674 



DEPARTMENT OF THE INTERIOR 



2 GEORGE V., A. 1912 



late not earlier than the Devonian period. The calcium, did not begin to 

 accumulate in similar excess until the general scavenging system was established 

 in the ' bathybial ' (not ' abyssal ') regions of the ocean floor — perhaps as late as 

 the Cretaceous period. When we also bear in mind that the sodium and potassium 

 salts have been slowly accumulating from the pre-Cambrian to the present time, 

 we are prepared to reach the rather probable conclusion that the pre-Cambrian 

 ocean really approximated a fresh-water (though faintly acid) condition. The 

 only escape from that conclusion seems to be offered in the view that a large 

 part of the existing ocean is made of nearly pure ' juvenile ' water emitted from 

 volcanic vents or from primary igneous rocks since the pre-Cambrian. 



10. The hypothesis suggests that, in general, secular variations in the 

 oceanic composition may be found to explain some features of biological history, 

 including certain accelerations and retardations in life development, especially 

 as regards the elaboration of the hard parts of animals and the rise and fall 

 of lime-secreting organisms. 



11. According to the hypothesis the outlines of developments may be tabula- 

 ted as follows : — 





x -f Oceanic 



Composition. 



i 



River influence on 



Oceanic 



Composition. 



Carbonate 

 Deposits. 



Azoic Period. 





i 



1 



Early Eozoic Period. 



Pelagic, soft-bodied, low Beginning of preci pita- 

 types of animals and tion of lime-salts, 

 plants. 



Gradual evolution of Followed by a long, 

 higher types of animals, nearly limeless stage, 

 all soft-bodied. 



Chief Fossils — Silicious ; 

 impressions of soft- 

 bodied animals ; pcssi- 



• bly tests of pure chitin; 

 plants ? 



Minimum ; land areas 

 small ; minimum area 

 of limestone exposed 

 to weathering 



Calcium carbonate fol- 

 lowed by mixed de- 

 posits of calcium 

 carbonate and mag- 

 nesium carbonate ; 

 iron carbonate. 



Late Eozoic (Post-Middle Huronian) Period. 



Relatively high types of 

 animals, soft-bodied. 



Chief Fossils — As in for- 

 mer period : also, per- 

 haps, some calcareo- 

 chitinous. 



Great and relatively ra- 

 pid increase of river- 

 borne carbonates of cal- 

 cium and magnesium. 



Orogenic revolution ; 

 land areas enlarged ; 

 special increase of 

 areas of weathering 

 lim e s t o n e s ; base- 

 levelling. 



Relative abundance < f 

 calcium carbonate ; 

 continued deposit of 

 magnesium and iron 

 carbonate. 



