For one and a half hours the air was filled with screaming, whistling shot and shell. An occasional Whitworth missile, from Oak Hill on the north, made, on account of its peculiar form, a noise that could be heard above the din of all others. The headquarters of General Meade at the Leister House formed a concentric point continually swept with a storm of shot and shell. Headquarters were therefore moved to Slocum’s headquarters at Powers’ Hill, along the Baltimore Pike. [Illustration: Locations, Buildings and Avenues as referred to in “The Battle of Gettysburg” High-resolution Map] Batteries on the Union line, especially at the Angle, were badly damaged, and General Hunt had others brought forward with additional supplies of ammunition. On the whole the losses inflicted upon the Union infantry were comparatively light. The stone wall and the undulations of the ground afforded protection, as most of the men were lying down. After the artillery had operated for about an hour and a half, Meade and Hunt deemed it prudent to stop the fire, in order to cool the guns, save ammunition, and allow the atmosphere between the lines to clear of the dense cloud of smoke before the expected attack was made. This pause in the fire led the Confederates to believe that the Union line was demoralized, and that the opportune time had arrived for the onset of the infantry. Accordingly, they moved forward and Pickett’s Charge was on. At the signal station on Little Round Top, General Warren and others saw gray infantry moving out across the plain in front of the Spangler Woods. Warren at once wig-wagged to General Hunt: “_They are moving out to attack._” This message was passed from man to man along the entire Union line. [Illustration: Devil’s Den.—Hid among the rocks of Devil’s Den, Confederate sharpshooters picked off officers and men occupying Little Round Top] Pickett’s Charge. Pickett’s Division of Longstreet’s Corps was moved from the rear to the ravine in front of the Spangler Woods and placed in line as follows: Kemper on the right; Garnett on the left in the front line; Armistead in the rear, overlapping Kemper’s left and Garnett’s right, in the second line. On the left of Garnett was ranged Archer’s Brigade of Hill’s Corps under Frye, then Pettigrew’s Brigade under Marshall. Next to Marshall came Davis’ Brigade of Hill’s Corps, and on the extreme left Brockenbrough’s Brigade, also of Hill’s Corps. In the rear of the right of Pickett were the brigades of Wilcox and Perry of Hill’s Corps and in the rear of Pettigrew were the brigades of Scales and Lane of Hill’s Corps, in command of Trimble. The column of assault consisted of 42 regiments—19 Virginia, 15 North Carolina, 2 Alabama, 3 Tennessee, and 3 Mississippi—a total of about 15,000 men.