GLACIAL EPOCHS AND POLAR CLIMATES. 29 



dicate creatures of vast size. Whether these giant 

 Birds or Bird-reptiles, for we have no positive evi- 

 dence of their structure, were capable of flight it 

 is impossible to say. Whether they were sedentary 

 or migratory in their habits is equally uncertain. 

 In the Oolitic or Jurassic System, the ages of the 

 gigantic Reptile and the Pterodactyl, a reptile-like 

 bat, more definite evidence of the existence of birds 

 is forthcoming in the famous fossil Archaeopteryx. 

 From this we pass on to the toothed birds of the 

 Cretaceous System, all of which, however, appear to 

 have become extinct before the Tertiary Period, in 

 which occur the fossilized remains of birds closely 

 allied to existing forms. 



We need not concern ourselves with the effects 

 of Glacial Epochs (even if such occurred, and the 

 evidence against such phenomena having occurred 

 earlier than the close of the Palaeozoic Period is 

 very conclusive, as will shortly be seen) previous 

 to Miocene and Eocene ages ; and what effects the 

 mighty terrestrial changes may have produced on 

 then existing life does not bear upon our present 

 subject. That vast changes in the earth's surface 

 and in her planetary movements took place in 

 Miocene and Eocene ages, there is apparently 

 sufficient geological and astronomical evidence to 

 suggest ; and in those remote ages Birds — creatures 

 as we know them to-day — lived and flourished. 

 We thus see that the Avian order of living beings 

 has been subjected to many and varied geographical 

 and astronomical disturbing influences from its 



