138 



SCIENCE 



[N. S. Vol. XXVI. No. G57 



sulphate we must expect to find it as well 

 as sulphate low in early times. 



We are thus brought face to face with 

 a very important problem of historic geol- 

 ogy, the chemical evolution of the ocean. 



Studying the Paleozoic waters, we find 

 unmistakable indications that they were 

 low in magnesium sulphate, but that they 

 contained relatively large quantities of cal- 

 cium chloride. This, as long ago noted by 

 Hunt and Goessman, is characteristic of the 

 Paleozoic brines. CaCl, must have been 

 precipitated little by little by the carbon- 

 ates and sulphates, forming the calcium 

 carbonate and sulphate of the sedimentary 

 rocks, while the sodium and magnesium re- 

 mained in solution. 



The ratio of calcium to magnesium in 

 the vital fluid is aboi;t 0.10 : 0.025, say four 

 to one, while in the Saginaw carboniferous 

 brines it is usually near three to one. 



Here for the third time we come to the 

 conclusion that the vital fluid has a com- 

 position that the ocean is likelj^ to have 

 had in times past, not at the beginning of 

 its progressive change, but at about the 

 time when we find the first trace of verte- 

 brate life. 



4. For the Ottawa meeting of the Geo- 

 logical Society of America I prepared a 

 paper on the chemical evolution of the 

 ocean, and I showed a diagram in which 

 analyses of waters from different strata 

 were arranged according to the ratio of 

 sodium to chlorine, which appeared to have 

 increased in the ocean from something like 

 .20 in Caloiferoiis times to .555 at present. 

 A change in concentration of from 8 to 10 

 parts up to 35 in the same time would be 

 of the same order, but would imply con- 

 siderable additions of chlorine in the same 

 time, which we should have to look to the 

 volcanoes and their rocks to furnish. It 

 would also imply, if both changes were 

 uniform, which does not seem likely, that 



when the concentration by river action 

 began the ratio of sodium to chlorine was 

 somewhat about 0.06. Even in the weakest 

 water and at the beginning the ratio of 

 sodium to chlorine must have had some 

 value, and this is about the ratio in the 

 deep water of the Keweenan copper mines, 

 and may be the ratio which comes from 

 juvenile waters, or those emitted by vol- 

 canoes, or may be that due to the leaching 

 of volcanic rocks. 



For the fourth time the suggestion is 

 forced upon us that the vital medium does 

 not represent the early ocean, not that 

 which fii-st began to cool, nor that in which 

 the rivers fii-st began to bear their burden 

 of dissolved salts. It does seem quite 

 nearly to correspond to that which we have 

 other reasons to believe existed at 'the 

 beginning of the Ordovician or end of the 

 Cambrian, not long before the time that 

 the first fishes are kno^vn to have existed, 

 but^much after life is known to have 

 existed. 



The evidence goes then to support Mac- 

 allum 's modification of Quinton 's ' theory 

 (conceived quite independently) that the 

 vital medium represents the ocean water at 

 the time the body cavity in the progress of 

 evolution became osmotically closed. 



It thus seems likely that we have found a 

 key by which we may date the develop- 

 ment of life and the deposition of beds in 

 terms of the development of the ocean, 

 whenever we can get a sample of the nor- 

 mal ocean water of the time, or approxi- 

 mate to it. I need hardly say that it is 

 not likely that this change in the ocean 

 proceeded at a uniform rate. Changes in 

 climate would affect the great distilling 

 process upon which the development rests. 

 Great ^^plifts might hasten the supply of 

 salts. Geographic conditions leading to 

 the deposition of enormous salt beds in 

 partially cut-off bays might reduce the con- 



