At first, the signal fire symbolizes rescue. But as it grows out of control, it symbolizes danger and death, foreshadowing how it will later become associated with destruction and savagery.
In chapter 2, Jack begins to display his domineering, disruptive behavior by interrupting Ralph's speech and unceremoniously ending the assembly as soon as Ralph mentions a signal fire. Jack's violent behavior and antagonistic attitude directed at Piggy foreshadows their future conflicts.
