No. 6. [From Proc. Roy. So<;. Edin. 1890, Vol. xvin. pp 17-39.] 



THE OCCURRENCE OF SULPHUR IN 

 MARINE MUDS AND NODULES, AND 

 ITS BEARING ON THEIR MODE OF 

 FORMATION 



IN the first section of the cruise of the "Challenger," that 

 from Teneriffe to Sombrero, the existence was established of 

 deep-sea muds, perfectly free from carbonate of lime, consisting 

 mainly of silicates mixed with ochreous material, principally 



rated oxides of iron and manganese, and of local concen 



i of these materials in the form of nodules and of coat 

 or incrustations on dead calcareous matter. The qualitative 

 composition of these concentrations was carefully determii 

 and it was particularly noted that whether in the form of 

 nodules or of incrustations they were aggregations of the 

 general materials of the bottom, and not concretions or coatings 

 of pure hydrous oxides. 



On the section between Bermuda and the Azores some 



very suggestive specimens were got from the bottom on 



ne 1873, when the ship dredged in 1675 fathoms in 



;8 18' N., long. 34 48' W. A number of light-coloured 



concretions were brought up which were much perforated 



by worm-holes, the walls of which were all stained black i-h 



brown. The substance of the concretions consisted of carbonate 



ites, and the black lining of the holes was 



peroxide of manganese. The various specimens obtained on 



occasion showed the deposition of oxide of manganese 



irious stages, from those which showed only specks or 



is to those containing a considerable percentage 1 . The 



-y are describe I x. Roy. Sac., 1876, vol 



p. 606. It Is reprinted as No. 5 of my Cotkctod Scientific Pmptft. published 

 by the Cambridge University Press, to i 



