DISCUSSION: FORESTS, RESERVOIRS, AND STREAM FLOW 495 
The forest increases the intensity of the run-off from snow-melt- mr. Chitten- 
ing primarily by its effect wpon the distribution of the snow, whereby %" 
the area exposed to the melting influences is increased over what it is 
in the open country where the snow is largely thrown into drifts. 
The forest, by virtue of its shade, delays melting from the direct 
action of the sun, and tends to hold the snow until warm-weather con- 
ditions arrive, when the snow melts with great rapidity. This applies 
more particularly to the central Rocky Mountain region, where the 
forests are evergreen, and where the sun shines a great deal. It has 
a smaller application to the eastern deciduous forests, where there is 
less shade and less clear weather. Smaller still is its application on 
the Northwest Coast, on account of the lack of sunshine in the season 
of melting. 
In the eastern forests, the flattened-out, and often frozen, layer 
of leaves from deciduous trees in a measure offsets the more general 
freezing of the ground in the open country in the matter of shedding 
the water from heavy rains and melting snow. 
On the Pacific Coast, the wet condition of the snow and its tendency 
to cling to trees and underbrush give the warm ocean winds, com- 
mon in that region, great effect in melting, and this circumstance 
adds materially to the intensity of the resulting freshets. 
As a general rule, therefore, in all situations, the effect of forests 
upon the run-off from snow-melting is to intensify it. 
After the above writing had been completed and forwarded for 
publication, a letter appeared in Hngineering News for January 28th, 
by Jeremiah Ahern, M. Am. Soc. C. E., District Engineer, U. S. 
Reclamation Service, strongly confirming the writer’s theory in regard 
to snow-melting in the mountains. He says that such snows always 
melt in the following order: 
“(1) Snow on the unforested areas not collected in drifts. 
“(2) Snow on the forest areas. 
“(3) And last, snow in drifts scattered over the unforested areas.” 
He quotes the late Major John W. Powell as follows: 
“When the mountain declivities are grassy slopes, the snows of 
winter drift behind ledges and cliffs and into great banks among the 
rocks, and they fill ravines and canyons, and are thus stored in com- 
pact bodies until they are melted by the summer suns and rains. But 
when forests stand on the slopes the snows are spread in comparatively 
thin sheets, and great surfaces of evaporation are presented to the sun 
and the wind. For all these reasons the forests of the upper regions 
are not advantageous to the people of the valleys, who depend on the 
streams for the fertilization of the farms.” 
Proposition 5. 
“Qoi] erosion does not result from forest cutting in itself, but from 
cultivation, using that term in a broad sense. The question of preventing 
such erosion or soil wash is altogether one of dispensing with cultivation 
