252 Geology and Botany of Northern Pacific Railroad. 



brian age. Below this, the road closely follows the course of 

 Clark's Fork, through one of the most picturesque valleys on the 

 continent. The immediate banks of the river are often precipi- 

 tous masses of limestone, above which the wooded mountains 

 rise to the height of 3000 or 4000 feet. The course of the 

 railroad is northwest, until it approaches within fifty miles of 

 the British line. This great deflection is caused by the western 

 ranges of the Rocky Mountains which are high and continuous 

 until the vicinity of Pend Oreille Lake is reached. Here they 

 fall off, and the road turns directly west through them. The 

 lake is an irregular sheet of water, crescent-shaped and fifty 

 miles in length ; set with numerous islands and surrounded with 

 mountains, it is extremely picturesque. The mountains con- 

 sist of granite, flanked by slate, quartzite and limestone, all 

 much metamorphosed, but apparently the palaeozoic series which 

 is seen holding the same relation to the granite in so many 

 places in Idaho and Montana. 



The western range of the Rocky Mountains, like the eastern, 

 is metalliferous, but to what degree is hardly known, because 

 most of it is yet unexplored. Veins of argentiferous galena and 

 auriferous quartz have been found in the vicinity of Pend 

 Oreille Lake, and the already famous but greatly over-rated 

 Cceur d'Alene mines lie a few miles south of the line of the road. 



FOKESTS OF THE ROCKY MOUNTAINS. 



The forest vegetation of the Rocky Mountains and the valley 

 of Clark's Fork, is abundant and interesting. About Helena, 

 are seen the trees which are characteristic of the Park and all 

 the eastern flank of the Rocky Mountains. The round leaved 

 cottonwood, Populus mo?iilifera, with willows, the buffalo-berry, 

 Shepardia argentea, etc., flourish along the rivers ; Pinus ponde- 

 rosa and Douglas's spruce in the foot hills ; on the mountain-sides, 

 the narrow-leaved poplar and the aspen, (Populus angustifolia 

 and P. trem.uloides) Engelmann's spruce and the western balsam 

 fir ; and Pinus contorta and Pinus fiexilis on the mountain sum- 

 mits. 



Immediately after passing the divide, however, the character- 

 istic elements of the Pacific coast vegetation begin to make their 



