88 GEOLOGICAL SUEVEY OF THE TEREITORIES. 



northwest and southeast on all sides, but there are many local dips and 

 variations from this direction. 



I was much interested to know whether any of the unchanged rocks 

 which are so well developed in the Laramie Plains occur in the North 

 Park. I found that the entire series of red and variegated beds, includ- 

 ing a portion of the Cretaceous strata, were fully represented, all inclin- 

 ing from the flanks of the mountains and gradually assuming a horizon- 

 tal position, or nearly so, toward the central portion of the park. 



The transition beds, or Lower Cretaceous No. 1, form quite conspicuous 

 ridges, inclining 19° to the southwest. They are composed of a very 

 beautiful pudding-stone, an aggregation of small rounded iDebbles, most 

 of them flint, cemented together with a siliceous paste. 



On the north side are cjuite large areas covered with loose sand, which 

 is blown about by the wind, resembling the sand-hills on the Mobrara 

 Eiver. A close examination of the sand shows that it is composed mostly 

 of rounded particles of quartz and feldspar. The surface sustains little 

 or no vegetation, presenting a peculiar barren appearance, the sand 

 moving readily with the wind. 



Hitherto it has been impossible to color on any map the geological 

 formations of any x)art of this mountain region, and no information has 

 ever been given in regard to the structure of the North Park. It will 

 be impossible even now, with the imperfect topography of any of the 

 maps, to color the geology iu detail ; but these explorations will enable 

 me to fix the outline of the formations, iu a general way, with a good 

 degree of accuracy. 



FoET Sandees, Wyoming Teeeitoey^, 



tS€j)teml)er 25, 1868. 



SiE : I have the honor to transmit the concluding portion of my field- 

 report of Wyoming Territory. Although written quite hastily and under 

 pressure of other duties in the field, I am sure it must commend itself 

 to your attention, from the fact that it is descriptive of a portion of the 

 West rich in coal and iron, but about which there was previously very 

 little information of a definite character. 



I shall be able to color on a map the outlines of the great geological 

 formations as far west as Fort Bridger. My collections are getting to 

 he quite large. Professor Agassiz, who is here now, regards them as 

 very remarkable and entirely new to science. Both the professors, 

 Hall and Agassiz, have given their testimony to the truthfulness of my 

 scientific labors here in the most emphatic terms. 



Colonel Smith is doing most excellent work in securing materials for 

 a map of this portion of the West. He is now copying the map of the 

 Union Pacific Eailroad office. He will be able to construct a map of 

 this portion of the West which will be far in advance of any preceding 

 one. 



No draft has yet come to me from the United States Treasury up to 

 this date. I have borrowed money from bank at 12 per cent, discount, 

 and drawn on my friends until I am very much embarrassed. I do not 

 like to go on my Colorado work until I know something more definite. 



Should you wish any more preliminary reports from the field, x^lease 

 mention it in your next communication. I have hurried this last one 

 so as to get it to you before the 1st of October. 



