35G 



Thus far wo have established the following: (a) Center Lake, during 

 part of the year, has a region devoid of free oxygen, (b) A number of living 

 organisms arc found in it during this time. 



Many of these organisms are ehlorophyl bearing. This made it desirable 

 to determine, if possible, whether or not any light reached the bottom of 

 this rather turbid lake. 



To answer this question a Brownie No. camera, boiled in paraffine lo 

 make it impervious to water, was fastened into a pail weighted in the bottom 

 with lead to sink it. (See Fig. 2.) The lever of the shutter was arranged 

 with strings running through opposite sides of the top of the pail (see Fig. 'S'm 

 so that when the camera was sunk to the desired depth the shutter could \^ 

 opened, exposing a bit of film arranged between two microscopic slides 

 Avhich were taped around the edges, serving the double purpose of keeping 

 the film dry and acting as a check. (See Fig. 4.) 



After an exposure of five minutes, the shutter was closed by means of the 

 other cord and the camera raised to the surface. The film was developed. 

 The exposed part of the film was distinctly darkened, showing that there 

 is some light at the bottom of the lake. The intensity and quality of this 

 light remains to be determined. 



Bibliography. 



Birge, E. A., and Juday, C. : 



('11) The Inland Lakes of Indiana. Wisconsin Survey Bulletin No. 22. 

 Conn, H. W., and Webster, L. W.: 



('08) A Preliminary Report on the Algae of the Fresh Waters of Con- 

 necticut. Conn. State Geology & Nat. History Surv., pp. 1-78. 



('05) The Protozoa of the Fresh Waters of Connecticut. 

 Edmondson, C. H.: 



('06) The Protozoa of Iowa. Proceedings of the Davenport Academy 

 of Science. Vol. XI, pp. 1-24. 

 Wolle, F. : 



('94) The Diatomaceae of N. A. Comenius Press, Bethlelem, Pa. 

 Sedgwick, A.: 



