V 
more than usually deep. The trachytes and rhyolites were 
poured out into the valleys cut in the Tertiary and Paleo- 
zoic rocks. Subsequent flows filled in the valleys eroded 
from the first flows, and so on through the basaltic and 
conglomerate producing period. On account, however, of 
the occurrence of so many products together, their relations 
are hard to make out. This may be remarked of the Tertiary 
strata, especially the several groups of which cannot easily 
be distinguished from the conglomerate formed in more recent 
times through alluvial and volcanic agencies, and .possible 
indent if icat ions are very nearly impossible. Of course, 
prolonged study may make everything clear.' 
that no attention has been paid to the penetrating observations 
of Holmes and his colleagues made over half a century ago. The 
report of 1878 is replete with careful observations and beauti- 
fully accurate drawings by this master artist of geological 
subjects and the scientific interpretation of scenery.” 
junction with the section near Red Rock, the arenaceous and 
argillaceous deposits near the bottom of the canyon probably 
represent the earlier stages in the filling of the first lake 
which was formed in this part of the canyon, the final stage 
of which is the conglomerate group at the base of the Red Rock 
section. The significance of this deposit did not escape 
"It seems remarkable to the authors of this paper 
A further citation is as follows: "Taken in con- 
