"Not that it is any of your business, but we were aware of the tunnel's existence while the Nome King was building it. After he returned to his own silly kingdom, we burned our way down through the rocks from the oasis above." "Why did you do that?" persisted the beaver King. The leader of the fire creatures hesitated for a moment then replied in an angry voice: "Because we enjoy the coolness of the tunnel. By contrast it makes the fiery sands of the desert even more pleasant. Now, be on your way back where you came from or we will advance upon you and blast you to cinders." "My, what a fiery tempered fellow," said Shaggy. This seemed to infuriate the fire creature and he was about to leap toward Shaggy when the beaver King stepped forward, holding out his beechwood wand. Instantly, from the tip of the wand there came forth a spray of water that showered on the row of fire creatures. As soon as it touched their flaming bodies, the water hissed into steam. The effect on the fire beings was amazing. They uttered loud howls of pain and fright and leaped like flames from a great fire into the air and through the rift in the rock. Their cries resounded as they dashed over the oasis to roll in the flaming sands of the desert. "Come," urged the beaver King, "let us hurry, although I do not think there is any danger of pursuit." The young beavers went first, followed by Shaggy and his friends. They hurried until they had passed out of sight of the sunlight that flowed down the rift into the tunnel. "I guess that's the first time those critters ever saw water," said the Shaggy Man grinning. "The water didn't hurt them," said the beaver King, "and the burning sands will soon restore whatever heat they lost. Nevertheless, I don't think they will cause us any further annoyance." They walked ahead rapidly hour after hour with the young beavers lighting the way through the Nome King's tunnel. CHAPTER 19 The Barrier of Invisibility Suddenly Shaggy stopped and stared about him. He was alone in the tunnel! He had been walking along looking at nothing in particular, when in a flash his companions had vanished. Just ahead of him he could hear the excited chattering of the twenty young beavers. But there was no sign of any living thing. Then Shaggy looked down at himself and cried out in amazement--he wasn't there either! He could see nothing of his body, although he felt as firm as ever. "You will be kind enough to remove your wand from my eye, please!" It was Twiffle's voice speaking somewhere near Shaggy. "I beg your pardon, we are both invisible, so my poking my wand in your eye was entirely unintentional, I assure you," the beaver King's voice answered. "Hey! Stay off my foot!" Tom called out. "Was that your foot? I'm sure I didn't see it," Twink's voice answered soothingly. "Neither do I, but it's there just the same," replied Tom's voice ruefully.