•1-H\ The American Geologist. April, 1894 
five per cent, of the time required for the deposition of these 
beds, the conditions were essentially the same as prevailed 
during the preceding time, when dolomite was deposited with- 
out interruption. If. therefore, in Iowa, different formational 
names are not to be applied to the strata in this portion of 
thi' geological column, some name, coextensive with Owen's 
Lower Magnesian limestone, -must be locally employed to em- 
brace all the dolomitic beds, together with the few thin beds of 
intercalated sandstone, lying between the top of the St. Croix 
series and the base of the massive, friable, quartzose deposits 
that beyond question belong to the St. Peter sandstone. In this 
great body of sediments we have a record of continuous depo- 
sition under practically similar conditions, these conditions 
being only temporarily interrupted by the deposition of thin 
beds of sandstone in the last forty or fifty feet of the forma- 
tion. For the present I am disposed to extend the application 
of McGee's name, and locally, so far as Iowa is concerned, call 
this whole assemblage of strata the Oneota limestone. 
This discussion seemed necessary to iix definitely the hori- 
zon of the sandstone to which reference is made in the title 
of this paper; for it is the siliceous bed, two or three feet in 
thickness, forty or fifty feet below the top of the Oneota for- 
mation as here defined, and probably the equivalent of the 
New Richmond sandstone of Minnesota and Wisconsin, that 
is to be considered. This sandstone is quite constant over a 
large area in the northeastern half of Allamakee county. 
Fragments of it are strewn in all the washes and waterways 
that cut below the level at which it lies. It breaks into pris- 
matic blocks which, notwithstanding the fact that it is easily 
friable, retain their form unusually well when compared with 
masses of sandstone derived from other sources. Its frag- 
ments are at once distinguished by certain peculiarities of 
appearance from all other blocks of sandstone with which 
they may be accidentally mingled. It looks sometimes as if 
the}- were partially vitrified, or rather they suggest the ap- 
pearance of blocks of porous sandstone saturated with some 
transparent non-volatile fluid. In the sunshine the freshly 
broken surfaces sparkle and glitter with numberless shining- 
points, as the light is reflected from myriads of minute crys- 
talline facets. Small fragments of the sandstone may be 
