202 University Geological Survey of Kansas. 
‘¢The mound is situated within 200 feet of a limestone bluff, 
which rises perhaps twenty feet above the level of the spring. 
The natural inference would be that the harder material of the 
mound protected it from erosion, which carried away the rock 
in the valley of the Solomon on the south, and the rock be- 
tween the spring and the bluff. 
‘‘Ts it not possible, however, that the mound has been really 
made by the successive deposits from the spring? Although 
the mound is plainly stratified, this need not interfere with the 
theory, for the water may have been intermittent in its flow. 
The rock is very porous, and on being ground to a thin section 
is shown to be concretionary in structure. 
‘An analysis of the water of the spring showed that it con- 
tained over 1120 grains of mineral matter per gallon, of which 
775 grains were sodium chlorid and 206 grains sodium sulfate, 
with 66 grains of magnesium sulfate, 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 ad- 
joining bluff were secured, and comparative analyses made, 
with the following result : 
Countty, Great Spirit 
rock. mound. 
Silica and insoluble residue................. 214: 4.10 
©xidesrofsironsandea hunni ase eee 332 2.66% 
Suir Gran niy.clinl Gaerne ee .00 0.34 
Garbontdioxidiin Ae eee er ee 40.90 39.10 
Calciumoxids shee Cae ee eee ee eee 51.90 41.28 
Mle yeraeMOhan, CEG. os ov ce cccavdcuccco ocou nace .63 1.15 
Water and organic matter undetermined..... 1.21 Boal 
100.00 100.00 
SPECiiCF Orava sch cece ee kee eo ae DB) 2.19 
‘“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 by its giving off a 
characteristic odor. The iron is practically of the ferrous va- 
riety, probably combined with carbonic acid, and the rock con- 
64. Mostly FeO., and so calculated. 
65. With alkalies. 
