Connected with this subject and in evidence of the identity of these tribes with the Aztecs, it should be stated that there exists numerous edifices of stone in a ruined state, on the banks of the Gila, some of great extent, resembling the terraced edifices and teocallis of Mexico and Yucatan. One of these structures measures four hundred and forty-five feet in length by two hundred and seventy in breadth, with walls four feet in thickness. It was three stories high, with a terrace. The whole surrounding plain is covered with broken pottery and earthen ware, painted in various colors. Vestiges of an artificial canal are also to be seen.[17] Among the fragments are found pieces of obsidian, a volcanic substance not common to the country, and which is also found in the mounds in the Mississippi and Ohio valleys, in both cases applied to the same uses. Some valuable contributions to the geography and ethnology of the vast region lying between the Rocky Mountains and Upper California and Oregon, have been made by Capt. Fremont of the U.S. corps of Engineers. The expedition under his command traversed the great desert, and examined portions of the country not before visited by white men. The information collected by this enterprising traveller will be of much service to the country in the new relations which may arise between the United States and California, as well as to persons who are seeking new homes in Oregon. The report of Captain, (now Col.) Fremont has been so widely circulated, and rendered so accessible to all who feel an interest in the subject, that it would be superfluous to give any analysis of the work at this time. So satisfactory were the results of the expedition of this accomplished officer to the country and the government, that he has again been sent to make further explorations of the country south of that previously visited by him, and which lies between Santa Fé and the Pacific Ocean. Colonel Fremont has in this expedition already rendered important services to the country, having the command of a detachment of troops in Upper California. This armed body of men will give him great advantages over an ordinary traveller in a wild and inhospitable country, where there are still tribes of Indians which have not yet been subjugated by the Spaniards, and which an unprotected traveller could not approach. Much interest has been awakened from the accounts already received from Col. Fremont, and it is to be hoped that ere long we shall be placed in possession of full reports of his explorations, which must throw much light on the geography of this vast region, its aboriginal inhabitants, productions, climate, &c.