Plate 6. A. Comparative light intens- 

 ities in air and at 0.6. 2.1 and 2.7 m. 

 depths on October 6, 1923. 



1 — exposed 1 sec. in ;iir. 



2 — exposed 2 1-.5 soc. ;it O.ll ni. dejitli. 



3 — exi)osed 3 4-.5 sec. :\t 2.1 m. depth. 



4 — exposed o sec. at 2.7 m. depth. 



Comparative light intensities in air 

 and just below the surface of the 

 lake on October 7, 1923. 



1 — exposed 1 1-5 sec. in air. 



2 — exposed 1 1-5 sec. at surface. 



3 — exposed 2 1-10 sec. at surface. 



4 — exposed 2 9-10 sec. at surface. 



Comparative light intensity in air 

 and at 91/2 m- and I2V2 m- 

 on November 4, 1923. 



1 — exposed 4-5 sec. in air. 



■_' — exi)osfd 29* sec. at 2.9 m. depth. 



:'. — cxiinsed 60* sec. at 2.9 m. depth. 



1 — exposed 120 sec. at 3.8 m. depth. 



*Possible error of 1 sec. 



