<ai.m-KT.] ALBUQUERQUE TO FLAGSTAFF. 471 



istic features of the system d<> not appear until the lava is left behind. 

 From near Bluewater to Mineral spring the train follows a mono- 

 elinal valley belonging to the northeastern Hank of the Zufii uplift. 

 Beneath the track is the lower division of the Jura-Trias. At the right 

 are a series of picturesque vermilion and orange bluffs and towers mark- 

 ing the outcrop of the Wingate sandstone farther back a second 

 cliff line marks the outcrop of the basal sandstone of the Cretaceous. 

 On the left rises the Zufii range, exhibiting over huge areas the upper 

 surface of the Aubrey limestone, denuded of all superior strata and 

 embodying on its surface the details of mountain structure. With 

 fa vor able light, a system of minor faults and monoclinal flexures can 

 be confidently traced from a distance. 



The slopes of the valley are gentle, but its drainage is curiously 

 divided, a part going to the Atlantic and another pari to the Pacific. 

 Quite unconscious that his train is surmounting a summit, the traveler 

 here crosses the Continental divide. 



i''Ki. 29. — The -Nutria fold. 



At Mineral spring the Nutria fold is crossed. To the northward the 

 strata can be seen to arch over and then suddenly descend. To the 

 southward the fold is marked by a line of rocky crags. Thence to 

 Manuelito the way lies among mesas of Cretaceous rock. A little west 

 of Manuelito the Defiance fold is encountered— a monoclinal similar to 

 that of Mineral spring, but of opposite throw. The J ura Trias is again 

 brought to the surface, and upon it the train continues to the crossing 

 of the bit tie Colorado at Winslow. 'flic beds here seen belong chiefly 

 to the lower portion of the system, including perhaps also the upper of 

 the strata referred to the Permian. Their varied hues in this desolate 

 region have given name to the Painted desert, but near the Little 

 Colorado they are partly concealed by alluvium. 



From Winslow to Flagstaff the prevailing rock is Aubrey limestone, 

 which rises westward from beneath the Jura Trias. Its surface is dis- 

 turbed by minor faults and folds, and diversified by basaltic mesa and 

 cinder cones; and about San Francisco Mountain it is clothed by a 

 noble forest of yellow pine (Pinw ponderosa). 



Where the drainage lines cross low anticlines of the limestone they 

 are sharply incised, and two such trenches are crossed by the railway. 



