FOEEST LANDS 'FOR THE PROTECTION OF WATERSHEDS. 47 



its velocity and according to the size of the grains of soil. It de- 

 posits them according as its velocity decreases and it is no longer 

 able to carry that silt. And so, as it goes down the stream, it erodes 

 here where its velocity is great and deposits there where its velocity 

 is small, and so it gradually carries the mass of soil to the sea. It 

 always carries some down, and although it may take years for silt to 

 reach the sea from the mountains, it finally reaches there. 



The CHAIRMAN. Of course, the silting process takes place in flat 

 countries as well as in mountain countries. The streams in Kansas, 

 for example, which, before the country was settled, were clear streams 

 with rock or gravel bottoms, are now covered with a thick deposit, 

 3 to 6 feet in the deeper pools, of mud washed in from the surround- 

 ing farms. 



Professor SWAIN. Yes. 



The CHAIRMAN. We could hardly put the country back into prairie 

 grass in order to restore the streams, could we? 



Professor SWAIN. No, sir; but you could protect the upper parts 

 of the streams, where the floods arise. 



The CHAIRMAN. That is the point I want to make. It is on the 

 mountain slopes where the floods take their rise. 



Professor SWAIN. And if those can be protected the floods will 

 be diminished. We can not, however, obviate floods. There will 

 always be floods, and I will explain that presently. In 1898 there 

 was a report of a committee on floods of the Mississippi River, and 

 of that committee Senator Nelson was chairman. In the report they 

 stated that they were unable to find any relation between the cutting 

 down of the woods on the upper Mississippi River and the floods of 

 the Mississippi. The explanation is perfectly reasonable. I pre- 

 sume that committee did not go into any very elaborate study of the 

 phenomena, as they did not have time to do it, and yet I am perfectly 

 ready to admit the general truth of that conclusion. The reason is 

 that that is a flat country, and there could be no relation traced be- 

 tween the floods and the cutting down of timber. That same report 

 states that all of the great floods of the Mississippi come from the 

 Ohio. There you have the thing in a nutshell. The Ohio drains 

 the western slope of the Allegheny Mountains. I think it might have 

 been said that the floods come from the upper portions of the Ohio 

 in the mountain regions. That is the birthplace of the floods, where 

 they gather, in the steep mountain sides and are carried down to the 

 streams. 



The CHAIRMAN. Does not the watershed increase in area as you 

 approach the navigable portions of the stream ? 



Professor SWAIN. Certainly. 



The CHAIRMAN. And is it not likely, therefore, as a matter of fact, 

 that the greater portion of the water which causes the flood falls upon 

 that part of the watershed immediately tributary to the navigable 

 portion, and not on the comparatively restricted area of the upper 

 tributaries ? 



Professor SWAIN. I think not. I think the birthplace of the floods 

 is in the high mountain slopes, and that the control there will 

 have a great deal more efficacy than the control anywhere else. In 

 studying this matter there are great difficulties in tracing their con- 

 nections, and I would like to dwell upon that just for a minute. The 

 reason of the difficulty is that we can not isolate the phenomena of 



