9. Permanent effects of igneous causes now in operation: Active volcanos and earthquakes--their effects and causes: chaps. xxiii. to xxxiii. BOOK III. CHANGES OF THE ORGANIC WORLD NOW IN PROGRESS. 10. Doctrine of the transmutation of species controverted, chaps. xxxiv. and xxxv. 11. Whether species have a real existence in nature, chaps. xxxvi. and xxxvii. 12. Laws which regulate the geographical distribution of species, chaps. xxxviii. to xl. 13. Creation and extinction of species, chaps. xli. to xliv. 14. Imbedding of organic bodies, including the remains of man and his works, in strata now forming, chaps. xlv. to l. 15. Formation of coral reefs, chap. li. It will be seen on comparing this analysis of the contents of the "Principles" with the headings of the chapters of the present work (see p. xxiii.), that the two treatises have but little in common; or, to repeat what I have said in the Preface to the 8th edition of the "Principles," they have the same kind of connection which Chemistry bears to Natural Philosophy, each being subsidiary to the other, and yet admitting of being considered as different departments of science.[vi-A] CHARLES LYELL. _11 Harley Street, London, December 10. 1851._ FOOTNOTES: [v-A] Postscript to 4th edition of the Manual, price 6_d._ [vi-A] As it is impossible to enable the reader to recognize rocks and minerals at sight by aid of verbal descriptions or figures, he will do well to obtain a well-arranged collection of specimens, such as may be procured from Mr. Tennant (149. Strand), teacher of Mineralogy at King's College, London. POSTSCRIPT. Tracks of a Lower Silurian reptile in Canada--Chelonian footprints in Old Red Sandstone, Morayshire--Skeleton of a reptile in the same formation in Scotland--Eggs of Batrachians (?) in a lower division of the "Old Red," or Devonian--Footprints of Lower Carboniferous reptiles in the United States--Fossil rain-marks of the Carboniferous period in Nova Scotia--Triassic Mammifer from the Keuper of Stuttgart--Cretaceous Gasteropoda--Dicotyledonous leaves in Lower Cretaceous strata--Bearing of the recent discoveries above-mentioned on the theory of the progressive development of animal life.