Some reflections upon the moon considered as a world, in reference to questions of habitability, and to the peculiar conditions which would attend a sojourn on the lunar surface, have appeared to us not inappropriate. These, though instructive, are rather curious than important. More worthy of respectful consideration are the few remarks we have offered upon the moon as a satellite and a benefactor to the inhabitants of this Earth.
In reference to the Illustrations accompanying this work, more especially those which represent certain portions of the lunar surface as they are revealed by the aid of powerful telescopes, such as those which we employed in our scrutiny, it is proper that we should say a few words here on the means by which they have been produced.——
During upwards of thirty years of assiduous observation, every favourable opportunity has been seized to educate the eye not only in respect to comprehending the general character of the moon’s surface, but also to examining minutely its marvellous details under every variety of phase, in the hope of rightly understanding their true nature as well as the causes which had produced them. This object was aided by making careful drawings of each portion or object when it was most favourably presented in the telescope. These drawings were again and again repeated, revised, and compared with the actual objects, the eye thus advancing in correctness and power of appreciating minute details, while the hand was acquiring, by assiduous practice, the art of rendering correct representations of the objects in view. In order to present these Illustrations with as near an approach as possible to the absolute integrity of the original objects, the idea occurred to us that by translating the drawings into models which, when placed in the sun’s rays, would faithfully reproduce the lunar effects of light and shadow, and then photographing the models so treated, we should produce most faithful representations of the original. The result was in every way highly satisfactory, and has yielded pictures of the details of the lunar surface such as we feel every confidence in submitting to those of our readers who have made a special study of the subject. It is hoped that those also who have not had opportunity to become intimately acquainted with the details of the lunar surface, will be enabled to become so by aid of these Illustrations.
In conclusion, we think it desirable to add that the photographic illustrations above referred to are printed by well-established pigment processes which ensure their entire permanency.
CONTENTS.
PAGE CHAPTER I. [ON THE COSMICAL ORIGIN OF THE PLANETS OF THE SOLAR SYSTEM.] 1 Origination of Material Things—Celestial Vapours—Nebulæ—Their vast Numbers—Sir W. Herschel’s Observations and Classification—Buffon’s Cosmogony—Laplace’s Nebular Hypothesis—Doubts upon its Validity—Support from Spectrum Analysis CHAPTER II. [THE GENERATION OF COSMICAL HEAT.] 11 Conservation of Force—Indestructibility of Force—Its Convertibility into Heat—Dawn of the Doctrine—Mayer’s Deductions—Joule’s Experiments—Mechanical Equivalent of Heat—Gravitation the Source of Cosmical Heat—Calculations of Mayer and Helmholtz—The Moon as an Incandescent Sphere—Not necessarily Burning—Loss of Heat by Radiation—Cooling of External Crust—Commencement of Selenological History CHAPTER III. [THE SUBSEQUENT COOLING OF THE IGNEOUS BODY.] 19 Cooling commenced from Outer Surface—Contraction by Cooling—Expansion of Molten Matter upon Solidification—Water not exceptional—Similar Behaviour of Molten Iron—Floating of Solid on Molten Metal—Currents in a Pot of Molten Metal—Bursting of Iron Bottle by Congelation of Bismuth within—Evidence from Furnace Slag—From the Crater of Vesuvius—Effects of Contraction of Moon’s Crust and Expansion of Interior—Production of Ridges and Wrinkles—Theory of Wrinkles—Examples from shrivelled Apple and Hand CHAPTER IV. [THE FORM, MAGNITUDE, WEIGHT, AND DENSITY OF THE LUNAR GLOBE.] 31 Form of Moon—Not perfectly Spherical—Bulged towards Earth—Diameter—Angular Measure—Linear Measure—Parallax of Moon—Distance—Area of Lunar Sphere—Solid Contents—Mass of Moon—Law of Gravitation—Mass determined by Tides and other Means—Density—How obtained—Specific Gravity of Lunar Matter—Force of Gravity at Surface—How determined—Weights of similar Bodies on Earth and Moon—Effects of like Forces acting against Gravity on Earth and Moon CHAPTER V. [ON THE EXISTENCE OR NON-EXISTENCE OF A LUNAR ATMOSPHERE.] 39 Subject of Controversy—Phenomena of Terrestrial Atmosphere—No Counterparts on Moon—Negative Evidence from Solar Eclipses—No Twilight on Moon—Evidence from Spectrum Analysis—From Occultations of Stars—Absence of Water or Moisture—Cryophorus—No Reddening of Sun’s Rays by Vapours on Moon—No Air or Water to complicate Discussions of Lunar Volcanic Phenomena CHAPTER VI. [THE GENERAL ASPECT OF THE LUNAR SURFACE.] 51 Pre-Telescopic Ideas—Human Countenance—Other supposed Resemblances—Portrait of Full Moon—Permanence of Features—Rotation of Moon—Solar Period and Solar Day on Moon—Libration—Diurnal—In Latitude—In Longitude—Visible and Invisible Hemispheres—Telescopic Scrutiny—Galileo’s Views—Features Visible with Low Power—Low Powers on small and large Telescopes—Salient Features—Craters—Plains—Bright Streaks—Mountains—Higher Telescopic Powers—Detail Scrutiny of Features therewith—Discussion of High Powers—Education of Eye—Highest practicable Power—Size of smallest Visible Objects CHAPTER VII. [TOPOGRAPHY OF THE MOON.] 65 Reasons for Mapping the Moon—Early Maps—Labours of Langreen—Hevelius—Riccioli—Cassini—Schroeter—Modern Maps—Lohrman’s—Beer and Maedler’s—Excellence of the last—Measurement of Mountain Heights—Need of a Picture Map—Formation of our own—Skeleton Map—Table of conspicuous Objects—Descriptions of special Objects—Copernicus—Gassendi—Eudoxus and Aristotle—Triesnecker—Theophilus, Cyrillus, and Catharina—Thebit—Plato—Valley of the Alps—Pico—Tycho—Wargentin—Aristarchus and Herodotus—Walter—Archimedes and the Apennines CHAPTER VIII. [ON LUNAR CRATERS.] 89 Use of term Crater for Terrestrial and Lunar Formations—Truly Volcanic Nature of Lunar Craters—Terrestrial and Lunar Volcanic Areas compared—Similarity—Difference only in Magnitude—Central Cone—Found in great and small Lunar Craters—Formative Process of Terrestrial Volcanoes—Example from Vesuvius—Vast Size of Lunar Craters—Reasons assigned—Origin of Moon’s Volcanic Force—Aqueous Vapour Theory untenable—Expansion upon Solidification Theory—Formative Process of a Lunar Crater—Volcanic Vent—Commencement of Eruption—Erection of Rampart—Hollowing of Crater—Formation of Central Cone—Of Plateau—Various Heights of Plateaux—Coneless Craters—Filled-up Craters—Multiple Cones—Craters on Plateau—Double Ramparts—Landslip Terraces—Rutted Ramparts—Overlapping and Superposition of Craters—Source-Connection of such—Froth-like Aggregations of Craters—Majestic Dimensions of Larger Craters CHAPTER IX. [ON THE GREAT RING-FORMATIONS NOT MANIFESTLY VOLCANIC.] 117 Absence of Central Cones—Vast Diameters—Difficult of Explanation—Hooke’s Idea—Suggested Cause of True Circularity—Scrope’s Hypothesis of Terrestrial Tumescences—Rozet’s Tourbillonic Theory—Dana’s Ebullition Theory CHAPTER X. [PEAKS AND MOUNTAIN RANGES.] 124 Paucity of extensive Mountain Systems on Moon—Contrast with Earth—Lunar Mountains found in less disturbed Regions—Lunar Apennines, Caucasus, and Alps—Valley of Alps—“Crag and Tail” Contour—Isolated Peaks—How produced—Analogy from Freezing Fountain—Terrestrial Counterparts and their Explanation by Scrope—Blowing Cone on Teneriffe—Comparative Gentleness of Mountain-forming Action—Relation between Mountain Systems and Crater Systems—Wrinkle Ridges CHAPTER XI. [CRACKS AND RADIATING STREAKS.] 133 Description—Divergence from Focal Craters—Experimental Explanation of their Cause—Radial Cracking of Crust—Outflow of Matter therefrom—Analogy from “Starred” Ice—No Shadows cast by Streaks—Their probable Slight Elevation—Open Cracks—Great Numbers—Length—Depth—In-fallen Fragments—Shrinkage a Cause of Cracks—Lateness of their Production CHAPTER XII. [COLOUR AND BRIGHTNESS OF LUNAR DETAILS: CHRONOLOGY OF FORMATIONS, AND FINALITY OF EXISTING FEATURES.] 143 Absence of Conspicuous Colour—Slight Tints of “Seas”—Cause—Probable Variety of Tints in small Patches—Diversity of Brightness of Details—Most Conspicuous at Full Moon—Classification of Shades—Exaggerated Contrasts in Photographs—Brightest Portions probably the latest formed—Chronology of Formations—Large Craters older than Small—Mountains older than Craters—Bright Streaks comparatively recent—Cracks most recent of all Features—Question of existing Change—Evidence from Observation—Paucity of such Evidence—Supposed Case of Linné—Theoretical Discussion—Relative Cooling Tendencies of Earth and Moon—Earth nearly assumed its final Condition—Moon probably cooled Ages upon Ages ago—Possible slight Changes from Solar Heating—Disintegrating Action CHAPTER XIII. [THE MOON AS A WORLD: DAY AND NIGHT UPON ITS SURFACE.] 155 Existence of Habitants on other Planets—Interest of the Question—Conditions of Life—Absence of these from Moon—No Air or Water and intense Heat and Cold—Possible Existence of Protogerms of Life—A Day on the Moon imagined—Instructiveness of the Realization—Length of Lunar Day—No Dawn or Twilight—Sudden Appearance of Light—Slowness of Sun in Rising—No Atmospheric Tints—Blackness of Sky and Visibility of Stars and fainter Luminosities at Noon-day—Appearance of the Earth as a Stationary Moon—Its Phases—Eclipse of Sun by Earth—Attendant Phenomena—Lunar Landscape—Height essential to secure a Point of View—Sunrise on a Crater—Desolation of Scene—No Vestige of Life—Colour of Volcanic Products—No Atmospheric Perspective—Blackness of Shadows—Impressions on other Senses than Sight—Heat of Sun untempered—Intense Cold in Shade—Dead Silence—No Medium to conduct Sound—Lunar Afternoon and Sunset—Night—The Earth a Moon—Its Size, Rotation, and Features—Shadow of Moon upon it—Lunar Night-Sky—Constellations—Comets and Planets—No Visible Meteors—Bombardment by Dark Meteoric Masses—Lunar Landscape by Night—Intensity of Cold CHAPTER XIV. [THE MOON AS A SATELLITE: ITS RELATION TO THE EARTH AND MAN.] 171 The Moon as a Luminary—Secondary Nature of Light-giving Function—Primary Office as a Sanitary Agent—Cleansing Effects of the Tides—Tidal Rivers and Transport thereby—The Moon a “Tug”—Available Power of Tides—Tide-Mills—Transfer of Tidal Power Inland—The Moon as a Navigator’s Guide—Longitude found by the Moon—Moon’s Motions—Discovered by Observations—Grouped into Theories—Represented by Tables—The Nautical Almanac—The Moon as a Long-Period Timekeeper—Reckoning by “Moons”—Eclipses the Starting-Points of Chronologies—Furnish indisputable Dates—Solar Surroundings revealed by Eclipses when Moon screens the Sun—Solar Corona—Moon as a Medal of Creation, a Half-formed World—Abuses of the Moon—Superstitions—Erroneous Ideas regarding Moonlight pourtrayed by Artists and Authors—The Moon and the Weather—Errors and Facts—Atmospheric Tides—Warmth from Moon—Paradoxical Effect in cooling the Earth CHAPTER XV. [CONCLUDING SUMMARY] 184
LIST OF PLATES.
PLATE PAGE [ Gassendi] Frontispiece [I.—Summit of Vesuvius] 26 [II.—Wrinkled Hand and Apple] 30 [III.—Full Moon Photograph] 52 [IV.—Picture-Map of the Moon] {To face each other.} [V.—Skeleton Map] 68 [VI.—Terrestrial and Lunar Volcanic Areas Compared] 88 [VII.—Progressive Series of Craters] 92 [VIII.—Copernicus] 96 [IX.—The Lunar Apennines, &c., &c.] 100 [X.—Aristotle and Eudoxus] 104 [XI.—Triesnecker] 108 [XII.—Theophilus, Cyrillus, and Catharina] 112 [XIII.—Arzachael, Ptolemy, and the Railway] 116 [XIV.—Plato, the Valley of the Alps, Pico, &c.] 120 [XV.—Mercator and Campanus] 124 [XVI.—Tycho and its Surroundings] 128 [XVII.—Wargentin] 132 [XVIII.—Aristarchus and Herodotus] 136 [XIX.—Glass Globe Cracked by Internal Pressure] 140 [XX.—Overlapping Craters] 148 [XXI.—Lunar Crater. Ideal Landscape] 156 [XXII.—Solar Eclipse as it would be seen from the Moon] 164 [XXIII.—Group of Mountains. Ideal Lunar Landscape] 170