412 REPORT UNITED STATES GEOLOGICAL SURVEY. 



The intervening table-lands obtain a very nearly uniform height of 

 500 feet, running up to over 1,000 feet as we approach the Dolores 

 divide. In the wider valleys the maximum is reached by successive 

 steps or benches, rising one back of the other, while in the narrow 

 caiions the ascent is more abrupt ; the upper third of the escarpment 

 being generally perpendicular, with the lower two-thirds composed of 

 talus. Their summits and sides are usually clothed with a growth of 

 scrubby piQon and juniper trees, increasing in density and size as we 

 approach the divide on the north, while the valleys below sustain dense 

 masses of sage-brush and greasewood, that, in some places, attain a 

 height of from 10 to 12 feet. Vigorous, fresh-looking cottonwoods line 

 the main channels, and are as deceptive to the thirsty traveller as a 

 mirage. One may travel for miles in the parched bed of the wash at 

 their feet, while overhead their wide-spreading branches cast a grate- 

 ful shade, and yet not be able to find a drop of water anywhere in their 

 vicinity. 



West of the Montezuma two or three small tributaries of the San 

 Juan head in the southern face of the Sierra Abajo, and then comes Ep- 

 som Creek, rising among the plateaus farther to the west — so called from 

 the water in one portion of its beds tasting like Epsom salts and having 

 its characteristic effect on the animal system. For a distance of some 

 25 miles above its mouth the valley of this creek presents upon its east- 

 ern side a remarkable wall, some 400 feet in height, insurmountable 

 throughout its whole length, with the exception of one place, where the 

 Indians have made a way for themselves. It is caused by an immense 

 fold in the sandstones, running north and south in a semicircular line, 

 for some 40 miles, and the valley has been eroded from the portion 

 where the strata stood nearly perpendicular. On the west the beds 

 sweep up in graceful curves to a nearly horizontal position, upon which 

 isolated mesas rise above the general level in bold relief against the 

 sky. 



The Eio San Juan drains a great interior basin, covering over 20,000 

 square miles, as well as several great mountain masses bordering it. 

 The river at the mouth of the McElmo has an average width of 50 

 yards, and a depth of from 4 to 6 feet ; its current moving somewhat 

 sluggishly in great sweeping curves that almost touch upon themselves 

 again. The water is warm, and well freighted with the soil, which it is 

 continually undermining ; contrasting strongly with the clear, ice-cold 

 tributaries which give it existence. The bottoms are from 3 to 5 miles 

 in width, and, bordering the stream, covered with dense growths of 

 cottonwoods and willows. The broad and fertile alluvial lands, well 

 covered with grass, and the low sage-brush benches bordering them, will 

 undoubtedly prove a rich agricultural possession at no distant day. 

 Back of all upon either hand rise the precipitous sandstone bluffs, pic- 

 turesque in. outline and color, that gradually close down upon the river 

 until it is engulfed in the great caiion which commences just below the 

 mouth of the Rio De Chelly. It is then lost to all knowledge until it re- 

 appears mingling its waters with those of the still more turbid Colorado. 



South of the San Juan, the Eio De Chelly, coming in opposite the 

 mouth of Epsom Creek, does not differ in its caiion character from those 

 of the north. The bordering plateau, however, is more massive and less 

 cut up by side caiions. The same aridity prevails througbout nearly its 

 whole length. 



Having thus superficially surveyed the region, on which are to be 

 found a vast number of prehistoric ruins, we will now return to the 

 Hovenweep, and examine, in such detail as our rapid reconnoissance will 

 allow, the more prominent of the abundant remains. 



