1856.] MOGGRIDGE SWANSEA DOCKS. 169 



ing every undulation, basin, and channel as when formed ages since 

 by the thundering ocean-wave. With regard to the period and 

 method of their formation, I must leave the subject to more ex- 

 perienced heads than mine, — gratified should the correct notice and 

 illustration of them afford interesting matter for discussion to the 

 members of the Geological Society. 



2. On the Section exposed in the Excavation of the Swansea 

 Docks. By M. Moggridge, Esq. 



[Communicated by Sir Roderick MurcMson, V.P.G.S.] 



Ancient legends which point out different courses for the Swansea 

 and Neath Rivers from those which they at present take, induced 

 me to watch the progress of the excavations made for the Swansea 

 Docks from their commencement. Of my success in tracing the old 

 bed of one if not both of those streams I need not here speak, — the 

 yeologieal features are those to which I would draw attention. 



The Swansea Docks consist of a " half-tide-" and a floating-basin. 

 They are situated on the brink of the sea, which lies to the S.E., 

 while the N.E. boundary is the harbour through which flows the 

 river Tawe. The entrance is from the harbour into the half- tide 

 basin ; and thence, through a large lock, vessels will pass into the 

 main dock. The greater part of the stuff" which has been removed 

 consists of gravel and rolled stones, many of which have been 

 transported full twenty miles. 



The sections exposed varied greatly in diff*erent parts of the cuttings, 

 but the best and most regular occurred at the N.E. end of the main 

 docks exhibiting (August, 1853) : — 



1. Made ground, sand, and loose gravel of variable thickness 

 from 20 feet to 6 feet. 



2. Peat, with leaves, trees, &c., 2 feet. 



3. Blue marine clay, 8 feet 6 inches. 



4. Peat of rather greater density than No. 2, 10 inches. 

 5c Blue marine clay, 4 feet 1 inch. 



6. Peat with trees, 3 feet 1 inch. 



7. Brown clay and gravel, not penetrated. 



The bottom of the dock is 24| feet below high water and A\ feet 

 above low water at ordinary spring tides. 



I have said " marine clay," because I found imbedded in it Scro- 

 bicularia piperata, a sea-shell still living on these coasts and burrow- 

 ing in a similar clay now forming in some of our estuaries. The 

 valves of this shell are dispersed in pairs throughout the whole of the 

 clay, but abound most in the upper portion of each stratum. 



As to the peat, I have been met with the remark, that it might 

 have been brought together by submarine currents, and that there- 

 fore the alternation of sea and land was not proved. To this I 

 answer that in very many cases roots still attached to plants which 

 constitute a portion of the peat descend into and ramify among the 

 clay, proving that those plants lived and died where they now are, 



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