20 FOREST LANDS FOR THE PROTECTION OF WATERSHEDS. 



tightly about the upper two-thirds of that cone and sprinkle lamp- 

 black over the lower third, and then have an artificial rain falling 

 on the whole cone. The water in the pan would be discolored immedi- 

 ately, would it not, by the washing of the lampblack? 



Doctor VAN HISE. Undoubtedly. 



The CHAIRMAN. Supposing now we reverse the situation, sprinkle 

 the lampblack over the upper two-thirds and bind the sponge tightly 

 on the lower third of the cone, then have your artificial rain; is it 

 not likely that the sponge would serve as a sort of filter and hold a 

 lareg proportion of the lampblack, and the water would not be so 

 discolored ? 



Doctor VAN HISE. That is so, but I would question, if you may 

 permit me, the applicability to the case. This lower land is not a 

 sponge, but it is, as I have explained, impervious, relatively, and is 

 soft enough so that it can be removed. 



The CHAIRMAN. All the advocates who have come before us have 

 compared a forest to a sponge. That is the reason I used the illus- 

 tration, and my application of it was this : That with the forest sponge 

 upon the lower slopes of the mountain, any erosion from the upper 

 slopes was much more likely to be retained and held and not to get 

 into the streams than if the upper slopes should be protected and the 

 lower slopes left bare, because then when erosion begins there is not 

 anything to filter the water, and it carries its load of soil into the 

 stream. My observation through that country has been that erosion 

 always takes place, if the lower slope is bare, no matter what the 

 declivity may be, and no matter whether the upper slope is covered 

 or not. It does not Always take place if the upper slope is bare, 

 while the lower slope is left covered. 



Doctor VAN HISE. I would not dissent from that. I did misunder- 

 stand. I feel I am taking too long a time, but I would like to put 

 the actual conditions before the committee. The cone does not cover 

 the case, because the mountains are not cones. The mountains are 

 mainly flat-topped ridges and valleys. Supposing this to be a moun- 

 tain [illustrating]. The condition is represented by that kind of a 

 curve. You start with a flat top, in that way, and you go down the 

 curve, getting steeper and steeper. The Hogarth line of beauty rep- 

 resents the curve of the valley to the top of the mountain. I would 

 quite agree with the chairman of the committee that this part away 

 up here would not be the part that is most eroded, because the streams 

 have not gathered sufficient volume, nor would the valley lands, which 

 would be this belt in between, where the streams have gathered suffi- 

 cient volume to become powerful and where the slope is steep. If you 

 premise here a belt, the forest being down here, it will in a measure 

 stop and check the work of erosion that is going on higher up. 



The CHAIRMAN. That being true, does it not follow that if you 

 are going to protect the hills, and in that way protect the streams 

 from silting up, you must keep the forest cover on the intermediate 

 slopes that vou speak of, rather than on the upper slopes? 



Doctor VAN HISE. Yes, sir. 



The CHAIRMAN. If that is true, the suggestion which has always 

 been made before this committee, and which is the whole burden of 

 the report from the Secretary of Agriculture last year on this ques- 

 tion, that we must preserve the upper slopes, has proceeded upon a 

 mistaken hypothesis? 



