78 The Geology of the Portland Promontory, 



appearance is best shewn in the sketch and section. (See 

 Sketches S^ and SI) 



At Cape Bridgewater a wide flat platform occurs in the 

 hard ash beds some three or fonr feet above low water level; 

 it has once been quite a mile long, but it has been greatly 

 broken down. It is now 50 feet wide in places, and it is 

 level in a striking degree. (See Sketch 0.) 



At Liddle's watering place there are two ledges in the 

 basalt, one about five feet, and another at about 25 feet 

 above sea level. (See Sketch R.) 



All these platforms are now disappearing. The action of 

 the sea at its present level is highly destructive of the lower 

 ones, and in the very act of breaking them down it is carving- 

 out a still lower shelf some 15 or 20 feet below those which 

 are being destroyed. 



In consequence of this action, the ledges everywhere are 

 more or less breached; in many places they have been almost 

 entirely removed, and the remnant form ragged edged, but 

 broad flanges along the clifl" foot. 



Another evidence of the altered levels is supplied 

 \)j the caves at Bridgewater. They occur only in the 

 cKffs which are composed of volcanic ash. The largest 

 one is situated at the extreme point of this Cape, which 

 it drills through. My examination of it was hurried 

 by the nature of the weather, so that I had not time to 

 measure its dimensions, but I should say, that it is about 800 

 feet long, 60 feet wide, and 40 feet high. At low water the 

 floor of the south or ocean end is three feet above the tide, 

 and that of the north or Bridgewater Bay end, has then 

 about four feet of water over its sill. The sea flows into the 

 cave for a distance of about 70 feet in ordinary weather, and 

 the waves break upon a steepl}" inclined beach of sand and 

 shingle. 



Fifty yards west of this cave there is another one 

 which is about 50 feet long, 30 feet wide, and 10 feet high 

 near the entrance. It is situated about 30 feet above sea 

 level, and its mouth is almost closed up with grass-gi'own 

 clifl- talus. The upper end of the cavern is full of large and 

 small water- worn boulders. The fishermen told me that the 

 cave mouth had been choked with fallen rock as I saw it, 

 during all the twenty-five years of their residence at the 

 Cape. 



A third cave, known as the water cave, lies immediately 

 north of the big cave. Its floor is still so deep undei' water 



