SUBSEQUENTLY, A UNIT WAS PLACED ON TOP OF 
PLANTAGENET Dank AT A DEPTH OF 21 FATHOMS, AND LATER 
YET ANOTHER WAS INSTALLED AT 5OO FATHOMS, BUT IN A 
DIFFERENT LOCATION ON THE FLANK OF THE BANK. ALL OF 
THESE UNITS, AND A LATER ONE WHICH MEASURED RELATIVE 
DIRECTION, WERE FLOATED 5O FEET OFF BOTTOM TO GET AWAY, 
IF POSSIBLE, FROM NEAR BOTTOM EFFECTS. FIGURE 2 SHOWS 
THE LOCATION OF THE VARIOUS UNITS, AND FIGURE 3 THE 
CURRENT METER INSTALLED ON BOTTOM, 
PLANTAGENET BANK SHOWS A LARGE MAGNETIC ANOMALY, 
AND MAGNETIC DIRECTION SENSING DEVICES WERE ELIMINATED 
AS POSSIBILITIES FOR DETERMING CURRENT DIRECTION IN 
THE AREA. A RELATIVE DIRECTION MEASURING DEVICE, CON- 
SISTING OF A CONTINUOUS ROTATING POTENTIOMETER WITH A 
VERY LONG LIFE EXPECTANCY, WAS BUILT, THE POTENTIOMETER 
IS CONNECTED TO A VANE WHICH HAS NEAR NEUTRAL BUOYANCY, 
ND IS RUN UPSIDE BOWN IN LIGHT OIL. A SMALL TIMING 
MOTOR AT THE INSTRUMENT END OF THE CABLE PROGRAMS THE 
SPEED AND RELATIVE DIRECTION UNITS, IF DESIRED, AND 
SENDS A ZERO AND 560° CALIBRATION MARK UP THE CABLE AT 
RECULAR INTERVALS. Frcoure 4 SHOWS BOTH SPEED AND DI- 
RECTION UNITS BUILT FOR DISPLAY PURPOSES. WHEN THE 
RELATIVE DIRECTION UNIT IS USED, THE WHOLE PACKAGE IS 
MOUNTZD AT THE TOP Or A 3/8" SOLID STEEL ROD TO PREVENT 
ROTATION WiTH RESPECT TO THE BOTTOM. 
213 
