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INTRODUCTION 



Geography and geology of Wisconsin. The state of Wisconsin lies 

 between Lake Superior, Lake Michigan and the Mississippi river and 

 has an area of 56,066 square miles, cr an area somewhat larger than 

 England. Its greatest breadth is about 295 miles and greatest length 

 320 miles. Within its borders are numerous lakes, the total number 

 probably reaching well into the thousands, with an estimated surface 

 area of about 1500 square miles. They vary in size from small lakelets 

 and ponds that cover but a few acres, to Lake Winnebago with an 

 area of 215 square miles. The great majority of the lakes, however, 

 have less than a square mile of surface area. There is likewise great 

 variation in depth, but for the most part they are shallow since the 

 deepest (Green Lake) has a maximum depth of 237 feet and only a 

 few have a depth of over a hundred feet. Certain phycologists have 

 tried to differentiate between the plankton floras of ponds (heleoplank- 

 ton) and lakes (limnoplankton). The lakes of this state grade so im- 

 perceptibly from the "pond" to the "lake" type that it has been im- 

 possible to distinguish between the two. To set arbitrarily a surface 

 area of a square mile and depth of 25 feet as the maximal limits for a 

 pond would involve many difficulties ; since the state presents such ex- 

 amples as Beasley Lake with a surface area of 0.019 square miles and 

 a depth of 51 feet or Lake Winnebago with a surface area of 215 square 

 miles and a maximum depth of 21 feet. I have, therefore, listed all 

 bodies of water as lakes but have given, in Table 2, all available data 

 on area and depth for those desiring to recapitulate into heleoplank- 

 ton and limnoplankton. 



There are, roughly speaking, three lake areas in the state ; the south- 

 eastern, northwestern and northeastern, all of which owe their origin 

 to glaciation. These lake areas are not uniformly distributed over the 

 state since the glacier invading this region was divided into lobes and 

 lakes are found in greatest abundance along the terminal and kettle 

 moraines of these various lobes. The southwestern portion of the state 

 possesses no lakes since it lies in a non-glaciated region. The south- 

 eastern lake area includes several scattered moderately sized lakes and 

 groups of smaller lakes some of which are among the deepest in the 

 state. The majority of them lie in a region of kames and pitted plains, 

 where the pits and lake basins owe their origin to the burial and sub- 



