220 THE LUKE OF THE LAND 



running streams. Attempts have been made to esti- 

 mate the quantities of silt carried in some of the great 

 rivers. The Geological Survey has made a number of 

 estimates of this, kind, and has come to the conclusion 

 that the quantity of silt carried by the Hudson River 

 is 240,000 tons a year; by the Susquehanna, 240,000 

 tons ; by the Roanoke, 3,000,000 tons ; by the Alabama, 

 3,000,000 tons; by the Tennessee, 11,000,000 tons; and 

 by the Missouri, 176,000,000 tons. 



In the Yearbook of the Department of Agriculture 

 for 1913, Mr. Davis gives an estimate of the losses 

 which occur to agriculture from erosion of the soils. 

 He says: 



It has been estimated that the Mississippi River, which 

 drains over one-third of the area of the United States, delivers 

 to the Gulf of Mexico from 370 to 680 million tons of sus- 

 pended material yearly. Accepting the lower figure and as- 

 suming a lower rate for the rest of the United States (500 

 million tons), the total amount of soil material carried to the 

 seas amounts to 870 million tons a year. Assuming that one- 

 half of this is unnecessary waste, there is an annual loss of 

 over 400 million tons of soil material. This means a prevent- 

 able waste yearly of more material than was removed in dig- 

 ging the Panama Canal. But this is only part of the story, 

 for only a small portion of the soil brought down from the 

 hills is carried to the mouths of the rivers. What proportion 

 it is impossible to estimate. . . . 



Some idea of the extent of this loss may be gained from the 

 fact that the National Conservation Conference in 1909 re- 

 ported nearly eleven million acres of abandoned farm land 

 in the United States, most of it damaged and over one-third 

 or about four million acres actually destroyed by erosion. At 

 an average original value of $10, the loss amounts to $40,000,- 

 000. The loss from non-production is probably as much 

 yearly. Added to this the losses to navigation and water 

 power and the expense of keeping open channels will almost 

 double the amount, so that annually the United States is suf- 



