24 DESOEIPTIVE GEOLOGY. 



that the mineral was well disseminated m this eastern Archaean upheaval. 

 The low percentage in lime points to the conclusion that the triclinic feld- 

 spars are not labradorite. 



The arrangement in parallel bands of the quartz and feldspar, already 

 mentioned, is shown in this rock ; it is, however, much better seen at a short 

 distance in the field than in a hand-specimen. The rock appears to have 

 undergone some movement since the formation of the bands, as the feld- 

 spars seemed curved and contorted, and frequently pressed together. 



On the west side of Long's Peak, there occur beds of very coarse gran- 

 ite, the quartz of which seems segregated in large masses, accompanied by 

 the other minerals in subordinate quantities. The feldspar also occurs in 

 large, irregular-shaped bodies, when it is ordinarily white, with a pearly 

 lustre. The mica present is also in segregated patches. There are also 

 dikes, of what is sometimes called graphic granite, where the feldspar in 

 massive form predominates, and has the quartz disseminated through it in 

 small crystalline particles, which present the appearance of hieroglyphic 

 figures and symbols. The associated mica is dark brown. Northward, on 

 the lower flanks of the peak, rocks with a prevailing gneissic structure, and 

 the mineral constituents finer-grained, are well developed. In the deeply-cut 

 glacier-canons of the higher portions of the peak are found excellent opportu- 

 nities for observing many striking features of the metamorphosed strata ; one, 

 especially, on the east side, presenting a mural face nearly 3,000 feet high. 

 Thin beds of compact, finely-laminated dark mica-slates, intercalated in the 

 lighter granitoid beds, occur on the west flanks of the mountain, the prevail- 

 ing constituent of which is mica, associated with quartz and feldspar. Under 

 the microscope, large quantities of apatite prisms are detected, while in the 

 quartz are thin plates, which Professor Zirkel has determined as muscovite. 

 The regions of Estes' Park, the North Branch of the Big Thompson, and 

 along the road leading from the Park to tlie Plains, is chiefly made up of 

 coarse granular granite, with but little mica, and the feldspars for the 

 greater part light reddish orthoclase. 



Of the rocks in one or two other localities, special mention may be 

 made. 



The region drained by Sportsman's and Fish Creeks and the North 



