DESCRIPTION OF PLATE VI. Illustrative of the structure of Fossil Teeth. Fig. 1a.-Tooth of Psammodus porosus, from the Oolite. See 16.-Vertical section, a portion × 75 linear. 1.-Transverse section of the same, x 75. 24.-Tooth of Plychodus polygurus, from the Chalk, near Lewes. See p. 616. 26.-Portion of longitudinal section, x 20. 2c.-Portion of transverse section, x 20. 3d.-Tooth of the Labyrinthodon Jægeri, from the New Red sandstone near Wirtemberg; half the natural size: the specimen presented by Dr. Jæger. See p. 786. 3a.-A moiety of a transverse polished section, x 20. 36.-Portion of a vertical section near the apex, x 20. 3.-One of the anfractuosities of fig. 3a XX. 44.-Crown or upper portion of a tooth of a young Iguanodon from Tilgate Forest. See p. 743. 46.-Portion of a vertical section of the above, x 20. 4c.-A small portion of a transverse section of the same, x 20. 64.-Tooth of a reptile (probably of the Hylæosaurus) from Tilgate Forest; half the natural size. See p. 738. 66.-Portion of a vertical section of the same, x 20. 7a.-Tooth of Megalosaurus from Tilgate Forest. See p. 733. 76.-Portion of a vertical section of the same, x 10. 8.-A very small portion of a vertical section of a tooth of Dendrodus, (Professor Owen). See p. 653. 9.-Portion of a transverse section of the base of a tooth of Ichthyosaurus, 20. (Professor Owen). See p. 710. 10.-Tooth of Lepidotus, Tilgate Forest. See p. 639. 106.-The upper figure is a transverse section, and the lower a vertical section of the same, x 20. MEDALS CREATION. INTRODUCTION. "Geology, in the magnitude and sublimity of the objects of which it treats, undoubtedly ranks next to Astronomy in the scale of the sciences."-Sir J. F. W. Herschel. GEOLOGY (a term derived from two Greek words, signifying a discourse of the Earth) may be denominated the physical history of the globe; it is the science that investigates the structure of the planet on which we live, and the character and causes of the various changes which have taken place in the organic and inorganic kingdoms of nature, and is therefore intimately connected with every other branch of natural philosophy. While in common with other scientific pursuits it possesses the power of conferring upon us the noblest and purest pleasures of which our natures are B susceptible, enabling us to see evidences of creative wisdom and benevolence in circumstances where the uninformed or uninquiring mind can perceive neither interest nor beauty, it has this peculiar claim upon our attention, that it offers an inexhaustible field of inquiry, and its cultivation, beyond that of any other department of science, is more independent of external circumstances, and can be pursued in whatever situation or condition of life we may happen to be placed. The eulogium passed by the most distinguished philosopher of our times on science in general, is strikingly applicable to geological researches. "The highest worldly prosperity, so far from being incompatible with them, supplies additional advantages for their pursuit; they may be alike enjoyed in the intervals of the most active business, while the calm and dispassionate interest with which they fill the mind, renders them a most delightful retreat from the agitations and dissensions of the world, and from the conflict of passions, prejudices, and interests, in which the man of business finds himself continually involved."* From the present advanced state of geological science, particularly of that department which it is the more especial object of these volumes to elucidate the study of organic remains - -it seems *Sir J. F. W. Herschel, "Discourse on the Study of Natural Philosophy." |