A brief review of the discovery of the Ruins and their locality will now be required. From a record by Huarros of Guatimala, and that on the authority of Fuentes, the ruins of Copan were known in 1700. Palenque was visited by Del Rio; and by Dupaix about 1805. In the beginning of the nineteenth century, the scientific Humboldt visited Mexico; he obtained drawings of the ruins of Mitla, in the Province of Oaxaca, and others of a similar character, but especially the terraced-pyramid of Cholula, which he visited. The investigations were published by the same scholastic traveller. At a later period, Uxmal (Yucatan) was explored under a commission of the Spanish Government by Waldeck; his work (folio) is most beautifully illustrated. In compliment to the nobleman who published the great work on the Ancient Mexican Paintings, he called one of the ruins, _The Pyramid of_ _Kingsborough_--an anachronism, perhaps, allowable when the motive is considered. Copan was visited by Galindo in 1836; but he lacked the perseverance necessary for a perfect exploration. This latter desideratum was fully evinced by Stephens and Catherwood who, in 1839-40, visited and explored all of the above (excepting those seen by Baron Humboldt), and several cities before unknown in general history. As a geographical position, the localities of these dead cities are between the capital of Mexico and the Isthmus of Darien, but chiefly in Guatimala; on the borders of Yucatan, and on that Peninsula; they therefore occupy the narrow part of the Continent between the two great oceans. A reference to the map of Central America, will aid the following remarks: The river Montagua empties itself into the Bay of Honduras, at or near, Omoa; approaching the source of this river, it branches off to the South, which branch is called Copan River; above the rapids of this branch-river, is situated on the banks the now celebrated ruined City of Copan, over _two miles_ in extant, parallel with the stream. Palenque is nearer Mexico. The ruins of Uxmal are in Yucatan. From the Architectural characteristics of the edifices, we find no difficulty in arranging the order of their being built, which, with all due respect for the opinion of others, we submit to be as follows: viz.--first, the city of Copan, then Cholula, followed by Quirigua, Tecpan-Guatimala, Quiché, Gueguetinango, Ocosingo, Mitla, Palenque, and lastly, Uxmal: and about the same period of building, the cities of Chi-Chen, Zayi, Kabah, Espita, and Ticol,--these last being in the Peninsula of Yucatan. Compared with these relics of past centuries, we consider the City of Mexico to be of comparatively modern date, _at the time of the Spanish conquest_ (A. D. 1520).