^EOLO&teAL SURVEY OP THE TERRITORIES. 81 



hornblenclic gneiss, or wliite quartz. All tliese rocks are nearly verti- 

 cal. Intercalated among these betls of syenite we found tlie beds of iron- 

 ore, which, though not continuous like the syenite, occur here in large 

 quantities. The ore-beds incline in the same direction with the others, 

 with the same joints and cleavage, and the surface of many of the layers 

 has the appearance of " slickeu-sides." Thousands of tons of this ore 

 have been detached from these beds and distributed about the valley of 

 the Chug water in a more or less worn condition. 



Although the amount of iron-ore which we were able to discover was 

 indefinite in extent, yet we had evidence of the existence of other beds 

 in the mountains at the sources of all the branches of the Chugwater. 



The Chugwater empties into the North Platte and ha-s a valley about 

 100 miles long. It has been for many years a favorite locality for win- 

 tering stock, not only for the excellence of the grass and water, but 

 also from the fact that the climate is mild throughout the winter. Cat- 

 tle and horses thrive well all winter without hay or shelter. 



The soil of the valleys of all the streams that flow into the ISTorth 

 Platte is fertile, and when the surface can be irrigated good crops of all 

 cereals and hardy vegetables can be raised without difficulty. While 

 my explorations this season will be confined mostly to the plain-coun- 

 try, yet my plans contemplate numerous side trips to interesting points 

 in the contiguous mountains. 



Within a few weeks a great excitement has been created at Fort San- 

 ders and Laramie City, by the reported discovery of rich gold-diggings 

 near the source of Little Laramie Eiver. This district has a regular 

 organization ; hundreds of claims have been staked out, and the name 

 of " Last Chance " diggings given to it. Some very large and valuable nug- 

 gets of gold have been taken from these mines, and the usually exag- 

 gerated reports of their richness were circulated everywhere. 



August 20. — I started from Fort Sanders to make an examination of 

 this district, under the auspices of Major-Geueral Gibbon, United States 

 Army, the commander of the Eocky Mountain district. We were so for- 

 tunate as to have the company of Professor James Hall, State geologist 

 of New York. Our course was nearly southwest up the valley of the 

 Little Laramie Eiver to its source in the Snowy Mountains. From Fort 

 Sanders to the Little Laramie Eiver the distance is 18 miles, over a 

 very nearly level country, underlain by Cretaceous beds holding a hori- 

 zontal position nearly. 



Nos. 2 and 3 are quite well shown. No. 2, with its dark plastic clays, 

 is first observed at the Big Laramie stage-station, six miles west ol 

 Fort Sanders, In the broad, level plain-country west of this point. No. 

 3 attains a thickness of 50 to 100 feet, sometimes exhibiting its usual 

 chalky character, but mostly composed of thinly laminated calcareous 

 shale. All through are thin layers of fibrous carbonate of lime. The 

 fibers are at right angles to the plane surface, and attached to these 

 masses or layers are myriads of the little oyster, Ostrea congesta. I also 

 found a number of vertebrae of a saurian animal. From the stage-sta- 

 -tioii we passed directly up the valley of the Little Laramie. On either 

 side were long ridges, covered with grass and water-worn rocks, but from 

 their sides projected a bed of rusty sandstone which contained Inocera- 

 miis and other marine fossils, which indicated the Upper Cretaceous or 

 No. 5. These beds continued for about 15 miles to a point where the 

 river issues from the foot-hills of the mountains, and thence to its 

 source we follow its windings through some most beautiful and rugged 

 scenery. 



The river itself has wrought its way through a synclinal valley, caused 

 6 H 



