662 DEPARTMENT OF THE INTERIOR 



2 GEORGE V., A. 1912 



note the fact that ammonium chloride formed in this way at the sea bottom 

 diffuses away to upper strata of the ocean waters and would not interfere with 

 the final completion of the reaction. 



Besides the element of time and the undoubted presence of an appreciable 

 amount of magnesium salts in the pre-Cambrian sea, another principal factor 

 must be considered. Hunt has shown that the precipitation of magnesium 

 carbonate from sea water by alkaline carbonates is facilitated if the calcium 

 salts be removed. Our hypothesis states that the latter were absent from the 

 bottom stratum through most of Eozoic time. 



Again we may turn to the noteworthy experiments of Murray and Irvine 

 for a suggestion of the truth of the foregoing statements. Their table is here 

 reproduced (No. XLI). It shows the composition of the precipitate thrown 

 out of a mixture of sea water and urine after standing seven days, the urine 

 meanwhile decomposing and furnishing the alkaline carbonate : — 



Table XLI. 



Water and organic matter containing ammonia (7-38 p. c.) 31-81 



Carbonate of lime 4-85 



Phosphate of magnesia and ammonia 5140 



Phosphate of lime 12-24 



100-00 



Table XLII. shows the composition of the precipitate thrown out of the 

 mixture -(after filtration from the precipitate which was thrown out in seven 

 days), standing other ten days: — 



Table XLII. . 



Water and organic matter 20-25 



Carbonate of lime 75-35 



Carbonate of magnesia 1-02 



Phosphate of magnesia 3-38 



100-00 



These tables* prove that the magnesium carbonate came down only after 

 much, perhaps nearly all, of the calcium was precipitated as carbonate. It should 

 also be observed that a considerable amount of the precipitating alkali, ammonia, 

 was removed from the mixture in the first precipitate. 



Murray and Irvine have also investigated the composition of the water 

 filtered out of the mud dredged from the bottom in Granton Harbour and also 

 near the Forth Bridget The following table gives the resulting total analysis 

 of the salts of the average mud-water and also bears a column indicating the 

 analysis of average sea water : — 



* J. Murray and R. Irvine, Proc. Roy. Soc. Edinburgh, Vol. 17, 1889, p. 104. 

 t Trans. Royal Society Edinburgh, Vol. 37, 1895, p. 490. 



