Chap 10, part 11
"There's a better one a little farther on, Jim," he said soothingly. Here Jimmy Reynolds joined the conversation.
"He wouldn't have dared stop on that island anyway, Jim," he said. "I don't know whether I should tell you fellows or not, but they are drilling secretly for oil there. I saw the big condensers they use to get water from the sea."
"What's that? What's that?" This was Rick yelling over from the other raft.
"The oil is a secret," Jimmy went on, "but I think Bill Cherry knows all about it."