246 P^of. Sedgwick on the Origin [April, 



supported many varieties of productions which are now so 

 deeply buried as to be reached only by occasional artificial 

 excavations. This remark at once explains the variable thick- 

 ness of different portions of the fen lands, and the extraordinary 

 appearances we sometimes meet with in digging through them. 

 For example : in excavating the foundations of the new lock on 

 the river Cam between Clay Hithe and Ely, they reached (after 

 passing through ten or twelve feet of common fen soil) a bed of 

 considerable thickness composed almost entirely of hazel wood 

 and hazel nuts. The wood could not, I think, have been drifted 

 from any great distance ; and the enormous accumulation of 

 nuts (many pecks of which might have been collected in the 

 space of a few square yards) seemed to be the production of an 

 ancient period when, year after year, the trees shed their fruit 

 on the ground, and there were no inhabitants to collect it. In 

 many other places, after passing through a thick coating of turf 

 bog and alluvial silt, we meet with the branches, trunks, and 

 even the roots of large timber trees. Some of these may have 

 been floated down during great floods from the neighbouring 

 high lands ; but the far greater number of them have unques- 

 tionably grown near the spots where we now find them. Exam- 

 ples of this kind are, 1 believe, supplied by almost all the exten- 

 sive fen regions in our island. 



Lastly, I shall briefly notice a class of facts which, although 

 admitting of a very easy explanation, have sometimes led to erro- 

 neous conclusions. In almost all the marsh lands which border 

 on the sea, the alluvium is separated from the old subjacent 

 strata by a quantity of marine silt, and sometimes by beds of 

 sea shells which appear to have lived and died on the spot 

 where they are now found. The extent of this marine deposit 

 towards the interior of the country plainly indicates the extent 

 to which the alluvial materials have been accumulated and 

 pushed down within the ancient line of the sea coast. But the 

 case is not always as simple as I have here stated it. The 

 lower portion of the marsh lands in question sometimes exhibit 

 several distinct alternations of marine silt and shells, with turf 

 bog and other freshwater deposits. Facts of this kind were (if 

 I have not been misinformed) observed in some of the lower 

 parts of the Eau Brink cut which was lately completed in the 

 neighbourhood of Lynn. Vve are not to suppose that such 

 facts indicate any sudden change in the relative level of land 

 and sea. All the alternations above described are below the 

 level of high-water, and naturallv result from the manner in 

 which the fen lands have been formed. We have only to recol- 

 lect that in the places alluded to, the tides have for many ages 

 been ebbing and flowing along a system of planes which have 

 been perpetually encroaching on the coast, and perpetually 



