Vice-President'' s Address. 1 87 



low grounds of Kussia with the Arctic Ocean. We know, 

 however, that the Archipelago of Southern Europe was in 

 direct connection with the Indian Ocean, and it is most 

 probable that a wide arm of the same sea stretched nortli 

 from the Aralo-Caspian area through Siberia. Indeed, mucli 

 of what are now the lowlands of western and northern Asia 

 were probably sea in Tertiary times. It seems likely, there- 

 fore, that, even at this late period, marine currents continued 

 to reach the Arctic zone, across the continental plateau. 

 When the warm waters of the Indian Ocean eventually 

 ceased to invade Europe, and the Mediterranean became 

 much restricted in area, the climate of the whole continent 

 could not fail to be profoundly affected. 



There is yet another line of evidence to which brief 

 reference may be made. I have spoken of the remarkable 

 uniformity of climatic conditions which obtained in Palaeozoic 

 times, and the gradual modification of those conditions 

 which subsequently supervened. JSTow, it is worthy of note 

 that, in their lithological characters, the oldest sedimentary 

 strata themselves likewise exhibit a prevalent uniformity 

 which, in later systems, becomes less and less conspicuous. 

 The Cambro-Silurian mechanical sediments, for example, 

 maintain much the same character all the world over; and 

 the like is true, although in a less degree, of the marine 

 accumulations of the Devonian period. The corresponding 

 mechanical deposits of later Palaeozoic ages continue to show 

 more and more diversity, but at the same time they preserve 

 a similarity of character over much more extensive areas 

 than is found to be the case with the analogous sediments 

 of the Mesozoic era. Finally, these last are more or less 

 strongly contrasted with the marine mechanical accumu- 

 lations of Cainozoic times, which are altogether more local 

 in character. This increasing differentiation is quite in 

 keeping with what we know of the evolution of our land- 

 areas. In early Palaeozoic ages, when insular conditions 

 prevailed and the major portion of the primeval continental 

 plateau was covered by shallow seas, it is obvious that 

 mechanical sediments would be swept by tidal and other 

 currents over enormous areas, and that these sediments 

 VOL. X. 



