The month of October passed. Pontoons were finally laid across the Potomac. They were down several days before the enemy moved, and General Lee, through his scouts and spies, undoubtedly had information of what was going on. The army commenced crossing on the 27th, but the divisions were not all over till the 1st of November. Lee had moved a week before, and was at Culpepper, with the exception of his rear-guard, Stuart's cavalry, and a force in the Shenandoah Valley. Up to this period of the war there had been but few brilliant cavalry achievements on either side. At Springfield, Missouri, Zagonyi, with his fearless riders, had cut their way through the hosts which surrounded them. It was gloriously done. The cavalry, with the army of the Potomac on the Peninsula, had accomplished nothing worthy of mention. General Stuart, commanding the Rebel cavalry, had audaciously rode round General McClellan's army at the Chickahominy and at Harper's Ferry. On the march from Berlin to Warrenton, General Pleasanton commanded the Union cavalry. He had the advance in the line of march. General Stuart covered the retreat of Lee. Day after day, from morning till night, there was an interchange of shots by the flying artillery of both armies,--Stuart holding his ground till Pleasanton's fire became too hot, then limbering up his guns, and retiring a mile to a new position. The Rebels had not all left the Shenandoah Valley. But a force of ten thousand men remained there prepared to pass through the gaps of the Blue Ridge, and fall on McClellan's rear, if he left it exposed. General Hancock's division of Porter's corps, which was nearest the Blue Ridge, or which held the right of the army, in its march, moved upon Snicker's Gap. Arriving at the top and looking westward, there was a beautiful panorama; the town of Winchester, its white houses and church spires gleaming in the November sun; the trees yet wearing their gorgeous livery; the numerous camp-fires of the enemy on the western bank of the Shenandoah; the blue smoke rising in columns and spirals to the clouds, the troops of the enemy moving with their long baggage trains towards the south. Captain Pettit wheeled his Parrott guns into position on the top of the mountain, and sighted the guns. The first shell exploded in the Rebel line. In an instant, evidently without waiting for orders, the men took to their heels, disappearing in the woods. An unexpected shot sometimes unnerves old soldiers, who never think of shrinking from duty on the battle-field.