PRACTICAL ARBORICULTURE 117 



Missouri, Yellowstoq*, Platte, Kansas, Arkansas, Red, Canadian, etc., and the 

 Rio Grande of the South, an international waterway, all rise in the Rocky 

 Mountain Range. 



The regularity of flow in all these streams is entirely dependent upon the 

 snowfall and its period of melting in this high mountain range. The South 

 feels the mighty influence of this power as the strength of the embankment 

 and the height of the levees along the Mississippi and numerous rivers and 

 bayous are controlled by this one cause ; while the navigation of Western 

 rivers, the period of navigable depth, and consequently the regularity of West- 

 ern commerce is also dependent upon the length of time occupied by these 

 mountain snows in melting. 



A very large area of the United States is, to a greater or less extent, arid, 

 must be irrigated to enable vegetation to exist and thus provide homes and 

 farms for the rapidly increasing population. 



The extent of the land which may be reclaimed from the desert, the 

 amount of wealth which must be expended in reservoir construction and 

 maintenance by the Nation, and as a consequence how great a population the 

 Nation may support, in the semi-arid belt, will all depend upon conditions 

 existing in the Rocky Mountain region, and which may, to a very large extent, 

 be controlled by man, and this again will depend upon the area of the forest 

 cover upon the mountain slopes. The great number of bridges which in the 

 past few years have been swept away by floods of water from the too rapid 

 melting of snows attest the vast influence of the Continental Divide upon the 

 railway commerce of the West, while the cities submerged, homes and prop- 

 erty destroyed, and lives lost in these floods are in evidence to show the 

 destruction which may be caused by water uncontrolled, and which are influ- 

 enced by conditions in this elevated mountain region. 



IMPORTANCE OF THE FORESTS. 



So long as the mountain slopes are covered with timber, the snow is held 

 in place, shaded from the rays of the sun, and thus gradually, with the advent 

 of warm weather, is melted away, requiring several weeks to entirely disap- 

 pear. Although, of course, at a few points in the higher mountains, and upon 

 northern slopes, some snow remains throughout the year. 



Removal of the forests, baring the rocks, enables the sun's rays to reacK 

 the snow-beds and melt it very rapidly. Thus the great volume of snow is 

 converted into water in a brief period, and, rushing down the steep gulches, 

 swells the streams to overflowing, creating havoc all the way to the sea. 

 More than this, the great rivers in the lower and level country, which have 

 thus tested the capacity of their banks and levees along their lower courses, 

 are soon reduced in volume, in depth, and in their capacity to bear the coun- 

 try's commerce. 



To remedy this condition and increase the navigable depth of rivers, the 

 Government expends annually many millions of dollars, under the enormous 

 appropriation for rivers and harbors improvement. Yet very much of this 

 work is ineffectual because the prime cause is lost sight of and only the 



