What does Ralph do once at the entrance of the Castle Rock?

As the boys approach Castle Rock, they are very nervous
about the whole situation, the drop to the sea below them, the fact that the other boys
are hiding, etc.  Ralph steps forward as the leader and takes the conch and begins to
blow on it, as though he is calling the boys to an assembly in the old
way.

He tries to tell the boys that he now sees as savages
that he is calling an assembly, expecting that perhaps they will respond out of a sense
of duty.

Once Jack returns from his hunting trip, however,
it becomes apparent that they are not going to be able to resolve their situation.  The
hunters are not willing to give back the glassesand the conflict leads to Piggy's
death.