ON ERRATIC BLOCKS OR BOULDERS. 



191 



Charnwood Forest and other Boidders, beneath marine sands and gravels, 



357 feet above the sea. 



At the base of Ketley gravel-pit, near "Wellington (Shropshire), is a bed 

 of very fine sand, containing a remarkable group of large angular and sub- 

 angular boulders. 



The sands and gravels extend to heights of from 25 to 30 feet, and yielded 

 13 species of raollusca, chiefly in fragments. 



Dentalium ? (very worn). 



Turritella terebra, Linn. 

 Natica eroenlandica, Beck. 



Cardium edule, Linn. 

 ■ echinatum, Litin. 



Cyprina islandica, Linn. 

 Astai-te borealis, Chemnitz. 



sulcata, Ba Costa. 



Tellina balthica, Linn. 

 Mactra solida, Li7in. 



Buccinum undatum, Linn. 

 Trophon truncatus, Strom. 

 Nassa reticulata, Linn. 



It wiU be observed that only one of these species is extinct in British 

 waters, viz. Astarte borealis. 



Throughout the sands and gravels waterworn pebbles are found, with 

 occasional masses of larger size, composed of the same material as the larger 

 boulders beneath. 



Beneath the marine sands and gravels some of the boulders are 8 feet by 

 5 feet, and theii- sides are planed very smoothly, and they have a subangular 

 shape. 



Out of 100 specimens, 80 per cent, consist of Permian sandstones from 

 the immediate neighbourhood. 



From the immediate neighbourhood also there are boulders of 



Mountain Limestone. I Silurian Limestone. 



Old Eed Sandstone. | Greenstone. 



The travelled boulders consist of 



Various granites, both red and grey (very numerous), probably from Cumberland or 



Scotland. * 



Eocks of Charnwood Forest, from a distance of 50 miles. 



One remarkable feature of this group of boulders is the intermixture of 

 boulders from the neighbourhood with those that have travelled from different 

 points of the compass, the whole group being buried beneath marine sands and 

 gravels, at the elevation of about 300 feet above the sea.. The elevation of 

 Ketley village is 357-319 feet above the sea. 



For the boulders of the neighbouring drift of the Severn valleys reference 

 may be made to an exhaustive paper by Mr. G. Maw (Quart. Journ. Geol. 

 Soc. vol. XX. p. 130). 



The Geological Section of the Birmingham Natiu-al-History Society has 

 commenced a systematic examination of the boulders of the Midland district, 

 and has favoured the Committee with the following preliminary lleport : — 



" The Ordnance Map of the neighbourhood of Birmingham has in the first 

 place been divided by ruled lines into squares of one inch side, each square 

 enclosing a representation of one square mile of country. Enlarged maps, on 

 the scale of six inches to the mile, were prepared from this ; and on these 

 enlarged maps the boulders were to be marked by circles, the number of 

 concentric circles representing the diameter of the boulder in feet. For col- 

 lecting specimens of the rocks of which the boulders are composed, bags were 

 made, and numbered corresponding to each square on the map ; at the same 

 time notes were to be made of any specimen that was of unusual interest. 



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