Complex sentence: She formed part of a squadron under Commodore Owen which was patrolling off the French port of Boulogne, and on 8 October took part in the bombardment of the town using Congreve rockets.
Split into simpler sentences: She formed part of a squadron under Commodore Owen that was patrolling off the French port of Boulogne. On 8 October she took part in the bombardment of the town using Congreve rockets.