40 Proceedings. 



end goes through Temperance river (or perhaps through Poplar river), 

 which empties into Lake Superior, some forty miles west of the mouth of 

 Bruld river. 



Following Dr. Grant, Mr. Upham spoke briefly of the 

 relative proportions of rainfall and evaporation. 



[abstract.] 



In that wooded Northern part of Minnesota and on its extensive 

 prairie areas southward. A chart of the rainfall of this state, compiled by 

 the speaker and previously referred to in the Bulletin of the Academy (Vol. 

 Ill, page 151), shows an average annual supply of 32 inches of rainfall 

 (including snow) in the region of Hunter's Island; while on the prairie 

 part of the state it ranges from 26 inches in the vicinity of Mankato to 22 

 inches along our western boundary at Big Stone lake and north to Moor- 

 head and Grand Forks. Careful records of rainfall in portions of New 

 England, with gauging of the discharge from reservoirs, as Lake Winni- 

 pesaukee, drawn from for the water power of milling cities along the 

 Merrimack River, shows that the evaporation from those areas of more 

 plentiful rainfall ranges from 50 to 60 per cent, of its total amount. The 

 proportion is probably nearly the same iu the wooded country of northern 

 Minnesota, including all the drainage areas tributary to Lake Superior and 

 to Rainy lake and the Lake of the Woods. On the somewhat dryer prairie 

 region the relative amount of evaporation is greater. It has been estimated 

 to be three-fourths of the rainfall on an average for the Ohio and upper 

 Mississippi river basins ; and it may be five-sixths of the whole rainfall for 

 the basin of the Minnesota river. The large tract of high plains, lying 

 farther west and extending to the Rocky Mountains, has a much less rain 

 supply, of which likewise it doubtless returns as much as five- sixths to the 

 atmospheric circulation by evaporation. 



Mr. Upham also spoke of the glacial and modified drift adjoining 

 nearly all the lakes of northern Minnesota on some portions of their 

 borders, so that if the drift were removed probably most of these lakes 

 could flow away, not being enclosed by rock basins. The opinion that 

 glacial erosion of rock-bounded depressions produced many of the lakes of 

 drift-bearing areas, long ago advocated by Ramsay, has been recently^ 

 brought again prominently to the attention of geologists by Sir Alfred 

 Russel Wallace, writing in the Fortnightly Review (Nov. and Dec. 1893). 

 This explanation, however, is far less frequently applicabls to the lakes of 

 the northern United States than the obstruction of drainage by irregular 

 deposition of drift. For the great Laurentian lakes, from Superior to 

 Ontario, Mr. Upham thinks, with Prof. J. W. Spencer, that their basins 

 were produced by differential epeirogenic movements, resulting in warping 

 of the earth's crust, during the Glacial period. 



Secretary Hall then remarked : 

 [abstract.] 

 Sec'y Hall followed Mr. Upham with some remarks of the advisability 

 of careful records and measurements of the determination of certain 



