For the great future water-ways which are needed for the Western, the North-western and the Mississippi Valley trade there are several routes that have been demonstrated to be practicable. One of these is by a projected canal to connect the Coosa River with the Alabama River, and thence following that stream to the Gulf of Mexico. This, if ever carried out, as eventually it is probable will be the case, would avoid the bars and dangers of the navigation of the lower Mississippi, and in a measure obviate the necessity of the proposed sub-canals in Louisiana and other engineering expedients to remove or turn the very serious river-obstacles to an outlet south of New Orleans. Another proposal is to connect the Ohio and Tennessee Rivers, and to run a canal from the latter to the Ocmulgee or Savannah River, and thence by the use of slack water to reach the harbors of Savannah and Charleston. This scheme has been clearly proved to be feasible, although the distance seems objectionable. The third (or central) water-line proposed is that so long agitated since the beginning of the present century, so often surveyed and re-surveyed by the most eminent engineers, and not long since by the United States Engineer Corps under the direction of General A. A. Humphreys, the chief engineer of the United States army. It is the shortest and most direct line, and has the advantage that it is, as we have seen, already nearly half completed, from the head of tide-water on the James River, above Lexington, to Buchanan, near the summit-level of the mountains. The engineers who have reported upon it--among whom are the late Colonel E. Lorraine, Benjamin H. Latrobe, Esq., and other eminent engineers--estimate that the largest sum required for its completion to the Kanawha River is $37,364,000, and the length of time required four years. "Of this large sum, however," they say, "it can be clearly shown that there will be no need of any other advance by government than the interest which will accumulate while the work is in progress, which, by issuing the bonds every six months, as required, will not reach the sum of _six million dollars. And this is every cent that will ever be required to be advanced_. Should the government undertake to make the work a fine one, it will of course cost the whole amount estimated, but this would be more than made up by its increased benefits to the whole country. "The work when completed, even at a low rate of tolls--not over about half the rate charged on the Erie Canal--will return the advance, pay the interest and redeem the principal in less than twenty years. [Illustration: BIRD'S-EYE VIEW OF THE TRANS-ALLEGHANY WATER-LINE.]