194 



ISLAND LIFE. 



[part 1. 



and some of them can be traced to the Welsh hills from 

 twenty to fifty miles distant. This remarkable formation was 

 first pointed out as proving a remote glacial period, by Professor 

 Eamsay ; and Sir Charles Lyell agreed that this is the only 

 possible explanation, that, with our present knowledge, we can 

 give of them. 



Permian breccias are also found in Ireland, containing blocks 

 of Silurian and Old Red sandstone rocks which Professor Hull 

 believes could only have been carried by floating ice. Similar 

 breccias occur in the south of Scotland, and these are stated 

 to be overlain by a deposit of glacial age, so similar 

 to the breccia below as to be with difficulty distinguished 

 from it." ^ 



These numerous physical indications of ice-action over a 

 considerable area during the same geological period, coinciding 

 with just such a poverty of organic remains as might be pro- 

 duced by a very cold climate, are very important, and seem 

 clearly to indicate that at this remote period geographical 

 conditions were such as to bring about a glacial epoch in our 

 part of the world. 



Boulder-beds also occur in the Carboniferous formation, both 

 in Scotland, on the continent of Europe, and in North America ; 

 and Professor Dawson considers that he has detected true 

 glacial deposits of the same age in Nova Scotia. Boulder-beds 

 also occur in the Silurian rocks of Scotland and North America, 

 and according to Professor Dawson, even in the Huronian, older 

 than our Cambrian. None of these indications are however 

 so satisfactory as those of Permian age, where we have the very 

 kind of evidence we looked for in vain throughout the whole of 

 the Tertiary and Secondary periods. Its presence in several 

 localities in such ancient rocks as the Permian is not only most 

 important as indicating a glacial epoch of some kind in Palseozoic 

 times, bat confirms us in the validity of our conclusion, that the 

 total absence of any such evidence throughout the Tertiary and 

 Secondary epochs demonstrates the absence of recurring glacial 

 epochs in the northern hemisphere, notwithstanding the frequent 

 recurrence of periods of high excentricity. 



^ Geological Magazine, 1873, p. 320. 



