XVI LETTEE OF TRANSMITTAL. 



Leverett, and myself conjointly in 1886. Later the whole work was 

 committed to Mr. Leverett, with the gratifying results of which this mon- 

 ograph is an expression. The relations of Mr. Leverett and myself during 

 the progress of the investigation have been unusually intimate, and it has 

 been a pleasure to contribute to the work such data and suggestions as my 

 studies in this and other regions permitted. I trust that the monograph will 

 prove a valuable contribution to the complex problem presented by the gla- 

 cial series of the Northern United States. 



Very respectfully, yours, T. C. Chambeelin, 



Geologist in charge. 

 Hon. Chaeles D. Walcott, 



Director United States Geological Survey. 



