12 



BULLETIlSr 181, XJ. S. DEPAETMENT OF AGBICULTUEE. 



The hydrograph shown in figure 4, A, is that for the Pearl River 

 at Jackson, Miss., covering a period from May 18 to July 17, 1909; 

 it indicates all fluctuations in rate of run-off during that period. The 







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o>i9niDso}j lOOooHs: Nos>fovp iiii^uonc} aiiqoozv/. 



initial rise occurring on May 18 was due to the rain of May 15, and 

 the final rain affecting the run-off for the period considered occurred 

 on July 9. The upper curve of the diagram represents the actual rate 

 of run-off for the period ; the lower curve indicates what the rate of 



