88 The American Geologist. August, 189a 
high as 60% of peroxide; of tlie extent and exact situation of 
the deposit it is not possible to write. 
An interesting discovery of a manganiferous spothic iron ore 
is reported by Dr. R. Bell in the report of the Geological Sur- 
\e\ 1877-78, wherein he states that a band of about twenty feet 
of the ore, carrying 25% metallic iron and 24% carbonate of 
manganese, occurs in the Nastapoka islands, a group off the east 
coast of Hudson bay. The ore is easily accessible and will no 
doubt eventually prove of value, the high percentage of man- 
ganese contained making it eminently suitable for the manufacture 
of speigeleisen. 
KEOKUK GROUP OF THE MISSISSIPPI VALLEY. 
CHARI.E8 S. Beachler, Crawfordsville, Indiana. 
Literature. 
The name Archimedes limestone was given by David Dale Owen, 1852, 
(jieological Survey Wisconsin, Iowa and Minnesota, to the forty feet of 
the heavy bedded, quarry, encrinital limestone, quarried in the bhiff at 
Keokuk, Iowa. This bed in his table of the sub Carboniferous rocks of 
the Mississippi valley is placed as the uppermost member of the lower 
sub-Carboniferous; he terms the preceding roclis the Cherty limestone. 
The Archimedes limestone bed is succeeded by the lowest two members 
of the upper sub-Carboniferous which he named (a.) Geodife ons Bed, 
and {h') Mag nesian limestone. From the great number of fossil shells 
found in the lower part of the Archimedes limestone he uses a special 
name, that of Shell Beds, to distinguish it. 
These four beds form what has developed into the Keokuk group of 
the sub-Carboniferous period. 
I ,. I /-. 1 -f ^ (b) Magnesian limestone. 
(Keokuk) I L PPer sub-Carboniferous ja') Geodiferous Bed. 
1 
1 St'' -J 
' "' ] (f) Archimedes limestone. 
Owen. | Lower sub -Carboniferous (e) Shell beds. 
I (d) Cherty limestone. 
S. C. Swallow, 1855, First and Second Annual Reports of the Geologi- 
cal Survey of Missouri, applies Owen's name Archimedes limestone to 
all the rocks from the summit of the Encrinital series to the base of the 
Saint Louis series; from the description on page 183 it seems that the 
Cherty bed was regarded as the summit of the Encrinital limestone series. 
No other divisions were made. 
Saint Louis limestone. 
(Keokuk) f 
1855. <{ Archimedes limestone. 
Swallow. (^ 
r. • •* 1 1- * ^ Cherty beds. 
Encrinital limestone j •' 
