Chapter I: Preface

In preparing the following work, it was intended to present a systematic and somewhat complete statement of the principles of Geology, within such limits that they may be thoroughly studied in the time usually allotted to this science.

A sufficient number of leading facts has been introduced to enable the learner to feel that every important principle is a conclusion to which he has himself arrived; and yet, for the purpose of compression, that fullness of detail has been avoided with which more extended works abound. In furtherance of the same object, authorities are seldom cited.

The consideration of geological changes is made a distinct chapter, subsequent to the one on the arrangement of materials. It should, however, be remembered that these processes of arranging and disturbing are not thus separated in time. In nature the two processes are always going on together.

It seemed important to exhibit the science with as much unity and completeness as possible; and hence, discussions upon debatable points in Theoretical Geology, so interesting to mature geologists, would have been out of place here; and yet those more intricate subjects have not been omitted. A large proportion of the work is devoted to the explanation of geological phenomena, in order to convey an idea of the modes of investigation adopted, and the kind of evidence relied on. Where diversities of opinion exist, that view has been selected which seemed most in harmony with the facts; and the connection has not often been interrupted to combat, or even to state, the antagonist view.

Technical terms have, in a few instances, been introduced, and principles referred to, which are subsequently explained. The index will, however, enable the student to understand them, without a separate glossary.

Some may prefer to commence with the second chapter, deferring the study of the elementary substances, minerals and rocks, to the last. Such a course may be pursued without special inconvenience.

Questions have been added, for the convenience of those teachers who may prefer to conduct their recitations by this means. But, when the circumstances of the case admit of it, a much more complete knowledge of the subject will be acquired by pupils who are required to analyze the sections, and proceed with the recitation themselves; while the teacher has only to correct misapprehension, explain what may seem obscure, and introduce additional illustrations.

LIST OF ILLUSTRATIONS.

1. Columnar Trap, New Holland. (_Dana._)

2. The four divisions of rocks, and their relative positions. _A_,
Volcanic Rocks. _B_, Granite. 1, 2, 3, 4, Granite of different
ages. _C_, Metamorphic Rocks. _D_, Fossiliferous Rocks.
(_Lyell._)

3. Granite veins in slate, Cape of Good Hope. (_Hall._)

4. Granite veins traversing granite. (_Hitchcock._)

5. Extinct volcanoes of Auvergne. (_Scrope._)

6. Lava of different ages, Auvergne. (_Lyell._)

7. Strata folded and compressed by upheaval of granite.

8. Favosites Gothlandica.

9. Catenipora escharoides. (Chain coral.)

10. Caryocrinus ornatus. (_Hall._)

{ Leptæna alternate. Orthis testudinaria. }
11. { }(_Hall._)
{ Delthyris Niagarensis. }

12. Section of a chambered shell, showing the chambers and the
siphuncle.

13. Orthoceras.

14. Curved Cephalopoda, _a_, Ammonite; _b_, Crioceras; _c_,
Scaphite; _d_, Ancyloceras; _e_, Hamite; _f_, Baculite;
_g_, Turrilite. (_Agassiz and Gould._)

15. Trilobite.

16. Cephalaspis Lyellii. (_Agassiz._)

17. Pterichthys oblongus. (_Agassiz._)

18. Fault in the coal formation, _a a_, layers of coal,
_b b_, surface and soil.

19. Stigmaria ficoides; Newcastle. (_Lindley and Hutton._)

20. Trunk of sigillaria. (_Trimmer._)

21. Bark of sigillaria. (Natural size.)

22. Sphenopteris crenata. (_Lindley._)

23. Pachypteris lanceolata. (_Brongn._)

24. Sigillaria levigata. (_Brongn._)

25. Lepidodendron Sternbergii, Bohemia. (_Sternberg._)

26. Calamite.

27. Heterocercal fish. Homocercal fish.

28. Impressions of Raindrops, Wethersfield, Conn. (_Hitchcock._)

29. _b_, Bird tracks in the Conn. River Sandstone, _a_, Consecutive
tracks; _c_, Track of Cheirotherium (probably a reptile),
Penn. and Germany.

30. Section in the Isle of Portland. (_Buckland._)

31. Apiocrinites rotundus, Bradford, Eng. (_Miller._)

32. Gryphea incurva.

33. _a_, Outline of Ichthyosaurus; _b_, Plesiosaurus.

34. Pterodactyle.

35. _a_, Diploctenium cordatum; _b_, Marsupites; _c_, Salenia; _d_,
Galerites; _e_, Micraster cor-anguinum. (_Agassiz & Gould._)

36. _b_, Belemnite. _a_, Restored outline of the animal to which it
belonged.

37. Cerithium intermedium.

38. Murex alveolatus.

39. Conus concinnus.

40. Nummulite.

41. Outline of paleotherium.

42. Outline of anoplotherium.

43. Skeleton of the mastodon.

44. Univalve with entire mouth.

45. Univalve with notched mouth.

46. Unimuscular bivalve.

47. Bimuscular bivalve.

48. Parallel planes of cleavage intersecting curved strata.
(_Sedgwick._)

49. _a b_, A vein of segregation; _c d_, A dike.

50. Faults and denuded strata.

51. Vertical conglomerate. (_Lyell._)

52. Inclined strata in Dorsetshire, England. (_Buckland._)

53. Dip of strata.

54. Axes and valleys in disturbed strata.

55. Curved strata of slate, Berwickshire, Eng. (_Lyell._)

56. Folded strata.

57. Slope of mountains.

58. Europe at the Silurian epoch. (_Guyot._)

59. Europe at the tertiary epoch.

60. Area of elevation and depression in the Pacific and Indian
Oceans. (_Darwin._)

61. _c c_, Coral wall. (_Trimmer._)

62. _c c_, Coral wall above the sea-level; _c' c'_, Second coral
wall.

63. Coral wall after partial subsidence.

64. Atoll. The coral wall only appearing. The original island
entirely submerged.

65. Remains of the temple of Jupiter Serapis, near Naples.

66. Detached hills of old red sandstone, Rosshire, Scotland.
(_Lyell._)

67. Section of denuded strata, Mass. (_Hitchcock._)

68. Grooved and striated surface of rocks.

69. Artesian wells.

70. Segregated masses in rocks.

71. Columnar form taken by basalt on solidification.

72. Layers of limestone now forming, San Vignone, Italy. (_Lyell._)

73. Erosion of rock by the action of the waves.

74. Marine currents.

75. Sediment deposited in horizontal layers.

76. Section of greensand, Bedfordshire, Eng. (_Lyell._)

77. Glacier, with lateral and medial moraines, _a a_, Terminal
moraines.

78. Iceberg.

79. Volcanic Eruption. (_Trimmer._)

80. Fractures produced by upheaval.

81. Fossiliferous rock altered by contact with granite.

82. Consecutive changes by which horizontal strata become vertical.

TABLE OF CONTENTS.

Page
CHAPTER I.

OF THE MATERIAL WHICH COMPOSE THE CRUST OF THE EARTH.

SECTION I.--ELEMENTARY SUBSTANCES, 11

SECTION II.--SIMPLE MINERALS, 13

SECTION III.--THE MINERAL MASSES WHICH FORM THE CRUST OF THE EARTH, 16

CHAPTER II.

OF THE ARRANGEMENT OF THE MATERIALS WHICH COMPOSE
THE CRUST OF THE EARTH.

SECTION I.--THE CLASSIFICATION OF ROCKS, 21

SECTION II.--THE PLUTONIC ROCKS, 23

SECTION III.--THE VOLCANIC ROCKS, 25

SECTION IV.--THE NON-FOSSILIFEROUS STRATIFIED (OR
METAMORPHIC) ROCKS, 30

SECTION V.--THE FOSSILIFEROUS ROCKS, 32

SECTION VI.--FOSSILS, 57

SECTION VII.--THE TIME NECESSARY FOR THE FORMATION OF THE
STRATIFIED ROCKS, 63

CHAPTER III.

OF THE CHANGES TO WHICH THE CRUST OF THE EARTH HAS
BEEN SUBJECTED.

SECTION I.--CHANGES WHICH HAVE TAKEN PLACE AT GREAT DEPTHS
BELOW THE SURFACE, 67

SECTION II.--CHANGES IN THE MASS OF THE STRATIFIED ROCKS, 68

SECTION III.--CHANGES OF ELEVATION AND SUBSIDENCE, 73

SECTION IV.--CHANGES ON THE SURFACE OF THE EARTH, 85

SECTION V.--CHANGES OF CLIMATE, 88

SECTION VI.--ADVANTAGES RESULTING FROM GEOLOGICAL CHANGES, 91

CHAPTER IV.

OF THE CAUSES OF GEOLOGICAL PHENOMENA.

SECTION I.--ATMOSPHERIC CAUSES, 95

SECTION II.--CHEMICAL ACTION, 97

SECTION III.--ORGANIC CAUSES, 101

SECTION IV.--AQUEOUS CAUSES, 103

SECTION V.--AQUEO-GLACIAL ACTION, 120

SECTION VI.--IGNEOUS CAUSES, 127

CHAPTER I.

OF THE MATERIALS WHICH COMPOSE THE CRUST OF THE EARTH.