the heights on the west side of Antietam Creek, displaying a large force of infantry and cavalry, with numerous batteries of artillery, which opened on our columns as they appeared in sight on the Keedysville road and Sharpsburg turnpike, which fire was returned by Captain Tidball's light battery, Second U. S. Artillery, and Pettit's battery, First New York Artillery. The division of General Richardson, following close on the heels of the retreating foe, halted and deployed near Antietam River, on the right of the Sharpsburg road. General Sykes,leading on the division of Regulars on the Old Sharpsburg road, came upend deployed to the left of General Richardson, on the left of the road.

Antietam Creek in this vicinity is crossed by four stone bridges-the upper one on the Keedysville and Williamsport road; the second on the Keedysville and Sharpsburg turnpike, some 2 1/2 miles below; the third about a mile below the second, on the Rohrersville and Sharpsburg road, and the fourth near the mouth of Antietam Creek, on the road leading from Harper's Ferry to Sharpsburg, some 3 miles below the third. The stream is sluggish, with few and difficult fords. After a rapid examination position, I found that it was too late to attack that day, and at once directed the placing of the batteries in position in the center, and indicated the bivouacs for the different corps, massing them near and on both sides of the Sharpsburg turnpike. The corps were not all in their positions until the next morning after sunrise.

On the morning of the 16th it was discovered that the enemy had changed the position of his batteries. The masses of his troops, however, were still concealed behind the opposite heights. Their left and center were upon and in front of the Sharpsburg and Hagerstown turnpike, hidden by woods and irregularities of the ground, their extreme left resting upon a wooded eminence near the cross-roads to the north of J. Miller's farm, their left resting upon the Potomac. Their line extended south, the right resting upon the hills to the south of Sharpsburg, near Snavely's farm.

The bridge over the Antietam, described as Numbers 3, near this point was strongly covered by riflemen, protected by rifle-pits, stone fences, &c., and enfiladed by artillery. The ground in front of this line consisted of undulating hills, their crests in turn commanded by others in their rear. On all favorable points the enemy's artillery was posted, and their reserves, hidden from view by the hills on which their line of battle was formed, could maneuver unobserved by our army, and, from the shortness of their line, could rapidly re-enforce any point threatened by our attack. Their position, stretching across the angle formed by the Potomac and Antietam, their flanks and rear protected by these streams, was one of the strongest to be found in this region of country,which is well adapted to defensive warfare.

On the right, near Keedysville, on both sides of the Sharpsburg turnpike, were Sumner's and Hooker's corps. In advance, on the right of the turnpike and near the Antietam River, General Richardson's division, of General Sumner's corps, was posted. General Sykes' division,of General Porter's corps, was on the left of the turnpike and in line with General Richardson, protecting the Bridge Numbers 2, over the Antietam. The left of the line, opposite to and some distance from Bridge Numbers 3, was occupied by General Burnside's corps.

Before giving General Hooker his orders to make the movement which will presently be described, I rode to the left of the line to

satisfy myself that the troops were properly posted there to secure our left flank from any attack made along the left bank of the Antietam, as well as to enable us to carry Bridge Numbers 3.