Brigade officers of the Horse Artillery commanded by Lt. Col. William Hays. Standing, left to right: Lt. Edmund Pendleton, PLt. Alex C. M. Pennington, Capt. Henry Benson, Capt, H. M. Gibson, Lt. James E. Wilson, Capt. John C. Tidball, Lt. William N. Dennison. Seated, left to right: Capt. Horatio Gibson, Lt. Peter C. Hains, Lt. Col. William Hays, Capt. James M. Robertson, Lt. J. W. Barlow. Seated on the ground, left to right: Lt. Robert H. Chapin, Lt. Robert Clarke, A.C. Vincent. (Library of Congress)