﻿1850.] TRIMMER ON THE ERRATICS OF NORFOLK. 



29 



rials derived, apparently, from the Kimmeridge clay : depth opened 

 about 12 feet. No fossils discovered in any part of the series. 



The following is the section at a pit about three furlongs east of 

 the last, on the south side of the road : — 



1. Sandy warp, filling pipes and cavities in No. 2, and varying in 

 depth from 1 to 4 feet. 



2. Sand and clayey sand, obscurely laminated, the lines of strati- 

 fication being transverse to the direction of the valley, with seams of 

 chalk pebbles, and fine chalk detritus ; the upper four or five feet 

 more calcareous and marly than the rest : total depth 1 5 feet. 



3. More clayey and with less appearance of lamination than No. 2. 

 Pebbles of chalk dispersed throughout : depth 1 2 feet ; based ap- 

 parently on sand. No fossils discovered in any of these beds. 



After passing an old pit on the north side of the road, in which the 

 nature of the deposits cannot be made out, another occurs also on the 

 north side of the road, a section of which, from east to west, or in the 

 direction of the valleys, is shown in fig. 2. 



In about five chains more these deposits cease, and chalk comes to 

 the surface, having only a covering of a sandy warp with dispersed 

 flints. This is the general covering of the higher grounds to the 

 east, resting either on the chalk, or on patches of chalky till with 

 oolitic fragments, and filling cavities in the subsoil on which it rests. 

 On Massingham Heath are some accumulations of gravel which I 

 have not yet examined ; similar accumulations of gravel in the upper 

 part of the Nar valley, by the road from Castleacre to Swaffham, ap- 

 pear reconstructed portions of the upper erratics. 



The extent of the Nar clay is only laid down on the Ordnance 

 sheets exhibited before the Society as far as Mr. Rose has traced it 

 in actual sections, but he has reason to believe that it extends some- 

 what further east, or nearly to Westacre. 



Postscript on the Contorted Strata of Cromer Cliffs. 



The phsenomena to be explained in the case of these contortions 

 (see above, p. 22) are the following : — 



1 . Horizontal strata, both of chalk and crag, below the till (Lyell, 

 Phil. Mag. vol. xvi. p. 363 ; and Proc. Geol. Soc. vol. hi. p. 173). 



2. The till, obscurely stratified, and passing upwards into lami- 

 nated blue clay, which again graduates into the yellow silt and sand 

 of the upper erratics. 



3. An irregular surface of this till, noticed by Sir Charles Lyell in 

 the following words : — " At some points where the stratified clay re- 

 poses on the till, the surface of the latter is very uneven, and was 

 evidently in that condition when the superior deposit was thrown down 

 upon it." (Proc. Geol. Soc. vol. iii. p. 176.) 



4. The contortions are confined to the hollows between the pro- 

 jecting points of till, and are the greatest where the surface of the 

 till is most irregular. I had asserted this (Proc. Geol. Soc. vol. iv. 

 p. 436 ; and Quart. Journ. Geol. Soc. vol. i. p. 219) before the ice 

 theory had occurred to me, as an indication that the till had exercised 



