60 A Retrospect of Oceanography 



When a freshly collected sample of submarine mud is care- 

 fully washed with a jet of water, until the finer flocculent 

 particles are removed, the mud which remains is in the form 

 of elongated casts of ellipsoidal form. Pressure with the finger 

 breaks them up into flocculent particles, which can be washed 

 away with the jet of water, leaving still some ellipsoids. By 

 continuing this treatment, finally all the flocculent matter can 

 be washed away, but the ochreous deposits thus freshly collected 

 and carefully examined are always found to be made up of these 

 ellipsoids which are nothing more nor less than present-day 

 coprolites. The animals, which live in abundance in the mud, 

 live by passing it through their bodies and extracting from it 

 what nutriment they can. The trituration of the mud in the 

 interior of the animals and in contact with living organic 

 matter reduces the sulphates of the sea-water to sulphides. 

 These, in contact with the ferric oxide of the mud, reduce 

 it to ferrous sulphide with separation of sulphur. Hence 

 the mud not immediately in contact with the water has a bluish- 

 black appearance. When it comes in contact with the water 

 which contains free oxygen, the ferrous sulphide is oxidised 

 and the surface layer becomes red. If this is the true explana- 

 tion we ought to be able to find traces of free sulphur in the mud, 

 although the finely divided sulphur which is produced in this 

 class of reaction is easily oxidised. 



Acting on this idea, and connecting it with Oscar Peschel's 

 brilliant application of the Relicten fauna of lakes and rivers in 

 the diagnosis of morphological terrestrial changes, I treated a 

 series of oceanic muds and manganese nodules with chloroform 

 for the extraction and determination of any sulphur that they 

 might contain. The experiment was successful in every case, 

 and the results are given in a paper 1 on the occurrence of sulphur 

 in marine muds, read before the Royal Society of Edinburgh. 

 When surveying the Gulf of Guinea in 1886 in the "Buccaneer," 

 I found this coprolitic character of the mud near the mouth 

 of the Congo so highly developed that in the reports of the 

 soundings I had to introduce a new designation for this class 

 of mud, namely coprolitic mud. 



1 See Paper No. 6, p. 133. 



