16 GUIDEBOOK OF THE WESTERN UNITED STATES, 
peratures ranging from 75° to 120° F. Hotels and bathhouses make 
the place very attractive to the traveler who can spend a few days 
in the bracing atmosphere of this mountain resort. 
The first really noteworthy discovery of gold in Colorado is com- 
memorated by a monument at the mouth of Chicago Gulch, a canyon 
entering that of Clear Creek from the left of the railroad nearly 
opposite the station at Idaho Springs. This discovery was made by 
George A. Jackson in January, 1859. When winter was over Jack- 
son returned to the mountains and on May 7 began placer mining 
on Jackson Bar. 
One of the most notable achievements of mining engineering in 
this region is the Argo (formerly Newhouse) tunnel, whose large 
waste dumps may be seen in the eastern part of Idaho Springs. This 
tunnel extends northward for 5 miles to a point beneath the town 
of Central City. It cuts many of the veins far below the surface, 
draining the upper workings and facilitating deep mining. Much 
ore is brought from the Central City district to Idaho Springs 
through this tunnel, and mining at or below its level has shown that 
rich gold ore cheat in many of the veins at very great depths. 
In the vicinity of Idaho Springs the canyon, although wider than 
it is in the neighborhood of Forks Creek, is still narrow and the 
walls are studded with jagged or loose rock as they were left by the 
cutting of the stream and the action of the weather, but from a 
point a few miles above the town to the crest of the range the canyon 
bottoms are broad and the slopes are generally smooth and round, 
so that a cross section of the valley resembles in shape the letter U. 
This form of valley (shown in fig. 4, p. 11) is due to the scouring 
action of a glacier that originated near the summit of the range and 
flowed down the canyon to a point where the ice melted faster than 
it was supplied from above and where the forward movement of the 
glacier consequently stopped. Although all this happened ages and 
ages ago, the surface features above and below this point still present 
a striking contrast, for the work of the glacier has not yet been 
obliterated by weathering. The end of the glacier, which was only 
a few miles above Idaho Springs, is also marked by a moraine—a 
great accumulation of rounded and scratched boulders that were 
brought down by the ice and dumped at its lower end. 
Both active and abandoned mines and many prospects may be seen 
on almost every slope of the canyon wall above Idaho Springs. In 
Gilpin and Clear Creek counties, as in most old mining regions, only 
a small proportion of the mines are in operation at any one time. 
Some of those that are not operated are “dead ”—that is, their ore 
bodies have been entirely worked out—but many are idle ‘only tem- 
porarily because of inefficient management or insufficient funds with 
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