The alert horsemen suddenly observed two Union officers coming toward them. Their careless manner showed they had no thought of danger, and they were strolling along, when several dark figures sprang up from the ground, shoved their pistols in their faces, and warned them if they made the least outcry they would be instantly shot. The prisoners saw the shadowy forms all around them, and were sensible enough to submit and give no trouble. The night gradually wore away, and just as it was growing light, and while the Union division on the heights of Cedar Run, where they were posted to protect the rear of General Warren, were preparing breakfast, they were alarmed by the firing of musketry from the advance of a Confederate column coming up the Warrenton road. "That means that Uncle Bob has sent us help!" was the gratified exclamation of Stuart to his delighted friends; "we must take a hand in this business." The cavalry opened fire on the Union lines, which were thrown into some confusion, during which Stuart limbered up his guns and quickly rejoined Ewell. STONEMAN'S RAID. As has been stated, General Hooker at the opening of the battle of Chancellorsville was confident that he was going to defeat Lee. In order to cut off his retreat, he sent General Stoneman, with 2,300 cavalry, on April 28th, to the rear of the Confederate army. Stoneman crossed the Rappahannock at Kelly's Ford, where his force was divided. One-half, led by General Averill, headed for the Orange Railroad, a little way above Culpeper, then occupied by Fitzhugh Lee, with a force of 500 men. He was attacked with such vigor that he hurriedly retreated across the Rapidan, burning the bridges behind him. Averill, instead of pursuing, turned about and made his way back to Hooker, in time to accompany him in his retreat to the northern bank of the Rappahannock. Meanwhile, Stoneman crossed the Rapidan on the 1st of May, and galloped to Louisa Station, on the Virginia Central Railroad, a dozen miles to the east of Gordonsville. There he paused and sent out several detachments, which wrought a great deal of mischief. One of them advanced to Ashland, only fifteen miles from Richmond, while another went still closer to the Confederate capital. These bodies of troopers caused much alarm, and a general converging of the enemy's cavalry caused Stoneman to start on his return, May 6th. For a time he was in great danger, but his men were excellently mounted, and, by hard riding, they effected a safe escape along the north bank of the Pamunkey and York Rivers, and rejoined their friends at Gloucester. GRIERSON'S RAID.