Marine Muds and Nodules 151 



equal to a loss of 70-1 per cent. Therefore the dry mud is 

 29-9 per cent, of the damp mud taken. The 7-881 grms. 

 damp mud therefore represent 2-3564 grms. dry mud, and 

 therefore we find that the mud taken as dry contains 0-47 

 per cent. FeS and 0-92 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 + 0-65 

 per cent. FeO were found. It is remarkable that the amount 

 of FeS 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 o-i per cent. FeO were found. 



In connection with this mud, which contained some shell 

 dtbris, 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 con- 

 taining carbonate of lime, precipitation of the ferric oxide 

 he lime immediately commences. This would not really 

 fere with the reaction, because the FeS would reduce 

 the precipitated Fe 2 O 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 

 ial 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 

 matt egetable origin, than that of the open sea with 



-round fauna. It d "in those 



of fresh-water lakes in being bathed by sea-water largely 

 tted with sulphates, f <.n^( .pientlv it is in the inner 



ns of sea loci e conditions for a constant prodn. 



ilphides are present, while the iai W hostile 



he presence of c Hence it i> in these 



hat the great titis of sulphides are f.mi.d 



ibove method i^ most appli. able. 



however, are so alterable by 



thai It i . . t h e y S I, OI ,M 



be itely on collection. For this purpose 



