160. Sills between shales and sandstones, Hound Point, Linlithgowshire 449 161. Section of Sill, Cramond Railway, Barnton, near Edinburgh 450 162. Intrusive dolerite sheet enclosing and sending threads into portions of shale, Salisbury Crags, Edinburgh 452 163. Intrusive sheet invading limestone and shale, Dodhead Quarry, near Burntisland 452 164. Spheroidal weathering of dolerite sill, quarry east of North Queensferry, Fife. 455 165. Two thin sills of "white trap" injected into black carbonaceous shale overlying the Hurlet Limestone, Hillhouse Quarry, Linlithgow 456 166. Dyke cutting the agglomerate of a neck. Binn of Burntisland 457 167. Boss of diabase cutting the Burdiehouse Limestone and sending sills and veins into the overlying shales. Railway cutting, West Quarry, East Calder, Midlothian 458 168. Side of columnar basalt-dyke in the same agglomerate as in Fig. 166 459 169. Dyke rising through the Hurlet Limestone and its overlying shales. Silvermine Quarry, Linlithgowshire 460 170. Junction of amygdaloidal basalt with shales and limestone, shore, half a mile east from Kinghorn, Fife 464 171. Columnar basalt, Pettycur, Kinghorn, Fife 469 172. Section across the Fife band of Sills 473 173. Section across the upper volcanic band of north Ayrshire. Length about four miles 474 174. Section showing the connection of the two volcanic bands in Liddesdale 476 175. Diagram to show the position of a mass of Upper Old Red Sandstone which has fallen into the great vent near Tudhope Hill, east of Mosspaul 476 MAPS I. General map of the Volcanic districts of the British Isles--_At the end of the volume_ II. Map of the Cambrian and Silurian volcanic region of North Wales _To face p. 256_ III. Map of the Old Red Sandstone volcanic region of "Lake Caledonia" in Central Scotland and North Ireland _To face p. 334_ IV. Map of the Carboniferous volcanic districts of Scotland _To face p. 476_ BOOK I GENERAL PRINCIPLES AND METHODS OF INVESTIGATION CHAPTER I