Of the immense carrying power and potential energy of this stream it is difficult to form an adequate conception. It yearly carries into the Mississippi 550,000,000 tons of earth, which has been brought an average distance of not less than 500 miles. The work thus represented is equivalent to 275,000,000,000 mile-tons, or tons carried one mile. The railroads of the United States carried in the year 1901 141,000,000,000 mile-tons of freight. [Sidenote: BEDS OF THE OLD RIVER.] That such an exercise of power should leave its impress deep upon the country through which the river flows is not to be wondered at. Every year thousands of acres of rich bottom lands are destroyed. Forests, meadows, cultivated fields, farmhouses, and villages fall before its tremendous onslaught, and the changes that have been wrought in the topography of the valley during the past one hundred years almost defy belief.[11] To one familiar with its history, the many crescent-shaped lakes and curvilinear benches show where the river once flowed and where it may flow again. In recent years the government has seriously undertaken to set metes and bounds to the migratory habits of the stream; but it has found a most refractory subject to deal with. Even with the expenditure of vast sums of money in the construction of the most powerful dikes and improved bank protection known to engineering, it can never feel certain that its prisoner will not break its bonds at any moment and escape. [Illustration: SNAGS IN THE MISSOURI RIVER (After Maximilian)] [Sidenote: SNAGS AND SAWYERS.]