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Show xxvi CONTENTS. PAGE CHAPTER XXVI. On the stratified rocks usually called 'primary'-Proofs from the disposition of their strata that they were originally deposited from water-Alter. nation of beds varying in composition and colour-Passage of gneiss into ranite-Alteration of sedimentary st.rata by trappean and granitic dikesinference as to the origin of the strata called 'primary' -Conversion of argillaceous into hornblende schist-The term 'Hypogene' proposed as a substitute for primary-' Metamorphic' for 'stratified primary' rocks-No regular order of succession of hypogene formations-Passage from the metamorphic to the sedimentary strata-Cause of the high relative antiquity of the visible hypogene formations-That antiquity consistent with the hypothesis that they have been produced at each successive }Jeriod in equal quantities-Great volume of hypogene rocks supposed to have been formed since the Eocene period-Concluding remarks 365 Table I. Showing the relations of the various classes of rocks, the Alluvial, the Aqueous, the Volcanic, and the Hypogene, of different periods 386 Table II. Showin~ the order of superposition of the principal European groups of sedimentary strata mentioned in this work • 389 Notes in explanation of the Tables of fossil shells iu Appendix I. 395 Appendix I. Tables of fossil shells by Monsieur G. P. Desha yes Appendix II. Lists of fossil Shells chiefly collected by the author in Sicily and Italy, named by M. Deshayes 53 Glossary, containing an explanation of geological and othcr scientific tenus used in this work • 61 Index 85 LIS'l' OF PLA1'ES AND WOOD-CUTS IN THE THIRD VOLUME. PLATES. Frontispiece. View of the volcanos around Olot, in Catalonia. See p. 186. This view is taken from a sketch by the author ; an attempt is made to represent by colours the different geological formations of which the country is composed. The blue line of mountains in the distance are the Pyrenees, which are to the north of the spectator, and consist of primary and ancient secondary rocks. In front of these arc the secondary formations, described in chap. xiv., coloured purplish-grey of different tints, to express different distances. The flank of the hill, in the foreground, called Costa di Pujou, is composed partly of secondary rocks, which are seen to the left of a small bridle-road, and partly of volcanic, the red colour expressing lava and scorire. Several very perfect volcanic cones, chiefly composed of red scorire, and having craters on their summits, are seen in the immediate neighbourhood of Olot, coloured red. The level plain on which that town stands has clearly been produced by the flowing down of many lava-streams from those hills into the bottom of a valley, probably once of considerable depth, like those of the surrounding country, but which has been in a great measure filled up by lava. The reader should be informed, that in many impressions of this plate Montsacopa is mis-spelt 'Montescopa,' and Mount Garrinada is mis-spelt ' Gradenada.' Plate I. The shells represented in this plate have been selected by M. Deshayes as characteristic of the Pliocene period of the Tables, Appendix I. The greater part of them are common both to the older and newer Pliocene periods of this work. Eight of the species, Nos. 1, 3, 5, 6, 7, 9, 13, and 14, are now living, but are given as being also found in the Older Pliocene formations. Fusus crispus is not found either recent |