A DAY WITH A NATURE GUIDE 187 



manuals. What the guide says is essentially na- 

 ture literature rather than encyclopedia natural 

 history. 



This party being interested in the distribution 

 of plant and animal life, and in erosion, the guide 

 made these the features of the day's excursion. In 

 a mountain region widely varying life zones are 

 seen side by side; and two or three types of ero- 

 sion may, in places, be seen from one viewpoint — 

 the wear and tear on the earth's surface by many 

 forces stands out unmistakably. 



All that the guide said concerning erosion could 

 be set down under the heading : The Biography of 

 a Canon. The various forces of erosion — running 

 water, frost, ice, and acid, each at work in its re- 

 spective place with distinctive tools — were prying, 

 wedging, cutting the canon wider and deeper. Roots 

 wedged the rocks and dissolved them with acids, 

 but at the same time helped also to resist these 

 tireless forces, placing a binding, holding network 

 of fibres. Gravity handled the transportation of 

 dislodged material. 



Each species of plant and animal is of orderly 

 distribution and is found in the places that furnish it 

 the necessities of life. On the middle slopes of the 

 Rocky Mountains are trees, flowers, and animals 

 that are not found a thousand feet farther up the 

 slopes nor down the slopes a thousand feet in the foot- 

 hills. The guide's discussion was the autobiography 

 of each species — ^The Story of My Life, or How I 



