Geology and Mineralogy considered with reference to Natural Theology/Plate 1

by William Buckland

EXPLANATION OF THE PLATES.

Introductory Notice, and Description of the Geological Phenomena illustrated by Plate I.

Plate 1,

Is an imaginary Section constructed to express, by the insertion of names, and colours, the relative positions of the most important classes, both of unstratified and stratified rocks, as far as they have yet been ascertained. It is founded on many series of accurate observations, on several lines taken across Europe, between the British islands and the Mediterranean Sea. Although no single straight line exhibits every formation complete in the full order of succession here represented, no fact is inserted for which authority cannot be found. The near approximation of this synoptic representation to the facts exhibited by an actual section, may be estimated by comparing it with the admirable section across Europe, published by Mr. Conybeare in the Report of the Proceedings of the British Association for the Advancement of Science, 1832, and with his sections of England, in Phillips and Conybeare's Geology of England and Wales.

The chief merit of the above Section is due to the Talents of Mr. Thomas Webster; it is founded on a more simple section which has for several years been used by him in his lectures, and which exhibits the relations of the Granitic and Volcanic rocks to the stratified formations, and to one another, more intelligibly than I have ever seen expressed elsewhere. This original drawing by Mr. Webster has formed the basis of the present enlarged and improved section, into which many important additions have been introduced by the joint suggestions of Mr. Webster and myself. The selection and arrangement of the animals and plants is my own; they have been drawn and engraved (together with a large proportion of the woodcuts) by Mr. J. Fisher, of St. Clements, Oxford.

For facility of reference, I have numbered the principal groups of stratified rocks represented in the section, according to their most usual order of succession; and I have designated by letters the crystalline or unstratified rocks, and the injected masses and dikes, as well as the metallic veins, and lines of fracture, producing dislocations or faults. The crowded condition in which all the Phenomena represented in this section, are set together, does not admit of the use of accurate relative proportions, between the stratified rocks and the intruded masses, veins, and dikes by which they are intersected. The adoption of false proportion is, however, unavoidable in these cases, because the veins and dikes would be invisible, unless expressed on a highly exaggerated scale. The scale of height throughout the whole section is also infinitely greater than that of breadth. The plants and animals also are figured on no uniform scale.

The extent of the different formations represented in this section, taking their average width as they occur in Europe, would occupy a breadth of five or six hundred miles. A scale of heights, at all approaching to this scale of breadth, would render the whole almost invisible. The same cause makes it also impossible to express correctly the effect of valleys of denudation, which are often excavated through strata of one formation into those of another subjacent formation.

As it would encumber the section to express Diluvium, wherever it is present, it is introduced in one place only, which shows its age to be more recent than the newest of the Tertiary strata; it is found also lodged indiscriminately upon the surface of rocks of every formation.

Granite.

In our early Chapters we have considered the Theory which refers unstratified rocks to an igneous Origin, to be that which is most consistent with all the known Phenomena of Geology, and the facts represented in the Section now before us are more consistent with the Postulates of this Hypothesis, than with those of any other that has hitherto been proposed. I have, therefore, felt it indispensable to adopt its language, as affording the only terms by which the facts under consideration can be adequately described.

Assuming that Fire and Water have been the two great Agents employed in reducing the surface of the globe to its actual condition, we see, in repeated operations of these agents, causes adequate to the production of those irregular Elevations and Depressions of the fundamental Rocks of the Granitic series, which are delineated in the lower Region of our Section, as forming the basis of the entire Superstructure of stratified Rocks.

Near the right extremity of this Section, the undulating surface of the fundamental Granite (a. 5. a. 6. a. 7. a. 8.) is represented as being, for the most part, beneath the level of the Sea.

On the left extremity of the Section (a. 1. a. 2. a. 3.) the Granite is elevated into one of those lofty Alpine ridges, which have affected, by their upward movement, the entire series of stratified Rocks.

Corresponding formations of Primary and Transition Strata, are represented as occurring on each side of this elevated Granite, which is supposed to have broken through, and to have carried up with it to their present elevated and highly inclined position, strata that were once continuous and nearly horizontal.^[1]

The general history of Elevation appears to be, that mountain chains of various extent, and various directions, have been formed at irregular intervals, during the deposition of stratified rocks of every age; and that Granite had, in many cases, acquired a state of solidity before the period of its elevation.

Within the primary Granite, we find other forms of Granitic matter, (a. 9.) which appear to have been intruded in a state of fusion, not only into fissures of the older Granite, but frequently also into the Primary stratified rocks in contact with it, and occasionally into strata of the Transition and Secondary series, (a. 10. a. 11.) these Granitic injections were probably in many cases, contemporaneous with the elevation of the rocks they intersect; they usually assume the Condition of Veins, terminating upwards in small branches; and vary in dimensions, from less than an inch, to an indefinite width. The direction of these veins is very irregular: they sometimes traverse the Primary strata at right angles to their planes of stratification, at other times they are protruded in a direction parallel to these planes, and assume the form of beds. Some of the relations of these Granitic Veins to the rocks intersected by them are represented at the left extremity of the Section, (a. 9.)^[2]

A. 10. represents a dike and protruded mass of Granite, intersecting and overlying stratified rocks of the Primary and Transition series. A. 11. represents the rare case of Granite intersecting Red Sandstone, Oolite, and Chalk.^[3]

Sienite, Porphyry, Serpentine, Greenstone.

Closely allied to Granite Veins, is a second series of irregularly injected rocks, composed of Sienite, Porphyry, Serpentine, and Greenstone (b. c. d. e.) which traverse the Primary and Transition formations, and the lower regions of the Secondary strata; not only intersecting them in various directions, but often forming also overlying masses, in places where these veins have terminated by overflowing at the surface, (b'. c'. d'. e'.) The crystalline rocks of this series, present so many modifications of their ingredients, that numerous varieties of Sienite, Porphyry, and Greenstone occur frequently in the products of Eruptions from a single vent.

The scale of our Section admits not of an accurate representation of the relations between many of these intruded rocks, and the strata they intersect; they are all placed, as if they had been injected, either at the time of, or after the elevation of all the strata, and had produced but little disturbance in the rocks through which they are protruded. It should however be understood, distinctly, that some Injections may have preceded the elevation of Strata to their present height, and that numerous and successive elevations and injections, attended by various degrees of fracture and disturbance, have prevailed in various localities during all periods, and throughout all formations; from the first upraising of the earliest Primary rocks, to the most recent movements produced by existing Volcanoes. M. Elie de Beaumont has discovered probable evidence of no less than twelve periods of elevation, affecting the strata of Europe.

Examples of the fractures and dislocations attending these movements, and producing faults, are represented in our Section by the lines designated by the letter 1. Some of these fractures do not reach to the present surface, as they affected the lower beds at periods anterior to the deposition of more recent strata, which cover unconformable the summits of the earlier fractures. (See l. l1. l2. l3. l6. l7)

Basalt.

A third series of Igneous Rocks is that which has formed dikes, and masses of Basalt and Trap, intruded into, and overlying formations of all ages, from the earliest Granites to the most recent Tertiary Strata. These basaltic rocks sometimes occur as Beds, nearly parallel to the strata, into which they are protruded, after the manner represented in the carboniferous Limestone of our Section, f. 2. More frequently they overspread the surface like expanded sheets of Lava. Our section gives examples of Trap under all these circumstances. At f. 1. it intersects and overlies Primary strata; at f. 2. f. 3. f. 4. f. 5. it stands in similar relations to Transition and Secondary strata; f. 6. represents an example of an extensive eruption of Basaltic matter, over Chalk and Tertiary strata, accompanied by an intrusion of vast irregular masses of the same materials into the body of the subjacent Primary and Transition rocks.

f. 7. represents strata of columnar Basalt, immediately beneath streams of cellular Lava, in regions occupied also by craters of extinct Volcanoes, f. 8. represents similar beds of columnar lava in the vicinity of active Volcanoes.

Trachyte and Lava.

The fourth and last class of intruded rocks, is that of modern volcanic Porphyries, Trachytes,^[4] and Lavas. The undeniable igneous origin of rocks of this class forms the strongest ground-work of our arguments, in favour of the igneous formation of the older unstratified and crystalline rocks; and their varied recent products, around the craters of active Volcanoes, present gradations of structure, and composition, which connect them with the most ancient Porphyries, Sienites, and Granites.

The simplest cases of volcanic action are those of Trachyte (g. l.) and of Lava (i. 5.) ejected through apertures in Granite; such cases prove that the source of volcanic fires, is wholly unconnected with the pseudo- volcanic results of the combustion of coal, bitumen, or sulphur, in stratified formations, and is seated deep beneath the Primary rocks.^[5]

Craters.

Our section represents three cases of Volcanic craters; the most simple (i. 5.) rising through Granite, or stratified rocks, at the bottom of the sea, and accumulating craters, which, like those of Lipari and Stromboli, Sabrina, and Graham Islands, are occasionally formed in various parts of the ocean.^[6] The second case is that of volcanoes, which, like Etna and Vesuvius, are still in action on the dry land, (i. 1. to i. 4.) The third is that of extinct volcanoes, like those in Auvergne, (h1. h2.) which, although there exist no historical records as to the period of their last eruptions, show by the perfect condition of their craters, that they have been formed since the latest of those aqueous inundations, that have affected the Basalts and Tertiary strata, through which they have burst forth.

One great difference between the more ancient Basaltic eruptions and those of the Lava and Trachyte of existing volcanoes, is that the emission of the former, probably taking place under the pressure of deep water, was not accompanied by the formation of any permanent craters.

In both cases, the fissures through some of which these Eruptions may have issued, are abundantly apparent under the form of Dikes, filled with materials similar to those which form the masses that have overflowed in the Vicinity of each Dike.^[7]

Changes effected by the Igneous Rocks, on the Strata in contact with them.

The peculiar condition of the rocks that form the side walls of Granitic Veins and Basaltic Dikes, affords another argument in favour of their igneous origin; thus wherever the early Slate rocks are intersected by Granitic Veins (a. 8.) they are usually altered to a state approximating to that of fine-grained Mica-slate, or Hornblende-slate.

The secondary and Tertiary rocks also, when they are intersected by basaltic Dikes, have frequently undergone some change; beds of Shale and Sandstone are indurated, and reduced to Jasper; compact Limestone and Chalk are converted to crystalline Marble, and Chalk-flints altered to a state like that resulting from heat in an artificial furnace.^[8]

In all these cases, the Phenomena appear to be throughout consistent with the theory of igneous Injection, and to be incapable of explanation on any other Hypothesis that has been proposed. A summary statement of the probable relations of the Granitic and Trappean Rocks to the other materials of the Globe, and to one another, may be found in De la Beche's Geological Researches, 1st Edit. Pag. 374, et seq.

Explanation of Letters and Figures used in the references to unstratified and crystalline Rods in Plate 1.

⁠a. Granite.	b. Sienite.	c. Porphyry,
⁠d. Greenstone.	e. Serpentine.	f. Basalt, or Trap,
⁠g. Trachyte.	h. Products of Extinct Volcanoes.
⁠i. Products of Active Volcanoes.
⁠a. 1.—a. 3. Mountains of Granite, raised into lofty ridges, from beneath Gneiss and Primary Slates.
⁠a. 4. Granite intermixed with Gneiss.
⁠a. 5.—a. 8. Granite, subjacent to stratified rocks of all ages, and intersected by volcanic rocks.
⁠a. 9. Granite Veins, intersecting Granite, Gneiss, and primary Slate.
⁠a. 10. Granite Vein, intersecting Primary and Transition rocks, and forming overlying masses at the surface.
⁠a. 11. Granite Vein intersecting Secondary strata, and overlying Chalk.[9]
⁠b. Dikes of Sienite.
⁠b. 1. Overlying masses of Sienite.
⁠c. Dikes of Porphyry.
⁠c. 1. Overlying masses of Porphyry.
⁠d. Dikes of ancient Greenstone.
⁠d. 1. Overlying masses of the same. The Rocks represented by d. and e. often pass into one another.
⁠e. Dikes of Serpentine.
⁠e. 1. Overlying masses of Serpentine.
⁠f. Dikes and intruded subterraneous masses of Basalt.
⁠f. 1. to f. 7. Masses of Basalt protruded through, and overlying strata of various ages.
⁠f. 8. Basaltiform products of Modern Volcanoes.
⁠g. Trachyte forming Dikes.
⁠g. 1. Trachyte forming overlying Domes. (PuydeDome.)
⁠h. 1. h. 2. Lava of extinct Volcanoes, forming undisturbed Cones. (Auvergne.)
⁠i.—i. 5. Lava, Scoriæ, and Craters of active Volcanoes, (i. 1.—i. 4. Etna. 1.—5. Stromboli.)
⁠k.—k. 24. Metalliferous Veins.
⁠k. 15'. Lateral expansions of Veins into metalliferous cavities, called by the Miners Pipe Veins, or Flats.
⁠l.—l. 7. Faults, or fractures and dislocations of the strata. The continuity of stratified Rocks is always interrupted, and their level more or less changed on the opposite sides of a fault.

It is unnecessary here to give detailed descriptions of the 28 divisions of the Stratified Rocks represented in our Section. Their usual Order of Succession and Names are expressed in their respective places, and detailed descriptions of their several characters may be found in all good Treatises on Geology.

The leading Groups of Formations are united by colours, marking their separation from the adjacent groups y and the same colours are repeated, in the headings above the figures of Plants and Animals that characterize the several series of Formations, to show the extent of the strata over which the Organic Remains of each Group are respectively distributed.

The Formation of Peat Bogs and Calcareous Tufa are of too local a nature to be included in the series of stratified Rocks represented in this Section; although they sometimes operate locally to a considerable extent, in adding permanent and solid matter to the surface of the Globe.

List of the Names of the Plants and Animals, represented in Pl. 1. to denote the prevailing Types of Vegetable and Animal Life, during the formation of the three great divisions of stratified Rocks.

REFERENCES.

r. recent, f. fossil. Ad. B. Adolphe Brongniart. L. Lindley. Ag. Agassiz. P. Page of Vol. I.

Remains in Transition Strata.

LAND PLANTS.

1. Araucaria. Norfolk Island Pine. r. & f. P. 364.

2. Equisetum. r. & f. P. 346.

3. Calamites nodosus. f. (L. Pl. 16.)

4. Asterophillites comosa. f. (L. 108.)

5. Asterophyllites foliosa. f. (L. 25.)

6. Aspidium. r. Pecopteris. f.

⁠7. Cyathea glauca, Tree Fern. r. (Ad. B. Hist. Veg. Foss. Pl. 38.) P. 349.

8. Osmunda. r.^[10] Neuropteris. f.

9. Lycopodiurn cernuum. r. (from Mirbel.) P. 350.

10. Lycopodiurn alopecuroides. r. (from Mirbel.) P. 350.

11. Lcpidodendron Sternbergii. f.

12. Lepidodendron gracile? f.

13. Flabelliform Palm. r. (from Mirbel.) Palmacites. f.

MARINE ANIMALS AND PLANTS.

14. Acanthodes. f. Ag.

15. Catopterus. f. Ag.

16. Amblypterus. f. Ag.

17. Orodus, extinct Shark, f. (imaginary restoration.)

⁠18. Cestracion Phillippi, Port Jackson Shark, r. (Phillip.) P. 220.^[11]

18'. Palatal Tooth of Cestracion Phillippi. r.

19. Tooth of Psammodus, from Derbyshire limestone, f.

19'. Tooth of Orodus, from Mountain limestone, near Bristol, f.

⁠20. Calymene. f.	$\left.{\begin{matrix}\ \\\ \end{matrix}}\right\}$	Trilobites. P. 295.
⁠21. Paradoxus, f.
⁠22. Asaph us. f.)

23. Euomphalus. f.

24. Producta. f.

25. Spirifer. f.

26. Actinocrinites. f. (Miller, P. 96.) P. 314.

27. Platycrinites. f. (Miller, P. 74.^[12])

⁠27a. Fucoides circinatus. f. (Ad. B.) From Transition sandstone, Sweden.

28. Caryophyllia. r. & f.

29. Astrea. r. & f.

30. Turbinolia. r. & f.

Remains in Secondary Strata.

LAND PLANTS.

31. Pinus. r. & f.

32. Thuia. r. & f.

33. Cycas circinalis. r. Cycadites. f.

34. Cycas revoluta. r. Cycadites. f.

35. Zamia horrida. r. Zamia. f.

36. Dracaena, r. Allied to Bucklandia and Clathraria. f.

37. Arborescent Fern. r. P. 350.

38. Pteris aquilina. r. Pecopteris. f.

⁠39. Scolopendrium. r. Tæniopteris in Oolite. Scarborough, f.

LAND ANIMALS.

40. Didelphys. r. Stonesfield slate, 2 small species, f.

41. Didelphys. r. Cheirotherium? f. P. 203.

42. Pterodactylus brevirostris. f.

43. Pterodactylus crassirostris. f.

44. Gavial. r. Allied to Teleosaurus. f.

45. Iguana, r. Iguanodon. f.

⁠46. Testudo, Land Tortoise, r. Scales of Tortoises, at Stonesfield, Oxon. f. Footsteps of Tortoises, Dumfries, f.

47. Emys. r. Soleure. f.

48. Buprestis. r. Stonesfield. f.

49. Libellula. r. Solenhofen. f.

MARINE ANIMALS, AND PLANTS.

50. Plesiosarus. f.

51. Ichthyosaurus, f.

52. Marine Turtle, r. At Luneville, in Muschel Kalk. f. P. 196.

⁠53. Pygopterus. f. (Ag. Vol. I. PI. D. 3.) In Magnesian Limestone.

54. Dapedium, in Lias. f.

⁠55. Hybodus. f. Extinct genus of Sharks. (Imaginary restoration.)

56. Loligo. r. Lyme Regis, f.

57. Nautilus Pompilius. r. Many species, f.

58. Ammonites Bucklandi. f. Peculiar to Lias.

59. Astacus. r. & f.

60. Limulus, King Crab. r. Solenhofen. f.

61. Trigonia. f. New Holland, r.

62. Ophiura. r. & f.

63. Asterias. r. & f.

64. Echinus, r. & f.

65. Apiocrinites. f.

⁠

Remains in Tertiary Strata.

LAND PLANTS.

⁠66. Mauritia aculeata. r. (Martius, T. 44.) Palmacites. Lamanonis. f. P. 166.

⁠67. Elaeis guineensis. r. (Martius, T. 56.) Fruits of Pinnate Palms, f. P. 386.

⁠68. Cocos nucifera. r. (Martius, Pl. 62.) Fossil Cocoanut, Sheppy, Brussels. P. 386.

69. Pinus, Pine. r. & f.

70. Ulmus, Elm. r. & f.

71. Populus, Poplar, r. & f.

72. Salix, Willow, r. & f.

LAND ANIMALS OF FIRST PERIOD.

Birds.

73. Scolopax, Woodcock, r. & f.

74. Ibis. r. & f.

75. Tringa, Sea Lark. r. & f.

76. Coturnix, Quail, r. & f.

77. Strix, Owl. r. & f.

78. Buteo, Buzzard, r. & f.

79. Phalacrocorax, Cormorant, r. Pelecanus. f.

Reptiles.

80. Emys, Fresh water Tortoise, r. & f.

81. Trionyx, Soft Tortoise, r. & f.

82. Crocodilus, Crocodile, r. & f.

Mammifers.

83. Vespertilio, Bat. r. & f.

84. Sciurus, Squirrel, r. & f.

85. Myoxus, Dormouse, r. & f.

86. Castor, Beaver, r. & f.

87. Genetta, Genet, r. & f.

88. Nasua, Coati. r. & f.

89. Procyon, Racoon, r. & f.

90. Canis Vulpes, Fox. r. & f.

91. Canis Lupus, Wolf. r. & f.

92. Didelphys, Opossum, small, r. & f.

93. Anoplotherium commune, f.

94. Anoplotherium gracile. f.

95. Palæotherium magnum, f.

96. Palæotherium minus, f.

MARINE ANIMALS.

Mollusks.

⁠Genera of Shells most characteristic of the Tertiary Periods.	$\left\{{\begin{matrix}\ \\\\\\\\\\\\\\\\\\\\\\\\\\\ \end{matrix}}\right.$	a. Planorbis. r. & f.
		b. Limæa. r. & f.
		c. Conus. r. & f.
		d. Bulla, r. & f.
		e. Cypræa. r. & f.
		f. Ampullaria. r. & C
		g. Scalaria. r. & f.
		h. Cerithium. r. & f.
		i. Cassis, r. & f.
		j. Pyrula. r. & f.
		k. Fusus. r. & f.
		l. Voluta. r. & f.
		m. Buccinum. r. & f.
		m. Rostellaria. r. & i.

Mammifers.

97. Phoca, Seal. r. & f.

98. Trichechus, Walrus, r. & f.

⁠99. Delphinus Orca, (Phocœna, Cuv.) Grampus, r. Delphinus. f.

100. Manatus, Lamantin. r. & f.

101. Balasna, Whale, r. & f.

LAND ANIMALS.^[13]

Birds.
Aves	$\left\{{\begin{matrix}\ \\\\\ \end{matrix}}\right.$	102. Columba, Pigeon, r. & f.
		103. Alauda, Lark. r. & f.
		104. Corvus, Raven, r. & f.
		105. Anas, Duck. r. & f.
Mammifers.
Ruminantia.	$\left\{{\begin{matrix}\ \\\\\ \end{matrix}}\right.$	106. Alces, Elk. r. & f.
		107. Elaphus, Stag. r. & f.
		108. Bos Urus, Bison, r. & f.
		109. Bos Taurus. Ox. r. & f.
Rodentia.		110. Lepus, Hare. r. & f.
Carnivora.	$\left\{{\begin{matrix}\ \\\\\ \end{matrix}}\right.$	111. Ursus, Bear. r. & f.
		112. Mustela, Weasel, r. & f.
		113. Hyaena, r. & f.
		114. Felis, Tiger, r. & f.
Pachydermata	$\left\{{\begin{matrix}\ \\\\\\\ \end{matrix}}\right.$	115. Sus, Hog. r. & f.
		116. Equus, Horse, r. & f.
		117. Rhinoceros, r. & f.
		118. Hippopotamus, r. & f.
		119. Elephas. r. Mammoth, f.
Animal of the present Epoch, supposed to have recently become extinct.
	120. Didus, Dodo. r. & f.

The bones of the Dodo have been found under lava of unknown age in the Isle of France, and in a cavern in the Island of Roderigue. See Zoological Journal, 1828, p. 554. London's Mag. Nat. Hist. Vol. II. p. 442. and London and Edin. Phil. Mag. Dec. 1832.

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1. Cases of Granite, thus elevated at a period posterior to the deposition of Tertiary Strata, occur in the Eastern Alps, where the Transition, Secondary, and Tertiary strata have all partaken of the same elevation which raised the central axis of the crystalline Granitic rocks. See Geol. Trans. N. S. Vol. III. Pl. 36. Fig. 1.
2. In the Granite at the right extremity of the Section, the granitic veins are omitted, because their insertion would interfere with the representation of the injections of Basaltic and Volcanic matter which the portion of the section is intended to illustrate.
3. An example of the rare Phenomenon of Granite intruded into the Chalk formation, in the hill of St. Martin, near Pont de la Fou in the Pyrenees, is described by M. Dufrenoy in the Bulletin de la Société Géologique de France, Tom. 2. p. 73.

   At Weinböhla, near Meissen in Saxony, Prof. Weiss has ascertained the presence of Sienite above strata of Chalk; and Prof. Nauman states, that, near Oberau, Cretaceous rocks are covered by Granite, and that near Zscheila and Neiderfehre, the Cretaceous rocks rest horizontally on Granite; at both these places the Limestone and Granite are entangled in each other, and irregular portions and veins of hard Limestone, with green grains and cretaceous fossils, are here and there imbedded in the Granite.

   De la Beche. Geol. Manual. 3d Edit. p. 295.

4. The appellation of Trachyte has been given to a volcanic Porphyry, usually containing Crystals of glassy felspar, and remarkably harsh to the touch, (hence its name from Tga^vc); it does not occur in Britain, but abounds in the neighbourhood of almost all extinct and active volcanic craters.
5. The occurrence of angular fragments of altered Granite, embedded in Pillars of columnar Lava, in the valley of Monpezat in the Ardéche, shows that these fragments were probably torn off during the upward passage of the Lava through fractures in the sordid Granite.

   At Graveneire, near Clermont, a stream of Lava still retains the exact form, in which it issued through a fissure in the side of a mountain of Granite, and overflowed the subjacent valley. Most accurate representations of this, and many similar productions of Volcanic Eruptions from the Granite of this District may be seen in Mr. Poulett Scrope's inimitable Panoramic Views of the Volcanic formations of Central France.

6. Within the last few years, the Volcanic Cones of Sabrina in the Atlantic, and of Graham Island in the Mediterranean, have risen suddenly in the sea and been soon levelled and dispersed by the Waves.
7. In many Dikes the materials have been variously modified, by their mode of cooling, and differ from the masses which overflowed the surface.
8. Examples of this kind occur on the sides of Basaltic Dikes intersecting Chalk in the County of Antrim, and in the Island of Raghlin, See Geol. Trans. London, O. S. vol. iii. p. 210. pl. 10.
9. In the locality quoted in the Explanation of Plates, Vol. II. p. 5, the Granite which comes to the surface over the Chalk, is not covered by Tertiary deposites, as represented in our section, Pl. 1.
10. An error in this figure represents the fructification as branching from the tallest frond, instead of rising by a separate rachis from the root.
11. This shark is the only known living representative of the extinct genus Psammodus.
12. Fig. 27. In most, if not all the species of Platycrinites the arms are subdivided; they are not so in this figure, as from its small size they could not well be represented. The figure is intended to give only a general idea of the subject.
13. Many of the following genera occur both in the second, third and fourth formations of the Tertiary series, and also in Caverns, Fissures, and Diluvium.