356 J. W. Poweli’s Survey of the Rocky Mountain Region. 
long enough after the close of the Eocene to allow for the accu- 
mulation of these vast bodies of voleanic beds. This may 
carry the period of faulting far into the Miocene period, or pos- 
sibly as far as the commencement of the Pliocene. But while 
One point which during the study of this region has engaged 
the careful attention of Captain Dutton, has been to ascertain 
whether it presents any such sequence in the lithological char- 
acter of the eruptions as is asserted by Baron Richthofen to 
prevail in the voleanic districts of Europe, South America, 
Asia Minor, and the Sierra Nevada. This asserted sequence 
has engaged the profound attention of most vulcanologists and 
is of great importance in relation to all questions bearing upon 
that the high plateaus of Utah exhibit in a deci anner 
essentially the e sequence which Richthofen claims for 
ther volcanic he earliest eruptions consist of roc 
the great displacements and partly through the agency of ero- 
sion, and wherever found it is seen to occupy the lowest posi- 
