ATLANT. DEEP-SEA EXPED. 1910. VOL. ll 



PHYSICAL OCEANOGRAPHY AND METEOROLOGY 



107 



50. APRIL 19J0 

 ILM.TS 3 



Fig. 42. The N.- and E.- components of the current at Slat. 18, 9 metres. 



affects the results of the harmonic analysis with regard 

 to the semi-diurnal variations and the rest current. 



The broken lines in Fig. 42 connect points (for 22 

 and 10 L.H.) which would have been found along the 

 same ordinates if the current had been composed of a 

 constant rest current and a semi-diurnal tidal current only. 

 The variations with a longer period than 12 lunar hours 

 are certainly not linear, but we may to some extent eli- 

 minate them in our analysis of the semi-diurnal variations 

 by taking them as linear. We can then reduce the hourly 

 values which were used in the harmonic analysis above. 

 In doing so we obtain the following equations: 

 t; = 21-6 — 380 cos 30 (H -^ 2) — 3-3 sin 30 (H -\- 2) 

 u -^ 50-3 - 47-9 cos 30 (H + 2) + 23-3 sin 30 (H + 2) 



This gives a rest current with a velocity — 55 cm./ 

 sec. towards N 67° E, and a maximum of the semi- 

 diurnal tidal current ~ 63-5 cm. /sec. towards N 56° E 

 and S 56° W. So far, the results are nearly the same 

 as those found by the first analysis, but in other respects 

 the results differ. The maximum ot the semi-diurnal tidal 

 current appears 3' '2 and not 4 lunar hours after the pas- 

 sage of the iTioon. While the major axis of the ellipse 

 is almost the saine in both cases, the minor axis comes 

 out a good deal greater with the reduced than with the 

 original values. The most striking difference between the 

 results of the two calculations is, however, that the second 

 analysis gives a semi-diurnal tidal current which turns 

 contia solem, while the first gave a turn cum sole. The 



