444 SCIENCE PROGRESS 



excessive weight. 1 Whether this cause of the sinking of vol- 

 canic cones is true or not, it is noteworthy that if the sub- 

 sidence of reef foundations is thus locally restricted, it may be 

 accompanied by a small rise of ocean level, as compared with 

 the time before the volcanic islands were built up. a Molen- 

 graaff 's idea may therefore be regarded as a valuable supplement 

 to Darwin's theory of coral reefs. It is, however, not intended 

 to exclude deformation of the ocean bottom as a cause of 

 change of levels ; for such deformation is highly probable near 

 the Tonga islands, and is abundantly proved for the Austra- 

 lasian archipelagoes. 



1 G. A. F. Molengraaff, "The Coral Reef Problem and Isostasy," Proc. Akad. 

 Wet. Amsterdam, xix. 191 7, 610-627. 



"■ "The Isostatic Subsidence of Volcanic Islands," Proc. Nat. Acad. Sci. 

 iii. 1917, 649-654. 



