78 



TeiiipcratKic. 

 Temperature readiugs were made by means of a tliermophoue, and 

 were taken simultaneously with the plankton catches. The temperature of 

 the surface water, during the summer, varied from .11° to 2G° ('. At the l)ot- 

 tom of the lake, only a slight vai-iation ranging from 8.3° C. to 9° C. oc- 

 curred. The thermocline was about 6 or 7 m. in thickness. The epilimnion 

 was 5.5 m. thick on July 1st; by the middle of August it had descended to 

 14.5 m. This descent of the thermocline was associated with the high wind 

 and cloudy days of the latter part of August. The average vertical readings 

 are given in the accompanying temperature graph. They were taken in 

 the deepest part of the lake at various times diu-ing the day. 



OUTLINE MAP OF 



WINONA LAKF 



SHOWING LOCATION OF STATIONS 



]\<(ilh( r. 

 Tlic suiiinicr nl' llilL' cxhil.ilcd \ci\ unsettled wcallicr (•iPiulvtMuis in the 

 vicinity of tlic lake. Sti-nnu winds prcNailcd mucli of tiic tinu'. especially 



