iT: 
Are Great Ocean Depths Permanent ? 
T has been suggested by the editor that English readers would like 
to hear my views on that much-debated question, the Perma- 
nence of Ocean Basins. I am rather at a loss how to deal with the 
subject, because this question involves so many difficult chapters 
in the history of our planet, and because I regret to see that discre- 
pancy of views exists on fundamental principles. 
Mr. Wallace begins by arguing from the principle that ‘on 
any large scale, elevation and subsidence must nearly balance each 
other, and thus, in order that any area of continental magnitude 
should rise from the ocean floor,. . . . some corresponding area 
must sink to alike amount.” I venture with deference to reply that I 
cannot agree to this. It seems, on the contrary, as if two different 
types of movement had been going on since the first formation of the 
terrestrial crust. In the first place, there is folding, recently explained 
in a masterly way by Professor Lapworth, in his Address to the 
British Association. Secondly, there is the sagging-down or “ effon- 
drement’”’ of smaller or greater parts of the crust, caused by the 
progressive diminution of the planet’s radius. This descent of parts of 
the eavth’s crust seems to be the true origin of the great oceanic basins. 
Sometimes the contour of the sunken area follows the trend of a 
folded mountain chain; at another time it may cut right across it. 
In smaller examples the outline very often takes a more or less irregu- 
larly circular or elliptical form. The descent of a considerable area, 
forming a large new depression, demands a certain part of the existing 
volume of oceanic waters for the filling of the new depth. The 
consequence is the sinking of the oceanic surface all over the planet, 
and the apparent step-like rising of coast lines. Thus is explained the 
apparently episodic elevation of whole continents, without any 
disturbance of horizontality, or the least alteration of the net of 
watercourses spread over the land. It is in this sense alone that a 
certain balance of ‘“‘ elevation” and “ subsidence ”’ might be conceded. 
In the entire Pacific region the limits of the oceanic basin are 
traced out by the trend of long mountain folds. So it is from New 
Zealand and New Caledonia to the borders of Eastern Asia, to the 
Aleutians, and all along the western coast of both Americas. This is 
not the case in the Atlantic, nor in the Indian Ocean; here the 
