GEOLOGY. SOT 



We believe the cause of these formations has now been explained, 

 and the credit of the discovery belongs to Major Beauregard, of the 

 U. S. Engineers. Under an appropriation by Congress, a board was 

 formed last autumn, to examine the bar of the Mississippi, and to re- 

 port a plan for deepening the channel. Upon the recommendation of 

 this board, a contract was entered into for the purpose of opening the 

 channel, and we have great satisfaction in announcing that the opera- 

 tions in consequence have been eminently successful. A channel 

 eighteen -feet deep at low water, and three hundred feet wiile, has 

 been formed and buoyed out, and ships drawing even twenty feet of 

 water can now be taken out at high tide. 



During the examination of the bar by the board of engineers, pre- 

 liminary to their report, extensive borings were made throughout its 

 extent, and it was found to consist generally of alternate layers of 

 mud, or river deposit, clay and sand. While on a recent visit to the 

 bar, this fact suggested to Major Beauregard an explanation of the 

 cause of the " mud lumps," of which we shall endeavor to give our 

 readers an idea as well as can be done without a diagram. It is an 

 admitted fact, that these lumps always appear on or about the bar of 

 the passes, but generally a little outside of them, and to the right or 

 left of the channel ; that they are of mud or clay, very little mixed 

 with sand, the latter being in such fine particles that it can hardly be 

 discovered except by trying it with the teeth ; that they rise to the 

 height of sometimes twelve or fifteen feet above the level of the sea ; 

 that a little brackish water, mixed at times with mud, issues from their 

 summits, the temperature of which is lower than that of the waters of 

 the Gulf. 



The form of the bar presents an inclined plane, on the inside, to 

 the current of the river as the water gradually shoals to its summit, 

 and again on the outside, the water gradually deepening, the bar pre- 

 sents a similar inclined plane to the waters of the Gulf. Now if we 

 suppose a tube to pass from the inside of the bar where the current is 

 more or less strong, towards the outside of it, where there is hardly 

 any current, i(. is evident that the force of the current will fill this 

 tube with that floating mud lying at the bottom of the river, and cause 

 it to issue at its other extremity to a higher or lower level, or not at 

 all, according to the strength of the current acting at the time. Its 

 temperature will necessarily be lower than that of the waters of the 

 Gulf, for the river water, especially at the bottom, is always much 

 colder, and is also generally brackish. The sandy particles con- 

 tained in that floating mud being the heaviest, will remain only in 

 the lower portion of the tube, allowing only the better dissolved 

 mud to pass through it. If the outlet of this tube be in the channel 

 over the bar, the flow of the current will carry off the mud which 

 passes out of it, unless it be in the still water under the lee of a ship 

 aground. 



The alternate layers of soft mud, clay and sand, which were found 

 by the borings to run through the bar, present in greater or less per- 

 fection these tubes, and the force of the current impinging upon their 



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