bailey: the great spirit spring mound. 87 



A specimen of the white scum, noticed above, only slightly mixed 

 with the green algse, was analyzed. The. acid solution of the ash con- 

 tains 1.26 per cent of soluble silica. This was of course a combined 

 silica, probably calcium silicate, which becomes the cementing mate- 

 rial in the rock. In another sample of ash, after removing all the sub- 

 stances soluble in hot water, the residue was found to contain 76.46 

 per cent of silica. 



The siliceous residue from the scum was examined by Dr. S. W. 

 Williston. It consists mostly of diatoms. He recognized 

 Navicula — 2 species 

 Nitzschia — 2 species 

 Asteronella — i species. 

 All three genera are found both in fresh and salt or brackish water. 



The green material consists essentially of Oscillaria and Confervae. 

 If the scum is allowed to stand for a short time a very strong sulphuret- 

 ted odor is developed, strangely suggestive of salt Avater marshes or mud 

 flats; and indeed the same odor is noticed in the vicinity of the spring. 

 No characteristic salt water organisms, that should occasion this peculiar 

 odor have, however, yet been observed here. A more extended and 

 special study of the organic life of these interior salt water marshes and 

 springs would be of great interest. 



