Ewell began his demonstration at 4 p.m. upon hearing the sound of Longstreet's guns to the south. For three hours, he chose to limit his demonstration to an artillery barrage from Benner's Hill, about a mile (1,600 m) to the northeast. Although the Union defenders on Cemetery Hill received some damage from this fire, they returned counterbattery fire with a vengeance. Cemetery Hill is over 50 feet (15 m) taller than Benner's Hill, and the geometry of artillery science meant that the Union gunners had a decided advantage. Ewell's four batteries were forced to withdraw with heavy losses, and his best artillerist, 19-year-old Joseph W. Latimer, the "Boy Major", was mortally wounded.