...'s brigades of infantry acted as rear-guard to the column. My reserve ordnance train, of about 80 wagons, had accompanied Lee's headquarters to Hagerstown, and had also followed the march back to Boonsboro . I was now ordered to cross the Potomac at Williamsport, and go thence to Shepherdstown, where I should leave the train and come in person to Sharpsburg. The moon was rising as I started, and abo...