692 OCEANOGRAPHY 



larger than their shallow-water allies, while others are much smaller. 

 All have a rather feeble development of calcareous shells and skele- 

 tons and a rather sombre color. All these modifications can be 

 satisfactorily explained by reference to the pressure, the tempera- 

 ture, the food, the light, and other physical and biological conditions 

 to which we have referred as prevailing in the deep water of the 

 great ocean basins. 



A point of some interest to paleontologists is that in deep marine 

 deposits the remains of marine organisms which lived on the bottom 

 in cold water with a temperature below zero are mingled with the 

 remains of surface organisms which lived at a temperature of 80 F. 

 It has been shown by hundreds of analyses of ocean-water from all 

 parts of the world that the chemical composition of sea-water, that is 

 to say, the ratio of acids to bases in sea-salts, is very constant, with 

 some insignificant exceptions. Sea-water has acted as a gigantic 

 solvent; it almost certainly now contains every known chemical ele- 

 ment. The salts now present in solution represent what water has 

 been able to leach and filter out of the solid crust and sea-water 

 has been able to retain in solution. The history of the composition of 

 sea-water should be the complement of all the terrestrial changes 

 that have taken place on the dry land of the continental areas. An en- 

 deavor may be now made to trace that history, in the same way that 

 the geologist and paleontologist trace the evolution of the stratified 

 rocks. We have now many indications that the composition of the 

 sea- water salts or rather, the proportion in them of the various 

 elements has continually changed from that of the primeval 

 ocean. 



It has been pointed out that Radiolaria, Diatoms, and other silica- 

 secreting Protozoa and Protophyta, are more abundant where sea- 

 water mixes with a large amount of fresh water in the present ocean, 

 as, for instance, in the tropical West Pacific and in the Antarctic. 

 When we remember the abundance of Radiolaria in Paleozoic schists, 

 it seems to show that in the early seas there was much more detrital 

 and colloid silicate of alumina in ocean waters than at the present 

 time, the oceans being on the whole much shallower and less salt. 

 Again, in the present seas lime-secreting organisms are much more 

 abundant in the warmest and saltest waters than elsewhere. This 

 indicates, when the small development of limestone in the earliest 

 stratified formations is considered, that lime was less abundant in 

 the pre-Cambrian oceans than in our seas. Indeed, water before the 

 formation of soil on the land surfaces would carry to the ocean 

 very different salts in solution from those carried at this time. Po- 

 tassium, for instance, is absorbed at the present time by all soils, and 

 the same element has from the earliest times been extracted from 

 the sea-water to form glauconite. Potassium is, then, probably much 



