Blockading the Mississippi.
Morton, Aug. 8.
--Col. Matt Johnson sunk one transport and disabled two others opposite Greenville last Tuesday.
Since that time he has caused to turn back some twelve steamboats laden with merchandize.
The Yankee gunboats came up and shelled the woods furiously for miles without doing any damage.
The success of this movement will cause numbers of light artillery batteries to be organized at once for the same purpose, and a few weeks will see the Mississippi more effectually blockaded than ever before.