The Third Corps is being overpowered—here and there its lines begin to break—the men begin to pour back to the rear in confusion—the enemy are close upon them and among them—organization is lost to a great degree—guns and caissons are abandoned and in the hands of the enemy—the Third Corps, after a heroic but unfortunate fight, is being literally swept from the field. That Corps gone, what is there between the Second Corps, and these yelling masses of the enemy? Do you not think that by this time we began to feel a personal interest in this fight? We did indeed. We had been mere observers—the time was at hand when we must be actors in this drama.

Up to this hour Gen. Gibbon had been in command of the Second Corps, since yesterday, but Gen. Hancock, relieved of his duties elsewhere, now assumed command. Five or six hundred yards away the Third Corps was making its last opposition; and the enemy was hotly pressing his advantages there, and throwing in fresh troops whose line extended still more along our front, when Generals Hancock and Gibbon rode along the lines of their troops; and at once cheer after cheer—not Rebel, mongrel cries, but genuine cheers—rang out all along the line, above the roar of battle, for “Hancock” and “Gibbon,” and “our Generals.” These were good. Had you heard their voices, you would have known these men would fight. Just at this time we saw another thing that made us glad:—we looked to our rear, and there, and all up the hillside which was the rear of the Third Corps before it went forward, were rapidly advancing large bodies of men from the extreme right of our line of battle, coming to the support of the part now so hotly pressed. There was the whole Twelfth Corps, with the exception of about one brigade, that is, the larger portion of the Divisions of Gens. Williams and Geary; the Third Division of the First Corps, Gen. Doubleday; and some other brigades from the same Corps—and some of them were moving at the double quick. They formed lines of battle at the foot of the Taneytown road, and when the broken fragments of the Third Corps were swarming by them towards the rear, without halting or wavering they came sweeping up, and with glorious old cheers, under fire, took their places on the crest in line of battle to the left of the Second Corps. Now Sickles’ blunder is repaired. Now, Rebel chief, hurl forward your howling lines and columns! Yell out your loudest and your last, for many of your best will never yell, or wave the spurious flag again!

The battle still rages all along the left, where the Fifth Corps is, and the West slope of Round Top is the scene of the conflict; and nearer us there was but short abatement, as the last of the Third Corps retired from the field, for the enemy is flushed with his success. He has been throwing forward brigade after brigade, and Division after Division, since the battle began, and his advancing line now extends almost as far to our right as the right of the Second Division of the Second Corps. The whole slope in our front is full of them; and in various formation, in line, in column, and in masses which are neither, with yells and thick volleys, they are rushing towards our crest. The Third Corps is out of the way. Now we are in for it. The battery men are ready by their loaded guns. All along the crest is ready. Now Arnold and Brown—now Cushing, and Woodruff, and Rhorty!—you three shall survive to-day! They drew the cords that moved the friction primers, and gun after gun, along the batteries, in rapid succession, leaped where it stood and bellowed its canister upon the enemy. The enemy still advance. The infantry open fire—first the two advance regiments, the 15th Mass. and the 82d N. Y.—then here and there throughout the length of the long line, at the points where the enemy comes nearest, and soon the whole crest, artillery and infantry, is one continued sheet of fire. From Round Top to near the Cemetery stretches an uninterrupted field of conflict. There is a great army upon each side, now hotly engaged.

To see the fight, while it went on in the valley below us, was terrible,—what must it be now, when we are in it, and it is all around us, in all its fury?

All senses for the time are dead but the one of sight. The roar of the discharges and the yells of the enemy all pass unheeded; but the impassioned soul is all eyes, and sees all things, that the smoke does not hide. How madly the battery men are driving home the double charges of canister in those broad-mouthed Napoleons, whose fire seems almost to reach the enemy. How rapidly these long, blue-coated lines of infantry deliver their file fire down the slope.

But there is no faltering—the men stand nobly to their work. Men are dropping dead or wounded on all sides, by scores and by hundreds, and the poor mutilated creatures, some with an arm dangling, some with a leg broken by a bullet, are limping and crawling towards the rear. They make no sound of complaint or pain, but are as silent as if dumb and mute. A sublime heroism seems to pervade all, and the intuition that to lose that crest, all is lost. How our officers, in the work of cheering on and directing the men, are falling.

We have heard that Gen. Zook and Col. Cross, in the First Division of our Corps, are mortally wounded—they both commanded brigades,—now near us Col. Ward of the 15th Mass.—he lost a leg at Balls Bluff—and Lieut. Col. Horton of the 82d N. Y., are mortally struck while trying to hold their commands, which are being forced back; Col. Revere, 20th Mass., grandson of old Paul Revere, of the Revolution, is killed, Lieut. Col. Max Thoman, commanding 59th N. Y., is mortally wounded, and a host of others that I cannot name. These were of Gibbon’s Division. Lieut. Brown is wounded among his guns—his position is a hundred yards in advance of the main line—the enemy is upon his battery, and he escapes, but leaves three of his six guns in the hands of the enemy.

The fire all along our crest is terrific, and it is a wonder how anything human could have stood before it, and yet the madness of the enemy drove them on, clear up to the muzzle of the guns, clear up to the lines of our infantry—but the lines stood right in their places. Gen. Hancock and his Aides rode up to Gibbon’s Division, under the smoke. Gen. Gibbon, with myself, was near, and there was a flag dimly visible, coming towards us from the direction of the enemy. “Here, what are these men falling back for?” said Hancock. The flag was no more than fifty yards away, but it was the head of a Rebel column, which at once opened fire with a volley. Lieut. Miller, Gen. Hancock’s Aide, fell, twice struck, but the General was unharmed, and he told the 1st Minn., which was near, to drive these people away. That splendid regiment, the less than three hundred that are left out of fifteen hundred that it has had, swings around upon the enemy, gives them a volley in their faces, and advances upon them with the bayonet. The Rebels fled in confusion, but Col. Colville, Lieut. Col. Adams and Major Downie, are all badly, dangerously wounded, and many of the other officers and men will never fight again. More than two-thirds fell.

Such fighting as this cannot last long. It is now near sundown, and the battle has gone on wonderfully long already. But if you will stop to notice it, a change has occurred. The Rebel cry has ceased, and the men of the Union begin to shout there, under the smoke, and their lines to advance. See, the Rebels are breaking! They are in confusion in all our front! The wave has rolled upon the rock, and the rock has smashed it. Let us shout, too!

First upon their extreme left the Rebels broke, where they had almost pierced our lines; thence the repulse extended rapidly to their right. They hung longest about Round Top, where the Fifth Corps punished them, but in a space of time incredibly short, after they first gave signs of weakness, the whole force of the Rebel assault along the whole line, in spite of waving red flags, and yells, and the entreaties of officers, and the pride of the chivalry, fled like chaff before the whirlwind, back down the slope, over the valley, across the Emmetsburg road, shattered, without organization in utter confusion, fugitive into the woods, and victory was with the arms of the Republic. The great Rebel assault, the greatest ever made upon this continent, has been made and signally repulsed, and upon this part of the field the fight of to-day is now soon over. Pursuit was made as rapidly and as far as practicable, but owing to the proximity of night, and the long distance which would have to be gone over before any of the enemy, where they would be likely to halt, could be overtaken, further success was not attainable to-day. Where the Rebel rout first commenced, a large number of prisoners, some thousands at least, were captured; almost all their dead, and such of their wounded as could not themselves get to the rear, were within our lines; several of their flags were gathered up, and a good many thousand muskets, some nine or ten guns and some caissons lost by the Third Corps, and the three of Brown’s battery—these last were in Rebel hands but a few minutes—were all safe now with us, the enemy having had no time to take them off.