154 
IOWA ACADEMY OF SCIENCE . Vol. XXIV, 1917 
this rock is the oldest .exposed stratum in the state. It is really 
the rook foundation upon which all subsequent formations are 
laid. This rock is the Sioux quartzite and the center of its in- 
terest is the natural depression perhaps twenty feet deep known 
as Jasper Pool. This represents the greatest thickness of the 
exposure in Iowa although on the Dakota side of the Big Sioux 
the rock has been quarried to much greater depths. It seems 
much to be desired that along with the natural bridges of Jack- 
Fig. 14. Jasper Pool, Lyon county. 
son county, the Waukon Sphinx, the great drift bowlders of the 
central plains, this little tract might be conserved as a state mon- 
ument, and so with the larger phenomena in a series of state or 
national parks might make accessible to all posterity the evi- 
dence of the activity of geologic forces, past and present, and 
keep before our eyes the uplifting, broadening, educative beauties 
of the realms of Nature. Iowa has a group of beauty spots which 
she may well hold in esteem and to care for them and insure their 
perpetuation will increase the feeling of pride with which every 
Iowan regards his state and so will add in every way to the 
state’s resources and attractiveness. 
Iowa Geological Survey, 
Des Moines. 
