... Lee's cavalry, with a battery of artillery, in all about three thousand five hundred men, crossed the Rappahannock, above Burnside's army, on Saturday, the twenty-seventh ult., and advancing between Brentsville and Stafford Court-House, were joined by Hampton's Legion, when they made a combined attack on Dumfries, on the Lower Potomac, at two o'clock the same afternoon. Dumfries was garrisoned by a port...