the inaccessibility of which must ever be a wonder, when considered as places of residence for human beings. Half-way down the cañon, one of Mr. Jackson’s party discovered a rather remarkable watch-tower, which, because of the accumulations of débris, he was not able to accurately measure, though approximate figures were given. Since his visit, the tower has been thoroughly examined by Mr. W. H. Holmes, to whose work in this field we will refer on a future page. Mr. Holmes’ measurements and ground-plan are, therefore, substituted for those of Mr. Jackson. The diameter of the outer wall is forty-three feet, that of the inner, twenty-five feet. The outer wall is still standing to the height of twelve feet at one point, and is in a fair state of preservation, with a thickness of twenty-one inches, and has the stones dressed to the curve. The ring-shaped space between the inner and outer wall is estimated to have contained ten compartments, two of which at present have complete walls. No door or window was observed in the outer wall, and it is supposed that access was obtained by means of a ladder. Two nearly rectangular openings were found connecting the outer apartments with the central part of the tower, which no doubt was used as an estufa.[477] Mr. Jackson, after leaving the tower which Mr. Holmes has so fully described (of which the above is but a condensed account), saw similar towers on a somewhat smaller scale. His next discovery in the face of the vertical rock, which here ran up from the bottom of the cañon and at a height of from fifty to one hundred feet, were a number of nest-like habitations, one of which is figured in the cut. [Illustration: Ground Plan of Tower in the Mancos Cañon.] [Illustration: Cliff-dwelling of the Mancos Cañon.]