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



103 



between Stats.68 and 66 for the isobaric surface of 1000 

 decibars. By equation (f) we find: 



rDe,. -D«s) 10^ _ ... -6175 



V 



1000 



= — 10 



1-08 



L 100 



r= 66-7 cm. /sec, 



which means that the gradient current at the surface has, 

 normally to the straight line between Stat. 68 and Stat. 

 67, a component which is 66-7 centimetres per second 



cm/sec 



the conditions in the sea west of the Bay of Biscay, where 

 there is probably no strong gradient current but some 

 eddies as shown in Figs. 39 and 40. 



Curves I and II show a maximum of the velocity- 

 components at about 25 metres below the surface. Dynamical 

 calculations from other areas sometimes show a similar 

 maximum at a short distance below the surface. This 

 feature of the current is difficult to explain, but it may 

 possibly depend partially on a comparatively great differ- 



- 200 



300 



- V)Q 



- 500 



600 



700 



600 



()00 



1000 



10 20 iO 



Fig. 41. Velocity components relatively to the components at 1000 metres depth. 



greater than the corresponding component at about 1000 

 metres, both components being reckoned in such a direc- 

 tion that Stat. 68 is found to the right. Similarly we can 

 find the differences of the velocity-components for various 

 depths relatively to the water at about 1000 metres. 



The five curves in Fig. 41 represent, in centimetres 

 per second, such differences of velocity components be- 

 tween the levels represented by the ordinates p and the 

 level for p ^-^ 1000 decibars. Each curve refers to the 

 average condition between two particular stations, the niuTi- 

 bers of which are written at the curve, begirniing with the 

 station on the left hand side of the current. 



The curves 1, II and III in Fig. 41 illustrate the con- 

 ditions in the Great Atlantic Current south of the Newfound- 

 land Banks, and curve IV the conditions in the current 

 midway between America and Europe. Curve V illustrates 



ence of direction between wind and gradient-current. As 

 a matter of fact such differences of direction must be 

 expected at the stations 66—69, where the gradient cur- 

 rent alters its course very rapidly owing to the topography 

 of the sea-bottom as already mentioned. But other ways 

 of explanation may also present themselves. 



Below the surface layers the velocity-components 

 decrease with the depth at a different rate. Curve I shows 

 a maximum of vertical variation at about 500 metres. Below 

 800 and 900 metres the vertical variations are comparati- 

 vely slight, indicating that we here approach the lower 

 boundary of the current. Similar conditions are also found 

 with regard to curves 11, III and IV. 



Our computations have so far resulted in numerical 

 values of the vertical variations of the velocity-components. 

 If the dynamic isobaths in the isobaric surfaces may be 



