Vice-President's A ddress. 175 



we simply mean certain extensive regions in which elevation 

 has, upon the wliole, been in excess of depression ; by 

 oceanic area, on the other hand, is meant that vast region 

 throughout which depression has exceeded elevation. Thus, 

 while the area of permanent or preponderating depression 

 has, from the earliest geological times, been occupied by 

 the ocean, the continental areas have been again and again 

 invaded by the sea — and even now extensive portions are 

 under water. It is not only the continental dry land, 

 therefore, but all the bordering belt of sea-floor which does 

 not exceed 1000 fathoms or so in depth, that must be 

 included in the region of dominant elevation. Were the 

 whole of this region to be raised above the level of the sea, 

 the present continents would become connected so as to 

 form one vast land-mass, or continental plateau. 



All the sedimentary strata with which we are acquainted 

 have been accumulated over the surface of that great plateau, 

 and consequently are of comparatively shallow-water origin. 

 They show us, in fact, that at no time in geological history 

 has that plateau ever been drowned in depths at all com- 

 parable to those of the deeper portions of our oceanic 

 troughs. The stratified rocks teach us, moreover, that the 

 present land- areas have been gradually evolved, and that, 

 notwithstanding many oscillations of level, these areas have 

 continued to increase in extent — so that there is probably 

 more land-surface now than at any previous era in the 

 history of our globe. To give even a meagre outline of 

 the evidence bearing upon this interesting subject is here 

 impossible. All that I can do is to indicate very briefly 

 some of the general results to which that evidence seems 

 to lead. 



The oldest rocks with which we are acquainted are tlie 

 so-called Archaean schists.^ But these have hitherto yielded 

 no unequivocal traces of organic life, and as their origin 

 is still doubtful, it would obviously be futile to speculate 

 upon the geographical conditions of the earth's surface 



^ I need hardly remind geologists that some of the so-called " Archii^an 

 schists" may really be the highly altered accumulations of later geological 

 periods. 



