PROMOTION IN THE NINETY-FIRST REGIMENT PENNSYLVANIA VOLUNTEERS.--Lieutenant HORACE B. FAUST has been promoted to Captain of Company D, the former Captain, JOSEPH H. SINEX, having received promotion to Lieutenant-Colonel of the regiment. Lieut. HALL has been promoted to Captain of Company E, and Captain JOHN D. LENTZ to Major of the regiment in place of Major TODD, who was killed at the battle of Fredericksburg, Va.