10 



round towers are very numerous in the valley of the Mancos. From 

 this point alone at least three others are in view, some on the higher 

 promontories, others quite low, within twenty or thirty feet of the river- 

 bed. I visited and measured seven along the lower fifteen miles of the 

 course of this stream. In dimensions they range from ten to sixteen 

 feet in diameter and from five to fifteen feet in height, while the walls 

 are from one to two feet in thickness. They are in nearly every case 

 connected with other structures, mostly rectangular in form. At the 

 mouth of the Mancos, however, a double circle occurs, the smaller 

 one having been the tower proper. It is fifteen feet in diameter, and 

 from eight to ten in height. The larger circular wall is forty feet in 

 diameter and from two to four feet high, and is built tangent to the 

 smaller. This ruin is at the point where the Mancos reaches the allu- 

 vial bottom bordering the Rio San Juan, and about one mile above its 

 junction with that river. On the opposite or south side of the river are 

 traces of somewhat extensive ruins, but so indistinct that the character 

 of the original structures cannot be made out, and indeed no single 

 mile of the lower fifty of the Mancos is without such remains. 



CANON OF THE EIO MANCOS. 



Fifteen miles from its junction with the San Juan, this stream emerges 

 from the southwest border of the Mesa Verde, through which it has cut 

 its way, producing a most remarkable caiion. This caiion has already 

 been oVce or twice described : but, in order to make my subsequent descrip- 

 tions better understood, I shall give here an outline. The Mesa Verde is 

 a somewhat irregular table-land, comprising an area of about seven hun- 

 dred square miles, and is formed of a great series of nearly horizontal 

 sedimentary rocks, of which the surrounding country has been denuded 

 This series of strata consists, in the upper part, of massive sandstones; in 

 the middle part, of alternating sandstones and shales ; and in the lower 

 one thousand feet, chiefly of shales and clay. These softer beds are, 

 when once exposed to the erosive agents, carried away with great rapid- 

 ity, and, as a consequence, the firmer rocks above are undermined and 

 break down in vertical cliffs, and, where soft and hard beds alternate, 

 a series of steps, with intervening slopes, is formed. It will readily be 

 seen that a caiion thus formed would consist in general of a narrow, 

 irregular river-bottom, long steep slopes of debris rising like the arms 

 of a letter V from this, then a succession of steeps and slopes, culminat- 

 ing above in a series of lofty, embattled cliifs. The caiion is nearly thirty 

 miles in length, and ranges from one to two thousand feet in depth. It 

 seems to have been a favorite resort of the cliff-building people, and 

 traces of their industry may be found everywhere, along the bottoms, 

 in the cliffs, and on the high, dry table-lands above. 



The four following plates will be taken up in the delineation of the 

 more interesting portions of these remains. 



PLATE IV. 



Figure 1 illustrates the method of walling up the cave-fronts as 

 described on a preceding page. This sketch was made at the last- 

 mentioned locality on the Rio Mancos. The group occurred in the cliff 

 about thirty feet from the base. The three doorways opened into as 

 many small apartments, and these were connected with each other by 

 very small passage-ways. The farther door could not be reached from 

 the outside, as the platform of rock had broken away. 



