430 



TYIiEB AND PREISENDORFER 



[OHAP. 8 



head with two RCA 931 -A multipher phototubes each coupled to an amplifier 

 with output proportional to the logarithm of the flux input. 



Measurements of radiance distribution in the meridional plane have recently 

 been made by Jerlov and Fukuda (1960) in the stratified waters of Gullmar 

 Fjord. In this work the instrument was guided into the water along a taut wire 

 which also served to maintain a fixed azimuth orientation of the measuring 

 head. The resolving power of the instrument was 7.0°. The near-surface experi- 

 mental measurements are compared with computed results based on a simple 

 theory that neglects multiple scattering. 



-REVOLVING 

 PHOTOMETER 



Fig. 10. Drawing of instrument developed by Sasaki et al. (1958) for radiance measure- 

 ments in the horizontal plane. 



A series of interesting studies has been made recently by Sasaki (Sasaki et al., 

 1958) on the influence of sky lighting and depth on the radiance distribution 

 in a horizontal plane. The instrument used by Sasaki is shown in Fig. 10. This 

 instrument employs a remotely indicated magnetic compass for azimuth 

 position information. No azimuth control is provided and evidently is not 

 necessary since the readings are taken at fixed angles from the compass heading, 

 which is always known. 



The maximum radiance reading locates the vertical plane containing the sun. 



