28. Section of neck filled with massive rock 68 29. Successive shiftings of vents giving rise to double or triple cones 70 30. Section to show the connection of a neck with a cone and surrounding bedded tuffs 71 31. Diagram illustrating the gradual emergence of buried volcanic cones through the influence of prolonged denudation 75 32. Dyke, Vein, and Sill 80 33. Section of Sill or Intrusive Sheet 83 34. Ideal section of three Laccolites. (After Mr. Gilbert) 86 35. Diagram illustrating the stratigraphical relations of the pre-Cambrian and Cambrian rocks of the North-west Highlands of Scotland 112 36. Map of a portion of the Lewisian gneiss of Ross-shire 118 37. Section showing the position of sills in the mica-schist series between Loch Tay and Amulree 124 38. Sketch of crushed basic igneous rock among the schists, E. side of Porth-tywyn-mawr, E. side of Holyhead Straits 128 39. Section across the Uriconian series of Caer Caradoc 132 40. Map of the volcanic district of St. David's 146 41. Section showing the interstratification of tuff and conglomerate above Lower Mill, St. David's 154 42. Basic dyke traversing quartz-porphyry and converted into a kind of slate by cleavage. West side of Llyn Padarn 162 43. Section of well-cleaved tuff, grit and breccia passing up into rudely-cleaved conglomerate and well-bedded cleaved fine conglomerate and grit. East side of Llyn Padarn 163 44. Section of Clegyr on the north-east side of Llyn Padarn, near the lower end 164 45. Section across the Cambrian formations of the Malvern Hills, showing the position of the intercalated igneous rocks. After Phillips 170 46. Section across Rhobell Fawr 178 47. Section at the Slate Quarry, Penrhyn Gwyn, north slopes of Cader Idris 180 48. Sketch-section across Cader Idris 182 49. Section across the Moelwyn Range 185 50. Section across the anticline of Corndon 190 51. Structure in finely-amygdaloidal diabase lava, south of mouth of Stinchar River, Ayrshire 193 52. View of Knockdolian Hill from the east 194