116 



GEOLOGICAL SURVEY OF THE TERRITORIES. 



The directors of the Union Pacific Railroad contemplate transporting 

 this beautiful rock to Omaha, to construct with it the piers of the bridge 

 across the Missouri River. I believe it will prove as durable and far 

 more elegant, on account of its brighter color, than Quincy granite. 



The cuts along the road furnish excellent opportunities for rock study. 

 They are, as it were, portions carved out of the crust, and we can thus 

 obtain more accurate notions of its geology than in any other way. The 

 surface has often been so changed by erosion that the loose material 

 that has fallen down the sides of natural gorges, in almost all cases, ob- 

 scures, to a greater or less extent, the true character of the rocks, and I 

 have found these excavations of the greatest importance in my exami- 

 nations, 'correcting many an erroneous view. 



Figure 7 is an excellent illustration of a canon through the different 

 kinds of granite. On the right side of the tract the rock has been dis- 

 integrated for a considerable distance down by moisture, and the feld- 

 spathic crystals project from its sides with great distinctness. A heavy 

 vein of quartzite is also distinctly shown. In the distance we. catch a 

 faint glimpse of one of these massive granite piles, which are so well 

 shown in Figure 9. The character of the surface of this range of moun- 

 tains, which is about twenty to thirty miles in width, is also well shown. 

 Large areas are comparatively level, and covered with a thick growth of 

 grass, with here and there a thin grove of pines. These trees are hardly 

 ever more than from fifty to sixty feet high, and seldom more than two 

 feet in diameter at the base. Further up in the higher ranges the white 

 spruce and several other species of coniferous trees are found. 



Fiff. 8. 



^sik: 



m5&~- - 



2 ;\^. -■ 



Virginia Dale, Summit Laramie Mountains. 



