202 



SEE— FURTHER RESEARCHES ON 



[April 24, 



Fig. 3. Relief Map of North America. (From Frye's Complete Geog- 

 raphy, by permis.sion of Ginn & Co., Publishers.) This map illustrates beauti- 

 fully the recession of the sea since the formation of the Rocky Mountains, 

 which were at one time the eastern border of the Pacific Ocean. 



