kmmons.] LKADVILLE TO MAXITOU. 423 



Granite was the thst town founded in this region, in ISo'O, by the 

 gold-placer miners. Above it on the cast arc the abrupt granite slopes 

 of the Mosquito range, cut through by frequent dikes of porphyry. 

 The road follows a narrow gorge cut by the stream on the east side of 

 the valley and then enters a broad, open valley of gently sloping Pleis- 

 tocene gravels, which it follows for over 30 miles. 



Prom Buena Vista line views are had of the high peaks of the 

 Sawateh range to the west. Mount Harvard (14,.'>7r> feet — 1,381 m.),is 

 an enormous mass; next to it, Mount Vale (14,187 feet — 4,321 m.)j to 

 the south of west rise Mount Princeton (14,240 feet — 4,342 in.). Mount 

 Antero (14,24(5 feet) and Mount Shavano (14,239 feet — 1,340 m.). Onthe 

 slopes of the Mosquito range, east of the town, can be distinguished 

 the line of the Colorado Midland road, which passes up the valley of 

 Trout creek and crosses the Mosquito range into the South Park. 

 Between Midway and Nathrop the road passes for a short distance 

 through a narrow gorge cut in the granite, on the east side of the 

 valley. 



[By Whitman Cross.] 



At Nathrop are several rhyolite masses forming oblong hills with 

 trend north-northwest to south-southeast. That these masses are 

 huge dikes is shown by steeply inclined contacts with gneiss, parallel 

 to which the eruptive rock is banded, the outer zone being glassy. 

 The rhyolite of Ruby hill, on the eastern bank of the Arkansas 

 directly opposite the station, is a lilac-colored banded rock with litho- 

 physal cavities arranged on certain planes, containing many beautiful 

 crystals of manganese garnet (spessartite) and topaz. 09 Good speci- 

 mens can easily be obtained, and many have been collected by mineral 

 dealers. On the west side of the river, near the railroad and north of 

 the station, a small ridge of rhyolite rises out of the valley bottom, 

 which is made of a rock containing phenocrysts of smoky quartz and 

 feldspar and small lithophysse containing minute topaz and garnet 

 crystals. 



At Browns canyon the road traverses another gorge on the east of 

 the valley cut in Archean rocks, mainly coarse granite and amphibo- 

 lite. 



At Salida a considerable stream, known as tin' South Arkansas, joins 

 the main river from the west. The original western line of the Den- 

 ver and Rio Grande railroad follows up the valley of the South Arkan- 

 sas, crossing the southern end of the Sawateh range at Marshall 

 pass (10,481 feet— 3,304 m.), and descending along the valley of the 

 Gunnison to Grand Junction. 



At Poncho, four miles west, are thermal springs. On the western side 

 of the valley, from here northward to Buena Vista, are gently sloping 



