As in previous years, routine salinity measui-ements were made 

 with a Wenner salinity bridge. Measurements and tests of the 

 instrument, made prior to the beginning of the 1955 field work, 

 indicated no requirement for the redetermination of its calibration 

 curve. During the routine measurements standardizations were 

 made with water from an oil-sealed carboy of sea water and at least twice 

 during each run a sample of Copenhagen water of the batch Pi 7 was 

 measured as an unknown. At the end of each survey these measure- 

 ments of Copenhagen water were used to compute such corrections 

 as had to be made to the salinities measured during the survey. 

 For the first survey and the post-season cruise the in- 

 dicated corrections did not exceed 0.005°/oo so no corrections have 

 been made to those salinities. For the second and third surveys 

 corrections of — 0.007°/co and +0.008°/oo respectively have been 

 applied. The dynamic topographic charts, however, were not redrawn 

 and the dynamic heights shown in figures 14 and 15 consequently are 

 respectively too low and too high by 5.2 and 6 dynamic mm. The 

 relative topography and derived velocities and transports are not 

 affected. 



The determinations of the total phosphorus concentration were 

 carried out by personnel of the Woods Hole Oceanographic Institution 

 as described in Bulletin No. 40 of this series. 



Figures 13, 14, 15 and 16 show, in chronological order, the current 

 charts resulting from the three surveys made during the season and the 

 post-season occupation of the Bonavista triangle. Figure 13 shows 

 that at the time of the first survey the dynamic heights on the Grand 

 Banks were about normal and the dynamic heights in the valley east 

 of the Labrador Current were nearly normal. The dynamic heights 

 on the seaward margin of the surveyed area were decidedly less than 

 usual with the maximum heights about 30 dynamic centimeters less 

 than usual. Thus, for the most part, the border of the Atlantic Cur- 

 rent was outside the surveyed area. The Labrador Current was flow- 

 ing with normal vigor from the northernmost section to the Tail of the 

 Banks. From this survey it was expected that any bergs which might 

 follow this path would not get further west than about 50°40' W,, 

 south of the Grand Banks before recurving eastward. It was expected, 

 further, that the southernmost point which such bergs might reach 

 would be south of the southern limits of the survey and could only be 

 estimated as about 40°20' N., occurring at about the 48th meridian. 

 The areas in which bergs might approach the North Atlantic Track 

 Agreement tracks were along the southern margin of the surveyed 

 area between 49° W., and 47° W., and along the eastern margin of the 

 surveyed area between 43° N., and 44° N. Eastward of the Labrador 

 Current north of about 43°30' N., the gradients in the dynamic topog- 

 raphy were so slight that if any bergs reached this area their move- 

 ments would have been gi'eatly aft"ected by winds and transient wind 



63 



