120 GEOLOGICAL SURVEY OF THE TERRITORIES, 



sandy material over an inclined plain; sometimes on one side of a ridge 

 or elevation, and sometimes on the other. Now, if this sand were 

 molded into rock, these layers of deposition would show distinctly 

 this same irregularity. Not far distant from this point is another group 

 of these weathered sandstones which show still more clearly these irreg- 

 ular layers. The softer portions have been worn away, causing each 

 thin layer to stand out of the sides of the rocks with great distinctness. 

 Sometimes the thin layers incline in one direction, sometimes in another. 

 These sandstones vary in height from fifty to one hundred and fifty feet. 

 On their summits the eagles are fond of building their nests, where they 

 will be inaccessible to their human enemies. Before closing our descrip- 

 tion of Figure 10, 1 ought to allude to the wild sage bush, which so pe- 

 culiarly characterizes these almost treeless plains. We are here more 

 than seven thousand five hundred feet above tide-water; at this eleva- 

 tion we find a species of sage which takes the place of the one on the 

 plains east of the mountains. It is called Artemisia tridentata on account 

 of its small, three-cootued leaf. It grows about the same size and very 

 much resembles the other species. This sage, as well as two or three 

 kinds of shrubs peculiar to the high places, are well shown in the figure. 



We have now described briefly the different sedimentary formations 

 as they incline on each side of this mountain range. It may be well to 

 remind the reader that this range is an excellent illustration of the plan 

 of development of these mountains. We find a series of formations 

 inclining from the eastern slope of the mountains; we pass over the 

 range and we again find the corresponding portions dipping in an oppo- 

 site direction over the western slope. We at once come to the conclu- 

 sion that these formations at some former period extended uninter- 

 ruptedly across the area now occupied by the granitic rocks, and that 

 the intermediate portions have been removed by erosion. Then the 

 query arises, at what time were these events brought about? It seems 

 to me it must have occurred as the surface was slowly emerging from 

 the waters of the ocean. As the bottom of the ancient sea along the 

 line of this mountain range slowly arose, the waters became shallow, 

 and they would be more easily disturbed by the winds and the erosive 

 forces be proportionately increased, and if the rocks arose above the sur 

 face the waves would dash against their sides and prove still more effec- 

 tive. The sediments would be wafted away and deposited in some other 

 part of the ocean, to enter into the composition of more recent rocks. 



The Laramie range, extending from a point near Long's Peak north- 

 ward to the Red Buttes on the North Platte and the Black Hills of 

 Dakota, form the most simple and complete examples of true anticlinals 

 on a gigantic scale that I have ever met with in my explorations. These 

 ranges are less complicated with basaltic outbursts than any others. 

 Some of the peaks, like Laramie Peak, are quite lofty, but as a general 

 rule they are low mountains, and for the most part composed of a nuclei 

 of massive red feldspathic granites inclosed on each side with true 

 gneissic strata. All these mountain ranges require a few more detailed 

 examinations than I have ever been able to give them, but the statements 

 that I have here made will, I think, prove to be mainly correct. 



