...the rest of the army should be in supporting distance, and Longstreet and Hill marched to the Potomac. The former crossed at Williamsport, and the latter at Shepherdstown. The columns reunited at Hagerstown , and advanced thence into Pennsylvania, encamping near Chambersburg on the 27th. No report had been received that the Federal army had crossed the Potomac, and the absence of the cavalry rendered i...