Polarization of scattered sunlight in deep water 



431 



both internally and with reference to relations indicated by previous shaliow-walcr 

 observations. 



A total of 1 1 stations were made. Of these the first 4 and No. 6 showed considerable 

 internal inconsistencies for azimuth, apparently arising from mcxpcrience w.th 

 difficuhies like those outlined. But on the basis of their coherence, the data for the 

 remaining 6 stations indicate that such interference had been minimized. These 

 include one set of records each at 30, 60, 100, 200 m and two at 150 m. 



RESULTS 



The data of these measurements provide information relevant to four or live ditfereni 

 aspects of the general problem. 



In the first place every photograph taken during the present deep-water series showed 

 a well-developed interference figure (Figs. 2, 3). This proved that the scattered hori- 

 zontal underwater illumination in the directions photographed was polarized at all 

 depths tested including the deepest, 200 m. Furthermore, as the interference pattern 

 clearly consisted of four quadrants of isochromatic curves made up of broken con- 

 centric rings with two diametrically opposite dark central sectors, this light must have 

 been linearly polarized. 



Station No. 9 



Sun's altitude: 34' 40' 



Angle of sunlight incidence: 55 



Depth of measurements : 60 m 



13' 



Table I 

 08' N, 59° 50-5' W. 



Dec. 2, 1954 



Sun's azimuth: 129° 



Calculated angle of refraction: 38"' 



Depth to bottom: 1150 m 



Although the method of polarized light analysis employed does not permit any close 

 estimate of percentage polarization, there is some evidence pertinent to this matter 

 in the photographs. In so far as it can be gauged by the intensity and extent of the 

 interference pattern photographed, the degree of light polarization at 200 m seemed 

 to be about as great as at any shallower depths. The number of concentric 

 isochromatic rings recorded at this deepest station is fully as large as at any other in 



the present series. 



Also it is clear from the same kind of evidence that in deeper water there is no marked 

 change in percent polarization with direction of view relative to the sun's a/imuih. 

 In fact No. 8 at 30 m (Fig. 2) was the only station obviously providing evidence for 

 this relation which was always found visually in shallow water (Watlrman. 1*^54 a). 



On the other hand, the effect of the relative bearing of the sun on the plane of polar- 

 ization was a prominent and highly significant feature of the records at all stations. 

 This is exemplified by the data for stations 9 and 1 1 which are presented m Tables I 

 and II and by Figs. 2 and 3 for stations 8 and 1 1 . 



