104: 



IGNEOUS AGENCIES. 



wonderful geyser region is situated in the northwest corner of Wyo- 

 ming, on an elevated volcanic plateau near the head-waters of the 

 Madison Biver, a tributary of the Missouri, and of the Snake River a 





mm 



Fig. 88.— Giant Geyeer (after Hayden). 



tributary of the Columbia. The basin is only about three miles wide. 

 About it are abundant evidences of prodigious volcanic activity in for- 

 mer times, and although primary volcanic activity has ceased, second- 

 ary volcanic phenomena are developed on a stupendous scale and of 



