I902-3'] The Pal^ochemistry of the Ocean. 547 



and gravels of the Cambrian sandstone of North America, in the 

 Quebec group of Canada and in the coarse Silurian sands of Bohemia. 

 In the Mesozoic period it was more abundantly formed and its deposits 

 are very marked in the strata of the Cretaceous division. It is also found 

 in the Tertiary from the lowest strata to the highest of the series. It is 

 thus shown that the formation of glauconite occurred in all the geolo- 

 gical periods from the commencement of the Palaeozoic Age to the 

 present time and that thus a very large proportion of the potassium 

 which the ocean would now contain, were it not for the formation of 

 glauconite, has been removed from it.* 



In the formation of glauconite, organisms appear to play a very 

 distinct part and amongst these the Foraminifera are the most important. 

 The decomposing organic matter of the dead forms liberates sulphur 

 which combines with the iron in deposits to form sulphide.f This 

 latter is converted into sulphuric acid which, acting on the fine clay 

 sets free colloidal silica and ferric hydrate in a condition which pro- 

 motes their union and the silicate so formed combines with potassium to 

 form glauconite. It is obvious that organic matter is a very important 

 factor in the process and that in the absence of animal organisms no 

 glauconite would be formed, a view which explains the almost complete 

 absence of this mineral from the deep sea areas, but it also postulates as 

 decidedly, that before the appearance of living forms in the primeval 

 ocean, there was little or no potassium eliminated from it, and this, taken 

 in conjunction with the fact that in earlier pre-Cambrian times there 

 could not have been much or any soil to affect the potassium in the 

 waters discharged from the land areas, makes it quite clear that there 

 was a period during which the potassium content of the ocean must 

 have increased absolutely and that this was succeeded by a period in 

 which the amount of the potassium ceased to increase or remained 

 practically stationary, while decreasing relatively to other constituent 

 elements. The beginning of this latter period coincided with the ap- 

 pearance of living forms in large numbers in the sea. 



The history of sodium in the ocean has been one of uniform in- 

 crease through all the geological ages. The addition that is to-day 

 being made by river discharge is large and must have obtained as 

 abundantly in the past. There have, on the other hand, been no im- 

 portant agencies which have served to eliminate it from the ocean. 

 The great salt deposits, some of which are as old as the Cambrian, are, 



* Forchhammer was the first to point out that potassium is being removed from the ocean, (British 

 Association Report, 1844, p. 153.) From his analysis of Fucoids and of the metamorphosed Fucoid schists of 

 Scandinavia he came to the conclusion that Fucoids constitute a very important factor in the process. 



t Murray and Renaud, op. cit., p. 389. 



