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26b. 27. 27a. 27b. 27c 27d. 27e. 27f. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38. 39. 40.
41. 42. 43. 44. 44'. 44". 45. 46. 46'. 46". 47. 48. 49.
Fossil Crocodileans and Chelonian.
LIST OF ENGRAVINGS. vii
Body of Encrinites Moniliformis dissected.
Total number of Plates 87. Total number of figures 705.
EXPLANATION OF THE PLATES.
Introductory Votice, and Description of the Geological
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,
WOL. II, l
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.