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NEW THEORIES IN
ASTRONOMY
BY
WILLIAM STIRLING
CIVIL ENGINEER
London:
E. & F. N. SPON, Limited, 57 HAYMARKET
New York:
SPON & CHAMBERLAIN, 123 LIBERTY STREET
1906
TO THE READER.
Mr. William Stirling, Civil Engineer, who devoted the last years of his life to writing this work, was born in Kilmarnock, Scotland, his father being the Rev. Robert Stirling, D.D., of that city, and his brothers, the late Mr. Patrick Stirling and Mr. James Stirling, the well known engineers and designers of Locomotive Engines for the Great Northern and South Eastern Railways respectively.
After completing his studies in Scotland he settled in South America, and was engaged as manager and constructing engineer in important railway enterprises on the west coast, besides other concerns both in Peru and Chile; his last work being the designing and construction of the railway from the port of Tocopilla on the Pacific Ocean to the Nitrate Fields of Toco in the interior, the property of the Anglo-Chilian and Nitrate Railway Company.
He died in Lima, Peru, on the 7th October, 1900, much esteemed and respected, leaving the MS. of the present work behind him, which is now published as a tribute to his memory, and wish to put before those who are interested in the Science of Astronomy his theories to which he devoted so much thought.
CONTENTS
PAGE INTRODUCTION 1CHAPTER I. The bases of modern astronomy. Their late formation 18 Instruments and measures used by ancient astronomers 19 Weights and measures sought out by modern astronomers 20 Means employed to discover the density of the earth. Measuring by means of plummets not sufficiently exact 20 Measurements with torsion and chemical balances more accurate 21 Sir George B. Airy's theory, and experiments at the Harton colliery 22 Results of experiments not reliable. Theory contrary to the Law of Attraction 23 Proof by arithmetical calculation of its error 24 Difficulties in comparing beats of pendulums at top and bottom of a mine 26 The theory upheld by text-books without proper examination 27 Of a particle of matter within the shell of a hollow sphere. Not exempt from the law of Attraction 28 A particle so situated confronted with the law of the inverse square ofdistance from an attracting body. Remarks thereon 29 It is not true that the attraction of a spherical shell is "zero" for a particle of matter within it 31
CHAPTER II.
The moon cannot have even an imaginary rotation on its axis, but is generally believed to have. Quotations to prove this 33 Proofs that there can be no rotation. The most confused assertion that there is rotation shown to be without foundations 35 A gin horse does not rotate on its axis in its revolution 37 A gin horse, or a substitute, driven instead of being a driver 38 Results of the wooden horse being driven by the mill 38 The same results produced by the revolution of the moon. Centrifugal force sufficient to drive air and water away from our side of the moon 39 That force not sufficient to drive them away from its other side 40 No one seems ever to have thought of centrifugal force in connection with air and water on the moon 41 Near approach made by Hansen to this notion 41 Far-fetched reasons given for the non-appearance of air and water 42 The moon must have both on the far-off hemisphere 44 Proofs of this deduced from its appearance at change 44 Where the evidences of this may be seen if looked for at the right place. The centrifugal force shown to be insufficient to drive off even air, and less water, altogether from the moon 45 The moon must have rotated on its axis at one period of its existence 47 The want of polar compression no proof to the contrary 48 Want of proper study gives rise to extravagant conceptions, jumping at conclusions, and formation of "curious theories" 48
CHAPTER III.
Remarks on some of the principal cosmogonies. Ancient notions 49 The Nebular hypothesis of Laplace. Early opinions on it. Received into favour. Again condemned as erroneous 50 Defects attributed to it as fatal. New cosmogonies advanced 51 Dr. Croll's collision, or impact, theory discussed 53 Dr. Braun's cosmogony examined 59 M. Faye's "Origine du Monde" defined 61 Shown to be without proper foundation, confused, and in some parts contradictory 65 Reference to other hypotheses not noticed. All more or less only variations on the nebular hypothesis 70 Necessity for more particular examination into it 71
CHAPTER IV.
Preliminaries to analysis of the Nebular hypothesis 72 Definition of the hypothesis 73 Elements of solar system. Tables of dimensions and masses 75 Explanation of tables and density of Saturn 78 Volume, density and mass of Saturn's rings, general remarks about them, and satellites to be made from them
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href="@public@vhost@g@gutenberg@html@files@45356@[email protected]#Page_79" class="pginternal" tag="{http://www.w3.org/1999/xhtml}a"> 79 Future of Saturn's rings 79 Notions about Saturn's satellites and their masses 80 Nature of rings seemingly not well understood 81 Masses given to the satellites of Uranus and Neptune. Explanations of 81 Volumes of the members of the solar system at density of water 82
CHAPTER V.
Analysis of the Nebular Hypothesis. Separation from the nebula of the rings for the separate planets, etc. 83 Excessive heat attributed to the nebula erroneous and impossible 84 Centigrade thermometer to be used for temperatures 85 Temperature of the nebula not far from absolute zero 86 Erroneous ideas about glowing gases produced by collisions of their atoms, or particles of cosmic matter in the form of vapours 86 Separation of ring for Neptune. It could not have been thrown off in one mass, but in a sheet of cosmic matter 87 Thickness and dimensions of the ring 88 Uranian ring abandoned, and its dimensions 89 Saturnian ring abandoned, and its dimensions 90 Jovian ring abandoned, and its dimensions 91 Asteroidal ring abandoned, and its dimensions 93 Martian ring abandoned, and its dimensions 94 Earth ring abandoned, and its dimensions 95 Venus ring abandoned, and its dimensions 96 Mercurian ring abandoned, and its dimensions 97 Residual mass. Condensation of Solar Nebula to various diameters, and relative temperatures and densities 98 Unaccountable confusion in the mode of counting absolute temperature examined and explained. Negative 274 degrees of heat only equal 2 degrees of absolute temperature 100 The Centigrade thermometric scale no better than any other, and cannot be made decimal 103 The sun's account current with the Nebula drawn up and represented by Table III. 104
CHAPTER VI.
Analysis continued. Excessive heat of nebula involved condensation only at the surface. Proof that this was Laplace's idea 108 Noteworthy that some astronomers still believe in excessive heat 109 Interdependence of temperature and pressure in gases and vapours. Collisions of atoms the source of heat 110 Conditions on which a nebula can be incandescent. Sir Robert Ball 110 No proper explanation yet given of incandescent or glowing gas 112 How matter was thrown off, or abandoned by the Jovian nebula 115 Division into rings of matter thrown off determined during contraction 116 How direct rotary motion was determined by friction and collisions of particles 117 Saturn's rings going through the same process. Left to show process 118 Form gradually assumed by nebulæ. Cause of Saturn's square-shouldered appearance 120 A lens-shaped nebula could not be formed by surface condensation 120 Retrograde rotary motion of Neptune and Uranus, and revolution of their satellites recognised by Laplace as possible 121 Satellites of Mars. Rapid revolution of inner one may be accounted for 123 Laplace's proportion of 4000 millions not reduced but enormously increased by discoveries of this century 124
CHAPTER VII.
Analysis continued. No contingent of heat could be imparted to any planet by the parent nebula 126 Only one degree of heat added to the nebula from the beginning till it had contracted to the density of 1/274th of an atmosphere 127 Increase in temperature from 0° to possible average of 274° when condensed to 4,150,000 miles in diameter 127 Time when the sun could begin to act as sustainer of life and light anywhere. Temperature of space 128 The ether devised as carrier of light, heat, etc. What effect it might have on the nebula 129 First measure of its density, as far as we know 130 The estimate too high. May be many times less 133 Return to the solar nebula at 63,232,000 miles in diameter 134 Plausible reason for the position of Neptune not conforming to Bode's Law. The ring being very wide had separated into two rings 134 Bode's law reversed. Ideas suggested by it 135 Rates of acceleration of revolution from one planet to another 137 Little possibility of there being a planet in the position assigned to Vulcan 138 Densities of planets compared. Seem to point to differences in the mass of matter abandoned by the nebula at different periods 138 Giving rise to the continuous sheet of matter separating into different masses.
CHAPTER V.
Analysis of the Nebular Hypothesis. Separation from the nebula of the rings for the separate planets, etc. 83 Excessive heat attributed to the nebula erroneous and impossible 84 Centigrade thermometer to be used for temperatures 85 Temperature of the nebula not far from absolute zero 86 Erroneous ideas about glowing gases produced by collisions of their atoms, or particles of cosmic matter in the form of vapours 86 Separation of ring for Neptune. It could not have been thrown off in one mass, but in a sheet of cosmic matter 87 Thickness and dimensions of the ring 88 Uranian ring abandoned, and its dimensions 89 Saturnian ring abandoned, and its dimensions 90 Jovian ring abandoned, and its dimensions 91 Asteroidal ring abandoned, and its dimensions 93 Martian ring abandoned, and its dimensions 94 Earth ring abandoned, and its dimensions 95 Venus ring abandoned, and its dimensions 96 Mercurian ring abandoned, and its dimensions 97 Residual mass. Condensation of Solar Nebula to various diameters, and relative temperatures and densities 98 Unaccountable confusion in the mode of counting absolute temperature examined and explained. Negative 274 degrees of heat only equal 2 degrees of absolute temperature 100 The Centigrade thermometric scale no better than any other, and cannot be made decimal 103 The sun's account current with the Nebula drawn up and represented by Table III. 104
CHAPTER VI.
Analysis continued. Excessive heat of nebula involved condensation only at the surface. Proof that this was Laplace's idea 108 Noteworthy that some astronomers still believe in excessive heat 109 Interdependence of temperature and pressure in gases and vapours. Collisions of atoms the source of heat 110 Conditions on which a nebula can be incandescent. Sir Robert Ball 110 No proper explanation yet given of incandescent or glowing gas 112 How matter was thrown off, or abandoned by the Jovian nebula 115 Division into rings of matter thrown off determined during contraction 116 How direct rotary motion was determined by friction and collisions of particles 117 Saturn's rings going through the same process. Left to show process 118 Form gradually assumed by nebulæ. Cause of Saturn's square-shouldered appearance 120 A lens-shaped nebula could not be formed by surface condensation 120 Retrograde rotary motion of Neptune and Uranus, and revolution of their satellites recognised by Laplace as possible 121 Satellites of Mars. Rapid revolution of inner one may be accounted for 123 Laplace's proportion of 4000 millions not reduced but enormously increased by discoveries of this century 124
CHAPTER VII.
Analysis continued. No contingent of heat could be imparted to any planet by the parent nebula 126 Only one degree of heat added to the nebula from the beginning till it had contracted to the density of 1/274th of an atmosphere 127 Increase in temperature from 0° to possible average of 274° when condensed to 4,150,000 miles in diameter 127 Time when the sun could begin to act as sustainer of life and light anywhere. Temperature of space 128 The ether devised as carrier of light, heat, etc. What effect it might have on the nebula 129 First measure of its density, as far as we know 130 The estimate too high. May be many times less 133 Return to the solar nebula at 63,232,000 miles in diameter 134 Plausible reason for the position of Neptune not conforming to Bode's Law. The ring being very wide had separated into two rings 134 Bode's law reversed. Ideas suggested by it 135 Rates of acceleration of revolution from one planet to another 137 Little possibility of there being a planet in the position assigned to Vulcan 138 Densities of planets compared. Seem to point to differences in the mass of matter abandoned by the nebula at different periods 138 Giving rise to the continuous sheet of matter separating into different masses.
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class="tdr"> Probably the rings had to arrive at a certain stage of density before contracting circumferentially 139 Possible average temperature of the sun at the present day. Central heat probably very much greater 140 Churning of matter going on in the interior of the sun, caused by unequal rotation between the equator and the poles 140
CHAPTER VIII.
Inquiry into the Interior Construction of the Earth. What is really known of the exterior or surface 142 What is known of the interior 143 Little to be learned from Geology, which reaches very few miles down 144 Various notions of the interior 145 What is learnt from earthquake and volcanoes. Igno-aqueous fusion, liquid magma. 146 Generally believed that the earth consists of solid matter to the centre. Mean density. Surface density 147 More detailed estimate of densities near the surface 148 Causes of increased surface density after the crust was formed 148 Calculations of densities for 9 miles deep, and from there to the centre forming Table IV. 150 Reflections on the results of the calculations 151 Notion that the centre is composed of the heaviest metals. "Sorting-out" theory absurd 151 Considerations as to how solid matter got to the centre 152 Gravitation might carry it there, but attraction could not 153 How the earth could be made out of cosmic matter, meteorites or meteors 154
CHAPTER IX.
Inquiry into the Interior Construction of the Earth—continued 165 The earth gasiform at one period. Density including the moon may have been 1/10,000th that of air. Must have been a hollow body. Proofs given 166 Division of the mass of the earth alone into two parts 169 Division of the two masses at 817 miles from surface 171 Reasons why the earth cannot be solid to the centre 172 Gasiform matter condensing in a cone leaves apex empty 172 Proportions of the matter in a cone 173 Calculations of the densities of the outer half of the hollow shell of the earth. Remarks upon the condensation 174 Calculations of inner half of the hollow shell 175 Remarks upon position of inner surface of the shell 177 Calculations of the same 179
CHAPTER X.
Inquiry into the interior construction of the Earth—continued 184 Density of 8·8 times that of water still too high for the possible compression of the component matter of the earth as known to us 185 Reasons for this conclusion drawn from crushing strains of materials 186 A limit to density shown thereby 187 The greatest density need not exceed 6·24 of water 188 Gases shut up in the hollow centre. Their weight must so far diminish the conceded maximum of 6·24 189 Density of inner half of earth at 3000 miles diameter. Greatest density may be less than 5·833 of water 190 Supposed pressure of inclosed gases very moderate 191 Meaning of heat limit to density. Temperature of interior half of shell and inclosed gases must be equal 193 State of the hollow interior 194 Results of the whole inquiry 195
CHAPTER XI.
The Earth. The idea entertained by some celebrated men, and others 197 Difficulties of forming a sphere out of a lens-shaped nebula 199 Various studies of the earth's interior made for specialy purposes. Difficulty some people find in conceiving how the average density of little over 5·66 can be possible, the earth being a hollow sphere 200 What is gained by its being a hollow shell 201 Geological theories of the interior discussed. Volcanoes and earthquakes in relation to the interior 202 Liquid matter on the interior surface of the shell, and gases in the hollow, better means for eruptions than magma layers 206 Focal depths of earthquakes within reach of water, but not of lavas 207 Minute vesicles in granite filled with gases, oxygen and hydrogen, but not water 209 The Moon. A small edition of the earth 211 Rotation stopped. Convulsions and cataclysms caused thereby. Air, water, vapour driven off thereby to far-off hemisphere. Liquid matter in hollow interior would gravitate to the inside of the nearest hemisphere 212 Form and dimensions during rotation. Altered form after it stopped 213 Agreeing very closely with Hansen's "curious theory"
CHAPTER VIII.
Inquiry into the Interior Construction of the Earth. What is really known of the exterior or surface 142 What is known of the interior 143 Little to be learned from Geology, which reaches very few miles down 144 Various notions of the interior 145 What is learnt from earthquake and volcanoes. Igno-aqueous fusion, liquid magma. 146 Generally believed that the earth consists of solid matter to the centre. Mean density. Surface density 147 More detailed estimate of densities near the surface 148 Causes of increased surface density after the crust was formed 148 Calculations of densities for 9 miles deep, and from there to the centre forming Table IV. 150 Reflections on the results of the calculations 151 Notion that the centre is composed of the heaviest metals. "Sorting-out" theory absurd 151 Considerations as to how solid matter got to the centre 152 Gravitation might carry it there, but attraction could not 153 How the earth could be made out of cosmic matter, meteorites or meteors 154
CHAPTER IX.
Inquiry into the Interior Construction of the Earth—continued 165 The earth gasiform at one period. Density including the moon may have been 1/10,000th that of air. Must have been a hollow body. Proofs given 166 Division of the mass of the earth alone into two parts 169 Division of the two masses at 817 miles from surface 171 Reasons why the earth cannot be solid to the centre 172 Gasiform matter condensing in a cone leaves apex empty 172 Proportions of the matter in a cone 173 Calculations of the densities of the outer half of the hollow shell of the earth. Remarks upon the condensation 174 Calculations of inner half of the hollow shell 175 Remarks upon position of inner surface of the shell 177 Calculations of the same 179
CHAPTER X.
Inquiry into the interior construction of the Earth—continued 184 Density of 8·8 times that of water still too high for the possible compression of the component matter of the earth as known to us 185 Reasons for this conclusion drawn from crushing strains of materials 186 A limit to density shown thereby 187 The greatest density need not exceed 6·24 of water 188 Gases shut up in the hollow centre. Their weight must so far diminish the conceded maximum of 6·24 189 Density of inner half of earth at 3000 miles diameter. Greatest density may be less than 5·833 of water 190 Supposed pressure of inclosed gases very moderate 191 Meaning of heat limit to density. Temperature of interior half of shell and inclosed gases must be equal 193 State of the hollow interior 194 Results of the whole inquiry 195
CHAPTER XI.
The Earth. The idea entertained by some celebrated men, and others 197 Difficulties of forming a sphere out of a lens-shaped nebula 199 Various studies of the earth's interior made for specialy purposes. Difficulty some people find in conceiving how the average density of little over 5·66 can be possible, the earth being a hollow sphere 200 What is gained by its being a hollow shell 201 Geological theories of the interior discussed. Volcanoes and earthquakes in relation to the interior 202 Liquid matter on the interior surface of the shell, and gases in the hollow, better means for eruptions than magma layers 206 Focal depths of earthquakes within reach of water, but not of lavas 207 Minute vesicles in granite filled with gases, oxygen and hydrogen, but not water 209 The Moon. A small edition of the earth 211 Rotation stopped. Convulsions and cataclysms caused thereby. Air, water, vapour driven off thereby to far-off hemisphere. Liquid matter in hollow interior would gravitate to the inside of the nearest hemisphere 212 Form and dimensions during rotation. Altered form after it stopped 213 Agreeing very closely with Hansen's "curious theory"
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class="tdr">214
CHAPTER XII.
Some of the results arising from the sun's being a hollow sphere 215 Repetition of the effects of condensation on the temperature of the nebula 216 Ideas called up by the apparently anomalous increase of temperature 217 How heat is carried from the sun to the earth 218 The sun supposed to radiate heat only to bodies that can receive and hold it, and not to all space. The heat of the sun accumulated in a hot box to considerably beyond the boiling point of water 219 The heat accumulated in this way supposed to be due to a peculiar function of the ether, as it is a fact that heat can be radiated from a cold to a hot body 220 The sun must be gaseous, or rather gasiform, throughout. No matter in it solid or even liquid. Divisions and densities of shell 221 The hollow centre filled with gases, whose mass naturally diminishes the mean density of the whole body 222 The amount of this reduction so far defined. The presence of gases or vapours in the hollow a natural result of condensation 223 The hollow centre filled with gases not incompatible with the sun's being a hollow sphere. The temperature at the centre may be anything, not depending on any law of gases 223 Further exposition of hollow-sphere theory put off till after further development of the construction of the sun 224
CHAPTER XIII.
The ether. Its nature considered. Behaves like a gas 226 Can be pumped out of a receive 227 Light and heat do not pass through a tube in vacuo. Laboratory experiments examined 228 Light and darkness in a partial vacuum, though high 229 Electricity not a carrying agent 230 Why there are light and dark strata in a high vacuum 232 The real carrying agent through a high vacuum is the residue of ether left in it. Digression to consider the aurora 233 How air may be carried to extraordinary heights. Zones of air carried up are made luminous by electricity 234 Comparison of this method with experiments quoted 236 Experiment suggested to prove whether light passes freely through a vacuum tube 237 The ether does not pervade all bodies freely 238 It must be renounced altogether or acknowledged to be a material body, subject to expansion, condensation, heating or cooling 239 How light and heat pass through glass 239 Temperature of the ether variable. Zodiacal light, cause of 240
CHAPTER XIV.
The ether considered and its nature explained. Further proofs given by Dr. Crookes's work, of its material substance 244 Highest vacuum yet produced. Absorbents cannot absorb the ether 246 Dr. Crookes's definition of a gas. Not satisfactory. Why 247 A fluid required to pump matter out of a vessel 248 Gas as described by Dr. Crookes would not suit 249 The ether the only elastic fluid we have. The only real gas,if it is a gas 250 A possible measure of the density of the ether 250 Causes of dark and light zones in high vacua 251 The real conductor of light in a high vacuum 252 How a vacuum tube glows, when electricity passes through it 254 Conclusions arrived at through foregoing discussions 255 Some exhibitions of light explained 256 Gases can be put in motion, but cannot move even themselves 257 The ether shown to be attraction. And primitive matter also 258 All chemical elements evolved from it. Its nature stated 259 Action at a distance explained by the ether and attraction being one and the same 259
CHAPTER XV.
Construction of the solar system. Matter out of which it was formed 261 Domains of the sun out of which the matter was collected 262 Stars nearest to the sun. Table VII. showing distances 263 Remarks on Binary Stars. Table VIII. showing spheres of attraction between the sun and a very few 265 Sirius actually our nearest neighbour. Form of the sun's domains of a very jagged nature 266 Creation of matter for the nebulæ, out of which the whole universe was elaborated. Beginning of construction 267 The law of attraction begins to operate through the agency of evolution 267 Form of the primitive solar nebula. The jagged peaks probably soon left behind in contraction 268 How the nebula contracted. Two views of the form it might take.
CHAPTER XII.
Some of the results arising from the sun's being a hollow sphere 215 Repetition of the effects of condensation on the temperature of the nebula 216 Ideas called up by the apparently anomalous increase of temperature 217 How heat is carried from the sun to the earth 218 The sun supposed to radiate heat only to bodies that can receive and hold it, and not to all space. The heat of the sun accumulated in a hot box to considerably beyond the boiling point of water 219 The heat accumulated in this way supposed to be due to a peculiar function of the ether, as it is a fact that heat can be radiated from a cold to a hot body 220 The sun must be gaseous, or rather gasiform, throughout. No matter in it solid or even liquid. Divisions and densities of shell 221 The hollow centre filled with gases, whose mass naturally diminishes the mean density of the whole body 222 The amount of this reduction so far defined. The presence of gases or vapours in the hollow a natural result of condensation 223 The hollow centre filled with gases not incompatible with the sun's being a hollow sphere. The temperature at the centre may be anything, not depending on any law of gases 223 Further exposition of hollow-sphere theory put off till after further development of the construction of the sun 224
CHAPTER XIII.
The ether. Its nature considered. Behaves like a gas 226 Can be pumped out of a receive 227 Light and heat do not pass through a tube in vacuo. Laboratory experiments examined 228 Light and darkness in a partial vacuum, though high 229 Electricity not a carrying agent 230 Why there are light and dark strata in a high vacuum 232 The real carrying agent through a high vacuum is the residue of ether left in it. Digression to consider the aurora 233 How air may be carried to extraordinary heights. Zones of air carried up are made luminous by electricity 234 Comparison of this method with experiments quoted 236 Experiment suggested to prove whether light passes freely through a vacuum tube 237 The ether does not pervade all bodies freely 238 It must be renounced altogether or acknowledged to be a material body, subject to expansion, condensation, heating or cooling 239 How light and heat pass through glass 239 Temperature of the ether variable. Zodiacal light, cause of 240
CHAPTER XIV.
The ether considered and its nature explained. Further proofs given by Dr. Crookes's work, of its material substance 244 Highest vacuum yet produced. Absorbents cannot absorb the ether 246 Dr. Crookes's definition of a gas. Not satisfactory. Why 247 A fluid required to pump matter out of a vessel 248 Gas as described by Dr. Crookes would not suit 249 The ether the only elastic fluid we have. The only real gas,if it is a gas 250 A possible measure of the density of the ether 250 Causes of dark and light zones in high vacua 251 The real conductor of light in a high vacuum 252 How a vacuum tube glows, when electricity passes through it 254 Conclusions arrived at through foregoing discussions 255 Some exhibitions of light explained 256 Gases can be put in motion, but cannot move even themselves 257 The ether shown to be attraction. And primitive matter also 258 All chemical elements evolved from it. Its nature stated 259 Action at a distance explained by the ether and attraction being one and the same 259
CHAPTER XV.
Construction of the solar system. Matter out of which it was formed 261 Domains of the sun out of which the matter was collected 262 Stars nearest to the sun. Table VII. showing distances 263 Remarks on Binary Stars. Table VIII. showing spheres of attraction between the sun and a very few 265 Sirius actually our nearest neighbour. Form of the sun's domains of a very jagged nature 266 Creation of matter for the nebulæ, out of which the whole universe was elaborated. Beginning of construction 267 The law of attraction begins to operate through the agency of evolution 267 Form of the primitive solar nebula. The jagged peaks probably soon left behind in contraction 268 How the nebula contracted. Two views of the form it might take.
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Comparison of the two forms, solid or hollow 269 The hollow centre form adopted. The jagged peaks left behind 272 The nebula assuming a spherical form. Shreds, masses, crescents separated from one side 273 Probable form of interior of nebula. Compared with envelopes in heads of some comets 274 Reflections on the nebula being hollow. Opinions of others quoted 275 The matter of a sphere solid to the centre must be inert there 276 Further proofs of the nebula being hollow 277 How rotary motion was instituted 278 Such a nebula might take one of two forms 279 The form depending on the class of nebula. Planetary in the case of the solar system. A similar conception of how rotary motion could be instituted 280
CHAPTER XVI.
The sun's neighbours still exercise their attraction over him 282 Regions of greatest density in the 9 nebulæ dealt with; compared with the orbits of the planets made from them 283 Results of comparison favourable to the theory 287 Differences of size in the planets have arisen from variations in the quantity of matter accumulating on the nebulæ 289 Causes of the retrograde motions in Neptune, Uranus, and their satellites 290 Probable causes of the anomalous position of Neptune 292 Rises and falls in the densities and dimensions of the planets explained 293 The form of the nebulæ must have resembled a dumb-bell 295 More about rises and falls in densities 296 Reason why the Asteroid nebula was the least dense of the system; 297 Not necessary to revise the dimensions given to the 9 nebulæ 298 Causes of the anomalies in the dimensions, densities, etc., of the Earth and Venus 299 The strictly spherical form of the sun accounted for. But it may yet be varied 299 Repetition that a spherical body could not be made from a lens-shaped nebula by attraction and condensation 300
CHAPTER XVII.
Former compromises taken up and begun to be fulfilled 301 Estimates of the heat-power of the sun made only from gravitation hitherto 302 Contraction and condensation of a nebula solid to the centre. Heat produced from attraction as well as by gravitation 303 What quantity of heat is produced by a stone falling upon the earth 304 Showing again that there is a difference between attraction and gravitation 305 Contraction and condensation of a hollow-sphere nebula, in the same manner as the solid one 305 Differences of rotation would be greater in a hollow nebula; because a great deal of the matter would be almost motionless in a solid sphere; 306 In neither case could matter be brought to rest, but only retarded in motion. Different periods of rotation accounted for 307 Table of different rates explained 309 Heat produced by gravitation, attraction and churning, not all constituents of the heat-power of the sun 310 There can be no matter in the sun so dense as water 311 The hollow part of the sun acting as a reservoir of gases, heat and pressure 312 The behaviour of heat produced in the nebula, and its power 313 How sun-spots are produced 314 Cyclonic motions observed in sun-spots. Why not all in certain directions, and why only observed in a very few 315 Cyclonic motions in prominences treated of 316 Many other things might be explained, on some of which we do not dare to venture. Concluding observations 317
CHAPTER XVIII.
Return to the peaks abandoned by the original nebula. An idea of their number 319 Example of their dimensions. What was made out of them 320 What could be made from one of them 321 How it could be divided into comets and meteor swarms 322 An example given. How a comet may rotate on its axis. And what might be explained thereby. Orbits and periods of revolution 323 Not ejected from planets. Their true origin 324 Study of the velocities in orbit of comets, and results thereof 326 How far comets may wander from the sun and return again 327 No reason why comets should wander from one sun to another. Confirmatory of the description, in Chapter XV. of the sun's domains 328 Of the eternal evolution and involution of matter. The atmosphere and corona of the sun 329 Partial analogy between it and the earth's atmosphere
CHAPTER XVI.
The sun's neighbours still exercise their attraction over him 282 Regions of greatest density in the 9 nebulæ dealt with; compared with the orbits of the planets made from them 283 Results of comparison favourable to the theory 287 Differences of size in the planets have arisen from variations in the quantity of matter accumulating on the nebulæ 289 Causes of the retrograde motions in Neptune, Uranus, and their satellites 290 Probable causes of the anomalous position of Neptune 292 Rises and falls in the densities and dimensions of the planets explained 293 The form of the nebulæ must have resembled a dumb-bell 295 More about rises and falls in densities 296 Reason why the Asteroid nebula was the least dense of the system; 297 Not necessary to revise the dimensions given to the 9 nebulæ 298 Causes of the anomalies in the dimensions, densities, etc., of the Earth and Venus 299 The strictly spherical form of the sun accounted for. But it may yet be varied 299 Repetition that a spherical body could not be made from a lens-shaped nebula by attraction and condensation 300
CHAPTER XVII.
Former compromises taken up and begun to be fulfilled 301 Estimates of the heat-power of the sun made only from gravitation hitherto 302 Contraction and condensation of a nebula solid to the centre. Heat produced from attraction as well as by gravitation 303 What quantity of heat is produced by a stone falling upon the earth 304 Showing again that there is a difference between attraction and gravitation 305 Contraction and condensation of a hollow-sphere nebula, in the same manner as the solid one 305 Differences of rotation would be greater in a hollow nebula; because a great deal of the matter would be almost motionless in a solid sphere; 306 In neither case could matter be brought to rest, but only retarded in motion. Different periods of rotation accounted for 307 Table of different rates explained 309 Heat produced by gravitation, attraction and churning, not all constituents of the heat-power of the sun 310 There can be no matter in the sun so dense as water 311 The hollow part of the sun acting as a reservoir of gases, heat and pressure 312 The behaviour of heat produced in the nebula, and its power 313 How sun-spots are produced 314 Cyclonic motions observed in sun-spots. Why not all in certain directions, and why only observed in a very few 315 Cyclonic motions in prominences treated of 316 Many other things might be explained, on some of which we do not dare to venture. Concluding observations 317
CHAPTER XVIII.
Return to the peaks abandoned by the original nebula. An idea of their number 319 Example of their dimensions. What was made out of them 320 What could be made from one of them 321 How it could be divided into comets and meteor swarms 322 An example given. How a comet may rotate on its axis. And what might be explained thereby. Orbits and periods of revolution 323 Not ejected from planets. Their true origin 324 Study of the velocities in orbit of comets, and results thereof 326 How far comets may wander from the sun and return again 327 No reason why comets should wander from one sun to another. Confirmatory of the description, in Chapter XV. of the sun's domains 328 Of the eternal evolution and involution of matter. The atmosphere and corona of the sun 329 Partial analogy between it and the earth's atmosphere
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tag="{http://www.w3.org/1999/xhtml}a">331 The density of it near the sun's surface cannot be normally less than 28 atmospheres, but might be so partially and accidentally 332 Probable causes of the enormous height of its atmosphere 332 The mass taken into account, but cannot be valued 334 Most probably no matter in the sun exceeds half the density of water. The unknown line in the spectrum of the corona belongs to the ether 335