i893- SHELLY-SANDS AND GRAVELS. 431 



on the plains, and the time that has elapsed since they were deposited, 

 in my estimation, is certainly not less than 60,000 years. I know that 

 some good geologists have persuaded themselves that not more than 

 10,000 years have elapsed since the melting of the ice, but, though 

 respecting their opinions, I cannot agree with their premises. 



3. — The shells are always broken as if a heavy body had moved over them. 



This formula is not strictly true, especially in the light of modern 

 discoveries. There is no doubt, however, that the generally frag- 

 mentary condition of the shells has been a source of difficulty to 

 observers in the past. The demands of the opponents of sub- 

 mergence are, however, rather exacting. They ask to be shown 

 bivalve shells with both valves united. I have personally never found 

 them in this condition, excepting in the Clyde Beds, but I am assured 

 by Mr. S. A. Stewart, of the Belfast Museum, that he has taken them 

 out of the glacial beds in the neighbourhood of that city with the 

 valves together. 6 In Xature' is the precis "of a most careful and 

 important investigation into the shell-bearing clays of Clava in Nairn," 

 in which a " shelly blue clay with stones in the lower part,'' 16 feet in 

 thickness, overlain by 63 feet of Boulder Clay and sands, and reposing 

 upon 36 feet of coarse gravel and sand and brown clay and stones, is 

 described. " The highest part of the shelly clay is 503^ feet above 

 sea-level, and the deposit appears continuous for a distance of 190 

 yards." " The shells are well preserved, neither rubbed nor striated, 

 and the deposit is a true marine silt which, if not in situ, must have 

 been transported in mass." The majority of the committee of inves- 

 tigation " consider the evidence sufficiently strong to prove a 

 submergence of at least 500 feet." Here, then, appears to be the 

 very thing the land glacialists are asking the submergers to produce ;. 

 but, unfortunately, their demands are again varied, as some are not 

 satisfied, and assume that the bed has been shifted en masse. 



Considering that the valves of bivalves are only held together 

 by ligaments that readily decay, it is not surprising if we do not 

 find them in apposition in deposits which show evidence of strong 

 current action, as most of the marine glacial deposits do, especially 

 the high-level shelly gravels ; perfect single valves are common 

 enough and delicate univalves such as Trophon, Nassa, and the fine 

 spires of Turritclla. 



The high-level shells are beach shells, that is, they consist of 

 shells such as are thrown up and can be found together on many 

 beaches. We do not, of course, get the exact fades, but in this connec- 

 tion I may say that I have found on the Crosby beach, with one 

 exception, the whole of the shells named by Forbes from Trimmer's 



6 See Mr. Stewart's " Molluscaof the Boulder Clay of the North-East of Ireland." 

 Proc. Belfast Naturalists' Field Club, 1S79-80. " Led.i fygtnaa — Nock, Woodburne, 

 Ballyrudder." " Almost invariably found in a perfect state." 



7 Reports of British Association papers, Section C, Nature, Sept. 28, 1S93, p. 532. 



