D. T. MacDougal — The Salton Sea. 



243 



travertine marks the u rid er-sur face layer of water for a longer 

 time than at the high level. (Fig. 4.) The geologist may no 

 longer assume that calcium is precipitated from saturated 

 solutions in lakes as in a test tube and the trend of recent 

 work seems to be accurately represented by the conclusion of 

 "Walcott, " that the origin of the Cordilleran Algonkian lime- 

 stones is largely owing to the action of lime-secreting algse 

 and bacteria, and that precipitation of calcium and magnesium 

 bicarbonates from a saturated solution is of very rare occur- 

 rence and not an important agent of deposition in geologic 

 time and that marine waters are not necessary for the deposi- 

 tion of magnesian limestone " (Smithsonian Misc. Coll., vol. 

 64, No. 2, p. 84, 1914). 



Fig. 4. 



Fig. 4. View southward near Travertine point showing high beach line 

 of Blake sea on rocks at right and Salton lake at level of 1912. The lighter 

 zone fringing the shore is the strip laid bare by the recession of the water 

 from 1907 to 1912. 



The special studies made of the changes in the stems and 

 branches of trees submerged by the Salton demonstrated the 

 fact that hydrolyzation of cell walls of cortical and other 

 unlignih'ed tissues occurred in material submerged one to five 

 years, and that this action did not take place when sterilized 

 Salton water was used for experimental tests in the laboratory. 

 The disintegration of the walls seemed to be due to an enzyme 

 produced by organisms of the Amylobacter group. The woody 

 cylinders of such stems might be held together submerged 

 for indefinite periods and would pass into the fossil condition 

 minus the cortical cells and the phloem. In anticipation of 

 possible future condition of the Salton, some attention was 

 devoted to the organisms inhabiting the pools and ponds along 

 the shore of San Francisco bay which pass with the season 



