Revieics — Hull's Sub-oceanic Lands. 475 



fjords, some of which show soundings of 5,000 to 6,000 feet in the 

 central part. That the coasts of Norway have in geological times 

 stood at a very much higher level than at present is shown by the 

 submerged lines and groovings of glacial erosion, which can be traced 

 on the sides of its fjords. There is also evidence of old sea beaches, 

 now greatly above the reach of tides, attesting a subsequent re- 

 elevation of the land in later times. 



Plate ix shows the physical conditions of the Northern Hemisphere 

 in the Glacial period. 



Plate X takes us, under the guidance of Professor J. W. Spencer, 

 to a survey of the submarine valleys along the American coast and 

 thence to the Gulf of Mexico and the submerged valleys and fjords of 

 the "West Indies. 



In plate xi we are introduced to the submerged valleys of the 

 Arctic basin and Greenland. 



In dealing with the mode of formation of the continental platform 

 and accompanying shelf, we have to recognize that the land of the 

 Northern Hemisphere has undergone enormous changes of level in 

 Pliocene and Pleistocene times — changes of elevation and depression 

 and of elevation again ; this, in the opinion of the authors, can be 

 abundantly proved by a consideration of the phenomena of the sub- 

 merged river valleys. 



The floor of the shelf was at one time a land surface, as shown by 

 the river channels by which, it is traversed, which could never have 

 been carved under the waters of the ocean itself, and the continental 

 slope constituted the coastline of the ocean at various stages of 

 elevation and depression. During this process of terrestrial movement 

 there were doubtless pauses when the surface of the platform was 

 swept by the Atlantic waves ; and the continental shelf was the out- 

 come mainly of wave-action and erosion on the one hand, and the 

 action of atmospheric denudation on the other, where the rains, rills, 

 and streams have reduced the coastal plains to levels of no erosion ; 

 in either case submerged terraces or platforms result upon the sinking 

 of the land or rise of the ocean level. The continental slope, formed 

 to some extent of terraces hewn out of the rock, as the land rose or 

 fell, assumed its present form somewhat as do the now emergent cliffs 

 on the rock-bound coasts of Norway, Scotland, and Ireland. Such in 

 general terms, writes Professor Hull, appears to have been the process 

 by which the submerged features were formed. It involves a recogni- 

 tion of a great lapse of time, which is difficult for the mind to realize, 

 especially at so recent a stage of the world's history ; nevertheless, the 

 evidence appears conclusive that, given the necessary time, these great 

 terrestrial results have been accomplished mainly by wave-action on 

 the lands during periods of elevation and depression, accompanied by 

 occasional pauses giving rise to terraces (p. 5). 



Slpace does not permit us to give a fuller notice of this important 

 work, which furnishes much information beyond the actual scope of 

 the title, although bearing upon the same subject. I recall a 

 MS. map by my father which must have dated back to 1825 or earlier, 

 showing the continental platform and proving how far back the attention 

 of geologists had been drawn to the former connexion of the British. 



