iv CONTENTS. 



PAGE 



fusion. 14. Siibject of geology. 15. How the structure oftlie 

 crust to a great depth is rendered manifest. 16. Section of the 

 crust where no disturbance has taken place strata occur in a 

 fixed order. 17. Rocks in their geological sense. 18. Their 

 classification in five principal divisions. 19. Lowest bed, being 

 the foundation of th^ crust, consists of igneous rocks produced by 

 the superficial cooling of the molten materials of the globe. 20. 

 Materials of which the igneous rocks are formed. -21. Consti- 

 tuents of granite, feldspar, mica, quartz. 22. These components 

 of igneous rocks agglomerated mechanically. 23. But the com- 

 ponents themselves are chemical compounds. 24. Varieties of 

 granite porphyry. 25. Gneiss. 26. Secondary rocks. 27. 

 Transition or metamorphic rocks. 28. Stratification. 29. Pro- 

 duced by aqueous deposition. 30. Stratified rocks of aqueous 

 origin. 31. Circumstances corroborating this inference. 32. 

 Stratified and unstratifiedjrocks. 33; Condition and materials of 

 transition rocks. 34. Animal remains found in them. 35. No 

 vegetable remains probable reason. 36. Fish and annelidans. 

 37. Stratified rocks in general. 38. Secondary rocks. 39. 

 Vast quantity of organic remains deposited in them. 40. Ter- 

 tiary rocks. 41. Diluvium, alluvium, and surface soil. 42. 

 Subdivision of these principal groups of strata. 43. General 

 inference as to the condition and ages of stratified rocks. 44. 

 They constitute a chronological scale. 45. Complexity and 

 defects of ; geological nomenclature ...... 33 



CHAP. II. 46. General section of the terrestrial crust tabulated. 47. 

 Approximate thickness of. strata. 48. Probable time necessary for 

 their deposition. 49. Recapitulation of the physical history of the 

 globe. 50. Deposition of organic forms. 51. Alternate elevation 

 and depression of the crust. 52. The strata are botanical and 

 zoological museums of past creations. 53. The gradual increase 

 of forms of life. 54. Creative power has always operated on the 

 same general plan. 55. But has varied from period to period in 

 details. 56. Animals created gradually ; the more perfect being 

 the more recent. 57. Tabular view of the progress of the ani- 

 malisation of the earth. 58. Great increase of vertebrates in the 

 tertiary period No human fossil Man characteristic of the 

 present period. 59. Temporary existence of certain extinct genera 

 and species. 60. Geological use of characteristic genera and 

 species. 61. Examples Trilobites characteristic of the Silurian 

 strata. 62. Description of them. 63. Dr. Buckland's reflections 

 on them. 64. Species characteristic of the lias Ichthyosaurus. 

 65. Characteristics of the Wealden Hylseosaurus Iguanodon. 

 66. Characteristics of the chalk. 67. Ammonites, their dis- 

 tribution between the Silurian and chalk. 68. Fossil cephalopocles 

 Nautilus Danians. 69. Fossil gasteropodes Bigranulosa mur- 

 chisonia Cyprsea elegans Voluta elongata Pterocera oceani. . 49 



CHAP. III. 70. Spondylus. 71. Pentamerus. 72. Reticulipora. 

 73. Ceratites. 74. Enormous masses of animal remains forming 

 entire islands and continents Ehrenberg's discoveries. 75. Dr. 

 Mantell's table of organic strata. 76. Forms of life in the Silu- 



