38 THE PLIOCENE AND PLEISTOCENE DEPOSITS OE MARYLAND 



more in harmony with those given by the author in the article above 

 mentioned and already published, than were the earlier statements of 

 Professor Salisbury in the New Jersey reports. Several differences of 

 moment materially affecting the classification were still maintained and 

 so far as known still exist. 



A detailed discussion of the Columbia Group around the head of the 

 Chesapeake Bay was given by the author in 1902 in his report on Cecil 

 county. 5 



A comparison of the classifications of Darton, Salisbury, and the author 

 is presented in the following tables : 



Darton ., . Shattuck Darton 



,,^ , . . Maryland and District ,_ ,, ,, n , 



(Washington region.) of Columbia.) (Southern Maryland. i 



Talbot 

 Wicomico j" 



Later Columbia •] w;„"™;,.„ J- Columbia 



Earlier Columbia Sunderland 



Lafayette Lafayette 



Lafayette 



Shattuck Salisbury 



(Maryland and District of Columbia.) (New Jersey.) 



Talbot (lower portions of Later Parts of Cape May and Pensauken. 



Columbia) 



Wicomico (higher portions of Later Parts of Cape May, Pensauken and 



Columbia) possibly Bridgeton. 



Sunderland (Earlier Columbia) Parts of Cape May, Pensauken and 



Bridgeton. 



A number of investigations have been made on the economic products 

 of the Lafayette and Columbia formations. The most important of these 

 have been contributed by Professors Wm. B. Clark and Milton Whitney, 

 Doctors E. B. Mathews, Heinrich Bies, and J. A. Bonsteel, and Messrs. 

 A. X. Johnson, C. W. Dorsey, and B. T. A. Burke. In 1891 Whitney 

 began a series of publications on the soils of Maryland in which he 

 described the particular soils found throughout the Lafayette and Co- 

 lumbia belts. These papers, however, were preliminary to a more ex- 

 tensive work carried on under his direction and in co-operation with the 

 Maryland Geological Survey by Messrs. Dorsey, Bonsteel, and Burke. 



5 Md. Geol. Survey, Cecil County, 1902, pp. 46-48, 169-173, 179-184. 



