WHAT IS THE REBEL ARMY OF VIRGINIA ABOUT? – There seems to be a great deal of ignorance and some little alarm at Washington concerning the mysterious movements of the rebel army in front of General Hooker. Is Lee sending off reinforcements to Suffolk, or to Tennessee, or to Vicksburg, or is he moving for another invasion of Maryland? Why not make an effort in the way of a reconnoissance to find out where General Lee’s strength really lies, and what it amounts to? Why there should be any mystery as to the present strength and positions occupied by Lee’s army we cannot divine, when General Stoneman and his splendid body of horsemen can in a few days settle all doubts upon the subject.