1890-91.] Mr J. Y. Buchanan on Sulphur in Marine Muds. 33 
2 *35 6 4 grins, dry mud, and therefore we find that the mud taken as 
dry contains 047 per cent. FeS and 092 per cent. FeO in some 
other easily decomposable combination. 
The other samples were treated in the same way, and in the Loch 
Duich mud, from 51 fathoms, 0'94 per cent. FeS + 065 per cent. FeO 
were found. It is remarkable that the amount of F 2 S should be so 
small in such offensive muds. 
In the outside mud from 120 fathoms in the Sound of Raasay 
only 0*05 per cent. FeS and OT per cent. FeO were found. 
In connection with this mud, which contained some shell 
debris, the method was found to be less applicable than to muds 
free from calcareous matter. The reason is obvious ; because, on 
adding a neutral ferric solution to a mud containing carbonate of 
lime, precipitation of the ferric oxide by the lime immediately 
commences. This would not really interfere with the reaction, 
because the FeS would reduce the precipitated Fe 2 0 3 all the same, 
and the ferrous salt can still be determined by permanganate ; but 
in truly calcareous bottoms this action is troublesome, and the 
method will require special study in this direction. In the semi- 
enclosed basins of the sea lochs, which, as has already been observed, 
form a transition between the open sea and fresh-water lakes, the 
bottom resembles more nearly that of the fresh-water lakes, in the 
absence of mollusca, and in the abundance of organic matter of 
vegetable origin, than that of the open sea with its abundant and 
varied ground fauna. It differs from those of fresh-water lakes in 
being bathed by sea-water largely impregnated with sulphates. Con- 
sequently it is in the inner basins of sea lochs that the conditions 
for a constant production of sulphides are present, while the same 
conditions are hostile to the presence of calcareous organisms. 
Hence it is in these basins that the greatest quantities of sulphides 
are found, and it is in their muds that the above method is most 
applicable. 
The sulphuretted muds, however, are so alterable by atmos- 
pheric influences that it is essential that they should be treated 
immediately on collection. For this purpose weighed wide- 
mouthed bottles with good stoppers should be provided. When 
a specimen of mud is brought up from the bottom, a sample 
of it is immediately taken with a spatula and put into one 
vol. xviii. 31/12/90 c 
