across the Labrador Sea and the Greenland triangle where the heights 

 have been referred to the 1,500-decibar surface. 



In addition to the usual measurements of temperature and salinity, 

 617 samples were taken during the occupation of the South Wolf 

 Island-Cape Farewell section and the Greenland triangle for ultimate 

 determination of total phosphorus concentration. At 293 stations 

 observations were made with black and white Secchi disks varying 

 in time from April to September and in location from the Grand 

 Banks region to the Greenland triangle with a variety of sky conditions 

 and with the sun's altitude var^'ing from 71° to 2° below the horizon. 



Temperatures were measured with deep-sea reversing thermom- 

 eters. Most of the protected thermometers used were of Richter and 

 Wiese manufacture, but a small percentage were made by Negretti 

 and Zambra, G. M. Manufacturing Co., and Kahl Scientific Instru- 

 ment Corp. The depths of observation were based on unprotected 

 thermometers made by Richter and Wiese and by Kahl. The 

 thermometers were used in pairs and a program of intercomparison 

 of protected thermometers was carried out by periodically changing 

 the individual thermometers comprising the pairs. This permitted 

 the identification of thermometers which were not functioning satis- 

 factorily and w4iich needed some thermal and mechanical manipula- 

 tion to restore them to normal performance. It also provided a meas- 

 ure of the uncertainty of the temperature measurements. After 

 eliminating constant corrections, these comparisons (2,994 in all) gave 

 a probable difference between the corrected readings of a pair of 

 thermometers of 0.011° C. Many of the thermometers had recent 

 laboratory comparisons with thermometers tested by the National 

 Bureau of Standards, and as in most cases the temperatures are means 

 of the corrected readings of a pair of thermometers, it is considered 

 that the observed temperatures listed in the table of oceanographic 

 data have a probable error of about ±0.01° C. 



The pressure coefficients of the unprotected thermometers used in 

 1954 are possibly in error by about one-half percent. The sign of the 

 error is such that the tabulated depths are too great. Further work 

 on the problem of more accurately determining the pressure coef- 

 ficient an unprotected thermometer will have under field conditions 

 is in progress at the Woods Hole Oceanographic Institution. 



As in previous years routine salinity measurements w^ere made with 

 a Wenner salinity bridge. Prior to the beginning of the 1954 field 

 work, the bridge was overhauled and cleaned and its calibration curve 

 redetermined. The 1950 determination had given the expression: 



S^ 9891.881 _^ 

 200. 2+m ' 



82 



