224 



AMERICAN FORESTRY 



its superiority consists in the .great 

 length and permanence of the record 

 and in the unmistakable character of the 

 data it furnishes to one skilled in read- 

 ing such a record. 



The meteorologist depends on gage 

 readings of flood heights, made by man 

 and often incomplete, the best of which 

 in this country extend back for only a 

 few score years and in Europe for only 

 a few hundred years. The geologist 

 depends upon records thousands of 

 years in length made during all the long 

 ages in which the valley and the flood 

 plain were forming and written in the 

 materials of the flood plain and in the 

 width, slopes, and other features of the 

 valley. Beside these records the length 

 of even the longest meteorological gage 

 records becomes insignificant. 



The flood plain deposits that have been 

 built up by the ages of slow flood activ- 

 ity reveal the character of the floods by 

 which they were formed. If these have 

 been gentle, the deposits will consist of 

 fine alluvium ; if they have been violent, 

 the deposits in a region such as the 

 Southern Appalachians, will be corres- 

 pondingly coarser and will consist of 

 sands, cobbles, or boulders. If the 

 sands, cobbles, and boulders that have 

 been repeatedly strewn over their flood- 

 plains in the last few years by such 

 streams as the Watauga, the Doe, the 

 Nolichucky, the Catawba, and other 

 southern rivers had been the kind of 

 material these rivers had for ages been 

 accustomed to deposit, their entire flood 

 plains would be composed of such coarse 

 materials instead of being, as they are, 

 of fine rich sandy loam or clay. Had 

 they at any time in their past history 

 been accustomed to build such coarse 

 material into their floodplains that mate- 

 rial would be there to-day as a mute wit- 

 ness of the fact. It is only of recent 

 years, however, that they have formed 

 such coarse deposits because only in re- 

 cent years have their floods had the 

 height, velocity, and power to enable 

 them to carry such coarse materials. 

 The normal change in the regimen of a 

 river as the ages pass is such as to make 

 its flood plain deposits grow constantly 

 finer. In these rivers, however, this 



process is reversed and thin deposits 

 have recently grown coarser. This re- 

 cent anomalous change in the regimen 

 of these rivers can only be due to the 

 denudation and erosion that have re- 

 sulted from man's activities in the re- 

 gion. TJie rivers of the region have re- 

 centl\ changed their regimen and floods 

 have become higher and moire violent, 

 else sands, cobbles, and boulders would 

 not have been stream during the past 

 decade over the liner alluvial accumula- 

 tions of many previous centuries. 



Finally, to say as Professor Moore 

 does in his summary, that the run-off is 

 not materially affected by any other 

 factor than precipitation is ridiculous. 



^ «r «r 



"THE INFLUENCE OF FORESTS ON 

 CLIMATE AND ON FLOODS" 



A Review of Prof. Willis L, Moore's Report 



By GEORGE F. SWAIN, LL.D, 

 Professor of Civil Engineering, Harvard University 



TT MAY be well to preface this dis- 

 1 cussion by a brief reference to the 

 proper methods of scientific investiga- 

 tion, because these are often forgot- 

 ten, even by those who lay claim to 

 scientific acquirements, and because it 

 will be shown in what follows that in 

 the paper under consideration such has 

 been the case. 



In the investigation of scientific phe- 

 nomena two methods alone may be em- 

 ployed : The inductive and the deduc- 

 tive. 



If the relations between two phe- 

 nomena are to be studied by the induc- 

 tive method, the process is to collect 

 observations, or to make experiments, in 

 which one of these phenomena is varied, 

 while the effects upon the other are ob- 

 served. The method consists in accu- 

 mulating a sufficient number of such 

 observations and experiments, and from 

 them drawing generalizations. It is a 

 statistical method — a reasoning from 

 particulars to general principles. 



In the deductive method the process 

 is reversed ; starting from general prin- 

 ciples all conclusions are deduced from 



