420 PROCEEDINGS OF THE ACADEMY OF [1888. 



square miles iu area and one mile in average depth. The filling of 

 such a valley with water must necessarily have caused a marked 

 lowering of the general ocean level. If the figures above given be 

 assumed as correct it is easy to calculate the amount of depression 

 of sea level. 



The area iu question is equal to that of Asia and Europe combined, 

 and the effect of its sinking would be equivalent to that of tiie sink- 

 ing of the Eurasian continent till covered with water to the averaire 

 depth of one mile; since to fill such a valley in the ocean bed would 

 require as much water as to cover a continent sinking to the same 

 depth. The area named is very nearly one seventh of the whole 

 ocean area, and to fill it to a depth of one mile would cause a general 

 oceanic depression of one-seventh of this depth, or about 750 feet. 

 If the average subsidence be taken at a somewhat greater figure, say 

 7000 feet, the consequence Avould be a depression of the ocean level 

 of 1000 feet. 



This is no fanciful conclusion. If the subsidence stated really 

 took place, without important elevation of the ocean bed elsewhere, 

 such a lowering of the general ocean level must necessarily have 

 occurred to an extent governed by the average extent of subsidence. 

 The effect on the relations of land and ocean altitude would be 

 equivalent to an elevation of the whole land surface of the earth to 

 a height of 750 or 1000 feet, or some other height dependant on the 

 real degree of subsidence. 



Such an effect must have left its marks, in the exposure of con- 

 siderable areas of new land along sloping shores, in the draining of 

 hays and estuaries, the possible conversion of bays into partly or 

 fully land-locked seas, and other drainage results. In fact if such a 

 virtual elevation of all the shore regions of the earth took place it 

 would seem as if it must have left some generally traceable indica- 

 tions, which would furnish an argument in favor of the subsidence 

 theory. Yet it may have been so complicated w'ith actual elevations 

 and d.^pressions of the land surface as to destroy evidences of its 

 existence in most localities. That land drainage and shore eleva- 

 tion did take place to a considerable extent during the Tertiary 

 epoch is acknowledged, but whether these were due to actual eleva- 

 tion, or to a sinking of the ocean level, is a problem which cannot 

 be de'iiiitely solved without much fuller evidence than we possess 

 at pn^sent. 



The following was ordered to be printed: — 



