60 



CARNEGIE INSTITUTION OF WASHINGTON. 



that river. Several hypotheses are possible as to the origin of the 

 depression and of the Delta dam which now separates this depression 

 from the sea. These hypotheses are fully discussed, with the con- 

 clusion that the present information warrants no final decision 

 between them. 



The soils of the basin are divided into two main types — the 

 gravelly and sandy soils of the desert foot-slopes and the silty allu- 

 vial soils of the Colorado Delta. Both types are represented on the 

 beaches of the Salton Sea, but neither this distinction nor any other 

 soil property seems to affect the vegetation directly. Indirect effects 

 through moisture relations and the like are occasionally apparent, 

 but usually subordinate to other factors. The occurrence and move- 



S . D 1 o n V s I sjC-— :Ci~s==^ 



f^;^o stoles 



\oS. C asernii-e 

 Isle dela 

 Precentacion \\ /(o S.Thomas de 

 Aquinae 



Detail of mouth of Colorado River and head of Gulf of California; 

 from maps by Bonne about 1770. 



ments of soil alkali are similarly unimportant ecologically, though 

 some general interest attaches to the fact that submergence in the 

 water of the Salton seems to have had surprisingly little permanent 

 effect upon the alkali content of the soils. 



Origin of Travertine or Tufa Deposits of Salton Sink, by J. C. Jones. 



Blake Sea, the body of water which once filled the Salton Sink, 

 left a deposit of calcium carbonate on the rocks bathed by its waters, 

 which is heaviest within a few feet of the maximum level of its waters. 

 The study of these tufas was taken up by Professor Jones for the pur- 

 pose of elucidating the history of the formation and disappearance of 

 the ancient sea. A consideration of the structure, composition, and 



