61 



The same line, near the 49th parallel, has probably a somewhat less 

 elevation. The lowest line of the plains is that along the Missouri, 

 and its elevation, taken near Bijou Hills, (a point about on the per- 

 pendicular to it from Fort Laramie,) is about 2,130 feet, which does 

 not differ materially from its height at the mouth of the Yellowstone. 

 The slope of all this part of the plains (being in a direction perpen- 

 dicular to the lines of equal elevation) has therefore its line of greatest 

 descent in a northeast direction, and north of the Niobrara ; this is the 

 direction in which a majority of the rivers flow till they join with the 

 Missouri or Yellowstone. To the south of the Niobrara the greatest 

 slope of the plains is to the southeast, towards the Gulf of Mexico, and 

 this is the direction pursued there by nearly all the rivers of the plains. 

 Thus the Niobrara would seem, as it were, to run along a swell or 

 ridge on the surface. The average slope of the plains from the Mis- 

 souri to the mountains make nowhere an angle greater than one-half 

 degree with the horizon. 



A remarkable feature in regard to this change of slope which occurs 

 in the neighborhood of the course of the Niobrara is the shortness of 

 its tributaries, the surface drainage seeming to be away from and not 

 towards its banks. A result of this is the absence of the amphitheatre- 

 like valley which rivers generally have, and which enable us to look 

 down at the stream often many miles distant. Through the greater 

 portion of the middle half of its course you have scarcely any indication 

 of it as you approach, till within close proximity, and then you look 

 down from the steep bluffs, and catch, at the distance of two hundred 

 to five hundred yards, only here and there a glimpse of the river 

 below, so much is it hidden by the precipitous bluffs which at the 

 bends stand at the water-edge. So strongly was I impressed with the 

 fact that the surface drainage could never have been directed along its 

 course so as to have worn out this channel, that I think a portion of 

 it must have originated in a fissure in the rocks which the waters 

 have since enlarged and made more uniform in size, and which the 

 soft nature of the rock would render easy of accomplishmeiu. It is 

 worthy of remark, in this connexion, that the bed of the stream in 

 longitude 102° is four hundred feet higher than that of the White 

 river at the point nearest to this ; White river having there cut its 

 way entirely through the tertiary formation, flows along tlie creta- 

 ceous, while the bed of the Niobrara is in the miocene tertiary, the 

 pliocene forming the bluffs. The bed of the Niobrara is also, in two- 

 thirds of its upper course, from three hundred to five hundred feet 

 above the bed of the Platte river at corresponding points at the south. 



In the section of the country through which the Niobrara flows the 

 soil is very sandy, so that what rain or snow falls sinks under the 

 surface, and none is lost by evaporation. This is gradually all poured 

 into the stream by the springs in the ravines, and in this way the 

 river is mainly supplied in seasons of low water, at which times it is 

 one of the largest streams of Nebraska. 



The question of the slope of the plains is a subject to which I have 

 given much attention, from its scientific as well as practical interest. 

 Our barometric observations have enabled us, in some measure, to till 

 up the gap between those of Governor Stevens on the north an.! 



