DISCUSSION : FORESTS, RESERVOIRS, AND STREAM FLOW 319 
DISCUSSION 
F. Cotuinewoop, M. Am. Soc. C. E. (by letter)—In these days Mr. Colling- 
of unrest, it would seem that no conclusions in any realm of thought ae 
or observation are so firmly established but that some acute thinker 
will bring forth arguments to prove their unsoundness. 
This is the case in this interesting paper, but, while acknowledging 
the force of the arguments advanced, the writer is unable to accept 
the author’s deductions as a whole. 
Four propositions are given, as covering the ordinarily received 
opinion as to the effect of forests on stream flow. 
The first of these relates to the effect of the humus acting as a 
sponge which absorbs the rain and melting snow and pays out the 
water in a more equable flow. The word, “humus,” does not fully 
cover the point involved, as consideration must be taken also of the 
sponge of dead leaves, and, in many cases, the great depth of moss 
growing upon the surface. Then, as helping in a marked degree to 
resist soil erosion, the matted roots of a forest must not be overlooked. 
These are particularly important in the case of a thin soil cover resting 
on sloping rock. Observation would seem to show that the young growth 
does not fully take the place of large trees, particularly in such 
locations. 
It must be admitted that in time of extensive and heavy down- 
pours of rain, when the ground is practically saturated with moisture, 
the effect of forests as regulators of stream flow is at a minimum; but 
it is not believed that it is ever entirely without effect. A rivulet 
which can run straight to its destination is one thing; but a rivulet 
which is constantly twisting and turning about obstacles of all sorts 
can never attain the eroding effect of the first. 
The author grants that, in periods of drought, springs and streams 
dry up more completely when a country is deforested, which is another 
way of saying that forests do, in a measure, regulate the run-off. As 
bearing upon this point, it was the writer’s good fortune, about fifty 
years ago, to listen to a series of lectures by the noted geologist, 
Professor James Hall. He stated that, in his memory, the removal of 
the forests from large sections of the State of New York had resulted 
in drying up a large portion of the springs formerly so abundant. 
This was especially noticeable in the removal of the watering troughs 
which had been so numerous along the public roads. This coincides 
with the writer’s memory as to Chemung County, in that State. 
The next point controverted by the author is that forests regulate 
the flow by retaining snow, which slowly melts at a later period, and 
thus replenishes the streams. In reply to this: the writer well remem- 
bers that, in the woods on the hills near Elmira, N. Y., the drifts 
