Chesapeake and Ohio Canal.– The Alexandria Gazette of Monday says– “whilst we are writing, the waters of the Potomac above Harper’s Ferry, are silently flowing into the Chesapeake and Ohio Canal. Passing the long contested Point of Rocks into the finished part to Seneca, they will connect the tide water of the District to the fertile region of the Shenandoah, and the upper part of Virginia and Maryland, watered by the Potomac and its tributary streams. This part of the canal has been my far the most expensive to construct, of the eastern section. By the commencement of next season, it is supposed that upwards of one hundred miles of the Canal will be completed– passing Shepherdstown and Williamsport, on its route westward.