The expense of these walls would be saved in part, from the fact that being vertical, or nearly so, the cross-section of the open cut would be much diminished, hence the estimate for excavation lessened; but in consideration of there necessarily arising many contingent expenses in the execution of a work which cannot appear in an original estimate, it is preferred that the above amount stand as an additional item and disconnected from others. CLEARING AND PREPARING BANKS OF HILLSBOROUGH RIVER. To prepare this river to serve as a continuation of the canal, it will be necessary to clear, smooth, and level the banks, in some places fill in and flag, in others cut away, in order to prepare a tow-path; in general, however, the banks will require comparatively little work, and it is estimated that $4,000 per mile will be sufficient. 7 miles, at $4,000..... $30,500 00 No item is inserted for ramming and dressing embankments, as it is considered far better to transport over it, and this can usually be done. The line across the peninsula is naturally divided into four divisions, as follows: Starting from the Saint John's, division No. 1 extends to the last of the series of locks necessary to ascend the valley of the Weekivah. Division No. 2 consists of the long level stretching from Lake Weekivah, and terminates at the summit-level. Division No. 3 is summit-level. Division No. 4, the line between summit-level and Tampa Bay. The cost of construction will be distributed according to estimate, as follows: Division No. 1, 17 miles, 880 yards in length, and 10 locks.. Division No. 4, 46 miles, 1,707 yards in length, and 17 locks $513, 205 70 504,703 36 1,671, 294 96 994, 208 34 Having embodied the results of the survey connected with the line in the foregoing remarks and estimates, I will refer briefly to a line run to the Ocklawaha River, and connecting with the one to Tampa. A line of canal across Florida, to be most valuable to commerce, evidently should take as direct a course from the Atlantic to the Gulf as practicable. To ascend the Saint John's to near its headwaters, and then cross to Tampa, is undoubtedly circuitous as a line of communication to avoid the straits of Florida, and the depth of water in the upper Saint John's is such as limits navigation to boats of light draught. It would, unquestionably, be better to connect the canal with the lower portion of the river, at some point to which the depth of water carried over its bar can be brought; more especially so if distance, at the same time, is saved. With the above in view, also, agreeably to your instruction directing any lines to be examined that might be deemed favorable, the survey was carried from a point of the first line known on the map as Fox Branch, to the headwaters of the Ocklawaha River. Supposing the canal to reach the Saint John's from Tampa, by continuing down the valley of the Ocklawaha, this route may be compared with the first, in a few words, as follows: The summit-level will be 18 feet lower; it has the same sources of supply, and numerous lakes near the headwaters of the Withlacoochee additional. The length of the canal to be constructed will be increased some 50 miles, and the transit across the peninsula shortened by about 30 miles. The expense of construction will be less in proportion to distance, since the sand-ridge cut by the summit-level of the first line is in this not met with. The fact of avoiding the sand-ridge, also being able to establish the summit-level lower, will decrease the estimate for con struction about $750,000 for an equal number of miles. This will make the entire cost of the Ocklawaha route about $400,000 more than the first line, dimensions of the two being the same. Taking up the data for supply of water already used, it can be easily shown that there is an abundance for a canal having a depth of 12 feet, and it is with a view to such a depth being desirable for the canal that the Ocklawaha route becomes of interest; its junction with the Saint John's would be near Pilatka, up to which point 10 to 11 feet can be carried. That such a depth is essential to the undertaking of the work as a national object, seems pretty evident, for without it there would be two extra transshipments, together with time, labor, and conse quent expense attending it. But, could vessels carrying on the coasting trade have a channel leading to the Gulf presented to them abso lutely free from the dangers incident to the navigation through the Straits of Florida, entailing no expense incident to a double handling of cargo, and by means of which the time of their arrival in the Gulf could be calculated with certainty, this time, too, being less than a voyage around Florida requires, it is believed that then, and only then, the elements of a successful line of water-transit are shown. If the river Saint John's had the requisite depth up to the mouth of the Weekivah, then would the first be a more favorable line than the second, as regards original cost of construction; there is water enough to sup ply the summit-level on either line, should the canal have 12 feet. depth of The points of the river presenting the shoal water are as follows: Near the mouth of the Ocklawaha the depth shoals to 10 feet; the outlet of Lake George has only 9 feet, and this general depth continues for some 3 miles. The inlet of Lake George has on its bar, ordinarily, 63 feet; rains will increase and wind may lessen this depth; beyond this, the river has a depth varying from 15 to 20 feet, up to Lake Monroe; outlet of Lake Monroe, scant 5 feet. The bars at the entrances to the different lakes are permanent obstacles, unless colstantly being improved; the expense attending such improvement would, doubtless, make the Ocklawaha much the cheaper route in the end, and the line' in this case would pass near to and through a much more fertile and important part of the State than if starting from the mouth of the Weekivah. The conclusion in reference to the two routes is this: If a depth of only 6 feet is given to the canal, then the first line is preferable; if the entire depth of water available in the Lower Saint John's is desirable to be carried across the peninsula, then the second or Ocklawaha route is preferable. It has already been stated that both are practicable, and can have a full supply of water. I take occasion to remark, in this connection, that the map shows a rather favorable line, starting from the harbor of Crystal River, and striking the Saint John's at the mouth of the Ocklawaha. How favorable the ridge dividing the Withlacoochee and Ocklawaha Rivers may be for crossing is not known; but, before deciding upon any line as the best for crossing the peninsula, this one should be examined; want of funds prevented this being done by myself. The main objections to the work are the two following: 1st. The line of transit embraced in present surveys is too circuitous. 2d. The depth of water (limited by the Saint John's and by the harbors on the western coast to 11 and 12 feet) is not as great as is desirable for an important ship-canal. The Saint John's above its bar could be deepened; but, in that event, the terminus on the eastern side (canal having a greater depth than mentioned) would be the mouth of the Saint Mary's, and would involve the necessity of deepening the inland passage between the Saint John's and Saint Mary's. Saint Mary's, or Fernandina Harbor, is the natural terminus for any canal connecting the Atlantic and Gulf, for it is the last port on the Atlantic coast capable of admitting vessels drawing more than about ten feet; hence the only point where trade would center on its way eastward, and be met by vessels for distribution to home and foreign markets. In concluding this report, the attention of the Colonel of Topographical Engineers is respectfully called to the subject of the practicability of a ship-canal across Florida as it now rests. There are at least four lines across the peninsula which should be surveyed before any one can be decided upon as preferable to the others; two of these lines only have been run, and either one of the two remaining, if found favorable, would be preferred to those reported upon; for, in the first place, being nearer the base of the peninsula, there would be less deviation from the general line of the Atlantic and Gulf coast-hence a decrease of the length of water-communication from south to north; next, the line of caual would be more direct, and would run across Florida at about its narrowest point. In view of the above, it is respectfully urged that an additional appropriation for continuing the Florida Canal survey be recommended, in order that the subject may be fully and completely discussed, and leave no unexamined points for future doubt. It is believed that $15,000 might, if economically used, enable all desirable information to be obtained; $20,000 is, however, considered a much safer amount to estimate for, and is the sum named and respectfully urged to be recommended by you. I am, very respectfully, sir, your obedient servant, Colonel J. J. ABERT. First Lieutenant Topographical Engineers. APPENDIX J. ANNUAL REPORT OF CAPTAIN C. W. HOWELL, CORPS OF ENGINEERS, FOR THE FISCAL YEAR ENDING JUNE 30, 1876. UNITED STATES ENGINEER OFFICE, GENERAL: I have the honor to transmit herewith the annual reports, for the fiscal year ending June 30, 1876, of the various works of river and harbor improvements under my charge. Very respectfully, your obedient servant, Brig. Gen. A. A. HUMPHREYS, Chief of Engineers, U. S. A. C. W. HOWELL, Captain of Engineers. J 1. IMPROVEMENT OF THE MOUTH OF THE MISSISSIPPI RIVER AT SOUTHWEST PASS. The work was conducted throughout the year in the same manner as during previous years. Even with the relatively increased volume of discharge through Southwest Pass, which has marked the year, and the positive increase in velocity of current, suggesting scour of banks and bottom of the body of the pass, with increased amount of deposit on its bar, the dredges have been able to maintain a more uniform depth and width of channel over the bar than has been reported for any previous year. While this channel has not been deep enough to allow the largest seagoing vessels trading with New Orleans to load to their maximum draught, it has yet, by careful management and by the generally considered action of those interested, been made to meet the necessities of this commerce better than heretofore. For many years past there have been notable blockades and detentions, resulting in great losses to the vessels detained. During the past year there has been no blockade such as heretofore, and no very serious detention, except that of the steamship Alabama, of 360 hours, caused by her loading to the excessive draught of 20 feet 4 inches. As a portion of the history of the work, a tabular statement is appended, of which the following is a synopsis: |