TEE MISSISSIPPI DELTA 243 



A comparison of the mud ejected with that forming the narrow 

 banks of resistant clay bordering the Passes, as above outlined, and also 

 the same resistant clay banks at the Head of the Passes which cause 

 their divergence, shows the materials to be undistinguishable. The 

 conclusion is inevitable that the entire bird-foot delta at least, and 

 doubtless also the narrow Neck in which the main river flows below 

 Forts Jackson and St. Philip, are the outcome of the formation and 

 destruction of mudlumps as the river progressed; and that these clay 

 banlvs constitute the normal mode of progression of the emerged por- 

 tion of the lower delta. 



The extraordinary resistance of the mudlump clay, when once con- 

 solidated in the channel hanlcs, to erosion by water, se-rves, together 

 with the somewhat similar characteristics of the underlying Port Hud- 

 son clay, to explain the exceptional form of the lower delta of the 

 Mississippi. 



I should add that a microscopic, physical and chemical examination 

 of the mudlump mud, and of the cla}'' from the banks of the Passes, 

 bear precisely the biological characteristics to be expected under the 

 conditions outlined. There is an intermixture of fresh-water and 

 brackish marine organisms; while the water forming the mud is mani- 

 festly sea-water in a condition of considerable dilution, and changed 

 by maceration with the organic debris brought down by the river. As 

 a result of such reductive maceration, the sulphates in sea-water have 

 been largely eliminated in the form of minute crystals of iron pyrites, 

 and the lime as carbonate ; while the ratios of the chlorids have suffered 

 little change. The details of this investigation are set forth in my paper 

 in the Journal of Science, already referred to. 



Eads's PropositiojST to Open the South Pass 



In the early 70's of the past century, even the widest of all, the 

 Southwest Pass, had become so obstructed by mudlumps that deep-sea 

 navigation was very difficult to maintain, despite the most active 

 dredging on the part of the government, and the construction of tugs 

 of enormous power, designed to pull deep-drawing vessels through the 

 upheaved mud. Captain James Eads, the builder of the St. Louis 

 bridge, then conceived the idea that, as the South Pass was unob- 

 structed by mudlumps, it might be made the main and permanently 

 navigable channel if sills of willow mattresses were placed across the 

 entrance of the other distributaries (the Southwest Pass and Pass a 

 I'Outre), and if jetties were constructed at its mouth to maintain a 

 current so strong as to carry away the obstacles caused by river de- 

 posits of all kinds. Accordingly, a bill was introduced into Congress 

 for the construction of these improvements. When this came to my 



