Review of Recent Geological Literature 387 
facts indicate that the entire surface of subaerial erosion on the 
Archaean rocks including the valley bottoms was pared by the 
Wyoming sea at least to a depth below the zone of weathering. 
This denudation erased the minor features of relief and reduced 
the major features. 
The contact of the Archaean granite and the Wyoming Red 
beds illustrates then that phase of case 2 in which marine erosion 
has cut beneath the valley bottoms of the subsiding surface of sub- 
aerial erosion. 
Case 3. Cliff erosion less rapid than shore line shifting by sub- 
mergence. Hypothetically the surface of marine denudation would 
in this case have a steeper slope than that of subaerial erosion. 
This is manifestly impossible unless an initial cliff is assumed. The 
case then becomes a later stage of a process begun under the con- 
ditions of Case 1 or Case 2. Assuming the development of such 
cliffs the surface of marine erosion will slope seaward intersecting 
first the deeper and then the shallower valleys. 
The principles illustrated by these three cases may be success- 
ively operative in controlling the contour of a single land surface, 
that is, the three cases given above represent conditions which 
obtain at different stages of cliff recession and shore line migration. 
If low initial cliffs, which are of common occurrence, be assumed, 
then cliff recession will be more rapid than shifting of the shore 
line due to subsidence, and the contour will be controlled by marine 
erosion (Case 1). The convex curve of subaerial erosion will be 
altered to a curve which is concave upwards. With the pro- 
gressive decrease in the rate of cliff cutting, due to their increasing 
hight there will arrive a stage in which conditions obtain similar to 
that of case 2, i. e., when cliff erosion will just equal the shore- 
shifting due to subsidence, and the contour curve will be at a lower 
level than the preexisting contour of subaerial erosion, but similar 
and parallel to it. Subsequently cliff-recession will become less 
rapid than shore-shifting and the conditions are similar to those of 
case 3. The curve of marine erosion becomes curved upward and 
will approach but never quite coincide with the curve of subaerial 
erosion. 
If the subsiding remnant of land be an undissected plain, it 
will be reduced by cliff cutting at an increasingly rapid rate as the 
hight of the cliffs grows less. If the subsiding remnant be dis- 
sected by valleys, islands will result from submergence, which will 
each reproduce the story of the entire land-mass. 
If instead of low initial cliffs, well developed cliffs, cut while 
the land is stationary, be assumed, that stage of the process rep- 
resented by case 1 will be omitted, otherwise the history of cliff- 
cutting and shore-shifting will remain the same as that given 
above. 
In this abstract the reviewer has followed more or less closely 
Mr. Fenneman's language, which is extremely concise so much so 
