"Why not call it by its proper name?" teased Roger, scratching his head with his left claw. "And I think it most unlikely we'll strike anything as curious and important as Tazander Forest. Two discoveries like that just couldn't happen two days running. Still, I'll just fly up to the main truck and have a look around." "Main truck?" Tandy wrinkled up his brows. "I thought I knew all the parts of this ship by now. You never told me about the main truck, Roger." "Just the top of the main mast, Brainless." Giving Tandy an affectionate little shove, Roger soared into the rigging and Tandy went joyfully off to have another look at the forest Samuel had insisted on naming after him. He had taken great pains with the painting and printing when he sketched it on the map, and now with a sigh of complete satisfaction he stood regarding the sea chart. Then, suddenly remembering he had promised to water Samuel Salt's plants, he jog trotted contentedly down to the hold. The tumbleweeds in their small red pots grew so rapidly Samuel had to cut them back every day. These Tandy watered very sparingly, snapping his fingers at Mo-fi, who was gravely chinning himself on a branch of his artificial tree. The slips of the sea trees in their covered aquarium required no attention at all. Ato had planted all the vegetable and fruit vines from Peakenspire on the rail outside the galley, so that left only the creeping vines from Patrippany Island to care for. He had just picked up one of the small potted creepers when a sharp rap tap under his toes made Tandy leap straight up in the air. Someone was knocking on the bottom of the boat. "Ato! Captain! ROGER!" shrilled the little boy, scurrying up from the hold faster than he had ever done before. "Su--su--SOMEBODY'S knocking on the bottom of the boat." Before he could explain, or tell them anything further, a perfectly terrific knock from below made the _Crescent Moon_ shiver from end to end. Samuel and Ato, leaning over the port rail, turned round so suddenly they bumped their heads smartly together. Next with a scrape, screech and splintering of timber, a giant white horn came tearing up through the decks. "Whale! Whale!" croaked Roger, falling off the main truck and coasting crazily down to the deck. "Wha--what ever'n ever's that?" he quavered, pointing a trembling claw at the rigid white column between the main and mizzenmasts. Samuel did not even try to explain, for at that instant the ship began to rise, to fall, to lash and plunge both up and down and east and west. Hooking his arms through the rail, Tandy blinked, gasped and shudderingly waited for the _Crescent Moon_ to fly asunder. "Narwhal, Mates!" panted Samuel Salt, throwing himself bodily upon the wheel. "Horn like a--uni--corn--branch of the Odontocetes and--"