PLAINS. 



PLAINS. 



640 



The savannas, or prairies, as they are also called, are divided by Flint, 

 an American writer, into three kinds : 1, the heathy or bushy, which 

 have springs and are covered with small shrubs, grape-vines, &c., very 

 common in Indiana, Illinois, and Missouri ; 2, dry or rolling (a desig- 

 nation which will be explained in the sequel), generally destitute of 

 water and almost of all vegetation but grass; they are the most 

 common and extensive : the traveller may wander for days in these 

 vast and nearly level plains without wood or water, and see no object 

 rising above the horizon ; 3, the alluvial or wet prairies, the smallest 

 division ; they are covered with a rich vegetation of tall rank grass. 

 The soil is deep, black, friable, and fertile, and abounding in pools 

 without issue, left by the floodings of the rainy season. It is over the 

 second kind chiefly that the bisons wander in herds of from 40,000 to 

 50,000. Stags, or more properly wapitis, are also very numerous ; and 

 between the Arkansas and Red rivers there are droves of wild horses. 

 Deer are also numerous ; and along the borders of the Missouri, above 

 the Platte, or shallow river, the antelope abounds in herds of several 

 hundreds. In summer wild goats are seen in vast numbers along the 

 Mississippi. Above the Mandan villages are grizzly bears; and 

 badgers, beavers, otters, foxes, wolves, racoons, opossums, squirrels, 

 porcupines, and skunks inhabit the same region. To this enumera- 

 tion of Warden's and Flint's, Lyell adds the jaguar. The waters teem 

 with alligators and tortoises, and their surface is covered with millions 

 of migratory water-fowl, which perform their annual voyage between 

 the Canadian lakes and the shores of the Mexican Gulf. 



Precise information on the extent and peculiar characters of the 

 Prairies, obtained in an elaborate survey, has recently been given by 

 Mr. James Hall, state geologist of Iowa, a man of science advantageously 

 known to English geologists. This is introduced in an account of the 

 physical geography of that region, forming Chapter L of Mr. Hall's 

 ' Report on the Geological Survey of the State of Iowa,' published by 

 authority of the legislature of that state, 1858. It involves many par- 

 ticulars having an important bearing on the structure of the plains of 

 North America in general, and with some slight omissions we shall 

 now transfer it to our columns. Fortunately for the investigation of 

 this subject, the state of Iowa consists, mainly, of prairie country. 



The prairie region of the west occupies a vast extent of country, 

 extending over the eastern part of the Ohio, Indiana, the southern 

 portion of Michigan, the southern part of Wisconsin, nearly the whole 

 of the states of Illinois and Iowa, and the northern portion of Missouri, 

 and gradually passing, in the territories of Kansas and Nebraska, into 

 the arid and desert region which lies at the base of the Rocky .Moun- 

 tains, called in that local technicality which is so characteristic of 

 America, and which, in every part of the world appears to have pre- 

 ceded scientific geographical description the Plains. This passage 

 takes place in the region between the parallels of 97 and 100, west of 

 which belt the country becomes too barren to be inhabited and worth- 

 less for cultivation. The passage from the heavily wooded region of 

 the north and east into the treeless plains of the west is a gradual one, 

 and the disappearance of the underwood and the predominance of 

 " oak openings," or groves of oak and other forest trees, not crowded 

 together, but scattered over the surface at a considerable distance from 

 one another, without any low shrubs or underbrush between them, 

 is the characteristic of the border of the prairie region. To one coming 

 from the dense thickets of low and tangled shrubs which choke the 

 forests of the north, and render travelling through them difficult, even 

 to the pedestrian, the open woods of the north-west offer a striking 

 contrast to that which has been left behind, and form a natural intro- 

 duction to the grassy plains or prairies. 



The elevation of the prairie region above the level of the sea gra- 

 dually increases from the east to the west. The lower part of Illinois 

 varies from 100 to 250 feet above the river at Cairo, or 400 to 550 feet 

 above the sea-level. In the central portions of the state the levelling* 

 along the line of the Illinois central railroad, indicate an average eleva- 

 tion of from 650 to 750 feet, which increases towards the northern 

 boundary to 800 or 900 feet above the sea. Some of the highest 

 swells of the prairie attain an elevation of nearly 1000 feet. The more 

 elevated portions of Southern Wisconsiu are about 1100 feet above 

 tide-water. The region from the Mississippi westward is a gradually 

 ascending plain as far as the very base of the Rocky Mountains. 

 Within the limits of Iowa the table-land along the water-parting 

 between the streams flowing into the Mississippi and the Missouri, the 

 " Plateau du C'oteau des Prairies " of Nicollet, attains the altitude of 

 from 1400 to 1500 feet above the sea ; and to the west of the Missouri 

 the ascent still continues, the soil being more and more arid, until at 

 the 105th meridian, an elevation of 5000 feet is attained. 



The prairie is designated as " flat " or " rolling," its surface in the 

 one case being nearly level, and in the other gently undulating. The 

 flat prairie is found chiefly south and west of Lake Michigan, on the 

 head-waters of the Illinois and Wabash rivers. In other districts the 

 rolling prairie greatly predominates over the flat, especially in Iowa, 

 where there are but few tracts of any extent which are not more or 

 lew undulating. Even in the rolling prairie the irregularities of the 

 surface are but trifling in amount, compared with the vast extent 

 which can be taken in at one view : so that it often happens that a 

 region which, seen from a distance, appears to be almost a dead level, 

 is, in reality, furrowed by broad depressions, which give a wave-like 

 character to its surface. Thus, the traveller crossing the prairie in any 



AET8 AND SCI. DIV. VOL. VI. 



direction except along its water-parting, will be' surprised to find himself 

 constantly ascending and descending, although only hills of moderate 

 elevation. The depth of these depressions below the mean level of 

 the prairie may frequently be as much as 50 feet ; but it does not 

 often greatly exceed that amount, without the drainage becoming suffi- 

 cient to convert the water, which collects in them, into a running 

 stream. The " swales," or " sloughs," of the prairie, as these depressions 

 are called, are wet and marshy except in the dry seasons, and, in the 

 spring and autumn make the roads almost impassable. 



The prairies are covered with a dense vegetation o grass and her- 

 baceous plants, to the almost entire exclusion of trees, which occur 

 only under peculiar circumstances of moisture and soil, iu scattered 

 groups called groves, or along the larger streams, or, occasionally, on 

 low rocky ridges which are sometimes met with. This growth of 

 timber in the river bottoms does not entirely disappear until we reach 

 the border of the " plains," in the longitude of about 98 west of 

 Greenwich. In the swales or depressions, which are comparatively 

 humid, the grass grows very tall and rank ; and the higher and drier 

 the prairie the finer its growth, and more dense and closely interwoven 

 the sod. Among the grasses of the prairies is interspersed a great 

 variety of flowering plants, which bloom in constant succession from 

 spring to autumn, and lend a peculiar charm to the landscape, giving 

 beauty and variety to what might otherwise be called a monotonous 

 scene. The characteristic herbs of the prairies would seem to be com- 

 positoe, especially Helianthwd Composites, according to Dr. Asa Gray, 

 who has enumerated the principal species in the ' American Journal 

 of Science,' Series II., vol xxiii. p. 397. 



The upper portion of the material constituting the superficial 

 covering of the prairie is always finely comminuted, and usually has 

 few loose boulders or fragments of rock scattered through it, although 

 they sometimes lie upon the surface in isolated groups, or singly. 

 Upon the great prairies in Central Iowa, one may frequently travel 

 over a large extent of surface without seeing a single stone, not even 

 so much as the smallest pebble. In the swales, and in some of the 

 bottom lands, especially in the southern part of the State, the rich 

 black vegetable mould is very deep, but on the prairies it is usually 

 from one to two feet. The subsoil is almost invariably a quite argil- 

 laceous loam, and there is a gradual passage downwards into a material 

 in which, though containing sandy portions and occasional pebbles, the 

 argillaceous element greatly predominates. 



The material of the superficial covering of the prairie has evident! v 

 not been transported to any great distance. It bears the marks ot' 

 having had its origin chiefly iu the decomposition of the rocks which 

 underlie it, and iu fact, the prairies are exclusively confined to regions 

 underlaid by soft sedimentary strata, especially shales and impuru 

 limestones. It would be difficult to imagine, Mr. Hall remarks, a 

 prairie soil existing on crystalline rocks. 



After describing the prairies, Mr. Hall proceeds to discuss, as follows, 

 the difficult and contested problem of their origin, and of the cause of 

 the absence of trees over so extensive a region : 



" The idea is very extensively entertained, throughout the west, that 

 the prairies were once covered with timber ; but that this has been 

 destroyed by the fires which the Indians have been in the habit of 

 starting in the dry grass, and which sweep over a vast extent of surface 

 every autumn. A few considerations will show that this theory is 

 entirely untenable. 



' In the first place, the prairies have been in existence at least as far 

 back as we have any knowledge of the couutry ; since the first 

 explorers of the west described them just as they now. are. There 

 may be limited areas once covered with woods, and now bare ; but, iu 

 general, the prairie region occupies the same surface which it did when 

 first visited by the white man. 



" But, again, the prairies are limited to a peculiar region, one 

 marked by certain characteristic topographical and geological features, 

 and they are by no means distributed about wherever the Indians have 

 roamed and used fire. Had the frequent occurrence of fires in the woods 

 been the means of removing the timber and covering the soil with a 

 dense growth of grass, there is no reason why prairies should not 

 exist in the eastern and middle states as well as in the western. The 

 whole northern portion of the United States was once inhabited by 

 tribes differing but little from each other in then- manner of living. 



" Again, were the prairies formerly covered by forest trees we should 

 probably now find some remains of them buried beneath the soil, or 

 other indications of their having formerly existed. Such is not the 

 case, for the occurrence of fragments of wood beneath the prairie sur- 

 face is quite rare ; and when they are found, it is in such a position as 

 to show that they have been removed to some distance from their place 

 of growth. 



" It has been maintained by some, that the want of sufficient 

 moisture in the air or soil was the cause of the absence of forests in 

 the north-west ; and it is indeed true that the prairie region does con- 

 tinue westward, and become merged in the arid plains which extend 

 along the base of the Rocky Mountains, where the extreme dryness is 

 undoubtedly the principal obstacle to the growth of anything but a 

 few shrubs, peculiarly adapted to the conditions of the climate and 

 soil which prevail in that region. This, however, cannot be the case 

 in the region east of the Mississippi and near Lake Michigan, where 

 the prairies occupy so large a surface ; since the results of metcoro- 



