FISHER: RIVER TERRACES. 
29 
which have suffered no weathering and only slight undercutting by 
the swinging of the brook. This simple ideal type, represented in 
text-figure I, shows at least one distinct terrace, with scarp concave 
toward the brook, and more or less cuspate,— the cusps formed between 
the concave incision of the meanders of the brook. xAs each meander 
sweeps down the brook valley, it probably diverges sufficiently from 
its original angle of incision 
to make a series of these con 
cave cuts, uniting in notice¬ 
able cusps. These cuspate 
edges are most apparent 
when the terrace scarp faces 
the brook, and are entirely 
wanting when the terrace 
scarp has been carved by the 
forward extension of an arm 
of the meander. The text- 
figure I shows that such 
sweeps of the terrace scarp 
face up-stream. An illustra¬ 
tion may be seen on plate 1. 
The low terrace facing the 
right side of the meadow is 
distinctly cuspate just before 
it makes the long, concave 
curve of the R-etreat scarp. 
A meander of the West River 
carved the deeply compressed 
Retreat scarp after it had suc¬ 
cessively cut the right-hand 
cusps. 
Three of the early stages 
in the development of the 
West River terraces may be traced as shown by diagrams (pi. 3, figs. 
1,2; pi. 4, fig. 3), which are necessarily more or less hypothetical, since 
it is impossible to-day to locate with absolute definiteness the positions 
occupied by the river thousands of years ago. The West River has 
been swinging and slowly degrading its aggraded valley since the 
glacial period. In following its left-hand wanderings, theie are lem- 
Fig. I.— Ideal terrace pattern; early stage. As 
each meander progresses down-valley, it 
vacillates sufficiently to carve the curves 
and cusps characteristic of the early stage of 
terrace scarps. 
