The quartermaster was directed, also, to throw all his supplies, not burned or sent to the army, up the James river, and there establish depots of supplies. General Casey, who was now in command of the guard at White House, was instructed to see these orders carried out. He burned immense quantities of stores, consisting of clothing, subsistence, and other war material, and then hastily marched his force to rejoin the army.

The evening of the 26th was passed in gladness over our victory; but while the army was rejoicing at this temporary success, it was losing one of the grandest opportunities ever presented it for entering the rebel capital. The whole plan of Lee had been based upon a false calculation; and had this mistake been improved by our commanders, the history of the war would have been entirely changed. Both Lee and Davis believed that the main body of our army was on the north side of the Chickahominy; whereas, of the five corps constituting our army, only one, that of Porter, remained on that side. Under this erroneous impression, Lee had brought nearly the whole of his army across the river to assail the Union army on its right. This was known to our generals, for while positive information had been received that Jackson, with his large army, was making for our rear, the prisoners taken during the day were from Hill's command, and from them it was known that the troops of A. P. Hill, Longstreet and D. H. Hill, were confronting us on the right. Thus, between our main force, of over seventy-six thousand men, and Richmond, less than twenty-five thousand rebels guarded their extensive line of works. A concentrated assault of the four corps on the south side of the river must have resulted in the utter rout of the force opposed to them, and the road to Richmond would have been opened.

But the error of General Lee was never suspected, and this grand opportunity was lost.

During the night of the 26th, the heavy artillery and baggage of Porter's corps was all sent across the river. McCall's whole division, except a line of pickets left as a blind, also fell back five miles below, to the vicinity of the bridge at Gaines' Farm, where the three divisions of the corps united.

The astonishment of the men on the south side of the river on discovering, in the morning, that Porter's corps had fallen back, was only equaled by their mortification and disappointment, as they saw the long lines of rebels advancing in the gray of the morning against our retreating column.

They had believed, when night came on, that our arms had achieved the first of a series of victories which was to give us the rebel capital. Now they saw that our army was already in retreat, and they gazed at the long train of artillery and wagons, which had parked near us, with downcast faces. From our camp, Porter's division could be distinctly seen, and we could watch the movements of the rebels as they arrived upon the highlands, formed their line on the range of hills opposite Porter, and planted their guns near the large barn on Dr. Gaines' farm.

The position of Porter's corps was a strong one; and he was ordered to hold it till night, and then to cross the bridge and burn it after him; the upper bridge having been burned during the night. The country between the two lines was rolling, somewhat wooded, but in parts cleared. Both parties went to work to cut down trees in their front.

The rebel forces, who supposed on the 26th that they were fighting our main army, were surprised, on the morning of the 27th, to find that only a picket line opposed them. They were early astir; and advancing against the slender line, drove it back. The whole rebel force advanced cautiously; A. P. Hill and Longstreet bearing to the right, while D. H. Hill turned to the left, to unite with Jackson, who was supposed to be coming in from the rear. Owing to the uneven country over which they were advancing, their march was slow; for they might fall upon a Union line of battle behind any rounding swell of land.

It was afternoon before the rebel army had fully formed its line on Gaines' Farm. The position of that army was nearly that of the same army when Grant attacked it at Coal Harbor two years later, only it was faced about. The battle opened about one o'clock, by skirmishing on both sides; but it was not till an hour later that Hill's division dashed across the open space, rushing through the swamp, and under a severe fire from our batteries and musketry, pushed up the slope on which was posted our line. The confederate troops advanced almost up to Sykes' line of battle on the right, and in other parts of the line actually forced back the Union troops; but they were able to hold their position only a short time, when they were forced back with great loss.

Longstreet now advanced against the left of our line, but he too met with a stern reception, and he withdrew to rearrange his plan of attack.