124 GUIDEBOOK OF THE WESTERN UNITED STATES. 
massive light-colored Madison limestone (Carboniferous) will attract 
attention on account of its many exposures on the hill slopes. West 
of the limestone is an intrusive mass of granite (quartz monzonite), 
which is very extensive, being the same as that which constitutes 
the mountains about Boulder and the summit over which the North- 
ern Pacific passes east of Butte. It is noteworthy on account of the 
peculiar way in which it weathers. Some parts seem to be harder 
than others and less subject to the action of the weather, and these 
parts stand up as towers and pinnacles. The projecting crags are 
particularly numerous and fantastic in the vicinity of Austin. 
The railway engineers, in order to obtain a regular grade to the 
summit, found it necessary to make large loops, and the open country 
about Austin gave them the opportunity they de- 
Austin. sired. Just east of the station two stretches of track, 
eeption #71 feet. one above the other, are visible on the right. The 
_ Paul 1,144 miles. ‘ = i 
steepness of the grade may be appreciated by listening 
to the laboring of the engine or by looking back after making the 
sharp turn above Austin. The track here runs along the contact of 
the limestone and the granite, and such localities are generally 
favorable for the deposition of ores. Many prospect pits have been 
_ sunk in search of the precious metals, but apparently without success. 
_ Above the great loops near Austin the track winds in and out, up the 
ravines and around the spurs, steadily climbing on the Madison lime- 
stone until it arrives at the east end of the Mullan tunnel. Originally 
the road was carried over the summit, but on the completion of the 
tunnel the high line was abandoned. The upgrade continues 
through the tunnel, which is 3,875 feet long, and 
reaches the highest point at Blossburg, at the far 
ie fad Pe we end. The tunnel was constructed entirely in the 
granite, although the limestone extends to the eastern 
portal and the sandstone and shale of the Cretaceous appear only a 
short distance west of the other portal. 
The traveler has now crossed the backbone of the continent, and 
as he starts down the Pacific slope and looks back at the summit he 
is probably surprised at the smoothness of the tops and the absence 
of the rugged features which most people have, in their minds, 
associated with Mullan Pass ' and the Continental Divide. 
Blossburg. 
Fe ane een et Tonnes rh Bat ese Ee Pe Ra es et 
‘ The first authentic account of a trip , sion of St. Mary (now Stevensville), in 
through Mullan Pass is that contained in | the Bitterroot Valley south of Missoula. 
the report of the Government engineers | From this camp engineers explored the 
who, in 1853, conducted systematic ex- passes through the mountains and re- 
plorations in order to find the best route ported on their feasibility for railroad 
for a Pacific railroad. This ition, | construction. 
under the command of Gov. Isaac I.| The two men connected with this work 
Stevens, of Washington Territory, estab- | who are best known to the public were 
lished field headquarters at the old mis-| Capt. George B. McClellan, who had 
