and on the Drift of the Eastern Counties. 191 



into beds that unquestionably underlie, and pass gradually into, 

 the great deposit of sands and gravels which cover the whole of 

 Suffolk and are extensively developed in Norfolk and Essex, and 

 which themselves pass upwards, without the least break, into 

 the more widely spread northern Clay drift. 

 . The geological conditions under which the peculiar formation 

 of beach Crags was accumulated demands a special considera- 

 tion, from the circumstance that it seems to afford a solution of 

 the question of the relationship between the Red and the Fluvio- 

 marine Crag. The latter, occurring at intervals from Norwich 

 to Thorpe, near Aldbro', ceases almost at the place where the 

 Red Crag first appears. The absence of any superposition in 

 the two formations has hitherto left their relative ages in doubt; 

 and since fluvio-marine conditions obtain in the one, and purely 

 marine conditions in the other, inferences that might otherwise 

 be drawn from a comparison of their fauna are consequently of 

 less value. 



The unvarying N.N.E. to S.S.W. direction presented every- 

 where south of Hollesley, and from Melton and Bealings on the 

 west to Bawdsey Cliff on the east, is precisely that possessed by 

 the trend of the Coralline Crag, uncovered by any Red beach 

 Crag, from the point where it first comes to the surface north 

 of Aldbro' to its termination at Gedgrave. This also is the 

 direction which was detected by Sir Charles Lyell in the cliff of 

 Coralline Crag buried in Red Crag at Sutton. According 

 to the view I take, it is, in reconstructing the bay of the Red 

 Crag, only necessary to assume the prolongation of that ridge 

 or barrier of Coralline Crag in the same direction from Gedgrave 

 southwards, over what is now covered by the sea. (See the con- 

 tinuation-line suggested on the map.) The production of this 

 ridge, composed as it is of the Bryozoon-bank of hard rock, 

 capable of resisting the waves, would give rise to a long tongue- 

 shaped bay running up between it and the shore-margin of soft 

 London Clay, in which these successive accumulations and de- 

 structions of beach-deposit might readily take place during 

 slight intervals of subsidence. The direction of beaching up, 

 then, would be determined by the particular contour of the bay 

 and the direction from which the sea had access to it. The evi- 

 dence available to show that the beach Crags never covered the 

 greater part of what now remains of this barrier, although ne- 

 cessarily only negative, is of the strongest character that such 

 evidence can afford. Firstly, it is along this line, and there only, 

 that the Coralline Crag occurs uncovered by the Red ; secondly, 

 the Coralline Crag consists of three parts, — the lower of sandy 

 beds, rich in Mollusca, preserved nearly as they lived; the middle 

 of the rocky Bryozoon-bank; and the upper of a thin bed, some 



