North Atlantic Pleistocene Problem — Sliattuck. loi 
youngest, the lowest portions of the region. Beginning with 
the oldest and enumerating them in succession, we have what 
the author has designated as the Lafayette, Sunderland, Wi- 
comico, Talbot and Recent. The Recent terrace is the one 
which the present sea is building. 
A correct understanding of the physiographic features of 
the terraces may be obtained by studying the manner in which 
this recent terrace is forming. At the present time the waves 
of the Atlantic ocean and Chesapeake bay are engaged in tear- 
ing away the land along their margins and in depositing it on a 
sub-aqueous platform or terrace. This terrace is everywhere 
present in a more or less perfect state of development, and may 
be found not only along the exposed shore, but also passing up 
the estuaries to their heads. The materials which compose it 
are extremely variable, depending not only on the detritus di- 
rectly surrendered to the sea by the land, but also on the cur- 
rents which sweep along the shore. Along an unbroken coast, 
then, the material has largely a local character, while near river 
mouths the terraces are composed of debris contributed from 
the entire river basin. Where the waves are weak, partially 
decayed material is torn from the bank and re-deposited prac- 
tically unharmed on the surface of the terrace, and continues, 
unchecked, its process of decay. 
In addition to building a terrace, the waves of the Atlantic 
and Chesapeake are cutting a sea cliff along their coast line, the 
hight of this cliff' depending not so much on the force of the 
breakers as on the relief of the land against which the waves 
beat. A low coast line yields a low sea cliff' and a high coast 
line the reverse, and the one passes into the other as often and 
as suddenly as the topograph)- changes, so that as one sails 
along the shore of the Chesapeake, high cliffs and low depres- 
sions are passed in succession. The wave-built terrace and the 
wave-cut cliff" then are constant features along the entire ex- 
tent of the bay shore, and should be sought for whenever other 
terrace surfaces are investigated. 
In addition to these features, bars, spits and other forma- 
tions of this character are frequently met with. Were the pres- 
ent coast line to be elevated, the sub-aqueous platform which 
is now building would appear as a well-defined terrace of vari- 
able width with a surface gently sloping toward the water. This 
