INTERGLACIAL EPOCHS. 



275 



the great probability that frost or floating-ice has had a share in 

 producing some of them at least. But even after admitting so 

 much there still remains for explanation the capricious distribu- 

 tion of the ledges, their presence in one place, their absence from 

 another, where the conditions would seem to be as near as may 

 be alike. Certain observations in Scotland have led me to 

 suggest an explanation of the phenomena, which I throw out here 

 for the consideration of my Norwegian friends. At several p]aces 

 on the Scottish coast, particularly in the neighbourhood of 

 Ballantrae in Ayrshire, I have observed rock-ledges of precisely 

 the same character as those which I saw in the north of Norway. 

 They occur at a greater elevation than is attained by any of 

 the late glacial and postglacial shelly clays, which is suggestive, 

 therefore, of their greater antiquity. But what settles this 

 point is the fact that they have been glaciated at a time 

 subsequent to their excavation — they are distinctly moutonndes. 

 In connection with this, I note the fact that I found till with 

 striated stones lying here and there in holes and hollows of the 

 surface, all of which puts it beyond doubt that the rock-terraces 

 in question were overflowed by the ice of the last glacial epoch. 

 I have little doubt, indeed, that they mark old sea-levels which 

 were excavated during the last interglacial epoch, and that they 

 are thus contemporaneous with the "middle sands" of Ireland and 

 the north-west of England. Now it seems not improbable that 

 many of the ancient strand-lines of Norway may belong to this 

 period. The glacial striae observed upon the strand-line in 

 Osterfjord by Sexe, seem to me to tell the same tale as the 

 roches moutonnSes and till on the Ayrshire rock -terraces. The 

 glaciation is certainly more recent than the formation of the 

 strand-line. If we might suppose, therefore, that many of the 

 old sea-margins of Norway pertained to the same interglacial 

 epoch as those of Scotland, we should explain in a natural way 

 some of the apparently conflicting phenomena to which reference 

 has been made. The absence of sea-shells, etc., and of sand and 

 gravel, or shingle, upon the rock-ledges, would no longer offer a 

 difficulty, for all such loose material would tend to be swept 



