71 
lines drawn from these soundings give a fairly correct idea of the topog- 
raphy of the lake bed. 
Almost every sounding in five feet of water showed a bottom of hard 
sand or gravel, while almost every sounding in water ten feet deep indi- 
cated a bottom of fine mud, usually marl, from eight to twenty feet or 
more deep. In water more than thirty feet deep the mud is finer and 
darker, but I could get no idea of its depth. The hard bottom is much 
wider on the east side of the lake. It may be that the westerly winds 
give rise to an undercurrent which sweeps the finer material into the 
deeper water. But the same phenomenon occurs on the bars in the central 
portions of the lake where the wind would hardly cause currents. A few 
observations of the temperature of the water in the lake at different times 
of the day showed considerable variation and might cause currents. July 
28th, at 7 a. m., the temperature in water about eighteen inches deep was 
78 degrees Fahr., at 2 p. m. it was 84 degrees and at 8 p. m. 82 degrees; 
July 29th, at 7 a. m., 77 degrees, at 2 p. m., 87 degrees, at 8 p. m., 80 de- 
grees; July 30th, at 7 a. m., it was 74 degrees, at 2 p. m., 82 degrees, at 8 
p. m., 78 degrees; July 31st, at 7 a. m., 75 degrees, at 2 p. m., 84 degrees, 
at 8 p. m., 80 degrees; August Ist, at 7 a. m., 76 degrees, at 2.p. m., 82 de- 
grees, at 8 p. m., 79 degrees; August 5th, at 7 a. m., 79 degrees, at 2 p. m., 
82 degrees, at 8 p. m., 80 degrees; August 6th, at 7 a. m., 75 degrees, at 2 
p. m., 80 degrees, at 8 p. m., 78 degrees. Whether changes of temperature 
ranging from five to ten degrees within twenty-four hours would cause cur- 
rents strong enough to move fine sediment I cannot tell, but the idea is 
suggestive, and investigation along this line may show interesting results. 
The lake shows considerable variations in level. Elevations taken by 
the Vandalia people at different dates in 1895, 1896, 1897 and 1898 show 
a variation from 733.3 to 735.17 feet, about 1.87 feet. In August, 1896, 
I saw arise of six inches as the result of two days’ rain. 
I added over 100 species to my list of plants and trees found about the 
lake, extending it to about 290 species. We have a list of thirty-one 
species of fish found in the lake. Six species of bivalve mollusks and three 
or four species of univalves have been identified, and I think five species 
of turtles are found about the lake. 
