BOOK I.

1. Historical sketch of the early progress of geology, chaps. i. to iv.

2. Circumstances which combined to make the first cultivators of the science regard the former course of nature as different from the present, and the former changes of the earth's surface as the effects of agents different in kind and degree from those now acting, chap. v.

3. Whether the former variations in climate established by geology are explicable by reference to existing causes, chaps. vi. to viii.

4. Theory of the progressive development of organic life in former ages, and the introduction of man into the earth, chap. ix.

5. Supposed former intensity of aqueous and igneous causes considered, chaps. x. and xi.

6. How far the older rocks differ in texture from those now forming, chap. xii.

7. Supposed alternate periods of repose and disorder, chap. xiii.