8. The removal of obstructions at the harbor of Dubuque, Iowa. 9. Improvement of the Tennessee within a stated length.

The information communicated is derived chiefly from the reports of Lieut. Col. S. H. Long; Lieut. Col. J. E. Johnston; J. Barney, esq., agent at Dubuque; G. A. Dunlap, esq., agent for the Illinois; and Lieut. Col. J. McClellan upon the Tennessee river.

"The portions of these rivers which are considered as having claims upon particular attention, not including the Tennessee, are the Ohio, from Pittsburg to its junction with the Mississippi, 1,000 miles; the Mississippi, from the mouth of the St. Peter's to Natchez, 1,785 miles; the Missouri, from its junction with the Mississippi, to Council Bluffs, 660 miles; the Arkansas, from its junction with the Mississippi, to Fort Gibson, 590 miles; the Illinois, from its junction with the Mississippi, to La Salle, 255 miles; making in the aggregate 4,280 miles of river way which requires improvement.

"The improvements consist in the dredging of sand bars, the removal of snags, rocks, sunken logs, impending trees, wrecks, &c.; the construction of wing dams, jettees, &c., for reducing width and increasing depth, and increasing depth of passes; the opening of channels across sand and gravel bars by dredging; the construction of canals and sluices at rocky shoals and rapids; the formation and protection of commodious harbors at commercial points, &c.

"A brief general view of the present condition of these several rivers will be given."

"From Rock island rapids to Dubuque, 83 miles, there are very few obstructions to low water navigation for boats drawing from 3 to 4 feet of water. The difficulties in this distance consist chiefly in the crookedness of the low water channel in its meanderings over shoals. From the Des Moines rapids to the mouth of the Missouri, 192 miles, the river abounds with shoals, with a low water channel-way of about 3 feet, and the channel-way across these shoals is exceedingly crooked, and lined with snags and logs-some of them very dangerous, particularly to night navigation.

"But it is considered that a few days of labor, with an efficient snag boat and crew, at a proper stage of water, would do much to suppress the dangers of the navigation.

"From the mouth of the Missouri down to Natchez, about 1,000 miles, snags, logs, wrecks, &c., are of frequent occurrence in the channel-way and on the bars, and especially in bends and along concave shores.

"The low water channel, throughout the entire distance above mentioned, has been successfully operated upon, and effectually cleared of all obstructions that were presented at the time when the work was in progress. The removal of snags, &c., from the Mississippi was com menced in the latter part of September, and has been prosecuted with all practicable diligence to the present date. Much remains to be done, however, on the bars in the island chutes, and even in the main channel itself; for it should be borne in mind that although the channel

depths are remarkably uniform in the lower stages of the river, yet on the subsidence of the latter the bottom of the channels subside at the same time, and new obstructions are continually presenting themselves at the bottom and sides of the channel thus deepened.

"The removal of these and similar obstructions from the sides of the channel, also the cutting of prostrate trees, &c., on the dry bars, the removal of snags, &c., from the chutes, the falling of impending trees, &c.

"In order to exhibit a more intelligible view of the bends, &c., at which the operations of the snag boats have been applied, I hereto subjoin a list of the more formidable and dangerous passes at which they have operated, beginning at the mouth of the Missouri and ending at Natchez, premising that the low water, or rather shoal channels, at all the localities to be noticed in the list, have been effectually cleared of all obstructions visible and discoverable at the time of operation. "The list is as follows:

Positions and distances from mouth of the Missouri (downward) to Natchez.

"In addition to the localities designated in the foregoing list, there are numerous others, intervening bends and beaches, in which snags and other obstructions to low water navigation are more or less frequently to be met with, besides numerous impediments to high water navigation, which abound in the shoals, and upon dry bars, and more especially in the island chutes.

“As before remarked, the low water channels have been effectually cleared of all snags, logs, &c., discoverable during the late low water season; while the shoals, at the sides of the channels, present numerous similar obstructions, not accessible to snag-boats in a low stage of water; and the dry bars are, in many places, overlaid and inlaid with prostrate and embedded trees and logs, not less formidable in higher stages."

"The Ohio river, and the dam at Cumberland island.

"From Pittsburgh to Brown's island, about 66 miles, the river presents a series of rocks, reefs, and shoals, at which the low water depth is too inconsiderable, in many places to admit the passage of steamers of the lightest drafts. Sluices have been opened at sundry points, and wing dams, jettees, &c., of stone, resting upon rock foundations, have been formed in numerous instances for the purpose of reducing the width of the channel, and compelling the water to flow in a narrower and deeper volume; much benefit has resulted from the construction of works of this sort, but much remains to be done in this way towards the completion of the improvements of which this portion of the river is susceptible.

"From Brown's island downward to Captina island, about 47 miles, rocks and gravel bars alternate with each other, at intervals of much greater extent than in the river above, the principal obstructions to navigation being occasioned by sand or gravel bars, more or less blended with pebbles, boulders, and rocks.

"Several wing dams have been partially constructed on this portion of the river, all of which ought to be completed, according to their original design, and some of them considerably extended; and, in addition thereto, the construction of others not yet commenced would, no doubt, contribute much to the improvement of low water navigation.

"From Captina island to Letart's falls, 128 miles, rocky reefs and shoals seldom occur, in the main natural channel of the river, but bars of sand and gravel, on which the low water depth is very inconsiderable and of frequent occurrence.

"At Marietta, Blennerhassett's island, and Buffington's island, side walls and wing dams of stone have been projected and partially constructed, for the purpose of diverting the water flow from its natural course, and directing it into the main low water channels.

"The dam at the head of Blennerhassett's island has, in some measure, produced the desired result; but the other works just mentioned have proved of doubtful efficacy. At these several points, and at many others on this part of the river, the process of dredging across sand and gravel bars may, no doubt, be applied to advantage.

"At Letart's falls the obstruction is occasioned by a reef of rocks extending quite across the bed of the river, through which the channel

is narrow and seriously obstructed by protruding rocks and boulders, over and between which the water is hurried with a velocity, and to a fall of about 5 feet, in a distance of less than half a mile.

"From Letart's downward, even to Louisville, 375 miles, the bed of the river is pretty generally destitute of rocky bars; but, in numerous instances, the river spreads to a great width, and the navigation is much obstructed by bars of sand and gravel, in very low stages of the river.

"The upper Ohio, commonly designated 'the Ohio above the falls,' presents, comparatively, but few snags and sunken logs; but its low water navigation is much endangered by wrecks of steamers, flat boats, and other craft.

"The most dangerous obstructions of this character, including snags, logs, &c., have been removed from the low water channel by the successful agency of the snag-boat Terror, (No. 5,) commanded by Captain J. K. Dillingham, who has been employed, during the last season, under the direction of C. A. Fuller, esq., on this portion of the river.

"From the falls downward to the mouth of the Ohio, about 400 miles, the navigation in low water is obstructed, at numerous points, by shoals occasioned by sand and gravel bars; and, in a single instance, by reefs of rocks extending across the bed of the river.

"The most troublesome bars are the following, viz: The Portland bar, a little below Sand island, and half a mile below the foot of the falls.

"No considerable effort has been made for the improvement of this shoal, although, it is believed, that such an improvement might readily be made.

"Formidable shoals again occur at Blue river island, and Flint island, respectively, 60 and 90 miles below Louisville, which are occasioned by indurated bars which present serious impediments in the way of low water navigation, especially the bar near the foot of French island. As yet, however, no attempts of any considerable moment have been made towards the improvement of either of these passes.

"At French island, 78 miles; Scuffletown, 88 miles; and Three Mile island, 96 miles below Flint island, wing dams of stone have been built for the purpose of retaining the low water flow to narrow channels leading across the shoal bars at these several points, but the results obtained in each case are of doubtful efficacy. In these several instances the shoals have been occasioned by extensive bars of loose sand stretching entirely across the bed of the river, which, in every case, is unusually broad.

"The dams having a mere bed of sand to rest upon, have been undermined and become dilapidated, and the water in low stages ceases to flow in the directions intended to be given by the dams.

"Bars of similar consistency, but of less extent, are of frequent occurrence in the lower Ohio, and many of them are nearly or quite as formidable as those above mentioned. In view of the inadequacy of wing-dams as a means of opening low-water channels across such bars, which has proved true in almost every instance of their introduction, I am inclined to repudiate their adoption in cases of the sort referred to, there are, no doubt, peculiar situations where their introduction and use may prove beneficial; but I doubt not that the process