6 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 65 



then extended to the south on the Gallatin, Madison, and Jefferson 

 rivers. 



It was found that the Prepaleozoic sedimentary rocks were exposed 

 by the uplift of the granite mass forming the summit of Mount 



Fig. 6. — Conglomerate in the sandstones illustrated by fig. 5, where there 

 are boulders and pebbles derived from the limestones beneath. This indicates 

 that the limestones were raised above the surface of the water, so that they 

 were broken up by weathering, and fragments of them carried by streams into 

 the near-by lake and embedded in the sand. Photograph by Walcott. 



Edith of the Big Belts, in such a way that the thickness of the 

 sandstones, limestones, and shales could be readily measured in the 

 numerous sections exposed in the canyons worn by waters descend- 



