328 Miscellaneous. 



and new layers of the living plant grew upon them, until the descent of 

 the land and encroachment of waters deposited the stone lid upon 

 their treasury of carbon, not to be unsealed until the long future 

 day of human empire. The alternations of land and water were 

 numerous. At one point on the Union Pacific railroad a section 

 displays one hundred and seventy-three distinct strata, of which 

 thirty-six are either coal or mingled with vegetable matter, while 

 the others are frequently composed almost exclusively of fresh- and 

 brackish- water shells. The elevation, however, exceeded the de- 

 pressions, the brackish estuaries and lagoons were transformed into 

 freshwater lakes, and at length the noble ranges of the Rocky 

 Mountains bounded the horizon in many directions. 



The salt ocean has not only been the dweUing-plaee of gill- 

 breathing fishes, but also of many forms of air-breathing vertebrates. 

 These were reptiles, and exhibited a great superiority of structure 

 over the air-breathers that peopled the swamps and land of the coal 

 period. When the land and the fresh waters claimed the great 

 west, the sea saurians perished ; for their limbs were not fitted for 

 the changed circumstances. Smaller races held the land, and, with 

 a few monsters that never had been ocean-dwellers, represented the 

 swarming reptilian life of the past. 



But a new dynasty was to rule the earth ; the mammal, with hot 

 blood and active brain, was to use the rich stores of the newer vege- 

 table world ; and life was to be exhibited on a higher platform. 



The lakes of the west were gradually dried by the cutting of their 

 discharging streams down to the level of their bottoms. This was 

 of course soonest accomplished in lakes of the greatest elevation — 

 for instance, those within the highest range of the mountain-chains. 

 Others continued for a longer period, and others to a comparatively 

 still more recent date. Their deposits contain a faithful record of 

 the life of the surrounding land, doubtless embracing many species 

 that ranged to the Atlantic ocean. We have thus the means of 

 studying the character of five successive periods, which must be to 

 us a mine of interesting inquiry, and a source of evidence as to the 

 nature of that life and the thoughts of its great Author. 



The names of the beds, with the regions where chiefly found, are 

 the following : — (1) The Lignite series or Upper Cretaceous (Mon- 

 tana, Dakota, Wyoming, Colorado) ; (2) Eocene Lake (\¥yoming, 

 West Colorado) ; (3) Miocene (Nebraska, Oregon, E. Colorado) ; 

 (4) Pliocene (Nebraska, Idaho, Oregon, E. Colorado) ; (5) Post- 

 pliocene (caves of the east). The quadrupeds begin in full blast in 

 the Eocene ; and none whatever are known from beds of the prece- 

 ding or cretaceous agea — a remarkable circumstance, and not easy to 

 account for, especially as it is the case all over the world, so far as 

 known ; yet there were a few of this high division during a period 

 that preceded the cretaceous. In Wyoming, therefore, we find life 

 first in the form with which it has pleased Divine power to invest 

 ourselves, but in no case presenting any close resemblance to the 

 hunian species. The predominant styles were those resembling the 

 tapir, the opossum, the bat, the mole, and the squirrel. There were 



