THE NORTHERN PACIFIC ROUTE. 105 
At Whitehall a branch of the Northern Pacific turns to the left, 
_ going up the valley of Jefferson River to Twin Bridges and Alder. 
The town at the end of the line was named from 
Whitehall. Alder Gulch, which was one of the most noted placer 
Elevation 4,371 feet. camps in the years immediately following its dis- 
Sr Parts bee cw. covery in 1863. It is said to have yielded at least 
$60,000,000 and is still producing in a small way. 
Alder Gulch lies near Virginia City, at one time the capital of Mon- 
tana. West of Whitehall the road begins the ascent of about 2,000 
feet to Homestake Pass, on the Continental Divide 23 miles away. 
Just beyond Whitehall the low hills on both sides of the track are 
composed of soft lake beds which are particularly well exposed just 
west of Pipestone. In the valley some distance to 
Pipestone. the south there are hot springs and a hotel. West of 
_. seek Pipestone the cuts along the railway show a fine- 
' grained, dense igneous rock (andesite). This is part 
of a large body of similar rock that lies to the right (north) of the 
railway and east of the great mass of granite that forms the Conti- 
nental Divide. Most of the andesite was poured out over this region 
as lava when the surface was very different from that which the 
traveler sees to-day, but some of it was intruded from below into the 
older sedimentary rocks. The volcanic activity which gave rise to 
the andesite took place long before the granite was intruded, as is 
proved by the fact that near Pipestone the granite includes frag- 
ments of the older rock which were broken off and mixed with the 
molten granite as it ascended through a fissure in the rocky crust of 
the earth. : 
Near milepost 48 the railway enters the great area of granite which 
extends northward along the range to Mullan Pass, west of Helena. 
The granite (quartz monzonite) came up from below in a molten con- 
dition, forcing the rocks asunder or melting them as it came. It 
probably did not reach the surface, but since it cooled and solidified 
it has been exposed by the streams, which have removed the ever- 
lying rocks and cut deep ravines in the granitic mass. : 
As the slope is too steep for a direct ascent, the road winds out and 
in, around projecting spurs, and up into the heads of valleys, but 
ever climbing toward the top. On the hills and upland the slopes 
are smooth and gentle, but in the gulches they are rocky in the 
extreme, 
Near milepost 50 the traveler, by looking ahead on the left, can 
see a bare dome of granite, known as Spire Rock, the base of which 
the train will pass farther up the grade. Other knobs or domes of 
gray granite appear from time to time, standing above the general 
surface. These landmarks resemble the domes of Yosemite Valley, 
which are formed of similar rock. Such domes and indeed the great 
