1895-96.] Mr W. 1ST. Hartley on Changes in Oceanic Deposits. 25 
On the Cause and Nature of the Chemical Changes 
occurring in Oceanic Deposits. By W. N. Hartley, 
F.R.S., Royal College of Science, Dublin. 
(Read December 16, 1895.) 
In Nature of January 24, 1895, appears an abstract of a paper 
read before the Royal Society of Edinburgh on March 7, 1892, 
by Dr John Murray and Mr Robert Irvine, and published in the 
Transactions of the Society, vol. xxxvii. part 2, No. 23, entitled 
“ Chemical Changes between Sea-water and Oceanic Deposits.” 
This is an account of a chemical examination of the sea-water 
salts in the water adhering to or retained in mud, with special 
reference to the formation of the deposit known as “ Blue Mud.” 
Dittmar’s analysis of sea- water is quoted and compared with an 
analysis of mud-water. The chief points of difference between the 
two is the occurrence in mud- water salts of 0*206 per cent, of 
ammonium sulphate, 0*729 per cent, of magnesium carbonate, and 
0*18 per cent, of manganous carbonate; also that the total salts are 
low in proportion to the chlorine they contain. 
The occurrence of ammonium sulphate in this mud, and also of 
manganous carbonate, are facts of much interest ; but there are 
some equations given to explain the chemical changes which the 
mud undergoes which are not strictly in accordance with facts. 
There are three points which I would desire to draw attention to : 
first, the reduction of the sulphates ; second, the oxidation of 
sulphuretted hydrogen ; and third, the formation of manganous 
■carbonate. 
The equations are written without reference to the part played 
hy water in the chemical changes involved, but it may have been 
thought that the accuracy sacrificed was compensated by the 
simpler form of the equations. 
Equation No. 1 reads as follows : — 
RS0 4 -1- 2C = 2C0 2 + RS. — 
where R is an alkaline earth metal. 
This, as a matter of fact, expresses what takes place in the “black- 
