130 



were noted. It appeared to assume its greatest velocit}^ in the vicinity 

 of the Tail on the eastern slope where a rate as high as 1.5 knots per 

 hour was observed, and several times the patrol vessel detected a cur- 

 rent of 0.8 knot per hour. Yet on several other occasions, separated 

 by an interval as much as two weeks, we were convinced, by means of 

 excellent astronomical sights, that no current flowed southward 

 along the east side of the Bank at that particular time. Wide varia- 

 tions in tlie rate of flow of the arctic water in this region have been 

 noted before, but no complete cessation has ever been recorded during 

 the ice season. 



An interesting example of tlie manner in which the icy curreni 

 mixes with the Atlantic water was shown by the behavior of berg 

 Xo. 2 as it drifted southward past the Tail into the mixed watei' 

 zone and finally floated in tropical Atlantic water where it even- 

 tually melted.*° While this berg was drifting through the mixed- 

 water zone which lay between the Tail of the Bank and the " cold 

 wall," it was approximately 150 feet high, and drew about 350 feet 

 (120 meters) and thus floated southwestward in water the surface 

 layers of which we found to be Arctic.^^ That upper 125 meters were 

 decidedly arctic, but below that depth the water became salty and 

 warm, the transition just below the 125-meter depth being strikingh' 

 abrupt unmistakably defined the division between the Arctic dis- 

 charge and the oceanic Atlantic. Berg No. 2 continued to follow !i 

 southwestward course until April 6, but its rate of drift diminished 

 from 1 knot per hour at the Tail to 0.5 knot per hour 45 miles south- 

 west of there. This furnishes an -excellent example of the manner in 

 which the Arctic water discharges become shallower and shallower 

 as it spreads off-shore in the mixing zone southwest of the Tail, yet 

 such relatively superficial circulation is sufficient to transport a 

 fairly large berg into menacing positions just north of the steamship 

 tracks. Another observation of the subsurface taken near berg No. 

 2 farther south than its position April 6 showed that the water of 

 arctic character became still shallower the nearer it approached the 

 '• cold wall." Arctic traces did not extend downM'ard over 50 meters 

 (27 fathoms) and on account of this the drift of berg No. 2 was 

 correspondingly retarded. It was in this locality that it drifted 

 from the mixed-water zone across the "cold wall " into tropical sur- 

 roundings. 



Sketch No. 6 shows the position of the Arctic discharge at a depth 

 of 50 meters (27 fathoms) below the surface with respect to tem- 

 perature distribution. It will be noted that Arctic water was more 

 clearly traced b}' means of the lowest temperature in a direction 



«See chart B. 



•' See occanoirrnpliic station tnUlc, p. ST. Station ".So. 



