PHYSIOGRAPHIC EXTENSION OF UNITED STATES 165 
The streams now occupying the longitudinal valleys have in part 
inherited courses from the earlier cycle, but they generally follow 
structural lines or have had their courses determined by folding 
70 80 100 20 
= SS SS T] <a 
Hs a 
Piet 
be aX 
Liye Mii 
Wi f= 
SR 4 Ww GY Li} XG y a We 
Ne Te Gils I NS 
oN al RN 
ee eS { Vite SS 
A NEEDS 
eee ORME ty 
Sueseeneneet'660ee7 
Ly le 
ALTE 
Mats? 
LL 
Sage 
aren 
EAR aan 
SRY ‘ ee 
. \ & me de gee asl 
dL NinSSRREES eee gee 
PREP REE POPE eet : 
Saqeeane ACER EE A cel 
pA QOCPEELE ET eer 
PHYSIOGRAPHI pee pees ene 
‘| | DIVISIONS ee TLE ae i 
NORTH AMERICA H- Boe anee s 
z Sette OF ee = RB v are 
since the period of peneplanation (as in the Olympic Mountains), 
and are therefore subsequent. 
In certain places, particularly in northern California, this sec- 
tion includes, besides the mountains proper, a tract of dissected 
