GEOLOGICAL SURVEY OF THE, TERRITORIES. 45 



five to forty bushels of wheat, fifty to sixty of oats, sixty to seventy-five 

 of corn per acre, being a no uncommon yield, and the present season 

 there will be even more than the average yield of former years. 



Grass is also fine everywhere, each acre averaging from one and a 

 half to three tons per acre. 



GEOLOGY OF NEBRASKA NORTH OF THE PLATTE RIVER. 



With the exception of a small portion of Douglas and Sarpy Counties, 

 bordering on the Missouri and Platte Elvers, the whole Srate of Ne- 

 braska north of the Platte Eiver is underlaid with rocks belonging to 

 the great geological eras. Cretaceous and Tertiary. 



The Cretaceous rocks make their appearance in their eastward exten- 

 sion in rather thin beds, capping the summits of the hills, and only the 

 more compact layers, resisting the eroding effects of water or atmos- 

 pheric agencies, remain to indicate its boundaries and extent. I am in- 

 clined to the belief that the rusty sandstones of the Dakota group once 

 extended in full force directly across the Missouri into Iowa, and that 

 the sandstones recently discovered by Dr. White on the Nishnabotna 

 River form a portion of the series, disconnected only by the wearing 

 away of the intervening rocks. There is no doubt that the greater 

 portion of Northwestern Iowa is underlaid by rocks of the Dakota 

 group. 



The green color on the geological maps of Nebraska in process of 

 preparation will show the eastern boundaries of this group wit*h accu- 

 racy. The limestones early begin to disappear north of the Papillion 

 Eiver. 



At Sarpy's old trading-post, near Bellevue Landing, some thin layers 

 of rock occur in the hills, and a thin seam of coal has been found, and 

 at low water two or three layers of rock are revealed which can be made 

 useful for building pur]30ses. • 



At Omaha five to ten feet of limestones are revealed near the water's 

 edge. The rock is grained to considerable extent ; but from the fact 

 that Omaha is almost entirely supplied with rocks and lime for building- 

 purposes from the Platte, we may infer that the quarries at Omaha are 

 not extensive. The cost of stripping the vast thickness of superincum- 

 bent gravel and yellow marl at Omaha must render the working of this 

 quarry very expensive. 



The next exposure is at Florence, where the limestones are seen only 

 at low water. ' 



The last exhibition is at Eockport, near De Soto, where at very low 

 water the limestones are seen at the edge of the river, but at neither 

 of the localities above named are there quarries of any special value. 



Along the Missouri bluffs there is no exposure of the underlying 

 rocks again until we reach Tekama, Burt County. Here the nuclei of 

 all the hills are sandstones and clays of the Dakota group. From Flor- 

 ence to Tekama, the bluffs or hills bordering on the Missouri are verj^ 

 rugged and high, but are composed entirely of drift-gravel at the bot- 

 tom and a great thickness of yellow marl at the top ; indeed, this yellow 

 marl or loam is not unfrequently fifty to one hundred feet in thickness. 

 It is so soft and yielding in its nature that little temporary streams 

 flowing down the bluffs wear out immense gorges one hundred to one 

 hundred and fifty feet in depth. The sides of these hills along the Mis- 

 souri bottom, on the Iowa as well as Nebraska side, are often very steep, 

 with an angle of descent of 30° to 40°, and I have seen vegetation clinging 

 quite thickly to their sides when the descent was 50^ to 55°, although 



