Popular Science Monthly 



Vol. 91 

 No. 1 



239 Fourth Avenue, New York City 



July, 1917 



$1.50 

 Annually 



A Bird with Four Wings 



When Nature decided to evolve a bird out of a reptile she 

 molded a four-winged flyer curiously like the first flying machine 



By Maurice Krosby 



BIRDS came later than fishes and 

 reptiles in the evolution of life. But 

 what manner of creature was it that 

 linked fish with bird? What was the first 



bird that ever fl( 



Fossil re- 



mains and imprints have so far 

 given only scant information 

 as to how the feathered de- 

 scendants of the fish or the rep- 

 tile gradually came into posses- 

 sion of the power of flight. 

 Intermediate links in the develop- 

 ment have left but few and faint 

 traces, and this is due, at least in 

 part, to the extreme remoteness 

 of the transition period durin 

 which birds became birds from 

 whatever they were before. The 

 change was so radical that it re- 

 quired millions of years by Na- 

 ture's slow methods. 



Fortunately a single natural 

 document has come down through 

 the ages which goes far toward explaining 

 the mechanics that made the elongated 

 swimming fish or crawling reptile fit for 

 sustaining, propelling and balancing it- 

 self in the air, and this document, as it 

 happens, also establishes a most curious 

 and interesting parallel between Nature's 

 experiments in flying and those funda- 

 mental experiments by Professor Langley 

 of the Smithsonian Institution in Washing- 

 ton to which the inauguration of the air- 

 plane era in flight is due, more than to any 

 other one cause. The document referred 

 to is a true document; for it was found 

 printed by natural forces on the rocks of 

 the Solinghofen quarry in Germany. Here, 

 in a formation not less than seven million 

 years old, one of the ancestors of the 



This is Nature's 

 first attempt at 

 creating a flyer 



modern bird, a strange feathered reptile, 

 had been imprisoned, caught unawares per- 

 haps in one of the every-day upheavals of 

 that formative age when mountain ranges, 

 continents and oceans were still 

 in the making. Its skeleton, its 

 outlines and its feathers are 

 here preserved, stamped in un- 

 mistakabledistinctnessin stone, 

 which is now hard but which 

 must have been plastic as clay 

 when the fluttering creature was 

 seized in deadly embrace. More 

 than twice as old as any of the 

 prehistoric monsters reconstructed 

 from their bones in our museums 

 of natural history, the fossil im- 

 print of the Tetrapteryx, as this 

 creature has been named (mean- 

 ing "four-winger"), represents an 

 indisputable and descriptive rec- 

 ord of perhaps the earliest feath- 

 ered flyer. 



The Tetrapteryx record was discovered 

 fifty-five years ago, but science has only re- 

 cently undertaken to interpret it mechani- 

 cally. William C. Beebe, while curator of 

 birds at the New York Zoological Park, 

 demonstrated that several species of modern 

 birds, and especially the white-winged dove, 

 show very marked traces of just such wings 

 on the legs, called pelvic wings, as the Tet- 

 rapteryx record reveals. On the very young 

 dove, at the time when its body is still bare 

 but for the sprouting flight feathers of wings 

 and tail, twelve flight feathers and six 

 coverts begin to grow from the outer and 

 upper edge of the leg, extending in two 

 rows from the knee almost to the base of the 

 tail. While the growth of these tell-tale 

 feathers is soon arrested and is covered up 



