See 
REVIEWS AND BOOK NOTICES. 731 
scenery on the continent. In passing up the valley of the upper 
Yellowstone, which is about three miles wide and has been carved 
out of this hard breccia, one could easily imagine himself in some 
enchanted land, where, on every side, were castles and palaces with- 
out number.” Farther on our author concludes that “the erosive 
forces have acted on a more stupendous scale than he had ever be- 
fore conceived of, and that the entire series of sedimentary strata, 
from the lowest Silurian to the highest Tertiary, known in the 
West, has extended in an unbroken mass all over the northwest ; 
and we find here and there by the exposure of the entire series, as 
at Cinnabar Mountain, and in many other localities, the most sat- 
isfactory proof of the statement which I have so often made. This 
Fig. 177. 
Index and Pilot Peaks. 
single statement implies that from 10,000 to 15,000 feet in thick- 
ness of unchanged rocks have been removed from this mountain 
Tegion, except what might be called remnants left behind, occu- 
pying restricted areas.” 
The period of intensest voleanic activity culminated during the 
later Tertiary period. The mountains resulting have now assumed 
such forms as are shown in Fig. 177 of Index and Pilot Peaks, 
while Fig. 176 is an example of basaltic columns, the result of 
