CHAPTER V I T . 

 THE DISSECTED VOLCANO OF CRANDALL BASIN, WYOMING. 



By Joseph Paxsojst Iddings. 



INTRODUCTION. 



The exploration of the country in the northeastern corner of the Yel- 

 lowstone Park and immediately east of it led to the discovery of a volcano 

 so eroded as to expose its internal structure and to permit the connection or 

 relationship between coarsely crystalline and glassy forms of the same 

 magmas to be distinctly made out. 1 More or less satisfactory demonstra- 

 tions of this relationship have been made at different times within the last 

 twenty-five years, but few of them have been based on occurrences where 

 the evidences of the former existence of a typical volcanic cone have been 

 unquestionable. 



The classic studies on "The secondary rocks of Scotland," 2 by Prof. 

 John W. Judd, and his memoir "On the ancient volcano of Schemnitz, 

 Hungary," 3 describing the "basal wrecks" of Tertiary volcanoes in these 

 regions, while accepted, by many as conclusively demonstrating the con- 

 temporaneity of the granular rocks and volcanic lavas at these localities, 

 failed to convince a large number, who imagined that the observations 

 might be susceptible of other interpretations. 



The dissected volcano of Tahiti, visited in 1839 by James D.Dana, 4 was 

 considered by him to have been sufficiently eroded to disclose a granular 

 core, but there was no opportunity offered at the time of his visit to explore 



1 Jour. Geol., Vol. 1, 1893, p. 606. 



2 Quart. Jour. Geol. Sou. London, Vol. XXX, 1874, pp. 220-302. 



3 Idem, Vol. XXXII, 1876, p. 292. 



4 United States Exploring Expedition during the years 1838, 1839, 1840, 1841, 1842, under the 

 command of Charles Wilkes, U. S. N., Vol. X, Geology, by James D. Dana, Philadelphia, 1849. 



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