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



the proportions of these two elements in primeval sea water, the propor- 

 tions must have slowly changed, and as a consequence the magnesium 

 must have gradually increased while the calcium practically remained 

 stationary. 



It must of course be admitted that magnesium is withdrawn from 

 the ocean by organisms, but the amount thus removed is very small, 

 and in no case is it an important method of eliminating the element 

 from sea water. In the hard part of corals it is as a rule under one* 

 per cent, and in the coralreefs it is less than that in amount, while the 

 calcium constitutes nearly 40 per cent. Forchhammer'sf analyses of the 

 ash of sea weeds reveal a quantity of magnesium which he regarded as 

 important, and he held that the Fucoids thus remove quantities of this 

 element and deposit them in the beds which contain the solid substances 

 of sea weeds as far as they are insoluble in water.^ According to the 

 analyses of Godechens,§ the ash of Fucoids contains from 4 to 7 per cent, 

 of magnesium. That the element is eliminated from sea water by these 

 forms may be conceded, but it is doubtful if the quantity removed in 

 this way is sufficient to affect materially in time the total amount 

 retained in the ocean. 



We may conclude, therefore, that in the formation of dolomites, of 

 magnesia-holding limestones and chalk deposits, and, to a minor degree, 

 in the activities of animals and plants, elimination of magnesium from 

 sea water has always obtained ; and, further, that the amount eliminated 

 annually does not equal the amount of magnesium added to the sea by 

 river discharge. This postulates a constant increase in the amount of 

 magnesium in the sea ; and in this respect it must be ranged with 

 sodium, which increases in amount at a greater rate, since, so far as is 

 known, there are for it no agencies of elimination in operation which 

 compare with those affecting the potassium, the calcium, and even the 

 magnesium. The sodium, therefore, though it is not added in greater 

 amount than in the case of the latter, is increasing at a greater rate, and 

 thus the proportion of sodium to magnesium in sea water is slowly alter- 

 ing. As pointed out above, the primeval ocean must have contained 

 but an exceeding small quantity of magnesium, and the amount of the 

 latter now in it is practically wholly derived from the leaching out of the 

 land surfaces during the intervening ages. 



As regards the calcium in sea water there is less uncertainty. The 



* According to Forchhammer the corals, Isis nobtlis and Corallitim nobile, contain 6.36 and a . i per cent, 

 respectively of magnesium carbonate. 



t Roth, op. cit., p. 616, where the results of analyses of a number of forms are given. 



X op. cit., p. 159. 



§ Ann. d Chem. und Pharm., Vol. 54, p. 351, 1854. 



