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 month 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

bottom to the cribs and extending on both sides, before the rock was placed. The falling leaves, drifting into the pocket formed by the bank and the dike, were filling the crevices in the dike and rapidly making it tight at the time of leaving it. The resultant channel enters on the left of the point of the dike and follows it until deep water is reached.

Six hundred and seventy-five cubic yards of rock was used in this dike. The fall here from pool to pool, a distance of 3,400 feet, was 2.5 feet, October 6, 1896.

Stake Shoal, 9 miles above the mouth.-At this point the channel is straight. The water leaves the quiet pool above, enters between two gravel bars, and flows over the shoal at a width of 250 feet and for a length of 1,300 feet before the pool below is reached. The aim at this point was to narrow the entrance of the water onto the shoal and to train it along a longitudinal dike until the pool below was reached. A dike was begun on the right bank near the foot of the shoal, and carried upstream 200 feet, complete except as to backing. The project calls for 1,100 feet, which would carry the dike to the head of the shoal. There were logs prepared for 600 feet of crib work, and 100 cubic yards additional rock was quarried. The fall at this shoal from pool to pool, a distance of 1,300 feet, is 1.7 feet. Removal of snags.-Snags were removed during the season from Pryors Bend and points below. Bryors Bend is a stretch of river 3 miles in length, the lower end of which is 30 miles from the mouth of the river. It is difficult of navigation, particularly to rafts, on account of its circuitous course, the swift current, due to a fall of 7 feet in its length, and to the snags which lodge more easily in the bend than at any other point on the river.

The total number of snags removed was 91, of which 82 were taken from Pryors Bend. There were 10 overhanging trees cut and 20 drift trees cut.

The snagging party was in the field from October 20 to November 12, operating twenty-one working days.

Surveys were made at Bocks Bar, two; Stake Shoal, Woodpecker Island, Upper Turnpike, and Brandts Shoal.

PROJECT FOR CONSTRUCTION OF LOCK AND DAM NO. 1, AT BRENNEKES SHOAL, OSAGE RIVER, MISSOURI.

MISSOURI RIVER COMMISSION,

OFFICE OF THE PRESIDENT,

St. Louis, Mo., May 18, 1897.

GENERAL: I have the honor to transmit herewith a complete project * for the construction of Lock and Dam No. 1, Osage River, Missouri, submitted by Capt. H. M. Chittenden, which has been approved by the Missouri River Commission in all of its general features, reserving decision upon the plans for operating machinery and the kind of cement to be used in concrete constructions until a later date, and leaving to Captain Chittenden's discretion the details of construction.

Respectfully referred to The Board of Engineers for examination, report, and recommendation.

To be returned.

JOHN M. WILSON,

Brig. Gen., Chief of Engineers, U. S. Army.

[Second indorsement.]

THE BOARD OF ENGINEERS,
New York City, June 24, 1897.

Respectfully returned to the Chief of Engineers, with report of The Board of Engineers, dated June 23, 1897.

G. L. GILLESPIE,

Colonel, Corps of Engineers, Senior Member Present.

PROJECT OF CAPT. HIRAM M. CHITTENDEN, CORPS OF ENGINEERS.

The revised project for the construction of Lock and Dam No. 1, as at present approved by the Missouri River Commission and the Chief of Engineers, covers only the following points:

(1) Dimensions of lock, 220 by 42 feet.

(2) Use of concrete in construction.

(3) Lower miter sill fixed at reference 94 feet.

The completed project for the lock as herewith submitted covers the following additional points:

(4) Reference of upper miter sill 103 feet.

(5) Filling valves to be in miter sill wall under gate. (Pls. III, V, VI.) (6) Emptying valves in lower gate. (Pl. VII.)

(7) Top of main walls at 120 feet.

(8) Top of head walls at 128 feet (above flood height).

*Drawings not printed.

(9) Foundation on piles; timber grillage under walls; concrete floor 3 feet thick under chamber, with piles (4 feet centers) cut off even with top surface, and notched to make good contact with concrete. ( (Pl. III.)

(10) Underflow in river bed to be cut off by Wakefield piling under miter wall down to reference 75 feet, or by such other means as may be found most effective when work is done.

(11) Foundation to be drained so as to relieve any possible leakage from upper pool.

(12) Sections of walls, and all other details, as in drawings. (Pls. III to VII.)

PROJECT FOR DAM.

(13) The dam is to be built in ten 75-foot sections, separated by 9 piers, 10 by 30 feet at base, with tops at reference 120 feet. (Pl. II.) (14) The dam is to rest on a pile foundation and is to consist of a fixed weir and a movable crest. (Pl. VIII.)

(15) References: Top of foundation, 97.5 feet; top of fixed weir, 109 feet; crest of movable dam up, 116 feet.

(16) The underflow of the river is to be cut off, if possible, down to reference 75 feet, the same as under the lock.

(17) Materials are wood, iron, and concrete.

(18) Details and general plans as in drawings. (Pls. VIII to XIII.)

DETAILED DESCRIPTION OF LOCK.

Length over all, 275 feet 3 inches.
Length between quoins, 220 feet.
Breadth of foundation, 76 feet.
Width of lock chamber, 42 feet.

Height of main lock walls, 27 feet.

Height of head walls of lock, 35 feet.

Thickness of head walls, 16 feet.

Thickness of foot walls, 14 feet at base, 11 feet 9 inches at top.
Thickness of main walls, 14 feet at base, 5 feet at top.

Foundation rests on piles. Beneath the walls the piles are 3 feet apart. Upon them is placed a timber grillage, consisting of 10 by 10 inch yellow pine timbers, surmounted by a floor of 4-inch oak plank. Between the walls, forming the floor of the lock, is a layer of concrete 3 feet thick. It extends 2 feet under the walls. The piles under the chamber are cut off level with the floor of the lock and the concrete is put in between them. The piles are notched in order to afford a more secure hold for the concrete. The concrete has a bearing surface of about 9 square feet on each pile and the piles are spaced 4 feet from center to center. It is believed that any upward pressure beneath the concrete would have to pull the piles before it could move the floor.

The necessity for this floor is to prevent leakage from the lock when the water within it stands above the level of the lower pool, and to prevent leakage into the lock should it become necessary to pump out the interior for repairs.

All leakage from the upper pool is cut off, as far as possible, by a row of Wakefield piling beneath the upper miter sill wall, extending down. to reference 75 feet, the reference of the lock floor being 93 feet. But the nature of the river bed is such that water will find its way under considerable pressure to the ground under the lock. To prevent any evil effects from this pressure the foundation is thoroughly drained. Immediately below the concrete of the foundation is a natural layer of heavy clay from 1 to 2 feet thick. Beneath this is water-bearing gravel, which is the place where the water pressure will develop. To relieve

this pressure a trench will be let down into this layer just below the row of sheet piling (see drawing), and will be filled with broken stone. It will communicate with a drainpipe extending along the lock wall on the shore side and with the lower pool on the river side. Along each side of the lock, at intervals of 30 feet, holes about 2 feet in diameter will be sunk into the gravel stratum and cased with sewer pipe. These will communicate on the shore side with the drainpipe and on the river side with the lower pool. By this means any tendency to develop pressure beneath the foundation is prevented, for relief is at once given through this connection with the lower pool.

The lock is to be filled through six culverts in the upper miter-sill wall. They are closed by wickets at their upper end, three being operated from each side on a single axis. The drawings make these details clear. The cross-section area of the filling culverts is about 61 square feet, calculated to fill the lock with a lift of 16 feet in three minutes, includ ing time of opening valves. The space above the culverts is protected from drift by a grating.

The lock is to be emptied through wickets in the lower gates similar to those now in use on the Kanawha River.

The head walls of the lock are carried up to 128 feet, so as to act as a guard in time of flood and prevent a current through the lock.

The gates are similar in general design to those in use on the Kanawha River, and present no features of special importance.

Through the upper miter sill wall are carried the pipes for operating the movable dam. (See description of dam.) The inlet culvert and valve for filling the chamber of the first section of the dam is in river wall of the lock opposite the upper gate. (See drawing.)

All other details, it is believed, are fully illustrated in the drawings. In the matter of the choice of cement for use in the concrete masonry, it is requested that the final decision be left open until certain experiments described below can be made. It is proposed to use both Portland and natural cements for this work. For all that portion of the

masonry below standard low water (105 feet) a good natural cement will be used. This portion of the work, being subject neither to the action of frost nor to the abrasion of boats, nor, to any considerable