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their flow, — a condition of great importance for all industries 

 dependent on irrigation and waterpower. 



PrcTcntion of Erosion. 



In close connection with these effects of forest cover upon the 

 flow of water stands its influence on the stability of the soil. The 

 Tendency of the rain waters falling on hills and mountains 

 is to carry in their descent to the valley loose particles of soil 

 Avith them and as the little rivulets run together and acquire 

 force gravel, stones, and even large rocks and boulders are broken 

 loose and moved to lower levels by the torrent. This action, 

 known as erosion, takes place everywhere more or less rapidly, 

 according to the presence or absence and character of the soil 

 cover and no better or more eflicient protection against it is to 

 be found than a dense forest cover. The forest alone is capable 

 of obstructing the mechanical eft"ect of the rainfall upon the soil, 

 and retarding the rapid surface drainage which becomes the 

 carrier of the debris. Here, again, the condition of the forest 

 floor, rather than the tree growth, is the eft'ective element. 



The losses caused by preventable erosion are enormous, have 

 ruined many sections of what was productive country, and have 

 a far-reaching eft'ect. \Miile this erosion, which has followed 

 deforestation in parts of these islands, may be manifested on a 

 smaller scale in this Territory, the examples displayed in other 

 countries should be a warning for us to prevent it wherever pos- 

 sible by protectnig our present forests and extending them where 

 their beneficial eft'ect is needed. 



The removal of a forest covering from the moimtains and 

 hills results in a largely increased burden of solid material in the 

 rivers. Upland meadows, in spite sometimes of even a grass 

 covering, are gullied and scoured until they are turned into worth- 

 less lands. The sediment is carried to the lower-lying regions and 

 much of it is deposited in the stream beds. The river channels 

 become so filled that navigation is greatly hindered or constant 

 dredging must be resorted to. Also, where storage reservoirs 

 have been built by constructing dams, the sediment is deposited in 

 the reservoirs and reduces their capacities. The silt carried by 

 some of the rivers in the United States amounts to millions of 

 tons annually and erosion renders large areas of fertile soil un- 

 fertile and at least temporarily useless for human occupancy. 



The pasturage of sheep in the Alps of Southern France which 

 resulted in the removal of the cover from the forest floor was the 

 chief cause of the destructive torrents with which the French gov- 

 ernment has been struggling for many years and has spent over 

 35 million dollars in trying to correct. The examples of the 

 destructive results caused by erosion and floods, following de- 

 forestation, are very numerous. Most of the springs and brooks 

 of Palestine, familiar to you from your Bible reading, and with 

 them the fertility still celebrated in the early middle ages, have 



