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 by 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.