Complex sentence: The lugger turned out to be the "Mouche" of Boulogne, commanded by a M. Gageux, and mounting fourteen 12-pounder and 6-pounder guns.
Split into simpler sentences: The lugger turned out to be the "Mouche" of Boulogne, under the command of M. Gageux. She had carried fourteen 12-pounder and 6-pounder guns.