There are two, and only two, conceivable sources from which the prodigious amount of energy possessed by our sun and solar system can possibly have been derived. Not only are these two sources radically distinct in their essential nature, but both are admitted to be real and not merely hypothetical sources of energy. The one source is gravitation; the other, the source discussed in the present volume, a source to which attention was directed some twenty years ago. A most important distinction between these two sources is this: the amount of energy available from the former can be accurately determined, but such is not the case in regard to the latter. We can tell with tolerable certainty the greatest amount of energy which gravitation could possibly have conferred on the sun and solar system; but we have, at present, no means of assigning a limit to the possible amount which might have been derived from the other source. It may have been equal to that which gravitation could afford, or it may have been twofold, fourfold, or even tenfold that amount.

We have evidently in this case a means of determining which of the two sources will ultimately have to be adopted as the source to which the energy of our solar system must be referred. For if it can be proved from the admitted facts of geology, biology, and other sciences, that the amount of energy in the form of heat which has been radiated into space by the sun during geological time is far greater than the amount which could possibly have been derived from gravitation, this will undoubtedly show that gravitation cannot account for the energy originally possessed by our system.

The First Part of the volume is devoted to the consideration of what I believe to be the probable origin of meteorites, comets, and nebulæ, and of the real source from which our sun derived his energy. The facts which support the theory here advocated, together with the light which that theory appears to cast upon those facts, are next considered; and it will be found, I think, that the theory has been very much strengthened by the recent important spectroscopic researches of Mr. Lockyer and others in reference to the constitution of nebulæ. The Second Part of the work deals with the evidence in support of the theory derived from the testimony of geology and biology as to the age of the sun’s heat. The Third, and last, Part has been devoted to questions relating to the pre-nebular condition of the universe, and the bearing which these have on theories of stellar evolution. Several subjects introduced in this part are only very briefly treated. These will, however, be considered at greater length in a future volume, “Determinism, not Force, the Foundation-stone of Evolution,” a work of a more general and abstract character, which was commenced many years ago.

Perth: January 2, 1889.

CONTENTS.

PART I.
THE IMPACT THEORY OF STELLAR EVOLUTION.
PAGE
Consideration of the Facts which support the Theory, and of the Light which the Theory appears to cast upon the Facts[12]
I. Probable Origin of Meteorites[12]
II. Motion of the Stars; how of such different velocities, and always in straight lines[14]
III. Motion of the Stars not due to their mutual attractions[14]
IV. Probable Origin of Comets[17]
V. Nebulæ[18]
1. Origin of Nebulæ[18]
2. How Nebulæ occupy so much space[18]
3. Why Nebulæ are of such various shapes[19]
4. Broken fragments in a Gaseous mass of an excessively high temperature the First stage of a Nebula[19]
5. The Gaseous condition the Second stage of a Nebula[24]
6. The Gaseous condition Essential to the Nebular Hypothesis[25]
7. The mass must have possessed an excessive temperature[26]
8. Gravitation could, under no possible condition, have generated the Amount of Heat required by the Nebular Hypothesis[27]
9. Condensation the Third and last stage of a Nebula[30]
10. How Nebulæ emit such feeble Light[30]
VI. Binary Systems[32]
VII. Sudden Outbursts of Stars[33]
VIII. Star Clusters[34]
IX. Age of the Sun’s Heat: a Crucial Test[34]
PART II.
EVIDENCE IN SUPPORT OF THE THEORY
FROM THE AGE OF THE SUN’S HEAT.
Testimony of Geology and Biology as to the Age of the Sun’s Heat[37]
Testimony of Geology: Method employed[39]
The Average Rate of Denudation in the Past probably not much greater than at the Present[44]
How the Method has been applied[47]
Method as applied by Professor Haughton[50]
Method as applied by Mr. Alfred R. Wallace[51]
Method as applied directly[52]
Evidence from “faults”[53]
Time required to effect the foregoing amount of Denudation[62]
Age of the Earth as determined by the Date of the Glacial Epoch[64]
Testimony of Biology[65]
PART III.
EVIDENCE IN SUPPORT OF THE THEORY
FROM THE PRE-NEBULAR CONDITION OF
THE UNIVERSE.
Professor A. Winchell on the pre-nebular condition of matter[71]
Mr. Charles Morris on the pre-nebular condition of matter[75]
Sir William R. Grove on the pre-nebular condition of matter[78]
Evolution of the Chemical Elements, and its Relations to Stellar Evolution[80]
Sir Benjamin Brodie on the pre-nebular condition of matter[84]
Dr. T. Sterry Hunt on the pre-nebular condition of matter[85]
Professor Oliver Lodge on the pre-nebular condition of matter[87]
Mr. William Crookes on the pre-nebular condition of matter[90]
Professor F. W. Clarke on the pre-nebular condition of matter[98]
Dr. G. Johnstone Stoney on the pre-nebular condition of matter[99]
The Impact Theory in relation to the foregoing Theories of the Pre-nebular Condition of Matter[102]
The Theories do not account for the Motion of the Stars[105]
The Theories do not account for the Amount of Heat required[106]
Evolution of Matter[107]
Objection considered[109]
Can we on Scientific grounds trace back the Evolution of the Universe to an Absolute First condition?[110]