100 EXPEDITION OF THE "CHALLENGER" in 



present, to frame any satisfactory explanation of 

 the mode of origin of this singular deposit of red 

 clay. 



I cannot say that the theory put forward 

 tentatively, and with much reservation by Pro- 

 fessor Thomson, that the calcareous matter is 

 dissolved out by the relatively fresh water of the 

 deep currents from the Antarctic regions, appears 

 satisfactory to me. Nor do I see my way to the 

 acceptance of the suggestion of Dr. Carpenter, thnt 

 the red clay is the result of the decomposition of 

 previously-formed greensand. At present there is 

 no evidence that greensand casts are ever formed 

 at great depths; nor has it been proved that 

 (Uauconitc is decomposable by the agency of water 

 and carbonic acid. 



I think it probable that we shall have to wait 

 some time for a sufficient explanation of the origin 

 of the abyssal red clay, no less than for that of the 

 sublittoral greensand in the intermediate zone. 

 But the importance of the establishment of the 

 fact that these various deposits are being formed 

 in the ocean, at the present day, remains the same, 

 whether its rationale be understood or not. 



For, suppose the globe to be evenly cohered with 

 sen, to a depth say of a thousand fathoms then, 

 whatever might be the mineral matter composing 

 the sea-bottom, little or no deposit would be 

 formed upon it, the abrading and denuding action 

 of water, at such a depth, being exceedingly slight, 



