FOEEST LANDS FOR THE PROTECTION OF WATERSHEDS. 49 



The CHAIRMAN. Is that result definite unless you know when the 

 rains occurred; that is, in what way they came? As you suggested a 

 little while ago, there might be one year of rainfall that would give 

 a certain number of floods, and another year of precisely equal rain- 

 fall that would give a different number of floods, because differently 

 distributed. m Does Mr. Leighton's report take account of that? 



Professor' SWAIN. -It takes some account of that; yes, sir. There 

 are difficulties in tracing any direct relation, and I think, Mr. Chair- 

 man, that the proper way to arrive at a conclusion, the way which 

 appeals to me, is by a study of the elementary influences, a study of 

 the forest bed. the measurement of the percolation into the soil, and 

 the actual observation of the way the streams come from the forest 

 land, and the way they come from the deforested land. Those, I 

 think, will convince anybody that there must be a relation there 

 which is definite, and that cutting down the trees has a large effect in 

 diminishing floods. 



I would like to refer briefly to one or two objections which are 

 sometimes made to that theory. Fifty years ago a French engineer 

 published a work in which he attempted to show that cutting down 

 the forests diminished the floods. That had no effect on the French 

 Government, and evidently was not shared by the government engi- 

 neers, because the French Government immediately began thereafter 

 to adopt a forest policy and to expend large sums in the reforesta- 

 tion of the mountains. Recently, within a few months, an American 

 engineer, a member of the Corps of the Engineers of the Army, has 

 published a paper, which the chairman has referred to. in which he 

 gives almost the identical arguments which were given fifty years ago 

 by the French engineer. I hope they will be followed by the same 

 action which was followed in France. One of the arguments made 

 is that sometimes the forests may increase the flood, as, for instance, 

 suppose the snow lies late in the forests and there comes a warm rain. 

 That warm rain carries off the snow and the flood results, and that 

 flood is larger than would have resulted from that warm rain if the 

 forests had not retained the snow. That is perfectly clear, but it is 

 equaly clear that if the forests had not been there that snow would 

 have gone off in the earlier floods, as Congressman Weeks has sug- 

 gested, and that those earlier floods would have been largely increased. 

 The effect of the forest is to distribute the discharge into the stream 

 in a given amount. 



Mr. WEEKS. Do you know any engineer of good standing who 

 agrees with Colonel Chittenden in his conclusion ? 



Professor SWAIN. I have not met with any, sir; and I hope that 

 the chairman of the committee will read the discussion on Colonel 

 Chitten den's paper which will appear in the proceedings of the 

 American society in connection with the paper itself. 



The CHAIRMAN. There is one other question more I would like to 

 ask Mr. Swain, because he has evidently studied this very deeply. 

 You will remember another argument of Colonel Chittenden is that 

 the forest will actually diminish the flow of water in a river by rea- 

 son of absorbing an ordinary rainfall which, if the forests were not 

 there, would floAv into the stream' and increase its volume, but which, 

 the forest being there, is absorbed and held and does not get into the 

 stream in time to do it any good. 



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