GEOLOGICAL INTRODUCTION. 



The testimony of the rocks is nowhere more marvellous than in the cen- 

 tral deserts of Wyoming Territory. Even the view obtained in passing 

 rapidly through this barren country cannot fail to arouse interest ; for to the 

 thoughtful traveller it seems that Nature here tells her story with peculiar sim- 

 plicity. The great elevation of the whole desert above the sea, the noble and 

 grotesque forms which centuries of wind and rain have carved out of the 

 sandstone bluffs, the brilliant colors which enable the observer to follow the 

 strata as they appear and disappear in bold outlying buttes and receding curves, 

 are all highly unique characters. The name Mauvaises Terres conveys an 

 impression of the singularly forbidding aspect of this country — of the vege- 

 tation, sparse from the protracted summer droughts, and of the naked strata 

 over which, in the rare atmosphere, the eye easily ranges from mile to mile. 

 Add to this the discovery that in these rocks are buried many generations 

 of animals whose genealogy can often be clearly followed, and it is unde- 

 niable that here, if anywhere, the records of an ancient land are written in char- 

 acters which cannot be mistaken. 



When the relations of the desert plains to the high mountains sur- 

 rounding them at all quarters became known, and the relative ages of the 

 mountains and the plains were ascertained from the fossils they contained, it 

 was a natural conclusion that these sedimentary beds were formed in inland 

 waters by erosion from the hills freshly emerged from the Secondary seas. 

 The earnest labors of Hayden, King, and Powell have thrown light upon 

 the different aspects of this geological problem. To the early studies and ex- 

 plorations of Dr. Leidy and the persevering efforts of Professors Cope and 

 Marsh are due most of our knowledge of the animals which these rocks 

 entombed. With these researches at hand, and those of Prof. Lesquereux, 

 who has devoted many years of study to the ancient flora, it follows that 

 we now have a considerable knowledge of the condition of animate and 

 inanimate nature of Eocene times in this region. 



The ancient geography and ancient fauna should be placed and studied 

 together even more intimately than has been done hitherto, in order to afford 

 the mind a comprehensive view of the whole. For facts of the structural pecu- 



