AND EIVER VALLEYS BORDERING THE BRITISH ISLES. olo- 



1,500 fathoms (7,200-9,000 feet), but, sa^ Professor J. Geikie 

 shows ill his Bathy-hypsonietrical map of the world, there is 

 a total range of 9,488 fathoms, or 56,932 feet, between the 

 highest altitudes of the laud aad the lowest depths of the 

 ocean. 



IX. General Conclusion. — From wdiat has been stated 

 above it will be seen that the North Atlantic Ocean down 

 to great depths along the European coast is characterised 

 by physical features similar to those we observe on the land 

 and due largely to similar causes, namely, marine and 

 atmospheric erosion. I hope to be able to produce additional 

 evidence of this conclusion Avheii describing the sub-oceanic 

 features of the Bay of Biscay. 



Postscript. 



Mr. A, J. Jukes-Browne in his Building of the British Isles, 

 2nd Edit., 1892, has very clearly described some of the 

 physical changes which the British Isles have undergone in 

 later Tertiary and Post-Tertiary times, and, as represented 

 in Plate xiii, has given a restoration of the drainage of the 

 British Isles during the Newer Pliocene Period, showing two 

 principal rivers entering the ocean — and draining the regions 

 now occupied by the Irish iSea and English Channel. But it 

 does not appear that he has recognised the channels and 

 canons, such as " the Hurd Deep," as determinable from a 

 study of the Admiralty charts, nor the great escarpment 

 which it is the special purpose of this paper to elucidate. 

 The chart of the Crag period originally drawn by Mr. 

 K. A. C. Godwin-Austen {Q.J.G.S., vol. xxii, p. 240) was 

 the first attempt to restore the physical geography of the 

 Pliocene period of these isles. 



