THE FLOOR OF THE OCEAN BOSWELL 287 



soluble compounds, the alkalies, calcium, magnesium, and so forth. 

 The insoluble residues are ultimately of clayey character, such as 

 hydrated silicates of aluminium and oxides of aluminium and iron. 

 Hitherto, we have distinguished between mechanical disintegration 

 and chemical decomposition as processes of degradation, but recent 

 investigations by Prof. A. Brammall of the Imperial College of 

 Science and Technology, as beautiful in their simplicity as they are 

 significant in their wide repercussions, have abolished that distinction. 

 For Professor Brammall has extended the work of Tamm and Stevens 

 by demonstrating that fine grinding of most common rock-forming 

 minerals brings them into a condition when they are hydroscopic and 

 become partially dissociated in water, so that the elements of the 

 alkalies and alkaline earths are liberated. 



Ultimately, then, the finer suspended material which reaches the 

 deeper parts of the sea consists almost exclusively of simple hydrated 

 silicates of aluminium in a fine state of division, that is, clay. In 

 addition to this detrital accumulation there are the deposits of cal- 

 careous and siliceous materials formed by organisms. It would seem 

 that there is thus an almost complete differentiation into a solution 

 (sea water) rich in its diverse dissolved elements, and "dull" floor 

 deposits of very restricted composition. Such must be the tendency 

 unless synthetic processes are proceeding in the depths to form new 

 minerals. J. L. Thiebaut claimed to have proved in 1925 that 

 marine clays were usually composed of complex silicates of aluminium, 

 iron, potash, calcium, and magnesium, in contradistinction to fresh- 

 water clays which are largely silicates of aluminium with a little iron 

 and magnesium. We may ask then — or formulate the question as a 

 problem for investigation — whether the elements in sea water are 

 being restored to the accumulating simple clays in the depths of the 

 sea, a region termed by Correns "Nature's laboratory," although 

 perhaps to speak of "factory" would be more appropriate. But in 

 the meantime even our small knowledge of the processes at work 

 convinces us, with Shakespeare, that "clay and clay differ in dignity." 



