . S.W. 
 
 Kastner 
 
 . S.W. 
 
 Maclear 
 
 . N.W. 
 
 Kepler 
 
 . N.E. 
 
 Macrobius . 
 
 . N.W. 
 
 Kies . 
 
 . S.E. 
 
 Mairan 
 
 . N.E. 
 
 Kirch . 
 
 . N.E. 
 
 Manginus . 
 
 . S.E. 
 
 Kircher 
 
 . S.E. 
 
 Manilius 
 
 . N.W. 
 
 Kraft . 
 
 . N.E. 
 
 Manzinus , 
 
 . S.W. 
 
 Kunowsky . 
 
 . N.E. 
 
 Maraldi 
 
 . N.W. 
 
 
 
 Marinus 
 
 . S.W. 
 
 Lacroix 
 
 . S.E. 
 
 Marius 
 
 . N.E. 
 
 Lagrange 
 
 . S.E. 
 
 Maskelyne . 
 
 . N.W. 
 
 Lagrenus 
 
 . S.W. 
 
 Maurolycus . 
 
 . S.W. 
 
 Lahire 
 
 . N.E. 
 
 Mayer, Ch. . 
 
 . N.W. 
 
 Lalande 
 
 . S.E. 
 
 Menelaus . 
 
 . N.W. 
 
 Lambert 
 
 . N.E. 
 
 Mercator 
 
 . S.E. 
 
 Landsberg . 
 
 . S.E. 
 
 Mercury 
 
 . N.W. 
 
 Lapeyrouse . 
 
 . S.W. 
 
 Mersenne . 
 
 . S.E. 
 
 Lassell 
 
 . S.E. 
 
 Messier 
 
 . S.W, 
 
 Lavoisier . 
 
 . N.E. 
 
 Milichius 
 
 . N.E. 
 
 Legendre . 
 
 . S.W. 
 
 Miller . 
 
 . S.E. 
 
 Lehmann . 
 
 . S.E. 
 
 Moigno 
 
 . N.W.
 
 i88 
 
 A DAY IN THE MOON 
 
 Hosting 
 Murus rectus 
 
 . S.E. 
 . S.E. 
 
 Posidonius . 
 Proclus 
 
 . N.W. 
 . N.W. 
 
 Mutus 
 
 . S.W. 
 
 Prom. Heraclides 
 
 . N.E. 
 
 Nasireddin . 
 Neander 
 Ne'per . 
 Nicolai 
 
 . S.E. 
 . S.W. 
 . N.W. 
 . S.W. 
 
 Prom. Laplace . 
 Ptolemy 
 Pyth agora . 
 Pytheas 
 
 . N.E. 
 . S.E. 
 . N.E. 
 . N.E. 
 
 Nicollet 
 
 . S.E. 
 
 Rabby 
 Ramsden . 
 
 . S.W. 
 . S.E. 
 
 CErsted 
 
 . N.W. 
 
 Reichenbach 
 
 . S.W. 
 
 Oken . 
 
 . S.W. 
 
 Reiner 
 
 . N.E. 
 
 Oriani . 
 
 . N.W. 
 
 Reinhold , 
 
 . N.E. 
 
 Pallas . 
 
 . N.E. 
 
 Repsold 
 Rhseticus 
 
 . N.E. 
 
 . N.W. 
 
 Pentland 
 
 . S.W. 
 
 Rheita 
 
 . S.W. 
 
 Petavius 
 
 . S.W. 
 
 Ricci . 
 
 . S.W. 
 
 Philolaus 
 
 . N.E. 
 
 Riccioli 
 
 . S.E. 
 
 Phocylides . 
 Piazzi . 
 
 . S.E. 
 . N.E. 
 
 Riphsean Mountains 
 Ritter . 
 
 . S.E. 
 . N.W. 
 
 Picard 
 
 . N.W. 
 
 Rocca 
 
 . S.E. 
 
 Piccolomini 
 
 . S.W. 
 
 Roemer 
 
 . N.W. 
 
 Pico . 
 Pictet . 
 Pitatus 
 
 . N.E. 
 . S.E. 
 . S.E. 
 
 Rook (Mts.) 
 Rosenberger 
 Ross . 
 
 . S.E. 
 . S.W. 
 
 . N.W. 
 
 Pitiscus V 
 
 . S.W. 
 
 Rost . 
 
 . S.E. 
 
 Plana . ' . fa ' '. 
 
 . N.W. 
 
 
 
 Plato . 
 
 . N.E. 
 
 Sabine 
 
 . N.W. 
 
 Playfair 
 Pliny . 
 Plutarch 
 
 . S.W. 
 
 . N.W. 
 . N.W. 
 
 Sacrobosco . 
 Santbech 
 Sasseride 
 
 . S.W. 
 . S.W. 
 . S.E. 
 
 Polybius 
 Pontanus 
 
 . S.W. 
 . S.W. 
 
 Saussure 
 Scheiner 
 
 . S.E. 
 . S.E. 
 
 Pont6coulant 
 
 . S.W. 
 
 Schiaparelli 
 
 . N.E.
 
 OBJECTS ON MAP OF MOON 189 
 
 Schickard . 
 
 . S.E. 
 
 Timaeus 
 
 . N.E. 
 
 Schiller . ..- 
 
 . S.E. 
 
 Timocharis . 
 
 . N.E. 
 
 Schrieter . . 
 
 . N.E. 
 
 Tobias Mayer 
 
 . N.E. 
 
 Schubert 
 
 . N.W. 
 
 Torricelli . . 
 
 . S.W. 
 
 Secchi 
 
 . N.W. 
 
 Trallus . 
 
 . N.W. 
 
 Segner 
 
 . S.E. 
 
 Tries necker . ; 
 
 . N.W. 
 
 Seleucus 
 
 . N.E. 
 
 Tycho . . 
 
 . S.E. 
 
 Sharp . 
 
 . N.E. 
 
 
 
 Short . 
 
 . S.E. 
 
 Ukert . 
 
 . N.W. 
 
 Snellius . . 
 
 . S.W. 
 
 Ulugh Bey . 
 
 . N.E. 
 
 Sommering . . 
 
 . N.W. 
 
 
 
 Sosigenes . . 
 
 . N.W. 
 
 Vega . 
 
 . S.W. 
 
 South . 
 
 . N.E. 
 
 Vendelinus . 
 
 . S.W. 
 
 Stadius . * 
 
 . N.E. 
 
 Vieta . 
 
 . S.E. 
 
 Steinheil . . 
 
 . S.W. 
 
 Vitello 
 
 . S.E. 
 
 Stevin . 
 
 . S.W. 
 
 Vitruvius . 
 
 . N.W. 
 
 Stiborius . : . 
 
 . S.W. 
 
 Vlacq . 
 
 . S.W. 
 
 Stoefler 
 
 . S.W. 
 
 
 
 Strabo 
 
 . N.W. 
 
 Walter 
 
 . S.E. 
 
 Straight Range . 
 
 . N.E. 
 
 Webb. . . 
 
 . S.W. 
 
 Street . . . 
 
 . S.E. 
 
 Weigel . . 
 
 . S.E. 
 
 Struve . 
 
 . N.E. 
 
 Werner . , 
 
 . S.W. 
 
 
 
 Wichmann . 
 
 . S.E. 
 
 Taruntius . . 
 
 . N.W. 
 
 Wilhelm I. . . 
 
 . S.E. 
 
 Taurus (Mts.) 
 
 . N.W. 
 
 Wolf (Mts.) 
 
 . N.E. 
 
 Taylor 
 
 . S.W. 
 
 Wurzelbauer 
 
 . S.E. 
 
 Thales 
 
 . N.W. 
 
 
 
 Theataetus . 
 
 . N.W. 
 
 Zagut . , . 
 
 . S.W. 
 
 Thebit 
 
 . S.E. 
 
 Zuchius . . 
 
 . S.E. 
 
 Theophilus . 
 
 . S.W. 
 
 Zupus . . _.-. . 
 
 . S.E.
 
 OBJECTS TO BE STUDIED ON EACH DAY 
 OF THE LUNATION 
 
 znd Day. Mare Crisium. Messala. Sunrise on the Sea of 
 Humboldt. Langrenus, Vendelinus, Condorcet, 
 Hansen, Gauss, Hahn, Berosus. 
 
 yd Day. Craters in the Mare Crisium. Taruntius, Picard, 
 Fraunhofer, Vega, Pontecoulant, Cleomedes, 
 Fournier, Petavius, Endyraion, Messier, Vlacq. 
 
 tfh Day. Mare Nectaris. Macrobius, Proclus. Sunrise on 
 Fracastorius, Rheita, and Maetius, with the valley 
 that separates them. Guttenberg, Colombo, Sant- 
 bech, the mountain region to the west of the 
 Mare Serenetatis, Hercules, Atlas. 
 
 $th Day. "Marsh of Sleep," Plana, Capella, Isidore, Polybius, 
 Piccolomini, Vitruvius, Littrow, Fabricius, Posi- 
 donius, Lemonnier, Theophilus, Cyril, Catherine. 
 
 6th Day. Tacitus, Maurolycus, Barocius, Dionysius, Sosi- 
 genes, Abulfeda, Descartes, Almanon, Gemma 
 Frisius, Pliny, Ross, Arago, Delambre, Aristotle, 
 Eudoxus, Julius Caesar, Linnaeus, Mnelas. 
 
 1th Day. Ptolemy, Albategnius, Manilius, Hyginus and its 
 rills, Hipparchus, Autolycus, Aritillus, Cassini, 
 Valley of the Alps, W. C. Bond, Walter, Miller, 
 Lacaille, Apennines, Triesnecker and its rays. 
 
 %th Day. Mare Frigoris, Arzachel, Alphonso, Alpetagrius, 
 Bode, Pallas, Archimedes, Plato, Maginus, 
 Moesting, Thebit, Murus Rectus, Saussure, Morel, 
 Lalande, Kirch. 
 
 190
 
 OBJECTS TO STUDY EACH DAY 191 
 
 f)tk Day. Tycho, Clavius, Eratosthenes, Stadius, Timocharis, 
 Pitatus, Gruemberger, Mountains of Teneriffe, 
 region to the west of Fontenelle, Gambart. 
 
 loth Day. Sinus Iridium, Copernicus, Hesiod and the fissure 
 to the east of it, Wilhelm I, Longomontanus, 
 Heinsius, Pytheas, Lambert, Helicon, Wurzel- 
 bauer. 
 
 nth Day. Boulliaud, Campanus, Mercator, Reinhold, 
 Riphsean Mountains, Hippalus, Capuanus, Blan- 
 canus, Tobias Mayer. 
 
 i.2th Day. Mare Imbrium, Gassendi, Aristarchus, Herodotus, 
 Marius, Flamsteed, Schiller, Mersenne, Doppel- 
 mayer. 
 
 \^th Day. Schickard, Wargentin, Grimaldi, Hevelius, Seleucus, 
 Cruger, Briggs. 
 
 i^th Day. Smith's Sea, Bouvard, Riccioli, Hercynian Moun- 
 tains, Cardan, Cordilleras, Pythagoras.
 
 LUNAR ELEMENTS 
 
 
 According to 
 Elger. 
 
 According to 
 the Author. 
 
 Mean apparent diameter 
 
 3i' 8" 
 
 31' 3-26" 
 
 Maximum apparent diameter . 
 
 33' 33'2o" 
 
 
 
 Minimum apparent diameter . 
 
 29' 23-65" 
 
 
 
 Real diameter in miles . 
 
 2,160 
 
 Volume (that of the Earth\ 
 being i). / 
 
 Mass (that of the Earth being i ){ 
 
 i 
 
 0^0204 
 I 
 
 or o 02033 
 49 2 
 
 o 01 28 or 
 8i'4 
 
 81-5 
 
 Density compared to the Earth 
 
 0-60419 
 
 o'6i 
 
 Density compared to water . 
 
 3 '444 
 
 3'42 
 
 Extent of surface . 
 
 14,657,402 sq. miles 
 
 Surface of the Earth 
 
 197,000,000 sq. miles 
 
 Surface of the Earth being i,"l 
 that of the Moon. / 
 
 Force of gravity at the surface-! 
 
 or abou 
 27 
 
 r\f fKrt*- 
 
 t 0^07407 
 
 i 
 ~6~ 
 
 6-065 
 on the Earth 
 
 Proportion of surface of the) 
 Moon that is never visible. J 
 
 0*4100 
 
 
 
 Surface of the Moon seen at\ 
 at one time or another. / 
 
 0*5900 
 
 
 
 192
 
 '93 
 
 
 According to 
 Elger. 
 
 According to 
 the Author. 
 
 Synodic month, or interval V 
 from one New Moon to the I 
 following New Moon (luna-j 
 tion). J 
 
 Sidereal month, or interval of 
 time between two successive 
 passages in front of the same 
 star. 
 
 Tropical month, or intervah 
 between two successive pas- 1 
 sages of the point Gamma j 
 
 (y). J 
 
 Anomalistic month, or inter-'i 
 val between two passages 
 through perigree. J 
 
 Nodical month, or interval] 
 between two passages of the j- 
 ascending node. 
 
 Mean distance in terms ofi 
 the Earth's radius at the 
 Equator. J 
 
 Mean distance in miles . 
 Maximum distance 
 Minimum distance 
 Mean excentricity of orbit 
 
 Mean inclination of the orbit \ 
 of the Moon to the Ecliptic./ 
 
 Inclination of the axis of the} 
 Moon to the Ecliptic. / 
 
 Inclination of the Moon's^ 
 equator to the Ecliptic. J 
 
 Maximum libration in latitude 
 13 
 
 29 days 12 hr. 44 min. 
 
 2*684 sec., or 
 2 9'535 8 87 days 
 
 27 days 7 hr. 43 min, 
 
 1 1 -545 sec., or 
 27-3216614 days 
 
 27 days 7 hr. 43 min. 
 
 4'68 sec., or 
 
 27-321582 days 
 
 27 days 13 hr. 18 min. 
 37-44 sec., or 
 2 7 '5 5 460 days 
 
 27 days 5 hr. 5 min. 
 35 '8 1 sec., or 
 27*21222 days 
 
 60-27 
 
 238,840 
 252,972 
 221,641 
 
 0*05490807 
 
 5 8' 39-96" 
 
 87 27' 5i" 
 
 1 32' 9" 
 60 44'
 
 '94 
 
 A DAY IN THE MOON 
 
 
 According to 
 Elger. 
 
 According to 
 the Author. 
 
 Maximum libration in lon-^ 
 gitude. / 
 
 Maximum total libration aO 
 the centre of the Earth. J 
 
 Maximum diurnal libration . 
 
 Angle subtended by a degree 
 of lunar latitude and longi- 
 tude in the centre of the 
 Moon's disc at mean dis- 
 tance. 
 
 Length of a degree in these 1 
 conditions. / 
 
 Lunar arc at the centre of the-| 
 Moon's surface subtending/ 
 an angle of a second of arc.J 
 
 Period of like phase 
 Or more exactly . 
 
 7o u 45 
 
 10 1 6' 
 i i' 28-8" 
 
 16-566* 
 18-97715 miles 
 
 59 days i hr. 28min. 
 2 lunations 
 
 442 days 23 hr. = 
 15 lunations
 
 On our English maps and diagrams of the Moon the old 
 Latin forms of the names of lunar "seas " are generally used. 
 In the following list some of the chief of these are given, with 
 the corresponding English meaning : 
 
 Mare Tranquillitatis 
 Mare Foecunditatis . 
 Mare Serenitatis 
 Mare Crisium . 
 Mare Frigoris . 
 Mare Vaporum 
 Mare Imbrium 
 Mare Nubium . 
 Mare Humorum 
 Mare Nectaris . 
 Mare Australis 
 Oceanus Procellarum 
 Lacus Mortis . : . 
 Lacus Somniorum . 
 Sinus Iridum . 
 Sinus Rons 
 
 Sea of Tranquillity 
 Sea of Fecundity 
 Sea of Serenity 
 Sea of Crises 
 Sea of Cold 
 Sea of Vapours 
 Sea of Rains 
 Sea of Clouds 
 Sea of Humours 
 Sea of Nectar 
 Southern Sea 
 Ocean of Tempests 
 Lake of Death 
 Lake of Dreams 
 Gulf of Rainbows 
 Gulf of Dew 
 
 195
 
 CHIEF CHAINS OF LUNAR MOUNTAINS 
 
 Name. 
 
 Greatest height. 
 Feet. 
 
 Length. 
 Miles. 
 
 Alps . . . 
 
 10,760 
 
 
 
 Caucasus ..... 
 
 18,700 
 
 
 
 Apennines ..... 
 
 19,600 
 
 400 
 
 Carpathians .... 
 
 6,500 
 
 1 80 
 
 Chain of the Sinus Iridium . 
 
 13,280 
 
 312 
 
 Taurus Mountains 
 
 9,840 
 
 
 
 Teneriffe Mountains . 
 
 7,870 
 
 
 
 Harbinger Mountains 
 
 6,890 
 
 
 
 Hercynian Mountains 
 
 8,200 
 
 
 
 Pyrenees . . . . 
 
 1 1, 800 
 
 190 
 
 Altai' Mountains .... 
 
 12,790 
 
 276 
 
 Riphaean Mountains . 
 
 2,95 
 
 IOO 
 
 Percy Mountains 
 
 
 
 
 
 Leibnitz Mountains . 
 
 25.S90 
 
 
 
 Doerfel Mountains 
 
 25.590 
 
 
 
 Rook Mountains 
 
 24,600 
 
 
 
 D'Alembert Mountains 
 
 19,680 
 
 
 
 196
 
 INDEX 
 
 In the following Index the names of objects in the Moon 
 (mountains, seas, etc.) are printed in italics. 
 
 Achilles Tatius, 9 
 
 Albergotti, theory of the Moon, 
 
 35 
 Albertus Magnus (description of 
 
 the Moon by), 31 
 Alexandria, pharos of, 25 
 Alphonso, 115 
 Alps, lunar, no 
 Apennines, lunar, 109 
 Arago, 59 
 Archimedes, no 
 Archimedes, use of concave 
 
 mirrors by, 24 
 Aristarchus on the phases of 
 
 the Moon, 34 
 Aristotle, 9 
 Arzachel, 115 
 Astrology, 153 
 Ayme (Henri), on alleged lunar 
 
 influence on vegetation, 140 
 
 Beer and Midler's map, 62, 63 
 Berosus, his theory of the Moon's 
 
 phases, 34 
 Birt, 115 
 
 Boulainvilliers, 167 
 Brewster, 23 
 Bruce, 176 
 Buffon, 25, 176 
 
 Carbonnier, experiments on 
 cryptogamic vegetation, 151 
 
 Cardan, Jerome, 158 
 
 Carpenter. See Nasmyth 
 
 Cassini, 58, 181, 182 
 
 Catharine de' Medici, 162, etc. 
 
 Charbonneaux, in 
 
 Charles VI, 173 
 
 Charles IX, 162 
 
 Clavius, 88, 116 
 
 Colonna, 167 
 
 Copernicus, 83, 87, 92,. 103, 108, 
 
 114 
 Cordier and Compiegne, on 
 
 lunar action on vegetation, 
 
 147 
 Cyrano de Bergerac, 67, 69 
 
 Delattre, discoveries on the site 
 
 of Carthage, 22 
 Democritus, theory of the Milky 
 
 Way, 24 
 
 Doerf el Mountains, 116 
 Dulaure, 163 
 
 Edward VI, 158 
 Elger, 64 
 Eratosthenes, 109 
 Euler, 44 
 
 Fontana, 177 
 Franz, 117 
 
 Galeotti (astrologer), 156 
 
 197
 
 198 
 
 INDEX 
 
 Galileo's discovery of the tele- 
 scope, 10 ; his first picture of 
 the Moon, 14 ; his methods 
 of argument, 35, 123, 124 
 
 Gall, 176 
 
 Galle-Defond, on alleged action 
 of the Moon on vegetation, 
 145 ; and on animal life, 172 
 
 Gassendi, 167 
 
 Gaudibert, 64 
 
 Gauss, 87 
 
 Goodacre's map, 64 
 
 Grimaldi, 88 
 
 Gruithuisen, 62 
 
 Henri II, 162 
 Henri III, 161 
 Heraclides, 182 
 Herschel, 59, 60 
 Herschel, 87 
 Hevelius, 54 
 Hipparchus, 115 
 Huggins, in 
 Humboldt, 88 
 Huyghens, no 
 Hyginus, 114 
 
 Jacques, on lunar influence on 
 
 tropical vegetation, 149 
 Joubert, 174 
 
 Kepler, 54, 123, 160, 161 
 Kepler, 114 
 Kolbe, 74 
 
 Krosigk, Baron, researches on 
 distance of the Moon, 74 
 
 Lacaille, 74 
 
 Lagrange, 87 
 
 La Hire's lunar globe, 59 
 
 Lalande, 74, 168 
 
 Langrenus (Van Langren), his 
 
 map of the Moon, 54 
 Laplace, 130 
 LarchevSque, on lunar influence 
 
 on vegetation, 137 
 Latourte, on lunar influence on 
 
 animal life, 172 
 Leibnitz Mountains, 116 
 
 Libration, 1 1 8 
 Lieutaud, 168 
 Lohrmann, 62, 63, in 
 Louis XI, 156 
 Louis XIII, 167 
 Louis XIV, 167 
 Louis XVIII, 129 
 
 Madler, 116. See Beer 
 
 Manginus, 87, 116 
 
 Marsh of Fogs, 1 10 
 
 Maurolycus, 87, 88, 116 
 
 Mayer's map, 59 
 
 Mead, 175 
 
 Menuret, 175 
 
 Messier, 1 1 1 
 
 Millochau, 1 1 1 
 
 Mont Blanc, 1 10 
 
 Moon, theories of the ancients, 
 8 ; Galileo's discoveries, 10 ; 
 relations with the earth as its 
 satellite, 28 ; origin of, 29 ; 
 always presents the same side 
 to the earth, 31 ; phases, 33 ; 
 obliquityof orbit, 38; apparent 
 size of disc, 38 ; distance, 47, 
 74 ; movements, 47 ; nomen- 
 clature of its mountains and 
 " seas," 57, 58 ; lunar land- 
 scapes, 82 ; volcanoes and 
 mountain rings, 83 ; the lunar 
 day, 89 ; colour on the Moon, 
 94 ; visibility of lunar ob- 
 jects, 99 ; action of gravita- 
 tion on, 104 ; theory of its 
 surface formations, 113; libra- 
 tion, 118; action on the 
 tides, 1 20 ; alleged influence on 
 the weather, 124 ; question of 
 lunar action on vegetable life, 
 137 ; and on animal life, 171 ; 
 suggestions for the study of 
 the Moon, 179, 180, 182, 183, 
 190 ; lunar elements (table 
 of), 192 ; list of lunar "seas," 
 195 ; mountain chains, 196 
 
 Morinus, 167 
 
 Muller, Johann. See Regio- 
 montanus
 
 INDEX 
 
 199 
 
 Napoleon, 169 
 
 Nasmyth and Carpenter, work 
 
 on the Moon, 63 
 Nelson, 63, 64 
 Newton, 46, 104, 106 
 
 Ocean of Storms, 92 
 
 Petavius, 87 
 Piso, 175 
 Plato, in 
 Pliny, 19, 23 
 Plutarch, 9 
 Ptolemy, 20 
 Ptolemy, 113, 115 
 Ptolemy Euergetes and the 
 pharos of Alexandria, 25 
 
 Regiomontanus, 157 
 
 Rheita, de, his map of the Moon, 
 
 Si. S3 
 
 Riccioli's map and system of 
 lunar nomenclature, 57 
 
 Scheiner, 54 
 Schmidt's map, 63, 64 
 Schroeter, 61, i n 
 Schroeter, 116, 182 
 Sea of Crises, 113 
 
 Sea of Mists, 115 
 Sea of Rains, 108, 113 
 Sea of Serenity, 1 1 1 , 113 
 Sea of Vapours, 109 
 Seneca, 20 
 Stoefler, 158 
 Stoefler, 88, 116 
 Straight Range, 115, 181 
 
 Tatius, Achilles. See Achilles 
 
 Tatius. 
 
 Telescope, invention of, 10 
 Thales, 34 
 Theatetus, no, 112 
 Theophilus, 113 
 Tides, 1 20 
 Torricelli, 124 
 Triesnecker, 114 
 Tycho, 113, 114, 116 
 Tycho Brahe, 159 
 
 Virgil, 153 
 Voltaire, 167 
 
 Wagner, William, 74 
 
 Weineck, 102 
 
 Wells, H. G., and the "Time 
 
 Machine," 97 
 Wolf Mountains, no
 
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