THE NORTHERN PACIFIC ROUTE. St 
The valley is wide, the immediate hills are low, and the slopes are 
gentle and rolling. At Silver Bow station, 7 miles from Butte, the 
Oregon Short Line (Union Pacific) turns to the 
Birer How. left (south) and after a short climb cro8ses the sum- 
~qlaeepreaadessag mit at Deer Lodge Pass. Beyond Silver Bow 
station the valley continues open for a distance of 
4 miles to a point where the stream enters a very narrow, rugged 
canyon cut in massive rhyolite, a volcanic rock that covers much of 
the country west of Butte. The rock when freshly broken is nearly 
white, but under the influence of the weather it turns to a deep, 
rich red, which gives a pleasing relief to the somber-gray color of 
the granite to the east. The Butte, Anaconda & Pacific Railroad 
(recently electrified) and the Chicago, Milwaukee & St. Paul and 
Northern Pacific railways also occupy the canyon, which, on account 
of its narrowness, is very much congested. (See Pl. XVII, p. 107.) 
Aside from its ruggedness and picturesqueness this canyon has 
an added interest because it owes its origin to the filling of the 
original valley on the north with lake sediment and the cutting of a 
new course by the stream, similar to that of Jefferson River, described 
on page 101. After the disappearance of the lake Silver Bow Creek 
came into existence, and on the swampy bottom of the lake it 
meandered broadly. In its windings it had assumed its present 
position, when, through the elevation of the land, it gained cutting 
power and began to deepen its channel. In doing so it encountered 
the rhyolite, but it continued to cut, and the canyon is the result. 
At Durant the train emerges from the canyon into a valley much 
broader than the one at Butte or Silver Bow. This, the renowned 
Deer Lodge Valley, is much too large to have been 
Durant. carved by the stream now occupying it. The eastern 
aoe — traveler has doubtless noticed that the valleys in 
= m=" this region are generally different from those with 
which he is familiar. Valleys that are the result of stream erosion 
have generally a width that is roughly proportional to the size of 
the stream, and as a rule they decrease in size toward the head of 
the stream. In the northern part of the Rocky 
iene Mountains many of the larger valleys are out of pro- 
ae pier portion to the size of the streams occupying them, 
oe and hence it does not seem probable that they were 
formed alone by the erosive action of the streams." 
The most conspicuous artificial object in the Deer Lodge Valley 
is the giant stack of the Anaconda smelter on the left (west), 350 
1As the origin of many of the broad | duced by movement in the earth’s crust, 
valleys of the northern Rocky Mountains | either the direct subsidence of the val- 
can not be attributed to erosion, it is | ley itself or the elevation ot th 
manifest that they must have been pro- | ing mountain masses. Subsidence may 
