248 



DEPARTMEXT OF THE NATAL SERVICE 



A picture of the ice block being projected on to a white sheet by means of an 

 arc lamp, it was seen that streaks were moving upward on the cloth, indicating that 

 some of the melting water from the surface of the ice rises to the surface of the 

 water, forming there a surface layer of fresher water; some portion of it, however, 

 doubtless becoming mixed ?vith the sea-water which is melting the ice and sinking 



Fig. 31. — Disti'ibution of .salinit.y near the ice. 



<lown with it. Vide figs. 31 and 32, showing distribution of salinity and temperature 

 in front of the ice block. 



In order to measure the movement of the water more exactly, a long capillary 

 pipette was filled with potassium permanganate solution, and introduced vertically to 

 the bottom of the tank from above. On being drawn up, it left behind it a fine vertical 

 thread of the solution, which was afterwards visibly curved by the current. After the 

 space of two' minutes, a drawing was made of the thread as it then appeared. Fig. 



Fig. 32. — Distribution of the tem])erature near the ice. 



33 shows the original vertical and subsequent altered course of the permanganate line. 

 The horizontal lines thus indicates the movement of the water particles during the 

 two minutes. 



