80 



The indentation south of the Tail of warm Atlantic water into the 



mixed zone and its comiterflow toward the southwest, as shown on 



Figure 38, p. 78, brings to mind a similar condition foimd by the Michael 



Sars on a section across this region in 1910. (Murray and Hjort, 



The Depths of the Ocean, p. 99.) As a result of the observations of 



this expedition, the impression is often held that the Gulf Stream 



south of Newfoundland is split by a cold southwesterly current, but 



as such a phenomenon has seldom been observed the true condition 



has remained obscure. The ice patrol observed a similar location of 



the two currents south of the Grand Bank in 1923, but evidence in 



the form of surface temperature charts proved the cold current to be 



temporary and caused by the great irregularity and distortion of the 



boundary between coastal and oceanic masses. A multitude of curling 



tongues and votices is a natural accompaniment along the border 



of two opposing ocean flows, and our present-day ability to plot the 



stream lines of the currents reveals hitherto unsuspected phenomena 



concerning the behavior of the water particles. The fact that the 



course of the northern edge of the Gulf Stream south of the Grand 



Bank is found so extremely sinuous, turning and bending back so 



sharply upon itself, strikingly emphasizes the great mobility of water 



in the open sea. 



SET III 



This set of observations, taken May 10 to 18, extends the view 

 from the neighborhood of the Tail, where the two former surveys 

 stopped, to the circulation along the entu'e eastern side of the Bank. 

 This is the first time that a dynamic survey has ever been made of 

 this particular region. The axis of the depression previously observed 

 off to the southwest of the Grand Bank was moved so much closer in 

 to the continental edge, as shown by Figure 41, that the rising slope 

 to be expected inshore of it no longer falls within the picture. Con- 

 sequently no westerly current appears there, though such a set no 

 doubt existed some few miles in on this part of the Bank. At the 

 same time the extreme tip of the projection of high surface previously 

 extending from west to east in the offing of the Tail had flattened out 

 and the low pool to the southeastward had also shifted correspond- 

 ingly to the westward. A second trough in the sea surface, as em- 

 braced by the dynamic contour of 728.70 dynamic meters, is seen on 

 Figure 41 projecting offshore from the shelf for about 80 miles between 

 the forty-third and forty-fourth parallels, and this formation is 

 probably a development of the shoaler depression seen in the same 

 general location on Figure 37. The ridgelike elevation to the 

 north of it persists in extending southwestward, even abutting the 

 50-fathom curve of the Bank. 



