“Six hours after that a second and very excited message told of the frantic, beaver-like work whereby a shallow shaft had been sunk and blasted; culminating in the discovery of slate fragments with several markings approximately like the one which had caused the original puzzlement.”
″‘Hello, Mr. Popper, up there in Stillwater. Thanks for your nice letter about the pictures of our last expedition. Watch for an answer. But not by letter, Mr. Popper. Watch for a surprise.‘”