Some rocks are young, and some are old, you know.

This is one of the old rocks." "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.