Page:Quarterly Journal of the Geological Society of London, vol. 25.djvu/168

74 dation than can be obtained from natural sections in brooks, where the different gravels are moved and mixed up together by the recent action of water. The total thickness of the gravel is 18 feet.

Near this well-known cave limestone-gravel lies on a very steep cliff of limestone, in some places sloping as much as 70° to the sea. The top surface of this gravel lies at an angle of 34°; and the bottom fills up the concavity in the limestone rocks. The path to the cave passes over this gravel, which is entirely composed of sharp angular fragments of limestone, cemented together by carbonate of lime, a process which seems to have been common in the Quaternary period. I noted, on a previous occasion, the manner in which lime-stone-blocks had been observed by Mr. Pengelly to be cemented together near Torquay, at a considerable height above the sea.

The mass of limestone-gravel falling down this cliff, accumulating in concavities, and sloping to the sea at an angle of 32° S. on the surface, may be seen at a height of 120 feet above the sea. In its course from the high cliffs above, it seems to have sent off a vein of gravel at a point 70 feet above the sea, to the east, at an angle of 11°.

This vein of angular gravel thickens to the east, and expands to a thickness of 25 feet when it reaches the opening in the limestone cliff called Bacon Hole, a deep fissure penetrating a long distance into the limestone cliff, in a northerly direction, and having a roof with an acute angle, which has often been described.