THE NORTHERN PACIFIC ROUTE. 129 
Drummond lies at the mtersection of two very broad, flat valleys, 
one along the main line of the Northern Pacific and 
ey en the other leading off to the southwest along a branch 
Population 383.* line running to the mining district of Philipsburg. 
St. Paul 1,200 miles. These valleys are filled with lake sediments, which 
show that a great lake existed here in Tertiary time. 
In the region above Drummond the rocks form a great flat syncline, 
with the Cretaceous occupying a wide area in the middle. In this 
central region the rocks were only slightly disturbed, but near Drum- 
mond, on the margin of the basin, the rocks are thrown into great folds 
which carry the limestone and quartzite beds of the Carboniferous and 
Devonian high into the mountain tops. In fact the Garnet Range 
consists of a series of such folds, trending in a northwesterly direction, 
which become more and more complicated toward the northwest. 
Clark Fork cuts into the foothills of the range west of Drummond, 
and the great folds can be seen and studied from the moving train. 
From Drummond the railway follows closely the axial line of a large 
syncline for a distance of about 7 miles. The youngest rocks exposed 
Drummond. 
porte 
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FIGURE 28.—Diagram of fold west of Drummond, rg Fork flows near the middle of a 
great basin, and the Madison limestone is folded back upon itself in the hill on the south. 
in this trough are the bright-red and maroon shale and sandstone of 
the Kootenai. The rim of the syncline is formed of the Madison lime- 
stone, which 3 miles west of Drummond forms conspicuous cliffs on 
the south and can be seen on the north in the tops of the high wooded 
hills about 2 miles distant from the track. gt 
To a point about 3 miles below Drummond the valley is still called 
the Deer Lodge Valley, but at that point the walls close in, especially 
on the left, and thence down to Missoula it is known as Hell Gate 
Canyon. It is probable that this name originated in the vicinity of 
Missoula, but it is now applied to the whole of the canyon. 
At the entrance to the canyon, near milepost 74, the Madison lime- 
stone caps the high hill on the south and makes a picturesque setting 
for the stream and valley at its foot. This cliff can best be seen from 
& point near milepost 75 late in the afternoon, when the slanting rays 
of the sun bring out every detail of the towers and pinnacles of the 
ed cliff. The limestone appears to lie horizontal, just as 1t was 
laid down on the bed of the ocean, but when studied carefully it 1s 
found to be turned completely over, as shown in figure 28. The over- 
95558°—Bull. 611—15——_9 
