260 GEOLOGICAL SURVEY OF THE TERRITORIES. 



partly composed of large pebbles and stones that could not have been 

 moved by the winds. This is especially the case in some of these hills 

 south and east of Kenesaw, in Adaras County. I suggest, as a pro- 

 visional explanation, the probability that south of the Platte the lines of 

 sand-hills show the track of a current in the old lake that produced the 

 Loess deposits. It is well known that fine sediment is deposited in still 

 water, but coarse materials, such as sand and pebbles, in the borders 

 and in tracks of currents. As the whole country rises toward the 

 west, the water here may have been very rapid, and the land in pro- 

 cess of drying up when it was yet deep at lower levels. Both causes, 

 the currents and the winds, may have co-operated to produce these de- 

 posits. I am also satisfied that in some localities the sand-hills are 

 nothing more than modified Loess deposits. They are Loess deposits, 

 with all the alumina, organic matter, and finest sands washed out of 

 them. This at least seems to be the origin of some of the sand-hills 

 on the Lower Loup, where they occupy a lower level than the Loess de- 

 posits. These two deposits so often shade into each other in the neigh- 

 borhood of the sand-hills, rendering it impossible to tell where the one 

 begins and the other ends, that the theory of their common origin 

 best explains the phenomena of these formations. After the western 

 portion of the Loess deposits first became dry land, water-agencies were 

 yet so powerful, especially in flood-times, that much of it must have 

 been remodified, and the coarser materials left to form sand-hills. On 

 the other hand, the sand-hills on the Upper Loup and the Niobrara 

 probably derived the bulk of their materials directly from Pliocene Ter- 

 tiary deposits, which were mainly loosely-compacted sands. This old 

 Pliocene lake was probably perpetuated here down through Loess times 

 to the borders of our own era. Even yet lakelets are numerous over 

 portions of this region, some of which are alkaline and others fresh- 

 water. The latter can easily be distinguished from the former at sight, by 

 the thick vegetation growing around their margins, of which the former 

 have very little, and sometimes not a trace. It is at least evident that 

 these freshwater lakes have had some common origin. Their fauna 

 would prove it. The same species of fish and fresh-water mollusks are 

 found in most of the large ones, even where there is no perceptible 

 present outlet. 



Although opposed to the views of eminent scientists, I have no doubt 

 that many of these hills are capable of cultivation and some day will be 

 cultivated. Not, indeed, until the rich lands that border them are im- 

 proved. But when better lands become scarce and costly, advtfnces 

 will gradually be made on the sand-hills. Already it has been proved 

 that they produce sweet-potatoes and other root-crops equal at least to 

 the New Jersey sands. The rich marl-beds in their vicinity will supply 

 an inexhaustible source for fertilizing them. 



Much as has been done by Hayden and others in exploring these sand- 

 hills, still much more remaiiis for the geologist before all the causes 

 that produced them are thoroughly understood. 



ALKALI LANDS. 



Every one in Nebraska will sooner or later hear of the so-called alkali 

 lands. They are not confined to any one geological formation, but are 

 found sometimes on the Drift, Alluvium, or the Loess. They increase in 

 number from the eastern to the western portions of the State. Yet one-half 

 of the counties of the State do not have any such lands, and often there 

 are only a few in a township or county. Where they have been closely 



