1893.] evidence fur the Recurrence of Ice Ages. 121 



40. Slickensides along bedding plane, interrupted by worm tubes. 

 Bala Beds, Constitution Hill, Aberystwith. 



41. Slickenside fluted by lumps and grains seen on the specimen. 

 Landslip in Barton Clay, with some surface material dragged in. 

 Barton Cliff", Hampshire. 



42. Fault breccia smoothed and scoi^ed by movement against the wall 

 of the fault. Cove below Daddy Hole, Torquay. 



43. Part of fault face in Silurian. The Grove, Bodfari, near St Asaph. 

 Showing strong parallel fluting. 



44. Fluted and slickensided face of grit with film of mineral. Nodale, 

 Stanstield Moor. 



45. Fluted and slickensided face of lode-stuff" with film of mineral. 

 Derbyshii-e. 



46. Curved slickenside on slate rock. Quarry north of Aberystwith. 



47. ' Fluted structure due to hard beds in rock, aff"ected by imperfect 



cleavage and joints. Tirgwyn, three miles E.N.E. of St Asaph. 



48. Part of a glaciated Silurian boulder from the drift of Maes Mynan 

 near Caerwys in North Wales. The strise seen on this fragment 

 however are almost all due to the weathering out of softer lines 

 in the rock. 



49. Fragment of Devonian sandy shale with the joints weathered out 

 into grooves. Foot of Rough Tor, about a mile from Okehampton 

 Station by the track leading up to Yes Tor, Dartmoor. 



50. Finer bed in the conglomerate at the base of the Carboniferous 

 Rocks showing striation across the matrix and included pebbles. 

 Holbeck Gill, between Dent and Garsdale, Yorkshire. 



51. Do. do. 



52. Scratched stone from do. do. 



53. Do. do. 



54. Striated pebble in Triassic conglomerate. Portskewet, Mon- 

 mouthshire. 



55. Hard lump included in the shale at the base of the Cambrian 

 Grit. IST.E. of Glyngarth, Menai Straits. 



56. Pebble from the conglomerate twisted into the Archaean Gneiss. 

 Obermitweida, Annaberg. 



57. Small boulder crushed and broken, and the several parts moi-e 

 or less separated and then cemented together' in the conglomerate 

 by mineral matter. Basement bed of the Carboniferous. Holbeck 

 Gill, between Dent and Garsdale, Yorkshire. 



58. Do. do. do. 



59. Do. do. do. 



60. Do. do. do. 



61. Surface of Coniston Flags smoothed and striated (slickensided) 

 by thrust at base of Conglomerate (Basement Bed Carboniferous). 

 Holbeck Gill, between Dent and Garsdale. 



62. Do. do. 



63. Stylolites from the London Clay, Sheppey. 



64. Flint which has been forced by earth movement through the 

 enveloping chalk. 



65. Fossils thrust through surrounding material. 



