The position of the Army of the Potomac is critical in the extreme. But several circumstances come to the rescue. It is almost dark. The rebel lines have become inextricably mixed. Colston, who has gradually moved up to Rodes's support, is so completely huddled together with this latter's command, that there is no organization left. Still Jackson's veterans press on, determined to crush our army beyond recovery, and drive it from United-States Ford. Stuart has in fact, at his own suggestion, got orders to move his cavalry division in that direction, and occupy the road to Ely's. A. P. Hill's division is still intact in rear of the two leading lines, now shuffled into one quite unmanageable mass, but still instinctively pushing forward.

So faulty have Hooker's dispositions been, in advancing his entire right centre without filling the gap, that the only available troops to throw into the breach, after the rapid destruction of the Eleventh Corps, are Berry's division of the old Third. These hardened soldiers are still in reserve on the clearing, north of headquarters. It is fortunate, indeed, that they are still there; for Sickles has just asked for their detail to join his own column out in the woods, and an hour ago Berry would certainly have been sent.

This division is at once thrown across the pike on the first crest below Fairview, west of Chancellorsville. The artillery of the Eleventh Corps is in part re-assembled. Capt. Best, chief of artillery of the Twelfth Corps, has already trained his guns upon the advancing Confederate columns, to protect the new line. But Berry is almost alone. Hays's brigade of the Second Corps, on his right, is his only support. The Excelsior brigade is rapidly pushed into the woods, north of the plank road; the Fourth Excelsior and the First Massachusetts south. Carr's brigade is kept in second line, one hundred and fifty yards in the rear. The men, with the instinctive pride of self-reliance, move up with the steadiness of veterans on drill, regardless of the stream of fugitives breaking through their intervals.

The flight of the Eleventh Corps has stampeded part of the Third Corps artillery. But it is re-assembled in short order, and at once thrown into service. Capt. Best manages by seven P.M. to get thirty-four guns into line on the crest, well served. Himself is omnipresent. Dimick's and Winslow's batteries under Osborn, Berry's chief of artillery, join this line on the hill, leaving a section of Dimick on the road. And such part of the disjecta membra of the Eleventh Corps as retains semblance of organization is gathered in support of the guns. Capt. Best has begun to fire solid shot over the heads of Berry's men into the woods beyond; and, as Gen. Lee says, the Confederate advance is checked in front of this crest by the vigorous opposition encountered.

Hurried orders are despatched to Geary to withdraw his attack, and re-occupy his breastworks. This he straightway accomplishes. Similar orders are carried to Williams. But, before the latter can retrace his steps, Jackson's columns have reached the right of his late position. Anderson also advances against him; so that Williams is obliged to move cautiously by his left, and change front when he arrives where his line had lately joined Geary's and, being unable to take up his old post, he goes into position, and prolongs Berry, south of the pike. It is long after dark before he ascertains his bearings, and succeeds in massing his division where it is needed.

Anxious as Jackson is to press on,—"Give me one hour more of daylight, and I will have United-States Ford!" cries he,—he finds that he must re-establish order in his scattered forces before he can launch this night attack upon our newly formed but stubbornly maintained lines.

Nor is the darkness the most potent influence toward this end. Illy as Sickles's advance has resulted thus far, it is now a sovereign element in the salvation of the Army of the Potomac. His force at the Furnace, Birney, Whipple, Barlow, and Pleasonton, amounts to fifteen thousand men, and over forty guns. None of these officers are the men to stand about idle. No sooner has Sickles been persuaded by a second courier,—the first he would not credit,—that the Eleventh Corps has been destroyed, and that Jackson is in his rear, than he comprehends that now, indeed, the time has come to batter Jackson's flank. He orders his column to the right about, and moves up with all speed to the clearing, where Pleasonton has held his cavalry, near Birney's old front.

Howard, upon being attacked, had sent hurriedly for a cavalry regiment. Pleasonton, having received orders to send him one, instructed Major Huey, commanding the Eighth Pennsylvania Cavalry, to march to Dowdall's and report to Howard. Huey set out by the wood road which leads through Hazel Grove into the plank road. From the testimony of the persons chiefly concerned it would appear that, at the time this order was given by Pleasonton to Huey, there was at Hazel Grove, where the cavalry regiments were drawn up, no sign whatever of the disaster to Howard. There were no fugitives nor any confusion. Nor does the evidence show that Pleasonton ordered any charge on the enemy: it rather shows that Huey was not directed to go at urgent speed. And he must have been very deliberate in his movement, for by the time the cavalry had reached the vicinity of the plank road, Jackson had demolished the Eleventh Corps, and had advanced so far that the head of this cavalry column, marching by twos, suddenly came upon the Confederate lines. The officers in the lead at once gave the order to charge, and right gallantly did these intrepid horsemen ride down into the seething mass of exultant Confederate infantry. The shock was nobly given and home, but was, of course, in the woods and against such odds, of no great effect. Thirty men and three officers, including Major Keenan, were killed. Only one Confederate report—Iverson's—mentions this charge. Its effect was local only.

Three batteries of Whipple's division had remained in the Hazel Grove clearing while the infantry had advanced towards the Furnace. When the rout of the Eleventh Corps became clear, these eighteen guns were ordered in battery, facing about north-west, by their commander, Capt. Huntington, and kept up a heavy fire upon the woods through which Jackson was pushing his way. Pleasonton, for his part, trained Martin's horse-battery in the same direction. Other guns were later added to these, and all expended a good deal of ammunition on the enemy's lines. But there was no fighting at Hazel Grove rising to the distinction of a battle. The importance given to it by Sickles and Pleasonton is not borne out by the facts. There was no Federal loss, to speak of; nor do the Confederate reports make any comment upon this phase of the battle. They probably supposed these guns to be an extension of the line of batteries at Fairview. As such they were, without question, of no inconsiderable use.

Meanwhile Birney, sending word to Barlow that they run danger of being cut off, and detailing the Twentieth Indiana and Sixty-third Pennsylvania Volunteers as rearguard, rejoins Sickles and Pleasonton in the clearing, and both move up to sustain his flank.

So soon as Jackson's guns gave Lee the intimation of his assault, the latter advanced upon the Union line with sufficient vigor to prevent Hooker from sending re-enforcements to his right. The attack was sharp; and a general inclination to the left was ordered, to connect with Jackson's right as the latter brought his columns nearer. "These orders were well executed, our troops advancing up to the enemy's intrenchments, while several batteries played with good effect upon his lines until prevented by increasing darkness." (Lee.)

McLaws reports: "My orders were to hold my position, not to engage seriously, but to press strongly so soon as it was discovered that Gen. Jackson had attacked... when I ordered an advance along the whole line to engage with the skirmishers, which were largely re-enforced, and to threaten, but not attack seriously; in doing which Gen. Wofford became so seriously engaged, that I directed him to withdraw, which was done in good order, his men in good spirits, after driving the enemy to their intrenchments."

The movement of Anderson towards the left made a gap of considerable distance in the Confederate line "but the skirmishers of Gen. Semmes, the entire Tenth Georgia, were perfectly reliable, and kept the enemy to his intrenchments."

These accounts vary in no wise from those of the Union generals, who held their positions in front of both Anderson and McLaws, and kept inside their field-works.

Meade, whose line on the left of the army was not disturbed, sent Sykes's division, so soon as the Eleventh Corps rout became known to him, to the junction of the roads to Ely's and United-States Fords, to hold that point at all hazards, and form a new right flank. This was done with Sykes's accustomed energy. Nor was he reached by Jackson's line, and before morning Reynolds fell in upon his right.