DAVIS: THE GRAND CANYON OF THE COLORADO. 193 
the more striking things are here presented in the hope that they may 
prove of service to more leisurely travellers. 
The dissection of Mt. San Francisco, as seen from the wagon road 
that runs northward from Flagstaff along the western base of the 
YN 
Uf / WS sh 
We Sh 
ee. AY 
Aa S \\ \ qi 
off cf fo Aes Ail 
SNS L Fight SSpLLe 
Vk on “~~ es 
¥ (aight 
PD | 
Basa) ) 
Figure 17. 
Diagram to illustrate a proposed terminology of spurs and ravines. Constructed from 
several sketches of the western side of Mt. San Francisco, a dissected volcano. 
mountain, suggested a simple terminology for spurs and ravines that 
might perhaps be serviceable in detailed descriptions of mountain forms. 
The scheme is illustrated 
in the accompanying fig- 
ure, 17, which repeats some 
of the features illustrated 
in the diagram of the Per- 
mian scarps (Figure 9). I 
shall hope to return to 
this phase of morphology 
f ; Th Fieure 18. 
asome Tubure bE 2 An ash cone and crater, north of Mt. San Francisco 
young ash cones, still hold- and east of Hull spring. 
ing unbreached craters, 
were numerous in the volcanic field north of Mt. San Francisco (Fig- 
ure 18). About ten miles west of Hull spring (on the Flagstaff-canyon 
road) a large ash cone was seen with a great breach in its eastern 
