4s FV. Hayden on the Geology of Northeastern Dakota. 
, but there were numerous specimens of cone in crystals, 
which characterize it in other localities. Resting on No. 2 is the 
Chalky marl of No. 3, not differing in aaa from the same 
rock before described as occurring vat ankton on the Missouri 
river. It here contains an abundance of its characteristic fossil, 
rom an examination of the slope above, I estimated its entire 
thickness at this point at from 80 to 100 feet. 
The formations at this locality, in descending order, are as 
follows: a. Yellow chalky marl No.3; 5. Black plastic clay with 
selenite crystals, undoubtedly No. 2; ¢. Reddish and rose-colored 
uartzites. 
From Fort James we again proceeded across the undulating 
seth in . ig apceiae a little south of east, about 635 miles, to 
Fort , at Sioux Falls, on the Big Sioux river. Nothing 
of eal iateest; ina geological point of view, met our eye 
except a small exposure of the reddish quartzite in the valiey of 
oe river. The soil of the prairie over which we passed, 
so the superficial deposits as shown along the streams, 
gave echasiaveioalsbe evidence that the surface features of all this 
region are due to the wearing away of the Cretaceous rocks 
2 and 3, and that they are the immediate underlying forse stil 
The most eee — which met the eye everywhere, 
a 
7 
were the boulders which cover large areas so thickly as to ren- 
der =. imposible ante! they are removed. ‘These rocks, 
however, will be found to be very useful to future settlers for 
ee and other economical 
x Falls there is a remarkable exhibition of the same 
red oad vessensied nubian described at James river. The 
are here exposed only in the valley of the river by the removal 
of the superincumbent Cretaceous rocks. The falls are five or 
six in number, oxten din the a distance of half a mile, and have a 
‘here are also beds of pudding 
stone, and the most beautiful illustrations of wave and ripple 
mornies that I have ever observed in my geological explora- 
ae was unable to discover any well defined fossils, but wher-— 
ever the surfaces of the rocks had been made smooth by the 
attrition of water, quite distinct rounded outlines of what ap- 
to be bivalve shells could be seen, so numerous that the 
rocks must have been charged with them. The matri x is 80 
