Uniformity in Geological Change 



tacea are the most generally diffused in a fossil 

 state, and may be called the medals principally 

 employed by nature in recording the chronology 

 of past events. In the Upper Miocene rocks we 

 begin to find a considerable number, although 

 still a minority, of recent species, intermixed 

 with some fossils common to the preceding, or 

 Eocene, epoch. We then arrive at the Pliocene 

 strata, in which species now contemporary with 

 man begin to preponderate, and in the newest of 

 which nine-tenths of the fossils agree with species 

 still inhabiting the neighbouring sea. It is in 

 the Post-Tertiary strata, where all the shells agree 

 with species now living, that we have discovered 

 the first or earliest known remains of man asso- 

 ciated with the bones of quadrupeds, some of 

 which are of extinct species. 



In thus passing from the older to the newer 

 members of the Tertiary system, we meet with 

 many chasms, but none which separate entirely, 

 by a broad line of demarkation, one state of 

 the organic world from another. There are 

 no signs of an abrupt termination of one fauna 

 and flora, and the starting into life of new and 

 wholly distinct forms. Although we are far 

 from being able to demonstrate geologically an 

 insensible transition from the Eocene to the 

 Miocene, or even from the latter to the recent 

 fauna, yet the more we enlarge and perfect our 

 general survey, the more nearly do we approxi- 

 mate to such a continuous series, and the more 

 gradually are we conducted from times when 

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