What are the distinguishing qualities and characteristics of each important character?

There are four main characters in Edgar Allan Poe's story "The Gold-Bug."
Narrator: The nameless narrator is a friend of Legrand. He gives very few details about himself in the story, instead functioning as a sort of neutral background against which Legrand is foregrounded. His style of speech and actions make him appear amiable, relatively well-educated, and in comfortable financial circumstances. 
Mr. William Legrand: Legrand, the protagonist of the novel, is described as being from wealthy "ancient Huguenot family" from New Orleans. Reduced to poverty by various undescribed "misfortunes," Legrand now lives in a hut on the rather remote and sparsely inhabited Sullivan's Island. He is portrayed as eccentric, intelligent, moody, and possessed of a certain sense of humor. 
Jupiter: Legrand's servant Jupiter is a freed slave, elderly and loyal, who speaks in dialect. He acts as a foil to Legrand, lacking his abstract intelligence, but possessing a degree of folk wisdom and common sense, and a cheerful and even temperament as opposed to Legrand's fits of enthusiasm and more erratic emotions. 
Lieutenant G.: Only mentioned briefly in the story, Lieutenant G. is an officer and amateur etymologist, as well as a friend to Legrand.