From Fortress Monroe.
Fortress Monroe, July 18.
--Steamers from Norfolk have been landing troops at Sewell's Point, where there is apparently a formidable force.
Preparations are being made to annoy the Federal shipping; doubtless by masked batteries at Willoughby's Point, and opposite the Rip Raps.
Two negroes from Pig's Point report the Southerners in considerable force opposite Newport News.