16 GEOLOGICAL SURVEY OF THE TERRITORIES. 



been much denuded, prior to the deposition of the sandstone. 1 think, 

 however, there has been no want of continuity in the beds, and that the 

 irregularity is caused by the change from quiet to turbulent waters. 

 Sometimes there is a sudden jog, so that the sandstone projects down 

 two to four feet, into the underlying bed of marl, or it will thin out 

 into indurated marl, to a great extent. For about ten miles these rocks 

 are worn by atmospheric influences into the singular formation de- 

 scribed, and then the, cap of sandstone disappears, and the surface is 

 more rounded and covered with grass. The texture of the rocks deter- 

 mines everywhere the surface outlines of the country. In the walls 

 of sandstone and marl are deep vertical fissures, much like those in the 

 metamorphic rocks. Sometimes they pass up through the sandstone 

 cap, and at others are checked by it. They are often filled with par- 

 tially crystallized material, or charged with fine arenaceous sediment 

 from above. The direction of these fissures, or shrinkage-cracks, is 

 northwest and southeast. The plains everywhere present the appear- 

 ance of remarkable table-lands, as if the surface had originally been 

 planed off with great regularity, and the valleys have been grad- 

 ually worn out by water. The mountains immediately north of the 

 " Chug" present a fine illustration of the style of flexure which is not un- 

 common throughout the Eocky Mountain district. The ridges of un- 

 changed formations seem to have suffered scarcely any erosion for a 

 distance often or fifteen miles north of the "Chug," and die out in the 

 plains, with a trend northeast and southwest. This causes a jog.of about 

 ten miles to the eastward. The pivotal point seems to be Laramie Peak. 

 Long lines of ridges may be seen running out from the main axis, nearly 

 to the head of Bitter Cottonwood ; and the trend of the axis extends 

 northwest. These flexures in most cases afford the best opportunities 

 for studying the unchanged rocks of different ages, in their order of se- 

 quence, from the granites to the most recent tertiary. 



In all my examinations, however, I have not detected the lignite ter- 

 tiary along the base of the mountains north of Cheyenne, until it makes 

 its appearance from beneath the White Eiver beds, about three miles 

 south of Fort Fetterman. 



The Chugwater has a valley about one hundred miles long. It has 

 been for many years a favorite locality for wintering stock, not only on 

 account of the excellence of the grass and water, but also from the fact 

 that the climate is mild throughout the winter. Cattle and horses thrive 

 well all winter without hay or shelter. 



The high walls or bluffs which inclose the rather broad valley protect 

 it from the strong cold winds. The soil is everywhere fertile, and, where 

 the surface can be irrigated, good crops of all kinds of cereals and 

 hardy vegetables can be raised without difficulty. From the Chugwater 

 we cross the table-like plains for ten miles, and descend to the beautiful 

 valley of the Laramie. From the plains the Laramie range comes out 

 in full view, with the Laramie Peak near the center, towering far above 

 all the other ranges. The main range, with the numerous minor ranges, 

 trend about northwest and southeast. The tertiary rocks on the Lara- 

 mie, near the crossing, have weathered into quite remarkable architec- 

 tural forms, much like those on White Eiver. The texture is similar, 

 also, with marls and calcareous concretions passing up into fine sand- 

 stones, which decompose so readily, that the valleys and the hills are 

 covered with loose sand. In the harder layers of sandstone are singular 

 whitish, concretion-like sticks and twigs. A few fossil remains were 

 found — as the teeth of Oreodon culbertsonii and Testudo nebrascensis. 

 Other bones were collected, which have not been determined. There are 



