p. 9.-Detailed statement of expenditures on account of contingencies Marine Corps-Continued. rooklyn Gas-Light Company. dams Express Company homas E. O'Brien ferman Boswell & Co.. F.D. Wyvill .D. Fricke ohn Seton. W. Schoenck.. Washington W. James.. Margaret Ryan. Per-diem roll, headquarters. Total for year. Quartermaster, United States Marine Corps. HEADQUARTERS MARINE CORPS, Quartermaster's Office, December 6, 1876. H. Ex. 11. -6 THE WORKS AT THE SOUTH PASS OF THE MISSISSIPPI RIVER. LETTER FROM THE SECRETARY OF WAR, TRANSMITTING The report of the engineer on the condition of the works at South Pass of the Mississippi River. DECEMBER 19, 1876.-Referred to the Committee on Commerce and ordered to be printed. WAR DEPARTMENT, The Secretary of War has the honor to transmit to the House of Representatives, in compliance with the provisions of paragraph 10 of the 4th section of the river and harbor act of March 3, 1875, the fifth report upon the improvement of the South Pass of the Mississippi River, showing the condition of the works on November 18, 1876, by C. B. Comstock, major of engineers, brevet brigadier-general, United States Army. J. D. CAMERON, Secretary of War. OFFICE OF UNITED STATES LAKE SURVEY, Detroit, Mich., December 6, 1876. SIR: I have the honor to report the condition of the works carried on by J. B. Eads, for the improvement of the South Pass of the Mississippi River, on November 18, 1876. My last report gave their condition on August 17, 1876. MOUTH OF SOUTH PASS. But little work has been done on the jetties since August 17. That on the east jetty has consisted mainly in the raising of the sea-end, where the piles had disappeared and the top of the jetty had sunk. Between 11,190 and 11,780 feet from East Point the piles had nearly all disappeared, and the top of the jetty was below the surface of the water. (Distances are counted from East Point station, which is 159 feet above the upper end of the east jetty.) In August and September the original row of piles was redriven with 20 feet intervals for this distance, and a parallel row was driven 35 feet near the channel of the pass, through the first and second tiers of mattresses already in position. Waling pieces were fastened to each of the rows, and scantling bridged the intervals between the waling-pieces. On these scantling mattresses were built, and when completed the scantling were pulled out and the mattresses dropped into their places. Thus this part of the jetty was brought above average flood-tide. Between 11,200 and 11,780 feet from East Point it required from two to four tiers of mattresses, equal to a height of from 5 to 10 feet. A quantity of rubble-stone was put on these mattresses, and twenty-one 6 by 12 inch timbers were run diagonally across the top mattresses to keep them in place, their ends being bolted to the piles. By October 15, the top mattresses had settled a foot between 11,470 and 11,480 feet from East Point, so as to be below average flood-tide, and a part of the stone has been washed off by the sea. The following table gives the settlement of certain piles at given distances from East Point in east jetty, and from upper end of jetty for west jetty. Interval of time is from July 18, 1876, to October 21, 1876. A quantity of stone has been put on the jetty between 5,250 and 6,090 feet, and between 8,580 and 8,900 feet from East Point, where there was none before. On the sea-side of this jetty foundation-mattresses, 50 feet wide and 2 feet thick, were sunk between 11,400 and 11,800 feet from East Point. Some stone has been placed on the west jetty. Several additional spur-dams have been constructed below and above the head of the west jetty, on both sides of the pass, their object being to obtain scour at special points. Their construction is about the same as heretofore, namely, a row of piles from 10 to 14 feet apart with mattresses inclined against the upper side. The new spur-dams are shown on traced sheet No. 1, herewith, and are marked Nos. 15, 16, A, B, C, D, E, F, G, H. As the inclined mattresses in the spur-dams previously built have in many cases settled down, thus allowing the water to pass freely through the piles, the new spur-dams have their mattresses fastened to the piles by ropes. Some of the mattresses for dams have had a covering of boards put on their upper surface to make them less pervious to water. Since August 17, as will be seen on comparing the map of that date with the one herewith, there has been no very marked change in depth of water. In some places there has been shoaling; in others (usually where new spur-dams have been constructed) there has been scour. The following table gives the depth of water that could be carried through each 2,000 feet below East Point station at different dates: On November 10th there was an aggregate distance of over 2,000 feet below East Point for which the channel of 20 feet or more was less than 200 feet wide. On the outer slope of the bar the 20-foot curve has moved in between the jetties. On August 17 part of it between the prolongations of the jetties was at an average distance of about 12,300 feet from East Point. On November 14 it had moved about 450 feet toward East Point, and had joined the 20-foot curve inside. On comparing the 30-foot curves of these two dates but little change will be seen on the whole. The main survey at the sea-ends of the jetties, which was completed November 10, gave a depth of 19.4 feet through the jetties, and is shown on sheet No. 1 herewith. A few additional soundings on November 14 indicated that there had been a deepening to 20.3 feet near the sea ends of the jetties, and I directed these soundings to be added to those of November 10. Unfortunately it was not done on sheet No. 1, and cannot now be done without much delay. Hence the statements in this report, which include the soundings of November 14, will give a greater depth of water at the sea end of the jetties than is shown on sheet No. 1. HEAD OF PASSES. On August 8 the piling of wing-dam No. 2, shown on tracing No. 3 herewith, had been completed, and soon after the inclined mattresses were placed against the upper side of the upper row of piling through. out its length. It will be recollected that the piling consisted of two parallel rows 12 feet apart, both driven through a foundation-layer of mattresses 35 feet wide and 22 inches thick. The inclined mattresses differed from those previously constructed in having the brush project on one edge of the mattress for eight or ten feet beyond the frame. In tilting the mattresses against the piling the brush of the mattress goes to the bottom, under the action of the current, when the other edge is raised by a pile-driver. In November an apron of boards, fastened to string-pieces, was placed on the upper side of the inclined mattresses for the whole length of this dam to make it tighter, but the apron was badly broken up a few days later by waves. Wing-dam No. 2, counting from the jetty, is 1,745 feet long, and a Thead has been put on its end, running in the general direction of the west entrance to the South Pass. This T-head is carried up stream about 800 feet from wing-dam No. 2, and a line of piling has been driven running down stream to the head of the island. Mattresses 35 feet wide were sunk in foundation-layer on the east and west sides of the upper part of this T-head. Another row of piles was driven through the mattress 10 feet east of the first row, from which they were braced, and mattresses 100' x 15'× 30′′ were inclined against the east side of this last row. In November a second layer of inclined mattresses, 30 inches thick, was placed over the first, making a total thickness of 5 feet, For 400 feet below wingdam No. 2 the line of piling has on both its sides a foundation-layer of mattresses 35 feet wide. For dam No. 3 a line of piling starting from shore near the lighthouse and running nearly north for 400 feet has been driven. Along it foundation-mattresses are laid, and in the deeper water an inclined mattress is placed against the piles. At its end a cross-line has been driven, forming another, or west, T-head. The west T-head is 900 feet long, and |