Cannon is a large gun used to fire various forms of projectiles at an enemy. On board British ships cannon took two forms, the long gun and the carronade.
Both forms of cannon fired black powder and the projectiles took many forms such as round shot, barshot, grapeshot, canistershot, and others.
A tampion is a plug kept in the muzzle of a cannon to keep out weather when the cannon is not in use.
Cannon at Wikipedia.