RIVER AND LAKE DEPOSITS 189 
This. filling action is aided by the waves that beat 
against the shore. These form cliffs by cutting into 
the rocky coasts, and build beaches on which the pebbles 
are worn backward and forward, and ground into finer 
bits. The gentle currents carry these away and deposit 
them over the lake floor. In the larger lakes, the ero- 
sive action of waves and the carrying power of -cur- 
rents, resemble the work done in the sea. This subject 
may therefore be left for the present (p. 237). 
Animal Deposits. — Animals inhabit lakes, and some- 
times bear an important share in the filling process. 
Fie. 98. 
Long Lake in the Adirondacks bounded by aswampy shore. Vegetation encroach- 
ing upon it. (Copyrighted, 1888, by S. R. Stoddard, Glens Falls, N. Y.) 
Where very little sediment is supplied, as in small 
shallow lakes, layers of animal remains may be deposi- 
ted to form marl or some other earth of organic origin. 
