132 REVIEWS AND BOOK NOTICES. 
overflows of lava, which forms the walls of the grand cañon of 
the Yellowstone. 
The last trace of this volcanic activity, for there are now no ac- 
tive voleanoes in Montanaor Idaho, is seen in the numerous hot 
Fig. 178. 
Geyser, East Fork of the Yellofvstone. 
springs or extinct geysers, in the valleys, of which Fig. 178 repre- 
sents a good example. How this region was drained we will 
answer in the author’s own words. 
