"But how do you know, Capt. Drummond?"
"I know by the signs," said the Captain.
"What is an old rock? how old?"
"I am sure I can't say, Daisy. Only that a young rock is apt to be a good deal older than Adam and Eve."
"How can you tell that?"
"When you see a man's hair grey, can't you tell that he is old?"
"But there are no grey hairs in rocks?" said Daisy.
"Yes, there are. Trilobites do just as well."
"But I say," said Daisy laughing, "how can you tell that the rock is old? You wouldn't know that grey hairs were a sign, if you saw them on young people."
"Pretty well, Daisy!" said the Captain, delighted to see her interested in something again;—"pretty well! But you will have to study something better than me, to find out about all that. Only it is true."