'8 BULLETIN 652, U. S. DEPARTMENT OF AGRICULTURE. 



Important exceptions to the foregoing general statement as to the relation 

 between the size of bayous and the ridges built by them are frequently 

 found. Prominent among those are the Bayou L'Ourse, in the southeastern 

 part of Lafourche Parish, and the Wax and Little Wax Bayous, in St. Mary 

 Parish. Bayou L'Ourse is an insignificant stream, occupying the center of a 

 long and important ridge. It is probable that at one time this bayou served as 

 an outlet for Lafourche, or possibly for some predecessor of the latter bayou 

 for draining in a more easterly direction through Bayou Blue, Lake Fields, and 

 Long Lake. Wax and Little Wax Bayous are streams of erosion rather than 

 of sedimentation and have been formed wholly or in part by the action' of 

 storms and the tidal flow, which is quite strong along this portion of the coast. 

 As a result, the bayous are bordered by the marsh or by very low ridges. Both 

 streams are from 10 to 50 feet in depth and 100 to 200 feet in width. 1 



In addition to the above, Bayous Terrebonne and Black, in Terrebonne 

 Parish, are typical examples of the sedimentation type; while Bayou des 

 Allemands, the connection between Lake Des Allemands and Lake Salvador, 

 is an excellent illustration of the tidal-erosion type. 



From the foregoing it may be seen that the chief difference between the 

 various types of soils is the variation in fineness of material rather than differ- 

 ence in chemical composition. 



CLASSIFICATION AXD EXTENT OF SOILS. 



The various types of soils grade imperceptibly into each other, but the 

 following classifications have been made by the Bureau of Soils: Yazoo sandy 

 loam, Yazoo loam, Yazoo clay, Sharkey clay, muck, and Galveston clay. The 

 first three are ridge soils and limited in extent ; they form a very small per- 

 centage of the total area. These soils have sufficient elevation to drain by 

 gravity, and as practically all are well drained and cultivated they will not be 

 discussed further. The last three classes include practically all the un- 

 drained soils of this section. The Sharkey clay is a heavy alluvial soil. For 

 the top 5 or 6 inches it is black, due to the heavy percentage of decayed vege- 

 table matter; the subsoil is a brown or drab, waxy, very impervious clay. 

 The soil shrinks greatly on drying, leaving large sun cracks. This, combined 

 with the effect of the decayed vegetable matter, causes the soil to break up 

 very readily under the plow. For the most part the Sharkey clay areas are 

 heavily forested, the better-drained portions having a dense growth of hard- 

 woods and the wettest portions being covered with cypress. 



The muck and Galveston clay areas are practically the same. On top of 

 the above-described Sharkey clay the decaying vegetation of the open grass- 

 covered prairies has formed a mass of material which is quite variable in 

 character. Where it is almost pure vegetable matter it is classed as muck 

 or peaty muck, and where the percentage of silt or clay is rather heavy it is 

 classed as Galveston clay. The depth of this layer of vegetable matter varies 

 from a few inches to several feet. In its natural state it nearly always is 

 covered with water and is very soft and boggy. : For a further description of 

 these soils see the publications of the Bureau of Soils. 2 



1 Manuscript report of A. M. Shaw. 



2 U. S. Dept. Agr., Field Operations of the Bureau of Soils, 1903, p. 451-453 ; also 1911. 



