AULHORS ABSLRA GETS. 981 
stitutes the southern extremity of the formation in Iowa. Although 
present as outliers, the maximum thickness of the deposit is as much 
as 115 feet. It is possible to consider these soft sandstones, with the 
associated clay shales and conglomerates of the same age, as Dakota— 
the Nishnabotna of White. ~ 
The Carboniferous is represented by only the Upper Coal Measures 
which here has a thickness of approximately 1500 feet; while the 
entire Upper Carboniferous is found to be about 2000 feet thick. To 
a depth of several hundred feet the Upper Coal Measures is made up 
almost exclusively of argillaceous shales and hard limestones. Occa- 
sional bituminous seams are prevalent, but heavy veins of coal are cer- 
tainly not present within accessible depths and deep borings indicate 
that none occur even to the base of the Upper Carboniferous. 
The district is supplied with various materials of great economic 
value. The eighteen-inch seam of coal found near the drainage level 
in the northwestern quarter of the county is being quite extensively 
mined. ‘The clays from two of the geological horizons are being used 
in the manufacture of various marketable products. The limestone 
ledges are being quarried at several points and utilized as building- 
stone, but the rock is also suitable for lime-making. There is also an 
abundance of less important yet useful substances. The fertility of 
the loess soil is probably not inferior to that of any other locality in 
the state. 
Flow Old is the Mississippi? By Francis M. Fuuitz. Proc. Iowa 
Acad. Sci., 1894. Vol. II., p. 39. Des Moines, 1895. 
The evidence set forth goes to show that the present Mississippi 
drainage system existed as early as the beginning of the Upper Bur- 
lington epoch; and that, although interrupted by frequent and perhaps 
prolonged submergences, it nevertheless still remains practically the 
same. 
Glacial Markings tn Southeastern Iowa. By Francis M. Futtz. 
Proc. Iowa Acad. Sci., 1894. Des Moines, 1895. Pp. 213-217. 
Recent discoveries of glacial scorings in southeastern Iowa are 
reported as follows: Near Kingston, in the northern part of Des Moines 
county, two patches within about half a mile of each other. The first 
presents a perfectly level surface, over one hundred feet in length and 
