R. A. Daly — Limeless Ocean of Pre- Cambrian Time. 103 



The whole series of experiments cited indicate the possi- 

 bility, first, that the pre-Cambrian ocean con Id hold but a 

 minute quantity of lime salts in solution unless those salts 

 were being continually and largely fed into the sea and prefer- 

 ably fed at the surface, farthest from the bottom stratum of 

 water charged with the products of decaying animal matter ; 

 and, secondly, that abundant life existed in water so nearly 

 limeless. 



2. Observations on the Black Sea. — The well known, 

 remarkable studies of Andrussow and others on the hydrog- 

 raphy and deposits of the Black Sea show that we have in a 

 large, existing basin a strong analogy to the imagined Eozoic 

 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 sul- 

 phuretted hydrogen, have been generated in enormous quanti- 

 ties at the bottom. The gas has poisoned the water from the 

 greatest depth (1227 fathoms) to the level of about 100 fath- 

 oms) 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 putrefac- 

 tion. 



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 sum- 

 marized by Murray and Irvine in the following equations : 



RS0 4 + 2C = 2CO„+RS 



RS + 2C0 2 + H 2 = H 2 S + RC0 3 CO„ 



RS + RC0 3 C0 2 + H 2 = 2RC0 3 + H\S 



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



These reactions presuppose the absence of free oxygen. Andrus- 

 sow points out, not only the incompatibility of oxygen and 



* Guide des Excursions, vii me Congres Geologique Internationale, No. 29, 



1897. 



