"So the men who reconstructed the Dinornis went at it. They set up the pelvis and leg bones and then, with plaster or some substance, and by working in proportion, they reconstructed the Dinornis, which is about the shape of the ostrich or the extinct moa of New Zealand, only larger. Here, I'll show you what I mean." Sitting down on a pile of dirt and shale rock, excavated by some of his workers, Professor Wright, on the back of an envelope, sketched the pelvic and leg bones and then from them he drew dotted lines in the shape of a big bird like an ostrich. "You see how it is proportionately balanced," he remarked. "A bird with that shape and size of leg would be about so tall--he could not be much taller or larger or his legs would not have been able to carry him around. "Take, for instance, the giraffe. If you found some of their long, thin leg bones, and had nothing else, and had never seen a giraffe, what sort of a beast would you imagine had been carried around on those legs?" he asked the boys. "Well, a giraffe is about the only kind of a beast that could logically walk on such long, thin legs," admitted Bud. "And there you are," said the professor. The boys were more interested than they had believed possible, and they began to look forward eagerly to the time when some of the giant bones might be uncovered. "What gets me, though," said Dick, believing that while knowledge was "on tap," he might as well get his fill, "what I can't understand is how long ago they figure these things lived--I mean the Dinornis and Dinosaurs," he added quickly, lest the professor resent his "pets" being called "things." "There's a good deal of guess-work about it," admitted the scientist. "The question is often asked--how long ago did such monsters live. But we are confronted with this difficulty. The least estimate put on the age of the earth is ten million years. The longest is, perhaps, six thousand million----" "Six thousand million!" murmured Bud in an awed voice. "And maybe more," said Professor Wright. "So you see it is pretty hard to set any estimate on just when an animal lived who may have passed away six billion years ago--it really isn't worth while. All we can say is that they lived many, many ages ago, and we are lucky if we can come upon any slight remains of them." "Do you really think you'll find some fossil bones?" asked Dick. "I'm sure of it!" was the answer. "Hello! That looks as if they had found something over there!" he cried, as some excitement was manifest amid a group of laboring Greasers some distance away. The professor hurried there, followed by the boys. They saw where some men, down in a shale pit had uncovered what at first looked to be a tree-trunk. "It is part of the hind leg of the great Brontosaurus!" cried Professor Wright, in intense excitement. "That's what it is--the Brontosaurus!" "But you want a _Brontotherium_," insisted one of the helpers, a professor in the making.