152 Transactions of the American Institute. 



numerous succession. In the Dinornis, you perceive, there is little 

 indication of a wing ; yet it is a bird. Therefore, you will ask by 

 what characteristic it was so strongly marked that Prof. Owen could 

 confidently predicate of it that it was a bird. Suppose this to repre- 

 sent [drawing in illustration] the leg-bone of a mammal. "We find 

 that in the bones of birds the outer wall is compact, but that they 

 are hollow, and the outer wall of bone is supported by a series of 

 splinters of other bones like little supporting beams, that afford a 

 free passage of air through the bone itself. The hollow condition 

 of the bone is an adaptation to fit the creature for raising its body in 

 the air, rendering the bone lighter with equal strength, and thus 

 tending to qualify the bird to fly. The bones of the leg of the 

 ostrich, which does not fly but which runs with great rapidity, are 

 provided with similar cavities, admitting warm air within the bone. 

 Therefore you at once see that in a piece of bone belonging to a bird, 

 however large, there are ca\'ities by which it can be 'discriminated. 

 Again, by the absence of these indications, and by the existence of 

 comparative solidity in the bones of reptiles, it is possible to discern 

 the difference, although the external forms may be alike, and there 

 may be no other difference than the internal structure. We find 

 that those birds that can walk but have no power to fly, much more 

 nearly associated with terrestial animals than those which are actually 

 birds of flight. But I shall presently show you that there are reptiles 

 that can fly, as there are birds that cannot fly. Yet the birds that 

 run, the ostrich, &c., are distinctly birds, and the reptiles that fly are 

 distinctl}'^ reptiles, fitted for the variety of their situations in the 

 economy of nature. Every terrestial ally that comes between the 

 two characters of the bird and the reptile, you will find to be inter- 

 mediate in form, but the general arrangement is the same. One of 

 these intermediate forms we have here. [The Hadrosaurus of Dr. 

 Leidy, recently restored by Mr. H., modeled from the original, was 

 here revealed, by removing the curtain before it.] Allow me to 

 state to you that this is no fable. It is truly a reconstruction, because 

 I had a few pieces from the original to commence with. In my early 

 interviews with the commissioners, I was expected to reconstruct 

 such giant forms as most of them had seen in England, at Sydenham; 

 but I sugo-ested that it would be more interestino^ and instructive if 



DO O 



the earlier forms exhibited as restorations should be from the bones 

 of fossils found here and belonging to the past history of this great 

 continent. [Applause.] I immediately searched the museums of 



