64 THE OCEAN 



only be renewed by diffusion, and by the 

 undercurrent from the Bosphorus, therefore 

 much too slowly to maintain life. The amount 

 of atmospheric gases diminishes with increase 

 of depth, and at the same time sulphuretted 

 hydrogen is formed and augments gradually 

 on descending into deeper water, being equal 

 to 33 cc. per litre (or parts per thousand) at 

 a depth of 100 fathoms, 222 cc. per litre at 

 200 fathoms, 555 at 950 fathoms, and 655 at 

 1185 fathoms. Similarly sulphides appear 

 and increase with the depth. The presence of 

 sulphuretted hydrogen is attributed to the 

 activity of bacteria ; it partially combines with 

 iron salts and partially penetrates into the 

 water, its conservation being favoured by the 

 poverty in oxygen of the deeper waters. 

 Other chemical modifications in the deeper 

 waters and deposits result, such as a relative 

 diminution of sulphates and increase of 

 carbonates, and the deposition of a powdery 

 precipitate of calcium carbonate. 



