2 The Americmi Geologist. July, i898 
cuspate forelands are developed in a wonderful degree of per- 
fection. In lake Cayuga there are three prominent forms of 
projecting forelands, the delta, the modified delta, and the 
spit (sometimes partly hooked). The delta represents merely 
the dumping of debris brought by a stream into the- lake, ac- 
compa,nied by a certain modification by lake waves and cur- 
rents. Sometimes the supply so far exceeds the action of 
waves and currents to remove it, that the delta form remains 
perfect ; but at times it is considerably modified by the action 
of lake waters. 
Spit oil Lake Cayuga Shore. — On the shore of lake 
Cayuga the modification of delta form has been mainly the 
result of wave work. This would be inferred from the size 
of the pebbles which occur on the delta front; and the truth 
of the inference is verified by a very slight study of the shore. 
In any body of water, but particularly in a narrow body with 
rather high valley walls, the direction of the wave attack is 
in nearly all cases diagonal to the coast. Only rarely can 
the waves advance directly upon the shore in a direction nor- 
mal to it. In a narrow valley of some depth, the waves that 
do reach the shore at right angles to the trend of the coast are 
slight in efifect, for they have only the breadth of the valley 
in which to form. It is the waves that advance most nearly 
parallel to the coast that are the largest, and hence the most 
effective. 
Therefore in a narrow and deep lake valley, like that of 
lake Cayuga, the most effective, as well as the most violent 
waves, come either diagonally or parallel to the coast. (PI. I, 
Fig. i). These may pass from a northerly or from a southerly 
direction; but in this lake the winds from the north are on 
the average more violent and more permanent than those 
from the south. Hence the conditions are these : in the great 
majority of cases the waves extend more or less parallel to 
the coast, and those from the south are less powerful and 
permanent than those from the north. This produces a de- 
cided efifect on the topography of the lake coast line. In the 
case of the deltas there is usually more modification on the 
north than on the south side. Sometimes this consists of the 
addition to the delta of wave-derived debris, wrested from 
the cliffs, and in other cases the driving of stream material 
