222 J, Lomas — An Ancient Glacial Shore-line. 



Another section, from the selvage of a large basaltic dyke in the 

 same area, is a superb example of palagonite, the altered tachylyte 

 having all the clear brown translucent character that is familiar 

 in Icelandic and Sicilian types. Spherulitic aggregates of a more 

 dusky brown colour began to form at one stage, but were in part 

 redissolved in the fluidal groundmass. Abundant oval yellow-brown 

 bodies, dark upon the exterior, occur in the palagonite, and are 

 probably the minute spherulites of the last phase of consolidation, 

 deformed by the flow at the edges of the dyke- 

 It is only by the brilliant play of colours when the section is 

 viewed between crossed nicols that one discovers that this beautiful 

 and apparently unaltered tachylyte has passed thoroughly into the 

 palagonitic and micro-crystalline condition. 



Enough has now been noted to confirm what was remarked two 

 years ago as to the frequency and variety of vitreous andesites and 

 basalts on this interesting coast of Mourne. I still feel that in all 

 probability this assemblage of dykes is of early Eocene age.^ 



VII. — An Ancient Glacial Shore. 

 By Joseph Lomas, A.E.C.S., F.G.S. 



FOR some time I have had under observation the sections of 

 drift exposed in the cuttings of the Seacombe branch of the 

 Wirral Railway, and hope to describe them on some future occasion 

 when the sections are nearer completion. 



However, Mr. Mellard Reade has forestalled me^ in the description 

 of one part of the sections, and professes to have found in them 

 evidence of " an ancient glacial shore." What does he produce 

 in favour of the statement ? 



In the first place "the bed is composed of pretty clean sand with 

 some small gravel, and is crowded with shell fragments in all 

 stages of decay." Secondly, it is of large extent and has a gentle 

 slope. Thirdly, rolled clay balls are found mixed with the sand. 



The bed in its composition does not differ from the ordinary 

 sands and gravels found so commonly in the glacial deposits of 

 Lancashire and Cheshire. 



Some of these contain rolled clay balls (though I have never met 

 with a section which displays them in such abundance). Some 

 equal or exceed the present example in extent. They often contain 

 shell fragments, which are sometimes planed and striated like 

 ordinary boulders. It is noteworthy, too, that the shelly deposits 

 only occur in places where we can prove by independent evidence 

 (such as boulder transport and glacial striae) that the ice to reach 

 that place must have traversed a sea bottom. 



Ihe beds are usually lenticular in shape, slope at all angles 

 and occur at all horizons. Two or three may often be seen above 

 each other in one section. Shall we consider all these as " ancient 

 ■glacial shores ? " 



1 See Proc. Eoy. Dublin Soc. vol. vii. (1892), p. 518. 



2 Geol. Mag, Feb. 1894. 



