have to be dredged after the construction of the training walls, I am not prepared to answer, although I am clearly of the opinion that the matter is worthy of consideration, and even of experiments, if necessary, before undertaking the further improvement of Mobile Bay. As the character of the improvement and the amount that can be profitably expended on it depends upon the commerce, present and prospective, that is to be provided for, such reliable information as I have been able to obtain is here given as to the former and facts and opinions regarding the latter. The work is situated in the collection district of Mobile, and Mobile is the port of entry. Its commercial statistics, as furnished by the collector of customs for the last fiscal year, is as follows: The Mobile Cotton Exchange in its annual statement, dated September 1, 1879, gives a clearer idea of the business of the port, and from it is condensed the table given below: In this connection perhaps should be mentioned the existence of three cotton and woolen mills in Mobile and vicinity, as showing a fair commencement in an important manufacturing industry, and the organization of a steamship company for the purpose of establishing a line of steamships to ply between Mobile and Liverpool. The first steamer for this line is already under construction. The country tributary to Mobile should include, it would seem, the whole Mobile or Alabama River basin, including the greater part of Alabama and a portion of Mississippi and Georgia, to say nothing of possible extension by an enterprising use of railroads already built and commenced, and canals already surveyed for. The Alabama basin contains approximately 33,000 square miles. The annual average rainfall is given by the signal service records as 43 feet, making over the whole basin about 28 cubic miles of water. This mass of water, after meeting with the usual losses from evaporation, &c., flows through the Oostenaula and Etowah, Coosa, and Tallapoosa, Little Tombigbee, Sipsey, and Black Warrior, Tombigbee, and Alabama, and other minor streams into the Mobile, which carries all the water in a single stream for about 5 miles, with an average width of 1,050 feet and depth of 39 feet; it then divides and subdivides, finally discharging into Mobile Bay an aggregate of about 100,000 cubic feet per second, through five mouths, the Blakeley, Appalachee, Tensas, Spanish, and Mobile forming a delta containing about 250 square miles, 186 of which (about) is heavily timbered, the balance being marshy. The river discharge then passes through Mobile Bay, which has an area of about 375 square miles, and finally reaches the open Gulf through three outlets, the main one between Sand Island and Dixie and Coffee, the others being between Coffee and Dixie and Mobile Point, and between Dauphin Island and Sand Island. There is still another outlet into Mississippi Sound, between Dauphin Island and Cedar Point. The rivers mentioned draining this basin are all navigable, or susceptible of improvement, so as to be made navigable, a total length of over 1,500 miles, reaching and passing through a country which has a capacity for producing over 1,000,000 bales of cotton; supplies of coal and iron that will compare favorably in character and extent with those of any other section of this country; building material, as granite, marble, gneiss, limestone (and various other mineral elements of wealth), and lumber. All these are accessible to water transportation by the river routes previously referred to, and when the improvements already in progress are completed coal should be delivered in Mobile at a cost of $2 per ton, and the other articles at sufficiently low rates to allow of successful competition with any other port on the Gulf of Mexico. In fact, though the Mobile Basin is insignificant when compared with that of the Mississippi, it is so merely on account of its inferior size, and I question whether there is any continuous area of the Mississippi Valley, of the same extent, that has been so bountifully supplied by the Almighty with the elements of wealth and progress. It is, in my opinion, to be as important a factor in the future of the country as any continuous 1,500 miles of the Mississippi River or its navigable tributaries, with the adjacent country. The cost of all the improvements required to develop the resources of this basin, it is believed, will be considerably less than that expended by Pennsylvania in water routes from the mines to Philadelphia. Mobile, a city at present of about 40,000 inhabitants, is situated at the junction of the river system with Mobile Bay, on the west bank, only 27 miles from a good channel of least depth of 22 feet, and only 36 miles from the deep water in the open gulf. Its growth has been continuous, though spasmodic, since its settlement on the present site in 1711. It has a railroad system already completed, giving competitive routes with the rivers to the lumber, cotton, coal, and iron. With the present commerce therefore as a basis, and the resources and transportation referred to and a deep channel to the sea, there is more than an ordinary probability that the commerce of the port would in a few years be increased at least 100,000 bales of cotton, 1,000,000 tons of coal, 10,000,000 cubic feet of lumber (lumber is now being towed, and transported by rail from Mobile Bay to Pensacola for shipment). In view of the large commerce present and prospective, and the fact that the development of the lumber trade depends for its greatest success upon as deep a channel as possible, I think no project should be adopted looking to a less depth than 21 feet at mean low tide, which at presents exists on the outer bar. The particular method of improvement should, in my opinion, be, as already suggested, either by dredging a channel of sufficient depth and width from the river to the anchorage, following the line of deepest water and carrying the dredged material to a distance, or to confine the entire river discharge to a single channel through the bay, to a point where the tidal current sweeping in and out of Mobile Bay is sufficiently strong to carry away any sediment brought down by the river current, and dredging out any material that might not be removed by the scouring power of the water. In this connection it should be borne in mind that the amount of tidal water which passes from the Gulf into the bay, and back into the Gulf, every twenty-four hours with the ebb and flow of the tide is more than twice as great as that discharged by the rivers, and that the outlet is so contracted that a very deep channel has been formed. The former has the success of previous work done in the bay in its favor, but the disadvantage of being a narrow channel, in the middle of a wide bay, exposed to cross winds and currents, making its navigation difficult at times, and rendering it possible that large expenditures might be required at some future time to remove deposits that might take place. The latter would have the apparent advantage of turning 24 miles of bay into river navigation-allowing rafts of lumber, or barges of coal, iron, or any such product, to proceed to the lower end, and meet sailing vessels at Alabama Port, within 15 miles of the open Gulf, to which point they could sail-of positive permanency when once fully accom plished, and possibly of greater economy in the end, if the construction of the necessary dams, dikes, and shore jetties will cause the current to do most of the work of excavation. A reasonable supposition, I think, as a glance at the map shows that the river has built its own banks, and scoured out between down a distance of over 40 miles of delta, and is now opening its way in the same manner down the bay at an average rate for the past 13 years of over 100 feet per annum, through 5 outlets, using its sediment to build banks. for each, which in turn confine the water to produce the scour. If, however, the river water would not scour with the rapidity or to the extent desirable, the fact remains that still the amount to be dredged would be much less than double the amount required in the other case, whereas the cost should not exceed one-half as much per cubic yard, for the following reasons: On the deep-water line, near the middle of the day, the material dredged would have to be carried by tugs and scows an average distance of over three miles, for deposit, to prevent its washing back in the cut. On the western shore line, with the dikes, &c., the material would be deposited by the dredges immediately on them or alongside the channel. Again, in the former case, a great deal of time would be lost and damage sustained either by being compelled to suspend work on account of, or by attempting to work in, rough water, whereas, in the other case, the dredge would be working under the protection of the western shore, on one side, and the dike on the other, or in comparatively smooth water. There is a question also whether a channel in shore, protected by banks on both sides 100 feet wide would not be better than one 200 feet wide in the middle of the bay without such protection, with a clear reach of 6 miles (average) open water on the sides, to produce rough water and cross currents, and length of 27 miles. The estimated cost of the work by the first system is as follows: For a channel with a width of 200 feet and depth of 17 feet: Dredging 9,900,000 cubic yards, at 20 cents per cubic yard........ For a training-wall from lower end of east bank of Tensas River to lower Dredging a channel 100 feet wide, 21 feet deep, 24 miles long, 7,509,312 cubic yards, at 15 cents... Additional spur-dikes and jetties, 5 miles long, at $10,000...... Total ... Contingencies and superintendence, 10 per cent Grand total $820,000 00 1,980,000 00 $15,000 00 666,736 00 1, 126, 396 80 50,000 00 1,858, 132 80 185,813 28 2,043, 946 08 An experiment might possibly be made at a reasonable cost at one of the river mouths, that would determine approximately the amount of scour for a given time that might be expected, on which the success or failure of the combined scouring and dredging system depends. In conclusion, I would recommend that the subject be referred to the Board of Engineers for harbor and river improvements for their consideration. There is forwarded herewith I. A map of the delta of Mobile River and Bay, of which the parts previously referred to are from the survey made, the rest being a compilation from the best authorities. II. A map showing work previously accomplished and present condition of channel dredged under former appropriations, and location of proposed improvements for securing a deeper channel. Skeleton map of Mobile Basin, cross-sections of the various rivers, and tables of current and sediment observations. Respectfully submitted. H. Ex. 64-2 A. N. DAMRELL, |