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the Urac ridge would seem to indicate the mechanical origin of these 

 deposits, though metamorphism has entirely obliterated every other 

 trace of their original character. The same metamorphic action may 

 yet be found to have extended to the more recent formations which rest 

 upon the flank of this great lateral spur. But the Cretaceous, as also 

 the Tertiary beds, have been removed by the erosion of the valley of the 

 Cimarroncito, so that the slope of the granitic ridge is barred, except 

 perhaps insignificant outliers of inclined Cretaceous strata, which have 

 escaped degradation, as if to aftbrd a clew to their former extent and 

 intimate relation to the subordinate axis of upheaval. Indeed, in the 

 low ridge through which the Cimarroncito has cut its lower caQon, and 

 not more than a mile north of the Urac Mountain, the Tertiary sand- 

 stones are gently upraised, and bear unmistakable evidences of meta- 

 morphism in their semi-quartzose character. Just beyond this point, 

 at the foot of a charming grassy nook, through which the merry little 

 stream winds in the descent of its bowlder-strewn bed, a picturesque 

 escarpment of light granitic rock rises over the stream, forming a craggy 

 battlement along its northern margin. So it would appear that we have 

 already gained the threshold of that old igneous belt which had its seat 

 of origin or culmination in Great Baldy, at the head of the Moreno Val- 

 ley, twenty miles to the northwest — an outburst of igneous activity 

 similar to, though less marked than, that in which originated the twin 

 cones of the Spanish Peaks, to the north of the Purgatory. 



Prom the eastern flank of Great Baldy northward, the Tertiary depos- 

 its follow the somewhat irregular zigzag trend of the main watershed 

 separating the drainage of the Canadian from the basin of the Bio 

 Grande, until reaching the Francisco Pass, at the initial point of the 

 Eaton Hills, on the northern boundary of the Territory, or about thirty 

 miles in a direct line nearly due north of Baldy. To- the east, the entire 

 country is occupied by the Lignite formation, which is abruptly termi- 

 nated in the lofty escarpments bounding the valley of the Canadian. 



The Eaton Hills form a broad-topped ridge, culminating in the water- 

 shed between the Purgatory, an aifluent of the Arkansas, and the head- 

 waters of the Canadian, and which attains an altitude of between 8,000 

 and 9,000 feet. From the point where it impinges upon the main range, 

 it stretches nearly due east forty miles, and abruptly terminates amidst 

 the wild ravines and pretty glades at the foot of the basaltic wall cap- 

 ping the Chicorica Mesa, in the neighborhood of the stage-road over the 

 Eaton Pass. From a high point near the summit of the pass, at an alti- 

 tude of near 8,000 feet, the topographical features of the ridge and its rela- 

 tions to the great Tertiary plateau are advantageously displayed. The 

 main divide perceptibly rises to the westward in rounded wooded heights; 

 but to the south westward files of successively lower undulations or ridges 

 appear, clothed with pine and a variety of dwarfish deciduous growth, 

 marking the courses of the numerous drainage-channels which traverse 

 the plateau from their sources in its western border. Here, too, are ob- 

 served those conspicuous terrace-like steps which are the records of early 

 shore-lines in the drainage of the ancient waters which occupied the region 

 bordering the eastern flank of the mountains during the epoch preceding 

 our own. These benches — variable in height and distinctness of defini- 

 tion, often forming considerable escarpments or sharp declivities, accord- 

 ing to the nature of the deposits, whether arenaceous shales or more con- 

 solidated sandstone, out of which they are wrought — constitute interest- 

 ing features in the topography of the plateau, distinctively i^eculiar to this 

 formation. Hence it is that when the gi^eat eastern escarpment is 

 viewed from a short distance out in the plains, the formation reveals 



