Rock, Bush, and Beasley's Shoals all present obstructions, but do not necessarily require improvement at the stage to which operations of this kind are applicable. From Carthage to Nashville, a distance of about one hundred and three miles, many bars are revealed at low water. Bartlett's Bar and Donaldson's Horse-ford should receive attention. Dams are required at both points, and the gravel-bar at the last point might be dredged with advantage.

From Carthage down to Nashville the following bars are merely named in their order: Carthage Island, Foster's Island, Hanging Rock Island, Bartlet's Island, Parker's Island, Goose Creek Island, Witly Island, Bartlet's Creek, Donaldson's Horse-ford, Burke's Ripple, and several others of unknown names.

The width of the river from the State line varies from 550 to 660 feet, and the descent to Nashville is at the average rate of 0.59 of a foot per mile: The bottoms are from one-half to one mile wide. At Carthage the bottoms expand on the left or south side into the Nashville basin. This remarkable basin is one hundred and twenty miles long and fifty to sixty miles wide, and extends longitudinally in a southwest direction. It lies wholly in the State of Tennessee, and contains the most flourishing cities and some of the most fertile lands in the State. Its surface, resting on silurian limestone, is undulating with isolated ridges or small hills, which rise occasionally to the level of the summit of the surrounding highlands. It is difficult to conceive of this basin as the result of erosion and aqueous denudation, but no other cause has left such unmistakable evidences of its action. Throughout the entire area of the cavernous limestone its operation is conspicuous. The conglomerate which covers the limestone and forms the surface of the highlands possesses extreme compactness and strength, and at the falls of the Cumberland has for ages resisted the action of rapid currents. After the water had once penetrated this rock, and reached the limestone, the caverns of the latter must have supplied subterranean reservoirs for the accumulation of the

water.

Before the water was able to find vent, the increasing hydrostatic pressure must have been proportionate to the subterranean area, multiplied into the height of a column, which, in the highland, must have varied from 400 to 600 feet. This enormous pressure would have been sufficient to have rent asunder the rock and to have opened channels for powerful currents. Evidences of this action are not confined to the Nashville basin, but are coextensive with the conglomerate and underlying cavernous limestone. It may not only be observed in the cañon-like ravines, the rock-bridge of Rockcastle River, the subterranean channel of the South Fork, the deep gorge-like valleys of the Cumberland and its tributaries, but also in the course of the Tennessee after it enters the same formation, and it is equally conspicuous in the denndation, down to the lower silurian, which characterizes the southern border of the blue-grass region of Kentucky.

The strata of the basin, composed of lower silurian, passes below the bed of the river below Harpeth Shoals. This dip controls the course of the river in its efforts to flow to the northwest, but the southwest direction of the greater part of its course may have been determined by the surface of the superincumbent conglomerate through which it must have cut its way before reaching the silurian limestone. The course of the tributaries is also controlled by this formation. All these streams have a general northwest direction. Caney Fork is worthy of note, because of the deep and rocky gorge and a vertical fall of 90 feet, by which the creek descends from the highland rim and enters the basin.

THIRD DIVISION.

From Nashville to the mouth of the river the distance, as determined by reconnaissances, is about one hundred and ninety-two miles; the descent by railroad levels is 79 feet, or at the rate of 0.41 of a foot per mile.

The obstructions in this division consist of rocky ledges in the upper part, and of brittle ferruginous conglomerate and gravel and sand in the lower. There are also snags and logs which should be removed. Four bridges cross the Cumberland in this division. Two at Nashville-a wire suspension-bridge and an iron railroad draw-bridge of the Louisville and Nashville Railroad. The third is at Clarksville, on the Louisville and Memphis Railroad, and is a draw-bridge of composite character, partly iron and wood. The fourth is in process of erection near the mouth of the river. The channelway has a clear distance of 115 feet at all these bridges.

The first point requiring attention below Nashville, after the removal of the foundation of an old pier at the city, is found at Nashville Island, two miles below. Several rocks, which obstruct the passage of the boats, should be removed from the channel. The island can, without difficulty, be connected with the left shore, and the increased volume of water would enable the boats to pass safely to the right of the island. But the same result can be accomplished at less cost by removing the rock, which is about 6 inches below the surface at low water. This rock appears to form part of the bed of the river. The main body of water is deflected into the right-hand channel by a bluff of rock, which extends above the landing, below the chair factory. The opposite bank

is much worn by the current, and should be protected. The average slope per mile, from the head of the island to the fish-trap below, a distance of 7,300 feet, was 2.14 feet; the maximum descent near the middle of the island was 6.35 feet, and the depth at low water on the bar is 1.2 feet.

From Nashville Island to Gower's Island the rocky banks have been worn by the water as smooth as a slope wall, and follow the course of the river with a regular curvature. A high bluff appears on the right, above the island, and here the river valley contracts, and the highland rim is again entered. The work required at this point consists in the removal of a portion of some cribs and wrecks. The channel on the left of the island is narrow and may require dredging.

Harpeth Shoals.-A succession of rocky ledges and gravel-bars, severally known as FlaxPatch Bar, Harpeth Island, Sycamore Creek, Harpeth River Bar, and Reed's Reef, are collectively designated Harpeth Shoals. These obstructions have been regarded as among the most serious on the river on account of the number and close succession. The entire length is 4.3 miles; the total descent 11.59 feet; the average slope per mile 2.17 feet, and the maximum slope 7.81 feet, which is near the lower part of the island. The shoals are probably formed by the increased dip of the strata. The work executed by the Government in 1834 has increased the depth of the water, but the lateral dams constructed at that time are greatly in want of repairs. Openings have been made in them by fishermen, to secure a passage for their canoes, and a large amount of water escapes behind the dams.

The first dam at Flax-Patch Bar is formed by loose stone (riprap) cast in along the line and rising to 5 feet above low water. The river is contracted by the dam from 720 to 320 feet. Entering the river obliquely, this dam extends for 530 feet to the angle, and then runs parallel with the current for 860 feet, terminating abruptly. Below, the channel crosses to the left over a gravel bar, with one foot upon it at low water.

Harpeth Island Dam commences about 1,700 feet lower down, and enters the river from the same bank, but more obliquely. From the bank to the angle, the distance is 800 feet; the island is 3,100 feet in length, and the dam extends, in a damaged condition, 1,600 feet below the end of the island. The entire length, including the island, was originally 5,500 feet. The water-way is contracted from 775 feet above the dam, to 450 feet near the upper, and 375 feet near the lower end. At the stage of 2.2 feet above low water, the maximum velocity above the Flax-Patch Dam was 1.72 feet per second, and about the middle of Harpeth Island the maximum velocity, about the same stage, was 3.48 feet per second. At this stage the Flax-Patch Dam was found to have raised the water 0.68 of a foot near the angle, and the Harpeth Dam 1.70 near the angle, and 0.87 near the foot of the island. The discharge of the river above FlaxPatch Dam, when the gauge read 2.2 feet, was 4,971 cubic feet per second, and the discharge near the middle of the island was 4,810 cubic feet per second; the difference between the two, 161 cubic feet per second, is equal to the quantity of water which escaped at the head of the island. Below the island the dam has been nearly destroyed by the steamboat men, in their efforts to warp up against the current. The stone has been used to give weight to the anchors employed for this purpose. If a dam is ever reconstructed at this point, it should be supplied with ring-bolts, firmly anchored in masses of rock. The contraction of the river has caused considerable abrasion of the banks, which should be protected. It has been stated that the deepest channel was originally on the left of the island, but that the engineer, fearing the formation of shoals below from the lighter gravel of this channel, threw the body of the river over the horizontal bottom of rock which composes the bed of the right channel; 2,500 feet below, the channel crosses to the left over a gravel bar and some detached rock opposite Sycamore Creek. From the creek to Harpeth River the channel is obstructed by detached rocks which have fallen from Harpeth Bluff. Opposite the mouth of Harpeth River a projecting reef and an irregular rocky bottom, for 150 yards, are the chief impediments. At Reed's Reef two rocks, one on each side of the channel, contract the water-way and make the channel difficult to pass at low water. In order to restore and improve the navigation at these points, the old dams should be repaired and extended, the rock removed at Sycamore Shoals, and the bar dredged. If these operations are insufficient a dam will be necessary. The rocks in the channel in front of Harpeth Bluff should be removed, and also portions of the reef opposite Harpeth River, and the irregularities of the bottom should be leveled.

The rocks at Reed's Reef should be removed from the channel. Until this work is executed, it is not easy to determine whether a dam should be placed near the mouth of Harpeth River, or below Reed's Reef. This question can be but determined during the progress of the other operations. Good cultivated bottoms, from three-quarters to one mile in width, are found on each side of the river about Harpeth Island, and continne as far as Harpeth Bluff on the left, and to the bluff below Reed's Reef on the right, with an elevation of about 35 or 45 feet.

Between Reed's Reef and Davis's Ripple the alluvial bottoms increase in extent, both in length and breadth, but no serious obstruction is formed as far as the latter

Davis's Ripple.-The average slope from a small ravine above the dam to the landing below, a distance of 1.34 miles, is 3.77 feet per mile; the maximum slope near the lower end of the dam is 9.16 feet per mile. The dam enters the river at an angle of 45°, and extends 420 feet to the angle, where, turning, it continues down stream for 850 feet, terminating abruptly. The width of the river is contracted from 520 feet above the dam to 240 feet, at the middle of the flank wall. This dam is of riprap, and, like the others, is about 5 feet above low water. Several gaps and a break near the shore permit the water to escape. A gravel bar extends below the dam, which has a depth of 1.4 feet at low water. A gravel bar at the mouth of a small branch contracts the channel opposite the lower end of the dam, and creates a rapid, oblique current. The repair of this dant and the dredging of the gravelly point will reduce the current and improve navigation at Davis's Ripple. A high bluff on the right contains good hydraulic limestone. Below this point gravel bars become more frequent, particularly at the mouths of the creeks. Those which occupy the bed of the river, are said to have retained their present form for twenty years. Any obstruction in the current becomes, however, the nucleus of a rapid accumulation of gravel and débris. The wing-dams in this part of the river are said to become packed with gravel, and watertight in two years after erection.

From Davis's Ripple to Clarksville, sixty-five miles from Nashville, the river winds in long and graceful curves, such as might have been designed by art. Throughout this section the dredge may be used with advantage, especially in connection with lateral dams. Natural circumstances favor the preservation of an artificial channel, which the stream cannot create. A straight part of the river walled in by rock on the right, just above Clarksville, is partially obstructed by brittle ferruginous conglomerate, which can be excavated with the dredge.

Approaching Palmyra Island, ten miles below Clarksville, the bottoms become lower and the banks are composed more largely of gravel and lighter alluvial. The change has increased .the number of islands and bars in the river below Palmyra, Wells, and Bald Islands, composed for the most part of gravel, which the decreasing velocity of the river here leaves in the broad reaches and eddies. These islands continue to increase until, acting as artificial wing-dams, they contract the stream and augment the velocity sufficiently to maintain a navigable channel.

Palmyra Island.-The river is, at ordinary stages, divided into three channels, which at low water are reduced to two by the drying up of the middle channel, leaving a gravel bar on the right of the island. The left chute is 30 feet wide. The right-hand channel being very narrow, and turning sharply to the right, becomes, at the head, difficult to navigate on account of a cross-current which forces the boats on the bar opposite. A small amount of dredging will remove this difficulty. The bank also should be protected from the current, which has cut deeply along the slope. The middle and left hand channel may then be beneficially closed by a dam rising 5 feet above low water. The river turns to the right against a bluff below, and the island appears to have formed in the eddy of the conflicting currents.

Elk Creek.--The shoal at this point is due to the gravel and sediment brought into a sluggish part of the river, by a rapid little creek. The creek enters with a comparatively rapid descent between soft and sliding alluvial banks. The average slope per mile of the river is 0.94 of a foot. The maximum slope is not more than 1.35, and the width of the river is 585 feet. The banks of the creek should be riprapped to prevent the erosion and the transfer of sediment to the river. After the bar has been dredged, it may be necessary to construct a lateral dam to keep the channel open. The banks are from 30 to 40 feet in height, and the bottoms from one-half to one mile wide. From Palmyra to Dover no other obstructions occur of sufficient importance to deserve notice, except the submerged logs below Wells Island. The river in this section is made up of straight reaches and long curves of sufficient depth, with banks well protected by shrubbery. The river-bottoms when not cultivated are covered with hickory, shellbark, oak, gum, and beach. The undergrowth is pawpaw and dogwood. The border of the river. is lined with willow and some cottonwood. Bald Island appears as a gravelly bar, covered by the river in ordinary stages, but requires no special notice. In front of the old Cumberland iron-works; the river is sluggish, but free from snags, and in good navigable condition.

The next point is found at Dover Island. The obstructions assume the form of rocky ledges, and a gravel bar in the right channel, and continue with interruptions as far as Dover's Landing, three miles lower down. The island is one mile long, connected with the left shore by a dam, and another short dam has been constructed about midway. The left-hand channel, originally the best, was probably condemned on account of its sliding banks. The left channel along the rocky bluff has a bed of rock, and is very shallow at low water. The current is rapid, the slope being 5.5 feet per mile. The average slope between the head of the island and Dover Landing, three miles below, is 1.82 feet. The width above the dam is 435; about midway of the island it is 250 feet. Notwithstanding this great contraction, the descent brings the rock of the bottom sufficiently near the surface at low water, (one foot,) to obstruct the passage

of steamboats. The dam is broken near the shore, but at the time of survey, when the river was 2.4 feet above low water, it raised the water about 0.43 of a foot. Little will be accomplished by the repair of this dam, if the rock is not at the same time removed from the point in the channel where the descent is greatest. Below the island the river is about 500 feet wide, and retains this width as far as Dover Landing. In the upper part of the reach, a gravel bar of regular form extends for 1,900 feet, and contracts the channel to 400 feet at low stages. Below this bar a dam enters the river at an angle of 45°, and extends for 380 feet with a flank wall 1,200 feet long. The water-way is contracted to 280 feet. The water is deep along the dam, but below it the channel is broken by gravel bars. Just above the ferry a cross-current forces the boats out of the channel, as they pass over the har (1.3 water) to the left shore. The dam should be extended nearly to the upper landing, and the bar below should be dredged in order to secure a straight and good channel to deep water below Dover Ferry. Observations were made at the dam above Dover, which give for the discharge of the river when the gauge read 1.9 above low water, 3,248 cubic feet per second.

The next point in order is found at Upper Gatlin Shoals. The channel here is winding Beginning with width of 420, it expands, as it turns to the right, to 610 feet, and again contracts to 420 feet as it turns to the left, 2,500 feet below. The bar extends from the left shore, and the channel on the right is narrow, shallow, and crooked. A dam to deflect and contract the current combined with dredging will remove the difficulty at this point. The maximum slope at Gatlin is 2.81, the average 0.74 of a foot per mile. The point next in order occurs at Line Island. Here a dam 1,420 feet long connects the right shore with the head of the island, which it follows for a short distance, and then extends in front of it for a distance of 5,080 feet. Above, the river is 500 feet wide, but is contracted by the dam to a width of 320 feet. The maximum slope per mile is 3.38 feet; the average slope is about 1.50.

The water is raised by the dam near the angle to 0.51 of a foot. Along the course of the dam the elevation is affected by openings. The distances from the angle and the height of the water, as affected by the breaks in the dam, are as follows:

The channel is obstructed at two points. About half way of the channel some wrecks upon the left are in the way at low water, and near the mouth of a small branch, just below the dam, a bar has formed in the line of the channel, which has a depth of 1.9 at low water. This dam should be repaired and extended, and a small amount of dredging should be executed in order to remove the obstructions to navigation. The work of excavation executed by the Government in 1834, at Devil's Chute, has removed the obstacles which once existed at this locality.

Race-Track Shoal.-The obstructions here consist of a gravel bar, and several boats are sometimes detained by the shallow water. The river approaches Devil's Elbow, where it is suddenly diverted to the right by a horizontal ledge of limestone which projects into the river about 8 feet above low water. In the reach above the rock, the river has a width of 420 feet, which is reduced at ordinary stages to 310 feet at the rock, and expanded to 540 feet below it. Here, about 600 feet below the elbow, a gravel bar has formed on the right. The material washed out of the angle above the rock, and also below it, by the current which is precipitated over it at ordinary high water, is deposited at the point where the width of the river expands to 540 feet. The maximum slope per mile at this point is 3.38 feet, and the average slope included in the length of the bend is 0.71 of a foot. It is impracticable to straighten the river without a considerable amount of work. But this end can be partially obtained by blasting off the rocky point in the elbow, and filling the bend above with the material. The bar should be dredged and the river below confined by a lateral dam, to reduce the width, which increases to 700 feet.

An examination was made of the shoal at Little River. The maximum slope was at the rate of 4.6 feet per mile; the minimum slope was 1.11 feet per mile. A bar is making from the left shore, but as it has two feet of water on it at low water, no work is required until the other bars are raised to the same standard.

Shelly's Island.-An examination was made of the channel from the head of the island to a point below the rolling-mills, a distance of one mile and a half. The average slope per mile is 1.12 feet; the maximum slope is 5.22 feet. A bar is forming from the left shore below the island, which contracts the channel and acts as an artificial dam to preserve sufficient depth of water. No work is required.

Ingram Shoals.-Four miles below the mills and about one hundred and forty-eight

miles from Nashville, the last formidable obstruction is found. From the head to the foot of these shoals is about three-quarters of a mile. The width of the river above is 560 feet, and expands to 640 feet near the middle of the shoals and contracts to 440 feet below. The average slope is 2.3 feet per mile, the maximum slope being 7.10 feet. This shoal is composed of gravel resting on blue clay. The river at this point is straight. Originally the channel passed from the left to the right side, but has been transferred wholly to the right by four sunken barges at the head of the shoal. About half way of the shoal and in the middle of the river a gravel bar extends for 1,300 feet, contracting the main channel to the width of 200 feet without increasing the depth. The shoalest part of the bar has 1.2 feet at low water.

In order to improve the channel at Ingram Shoal, it is evident that a considerable amount of dredging will have to be executed in order to make a lateral dam efficient. Both are recommended. There are several other bars and difficult channels in this division, which have been passed over in order to select those which most require improvement. Those which have been omitted are named as follows: Wood's Island, Martin's Shoal, Well's Island, Checkered House, and Bull Pasture Shoals, Yellow Creek Towhead, Wild Cat Shoal, Boyd's Shoal, McKnab's Bar; below Ingram there are Big and Little Eddy, Big and Little Horseford, and a rocky point four miles below Camp Rowdy.

Steamboats pass all these points without difficulty, when obstacles are encountered at all the localities recommended for improvement. Under the influence of the back water of the Ohio, this part of the river is subject to change, but in its present condition no improvement is required.

CHARACTER OF OBSTRUCTIONS AND THE IMPROVEMENT PROPOSED.

From the description above given of the obstructions to navigation, it is evident that they may be classed under the following heads:

1st. Overhanging trees in the upper part of the river and some logs and snags in the lower.

2d. Horizontal ledges of rock, revealed at low water, at points where the river passes from a higher to a lower level.

3d. Bars composed of the débris of the bluffs and of the bed of the river and of heavy gravel.

4th. Bars composed of a horizontal layer of ferruginous conglomerate of sand and gravel, found in the lower part of the river.

5th. Wrecks of barges and old cribs.

The ledges of rock and bars of rocky débris become so numerous above Nashville at low water, that any attempt to improve navigation at this stage, by contracting the channel or by excavating the bed, is impracticable. The only feasible low-water improvement is by locks and dams. This method might be adopted with advantage, as far as the dividing line between Kentucky and Tennessee. It would be an efficient method of improving the great shoals. But since it is excluded from consideration by reason of its cost, it becomes necessary to determine whether the improvement of the natural channel is not practicable at some other than the low-water stage. The river from Nashville to Point Burnside is navigable for steamboats at a stage varying from 6 to 8 feet, and from Poplar Mountain "tows" drawing six feet water can make regular trips when the river is 10 feet above low water. Any improvement of the natural channel must facilitate navigation at these stages.

Low water, according to pilots, is the stage which permits the passage of the smaller steamers, drawing one foot without freight. This may be called steamboat low water, and is one foot above the ordinary low water of summer. In this acceptation the words are used in this report. From the mouth of the river to Nashville navigation is practicable at from one foot to one foot and a half above low water; from thence to Carthage 4 feet is necessary; thence to Burkville, 5 feet; thence to Point Burnside, 6 to 8 feet. In this division the period of navigation is usually six months. Five months, with a depth of from 8 to 10 feet, is counted on by the pilots of the Poplar Mountain coal trade for their tows of 6-feet draught. Above Point Burnside a flood of 15.7 feet at the foot of the shoals, and 4.5 feet at the head, and 16.8 feet at the point where the coal-boats receive their loads, is requisite for the safe descent of the coal-barges from the coal-mines of Pulaski County. This stage of water is equivalent to 334 feet at Nashville. The coalbarges which make the trip unassisted by the steamers are compelled to wait for the flood. If the river at this point could be so improved that the barges might take advantage of intermediate floods of less elevation, the shipment of coal would be largely increased.

It is evident, therefore, that the improvement of the bed of the stream may be made efficient, by adapting this method to the changing conditions of the river at different stages and in different sections. On account of the variation of the descent, depth, and navigable period in different parts of the river, a uniform standard of navigation is im