8 BRITISH EOCENE ELORA. 



more and more south as climates chilled, and at last, in the Miocene time, occupied our 

 latitudes. The relative preponderance of these elements, I believe, will assist in 

 determining the age of Tertiary deposits in Europe, more than any minute comparisons 

 of species. Thus it is useless to seek in the Arctic Regions for Eocene floras, as we 

 know them in our latitudes, for during the Tertiary period the climatic conditions of 

 the earth did not permit their growth there. Arctic fossil floras of temperate, and 

 therefore Miocene aspect, are in all probability of Eocene age, and what has been recog- 

 nised in them as a newer or JVliocene facies is due to their having been first studied in 

 Europe in latitudes which only became fitted for them in Miocene times. 



When stratigraphical evidence is absent or inconclusive, this unexpected persistence of 

 plant types or species throughout the Tertiaries should be remembered, and the degrees 

 of latitude in which they are found should be well considered before conclusions are 

 published respecting their relative age. 



