Marine Muds and Nodules 155 



get reduction of the ferric salt without formation of FeS. 

 On adding excess of MnS, we get formation of FeS, and then 

 on adding excess of Fe 2 (SO) 4 we get back to the same state 

 of things as at first. 



The reaction of equation (i) can be obtained by very 

 cautiously adding small quantities of suspended MnS to a 

 \( rv large excess of Fe 2 (SO 4 ) 3 . Still there is always local 

 formation of FeS which disappears on mixing, so that the 

 reaction is really that of the whole cycle. The action, there- 

 fore, of MnS on soluble iron salts is in the first instance to reduce 

 whatever is in the ferric state to the ferrous, and then at once 

 to precipitate the ferrous salt as sulphide, a manganous salt 

 taking the place of the ferrous salt in the solution. 



\Yhen added in great excess to solutions of nickel sulphate, 

 manganous sulphide precipitates it as NiS. When added to 

 solution of sulphate of zinc, it either does not precipitate 

 it at all or only very slightly at ordinary temperatures. 

 Sulphide of zinc was not found to precipitate manganese 

 sulphate solution. 



As the result, then, of the observations and experiments 

 which have been recited I was led to believe that the principal 

 agent in the comminution of the mineral matter found at the 

 bottom of both deep and shallow seas and oceans is the ground 

 fauna of the sea, which depends for its subsistence on the 

 organic matter which it can extract from the mud. 



In order to fit them for collecting their nutriment in this 



the animals have been fitted with different forms of 



i ting or milling apparatus, so as to thoroughly deal 



with the matter which they pass through their bodies. It 



leen shown that most silicates are decomposed to a certain 



t win n ground or pulverised under water; so that the 



mere mastication of the sand or mud in presence of pure \v 



would have a decomposing action on the silicates whirh it 



in-. Thi- action H mm h ittfetod, in the case of in, mm- 



animals, by the fact that the wat r win. h they pass through 



along with : rged \\itli Milphntes. 



te are e.i iuced to sulphides by the action of the 



natter of the secretions of th< animals. The resulting 



