PART I.. _the Impact Theory of Stellar Evolution._

THE IMPACT THEORY OF STELLAR EVOLUTION.

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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