DISCUSSION : FORESTS, RESERVOIRS, AND STREAM FLOW 509 
evidence that there seems to be no instance on record in this or any Mr. Chitten- 
other country where a scheme for the improvement or regulation of a ao 
navigable stream has embraced as an essential feature the reforesting 
of any part of its water-shed. 
Such is a brief summary of the evidence concerning the “experience 
of mankind” on this particular subject. The “firmly established” con- 
clusions are no conclusions at all. On the one hand are the forestry 
advocates in this and other countries claiming that the welfare of our 
rivers depends upon the preservation of our forests; on the other is 
the practical engineer who holds that our rivers cannot be regulated 
by any such means. If Mr. Collingwood had said that these views 
are firmly established in popular thought he would have been entirely 
correct; but that is not a sufficient reason for believing them to be 
true. Whether a popular belief is correct or not depends upon how it 
originated. Since the appearance of this paper many have said or 
written to the writer that they had never even thought that there 
were two sides to the question; that they had accepted unquestioningly 
the current theories, as put forth by writers and lecturers, without in- 
vestigating at all. Manifestly, such a belief is worth as much as the 
source from which it is derived and no more. Remember that “truth 
does not depend upon the number of its adherents.” Authority cannot 
change the laws of Nature, nor can the most implicit belief in the 
influence of forests upon stream flow make that influence a fact where 
it does not exist. 
As to the work of the scientific bureaus, upon this particular sub- 
ject, it is extremely difficult to determine precisely what it is or what 
their views are. It is an excellent example in which “doctors dis- 
agree.” At one time it is held that forests diminish floods, and at 
another that no “well-informed” person entertains such a view. It 
was announced not long ago that the forest bed is a great reservoir; 
now, that it is held to be such in only a “nominal sense.” Deforestation 
is said, in one breath, to increase the height and shorten the duration of 
freshets, and, in the next, to increase both height and duration. One 
authority declares that the lower layers of the soil are always drier in 
the forest than in the open, while others strenuously insist that the 
contrary is the case. A little while ago the country was told that a 
thousand tons of soil are yearly washing from our agricultural lands 
into the sea, while just recently it is stated that only an insignificant 
portion comes from that source. In a formal public document it is 
stated that deforestation of the Appalachian slopes would speedily 
destroy any reservoir that might be built in that region; and in an 
equally formal professional paper it is shown that, even where defor- 
estation already covers 50 and 60% of the land, it would take from 
10000 to 20000 years to fill the proposed reservoirs with sediment. 
Some authorities hold that rainfall and climate are changing for the 
