TRANSACTIONS OF THE SECTIONS. 203 



bars at the mouths of the passes has for some time past tended to divert trade, and 

 the grain-trade especially, to the Atlantic seaports. 



Moreover, the war of secession interposed a sudden check to commercial inter- 

 course between the North-western States of the Union and New Orleans. When, 

 however, the trade between the Northern and Southern States began to revive, after 

 the wars of secession, the merchants of St. Louis urged upon the United-States 

 Government the necessity of improving the access from the sea to New Orleans. 



The United-States Corps of Engineers, in 1873-4, were consequently called to 

 advise ; and they submitted a project for a ship-canal, which was to be protected by 

 lock-gates, and was to be constructed from Fort St. Philip, a point in the Mississippi 

 some 18 miles above the passes, in an easterly direction, into water of about 30 feet 

 depth, in Isle-of-Breton Sound, whence the ships would pass out into the Gulf of 

 Mexico. 



The canal was to be entered by a lock. It would have required about 10 years 

 for completion ; its cost was estimated at $10,000,000, and it would only, when 

 completed, have been able to accommodate a limited trade. 



Mr. Eads at the same time proposed a rival scheme for improving one of the 

 passes, by increasing and controlling the flow of water through it. 



He proposed to improve the South-west Pass, which aflbrded the best prospect 

 of success. The United-States Government refused this, but allowed Mr. Eads to 

 experiment on the South Pass, provided he undertook the work at his own risk. 



In addition to the bar at the mouth of the South Pass, there was also a shoal of 

 about 12 feet deep at the head of the pass. Mr. Eads's confidence, and that of his 

 friends, in his scheme enabled him to accept the Government offer. The following 

 are the terms on which he has undertaken the work:— 



When a depth of 20 feet for a width of 200 feet has been obtained through the 

 channel, he was to receive a sum of $500,000; for each succeeding depth of two feet 

 down to a depth of 30 feet he is to receive a further sum of $-500,000, with several 

 further sums of $250,000, each contingent upon the several depths being maintained 

 for 12 months each respectively — making the total payment $4,500,000, when a 

 depth of 30 feet has been maintained for 12 months. He is to receive two further 

 payments of $500,000 each when the work has been effective for 10 years and 20 

 years, in addition to $100,000 a year for maintaining the work during 20 years. 



The work was commenced on the 15th of June 1875. 



The object of the works is to concentrate an increased flow of water in the South 

 Pass as well as across the shoal-bars at each end— first, by means of lines of jetties, 

 funnel-shaped at the head of the pass and parallel at its lower end ; secondly, by 

 closing the Grand Bayon, which diverted a portion of the water after it had entered 

 the South Pass and prevented its reaching its lower end ; and thirdly, by regulating 

 the proportion of water to be admitted into the Pass a Loutre and the South-west 

 Pass. 



The jetties and all works in the water are constructed in a simple and compara- 

 tively inexpensive manner. Stone is not found on the lower Mississippi ; that which 

 has been used came either in ships as ballast, or has been brought down the Missis- 

 sippi from the Ohio river : if stone alone had been used, the light mud of which 

 the bottom is formed woxdd have swallowed up an enormous quantity, and a very 

 long time woidd have been occupied in the formation of the jetties. 



The construction which has been adopted is as follows : — Piles are driven in the 

 line of the proposed jetties at about 10 feet apart : against these piles mattresses of 

 willow-branches about 2 feet thick are sunk. These mattresses vary in size from 75 

 feet in length and 40 feet wide to smaller widths and shorter lengths as may 

 be desired. To make the mattress, strips of pine- wood about 3 inches by 2 inches 

 are laid parallel to each other on inclined ways on the river-bank; they are kept in 

 position by cross strips nailed to them at intervals : into these longitudinal strips 

 pegs of hickory, two feet long, are fixed at six-feet intervals, the top of the peg being 

 turned so as to correspond with a hole in a second strip of pine-wood to be eventually 

 put on ; after the pegs of hickory have been fixed into the longitudinal strips first 

 mentioned, a layer of willow-branches is laid across and trodden down, then a second 

 layer lengthways, and so on alternately until the thickness of two feet is attained, 

 when the whole is kept in place by the second mentioned strip of pine-wood being 



16* 



