114 FOREST LANDS FOE THE PROTECTION OF WATERSHEDS. 



searches have been cited. I have examined his numerous tables and I can 

 only give it as my professional opinion that his argument is hopelessly defective 

 for lack of sufficient data. On the Ohio River, for instance, he takes a period 

 of twenty-four years, divides it into two twelve-year periods, and shows that in 

 the second of these periods moderate floods were more frequent than they were 

 before. This period runs from 1876 to 1900, beginning long after the bulk of 

 the deforestation of the Allegheny and Monongahela watersheds had taken 

 place. 



From information recently collected at the United States Engineer office at 

 Pittsburg it appears that the change in forest areas on these two watersheds 

 during this entire period amounted to barely 6 per cent of the area of the 

 watersheds, and that the mean change from the middle of one period to the 

 middle of the next was only 3 per cent. Manifestly to draw any conclusions 

 as to the effect of such a change upon the flow of these streams is absurd. It is 

 not at all unlikely that another period of twelve years will show a reversal of 

 the above conditions. 



The same is also true of the Connecticut River watershed, where it is an 

 admitted fact that the forest area is now even more extensive than it was forty 

 or fifty years ago. I have not the data on hand to test Mr. Leighton's findings 

 in regard to the Tennessee River watershed, but, in any case, there is one hope- 

 less lack of data, and that is the relation between each particular flood and the 

 rain that produces it. It is not a question of " means ; " it is a question of spe- 

 cific cases. It often happens that a smaller rain, coming upon a watershed 

 already soaked with previous rains, will produce a greater flood than a much 

 heavier rain upon the same watershed when the latter is dry, and, unless these 

 conditions are known and the manifold circumstances attending them, any such 

 conclusions as Mr. Leighton has drawn, when applied to particular local water- 

 sheds, are unwarranted. In my paper I was very careful not to run into this 

 error. I took only the broad, general results as summed up in the final flow 

 of our great rivers, and from them it was conclusively shown that deforestation 

 has not diminished the extremes of flow at all. 



In regard to the question of erosion I give the result of my own observation, 

 and that is that it is almost universally a question of cultivation. A tree has 

 no power to prevent erosion, except that portion which is directly on the ground, 

 and if the tree is cut down and removed the condition of the ground remains 

 as it was before, except where logging roads or chutes are constructed for the 

 removal of the timber. When the cutting of timber is immediately followed 

 by undergrowth, the latter is in every sense as effective, and often very much 

 more effective, in preventing erosion than the timber itself. It may be replied 

 that trees are cut down only to give place to cultivation and that, therefore, de- 

 forestation and tree cutting mean the same thing ; but they do not by any means, 

 and there are vast areas all over our country to-day that are deforested, i. e., 

 the virgin timber has been removed, but have not been reduced to cultivation 

 at all. In the matter of preventing erosion of our fields, it is a question of 

 what kind of cover will best serve this purpose and meet the other uses to 

 which the soil is to be put If that cover is a forest, let it be adopted, but do 

 not attempt to establish any hard-and-fast rule of general application that the 

 removal of our forests leads to the erosion and ruin of our fields. It does so 

 in only special cases where the soil is extremely unstable and liable to wash 

 away upon any disturbance. 



Doctor Swain states, on page 6, that I have not proven that forests never 

 diminish great floods, or that they probably do increase them somewhat, and 

 that it is therefore only a matter of my personal opinion. In reply to this I 

 invite your attention to the tables showing the great floods on our principal 

 rivers, as far back as records have been kept, and you will there find that both 

 the great floods and the extreme low waters were quite as great and quite as 

 frequent in the earlier periods as they are at the present day. 



Doctor Swain's criticisms of my reference to the reservoir scheme projected 

 for the river Rhone are not well taken, in the absence of information on his 

 part. If he will read the remarks of the French engineers upon this subject, 

 he will see that they found, after very exhaustive study, that the system of 

 reservoirs they proposed with outlets permanently opened would have aggra- 

 vated the flood which actually occurred in the lower portions of that valley in 

 1856. 



The doctor's criticism of my reference to the flood of 1908 in western Mon- 

 tana (p. 9) is also not well taken. It was not a matter of opinion at all, but 

 a practical, logical proposition, as capable of demonstration as any proposition 

 in mathematics. 



