VARIED COMPOSITION OF THE NORTHERN DRIFT. 



531 



sea shells of existing species ; and that by these features, both the direction in which 

 the chief detritus was carried, and the epoch of its deposit are clearly established. It 

 would fatigue my readers, and convey no additional knowledge, to describe all the 

 situations where such phenomena have been observed. So numerous, indeed, are the 

 localities over the region in question, where northern bowlders and modern sea shells are 

 grouped together, that no doubt can exist, that the phenomena were due to a submarine 

 agency extending over a very large region. When we examine the details, very great 

 diversities of composition are, it is true, observable in the arrangement and composition 

 of the drift at different localities. Thus, in Cheshire, gravel, like that of a sea shore, 

 containing marine shells, has been discovered by Sir Philip Egerton in several localities 1 ; 

 while throughout the long, low tract, recently laid open by the cutting of the Grand 

 Junction Kail-road, the drift is a thick argillaceous mass, with here and there a 

 few fragments of northern rocks, and at intervals sea shells. Varieties of equal or 

 greater diversity occur throughout North Shropshire. About Marrington Green, seven 

 miles north of Shrewsbury, it is mostly a heavy clay, though in other contiguous places 

 a coarse gravel, in which shells have also been discovered. Near Wellington the fine 

 gravel is still more abundant in shells, and the gravelly deposits on the north-western 

 slopes of the Wrekin 2 are rich in various irregular layers of sand and gravel, the 

 latter both coarse and fine, with many quartz pebbles and bowlders of granite and 

 greenstone of northern origin, irregularly distributed with the shells. At this spot, 

 between hillocks of northern drift, is a small patch of purely local detritus, consisting 



1 See account of this gravel with sea shells by Sir Philip Grey Egerton, Bart. Geol. Proc. voh ii. p. 189. 



2 This locality was first noticed by Mr. Trimmer, to whom I am indebted for having called my attention to it. 

 The inferences which he drew from the appearances at this spot, of a former terrestrial condition of this part of the 

 country, which was supposed to have been covered with trees, and of its having been submerged by a sudden 

 inundation of the sea, were the result of a hurried visit. Subsequent examination, in which I was assisted by 

 Dr. Du Gard, having convinced me that the supposed stumps of trees covered by gravel, were nothing 

 more than the sharpened stakes and piles of a road (probably the old Roman via leading to Uriconium 

 (Wroxeter) over which some of the gravel from the adjoining hillocks had been thrown, I offered an expla- 

 nation of the deceptive phenomena. (See Proceedings of the Geological Society, vol. ii. p. 200.) Mr. Trimmer 

 has since acknowledged the error, into which he was drawn through the hurry of his examination, and I would 

 not here have alluded to the fact, did it not show how much caution is required in examining such phenomena, 

 when a geologist of Mr. Trimmer's ability, and who had thrown so much light on this branch of inquiry, was 

 for a moment misled by the specious appearances at this spot. The accompanying wood-cut explains the case. 



108. 



a. Sharp sand and gravel, with granite bowlders, and forming hillocks, b. Swampy depression between the hillocks 

 into which vertical piles had been driven, c. The piles and osier, d. Gravel thrown in from the adjoining hillocks to 

 form the old road. 



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