278 Hicks on Geyserite in Nebraska. 
peculiar flour-like material that appears in beds of greater or less thick- 
ness and extent on the Republican, Loup and Niobrara rivers, and in 
other sections of the state. When I first examined it under the micro- 
scope a few diatoms were collected, from which circumstance it was re- 
garded as probably of the character of tripoli. Since then, in many 
specimens that have come under my observation, a diatom has rarely been 
found. The chemical analysis of this earth is, moreover, very different 
from tripoli. It is proved to be a silicate of the alkaline earths, and most 
generally of soda, potash, magnesia, and lime. Sometimes only one, 
and sometimes several of these alkalies are present. It ranges in color 
from light gray to snow white, green and yellowish. All these colors 
are sometimes fovind in the same bed, and the chemical composition 
varies even more than the color. To the touch it feels very much like 
flour. The best specimens have no grit, and when used as polishing 
powder no scratches can be detected, even with the microscope. It is most 
abundant along the Republican river, where it is found in almost every 
county. It is exposed on the east half of the northeast quarter of section 
eight, and on the west half of the northwest quarter of section nine, 
town three north, range twenty-one west of the sixth principal meridian, 
in Furnas county, south of the Republican river and about eight miles 
southeast of Arapahoe. One of the exposures here is nearly a quarter 
of a mile long, and is a characteristic section. The measurements are 
from the top down. 
Loess 6 fe&t 
Drift (?) 3 " 
Compact silicate of lime and limestone S " 
Flour-like earth 12 " 
This bed is made up of layers one fourth of an inch in thickness, of 
snowy whiteness, and other layers, from nine inches to a foot thick, of a 
grayish white color. Nine feet from the top there is a layer two inches 
thick of a greenish color, which contains potash and iron. 
As already intimated it polishes as successfully and as finely as the 
best tripoli. 
Origin of this Flour-like Earth. — Near or in many of these beds are found 
many extinct geyser tubes, and sometimes old geyser basins. Of these I 
observed at least thirty between Arapahoe and the west line of the state. 
I have also found them in the Loup region and on the Niobrara. 
As some of these geyser tubes had their exit in the Fort Pierre group, 
on the upper Republican, it is probable that they commenced their work 
in the Cretaceous period, and were in operation all through the long 
centuries of the Eocene, Miocene and Pliocene epochs, and far into the 
Quaternary. A similar bed exists on Oak creek which was deposited in 
interglacial times. Nebraska and northern Kansas was in fact a great 
geyser region all through the Tertiary period. Few memorials of these 
extinct geysers are visible at the present time, owing to their being cov- 
ered tip by the superincumbent Quarternary deposits, but enough remain 
to show that a prodigous number must have existed. It is probable that 
