AT1.ANT. DEEP-SEA EXPED. 1910. VOL. i] PHYSICAL OCEANOGRAPHY AND METEOROLOGY 



113 



between the registration and heading being found at 9 

 metres. There seems to be a difference in the currents 

 between the various levels of the observations, but the 

 currents were probably ratiier weak. 



At Stat 49 C two current-metres were used simultane- 

 ously, one at 9 metres and another at different depths 

 lower down as far as 1829 metres (1000 fathoms). The 

 results are plotted out in ordinary Carthesian co-ordinates 

 in Fig. 47. The movements of the ship were reduced 

 by means of a big net suspended liy the trawl-wire at a 

 depth of 1000 metres. The depth to the bottom was about 

 5000 metres 



The heading of the ship varied between S. and W. 

 (curve marked "M. S."), while the observations at 9 metres 

 exhibit variations in the direction of the apparent current, 

 mostly between W. and N., /. e. about 90° different from 

 the ship's direction. The two curves show almost the 

 same variations. 



The velocities observed show considerable variations 



with the depth. During the first two hours of observations 



the velocities were 10- 15 cm. /sec. greater at 9 metres 

 than at 91, 274 and 1829 metres while the directions 

 recorded were pretty nearly the same at all 4 depths. 

 The velocity at 9 metres decreased fairly evenly during 

 6—7 hours, while at the other levels the registered velo- 

 city showed a general increase. 



The deepest observations are two from 1829 metres. 

 If we suppose that the real rest-current at this depth is 

 negligible, the movement of the ship can be determined 

 and eliminated from the observation simultaneously made 

 at 9 metres. In so doing we find that the current at 9 

 metres at 23'^ 42"' L. M. T. on the 1st of June 1910 had 

 a velocity of 11 cm./sec. towards N 38'' W, and at 5" IT" 

 on the 2nd of June 12 cm./sec. towards S 86° E. This 

 indicates that there are rotatory tidal currents which have 

 a different velocity and direction at different levels, and 

 that the tidal currents may be quite distinct and measurable 

 even if the depth to the bottom is very great. 



