548 



Fisher — Denudations of Norfolk. 



the forest upon the old muddy bottom. To discuss the cause of this desiccation is 

 beyond the province of the present paper, but I am inclined to think it cosmical, 

 or at any rate one affecting so large a portion of the earth's surface as not to have 

 left any traces of its occurrence in local faults, or appreciable undulations of the 

 strata. 



There is reason to believe that the elevated condition of the surface must have 

 lasted for a long period, and it seems from the fauna of the Forest bed to have been 

 synchronous with a warmer climate, than that which preceded or followed it. 



I am unable to describe the condition of the Forest bed from my own observa- 

 tion, since it has never been uncovered, when I have visited the coast. The por- 

 tion of a Forest bed, which is always to be seen near Happisburgh, may pro- 

 bably, I think, belong to another and much later period. Mr. Gunn's account 

 of the old forest, as it appeared in the winter of 1862, informs us that the 

 indurated gravel, and occasionally the argillaceous sand (the soil I presume), 

 hardened by oxide of iron, were found to lie in low ridges or undulations, five or 

 six feet above the ordinary level of the Forest bed, and at unequal distances. This 

 arrangement, I should conjecture, was owing to the distribution of the iron oxide 

 or cementing matter determining the undenuded parts. The Forest soil on the 

 beach, he adds, was seen to be twisted and contorted in the most remarkable man- 

 ner, lying in the space of 20 yards in every possible direction, and occasionally 

 broken into fragmentary masses. But so far from being surprised at the partial 

 denudation suffered by this deposit as seen upon the beach, the wonder is that 

 any of it remains ; and if the area where it is seen had not been flat low-lying 

 land, so that in the process of going down (or possibly of being overflowed from a 

 river breaking its banks in times of flood), it had become protected by a coating of 

 sand and silt, when the sea water was admitted afterwards, it would have all been 

 swept away, as the water gained upon it. For an expanse of water of only mode- 

 rate size gets up breakers on its shores, and these cut away the land, so that all 

 traces of its original subaerial surface become obliterated ; and in a gradually 

 sinking area this process must continually go on as the water advances further and 

 further upon the land, unless the land should go down by one sudden engulphment, 

 and the sea flow over it before the waves have had time to cut away the surface. 

 Indeed, I should suspect that this result of a sudden influx of the sea may have 

 occurred in the present case, not by a paroxysmal sinking of the land, but by the 

 destruction of some seaward barrier, which converted what had been first forest 

 land, and next a freshwater lagoon, into an estuary. 



It is probable that the Forest extended towards the Chalk upland as far as the sub- 

 soil of clay extended, but from the causes just explained, it is not probable that 

 vestiges of it would always be preserved. Indeed, to say nothing of the risk of 

 denudation, the only conditions under which vegetable matter, or even the hard 

 parts of animals, can long resist decomposition, is by their being submerged and 

 covered with clay. 



Hence as the land continued to sink to a lower and lower level, the laminated 

 strata of sands, clays, and gravels would accumulate and extend westward, but the 

 Forest bed would not be preserved beneath them, except at those levels where it 

 had become submerged before the area communicated with the open sea. 



If it be asked how far the waters extended which drifted the laminated beds into 

 the position now occupied by them, I am not aware that there is any very definite 

 ground of answer. But their close relationship to the Crag beds in position (not 

 in time, because the forest intervened,) would lead one to infer that the coast line 

 differed little from the coast line of the Crag, though it may have possibly advanced 

 somewhat further upon the Chalk land. 



Subaerial denudation must necessarily have been going on upon the high lands 

 during the period of the Forest : but all records of it must have perished. 



The great Glacial series of deposits follows next in ascending order. In speaking 

 of these I shall adopt Mr. Searles V. Wood junior's division into Lower, Middle, 

 and Upper Drift ; and I am bound to say that I believe he has rendered very great 

 service to Geology in making out their sequence, and in mapping the outcrop of 

 the three members of that great formation. ^ 



» Messrs. Wood and Harmer subsequently read an elaborate paper on the Glacial and Post- 

 glacial structure of Norfolk and Suffolk. See an abstract Geol. Mag,, vol. V. p. 452. 



