660 DEPARTMENT OF THE INTERIOR 



2 GEORGE V., A. 1912 



ocean.* As a result of a special series of geological events, this sea basin is 

 devoid of bottom scavengers over the greater part of its area. On the other hand, 

 the surface fauna has always been abundant. The bottom has therefore received 

 the fallen carcasses of the surface animals which, unceasingly, have putrefied 

 in the relatively high temperature of that sea floor. Two soluble products, 

 ammonium carbonate and sulphuretted hydrogen, have been generated in 

 enormous quantities at the bottom. The gas has poisoned the water from the 

 greatest depth (1,227 fathoms) to the level of about 100 fathoms from the 

 surface. Below the 100-fathom level no life is possible except that of a few 

 anaerobic bacteria, one of which has been studied and named as the primary 

 cause of putrefaction. 



Corresponding to our hypothesis, it has been found that the bottom muds 

 of the Black Sea basin are rich in a powdery deposit of carbonate of calcium. 

 Far from shore, and thus in areas not so abundantly supplied with silts, the 

 carbonate occurs in thin white layers. In shallower water, from ' 300 to 717 

 fathoms,' the mud is black and the presence of the carbonate is masked by the 

 relative increase of mechanical deposit. 



The black muds, and less conspicuously the deposits of the greater depths, 

 are strongly charged with disseminated iron sulphide. The mode of formation 

 of this sulphide is summarized by Murray and Irvine in the following equations : 



RS0 4 + 2C = 2CO. + RS 

 RS + 2CO, + H 2 = ELS + RC0 3 C<X 

 RS + RC0 3 CO, + H„6 = 2RCO3 + H.S 

 Fe 2 8 + 3H ; S = 2FeS + S + 3H 2 



These reactions presuppose the absence of free oxygen. Andrussow points out, 

 not only the incompatibility of oxygen and free sulphuretted hydrogen, but also 

 states another cause of the poverty of the bottom waters in free oxygen. It is 

 in part due to the lack of normal vertical currents in the Black Sea; these are 

 impossible because of the peculiar density stratification of this basin. 



The equations show that, in the presence of ferruginous muds, free sulphur 

 is precipitated along with the sulphide of iron. It is thus easy to understand 

 the formation of the numerous nodules of iron pyrites found in the black muds. 

 In the main ocean near muddy shores the foregoing reactions also apply to a 

 part of the changes produced by putrefaction. The analogous case of the Black 

 Sea, therefore, proves the truth of the prevailing views as to the formation of 

 iron pyrites in marine sediments, and also the corollary of our hypothesis as 

 to the gradual destruction of the sulphuric acid radical in Eozoic sea water. 

 That all the lime salts have not been precipitated from the Black Sea water is, 

 of course, due to the large amount of Mediterranean water constantly renewing 

 the lime salts by way of the bottom current at the Bosphorus. 



It seems clear that the Black Sea is carrying on a gigantic natural experi- 

 ment which strengthens belief in the main deductions so far made as to the 

 physical and biological conditions of the Eozoic sea. In one important respect 



• Guide des Excursions, VII m e Congres Geologique Internationale, No. 29, 1897. 



