138 THE OCEAN FLOOR 



conditions were often met with above the rugged parts 

 of the floor of the Atlantic Ocean. In collecting samples 

 from the bottom water we found that preventing dust 

 and atmospheric gases from contaminating the water is 

 essential. Chemical properties were determined at once 

 by our chemist from part of the sample, and from an- 

 other part the optical properties were studied by the 

 Tyndall method by Jerlov himself. It should be added 

 that similar optical tests were made on samples from 

 other water layers, including surface water, and that 

 the results have proved most illuminating for the study 

 of the dynamics of upper and intermediate water strata. 

 Two figures setting forth Jerlov's results pertaining to 

 the bottom water at a few Atlantic stations are re- 

 produced here. 



It is seen that in certain localities the bottom water 

 remains practically crystal clear down to the lowest 

 level examined, proving that there is no apparent stir- 

 ring up of sediment particles below. In other localities 

 the number of suspended particles distinctly increases 

 as one approaches the bottom, which proves that there 

 is some kind of turbulent motion going on. It is of 

 interest to note also the results of examining samples 

 from somewhat higher levels, where Jerlov found 

 distinct clouds of particles. A similar find was made 

 some years earlier by Kalle, the German oceanog- 

 rapher, working in the North Atlantic Ocean. ^ He 

 assumed these clouds to be remnants of volcanic ash 

 rains that had not had time to settle to the bottom. 



