GRANITIC ROCKS OF PIKES PEAK QUADRANGLE 215 
granular igneous rocks comprising the summit of Pikes Peak, 
and the area to the west of it, included within the Pikes Peak 
quadrangle of the Geologic Atlas of the United States. The 
field observations were made during the seasons of 1893 and 
1894, and the laboratory studies during the succeeding winters. 
The quadrangle studied contains, approximately, 930 square 
miles and embraces the greater portion of the southern termina- 
Fic. 1.—Pikes Peak seen from the plain. 
tion of the Front or Colorado range in its en eschelon enaing east 
of the Royal Gorge of the Arkansas. The topographic features 
of the area are the mountain massif on the east, rising rapidly as 
shown in Fig. 1, from the level of the plateau to the height of 
14,108 feet above the sea. Westward from the summit the slope 
is much gentler, as shown in Fig. 2, to the somewhat dissected 
plateau of Cripple Creek and Florissant, drained on the north by 
the tributaries of the South Platte River and on the south by Oil 
Creek and its tributaries which drain into the Arkansas River 
The divide between these two drainages does not include the 
summit of Pikes Peak but passes somewhat to the north and 
west of the mountain mass. 
