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held the head of the mat in place during construction, kept the drift off the mat to a great extent, and was of great assistance in sinking

When the mooring barge had been securely fastened, the mat barge was brought up against it on the downstream side, anıt the mat construction was begun, the head of the mat being fastened to the mooring barge and also by cables passing under this barge to the shore above. This was done by securely tying to the mat-head short loops of 2-inch rope, called "strap" lines; the bights of these strap lines were connected with the head cables by iron shackles, the pins of which could be pulled after the mat was sunk, and thus all lines, except the straps, recovered.

To hold the mat to the mooring barge and to control it while being sunk, lines, with one end fastened to timber heads on the mooring barge, were passed around the poles of the mat-head, and thence back to the barge and around the same timber heads. These lines could be steadily payed out by the workmen while the mat was being lowered to the bottom of the river, care being taken to keep as far as possible uniform strains on them. They were called "slip” lines, were about 1-inch diameter rope, and were placed at intervals of about 16 feet along the mat-head.

When the mat had been constructed floating on the surface, the next step was to ballast it. A barge of stone was fastened along its outer edge, plank runways were placed from the barge to the mat and over the surface of the mat, and stone was carried to the mat by hand or in wheel-barrows, and was distributed on it evenly, so as to nearly overcome the buoyancy.

When ballasted, stone was next cast from the mooring barge on to the mat near its head, and this head was allowed to sink gradually, being lowered by the slip lines to a depth sufficient to allow a barge of stone to be floated in over it. This barge was pulled in parallel to the mooring barge, to which it was made fast by two lines, another line being run from the stone barge to the shore, where it was held by a gang of men. When all was in readiness, stone was cast overboard from all sides of the barge, and the slip lines were slacked out slowly and the head of the mat lowered to the bottom steadily and without surging. As the head of the mat sank, the stone barge was dropped downstream slowly over the mat, and the rest of the mat was sunk, the movements of the barge being controlled by the lines to the mooring barge and to the shore.

At times a steamboat was used to assist in handling the stone barge.

After the mat was sunk, the stone barge was again dropped over it a second time and more stone cast on to weight it safely. As soon as the mat was found to be on the bottom at all places the mat lines were released, the shackle pins pulled out, all lines removed, and the mooring barge placed at the locality for building the next mat This was usually placed so as to lap over the first mat by at least 25 feet.

The upper bank was graded by the hydraulic process to a slope of 1 vertical to 3 horizontal. Three streams were generally used, the two upper for cutting and the lower for washing down the material

. The nozzles were 134 and 2-inch diameter, mounted over a piece of gas pipe driven in the ground, where they had a universal joint permitting their control in almost any direction. In operating, the nozzles were held quite close to the bank to be graded and were moved through a range of from 45 degrees to 90 degrees with the face. The upper portion of the bank was cut slightly ahead so that the water could run down close to the face.

SEASON OF 1882

(Plate L.) During the season four mats were built and sunk, all 110 feet wide, extending from the mouth of Mound City Chute downstream 1,127 linear feet. The reason the mats were built in suh short lengths was that the rising river and the drift which Jorged syninst the mooring barges caused such heavy strains on the linne that it was not considered safe to build them longer. After th, mats were sunk it was found that in two places, instead of the Phile lopping, there were gaps of 15 feet between them. When it was time to sink the third mat, the stone supply was exhausted, and 14 *** sunk with wacks filled with buckshot clay. In addition to the soron toists, two parrow connecting mats were placed in an indenta#tite to the bank to connect the river mats with the shore. The youding we worked one month, and about 1,900 linear feet of bank nase strobell, Innut po upper bank work was placed, as the river rose

SEASON OF 1883

nedomly after the subsidence of the high water of 1883 the work of thw prowading year appeared to be in good condition and no kaving haud securred, although the bank below had caved badly, but later in the sonson faults began to appear. On September 5, a cave ocurred between mats Nos. 3 and 4, which had failed to lap

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No. 8. Shows different stages of the upper bank revetment; part is complete and ready for ballasting. The brush here is placed at an

here

in all

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angle of 45 degrees with the bank line.

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by from 10 to 15 feet. This cave was of considerable size; it took in most of the graded bank, but from soundings made at the tine did not extend far toward deep water. It was at once repaired with a river mat 300 by 100 feet and a revetment of the upper bank.

Operations were then begun on the continuation of the revetment downstream from the end of the work of the preceding season. The method of building and sinking the mats this season was the same as during the preceding season, except towards the latter part of the season, when wire strands were placed along alternate weaving poles to increase the longitudinal strength; these strands were made in short lengths and tied together. The same construction plant was used, and all river mats were made 145 feet wide. Their lengths, however, were materially increased, and after sinking five mats, varying in length from 493 feet to 1,032 feet, it was decided to build continuously, and the next mat was built to a length of 2,561 feet and sunk in two operations, when the mooring barge had to be removed to clear the drift. The next mat was 1,516 feet long and sunk November 20, after which a rising river and running drift prevented the building of very long mats. The first loss was sustained on November 30, in attempting to sink a mat 1,057 feet long. At this time a large amount of drift had accumulated above the mooring barge, and considerable had gotten under the head of the mat.

The river at the time was rising and the current was strong. After ballasting the mat well and lowering the head some distance, much drift moved under the mooring barge and over the mat, tearing it away about 200 feet below its head. A few seconds later the mat lines broke, thus throwing all the strain on the slip lines, which transmitted it to the mooring barge lines, causing them

break, and the mat and the mooring barge were thus torn adrift and started to float down the river. Extra lines were rapidly cast from the mooring barge to the bank and there made fast, the slip lines were thrown loose, and the mat moved away from the mooring barge, which swung around parallel with the bank. The mat, with stone barges attached to it, moved downstream, and the mat was abandoned as a total loss, the steamer towing the stone barges back to the work. In this accident all head lines parted, , there being nine in all of from 11,2 to 2-inch diameter, of which six were attached to the mooring barge and three to the head of the mat.

In the meanwhile another break had occurred in the 1882 work.

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