ENDLICH ON EEOSION IN COLORADO. 839 



it no longer occupies its prominent position. Numerous fragments or 

 bowlders of tbe characteristic red conglomerate give testimony of the 

 former existence of monuments. 



Eeference to the Eeport of the United States Geological and Geo- 

 graphical Survey for 1873, Figures 4 and 5, and Plate III, opposite pages 

 32 and 36, will furnish some idea as to the forms of such products. The 

 monuments therein represented occur in Monument Park, and the col- 

 lection may be regarded as presenting typical forms of these curious 

 products. Any description of them must necessarily fall short, and 

 may easily fail entirely to convey an adequate impression. To one who 

 has never seen either these or similar occurrences, it must be a difficult 

 matter to appreciate the great variety of form and coloring. 



DOUaLAS'S CREEK. 



Similar in shape, though of different structure as compared with 

 those near the Front Kange, are some monuments on Douglas's Creek. 

 This stream is one of the largest southerly tributaries of White Eiver, 

 entering it about 15 miles east of the western boundary of Colorado, 

 near north latitude 40° 05'. For a long distance, Douglas's Creek, so 

 named after the head-chief of the White Eiver Utes, passes through 

 sandstones and shales belonging to the Wasatch Group of the Tertiary. 

 Steep bluffs enclose the valley of the stream, showing along their 

 edges unmistakable evidence of aqueous erosion. Although the entire 

 region is a very dry one during certain seasons, large quantities of water 

 flow there at times. It was on the top of a small bluff that a number 

 of "monuments" were noticed in this region.* A cylindrical or some- 

 what angular column of argillaceous, partly arenaceous shales, sustains 

 u huge slab of sandstone. Standing, as they do, near the upper, steep 

 edge of a bluff', these rocks resemble more nearly mushrooms than any- 

 thing else in their general outlines. They are from 8 to 12 feet high. 

 Gray, yellow, and brownish shales make up the column, showing very 

 clearly the planes of original stratification. Slight changes of color 

 or of shades produce a banded appearance. Upon this base rests a 

 protecting cap of fine-grained yellow sandstone. 



Considerable interest attaches itself to the formation of this group. 

 Originally the joints of the sandstone probably afforded the first cause 

 for their present existence. Water entering and gradually widening 

 these fissures, during its flow from the top of the bluff towards its steep 

 edge, eventually succeeded in isolating certain portions of the rock-mass. 

 Having been aided by the existing joint-fissures, this isolation was a 

 matter of little difficulty. Atmospheric agents rapidly attacked the 

 shales supporting fragments of sandstone, and reduced the diameter of 

 the columns. Frost, probably, here proved to be the most destructive 

 factor. The large number of small jointing planes traversing the shales 

 greatly facilitated the process of reduction. In addition to aiding the 



* Compare illustrations in Eeport of tbe United States Geological and Geographical 

 Survey for 1876. 



