The Ninth Corps occupied its position on the heights west of the Antietam without further molestation, except an irritating picket firing, till the Confederate army retreated on the 19th of September. But the position was one in which no shelter from the weather could be had, nor could any cooking be done; and the troops were short of rations. My division wagon-train, which I had brought from the West, here stood us in good stead, for the corps as a whole was very short of transportation. The energy of Captain Fitch, my quartermaster, forced the train back and forth between us and the nearest depot of supplies, and for several days the whole corps had the benefit of the provisions thus brought forward. Late in the afternoon of Thursday the 18th, Morell's division of Porter's corps was ordered to report to Burnside to relieve the picket line and some of the regiments in the most exposed position. One brigade was sent over the Antietam for this purpose, and a few of the Ninth Corps regiments were enabled to withdraw far enough to cook some rations, of which they had been in need for twenty-four hours. [Footnote: General Porter in his report says Morell took the place of the whole Ninth Corps. In this he is entirely mistaken, as the reports from Morell's division, as well as those of the Ninth Corps, show.] Harland's brigade of Rodman's division had been taken to the east side of the stream to be reorganized, on the evening of Wednesday the 17th. The sounds heard within the enemy's lines by our pickets gave an inkling of their retrograde movement in the night of Thursday, and at break of day on Friday morning the retreat of Lee's whole army was discovered by advancing the picket line. Reconnoissances sent to the front discovered that the whole Confederate army had crossed the Potomac.