GEOLOGICAL SUKVEY OF THE TERRITORIES. 141 



not yet well explain. The water divide is the long bench which extends 

 down from the very base of the mountains eastward, and forms the line 

 of separation between the sources of the streams which flow southward 

 into the Arkansas on the one side and into the South Platte on the other. 

 This water divide is well worthy of especial notice, inasmuch as it is 

 composed of the Monument Creek formation, and -juts up against the 

 almost vertical metamorphic rocks, retaining its nearly horizontal posi- 

 tion, and i^erfectly concealing all the older rocks for at least five miles 

 north of the line of separation. 



The valleys of Plum Creek and of its branches are quite wide, and 

 are scooped out of the modern deposits so as to form a most beautiful 

 and fertile lands, while on each side a bench extends down from the 

 mountains like a lawn. The series of older rocks are exposed by the 

 stripping oft' of the_ newer tertiaries in the valley of Plum Creek. The 

 bench on the north side conceals them, for the most part, close up to the 

 foot of the mountains, while on the south side they are entirely concealed 

 until they reappear near Colorado City. 



The divide forms a high ridge with a mesa-like top, stretching far east- 

 ward beyond the horizon, covered with pines. On each side the beds ot 

 whitish-yellow and reddish sandstones appear like fortifications, holding 

 a nearly horizontal position. Xear the foot-hills there is a narrow val- 

 ley, perhaps one-fourth of a mile wide, and lying against the sides of the 

 mountains are remnants left after the erosion. I at first mistook them for 

 the red triassic beds, but on a close examination I found them to be a coarse 

 aggregate of feldspar and quartz, colored extensively with iron. There 

 are inclosed in the rock various water-worn pebbles of all sizes and 

 textures. This rock decomposes readily, especially by the process of 

 exfoliation. The whole rock is so massive and compact that it might 

 easily be mistaken for a metamorphic sandstone. 



Just south of the first branch of Monument Creek there is a fine ex- 

 hibition of the erosion of the sandstones. At one locality they lie snug- 

 up against gneissoid rocks, showing the discordant relations perfectly. 

 These illustrations seem to show plainly that the sediments of this recent 

 tertiary deposit have all been derived from the disintegration or erosion 

 of the metamorphic rocks and perhaps the older sedimentary beds in the 

 immediate vicinity. 



In a beautiful little basin near Monument Creek, which leads to the 

 creek, is a lone pillar or column of sandstone, three-cornered, with the 

 strata perfectly horizontal, about thirty feet high. The sands compos- 

 ing this are coarse and of a yellowish or whitish color. It has been for 

 a long time a favorite object for the photographer. 



At one point on Monument Creek the red granites, high up on the 

 mountain side, show the perpendicular lines of cleavage in a marked 

 manner. Some of the openings are several feet wide: The strike of 

 these lines of cleavage is about southwest and northeast. 



For a considerabledistance, some ten or fifteen miles, along the imme- 

 diate base of the mountains, on the west side of Monument Creek, the 

 Jong, smooth, grassy benches .slope down toward the creek, sliced as it 

 were or cut by the numerous little branches. These lawn-like slopes or 

 benches vary in height. Sometimes on the side of a little branch, vdiere 

 the valley is deep, there is an intermediate terrace or step to the higher 

 ridge. 



All these valleys seem to be occupied by farmers and stock-raisers. 

 Almost every available spot is taken up by actual settlers. 



The first range of mountains on the east side, from the divide to a 

 point near Colorado City, appears to me to present a fine illustration of 



