39 



In 1939, after the salinity britlgc had boon tak?n apart and cleaned, 

 nnmerous measurements by both bridge and titration methods, on 

 seven oil-sealed carboys of actual sea water, approximately evenly 

 distributed over the salinity range of 32.6 %o to 36.6/oo, gave an equa- 

 tion for the calibration curve which was: 



^=10100.637/(204.475+ilf) -4.671 



where S represents salinity in parts per thousand and M represents 

 the resistance, in ohms, of the X arm of the salinity bridge as given 

 by the dial readings at balance. More careful silver nitrate titrations 

 of six of these seven carboys by Barnes in February and March 1940 

 gave an improved calibration curve expressed by the equation: 



5'=9851.4876/(200.000+il/) -4.375 



where S and M have the same significance as described above. This 

 improved formula is in closer harmony with separate resistance 

 measurements of parts of the bridge and has been used in determining 

 the salinities reported here. The precision of the bridge measurements 

 is regarded as about ±0.004%o salinity, the accuracy, however, being 

 no better than the titration method used in calibration. 



The current maps prepared during the season as well as that showing- 

 current conditions during the post-season cruise were made following 

 the procedure used in the past several years, the season's maps being- 

 referred to the 1,000-decibar surface and the post-season map to the 

 2,000-decibar surface. 



The current map resulting from the first survey, made between 

 March 30 and April 9, is shown in figm-e 23. It will be seen from the 

 figure that the Labrador Current was flowing with sufficient strength 

 to carry any bergs which might have entered it to and west of the 

 Tail of the Grand Banks with a westerly limit of about longitude 

 52° W. The warmer waters on the border of the Atlantic Current 

 were mixed water and although this mixed water had the direction 

 and velocity of flow necessary to return bergs northeastward, the 

 cooler temperatures and lower salinities observed, indicated that the 

 northern edge of the Atlantic Current was not as far north as is usual 

 for this season of the year. On the other hand the Labrador Current 

 had decidedly warmer minimum temperatures than is usual and sur- 

 face temperatures on the Grand Banks indicated that the season was 

 farther advanced than usual. A trough of low dynamic height pro- 

 duced an eddy which is seen to have been centered near 43° N., 48° W., 

 and a pattern of intertwining tongues at about 45° N., seems to indi- 

 cate the dissipation, in that vicinity, of another whorl. These two 

 features were probably the result of a continued series of north- 

 westerly gales just preceding the survey. 



