362 TEE BOTTOM OF THE SEA. 



with earth, forming floatiDg islands ; and being 

 stranded on the banks described above, the growth 

 of the latter is much facih'tated. 



In the popular " Tour du Monde," published under 

 the direction of ' Mons. E. Charton, an interesting 

 account is given, by Mons. E. Eeclus, of a voyage on 

 the Mississippi as far as New Orleans. He describes 

 all the phases of the phenomena of deltas, shows the 

 fresh-water separated from the ocean by a moveable 

 line of demarcation of sandy mud, forming low islands 

 and marshes, and ultimately dry land. 



" All night," he says, " our vessel dragged over a 

 bottom of nauseous mud ; but, far from complaining, 

 I congratulated myself on the opportunity of wit- 

 nessing what I had travelled 2000 leagues to see. 

 What can be more interesting, from a geological 

 point of view, than this vast stretch of alluvial soil 

 in a semiliquid state ! Produced by the slow cor- 

 rosion of flowing waters during many ages from the 

 mountain-chains of North America, this sand and 

 clay form in the Grulf of Mexico a thick bed of from 

 200 to 300 yards in depth, which sooner or later, by 

 subsidence and the influence of tropical heat, will 

 become transformed into vast strata of rock, and will 

 serve as a base for fertile and populous regions. In 

 their work of creation these suspended particles are 

 sifted by the sea into deposits of various sizes, and 



