Falls, Minn 255 75. Argillite implement found by H. T. Cresson, 1887 259 76. General view of Baltimore and Ohio Railroad cut, Claymont, Del. 260 77. Section across valley of the Somme 262 78. Mouth of Kent's Hole 268 79. Engis skull (reduced) 274 80. Comparison of forms of skulls 276 81. Skull of the Man of Spy 277 82. Tooth of Machairodus neogæus 281 83. Perfect tooth of an Elephas 281 84. Skull of Hyena spelæa 282 85. Celebrated skeleton of mammoth in St. Petersburg Museum 283 86. Molar tooth of mammoth 284 87. Tooth of Mastodon Americanus 284 88. Skeleton of Mastodon Americanus 286 89. Skeleton of Rhinoceros tichorhinus 287 90. Skull of cave-bear 287 91. Skeleton of the Irish elk 288 92. Musk-sheep 289 93. Reindeer 290 94. Section across Table Mountain, Tuolumne County, Cal. 294 95. Calaveras skull 295 96. Three views of Nampa image, drawn to scale 298 97. Map showing Pocatello, Nampa, and the valley of Snake River 299 98. Section across the channel of the Stanislaus River 300 99. Diagram showing effect of precession 308 100. Map showing course of currents in the Atlantic Ocean 314 101. Map showing how the land clusters about the north pole 319 102. Diagram showing oscillations of land-surface and ice-surface during the Glacial epoch 323 103. Diagram of eccentricity and precession 333 104. Map of the Niagara River below the Falls 334 105. Section of strata along the Niagara Gorge 336 106. Map showing the recession of the Horseshoe Falls since 1842 338 107. Section of kettle-hole near Pomp's Pond, Andover, Mass. 345 108. Flint-flakes collected by Abbé Bourgeois 368 MAPS. TO FACE PAGE Contour and glacial map of the British Isles _Frontispiece._ Map showing the glacial geology of the United States 66