part.'}] MESS, ETC. OF TIIL DURHAM COAST. L91 



Iii my previous paper on the Durham Drifts I described some 

 water-deposited gravels, which occupy certain depressions in the 

 Bfagnesian Limestone immediately underlying the Main Drift. 

 One of the best examples of these occurs at a place known as 

 Limekiln Gill, 1 miles north of Hartlepool, and another near 

 Horden Point. 3| miles north-west of the last-mentioned occur- 

 rence. I gave an enumeration of the different stones that constitute 

 the gravel at Limekiln Gill, where an unusually large proportion 

 of gneisses and schists and of Scottish olivine-hasalts occurs. At 

 Hrst, 1 was inclined to think that these gravels were deposited 

 during a recession of the ice-sheet; but now, although the gravels 

 underlie the main Cheviot Drift, 1 rather fancy that they were 

 formed contemporaneously with the overlying Drift by subglacial 

 streams, which probably at the same time eroded the small valleys 

 wherein they are found. The general similarity of the material in 

 the gravel to that forming the Main Drift, and the rather in- 

 definite manner in which these gravels and sands merge into the 

 overlying Drift, also induce one to take this view of their origin. 



Prof. P. G. H. Boswell has recently described similar gravel- 

 deposits in the Suffolk Drifts, 1 and has compared them with 

 phenomena known in Sehleswig-Holstein as Fohrden or Fbrden. 



The evidence pointing to possible Interglacial episodes of any 

 long duration among the local English and Scottish Drifts of 

 Durham is, therefore, much less certain than that which relates 

 to the pause following the retreat of the Scandinavian ice. 



A mere superposition of one Drift upon the other, containing a 

 series of erratics derived from another area, does not necessarily 

 imply an Interglacial period; but it suggests that some interval of 

 time may have occurred, to account for the shifting of the direction 

 of flow and the readjustment of the ice-sheets. 



There is a very definite case, in the Hartlepool area, of super- 

 position of Drifts from different districts. An excavation to a 

 depth of about 40 feet below sea-level in connexion with dock- 

 exeavations at Hartlepool showed the presence of a Drift certainly 

 later than the Scandinavian Drift, but anterior to the Northern and 

 Cheviot Drift which caps the sea-cliffs at Hartlepool. 



This Boulder-Clay tills up an old Preglacial depression left by 

 the solution of a mass of anhydrite and gypsum at Hartlepool, and 

 contains erratics which, so far as I could see, were all of western 

 origin, among them being those that had been carried across the 

 Pennine Chain over the Stainmoor Gap. The opportunity that 

 I had of examining this Drift some years ago led me to conclude 

 that the Cheviot and other Northern erratics were absent from it. 

 Unfortunately, it is nowhere exposed at the surface, and consequently 

 the nature of its junction with the overlying Cheviot Drift cannot 

 be seen ; but it is possible thai a pause of the nature of an Inter- 

 glacial interval may have occurred between the deposition of thi> 

 Drift and the oncoming of the ice that carried the Cheviot Drift, 

 during which time the lobe of ice that crossed the Stainmoor Gap 



1 Q. J. G. S. vol. lxix (1913) p. till. 



