1865.] GODWIN-AUSTElSr PORLOCK EOEEST-BEDS. 5 



where to be seen on the inner or land-side, and the series of deposits 

 which it overlies show that, with reference to past conditions, the 

 most recent change has been one of slight depression. 



3. Marine silt. — On the land-side of the shingle ridge is an ex- 

 panse of salt-meadows, which at present are but occasionally, par- 

 tially, and for short intervals covered with water ; their level is at 

 the very upper limit of the Bristol Channel waters. From the ma- 

 terials thrown out from the dykes cut across this flat, as also in the 

 sections thus exhibited, the nature of the subsoil is well seen, con- 

 sisting of mud- deposits. Of these the uppermost is of a yellowish- 

 brown colour, and contains the shells of Scrohicularia j^iperata, with 

 the valves united, and of all ages. The presence of these shells 

 shows that the lower part of the Porlock valley was at one time in 

 the condition of a mud-flat, whollj?^ covered by the sea at every tide, 

 perhaps even permanently covered — that they were then at or near 

 the low-water level, or that the area was then depressed to the 

 extent of the difierence between high and low water; the range 

 of Scrohicularia piperata being from low water to four fathoms 

 beneath. 



Beneath the Scrobicularian mud of the meadows is a band of 

 vegetable matter, and under that a dark tenacious clay ; these are 

 better seen on the coast. 



4. Surface of Plant-growths. — At low water, and when the coast 

 has been swept clean of shingle, there is presented an expanse of 

 mud-deposits, with the stumps of trees studded about. The mud- 

 deposits occur in patches, owing to the action of the breakers, which 

 cut out portions ; around these patches are good sections. 



The uppermost mud- deposit, that with the Scrobicularise, is not very 

 resisting, so that it occurs only occasionally over the area left by 

 the tide ; enough, however, remains to show that it was at one time 

 spread out continuously, with a like composition and under the same 

 conditions as are presented by the beds beneath the meadows ; as 

 such it passes down beneath the present lowest water-level. Under 

 the yellow mud-deposit is a dark band, and when the mud has 

 been removed, the surface presents a layer of matted vegetable 

 matter, seemingly composed of roots. This seam is in places several 

 inches thick; on the underside roots descend into the subjacent clay, 

 showing that it has been an old surface of plant-growths. 



The stools of trees project slightly above the level of this old land 

 surface ; and upon it lie the trunks of trees. In every instance that 

 I examined, the surface of plant-growths was interposed between 

 the prostrate trunks and the underlying blue clay. There were 

 stems measuring from 10 to 20 feet and more in length. They 

 were mostly, if not altogether, the remains of trees which had died, 

 and become bare of bark, some much decayed before they fell ; they 

 projected above the surface, and had not sunk into it, or the surface 

 was firm, and not in the condition of a soft morass, when the trees 

 fell upon it. 



The roots and long leaves seemed to belong to an Iris, such as the 

 common " Yellow Flag." 



