18 



metering installation will reveal whether or not the station is operating satis- 

 factorily as well as provide a running account of the occurrences at its position. 

 Such information would help in planning cruises as well as improve their effec- 

 tivness while in progress. But since buoys may not always remain on the sur- 

 face or transmitters may fail, the telemeter link may be broken from time to 

 time. Records made within the buoy would help to fill the gaps in the teleme- 

 tered record and provide a running check on the accuracy or origin of the infor- 

 mation received by radio. 



Recording apparatus for observations over an extended time is in proc- 

 ess of development. Stommel and Frantz are considering designs for a re- 

 cording buoy which will sink to the bottom and record the pressure. If the bot- 

 tom pressure fluctuates tidally and level isobaric surfaces lie above the bottom, 

 something may be learned of the ocean tides and the pressure fields associated 

 with the deep circulation from such bottom mounted instruments. If the pres- 

 sure fields associated with the motions above the thermocline are not in geo- 

 strophic equilibrium, the secular change in these may be recorded as well. 

 Stommel has considered the problem of recovering these objects and believes 

 that if a sufficient length of submarine cable is attached to each instrument, it 

 should be possible to grapple for the cable, following the successful precedents 

 of commercial cable companies. The results of recent experiments in shoal 

 water are encouraging. 



Other unattended recording instruments are actually in existence; name- 

 ly the recording thermograph and the recording current meter designed by Kleb- 

 ba. These instruments cannot be set out at great depths as they are built at 

 present, but they will record events for 400 days. 



DRIFTING BUOYS 



In connection with present observational techniques, one of the most 

 pressing interpretative problems is that of joining with pencil lines the scalar 

 and vector observations made on successive traverses by one or more ships. 

 Contours may be drawn through a field of scalars in several equally acceptable 

 ways. Choices are more limited for a vector field and no choice can be justi- 

 fied without reference to at least a few representative streamlines or particle 

 trajectories. There are also purely navigational difficulties of knowing 



where each observation was made in the geographic framework and since it 

 takes time for ships to move about through the changing fluid structure, purely 

 geographic considerations may not suffice. Usually we have no assurance that 

 the changes in the fluid system are slow enough to be neglected in connecting 

 the observations made at different times. The results of the multiple ship sur- 

 vey of the Gulf Stream in 1950 suggest that data from six ships could be safely 

 collected for each day and treated as though they had all been taken simultane- 

 ously. The element of convenience doubtless weighed heavily in coming to this 

 conclusion. From this, one is led to think that had it been posible to have not 

 only moving ships in the field but drifting ships as well, the paths of motion and 

 observations made by the ships drifting with the flow would have been useful 

 guides in connecting observed points between the traverses made by the ships 

 moving across the grain of the fluid structure. 



Rather than drifting ships, it is, of course, more economical to use 

 drifting buoys equipped to detect the local temperature and position and either 

 to record these against time or telemeter the data to the ships or to shore. The 

 streamlines described by drift of the buoys suggest a proper mode of interpola- 

 tion between observations made on adjacent traverses by nearby ships. As 

 each wave of buoys drifts through the same area, changes in the pattern of mo- 



