212 



Tlu' shiiilarity of tlie lake bottom to the surrounding country, which seems to 

 have heen little changed by erosion, makes it quite certain that the lake basin is 

 line to the irregular dumping in a terminal moraine, parts of it containing deeper 

 kettle holes. 



The lake was never much more extensive than now. There are evidences 

 that the surface was a few feet higher. These will be considered in a later report. 

 The lake is surrounded by extensive swamps on the east, north, and west; these 

 MCtically all be covered by water should the surface of the lake be raised 

 live leet. The hydrographic basin is so small that at present but seven inches of 

 water are removed from the surface by outHow, while thirty are removed by evap- 

 oration. The lake having a surface of 5.6 stjuare miles, an increase of this sur- 

 face by .',,, oi' about one and a third square miles, would be sufficient to allow 

 all the water coming into the lake to be lost by evaporation e.xcept in wet seasons. 

 The surface of the lake, therefore, can not have been very much higher than at 

 pre>cnt il the present preci])itation and evaporation have been constant since the 

 ice leli this region. The lake has been about six or seven feet lower, having been 

 rai>cd to its present height by the building of a dam across its outlet. The changes 

 due to this dam and to the encroachment of plants will be considei'cd in another 

 report. 



.•^i/.K. - The total area now under water is 5.G59722 sipiare miles. This area, 

 was obtained iiv weighing a sheet of pa[)er of uniform thickness and of the shape 

 of the whole area to be calculated, and comparing this weight with the weight of 

 a s<iuare of the same paper covering a square mile. This method is much more 

 expeditious than calculating such an irregular body as these lakes in the absence 

 of a planimeter, and (piite as exact. The same method was used in determining 

 the areas below which there is a certain dei)tli of water, with the following results: 



I»eiJth of Area in Amount of Water 



Witter. Square Miles. in Cubic Miles. 



1-10 feet 3.27777 .00310395 



10-20 feet 59027 _ .00167690 



20 30 fctt 62500 .00314867 



30-40 feel 45833 .00303817 



4(1-50 feet 39583 .00337165 



50-60 feet 22918 .00231162 



60-70 feet 0694 .00082026 



5.64576 • .0174712 



Error to be distributed . 1396 



5.65972 



