REPORT OF THE DIRECTOR I917 145 



23 The gradual withdrawal of the ice, by melting faster than its 

 forward rate of movement, caused the damming of the valleys and 

 the flooding of the district by a succession of glacial lakes. 



24 Extinction of the glacial lakes by the complete withdrawal of 

 the ice, leaving a drift-covered surface dotted with lakes and ponds. 



25 Postlacus trine uplift and warping of the land. 



26 Slight readjustments of the streams. 



27 Present condition; Lake Clear. 



Acknowledgment 



The writer takes pleasure in expressing his indebtedness to Dr 

 W. M. Smallwood, who opened the way for this little paper; to 

 Dr H. P. Cushing for advice freely given on points on the petrology; 

 to Prof. George H. Chadwick, who assisted by critically reading 

 the manuscript; and to Mr R. J. Howard for assistance in the field. 



