32 WORLD-MAKING 



is concerned. Prof. Hull of the Geological Survey of Ireland 

 has had the boldness to reduce the fluctuations of land and 

 water, as evidenced in the British Islands, to the form of a 

 series of maps intended to show the physical geography of each 

 successive period. The attempt is probably premature, and 

 has been met with much adverse criticism ; but there can be no 

 doubt that it has an element of truth. When we attempt to 

 calculate what could have been supplied from the old Eozoic 

 nucleus by decay and aqueous erosion, and when we take into 

 account the greater local thickness of sediments towards the 

 present sea-basins, we can scarcely avoid the conclusion that 

 extensive areas once occupied by high land are now under the 

 sea. But to ascertain the precise areas and position of these 

 perished lands may now be impossible. 



In point of fact we are obliged to believe in the contempo- 

 raneous existence in all geological periods, except perhaps the 

 very oldest, of three sorts of areas on the surface of the earth : 

 (i) Oceanic areas of deep sea, which must always have oc- 

 cupied the bed of the present ocean, or parts of it ; (2) Conti- 

 nental plateaus sometimes existing as low flats, or as higher 

 table-lands, and sometimes submerged ; (3) Areas of plication 

 or folding, more especially along the borders of the oceans, 

 forming elevated lands rarely submerged and constantly afford- 

 ing the material of sedimentary accumulations. We shall find, 

 however, that these have changed places in a remarkable man- 

 ner, though always in such a way that neither the life of the 

 land nor of the waters was wholly extinguished in the process. 



Every geologist knows the contention which has been 

 occasioned by the attempts to correlate the earlier Palaeozoic 

 deposits of the Atlantic margin of North America with those 

 forming at the same time on the interior plateau, and with 

 those of intervening lines of plication and igneous disturbance. 

 Stratigraphy, lithology and fossils are all more or less at fault 

 in dealing with these questions, and while the general nature 



