322 GEOLOGICAL SURVEY OF THE TERRITORIES. 



markable liills, and for the study of the distribution of tlieir geological 

 strata and of tbeir characters. South of Trinidad the lignitic measures 

 have been followed nearly without interruption to the Maxwell estate,* 

 about fifty miles. As it is not as yet ascertained, however, how far they 

 go to the west, the area which they cover at and around the liaton 

 Mountains cannot be positively marked. It is not exaggeration to 

 estimate it at a few hundred, say six to eight hundred square miles. 

 Besides this, the same formation is reported farther south, near and 

 around Santa ¥6; in the Gallisteo Valley; along the mountains to 

 Albuquerque, and in the valley of the Rio Grande as far south as Fort 

 Craig. Everywhere, with a single exception, which shall be considered 

 hereafter,theselignitic measures have exposed, by their relative position, 

 by the absence of animal remains in the thick beds of sandstone which 

 indicate their base and constitute their foundation, by the homology of 

 their marine and land flora, as recognized in the remains of fossil-plants 

 "which they contain in abundance, all the characters indicated above as 

 authorizing, if generally marked, the separation of this group from the 

 Cretaceous formation. 



§ 2. The Arkansas Valley fro3i Pueblo to Canon City. 



From Pueblo to Canon City, forty-five miles, the stage-road follows a 

 broad valley, closed on the south side by the Greenhorn Mountains, on the 

 north side by the Eim Eange of the Colorado Mountains, over which 

 towers Pike's Peak, whose summit is visible all the time. The whole 

 valley is essentially Cretaceous ; all the eminences, either near the bor- 

 ders or in the middle, are htlls of this formation, molded by the erosions 

 of the Arkansas Iliver, which has dug numerous beds in this soft ma- 

 terial. The borders of its present bed, like those of its old ones, where 

 the road sometimes meanders, as in a labyrinth, are picturesquely 

 marked by rocks of diversified forms, resembling monuments built 

 by the hand of man, towers, columns, ruins, &c., often strewn 

 ftround in confusion. On the south side of the river, however, about 

 fifteen miles before reaching Cahon City, the aspect of the country is 

 modified by the appearance of a group of hills of the Lignitic, filling the 

 space from the base of the Greenhorn Mountains to the borders of the 

 river, three to four miles in width. The whole area covered here by 

 the Lignitic is, from the report of Mr. Neilson Clark, civil engineer and 

 superintendent of the mines, about thirty-three square miles.t The 

 lower strata, overlying the sandstone, rise abruptly about 50 feet 

 above the Arkansas River, forming a kind of narrow plateau, over which 

 the hills of the Upper Lignitic rise up to about 500 feet. The whole 

 thickness of the lignite-bearing strata is estimated, in the journal 

 quoted above, at about GOO feet. The following section is taken on the 

 land of the Central Colorado Improvement Company, where coal-beds 

 are already now extensively worked.f It is written from bottom up- 

 ward : 



Underlyinj; tbo bottom sand-rock is a thick bed of clay, interlaid with seams of 

 sand-rock, whose thickness cannot be less than 200 feet. 



* Dr. F. V. Hayden's Report, 1869, p. 57. 



+ Engineering and Mining Journal, November 12, 1872. I owe also to Mr. Clark, who 

 had the kindness to take me to the mines, the details of the following section, and 

 other valuable information. 



t Details on the lignite, its comparative value, thickness, &c., are given in a separate 

 chapter. 



