When these arrangements had been made, I rode to the position Burnside had selected for himself, which was upon a high knoll northeast of the Burnside bridge, near a haystack which was a prominent landmark. Near by was Benjamin's battery of twenty-pounder Parrotts, and a little further still to the right, on the same ridge, General Sturgis had sent in Durell's battery. [Footnote: _Ibid_.] These were exchanging shots with the enemy's guns opposite, and had the advantage in range and weight of metal. At this point I remained until the order for our attack came, later in the day. We anxiously watched what we could see at the right, and noted the effect of the fire of the heavy guns of Benjamin's battery. We could see nothing distinctly that occurred beyond the Dunker Church, for the East and West Woods with farm-houses and orchards between made an impenetrable screen. A column of smoke stood over the burning Mumma house, marking plainly its situation. As the morning wore on, we saw lines of troops advancing from our right upon the other side of the Antietam, and engaging the enemy between us and the East Wood. The Confederate lines facing them now also rose into view. From our position we looked, as it were, down between the opposing lines as if they had been the sides of a street, and as the fire opened we saw wounded men carried to the rear and stragglers making off. Our lines halted, and we were tortured with anxiety as we speculated whether our men would charge or retreat. The enemy occupied lines of fences and stone walls, and their batteries made gaps in the National ranks. Our long-range guns were immediately turned in that direction, and we cheered every well-aimed shot. One of our shells blew up a caisson close to the Confederate line. This contest was going on, and it was yet uncertain which would succeed, when one of McClellan's staff rode up with an order to Burnside. The latter turned to me, saying we were ordered to make our attack. I left the hill-top at once to give personal supervision to the movement ordered, and did not return to it. My knowledge by actual vision of what occurred on the right ceased. The question at what hour Burnside received this order, has been warmly disputed. The manner in which we had waited, the free discussion of what was occurring under our eyes and of our relation to it, the public receipt of the order by Burnside in the usual and business-like form, all forbid the supposition that this was any reiteration of a former order. [Footnote: I leave this as originally written, although the order itself has since come to light; for the discussion of the circumstantial evidence may be useful in determining the value of McClellan's report of 1863 where it differs in other respects from his original report of 1862 and from other contemporaneous documents. "HEAD-QUARTERS, ARMY OF THE POTOMAC, September 17, 1862,--9.10 A. M.