If we are to judge by the great number of ruined cities scattered everywhere through the forests of the peninsula; by the architectural beauty of the monuments still extant, the specimens of their artistic attainments in drawing and sculpture which have reached us in the bas-reliefs, statues and mural paintings of Uxmal and Chichen-Itza; by their knowledge in mathematical and astronomical sciences, as manifested in the construction of the gnomon found by me in the ruins of Mayapan; by the complexity of the grammatical form and syntaxis of their language, still spoken to-day by the majority of the inhabitants of Yucatan; by their mode of expressing their thoughts on paper, made from the bark of certain trees, with alphabetical and phonetical characters, we must of necessity believe that, at some time or other, the country was not only densely populated, but that the inhabitants had reached a high degree of civilization. To-day we can conceive of very few of their attainments by the scanty remains of their handiwork, as they have come to us injured by the hand of time, and, more so yet, by that of man, during the wars, the invasions, the social and religious convulsions which have taken place among these people, as among all other nations. Only the opening of the buildings which contain the libraries of their learned men, and the reading of their works, could solve the mystery, and cause us to know how much they had advanced in the discovery and explanation of Nature’s arcana; how much they knew of mankind’s past history, and of the nations with which they held intercourse. Let us hope that the day may yet come when the Mexican government will grant to me the requisite permission, in order that I may bring forth, from the edifices where they are hidden, the precious volumes, without opposition from the owners of the property where the monuments exist. Until then we must content ourselves with the study of the inscriptions carved on the walls, and becoming acquainted with the history of their builders, and continue to conjecture what knowledge they possessed in order to be able to rear such enduring structures, besides the art of designing the plans and ornaments, and the manner of carving them on stone.