576 NOAH FIELDS DRAKE 
decreasing amount for two or three miles into the valley and to 
the right and to the left along the mountain side. This feature is 
beautifully shown on some of the United States Geological Survey 
topographic sheets* of southern California, where at the mouths 
of large canyons, such as the San Gabriel, instead of the contours 
running up towards the canyon, they circle around or away from 
it. Where the rainfall is somewhat greater the débris is carried 
further and distributed over a wider area, forming a fanlike 
extension of sediments. This feature has already been referred 
to in the discussion of the California Valley. 
Superimposed drainage —Near the head of Salinas Valley or 
immediately south of Santa Margarita, there is a valley from 
one to two miles wide underlaid by rather soft Tertiary sand- 
stones and shales. To the east of the valley there is a granitic 
mountain range nearly 2000 feet high, while to the west there is 
a parallel range about 3000 feet high which is composed of 
rather soft Tertiary shales and sandstones. The Salinas River, 
instead of running through this valley, runs close by and paral- - 
lel to it through a narrow deep canyon in the granitic mountain 
range. One stream in particular, and others to some degree, 
that run down from the western or sedimentary range of moun- 
tains, follow the valley for a few miles and then cut through the 
granitic hills by narrow canyons and flow into the Salinas River. 
The divides in the valley deflecting the streams are only about 
100 feet? above the bed of the river while the narrow strip of 
granitic hills cut off between the river and valley, rises six and 
seven hundred feet above the river bed. 
It seems most probable that in this case the soft sandstone 
and shales originally extended over the granitic mountains, as 
well as the valley and mountains to the west, and that the river 
was originally situated vertically over its present course, so that 
it has carved its way down through the soft covering and thence 
into the granite, and has so far kept below the more recent 
erosion-valley in the soft beds by its side. 
*The Cucomonga and San Bernardino sheets of the U. S. Geol. Survey. 
?See San Luis Obispo sheet U. S. Geol. surv. maps, surveyed in 1895. 
