Vol. 54.] IN SOUTH WALES, DEVOID, AND COENWALL. 273 



Torbay, and 14 miles from the shore in West Bay between the Exe 

 and Portland. About the same elevation of the land would be 

 necessary to raise the bottom of the rock-valley at the entrance to 

 Hamoaze to low-water level ; though, as its bed now lies, much less 

 would lay all Plymouth Sound dry. The 10-fathom line on the 

 chart is well outside the Sound, and the 20-fathom line only | to 1| 

 mile farther out. 



An elevation of the land to the extent of 120 feet during the 

 Glacial Period is a very moderate supposition. It was probably much 

 more. Whatever it was in the areas under notice, there must have 

 occurred subsequently the depression required to bring the raised 

 beaches down to the sea-level, after that the elevation necessary for 

 the growth of peat and forests now far below the level of the sea, 

 and then the depression of the land to its present level. 



To the last period of the long duration of time covered by these 

 and other movements the greater part of the deposits now filling up 

 the submerged valleys appears to belong. In the South Wales 

 sections the upper part of the silt is quite recent, being the Scrohi- 

 cularia-clsij common in the Bristol Channel. Beneath this, in the 

 Chepstow cylinders the clay, silt, and sand containing stalks of plants, 

 nuts, leaves, and timber extend downward to the red gravel with 

 boulders, and in one cylinder oak-timber was found in the gravel 

 close to the rock-bottom. In the cutting east of the Severn Tunnel, 

 the silt with peat-beds extends down to the sand over the gravel- 

 with-boulders. In many sections on the borders of the Bristol 

 Channel gravel is found beneath the silt with peat, the division be- 

 tween them being marked. 



The submerged rock- valleys around Plymouth are filled in with 

 recent marine deposits. There are beds of oysters in the sand 

 of the Laira section, and many oyster-shells and fragments of 

 other shells were found in the Saltash cylinders. A marine deposit 

 appears to extend down to the clay-with-stones in the Tavy and 

 the Coombe Lake sections, and down to the rock at Saltash, except 

 where patches of yellow clay, gravel, and stones were found on the 

 rock. 



In the stream-tin sections in Cornwall, the deposits down to the 

 ' tin-ground ' are also of recent date. At Pentuan oak-trees were 

 found rooted in the tin-ground. Peat immediately cverlies the tin- 

 ground at Sandycock and Poth in the neighbouring valley, under 

 36 feet of recent marine and fluviatile deposits. In Eestronguet 

 Creek horns and bones of deer were found in the silt over the tin- 

 ground, and at Narabo Inlet human skuUs were found in the bed 

 immediately over the tin-ground. In these sections there is an 

 alternation of marine and freshwater deposits. Higher up the 

 valleys where the marine deposits do not extend, the contents show 

 that the beds down to the tin-ground are of quite recent date. In 

 the tin-ground itself no organic remains have been discovered. 



It thus appears that the upper portions of the deposits filling in 

 the submerged rock-valleys down to the gravel-with-boulders in 

 the Bristol Channel, to the clay-with-boulders near Plymouth, and 



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