602 TIC. ALLA EBT ETN 
nearly constant. It is reduced, indeed, by the growing width 
of the sea-shelf. But the growth of the sea-shelf on its abysmal 
border must necessarily be slow because of the great depth to 
be filled, and hence, unless the shelf grows inland, its extension 
is relatively slight and the ability of the sea to dispose of the 
detritus borne into it remains nearly constant. With the inevi- 
table decline in the delivery of land wash, as base level is 
approached, the disposing power of the sea must gain the 
ascendancy. It would seem to be almost obvious that if there 
were no movements of the crust for an indefinite period the ulti- 
mate result must be the complete truncation of the land to a 
level below the effective reach of the waves. 
But the case does not rest simply with the results of the con- 
test between the diminishing stream action and the nearly con- 
stant wave action. There are two supplementary factors which 
aid the latter. (1) The deposit of the detritus of the land in 
the sea raises its level. If the average elevation of the present 
land be taken at Lapparent’s figures, 2120 feet, its truncation 
and, removal ito the ocean would Jhit. “the sea level 7ooireet 
(making no allowance for the spread of the sea). This would 
certainly be effective in advancing the sea upon the land. (2) 
The continents after the relative upthrusts attendant upon 
crustal readjustment probably stand on the average above the 
plane of isostatic equilibrium, as indicated in the existing status 
by pendulum observations. From this they should settle back 
toward equilibrium by virtue of the quasi-fluency of the rocks. 
The effects of this might, perhaps, decline as erosion proceeded, 
but the shifting of the load to the borders of the continent 
would probably aid in depressing them and facilitating the 
advance of the sea. 
The inland extensions of the sea attendant upon such an 
advance may be conveniently designated epicontinental seas. 
The great sea which lies between Europe and Africa is properly 
termed a mediterranean sea, since it really lies between the con- 
tinents in a deep basin descending to depths of 6000 feet and 
more. But the seas here referred to as epicontinental are not 
