Trails 205 
mountain trail is now over sedimentary rock, 
now over lavas, again through crumbling 
shale or over a glacial moraine, and borrows 
character from each in turn, according a 
practical view of these things. 
The effect of much following of trails is to 
imbue one with a sense of topography. An 
old prospector can judge what kind of travel- 
ling it will be on a distant range from its 
topography, which also reveals some features 
of its geology. In this Giant Cactus country, 
the mountains are largely granite, schist, or 
andesite, while the mesas are basalt, and each 
has its characteristic outlines, so that far in 
the distance it is possible to make a good 
guess as to what a mountain is made of. An 
eye that has had long training scans a range 
or bit of rough country, much as a general 
looks over a battle-field, and decides where are 
the best approaches and the point of attack. 
When the trail is lost, or vanishes now and 
then, as it does hereabouts, to reappear farther 
on, the practised eye knows where it ought 
to be and so one manages to pick it up again 
like a broken thread. Now the possessor of 
such an eye bears in mind whenever he follows 
a new trail that he will very likely wish to 
return and that landmarks are of the greatest 
