RIVER AND LAKE DEPOSITS 177 
(Fig. 89). The alluvial fan is particularly well de- 
veloped in mountain districts, although we also find 
it, in less distinct form, in hilly regions, where streams 
with steep slopes emerge upon a valley plain. Similar 
accumulations are often seen near the base of a cliff, 
where the talus locally assumes cone shapes (Fig. 90). 
Fic. 89. 
Alluvial cones formed by washing gravel for gold. Gravel carried in the sluices 
is dropped when the current emerges from them, and hence loses its velocity. 
Bars. — Where an obstruction exists in a sediment- 
laden stream, bars may be built in the eddy of the 
current (Fig. 91), or formed opposite the mouth of a 
tributary. These bars are constantly altering their 
form and position; and if the current changes, may 
N 
