INTRODUCTION. 3 



When our British Eocene floras are compared with those of other countries we can 

 hardly fail to observe that no Eocene or Oligocene fossils are described as occurring 

 within upwards of two thousand miles of the Pole. All the fossil floras containing 

 Dycotyledons within that radius have been in fact described as either Cretaceous or 

 Miocene. 



The correctness of this classification, which has been maintained and extended by 

 Heer even in his latest works, is open to doubt, for there is no evidence in those regions 

 of any break in the physical conditions which could have rendered unlikely the deposition 

 of materials similarly adapted to the preservation of plant remains. Further, the 

 supposed Miocene either rests directly upon, or is separated by not more than one 

 thousand feet from the deposits described as Cretaceous. From the unquestioning way 

 in which this classification has been generally received, we should expect to find it based 

 upon well-nigh irresistible evidence. Instead of this, the Miocene hypothesis supposes 

 that at least 25 per cent, of the forest trees and shrubs ranged at that period from 

 Spitzbergen to Switzerland, and from Disco to Italy ; a distribution without parallel at 

 the present day. On the other hand, the temperature of the Eocene period would have 

 been far more favorable to the growth of temperate floras in high latitudes ; for the 

 minimum estimated temperatures of our Middle Eocene and of the so-called Greenland 

 Miocene differ by only 20° Fahr., or as nearly as possible one degree for each degree of 

 latitude. At the present day the distance from England to Madeira produces an almost 

 identical variation of temperature and a practically similar change in the flora. Setting 

 aside, however, all other considerations, I believe I shall be able during the progress 

 of this work to show that the evidence of the fossil plants themselves, relied upon by 

 Heer, does not support the anomalies introduced by his classification, but, on the contrary, 

 favours the view that deposition of sediment in which plants have been preserved did 

 not cease in high latitudes during the Eocene period. 



It is obvious, in such an inquiry, that floras from the south of England, supposed to be 

 of the same age, are too widely separated in latitude from those of Greenland to permit of 

 any useful comparison being made directly between their species. It would be almost 

 tantamount to a person, totally unacquainted with the flora of the intervening American 

 mainland, comparing the leaves of the forest trees of Cuba with those of Nova Scotia, in 

 the hope of identifying them together. Their mutual relationship must chiefly be tracedj 

 and the problems contingent upon it solved, either through the older temperate Eocene 

 floras, of which they may be supposed in part descendants, or through the deposits con- 

 taining dicotyledonous plants preserved in intervening lands. Instances of the former 

 are found at Reading, Newhaven, Bromley, &c., and of the latter in some of the western 

 isles of Scotland, in Antrim County in Ireland, at several localities in Iceland, and pos- 

 sibly also in some of the many deposits of lignite in the Faroe Isles. 



The specimens already obtained from Mull, though not very numerous, contain some 

 striking forms of the English sub-tropical Middle Eocene, such as Podocarpus, mixed with 



