“Can’t just say, Daisy.  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.  Only it is true.”

“And you were not laughing?”

“Not a bit of it.  That little fellow, I suppose, lived a thousand million years ago; may as well say a thousand as anything.”

“I can’t see how you can tell,” said Daisy, looking puzzled.

“That was a strange old time, when he was swimming about—­or when most of them were.  There were no trees, to speak of; and no grass or anything but sea-weed and mosses; and no living things but fishes and oysters and such creatures?”

“Where were the beasts then, and the birds?”

“They were not made yet.  That’s the reason, I suppose, there was no grass for them to eat.”

Daisy looked down at the trilobite; and looked profoundly thoughtful.  That little, shiny, black, stony thing, that had lived and flourished so many ages ago!  Once more she looked up into the Captain’s face to see if he were trifling with her.  He shook his head.

“True as a book, Daisy.”

“But Capt.  Drummond, please, how do you know it?”

“Just think, Daisy,—­this little fellow frolicked away in the mud at the bottom of the sea, with his half moons of eyes—­and round him swam all sorts of fishes that do not live now-a-days; fishes with plate armour like himself; everybody was in armour.”

“Half moons of eyes, Capt.  Drummond?”

“Yes.  He had, or some of them had, two semi-circular walls of eyes—­one looked before and behind and all round to the right, and the other looked before and behind and all round at the left; and in each wall were two hundred eyes.”

The Captain smiled to himself to see Daisy’s face at this statement, though outwardly he kept perfectly grave.  Daisy’s own simple orbs were so full and intent.  She looked from him to the fossil.

“But Capt.  Drummond——­” she began slowly.

“Well, Daisy?  After you have done, I shall begin.”

“Did you say that this thing lived at the bottom of the sea?”