500 John Smith — The Great Submergence. 



during the subsidence, from which the strife had not been wholly 

 removed by subsequent attrition. 



As no one holds the opinion that the shelly clay was transported 

 en masse, this point need not be discussed. I merely remark that we 

 see how Carboniferous shale which had been torn up by a glacier 

 may be drawn out into a long thin band before it travels many yards. 

 This would be the fate of auy shelly clay adhering to the bottom of 

 a glacier. 



Mr. Bell, in his paper published in the Geological Magazine in 

 July, August, and September, 1895 (pp. 321, 348, and 402), offers 

 the following explanation of the mode of formation of the shelly till. 

 He says : " We have said that, if transported by the ice, it does not 

 ' necessarily follow ' that the whole of this deposit was conveyed 

 simultaneously, or en masse. Briefly, our idea is that it may have 

 been conveyed very gradually, and deposited in an extra-glacial lake, 

 formed at this point along the side of the ice-sheet, into which part 

 of the materials being carried by the latter (fine mud, rounded 

 stones, shells, etc.) dropped and were accumulated." 



I have already stated that it is physically impossible that 

 part of a sea-bottom could be taken up and carried forward by 

 ice (in the Clava case the marine material would require to 

 have travelled over " hill and dale " some ten miles) without the 

 shells being striated. We have plenty of shelly tills that have 

 been dragged a bit by land-ice, but in them the shells (nearly 

 always fragments) are mostly striated. Two stones from the 

 shelly clay had several Balani attached to them, and three others 

 had marks of the bases of Balani still upon them. Some of the 

 shells of Astarte had both valves in position, but crushed. 



But for argument's sake let us suppose that the ice has delivered 

 its burden at Mr. Bell's hypothetical lake some 500 feet above the 

 present sea-level, or some 400 feet above the then sea-level, for 

 Mr. Bell's hypothesis demands a small subsidence. In the first 

 place, the stones (now in the shelly till) would require to have 

 had their stria? removed, which could only have been done by 

 being rolled in water. (They are all well-rounded stones, and 

 could not have fallen as splinters from a cliff upon the top of a 

 glacier.) Now the Clava shelly clay says — "No, this cannot have been 

 the case. I am a mud; there ivere no currents flowing tohere I icas laid 

 down ; there is not a single line of stratification in me." In the second 

 place, there would be water flowing through this hypothetical lake 

 which would cause the deposits to be stratified. Aud there would 

 be the further impossibility of substituting complete for broken and 

 scratched shells. 



It is clear, then, that this deposit (the shelly clay) could not 

 possibly be formed in this way ; it is a deep-water deposit formed in 

 the sea where there were no bottom currents. Had it been formed 

 in an upland tarn it ought to have contained abundance of vegetable 

 matter, fresh-water mollusca, fresh-water diatoms, fresh-water 

 Ostracnda, etc. ; but there is not a vestige of anything organic in it 

 that is not marine. 



