58 INTERNATIONAL ICE OBSERVATION AND ICE PATROL SERVICE. 



March 27 in lat. 41° 40' N., long. 51° 07' W. This is the well-known 

 "cold wall" of oceanographers. (See plate 5.) The surface of the 

 water on the cold side of the wall was smooth and glassy, its temper- 

 ature registering 34° F., while on the south side of the wall the surface 

 was chopped and rippled, vnth a temperature of 56° F. At places the 

 demarcation was very pronounced, and was indicated by a series of 

 small eddies, which caused air bubbles and froth to form. The 

 boundary was still more clearly defined by driftwood and d6bris 

 which had collected here and there. This would appear to indicate 

 the presence of a suction force which caused the flow of surface 

 waters toward the demarcation line. This phenomenon is present to 

 a less marked degree along the northern and western sides of the Gulf 

 Stream where it parallels the coastal reservoir of the United States 

 and has been observed off Cape Hatteras. 



During this cruise the direction and force of the wind was averaged 

 for each 12-hour period. The mean force and direction is shown by 

 the radial lines in the center of chart "I," and the Beaufort scale is 

 drawn in the lower right-hand corner. There were three 12-hour 

 periods of calm. From the 15th to the 28th calms to light southerly 

 and easterly winds were experienced, but from the 28th to the 31st 

 strong north to west winds prevailed. The usual amount of fog was 

 observed. 



To sum up : During the first part of the month the Great Bank was 

 covered watn field ice, which disappeared by the end of the month, 

 leaving traces of the old fields along the east slope of the Bank and 

 south to lat. 43° 20' N. The first icebergs appeared at parallel 45° N. 

 on the 9th and drifted southward along the east side of the bank at 

 the rate of 0.25 knot per hour. The first berg arrived at the Tail of 

 the Bank on March 20. It is estimated that there were not over 5 

 bergs and 10 growlers in the vicinity of the Tail of the Bank during 

 the month. The Labrador Current at the end of the month had 

 attained a velocity of 0.25 knot per hour. The "cold wall" had 

 assumed a position as shown on the oceanographical chart (chart " I ") . 



APRIL. 



Since the physical phenomena in general will be discussed later in 

 the bulletin, under the heading " Oceanographic summary," the 

 monthly reports will be reduced to a minimum. 



Various cnanges will be noted in the position of the "cold wall" as 

 shown by the isotherms on the surface temperature charts "J" 

 and "K." The "cold wall" south of the Tail of the Bank moved 30 

 miles to the northward in the course of the month. Southeast of the 

 Grand Banks the so-called "knuckle" of cold water formed by the 

 Labrador Current became manifest. The head of warm water west 

 of the Tail of the Bank, which was so noticeable during the early 

 part of the year, began to break up during April, and receded south- 

 ward to 42*^ 30' N., 54° 00' W. The subnormal amount of ice ob- 

 served during the month should be noted. The two bergs that drifted 

 around the Tail of the Bank and grounded on its southwest slope 

 during March drifted off into deep water. The drift of one of these 

 bergs is shown on berg chart " D. This berg was sighted on April 2, 

 10, 14, and 15. When last observed, it was drifting due north at a 

 rate of 0.4 knot per hour and had disintegrated to such an extent 



