Rumors and Threats.
Washington, Aug. 20.
--There are rumors of fighting near the Chain Bridge, but they are doubtless untrue.
The National Republican, (Lincoln's organ,) referring to the supposed intention of the Confederates of crossing the Potomac, for the purpose of invading lower Maryland, says that ‘"negro insurrections are more probable,"’ and threatens ‘"a formidable emancipation movement unless the holders of slaves are loyal."’