476 MR. A. STRAHAtf ON SUBMERGED LAND-SURFACES [Aug. 1896,. 



for this purpose that I had the opportunity of examining in the 

 course of my duties on the Geological Survey in 1895. 



The history of the invasion of the river-valley by the sea through 

 the gap mentioned clearly reveals itself in the sequence of deposits ; 

 but, more than this, the river-alluvium presents a series of freshwater 

 beds and land-surfaces, whose position in relation to the present 

 sea-level proves that a great change in the level of the land took 

 place during and after Neolithic times. 



On some of my visits to the Dock I had the advantage of the 

 assistance of Mr. F. T. Howard, F.G.S., and of Mr. J. Storrie, to the 

 latter of whom I am indebted for much information respecting the 

 sections exposed in the earlier dock, and also for the identification 

 of some of the specimens from the present excavation. To my 

 colleague Mr. Clement Reid, however, I am indebted for a thorough 

 examination of the whole of my specimens, and for the identification 

 of both plants and shells, together with critical remarks thereon.. 

 Prof. Rupert Jones, F.R.S., has kindly furnished me with the list 

 of ostracoda, etc., given in the Appendix. 



The natural topography of the tract is preserved on the 6-inch 

 Ordnance maps, Glamorgan L. and LI. (published 1885, surveyed in 

 1878), from which the accompanying map (p. 475) has been prepared. 

 The high-water mark of ordinary tides being shown on these maps 

 in the usual manner, we are able to see that the whole of the new 

 dock is being excavated in ground that was covered at high tide, 

 though it pretty closely approaches the eastern shore at a point 

 known as Warren Tump (now levelled). The extreme southern 

 point of the dock lies near what was formerly a shoal known as 

 Coston Rock. In both these parts the excavation is principally in 

 the solid rock, but elsewhere it generally fails to reach the bottom 

 of the alluvial deposits. These may be enumerated as follows : — 



1. Blown Sand. "j 



2. Scrobicularia-clay. I Recent subaerial and tidal deposits. 



3. Sand and gravel. J 



Strong line of erosion. 



4. Blue silt, with many sedges. 



5. The Upper Peat Bed ; about 4 feet below Ordnance-datum. 



6. Blue silty clay, with many sedges. 



7. The Second Peat, a thin layer only. 



8. Blue silty clay, as no. 6. 



9. The Third Peat, many large logs and stools, and roots in place underneath - 7 



about 20 feet below Ordnance-datum. 



10. Blue silty clay, with reeds, willow-leaves, and freshwater shells. 



11. The Fourth Peat, with large trees and roots in place. Land-shells 



numerous. 



12. An old soil with roots and land-shells ; about 35 feet below Ordnance- 



datum. 

 Rock in place. 



By the kindness of Mr. James Bell, Engineer to the Barry Dock 

 Company, I have been furnished with the following levels : — 



