The Port Gibson Correspondent

Improvement of the Mississippi.—We are rejoiced to see that two of our representatives, Messrs. Thompson and Davis, have taken active measures for securing the opening of Pass Manchac and Iberville from Mississippi to Lake Pontchartrain.

These Passes, it will be remembered, were closed by Genl. Jackson during the last war to prevent the British getting into the river through them. Since that time they have gradually become more and more obstructed by drift wood and sediment until now they are nearly totally closed.

The benefit of opening this Pass will be twofold. In the first place it will lessen nearly one half the delay and expense of getting supplies to the Navy yards at Mobile and Pensacola, as the passage from the great markets of the west would be shortened more than a hundred miles; and in the next place, it would at once reclaim the vast bottoms of the Mississippi, and thus pour millions into the National Treasury by the increased value of lands in this quarter.

From the out-let of this Pass on the Mississippi, it is only nine miles to the level of the Ocean. Yet the waters, instead of being permitted to flow in this natural out-let, are dammed out, and forced to seek the ocean by N. Orleans, near 100 miles further. This simple fact shows at once how the vast bottoms of the Mississippi may be reclaimed. Nine miles from the ocean, with a sufficient passage, the water never could rise more than a few feet above the tide-water level; and to secure this level, at a point thus some 200 miles above its present disemboguement it may be mathematically demonstrated, would keep the waters from rising out of the banks for a distance far above this place in any freshets ever known.