Transcription: After ten hours walking, we sat down to eat. We ate ravenously. One thing however caused us great uneasiness. Our water reserve was already half exhausted. We had only five days supply left, but my uncle was confident we would find subterranean resources. I was also surprised that the heat was not greater than it was. What does the thermometer say? asked the professor. Scarcely 15 degrees, I said. It's an increase of nine degrees since we left. What do you make of that? he asked. Well, I explained as best I could, we know from observations that temperature increases for every 100 feet you go i ...
