212 



The similarity of the lake bottom to the surrounding country, which seems to 

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

 due 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 

 would practically all be covered by water should the surface of the lake be raised 

 five feet. The hydrographic basin is so small that at present but seven inches of 

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

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

 face by 3%, or about one and a third square miles, would be sufficient to allow 

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

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

 present if the present precipitation and evaporation have been constant since the 

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

 raised 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 considered in another 

 report. 



Size. — The total area now under water is 5.659722 scjuare miles. This area 

 was obtained by weighing a sheet of paper of uniform thickness and of the shape 

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

 a square 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 quite as exact. The same method was used in determining 

 the areas below which there is a certain depth of water, with the following results: 



Depth of Area in Amount of Water 



Water. Square Miles. in Cubic Miles. 



1-10 feet 3.27777 .00310395 



10-20 feet 59027 .00167690 



20-30 feet 62500 .00314867 



30-40 feet 45833 .00303817 



40-50 feet 39583 .00337165 



50-60 feet 22918 .00231162 



60-70 feet 0694 .00082026 



5.64576 .0174712 



Error to be distributed . 1396 



5.65972 



