Conductivity on 22 August ranged from 76,000 to 80,000 micromhos/cm ; 

 the lowest reading was at 500 meters, and the higher readings at 

 various depths (0, 10, 100, and 300 meters). Values of pH were de- 

 termined on 9 February 1961; the results ranged from a high of 8.17 

 at 10 meters to 7.72 at 250 meters. There was no apparent order of 

 vertical progression in either conductivity or pH values. At Mawson, 

 the pH range was somewhat greater (6.87 to 8.86), pH tending to 

 increase slightly with depth. The opposite was noted at McMurdo. 



G. Transparency 



Transparencies were taken with a white Secchi disc under the two 

 lights over the "A" frame. Transparency ranged from 10 to 16 meters 

 under these conditions. Unfortunately, the water became fouled by 

 rust from the metal liner of the hole and for this reason transparency 

 readings had to be discontinued. The water in McMurdo Sound often 

 shows a high degree of transparency at times when diatom growth is 

 not excessive. In early November 1956, a transparency reading of 47 

 meters was observed in McMurdo Sound. A month later this had been 

 reduced to 5 meters by the spring diatom crop. (U. S. Navy Hydro- 

 graphic Office TR-33). 



H. Currents 



The results of current measurements made at the icehole from May 

 through December 1960, are shown in Table 9, and the majority of 

 current stations are shown graphically in Figures 9 through 24. Blank 

 spaces occurring in the table, show either malfunction of the current 

 meter or slack water, although the current meter was brand new and 

 seemed to be functioning very well most of the time. On 15 July 1960, 

 for example, the meter appeared to function perfectly in the air and 

 just below the surface, so slack water was probably the cause of no 

 current. 



In Table 9, times are local and indicate the commencement of the 

 reading; the duration of current measurement was usually 10 minutes. 

 In Figures 9 through 24 mid-current time is plotted. Table 10 shows 

 the phases and positions of the moon throughout the year. Reference 

 to this table will show the state of the tide at any given day. Tidal 

 indications have been made on some of the figures. Of the 271 cur- 

 rent measurements made at the icehole for which direction was obtained, 

 142 observations had an easterly and 129 a westerly set. A further 

 breakdown shows the set of all currents (including all depths) to be 

 in the following sectors: 44% 0° to 90° sector, 30% in the 270° to 

 360° sector, 15% between 180° and 270°, and 11% between 90° and 180°. 

 Except for one measurement all currents below 300 meters depth set 

 between 0° and 95° (average set of 70° true). This is shown in 

 Figure 21 where the set of the current at 562 meters varied only 15° 



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