The reason which prompted this bold and enterprising commander to observe unusual circumspection in his advance up the Cumberland Valley is obvious. He held the extreme right of the rebel line, whose left could not have been much short of fifty miles distant. The militia of Pennsylvania, Ohio, New Jersey and New York, had been summoned in haste to the border, and for ten days they had been pouring down in unknown numbers. Thus Ewell found himself confronted by an unreckoned host, whose numbers would naturally, by one in his exposed situation, be magnified. The position of defence was a strong one, and to have failed in an assault upon it might easily have involved his destruction, and, as a consequence, the destruction of the whole rebel army. Could he have had a day or two longer to enable him to gain correct information of the strength of the works, and of the garrison, he would not probably have hesitated to attempt the capture of the place. But the action of the great drama was now moving forward with startling rapidity. Meade was concentrating on the flank of Lee, who saw that not a day was to be lost in distant and secondary expeditions. Ewell was accordingly recalled with all haste; and happy had it been for the Union cause had the General commanding the Department of the Susquehanna been early enough apprised of the hurried withdrawal of the enemy to make the services of the militia available at Gettysburg. But the defence of Harrisburg, which was the main objective of General Lee in his raid up the Susquehanna Valley, is not the only title which the New York Militia hold to the gratitude of Pennsylvania and of the Nation. Who shall undertake to say how far the result of the battle of Gettysburg was determined by the fact of Union militia reinforcements being near at hand--their strength vastly over-estimated, there is no doubt, by both armies? Indeed there was reason to suppose, and many believed, while the battle was raging, that they had already come up and were actually engaged. The moral effect of such a report circulated through the ranks of contending forces, and even half credited, is immense. The one it fills with enthusiasm and animates to heroic endurance, for it summons them to victory; the other it fills with terror, and makes effort seem useless, for it is to them the omen of coming defeat. Nevertheless there can be little doubt that at the close of the third day of conflict the rebel army was still a powerful host--its organization not irreparably broken, its numbers equal if not, indeed, superior to those opposed to it. True, it had been repulsed with terrible slaughter, but it was far from being vanquished, for it was made up of hardy and oft victorious veterans, to whom repulse was not defeat. General Meade did not feel strong enough to assume the offensive; and who shall undertake to say that there had yet arisen an imperious necessity for the withdrawal of Lee across the