DIVIDES. 9

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

San Bernardino Mountains, Cal.

19. Divides.

The slopes of the large valleys in this
picture begin at the tops of the high ridges.
Each slope starts at a divide.

Some divides are on high land where snow
lies all the year. Other divides are low. If
it were not for running water it would be
hard to find them. '

The rain that falls on any slope flows into
the valley to which that slope belongs.

A divide is often called a water parting.
Can you tell why?

Find on the map a water parting that is
on very high land. Find one on low hills;
another on land that is nearly level. __

Point as near as you can to the sources of
all the streams that flow into the Santa Ana
river. All the slopes that send water to these
streams are in the Santa Ana basin. Trace
the divide that bounds this river basin.

 

 

 

 

 

 

 

 

 

San Jacinto Mountains.
20. How Slopes Are Worn.

Find a piece of wood that has lain a long
time on the ground. Cut into it. Has any
part begun to decay ?

Break open a small round stone, or a large
pebble. Which part has begun to decay?
Which part looks brightest ?

Wood decays, and so do rocks decay. All
rocks, both large and small, slowly crumble
into soil.

Wind blows dust and sand about. Rain-
drops wash tiny grains of rock together, and
make them finer.

Frost splits many rocks, and even wedges
off large pieces from cliffs.

Little by little the raindrops, rills, brooks
and rivers wash the fine rock or soil down
the slopes.

Thus, most slopes are slowly crumbling
and wasting away.