560 Transactions of the Canadian Institute. [Vol. VII. 



SUMMARY. 



The points discussed in the preceding pages may be summarized as 

 follows : — 



1. The composition of the ocean represents the result, on the one 

 hand, of the leaching action of water on the land surfaces of the globe 

 continued throughout all the geological periods, and, on the other, of 

 the chemical and other agencies modifying or enhancing the power 

 of sea water to retain in solution the mineral constituents derived from 

 the land surfaces through river water since the beginning of the primeval 

 period. 



2. The relative proportions of the elements, and especially of 

 sodium, potassium, calcium, and magnesium, in river discharge are not 

 parallel to those of the same elements found in the sea. In river water, 

 the calcium is always more, and the potassium less, abundant than the 

 sodium, while the magnesium appears to approximate in amount the 

 latter. In the sea, on the other hand, the sodium is much more abun- 

 dant than the other three elements, and this is due to the continuous pre- 

 cipitation of a very great portion of the calcium added by rivers as 

 carbonate, to the subsequent fixation in the limestone so formed of the 

 magnesium as carbonate, and to the removal, continually taking place, 

 of potassium, which is affected through animal and vegetable forms, and 

 its consequent fixation in submarine deposits as glauconite and other 

 potassium-holding minerals. The calcium and potassium appear to be 

 stationary in amount, while the magnesium added by river water appears 

 to exceed in amount that removed from the sea, and, in consequence, is 

 slowly on the increase in the ocean, but its rate of increase is far behind 

 that of the sodium. 



3. The relative proportions of the elements in the ocean have, 

 therefore, always been changing, and these proportions must have been, 

 in the earlier geological periods, very different from what they are now. 

 In the ocean of the earliest period the relative proportions of the 

 elements approximated those found in river discharge, or rather those 

 found in fresh water shed from areas covered with Archaean rocks. In 

 this the potassium approaches the sodium in amount while the magnes- 

 ium exceeds the latter, and the calcium is relatively very abundant. 



4. This condition must have continued until living forms made 



