In one case there is a 28-inch 
band of variegated flint, having" 
a considerable lateral extent, 
interbedded in the tuff. The 
origin of this is a matter for 
curious speculation; at a dis- 
tance we supposed it a bed of 
"*' i/ri'' e i:)itchstone. No other materials 
not strictly autnchthonous to 
to the volcano were observed. 
The dip of this bed is high and 
away from the theatre of activ- 
ity in a gentle arch but still 
outside are bads which dip 
irregularly and correspond to 
what has generally been iden- 
tified as Tertiary. They contain 
chiefly the same materials as the 
tuff deposits just described with 
additions from the near-by por- 
tions of the range at large; but, 
at a short distance from the 
mountains, only fine-grained 
materials remain and gypsum 
and other evidences of marine 
conditions appear. 
It may be that the conditions 
described are to be understood 
in the sense that the eruption of 
the rhyolitic period were during 
late Tertiary time. At any rate 
the explosive phases of the 
eruption took place at a time 
when, the bases of the uplift 
were washed by the sea and the 
question as to the contempor- 
aneity of the talus beds and the 
more distant marly sands must 
be left open for the present. 
o -5 
