256 MR. T. COJDEINGTON ON SUBMERGED ROCK-VALLEYS [Aug. 1 898, 



much as 10 feet thick, over which is gravel, with loose rocks, and 

 then silt and mud, also containing loose stones. These deposits are 

 about 15 feet thick, and rise considerably above half-tide level. It 

 is unfortunately not known whether the rock- fragments are of 



limestone, a talus from the cliff 

 above, or whether they consist 

 of rocks from a distance. Por 

 170 feet the rock-bottom was 

 unexplored, but at 300 feet 

 from the face of the cliff is the 

 group of six 8-foot cylinders 

 forming the main pier of the 

 bridge, and occupying an area 

 of about 50 X 20 feet. They 

 were sunk through 44 feet of 

 overlying deposits to the rock, 

 which was reached at 31 to 

 42 feet below the level of low 

 water. The three cylinders 

 north - west of a diagonal 

 across the pier are upon lime- 

 stone, dipping 40° east, and 

 the three cylinders on the 

 south-east are upon what is 

 recorded as ' hard sandstone,' 

 ' sandstone alternating with 

 red marl,' ' hard red marl and 

 sandstone in thin beds.' It 

 would seem that the fault 

 shown on the Geological Sur- 

 vey map not far off, with a 

 downthrow to the west, is here, 

 and that the beds south-east 

 of the limestone are Old Red 

 Sandstone. 



At 100 feet west of the main 

 pier is another pier, of three 

 6-foot cylinders, and at 100 

 feet still farther west a similar 

 pier. All these cylinders are 

 founded on dark Carboniferous 

 Limestone, at 13 to 16 feet 

 below the level of low water. 



The rock-bottom was traced 

 by boring all the way from the 

 main pier to 75 feet west of the westernmost pier, where it was 

 10 feet above low -water level, still under 25 feet of clay, gravel, and 

 silt. "Within about 350 yards to the westward on the line of the 

 section, the limestone reaches the same height as it does east of the 

 river. 



