174 DALY. 



of the ocean would be specially affected by the gravitative depression 

 of water level. Elsewhere the tropical seas would in less degree feel 

 the same effect, to which must be added the lowering effect of contem- 

 poraneous glaciers in Europe and other regions of the globe. The 

 total gravitative effect of all excess Pleistocene ice was probably 

 nowhere within the tropics sufficient of itself to lower sea-level as 

 much as 15 m.; an average for the coral-sea zone of 10 m., or about 

 5 fathoms, may be assumed without involving serious error in the 

 following discussion. 



Conclusion. Combining results, it is seen that, at the time of maxi- 

 mum glaciation, the tropical seas probably had an average level which 

 was 60 m. to 70 m. (33 to 38 fathoms) lower than at the present time. 



Islands and Continental Shores During the Glacial Period. 



The full consequences of Pleistocene chilling and lowering of the 

 tropical-sea level represent a problem having to do with the nature 

 of the Pleistocene land masses and shoals, and with the amount of 

 abrasion by Pleistocene waves. 



Character of the Shore Rocks. The extent of wave-benching at the 

 low sea-levels of Pleistocene time must have been highly variable, 

 owing to the enormous differences in the resistance of the materials 

 composing the shore belts of islands and continents alike. At the 

 first low-water stage those materials would include the following: 



1. Massive, strong lavas, among which were the flows erupted 

 during the shift of level; 



2. Weak pyroclastic deposits associated with those lavas; 



3. Strong volcanic or other formations exposed to wave action 

 through faulting or other t;ypes of crustal movement; 



4. Very weak mud and sand deposits which had been formed 

 under the sea by destruction of pre-Glacial lands and coral reefs ; 



5. Similar deposits locally somewhat strengthened by interbedded 

 coral reefs or by calcareous cementation; 



6. Mixtures of weak sediments or pyroclastic deposits with occa- 

 sional stronger lava flows; 



7. Coral reefs of pre-Glacial age; 



8. Weak deposits of shells etc., formed in offshore banks before the 

 shift of level ; 



9. Comparatively weak material residual after the secular weather- 

 ing of the pre-Glacial lands. 



