Petty Officer

Encyclopedia Appendix C - Petty Officers
Master-at-Arms - This is different from others, in that he is a Petty Officer, but holds a Warrant from the Admiralty. The Master-at-Arms provided the ship's police force. The Master-at-Arms was aided by one or more of the ship's Corporals. During battle the Master-at-Arms manned the light room with the Cook.