1902-3.] The Pal^ochemistry of the Ocean. 551 



calcium of river discharge greatly exceeds in amount that of the three 

 other elements, and yet it is less abundant than either in the ocean. If 

 there were no elimination of calcium from sea water, the salts of the 

 latter element would long have reached the point of saturation in the 

 ocean. The present condition is easy of explanation. On the one hand 

 calcium separates from sea water through the formation of sulphate and 

 carbonate of lime, which are to a high degree insoluble. This constit- 

 utes in part the origin of the gypsum beds and of the limestones of 

 sedimentary origin. On the other hand the myriads of organisms that 

 have their habitat in the sea have the lime "habit," and they conse- 

 quently remove from solution enormous quantities of calcium. This is 

 the case not only with all forms provided with exoskeleta and endos- 

 keleta, into the composition of which lime largely enters, but also with 

 those which exercise the precipitating effect on the calcium salts they 

 absorb from sea water, the precipitation rarely going so far as to form a 

 distinct deposit in the cells or tissues of the organism. This power to 

 precipitate is universal, as shown by the fact that the capacity to form 

 calcareous skeleta is almost universal, and this capacity is merely an 

 enhancement of the power to precipitate. The latter, therefore, operat- 

 ing so largely, separates calcium from sea water, and on the death and 

 disintegration of the organisms, the element is deposited on the sea 

 bottom either as phosphate or carbonate of calcium.* These deposits, 

 owing to the fact that they contain few calciferous fossils, are regarded 

 as due to chemical reactions alone ; but if they are, sedimentary lime- 

 stones should be of a more uniform distribution, whereas we find them 

 more or less localized. The explanation that they are due to protoplasmic 

 " secretion " and not to either chemical reaction or skeletal deposition in 

 living forms accounts for much, and indicates what a factor living proto- 

 plasm, animal and vegetable, is in the separation of calcium from sea 

 water. 



Sterry Huntf advanced the view that in the primeval ocean the 

 chief salts were chlorides of calcium and magnesium, and that the 

 constant, large output by river water of carbonates of sodium and 

 potassium, and particularly of the former, affected a conversion of these 

 into carbonate of lime and chlorides of sodium and potassium which 

 were retained in solution, while the carbonate was deposited. The 

 objection to this view is that, if it is correct, the conversion ought to have 

 taken place in the pre-Cambrian period, and, therefore, there ought to be 

 extensive limestone deposits in the rocks attributed to that period. 



* Sterry Hunt, op. cit., pp. 82 and 311. 

 t Op. cit.. pp. 2 and 41. 



