Lake Maxinkuckee, Physical and Biological Survey 217 



at considerable depths, it exhibited an indescribable play of trans- 

 parent green, something like that of an opal in some lights. 



Unfortunately, we have not a long series of records taken under 

 different conditions the year round which would give an absolute 

 test, and if there were such records, it would be difficult to find a 

 large number of other lakes with records with which it might be 

 compared. On September 20, 1907, when the sky was well clouded 

 over, a secchi disk was visible at 9 feet. The same disk at Holem 

 Lake, of the Twin Lakes, Indiana, on September 23, 1907, when 

 the sky was bright and clear, was visible at 13 feet, and at Cook 

 Lake, another of the Twin Lakes, under the same conditions, at the 

 same depth. At Lake Mendota, Minn., September 18, 1907, with 

 a cloudy sky, the same disk was visible at a depth of 6 feet. 



One might, indeed, take as a measure of the clearness of the 

 water, the depth at which green plants grow in the lake, the chief 

 limiting factor in this case being the depth to which light pene- 

 trates. The lower limit of plant life in the lake is about 25 feet. 



A remarkable feature of the water is its freedom from mud. 

 Even after heavy rains the inlets bring in but little water, and be- 

 cause of the general absence of clay, they bring in but little mud 

 even when they have the swiftest current. Strong winds may 

 make the water turbid near shore, and on one occasion, in the 

 autumn of 1900, the whole lake was rendered slightly turbid by a 

 long continued wind and rough lake, but in all cases the lake soon 

 settles clear. During the winter of 1900-1901, the Chara and 

 Potamogeton robbinsii showed up so clearly through several feet 

 of water and clear ice that they impressed a very excellent image 

 on a photographic plate, and the experience of traveling over this 

 clear ice and seeing the fine meadows in the bottom, with the 

 turtles and gars and dogfish resting quietly or moving slowly 

 about, impresses one with the great opportunity offered along the 

 lines of a new field of photography, that of subaqueous landscapes. 



Any one looking down in the water on a calm, bright day and 

 studying it attentively will note small flecks or motes, the number 

 of these differing in different seasons of the year and in different 

 lakes. These motes usually represent low algal forms which make 

 up the phyto-plankton of the lake. In Winona Lake this suspended 

 matter was so abundant that the sun's rays lighted up the particles 

 in long lines, as in the familiar phenomenon of the light entering 

 a slit in a dark, dusty room, or the "sun drawing water." In some 

 cases the algaB forming these motes have colonies of sufficiently 

 characteristic shape to be recognizable, but generally not. Lyngbya 

 has the appearance of short hair clippings; Clathrocystis has the 



