1 14 Bulletin of Laboratories of Denison University [Voi. xi. 
and other dykes extend in various directions into the surround- 
ing country. To the east there have been extensive flows the 
sedimentary rock having been removed to a great extent and 
the important flows being of andesite and an acid “ felsitic ” 
material. In the vicinity of Golden there has been some ex- 
tensive placer working, the results of which it is yet too early 
to ascertain. 
The northeastern part of the territory, from a line passing 
through Raton and Las Vegas and thence southeast, is said by 
Professor R. T. Hill to have formed a part of the Tertiary con- 
tinent and not to have been submerged since the Cretaceous. 
(Bui. Geol. Soc. Am. Ill, 86, et seq.) “The cities of Trini- 
dad, Folsom, and Las Vegas may be considered as bench marks 
along the northern, eastern, and western boundaries respective- 
ly of this region, while Raton, Springer, Maxwell, and other 
points along the Santa Fe railroad between the Purgatoire, at 
Trinidad, and the Pecos are located upon it. The southern 
boundary is the superb escarpment of the Canadian Pecos 
valley. ” 
“ Everywhere is seen the grand result of profound erosion 
by which the overlapping formations (Dakota, Denison, and 
Trinity beds) have been stripped from the horizontal red beds, 
which constitute the valley floor, and has left standing in the 
valley numerous remnants of the plain in the shape of great 
circular buttes and mesas, such as El Corazon, The Gavilan, 
Mesa Rico, Mesa Redondo, the big and little Haarfando Mesa, 
Tucumcari, and others, every stratum of their red, brown and 
white beds being visible in horizontal bands for scores of 
miles.” 
“The erosion from top to bottom of the successive plains 
of stratification has partially removed more than 5000 feet in 
thickness of sedimentary strata.” 
8 , 
THE CARBONIFEROUS. 
In the Rio Grande region of New Mexico the Carbonifer- 
ous formation is remarkably homogeneous. It always rests 
