d Proceedings of the Royal Irish Academy. 



joining Scotland, Iceland, and Greenland with America, must have existed in 

 later Tertiary times. This does not materially alter the general i^rinciple 

 of my original ^dews ; and I still adhere to the belief in a North Atlantic 

 land-bridge between Europe and America during the lifetime of the reindeer. 

 (Fig. 1.) In defence of my opinion I propose to enlarge the scope of my 

 arguments by bringing forward some additional pieces of ev-idence. 



The testimony in favour of my theory is of a twofold character. It is 

 based on an investigation of the sea-floor, and on a study of the plants and 

 animals of the countries supposed to have been joined to one another by 

 land. 



In 1897, Mr. W. S. Green gave us the results of his expedition to the 

 Kockall Bank. SuiTounded by deep water on all sides, this bank is of an average 

 depth of 100 fathoms, and lies far out in the Atlantic to the west of Scotland. 

 Dredging on the bank yielded only such shallow-water species of molluscs 

 and other marine invertebrates as could not have lived there under the 

 present conditions. IMoreover, as all the specimens were dead, it was con- 

 cluded that the bank had only subsided to its present depth within com- 

 paratively recent times.' In 1900 the Danish ' Ingolf ' expedition to Iceland 

 likewise reported having met littoral molluscs near the island at considerable 

 depths where these animals could not possibly have lived. That such cases as 

 these are due to accidental dispci-sal by floating icebergs containing shells in 

 the ice-foot or by floating seaweeds, had been suggested ; but the view that 

 the occurrence of shore forms of animal life in deep water implies a depression 

 of the land seems to meet with more general favour, especially as no icebergs 

 are known to stray to the Rockall Bank at present. 



It has been demonstrated by Sir Archibald Geikie that a considerable 

 subsidence has taken place in the area between the west of Scotland and 

 Iceland since the time of the volcanic eruptions that produced the great 

 basalt plateau of north-western Europe.' 



Many other geologists, notably Professor de Lapparant and Professor 

 M' Kenny Hughes, have directed attention to the evidences indicating a 

 sinking of the land in the same region. But the subject was also studied 

 from another point of view. It was Mr. Austen, I believe, who first brought 

 under our notice the continental shelves or platforms of submerged land 

 surrounding the British Isles.' 



' Or«n. W. S., " Note, on Rockall Island." 



= Geikie, A., •'Tertiary Basalt Plateaux of .Nurlh-wcalcrii Europe," p. 391). 



' Austen, R. A. C, •* Valley of £ngUsh Chaanel," p. 94. 



