THE GRANITE EXOTIC. , 229 



and regular fissures between the lamellae of the schists formed in the fold- 

 ing of the rocks, and are in fact interlaminated fissure veins. 



The quartz is often mixed with a large proportion of brown and yellow 

 oxides of iron, resulting probably from the decomposition of pyrites, and 

 the gold now found in the gravel-deposits along the streams has been 

 derived from the disintegration and denudation of these ledges in the schists. 



But little prospecting could be done in the numerous quartz-veins of 

 this district for want of time and proper tools. The miners reported gold 

 in small quantities from several veins which they discovered and opened. 



Near the stockade on French Creek a mass of schist was noticed, about 

 150 feet in length, upturned on edge and completely inclosed by a broad 

 rim of granite. This fragment of schist was traversed by a ledge of quartz 

 and limonite several feet in width, conformable to the stratification, and cut 

 off at each end by the subsequent intrusion of the granite. From the uni- 

 formity in the composition and appearance of the granite from all parts of 

 the Harney Peak range, the dike character of the ridges, the presence of 

 slickensides, and the observed instances of inclosed fragments of schists, I 

 can but regard the granite of this region as injected. There are occurrences 

 of small, narrow veins of feldspar leading from the granite into the schist, 

 probably deposited by chemical solutions accompanying the intrusion, 

 which would seem to indicate that the fluidity of the injected granite was 

 due more to the presence of water than to the intensity of the heat. 



French Creek rises in the level park country southwest of Harney 

 Peak, among granite, gneiss, and schistose rocks, and flows in a general 

 easterly and southeasterly course about fifteen miles, until, entering a deep 

 canon in the limestone formation, it sinks among the bowlders in the bed 

 of the channel and disappears before reaching the foothills, continuing as 

 a dry arroyo, wilh water-holes at intervals, to the Cheyenne. Near its 

 head it is a sluggish stream with long stretches of slack water; in midsum- 

 mer, notwithstanding frequent showers of rain, drying up to a chain of 

 water- holes. A few miles below the stockade it is swelled by springs and 

 side branches to a creek 10 to 15 feet in width and about 8 to 12 inches 

 deep, flowing with a moderately- rapid current until it is lost in the canon. 



Gold was discovered in gravel bars on French Creek early in August, 



