270 GLACIAL FORMATIONS IN IRELAND. CHAP. xiv. 



precisely resemble hundreds of dome-shaped protuberances in 

 North Wales, Sweden, and North America.* 



The marks of glaciation on the rocks, and the trans 

 portation of erratics from Cumberland to the eastward, have 

 been traced by Professor Phillips over a large part of York 

 shire, extending to a height of 1,500 feet above the sea; and 

 similar northern drift has been observed in Lancashire, 

 Cheshire, Derbyshire, Shropshire, Staffordshire, and Worcester 

 shire. It is rare to find marine shells, except at heights of 

 200 or 300 feet ; but a few instances of their occurrence have 

 been noticed, especially of Turritella communis (a gregarious 

 shell), far in the interior, at elevations of 500 feet, and even 

 of 700 in Derbyshire, and some adjacent counties, as I learn 

 from Mr. Binney and Mr. Prestwich. 



Such instances are of no small theoretical interest, as 

 enabling us to account for the scattering of large erratic 

 blocks at equal or much greater elevations, over a large part 

 of the northern and midland counties, such as could only 

 have been conveyed to their present sites by floating ice. 

 Of this nature, among others, is a remarkable angular block 

 of syenitic greenstone, four feet and a half by four feet square, 

 and two feet thick, which Mr. Darwin describes as lying on 

 the summit of Ashley Heath, in Staffordshire, 803 feet above 

 the sea, resting on new red sandstone, f 



Signs of Ice-action and Submergence in Ireland during 

 the Glacial Period. 



In Ireland we encounter the same difficulty as in Scotland, 

 in determining how much of the glaciation of the higher 

 mountains should be referred to land glaciers, and how much 



* Hull, Edinburgh New Philoso- shire, Philosophical Magazine, series 

 phical Journal, July 1860. 3, xxi. p. 180. 



f Ancient Glaciers of Caernarvon- 



