543 T. Mellaril Reade— 



be, was land ice. In proof of tins, the fragmentary character of 

 the shells, their worn appearance, and the occasional etrise found 

 upon them, are adduced. 



I am far from alleging that the fragmentary character of the 

 shells presents no difficulty, for I distinctly pointed it out in my 

 earlier writings. But do not the opponents of the marine origin of 

 the Shelly Drift, however, make too much of it? Anyone who will 

 take the trouble to examine a gravelly beach at the present day 

 will find a preponderantly large assortment of shell fragments as 

 compared with perfect valves ; he will also find them much worn 

 and rounded at the edges, and seldom will he see any epidermis 

 preserved. Dredgings of the sea-bottom also often bring up remains 

 of broken and rounded shells, so that if, in addition to the ordinary 

 agencies of waves and tides shore-ice were introduced, the pounding 

 of this mill would, as Sir Wm. Dawson informs me is at present the 

 case in the St. Lawrence, work destruction even on the living shells. 1 



I have pointed out that in our Low-level Boulder-clays of the 

 north-west of England the fragments as a rule are minute enough 

 to be carried about by marine currents, in which case they may be 

 looked upon as " boulders " without the intervention of land-ice. 

 Perfect valves are, however, found, and Turritellce are very 

 frequently perfect ; also small Gasteropods, such as Trophon 

 truncatus and Fusus, are in perfect preservation. At Gloppa, as 

 Mr. Nicholson's collection shows, there are many very perfect 

 specimens and a wide range of species. I have, however, pointed 

 out again and again that negative evidence is pretty sure in the end 

 to prove fallacious. In Natural Science 2 (1893) I urged that the 

 High-level Shelly Drifts, so far from being "sporadic" examples, 

 which some had contended, were simply limited by the difficulty of 

 observation, the known sections having only been exposed by 

 artificial excavations, which are not often required in these out-of- 

 the-way localities. I was not, however, prepared for such a 

 tremendous demonstration of the possibility of natural sections 

 exposing shelly drift having been overlooked by geologists as those in 

 Ayrshire appear to have been. It is a striking demonstration of the 

 truth that things that are not expected to be found are not looked for. 

 The strias on the rocks of Ayrshire work out in a north-westerly 

 direction from Loch Doon, turning more to the westward as they 



1 Since this was written I have had the pleasure of reading Sir "Wm. Dawson's 

 "Canadian Ice Age" (Montreal, 1893), which renders clear many phenomena 

 I have observed in Britain on which I could previously only surmise. 



2 The following is the substance of what I said: — " In working out this objection 

 the supporters of the Irish Sea Glacier unconsciously minimise the quantity of 

 High-level Shelly Drift ; there is much more in existence than they have persuaded 

 themselves to believe. There is no occasion for me to name the localities over 

 again, as I have stated them at the commencement of this paper. Again, it can 

 hardly be expected that all High-level deposits laid down by the sea should contain 

 shells, and further it is unphilosophical to assume that all High-level drifts have 

 been discovered. Their discovery has generally been in the nature of an accident. 

 I fear the advocates of the Irish Sea Glacier are continually forgetting how difficult 

 it is to prove a negative, and unfortunately the arguments are too frequently of the 

 negative kind." — Natural Science, vol. iii, p. 430, 1893. 





