484 DR JOHN MURRAY AND MR ROBERT IRVINE ON THE 



Specific Gravity of the Mud-Waters. — The specific gravity of the water from the mud 

 in Granton Harbour ranged from 1024*3 to 1025'7, that of the superincumbent water 

 averaging 1024'57. In the 1st portions of the water from Granton Harbour and 

 Queensferry muds a higher density was observed, owing, as we shall show, to an increase 

 of sulphates formed by the oxidation — during the dripping process — of the sulphide of 

 iron (FeS) present in the outer portions of mud resting on the inner surface of the bag, 

 and therefore more or less exposed to the air. The subsequent portions were lower in 

 density, till towards the end of the dripping there was again a slight increase of density 

 caused by the evaporation of the water which then drips very slowly (see tables).* 



Sulphuric Acid in Mud- Waters. — A reference to the tables that follow will show that 

 in the case of the waters obtained from the Granton Harbour and Queensferry muds, the 

 1st portion which came through the filter-bag contained more sulphuric acid (S0 3 ) than 

 normal sea-water. This was evidently due to the oxidation of the sulphide of iron after 

 the mud was removed from the sea and while dripping through the bag, as stated above. 

 In the 2nd portion obtained from the dripping bag there was a marked decrease in the 

 sulphuric acid (S0 3 ), and this decrease was maintained in the following and later portions 

 obtained in the same way. 



It will also be seen by reference to the tables that the 1st portions of the mud 

 waters from the two samples taken in the Granton Quarry differ from the 1st portions 

 above mentioned, in containing less sulphuric acid than normal sea-water, the oxidation 

 of the sulphide on the internal surface of the bag not sufficing in these, as in the other 

 1st portions, to raise the sulphuric acid above the normal. The portions marked 3rd, 4th, 

 5th, 6th, 7th, and 8th in the tables may in all the samples be taken to fairly represent 

 the water associated with the mud, and all these samples contain less sulphuric acid than 

 is found in normal sea-water. 



Albuminoid and Saline Nitrogen in Mud- Waters. — In all the mud-waters the saline 

 ammonia was enormously in excess of that usually present in normal sea-water, varying 

 from 4 to 80 parts per million, while ordinary sea- water from the open ocean contains, 

 as a rule, about 0'02 part per million. In the sea-water lying directly above and in 

 contact with the Blue Muds of Granton Harbour and Granton Quarry, the saline ammonia 

 averaged about 2 parts per million,t thus showing that the sea-water immediately above 

 a Blue Mud differed much in this respect from ordinary sea-water from the open ocean. 



Albuminoid or Fixed Nitrogen was found in solution in the mud- waters to range from 

 1*17 to 5"63 parts per million, presumably due to the less or greater abundance of 

 animal life or dead organic matters present in the deposit. The mud itself was found 



* From a quantity of mud taken from the bed of the Clyde opposite the Gareloch, mud-waters were obtained having 

 a mean density of 1035 ; these waters were not chemically changed, and should this observation be verified it may point 

 to a process of concentration in sea- water muds, even when covered by water of normal density. 



t The method adopted for the determination of the saline ammonia was as follows : — Pure potash solution was 

 added to the sea-water, and the precipitate formed removed by filtration through filter-paper, from which any trace of 

 ammonia (generally present in filter-paper) had been removed by washing with pure potash solution, the clear filtrate 

 being nesslerised in the usual manner. The saline ammonia is more abundant in tropical oceanic waters than in water 

 of temperate zones (see Murray and Irvine on Coral-Reefs, &c, Proc. Roy. Soc. Edin., 1889-90, p. 89). 



