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The following table shows the breaking strain per square inch of the various specimens:

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All the Louisville was from the same mill (J. Hulme). A number of concrete bars were made in molds 6 by 6 by 27 inches long, and kept for various lengths of time. The concrete was made of cement (weighed), Osage River sand, and Osage River gravel.

The sand is a very good one, being perfectly clean and sharp, but contains possibly a little more than the ordinary proportion of fine particles; it contains 37 per cent of voids. The gravel is a very clean, hard, water-worn flint, containing 37 per cent of

voids.

An inspection showed the concrete made of natural cement to be very unsatisfactory for use in constructing lock walls.

To determine the adhesion of the two kinds of concrete, several bars were made with one-half made of Portland and one-half of natural cement. The joint was made as near the center of the mold as possible, but no smooth joint was made. On the other hand, care was taken that the two kinds of concrete should interlock, and were thoroughly rammed together. All concrete was mixed with as much water as it would hold without quaking, and was thoroughly rammed with an iron rammer weighing about 10 pounds. The molds were thoroughly soaked in water before being used. They were put together with screws so that they could be taken away from the bars without disturbing them. The bars were kept moderately moist for about a week after making them, and were kept under cover from the sun for the entire time. The attached table gives the results of 15 bars which were broken. Nos. 5, 6, 10, and 13 were combination bars; none of them broke through the joint, showing that the joint was stronger than the weaker concrete. Nos. 4, 7, 11, and 12 were Louisville bars, made respectively at the same time as above combination bars, and, with the exception of Nos. 4 and 5, the combination bars were the strongest. Nos. 1, 2, and 3 are bars of Portland concrete made in theoretical proportions necessary to just fill the voids in the sand and gravel. Nos. 1 to 8, inclusive, were made of unscreened Osage sand; Nos. 9, 12, 13, and 15 of unscreened Meramec River sand, which is considerably finer than Osage sand. Some question having been raised as to the effect of fine sand, Nos. 10, 11, and 14 were made of sand screened to pass a No. 20 and be retained on a No. 30 screen. No. 15 is a bar made of Portland cement in proportion of 1-4-9.5.

The proportions given are for parts of packed cement weighing, for natural, 75 pounds, and for Portland, 104 pounds per cubic foot, and for parts of loose sand and gravel. It is realized that a much larger number of tests should be made in order to draw any definite conclusions as to the relative strength of various cement concretes, but it is hoped that the list attached may be of some value. Very respectfully, your obedient servant,

Capt. HIRAM M. CHITTENDEN,

F. B. MALTBY, Assistant Engineer.

Corps of Engineers, U. S. A.,
Secretary Missouri River Commission.

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Upper half of briquets imported Portland; lower half of briquets native natural. Nos. 1 to 10, inclusive, Alsen [imported Portland] and Utica, Ill. [natural].
Nos. 11 to 18, inclusive, Alsen [imported Portland] and Louisville, Ky. [natural].

Number.

Tabular statement of strength of various concrete bars.

[All bars were made 27 inches long, supported 24 inches apart, load applied at center.]

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ANNUAL REPORT OF MR. L. P. BUTLER, ASSISTANT ENGINEER.

ST. LOUIS, MO., December 5, 1896.

CAPTAIN: I have the honor to report on the work of improving the Gasconade River during the fall of 1896.

In the office there were platted thirteen sheets and an index sheet from the notes of the survey of the Gasconade River in 1895. These sheets represent 29.5 miles of river between Indian Head and Arlington, Mo. They are platted with soundings and profiles, and are all inked with the exception of hachures and cultivated land, which are indicated in pencil.

The accumulation of materials at the mouth of the river was begun October 31. The construction of a barge was begun September 1 and completed September 19. The barge built is 50 feet long, 15 feet 10 inches beam, and 19 inches deep. The deck, bottom planking, and gunwales are of yellow pine; the frames, bracing, and all inside work of white pine; and the end blocks and nosing of oak. It was designed for carrying rock over shoal water, and for that reason was built shallow, which necessitated a longitudinal bulkhead. It was only required in loading that the greatest weight be put at the ends. It was fitted with one Providence hand capstan.

While the barge was being built a force was put to work quarrying rock and getting out logs at Bocks Bar. This work was completed when the barge was ready for use, and the quarry force was sent to Woodpecker Island while a separate force was engaged in the construction work at Bocks Bar.

The season's field work consisted in the construction of dikes to direct the water at shoals and in the removal of snags.

The dikes are built of cribs filled with rock and backed with rock on either side. The backing on the pocket side of dike is laid on willows. The cribs are built of 20-foot logs with cross pieces 3 feet from each end, notched in. The width of cribs

is 5 feet inside. The logs are from 6 inches to 10 inches in diameter, and the notching does not close the spaces between them by from 4 inches to 6 inches, so that a crib of four logs on a side is about 4 feet in height. The logs are drift bolted together at the four corners of each crib, three-fourths inch square drift bolts being used at first, and afterwards three-fourths inch round with upset heads. At the center of each crib there are three 4-inch cross sticks notched into and spiked to the lowest longitudinal logs, forming a narrow floor, intended to assist in sinking the crib. Stakes were driven 5 feet apart in the line of the down-stream side, or current side, of the proposed dike. The cribs were built on the shore and dragged, with the aid of the current, to place against the row of stakes. Where, as was the case at Woodpecker Island, some of the cribs were 6 feet high they were built on a barge and launched from it into place. The cribs could not be floated to place without the assistance of current unless they were low, as the logs used were heavier than water. The cribs when in place were filled with rock, one-man size being used, finished with smaller rock on top. Willows were forced to the bottom against the up-stream side, or inclosing side, of dike, and rock placed on them. Rock was also placed on the down-stream or current side of dike, piled nearly to the surface of the water and sloping naturally.

Bocks Bar, 24 miles above the mouth.-This is the first shoal from the mouth of the river over which there is a marked fall. Just below the mouth of First Creek, 1 mile from the mouth of the Gasconade River, there is rather shoal water; but at a low stage there is no appreciable fall and the point has not been reported, within my knowledge, as being troublesome.

At Bocks Bar there had been built, some years ago, a dike from the right bank, extending to within 120 feet of the present left bank and ending in a 75-foot spur upstream. This season there was shoal water just above the end of the spur. The water was not as low, however, as in November, 1895, at which time there was a bar out of water immediately above the end of the spur, and the main body of water flowed between it and the spur, whipping around the latter in a direction nearly at right angles to the direction of the stream above and below.

The work done at this point consisted in building a dike as an extension to the existing spur, running it directly upstream, and in making repairs to the old dike. The new dike is 260 feet in length. The height varies from 2 feet to 5 feet, its top being about 1 foot above the level of the water in the pocket at the stage of water of the time of building, which was moderately low. The last crib was placed at an angle of 30° with the direction of the first 240 feet of dike, forming a funnelshaped entrance for the water into the channel made between the bank of the river on the left and the dike, followed by the bar, on the right. This channel is 100 feet in width for a length of 900 feet. Below this the channel widens to 150 feet when the end of the bar and quiet water is reached. The fall in the first 330 feet was 1 foot September 9, 1896, the total fall from pool to pool, a distance of 1,600 feet, being 1.2 feet. October 19, 1896, the fall in the first 330 feet was 1.1 feet, and the fall from pool to pool 1.5 feet.

Bocks Bar being the first point above the mouth of the river at which there is a marked fall, the fall here depends upon the stage of water in the Gasconade River and in the Missouri, so that often there is no fall at Bocks Bar, owing to backwater from the Missouri River. At a low stage of the Missouri the water of the Gasconade flows through the channel at Bocks Bar with great velocity. The shoal forms a natural dam, holding the water in the river above. In the improvement of this shoal, as in every other, the idea was to maintain this dam system and merely direct the water through one channel, lessen the slope by distributing the fall over a greater length, and gain the greatest depth possible for the quantity of water it was practicable should flow. Too great a quantity flowing over any one shoal would lower the water in the pool and on the shoal above.

Steamers are obliged to use a line over Bocks Bar when the Missouri River is low. There were used on the new dike 170 cubic yards of rock, and in repairing the old dike 22 cubic yards of rock.

Woodpecker Island, 11 miles above the mouth.-At this point, several years ago, there was a wooded island in the river with apparently an equal volume of water flowing on either side. The left bank channel had been cut off by a dam. The island, which was wooded, was wearing away at the time the dam was built and now is a gravel bar. There is a small break round the end of the dam, but the right bank channel, though swift, contains good water until the foot of the bar is reached, when it comes against the main left bank of the river and again leaves it to break into four channels separated by gravel bars.

The work done at this point consisted in cutting off the two right bank channels by a dike or wing dam running from the right bank of the river, which is the left side of another island, diagonally upstream to the central bar. This dike is 560 feet in length. The depth for 200 feet midway is 6 feet, the depth for the remaining length varies from 63 feet to 2 feet, the last 60 feet being built on the bar, at the time out of water. On these last 60 feet willows were laid, forming a mat as a

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