of dredging, with apparatus properly constructed and adapted to the removal of sand, gravel, &c., from the low water channels across the bars, would prove more efficacious and economical in general, and at the same time less objectionable, on very many accounts, than the construction of wing-dams, jettees, &c., on sandy foundations.

"In this connexion I take occasion to observe, that the two dredge boats constructed for use on the western rivers, though very well adapted to the improvement of harbors, and to the deepening and widening of channels across sand and mud bars, upon which the water has a depth of about 3 feet, yet, when they are not applicable, and cannot be used to advantage on bars having a less depth of water above them.

"The Cumberland dam affords a remarkable example of the ability of a rip-rap structure composed of stones of irregular forms, sizes, and dimensions, and based on a mere bed of sand of great depth, to withstand a head and fall of more than four feet of water. However questionable the propriety of its ever having been constructed may be, yet the fact above stated has an important bearing upon numerous subjects connected intimately with the improvement of many of the western rivers.

"This dam has been considerably enlarged and extended under the direction of C. A. Fuller, esq., during last summer, but is not yet completed; the operations upon it have, nevertheless, contributed to the formation of a navigable channel, in low water, between Cumberland island and the Kentucky shore, and to open an easy communication in a low stage of the river, between the Ohio, at the head of the island, and Smithiand, at the mouth of the Cumberland-a communication that could not previously be had either above or below the island.

"The same operations have no doubt contributed to the formation of shoals at, or a little below, the foot of the island, (between four and five hundred yards below,) across which the low water depth is about three feet only, when a depth of four feet may be found on the bars both above and below the dam.

"The dredge-boat Gopher (No. 2) has been employed some time in efforts to open a channel across the shoal, but has failed of success, partly by reason of frequent interruptions from passing boats through the channel intended to be opened, and partly for the want of a sufficient depth of water at the shoals to admit the working of the dredgeboat. A dredge-boat of the character before suggested, could, no doubt, be used to better advantage in opening the desired channel at this point.

"Numerous bars on this part of the river, both above and below Cumberland island, require the operation of dredging, for the purpose of opening a low water channel across them; and it is confidently believed that the means and manner of operations before proposed, would prove more economical and efficacious than any others heretofore applied for similar purposes.

"The rocky reefs called the Little and Grand chains of the Ohio, respectively 16 and 34 miles above its mouth, are rendered somewhat dangerous by reason of numerous large boulders and other rocks situated in and near the low-water channel. Many of the rocks at the

Grand chain have been blasted and removed, while others remain at both chains, opposing obstructions in the way of free and safe navigation in low stages of the river.

66

Snags, logs, and wrecks are accordingly to be met with on the lower Ohio, and have occasioned the destruction of several steamers; it is believed, however, that the most formidable of these obstructions will have been removed within the present month by the snag-boat Terror, (No. 5,) under the command of Captain J. K. Dillingham, who has been employed on this part of the river for several weeks.

"In further reply in reference to the Ohio river and the Cumberland dam, I submit a copy of the annual report of the agent, C. A. Fuller, dated September 1, 1853."

"Missouri river.

"The obstructions in this river are quite as numerous and formidable as those in the Arkansas, while the channels of the former are much broader, and the sand bars much less compact, and, of course, the snags much less firmly imbedded than those of the Arkansas.

"Two of the snag boats were employed in removing snags, &c., from an early date in August (about the 10th) till the latter part of September, (about the 20th,) when the river had subsided so much as to render a retreat to the Mississippi quite precarious.

"These boats succeeded in removing upwards of 500 dangerous snags from the low water channel, besides the cutting of trees and logs on the bars, and shoals, felling impending trees, &c. The portion of the river operated upon extends from its mouth to Smith's bar, about 160 miles, beyond which they could not ascend for want of a sufficient depth of water in the deepest channel.

The shoals at the sides of the channels operated upon were more or less frequently beset with snags, which were not accessible to the snag boats, by reason of the shoalness of the water.

In more elevated stages, these obstructions become serious impediments in the way of navigation, and their removal can only be effected by repeated efforts of the snag boats, applied whenever the river is sufficiently full for the purpose.

"The craft best adapted to the removal of snags, &c., in the Missouri, should consist of one or more twin snag-boats of the largest class; a light draft snag-boat with a single hull, and one or more machine boats, susceptible of being towed from place to place, by either of the other boats; by means of such a flotilla, the more stubborn snags may be removed by the twin boat, while the single hull boat, and the machine boat can be employed to great advantage in removing obstructions from the shoaler parts of the river; moreover the light draft boat in company with the machine boat, can, without much inconvenience, continue their operations on any portion of the river between its mouth and the Council Bluffs, during the entire low water season, or from about the middle of July to the middle of November."

"In reference to the low water channels of the Mississippi, Missouri, and Arkansas, and especially in reference to those of the two former rivers, it should be particularly observed, that they are seldom identical

with, and cannot occupy the position of the deepest channels in more elevated stages; also that the bars formed on the more elevated stages overrun, fill up, and obliterate the low water channels; consequently, on the subsidence of the waters after every freshet, and especially after high floods, shoals begin to be presented when the surface of the rivers have an elevation of some 6, 8, or even 10 feet above their extreme low water marks. Hence the removal of snags, &c. from the shoal channels, first formed after the subsidence of the rivers affords no assurance that these same channels will remain unobstructed during the entire progress of the subsidence to extreme low water mark.

"However protracted this period may be, the depth of the shoal channels remains nearly equable, while the surfaces of the rivers are constantly subsiding; and although these channels may have been effectually cleared of obstructions at the more elevated stages, the progress of removing their obstructions must be repeated again and again some three or four times, in order to keep them unobstructed, till the river falls to its lowest stage.

"Accordingly the phrase 'low water channel,' as used under the three last heads, is intended to be applied in all stages of the rivers at which shoals and the clause 'effectually cleared' has reference only to that stage, at which all obstructions had been removed from the main channels leading across the shoals existing at that stage.

"Hence it is obvious that the removal of all obstructions from low water or shoal channels, and the opening of free and safe navigation through them at one stage of the river, do not ensure safe navigation through them at a lower stage; also, that in order to accomplish this object, the operations of the snag-boats must be repeated from time to time, not only in the same localities, but at intervening points, at every considerable subsidence of the rivers, from the time when channel obstructions are first presented till the rivers shall have fallen to their lowest stage."

"In conclusion, under these heads, it should be observed that, at the time of my late inspections the depths of the water in the main channel across the shoal bars of the Mississippi did not exceed the ordinary depths of the same channels in extreme low water, although the river surface at the same points was elevated 6 to 10 feet above extreme low water mark."

"Arkansas river.

"The region drained by this river is apparently quite as spacious as that drained by the Ohio, while the extent of navigation afforded by the former and its tributaries is less than one-fourth of that afforded by the latter and its tributaries.

"The Arkansas river is navigable only to the junction of three forks distinguished by the names of the Arkansas, Verdigris, and Neosho, viz: a little less than 600 miles from its mouth. Its channel throughout this portion of the river is, for the most part, narrow and very crooked; its current rapid, corresponding to an average declivity of about 8 inches per mile; its bars occur at every bend, and are composed of sand and gravel firmly compacted, rocky reefs extending quite

across the channel, and of frequent occurrence on the upper half of the navigable portion, while snags and logs of large size and deeply imbedded in hard bars are abundant, especially on the lower half.

"The proper season for prosecuting the snag business on this river commences about the first of April, and terminates about the last of July.

"A rise occasionally takes place in October or November, but seldom continues long enough for successful operations with the snag-boats.

"During the last season the snag-boat, No. 4, entered the Arkansas, early in August, and succeeded in removing the snags from the low water channel through a distance of about 60 miles, upward from its mouth. In attempting to retreat from the river, this boat grounded on a bar a little below the White river cut-off, and was detained in consequence during an entire month, or 31 days.

"It is proper to observe in this place that the craft best adapted to the removal of snags, &c., from the Arkansas, is as follows, viz:*

"A light draft snag-boat with single hull, accompanied by one or more machine boats of the usual construction, the latter being susceptible of towage from place to place by the former.

"The channel of the rivers, especially in low water, is too narrow and crooked, and the current too rapid to admit of the successful operation of a twin snag-boat of the usual size, although in an elevated stage of the river such a boat may operate to great advantage.”

Aggregate of the obstructions removed by all of the snag-boats-five in

number.

(e.) "No. 5.-Commenced work in the upper Ohio about the 1st of May; was rendered inoperative at the head of the falls, from July 22 to November 10, by reason of low water. On the date last mentioned, she crossed the falls and resumed operations in the lower Ohio. During the detention above mentioned, she received needful alterations and repairs, including two derricks at her bows, a set of cross hog chains, with Sampson posts, an enlargement of her cutting beam, and fastening for cylinder timbers; recaulking of boot tops, &c."