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 surface flow in volume. The Loup system is remarkable for the even dip of its parallel feeders, which once joined the Platte separately, until the latter banked up its deposits across the mouths of their more sluggish currents. The Republican and South Platte—the former an intermittent stream—suffer in their flow from the drain made upon their waters in Colorado for irrigation. The upper course of the Niobrara above the Keya Paha is in a narrow gorge. Its immediate bluffs and the shores of some of its tributaries, notably the Snake, are modified by cañons. This system is also notable among Nebraska streams for a number of pretty water-falls. The White river, heading on Pine Ridge, falls 1100 ft. in 20 m. Some streams wholly dry up in the dry seasons, and in the foot-hills and sand-hills there are a few that disappear by sinking or evaporation.

Surface Water.—Swamps and bogs, apart from purely temporary weather ponds, are confined to a few restricted regions of the Missouri river bottoms and the prairies of the S.E. There are some cut-offs or oxbow lakes along the Missouri, and many lakelets originally such are scattered along the Platte, Elkhorn, Big Blue and other rivers. Scores of lakes are scattered about the heads of streams rising in the sand-hills, especially in Cherry county. Some of them are fresh and some alkaline. Springs also are numerous in the sand-hills, where they form considerable streams. They often flow with force and are known locally from this peculiarity as “artesian” springs, or sometimes, from this and their large size, as “mound” springs. The state fish-hatchery is on springs at South Bend; at Long Pine springs of large flow supply the town and railway shops with water, and led to the establishment here of Chautauqua grounds.

Underground Water.—The so-called blowing-wells are peculiar. They occur over much of the state, but most frequently S. of the Platte, and are evidently sensitive to barometric conditions; alternately “blowing” or “sucking” as these vary; so that, in cold weather water-pipes may be frozen 100 or more feet below the surface of the ground. Atmospheric pressure is probably the principal cause of their action; they are therefore termed “weather wells” in some localities. Nearly all counties have a practically inexhaustible supply of ground water. Well-depths vary from 15 to 20 ft. in the stream valleys and from 30 to 35 ft. on the loess prairies to 100-400 ft. in the western foot-hill region and isolated prairie areas. Artesian water is also available in many parts of the state. At Niobrara, in Knox county, a well 656 ft. deep, drilled in 1896, yielded for a time 2500 gallons per minute at 95-&#8468; pressure (in 1903 1900 gallons at 65-&#8468; pressure), and furnishes power for a flour-mill and municipal water and electric lighting works; the pressure forces the water about 210 ft. above the mouth of the well, i.e. to a height of 1450 ft. Another (1430 ft. deep), in the environs of Omaha, supplies a daily flow of 1,100,000 gallons under a pressure of 15 ℔. In some small and exceptional regions the water is very alkaline, and in the counties of the south-east it is so generally saline that it is difficult, below 150 ft., to avoid an inflow of salt water. Saline wells at Lincoln (2463, 1050 and 570 ft. deep) and at Beatrice (1260 ft.) are notable in this regard.

Geology.—The eastern part of the state is covered with a thick mantle of Quaternary (Pleistocene), and the greatest part of the western portion with very thick deposits of Miocene and Pliocene (Tertiary). To the Pleistocene belong the alluvium, loess and glacial drift, and in part the sand-hills. The drift covers the eastern fifth of the state. In striking contrast to Iowa, the Nebraska deposit is very thin, seldom thicker than 1 or 2 ft. Above the drift there is usually a heavy covering of loess or “bluff deposit” (particularly typical in the neighbourhood of Omaha and Council Bluffs). Though thin and worn out in places, it averages probably 100 ft., and is often as much as 200 ft. in thickness, and runs diagonally across the state from the N.E. to the Colorado inset. The opinion that it is of aqueous origin (and probably dates from the close of the glacial time) has the weight of authority. It was spread by the rivers: some evidences of wind action may be attributed to a later period. The sand-hills, which overlap the loess N. of the Platte, are probably mainly derived from the Arikaree, but probably also in part from the early Pleistocene. West of 102° long. there are beds several hundred feet thick of late Tertiary sands and clays. The Arikaree (Miocene) and Ogallala (Pliocene) formations of the North Loup beds are superficial over much of the western half of the state, the former to the N., the latter to the S. The buttes are characteristically Arikaree or Gering formations topping Brule clay. The same is true of at least considerable parts of Pine Ridge. In the Bad Lands there are scanty outcrops of the Chadron formation (known also as “Titanotherium beds”), the oldest of the Tertiary beds. The thick superficial coverings over the state make difficult the determination of the underlying strata. There are only very scanty outcrops except along the rivers. No Archean rocks are exposed in Nebraska, and the sedimentary formations are undisturbed in situ. The Palaeozoic era is represented only by the Pennsylvanian series of the Upper Carboniferous and a scanty strip of Kansas-Nebraska Permian, and is confined to the S.E. counties. But, though small in area, the Carboniferous is by far the most important formation as regards mineral resources within the state. It is buried probably 2000 or 3000 ft. in central Nebraska, outcropping again only in the Rocky Mountains. Upon it, in the trough thus formed, rest conformably the basal strata of the Cretaceous; the Jurassic and Triassic being wholly absent (unless in the extreme north-west). The E. limit of

the Cretaceous extends across the state from N. to S. between 98° and 99° W. long. Its groups include the Dakota formation, characterized by a very peculiar rusty sandstone, and the Benton, both of which are rather widely accessible and heavy; the Niobrara; the Pierre shales, which apparently underlie about three-quarters of the state in a deep and heavy bed; and, in the extreme west, the Laramie. There are almost no Cretaceous outcrops except on the streams, especially the Niobrara, Republican and Platte rivers—and in the Bad Lands. The superficial Miocene and Pliocene deposits in the west, above referred to, are underlaid by the White river groups of the Oligocene, whose outcrops of Brule clay and Chadron formation also have been mentioned. The Bad Lands are essentially nothing but fresh-water mud excessively weathered and eroded. They are often intersected by dikes of chalcedony, formerly mistaken for lava. The Bad Lands and the Arikaree are famous fossil fields, the latter being the source of the Daemonelix, or “Devil’s cork-screw,” a large spiral fossil, apparently a lacustrine alga. It was once generally supposed that the Pliocene epoch in Nebraska was distinguished by the activity of geysers; but the so-called “geyserite” now known commonly and correctly as “natural pumice” and “volcanic ash,” which is found in the Oligocene and later formations, has no connexion whatever with geysers, but is produced by the shattering of volcanic rock. It occurs widely in Nebraska and adjoining states.

Minerals.—Mineral resources are decidedly limited; the total value of the mineral output (excluding coal) in 1907 was $1,383,916, of which $953,432 was the value of clay products, $324,239 of stone, and $54,227 of sand and gravel. The state, however, is particularly rich in good clays, which are probably its greatest mineral resource. Calcite of excellent quality is the commonest mineral. Gravel is widely obtainable, and sand of the finest quality is available in inexhaustible quantities, and is an important article of export. Flint (valuable for railway ballast) occurs in immense quantities about Wymore and Blue Springs. The underground salt water flow promised once to be a resource of value, especially in the vicinity of Lincoln, but has proved of little or no value in comparison with the great salt-beds of Kansas. A native plaster is yielded by the Arikaree and Ogallala rocks, but though otherwise of excellent qualities it is ruined by slight exposure to the water. A diatomaceous earth in central Nebraska, occurring especially in the region of Loup, is a good polishing powder, and is used for packing steam pipes. Limonite in the form of ochre occurs in considerable quantity. Of building stones limestones are the most abundant and important, the best comes from the Benton beds and when “green” can be sawed into blocks. The Dakota formation, though its sand-stones are in general coarse or otherwise inferior, yields some of splendid quality. Its clays, which are of all colours, are the most valuable of the state. The finest building stone is a beautiful green quartzite rock of dense, fine texture and lasting quality. It is related to the Ogallala beds and occurs only in small areas. The quarries and clay pits of the state are mainly in the Carboniferous region of the S.E. Cretaceous lignite occurs in small quantities in the N.E., and peat more widely. The Carboniferous formations carry only thin seams of coal, never thicker than about 2 ft., and rarely readily accessible, and they can never be of more than small and merely local importance.

Flora.—Nebraska lies partly in the arid, or Upper Sonoran, and partly in the humid, or Carolinian, area of the Upper Austral life-zone; the divisional line being placed by the United States Biological Survey at about 100° W. long. The most marked characteristic of Nebraskan vegetation is its immigrant character, and the state has been called “one of the finest illustrations of the commingling of contiguous species to be found anywhere in America” (C. E. Bessey). Immigrant species have even come from Texas and New Mexico, from the Dakotas and the Rockies. From the last-named various species have crept two-thirds of the way across the state, one (the buffalo berry) wholly covers it, and some have barely crossed into the border foot-hills from Wyoming. A very few trees and shrubs, and some grasses, are strictly endemic to the plains and to Nebraska. Four floral regions lying in north to south belts across the state, and closely corresponding to—though in boundaries by no means coinciding with—its great topographic divisions are distinguished in the regions of the Missouri border, the prairies, sand-hills and foot-hills. In 1896 some 3196, and by 1905 fully 3300 species had been listed, “representing every branch and nearly every class of the vegetable kingdom” (C. E. Bessey). There are at least 64 trees and at least 77 shrubs growing native in the state; but of their joint number a mere half-dozen or so can be classed as strictly endemic. Small woods of broad-leaf trees (and red cedars) grow very generally along all the water-courses of the state; and coniferous species grow along Pine Ridge and the Wild Cat Mountains. In the East, various trees are readily grown on the uplands; in the West the honey-locust, the Osage orange and Russian mulberry for windbreaks; the green ash, and red cedar are perhaps the most valuable drought resisting species. The conifers are spreading naturally. In the sand-hills the sand-bar willow of the rivers and the cottonwood growing naturally, evidence the good conditions of moisture; and the forestation of much of the region is undoubtedly possible. Forest reserves were established on the Dismal river in 1902 and millions of seedlings had been grown by 1906 for transplantation in Nebraska and other states