I IQ BXPLOEING EXPEDITION PROM SANTA Ffi 



western base of the Nacimiento Mountain, until, reaching a practicable puss near its 

 southern extremity, we crossed over to the peublo of Jeraez. The country traversed 

 in this pari of our route we found to be much like the foot-hill region bordering the 

 northern mountains, very picturesque, well watered, covered with tine timber, the 

 valleys rich and productive, hut from their great elevation early touched with IVost 

 and doubtless very cold in midwinter. Here, as almost everywhere else on our route, 

 we found numerous ruins of stone-built structures, evidence of the presence in ancient 

 time of a large population, where now neither Indian nor white man dwells. 



In geology our experience was for the most part but a repetition of that already 

 described, as we were passing in review all the strata before so fully examined in the 

 valley of the San Juan. 



The exposures were here, however, exceedingly full and satisfactory, ami 1 had 

 constantly recurring opportunities of testing the accuracy of the classification pre- 

 viously adopted. 



That the evidence furnished by our observations in this interesting region may be 

 consulted in the solution of any question that may be raised in regard to the geological 

 structure of this portion of New Mexico, 1 transcribe from my note-book some of the 

 records made from day to day as we progressed on our journey. 



"S&ptemher '21, Camp 50 to 51. — To-day we followed south along the western base 

 of the Xaciiniento Mountain, over a rolling surface, crossing many wooded hills and 

 pretty valleys formed by the erosion of the Cretaceous strata. This formation, as we 

 can see, occupies all the country southeast from us as far as Mount Taylor; there, as 

 1 learned on a former expedition, it is cut through by the valley of the San Jose, but 

 beyond that extends, we know not how far, southward At Camp 51 we have precisely 

 the same section as that described at Camp 50; all the formations, from the Carbon- 

 iferous to the Upper Cretaceous, lying in sheets, with edges upturned, along the base 

 of the mountain. 'There is, however, here a distinct valley worn out between the 

 Cretaceous table-land and the mountain. Near our camp are buttes and mesas several 

 hundred feet in height, composed of the yellow sandstones of Canon Largo, of which 

 the summits are thickly strewn with bowlders of red granite and limestone, evidently 

 washed down from the neighboring mountain before the intervening valley had been 

 cut out by the stream which now flows through it. The amount of erosion indicated 

 by the presence of this local drift where it is now found is enormous. I previously 

 noticed the same phenomena in many localities among the foot-hills of the northern 

 mountains. We find here everywhere in the sandstones great numbers of silicitied 

 trees, many of them of very large size, apparently all coniferous.' Fragments of these 

 trunks are strewed so abundantly over the surface that they have been used very 

 generally as building-stones in the construction of the ancient pueblos. 



"In seams and pockeis of fine; clay in the sandstones I find abundant impressions 

 of angiospermOUS leaves, apparently of those of sycamore, alder, oak, &&, but the 

 material inclosing them is so friable that they cannot be taken out entire, nor can the 

 fragments be transported for determination. Among these impressions are some conif- 

 erous leaves and stems of a conifer or cycad, very much like the Ulodendron of the Coal- 

 Measures ; a scaly trunk with elliptical disks three inches in diameter. I also obtained 

 fragments of fern leaves, but, too imperfect for determination. 



