352 Professor E. Hull — Submerged Terraces 5f Valleys, 



land connection of Iceland with the British Isles. He remarks that 

 "the first thing that strikes a visitor from the latter country is not 

 the number of Arctic species, but the great abundance of plants 

 that are very rare and local in Britain, such as Saxifraga ccespitosn, 

 Lichiis alpina, and Erigeron alpi')m7n, etc." The disappearance of the 

 former glacial conditions from the British Isles and their continuance 

 in Iceland account for the remarkable abundance of the plants 

 referred to. 



The very ample survey of the insects given by Dr. Walker leads 

 him to the following conclusions : — 



1. The total absence of diurnal Lepidoptera. 



2. ,, ,, Orthoptera. 



3. Neuroptera only represented by Phryganidee. 



4. The most abundant tribes of insects in Iceland are moths 



and Diptera. 



On the whole, the insect fauna, as well as the flora, of this island 

 bear a remarkable affinity to those of Scotland.' 



Now, we must not forget that this community of fauna and flora 

 is characteristic of existing genera and species, and indicates a very 

 recent physical, or land, continuity. It may date back, perhaps, as 

 far as Pliocene times, passing into Recent, but not earlier ; and if 

 this be so, we have to consider to what extent the bed of the 

 Atlantic Ocean requires to be raised in order to establish such a land 

 connection, or in other words the amount of recent submergence 

 which it has undergone ; we have also to determine the tract of the 

 ocean over which the continuity of land surface formerly existed. 



The remarkable results established by American naturalists 

 regarding the submerged terraces and river-valleys adjoining the 

 American continent and prolonged into the North Atlantic, which 

 have already been communicated to the Institute by Mr. Warren 

 Upham,^ and more recently by mj'self, have induced me to take 

 up the investigation of the sub-oceanic region adjoining the British 

 Isles with the aid of the Admiralty charts of soundings, which afford 

 most ample mateinals for such investigation. The results, which 

 appear to me of remarkable interest, I now venture to place before 

 the Institute ; from which it will be found that all tend to confirm 

 the view of a very recent elevation of the British, and adjoining 

 continental, areas to the extent of several thousand feet as compared 

 with the level of the ocean surface at the present day. 



II. Land Connection with Iceland. — An examination of the 

 hydrographical charts shows that it would be necessary to raise 

 the bed of the ocean to the extent of 1,320 feet (220 fathoms) in 

 order to establish a land connection between the British Isles and 

 Iceland. The actual amount of elevation was probably greater and 

 may have reached about 6,000 feet. The evidence for this will 

 be seen further on : and it corresponds very closely with the amount 

 of elevation determined for the coast of North America by the 



1 Supra cit., p. 241'. 



^ Trans. Yict. Inst., vol. xxix. 



