After Jack invades the camp and steals Piggy's glasses, what does Ralph do?
Ralph tries, desperately in vain, to relight the fire, blowing where the fire used to be:
Ralph continued to blow till his ears were singing with the effort, but then the first breeze of dawn took the job off his hands and blinded him with ashes. He squatted back, swore, and rubbed water out of his eyes.
Eric looked down at him through a mask of dried blood. Piggy peered in the general direction of Ralph.
“ ’Course it’s no use, Ralph. Now we got no fire.”
Without the glasses, there's no way they can make a signal fire. Piggy is the one who suggests the real idea:
I’m going to him [Jack] with this conch in my hands. I’m going to hold it out. Look, I’m goin’ to say, you’re stronger than I am and you haven’t got asthma. You can see, I’m goin’ to say, and with both eyes. But I don’t ask for my glasses back, not as a favor. I don’t ask you to be a sport, I’ll say, not because you’re strong, but because what’s right’s right. Give me my glasses, I’m going to say—you got to!
And that's what they eventually do. Ralph is very quiet, listening to the suggestions from Piggy and Samneric, and then eventually just says "Let's go". It turns out to be Piggy's last trip.