334 
THE ECONOMIC ASPECTS OF SOIL EROSION 
quent uprising of the continent would not cause them to be re- 
vealed. 
Along the eastern face of North America, from South Carolina 
to Newfoundland, there exists a series of old mountain ranges, 
to which we may give the name of the Lost Appalachians, that 
have been worn down to their roots by some j^rocess of erosion. 
West of these deeply wasted mountains in the section from Penn- 
sylvania southward we have the yet older ranges of the Blue 
Ridge or Central Appalachians, which on their eastern face have 
been worn away, though their western parts retain a consider- 
able relief. Still further to the west, behind the wall of the 
Middle Appalachians, lie the West Appalachians or Cumberland 
and Alleghany ranges. These last-named elevations retain their 
original reliefs much more perfectly than the seaward moun- 
tains ; they are relatively little degraded. They are recognized 
as mountains in common speech, while those along the Atlantic 
coast, though of younger age, have lost to the common eye their 
mountainous character and are known to the geologist only by 
the altitudes of their rocks. 
Considering from the point of view of economic interests the 
erosion or land destruction which is accomplished by the sea, 
we note that even in historic times it has wrought changes of 
considerable moment to mankind. Wherever the shores are 
bordered by very hard rocks or walled-in by sand beaches, the 
processes by which the land is stri}>ped away and its debris 
carried into the sea are slow ; the destruction is distributed over 
a long ])eriod, and there is no distinct effect in the interest of 
men. Where, however, the coasts are of soft rocks, the waste is 
often so rapid that it may dispossess communities of their in- 
heritance. Thus, at the rate of marine invasion which is now 
going on on the southern shores of Nantucket, that island is 
likely to disappear in the course of two or three thousand years, 
being in the end reduced to the condition of a shoal such as we 
now find in the shallows which stretch far to the southeastward 
of that island, shallows which seem to mark the position of 
ancient lands that have been swept away by the waves. George’s 
shoals and other shoals extending along the coast to the north- 
ern end of the banks of Newfoundland can best be explained by 
supposing that they mark the sites of islands that have been 
planed down by the sea. 
The recorded history of this country is too brief to afford any 
very important instances of marine erosion. In the Old World, 
