Symbolism, Imagery, Allegory
The Jolly Roger, the pirate flag with a white skull and crossbones on a black background, represents Long John Silver's authority. When Jim takes over the Hispaniola, one of his first acts is to bring down the pirate colors and drop them into the sea. The good guys have a flag, too: the British Union Jack. This flag represents order, discipline, and national pride, so it's no wonder that Captain Smollett (the most dutiful man in the novel) carries not just one, but several Union Jacks with him. For a further consideration of the Union Jack and its symbolic relation to authority, see our thoughts on Captain Smollett under "Characters."