Page:Encyclopædia Britannica, Ninth Edition, v. 16.djvu/541

Rh MISSISSIPPI 519 in 5000 feet, but the normal fall in the first mile is about 7 feet. Thus apparently following a low ridge through the bottom lands, the tawny sea sweeps onward with great velocity, eroding its banks in the bends and rebuilding them on the points, now forming islands by its deposits, and now removing them as the direction of the flow is modified by the never-ending changes in progress. Chief among such changes is the formation of cut-offs. Two eroding bends gradually approach each other until the water forces a passage across the narrow neck. As the channel distance between these bends may be many miles, a cascade perhaps 5 or 6 feet in height is formed, and the torrent rushes through with a roar audible for miles. The banks dissolve like sugar. In a single day the course of the river is changed, and steamboats pass where a few hours before the plough had been at work. The checking of the current at the upper and lower mouths of the abandoned channel soon obstructs them by deposit, and forms in a few years one of the characteristic crescent lakes which are so marked a feature on the maps. The total area of the bottom lands is about 32,000 square miles, of which only a narrow strip along the immediate banks of the main river and of its principal bayous and tributaries has even yet been brought under cultivation. A proper system of protection against overflow would throw open 2,500,000 acres of rich sugar land, 7,000,000 acres of the best cotton land in the world, and 1,000,000 acres of corn land of unsurpassed fertility. The work of embankment began in 1717, when the engineer De la Tour erected a dyke or levee 1 mile long to protect the infant city of New Orleans from overflow. Progress at first was slow. In 1770 the settlements extended only 30 miles above and 20 miles below New Orleans ; but by 1828 the levees, although quite insufficient in dimensions, had become continuous nearly to the mouth of Red River. In 1850 a great impulse was given to systematic embankment by the U.S. Government, which gave over to the several States all unsold swamp and over flowed lands within their limits to provide a fund for re claiming the districts liable to inundation. The action Tributaries of the Lou-er Mississippi. River. Distance from Mouth. Elevation above Sea. Width between Banks. Range between High and Low Water. High Water Cross Section. Remarks. Missouri Source Miles. 2,908 Feet. 6 800? Feet. Feet, Square Feet. Three Forks.. 2 824 4 319 Area of basin, 518,000 square miles* rainfall 20 9 Fort Benton 2 644 2 845 1 500 6 inches; annual discharge, 3y^f billions [i.e., Fort Union 1 894 2 188 1 500 - 3,780,000,000,000] cubic feet ; ratio between Sioux City 842 1 065 2,500 drainage and rainfall, -j^ ; mean discharge per St Joseph 484 756 3 000 20 75 000 second, 120,000 cubic feet. Mouth

381 3 000 35 75,000 Upper Mississippi Source 1 330 1 680 Swan River 998 1 290 120 ] Area of basin, 169,000 square miles; rainfall, 35 2 St Paul. . 658 670 1 200 20 100 000 I inches ; annual discharge, 3^ billions cubic Rock Island 310 505
 * &amp;gt; (Mm

16 100 000 j feet ; ratio between drainage and rainfall, & ; Mouth

381 5,000 35 100,000 mean discharge per second, 105,000 cubic feet. Ohio Coudersport 1,265 1 649 1 Area of basin, 214,000 square miles; rainfall, 41 5 Pittsburg 975 699 1,200 45 50,000 ! inches ; annual discharge, 5 billions cubic ft et ; Cincinnati 515 432 42 i ratio between drainage and rainfall, $ ; mean Mouth

275 3 000 51 150,000 ) discharge per second, 158,000 cubic feet. A rkansas Source 1,514 10 000 150 &quot;j Bent s Fort 1,289 3,672 5,000 &quot;6 30,000 Area of basin, 189,000 square miles; rainfall, 29 3 Great Bend 992 1,658 5 000 [ inches; annual discharge, 2 billions cubic feet; Fort Smith 522 418 1,500 25 70 000 1 ratio between drainage and rainfall, ^^ ; mean Little Rock . . . 250 252 1 500 35 70 000 discharge per second, 63,000 cubic feet. Mouth

162 1,500 45 70 000 Red River Near source 1,200 2 450 2 000 8 12 000 1 Area of basin, 97,000 square miles; rainfall, 39 Preston. . 820 641 2 000 inches annual discharge 1 j^ billions cubic feet ; Shreveport 330 180 800 25 40 000 ratio between drainage and rainfall, -j 2 ^ ; mean Mouth

54 800 45 40 000 J discharge per second, 57,000 cubic feet. The Lower Mississippi. Distance from Mouth. High Water Elevation above Sea. Fall per Mile. Width between Banks. Least Low Water Depth upon the Bars. Range between High and Low Water. Area of Cross Section at High Water. Remarks. Mouth of Missouri Miles. 1,286 Feet. 416 Feet Feet. Feet Feet. Square Feet.

St Louis 1 270 408 0-500 2 37-0 Cairo 1 097 322 497 ) 51-0 ) Columbus 1 076 310 571 &amp;gt; 4,470 47-0 } 191,000 miles; rainfall, 30 4 Memphis 872 221-0 436 5 40 Gaines landing 647 149 0-320 i charge (including Natchez 378 66 0-309 !4 080 6 51 } 199,000 three outlet bay- Red River landing 316 49-5 0-966 44-3 ( / ous), 21 ^billions Baton Rouge 245 33 9 220 31-1 of cubic feet ; ratio Donaldsonville 193 25 -8 156 3,000 24-3 200,000 Carrollton 121 15 2 0-147 14-4 ) and rainfall, vcro-; Fort St Philip 37 5-2 0-119 2,470 4-5 f 199,000 Head of Passes 17 2 9 115 2-3 j Gulf

o-o 0-171 o-o cubic feet.