SHEPPARD : SHAP GRANITE, ETC., IN LINCOLNSHIRE. 337 



England/ So far as I am concerned, I shall be glad at any time to 

 render what services I can, and if any of our Lincolnshire friends 

 would care to have specimens of the commoner of the Norwegian 

 rocks, I shall be only too pleased to have the opportunity of 

 supplying them. Mr. Tuckwell, the Secretary of the Boulder 

 Committee, would, I am sure, answer any inquiries respecting the 

 boulders of his county, or receive any information respecting the 

 erratics of any part of Lincolnshire. 



With regard to the manner in which the various far-travelled stones 

 have reached their present positions, the following is the view generally 

 accepted by those geologists who make a special study of the subject. 



During the last of the series of great geological events, viz., the 

 ' Glacial Period/ the climate gradually grew colder and colder, and 

 the snow accumulated on the great hill-centres of the Northern 

 Hemisphere, and probably of the whole world. The cause of this 

 it is not necessary at the present moment to discuss. 



As the accumulated snow was in excess of the quantity annually 

 melted, glaciers began to descend, first of all into the Irish Sea from 

 all sides, namely, North Wales, Ireland, the Clyde, and the English 

 Lake District, and into the North and Baltic Seas from the 



Scandinavian Mountains. Year after year, the glaciers increased 



in magnitude, and the ice flowing into the Irish Sea (which is only, 

 comparatively speaking, very shallow) coalesced, entirely excluding 

 the water,! and finally diverted the ice from the Lake District over 

 the Lower Stainmoor Pass into Teesdale, down which it flowed 

 towards the North Sea. 



In the meantime the ice from the Scandinavian Mountains, 

 advancing in a huge sheet (which would resemble the Greenland 

 Ice-cap of the present day), encroached upon the waters of the 

 North Sea,j| and, after reaching our shores, the two glaciers flowed 

 down the east coast. The Norse ice brought with it the boulders 

 of rhomb-porphyry, augite-syenite, etc., while the Teesdale glacier 

 carried the boulders of Shap Granite, ' Brockram/' and other Lake 

 District rocks, together with boulders of carboniferous limestone 

 from the sides of Teesdale itself. It was at this stage, when the 

 Scandinavian arrested the progress of the Teesdale ice, that the 

 bulk of the latter glacier was diverted down the Vale of York and 



* The subject has been fully dealt with by Mr. P. F. Kendall, F.G.S., in 'The 

 Cause of an Ice Age.' Trans. Leeds Geol Ass., part viii, 1893. 



t We have proof that it covered Son Fell (2,034 feet), the highest peak in the 

 Isle of Man, Kendall, 'On the Glacial Geology of the Isle of Man.' Yn Lioar 



894 



Sea, is exceedingly 



Nov. 1896. 



X 



