In Chapter 6, when the boys roll a rock into the sea, what is Ralph's reaction?
Here's the bit from the novel you need:
A knot of boys, making a great noise that he had not noticed, were heaving and pushing at a rock. As he turned, the base cracked and the whole mass toppled into the sea so that a thunderous plume of spray leapt half-way up the cliff.
“We want smoke. And you go wasting your time. You roll rocks."
Here's Ralph's reaction very clearly. He's desperately trying to keep a hold on his authority as chief, and of the adult mode of thinking he's earlier found in this chapter. He knows in his heart that they need to focus on the signal, and he knows that the boys' behaviour is an unhelpful distraction. So he tries to assert his authority and control over them and tell them what to do. And he can feel the dissent breeding.
At the end of the chapter, Ralph reasserts this logic, to a disconcertingly quiet response from the boys:
"I’m chief. We’ve got to make certain. Can’t you see the mountain? There’s no signal showing. There may be a ship out there. Are you all off your rockers?”