4 
Bulletin 55. 
the headwaters of the Cache a la Pondre. Two places, some twenty 
mile apart, were visited. One on the divide between the Poudre River 
and Estes Park, and the other on the headwaters of the Laramie River. 
The former was visited under the guidance of Mr. John Zimmerman, 
who is a native of Switzerland, and who has lived in the high elevations 
of Colorado for nearly twenty years; the latter, under the direction of 
Mr. John McNabb, who has also had a long and intimate acquaintance 
with high elevations. The results are shown in the plates, which speak 
for the photographic skill and successful carrying out of instructions 
by Mr. J. D. Stannard, then assistant in the Department of Engineer¬ 
ing. It is believed that no more striking series of photographs on this 
subject has been brought together. They enable a comparison of the 
conditions to be made by the reader and repay examination and thought¬ 
ful consideration in connection with the charts. 
We hoped to obtain an additional series of photographs during the 
subsequent winter, but the character of the snowfall was unfavorable 
for this purpose. 
A general description of the condition of the streams, as connected 
with the melting of the snows, is desirable as a basis for the explana¬ 
tion of the views. 
CHARACTER OF THE STREAMS. 
Colorado is moderately supplied with rain, the annual precipitation 
averaging about fourteen inches. In the mountain areas, the amount 
varies with the elevation and topographical conditions, but the increase 
with elevation is not marked until the extremely high elevations are 
reached. In these places observations are under exceptional conditions, 
and too few in number to form a safe guide. On the eastern slope of 
the mountains, the precipitation is mostly due to the easterly winds 
brought in by the passage of an area of low barometer to the south. 
The air is forced up by the mountain ranges, and cooled by the eleva¬ 
tion enough to cause condensation and precipitation. Sometimes there 
are extremely heavy local showers, often called cloudbursts. Much of 
the precipitation at the higher elevations, even in the summer months, 
is in the form of snow. June, July and August are practically the 
only months in the year when rain falls at or above timber line. Snow¬ 
falls are not uncommon down to an elevation of 6,000 feet, even in May. 
The rain runs off quickly and may immediately influence the 
streams. The snow remains until it is melted or evaporates. Its effect 
is gradual, and may thus last for some time. Most of the winter pre¬ 
cipitation in the mountains remains on the ground in the form of snow 
until spring. A portion, sometimes not inconsiderable, evaporates, es¬ 
pecially when the snow is porous or soft. It may then be seen to vis¬ 
ibly decrease. Heavy winds which blow the snow about increase this 
loss. Some of the mountain observers say, “The wind just naturally 
wears it out.” 
In the case of land denuded of timber the surface is generally hard, 
and the water runs off rather than penetrates. In the forest areas the 
soil is looser, more porous and absorbent, and takes up water freely. 
In such areas springs, or springy soil, are more common, while they are 
