388 KEPOKT UNITED STATES GEOLOGICAL SURVEY. 



two miles in circuit, has no natural defensive advantages whatever. 

 Ijfeither are there traces of ditches, nor of anything that might throw 

 important light upon the habits or occupations of the people. A few 

 arrow-heads and minute cutting-implements were picked up. Countless 

 chips of jasper, obsidian, and flint were scattered around, aud the soil 

 was literally full of fragments of painted and indented pottery. 



On the opposite side of the river, and at intervals above and below, 

 are isolated groups of ruins and heaps of debris — certainly the remains 

 of dwellings. These seem to be distributed very much as dwelling-houses 

 are in the rural districts of civilized and peaceable communities. 



It is possible that there are undiscovered ruins on this stream equally 

 important with those described ; for, in pursuing my geologic investiga- 

 tions, I was compelled to take a long detour to the westward from this 

 point, returning to the La Plata again a few miles above its junction 

 with the San Juan. On this occasion, while riding through a desert- 

 like locality, quite naked and barren, much resembling the well-known 

 Mauvaises terres, I was surprised to observe fragments of pottery strewn 

 around, and presently a number of ruins, in a very reduced state and 

 almost covered by the drifting sand, and this six or eight miles from water. 

 On the high, dry table-lands, on all sides, fragments of pottery were 

 picked up. What could have induced people to build and dwell in such 

 a locality it is useless to surmise. 



GROUP OF CAVE-DWELLINGS AND TOWERS ON THE RIO SAN JUAN. 



Plate XXXI. 



On the San Juan River, about thirty-five miles below the mouth of the 

 La Plata and ten miles above the Maucos, occurs the group of ruins 

 figured in Plate 11. 



The river is bordered here by low lines of bluffs formed from the more 

 compact portions of the Middle Cretaceous shales. At this particular 

 place, the vertical-bluff face is from 35 to 40 feet in height. 



I observed, in approaching from above, that a ruined tower stood 

 near the brink of the cliff, at a point where it curves outward toward 

 the river, and in studying it with my glass detected a number of cave- 

 like openings in the cliff-face about half-way up. On examination, I 

 found them to have been shaped by the hand of man, but so weathered 

 out and changed by the slow process of atmospheric erosion that the 

 evidences of art were almost obliterated. 



The openings are arched irregularly above, and generally quite shal- 

 low, being governed very much in contour and depth by the quality of 

 the rock. The work of excavation has not been an extremely great 

 one, even with the imperfect implements that must have been used, as 

 the shale is for the most part soft and friable. 



A hard stratum served as a floor, and projecting in many places made 

 a narrow platform by which the inhabitants were enabled to pass along 

 from one house to another. 



Small fragments of mortar still adhered to the firmer parts of the 

 walls, from which it is inferred that they were at one time plastered. It 

 is also extremely probable that they were walled up in front and fur- 

 nished with doors and windows, yet no fragment of wall has been pre- 

 served. Indeed, so great has been the erosion that many of the caves 

 have, been almost obliterated, and are now not deep enough to give 

 shelter to a bird or bat. 



This circumstance should be considered in reference to its bearing 



