I 



278 GEOLOGICAL CONTEMPORANEITY ix 



tions, which may be found implicitly, or explicitly. 

 in the works in question, are regarded by the mass 

 of palaeontologists and geologists, not only on the 

 Continent but in this country, as expressing some 

 of the best-established results of palaeontology. 

 Thus : 



Animals and plants began their existence to- 

 gether, not long after the commencement of the 

 deposition of the sedimentary rocks; and then 

 succeeded one another, in such a manner, that 

 totally distinct faunae and florae occupied the whole 

 surface of the earth, one after the other, and dur- 

 ing distinct epochs of time. 



A geological formation is the sum of all the 

 strata deposited over the whole surface of the 

 earth during one of these epochs: a geolo- 

 gical fauna or flora is the sum of all the 

 species of animals or plants which occupied the 

 whole surface of the globe, during one of these 

 epochs. 



The population of the earth's surface was at first 

 very similar in all parts, and only from the middle 

 of the Tertiary epoch onwards, began to show a 

 distinct distribution in zones. 



The constitution of the original population, as 

 well as the numerical proportions of its members, 

 indicates a warmer and, on the whole, somewhat 

 tropical climate, which remained tolerably equable 

 throughout the year. The subsequent distribution 

 of living beings in zones is the result of a gradual 



