Plate XXI 



Fig. 1. A monadnock. A mass of igneous rock isolated by erosion, 

 and remaining because of its superior hardness. Matteo Tepee, 

 Wyo. (Detroit Photo. Company.) 



Fig. 2. A branching stream. Junction of the Cooper and Yukon 

 rivers. Alaska"; shows bars also. (TJ. S. Geol. Surv.) 



