82 



THE VOYAGE OF H.M.S. CHALLENGER. 



during this time the surface water itself may have been moving, the actual movement of 

 the watch buoy, with reference to a fixed point, was therefore represented by the 

 resultant of the movement of the surface water and the movement of the watch buoy 

 through the surface water. 



Figure 26 shows the result of the observations made on the currents on the 24th April 

 1873. The surface current was found to be nearly N. 60° E. 0"24 mile per hour; the 

 watch buoy of the drag at 50 fathoms was found to move E. 0"24 mile per hour from 

 the surface current log ; the movement of the watch buoy from a fixed point was there- 

 fore N. 75° E. - 46 mile per hour. In the same manner the current was ascertained 

 at 100 fathoms, 200 fathoms, &c. 



These results were assumed as giving the rate and direction of the current at 

 different depths with sufficient accuracy to ascertain any marked movements, but it is 

 evident that they are not strictly accurate, as no allowance was made for the retarding 

 or accelerating influence of the surface water on the watch buoy, or of the intermediate 

 water on the line. 



To facilitate lowering and hauling in the current drag, a small derrick was made to 

 ship in the boat where the foremast stepped. 



