Wright and Muff — Pre-glacial Raised Beach. 273 



top of the pre-glacial cliff may often be detected. This feature 

 serves to show that the pre-glacial shore was in these places not 

 far seawards of the modern one. 



The pre-glacial coast-line can also be seen to coincide with the 

 present one in one or two places in the neighbourhood of County 

 Dublin. On the south and east sides of Howth the glacial deposits 

 are banked against an old cliff-slope. Near the Lion's Head a 

 coarse, angular quartzite rubble underlies the glacial drifts. On the 

 south side of Bray Head a rubble-drift, composed of angular slate 

 fragments similar in structure to the head on the south coast, is 

 banked against a degraded cliff, and overlaid by boulder-clay. At 

 the foot of the cliff there are traces of rock-platform at about the 

 same level above the sea as on the south coast. These two localities 

 are situated on the lee-side, with reference to the direction of ice- 

 flow, of two high headlands — a position in which pre-glacial 

 deposits are more likely to be preserved than elsewhere in the 

 same district. 



Of the Isle of Man, Mr. Lamplugh says 1 : — " The recession of 

 the rocky part of the coast since glacial times has not been suffi- 

 cient to affect materially the outline of the old massif, and there 

 are many indications that cliffs of the slate rocks were in existenoe 

 in pre-glacial times in approximately the same position as those of 

 the present day. The rocky tidal shelf on the more exposed parts 

 of the coast appears usually to represent the extent of post-glacial 

 erosion, while in some of the larger bays, e.g., those of Douglas, 

 Port St. Mary, and Port Erin, where the foreshore is broad and 

 smooth, there are patches of drift upon the rocky platform, 

 apparently indicating that even this feature may sometimes be 

 pre-glacial ; and in a few sheltered recesses, the ancient cliff-slope 

 is still unbroken." 



A raised beach, fringing the shores of the Bristol and English 

 Channels, 2 is buried beneath blown-sand and head or coombe- 

 rock. Mr. Tiddemann proved, 3 in 1900, that along the coast of 



1 " Geology of the Isle of Man," p. 14.— Mem. Geol. Surv. U.K., 1903. 



2 See Ussher, "The Post-Tertiary Geology of Cornwall." Printed for private 

 circulation. Hertford, 1879. Prestwich, "The Eaised Beaches and 'Head' or 

 Rubble- drift of the South of England." Quart. Jour. Geol. Soc, vol. slviii., p. 263, 

 1892. And others. 



3 Eep. Erit. Assoc, 1900, p. 760. 



