Mississippi River (Indian, Mclie Sepe, as spelled by some old writers, and translated the "Great River" and "the Great Father of Waters "), the principal river of North America, and, in connection with its largest tributary the Missouri, the longest river in the world, except perhaps the Nile. It drains the greater part of the territory of the United States lying between the Alleghany and Rocky mountains, a region nearly half as large as Europe. The true Mississippi river begins at the confluence of the Missouri and the Upper Mississippi. It has eight principal tributaries, which, in the order of the extent of the regions drained by them, are the Missouri, Ohio, Upper Mississippi, Arkansas, Red, White, Yazoo, and St. Francis. The source of the Mississippi, according to Schoolcraft, who visited it in 1832, is a lake called by him Itasca, by the Chippewa Indians Omoshkos Sagaigon, and by the French traders Lac la Biche. It is a beautiful sheet of water, clear and deep, about 7 m. long and 1 m. to 3 m. wide, in lat. 47° 14' N, Ion. 95° 2' W., about 1,575 ft. above the sea. Five creeks fall into Lake Itasca, the principal one of which has its origin about 6 m. distant, in a pond formed by water oozing from the bases of the hills known as Hauteurs de Terre, which are about 100 ft. high.

The Mississippi at the outlet of the lake is 10 or 12 ft. wide and 18 in. deep, and flows N. E. over petty falls and rapids through a series of small lakes and marshes till it reaches Lac Travers, its most northern point. This is a beautiful sheet of water from 10 to 12 m. long and from 4 to 5 m. wide, surrounded by wooded hills sloping to a beach of pure white sand. From Lac Travers the river flows S. E. and S., and in the first 25 m. is broken into a series of small rapids, from the foot of which it flows with an even current 40 or 50 yards wide and from 2 to 6 ft. deep to Cass lake, which has an area of about 120 sq. m.; thence S. through a series of savannas, separated by several lakes, to the falls of Peckagama, where it is compressed into a channel 80 ft. wide. Here the river rushes down a rugged bed of sandstone 20 ft. in 300 yards. Below these falls the river is very crooked, and averages about 40 yards in width. It is broken by six rapids between Swan and Sandy Lake rivers. Savanna river enters the Sandy lake, and is the main canoe route between the Mississippi and Lake Superior. From the outlet of Sandy lake to Pine river, 100 m., the river presents several rapids and islands, and receives a number of small tributaries.

Crow Wing river, the largest tributary above the falls of St. Anthony, is nearly equal to the Mississippi itself. The Elk river, the Little falls, Big falls, Prairie rapids, and St. Francis river follow in the order named; and finally the falls of St. Anthony are reached, where the river pitches over a perpendicular face of sandstone 18 ft. high. An island at the brink of the falls divides the current into two channels, the largest of which flows by the west side, and affords a great water power. Including the rapids above and below the falls, the entire descent of the river is about 65 ft. within three quarters of a mile. These falls are about 2,200 m. from the gulf of Mexico, and constitute the natural head of steamboat navigation; but small vessels ply regularly above the falls for several hundred miles, according to the stage of water. The next natural obstruction to navigation below the falls of St. Anthony are the Rock Island rapids, extending from Le-claire to the cities of Rock Island and Davenport, a distance of 14 m. The descent is 24 ft. at extreme low water. The bed of the river throughout the rapids is stratified limestone, more or less folded, and forming chains or barriers which extend entirely across the channel at six or seven points.

In 1866 congress directed the removal of these chains, and also the improvement of the lower or Des Moines rapid, 130 m. below the upper rapid, and between Montrose and Keokuk. The length of the latter is 12 m., and the descent 23 ft. at low water. Before the improvements were undertaken, there was about 11 m. of deep water and good navigation on the upper rapids, and only 3 1/2 m. on the lower rapids. The duty of devising plans for the improvement of the rapids was assigned to Gen. J. H. Wilson, U. S. A., who recommended that the obstruction at the upper rapids should be removed mainly by the use of coffer dams (see Dam, vol. v., p. 650), and that the lower rapids should be improved by similar means, supplemented by a lateral canal 7 m. long, 300 ft. wide, and having three locks each 80 ft. wide and 350 ft. long. A board of engineers approved these plans, and congress ordered them to be carried into effect. The improvements, under the supervision of Gen. Wilson and his successor Col. Macomb, have been pushed forward as fast as the appropriations would permit, and are now (November, 1874) almost completed at the upper rapids, while four fifths of the work has been done at the lower rapids.

The improvements will cost about $5,000,000, and when completed will enable the largest boats to pass the rapids, whenever they can reach them either from above or below. But the navigation of the entire Upper Mississippi is rendered very difii-cult during the dry season by the frequent recurrence of sand bars; and although the government has done something by the use of dredge boats and wing dams to deepen the water on the worst of these, no systematic plan of improvement has yet been devised or can be carried out till a much denser and richer population shall inhabit the regions to be benefited. But it is safe to say that between the falls of St. Anthony and the mouth of the Ohio there is water enough at the driest season, if properly regulated and controlled, to give a navigable depth of 6 ft, and ample width for all uses to which it can be put. - The Mississippi river, from the mouth of the Missouri to the gulf, is 1,286 m. long; from the source of the Upper Mississippi, 2,616 m. The distance from the Madison fork source of the Missouri to the gulf is 4,194 m., and from the head of the Ohio river at Coudersport, Pa., to the gulf, 2,551 m.

The numerous branches of the navigable waters connected with the Mississippi penetrate all the states and territories between the Rocky and Alleghany mountains. The capacity of these branches for navigation has been as yet only partially developed, but a careful compilation shows that they constitute a natural system of water communication having an aggregate extent of about 1,500 m. - The following table, taken from Humphreys and Abbot's "Report upon the Hydraulics of the Mississippi River " (4to, Philadelphia, 1861), shows the area of the basins, downfall of rain, and annual drainage of the Mississippi and its principal tributaries:

BASIN.

Area, square miles.

Annual downfall, in cubic feet.

Annual drainage, in cubic feet.

Ratio.

Ohio river...

214,000

20,700.000.000,000

5.000,000,000,000

0.24

Missouri river...

518,000

25,200,000,000,000

3.780,000,000,000

0.15

Upper Mississippi...

169,000

13,800.000,000,000

3,300,000,000,000

0.24

Small tributaries...

32 400

3,600,000,000,000

3.240,000,000,000

0.90

Arkansas and White rivers...

189.000

13,000,000,000,000

2.000,000,000,000

0.15

Red river...

97,000

8,800.000,000,000

1.800,000,000,000

0.20

Yazoo river...

13.850

1.500.000,000,000

1,350,000,000,000

0.90

St.Francis river...

10.500

1,100,000,000,000

9,990,000,000,000

0.00

Entire Mississippi exclusive of Red river........

1,147.000

78,900,000,000,000

18,000,000,000,000

0.25

Below the mouth of Red river, the Mississippi is divided into numerous arms or passes, each of which pursues an independent course to the gulf. The highest of these is the Atchafalaya on the W. side of the river. Below its point of separation from the Mississippi the region of swampy lands, of bayous and creeks, is known as the delta. Above this the alluvial plain of the river extends to the Chains, 30 m. above the mouth of the Ohio, and to Capo Girardeau in Missouri, where precipitous rocky hank- are first met with. These are the lower secondary lime-tone strata lying in nearly horizontal beds. The total length of the plain from the mouth of the Ohio to the gulf is estimated at 500 m. Its breadth at the upper extremity varies from 30 to 50 m.; at Memphis it is about 30 m., and at the mouth of White river 80 m. The extreme width of the delta is rated at 150 m., its average width is probably 90 m., and its area 12,300 sq. m. The elevation of the bottom lands at Cairo above the sea level is about 310 ft,, while the slope of the high water surface from that place to the gulf is from 322 to 0. These bottom lands are subject to inundation, and consequent annual enrichment.

Under the system of slave labor large plantations were opened in the dense forests which cover them, but vast tracts of unsurpassed fertility are vet cov-ered with canebrakes and cypress. The alluvial plain, extending from above Cairo to the gulf, is terminated on the east and the west by a line of bluffs of irregular height and direction, composed of strata of the eocene and later tertiary formations. Down this plain the river flows in a serpentine course, frequently washing the base of the hills on the E. side, as at Columbus, Randolph, Memphis, Vieksburg, Grand Gulf, Natchez, and Baton Rouge, and once passing to the opposite side at Helena. The actual length of the river from the mouth of the Ohio to the gulf is 1,097 m.. increasing the distance in a straight line by about 600 m., and by its llexures also reducing the rate of its descent to less than half the inclination of the plain down which it flows. The range between high and low water at Cairo, near the head of the plain, is 51 ft., and at New Orleans it is 14 4 ft. The river flows in a trough about 4,470 ft. wide at the head, and 3,000 ft. at the foot.

The Immense curve, of the stream in its course through the alluvial plain sweep around in Half circles, and the river sometimes, after traversing 25 or 30 m., is brought within a mile or less of the place it had before passed. In heavy Hoods the water occasionally bursts through the tongue of land, and form what is called a "cut-off," which may become a new and permanent channel. The height of the banks and the great depth of the river bed check the frequent formation of these cut-offs, and attempts to produce them artificially have often failed, especially when the soil is a tough blue clay, which is not readily worn away by flowing water. This was the case at Bayou Sara, where in 1845 an excavation intended to turn the river was made, by which a circuit of 25 m. would have been reduced to a cut of one mile; and also at Vicksbnrg in 1862-'3, where the Union army endeavored to make a cut-off out of range of the confederate guns. Semicircular lakes, which are deserted river bends, are scattered over the alluvial tract. These are inhabited by alligators, wild fowl, and gar fish, which the steamboats have nearly driven away from the main river. At high water the river overflows into these lakes.

The low country around is then entirely submerged, and extensive seas spread out on either side, the river itself being marked by the clear broad band of water in the midst of the forests that appear above it. The great freshets usually occur in the spring, and are often attended with very serious consequences. Crevasses are formed in the banks and increase with the flow, which becomes so violent that boats are occasionally carried with their crews into the intricacies of the bayous which lead the waters to the streams at the foot of the bluffs. - The lower portion of the alluvial plain, called the delta, rises from a few inches to 10 ft. only above the level of the sea, and is formed of sands and clays in horizontal layers. The delta protrudes into the gulf of Mexico far beyond the general coast line, and is slowly but imperceptibly advancing into the gulf by the shoaling caused by the deposition of the sediment brought down the river. This is mostly dispersed by the waves and currents, and distributed over the bottom of the gulf.

Although the banks of the passes are sometimes observed to have advanced in the course of a few years simsibly into the gulf, these are but narrow strips of land, which may be swept away by the rush of the gulf waters driven up by storms, leaving the long coast of the delta but slightly changed. The old French maps of the early part of the last century still very correctly represent many of the mud banks and channels or bayous around the Balize, which is the station of the pilots at the mouth of the river. Here only, for a distance of 100 m. from the gulf, is the river seriously obstructed by bars. Over these the depth of water is sometimes only 15 ft.; but this is very changeable, as the channels are shifted by the floods in the river and the gulf storms. These bars are composed of blue clay mud, through which vessels drawing 2 or 3 ft. more water than the actual depth can be taken by steam tugs. Great efforts have been made by the government to remove these obstructions by dredging, and the depth of water has been increased thereby to 21 ft.; but owing to the difficulty of maintaining such a great depth with dredges, congress has appointed a board of engineers to investigate the subject and report a plan. - The sediment of the lower Mississippi is chiefly a fine clayey matter, so universally suspended in the water as to give it a thick muddy appearance.

The Upper Mississippi is clear, but the Missouri pours into it a vast amount of whitish muddy matter, which renders the water so turbid that at St. Louis one cannot see through a tumbler filled with it. This, however, does not prevent its being generally used for drinking, and for culinary purposes. The Ohio adds to it a greenish current, and the Arkansas and Red rivers pour in the red ochreous sediment already referred to; while the Mississippi itself excavates its alluvial plain and sweeps down, intermingled with the rest, vast quantities of vegetable soil that falls in the banks of the' river. The coarser pebbles and sands accumulate in the bends and eddies, forming bars, and the lighter materials are deposited in the gulf of Mexico. According to the report of Capt. (now Gen.) Humphreys and Lieut, (now Gen.) Abbot, a comparison of the results of many observations during a long period leads to the belief that the weight of the sediment of the Mississippi is 1/15,00 that of the water, and its bulk 1/2900; and if the mean annual discharge of the river be assumed to be 19.500,000,000,000 cubic feet, it follows that 812,500,000,000 pounds of sedimentary matter, constituting one square mile of deposit 241 ft. in depth, are yearly transported to the gulf.

In addition to the amount held in suspension, the Mississippi pushes along large quantities of earthy matter. No exact measurement of this can be made, but from the yearly rate of progress of the bars into the gulf, it appears to be about 750,000,000 cubic feet, which would cover a square mile about 27 ft. deep. The total yearly contributions from the river to the gulf amount then to a prism 268 ft. high, with a base of one square mile. - The uniformity of width of the Mississippi is very remarkable. At New Orleans it is about 3,000 ft. wide, and from this it varies little for a distance of nearly 2,000 m., except that in the bends it swells out to 1 or even 1 1/2 m. The junction of its principal branches produces no increase in the width. The depth is very variable, sometimes reaching 150 ft., but the maximum is more commonly from 120 to 130 ft. The mean depth at high-water mark is about the same at Carrollton and at Natchez, 300 m. further up. A section of the river at Carrollton, made at high-watermark in 1858, comprises 184,000 square feet, and at Natchez 221,000. The mean rate of descent varies at low water from -005 of a foot per mile at the head of the passes, to .578 of a foot at Cairo, and in high-water from .115 of a foot to .497 of a foot per mile.

The velocity varies at Carrollton from 1.45 to 2.61 m. per hour, according to the stage of the water and the direction of the wind. - The Mississippi, like the other great rivers of the west, is continually gathering into its current numbers of trees, as the banks upon which they grew are undermined. They are frequently left in the main channels, their roots fixed to the bottom, and their tops pointing down stream. In this condition they are known as snags and sawyers, and present to boats ascending the river, especially at night, a most dangerous obstruction. But continual care is now given to the removal of these obstructions. The accumulations of the drift materials in the arms of the river have sometimes been so great as to bridge these over and extend for miles up the current. The obstruction is then known by the name of raft. From about the year 1778 such an accumulation had been gathering in the Atchafalaya, until in 1816 it had extended to full 10 m. in length, over 600 ft. in width and about 8 ft. in depth. Though rising and falling with the water, it afforded a soil for the growth of bushes and of trees, some of which reached the height of 60 ft.

In 1835 the state of Louisiana took measures to have it removed, and this was finally accomplished at a heavy cost in the course of four years. The Red river raft is still more famous for the large sums which have been appropriated by congress to effect its removal, the work upon which has been carried on with great success of late years, and is now almost completed. The appropriations made from time to time by congress for the Mississippi river comprise the following items:

Mouth of Mississippi river, from 1836 to 1856.....

$690,000

" " " " " 1856 to 1875.....

1.224,860

Mississippi river, between Illinois and Ohio rivers.

665,000

Des Moines rapids...

8,028,200

Rock Island rapids....

1,030,650

Upper Mississippi river, including falls of St. Anthony...

677,640

Mississippi river, including rapids (1836 to I856)...

465,000

Total...

$7,789,840

For a full statement of measurements, all the phenomena, physical elements, and laws relating to this great river, see the " Report upon the Physics and Hydraulics of the Mississippi River," prepared by Capt.. A. A. Humphreys and Lieut. H. L. Abbot, U. S. army (4to, Philadelphia, 1861), and also the official reports of the chief of engineers to the war department. - The first European explorer of the Mississippi valley was De Soto, who with his party reached the river in June, 1541, as is supposed not far below the site of Helena in Arkansas. (See De Soto.) In 1073 Marquette and Joliet descended the river to within three days' journey of its mouth. La Salle in 1682 descended the river to the gulf of Nfexico, and took possession of the country in the name of the king of France. About the year 1699 Iberville built a fort upon the banks of the river, and in 1703 the settlement of St. Peter's was made upon the Yazoo branch. New Orleans was laid out in 1718, and levees were immediately commenced, which were completed in front of the city ten years afterward.

At that time the levee system of lower Louisiana was fully established.