of the state are grown. Long bar-like “islands” (conspicuous high land rising above the marsh and prairie)—Orange, Petite Anse, Grand Cote, Cote Blanche and Belle Isle—offer very interesting topographical and geological problems. “Trembling prairies”—land that trembles under the tread of men or cattle—are common near the coast. Most of the swamp fringe is reclaimable. The marshes encroach most upon the parishes of St Charles, Orleans and Plaquemines. In St Charles the cultivable strip of land along the river is only about 3 m. wide. In Orleans the city of New Orleans occupies nearly all the high ground and encroaches on the swamps. In Plaquemines there is practically no cultivable land below Forts Jackson and St Philip, and above there is only a narrow strip.
The alluvial lands include the river flood plains. The principal rivers are the Mississippi, which flows nearly 600 m. through and along the border of the state, the Red river, the Ouachita (or Washita), Sabine and Pearl; all except the last are navigable at all stages of the water. There are many “bayous,” several of which are of great importance, both for navigation and for drainage. They may be characterized as secondary outlets of the rivers or flood distributaries. Among them are Bayou Teche, Bayou Plaquemine, Atchafalaya Bayou, Bayou Lafourche and Bayou Bœuf. Almost all secondary water-courses, particularly if they have sluggish currents, are known as bayous. Some might well be called lakes, and others rivers. The alluvial portion of the state, especially below the mouth of the Red river, is an intricate network of these bayous, which, before their closure by a levee system, served partially, in time of flood, to carry off the escaping surplus of river waters. They are comparatively inactive at all seasons; indeed, the action of the tides and back-waters and the tangle of vegetation in the sombre swamps and forests through which they run, often render their currents almost imperceptible at ordinary water. Navigable waters are said to penetrate all but four of the parishes of the state, their total length approximating 3800 m.
Each of the larger streams, as well as a large proportion of the smaller ones, is accompanied by a belt of bottom land, of greater or less width, lying low as regards the stream, and liable to overflow at times of high water. These flood plains form collectively what is known as the alluvial region, which extends in a broad belt down the Mississippi, from the mouth of the Ohio to the Gulf of Mexico, and up the Ouachita and its branches and the Red river to and beyond the limits of the state. Its breadth along the Mississippi within Louisiana ranges from 10 to 50 or 60 m., and that along the Red river and the Ouachita has an average breadth of 10 m. Through its great flood-plain the Mississippi river winds upon the summit of a ridge formed by its own deposits. In each direction the country falls away in a succession of minor undulations, the summits of the ridges being occupied by the streams and bayous. Nearly all of this vast flood-plain lies below the level of high water in the Mississippi, and, but for the protection afforded by the levees, every considerable rise of its waters would inundate vast areas of fertile and cultivated land. The low regions of Louisiana, including the alluvial lands and the coast swamps, comprise about 20,000 sq. m., or nearly one-half the area of the state. The remainder consists of the uplands of prairie and forest.
The alluvial region of the state in 1909 was mainly protected against overflow from the Mississippi river by 754 m. of levee on the Mississippi river within the state, and 84 m. on the Mississippi river, Cypress and Amos Bayou in Arkansas, forming part of the general system which extends through other states, 1000 m. up to the highlands about the junction of the Ohio river. The state and the national government co-operate in the construction and maintenance of this system, but the Federal government did not give material aid (the only exception being the grant of swamp lands in 1850) until the exceptionally disastrous flood in 1882. For about a century and a half before that time, levee building had been undertaken in a more or less spasmodic and tentative way, first by riparian proprietors, then by local combinations of public and private interests, and finally by the state, acting through levee districts, advised by a Board of Engineers. The Federal government, after its participation in the work, acted through a Board of Engineers, known as the “Mississippi River Commission.” The system of 754 m. of Mississippi river levees, within the state, was built almost entirely after 1866, and represents an expenditure of about $43,000,000 for primary construction alone; of this sum, the national government contributed probably a third (the state expended about $24,000,000 on levees before the Civil War). Some of the levees, especially those in swampy regions where outlet bayous are closed, are of extraordinary solidity and dimensions, being 20 to 40 ft. high, or even more, across streams or bayous—formerly outlets—with bases of 8 or 10 ft. to one of height. The task of maintenance consists almost entirely in closing the gaps which occur when the banks on which the levees are built cave into the river. Levee systems on some of the interior or tributary rivers, aggregating some 602 m., are exclusively built and maintained by the state. Louisiana also contributes largely to the 84 m. of levee in Arkansas, necessary to its security from overflow. The improvement of bayous, channels, the construction of canals and the drainage of swamp lands also contribute to the protection of the state.
The lakes are mainly in three classes. First come the coast lagoons, many of which are merely landlocked salt-water bays, the waters of which rise and fall with the tides. Of this class are Pontchartrain, Borgne, Maurepas and Sabine. These are simply parts of the sea which have escaped the filling-in process carried on by the great river and the lesser streams. A second class, called “ox-bow” lakes, large in numbers but small in area, includes ordinary cut-off meanders along the Mississippi and Red rivers. A third class, those upon the Red river and its branches, are caused mainly by the partial stoppage of the water above Shreveport by the “raft,” a mass of drift such as frequently gathers in western rivers, which for a distance of 45 m. almost completely closed the channel until it was broken up by government engineers. These lakes are much larger at flood season than at other times, and have been much reduced in size by the cutting of a channel through the raft. Lakes of this class are sometimes formed by the choking of the mouth of feeble tributaries by silt deposited by the Red river where the currents meet.
Mineral Resources.—Mineral resources are few, but important. In the Tertiary region are found small quantities of iron ore and an indifferent brown coal. The important mineral products are salt, sulphur, petroleum and natural gas. The deposit of rock salt on Petite Anse Island, in the coast swamp region, has been extensively worked since its discovery during the Civil War. The deposit is in places 1000 ft. thick, and yields salt of extraordinary purity (sometimes 99% pure). There are large deposits also on Orange Island (in places at least 1800 ft. thick), on Week’s Island, on Belle Isle and probably beneath the intervening marshes. In 1907 Louisiana ranked sixth among the salt-producing states of the country (after New York, Michigan, Ohio, Kansas and California), its output being valued at $226,892, only a few hundred dollars more than that of Texas. Near Lake Charles, at Sulphur, are very extraordinary sulphur deposits. The beds lie several (for the most part four to six) hundred feet underground and are of disputed origin. Many regard them as products of an extinct volcano; according to others they are of vegetable origin (they are found in conjunction with gypsum). They were discovered before 1870 by searchers after petroleum, but their exploitation remained in the experimental stage until about 1900. The sulphur is dissolved by superheated water forced down pipes, and the water with sulphur in solution is forced upward by hot air pressure through other pipes; the sulphur comes, 99% pure, to the surface of the ground, where it is cooled in immense bins, and then broken up and loaded directly upon cars for shipment. These mines divide with the Sicilian mines the control of the sulphur market of the world. The value of the sulphur taken from the mines of Louisiana in 1907 was a little more than $5,000,000. Evidences of petroleum were discovered long ago, in the very field where in recent years the Beaumont and Vinton wells were bored. In 1909 Jennings was the chief field in Louisiana, lesser fields being at Welsh, Anse la Butte, Caddo and Vinton. The Jennings field, one of the greatest in the United States, produced up to and including 1907 more than 26,000,000 barrels of high-grade oil, twelve-thirteenths of which came from an area of only 50 acres, one well producing a tenth of the entire output. In 1907 the state produced 5,000,221 barrels of petroleum, valued at $4,063,033. Natural gas is found in Caddo parish, about 20 m. N. of Shreveport. The depth of the wells is from 840 to 2150 ft.; two wells completed in 1907 had a daily capacity estimated at 35,000,000 to 50,000,000 ft. Shreveport, Oil City, Blanchard, Mooringsport, Bossier City and Texarkana are supplied with natural gas by pipe lines from this field. Kaolin is found in the state; in 1907 the total value of all clay products was $928,579.
Climate.—The climate is semi-tropical and exceptionally equable over large areas. In the S. and S.E. the equable temperature is largely the effect of the network of bays, bayous and lakes, and throughout the state the climate is materially influenced by the prevailing southerly winds from the Gulf of Mexico. Some daily variation in the temperature of adjoining localities is caused by a dark soil in the one and a light soil in the other, but the differences of mean annual temperature are almost wholly due to differences of latitude and elevation. The mean annual temperature for a period of nineteen years (Jan. 1888 to Dec. 1906) ranged from 70° F. at Port Eads, in the extreme S.E., to 65° F. at Lake Providence, in the N.E. The mean temperature of July, the hottest month, is comparatively uniform over the state, varying only from 81° to 83°; the mean for January, the coldest month, varies from 46° in the extreme north to 56° in the extreme south. Even in the coldest localities eight or nine months are wholly free from frost, and in the coast parishes frost occurs only a few days in each year. Rainfall is usually heavy in the S.E., but it decreases toward the N.W. As much as 85.6 in. have fallen within a year at New Orleans, but in this locality the average for a year is about 57.6 in.; at Shreveport the average is 46 in., and for the entire state it is 55 in. Much more rain falls in summer than in any other season, but in some parts the heaviest rainfall is in the spring and in others in the winter. A light fall of snow is not uncommon in the northern parishes, but in the southern part of the state snow falls not oftener than once in three to five years. Hailstorms are infrequent everywhere, but especially so
- The original channel of the Red river. It has been so useful in relieving the Mississippi of floods, that the Red river may possibly be permanently diverted again into the bayou artificially.