BAOOT.J JAMESTOWN TO LIVINGSTON. 325 



encountered. Just cast of the town the Fox Hills sandstones, together 

 with the underlying Fort Pierre shales, are brought to the surface by 

 an eroded anticline. The Pierre shales form the broad bottomland of 

 the valley for several miles westward, and produce a marked contrast 

 to the narrow valley and rugged inclosing bluffs of the Laramie. The 

 town is built upon these Pierre shales that have been penetrated foi 

 800 feet by an artesian-well boring. North of the town the shales form 

 the smoothly sculptured base of a steep escarpment, being capped by 

 a massive ledge, 75 feet in thickness, of Fox Hills sandstone, which is 

 largely quarried and used as building -stone in the town. Overlying 

 the Fox Hills are the thinly bedded gray sandstones of the Laramie, 

 forming the highest dill's bordering the liver. Loth series of sand- 

 Stones present quite persistent bluffs on opposite sides of the valley, 

 and about 25 miles (40 km.) west of Billings replace the Fort Pierre 

 shales on the river bottom, the valley becoming narrow and canyon like. 



At Laurel a branch road crosses the river, running southward about 

 40 miles to the Red Lodge coal mines that supply the fuel used by the 

 Locomotives of the Northern Pacific Pail way.' 7 



West of Park City only Laramie rocks occur, but the country grad- 

 ually becomes more rugged and the scenery diversified. 



Big Timber, situated at the mouth of the Boulder, is built upon a 

 broad terrace of Livingston deposits that extend back to the moun- 

 tains, but have not as yet been traced more than a few miles to the 

 east. The Livingston beds, however, stretch almost continuously as 

 far west as the Bozeman Tunnel, through which the railway passes in 

 crossing the Bridger range. The exposures of the interbedded volcanic 

 agglomerates, largely made up of andesitic material, may be seen in the 

 bluffs just west of Springdale, where the beds dip at an angle of 20° to 

 the northeast. At one locality these agglomerates attain a thickness 

 of 2,000 feet. Just beyond this place the railroad passes through a 

 short ravine, showing an anticline of bedded clays and sandstones that 

 form the base of the Livingston, the rocks being much disturbed, show- 

 ing local folds and flexures. 



Sheep ('litis, just north of the river and midway between Springdale 

 and Livingston, are especially interesting, a8 they show a massive sheet, 

 of theralih intruded in Hie Livingston sandstone. This rare rock is 

 here exceedingly tine-grained, almost black in color, with porphyritic 

 crystals of augite and biofite: nepheline crystals only occur in the 

 dense ground-mass of the rock. Much larger masses of this rock occur 

 as intrusive sheets in the sandstones of the Crazy Mountains' 5 to the 

 north. 



At Livingston the railroad crosses the Yellowstone for the last time, 

 and immediately begins the ascenr of the first range of the Rocky 

 Mountains. 



