Two separate explorations and reports upon the Chaco ruins have been made. The first was by Lieut. J. H. Simpson, who examined them in 1849 and first brought them to notice, and the second was a re-examination by William H. Jackson in 1877. He was connected with Prof. F. V. Hayden's Geological and Geographical Survey of the Territories, and his report is in that of Professor Hayden, published in 1878, p. 411.
The cañon of the Chaco, which commences about one hundred and ten miles northwest from Santo Domingo, on the Rio Grande, is quite remarkable. It has enough of the characteristics of the cañon to justify, the application of this peculiar term But it differs from the great cañons in the lowness of the bordering walls and in the great breadth of the space between. Neither Simpson nor Jackson describe the cañon or valley with as much particularity as could be desired, but Mr. Jackson has furnished a map. Fig. 29, showing the course of the stream with the walls of the canon shaded in, and with the breaks or gullies through these walls reduced to a scale. This shows that the level plain between the encompassing walls ranges from half a mile to a mile in places. The walls of the cañon are composed of friable sandstone, and are usually vertical. Their height is not given with precision. The engraving also shows the outline forms and comparative size of the several structures, with specimens of three varieties of masonry used in the walls. No. 2 shows an alternation of courses of stone from four to six inches thick and from eight to twelve inches long, with intervening courses of several thin stones. The same alternation of courses reappears in the pueblos in ruins on the Animas River, about sixty miles north. The cañon commences very much like the McElmo Cañon in Southwestern Colorado, whose vertical walls are at first about three feet high, with a level space between from three hundred to five hundred feet in width; its walls rising slowly as you descend. Without a present running stream, and bordered with open prairie land, it makes a novel appearance to the eye. Lieutenant Simpson remarks that after leaving the pueblo Pintado, which is above the commencement of the cañon, "two miles over a slightly rolling country, our general course still being to the northwest, brought us to the commencement of the Cañon de Chaco, its width here being about two hundred yards. Friable sandstone rocks, massive above,
