The Past 9 



Tertiary time. It appears rather that there has been a sort of 

 kaleidoscopic shuffle producing indeed a host of different species, 

 but little steady or progressive advance in type. 



The accompanying fossil plants are of diverse types, but the 

 flora differs from that of Florissant in including palms. The 

 climate indicated is warm temperate, by no means distinctly 

 tropical. 



THE MIOCENE SHALES OF FLORISSANT 



In the early seventies of the last century, a party of the United 

 States Geological Survey was camped in an upland valley directly 

 west of the base of Pike's Peak. The surrounding hills were known 

 to be granite, and it was supposed that sedimentary rocks were 

 lacking. Dr. A. C. Peale, while supper was being prepared, 

 strolled about in the vicinity of the camp, and was surprised to 

 pick up a well preserved fossil leaf. This of course led to further 

 investigations, and it was soon ascertained that the whole valley 

 was filled with fossilferous shales, derived from deposits of volcanic 

 ash in an ancient lake. It was even possible to find old volcanic 

 vents, and to map the outlines of the former lake, which had been 

 drained by the tilting of the land, leaving only a small stream 

 flowing down the valley. This stream, though of no great size, 

 except when swollen by cloud-bursts, had been cutting into the 

 soft shales for some millions of years, removing a large part of the 

 deposit, and destroying innumerable fossils. As a result there 

 were numerous places where the shale was exposed, or only covered 

 by a certain amount of gravel, making it relatively easy to dig it 

 out and split it into thin slabs. On such slabs are found not only 

 fossil leaves, but many beautifully preserved remains of insects, 

 occasional fish, and at extremely rare intervals a bird, though 

 feathers are not uncommon. In 1877 Dr. S. H. Scudder, who was 

 then the leading authority on fossil insects, spent the summer in 

 this locality, which is known as the Florissant Valley. The little 

 town of Florissant possibly got its name from that of a place in 

 the vicinity of Geneva, and as it has to be referred to very fre- 

 quently in scientific literature, we are thankful to the Swiss who 

 may have remembered his ancestral home, and glad that no unro- 

 mantic American thought to call the place Tin Cup, Hell Gate or 



