ENDLICH ON EROSION IN COLORADO. 837 



though retaining .the general outline of form, the monuments vary in 

 height. They are found from 4 feet to 30 feet high, grouped together 

 often as an aifectiouate family might be supposed to place itself. With- 

 in certain areas an arrangement of the monuments in rows is sometimes 

 noticeable. This is due to the influences of primary erosion. 



Structurally the monuments present very definite features. They are 

 composed of sandstone, varying in texture. Portions of it are exceed- 

 ingly fine-grained, while others show the character of conglomerates. 

 A priori it must be accepted that the protecting cap is formed of harder 

 material than the column. Dr. Peale furnishes* a description from 

 Monument Park. According to his and Mr. Taggart's examinations, 

 " the lower third of the exposed rock is fine-grained, containing argil- 

 laceous layers ". Above that the sandstones become coarser, "almost 

 conglomeratic". The capping of these monuments is formed by a hard 

 conglomerate, firmly cemented by clay-iron-stone. While the shaft 

 exhibits mainly lighter shades, the "cap" is of a dark-red or rusty brown 

 color. White, grayish, yellow, and pink tints are exhibited by the 

 column, often blending into each other very well. Surmounting this is 

 the prominent, dark cap-stone. So thoroughly has this resisted erosion 

 that not unfrequently the caps of several columns are formed by the 

 same piece of conglomerate. All the bright colors exhibited, among 

 which green may sometimes be found, are due to the presence of ferric 

 oxygen-compounds. The entire monument represents an unbroken 

 series of mechanically deposited sediment. From the base to the cap- 

 stone, the rock belongs to one definite period, and must be regarded as 

 a unit. It is with especial reference to this point that I have distin- 

 guished between normal and accidental monuments. Each rock that 

 to day stands isolated speaks to us of the history of its locality. It is 

 the mute yet convincing witness to conditions existing long before the 

 history of man. It tells us of the great changes that time and nature's 

 agents have wrought in a region that now bears no resemblance to what 

 it formerly was. Where broad valleys with streams and fertile meadows 

 may at present be found, sandstones and conglomerates originally cov- 

 ered the entire region. Where deep ravines and narrow caGons contain 

 swiltly flowing streams, there nothing existed formerly but an even, gen- 

 tle slope eastward. Viewing thus the testimony furnished by the exist- 

 ence of these monuments, we cannot but marvel at the enormous amount 

 of work done by the never-ceasing action of nature's agents. Masses 

 have been removed and transported for many miles, that would form 

 mountains coukKthey be collected together. Decomposition, erosion, 

 and removal of the material have so thoroughly altered the character of 

 that section of country, that, were it not for the monuments, we should 

 be at a loss how to reconstruct it. As it is, we have at hand applicable 

 data to guide our inference, and founding our arguments upon observa- 

 tion, they stand or fall with the accuracy of the latter. Transportation 

 ' * Rep. U. S. Geol. Surv., 1873, p. 200, 



