"But I thought the air at A had risen."
"Not all of it. And that makes it rain."
"Why?"
"Oh, well, I can't go into that. It's something to do with condensation. Air absorbs more moisture when it is hot than when it is cold—"
"So do I. I understand that."
"When the air cools the water condenses."
"Is it fine then?"
"No, it rains, you fool."
"When is it fine?"
"Wait a bit. The falling of the rain of course generates heat—"