472 
Van Else—Earth Movements. 
mulative. The water that goes to the ocean or some equiva¬ 
lent amount is returned to the land through the atmosphere 
by the power of the sun. The land dumped into the sea does 
not return, but remains to build up a great deposit fringing 
the coast. 
In this process of erosion two things are happening to the 
continental ship: its interior is being unloaded, and its periph¬ 
ery is being loaded. If there were isostatic equilibrium at 
the beginning, or at some time during the process, and erosion 
afterwards long continued, this would result in differential 
stresses between the interior and the periphery of the conti¬ 
nents. At the first place the pressure is upward, and at the 
second downward. A study of the coastal features of the conti¬ 
nents by physiographers shows beyond all question that where 
many of the great deposits are forming, there the border is 
sinking. As evidence of this subsidence, and the consequent 
encroachment of the ocean are the keys, estuaries, divided 
rivers, and other phenomena. There is also clear evidence in 
deformed beaches of lakes, that the interior and northern parts 
of the north American continent, which is being unloaded, is 
rising. 
In order that these correlative movements shall occur, deep- 
seated flow of material under the continental border toward the 
interior must take place. 1 Such deep-seated flowage does not 
involve more than a slight movement of any part of the mater¬ 
ial, just as when a faucet is opened the cubic inch of water oc¬ 
cupying the front of the pipe is the first to issue, and there is 
an average forward movement of but an inch all along the pipe. 
The lateral transfer of material involved in denudation may 
work toward or from isostatic equilibrium. If the land area has 
an excess of material and the adjacent sea is deficient in mater¬ 
ial, the work is at first toward isostatic equilibrium, and this 
state may finally be attained, although it is improbable that this 
ever exactly occurs. When the excess of material is removed 
from the land, if the area is still above sea level, denudation 
continues, and from this time the removal of material from the 
1 The mechanics of Appalachian structure, by Bailey Willis: Thir¬ 
teenth Ann. Kept., U. S. G. S., Part II, 1893, pp. 280-281. 
