86 KANSAS UNIVERSITY QUARTERLY. 



An analysis of the water of the spring (loc. cit.) showed that it con- 

 tained over 1 1 20 grains of mineral matter per gallon, of which 775 

 grains were sodium chloride and 206 grains sodium sulphate, with 66 

 grains of magnesium sulphate, 41 grains of magnesium carbonate, and 

 31 grains of calcium carbonate. An analysis by the author shows that 

 there are 0.874 grains of silica. 



Samples of the rock composing the mound, and of the adjoining 

 bluff were secured, and comparative analyses made, with the following 

 results: 



COUNTRY ROCK. GREAT SPIRIT MOUND. 



Silica and insoluble residue 2.14 4.10 



Oxides of Iron and Alumina 3.22 *2.66 



Sulphuric Anhydride 00 o-34 



Carbon Dioxide 40. 90 39. 10 



Calcium Oxide 5i-9° 49.28 



Magnesium Oxide o. 63 1.15 



Water and organic matter, undeter- 

 mined 1. 21 t3-37 



100.00 100.00 



Specific gravity 2.52 2.79 



The rocks are entirely different in appearance and structure, that 

 of the mound being twice as hard as that of the bluff. The former 

 contains much organic matter as is shown by blackening when it is 

 heated in a tube and giving off the characteristic odor. The iron is 

 practically of the ferrous variety, probably combined with carbonic 

 acid, and the rock contains traces of chlorides. The particular sam- 

 ple taken was at some distance from the spring, and had been thorough- 

 ly exposed to the weather. 



The rock of the mound is of just such a character as might have 

 been built up by deposition from the water, as it contains the least 

 soluble constituents of the water. The process of solidification would 

 have been assisted by the silica in the water, forming insoluble ce- 

 menting silicates, as noticed by Prof. Patrick. The analysis given 

 above shows that there is abundant silica in the water for this purpose. 



Mention has been made of the organic growth in the adjacent 

 springs. The mixed scum on being heated changes from a dull green 

 to a vivid grass-green, and if ignited it swells up and emits an ill-smell- 

 ing vapor, which is evidently nitrogenous in its character. A grayish 

 white ash is left, which contains much carbonate of lime. This is ev- 

 idently freshly deposited, as it is entangled in the algae in granular 

 lumps. 



♦Mostly FeO. and so calculateci. 

 tWith alkalies, 



