General Position of Drift with extinct Mammalia in Valleys. Discoveries of M. Boucher de Perthes at Abbeville. Flint Implements found also at St. Acheul, near Amiens. Curiosity awakened by the systematic Exploration of the Brixham Cave. Flint Knives in same, with Bones of extinct Mammalia. Superposition of Deposits in the Cave. Visits of English and French Geologists to Abbeville and Amiens. CHAP. 7. PEAT AND PLEISTOCENE ALLUVIUM OF THE VALLEY OF THE SOMME. Geological Structure of the Valley of the Somme and of the surrounding Country. Position of Alluvium of different Ages. Peat near Abbeville. Its animal and vegetable Contents. Works of Art in Peat. Probable Antiquity of the Peat, and Changes of Level since its Growth began. Flint Implements of antique Type in older Alluvium. Their various Forms and great Numbers. CHAP. 8. PLEISTOCENE ALLUVIUM WITH FLINT IMPLEMENTS OF THE VALLEY OF THE SOMME--concluded. Fluvio-marine Strata, with Flint Implements, near Abbeville. Marine Shells in same. Cyrena fluminalis. Mammalia. Entire Skeleton of Rhinoceros. Flint Implements, why found low down in Fluviatile Deposits. Rivers shifting their Channels. Relative Ages of higher and lower-level Gravels. Section of Alluvium of St. Acheul. Two Species of Elephant and Hippopotamus coexisting with Man in France. Volume of Drift, proving Antiquity of Flint Implements. Absence of Human Bones in tool-bearing Alluvium, how explained. Value of certain Kinds of negative Evidence tested thereby. Human Bones not found in drained Lake of Haarlem. CHAP. 9. WORKS OF ART IN PLEISTOCENE ALLUVIUM OF FRANCE AND ENGLAND. Flint Implements in ancient Alluvium of the Basin of the Seine. Bones of Man and of extinct Mammalia in the Cave of Arcy. Extinct Mammalia in the Valley of the Oise. Flint Implement in Gravel of same Valley. Works of Art in Pleistocene Drift in Valley of the Thames. Musk Ox. Meeting of northern and southern Fauna. Migrations of Quadrupeds. Mammals of Mongolia. Chronological Relation of the older Alluvium of the Thames to the Glacial Drift. Flint Implements of Pleistocene Period in Surrey, Middlesex, Kent, Bedfordshire, and Suffolk. CHAP. 10. CAVERN DEPOSITS, AND PLACES OF SEPULTURE OF THE PLEISTOCENE PERIOD. Flint Implements in Cave containing Hyaena and other extinct Mammalia in Somersetshire. Caves of the Gower Peninsula in South Wales. Rhinoceros hemitoechus. Ossiferous Caves near Palermo. Sicily once part of Africa. Rise of Bed of the Mediterranean to the Height of three hundred Feet in the Human Period in Sardinia. Burial-place of Pleistocene Date of Aurignac in the South of France. Rhinoceros tichorhinus eaten by Man. M. Lartet on extinct Mammalia and Works of Art found in the Aurignac Cave. Relative Antiquity of the same considered. CHAP. 11.