SECT. 4] 



443 



plate which hmits the angle of incidence on the filter to 5° (see Fig. 24). The 

 instrument is equipped with a pressure transducer and can withstand pressures 

 down to 600 m depth. A series of remotely controlled aperture stops and an 

 electronic circuit, designed to yield readings proportional to the logarithm of 

 the light flux, give the instrument a wide range. 



Fig. 24. Instrviment developed by Boden, Kampa and tSnodgrass (1960). The irradiance 

 measuring head with amplifier below is on the right. 



The instrument designed by Hubbard and Richardson employs a similar 

 irradiance collector but the flux is sampled by means of a submersible mono- 

 chromator shown in Fig. 25. The data obtained is automatically corrected for the 

 spectral sensitivity of the multiplier phototube as well as for the nonlinear 

 dispersion of the monochromator. The recorded voltage is, therefore, directly 

 proportional to the flux per unit wavelength. 



Monochromatic data for the diffuse attenuation function is given in 

 Table XIII. 



