TTLOR QTJATEENAEY GKAVBLS. 75 



The gravel here includes some enormous blocks of limestone, 

 which have fallen into it from the rock above. When this stream 

 of gravel reaches the mouth of Bacon Hole, it turns sharp round into 

 the cave in a northerly direction, the angle of deposition changing to 

 25° jS"., the floor of the cave being about 30 feet above high water. 

 The limestone-gravel is covered with the black bone-earth in which 

 so many remains of Elephant and Ehinoceros have been found in the 

 cave, and is mixed with marine shells of species now living on the 

 coast and in the sea-sand. The whole is covered with stalagmite, from 

 2 to 3 feet thick, also sloping northwards at an angle of 25° N. There 

 are layers of stalagmite included within the limestone -breccia 

 (proving changes in the conditions of deposition at intervals) in the 

 cave ; but the gravel, although so much higher on the side of the 

 cliff to the west, does not fill up the whole of the cave. 



Looking at Dr. Buckland's drawings of caves, I think there is 

 evidence that much of the loose materials which have formed the 

 cave-deposit have passed downwards from the subaerial gravels on 

 higher levels, and continued through and over the caves as far as the 

 level of the sea, lake, or river below them. 



All English bone-caves are at levels within 150 feet of running 

 water at the present time, or of the sea ; and the great majority are 

 within the limit of 70 or 80 feet, their fossiliferous contents cor- 

 responding in level with all the known fossiliferous gravels con- 

 taining mammalian remains, including the Crag. 



In the period referred to, water ran apparently in the bottom of 

 the valleys which are now dry. 



All bone-caves seem, at the time of the deposition of their con- 

 tents, to have been in situations where water traversed them from 

 fissures above, and flowed into them from the side streams flowing 

 along the valleys in which they are situated, and they ofier evidence 

 of an immense rainfall at the period of the deposition of the cave- 

 gravels. The very washed condition of the materials found in bone- 

 caves, and the manner of accumulation, indicate that their contents 

 were more derived from above than below ; and the enormous pieces 

 of limestone which have fallen into the gravel at Kent's Hole and 

 Bacon Hole show that there must have been not only the action of 

 running water thereon, but the force of a column of water upon the 

 cave to dislodge the pieces from the roof. 



There are in all caves apertures in the roof, evidently worn by 

 water coming through it. I observed a good instance of this 

 in the Paviland Cave at Gower (close as it is to the sea), and another 

 in Brixham Cave. Some years since, I believe, it was remarked by 

 Dr. Buckland that there were always at least three openings in bone- 

 caves, two of them from higher levels than the mouth. 



The subaerial gravel comes down the steep slopes of the limestone 

 cliffs at Gower from a great height, and falls into a stratified marine 

 deposit, just as it falls down the steep cliffs into the Hopes-ISTose 

 raised beach, near Torquay, where it is mingled with the sea-sand, 

 pebbles, and shells deposited almost horizontally on the limestone 

 rock. 



