PHYSICAL OCEANOGRAPHY 



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whether the variations were due to a progressive wave, or to 

 fluctuations in the current, or to standing waves. The results 

 have not yet been worked out, so we can only discuss some of the 

 " Michael Sars " observations. Unfortunately it was impossible 

 to make direct current-measurements, as the weather was too 

 rough. 



During the twenty-four hours we made 86 observations at 

 the buoy, care being taken that the line was absolutely vertical. 

 Surface-observations apart, most of the measurements were made 

 at a depth of 300 metres (19 observations). The temperatures 

 found at this depth are noted in Fig. 189 along the vertical scale, 

 while the hours are put down along the horizontal scale. There 

 were considerable variations : on the 13th August at 5.8 p.m the 

 temperature was 5.60° C, and on the 14th August at 12.25 a.m. 



l3 Vllt /9/0 



Fig. 189. — Temperature Variations at 300 metres at Station 115 

 (13th- 14th August 1910). 



it was 4.73" C. — a difference of 0.87° C. When the mean 

 temperatures of the different water- layers are calculated and 

 represented in curves, it is easy to see how much the tempera- 

 ture altered for each metre of depth. At about 300 metres the 

 temperature decreased with increase of depth to such an extent 

 that a difference in temperature of 0.87° C. corresponded to a 

 difference in depth of about 35 metres. In the other layers 

 there were similar variations, indicating vertical oscillations of 

 between 15 and 35 metres. These observations go far to prove 

 the presence of such undulations of the water-layers, which is 

 indicated also by the form of the curve in the figure, among 

 other things. But these variations are not comprised in one 

 single period, as if they were due to an ordinary progressive 

 wave, or an ordinary standing wave alone. The shape of the 

 curve points to complicated fluctuations of the velocity as the 

 cause of the variations, but it is possible, nay probable, that we 



