74 THE ADVENTURES OF A NATURE GUIDE 



Only a few of the earth's numerous tree people 

 dwell at timberline. Those most commonly found 

 both at timberline in the heights and the low levels 

 of the north are pine, spruce, fir, aspen, birch, and 

 willow. On the eastern slope of Long's Peak 

 timberline is approximately two miles above sea- 

 level. Here, in a moist place by a tiny tributary 

 of the Mississippi, grow Engelmann spruce, Al- 

 pine fir, black birch, aspen, and Arctic willow. On 

 a near-by dry slope all the trees are limber pines. 



On Mount Orizaba, close to the equator, timber- 

 line is maintained above the altitude of 13,000 feet. 

 In the Rockies of Colorado and in the Sierras it is 

 at approximately 1 1,500 feet. The highest tim- 

 berline of normal trees in the United States that I 

 have found is on a gulch of the San Juan Mountains 

 at an altitude of 12,300 feet. Here are upright trees 

 more than a foot in diameter and 60 feet high. Tim- 

 berline in Switzerland is about 6,500 feet; on Mount 

 Washington about 5,000; on Mount Rainier about 

 7,000. In most localities it is higher on the south- 

 erly mountain slopes than on the northerly. In 

 the far north the altitudinal and latitudinal tim- 

 berlines converge and form the defensive outpost 

 of the forest on the edge of the polar world. 



Broken wild-flower gardens crowd and colour 

 every ragged opening among the picturesque tree 

 groups on the forest frontier. Many of these 

 flowers are dwarfed and tiny but in moist places 

 they grow thickly and tall. Among the last trees 



