310 ANNUAL REPORT SMITHSONIAN INSTITUTION, 19 3 8 



floodwaters back. You will have noticed how the last Mississippi 

 flood of 1936 was the wildest and most dangerous of any in the history 

 of the river, notwithstanding all the protective measures that had 

 been carried out, simply because the lower river is being raised more 

 and more above the level of the surrounding country. 



A large amount of work is now being done in the United States to 

 control gullying and to reclaim the devastated land. In the early stages 

 gullying can be checked by throwing dams across the gash, dams 

 which may be timber or concrete or just bushes, alive or dead, any- 

 thing that will check the rush of water and cause the sediment to 

 begin to accumulate. Even more effective has been the introduction 

 of rapidly growing vegetation, e. g., Kudzu (Pueriana Thunbergiana 

 hirsuta), a creeping leguminous plant, which not only checks the flow 

 of water and filters out the silt but binds the earth and stops further 

 washing, and at the same time gathers nitrogen and begins to build up 

 a new soil. The Soil Conservation Service in the United States is 

 bringing into play all the resources of science and engineering to 

 repair the damage which has been inflicted upon the land of the 

 United States by hasty exploitation. I would instance again the 

 Civilian Conservation Corps, that inspiration of President Roose- 

 velt's, who in 1932, when the youth of America found no prospect of 

 employment of any kind on leaving school or college, gathered some 

 300,000 of them into a service and set them to work to clean up the 

 countryside. They were turned on to fire-prevention work in the 

 forests, to checking erosion, to road maldng and vermin destruction in 

 the national parks, to various forms of reclamation and salvage work — 

 the corps itself being the most magnificent piece of human salvage 

 this generation has known. One cannot but think that it would be 

 of value to our population if all our young men could be conscripted 

 for 6 months of their life to carry out public work for the improvement 

 of our countryside. 



The examples of erosion I have been putting before you are all due 

 to unthinking exploitations of the soil by civilized men. I now want 

 you to consider what is going on in Africa under native systems of 

 farming. To begin with, we must realize that none of the African 

 tribes had arrived at what may be called a "conservative" system of 

 farming, such as has been the custom of European races and of many 

 Asiatics from the earliest times of which we have record. European 

 farming is essentially founded upon a rotation of crops in which a 

 recuperative legume like clover or beans finds a place, and in which 

 again livestock play their part in converting into manure such parts 

 of the crops, like straw, as are not available for human food, together 

 with grass and other rough fodder from the uncultivated land. The 

 African tribes are still in the more primitive stage of "shifting culture." 

 The cultivator is allotted a particular plot in the area of jungle or 



