In Chapter 3 describe Jack.What is he wearing? What looks different now from when he first arrived on the island?

Golding uses the description of Jack at the beginning of Chapter 3 for several purposes.  First, he tells the reader that Jack's hair has grown; it is shaggy and almost covers his eyes.  This of course, connotes the passage of time since the boys first landed on the island.  His clothes are torn and his skin is bronzed from the sun.  Secondly, it is important to note Jack's posture:  He is trailing a pig in a crouched position, almost on all fours.  He is using not only his eyes but also his ears and nose to follow the trail.  Golding is subtly showing the reader that Jack is digressing to a more primitive state, one in which instincts are valued over reason and common sense.  This portrayal sets up the conflict that follows between Jack and Ralph, who is concerned with building a sturdy shelter for the younger boys so they won't be frightened and have nightmares.  Also, Jack carries a stick that has been sharpened to be used as a spear.  As the novel progresses, this stick will eventually be sharpened at both ends, signifying Jack's complete disintegration into savagery.