The major problem encountered with the current meters was the rapid 

 disintegration of the lignum-vltae bearings due to molar agents in the sea 

 water. Average bearing life was approximately 3 days. Bearings constructed 

 of polytetrafluoroethylene (Teflon) were used during the month of August 

 with excellent results. By the end of the month none of the original 

 bearings showed any appreciable wear. One meter had 4-09 hours of operation. 

 A current-meter problem was caused by the rotary currents which resulted 

 in the twisting of the cables leading to the recorders. A swivel contain- 

 ing slip rings to conduct the electrical pulses was developed and proved 

 successful during August tests. Figure 8 shows three current meters being 

 lowered on the guide cable s. 



Since the installation of current instruments, 755 hourly observations 

 were made at the 10-foot depth, 86 at the 50-foot depth, and 27 at the 

 25-foot depth. The raw data are in tape form as shown on figure 10. These 

 data are tabulated as so©n as practical and eventually punched on the 

 specially designed IBM card shown in figure 11. 



Currents are rotary and generally range from 0.8-1.8 knots in speed 

 at the surface. Bottom currents are slightly weaker, about 0.3-1.2 knots. 



The strongest current observed at the surface was 1„9 knots and at 

 the bottom, 1.5 knots . An example of a typical tidal cycle is shown on 

 figure 12 where surface and bottom currents are plotted over a 24--hour 

 period. 



Previous reports of 3-5 knot currents in the area have not been verified 

 by observations taken from the tower, A conspicuous current rip is a semi- 

 permanent feature running NW-SE, passing about 200 yards NE of the tower. 

 Stronger currents may very likely occur over this shoal area* 



3. Thermal Structure 



Thermal structure is presently being measured by means of the bathy- 

 thermograph. No thermal stratification has been observed at any time 

 between April and September. It is believed that mixing is primarily due 

 to currents since several extended periods of low wave heights were observed 

 with no change in thermal gradient. The prospect of studying thermal 

 structure from this tower is therefore limited. 



4-« Waves 



Two flexible step-gage resistance wave staffs were used. A detailed 

 description of this system will be found in H.O. Pub. 607, Instruction 

 Manual for Oceanographic Observations, TJ. S. Navy Bydrographic Office, 

 Washington, D. C.„ 1955. One staff is 12 feet long with A-inch step 

 intervals and the other is 36 feet long with 1-foot step intervals. 

 Figure 9 shows a wave staff being lowered on guide cables. 



