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



There is, indeed, in these rocks only a small amount of crystalline or 

 other limestone, and there appears to be still less in the divisions of the 

 Huronian, which, as pointed out, have a thickness in the Lake of the 

 Woods and Rainy Lake districts, according to Lawson,* aggregating 

 50,000 feet, all representing sedimentary formations. What limestone 

 and gypsum are present in pre-Cambrian rocks can very well be attri- 

 buted to the occurrence of calcium salts in the oceans of the Archaean 

 in quantities, however, which could not have very greatly exceeded those 

 which obtain to-day in sea water. 



v.— The Relation of the Salts in the Ocean to 

 Protoplasm. 



From the considerations advanced in the preceding section of this 

 paper, it follows that the ocean has been, and is now, slowly changing, 

 not in its composition, but in the proportions in it of the various 

 elements to each other, and that, as a consequence, it is now in this 

 respect greatly different from what the primeval ocean was in the 

 period following the first condensations of water vapour on the rock 

 crust of the globe. It may again be noted that in all these changes 

 there are two distinct periods. In the first, or older, life was not 

 represented except towards its close, and therefore, the only factors 

 engaged in eliminating any of the elements from the sea were purely 

 chemical ones such as are illustrated in the precipitation of lime as 

 carbonate and sulphate and of magnesia as carbonate. In this period 

 the elements must have differed in amounts from each other less 

 markedly than they do to-day, and the constant addition to these 

 from the discharge from the land surfaces did not tend to alter, even 

 after a very long interval, the proportions which first obtained. This 

 period must have terminated some considerable time after the appear- 

 ance of living forms on the globe, and especially only after the adapta- 

 tion of vegetable forms to a land life, and the consequent production 

 of soils. The second period could not have begun at once after the 

 appearance of living forms, for these must first have acquired a relation 

 to the elements and then have developed the habit of disposing of the 

 various salts which they took out of the sea water. This period may 

 well be supposed to have begun when there had developed not only a 

 considerable diversity of forms in the sea, but also the organisms 

 which contribute to the production of organic matter in soils. In this 

 period the removal of potassium from the land surfaces decreased, 



* Loc cit. 



