[26] Dr. George F. Kunz has kindly placed in our hands his publications relating to precious stones. In this connection consult his Gems and Precious Stones, New York, 1892; his important paper, New Observations on the Occurrences of Precious Stones of Archæological Interest in America (extrait des _Mémoires et Déliberations du XVᵉ Congrès des Américanistes tenue à Québec du 10 au 15 Septembre 1906_, Quebec, 1907); and Gems and Precious Stones of Mexico, Mexico, 1907. [27] The work of Rafael Aguilar y Santillan is entitled Bibliografía Geológica y Minera de la República Mexicana completada hasta el año de 1904, _Boletín del Instituto Geológico de México_, núm. 17, Mexico, 1908. [28] The interesting study of Luigi Pigorini describing the Mexican mosaics in Rome is entitled Gli Antichi Oggetti Messicani Incrostati di Mosaico esistenti nel Museo Preistorico ed Etnografico di Roma, _Reale Accademia dei Lincei_, Rome, Anno CCLXXXII, 1884-85, 3ª serie, vol. XII, pp. 1-9, I pl. with 5 colored illustrations. [29] The important study by Joseph E. Pogue, The Turquois. A Study of its History, Mineralogy, Geology, Ethnology, Archæology, Mythology, Folklore, and Technology, appears as the third memoir of Vol. XII, _Memoirs of the National Academy of Sciences_, Washington, 1915. [30] Fray Bernardino de Sahagun, Historia General de las Cosas de Nueva España que en Doce Libros y Dos Volúmenes Escribió el R. P. Fr. Bernardino de Sahagun, published by Carlos María de Bustamante, 4 vols., Mexico, 1829. Also published by Lord Kingsborough. The quotations are from the Bustamante edition, tomo III, lib. II, cap. VII, p. 284, and cap. VIII, pp. 296-297. [31] On this subject consult the paper by Dr. A. B. Meyer, Die Nephritfrage, ein ethnologisches Problem, Berlin, 1883, of which an abstract (“The Nephrite Question”) was published in _American Anthropologist_, O. S., vol. I, no. 3, Washington, July, 1888. [32] Saville, A Votive Adze of Jadeite from Mexico, _Monumental Records_, New York, May, 1900. [33] Sahagun, op. cit., tomo III, lib. 10, cap. XXIX, p. 107. [34] Ibid., cap. vii, p. 19. [35] The pictorial part of the section of the great work of Sahagun in Florence was reproduced in facsimile by the late Mexican scholar, Sr. D. Francisco del Paso y Troncoso, for the Mexican government. Only recently has the work been received in Mexico, and we are under the greatest obligations to Sr. D. Luis Castillo Ledon, Director of the Museo Nacional, Mexico, for a copy which we have recently received, and which has been of such great assistance in the preparation of this study of Mexican mosaics. It is an Atlas, denominated Vol. V, of 158 estampas (plates). The plates relating to arts and crafts are to illustrate Libro IX, and include pl. lv to lxxvi. [36] We refer the student to the edition of Lord Kingsborough, vol. I.