Hicks on Geyser ite in Nebraska. 
279 
this flour-like silico-alkaline earth owes its origin to these old geysers. 
It is well known that hot alkaline waters dissolve silica. When, there- 
fore, the geyser streams holding silica and alkalies in solution were 
poured into this old lake the mineral in question was precipitated. In- 
deed many of the flakes of this earth, under the microscope, clearly re- 
semble the dried flocculent flakes of aluminic silicate which the chemist 
obtains by pouring soluble sodic silicate into a solution of sodic alumin- 
ate. 
Another fact which tends to establish the probability of this theory 
is that this silico-alkaline earth, on analysis, bears a striking resemblance 
to gtyserifc, which is obtained from the deposits of existing geysers. 
The following analyses are illustrations of this statement. No. i is an 
analysis of this earth from the deposit near Arapahoe; No. 2 from the 
Loup region; No. 3 from Iceland; and No. 4 from the Yellowstone. 
Nos. 1 and 2 were made by myself; No. 3 was made by Forchhammar; 
and No. 4 by Dr. F. M. Endlich. 
No. 1. 
No. 2. 
No. 3. 
No. 4. 
Loss on ignition 
8.00 
Silica 
67.01 
8.03 
7.11 
2.81 
2.01 
7.87 
80.17 
7.43 
4.71 
3.01 
0.92 
2.27 
0.80 
84.43 
7.88 
3 07 
1.91 
0.70 
0.92 
1.00 
76.80 
Water _ 
5 00 
Alumina 
9 46 
1.80 
98.89 
99.31 
99.98 
10] .06 
From these analyses it is evident that the principal difference between 
this Pliocene earth and geyserite is that the former contains a much 
larger per cent, of alkalies; though the specimen from the Loup is much 
like the geyserite from Iceland. By reference to Dr. Endlich's report 
on the composition of the geyserites of the Yellowstone * it will be seen 
that they differ very much in the proportions of their constituent ele- 
ments. In the great number of analyses reported by hiin from as many 
different geysers, no two are alike. Often geysers only a few feet apari 
produce very different qualities of geyserite. The same is true of this 
peculiar earth under discussion. It not only differs a great deal in differ- 
ent localities, but even in different layers of the same stratum. It differs 
most in the quantity of the alkalies which it contains. Some specimens 
contain twenty per cent or more, while others contain only a trace, the 
latter approximating closely in chemical, though not in physical consti- 
tution, to the true geyserite. I submit whether these facts do not indicate 
a similar origin. It is possible that the peculiar modification of geyserite 
into a flour-like alkaline silicate may have resulted from geysers that 
were active in the waters of this old Pliocene lake. 
The deposits of a similar character in the Quaternary contain, where 
1 Hayden's Report for 1872, p, 157. 
