"Vol. 56.] ME. F. W. HAEMER ON THE CRAG OP ESSEX. 733 



succession of foldings which shifted the area of deposition from time 

 to time. la this way, I think, a series of land-locked bays were 

 formed, one after the other, and were successively silted-up by 

 sediment, deposited, partly against the shore, and partly as banks 

 or shoals in the shallow water. Under such circumstances the beds 

 would dip, of course, in different directions on the opposite sides of 

 the bays. 1 



The position which these bays of the Eed Crag Period successively 

 occupied may be, I think, approximately denned. A reference to the 

 map (fig. 3, p. 714) will show that the geographical divisions of the 

 Crag, indicated by the differing character of their molluscan fauna, 

 are bounded,, broadly speaking, by the estuaries of the Stour, Orwell, 

 and Deben, which radiate from a point slightly east of Harwich : 

 the Waltonian Beds being confined to Essex, south of the Stour ; 

 the Newbournian occurring principally between the Orwell and 

 the Deben ; and the Butleyan being found only to the east of the 

 latter. 



If S. V. Wood's opinion be correct, that the Crag of Behtley (which 

 possibly represents that of the unexplored district between the Stour 

 and the Orwell) is intermediate in age between the Crags of 

 Walton and Newbourn, the whole of the K,ed Crag divides itself into 

 zones, the geographical limits of which coincide nearly with those 

 of the estuaries named. 2 Thirty-five years ago his son expressed 

 the opinion that the principal valleys of the East of England 

 form more than one series of concentric and inosculating arcs, 

 caused by tectonic disturbances which had their foci in the South 

 of England, 3 and at a later date he returned again to the subject. 4 

 The Crag district has certainly been subjected to some such folding 

 process, and the coincidences alluded to may possibly hereafter 

 prove worthy of further notice. 



Although it appears, from the researches of Mr. Lomas, that there 

 is little difference in composition between the sands of the Ked and 

 the Norwich Crags, except that the latter are more micaceous 

 (implying, I think, a closer connection, during their deposition r 



1 Instances of the silting-up of such bays in recent times are by no means 

 uncommon, especially in Holland. There is an area- south of the Hoek van 

 Holland, for example, which seems to me to represent exactly the condition 

 of East Anglia during the Red Crag Period. What was formerly a bay or 

 inlet is now nearly choked with shelly sand, which is, however, still accumu- 

 lating along the shores of the Maas estuary, on the edges of shoals, and in 

 channels formerly occupied by the river, being often bedded at a high angle, 

 dipping of course in different directions as the deposits follow the sinuous 

 winding of the banks. Farther inland, also, are similar beds of shelly sand — 

 the deposits, under similar conditions, of an earlier, though geologically recent 

 period. 



2 The Red Crag sea does not seem to have extended westward beyond the 

 limits of the Eocene beds, so as to reach the Chalk outcrop, or littoral 

 accumulations of chalk-flints would have resulted. Indeed at Sudbury, the 

 westernmost point to which the Crag has been traced, it shows evident signs of 

 thinning out against the old shore-line. 



3 Phil. Mag. ser. 4, vol. xxvii (1864) p. 180. 



4 MS. paper in the Geological Society's Library. 



