RELATIVE 6E0r.0GICAL ANTIQUITY OP TREES. 139 



With this gradual increase in the variety of the external 

 conditions, the dull uniformity of former creations passed 

 away ; and as the difference of temperature in the several re- 

 gions of the earth slowly increased, there became gradually 

 organized that immense variety of animals and plants which 

 now occupy the air, the earth, and the water. 



Hence it 'is that the Tertiary fossils consist of the remains 

 of species now in existence, intermingled with such as have 

 become extinct. Sir Charles iyell, the English geologist, has 

 proposed a classification of the Tertiary beds, based on the 

 relative proportion of extinct and recent species found among 

 the fossils of each formation, which has been generally adopted. 

 He divides the Tertiary group into the Eocene; Miocene, and 

 Pliocene formations. These three words originate from the 

 Greek. Eocene is derived from Gr. eos twilight and kainos 

 recent, which designates very beautifully the commencement 

 of this new geological period, as the morning rays of the 

 present creation. Miocene from Gr. meion less, and Jcainos ; 

 and Pleiocene from Gr. pMon more and kainos. 



It is probable that there was very little ice formed in the 

 northern hemisphere until about the close of the Tertiary 

 epoch ; because the plants found in the Tertiary beds clearly 

 indicate the prevalence of a much higher temperature within 

 the temperate zones than that which now exists there. Both 

 London and Paris stand on the Tertiary strata. The same 

 formations are also met with in Hampshire, and in the Isle of 

 "Wight, England, and in the South of Europe, Asia, and 

 America. 



The plants found in the Tertiary beds are totally. different 

 from those which are obtained from the Paleozoic and Second- 

 ary rocks. The land appears to have been richly, clothed 

 with a vegetation not very different from that which prevails 

 in warm climates at the present day. The leaves of the Elm, 

 Maple, Beech, Poplar, Oak, and other modern forest trees have 

 been found ; also pieces of wood which present the structure 

 of pepper plants and palms. The fossil plants of the Isle of 

 Sheppey, which is situated near the English coast, have been 

 examined by Bowerbank, and have led to the determination 



