T07ifb %\\t on t%t (Boc^s 



in the middle mountain-zone, and observe how 

 unlike the trees are which thrive on opposite 

 sides. On the southerly slopes that come down to 

 the water is an open forest of yellow pine, and on 

 the opposite side, the south bank, a dense forest 

 of Douglas spruce. If one be told the altitude, 

 the slope, and the moisture conditions of a place 

 on the Rockies, he should, if acquainted with the 

 Rockies, be able to name the kinds of trees grow- 

 ing there. Some trees grow only in moist places, 

 others only in dry places, some never below or 

 above a certain altitude. Indeed, so regular is the 

 tree-distribution over the Rockies that I feel cer- 

 tain, if I were to awaken from a Rip Van Winkle 

 sleep in the forests on the middle or upper slopes 

 of these mountains, I could, after examining a 

 few of the trees around me, tell the points of the 

 compass, the altitude above sea-level, and the 

 season of the year. 



At an altitude of about sixty-five hundred feet 

 Cottonwood, which has accompanied the streams 

 from the foothills, begins to be displaced by as- 

 pen. The aspen {Populus tremuloides) is found 



growing in groups and groves from this altitude 



204 



