218 Lake Maxinkuckee, Physical and Biological Survey 



appearance of minute smoke rings ; Aphanizomenon, which is rare 

 in our Indiana lakes but is common in some northern Minnesota 

 lakes and in the Mississippi River, is easily recognizable, as rather 

 large, green colonies, acute at each end, much like the little duck- 

 weed, Wolffiella. Anabaena, the most common alga of Lake Max- 

 inkuckee, has no definite form. In Lake Maxinkuckee it is rare 

 that great areas are covered with algal scum, though there are 

 sometimes rather long stretches in sheltered bays. The plankton 

 scum usually makes its first appearance about the end of July and 

 continues on calm days until freezing. 



The entire lake surface is not frequently calm for longer in- 

 tervals than a day ; June, July and August are generally the calmer 

 months. The surface is generally rippled, usually pretty rough, 

 during the spring and later autumn. Periods of calm during the 

 morning and evening are frequent the year round during fine 

 weather. 



Chemical condition: An important feature of the water is its 

 chemical condition. A chemical examination of the water was 

 made by Prof. Chancey Juday of the University of Wisconsin. The 

 test for hardness used was Siler's method, in which a coal tar prod- 

 uct, methyl orange, is used to color the water. The amount of 

 hydrochloric acid necessary to turn it faintly pink indicates the 

 hardness. 



The test used for oxygen was Winkler's method given in 

 Sutton's Volumetric Analysis, and is as follows : 



1. Add manganous chloride. 



2. Add KOH + KI = a precipitate with brown, if oxygen is present. 



3. Add Cone. HC1. dissolves precipitate. If oxygen is not present the 



liquid is clear. If oxygen is present it is yellowish or brownish. 

 It may now be left several days. 



4. To determine amount of oxygen, titrate with hypo, 1/80 normal, 



using (cooked) starch as an indicator. The amount of hypo re- 

 quired to clear up the blue caused by addition of starch is an index 

 to the amount of oxygen. In the following tables, prepared by 

 Prof. Juday, is shown the character of the water. 



Both the C0 2 and the oxygen are expressed in cubic centi- 

 meters per liter of water. The full face figures indicate the 

 amount of the alkalinity, i. e., it would require that number of cubic 

 centimeters of free C0 2 to make the water neutral. The light face 

 figures in the column marked free C0 2 indicate the acidity. Cal- 

 cium and magnesium are found in water almost entirely as bicar- 

 bonates, and chemists regard the CO 2 as half-bound or bicarbonate 

 C0 2 , and bound or carbonate C0 2 , so we have indicated them in this 

 way on the tables. In neutral or acid water they are regarded as 



