They now heard a low and deep "thump!----thump!----thump!" which echoed throughout the valley and seemed to grow louder as they advanced. Then, turning a corner of rock, they saw before them a huge form, which towered above the path for more than a hundred feet. The form was that of a gigantic man built out of plates of cast iron, and it stood with one foot on either side of the narrow road and swung over its right shoulder an immense iron mallet, with which it constantly pounded the earth. These resounding blows explained the thumping sounds they had heard, for the mallet was much bigger than a barrel, and where it struck the path between the rocky sides of the mountain it filled all the space through which our travelers would be obliged to pass. Of course they at once halted, a safe distance away from the terrible iron mallet. The magic carpet would do them no good in this case, for it was only meant to protect them from any dangers upon the ground beneath their feet, and not from dangers that appeared in the air above them. "Wow!" said the Cowardly Lion, with a shudder. "It makes me dreadfully nervous to see that big hammer pounding so near my head. One blow would crush me into a door-mat." "The ir-on gi-ant is a fine fel-low," said Tiktok, "and works as stead-i-ly as a clock. He was made for the Nome King by Smith & Tin-ker, who made me, and his du-ty is to keep folks from find-ing the un-der-ground pal-ace. Is he not a great work of art?" "Can he think, and speak, as you do?" asked Ozma, regarding the giant with wondering eyes. "No," replied the machine; "he is on-ly made to pound the road, and has no think-ing or speak-ing at-tach-ment. But he pounds ve-ry well, I think." "Too well," observed the Scarecrow. "He is keeping us from going farther. Is there no way to stop his machinery?" "On-ly the Nome King, who has the key, can do that," answered Tiktok. "Then," said Dorothy, anxiously, "what shall we do?" "Excuse me for a few minutes," said the Scarecrow, "and I will think it over." He retired, then, to a position in the rear, where he turned his painted face to the rocks and began to think. Meantime the giant continued to raise his iron mallet high in the air and to strike the path terrific blows that echoed through the mountains like the roar of a cannon. Each time the mallet lifted, however, there was a moment when the path beneath the monster was free, and perhaps the Scarecrow had noticed this, for when he came back to the others he said: "The matter is a very simple one, after all. We have but to run under the hammer, one at a time, when it is lifted, and pass to the other side before it falls again." [Illustration: THE TIGER WENT NEXT] "It will require quick work, if we escape the blow," said the Tin Woodman, with a shake of his head. "But it really seems the only thing to be done. Who will make the first attempt?"