_A Commissary of Musters._ _A Provost Marshal._ _A Signal Officer._ [These officers are detailed from the line, and have the ranks which there belongs to them. The signal corps is, however, now being organized, with ranks prescribed by law.] _Aides-de-Camp_--one with the rank of major, and two with the rank of captain. Besides these, additional aides are sent to the corps from those created under an act of Congress of 1861--now repealed--and are detailed from the line. * * * * * The quartermaster, commissary, and medical director generally have assistant officers. There is a squadron of cavalry and usually a company of infantry at each corps headquarters. The staffs of divisions and brigades resemble those of the corps, except that the regular staff officers usually rank only as captains, except in cases where a major-general commands; he is entitled to an assistant adjutant-general with the rank of major. Officers detailed from the line to act on any staff in any capacity, bring with them the rank they hold in the line. They are not entitled, except the authorized aides and in some other particular cases, when ordered by the War Department, to additional allowances; but if they are foot officers, and are properly detailed for mounted duty, the quartermaster of the staff on which they serve is obligated to furnish them a horse and equipments. Divisions usually have an _ordnance officer_, whose duty it is to take charge of the ammunition of the division, keep the quantity ordered, and supply the troops in time of battle. By law the chief of artillery at corps headquarters is the chief ordnance officer for the corps, but this arrangement has been found impracticable. In the Army of the Potomac the chief of artillery does not remain at corps headquarters, but is assigned directly to the command of the artillery, where he also has a staff, including an ordnance officer, who supplies ammunition and other articles pertaining to his department, exclusively to the artillery.