174 S. V. Wood, Jim. — Reply to Mr. James Geikie. 



deposits liaYing followed the ice edge as- it receded, and the succeed- 

 ing deposits having overlapped for a certain distance the preceding 

 ones, but having been principally laid down upon places that were 

 previously occupied only by ice, — a process which is, to my apprehen- 

 sion, very clearly exhibited by the Great Chalky Clay and its over- 

 lying purple clay, as we follow them northwards from the Humber 

 towards that edge of the Eastern Moorlands which comes down to 

 the coast at Scarborough, 



During this recession of the ice, the mountainous districts which 

 formed its chief gathering ground would be the last vacated by it ; 

 , and, consequently, the deposits of and contiguous to those regions 

 ■would be the latest in the whole sequence ; and this physical hypo- 

 thesis exactly accords with the palseontological evidence. Thus, the 

 position of the Bridlington bed is at the horizon in the purple clay, 

 where the chalk debris begins greatly to fall off ; and as we ascend 

 in the section of that clay, this debris ceases altogether, showing the 

 eventual total release of the 'chalk from its icy cap, the debris from 

 rocks lying nearer to the mountainous region than the Chalk Wold 

 remaining undiminished. Contrary now to this, the East Anglian 

 beds are equally chalky throughout, being chiefly made up of that 

 material. The fauna of this Bridlington bed we see is decidedly 

 newer than that of the East Anglian beds, while on the other hand, 

 it is also clearly older than the Scotch Till (taking the Caithness 

 clay as exhibiting the fauna of the Till period), tallying in this way 

 with its intermediate physical position between the period of the 

 East Anglian beds, when the ice-sheet extended over the chalk 

 country into Norfolk and Suffolk, and the period of the Scotch Till 

 and Caithness Clay, when the sheet had receded altogether from the 

 Yorkshire Wold and other chalk districts, but still retained in its em- 

 brace the mountain districts of the North of England and of Scotland. 



The East Anglian Lower Glacial therefore appears to me to form 

 the nether, or older, extremity of the Glacial series, and the boulder 

 sands and gravel of the mountain districts of Britain (whose fauna 

 may be typified by that of the Moel Tryfaen bed) the upper, or 

 newer, extremity ; and as I take it that it was only near the ice-edge 

 where deposits of such a thickness as would escape denudation 

 during the subsequent emergence were formed, the newer terms of 

 the series are thus unrepresented over the chief part of the areas 

 where the older terms occur. The East Anglian Glacial beds are 

 more distant than any others in Britain from the mountainous 

 districts; and we should 'thus look for an older facies in any fauna 

 they might furnish, than would be afforded by the Glacial beds of 

 any other part of Britain. Having found the faunae of these respec- 

 tive areas to present just this feature, are we then to shut our eyes 

 to it and ignore its obvious bearing ? 



The Hessle beds do not, I contend, belong to the Glacial period at 

 all. They followed the re-occupation of the terrestrial surface of this 

 country by the Great Mammalia,^ of the rivers by Cijrena fiuminalis, 



1 Elephas primigenius and the horse are mentioned by Prof. Phillips as having 

 occurred in abundance in the gravel below the Hessle clay at Hessle. 



