The position of Porter and Couch was every moment becoming more critical, as everything depended upon the successful resistance of what was felt to be the enemy’s final assault. Sickles and Meagher were ordered to withdraw their brigades, as soon as it was considered prudent, and to reinforce the part of the line which was being so hardly pressed. Certain regiments of Porter’s and Couch’s division had entirely expended their ammunition, and their places were at once filled from the Sickles and Meagher brigades; and batteries from the rear were pushed forward to supply the place of those who were exhausted. The enemy was slow to acknowledge himself beaten, and, until dark, persisted in unwearied efforts to take the position so tenaciously held by the patriots. Despite his vastly superior numbers, however, he was continually repulsed as often as he attacked, till darkness ended the battle of Malvern Hill, though artillery firing continued up to nine o’clock. The loss sustained by General McClellan’s army, in the course of those bloody engagements that marked the retreat from the Chickahominy to Harrison’s Landing was very heavy. McClellan himself computed the loss at upwards of 15,000 men. The stubborn resistance and gallant courage of the Union soldiers, at Malvern Hill, preserved the army from sad discomfiture, if not destruction. The withdrawal to Harrison’s Landing was, however, regarded with great disfavor by many Union officers, and to the people of the North was the occasion of much criticism and regret. Gloom succeeded cheerful hope, in the bosoms of many patriots, at this juncture, and it was not until good news arrived from the west and southwest, that confidence in the success of the Union arms was again revived. The Army of the Potomac, meanwhile, took a short season of rest, preparatory to new movements. EVACUATION OF PENSACOLA. MAY 9, 1862. On the night of the 9th of May, the rebels, believing that an attack was about to be made by the Union fleet, under Captain, now Commodore Porter, set fire to the Pensacola Navy Yard, Fort McRea, the Naval Hospital, Warrington, and Pensacola itself. General Arnold, divining their destructive object, immediately opened fire from Fort Pickens, and kept up a heavy bombardment, for five hours, thus preventing the rebels from fulfilling their plan, which contemplated the destruction of the entire town. A demand was then made for the surrender of Pensacola, and, Mayor Bode complying, the Union forces took possession of the place, capturing a quantity of valuable lumber, many thousand dollars’ worth of oil, and rebel arms and equipments. The enemy, however, had succeeded in destroying a good deal of property, and had then retired, about one thousand strong, led by General Bragg, to a camp, five miles outside of Mobile.