1895 - 96 .] Mr W. N. Hartley on Changes in Oceanic Deposits. 33 
I will now refer to the occurrence of manganese carbonate in 
the mud- water, which was found to amount to 0*18 per cent., 
although no manganese was found in the sea-water. 
In a paper by Mr W. E. Adeney, in the Scientific Proc ., Royal 
Dublin Society, April 1894, a very lucid account is given of 
the changes which take place in sludge derived from sewage which 
had been submitted to the action of permanganate. 
It was found that the manganese dioxide which appears to be 
the first product of the reducing action of the organic matter 
became converted into manganese carbonate whether in presence 
of much water or not. The author suggests that the reduction 
and conversion into a carbonate of such a stable oxide is due to a 
similar action to that whereby Gayon and Dupetit found nitre to 
be converted into nitrogen and potassium carbonate, under the 
influence of two micro-organisms isolated from sewage and named 
the a. and /3 bacterium denitrificans. 
It is supposed that the available oxygen in the manganic oxide 
is used up by an organism in destroying the carbon of organic 
matter, and by thermo-chemical equations it is shown that this 
can be a considerable source of energy to the organism. It is 
extremely probable that the manganese in this case furnishes 
oxygen to such an organism as the baciltus amylobacter , and is 
utilised in the destruction of cellulose, or in destroying the methane 
which is evolved during the fermentation of this substance. 
Conclusions. 
1. The sulphates in fresh and sea water mud are reduced to 
carbonates and sulphuretted hydrogen by the fermentation of cellu- 
lose through the agency of different species of bacteria. 
2. We have no evidence whatever that calcium sulphide or 
calcium sulphydrate is formed in the course of the chemical 
change, and therefore the equations 1, 2, 3 of Messrs Murray and 
Irvine are not to be relied on for an exact explanation of the 
reactions which occur in mud-waters. 
(1) RS0 4 + 2C = 2C0 2 + RS. 
(2) RS + 2C0 2 + H 2 0 = H 2 S + RC0 3 C0 2 . 
(3) RS + RC0 3 .C0 2 + H 2 0 = 2RC0 3 -i-H 2 S. 
VOL. XXI. 5 / 3 / 96 . 
C 
