44 The Chicago Academy of Sciences. 



These boundaries include an area of about forty- 

 eight or fifty miles square, which, after deducting" the 

 approximate area of the lake covered portions, leaver 

 nearly 1,800 square miles of land surface. It comprises 

 all of Cook and DuPage counties, the nine north town- 

 ships of Will county, and a portion of Lake county, Ind. 



The importance of this survey will be appreciated 

 when the rapid growth of the city of Chicago is con- 

 sidered. The surface of the area is constantly changing^ 



PRESIDENT THOMAS C. CHAMBERLIN. 



both because of the agency of man and of other forces. 

 The numerous railroads centering here are constantly 

 bringing new things to the soil, which, finding a con- 

 genial climate, finally become a fixed part of our 

 natural history. More important still is the recording 

 of natural features that are being exterminated or 

 effaced, and of which no indication will be left except 

 in printed records. The historians of Chicago and its 

 environments in future generations will have to depend 



