34 The Make-Up and the Wordings of the Earth 



centuries. Then there are the larger plants and animals that 

 lived on the land, or in the air, and whose bodies were either 

 devoured by other living things, or decayed and scattered. 

 For we must remember that as a rule fossils were formed 

 only where dead bodies were buried in mud or sand. 



Now there are a few exceptional finds that point to 

 extinct forms of a kind that we should not ordinarily expect 

 among the fossils. In Siberia, buried in ice and preserved 

 for countless centuries, there have been found several speci- 

 mens of an extinct relative of the elephant, the mammoth, 

 with flesh and hide and hairs and all. There they were, about 

 as large as life, saved from decay by the low temperature, 

 and, by being buried in the ice, saved from destruction by 

 other animals and by the weather. Indeed, so well preserved 

 was the flesh that the dogs ate it with relish. A tar pool in 

 California yielded the nearly intact re^nains of elephants, 

 camels, horses, wolves and saber-tooth tigers, all animals that 

 have not been living on this continent for millions of years." 



The conditions under which fossils are formed, the ease 

 with which dead remains of living things are devoured, de- 

 cayed and scattered, and the operation of destructive forces 

 and upheavals, all make for incompleteness in the geological 

 record. Perhaps we can realize this if we consider that of 

 the thousands upon thousands of wild bisons or " buffalo " 

 that roamed our prairies within the memory of middle-aged 

 men and women, there are few skeletons ever found. What 

 should we expect to find of the other land animals and birds 

 that undoubtedly occupied this land when Columbus arrived? 

 Where can we find relics of the passenger pigeon that oc- 

 curred a generation ago in vast swarms? Or of the antelope? 

 Or of the prairie dog? Our record must necessarily be in- 

 complete, and only a small fraction of it has in any case been 

 reached by the explorers. Such as it is, however, it points not 

 only to a succession of diverging species, but also to a suc- 



^ The ancestors of the modern horse that lived on this continent 

 in ancient times died out completely. The modern horse was brought 

 here by Europeans after Columbus, see p. 39. 



