...he Potomac. We have intelligence that McDowell is making preparations to advance against our forces at Manassas. Gen. Johnston is expected to be there in time; and for that purpose is manoeuvring Gen. Patterson out of the way. Our men have caps now-and will be found in readiness. They have shortcommons under the Commissary Department; but even with empty stomachs, they can beat the Yankees at the ordeal o...