67 



Throughout 1928 the saHnities were determined and the stations 

 were computed at sea, as in 1926 and 1927, very quickly after the 

 actual stations were occupied. In running the electric salinity cabi- 

 nets the need was felt for standard water of dependably known salin- 

 ity for calibrating and frequent check purposes. The carboys of 

 tested water on hand from the previous year were of somewhat 

 doubtful salinity. 



Graphical curves of temperature with depth should be made at 

 every station before the ship is started ahead. Questionable — that is, 

 seemingly erratic or unreasonable — values of temperature should mean 

 the retaking of the whole station at once, or at least the retaking of 

 the doubtful and adjacent levels. Irregular values of salinity should 

 be watched for also in the same manner. When they are found the 

 water from the level in question should be retested, this time in another 

 electric cell from the one first used. As the salinities can not be de- 

 termined for some little time after the stations are finished, the ship 

 will always be too far from the station to permit the procuring of a 

 new bottle of water. If reasonable results can not be obtained, inter- 

 polation between adjacent levels must be resorted to. Where inter- 

 polated values were used in 1928 the fact is noted in the table of station 

 data. So delicate is the balance of the various water masses in the 

 sea that the greatest methodical care in all work connected with the 

 taking and computing of the stations is the only insurance against 

 gross errors in the final results. 



The 1928 stations have been divided into seven groups or sets as 

 shown in figures 14 to 20. Each set is made up of stations taken 

 within a period of time short enough to permit the hydrodynamic 

 values to be compared with reasonable safety for general current work. 



The arrows on the current charts were put in much like wind arrows 

 could be put on a weather map if the barometric pressures at a number 

 of observing stations were known. The four group iSgures by the 

 dots that represent the various stations show in tenths of dynamic 

 millimeters the height of the average sea surface above 728 dynamic 

 meters that must have existed above the 750 decibar pressure level. 

 (A decibar is a pressure equal to one-tenth of an atmosphere. A 

 dynamic meter is approximately the same as an ordinary meter. 

 It is a vertical unit of distance that varies from place to place in the 

 same ratio as the force of gravity varies.) The four figure distances 

 were computed from the known distribution of salinity and tempera- 

 ture in the water of the various levels at each station. 



Seven hundred and fifty decibars was the deepest pressure level 

 that was sampled during the 1928 ice patrol. If more time were 

 available it would have been advantageous to go down to the 1,000 

 or even the 1,500-decibar levels at the deeper stations in order to be 

 sure of determining all the current. It is beUeved, however, that not a 



