Rev. T. G. Bonney — Ice-Scratches in Derbyshire. 269 



The absence of Eeindeer at Crayford is an unusual circumstance 

 iu connexion with the presence of worked flints.' 



I noticed that the Brick-earth in Slades Green Pit is deposited 

 against an old talus of chalk, which had previously fallen from a cliff 

 which formed the side of the river- valley at that place. This talus 

 may be seen by going through the tunnel on the south side of the 

 pit, and examining the chalk-pit into which it opens. The chalk 

 next the tunnel consists of fallen rubble, and, although the junction 

 is not exposed, it is clear that the brick-earth must abut upon it. I 

 should argue from this, that the river or estuary- waters remained for 

 some while at a considerably lower level than that which they after- 

 wards attained, when the flood-waters deposited the brick-earth. 

 Such a rise of the wafcer-level seems to require subsidence to account 

 for it, and that the subsidence brought the Thames valley a few 

 miles lower down, under strong tidal action, appears to be shown by 

 the cross-bedded sands of Gray's Thurrock. Whatever it may have 

 been at some periods of its history, the Thames could scarcely have 

 been at that time a tributary of the Ehine, but must have possessed 

 an estuary of its own as at present, and probably the tide came even 

 higher up then than it does now. 



Subsidence, at a period which was in all probability nearly the 

 same, is evidenced by the estuarine beds which overlie the mammalian 

 deposit at Clacton, in Essex.^ 



Mr. Dawkins has furnished me with the following list of Mammalia 

 which have been obtained from the Brick-earth at Crayford : 



Rhinoceros megarhinus. 



hamitwchus. 



• — tichorhinus. 



Ovibos moschatus. 

 Bos urus. 



■ bison. 



Cervus elaphws. 



Elephas antiquus. 



primigetiius. 



Equus caballus. 

 Felis leo (var. speloea). 

 Cams lupus. 



vulpes. 



Arvicola. 



IX. — Ice Scratches in Derbyshire. 

 By the Rev. T. G. Bonnet, M.A., F.G.S. 



AT page 440, Vol. II., of the Geol. Mag., is a very careful and 

 accurate description, by Mr. A. H. Green, of certain markings 

 on an exposed rock near Matlock, locally named the Bloody Stone. 

 These markings he refers, though not without some hesitation, to 

 the action of ice. I have lately visited Matlock, and twice examined 

 this spot. On the first occasion the surface was wet from recent 

 rain, on the second it was dry. 



It was at once obvious that, as Mr. Green has stated, " these mark- 

 ings must be one of two things, either ice scratches or slickensides." 

 At the first glance the former seemed the most probable, but a closer 

 examination caused me to incline ultimately very strongly to the 

 latter, and for the following reasons : — 



The chert appeared in several places to occur rather as a super- 



1 Dawkins, Geol. Journ., vol. xxiii., p. 101. 



2 See Mr. J. Brown's section in the writer's notes on Clacton. — Geol. Mag., 

 Vol. v., p. 213. 



