ccxvi GENERAL SUMMARY OF SCIENTIFIC AND 



During the year 1876 work upon the jetties at the South Pass of 

 the Mississippi has been rapidly advanced, and, so far as may be in- 

 ferred from what has ah*eady been accomplished, with every indica- 

 tion of ultimate success. The extent and location of the jetties are 

 as follows: The lines of the jetties are 1000 feet apart. The length 

 of the East"" Jetty, from the land's end to the deep water where the 

 jetty-heads will be constructed, is about 13,500 feet. This extends 

 out in nearly a straight line for 800 feet, and then curves to the west 

 in order to strike more favorably the littoral current from the east 

 which has been ascertained to exist. For most of its length this 

 jetty is constructed on a lateral shoal where depths averaged not 

 more than six or seven feet. At the other end it stops in thirty feet 

 of water. The West Jetty, on account of the farther extension of 

 the river-bank on that side, begins about 4000 feet farther down 

 than the east one, and extends parallel to it out to the same point. 

 At its beginning it was constructed in much deeper water than was 

 the East Jetty, it being in fifteen feet of water, in what was the deep- 

 est channel of the bar at that point. This depth gradually shoaled 

 to the crest of the bar, where it was from six to eight feet. The meth- 

 od of constructing the jetties has been fully described in our last 

 year's Ilecord, and need not, therefore, be here repeated. The im- 

 provements comprise, in addition to the building of the jetties, two 

 other auxiliary w^orks, namely, the closure of Grand Bayou and the 

 construction of a dike at the head of the Pass. The jnu-pose of these 

 works is to deflect more water into the South Pass, and thus increase 

 the velocity, and consequently the scouring action, of the current. 

 Both of these auxiliary w^orks, it is affirmed, have been comjDleted. 

 The following statement, given on the authority of D.W. Bowman, 

 C.E., South Pass Jetty Works,* presents the condition of the jetties 

 on the 26th of May last, since which time, although considerable 

 progress has been made, no official statement of the actual condition 

 of the work has come into our possession. This statement, although 

 not as recent as could be desired, gives nevertheless a good idea of 

 the rapidity with which the work under Captain Eads' superintend- 

 ence is being pushed forward. At the date named the condition of 

 the jetties was as follows: For a distance of about 11,500 feet from 

 the land's end on East Bank the mattresses of both jetties were built 

 up to average flood -tide, and confined nearly all the water. For 

 about 500 feet farther the jetties were partially constructed, but did 

 not reach the surface by several feet, the current flowing laterally 

 over them. This work rejjresents, at the expiration of eleven months 

 from the commencement of operations, a total length of nearly 20,000 

 feet, or about four miles, exclusive of the work done at Grand Bayou 



* Sec a complete resume of this subject by this author in Engineerivg News, 

 lll.,im et seq. 



